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1 \input texinfo @c -*-texinfo-*-
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2 @c %**start of header
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3 @setfilename ../../info/internals.info
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4 @settitle XEmacs Internals Manual
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5 @c %**end of header
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6
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7 @ifinfo
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8 @dircategory XEmacs Editor
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9 @direntry
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10 * Internals: (internals). XEmacs Internals Manual.
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11 @end direntry
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12
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13 Copyright @copyright{} 1992 - 1996 Ben Wing.
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14 Copyright @copyright{} 1996, 1997 Sun Microsystems.
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15 Copyright @copyright{} 1994 - 1998 Free Software Foundation.
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16 Copyright @copyright{} 1994, 1995 Board of Trustees, University of Illinois.
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17
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18
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19 Permission is granted to make and distribute verbatim copies of this
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20 manual provided the copyright notice and this permission notice are
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21 preserved on all copies.
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22
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23 @ignore
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24 Permission is granted to process this file through TeX and print the
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25 results, provided the printed document carries copying permission notice
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26 identical to this one except for the removal of this paragraph (this
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27 paragraph not being relevant to the printed manual).
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28
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29 @end ignore
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30 Permission is granted to copy and distribute modified versions of this
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31 manual under the conditions for verbatim copying, provided that the
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32 entire resulting derived work is distributed under the terms of a
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33 permission notice identical to this one.
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34
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35 Permission is granted to copy and distribute translations of this manual
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36 into another language, under the above conditions for modified versions,
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37 except that this permission notice may be stated in a translation
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38 approved by the Foundation.
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39
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40 Permission is granted to copy and distribute modified versions of this
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41 manual under the conditions for verbatim copying, provided also that the
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42 section entitled ``GNU General Public License'' is included exactly as
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43 in the original, and provided that the entire resulting derived work is
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44 distributed under the terms of a permission notice identical to this
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45 one.
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46
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47 Permission is granted to copy and distribute translations of this manual
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48 into another language, under the above conditions for modified versions,
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49 except that the section entitled ``GNU General Public License'' may be
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50 included in a translation approved by the Free Software Foundation
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51 instead of in the original English.
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52 @end ifinfo
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53
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54 @c Combine indices.
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55 @synindex cp fn
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56 @syncodeindex vr fn
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57 @syncodeindex ky fn
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58 @syncodeindex pg fn
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59 @syncodeindex tp fn
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60
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61 @setchapternewpage odd
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62 @finalout
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63
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64 @titlepage
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65 @title XEmacs Internals Manual
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66 @subtitle Version 1.3, August 1999
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67
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68 @author Ben Wing
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69 @author Martin Buchholz
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70 @author Hrvoje Niksic
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71 @author Matthias Neubauer
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72 @author Olivier Galibert
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73 @page
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74 @vskip 0pt plus 1fill
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75
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76 @noindent
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77 Copyright @copyright{} 1992 - 1996 Ben Wing. @*
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78 Copyright @copyright{} 1996, 1997 Sun Microsystems, Inc. @*
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79 Copyright @copyright{} 1994 - 1998 Free Software Foundation. @*
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80 Copyright @copyright{} 1994, 1995 Board of Trustees, University of Illinois.
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81
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82 @sp 2
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83 Version 1.3 @*
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84 August 1999.@*
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85
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86 Permission is granted to make and distribute verbatim copies of this
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87 manual provided the copyright notice and this permission notice are
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88 preserved on all copies.
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89
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90 Permission is granted to copy and distribute modified versions of this
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91 manual under the conditions for verbatim copying, provided also that the
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92 section entitled ``GNU General Public License'' is included
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93 exactly as in the original, and provided that the entire resulting
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94 derived work is distributed under the terms of a permission notice
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95 identical to this one.
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96
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97 Permission is granted to copy and distribute translations of this manual
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98 into another language, under the above conditions for modified versions,
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99 except that the section entitled ``GNU General Public License'' may be
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100 included in a translation approved by the Free Software Foundation
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101 instead of in the original English.
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102 @end titlepage
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103 @page
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104
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105 @node Top, A History of Emacs, (dir), (dir)
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106
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107 @ifinfo
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108 This Info file contains v1.0 of the XEmacs Internals Manual.
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109 @end ifinfo
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110
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111 @menu
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112 * A History of Emacs:: Times, dates, important events.
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113 * XEmacs From the Outside:: A broad conceptual overview.
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114 * The Lisp Language:: An overview.
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115 * XEmacs From the Perspective of Building::
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116 * XEmacs From the Inside::
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117 * The XEmacs Object System (Abstractly Speaking)::
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118 * How Lisp Objects Are Represented in C::
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119 * Rules When Writing New C Code::
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120 * A Summary of the Various XEmacs Modules::
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121 * Allocation of Objects in XEmacs Lisp::
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398
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122 * Dumping::
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123 * Events and the Event Loop::
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124 * Evaluation; Stack Frames; Bindings::
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125 * Symbols and Variables::
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126 * Buffers and Textual Representation::
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127 * MULE Character Sets and Encodings::
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128 * The Lisp Reader and Compiler::
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129 * Lstreams::
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130 * Consoles; Devices; Frames; Windows::
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131 * The Redisplay Mechanism::
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132 * Extents::
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398
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133 * Faces::
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134 * Glyphs::
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135 * Specifiers::
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136 * Menus::
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137 * Subprocesses::
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138 * Interface to X Windows::
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398
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139 * Index::
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140
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141 @detailmenu --- The Detailed Node Listing ---
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142
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143 A History of Emacs
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144
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145 * Through Version 18:: Unification prevails.
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146 * Lucid Emacs:: One version 19 Emacs.
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147 * GNU Emacs 19:: The other version 19 Emacs.
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398
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148 * GNU Emacs 20:: The other version 20 Emacs.
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149 * XEmacs:: The continuation of Lucid Emacs.
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150
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151 Rules When Writing New C Code
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152
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153 * General Coding Rules::
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154 * Writing Lisp Primitives::
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155 * Adding Global Lisp Variables::
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398
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156 * Coding for Mule::
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157 * Techniques for XEmacs Developers::
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158
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159 Coding for Mule
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160
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161 * Character-Related Data Types::
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162 * Working With Character and Byte Positions::
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163 * Conversion to and from External Data::
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164 * General Guidelines for Writing Mule-Aware Code::
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165 * An Example of Mule-Aware Code::
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166
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167 A Summary of the Various XEmacs Modules
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168
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169 * Low-Level Modules::
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170 * Basic Lisp Modules::
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171 * Modules for Standard Editing Operations::
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172 * Editor-Level Control Flow Modules::
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173 * Modules for the Basic Displayable Lisp Objects::
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174 * Modules for other Display-Related Lisp Objects::
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175 * Modules for the Redisplay Mechanism::
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176 * Modules for Interfacing with the File System::
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177 * Modules for Other Aspects of the Lisp Interpreter and Object System::
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178 * Modules for Interfacing with the Operating System::
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179 * Modules for Interfacing with X Windows::
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180 * Modules for Internationalization::
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181
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182 Allocation of Objects in XEmacs Lisp
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183
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184 * Introduction to Allocation::
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185 * Garbage Collection::
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186 * GCPROing::
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398
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187 * Garbage Collection - Step by Step::
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188 * Integers and Characters::
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189 * Allocation from Frob Blocks::
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190 * lrecords::
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191 * Low-level allocation::
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192 * Pure Space::
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193 * Cons::
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194 * Vector::
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195 * Bit Vector::
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196 * Symbol::
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197 * Marker::
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198 * String::
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380
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199 * Compiled Function::
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200
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398
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201 Garbage Collection - Step by Step
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202
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203 * Invocation::
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204 * garbage_collect_1::
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205 * mark_object::
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206 * gc_sweep::
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207 * sweep_lcrecords_1::
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208 * compact_string_chars::
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209 * sweep_strings::
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210 * sweep_bit_vectors_1::
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211
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212 Dumping
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213
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214 * Overview::
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215 * Data descriptions::
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216 * Dumping phase::
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217 * Reloading phase::
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218
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219 Dumping phase
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220
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221 * Object inventory::
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222 * Address allocation::
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223 * The header::
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224 * Data dumping::
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225 * Pointers dumping::
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226
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227 Events and the Event Loop
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228
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229 * Introduction to Events::
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230 * Main Loop::
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231 * Specifics of the Event Gathering Mechanism::
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232 * Specifics About the Emacs Event::
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233 * The Event Stream Callback Routines::
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234 * Other Event Loop Functions::
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235 * Converting Events::
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236 * Dispatching Events; The Command Builder::
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237
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238 Evaluation; Stack Frames; Bindings
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239
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240 * Evaluation::
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241 * Dynamic Binding; The specbinding Stack; Unwind-Protects::
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242 * Simple Special Forms::
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243 * Catch and Throw::
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244
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245 Symbols and Variables
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246
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247 * Introduction to Symbols::
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248 * Obarrays::
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249 * Symbol Values::
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250
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251 Buffers and Textual Representation
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252
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253 * Introduction to Buffers:: A buffer holds a block of text such as a file.
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193
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254 * The Text in a Buffer:: Representation of the text in a buffer.
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255 * Buffer Lists:: Keeping track of all buffers.
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256 * Markers and Extents:: Tagging locations within a buffer.
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257 * Bufbytes and Emchars:: Representation of individual characters.
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258 * The Buffer Object:: The Lisp object corresponding to a buffer.
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259
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260 MULE Character Sets and Encodings
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261
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262 * Character Sets::
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263 * Encodings::
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264 * Internal Mule Encodings::
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398
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265 * CCL::
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266
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267 Encodings
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268
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269 * Japanese EUC (Extended Unix Code)::
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270 * JIS7::
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271
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272 Internal Mule Encodings
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273
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274 * Internal String Encoding::
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275 * Internal Character Encoding::
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276
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277 Lstreams
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278
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398
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279 * Creating an Lstream:: Creating an lstream object.
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280 * Lstream Types:: Different sorts of things that are streamed.
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281 * Lstream Functions:: Functions for working with lstreams.
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282 * Lstream Methods:: Creating new lstream types.
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283
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284 Consoles; Devices; Frames; Windows
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285
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286 * Introduction to Consoles; Devices; Frames; Windows::
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287 * Point::
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288 * Window Hierarchy::
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398
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289 * The Window Object::
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290
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291 The Redisplay Mechanism
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292
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293 * Critical Redisplay Sections::
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294 * Line Start Cache::
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398
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295 * Redisplay Piece by Piece::
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296
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297 Extents
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298
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299 * Introduction to Extents:: Extents are ranges over text, with properties.
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300 * Extent Ordering:: How extents are ordered internally.
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301 * Format of the Extent Info:: The extent information in a buffer or string.
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302 * Zero-Length Extents:: A weird special case.
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398
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303 * Mathematics of Extent Ordering:: A rigorous foundation.
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304 * Extent Fragments:: Cached information useful for redisplay.
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305
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398
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306 @end detailmenu
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307 @end menu
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308
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309 @node A History of Emacs, XEmacs From the Outside, Top, Top
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310 @chapter A History of Emacs
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311 @cindex history of Emacs
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312 @cindex Hackers (Steven Levy)
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313 @cindex Levy, Steven
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314 @cindex ITS (Incompatible Timesharing System)
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315 @cindex Stallman, Richard
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316 @cindex RMS
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317 @cindex MIT
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318 @cindex TECO
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319 @cindex FSF
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320 @cindex Free Software Foundation
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321
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322 XEmacs is a powerful, customizable text editor and development
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323 environment. It began as Lucid Emacs, which was in turn derived from
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324 GNU Emacs, a program written by Richard Stallman of the Free Software
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325 Foundation. GNU Emacs dates back to the 1970's, and was modelled
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326 after a package called ``Emacs'', written in 1976, that was a set of
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327 macros on top of TECO, an old, old text editor written at MIT on the
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328 DEC PDP 10 under one of the earliest time-sharing operating systems,
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329 ITS (Incompatible Timesharing System). (ITS dates back well before
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330 Unix.) ITS, TECO, and Emacs were products of a group of people at MIT
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331 who called themselves ``hackers'', who shared an idealistic belief
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332 system about the free exchange of information and were fanatical in
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333 their devotion to and time spent with computers. (The hacker
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334 subculture dates back to the late 1950's at MIT and is described in
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335 detail in Steven Levy's book @cite{Hackers}. This book also includes
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336 a lot of information about Stallman himself and the development of
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337 Lisp, a programming language developed at MIT that underlies Emacs.)
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338
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339 @menu
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340 * Through Version 18:: Unification prevails.
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341 * Lucid Emacs:: One version 19 Emacs.
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342 * GNU Emacs 19:: The other version 19 Emacs.
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193
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343 * GNU Emacs 20:: The other version 20 Emacs.
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344 * XEmacs:: The continuation of Lucid Emacs.
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345 @end menu
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346
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398
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347 @node Through Version 18, Lucid Emacs, A History of Emacs, A History of Emacs
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348 @section Through Version 18
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349 @cindex Gosling, James
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350 @cindex Great Usenet Renaming
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351
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352 Although the history of the early versions of GNU Emacs is unclear,
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353 the history is well-known from the middle of 1985. A time line is:
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354
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355 @itemize @bullet
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356 @item
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357 GNU Emacs version 15 (15.34) was released sometime in 1984 or 1985 and
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358 shared some code with a version of Emacs written by James Gosling (the
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359 same James Gosling who later created the Java language).
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360 @item
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361 GNU Emacs version 16 (first released version was 16.56) was released on
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362 July 15, 1985. All Gosling code was removed due to potential copyright
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363 problems with the code.
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364 @item
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365 version 16.57: released on September 16, 1985.
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366 @item
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367 versions 16.58, 16.59: released on September 17, 1985.
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368 @item
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369 version 16.60: released on September 19, 1985. These later version 16's
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370 incorporated patches from the net, esp. for getting Emacs to work under
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371 System V.
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372 @item
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373 version 17.36 (first official v17 release) released on December 20,
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374 1985. Included a TeX-able user manual. First official unpatched
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375 version that worked on vanilla System V machines.
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376 @item
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377 version 17.43 (second official v17 release) released on January 25,
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378 1986.
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379 @item
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380 version 17.45 released on January 30, 1986.
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381 @item
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382 version 17.46 released on February 4, 1986.
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383 @item
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384 version 17.48 released on February 10, 1986.
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385 @item
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386 version 17.49 released on February 12, 1986.
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387 @item
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388 version 17.55 released on March 18, 1986.
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389 @item
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390 version 17.57 released on March 27, 1986.
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391 @item
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392 version 17.58 released on April 4, 1986.
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393 @item
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394 version 17.61 released on April 12, 1986.
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395 @item
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396 version 17.63 released on May 7, 1986.
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397 @item
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398 version 17.64 released on May 12, 1986.
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399 @item
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400 version 18.24 (a beta version) released on October 2, 1986.
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401 @item
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402 version 18.30 (a beta version) released on November 15, 1986.
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403 @item
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404 version 18.31 (a beta version) released on November 23, 1986.
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405 @item
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406 version 18.32 (a beta version) released on December 7, 1986.
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407 @item
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408 version 18.33 (a beta version) released on December 12, 1986.
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409 @item
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410 version 18.35 (a beta version) released on January 5, 1987.
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411 @item
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412 version 18.36 (a beta version) released on January 21, 1987.
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413 @item
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2
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414 January 27, 1987: The Great Usenet Renaming. net.emacs is now
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415 comp.emacs.
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416 @item
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0
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417 version 18.37 (a beta version) released on February 12, 1987.
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418 @item
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419 version 18.38 (a beta version) released on March 3, 1987.
|
|
|
420 @item
|
|
|
421 version 18.39 (a beta version) released on March 14, 1987.
|
|
|
422 @item
|
|
|
423 version 18.40 (a beta version) released on March 18, 1987.
|
|
|
424 @item
|
|
|
425 version 18.41 (the first ``official'' release) released on March 22,
|
|
|
426 1987.
|
|
|
427 @item
|
|
|
428 version 18.45 released on June 2, 1987.
|
|
|
429 @item
|
|
|
430 version 18.46 released on June 9, 1987.
|
|
|
431 @item
|
|
|
432 version 18.47 released on June 18, 1987.
|
|
|
433 @item
|
|
|
434 version 18.48 released on September 3, 1987.
|
|
|
435 @item
|
|
|
436 version 18.49 released on September 18, 1987.
|
|
|
437 @item
|
|
|
438 version 18.50 released on February 13, 1988.
|
|
|
439 @item
|
|
|
440 version 18.51 released on May 7, 1988.
|
|
|
441 @item
|
|
|
442 version 18.52 released on September 1, 1988.
|
|
|
443 @item
|
|
|
444 version 18.53 released on February 24, 1989.
|
|
|
445 @item
|
|
|
446 version 18.54 released on April 26, 1989.
|
|
|
447 @item
|
|
|
448 version 18.55 released on August 23, 1989. This is the earliest version
|
|
|
449 that is still available by FTP.
|
|
|
450 @item
|
|
|
451 version 18.56 released on January 17, 1991.
|
|
|
452 @item
|
|
|
453 version 18.57 released late January, 1991.
|
|
|
454 @item
|
|
|
455 version 18.58 released ?????.
|
|
|
456 @item
|
|
|
457 version 18.59 released October 31, 1992.
|
|
|
458 @end itemize
|
|
|
459
|
|
398
|
460 @node Lucid Emacs, GNU Emacs 19, Through Version 18, A History of Emacs
|
|
0
|
461 @section Lucid Emacs
|
|
|
462 @cindex Lucid Emacs
|
|
|
463 @cindex Lucid Inc.
|
|
|
464 @cindex Energize
|
|
|
465 @cindex Epoch
|
|
|
466
|
|
|
467 Lucid Emacs was developed by the (now-defunct) Lucid Inc., a maker of
|
|
|
468 C++ and Lisp development environments. It began when Lucid decided they
|
|
|
469 wanted to use Emacs as the editor and cornerstone of their C++
|
|
|
470 development environment (called ``Energize''). They needed many features
|
|
|
471 that were not available in the existing version of GNU Emacs (version
|
|
|
472 18.5something), in particular good and integrated support for GUI
|
|
|
473 elements such as mouse support, multiple fonts, multiple window-system
|
|
|
474 windows, etc. A branch of GNU Emacs called Epoch, written at the
|
|
|
475 University of Illinois, existed that supplied many of these features;
|
|
|
476 however, Lucid needed more than what existed in Epoch. At the time, the
|
|
|
477 Free Software Foundation was working on version 19 of Emacs (this was
|
|
|
478 sometime around 1991), which was planned to have similar features, and
|
|
|
479 so Lucid decided to work with the Free Software Foundation. Their plan
|
|
|
480 was to add features that they needed, and coordinate with the FSF so
|
|
|
481 that the features would get included back into Emacs version 19.
|
|
|
482
|
|
|
483 Delays in the release of version 19 occurred, however (resulting in it
|
|
|
484 finally being released more than a year after what was initially
|
|
|
485 planned), and Lucid encountered unexpected technical resistance in
|
|
|
486 getting their changes merged back into version 19, so they decided to
|
|
|
487 release their own version of Emacs, which became Lucid Emacs 19.0.
|
|
|
488
|
|
|
489 @cindex Zawinski, Jamie
|
|
|
490 @cindex Sexton, Harlan
|
|
|
491 @cindex Benson, Eric
|
|
|
492 @cindex Devin, Matthieu
|
|
|
493 The initial authors of Lucid Emacs were Matthieu Devin, Harlan Sexton,
|
|
|
494 and Eric Benson, and the work was later taken over by Jamie Zawinski,
|
|
|
495 who became ``Mr. Lucid Emacs'' for many releases.
|
|
|
496
|
|
|
497 A time line for Lucid Emacs/XEmacs is
|
|
|
498
|
|
|
499 @itemize @bullet
|
|
|
500 @item
|
|
|
501 version 19.0 shipped with Energize 1.0, April 1992.
|
|
|
502 @item
|
|
|
503 version 19.1 released June 4, 1992.
|
|
|
504 @item
|
|
|
505 version 19.2 released June 19, 1992.
|
|
|
506 @item
|
|
|
507 version 19.3 released September 9, 1992.
|
|
|
508 @item
|
|
|
509 version 19.4 released January 21, 1993.
|
|
|
510 @item
|
|
|
511 version 19.5 was a repackaging of 19.4 with a few bug fixes and
|
|
|
512 shipped with Energize 2.0. Never released to the net.
|
|
|
513 @item
|
|
|
514 version 19.6 released April 9, 1993.
|
|
|
515 @item
|
|
|
516 version 19.7 was a repackaging of 19.6 with a few bug fixes and
|
|
|
517 shipped with Energize 2.1. Never released to the net.
|
|
|
518 @item
|
|
|
519 version 19.8 released September 6, 1993.
|
|
|
520 @item
|
|
|
521 version 19.9 released January 12, 1994.
|
|
|
522 @item
|
|
|
523 version 19.10 released May 27, 1994.
|
|
|
524 @item
|
|
|
525 version 19.11 (first XEmacs) released September 13, 1994.
|
|
|
526 @item
|
|
|
527 version 19.12 released June 23, 1995.
|
|
|
528 @item
|
|
|
529 version 19.13 released September 1, 1995.
|
|
112
|
530 @item
|
|
|
531 version 19.14 released June 23, 1996.
|
|
|
532 @item
|
|
|
533 version 20.0 released February 9, 1997.
|
|
120
|
534 @item
|
|
|
535 version 19.15 released March 28, 1997.
|
|
149
|
536 @item
|
|
|
537 version 20.1 (not released to the net) April 15, 1997.
|
|
|
538 @item
|
|
|
539 version 20.2 released May 16, 1997.
|
|
209
|
540 @item
|
|
|
541 version 19.16 released October 31, 1997.
|
|
219
|
542 @item
|
|
|
543 version 20.3 (the first stable version of XEmacs 20.x) released November 30,
|
|
|
544 1997.
|
|
259
|
545 version 20.4 released February 28, 1998.
|
|
0
|
546 @end itemize
|
|
|
547
|
|
398
|
548 @node GNU Emacs 19, GNU Emacs 20, Lucid Emacs, A History of Emacs
|
|
0
|
549 @section GNU Emacs 19
|
|
|
550 @cindex GNU Emacs 19
|
|
|
551 @cindex FSF Emacs
|
|
|
552
|
|
|
553 About a year after the initial release of Lucid Emacs, the FSF
|
|
|
554 released a beta of their version of Emacs 19 (referred to here as ``GNU
|
|
|
555 Emacs''). By this time, the current version of Lucid Emacs was
|
|
|
556 19.6. (Strangely, the first released beta from the FSF was GNU Emacs
|
|
|
557 19.7.) A time line for GNU Emacs version 19 is
|
|
|
558
|
|
|
559 @itemize @bullet
|
|
|
560 @item
|
|
|
561 version 19.8 (beta) released May 27, 1993.
|
|
|
562 @item
|
|
|
563 version 19.9 (beta) released May 27, 1993.
|
|
|
564 @item
|
|
|
565 version 19.10 (beta) released May 30, 1993.
|
|
|
566 @item
|
|
|
567 version 19.11 (beta) released June 1, 1993.
|
|
|
568 @item
|
|
|
569 version 19.12 (beta) released June 2, 1993.
|
|
|
570 @item
|
|
|
571 version 19.13 (beta) released June 8, 1993.
|
|
|
572 @item
|
|
|
573 version 19.14 (beta) released June 17, 1993.
|
|
|
574 @item
|
|
|
575 version 19.15 (beta) released June 19, 1993.
|
|
|
576 @item
|
|
|
577 version 19.16 (beta) released July 6, 1993.
|
|
|
578 @item
|
|
|
579 version 19.17 (beta) released late July, 1993.
|
|
|
580 @item
|
|
|
581 version 19.18 (beta) released August 9, 1993.
|
|
|
582 @item
|
|
|
583 version 19.19 (beta) released August 15, 1993.
|
|
|
584 @item
|
|
|
585 version 19.20 (beta) released November 17, 1993.
|
|
|
586 @item
|
|
|
587 version 19.21 (beta) released November 17, 1993.
|
|
|
588 @item
|
|
|
589 version 19.22 (beta) released November 28, 1993.
|
|
|
590 @item
|
|
|
591 version 19.23 (beta) released May 17, 1994.
|
|
|
592 @item
|
|
|
593 version 19.24 (beta) released May 16, 1994.
|
|
|
594 @item
|
|
|
595 version 19.25 (beta) released June 3, 1994.
|
|
|
596 @item
|
|
|
597 version 19.26 (beta) released September 11, 1994.
|
|
|
598 @item
|
|
|
599 version 19.27 (beta) released September 14, 1994.
|
|
|
600 @item
|
|
|
601 version 19.28 (first ``official'' release) released November 1, 1994.
|
|
|
602 @item
|
|
|
603 version 19.29 released June 21, 1995.
|
|
112
|
604 @item
|
|
|
605 version 19.30 released November 24, 1995.
|
|
|
606 @item
|
|
|
607 version 19.31 released May 25, 1996.
|
|
|
608 @item
|
|
|
609 version 19.32 released July 31, 1996.
|
|
|
610 @item
|
|
|
611 version 19.33 released August 11, 1996.
|
|
|
612 @item
|
|
|
613 version 19.34 released August 21, 1996.
|
|
|
614 @item
|
|
|
615 version 19.34b released September 6, 1996.
|
|
0
|
616 @end itemize
|
|
|
617
|
|
|
618 @cindex Mlynarik, Richard
|
|
|
619 In some ways, GNU Emacs 19 was better than Lucid Emacs; in some ways,
|
|
|
620 worse. Lucid soon began incorporating features from GNU Emacs 19 into
|
|
|
621 Lucid Emacs; the work was mostly done by Richard Mlynarik, who had been
|
|
|
622 working on and using GNU Emacs for a long time (back as far as version
|
|
|
623 16 or 17).
|
|
|
624
|
|
398
|
625 @node GNU Emacs 20, XEmacs, GNU Emacs 19, A History of Emacs
|
|
193
|
626 @section GNU Emacs 20
|
|
|
627 @cindex GNU Emacs 20
|
|
|
628 @cindex FSF Emacs
|
|
|
629
|
|
|
630 On February 2, 1997 work began on GNU Emacs to integrate Mule. The first
|
|
|
631 release was made in September of that year.
|
|
|
632
|
|
|
633 A timeline for Emacs 20 is
|
|
|
634
|
|
|
635 @itemize @bullet
|
|
|
636 @item
|
|
|
637 version 20.1 released September 17, 1997.
|
|
195
|
638 @item
|
|
|
639 version 20.2 released September 20, 1997.
|
|
373
|
640 @item
|
|
|
641 version 20.3 released August 19, 1998.
|
|
193
|
642 @end itemize
|
|
|
643
|
|
398
|
644 @node XEmacs, , GNU Emacs 20, A History of Emacs
|
|
0
|
645 @section XEmacs
|
|
|
646 @cindex XEmacs
|
|
|
647
|
|
|
648 @cindex Sun Microsystems
|
|
|
649 @cindex University of Illinois
|
|
|
650 @cindex Illinois, University of
|
|
|
651 @cindex SPARCWorks
|
|
|
652 @cindex Andreessen, Marc
|
|
120
|
653 @cindex Baur, Steve
|
|
|
654 @cindex Buchholz, Martin
|
|
0
|
655 @cindex Kaplan, Simon
|
|
|
656 @cindex Wing, Ben
|
|
|
657 @cindex Thompson, Chuck
|
|
|
658 @cindex Win-Emacs
|
|
|
659 @cindex Epoch
|
|
|
660 @cindex Amdahl Corporation
|
|
|
661 Around the time that Lucid was developing Energize, Sun Microsystems
|
|
|
662 was developing their own development environment (called ``SPARCWorks'')
|
|
|
663 and also decided to use Emacs. They joined forces with the Epoch team
|
|
|
664 at the University of Illinois and later with Lucid. The maintainer of
|
|
|
665 the last-released version of Epoch was Marc Andreessen, but he dropped
|
|
|
666 out and the Epoch project, headed by Simon Kaplan, lured Chuck Thompson
|
|
|
667 away from a system administration job to become the primary Lucid Emacs
|
|
|
668 author for Epoch and Sun. Chuck's area of specialty became the
|
|
|
669 redisplay engine (he replaced the old Lucid Emacs redisplay engine with
|
|
|
670 a ported version from Epoch and then later rewrote it from scratch).
|
|
|
671 Sun also hired Ben Wing (the author of Win-Emacs, a port of Lucid Emacs
|
|
|
672 to Microsoft Windows 3.1) in 1993, for what was initially a one-month
|
|
|
673 contract to fix some event problems but later became a many-year
|
|
|
674 involvement, punctuated by a six-month contract with Amdahl Corporation.
|
|
|
675
|
|
|
676 @cindex rename to XEmacs
|
|
|
677 In 1994, Sun and Lucid agreed to rename Lucid Emacs to XEmacs (a name
|
|
|
678 not favorable to either company); the first release called XEmacs was
|
|
|
679 version 19.11. In June 1994, Lucid folded and Jamie quit to work for
|
|
|
680 the newly formed Mosaic Communications Corp., later Netscape
|
|
|
681 Communications Corp. (co-founded by the same Marc Andreessen, who had
|
|
|
682 quit his Epoch job to work on a graphical browser for the World Wide
|
|
|
683 Web). Chuck then become the primary maintainer of XEmacs, and put out
|
|
120
|
684 versions 19.11 through 19.14 in conjunction with Ben. For 19.12 and
|
|
0
|
685 19.13, Chuck added the new redisplay and many other display improvements
|
|
|
686 and Ben added MULE support (support for Asian and other languages) and
|
|
|
687 redesigned most of the internal Lisp subsystems to better support the
|
|
120
|
688 MULE work and the various other features being added to XEmacs. After
|
|
|
689 19.14 Chuck retired as primary maintainer and Steve Baur stepped in.
|
|
|
690
|
|
|
691 @cindex MULE merged XEmacs appears
|
|
|
692 Soon after 19.13 was released, work began in earnest on the MULE
|
|
|
693 internationalization code and the source tree was divided into two
|
|
|
694 development paths. The MULE version was initially called 19.20, but was
|
|
|
695 soon renamed to 20.0. In 1996 Martin Buchholz of Sun Microsystems took
|
|
|
696 over the care and feeding of it and worked on it in parallel with the
|
|
|
697 19.14 development that was occurring at the same time. After much work
|
|
|
698 by Martin, it was decided to release 20.0 ahead of 19.15 in February
|
|
219
|
699 1997. The source tree remained divided until 20.2 when the version 19
|
|
|
700 source was finally retired at version 19.16.
|
|
|
701
|
|
|
702 @cindex Baur, Steve
|
|
|
703 @cindex Buchholz, Martin
|
|
|
704 @cindex Jones, Kyle
|
|
|
705 @cindex Niksic, Hrvoje
|
|
|
706 @cindex XEmacs goes it alone
|
|
|
707 In 1997, Sun finally dropped all pretense of support for XEmacs and
|
|
|
708 Martin Buchholz left the company in November. Since then, and mostly
|
|
|
709 for the previous year, because Steve Baur was never paid to work on
|
|
|
710 XEmacs, XEmacs has existed solely on the contributions of volunteers
|
|
|
711 from the Free Software Community. Starting from 1997, Hrvoje Niksic and
|
|
|
712 Kyle Jones have figured prominently in XEmacs development.
|
|
0
|
713
|
|
|
714 @cindex merging attempts
|
|
|
715 Many attempts have been made to merge XEmacs and GNU Emacs, but they
|
|
219
|
716 have consistently failed.
|
|
0
|
717
|
|
|
718 A more detailed history is contained in the XEmacs About page.
|
|
|
719
|
|
|
720 @node XEmacs From the Outside, The Lisp Language, A History of Emacs, Top
|
|
|
721 @chapter XEmacs From the Outside
|
|
|
722 @cindex read-eval-print
|
|
|
723
|
|
|
724 XEmacs appears to the outside world as an editor, but it is really a
|
|
|
725 Lisp environment. At its heart is a Lisp interpreter; it also
|
|
|
726 ``happens'' to contain many specialized object types (e.g. buffers,
|
|
|
727 windows, frames, events) that are useful for implementing an editor.
|
|
|
728 Some of these objects (in particular windows and frames) have
|
|
|
729 displayable representations, and XEmacs provides a function
|
|
|
730 @code{redisplay()} that ensures that the display of all such objects
|
|
|
731 matches their internal state. Most of the time, a standard Lisp
|
|
398
|
732 environment is in a @dfn{read-eval-print} loop---i.e. ``read some Lisp
|
|
0
|
733 code, execute it, and print the results''. XEmacs has a similar loop:
|
|
|
734
|
|
|
735 @itemize @bullet
|
|
|
736 @item
|
|
|
737 read an event
|
|
|
738 @item
|
|
|
739 dispatch the event (i.e. ``do it'')
|
|
|
740 @item
|
|
|
741 redisplay
|
|
|
742 @end itemize
|
|
|
743
|
|
|
744 Reading an event is done using the Lisp function @code{next-event},
|
|
|
745 which waits for something to happen (typically, the user presses a key
|
|
|
746 or moves the mouse) and returns an event object describing this.
|
|
|
747 Dispatching an event is done using the Lisp function
|
|
|
748 @code{dispatch-event}, which looks up the event in a keymap object (a
|
|
|
749 particular kind of object that associates an event with a Lisp function)
|
|
|
750 and calls that function. The function ``does'' what the user has
|
|
|
751 requested by changing the state of particular frame objects, buffer
|
|
|
752 objects, etc. Finally, @code{redisplay()} is called, which updates the
|
|
|
753 display to reflect those changes just made. Thus is an ``editor'' born.
|
|
|
754
|
|
|
755 @cindex bridge, playing
|
|
|
756 @cindex taxes, doing
|
|
|
757 @cindex pi, calculating
|
|
|
758 Note that you do not have to use XEmacs as an editor; you could just
|
|
|
759 as well make it do your taxes, compute pi, play bridge, etc. You'd just
|
|
|
760 have to write functions to do those operations in Lisp.
|
|
|
761
|
|
|
762 @node The Lisp Language, XEmacs From the Perspective of Building, XEmacs From the Outside, Top
|
|
|
763 @chapter The Lisp Language
|
|
|
764 @cindex Lisp vs. C
|
|
|
765 @cindex C vs. Lisp
|
|
|
766 @cindex Lisp vs. Java
|
|
|
767 @cindex Java vs. Lisp
|
|
|
768 @cindex dynamic scoping
|
|
|
769 @cindex scoping, dynamic
|
|
|
770 @cindex dynamic types
|
|
|
771 @cindex types, dynamic
|
|
|
772 @cindex Java
|
|
|
773 @cindex Common Lisp
|
|
|
774 @cindex Gosling, James
|
|
|
775
|
|
|
776 Lisp is a general-purpose language that is higher-level than C and in
|
|
|
777 many ways more powerful than C. Powerful dialects of Lisp such as
|
|
|
778 Common Lisp are probably much better languages for writing very large
|
|
|
779 applications than is C. (Unfortunately, for many non-technical
|
|
|
780 reasons C and its successor C++ have become the dominant languages for
|
|
|
781 application development. These languages are both inadequate for
|
|
|
782 extremely large applications, which is evidenced by the fact that newer,
|
|
|
783 larger programs are becoming ever harder to write and are requiring ever
|
|
|
784 more programmers despite great increases in C development environments;
|
|
|
785 and by the fact that, although hardware speeds and reliability have been
|
|
|
786 growing at an exponential rate, most software is still generally
|
|
|
787 considered to be slow and buggy.)
|
|
|
788
|
|
|
789 The new Java language holds promise as a better general-purpose
|
|
|
790 development language than C. Java has many features in common with
|
|
|
791 Lisp that are not shared by C (this is not a coincidence, since
|
|
|
792 Java was designed by James Gosling, a former Lisp hacker). This
|
|
|
793 will be discussed more later.
|
|
|
794
|
|
|
795 For those used to C, here is a summary of the basic differences between
|
|
|
796 C and Lisp:
|
|
|
797
|
|
|
798 @enumerate
|
|
|
799 @item
|
|
|
800 Lisp has an extremely regular syntax. Every function, expression,
|
|
|
801 and control statement is written in the form
|
|
|
802
|
|
|
803 @example
|
|
|
804 (@var{func} @var{arg1} @var{arg2} ...)
|
|
|
805 @end example
|
|
|
806
|
|
|
807 This is as opposed to C, which writes functions as
|
|
|
808
|
|
|
809 @example
|
|
|
810 func(@var{arg1}, @var{arg2}, ...)
|
|
|
811 @end example
|
|
|
812
|
|
|
813 but writes expressions involving operators as (e.g.)
|
|
|
814
|
|
|
815 @example
|
|
|
816 @var{arg1} + @var{arg2}
|
|
|
817 @end example
|
|
|
818
|
|
|
819 and writes control statements as (e.g.)
|
|
|
820
|
|
|
821 @example
|
|
|
822 while (@var{expr}) @{ @var{statement1}; @var{statement2}; ... @}
|
|
|
823 @end example
|
|
|
824
|
|
|
825 Lisp equivalents of the latter two would be
|
|
|
826
|
|
|
827 @example
|
|
|
828 (+ @var{arg1} @var{arg2} ...)
|
|
|
829 @end example
|
|
|
830
|
|
|
831 and
|
|
|
832
|
|
|
833 @example
|
|
|
834 (while @var{expr} @var{statement1} @var{statement2} ...)
|
|
|
835 @end example
|
|
|
836
|
|
|
837 @item
|
|
|
838 Lisp is a safe language. Assuming there are no bugs in the Lisp
|
|
|
839 interpreter/compiler, it is impossible to write a program that ``core
|
|
|
840 dumps'' or otherwise causes the machine to execute an illegal
|
|
|
841 instruction. This is very different from C, where perhaps the most
|
|
|
842 common outcome of a bug is exactly such a crash. A corollary of this is that
|
|
|
843 the C operation of casting a pointer is impossible (and unnecessary) in
|
|
|
844 Lisp, and that it is impossible to access memory outside the bounds of
|
|
|
845 an array.
|
|
|
846
|
|
|
847 @item
|
|
|
848 Programs and data are written in the same form. The
|
|
|
849 parenthesis-enclosing form described above for statements is the same
|
|
|
850 form used for the most common data type in Lisp, the list. Thus, it is
|
|
|
851 possible to represent any Lisp program using Lisp data types, and for
|
|
|
852 one program to construct Lisp statements and then dynamically
|
|
|
853 @dfn{evaluate} them, or cause them to execute.
|
|
|
854
|
|
|
855 @item
|
|
|
856 All objects are @dfn{dynamically typed}. This means that part of every
|
|
|
857 object is an indication of what type it is. A Lisp program can
|
|
|
858 manipulate an object without knowing what type it is, and can query an
|
|
|
859 object to determine its type. This means that, correspondingly,
|
|
|
860 variables and function parameters can hold objects of any type and are
|
|
|
861 not normally declared as being of any particular type. This is opposed
|
|
|
862 to the @dfn{static typing} of C, where variables can hold exactly one
|
|
|
863 type of object and must be declared as such, and objects do not contain
|
|
|
864 an indication of their type because it's implicit in the variables they
|
|
|
865 are stored in. It is possible in C to have a variable hold different
|
|
|
866 types of objects (e.g. through the use of @code{void *} pointers or
|
|
|
867 variable-argument functions), but the type information must then be
|
|
|
868 passed explicitly in some other fashion, leading to additional program
|
|
|
869 complexity.
|
|
|
870
|
|
|
871 @item
|
|
|
872 Allocated memory is automatically reclaimed when it is no longer in use.
|
|
|
873 This operation is called @dfn{garbage collection} and involves looking
|
|
|
874 through all variables to see what memory is being pointed to, and
|
|
|
875 reclaiming any memory that is not pointed to and is thus
|
|
|
876 ``inaccessible'' and out of use. This is as opposed to C, in which
|
|
|
877 allocated memory must be explicitly reclaimed using @code{free()}. If
|
|
|
878 you simply drop all pointers to memory without freeing it, it becomes
|
|
|
879 ``leaked'' memory that still takes up space. Over a long period of
|
|
|
880 time, this can cause your program to grow and grow until it runs out of
|
|
|
881 memory.
|
|
|
882
|
|
|
883 @item
|
|
|
884 Lisp has built-in facilities for handling errors and exceptions. In C,
|
|
|
885 when an error occurs, usually either the program exits entirely or the
|
|
|
886 routine in which the error occurs returns a value indicating this. If
|
|
|
887 an error occurs in a deeply-nested routine, then every routine currently
|
|
|
888 called must unwind itself normally and return an error value back up to
|
|
|
889 the next routine. This means that every routine must explicitly check
|
|
|
890 for an error in all the routines it calls; if it does not do so,
|
|
|
891 unexpected and often random behavior results. This is an extremely
|
|
|
892 common source of bugs in C programs. An alternative would be to do a
|
|
|
893 non-local exit using @code{longjmp()}, but that is often very dangerous
|
|
|
894 because the routines that were exited past had no opportunity to clean
|
|
|
895 up after themselves and may leave things in an inconsistent state,
|
|
|
896 causing a crash shortly afterwards.
|
|
|
897
|
|
|
898 Lisp provides mechanisms to make such non-local exits safe. When an
|
|
|
899 error occurs, a routine simply signals that an error of a particular
|
|
|
900 class has occurred, and a non-local exit takes place. Any routine can
|
|
|
901 trap errors occurring in routines it calls by registering an error
|
|
|
902 handler for some or all classes of errors. (If no handler is registered,
|
|
|
903 a default handler, generally installed by the top-level event loop, is
|
|
|
904 executed; this prints out the error and continues.) Routines can also
|
|
|
905 specify cleanup code (called an @dfn{unwind-protect}) that will be
|
|
|
906 called when control exits from a block of code, no matter how that exit
|
|
398
|
907 occurs---i.e. even if a function deeply nested below it causes a
|
|
0
|
908 non-local exit back to the top level.
|
|
|
909
|
|
|
910 Note that this facility has appeared in some recent vintages of C, in
|
|
|
911 particular Visual C++ and other PC compilers written for the Microsoft
|
|
|
912 Win32 API.
|
|
|
913
|
|
|
914 @item
|
|
|
915 In Emacs Lisp, local variables are @dfn{dynamically scoped}. This means
|
|
|
916 that if you declare a local variable in a particular function, and then
|
|
|
917 call another function, that subfunction can ``see'' the local variable
|
|
|
918 you declared. This is actually considered a bug in Emacs Lisp and in
|
|
|
919 all other early dialects of Lisp, and was corrected in Common Lisp. (In
|
|
|
920 Common Lisp, you can still declare dynamically scoped variables if you
|
|
398
|
921 want to---they are sometimes useful---but variables by default are
|
|
0
|
922 @dfn{lexically scoped} as in C.)
|
|
|
923 @end enumerate
|
|
|
924
|
|
|
925 For those familiar with Lisp, Emacs Lisp is modelled after MacLisp, an
|
|
|
926 early dialect of Lisp developed at MIT (no relation to the Macintosh
|
|
|
927 computer). There is a Common Lisp compatibility package available for
|
|
|
928 Emacs that provides many of the features of Common Lisp.
|
|
|
929
|
|
|
930 The Java language is derived in many ways from C, and shares a similar
|
|
|
931 syntax, but has the following features in common with Lisp (and different
|
|
|
932 from C):
|
|
|
933
|
|
|
934 @enumerate
|
|
|
935 @item
|
|
|
936 Java is a safe language, like Lisp.
|
|
|
937 @item
|
|
|
938 Java provides garbage collection, like Lisp.
|
|
|
939 @item
|
|
|
940 Java has built-in facilities for handling errors and exceptions, like
|
|
|
941 Lisp.
|
|
|
942 @item
|
|
|
943 Java has a type system that combines the best advantages of both static
|
|
|
944 and dynamic typing. Objects (except very simple types) are explicitly
|
|
|
945 marked with their type, as in dynamic typing; but there is a hierarchy
|
|
|
946 of types and functions are declared to accept only certain types, thus
|
|
|
947 providing the increased compile-time error-checking of static typing.
|
|
|
948 @end enumerate
|
|
|
949
|
|
380
|
950 The Java language also has some negative attributes:
|
|
|
951
|
|
|
952 @enumerate
|
|
|
953 @item
|
|
|
954 Java uses the edit/compile/run model of software development. This
|
|
|
955 makes it hard to use interactively. For example, to use Java like
|
|
|
956 @code{bc} it is necessary to write a special purpose, albeit tiny,
|
|
|
957 application. In Emacs Lisp, a calculator comes built-in without any
|
|
|
958 effort - one can always just type an expression in the @code{*scratch*}
|
|
|
959 buffer.
|
|
|
960 @item
|
|
|
961 Java tries too hard to enforce, not merely enable, portability, making
|
|
|
962 ordinary access to standard OS facilities painful. Java has an
|
|
|
963 @dfn{agenda}. I think this is why @code{chdir} is not part of standard
|
|
|
964 Java, which is inexcusable.
|
|
|
965 @end enumerate
|
|
|
966
|
|
|
967 Unfortunately, there is no perfect language. Static typing allows a
|
|
|
968 compiler to catch programmer errors and produce more efficient code, but
|
|
|
969 makes programming more tedious and less fun. For the forseeable future,
|
|
|
970 an Ideal Editing and Programming Environment (and that is what XEmacs
|
|
|
971 aspires to) will be programmable in multiple languages: high level ones
|
|
|
972 like Lisp for user customization and prototyping, and lower level ones
|
|
|
973 for infrastructure and industrial strength applications. If I had my
|
|
|
974 way, XEmacs would be friendly towards the Python, Scheme, C++, ML,
|
|
|
975 etc... communities. But there are serious technical difficulties to
|
|
|
976 achieving that goal.
|
|
|
977
|
|
|
978 The word @dfn{application} in the previous paragraph was used
|
|
|
979 intentionally. XEmacs implements an API for programs written in Lisp
|
|
|
980 that makes it a full-fledged application platform, very much like an OS
|
|
|
981 inside the real OS.
|
|
|
982
|
|
0
|
983 @node XEmacs From the Perspective of Building, XEmacs From the Inside, The Lisp Language, Top
|
|
|
984 @chapter XEmacs From the Perspective of Building
|
|
|
985
|
|
380
|
986 The heart of XEmacs is the Lisp environment, which is written in C.
|
|
0
|
987 This is contained in the @file{src/} subdirectory. Underneath
|
|
|
988 @file{src/} are two subdirectories of header files: @file{s/} (header
|
|
|
989 files for particular operating systems) and @file{m/} (header files for
|
|
|
990 particular machine types). In practice the distinction between the two
|
|
|
991 types of header files is blurred. These header files define or undefine
|
|
|
992 certain preprocessor constants and macros to indicate particular
|
|
|
993 characteristics of the associated machine or operating system. As part
|
|
|
994 of the configure process, one @file{s/} file and one @file{m/} file is
|
|
|
995 identified for the particular environment in which XEmacs is being
|
|
|
996 built.
|
|
|
997
|
|
380
|
998 XEmacs also contains a great deal of Lisp code. This implements the
|
|
|
999 operations that make XEmacs useful as an editor as well as just a Lisp
|
|
|
1000 environment, and also contains many add-on packages that allow XEmacs to
|
|
|
1001 browse directories, act as a mail and Usenet news reader, compile Lisp
|
|
|
1002 code, etc. There is actually more Lisp code than C code associated with
|
|
|
1003 XEmacs, but much of the Lisp code is peripheral to the actual operation
|
|
|
1004 of the editor. The Lisp code all lies in subdirectories underneath the
|
|
|
1005 @file{lisp/} directory.
|
|
|
1006
|
|
|
1007 The @file{lwlib/} directory contains C code that implements a
|
|
0
|
1008 generalized interface onto different X widget toolkits and also
|
|
|
1009 implements some widgets of its own that behave like Motif widgets but
|
|
|
1010 are faster, free, and in some cases more powerful. The code in this
|
|
|
1011 directory compiles into a library and is mostly independent from XEmacs.
|
|
|
1012
|
|
380
|
1013 The @file{etc/} directory contains various data files associated with
|
|
0
|
1014 XEmacs. Some of them are actually read by XEmacs at startup; others
|
|
|
1015 merely contain useful information of various sorts.
|
|
|
1016
|
|
380
|
1017 The @file{lib-src/} directory contains C code for various auxiliary
|
|
0
|
1018 programs that are used in connection with XEmacs. Some of them are used
|
|
|
1019 during the build process; others are used to perform certain functions
|
|
|
1020 that cannot conveniently be placed in the XEmacs executable (e.g. the
|
|
116
|
1021 @file{movemail} program for fetching mail out of @file{/var/spool/mail},
|
|
|
1022 which must be setgid to @file{mail} on many systems; and the
|
|
|
1023 @file{gnuclient} program, which allows an external script to communicate
|
|
|
1024 with a running XEmacs process).
|
|
0
|
1025
|
|
380
|
1026 The @file{man/} directory contains the sources for the XEmacs
|
|
0
|
1027 documentation. It is mostly in a form called Texinfo, which can be
|
|
116
|
1028 converted into either a printed document (by passing it through @TeX{})
|
|
|
1029 or into on-line documentation called @dfn{info files}.
|
|
0
|
1030
|
|
380
|
1031 The @file{info/} directory contains the results of formatting the XEmacs
|
|
|
1032 documentation as @dfn{info files}, for on-line use. These files are
|
|
|
1033 used when you enter the Info system using @kbd{C-h i} or through the
|
|
0
|
1034 Help menu.
|
|
|
1035
|
|
380
|
1036 The @file{dynodump/} directory contains auxiliary code used to build
|
|
0
|
1037 XEmacs on Solaris platforms.
|
|
|
1038
|
|
380
|
1039 The other directories contain various miscellaneous code and information
|
|
|
1040 that is not normally used or needed.
|
|
|
1041
|
|
|
1042 The first step of building involves running the @file{configure} program
|
|
|
1043 and passing it various parameters to specify any optional features you
|
|
|
1044 want and compiler arguments and such, as described in the @file{INSTALL}
|
|
|
1045 file. This determines what the build environment is, chooses the
|
|
|
1046 appropriate @file{s/} and @file{m/} file, and runs a series of tests to
|
|
|
1047 determine many details about your environment, such as which library
|
|
|
1048 functions are available and exactly how they work. The reason for
|
|
|
1049 running these tests is that it allows XEmacs to be compiled on a much
|
|
|
1050 wider variety of platforms than those that the XEmacs developers happen
|
|
|
1051 to be familiar with, including various sorts of hybrid platforms. This
|
|
|
1052 is especially important now that many operating systems give you a great
|
|
|
1053 deal of control over exactly what features you want installed, and allow
|
|
|
1054 for easy upgrading of parts of a system without upgrading the rest. It
|
|
0
|
1055 would be impossible to pre-determine and pre-specify the information for
|
|
|
1056 all possible configurations.
|
|
|
1057
|
|
380
|
1058 In fact, the @file{s/} and @file{m/} files are basically @emph{evil},
|
|
|
1059 since they contain unmaintainable platform-specific hard-coded
|
|
|
1060 information. XEmacs has been moving in the direction of having all
|
|
|
1061 system-specific information be determined dynamically by
|
|
|
1062 @file{configure}. Perhaps someday we can @code{rm -rf src/s src/m}.
|
|
|
1063
|
|
|
1064 When configure is done running, it generates @file{Makefile}s and
|
|
|
1065 @file{GNUmakefile}s and the file @file{src/config.h} (which describes
|
|
|
1066 the features of your system) from template files. You then run
|
|
|
1067 @file{make}, which compiles the auxiliary code and programs in
|
|
|
1068 @file{lib-src/} and @file{lwlib/} and the main XEmacs executable in
|
|
|
1069 @file{src/}. The result of compiling and linking is an executable
|
|
|
1070 called @file{temacs}, which is @emph{not} the final XEmacs executable.
|
|
|
1071 @file{temacs} by itself is not intended to function as an editor or even
|
|
|
1072 display any windows on the screen, and if you simply run it, it will
|
|
|
1073 exit immediately. The @file{Makefile} runs @file{temacs} with certain
|
|
|
1074 options that cause it to initialize itself, read in a number of basic
|
|
|
1075 Lisp files, and then dump itself out into a new executable called
|
|
|
1076 @file{xemacs}. This new executable has been pre-initialized and
|
|
|
1077 contains pre-digested Lisp code that is necessary for the editor to
|
|
|
1078 function (this includes most basic editing functions,
|
|
|
1079 e.g. @code{kill-line}, that can be defined in terms of other Lisp
|
|
|
1080 primitives; some initialization code that is called when certain
|
|
|
1081 objects, such as frames, are created; and all of the standard
|
|
|
1082 keybindings and code for the actions they result in). This executable,
|
|
|
1083 @file{xemacs}, is the executable that you run to use the XEmacs editor.
|
|
272
|
1084
|
|
|
1085 Although @file{temacs} is not intended to be run as an editor, it can,
|
|
|
1086 by using the incantation @code{temacs -batch -l loadup.el run-temacs}.
|
|
|
1087 This is useful when the dumping procedure described above is broken, or
|
|
|
1088 when using certain program debugging tools such as Purify. These tools
|
|
|
1089 get mighty confused by the tricks played by the XEmacs build process,
|
|
|
1090 such as allocation memory in one process, and freeing it in the next.
|
|
0
|
1091
|
|
|
1092 @node XEmacs From the Inside, The XEmacs Object System (Abstractly Speaking), XEmacs From the Perspective of Building, Top
|
|
|
1093 @chapter XEmacs From the Inside
|
|
|
1094
|
|
380
|
1095 Internally, XEmacs is quite complex, and can be very confusing. To
|
|
0
|
1096 simplify things, it can be useful to think of XEmacs as containing an
|
|
|
1097 event loop that ``drives'' everything, and a number of other subsystems,
|
|
116
|
1098 such as a Lisp engine and a redisplay mechanism. Each of these other
|
|
0
|
1099 subsystems exists simultaneously in XEmacs, and each has a certain
|
|
|
1100 state. The flow of control continually passes in and out of these
|
|
|
1101 different subsystems in the course of normal operation of the editor.
|
|
|
1102
|
|
380
|
1103 It is important to keep in mind that, most of the time, the editor is
|
|
0
|
1104 ``driven'' by the event loop. Except during initialization and batch
|
|
|
1105 mode, all subsystems are entered directly or indirectly through the
|
|
|
1106 event loop, and ultimately, control exits out of all subsystems back up
|
|
|
1107 to the event loop. This cycle of entering a subsystem, exiting back out
|
|
|
1108 to the event loop, and starting another iteration of the event loop
|
|
|
1109 occurs once each keystroke, mouse motion, etc.
|
|
|
1110
|
|
380
|
1111 If you're trying to understand a particular subsystem (other than the
|
|
0
|
1112 event loop), think of it as a ``daemon'' process or ``servant'' that is
|
|
|
1113 responsible for one particular aspect of a larger system, and
|
|
|
1114 periodically receives commands or environment changes that cause it to
|
|
|
1115 do something. Ultimately, these commands and environment changes are
|
|
|
1116 always triggered by the event loop. For example:
|
|
|
1117
|
|
|
1118 @itemize @bullet
|
|
|
1119 @item
|
|
|
1120 The window and frame mechanism is responsible for keeping track of what
|
|
|
1121 windows and frames exist, what buffers are in them, etc. It is
|
|
|
1122 periodically given commands (usually from the user) to make a change to
|
|
|
1123 the current window/frame state: i.e. create a new frame, delete a
|
|
|
1124 window, etc.
|
|
|
1125
|
|
|
1126 @item
|
|
|
1127 The buffer mechanism is responsible for keeping track of what buffers
|
|
|
1128 exist and what text is in them. It is periodically given commands
|
|
|
1129 (usually from the user) to insert or delete text, create a buffer, etc.
|
|
116
|
1130 When it receives a text-change command, it notifies the redisplay
|
|
|
1131 mechanism.
|
|
0
|
1132
|
|
|
1133 @item
|
|
|
1134 The redisplay mechanism is responsible for making sure that windows and
|
|
|
1135 frames are displayed correctly. It is periodically told (by the event
|
|
|
1136 loop) to actually ``do its job'', i.e. snoop around and see what the
|
|
|
1137 current state of the environment (mostly of the currently-existing
|
|
|
1138 windows, frames, and buffers) is, and make sure that that state matches
|
|
|
1139 what's actually displayed. It keeps lots and lots of information around
|
|
|
1140 (such as what is actually being displayed currently, and what the
|
|
|
1141 environment was last time it checked) so that it can minimize the work
|
|
|
1142 it has to do. It is also helped along in that whenever a relevant
|
|
|
1143 change to the environment occurs, the redisplay mechanism is told about
|
|
|
1144 this, so it has a pretty good idea of where it has to look to find
|
|
|
1145 possible changes and doesn't have to look everywhere.
|
|
|
1146
|
|
|
1147 @item
|
|
|
1148 The Lisp engine is responsible for executing the Lisp code in which most
|
|
|
1149 user commands are written. It is entered through a call to @code{eval}
|
|
|
1150 or @code{funcall}, which occurs as a result of dispatching an event from
|
|
|
1151 the event loop. The functions it calls issue commands to the buffer
|
|
|
1152 mechanism, the window/frame subsystem, etc.
|
|
|
1153
|
|
|
1154 @item
|
|
|
1155 The Lisp allocation subsystem is responsible for keeping track of Lisp
|
|
|
1156 objects. It is given commands from the Lisp engine to allocate objects,
|
|
|
1157 garbage collect, etc.
|
|
|
1158 @end itemize
|
|
|
1159
|
|
|
1160 etc.
|
|
|
1161
|
|
|
1162 The important idea here is that there are a number of independent
|
|
2
|
1163 subsystems each with its own responsibility and persistent state, just
|
|
0
|
1164 like different employees in a company, and each subsystem is
|
|
|
1165 periodically given commands from other subsystems. Commands can flow
|
|
|
1166 from any one subsystem to any other, but there is usually some sort of
|
|
|
1167 hierarchy, with all commands originating from the event subsystem.
|
|
|
1168
|
|
|
1169 XEmacs is entered in @code{main()}, which is in @file{emacs.c}. When
|
|
|
1170 this is called the first time (in a properly-invoked @file{temacs}), it
|
|
|
1171 does the following:
|
|
|
1172
|
|
|
1173 @enumerate
|
|
|
1174 @item
|
|
|
1175 It does some very basic environment initializations, such as determining
|
|
|
1176 where it and its directories (e.g. @file{lisp/} and @file{etc/}) reside
|
|
|
1177 and setting up signal handlers.
|
|
|
1178 @item
|
|
|
1179 It initializes the entire Lisp interpreter.
|
|
|
1180 @item
|
|
|
1181 It sets the initial values of many built-in variables (including many
|
|
|
1182 variables that are visible to Lisp programs), such as the global keymap
|
|
|
1183 object and the built-in faces (a face is an object that describes the
|
|
|
1184 display characteristics of text). This involves creating Lisp objects
|
|
|
1185 and thus is dependent on step (2).
|
|
|
1186 @item
|
|
|
1187 It performs various other initializations that are relevant to the
|
|
|
1188 particular environment it is running in, such as retrieving environment
|
|
|
1189 variables, determining the current date and the user who is running the
|
|
|
1190 program, examining its standard input, creating any necessary file
|
|
|
1191 descriptors, etc.
|
|
|
1192 @item
|
|
|
1193 At this point, the C initialization is complete. A Lisp program that
|
|
|
1194 was specified on the command line (usually @file{loadup.el}) is called
|
|
|
1195 (temacs is normally invoked as @code{temacs -batch -l loadup.el dump}).
|
|
|
1196 @file{loadup.el} loads all of the other Lisp files that are needed for
|
|
|
1197 the operation of the editor, calls the @code{dump-emacs} function to
|
|
|
1198 write out @file{xemacs}, and then kills the temacs process.
|
|
|
1199 @end enumerate
|
|
|
1200
|
|
|
1201 When @file{xemacs} is then run, it only redoes steps (1) and (4)
|
|
|
1202 above; all variables already contain the values they were set to when
|
|
|
1203 the executable was dumped, and all memory that was allocated with
|
|
|
1204 @code{malloc()} is still around. (XEmacs knows whether it is being run
|
|
|
1205 as @file{xemacs} or @file{temacs} because it sets the global variable
|
|
|
1206 @code{initialized} to 1 after step (4) above.) At this point,
|
|
|
1207 @file{xemacs} calls a Lisp function to do any further initialization,
|
|
|
1208 which includes parsing the command-line (the C code can only do limited
|
|
|
1209 command-line parsing, which includes looking for the @samp{-batch} and
|
|
|
1210 @samp{-l} flags and a few other flags that it needs to know about before
|
|
|
1211 initialization is complete), creating the first frame (or @dfn{window}
|
|
|
1212 in standard window-system parlance), running the user's init file
|
|
|
1213 (usually the file @file{.emacs} in the user's home directory), etc. The
|
|
|
1214 function to do this is usually called @code{normal-top-level};
|
|
|
1215 @file{loadup.el} tells the C code about this function by setting its
|
|
|
1216 name as the value of the Lisp variable @code{top-level}.
|
|
|
1217
|
|
|
1218 When the Lisp initialization code is done, the C code enters the event
|
|
|
1219 loop, and stays there for the duration of the XEmacs process. The code
|
|
|
1220 for the event loop is contained in @file{keyboard.c}, and is called
|
|
|
1221 @code{Fcommand_loop_1()}. Note that this event loop could very well be
|
|
|
1222 written in Lisp, and in fact a Lisp version exists; but apparently,
|
|
|
1223 doing this makes XEmacs run noticeably slower.
|
|
|
1224
|
|
|
1225 Notice how much of the initialization is done in Lisp, not in C.
|
|
|
1226 In general, XEmacs tries to move as much code as is possible
|
|
|
1227 into Lisp. Code that remains in C is code that implements the
|
|
|
1228 Lisp interpreter itself, or code that needs to be very fast, or
|
|
|
1229 code that needs to do system calls or other such stuff that
|
|
|
1230 needs to be done in C, or code that needs to have access to
|
|
|
1231 ``forbidden'' structures. (One conscious aspect of the design of
|
|
|
1232 Lisp under XEmacs is a clean separation between the external
|
|
|
1233 interface to a Lisp object's functionality and its internal
|
|
|
1234 implementation. Part of this design is that Lisp programs
|
|
|
1235 are forbidden from accessing the contents of the object other
|
|
|
1236 than through using a standard API. In this respect, XEmacs Lisp
|
|
|
1237 is similar to modern Lisp dialects but differs from GNU Emacs,
|
|
|
1238 which tends to expose the implementation and allow Lisp
|
|
|
1239 programs to look at it directly. The major advantage of
|
|
|
1240 hiding the implementation is that it allows the implementation
|
|
|
1241 to be redesigned without affecting any Lisp programs, including
|
|
|
1242 those that might want to be ``clever'' by looking directly at
|
|
|
1243 the object's contents and possibly manipulating them.)
|
|
|
1244
|
|
|
1245 Moving code into Lisp makes the code easier to debug and maintain and
|
|
|
1246 makes it much easier for people who are not XEmacs developers to
|
|
|
1247 customize XEmacs, because they can make a change with much less chance
|
|
|
1248 of obscure and unwanted interactions occurring than if they were to
|
|
|
1249 change the C code.
