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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
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3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, |
4 | @c 2003, 2004, 2005 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. | |
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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 |
a44af9f2 | 105 | mode. |
a3ee0299 | 106 | * Mode Hooks:: Hooks run at the end of major mode functions. |
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107 | @end menu |
108 | ||
109 | @node Major Mode Conventions | |
110 | @subsection Major Mode Conventions | |
111 | ||
112 | The code for existing major modes follows various coding conventions, | |
113 | including conventions for local keymap and syntax table initialization, | |
114 | global names, and hooks. Please follow these conventions when you | |
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115 | define a new major mode. |
116 | ||
117 | This list of conventions is only partial, because each major mode | |
118 | should aim for consistency in general with other Emacs major modes. | |
119 | This makes Emacs as a whole more coherent. It is impossible to list | |
120 | here all the possible points where this issue might come up; if the | |
121 | Emacs developers point out an area where your major mode deviates from | |
122 | the usual conventions, please make it compatible. | |
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123 | |
124 | @itemize @bullet | |
125 | @item | |
126 | Define a command whose name ends in @samp{-mode}, with no arguments, | |
127 | that switches to the new mode in the current buffer. This command | |
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128 | should set up the keymap, syntax table, and buffer-local variables in an |
129 | existing buffer, without changing the buffer's contents. | |
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130 | |
131 | @item | |
de9f0bd9 | 132 | Write a documentation string for this command that describes the |
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133 | special commands available in this mode. @kbd{C-h m} |
134 | (@code{describe-mode}) in your mode will display this string. | |
135 | ||
136 | The documentation string may include the special documentation | |
137 | substrings, @samp{\[@var{command}]}, @samp{\@{@var{keymap}@}}, and | |
86494bd5 | 138 | @samp{\<@var{keymap}>}, which enable the documentation to adapt |
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139 | automatically to the user's own key bindings. @xref{Keys in |
140 | Documentation}. | |
141 | ||
142 | @item | |
143 | The major mode command should start by calling | |
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144 | @code{kill-all-local-variables}. This is what gets rid of the |
145 | buffer-local variables of the major mode previously in effect. | |
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146 | |
147 | @item | |
148 | The major mode command should set the variable @code{major-mode} to the | |
149 | major mode command symbol. This is how @code{describe-mode} discovers | |
150 | which documentation to print. | |
151 | ||
152 | @item | |
153 | The major mode command should set the variable @code{mode-name} to the | |
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154 | ``pretty'' name of the mode, as a string. This string appears in the |
155 | mode line. | |
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156 | |
157 | @item | |
158 | @cindex functions in modes | |
159 | Since all global names are in the same name space, all the global | |
160 | variables, constants, and functions that are part of the mode should | |
161 | have names that start with the major mode name (or with an abbreviation | |
a4b12c74 | 162 | of it if the name is long). @xref{Coding Conventions}. |
a44af9f2 | 163 | |
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164 | @item |
165 | In a major mode for editing some kind of structured text, such as a | |
166 | programming language, indentation of text according to structure is | |
167 | probably useful. So the mode should set @code{indent-line-function} | |
168 | to a suitable function, and probably customize other variables | |
169 | for indentation. | |
170 | ||
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171 | @item |
172 | @cindex keymaps in modes | |
173 | The major mode should usually have its own keymap, which is used as the | |
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174 | local keymap in all buffers in that mode. The major mode command should |
175 | call @code{use-local-map} to install this local map. @xref{Active | |
176 | Keymaps}, for more information. | |
a44af9f2 | 177 | |
969fe9b5 | 178 | This keymap should be stored permanently in a global variable named |
a44af9f2 | 179 | @code{@var{modename}-mode-map}. Normally the library that defines the |
de9f0bd9 | 180 | mode sets this variable. |
a44af9f2 | 181 | |
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182 | @xref{Tips for Defining}, for advice about how to write the code to set |
183 | up the mode's keymap variable. | |
184 | ||
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185 | @item |
186 | The key sequences bound in a major mode keymap should usually start with | |
969fe9b5 | 187 | @kbd{C-c}, followed by a control character, a digit, or @kbd{@{}, |
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188 | @kbd{@}}, @kbd{<}, @kbd{>}, @kbd{:} or @kbd{;}. The other punctuation |
189 | characters are reserved for minor modes, and ordinary letters are | |
190 | reserved for users. | |
191 | ||
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192 | A major mode can also rebind the keys @kbd{M-n}, @kbd{M-p} and |
193 | @kbd{M-s}. The bindings for @kbd{M-n} and @kbd{M-p} should normally | |
194 | be some kind of ``moving forward and backward,'' but this does not | |
195 | necessarily mean cursor motion. | |
196 | ||
197 | It is legitimate for a major mode to rebind a standard key sequence if | |
198 | it provides a command that does ``the same job'' in a way better | |
199 | suited to the text this mode is used for. For example, a major mode | |
200 | for editing a programming language might redefine @kbd{C-M-a} to | |
201 | ``move to the beginning of a function'' in a way that works better for | |
202 | that language. | |
203 | ||
204 | It is also legitimate for a major mode to rebind a standard key | |
205 | sequence whose standard meaning is rarely useful in that mode. For | |
206 | instance, minibuffer modes rebind @kbd{M-r}, whose standard meaning is | |
207 | rarely of any use in the minibuffer. Major modes such as Dired or | |
208 | Rmail that do not allow self-insertion of text can reasonably redefine | |
209 | letters and other printing characters as special commands. | |
a4b12c74 | 210 | |
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211 | @item |
212 | Major modes must not define @key{RET} to do anything other than insert | |
213 | a newline. The command to insert a newline and then indent is | |
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214 | @kbd{C-j}. Please keep this distinction uniform for all major modes. |
215 | ||
216 | @item | |
2a233172 | 217 | Major modes should not alter options that are primarily a matter of user |
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218 | preference, such as whether Auto-Fill mode is enabled. Leave this to |
219 | each user to decide. However, a major mode should customize other | |
220 | variables so that Auto-Fill mode will work usefully @emph{if} the user | |
221 | decides to use it. | |
c2e903c0 | 222 | |
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223 | @item |
224 | @cindex syntax tables in modes | |
225 | The mode may have its own syntax table or may share one with other | |
226 | related modes. If it has its own syntax table, it should store this in | |
de9f0bd9 | 227 | a variable named @code{@var{modename}-mode-syntax-table}. @xref{Syntax |
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228 | Tables}. |
229 | ||
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230 | @item |
231 | If the mode handles a language that has a syntax for comments, it should | |
232 | set the variables that define the comment syntax. @xref{Options for | |
233 | Comments,, Options Controlling Comments, emacs, The GNU Emacs Manual}. | |
234 | ||
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235 | @item |
236 | @cindex abbrev tables in modes | |
237 | The mode may have its own abbrev table or may share one with other | |
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238 | related modes. If it has its own abbrev table, it should store this |
239 | in a variable named @code{@var{modename}-mode-abbrev-table}. If the | |
240 | major mode command defines any abbrevs itself, it should pass @code{t} | |
241 | for the @var{system-flag} argument to @code{define-abbrev}. | |
242 | @xref{Abbrev Tables}. | |
a44af9f2 | 243 | |
be9345cf | 244 | @item |
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245 | The mode should specify how to do highlighting for Font Lock mode, by |
246 | setting up a buffer-local value for the variable | |
969fe9b5 | 247 | @code{font-lock-defaults} (@pxref{Font Lock Mode}). |
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248 | |
249 | @item | |
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250 | The mode should specify how Imenu should find the definitions or |
251 | sections of a buffer, by setting up a buffer-local value for the | |
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252 | variable @code{imenu-generic-expression}, for the pair of variables |
253 | @code{imenu-prev-index-position-function} and | |
254 | @code{imenu-extract-index-name-function}, or for the variable | |
969fe9b5 | 255 | @code{imenu-create-index-function} (@pxref{Imenu}). |
be9345cf | 256 | |
de9f0bd9 | 257 | @item |
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258 | Use @code{defvar} or @code{defcustom} to set mode-related variables, so |
259 | that they are not reinitialized if they already have a value. (Such | |
260 | reinitialization could discard customizations made by the user.) | |
de9f0bd9 | 261 | |
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262 | @item |
263 | @cindex buffer-local variables in modes | |
264 | To make a buffer-local binding for an Emacs customization variable, use | |
265 | @code{make-local-variable} in the major mode command, not | |
266 | @code{make-variable-buffer-local}. The latter function would make the | |
267 | variable local to every buffer in which it is subsequently set, which | |
268 | would affect buffers that do not use this mode. It is undesirable for a | |
269 | mode to have such global effects. @xref{Buffer-Local Variables}. | |
270 | ||
177c0ea7 | 271 | With rare exceptions, the only reasonable way to use |
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272 | @code{make-variable-buffer-local} in a Lisp package is for a variable |
273 | which is used only within that package. Using it on a variable used by | |
274 | other packages would interfere with them. | |
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275 | |
276 | @item | |
277 | @cindex mode hook | |
278 | @cindex major mode hook | |
279 | Each major mode should have a @dfn{mode hook} named | |
280 | @code{@var{modename}-mode-hook}. The major mode command should run that | |
fdba9ef4 | 281 | hook, with @code{run-mode-hooks}, as the very last thing it |
a3ee0299 | 282 | does. @xref{Mode Hooks}. |
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283 | |
284 | @item | |
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285 | The major mode command may start by calling some other major mode |
286 | command (called the @dfn{parent mode}) and then alter some of its | |
287 | settings. A mode that does this is called a @dfn{derived mode}. The | |
288 | recommended way to define one is to use @code{define-derived-mode}, | |
289 | but this is not required. Such a mode should use | |
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290 | @code{delay-mode-hooks} around its entire body (including the call to |
291 | the parent mode command) @emph{except} for the final call to | |
292 | @code{run-mode-hooks}, which runs the derived mode's hook. (Using | |
293 | @code{define-derived-mode} does this automatically.) @xref{Derived | |
294 | Modes}, and @ref{Mode Hooks}. | |
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295 | |
296 | @item | |
297 | If something special should be done if the user switches a buffer from | |
f9f59935 | 298 | this mode to any other major mode, this mode can set up a buffer-local |
969fe9b5 | 299 | value for @code{change-major-mode-hook} (@pxref{Creating Buffer-Local}). |
