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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/modes.info
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6 @node Modes, Documentation, Drag and Drop, Top
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7 @chapter Major and Minor Modes
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8 @cindex mode
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9
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10 A @dfn{mode} is a set of definitions that customize XEmacs and can be
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11 turned on and off while you edit. There are two varieties of modes:
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12 @dfn{major modes}, which are mutually exclusive and used for editing
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13 particular kinds of text, and @dfn{minor modes}, which provide features
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14 that users can enable individually.
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15
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16 This chapter describes how to write both major and minor modes, how to
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17 indicate them in the modeline, and how they run hooks supplied by the
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18 user. For related topics such as keymaps and syntax tables, see
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19 @ref{Keymaps}, and @ref{Syntax Tables}.
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20
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21 @menu
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22 * Major Modes:: Defining major modes.
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23 * Minor Modes:: Defining minor modes.
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24 * Modeline Format:: Customizing the text that appears in the modeline.
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25 * Hooks:: How to use hooks; how to write code that provides hooks.
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26 @end menu
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27
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28 @node Major Modes
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29 @section Major Modes
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30 @cindex major mode
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31 @cindex Fundamental mode
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32
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33 Major modes specialize XEmacs for editing particular kinds of text.
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34 Each buffer has only one major mode at a time.
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35
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36 The least specialized major mode is called @dfn{Fundamental mode}.
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37 This mode has no mode-specific definitions or variable settings, so each
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38 XEmacs command behaves in its default manner, and each option is in its
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39 default state. All other major modes redefine various keys and options.
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40 For example, Lisp Interaction mode provides special key bindings for
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41 @key{LFD} (@code{eval-print-last-sexp}), @key{TAB}
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42 (@code{lisp-indent-line}), and other keys.
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43
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44 When you need to write several editing commands to help you perform a
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45 specialized editing task, creating a new major mode is usually a good
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46 idea. In practice, writing a major mode is easy (in contrast to
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47 writing a minor mode, which is often difficult).
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48
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49 If the new mode is similar to an old one, it is often unwise to modify
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50 the old one to serve two purposes, since it may become harder to use and
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51 maintain. Instead, copy and rename an existing major mode definition
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52 and alter the copy---or define a @dfn{derived mode} (@pxref{Derived
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53 Modes}). For example, Rmail Edit mode, which is in
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54 @file{emacs/lisp/rmailedit.el}, is a major mode that is very similar to
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55 Text mode except that it provides three additional commands. Its
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56 definition is distinct from that of Text mode, but was derived from it.
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57
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58 Rmail Edit mode is an example of a case where one piece of text is put
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59 temporarily into a different major mode so it can be edited in a
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60 different way (with ordinary XEmacs commands rather than Rmail). In such
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61 cases, the temporary major mode usually has a command to switch back to
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62 the buffer's usual mode (Rmail mode, in this case). You might be
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63 tempted to present the temporary redefinitions inside a recursive edit
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64 and restore the usual ones when the user exits; but this is a bad idea
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65 because it constrains the user's options when it is done in more than
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66 one buffer: recursive edits must be exited most-recently-entered first.
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67 Using alternative major modes avoids this limitation. @xref{Recursive
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68 Editing}.
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69
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70 The standard XEmacs Lisp library directory contains the code for
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71 several major modes, in files including @file{text-mode.el},
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72 @file{texinfo.el}, @file{lisp-mode.el}, @file{c-mode.el}, and
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73 @file{rmail.el}. You can look at these libraries to see how modes are
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74 written. Text mode is perhaps the simplest major mode aside from
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75 Fundamental mode. Rmail mode is a complicated and specialized mode.
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76
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77 @menu
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78 * Major Mode Conventions:: Coding conventions for keymaps, etc.
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79 * Example Major Modes:: Text mode and Lisp modes.
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80 * Auto Major Mode:: How XEmacs chooses the major mode automatically.
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81 * Mode Help:: Finding out how to use a mode.
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82 * Derived Modes:: Defining a new major mode based on another major
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83 mode.
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84 @end menu
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85
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86 @node Major Mode Conventions
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87 @subsection Major Mode Conventions
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88
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89 The code for existing major modes follows various coding conventions,
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90 including conventions for local keymap and syntax table initialization,
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91 global names, and hooks. Please follow these conventions when you
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92 define a new major mode:
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93
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94 @itemize @bullet
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95 @item
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96 Define a command whose name ends in @samp{-mode}, with no arguments,
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97 that switches to the new mode in the current buffer. This command
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98 should set up the keymap, syntax table, and local variables in an
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99 existing buffer without changing the buffer's text.
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100
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101 @item
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102 Write a documentation string for this command that describes the
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103 special commands available in this mode. @kbd{C-h m}
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104 (@code{describe-mode}) in your mode will display this string.
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105
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106 The documentation string may include the special documentation
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107 substrings, @samp{\[@var{command}]}, @samp{\@{@var{keymap}@}}, and
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108 @samp{\<@var{keymap}>}, that enable the documentation to adapt
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109 automatically to the user's own key bindings. @xref{Keys in
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110 Documentation}.
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111
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112 @item
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113 The major mode command should start by calling
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114 @code{kill-all-local-variables}. This is what gets rid of the local
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115 variables of the major mode previously in effect.
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116
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117 @item
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118 The major mode command should set the variable @code{major-mode} to the
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119 major mode command symbol. This is how @code{describe-mode} discovers
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120 which documentation to print.
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121
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122 @item
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123 The major mode command should set the variable @code{mode-name} to the
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124 ``pretty'' name of the mode, as a string. This appears in the mode
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125 line.
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126
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127 @item
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128 @cindex functions in modes
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129 Since all global names are in the same name space, all the global
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130 variables, constants, and functions that are part of the mode should
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131 have names that start with the major mode name (or with an abbreviation
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132 of it if the name is long). @xref{Style Tips}.
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133
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134 @item
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135 @cindex keymaps in modes
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136 The major mode should usually have its own keymap, which is used as the
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137 local keymap in all buffers in that mode. The major mode function
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138 should call @code{use-local-map} to install this local map.
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139 @xref{Active Keymaps}, for more information.
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140
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141 This keymap should be kept in a global variable named
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142 @code{@var{modename}-mode-map}. Normally the library that defines the
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143 mode sets this variable.
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144
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145 @item
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146 @cindex syntax tables in modes
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147 The mode may have its own syntax table or may share one with other
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148 related modes. If it has its own syntax table, it should store this in
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149 a variable named @code{@var{modename}-mode-syntax-table}. @xref{Syntax
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150 Tables}.
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151
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152 @item
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153 @cindex abbrev tables in modes
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154 The mode may have its own abbrev table or may share one with other
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155 related modes. If it has its own abbrev table, it should store this in
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156 a variable named @code{@var{modename}-mode-abbrev-table}. @xref{Abbrev
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157 Tables}.
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158
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159 @item
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160 Use @code{defvar} to set mode-related variables, so that they are not
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161 reinitialized if they already have a value. (Such reinitialization
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162 could discard customizations made by the user.)
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163
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164 @item
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165 @cindex buffer-local variables in modes
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166 To make a buffer-local binding for an Emacs customization variable, use
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167 @code{make-local-variable} in the major mode command, not
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168 @code{make-variable-buffer-local}. The latter function would make the
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169 variable local to every buffer in which it is subsequently set, which
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170 would affect buffers that do not use this mode. It is undesirable for a
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171 mode to have such global effects. @xref{Buffer-Local Variables}.
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172
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173 It's ok to use @code{make-variable-buffer-local}, if you wish, for a
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174 variable used only within a single Lisp package.
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175
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176 @item
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177 @cindex mode hook
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178 @cindex major mode hook
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179 Each major mode should have a @dfn{mode hook} named
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180 @code{@var{modename}-mode-hook}. The major mode command should run that
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181 hook, with @code{run-hooks}, as the very last thing it
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182 does. @xref{Hooks}.
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183
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184 @item
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185 The major mode command may also run the hooks of some more basic modes.
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186 For example, @code{indented-text-mode} runs @code{text-mode-hook} as
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187 well as @code{indented-text-mode-hook}. It may run these other hooks
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188 immediately before the mode's own hook (that is, after everything else),
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189 or it may run them earlier.
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190
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191 @item
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192 If something special should be done if the user switches a buffer from
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193 this mode to any other major mode, the mode can set a local value for
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194 @code{change-major-mode-hook}.
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195
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196 @item
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197 If this mode is appropriate only for specially-prepared text, then the
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198 major mode command symbol should have a property named @code{mode-class}
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199 with value @code{special}, put on as follows:
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200
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201 @cindex @code{mode-class} property
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202 @cindex @code{special}
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203 @example
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204 (put 'funny-mode 'mode-class 'special)
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205 @end example
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206
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207 @noindent
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208 This tells XEmacs that new buffers created while the current buffer has
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209 Funny mode should not inherit Funny mode. Modes such as Dired, Rmail,
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210 and Buffer List use this feature.
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211
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212 @item
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213 If you want to make the new mode the default for files with certain
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214 recognizable names, add an element to @code{auto-mode-alist} to select
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215 the mode for those file names. If you define the mode command to
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216 autoload, you should add this element in the same file that calls
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217 @code{autoload}. Otherwise, it is sufficient to add the element in the
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218 file that contains the mode definition. @xref{Auto Major Mode}.
