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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
f8cecb20 | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2003 |
177c0ea7 | 4 | @c Free Software Foundation, Inc. |
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5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/modes | |
3ebe0346 | 7 | @node Modes, Documentation, Keymaps, Top |
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8 | @chapter Major and Minor Modes |
9 | @cindex mode | |
10 | ||
11 | A @dfn{mode} is a set of definitions that customize Emacs and can be | |
12 | turned on and off while you edit. There are two varieties of modes: | |
13 | @dfn{major modes}, which are mutually exclusive and used for editing | |
14 | particular kinds of text, and @dfn{minor modes}, which provide features | |
15 | that users can enable individually. | |
16 | ||
17 | This chapter describes how to write both major and minor modes, how to | |
18 | indicate them in the mode line, and how they run hooks supplied by the | |
19 | user. For related topics such as keymaps and syntax tables, see | |
20 | @ref{Keymaps}, and @ref{Syntax Tables}. | |
21 | ||
22 | @menu | |
23 | * Major Modes:: Defining major modes. | |
24 | * Minor Modes:: Defining minor modes. | |
25 | * Mode Line Format:: Customizing the text that appears in the mode line. | |
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26 | * Imenu:: How a mode can provide a menu |
27 | of definitions in the buffer. | |
28 | * Font Lock Mode:: How modes can highlight text according to syntax. | |
f730cc62 LH |
29 | * Desktop Save Mode:: How modes can have buffer state saved between |
30 | Emacs sessions. | |
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31 | * Hooks:: How to use hooks; how to write code that provides hooks. |
32 | @end menu | |
33 | ||
34 | @node Major Modes | |
35 | @section Major Modes | |
36 | @cindex major mode | |
37 | @cindex Fundamental mode | |
38 | ||
39 | Major modes specialize Emacs for editing particular kinds of text. | |
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40 | Each buffer has only one major mode at a time. For each major mode |
41 | there is a function to switch to that mode in the current buffer; its | |
42 | name should end in @samp{-mode}. These functions work by setting | |
43 | buffer-local variable bindings and other data associated with the | |
44 | buffer, such as a local keymap. The effect lasts until you switch | |
45 | to another major mode in the same buffer. | |
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46 | |
47 | The least specialized major mode is called @dfn{Fundamental mode}. | |
48 | This mode has no mode-specific definitions or variable settings, so each | |
49 | Emacs command behaves in its default manner, and each option is in its | |
50 | default state. All other major modes redefine various keys and options. | |
51 | For example, Lisp Interaction mode provides special key bindings for | |
969fe9b5 | 52 | @kbd{C-j} (@code{eval-print-last-sexp}), @key{TAB} |
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53 | (@code{lisp-indent-line}), and other keys. |
54 | ||
55 | When you need to write several editing commands to help you perform a | |
56 | specialized editing task, creating a new major mode is usually a good | |
57 | idea. In practice, writing a major mode is easy (in contrast to | |
58 | writing a minor mode, which is often difficult). | |
59 | ||
60 | If the new mode is similar to an old one, it is often unwise to modify | |
61 | the old one to serve two purposes, since it may become harder to use and | |
62 | maintain. Instead, copy and rename an existing major mode definition | |
63 | and alter the copy---or define a @dfn{derived mode} (@pxref{Derived | |
64 | Modes}). For example, Rmail Edit mode, which is in | |
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65 | @file{emacs/lisp/mail/rmailedit.el}, is a major mode that is very similar to |
66 | Text mode except that it provides two additional commands. Its | |
67 | definition is distinct from that of Text mode, but uses that of Text mode. | |
a44af9f2 | 68 | |
5858d11f | 69 | Even if the new mode is not an obvious derivative of any other mode, |
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70 | it is convenient to use @code{define-derived-mode} with a @code{nil} |
71 | parent argument, since it automatically enforces the most important | |
72 | coding conventions for you. | |
5858d11f | 73 | |
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74 | @findex define-generic-mode |
75 | For a very simple programming language major mode that handles | |
76 | comments and fontification, you can use @code{define-generic-mode} | |
77 | in @file{generic.el}. | |
78 | ||
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79 | Rmail Edit mode offers an example of changing the major mode |
80 | temporarily for a buffer, so it can be edited in a different way (with | |
1911e6e5 | 81 | ordinary Emacs commands rather than Rmail commands). In such cases, the |
8241495d | 82 | temporary major mode usually provides a command to switch back to the |
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83 | buffer's usual mode (Rmail mode, in this case). You might be tempted to |
84 | present the temporary redefinitions inside a recursive edit and restore | |
85 | the usual ones when the user exits; but this is a bad idea because it | |
86 | constrains the user's options when it is done in more than one buffer: | |
87 | recursive edits must be exited most-recently-entered first. Using an | |
88 | alternative major mode avoids this limitation. @xref{Recursive | |
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89 | Editing}. |
90 | ||
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91 | The standard GNU Emacs Lisp library directory tree contains the code |
92 | for several major modes, in files such as @file{text-mode.el}, | |
a44af9f2 | 93 | @file{texinfo.el}, @file{lisp-mode.el}, @file{c-mode.el}, and |
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94 | @file{rmail.el}. They are found in various subdirectories of the |
95 | @file{lisp} directory. You can study these libraries to see how modes | |
96 | are written. Text mode is perhaps the simplest major mode aside from | |
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97 | Fundamental mode. Rmail mode is a complicated and specialized mode. |
98 | ||
99 | @menu | |
100 | * Major Mode Conventions:: Coding conventions for keymaps, etc. | |
101 | * Example Major Modes:: Text mode and Lisp modes. | |
102 | * Auto Major Mode:: How Emacs chooses the major mode automatically. | |
103 | * Mode Help:: Finding out how to use a mode. | |
177c0ea7 | 104 | * Derived Modes:: Defining a new major mode based on another major |
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105 | mode. |
106 | @end menu | |
107 | ||
108 | @node Major Mode Conventions | |
109 | @subsection Major Mode Conventions | |
110 | ||
111 | The code for existing major modes follows various coding conventions, | |
112 | including conventions for local keymap and syntax table initialization, | |
113 | global names, and hooks. Please follow these conventions when you | |
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114 | define a new major mode. |
115 | ||
116 | This list of conventions is only partial, because each major mode | |
117 | should aim for consistency in general with other Emacs major modes. | |
118 | This makes Emacs as a whole more coherent. It is impossible to list | |
119 | here all the possible points where this issue might come up; if the | |
120 | Emacs developers point out an area where your major mode deviates from | |
121 | the usual conventions, please make it compatible. | |
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122 | |
123 | @itemize @bullet | |
124 | @item | |
125 | Define a command whose name ends in @samp{-mode}, with no arguments, | |
126 | that switches to the new mode in the current buffer. This command | |
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127 | should set up the keymap, syntax table, and buffer-local variables in an |
128 | existing buffer, without changing the buffer's contents. | |
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129 | |
130 | @item | |
de9f0bd9 | 131 | Write a documentation string for this command that describes the |
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132 | special commands available in this mode. @kbd{C-h m} |
133 | (@code{describe-mode}) in your mode will display this string. | |
134 | ||
135 | The documentation string may include the special documentation | |
136 | substrings, @samp{\[@var{command}]}, @samp{\@{@var{keymap}@}}, and | |
86494bd5 | 137 | @samp{\<@var{keymap}>}, which enable the documentation to adapt |
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138 | automatically to the user's own key bindings. @xref{Keys in |
139 | Documentation}. | |
140 | ||
141 | @item | |
142 | The major mode command should start by calling | |
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143 | @code{kill-all-local-variables}. This is what gets rid of the |
144 | buffer-local variables of the major mode previously in effect. | |
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145 | |
146 | @item | |
147 | The major mode command should set the variable @code{major-mode} to the | |
148 | major mode command symbol. This is how @code{describe-mode} discovers | |
149 | which documentation to print. | |
150 | ||
151 | @item | |
152 | The major mode command should set the variable @code{mode-name} to the | |
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153 | ``pretty'' name of the mode, as a string. This string appears in the |
154 | mode line. | |
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155 | |
156 | @item | |
157 | @cindex functions in modes | |
158 | Since all global names are in the same name space, all the global | |
159 | variables, constants, and functions that are part of the mode should | |
160 | have names that start with the major mode name (or with an abbreviation | |
a4b12c74 | 161 | of it if the name is long). @xref{Coding Conventions}. |
a44af9f2 | 162 | |
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163 | @item |
164 | In a major mode for editing some kind of structured text, such as a | |
165 | programming language, indentation of text according to structure is | |
166 | probably useful. So the mode should set @code{indent-line-function} | |
167 | to a suitable function, and probably customize other variables | |
168 | for indentation. | |
169 | ||
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170 | @item |
171 | @cindex keymaps in modes | |
172 | The major mode should usually have its own keymap, which is used as the | |
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173 | local keymap in all buffers in that mode. The major mode command should |
174 | call @code{use-local-map} to install this local map. @xref{Active | |
175 | Keymaps}, for more information. | |
a44af9f2 | 176 | |
969fe9b5 | 177 | This keymap should be stored permanently in a global variable named |
a44af9f2 | 178 | @code{@var{modename}-mode-map}. Normally the library that defines the |
de9f0bd9 | 179 | mode sets this variable. |
a44af9f2 | 180 | |
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181 | @xref{Tips for Defining}, for advice about how to write the code to set |
182 | up the mode's keymap variable. | |
183 | ||
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184 | @item |
185 | The key sequences bound in a major mode keymap should usually start with | |
969fe9b5 | 186 | @kbd{C-c}, followed by a control character, a digit, or @kbd{@{}, |
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187 | @kbd{@}}, @kbd{<}, @kbd{>}, @kbd{:} or @kbd{;}. The other punctuation |
188 | characters are reserved for minor modes, and ordinary letters are | |
189 | reserved for users. | |
190 | ||
191 | It is reasonable for a major mode to rebind a key sequence with a | |
192 | standard meaning, if it implements a command that does ``the same job'' | |
193 | in a way that fits the major mode better. For example, a major mode for | |
194 | editing a programming language might redefine @kbd{C-M-a} to ``move to | |
195 | the beginning of a function'' in a way that works better for that | |
196 | language. | |
197 | ||
198 | Major modes such as Dired or Rmail that do not allow self-insertion of | |
199 | text can reasonably redefine letters and other printing characters as | |
200 | editing commands. Dired and Rmail both do this. | |
201 | ||
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202 | @item |
203 | Major modes must not define @key{RET} to do anything other than insert | |
204 | a newline. The command to insert a newline and then indent is | |
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205 | @kbd{C-j}. Please keep this distinction uniform for all major modes. |
206 | ||
207 | @item | |
2a233172 | 208 | Major modes should not alter options that are primarily a matter of user |
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209 | preference, such as whether Auto-Fill mode is enabled. Leave this to |
210 | each user to decide. However, a major mode should customize other | |
211 | variables so that Auto-Fill mode will work usefully @emph{if} the user | |
212 | decides to use it. | |
c2e903c0 | 213 | |
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214 | @item |
215 | @cindex syntax tables in modes | |
216 | The mode may have its own syntax table or may share one with other | |
217 | related modes. If it has its own syntax table, it should store this in | |
de9f0bd9 | 218 | a variable named @code{@var{modename}-mode-syntax-table}. @xref{Syntax |
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219 | Tables}. |
220 | ||
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221 | @item |
222 | If the mode handles a language that has a syntax for comments, it should | |
223 | set the variables that define the comment syntax. @xref{Options for | |
224 | Comments,, Options Controlling Comments, emacs, The GNU Emacs Manual}. | |
225 | ||
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226 | @item |
227 | @cindex abbrev tables in modes | |
228 | The mode may have its own abbrev table or may share one with other | |
229 | related modes. If it has its own abbrev table, it should store this in | |
230 | a variable named @code{@var{modename}-mode-abbrev-table}. @xref{Abbrev | |
231 | Tables}. | |
232 | ||
be9345cf | 233 | @item |
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234 | The mode should specify how to do highlighting for Font Lock mode, by |
235 | setting up a buffer-local value for the variable | |
969fe9b5 | 236 | @code{font-lock-defaults} (@pxref{Font Lock Mode}). |
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237 | |
238 | @item | |
be9345cf RS |
239 | The mode should specify how Imenu should find the definitions or |
240 | sections of a buffer, by setting up a buffer-local value for the | |
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241 | variable @code{imenu-generic-expression}, for the pair of variables |
242 | @code{imenu-prev-index-position-function} and | |
243 | @code{imenu-extract-index-name-function}, or for the variable | |
969fe9b5 | 244 | @code{imenu-create-index-function} (@pxref{Imenu}). |
be9345cf | 245 | |
de9f0bd9 | 246 | @item |
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247 | Use @code{defvar} or @code{defcustom} to set mode-related variables, so |
248 | that they are not reinitialized if they already have a value. (Such | |
249 | reinitialization could discard customizations made by the user.) | |
de9f0bd9 | 250 | |
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251 | @item |
252 | @cindex buffer-local variables in modes | |
253 | To make a buffer-local binding for an Emacs customization variable, use | |
254 | @code{make-local-variable} in the major mode command, not | |
255 | @code{make-variable-buffer-local}. The latter function would make the | |
256 | variable local to every buffer in which it is subsequently set, which | |
257 | would affect buffers that do not use this mode. It is undesirable for a | |
258 | mode to have such global effects. @xref{Buffer-Local Variables}. | |
259 | ||
177c0ea7 | 260 | With rare exceptions, the only reasonable way to use |
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261 | @code{make-variable-buffer-local} in a Lisp package is for a variable |
262 | which is used only within that package. Using it on a variable used by | |
263 | other packages would interfere with them. | |
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264 | |
265 | @item | |
266 | @cindex mode hook | |
267 | @cindex major mode hook | |
268 | Each major mode should have a @dfn{mode hook} named | |
269 | @code{@var{modename}-mode-hook}. The major mode command should run that | |
fdba9ef4 | 270 | hook, with @code{run-mode-hooks}, as the very last thing it |
a4b12c74 | 271 | does. @xref{Hooks}. |
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272 | |
273 | @item | |
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274 | The major mode command may start by calling some other major mode |