|
|
|
1250
|
|
|
1251 @node The XEmacs Object System (Abstractly Speaking), How Lisp Objects Are Represented in C, XEmacs From the Inside, Top
|
|
|
1252 @chapter The XEmacs Object System (Abstractly Speaking)
|
|
|
1253
|
|
|
1254 At the heart of the Lisp interpreter is its management of objects.
|
|
|
1255 XEmacs Lisp contains many built-in objects, some of which are
|
|
|
1256 simple and others of which can be very complex; and some of which
|
|
|
1257 are very common, and others of which are rarely used or are only
|
|
|
1258 used internally. (Since the Lisp allocation system, with its
|
|
|
1259 automatic reclamation of unused storage, is so much more convenient
|
|
|
1260 than @code{malloc()} and @code{free()}, the C code makes extensive use of it
|
|
|
1261 in its internal operations.)
|
|
|
1262
|
|
|
1263 The basic Lisp objects are
|
|
|
1264
|
|
|
1265 @table @code
|
|
|
1266 @item integer
|
|
380
|
1267 28 or 31 bits of precision, or 60 or 63 bits on 64-bit machines; the
|
|
|
1268 reason for this is described below when the internal Lisp object
|
|
|
1269 representation is described.
|
|
0
|
1270 @item float
|
|
|
1271 Same precision as a double in C.
|
|
|
1272 @item cons
|
|
|
1273 A simple container for two Lisp objects, used to implement lists and
|
|
|
1274 most other data structures in Lisp.
|
|
|
1275 @item char
|
|
|
1276 An object representing a single character of text; chars behave like
|
|
|
1277 integers in many ways but are logically considered text rather than
|
|
|
1278 numbers and have a different read syntax. (the read syntax for a char
|
|
398
|
1279 contains the char itself or some textual encoding of it---for example,
|
|
0
|
1280 a Japanese Kanji character might be encoded as @samp{^[$(B#&^[(B} using the
|
|
398
|
1281 ISO-2022 encoding standard---rather than the numerical representation
|
|
0
|
1282 of the char; this way, if the mapping between chars and integers
|
|
|
1283 changes, which is quite possible for Kanji characters and other extended
|
|
|
1284 characters, the same character will still be created. Note that some
|
|
|
1285 primitives confuse chars and integers. The worst culprit is @code{eq},
|
|
|
1286 which makes a special exception and considers a char to be @code{eq} to
|
|
|
1287 its integer equivalent, even though in no other case are objects of two
|
|
|
1288 different types @code{eq}. The reason for this monstrosity is
|
|
|
1289 compatibility with existing code; the separation of char from integer
|
|
|
1290 came fairly recently.)
|
|
|
1291 @item symbol
|
|
|
1292 An object that contains Lisp objects and is referred to by name;
|
|
|
1293 symbols are used to implement variables and named functions
|
|
|
1294 and to provide the equivalent of preprocessor constants in C.
|
|
|
1295 @item vector
|
|
|
1296 A one-dimensional array of Lisp objects providing constant-time access
|
|
|
1297 to any of the objects; access to an arbitrary object in a vector is
|
|
|
1298 faster than for lists, but the operations that can be done on a vector
|
|
|
1299 are more limited.
|
|
|
1300 @item string
|
|
|
1301 Self-explanatory; behaves much like a vector of chars
|
|
|
1302 but has a different read syntax and is stored and manipulated
|
|
380
|
1303 more compactly.
|
|
0
|
1304 @item bit-vector
|
|
|
1305 A vector of bits; similar to a string in spirit.
|
|
|
1306 @item compiled-function
|
|
380
|
1307 An object containing compiled Lisp code, known as @dfn{byte code}.
|
|
0
|
1308 @item subr
|
|
380
|
1309 A Lisp primitive, i.e. a Lisp-callable function implemented in C.
|
|
0
|
1310 @end table
|
|
|
1311
|
|
|
1312 @cindex closure
|
|
380
|
1313 Note that there is no basic ``function'' type, as in more powerful
|
|
0
|
1314 versions of Lisp (where it's called a @dfn{closure}). XEmacs Lisp does
|
|
|
1315 not provide the closure semantics implemented by Common Lisp and Scheme.
|
|
|
1316 The guts of a function in XEmacs Lisp are represented in one of four
|
|
|
1317 ways: a symbol specifying another function (when one function is an
|
|
380
|
1318 alias for another), a list (whose first element must be the symbol
|
|
|
1319 @code{lambda}) containing the function's source code, a
|
|
|
1320 compiled-function object, or a subr object. (In other words, given a
|
|
|
1321 symbol specifying the name of a function, calling @code{symbol-function}
|
|
|
1322 to retrieve the contents of the symbol's function cell will return one
|
|
|
1323 of these types of objects.)
|
|
|
1324
|
|
|
1325 XEmacs Lisp also contains numerous specialized objects used to implement
|
|
|
1326 the editor:
|
|
0
|
1327
|
|
116
|
1328 @table @code
|
|
0
|
1329 @item buffer
|
|
|
1330 Stores text like a string, but is optimized for insertion and deletion
|
|
|
1331 and has certain other properties that can be set.
|
|
|
1332 @item frame
|
|
|
1333 An object with various properties whose displayable representation is a
|
|
|
1334 @dfn{window} in window-system parlance.
|
|
|
1335 @item window
|
|
|
1336 A section of a frame that displays the contents of a buffer;
|
|
|
1337 often called a @dfn{pane} in window-system parlance.
|
|
|
1338 @item window-configuration
|
|
|
1339 An object that represents a saved configuration of windows in a frame.
|
|
|
1340 @item device
|
|
|
1341 An object representing a screen on which frames can be displayed;
|
|
|
1342 equivalent to a @dfn{display} in the X Window System and a @dfn{TTY} in
|
|
|
1343 character mode.
|
|
|
1344 @item face
|
|
380
|
1345 An object specifying the appearance of text or graphics; it has
|
|
|
1346 properties such as font, foreground color, and background color.
|
|
0
|
1347 @item marker
|
|
|
1348 An object that refers to a particular position in a buffer and moves
|
|
|
1349 around as text is inserted and deleted to stay in the same relative
|
|
|
1350 position to the text around it.
|
|
|
1351 @item extent
|
|
|
1352 Similar to a marker but covers a range of text in a buffer; can also
|
|
|
1353 specify properties of the text, such as a face in which the text is to
|
|
|
1354 be displayed, whether the text is invisible or unmodifiable, etc.
|
|
|
1355 @item event
|
|
|
1356 Generated by calling @code{next-event} and contains information
|
|
|
1357 describing a particular event happening in the system, such as the user
|
|
|
1358 pressing a key or a process terminating.
|
|
|
1359 @item keymap
|
|
|
1360 An object that maps from events (described using lists, vectors, and
|
|
|
1361 symbols rather than with an event object because the mapping is for
|
|
|
1362 classes of events, rather than individual events) to functions to
|
|
|
1363 execute or other events to recursively look up; the functions are
|
|
|
1364 described by name, using a symbol, or using lists to specify the
|
|
|
1365 function's code.
|
|
|
1366 @item glyph
|
|
|
1367 An object that describes the appearance of an image (e.g. pixmap) on
|
|
|
1368 the screen; glyphs can be attached to the beginning or end of extents
|
|
|
1369 and in some future version of XEmacs will be able to be inserted
|
|
|
1370 directly into a buffer.
|
|
|
1371 @item process
|
|
|
1372 An object that describes a connection to an externally-running process.
|
|
|
1373 @end table
|
|
|
1374
|
|
|
1375 There are some other, less-commonly-encountered general objects:
|
|
|
1376
|
|
116
|
1377 @table @code
|
|
380
|
1378 @item hash-table
|
|
0
|
1379 An object that maps from an arbitrary Lisp object to another arbitrary
|
|
|
1380 Lisp object, using hashing for fast lookup.
|
|
|
1381 @item obarray
|
|
380
|
1382 A limited form of hash-table that maps from strings to symbols; obarrays
|
|
0
|
1383 are used to look up a symbol given its name and are not actually their
|
|
|
1384 own object type but are kludgily represented using vectors with hidden
|
|
|
1385 fields (this representation derives from GNU Emacs).
|
|
|
1386 @item specifier
|
|
|
1387 A complex object used to specify the value of a display property; a
|
|
|
1388 default value is given and different values can be specified for
|
|
|
1389 particular frames, buffers, windows, devices, or classes of device.
|
|
|
1390 @item char-table
|
|
|
1391 An object that maps from chars or classes of chars to arbitrary Lisp
|
|
|
1392 objects; internally char tables use a complex nested-vector
|
|
|
1393 representation that is optimized to the way characters are represented
|
|
|
1394 as integers.
|
|
|
1395 @item range-table
|
|
|
1396 An object that maps from ranges of integers to arbitrary Lisp objects.
|
|
|
1397 @end table
|
|
|
1398
|
|
|
1399 And some strange special-purpose objects:
|
|
|
1400
|
|
116
|
1401 @table @code
|
|
0
|
1402 @item charset
|
|
|
1403 @itemx coding-system
|
|
|
1404 Objects used when MULE, or multi-lingual/Asian-language, support is
|
|
|
1405 enabled.
|
|
|
1406 @item color-instance
|
|
|
1407 @itemx font-instance
|
|
|
1408 @itemx image-instance
|
|
|
1409 An object that encapsulates a window-system resource; instances are
|
|
|
1410 mostly used internally but are exposed on the Lisp level for cleanness
|
|
|
1411 of the specifier model and because it's occasionally useful for Lisp
|
|
|
1412 program to create or query the properties of instances.
|
|
|
1413 @item subwindow
|
|
|
1414 An object that encapsulate a @dfn{subwindow} resource, i.e. a
|
|
|
1415 window-system child window that is drawn into by an external process;
|
|
|
1416 this object should be integrated into the glyph system but isn't yet,
|
|
|
1417 and may change form when this is done.
|
|
|
1418 @item tooltalk-message
|
|
|
1419 @itemx tooltalk-pattern
|
|
|
1420 Objects that represent resources used in the ToolTalk interprocess
|
|
|
1421 communication protocol.
|
|
|
1422 @item toolbar-button
|
|
|
1423 An object used in conjunction with the toolbar.
|
|
|
1424 @end table
|
|
|
1425
|
|
|
1426 And objects that are only used internally:
|
|
|
1427
|
|
380
|
1428 @table @code
|
|
0
|
1429 @item opaque
|
|
|
1430 A generic object for encapsulating arbitrary memory; this allows you the
|
|
|
1431 generality of @code{malloc()} and the convenience of the Lisp object
|
|
|
1432 system.
|
|
|
1433 @item lstream
|
|
|
1434 A buffering I/O stream, used to provide a unified interface to anything
|
|
|
1435 that can accept output or provide input, such as a file descriptor, a
|
|
|
1436 stdio stream, a chunk of memory, a Lisp buffer, a Lisp string, etc.;
|
|
|
1437 it's a Lisp object to make its memory management more convenient.
|
|
|
1438 @item char-table-entry
|
|
|
1439 Subsidiary objects in the internal char-table representation.
|
|
|
1440 @item extent-auxiliary
|
|
|
1441 @itemx menubar-data
|
|
|
1442 @itemx toolbar-data
|
|
|
1443 Various special-purpose objects that are basically just used to
|
|
|
1444 encapsulate memory for particular subsystems, similar to the more
|
|
|
1445 general ``opaque'' object.
|
|
|
1446 @item symbol-value-forward
|
|
|
1447 @itemx symbol-value-buffer-local
|
|
|
1448 @itemx symbol-value-varalias
|
|
|
1449 @itemx symbol-value-lisp-magic
|
|
|
1450 Special internal-only objects that are placed in the value cell of a
|
|
|
1451 symbol to indicate that there is something special with this variable --
|
|
|
1452 e.g. it has no value, it mirrors another variable, or it mirrors some C
|
|
|
1453 variable; there is really only one kind of object, called a
|
|
|
1454 @dfn{symbol-value-magic}, but it is sort-of halfway kludged into
|
|
|
1455 semi-different object types.
|
|
|
1456 @end table
|
|
|
1457
|
|
|
1458 @cindex permanent objects
|
|
|
1459 @cindex temporary objects
|
|
|
1460 Some types of objects are @dfn{permanent}, meaning that once created,
|
|
|
1461 they do not disappear until explicitly destroyed, using a function such
|
|
|
1462 as @code{delete-buffer}, @code{delete-window}, @code{delete-frame}, etc.
|
|
|
1463 Others will disappear once they are not longer used, through the garbage
|
|
|
1464 collection mechanism. Buffers, frames, windows, devices, and processes
|
|
|
1465 are among the objects that are permanent. Note that some objects can go
|
|
|
1466 both ways: Faces can be created either way; extents are normally
|
|
|
1467 permanent, but detached extents (extents not referring to any text, as
|
|
|
1468 happens to some extents when the text they are referring to is deleted)
|
|
|
1469 are temporary. Note that some permanent objects, such as faces and
|
|
|
1470 coding systems, cannot be deleted. Note also that windows are unique in
|
|
|
1471 that they can be @emph{undeleted} after having previously been
|
|
|
1472 deleted. (This happens as a result of restoring a window configuration.)
|
|
|
1473
|
|
|
1474 @cindex read syntax
|
|
|
1475 Note that many types of objects have a @dfn{read syntax}, i.e. a way of
|
|
|
1476 specifying an object of that type in Lisp code. When you load a Lisp
|
|
|
1477 file, or type in code to be evaluated, what really happens is that the
|
|
|
1478 function @code{read} is called, which reads some text and creates an object
|
|
|
1479 based on the syntax of that text; then @code{eval} is called, which
|
|
|
1480 possibly does something special; then this loop repeats until there's
|
|
|
1481 no more text to read. (@code{eval} only actually does something special
|
|
|
1482 with symbols, which causes the symbol's value to be returned,
|
|
|
1483 similar to referencing a variable; and with conses [i.e. lists],
|
|
|
1484 which cause a function invocation. All other values are returned
|
|
|
1485 unchanged.)
|
|
|
1486
|
|
|
1487 The read syntax
|
|
|
1488
|
|
|
1489 @example
|
|
|
1490 17297
|
|
|
1491 @end example
|
|
|
1492
|
|
|
1493 converts to an integer whose value is 17297.
|
|
|
1494
|
|
|
1495 @example
|
|
|
1496 1.983e-4
|
|
|
1497 @end example
|
|
|
1498
|
|
398
|
1499 converts to a float whose value is 1.983e-4, or .0001983.
|
|
0
|
1500
|
|
|
1501 @example
|
|
|
1502 ?b
|
|
|
1503 @end example
|
|
|
1504
|
|
|
1505 converts to a char that represents the lowercase letter b.
|
|
|
1506
|
|
|
1507 @example
|
|
|
1508 ?^[$(B#&^[(B
|
|
|
1509 @end example
|
|
|
1510
|
|
|
1511 (where @samp{^[} actually is an @samp{ESC} character) converts to a
|
|
116
|
1512 particular Kanji character when using an ISO2022-based coding system for
|
|
380
|
1513 input. (To decode this goo: @samp{ESC} begins an escape sequence;
|
|
116
|
1514 @samp{ESC $ (} is a class of escape sequences meaning ``switch to a
|
|
|
1515 94x94 character set''; @samp{ESC $ ( B} means ``switch to Japanese
|
|
|
1516 Kanji''; @samp{#} and @samp{&} collectively index into a 94-by-94 array
|
|
|
1517 of characters [subtract 33 from the ASCII value of each character to get
|
|
|
1518 the corresponding index]; @samp{ESC (} is a class of escape sequences
|
|
|
1519 meaning ``switch to a 94 character set''; @samp{ESC (B} means ``switch
|
|
|
1520 to US ASCII''. It is a coincidence that the letter @samp{B} is used to
|
|
|
1521 denote both Japanese Kanji and US ASCII. If the first @samp{B} were
|
|
|
1522 replaced with an @samp{A}, you'd be requesting a Chinese Hanzi character
|
|
|
1523 from the GB2312 character set.)
|
|
0
|
1524
|
|
|
1525 @example
|
|
|
1526 "foobar"
|
|
|
1527 @end example
|
|
|
1528
|
|
|
1529 converts to a string.
|
|
|
1530
|
|
|
1531 @example
|
|
|
1532 foobar
|
|
|
1533 @end example
|
|
|
1534
|
|
|
1535 converts to a symbol whose name is @code{"foobar"}. This is done by
|
|
|
1536 looking up the string equivalent in the global variable
|
|
|
1537 @code{obarray}, whose contents should be an obarray. If no symbol
|
|
|
1538 is found, a new symbol with the name @code{"foobar"} is automatically
|
|
272
|
1539 created and added to @code{obarray}; this process is called
|
|
380
|
1540 @dfn{interning} the symbol.
|
|
0
|
1541 @cindex interning
|
|
|
1542
|
|
|
1543 @example
|
|
|
1544 (foo . bar)
|
|
|
1545 @end example
|
|
|
1546
|
|
|
1547 converts to a cons cell containing the symbols @code{foo} and @code{bar}.
|
|
|
1548
|
|
|
1549 @example
|
|
|
1550 (1 a 2.5)
|
|
|
1551 @end example
|
|
|
1552
|
|
|
1553 converts to a three-element list containing the specified objects
|
|
|
1554 (note that a list is actually a set of nested conses; see the
|
|
|
1555 XEmacs Lisp Reference).
|
|
|
1556
|
|
|
1557 @example
|
|
|
1558 [1 a 2.5]
|
|
|
1559 @end example
|
|
|
1560
|
|
|
1561 converts to a three-element vector containing the specified objects.
|
|
|
1562
|
|
|
1563 @example
|
|
|
1564 #[... ... ... ...]
|
|
|
1565 @end example
|
|
|
1566
|
|
|
1567 converts to a compiled-function object (the actual contents are not
|
|
|
1568 shown since they are not relevant here; look at a file that ends with
|
|
|
1569 @file{.elc} for examples).
|
|
|
1570
|
|
|
1571 @example
|
|
|
1572 #*01110110
|
|
|
1573 @end example
|
|
|
1574
|
|
|
1575 converts to a bit-vector.
|
|
|
1576
|
|
|
1577 @example
|
|
380
|
1578 #s(hash-table ... ...)
|
|
|
1579 @end example
|
|
|
1580
|
|
|
1581 converts to a hash table (the actual contents are not shown).
|
|
|
1582
|
|
|
1583 @example
|
|
0
|
1584 #s(range-table ... ...)
|
|
|
1585 @end example
|
|
|
1586
|
|
|
1587 converts to a range table (the actual contents are not shown).
|
|
|
1588
|
|
|
1589 @example
|
|
|
1590 #s(char-table ... ...)
|
|
|
1591 @end example
|
|
|
1592
|
|
|
1593 converts to a char table (the actual contents are not shown).
|
|
380
|
1594
|
|
|
1595 Note that the @code{#s()} syntax is the general syntax for structures,
|
|
|
1596 which are not really implemented in XEmacs Lisp but should be.
|
|
|
1597
|
|
|
1598 When an object is printed out (using @code{print} or a related
|
|
0
|
1599 function), the read syntax is used, so that the same object can be read
|
|
|
1600 in again.
|
|
|
1601
|
|
380
|
1602 The other objects do not have read syntaxes, usually because it does not
|
|
|
1603 really make sense to create them in this fashion (i.e. processes, where
|
|
|
1604 it doesn't make sense to have a subprocess created as a side effect of
|
|
|
1605 reading some Lisp code), or because they can't be created at all
|
|
|
1606 (e.g. subrs). Permanent objects, as a rule, do not have a read syntax;
|
|
|
1607 nor do most complex objects, which contain too much state to be easily
|
|
|
1608 initialized through a read syntax.
|
|
0
|
1609
|
|
|
1610 @node How Lisp Objects Are Represented in C, Rules When Writing New C Code, The XEmacs Object System (Abstractly Speaking), Top
|
|
|
1611 @chapter How Lisp Objects Are Represented in C
|
|
|
1612
|
|
380
|
1613 Lisp objects are represented in C using a 32-bit or 64-bit machine word
|
|
0
|
1614 (depending on the processor; i.e. DEC Alphas use 64-bit Lisp objects and
|
|
|
1615 most other processors use 32-bit Lisp objects). The representation
|
|
|
1616 stuffs a pointer together with a tag, as follows:
|
|
|
1617
|
|
|
1618 @example
|
|
|
1619 [ 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 ]
|
|
|
1620 [ 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 ]
|
|
|
1621
|
|
380
|
1622 <---> ^ <------------------------------------------------------>
|
|
|
1623 tag | a pointer to a structure, or an integer
|
|
|
1624 |
|
|
|
1625 mark bit
|
|
|
1626 @end example
|
|
|
1627
|
|
|
1628 The tag describes the type of the Lisp object. For integers and chars,
|
|
|
1629 the lower 28 bits contain the value of the integer or char; for all
|
|
|
1630 others, the lower 28 bits contain a pointer. The mark bit is used
|
|
0
|
1631 during garbage-collection, and is always 0 when garbage collection is
|
|
380
|
1632 not happening. (The way that garbage collection works, basically, is that it
|
|
398
|
1633 loops over all places where Lisp objects could exist---this includes
|
|
0
|
1634 all global variables in C that contain Lisp objects [including
|
|
|
1635 @code{Vobarray}, the C equivalent of @code{obarray}; through this, all
|
|
398
|
1636 Lisp variables will get marked], plus various other places---and
|
|
0
|
1637 recursively scans through the Lisp objects, marking each object it finds
|
|
|
1638 by setting the mark bit. Then it goes through the lists of all objects
|
|
380
|
1639 allocated, freeing the ones that are not marked and turning off the mark
|
|
|
1640 bit of the ones that are marked.)
|
|
|
1641
|
|
|
1642 Lisp objects use the typedef @code{Lisp_Object}, but the actual C type
|
|
0
|
1643 used for the Lisp object can vary. It can be either a simple type
|
|
|
1644 (@code{long} on the DEC Alpha, @code{int} on other machines) or a
|
|
272
|
1645 structure whose fields are bit fields that line up properly (actually, a
|
|
380
|
1646 union of structures is used). Generally the simple integral type is
|
|
272
|
1647 preferable because it ensures that the compiler will actually use a
|
|
|
1648 machine word to represent the object (some compilers will use more
|
|
0
|
1649 general and less efficient code for unions and structs even if they can
|
|
|
1650 fit in a machine word). The union type, however, has the advantage of
|
|
|
1651 stricter type checking (if you accidentally pass an integer where a Lisp
|
|
|
1652 object is desired, you get a compile error), and it makes it easier to
|
|
|
1653 decode Lisp objects when debugging. The choice of which type to use is
|
|
380
|
1654 determined by the preprocessor constant @code{USE_UNION_TYPE} which is
|
|
|
1655 defined via the @code{--use-union-type} option to @code{configure}.
|
|
0
|
1656
|
|
|
1657 @cindex record type
|
|
380
|
1658
|
|
|
1659 Note that there are only eight types that the tag can represent, but
|
|
|
1660 many more actual types than this. This is handled by having one of the
|
|
|
1661 tag types specify a meta-type called a @dfn{record}; for all such
|
|
|
1662 objects, the first four bytes of the pointed-to structure indicate what
|
|
|
1663 the actual type is.
|
|
|
1664
|
|
|
1665 Note also that having 28 bits for pointers and integers restricts a lot
|
|
|
1666 of things to 256 megabytes of memory. (Basically, enough pointers and
|
|
|
1667 indices and whatnot get stuffed into Lisp objects that the total amount
|
|
|
1668 of memory used by XEmacs can't grow above 256 megabytes. In older
|
|
|
1669 versions of XEmacs and GNU Emacs, the tag was 5 bits wide, allowing for
|
|
|
1670 32 types, which was more than the actual number of types that existed at
|
|
|
1671 the time, and no ``record'' type was necessary. However, this limited
|
|
|
1672 the editor to 64 megabytes total, which some users who edited large
|
|
|
1673 files might conceivably exceed.)
|
|
|
1674
|
|
|
1675 Also, note that there is an implicit assumption here that all pointers
|
|
0
|
1676 are low enough that the top bits are all zero and can just be chopped
|
|
|
1677 off. On standard machines that allocate memory from the bottom up (and
|
|
|
1678 give each process its own address space), this works fine. Some
|
|
|
1679 machines, however, put the data space somewhere else in memory
|
|
|
1680 (e.g. beginning at 0x80000000). Those machines cope by defining
|
|
|
1681 @code{DATA_SEG_BITS} in the corresponding @file{m/} or @file{s/} file to
|
|
|
1682 the proper mask. Then, pointers retrieved from Lisp objects are
|
|
|
1683 automatically OR'ed with this value prior to being used.
|
|
|
1684
|
|
380
|
1685 A corollary of the previous paragraph is that @strong{(pointers to)
|
|
116
|
1686 stack-allocated structures cannot be put into Lisp objects}. The stack
|
|
|
1687 is generally located near the top of memory; if you put such a pointer
|
|
|
1688 into a Lisp object, it will get its top bits chopped off, and you will
|
|
|
1689 lose.
|
|
0
|
1690
|
|
380
|
1691 Actually, there's an alternative representation of a @code{Lisp_Object},
|
|
|
1692 invented by Kyle Jones, that is used when the
|
|
|
1693 @code{--use-minimal-tagbits} option to @code{configure} is used. In
|
|
|
1694 this case the 2 lower bits are used for the tag bits. This
|
|
|
1695 representation assumes that pointers to structs are always aligned to
|
|
|
1696 multiples of 4, so the lower 2 bits are always zero.
|
|
|
1697
|
|
|
1698 @example
|
|
|
1699 [ 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 ]
|
|
|
1700 [ 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 ]
|
|
|
1701
|
|
|
1702 <---------------------------------------------------------> <->
|
|
|
1703 a pointer to a structure, or an integer tag
|
|
|
1704 @end example
|
|
|
1705
|
|
|
1706 A tag of 00 is used for all pointer object types, a tag of 10 is used
|
|
|
1707 for characters, and the other two tags 01 and 11 are joined together to
|
|
|
1708 form the integer object type. The markbit is moved to part of the
|
|
|
1709 structure being pointed at (integers and chars do not need to be marked,
|
|
|
1710 since no memory is allocated). This representation has these
|
|
|
1711 advantages:
|
|
|
1712
|
|
|
1713 @enumerate
|
|
|
1714 @item
|
|
|
1715 31 bits can be used for Lisp Integers.
|
|
|
1716 @item
|
|
|
1717 @emph{Any} pointer can be represented directly, and no bit masking
|
|
|
1718 operations are necessary.
|
|
|
1719 @end enumerate
|
|
|
1720
|
|
|
1721 The disadvantages are:
|
|
|
1722
|
|
|
1723 @enumerate
|
|
|
1724 @item
|
|
|
1725 An extra level of indirection is needed when accessing the object types
|
|
|
1726 that were not record types. So checking whether a Lisp object is a cons
|
|
|
1727 cell becomes a slower operation.
|
|
|
1728 @item
|
|
|
1729 Mark bits can no longer be stored directly in Lisp objects, so another
|
|
|
1730 place for them must be found. This means that a cons cell requires more
|
|
|
1731 memory than merely room for 2 lisp objects, leading to extra memory use.
|
|
|
1732 @end enumerate
|
|
|
1733
|
|
|
1734 Various macros are used to construct Lisp objects and extract the
|
|
0
|
1735 components. Macros of the form @code{XINT()}, @code{XCHAR()},
|
|
|
1736 @code{XSTRING()}, @code{XSYMBOL()}, etc. mask out the pointer/integer
|
|
|
1737 field and cast it to the appropriate type. All of the macros that
|
|
|
1738 construct pointers will @code{OR} with @code{DATA_SEG_BITS} if
|
|
|
1739 necessary. @code{XINT()} needs to be a bit tricky so that negative
|
|
|
1740 numbers are properly sign-extended: Usually it does this by shifting the
|
|
|
1741 number four bits to the left and then four bits to the right. This
|
|
|
1742 assumes that the right-shift operator does an arithmetic shift (i.e. it
|
|
|
1743 leaves the most-significant bit as-is rather than shifting in a zero, so
|
|
|
1744 that it mimics a divide-by-two even for negative numbers). Not all
|
|
|
1745 machines/compilers do this, and on the ones that don't, a more
|
|
|
1746 complicated definition is selected by defining
|
|
|
1747 @code{EXPLICIT_SIGN_EXTEND}.
|
|
|
1748
|
|
380
|
1749 Note that when @code{ERROR_CHECK_TYPECHECK} is defined, the extractor
|
|
398
|
1750 macros become more complicated---they check the tag bits and/or the
|
|
0
|
1751 type field in the first four bytes of a record type to ensure that the
|
|
|
1752 object is really of the correct type. This is great for catching places
|
|
398
|
1753 where an incorrect type is being dereferenced---this typically results
|
|
0
|
1754 in a pointer being dereferenced as the wrong type of structure, with
|
|
|
1755 unpredictable (and sometimes not easily traceable) results.
|
|
|
1756
|
|
380
|
1757 There are similar @code{XSET@var{TYPE}()} macros that construct a Lisp
|
|
|
1758 object. These macros are of the form @code{XSET@var{TYPE}
|
|
|
1759 (@var{lvalue}, @var{result})},
|
|
0
|
1760 i.e. they have to be a statement rather than just used in an expression.
|
|
|
1761 The reason for this is that standard C doesn't let you ``construct'' a
|
|
|
1762 structure (but GCC does). Granted, this sometimes isn't too convenient;
|
|
|
1763 for the case of integers, at least, you can use the function
|
|
272
|
1764 @code{make_int()}, which constructs and @emph{returns} an integer
|
|
116
|
1765 Lisp object. Note that the @code{XSET@var{TYPE}()} macros are also
|
|
|
1766 affected by @code{ERROR_CHECK_TYPECHECK} and make sure that the
|
|
|
1767 structure is of the right type in the case of record types, where the
|
|
|
1768 type is contained in the structure.
|
|
0
|
1769
|
|
380
|
1770 The C programmer is responsible for @strong{guaranteeing} that a
|
|
|
1771 Lisp_Object is is the correct type before using the @code{X@var{TYPE}}
|
|
|
1772 macros. This is especially important in the case of lists. Use
|
|
|
1773 @code{XCAR} and @code{XCDR} if a Lisp_Object is certainly a cons cell,
|
|
|
1774 else use @code{Fcar()} and @code{Fcdr()}. Trust other C code, but not
|
|
|
1775 Lisp code. On the other hand, if XEmacs has an internal logic error,
|
|
|
1776 it's better to crash immediately, so sprinkle ``unreachable''
|
|
|
1777 @code{abort()}s liberally about the source code.
|
|
|
1778
|
|
0
|
1779 @node Rules When Writing New C Code, A Summary of the Various XEmacs Modules, How Lisp Objects Are Represented in C, Top
|
|
|
1780 @chapter Rules When Writing New C Code
|
|
|
1781
|
|
380
|
1782 The XEmacs C Code is extremely complex and intricate, and there are many
|
|
|
1783 rules that are more or less consistently followed throughout the code.
|
|
0
|
1784 Many of these rules are not obvious, so they are explained here. It is
|
|
380
|
1785 of the utmost importance that you follow them. If you don't, you may
|
|
|
1786 get something that appears to work, but which will crash in odd
|
|
|
1787 situations, often in code far away from where the actual breakage is.
|
|
0
|
1788
|
|
|
1789 @menu
|
|
|
1790 * General Coding Rules::
|
|
|
1791 * Writing Lisp Primitives::
|
|
|
1792 * Adding Global Lisp Variables::
|
|
373
|
1793 * Coding for Mule::
|
|
2
|
1794 * Techniques for XEmacs Developers::
|
|
0
|
1795 @end menu
|
|
|
1796
|
|
398
|
1797 @node General Coding Rules, Writing Lisp Primitives, Rules When Writing New C Code, Rules When Writing New C Code
|
|
0
|
1798 @section General Coding Rules
|
|
|
1799
|
|
380
|
1800 The C code is actually written in a dialect of C called @dfn{Clean C},
|
|
|
1801 meaning that it can be compiled, mostly warning-free, with either a C or
|
|
|
1802 C++ compiler. Coding in Clean C has several advantages over plain C.
|
|
|
1803 C++ compilers are more nit-picking, and a number of coding errors have
|
|
|
1804 been found by compiling with C++. The ability to use both C and C++
|
|
|
1805 tools means that a greater variety of development tools are available to
|
|
|
1806 the developer.
|
|
|
1807
|
|
|
1808 Almost every module contains a @code{syms_of_*()} function and a
|
|
0
|
1809 @code{vars_of_*()} function. The former declares any Lisp primitives
|
|
|
1810 you have defined and defines any symbols you will be using. The latter
|
|
|
1811 declares any global Lisp variables you have added and initializes global
|
|
|
1812 C variables in the module. For each such function, declare it in
|
|
|
1813 @file{symsinit.h} and make sure it's called in the appropriate place in
|
|
116
|
1814 @file{emacs.c}. @strong{Important}: There are stringent requirements on
|
|
0
|
1815 exactly what can go into these functions. See the comment in
|
|
116
|
1816 @file{emacs.c}. The reason for this is to avoid obscure unwanted
|
|
0
|
1817 interactions during initialization. If you don't follow these rules,
|
|
|
1818 you'll be sorry! If you want to do anything that isn't allowed, create
|
|
|
1819 a @code{complex_vars_of_*()} function for it. Doing this is tricky,
|
|
|
1820 though: You have to make sure your function is called at the right time
|
|
|
1821 so that all the initialization dependencies work out.
|
|
|
1822
|
|
380
|
1823 Every module includes @file{<config.h>} (angle brackets so that
|
|
116
|
1824 @samp{--srcdir} works correctly; @file{config.h} may or may not be in
|
|
|
1825 the same directory as the C sources) and @file{lisp.h}. @file{config.h}
|
|
380
|
1826 must always be included before any other header files (including
|
|
0
|
1827 system header files) to ensure that certain tricks played by various
|
|
|
1828 @file{s/} and @file{m/} files work out correctly.
|
|
|
1829
|
|
398
|
1830 When including header files, always use angle brackets, not double
|
|
|
1831 quotes, except when the file to be included is in the same directory as
|
|
|
1832 the including file. If either file is a generated file, then that is
|
|
|
1833 not likely to be the case. In order to understand why we have this
|
|
|
1834 rule, imagine what happens when you do a build in the source directory
|
|
|
1835 using @samp{./configure} and another build in another directory using
|
|
|
1836 @samp{../work/configure}. There will be two different @file{config.h}
|
|
|
1837 files. Which one will be used if you @samp{#include "config.h"}?
|
|
|
1838
|
|
380
|
1839 @strong{All global and static variables that are to be modifiable must
|
|
|
1840 be declared uninitialized.} This means that you may not use the
|
|
|
1841 ``declare with initializer'' form for these variables, such as @code{int
|
|
0
|
1842 some_variable = 0;}. The reason for this has to do with some kludges
|
|
|
1843 done during the dumping process: If possible, the initialized data
|
|
|
1844 segment is re-mapped so that it becomes part of the (unmodifiable) code
|
|
|
1845 segment in the dumped executable. This allows this memory to be shared
|
|
|
1846 among multiple running XEmacs processes. XEmacs is careful to place as
|
|
|
1847 much constant data as possible into initialized variables (in
|
|
398
|
1848 particular, into what's called the @dfn{pure space}---see below) during
|
|
0
|
1849 the @file{temacs} phase.
|
|
|
1850
|
|
|
1851 @cindex copy-on-write
|
|
380
|
1852 @strong{Please note:} This kludge only works on a few systems nowadays,
|
|
|
1853 and is rapidly becoming irrelevant because most modern operating systems
|
|
|
1854 provide @dfn{copy-on-write} semantics. All data is initially shared
|
|
|
1855 between processes, and a private copy is automatically made (on a
|
|
|
1856 page-by-page basis) when a process first attempts to write to a page of
|
|
|
1857 memory.
|
|
|
1858
|
|
|
1859 Formerly, there was a requirement that static variables not be declared
|
|
|
1860 inside of functions. This had to do with another hack along the same
|
|
|
1861 vein as what was just described: old USG systems put statically-declared
|
|
|
1862 variables in the initialized data space, so those header files had a
|
|
|
1863 @code{#define static} declaration. (That way, the data-segment remapping
|
|
|
1864 described above could still work.) This fails badly on static variables
|
|
|
1865 inside of functions, which suddenly become automatic variables;
|
|
|
1866 therefore, you weren't supposed to have any of them. This awful kludge
|
|
|
1867 has been removed in XEmacs because
|
|
0
|
1868
|
|
|
1869 @enumerate
|
|
|
1870 @item
|
|
|
1871 almost all of the systems that used this kludge ended up having
|
|
|
1872 to disable the data-segment remapping anyway;
|
|
|
1873 @item
|
|
|
1874 the only systems that didn't were extremely outdated ones;
|
|
|
1875 @item
|
|
|
1876 this hack completely messed up inline functions.
|
|
|
1877 @end enumerate
|
|
|
1878
|
|
380
|
1879 The C source code makes heavy use of C preprocessor macros. One popular
|
|
|
1880 macro style is:
|
|
|
1881
|
|
|
1882 @example
|
|
398
|
1883 #define FOO(var, value) do @{ \
|
|
|
1884 Lisp_Object FOO_value = (value); \
|
|
|
1885 ... /* compute using FOO_value */ \
|
|
|
1886 (var) = bar; \
|
|
380
|
1887 @} while (0)
|
|
|
1888 @end example
|
|
|
1889
|
|
|
1890 The @code{do @{...@} while (0)} is a standard trick to allow FOO to have
|
|
|
1891 statement semantics, so that it can safely be used within an @code{if}
|
|
|
1892 statement in C, for example. Multiple evaluation is prevented by
|
|
|
1893 copying a supplied argument into a local variable, so that
|
|
|
1894 @code{FOO(var,fun(1))} only calls @code{fun} once.
|
|
|
1895
|
|
|
1896 Lisp lists are popular data structures in the C code as well as in
|
|
|
1897 Elisp. There are two sets of macros that iterate over lists.
|
|
|
1898 @code{EXTERNAL_LIST_LOOP_@var{n}} should be used when the list has been
|
|
|
1899 supplied by the user, and cannot be trusted to be acyclic and
|
|
|
1900 nil-terminated. A @code{malformed-list} or @code{circular-list} error
|
|
|
1901 will be generated if the list being iterated over is not entirely
|
|
|
1902 kosher. @code{LIST_LOOP_@var{n}}, on the other hand, is faster and less
|
|
|
1903 safe, and can be used only on trusted lists.
|
|
|
1904
|
|
|
1905 Related macros are @code{GET_EXTERNAL_LIST_LENGTH} and
|
|
|
1906 @code{GET_LIST_LENGTH}, which calculate the length of a list, and in the
|
|
|
1907 case of @code{GET_EXTERNAL_LIST_LENGTH}, validating the properness of
|
|
|
1908 the list. The macros @code{EXTERNAL_LIST_LOOP_DELETE_IF} and
|
|
|
1909 @code{LIST_LOOP_DELETE_IF} delete elements from a lisp list satisfying some
|
|
|
1910 predicate.
|
|
|
1911
|
|
398
|
1912 @node Writing Lisp Primitives, Adding Global Lisp Variables, General Coding Rules, Rules When Writing New C Code
|
|
0
|
1913 @section Writing Lisp Primitives
|
|
|
1914
|
|
380
|
1915 Lisp primitives are Lisp functions implemented in C. The details of
|
|
0
|
1916 interfacing the C function so that Lisp can call it are handled by a few
|
|
|
1917 C macros. The only way to really understand how to write new C code is
|
|
|
1918 to read the source, but we can explain some things here.
|
|
|
1919
|
|
380
|
1920 An example of a special form is the definition of @code{prog1}, from
|
|
0
|
1921 @file{eval.c}. (An ordinary function would have the same general
|
|
|
1922 appearance.)
|
|
|
1923
|
|
|
1924 @cindex garbage collection protection
|
|
|
1925 @smallexample
|
|
|
1926 @group
|
|
380
|
1927 DEFUN ("prog1", Fprog1, 1, UNEVALLED, 0, /*
|
|
|
1928 Similar to `progn', but the value of the first form is returned.
|
|
|
1929 \(prog1 FIRST BODY...): All the arguments are evaluated sequentially.
|
|
|
1930 The value of FIRST is saved during evaluation of the remaining args,
|
|
|
1931 whose values are discarded.
|
|
44
|
1932 */
|
|
|
1933 (args))
|
|
0
|
1934 @{
|
|
|
1935 /* This function can GC */
|
|
380
|
1936 REGISTER Lisp_Object val, form, tail;
|
|
0
|
1937 struct gcpro gcpro1;
|
|
44
|
1938
|
|
380
|
1939 val = Feval (XCAR (args));
|
|
|
1940
|
|
|
1941 GCPRO1 (val);
|
|
|
1942
|
|
|
1943 LIST_LOOP_3 (form, XCDR (args), tail)
|
|
|
1944 Feval (form);
|
|
44
|
1945
|
|
0
|
1946 UNGCPRO;
|
|
|
1947 return val;
|
|
|
1948 @}
|
|
|
1949 @end group
|
|
|
1950 @end smallexample
|
|
|
1951
|
|
|
1952 Let's start with a precise explanation of the arguments to the
|
|
|
1953 @code{DEFUN} macro. Here is a template for them:
|
|
|
1954
|
|
|
1955 @example
|
|
380
|
1956 @group
|
|
|
1957 DEFUN (@var{lname}, @var{fname}, @var{min_args}, @var{max_args}, @var{interactive}, /*
|
|
|
1958 @var{docstring}
|
|
|
1959 */
|
|
|
1960 (@var{arglist}))
|
|
|
1961 @end group
|
|
0
|
1962 @end example
|
|
|
1963
|
|
|
1964 @table @var
|
|
|
1965 @item lname
|
|
116
|
1966 This string is the name of the Lisp symbol to define as the function
|
|
380
|
1967 name; in the example above, it is @code{"prog1"}.
|
|
0
|
1968
|
|
|
1969 @item fname
|
|
44
|
1970 This is the C function name for this function. This is the name that is
|
|
|
1971 used in C code for calling the function. The name is, by convention,
|
|
|
1972 @samp{F} prepended to the Lisp name, with all dashes (@samp{-}) in the
|
|
|
1973 Lisp name changed to underscores. Thus, to call this function from C
|
|
380
|
1974 code, call @code{Fprog1}. Remember that the arguments are of type
|
|
44
|
1975 @code{Lisp_Object}; various macros and functions for creating values of
|
|
|
1976 type @code{Lisp_Object} are declared in the file @file{lisp.h}.
|
|
0
|
1977
|
|
|
1978 Primitives whose names are special characters (e.g. @code{+} or
|
|
|
1979 @code{<}) are named by spelling out, in some fashion, the special
|
|
|
1980 character: e.g. @code{Fplus()} or @code{Flss()}. Primitives whose names
|
|
|
1981 begin with normal alphanumeric characters but also contain special
|
|
|
1982 characters are spelled out in some creative way, e.g. @code{let*}
|
|
|
1983 becomes @code{FletX()}.
|
|
|
1984
|
|
44
|
1985 Each function also has an associated structure that holds the data for
|
|
0
|
1986 the subr object that represents the function in Lisp. This structure
|
|
|
1987 conveys the Lisp symbol name to the initialization routine that will
|
|
44
|
1988 create the symbol and store the subr object as its definition. The C
|
|
|
1989 variable name of this structure is always @samp{S} prepended to the
|
|
|
1990 @var{fname}. You hardly ever need to be aware of the existence of this
|
|
380
|
1991 structure, since @code{DEFUN} plus @code{DEFSUBR} takes care of all the
|
|
|
1992 details.
|
|
|
1993
|
|
|
1994 @item min_args
|
|
0
|
1995 This is the minimum number of arguments that the function requires. The
|
|
380
|
1996 function @code{prog1} allows a minimum of one argument.
|
|
|
1997
|
|
|
1998 @item max_args
|
|
0
|
1999 This is the maximum number of arguments that the function accepts, if
|
|
|
2000 there is a fixed maximum. Alternatively, it can be @code{UNEVALLED},
|
|
|
2001 indicating a special form that receives unevaluated arguments, or
|
|
|
2002 @code{MANY}, indicating an unlimited number of evaluated arguments (the
|
|
380
|
2003 C equivalent of @code{&rest}). Both @code{UNEVALLED} and @code{MANY}
|
|
|
2004 are macros. If @var{max_args} is a number, it may not be less than
|
|
|
2005 @var{min_args} and it may not be greater than 8. (If you need to add a
|
|
|
2006 function with more than 8 arguments, use the @code{MANY} form. Resist
|
|
|
2007 the urge to edit the definition of @code{DEFUN} in @file{lisp.h}. If
|
|
|
2008 you do it anyways, make sure to also add another clause to the switch
|
|
|
2009 statement in @code{primitive_funcall().})
|
|
0
|
2010
|
|
|
2011 @item interactive
|
|
|
2012 This is an interactive specification, a string such as might be used as
|
|
|
2013 the argument of @code{interactive} in a Lisp function. In the case of
|
|
380
|
2014 @code{prog1}, it is 0 (a null pointer), indicating that @code{prog1}
|
|
|
2015 cannot be called interactively. A value of @code{""} indicates a
|
|
|
2016 function that should receive no arguments when called interactively.
|
|
0
|
2017
|
|
44
|
2018 @item docstring
|
|
0
|
2019 This is the documentation string. It is written just like a
|
|
44
|
2020 documentation string for a function defined in Lisp; in particular, the
|
|
|
2021 first line should be a single sentence. Note how the documentation
|
|
|
2022 string is enclosed in a comment, none of the documentation is placed on
|
|
|
2023 the same lines as the comment-start and comment-end characters, and the
|
|
|
2024 comment-start characters are on the same line as the interactive
|
|
0
|
2025 specification. @file{make-docfile}, which scans the C files for
|
|
44
|
2026 documentation strings, is very particular about what it looks for, and
|
|
116
|
2027 will not properly extract the doc string if it's not in this exact format.
|
|
44
|
2028
|
|
380
|
2029 In order to make both @file{etags} and @file{make-docfile} happy, make
|
|
|
2030 sure that the @code{DEFUN} line contains the @var{lname} and
|
|
|
2031 @var{fname}, and that the comment-start characters for the doc string
|
|
|
2032 are on the same line as the interactive specification, and put a newline
|
|
|
2033 directly after them (and before the comment-end characters).
|
|
44
|
2034
|
|
|
2035 @item arglist
|
|
|
2036 This is the comma-separated list of arguments to the C function. For a
|
|
|
2037 function with a fixed maximum number of arguments, provide a C argument
|
|
|
2038 for each Lisp argument. In this case, unlike regular C functions, the
|
|
|
2039 types of the arguments are not declared; they are simply always of type
|
|
380
|
2040 @code{Lisp_Object}.
|
|
44
|
2041
|
|
|
2042 The names of the C arguments will be used as the names of the arguments
|
|
|
2043 to the Lisp primitive as displayed in its documentation, modulo the same
|
|
|
2044 concerns described above for @code{F...} names (in particular,
|
|
0
|
2045 underscores in the C arguments become dashes in the Lisp arguments).
|
|
173
|
2046
|
|
|
2047 There is one additional kludge: A trailing `_' on the C argument is
|
|
|
2048 discarded when forming the Lisp argument. This allows C language
|
|
|
2049 reserved words (like @code{default}) or global symbols (like
|
|
|
2050 @code{dirname}) to be used as argument names without compiler warnings
|
|
|
2051 or errors.
|
|
0
|
2052
|
|
380
|
2053 A Lisp function with @w{@var{max_args} = @code{UNEVALLED}} is a
|
|
44
|
2054 @w{@dfn{special form}}; its arguments are not evaluated. Instead it
|
|
|
2055 receives one argument of type @code{Lisp_Object}, a (Lisp) list of the
|
|
|
2056 unevaluated arguments, conventionally named @code{(args)}.
|
|
|
2057
|
|
|
2058 When a Lisp function has no upper limit on the number of arguments,
|
|
380
|
2059 specify @w{@var{max_args} = @code{MANY}}. In this case its implementation in
|
|
44
|
2060 C actually receives exactly two arguments: the number of Lisp arguments
|
|
|
2061 (an @code{int}) and the address of a block containing their values (a
|
|
|
2062 @w{@code{Lisp_Object *}}). In this case only are the C types specified
|
|
|
2063 in the @var{arglist}: @w{@code{(int nargs, Lisp_Object *args)}}.
|
|
|
2064
|
|
|
2065 @end table
|
|
0
|
2066
|
|
380
|
2067 Within the function @code{Fprog1} itself, note the use of the macros
|
|
0
|
2068 @code{GCPRO1} and @code{UNGCPRO}. @code{GCPRO1} is used to ``protect''
|
|
|
2069 a variable from garbage collection---to inform the garbage collector
|
|
380
|
2070 that it must look in that variable and regard the object pointed at by
|
|
|
2071 its contents as an accessible object. This is necessary whenever you
|
|
|
2072 call @code{Feval} or anything that can directly or indirectly call
|
|
|
2073 @code{Feval} (this includes the @code{QUIT} macro!). At such a time,
|
|
|
2074 any Lisp object that you intend to refer to again must be protected
|
|
|
2075 somehow. @code{UNGCPRO} cancels the protection of the variables that
|
|
|
2076 are protected in the current function. It is necessary to do this
|
|
|
2077 explicitly.
|
|
|
2078
|
|
|
2079 The macro @code{GCPRO1} protects just one local variable. If you want
|
|
0
|
2080 to protect two, use @code{GCPRO2} instead; repeating @code{GCPRO1} will
|
|
|
2081 not work. Macros @code{GCPRO3} and @code{GCPRO4} also exist.
|
|
|
2082
|
|
380
|
2083 These macros implicitly use local variables such as @code{gcpro1}; you
|
|
0
|
2084 must declare these explicitly, with type @code{struct gcpro}. Thus, if
|
|
|
2085 you use @code{GCPRO2}, you must declare @code{gcpro1} and @code{gcpro2}.
|
|
|
2086
|
|
|
2087 @cindex caller-protects (@code{GCPRO} rule)
|
|
380
|
2088 Note also that the general rule is @dfn{caller-protects}; i.e. you are
|
|
|
2089 only responsible for protecting those Lisp objects that you create. Any
|
|
|
2090 objects passed to you as arguments should have been protected by whoever
|
|
|
2091 created them, so you don't in general have to protect them.
|
|
|
2092
|
|
|
2093 In particular, the arguments to any Lisp primitive are always
|
|
|
2094 automatically @code{GCPRO}ed, when called ``normally'' from Lisp code or
|
|
|
2095 bytecode. So only a few Lisp primitives that are called frequently from
|
|
|
2096 C code, such as @code{Fprogn} protect their arguments as a service to
|
|
|
2097 their caller. You don't need to protect your arguments when writing a
|
|
|
2098 new @code{DEFUN}.
|
|
|
2099
|
|
|
2100 @code{GCPRO}ing is perhaps the trickiest and most error-prone part of
|
|
|
2101 XEmacs coding. It is @strong{extremely} important that you get this
|
|
0
|
2102 right and use a great deal of discipline when writing this code.
|
|
|
2103 @xref{GCPROing, ,@code{GCPRO}ing}, for full details on how to do this.
|
|
|
2104
|
|
380
|
2105 What @code{DEFUN} actually does is declare a global structure of type
|
|
|
2106 @code{Lisp_Subr} whose name begins with capital @samp{SF} and which
|
|
|
2107 contains information about the primitive (e.g. a pointer to the
|
|
0
|
2108 function, its minimum and maximum allowed arguments, a string describing
|
|
380
|
2109 its Lisp name); @code{DEFUN} then begins a normal C function declaration
|
|
|
2110 using the @code{F...} name. The Lisp subr object that is the function
|
|
|
2111 definition of a primitive (i.e. the object in the function slot of the
|
|
|
2112 symbol that names the primitive) actually points to this @samp{SF}
|
|
|
2113 structure; when @code{Feval} encounters a subr, it looks in the
|
|
0
|
2114 structure to find out how to call the C function.
|
|
|
2115
|
|
380
|
2116 Defining the C function is not enough to make a Lisp primitive
|
|
0
|
2117 available; you must also create the Lisp symbol for the primitive (the
|
|
|
2118 symbol is @dfn{interned}; @pxref{Obarrays}) and store a suitable subr
|
|
|
2119 object in its function cell. (If you don't do this, the primitive won't
|
|
|
2120 be seen by Lisp code.) The code looks like this:
|
|
|
2121
|
|
|
2122 @example
|
|
116
|
2123 DEFSUBR (@var{fname});
|
|
0
|
2124 @end example
|
|
|
2125
|
|
380
|
2126 @noindent
|
|
|
2127 Here @var{fname} is the same name you used as the second argument to
|
|
116
|
2128 @code{DEFUN}.
|
|
|
2129
|
|
380
|
2130 This call to @code{DEFSUBR} should go in the @code{syms_of_*()} function
|
|
|
2131 at the end of the module. If no such function exists, create it and
|
|
|
2132 make sure to also declare it in @file{symsinit.h} and call it from the
|
|
|
2133 appropriate spot in @code{main()}. @xref{General Coding Rules}.
|
|
|
2134
|
|
|
2135 Note that C code cannot call functions by name unless they are defined
|
|
116
|
2136 in C. The way to call a function written in Lisp from C is to use
|
|
0
|
2137 @code{Ffuncall}, which embodies the Lisp function @code{funcall}. Since
|
|
|
2138 the Lisp function @code{funcall} accepts an unlimited number of
|
|
|
2139 arguments, in C it takes two: the number of Lisp-level arguments, and a
|
|
|
2140 one-dimensional array containing their values. The first Lisp-level
|
|
|
2141 argument is the Lisp function to call, and the rest are the arguments to
|
|
|
2142 pass to it. Since @code{Ffuncall} can call the evaluator, you must
|
|
|
2143 protect pointers from garbage collection around the call to
|
|
|
2144 @code{Ffuncall}. (However, @code{Ffuncall} explicitly protects all of
|
|
380
|
2145 its parameters, so you don't have to protect any pointers passed as
|
|
|
2146 parameters to it.)
|
|
|
2147
|
|
|
2148 The C functions @code{call0}, @code{call1}, @code{call2}, and so on,
|
|
0
|
2149 provide handy ways to call a Lisp function conveniently with a fixed
|
|
|
2150 number of arguments. They work by calling @code{Ffuncall}.
|
|
|
2151
|
|
380
|
2152 @file{eval.c} is a very good file to look through for examples;
|
|
|
2153 @file{lisp.h} contains the definitions for important macros and
|
|
0
|
2154 functions.
|
|
|
2155
|
|
398
|
2156 @node Adding Global Lisp Variables, Coding for Mule, Writing Lisp Primitives, Rules When Writing New C Code
|
|
0
|
2157 @section Adding Global Lisp Variables
|
|
|
2158
|
|
380
|
2159 Global variables whose names begin with @samp{Q} are constants whose
|
|
0
|
2160 value is a symbol of a particular name. The name of the variable should
|
|
|
2161 be derived from the name of the symbol using the same rules as for Lisp
|
|
|
2162 primitives. These variables are initialized using a call to
|
|
|
2163 @code{defsymbol()} in the @code{syms_of_*()} function. (This call
|
|
|
2164 interns a symbol, sets the C variable to the resulting Lisp object, and
|
|
|
2165 calls @code{staticpro()} on the C variable to tell the
|
|
|
2166 garbage-collection mechanism about this variable. What
|
|
|
2167 @code{staticpro()} does is add a pointer to the variable to a large
|
|
|
2168 global array; when garbage-collection happens, all pointers listed in
|
|
|
2169 the array are used as starting points for marking Lisp objects. This is
|
|
|
2170 important because it's quite possible that the only current reference to
|
|
|
2171 the object is the C variable. In the case of symbols, the
|
|
|
2172 @code{staticpro()} doesn't matter all that much because the symbol is
|
|
|
2173 contained in @code{obarray}, which is itself @code{staticpro()}ed.
|
|
|
2174 However, it's possible that a naughty user could do something like
|
|
|
2175 uninterning the symbol out of @code{obarray} or even setting
|
|
|
2176 @code{obarray} to a different value [although this is likely to make
|
|
|
2177 XEmacs crash!].)
|
|
|
2178
|
|
298
|
2179 @strong{Please note:} It is potentially deadly if you declare a
|
|
|
2180 @samp{Q...} variable in two different modules. The two calls to
|
|
|
2181 @code{defsymbol()} are no problem, but some linkers will complain about
|
|
|
2182 multiply-defined symbols. The most insidious aspect of this is that
|
|
|
2183 often the link will succeed anyway, but then the resulting executable
|
|
|
2184 will sometimes crash in obscure ways during certain operations! To
|
|
|
2185 avoid this problem, declare any symbols with common names (such as
|
|
|
2186 @code{text}) that are not obviously associated with this particular
|
|
|
2187 module in the module @file{general.c}.
|
|
0
|
2188
|
|
|
2189 Global variables whose names begin with @samp{V} are variables that
|
|
|
2190 contain Lisp objects. The convention here is that all global variables
|
|
|
2191 of type @code{Lisp_Object} begin with @samp{V}, and all others don't
|
|
|
2192 (including integer and boolean variables that have Lisp
|
|
|
2193 equivalents). Most of the time, these variables have equivalents in
|
|
|
2194 Lisp, but some don't. Those that do are declared this way by a call to
|
|
|
2195 @code{DEFVAR_LISP()} in the @code{vars_of_*()} initializer for the
|
|
|
2196 module. What this does is create a special @dfn{symbol-value-forward}
|
|
|
2197 Lisp object that contains a pointer to the C variable, intern a symbol
|
|
|
2198 whose name is as specified in the call to @code{DEFVAR_LISP()}, and set
|
|
|
2199 its value to the symbol-value-forward Lisp object; it also calls
|
|
|
2200 @code{staticpro()} on the C variable to tell the garbage-collection
|
|
|
2201 mechanism about the variable. When @code{eval} (or actually
|
|
|
2202 @code{symbol-value}) encounters this special object in the process of
|
|
|
2203 retrieving a variable's value, it follows the indirection to the C
|
|
|
2204 variable and gets its value. @code{setq} does similar things so that
|
|
|
2205 the C variable gets changed.
|
|
|
2206
|
|
|
2207 Whether or not you @code{DEFVAR_LISP()} a variable, you need to
|
|
|
2208 initialize it in the @code{vars_of_*()} function; otherwise it will end
|
|
|
2209 up as all zeroes, which is the integer 0 (@emph{not} @code{nil}), and
|
|
|
2210 this is probably not what you want. Also, if the variable is not
|
|
|
2211 @code{DEFVAR_LISP()}ed, @strong{you must call} @code{staticpro()} on the
|
|
|
2212 C variable in the @code{vars_of_*()} function. Otherwise, the
|
|
|
2213 garbage-collection mechanism won't know that the object in this variable
|
|
|
2214 is in use, and will happily collect it and reuse its storage for another
|
|
|
2215 Lisp object, and you will be the one who's unhappy when you can't figure
|
|
|
2216 out how your variable got overwritten.
|
|
|
2217
|
|
398
|
2218 @node Coding for Mule, Techniques for XEmacs Developers, Adding Global Lisp Variables, Rules When Writing New C Code
|
|
373
|
2219 @section Coding for Mule
|
|
|
2220 @cindex Coding for Mule
|
|
|
2221
|
|
|
2222 Although Mule support is not compiled by default in XEmacs, many people
|
|
|
2223 are using it, and we consider it crucial that new code works correctly
|
|
|
2224 with multibyte characters. This is not hard; it is only a matter of
|
|
|
2225 following several simple user-interface guidelines. Even if you never
|
|
|
2226 compile with Mule, with a little practice you will find it quite easy
|
|
|
2227 to code Mule-correctly.
|
|
|
2228
|
|
|
2229 Note that these guidelines are not necessarily tied to the current Mule
|
|
|
2230 implementation; they are also a good idea to follow on the grounds of
|
|
|
2231 code generalization for future I18N work.
|
|
|
2232
|
|
|
2233 @menu
|
|
|
2234 * Character-Related Data Types::
|
|
|
2235 * Working With Character and Byte Positions::
|
|
377
|
2236 * Conversion to and from External Data::
|
|
373
|
2237 * General Guidelines for Writing Mule-Aware Code::
|
|
|
2238 * An Example of Mule-Aware Code::
|
|
|
2239 @end menu
|
|
|
2240
|
|
398
|
2241 @node Character-Related Data Types, Working With Character and Byte Positions, Coding for Mule, Coding for Mule
|
|
373
|
2242 @subsection Character-Related Data Types
|
|
|
2243
|
|
377
|
2244 First, let's review the basic character-related datatypes used by
|
|
|
2245 XEmacs. Note that the separate @code{typedef}s are not mandatory in the
|
|
|
2246 current implementation (all of them boil down to @code{unsigned char} or
|
|
373
|
2247 @code{int}), but they improve clarity of code a great deal, because one
|
|
|
2248 glance at the declaration can tell the intended use of the variable.
|
|
|
2249
|
|
|
2250 @table @code
|
|
|
2251 @item Emchar
|
|
|
2252 @cindex Emchar
|
|
|
2253 An @code{Emchar} holds a single Emacs character.
|
|
|
2254
|
|
|
2255 Obviously, the equality between characters and bytes is lost in the Mule
|
|
|
2256 world. Characters can be represented by one or more bytes in the
|
|
|
2257 buffer, and @code{Emchar} is the C type large enough to hold any
|
|
|
2258 character.
|
|
|
2259
|
|
|
2260 Without Mule support, an @code{Emchar} is equivalent to an
|
|
|
2261 @code{unsigned char}.
|
|
|
2262
|
|
|
2263 @item Bufbyte
|
|
|
2264 @cindex Bufbyte
|
|
|
2265 The data representing the text in a buffer or string is logically a set
|
|
|
2266 of @code{Bufbyte}s.
|
|
|
2267
|
|
|
2268 XEmacs does not work with character formats all the time; when reading
|
|
|
2269 characters from the outside, it decodes them to an internal format, and
|
|
|
2270 likewise encodes them when writing. @code{Bufbyte} (in fact
|
|
|
2271 @code{unsigned char}) is the basic unit of XEmacs internal buffers and
|
|
|
2272 strings format.
|
|
|
2273
|
|
|
2274 One character can correspond to one or more @code{Bufbyte}s. In the
|
|
|
2275 current implementation, an ASCII character is represented by the same
|
|
|
2276 @code{Bufbyte}, and extended characters are represented by a sequence of
|
|
|
2277 @code{Bufbyte}s.
|
|
|
2278
|
|
|
2279 Without Mule support, a @code{Bufbyte} is equivalent to an
|
|
|
2280 @code{Emchar}.
|
|
|
2281
|
|
|
2282 @item Bufpos
|
|
|
2283 @itemx Charcount
|
|
377
|
2284 @cindex Bufpos
|
|
|
2285 @cindex Charcount
|
|
373
|
2286 A @code{Bufpos} represents a character position in a buffer or string.
|
|
|
2287 A @code{Charcount} represents a number (count) of characters.
|
|
|
2288 Logically, subtracting two @code{Bufpos} values yields a
|
|
|
2289 @code{Charcount} value. Although all of these are @code{typedef}ed to
|
|
|
2290 @code{int}, we use them in preference to @code{int} to make it clear
|
|
|
2291 what sort of position is being used.
|
|
|
2292
|
|
|
2293 @code{Bufpos} and @code{Charcount} values are the only ones that are
|
|
|
2294 ever visible to Lisp.
|
|
|
2295
|
|
|
2296 @item Bytind
|
|
|
2297 @itemx Bytecount
|
|
377
|
2298 @cindex Bytind
|
|
|
2299 @cindex Bytecount
|
|
373
|
2300 A @code{Bytind} represents a byte position in a buffer or string. A
|
|
|
2301 @code{Bytecount} represents the distance between two positions in bytes.
|
|
|
2302 The relationship between @code{Bytind} and @code{Bytecount} is the same
|
|
|
2303 as the relationship between @code{Bufpos} and @code{Charcount}.