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300 | |
301 | @item | |
302 | If this mode is appropriate only for specially-prepared text, then the | |
303 | major mode command symbol should have a property named @code{mode-class} | |
304 | with value @code{special}, put on as follows: | |
305 | ||
ace41f7d | 306 | @kindex mode-class @r{(property)} |
a44af9f2 RS |
307 | @cindex @code{special} |
308 | @example | |
309 | (put 'funny-mode 'mode-class 'special) | |
310 | @end example | |
311 | ||
312 | @noindent | |
ec9b0882 RS |
313 | This tells Emacs that new buffers created while the current buffer is |
314 | in Funny mode should not inherit Funny mode, in case | |
315 | @code{default-major-mode} is @code{nil}. Modes such as Dired, Rmail, | |
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316 | and Buffer List use this feature. |
317 | ||
318 | @item | |
319 | If you want to make the new mode the default for files with certain | |
320 | recognizable names, add an element to @code{auto-mode-alist} to select | |
321 | the mode for those file names. If you define the mode command to | |
322 | autoload, you should add this element in the same file that calls | |
323 | @code{autoload}. Otherwise, it is sufficient to add the element in the | |
324 | file that contains the mode definition. @xref{Auto Major Mode}. | |
325 | ||
326 | @item | |
ec9b0882 RS |
327 | In the comments that document the file, you should provide a sample |
328 | @code{autoload} form and an example of how to add to | |
329 | @code{auto-mode-alist}, that users can include in their init files | |
330 | (@pxref{Init File}). | |
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331 | |
332 | @item | |
333 | @cindex mode loading | |
de9f0bd9 | 334 | The top-level forms in the file defining the mode should be written so |
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335 | that they may be evaluated more than once without adverse consequences. |
336 | Even if you never load the file more than once, someone else will. | |
337 | @end itemize | |
338 | ||
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339 | @node Example Major Modes |
340 | @subsection Major Mode Examples | |
341 | ||
342 | Text mode is perhaps the simplest mode besides Fundamental mode. | |
343 | Here are excerpts from @file{text-mode.el} that illustrate many of | |
344 | the conventions listed above: | |
345 | ||
346 | @smallexample | |
347 | @group | |
ec9b0882 RS |
348 | ;; @r{Create the syntax table for this mode.} |
349 | (defvar text-mode-syntax-table | |
350 | (let ((st (make-syntax-table))) | |
351 | (modify-syntax-entry ?\" ". " st) | |
352 | (modify-syntax-entry ?\\ ". " st) | |
353 | ;; We add `p' so that M-c on 'hello' leads to 'Hello' rather than 'hello'. | |
354 | (modify-syntax-entry ?' "w p" st) | |
355 | st) | |
356 | "Syntax table used while in `text-mode'.") | |
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357 | @end group |
358 | ||
ec9b0882 | 359 | ;; @r{Create the keymap for this mode.} |
a44af9f2 | 360 | @group |
ec9b0882 RS |
361 | (defvar text-mode-map |
362 | (let ((map (make-sparse-keymap))) | |
363 | (define-key map "\e\t" 'ispell-complete-word) | |
364 | (define-key map "\es" 'center-line) | |
365 | (define-key map "\eS" 'center-paragraph) | |
366 | map) | |
367 | "Keymap for `text-mode'. | |
368 | Many other modes, such as `mail-mode', `outline-mode' and `indented-text-mode', | |
369 | inherit all the commands defined in this map.") | |
a44af9f2 | 370 | @end group |
ec9b0882 | 371 | @end smallexample |
a44af9f2 | 372 | |
ec9b0882 RS |
373 | Here is how the actual mode command is defined now: |
374 | ||
375 | @smallexample | |
a44af9f2 | 376 | @group |
ec9b0882 RS |
377 | (define-derived-mode text-mode nil "Text" |
378 | "Major mode for editing text written for humans to read. | |
379 | In this mode, paragraphs are delimited only by blank or white lines. | |
380 | You can thus get the full benefit of adaptive filling | |
381 | (see the variable `adaptive-fill-mode'). | |
1f9ad95a | 382 | \\@{text-mode-map@} |
ec9b0882 | 383 | Turning on Text mode runs the normal hook `text-mode-hook'." |
a44af9f2 | 384 | @end group |
a44af9f2 | 385 | @group |
ec9b0882 RS |
386 | (make-local-variable 'text-mode-variant) |
387 | (setq text-mode-variant t) | |
388 | ;; @r{These two lines are a feature added recently.} | |
389 | (set (make-local-variable 'require-final-newline) | |
390 | mode-require-final-newline) | |
391 | (set (make-local-variable 'indent-line-function) 'indent-relative)) | |
a44af9f2 RS |
392 | @end group |
393 | @end smallexample | |
394 | ||
ec9b0882 RS |
395 | But here is how it was defined formerly, before |
396 | @code{define-derived-mode} existed: | |
a44af9f2 RS |
397 | |
398 | @smallexample | |
ec9b0882 RS |
399 | @group |
400 | ;; @r{This isn't needed nowadays, since @code{define-derived-mode} does it.} | |
401 | (defvar text-mode-abbrev-table nil | |
402 | "Abbrev table used while in text mode.") | |
403 | (define-abbrev-table 'text-mode-abbrev-table ()) | |
404 | @end group | |
405 | ||
a44af9f2 RS |
406 | @group |
407 | (defun text-mode () | |
29b677db | 408 | "Major mode for editing text intended for humans to read... |
a44af9f2 RS |
409 | Special commands: \\@{text-mode-map@} |
410 | @end group | |
411 | @group | |
412 | Turning on text-mode runs the hook `text-mode-hook'." | |
413 | (interactive) | |
414 | (kill-all-local-variables) | |
969fe9b5 | 415 | (use-local-map text-mode-map) |
a44af9f2 RS |
416 | @end group |
417 | @group | |
a44af9f2 RS |
418 | (setq local-abbrev-table text-mode-abbrev-table) |
419 | (set-syntax-table text-mode-syntax-table) | |
969fe9b5 RS |
420 | @end group |
421 | @group | |
ec9b0882 RS |
422 | ;; @r{These four lines are absent from the current version} |
423 | ;; @r{not because this is done some other way, but rather} | |
424 | ;; @r{because nowadays Text mode uses the normal definition of paragraphs.} | |
969fe9b5 RS |
425 | (make-local-variable 'paragraph-start) |
426 | (setq paragraph-start (concat "[ \t]*$\\|" page-delimiter)) | |
427 | (make-local-variable 'paragraph-separate) | |
428 | (setq paragraph-separate paragraph-start) | |
a40d4712 PR |
429 | (make-local-variable 'indent-line-function) |
430 | (setq indent-line-function 'indent-relative-maybe) | |
969fe9b5 RS |
431 | @end group |
432 | @group | |
433 | (setq mode-name "Text") | |
434 | (setq major-mode 'text-mode) | |
fdba9ef4 | 435 | (run-mode-hooks 'text-mode-hook)) ; @r{Finally, this permits the user to} |
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436 | ; @r{customize the mode with a hook.} |
437 | @end group | |
438 | @end smallexample | |
439 | ||
440 | @cindex @file{lisp-mode.el} | |
441 | The three Lisp modes (Lisp mode, Emacs Lisp mode, and Lisp | |
442 | Interaction mode) have more features than Text mode and the code is | |
443 | correspondingly more complicated. Here are excerpts from | |
444 | @file{lisp-mode.el} that illustrate how these modes are written. | |
445 | ||
446 | @cindex syntax table example | |
447 | @smallexample | |
448 | @group | |
449 | ;; @r{Create mode-specific table variables.} | |
177c0ea7 | 450 | (defvar lisp-mode-syntax-table nil "") |
a44af9f2 RS |
451 | (defvar lisp-mode-abbrev-table nil "") |
452 | @end group | |
453 | ||
454 | @group | |
ec9b0882 RS |
455 | (defvar emacs-lisp-mode-syntax-table |
456 | (let ((table (make-syntax-table))) | |
a44af9f2 | 457 | (let ((i 0)) |
a44af9f2 RS |
458 | @end group |
459 | ||
460 | @group | |
ec9b0882 | 461 | ;; @r{Set syntax of chars up to @samp{0} to say they are} |
a44af9f2 | 462 | ;; @r{part of symbol names but not words.} |
ec9b0882 | 463 | ;; @r{(The digit @samp{0} is @code{48} in the @acronym{ASCII} character set.)} |
177c0ea7 | 464 | (while (< i ?0) |
ec9b0882 RS |
465 | (modify-syntax-entry i "_ " table) |
466 | (setq i (1+ i))) | |
467 | ;; @r{@dots{} similar code follows for other character ranges.} | |
a44af9f2 RS |
468 | @end group |
469 | @group | |
ec9b0882 RS |
470 | ;; @r{Then set the syntax codes for characters that are special in Lisp.} |
471 | (modify-syntax-entry ? " " table) | |
472 | (modify-syntax-entry ?\t " " table) | |
473 | (modify-syntax-entry ?\f " " table) | |
474 | (modify-syntax-entry ?\n "> " table) | |
a44af9f2 RS |
475 | @end group |
476 | @group | |
ec9b0882 RS |
477 | ;; @r{Give CR the same syntax as newline, for selective-display.} |
478 | (modify-syntax-entry ?\^m "> " table) | |
479 | (modify-syntax-entry ?\; "< " table) | |
480 | (modify-syntax-entry ?` "' " table) | |
481 | (modify-syntax-entry ?' "' " table) | |
482 | (modify-syntax-entry ?, "' " table) | |
483 | @end group | |
ec9b0882 RS |
484 | @group |
485 | ;; @r{@dots{}likewise for many other characters@dots{}} | |
486 | (modify-syntax-entry ?\( "() " table) | |
487 | (modify-syntax-entry ?\) ")( " table) | |
488 | (modify-syntax-entry ?\[ "(] " table) | |
489 | (modify-syntax-entry ?\] ")[ " table)) | |
490 | table)) | |
491 | @end group | |
1f9ad95a | 492 | @group |
a44af9f2 RS |
493 | ;; @r{Create an abbrev table for lisp-mode.} |
494 | (define-abbrev-table 'lisp-mode-abbrev-table ()) | |
495 | @end group | |
496 | @end smallexample | |
497 | ||
498 | Much code is shared among the three Lisp modes. The following | |
499 | function sets various variables; it is called by each of the major Lisp | |
500 | mode functions: | |
501 | ||
502 | @smallexample | |
503 | @group | |
504 | (defun lisp-mode-variables (lisp-syntax) | |
ec9b0882 RS |
505 | (when lisp-syntax |
506 | (set-syntax-table lisp-mode-syntax-table)) | |
a44af9f2 | 507 | (setq local-abbrev-table lisp-mode-abbrev-table) |
a9f0a989 | 508 | @dots{} |
a44af9f2 RS |
509 | @end group |
510 | @end smallexample | |
511 | ||
512 | Functions such as @code{forward-paragraph} use the value of the | |
513 | @code{paragraph-start} variable. Since Lisp code is different from | |
514 | ordinary text, the @code{paragraph-start} variable needs to be set | |
515 | specially to handle Lisp. Also, comments are indented in a special | |
516 | fashion in Lisp and the Lisp modes need their own mode-specific | |
517 | @code{comment-indent-function}. The code to set these variables is the | |
518 | rest of @code{lisp-mode-variables}. | |
519 | ||
520 | @smallexample | |
521 | @group | |
522 | (make-local-variable 'paragraph-start) | |
969fe9b5 RS |
523 | (setq paragraph-start (concat page-delimiter "\\|$" )) |
524 | (make-local-variable 'paragraph-separate) | |
525 | (setq paragraph-separate paragraph-start) | |
a44af9f2 RS |
526 | @dots{} |
527 | @end group | |
528 | @group | |
529 | (make-local-variable 'comment-indent-function) | |
530 | (setq comment-indent-function 'lisp-comment-indent)) | |
a40d4712 | 531 | @dots{} |
a44af9f2 RS |
532 | @end group |
533 | @end smallexample | |
534 | ||
535 | Each of the different Lisp modes has a slightly different keymap. For | |
f9f59935 | 536 | example, Lisp mode binds @kbd{C-c C-z} to @code{run-lisp}, but the other |
a44af9f2 | 537 | Lisp modes do not. However, all Lisp modes have some commands in |
969fe9b5 | 538 | common. The following code sets up the common commands: |
a44af9f2 RS |
539 | |
540 | @smallexample | |
541 | @group | |
969fe9b5 RS |
542 | (defvar shared-lisp-mode-map () |
543 | "Keymap for commands shared by all sorts of Lisp modes.") | |
544 | ||
ec9b0882 | 545 | ;; @r{Putting this @code{if} after the @code{defvar} is an older style.} |
969fe9b5 RS |
546 | (if shared-lisp-mode-map |
547 | () | |
548 | (setq shared-lisp-mode-map (make-sparse-keymap)) | |
549 | (define-key shared-lisp-mode-map "\e\C-q" 'indent-sexp) | |
550 | (define-key shared-lisp-mode-map "\177" | |
551 | 'backward-delete-char-untabify)) | |
a44af9f2 RS |
552 | @end group |
553 | @end smallexample | |
554 | ||
969fe9b5 RS |
555 | @noindent |
556 | And here is the code to set up the keymap for Lisp mode: | |
a44af9f2 RS |
557 | |
558 | @smallexample | |
559 | @group | |
969fe9b5 | 560 | (defvar lisp-mode-map () |
29b677db | 561 | "Keymap for ordinary Lisp mode...") |
969fe9b5 RS |
562 | |
563 | (if lisp-mode-map | |
a44af9f2 | 564 | () |
969fe9b5 RS |
565 | (setq lisp-mode-map (make-sparse-keymap)) |
566 | (set-keymap-parent lisp-mode-map shared-lisp-mode-map) | |
567 | (define-key lisp-mode-map "\e\C-x" 'lisp-eval-defun) | |
568 | (define-key lisp-mode-map "\C-c\C-z" 'run-lisp)) | |
a44af9f2 RS |
569 | @end group |
570 | @end smallexample | |
571 | ||
572 | Finally, here is the complete major mode function definition for | |
177c0ea7 | 573 | Lisp mode. |
a44af9f2 RS |
574 | |
575 | @smallexample | |
576 | @group | |
969fe9b5 RS |
577 | (defun lisp-mode () |
578 | "Major mode for editing Lisp code for Lisps other than GNU Emacs Lisp. | |
a44af9f2 RS |
579 | Commands: |
580 | Delete converts tabs to spaces as it moves back. | |
581 | Blank lines separate paragraphs. Semicolons start comments. | |
969fe9b5 RS |
