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1 @c -*-texinfo-*-
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2 @c This is part of the XEmacs Lisp Reference Manual.
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3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
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4 @c See the file lispref.texi for copying conditions.
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5 @setfilename ../../info/help.info
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6 @node Documentation, Files, Modes, Top
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7 @chapter Documentation
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8 @cindex documentation strings
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9
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10 XEmacs Lisp has convenient on-line help facilities, most of which
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11 derive their information from the documentation strings associated with
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12 functions and variables. This chapter describes how to write good
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13 documentation strings for your Lisp programs, as well as how to write
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14 programs to access documentation.
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15
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16 Note that the documentation strings for XEmacs are not the same thing
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17 as the XEmacs manual. Manuals have their own source files, written in
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18 the Texinfo language; documentation strings are specified in the
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19 definitions of the functions and variables they apply to. A collection
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20 of documentation strings is not sufficient as a manual because a good
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21 manual is not organized in that fashion; it is organized in terms of
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22 topics of discussion.
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23
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24 @menu
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25 * Documentation Basics:: Good style for doc strings.
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26 Where to put them. How XEmacs stores them.
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27 * Accessing Documentation:: How Lisp programs can access doc strings.
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28 * Keys in Documentation:: Substituting current key bindings.
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29 * Describing Characters:: Making printable descriptions of
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30 non-printing characters and key sequences.
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31 * Help Functions:: Subroutines used by XEmacs help facilities.
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32 * Obsoleteness:: Upgrading Lisp functionality over time.
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33 @end menu
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34
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35 @node Documentation Basics
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36 @section Documentation Basics
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37 @cindex documentation conventions
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38 @cindex writing a documentation string
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39 @cindex string, writing a doc string
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40
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41 A documentation string is written using the Lisp syntax for strings,
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42 with double-quote characters surrounding the text of the string. This
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43 is because it really is a Lisp string object. The string serves as
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44 documentation when it is written in the proper place in the definition
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45 of a function or variable. In a function definition, the documentation
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46 string follows the argument list. In a variable definition, the
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47 documentation string follows the initial value of the variable.
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48
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49 When you write a documentation string, make the first line a complete
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50 sentence (or two complete sentences) since some commands, such as
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51 @code{apropos}, show only the first line of a multi-line documentation
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52 string. Also, you should not indent the second line of a documentation
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53 string, if you have one, because that looks odd when you use @kbd{C-h f}
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54 (@code{describe-function}) or @kbd{C-h v} (@code{describe-variable}).
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55 @xref{Documentation Tips}.
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56
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57 Documentation strings may contain several special substrings, which
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58 stand for key bindings to be looked up in the current keymaps when the
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59 documentation is displayed. This allows documentation strings to refer
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60 to the keys for related commands and be accurate even when a user
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61 rearranges the key bindings. (@xref{Accessing Documentation}.)
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62
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63 Within the Lisp world, a documentation string is accessible through
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64 the function or variable that it describes:
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65
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66 @itemize @bullet
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67 @item
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68 The documentation for a function is stored in the function definition
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69 itself (@pxref{Lambda Expressions}). The function
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70 @code{documentation} knows how to extract it.
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71
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72 @item
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73 @kindex variable-documentation
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74 The documentation for a variable is stored in the variable's property
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75 list under the property name @code{variable-documentation}. The
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76 function @code{documentation-property} knows how to extract it.
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77 @end itemize
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78
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79 @cindex @file{DOC} (documentation) file
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80 To save space, the documentation for preloaded functions and variables
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81 (including primitive functions and autoloaded functions) is stored in
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82 the @dfn{internal doc file} @file{DOC}. The documentation for functions
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83 and variables loaded during the XEmacs session from byte-compiled files
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84 is stored in those very same byte-compiled files (@pxref{Docs and
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85 Compilation}).
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86
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87 XEmacs does not keep documentation strings in memory unless necessary.
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88 Instead, XEmacs maintains, for preloaded symbols, an integer offset into
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89 the internal doc file, and for symbols loaded from byte-compiled files,
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90 a list containing the filename of the byte-compiled file and an integer
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91 offset, in place of the documentation string. The functions
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92 @code{documentation} and @code{documentation-property} use that
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93 information to read the documentation from the appropriate file; this is
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94 transparent to the user.