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219
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220 @item
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221 @cindex @file{.emacs} customization
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222 In the documentation, you should provide a sample @code{autoload} form
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223 and an example of how to add to @code{auto-mode-alist}, that users can
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224 include in their @file{.emacs} files.
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225
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226 @item
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227 @cindex mode loading
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228 The top-level forms in the file defining the mode should be written so
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229 that they may be evaluated more than once without adverse consequences.
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230 Even if you never load the file more than once, someone else will.
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231 @end itemize
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232
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233 @defvar change-major-mode-hook
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234 This normal hook is run by @code{kill-all-local-variables} before it
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235 does anything else. This gives major modes a way to arrange for
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236 something special to be done if the user switches to a different major
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237 mode. For best results, make this variable buffer-local, so that it
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238 will disappear after doing its job and will not interfere with the
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239 subsequent major mode. @xref{Hooks}.
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240 @end defvar
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241
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242 @node Example Major Modes
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243 @subsection Major Mode Examples
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244
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245 Text mode is perhaps the simplest mode besides Fundamental mode.
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246 Here are excerpts from @file{text-mode.el} that illustrate many of
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247 the conventions listed above:
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248
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249 @smallexample
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250 @group
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251 ;; @r{Create mode-specific tables.}
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252 (defvar text-mode-syntax-table nil
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253 "Syntax table used while in text mode.")
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254 @end group
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255
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256 @group
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257 (if text-mode-syntax-table
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258 () ; @r{Do not change the table if it is already set up.}
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259 (setq text-mode-syntax-table (make-syntax-table))
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260 (modify-syntax-entry ?\" ". " text-mode-syntax-table)
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261 (modify-syntax-entry ?\\ ". " text-mode-syntax-table)
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262 (modify-syntax-entry ?' "w " text-mode-syntax-table))
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263 @end group
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264
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265 @group
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266 (defvar text-mode-abbrev-table nil
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267 "Abbrev table used while in text mode.")
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268 (define-abbrev-table 'text-mode-abbrev-table ())
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269 @end group
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270
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271 @group
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272 (defvar text-mode-map nil) ; @r{Create a mode-specific keymap.}
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273
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274 (if text-mode-map
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275 () ; @r{Do not change the keymap if it is already set up.}
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276 (setq text-mode-map (make-sparse-keymap))
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277 (define-key text-mode-map "\t" 'tab-to-tab-stop)
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278 (define-key text-mode-map "\es" 'center-line)
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279 (define-key text-mode-map "\eS" 'center-paragraph))
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280 @end group
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281 @end smallexample
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282
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283 Here is the complete major mode function definition for Text mode:
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284
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285 @smallexample
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286 @group
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287 (defun text-mode ()
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288 "Major mode for editing text intended for humans to read.
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289 Special commands: \\@{text-mode-map@}
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290 @end group
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291 @group
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292 Turning on text-mode runs the hook `text-mode-hook'."
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293 (interactive)
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294 (kill-all-local-variables)
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295 @end group
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296 @group
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297 (use-local-map text-mode-map) ; @r{This provides the local keymap.}
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298 (setq mode-name "Text") ; @r{This name goes into the modeline.}
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299 (setq major-mode 'text-mode) ; @r{This is how @code{describe-mode}}
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300 ; @r{finds the doc string to print.}
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301 (setq local-abbrev-table text-mode-abbrev-table)
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302 (set-syntax-table text-mode-syntax-table)
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303 (run-hooks 'text-mode-hook)) ; @r{Finally, this permits the user to}
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304 ; @r{customize the mode with a hook.}
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305 @end group
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306 @end smallexample
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307
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308 @cindex @file{lisp-mode.el}
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309 The three Lisp modes (Lisp mode, Emacs Lisp mode, and Lisp
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310 Interaction mode) have more features than Text mode and the code is
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311 correspondingly more complicated. Here are excerpts from
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312 @file{lisp-mode.el} that illustrate how these modes are written.
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313
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314 @cindex syntax table example
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315 @smallexample
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316 @group
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317 ;; @r{Create mode-specific table variables.}
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318 (defvar lisp-mode-syntax-table nil "")
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319 (defvar emacs-lisp-mode-syntax-table nil "")
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320 (defvar lisp-mode-abbrev-table nil "")
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321 @end group
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322
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323 @group
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324 (if (not emacs-lisp-mode-syntax-table) ; @r{Do not change the table}
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325 ; @r{if it is already set.}
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326 (let ((i 0))
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327 (setq emacs-lisp-mode-syntax-table (make-syntax-table))
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328 @end group
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329
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330 @group
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331 ;; @r{Set syntax of chars up to 0 to class of chars that are}
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332 ;; @r{part of symbol names but not words.}
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333 ;; @r{(The number 0 is @code{48} in the @sc{ascii} character set.)}
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444
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334 (while (< i ?0)
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335 (modify-syntax-entry i "_ " emacs-lisp-mode-syntax-table)
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336 (setq i (1+ i)))
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337 @dots{}
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338 @end group
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339 @group
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340 ;; @r{Set the syntax for other characters.}
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341 (modify-syntax-entry ? " " emacs-lisp-mode-syntax-table)
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342 (modify-syntax-entry ?\t " " emacs-lisp-mode-syntax-table)
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343 @dots{}
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344 @end group
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345 @group
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346 (modify-syntax-entry ?\( "() " emacs-lisp-mode-syntax-table)
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347 (modify-syntax-entry ?\) ")( " emacs-lisp-mode-syntax-table)
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348 @dots{}))
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349 ;; @r{Create an abbrev table for lisp-mode.}
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350 (define-abbrev-table 'lisp-mode-abbrev-table ())
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351 @end group
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352 @end smallexample
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353
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354 Much code is shared among the three Lisp modes. The following
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355 function sets various variables; it is called by each of the major Lisp
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356 mode functions:
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357
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358 @smallexample
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359 @group
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360 (defun lisp-mode-variables (lisp-syntax)
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361 ;; @r{The @code{lisp-syntax} argument is @code{nil} in Emacs Lisp mode,}
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362 ;; @r{and @code{t} in the other two Lisp modes.}
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363 (cond (lisp-syntax
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364 (if (not lisp-mode-syntax-table)
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365 ;; @r{The Emacs Lisp mode syntax table always exists, but}
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366 ;; @r{the Lisp Mode syntax table is created the first time a}
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367 ;; @r{mode that needs it is called. This is to save space.}
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368 @end group
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369 @group
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370 (progn (setq lisp-mode-syntax-table
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371 (copy-syntax-table emacs-lisp-mode-syntax-table))
|
|
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372 ;; @r{Change some entries for Lisp mode.}
|
|
|
373 (modify-syntax-entry ?\| "\" "
|
|
|
374 lisp-mode-syntax-table)
|
|
|
375 (modify-syntax-entry ?\[ "_ "
|
|
|
376 lisp-mode-syntax-table)
|
|
|
377 (modify-syntax-entry ?\] "_ "
|
|
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378 lisp-mode-syntax-table)))
|
|
|
379 @end group
|
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380 @group
|
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381 (set-syntax-table lisp-mode-syntax-table)))
|
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382 (setq local-abbrev-table lisp-mode-abbrev-table)
|
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383 @dots{})
|
|
|
384 @end group
|
|
|
385 @end smallexample
|
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386
|
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387 Functions such as @code{forward-paragraph} use the value of the
|
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388 @code{paragraph-start} variable. Since Lisp code is different from
|
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|
389 ordinary text, the @code{paragraph-start} variable needs to be set
|
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|
390 specially to handle Lisp. Also, comments are indented in a special
|
|
|
391 fashion in Lisp and the Lisp modes need their own mode-specific
|
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392 @code{comment-indent-function}. The code to set these variables is the
|
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|
393 rest of @code{lisp-mode-variables}.
|
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394
|
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395 @smallexample
|
|
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396 @group
|
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397 (make-local-variable 'paragraph-start)
|
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398 ;; @r{Having @samp{^} is not clean, but @code{page-delimiter}}
|
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399 ;; @r{has them too, and removing those is a pain.}
|
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400 (setq paragraph-start (concat "^$\\|" page-delimiter))
|
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401 @dots{}
|
|
|
402 @end group
|
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|
403 @group
|
|
|
404 (make-local-variable 'comment-indent-function)
|
|
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405 (setq comment-indent-function 'lisp-comment-indent))
|
|
|
406 @end group
|
|
|
407 @end smallexample
|
|
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408
|
|
|
409 Each of the different Lisp modes has a slightly different keymap. For
|
|
|
410 example, Lisp mode binds @kbd{C-c C-l} to @code{run-lisp}, but the other
|
|
|
411 Lisp modes do not. However, all Lisp modes have some commands in
|
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|
412 common. The following function adds these common commands to a given
|
|
|
413 keymap.