582 | \\@{lisp-mode-map@} |
583 | Note that `run-lisp' may be used either to start an inferior Lisp job | |
584 | or to switch back to an existing one. | |
a44af9f2 | 585 | @end group |
969fe9b5 | 586 | |
a44af9f2 | 587 | @group |
969fe9b5 RS |
588 | Entry to this mode calls the value of `lisp-mode-hook' |
589 | if that value is non-nil." | |
a44af9f2 RS |
590 | (interactive) |
591 | (kill-all-local-variables) | |
a44af9f2 RS |
592 | @end group |
593 | @group | |
969fe9b5 RS |
594 | (use-local-map lisp-mode-map) ; @r{Select the mode's keymap.} |
595 | (setq major-mode 'lisp-mode) ; @r{This is how @code{describe-mode}} | |
a44af9f2 | 596 | ; @r{finds out what to describe.} |
969fe9b5 RS |
597 | (setq mode-name "Lisp") ; @r{This goes into the mode line.} |
598 | (lisp-mode-variables t) ; @r{This defines various variables.} | |
ec9b0882 RS |
599 | (make-local-variable 'comment-start-skip) |
600 | (setq comment-start-skip | |
601 | "\\(\\(^\\|[^\\\\\n]\\)\\(\\\\\\\\\\)*\\)\\(;+\\|#|\\) *") | |
602 | (make-local-variable 'font-lock-keywords-case-fold-search) | |
603 | (setq font-lock-keywords-case-fold-search t) | |
969fe9b5 RS |
604 | @end group |
605 | @group | |
606 | (setq imenu-case-fold-search t) | |
607 | (set-syntax-table lisp-mode-syntax-table) | |
fdba9ef4 | 608 | (run-mode-hooks 'lisp-mode-hook)) ; @r{This permits the user to use a} |
a44af9f2 RS |
609 | ; @r{hook to customize the mode.} |
610 | @end group | |
611 | @end smallexample | |
612 | ||
613 | @node Auto Major Mode | |
614 | @subsection How Emacs Chooses a Major Mode | |
615 | ||
616 | Based on information in the file name or in the file itself, Emacs | |
617 | automatically selects a major mode for the new buffer when a file is | |
969fe9b5 | 618 | visited. It also processes local variables specified in the file text. |
a44af9f2 RS |
619 | |
620 | @deffn Command fundamental-mode | |
621 | Fundamental mode is a major mode that is not specialized for anything | |
622 | in particular. Other major modes are defined in effect by comparison | |
623 | with this one---their definitions say what to change, starting from | |
624 | Fundamental mode. The @code{fundamental-mode} function does @emph{not} | |
a3ee0299 | 625 | run any mode hooks; you're not supposed to customize it. (If you want Emacs |
a44af9f2 RS |
626 | to behave differently in Fundamental mode, change the @emph{global} |
627 | state of Emacs.) | |
628 | @end deffn | |
629 | ||
630 | @deffn Command normal-mode &optional find-file | |
969fe9b5 | 631 | This function establishes the proper major mode and buffer-local variable |
a44af9f2 RS |
632 | bindings for the current buffer. First it calls @code{set-auto-mode}, |
633 | then it runs @code{hack-local-variables} to parse, and bind or | |
969fe9b5 | 634 | evaluate as appropriate, the file's local variables. |
a44af9f2 | 635 | |
969fe9b5 RS |
636 | If the @var{find-file} argument to @code{normal-mode} is non-@code{nil}, |
637 | @code{normal-mode} assumes that the @code{find-file} function is calling | |
638 | it. In this case, it may process a local variables list at the end of | |
639 | the file and in the @samp{-*-} line. The variable | |
640 | @code{enable-local-variables} controls whether to do so. @xref{File | |
641 | variables, , Local Variables in Files, emacs, The GNU Emacs Manual}, for | |
642 | the syntax of the local variables section of a file. | |
a44af9f2 | 643 | |
bfe721d1 | 644 | If you run @code{normal-mode} interactively, the argument |
a44af9f2 RS |
645 | @var{find-file} is normally @code{nil}. In this case, |
646 | @code{normal-mode} unconditionally processes any local variables list. | |
a44af9f2 RS |
647 | |
648 | @cindex file mode specification error | |
bfe721d1 | 649 | @code{normal-mode} uses @code{condition-case} around the call to the |
a44af9f2 RS |
650 | major mode function, so errors are caught and reported as a @samp{File |
651 | mode specification error}, followed by the original error message. | |
652 | @end deffn | |
653 | ||
a44af9f2 RS |
654 | @defun set-auto-mode |
655 | @cindex visited file mode | |
656 | This function selects the major mode that is appropriate for the | |
657 | current buffer. It may base its decision on the value of the @w{@samp{-*-}} | |
76352dc1 RS |
658 | line, on the visited file name (using @code{auto-mode-alist}), on the |
659 | @w{@samp{#!}} line (using @code{interpreter-mode-alist}), or on the | |
969fe9b5 | 660 | file's local variables list. However, this function does not look for |
a44af9f2 RS |
661 | the @samp{mode:} local variable near the end of a file; the |
662 | @code{hack-local-variables} function does that. @xref{Choosing Modes, , | |
663 | How Major Modes are Chosen, emacs, The GNU Emacs Manual}. | |
664 | @end defun | |
665 | ||
177c0ea7 | 666 | @defopt default-major-mode |
969fe9b5 | 667 | This variable holds the default major mode for new buffers. The |
a44af9f2 RS |
668 | standard value is @code{fundamental-mode}. |
669 | ||
969fe9b5 | 670 | If the value of @code{default-major-mode} is @code{nil}, Emacs uses |
a44af9f2 | 671 | the (previously) current buffer's major mode for the major mode of a new |
f9f59935 | 672 | buffer. However, if that major mode symbol has a @code{mode-class} |
a44af9f2 RS |
673 | property with value @code{special}, then it is not used for new buffers; |
674 | Fundamental mode is used instead. The modes that have this property are | |
675 | those such as Dired and Rmail that are useful only with text that has | |
676 | been specially prepared. | |
677 | @end defopt | |
678 | ||
22697dac KH |
679 | @defun set-buffer-major-mode buffer |
680 | This function sets the major mode of @var{buffer} to the value of | |
681 | @code{default-major-mode}. If that variable is @code{nil}, it uses | |
682 | the current buffer's major mode (if that is suitable). | |
683 | ||
684 | The low-level primitives for creating buffers do not use this function, | |
bfe721d1 KH |
685 | but medium-level commands such as @code{switch-to-buffer} and |
686 | @code{find-file-noselect} use it whenever they create buffers. | |
22697dac KH |
687 | @end defun |
688 | ||
a44af9f2 RS |
689 | @defvar initial-major-mode |
690 | @cindex @samp{*scratch*} | |
691 | The value of this variable determines the major mode of the initial | |
692 | @samp{*scratch*} buffer. The value should be a symbol that is a major | |
f9f59935 | 693 | mode command. The default value is @code{lisp-interaction-mode}. |
a44af9f2 RS |
694 | @end defvar |
695 | ||
696 | @defvar auto-mode-alist | |
697 | This variable contains an association list of file name patterns | |
698 | (regular expressions; @pxref{Regular Expressions}) and corresponding | |
f9f59935 RS |
699 | major mode commands. Usually, the file name patterns test for suffixes, |
700 | such as @samp{.el} and @samp{.c}, but this need not be the case. An | |
701 | ordinary element of the alist looks like @code{(@var{regexp} . | |
a44af9f2 RS |
702 | @var{mode-function})}. |
703 | ||
704 | For example, | |
705 | ||
706 | @smallexample | |
707 | @group | |
969fe9b5 | 708 | (("\\`/tmp/fol/" . text-mode) |
24675e99 RS |
709 | ("\\.texinfo\\'" . texinfo-mode) |
710 | ("\\.texi\\'" . texinfo-mode) | |
a44af9f2 RS |
711 | @end group |
712 | @group | |
24675e99 | 713 | ("\\.el\\'" . emacs-lisp-mode) |
177c0ea7 | 714 | ("\\.c\\'" . c-mode) |
24675e99 | 715 | ("\\.h\\'" . c-mode) |
a44af9f2 RS |
716 | @dots{}) |
717 | @end group | |
718 | @end smallexample | |
719 | ||
720 | When you visit a file whose expanded file name (@pxref{File Name | |
721 | Expansion}) matches a @var{regexp}, @code{set-auto-mode} calls the | |
722 | corresponding @var{mode-function}. This feature enables Emacs to select | |
723 | the proper major mode for most files. | |
724 | ||
725 | If an element of @code{auto-mode-alist} has the form @code{(@var{regexp} | |
726 | @var{function} t)}, then after calling @var{function}, Emacs searches | |
727 | @code{auto-mode-alist} again for a match against the portion of the file | |
969fe9b5 RS |
728 | name that did not match before. This feature is useful for |
729 | uncompression packages: an entry of the form @code{("\\.gz\\'" | |
730 | @var{function} t)} can uncompress the file and then put the uncompressed | |
731 | file in the proper mode according to the name sans @samp{.gz}. | |
a44af9f2 RS |
732 | |
733 | Here is an example of how to prepend several pattern pairs to | |
734 | @code{auto-mode-alist}. (You might use this sort of expression in your | |
a40d4712 | 735 | init file.) |
a44af9f2 RS |
736 | |
737 | @smallexample | |
738 | @group | |
739 | (setq auto-mode-alist | |
177c0ea7 | 740 | (append |
f9f59935 | 741 | ;; @r{File name (within directory) starts with a dot.} |
177c0ea7 | 742 | '(("/\\.[^/]*\\'" . fundamental-mode) |
de9f0bd9 | 743 | ;; @r{File name has no dot.} |
177c0ea7 | 744 | ("[^\\./]*\\'" . fundamental-mode) |
de9f0bd9 | 745 | ;; @r{File name ends in @samp{.C}.} |
24675e99 | 746 | ("\\.C\\'" . c++-mode)) |
a44af9f2 RS |
747 | auto-mode-alist)) |
748 | @end group | |
749 | @end smallexample | |
750 | @end defvar | |
751 | ||
752 | @defvar interpreter-mode-alist | |
f9f59935 | 753 | This variable specifies major modes to use for scripts that specify a |
86494bd5 | 754 | command interpreter in a @samp{#!} line. Its value is a list of |
a44af9f2 RS |
755 | elements of the form @code{(@var{interpreter} . @var{mode})}; for |
756 | example, @code{("perl" . perl-mode)} is one element present by default. | |
757 | The element says to use mode @var{mode} if the file specifies | |
f9f59935 RS |
758 | an interpreter which matches @var{interpreter}. The value of |
759 | @var{interpreter} is actually a regular expression. | |
a44af9f2 | 760 | |
de9f0bd9 RS |
761 | This variable is applicable only when the @code{auto-mode-alist} does |
762 | not indicate which major mode to use. | |
a44af9f2 RS |
763 | @end defvar |
764 | ||
a44af9f2 RS |
765 | @node Mode Help |
766 | @subsection Getting Help about a Major Mode | |
767 | @cindex mode help | |
768 | @cindex help for major mode | |
769 | @cindex documentation for major mode | |
770 | ||
771 | The @code{describe-mode} function is used to provide information | |
772 | about major modes. It is normally called with @kbd{C-h m}. The | |
773 | @code{describe-mode} function uses the value of @code{major-mode}, | |
774 | which is why every major mode function needs to set the | |
775 | @code{major-mode} variable. | |
776 | ||
777 | @deffn Command describe-mode | |
778 | This function displays the documentation of the current major mode. | |
779 | ||
780 | The @code{describe-mode} function calls the @code{documentation} | |
781 | function using the value of @code{major-mode} as an argument. Thus, it | |
782 | displays the documentation string of the major mode function. | |
783 | (@xref{Accessing Documentation}.) | |
784 | @end deffn | |
785 | ||
786 | @defvar major-mode | |
787 | This variable holds the symbol for the current buffer's major mode. | |
de9f0bd9 | 788 | This symbol should have a function definition that is the command to |
a44af9f2 | 789 | switch to that major mode. The @code{describe-mode} function uses the |
de9f0bd9 | 790 | documentation string of the function as the documentation of the major |
a44af9f2 RS |
791 | mode. |
792 | @end defvar | |
793 | ||
794 | @node Derived Modes | |
795 | @subsection Defining Derived Modes | |
796 | ||
797 | It's often useful to define a new major mode in terms of an existing | |
798 | one. An easy way to do this is to use @code{define-derived-mode}. | |
799 | ||
de9f0bd9 | 800 | @defmac define-derived-mode variant parent name docstring body@dots{} |
a44af9f2 | 801 | This construct defines @var{variant} as a major mode command, using |
de9f0bd9 | 802 | @var{name} as the string form of the mode name. |
a44af9f2 | 803 | |
de9f0bd9 RS |
804 | The new command @var{variant} is defined to call the function |
805 | @var{parent}, then override certain aspects of that parent mode: | |
a44af9f2 | 806 | |
177c0ea7 | 807 | @itemize @bullet |
a44af9f2 RS |
808 | @item |
809 | The new mode has its own keymap, named @code{@var{variant}-map}. | |
810 | @code{define-derived-mode} initializes this map to inherit from | |
811 | @code{@var{parent}-map}, if it is not already set. | |
812 | ||
813 | @item | |
de9f0bd9 | 814 | The new mode has its own syntax table, kept in the variable |
a44af9f2 | 815 | @code{@var{variant}-syntax-table}. |
177c0ea7 | 816 | @code{define-derived-mode} initializes this variable by copying |
a44af9f2 RS |
817 | @code{@var{parent}-syntax-table}, if it is not already set. |
818 | ||
819 | @item | |
de9f0bd9 | 820 | The new mode has its own abbrev table, kept in the variable |
a44af9f2 | 821 | @code{@var{variant}-abbrev-table}. |
177c0ea7 | 822 | @code{define-derived-mode} initializes this variable by copying |
a44af9f2 RS |
823 | @code{@var{parent}-abbrev-table}, if it is not already set. |