275 | command (called the @dfn{parent mode}) and then alter some of its | |
276 | settings. A mode that does this is called a @dfn{derived mode}. The | |
277 | recommended way to define one is to use @code{define-derived-mode}, | |
278 | but this is not required. Such a mode should use | |
279 | @code{delay-mode-hooks} around its entire body, including the call to | |
280 | the parent mode command and the final call to @code{run-mode-hooks}. | |
06862374 | 281 | (Using @code{define-derived-mode} does this automatically.) |
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282 | |
283 | @item | |
284 | If something special should be done if the user switches a buffer from | |
f9f59935 | 285 | this mode to any other major mode, this mode can set up a buffer-local |
969fe9b5 | 286 | value for @code{change-major-mode-hook} (@pxref{Creating Buffer-Local}). |
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287 | |
288 | @item | |
289 | If this mode is appropriate only for specially-prepared text, then the | |
290 | major mode command symbol should have a property named @code{mode-class} | |
291 | with value @code{special}, put on as follows: | |
292 | ||
ace41f7d | 293 | @kindex mode-class @r{(property)} |
a44af9f2 RS |
294 | @cindex @code{special} |
295 | @example | |
296 | (put 'funny-mode 'mode-class 'special) | |
297 | @end example | |
298 | ||
299 | @noindent | |
8241495d | 300 | This tells Emacs that new buffers created while the current buffer is in |
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301 | Funny mode should not inherit Funny mode. Modes such as Dired, Rmail, |
302 | and Buffer List use this feature. | |
303 | ||
304 | @item | |
305 | If you want to make the new mode the default for files with certain | |
306 | recognizable names, add an element to @code{auto-mode-alist} to select | |
307 | the mode for those file names. If you define the mode command to | |
308 | autoload, you should add this element in the same file that calls | |
309 | @code{autoload}. Otherwise, it is sufficient to add the element in the | |
310 | file that contains the mode definition. @xref{Auto Major Mode}. | |
311 | ||
312 | @item | |
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313 | In the documentation, you should provide a sample @code{autoload} form |
314 | and an example of how to add to @code{auto-mode-alist}, that users can | |
a40d4712 | 315 | include in their init files (@pxref{Init File}). |
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316 | |
317 | @item | |
318 | @cindex mode loading | |
de9f0bd9 | 319 | The top-level forms in the file defining the mode should be written so |
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320 | that they may be evaluated more than once without adverse consequences. |
321 | Even if you never load the file more than once, someone else will. | |
322 | @end itemize | |
323 | ||
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324 | @node Example Major Modes |
325 | @subsection Major Mode Examples | |
326 | ||
327 | Text mode is perhaps the simplest mode besides Fundamental mode. | |
328 | Here are excerpts from @file{text-mode.el} that illustrate many of | |
329 | the conventions listed above: | |
330 | ||
331 | @smallexample | |
332 | @group | |
333 | ;; @r{Create mode-specific tables.} | |
177c0ea7 | 334 | (defvar text-mode-syntax-table nil |
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335 | "Syntax table used while in text mode.") |
336 | @end group | |
337 | ||
338 | @group | |
339 | (if text-mode-syntax-table | |
340 | () ; @r{Do not change the table if it is already set up.} | |
341 | (setq text-mode-syntax-table (make-syntax-table)) | |
342 | (modify-syntax-entry ?\" ". " text-mode-syntax-table) | |
343 | (modify-syntax-entry ?\\ ". " text-mode-syntax-table) | |
344 | (modify-syntax-entry ?' "w " text-mode-syntax-table)) | |
345 | @end group | |
346 | ||
347 | @group | |
348 | (defvar text-mode-abbrev-table nil | |
349 | "Abbrev table used while in text mode.") | |
350 | (define-abbrev-table 'text-mode-abbrev-table ()) | |
351 | @end group | |
352 | ||
353 | @group | |
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354 | (defvar text-mode-map nil ; @r{Create a mode-specific keymap.} |
355 | "Keymap for Text mode. | |
356 | Many other modes, such as Mail mode, Outline mode and Indented Text mode, | |
357 | inherit all the commands defined in this map.") | |
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358 | |
359 | (if text-mode-map | |
360 | () ; @r{Do not change the keymap if it is already set up.} | |
361 | (setq text-mode-map (make-sparse-keymap)) | |
a40d4712 | 362 | (define-key text-mode-map "\e\t" 'ispell-complete-word) |
a9f0a989 | 363 | (define-key text-mode-map "\t" 'indent-relative) |
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364 | (define-key text-mode-map "\es" 'center-line) |
365 | (define-key text-mode-map "\eS" 'center-paragraph)) | |
366 | @end group | |
367 | @end smallexample | |
368 | ||
fdba9ef4 | 369 | This was formerly the complete major mode function definition for Text mode: |
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370 | |
371 | @smallexample | |
372 | @group | |
373 | (defun text-mode () | |
29b677db | 374 | "Major mode for editing text intended for humans to read... |
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375 | Special commands: \\@{text-mode-map@} |
376 | @end group | |
377 | @group | |
378 | Turning on text-mode runs the hook `text-mode-hook'." | |
379 | (interactive) | |
380 | (kill-all-local-variables) | |
969fe9b5 | 381 | (use-local-map text-mode-map) |
a44af9f2 RS |
382 | @end group |
383 | @group | |
a44af9f2 RS |
384 | (setq local-abbrev-table text-mode-abbrev-table) |
385 | (set-syntax-table text-mode-syntax-table) | |
969fe9b5 RS |
386 | @end group |
387 | @group | |
388 | (make-local-variable 'paragraph-start) | |
389 | (setq paragraph-start (concat "[ \t]*$\\|" page-delimiter)) | |
390 | (make-local-variable 'paragraph-separate) | |
391 | (setq paragraph-separate paragraph-start) | |
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392 | (make-local-variable 'indent-line-function) |
393 | (setq indent-line-function 'indent-relative-maybe) | |
969fe9b5 RS |
394 | @end group |
395 | @group | |
396 | (setq mode-name "Text") | |
397 | (setq major-mode 'text-mode) | |
fdba9ef4 | 398 | (run-mode-hooks 'text-mode-hook)) ; @r{Finally, this permits the user to} |
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399 | ; @r{customize the mode with a hook.} |
400 | @end group | |
401 | @end smallexample | |
402 | ||
403 | @cindex @file{lisp-mode.el} | |
404 | The three Lisp modes (Lisp mode, Emacs Lisp mode, and Lisp | |
405 | Interaction mode) have more features than Text mode and the code is | |
406 | correspondingly more complicated. Here are excerpts from | |
407 | @file{lisp-mode.el} that illustrate how these modes are written. | |
408 | ||
409 | @cindex syntax table example | |
410 | @smallexample | |
411 | @group | |
412 | ;; @r{Create mode-specific table variables.} | |
177c0ea7 | 413 | (defvar lisp-mode-syntax-table nil "") |
a44af9f2 RS |
414 | (defvar emacs-lisp-mode-syntax-table nil "") |
415 | (defvar lisp-mode-abbrev-table nil "") | |
416 | @end group | |
417 | ||
418 | @group | |
419 | (if (not emacs-lisp-mode-syntax-table) ; @r{Do not change the table} | |
420 | ; @r{if it is already set.} | |
421 | (let ((i 0)) | |
422 | (setq emacs-lisp-mode-syntax-table (make-syntax-table)) | |
423 | @end group | |
424 | ||
425 | @group | |
426 | ;; @r{Set syntax of chars up to 0 to class of chars that are} | |
427 | ;; @r{part of symbol names but not words.} | |
ad800164 | 428 | ;; @r{(The number 0 is @code{48} in the @acronym{ASCII} character set.)} |
177c0ea7 | 429 | (while (< i ?0) |
a44af9f2 RS |
430 | (modify-syntax-entry i "_ " emacs-lisp-mode-syntax-table) |
431 | (setq i (1+ i))) | |
432 | @dots{} | |
433 | @end group | |
434 | @group | |
435 | ;; @r{Set the syntax for other characters.} | |
436 | (modify-syntax-entry ? " " emacs-lisp-mode-syntax-table) | |
437 | (modify-syntax-entry ?\t " " emacs-lisp-mode-syntax-table) | |
438 | @dots{} | |
439 | @end group | |
440 | @group | |
441 | (modify-syntax-entry ?\( "() " emacs-lisp-mode-syntax-table) | |
442 | (modify-syntax-entry ?\) ")( " emacs-lisp-mode-syntax-table) | |
443 | @dots{})) | |
444 | ;; @r{Create an abbrev table for lisp-mode.} | |
445 | (define-abbrev-table 'lisp-mode-abbrev-table ()) | |
446 | @end group | |
447 | @end smallexample | |
448 | ||
449 | Much code is shared among the three Lisp modes. The following | |
450 | function sets various variables; it is called by each of the major Lisp | |
451 | mode functions: | |
452 | ||
453 | @smallexample | |
454 | @group | |
455 | (defun lisp-mode-variables (lisp-syntax) | |
a44af9f2 | 456 | (cond (lisp-syntax |
969fe9b5 | 457 | (set-syntax-table lisp-mode-syntax-table))) |
a44af9f2 | 458 | (setq local-abbrev-table lisp-mode-abbrev-table) |
a9f0a989 | 459 | @dots{} |
a44af9f2 RS |
460 | @end group |
461 | @end smallexample | |
462 | ||
463 | Functions such as @code{forward-paragraph} use the value of the | |
464 | @code{paragraph-start} variable. Since Lisp code is different from | |
465 | ordinary text, the @code{paragraph-start} variable needs to be set | |
466 | specially to handle Lisp. Also, comments are indented in a special | |
467 | fashion in Lisp and the Lisp modes need their own mode-specific | |
468 | @code{comment-indent-function}. The code to set these variables is the | |
469 | rest of @code{lisp-mode-variables}. | |
470 | ||
471 | @smallexample | |
472 | @group | |
473 | (make-local-variable 'paragraph-start) | |
969fe9b5 RS |
474 | (setq paragraph-start (concat page-delimiter "\\|$" )) |
475 | (make-local-variable 'paragraph-separate) | |
476 | (setq paragraph-separate paragraph-start) | |
a44af9f2 RS |
477 | @dots{} |
478 | @end group | |
479 | @group | |
480 | (make-local-variable 'comment-indent-function) | |
481 | (setq comment-indent-function 'lisp-comment-indent)) | |
a40d4712 | 482 | @dots{} |
a44af9f2 RS |
483 | @end group |
484 | @end smallexample | |
485 | ||
486 | Each of the different Lisp modes has a slightly different keymap. For | |
f9f59935 | 487 | example, Lisp mode binds @kbd{C-c C-z} to @code{run-lisp}, but the other |
a44af9f2 | 488 | Lisp modes do not. However, all Lisp modes have some commands in |
969fe9b5 | 489 | common. The following code sets up the common commands: |
a44af9f2 RS |
490 | |
491 | @smallexample | |
492 | @group | |
969fe9b5 RS |
493 | (defvar shared-lisp-mode-map () |
494 | "Keymap for commands shared by all sorts of Lisp modes.") | |
495 | ||
496 | (if shared-lisp-mode-map | |
497 | () | |
498 | (setq shared-lisp-mode-map (make-sparse-keymap)) | |
499 | (define-key shared-lisp-mode-map "\e\C-q" 'indent-sexp) | |
500 | (define-key shared-lisp-mode-map "\177" | |
501 | 'backward-delete-char-untabify)) | |
a44af9f2 RS |
502 | @end group |
503 | @end smallexample | |
504 | ||
969fe9b5 RS |
505 | @noindent |
506 | And here is the code to set up the keymap for Lisp mode: | |
a44af9f2 RS |
507 | |
508 | @smallexample | |
509 | @group | |
969fe9b5 | 510 | (defvar lisp-mode-map () |
29b677db | 511 | "Keymap for ordinary Lisp mode...") |
969fe9b5 RS |
512 | |
513 | (if lisp-mode-map | |
a44af9f2 | 514 | () |
969fe9b5 RS |
515 | (setq lisp-mode-map (make-sparse-keymap)) |
516 | (set-keymap-parent lisp-mode-map shared-lisp-mode-map) | |
517 | (define-key lisp-mode-map "\e\C-x" 'lisp-eval-defun) | |
518 | (define-key lisp-mode-map "\C-c\C-z" 'run-lisp)) | |
a44af9f2 RS |
519 | @end group |
520 | @end smallexample | |
521 | ||
522 | Finally, here is the complete major mode function definition for | |
177c0ea7 | 523 | Lisp mode. |
a44af9f2 RS |
524 | |
525 | @smallexample | |
526 | @group | |
969fe9b5 RS |
527 | (defun lisp-mode () |
528 | "Major mode for editing Lisp code for Lisps other than GNU Emacs Lisp. | |
a44af9f2 RS |
529 | Commands: |
530 | Delete converts tabs to spaces as it moves back. | |
531 | Blank lines separate paragraphs. Semicolons start comments. | |
969fe9b5 RS |
532 | \\@{lisp-mode-map@} |
533 | Note that `run-lisp' may be used either to start an inferior Lisp job | |
534 | or to switch back to an existing one. | |
a44af9f2 | 535 | @end group |
969fe9b5 | 536 | |
a44af9f2 | 537 | @group |
969fe9b5 RS |
538 | Entry to this mode calls the value of `lisp-mode-hook' |
539 | if that value is non-nil." | |
a44af9f2 RS |
540 | (interactive) |
541 | (kill-all-local-variables) | |
a44af9f2 RS |
542 | @end group |
543 | @group | |
969fe9b5 RS |
544 | (use-local-map lisp-mode-map) ; @r{Select the mode's keymap.} |
545 | (setq major-mode 'lisp-mode) ; @r{This is how @code{describe-mode}} | |
a44af9f2 | 546 | ; @r{finds out what to describe.} |
969fe9b5 RS |
547 | (setq mode-name "Lisp") ; @r{This goes into the mode line.} |
548 | (lisp-mode-variables t) ; @r{This defines various variables.} | |
549 | @end group | |
550 | @group | |
551 | (setq imenu-case-fold-search t) | |
552 | (set-syntax-table lisp-mode-syntax-table) | |
fdba9ef4 | 553 | (run-mode-hooks 'lisp-mode-hook)) ; @r{This permits the user to use a} |
a44af9f2 RS |
554 | ; @r{hook to customize the mode.} |
555 | @end group | |
556 | @end smallexample | |
557 | ||
558 | @node Auto Major Mode | |
559 | @subsection How Emacs Chooses a Major Mode | |
560 | ||
561 | Based on information in the file name or in the file itself, Emacs | |
562 | automatically selects a major mode for the new buffer when a file is | |
969fe9b5 | 563 | visited. It also processes local variables specified in the file text. |
a44af9f2 RS |
564 | |
565 | @deffn Command fundamental-mode | |
566 | Fundamental mode is a major mode that is not specialized for anything | |
567 | in particular. Other major modes are defined in effect by comparison | |
568 | with this one---their definitions say what to change, starting from | |
569 | Fundamental mode. The @code{fundamental-mode} function does @emph{not} | |
570 | run any hooks; you're not supposed to customize it. (If you want Emacs | |
571 | to behave differently in Fundamental mode, change the @emph{global} | |
572 | state of Emacs.) | |
573 | @end deffn | |
574 | ||
575 | @deffn Command normal-mode &optional find-file | |
969fe9b5 | 576 | This function establishes the proper major mode and buffer-local variable |
a44af9f2 RS |
577 | bindings for the current buffer. First it calls @code{set-auto-mode}, |
578 | then it runs @code{hack-local-variables} to parse, and bind or | |
969fe9b5 | 579 | evaluate as appropriate, the file's local variables. |
a44af9f2 | 580 | |
969fe9b5 RS |
581 | If the @var{find-file} argument to @code{normal-mode} is non-@code{nil}, |
582 | @code{normal-mode} assumes that the @code{find-file} function is calling | |
583 | it. In this case, it may process a local variables list at the end of | |
584 | the file and in the @samp{-*-} line. The variable | |
585 | @code{enable-local-variables} controls whether to do so. @xref{File | |
586 | variables, , Local Variables in Files, emacs, The GNU Emacs Manual}, for | |
587 | the syntax of the local variables section of a file. | |
a44af9f2 | 588 | |
bfe721d1 | 589 | If you run @code{normal-mode} interactively, the argument |
a44af9f2 RS |
590 | @var{find-file} is normally @code{nil}. In this case, |
591 | @code{normal-mode} unconditionally processes any local variables list. | |
a44af9f2 RS |
592 | |
593 | @cindex file mode specification error | |
bfe721d1 | 594 | @code{normal-mode} uses @code{condition-case} around the call to the |
a44af9f2 RS |
595 | major mode function, so errors are caught and reported as a @samp{File |
596 | mode specification error}, followed by the original error message. | |
597 | @end deffn | |
598 | ||
a44af9f2 RS |
599 | @defun set-auto-mode |
600 | @cindex visited file mode | |
601 | This function selects the major mode that is appropriate for the | |
602 | current buffer. It may base its decision on the value of the @w{@samp{-*-}} | |
76352dc1 RS |
603 | line, on the visited file name (using @code{auto-mode-alist}), on the |
604 | @w{@samp{#!}} line (using @code{interpreter-mode-alist}), or on the | |
969fe9b5 | 605 | file's local variables list. However, this function does not look for |
a44af9f2 RS |
606 | the @samp{mode:} local variable near the end of a file; the |
607 | @code{hack-local-variables} function does that. @xref{Choosing Modes, , | |
608 | How Major Modes are Chosen, emacs, The GNU Emacs Manual}. | |
609 | @end defun | |
610 | ||
177c0ea7 | 611 | @defopt default-major-mode |
969fe9b5 | 612 | This variable holds the default major mode for new buffers. The |
a44af9f2 RS |
613 | standard value is @code{fundamental-mode}. |
614 | ||
969fe9b5 | 615 | If the value of @code{default-major-mode} is @code{nil}, Emacs uses |
a44af9f2 | 616 | the (previously) current buffer's major mode for the major mode of a new |
f9f59935 | 617 | buffer. However, if that major mode symbol has a @code{mode-class} |
a44af9f2 RS |
618 | property with value @code{special}, then it is not used for new buffers; |
619 | Fundamental mode is used instead. The modes that have this property are | |
620 | those such as Dired and Rmail that are useful only with text that has | |
621 | been specially prepared. | |
622 | @end defopt | |
623 | ||