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|
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414
|
|
|
415 @smallexample
|
|
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416 @group
|
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417 (defun lisp-mode-commands (map)
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418 (define-key map "\e\C-q" 'indent-sexp)
|
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|
419 (define-key map "\177" 'backward-delete-char-untabify)
|
|
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420 (define-key map "\t" 'lisp-indent-line))
|
|
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421 @end group
|
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422 @end smallexample
|
|
|
423
|
|
|
424 Here is an example of using @code{lisp-mode-commands} to initialize a
|
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|
425 keymap, as part of the code for Emacs Lisp mode. First we declare a
|
|
|
426 variable with @code{defvar} to hold the mode-specific keymap. When this
|
|
|
427 @code{defvar} executes, it sets the variable to @code{nil} if it was
|
|
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428 void. Then we set up the keymap if the variable is @code{nil}.
|
|
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429
|
|
|
430 This code avoids changing the keymap or the variable if it is already
|
|
|
431 set up. This lets the user customize the keymap.
|
|
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432
|
|
|
433 @smallexample
|
|
|
434 @group
|
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444
|
435 (defvar emacs-lisp-mode-map () "")
|
|
428
|
436 (if emacs-lisp-mode-map
|
|
|
437 ()
|
|
|
438 (setq emacs-lisp-mode-map (make-sparse-keymap))
|
|
|
439 (define-key emacs-lisp-mode-map "\e\C-x" 'eval-defun)
|
|
|
440 (lisp-mode-commands emacs-lisp-mode-map))
|
|
|
441 @end group
|
|
|
442 @end smallexample
|
|
|
443
|
|
|
444 Finally, here is the complete major mode function definition for
|
|
444
|
445 Emacs Lisp mode.
|
|
428
|
446
|
|
|
447 @smallexample
|
|
|
448 @group
|
|
|
449 (defun emacs-lisp-mode ()
|
|
|
450 "Major mode for editing Lisp code to run in XEmacs.
|
|
|
451 Commands:
|
|
|
452 Delete converts tabs to spaces as it moves back.
|
|
|
453 Blank lines separate paragraphs. Semicolons start comments.
|
|
|
454 \\@{emacs-lisp-mode-map@}
|
|
|
455 @end group
|
|
|
456 @group
|
|
|
457 Entry to this mode runs the hook `emacs-lisp-mode-hook'."
|
|
|
458 (interactive)
|
|
|
459 (kill-all-local-variables)
|
|
|
460 (use-local-map emacs-lisp-mode-map) ; @r{This provides the local keymap.}
|
|
|
461 (set-syntax-table emacs-lisp-mode-syntax-table)
|
|
|
462 @end group
|
|
|
463 @group
|
|
|
464 (setq major-mode 'emacs-lisp-mode) ; @r{This is how @code{describe-mode}}
|
|
|
465 ; @r{finds out what to describe.}
|
|
|
466 (setq mode-name "Emacs-Lisp") ; @r{This goes into the modeline.}
|
|
|
467 (lisp-mode-variables nil) ; @r{This defines various variables.}
|
|
|
468 (run-hooks 'emacs-lisp-mode-hook)) ; @r{This permits the user to use a}
|
|
|
469 ; @r{hook to customize the mode.}
|
|
|
470 @end group
|
|
|
471 @end smallexample
|
|
|
472
|
|
|
473 @node Auto Major Mode
|
|
|
474 @subsection How XEmacs Chooses a Major Mode
|
|
|
475
|
|
|
476 Based on information in the file name or in the file itself, XEmacs
|
|
|
477 automatically selects a major mode for the new buffer when a file is
|
|
|
478 visited.
|
|
|
479
|
|
|
480 @deffn Command fundamental-mode
|
|
|
481 Fundamental mode is a major mode that is not specialized for anything
|
|
|
482 in particular. Other major modes are defined in effect by comparison
|
|
|
483 with this one---their definitions say what to change, starting from
|
|
|
484 Fundamental mode. The @code{fundamental-mode} function does @emph{not}
|
|
|
485 run any hooks; you're not supposed to customize it. (If you want Emacs
|
|
|
486 to behave differently in Fundamental mode, change the @emph{global}
|
|
|
487 state of Emacs.)
|
|
|
488 @end deffn
|
|
|
489
|
|
|
490 @deffn Command normal-mode &optional find-file
|
|
|
491 This function establishes the proper major mode and local variable
|
|
|
492 bindings for the current buffer. First it calls @code{set-auto-mode},
|
|
|
493 then it runs @code{hack-local-variables} to parse, and bind or
|
|
|
494 evaluate as appropriate, any local variables.
|
|
|
495
|
|
|
496 If the @var{find-file} argument to @code{normal-mode} is
|
|
|
497 non-@code{nil}, @code{normal-mode} assumes that the @code{find-file}
|
|
|
498 function is calling it. In this case, it may process a local variables
|
|
|
499 list at the end of the file and in the @samp{-*-} line. The variable
|
|
|
500 @code{enable-local-variables} controls whether to do so.
|
|
|
501
|
|
|
502 If you run @code{normal-mode} interactively, the argument
|
|
|
503 @var{find-file} is normally @code{nil}. In this case,
|
|
|
504 @code{normal-mode} unconditionally processes any local variables list.
|
|
446
|
505 @xref{File variables, , Local Variables in Files, xemacs, The XEmacs
|
|
428
|
506 Reference Manual}, for the syntax of the local variables section of a file.
|
|
|
507
|
|
|
508 @cindex file mode specification error
|
|
|
509 @code{normal-mode} uses @code{condition-case} around the call to the
|
|
|
510 major mode function, so errors are caught and reported as a @samp{File
|
|
|
511 mode specification error}, followed by the original error message.
|
|
|
512 @end deffn
|
|
|
513
|
|
|
514 @defopt enable-local-variables
|
|
|
515 This variable controls processing of local variables lists in files
|
|
|
516 being visited. A value of @code{t} means process the local variables
|
|
|
517 lists unconditionally; @code{nil} means ignore them; anything else means
|
|
|
518 ask the user what to do for each file. The default value is @code{t}.
|
|
|
519 @end defopt
|
|
|
520
|
|
|
521 @defvar ignored-local-variables
|
|
|
522 This variable holds a list of variables that should not be
|
|
|
523 set by a local variables list. Any value specified
|
|
|
524 for one of these variables is ignored.
|
|
|
525 @end defvar
|
|
|
526
|
|
|
527 In addition to this list, any variable whose name has a non-@code{nil}
|
|
|
528 @code{risky-local-variable} property is also ignored.
|
|
|
529
|
|
|
530 @defopt enable-local-eval
|
|
|
531 This variable controls processing of @samp{Eval:} in local variables
|
|
|
532 lists in files being visited. A value of @code{t} means process them
|
|
|
533 unconditionally; @code{nil} means ignore them; anything else means ask
|
|
|
534 the user what to do for each file. The default value is @code{maybe}.
|
|
|
535 @end defopt
|
|
|
536
|
|
|
537 @defun set-auto-mode
|
|
|
538 @cindex visited file mode
|
|
|
539 This function selects the major mode that is appropriate for the
|
|
|
540 current buffer. It may base its decision on the value of the @w{@samp{-*-}}
|
|
|
541 line, on the visited file name (using @code{auto-mode-alist}), or on the
|
|
|
542 value of a local variable. However, this function does not look for
|
|
|
543 the @samp{mode:} local variable near the end of a file; the
|
|
|
544 @code{hack-local-variables} function does that. @xref{Choosing Modes, ,
|
|
446
|
545 How Major Modes are Chosen, xemacs, The XEmacs Lisp Reference Manual}.
|
|
428
|
546 @end defun
|
|
|
547
|
|
444
|
548 @defopt default-major-mode
|
|
428
|
549 This variable holds the default major mode for new buffers. The
|
|
|
550 standard value is @code{fundamental-mode}.
|
|
|
551
|
|
|
552 If the value of @code{default-major-mode} is @code{nil}, XEmacs uses
|
|
|
553 the (previously) current buffer's major mode for the major mode of a new
|
|
|
554 buffer. However, if the major mode symbol has a @code{mode-class}
|
|
|
555 property with value @code{special}, then it is not used for new buffers;
|
|
|
556 Fundamental mode is used instead. The modes that have this property are
|
|
|
557 those such as Dired and Rmail that are useful only with text that has
|
|
|
558 been specially prepared.
|
|
|
559 @end defopt
|
|
|
560
|
|
|
561 @defun set-buffer-major-mode buffer
|
|
|
562 This function sets the major mode of @var{buffer} to the value of
|
|
|
563 @code{default-major-mode}. If that variable is @code{nil}, it uses
|
|
|
564 the current buffer's major mode (if that is suitable).
|
|
|
565
|
|
|
566 The low-level primitives for creating buffers do not use this function,
|
|
|
567 but medium-level commands such as @code{switch-to-buffer} and
|
|
|
568 @code{find-file-noselect} use it whenever they create buffers.
|
|
|
569 @end defun
|
|
|
570
|
|
|
571 @defvar initial-major-mode
|
|
|
572 @cindex @samp{*scratch*}
|
|
|
573 The value of this variable determines the major mode of the initial
|
|
|
574 @samp{*scratch*} buffer. The value should be a symbol that is a major
|
|
|
575 mode command name. The default value is @code{lisp-interaction-mode}.
|
|
|
576 @end defvar
|
|
|
577
|
|
|
578 @defvar auto-mode-alist
|
|
|
579 This variable contains an association list of file name patterns
|
|
|
580 (regular expressions; @pxref{Regular Expressions}) and corresponding
|
|
|
581 major mode functions. Usually, the file name patterns test for
|
|
|
582 suffixes, such as @samp{.el} and @samp{.c}, but this need not be the
|
|
|
583 case. An ordinary element of the alist looks like @code{(@var{regexp} .