|
|
|
2304
|
|
|
2305 @item Extbyte
|
|
|
2306 @itemx Extcount
|
|
377
|
2307 @cindex Extbyte
|
|
|
2308 @cindex Extcount
|
|
373
|
2309 When dealing with the outside world, XEmacs works with @code{Extbyte}s,
|
|
|
2310 which are equivalent to @code{unsigned char}. Obviously, an
|
|
|
2311 @code{Extcount} is the distance between two @code{Extbyte}s. Extbytes
|
|
|
2312 and Extcounts are not all that frequent in XEmacs code.
|
|
|
2313 @end table
|
|
|
2314
|
|
398
|
2315 @node Working With Character and Byte Positions, Conversion to and from External Data, Character-Related Data Types, Coding for Mule
|
|
373
|
2316 @subsection Working With Character and Byte Positions
|
|
|
2317
|
|
|
2318 Now that we have defined the basic character-related types, we can look
|
|
|
2319 at the macros and functions designed for work with them and for
|
|
|
2320 conversion between them. Most of these macros are defined in
|
|
|
2321 @file{buffer.h}, and we don't discuss all of them here, but only the
|
|
|
2322 most important ones. Examining the existing code is the best way to
|
|
|
2323 learn about them.
|
|
|
2324
|
|
|
2325 @table @code
|
|
|
2326 @item MAX_EMCHAR_LEN
|
|
377
|
2327 @cindex MAX_EMCHAR_LEN
|
|
373
|
2328 This preprocessor constant is the maximum number of buffer bytes per
|
|
|
2329 Emacs character, i.e. the byte length of an @code{Emchar}. It is useful
|
|
|
2330 when allocating temporary strings to keep a known number of characters.
|
|
|
2331 For instance:
|
|
|
2332
|
|
|
2333 @example
|
|
|
2334 @group
|
|
|
2335 @{
|
|
|
2336 Charcount cclen;
|
|
|
2337 ...
|
|
|
2338 @{
|
|
|
2339 /* Allocate place for @var{cclen} characters. */
|
|
380
|
2340 Bufbyte *buf = (Bufbyte *)alloca (cclen * MAX_EMCHAR_LEN);
|
|
373
|
2341 ...
|
|
|
2342 @end group
|
|
|
2343 @end example
|
|
|
2344
|
|
|
2345 If you followed the previous section, you can guess that, logically,
|
|
380
|
2346 multiplying a @code{Charcount} value with @code{MAX_EMCHAR_LEN} produces
|
|
373
|
2347 a @code{Bytecount} value.
|
|
|
2348
|
|
|
2349 In the current Mule implementation, @code{MAX_EMCHAR_LEN} equals 4.
|
|
|
2350 Without Mule, it is 1.
|
|
|
2351
|
|
|
2352 @item charptr_emchar
|
|
377
|
2353 @itemx set_charptr_emchar
|
|
|
2354 @cindex charptr_emchar
|
|
|
2355 @cindex set_charptr_emchar
|
|
|
2356 The @code{charptr_emchar} macro takes a @code{Bufbyte} pointer and
|
|
|
2357 returns the @code{Emchar} stored at that position. If it were a
|
|
|
2358 function, its prototype would be:
|
|
373
|
2359
|
|
|
2360 @example
|
|
|
2361 Emchar charptr_emchar (Bufbyte *p);
|
|
|
2362 @end example
|
|
|
2363
|
|
|
2364 @code{set_charptr_emchar} stores an @code{Emchar} to the specified byte
|
|
|
2365 position. It returns the number of bytes stored:
|
|
|
2366
|
|
|
2367 @example
|
|
|
2368 Bytecount set_charptr_emchar (Bufbyte *p, Emchar c);
|
|
|
2369 @end example
|
|
|
2370
|
|
|
2371 It is important to note that @code{set_charptr_emchar} is safe only for
|
|
|
2372 appending a character at the end of a buffer, not for overwriting a
|
|
|
2373 character in the middle. This is because the width of characters
|
|
|
2374 varies, and @code{set_charptr_emchar} cannot resize the string if it
|
|
|
2375 writes, say, a two-byte character where a single-byte character used to
|
|
|
2376 reside.
|
|
|
2377
|
|
|
2378 A typical use of @code{set_charptr_emchar} can be demonstrated by this
|
|
|
2379 example, which copies characters from buffer @var{buf} to a temporary
|
|
|
2380 string of Bufbytes.
|
|
|
2381
|
|
|
2382 @example
|
|
|
2383 @group
|
|
|
2384 @{
|
|
|
2385 Bufpos pos;
|
|
|
2386 for (pos = beg; pos < end; pos++)
|
|
|
2387 @{
|
|
|
2388 Emchar c = BUF_FETCH_CHAR (buf, pos);
|
|
|
2389 p += set_charptr_emchar (buf, c);
|
|
|
2390 @}
|
|
|
2391 @}
|
|
|
2392 @end group
|
|
|
2393 @end example
|
|
|
2394
|
|
|
2395 Note how @code{set_charptr_emchar} is used to store the @code{Emchar}
|
|
|
2396 and increment the counter, at the same time.
|
|
|
2397
|
|
|
2398 @item INC_CHARPTR
|
|
|
2399 @itemx DEC_CHARPTR
|
|
377
|
2400 @cindex INC_CHARPTR
|
|
|
2401 @cindex DEC_CHARPTR
|
|
373
|
2402 These two macros increment and decrement a @code{Bufbyte} pointer,
|
|
377
|
2403 respectively. They will adjust the pointer by the appropriate number of
|
|
|
2404 bytes according to the byte length of the character stored there. Both
|
|
|
2405 macros assume that the memory address is located at the beginning of a
|
|
|
2406 valid character.
|
|
373
|
2407
|
|
|
2408 Without Mule support, @code{INC_CHARPTR (p)} and @code{DEC_CHARPTR (p)}
|
|
|
2409 simply expand to @code{p++} and @code{p--}, respectively.
|
|
|
2410
|
|
|
2411 @item bytecount_to_charcount
|
|
377
|
2412 @cindex bytecount_to_charcount
|
|
373
|
2413 Given a pointer to a text string and a length in bytes, return the
|
|
|
2414 equivalent length in characters.
|
|
|
2415
|
|
|
2416 @example
|
|
|
2417 Charcount bytecount_to_charcount (Bufbyte *p, Bytecount bc);
|
|
|
2418 @end example
|
|
|
2419
|
|
|
2420 @item charcount_to_bytecount
|
|
377
|
2421 @cindex charcount_to_bytecount
|
|
373
|
2422 Given a pointer to a text string and a length in characters, return the
|
|
|
2423 equivalent length in bytes.
|
|
|
2424
|
|
|
2425 @example
|
|
|
2426 Bytecount charcount_to_bytecount (Bufbyte *p, Charcount cc);
|
|
|
2427 @end example
|
|
|
2428
|
|
|
2429 @item charptr_n_addr
|
|
377
|
2430 @cindex charptr_n_addr
|
|
373
|
2431 Return a pointer to the beginning of the character offset @var{cc} (in
|
|
|
2432 characters) from @var{p}.
|
|
|
2433
|
|
|
2434 @example
|
|
|
2435 Bufbyte *charptr_n_addr (Bufbyte *p, Charcount cc);
|
|
|
2436 @end example
|
|
|
2437 @end table
|
|
|
2438
|
|
398
|
2439 @node Conversion to and from External Data, General Guidelines for Writing Mule-Aware Code, Working With Character and Byte Positions, Coding for Mule
|
|
377
|
2440 @subsection Conversion to and from External Data
|
|
373
|
2441
|
|
|
2442 When an external function, such as a C library function, returns a
|
|
377
|
2443 @code{char} pointer, you should almost never treat it as @code{Bufbyte}.
|
|
|
2444 This is because these returned strings may contain 8bit characters which
|
|
|
2445 can be misinterpreted by XEmacs, and cause a crash. Likewise, when
|
|
|
2446 exporting a piece of internal text to the outside world, you should
|
|
380
|
2447 always convert it to an appropriate external encoding, lest the internal
|
|
377
|
2448 stuff (such as the infamous \201 characters) leak out.
|
|
|
2449
|
|
|
2450 The interface to conversion between the internal and external
|
|
|
2451 representations of text are the numerous conversion macros defined in
|
|
|
2452 @file{buffer.h}. Before looking at them, we'll look at the external
|
|
|
2453 formats supported by these macros.
|
|
373
|
2454
|
|
|
2455 Currently meaningful formats are @code{FORMAT_BINARY},
|
|
380
|
2456 @code{FORMAT_FILENAME}, @code{FORMAT_OS}, and @code{FORMAT_CTEXT}. Here
|
|
377
|
2457 is a description of these.
|
|
373
|
2458
|
|
|
2459 @table @code
|
|
377
|
2460 @item FORMAT_BINARY
|
|
|
2461 Binary format. This is the simplest format and is what we use in the
|
|
|
2462 absence of a more appropriate format. This converts according to the
|
|
|
2463 @code{binary} coding system:
|
|
|
2464
|
|
|
2465 @enumerate a
|
|
|
2466 @item
|
|
|
2467 On input, bytes 0--255 are converted into characters 0--255.
|
|
|
2468 @item
|
|
|
2469 On output, characters 0--255 are converted into bytes 0--255 and other
|
|
|
2470 characters are converted into `X'.
|
|
|
2471 @end enumerate
|
|
|
2472
|
|
|
2473 @item FORMAT_FILENAME
|
|
|
2474 Format used for filenames. In the original Mule, this is user-definable
|
|
|
2475 with the @code{pathname-coding-system} variable. For the moment, we
|
|
|
2476 just use the @code{binary} coding system.
|
|
|
2477
|
|
|
2478 @item FORMAT_OS
|
|
|
2479 Format used for the external Unix environment---@code{argv[]}, stuff
|
|
|
2480 from @code{getenv()}, stuff from the @file{/etc/passwd} file, etc.
|
|
|
2481
|
|
|
2482 Perhaps should be the same as FORMAT_FILENAME.
|
|
|
2483
|
|
|
2484 @item FORMAT_CTEXT
|
|
|
2485 Compound--text format. This is the standard X format used for data
|
|
|
2486 stored in properties, selections, and the like. This is an 8-bit
|
|
|
2487 no-lock-shift ISO2022 coding system.
|
|
|
2488 @end table
|
|
|
2489
|
|
380
|
2490 The macros to convert between these formats and the internal format, and
|
|
377
|
2491 vice versa, follow.
|
|
|
2492
|
|
|
2493 @table @code
|
|
|
2494 @item GET_CHARPTR_INT_DATA_ALLOCA
|
|
|
2495 @itemx GET_CHARPTR_EXT_DATA_ALLOCA
|
|
|
2496 These two are the most basic conversion macros.
|
|
|
2497 @code{GET_CHARPTR_INT_DATA_ALLOCA} converts external data to internal
|
|
|
2498 format, and @code{GET_CHARPTR_EXT_DATA_ALLOCA} converts the other way
|
|
|
2499 around. The arguments each of these receives are @var{ptr} (pointer to
|
|
|
2500 the text in external format), @var{len} (length of texts in bytes),
|
|
|
2501 @var{fmt} (format of the external text), @var{ptr_out} (lvalue to which
|
|
|
2502 new text should be copied), and @var{len_out} (lvalue which will be
|
|
|
2503 assigned the length of the internal text in bytes). The resulting text
|
|
|
2504 is stored to a stack-allocated buffer. If the text doesn't need
|
|
|
2505 changing, these macros will do nothing, except for setting
|
|
|
2506 @var{len_out}.
|
|
|
2507
|
|
|
2508 The macros above take many arguments which makes them unwieldy. For
|
|
|
2509 this reason, a number of convenience macros are defined with obvious
|
|
|
2510 functionality, but accepting less arguments. The general rule is that
|
|
|
2511 macros with @samp{INT} in their name convert text to internal Emacs
|
|
|
2512 representation, whereas the @samp{EXT} macros convert to external
|
|
|
2513 representation.
|
|
|
2514
|
|
|
2515 @item GET_C_CHARPTR_INT_DATA_ALLOCA
|
|
|
2516 @itemx GET_C_CHARPTR_EXT_DATA_ALLOCA
|
|
|
2517 As their names imply, these macros work on C char pointers, which are
|
|
|
2518 zero-terminated, and thus do not need @var{len} or @var{len_out}
|
|
|
2519 parameters.
|
|
373
|
2520
|
|
|
2521 @item GET_STRING_EXT_DATA_ALLOCA
|
|
|
2522 @itemx GET_C_STRING_EXT_DATA_ALLOCA
|
|
377
|
2523 These two macros convert a Lisp string into an external representation.
|
|
|
2524 The difference between them is that @code{GET_STRING_EXT_DATA_ALLOCA}
|
|
|
2525 stores its output to a generic string, providing @var{len_out}, the
|
|
|
2526 length of the resulting external string. On the other hand,
|
|
|
2527 @code{GET_C_STRING_EXT_DATA_ALLOCA} assumes that the caller will be
|
|
|
2528 satisfied with output string being zero-terminated.
|
|
|
2529
|
|
|
2530 Note that for Lisp strings only one conversion direction makes sense.
|
|
373
|
2531
|
|
|
2532 @item GET_C_CHARPTR_EXT_BINARY_DATA_ALLOCA
|
|
377
|
2533 @itemx GET_CHARPTR_EXT_BINARY_DATA_ALLOCA
|
|
|
2534 @itemx GET_STRING_BINARY_DATA_ALLOCA
|
|
|
2535 @itemx GET_C_STRING_BINARY_DATA_ALLOCA
|
|
373
|
2536 @itemx GET_C_CHARPTR_EXT_FILENAME_DATA_ALLOCA
|
|
|
2537 @itemx ...
|
|
377
|
2538 These macros convert internal text to a specific external
|
|
|
2539 representation, with the external format being encoded into the name of
|
|
|
2540 the macro. Note that the @code{GET_STRING_...} and
|
|
|
2541 @code{GET_C_STRING...} macros lack the @samp{EXT} tag, because they
|
|
|
2542 only make sense in that direction.
|
|
|
2543
|
|
|
2544 @item GET_C_CHARPTR_INT_BINARY_DATA_ALLOCA
|
|
|
2545 @itemx GET_CHARPTR_INT_BINARY_DATA_ALLOCA
|
|
|
2546 @itemx GET_C_CHARPTR_INT_FILENAME_DATA_ALLOCA
|
|
|
2547 @itemx ...
|
|
|
2548 These macros convert external text of a specific format to its internal
|
|
|
2549 representation, with the external format being incoded into the name of
|
|
|
2550 the macro.
|
|
373
|
2551 @end table
|
|
|
2552
|
|
398
|
2553 @node General Guidelines for Writing Mule-Aware Code, An Example of Mule-Aware Code, Conversion to and from External Data, Coding for Mule
|
|
373
|
2554 @subsection General Guidelines for Writing Mule-Aware Code
|
|
|
2555
|
|
|
2556 This section contains some general guidance on how to write Mule-aware
|
|
|
2557 code, as well as some pitfalls you should avoid.
|
|
|
2558
|
|
|
2559 @table @emph
|
|
|
2560 @item Never use @code{char} and @code{char *}.
|
|
|
2561 In XEmacs, the use of @code{char} and @code{char *} is almost always a
|
|
|
2562 mistake. If you want to manipulate an Emacs character from ``C'', use
|
|
|
2563 @code{Emchar}. If you want to examine a specific octet in the internal
|
|
|
2564 format, use @code{Bufbyte}. If you want a Lisp-visible character, use a
|
|
|
2565 @code{Lisp_Object} and @code{make_char}. If you want a pointer to move
|
|
|
2566 through the internal text, use @code{Bufbyte *}. Also note that you
|
|
|
2567 almost certainly do not need @code{Emchar *}.
|
|
|
2568
|
|
|
2569 @item Be careful not to confuse @code{Charcount}, @code{Bytecount}, and @code{Bufpos}.
|
|
380
|
2570 The whole point of using different types is to avoid confusion about the
|
|
|
2571 use of certain variables. Lest this effect be nullified, you need to be
|
|
373
|
2572 careful about using the right types.
|
|
|
2573
|
|
|
2574 @item Always convert external data
|
|
|
2575 It is extremely important to always convert external data, because
|
|
380
|
2576 XEmacs can crash if unexpected 8bit sequences are copied to its internal
|
|
373
|
2577 buffers literally.
|
|
|
2578
|
|
|
2579 This means that when a system function, such as @code{readdir}, returns
|
|
|
2580 a string, you need to convert it using one of the conversion macros
|
|
|
2581 described in the previous chapter, before passing it further to Lisp.
|
|
|
2582 In the case of @code{readdir}, you would use the
|
|
|
2583 @code{GET_C_CHARPTR_INT_FILENAME_DATA_ALLOCA} macro.
|
|
|
2584
|
|
|
2585 Also note that many internal functions, such as @code{make_string},
|
|
|
2586 accept Bufbytes, which removes the need for them to convert the data
|
|
|
2587 they receive. This increases efficiency because that way external data
|
|
|
2588 needs to be decoded only once, when it is read. After that, it is
|
|
|
2589 passed around in internal format.
|
|
|
2590 @end table
|
|
|
2591
|
|
398
|
2592 @node An Example of Mule-Aware Code, , General Guidelines for Writing Mule-Aware Code, Coding for Mule
|
|
373
|
2593 @subsection An Example of Mule-Aware Code
|
|
|
2594
|
|
|
2595 As an example of Mule-aware code, we shall will analyze the
|
|
|
2596 @code{string} function, which conses up a Lisp string from the character
|
|
|
2597 arguments it receives. Here is the definition, pasted from
|
|
|
2598 @code{alloc.c}:
|
|
|
2599
|
|
|
2600 @example
|
|
|
2601 @group
|
|
|
2602 DEFUN ("string", Fstring, 0, MANY, 0, /*
|
|
|
2603 Concatenate all the argument characters and make the result a string.
|
|
|
2604 */
|
|
|
2605 (int nargs, Lisp_Object *args))
|
|
|
2606 @{
|
|
|
2607 Bufbyte *storage = alloca_array (Bufbyte, nargs * MAX_EMCHAR_LEN);
|
|
|
2608 Bufbyte *p = storage;
|
|
|
2609
|
|
|
2610 for (; nargs; nargs--, args++)
|
|
|
2611 @{
|
|
|
2612 Lisp_Object lisp_char = *args;
|
|
|
2613 CHECK_CHAR_COERCE_INT (lisp_char);
|
|
|
2614 p += set_charptr_emchar (p, XCHAR (lisp_char));
|
|
|
2615 @}
|
|
|
2616 return make_string (storage, p - storage);
|
|
|
2617 @}
|
|
|
2618 @end group
|
|
|
2619 @end example
|
|
|
2620
|
|
|
2621 Now we can analyze the source line by line.
|
|
|
2622
|
|
|
2623 Obviously, string will be as long as there are arguments to the
|
|
|
2624 function. This is why we allocate @code{MAX_EMCHAR_LEN} * @var{nargs}
|
|
|
2625 bytes on the stack, i.e. the worst-case number of bytes for @var{nargs}
|
|
|
2626 @code{Emchar}s to fit in the string.
|
|
|
2627
|
|
|
2628 Then, the loop checks that each element is a character, converting
|
|
|
2629 integers in the process. Like many other functions in XEmacs, this
|
|
|
2630 function silently accepts integers where characters are expected, for
|
|
|
2631 historical and compatibility reasons. Unless you know what you are
|
|
|
2632 doing, @code{CHECK_CHAR} will also suffice. @code{XCHAR (lisp_char)}
|
|
|
2633 extracts the @code{Emchar} from the @code{Lisp_Object}, and
|
|
|
2634 @code{set_charptr_emchar} stores it to storage, increasing @code{p} in
|
|
|
2635 the process.
|
|
|
2636
|
|
380
|
2637 Other instructive examples of correct coding under Mule can be found all
|
|
|
2638 over the XEmacs code. For starters, I recommend
|
|
373
|
2639 @code{Fnormalize_menu_item_name} in @file{menubar.c}. After you have
|
|
|
2640 understood this section of the manual and studied the examples, you can
|
|
|
2641 proceed writing new Mule-aware code.
|
|
|
2642
|
|
398
|
2643 @node Techniques for XEmacs Developers, , Coding for Mule, Rules When Writing New C Code
|
|
2
|
2644 @section Techniques for XEmacs Developers
|
|
|
2645
|
|
|
2646 To make a quantified XEmacs, do: @code{make quantmacs}.
|
|
|
2647
|
|
|
2648 You simply can't dump Quantified and Purified images. Run the image
|
|
380
|
2649 like so: @code{quantmacs -batch -l loadup.el run-temacs @var{xemacs-args...}}.
|
|
2
|
2650
|
|
|
2651 Before you go through the trouble, are you compiling with all
|
|
|
2652 debugging and error-checking off? If not try that first. Be warned
|
|
|
2653 that while Quantify is directly responsible for quite a few
|
|
|
2654 optimizations which have been made to XEmacs, doing a run which
|
|
|
2655 generates results which can be acted upon is not necessarily a trivial
|
|
|
2656 task.
|
|
|
2657
|
|
|
2658 Also, if you're still willing to do some runs make sure you configure
|
|
|
2659 with the @samp{--quantify} flag. That will keep Quantify from starting
|
|
|
2660 to record data until after the loadup is completed and will shut off
|
|
|
2661 recording right before it shuts down (which generates enough bogus data
|
|
|
2662 to throw most results off). It also enables three additional elisp
|
|
|
2663 commands: @code{quantify-start-recording-data},
|
|
|
2664 @code{quantify-stop-recording-data} and @code{quantify-clear-data}.
|
|
|
2665
|
|
380
|
2666 If you want to make XEmacs faster, target your favorite slow benchmark,
|
|
|
2667 run a profiler like Quantify, @code{gprof}, or @code{tcov}, and figure
|
|
|
2668 out where the cycles are going. Specific projects:
|
|
|
2669
|
|
|
2670 @itemize @bullet
|
|
|
2671 @item
|
|
|
2672 Make the garbage collector faster. Figure out how to write an
|
|
|
2673 incremental garbage collector.
|
|
|
2674 @item
|
|
|
2675 Write a compiler that takes bytecode and spits out C code.
|
|
|
2676 Unfortunately, you will then need a C compiler and a more fully
|
|
|
2677 developed module system.
|
|
|
2678 @item
|
|
|
2679 Speed up redisplay.
|
|
|
2680 @item
|
|
|
2681 Speed up syntax highlighting. Maybe moving some of the syntax
|
|
|
2682 highlighting capabilities into C would make a difference.
|
|
|
2683 @item
|
|
|
2684 Implement tail recursion in Emacs Lisp (hard!).
|
|
|
2685 @end itemize
|
|
|
2686
|
|
|
2687 Unfortunately, Emacs Lisp is slow, and is going to stay slow. Function
|
|
|
2688 calls in elisp are especially expensive. Iterating over a long list is
|
|
|
2689 going to be 30 times faster implemented in C than in Elisp.
|
|
|
2690
|
|
398
|
2691 To get started debugging XEmacs, take a look at the @file{.gdbinit} and
|
|
|
2692 @file{.dbxrc} files in the @file{src} directory.
|
|
380
|
2693 @xref{Q2.1.15 - How to Debug an XEmacs problem with a debugger,,,
|
|
282
|
2694 xemacs-faq, XEmacs FAQ}.
|
|
|
2695
|
|
380
|
2696 After making source code changes, run @code{make check} to ensure that
|
|
|
2697 you haven't introduced any regressions. If you're feeling ambitious,
|
|
|
2698 you can try to improve the test suite in @file{tests/automated}.
|
|
282
|
2699
|
|
|
2700 Here are things to know when you create a new source file:
|
|
|
2701
|
|
|
2702 @itemize @bullet
|
|
|
2703 @item
|
|
380
|
2704 All @file{.c} files should @code{#include <config.h>} first. Almost all
|
|
|
2705 @file{.c} files should @code{#include "lisp.h"} second.
|
|
|
2706
|
|
|
2707 @item
|
|
|
2708 Generated header files should be included using the @code{#include <...>} syntax,
|
|
|
2709 not the @code{#include "..."} syntax. The generated headers are:
|
|
|
2710
|
|
|
2711 @file{config.h puresize-adjust.h sheap-adjust.h paths.h Emacs.ad.h}
|
|
282
|
2712
|
|
|
2713 The basic rule is that you should assume builds using @code{--srcdir}
|
|
380
|
2714 and the @code{#include <...>} syntax needs to be used when the
|
|
|
2715 to-be-included generated file is in a potentially different directory
|
|
|
2716 @emph{at compile time}. The non-obvious C rule is that @code{#include "..."}
|
|
|
2717 means to search for the included file in the same directory as the
|
|
|
2718 including file, @emph{not} in the current directory.
|
|
|
2719
|
|
|
2720 @item
|
|
|
2721 Header files should @emph{not} include @code{<config.h>} and
|
|
|
2722 @code{"lisp.h"}. It is the responsibility of the @file{.c} files that
|
|
|
2723 use it to do so.
|
|
|
2724
|
|
|
2725 @item
|
|
388
|
2726 If the header uses @code{INLINE}, either directly or through
|
|
380
|
2727 @code{DECLARE_LRECORD}, then it must be added to @file{inline.c}'s
|
|
|
2728 includes.
|
|
|
2729
|
|
|
2730 @item
|
|
|
2731 Try compiling at least once with
|
|
282
|
2732
|
|
|
2733 @example
|
|
|
2734 gcc --with-mule --with-union-type --error-checking=all
|
|
|
2735 @end example
|
|
380
|
2736
|
|
|
2737 @item
|
|
|
2738 Did I mention that you should run the test suite?
|
|
|
2739 @example
|
|
|
2740 make check
|
|
|
2741 @end example
|
|
282
|
2742 @end itemize
|
|
2
|
2743
|
|
380
|
2744
|
|
0
|
2745 @node A Summary of the Various XEmacs Modules, Allocation of Objects in XEmacs Lisp, Rules When Writing New C Code, Top
|
|
|
2746 @chapter A Summary of the Various XEmacs Modules
|
|
|
2747
|
|
|
2748 This is accurate as of XEmacs 20.0.
|
|
|
2749
|
|
|
2750 @menu
|
|
|
2751 * Low-Level Modules::
|
|
|
2752 * Basic Lisp Modules::
|
|
|
2753 * Modules for Standard Editing Operations::
|
|
|
2754 * Editor-Level Control Flow Modules::
|
|
|
2755 * Modules for the Basic Displayable Lisp Objects::
|
|
|
2756 * Modules for other Display-Related Lisp Objects::
|
|
|
2757 * Modules for the Redisplay Mechanism::
|
|
|
2758 * Modules for Interfacing with the File System::
|
|
|
2759 * Modules for Other Aspects of the Lisp Interpreter and Object System::
|
|
|
2760 * Modules for Interfacing with the Operating System::
|
|
|
2761 * Modules for Interfacing with X Windows::
|
|
|
2762 * Modules for Internationalization::
|
|
|
2763 @end menu
|
|
|
2764
|
|
398
|
2765 @node Low-Level Modules, Basic Lisp Modules, A Summary of the Various XEmacs Modules, A Summary of the Various XEmacs Modules
|
|
0
|
2766 @section Low-Level Modules
|
|
|
2767
|
|
|
2768 @example
|
|
380
|
2769 config.h
|
|
0
|
2770 @end example
|
|
|
2771
|
|
|
2772 This is automatically generated from @file{config.h.in} based on the
|
|
|
2773 results of configure tests and user-selected optional features and
|
|
|
2774 contains preprocessor definitions specifying the nature of the
|
|
|
2775 environment in which XEmacs is being compiled.
|
|
|
2776
|
|
|
2777
|
|
|
2778
|
|
|
2779 @example
|
|
380
|
2780 paths.h
|
|
0
|
2781 @end example
|
|
|
2782
|
|
|
2783 This is automatically generated from @file{paths.h.in} based on supplied
|
|
|
2784 configure values, and allows for non-standard installed configurations
|
|
|
2785 of the XEmacs directories. It's currently broken, though.
|
|
|
2786
|
|
|
2787
|
|
|
2788
|
|
|
2789 @example
|
|
380
|
2790 emacs.c
|
|
|
2791 signal.c
|
|
0
|
2792 @end example
|
|
|
2793
|
|
|
2794 @file{emacs.c} contains @code{main()} and other code that performs the most
|
|
|
2795 basic environment initializations and handles shutting down the XEmacs
|
|
|
2796 process (this includes @code{kill-emacs}, the normal way that XEmacs is
|
|
|
2797 exited; @code{dump-emacs}, which is used during the build process to
|
|
|
2798 write out the XEmacs executable; @code{run-emacs-from-temacs}, which can
|
|
|
2799 be used to start XEmacs directly when temacs has finished loading all
|
|
|
2800 the Lisp code; and emergency code to handle crashes [XEmacs tries to
|
|
|
2801 auto-save all files before it crashes]).
|
|
|
2802
|
|
|
2803 Low-level code that directly interacts with the Unix signal mechanism,
|
|
|
2804 however, is in @file{signal.c}. Note that this code does not handle system
|
|
|
2805 dependencies in interfacing to signals; that is handled using the
|
|
|
2806 @file{syssignal.h} header file, described in section J below.
|
|
|
2807
|
|
|
2808
|
|
|
2809
|
|
|
2810 @example
|
|
380
|
2811 unexaix.c
|
|
|
2812 unexalpha.c
|
|
|
2813 unexapollo.c
|
|
|
2814 unexconvex.c
|
|
|
2815 unexec.c
|
|
|
2816 unexelf.c
|
|
|
2817 unexelfsgi.c
|
|
|
2818 unexencap.c
|
|
|
2819 unexenix.c
|
|
|
2820 unexfreebsd.c
|
|
|
2821 unexfx2800.c
|
|
|
2822 unexhp9k3.c
|
|
|
2823 unexhp9k800.c
|
|
|
2824 unexmips.c
|
|
|
2825 unexnext.c
|
|
|
2826 unexsol2.c
|
|
|
2827 unexsunos4.c
|
|
0
|
2828 @end example
|
|
|
2829
|
|
|
2830 These modules contain code dumping out the XEmacs executable on various
|
|
|
2831 different systems. (This process is highly machine-specific and
|
|
|
2832 requires intimate knowledge of the executable format and the memory map
|
|
|
2833 of the process.) Only one of these modules is actually used; this is
|
|
|
2834 chosen by @file{configure}.
|
|
|
2835
|
|
|
2836
|
|
|
2837
|
|
|
2838 @example
|
|
380
|
2839 crt0.c
|
|
|
2840 lastfile.c
|
|
|
2841 pre-crt0.c
|
|
0
|
2842 @end example
|
|
|
2843
|
|
|
2844 These modules are used in conjunction with the dump mechanism. On some
|
|
|
2845 systems, an alternative version of the C startup code (the actual code
|
|
|
2846 that receives control from the operating system when the process is
|
|
|
2847 started, and which calls @code{main()}) is required so that the dumping
|
|
|
2848 process works properly; @file{crt0.c} provides this.
|
|
|
2849
|
|
|
2850 @file{pre-crt0.c} and @file{lastfile.c} should be the very first and
|
|
|
2851 very last file linked, respectively. (Actually, this is not really true.
|
|
|
2852 @file{lastfile.c} should be after all Emacs modules whose initialized
|
|
|
2853 data should be made constant, and before all other Emacs files and all
|
|
|
2854 libraries. In particular, the allocation modules @file{gmalloc.c},
|
|
|
2855 @file{alloca.c}, etc. are normally placed past @file{lastfile.c}, and
|
|
|
2856 all of the files that implement Xt widget classes @emph{must} be placed
|
|
|
2857 after @file{lastfile.c} because they contain various structures that
|
|
|
2858 must be statically initialized and into which Xt writes at various
|
|
|
2859 times.) @file{pre-crt0.c} and @file{lastfile.c} contain exported symbols
|
|
116
|
2860 that are used to determine the start and end of XEmacs' initialized
|
|
0
|
2861 data space when dumping.
|
|
|
2862
|
|
|
2863
|
|
|
2864
|
|
|
2865 @example
|
|
380
|
2866 alloca.c
|
|
|
2867 free-hook.c
|
|
|
2868 getpagesize.h
|
|
|
2869 gmalloc.c
|
|
|
2870 malloc.c
|
|
|
2871 mem-limits.h
|
|
|
2872 ralloc.c
|
|
|
2873 vm-limit.c
|
|
0
|
2874 @end example
|
|
|
2875
|
|
|
2876 These handle basic C allocation of memory. @file{alloca.c} is an emulation of
|
|
|
2877 the stack allocation function @code{alloca()} on machines that lack
|
|
|
2878 this. (XEmacs makes extensive use of @code{alloca()} in its code.)
|
|
|
2879
|
|
|
2880 @file{gmalloc.c} and @file{malloc.c} are two implementations of the standard C
|
|
|
2881 functions @code{malloc()}, @code{realloc()} and @code{free()}. They are
|
|
|
2882 often used in place of the standard system-provided @code{malloc()}
|
|
|
2883 because they usually provide a much faster implementation, at the
|
|
|
2884 expense of additional memory use. @file{gmalloc.c} is a newer implementation
|
|
|
2885 that is much more memory-efficient for large allocations than @file{malloc.c},
|
|
|
2886 and should always be preferred if it works. (At one point, @file{gmalloc.c}
|
|
|
2887 didn't work on some systems where @file{malloc.c} worked; but this should be
|
|
|
2888 fixed now.)
|
|
|
2889
|
|
|
2890 @cindex relocating allocator
|
|
380
|
2891 @file{ralloc.c} is the @dfn{relocating allocator}. It provides
|
|
|
2892 functions similar to @code{malloc()}, @code{realloc()} and @code{free()}
|
|
|
2893 that allocate memory that can be dynamically relocated in memory. The
|
|
|
2894 advantage of this is that allocated memory can be shuffled around to
|
|
|
2895 place all the free memory at the end of the heap, and the heap can then
|
|
|
2896 be shrunk, releasing the memory back to the operating system. The use
|
|
|
2897 of this can be controlled with the configure option @code{--rel-alloc};
|
|
|
2898 if enabled, memory allocated for buffers will be relocatable, so that if
|
|
|
2899 a very large file is visited and the buffer is later killed, the memory
|
|
|
2900 can be released to the operating system. (The disadvantage of this
|
|
|
2901 mechanism is that it can be very slow. On systems with the
|
|
|
2902 @code{mmap()} system call, the XEmacs version of @file{ralloc.c} uses
|
|
|
2903 this to move memory around without actually having to block-copy it,
|
|
|
2904 which can speed things up; but it can still cause noticeable performance
|
|
|
2905 degradation.)
|
|
0
|
2906
|
|
|
2907 @file{free-hook.c} contains some debugging functions for checking for invalid
|
|
|
2908 arguments to @code{free()}.
|
|
|
2909
|
|
|
2910 @file{vm-limit.c} contains some functions that warn the user when memory is
|
|
|
2911 getting low. These are callback functions that are called by @file{gmalloc.c}
|
|
|
2912 and @file{malloc.c} at appropriate times.
|
|
|
2913
|
|
|
2914 @file{getpagesize.h} provides a uniform interface for retrieving the size of a
|
|
|
2915 page in virtual memory. @file{mem-limits.h} provides a uniform interface for
|
|
|
2916 retrieving the total amount of available virtual memory. Both are
|
|
|
2917 similar in spirit to the @file{sys*.h} files described in section J, below.
|
|
|
2918
|
|
|
2919
|
|
|
2920
|
|
|
2921 @example
|
|
380
|
2922 blocktype.c
|
|
|
2923 blocktype.h
|
|
|
2924 dynarr.c
|
|
0
|
2925 @end example
|
|
|
2926
|
|
|
2927 These implement a couple of basic C data types to facilitate memory
|
|
|
2928 allocation. The @code{Blocktype} type efficiently manages the
|
|
|
2929 allocation of fixed-size blocks by minimizing the number of times that
|
|
|
2930 @code{malloc()} and @code{free()} are called. It allocates memory in
|
|
|
2931 large chunks, subdivides the chunks into blocks of the proper size, and
|
|
|
2932 returns the blocks as requested. When blocks are freed, they are placed
|
|
|
2933 onto a linked list, so they can be efficiently reused. This data type
|
|
|
2934 is not much used in XEmacs currently, because it's a fairly new
|
|
|
2935 addition.
|
|
|
2936
|
|
|
2937 @cindex dynamic array
|
|
|
2938 The @code{Dynarr} type implements a @dfn{dynamic array}, which is
|
|
|
2939 similar to a standard C array but has no fixed limit on the number of
|
|
|
2940 elements it can contain. Dynamic arrays can hold elements of any type,
|
|
|
2941 and when you add a new element, the array automatically resizes itself
|
|
|
2942 if it isn't big enough. Dynarrs are extensively used in the redisplay
|
|
|
2943 mechanism.
|
|
|
2944
|
|
|
2945
|
|
|
2946
|
|
|
2947 @example
|
|
380
|
2948 inline.c
|
|
0
|
2949 @end example
|
|
|
2950
|
|
|
2951 This module is used in connection with inline functions (available in
|
|
|
2952 some compilers). Often, inline functions need to have a corresponding
|
|
|
2953 non-inline function that does the same thing. This module is where they
|
|
|
2954 reside. It contains no actual code, but defines some special flags that
|
|
|
2955 cause inline functions defined in header files to be rendered as actual
|
|
|
2956 functions. It then includes all header files that contain any inline
|
|
|
2957 function definitions, so that each one gets a real function equivalent.
|
|
|
2958
|
|
|
2959
|
|
|
2960
|
|
|
2961 @example
|
|
380
|
2962 debug.c
|
|
|
2963 debug.h
|
|
0
|
2964 @end example
|
|
|
2965
|
|
|
2966 These functions provide a system for doing internal consistency checks
|
|
|
2967 during code development. This system is not currently used; instead the
|
|
|
2968 simpler @code{assert()} macro is used along with the various checks
|
|
|
2969 provided by the @samp{--error-check-*} configuration options.
|
|
|
2970
|
|
|
2971
|
|
|
2972
|
|
|
2973 @example
|
|
380
|
2974 prefix-args.c
|
|
0
|
2975 @end example
|
|
|
2976
|
|
|
2977 This is actually the source for a small, self-contained program
|
|
|
2978 used during building.
|
|
|
2979
|
|
|
2980
|
|
|
2981 @example
|
|
380
|
2982 universe.h
|
|
0
|
2983 @end example
|
|
|
2984
|
|
|
2985 This is not currently used.
|
|
|
2986
|
|
|
2987
|
|
|
2988
|
|
398
|
2989 @node Basic Lisp Modules, Modules for Standard Editing Operations, Low-Level Modules, A Summary of the Various XEmacs Modules
|
|
0
|
2990 @section Basic Lisp Modules
|
|
|
2991
|
|
|
2992 @example
|
|
380
|
2993 emacsfns.h
|
|
|
2994 lisp-disunion.h
|
|
|
2995 lisp-union.h
|
|
|
2996 lisp.h
|
|
|
2997 lrecord.h
|
|
|
2998 symsinit.h
|
|
0
|
2999 @end example
|
|
|
3000
|
|
|
3001 These are the basic header files for all XEmacs modules. Each module
|
|
|
3002 includes @file{lisp.h}, which brings the other header files in.
|
|
|
3003 @file{lisp.h} contains the definitions of the structures and extractor
|
|
|
3004 and constructor macros for the basic Lisp objects and various other
|
|
|
3005 basic definitions for the Lisp environment, as well as some
|
|
|
3006 general-purpose definitions (e.g. @code{min()} and @code{max()}).
|
|
|
3007 @file{lisp.h} includes either @file{lisp-disunion.h} or
|
|
272
|
3008 @file{lisp-union.h}, depending on whether @code{USE_UNION_TYPE} is
|
|
0
|
3009 defined. These files define the typedef of the Lisp object itself (as
|
|
|
3010 described above) and the low-level macros that hide the actual
|
|
|
3011 implementation of the Lisp object. All extractor and constructor macros
|
|
|
3012 for particular types of Lisp objects are defined in terms of these
|
|
|
3013 low-level macros.
|
|
|
3014
|
|
|
3015 As a general rule, all typedefs should go into the typedefs section of
|
|
|
3016 @file{lisp.h} rather than into a module-specific header file even if the
|
|
|
3017 structure is defined elsewhere. This allows function prototypes that
|
|
388
|
3018 use the typedef to be placed into other header files. Forward structure
|
|
0
|
3019 declarations (i.e. a simple declaration like @code{struct foo;} where
|
|
|
3020 the structure itself is defined elsewhere) should be placed into the
|
|
|
3021 typedefs section as necessary.
|
|
|
3022
|
|
|
3023 @file{lrecord.h} contains the basic structures and macros that implement
|
|
398
|
3024 all record-type Lisp objects---i.e. all objects whose type is a field
|
|
0
|
3025 in their C structure, which includes all objects except the few most
|
|
|
3026 basic ones.
|
|
|
3027
|
|
380
|
3028 @file{lisp.h} contains prototypes for most of the exported functions in
|
|
|
3029 the various modules. Lisp primitives defined using @code{DEFUN} that
|
|
|
3030 need to be called by C code should be declared using @code{EXFUN}.
|
|
|
3031 Other function prototypes should be placed either into the appropriate
|
|
|
3032 section of @code{lisp.h}, or into a module-specific header file,
|
|
|
3033 depending on how general-purpose the function is and whether it has
|
|
|
3034 special-purpose argument types requiring definitions not in
|
|
|
3035 @file{lisp.h}.) All initialization functions are prototyped in
|
|
|
3036 @file{symsinit.h}.
|
|
|
3037
|
|
|
3038
|
|
|
3039
|
|
|
3040 @example
|
|
|
3041 alloc.c
|
|
|
3042 pure.c
|
|
|
3043 puresize.h
|
|
0
|
3044 @end example
|
|
|
3045
|
|
|
3046 The large module @file{alloc.c} implements all of the basic allocation and
|
|
|
3047 garbage collection for Lisp objects. The most commonly used Lisp
|
|
|
3048 objects are allocated in chunks, similar to the Blocktype data type
|
|
|
3049 described above; others are allocated in individually @code{malloc()}ed
|
|
|
3050 blocks. This module provides the foundation on which all other aspects
|
|
|
3051 of the Lisp environment sit, and is the first module initialized at
|
|
|
3052 startup.
|
|
|
3053
|
|
|
3054 Note that @file{alloc.c} provides a series of generic functions that are
|
|
|
3055 not dependent on any particular object type, and interfaces to
|
|
|
3056 particular types of objects using a standardized interface of
|
|
|
3057 type-specific methods. This scheme is a fundamental principle of
|
|
|
3058 object-oriented programming and is heavily used throughout XEmacs. The
|
|
|
3059 great advantage of this is that it allows for a clean separation of
|
|
398
|
3060 functionality into different modules---new classes of Lisp objects, new
|
|
0
|
3061 event interfaces, new device types, new stream interfaces, etc. can be
|
|
|
3062 added transparently without affecting code anywhere else in XEmacs.
|
|
|
3063 Because the different subsystems are divided into general and specific
|
|
|
3064 code, adding a new subtype within a subsystem will in general not
|
|
|
3065 require changes to the generic subsystem code or affect any of the other
|
|
|
3066 subtypes in the subsystem; this provides a great deal of robustness to
|
|
|
3067 the XEmacs code.
|
|
|
3068
|
|
|
3069 @cindex pure space
|
|
|
3070 @file{pure.c} contains the declaration of the @dfn{purespace} array.
|
|
|
3071 Pure space is a hack used to place some constant Lisp data into the code
|
|
|
3072 segment of the XEmacs executable, even though the data needs to be
|
|
|
3073 initialized through function calls. (See above in section VIII for more
|
|
|
3074 info about this.) During startup, certain sorts of data is
|
|
|
3075 automatically copied into pure space, and other data is copied manually
|
|
|
3076 in some of the basic Lisp files by calling the function @code{purecopy},
|
|
|
3077 which copies the object if possible (this only works in temacs, of
|
|
|
3078 course) and returns the new object. In particular, while temacs is
|
|
|
3079 executing, the Lisp reader automatically copies all compiled-function
|
|
|
3080 objects that it reads into pure space. Since compiled-function objects
|
|
|
3081 are large, are never modified, and typically comprise the majority of
|
|
|
3082 the contents of a compiled-Lisp file, this works well. While XEmacs is
|
|
|
3083 running, any attempt to modify an object that resides in pure space
|
|
|
3084 causes an error. Objects in pure space are never garbage collected --
|
|
|
3085 almost all of the time, they're intended to be permanent, and in any
|
|
|
3086 case you can't write into pure space to set the mark bits.
|
|
|
3087
|
|
|
3088 @file{puresize.h} contains the declaration of the size of the pure space
|
|
|
3089 array. This depends on the optional features that are compiled in, any
|
|
|
3090 extra purespace requested by the user at compile time, and certain other
|
|
|
3091 factors (e.g. 64-bit machines need more pure space because their Lisp
|
|
|
3092 objects are larger). The smallest size that suffices should be used, so
|
|
|
3093 that there's no wasted space. If there's not enough pure space, you
|
|
|
3094 will get an error during the build process, specifying how much more
|
|
|
3095 pure space is needed.
|
|
|
3096
|
|
|
3097
|
|
|
3098
|
|
|
3099 @example
|
|
380
|
3100 eval.c
|
|
|
3101 backtrace.h
|
|
0
|
3102 @end example
|
|
|
3103
|
|
|
3104 This module contains all of the functions to handle the flow of control.
|
|
|
3105 This includes the mechanisms of defining functions, calling functions,
|
|
|
3106 traversing stack frames, and binding variables; the control primitives
|
|
|
3107 and other special forms such as @code{while}, @code{if}, @code{eval},
|
|
|
3108 @code{let}, @code{and}, @code{or}, @code{progn}, etc.; handling of
|
|
|
3109 non-local exits, unwind-protects, and exception handlers; entering the
|
|
|
3110 debugger; methods for the subr Lisp object type; etc. It does
|
|
|
3111 @emph{not} include the @code{read} function, the @code{print} function,
|
|
|
3112 or the handling of symbols and obarrays.
|
|
|
3113
|
|
|
3114 @file{backtrace.h} contains some structures related to stack frames and the
|
|
|
3115 flow of control.
|
|
|
3116
|
|
|
3117
|
|
|
3118
|
|
|
3119 @example
|
|
380
|
3120 lread.c
|
|
0
|
3121 @end example
|
|
|
3122
|
|
|
3123 This module implements the Lisp reader and the @code{read} function,
|
|
|
3124 which converts text into Lisp objects, according to the read syntax of
|
|
|
3125 the objects, as described above. This is similar to the parser that is
|
|
|
3126 a part of all compilers.
|
|
|
3127
|
|
|
3128
|
|
|
3129
|
|
|
3130 @example
|
|
380
|
3131 print.c
|
|
0
|
3132 @end example
|
|
|
3133
|
|
|
3134 This module implements the Lisp print mechanism and the @code{print}
|
|
|
3135 function and related functions. This is the inverse of the Lisp reader
|
|
|
3136 -- it converts Lisp objects to a printed, textual representation.
|
|
|
3137 (Hopefully something that can be read back in using @code{read} to get
|
|
|
3138 an equivalent object.)
|
|
|
3139
|
|
|
3140
|
|
|
3141
|
|
|
3142 @example
|
|
380
|
3143 general.c
|
|
|
3144 symbols.c
|
|
|
3145 symeval.h
|
|
0
|
3146 @end example
|
|
|
3147
|
|
|
3148 @file{symbols.c} implements the handling of symbols, obarrays, and
|
|
|
3149 retrieving the values of symbols. Much of the code is devoted to
|
|
|
3150 handling the special @dfn{symbol-value-magic} objects that define
|
|
398
|
3151 special types of variables---this includes buffer-local variables,
|
|
0
|
3152 variable aliases, variables that forward into C variables, etc. This
|
|
|
3153 module is initialized extremely early (right after @file{alloc.c}),
|
|
|
3154 because it is here that the basic symbols @code{t} and @code{nil} are
|
|
|
3155 created, and those symbols are used everywhere throughout XEmacs.
|
|
|
3156
|
|
|
3157 @file{symeval.h} contains the definitions of symbol structures and the
|
|
|
3158 @code{DEFVAR_LISP()} and related macros for declaring variables.
|
|
|
3159
|
|
|
3160
|
|
|
3161
|
|
|
3162 @example
|
|
380
|
3163 data.c
|
|
|
3164 floatfns.c
|
|
|
3165 fns.c
|
|
0
|
3166 @end example
|
|
|
3167
|
|
|
3168 These modules implement the methods and standard Lisp primitives for all
|
|
|
3169 the basic Lisp object types other than symbols (which are described
|
|
|
3170 above). @file{data.c} contains all the predicates (primitives that return
|
|
|
3171 whether an object is of a particular type); the integer arithmetic
|
|
|
3172 functions; and the basic accessor and mutator primitives for the various
|
|
|
3173 object types. @file{fns.c} contains all the standard predicates for working
|
|
|
3174 with sequences (where, abstractly speaking, a sequence is an ordered set
|
|
|
3175 of objects, and can be represented by a list, string, vector, or
|
|
|
3176 bit-vector); it also contains @code{equal}, perhaps on the grounds that
|
|
|
3177 bulk of the operation of @code{equal} is comparing sequences.
|
|
|
3178 @file{floatfns.c} contains methods and primitives for floats and floating-point
|
|
|
3179 arithmetic.
|
|
|
3180
|
|
|
3181
|
|
|
3182
|
|
|
3183 @example
|
|
380
|
3184 bytecode.c
|
|
|
3185 bytecode.h
|
|
|
3186 @end example
|
|
|
3187
|
|
|
3188 @file{bytecode.c} implements the byte-code interpreter and
|
|
|
3189 compiled-function objects, and @file{bytecode.h} contains associated
|
|
|
3190 structures. Note that the byte-code @emph{compiler} is written in Lisp.
|
|
0
|
3191
|
|
|
3192
|
|
|
3193
|
|
|
3194
|
|
398
|
3195 @node Modules for Standard Editing Operations, Editor-Level Control Flow Modules, Basic Lisp Modules, A Summary of the Various XEmacs Modules
|
|
0
|
3196 @section Modules for Standard Editing Operations
|
|
|
3197
|
|
|
3198 @example
|
|
380
|
3199 buffer.c
|
|
|
3200 buffer.h
|
|
|
3201 bufslots.h
|
|
0
|
3202 @end example
|
|
|
3203
|
|
2
|
3204 @file{buffer.c} implements the @dfn{buffer} Lisp object type. This
|
|
|
3205 includes functions that create and destroy buffers; retrieve buffers by
|
|
|
3206 name or by other properties; manipulate lists of buffers (remember that
|
|
|
3207 buffers are permanent objects and stored in various ordered lists);
|
|
|
3208 retrieve or change buffer properties; etc. It also contains the
|
|
|
3209 definitions of all the built-in buffer-local variables (which can be
|
|
|
3210 viewed as buffer properties). It does @emph{not} contain code to
|
|
|
3211 manipulate buffer-local variables (that's in @file{symbols.c}, described
|
|
|
3212 above); or code to manipulate the text in a buffer.
|
|
0
|
3213
|
|
|
3214 @file{buffer.h} defines the structures associated with a buffer and the various
|
|
|
3215 macros for retrieving text from a buffer and special buffer positions
|
|
|
3216 (e.g. @code{point}, the default location for text insertion). It also
|
|
|
3217 contains macros for working with buffer positions and converting between
|
|
|
3218 their representations as character offsets and as byte offsets (under
|
|
|
3219 MULE, they are different, because characters can be multi-byte). It is
|
|
|
3220 one of the largest header files.
|
|
|
3221
|
|
|
3222 @file{bufslots.h} defines the fields in the buffer structure that correspond to
|
|
|
3223 the built-in buffer-local variables. It is its own header file because
|
|
|
3224 it is included many times in @file{buffer.c}, as a way of iterating over all
|
|
|
3225 the built-in buffer-local variables.
|
|
|
3226
|
|
|
3227
|
|
|
3228
|
|
|
3229 @example
|
|
380
|
3230 insdel.c
|
|
|
3231 insdel.h
|
|
0
|
3232 @end example
|
|
|
3233
|
|
|
3234 @file{insdel.c} contains low-level functions for inserting and deleting text in
|
|
|
3235 a buffer, keeping track of changed regions for use by redisplay, and
|
|
|
3236 calling any before-change and after-change functions that may have been
|
|
|
3237 registered for the buffer. It also contains the actual functions that
|
|
|
3238 convert between byte offsets and character offsets.
|
|
|
3239
|
|
|
3240 @file{insdel.h} contains associated headers.
|
|
|
3241
|
|
|
3242
|
|
|
3243
|
|
|
3244 @example
|
|
380
|
3245 marker.c
|
|
0
|
3246 @end example
|
|
|
3247
|
|
2
|
3248 This module implements the @dfn{marker} Lisp object type, which
|
|
|
3249 conceptually is a pointer to a text position in a buffer that moves
|
|
|
3250 around as text is inserted and deleted, so as to remain in the same
|
|
|
3251 relative position. This module doesn't actually move the markers around
|
|
|
3252 -- that's handled in @file{insdel.c}. This module just creates them and
|
|
|
3253 implements the primitives for working with them. As markers are simple
|
|
|
3254 objects, this does not entail much.
|
|
0
|
3255
|
|
|
3256 Note that the standard arithmetic primitives (e.g. @code{+}) accept
|
|
|
3257 markers in place of integers and automatically substitute the value of
|
|
|
3258 @code{marker-position} for the marker, i.e. an integer describing the
|
|
|
3259 current buffer position of the marker.
|
|
|
3260
|
|
|
3261
|
|
|
3262
|
|
|
3263 @example
|
|
380
|
3264 extents.c
|
|
|
3265 extents.h
|
|
0
|
3266 @end example
|
|
|
3267
|
|
2
|
3268 This module implements the @dfn{extent} Lisp object type, which is like
|
|
|
3269 a marker that works over a range of text rather than a single position.
|
|
0
|
3270 Extents are also much more complex and powerful than markers and have a
|
|
|
3271 more efficient (and more algorithmically complex) implementation. The
|
|
|
3272 implementation is described in detail in comments in @file{extents.c}.
|
|
|
3273
|
|
|
3274 The code in @file{extents.c} works closely with @file{insdel.c} so that
|
|
|
3275 extents are properly moved around as text is inserted and deleted.
|
|
|
3276 There is also code in @file{extents.c} that provides information needed
|
|
|
3277 by the redisplay mechanism for efficient operation. (Remember that
|
|
|
3278 extents can have display properties that affect [sometimes drastically,
|
|
|
3279 as in the @code{invisible} property] the display of the text they
|
|
|
3280 cover.)
|
|
|
3281
|
|
|
3282
|
|
|
3283
|
|
|
3284 @example
|
|
380
|
3285 editfns.c
|
|
0
|
3286 @end example
|
|
|
3287
|
|
|
3288 @file{editfns.c} contains the standard Lisp primitives for working with
|
|
|
3289 a buffer's text, and calls the low-level functions in @file{insdel.c}.
|
|
|
3290 It also contains primitives for working with @code{point} (the default
|
|
|
3291 buffer insertion location).
|
|
|
3292
|
|
|
3293 @file{editfns.c} also contains functions for retrieving various
|
|
|
3294 characteristics from the external environment: the current time, the
|
|
|
3295 process ID of the running XEmacs process, the name of the user who ran
|
|
|
3296 this XEmacs process, etc. It's not clear why this code is in
|
|
|
3297 @file{editfns.c}.
|
|
|
3298
|
|
|
3299
|
|
|
3300
|
|
|
3301 @example
|
|
380
|
3302 callint.c
|
|
|
3303 cmds.c
|
|
|
3304 commands.h
|
|
0
|
3305 @end example
|
|
|
3306
|
|
|
3307 @cindex interactive
|
|
|
3308 These modules implement the basic @dfn{interactive} commands,
|
|
|
3309 i.e. user-callable functions. Commands, as opposed to other functions,
|
|
|
3310 have special ways of getting their parameters interactively (by querying
|
|
|
3311 the user), as opposed to having them passed in a normal function
|
|
|
3312 invocation. Many commands are not really meant to be called from other
|
|
|
3313 Lisp functions, because they modify global state in a way that's often
|
|
|
3314 undesired as part of other Lisp functions.
|
|
|
3315
|
|
|
3316 @file{callint.c} implements the mechanism for querying the user for
|
|
|
3317 parameters and calling interactive commands. The bulk of this module is
|
|
|
3318 code that parses the interactive spec that is supplied with an
|
|
|
3319 interactive command.
|
|
|
3320
|
|
|
3321 @file{cmds.c} implements the basic, most commonly used editing commands:
|
|
|
3322 commands to move around the current buffer and insert and delete
|
|
|
3323 characters. These commands are implemented using the Lisp primitives
|
|
|
3324 defined in @file{editfns.c}.
|
|
|
3325
|
|
|
3326 @file{commands.h} contains associated structure definitions and prototypes.
|
|
|
3327
|
|
|
3328
|
|
|
3329
|
|
|
3330 @example
|
|
380
|
3331 regex.c
|
|
|
3332 regex.h
|
|
|
3333 search.c
|
|
0
|
3334 @end example
|
|
|
3335
|
|
|
3336 @file{search.c} implements the Lisp primitives for searching for text in
|
|
|
3337 a buffer, and some of the low-level algorithms for doing this. In
|
|
|
3338 particular, the fast fixed-string Boyer-Moore search algorithm is
|
|
|
3339 implemented in @file{search.c}. The low-level algorithms for doing
|
|
|
3340 regular-expression searching, however, are implemented in @file{regex.c}
|
|
|
3341 and @file{regex.h}. These two modules are largely independent of
|
|
|
3342 XEmacs, and are similar to (and based upon) the regular-expression
|
|
|
3343 routines used in @file{grep} and other GNU utilities.
|
|
|
3344
|
|
|
3345
|
|
|
3346
|
|
|
3347 @example
|
|
380
|
3348 doprnt.c
|
|
0
|
3349 @end example
|
|
|
3350
|
|
|
3351 @file{doprnt.c} implements formatted-string processing, similar to
|
|
|
3352 @code{printf()} command in C.
|
|
|
3353
|
|
|
3354
|
|
|
3355
|
|
|
3356 @example
|
|
380
|
3357 undo.c
|
|
0
|
3358 @end example
|
|
|
3359
|
|
|
3360 This module implements the undo mechanism for tracking buffer changes.
|
|
|
3361 Most of this could be implemented in Lisp.
|
|
|
3362
|
|
|
3363
|
|
|
3364
|
|
398
|
3365 @node Editor-Level Control Flow Modules, Modules for the Basic Displayable Lisp Objects, Modules for Standard Editing Operations, A Summary of the Various XEmacs Modules
|
|
0
|
3366 @section Editor-Level Control Flow Modules
|
|
|
3367
|
|
|
3368 @example
|
|
380
|
3369 event-Xt.c
|
|
|
3370 event-stream.c
|
|
|
3371 event-tty.c
|
|
|
3372 events.c
|
|
|
3373 events.h
|
|
0
|
3374 @end example
|
|
|
3375
|
|
|
3376 These implement the handling of events (user input and other system
|
|
|
3377 notifications).
|
|
|
3378
|
|
2
|
3379 @file{events.c} and @file{events.h} define the @dfn{event} Lisp object
|
|
|
3380 type and primitives for manipulating it.
|
|
0
|
3381
|
|
|
3382 @file{event-stream.c} implements the basic functions for working with
|
|
|
3383 event queues, dispatching an event by looking it up in relevant keymaps
|
|
|
3384 and such, and handling timeouts; this includes the primitives
|
|
|
3385 @code{next-event} and @code{dispatch-event}, as well as related
|
|
|
3386 primitives such as @code{sit-for}, @code{sleep-for}, and
|
|
|
3387 @code{accept-process-output}. (@file{event-stream.c} is one of the
|
|
|
3388 hairiest and trickiest modules in XEmacs. Beware! You can easily mess
|
|
|
3389 things up here.)
|
|
|
3390
|
|
|
3391 @file{event-Xt.c} and @file{event-tty.c} implement the low-level
|
|
|
3392 interfaces onto retrieving events from Xt (the X toolkit) and from TTY's
|
|
|
3393 (using @code{read()} and @code{select()}), respectively. The event
|
|
|
3394 interface enforces a clean separation between the specific code for
|
|
|
3395 interfacing with the operating system and the generic code for working
|
|
|
3396 with events, by defining an API of basic, low-level event methods;
|
|
|
3397 @file{event-Xt.c} and @file{event-tty.c} are two different
|
|
|
3398 implementations of this API. To add support for a new operating system
|
|
|
3399 (e.g. NeXTstep), one merely needs to provide another implementation of
|
|
|
3400 those API functions.
|
|
|
3401
|
|
|
3402 Note that the choice of whether to use @file{event-Xt.c} or
|
|
|
3403 @file{event-tty.c} is made at compile time! Or at the very latest, it
|
|
|
3404 is made at startup time. @file{event-Xt.c} handles events for
|
|
|
3405 @emph{both} X and TTY frames; @file{event-tty.c} is only used when X
|
|
|
3406 support is not compiled into XEmacs. The reason for this is that there
|
|
|
3407 is only one event loop in XEmacs: thus, it needs to be able to receive
|
|
|
3408 events from all different kinds of frames.
|
|
|
3409
|
|
|
3410
|
|
|
3411
|
|
|
3412 @example
|
|
380
|
3413 keymap.c
|
|
|
3414 keymap.h
|
|
0
|
3415 @end example
|
|
|
3416
|
|
2
|
3417 @file{keymap.c} and @file{keymap.h} define the @dfn{keymap} Lisp object
|
|
|
3418 type and associated methods and primitives. (Remember that keymaps are
|
|
0
|
3419 objects that associate event descriptions with functions to be called to
|
|
|
3420 ``execute'' those events; @code{dispatch-event} looks up events in the
|
|
|
3421 relevant keymaps.)
|
|
|
3422
|
|
|
3423
|
|
|
3424
|
|
|
3425 @example
|
|
380
|
3426 keyboard.c
|
|
0
|
3427 @end example
|
|
|
3428
|
|
|
3429 @file{keyboard.c} contains functions that implement the actual editor
|
|
398
|
3430 command loop---i.e. the event loop that cyclically retrieves and
|
|
0
|
3431 dispatches events. This code is also rather tricky, just like
|
|
|
3432 @file{event-stream.c}.
|
|
|
3433
|
|
|
3434
|
|
|
3435
|
|
|
3436 @example
|
|
380
|
3437 macros.c
|
|
|
3438 macros.h
|
|
0
|
3439 @end example
|
|
|
3440
|
|
|
3441 These two modules contain the basic code for defining keyboard macros.
|
|
|
3442 These functions don't actually do much; most of the code that handles keyboard
|
|
|
3443 macros is mixed in with the event-handling code in @file{event-stream.c}.
|
|
|
3444
|
|
|
3445
|
|
|
3446
|
|
|
3447 @example
|
|
380
|
3448 minibuf.c
|
|
0
|
3449 @end example
|
|
|
3450
|
|
|
3451 This contains some miscellaneous code related to the minibuffer (most of
|
|
|
3452 the minibuffer code was moved into Lisp by Richard Mlynarik). This
|
|
|
3453 includes the primitives for completion (although filename completion is
|
|
|
3454 in @file{dired.c}), the lowest-level interface to the minibuffer (if the
|
|
|
3455 command loop were cleaned up, this too could be in Lisp), and code for
|
|
|
3456 dealing with the echo area (this, too, was mostly moved into Lisp, and
|
|
|
3457 the only code remaining is code to call out to Lisp or provide simple
|
|
|
3458 bootstrapping implementations early in temacs, before the echo-area Lisp
|
|
|
3459 code is loaded).