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95
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96 For information on the uses of documentation strings, see @ref{Help, ,
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97 Help, emacs, The XEmacs Reference Manual}.
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98
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99 @c Wordy to prevent overfull hbox. --rjc 15mar92
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100 The @file{emacs/lib-src} directory contains two utilities that you can
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101 use to print nice-looking hardcopy for the file
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102 @file{emacs/etc/DOC-@var{version}}. These are @file{sorted-doc.c} and
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103 @file{digest-doc.c}.
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104
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105 @node Accessing Documentation
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106 @section Access to Documentation Strings
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107
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108 @defun documentation-property symbol property &optional verbatim
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109 This function returns the documentation string that is recorded in
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110 @var{symbol}'s property list under property @var{property}. It
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111 retrieves the text from a file if necessary, and runs
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112 @code{substitute-command-keys} to substitute actual key bindings. (This
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113 substitution is not done if @var{verbatim} is non-@code{nil}; the
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114 @var{verbatim} argument exists only as of Emacs 19.)
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115
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116 @smallexample
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117 @group
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118 (documentation-property 'command-line-processed
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119 'variable-documentation)
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120 @result{} "t once command line has been processed"
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121 @end group
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122 @group
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123 (symbol-plist 'command-line-processed)
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124 @result{} (variable-documentation 188902)
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125 @end group
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126 @end smallexample
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127 @end defun
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128
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129 @defun documentation function &optional verbatim
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130 This function returns the documentation string of @var{function}. It
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131 reads the text from a file if necessary. Then (unless @var{verbatim} is
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132 non-@code{nil}) it calls @code{substitute-command-keys}, to return a
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133 value containing the actual (current) key bindings.
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134
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135 The function @code{documentation} signals a @code{void-function} error
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136 if @var{function} has no function definition. However, it is ok if
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137 the function definition has no documentation string. In that case,
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138 @code{documentation} returns @code{nil}.
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139 @end defun
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140
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141 @c Wordy to prevent overfull hboxes. --rjc 15mar92
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142 Here is an example of using the two functions, @code{documentation} and
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143 @code{documentation-property}, to display the documentation strings for
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144 several symbols in a @samp{*Help*} buffer.
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145
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146 @smallexample
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147 @group
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148 (defun describe-symbols (pattern)
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149 "Describe the XEmacs Lisp symbols matching PATTERN.
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150 All symbols that have PATTERN in their name are described
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151 in the `*Help*' buffer."
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152 (interactive "sDescribe symbols matching: ")
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153 (let ((describe-func
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154 (function
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155 (lambda (s)
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156 @end group
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157 @group
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158 ;; @r{Print description of symbol.}
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159 (if (fboundp s) ; @r{It is a function.}
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160 (princ
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161 (format "%s\t%s\n%s\n\n" s
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162 (if (commandp s)
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163 (let ((keys (where-is-internal s)))
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164 (if keys
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165 (concat
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166 "Keys: "
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167 (mapconcat 'key-description
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168 keys " "))
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169 "Keys: none"))
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170 "Function")
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171 @end group
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172 @group
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173 (or (documentation s)
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174 "not documented"))))
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175
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176 (if (boundp s) ; @r{It is a variable.}
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177 @end group
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178 @group
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179 (princ
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180 (format "%s\t%s\n%s\n\n" s
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181 (if (user-variable-p s)
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182 "Option " "Variable")
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183 @end group
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184 @group
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185 (or (documentation-property
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186 s 'variable-documentation)
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187 "not documented")))))))
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188 sym-list)
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189 @end group
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190
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191 @group
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192 ;; @r{Build a list of symbols that match pattern.}
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193 (mapatoms (function
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194 (lambda (sym)
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195 (if (string-match pattern (symbol-name sym))
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196 (setq sym-list (cons sym sym-list))))))
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197 @end group
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198
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199 @group
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200 ;; @r{Display the data.}
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201 (with-output-to-temp-buffer "*Help*"
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202 (mapcar describe-func (sort sym-list 'string<))
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203 (print-help-return-message))))
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204 @end group
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205 @end smallexample
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206
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207 The @code{describe-symbols} function works like @code{apropos},
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208 but provides more information.
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209
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210 @smallexample
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211 @group
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212 (describe-symbols "goal")
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213
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214 ---------- Buffer: *Help* ----------
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215 goal-column Option
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216 *Semipermanent goal column for vertical motion, as set by C-x C-n, or nil.