|
|
|
584 @var{mode-function})}.
|
|
|
585
|
|
|
586 For example,
|
|
|
587
|
|
|
588 @smallexample
|
|
|
589 @group
|
|
|
590 (("^/tmp/fol/" . text-mode)
|
|
|
591 ("\\.texinfo\\'" . texinfo-mode)
|
|
|
592 ("\\.texi\\'" . texinfo-mode)
|
|
|
593 @end group
|
|
|
594 @group
|
|
|
595 ("\\.el\\'" . emacs-lisp-mode)
|
|
444
|
596 ("\\.c\\'" . c-mode)
|
|
428
|
597 ("\\.h\\'" . c-mode)
|
|
|
598 @dots{})
|
|
|
599 @end group
|
|
|
600 @end smallexample
|
|
|
601
|
|
|
602 When you visit a file whose expanded file name (@pxref{File Name
|
|
|
603 Expansion}) matches a @var{regexp}, @code{set-auto-mode} calls the
|
|
|
604 corresponding @var{mode-function}. This feature enables XEmacs to select
|
|
|
605 the proper major mode for most files.
|
|
|
606
|
|
|
607 If an element of @code{auto-mode-alist} has the form @code{(@var{regexp}
|
|
|
608 @var{function} t)}, then after calling @var{function}, XEmacs searches
|
|
|
609 @code{auto-mode-alist} again for a match against the portion of the file
|
|
|
610 name that did not match before.
|
|
|
611
|
|
|
612 This match-again feature is useful for uncompression packages: an entry
|
|
|
613 of the form @code{("\\.gz\\'" . @var{function})} can uncompress the file
|
|
|
614 and then put the uncompressed file in the proper mode according to the
|
|
|
615 name sans @samp{.gz}.
|
|
|
616
|
|
|
617 Here is an example of how to prepend several pattern pairs to
|
|
|
618 @code{auto-mode-alist}. (You might use this sort of expression in your
|
|
|
619 @file{.emacs} file.)
|
|
|
620
|
|
|
621 @smallexample
|
|
|
622 @group
|
|
|
623 (setq auto-mode-alist
|
|
444
|
624 (append
|
|
428
|
625 ;; @r{File name starts with a dot.}
|
|
444
|
626 '(("/\\.[^/]*\\'" . fundamental-mode)
|
|
428
|
627 ;; @r{File name has no dot.}
|
|
444
|
628 ("[^\\./]*\\'" . fundamental-mode)
|
|
428
|
629 ;; @r{File name ends in @samp{.C}.}
|
|
|
630 ("\\.C\\'" . c++-mode))
|
|
|
631 auto-mode-alist))
|
|
|
632 @end group
|
|
|
633 @end smallexample
|
|
|
634 @end defvar
|
|
|
635
|
|
|
636 @defvar interpreter-mode-alist
|
|
|
637 This variable specifies major modes to use for scripts that specify a
|
|
|
638 command interpreter in an @samp{#!} line. Its value is a list of
|
|
|
639 elements of the form @code{(@var{interpreter} . @var{mode})}; for
|
|
|
640 example, @code{("perl" . perl-mode)} is one element present by default.
|
|
|
641 The element says to use mode @var{mode} if the file specifies
|
|
|
642 @var{interpreter}.
|
|
|
643
|
|
|
644 This variable is applicable only when the @code{auto-mode-alist} does
|
|
|
645 not indicate which major mode to use.
|
|
|
646 @end defvar
|
|
|
647
|
|
|
648 @defun hack-local-variables &optional force
|
|
|
649 This function parses, and binds or evaluates as appropriate, any local
|
|
|
650 variables for the current buffer.
|
|
|
651
|
|
|
652 The handling of @code{enable-local-variables} documented for
|
|
|
653 @code{normal-mode} actually takes place here. The argument @var{force}
|
|
|
654 usually comes from the argument @var{find-file} given to
|
|
|
655 @code{normal-mode}.
|
|
|
656 @end defun
|
|
|
657
|
|
|
658 @node Mode Help
|
|
|
659 @subsection Getting Help about a Major Mode
|
|
|
660 @cindex mode help
|
|
|
661 @cindex help for major mode
|
|
|
662 @cindex documentation for major mode
|
|
|
663
|
|
|
664 The @code{describe-mode} function is used to provide information
|
|
|
665 about major modes. It is normally called with @kbd{C-h m}. The
|
|
|
666 @code{describe-mode} function uses the value of @code{major-mode},
|
|
|
667 which is why every major mode function needs to set the
|
|
|
668 @code{major-mode} variable.
|
|
|
669
|
|
|
670 @deffn Command describe-mode
|
|
|
671 This function displays the documentation of the current major mode.
|
|
|
672
|
|
|
673 The @code{describe-mode} function calls the @code{documentation}
|
|
|
674 function using the value of @code{major-mode} as an argument. Thus, it
|
|
|
675 displays the documentation string of the major mode function.
|
|
|
676 (@xref{Accessing Documentation}.)
|
|
|
677 @end deffn
|
|
|
678
|
|
|
679 @defvar major-mode
|
|
|
680 This variable holds the symbol for the current buffer's major mode.
|
|
|
681 This symbol should have a function definition that is the command to
|
|
|
682 switch to that major mode. The @code{describe-mode} function uses the
|
|
|
683 documentation string of the function as the documentation of the major
|
|
|
684 mode.
|
|
|
685 @end defvar
|
|
|
686
|
|
|
687 @node Derived Modes
|
|
|
688 @subsection Defining Derived Modes
|
|
|
689
|
|
|
690 It's often useful to define a new major mode in terms of an existing
|
|
|
691 one. An easy way to do this is to use @code{define-derived-mode}.
|
|
|
692
|
|
|
693 @defmac define-derived-mode variant parent name docstring body@dots{}
|
|
|
694 This construct defines @var{variant} as a major mode command, using
|
|
|
695 @var{name} as the string form of the mode name.
|
|
|
696
|
|
|
697 The new command @var{variant} is defined to call the function
|
|
|
698 @var{parent}, then override certain aspects of that parent mode:
|
|
|
699
|
|
444
|
700 @itemize @bullet
|
|
428
|
701 @item
|
|
|
702 The new mode has its own keymap, named @code{@var{variant}-map}.
|
|
|
703 @code{define-derived-mode} initializes this map to inherit from
|
|
|
704 @code{@var{parent}-map}, if it is not already set.
|
|
|
705
|
|
|
706 @item
|
|
|
707 The new mode has its own syntax table, kept in the variable
|
|
|
708 @code{@var{variant}-syntax-table}.
|
|
444
|
709 @code{define-derived-mode} initializes this variable by copying
|
|
428
|
710 @code{@var{parent}-syntax-table}, if it is not already set.
|
|
|
711
|
|
|
712 @item
|
|
|
713 The new mode has its own abbrev table, kept in the variable
|
|
|
714 @code{@var{variant}-abbrev-table}.
|
|
444
|
715 @code{define-derived-mode} initializes this variable by copying
|
|
428
|
716 @code{@var{parent}-abbrev-table}, if it is not already set.
|
|
|
717
|
|
|
718 @item
|
|
|
719 The new mode has its own mode hook, @code{@var{variant}-hook},
|
|
|
720 which it runs in standard fashion as the very last thing that it does.
|
|
444
|
721 (The new mode also runs the mode hook of @var{parent} as part
|
|
428
|
722 of calling @var{parent}.)
|
|
|
723 @end itemize
|
|
|
724
|
|
|
725 In addition, you can specify how to override other aspects of
|
|
|
726 @var{parent} with @var{body}. The command @var{variant}
|
|
444
|
727 evaluates the forms in @var{body} after setting up all its usual
|
|
428
|
728 overrides, just before running @code{@var{variant}-hook}.
|
|
|
729
|
|
|
730 The argument @var{docstring} specifies the documentation string for the
|
|
|
731 new mode. If you omit @var{docstring}, @code{define-derived-mode}
|
|
|
732 generates a documentation string.
|
|
|
733
|
|
|
734 Here is a hypothetical example:
|
|
|
735
|
|
|
736 @example
|
|
|
737 (define-derived-mode hypertext-mode
|
|
|
738 text-mode "Hypertext"
|
|
|
739 "Major mode for hypertext.
|
|
|
740 \\@{hypertext-mode-map@}"
|
|
|
741 (setq case-fold-search nil))
|
|
|
742
|
|
|
743 (define-key hypertext-mode-map
|
|
|
744 [down-mouse-3] 'do-hyper-link)
|
|
|
745 @end example
|
|
|
746 @end defmac
|
|
|
747
|
|
|
748 @node Minor Modes
|
|
|
749 @section Minor Modes
|
|
|
750 @cindex minor mode
|
|
|
751
|
|
|
752 A @dfn{minor mode} provides features that users may enable or disable
|
|
|
753 independently of the choice of major mode. Minor modes can be enabled
|
|
|
754 individually or in combination. Minor modes would be better named
|
|
|
755 ``Generally available, optional feature modes'' except that such a name is
|
|
|
756 unwieldy.
|
|
|
757
|
|
|
758 A minor mode is not usually a modification of single major mode. For
|
|
|
759 example, Auto Fill mode may be used in any major mode that permits text
|
|
|
760 insertion. To be general, a minor mode must be effectively independent
|
|
|
761 of the things major modes do.