824 | ||
825 | @item | |
826 | The new mode has its own mode hook, @code{@var{variant}-hook}, | |
827 | which it runs in standard fashion as the very last thing that it does. | |
177c0ea7 | 828 | (The new mode also runs the mode hook of @var{parent} as part |
a44af9f2 RS |
829 | of calling @var{parent}.) |
830 | @end itemize | |
831 | ||
832 | In addition, you can specify how to override other aspects of | |
de9f0bd9 | 833 | @var{parent} with @var{body}. The command @var{variant} |
177c0ea7 | 834 | evaluates the forms in @var{body} after setting up all its usual |
a44af9f2 RS |
835 | overrides, just before running @code{@var{variant}-hook}. |
836 | ||
837 | The argument @var{docstring} specifies the documentation string for the | |
838 | new mode. If you omit @var{docstring}, @code{define-derived-mode} | |
839 | generates a documentation string. | |
840 | ||
841 | Here is a hypothetical example: | |
842 | ||
843 | @example | |
844 | (define-derived-mode hypertext-mode | |
845 | text-mode "Hypertext" | |
846 | "Major mode for hypertext. | |
847 | \\@{hypertext-mode-map@}" | |
848 | (setq case-fold-search nil)) | |
849 | ||
850 | (define-key hypertext-mode-map | |
851 | [down-mouse-3] 'do-hyper-link) | |
852 | @end example | |
f140458b RS |
853 | |
854 | Do not write an @code{interactive} spec in the definition; | |
855 | @code{define-derived-mode} does that automatically. | |
a44af9f2 RS |
856 | @end defmac |
857 | ||
a3ee0299 LT |
858 | @node Mode Hooks |
859 | @subsection Mode Hooks | |
860 | ||
861 | The two last things a major mode function does is to run its mode | |
862 | hook and finally the mode independent normal hook | |
863 | @code{after-change-major-mode-hook}. If the major mode is a derived | |
864 | mode, that is if it calls another major mode (the parent mode) in its | |
865 | body, then the parent's mode hook is run just before the derived | |
866 | mode's hook. Neither the parent's mode hook nor | |
867 | @code{after-change-major-mode-hook} are run at the end of the actual | |
868 | call to the parent mode. This applies recursively if the parent mode | |
869 | has itself a parent. That is, the mode hooks of all major modes called | |
870 | directly or indirectly by the major mode function are all run in | |
871 | sequence at the end, just before @code{after-change-major-mode-hook}. | |
872 | ||
873 | If you are customizing a major mode, rather than defining one, the | |
874 | above is all you need to know about the hooks run at the end of a | |
875 | major mode. This also applies if you use @code{define-derived-mode} | |
876 | to define a major mode, because that macro will automatically | |
877 | implement the above for you. | |
878 | ||
879 | Programmers wishing to define a major mode without using | |
880 | @code{define-derived-mode}, should make sure that their major mode | |
881 | follows the above conventions. @xref{Major Mode Conventions}, for how | |
882 | this should be accomplished. Below, we give some implementation | |
883 | details. | |
884 | ||
885 | @defun run-mode-hooks &rest hookvars | |
886 | Major modes should run their mode hook using this function. It is | |
887 | similar to @code{run-hooks} (@pxref{Hooks}), but if run inside a | |
888 | @code{delay-mode-hooks} form, this function does not run any hooks. | |
889 | Instead, it arranges for @var{hookvars} to be run at a later call to | |
890 | the function. Otherwise, @code{run-mode-hooks} runs any delayed hooks | |
891 | in order, then @var{hookvars} and finally | |
892 | @code{after-change-major-mode-hook}. | |
893 | @end defun | |
894 | ||
895 | @defmac delay-mode-hooks body... | |
896 | This macro executes @var{body} like @code{progn}, but all calls to | |
897 | @code{run-mode-hooks} inside @var{body} delay running their hooks. | |
898 | They will be run by the first call to @code{run-mode-hooks} after exit | |
899 | from @code{delay-mode-hooks}. | |
900 | @end defmac | |
901 | ||
902 | @defvar after-change-major-mode-hook | |
903 | Every major mode function should run this normal hook at its very end. | |
904 | It normally does not need to do so explicitly. Indeed, a major mode | |
905 | function should normally run its mode hook with @code{run-mode-hooks} | |
906 | as the very last thing it does and @code{run-mode-hooks} runs | |
907 | @code{after-change-major-mode-hook} at its very end. | |
908 | @end defvar | |
909 | ||
a44af9f2 RS |
910 | @node Minor Modes |
911 | @section Minor Modes | |
912 | @cindex minor mode | |
913 | ||
914 | A @dfn{minor mode} provides features that users may enable or disable | |
915 | independently of the choice of major mode. Minor modes can be enabled | |
916 | individually or in combination. Minor modes would be better named | |
969fe9b5 RS |
917 | ``generally available, optional feature modes,'' except that such a name |
918 | would be unwieldy. | |
a44af9f2 | 919 | |
8241495d RS |
920 | A minor mode is not usually meant as a variation of a single major mode. |
921 | Usually they are general and can apply to many major modes. For | |
969fe9b5 | 922 | example, Auto Fill mode works with any major mode that permits text |
a44af9f2 RS |
923 | insertion. To be general, a minor mode must be effectively independent |
924 | of the things major modes do. | |
925 | ||
926 | A minor mode is often much more difficult to implement than a major | |
927 | mode. One reason is that you should be able to activate and deactivate | |
de9f0bd9 RS |
928 | minor modes in any order. A minor mode should be able to have its |
929 | desired effect regardless of the major mode and regardless of the other | |
930 | minor modes in effect. | |
a44af9f2 RS |
931 | |
932 | Often the biggest problem in implementing a minor mode is finding a | |
933 | way to insert the necessary hook into the rest of Emacs. Minor mode | |
bfe721d1 | 934 | keymaps make this easier than it used to be. |
a44af9f2 | 935 | |
fdba9ef4 RS |
936 | @defvar minor-mode-list |
937 | The value of this variable is a list of all minor mode commands. | |
938 | @end defvar | |
939 | ||
a44af9f2 RS |
940 | @menu |
941 | * Minor Mode Conventions:: Tips for writing a minor mode. | |
942 | * Keymaps and Minor Modes:: How a minor mode can have its own keymap. | |
2468d0c0 | 943 | * Defining Minor Modes:: A convenient facility for defining minor modes. |
a44af9f2 RS |
944 | @end menu |
945 | ||
946 | @node Minor Mode Conventions | |
947 | @subsection Conventions for Writing Minor Modes | |
948 | @cindex minor mode conventions | |
949 | @cindex conventions for writing minor modes | |
950 | ||
951 | There are conventions for writing minor modes just as there are for | |
952 | major modes. Several of the major mode conventions apply to minor | |
953 | modes as well: those regarding the name of the mode initialization | |
954 | function, the names of global symbols, and the use of keymaps and | |
955 | other tables. | |
956 | ||
957 | In addition, there are several conventions that are specific to | |
ec9b0882 RS |
958 | minor modes. (The easiest way to follow all the conventions is to use |
959 | the macro @code{define-minor-mode}; @ref{Defining Minor Modes}.) | |
a44af9f2 RS |
960 | |
961 | @itemize @bullet | |
962 | @item | |
963 | @cindex mode variable | |
969fe9b5 RS |
964 | Make a variable whose name ends in @samp{-mode} to control the minor |
965 | mode. We call this the @dfn{mode variable}. The minor mode command | |
966 | should set this variable (@code{nil} to disable; anything else to | |
1911e6e5 | 967 | enable). |
969fe9b5 | 968 | |
8241495d | 969 | If possible, implement the mode so that setting the variable |
969fe9b5 | 970 | automatically enables or disables the mode. Then the minor mode command |
1911e6e5 | 971 | does not need to do anything except set the variable. |
a44af9f2 RS |
972 | |
973 | This variable is used in conjunction with the @code{minor-mode-alist} to | |
974 | display the minor mode name in the mode line. It can also enable | |
975 | or disable a minor mode keymap. Individual commands or hooks can also | |
976 | check the variable's value. | |
977 | ||
978 | If you want the minor mode to be enabled separately in each buffer, | |
979 | make the variable buffer-local. | |
980 | ||
981 | @item | |
982 | Define a command whose name is the same as the mode variable. | |
983 | Its job is to enable and disable the mode by setting the variable. | |
984 | ||
985 | The command should accept one optional argument. If the argument is | |
8cd4f018 RS |
986 | @code{nil}, it should toggle the mode (turn it on if it is off, and |
987 | off if it is on). It should turn the mode on if the argument is a | |
988 | positive integer, the symbol @code{t}, or a list whose @sc{car} is one | |
989 | of those. It should turn the mode off if the argument is a negative | |
4d386728 RS |
990 | integer or zero, the symbol @code{-}, or a list whose @sc{car} is a |
991 | negative integer or zero. The meaning of other arguments is not | |
992 | specified. | |
a44af9f2 | 993 | |
bfe721d1 KH |
994 | Here is an example taken from the definition of @code{transient-mark-mode}. |
995 | It shows the use of @code{transient-mark-mode} as a variable that enables or | |
de9f0bd9 RS |
996 | disables the mode's behavior, and also shows the proper way to toggle, |
997 | enable or disable the minor mode based on the raw prefix argument value. | |
a44af9f2 RS |
998 | |
999 | @smallexample | |
1000 | @group | |
bfe721d1 KH |
1001 | (setq transient-mark-mode |
1002 | (if (null arg) (not transient-mark-mode) | |
a44af9f2 RS |
1003 | (> (prefix-numeric-value arg) 0))) |
1004 | @end group | |
1005 | @end smallexample | |
1006 | ||
1007 | @item | |
1008 | Add an element to @code{minor-mode-alist} for each minor mode | |
969fe9b5 RS |
1009 | (@pxref{Mode Line Variables}), if you want to indicate the minor mode in |
1010 | the mode line. This element should be a list of the following form: | |
a44af9f2 RS |
1011 | |
1012 | @smallexample | |
1013 | (@var{mode-variable} @var{string}) | |
1014 | @end smallexample | |
1015 | ||
de9f0bd9 | 1016 | Here @var{mode-variable} is the variable that controls enabling of the |
a44af9f2 RS |
1017 | minor mode, and @var{string} is a short string, starting with a space, |
1018 | to represent the mode in the mode line. These strings must be short so | |
1019 | that there is room for several of them at once. | |
1020 | ||
1021 | When you add an element to @code{minor-mode-alist}, use @code{assq} to | |
1022 | check for an existing element, to avoid duplication. For example: | |
1023 | ||
1024 | @smallexample | |
1025 | @group | |
a40d4712 PR |
1026 | (unless (assq 'leif-mode minor-mode-alist) |
1027 | (setq minor-mode-alist | |
1028 | (cons '(leif-mode " Leif") minor-mode-alist))) | |
a44af9f2 RS |
1029 | @end group |
1030 | @end smallexample | |
a44af9f2 | 1031 | |
a40d4712 PR |
1032 | @noindent |
1033 | or like this, using @code{add-to-list} (@pxref{Setting Variables}): | |
1034 | ||
1035 | @smallexample | |
1036 | @group | |
1037 | (add-to-list 'minor-mode-alist '(leif-mode " Leif")) | |
1038 | @end group | |
1039 | @end smallexample | |
1040 | @end itemize | |
1911e6e5 | 1041 | |
8241495d RS |
1042 | Global minor modes distributed with Emacs should if possible support |
1043 | enabling and disabling via Custom (@pxref{Customization}). To do this, | |
1044 | the first step is to define the mode variable with @code{defcustom}, and | |
1045 | specify @code{:type boolean}. | |
1046 | ||
1047 | If just setting the variable is not sufficient to enable the mode, you | |
1048 | should also specify a @code{:set} method which enables the mode by | |
ec9b0882 | 1049 | invoking the mode command. Note in the variable's documentation string that |
8241495d RS |
1050 | setting the variable other than via Custom may not take effect. |
1051 | ||
1052 | Also mark the definition with an autoload cookie (@pxref{Autoload}), | |
1053 | and specify a @code{:require} so that customizing the variable will load | |
1054 | the library that defines the mode. This will copy suitable definitions | |
1055 | into @file{loaddefs.el} so that users can use @code{customize-option} to | |
1056 | enable the mode. For example: | |
1057 | ||
1058 | @smallexample | |
1059 | @group | |
1060 | ||
1061 | ;;;###autoload | |
1062 | (defcustom msb-mode nil | |
1063 | "Toggle msb-mode. | |
1064 | Setting this variable directly does not take effect; | |
1065 | use either \\[customize] or the function `msb-mode'." | |
1066 | :set (lambda (symbol value) | |
1067 | (msb-mode (or value 0))) | |
1068 | :initialize 'custom-initialize-default | |
1069 | :version "20.4" | |
1070 | :type 'boolean | |
1071 | :group 'msb | |
1072 | :require 'msb) | |
1073 | @end group | |
1074 | @end smallexample | |
1075 | ||
a44af9f2 RS |
1076 | @node Keymaps and Minor Modes |
1077 | @subsection Keymaps and Minor Modes | |
1078 | ||
bfe721d1 KH |