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217 @end group
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218 @c Do not blithely break or fill these lines.
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219 @c That makes them incorrect.
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220
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221 @group
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222 set-goal-column Command: C-x C-n
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223 Set the current horizontal position as a goal for C-n and C-p.
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224 @end group
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225 @c DO NOT put a blank line here! That is factually inaccurate!
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226 @group
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227 Those commands will move to this position in the line moved to
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228 rather than trying to keep the same horizontal position.
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229 With a non-nil argument, clears out the goal column
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230 so that C-n and C-p resume vertical motion.
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231 The goal column is stored in the variable `goal-column'.
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232 @end group
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233
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234 @group
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235 temporary-goal-column Variable
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236 Current goal column for vertical motion.
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237 It is the column where point was
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238 at the start of current run of vertical motion commands.
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239 When the `track-eol' feature is doing its job, the value is 9999.
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240 ---------- Buffer: *Help* ----------
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241 @end group
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242 @end smallexample
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243
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244 @defun Snarf-documentation filename
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245 This function is used only during XEmacs initialization, just before
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246 the runnable XEmacs is dumped. It finds the file offsets of the
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247 documentation strings stored in the file @var{filename}, and records
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248 them in the in-core function definitions and variable property lists in
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249 place of the actual strings. @xref{Building XEmacs}.
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250
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251 XEmacs finds the file @var{filename} in the @file{lib-src} directory.
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252 When the dumped XEmacs is later executed, the same file is found in the
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253 directory @code{doc-directory}. The usual value for @var{filename} is
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254 @file{DOC}, but this can be changed by modifying the variable
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255 @code{internal-doc-file-name}.
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256 @end defun
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257
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258 @defvar internal-doc-file-name
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259 This variable holds the name of the file containing documentation
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260 strings of built-in symbols, usually @file{DOC}. The full pathname of
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261 the internal doc file is @samp{(concat doc-directory internal-doc-file-name)}.
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262 @end defvar
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263
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264 @defvar doc-directory
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265 This variable holds the name of the directory which contains the
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266 @dfn{internal doc file} that contains documentation strings for built-in
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267 and preloaded functions and variables.
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268
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269 In most cases, this is the same as @code{exec-directory}. They may be
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270 different when you run XEmacs from the directory where you built it,
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271 without actually installing it. See @code{exec-directory} in @ref{Help
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272 Functions}.
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273
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274 In older Emacs versions, @code{exec-directory} was used for this.
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275 @end defvar
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276
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277 @defvar data-directory
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278 This variable holds the name of the directory in which XEmacs finds
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279 certain system independent documentation and text files that come
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280 with XEmacs. In older Emacs versions, @code{exec-directory} was used for
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281 this.
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282 @end defvar
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283
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284 @node Keys in Documentation
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285 @section Substituting Key Bindings in Documentation
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286 @cindex documentation, keys in
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287 @cindex keys in documentation strings
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288 @cindex substituting keys in documentation
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289
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290 When documentation strings refer to key sequences, they should use the
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291 current, actual key bindings. They can do so using certain special text
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292 sequences described below. Accessing documentation strings in the usual
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293 way substitutes current key binding information for these special
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294 sequences. This works by calling @code{substitute-command-keys}. You
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295 can also call that function yourself.
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296
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297 Here is a list of the special sequences and what they mean:
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298
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299 @table @code
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300 @item \[@var{command}]
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301 stands for a key sequence that will invoke @var{command}, or @samp{M-x
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302 @var{command}} if @var{command} has no key bindings.
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303
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304 @item \@{@var{mapvar}@}
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305 stands for a summary of the value of @var{mapvar}, which should be a
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306 keymap. The summary is made by @code{describe-bindings}.
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307
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308 @item \<@var{mapvar}>
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309 stands for no text itself. It is used for a side effect: it specifies
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310 @var{mapvar} as the keymap for any following @samp{\[@var{command}]}
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311 sequences in this documentation string.
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312
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313 @item \=
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314 quotes the following character and is discarded; this @samp{\=\=} puts
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315 @samp{\=} into the output, and @samp{\=\[} puts @samp{\[} into the output.
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316 @end table
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317
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318 @strong{Please note:} Each @samp{\} must be doubled when written in a
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319 string in XEmacs Lisp.