22697dac KH |
624 | @defun set-buffer-major-mode buffer |
625 | This function sets the major mode of @var{buffer} to the value of | |
626 | @code{default-major-mode}. If that variable is @code{nil}, it uses | |
627 | the current buffer's major mode (if that is suitable). | |
628 | ||
629 | The low-level primitives for creating buffers do not use this function, | |
bfe721d1 KH |
630 | but medium-level commands such as @code{switch-to-buffer} and |
631 | @code{find-file-noselect} use it whenever they create buffers. | |
22697dac KH |
632 | @end defun |
633 | ||
a44af9f2 RS |
634 | @defvar initial-major-mode |
635 | @cindex @samp{*scratch*} | |
636 | The value of this variable determines the major mode of the initial | |
637 | @samp{*scratch*} buffer. The value should be a symbol that is a major | |
f9f59935 | 638 | mode command. The default value is @code{lisp-interaction-mode}. |
a44af9f2 RS |
639 | @end defvar |
640 | ||
641 | @defvar auto-mode-alist | |
642 | This variable contains an association list of file name patterns | |
643 | (regular expressions; @pxref{Regular Expressions}) and corresponding | |
f9f59935 RS |
644 | major mode commands. Usually, the file name patterns test for suffixes, |
645 | such as @samp{.el} and @samp{.c}, but this need not be the case. An | |
646 | ordinary element of the alist looks like @code{(@var{regexp} . | |
a44af9f2 RS |
647 | @var{mode-function})}. |
648 | ||
649 | For example, | |
650 | ||
651 | @smallexample | |
652 | @group | |
969fe9b5 | 653 | (("\\`/tmp/fol/" . text-mode) |
24675e99 RS |
654 | ("\\.texinfo\\'" . texinfo-mode) |
655 | ("\\.texi\\'" . texinfo-mode) | |
a44af9f2 RS |
656 | @end group |
657 | @group | |
24675e99 | 658 | ("\\.el\\'" . emacs-lisp-mode) |
177c0ea7 | 659 | ("\\.c\\'" . c-mode) |
24675e99 | 660 | ("\\.h\\'" . c-mode) |
a44af9f2 RS |
661 | @dots{}) |
662 | @end group | |
663 | @end smallexample | |
664 | ||
665 | When you visit a file whose expanded file name (@pxref{File Name | |
666 | Expansion}) matches a @var{regexp}, @code{set-auto-mode} calls the | |
667 | corresponding @var{mode-function}. This feature enables Emacs to select | |
668 | the proper major mode for most files. | |
669 | ||
670 | If an element of @code{auto-mode-alist} has the form @code{(@var{regexp} | |
671 | @var{function} t)}, then after calling @var{function}, Emacs searches | |
672 | @code{auto-mode-alist} again for a match against the portion of the file | |
969fe9b5 RS |
673 | name that did not match before. This feature is useful for |
674 | uncompression packages: an entry of the form @code{("\\.gz\\'" | |
675 | @var{function} t)} can uncompress the file and then put the uncompressed | |
676 | file in the proper mode according to the name sans @samp{.gz}. | |
a44af9f2 RS |
677 | |
678 | Here is an example of how to prepend several pattern pairs to | |
679 | @code{auto-mode-alist}. (You might use this sort of expression in your | |
a40d4712 | 680 | init file.) |
a44af9f2 RS |
681 | |
682 | @smallexample | |
683 | @group | |
684 | (setq auto-mode-alist | |
177c0ea7 | 685 | (append |
f9f59935 | 686 | ;; @r{File name (within directory) starts with a dot.} |
177c0ea7 | 687 | '(("/\\.[^/]*\\'" . fundamental-mode) |
de9f0bd9 | 688 | ;; @r{File name has no dot.} |
177c0ea7 | 689 | ("[^\\./]*\\'" . fundamental-mode) |
de9f0bd9 | 690 | ;; @r{File name ends in @samp{.C}.} |
24675e99 | 691 | ("\\.C\\'" . c++-mode)) |
a44af9f2 RS |
692 | auto-mode-alist)) |
693 | @end group | |
694 | @end smallexample | |
695 | @end defvar | |
696 | ||
697 | @defvar interpreter-mode-alist | |
f9f59935 | 698 | This variable specifies major modes to use for scripts that specify a |
86494bd5 | 699 | command interpreter in a @samp{#!} line. Its value is a list of |
a44af9f2 RS |
700 | elements of the form @code{(@var{interpreter} . @var{mode})}; for |
701 | example, @code{("perl" . perl-mode)} is one element present by default. | |
702 | The element says to use mode @var{mode} if the file specifies | |
f9f59935 RS |
703 | an interpreter which matches @var{interpreter}. The value of |
704 | @var{interpreter} is actually a regular expression. | |
a44af9f2 | 705 | |
de9f0bd9 RS |
706 | This variable is applicable only when the @code{auto-mode-alist} does |
707 | not indicate which major mode to use. | |
a44af9f2 RS |
708 | @end defvar |
709 | ||
a44af9f2 RS |
710 | @node Mode Help |
711 | @subsection Getting Help about a Major Mode | |
712 | @cindex mode help | |
713 | @cindex help for major mode | |
714 | @cindex documentation for major mode | |
715 | ||
716 | The @code{describe-mode} function is used to provide information | |
717 | about major modes. It is normally called with @kbd{C-h m}. The | |
718 | @code{describe-mode} function uses the value of @code{major-mode}, | |
719 | which is why every major mode function needs to set the | |
720 | @code{major-mode} variable. | |
721 | ||
722 | @deffn Command describe-mode | |
723 | This function displays the documentation of the current major mode. | |
724 | ||
725 | The @code{describe-mode} function calls the @code{documentation} | |
726 | function using the value of @code{major-mode} as an argument. Thus, it | |
727 | displays the documentation string of the major mode function. | |
728 | (@xref{Accessing Documentation}.) | |
729 | @end deffn | |
730 | ||
731 | @defvar major-mode | |
732 | This variable holds the symbol for the current buffer's major mode. | |
de9f0bd9 | 733 | This symbol should have a function definition that is the command to |
a44af9f2 | 734 | switch to that major mode. The @code{describe-mode} function uses the |
de9f0bd9 | 735 | documentation string of the function as the documentation of the major |
a44af9f2 RS |
736 | mode. |
737 | @end defvar | |
738 | ||
739 | @node Derived Modes | |
740 | @subsection Defining Derived Modes | |
741 | ||
742 | It's often useful to define a new major mode in terms of an existing | |
743 | one. An easy way to do this is to use @code{define-derived-mode}. | |
744 | ||
de9f0bd9 | 745 | @defmac define-derived-mode variant parent name docstring body@dots{} |
a44af9f2 | 746 | This construct defines @var{variant} as a major mode command, using |
de9f0bd9 | 747 | @var{name} as the string form of the mode name. |
a44af9f2 | 748 | |
de9f0bd9 RS |
749 | The new command @var{variant} is defined to call the function |
750 | @var{parent}, then override certain aspects of that parent mode: | |
a44af9f2 | 751 | |
177c0ea7 | 752 | @itemize @bullet |
a44af9f2 RS |
753 | @item |
754 | The new mode has its own keymap, named @code{@var{variant}-map}. | |
755 | @code{define-derived-mode} initializes this map to inherit from | |
756 | @code{@var{parent}-map}, if it is not already set. | |
757 | ||
758 | @item | |
de9f0bd9 | 759 | The new mode has its own syntax table, kept in the variable |
a44af9f2 | 760 | @code{@var{variant}-syntax-table}. |
177c0ea7 | 761 | @code{define-derived-mode} initializes this variable by copying |
a44af9f2 RS |
762 | @code{@var{parent}-syntax-table}, if it is not already set. |
763 | ||
764 | @item | |
de9f0bd9 | 765 | The new mode has its own abbrev table, kept in the variable |
a44af9f2 | 766 | @code{@var{variant}-abbrev-table}. |
177c0ea7 | 767 | @code{define-derived-mode} initializes this variable by copying |
a44af9f2 RS |
768 | @code{@var{parent}-abbrev-table}, if it is not already set. |
769 | ||
770 | @item | |
771 | The new mode has its own mode hook, @code{@var{variant}-hook}, | |
772 | which it runs in standard fashion as the very last thing that it does. | |
177c0ea7 | 773 | (The new mode also runs the mode hook of @var{parent} as part |
a44af9f2 RS |
774 | of calling @var{parent}.) |
775 | @end itemize | |
776 | ||
777 | In addition, you can specify how to override other aspects of | |
de9f0bd9 | 778 | @var{parent} with @var{body}. The command @var{variant} |
177c0ea7 | 779 | evaluates the forms in @var{body} after setting up all its usual |
a44af9f2 RS |
780 | overrides, just before running @code{@var{variant}-hook}. |
781 | ||
782 | The argument @var{docstring} specifies the documentation string for the | |
783 | new mode. If you omit @var{docstring}, @code{define-derived-mode} | |
784 | generates a documentation string. | |
785 | ||
786 | Here is a hypothetical example: | |
787 | ||
788 | @example | |
789 | (define-derived-mode hypertext-mode | |
790 | text-mode "Hypertext" | |
791 | "Major mode for hypertext. | |
792 | \\@{hypertext-mode-map@}" | |
793 | (setq case-fold-search nil)) | |
794 | ||
795 | (define-key hypertext-mode-map | |
796 | [down-mouse-3] 'do-hyper-link) | |
797 | @end example | |
f140458b RS |
798 | |
799 | Do not write an @code{interactive} spec in the definition; | |
800 | @code{define-derived-mode} does that automatically. | |
a44af9f2 RS |
801 | @end defmac |
802 | ||
803 | @node Minor Modes | |
804 | @section Minor Modes | |
805 | @cindex minor mode | |
806 | ||
807 | A @dfn{minor mode} provides features that users may enable or disable | |
808 | independently of the choice of major mode. Minor modes can be enabled | |
809 | individually or in combination. Minor modes would be better named | |
969fe9b5 RS |
810 | ``generally available, optional feature modes,'' except that such a name |
811 | would be unwieldy. | |
a44af9f2 | 812 | |
8241495d RS |
813 | A minor mode is not usually meant as a variation of a single major mode. |
814 | Usually they are general and can apply to many major modes. For | |
969fe9b5 | 815 | example, Auto Fill mode works with any major mode that permits text |
a44af9f2 RS |
816 | insertion. To be general, a minor mode must be effectively independent |
817 | of the things major modes do. | |
818 | ||
819 | A minor mode is often much more difficult to implement than a major | |
820 | mode. One reason is that you should be able to activate and deactivate | |
de9f0bd9 RS |
821 | minor modes in any order. A minor mode should be able to have its |
822 | desired effect regardless of the major mode and regardless of the other | |
823 | minor modes in effect. | |
a44af9f2 RS |
824 | |
825 | Often the biggest problem in implementing a minor mode is finding a | |
826 | way to insert the necessary hook into the rest of Emacs. Minor mode | |
bfe721d1 | 827 | keymaps make this easier than it used to be. |
a44af9f2 | 828 | |
fdba9ef4 RS |
829 | @defvar minor-mode-list |
830 | The value of this variable is a list of all minor mode commands. | |
831 | @end defvar | |
832 | ||
a44af9f2 RS |
833 | @menu |
834 | * Minor Mode Conventions:: Tips for writing a minor mode. | |
835 | * Keymaps and Minor Modes:: How a minor mode can have its own keymap. | |
2468d0c0 | 836 | * Defining Minor Modes:: A convenient facility for defining minor modes. |
a44af9f2 RS |
837 | @end menu |
838 | ||
839 | @node Minor Mode Conventions | |
840 | @subsection Conventions for Writing Minor Modes | |
841 | @cindex minor mode conventions | |
842 | @cindex conventions for writing minor modes | |
843 | ||
844 | There are conventions for writing minor modes just as there are for | |
845 | major modes. Several of the major mode conventions apply to minor | |
846 | modes as well: those regarding the name of the mode initialization | |
847 | function, the names of global symbols, and the use of keymaps and | |
848 | other tables. | |
849 | ||
850 | In addition, there are several conventions that are specific to | |
851 | minor modes. | |
852 | ||
853 | @itemize @bullet | |
854 | @item | |
855 | @cindex mode variable | |
969fe9b5 RS |
856 | Make a variable whose name ends in @samp{-mode} to control the minor |
857 | mode. We call this the @dfn{mode variable}. The minor mode command | |
858 | should set this variable (@code{nil} to disable; anything else to | |
1911e6e5 | 859 | enable). |
969fe9b5 | 860 | |
8241495d | 861 | If possible, implement the mode so that setting the variable |
969fe9b5 | 862 | automatically enables or disables the mode. Then the minor mode command |
1911e6e5 | 863 | does not need to do anything except set the variable. |
a44af9f2 RS |
864 | |
865 | This variable is used in conjunction with the @code{minor-mode-alist} to | |
866 | display the minor mode name in the mode line. It can also enable | |
867 | or disable a minor mode keymap. Individual commands or hooks can also | |
868 | check the variable's value. | |
869 | ||
870 | If you want the minor mode to be enabled separately in each buffer, | |
871 | make the variable buffer-local. | |
872 | ||
873 | @item | |
874 | Define a command whose name is the same as the mode variable. | |
875 | Its job is to enable and disable the mode by setting the variable. | |
876 | ||
877 | The command should accept one optional argument. If the argument is | |
8cd4f018 RS |
878 | @code{nil}, it should toggle the mode (turn it on if it is off, and |
879 | off if it is on). It should turn the mode on if the argument is a | |
880 | positive integer, the symbol @code{t}, or a list whose @sc{car} is one | |
881 | of those. It should turn the mode off if the argument is a negative | |
882 | integer or zero, the symbol @code{-}, or a list whose @sc{car} is one | |
883 | of those. The meaning of other arguments is not specified. | |
a44af9f2 | 884 | |
bfe721d1 KH |
885 | Here is an example taken from the definition of @code{transient-mark-mode}. |
886 | It shows the use of @code{transient-mark-mode} as a variable that enables or | |
de9f0bd9 RS |
887 | disables the mode's behavior, and also shows the proper way to toggle, |
888 | enable or disable the minor mode based on the raw prefix argument value. | |
a44af9f2 RS |
889 | |
890 | @smallexample | |
891 | @group | |
bfe721d1 KH |
892 | (setq transient-mark-mode |
893 | (if (null arg) (not transient-mark-mode) | |
a44af9f2 RS |
894 | (> (prefix-numeric-value arg) 0))) |
895 | @end group | |
896 | @end smallexample | |
897 | ||
898 | @item | |
899 | Add an element to @code{minor-mode-alist} for each minor mode | |
969fe9b5 RS |
900 | (@pxref{Mode Line Variables}), if you want to indicate the minor mode in |
901 | the mode line. This element should be a list of the following form: | |
a44af9f2 RS |
902 | |
903 | @smallexample | |
904 | (@var{mode-variable} @var{string}) | |
905 | @end smallexample | |
906 | ||
de9f0bd9 | 907 | Here @var{mode-variable} is the variable that controls enabling of the |
a44af9f2 RS |
908 | minor mode, and @var{string} is a short string, starting with a space, |
909 | to represent the mode in the mode line. These strings must be short so | |
910 | that there is room for several of them at once. | |
911 | ||
912 | When you add an element to @code{minor-mode-alist}, use @code{assq} to | |
913 | check for an existing element, to avoid duplication. For example: | |
914 | ||
915 | @smallexample | |
916 | @group | |
a40d4712 PR |
917 | (unless (assq 'leif-mode minor-mode-alist) |
918 | (setq minor-mode-alist | |
919 | (cons '(leif-mode " Leif") minor-mode-alist))) | |
a44af9f2 RS |
920 | @end group |
921 | @end smallexample | |
a44af9f2 | 922 | |
a40d4712 PR |
923 | @noindent |
924 | or like this, using @code{add-to-list} (@pxref{Setting Variables}): | |
925 | ||
926 | @smallexample | |
927 | @group | |
928 | (add-to-list 'minor-mode-alist '(leif-mode " Leif")) | |
929 | @end group | |
930 | @end smallexample | |
931 | @end itemize | |
1911e6e5 | 932 | |
8241495d RS |
933 | Global minor modes distributed with Emacs should if possible support |
934 | enabling and disabling via Custom (@pxref{Customization}). To do this, | |
935 | the first step is to define the mode variable with @code{defcustom}, and | |
936 | specify @code{:type boolean}. | |
937 | ||
938 | If just setting the variable is not sufficient to enable the mode, you | |
939 | should also specify a @code{:set} method which enables the mode by | |
940 | invoke the mode command. Note in the variable's documentation string that | |
941 | setting the variable other than via Custom may not take effect. | |
942 | ||
943 | Also mark the definition with an autoload cookie (@pxref{Autoload}), | |
944 | and specify a @code{:require} so that customizing the variable will load | |
945 | the library that defines the mode. This will copy suitable definitions | |
946 | into @file{loaddefs.el} so that users can use @code{customize-option} to | |
947 | enable the mode. For example: | |
948 | ||
949 | @smallexample | |
950 | @group | |
951 | ||
952 | ;;;###autoload | |
953 | (defcustom msb-mode nil | |
954 | "Toggle msb-mode. | |
955 | Setting this variable directly does not take effect; | |
956 | use either \\[customize] or the function `msb-mode'." | |
957 | :set (lambda (symbol value) | |
958 | (msb-mode (or value 0))) | |
959 | :initialize 'custom-initialize-default | |
960 | :version "20.4" | |
961 | :type 'boolean | |
962 | :group 'msb | |
963 | :require 'msb) | |
964 | @end group | |
965 | @end smallexample | |
966 | ||
a44af9f2 RS |
967 | @node Keymaps and Minor Modes |
968 | @subsection Keymaps and Minor Modes | |
969 | ||
bfe721d1 KH |
970 | Each minor mode can have its own keymap, which is active when the mode |
971 | is enabled. To set up a keymap for a minor mode, add an element to the | |
972 | alist @code{minor-mode-map-alist}. @xref{Active Keymaps}. | |
a44af9f2 RS |
973 | |
974 | @cindex @code{self-insert-command}, minor modes | |
f9f59935 | 975 | One use of minor mode keymaps is to modify the behavior of certain |