1079 | Each minor mode can have its own keymap, which is active when the mode |
1080 | is enabled. To set up a keymap for a minor mode, add an element to the | |
1081 | alist @code{minor-mode-map-alist}. @xref{Active Keymaps}. | |
a44af9f2 RS |
1082 | |
1083 | @cindex @code{self-insert-command}, minor modes | |
f9f59935 | 1084 | One use of minor mode keymaps is to modify the behavior of certain |
a44af9f2 RS |
1085 | self-inserting characters so that they do something else as well as |
1086 | self-insert. In general, this is the only way to do that, since the | |
1087 | facilities for customizing @code{self-insert-command} are limited to | |
1088 | special cases (designed for abbrevs and Auto Fill mode). (Do not try | |
1089 | substituting your own definition of @code{self-insert-command} for the | |
1090 | standard one. The editor command loop handles this function specially.) | |
1091 | ||
a4b12c74 RS |
1092 | The key sequences bound in a minor mode should consist of @kbd{C-c} |
1093 | followed by a punctuation character @emph{other than} @kbd{@{}, | |
8241495d | 1094 | @kbd{@}}, @kbd{<}, @kbd{>}, @kbd{:}, and @kbd{;}. (Those few punctuation |
a4b12c74 RS |
1095 | characters are reserved for major modes.) |
1096 | ||
2468d0c0 DL |
1097 | @node Defining Minor Modes |
1098 | @subsection Defining Minor Modes | |
f9f59935 | 1099 | |
2468d0c0 | 1100 | The macro @code{define-minor-mode} offers a convenient way of |
8dc811d3 | 1101 | implementing a mode in one self-contained definition. |
f9f59935 | 1102 | |
f24be0a7 | 1103 | @defmac define-minor-mode mode doc [init-value [lighter [keymap]]] keyword-args... body... |
2468d0c0 | 1104 | @tindex define-minor-mode |
fdba9ef4 RS |
1105 | This macro defines a new minor mode whose name is @var{mode} (a |
1106 | symbol). It defines a command named @var{mode} to toggle the minor | |
2468d0c0 DL |
1107 | mode, with @var{doc} as its documentation string. It also defines a |
1108 | variable named @var{mode}, which is set to @code{t} or @code{nil} by | |
1109 | enabling or disabling the mode. The variable is initialized to | |
1110 | @var{init-value}. | |
f9f59935 | 1111 | |
fdba9ef4 | 1112 | The string @var{lighter} says what to display in the mode line |
f9f59935 RS |
1113 | when the mode is enabled; if it is @code{nil}, the mode is not displayed |
1114 | in the mode line. | |
1115 | ||
1116 | The optional argument @var{keymap} specifies the keymap for the minor mode. | |
1117 | It can be a variable name, whose value is the keymap, or it can be an alist | |
1118 | specifying bindings in this form: | |
1119 | ||
1120 | @example | |
1121 | (@var{key-sequence} . @var{definition}) | |
1122 | @end example | |
fdba9ef4 | 1123 | |
f24be0a7 LK |
1124 | The above three arguments @var{init-value}, @var{lighter}, and |
1125 | @var{keymap} can be (partially) omitted when @var{keyword-args} are | |
1126 | used. The @var{keyword-args} consist of keywords followed by | |
1127 | corresponding values. A few keywords have special meanings: | |
fdba9ef4 RS |
1128 | |
1129 | @table @code | |
1130 | @item :global @var{global} | |
1131 | If non-@code{nil} specifies that the minor mode should be global. | |
1132 | By default, minor modes are buffer-local. | |
1133 | ||
1134 | @item :init-value @var{init-value} | |
1135 | This is equivalent to specifying @var{init-value} positionally. | |
1136 | ||
1137 | @item :lighter @var{lighter} | |
1138 | This is equivalent to specifying @var{lighter} positionally. | |
1139 | ||
1140 | @item :keymap @var{keymap} | |
1141 | This is equivalent to specifying @var{keymap} positionally. | |
1142 | @end table | |
1143 | ||
1144 | Any other keyword arguments are passed passed directly to the | |
1145 | @code{defcustom} generated for the variable @var{mode}. | |
1146 | ||
1147 | The command named @var{mode} finishes by executing the @var{body} forms, | |
1148 | if any, after it has performed the standard actions such as setting | |
1149 | the variable named @var{mode}. | |
f9f59935 RS |
1150 | @end defmac |
1151 | ||
fdba9ef4 RS |
1152 | @findex easy-mmode-define-minor-mode |
1153 | The name @code{easy-mmode-define-minor-mode} is an alias | |
1154 | for this macro. | |
1155 | ||
2468d0c0 | 1156 | Here is an example of using @code{define-minor-mode}: |
f9f59935 RS |
1157 | |
1158 | @smallexample | |
2468d0c0 | 1159 | (define-minor-mode hungry-mode |
969fe9b5 | 1160 | "Toggle Hungry mode. |
177c0ea7 | 1161 | With no argument, this command toggles the mode. |
f9f59935 RS |
1162 | Non-null prefix argument turns on the mode. |
1163 | Null prefix argument turns off the mode. | |
1164 | ||
1165 | When Hungry mode is enabled, the control delete key | |
1166 | gobbles all preceding whitespace except the last. | |
1167 | See the command \\[hungry-electric-delete]." | |
1168 | ;; The initial value. | |
1169 | nil | |
1170 | ;; The indicator for the mode line. | |
1171 | " Hungry" | |
1172 | ;; The minor mode bindings. | |
ec9b0882 | 1173 | '(("\C-\^?" . hungry-electric-delete)) |
fdba9ef4 | 1174 | :group 'hunger) |
f9f59935 RS |
1175 | @end smallexample |
1176 | ||
1177 | @noindent | |
1178 | This defines a minor mode named ``Hungry mode'', a command named | |
1179 | @code{hungry-mode} to toggle it, a variable named @code{hungry-mode} | |
1180 | which indicates whether the mode is enabled, and a variable named | |
1181 | @code{hungry-mode-map} which holds the keymap that is active when the | |
ec9b0882 RS |
1182 | mode is enabled. It initializes the keymap with a key binding for |
1183 | @kbd{C-@key{DEL}}. It puts the variable @code{hungry-mode} into | |
1184 | custom group @code{hunger}. There are no @var{body} forms---many | |
1185 | minor modes don't need any. | |
f9f59935 | 1186 | |
fdba9ef4 | 1187 | Here's an equivalent way to write it: |
2468d0c0 | 1188 | |
fdba9ef4 RS |
1189 | @smallexample |
1190 | (define-minor-mode hungry-mode | |
1191 | "Toggle Hungry mode. | |
1192 | With no argument, this command toggles the mode. | |
1193 | Non-null prefix argument turns on the mode. | |
1194 | Null prefix argument turns off the mode. | |
1195 | ||
1196 | When Hungry mode is enabled, the control delete key | |
1197 | gobbles all preceding whitespace except the last. | |
1198 | See the command \\[hungry-electric-delete]." | |
1199 | ;; The initial value. | |
1200 | :initial-value nil | |
1201 | ;; The indicator for the mode line. | |
1202 | :lighter " Hungry" | |
1203 | ;; The minor mode bindings. | |
1204 | :keymap | |
1205 | '(("\C-\^?" . hungry-electric-delete) | |
1206 | ("\C-\M-\^?" | |
1207 | . (lambda () | |
1208 | (interactive) | |
1209 | (hungry-electric-delete t)))) | |
1210 | :group 'hunger) | |
1211 | @end smallexample | |
2468d0c0 | 1212 | |
a44af9f2 | 1213 | @node Mode Line Format |
06862374 | 1214 | @section Mode-Line Format |
a44af9f2 RS |
1215 | @cindex mode line |
1216 | ||
8241495d RS |
1217 | Each Emacs window (aside from minibuffer windows) typically has a mode |
1218 | line at the bottom, which displays status information about the buffer | |
1219 | displayed in the window. The mode line contains information about the | |
1220 | buffer, such as its name, associated file, depth of recursive editing, | |
1221 | and major and minor modes. A window can also have a @dfn{header | |
1222 | line}, which is much like the mode line but appears at the top of the | |
8caa1356 | 1223 | window. |
a44af9f2 | 1224 | |
8241495d RS |
1225 | This section describes how to control the contents of the mode line |
1226 | and header line. We include it in this chapter because much of the | |
a44af9f2 RS |
1227 | information displayed in the mode line relates to the enabled major and |
1228 | minor modes. | |
1229 | ||
1230 | @code{mode-line-format} is a buffer-local variable that holds a | |
1231 | template used to display the mode line of the current buffer. All | |
8241495d RS |
1232 | windows for the same buffer use the same @code{mode-line-format}, so |
1233 | their mode lines appear the same---except for scrolling percentages, and | |
1234 | line and column numbers, since those depend on point and on how the | |
1235 | window is scrolled. @code{header-line-format} is used likewise for | |
1236 | header lines. | |
1237 | ||
8e0f7b5b RS |
1238 | For efficiency, Emacs does not recompute the mode line and header |
1239 | line of a window in every redisplay. It does so when circumstances | |
1240 | appear to call for it---for instance, if you change the window | |
1241 | configuration, switch buffers, narrow or widen the buffer, scroll, or | |
1242 | change the buffer's modification status. If you modify any of the | |
1243 | variables referenced by @code{mode-line-format} (@pxref{Mode Line | |
1244 | Variables}), or any other variables and data structures that affect | |
1245 | how text is displayed (@pxref{Display}), you may want to force an | |
1246 | update of the mode line so as to display the new information or | |
1247 | display it in the new way. | |
a44af9f2 RS |
1248 | |
1249 | @c Emacs 19 feature | |
0ad8cce8 | 1250 | @defun force-mode-line-update &optional all |
8241495d | 1251 | Force redisplay of the current buffer's mode line and header line. |
8e0f7b5b | 1252 | The next redisplay will update the mode line and header line based on |
0ad8cce8 LK |
1253 | the latest values of all relevant variables. With optional |
1254 | non-@code{nil} @var{all}, force redisplay of all mode lines and header | |
1255 | lines. | |
8e0f7b5b RS |
1256 | |
1257 | This function also forces recomputation of the menu bar menus | |
1258 | and the frame title. | |
a44af9f2 RS |
1259 | @end defun |
1260 | ||
ec9b0882 RS |
1261 | The selected window's mode line is usually displayed in a different |
1262 | color using the face @code{mode-line}. Other windows' mode lines | |
1263 | appear in the face @code{mode-line-inactive} instead. @xref{Faces}. | |
a44af9f2 | 1264 | |
a1112b37 RS |
1265 | A window that is just one line tall does not display either a mode |
1266 | line or a header line, even if the variables call for one. A window | |
1267 | that is two lines tall cannot display both a mode line and a header | |
1268 | line at once; if the variables call for both, only the mode line | |
1269 | actually appears. | |
1270 | ||
a44af9f2 RS |
1271 | @menu |
1272 | * Mode Line Data:: The data structure that controls the mode line. | |
1273 | * Mode Line Variables:: Variables used in that data structure. | |
1274 | * %-Constructs:: Putting information into a mode line. | |
8241495d RS |
1275 | * Properties in Mode:: Using text properties in the mode line. |
1276 | * Header Lines:: Like a mode line, but at the top. | |
3ebe0346 | 1277 | * Emulating Mode Line:: Formatting text as the mode line would. |
a44af9f2 RS |
1278 | @end menu |
1279 | ||
1280 | @node Mode Line Data | |
1281 | @subsection The Data Structure of the Mode Line | |
06862374 | 1282 | @cindex mode-line construct |
a44af9f2 | 1283 | |
06862374 | 1284 | The mode-line contents are controlled by a data structure of lists, |
a40d4712 | 1285 | strings, symbols, and numbers kept in buffer-local variables. The data |
06862374 LK |
1286 | structure is called a @dfn{mode-line construct}, and it is built in |
1287 | recursive fashion out of simpler mode-line constructs. The same data | |
a40d4712 PR |
1288 | structure is used for constructing frame titles (@pxref{Frame Titles}) |
1289 | and header lines (@pxref{Header Lines}). | |
a44af9f2 RS |
1290 | |
1291 | @defvar mode-line-format | |
06862374 LK |
1292 | The value of this variable is a mode-line construct with overall |
1293 | responsibility for the mode-line format. The value of this variable | |
1294 | controls which other variables are used to form the mode-line text, and | |
a44af9f2 | 1295 | where they appear. |
8241495d RS |
1296 | |
1297 | If you set this variable to @code{nil} in a buffer, that buffer does not | |
8caa1356 | 1298 | have a mode line. |
a44af9f2 RS |
1299 | @end defvar |
1300 | ||
06862374 | 1301 | A mode-line construct may be as simple as a fixed string of text, but |
a44af9f2 | 1302 | it usually specifies how to use other variables to construct the text. |
06862374 | 1303 | Many of these variables are themselves defined to have mode-line |
a44af9f2 RS |
1304 | constructs as their values. |
1305 | ||
1306 | The default value of @code{mode-line-format} incorporates the values | |
06862374 LK |
1307 | of variables such as @code{mode-line-position} and |
1308 | @code{mode-line-modes} (which in turn incorporates the values of the | |
1309 | variables @code{mode-name} and @code{minor-mode-alist}). Because of | |
1310 | this, very few modes need to alter @code{mode-line-format} itself. For | |
1311 | most purposes, it is sufficient to alter some of the variables that | |
1312 | @code{mode-line-format} either directly or indirectly refers to. | |
1313 | ||
1314 | A mode-line construct may be a list, a symbol, or a string. If the | |