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320
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321 @defun substitute-command-keys string
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322 This function scans @var{string} for the above special sequences and
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323 replaces them by what they stand for, returning the result as a string.
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324 This permits display of documentation that refers accurately to the
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325 user's own customized key bindings.
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326 @end defun
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327
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328 Here are examples of the special sequences:
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329
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330 @smallexample
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331 @group
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332 (substitute-command-keys
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333 "To abort recursive edit, type: \\[abort-recursive-edit]")
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334 @result{} "To abort recursive edit, type: C-]"
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335 @end group
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336
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337 @group
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338 (substitute-command-keys
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339 "The keys that are defined for the minibuffer here are:
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340 \\@{minibuffer-local-must-match-map@}")
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341 @result{} "The keys that are defined for the minibuffer here are:
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342 @end group
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343
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344 ? minibuffer-completion-help
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345 SPC minibuffer-complete-word
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346 TAB minibuffer-complete
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347 LFD minibuffer-complete-and-exit
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348 RET minibuffer-complete-and-exit
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349 C-g abort-recursive-edit
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350 "
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351
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352 @group
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353 (substitute-command-keys
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354 "To abort a recursive edit from the minibuffer, type\
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355 \\<minibuffer-local-must-match-map>\\[abort-recursive-edit].")
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356 @result{} "To abort a recursive edit from the minibuffer, type C-g."
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357 @end group
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358
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359 @group
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360 (substitute-command-keys
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361 "Substrings of the form \\=\\@{MAPVAR@} are replaced by summaries
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362 \(made by describe-bindings) of the value of MAPVAR, taken as a keymap.
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363 Substrings of the form \\=\\<MAPVAR> specify to use the value of MAPVAR
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364 as the keymap for future \\=\\[COMMAND] substrings.
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365 \\=\\= quotes the following character and is discarded;
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366 thus, \\=\\=\\=\\= puts \\=\\= into the output,
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367 and \\=\\=\\=\\[ puts \\=\\[ into the output.")
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368 @result{} "Substrings of the form \@{MAPVAR@} are replaced by summaries
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369 (made by describe-bindings) of the value of MAPVAR, taken as a keymap.
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370 Substrings of the form \<MAPVAR> specify to use the value of MAPVAR
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371 as the keymap for future \[COMMAND] substrings.
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372 \= quotes the following character and is discarded;
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373 thus, \=\= puts \= into the output,
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374 and \=\[ puts \[ into the output."
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375 @end group
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376 @end smallexample
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377
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378 @node Describing Characters
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379 @section Describing Characters for Help Messages
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380
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381 These functions convert events, key sequences or characters to textual
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382 descriptions. These descriptions are useful for including arbitrary
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383 text characters or key sequences in messages, because they convert
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384 non-printing and whitespace characters to sequences of printing
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385 characters. The description of a non-whitespace printing character is
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386 the character itself.
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387
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388 @defun key-description sequence
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389 @cindex XEmacs event standard notation
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390 This function returns a string containing the XEmacs standard notation
|
|
|
391 for the input events in @var{sequence}. The argument @var{sequence} may
|
|
|
392 be a string, vector or list. @xref{Events}, for more information about
|
|
|
393 valid events. See also the examples for @code{single-key-description},
|
|
|
394 below.
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|
|
395 @end defun
|
|
|
396
|
|
|
397 @defun single-key-description key
|
|
|
398 @cindex event printing
|
|
|
399 @cindex character printing
|
|
|
400 @cindex control character printing
|
|
|
401 @cindex meta character printing
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|
|
402 This function returns a string describing @var{key} in the standard
|
|
|
403 XEmacs notation for keyboard input. A normal printing character appears
|
|
|
404 as itself, but a control character turns into a string starting with
|
|
|
405 @samp{C-}, a meta character turns into a string starting with @samp{M-},
|
|
|
406 and space, linefeed, etc.@: appear as @samp{SPC}, @samp{LFD}, etc. A
|
|
|
407 symbol appears as the name of the symbol. An event that is a list
|
|
|
408 appears as the name of the symbol in the @sc{car} of the list.