|
|
|
762
|
|
|
763 A minor mode is often much more difficult to implement than a major
|
|
|
764 mode. One reason is that you should be able to activate and deactivate
|
|
|
765 minor modes in any order. A minor mode should be able to have its
|
|
|
766 desired effect regardless of the major mode and regardless of the other
|
|
|
767 minor modes in effect.
|
|
|
768
|
|
|
769 Often the biggest problem in implementing a minor mode is finding a
|
|
|
770 way to insert the necessary hook into the rest of XEmacs. Minor mode
|
|
|
771 keymaps make this easier than it used to be.
|
|
|
772
|
|
|
773 @menu
|
|
|
774 * Minor Mode Conventions:: Tips for writing a minor mode.
|
|
|
775 * Keymaps and Minor Modes:: How a minor mode can have its own keymap.
|
|
|
776 @end menu
|
|
|
777
|
|
|
778 @node Minor Mode Conventions
|
|
|
779 @subsection Conventions for Writing Minor Modes
|
|
|
780 @cindex minor mode conventions
|
|
|
781 @cindex conventions for writing minor modes
|
|
|
782
|
|
|
783 There are conventions for writing minor modes just as there are for
|
|
|
784 major modes. Several of the major mode conventions apply to minor
|
|
|
785 modes as well: those regarding the name of the mode initialization
|
|
|
786 function, the names of global symbols, and the use of keymaps and
|
|
|
787 other tables.
|
|
|
788
|
|
|
789 In addition, there are several conventions that are specific to
|
|
|
790 minor modes.
|
|
|
791
|
|
|
792 @itemize @bullet
|
|
|
793 @item
|
|
|
794 @cindex mode variable
|
|
|
795 Make a variable whose name ends in @samp{-mode} to represent the minor
|
|
|
796 mode. Its value should enable or disable the mode (@code{nil} to
|
|
|
797 disable; anything else to enable.) We call this the @dfn{mode
|
|
|
798 variable}.
|
|
|
799
|
|
|
800 This variable is used in conjunction with the @code{minor-mode-alist} to
|
|
|
801 display the minor mode name in the modeline. It can also enable
|
|
|
802 or disable a minor mode keymap. Individual commands or hooks can also
|
|
|
803 check the variable's value.
|
|
|
804
|
|
|
805 If you want the minor mode to be enabled separately in each buffer,
|
|
|
806 make the variable buffer-local.
|
|
|
807
|
|
|
808 @item
|
|
|
809 Define a command whose name is the same as the mode variable.
|
|
|
810 Its job is to enable and disable the mode by setting the variable.
|
|
|
811
|
|
|
812 The command should accept one optional argument. If the argument is
|
|
|
813 @code{nil}, it should toggle the mode (turn it on if it is off, and off
|
|
|
814 if it is on). Otherwise, it should turn the mode on if the argument is
|
|
|
815 a positive integer, a symbol other than @code{nil} or @code{-}, or a
|
|
|
816 list whose @sc{car} is such an integer or symbol; it should turn the
|
|
|
817 mode off otherwise.
|
|
|
818
|
|
|
819 Here is an example taken from the definition of @code{transient-mark-mode}.
|
|
|
820 It shows the use of @code{transient-mark-mode} as a variable that enables or
|
|
|
821 disables the mode's behavior, and also shows the proper way to toggle,
|
|
|
822 enable or disable the minor mode based on the raw prefix argument value.
|
|
|
823
|
|
|
824 @smallexample
|
|
|
825 @group
|
|
|
826 (setq transient-mark-mode
|
|
|
827 (if (null arg) (not transient-mark-mode)
|
|
|
828 (> (prefix-numeric-value arg) 0)))
|
|
|
829 @end group
|
|
|
830 @end smallexample
|
|
|
831
|
|
|
832 @item
|
|
|
833 Add an element to @code{minor-mode-alist} for each minor mode
|
|
|
834 (@pxref{Modeline Variables}). This element should be a list of the
|
|
|
835 following form:
|
|
|
836
|
|
|
837 @smallexample
|
|
|
838 (@var{mode-variable} @var{string})
|
|
|
839 @end smallexample
|
|
|
840
|
|
|
841 Here @var{mode-variable} is the variable that controls enabling of the
|
|
|
842 minor mode, and @var{string} is a short string, starting with a space,
|
|
|
843 to represent the mode in the modeline. These strings must be short so
|
|
|
844 that there is room for several of them at once.
|
|
|
845
|
|
|
846 When you add an element to @code{minor-mode-alist}, use @code{assq} to
|
|
|
847 check for an existing element, to avoid duplication. For example:
|
|
|
848
|
|
|
849 @smallexample
|
|
|
850 @group
|
|
|
851 (or (assq 'leif-mode minor-mode-alist)
|
|
|
852 (setq minor-mode-alist
|
|
|
853 (cons '(leif-mode " Leif") minor-mode-alist)))
|
|
|
854 @end group
|
|
|
855 @end smallexample
|
|
|
856 @end itemize
|
|
|
857
|
|
|
858 @node Keymaps and Minor Modes
|
|
|
859 @subsection Keymaps and Minor Modes
|
|
|
860
|
|
|
861 Each minor mode can have its own keymap, which is active when the mode
|
|
|
862 is enabled. To set up a keymap for a minor mode, add an element to the
|
|
|
863 alist @code{minor-mode-map-alist}. @xref{Active Keymaps}.
|
|
|
864
|
|
|
865 @cindex @code{self-insert-command}, minor modes
|
|
|
866 One use of minor mode keymaps is to modify the behavior of certain
|
|
|
867 self-inserting characters so that they do something else as well as
|
|
|
868 self-insert. In general, this is the only way to do that, since the
|
|
|
869 facilities for customizing @code{self-insert-command} are limited to
|
|
|
870 special cases (designed for abbrevs and Auto Fill mode). (Do not try
|
|
|
871 substituting your own definition of @code{self-insert-command} for the
|
|
|
872 standard one. The editor command loop handles this function specially.)
|
|
|
873
|
|
|
874 @node Modeline Format
|
|
|
875 @section Modeline Format
|
|
|
876 @cindex modeline
|
|
|
877
|
|
|
878 Each Emacs window (aside from minibuffer windows) includes a modeline,
|
|
|
879 which displays status information about the buffer displayed in the
|
|
|
880 window. The modeline contains information about the buffer, such as its
|
|
|
881 name, associated file, depth of recursive editing, and the major and
|
|
|
882 minor modes.
|
|
|
883
|
|
|
884 This section describes how the contents of the modeline are
|
|
|
885 controlled. It is in the chapter on modes because much of the
|
|
|
886 information displayed in the modeline relates to the enabled major and
|
|
|
887 minor modes.
|
|
|
888
|
|
|
889 @code{modeline-format} is a buffer-local variable that holds a
|
|
|
890 template used to display the modeline of the current buffer. All
|
|
|
891 windows for the same buffer use the same @code{modeline-format} and
|
|
|
892 their modelines appear the same (except for scrolling percentages and
|
|
|
893 line numbers).
|
|
|
894
|
|
|
895 The modeline of a window is normally updated whenever a different
|
|
|
896 buffer is shown in the window, or when the buffer's modified-status
|
|
|
897 changes from @code{nil} to @code{t} or vice-versa. If you modify any of
|
|
|
898 the variables referenced by @code{modeline-format} (@pxref{Modeline
|
|
|
899 Variables}), you may want to force an update of the modeline so as to
|
|
|
900 display the new information.
|
|
|
901
|
|
|
902 @c Emacs 19 feature
|
|
|
903 @defun redraw-modeline &optional all
|
|
|
904 Force redisplay of the current buffer's modeline. If @var{all} is
|
|
|
905 non-@code{nil}, then force redisplay of all modelines.
|
|
|
906 @end defun
|
|
|
907
|
|
|
908 The modeline is usually displayed in inverse video. This
|
|
|
909 is controlled using the @code{modeline} face. @xref{Faces}.
|
|
|
910
|
|
|
911 @menu
|
|
|
912 * Modeline Data:: The data structure that controls the modeline.
|
|
|
913 * Modeline Variables:: Variables used in that data structure.
|
|
|
914 * %-Constructs:: Putting information into a modeline.
|
|
|
915 @end menu
|
|
|
916
|
|
|
917 @node Modeline Data
|
|
|
918 @subsection The Data Structure of the Modeline
|
|
|
919 @cindex modeline construct
|
|
|
920
|
|
|
921 The modeline contents are controlled by a data structure of lists,
|
|
|
922 strings, symbols, and numbers kept in the buffer-local variable
|
|
442
|
923 @code{modeline-format}. The data structure is called a @dfn{modeline
|
|
428
|
924 construct}, and it is built in recursive fashion out of simpler modeline
|
|
|
925 constructs. The same data structure is used for constructing
|
|
|
926 frame titles (@pxref{Frame Titles}).
|
|
|
927
|
|
|
928 @defvar modeline-format
|
|
|
929 The value of this variable is a modeline construct with overall
|
|
|
930 responsibility for the modeline format. The value of this variable
|
|
|
931 controls which other variables are used to form the modeline text, and
|
|
|
932 where they appear.
|
|
|
933 @end defvar
|
|
|
934
|
|
|
935 A modeline construct may be as simple as a fixed string of text, but
|
|
|
936 it usually specifies how to use other variables to construct the text.