de9f0bd9 | 1315 | value is a list, each element may be a list, a symbol, or a string. |
a44af9f2 | 1316 | |
8241495d RS |
1317 | The mode line can display various faces, if the strings that control |
1318 | it have the @code{face} property. @xref{Properties in Mode}. In | |
1319 | addition, the face @code{mode-line} is used as a default for the whole | |
1320 | mode line (@pxref{Standard Faces}). | |
1321 | ||
a44af9f2 RS |
1322 | @table @code |
1323 | @cindex percent symbol in mode line | |
1324 | @item @var{string} | |
06862374 | 1325 | A string as a mode-line construct is displayed verbatim in the mode line |
bfe721d1 | 1326 | except for @dfn{@code{%}-constructs}. Decimal digits after the @samp{%} |
a44af9f2 RS |
1327 | specify the field width for space filling on the right (i.e., the data |
1328 | is left justified). @xref{%-Constructs}. | |
1329 | ||
1330 | @item @var{symbol} | |
06862374 LK |
1331 | A symbol as a mode-line construct stands for its value. The value of |
1332 | @var{symbol} is used as a mode-line construct, in place of @var{symbol}. | |
8241495d | 1333 | However, the symbols @code{t} and @code{nil} are ignored, as is any |
de9f0bd9 | 1334 | symbol whose value is void. |
a44af9f2 RS |
1335 | |
1336 | There is one exception: if the value of @var{symbol} is a string, it is | |
de9f0bd9 | 1337 | displayed verbatim: the @code{%}-constructs are not recognized. |
a44af9f2 | 1338 | |
a232a240 LK |
1339 | Unless @var{symbol} is marked as ``risky'' (i.e., it has a |
1340 | non-@code{nil} @code{risky-local-variable} property), all properties in | |
1341 | any strings, as well as all @code{:eval} and @code{:propertize} forms in | |
1342 | the value of that symbol will be ignored. | |
1343 | ||
a44af9f2 | 1344 | @item (@var{string} @var{rest}@dots{}) @r{or} (@var{list} @var{rest}@dots{}) |
de9f0bd9 RS |
1345 | A list whose first element is a string or list means to process all the |
1346 | elements recursively and concatenate the results. This is the most | |
06862374 | 1347 | common form of mode-line construct. |
a44af9f2 | 1348 | |
8241495d RS |
1349 | @item (:eval @var{form}) |
1350 | A list whose first element is the symbol @code{:eval} says to evaluate | |
1351 | @var{form}, and use the result as a string to display. | |
8241495d | 1352 | |
06862374 LK |
1353 | @item (:propertize @var{elt} @var{props}@dots{}) |
1354 | A list whose first element is the symbol @code{:propertize} says to | |
1355 | process the mode-line construct @var{elt} recursively and add the text | |
1356 | properties specified by @var{props} to the result. The argument | |
1357 | @var{props} should consist of zero or more pairs @var{text-property} | |
bf247b6e | 1358 | @var{value}. (This feature is new as of Emacs 22.1.) |
06862374 | 1359 | |
a44af9f2 | 1360 | @item (@var{symbol} @var{then} @var{else}) |
8241495d RS |
1361 | A list whose first element is a symbol that is not a keyword specifies a |
1362 | conditional. Its meaning depends on the value of @var{symbol}. If the | |
1363 | value is non-@code{nil}, the second element, @var{then}, is processed | |
06862374 | 1364 | recursively as a mode-line element. But if the value of @var{symbol} is |
8241495d | 1365 | @code{nil}, the third element, @var{else}, is processed recursively. |
06862374 | 1366 | You may omit @var{else}; then the mode-line element displays nothing if |
8241495d | 1367 | the value of @var{symbol} is @code{nil}. |
a44af9f2 RS |
1368 | |
1369 | @item (@var{width} @var{rest}@dots{}) | |
1370 | A list whose first element is an integer specifies truncation or | |
1371 | padding of the results of @var{rest}. The remaining elements | |
06862374 | 1372 | @var{rest} are processed recursively as mode-line constructs and |
a44af9f2 RS |
1373 | concatenated together. Then the result is space filled (if |
1374 | @var{width} is positive) or truncated (to @minus{}@var{width} columns, | |
1375 | if @var{width} is negative) on the right. | |
1376 | ||
1377 | For example, the usual way to show what percentage of a buffer is above | |
de9f0bd9 | 1378 | the top of the window is to use a list like this: @code{(-3 "%p")}. |
a44af9f2 RS |
1379 | @end table |
1380 | ||
1381 | If you do alter @code{mode-line-format} itself, the new value should | |
de9f0bd9 RS |
1382 | use the same variables that appear in the default value (@pxref{Mode |
1383 | Line Variables}), rather than duplicating their contents or displaying | |
1384 | the information in another fashion. This way, customizations made by | |
bfe721d1 KH |
1385 | the user or by Lisp programs (such as @code{display-time} and major |
1386 | modes) via changes to those variables remain effective. | |
a44af9f2 RS |
1387 | |
1388 | @cindex Shell mode @code{mode-line-format} | |
1389 | Here is an example of a @code{mode-line-format} that might be | |
969fe9b5 | 1390 | useful for @code{shell-mode}, since it contains the host name and default |
a44af9f2 RS |
1391 | directory. |
1392 | ||
1393 | @example | |
1394 | @group | |
1395 | (setq mode-line-format | |
969fe9b5 RS |
1396 | (list "-" |
1397 | 'mode-line-mule-info | |
a44af9f2 | 1398 | 'mode-line-modified |
969fe9b5 | 1399 | 'mode-line-frame-identification |
177c0ea7 | 1400 | "%b--" |
a44af9f2 | 1401 | @end group |
f9f59935 RS |
1402 | @group |
1403 | ;; @r{Note that this is evaluated while making the list.} | |
06862374 | 1404 | ;; @r{It makes a mode-line construct which is just a string.} |
f9f59935 RS |
1405 | (getenv "HOST") |
1406 | @end group | |
177c0ea7 | 1407 | ":" |
a44af9f2 RS |
1408 | 'default-directory |
1409 | " " | |
1410 | 'global-mode-string | |
de9f0bd9 | 1411 | " %[(" |
8241495d | 1412 | '(:eval (mode-line-mode-name)) |
177c0ea7 JB |
1413 | 'mode-line-process |
1414 | 'minor-mode-alist | |
1415 | "%n" | |
969fe9b5 | 1416 | ")%]--" |
a44af9f2 | 1417 | @group |
969fe9b5 | 1418 | '(which-func-mode ("" which-func-format "--")) |
bfe721d1 | 1419 | '(line-number-mode "L%l--") |
969fe9b5 | 1420 | '(column-number-mode "C%c--") |
a232a240 | 1421 | '(-3 "%p") |
a44af9f2 RS |
1422 | "-%-")) |
1423 | @end group | |
1424 | @end example | |
1425 | ||
1911e6e5 RS |
1426 | @noindent |
1427 | (The variables @code{line-number-mode}, @code{column-number-mode} | |
1428 | and @code{which-func-mode} enable particular minor modes; as usual, | |
1429 | these variable names are also the minor mode command names.) | |
1430 | ||
a44af9f2 RS |
1431 | @node Mode Line Variables |
1432 | @subsection Variables Used in the Mode Line | |
1433 | ||
1434 | This section describes variables incorporated by the | |
1435 | standard value of @code{mode-line-format} into the text of the mode | |
1436 | line. There is nothing inherently special about these variables; any | |
1437 | other variables could have the same effects on the mode line if | |
1438 | @code{mode-line-format} were changed to use them. | |
1439 | ||
969fe9b5 RS |
1440 | @defvar mode-line-mule-info |
1441 | This variable holds the value of the mode-line construct that displays | |
1442 | information about the language environment, buffer coding system, and | |
a9f0a989 | 1443 | current input method. @xref{Non-ASCII Characters}. |
969fe9b5 RS |
1444 | @end defvar |
1445 | ||
a44af9f2 | 1446 | @defvar mode-line-modified |
de9f0bd9 | 1447 | This variable holds the value of the mode-line construct that displays |
a44af9f2 RS |
1448 | whether the current buffer is modified. |
1449 | ||
969fe9b5 RS |
1450 | The default value of @code{mode-line-modified} is @code{("%1*%1+")}. |
1451 | This means that the mode line displays @samp{**} if the buffer is | |
1452 | modified, @samp{--} if the buffer is not modified, @samp{%%} if the | |
1453 | buffer is read only, and @samp{%*} if the buffer is read only and | |
1454 | modified. | |
a44af9f2 RS |
1455 | |
1456 | Changing this variable does not force an update of the mode line. | |
1457 | @end defvar | |
1458 | ||
969fe9b5 RS |
1459 | @defvar mode-line-frame-identification |
1460 | This variable identifies the current frame. The default value is | |
06862374 LK |
1461 | @code{" "} if you are using a window system which can show multiple |
1462 | frames, or @code{"-%F "} on an ordinary terminal which shows only one | |
969fe9b5 RS |
1463 | frame at a time. |
1464 | @end defvar | |
1465 | ||
a44af9f2 | 1466 | @defvar mode-line-buffer-identification |
de9f0bd9 | 1467 | This variable identifies the buffer being displayed in the window. Its |
ebc6903b RS |
1468 | default value is @code{("%12b")}, which displays the buffer name, padded |
1469 | with spaces to at least 12 columns. | |
a44af9f2 RS |
1470 | @end defvar |
1471 | ||
06862374 LK |
1472 | @defvar mode-line-position |
1473 | This variable indicates the position in the buffer. Here is a | |
1474 | simplified version of its default value. The actual default value | |
1475 | also specifies addition of the @code{help-echo} text property. | |
a44af9f2 | 1476 | |
06862374 LK |
1477 | @example |
1478 | @group | |
a232a240 | 1479 | ((-3 "%p") |
06862374 LK |
1480 | (size-indication-mode (8 " of %I")) |
1481 | @end group | |
1482 | @group | |
1483 | (line-number-mode | |
1484 | ((column-number-mode | |
1485 | (10 " (%l,%c)") | |
1486 | (6 " L%l"))) | |
1487 | ((column-number-mode | |
1488 | (5 " C%c"))))) | |
1489 | @end group | |
1490 | @end example | |
1491 | ||
1492 | This means that @code{mode-line-position} displays at least the buffer | |
1493 | percentage and possibly the buffer size, the line number and the column | |
1494 | number. | |
1495 | @end defvar | |
1496 | ||
1497 | @defvar vc-mode | |
1498 | The variable @code{vc-mode}, buffer-local in each buffer, records | |
1499 | whether the buffer's visited file is maintained with version control, | |
1500 | and, if so, which kind. Its value is a string that appears in the mode | |
1501 | line, or @code{nil} for no version control. | |
a44af9f2 RS |
1502 | @end defvar |
1503 | ||
06862374 LK |
1504 | @defvar mode-line-modes |
1505 | This variable displays the buffer's major and minor modes. Here is a | |
1506 | simplified version of its default value. The real default value also | |
1507 | specifies addition of text properties. | |
1508 | ||
1509 | @example | |
1510 | @group | |
1511 | ("%[(" mode-name | |
1512 | mode-line-process minor-mode-alist | |
1513 | "%n" ")%]--") | |
1514 | @end group | |
1515 | @end example | |
1516 | ||
1517 | So @code{mode-line-modes} normally also displays the recursive editing | |
1518 | level, information on the process status and whether narrowing is in | |
1519 | effect. | |
1520 | @end defvar | |
1521 | ||
1522 | The following three variables are used in @code{mode-line-modes}: | |
1523 | ||
a44af9f2 | 1524 | @defvar mode-name |
de9f0bd9 | 1525 | This buffer-local variable holds the ``pretty'' name of the current |
a44af9f2 RS |
1526 | buffer's major mode. Each major mode should set this variable so that the |
1527 | mode name will appear in the mode line. | |
1528 | @end defvar | |
1529 | ||
06862374 LK |
1530 | @defvar mode-line-process |
1531 | This buffer-local variable contains the mode-line information on process | |
1532 | status in modes used for communicating with subprocesses. It is | |
1533 | displayed immediately following the major mode name, with no intervening | |
1534 | space. For example, its value in the @samp{*shell*} buffer is | |
1535 | @code{(":%s")}, which allows the shell to display its status along | |
1536 | with the major mode as: @samp{(Shell:run)}. Normally this variable | |
1537 | is @code{nil}. | |
1538 | @end defvar | |
1539 | ||
a44af9f2 | 1540 | @defvar minor-mode-alist |
de9f0bd9 | 1541 | This variable holds an association list whose elements specify how the |
a44af9f2 RS |
1542 | mode line should indicate that a minor mode is active. Each element of |
1543 | the @code{minor-mode-alist} should be a two-element list: | |
1544 | ||
1545 | @example | |
1546 | (@var{minor-mode-variable} @var{mode-line-string}) | |
1547 | @end example | |
1548 | ||
06862374 LK |
1549 | More generally, @var{mode-line-string} can be any mode-line spec. It |
1550 | appears in the mode line when the value of @var{minor-mode-variable} | |
1551 | is non-@code{nil}, and not otherwise. These strings should begin with | |
a44af9f2 | 1552 | spaces so that they don't run together. Conventionally, the |
06862374 LK |
1553 | @var{minor-mode-variable} for a specific mode is set to a |
1554 | non-@code{nil} value when that minor mode is activated. | |
a44af9f2 | 1555 | |
f9f59935 RS |
1556 | @code{minor-mode-alist} itself is not buffer-local. Each variable |
1557 | mentioned in the alist should be buffer-local if its minor mode can be | |
1558 | enabled separately in each buffer. | |
a44af9f2 RS |
1559 | @end defvar |
1560 | ||
06862374 | 1561 | @defvar global-mode-string |
1074a881 JB |
1562 | This variable holds a mode-line spec that, by default, appears in the |