|
|
|
409
|
|
|
410 @smallexample
|
|
|
411 @group
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|
|
412 (single-key-description ?\C-x)
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|
413 @result{} "C-x"
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|
|
414 @end group
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|
415 @group
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|
416 (key-description "\C-x \M-y \n \t \r \f123")
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|
417 @result{} "C-x SPC M-y SPC LFD SPC TAB SPC RET SPC C-l 1 2 3"
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|
|
418 @end group
|
|
|
419 @group
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|
54
|
420 (single-key-description 'kp_next)
|
|
|
421 @result{} "kp_next"
|
|
0
|
422 @end group
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|
|
423 @group
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|
424 (single-key-description '(shift button1))
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|
425 @result{} "Sh-button1"
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426 @end group
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|
|
427 @end smallexample
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|
|
428 @end defun
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|
|
429
|
|
|
430 @defun text-char-description character
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|
431 This function returns a string describing @var{character} in the
|
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432 standard XEmacs notation for characters that appear in text---like
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|
433 @code{single-key-description}, except that control characters are
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|
|
434 represented with a leading caret (which is how control characters in
|
|
|
435 XEmacs buffers are usually displayed).
|
|
|
436
|
|
|
437 @smallexample
|
|
|
438 @group
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|
|
439 (text-char-description ?\C-c)
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|
|
440 @result{} "^C"
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|
|
441 @end group
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|
|
442 @group
|
|
|
443 (text-char-description ?\M-m)
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|
444 @result{} "M-m"
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|
|
445 @end group
|
|
|
446 @group
|
|
|
447 (text-char-description ?\C-\M-m)
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|
|
448 @result{} "M-^M"
|
|
|
449 @end group
|
|
|
450 @end smallexample
|
|
|
451 @end defun
|
|
|
452
|
|
|
453 @node Help Functions
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|
|
454 @section Help Functions
|
|
|
455
|
|
|
456 XEmacs provides a variety of on-line help functions, all accessible to
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|
|
457 the user as subcommands of the prefix @kbd{C-h}, or on some keyboards,
|
|
|
458 @kbd{help}. For more information about them, see @ref{Help, , Help,
|
|
|
459 emacs, The XEmacs Reference Manual}. Here we describe some
|
|
|
460 program-level interfaces to the same information.
|
|
|
461
|
|
|
462 @deffn Command apropos regexp &optional do-all predicate
|
|
|
463 This function finds all symbols whose names contain a match for the
|
|
|
464 regular expression @var{regexp}, and returns a list of them
|
|
|
465 (@pxref{Regular Expressions}). It also displays the symbols in a buffer
|
|
|
466 named @samp{*Help*}, each with a one-line description.
|
|
|
467
|
|
|
468 @c Emacs 19 feature
|
|
|
469 If @var{do-all} is non-@code{nil}, then @code{apropos} also shows
|
|
|
470 key bindings for the functions that are found.
|
|
|
471
|
|
|
472 If @var{predicate} is non-@code{nil}, it should be a function to be
|
|
|
473 called on each symbol that has matched @var{regexp}. Only symbols for
|
|
|
474 which @var{predicate} returns a non-@code{nil} value are listed or
|
|
|
475 displayed.
|
|
|
476
|
|
|
477 In the first of the following examples, @code{apropos} finds all the
|
|
|
478 symbols with names containing @samp{exec}. In the second example, it
|
|
|
479 finds and returns only those symbols that are also commands.
|
|
|
480 (We don't show the output that results in the @samp{*Help*} buffer.)
|
|
|
481
|
|
|
482 @smallexample
|
|
|
483 @group
|
|
|
484 (apropos "exec")
|
|
|
485 @result{} (Buffer-menu-execute command-execute exec-directory
|
|
|
486 exec-path execute-extended-command execute-kbd-macro
|
|
|
487 executing-kbd-macro executing-macro)
|
|
|
488 @end group
|
|
|
489
|
|
|
490 @group
|
|
|
491 (apropos "exec" nil 'commandp)
|
|
|
492 @result{} (Buffer-menu-execute execute-extended-command)
|
|
|
493 @end group
|
|
|
494 @ignore
|
|
|
495 @group
|
|
|
496 ---------- Buffer: *Help* ----------
|
|
|
497 Buffer-menu-execute
|
|
|
498 Function: Save and/or delete buffers marked with
|
|
|
499 M-x Buffer-menu-save or M-x Buffer-menu-delete commands.
|
|
|
500 execute-extended-command ESC x
|
|
|
501 Function: Read function name, then read its
|
|
|
502 arguments and call it.