|
|
|
3460
|
|
|
3461
|
|
|
3462
|
|
398
|
3463 @node Modules for the Basic Displayable Lisp Objects, Modules for other Display-Related Lisp Objects, Editor-Level Control Flow Modules, A Summary of the Various XEmacs Modules
|
|
0
|
3464 @section Modules for the Basic Displayable Lisp Objects
|
|
|
3465
|
|
|
3466 @example
|
|
380
|
3467 device-ns.h
|
|
|
3468 device-stream.c
|
|
|
3469 device-stream.h
|
|
|
3470 device-tty.c
|
|
|
3471 device-tty.h
|
|
|
3472 device-x.c
|
|
|
3473 device-x.h
|
|
|
3474 device.c
|
|
|
3475 device.h
|
|
0
|
3476 @end example
|
|
|
3477
|
|
2
|
3478 These modules implement the @dfn{device} Lisp object type. This
|
|
|
3479 abstracts a particular screen or connection on which frames are
|
|
|
3480 displayed. As with Lisp objects, event interfaces, and other
|
|
|
3481 subsystems, the device code is separated into a generic component that
|
|
|
3482 contains a standardized interface (in the form of a set of methods) onto
|
|
|
3483 particular device types.
|
|
0
|
3484
|
|
|
3485 The device subsystem defines all the methods and provides method
|
|
|
3486 services for not only device operations but also for the frame, window,
|
|
|
3487 menubar, scrollbar, toolbar, and other displayable-object subsystems.
|
|
|
3488 The reason for this is that all of these subsystems have the same
|
|
|
3489 subtypes (X, TTY, NeXTstep, Microsoft Windows, etc.) as devices do.
|
|
|
3490
|
|
|
3491
|
|
|
3492
|
|
|
3493 @example
|
|
380
|
3494 frame-ns.h
|
|
|
3495 frame-tty.c
|
|
|
3496 frame-x.c
|
|
|
3497 frame-x.h
|
|
|
3498 frame.c
|
|
|
3499 frame.h
|
|
0
|
3500 @end example
|
|
|
3501
|
|
|
3502 Each device contains one or more frames in which objects (e.g. text) are
|
|
|
3503 displayed. A frame corresponds to a window in the window system;
|
|
|
3504 usually this is a top-level window but it could potentially be one of a
|
|
|
3505 number of overlapping child windows within a top-level window, using the
|
|
|
3506 MDI (Multiple Document Interface) protocol in Microsoft Windows or a
|
|
|
3507 similar scheme.
|
|
|
3508
|
|
2
|
3509 The @file{frame-*} files implement the @dfn{frame} Lisp object type and
|
|
|
3510 provide the generic and device-type-specific operations on frames
|
|
|
3511 (e.g. raising, lowering, resizing, moving, etc.).
|
|
0
|
3512
|
|
|
3513
|
|
|
3514
|
|
|
3515 @example
|
|
380
|
3516 window.c
|
|
|
3517 window.h
|
|
0
|
3518 @end example
|
|
|
3519
|
|
|
3520 @cindex window (in Emacs)
|
|
|
3521 @cindex pane
|
|
|
3522 Each frame consists of one or more non-overlapping @dfn{windows} (better
|
|
|
3523 known as @dfn{panes} in standard window-system terminology) in which a
|
|
|
3524 buffer's text can be displayed. Windows can also have scrollbars
|
|
|
3525 displayed around their edges.
|
|
|
3526
|
|
2
|
3527 @file{window.c} and @file{window.h} implement the @dfn{window} Lisp
|
|
|
3528 object type and provide code to manage windows. Since windows have no
|
|
0
|
3529 associated resources in the window system (the window system knows only
|
|
|
3530 about the frame; no child windows or anything are used for XEmacs
|
|
|
3531 windows), there is no device-type-specific code here; all of that code
|
|
|
3532 is part of the redisplay mechanism or the code for particular object
|
|
|
3533 types such as scrollbars.
|
|
|
3534
|
|
|
3535
|
|
|
3536
|
|
398
|
3537 @node Modules for other Display-Related Lisp Objects, Modules for the Redisplay Mechanism, Modules for the Basic Displayable Lisp Objects, A Summary of the Various XEmacs Modules
|
|
0
|
3538 @section Modules for other Display-Related Lisp Objects
|
|
|
3539
|
|
|
3540 @example
|
|
380
|
3541 faces.c
|
|
|
3542 faces.h
|
|
|
3543 @end example
|
|
|
3544
|
|
|
3545
|
|
|
3546
|
|
|
3547 @example
|
|
|
3548 bitmaps.h
|
|
|
3549 glyphs-ns.h
|
|
|
3550 glyphs-x.c
|
|
|
3551 glyphs-x.h
|
|
|
3552 glyphs.c
|
|
|
3553 glyphs.h
|
|
|
3554 @end example
|
|
|
3555
|
|
|
3556
|
|
|
3557
|
|
|
3558 @example
|
|
|
3559 objects-ns.h
|
|
|
3560 objects-tty.c
|
|
|
3561 objects-tty.h
|
|
|
3562 objects-x.c
|
|
|
3563 objects-x.h
|
|
|
3564 objects.c
|
|
|
3565 objects.h
|
|
|
3566 @end example
|
|
|
3567
|
|
|
3568
|
|
|
3569
|
|
|
3570 @example
|
|
|
3571 menubar-x.c
|
|
|
3572 menubar.c
|
|
|
3573 @end example
|
|
|
3574
|
|
|
3575
|
|
|
3576
|
|
|
3577 @example
|
|
|
3578 scrollbar-x.c
|
|
|
3579 scrollbar-x.h
|
|
|
3580 scrollbar.c
|
|
|
3581 scrollbar.h
|
|
|
3582 @end example
|
|
|
3583
|
|
|
3584
|
|
|
3585
|
|
|
3586 @example
|
|
|
3587 toolbar-x.c
|
|
|
3588 toolbar.c
|
|
|
3589 toolbar.h
|
|
|
3590 @end example
|
|
|
3591
|
|
|
3592
|
|
|
3593
|
|
|
3594 @example
|
|
|
3595 font-lock.c
|
|
0
|
3596 @end example
|
|
|
3597
|
|
398
|
3598 This file provides C support for syntax highlighting---i.e.
|
|
0
|
3599 highlighting different syntactic constructs of a source file in
|
|
|
3600 different colors, for easy reading. The C support is provided so that
|
|
|
3601 this is fast.
|
|
|
3602
|
|
|
3603
|
|
|
3604
|
|
|
3605 @example
|
|
380
|
3606 dgif_lib.c
|
|
|
3607 gif_err.c
|
|
|
3608 gif_lib.h
|
|
|
3609 gifalloc.c
|
|
0
|
3610 @end example
|
|
|
3611
|
|
|
3612 These modules decode GIF-format image files, for use with glyphs.
|
|
|
3613
|
|
|
3614
|
|
|
3615
|
|
398
|
3616 @node Modules for the Redisplay Mechanism, Modules for Interfacing with the File System, Modules for other Display-Related Lisp Objects, A Summary of the Various XEmacs Modules
|
|
0
|
3617 @section Modules for the Redisplay Mechanism
|
|
|
3618
|
|
|
3619 @example
|
|
380
|
3620 redisplay-output.c
|
|
|
3621 redisplay-tty.c
|
|
|
3622 redisplay-x.c
|
|
|
3623 redisplay.c
|
|
|
3624 redisplay.h
|
|
0
|
3625 @end example
|
|
|
3626
|
|
|
3627 These files provide the redisplay mechanism. As with many other
|
|
|
3628 subsystems in XEmacs, there is a clean separation between the general
|
|
|
3629 and device-specific support.
|
|
|
3630
|
|
|
3631 @file{redisplay.c} contains the bulk of the redisplay engine. These
|
|
|
3632 functions update the redisplay structures (which describe how the screen
|
|
|
3633 is to appear) to reflect any changes made to the state of any
|
|
|
3634 displayable objects (buffer, frame, window, etc.) since the last time
|
|
|
3635 that redisplay was called. These functions are highly optimized to
|
|
|
3636 avoid doing more work than necessary (since redisplay is called
|
|
|
3637 extremely often and is potentially a huge time sink), and depend heavily
|
|
|
3638 on notifications from the objects themselves that changes have occurred,
|
|
|
3639 so that redisplay doesn't explicitly have to check each possible object.
|
|
|
3640 The redisplay mechanism also contains a great deal of caching to further
|
|
|
3641 speed things up; some of this caching is contained within the various
|
|
|
3642 displayable objects.
|
|
|
3643
|
|
|
3644 @file{redisplay-output.c} goes through the redisplay structures and converts
|
|
|
3645 them into calls to device-specific methods to actually output the screen
|
|
|
3646 changes.
|
|
|
3647
|
|
|
3648 @file{redisplay-x.c} and @file{redisplay-tty.c} are two implementations
|
|
|
3649 of these redisplay output methods, for X frames and TTY frames,
|
|
|
3650 respectively.
|
|
|
3651
|
|
|
3652
|
|
|
3653
|
|
|
3654 @example
|
|
380
|
3655 indent.c
|
|
0
|
3656 @end example
|
|
|
3657
|
|
|
3658 This module contains various functions and Lisp primitives for
|
|
|
3659 converting between buffer positions and screen positions. These
|
|
|
3660 functions call the redisplay mechanism to do most of the work, and then
|
|
|
3661 examine the redisplay structures to get the necessary information. This
|
|
|
3662 module needs work.
|
|
|
3663
|
|
|
3664
|
|
|
3665
|
|
|
3666 @example
|
|
380
|
3667 termcap.c
|
|
|
3668 terminfo.c
|
|
|
3669 tparam.c
|
|
0
|
3670 @end example
|
|
|
3671
|
|
|
3672 These files contain functions for working with the termcap (BSD-style)
|
|
|
3673 and terminfo (System V style) databases of terminal capabilities and
|
|
|
3674 escape sequences, used when XEmacs is displaying in a TTY.
|
|
|
3675
|
|
|
3676
|
|
|
3677
|
|
|
3678 @example
|
|
380
|
3679 cm.c
|
|
|
3680 cm.h
|
|
0
|
3681 @end example
|
|
|
3682
|
|
|
3683 These files provide some miscellaneous TTY-output functions and should
|
|
|
3684 probably be merged into @file{redisplay-tty.c}.
|
|
|
3685
|
|
|
3686
|
|
|
3687
|
|
398
|
3688 @node Modules for Interfacing with the File System, Modules for Other Aspects of the Lisp Interpreter and Object System, Modules for the Redisplay Mechanism, A Summary of the Various XEmacs Modules
|
|
0
|
3689 @section Modules for Interfacing with the File System
|
|
|
3690
|
|
|
3691 @example
|
|
380
|
3692 lstream.c
|
|
|
3693 lstream.h
|
|
0
|
3694 @end example
|
|
|
3695
|
|
2
|
3696 These modules implement the @dfn{stream} Lisp object type. This is an
|
|
0
|
3697 internal-only Lisp object that implements a generic buffering stream.
|
|
|
3698 The idea is to provide a uniform interface onto all sources and sinks of
|
|
|
3699 data, including file descriptors, stdio streams, chunks of memory, Lisp
|
|
|
3700 buffers, Lisp strings, etc. That way, I/O functions can be written to
|
|
|
3701 the stream interface and can transparently handle all possible sources
|
|
|
3702 and sinks. (For example, the @code{read} function can read data from a
|
|
|
3703 file, a string, a buffer, or even a function that is called repeatedly
|
|
|
3704 to return data, without worrying about where the data is coming from or
|
|
|
3705 what-size chunks it is returned in.)
|
|
|
3706
|
|
|
3707 @cindex lstream
|
|
|
3708 Note that in the C code, streams are called @dfn{lstreams} (for ``Lisp
|
|
|
3709 streams'') to distinguish them from other kinds of streams, e.g. stdio
|
|
|
3710 streams and C++ I/O streams.
|
|
|
3711
|
|
|
3712 Similar to other subsystems in XEmacs, lstreams are separated into
|
|
|
3713 generic functions and a set of methods for the different types of
|
|
|
3714 lstreams. @file{lstream.c} provides implementations of many different
|
|
|
3715 types of streams; others are provided, e.g., in @file{mule-coding.c}.
|
|
|
3716
|
|
|
3717
|
|
|
3718
|
|
|
3719 @example
|
|
380
|
3720 fileio.c
|
|
0
|
3721 @end example
|
|
|
3722
|
|
|
3723 This implements the basic primitives for interfacing with the file
|
|
|
3724 system. This includes primitives for reading files into buffers,
|
|
|
3725 writing buffers into files, checking for the presence or accessibility
|
|
|
3726 of files, canonicalizing file names, etc. Note that these primitives
|
|
|
3727 are usually not invoked directly by the user: There is a great deal of
|
|
|
3728 higher-level Lisp code that implements the user commands such as
|
|
|
3729 @code{find-file} and @code{save-buffer}. This is similar to the
|
|
|
3730 distinction between the lower-level primitives in @file{editfns.c} and
|
|
|
3731 the higher-level user commands in @file{commands.c} and
|
|
|
3732 @file{simple.el}.
|
|
|
3733
|
|
|
3734
|
|
|
3735
|
|
|
3736 @example
|
|
380
|
3737 filelock.c
|
|
0
|
3738 @end example
|
|
|
3739
|
|
|
3740 This file provides functions for detecting clashes between different
|
|
|
3741 processes (e.g. XEmacs and some external process, or two different
|
|
|
3742 XEmacs processes) modifying the same file. (XEmacs can optionally use
|
|
|
3743 the @file{lock/} subdirectory to provide a form of ``locking'' between
|
|
|
3744 different XEmacs processes.) This module is also used by the low-level
|
|
|
3745 functions in @file{insdel.c} to ensure that, if the first modification
|
|
|
3746 is being made to a buffer whose corresponding file has been externally
|
|
|
3747 modified, the user is made aware of this so that the buffer can be
|
|
|
3748 synched up with the external changes if necessary.
|
|
|
3749
|
|
|
3750
|
|
|
3751 @example
|
|
380
|
3752 filemode.c
|
|
0
|
3753 @end example
|
|
|
3754
|
|
|
3755 This file provides some miscellaneous functions that construct a
|
|
|
3756 @samp{rwxr-xr-x}-type permissions string (as might appear in an
|
|
|
3757 @file{ls}-style directory listing) given the information returned by the
|
|
|
3758 @code{stat()} system call.
|
|
|
3759
|
|
|
3760
|
|
|
3761
|
|
|
3762 @example
|
|
380
|
3763 dired.c
|
|
|
3764 ndir.h
|
|
0
|
3765 @end example
|
|
|
3766
|
|
|
3767 These files implement the XEmacs interface to directory searching. This
|
|
|
3768 includes a number of primitives for determining the files in a directory
|
|
|
3769 and for doing filename completion. (Remember that generic completion is
|
|
|
3770 handled by a different mechanism, in @file{minibuf.c}.)
|
|
|
3771
|
|
|
3772 @file{ndir.h} is a header file used for the directory-searching
|
|
|
3773 emulation functions provided in @file{sysdep.c} (see section J below),
|
|
|
3774 for systems that don't provide any directory-searching functions. (On
|
|
|
3775 those systems, directories can be read directly as files, and parsed.)
|
|
|
3776
|
|
|
3777
|
|
|
3778
|
|
|
3779 @example
|
|
380
|
3780 realpath.c
|
|
0
|
3781 @end example
|
|
|
3782
|
|
|
3783 This file provides an implementation of the @code{realpath()} function
|
|
|
3784 for expanding symbolic links, on systems that don't implement it or have
|
|
|
3785 a broken implementation.
|
|
|
3786
|
|
|
3787
|
|
|
3788
|
|
398
|
3789 @node Modules for Other Aspects of the Lisp Interpreter and Object System, Modules for Interfacing with the Operating System, Modules for Interfacing with the File System, A Summary of the Various XEmacs Modules
|
|
0
|
3790 @section Modules for Other Aspects of the Lisp Interpreter and Object System
|
|
|
3791
|
|
|
3792 @example
|
|
380
|
3793 elhash.c
|
|
|
3794 elhash.h
|
|
|
3795 hash.c
|
|
|
3796 hash.h
|
|
|
3797 @end example
|
|
|
3798
|
|
|
3799 These files provide two implementations of hash tables. Files
|
|
2
|
3800 @file{hash.c} and @file{hash.h} provide a generic C implementation of
|
|
380
|
3801 hash tables which can stand independently of XEmacs. Files
|
|
|
3802 @file{elhash.c} and @file{elhash.h} provide a separate implementation of
|
|
|
3803 hash tables that can store only Lisp objects, and knows about Lispy
|
|
|
3804 things like garbage collection, and implement the @dfn{hash-table} Lisp
|
|
|
3805 object type.
|
|
|
3806
|
|
|
3807
|
|
|
3808 @example
|
|
|
3809 specifier.c
|
|
|
3810 specifier.h
|
|
0
|
3811 @end example
|
|
|
3812
|
|
2
|
3813 This module implements the @dfn{specifier} Lisp object type. This is
|
|
0
|
3814 primarily used for displayable properties, and allows for values that
|
|
|
3815 are specific to a particular buffer, window, frame, device, or device
|
|
|
3816 class, as well as a default value existing. This is used, for example,
|
|
|
3817 to control the height of the horizontal scrollbar or the appearance of
|
|
|
3818 the @code{default}, @code{bold}, or other faces. The specifier object
|
|
|
3819 consists of a number of specifications, each of which maps from a
|
|
|
3820 buffer, window, etc. to a value. The function @code{specifier-instance}
|
|
|
3821 looks up a value given a window (from which a buffer, frame, and device
|
|
|
3822 can be derived).
|
|
|
3823
|
|
|
3824
|
|
|
3825 @example
|
|
380
|
3826 chartab.c
|
|
|
3827 chartab.h
|
|
|
3828 casetab.c
|
|
0
|
3829 @end example
|
|
|
3830
|
|
116
|
3831 @file{chartab.c} and @file{chartab.h} implement the @dfn{char table}
|
|
|
3832 Lisp object type, which maps from characters or certain sorts of
|
|
|
3833 character ranges to Lisp objects. The implementation of this object
|
|
|
3834 type is optimized for the internal representation of characters. Char
|
|
|
3835 tables come in different types, which affect the allowed object types to
|
|
|
3836 which a character can be mapped and also dictate certain other
|
|
|
3837 properties of the char table.
|
|
0
|
3838
|
|
|
3839 @cindex case table
|
|
|
3840 @file{casetab.c} implements one sort of char table, the @dfn{case
|
|
|
3841 table}, which maps characters to other characters of possibly different
|
|
|
3842 case. These are used by XEmacs to implement case-changing primitives
|
|
|
3843 and to do case-insensitive searching.
|
|
|
3844
|
|
|
3845
|
|
|
3846
|
|
|
3847 @example
|
|
380
|
3848 syntax.c
|
|
|
3849 syntax.h
|
|
0
|
3850 @end example
|
|
|
3851
|
|
|
3852 @cindex scanner
|
|
116
|
3853 This module implements @dfn{syntax tables}, another sort of char table
|
|
|
3854 that maps characters into syntax classes that define the syntax of these
|
|
|
3855 characters (e.g. a parenthesis belongs to a class of @samp{open}
|
|
|
3856 characters that have corresponding @samp{close} characters and can be
|
|
|
3857 nested). This module also implements the Lisp @dfn{scanner}, a set of
|
|
|
3858 primitives for scanning over text based on syntax tables. This is used,
|
|
|
3859 for example, to find the matching parenthesis in a command such as
|
|
0
|
3860 @code{forward-sexp}, and by @file{font-lock.c} to locate quoted strings,
|
|
|
3861 comments, etc.
|
|
|
3862
|
|
|
3863
|
|
|
3864
|
|
|
3865 @example
|
|
380
|
3866 casefiddle.c
|
|
0
|
3867 @end example
|
|
|
3868
|
|
|
3869 This module implements various Lisp primitives for upcasing, downcasing
|
|
|
3870 and capitalizing strings or regions of buffers.
|
|
|
3871
|
|
|
3872
|
|
|
3873
|
|
|
3874 @example
|
|
380
|
3875 rangetab.c
|
|
0
|
3876 @end example
|
|
|
3877
|
|
2
|
3878 This module implements the @dfn{range table} Lisp object type, which
|
|
|
3879 provides for a mapping from ranges of integers to arbitrary Lisp
|
|
|
3880 objects.
|
|
0
|
3881
|
|
|
3882
|
|
|
3883
|
|
|
3884 @example
|
|
380
|
3885 opaque.c
|
|
|
3886 opaque.h
|
|
0
|
3887 @end example
|
|
|
3888
|
|
2
|
3889 This module implements the @dfn{opaque} Lisp object type, an
|
|
|
3890 internal-only Lisp object that encapsulates an arbitrary block of memory
|
|
|
3891 so that it can be managed by the Lisp allocation system. To create an
|
|
|
3892 opaque object, you call @code{make_opaque()}, passing a pointer to a
|
|
|
3893 block of memory. An object is created that is big enough to hold the
|
|
|
3894 memory, which is copied into the object's storage. The object will then
|
|
|
3895 stick around as long as you keep pointers to it, after which it will be
|
|
0
|
3896 automatically reclaimed.
|
|
|
3897
|
|
|
3898 @cindex mark method
|
|
|
3899 Opaque objects can also have an arbitrary @dfn{mark method} associated
|
|
|
3900 with them, in case the block of memory contains other Lisp objects that
|
|
|
3901 need to be marked for garbage-collection purposes. (If you need other
|
|
|
3902 object methods, such as a finalize method, you should just go ahead and
|
|
398
|
3903 create a new Lisp object type---it's not hard.)
|
|
0
|
3904
|
|
|
3905
|
|
|
3906
|
|
|
3907 @example
|
|
380
|
3908 abbrev.c
|
|
0
|
3909 @end example
|
|
|
3910
|
|
|
3911 This function provides a few primitives for doing dynamic abbreviation
|
|
|
3912 expansion. In XEmacs, most of the code for this has been moved into
|
|
|
3913 Lisp. Some C code remains for speed and because the primitive
|
|
|
3914 @code{self-insert-command} (which is executed for all self-inserting
|
|
|
3915 characters) hooks into the abbrev mechanism. (@code{self-insert-command}
|
|
|
3916 is itself in C only for speed.)
|
|
|
3917
|
|
|
3918
|
|
|
3919
|
|
|
3920 @example
|
|
380
|
3921 doc.c
|
|
0
|
3922 @end example
|
|
|
3923
|
|
|
3924 This function provides primitives for retrieving the documentation
|
|
|
3925 strings of functions and variables. These documentation strings contain
|
|
|
3926 certain special markers that get dynamically expanded (e.g. a
|
|
|
3927 reverse-lookup is performed on some named functions to retrieve their
|
|
|
3928 current key bindings). Some documentation strings (in particular, for
|
|
|
3929 the built-in primitives and pre-loaded Lisp functions) are stored
|
|
|
3930 externally in a file @file{DOC} in the @file{lib-src/} directory and
|
|
|
3931 need to be fetched from that file. (Part of the build stage involves
|
|
|
3932 building this file, and another part involves constructing an index for
|
|
|
3933 this file and embedding it into the executable, so that the functions in
|
|
|
3934 @file{doc.c} do not have to search the entire @file{DOC} file to find
|
|
|
3935 the appropriate documentation string.)
|
|
|
3936
|
|
|
3937
|
|
|
3938
|
|
|
3939 @example
|
|
380
|
3940 md5.c
|
|
0
|
3941 @end example
|
|
|
3942
|
|
|
3943 This function provides a Lisp primitive that implements the MD5 secure
|
|
|
3944 hashing scheme, used to create a large hash value of a string of data such that
|
|
|
3945 the data cannot be derived from the hash value. This is used for
|
|
|
3946 various security applications on the Internet.
|
|
|
3947
|
|
|
3948
|
|
|
3949
|
|
|
3950
|
|
398
|
3951 @node Modules for Interfacing with the Operating System, Modules for Interfacing with X Windows, Modules for Other Aspects of the Lisp Interpreter and Object System, A Summary of the Various XEmacs Modules
|
|
0
|
3952 @section Modules for Interfacing with the Operating System
|
|
|
3953
|
|
|
3954 @example
|
|
380
|
3955 callproc.c
|
|
|
3956 process.c
|
|
|
3957 process.h
|
|
0
|
3958 @end example
|
|
|
3959
|
|
|
3960 These modules allow XEmacs to spawn and communicate with subprocesses
|
|
|
3961 and network connections.
|
|
|
3962
|
|
|
3963 @cindex synchronous subprocesses
|
|
|
3964 @cindex subprocesses, synchronous
|
|
|
3965 @file{callproc.c} implements (through the @code{call-process}
|
|
|
3966 primitive) what are called @dfn{synchronous subprocesses}. This means
|
|
|
3967 that XEmacs runs a program, waits till it's done, and retrieves its
|
|
|
3968 output. A typical example might be calling the @file{ls} program to get
|
|
|
3969 a directory listing.
|
|
|
3970
|
|
|
3971 @cindex asynchronous subprocesses
|
|
|
3972 @cindex subprocesses, asynchronous
|
|
|
3973 @file{process.c} and @file{process.h} implement @dfn{asynchronous
|
|
|
3974 subprocesses}. This means that XEmacs starts a program and then
|
|
|
3975 continues normally, not waiting for the process to finish. Data can be
|
|
|
3976 sent to the process or retrieved from it as it's running. This is used
|
|
|
3977 for the @code{shell} command (which provides a front end onto a shell
|
|
|
3978 program such as @file{csh}), the mail and news readers implemented in
|
|
|
3979 XEmacs, etc. The result of calling @code{start-process} to start a
|
|
|
3980 subprocess is a process object, a particular kind of object used to
|
|
|
3981 communicate with the subprocess. You can send data to the process by
|
|
|
3982 passing the process object and the data to @code{send-process}, and you
|
|
|
3983 can specify what happens to data retrieved from the process by setting
|
|
|
3984 properties of the process object. (When the process sends data, XEmacs
|
|
|
3985 receives a process event, which says that there is data ready. When
|
|
|
3986 @code{dispatch-event} is called on this event, it reads the data from
|
|
|
3987 the process and does something with it, as specified by the process
|
|
|
3988 object's properties. Typically, this means inserting the data into a
|
|
|
3989 buffer or calling a function.) Another property of the process object is
|
|
|
3990 called the @dfn{sentinel}, which is a function that is called when the
|
|
|
3991 process terminates.
|
|
|
3992
|
|
|
3993 @cindex network connections
|
|
|
3994 Process objects are also used for network connections (connections to a
|
|
|
3995 process running on another machine). Network connections are started
|
|
|
3996 with @code{open-network-stream} but otherwise work just like
|
|
|
3997 subprocesses.
|
|
|
3998
|
|
|
3999
|
|
|
4000
|
|
|
4001 @example
|
|
380
|
4002 sysdep.c
|
|
|
4003 sysdep.h
|
|
0
|
4004 @end example
|
|
|
4005
|
|
|
4006 These modules implement most of the low-level, messy operating-system
|
|
|
4007 interface code. This includes various device control (ioctl) operations
|
|
|
4008 for file descriptors, TTY's, pseudo-terminals, etc. (usually this stuff
|
|
|
4009 is fairly system-dependent; thus the name of this module), and emulation
|
|
|
4010 of standard library functions and system calls on systems that don't
|
|
|
4011 provide them or have broken versions.
|
|
|
4012
|
|
|
4013
|
|
|
4014
|
|
|
4015 @example
|
|
380
|
4016 sysdir.h
|
|
|
4017 sysfile.h
|
|
|
4018 sysfloat.h
|
|
|
4019 sysproc.h
|
|
|
4020 syspwd.h
|
|
|
4021 syssignal.h
|
|
|
4022 systime.h
|
|
|
4023 systty.h
|
|
|
4024 syswait.h
|
|
0
|
4025 @end example
|
|
|
4026
|
|
|
4027 These header files provide consistent interfaces onto system-dependent
|
|
|
4028 header files and system calls. The idea is that, instead of including a
|
|
|
4029 standard header file like @file{<sys/param.h>} (which may or may not
|
|
|
4030 exist on various systems) or having to worry about whether all system
|
|
|
4031 provide a particular preprocessor constant, or having to deal with the
|
|
|
4032 four different paradigms for manipulating signals, you just include the
|
|
|
4033 appropriate @file{sys*.h} header file, which includes all the right
|
|
|
4034 system header files, defines and missing preprocessor constants,
|
|
|
4035 provides a uniform interface onto system calls, etc.
|
|
|
4036
|
|
|
4037 @file{sysdir.h} provides a uniform interface onto directory-querying
|
|
|
4038 functions. (In some cases, this is in conjunction with emulation
|
|
|
4039 functions in @file{sysdep.c}.)
|
|
|
4040
|
|
|
4041 @file{sysfile.h} includes all the necessary header files for standard
|
|
|
4042 system calls (e.g. @code{read()}), ensures that all necessary
|
|
|
4043 @code{open()} and @code{stat()} preprocessor constants are defined, and
|
|
|
4044 possibly (usually) substitutes sugared versions of @code{read()},
|
|
|
4045 @code{write()}, etc. that automatically restart interrupted I/O
|
|
|
4046 operations.
|
|
|
4047
|
|
|
4048 @file{sysfloat.h} includes the necessary header files for floating-point
|
|
|
4049 operations.
|
|
|
4050
|
|
|
4051 @file{sysproc.h} includes the necessary header files for calling
|
|
|
4052 @code{select()}, @code{fork()}, @code{execve()}, socket operations, and
|
|
|
4053 the like, and ensures that the @code{FD_*()} macros for descriptor-set
|
|
|
4054 manipulations are available.
|
|
|
4055
|
|
|
4056 @file{syspwd.h} includes the necessary header files for obtaining
|
|
|
4057 information from @file{/etc/passwd} (the functions are emulated under
|
|
|
4058 VMS).
|
|
|
4059
|
|
|
4060 @file{syssignal.h} includes the necessary header files for
|
|
|
4061 signal-handling and provides a uniform interface onto the different
|
|
|
4062 signal-handling and signal-blocking paradigms.
|
|
|
4063
|
|
|
4064 @file{systime.h} includes the necessary header files and provides
|
|
|
4065 uniform interfaces for retrieving the time of day, setting file
|
|
|
4066 access/modification times, getting the amount of time used by the XEmacs
|
|
|
4067 process, etc.
|
|
|
4068
|
|
|
4069 @file{systty.h} buffers against the infinitude of different ways of
|
|
|
4070 controlling TTY's.
|
|
|
4071
|
|
|
4072 @file{syswait.h} provides a uniform way of retrieving the exit status
|
|
|
4073 from a @code{wait()}ed-on process (some systems use a union, others use
|
|
|
4074 an int).
|
|
|
4075
|
|
|
4076
|
|
|
4077
|
|
|
4078 @example
|
|
380
|
4079 hpplay.c
|
|
|
4080 libsst.c
|
|
|
4081 libsst.h
|
|
|
4082 libst.h
|
|
|
4083 linuxplay.c
|
|
|
4084 nas.c
|
|
|
4085 sgiplay.c
|
|
|
4086 sound.c
|
|
|
4087 sunplay.c
|
|
0
|
4088 @end example
|
|
|
4089
|
|
|
4090 These files implement the ability to play various sounds on some types
|
|
|
4091 of computers. You have to configure your XEmacs with sound support in
|
|
|
4092 order to get this capability.
|
|
|
4093
|
|
|
4094 @file{sound.c} provides the generic interface. It implements various
|
|
|
4095 Lisp primitives and variables that let you specify which sounds should
|
|
|
4096 be played in certain conditions. (The conditions are identified by
|
|
|
4097 symbols, which are passed to @code{ding} to make a sound. Various
|
|
|
4098 standard functions call this function at certain times; if sound support
|
|
|
4099 does not exist, a simple beep results.
|
|
|
4100
|
|
|
4101 @cindex native sound
|
|
|
4102 @cindex sound, native
|
|
|
4103 @file{sgiplay.c}, @file{sunplay.c}, @file{hpplay.c}, and
|
|
|
4104 @file{linuxplay.c} interface to the machine's speaker for various
|
|
|
4105 different kind of machines. This is called @dfn{native} sound.
|
|
|
4106
|
|
|
4107 @cindex sound, network
|
|
|
4108 @cindex network sound
|
|
|
4109 @cindex NAS
|
|
|
4110 @file{nas.c} interfaces to a computer somewhere else on the network
|
|
|
4111 using the NAS (Network Audio Server) protocol, playing sounds on that
|
|
|
4112 machine. This allows you to run XEmacs on a remote machine, with its
|
|
|
4113 display set to your local machine, and have the sounds be made on your
|
|
|
4114 local machine, provided that you have a NAS server running on your local
|
|
|
4115 machine.
|
|
|
4116
|
|
|
4117 @file{libsst.c}, @file{libsst.h}, and @file{libst.h} provide some
|
|
|
4118 additional functions for playing sound on a Sun SPARC but are not
|
|
|
4119 currently in use.
|
|
|
4120
|
|
|
4121
|
|
|
4122
|
|
|
4123 @example
|
|
380
|
4124 tooltalk.c
|
|
|
4125 tooltalk.h
|
|
0
|
4126 @end example
|
|
|
4127
|
|
|
4128 These two modules implement an interface to the ToolTalk protocol, which
|
|
|
4129 is an interprocess communication protocol implemented on some versions
|
|
|
4130 of Unix. ToolTalk is a high-level protocol that allows processes to
|
|
|
4131 register themselves as providers of particular services; other processes
|
|
|
4132 can then request a service without knowing or caring exactly who is
|
|
|
4133 providing the service. It is similar in spirit to the DDE protocol
|
|
|
4134 provided under Microsoft Windows. ToolTalk is a part of the new CDE
|
|
|
4135 (Common Desktop Environment) specification and is used to connect the
|
|
|
4136 parts of the SPARCWorks development environment.
|
|
|
4137
|
|
|
4138
|
|
|
4139
|
|
|
4140 @example
|
|
380
|
4141 getloadavg.c
|
|
0
|
4142 @end example
|
|
|
4143
|
|
|
4144 This module provides the ability to retrieve the system's current load
|
|
|
4145 average. (The way to do this is highly system-specific, unfortunately,
|
|
|
4146 and requires a lot of special-case code.)
|
|
|
4147
|
|
|
4148
|
|
|
4149
|
|
|
4150 @example
|
|
380
|
4151 sunpro.c
|
|
0
|
4152 @end example
|
|
|
4153
|
|
|
4154 This module provides a small amount of code used internally at Sun to
|
|
|
4155 keep statistics on the usage of XEmacs.
|
|
|
4156
|
|
|
4157
|
|
|
4158
|
|
|
4159 @example
|
|
380
|
4160 broken-sun.h
|
|
|
4161 strcmp.c
|
|
|
4162 strcpy.c
|
|
|
4163 sunOS-fix.c
|
|
0
|
4164 @end example
|
|
|
4165
|
|
|
4166 These files provide replacement functions and prototypes to fix numerous
|
|
|
4167 bugs in early releases of SunOS 4.1.
|
|
|
4168
|
|
|
4169
|
|
|
4170
|
|
|
4171 @example
|
|
380
|
4172 hftctl.c
|
|
0
|
4173 @end example
|
|
|
4174
|
|
|
4175 This module provides some terminal-control code necessary on versions of
|
|
|
4176 AIX prior to 4.1.
|
|
|
4177
|
|
|
4178
|
|
|
4179
|
|
|
4180 @example
|
|
380
|
4181 msdos.c
|
|
|
4182 msdos.h
|
|
0
|
4183 @end example
|
|
|
4184
|
|
|
4185 These modules are used for MS-DOS support, which does not work in
|
|
|
4186 XEmacs.
|
|
|
4187
|
|
|
4188
|
|
|
4189
|
|
398
|
4190 @node Modules for Interfacing with X Windows, Modules for Internationalization, Modules for Interfacing with the Operating System, A Summary of the Various XEmacs Modules
|
|
0
|
4191 @section Modules for Interfacing with X Windows
|
|
|
4192
|
|
|
4193 @example
|
|
380
|
4194 Emacs.ad.h
|
|
0
|
4195 @end example
|
|
|
4196
|
|
|
4197 A file generated from @file{Emacs.ad}, which contains XEmacs-supplied
|
|
|
4198 fallback resources (so that XEmacs has pretty defaults).
|
|
|
4199
|
|
|
4200
|
|
|
4201
|
|
|
4202 @example
|
|
380
|
4203 EmacsFrame.c
|
|
|
4204 EmacsFrame.h
|
|
|
4205 EmacsFrameP.h
|
|
0
|
4206 @end example
|
|
|
4207
|
|
|
4208 These modules implement an Xt widget class that encapsulates a frame.
|
|
|
4209 This is for ease in integrating with Xt. The EmacsFrame widget covers
|
|
|
4210 the entire X window except for the menubar; the scrollbars are
|
|
|
4211 positioned on top of the EmacsFrame widget.
|
|
|
4212
|
|
|
4213 @strong{Warning:} Abandon hope, all ye who enter here. This code took
|
|
|
4214 an ungodly amount of time to get right, and is likely to fall apart
|
|
|
4215 mercilessly at the slightest change. Such is life under Xt.
|
|
|
4216
|
|
|
4217
|
|
|
4218
|
|
|
4219 @example
|
|
380
|
4220 EmacsManager.c
|
|
|
4221 EmacsManager.h
|
|
|
4222 EmacsManagerP.h
|
|
0
|
4223 @end example
|
|
|
4224
|
|
|
4225 These modules implement a simple Xt manager (i.e. composite) widget
|
|
|
4226 class that simply lets its children set whatever geometry they want.
|
|
|
4227 It's amazing that Xt doesn't provide this standardly, but on second
|
|
|
4228 thought, it makes sense, considering how amazingly broken Xt is.
|
|
|
4229
|
|
|
4230
|
|
|
4231 @example
|
|
380
|
4232 EmacsShell-sub.c
|
|
|
4233 EmacsShell.c
|
|
|
4234 EmacsShell.h
|
|
|
4235 EmacsShellP.h
|
|
0
|
4236 @end example
|
|
|
4237
|
|
|
4238 These modules implement two Xt widget classes that are subclasses of
|
|
|
4239 the TopLevelShell and TransientShell classes. This is necessary to deal
|
|
|
4240 with more brokenness that Xt has sadistically thrust onto the backs of
|
|
|
4241 developers.
|
|
|
4242
|
|
|
4243
|
|
|
4244
|
|
|
4245 @example
|
|
380
|
4246 xgccache.c
|
|
|
4247 xgccache.h
|
|
0
|
4248 @end example
|
|
|
4249
|
|
|
4250 These modules provide functions for maintenance and caching of GC's
|
|
|
4251 (graphics contexts) under the X Window System. This code is junky and
|
|
|
4252 needs to be rewritten.
|
|
|
4253
|
|
|
4254
|
|
|
4255
|
|
|
4256 @example
|
|
380
|
4257 xselect.c
|
|
0
|
4258 @end example
|
|
|
4259
|
|
|
4260 @cindex selections
|
|
|
4261 This module provides an interface to the X Window System's concept of
|
|
|
4262 @dfn{selections}, the standard way for X applications to communicate
|
|
|
4263 with each other.
|
|
|
4264
|
|
|
4265
|
|
|
4266
|
|
|
4267 @example
|
|
380
|
4268 xintrinsic.h
|
|
|
4269 xintrinsicp.h
|
|
|
4270 xmmanagerp.h
|
|
|
4271 xmprimitivep.h
|
|
0
|
4272 @end example
|
|
|
4273
|
|
|
4274 These header files are similar in spirit to the @file{sys*.h} files and buffer
|
|
|
4275 against different implementations of Xt and Motif.
|
|
|
4276
|
|
|
4277 @itemize @bullet
|
|
|
4278 @item
|
|
|
4279 @file{xintrinsic.h} should be included in place of @file{<Intrinsic.h>}.
|
|
|
4280 @item
|
|
|
4281 @file{xintrinsicp.h} should be included in place of @file{<IntrinsicP.h>}.
|
|
|
4282 @item
|
|
|
4283 @file{xmmanagerp.h} should be included in place of @file{<XmManagerP.h>}.
|
|
|
4284 @item
|
|
|
4285 @file{xmprimitivep.h} should be included in place of @file{<XmPrimitiveP.h>}.
|
|
|
4286 @end itemize
|
|
|
4287
|
|
|
4288
|
|
|
4289
|
|
|
4290 @example
|
|
380
|
4291 xmu.c
|
|
|
4292 xmu.h
|
|
0
|
4293 @end example
|
|
|
4294
|
|
|
4295 These files provide an emulation of the Xmu library for those systems
|
|
|
4296 (i.e. HPUX) that don't provide it as a standard part of X.
|
|
|
4297
|
|
|
4298
|
|
|
4299
|
|
|
4300 @example
|
|
380
|
4301 ExternalClient-Xlib.c
|
|
|
4302 ExternalClient.c
|
|
|
4303 ExternalClient.h
|
|
|
4304 ExternalClientP.h
|
|
|
4305 ExternalShell.c
|
|
|
4306 ExternalShell.h
|
|
|
4307 ExternalShellP.h
|
|
|
4308 extw-Xlib.c
|
|
|
4309 extw-Xlib.h
|
|
|
4310 extw-Xt.c
|
|
|
4311 extw-Xt.h
|
|
0
|
4312 @end example
|
|
|
4313
|
|
|
4314 @cindex external widget
|
|
|
4315 These files provide the @dfn{external widget} interface, which allows an
|
|
|
4316 XEmacs frame to appear as a widget in another application. To do this,
|
|
|
4317 you have to configure with @samp{--external-widget}.
|
|
|
4318
|
|
|
4319 @file{ExternalShell*} provides the server (XEmacs) side of the
|
|
|
4320 connection.
|
|
|
4321
|
|
|
4322 @file{ExternalClient*} provides the client (other application) side of
|
|
|
4323 the connection. These files are not compiled into XEmacs but are
|
|
|
4324 compiled into libraries that are then linked into your application.
|
|
|
4325
|
|
|
4326 @file{extw-*} is common code that is used for both the client and server.
|
|
|
4327
|
|
|
4328 Don't touch this code; something is liable to break if you do.
|
|
|
4329
|
|
|
4330
|
|
|
4331
|
|
398
|
4332 @node Modules for Internationalization, , Modules for Interfacing with X Windows, A Summary of the Various XEmacs Modules
|
|
0
|
4333 @section Modules for Internationalization
|
|
|
4334
|
|
|
4335 @example
|
|
380
|
4336 mule-canna.c
|
|
|
4337 mule-ccl.c
|
|
|
4338 mule-charset.c
|
|
|
4339 mule-charset.h
|
|
|
4340 mule-coding.c
|
|
|
4341 mule-coding.h
|
|
|
4342 mule-mcpath.c
|
|
|
4343 mule-mcpath.h
|
|
|
4344 mule-wnnfns.c
|
|
|
4345 mule.c
|
|
0
|
4346 @end example
|
|
|
4347
|
|
|
4348 These files implement the MULE (Asian-language) support. Note that MULE
|
|
|
4349 actually provides a general interface for all sorts of languages, not
|
|
|
4350 just Asian languages (although they are generally the most complicated
|
|
|
4351 to support). This code is still in beta.
|
|
|
4352
|
|
|
4353 @file{mule-charset.*} and @file{mule-coding.*} provide the heart of the
|
|
2
|
4354 XEmacs MULE support. @file{mule-charset.*} implements the @dfn{charset}
|
|
|
4355 Lisp object type, which encapsulates a character set (an ordered one- or
|
|
|
4356 two-dimensional set of characters, such as US ASCII or JISX0208 Japanese
|
|
380
|
4357 Kanji).
|
|
2
|
4358
|
|
|
4359 @file{mule-coding.*} implements the @dfn{coding-system} Lisp object
|
|
|
4360 type, which encapsulates a method of converting between different
|
|
116
|
4361 encodings. An encoding is a representation of a stream of characters,
|
|
|
4362 possibly from multiple character sets, using a stream of bytes or words,
|
|
|
4363 and defines (e.g.) which escape sequences are used to specify particular
|
|
2
|
4364 character sets, how the indices for a character are converted into bytes
|
|
|
4365 (sometimes this involves setting the high bit; sometimes complicated
|
|
|
4366 rearranging of the values takes place, as in the Shift-JIS encoding),
|
|
|
4367 etc.
|
|
0
|
4368
|
|
|
4369 @file{mule-ccl.c} provides the CCL (Code Conversion Language)
|
|
|
4370 interpreter. CCL is similar in spirit to Lisp byte code and is used to
|
|
|
4371 implement converters for custom encodings.
|
|
|
4372
|
|
|
4373 @file{mule-canna.c} and @file{mule-wnnfns.c} implement interfaces to
|
|
|
4374 external programs used to implement the Canna and WNN input methods,
|
|
116
|
4375 respectively. This is currently in beta.
|
|
44
|
4376
|
|
|
4377 @file{mule-mcpath.c} provides some functions to allow for pathnames
|
|
|
4378 containing extended characters. This code is fragmentary, obsolete, and
|
|
|
4379 completely non-working. Instead, @var{pathname-coding-system} is used
|
|
|
4380 to specify conversions of names of files and directories. The standard
|
|
|
4381 C I/O functions like @samp{open()} are wrapped so that conversion occurs
|
|
|
4382 automatically.
|
|
0
|
4383
|
|
|
4384 @file{mule.c} provides a few miscellaneous things that should probably
|
|
|
4385 be elsewhere.
|
|
|
4386
|
|
|
4387
|
|
|
4388
|
|
|
4389 @example
|
|
380
|
4390 intl.c
|
|
0
|
4391 @end example
|
|
|
4392
|
|
|
4393 This provides some miscellaneous internationalization code for
|
|
|
4394 implementing message translation and interfacing to the Ximp input
|
|
|
4395 method. None of this code is currently working.
|
|
|
4396
|
|
|
4397
|
|
|
4398
|
|
|
4399 @example
|
|
380
|
4400 iso-wide.h
|
|
0
|
4401 @end example
|
|
|
4402
|
|
|
4403 This contains leftover code from an earlier implementation of
|
|
|
4404 Asian-language support, and is not currently used.
|
|
|
4405
|
|
|
4406
|
|
|
4407
|
|
|
4408
|
|
398
|
4409 @node Allocation of Objects in XEmacs Lisp, Dumping, A Summary of the Various XEmacs Modules, Top
|
|
0
|
4410 @chapter Allocation of Objects in XEmacs Lisp
|
|
|
4411
|
|
|
4412 @menu
|
|
|
4413 * Introduction to Allocation::
|
|
|
4414 * Garbage Collection::
|
|
|
4415 * GCPROing::
|
|
398
|
4416 * Garbage Collection - Step by Step::
|
|
0
|
4417 * Integers and Characters::
|
|
|
4418 * Allocation from Frob Blocks::
|
|
|
4419 * lrecords::
|
|
|
4420 * Low-level allocation::
|
|
|
4421 * Pure Space::
|
|
|
4422 * Cons::
|
|
|
4423 * Vector::
|
|
|
4424 * Bit Vector::
|
|
|
4425 * Symbol::
|
|
|
4426 * Marker::
|
|
|
4427 * String::
|
|
380
|
4428 * Compiled Function::
|
|
0
|
4429 @end menu
|
|
|
4430
|
|
398
|
4431 @node Introduction to Allocation, Garbage Collection, Allocation of Objects in XEmacs Lisp, Allocation of Objects in XEmacs Lisp
|
|
0
|
4432 @section Introduction to Allocation
|
|
|
4433
|
|
|
4434 Emacs Lisp, like all Lisps, has garbage collection. This means that
|
|
|
4435 the programmer never has to explicitly free (destroy) an object; it
|
|
|
4436 happens automatically when the object becomes inaccessible. Most
|
|
|
4437 experts agree that garbage collection is a necessity in a modern,
|
|
|
4438 high-level language. Its omission from C stems from the fact that C was
|
|
|
4439 originally designed to be a nice abstract layer on top of assembly
|
|
|
4440 language, for writing kernels and basic system utilities rather than
|
|
|
4441 large applications.
|
|
|
4442
|
|
|
4443 Lisp objects can be created by any of a number of Lisp primitives.
|
|
|
4444 Most object types have one or a small number of basic primitives
|
|
|
4445 for creating objects. For conses, the basic primitive is @code{cons};
|
|
|
4446 for vectors, the primitives are @code{make-vector} and @code{vector}; for
|
|
|
4447 symbols, the primitives are @code{make-symbol} and @code{intern}; etc.
|
|
|
4448 Some Lisp objects, especially those that are primarily used internally,
|
|
|
4449 have no corresponding Lisp primitives. Every Lisp object, though,
|
|
|
4450 has at least one C primitive for creating it.
|
|
|
4451
|
|
|
4452 Recall from section (VII) that a Lisp object, as stored in a 32-bit
|
|
|
4453 or 64-bit word, has a mark bit, a few tag bits, and a ``value'' that
|
|
|
4454 occupies the remainder of the bits. We can separate the different
|
|
|
4455 Lisp object types into four broad categories:
|
|
|
4456
|
|
|
4457 @itemize @bullet
|
|
|
4458 @item
|
|
|
4459 (a) Those for whom the value directly represents the contents of the
|
|
|
4460 Lisp object. Only two types are in this category: integers and
|
|
|
4461 characters. No special allocation or garbage collection is necessary
|
|
380
|
4462 for such objects. Lisp objects of these types do not need to be
|
|
116
|
4463 @code{GCPRO}ed.
|
|
0
|
4464 @end itemize
|
|
|
4465
|
|
|
4466 In the remaining three categories, the value is a pointer to a
|
|
|
4467 structure.
|
|
|
4468
|
|
|
4469 @itemize @bullet
|
|
|
4470 @item
|
|
|
4471 @cindex frob block
|
|
|
4472 (b) Those for whom the tag directly specifies the type. Recall that
|
|
|
4473 there are only three tag bits; this means that at most five types can be
|
|
|
4474 specified this way. The most commonly-used types are stored in this
|
|
|
4475 format; this includes conses, strings, vectors, and sometimes symbols.
|
|
|
4476 With the exception of vectors, objects in this category are allocated in
|
|
|
4477 @dfn{frob blocks}, i.e. large blocks of memory that are subdivided into
|
|
|
4478 individual objects. This saves a lot on malloc overhead, since there
|
|
|
4479 are typically quite a lot of these objects around, and the objects are
|
|
398
|
4480 small. (A cons, for example, occupies 8 bytes on 32-bit machines---4
|
|
0
|
4481 bytes for each of the two objects it contains.) Vectors are individually
|
|
|
4482 @code{malloc()}ed since they are of variable size. (It would be
|
|
|
4483 possible, and desirable, to allocate vectors of certain small sizes out
|
|
|
4484 of frob blocks, but it isn't currently done.) Strings are handled
|
|
|
4485 specially: Each string is allocated in two parts, a fixed size structure
|
|
|
4486 containing a length and a data pointer, and the actual data of the
|
|
|
4487 string. The former structure is allocated in frob blocks as usual, and
|
|
|
4488 the latter data is stored in @dfn{string chars blocks} and is relocated
|
|
|
4489 during garbage collection to eliminate holes.
|
|
|
4490 @end itemize
|
|
|
4491
|
|
|
4492 In the remaining two categories, the type is stored in the object
|
|
|
4493 itself. The tag for all such objects is the generic @dfn{lrecord}
|
|
|
4494 (Lisp_Record) tag. The first four bytes (or eight, for 64-bit machines)
|
|
|
4495 of the object's structure are a pointer to a structure that describes
|
|
|
4496 the object's type, which includes method pointers and a pointer to a
|
|
|
4497 string naming the type. Note that it's possible to save some space by
|
|
|
4498 using a one- or two-byte tag, rather than a four- or eight-byte pointer
|
|
|
4499 to store the type, but it's not clear it's worth making the change.
|
|
|
4500
|
|
|
4501 @itemize @bullet
|
|
|
4502 @item
|
|
|
4503 (c) Those lrecords that are allocated in frob blocks (see above). This
|
|
|
4504 includes the objects that are most common and relatively small, and
|
|
380
|
4505 includes floats, compiled functions, symbols (when not in category (b)),
|
|
|
4506 extents, events, and markers. With the cleanup of frob blocks done in
|
|
|
4507 19.12, it's not terribly hard to add more objects to this category, but
|
|
|
4508 it's a bit trickier than adding an object type to type (d) (esp. if the
|
|
|
4509 object needs a finalization method), and is not likely to save much
|
|
|
4510 space unless the object is small and there are many of them. (In fact,
|
|
|
4511 if there are very few of them, it might actually waste space.)
|
|
0
|
4512 @item
|
|
|
4513 (d) Those lrecords that are individually @code{malloc()}ed. These are
|
|
|
4514 called @dfn{lcrecords}. All other types are in this category. Adding a
|
|
|
4515 new type to this category is comparatively easy, and all types added
|
|
|
4516 since 19.8 (when the current allocation scheme was devised, by Richard
|
|
|
4517 Mlynarik), with the exception of the character type, have been in this
|
|
|
4518 category.
|
|
|
4519 @end itemize
|
|
|
4520
|
|
|
4521 Note that bit vectors are a bit of a special case. They are
|
|
|
4522 simple lrecords as in category (c), but are individually @code{malloc()}ed
|
|
|
4523 like vectors. You can basically view them as exactly like vectors
|
|
|
4524 except that their type is stored in lrecord fashion rather than
|
|
|
4525 in directly-tagged fashion.
|
|
|
4526
|
|
|
4527 Note that FSF Emacs redesigned their object system in 19.29 to follow
|
|
|
4528 a similar scheme. However, given RMS's expressed dislike for data
|
|
|
4529 abstraction, the FSF scheme is not nearly as clean or as easy to
|
|
|
4530 extend. (FSF calls items of type (c) @code{Lisp_Misc} and items of type
|
|
|
4531 (d) @code{Lisp_Vectorlike}, with separate tags for each, although
|
|
|
4532 @code{Lisp_Vectorlike} is also used for vectors.)
|
|
|
4533
|
|
398
|
4534 @node Garbage Collection, GCPROing, Introduction to Allocation, Allocation of Objects in XEmacs Lisp
|
|
0
|
4535 @section Garbage Collection
|
|
|
4536 @cindex garbage collection
|
|
|
4537
|
|
|
4538 @cindex mark and sweep
|
|
|
4539 Garbage collection is simple in theory but tricky to implement.
|
|
|
4540 Emacs Lisp uses the oldest garbage collection method, called
|
|
|
4541 @dfn{mark and sweep}. Garbage collection begins by starting with
|
|
|
4542 all accessible locations (i.e. all variables and other slots where
|
|
|
4543 Lisp objects might occur) and recursively traversing all objects
|
|
|
4544 accessible from those slots, marking each one that is found.
|
|
|
4545 We then go through all of memory and free each object that is
|
|
|
4546 not marked, and unmarking each object that is marked. Note
|
|
|
4547 that ``all of memory'' means all currently allocated objects.
|
|
|
4548 Traversing all these objects means traversing all frob blocks,
|
|
|
4549 all vectors (which are chained in one big list), and all
|
|
|
4550 lcrecords (which are likewise chained).
|
|
|
4551
|
|
|
4552 Note that, when an object is marked, the mark has to occur
|
|
|
4553 inside of the object's structure, rather than in the 32-bit
|
|
|
4554 @code{Lisp_Object} holding the object's pointer; i.e. you can't just
|
|
|
4555 set the pointer's mark bit. This is because there may be many
|
|
|
4556 pointers to the same object. This means that the method of
|
|
|
4557 marking an object can differ depending on the type. The
|
|
|
4558 different marking methods are approximately as follows:
|
|
|
4559
|
|
|
4560 @enumerate
|
|
|
4561 @item
|
|
|
4562 For conses, the mark bit of the car is set.
|
|
|
4563 @item
|
|
|
4564 For strings, the mark bit of the string's plist is set.
|
|
|
4565 @item
|
|
|
4566 For symbols when not lrecords, the mark bit of the
|
|
|
4567 symbol's plist is set.
|
|
|
4568 @item
|
|
|
4569 For vectors, the length is negated after adding 1.
|
|
|
4570 @item
|
|
|
4571 For lrecords, the pointer to the structure describing
|
|
|
4572 the type is changed (see below).
|
|
|
4573 @item
|
|
|
4574 Integers and characters do not need to be marked, since
|
|
|
4575 no allocation occurs for them.
|
|
|
4576 @end enumerate
|
|
|
4577
|
|
|
4578 The details of this are in the @code{mark_object()} function.
|
|
|
4579
|
|
|
4580 Note that any code that operates during garbage collection has
|
|
|
4581 to be especially careful because of the fact that some objects
|
|
|
4582 may be marked and as such may not look like they normally do.
|
|
|
4583 In particular:
|
|
|
4584
|
|
|
4585 @itemize @bullet
|
|
|
4586 Some object pointers may have their mark bit set. This will make
|
|
|
4587 @code{FOOBARP()} predicates fail. Use @code{GC_FOOBARP()} to deal with
|
|
|
4588 this.
|
|
|
4589 @item
|
|
|
4590 Even if you clear the mark bit, @code{FOOBARP()} will still fail
|
|
|
4591 for lrecords because the implementation pointer has been
|
|
|
4592 changed (see below). @code{GC_FOOBARP()} will correctly deal with
|
|
|
4593 this.
|
|
|
4594 @item
|
|
|
4595 Vectors have their size field munged, so anything that
|
|
|
4596 looks at this field will fail.
|
|
|
4597 @item
|
|
|
4598 Note that @code{XFOOBAR()} macros @emph{will} work correctly on object
|
|
|
4599 pointers with their mark bit set, because the logical shift operations
|
|
|
4600 that remove the tag also remove the mark bit.
|
|
|
4601 @end itemize
|
|
|
4602
|
|
|
4603 Finally, note that garbage collection can be invoked explicitly
|
|
|
4604 by calling @code{garbage-collect} but is also called automatically
|
|
|
4605 by @code{eval}, once a certain amount of memory has been allocated
|
|
|
4606 since the last garbage collection (according to @code{gc-cons-threshold}).
|
|
|
4607
|
|
398
|
4608 @node GCPROing, Garbage Collection - Step by Step, Garbage Collection, Allocation of Objects in XEmacs Lisp
|
|
0
|
4609 @section @code{GCPRO}ing
|
|
|
4610
|
|
|
4611 @code{GCPRO}ing is one of the ugliest and trickiest parts of Emacs
|
|
|
4612 internals. The basic idea is that whenever garbage collection
|
|
|
4613 occurs, all in-use objects must be reachable somehow or
|
|
|
4614 other from one of the roots of accessibility. The roots
|
|
|
4615 of accessibility are:
|
|
|
4616
|
|
|
4617 @enumerate
|
|
|
4618 @item
|
|
|
4619 All objects that have been @code{staticpro()}d. This is used for
|
|
|
4620 any global C variables that hold Lisp objects. A call to
|
|
|
4621 @code{staticpro()} happens implicitly as a result of any symbols
|
|
|
4622 declared with @code{defsymbol()} and any variables declared with
|
|
|
4623 @code{DEFVAR_FOO()}. You need to explicitly call @code{staticpro()}
|
|
|
4624 (in the @code{vars_of_foo()} method of a module) for other global
|
|
|
4625 C variables holding Lisp objects. (This typically includes
|
|
|
4626 internal lists and such things.)
|
|
|
4627
|
|
|
4628 Note that @code{obarray} is one of the @code{staticpro()}d things.
|
|
|
4629 Therefore, all functions and variables get marked through this.
|
|
|
4630 @item
|
|
272
|
4631 Any shadowed bindings that are sitting on the @code{specpdl} stack.
|
|
0
|
4632 @item
|
|
116
|
4633 Any objects sitting in currently active (Lisp) stack frames,
|
|
0
|
4634 catches, and condition cases.
|
|
|
4635 @item
|
|
|
4636 A couple of special-case places where active objects are
|
|
|
4637 located.
|
|
|
4638 @item
|
|
|
4639 Anything currently marked with @code{GCPRO}.
|
|
|
4640 @end enumerate
|
|
|
4641
|
|
|
4642 Marking with @code{GCPRO} is necessary because some C functions (quite
|
|
|
4643 a lot, in fact), allocate objects during their operation. Quite
|
|
|
4644 frequently, there will be no other pointer to the object while the
|
|
|
4645 function is running, and if a garbage collection occurs and the object
|
|
|
4646 needs to be referenced again, bad things will happen. The solution is
|
|
|
4647 to mark those objects with @code{GCPRO}. Unfortunately this is easy to
|
|
|
4648 forget, and there is basically no way around this problem. Here are
|
|
|
4649 some rules, though:
|
|
|
4650
|
|
|
4651 @enumerate
|
|
|
4652 @item
|
|
|
4653 For every @code{GCPRO@var{n}}, there have to be declarations of
|
|
|
4654 @code{struct gcpro gcpro1, gcpro2}, etc.
|
|
|
4655
|
|
|
4656 @item
|
|
|
4657 You @emph{must} @code{UNGCPRO} anything that's @code{GCPRO}ed, and you
|
|
|
4658 @emph{must not} @code{UNGCPRO} if you haven't @code{GCPRO}ed. Getting
|
|
|
4659 either of these wrong will lead to crashes, often in completely random
|
|
|
4660 places unrelated to where the problem lies.
|
|
|
4661
|
|
|
4662 @item
|
|
|
4663 The way this actually works is that all currently active @code{GCPRO}s
|
|
|
4664 are chained through the @code{struct gcpro} local variables, with the
|
|
|
4665 variable @samp{gcprolist} pointing to the head of the list and the nth
|
|
|
4666 local @code{gcpro} variable pointing to the first @code{gcpro} variable
|
|
|
4667 in the next enclosing stack frame. Each @code{GCPRO}ed thing is an
|
|
|
4668 lvalue, and the @code{struct gcpro} local variable contains a pointer to
|
|
|
4669 this lvalue. This is why things will mess up badly if you don't pair up
|
|
398
|
4670 the @code{GCPRO}s and @code{UNGCPRO}s---you will end up with
|
|
0
|
4671 @code{gcprolist}s containing pointers to @code{struct gcpro}s or local
|
|
|
4672 @code{Lisp_Object} variables in no-longer-active stack frames.
|
|
|
4673
|
|
|
4674 @item
|
|
|
4675 It is actually possible for a single @code{struct gcpro} to
|
|
|
4676 protect a contiguous array of any number of values, rather than
|
|
|
4677 just a single lvalue. To effect this, call @code{GCPRO@var{n}} as usual on
|
|
272
|
4678 the first object in the array and then set @code{gcpro@var{n}.nvars}.
|
|
0
|
4679
|
|
|
4680 @item
|
|
|
4681 @strong{Strings are relocated.} What this means in practice is that the
|
|
116
|
4682 pointer obtained using @code{XSTRING_DATA()} is liable to change at any
|
|
0
|
4683 time, and you should never keep it around past any function call, or
|
|
|
4684 pass it as an argument to any function that might cause a garbage
|
|
|
4685 collection. This is why a number of functions accept either a
|
|
|
4686 ``non-relocatable'' @code{char *} pointer or a relocatable Lisp string,
|
|
|
4687 and only access the Lisp string's data at the very last minute. In some
|
|
|
4688 cases, you may end up having to @code{alloca()} some space and copy the
|
|
|
4689 string's data into it.