|
|
|
937 Many of these variables are themselves defined to have modeline
|
|
|
938 constructs as their values.
|
|
|
939
|
|
|
940 The default value of @code{modeline-format} incorporates the values
|
|
|
941 of variables such as @code{mode-name} and @code{minor-mode-alist}.
|
|
|
942 Because of this, very few modes need to alter @code{modeline-format}.
|
|
|
943 For most purposes, it is sufficient to alter the variables referenced by
|
|
|
944 @code{modeline-format}.
|
|
|
945
|
|
442
|
946 A modeline construct may be a string, symbol, glyph, generic
|
|
|
947 specifier, list or cons cell.
|
|
428
|
948
|
|
|
949 @table @code
|
|
|
950 @cindex percent symbol in modeline
|
|
|
951 @item @var{string}
|
|
|
952 A string as a modeline construct is displayed verbatim in the mode line
|
|
|
953 except for @dfn{@code{%}-constructs}. Decimal digits after the @samp{%}
|
|
|
954 specify the field width for space filling on the right (i.e., the data
|
|
|
955 is left justified). @xref{%-Constructs}.
|
|
|
956
|
|
|
957 @item @var{symbol}
|
|
|
958 A symbol as a modeline construct stands for its value. The value of
|
|
442
|
959 @var{symbol} is processed as a modeline construct, in place of
|
|
|
960 @var{symbol}. However, the symbols @code{t} and @code{nil} are ignored;
|
|
|
961 so is any symbol whose value is void.
|
|
428
|
962
|
|
|
963 There is one exception: if the value of @var{symbol} is a string, it is
|
|
|
964 displayed verbatim: the @code{%}-constructs are not recognized.
|
|
|
965
|
|
442
|
966 @item @var{glyph}
|
|
|
967 A glyph is displayed as is.
|
|
|
968
|
|
|
969 @item @var{generic-specifier}
|
|
|
970 A @var{generic-specifier} (i.e. a specifier of type @code{generic})
|
|
|
971 stands for its instance. The instance of @var{generic-specifier} is
|
|
|
972 computed in the current window using the equivalent of
|
|
|
973 @code{specifier-instance} and the value is processed.
|
|
|
974
|
|
428
|
975 @item (@var{string} @var{rest}@dots{}) @r{or} (@var{list} @var{rest}@dots{})
|
|
|
976 A list whose first element is a string or list means to process all the
|
|
|
977 elements recursively and concatenate the results. This is the most
|
|
|
978 common form of mode line construct.
|
|
|
979
|
|
|
980 @item (@var{symbol} @var{then} @var{else})
|
|
|
981 A list whose first element is a symbol is a conditional. Its meaning
|
|
|
982 depends on the value of @var{symbol}. If the value is non-@code{nil},
|
|
|
983 the second element, @var{then}, is processed recursively as a modeline
|
|
|
984 element. But if the value of @var{symbol} is @code{nil}, the third
|
|
|
985 element, @var{else}, is processed recursively. You may omit @var{else};
|
|
|
986 then the mode line element displays nothing if the value of @var{symbol}
|
|
|
987 is @code{nil}.
|
|
|
988
|
|
|
989 @item (@var{width} @var{rest}@dots{})
|
|
|
990 A list whose first element is an integer specifies truncation or
|
|
|
991 padding of the results of @var{rest}. The remaining elements
|
|
|
992 @var{rest} are processed recursively as modeline constructs and
|
|
|
993 concatenated together. Then the result is space filled (if
|
|
|
994 @var{width} is positive) or truncated (to @minus{}@var{width} columns,
|
|
|
995 if @var{width} is negative) on the right.
|
|
|
996
|
|
|
997 For example, the usual way to show what percentage of a buffer is above
|
|
|
998 the top of the window is to use a list like this: @code{(-3 "%p")}.
|
|
442
|
999
|
|
|
1000 @item (@var{extent} @var{rest}@dots{})
|
|
|
1001
|
|
|
1002 A list whose car is an extent means the cdr of the list is processed
|
|
|
1003 normally but the results are displayed using the face of the extent, and
|
|
|
1004 mouse clicks over this section are processed using the keymap of the
|
|
|
1005 extent. (In addition, if the extent has a help-echo property, that
|
|
|
1006 string will be echoed when the mouse moves over this section.) If
|
|
|
1007 extents are nested, all keymaps are properly consulted when processing
|
|
|
1008 mouse clicks, but multiple faces are not correctly merged (only the
|
|
|
1009 first face is used), and lists of faces are not correctly handled.
|
|
|
1010 @c #### Document generate-modeline-string.
|
|
|
1011 @c See `generated-modeline-string' for more information.
|
|
428
|
1012 @end table
|
|
|
1013
|
|
|
1014 If you do alter @code{modeline-format} itself, the new value should
|
|
|
1015 use the same variables that appear in the default value (@pxref{Modeline
|
|
|
1016 Variables}), rather than duplicating their contents or displaying
|
|
|
1017 the information in another fashion. This way, customizations made by
|
|
|
1018 the user or by Lisp programs (such as @code{display-time} and major
|
|
|
1019 modes) via changes to those variables remain effective.
|
|
|
1020
|
|
|
1021 @cindex Shell mode @code{modeline-format}
|
|
|
1022 Here is an example of a @code{modeline-format} that might be
|
|
|
1023 useful for @code{shell-mode}, since it contains the hostname and default
|
|
|
1024 directory.
|
|
|
1025
|
|
|
1026 @example
|
|
|
1027 @group
|
|
|
1028 (setq modeline-format
|
|
|
1029 (list ""
|
|
|
1030 'modeline-modified
|
|
444
|
1031 "%b--"
|
|
428
|
1032 @end group
|
|
|
1033 (getenv "HOST") ; @r{One element is not constant.}
|
|
444
|
1034 ":"
|
|
428
|
1035 'default-directory
|
|
|
1036 " "
|
|
|
1037 'global-mode-string
|
|
|
1038 " %[("
|
|
444
|
1039 'mode-name
|
|
|
1040 'modeline-process
|
|
|
1041 'minor-mode-alist
|
|
|
1042 "%n"
|
|
428
|
1043 ")%]----"
|
|
|
1044 @group
|
|
|
1045 '(line-number-mode "L%l--")
|
|
|
1046 '(-3 . "%p")
|
|
|
1047 "-%-"))
|
|
|
1048 @end group
|
|
|
1049 @end example
|
|
|
1050
|
|
|
1051 @node Modeline Variables
|
|
|
1052 @subsection Variables Used in the Modeline
|
|
|
1053
|
|
|
1054 This section describes variables incorporated by the
|
|
|
1055 standard value of @code{modeline-format} into the text of the mode
|
|
|
1056 line. There is nothing inherently special about these variables; any
|
|
|
1057 other variables could have the same effects on the modeline if
|
|
|
1058 @code{modeline-format} were changed to use them.
|
|
|
1059
|
|
|
1060 @defvar modeline-modified
|
|
|
1061 This variable holds the value of the modeline construct that displays
|
|
|
1062 whether the current buffer is modified.
|
|
|
1063
|
|
|
1064 The default value of @code{modeline-modified} is @code{("--%1*%1+-")}.
|
|
|
1065 This means that the modeline displays @samp{--**-} if the buffer is
|
|
|
1066 modified, @samp{-----} if the buffer is not modified, @samp{--%%-} if
|
|
|
1067 the buffer is read only, and @samp{--%*--} if the buffer is read only
|
|
|
1068 and modified.
|
|
|
1069
|
|
|
1070 Changing this variable does not force an update of the modeline.
|
|
|
1071 @end defvar
|
|
|
1072
|
|
|
1073 @defvar modeline-buffer-identification
|
|
|
1074 This variable identifies the buffer being displayed in the window. Its
|
|
|
1075 default value is @code{("%F: %17b")}, which means that it usually
|
|
|
1076 displays @samp{Emacs:} followed by seventeen characters of the buffer
|
|
|
1077 name. (In a terminal frame, it displays the frame name instead of
|
|
|
1078 @samp{Emacs}; this has the effect of showing the frame number.) You may
|
|
|
1079 want to change this in modes such as Rmail that do not behave like a
|
|
|
1080 ``normal'' XEmacs.
|
|
|
1081 @end defvar
|
|
|
1082
|
|
|
1083 @defvar global-mode-string
|
|
|
1084 This variable holds a modeline spec that appears in the mode line by
|
|
|
1085 default, just after the buffer name. The command @code{display-time}
|
|
|
1086 sets @code{global-mode-string} to refer to the variable
|
|
|
1087 @code{display-time-string}, which holds a string containing the time and
|
|
|
1088 load information.
|
|
|
1089
|
|
|
1090 The @samp{%M} construct substitutes the value of
|
|
|
1091 @code{global-mode-string}, but this is obsolete, since the variable is
|
|
|
1092 included directly in the modeline.
|
|
|
1093 @end defvar
|
|
|
1094
|
|
|
1095 @defvar mode-name
|
|
|
1096 This buffer-local variable holds the ``pretty'' name of the current
|
|
|
1097 buffer's major mode. Each major mode should set this variable so that the
|
|
|
1098 mode name will appear in the modeline.