|
|
|
503 ---------- Buffer: *Help* ----------
|
|
|
504 @end group
|
|
|
505 @end ignore
|
|
|
506 @end smallexample
|
|
|
507
|
|
|
508 @code{apropos} is used by various user-level commands, such as @kbd{C-h
|
|
|
509 a} (@code{hyper-apropos}), a graphical front-end to @code{apropos}; and
|
|
|
510 @kbd{C-h A} (@code{command-apropos}), which does an apropos over only
|
|
|
511 those functions which are user commands. @code{command-apropos} calls
|
|
|
512 @code{apropos}, specifying a @var{predicate} to restrict the output to
|
|
|
513 symbols that are commands. The call to @code{apropos} looks like this:
|
|
|
514
|
|
|
515 @smallexample
|
|
|
516 (apropos string t 'commandp)
|
|
|
517 @end smallexample
|
|
|
518 @end deffn
|
|
|
519
|
|
|
520 @c Emacs 19 feature
|
|
|
521 @c super-apropos is obsolete - function absorbed by apropos --mrb
|
|
|
522 @ignore
|
|
|
523 @deffn Command super-apropos regexp &optional do-all
|
|
|
524 This function differs from @code{apropos} in that it searches
|
|
|
525 documentation strings as well as symbol names for matches for
|
|
|
526 @var{regexp}. By default, it searches the documentation strings only
|
|
|
527 for preloaded functions and variables. If @var{do-all} is
|
|
|
528 non-@code{nil}, it scans the names and documentation strings of all
|
|
|
529 functions and variables.
|
|
|
530 @end deffn
|
|
|
531 @end ignore
|
|
|
532
|
|
|
533 @defvar help-map
|
|
|
534 The value of this variable is a local keymap for characters following the
|
|
|
535 Help key, @kbd{C-h}.
|
|
|
536 @end defvar
|
|
|
537
|
|
|
538 @deffn {Prefix Command} help-command
|
|
|
539 This symbol is not a function; its function definition is actually the
|
|
|
540 keymap known as @code{help-map}. It is defined in @file{help.el} as
|
|
|
541 follows:
|
|
|
542
|
|
|
543 @smallexample
|
|
|
544 @group
|
|
|
545 (define-key global-map "\C-h" 'help-command)
|
|
|
546 (fset 'help-command help-map)
|
|
|
547 @end group
|
|
|
548 @end smallexample
|
|
|
549 @end deffn
|
|
|
550
|
|
|
551 @defun print-help-return-message &optional function
|
|
|
552 This function builds a string that explains how to restore the previous
|
|
|
553 state of the windows after a help command. After building the message,
|
|
|
554 it applies @var{function} to it if @var{function} is non-@code{nil}.
|
|
|
555 Otherwise it calls @code{message} to display it in the echo area.
|
|
|
556
|
|
|
557 This function expects to be called inside a
|
|
|
558 @code{with-output-to-temp-buffer} special form, and expects
|
|
|
559 @code{standard-output} to have the value bound by that special form.
|
|
|
560 For an example of its use, see the long example in @ref{Accessing
|
|
|
561 Documentation}.
|
|
|
562 @end defun
|
|
|
563
|
|
|
564 @defvar help-char
|
|
|
565 The value of this variable is the help character---the character that
|
|
|
566 XEmacs recognizes as meaning Help. By default, it is the character
|
|
|
567 @samp{?\^H} (ASCII 8), which is @kbd{C-h}. When XEmacs reads this
|
|
|
568 character, if @code{help-form} is non-@code{nil} Lisp expression, it
|
|
|
569 evaluates that expression, and displays the result in a window if it is
|
|
|
570 a string.
|
|
|
571
|
|
|
572 @code{help-char} can be a character or a key description such as
|
|
|
573 @code{help} or @code{(meta h)}.
|
|
|
574
|
|
|
575 Usually the value of @code{help-form}'s value is @code{nil}. Then the
|
|
|
576 help character has no special meaning at the level of command input, and
|
|
|
577 it becomes part of a key sequence in the normal way. The standard key
|
|
|
578 binding of @kbd{C-h} is a prefix key for several general-purpose help
|
|
|
579 features.
|
|
|
580
|
|
|
581 The help character is special after prefix keys, too. If it has no
|
|
|
582 binding as a subcommand of the prefix key, it runs
|
|
|
583 @code{describe-prefix-bindings}, which displays a list of all the
|
|
|
584 subcommands of the prefix key.