|
|
|
4690
|
|
|
4691 @item
|
|
|
4692 By convention, if you have to nest @code{GCPRO}'s, use @code{NGCPRO@var{n}}
|
|
|
4693 (along with @code{struct gcpro ngcpro1, ngcpro2}, etc.), @code{NNGCPRO@var{n}},
|
|
|
4694 etc. This avoids compiler warnings about shadowed locals.
|
|
|
4695
|
|
|
4696 @item
|
|
|
4697 It is @emph{always} better to err on the side of extra @code{GCPRO}s
|
|
|
4698 rather than too few. The extra cycles spent on this are
|
|
|
4699 almost never going to make a whit of difference in the
|
|
|
4700 speed of anything.
|
|
|
4701
|
|
|
4702 @item
|
|
|
4703 The general rule to follow is that caller, not callee, @code{GCPRO}s.
|
|
|
4704 That is, you should not have to explicitly @code{GCPRO} any Lisp objects
|
|
265
|
4705 that are passed in as parameters.
|
|
|
4706
|
|
|
4707 One exception from this rule is if you ever plan to change the parameter
|
|
|
4708 value, and store a new object in it. In that case, you @emph{must}
|
|
|
4709 @code{GCPRO} the parameter, because otherwise the new object will not be
|
|
|
4710 protected.
|
|
|
4711
|
|
|
4712 So, if you create any Lisp objects (remember, this happens in all sorts
|
|
|
4713 of circumstances, e.g. with @code{Fcons()}, etc.), you are responsible
|
|
|
4714 for @code{GCPRO}ing them, unless you are @emph{absolutely sure} that
|
|
|
4715 there's no possibility that a garbage-collection can occur while you
|
|
|
4716 need to use the object. Even then, consider @code{GCPRO}ing.
|
|
0
|
4717
|
|
|
4718 @item
|
|
|
4719 A garbage collection can occur whenever anything calls @code{Feval}, or
|
|
|
4720 whenever a QUIT can occur where execution can continue past
|
|
|
4721 this. (Remember, this is almost anywhere.)
|
|
|
4722
|
|
|
4723 @item
|
|
|
4724 If you have the @emph{least smidgeon of doubt} about whether
|
|
|
4725 you need to @code{GCPRO}, you should @code{GCPRO}.
|
|
|
4726
|
|
|
4727 @item
|
|
|
4728 Beware of @code{GCPRO}ing something that is uninitialized. If you have
|
|
116
|
4729 any shade of doubt about this, initialize all your variables to @code{Qnil}.
|
|
0
|
4730
|
|
|
4731 @item
|
|
|
4732 Be careful of traps, like calling @code{Fcons()} in the argument to
|
|
|
4733 another function. By the ``caller protects'' law, you should be
|
|
|
4734 @code{GCPRO}ing the newly-created cons, but you aren't. A certain
|
|
|
4735 number of functions that are commonly called on freshly created stuff
|
|
|
4736 (e.g. @code{nconc2()}, @code{Fsignal()}), break the ``caller protects''
|
|
|
4737 law and go ahead and @code{GCPRO} their arguments so as to simplify
|
|
|
4738 things, but make sure and check if it's OK whenever doing something like
|
|
|
4739 this.
|
|
|
4740
|
|
|
4741 @item
|
|
|
4742 Once again, remember to @code{GCPRO}! Bugs resulting from insufficient
|
|
|
4743 @code{GCPRO}ing are intermittent and extremely difficult to track down,
|
|
|
4744 often showing up in crashes inside of @code{garbage-collect} or in
|
|
|
4745 weirdly corrupted objects or even in incorrect values in a totally
|
|
|
4746 different section of code.
|
|
|
4747 @end enumerate
|
|
|
4748
|
|
|
4749 @cindex garbage collection, conservative
|
|
|
4750 @cindex conservative garbage collection
|
|
|
4751 Given the extremely error-prone nature of the @code{GCPRO} scheme, and
|
|
|
4752 the difficulties in tracking down, it should be considered a deficiency
|
|
|
4753 in the XEmacs code. A solution to this problem would involve
|
|
|
4754 implementing so-called @dfn{conservative} garbage collection for the C
|
|
|
4755 stack. That involves looking through all of stack memory and treating
|
|
|
4756 anything that looks like a reference to an object as a reference. This
|
|
|
4757 will result in a few objects not getting collected when they should, but
|
|
|
4758 it obviates the need for @code{GCPRO}ing, and allows garbage collection
|
|
|
4759 to happen at any point at all, such as during object allocation.
|
|
|
4760
|
|
398
|
4761 @node Garbage Collection - Step by Step, Integers and Characters, GCPROing, Allocation of Objects in XEmacs Lisp
|
|
|
4762 @section Garbage Collection - Step by Step
|
|
|
4763 @cindex garbage collection step by step
|
|
|
4764
|
|
|
4765 @menu
|
|
|
4766 * Invocation::
|
|
|
4767 * garbage_collect_1::
|
|
|
4768 * mark_object::
|
|
|
4769 * gc_sweep::
|
|
|
4770 * sweep_lcrecords_1::
|
|
|
4771 * compact_string_chars::
|
|
|
4772 * sweep_strings::
|
|
|
4773 * sweep_bit_vectors_1::
|
|
|
4774 @end menu
|
|
|
4775
|
|
|
4776 @node Invocation, garbage_collect_1, Garbage Collection - Step by Step, Garbage Collection - Step by Step
|
|
|
4777 @subsection Invocation
|
|
|
4778 @cindex garbage collection, invocation
|
|
|
4779
|
|
|
4780 The first thing that anyone should know about garbage collection is:
|
|
|
4781 when and how the garbage collector is invoked. One might think that this
|
|
|
4782 could happen every time new memory is allocated, e.g. new objects are
|
|
|
4783 created, but this is @emph{not} the case. Instead, we have the following
|
|
|
4784 situation:
|
|
|
4785
|
|
|
4786 The entry point of any process of garbage collection is an invocation
|
|
|
4787 of the function @code{garbage_collect_1} in file @code{alloc.c}. The
|
|
|
4788 invocation can occur @emph{explicitly} by calling the function
|
|
|
4789 @code{Fgarbage_collect} (in addition this function provides information
|
|
|
4790 about the freed memory), or can occur @emph{implicitly} in four different
|
|
|
4791 situations:
|
|
|
4792 @enumerate
|
|
|
4793 @item
|
|
|
4794 In function @code{main_1} in file @code{emacs.c}. This function is called
|
|
|
4795 at each startup of xemacs. The garbage collection is invoked after all
|
|
|
4796 initial creations are completed, but only if a special internal error
|
|
|
4797 checking-constant @code{ERROR_CHECK_GC} is defined.
|
|
|
4798 @item
|
|
|
4799 In function @code{disksave_object_finalization} in file
|
|
|
4800 @code{alloc.c}. The only purpose of this function is to clear the
|
|
|
4801 objects from memory which need not be stored with xemacs when we dump out
|
|
|
4802 an executable. This is only done by @code{Fdump_emacs} or by
|
|
|
4803 @code{Fdump_emacs_data} respectively (both in @code{emacs.c}). The
|
|
|
4804 actual clearing is accomplished by making these objects unreachable and
|
|
|
4805 starting a garbage collection. The function is only used while building
|
|
|
4806 xemacs.
|
|
|
4807 @item
|
|
|
4808 In function @code{Feval / eval} in file @code{eval.c}. Each time the
|
|
|
4809 well known and often used function eval is called to evaluate a form,
|
|
|
4810 one of the first things that could happen, is a potential call of
|
|
|
4811 @code{garbage_collect_1}. There exist three global variables,
|
|
|
4812 @code{consing_since_gc} (counts the created cons-cells since the last
|
|
|
4813 garbage collection), @code{gc_cons_threshold} (a specified threshold
|
|
|
4814 after which a garbage collection occurs) and @code{always_gc}. If
|
|
|
4815 @code{always_gc} is set or if the threshold is exceeded, the garbage
|
|
|
4816 collection will start.
|
|
|
4817 @item
|
|
|
4818 In function @code{Ffuncall / funcall} in file @code{eval.c}. This
|
|
|
4819 function evaluates calls of elisp functions and works according to
|
|
|
4820 @code{Feval}.
|
|
|
4821 @end enumerate
|
|
|
4822
|
|
|
4823 The upshot is that garbage collection can basically occur everywhere
|
|
|
4824 @code{Feval}, respectively @code{Ffuncall}, is used - either directly or
|
|
|
4825 through another function. Since calls to these two functions are
|
|
|
4826 hidden in various other functions, many calls to
|
|
|
4827 @code{garabge_collect_1} are not obviously foreseeable, and therefore
|
|
|
4828 unexpected. Instances where they are used that are worth remembering are
|
|
|
4829 various elisp commands, as for example @code{or},
|
|
|
4830 @code{and}, @code{if}, @code{cond}, @code{while}, @code{setq}, etc.,
|
|
|
4831 miscellaneous @code{gui_item_...} functions, everything related to
|
|
|
4832 @code{eval} (@code{Feval_buffer}, @code{call0}, ...) and inside
|
|
|
4833 @code{Fsignal}. The latter is used to handle signals, as for example the
|
|
|
4834 ones raised by every @code{QUITE}-macro triggered after pressing Ctrl-g.
|
|
|
4835
|
|
|
4836 @node garbage_collect_1, mark_object, Invocation, Garbage Collection - Step by Step
|
|
|
4837 @subsection @code{garbage_collect_1}
|
|
|
4838 @cindex @code{garbage_collect_1}
|
|
|
4839
|
|
|
4840 We can now describe exactly what happens after the invocation takes
|
|
|
4841 place.
|
|
|
4842 @enumerate
|
|
|
4843 @item
|
|
|
4844 There are several cases in which the garbage collector is left immediately:
|
|
|
4845 when we are already garbage collecting (@code{gc_in_progress}), when
|
|
|
4846 the garbage collection is somehow forbidden
|
|
|
4847 (@code{gc_currently_forbidden}), when we are currently displaying something
|
|
|
4848 (@code{in_display}) or when we are preparing for the armageddon of the
|
|
|
4849 whole system (@code{preparing_for_armageddon}).
|
|
|
4850 @item
|
|
|
4851 Next the correct frame in which to put
|
|
|
4852 all the output occurring during garbage collecting is determined. In
|
|
|
4853 order to be able to restore the old display's state after displaying the
|
|
|
4854 message, some data about the current cursor position has to be
|
|
|
4855 saved. The variables @code{pre_gc_curser} and @code{cursor_changed} take
|
|
|
4856 care of that.
|
|
|
4857 @item
|
|
|
4858 The state of @code{gc_currently_forbidden} must be restored after
|
|
|
4859 the garbage collection, no matter what happens during the process. We
|
|
|
4860 accomplish this by @code{record_unwind_protect}ing the suitable function
|
|
|
4861 @code{restore_gc_inhibit} together with the current value of
|
|
|
4862 @code{gc_currently_forbidden}.
|
|
|
4863 @item
|
|
|
4864 If we are concurrently running an interactive xemacs session, the next step
|
|
|
4865 is simply to show the garbage collector's cursor/message.
|
|
|
4866 @item
|
|
|
4867 The following steps are the intrinsic steps of the garbage collector,
|
|
|
4868 therefore @code{gc_in_progress} is set.
|
|
|
4869 @item
|
|
|
4870 For debugging purposes, it is possible to copy the current C stack
|
|
|
4871 frame. However, this seems to be a currently unused feature.
|
|
|
4872 @item
|
|
|
4873 Before actually starting to go over all live objects, references to
|
|
|
4874 objects that are no longer used are pruned. We only have to do this for events
|
|
|
4875 (@code{clear_event_resource}) and for specifiers
|
|
|
4876 (@code{cleanup_specifiers}).
|
|
|
4877 @item
|
|
|
4878 Now the mark phase begins and marks all accessible elements. In order to
|
|
|
4879 start from
|
|
|
4880 all slots that serve as roots of accessibility, the function
|
|
|
4881 @code{mark_object} is called for each root individually to go out from
|
|
|
4882 there to mark all reachable objects. All roots that are traversed are
|
|
|
4883 shown in their processed order:
|
|
|
4884 @itemize @bullet
|
|
|
4885 @item
|
|
|
4886 all constant symbols and static variables that are registered via
|
|
|
4887 @code{staticpro}@ in the array @code{staticvec}.
|
|
|
4888 @xref{Adding Global Lisp Variables}.
|
|
|
4889 @item
|
|
|
4890 all Lisp objects that are created in C functions and that must be
|
|
|
4891 protected from freeing them. They are registered in the global
|
|
|
4892 list @code{gcprolist}.
|
|
|
4893 @xref{GCPROing}.
|
|
|
4894 @item
|
|
|
4895 all local variables (i.e. their name fields @code{symbol} and old
|
|
|
4896 values @code{old_values}) that are bound during the evaluation by the Lisp
|
|
|
4897 engine. They are stored in @code{specbinding} structs pushed on a stack
|
|
|
4898 called @code{specpdl}.
|
|
|
4899 @xref{Dynamic Binding; The specbinding Stack; Unwind-Protects}.
|
|
|
4900 @item
|
|
|
4901 all catch blocks that the Lisp engine encounters during the evaluation
|
|
|
4902 cause the creation of structs @code{catchtag} inserted in the list
|
|
|
4903 @code{catchlist}. Their tag (@code{tag}) and value (@code{val} fields
|
|
|
4904 are freshly created objects and therefore have to be marked.
|
|
|
4905 @xref{Catch and Throw}.
|
|
|
4906 @item
|
|
|
4907 every function application pushes new structs @code{backtrace}
|
|
|
4908 on the call stack of the Lisp engine (@code{backtrace_list}). The unique
|
|
|
4909 parts that have to be marked are the fields for each function
|
|
|
4910 (@code{function}) and all their arguments (@code{args}).
|
|
|
4911 @xref{Evaluation}.
|
|
|
4912 @item
|
|
|
4913 all objects that are used by the redisplay engine that must not be freed
|
|
|
4914 are marked by a special function called @code{mark_redisplay} (in
|
|
|
4915 @code{redisplay.c}).
|
|
|
4916 @item
|
|
|
4917 all objects created for profiling purposes are allocated by C functions
|
|
|
4918 instead of using the lisp allocation mechanisms. In order to receive the
|
|
|
4919 right ones during the sweep phase, they also have to be marked
|
|
|
4920 manually. That is done by the function @code{mark_profiling_info}
|
|
|
4921 @end itemize
|
|
|
4922 @item
|
|
|
4923 Hash tables in XEmacs belong to a kind of special objects that
|
|
|
4924 make use of a concept often called 'weak pointers'.
|
|
|
4925 To make a long story short, these kind of pointers are not followed
|
|
|
4926 during the estimation of the live objects during garbage collection.
|
|
|
4927 Any object referenced only by weak pointers is collected
|
|
|
4928 anyway, and the reference to it is cleared. In hash tables there are
|
|
|
4929 different usage patterns of them, manifesting in different types of hash
|
|
|
4930 tables, namely 'non-weak', 'weak', 'key-weak' and 'value-weak'
|
|
|
4931 (internally also 'key-car-weak' and 'value-car-weak') hash tables, each
|
|
|
4932 clearing entries depending on different conditions. More information can
|
|
|
4933 be found in the documentation to the function @code{make-hash-table}.
|
|
|
4934
|
|
|
4935 Because there are complicated dependency rules about when and what to
|
|
|
4936 mark while processing weak hash tables, the standard @code{marker}
|
|
|
4937 method is only active if it is marking non-weak hash tables. As soon as
|
|
|
4938 a weak component is in the table, the hash table entries are ignored
|
|
|
4939 while marking. Instead their marking is done each separately by the
|
|
|
4940 function @code{finish_marking_weak_hash_tables}. This function iterates
|
|
|
4941 over each hash table entry @code{hentries} for each weak hash table in
|
|
|
4942 @code{Vall_weak_hash_tables}. Depending on the type of a table, the
|
|
|
4943 appropriate action is performed.
|
|
|
4944 If a table is acting as @code{HASH_TABLE_KEY_WEAK}, and a key already marked,
|
|
|
4945 everything reachable from the @code{value} component is marked. If it is
|
|
|
4946 acting as a @code{HASH_TABLE_VALUE_WEAK} and the value component is
|
|
|
4947 already marked, the marking starts beginning only from the
|
|
|
4948 @code{key} component.
|
|
|
4949 If it is a @code{HASH_TABLE_KEY_CAR_WEAK} and the car
|
|
|
4950 of the key entry is already marked, we mark both the @code{key} and
|
|
|
4951 @code{value} components.
|
|
|
4952 Finally, if the table is of the type @code{HASH_TABLE_VALUE_CAR_WEAK}
|
|
|
4953 and the car of the value components is already marked, again both the
|
|
|
4954 @code{key} and the @code{value} components get marked.
|
|
|
4955
|
|
|
4956 Again, there are lists with comparable properties called weak
|
|
|
4957 lists. There exist different peculiarities of their types called
|
|
|
4958 @code{simple}, @code{assoc}, @code{key-assoc} and
|
|
|
4959 @code{value-assoc}. You can find further details about them in the
|
|
|
4960 description to the function @code{make-weak-list}. The scheme of their
|
|
|
4961 marking is similar: all weak lists are listed in @code{Qall_weak_lists},
|
|
|
4962 therefore we iterate over them. The marking is advanced until we hit an
|
|
|
4963 already marked pair. Then we know that during a former run all
|
|
|
4964 the rest has been marked completely. Again, depending on the special
|
|
|
4965 type of the weak list, our jobs differ. If it is a @code{WEAK_LIST_SIMPLE}
|
|
|
4966 and the elem is marked, we mark the @code{cons} part. If it is a
|
|
|
4967 @code{WEAK_LIST_ASSOC} and not a pair or a pair with both marked car and
|
|
|
4968 cdr, we mark the @code{cons} and the @code{elem}. If it is a
|
|
|
4969 @code{WEAK_LIST_KEY_ASSOC} and not a pair or a pair with a marked car of
|
|
|
4970 the elem, we mark the @code{cons} and the @code{elem}. Finally, if it is
|
|
|
4971 a @code{WEAK_LIST_VALUE_ASSOC} and not a pair or a pair with a marked
|
|
|
4972 cdr of the elem, we mark both the @code{cons} and the @code{elem}.
|
|
|
4973
|
|
|
4974 Since, by marking objects in reach from weak hash tables and weak lists,
|
|
|
4975 other objects could get marked, this perhaps implies further marking of
|
|
|
4976 other weak objects, both finishing functions are redone as long as
|
|
|
4977 yet unmarked objects get freshly marked.
|
|
|
4978
|
|
|
4979 @item
|
|
|
4980 After completing the special marking for the weak hash tables and for the weak
|
|
|
4981 lists, all entries that point to objects that are going to be swept in
|
|
|
4982 the further process are useless, and therefore have to be removed from
|
|
|
4983 the table or the list.
|
|
|
4984
|
|
|
4985 The function @code{prune_weak_hash_tables} does the job for weak hash
|
|
|
4986 tables. Totally unmarked hash tables are removed from the list
|
|
|
4987 @code{Vall_weak_hash_tables}. The other ones are treated more carefully
|
|
|
4988 by scanning over all entries and removing one as soon as one of
|
|
|
4989 the components @code{key} and @code{value} is unmarked.
|
|
|
4990
|
|
|
4991 The same idea applies to the weak lists. It is accomplished by
|
|
|
4992 @code{prune_weak_lists}: An unmarked list is pruned from
|
|
|
4993 @code{Vall_weak_lists} immediately. A marked list is treated more
|
|
|
4994 carefully by going over it and removing just the unmarked pairs.
|
|
|
4995
|
|
|
4996 @item
|
|
|
4997 The function @code{prune_specifiers} checks all listed specifiers held
|
|
|
4998 in @code{Vall_speficiers} and removes the ones from the lists that are
|
|
|
4999 unmarked.
|
|
|
5000
|
|
|
5001 @item
|
|
|
5002 All syntax tables are stored in a list called
|
|
|
5003 @code{Vall_syntax_tables}. The function @code{prune_syntax_tables} walks
|
|
|
5004 through it and unlinks the tables that are unmarked.
|
|
|
5005
|
|
|
5006 @item
|
|
|
5007 Next, we will attack the complete sweeping - the function
|
|
|
5008 @code{gc_sweep} which holds the predominance.
|
|
|
5009 @item
|
|
|
5010 First, all the variables with respect to garbage collection are
|
|
|
5011 reset. @code{consing_since_gc} - the counter of the created cells since
|
|
|
5012 the last garbage collection - is set back to 0, and
|
|
|
5013 @code{gc_in_progress} is not @code{true} anymore.
|
|
|
5014 @item
|
|
|
5015 In case the session is interactive, the displayed cursor and message are
|
|
|
5016 removed again.
|
|
|
5017 @item
|
|
|
5018 The state of @code{gc_inhibit} is restored to the former value by
|
|
|
5019 unwinding the stack.
|
|
|
5020 @item
|
|
|
5021 A small memory reserve is always held back that can be reached by
|
|
|
5022 @code{breathing_space}. If nothing more is left, we create a new reserve
|
|
|
5023 and exit.
|
|
|
5024 @end enumerate
|
|
|
5025
|
|
|
5026 @node mark_object, gc_sweep, garbage_collect_1, Garbage Collection - Step by Step
|
|
|
5027 @subsection @code{mark_object}
|
|
|
5028 @cindex @code{mark_object}
|
|
|
5029
|
|
|
5030 The first thing that is checked while marking an object is whether the
|
|
|
5031 object is a real Lisp object @code{Lisp_Type_Record} or just an integer
|
|
|
5032 or a character. Integers and characters are the only two types that are
|
|
|
5033 stored directly - without another level of indirection, and therefore they
|
|
|
5034 don't have to be marked and collected.
|
|
|
5035 @xref{How Lisp Objects Are Represented in C}.
|
|
|
5036
|
|
|
5037 The second case is the one we have to handle. It is the one when we are
|
|
|
5038 dealing with a pointer to a Lisp object. But, there exist also three
|
|
|
5039 possibilities, that prevent us from doing anything while marking: The
|
|
|
5040 object is read only which prevents it from being garbage collected,
|
|
|
5041 i.e. marked (@code{C_READONLY_RECORD_HEADER}). The object in question is
|
|
|
5042 already marked, and need not be marked for the second time (checked by
|
|
|
5043 @code{MARKED_RECORD_HEADER_P}). If it is a special, unmarkable object
|
|
|
5044 (@code{UNMARKABLE_RECORD_HEADER_P}, apparently, these are objects that
|
|
|
5045 sit in some const space, and can therefore not be marked, see
|
|
|
5046 @code{this_one_is_unmarkable} in @code{alloc.c}).
|
|
|
5047
|
|
|
5048 Now, the actual marking is feasible. We do so by once using the macro
|
|
|
5049 @code{MARK_RECORD_HEADER} to mark the object itself (actually the
|
|
|
5050 special flag in the lrecord header), and calling its special marker
|
|
|
5051 "method" @code{marker} if available. The marker method marks every
|
|
|
5052 other object that is in reach from our current object. Note, that these
|
|
|
5053 marker methods should not call @code{mark_object} recursively, but
|
|
|
5054 instead should return the next object from where further marking has to
|
|
|
5055 be performed.
|
|
|
5056
|
|
|
5057 In case another object was returned, as mentioned before, we reiterate
|
|
|
5058 the whole @code{mark_object} process beginning with this next object.
|
|
|
5059
|
|
|
5060 @node gc_sweep, sweep_lcrecords_1, mark_object, Garbage Collection - Step by Step
|
|
|
5061 @subsection @code{gc_sweep}
|
|
|
5062 @cindex @code{gc_sweep}
|
|
|
5063
|
|
|
5064 The job of this function is to free all unmarked records from memory. As
|
|
|
5065 we know, there are different types of objects implemented and managed, and
|
|
|
5066 consequently different ways to free them from memory.
|
|
|
5067 @xref{Introduction to Allocation}.
|
|
|
5068
|
|
|
5069 We start with all objects stored through @code{lcrecords}. All
|
|
|
5070 bulkier objects are allocated and handled using that scheme of
|
|
|
5071 @code{lcrecords}. Each object is @code{malloc}ed separately
|
|
|
5072 instead of placing it in one of the contiguous frob blocks. All types
|
|
|
5073 that are currently stored
|
|
|
5074 using @code{lcrecords}'s @code{alloc_lcrecord} and
|
|
|
5075 @code{make_lcrecord_list} are the types: vectors, buffers,
|
|
|
5076 char-table, char-table-entry, console, weak-list, database, device,
|
|
|
5077 ldap, hash-table, command-builder, extent-auxiliary, extent-info, face,
|
|
|
5078 coding-system, frame, image-instance, glyph, popup-data, gui-item,
|
|
|
5079 keymap, charset, color_instance, font_instance, opaque, opaque-list,
|
|
|
5080 process, range-table, specifier, symbol-value-buffer-local,
|
|
|
5081 symbol-value-lisp-magic, symbol-value-varalias, toolbar-button,
|
|
|
5082 tooltalk-message, tooltalk-pattern, window, and window-configuration. We
|
|
|
5083 take care of them in the fist place
|
|
|
5084 in order to be able to handle and to finalize items stored in them more
|
|
|
5085 easily. The function @code{sweep_lcrecords_1} as described below is
|
|
|
5086 doing the whole job for us.
|
|
|
5087 For a description about the internals: @xref{lrecords}.
|
|
|
5088
|
|
|
5089 Our next candidates are the other objects that behave quite differently
|
|
|
5090 than everything else: the strings. They consists of two parts, a
|
|
|
5091 fixed-size portion (@code{struct Lisp_string}) holding the string's
|
|
|
5092 length, its property list and a pointer to the second part, and the
|
|
|
5093 actual string data, which is stored in string-chars blocks comparable to
|
|
|
5094 frob blocks. In this block, the data is not only freed, but also a
|
|
|
5095 compression of holes is made, i.e. all strings are relocated together.
|
|
|
5096 @xref{String}. This compacting phase is performed by the function
|
|
|
5097 @code{compact_string_chars}, the actual sweeping by the function
|
|
|
5098 @code{sweep_strings} is described below.
|
|
|
5099
|
|
|
5100 After that, the other types are swept step by step using functions
|
|
|
5101 @code{sweep_conses}, @code{sweep_bit_vectors_1},
|
|
|
5102 @code{sweep_compiled_functions}, @code{sweep_floats},
|
|
|
5103 @code{sweep_symbols}, @code{sweep_extents}, @code{sweep_markers} and
|
|
|
5104 @code{sweep_extents}. They are the fixed-size types cons, floats,
|
|
|
5105 compiled-functions, symbol, marker, extent, and event stored in
|
|
|
5106 so-called "frob blocks", and therefore we can basically do the same on
|
|
|
5107 every type objects, using the same macros, especially defined only to
|
|
|
5108 handle everything with respect to fixed-size blocks. The only fixed-size
|
|
|
5109 type that is not handled here are the fixed-size portion of strings,
|
|
|
5110 because we took special care of them earlier.
|
|
|
5111
|
|
|
5112 The only big exceptions are bit vectors stored differently and
|
|
|
5113 therefore treated differently by the function @code{sweep_bit_vectors_1}
|
|
|
5114 described later.
|
|
|
5115
|
|
|
5116 At first, we need some brief information about how
|
|
|
5117 these fixed-size types are managed in general, in order to understand
|
|
|
5118 how the sweeping is done. They have all a fixed size, and are therefore
|
|
|
5119 stored in big blocks of memory - allocated at once - that can hold a
|
|
|
5120 certain amount of objects of one type. The macro
|
|
|
5121 @code{DECLARE_FIXED_TYPE_ALLOC} creates the suitable structures for
|
|
|
5122 every type. More precisely, we have the block struct
|
|
|
5123 (holding a pointer to the previous block @code{prev} and the
|
|
|
5124 objects in @code{block[]}), a pointer to current block
|
|
|
5125 (@code{current_..._block)}) and its last index
|
|
|
5126 (@code{current_..._block_index}), and a pointer to the free list that
|
|
|
5127 will be created. Also a macro @code{FIXED_TYPE_FROM_BLOCK} plus some
|
|
|
5128 related macros exists that are used to obtain a new object, either from
|
|
|
5129 the free list @code{ALLOCATE_FIXED_TYPE_1} if there is an unused object
|
|
|
5130 of that type stored or by allocating a completely new block using
|
|
|
5131 @code{ALLOCATE_FIXED_TYPE_FROM_BLOCK}.
|
|
|
5132
|
|
|
5133 The rest works as follows: all of them define a
|
|
|
5134 macro @code{UNMARK_...} that is used to unmark the object. They define a
|
|
|
5135 macro @code{ADDITIONAL_FREE_...} that defines additional work that has
|
|
|
5136 to be done when converting an object from in use to not in use (so far,
|
|
|
5137 only markers use it in order to unchain them). Then, they all call
|
|
|
5138 the macro @code{SWEEP_FIXED_TYPE_BLOCK} instantiated with their type name
|
|
|
5139 and their struct name.
|
|
|
5140
|
|
|
5141 This call in particular does the following: we go over all blocks
|
|
|
5142 starting with the current moving towards the oldest.
|
|
|
5143 For each block, we look at every object in it. If the object already
|
|
|
5144 freed (checked with @code{FREE_STRUCT_P} using the first pointer of the
|
|
|
5145 object), or if it is
|
|
|
5146 set to read only (@code{C_READONLY_RECORD_HEADER_P}, nothing must be
|
|
|
5147 done. If it is unmarked (checked with @code{MARKED_RECORD_HEADER_P}), it
|
|
|
5148 is put in the free list and set free (using the macro
|
|
|
5149 @code{FREE_FIXED_TYPE}, otherwise it stays in the block, but is unmarked
|
|
|
5150 (by @code{UNMARK_...}). While going through one block, we note if the
|
|
|
5151 whole block is empty. If so, the whole block is freed (using
|
|
|
5152 @code{xfree}) and the free list state is set to the state it had before
|
|
|
5153 handling this block.
|
|
|
5154
|
|
|
5155 @node sweep_lcrecords_1, compact_string_chars, gc_sweep, Garbage Collection - Step by Step
|
|
|
5156 @subsection @code{sweep_lcrecords_1}
|
|
|
5157 @cindex @code{sweep_lcrecords_1}
|
|
|
5158
|
|
|
5159 After nullifying the complete lcrecord statistics, we go over all
|
|
|
5160 lcrecords two separate times. They are all chained together in a list with
|
|
|
5161 a head called @code{all_lcrecords}.
|
|
|
5162
|
|
|
5163 The first loop calls for each object its @code{finalizer} method, but only
|
|
|
5164 in the case that it is not read only
|
|
|
5165 (@code{C_READONLY_RECORD_HEADER_P)}, it is not already marked
|
|
|
5166 (@code{MARKED_RECORD_HEADER_P}), it is not already in a free list (list of
|
|
|
5167 freed objects, field @code{free}) and finally it owns a finalizer
|
|
|
5168 method.
|
|
|
5169
|
|
|
5170 The second loop actually frees the appropriate objects again by iterating
|
|
|
5171 through the whole list. In case an object is read only or marked, it
|
|
|
5172 has to persist, otherwise it is manually freed by calling
|
|
|
5173 @code{xfree}. During this loop, the lcrecord statistics are kept up to
|
|
|
5174 date by calling @code{tick_lcrecord_stats} with the right arguments,
|
|
|
5175
|
|
|
5176 @node compact_string_chars, sweep_strings, sweep_lcrecords_1, Garbage Collection - Step by Step
|
|
|
5177 @subsection @code{compact_string_chars}
|
|
|
5178 @cindex @code{compact_string_chars}
|
|
|
5179
|
|
|
5180 The purpose of this function is to compact all the data parts of the
|
|
|
5181 strings that are held in so-called @code{string_chars_block}, i.e. the
|
|
|
5182 strings that do not exceed a certain maximal length.
|
|
|
5183
|
|
|
5184 The procedure with which this is done is as follows. We are keeping two
|
|
|
5185 positions in the @code{string_chars_block}s using two pointer/integer
|
|
|
5186 pairs, namely @code{from_sb}/@code{from_pos} and
|
|
|
5187 @code{to_sb}/@code{to_pos}. They stand for the actual positions, from
|
|
|
5188 where to where, to copy the actually handled string.
|
|
|
5189
|
|
|
5190 While going over all chained @code{string_char_block}s and their held
|
|
|
5191 strings, staring at @code{first_string_chars_block}, both pointers
|
|
|
5192 are advanced and eventually a string is copied from @code{from_sb} to
|
|
|
5193 @code{to_sb}, depending on the status of the pointed at strings.
|
|
|
5194
|
|
|
5195 More precisely, we can distinguish between the following actions.
|
|
|
5196 @itemize @bullet
|
|
|
5197 @item
|
|
|
5198 The string at @code{from_sb}'s position could be marked as free, which
|
|
|
5199 is indicated by an invalid pointer to the pointer that should point back
|
|
|
5200 to the fixed size string object, and which is checked by
|
|
|
5201 @code{FREE_STRUCT_P}. In this case, the @code{from_sb}/@code{from_pos}
|
|
|
5202 is advanced to the next string, and nothing has to be copied.
|
|
|
5203 @item
|
|
|
5204 Also, if a string object itself is unmarked, nothing has to be
|
|
|
5205 copied. We likewise advance the @code{from_sb}/@code{from_pos}
|
|
|
5206 pair as described above.
|
|
|
5207 @item
|
|
|
5208 In all other cases, we have a marked string at hand. The string data
|
|
|
5209 must be moved from the from-position to the to-position. In case
|
|
|
5210 there is not enough space in the actual @code{to_sb}-block, we advance
|
|
|
5211 this pointer to the beginning of the next block before copying. In case the
|
|
|
5212 from and to positions are different, we perform the
|
|
|
5213 actual copying using the library function @code{memmove}.
|
|
|
5214 @end itemize
|
|
|
5215
|
|
|
5216 After compacting, the pointer to the current
|
|
|
5217 @code{string_chars_block}, sitting in @code{current_string_chars_block},
|
|
|
5218 is reset on the last block to which we moved a string,
|
|
|
5219 i.e. @code{to_block}, and all remaining blocks (we know that they just
|
|
|
5220 carry garbage) are explicitly @code{xfree}d.
|
|
|
5221
|
|
|
5222 @node sweep_strings, sweep_bit_vectors_1, compact_string_chars, Garbage Collection - Step by Step
|
|
|
5223 @subsection @code{sweep_strings}
|
|
|
5224 @cindex @code{sweep_strings}
|
|
|
5225
|
|
|
5226 The sweeping for the fixed sized string objects is essentially exactly
|
|
|
5227 the same as it is for all other fixed size types. As before, the freeing
|
|
|
5228 into the suitable free list is done by using the macro
|
|
|
5229 @code{SWEEP_FIXED_SIZE_BLOCK} after defining the right macros
|
|
|
5230 @code{UNMARK_string} and @code{ADDITIONAL_FREE_string}. These two
|
|
|
5231 definitions are a little bit special compared to the ones used
|
|
|
5232 for the other fixed size types.
|
|
|
5233
|
|
|
5234 @code{UNMARK_string} is defined the same way except some additional code
|
|
|
5235 used for updating the bookkeeping information.
|
|
|
5236
|
|
|
5237 For strings, @code{ADDITIONAL_FREE_string} has to do something in
|
|
|
5238 addition: in case, the string was not allocated in a
|
|
|
5239 @code{string_chars_block} because it exceeded the maximal length, and
|
|
|
5240 therefore it was @code{malloc}ed separately, we know also @code{xfree}
|
|
|
5241 it explicitly.
|
|
|
5242
|
|
|
5243 @node sweep_bit_vectors_1, , sweep_strings, Garbage Collection - Step by Step
|
|
|
5244 @subsection @code{sweep_bit_vectors_1}
|
|
|
5245 @cindex @code{sweep_bit_vectors_1}
|
|
|
5246
|
|
|
5247 Bit vectors are also one of the rare types that are @code{malloc}ed
|
|
|
5248 individually. Consequently, while sweeping, all further needless
|
|
|
5249 bit vectors must be freed by hand. This is done, as one might imagine,
|
|
|
5250 the expected way: since they are all registered in a list called
|
|
|
5251 @code{all_bit_vectors}, all elements of that list are traversed,
|
|
|
5252 all unmarked bit vectors are unlinked by calling @code{xfree} and all of
|
|
|
5253 them become unmarked.
|
|
|
5254 In addition, the bookkeeping information used for garbage
|
|
|
5255 collector's output purposes is updated.
|
|
|
5256
|
|
|
5257 @node Integers and Characters, Allocation from Frob Blocks, Garbage Collection - Step by Step, Allocation of Objects in XEmacs Lisp
|
|
0
|
5258 @section Integers and Characters
|
|
|
5259
|
|
|
5260 Integer and character Lisp objects are created from integers using the
|
|
|
5261 macros @code{XSETINT()} and @code{XSETCHAR()} or the equivalent
|
|
|
5262 functions @code{make_int()} and @code{make_char()}. (These are actually
|
|
|
5263 macros on most systems.) These functions basically just do some moving
|
|
|
5264 of bits around, since the integral value of the object is stored
|
|
|
5265 directly in the @code{Lisp_Object}.
|
|
|
5266
|
|
|
5267 @code{XSETINT()} and the like will truncate values given to them that
|
|
|
5268 are too big; i.e. you won't get the value you expected but the tag bits
|
|
|
5269 will at least be correct.
|
|
|
5270
|
|
398
|
5271 @node Allocation from Frob Blocks, lrecords, Integers and Characters, Allocation of Objects in XEmacs Lisp
|
|
0
|
5272 @section Allocation from Frob Blocks
|
|
|
5273
|
|
|
5274 The uninitialized memory required by a @code{Lisp_Object} of a particular type
|
|
|
5275 is allocated using
|
|
|
5276 @code{ALLOCATE_FIXED_TYPE()}. This only occurs inside of the
|
|
|
5277 lowest-level object-creating functions in @file{alloc.c}:
|
|
|
5278 @code{Fcons()}, @code{make_float()}, @code{Fmake_byte_code()},
|
|
|
5279 @code{Fmake_symbol()}, @code{allocate_extent()},
|
|
|
5280 @code{allocate_event()}, @code{Fmake_marker()}, and
|
|
|
5281 @code{make_uninit_string()}. The idea is that, for each type, there are
|
|
|
5282 a number of frob blocks (each 2K in size); each frob block is divided up
|
|
|
5283 into object-sized chunks. Each frob block will have some of these
|
|
|
5284 chunks that are currently assigned to objects, and perhaps some that are
|
|
|
5285 free. (If a frob block has nothing but free chunks, it is freed at the
|
|
|
5286 end of the garbage collection cycle.) The free chunks are stored in a
|
|
|
5287 free list, which is chained by storing a pointer in the first four bytes
|
|
|
5288 of the chunk. (Except for the free chunks at the end of the last frob
|
|
|
5289 block, which are handled using an index which points past the end of the
|
|
|
5290 last-allocated chunk in the last frob block.)
|
|
|
5291 @code{ALLOCATE_FIXED_TYPE()} first tries to retrieve a chunk from the
|
|
|
5292 free list; if that fails, it calls
|
|
|
5293 @code{ALLOCATE_FIXED_TYPE_FROM_BLOCK()}, which looks at the end of the
|
|
|
5294 last frob block for space, and creates a new frob block if there is
|
|
|
5295 none. (There are actually two versions of these macros, one of which is
|
|
|
5296 more defensive but less efficient and is used for error-checking.)
|
|
|
5297
|
|
398
|
5298 @node lrecords, Low-level allocation, Allocation from Frob Blocks, Allocation of Objects in XEmacs Lisp
|
|
0
|
5299 @section lrecords
|
|
|
5300
|
|
|
5301 [see @file{lrecord.h}]
|
|
|
5302
|
|
|
5303 All lrecords have at the beginning of their structure a @code{struct
|
|
|
5304 lrecord_header}. This just contains a pointer to a @code{struct
|
|
|
5305 lrecord_implementation}, which is a structure containing method pointers
|
|
|
5306 and such. There is one of these for each type, and it is a global,
|
|
|
5307 constant, statically-declared structure that is declared in the
|
|
|
5308 @code{DEFINE_LRECORD_IMPLEMENTATION()} macro. (This macro actually
|
|
|
5309 declares an array of two @code{struct lrecord_implementation}
|
|
|
5310 structures. The first one contains all the standard method pointers,
|
|
|
5311 and is used in all normal circumstances. During garbage collection,
|
|
|
5312 however, the lrecord is @dfn{marked} by bumping its implementation
|
|
|
5313 pointer by one, so that it points to the second structure in the array.
|
|
|
5314 This structure contains a special indication in it that it's a
|
|
|
5315 @dfn{marked-object} structure: the finalize method is the special
|
|
|
5316 function @code{this_marks_a_marked_record()}, and all other methods are
|
|
|
5317 null pointers. At the end of garbage collection, all lrecords will
|
|
|
5318 either be reclaimed or unmarked by decrementing their implementation
|
|
|
5319 pointers, so this second structure pointer will never remain past
|
|
|
5320 garbage collection.
|
|
|
5321
|
|
|
5322 Simple lrecords (of type (c) above) just have a @code{struct
|
|
|
5323 lrecord_header} at their beginning. lcrecords, however, actually have a
|
|
|
5324 @code{struct lcrecord_header}. This, in turn, has a @code{struct
|
|
|
5325 lrecord_header} at its beginning, so sanity is preserved; but it also
|
|
2
|
5326 has a pointer used to chain all lcrecords together, and a special ID
|
|
0
|
5327 field used to distinguish one lcrecord from another. (This field is used
|
|
|
5328 only for debugging and could be removed, but the space gain is not
|
|
|
5329 significant.)
|
|
|
5330
|
|
|
5331 Simple lrecords are created using @code{ALLOCATE_FIXED_TYPE()}, just
|
|
|
5332 like for other frob blocks. The only change is that the implementation
|
|
|
5333 pointer must be initialized correctly. (The implementation structure for
|
|
|
5334 an lrecord, or rather the pointer to it, is named @code{lrecord_float},
|
|
|
5335 @code{lrecord_extent}, @code{lrecord_buffer}, etc.)
|
|
|
5336
|
|
|
5337 lcrecords are created using @code{alloc_lcrecord()}. This takes a
|
|
|
5338 size to allocate and an implementation pointer. (The size needs to be
|
|
|
5339 passed because some lcrecords, such as window configurations, are of
|
|
|
5340 variable size.) This basically just @code{malloc()}s the storage,
|
|
|
5341 initializes the @code{struct lcrecord_header}, and chains the lcrecord
|
|
|
5342 onto the head of the list of all lcrecords, which is stored in the
|
|
|
5343 variable @code{all_lcrecords}. The calls to @code{alloc_lcrecord()}
|
|
|
5344 generally occur in the lowest-level allocation function for each lrecord
|
|
|
5345 type.
|
|
|
5346
|
|
|
5347 Whenever you create an lrecord, you need to call either
|
|
|
5348 @code{DEFINE_LRECORD_IMPLEMENTATION()} or
|
|
|
5349 @code{DEFINE_LRECORD_SEQUENCE_IMPLEMENTATION()}. This needs to be
|
|
|
5350 specified in a C file, at the top level. What this actually does is
|
|
|
5351 define and initialize the implementation structure for the lrecord. (And
|
|
|
5352 possibly declares a function @code{error_check_foo()} that implements
|
|
|
5353 the @code{XFOO()} macro when error-checking is enabled.) The arguments
|
|
|
5354 to the macros are the actual type name (this is used to construct the C
|
|
|
5355 variable name of the lrecord implementation structure and related
|
|
|
5356 structures using the @samp{##} macro concatenation operator), a string
|
|
|
5357 that names the type on the Lisp level (this may not be the same as the C
|
|
|
5358 type name; typically, the C type name has underscores, while the Lisp
|
|
|
5359 string has dashes), various method pointers, and the name of the C
|
|
|
5360 structure that contains the object. The methods are used to encapsulate
|
|
|
5361 type-specific information about the object, such as how to print it or
|
|
|
5362 mark it for garbage collection, so that it's easy to add new object
|
|
|
5363 types without having to add a specific case for each new type in a bunch
|
|
|
5364 of different places.
|
|
|
5365
|
|
|
5366 The difference between @code{DEFINE_LRECORD_IMPLEMENTATION()} and
|
|
|
5367 @code{DEFINE_LRECORD_SEQUENCE_IMPLEMENTATION()} is that the former is
|
|
|
5368 used for fixed-size object types and the latter is for variable-size
|
|
|
5369 object types. Most object types are fixed-size; some complex
|
|
|
5370 types, however (e.g. window configurations), are variable-size.
|
|
|
5371 Variable-size object types have an extra method, which is called
|
|
|
5372 to determine the actual size of a particular object of that type.
|
|
|
5373 (Currently this is only used for keeping allocation statistics.)
|
|
|
5374
|
|
|
5375 For the purpose of keeping allocation statistics, the allocation
|
|
|
5376 engine keeps a list of all the different types that exist. Note that,
|
|
|
5377 since @code{DEFINE_LRECORD_IMPLEMENTATION()} is a macro that is
|
|
|
5378 specified at top-level, there is no way for it to add to the list of all
|
|
|
5379 existing types. What happens instead is that each implementation
|
|
|
5380 structure contains in it a dynamically assigned number that is
|
|
|
5381 particular to that type. (Or rather, it contains a pointer to another
|
|
|
5382 structure that contains this number. This evasiveness is done so that
|
|
|
5383 the implementation structure can be declared const.) In the sweep stage
|
|
|
5384 of garbage collection, each lrecord is examined to see if its
|
|
|
5385 implementation structure has its dynamically-assigned number set. If
|
|
|
5386 not, it must be a new type, and it is added to the list of known types
|
|
|
5387 and a new number assigned. The number is used to index into an array
|
|
|
5388 holding the number of objects of each type and the total memory
|
|
|
5389 allocated for objects of that type. The statistics in this array are
|
|
|
5390 also computed during the sweep stage. These statistics are returned by
|
|
|
5391 the call to @code{garbage-collect} and are printed out at the end of the
|
|
|
5392 loadup phase.
|
|
|
5393
|
|
|
5394 Note that for every type defined with a @code{DEFINE_LRECORD_*()}
|
|
|
5395 macro, there needs to be a @code{DECLARE_LRECORD_IMPLEMENTATION()}
|
|
|
5396 somewhere in a @file{.h} file, and this @file{.h} file needs to be
|
|
|
5397 included by @file{inline.c}.
|
|
|
5398
|
|
|
5399 Furthermore, there should generally be a set of @code{XFOOBAR()},
|
|
|
5400 @code{FOOBARP()}, etc. macros in a @file{.h} (or occasionally @file{.c})
|
|
|
5401 file. To create one of these, copy an existing model and modify as
|
|
|
5402 necessary.
|
|
|
5403
|
|
|
5404 The various methods in the lrecord implementation structure are:
|
|
|
5405
|
|
|
5406 @enumerate
|
|
|
5407 @item
|
|
|
5408 @cindex mark method
|
|
|
5409 A @dfn{mark} method. This is called during the marking stage and passed
|
|
|
5410 a function pointer (usually the @code{mark_object()} function), which is
|
|
|
5411 used to mark an object. All Lisp objects that are contained within the
|
|
|
5412 object need to be marked by applying this function to them. The mark
|
|
|
5413 method should also return a Lisp object, which should be either nil or
|
|
|
5414 an object to mark. (This can be used in lieu of calling
|
|
|
5415 @code{mark_object()} on the object, to reduce the recursion depth, and
|
|
|
5416 consequently should be the most heavily nested sub-object, such as a
|
|
|
5417 long list.)
|
|
|
5418
|
|
298
|
5419 @strong{Please note:} When the mark method is called, garbage collection
|
|
|
5420 is in progress, and special precautions need to be taken when accessing
|
|
|
5421 objects; see section (B) above.
|
|
0
|
5422
|
|
|
5423 If your mark method does not need to do anything, it can be
|
|
|
5424 @code{NULL}.
|
|
|
5425
|
|
|
5426 @item
|
|
|
5427 A @dfn{print} method. This is called to create a printed representation
|
|
|
5428 of the object, whenever @code{princ}, @code{prin1}, or the like is
|
|
|
5429 called. It is passed the object, a stream to which the output is to be
|
|
|
5430 directed, and an @code{escapeflag} which indicates whether the object's
|
|
|
5431 printed representation should be @dfn{escaped} so that it is
|
|
|
5432 readable. (This corresponds to the difference between @code{princ} and
|
|
|
5433 @code{prin1}.) Basically, @dfn{escaped} means that strings will have
|
|
|
5434 quotes around them and confusing characters in the strings such as
|
|
|
5435 quotes, backslashes, and newlines will be backslashed; and that special
|
|
|
5436 care will be taken to make symbols print in a readable fashion
|
|
|
5437 (e.g. symbols that look like numbers will be backslashed). Other
|
|
|
5438 readable objects should perhaps pass @code{escapeflag} on when
|
|
|
5439 sub-objects are printed, so that readability is preserved when necessary
|
|
|
5440 (or if not, always pass in a 1 for @code{escapeflag}). Non-readable
|
|
|
5441 objects should in general ignore @code{escapeflag}, except that some use
|
|
|
5442 it as an indication that more verbose output should be given.
|
|
|
5443
|
|
|
5444 Sub-objects are printed using @code{print_internal()}, which takes
|
|
|
5445 exactly the same arguments as are passed to the print method.
|
|
|
5446
|
|
|
5447 Literal C strings should be printed using @code{write_c_string()},
|
|
|
5448 or @code{write_string_1()} for non-null-terminated strings.
|
|
|
5449
|
|
|
5450 Functions that do not have a readable representation should check the
|
|
|
5451 @code{print_readably} flag and signal an error if it is set.
|
|
|
5452
|
|
|
5453 If you specify NULL for the print method, the
|
|
|
5454 @code{default_object_printer()} will be used.
|
|
|
5455
|
|
|
5456 @item
|
|
|
5457 A @dfn{finalize} method. This is called at the beginning of the sweep
|
|
|
5458 stage on lcrecords that are about to be freed, and should be used to
|
|
|
5459 perform any extra object cleanup. This typically involves freeing any
|
|
|
5460 extra @code{malloc()}ed memory associated with the object, releasing any
|
|
|
5461 operating-system and window-system resources associated with the object
|
|
|
5462 (e.g. pixmaps, fonts), etc.
|
|
|
5463
|
|
|
5464 The finalize method can be NULL if nothing needs to be done.
|
|
|
5465
|
|
|
5466 WARNING #1: The finalize method is also called at the end of the dump
|
|
|
5467 phase; this time with the for_disksave parameter set to non-zero. The
|
|
|
5468 object is @emph{not} about to disappear, so you have to make sure to
|
|
|
5469 @emph{not} free any extra @code{malloc()}ed memory if you're going to
|
|
|
5470 need it later. (Also, signal an error if there are any operating-system
|
|
|
5471 and window-system resources here, because they can't be dumped.)
|
|
|
5472
|
|
|
5473 Finalize methods should, as a rule, set to zero any pointers after
|
|
|
5474 they've been freed, and check to make sure pointers are not zero before
|
|
|
5475 freeing. Although I'm pretty sure that finalize methods are not called
|
|
|
5476 twice on the same object (except for the @code{for_disksave} proviso),
|
|
|
5477 we've gotten nastily burned in some cases by not doing this.
|
|
|
5478
|
|
|
5479 WARNING #2: The finalize method is @emph{only} called for
|
|
|
5480 lcrecords, @emph{not} for simply lrecords. If you need a
|
|
|
5481 finalize method for simple lrecords, you have to stick
|
|
|
5482 it in the @code{ADDITIONAL_FREE_foo()} macro in @file{alloc.c}.
|
|
|
5483
|
|
|
5484 WARNING #3: Things are in an @emph{extremely} bizarre state
|
|
|
5485 when @code{ADDITIONAL_FREE_foo()} is called, so you have to
|
|
|
5486 be incredibly careful when writing one of these functions.
|
|
|
5487 See the comment in @code{gc_sweep()}. If you ever have to add
|
|
|
5488 one of these, consider using an lcrecord or dealing with
|
|
|
5489 the problem in a different fashion.
|
|
|
5490
|
|
|
5491 @item
|
|
|
5492 An @dfn{equal} method. This compares the two objects for similarity,
|
|
|
5493 when @code{equal} is called. It should compare the contents of the
|
|
|
5494 objects in some reasonable fashion. It is passed the two objects and a
|
|
|
5495 @dfn{depth} value, which is used to catch circular objects. To compare
|
|
|
5496 sub-Lisp-objects, call @code{internal_equal()} and bump the depth value
|
|
|
5497 by one. If this value gets too high, a @code{circular-object} error
|
|
|
5498 will be signaled.
|
|
|
5499
|
|
|
5500 If this is NULL, objects are @code{equal} only when they are @code{eq},
|
|
|
5501 i.e. identical.
|
|
|
5502
|
|
|
5503 @item
|
|
|
5504 A @dfn{hash} method. This is used to hash objects when they are to be
|
|
|
5505 compared with @code{equal}. The rule here is that if two objects are
|
|
|
5506 @code{equal}, they @emph{must} hash to the same value; i.e. your hash
|
|
|
5507 function should use some subset of the sub-fields of the object that are
|
|
|
5508 compared in the ``equal'' method. If you specify this method as
|
|
|
5509 @code{NULL}, the object's pointer will be used as the hash, which will
|
|
|
5510 @emph{fail} if the object has an @code{equal} method, so don't do this.
|
|
|
5511
|
|
|
5512 To hash a sub-Lisp-object, call @code{internal_hash()}. Bump the
|
|
|
5513 depth by one, just like in the ``equal'' method.
|
|
|
5514
|
|
|
5515 To convert a Lisp object directly into a hash value (using
|
|
|
5516 its pointer), use @code{LISP_HASH()}. This is what happens when
|
|
|
5517 the hash method is NULL.
|
|
|
5518
|
|
|
5519 To hash two or more values together into a single value, use
|
|
|
5520 @code{HASH2()}, @code{HASH3()}, @code{HASH4()}, etc.
|
|
|
5521
|
|
|
5522 @item
|
|
|
5523 @dfn{getprop}, @dfn{putprop}, @dfn{remprop}, and @dfn{plist} methods.
|
|
|
5524 These are used for object types that have properties. I don't feel like
|
|
|
5525 documenting them here. If you create one of these objects, you have to
|
|
|
5526 use different macros to define them,
|
|
|
5527 i.e. @code{DEFINE_LRECORD_IMPLEMENTATION_WITH_PROPS()} or
|
|
|
5528 @code{DEFINE_LRECORD_SEQUENCE_IMPLEMENTATION_WITH_PROPS()}.
|
|
|
5529
|
|
|
5530 @item
|
|
|
5531 A @dfn{size_in_bytes} method, when the object is of variable-size.
|
|
|
5532 (i.e. declared with a @code{_SEQUENCE_IMPLEMENTATION} macro.) This should
|
|
|
5533 simply return the object's size in bytes, exactly as you might expect.
|
|
|
5534 For an example, see the methods for window configurations and opaques.
|
|
|
5535 @end enumerate
|
|
|
5536
|
|
398
|
5537 @node Low-level allocation, Pure Space, lrecords, Allocation of Objects in XEmacs Lisp
|
|
0
|
5538 @section Low-level allocation
|
|
|
5539
|
|
|
5540 Memory that you want to allocate directly should be allocated using
|
|
|
5541 @code{xmalloc()} rather than @code{malloc()}. This implements
|
|
|
5542 error-checking on the return value, and once upon a time did some more
|
|
|
5543 vital stuff (i.e. @code{BLOCK_INPUT}, which is no longer necessary).
|
|
|
5544 Free using @code{xfree()}, and realloc using @code{xrealloc()}. Note
|
|
|
5545 that @code{xmalloc()} will do a non-local exit if the memory can't be
|
|
|
5546 allocated. (Many functions, however, do not expect this, and thus XEmacs
|
|
|
5547 will likely crash if this happens. @strong{This is a bug.} If you can,
|
|
|
5548 you should strive to make your function handle this OK. However, it's
|
|
|
5549 difficult in the general circumstance, perhaps requiring extra
|
|
|
5550 unwind-protects and such.)
|
|
|
5551
|
|
|
5552 Note that XEmacs provides two separate replacements for the standard
|
|
|
5553 @code{malloc()} library function. These are called @dfn{old GNU malloc}
|
|
|
5554 (@file{malloc.c}) and @dfn{new GNU malloc} (@file{gmalloc.c}),
|
|
|
5555 respectively. New GNU malloc is better in pretty much every way than
|
|
|
5556 old GNU malloc, and should be used if possible. (It used to be that on
|
|
|
5557 some systems, the old one worked but the new one didn't. I think this
|
|
|
5558 was due specifically to a bug in SunOS, which the new one now works
|
|
|
5559 around; so I don't think the old one ever has to be used any more.) The
|
|
|
5560 primary difference between both of these mallocs and the standard system
|
|
|
5561 malloc is that they are much faster, at the expense of increased space.
|
|
|
5562 The basic idea is that memory is allocated in fixed chunks of powers of
|
|
|
5563 two. This allows for basically constant malloc time, since the various
|
|
|
5564 chunks can just be kept on a number of free lists. (The standard system
|
|
|
5565 malloc typically allocates arbitrary-sized chunks and has to spend some
|
|
|
5566 time, sometimes a significant amount of time, walking the heap looking
|
|
|
5567 for a free block to use and cleaning things up.) The new GNU malloc
|
|
|
5568 improves on things by allocating large objects in chunks of 4096 bytes
|
|
|
5569 rather than in ever larger powers of two, which results in ever larger
|
|
|
5570 wastage. There is a slight speed loss here, but it's of doubtful
|
|
|
5571 significance.
|
|
|
5572
|
|
|
5573 NOTE: Apparently there is a third-generation GNU malloc that is
|
|
|
5574 significantly better than the new GNU malloc, and should probably
|
|
|
5575 be included in XEmacs.
|
|
|
5576
|
|
|
5577 There is also the relocating allocator, @file{ralloc.c}. This actually
|
|
|
5578 moves blocks of memory around so that the @code{sbrk()} pointer shrunk
|
|
|
5579 and virtual memory released back to the system. On some systems,
|
|
|
5580 this is a big win. On all systems, it causes a noticeable (and
|
|
|
5581 sometimes huge) speed penalty, so I turn it off by default.
|
|
|
5582 @file{ralloc.c} only works with the new GNU malloc in @file{gmalloc.c}.
|
|
|
5583 There are also two versions of @file{ralloc.c}, one that uses @code{mmap()}
|
|
|
5584 rather than block copies to move data around. This purports to
|
|
|
5585 be faster, although that depends on the amount of data that would
|
|
|
5586 have had to be block copied and the system-call overhead for
|
|
|
5587 @code{mmap()}. I don't know exactly how this works, except that the
|
|
|
5588 relocating-allocation routines are pretty much used only for
|
|
|
5589 the memory allocated for a buffer, which is the biggest consumer
|
|
|
5590 of space, esp. of space that may get freed later.
|
|
|
5591
|
|
|
5592 Note that the GNU mallocs have some ``memory warning'' facilities.
|
|
|
5593 XEmacs taps into them and issues a warning through the standard
|
|
|
5594 warning system, when memory gets to 75%, 85%, and 95% full.
|
|
|
5595 (On some systems, the memory warnings are not functional.)
|
|
|
5596
|
|
|
5597 Allocated memory that is going to be used to make a Lisp object
|
|
|
5598 is created using @code{allocate_lisp_storage()}. This calls @code{xmalloc()}
|
|
|
5599 but also verifies that the pointer to the memory can fit into
|
|
|
5600 a Lisp word (remember that some bits are taken away for a type
|
|
|
5601 tag and a mark bit). If not, an error is issued through @code{memory_full()}.
|
|
|
5602 @code{allocate_lisp_storage()} is called by @code{alloc_lcrecord()},
|
|
|
5603 @code{ALLOCATE_FIXED_TYPE()}, and the vector and bit-vector creation
|
|
|
5604 routines. These routines also call @code{INCREMENT_CONS_COUNTER()} at the
|
|
|
5605 appropriate times; this keeps statistics on how much memory is
|
|
|
5606 allocated, so that garbage-collection can be invoked when the
|
|
|
5607 threshold is reached.
|
|
|
5608
|
|
398
|
5609 @node Pure Space, Cons, Low-level allocation, Allocation of Objects in XEmacs Lisp
|
|
0
|
5610 @section Pure Space
|
|
|
5611
|
|
|
5612 Not yet documented.
|
|
|
5613
|
|
398
|
5614 @node Cons, Vector, Pure Space, Allocation of Objects in XEmacs Lisp
|
|
0
|
5615 @section Cons
|
|
|
5616
|
|
|
5617 Conses are allocated in standard frob blocks. The only thing to
|
|
|
5618 note is that conses can be explicitly freed using @code{free_cons()}
|
|
|
5619 and associated functions @code{free_list()} and @code{free_alist()}. This
|
|
|
5620 immediately puts the conses onto the cons free list, and decrements
|
|
|
5621 the statistics on memory allocation appropriately. This is used
|
|
|
5622 to good effect by some extremely commonly-used code, to avoid
|
|
|
5623 generating extra objects and thereby triggering GC sooner.
|
|
|
5624 However, you have to be @emph{extremely} careful when doing this.
|
|
|
5625 If you mess this up, you will get BADLY BURNED, and it has happened
|
|
|
5626 before.
|
|
|
5627
|
|
398
|
5628 @node Vector, Bit Vector, Cons, Allocation of Objects in XEmacs Lisp
|
|
0
|
5629 @section Vector
|
|
|
5630
|
|
|
5631 As mentioned above, each vector is @code{malloc()}ed individually, and
|
|
|
5632 all are threaded through the variable @code{all_vectors}. Vectors are
|
|
|
5633 marked strangely during garbage collection, by kludging the size field.
|
|
116
|
5634 Note that the @code{struct Lisp_Vector} is declared with its
|
|
|
5635 @code{contents} field being a @emph{stretchy} array of one element. It
|
|
|
5636 is actually @code{malloc()}ed with the right size, however, and access
|
|
|
5637 to any element through the @code{contents} array works fine.
|
|
0
|
5638
|
|
398
|
5639 @node Bit Vector, Symbol, Vector, Allocation of Objects in XEmacs Lisp
|
|
0
|
5640 @section Bit Vector
|
|
|
5641
|
|
|
5642 Bit vectors work exactly like vectors, except for more complicated
|
|
|
5643 code to access an individual bit, and except for the fact that bit
|
|
|
5644 vectors are lrecords while vectors are not. (The only difference here is
|
|
|
5645 that there's an lrecord implementation pointer at the beginning and the
|
|
|
5646 tag field in bit vector Lisp words is ``lrecord'' rather than
|
|
|
5647 ``vector''.)
|
|
|
5648
|
|
398
|
5649 @node Symbol, Marker, Bit Vector, Allocation of Objects in XEmacs Lisp
|
|
0
|
5650 @section Symbol
|
|
|
5651
|
|
|
5652 Symbols are also allocated in frob blocks. Note that the code
|
|
|
5653 exists for symbols to be either lrecords (category (c) above)
|
|
|
5654 or simple types (category (b) above), and are lrecords by
|
|
|
5655 default (I think), although there is no good reason for this.
|
|
|
5656
|
|
|
5657 Note that symbols in the awful horrible obarray structure are
|
|
|
5658 chained through their @code{next} field.
|
|
|
5659
|
|
|
5660 Remember that @code{intern} looks up a symbol in an obarray, creating
|
|
|
5661 one if necessary.