a44af9f2 RS |
976 | self-inserting characters so that they do something else as well as |
977 | self-insert. In general, this is the only way to do that, since the | |
978 | facilities for customizing @code{self-insert-command} are limited to | |
979 | special cases (designed for abbrevs and Auto Fill mode). (Do not try | |
980 | substituting your own definition of @code{self-insert-command} for the | |
981 | standard one. The editor command loop handles this function specially.) | |
982 | ||
a4b12c74 RS |
983 | The key sequences bound in a minor mode should consist of @kbd{C-c} |
984 | followed by a punctuation character @emph{other than} @kbd{@{}, | |
8241495d | 985 | @kbd{@}}, @kbd{<}, @kbd{>}, @kbd{:}, and @kbd{;}. (Those few punctuation |
a4b12c74 RS |
986 | characters are reserved for major modes.) |
987 | ||
2468d0c0 DL |
988 | @node Defining Minor Modes |
989 | @subsection Defining Minor Modes | |
f9f59935 | 990 | |
2468d0c0 DL |
991 | The macro @code{define-minor-mode} offers a convenient way of |
992 | implementing a mode in one self-contained definition. It supports only | |
8241495d | 993 | buffer-local minor modes, not global ones. |
f9f59935 | 994 | |
fdba9ef4 | 995 | @defmac define-minor-mode mode doc [init-value [lighter [keymap keyword-args... body...]]] |
2468d0c0 | 996 | @tindex define-minor-mode |
fdba9ef4 RS |
997 | This macro defines a new minor mode whose name is @var{mode} (a |
998 | symbol). It defines a command named @var{mode} to toggle the minor | |
2468d0c0 DL |
999 | mode, with @var{doc} as its documentation string. It also defines a |
1000 | variable named @var{mode}, which is set to @code{t} or @code{nil} by | |
1001 | enabling or disabling the mode. The variable is initialized to | |
1002 | @var{init-value}. | |
f9f59935 | 1003 | |
fdba9ef4 | 1004 | The string @var{lighter} says what to display in the mode line |
f9f59935 RS |
1005 | when the mode is enabled; if it is @code{nil}, the mode is not displayed |
1006 | in the mode line. | |
1007 | ||
1008 | The optional argument @var{keymap} specifies the keymap for the minor mode. | |
1009 | It can be a variable name, whose value is the keymap, or it can be an alist | |
1010 | specifying bindings in this form: | |
1011 | ||
1012 | @example | |
1013 | (@var{key-sequence} . @var{definition}) | |
1014 | @end example | |
fdba9ef4 RS |
1015 | |
1016 | The @var{keyword-args} consist of keywords followed by corresponding | |
1017 | values. A few keywords have special meanings: | |
1018 | ||
1019 | @table @code | |
1020 | @item :global @var{global} | |
1021 | If non-@code{nil} specifies that the minor mode should be global. | |
1022 | By default, minor modes are buffer-local. | |
1023 | ||
1024 | @item :init-value @var{init-value} | |
1025 | This is equivalent to specifying @var{init-value} positionally. | |
1026 | ||
1027 | @item :lighter @var{lighter} | |
1028 | This is equivalent to specifying @var{lighter} positionally. | |
1029 | ||
1030 | @item :keymap @var{keymap} | |
1031 | This is equivalent to specifying @var{keymap} positionally. | |
1032 | @end table | |
1033 | ||
1034 | Any other keyword arguments are passed passed directly to the | |
1035 | @code{defcustom} generated for the variable @var{mode}. | |
1036 | ||
1037 | The command named @var{mode} finishes by executing the @var{body} forms, | |
1038 | if any, after it has performed the standard actions such as setting | |
1039 | the variable named @var{mode}. | |
f9f59935 RS |
1040 | @end defmac |
1041 | ||
fdba9ef4 RS |
1042 | @findex easy-mmode-define-minor-mode |
1043 | The name @code{easy-mmode-define-minor-mode} is an alias | |
1044 | for this macro. | |
1045 | ||
2468d0c0 | 1046 | Here is an example of using @code{define-minor-mode}: |
f9f59935 RS |
1047 | |
1048 | @smallexample | |
2468d0c0 | 1049 | (define-minor-mode hungry-mode |
969fe9b5 | 1050 | "Toggle Hungry mode. |
177c0ea7 | 1051 | With no argument, this command toggles the mode. |
f9f59935 RS |
1052 | Non-null prefix argument turns on the mode. |
1053 | Null prefix argument turns off the mode. | |
1054 | ||
1055 | When Hungry mode is enabled, the control delete key | |
1056 | gobbles all preceding whitespace except the last. | |
1057 | See the command \\[hungry-electric-delete]." | |
1058 | ;; The initial value. | |
1059 | nil | |
1060 | ;; The indicator for the mode line. | |
1061 | " Hungry" | |
1062 | ;; The minor mode bindings. | |
1063 | '(("\C-\^?" . hungry-electric-delete) | |
1064 | ("\C-\M-\^?" | |
177c0ea7 | 1065 | . (lambda () |
f9f59935 | 1066 | (interactive) |
fdba9ef4 RS |
1067 | (hungry-electric-delete t)))) |
1068 | :group 'hunger) | |
f9f59935 RS |
1069 | @end smallexample |
1070 | ||
1071 | @noindent | |
1072 | This defines a minor mode named ``Hungry mode'', a command named | |
1073 | @code{hungry-mode} to toggle it, a variable named @code{hungry-mode} | |
1074 | which indicates whether the mode is enabled, and a variable named | |
1075 | @code{hungry-mode-map} which holds the keymap that is active when the | |
1076 | mode is enabled. It initializes the keymap with key bindings for | |
fdba9ef4 RS |
1077 | @kbd{C-@key{DEL}} and @kbd{C-M-@key{DEL}}. It puts the variable |
1078 | @code{hungry-mode} into custom group @code{hunger}. There are no | |
1079 | @var{body} forms---many minor modes don't need any. | |
f9f59935 | 1080 | |
fdba9ef4 | 1081 | Here's an equivalent way to write it: |
2468d0c0 | 1082 | |
fdba9ef4 RS |
1083 | @smallexample |
1084 | (define-minor-mode hungry-mode | |
1085 | "Toggle Hungry mode. | |
1086 | With no argument, this command toggles the mode. | |
1087 | Non-null prefix argument turns on the mode. | |
1088 | Null prefix argument turns off the mode. | |
1089 | ||
1090 | When Hungry mode is enabled, the control delete key | |
1091 | gobbles all preceding whitespace except the last. | |
1092 | See the command \\[hungry-electric-delete]." | |
1093 | ;; The initial value. | |
1094 | :initial-value nil | |
1095 | ;; The indicator for the mode line. | |
1096 | :lighter " Hungry" | |
1097 | ;; The minor mode bindings. | |
1098 | :keymap | |
1099 | '(("\C-\^?" . hungry-electric-delete) | |
1100 | ("\C-\M-\^?" | |
1101 | . (lambda () | |
1102 | (interactive) | |
1103 | (hungry-electric-delete t)))) | |
1104 | :group 'hunger) | |
1105 | @end smallexample | |
2468d0c0 | 1106 | |
a44af9f2 | 1107 | @node Mode Line Format |
06862374 | 1108 | @section Mode-Line Format |
a44af9f2 RS |
1109 | @cindex mode line |
1110 | ||
8241495d RS |
1111 | Each Emacs window (aside from minibuffer windows) typically has a mode |
1112 | line at the bottom, which displays status information about the buffer | |
1113 | displayed in the window. The mode line contains information about the | |
1114 | buffer, such as its name, associated file, depth of recursive editing, | |
1115 | and major and minor modes. A window can also have a @dfn{header | |
1116 | line}, which is much like the mode line but appears at the top of the | |
1117 | window (starting in Emacs 21). | |
a44af9f2 | 1118 | |
8241495d RS |
1119 | This section describes how to control the contents of the mode line |
1120 | and header line. We include it in this chapter because much of the | |
a44af9f2 RS |
1121 | information displayed in the mode line relates to the enabled major and |
1122 | minor modes. | |
1123 | ||
1124 | @code{mode-line-format} is a buffer-local variable that holds a | |
1125 | template used to display the mode line of the current buffer. All | |
8241495d RS |
1126 | windows for the same buffer use the same @code{mode-line-format}, so |
1127 | their mode lines appear the same---except for scrolling percentages, and | |
1128 | line and column numbers, since those depend on point and on how the | |
1129 | window is scrolled. @code{header-line-format} is used likewise for | |
1130 | header lines. | |
1131 | ||
8e0f7b5b RS |
1132 | For efficiency, Emacs does not recompute the mode line and header |
1133 | line of a window in every redisplay. It does so when circumstances | |
1134 | appear to call for it---for instance, if you change the window | |
1135 | configuration, switch buffers, narrow or widen the buffer, scroll, or | |
1136 | change the buffer's modification status. If you modify any of the | |
1137 | variables referenced by @code{mode-line-format} (@pxref{Mode Line | |
1138 | Variables}), or any other variables and data structures that affect | |
1139 | how text is displayed (@pxref{Display}), you may want to force an | |
1140 | update of the mode line so as to display the new information or | |
1141 | display it in the new way. | |
a44af9f2 RS |
1142 | |
1143 | @c Emacs 19 feature | |
0ad8cce8 | 1144 | @defun force-mode-line-update &optional all |
8241495d | 1145 | Force redisplay of the current buffer's mode line and header line. |
8e0f7b5b | 1146 | The next redisplay will update the mode line and header line based on |
0ad8cce8 LK |
1147 | the latest values of all relevant variables. With optional |
1148 | non-@code{nil} @var{all}, force redisplay of all mode lines and header | |
1149 | lines. | |
8e0f7b5b RS |
1150 | |
1151 | This function also forces recomputation of the menu bar menus | |
1152 | and the frame title. | |
a44af9f2 RS |
1153 | @end defun |
1154 | ||
1155 | The mode line is usually displayed in inverse video; see | |
1156 | @code{mode-line-inverse-video} in @ref{Inverse Video}. | |
1157 | ||
a1112b37 RS |
1158 | A window that is just one line tall does not display either a mode |
1159 | line or a header line, even if the variables call for one. A window | |
1160 | that is two lines tall cannot display both a mode line and a header | |
1161 | line at once; if the variables call for both, only the mode line | |
1162 | actually appears. | |
1163 | ||
a44af9f2 RS |
1164 | @menu |
1165 | * Mode Line Data:: The data structure that controls the mode line. | |
1166 | * Mode Line Variables:: Variables used in that data structure. | |
1167 | * %-Constructs:: Putting information into a mode line. | |
8241495d RS |
1168 | * Properties in Mode:: Using text properties in the mode line. |
1169 | * Header Lines:: Like a mode line, but at the top. | |
3ebe0346 | 1170 | * Emulating Mode Line:: Formatting text as the mode line would. |
a44af9f2 RS |
1171 | @end menu |
1172 | ||
1173 | @node Mode Line Data | |
1174 | @subsection The Data Structure of the Mode Line | |
06862374 | 1175 | @cindex mode-line construct |
a44af9f2 | 1176 | |
06862374 | 1177 | The mode-line contents are controlled by a data structure of lists, |
a40d4712 | 1178 | strings, symbols, and numbers kept in buffer-local variables. The data |
06862374 LK |
1179 | structure is called a @dfn{mode-line construct}, and it is built in |
1180 | recursive fashion out of simpler mode-line constructs. The same data | |
a40d4712 PR |
1181 | structure is used for constructing frame titles (@pxref{Frame Titles}) |
1182 | and header lines (@pxref{Header Lines}). | |
a44af9f2 RS |
1183 | |
1184 | @defvar mode-line-format | |
06862374 LK |
1185 | The value of this variable is a mode-line construct with overall |
1186 | responsibility for the mode-line format. The value of this variable | |
1187 | controls which other variables are used to form the mode-line text, and | |
a44af9f2 | 1188 | where they appear. |
8241495d RS |
1189 | |
1190 | If you set this variable to @code{nil} in a buffer, that buffer does not | |
1191 | have a mode line. (This feature was added in Emacs 21.) | |
a44af9f2 RS |
1192 | @end defvar |
1193 | ||
06862374 | 1194 | A mode-line construct may be as simple as a fixed string of text, but |
a44af9f2 | 1195 | it usually specifies how to use other variables to construct the text. |
06862374 | 1196 | Many of these variables are themselves defined to have mode-line |
a44af9f2 RS |
1197 | constructs as their values. |
1198 | ||
1199 | The default value of @code{mode-line-format} incorporates the values | |
06862374 LK |
1200 | of variables such as @code{mode-line-position} and |
1201 | @code{mode-line-modes} (which in turn incorporates the values of the | |
1202 | variables @code{mode-name} and @code{minor-mode-alist}). Because of | |
1203 | this, very few modes need to alter @code{mode-line-format} itself. For | |
1204 | most purposes, it is sufficient to alter some of the variables that | |
1205 | @code{mode-line-format} either directly or indirectly refers to. | |
1206 | ||
1207 | A mode-line construct may be a list, a symbol, or a string. If the | |
de9f0bd9 | 1208 | value is a list, each element may be a list, a symbol, or a string. |
a44af9f2 | 1209 | |
8241495d RS |
1210 | The mode line can display various faces, if the strings that control |
1211 | it have the @code{face} property. @xref{Properties in Mode}. In | |
1212 | addition, the face @code{mode-line} is used as a default for the whole | |
1213 | mode line (@pxref{Standard Faces}). | |
1214 | ||
a44af9f2 RS |
1215 | @table @code |
1216 | @cindex percent symbol in mode line | |
1217 | @item @var{string} | |
06862374 | 1218 | A string as a mode-line construct is displayed verbatim in the mode line |
bfe721d1 | 1219 | except for @dfn{@code{%}-constructs}. Decimal digits after the @samp{%} |
a44af9f2 RS |
1220 | specify the field width for space filling on the right (i.e., the data |
1221 | is left justified). @xref{%-Constructs}. | |
1222 | ||
1223 | @item @var{symbol} | |
06862374 LK |
1224 | A symbol as a mode-line construct stands for its value. The value of |
1225 | @var{symbol} is used as a mode-line construct, in place of @var{symbol}. | |
8241495d | 1226 | However, the symbols @code{t} and @code{nil} are ignored, as is any |
de9f0bd9 | 1227 | symbol whose value is void. |
a44af9f2 RS |
1228 | |
1229 | There is one exception: if the value of @var{symbol} is a string, it is | |
de9f0bd9 | 1230 | displayed verbatim: the @code{%}-constructs are not recognized. |
a44af9f2 | 1231 | |
a232a240 LK |
1232 | Unless @var{symbol} is marked as ``risky'' (i.e., it has a |
1233 | non-@code{nil} @code{risky-local-variable} property), all properties in | |
1234 | any strings, as well as all @code{:eval} and @code{:propertize} forms in | |
1235 | the value of that symbol will be ignored. | |
1236 | ||
a44af9f2 | 1237 | @item (@var{string} @var{rest}@dots{}) @r{or} (@var{list} @var{rest}@dots{}) |
de9f0bd9 RS |
1238 | A list whose first element is a string or list means to process all the |
1239 | elements recursively and concatenate the results. This is the most | |
06862374 | 1240 | common form of mode-line construct. |
a44af9f2 | 1241 | |
8241495d RS |
1242 | @item (:eval @var{form}) |
1243 | A list whose first element is the symbol @code{:eval} says to evaluate | |
1244 | @var{form}, and use the result as a string to display. | |
1245 | (This feature is new as of Emacs 21.) | |
1246 | ||
06862374 LK |
1247 | @item (:propertize @var{elt} @var{props}@dots{}) |
1248 | A list whose first element is the symbol @code{:propertize} says to | |
1249 | process the mode-line construct @var{elt} recursively and add the text | |
1250 | properties specified by @var{props} to the result. The argument | |
1251 | @var{props} should consist of zero or more pairs @var{text-property} | |
1252 | @var{value}. (This feature is new as of Emacs 21.4.) | |
1253 | @c FIXME: This might be Emacs 21.5. | |
1254 | ||
a44af9f2 | 1255 | @item (@var{symbol} @var{then} @var{else}) |
8241495d RS |
1256 | A list whose first element is a symbol that is not a keyword specifies a |
1257 | conditional. Its meaning depends on the value of @var{symbol}. If the | |
1258 | value is non-@code{nil}, the second element, @var{then}, is processed | |
06862374 | 1259 | recursively as a mode-line element. But if the value of @var{symbol} is |
8241495d | 1260 | @code{nil}, the third element, @var{else}, is processed recursively. |
06862374 | 1261 | You may omit @var{else}; then the mode-line element displays nothing if |
8241495d | 1262 | the value of @var{symbol} is @code{nil}. |
a44af9f2 RS |
1263 | |
1264 | @item (@var{width} @var{rest}@dots{}) | |
1265 | A list whose first element is an integer specifies truncation or | |
1266 | padding of the results of @var{rest}. The remaining elements | |
06862374 | 1267 | @var{rest} are processed recursively as mode-line constructs and |
a44af9f2 RS |
1268 | concatenated together. Then the result is space filled (if |
1269 | @var{width} is positive) or truncated (to @minus{}@var{width} columns, | |
1270 | if @var{width} is negative) on the right. | |
1271 | ||
1272 | For example, the usual way to show what percentage of a buffer is above | |
de9f0bd9 | 1273 | the top of the window is to use a list like this: @code{(-3 "%p")}. |
a44af9f2 RS |
1274 | @end table |
1275 | ||
1276 | If you do alter @code{mode-line-format} itself, the new value should | |
de9f0bd9 RS |
1277 | use the same variables that appear in the default value (@pxref{Mode |
1278 | Line Variables}), rather than duplicating their contents or displaying | |
1279 | the information in another fashion. This way, customizations made by | |
bfe721d1 KH |
1280 | the user or by Lisp programs (such as @code{display-time} and major |
1281 | modes) via changes to those variables remain effective. | |
a44af9f2 RS |
1282 | |
1283 | @cindex Shell mode @code{mode-line-format} | |
1284 | Here is an example of a @code{mode-line-format} that might be | |