|
|
|
585 @end defvar
|
|
|
586
|
|
|
587 @defvar help-form
|
|
|
588 If this variable is non-@code{nil}, its value is a form to evaluate
|
|
|
589 whenever the character @code{help-char} is read. If evaluating the form
|
|
|
590 produces a string, that string is displayed.
|
|
|
591
|
|
|
592 A command that calls @code{next-command-event} or @code{next-event}
|
|
|
593 probably should bind @code{help-form} to a non-@code{nil} expression
|
|
|
594 while it does input. (The exception is when @kbd{C-h} is meaningful
|
|
|
595 input.) Evaluating this expression should result in a string that
|
|
|
596 explains what the input is for and how to enter it properly.
|
|
|
597
|
|
|
598 Entry to the minibuffer binds this variable to the value of
|
|
|
599 @code{minibuffer-help-form} (@pxref{Minibuffer Misc}).
|
|
|
600 @end defvar
|
|
|
601
|
|
|
602 @defvar prefix-help-command
|
|
|
603 This variable holds a function to print help for a prefix character.
|
|
|
604 The function is called when the user types a prefix key followed by the
|
|
|
605 help character, and the help character has no binding after that prefix.
|
|
|
606 The variable's default value is @code{describe-prefix-bindings}.
|
|
|
607 @end defvar
|
|
|
608
|
|
|
609 @defun describe-prefix-bindings
|
|
|
610 This function calls @code{describe-bindings} to display a list of all
|
|
|
611 the subcommands of the prefix key of the most recent key sequence. The
|
|
|
612 prefix described consists of all but the last event of that key
|
|
|
613 sequence. (The last event is, presumably, the help character.)
|
|
|
614 @end defun
|
|
|
615
|
|
|
616 The following two functions are found in the library @file{helper}.
|
|
|
617 They are for modes that want to provide help without relinquishing
|
|
|
618 control, such as the ``electric'' modes. You must load that library
|
|
|
619 with @code{(require 'helper)} in order to use them. Their names begin
|
|
|
620 with @samp{Helper} to distinguish them from the ordinary help functions.
|
|
|
621
|
|
|
622 @deffn Command Helper-describe-bindings
|
|
|
623 This command pops up a window displaying a help buffer containing a
|
|
|
624 listing of all of the key bindings from both the local and global keymaps.
|
|
|
625 It works by calling @code{describe-bindings}.
|
|
|
626 @end deffn
|
|
|
627
|
|
|
628 @deffn Command Helper-help
|
|
|
629 This command provides help for the current mode. It prompts the user
|
|
|
630 in the minibuffer with the message @samp{Help (Type ? for further
|
|
|
631 options)}, and then provides assistance in finding out what the key
|
|
|
632 bindings are, and what the mode is intended for. It returns @code{nil}.
|
|
|
633
|
|
|
634 This can be customized by changing the map @code{Helper-help-map}.
|
|
|
635 @end deffn
|
|
|
636
|
|
|
637 @ignore @c Not in XEmacs currently
|
|
|
638 @c Emacs 19 feature
|
|
|
639 @defmac make-help-screen fname help-line help-text help-map
|
|
|
640 This macro defines a help command named @var{fname} that acts like a
|
|
|
641 prefix key that shows a list of the subcommands it offers.
|
|
|
642
|
|
|
643 When invoked, @var{fname} displays @var{help-text} in a window, then
|
|
|
644 reads and executes a key sequence according to @var{help-map}. The
|
|
|
645 string @var{help-text} should describe the bindings available in
|
|
|
646 @var{help-map}.
|
|
|
647
|
|
|
648 The command @var{fname} is defined to handle a few events itself, by
|
|
|
649 scrolling the display of @var{help-text}. When @var{fname} reads one of
|
|
|
650 those special events, it does the scrolling and then reads another
|
|
|
651 event. When it reads an event that is not one of those few, and which
|
|
|
652 has a binding in @var{help-map}, it executes that key's binding and
|
|
|
653 then returns.
|
|
|
654
|
|
|
655 The argument @var{help-line} should be a single-line summary of the
|
|
|
656 alternatives in @var{help-map}. In the current version of Emacs, this
|
|
|
657 argument is used only if you set the option @code{three-step-help} to
|
|
|
658 @code{t}.