|
|
|
5662
|
|
398
|
5663 @node Marker, String, Symbol, Allocation of Objects in XEmacs Lisp
|
|
0
|
5664 @section Marker
|
|
|
5665
|
|
|
5666 Markers are allocated in frob blocks, as usual. They are kept
|
|
|
5667 in a buffer unordered, but in a doubly-linked list so that they
|
|
|
5668 can easily be removed. (Formerly this was a singly-linked list,
|
|
|
5669 but in some cases garbage collection took an extraordinarily
|
|
|
5670 long time due to the O(N^2) time required to remove lots of
|
|
|
5671 markers from a buffer.) Markers are removed from a buffer in
|
|
|
5672 the finalize stage, in @code{ADDITIONAL_FREE_marker()}.
|
|
|
5673
|
|
398
|
5674 @node String, Compiled Function, Marker, Allocation of Objects in XEmacs Lisp
|
|
0
|
5675 @section String
|
|
|
5676
|
|
|
5677 As mentioned above, strings are a special case. A string is logically
|
|
|
5678 two parts, a fixed-size object (containing the length, property list,
|
|
|
5679 and a pointer to the actual data), and the actual data in the string.
|
|
|
5680 The fixed-size object is a @code{struct Lisp_String} and is allocated in
|
|
|
5681 frob blocks, as usual. The actual data is stored in special
|
|
|
5682 @dfn{string-chars blocks}, which are 8K blocks of memory.
|
|
|
5683 Currently-allocated strings are simply laid end to end in these
|
|
|
5684 string-chars blocks, with a pointer back to the @code{struct Lisp_String}
|
|
|
5685 stored before each string in the string-chars block. When a new string
|
|
|
5686 needs to be allocated, the remaining space at the end of the last
|
|
|
5687 string-chars block is used if there's enough, and a new string-chars
|
|
|
5688 block is created otherwise.
|
|
|
5689
|
|
|
5690 There are never any holes in the string-chars blocks due to the string
|
|
|
5691 compaction and relocation that happens at the end of garbage collection.
|
|
|
5692 During the sweep stage of garbage collection, when objects are
|
|
|
5693 reclaimed, the garbage collector goes through all string-chars blocks,
|
|
|
5694 looking for unused strings. Each chunk of string data is preceded by a
|
|
|
5695 pointer to the corresponding @code{struct Lisp_String}, which indicates
|
|
|
5696 both whether the string is used and how big the string is, i.e. how to
|
|
2
|
5697 get to the next chunk of string data. Holes are compressed by
|
|
0
|
5698 block-copying the next string into the empty space and relocating the
|
|
|
5699 pointer stored in the corresponding @code{struct Lisp_String}.
|
|
|
5700 @strong{This means you have to be careful with strings in your code.}
|
|
|
5701 See the section above on @code{GCPRO}ing.
|
|
|
5702
|
|
|
5703 Note that there is one situation not handled: a string that is too big
|
|
|
5704 to fit into a string-chars block. Such strings, called @dfn{big
|
|
|
5705 strings}, are all @code{malloc()}ed as their own block. (#### Although it
|
|
|
5706 would make more sense for the threshold for big strings to be somewhat
|
|
|
5707 lower, e.g. 1/2 or 1/4 the size of a string-chars block. It seems that
|
|
398
|
5708 this was indeed the case formerly---indeed, the threshold was set at
|
|
|
5709 1/8---but Mly forgot about this when rewriting things for 19.8.)
|
|
0
|
5710
|
|
|
5711 Note also that the string data in string-chars blocks is padded as
|
|
|
5712 necessary so that proper alignment constraints on the @code{struct
|
|
|
5713 Lisp_String} back pointers are maintained.
|
|
|
5714
|
|
|
5715 Finally, strings can be resized. This happens in Mule when a
|
|
|
5716 character is substituted with a different-length character, or during
|
|
|
5717 modeline frobbing. (You could also export this to Lisp, but it's not
|
|
|
5718 done so currently.) Resizing a string is a potentially tricky process.
|
|
|
5719 If the change is small enough that the padding can absorb it, nothing
|
|
|
5720 other than a simple memory move needs to be done. Keep in mind,
|
|
|
5721 however, that the string can't shrink too much because the offset to the
|
|
|
5722 next string in the string-chars block is computed by looking at the
|
|
|
5723 length and rounding to the nearest multiple of four or eight. If the
|
|
|
5724 string would shrink or expand beyond the correct padding, new string
|
|
|
5725 data needs to be allocated at the end of the last string-chars block and
|
|
|
5726 the data moved appropriately. This leaves some dead string data, which
|
|
|
5727 is marked by putting a special marker of 0xFFFFFFFF in the @code{struct
|
|
|
5728 Lisp_String} pointer before the data (there's no real @code{struct
|
|
|
5729 Lisp_String} to point to and relocate), and storing the size of the dead
|
|
|
5730 string data (which would normally be obtained from the now-non-existent
|
|
|
5731 @code{struct Lisp_String}) at the beginning of the dead string data gap.
|
|
|
5732 The string compactor recognizes this special 0xFFFFFFFF marker and
|
|
|
5733 handles it correctly.
|
|
|
5734
|
|
398
|
5735 @node Compiled Function, , String, Allocation of Objects in XEmacs Lisp
|
|
380
|
5736 @section Compiled Function
|
|
0
|
5737
|
|
|
5738 Not yet documented.
|
|
|
5739
|
|
398
|
5740
|
|
|
5741 @node Dumping, Events and the Event Loop, Allocation of Objects in XEmacs Lisp, Top
|
|
|
5742 @chapter Dumping
|
|
|
5743
|
|
|
5744 @section What is dumping and its justification
|
|
|
5745
|
|
|
5746 The C code of XEmacs is just a Lisp engine with a lot of built-in
|
|
|
5747 primitives useful for writing an editor. The editor itself is written
|
|
|
5748 mostly in Lisp, and represents around 100K lines of code. Loading and
|
|
|
5749 executing the initialization of all this code takes a bit a time (five
|
|
|
5750 to ten times the usual startup time of current xemacs) and requires
|
|
|
5751 having all the lisp source files around. Having to reload them each
|
|
|
5752 time the editor is started would not be acceptable.
|
|
|
5753
|
|
|
5754 The traditional solution to this problem is called dumping: the build
|
|
|
5755 process first creates the lisp engine under the name @file{temacs}, then
|
|
|
5756 runs it until it has finished loading and initializing all the lisp
|
|
|
5757 code, and eventually creates a new executable called @file{xemacs}
|
|
|
5758 including both the object code in @file{temacs} and all the contents of
|
|
|
5759 the memory after the initialization.
|
|
|
5760
|
|
|
5761 This solution, while working, has a huge problem: the creation of the
|
|
|
5762 new executable from the actual contents of memory is an extremely
|
|
|
5763 system-specific process, quite error-prone, and which interferes with a
|
|
|
5764 lot of system libraries (like malloc). It is even getting worse
|
|
|
5765 nowadays with libraries using constructors which are automatically
|
|
|
5766 called when the program is started (even before main()) which tend to
|
|
|
5767 crash when they are called multiple times, once before dumping and once
|
|
|
5768 after (IRIX 6.x libz.so pulls in some C++ image libraries thru
|
|
|
5769 dependencies which have this problem). Writing the dumper is also one
|
|
|
5770 of the most difficult parts of porting XEmacs to a new operating system.
|
|
|
5771 Basically, `dumping' is an operation that is just not officially
|
|
|
5772 supported on many operating systems.
|
|
|
5773
|
|
|
5774 The aim of the portable dumper is to solve the same problem as the
|
|
|
5775 system-specific dumper, that is to be able to reload quickly, using only
|
|
|
5776 a small number of files, the fully initialized lisp part of the editor,
|
|
|
5777 without any system-specific hacks.
|
|
|
5778
|
|
|
5779 @menu
|
|
|
5780 * Overview::
|
|
|
5781 * Data descriptions::
|
|
|
5782 * Dumping phase::
|
|
|
5783 * Reloading phase::
|
|
|
5784 * Remaining issues::
|
|
|
5785 @end menu
|
|
|
5786
|
|
|
5787 @node Overview, Data descriptions, Dumping, Dumping
|
|
|
5788 @section Overview
|
|
|
5789
|
|
|
5790 The portable dumping system has to:
|
|
|
5791
|
|
|
5792 @enumerate
|
|
|
5793 @item
|
|
|
5794 At dump time, write all initialized, non-quickly-rebuildable data to a
|
|
|
5795 file [Note: currently named @file{xemacs.dmp}, but the name will
|
|
|
5796 change], along with all informations needed for the reloading.
|
|
|
5797
|
|
|
5798 @item
|
|
|
5799 When starting xemacs, reload the dump file, relocate it to its new
|
|
|
5800 starting address if needed, and reinitialize all pointers to this
|
|
|
5801 data. Also, rebuild all the quickly rebuildable data.
|
|
|
5802 @end enumerate
|
|
|
5803
|
|
|
5804 @node Data descriptions, Dumping phase, Overview, Dumping
|
|
|
5805 @section Data descriptions
|
|
|
5806
|
|
|
5807 The more complex task of the dumper is to be able to write lisp objects
|
|
|
5808 (lrecords) and C structs to disk and reload them at a different address,
|
|
|
5809 updating all the pointers they include in the process. This is done by
|
|
|
5810 using external data descriptions that give information about the layout
|
|
|
5811 of the structures in memory.
|
|
|
5812
|
|
|
5813 The specification of these descriptions is in lrecord.h. A description
|
|
|
5814 of an lrecord is an array of struct lrecord_description. Each of these
|
|
|
5815 structs include a type, an offset in the structure and some optional
|
|
|
5816 parameters depending on the type. For instance, here is the string
|
|
|
5817 description:
|
|
|
5818
|
|
|
5819 @example
|
|
|
5820 static const struct lrecord_description string_description[] = @{
|
|
|
5821 @{ XD_BYTECOUNT, offsetof (Lisp_String, size) @},
|
|
|
5822 @{ XD_OPAQUE_DATA_PTR, offsetof (Lisp_String, data), XD_INDIRECT(0, 1) @},
|
|
|
5823 @{ XD_LISP_OBJECT, offsetof (Lisp_String, plist) @},
|
|
|
5824 @{ XD_END @}
|
|
|
5825 @};
|
|
|
5826 @end example
|
|
|
5827
|
|
|
5828 The first line indicates a member of type Bytecount, which is used by
|
|
|
5829 the next, indirect directive. The second means "there is a pointer to
|
|
|
5830 some opaque data in the field @code{data}". The length of said data is
|
|
|
5831 given by the expression @code{XD_INDIRECT(0, 1)}, which means "the value
|
|
|
5832 in the 0th line of the description (welcome to C) plus one". The third
|
|
|
5833 line means "there is a Lisp_Object member @code{plist} in the Lisp_String
|
|
|
5834 structure". @code{XD_END} then ends the description.
|
|
|
5835
|
|
|
5836 This gives us all the information we need to move around what is pointed
|
|
|
5837 to by a structure (C or lrecord) and, by transitivity, everything that
|
|
|
5838 it points to. The only missing information for dumping is the size of
|
|
|
5839 the structure. For lrecords, this is part of the
|
|
|
5840 lrecord_implementation, so we don't need to duplicate it. For C
|
|
|
5841 structures we use a struct struct_description, which includes a size
|
|
|
5842 field and a pointer to an associated array of lrecord_description.
|
|
|
5843
|
|
|
5844 @node Dumping phase, Reloading phase, Data descriptions, Dumping
|
|
|
5845 @section Dumping phase
|
|
|
5846
|
|
|
5847 Dumping is done by calling the function pdump() (in alloc.c) which is
|
|
|
5848 invoked from Fdump_emacs (in emacs.c). This function performs a number
|
|
|
5849 of tasks.
|
|
|
5850
|
|
|
5851 @menu
|
|
|
5852 * Object inventory::
|
|
|
5853 * Address allocation::
|
|
|
5854 * The header::
|
|
|
5855 * Data dumping::
|
|
|
5856 * Pointers dumping::
|
|
|
5857 @end menu
|
|
|
5858
|
|
|
5859 @node Object inventory, Address allocation, Dumping phase, Dumping phase
|
|
|
5860 @subsection Object inventory
|
|
|
5861
|
|
|
5862 The first task is to build the list of the objects to dump. This
|
|
|
5863 includes:
|
|
|
5864
|
|
|
5865 @itemize @bullet
|
|
|
5866 @item lisp objects
|
|
|
5867 @item C structures
|
|
|
5868 @end itemize
|
|
|
5869
|
|
|
5870 We end up with one @code{pdump_entry_list_elmt} per object group (arrays
|
|
|
5871 of C structs are kept together) which includes a pointer to the first
|
|
|
5872 object of the group, the per-object size and the count of objects in the
|
|
|
5873 group, along with some other information which is initialized later.
|
|
|
5874
|
|
|
5875 These entries are linked together in @code{pdump_entry_list} structures
|
|
|
5876 and can be enumerated thru either:
|
|
|
5877
|
|
|
5878 @enumerate
|
|
|
5879 @item
|
|
|
5880 the @code{pdump_object_table}, an array of @code{pdump_entry_list}, one
|
|
|
5881 per lrecord type, indexed by type number.
|
|
|
5882
|
|
|
5883 @item
|
|
|
5884 the @code{pdump_opaque_data_list}, used for the opaque data which does
|
|
|
5885 not include pointers, and hence does not need descriptions.
|
|
|
5886
|
|
|
5887 @item
|
|
|
5888 the @code{pdump_struct_table}, which is a vector of
|
|
|
5889 @code{struct_description}/@code{pdump_entry_list} pairs, used for
|
|
|
5890 non-opaque C structures.
|
|
|
5891 @end enumerate
|
|
|
5892
|
|
|
5893 This uses a marking strategy similar to the garbage collector. Some
|
|
|
5894 differences though:
|
|
|
5895
|
|
|
5896 @enumerate
|
|
|
5897 @item
|
|
|
5898 We do not use the mark bit (which does not exist for C structures
|
|
|
5899 anyway), we use a big hash table instead.
|
|
|
5900
|
|
|
5901 @item
|
|
|
5902 We do not use the mark function of lrecords but instead rely on the
|
|
|
5903 external descriptions. This happens essentially because we need to
|
|
|
5904 follow pointers to C structures and opaque data in addition to
|
|
|
5905 Lisp_Object members.
|
|
|
5906 @end enumerate
|
|
|
5907
|
|
|
5908 This is done by @code{pdump_register_object}, which handles Lisp_Object
|
|
|
5909 variables, and pdump_register_struct which handles C structures, which
|
|
|
5910 both delegate the description management to pdump_register_sub.
|
|
|
5911
|
|
|
5912 The hash table doubles as a map object to pdump_entry_list_elmt (i.e.
|
|
|
5913 allows us to look up a pdump_entry_list_elmt with the object it points
|
|
|
5914 to). Entries are added with @code{pdump_add_entry()} and looked up with
|
|
|
5915 @code{pdump_get_entry()}. There is no need for entry removal. The hash
|
|
|
5916 value is computed quite basically from the object pointer by
|
|
|
5917 @code{pdump_make_hash()}.
|
|
|
5918
|
|
|
5919 The roots for the marking are:
|
|
|
5920
|
|
|
5921 @enumerate
|
|
|
5922 @item
|
|
|
5923 the @code{staticpro}'ed variables (there is a special @code{staticpro_nodump()}
|
|
|
5924 call for protected variables we do not want to dump).
|
|
|
5925
|
|
|
5926 @item
|
|
|
5927 the @code{pdump_wire}'d variables (@code{staticpro} is equivalent to
|
|
|
5928 @code{staticpro_nodump()} + @code{pdump_wire()}).
|
|
|
5929
|
|
|
5930 @item
|
|
|
5931 the @code{dumpstruct}'ed variables, which points to C structures.
|
|
|
5932 @end enumerate
|
|
|
5933
|
|
|
5934 This does not include the GCPRO'ed variables, the specbinds, the
|
|
|
5935 catchtags, the backlist, the redisplay or the profiling info, since we
|
|
|
5936 do not want to rebuild the actual chain of lisp calls which end up to
|
|
|
5937 the dump-emacs call, only the global variables.
|
|
|
5938
|
|
|
5939 Weak lists and weak hash tables are dumped as if they were their
|
|
|
5940 non-weak equivalent (without changing their type, of course). This has
|
|
|
5941 not yet been a problem.
|
|
|
5942
|
|
|
5943 @node Address allocation, The header, Object inventory, Dumping phase
|
|
|
5944 @subsection Address allocation
|
|
|
5945
|
|
|
5946
|
|
|
5947 The next step is to allocate the offsets of each of the objects in the
|
|
|
5948 final dump file. This is done by @code{pdump_allocate_offset()} which
|
|
|
5949 is called indirectly by @code{pdump_scan_by_alignment()}.
|
|
|
5950
|
|
|
5951 The strategy to deal with alignment problems uses these facts:
|
|
|
5952
|
|
|
5953 @enumerate
|
|
|
5954 @item
|
|
|
5955 real world alignment requirements are powers of two.
|
|
|
5956
|
|
|
5957 @item
|
|
|
5958 the C compiler is required to adjust the size of a struct so that you
|
|
|
5959 can have an array of them next to each other. This means you can have a
|
|
|
5960 upper bound of the alignment requirements of a given structure by
|
|
|
5961 looking at which power of two its size is a multiple.
|
|
|
5962
|
|
|
5963 @item
|
|
|
5964 the non-variant part of variable size lrecords has an alignment
|
|
|
5965 requirement of 4.
|
|
|
5966 @end enumerate
|
|
|
5967
|
|
|
5968 Hence, for each lrecord type, C struct type or opaque data block the
|
|
|
5969 alignment requirement is computed as a power of two, with a minimum of
|
|
|
5970 2^2 for lrecords. @code{pdump_scan_by_alignment()} then scans all the
|
|
|
5971 @code{pdump_entry_list_elmt}'s, the ones with the highest requirements
|
|
|
5972 first. This ensures the best packing.
|
|
|
5973
|
|
|
5974 The maximum alignment requirement we take into account is 2^8.
|
|
|
5975
|
|
|
5976 @code{pdump_allocate_offset()} only has to do a linear allocation,
|
|
|
5977 starting at offset 256 (this leaves room for the header and keep the
|
|
|
5978 alignments happy).
|
|
|
5979
|
|
|
5980 @node The header, Data dumping, Address allocation, Dumping phase
|
|
|
5981 @subsection The header
|
|
|
5982
|
|
|
5983 The next step creates the file and writes a header with a signature and
|
|
|
5984 some random informations in it (number of staticpro, number of assigned
|
|
|
5985 lrecord types, etc...). The reloc_address field, which indicates at
|
|
|
5986 which address the file should be loaded if we want to avoid post-reload
|
|
|
5987 relocation, is set to 0. It then seeks to offset 256 (base offset for
|
|
|
5988 the objects).
|
|
|
5989
|
|
|
5990 @node Data dumping, Pointers dumping, The header, Dumping phase
|
|
|
5991 @subsection Data dumping
|
|
|
5992
|
|
|
5993 The data is dumped in the same order as the addresses were allocated by
|
|
|
5994 @code{pdump_dump_data()}, called from @code{pdump_scan_by_alignment()}.
|
|
|
5995 This function copies the data to a temporary buffer, relocates all
|
|
|
5996 pointers in the object to the addresses allocated in step Address
|
|
|
5997 Allocation, and writes it to the file. Using the same order means that,
|
|
|
5998 if we are careful with lrecords whose size is not a multiple of 4, we
|
|
|
5999 are ensured that the object is always written at the offset in the file
|
|
|
6000 allocated in step Address Allocation.
|
|
|
6001
|
|
|
6002 @node Pointers dumping, , Data dumping, Dumping phase
|
|
|
6003 @subsection Pointers dumping
|
|
|
6004
|
|
|
6005 A bunch of tables needed to reassign properly the global pointers are
|
|
|
6006 then written. They are:
|
|
|
6007
|
|
|
6008 @enumerate
|
|
|
6009 @item the staticpro array
|
|
|
6010 @item the dumpstruct array
|
|
|
6011 @item the lrecord_implementation_table array
|
|
|
6012 @item a vector of all the offsets to the objects in the file that include a
|
|
|
6013 description (for faster relocation at reload time)
|
|
|
6014 @item the pdump_wired and pdump_wired_list arrays
|
|
|
6015 @end enumerate
|
|
|
6016
|
|
|
6017 For each of the arrays we write both the pointer to the variables and
|
|
|
6018 the relocated offset of the object they point to. Since these variables
|
|
|
6019 are global, the pointers are still valid when restarting the program and
|
|
|
6020 are used to regenerate the global pointers.
|
|
|
6021
|
|
|
6022 The @code{pdump_wired_list} array is a special case. The variables it
|
|
|
6023 points to are the head of weak linked lists of lisp objects of the same
|
|
|
6024 type. Not all objects of this list are dumped so the relocated pointer
|
|
|
6025 we associate with them points to the first dumped object of the list, or
|
|
|
6026 Qnil if none is available. This is also the reason why they are not
|
|
|
6027 used as roots for the purpose of object enumeration.
|
|
|
6028
|
|
|
6029 This is the end of the dumping part.
|
|
|
6030
|
|
|
6031 @node Reloading phase, Remaining issues, Dumping phase, Dumping
|
|
|
6032 @section Reloading phase
|
|
|
6033
|
|
|
6034 @subsection File loading
|
|
|
6035
|
|
|
6036 The file is mmap'ed in memory (which ensures a PAGESIZE alignment, at
|
|
|
6037 least 4096), or if mmap is unavailable or fails, a 256-bytes aligned
|
|
|
6038 malloc is done and the file is loaded.
|
|
|
6039
|
|
|
6040 Some variables are reinitialized from the values found in the header.
|
|
|
6041
|
|
|
6042 The difference between the actual loading address and the reloc_address
|
|
|
6043 is computed and will be used for all the relocations.
|
|
|
6044
|
|
|
6045
|
|
|
6046 @subsection Putting back the staticvec
|
|
|
6047
|
|
|
6048 The staticvec array is memcpy'd from the file and the variables it
|
|
|
6049 points to are reset to the relocated objects addresses.
|
|
|
6050
|
|
|
6051
|
|
|
6052 @subsection Putting back the dumpstructed variables
|
|
|
6053
|
|
|
6054 The variables pointed to by dumpstruct in the dump phase are reset to
|
|
|
6055 the right relocated object addresses.
|
|
|
6056
|
|
|
6057
|
|
|
6058 @subsection lrecord_implementations_table
|
|
|
6059
|
|
|
6060 The lrecord_implementations_table is reset to its dump time state and
|
|
|
6061 the right lrecord_type_index values are put in.
|
|
|
6062
|
|
|
6063
|
|
|
6064 @subsection Object relocation
|
|
|
6065
|
|
|
6066 All the objects are relocated using their description and their offset
|
|
|
6067 by @code{pdump_reloc_one}. This step is unnecessary if the
|
|
|
6068 reloc_address is equal to the file loading address.
|
|
|
6069
|
|
|
6070
|
|
|
6071 @subsection Putting back the pdump_wire and pdump_wire_list variables
|
|
|
6072
|
|
|
6073 Same as Putting back the dumpstructed variables.
|
|
|
6074
|
|
|
6075
|
|
|
6076 @subsection Reorganize the hash tables
|
|
|
6077
|
|
|
6078 Since some of the hash values in the lisp hash tables are
|
|
|
6079 address-dependent, their layout is now wrong. So we go through each of
|
|
|
6080 them and have them resorted by calling @code{pdump_reorganize_hash_table}.
|
|
|
6081
|
|
|
6082 @node Remaining issues, , Reloading phase, Dumping
|
|
|
6083 @section Remaining issues
|
|
|
6084
|
|
|
6085 The build process will have to start a post-dump xemacs, ask it the
|
|
|
6086 loading address (which will, hopefully, be always the same between
|
|
|
6087 different xemacs invocations) and relocate the file to the new address.
|
|
|
6088 This way the object relocation phase will not have to be done, which
|
|
|
6089 means no writes in the objects and that, because of the use of mmap, the
|
|
|
6090 dumped data will be shared between all the xemacs running on the
|
|
|
6091 computer.
|
|
|
6092
|
|
|
6093 Some executable signature will be necessary to ensure that a given dump
|
|
|
6094 file is really associated with a given executable, or random crashes
|
|
|
6095 will occur. Maybe a random number set at compile or configure time thru
|
|
|
6096 a define. This will also allow for having differently-compiled xemacsen
|
|
|
6097 on the same system (mule and no-mule comes to mind).
|
|
|
6098
|
|
|
6099 The DOC file contents should probably end up in the dump file.
|
|
|
6100
|
|
|
6101
|
|
|
6102 @node Events and the Event Loop, Evaluation; Stack Frames; Bindings, Dumping, Top
|
|
0
|
6103 @chapter Events and the Event Loop
|
|
|
6104
|
|
|
6105 @menu
|
|
|
6106 * Introduction to Events::
|
|
|
6107 * Main Loop::
|
|
|
6108 * Specifics of the Event Gathering Mechanism::
|
|
|
6109 * Specifics About the Emacs Event::
|
|
|
6110 * The Event Stream Callback Routines::
|
|
|
6111 * Other Event Loop Functions::
|
|
|
6112 * Converting Events::
|
|
|
6113 * Dispatching Events; The Command Builder::
|
|
|
6114 @end menu
|
|
|
6115
|
|
398
|
6116 @node Introduction to Events, Main Loop, Events and the Event Loop, Events and the Event Loop
|
|
0
|
6117 @section Introduction to Events
|
|
|
6118
|
|
|
6119 An event is an object that encapsulates information about an
|
|
|
6120 interesting occurrence in the operating system. Events are
|
|
|
6121 generated either by user action, direct (e.g. typing on the
|
|
|
6122 keyboard or moving the mouse) or indirect (moving another
|
|
|
6123 window, thereby generating an expose event on an Emacs frame),
|
|
|
6124 or as a result of some other typically asynchronous action happening,
|
|
|
6125 such as output from a subprocess being ready or a timer expiring.
|
|
|
6126 Events come into the system in an asynchronous fashion (typically
|
|
|
6127 through a callback being called) and are converted into a
|
|
|
6128 synchronous event queue (first-in, first-out) in a process that
|
|
|
6129 we will call @dfn{collection}.
|
|
|
6130
|
|
2
|
6131 Note that each application has its own event queue. (It is
|
|
0
|
6132 immaterial whether the collection process directly puts the
|
|
|
6133 events in the proper application's queue, or puts them into
|
|
|
6134 a single system queue, which is later split up.)
|
|
|
6135
|
|
|
6136 The most basic level of event collection is done by the
|
|
|
6137 operating system or window system. Typically, XEmacs does
|
|
|
6138 its own event collection as well. Often there are multiple
|
|
|
6139 layers of collection in XEmacs, with events from various
|
|
|
6140 sources being collected into a queue, which is then combined
|
|
|
6141 with other sources to go into another queue (i.e. a second
|
|
|
6142 level of collection), with perhaps another level on top of
|
|
|
6143 this, etc.
|
|
|
6144
|
|
|
6145 XEmacs has its own types of events (called @dfn{Emacs events}),
|
|
|
6146 which provides an abstract layer on top of the system-dependent
|
|
|
6147 nature of the most basic events that are received. Part of the
|
|
|
6148 complex nature of the XEmacs event collection process involves
|
|
|
6149 converting from the operating-system events into the proper
|
|
398
|
6150 Emacs events---there may not be a one-to-one correspondence.
|
|
0
|
6151
|
|
|
6152 Emacs events are documented in @file{events.h}; I'll discuss them
|
|
|
6153 later.
|
|
|
6154
|
|
398
|
6155 @node Main Loop, Specifics of the Event Gathering Mechanism, Introduction to Events, Events and the Event Loop
|
|
0
|
6156 @section Main Loop
|
|
|
6157
|
|
|
6158 The @dfn{command loop} is the top-level loop that the editor is always
|
|
|
6159 running. It loops endlessly, calling @code{next-event} to retrieve an
|
|
|
6160 event and @code{dispatch-event} to execute it. @code{dispatch-event} does
|
|
|
6161 the appropriate thing with non-user events (process, timeout,
|
|
|
6162 magic, eval, mouse motion); this involves calling a Lisp handler
|
|
|
6163 function, redrawing a newly-exposed part of a frame, reading
|
|
|
6164 subprocess output, etc. For user events, @code{dispatch-event}
|
|
|
6165 looks up the event in relevant keymaps or menubars; when a
|
|
|
6166 full key sequence or menubar selection is reached, the appropriate
|
|
|
6167 function is executed. @code{dispatch-event} may have to keep state
|
|
|
6168 across calls; this is done in the ``command-builder'' structure
|
|
|
6169 associated with each console (remember, there's usually only
|
|
|
6170 one console), and the engine that looks up keystrokes and
|
|
|
6171 constructs full key sequences is called the @dfn{command builder}.
|
|
|
6172 This is documented elsewhere.
|
|
|
6173
|
|
|
6174 The guts of the command loop are in @code{command_loop_1()}. This
|
|
398
|
6175 function doesn't catch errors, though---that's the job of
|
|
0
|
6176 @code{command_loop_2()}, which is a condition-case (i.e. error-trapping)
|
|
|
6177 wrapper around @code{command_loop_1()}. @code{command_loop_1()} never
|
|
|
6178 returns, but may get thrown out of.
|
|
|
6179
|
|
|
6180 When an error occurs, @code{cmd_error()} is called, which usually
|
|
|
6181 invokes the Lisp error handler in @code{command-error}; however, a
|
|
|
6182 default error handler is provided if @code{command-error} is @code{nil}
|
|
|
6183 (e.g. during startup). The purpose of the error handler is simply to
|
|
|
6184 display the error message and do associated cleanup; it does not need to
|
|
|
6185 throw anywhere. When the error handler finishes, the condition-case in
|
|
|
6186 @code{command_loop_2()} will finish and @code{command_loop_2()} will
|
|
|
6187 reinvoke @code{command_loop_1()}.
|
|
|
6188
|
|
|
6189 @code{command_loop_2()} is invoked from three places: from
|
|
|
6190 @code{initial_command_loop()} (called from @code{main()} at the end of
|
|
|
6191 internal initialization), from the Lisp function @code{recursive-edit},
|
|
|
6192 and from @code{call_command_loop()}.
|
|
|
6193
|
|
|
6194 @code{call_command_loop()} is called when a macro is started and when
|
|
|
6195 the minibuffer is entered; normal termination of the macro or minibuffer
|
|
|
6196 causes a throw out of the recursive command loop. (To
|
|
|
6197 @code{execute-kbd-macro} for macros and @code{exit} for minibuffers.
|
|
|
6198 Note also that the low-level minibuffer-entering function,
|
|
|
6199 @code{read-minibuffer-internal}, provides its own error handling and
|
|
|
6200 does not need @code{command_loop_2()}'s error encapsulation; so it tells
|
|
|
6201 @code{call_command_loop()} to invoke @code{command_loop_1()} directly.)
|
|
|
6202
|
|
|
6203 Note that both read-minibuffer-internal and recursive-edit set up a
|
|
|
6204 catch for @code{exit}; this is why @code{abort-recursive-edit}, which
|
|
|
6205 throws to this catch, exits out of either one.
|
|
|
6206
|
|
|
6207 @code{initial_command_loop()}, called from @code{main()}, sets up a
|
|
|
6208 catch for @code{top-level} when invoking @code{command_loop_2()},
|
|
|
6209 allowing functions to throw all the way to the top level if they really
|
|
|
6210 need to. Before invoking @code{command_loop_2()},
|
|
|
6211 @code{initial_command_loop()} calls @code{top_level_1()}, which handles
|
|
|
6212 all of the startup stuff (creating the initial frame, handling the
|
|
|
6213 command-line options, loading the user's @file{.emacs} file, etc.). The
|
|
|
6214 function that actually does this is in Lisp and is pointed to by the
|
|
|
6215 variable @code{top-level}; normally this function is
|
|
|
6216 @code{normal-top-level}. @code{top_level_1()} is just an error-handling
|
|
|
6217 wrapper similar to @code{command_loop_2()}. Note also that
|
|
|
6218 @code{initial_command_loop()} sets up a catch for @code{top-level} when
|
|
|
6219 invoking @code{top_level_1()}, just like when it invokes
|
|
|
6220 @code{command_loop_2()}.
|
|
|
6221
|
|
398
|
6222 @node Specifics of the Event Gathering Mechanism, Specifics About the Emacs Event, Main Loop, Events and the Event Loop
|
|
0
|
6223 @section Specifics of the Event Gathering Mechanism
|
|
|
6224
|
|
|
6225 Here is an approximate diagram of the collection processes
|
|
|
6226 at work in XEmacs, under TTY's (TTY's are simpler than X
|
|
|
6227 so we'll look at this first):
|
|
|
6228
|
|
|
6229 @noindent
|
|
|
6230 @example
|
|
380
|
6231 asynch. asynch. asynch. asynch. [Collectors in
|
|
|
6232 kbd events kbd events process process the OS]
|
|
|
6233 | | output output
|
|
|
6234 | | | |
|
|
|
6235 | | | | SIGINT, [signal handlers
|
|
|
6236 | | | | SIGQUIT, in XEmacs]
|
|
0
|
6237 V V V V SIGWINCH,
|
|
|
6238 file file file file SIGALRM
|
|
|
6239 desc. desc. desc. desc. |
|
|
|
6240 (TTY) (TTY) (pipe) (pipe) |
|
|
|
6241 | | | | fake timeouts
|
|
|
6242 | | | | file |
|
|
|
6243 | | | | desc. |
|
|
|
6244 | | | | (pipe) |
|
|
|
6245 | | | | | |
|
|
|
6246 | | | | | |
|
|
|
6247 | | | | | |
|
|
|
6248 V V V V V V
|
|
|
6249 ------>-----------<----------------<----------------
|
|
380
|
6250 |
|
|
|
6251 |
|
|
|
6252 | [collected using select() in emacs_tty_next_event()
|
|
|
6253 | and converted to the appropriate Emacs event]
|
|
|
6254 |
|
|
|
6255 |
|
|
|
6256 V (above this line is TTY-specific)
|
|
|
6257 Emacs -----------------------------------------------
|
|
|
6258 event (below this line is the generic event mechanism)
|
|
|
6259 |
|
|
|
6260 |
|
|
|
6261 was there if not, call
|
|
|
6262 a SIGINT? emacs_tty_next_event()
|
|
|
6263 | |
|
|
|
6264 | |
|
|
|
6265 | |
|
|
|
6266 V V
|
|
|
6267 --->------<----
|
|
0
|
6268 |
|
|
380
|
6269 | [collected in event_stream_next_event();
|
|
|
6270 | SIGINT is converted using maybe_read_quit_event()]
|
|
0
|
6271 V
|
|
|
6272 Emacs
|
|
|
6273 event
|
|
|
6274 |
|
|
|
6275 \---->------>----- maybe_kbd_translate() ---->---\
|
|
|
6276 |
|
|
|
6277 |
|
|
|
6278 |
|
|
|
6279 command event queue |
|
|
380
|
6280 if not from command
|
|
|
6281 (contains events that were event queue, call
|
|
|
6282 read earlier but not processed, event_stream_next_event()
|
|
0
|
6283 typically when waiting in a |
|
|
|
6284 sit-for, sleep-for, etc. for |
|
|
|
6285 a particular event to be received) |
|
|
|
6286 | |
|
|
|
6287 | |
|
|
|
6288 V V
|
|
|
6289 ---->------------------------------------<----
|
|
|
6290 |
|
|
380
|
6291 | [collected in
|
|
|
6292 | next_event_internal()]
|
|
0
|
6293 |
|
|
|
6294 unread- unread- event from |
|
|
|
6295 command- command- keyboard else, call
|
|
|
6296 events event macro next_event_internal()
|
|
|
6297 | | | |
|
|
|
6298 | | | |
|
|
|
6299 | | | |
|
|
|
6300 V V V V
|
|
|
6301 --------->----------------------<------------
|
|
|
6302 |
|
|
|
6303 | [collected in `next-event', which may loop
|
|
|
6304 | more than once if the event it gets is on
|
|
|
6305 | a dead frame, device, etc.]
|
|
|
6306 |
|
|
|
6307 |
|
|
|
6308 V
|
|
|
6309 feed into top-level event loop,
|
|
|
6310 which repeatedly calls `next-event'
|
|
|
6311 and then dispatches the event
|
|
|
6312 using `dispatch-event'
|
|
|
6313 @end example
|
|
|
6314
|
|
|
6315 Notice the separation between TTY-specific and generic event mechanism.
|
|
|
6316 When using the Xt-based event loop, the TTY-specific stuff is replaced
|
|
|
6317 but the rest stays the same.
|
|
|
6318
|
|
|
6319 It's also important to realize that only one different kind of
|
|
|
6320 system-specific event loop can be operating at a time, and must be able
|
|
|
6321 to receive all kinds of events simultaneously. For the two existing
|
|
|
6322 event loops (implemented in @file{event-tty.c} and @file{event-Xt.c},
|
|
|
6323 respectively), the TTY event loop @emph{only} handles TTY consoles,
|
|
|
6324 while the Xt event loop handles @emph{both} TTY and X consoles. This
|
|
|
6325 situation is different from all of the output handlers, where you simply
|
|
|
6326 have one per console type.
|
|
|
6327
|
|
|
6328 Here's the Xt Event Loop Diagram (notice that below a certain point,
|
|
|
6329 it's the same as the above diagram):
|
|
|
6330
|
|
|
6331 @example
|
|
|
6332 asynch. asynch. asynch. asynch. [Collectors in
|
|
|
6333 kbd kbd process process the OS]
|
|
380
|
6334 events events output output
|
|
|
6335 | | | |
|
|
|
6336 | | | | asynch. asynch. [Collectors in the
|
|
|
6337 | | | | X X OS and X Window System]
|
|
|
6338 | | | | events events
|
|
0
|
6339 | | | | | |
|
|
|
6340 | | | | | |
|
|
380
|
6341 | | | | | | SIGINT, [signal handlers
|
|
|
6342 | | | | | | SIGQUIT, in XEmacs]
|
|
|
6343 | | | | | | SIGWINCH,
|
|
|
6344 | | | | | | SIGALRM
|
|
|
6345 | | | | | | |
|
|
|
6346 | | | | | | |
|
|
|
6347 | | | | | | | timeouts
|
|
0
|
6348 | | | | | | | |
|
|
|
6349 | | | | | | | |
|
|
|
6350 | | | | | | V |
|
|
380
|
6351 V V V V V V fake |
|
|
|
6352 file file file file file file file |
|
|
|
6353 desc. desc. desc. desc. desc. desc. desc. |
|
|
|
6354 (TTY) (TTY) (pipe) (pipe) (socket) (socket) (pipe) |
|
|
0
|
6355 | | | | | | | |
|
|
|
6356 | | | | | | | |
|
|
|
6357 | | | | | | | |
|
|
380
|
6358 V V V V V V V V
|
|
0
|
6359 --->----------------------------------------<---------<------
|
|
|
6360 | | |
|
|
380
|
6361 | | |[collected using select() in
|
|
|
6362 | | | _XtWaitForSomething(), called
|
|
|
6363 | | | from XtAppProcessEvent(), called
|
|
|
6364 | | | in emacs_Xt_next_event();
|
|
|
6365 | | | dispatched to various callbacks]
|
|
0
|
6366 | | |
|
|
|
6367 | | |
|
|
380
|
6368 emacs_Xt_ p_s_callback(), | [popup_selection_callback]
|
|
|
6369 event_handler() x_u_v_s_callback(),| [x_update_vertical_scrollbar_
|
|
|
6370 | x_u_h_s_callback(),| callback]
|
|
|
6371 | search_callback() | [x_update_horizontal_scrollbar_
|
|
|
6372 | | | callback]
|
|
0
|
6373 | | |
|
|
|
6374 | | |
|
|
|
6375 enqueue_Xt_ signal_special_ |
|
|
|
6376 dispatch_event() Xt_user_event() |
|
|
|
6377 [maybe multiple | |
|
|
|
6378 times, maybe 0 | |
|
|
|
6379 times] | |
|
|
|
6380 | enqueue_Xt_ |
|
|
|
6381 | dispatch_event() |
|
|
|
6382 | | |
|
|
|
6383 | | |
|
|
|
6384 V V |
|
|
|
6385 -->----------<-- |
|
|
|
6386 | |
|
|
|
6387 | |
|
|
380
|
6388 dispatch Xt_what_callback()
|
|
0
|
6389 event sets flags
|
|
|
6390 queue |
|
|
|
6391 | |
|
|
|
6392 | |
|
|
|
6393 | |
|
|
|
6394 | |
|
|
|
6395 ---->-----------<--------
|
|
380
|
6396 |
|
|
0
|
6397 |
|
|
|
6398 | [collected and converted as appropriate in
|
|
|
6399 | emacs_Xt_next_event()]
|
|
380
|
6400 |
|
|
|
6401 |
|
|
|
6402 V (above this line is Xt-specific)
|
|
|
6403 Emacs ------------------------------------------------
|
|
|
6404 event (below this line is the generic event mechanism)
|
|
0
|
6405 |
|
|
|
6406 |
|
|
|
6407 was there if not, call
|
|
|
6408 a SIGINT? emacs_Xt_next_event()
|
|
|
6409 | |
|
|
|
6410 | |
|
|
|
6411 | |
|
|
|
6412 V V
|
|
|
6413 --->-------<----
|
|
|
6414 |
|
|
|
6415 | [collected in event_stream_next_event();
|
|
|
6416 | SIGINT is converted using maybe_read_quit_event()]
|
|
|
6417 V
|
|
|
6418 Emacs
|
|
|
6419 event
|
|
|
6420 |
|
|
|
6421 \---->------>----- maybe_kbd_translate() -->-----\
|
|
|
6422 |
|
|
|
6423 |
|
|
|
6424 |
|
|
|
6425 command event queue |
|
|
380
|
6426 if not from command
|
|
|
6427 (contains events that were event queue, call
|
|
|
6428 read earlier but not processed, event_stream_next_event()
|
|
0
|
6429 typically when waiting in a |
|
|
|
6430 sit-for, sleep-for, etc. for |
|
|
|
6431 a particular event to be received) |
|
|
|
6432 | |
|
|
|
6433 | |
|
|
|
6434 V V
|
|
|
6435 ---->----------------------------------<------
|
|
|
6436 |
|
|
380
|
6437 | [collected in
|
|
|
6438 | next_event_internal()]
|
|
0
|
6439 |
|
|
|
6440 unread- unread- event from |
|
|
|
6441 command- command- keyboard else, call
|
|
|
6442 events event macro next_event_internal()
|
|
|
6443 | | | |
|
|
|
6444 | | | |
|
|
|
6445 | | | |
|
|
|
6446 V V V V
|
|
|
6447 --------->----------------------<------------
|
|
|
6448 |
|
|
|
6449 | [collected in `next-event', which may loop
|
|
|
6450 | more than once if the event it gets is on
|
|
|
6451 | a dead frame, device, etc.]
|
|
|
6452 |
|
|
|
6453 |
|
|
|
6454 V
|
|
|
6455 feed into top-level event loop,
|
|
|
6456 which repeatedly calls `next-event'
|
|
|
6457 and then dispatches the event
|
|
|
6458 using `dispatch-event'
|
|
|
6459 @end example
|
|
|
6460
|
|
398
|
6461 @node Specifics About the Emacs Event, The Event Stream Callback Routines, Specifics of the Event Gathering Mechanism, Events and the Event Loop
|
|
0
|
6462 @section Specifics About the Emacs Event
|
|
|
6463
|
|
398
|
6464 @node The Event Stream Callback Routines, Other Event Loop Functions, Specifics About the Emacs Event, Events and the Event Loop
|
|
0
|
6465 @section The Event Stream Callback Routines
|
|
|
6466
|
|
398
|
6467 @node Other Event Loop Functions, Converting Events, The Event Stream Callback Routines, Events and the Event Loop
|
|
0
|
6468 @section Other Event Loop Functions
|
|
|
6469
|
|
|
6470 @code{detect_input_pending()} and @code{input-pending-p} look for
|
|
|
6471 input by calling @code{event_stream->event_pending_p} and looking in
|
|
|
6472 @code{[V]unread-command-event} and the @code{command_event_queue} (they
|
|
|
6473 do not check for an executing keyboard macro, though).
|
|
|
6474
|
|
|
6475 @code{discard-input} cancels any command events pending (and any
|
|
|
6476 keyboard macros currently executing), and puts the others onto the
|
|
|
6477 @code{command_event_queue}. There is a comment about a ``race
|
|
|
6478 condition'', which is not a good sign.
|
|
|
6479
|
|
|
6480 @code{next-command-event} and @code{read-char} are higher-level
|
|
|
6481 interfaces to @code{next-event}. @code{next-command-event} gets the
|
|
116
|
6482 next @dfn{command} event (i.e. keypress, mouse event, menu selection,
|
|
|
6483 or scrollbar action), calling @code{dispatch-event} on any others.
|
|
|
6484 @code{read-char} calls @code{next-command-event} and uses
|
|
|
6485 @code{event_to_character()} to return the character equivalent. With
|
|
|
6486 the right kind of input method support, it is possible for (read-char)
|
|
|
6487 to return a Kanji character.
|
|
0
|
6488
|
|
398
|
6489 @node Converting Events, Dispatching Events; The Command Builder, Other Event Loop Functions, Events and the Event Loop
|
|
0
|
6490 @section Converting Events
|
|
|
6491
|
|
|
6492 @code{character_to_event()}, @code{event_to_character()},
|
|
|
6493 @code{event-to-character}, and @code{character-to-event} convert between
|
|
116
|
6494 characters and keypress events corresponding to the characters. If the
|
|
0
|
6495 event was not a keypress, @code{event_to_character()} returns -1 and
|
|
|
6496 @code{event-to-character} returns @code{nil}. These functions convert
|
|
116
|
6497 between character representation and the split-up event representation
|
|
0
|
6498 (keysym plus mod keys).
|
|
|
6499
|
|
398
|
6500 @node Dispatching Events; The Command Builder, , Converting Events, Events and the Event Loop
|
|
0
|
6501 @section Dispatching Events; The Command Builder
|
|
|
6502
|
|
|
6503 Not yet documented.
|
|
|
6504
|
|
|
6505 @node Evaluation; Stack Frames; Bindings, Symbols and Variables, Events and the Event Loop, Top
|
|
|
6506 @chapter Evaluation; Stack Frames; Bindings
|
|
|
6507
|
|
|
6508 @menu
|
|
|
6509 * Evaluation::
|
|
|
6510 * Dynamic Binding; The specbinding Stack; Unwind-Protects::
|
|
|
6511 * Simple Special Forms::
|
|
|
6512 * Catch and Throw::
|
|
|
6513 @end menu
|
|
|
6514
|
|
398
|
6515 @node Evaluation, Dynamic Binding; The specbinding Stack; Unwind-Protects, Evaluation; Stack Frames; Bindings, Evaluation; Stack Frames; Bindings
|
|
0
|
6516 @section Evaluation
|
|
|
6517
|
|
|
6518 @code{Feval()} evaluates the form (a Lisp object) that is passed to
|
|
|
6519 it. Note that evaluation is only non-trivial for two types of objects:
|
|
253
|
6520 symbols and conses. A symbol is evaluated simply by calling
|
|
380
|
6521 @code{symbol-value} on it and returning the value.
|
|
0
|
6522
|
|
|
6523 Evaluating a cons means calling a function. First, @code{eval} checks
|
|
|
6524 to see if garbage-collection is necessary, and calls
|
|
380
|
6525 @code{garbage_collect_1()} if so. It then increases the evaluation
|
|
|
6526 depth by 1 (@code{lisp_eval_depth}, which is always less than
|
|
|
6527 @code{max_lisp_eval_depth}) and adds an element to the linked list of
|
|
|
6528 @code{struct backtrace}'s (@code{backtrace_list}). Each such structure
|
|
|
6529 contains a pointer to the function being called plus a list of the
|
|
|
6530 function's arguments. Originally these values are stored unevalled, and
|
|
|
6531 as they are evaluated, the backtrace structure is updated. Garbage
|
|
|
6532 collection pays attention to the objects pointed to in the backtrace
|
|
|
6533 structures (garbage collection might happen while a function is being
|
|
|
6534 called or while an argument is being evaluated, and there could easily
|
|
|
6535 be no other references to the arguments in the argument list; once an
|
|
|
6536 argument is evaluated, however, the unevalled version is not needed by
|
|
|
6537 eval, and so the backtrace structure is changed).
|
|
|
6538
|
|
|
6539 At this point, the function to be called is determined by looking at
|
|
0
|
6540 the car of the cons (if this is a symbol, its function definition is
|
|
|
6541 retrieved and the process repeated). The function should then consist
|
|
380
|
6542 of either a @code{Lisp_Subr} (built-in function written in C), a
|
|
|
6543 @code{Lisp_Compiled_Function} object, or a cons whose car is one of the
|
|
|
6544 symbols @code{autoload}, @code{macro} or @code{lambda}.
|
|
116
|
6545
|
|
|
6546 If the function is a @code{Lisp_Subr}, the lisp object points to a
|
|
|
6547 @code{struct Lisp_Subr} (created by @code{DEFUN()}), which contains a
|
|
|
6548 pointer to the C function, a minimum and maximum number of arguments
|
|
380
|
6549 (or possibly the special constants @code{MANY} or @code{UNEVALLED}), a
|
|
116
|
6550 pointer to the symbol referring to that subr, and a couple of other
|
|
|
6551 things. If the subr wants its arguments @code{UNEVALLED}, they are
|
|
|
6552 passed raw as a list. Otherwise, an array of evaluated arguments is
|
|
|
6553 created and put into the backtrace structure, and either passed whole
|
|
|
6554 (@code{MANY}) or each argument is passed as a C argument.
|
|
|
6555
|
|
380
|
6556 If the function is a @code{Lisp_Compiled_Function},
|
|
|
6557 @code{funcall_compiled_function()} is called. If the function is a
|
|
|
6558 lambda list, @code{funcall_lambda()} is called. If the function is a
|
|
|
6559 macro, [..... fill in] is done. If the function is an autoload,
|
|
0
|
6560 @code{do_autoload()} is called to load the definition and then eval
|
|
253
|
6561 starts over [explain this more].
|
|
0
|
6562
|
|
380
|
6563 When @code{Feval()} exits, the evaluation depth is reduced by one, the
|
|
0
|
6564 debugger is called if appropriate, and the current backtrace structure
|
|
|
6565 is removed from the list.
|
|
|
6566
|
|
380
|
6567 Both @code{funcall_compiled_function()} and @code{funcall_lambda()} need
|
|
|
6568 to go through the list of formal parameters to the function and bind
|
|
|
6569 them to the actual arguments, checking for @code{&rest} and
|
|
|
6570 @code{&optional} symbols in the formal parameters and making sure the
|
|
|
6571 number of actual arguments is correct.
|
|
|
6572 @code{funcall_compiled_function()} can do this a little more
|
|
|
6573 efficiently, since the formal parameter list can be checked for sanity
|
|
|
6574 when the compiled function object is created.
|
|
|
6575
|
|
|
6576 @code{funcall_lambda()} simply calls @code{Fprogn} to execute the code
|
|
|
6577 in the lambda list.
|
|
|
6578
|
|
|
6579 @code{funcall_compiled_function()} calls the real byte-code interpreter
|
|
|
6580 @code{execute_optimized_program()} on the byte-code instructions, which
|
|
|
6581 are converted into an internal form for faster execution.
|
|
|
6582
|
|
|
6583 When a compiled function is executed for the first time by
|
|
|
6584 @code{funcall_compiled_function()}, or when it is @code{Fpurecopy()}ed
|
|
|
6585 during the dump phase of building XEmacs, the byte-code instructions are
|
|
|
6586 converted from a @code{Lisp_String} (which is inefficient to access,
|
|
|
6587 especially in the presence of MULE) into a @code{Lisp_Opaque} object
|
|
|
6588 containing an array of unsigned char, which can be directly executed by
|
|
|
6589 the byte-code interpreter. At this time the byte code is also analyzed
|
|
|
6590 for validity and transformed into a more optimized form, so that
|
|
|
6591 @code{execute_optimized_program()} can really fly.
|
|
|
6592
|
|
|
6593 Here are some of the optimizations performed by the internal byte-code
|
|
|
6594 transformer:
|
|
|
6595 @enumerate
|
|
|
6596 @item
|
|
|
6597 References to the @code{constants} array are checked for out-of-range
|
|
|
6598 indices, so that the byte interpreter doesn't have to.
|
|
|
6599 @item
|
|
|
6600 References to the @code{constants} array that will be used as a Lisp
|
|
|
6601 variable are checked for being correct non-constant (i.e. not @code{t},
|
|
|
6602 @code{nil}, or @code{keywordp}) symbols, so that the byte interpreter
|
|
|
6603 doesn't have to.
|
|
|
6604 @item
|
|
|
6605 The maxiumum number of variable bindings in the byte-code is
|
|
|
6606 pre-computed, so that space on the @code{specpdl} stack can be
|
|
|
6607 pre-reserved once for the whole function execution.
|
|
|
6608 @item
|
|
|
6609 All byte-code jumps are relative to the current program counter instead
|
|
|
6610 of the start of the program, thereby saving a register.
|
|
|
6611 @item
|
|
|
6612 One-byte relative jumps are converted from the byte-code form of unsigned
|
|
|
6613 chars offset by 127 to machine-friendly signed chars.
|
|
|
6614 @end enumerate
|
|
|
6615
|
|
|
6616 Of course, this transformation of the @code{instructions} should not be
|
|
|
6617 visible to the user, so @code{Fcompiled_function_instructions()} needs
|
|
|
6618 to know how to convert the optimized opaque object back into a Lisp
|
|
|
6619 string that is identical to the original string from the @file{.elc}
|
|
|
6620 file. (Actually, the resulting string may (rarely) contain slightly
|
|
|
6621 different, yet equivalent, byte code.)
|
|
|
6622
|
|
|
6623 @code{Ffuncall()} implements Lisp @code{funcall}. @code{(funcall fun
|
|
0
|
6624 x1 x2 x3 ...)} is equivalent to @code{(eval (list fun (quote x1) (quote
|
|
|
6625 x2) (quote x3) ...))}. @code{Ffuncall()} contains its own code to do
|
|
380
|
6626 the evaluation, however, and is very similar to @code{Feval()}.
|
|
|
6627
|
|
|
6628 From the performance point of view, it is worth knowing that most of the
|
|
|
6629 time in Lisp evaluation is spent executing @code{Lisp_Subr} and
|
|
|
6630 @code{Lisp_Compiled_Function} objects via @code{Ffuncall()} (not
|
|
|
6631 @code{Feval()}).
|
|
|
6632
|
|
|
6633 @code{Fapply()} implements Lisp @code{apply}, which is very similar to
|
|
272
|
6634 @code{funcall} except that if the last argument is a list, the result is the
|
|
0
|
6635 same as if each of the arguments in the list had been passed separately.
|
|
|
6636 @code{Fapply()} does some business to expand the last argument if it's a
|
|
|
6637 list, then calls @code{Ffuncall()} to do the work.
|
|
|
6638
|
|
380
|
6639 @code{apply1()}, @code{call0()}, @code{call1()}, @code{call2()}, and
|
|
0
|
6640 @code{call3()} call a function, passing it the argument(s) given (the
|
|
|
6641 arguments are given as separate C arguments rather than being passed as
|
|
380
|
6642 an array). @code{apply1()} uses @code{Fapply()} while the others use
|
|
|
6643 @code{Ffuncall()} to do the real work.
|
|
0
|
6644
|
|
398
|
6645 @node Dynamic Binding; The specbinding Stack; Unwind-Protects, Simple Special Forms, Evaluation, Evaluation; Stack Frames; Bindings
|
|
0
|
6646 @section Dynamic Binding; The specbinding Stack; Unwind-Protects
|
|
|
6647
|
|
|
6648 @example
|
|
|
6649 struct specbinding
|
|
|
6650 @{
|
|
380
|
6651 Lisp_Object symbol;
|
|
|
6652 Lisp_Object old_value;
|
|
2
|
6653 Lisp_Object (*func) (Lisp_Object); /* for unwind-protect */
|
|
0
|
6654 @};
|
|
|
6655 @end example
|
|
|
6656
|
|
|
6657 @code{struct specbinding} is used for local-variable bindings and
|
|
|
6658 unwind-protects. @code{specpdl} holds an array of @code{struct specbinding}'s,
|
|
|
6659 @code{specpdl_ptr} points to the beginning of the free bindings in the
|
|
|
6660 array, @code{specpdl_size} specifies the total number of binding slots
|
|
|
6661 in the array, and @code{max_specpdl_size} specifies the maximum number
|
|
|
6662 of bindings the array can be expanded to hold. @code{grow_specpdl()}
|
|
272
|
6663 increases the size of the @code{specpdl} array, multiplying its size by
|
|
|
6664 2 but never exceeding @code{max_specpdl_size} (except that if this
|
|
|
6665 number is less than 400, it is first set to 400).
|
|
0
|
6666
|
|
|
6667 @code{specbind()} binds a symbol to a value and is used for local
|
|
|
6668 variables and @code{let} forms. The symbol and its old value (which
|
|
|
6669 might be @code{Qunbound}, indicating no prior value) are recorded in the
|
|
|
6670 specpdl array, and @code{specpdl_size} is increased by 1.
|
|
|
6671
|
|
|
6672 @code{record_unwind_protect()} implements an @dfn{unwind-protect},
|
|
|
6673 which, when placed around a section of code, ensures that some specified
|
|
|
6674 cleanup routine will be executed even if the code exits abnormally
|
|
116
|
6675 (e.g. through a @code{throw} or quit). @code{record_unwind_protect()}
|
|
272
|
6676 simply adds a new specbinding to the @code{specpdl} array and stores the
|
|
116
|
6677 appropriate information in it. The cleanup routine can either be a C
|
|
|
6678 function, which is stored in the @code{func} field, or a @code{progn}
|
|
|
6679 form, which is stored in the @code{old_value} field.
|
|
0
|
6680
|
|
272
|
6681 @code{unbind_to()} removes specbindings from the @code{specpdl} array
|
|
|
6682 until the specified position is reached. Each specbinding can be one of
|
|
|
6683 three types:
|
|
0
|
6684
|
|
|
6685 @enumerate
|
|
|
6686 @item
|
|
116
|
6687 an unwind-protect with a C cleanup function (@code{func} is not 0, and
|
|
0
|
6688 @code{old_value} holds an argument to be passed to the function);
|
|
|
6689 @item
|
|
116
|
6690 an unwind-protect with a Lisp form (@code{func} is 0, @code{symbol}
|
|
|
6691 is @code{nil}, and @code{old_value} holds the form to be executed with
|
|
0
|
6692 @code{Fprogn()}); or
|
|
|
6693 @item
|
|
116
|
6694 a local-variable binding (@code{func} is 0, @code{symbol} is not
|
|
|
6695 @code{nil}, and @code{old_value} holds the old value, which is stored as
|
|
0
|
6696 the symbol's value).
|
|
|
6697 @end enumerate
|
|
|
6698
|
|
398
|
6699 @node Simple Special Forms, Catch and Throw, Dynamic Binding; The specbinding Stack; Unwind-Protects, Evaluation; Stack Frames; Bindings
|
|
0
|
6700 @section Simple Special Forms
|
|
|
6701
|
|
|
6702 @code{or}, @code{and}, @code{if}, @code{cond}, @code{progn},
|
|
|
6703 @code{prog1}, @code{prog2}, @code{setq}, @code{quote}, @code{function},
|
|
|
6704 @code{let*}, @code{let}, @code{while}
|
|
|
6705
|
|
380
|
6706 All of these are very simple and work as expected, calling
|
|
0
|
6707 @code{Feval()} or @code{Fprogn()} as necessary and (in the case of
|
|
|
6708 @code{let} and @code{let*}) using @code{specbind()} to create bindings
|
|
380
|
6709 and @code{unbind_to()} to undo the bindings when finished.
|
|
|
6710
|
|
|
6711 Note that, with the exeption of @code{Fprogn}, these functions are
|
|
|
6712 typically called in real life only in interpreted code, since the byte
|
|
|
6713 compiler knows how to convert calls to these functions directly into
|
|
|
6714 byte code.
|
|
0
|
6715
|
|
398
|
6716 @node Catch and Throw, , Simple Special Forms, Evaluation; Stack Frames; Bindings
|
|
0
|
6717 @section Catch and Throw
|
|
|
6718
|
|
|
6719 @example
|
|
|
6720 struct catchtag
|
|
|
6721 @{
|
|
|
6722 Lisp_Object tag;
|
|
|
6723 Lisp_Object val;
|
|
|
6724 struct catchtag *next;
|
|
|
6725 struct gcpro *gcpro;
|
|
|
6726 jmp_buf jmp;
|
|
|
6727 struct backtrace *backlist;
|
|
|
6728 int lisp_eval_depth;
|
|
|
6729 int pdlcount;
|
|
|
6730 @};
|
|
|
6731 @end example
|
|
|
6732
|
|
|
6733 @code{catch} is a Lisp function that places a catch around a body of
|
|
|
6734 code. A catch is a means of non-local exit from the code. When a catch
|
|
|
6735 is created, a tag is specified, and executing a @code{throw} to this tag
|
|
|
6736 will exit from the body of code caught with this tag, and its value will
|
|
|
6737 be the value given in the call to @code{throw}. If there is no such
|
|
|
6738 call, the code will be executed normally.
|
|
|
6739
|
|
|
6740 Information pertaining to a catch is held in a @code{struct catchtag},
|
|
|
6741 which is placed at the head of a linked list pointed to by
|
|
|
6742 @code{catchlist}. @code{internal_catch()} is passed a C function to
|
|
|
6743 call (@code{Fprogn()} when Lisp @code{catch} is called) and arguments to
|
|
|
6744 give it, and places a catch around the function. Each @code{struct
|
|
|
6745 catchtag} is held in the stack frame of the @code{internal_catch()}
|
|
|
6746 instance that created the catch.
|
|
|
6747
|
|
|
6748 @code{internal_catch()} is fairly straightforward. It stores into the
|
|
|
6749 @code{struct catchtag} the tag name and the current values of
|
|
|
6750 @code{backtrace_list}, @code{lisp_eval_depth}, @code{gcprolist}, and the
|
|
272
|
6751 offset into the @code{specpdl} array, sets a jump point with @code{_setjmp()}
|
|
0
|
6752 (storing the jump point into the @code{struct catchtag}), and calls the
|
|
|
6753 function. Control will return to @code{internal_catch()} either when
|
|
|
6754 the function exits normally or through a @code{_longjmp()} to this jump
|
|
|
6755 point. In the latter case, @code{throw} will store the value to be
|
|
|
6756 returned into the @code{struct catchtag} before jumping. When it's
|
|
|
6757 done, @code{internal_catch()} removes the @code{struct catchtag} from
|
|
|
6758 the catchlist and returns the proper value.
|
|
|
6759
|
|
|
6760 @code{Fthrow()} goes up through the catchlist until it finds one with
|
|
|
6761 a matching tag. It then calls @code{unbind_catch()} to restore
|
|
|
6762 everything to what it was when the appropriate catch was set, stores the
|
|
|
6763 return value in the @code{struct catchtag}, and jumps (with
|
|
|
6764 @code{_longjmp()}) to its jump point.
|
|
|
6765
|
|
|
6766 @code{unbind_catch()} removes all catches from the catchlist until it
|
|
|
6767 finds the correct one. Some of the catches might have been placed for
|
|
|
6768 error-trapping, and if so, the appropriate entries on the handlerlist
|
|
|
6769 must be removed (see ``errors''). @code{unbind_catch()} also restores
|
|
|
6770 the values of @code{gcprolist}, @code{backtrace_list}, and
|
|
|
6771 @code{lisp_eval}, and calls @code{unbind_to()} to undo any specbindings
|
|
|
6772 created since the catch.