1563 | mode line just after the @code{which-func-mode} minor mode if set, | |
1564 | else after @code{mode-line-modes}. The command @code{display-time} | |
06862374 | 1565 | sets @code{global-mode-string} to refer to the variable |
1074a881 JB |
1566 | @code{display-time-string}, which holds a string containing the time |
1567 | and load information. | |
a40d4712 | 1568 | |
06862374 LK |
1569 | The @samp{%M} construct substitutes the value of |
1570 | @code{global-mode-string}, but that is obsolete, since the variable is | |
1571 | included in the mode line from @code{mode-line-format}. | |
a40d4712 PR |
1572 | @end defvar |
1573 | ||
1574 | The variable @code{default-mode-line-format} is where | |
1575 | @code{mode-line-format} usually gets its value: | |
1576 | ||
a44af9f2 | 1577 | @defvar default-mode-line-format |
de9f0bd9 | 1578 | This variable holds the default @code{mode-line-format} for buffers |
a44af9f2 RS |
1579 | that do not override it. This is the same as @code{(default-value |
1580 | 'mode-line-format)}. | |
1581 | ||
06862374 LK |
1582 | Here is a simplified version of the default value of |
1583 | @code{default-mode-line-format}. The real default value also | |
1584 | specifies addition of text properties. | |
a44af9f2 RS |
1585 | |
1586 | @example | |
1587 | @group | |
f9f59935 RS |
1588 | ("-" |
1589 | mode-line-mule-info | |
a44af9f2 | 1590 | mode-line-modified |
f9f59935 | 1591 | mode-line-frame-identification |
a44af9f2 | 1592 | mode-line-buffer-identification |
f9f59935 | 1593 | @end group |
a44af9f2 | 1594 | " " |
06862374 LK |
1595 | mode-line-position |
1596 | (vc-mode vc-mode) | |
1597 | " " | |
f9f59935 | 1598 | @group |
06862374 | 1599 | mode-line-modes |
f9f59935 | 1600 | (which-func-mode ("" which-func-format "--")) |
06862374 | 1601 | (global-mode-string ("--" global-mode-string)) |
a44af9f2 RS |
1602 | "-%-") |
1603 | @end group | |
1604 | @end example | |
1605 | @end defvar | |
1606 | ||
1607 | @node %-Constructs | |
1608 | @subsection @code{%}-Constructs in the Mode Line | |
1609 | ||
1610 | The following table lists the recognized @code{%}-constructs and what | |
de9f0bd9 RS |
1611 | they mean. In any construct except @samp{%%}, you can add a decimal |
1612 | integer after the @samp{%} to specify how many characters to display. | |
a44af9f2 RS |
1613 | |
1614 | @table @code | |
1615 | @item %b | |
1616 | The current buffer name, obtained with the @code{buffer-name} function. | |
1617 | @xref{Buffer Names}. | |
1618 | ||
a40d4712 PR |
1619 | @item %c |
1620 | The current column number of point. | |
1621 | ||
a44af9f2 RS |
1622 | @item %f |
1623 | The visited file name, obtained with the @code{buffer-file-name} | |
1624 | function. @xref{Buffer File Name}. | |
1625 | ||
22697dac | 1626 | @item %F |
969fe9b5 RS |
1627 | The title (only on a window system) or the name of the selected frame. |
1628 | @xref{Window Frame Parameters}. | |
22697dac | 1629 | |
08622028 LK |
1630 | @item %i |
1631 | The size of the accessible part of the current buffer; basically | |
1632 | @code{(- (point-max) (point-min))}. | |
1633 | ||
1634 | @item %I | |
1635 | Like @samp{%i}, but the size is printed in a more readable way by using | |
1636 | @samp{k} for 10^3, @samp{M} for 10^6, @samp{G} for 10^9, etc., to | |
1637 | abbreviate. | |
1638 | ||
22697dac | 1639 | @item %l |
8241495d RS |
1640 | The current line number of point, counting within the accessible portion |
1641 | of the buffer. | |
22697dac | 1642 | |
a40d4712 PR |
1643 | @item %n |
1644 | @samp{Narrow} when narrowing is in effect; nothing otherwise (see | |
1645 | @code{narrow-to-region} in @ref{Narrowing}). | |
1646 | ||
1647 | @item %p | |
1648 | The percentage of the buffer text above the @strong{top} of window, or | |
1649 | @samp{Top}, @samp{Bottom} or @samp{All}. Note that the default | |
1650 | mode-line specification truncates this to three characters. | |
1651 | ||
1652 | @item %P | |
1653 | The percentage of the buffer text that is above the @strong{bottom} of | |
1654 | the window (which includes the text visible in the window, as well as | |
1655 | the text above the top), plus @samp{Top} if the top of the buffer is | |
1656 | visible on screen; or @samp{Bottom} or @samp{All}. | |
1657 | ||
1658 | @item %s | |
1659 | The status of the subprocess belonging to the current buffer, obtained with | |
1660 | @code{process-status}. @xref{Process Information}. | |
1661 | ||
1662 | @item %t | |
1663 | Whether the visited file is a text file or a binary file. This is a | |
1664 | meaningful distinction only on certain operating systems (@pxref{MS-DOS | |
1665 | File Types}). | |
1666 | ||
a44af9f2 RS |
1667 | @item %* |
1668 | @samp{%} if the buffer is read only (see @code{buffer-read-only}); @* | |
1669 | @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @* | |
1670 | @samp{-} otherwise. @xref{Buffer Modification}. | |
1671 | ||
1672 | @item %+ | |
22697dac KH |
1673 | @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @* |
1674 | @samp{%} if the buffer is read only (see @code{buffer-read-only}); @* | |
1675 | @samp{-} otherwise. This differs from @samp{%*} only for a modified | |
1676 | read-only buffer. @xref{Buffer Modification}. | |
1677 | ||
1678 | @item %& | |
de9f0bd9 | 1679 | @samp{*} if the buffer is modified, and @samp{-} otherwise. |
a44af9f2 | 1680 | |
a44af9f2 RS |
1681 | @item %[ |
1682 | An indication of the depth of recursive editing levels (not counting | |
1683 | minibuffer levels): one @samp{[} for each editing level. | |
1684 | @xref{Recursive Editing}. | |
1685 | ||
1686 | @item %] | |
1687 | One @samp{]} for each recursive editing level (not counting minibuffer | |
1688 | levels). | |
1689 | ||
a40d4712 PR |
1690 | @item %- |
1691 | Dashes sufficient to fill the remainder of the mode line. | |
1692 | ||
a44af9f2 RS |
1693 | @item %% |
1694 | The character @samp{%}---this is how to include a literal @samp{%} in a | |
1695 | string in which @code{%}-constructs are allowed. | |
a44af9f2 RS |
1696 | @end table |
1697 | ||
1698 | The following two @code{%}-constructs are still supported, but they are | |
1699 | obsolete, since you can get the same results with the variables | |
1700 | @code{mode-name} and @code{global-mode-string}. | |
1701 | ||
1702 | @table @code | |
1703 | @item %m | |
1704 | The value of @code{mode-name}. | |
1705 | ||
1706 | @item %M | |
1707 | The value of @code{global-mode-string}. Currently, only | |
1708 | @code{display-time} modifies the value of @code{global-mode-string}. | |
1709 | @end table | |
1710 | ||
8241495d RS |
1711 | @node Properties in Mode |
1712 | @subsection Properties in the Mode Line | |
06862374 | 1713 | @cindex text properties in the mode line |
8241495d | 1714 | |
8caa1356 | 1715 | Certain text properties are meaningful in the |
8241495d RS |
1716 | mode line. The @code{face} property affects the appearance of text; the |
1717 | @code{help-echo} property associate help strings with the text, and | |
ce75fd23 | 1718 | @code{local-map} can make the text mouse-sensitive. |
8241495d | 1719 | |
06862374 | 1720 | There are four ways to specify text properties for text in the mode |
8241495d RS |
1721 | line: |
1722 | ||
1723 | @enumerate | |
1724 | @item | |
06862374 LK |
1725 | Put a string with a text property directly into the mode-line data |
1726 | structure. | |
1727 | ||
1728 | @item | |
1729 | Put a text property on a mode-line %-construct such as @samp{%12b}; then | |
1730 | the expansion of the %-construct will have that same text property. | |
8241495d RS |
1731 | |
1732 | @item | |
06862374 LK |
1733 | Use a @code{(:propertize @var{elt} @var{props}@dots{})} construct to |
1734 | give @var{elt} a text property specified by @var{props}. | |
8241495d RS |
1735 | |
1736 | @item | |
1737 | Use a list containing @code{:eval @var{form}} in the mode-line data | |
06862374 LK |
1738 | structure, and make @var{form} evaluate to a string that has a text |
1739 | property. | |
8241495d RS |
1740 | @end enumerate |
1741 | ||
ce75fd23 | 1742 | You use the @code{local-map} property to specify a keymap. Like any |
8241495d | 1743 | keymap, it can bind character keys and function keys; but that has no |
a40d4712 | 1744 | effect, since it is impossible to move point into the mode line. This |
8241495d RS |
1745 | keymap can only take real effect for mouse clicks. |
1746 | ||
ec9b0882 RS |
1747 | When the mode line refers to a variable which does not have a |
1748 | non-@code{nil} @code{risky-local-variable} property, any text | |
1749 | properties given or specified within that variable's values are | |
1750 | ignored. This is because such properties could otherwise specify | |
1751 | functions to be called, and those functions could come from file | |
1752 | local variables. | |
1753 | ||
8241495d RS |
1754 | @node Header Lines |
1755 | @subsection Window Header Lines | |
1756 | @cindex header line (of a window) | |
1757 | @cindex window header line | |
1758 | ||
8caa1356 | 1759 | A window can have a @dfn{header line} at the |
8241495d | 1760 | top, just as it can have a mode line at the bottom. The header line |
06862374 | 1761 | feature works just like the mode-line feature, except that it's |
8241495d RS |
1762 | controlled by different variables. |
1763 | ||
1764 | @tindex header-line-format | |
1765 | @defvar header-line-format | |
1766 | This variable, local in every buffer, specifies how to display the | |
1767 | header line, for windows displaying the buffer. The format of the value | |
13ede7fc | 1768 | is the same as for @code{mode-line-format} (@pxref{Mode Line Data}). |
8241495d RS |
1769 | @end defvar |
1770 | ||
1771 | @tindex default-header-line-format | |
1772 | @defvar default-header-line-format | |
1773 | This variable holds the default @code{header-line-format} for buffers | |
1774 | that do not override it. This is the same as @code{(default-value | |
1775 | 'header-line-format)}. | |
1776 | ||
1777 | It is normally @code{nil}, so that ordinary buffers have no header line. | |
1778 | @end defvar | |
1779 | ||
bda7c6dd | 1780 | @node Emulating Mode Line |
06862374 | 1781 | @subsection Emulating Mode-Line Formatting |
bda7c6dd RS |
1782 | |
1783 | You can use the function @code{format-mode-line} to compute | |
1784 | the text that would appear in a mode line or header line | |
06862374 | 1785 | based on certain mode-line specification. |
bda7c6dd | 1786 | |
f2dfc856 | 1787 | @defun format-mode-line format &optional face window buffer |
bda7c6dd RS |
1788 | This function formats a line of text according to @var{format} as if |
1789 | it were generating the mode line for @var{window}, but instead of | |
1790 | displaying the text in the mode line or the header line, it returns | |
0a54d76e RS |
1791 | the text as a string. The argument @var{window} defaults to the |
1792 | selected window. If @var{buffer} is non-@code{nil}, all the | |
1793 | information used is taken from @var{buffer}; by default, it comes from | |
1794 | @var{window}'s buffer. | |
bda7c6dd RS |
1795 | |
1796 | The value string normally has text properties that correspond to the | |
0fee24ae RS |
1797 | faces, keymaps, etc., that the mode line would have. And any character |
1798 | for which no @code{face} property is specified gets a default | |
1799 | value which is usually @var{face}. (If @var{face} is @code{t}, | |
1800 | that stands for either @code{mode-line} if @var{window} is selected, | |
1801 | otherwise @code{mode-line-inactive}.) | |
1802 | ||
f2dfc856 | 1803 | However, if @var{face} is an integer, the value has no text properties. |
0a54d76e RS |
1804 | |
1805 | For example, @code{(format-mode-line header-line-format)} returns the | |
1806 | text that would appear in the selected window's header line (@code{""} | |
0fee24ae | 1807 | if it has no header line). @code{(format-mode-line header-line-format |
f2dfc856 | 1808 | 'header-line)} returns the same text, with each character |
0fee24ae | 1809 | carrying the face that it will have in the header line itself. |
bda7c6dd RS |
1810 | @end defun |
1811 | ||
f9f59935 RS |
1812 | @node Imenu |
1813 | @section Imenu | |
1814 | ||
1815 | @cindex Imenu | |
969fe9b5 RS |
1816 | @dfn{Imenu} is a feature that lets users select a definition or |
1817 | section in the buffer, from a menu which lists all of them, to go | |
5a5d2aec RS |
1818 | directly to that location in the buffer. Imenu works by constructing |
1819 | a buffer index which lists the names and buffer positions of the | |
a40d4712 | 1820 | definitions, or other named portions of the buffer; then the user can |
ec9b0882 RS |
1821 | choose one of them and move point to it. Major modes can add a menu |
1822 | bar item to use Imenu using @code{imenu-add-to-menubar}. | |
1823 | ||
1824 | @defun imenu-add-to-menubar name | |
1825 | This function defines a local menu bar item named @var{name} | |
1826 | to run Imenu. | |
1827 | @end defun | |