|
|
|
659 @end defmac
|
|
|
660
|
|
|
661 @defopt three-step-help
|
|
|
662 If this variable is non-@code{nil}, commands defined with
|
|
|
663 @code{make-help-screen} display their @var{help-line} strings in the
|
|
|
664 echo area at first, and display the longer @var{help-text} strings only
|
|
|
665 if the user types the help character again.
|
|
|
666 @end defopt
|
|
|
667 @end ignore
|
|
|
668
|
|
|
669 @node Obsoleteness
|
|
|
670 @section Obsoleteness
|
|
|
671
|
|
|
672 As you add functionality to a package, you may at times want to
|
|
|
673 replace an older function with a new one. To preserve compatibility
|
|
|
674 with existing code, the older function needs to still exist; but
|
|
|
675 users of that function should be told to use the newer one instead.
|
|
|
676 XEmacs Lisp lets you mark a function or variable as @dfn{obsolete},
|
|
|
677 and indicate what should be used instead.
|
|
|
678
|
|
|
679 @defun make-obsolete function new
|
|
|
680 This function indicates that @var{function} is an obsolete function,
|
|
|
681 and the function @var{new} should be used instead. The byte compiler
|
|
|
682 will issue a warning to this effect when it encounters a usage of the
|
|
|
683 older function, and the help system will also note this in the function's
|
|
|
684 documentation. @var{new} can also be a string (if there is not a single
|
|
|
685 function with the same functionality any more), and should be a descriptive
|
|
|
686 statement, such as "use @var{foo} or @var{bar} instead" or "this function is
|
|
|
687 unnecessary".
|
|
|
688 @end defun
|
|
|
689
|
|
|
690 @defun make-obsolete-variable variable new
|
|
|
691 This is like @code{make-obsolete} but is for variables instead of functions.
|
|
|
692 @end defun
|
|
|
693
|
|
|
694 @defun define-obsolete-function-alias oldfun newfun
|
|
|
695 This function combines @code{make-obsolete} and @code{define-function},
|
|
|
696 declaring @var{oldfun} to be an obsolete variant of @var{newfun} and
|
|
|
697 defining @var{oldfun} as an alias for @var{newfun}.
|
|
|
698 @end defun
|
|
|
699
|
|
|
700 @defun define-obsolete-variable-alias oldvar newvar
|
|
|
701 This is like @code{define-obsolete-function-alias} but for variables.
|
|
|
702 @end defun
|
|
|
703
|
|
|
704 Note that you should not normally put obsoleteness information
|
|
|
705 explicitly in a function or variable's doc string. The obsoleteness
|
|
|
706 information that you specify using the above functions will be displayed
|
|
|
707 whenever the doc string is displayed, and by adding it explicitly the
|
|
|
708 result is redundancy.
|
|
|
709
|
|
|
710 Also, if an obsolete function is substantially the same as a newer one
|
|
|
711 but is not actually an alias, you should consider omitting the doc
|
|
|
712 string entirely (use a null string @samp{""} as the doc string). That
|
|
|
713 way, the user is told about the obsoleteness and is forced to look at
|
|
|
714 the documentation of the new function, making it more likely that he
|
|
|
715 will use the new function.
|
|
|
716
|
|
|
717 @defun function-obsoleteness-doc function
|
|
|
718 If @var{function} is obsolete, this function returns a string describing
|
|
|
719 this. This is the message that is printed out during byte compilation
|
|
|
720 or in the function's documentation. If @var{function} is not obsolete,
|
|
|
721 @code{nil} is returned.
|
|
|
722 @end defun
|
|
|
723
|
|
|
724 @defun variable-obsoleteness-doc variable
|
|
|
725 This is like @code{function-obsoleteness-doc} but for variables.
|
|
|
726 @end defun
|
|
|
727
|
|
|
728 The obsoleteness information is stored internally by putting a property
|
|
|
729 @code{byte-obsolete-info} (for functions) or
|
|
|
730 @code{byte-obsolete-variable} (for variables) on the symbol that
|
|
|
731 specifies the obsolete function or variable. For more information, see
|
|
|
732 the implementation of @code{make-obsolete} and
|
|
|
733 @code{make-obsolete-variable} in
|
|
|
734 @file{lisp/bytecomp/bytecomp-runtime.el}.
|