969fe9b5 | 1285 | useful for @code{shell-mode}, since it contains the host name and default |
a44af9f2 RS |
1286 | directory. |
1287 | ||
1288 | @example | |
1289 | @group | |
1290 | (setq mode-line-format | |
969fe9b5 RS |
1291 | (list "-" |
1292 | 'mode-line-mule-info | |
a44af9f2 | 1293 | 'mode-line-modified |
969fe9b5 | 1294 | 'mode-line-frame-identification |
177c0ea7 | 1295 | "%b--" |
a44af9f2 | 1296 | @end group |
f9f59935 RS |
1297 | @group |
1298 | ;; @r{Note that this is evaluated while making the list.} | |
06862374 | 1299 | ;; @r{It makes a mode-line construct which is just a string.} |
f9f59935 RS |
1300 | (getenv "HOST") |
1301 | @end group | |
177c0ea7 | 1302 | ":" |
a44af9f2 RS |
1303 | 'default-directory |
1304 | " " | |
1305 | 'global-mode-string | |
de9f0bd9 | 1306 | " %[(" |
8241495d | 1307 | '(:eval (mode-line-mode-name)) |
177c0ea7 JB |
1308 | 'mode-line-process |
1309 | 'minor-mode-alist | |
1310 | "%n" | |
969fe9b5 | 1311 | ")%]--" |
a44af9f2 | 1312 | @group |
969fe9b5 | 1313 | '(which-func-mode ("" which-func-format "--")) |
bfe721d1 | 1314 | '(line-number-mode "L%l--") |
969fe9b5 | 1315 | '(column-number-mode "C%c--") |
a232a240 | 1316 | '(-3 "%p") |
a44af9f2 RS |
1317 | "-%-")) |
1318 | @end group | |
1319 | @end example | |
1320 | ||
1911e6e5 RS |
1321 | @noindent |
1322 | (The variables @code{line-number-mode}, @code{column-number-mode} | |
1323 | and @code{which-func-mode} enable particular minor modes; as usual, | |
1324 | these variable names are also the minor mode command names.) | |
1325 | ||
a44af9f2 RS |
1326 | @node Mode Line Variables |
1327 | @subsection Variables Used in the Mode Line | |
1328 | ||
1329 | This section describes variables incorporated by the | |
1330 | standard value of @code{mode-line-format} into the text of the mode | |
1331 | line. There is nothing inherently special about these variables; any | |
1332 | other variables could have the same effects on the mode line if | |
1333 | @code{mode-line-format} were changed to use them. | |
1334 | ||
969fe9b5 RS |
1335 | @defvar mode-line-mule-info |
1336 | This variable holds the value of the mode-line construct that displays | |
1337 | information about the language environment, buffer coding system, and | |
a9f0a989 | 1338 | current input method. @xref{Non-ASCII Characters}. |
969fe9b5 RS |
1339 | @end defvar |
1340 | ||
a44af9f2 | 1341 | @defvar mode-line-modified |
de9f0bd9 | 1342 | This variable holds the value of the mode-line construct that displays |
a44af9f2 RS |
1343 | whether the current buffer is modified. |
1344 | ||
969fe9b5 RS |
1345 | The default value of @code{mode-line-modified} is @code{("%1*%1+")}. |
1346 | This means that the mode line displays @samp{**} if the buffer is | |
1347 | modified, @samp{--} if the buffer is not modified, @samp{%%} if the | |
1348 | buffer is read only, and @samp{%*} if the buffer is read only and | |
1349 | modified. | |
a44af9f2 RS |
1350 | |
1351 | Changing this variable does not force an update of the mode line. | |
1352 | @end defvar | |
1353 | ||
969fe9b5 RS |
1354 | @defvar mode-line-frame-identification |
1355 | This variable identifies the current frame. The default value is | |
06862374 LK |
1356 | @code{" "} if you are using a window system which can show multiple |
1357 | frames, or @code{"-%F "} on an ordinary terminal which shows only one | |
969fe9b5 RS |
1358 | frame at a time. |
1359 | @end defvar | |
1360 | ||
a44af9f2 | 1361 | @defvar mode-line-buffer-identification |
de9f0bd9 | 1362 | This variable identifies the buffer being displayed in the window. Its |
ebc6903b RS |
1363 | default value is @code{("%12b")}, which displays the buffer name, padded |
1364 | with spaces to at least 12 columns. | |
a44af9f2 RS |
1365 | @end defvar |
1366 | ||
06862374 LK |
1367 | @defvar mode-line-position |
1368 | This variable indicates the position in the buffer. Here is a | |
1369 | simplified version of its default value. The actual default value | |
1370 | also specifies addition of the @code{help-echo} text property. | |
a44af9f2 | 1371 | |
06862374 LK |
1372 | @example |
1373 | @group | |
a232a240 | 1374 | ((-3 "%p") |
06862374 LK |
1375 | (size-indication-mode (8 " of %I")) |
1376 | @end group | |
1377 | @group | |
1378 | (line-number-mode | |
1379 | ((column-number-mode | |
1380 | (10 " (%l,%c)") | |
1381 | (6 " L%l"))) | |
1382 | ((column-number-mode | |
1383 | (5 " C%c"))))) | |
1384 | @end group | |
1385 | @end example | |
1386 | ||
1387 | This means that @code{mode-line-position} displays at least the buffer | |
1388 | percentage and possibly the buffer size, the line number and the column | |
1389 | number. | |
1390 | @end defvar | |
1391 | ||
1392 | @defvar vc-mode | |
1393 | The variable @code{vc-mode}, buffer-local in each buffer, records | |
1394 | whether the buffer's visited file is maintained with version control, | |
1395 | and, if so, which kind. Its value is a string that appears in the mode | |
1396 | line, or @code{nil} for no version control. | |
a44af9f2 RS |
1397 | @end defvar |
1398 | ||
06862374 LK |
1399 | @defvar mode-line-modes |
1400 | This variable displays the buffer's major and minor modes. Here is a | |
1401 | simplified version of its default value. The real default value also | |
1402 | specifies addition of text properties. | |
1403 | ||
1404 | @example | |
1405 | @group | |
1406 | ("%[(" mode-name | |
1407 | mode-line-process minor-mode-alist | |
1408 | "%n" ")%]--") | |
1409 | @end group | |
1410 | @end example | |
1411 | ||
1412 | So @code{mode-line-modes} normally also displays the recursive editing | |
1413 | level, information on the process status and whether narrowing is in | |
1414 | effect. | |
1415 | @end defvar | |
1416 | ||
1417 | The following three variables are used in @code{mode-line-modes}: | |
1418 | ||
a44af9f2 | 1419 | @defvar mode-name |
de9f0bd9 | 1420 | This buffer-local variable holds the ``pretty'' name of the current |
a44af9f2 RS |
1421 | buffer's major mode. Each major mode should set this variable so that the |
1422 | mode name will appear in the mode line. | |
1423 | @end defvar | |
1424 | ||
06862374 LK |
1425 | @defvar mode-line-process |
1426 | This buffer-local variable contains the mode-line information on process | |
1427 | status in modes used for communicating with subprocesses. It is | |
1428 | displayed immediately following the major mode name, with no intervening | |
1429 | space. For example, its value in the @samp{*shell*} buffer is | |
1430 | @code{(":%s")}, which allows the shell to display its status along | |
1431 | with the major mode as: @samp{(Shell:run)}. Normally this variable | |
1432 | is @code{nil}. | |
1433 | @end defvar | |
1434 | ||
a44af9f2 | 1435 | @defvar minor-mode-alist |
de9f0bd9 | 1436 | This variable holds an association list whose elements specify how the |
a44af9f2 RS |
1437 | mode line should indicate that a minor mode is active. Each element of |
1438 | the @code{minor-mode-alist} should be a two-element list: | |
1439 | ||
1440 | @example | |
1441 | (@var{minor-mode-variable} @var{mode-line-string}) | |
1442 | @end example | |
1443 | ||
06862374 LK |
1444 | More generally, @var{mode-line-string} can be any mode-line spec. It |
1445 | appears in the mode line when the value of @var{minor-mode-variable} | |
1446 | is non-@code{nil}, and not otherwise. These strings should begin with | |
a44af9f2 | 1447 | spaces so that they don't run together. Conventionally, the |
06862374 LK |
1448 | @var{minor-mode-variable} for a specific mode is set to a |
1449 | non-@code{nil} value when that minor mode is activated. | |
a44af9f2 | 1450 | |
f9f59935 RS |
1451 | @code{minor-mode-alist} itself is not buffer-local. Each variable |
1452 | mentioned in the alist should be buffer-local if its minor mode can be | |
1453 | enabled separately in each buffer. | |
a44af9f2 RS |
1454 | @end defvar |
1455 | ||
06862374 | 1456 | @defvar global-mode-string |
1074a881 JB |
1457 | This variable holds a mode-line spec that, by default, appears in the |
1458 | mode line just after the @code{which-func-mode} minor mode if set, | |
1459 | else after @code{mode-line-modes}. The command @code{display-time} | |
06862374 | 1460 | sets @code{global-mode-string} to refer to the variable |
1074a881 JB |
1461 | @code{display-time-string}, which holds a string containing the time |
1462 | and load information. | |
a40d4712 | 1463 | |
06862374 LK |
1464 | The @samp{%M} construct substitutes the value of |
1465 | @code{global-mode-string}, but that is obsolete, since the variable is | |
1466 | included in the mode line from @code{mode-line-format}. | |
a40d4712 PR |
1467 | @end defvar |
1468 | ||
1469 | The variable @code{default-mode-line-format} is where | |
1470 | @code{mode-line-format} usually gets its value: | |
1471 | ||
a44af9f2 | 1472 | @defvar default-mode-line-format |
de9f0bd9 | 1473 | This variable holds the default @code{mode-line-format} for buffers |
a44af9f2 RS |
1474 | that do not override it. This is the same as @code{(default-value |
1475 | 'mode-line-format)}. | |
1476 | ||
06862374 LK |
1477 | Here is a simplified version of the default value of |
1478 | @code{default-mode-line-format}. The real default value also | |
1479 | specifies addition of text properties. | |
a44af9f2 RS |
1480 | |
1481 | @example | |
1482 | @group | |
f9f59935 RS |
1483 | ("-" |
1484 | mode-line-mule-info | |
a44af9f2 | 1485 | mode-line-modified |
f9f59935 | 1486 | mode-line-frame-identification |
a44af9f2 | 1487 | mode-line-buffer-identification |
f9f59935 | 1488 | @end group |
a44af9f2 | 1489 | " " |
06862374 LK |
1490 | mode-line-position |
1491 | (vc-mode vc-mode) | |
1492 | " " | |
f9f59935 | 1493 | @group |
06862374 | 1494 | mode-line-modes |
f9f59935 | 1495 | (which-func-mode ("" which-func-format "--")) |
06862374 | 1496 | (global-mode-string ("--" global-mode-string)) |
a44af9f2 RS |
1497 | "-%-") |
1498 | @end group | |
1499 | @end example | |
1500 | @end defvar | |
1501 | ||
1502 | @node %-Constructs | |
1503 | @subsection @code{%}-Constructs in the Mode Line | |
1504 | ||
1505 | The following table lists the recognized @code{%}-constructs and what | |
de9f0bd9 RS |
1506 | they mean. In any construct except @samp{%%}, you can add a decimal |
1507 | integer after the @samp{%} to specify how many characters to display. | |
a44af9f2 RS |
1508 | |
1509 | @table @code | |
1510 | @item %b | |
1511 | The current buffer name, obtained with the @code{buffer-name} function. | |
1512 | @xref{Buffer Names}. | |
1513 | ||
a40d4712 PR |
1514 | @item %c |
1515 | The current column number of point. | |
1516 | ||
a44af9f2 RS |
1517 | @item %f |
1518 | The visited file name, obtained with the @code{buffer-file-name} | |
1519 | function. @xref{Buffer File Name}. | |
1520 | ||
22697dac | 1521 | @item %F |
969fe9b5 RS |
1522 | The title (only on a window system) or the name of the selected frame. |
1523 | @xref{Window Frame Parameters}. | |
22697dac | 1524 | |
08622028 LK |
1525 | @item %i |
1526 | The size of the accessible part of the current buffer; basically | |
1527 | @code{(- (point-max) (point-min))}. | |
1528 | ||
1529 | @item %I | |
1530 | Like @samp{%i}, but the size is printed in a more readable way by using | |
1531 | @samp{k} for 10^3, @samp{M} for 10^6, @samp{G} for 10^9, etc., to | |
1532 | abbreviate. | |
1533 | ||
22697dac | 1534 | @item %l |
8241495d RS |
1535 | The current line number of point, counting within the accessible portion |
1536 | of the buffer. | |
22697dac | 1537 | |
a40d4712 PR |
1538 | @item %n |
1539 | @samp{Narrow} when narrowing is in effect; nothing otherwise (see | |
1540 | @code{narrow-to-region} in @ref{Narrowing}). | |
1541 | ||
1542 | @item %p | |
1543 | The percentage of the buffer text above the @strong{top} of window, or | |
1544 | @samp{Top}, @samp{Bottom} or @samp{All}. Note that the default | |
1545 | mode-line specification truncates this to three characters. | |
1546 | ||
1547 | @item %P | |
1548 | The percentage of the buffer text that is above the @strong{bottom} of | |
1549 | the window (which includes the text visible in the window, as well as | |
1550 | the text above the top), plus @samp{Top} if the top of the buffer is | |
1551 | visible on screen; or @samp{Bottom} or @samp{All}. | |
1552 | ||
1553 | @item %s | |
1554 | The status of the subprocess belonging to the current buffer, obtained with | |
1555 | @code{process-status}. @xref{Process Information}. | |
1556 | ||
1557 | @item %t | |
1558 | Whether the visited file is a text file or a binary file. This is a | |
1559 | meaningful distinction only on certain operating systems (@pxref{MS-DOS | |
1560 | File Types}). | |
1561 | ||
a44af9f2 RS |
1562 | @item %* |
1563 | @samp{%} if the buffer is read only (see @code{buffer-read-only}); @* | |
1564 | @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @* | |
1565 | @samp{-} otherwise. @xref{Buffer Modification}. | |
1566 | ||
1567 | @item %+ | |
22697dac KH |
1568 | @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @* |
1569 | @samp{%} if the buffer is read only (see @code{buffer-read-only}); @* | |
1570 | @samp{-} otherwise. This differs from @samp{%*} only for a modified | |
1571 | read-only buffer. @xref{Buffer Modification}. | |
1572 | ||
1573 | @item %& | |
de9f0bd9 | 1574 | @samp{*} if the buffer is modified, and @samp{-} otherwise. |
a44af9f2 | 1575 | |
a44af9f2 RS |
1576 | @item %[ |
1577 | An indication of the depth of recursive editing levels (not counting | |
1578 | minibuffer levels): one @samp{[} for each editing level. | |
1579 | @xref{Recursive Editing}. | |
1580 | ||
1581 | @item %] | |
1582 | One @samp{]} for each recursive editing level (not counting minibuffer | |
1583 | levels). | |
1584 | ||
a40d4712 PR |
1585 | @item %- |
1586 | Dashes sufficient to fill the remainder of the mode line. | |
1587 | ||
a44af9f2 RS |
1588 | @item %% |
1589 | The character @samp{%}---this is how to include a literal @samp{%} in a | |
1590 | string in which @code{%}-constructs are allowed. | |
a44af9f2 RS |
1591 | @end table |
1592 | ||
1593 | The following two @code{%}-constructs are still supported, but they are | |
1594 | obsolete, since you can get the same results with the variables | |
1595 | @code{mode-name} and @code{global-mode-string}. | |
1596 | ||
1597 | @table @code | |
1598 | @item %m | |
1599 | The value of @code{mode-name}. | |
1600 | ||
1601 | @item %M | |
1602 | The value of @code{global-mode-string}. Currently, only | |
1603 | @code{display-time} modifies the value of @code{global-mode-string}. | |
1604 | @end table | |
1605 | ||
8241495d RS |
1606 | @node Properties in Mode |
1607 | @subsection Properties in the Mode Line | |
06862374 | 1608 | @cindex text properties in the mode line |
8241495d RS |
1609 | |
1610 | Starting in Emacs 21, certain text properties are meaningful in the | |
1611 | mode line. The @code{face} property affects the appearance of text; the | |
1612 | @code{help-echo} property associate help strings with the text, and | |
ce75fd23 | 1613 | @code{local-map} can make the text mouse-sensitive. |
8241495d | 1614 | |
06862374 | 1615 | There are four ways to specify text properties for text in the mode |
8241495d RS |
1616 | line: |
1617 | ||
1618 | @enumerate | |
1619 | @item | |
06862374 LK |
1620 | Put a string with a text property directly into the mode-line data |
1621 | structure. | |
1622 | ||
1623 | @item | |
1624 | Put a text property on a mode-line %-construct such as @samp{%12b}; then | |
1625 | the expansion of the %-construct will have that same text property. | |
8241495d RS |
1626 | |
1627 | @item | |
06862374 LK |
1628 | Use a @code{(:propertize @var{elt} @var{props}@dots{})} construct to |
1629 | give @var{elt} a text property specified by @var{props}. | |
8241495d RS |
1630 | |
1631 | @item | |
1632 | Use a list containing @code{:eval @var{form}} in the mode-line data | |
06862374 LK |
1633 | structure, and make @var{form} evaluate to a string that has a text |
1634 | property. | |
8241495d RS |
1635 | @end enumerate |
1636 | ||
ce75fd23 | 1637 | You use the @code{local-map} property to specify a keymap. Like any |
8241495d | 1638 | keymap, it can bind character keys and function keys; but that has no |
a40d4712 | 1639 | effect, since it is impossible to move point into the mode line. This |
8241495d RS |
1640 | keymap can only take real effect for mouse clicks. |
1641 | ||
1642 | @node Header Lines | |
1643 | @subsection Window Header Lines | |
1644 | @cindex header line (of a window) | |
1645 | @cindex window header line | |
1646 | ||
1647 | Starting in Emacs 21, a window can have a @dfn{header line} at the | |
1648 | top, just as it can have a mode line at the bottom. The header line | |
06862374 | 1649 | feature works just like the mode-line feature, except that it's |
8241495d RS |
1650 | controlled by different variables. |
1651 | ||
1652 | @tindex header-line-format | |
1653 | @defvar header-line-format | |
1654 | This variable, local in every buffer, specifies how to display the | |
1655 | header line, for windows displaying the buffer. The format of the value | |
13ede7fc | 1656 | is the same as for @code{mode-line-format} (@pxref{Mode Line Data}). |
8241495d RS |
1657 | @end defvar |
1658 | ||
1659 | @tindex default-header-line-format | |
1660 | @defvar default-header-line-format | |