|
|
|
1099 @end defvar
|
|
|
1100
|
|
|
1101 @defvar minor-mode-alist
|
|
|
1102 This variable holds an association list whose elements specify how the
|
|
|
1103 modeline should indicate that a minor mode is active. Each element of
|
|
|
1104 the @code{minor-mode-alist} should be a two-element list:
|
|
|
1105
|
|
|
1106 @example
|
|
|
1107 (@var{minor-mode-variable} @var{modeline-string})
|
|
|
1108 @end example
|
|
|
1109
|
|
|
1110 More generally, @var{modeline-string} can be any mode line spec. It
|
|
|
1111 appears in the mode line when the value of @var{minor-mode-variable} is
|
|
|
1112 non-@code{nil}, and not otherwise. These strings should begin with
|
|
|
1113 spaces so that they don't run together. Conventionally, the
|
|
|
1114 @var{minor-mode-variable} for a specific mode is set to a non-@code{nil}
|
|
|
1115 value when that minor mode is activated.
|
|
|
1116
|
|
|
1117 The default value of @code{minor-mode-alist} is:
|
|
|
1118
|
|
|
1119 @example
|
|
|
1120 @group
|
|
|
1121 minor-mode-alist
|
|
|
1122 @result{} ((vc-mode vc-mode)
|
|
444
|
1123 (abbrev-mode " Abbrev")
|
|
|
1124 (overwrite-mode overwrite-mode)
|
|
|
1125 (auto-fill-function " Fill")
|
|
428
|
1126 (defining-kbd-macro " Def")
|
|
|
1127 (isearch-mode isearch-mode))
|
|
|
1128 @end group
|
|
|
1129 @end example
|
|
|
1130
|
|
|
1131 @code{minor-mode-alist} is not buffer-local. The variables mentioned
|
|
|
1132 in the alist should be buffer-local if the minor mode can be enabled
|
|
|
1133 separately in each buffer.
|
|
|
1134 @end defvar
|
|
|
1135
|
|
|
1136 @defvar modeline-process
|
|
|
1137 This buffer-local variable contains the modeline information on process
|
|
|
1138 status in modes used for communicating with subprocesses. It is
|
|
|
1139 displayed immediately following the major mode name, with no intervening
|
|
|
1140 space. For example, its value in the @samp{*shell*} buffer is
|
|
|
1141 @code{(":@: %s")}, which allows the shell to display its status along
|
|
|
1142 with the major mode as: @samp{(Shell:@: run)}. Normally this variable
|
|
|
1143 is @code{nil}.
|
|
|
1144 @end defvar
|
|
|
1145
|
|
|
1146 @defvar default-modeline-format
|
|
|
1147 This variable holds the default @code{modeline-format} for buffers
|
|
|
1148 that do not override it. This is the same as @code{(default-value
|
|
|
1149 'modeline-format)}.
|
|
|
1150
|
|
|
1151 The default value of @code{default-modeline-format} is:
|
|
|
1152
|
|
|
1153 @example
|
|
|
1154 @group
|
|
|
1155 (""
|
|
|
1156 modeline-modified
|
|
|
1157 modeline-buffer-identification
|
|
|
1158 " "
|
|
|
1159 global-mode-string
|
|
|
1160 " %[("
|
|
444
|
1161 mode-name
|
|
428
|
1162 @end group
|
|
|
1163 @group
|
|
|
1164 modeline-process
|
|
444
|
1165 minor-mode-alist
|
|
|
1166 "%n"
|
|
428
|
1167 ")%]----"
|
|
|
1168 (line-number-mode "L%l--")
|
|
|
1169 (-3 . "%p")
|
|
|
1170 "-%-")
|
|
|
1171 @end group
|
|
|
1172 @end example
|
|
|
1173 @end defvar
|
|
|
1174
|
|
|
1175 @defvar vc-mode
|
|
|
1176 The variable @code{vc-mode}, local in each buffer, records whether the
|
|
|
1177 buffer's visited file is maintained with version control, and, if so,
|
|
|
1178 which kind. Its value is @code{nil} for no version control, or a string
|
|
|
1179 that appears in the mode line.
|
|
|
1180 @end defvar
|
|
|
1181
|
|
|
1182 @node %-Constructs
|
|
|
1183 @subsection @code{%}-Constructs in the ModeLine
|
|
|
1184
|
|
|
1185 The following table lists the recognized @code{%}-constructs and what
|
|
|
1186 they mean. In any construct except @samp{%%}, you can add a decimal
|
|
|
1187 integer after the @samp{%} to specify how many characters to display.
|
|
|
1188
|
|
|
1189 @table @code
|
|
|
1190 @item %b
|
|
|
1191 The current buffer name, obtained with the @code{buffer-name} function.
|
|
|
1192 @xref{Buffer Names}.
|
|
|
1193
|
|
|
1194 @item %f
|
|
|
1195 The visited file name, obtained with the @code{buffer-file-name}
|
|
|
1196 function. @xref{Buffer File Name}.
|
|
|
1197
|
|
|
1198 @item %F
|
|
|
1199 The name of the selected frame.
|
|
|
1200
|
|
|
1201 @item %c
|
|
|
1202 The current column number of point.
|
|
|
1203
|
|
|
1204 @item %l
|
|
|
1205 The current line number of point.
|
|
|
1206
|
|
|
1207 @item %*
|
|
|
1208 @samp{%} if the buffer is read only (see @code{buffer-read-only}); @*
|
|
|
1209 @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @*
|
|
|
1210 @samp{-} otherwise. @xref{Buffer Modification}.
|
|
|
1211
|
|
|
1212 @item %+
|
|
|
1213 @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @*
|
|
|
1214 @samp{%} if the buffer is read only (see @code{buffer-read-only}); @*
|
|
|
1215 @samp{-} otherwise. This differs from @samp{%*} only for a modified
|
|
|
1216 read-only buffer. @xref{Buffer Modification}.
|
|
|
1217
|
|
|
1218 @item %&
|
|
|
1219 @samp{*} if the buffer is modified, and @samp{-} otherwise.
|
|
|
1220
|
|
|
1221 @item %s
|
|
|
1222 The status of the subprocess belonging to the current buffer, obtained with
|
|
|
1223 @code{process-status}. @xref{Process Information}.
|
|
|
1224
|
|
|
1225 @c The following two may only apply in XEmacs.
|
|
|
1226 @item %l
|
|
442
|
1227 The current line number.
|
|
428
|
1228
|
|
|
1229 @item %S
|
|
442
|
1230 The name of the selected frame; this is only meaningful under the
|
|
428
|
1231 X Window System. @xref{Frame Name}.
|
|
|
1232
|
|
|
1233 @item %t
|
|
|
1234 Whether the visited file is a text file or a binary file. (This is a
|
|
|
1235 meaningful distinction only on certain operating systems.)
|
|
|
1236
|
|
|
1237 @item %p
|
|
|
1238 The percentage of the buffer text above the @strong{top} of window, or
|
|
|
1239 @samp{Top}, @samp{Bottom} or @samp{All}.
|
|
|
1240
|
|
|
1241 @item %P
|
|
|
1242 The percentage of the buffer text that is above the @strong{bottom} of
|
|
|
1243 the window (which includes the text visible in the window, as well as
|
|
|
1244 the text above the top), plus @samp{Top} if the top of the buffer is
|
|
|
1245 visible on screen; or @samp{Bottom} or @samp{All}.
|
|
|
1246
|
|
|
1247 @item %n
|
|
|
1248 @samp{Narrow} when narrowing is in effect; nothing otherwise (see
|
|
|
1249 @code{narrow-to-region} in @ref{Narrowing}).
|
|
|
1250
|
|
442
|
1251 @item %C
|
|
|
1252 Under XEmacs/mule, the mnemonic for @code{buffer-file-coding-system}.
|
|
|
1253
|
|
428
|
1254 @item %[
|
|
|
1255 An indication of the depth of recursive editing levels (not counting
|
|
|
1256 minibuffer levels): one @samp{[} for each editing level.
|
|
|
1257 @xref{Recursive Editing}.
|
|
|
1258
|
|
|
1259 @item %]
|
|
|
1260 One @samp{]} for each recursive editing level (not counting minibuffer
|
|
|
1261 levels).
|
|
|
1262
|
|
|
1263 @item %%
|
|
|
1264 The character @samp{%}---this is how to include a literal @samp{%} in a
|
|
|
1265 string in which @code{%}-constructs are allowed.
|
|
|
1266
|
|
|
1267 @item %-
|
|
|
1268 Dashes sufficient to fill the remainder of the modeline.
|
|
|
1269 @end table
|
|
|
1270
|
|
|
1271 The following two @code{%}-constructs are still supported, but they are
|
|
|
1272 obsolete, since you can get the same results with the variables
|
|
|
1273 @code{mode-name} and @code{global-mode-string}.
|
|
|
1274
|
|
|
1275 @table @code
|
|
|
1276 @item %m
|
|
|
1277 The value of @code{mode-name}.
|
|
|
1278
|
|
|
1279 @item %M
|
|
|
1280 The value of @code{global-mode-string}. Currently, only
|
|
|
1281 @code{display-time} modifies the value of @code{global-mode-string}.