|
|
|
6773
|
|
|
6774
|
|
|
6775 @node Symbols and Variables, Buffers and Textual Representation, Evaluation; Stack Frames; Bindings, Top
|
|
|
6776 @chapter Symbols and Variables
|
|
|
6777
|
|
|
6778 @menu
|
|
|
6779 * Introduction to Symbols::
|
|
|
6780 * Obarrays::
|
|
|
6781 * Symbol Values::
|
|
|
6782 @end menu
|
|
|
6783
|
|
398
|
6784 @node Introduction to Symbols, Obarrays, Symbols and Variables, Symbols and Variables
|
|
0
|
6785 @section Introduction to Symbols
|
|
|
6786
|
|
|
6787 A symbol is basically just an object with four fields: a name (a
|
|
|
6788 string), a value (some Lisp object), a function (some Lisp object), and
|
|
|
6789 a property list (usually a list of alternating keyword/value pairs).
|
|
|
6790 What makes symbols special is that there is usually only one symbol with
|
|
|
6791 a given name, and the symbol is referred to by name. This makes a
|
|
|
6792 symbol a convenient way of calling up data by name, i.e. of implementing
|
|
|
6793 variables. (The variable's value is stored in the @dfn{value slot}.)
|
|
|
6794 Similarly, functions are referenced by name, and the definition of the
|
|
|
6795 function is stored in a symbol's @dfn{function slot}. This means that
|
|
|
6796 there can be a distinct function and variable with the same name. The
|
|
|
6797 property list is used as a more general mechanism of associating
|
|
|
6798 additional values with particular names, and once again the namespace is
|
|
|
6799 independent of the function and variable namespaces.
|
|
|
6800
|
|
398
|
6801 @node Obarrays, Symbol Values, Introduction to Symbols, Symbols and Variables
|
|
0
|
6802 @section Obarrays
|
|
|
6803
|
|
|
6804 The identity of symbols with their names is accomplished through a
|
|
|
6805 structure called an obarray, which is just a poorly-implemented hash
|
|
|
6806 table mapping from strings to symbols whose name is that string. (I say
|
|
|
6807 ``poorly implemented'' because an obarray appears in Lisp as a vector
|
|
|
6808 with some hidden fields rather than as its own opaque type. This is an
|
|
|
6809 Emacs Lisp artifact that should be fixed.)
|
|
|
6810
|
|
|
6811 Obarrays are implemented as a vector of some fixed size (which should
|
|
|
6812 be a prime for best results), where each ``bucket'' of the vector
|
|
|
6813 contains one or more symbols, threaded through a hidden @code{next}
|
|
|
6814 field in the symbol. Lookup of a symbol in an obarray, and adding a
|
|
|
6815 symbol to an obarray, is accomplished through standard hash-table
|
|
|
6816 techniques.
|
|
|
6817
|
|
|
6818 The standard Lisp function for working with symbols and obarrays is
|
|
|
6819 @code{intern}. This looks up a symbol in an obarray given its name; if
|
|
|
6820 it's not found, a new symbol is automatically created with the specified
|
|
|
6821 name, added to the obarray, and returned. This is what happens when the
|
|
|
6822 Lisp reader encounters a symbol (or more precisely, encounters the name
|
|
|
6823 of a symbol) in some text that it is reading. There is a standard
|
|
|
6824 obarray called @code{obarray} that is used for this purpose, although
|
|
|
6825 the Lisp programmer is free to create his own obarrays and @code{intern}
|
|
|
6826 symbols in them.
|
|
|
6827
|
|
|
6828 Note that, once a symbol is in an obarray, it stays there until
|
|
|
6829 something is done about it, and the standard obarray @code{obarray}
|
|
|
6830 always stays around, so once you use any particular variable name, a
|
|
|
6831 corresponding symbol will stay around in @code{obarray} until you exit
|
|
|
6832 XEmacs.
|
|
|
6833
|
|
|
6834 Note that @code{obarray} itself is a variable, and as such there is a
|
|
|
6835 symbol in @code{obarray} whose name is @code{"obarray"} and which
|
|
|
6836 contains @code{obarray} as its value.
|
|
|
6837
|
|
|
6838 Note also that this call to @code{intern} occurs only when in the Lisp
|
|
|
6839 reader, not when the code is executed (at which point the symbol is
|
|
|
6840 already around, stored as such in the definition of the function).
|
|
|
6841
|
|
|
6842 You can create your own obarray using @code{make-vector} (this is
|
|
|
6843 horrible but is an artifact) and intern symbols into that obarray.
|
|
|
6844 Doing that will result in two or more symbols with the same name.
|
|
|
6845 However, at most one of these symbols is in the standard @code{obarray}:
|
|
|
6846 You cannot have two symbols of the same name in any particular obarray.
|
|
|
6847 Note that you cannot add a symbol to an obarray in any fashion other
|
|
|
6848 than using @code{intern}: i.e. you can't take an existing symbol and put
|
|
|
6849 it in an existing obarray. Nor can you change the name of an existing
|
|
|
6850 symbol. (Since obarrays are vectors, you can violate the consistency of
|
|
|
6851 things by storing directly into the vector, but let's ignore that
|
|
|
6852 possibility.)
|
|
|
6853
|
|
|
6854 Usually symbols are created by @code{intern}, but if you really want,
|
|
|
6855 you can explicitly create a symbol using @code{make-symbol}, giving it
|
|
|
6856 some name. The resulting symbol is not in any obarray (i.e. it is
|
|
|
6857 @dfn{uninterned}), and you can't add it to any obarray. Therefore its
|
|
116
|
6858 primary purpose is as a symbol to use in macros to avoid namespace
|
|
|
6859 pollution. It can also be used as a carrier of information, but cons
|
|
|
6860 cells could probably be used just as well.
|
|
0
|
6861
|
|
|
6862 You can also use @code{intern-soft} to look up a symbol but not create
|
|
|
6863 a new one, and @code{unintern} to remove a symbol from an obarray. This
|
|
|
6864 returns the removed symbol. (Remember: You can't put the symbol back
|
|
|
6865 into any obarray.) Finally, @code{mapatoms} maps over all of the symbols
|
|
|
6866 in an obarray.
|
|
|
6867
|
|
398
|
6868 @node Symbol Values, , Obarrays, Symbols and Variables
|
|
0
|
6869 @section Symbol Values
|
|
|
6870
|
|
|
6871 The value field of a symbol normally contains a Lisp object. However,
|
|
|
6872 a symbol can be @dfn{unbound}, meaning that it logically has no value.
|
|
|
6873 This is internally indicated by storing a special Lisp object, called
|
|
|
6874 @dfn{the unbound marker} and stored in the global variable
|
|
|
6875 @code{Qunbound}. The unbound marker is of a special Lisp object type
|
|
|
6876 called @dfn{symbol-value-magic}. It is impossible for the Lisp
|
|
|
6877 programmer to directly create or access any object of this type.
|
|
|
6878
|
|
|
6879 @strong{You must not let any ``symbol-value-magic'' object escape to
|
|
|
6880 the Lisp level.} Printing any of these objects will cause the message
|
|
|
6881 @samp{INTERNAL EMACS BUG} to appear as part of the print representation.
|
|
|
6882 (You may see this normally when you call @code{debug_print()} from the
|
|
|
6883 debugger on a Lisp object.) If you let one of these objects escape to
|
|
|
6884 the Lisp level, you will violate a number of assumptions contained in
|
|
|
6885 the C code and make the unbound marker not function right.
|
|
|
6886
|
|
|
6887 When a symbol is created, its value field (and function field) are set
|
|
|
6888 to @code{Qunbound}. The Lisp programmer can restore these conditions
|
|
|
6889 later using @code{makunbound} or @code{fmakunbound}, and can query to
|
|
|
6890 see whether the value of function fields are @dfn{bound} (i.e. have a
|
|
|
6891 value other than @code{Qunbound}) using @code{boundp} and
|
|
|
6892 @code{fboundp}. The fields are set to a normal Lisp object using
|
|
|
6893 @code{set} (or @code{setq}) and @code{fset}.
|
|
|
6894
|
|
|
6895 Other symbol-value-magic objects are used as special markers to
|
|
|
6896 indicate variables that have non-normal properties. This includes any
|
|
|
6897 variables that are tied into C variables (setting the variable magically
|
|
|
6898 sets some global variable in the C code, and likewise for retrieving the
|
|
|
6899 variable's value), variables that magically tie into slots in the
|
|
|
6900 current buffer, variables that are buffer-local, etc. The
|
|
|
6901 symbol-value-magic object is stored in the value cell in place of
|
|
|
6902 a normal object, and the code to retrieve a symbol's value
|
|
|
6903 (i.e. @code{symbol-value}) knows how to do special things with them.
|
|
|
6904 This means that you should not just fetch the value cell directly if you
|
|
|
6905 want a symbol's value.
|
|
|
6906
|
|
|
6907 The exact workings of this are rather complex and involved and are
|
|
|
6908 well-documented in comments in @file{buffer.c}, @file{symbols.c}, and
|
|
|
6909 @file{lisp.h}.
|
|
|
6910
|
|
|
6911 @node Buffers and Textual Representation, MULE Character Sets and Encodings, Symbols and Variables, Top
|
|
|
6912 @chapter Buffers and Textual Representation
|
|
|
6913
|
|
|
6914 @menu
|
|
|
6915 * Introduction to Buffers:: A buffer holds a block of text such as a file.
|
|
193
|
6916 * The Text in a Buffer:: Representation of the text in a buffer.
|
|
0
|
6917 * Buffer Lists:: Keeping track of all buffers.
|
|
|
6918 * Markers and Extents:: Tagging locations within a buffer.
|
|
|
6919 * Bufbytes and Emchars:: Representation of individual characters.
|
|
|
6920 * The Buffer Object:: The Lisp object corresponding to a buffer.
|
|
|
6921 @end menu
|
|
|
6922
|
|
398
|
6923 @node Introduction to Buffers, The Text in a Buffer, Buffers and Textual Representation, Buffers and Textual Representation
|
|
0
|
6924 @section Introduction to Buffers
|
|
|
6925
|
|
|
6926 A buffer is logically just a Lisp object that holds some text.
|
|
|
6927 In this, it is like a string, but a buffer is optimized for
|
|
|
6928 frequent insertion and deletion, while a string is not. Furthermore:
|
|
|
6929
|
|
|
6930 @enumerate
|
|
|
6931 @item
|
|
116
|
6932 Buffers are @dfn{permanent} objects, i.e. once you create them, they
|
|
0
|
6933 remain around, and need to be explicitly deleted before they go away.
|
|
|
6934 @item
|
|
|
6935 Each buffer has a unique name, which is a string. Buffers are
|
|
|
6936 normally referred to by name. In this respect, they are like
|
|
|
6937 symbols.
|
|
|
6938 @item
|
|
|
6939 Buffers have a default insertion position, called @dfn{point}.
|
|
|
6940 Inserting text (unless you explicitly give a position) goes at point,
|
|
|
6941 and moves point forward past the text. This is what is going on when
|
|
|
6942 you type text into Emacs.
|
|
|
6943 @item
|
|
|
6944 Buffers have lots of extra properties associated with them.
|
|
|
6945 @item
|
|
|
6946 Buffers can be @dfn{displayed}. What this means is that there
|
|
|
6947 exist a number of @dfn{windows}, which are objects that correspond
|
|
|
6948 to some visible section of your display, and each window has
|
|
|
6949 an associated buffer, and the current contents of the buffer
|
|
|
6950 are shown in that section of the display. The redisplay mechanism
|
|
|
6951 (which takes care of doing this) knows how to look at the
|
|
|
6952 text of a buffer and come up with some reasonable way of displaying
|
|
|
6953 this. Many of the properties of a buffer control how the
|
|
|
6954 buffer's text is displayed.
|
|
|
6955 @item
|
|
|
6956 One buffer is distinguished and called the @dfn{current buffer}. It is
|
|
|
6957 stored in the variable @code{current_buffer}. Buffer operations operate
|
|
|
6958 on this buffer by default. When you are typing text into a buffer, the
|
|
|
6959 buffer you are typing into is always @code{current_buffer}. Switching
|
|
|
6960 to a different window changes the current buffer. Note that Lisp code
|
|
|
6961 can temporarily change the current buffer using @code{set-buffer} (often
|
|
|
6962 enclosed in a @code{save-excursion} so that the former current buffer
|
|
|
6963 gets restored when the code is finished). However, calling
|
|
|
6964 @code{set-buffer} will NOT cause a permanent change in the current
|
|
|
6965 buffer. The reason for this is that the top-level event loop sets
|
|
380
|
6966 @code{current_buffer} to the buffer of the selected window, each time
|
|
116
|
6967 it finishes executing a user command.
|
|
0
|
6968 @end enumerate
|
|
|
6969
|
|
|
6970 Make sure you understand the distinction between @dfn{current buffer}
|
|
|
6971 and @dfn{buffer of the selected window}, and the distinction between
|
|
|
6972 @dfn{point} of the current buffer and @dfn{window-point} of the selected
|
|
|
6973 window. (This latter distinction is explained in detail in the section
|
|
|
6974 on windows.)
|
|
|
6975
|
|
398
|
6976 @node The Text in a Buffer, Buffer Lists, Introduction to Buffers, Buffers and Textual Representation
|
|
193
|
6977 @section The Text in a Buffer
|
|
0
|
6978
|
|
|
6979 The text in a buffer consists of a sequence of zero or more
|
|
|
6980 characters. A @dfn{character} is an integer that logically represents
|
|
|
6981 a letter, number, space, or other unit of text. Most of the characters
|
|
|
6982 that you will typically encounter belong to the ASCII set of characters,
|
|
|
6983 but there are also characters for various sorts of accented letters,
|
|
|
6984 special symbols, Chinese and Japanese ideograms (i.e. Kanji, Katakana,
|
|
|
6985 etc.), Cyrillic and Greek letters, etc. The actual number of possible
|
|
|
6986 characters is quite large.
|
|
|
6987
|
|
|
6988 For now, we can view a character as some non-negative integer that
|
|
|
6989 has some shape that defines how it typically appears (e.g. as an
|
|
116
|
6990 uppercase A). (The exact way in which a character appears depends on the
|
|
|
6991 font used to display the character.) The internal type of characters in
|
|
|
6992 the C code is an @code{Emchar}; this is just an @code{int}, but using a
|
|
|
6993 symbolic type makes the code clearer.
|
|
0
|
6994
|
|
|
6995 Between every character in a buffer is a @dfn{buffer position} or
|
|
|
6996 @dfn{character position}. We can speak of the character before or after
|
|
|
6997 a particular buffer position, and when you insert a character at a
|
|
|
6998 particular position, all characters after that position end up at new
|
|
|
6999 positions. When we speak of the character @dfn{at} a position, we
|
|
|
7000 really mean the character after the position. (This schizophrenia
|
|
|
7001 between a buffer position being ``between'' a character and ``on'' a
|
|
|
7002 character is rampant in Emacs.)
|
|
|
7003
|
|
|
7004 Buffer positions are numbered starting at 1. This means that
|
|
|
7005 position 1 is before the first character, and position 0 is not
|
|
|
7006 valid. If there are N characters in a buffer, then buffer
|
|
|
7007 position N+1 is after the last one, and position N+2 is not valid.
|
|
|
7008
|
|
|
7009 The internal makeup of the Emchar integer varies depending on whether
|
|
|
7010 we have compiled with MULE support. If not, the Emchar integer is an
|
|
|
7011 8-bit integer with possible values from 0 - 255. 0 - 127 are the
|
|
|
7012 standard ASCII characters, while 128 - 255 are the characters from the
|
|
|
7013 ISO-8859-1 character set. If we have compiled with MULE support, an
|
|
|
7014 Emchar is a 19-bit integer, with the various bits having meanings
|
|
|
7015 according to a complex scheme that will be detailed later. The
|
|
|
7016 characters numbered 0 - 255 still have the same meanings as for the
|
|
|
7017 non-MULE case, though.
|
|
|
7018
|
|
|
7019 Internally, the text in a buffer is represented in a fairly simple
|
|
|
7020 fashion: as a contiguous array of bytes, with a @dfn{gap} of some size
|
|
|
7021 in the middle. Although the gap is of some substantial size in bytes,
|
|
|
7022 there is no text contained within it: From the perspective of the text
|
|
|
7023 in the buffer, it does not exist. The gap logically sits at some buffer
|
|
|
7024 position, between two characters (or possibly at the beginning or end of
|
|
|
7025 the buffer). Insertion of text in a buffer at a particular position is
|
|
|
7026 always accomplished by first moving the gap to that position
|
|
|
7027 (i.e. through some block moving of text), then writing the text into the
|
|
|
7028 beginning of the gap, thereby shrinking the gap. If the gap shrinks
|
|
|
7029 down to nothing, a new gap is created. (What actually happens is that a
|
|
|
7030 new gap is ``created'' at the end of the buffer's text, which requires
|
|
|
7031 nothing more than changing a couple of indices; then the gap is
|
|
|
7032 ``moved'' to the position where the insertion needs to take place by
|
|
|
7033 moving up in memory all the text after that position.) Similarly,
|
|
|
7034 deletion occurs by moving the gap to the place where the text is to be
|
|
|
7035 deleted, and then simply expanding the gap to include the deleted text.
|
|
|
7036 (@dfn{Expanding} and @dfn{shrinking} the gap as just described means
|
|
|
7037 just that the internal indices that keep track of where the gap is
|
|
|
7038 located are changed.)
|
|
|
7039
|
|
|
7040 Note that the total amount of memory allocated for a buffer text never
|
|
|
7041 decreases while the buffer is live. Therefore, if you load up a
|
|
|
7042 20-megabyte file and then delete all but one character, there will be a
|
|
|
7043 20-megabyte gap, which won't get any smaller (except by inserting
|
|
|
7044 characters back again). Once the buffer is killed, the memory allocated
|
|
|
7045 for the buffer text will be freed, but it will still be sitting on the
|
|
|
7046 heap, taking up virtual memory, and will not be released back to the
|
|
|
7047 operating system. (However, if you have compiled XEmacs with rel-alloc,
|
|
|
7048 the situation is different. In this case, the space @emph{will} be
|
|
116
|
7049 released back to the operating system. However, this tends to result in a
|
|
0
|
7050 noticeable speed penalty.)
|
|
|
7051
|
|
|
7052 Astute readers may notice that the text in a buffer is represented as
|
|
|
7053 an array of @emph{bytes}, while (at least in the MULE case) an Emchar is
|
|
|
7054 a 19-bit integer, which clearly cannot fit in a byte. This means (of
|
|
|
7055 course) that the text in a buffer uses a different representation from
|
|
|
7056 an Emchar: specifically, the 19-bit Emchar becomes a series of one to
|
|
|
7057 four bytes. The conversion between these two representations is complex
|
|
|
7058 and will be described later.
|
|
|
7059
|
|
|
7060 In the non-MULE case, everything is very simple: An Emchar
|
|
|
7061 is an 8-bit value, which fits neatly into one byte.
|
|
|
7062
|
|
|
7063 If we are given a buffer position and want to retrieve the
|
|
|
7064 character at that position, we need to follow these steps:
|
|
|
7065
|
|
|
7066 @enumerate
|
|
|
7067 @item
|
|
|
7068 Pretend there's no gap, and convert the buffer position into a @dfn{byte
|
|
|
7069 index} that indexes to the appropriate byte in the buffer's stream of
|
|
|
7070 textual bytes. By convention, byte indices begin at 1, just like buffer
|
|
|
7071 positions. In the non-MULE case, byte indices and buffer positions are
|
|
|
7072 identical, since one character equals one byte.
|
|
|
7073 @item
|
|
|
7074 Convert the byte index into a @dfn{memory index}, which takes the gap
|
|
|
7075 into account. The memory index is a direct index into the block of
|
|
|
7076 memory that stores the text of a buffer. This basically just involves
|
|
|
7077 checking to see if the byte index is past the gap, and if so, adding the
|
|
|
7078 size of the gap to it. By convention, memory indices begin at 1, just
|
|
|
7079 like buffer positions and byte indices, and when referring to the
|
|
|
7080 position that is @dfn{at} the gap, we always use the memory position at
|
|
|
7081 the @emph{beginning}, not at the end, of the gap.
|
|
|
7082 @item
|
|
|
7083 Fetch the appropriate bytes at the determined memory position.
|
|
|
7084 @item
|
|
|
7085 Convert these bytes into an Emchar.
|
|
|
7086 @end enumerate
|
|
|
7087
|
|
|
7088 In the non-Mule case, (3) and (4) boil down to a simple one-byte
|
|
|
7089 memory access.
|
|
|
7090
|
|
|
7091 Note that we have defined three types of positions in a buffer:
|
|
|
7092
|
|
|
7093 @enumerate
|
|
|
7094 @item
|
|
|
7095 @dfn{buffer positions} or @dfn{character positions}, typedef @code{Bufpos}
|
|
|
7096 @item
|
|
|
7097 @dfn{byte indices}, typedef @code{Bytind}
|
|
|
7098 @item
|
|
|
7099 @dfn{memory indices}, typedef @code{Memind}
|
|
|
7100 @end enumerate
|
|
|
7101
|
|
116
|
7102 All three typedefs are just @code{int}s, but defining them this way makes
|
|
0
|
7103 things a lot clearer.
|
|
|
7104
|
|
|
7105 Most code works with buffer positions. In particular, all Lisp code
|
|
|
7106 that refers to text in a buffer uses buffer positions. Lisp code does
|
|
|
7107 not know that byte indices or memory indices exist.
|
|
|
7108
|
|
|
7109 Finally, we have a typedef for the bytes in a buffer. This is a
|
|
|
7110 @code{Bufbyte}, which is an unsigned char. Referring to them as
|
|
|
7111 Bufbytes underscores the fact that we are working with a string of bytes
|
|
|
7112 in the internal Emacs buffer representation rather than in one of a
|
|
116
|
7113 number of possible alternative representations (e.g. EUC-encoded text,
|
|
0
|
7114 etc.).
|
|
|
7115
|
|
398
|
7116 @node Buffer Lists, Markers and Extents, The Text in a Buffer, Buffers and Textual Representation
|
|
0
|
7117 @section Buffer Lists
|
|
|
7118
|
|
|
7119 Recall earlier that buffers are @dfn{permanent} objects, i.e. that
|
|
|
7120 they remain around until explicitly deleted. This entails that there is
|
|
|
7121 a list of all the buffers in existence. This list is actually an
|
|
|
7122 assoc-list (mapping from the buffer's name to the buffer) and is stored
|
|
|
7123 in the global variable @code{Vbuffer_alist}.
|
|
|
7124
|
|
|
7125 The order of the buffers in the list is important: the buffers are
|
|
|
7126 ordered approximately from most-recently-used to least-recently-used.
|
|
|
7127 Switching to a buffer using @code{switch-to-buffer},
|
|
|
7128 @code{pop-to-buffer}, etc. and switching windows using
|
|
|
7129 @code{other-window}, etc. usually brings the new current buffer to the
|
|
|
7130 front of the list. @code{switch-to-buffer}, @code{other-buffer},
|
|
|
7131 etc. look at the beginning of the list to find an alternative buffer to
|
|
|
7132 suggest. You can also explicitly move a buffer to the end of the list
|
|
|
7133 using @code{bury-buffer}.
|
|
|
7134
|
|
|
7135 In addition to the global ordering in @code{Vbuffer_alist}, each frame
|
|
|
7136 has its own ordering of the list. These lists always contain the same
|
|
|
7137 elements as in @code{Vbuffer_alist} although possibly in a different
|
|
|
7138 order. @code{buffer-list} normally returns the list for the selected
|
|
|
7139 frame. This allows you to work in separate frames without things
|
|
|
7140 interfering with each other.
|
|
|
7141
|
|
|
7142 The standard way to look up a buffer given a name is
|
|
|
7143 @code{get-buffer}, and the standard way to create a new buffer is
|
|
|
7144 @code{get-buffer-create}, which looks up a buffer with a given name,
|
|
|
7145 creating a new one if necessary. These operations correspond exactly
|
|
|
7146 with the symbol operations @code{intern-soft} and @code{intern},
|
|
|
7147 respectively. You can also force a new buffer to be created using
|
|
|
7148 @code{generate-new-buffer}, which takes a name and (if necessary) makes
|
|
|
7149 a unique name from this by appending a number, and then creates the
|
|
|
7150 buffer. This is basically like the symbol operation @code{gensym}.
|
|
|
7151
|
|
398
|
7152 @node Markers and Extents, Bufbytes and Emchars, Buffer Lists, Buffers and Textual Representation
|
|
0
|
7153 @section Markers and Extents
|
|
|
7154
|
|
|
7155 Among the things associated with a buffer are things that are
|
|
|
7156 logically attached to certain buffer positions. This can be used to
|
|
|
7157 keep track of a buffer position when text is inserted and deleted, so
|
|
|
7158 that it remains at the same spot relative to the text around it; to
|
|
|
7159 assign properties to particular sections of text; etc. There are two
|
|
|
7160 such objects that are useful in this regard: they are @dfn{markers} and
|
|
|
7161 @dfn{extents}.
|
|
|
7162
|
|
|
7163 A @dfn{marker} is simply a flag placed at a particular buffer
|
|
|
7164 position, which is moved around as text is inserted and deleted.
|
|
|
7165 Markers are used for all sorts of purposes, such as the @code{mark} that
|
|
|
7166 is the other end of textual regions to be cut, copied, etc.
|
|
|
7167
|
|
|
7168 An @dfn{extent} is similar to two markers plus some associated
|
|
|
7169 properties, and is used to keep track of regions in a buffer as text is
|
|
|
7170 inserted and deleted, and to add properties (e.g. fonts) to particular
|
|
|
7171 regions of text. The external interface of extents is explained
|
|
|
7172 elsewhere.
|
|
|
7173
|
|
|
7174 The important thing here is that markers and extents simply contain
|
|
|
7175 buffer positions in them as integers, and every time text is inserted or
|
|
|
7176 deleted, these positions must be updated. In order to minimize the
|
|
|
7177 amount of shuffling that needs to be done, the positions in markers and
|
|
|
7178 extents (there's one per marker, two per extent) and stored in Meminds.
|
|
|
7179 This means that they only need to be moved when the text is physically
|
|
|
7180 moved in memory; since the gap structure tries to minimize this, it also
|
|
|
7181 minimizes the number of marker and extent indices that need to be
|
|
|
7182 adjusted. Look in @file{insdel.c} for the details of how this works.
|
|
|
7183
|
|
|
7184 One other important distinction is that markers are @dfn{temporary}
|
|
|
7185 while extents are @dfn{permanent}. This means that markers disappear as
|
|
|
7186 soon as there are no more pointers to them, and correspondingly, there
|
|
|
7187 is no way to determine what markers are in a buffer if you are just
|
|
|
7188 given the buffer. Extents remain in a buffer until they are detached
|
|
|
7189 (which could happen as a result of text being deleted) or the buffer is
|
|
|
7190 deleted, and primitives do exist to enumerate the extents in a buffer.
|
|
|
7191
|
|
398
|
7192 @node Bufbytes and Emchars, The Buffer Object, Markers and Extents, Buffers and Textual Representation
|
|
0
|
7193 @section Bufbytes and Emchars
|
|
|
7194
|
|
|
7195 Not yet documented.
|
|
|
7196
|
|
398
|
7197 @node The Buffer Object, , Bufbytes and Emchars, Buffers and Textual Representation
|
|
0
|
7198 @section The Buffer Object
|
|
|
7199
|
|
|
7200 Buffers contain fields not directly accessible by the Lisp programmer.
|
|
|
7201 We describe them here, naming them by the names used in the C code.
|
|
|
7202 Many are accessible indirectly in Lisp programs via Lisp primitives.
|
|
|
7203
|
|
|
7204 @table @code
|
|
|
7205 @item name
|
|
|
7206 The buffer name is a string that names the buffer. It is guaranteed to
|
|
371
|
7207 be unique. @xref{Buffer Names,,, lispref, XEmacs Lisp Programmer's
|
|
0
|
7208 Manual}.
|
|
|
7209
|
|
|
7210 @item save_modified
|
|
|
7211 This field contains the time when the buffer was last saved, as an
|
|
371
|
7212 integer. @xref{Buffer Modification,,, lispref, XEmacs Lisp Programmer's
|
|
0
|
7213 Manual}.
|
|
|
7214
|
|
|
7215 @item modtime
|
|
|
7216 This field contains the modification time of the visited file. It is
|
|
|
7217 set when the file is written or read. Every time the buffer is written
|
|
|
7218 to the file, this field is compared to the modification time of the
|
|
371
|
7219 file. @xref{Buffer Modification,,, lispref, XEmacs Lisp Programmer's
|
|
0
|
7220 Manual}.
|
|
|
7221
|
|
|
7222 @item auto_save_modified
|
|
|
7223 This field contains the time when the buffer was last auto-saved.
|
|
|
7224
|
|
|
7225 @item last_window_start
|
|
|
7226 This field contains the @code{window-start} position in the buffer as of
|
|
|
7227 the last time the buffer was displayed in a window.
|
|
|
7228
|
|
|
7229 @item undo_list
|
|
|
7230 This field points to the buffer's undo list. @xref{Undo,,, lispref,
|
|
371
|
7231 XEmacs Lisp Programmer's Manual}.
|
|
0
|
7232
|
|
|
7233 @item syntax_table_v
|
|
|
7234 This field contains the syntax table for the buffer. @xref{Syntax
|
|
371
|
7235 Tables,,, lispref, XEmacs Lisp Programmer's Manual}.
|
|
0
|
7236
|
|
|
7237 @item downcase_table
|
|
|
7238 This field contains the conversion table for converting text to lower
|
|
371
|
7239 case. @xref{Case Tables,,, lispref, XEmacs Lisp Programmer's Manual}.
|
|
0
|
7240
|
|
|
7241 @item upcase_table
|
|
|
7242 This field contains the conversion table for converting text to upper
|
|
371
|
7243 case. @xref{Case Tables,,, lispref, XEmacs Lisp Programmer's Manual}.
|
|
0
|
7244
|
|
|
7245 @item case_canon_table
|
|
|
7246 This field contains the conversion table for canonicalizing text for
|
|
|
7247 case-folding search. @xref{Case Tables,,, lispref, XEmacs Lisp
|
|
371
|
7248 Programmer's Manual}.
|
|
0
|
7249
|
|
|
7250 @item case_eqv_table
|
|
|
7251 This field contains the equivalence table for case-folding search.
|
|
371
|
7252 @xref{Case Tables,,, lispref, XEmacs Lisp Programmer's Manual}.
|
|
0
|
7253
|
|
|
7254 @item display_table
|
|
|
7255 This field contains the buffer's display table, or @code{nil} if it
|
|
|
7256 doesn't have one. @xref{Display Tables,,, lispref, XEmacs Lisp
|
|
371
|
7257 Programmer's Manual}.
|
|
0
|
7258
|
|
|
7259 @item markers
|
|
|
7260 This field contains the chain of all markers that currently point into
|
|
|
7261 the buffer. Deletion of text in the buffer, and motion of the buffer's
|
|
|
7262 gap, must check each of these markers and perhaps update it.
|
|
371
|
7263 @xref{Markers,,, lispref, XEmacs Lisp Programmer's Manual}.
|
|
0
|
7264
|
|
|
7265 @item backed_up
|
|
|
7266 This field is a flag that tells whether a backup file has been made for
|
|
|
7267 the visited file of this buffer.
|
|
|
7268
|
|
|
7269 @item mark
|
|
|
7270 This field contains the mark for the buffer. The mark is a marker,
|
|
|
7271 hence it is also included on the list @code{markers}. @xref{The Mark,,,
|
|
371
|
7272 lispref, XEmacs Lisp Programmer's Manual}.
|
|
0
|
7273
|
|
|
7274 @item mark_active
|
|
|
7275 This field is non-@code{nil} if the buffer's mark is active.
|
|
|
7276
|
|
|
7277 @item local_var_alist
|
|
|
7278 This field contains the association list describing the variables local
|
|
|
7279 in this buffer, and their values, with the exception of local variables
|
|
|
7280 that have special slots in the buffer object. (Those slots are omitted
|
|
|
7281 from this table.) @xref{Buffer-Local Variables,,, lispref, XEmacs Lisp
|
|
371
|
7282 Programmer's Manual}.
|
|
0
|
7283
|
|
|
7284 @item modeline_format
|
|
|
7285 This field contains a Lisp object which controls how to display the mode
|
|
|
7286 line for this buffer. @xref{Modeline Format,,, lispref, XEmacs Lisp
|
|
371
|
7287 Programmer's Manual}.
|
|
0
|
7288
|
|
|
7289 @item base_buffer
|
|
|
7290 This field holds the buffer's base buffer (if it is an indirect buffer),
|
|
|
7291 or @code{nil}.
|
|
|
7292 @end table
|
|
|
7293
|
|
|
7294 @node MULE Character Sets and Encodings, The Lisp Reader and Compiler, Buffers and Textual Representation, Top
|
|
|
7295 @chapter MULE Character Sets and Encodings
|
|
|
7296
|
|
|
7297 Recall that there are two primary ways that text is represented in
|
|
|
7298 XEmacs. The @dfn{buffer} representation sees the text as a series of
|
|
|
7299 bytes (Bufbytes), with a variable number of bytes used per character.
|
|
|
7300 The @dfn{character} representation sees the text as a series of integers
|
|
|
7301 (Emchars), one per character. The character representation is a cleaner
|
|
|
7302 representation from a theoretical standpoint, and is thus used in many
|
|
|
7303 cases when lots of manipulations on a string need to be done. However,
|
|
|
7304 the buffer representation is the standard representation used in both
|
|
|
7305 Lisp strings and buffers, and because of this, it is the ``default''
|
|
|
7306 representation that text comes in. The reason for using this
|
|
|
7307 representation is that it's compact and is compatible with ASCII.
|
|
|
7308
|
|
|
7309 @menu
|
|
|
7310 * Character Sets::
|
|
|
7311 * Encodings::
|
|
|
7312 * Internal Mule Encodings::
|
|
|
7313 * CCL::
|
|
|
7314 @end menu
|
|
|
7315
|
|
398
|
7316 @node Character Sets, Encodings, MULE Character Sets and Encodings, MULE Character Sets and Encodings
|
|
0
|
7317 @section Character Sets
|
|
|
7318
|
|
|
7319 A character set (or @dfn{charset}) is an ordered set of characters. A
|
|
|
7320 particular character in a charset is indexed using one or more
|
|
|
7321 @dfn{position codes}, which are non-negative integers. The number of
|
|
|
7322 position codes needed to identify a particular character in a charset is
|
|
|
7323 called the @dfn{dimension} of the charset. In XEmacs/Mule, all charsets
|
|
|
7324 have dimension 1 or 2, and the size of all charsets (except for a few
|
|
|
7325 special cases) is either 94, 96, 94 by 94, or 96 by 96. The range of
|
|
|
7326 position codes used to index characters from any of these types of
|
|
|
7327 character sets is as follows:
|
|
|
7328
|
|
|
7329 @example
|
|
|
7330 Charset type Position code 1 Position code 2
|
|
|
7331 ------------------------------------------------------------
|
|
|
7332 94 33 - 126 N/A
|
|
|
7333 96 32 - 127 N/A
|
|
|
7334 94x94 33 - 126 33 - 126
|
|
|
7335 96x96 32 - 127 32 - 127
|
|
|
7336 @end example
|
|
|
7337
|
|
|
7338 Note that in the above cases position codes do not start at an
|
|
|
7339 expected value such as 0 or 1. The reason for this will become clear
|
|
|
7340 later.
|
|
|
7341
|
|
|
7342 For example, Latin-1 is a 96-character charset, and JISX0208 (the
|
|
|
7343 Japanese national character set) is a 94x94-character charset.
|
|
|
7344
|
|
|
7345 [Note that, although the ranges above define the @emph{valid} position
|
|
|
7346 codes for a charset, some of the slots in a particular charset may in
|
|
|
7347 fact be empty. This is the case for JISX0208, for example, where (e.g.)
|
|
|
7348 all the slots whose first position code is in the range 118 - 127 are
|
|
|
7349 empty.]
|
|
|
7350
|
|
|
7351 There are three charsets that do not follow the above rules. All of
|
|
|
7352 them have one dimension, and have ranges of position codes as follows:
|
|
|
7353
|
|
|
7354 @example
|
|
|
7355 Charset name Position code 1
|
|
|
7356 ------------------------------------
|
|
|
7357 ASCII 0 - 127
|
|
|
7358 Control-1 0 - 31
|
|
|
7359 Composite 0 - some large number
|
|
|
7360 @end example
|
|
|
7361
|
|
|
7362 (The upper bound of the position code for composite characters has not
|
|
|
7363 yet been determined, but it will probably be at least 16,383).
|
|
|
7364
|
|
|
7365 ASCII is the union of two subsidiary character sets: Printing-ASCII
|
|
|
7366 (the printing ASCII character set, consisting of position codes 33 -
|
|
|
7367 126, like for a standard 94-character charset) and Control-ASCII (the
|
|
|
7368 non-printing characters that would appear in a binary file with codes 0
|
|
|
7369 - 32 and 127).
|
|
|
7370
|
|
|
7371 Control-1 contains the non-printing characters that would appear in a
|
|
|
7372 binary file with codes 128 - 159.
|
|
|
7373
|
|
|
7374 Composite contains characters that are generated by overstriking one
|
|
|
7375 or more characters from other charsets.
|
|
|
7376
|
|
|
7377 Note that some characters in ASCII, and all characters in Control-1,
|
|
|
7378 are @dfn{control} (non-printing) characters. These have no printed
|
|
|
7379 representation but instead control some other function of the printing
|
|
|
7380 (e.g. TAB or 8 moves the current character position to the next tab
|
|
|
7381 stop). All other characters in all charsets are @dfn{graphic}
|
|
|
7382 (printing) characters.
|
|
|
7383
|
|
|
7384 When a binary file is read in, the bytes in the file are assigned to
|
|
|
7385 character sets as follows:
|
|
|
7386
|
|
|
7387 @example
|
|
|
7388 Bytes Character set Range
|
|
|
7389 --------------------------------------------------
|
|
|
7390 0 - 127 ASCII 0 - 127
|
|
|
7391 128 - 159 Control-1 0 - 31
|
|
|
7392 160 - 255 Latin-1 32 - 127
|
|
|
7393 @end example
|
|
|
7394
|
|
|
7395 This is a bit ad-hoc but gets the job done.
|
|
|
7396
|
|
398
|
7397 @node Encodings, Internal Mule Encodings, Character Sets, MULE Character Sets and Encodings
|
|
0
|
7398 @section Encodings
|
|
|
7399
|
|
|
7400 An @dfn{encoding} is a way of numerically representing characters from
|
|
|
7401 one or more character sets. If an encoding only encompasses one
|
|
|
7402 character set, then the position codes for the characters in that
|
|
|
7403 character set could be used directly. This is not possible, however, if
|
|
|
7404 more than one character set is to be used in the encoding.
|
|
|
7405
|
|
|
7406 For example, the conversion detailed above between bytes in a binary
|
|
|
7407 file and characters is effectively an encoding that encompasses the
|
|
|
7408 three character sets ASCII, Control-1, and Latin-1 in a stream of 8-bit
|
|
|
7409 bytes.
|
|
|
7410
|
|
|
7411 Thus, an encoding can be viewed as a way of encoding characters from a
|
|
|
7412 specified group of character sets using a stream of bytes, each of which
|
|
|
7413 contains a fixed number of bits (but not necessarily 8, as in the common
|
|
|
7414 usage of ``byte'').
|
|
|
7415
|
|
|
7416 Here are descriptions of a couple of common
|
|
|
7417 encodings:
|
|
|
7418
|
|
|
7419 @menu
|
|
|
7420 * Japanese EUC (Extended Unix Code)::
|
|
|
7421 * JIS7::
|
|
|
7422 @end menu
|
|
|
7423
|
|
398
|
7424 @node Japanese EUC (Extended Unix Code), JIS7, Encodings, Encodings
|
|
0
|
7425 @subsection Japanese EUC (Extended Unix Code)
|
|
|
7426
|
|
380
|
7427 This encompasses the character sets Printing-ASCII, Japanese-JISX0201,
|
|
44
|
7428 and Japanese-JISX0208-Kana (half-width katakana, the right half of
|
|
0
|
7429 JISX0201). It uses 8-bit bytes.
|
|
|
7430
|
|
44
|
7431 Note that Printing-ASCII and Japanese-JISX0201-Kana are 94-character
|
|
|
7432 charsets, while Japanese-JISX0208 is a 94x94-character charset.
|
|
|
7433
|
|
|
7434 The encoding is as follows:
|
|
0
|
7435
|
|
|
7436 @example
|
|
44
|
7437 Character set Representation (PC=position-code)
|
|
|
7438 ------------- --------------
|
|
|
7439 Printing-ASCII PC1
|
|
|
7440 Japanese-JISX0201-Kana 0x8E | PC1 + 0x80
|
|
|
7441 Japanese-JISX0208 PC1 + 0x80 | PC2 + 0x80
|
|
|
7442 Japanese-JISX0212 PC1 + 0x80 | PC2 + 0x80
|
|
0
|
7443 @end example
|
|
|
7444
|
|
|
7445
|
|
398
|
7446 @node JIS7, , Japanese EUC (Extended Unix Code), Encodings
|
|
0
|
7447 @subsection JIS7
|
|
|
7448
|
|
44
|
7449 This encompasses the character sets Printing-ASCII,
|
|
|
7450 Japanese-JISX0201-Roman (the left half of JISX0201; this character set
|
|
|
7451 is very similar to Printing-ASCII and is a 94-character charset),
|
|
|
7452 Japanese-JISX0208, and Japanese-JISX0201-Kana. It uses 7-bit bytes.
|
|
|
7453
|
|
|
7454 Unlike Japanese EUC, this is a @dfn{modal} encoding, which
|
|
0
|
7455 means that there are multiple states that the encoding can
|
|
|
7456 be in, which affect how the bytes are to be interpreted.
|
|
|
7457 Special sequences of bytes (called @dfn{escape sequences})
|
|
|
7458 are used to change states.
|
|
|
7459
|
|
|
7460 The encoding is as follows:
|
|
|
7461
|
|
|
7462 @example
|
|
44
|
7463 Character set Representation (PC=position-code)
|
|
|
7464 ------------- --------------
|
|
|
7465 Printing-ASCII PC1
|
|
|
7466 Japanese-JISX0201-Roman PC1
|
|
|
7467 Japanese-JISX0201-Kana PC1
|
|
|
7468 Japanese-JISX0208 PC1 PC2
|
|
0
|
7469
|
|
|
7470
|
|
|
7471 Escape sequence ASCII equivalent Meaning
|
|
|
7472 --------------- ---------------- -------
|
|
44
|
7473 0x1B 0x28 0x4A ESC ( J invoke Japanese-JISX0201-Roman
|
|
|
7474 0x1B 0x28 0x49 ESC ( I invoke Japanese-JISX0201-Kana
|
|
|
7475 0x1B 0x24 0x42 ESC $ B invoke Japanese-JISX0208
|
|
0
|
7476 0x1B 0x28 0x42 ESC ( B invoke Printing-ASCII
|
|
|
7477 @end example
|
|
|
7478
|
|
|
7479 Initially, Printing-ASCII is invoked.
|
|
|
7480
|
|
398
|
7481 @node Internal Mule Encodings, CCL, Encodings, MULE Character Sets and Encodings
|
|
0
|
7482 @section Internal Mule Encodings
|
|
|
7483
|
|
44
|
7484 In XEmacs/Mule, each character set is assigned a unique number, called a
|
|
|
7485 @dfn{leading byte}. This is used in the encodings of a character.
|
|
|
7486 Leading bytes are in the range 0x80 - 0xFF (except for ASCII, which has
|
|
|
7487 a leading byte of 0), although some leading bytes are reserved.
|
|
|
7488
|
|
|
7489 Charsets whose leading byte is in the range 0x80 - 0x9F are called
|
|
|
7490 @dfn{official} and are used for built-in charsets. Other charsets are
|
|
|
7491 called @dfn{private} and have leading bytes in the range 0xA0 - 0xFF;
|
|
|
7492 these are user-defined charsets.
|
|
0
|
7493
|
|
|
7494 More specifically:
|
|
|
7495
|
|
|
7496 @example
|
|
|
7497 Character set Leading byte
|
|
|
7498 ------------- ------------
|
|
|
7499 ASCII 0
|
|
|
7500 Composite 0x80
|
|
|
7501 Dimension-1 Official 0x81 - 0x8D
|
|
|
7502 (0x8E is free)
|
|
|
7503 Control-1 0x8F
|
|
|
7504 Dimension-2 Official 0x90 - 0x99
|
|
|
7505 (0x9A - 0x9D are free;
|
|
|
7506 0x9E and 0x9F are reserved)
|
|
|
7507 Dimension-1 Private 0xA0 - 0xEF
|
|
|
7508 Dimension-2 Private 0xF0 - 0xFF
|
|
|
7509 @end example
|
|
|
7510
|
|
44
|
7511 There are two internal encodings for characters in XEmacs/Mule. One is
|
|
|
7512 called @dfn{string encoding} and is an 8-bit encoding that is used for
|
|
|
7513 representing characters in a buffer or string. It uses 1 to 4 bytes per
|
|
|
7514 character. The other is called @dfn{character encoding} and is a 19-bit
|
|
|
7515 encoding that is used for representing characters individually in a
|
|
|
7516 variable.
|
|
|
7517
|
|
|
7518 (In the following descriptions, we'll ignore composite characters for
|
|
|
7519 the moment. We also give a general (structural) overview first,
|
|
|
7520 followed later by the exact details.)
|
|
0
|
7521
|
|
|
7522 @menu
|
|
|
7523 * Internal String Encoding::
|
|
|
7524 * Internal Character Encoding::
|
|
|
7525 @end menu
|
|
|
7526
|
|
398
|
7527 @node Internal String Encoding, Internal Character Encoding, Internal Mule Encodings, Internal Mule Encodings
|
|
0
|
7528 @subsection Internal String Encoding
|
|
|
7529
|
|
44
|
7530 ASCII characters are encoded using their position code directly. Other
|
|
|
7531 characters are encoded using their leading byte followed by their
|
|
|
7532 position code(s) with the high bit set. Characters in private character
|
|
|
7533 sets have their leading byte prefixed with a @dfn{leading byte prefix},
|
|
|
7534 which is either 0x9E or 0x9F. (No character sets are ever assigned these
|
|
|
7535 leading bytes.) Specifically:
|
|
0
|
7536
|
|
|
7537 @example
|
|
|
7538 Character set Encoding (PC=position-code, LB=leading-byte)
|
|
|
7539 ------------- --------
|
|
|
7540 ASCII PC-1 |
|
|
|
7541 Control-1 LB | PC1 + 0xA0 |
|
|
|
7542 Dimension-1 official LB | PC1 + 0x80 |
|
|
|
7543 Dimension-1 private 0x9E | LB | PC1 + 0x80 |
|
|
|
7544 Dimension-2 official LB | PC1 + 0x80 | PC2 + 0x80 |
|
|
|
7545 Dimension-2 private 0x9F | LB | PC1 + 0x80 | PC2 + 0x80
|
|
|
7546 @end example
|
|
|
7547
|
|
|
7548 The basic characteristic of this encoding is that the first byte
|
|
|
7549 of all characters is in the range 0x00 - 0x9F, and the second and
|
|
|
7550 following bytes of all characters is in the range 0xA0 - 0xFF.
|
|
|
7551 This means that it is impossible to get out of sync, or more
|
|
|
7552 specifically:
|
|
|
7553
|
|
|
7554 @enumerate
|
|
|
7555 @item
|
|
|
7556 Given any byte position, the beginning of the character it is
|
|
|
7557 within can be determined in constant time.
|
|
|
7558 @item
|
|
|
7559 Given any byte position at the beginning of a character, the
|
|
|
7560 beginning of the next character can be determined in constant
|
|
|
7561 time.
|
|
|
7562 @item
|
|
|
7563 Given any byte position at the beginning of a character, the
|
|
|
7564 beginning of the previous character can be determined in constant
|
|
|
7565 time.
|
|
|
7566 @item
|
|
|
7567 Textual searches can simply treat encoded strings as if they
|
|
|
7568 were encoded in a one-byte-per-character fashion rather than
|
|
|
7569 the actual multi-byte encoding.
|
|
|
7570 @end enumerate
|
|
|
7571
|
|
|
7572 None of the standard non-modal encodings meet all of these
|
|
|
7573 conditions. For example, EUC satisfies only (2) and (3), while
|
|
|
7574 Shift-JIS and Big5 (not yet described) satisfy only (2). (All
|
|
|
7575 non-modal encodings must satisfy (2), in order to be unambiguous.)
|
|
|
7576
|
|
398
|
7577 @node Internal Character Encoding, , Internal String Encoding, Internal Mule Encodings
|
|
0
|
7578 @subsection Internal Character Encoding
|
|
|
7579
|
|
|
7580 One 19-bit word represents a single character. The word is
|
|
|
7581 separated into three fields:
|
|
|
7582
|
|
|
7583 @example
|
|
|
7584 Bit number: 18 17 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
|
|
|
7585 <------------> <------------------> <------------------>
|
|
|
7586 Field: 1 2 3
|
|
|
7587 @end example
|
|
|
7588
|
|
|
7589 Note that fields 2 and 3 hold 7 bits each, while field 1 holds 5 bits.
|
|
|
7590
|
|
|
7591 @example
|
|
|
7592 Character set Field 1 Field 2 Field 3
|
|
|
7593 ------------- ------- ------- -------
|
|
|
7594 ASCII 0 0 PC1
|
|
|
7595 range: (00 - 7F)
|
|
|
7596 Control-1 0 1 PC1
|
|
|
7597 range: (00 - 1F)
|
|
|
7598 Dimension-1 official 0 LB - 0x80 PC1
|
|
|
7599 range: (01 - 0D) (20 - 7F)
|
|
|
7600 Dimension-1 private 0 LB - 0x80 PC1
|
|
|
7601 range: (20 - 6F) (20 - 7F)
|
|
|
7602 Dimension-2 official LB - 0x8F PC1 PC2
|
|
|
7603 range: (01 - 0A) (20 - 7F) (20 - 7F)
|
|
|
7604 Dimension-2 private LB - 0xE1 PC1 PC2
|
|
|
7605 range: (0F - 1E) (20 - 7F) (20 - 7F)
|
|
|
7606 Composite 0x1F ? ?
|
|
|
7607 @end example
|
|
|
7608
|
|
|
7609 Note that character codes 0 - 255 are the same as the ``binary encoding''
|
|
|
7610 described above.
|
|
|
7611
|
|
398
|
7612 @node CCL, , Internal Mule Encodings, MULE Character Sets and Encodings
|
|
0
|
7613 @section CCL
|
|
|
7614
|
|
|
7615 @example
|
|
|
7616 CCL PROGRAM SYNTAX:
|
|
380
|
7617 CCL_PROGRAM := (CCL_MAIN_BLOCK
|
|
|
7618 [ CCL_EOF_BLOCK ])
|
|
|
7619
|
|
|
7620 CCL_MAIN_BLOCK := CCL_BLOCK
|
|
|
7621 CCL_EOF_BLOCK := CCL_BLOCK
|
|
|
7622
|
|
|
7623 CCL_BLOCK := STATEMENT | (STATEMENT [STATEMENT ...])
|
|
|
7624 STATEMENT :=
|
|
|
7625 SET | IF | BRANCH | LOOP | REPEAT | BREAK
|
|
|
7626 | READ | WRITE
|
|
|
7627
|
|
|
7628 SET := (REG = EXPRESSION) | (REG SELF_OP EXPRESSION)
|
|
|
7629 | INT-OR-CHAR
|
|
|
7630
|
|
|
7631 EXPRESSION := ARG | (EXPRESSION OP ARG)
|
|
|
7632
|
|
|
7633 IF := (if EXPRESSION CCL_BLOCK CCL_BLOCK)
|
|
|
7634 BRANCH := (branch EXPRESSION CCL_BLOCK [CCL_BLOCK ...])
|
|
|
7635 LOOP := (loop STATEMENT [STATEMENT ...])
|
|
|
7636 BREAK := (break)
|
|
|
7637 REPEAT := (repeat)
|
|
|
7638 | (write-repeat [REG | INT-OR-CHAR | string])
|
|
|
7639 | (write-read-repeat REG [INT-OR-CHAR | string | ARRAY]?)
|
|
|
7640 READ := (read REG) | (read REG REG)
|
|
|
7641 | (read-if REG ARITH_OP ARG CCL_BLOCK CCL_BLOCK)
|
|
|
7642 | (read-branch REG CCL_BLOCK [CCL_BLOCK ...])
|
|
|
7643 WRITE := (write REG) | (write REG REG)
|
|
|
7644 | (write INT-OR-CHAR) | (write STRING) | STRING
|
|
|
7645 | (write REG ARRAY)
|
|
|
7646 END := (end)
|
|
|
7647
|
|
|
7648 REG := r0 | r1 | r2 | r3 | r4 | r5 | r6 | r7
|
|
|
7649 ARG := REG | INT-OR-CHAR
|
|
|
7650 OP := + | - | * | / | % | & | '|' | ^ | << | >> | <8 | >8 | //
|
|
|
7651 | < | > | == | <= | >= | !=
|
|
|
7652 SELF_OP :=
|
|
|
7653 += | -= | *= | /= | %= | &= | '|=' | ^= | <<= | >>=
|
|
|
7654 ARRAY := '[' INT-OR-CHAR ... ']'
|
|
|
7655 INT-OR-CHAR := INT | CHAR
|
|
0
|
7656
|
|
|
7657 MACHINE CODE:
|
|
|
7658
|
|
|
7659 The machine code consists of a vector of 32-bit words.
|
|
|
7660 The first such word specifies the start of the EOF section of the code;
|
|
|
7661 this is the code executed to handle any stuff that needs to be done
|
|
|
7662 (e.g. designating back to ASCII and left-to-right mode) after all
|
|
|
7663 other encoded/decoded data has been written out. This is not used for
|
|
|
7664 charset CCL programs.
|
|
|
7665
|
|
371
|
7666 REGISTER: 0..7 -- refered by RRR or rrr
|
|
0
|
7667
|
|
|
7668 OPERATOR BIT FIELD (27-bit): XXXXXXXXXXXXXXX RRR TTTTT
|
|
|
7669 TTTTT (5-bit): operator type
|
|
|
7670 RRR (3-bit): register number
|
|
|
7671 XXXXXXXXXXXXXXXX (15-bit):
|
|
|
7672 CCCCCCCCCCCCCCC: constant or address
|
|
|
7673 000000000000rrr: register number
|
|
|
7674
|
|
380
|
7675 AAAA: 00000 +
|
|
|
7676 00001 -
|
|
|
7677 00010 *
|
|
|
7678 00011 /
|
|
|
7679 00100 %
|
|
|
7680 00101 &
|
|
|
7681 00110 |
|
|
0
|
7682 00111 ~
|
|
|
7683
|
|
|
7684 01000 <<
|
|
|
7685 01001 >>
|
|
|
7686 01010 <8
|
|
|
7687 01011 >8
|
|
|
7688 01100 //
|
|
|
7689 01101 not used
|
|
|
7690 01110 not used
|
|
|
7691 01111 not used
|
|
|
7692
|
|
380
|
7693 10000 <
|
|
|
7694 10001 >
|
|
0
|
7695 10010 ==
|
|
|
7696 10011 <=
|
|
|
7697 10100 >=
|
|
|
7698 10101 !=
|
|
|
7699
|
|
|
7700 OPERATORS: TTTTT RRR XX..
|
|
|
7701
|
|
380
|
7702 SetCS: 00000 RRR C...C RRR = C...C
|
|
|
7703 SetCL: 00001 RRR ..... RRR = c...c
|
|
0
|
7704 c.............c
|
|
380
|
7705 SetR: 00010 RRR ..rrr RRR = rrr
|
|
|
7706 SetA: 00011 RRR ..rrr RRR = array[rrr]
|
|
|
7707 C.............C size of array = C...C
|
|
|
7708 c.............c contents = c...c
|
|
|
7709
|
|
|
7710 Jump: 00100 000 c...c jump to c...c
|
|
|
7711 JumpCond: 00101 RRR c...c if (!RRR) jump to c...c
|
|
|
7712 WriteJump: 00110 RRR c...c Write1 RRR, jump to c...c
|
|
|
7713 WriteReadJump: 00111 RRR c...c Write1, Read1 RRR, jump to c...c
|
|
|
7714 WriteCJump: 01000 000 c...c Write1 C...C, jump to c...c
|
|
0
|
7715 C...C
|
|
380
|
7716 WriteCReadJump: 01001 RRR c...c Write1 C...C, Read1 RRR,
|
|
|
7717 C.............C and jump to c...c
|
|
|
7718 WriteSJump: 01010 000 c...c WriteS, jump to c...c
|
|
0
|
7719 C.............C
|
|
|
7720 S.............S
|
|
|
7721 ...
|
|
380
|
7722 WriteSReadJump: 01011 RRR c...c WriteS, Read1 RRR, jump to c...c
|
|
0
|
7723 C.............C
|
|
|
7724 S.............S
|
|
|
7725 ...
|
|
380
|
7726 WriteAReadJump: 01100 RRR c...c WriteA, Read1 RRR, jump to c...c
|
|
|
7727 C.............C size of array = C...C
|
|
|
7728 c.............c contents = c...c
|
|
0
|
7729 ...
|
|
380
|
7730 Branch: 01101 RRR C...C if (RRR >= 0 && RRR < C..)
|
|
|
7731 c.............c branch to (RRR+1)th address
|
|
|
7732 Read1: 01110 RRR ... read 1-byte to RRR
|
|
|
7733 Read2: 01111 RRR ..rrr read 2-byte to RRR and rrr
|
|
|
7734 ReadBranch: 10000 RRR C...C Read1 and Branch
|
|
0
|
7735 c.............c
|
|
|
7736 ...
|
|
380
|
7737 Write1: 10001 RRR ..... write 1-byte RRR
|
|
|
7738 Write2: 10010 RRR ..rrr write 2-byte RRR and rrr
|
|
|
7739 WriteC: 10011 000 ..... write 1-char C...CC
|
|
0
|
7740 C.............C
|
|
380
|
7741 WriteS: 10100 000 ..... write C..-byte of string
|
|
0
|
7742 C.............C
|
|
|
7743 S.............S
|
|
|
7744 ...
|
|
380
|
7745 WriteA: 10101 RRR ..... write array[RRR]
|
|
|
7746 C.............C size of array = C...C
|
|
|
7747 c.............c contents = c...c
|
|
0
|
7748 ...
|
|
380
|
7749 End: 10110 000 ..... terminate the execution
|
|
|
7750
|
|
|
7751 SetSelfCS: 10111 RRR C...C RRR AAAAA= C...C
|
|
0
|
7752 ..........AAAAA
|
|
380
|
7753 SetSelfCL: 11000 RRR ..... RRR AAAAA= c...c
|
|
0
|
7754 c.............c
|
|
|
7755 ..........AAAAA
|
|
380
|
7756 SetSelfR: 11001 RRR ..Rrr RRR AAAAA= rrr
|
|
0
|
7757 ..........AAAAA
|
|
380
|
7758 SetExprCL: 11010 RRR ..Rrr RRR = rrr AAAAA c...c
|
|
0
|
7759 c.............c
|
|
|
7760 ..........AAAAA
|
|
380
|
7761 SetExprR: 11011 RRR ..rrr RRR = rrr AAAAA Rrr
|
|
0
|
7762 ............Rrr
|
|
|
7763 ..........AAAAA
|
|
380
|
7764 JumpCondC: 11100 RRR c...c if !(RRR AAAAA C..) jump to c...c
|
|
0
|
7765 C.............C
|
|
|
7766 ..........AAAAA
|
|
380
|
7767 JumpCondR: 11101 RRR c...c if !(RRR AAAAA rrr) jump to c...c
|
|
0
|
7768 ............rrr
|
|
|
7769 ..........AAAAA
|
|
380
|
7770 ReadJumpCondC: 11110 RRR c...c Read1 and JumpCondC
|
|
0
|
7771 C.............C
|
|
|
7772 ..........AAAAA
|
|
380
|
7773 ReadJumpCondR: 11111 RRR c...c Read1 and JumpCondR
|
|
0
|
7774 ............rrr
|
|
|
7775 ..........AAAAA
|
|
|
7776 @end example
|
|
|
7777
|
|
|
7778 @node The Lisp Reader and Compiler, Lstreams, MULE Character Sets and Encodings, Top
|
|
|
7779 @chapter The Lisp Reader and Compiler
|
|
|
7780
|
|
|
7781 Not yet documented.
|
|
|
7782
|
|
|
7783 @node Lstreams, Consoles; Devices; Frames; Windows, The Lisp Reader and Compiler, Top
|
|
|
7784 @chapter Lstreams
|
|
|
7785
|
|
|
7786 An @dfn{lstream} is an internal Lisp object that provides a generic
|
|
|
7787 buffering stream implementation. Conceptually, you send data to the
|
|
|
7788 stream or read data from the stream, not caring what's on the other end
|
|
|
7789 of the stream. The other end could be another stream, a file
|
|
|
7790 descriptor, a stdio stream, a fixed block of memory, a reallocating
|
|
|
7791 block of memory, etc. The main purpose of the stream is to provide a
|
|
|
7792 standard interface and to do buffering. Macros are defined to read or
|
|
|
7793 write characters, so the calling functions do not have to worry about
|
|
|
7794 blocking data together in order to achieve efficiency.
|
|
|
7795
|
|
|
7796 @menu
|
|
|
7797 * Creating an Lstream:: Creating an lstream object.
|
|
|
7798 * Lstream Types:: Different sorts of things that are streamed.
|
|
|
7799 * Lstream Functions:: Functions for working with lstreams.
|
|
|
7800 * Lstream Methods:: Creating new lstream types.
|
|
|
7801 @end menu
|
|
|
7802
|
|
398
|
7803 @node Creating an Lstream, Lstream Types, Lstreams, Lstreams
|
|
0
|
7804 @section Creating an Lstream
|
|
|
7805
|
|
|
7806 Lstreams come in different types, depending on what is being interfaced
|
|
|
7807 to. Although the primitive for creating new lstreams is
|
|
|
7808 @code{Lstream_new()}, generally you do not call this directly. Instead,
|
|
|
7809 you call some type-specific creation function, which creates the lstream
|
|
|
7810 and initializes it as appropriate for the particular type.
|
|
|
7811
|
|
|
7812 All lstream creation functions take a @var{mode} argument, specifying
|
|
|
7813 what mode the lstream should be opened as. This controls whether the
|
|
|
7814 lstream is for input and output, and optionally whether data should be
|
|
|
7815 blocked up in units of MULE characters. Note that some types of
|
|
|
7816 lstreams can only be opened for input; others only for output; and
|
|
|
7817 others can be opened either way. #### Richard Mlynarik thinks that
|
|
|
7818 there should be a strict separation between input and output streams,
|
|
|
7819 and he's probably right.