1661 | This variable holds the default @code{header-line-format} for buffers | |
1662 | that do not override it. This is the same as @code{(default-value | |
1663 | 'header-line-format)}. | |
1664 | ||
1665 | It is normally @code{nil}, so that ordinary buffers have no header line. | |
1666 | @end defvar | |
1667 | ||
bda7c6dd | 1668 | @node Emulating Mode Line |
06862374 | 1669 | @subsection Emulating Mode-Line Formatting |
bda7c6dd RS |
1670 | |
1671 | You can use the function @code{format-mode-line} to compute | |
1672 | the text that would appear in a mode line or header line | |
06862374 | 1673 | based on certain mode-line specification. |
bda7c6dd RS |
1674 | |
1675 | @defun format-mode-line &optional format window no-props | |
1676 | This function formats a line of text according to @var{format} as if | |
1677 | it were generating the mode line for @var{window}, but instead of | |
1678 | displaying the text in the mode line or the header line, it returns | |
1679 | the text as a string. | |
1680 | ||
1681 | If @var{format} is @code{nil}, that means to use | |
1682 | @code{mode-line-format} and return the text that would appear in the | |
1683 | mode line. If @var{format} is @code{t}, that means to use | |
1684 | @code{header-line-format} so as to return the text that would appear | |
1685 | in the header line (@code{""} if the window has no header line). | |
1686 | The argument @var{window} defaults to the selected window. | |
1687 | ||
1688 | The value string normally has text properties that correspond to the | |
1689 | faces, keymaps, etc., that the mode line would have. If | |
1690 | @var{no-props} is non-@code{nil}, the value has no text properties. | |
1691 | @end defun | |
1692 | ||
f9f59935 RS |
1693 | @node Imenu |
1694 | @section Imenu | |
1695 | ||
1696 | @cindex Imenu | |
969fe9b5 RS |
1697 | @dfn{Imenu} is a feature that lets users select a definition or |
1698 | section in the buffer, from a menu which lists all of them, to go | |
5a5d2aec RS |
1699 | directly to that location in the buffer. Imenu works by constructing |
1700 | a buffer index which lists the names and buffer positions of the | |
a40d4712 | 1701 | definitions, or other named portions of the buffer; then the user can |
5a5d2aec RS |
1702 | choose one of them and move point to it. The user-level commands for |
1703 | using Imenu are described in the Emacs Manual (@pxref{Imenu,, Imenu, | |
1704 | emacs, the Emacs Manual}). This section explains how to customize | |
1705 | Imenu's method of finding definitions or buffer portions for a | |
a40d4712 | 1706 | particular major mode. |
969fe9b5 RS |
1707 | |
1708 | The usual and simplest way is to set the variable | |
1709 | @code{imenu-generic-expression}: | |
f9f59935 RS |
1710 | |
1711 | @defvar imenu-generic-expression | |
10ee4e90 LK |
1712 | This variable, if non-@code{nil}, is a list that specifies regular |
1713 | expressions for finding definitions for Imenu. Simple elements of | |
1714 | @code{imenu-generic-expression} look like this: | |
f9f59935 RS |
1715 | |
1716 | @example | |
10ee4e90 | 1717 | (@var{menu-title} @var{regexp} @var{index}) |
f9f59935 RS |
1718 | @end example |
1719 | ||
1720 | Here, if @var{menu-title} is non-@code{nil}, it says that the matches | |
1721 | for this element should go in a submenu of the buffer index; | |
1722 | @var{menu-title} itself specifies the name for the submenu. If | |
1723 | @var{menu-title} is @code{nil}, the matches for this element go directly | |
1724 | in the top level of the buffer index. | |
1725 | ||
1726 | The second item in the list, @var{regexp}, is a regular expression | |
10ee4e90 LK |
1727 | (@pxref{Regular Expressions}); anything in the buffer that it matches |
1728 | is considered a definition, something to mention in the buffer index. | |
1729 | The third item, @var{index}, is a non-negative integer that indicates | |
1730 | which subexpression in @var{regexp} matches the definition's name. | |
f9f59935 RS |
1731 | |
1732 | An element can also look like this: | |
1733 | ||
1734 | @example | |
1735 | (@var{menu-title} @var{regexp} @var{index} @var{function} @var{arguments}@dots{}) | |
1736 | @end example | |
1737 | ||
10ee4e90 LK |
1738 | Like in the previous case, each match for this element creates an |
1739 | index item. However, if this index item is selected by the user, it | |
1740 | calls @var{function} with arguments consisting of the item name, the | |
1741 | buffer position, and @var{arguments}. | |
f9f59935 | 1742 | |
10ee4e90 LK |
1743 | For Emacs Lisp mode, @code{imenu-generic-expression} could look like |
1744 | this: | |
f9f59935 | 1745 | |
a9f0a989 | 1746 | @c should probably use imenu-syntax-alist and \\sw rather than [-A-Za-z0-9+] |
f9f59935 RS |
1747 | @example |
1748 | @group | |
1749 | ((nil "^\\s-*(def\\(un\\|subst\\|macro\\|advice\\)\ | |
1750 | \\s-+\\([-A-Za-z0-9+]+\\)" 2) | |
1751 | @end group | |
1752 | @group | |
1753 | ("*Vars*" "^\\s-*(def\\(var\\|const\\)\ | |
1754 | \\s-+\\([-A-Za-z0-9+]+\\)" 2) | |
1755 | @end group | |
1756 | @group | |
1757 | ("*Types*" | |
a9f0a989 RS |
1758 | "^\\s-*\ |
1759 | (def\\(type\\|struct\\|class\\|ine-condition\\)\ | |
f9f59935 RS |
1760 | \\s-+\\([-A-Za-z0-9+]+\\)" 2)) |
1761 | @end group | |
1762 | @end example | |
1763 | ||
969fe9b5 | 1764 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
1765 | @end defvar |
1766 | ||
1767 | @defvar imenu-case-fold-search | |
10ee4e90 LK |
1768 | This variable controls whether matching against the regular |
1769 | expressions in the value of @code{imenu-generic-expression} is | |
1770 | case-sensitive: @code{t}, the default, means matching should ignore | |
1771 | case. | |
a9f0a989 RS |
1772 | |
1773 | Setting this variable makes it buffer-local in the current buffer. | |
1774 | @end defvar | |
1775 | ||
1776 | @defvar imenu-syntax-alist | |
1777 | This variable is an alist of syntax table modifiers to use while | |
1911e6e5 RS |
1778 | processing @code{imenu-generic-expression}, to override the syntax table |
1779 | of the current buffer. Each element should have this form: | |
a9f0a989 RS |
1780 | |
1781 | @example | |
1782 | (@var{characters} . @var{syntax-description}) | |
1783 | @end example | |
1784 | ||
1785 | The @sc{car}, @var{characters}, can be either a character or a string. | |
1786 | The element says to give that character or characters the syntax | |
1787 | specified by @var{syntax-description}, which is passed to | |
1788 | @code{modify-syntax-entry} (@pxref{Syntax Table Functions}). | |
1789 | ||
1790 | This feature is typically used to give word syntax to characters which | |
1791 | normally have symbol syntax, and thus to simplify | |
1792 | @code{imenu-generic-expression} and speed up matching. | |
1793 | For example, Fortran mode uses it this way: | |
1794 | ||
1795 | @example | |
5a5d2aec | 1796 | (setq imenu-syntax-alist '(("_$" . "w"))) |
a9f0a989 RS |
1797 | @end example |
1798 | ||
10ee4e90 LK |
1799 | The @code{imenu-generic-expression} regular expressions can then use |
1800 | @samp{\\sw+} instead of @samp{\\(\\sw\\|\\s_\\)+}. Note that this | |
1801 | technique may be inconvenient when the mode needs to limit the initial | |
1802 | character of a name to a smaller set of characters than are allowed in | |
1803 | the rest of a name. | |
f9f59935 | 1804 | |
969fe9b5 | 1805 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
1806 | @end defvar |
1807 | ||
1808 | Another way to customize Imenu for a major mode is to set the | |
1809 | variables @code{imenu-prev-index-position-function} and | |
969fe9b5 | 1810 | @code{imenu-extract-index-name-function}: |
f9f59935 RS |
1811 | |
1812 | @defvar imenu-prev-index-position-function | |
05aea714 | 1813 | If this variable is non-@code{nil}, its value should be a function that |
a40d4712 PR |
1814 | finds the next ``definition'' to put in the buffer index, scanning |
1815 | backward in the buffer from point. It should return @code{nil} if it | |
5fe3b9bc | 1816 | doesn't find another ``definition'' before point. Otherwise it should |
a40d4712 PR |
1817 | leave point at the place it finds a ``definition,'' and return any |
1818 | non-@code{nil} value. | |
f9f59935 | 1819 | |
969fe9b5 | 1820 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
1821 | @end defvar |
1822 | ||
1823 | @defvar imenu-extract-index-name-function | |
1824 | If this variable is non-@code{nil}, its value should be a function to | |
969fe9b5 RS |
1825 | return the name for a definition, assuming point is in that definition |
1826 | as the @code{imenu-prev-index-position-function} function would leave | |
1827 | it. | |
f9f59935 | 1828 | |
969fe9b5 | 1829 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
1830 | @end defvar |
1831 | ||
969fe9b5 | 1832 | The last way to customize Imenu for a major mode is to set the |
a40d4712 | 1833 | variable @code{imenu-create-index-function}: |
969fe9b5 | 1834 | |
f9f59935 | 1835 | @defvar imenu-create-index-function |
10ee4e90 LK |
1836 | This variable specifies the function to use for creating a buffer |
1837 | index. The function should take no arguments, and return an index | |
1838 | alist for the current buffer. It is called within | |
1839 | @code{save-excursion}, so where it leaves point makes no difference. | |
f9f59935 | 1840 | |
10ee4e90 LK |
1841 | The index alist can have three types of elements. Simple elements |
1842 | look like this: | |
f9f59935 | 1843 | |
10ee4e90 LK |
1844 | @example |
1845 | (@var{index-name} . @var{index-position}) | |
1846 | @end example | |
f9f59935 | 1847 | |
10ee4e90 LK |
1848 | Selecting a simple element has the effect of moving to position |
1849 | @var{index-position} in the buffer. Special elements look like this: | |
f9f59935 | 1850 | |
10ee4e90 LK |
1851 | @example |
1852 | (@var{index-name} @var{index-position} @var{function} @var{arguments}@dots{}) | |
1853 | @end example | |
f9f59935 | 1854 | |
10ee4e90 | 1855 | Selecting a special element performs: |
f9f59935 RS |
1856 | |
1857 | @example | |
c22c5da6 | 1858 | (funcall @var{function} |
10ee4e90 | 1859 | @var{index-name} @var{index-position} @var{arguments}@dots{}) |
f9f59935 RS |
1860 | @end example |
1861 | ||
10ee4e90 LK |
1862 | A nested sub-alist element looks like this: |
1863 | ||
1864 | @example | |
f008b925 | 1865 | (@var{menu-title} @var{sub-alist}) |
10ee4e90 LK |
1866 | @end example |
1867 | ||
f008b925 | 1868 | It creates the submenu @var{menu-title} specified by @var{sub-alist}. |
10ee4e90 | 1869 | |
f008b925 LK |
1870 | The default value of @code{imenu-create-index-function} is |
1871 | @code{imenu-default-create-index-function}. This function uses | |
1872 | @code{imenu-prev-index-position-function} and | |
10ee4e90 LK |
1873 | @code{imenu-extract-index-name-function} to produce the index alist. |
1874 | However, if either of these two variables is @code{nil}, the default | |
1875 | function uses @code{imenu-generic-expression} instead. | |
1876 | ||
1877 | Setting this variable makes it buffer-local in the current buffer. | |
f9f59935 RS |
1878 | @end defvar |
1879 | ||
1880 | @node Font Lock Mode | |
1881 | @section Font Lock Mode | |
1882 | @cindex Font Lock Mode | |
1883 | ||
1884 | @dfn{Font Lock mode} is a feature that automatically attaches | |
1885 | @code{face} properties to certain parts of the buffer based on their | |
1886 | syntactic role. How it parses the buffer depends on the major mode; | |
a40d4712 | 1887 | most major modes define syntactic criteria for which faces to use in |
969fe9b5 | 1888 | which contexts. This section explains how to customize Font Lock for a |
a40d4712 | 1889 | particular major mode. |
f9f59935 RS |
1890 | |
1891 | Font Lock mode finds text to highlight in two ways: through syntactic | |
1892 | parsing based on the syntax table, and through searching (usually for | |
1893 | regular expressions). Syntactic fontification happens first; it finds | |
1894 | comments and string constants, and highlights them using | |
1895 | @code{font-lock-comment-face} and @code{font-lock-string-face} | |
a40d4712 | 1896 | (@pxref{Faces for Font Lock}). Search-based fontification follows. |
f9f59935 RS |
1897 | |
1898 | @menu | |
1899 | * Font Lock Basics:: | |
1900 | * Search-based Fontification:: | |
1901 | * Other Font Lock Variables:: | |
1902 | * Levels of Font Lock:: | |
651f7556 | 1903 | * Precalculated Fontification:: |
f9f59935 | 1904 | * Faces for Font Lock:: |
969fe9b5 | 1905 | * Syntactic Font Lock:: |
f9f59935 RS |
1906 | @end menu |
1907 | ||
1908 | @node Font Lock Basics | |
1909 | @subsection Font Lock Basics | |
1910 | ||
1911 | There are several variables that control how Font Lock mode highlights | |
1912 | text. But major modes should not set any of these variables directly. | |
86494bd5 | 1913 | Instead, they should set @code{font-lock-defaults} as a buffer-local |
969fe9b5 RS |
1914 | variable. The value assigned to this variable is used, if and when Font |
1915 | Lock mode is enabled, to set all the other variables. | |
f9f59935 RS |
1916 | |
1917 | @defvar font-lock-defaults | |
1918 | This variable is set by major modes, as a buffer-local variable, to | |
1919 | specify how to fontify text in that mode. The value should look like | |
1920 | this: | |
1921 | ||
1922 | @example | |
1923 | (@var{keywords} @var{keywords-only} @var{case-fold} | |
1924 | @var{syntax-alist} @var{syntax-begin} @var{other-vars}@dots{}) | |
1925 | @end example | |
1926 | ||
1927 | The first element, @var{keywords}, indirectly specifies the value of | |
1928 | @code{font-lock-keywords}. It can be a symbol, a variable whose value | |
a40d4712 | 1929 | is the list to use for @code{font-lock-keywords}. It can also be a list of |
f9f59935 RS |
1930 | several such symbols, one for each possible level of fontification. The |
1931 | first symbol specifies how to do level 1 fontification, the second | |
1932 | symbol how to do level 2, and so on. | |
1933 | ||
1934 | The second element, @var{keywords-only}, specifies the value of the | |
a9f0a989 | 1935 | variable @code{font-lock-keywords-only}. If this is non-@code{nil}, |
969fe9b5 | 1936 | syntactic fontification (of strings and comments) is not performed. |
f9f59935 RS |
1937 | |
1938 | The third element, @var{case-fold}, specifies the value of | |
1939 | @code{font-lock-case-fold-search}. If it is non-@code{nil}, Font Lock | |
969fe9b5 RS |
1940 | mode ignores case when searching as directed by |
1941 | @code{font-lock-keywords}. | |
f9f59935 RS |
1942 | |
1943 | If the fourth element, @var{syntax-alist}, is non-@code{nil}, it should be | |
1944 | a list of cons cells of the form @code{(@var{char-or-string} | |
1945 | . @var{string})}. These are used to set up a syntax table for | |
1946 | fontification (@pxref{Syntax Table Functions}). The resulting syntax | |
1947 | table is stored in @code{font-lock-syntax-table}. | |
1948 | ||
1949 | The fifth element, @var{syntax-begin}, specifies the value of | |
969fe9b5 | 1950 | @code{font-lock-beginning-of-syntax-function} (see below). |
f9f59935 | 1951 | |
a40d4712 PR |
1952 | All the remaining elements (if any) are collectively called |
1953 | @var{other-vars}. Each of these elements should have the form | |
1954 | @code{(@var{variable} . @var{value})}---which means, make @var{variable} | |
1955 | buffer-local and then set it to @var{value}. You can use these | |
1956 | @var{other-vars} to set other variables that affect fontification, | |
1957 | aside from those you can control with the first five elements. | |
f9f59935 RS |
1958 | @end defvar |
1959 | ||
1960 | @node Search-based Fontification | |
1961 | @subsection Search-based Fontification | |
1962 | ||
1963 | The most important variable for customizing Font Lock mode is | |
1964 | @code{font-lock-keywords}. It specifies the search criteria for | |
1965 | search-based fontification. | |
1966 | ||
1967 | @defvar font-lock-keywords | |
1968 | This variable's value is a list of the keywords to highlight. Be | |
969fe9b5 RS |
1969 | careful when composing regular expressions for this list; a poorly |
1970 | written pattern can dramatically slow things down! | |
f9f59935 RS |
1971 | @end defvar |
1972 | ||
1973 | Each element of @code{font-lock-keywords} specifies how to find | |
969fe9b5 RS |
1974 | certain cases of text, and how to highlight those cases. Font Lock mode |
1975 | processes the elements of @code{font-lock-keywords} one by one, and for | |
1976 | each element, it finds and handles all matches. Ordinarily, once | |
1977 | part of the text has been fontified already, this cannot be overridden | |
1978 | by a subsequent match in the same text; but you can specify different | |
1979 | behavior using the @var{override} element of a @var{highlighter}. | |
1980 | ||
1981 | Each element of @code{font-lock-keywords} should have one of these | |
1982 | forms: | |
f9f59935 RS |
1983 | |
1984 | @table @code | |
1985 | @item @var{regexp} | |
1986 | Highlight all matches for @var{regexp} using | |
1987 | @code{font-lock-keyword-face}. For example, | |
1988 | ||
1989 | @example | |
1990 | ;; @r{Highlight discrete occurrences of @samp{foo}} | |
1991 | ;; @r{using @code{font-lock-keyword-face}.} | |
1992 | "\\<foo\\>" | |
1993 | @end example | |
1994 | ||
969fe9b5 RS |
1995 | The function @code{regexp-opt} (@pxref{Syntax of Regexps}) is useful for |
1996 | calculating optimal regular expressions to match a number of different | |