|
|
|
1282 @end table
|
|
|
1283
|
|
|
1284 @node Hooks
|
|
|
1285 @section Hooks
|
|
|
1286 @cindex hooks
|
|
|
1287
|
|
|
1288 A @dfn{hook} is a variable where you can store a function or functions
|
|
|
1289 to be called on a particular occasion by an existing program. XEmacs
|
|
|
1290 provides hooks for the sake of customization. Most often, hooks are set
|
|
|
1291 up in the @file{.emacs} file, but Lisp programs can set them also.
|
|
|
1292 @xref{Standard Hooks}, for a list of standard hook variables.
|
|
|
1293
|
|
|
1294 Most of the hooks in XEmacs are @dfn{normal hooks}. These variables
|
|
|
1295 contain lists of functions to be called with no arguments. The reason
|
|
|
1296 most hooks are normal hooks is so that you can use them in a uniform
|
|
444
|
1297 way. You can usually tell when a hook is a normal hook, because its
|
|
428
|
1298 name ends in @samp{-hook}.
|
|
|
1299
|
|
|
1300 The recommended way to add a hook function to a normal hook is by
|
|
|
1301 calling @code{add-hook} (see below). The hook functions may be any of
|
|
|
1302 the valid kinds of functions that @code{funcall} accepts (@pxref{What Is
|
|
|
1303 a Function}). Most normal hook variables are initially void;
|
|
|
1304 @code{add-hook} knows how to deal with this.
|
|
|
1305
|
|
|
1306 As for abnormal hooks, those whose names end in @samp{-function} have
|
|
|
1307 a value that is a single function. Those whose names end in
|
|
|
1308 @samp{-hooks} have a value that is a list of functions. Any hook that
|
|
|
1309 is abnormal is abnormal because a normal hook won't do the job; either
|
|
|
1310 the functions are called with arguments, or their values are meaningful.
|
|
|
1311 The name shows you that the hook is abnormal and that you should look at
|
|
|
1312 its documentation string to see how to use it properly.
|
|
|
1313
|
|
|
1314 Major mode functions are supposed to run a hook called the @dfn{mode
|
|
|
1315 hook} as the last step of initialization. This makes it easy for a user
|
|
|
1316 to customize the behavior of the mode, by overriding the local variable
|
|
|
1317 assignments already made by the mode. But hooks are used in other
|
|
|
1318 contexts too. For example, the hook @code{suspend-hook} runs just
|
|
|
1319 before XEmacs suspends itself (@pxref{Suspending XEmacs}).
|
|
|
1320
|
|
|
1321 Here's an expression that uses a mode hook to turn on Auto Fill mode
|
|
|
1322 when in Lisp Interaction mode:
|
|
|
1323
|
|
|
1324 @example
|
|
|
1325 (add-hook 'lisp-interaction-mode-hook 'turn-on-auto-fill)
|
|
|
1326 @end example
|
|
|
1327
|
|
|
1328 The next example shows how to use a hook to customize the way XEmacs
|
|
|
1329 formats C code. (People often have strong personal preferences for one
|
|
|
1330 format or another.) Here the hook function is an anonymous lambda
|
|
|
1331 expression.
|
|
|
1332
|
|
|
1333 @cindex lambda expression in hook
|
|
|
1334 @example
|
|
|
1335 @group
|
|
444
|
1336 (add-hook 'c-mode-hook
|
|
428
|
1337 (function (lambda ()
|
|
|
1338 (setq c-indent-level 4
|
|
|
1339 c-argdecl-indent 0
|
|
|
1340 c-label-offset -4
|
|
|
1341 @end group
|
|
|
1342 @group
|
|
|
1343 c-continued-statement-indent 0
|
|
|
1344 c-brace-offset 0
|
|
|
1345 comment-column 40))))
|
|
|
1346
|
|
|
1347 (setq c++-mode-hook c-mode-hook)
|
|
|
1348 @end group
|
|
|
1349 @end example
|
|
|
1350
|
|
|
1351 The final example shows how the appearance of the modeline can be
|
|
|
1352 modified for a particular class of buffers only.
|
|
|
1353
|
|
|
1354 @example
|
|
|
1355 @group
|
|
|
1356 (add-hook 'text-mode-hook
|
|
|
1357 (function (lambda ()
|
|
|
1358 (setq modeline-format
|
|
|
1359 '(modeline-modified
|
|
|
1360 "Emacs: %14b"
|
|
444
|
1361 " "
|
|
428
|
1362 @end group
|
|
|
1363 @group
|
|
|
1364 default-directory
|
|
|
1365 " "
|
|
|
1366 global-mode-string
|
|
444
|
1367 "%[("
|
|
|
1368 mode-name
|
|
|
1369 minor-mode-alist
|
|
|
1370 "%n"
|
|
|
1371 modeline-process
|
|
428
|
1372 ") %]---"
|
|
|
1373 (-3 . "%p")
|
|
|
1374 "-%-")))))
|
|
|
1375 @end group
|
|
|
1376 @end example
|
|
|
1377
|
|
|
1378 At the appropriate time, XEmacs uses the @code{run-hooks} function to
|
|
|
1379 run particular hooks. This function calls the hook functions you have
|
|
|
1380 added with @code{add-hooks}.
|
|
|
1381
|
|
|
1382 @defun run-hooks &rest hookvar
|
|
|
1383 This function takes one or more hook variable names as arguments, and
|
|
|
1384 runs each hook in turn. Each @var{hookvar} argument should be a symbol
|
|
|
1385 that is a hook variable. These arguments are processed in the order
|
|
|
1386 specified.
|
|
|
1387
|
|
|
1388 If a hook variable has a non-@code{nil} value, that value may be a
|
|
|
1389 function or a list of functions. If the value is a function (either a
|
|
|
1390 lambda expression or a symbol with a function definition), it is
|
|
|
1391 called. If it is a list, the elements are called, in order.
|
|
|
1392 The hook functions are called with no arguments.
|
|
|
1393
|
|
|
1394 For example, here's how @code{emacs-lisp-mode} runs its mode hook:
|
|
|
1395
|
|
|
1396 @example
|
|
|
1397 (run-hooks 'emacs-lisp-mode-hook)
|
|
|
1398 @end example
|
|
|
1399 @end defun
|
|
|
1400
|
|
|
1401 @defun add-hook hook function &optional append local
|
|
|
1402 This function is the handy way to add function @var{function} to hook
|
|
|
1403 variable @var{hook}. The argument @var{function} may be any valid Lisp
|
|
|
1404 function with the proper number of arguments. For example,
|
|
|
1405
|
|
|
1406 @example
|
|
|
1407 (add-hook 'text-mode-hook 'my-text-hook-function)
|
|
|
1408 @end example
|
|
|
1409
|
|
|
1410 @noindent
|
|
|
1411 adds @code{my-text-hook-function} to the hook called @code{text-mode-hook}.
|
|
|
1412
|
|
|
1413 You can use @code{add-hook} for abnormal hooks as well as for normal
|
|
|
1414 hooks.
|
|
|
1415
|
|
|
1416 It is best to design your hook functions so that the order in which they
|
|
|
1417 are executed does not matter. Any dependence on the order is ``asking
|
|
|
1418 for trouble.'' However, the order is predictable: normally,
|
|
|
1419 @var{function} goes at the front of the hook list, so it will be
|
|
|
1420 executed first (barring another @code{add-hook} call).
|
|
|
1421
|
|
|
1422 If the optional argument @var{append} is non-@code{nil}, the new hook
|
|
|
1423 function goes at the end of the hook list and will be executed last.
|
|
|
1424
|
|
|
1425 If @var{local} is non-@code{nil}, that says to make the new hook
|
|
|
1426 function local to the current buffer. Before you can do this, you must
|
|
|
1427 make the hook itself buffer-local by calling @code{make-local-hook}
|
|
|
1428 (@strong{not} @code{make-local-variable}). If the hook itself is not
|
|
|
1429 buffer-local, then the value of @var{local} makes no difference---the
|
|
|
1430 hook function is always global.
|
|
|
1431 @end defun
|
|
|
1432
|
|
|
1433 @defun remove-hook hook function &optional local
|
|
|
1434 This function removes @var{function} from the hook variable @var{hook}.
|
|
|
1435
|
|
|
1436 If @var{local} is non-@code{nil}, that says to remove @var{function}
|
|
|
1437 from the local hook list instead of from the global hook list. If the
|
|
|
1438 hook itself is not buffer-local, then the value of @var{local} makes no
|
|
|
1439 difference.
|
|
|
1440 @end defun
|
|
|
1441
|
|
|
1442 @defun make-local-hook hook
|
|
444
|
1443 This function makes the hook variable @var{hook} local to the current
|
|
428
|
1444 buffer. When a hook variable is local, it can have local and global
|
|
|
1445 hook functions, and @code{run-hooks} runs all of them.
|
|
|
1446
|
|
|
1447 This function works by making @code{t} an element of the buffer-local
|
|
|
1448 value. That serves as a flag to use the hook functions in the default
|
|
|
1449 value of the hook variable as well as those in the local value. Since
|
|
|
1450 @code{run-hooks} understands this flag, @code{make-local-hook} works
|
|
|
1451 with all normal hooks. It works for only some non-normal hooks---those
|
|
|
1452 whose callers have been updated to understand this meaning of @code{t}.
|
|
|
1453
|
|
|
1454 Do not use @code{make-local-variable} directly for hook variables; it is
|
|
|
1455 not sufficient.
|
|
|
1456 @end defun
|