|
|
|
7820
|
|
|
7821 @var{mode} is a string, one of
|
|
|
7822
|
|
|
7823 @table @code
|
|
|
7824 @item "r"
|
|
|
7825 Open for reading.
|
|
|
7826 @item "w"
|
|
|
7827 Open for writing.
|
|
|
7828 @item "rc"
|
|
|
7829 Open for reading, but ``read'' never returns partial MULE characters.
|
|
|
7830 @item "wc"
|
|
|
7831 Open for writing, but never writes partial MULE characters.
|
|
|
7832 @end table
|
|
|
7833
|
|
398
|
7834 @node Lstream Types, Lstream Functions, Creating an Lstream, Lstreams
|
|
0
|
7835 @section Lstream Types
|
|
|
7836
|
|
|
7837 @table @asis
|
|
|
7838 @item stdio
|
|
|
7839
|
|
|
7840 @item filedesc
|
|
|
7841
|
|
|
7842 @item lisp-string
|
|
|
7843
|
|
|
7844 @item fixed-buffer
|
|
|
7845
|
|
|
7846 @item resizing-buffer
|
|
|
7847
|
|
|
7848 @item dynarr
|
|
|
7849
|
|
|
7850 @item lisp-buffer
|
|
|
7851
|
|
|
7852 @item print
|
|
|
7853
|
|
|
7854 @item decoding
|
|
|
7855
|
|
|
7856 @item encoding
|
|
|
7857 @end table
|
|
|
7858
|
|
398
|
7859 @node Lstream Functions, Lstream Methods, Lstream Types, Lstreams
|
|
0
|
7860 @section Lstream Functions
|
|
|
7861
|
|
398
|
7862 @deftypefun {Lstream *} Lstream_new (Lstream_implementation *@var{imp}, const char *@var{mode})
|
|
0
|
7863 Allocate and return a new Lstream. This function is not really meant to
|
|
|
7864 be called directly; rather, each stream type should provide its own
|
|
|
7865 stream creation function, which creates the stream and does any other
|
|
|
7866 necessary creation stuff (e.g. opening a file).
|
|
|
7867 @end deftypefun
|
|
|
7868
|
|
|
7869 @deftypefun void Lstream_set_buffering (Lstream *@var{lstr}, Lstream_buffering @var{buffering}, int @var{buffering_size})
|
|
|
7870 Change the buffering of a stream. See @file{lstream.h}. By default the
|
|
|
7871 buffering is @code{STREAM_BLOCK_BUFFERED}.
|
|
|
7872 @end deftypefun
|
|
|
7873
|
|
|
7874 @deftypefun int Lstream_flush (Lstream *@var{lstr})
|
|
|
7875 Flush out any pending unwritten data in the stream. Clear any buffered
|
|
|
7876 input data. Returns 0 on success, -1 on error.
|
|
|
7877 @end deftypefun
|
|
|
7878
|
|
|
7879 @deftypefn Macro int Lstream_putc (Lstream *@var{stream}, int @var{c})
|
|
|
7880 Write out one byte to the stream. This is a macro and so it is very
|
|
|
7881 efficient. The @var{c} argument is only evaluated once but the @var{stream}
|
|
|
7882 argument is evaluated more than once. Returns 0 on success, -1 on
|
|
|
7883 error.
|
|
|
7884 @end deftypefn
|
|
|
7885
|
|
|
7886 @deftypefn Macro int Lstream_getc (Lstream *@var{stream})
|
|
|
7887 Read one byte from the stream. This is a macro and so it is very
|
|
|
7888 efficient. The @var{stream} argument is evaluated more than once. Return
|
|
|
7889 value is -1 for EOF or error.
|
|
|
7890 @end deftypefn
|
|
|
7891
|
|
|
7892 @deftypefn Macro void Lstream_ungetc (Lstream *@var{stream}, int @var{c})
|
|
|
7893 Push one byte back onto the input queue. This will be the next byte
|
|
|
7894 read from the stream. Any number of bytes can be pushed back and will
|
|
398
|
7895 be read in the reverse order they were pushed back---most recent
|
|
|
7896 first. (This is necessary for consistency---if there are a number of
|
|
0
|
7897 bytes that have been unread and I read and unread a byte, it needs to be
|
|
|
7898 the first to be read again.) This is a macro and so it is very
|
|
|
7899 efficient. The @var{c} argument is only evaluated once but the @var{stream}
|
|
|
7900 argument is evaluated more than once.
|
|
|
7901 @end deftypefn
|
|
|
7902
|
|
|
7903 @deftypefun int Lstream_fputc (Lstream *@var{stream}, int @var{c})
|
|
|
7904 @deftypefunx int Lstream_fgetc (Lstream *@var{stream})
|
|
|
7905 @deftypefunx void Lstream_fungetc (Lstream *@var{stream}, int @var{c})
|
|
|
7906 Function equivalents of the above macros.
|
|
|
7907 @end deftypefun
|
|
|
7908
|
|
398
|
7909 @deftypefun ssize_t Lstream_read (Lstream *@var{stream}, void *@var{data}, size_t @var{size})
|
|
0
|
7910 Read @var{size} bytes of @var{data} from the stream. Return the number
|
|
|
7911 of bytes read. 0 means EOF. -1 means an error occurred and no bytes
|
|
|
7912 were read.
|
|
|
7913 @end deftypefun
|
|
|
7914
|
|
398
|
7915 @deftypefun ssize_t Lstream_write (Lstream *@var{stream}, void *@var{data}, size_t @var{size})
|
|
0
|
7916 Write @var{size} bytes of @var{data} to the stream. Return the number
|
|
|
7917 of bytes written. -1 means an error occurred and no bytes were written.
|
|
|
7918 @end deftypefun
|
|
|
7919
|
|
398
|
7920 @deftypefun void Lstream_unread (Lstream *@var{stream}, void *@var{data}, size_t @var{size})
|
|
0
|
7921 Push back @var{size} bytes of @var{data} onto the input queue. The next
|
|
|
7922 call to @code{Lstream_read()} with the same size will read the same
|
|
|
7923 bytes back. Note that this will be the case even if there is other
|
|
|
7924 pending unread data.
|
|
|
7925 @end deftypefun
|
|
|
7926
|
|
|
7927 @deftypefun int Lstream_close (Lstream *@var{stream})
|
|
|
7928 Close the stream. All data will be flushed out.
|
|
|
7929 @end deftypefun
|
|
|
7930
|
|
|
7931 @deftypefun void Lstream_reopen (Lstream *@var{stream})
|
|
|
7932 Reopen a closed stream. This enables I/O on it again. This is not
|
|
|
7933 meant to be called except from a wrapper routine that reinitializes
|
|
398
|
7934 variables and such---the close routine may well have freed some
|
|
0
|
7935 necessary storage structures, for example.
|
|
|
7936 @end deftypefun
|
|
|
7937
|
|
|
7938 @deftypefun void Lstream_rewind (Lstream *@var{stream})
|
|
|
7939 Rewind the stream to the beginning.
|
|
|
7940 @end deftypefun
|
|
|
7941
|
|
398
|
7942 @node Lstream Methods, , Lstream Functions, Lstreams
|
|
0
|
7943 @section Lstream Methods
|
|
|
7944
|
|
398
|
7945 @deftypefn {Lstream Method} ssize_t reader (Lstream *@var{stream}, unsigned char *@var{data}, size_t @var{size})
|
|
0
|
7946 Read some data from the stream's end and store it into @var{data}, which
|
|
|
7947 can hold @var{size} bytes. Return the number of bytes read. A return
|
|
|
7948 value of 0 means no bytes can be read at this time. This may be because
|
|
|
7949 of an EOF, or because there is a granularity greater than one byte that
|
|
|
7950 the stream imposes on the returned data, and @var{size} is less than
|
|
|
7951 this granularity. (This will happen frequently for streams that need to
|
|
|
7952 return whole characters, because @code{Lstream_read()} calls the reader
|
|
|
7953 function repeatedly until it has the number of bytes it wants or until 0
|
|
|
7954 is returned.) The lstream functions do not treat a 0 return as EOF or
|
|
|
7955 do anything special; however, the calling function will interpret any 0
|
|
|
7956 it gets back as EOF. This will normally not happen unless the caller
|
|
|
7957 calls @code{Lstream_read()} with a very small size.
|
|
|
7958
|
|
|
7959 This function can be @code{NULL} if the stream is output-only.
|
|
|
7960 @end deftypefn
|
|
|
7961
|
|
398
|
7962 @deftypefn {Lstream Method} ssize_t writer (Lstream *@var{stream}, const unsigned char *@var{data}, size_t @var{size})
|
|
0
|
7963 Send some data to the stream's end. Data to be sent is in @var{data}
|
|
|
7964 and is @var{size} bytes. Return the number of bytes sent. This
|
|
|
7965 function can send and return fewer bytes than is passed in; in that
|
|
|
7966 case, the function will just be called again until there is no data left
|
|
|
7967 or 0 is returned. A return value of 0 means that no more data can be
|
|
|
7968 currently stored, but there is no error; the data will be squirreled
|
|
|
7969 away until the writer can accept data. (This is useful, e.g., if you're
|
|
|
7970 dealing with a non-blocking file descriptor and are getting
|
|
|
7971 @code{EWOULDBLOCK} errors.) This function can be @code{NULL} if the
|
|
|
7972 stream is input-only.
|
|
|
7973 @end deftypefn
|
|
|
7974
|
|
|
7975 @deftypefn {Lstream Method} int rewinder (Lstream *@var{stream})
|
|
|
7976 Rewind the stream. If this is @code{NULL}, the stream is not seekable.
|
|
|
7977 @end deftypefn
|
|
|
7978
|
|
|
7979 @deftypefn {Lstream Method} int seekable_p (Lstream *@var{stream})
|
|
398
|
7980 Indicate whether this stream is seekable---i.e. it can be rewound.
|
|
0
|
7981 This method is ignored if the stream does not have a rewind method. If
|
|
|
7982 this method is not present, the result is determined by whether a rewind
|
|
|
7983 method is present.
|
|
|
7984 @end deftypefn
|
|
|
7985
|
|
|
7986 @deftypefn {Lstream Method} int flusher (Lstream *@var{stream})
|
|
|
7987 Perform any additional operations necessary to flush the data in this
|
|
|
7988 stream.
|
|
|
7989 @end deftypefn
|
|
|
7990
|
|
|
7991 @deftypefn {Lstream Method} int pseudo_closer (Lstream *@var{stream})
|
|
|
7992 @end deftypefn
|
|
|
7993
|
|
|
7994 @deftypefn {Lstream Method} int closer (Lstream *@var{stream})
|
|
|
7995 Perform any additional operations necessary to close this stream down.
|
|
|
7996 May be @code{NULL}. This function is called when @code{Lstream_close()}
|
|
|
7997 is called or when the stream is garbage-collected. When this function
|
|
|
7998 is called, all pending data in the stream will already have been written
|
|
|
7999 out.
|
|
|
8000 @end deftypefn
|
|
|
8001
|
|
|
8002 @deftypefn {Lstream Method} Lisp_Object marker (Lisp_Object @var{lstream}, void (*@var{markfun}) (Lisp_Object))
|
|
|
8003 Mark this object for garbage collection. Same semantics as a standard
|
|
|
8004 @code{Lisp_Object} marker. This function can be @code{NULL}.
|
|
|
8005 @end deftypefn
|
|
|
8006
|
|
|
8007 @node Consoles; Devices; Frames; Windows, The Redisplay Mechanism, Lstreams, Top
|
|
|
8008 @chapter Consoles; Devices; Frames; Windows
|
|
|
8009
|
|
|
8010 @menu
|
|
|
8011 * Introduction to Consoles; Devices; Frames; Windows::
|
|
|
8012 * Point::
|
|
|
8013 * Window Hierarchy::
|
|
|
8014 * The Window Object::
|
|
|
8015 @end menu
|
|
|
8016
|
|
398
|
8017 @node Introduction to Consoles; Devices; Frames; Windows, Point, Consoles; Devices; Frames; Windows, Consoles; Devices; Frames; Windows
|
|
0
|
8018 @section Introduction to Consoles; Devices; Frames; Windows
|
|
|
8019
|
|
|
8020 A window-system window that you see on the screen is called a
|
|
|
8021 @dfn{frame} in Emacs terminology. Each frame is subdivided into one or
|
|
|
8022 more non-overlapping panes, called (confusingly) @dfn{windows}. Each
|
|
|
8023 window displays the text of a buffer in it. (See above on Buffers.) Note
|
|
|
8024 that buffers and windows are independent entities: Two or more windows
|
|
|
8025 can be displaying the same buffer (potentially in different locations),
|
|
|
8026 and a buffer can be displayed in no windows.
|
|
|
8027
|
|
|
8028 A single display screen that contains one or more frames is called
|
|
|
8029 a @dfn{display}. Under most circumstances, there is only one display.
|
|
|
8030 However, more than one display can exist, for example if you have
|
|
|
8031 a @dfn{multi-headed} console, i.e. one with a single keyboard but
|
|
|
8032 multiple displays. (Typically in such a situation, the various
|
|
|
8033 displays act like one large display, in that the mouse is only
|
|
|
8034 in one of them at a time, and moving the mouse off of one moves
|
|
|
8035 it into another.) In some cases, the different displays will
|
|
|
8036 have different characteristics, e.g. one color and one mono.
|
|
|
8037
|
|
|
8038 XEmacs can display frames on multiple displays. It can even deal
|
|
|
8039 simultaneously with frames on multiple keyboards (called @dfn{consoles} in
|
|
|
8040 XEmacs terminology). Here is one case where this might be useful: You
|
|
|
8041 are using XEmacs on your workstation at work, and leave it running.
|
|
|
8042 Then you go home and dial in on a TTY line, and you can use the
|
|
|
8043 already-running XEmacs process to display another frame on your local
|
|
|
8044 TTY.
|
|
|
8045
|
|
|
8046 Thus, there is a hierarchy console -> display -> frame -> window.
|
|
|
8047 There is a separate Lisp object type for each of these four concepts.
|
|
380
|
8048 Furthermore, there is logically a @dfn{selected console},
|
|
0
|
8049 @dfn{selected display}, @dfn{selected frame}, and @dfn{selected window}.
|
|
2
|
8050 Each of these objects is distinguished in various ways, such as being the
|
|
|
8051 default object for various functions that act on objects of that type.
|
|
371
|
8052 Note that every containing object rememembers the ``selected'' object
|
|
2
|
8053 among the objects that it contains: e.g. not only is there a selected
|
|
|
8054 window, but every frame remembers the last window in it that was
|
|
|
8055 selected, and changing the selected frame causes the remembered window
|
|
|
8056 within it to become the selected window. Similar relationships apply
|
|
|
8057 for consoles to devices and devices to frames.
|
|
0
|
8058
|
|
398
|
8059 @node Point, Window Hierarchy, Introduction to Consoles; Devices; Frames; Windows, Consoles; Devices; Frames; Windows
|
|
0
|
8060 @section Point
|
|
|
8061
|
|
|
8062 Recall that every buffer has a current insertion position, called
|
|
|
8063 @dfn{point}. Now, two or more windows may be displaying the same buffer,
|
|
|
8064 and the text cursor in the two windows (i.e. @code{point}) can be in
|
|
|
8065 two different places. You may ask, how can that be, since each
|
|
|
8066 buffer has only one value of @code{point}? The answer is that each window
|
|
|
8067 also has a value of @code{point} that is squirreled away in it. There
|
|
|
8068 is only one selected window, and the value of ``point'' in that buffer
|
|
|
8069 corresponds to that window. When the selected window is changed
|
|
|
8070 from one window to another displaying the same buffer, the old
|
|
|
8071 value of @code{point} is stored into the old window's ``point'' and the
|
|
|
8072 value of @code{point} from the new window is retrieved and made the
|
|
|
8073 value of @code{point} in the buffer. This means that @code{window-point}
|
|
|
8074 for the selected window is potentially inaccurate, and if you
|
|
|
8075 want to retrieve the correct value of @code{point} for a window,
|
|
|
8076 you must special-case on the selected window and retrieve the
|
|
|
8077 buffer's point instead. This is related to why @code{save-window-excursion}
|
|
|
8078 does not save the selected window's value of @code{point}.
|
|
|
8079
|
|
398
|
8080 @node Window Hierarchy, The Window Object, Point, Consoles; Devices; Frames; Windows
|
|
0
|
8081 @section Window Hierarchy
|
|
|
8082 @cindex window hierarchy
|
|
|
8083 @cindex hierarchy of windows
|
|
|
8084
|
|
|
8085 If a frame contains multiple windows (panes), they are always created
|
|
|
8086 by splitting an existing window along the horizontal or vertical axis.
|
|
|
8087 Terminology is a bit confusing here: to @dfn{split a window
|
|
|
8088 horizontally} means to create two side-by-side windows, i.e. to make a
|
|
|
8089 @emph{vertical} cut in a window. Likewise, to @dfn{split a window
|
|
|
8090 vertically} means to create two windows, one above the other, by making
|
|
|
8091 a @emph{horizontal} cut.
|
|
|
8092
|
|
|
8093 If you split a window and then split again along the same axis, you
|
|
|
8094 will end up with a number of panes all arranged along the same axis.
|
|
|
8095 The precise way in which the splits were made should not be important,
|
|
|
8096 and this is reflected internally. Internally, all windows are arranged
|
|
|
8097 in a tree, consisting of two types of windows, @dfn{combination} windows
|
|
|
8098 (which have children, and are covered completely by those children) and
|
|
|
8099 @dfn{leaf} windows, which have no children and are visible. Every
|
|
|
8100 combination window has two or more children, all arranged along the same
|
|
|
8101 axis. There are (logically) two subtypes of windows, depending on
|
|
|
8102 whether their children are horizontally or vertically arrayed. There is
|
|
|
8103 always one root window, which is either a leaf window (if the frame
|
|
|
8104 contains only one window) or a combination window (if the frame contains
|
|
|
8105 more than one window). In the latter case, the root window will have
|
|
|
8106 two or more children, either horizontally or vertically arrayed, and
|
|
|
8107 each of those children will be either a leaf window or another
|
|
|
8108 combination window.
|
|
|
8109
|
|
|
8110 Here are some rules:
|
|
|
8111
|
|
|
8112 @enumerate
|
|
|
8113 @item
|
|
2
|
8114 Horizontal combination windows can never have children that are
|
|
|
8115 horizontal combination windows; same for vertical.
|
|
0
|
8116
|
|
|
8117 @item
|
|
|
8118 Only leaf windows can be split (obviously) and this splitting does one
|
|
|
8119 of two things: (a) turns the leaf window into a combination window and
|
|
|
8120 creates two new leaf children, or (b) turns the leaf window into one of
|
|
|
8121 the two new leaves and creates the other leaf. Rule (1) dictates which
|
|
|
8122 of these two outcomes happens.
|
|
|
8123
|
|
|
8124 @item
|
|
|
8125 Every combination window must have at least two children.
|
|
|
8126
|
|
|
8127 @item
|
|
|
8128 Leaf windows can never become combination windows. They can be deleted,
|
|
|
8129 however. If this results in a violation of (3), the parent combination
|
|
|
8130 window also gets deleted.
|
|
|
8131
|
|
|
8132 @item
|
|
|
8133 All functions that accept windows must be prepared to accept combination
|
|
|
8134 windows, and do something sane (e.g. signal an error if so).
|
|
|
8135 Combination windows @emph{do} escape to the Lisp level.
|
|
|
8136
|
|
|
8137 @item
|
|
|
8138 All windows have three fields governing their contents:
|
|
|
8139 these are @dfn{hchild} (a list of horizontally-arrayed children),
|
|
|
8140 @dfn{vchild} (a list of vertically-arrayed children), and @dfn{buffer}
|
|
|
8141 (the buffer contained in a leaf window). Exactly one of
|
|
|
8142 these will be non-nil. Remember that @dfn{horizontally-arrayed}
|
|
|
8143 means ``side-by-side'' and @dfn{vertically-arrayed} means
|
|
|
8144 @dfn{one above the other}.
|
|
|
8145
|
|
|
8146 @item
|
|
|
8147 Leaf windows also have markers in their @code{start} (the
|
|
|
8148 first buffer position displayed in the window) and @code{pointm}
|
|
398
|
8149 (the window's stashed value of @code{point}---see above) fields,
|
|
0
|
8150 while combination windows have nil in these fields.
|
|
|
8151
|
|
|
8152 @item
|
|
|
8153 The list of children for a window is threaded through the
|
|
|
8154 @code{next} and @code{prev} fields of each child window.
|
|
|
8155
|
|
|
8156 @item
|
|
|
8157 @strong{Deleted windows can be undeleted}. This happens as a result of
|
|
|
8158 restoring a window configuration, and is unlike frames, displays, and
|
|
|
8159 consoles, which, once deleted, can never be restored. Deleting a window
|
|
|
8160 does nothing except set a special @code{dead} bit to 1 and clear out the
|
|
|
8161 @code{next}, @code{prev}, @code{hchild}, and @code{vchild} fields, for
|
|
|
8162 GC purposes.
|
|
|
8163
|
|
|
8164 @item
|
|
398
|
8165 Most frames actually have two top-level windows---one for the
|
|
0
|
8166 minibuffer and one (the @dfn{root}) for everything else. The modeline
|
|
|
8167 (if present) separates these two. The @code{next} field of the root
|
|
|
8168 points to the minibuffer, and the @code{prev} field of the minibuffer
|
|
|
8169 points to the root. The other @code{next} and @code{prev} fields are
|
|
|
8170 @code{nil}, and the frame points to both of these windows.
|
|
|
8171 Minibuffer-less frames have no minibuffer window, and the @code{next}
|
|
|
8172 and @code{prev} of the root window are @code{nil}. Minibuffer-only
|
|
|
8173 frames have no root window, and the @code{next} of the minibuffer window
|
|
|
8174 is @code{nil} but the @code{prev} points to itself. (#### This is an
|
|
|
8175 artifact that should be fixed.)
|
|
|
8176 @end enumerate
|
|
|
8177
|
|
398
|
8178 @node The Window Object, , Window Hierarchy, Consoles; Devices; Frames; Windows
|
|
0
|
8179 @section The Window Object
|
|
|
8180
|
|
|
8181 Windows have the following accessible fields:
|
|
|
8182
|
|
|
8183 @table @code
|
|
|
8184 @item frame
|
|
|
8185 The frame that this window is on.
|
|
|
8186
|
|
|
8187 @item mini_p
|
|
|
8188 Non-@code{nil} if this window is a minibuffer window.
|
|
|
8189
|
|
|
8190 @item buffer
|
|
|
8191 The buffer that the window is displaying. This may change often during
|
|
|
8192 the life of the window.
|
|
|
8193
|
|
|
8194 @item dedicated
|
|
|
8195 Non-@code{nil} if this window is dedicated to its buffer.
|
|
|
8196
|
|
|
8197 @item pointm
|
|
|
8198 @cindex window point internals
|
|
|
8199 This is the value of point in the current buffer when this window is
|
|
|
8200 selected; when it is not selected, it retains its previous value.
|
|
|
8201
|
|
|
8202 @item start
|
|
|
8203 The position in the buffer that is the first character to be displayed
|
|
|
8204 in the window.
|
|
|
8205
|
|
|
8206 @item force_start
|
|
|
8207 If this flag is non-@code{nil}, it says that the window has been
|
|
|
8208 scrolled explicitly by the Lisp program. This affects what the next
|
|
|
8209 redisplay does if point is off the screen: instead of scrolling the
|
|
|
8210 window to show the text around point, it moves point to a location that
|
|
|
8211 is on the screen.
|
|
|
8212
|
|
|
8213 @item last_modified
|
|
|
8214 The @code{modified} field of the window's buffer, as of the last time
|
|
|
8215 a redisplay completed in this window.
|
|
|
8216
|
|
|
8217 @item last_point
|
|
|
8218 The buffer's value of point, as of the last time
|
|
|
8219 a redisplay completed in this window.
|
|
|
8220
|
|
|
8221 @item left
|
|
|
8222 This is the left-hand edge of the window, measured in columns. (The
|
|
|
8223 leftmost column on the screen is @w{column 0}.)
|
|
|
8224
|
|
|
8225 @item top
|
|
|
8226 This is the top edge of the window, measured in lines. (The top line on
|
|
|
8227 the screen is @w{line 0}.)
|
|
|
8228
|
|
|
8229 @item height
|
|
|
8230 The height of the window, measured in lines.
|
|
|
8231
|
|
|
8232 @item width
|
|
|
8233 The width of the window, measured in columns.
|
|
|
8234
|
|
|
8235 @item next
|
|
|
8236 This is the window that is the next in the chain of siblings. It is
|
|
|
8237 @code{nil} in a window that is the rightmost or bottommost of a group of
|
|
|
8238 siblings.
|
|
|
8239
|
|
|
8240 @item prev
|
|
|
8241 This is the window that is the previous in the chain of siblings. It is
|
|
|
8242 @code{nil} in a window that is the leftmost or topmost of a group of
|
|
|
8243 siblings.
|
|
|
8244
|
|
|
8245 @item parent
|
|
|
8246 Internally, XEmacs arranges windows in a tree; each group of siblings has
|
|
|
8247 a parent window whose area includes all the siblings. This field points
|
|
|
8248 to a window's parent.
|
|
|
8249
|
|
|
8250 Parent windows do not display buffers, and play little role in display
|
|
|
8251 except to shape their child windows. Emacs Lisp programs usually have
|
|
|
8252 no access to the parent windows; they operate on the windows at the
|
|
|
8253 leaves of the tree, which actually display buffers.
|
|
|
8254
|
|
|
8255 @item hscroll
|
|
|
8256 This is the number of columns that the display in the window is scrolled
|
|
|
8257 horizontally to the left. Normally, this is 0.
|
|
|
8258
|
|
|
8259 @item use_time
|
|
|
8260 This is the last time that the window was selected. The function
|
|
|
8261 @code{get-lru-window} uses this field.
|
|
|
8262
|
|
|
8263 @item display_table
|
|
|
8264 The window's display table, or @code{nil} if none is specified for it.
|
|
|
8265
|
|
|
8266 @item update_mode_line
|
|
|
8267 Non-@code{nil} means this window's mode line needs to be updated.
|
|
|
8268
|
|
|
8269 @item base_line_number
|
|
|
8270 The line number of a certain position in the buffer, or @code{nil}.
|
|
|
8271 This is used for displaying the line number of point in the mode line.
|
|
|
8272
|
|
|
8273 @item base_line_pos
|
|
|
8274 The position in the buffer for which the line number is known, or
|
|
|
8275 @code{nil} meaning none is known.
|
|
|
8276
|
|
|
8277 @item region_showing
|
|
|
8278 If the region (or part of it) is highlighted in this window, this field
|
|
|
8279 holds the mark position that made one end of that region. Otherwise,
|
|
|
8280 this field is @code{nil}.
|
|
|
8281 @end table
|
|
|
8282
|
|
|
8283 @node The Redisplay Mechanism, Extents, Consoles; Devices; Frames; Windows, Top
|
|
|
8284 @chapter The Redisplay Mechanism
|
|
|
8285
|
|
|
8286 The redisplay mechanism is one of the most complicated sections of
|
|
|
8287 XEmacs, especially from a conceptual standpoint. This is doubly so
|
|
|
8288 because, unlike for the basic aspects of the Lisp interpreter, the
|
|
|
8289 computer science theories of how to efficiently handle redisplay are not
|
|
|
8290 well-developed.
|
|
|
8291
|
|
|
8292 When working with the redisplay mechanism, remember the Golden Rules
|
|
|
8293 of Redisplay:
|
|
|
8294
|
|
|
8295 @enumerate
|
|
|
8296 @item
|
|
|
8297 It Is Better To Be Correct Than Fast.
|
|
|
8298 @item
|
|
|
8299 Thou Shalt Not Run Elisp From Within Redisplay.
|
|
|
8300 @item
|
|
|
8301 It Is Better To Be Fast Than Not To Be.
|
|
|
8302 @end enumerate
|
|
|
8303
|
|
|
8304 @menu
|
|
|
8305 * Critical Redisplay Sections::
|
|
|
8306 * Line Start Cache::
|
|
398
|
8307 * Redisplay Piece by Piece::
|
|
0
|
8308 @end menu
|
|
|
8309
|
|
398
|
8310 @node Critical Redisplay Sections, Line Start Cache, The Redisplay Mechanism, The Redisplay Mechanism
|
|
0
|
8311 @section Critical Redisplay Sections
|
|
|
8312 @cindex critical redisplay sections
|
|
|
8313
|
|
|
8314 Within this section, we are defenseless and assume that the
|
|
|
8315 following cannot happen:
|
|
|
8316
|
|
|
8317 @enumerate
|
|
|
8318 @item
|
|
|
8319 garbage collection
|
|
|
8320 @item
|
|
|
8321 Lisp code evaluation
|
|
|
8322 @item
|
|
|
8323 frame size changes
|
|
|
8324 @end enumerate
|
|
|
8325
|
|
|
8326 We ensure (3) by calling @code{hold_frame_size_changes()}, which
|
|
|
8327 will cause any pending frame size changes to get put on hold
|
|
|
8328 till after the end of the critical section. (1) follows
|
|
|
8329 automatically if (2) is met. #### Unfortunately, there are
|
|
|
8330 some places where Lisp code can be called within this section.
|
|
|
8331 We need to remove them.
|
|
|
8332
|
|
|
8333 If @code{Fsignal()} is called during this critical section, we
|
|
|
8334 will @code{abort()}.
|
|
|
8335
|
|
|
8336 If garbage collection is called during this critical section,
|
|
|
8337 we simply return. #### We should abort instead.
|
|
|
8338
|
|
|
8339 #### If a frame-size change does occur we should probably
|
|
|
8340 actually be preempting redisplay.
|
|
|
8341
|
|
398
|
8342 @node Line Start Cache, Redisplay Piece by Piece, Critical Redisplay Sections, The Redisplay Mechanism
|
|
0
|
8343 @section Line Start Cache
|
|
|
8344 @cindex line start cache
|
|
|
8345
|
|
|
8346 The traditional scrolling code in Emacs breaks in a variable height
|
|
|
8347 world. It depends on the key assumption that the number of lines that
|
|
|
8348 can be displayed at any given time is fixed. This led to a complete
|
|
|
8349 separation of the scrolling code from the redisplay code. In order to
|
|
|
8350 fully support variable height lines, the scrolling code must actually be
|
|
|
8351 tightly integrated with redisplay. Only redisplay can determine how
|
|
|
8352 many lines will be displayed on a screen for any given starting point.
|
|
|
8353
|
|
|
8354 What is ideally wanted is a complete list of the starting buffer
|
|
|
8355 position for every possible display line of a buffer along with the
|
|
|
8356 height of that display line. Maintaining such a full list would be very
|
|
|
8357 expensive. We settle for having it include information for all areas
|
|
|
8358 which we happen to generate anyhow (i.e. the region currently being
|
|
|
8359 displayed) and for those areas we need to work with.
|
|
|
8360
|
|
|
8361 In order to ensure that the cache accurately represents what redisplay
|
|
|
8362 would actually show, it is necessary to invalidate it in many
|
|
|
8363 situations. If the buffer changes, the starting positions may no longer
|
|
|
8364 be correct. If a face or an extent has changed then the line heights
|
|
|
8365 may have altered. These events happen frequently enough that the cache
|
|
|
8366 can end up being constantly disabled. With this potentially constant
|
|
|
8367 invalidation when is the cache ever useful?
|
|
|
8368
|
|
|
8369 Even if the cache is invalidated before every single usage, it is
|
|
|
8370 necessary. Scrolling often requires knowledge about display lines which
|
|
|
8371 are actually above or below the visible region. The cache provides a
|
|
|
8372 convenient light-weight method of storing this information for multiple
|
|
|
8373 display regions. This knowledge is necessary for the scrolling code to
|
|
|
8374 always obey the First Golden Rule of Redisplay.
|
|
|
8375
|
|
|
8376 If the cache already contains all of the information that the scrolling
|
|
|
8377 routines happen to need so that it doesn't have to go generate it, then
|
|
|
8378 we are able to obey the Third Golden Rule of Redisplay. The first thing
|
|
|
8379 we do to help out the cache is to always add the displayed region. This
|
|
|
8380 region had to be generated anyway, so the cache ends up getting the
|
|
|
8381 information basically for free. In those cases where a user is simply
|
|
|
8382 scrolling around viewing a buffer there is a high probability that this
|
|
|
8383 is sufficient to always provide the needed information. The second
|
|
|
8384 thing we can do is be smart about invalidating the cache.
|
|
|
8385
|
|
398
|
8386 TODO---Be smart about invalidating the cache. Potential places:
|
|
0
|
8387
|
|
|
8388 @itemize @bullet
|
|
|
8389 @item
|
|
|
8390 Insertions at end-of-line which don't cause line-wraps do not alter the
|
|
|
8391 starting positions of any display lines. These types of buffer
|
|
|
8392 modifications should not invalidate the cache. This is actually a large
|
|
|
8393 optimization for redisplay speed as well.
|
|
|
8394 @item
|
|
|
8395 Buffer modifications frequently only affect the display of lines at and
|
|
|
8396 below where they occur. In these situations we should only invalidate
|
|
|
8397 the part of the cache starting at where the modification occurs.
|
|
|
8398 @end itemize
|
|
|
8399
|
|
|
8400 In case you're wondering, the Second Golden Rule of Redisplay is not
|
|
|
8401 applicable.
|
|
|
8402
|
|
398
|
8403 @node Redisplay Piece by Piece, , Line Start Cache, The Redisplay Mechanism
|
|
|
8404 @section Redisplay Piece by Piece
|
|
|
8405 @cindex Redisplay Piece by Piece
|
|
|
8406
|
|
|
8407 As you can begin to see redisplay is complex and also not well
|
|
|
8408 documented. Chuck no longer works on XEmacs so this section is my take
|
|
|
8409 on the workings of redisplay.
|
|
|
8410
|
|
|
8411 Redisplay happens in three phases:
|
|
|
8412
|
|
|
8413 @enumerate
|
|
|
8414 @item
|
|
|
8415 Determine desired display in area that needs redisplay.
|
|
|
8416 Implemented by @code{redisplay.c}
|
|
|
8417 @item
|
|
|
8418 Compare desired display with current display
|
|
|
8419 Implemented by @code{redisplay-output.c}
|
|
|
8420 @item
|
|
|
8421 Output changes Implemented by @code{redisplay-output.c},
|
|
|
8422 @code{redisplay-x.c}, @code{redisplay-msw.c} and @code{redisplay-tty.c}
|
|
|
8423 @end enumerate
|
|
|
8424
|
|
|
8425 Steps 1 and 2 are device-independant and relatively complex. Step 3 is
|
|
|
8426 mostly device-dependent.
|
|
|
8427
|
|
|
8428 Determining the desired display
|
|
|
8429
|
|
|
8430 Display attributes are stored in @code{display_line} structures. Each
|
|
|
8431 @code{display_line} consists of a set of @code{display_block}'s and each
|
|
|
8432 @code{display_block} contains a number of @code{rune}'s. Generally
|
|
|
8433 dynarr's of @code{display_line}'s are held by each window representing
|
|
|
8434 the current display and the desired display.
|
|
|
8435
|
|
|
8436 The @code{display_line} structures are tighly tied to buffers which
|
|
|
8437 presents a problem for redisplay as this connection is bogus for the
|
|
|
8438 modeline. Hence the @code{display_line} generation routines are
|
|
|
8439 duplicated for generating the modeline. This means that the modeline
|
|
|
8440 display code has many bugs that the standard redisplay code does not.
|
|
|
8441
|
|
|
8442 The guts of @code{display_line} generation are in
|
|
|
8443 @code{create_text_block}, which creates a single display line for the
|
|
|
8444 desired locale. This incrementally parses the characters on the current
|
|
|
8445 line and generates redisplay structures for each.
|
|
|
8446
|
|
|
8447 Gutter redisplay is different. Because the data to display is stored in
|
|
|
8448 a string we cannot use @code{create_text_block}. Instead we use
|
|
|
8449 @code{create_text_string_block} which performs the same function as
|
|
|
8450 @code{create_text_block} but for strings. Many of the complexities of
|
|
|
8451 @code{create_text_block} to do with cursor handling and selective
|
|
|
8452 display have been removed.
|
|
|
8453
|
|
|
8454 @node Extents, Faces, The Redisplay Mechanism, Top
|
|
0
|
8455 @chapter Extents
|
|
|
8456
|
|
|
8457 @menu
|
|
|
8458 * Introduction to Extents:: Extents are ranges over text, with properties.
|
|
|
8459 * Extent Ordering:: How extents are ordered internally.
|
|
|
8460 * Format of the Extent Info:: The extent information in a buffer or string.
|
|
|
8461 * Zero-Length Extents:: A weird special case.
|
|
398
|
8462 * Mathematics of Extent Ordering:: A rigorous foundation.
|
|
0
|
8463 * Extent Fragments:: Cached information useful for redisplay.
|
|
|
8464 @end menu
|
|
|
8465
|
|
398
|
8466 @node Introduction to Extents, Extent Ordering, Extents, Extents
|
|
0
|
8467 @section Introduction to Extents
|
|
|
8468
|
|
|
8469 Extents are regions over a buffer, with a start and an end position
|
|
|
8470 denoting the region of the buffer included in the extent. In
|
|
|
8471 addition, either end can be closed or open, meaning that the endpoint
|
|
|
8472 is or is not logically included in the extent. Insertion of a character
|
|
|
8473 at a closed endpoint causes the character to go inside the extent;
|
|
|
8474 insertion at an open endpoint causes the character to go outside.
|
|
|
8475
|
|
|
8476 Extent endpoints are stored using memory indices (see @file{insdel.c}),
|
|
|
8477 to minimize the amount of adjusting that needs to be done when
|
|
|
8478 characters are inserted or deleted.
|
|
|
8479
|
|
|
8480 (Formerly, extent endpoints at the gap could be either before or
|
|
|
8481 after the gap, depending on the open/closedness of the endpoint.
|
|
|
8482 The intent of this was to make it so that insertions would
|
|
|
8483 automatically go inside or out of extents as necessary with no
|
|
|
8484 further work needing to be done. It didn't work out that way,
|
|
|
8485 however, and just ended up complexifying and buggifying all the
|
|
|
8486 rest of the code.)
|
|
|
8487
|
|
398
|
8488 @node Extent Ordering, Format of the Extent Info, Introduction to Extents, Extents
|
|
0
|
8489 @section Extent Ordering
|
|
|
8490
|
|
|
8491 Extents are compared using memory indices. There are two orderings
|
|
|
8492 for extents and both orders are kept current at all times. The normal
|
|
|
8493 or @dfn{display} order is as follows:
|
|
|
8494
|
|
|
8495 @example
|
|
380
|
8496 Extent A is ``less than'' extent B,
|
|
|
8497 that is, earlier in the display order,
|
|
|
8498 if: A-start < B-start,
|
|
|
8499 or if: A-start = B-start, and A-end > B-end
|
|
0
|
8500 @end example
|
|
|
8501
|
|
|
8502 So if two extents begin at the same position, the larger of them is the
|
|
|
8503 earlier one in the display order (@code{EXTENT_LESS} is true).
|
|
|
8504
|
|
|
8505 For the e-order, the same thing holds:
|
|
|
8506
|
|
|
8507 @example
|
|
380
|
8508 Extent A is ``less than'' extent B in e-order,
|
|
|
8509 that is, later in the buffer,
|
|
|
8510 if: A-end < B-end,
|
|
|
8511 or if: A-end = B-end, and A-start > B-start
|
|
0
|
8512 @end example
|
|
|
8513
|
|
|
8514 So if two extents end at the same position, the smaller of them is the
|
|
|
8515 earlier one in the e-order (@code{EXTENT_E_LESS} is true).
|
|
|
8516
|
|
|
8517 The display order and the e-order are complementary orders: any
|
|
|
8518 theorem about the display order also applies to the e-order if you swap
|
|
|
8519 all occurrences of ``display order'' and ``e-order'', ``less than'' and
|
|
|
8520 ``greater than'', and ``extent start'' and ``extent end''.
|
|
|
8521
|
|
398
|
8522 @node Format of the Extent Info, Zero-Length Extents, Extent Ordering, Extents
|
|
0
|
8523 @section Format of the Extent Info
|
|
|
8524
|
|
|
8525 An extent-info structure consists of a list of the buffer or string's
|
|
|
8526 extents and a @dfn{stack of extents} that lists all of the extents over
|
|
|
8527 a particular position. The stack-of-extents info is used for
|
|
398
|
8528 optimization purposes---it basically caches some info that might
|
|
0
|
8529 be expensive to compute. Certain otherwise hard computations are easy
|
|
|
8530 given the stack of extents over a particular position, and if the
|
|
|
8531 stack of extents over a nearby position is known (because it was
|
|
|
8532 calculated at some prior point in time), it's easy to move the stack
|
|
|
8533 of extents to the proper position.
|
|
|
8534
|
|
|
8535 Given that the stack of extents is an optimization, and given that
|
|
|
8536 it requires memory, a string's stack of extents is wiped out each
|
|
|
8537 time a garbage collection occurs. Therefore, any time you retrieve
|
|
|
8538 the stack of extents, it might not be there. If you need it to
|
|
|
8539 be there, use the @code{_force} version.
|
|
|
8540
|
|
|
8541 Similarly, a string may or may not have an extent_info structure.
|
|
|
8542 (Generally it won't if there haven't been any extents added to the
|
|
|
8543 string.) So use the @code{_force} version if you need the extent_info
|
|
|
8544 structure to be there.
|
|
|
8545
|
|
|
8546 A list of extents is maintained as a double gap array: one gap array
|
|
|
8547 is ordered by start index (the @dfn{display order}) and the other is
|
|
|
8548 ordered by end index (the @dfn{e-order}). Note that positions in an
|
|
|
8549 extent list should logically be conceived of as referring @emph{to} a
|
|
|
8550 particular extent (as is the norm in programs) rather than sitting
|
|
|
8551 between two extents. Note also that callers of these functions should
|
|
|
8552 not be aware of the fact that the extent list is implemented as an
|
|
|
8553 array, except for the fact that positions are integers (this should be
|
|
|
8554 generalized to handle integers and linked list equally well).
|
|
|
8555
|
|
398
|
8556 @node Zero-Length Extents, Mathematics of Extent Ordering, Format of the Extent Info, Extents
|
|
0
|
8557 @section Zero-Length Extents
|
|
|
8558
|
|
|
8559 Extents can be zero-length, and will end up that way if their endpoints
|
|
|
8560 are explicitly set that way or if their detachable property is nil
|
|
|
8561 and all the text in the extent is deleted. (The exception is open-open
|
|
|
8562 zero-length extents, which are barred from existing because there is
|
|
|
8563 no sensible way to define their properties. Deletion of the text in
|
|
|
8564 an open-open extent causes it to be converted into a closed-open
|
|
|
8565 extent.) Zero-length extents are primarily used to represent
|
|
|
8566 annotations, and behave as follows:
|
|
|
8567
|
|
|
8568 @enumerate
|
|
|
8569 @item
|
|
|
8570 Insertion at the position of a zero-length extent expands the extent
|
|
|
8571 if both endpoints are closed; goes after the extent if it is closed-open;
|
|
|
8572 and goes before the extent if it is open-closed.
|
|
|
8573
|
|
|
8574 @item
|
|
|
8575 Deletion of a character on a side of a zero-length extent whose
|
|
|
8576 corresponding endpoint is closed causes the extent to be detached if
|
|
|
8577 it is detachable; if the extent is not detachable or the corresponding
|
|
|
8578 endpoint is open, the extent remains in the buffer, moving as necessary.
|
|
|
8579 @end enumerate
|
|
|
8580
|
|
|
8581 Note that closed-open, non-detachable zero-length extents behave
|
|
|
8582 exactly like markers and that open-closed, non-detachable zero-length
|
|
|
8583 extents behave like the ``point-type'' marker in Mule.
|
|
|
8584
|
|
398
|
8585 @node Mathematics of Extent Ordering, Extent Fragments, Zero-Length Extents, Extents
|
|
0
|
8586 @section Mathematics of Extent Ordering
|
|
|
8587 @cindex extent mathematics
|
|
|
8588 @cindex mathematics of extents
|
|
|
8589 @cindex extent ordering
|
|
|
8590
|
|
|
8591 @cindex display order of extents
|
|
|
8592 @cindex extents, display order
|
|
|
8593 The extents in a buffer are ordered by ``display order'' because that
|
|
|
8594 is that order that the redisplay mechanism needs to process them in.
|
|
|
8595 The e-order is an auxiliary ordering used to facilitate operations
|
|
|
8596 over extents. The operations that can be performed on the ordered
|
|
|
8597 list of extents in a buffer are
|
|
|
8598
|
|
|
8599 @enumerate
|
|
|
8600 @item
|
|
|
8601 Locate where an extent would go if inserted into the list.
|
|
|
8602 @item
|
|
|
8603 Insert an extent into the list.
|
|
|
8604 @item
|
|
|
8605 Remove an extent from the list.
|
|
|
8606 @item
|
|
|
8607 Map over all the extents that overlap a range.
|
|
|
8608 @end enumerate
|
|
|
8609
|
|
|
8610 (4) requires being able to determine the first and last extents
|
|
|
8611 that overlap a range.
|
|
|
8612
|
|
|
8613 NOTE: @dfn{overlap} is used as follows:
|
|
|
8614
|
|
|
8615 @itemize @bullet
|
|
|
8616 @item
|
|
|
8617 two ranges overlap if they have at least one point in common.
|
|
|
8618 Whether the endpoints are open or closed makes a difference here.
|
|
|
8619 @item
|
|
|
8620 a point overlaps a range if the point is contained within the
|
|
|
8621 range; this is equivalent to treating a point @math{P} as the range
|
|
|
8622 @math{[P, P]}.
|
|
|
8623 @item
|
|
|
8624 In the case of an @emph{extent} overlapping a point or range, the extent
|
|
|
8625 is normally treated as having closed endpoints. This applies
|
|
|
8626 consistently in the discussion of stacks of extents and such below.
|
|
|
8627 Note that this definition of overlap is not necessarily consistent with
|
|
|
8628 the extents that @code{map-extents} maps over, since @code{map-extents}
|
|
|
8629 sometimes pays attention to whether the endpoints of an extents are open
|
|
|
8630 or closed. But for our purposes, it greatly simplifies things to treat
|
|
|
8631 all extents as having closed endpoints.
|
|
|
8632 @end itemize
|
|
|
8633
|
|
|
8634 First, define @math{>}, @math{<}, @math{<=}, etc. as applied to extents
|
|
|
8635 to mean comparison according to the display order. Comparison between
|
|
|
8636 an extent @math{E} and an index @math{I} means comparison between
|
|
|
8637 @math{E} and the range @math{[I, I]}.
|
|
|
8638
|
|
|
8639 Also define @math{e>}, @math{e<}, @math{e<=}, etc. to mean comparison
|
|
|
8640 according to the e-order.
|
|
|
8641
|
|
|
8642 For any range @math{R}, define @math{R(0)} to be the starting index of
|
|
|
8643 the range and @math{R(1)} to be the ending index of the range.
|
|
|
8644
|
|
|
8645 For any extent @math{E}, define @math{E(next)} to be the extent directly
|
|
|
8646 following @math{E}, and @math{E(prev)} to be the extent directly
|
|
|
8647 preceding @math{E}. Assume @math{E(next)} and @math{E(prev)} can be
|
|
|
8648 determined from @math{E} in constant time. (This is because we store
|
|
|
8649 the extent list as a doubly linked list.)
|
|
|
8650
|
|
|
8651 Similarly, define @math{E(e-next)} and @math{E(e-prev)} to be the
|
|
|
8652 extents directly following and preceding @math{E} in the e-order.
|
|
|
8653
|
|
|
8654 Now:
|
|
|
8655
|
|
|
8656 Let @math{R} be a range.
|
|
|
8657 Let @math{F} be the first extent overlapping @math{R}.
|
|
|
8658 Let @math{L} be the last extent overlapping @math{R}.
|
|
|
8659
|
|
|
8660 Theorem 1: @math{R(1)} lies between @math{L} and @math{L(next)},
|
|
|
8661 i.e. @math{L <= R(1) < L(next)}.
|
|
|
8662
|
|
|
8663 This follows easily from the definition of display order. The
|
|
|
8664 basic reason that this theorem applies is that the display order
|
|
|
8665 sorts by increasing starting index.
|
|
|
8666
|
|
|
8667 Therefore, we can determine @math{L} just by looking at where we would
|
|
|
8668 insert @math{R(1)} into the list, and if we know @math{F} and are moving
|
|
|
8669 forward over extents, we can easily determine when we've hit @math{L} by
|
|
|
8670 comparing the extent we're at to @math{R(1)}.
|
|
|
8671
|
|
|
8672 @example
|
|
|
8673 Theorem 2: @math{F(e-prev) e< [1, R(0)] e<= F}.
|
|
|
8674 @end example
|
|
|
8675
|
|
|
8676 This is the analog of Theorem 1, and applies because the e-order
|
|
|
8677 sorts by increasing ending index.
|
|
|
8678
|
|
|
8679 Therefore, @math{F} can be found in the same amount of time as
|
|
|
8680 operation (1), i.e. the time that it takes to locate where an extent
|
|
|
8681 would go if inserted into the e-order list.
|
|
|
8682
|
|
|
8683 If the lists were stored as balanced binary trees, then operation (1)
|
|
|
8684 would take logarithmic time, which is usually quite fast. However,
|
|
|
8685 currently they're stored as simple doubly-linked lists, and instead we
|
|
|
8686 do some caching to try to speed things up.
|
|
|
8687
|
|
|
8688 Define a @dfn{stack of extents} (or @dfn{SOE}) as the set of extents
|
|
|
8689 (ordered in the display order) that overlap an index @math{I}, together
|
|
|
8690 with the SOE's @dfn{previous} extent, which is an extent that precedes
|
|
|
8691 @math{I} in the e-order. (Hopefully there will not be very many extents
|
|
|
8692 between @math{I} and the previous extent.)
|
|
|
8693
|
|
|
8694 Now:
|
|
|
8695
|
|
|
8696 Let @math{I} be an index, let @math{S} be the stack of extents on
|
|
|
8697 @math{I}, let @math{F} be the first extent in @math{S}, and let @math{P}
|
|
|
8698 be @math{S}'s previous extent.
|
|
|
8699
|
|
|
8700 Theorem 3: The first extent in @math{S} is the first extent that overlaps
|
|
|
8701 any range @math{[I, J]}.
|
|
|
8702
|
|
|
8703 Proof: Any extent that overlaps @math{[I, J]} but does not include
|
|
|
8704 @math{I} must have a start index @math{> I}, and thus be greater than
|
|
|
8705 any extent in @math{S}.
|
|
|
8706
|
|
|
8707 Therefore, finding the first extent that overlaps a range @math{R} is
|
|
|
8708 the same as finding the first extent that overlaps @math{R(0)}.
|
|
|
8709
|
|
|
8710 Theorem 4: Let @math{I2} be an index such that @math{I2 > I}, and let
|
|
|
8711 @math{F2} be the first extent that overlaps @math{I2}. Then, either
|
|
|
8712 @math{F2} is in @math{S} or @math{F2} is greater than any extent in
|
|
|
8713 @math{S}.
|
|
|
8714
|
|
|
8715 Proof: If @math{F2} does not include @math{I} then its start index is
|
|
|
8716 greater than @math{I} and thus it is greater than any extent in
|
|
|
8717 @math{S}, including @math{F}. Otherwise, @math{F2} includes @math{I}
|
|
|
8718 and thus is in @math{S}, and thus @math{F2 >= F}.
|
|
|
8719
|
|
398
|
8720 @node Extent Fragments, , Mathematics of Extent Ordering, Extents
|
|
0
|
8721 @section Extent Fragments
|
|
|
8722 @cindex extent fragment
|
|
|
8723
|
|
|
8724 Imagine that the buffer is divided up into contiguous, non-overlapping
|
|
|
8725 @dfn{runs} of text such that no extent starts or ends within a run
|
|
|
8726 (extents that abut the run don't count).
|
|
|
8727
|
|
|
8728 An extent fragment is a structure that holds data about the run that
|
|
|
8729 contains a particular buffer position (if the buffer position is at the
|
|
398
|
8730 junction of two runs, the run after the position is used)---the
|
|
0
|
8731 beginning and end of the run, a list of all of the extents in that run,
|
|
|
8732 the @dfn{merged face} that results from merging all of the faces
|
|
|
8733 corresponding to those extents, the begin and end glyphs at the
|
|
|
8734 beginning of the run, etc. This is the information that redisplay needs
|
|
|
8735 in order to display this run.
|
|
|
8736
|
|
|
8737 Extent fragments have to be very quick to update to a new buffer
|
|
|
8738 position when moving linearly through the buffer. They rely on the
|
|
|
8739 stack-of-extents code, which does the heavy-duty algorithmic work of
|
|
|
8740 determining which extents overly a particular position.
|
|
|
8741
|
|
398
|
8742 @node Faces, Glyphs, Extents, Top
|
|
|
8743 @chapter Faces
|
|
0
|
8744
|
|
|
8745 Not yet documented.
|
|
|
8746
|
|
398
|
8747 @node Glyphs, Specifiers, Faces, Top
|
|
|
8748 @chapter Glyphs
|
|
|
8749
|
|
|
8750 Glyphs are graphical elements that can be displayed in XEmacs buffers or
|
|
|
8751 gutters. We use the term graphical element here in the broadest possible
|
|
|
8752 sense since glyphs can be as mundane as text to as arcane as a native
|
|
|
8753 tab widget.
|
|
|
8754
|
|
|
8755 In XEmacs, glyphs represent the uninstantiated state of graphical
|
|
|
8756 elements, i.e. they hold all the information necessary to produce an
|
|
|
8757 image on-screen but the image does not exist at this stage.
|
|
|
8758
|
|
|
8759 Glyphs are lazily instantiated by calling one of the glyph
|
|
|
8760 functions. This usually occurs within redisplay when
|
|
|
8761 @code{Fglyph_height} is called. Instantiation causes an image-instance
|
|
|
8762 to be created and cached. This cache is on a device basis for all glyphs
|
|
|
8763 except glyph-widgets, and on a window basis for glyph widgets. The
|
|
|
8764 caching is done by @code{image_instantiate} and is necessary because it
|
|
|
8765 is generally possible to display an image-instance in multiple
|
|
|
8766 domains. For instance if we create a Pixmap, we can actually display
|
|
|
8767 this on multiple windows - even though we only need a single Pixmap
|
|
|
8768 instance to do this. If caching wasn't done then it would be necessary
|
|
|
8769 to create image-instances for every displayable occurrance of a glyph -
|
|
|
8770 and every usage - and this would be extremely memory and cpu intensive.
|
|
|
8771
|
|
|
8772 Widget-glyphs (a.k.a native widgets) are not cached in this way. This is
|
|
|
8773 because widget-glyph image-instances on screen are toolkit windows, and
|
|
|
8774 thus cannot be reused in multiple XEmacs domains. Thus widget-glyphs are
|
|
|
8775 cached on a window basis.
|
|
|
8776
|
|
|
8777 Any action on a glyph first consults the cache before actually
|
|
|
8778 instantiating a widget.
|
|
|
8779
|
|
|
8780 @section Widget-Glyphs in the MS-Windows Environment
|
|
|
8781
|
|
|
8782 To Do
|
|
|
8783
|
|
|
8784 @section Widget-Glyphs in the X Environment
|
|
|
8785
|
|
|
8786 Widget-glyphs under X make heavy use of lwlib for manipulating the
|
|
|
8787 native toolkit objects. This is primarily so that different toolkits can
|
|
|
8788 be supported for widget-glyphs, just as they are supported for features
|
|
|
8789 such as menubars etc.
|
|
|
8790
|
|
|
8791 Lwlib is extremely poorly documented and quite hairy so here is my
|
|
|
8792 understanding of what goes on.
|
|
|
8793
|
|
|
8794 Lwlib maintains a set of widget_instances which mirror the hierarchical
|
|
|
8795 state of Xt widgets. I think this is so that widgets can be updated and
|
|
|
8796 manipulated generically by the lwlib library. For instance
|
|
|
8797 update_one_widget_instance can cope with multiple types of widget and
|
|
|
8798 multiple types of toolkit. Each element in the widget hierarchy is updated
|
|
|
8799 from its corresponding widget_instance by walking the widget_instance
|
|
|
8800 tree recursively.
|
|
|
8801
|
|
|
8802 This has desirable properties such as lw_modify_all_widgets which is
|
|
|
8803 called from glyphs-x.c and updates all the properties of a widget
|
|
|
8804 without having to know what the widget is or what toolkit it is from.
|
|
|
8805 Unfortunately this also has hairy properrties such as making the lwlib
|
|
|
8806 code quite complex. And of course lwlib has to know at some level what
|
|
|
8807 the widget is and how to set its properties.
|
|
|
8808
|
|
|
8809 @node Specifiers, Menus, Glyphs, Top
|
|
0
|
8810 @chapter Specifiers
|
|
|
8811
|
|
|
8812 Not yet documented.
|
|
|
8813
|
|
|
8814 @node Menus, Subprocesses, Specifiers, Top
|
|
|
8815 @chapter Menus
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|
|
8816
|
|
|
8817 A menu is set by setting the value of the variable
|
|
|
8818 @code{current-menubar} (which may be buffer-local) and then calling
|
|
|
8819 @code{set-menubar-dirty-flag} to signal a change. This will cause the
|
|
|
8820 menu to be redrawn at the next redisplay. The format of the data in
|
|
|
8821 @code{current-menubar} is described in @file{menubar.c}.
|
|
|
8822
|
|
|
8823 Internally the data in current-menubar is parsed into a tree of
|
|
|
8824 @code{widget_value's} (defined in @file{lwlib.h}); this is accomplished
|
|
|
8825 by the recursive function @code{menu_item_descriptor_to_widget_value()},
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|
|
8826 called by @code{compute_menubar_data()}. Such a tree is deallocated
|
|
|
8827 using @code{free_widget_value()}.
|
|
|
8828
|
|
|
8829 @code{update_screen_menubars()} is one of the external entry points.
|
|
|
8830 This checks to see, for each screen, if that screen's menubar needs to
|
|
|
8831 be updated. This is the case if
|
|
|
8832
|
|
|
8833 @enumerate
|
|
|
8834 @item
|
|
|
8835 @code{set-menubar-dirty-flag} was called since the last redisplay. (This
|
|
|
8836 function sets the C variable menubar_has_changed.)
|
|
|
8837 @item
|
|
|
8838 The buffer displayed in the screen has changed.
|
|
|
8839 @item
|
|
|
8840 The screen has no menubar currently displayed.
|
|
|
8841 @end enumerate
|
|
|
8842
|
|
|
8843 @code{set_screen_menubar()} is called for each such screen. This
|
|
|
8844 function calls @code{compute_menubar_data()} to create the tree of
|
|
|
8845 widget_value's, then calls @code{lw_create_widget()},
|
|
|
8846 @code{lw_modify_all_widgets()}, and/or @code{lw_destroy_all_widgets()}
|
|
|
8847 to create the X-Toolkit widget associated with the menu.
|
|
|
8848
|
|
|
8849 @code{update_psheets()}, the other external entry point, actually
|
|
|
8850 changes the menus being displayed. It uses the widgets fixed by
|
|
|
8851 @code{update_screen_menubars()} and calls various X functions to ensure
|
|
|
8852 that the menus are displayed properly.
|
|
|
8853
|
|
|
8854 The menubar widget is set up so that @code{pre_activate_callback()} is
|
|
|
8855 called when the menu is first selected (i.e. mouse button goes down),
|
|
|
8856 and @code{menubar_selection_callback()} is called when an item is
|
|
|
8857 selected. @code{pre_activate_callback()} calls the function in
|
|
|
8858 activate-menubar-hook, which can change the menubar (this is described
|
|
|
8859 in @file{menubar.c}). If the menubar is changed,
|
|
|
8860 @code{set_screen_menubars()} is called.
|
|
|
8861 @code{menubar_selection_callback()} enqueues a menu event, putting in it
|
|
|
8862 a function to call (either @code{eval} or @code{call-interactively}) and
|
|
|
8863 its argument, which is the callback function or form given in the menu's
|
|
|
8864 description.
|
|
|
8865
|
|
|
8866 @node Subprocesses, Interface to X Windows, Menus, Top
|
|
|
8867 @chapter Subprocesses
|
|
|
8868
|
|
|
8869 The fields of a process are:
|
|
|
8870
|
|
|
8871 @table @code
|
|
|
8872 @item name
|
|
|
8873 A string, the name of the process.
|
|
|
8874
|
|
|
8875 @item command
|
|
|
8876 A list containing the command arguments that were used to start this
|
|
|
8877 process.
|
|
|
8878
|
|
|
8879 @item filter
|
|
|
8880 A function used to accept output from the process instead of a buffer,
|
|
|
8881 or @code{nil}.
|
|
|
8882
|
|
|
8883 @item sentinel
|
|
|
8884 A function called whenever the process receives a signal, or @code{nil}.
|
|
|
8885
|
|
|
8886 @item buffer
|
|
|
8887 The associated buffer of the process.
|
|
|
8888
|
|
|
8889 @item pid
|
|
|
8890 An integer, the Unix process @sc{id}.
|
|
|
8891
|
|
|
8892 @item childp
|
|
|
8893 A flag, non-@code{nil} if this is really a child process.
|
|
|
8894 It is @code{nil} for a network connection.
|
|
|
8895
|
|
|
8896 @item mark
|
|
|
8897 A marker indicating the position of the end of the last output from this
|
|
|
8898 process inserted into the buffer. This is often but not always the end
|
|
|
8899 of the buffer.
|
|
|
8900
|
|
|
8901 @item kill_without_query
|
|
|
8902 If this is non-@code{nil}, killing XEmacs while this process is still
|
|
|
8903 running does not ask for confirmation about killing the process.
|
|
|
8904
|
|
|
8905 @item raw_status_low
|
|
|
8906 @itemx raw_status_high
|
|
|
8907 These two fields record 16 bits each of the process status returned by
|
|
|
8908 the @code{wait} system call.
|
|
|
8909
|
|
|
8910 @item status
|
|
|
8911 The process status, as @code{process-status} should return it.
|
|
|
8912
|
|
|
8913 @item tick
|
|
|
8914 @itemx update_tick
|
|
|
8915 If these two fields are not equal, a change in the status of the process
|
|
|
8916 needs to be reported, either by running the sentinel or by inserting a
|
|
|
8917 message in the process buffer.
|
|
|
8918
|
|
|
8919 @item pty_flag
|
|
|
8920 Non-@code{nil} if communication with the subprocess uses a @sc{pty};
|
|
|
8921 @code{nil} if it uses a pipe.
|
|
|
8922
|
|
|
8923 @item infd
|
|
|
8924 The file descriptor for input from the process.
|
|
|
8925
|
|
|
8926 @item outfd
|
|
|
8927 The file descriptor for output to the process.
|
|
|
8928
|
|
|
8929 @item subtty
|
|
|
8930 The file descriptor for the terminal that the subprocess is using. (On
|
|
|
8931 some systems, there is no need to record this, so the value is
|
|
|
8932 @code{-1}.)
|
|
|
8933
|
|
|
8934 @item tty_name
|
|
|
8935 The name of the terminal that the subprocess is using,
|
|
|
8936 or @code{nil} if it is using pipes.
|
|
|
8937 @end table
|
|
|
8938
|
|
398
|
8939 @node Interface to X Windows, Index , Subprocesses, Top
|
|
0
|
8940 @chapter Interface to X Windows
|
|
|
8941
|
|
|
8942 Not yet documented.
|
|
|
8943
|
|
|
8944 @include index.texi
|
|
|
8945
|
|
|
8946 @c Print the tables of contents
|
|
|
8947 @summarycontents
|
|
|
8948 @contents
|
|
|
8949 @c That's all
|
|
|
8950
|
|
|
8951 @bye
|
|
|
8952
|