1997 | keywords. | |
f9f59935 RS |
1998 | |
1999 | @item @var{function} | |
2000 | Find text by calling @var{function}, and highlight the matches | |
2001 | it finds using @code{font-lock-keyword-face}. | |
2002 | ||
2003 | When @var{function} is called, it receives one argument, the limit of | |
022cb162 | 2004 | the search; it should begin searching at point, and not search beyond the |
07f7b41c RS |
2005 | limit. It should return non-@code{nil} if it succeeds, and set the |
2006 | match data to describe the match that was found. Returning @code{nil} | |
2007 | indicates failure of the search. | |
2008 | ||
2009 | Fontification will call @var{function} repeatedly with the same limit, | |
2010 | and with point where the previous invocation left it, until | |
2011 | @var{function} fails. On failure, @var{function} need not reset point | |
2012 | in any particular way. | |
f9f59935 RS |
2013 | |
2014 | @item (@var{matcher} . @var{match}) | |
86494bd5 | 2015 | In this kind of element, @var{matcher} is either a regular |
f9f59935 RS |
2016 | expression or a function, as described above. The @sc{cdr}, |
2017 | @var{match}, specifies which subexpression of @var{matcher} should be | |
969fe9b5 | 2018 | highlighted (instead of the entire text that @var{matcher} matched). |
f9f59935 RS |
2019 | |
2020 | @example | |
8241495d | 2021 | ;; @r{Highlight the @samp{bar} in each occurrence of @samp{fubar},} |
f9f59935 RS |
2022 | ;; @r{using @code{font-lock-keyword-face}.} |
2023 | ("fu\\(bar\\)" . 1) | |
2024 | @end example | |
2025 | ||
969fe9b5 | 2026 | If you use @code{regexp-opt} to produce the regular expression |
f9f59935 RS |
2027 | @var{matcher}, then you can use @code{regexp-opt-depth} (@pxref{Syntax |
2028 | of Regexps}) to calculate the value for @var{match}. | |
2029 | ||
3ab66863 RS |
2030 | @item (@var{matcher} . @var{facespec}) |
2031 | In this kind of element, @var{facespec} is an object which specifies | |
2032 | the face variable to use for highlighting. In the simplest case, it | |
2033 | is a Lisp variable (a symbol), whose value should be a face name. | |
f9f59935 RS |
2034 | |
2035 | @example | |
2036 | ;; @r{Highlight occurrences of @samp{fubar},} | |
2037 | ;; @r{using the face which is the value of @code{fubar-face}.} | |
2038 | ("fubar" . fubar-face) | |
2039 | @end example | |
2040 | ||
3ab66863 | 2041 | However, @var{facespec} can also be a list of the form |
fdba9ef4 RS |
2042 | |
2043 | @example | |
2044 | (face @var{face} @var{prop1} @var{val1} @var{prop2} @var{val2}@dots{}) | |
2045 | @end example | |
2046 | ||
2047 | to specify various text properties to put on the text that matches. | |
2048 | If you do this, be sure to add the other text property names that you | |
2049 | set in this way to the value of @code{font-lock-extra-managed-props} | |
2050 | so that the properties will also be cleared out when they are no longer | |
2051 | appropriate. | |
2052 | ||
f9f59935 RS |
2053 | @item (@var{matcher} . @var{highlighter}) |
2054 | In this kind of element, @var{highlighter} is a list | |
2055 | which specifies how to highlight matches found by @var{matcher}. | |
2056 | It has the form | |
2057 | ||
2058 | @example | |
3ab66863 | 2059 | (@var{subexp} @var{facespec} @var{override} @var{laxmatch}) |
f9f59935 RS |
2060 | @end example |
2061 | ||
2062 | The @sc{car}, @var{subexp}, is an integer specifying which subexpression | |
969fe9b5 | 2063 | of the match to fontify (0 means the entire matching text). The second |
3ab66863 | 2064 | subelement, @var{facespec}, specifies the face, as described above. |
f9f59935 RS |
2065 | |
2066 | The last two values in @var{highlighter}, @var{override} and | |
bda7c6dd RS |
2067 | @var{laxmatch}, are flags. If @var{override} is @code{t}, this |
2068 | element can override existing fontification made by previous elements | |
2069 | of @code{font-lock-keywords}. If it is @code{keep}, then each | |
2070 | character is fontified if it has not been fontified already by some | |
3ab66863 RS |
2071 | other element. If it is @code{prepend}, the face specified by |
2072 | @var{facespec} is added to the beginning of the @code{font-lock-face} | |
2073 | property. If it is @code{append}, the face is added to the end of the | |
bda7c6dd | 2074 | @code{font-lock-face} property. |
f9f59935 RS |
2075 | |
2076 | If @var{laxmatch} is non-@code{nil}, it means there should be no error | |
2077 | if there is no subexpression numbered @var{subexp} in @var{matcher}. | |
99b62845 GM |
2078 | Obviously, fontification of the subexpression numbered @var{subexp} will |
2079 | not occur. However, fontification of other subexpressions (and other | |
2080 | regexps) will continue. If @var{laxmatch} is @code{nil}, and the | |
2081 | specified subexpression is missing, then an error is signalled which | |
2082 | terminates search-based fontification. | |
f9f59935 RS |
2083 | |
2084 | Here are some examples of elements of this kind, and what they do: | |
2085 | ||
2086 | @smallexample | |
2087 | ;; @r{Highlight occurrences of either @samp{foo} or @samp{bar},} | |
2088 | ;; @r{using @code{foo-bar-face}, even if they have already been highlighted.} | |
2089 | ;; @r{@code{foo-bar-face} should be a variable whose value is a face.} | |
2090 | ("foo\\|bar" 0 foo-bar-face t) | |
2091 | ||
8241495d | 2092 | ;; @r{Highlight the first subexpression within each occurrence} |
f9f59935 RS |
2093 | ;; @r{that the function @code{fubar-match} finds,} |
2094 | ;; @r{using the face which is the value of @code{fubar-face}.} | |
2095 | (fubar-match 1 fubar-face) | |
2096 | @end smallexample | |
2097 | ||
2098 | @item (@var{matcher} @var{highlighters}@dots{}) | |
2099 | This sort of element specifies several @var{highlighter} lists for a | |
2100 | single @var{matcher}. In order for this to be useful, each | |
2101 | @var{highlighter} should have a different value of @var{subexp}; that is, | |
2102 | each one should apply to a different subexpression of @var{matcher}. | |
2103 | ||
2104 | @ignore | |
2105 | @item (@var{matcher} . @var{anchored}) | |
2106 | In this kind of element, @var{anchored} acts much like a | |
2107 | @var{highlighter}, but it is more complex and can specify multiple | |
2108 | successive searches. | |
2109 | ||
2110 | For highlighting single items, typically only @var{highlighter} is | |
2111 | required. However, if an item or (typically) items are to be | |
2112 | highlighted following the instance of another item (the anchor) then | |
2113 | @var{anchored} may be required. | |
2114 | ||
2115 | It has this format: | |
2116 | ||
2117 | @example | |
2118 | (@var{submatcher} @var{pre-match-form} @var{post-match-form} @var{highlighters}@dots{}) | |
2119 | @end example | |
2120 | ||
2121 | @c I can't parse this text -- rms | |
2122 | where @var{submatcher} is much like @var{matcher}, with one | |
2123 | exception---see below. @var{pre-match-form} and @var{post-match-form} | |
2124 | are evaluated before the first, and after the last, instance | |
2125 | @var{anchored}'s @var{submatcher} is used. Therefore they can be used | |
a9f0a989 | 2126 | to initialize before, and cleanup after, @var{submatcher} is used. |
f9f59935 RS |
2127 | Typically, @var{pre-match-form} is used to move to some position |
2128 | relative to the original @var{submatcher}, before starting with | |
2129 | @var{anchored}'s @var{submatcher}. @var{post-match-form} might be used | |
2130 | to move, before resuming with @var{anchored}'s parent's @var{matcher}. | |
2131 | ||
2132 | For example, an element of the form highlights (if not already highlighted): | |
2133 | ||
2134 | @example | |
2135 | ("\\<anchor\\>" (0 anchor-face) ("\\<item\\>" nil nil (0 item-face))) | |
2136 | @end example | |
2137 | ||
2138 | Discrete occurrences of @samp{anchor} in the value of | |
2139 | @code{anchor-face}, and subsequent discrete occurrences of @samp{item} | |
2140 | (on the same line) in the value of @code{item-face}. (Here | |
2141 | @var{pre-match-form} and @var{post-match-form} are @code{nil}. | |
2142 | Therefore @samp{item} is initially searched for starting from the end of | |
2143 | the match of @samp{anchor}, and searching for subsequent instance of | |
2144 | @samp{anchor} resumes from where searching for @samp{item} concluded.) | |
2145 | ||
2146 | The above-mentioned exception is as follows. The limit of the | |
2147 | @var{submatcher} search defaults to the end of the line after | |
2148 | @var{pre-match-form} is evaluated. However, if @var{pre-match-form} | |
2149 | returns a position greater than the position after @var{pre-match-form} | |
2150 | is evaluated, that position is used as the limit of the search. It is | |
2151 | generally a bad idea to return a position greater than the end of the | |
2152 | line; in other words, the @var{submatcher} search should not span lines. | |
2153 | ||
2154 | @item (@var{matcher} @var{highlighters-or-anchoreds} ...) | |
2155 | @end ignore | |
2156 | ||
2157 | @item (eval . @var{form}) | |
969fe9b5 | 2158 | Here @var{form} is an expression to be evaluated the first time |
f9f59935 | 2159 | this value of @code{font-lock-keywords} is used in a buffer. |
969fe9b5 | 2160 | Its value should have one of the forms described in this table. |
f9f59935 RS |
2161 | @end table |
2162 | ||
2163 | @strong{Warning:} Do not design an element of @code{font-lock-keywords} | |
2164 | to match text which spans lines; this does not work reliably. While | |
2165 | @code{font-lock-fontify-buffer} handles multi-line patterns correctly, | |
2166 | updating when you edit the buffer does not, since it considers text one | |
8ba2808b SM |
2167 | line at a time. If you have patterns that typically only span one |
2168 | line but can occasionally span two or three, such as | |
2169 | @samp{<title>...</title>}, you can ask font-lock to be more careful by | |
2170 | setting @code{font-lock-multiline} to @code{t}. But it still will not | |
2171 | work in all cases. | |
f9f59935 | 2172 | |
f9f59935 RS |
2173 | @node Other Font Lock Variables |
2174 | @subsection Other Font Lock Variables | |
2175 | ||
2176 | This section describes additional variables that a major mode | |
2177 | can set by means of @code{font-lock-defaults}. | |
2178 | ||
2179 | @defvar font-lock-keywords-only | |
2180 | Non-@code{nil} means Font Lock should not fontify comments or strings | |
969fe9b5 RS |
2181 | syntactically; it should only fontify based on |
2182 | @code{font-lock-keywords}. | |
f9f59935 RS |
2183 | @end defvar |
2184 | ||
2185 | @ignore | |
a9f0a989 | 2186 | Other variables include those for buffer-specialized fontification functions, |
f9f59935 RS |
2187 | `font-lock-fontify-buffer-function', `font-lock-unfontify-buffer-function', |
2188 | `font-lock-fontify-region-function', `font-lock-unfontify-region-function', | |
2189 | `font-lock-inhibit-thing-lock' and `font-lock-maximum-size'. | |
2190 | @end ignore | |
2191 | ||
2192 | @defvar font-lock-keywords-case-fold-search | |
969fe9b5 RS |
2193 | Non-@code{nil} means that regular expression matching for the sake of |
2194 | @code{font-lock-keywords} should be case-insensitive. | |
f9f59935 RS |
2195 | @end defvar |
2196 | ||
969fe9b5 RS |
2197 | @defvar font-lock-syntax-table |
2198 | This variable specifies the syntax table to use for fontification of | |
2199 | comments and strings. | |
2200 | @end defvar | |
f9f59935 | 2201 | |
969fe9b5 RS |
2202 | @defvar font-lock-beginning-of-syntax-function |
2203 | If this variable is non-@code{nil}, it should be a function to move | |
2204 | point back to a position that is syntactically at ``top level'' and | |
2205 | outside of strings or comments. Font Lock uses this when necessary | |
2206 | to get the right results for syntactic fontification. | |
f9f59935 RS |
2207 | |
2208 | This function is called with no arguments. It should leave point at the | |
2209 | beginning of any enclosing syntactic block. Typical values are | |
2210 | @code{beginning-of-line} (i.e., the start of the line is known to be | |
2211 | outside a syntactic block), or @code{beginning-of-defun} for programming | |
2212 | modes or @code{backward-paragraph} for textual modes (i.e., the | |
2213 | mode-dependent function is known to move outside a syntactic block). | |
2214 | ||
2215 | If the value is @code{nil}, the beginning of the buffer is used as a | |
969fe9b5 RS |
2216 | position outside of a syntactic block. This cannot be wrong, but it can |
2217 | be slow. | |
f9f59935 RS |
2218 | @end defvar |
2219 | ||
2220 | @defvar font-lock-mark-block-function | |
969fe9b5 RS |
2221 | If this variable is non-@code{nil}, it should be a function that is |
2222 | called with no arguments, to choose an enclosing range of text for | |
2223 | refontification for the command @kbd{M-g M-g} | |
2224 | (@code{font-lock-fontify-block}). | |
2225 | ||
2226 | The function should report its choice by placing the region around it. | |
2227 | A good choice is a range of text large enough to give proper results, | |
2228 | but not too large so that refontification becomes slow. Typical values | |
2229 | are @code{mark-defun} for programming modes or @code{mark-paragraph} for | |
2230 | textual modes. | |
f9f59935 RS |
2231 | @end defvar |
2232 | ||
fdba9ef4 | 2233 | @defvar font-lock-extra-managed-props |
bda7c6dd RS |
2234 | Additional properties (other than @code{font-lock-face}) that are |
2235 | being managed by Font Lock mode. Font Lock mode normally manages only | |
2236 | the @code{font-lock-face} property; if you want it to manage others as | |
3ab66863 | 2237 | well, you must specify them in a @var{facespec} in |
bda7c6dd | 2238 | @code{font-lock-keywords} as well as adding them to this list. |
fdba9ef4 RS |
2239 | @end defvar |
2240 | ||
8ba2808b SM |
2241 | @defvar font-lock-syntactic-face-function |
2242 | A function to determine which face to use for a given syntactic | |
2243 | element (a string or a comment). The function is called with one | |
2244 | argument, the parse state at point returned by | |
2245 | @code{parse-partial-sexp}, and should return a face. The default | |
2246 | value returns @code{font-lock-comment-face} for comments and | |
2247 | @code{font-lock-string-face} for strings. | |
2248 | ||
2249 | This can be used to highlighting different kinds of strings or | |
2250 | comments differently. It is also sometimes abused together with | |
2251 | @code{font-lock-syntactic-keywords} to highlight elements that span | |
2252 | multiple lines, but this is too obscure to document in this manual. | |
2253 | @end defvar | |
2254 | ||
f9f59935 RS |
2255 | @node Levels of Font Lock |
2256 | @subsection Levels of Font Lock | |
2257 | ||
2258 | Many major modes offer three different levels of fontification. You | |
2259 | can define multiple levels by using a list of symbols for @var{keywords} | |
2260 | in @code{font-lock-defaults}. Each symbol specifies one level of | |
2261 | fontification; it is up to the user to choose one of these levels. The | |
2262 | chosen level's symbol value is used to initialize | |
2263 | @code{font-lock-keywords}. | |
2264 | ||
969fe9b5 RS |
2265 | Here are the conventions for how to define the levels of |
2266 | fontification: | |
2267 | ||
f9f59935 RS |
2268 | @itemize @bullet |
2269 | @item | |
2270 | Level 1: highlight function declarations, file directives (such as include or | |
2271 | import directives), strings and comments. The idea is speed, so only | |
2272 | the most important and top-level components are fontified. | |
2273 | ||
2274 | @item | |
969fe9b5 RS |
2275 | Level 2: in addition to level 1, highlight all language keywords, |
2276 | including type names that act like keywords, as well as named constant | |
2277 | values. The idea is that all keywords (either syntactic or semantic) | |
2278 | should be fontified appropriately. | |
f9f59935 RS |
2279 | |
2280 | @item | |
969fe9b5 RS |
2281 | Level 3: in addition to level 2, highlight the symbols being defined in |
2282 | function and variable declarations, and all builtin function names, | |
2283 | wherever they appear. | |
f9f59935 RS |
2284 | @end itemize |
2285 | ||
651f7556 CW |
2286 | @node Precalculated Fontification |
2287 | @subsection Precalculated Fontification | |
2288 | ||
2289 | In addition to using @code{font-lock-defaults} for search-based | |
2290 | fontification, you may use the special character property | |
2291 | @code{font-lock-face} (@pxref{Special Properties}). This property | |
2292 | acts just like the explicit @code{face} property, but its activation | |
2293 | is toggled when the user calls @kbd{M-x font-lock-mode}. Using | |
06862374 | 2294 | @code{font-lock-face} is especially convenient for special modes |
651f7556 CW |
2295 | which construct their text programmatically, such as |
2296 | @code{list-buffers} and @code{occur}. | |
2297 | ||
0ab0c481 CW |
2298 | If your mode does not use any of the other machinery of Font Lock |
2299 | (i.e. it only uses the @code{font-lock-face} property), you can tell | |
2300 | Emacs not to load all of font-lock.el (unless it's already loaded), by | |
6fe50867 RS |
2301 | setting the variable @code{font-lock-core-only} to non-@code{nil} as |
2302 | part of the @code{font-lock-defaults} settings. Here is the canonical | |
2303 | way to do this: | |
0ab0c481 CW |
2304 | |
2305 | @example | |
2306 | (set (make-local-variable 'font-lock-defaults) | |
2307 | '(nil t nil nil nil (font-lock-core-only . t))) | |
2308 | @end example | |
2309 | ||
f9f59935 RS |
2310 | @node Faces for Font Lock |
2311 | @subsection Faces for Font Lock | |
2312 | ||
2313 | You can make Font Lock mode use any face, but several faces are | |
2314 | defined specifically for Font Lock mode. Each of these symbols is both | |
2315 | a face name, and a variable whose default value is the symbol itself. | |
2316 | Thus, the default value of @code{font-lock-comment-face} is | |
2317 | @code{font-lock-comment-face}. This means you can write | |
2318 | @code{font-lock-comment-face} in a context such as | |
2319 | @code{font-lock-keywords} where a face-name-valued expression is used. | |
2320 | ||
2321 | @table @code | |
2322 | @item font-lock-comment-face | |
2323 | @vindex font-lock-comment-face | |
f9f59935 RS |
2324 | Used (typically) for comments. |
2325 | ||
2326 | @item font-lock-string-face | |
2327 | @vindex font-lock-string-face | |
f9f59935 RS |
2328 | Used (typically) for string constants. |
2329 | ||
2330 | @item font-lock-keyword-face | |
2331 | @vindex font-lock-keyword-face | |
f9f59935 RS |
2332 | Used (typically) for keywords---names that have special syntactic |
2333 | significance, like @code{for} and @code{if} in C. | |
2334 | ||
2335 | @item font-lock-builtin-face | |
2336 | @vindex font-lock-builtin-face | |
f9f59935 RS |
2337 | Used (typically) for built-in function names. |
2338 | ||
2339 | @item font-lock-function-name-face | |
2340 | @vindex font-lock-function-name-face | |
f9f59935 | 2341 | Used (typically) for the name of a function being defined or declared, |
177c0ea7 | 2342 | in a function definition or declaration. |
f9f59935 RS |
2343 | |
2344 | @item font-lock-variable-name-face | |
2345 | @vindex font-lock-variable-name-face | |
f9f59935 RS |
2346 | Used (typically) for the name of a variable being defined or declared, |
2347 | in a variable definition or declaration. | |
2348 | ||
2349 | @item font-lock-type-face | |
2350 | @vindex font-lock-type-face | |
f9f59935 RS |
2351 | Used (typically) for names of user-defined data types, |
2352 | where they are defined and where they are used. | |
2353 | ||
2354 | @item font-lock-constant-face | |
2355 | @vindex font-lock-constant-face | |
f9f59935 RS |
2356 | Used (typically) for constant names. |
2357 | ||
c22c5da6 LK |
2358 | @item font-lock-preprocessor-face |
2359 | @vindex font-lock-preprocessor-face | |
fdba9ef4 RS |
2360 | Used (typically) for preprocessor commands. |
2361 | ||
f9f59935 RS |
2362 | @item font-lock-warning-face |
2363 | @vindex font-lock-warning-face | |
f9f59935 RS |
2364 | Used (typically) for constructs that are peculiar, or that greatly |
2365 | change the meaning of other text. For example, this is used for | |
2366 | @samp{;;;###autoload} cookies in Emacs Lisp, and for @code{#error} | |
2367 | directives in C. | |
2368 | @end table | |
2369 | ||
969fe9b5 RS |
2370 | @node Syntactic Font Lock |
2371 | @subsection Syntactic Font Lock | |
2372 | ||
2373 | Font Lock mode can be used to update @code{syntax-table} properties | |
2374 | automatically. This is useful in languages for which a single syntax | |
2375 | table by itself is not sufficient. | |
2376 | ||
2377 | @defvar font-lock-syntactic-keywords | |
f8cecb20 DL |
2378 | This variable enables and controls syntactic Font Lock. It is |
2379 | normally set via @code{font-lock-defaults}. Its value should be a | |
2380 | list of elements of this form: | |
969fe9b5 RS |
2381 | |
2382 | @example | |
2383 | (@var{matcher} @var{subexp} @var{syntax} @var{override} @var{laxmatch}) | |
2384 | @end example | |
2385 | ||
2386 | The parts of this element have the same meanings as in the corresponding | |
2387 | sort of element of @code{font-lock-keywords}, | |
2388 | ||
2389 | @example | |
2390 | (@var{matcher} @var{subexp} @var{facename} @var{override} @var{laxmatch}) | |
2391 | @end example | |
2392 | ||
2393 | However, instead of specifying the value @var{facename} to use for the | |
f8cecb20 DL |
2394 | @code{face} property, it specifies the value @var{syntax} to use for |
2395 | the @code{syntax-table} property. Here, @var{syntax} can be a string | |
2396 | (as taken by @code{modify-syntax-entry}), a syntax table, a cons cell | |
2397 | (as returned by @code{string-to-syntax}), or an expression whose value | |
2398 | is one of those two types. @var{override} cannot be @code{prepend} or | |
2399 | @code{append}. | |
2400 | ||
2401 | For example, an element of the form: | |
2402 | ||
2403 | @example | |
2404 | ("\\$\\(#\\)" 1 ".") | |
2405 | @end example | |
2406 | ||
2407 | highlights syntactically a hash character when following a dollar | |
2408 | character, with a SYNTAX of @code{"."} (meaning punctuation syntax). | |
2409 | Assuming that the buffer syntax table specifies hash characters to | |
2410 | have comment start syntax, the element will only highlight hash | |
2411 | characters that do not follow dollar characters as comments | |
2412 | syntactically. | |
2413 | ||
2414 | An element of the form: | |
2415 | ||
2416 | @example | |
2417 | ("\\('\\).\\('\\)" | |
2418 | (1 "\"") | |
2419 | (2 "\"")) | |
2420 | @end example | |
2421 | ||
2422 | highlights syntactically both single quotes which surround a single | |
2423 | character, with a SYNTAX of @code{"\""} (meaning string quote syntax). | |
2424 | Assuming that the buffer syntax table does not specify single quotes | |
2425 | to have quote syntax, the element will only highlight single quotes of | |
2426 | the form @samp{'@var{c}'} as strings syntactically. Other forms, such | |
2427 | as @samp{foo'bar} or @samp{'fubar'}, will not be highlighted as | |
2428 | strings. | |
2429 | ||
969fe9b5 RS |
2430 | @end defvar |
2431 | ||
f730cc62 LH |
2432 | @node Desktop Save Mode |
2433 | @section Desktop Save Mode | |
2434 | @cindex desktop save mode | |
2435 | ||
2436 | @dfn{Desktop Save Mode} is a feature to save the state of Emacs from | |
2437 | one session to another. The user-level commands for using Desktop | |
2438 | Save Mode are described in the GNU Emacs Manual (@pxref{Saving Emacs | |
2439 | Sessions,,, emacs, the GNU Emacs Manual}). Modes whose buffers visit | |
2440 | a file, don't have to do anything to use this feature. | |
2441 | ||
2442 | For buffers not visiting a file to have their state saved, the major | |
2443 | mode must bind the buffer local variable @code{desktop-save-buffer} to | |
2444 | a non-nil value. | |
2445 | ||
2446 | @defvar desktop-save-buffer | |
2447 | If this buffer-local variable is non-@code{nil}, the buffer will have | |
2448 | its state saved in the desktop file at desktop save. If the value is | |
2449 | a function, it is called at desktop save with argument | |
2450 | @var{desktop-dirname}, and its value is saved in the desktop file along | |
2451 | with the state of the buffer for which it was called. When file names | |
2452 | are returned as part of the auxiliary information, they should be | |
2453 | formatted using the call | |
2454 | ||
2455 | @example | |
2456 | (desktop-file-name @var{file-name} @var{desktop-dirname}) | |
2457 | @end example | |
2458 | ||
2459 | @end defvar | |
2460 | ||
2461 | For buffers not visiting a file to be restored, the major mode must | |
2462 | define a function to do the job, and that function must be listed in | |
2463 | the alist @code{desktop-buffer-mode-handlers}. | |
2464 | ||
2465 | @defvar desktop-buffer-mode-handlers | |
2466 | Alist with elements | |
2467 | ||
2468 | @example | |
2469 | (@var{major-mode} . @var{restore-buffer-function}) | |
2470 | @end example | |
2471 | ||
2472 | The function @var{restore-buffer-function} will be called with | |
2473 | argument list | |
2474 | ||
2475 | @example | |
2476 | (@var{buffer-file-name} @var{buffer-name} @var{desktop-buffer-misc}) | |
2477 | @end example | |
2478 | ||
2479 | and it should return the restored buffer. | |
2480 | Here @var{desktop-buffer-misc} is the value returned by the function | |
2481 | optionally bound to @code{desktop-save-buffer}. | |
2482 | ||
2483 | @end defvar | |
2484 | ||
a44af9f2 RS |
2485 | @node Hooks |
2486 | @section Hooks | |
2487 | @cindex hooks | |
2488 | ||
2489 | A @dfn{hook} is a variable where you can store a function or functions | |
2490 | to be called on a particular occasion by an existing program. Emacs | |
2491 | provides hooks for the sake of customization. Most often, hooks are set | |
a40d4712 | 2492 | up in the init file (@pxref{Init File}), but Lisp programs can set them also. |
a44af9f2 RS |
2493 | @xref{Standard Hooks}, for a list of standard hook variables. |
2494 | ||
f9f59935 | 2495 | @cindex normal hook |
a44af9f2 | 2496 | Most of the hooks in Emacs are @dfn{normal hooks}. These variables |
dd73b091 RS |
2497 | contain lists of functions to be called with no arguments. When the |
2498 | hook name ends in @samp{-hook}, that tells you it is normal. We try to | |
2499 | make all hooks normal, as much as possible, so that you can use them in | |
2500 | a uniform way. | |
2501 | ||
2502 | Every major mode function is supposed to run a normal hook called the | |
2503 | @dfn{mode hook} as the last step of initialization. This makes it easy | |
2504 | for a user to customize the behavior of the mode, by overriding the | |
969fe9b5 RS |
2505 | buffer-local variable assignments already made by the mode. But hooks |
2506 | are used in other contexts too. For example, the hook | |
2507 | @code{suspend-hook} runs just before Emacs suspends itself | |
2508 | (@pxref{Suspending Emacs}). | |
a44af9f2 RS |
2509 | |
2510 | The recommended way to add a hook function to a normal hook is by | |
2511 | calling @code{add-hook} (see below). The hook functions may be any of | |
da3178e2 RS |
2512 | the valid kinds of functions that @code{funcall} accepts (@pxref{What |
2513 | Is a Function}). Most normal hook variables are initially void; | |
2514 | @code{add-hook} knows how to deal with this. You can add hooks either | |
2515 | globally or buffer-locally with @code{add-hook}. | |
c22c5da6 | 2516 | |
f9f59935 | 2517 | @cindex abnormal hook |
dd73b091 | 2518 | If the hook variable's name does not end with @samp{-hook}, that |
a40d4712 | 2519 | indicates it is probably an @dfn{abnormal hook}. Then you should look at its |
dd73b091 RS |
2520 | documentation to see how to use the hook properly. |
2521 | ||
2522 | If the variable's name ends in @samp{-functions} or @samp{-hooks}, | |
2523 | then the value is a list of functions, but it is abnormal in that either | |
2524 | these functions are called with arguments or their values are used in | |
2525 | some way. You can use @code{add-hook} to add a function to the list, | |
2526 | but you must take care in writing the function. (A few of these | |
89cda0c5 SM |
2527 | variables, notably those ending in @samp{-hooks}, are actually |
2528 | normal hooks which were named before we established the convention of | |
2529 | using @samp{-hook} for them.) | |
dd73b091 RS |
2530 | |
2531 | If the variable's name ends in @samp{-function}, then its value | |
2532 | is just a single function, not a list of functions. | |
a44af9f2 | 2533 | |
969fe9b5 RS |
2534 | Here's an example that uses a mode hook to turn on Auto Fill mode when |
2535 | in Lisp Interaction mode: | |
a44af9f2 RS |
2536 | |
2537 | @example | |
2538 | (add-hook 'lisp-interaction-mode-hook 'turn-on-auto-fill) | |
a44af9f2 RS |
2539 | @end example |
2540 | ||
2541 | At the appropriate time, Emacs uses the @code{run-hooks} function to | |
bfe721d1 KH |
2542 | run particular hooks. This function calls the hook functions that have |
2543 | been added with @code{add-hook}. | |
a44af9f2 | 2544 | |
a40d4712 | 2545 | @defun run-hooks &rest hookvars |
c22c5da6 LK |
2546 | This function takes one or more normal hook variable names as |
2547 | arguments, and runs each hook in turn. Each argument should be a | |
da3178e2 RS |
2548 | symbol that is a normal hook variable. These arguments are processed |
2549 | in the order specified. | |
a44af9f2 RS |
2550 | |
2551 | If a hook variable has a non-@code{nil} value, that value may be a | |
da3178e2 RS |
2552 | function or a list of functions. (The former option is considered |
2553 | obsolete.) If the value is a function (either a lambda expression or | |
2554 | a symbol with a function definition), it is called. If it is a list | |
2555 | that isn't a function, its elements are called, consecutively. All | |
2556 | the hook functions are called with no arguments. | |
a44af9f2 | 2557 | |
bfe721d1 | 2558 | For example, here's how @code{emacs-lisp-mode} runs its mode hook: |
a44af9f2 RS |
2559 | |
2560 | @example | |
2561 | (run-hooks 'emacs-lisp-mode-hook) | |
2562 | @end example | |
2563 | @end defun | |
2564 | ||
fdba9ef4 RS |
2565 | @defun run-mode-hooks &rest hookvars |
2566 | Like @code{run-hooks}, but is affected by the @code{delay-mode-hooks} | |
2567 | macro. | |
2568 | @end defun | |
2569 | ||
2570 | @defmac delay-mode-hooks body... | |
2571 | This macro executes the @var{body} forms but defers all calls to | |
2572 | @code{run-mode-hooks} within them until the end of @var{body}. | |
2573 | This macro enables a derived mode to arrange not to run | |
2574 | its parent modes' mode hooks until the end. | |
2575 | @end defmac | |
2576 | ||
a9f0a989 | 2577 | @defun run-hook-with-args hook &rest args |
da3178e2 RS |
2578 | This function is the way to run an abnormal hook and always call all |
2579 | of the hook functions. It calls each of the hook functions one by | |
2580 | one, passing each of them the arguments @var{args}. | |
a9f0a989 RS |
2581 | @end defun |
2582 | ||
2583 | @defun run-hook-with-args-until-failure hook &rest args | |
c22c5da6 LK |
2584 | This function is the way to run an abnormal hook until one of the hook |
2585 | functions fails. It calls each of the hook functions, passing each of | |
2586 | them the arguments @var{args}, until some hook function returns | |
2587 | @code{nil}. It then stops and returns @code{nil}. If none of the | |
2588 | hook functions return @code{nil}, it returns a non-@code{nil} value. | |
a9f0a989 RS |
2589 | @end defun |
2590 | ||
2591 | @defun run-hook-with-args-until-success hook &rest args | |
c22c5da6 LK |
2592 | This function is the way to run an abnormal hook until a hook function |
2593 | succeeds. It calls each of the hook functions, passing each of them | |
2594 | the arguments @var{args}, until some hook function returns | |
2595 | non-@code{nil}. Then it stops, and returns whatever was returned by | |
2596 | the last hook function that was called. If all hook functions return | |
2597 | @code{nil}, it returns @code{nil} as well. | |
a9f0a989 RS |
2598 | @end defun |
2599 | ||
22697dac | 2600 | @defun add-hook hook function &optional append local |
a44af9f2 | 2601 | This function is the handy way to add function @var{function} to hook |
da3178e2 RS |
2602 | variable @var{hook}. You can use it for abnormal hooks as well as for |
2603 | normal hooks. @var{function} can be any Lisp function that can accept | |
2604 | the proper number of arguments for @var{hook}. For example, | |
a44af9f2 RS |
2605 | |
2606 | @example | |
2607 | (add-hook 'text-mode-hook 'my-text-hook-function) | |
2608 | @end example | |
2609 | ||
2610 | @noindent | |
2611 | adds @code{my-text-hook-function} to the hook called @code{text-mode-hook}. | |
2612 | ||
da3178e2 RS |
2613 | If @var{function} is already present in @var{hook} (comparing using |
2614 | @code{equal}), then @code{add-hook} does not add it a second time. | |
de9f0bd9 | 2615 | |
a44af9f2 RS |
2616 | It is best to design your hook functions so that the order in which they |
2617 | are executed does not matter. Any dependence on the order is ``asking | |
c22c5da6 | 2618 | for trouble''. However, the order is predictable: normally, |
a44af9f2 | 2619 | @var{function} goes at the front of the hook list, so it will be |
969fe9b5 RS |
2620 | executed first (barring another @code{add-hook} call). If the optional |
2621 | argument @var{append} is non-@code{nil}, the new hook function goes at | |
2622 | the end of the hook list and will be executed last. | |
22697dac | 2623 | |
c22c5da6 LK |
2624 | If @var{local} is non-@code{nil}, that says to add @var{function} to |
2625 | the buffer-local hook list instead of to the global hook list. If | |
2626 | needed, this makes the hook buffer-local and adds @code{t} to the | |
2627 | buffer-local value. The latter acts as a flag to run the hook | |
2628 | functions in the default value as well as in the local value. | |
a44af9f2 RS |
2629 | @end defun |
2630 | ||
22697dac | 2631 | @defun remove-hook hook function &optional local |
c22c5da6 | 2632 | This function removes @var{function} from the hook variable |
da3178e2 RS |
2633 | @var{hook}. It compares @var{function} with elements of @var{hook} |
2634 | using @code{equal}, so it works for both symbols and lambda | |
2635 | expressions. | |
c44d2ced | 2636 | |
22697dac | 2637 | If @var{local} is non-@code{nil}, that says to remove @var{function} |
969fe9b5 | 2638 | from the buffer-local hook list instead of from the global hook list. |
22697dac | 2639 | @end defun |
ab5796a9 MB |
2640 | |
2641 | @ignore | |
2642 | arch-tag: 4c7bff41-36e6-4da6-9e7f-9b9289e27c8e | |
2643 | @end ignore |