1828 | ||
1829 | The user-level commands for using Imenu are described in the Emacs | |
1830 | Manual (@pxref{Imenu,, Imenu, emacs, the Emacs Manual}). This section | |
1831 | explains how to customize Imenu's method of finding definitions or | |
1832 | buffer portions for a particular major mode. | |
969fe9b5 RS |
1833 | |
1834 | The usual and simplest way is to set the variable | |
1835 | @code{imenu-generic-expression}: | |
f9f59935 RS |
1836 | |
1837 | @defvar imenu-generic-expression | |
10ee4e90 LK |
1838 | This variable, if non-@code{nil}, is a list that specifies regular |
1839 | expressions for finding definitions for Imenu. Simple elements of | |
1840 | @code{imenu-generic-expression} look like this: | |
f9f59935 RS |
1841 | |
1842 | @example | |
10ee4e90 | 1843 | (@var{menu-title} @var{regexp} @var{index}) |
f9f59935 RS |
1844 | @end example |
1845 | ||
1846 | Here, if @var{menu-title} is non-@code{nil}, it says that the matches | |
1847 | for this element should go in a submenu of the buffer index; | |
1848 | @var{menu-title} itself specifies the name for the submenu. If | |
1849 | @var{menu-title} is @code{nil}, the matches for this element go directly | |
1850 | in the top level of the buffer index. | |
1851 | ||
1852 | The second item in the list, @var{regexp}, is a regular expression | |
10ee4e90 LK |
1853 | (@pxref{Regular Expressions}); anything in the buffer that it matches |
1854 | is considered a definition, something to mention in the buffer index. | |
1855 | The third item, @var{index}, is a non-negative integer that indicates | |
1856 | which subexpression in @var{regexp} matches the definition's name. | |
f9f59935 RS |
1857 | |
1858 | An element can also look like this: | |
1859 | ||
1860 | @example | |
1861 | (@var{menu-title} @var{regexp} @var{index} @var{function} @var{arguments}@dots{}) | |
1862 | @end example | |
1863 | ||
10ee4e90 LK |
1864 | Like in the previous case, each match for this element creates an |
1865 | index item. However, if this index item is selected by the user, it | |
1866 | calls @var{function} with arguments consisting of the item name, the | |
1867 | buffer position, and @var{arguments}. | |
f9f59935 | 1868 | |
10ee4e90 LK |
1869 | For Emacs Lisp mode, @code{imenu-generic-expression} could look like |
1870 | this: | |
f9f59935 | 1871 | |
a9f0a989 | 1872 | @c should probably use imenu-syntax-alist and \\sw rather than [-A-Za-z0-9+] |
f9f59935 RS |
1873 | @example |
1874 | @group | |
1875 | ((nil "^\\s-*(def\\(un\\|subst\\|macro\\|advice\\)\ | |
1876 | \\s-+\\([-A-Za-z0-9+]+\\)" 2) | |
1877 | @end group | |
1878 | @group | |
1879 | ("*Vars*" "^\\s-*(def\\(var\\|const\\)\ | |
1880 | \\s-+\\([-A-Za-z0-9+]+\\)" 2) | |
1881 | @end group | |
1882 | @group | |
1883 | ("*Types*" | |
a9f0a989 RS |
1884 | "^\\s-*\ |
1885 | (def\\(type\\|struct\\|class\\|ine-condition\\)\ | |
f9f59935 RS |
1886 | \\s-+\\([-A-Za-z0-9+]+\\)" 2)) |
1887 | @end group | |
1888 | @end example | |
1889 | ||
969fe9b5 | 1890 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
1891 | @end defvar |
1892 | ||
1893 | @defvar imenu-case-fold-search | |
10ee4e90 LK |
1894 | This variable controls whether matching against the regular |
1895 | expressions in the value of @code{imenu-generic-expression} is | |
1896 | case-sensitive: @code{t}, the default, means matching should ignore | |
1897 | case. | |
a9f0a989 RS |
1898 | |
1899 | Setting this variable makes it buffer-local in the current buffer. | |
1900 | @end defvar | |
1901 | ||
1902 | @defvar imenu-syntax-alist | |
1903 | This variable is an alist of syntax table modifiers to use while | |
1911e6e5 RS |
1904 | processing @code{imenu-generic-expression}, to override the syntax table |
1905 | of the current buffer. Each element should have this form: | |
a9f0a989 RS |
1906 | |
1907 | @example | |
1908 | (@var{characters} . @var{syntax-description}) | |
1909 | @end example | |
1910 | ||
1911 | The @sc{car}, @var{characters}, can be either a character or a string. | |
1912 | The element says to give that character or characters the syntax | |
1913 | specified by @var{syntax-description}, which is passed to | |
1914 | @code{modify-syntax-entry} (@pxref{Syntax Table Functions}). | |
1915 | ||
1916 | This feature is typically used to give word syntax to characters which | |
1917 | normally have symbol syntax, and thus to simplify | |
1918 | @code{imenu-generic-expression} and speed up matching. | |
1919 | For example, Fortran mode uses it this way: | |
1920 | ||
1921 | @example | |
5a5d2aec | 1922 | (setq imenu-syntax-alist '(("_$" . "w"))) |
a9f0a989 RS |
1923 | @end example |
1924 | ||
10ee4e90 LK |
1925 | The @code{imenu-generic-expression} regular expressions can then use |
1926 | @samp{\\sw+} instead of @samp{\\(\\sw\\|\\s_\\)+}. Note that this | |
1927 | technique may be inconvenient when the mode needs to limit the initial | |
1928 | character of a name to a smaller set of characters than are allowed in | |
1929 | the rest of a name. | |
f9f59935 | 1930 | |
969fe9b5 | 1931 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
1932 | @end defvar |
1933 | ||
1934 | Another way to customize Imenu for a major mode is to set the | |
1935 | variables @code{imenu-prev-index-position-function} and | |
969fe9b5 | 1936 | @code{imenu-extract-index-name-function}: |
f9f59935 RS |
1937 | |
1938 | @defvar imenu-prev-index-position-function | |
05aea714 | 1939 | If this variable is non-@code{nil}, its value should be a function that |
a40d4712 PR |
1940 | finds the next ``definition'' to put in the buffer index, scanning |
1941 | backward in the buffer from point. It should return @code{nil} if it | |
5fe3b9bc | 1942 | doesn't find another ``definition'' before point. Otherwise it should |
a40d4712 PR |
1943 | leave point at the place it finds a ``definition,'' and return any |
1944 | non-@code{nil} value. | |
f9f59935 | 1945 | |
969fe9b5 | 1946 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
1947 | @end defvar |
1948 | ||
1949 | @defvar imenu-extract-index-name-function | |
1950 | If this variable is non-@code{nil}, its value should be a function to | |
969fe9b5 RS |
1951 | return the name for a definition, assuming point is in that definition |
1952 | as the @code{imenu-prev-index-position-function} function would leave | |
1953 | it. | |
f9f59935 | 1954 | |
969fe9b5 | 1955 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
1956 | @end defvar |
1957 | ||
969fe9b5 | 1958 | The last way to customize Imenu for a major mode is to set the |
a40d4712 | 1959 | variable @code{imenu-create-index-function}: |
969fe9b5 | 1960 | |
f9f59935 | 1961 | @defvar imenu-create-index-function |
10ee4e90 LK |
1962 | This variable specifies the function to use for creating a buffer |
1963 | index. The function should take no arguments, and return an index | |
1964 | alist for the current buffer. It is called within | |
1965 | @code{save-excursion}, so where it leaves point makes no difference. | |
f9f59935 | 1966 | |
10ee4e90 LK |
1967 | The index alist can have three types of elements. Simple elements |
1968 | look like this: | |
f9f59935 | 1969 | |
10ee4e90 LK |
1970 | @example |
1971 | (@var{index-name} . @var{index-position}) | |
1972 | @end example | |
f9f59935 | 1973 | |
10ee4e90 LK |
1974 | Selecting a simple element has the effect of moving to position |
1975 | @var{index-position} in the buffer. Special elements look like this: | |
f9f59935 | 1976 | |
10ee4e90 LK |
1977 | @example |
1978 | (@var{index-name} @var{index-position} @var{function} @var{arguments}@dots{}) | |
1979 | @end example | |
f9f59935 | 1980 | |
10ee4e90 | 1981 | Selecting a special element performs: |
f9f59935 RS |
1982 | |
1983 | @example | |
c22c5da6 | 1984 | (funcall @var{function} |
10ee4e90 | 1985 | @var{index-name} @var{index-position} @var{arguments}@dots{}) |
f9f59935 RS |
1986 | @end example |
1987 | ||
10ee4e90 LK |
1988 | A nested sub-alist element looks like this: |
1989 | ||
1990 | @example | |
f008b925 | 1991 | (@var{menu-title} @var{sub-alist}) |
10ee4e90 LK |
1992 | @end example |
1993 | ||
f008b925 | 1994 | It creates the submenu @var{menu-title} specified by @var{sub-alist}. |
10ee4e90 | 1995 | |
f008b925 LK |
1996 | The default value of @code{imenu-create-index-function} is |
1997 | @code{imenu-default-create-index-function}. This function uses | |
1998 | @code{imenu-prev-index-position-function} and | |
10ee4e90 LK |
1999 | @code{imenu-extract-index-name-function} to produce the index alist. |
2000 | However, if either of these two variables is @code{nil}, the default | |
2001 | function uses @code{imenu-generic-expression} instead. | |
2002 | ||
2003 | Setting this variable makes it buffer-local in the current buffer. | |
f9f59935 RS |
2004 | @end defvar |
2005 | ||
2006 | @node Font Lock Mode | |
2007 | @section Font Lock Mode | |
2008 | @cindex Font Lock Mode | |
2009 | ||
2010 | @dfn{Font Lock mode} is a feature that automatically attaches | |
2011 | @code{face} properties to certain parts of the buffer based on their | |
2012 | syntactic role. How it parses the buffer depends on the major mode; | |
a40d4712 | 2013 | most major modes define syntactic criteria for which faces to use in |
969fe9b5 | 2014 | which contexts. This section explains how to customize Font Lock for a |
a40d4712 | 2015 | particular major mode. |
f9f59935 RS |
2016 | |
2017 | Font Lock mode finds text to highlight in two ways: through syntactic | |
2018 | parsing based on the syntax table, and through searching (usually for | |
2019 | regular expressions). Syntactic fontification happens first; it finds | |
2020 | comments and string constants, and highlights them using | |
2021 | @code{font-lock-comment-face} and @code{font-lock-string-face} | |
a40d4712 | 2022 | (@pxref{Faces for Font Lock}). Search-based fontification follows. |
f9f59935 RS |
2023 | |
2024 | @menu | |
ec9b0882 RS |
2025 | * Font Lock Basics:: Overview of customizing Font Lock. |
2026 | * Search-based Fontification:: Fontification based on regexps. | |
2027 | * Other Font Lock Variables:: Additional customization facilities. | |
2028 | * Levels of Font Lock:: Each mode can define alternative levels | |
2029 | so that the user can select more or less. | |
2030 | * Precalculated Fontification:: How Lisp programs that produce the buffer | |
2031 | contents can also specify how to fontify it. | |
2032 | * Faces for Font Lock:: Special faces specifically for Font Lock. | |
2033 | * Syntactic Font Lock:: Defining character syntax based on context | |
2034 | using the Font Lock mechanism. | |
f9f59935 RS |
2035 | @end menu |
2036 | ||
2037 | @node Font Lock Basics | |
2038 | @subsection Font Lock Basics | |
2039 | ||
2040 | There are several variables that control how Font Lock mode highlights | |
2041 | text. But major modes should not set any of these variables directly. | |
86494bd5 | 2042 | Instead, they should set @code{font-lock-defaults} as a buffer-local |
969fe9b5 RS |
2043 | variable. The value assigned to this variable is used, if and when Font |
2044 | Lock mode is enabled, to set all the other variables. | |
f9f59935 RS |
2045 | |
2046 | @defvar font-lock-defaults | |
2047 | This variable is set by major modes, as a buffer-local variable, to | |
2048 | specify how to fontify text in that mode. The value should look like | |
2049 | this: | |
2050 | ||
2051 | @example | |
2052 | (@var{keywords} @var{keywords-only} @var{case-fold} | |
2053 | @var{syntax-alist} @var{syntax-begin} @var{other-vars}@dots{}) | |
2054 | @end example | |
2055 | ||
2056 | The first element, @var{keywords}, indirectly specifies the value of | |
2057 | @code{font-lock-keywords}. It can be a symbol, a variable whose value | |
a40d4712 | 2058 | is the list to use for @code{font-lock-keywords}. It can also be a list of |
f9f59935 RS |
2059 | several such symbols, one for each possible level of fontification. The |
2060 | first symbol specifies how to do level 1 fontification, the second | |
2061 | symbol how to do level 2, and so on. | |
2062 | ||
2063 | The second element, @var{keywords-only}, specifies the value of the | |
a9f0a989 | 2064 | variable @code{font-lock-keywords-only}. If this is non-@code{nil}, |
969fe9b5 | 2065 | syntactic fontification (of strings and comments) is not performed. |
f9f59935 RS |
2066 | |
2067 | The third element, @var{case-fold}, specifies the value of | |
10980463 | 2068 | @code{font-lock-keywords-case-fold-search}. If it is non-@code{nil}, Font Lock |
969fe9b5 RS |
2069 | mode ignores case when searching as directed by |
2070 | @code{font-lock-keywords}. | |
f9f59935 RS |
2071 | |
2072 | If the fourth element, @var{syntax-alist}, is non-@code{nil}, it should be | |
2073 | a list of cons cells of the form @code{(@var{char-or-string} | |
2074 | . @var{string})}. These are used to set up a syntax table for | |
2075 | fontification (@pxref{Syntax Table Functions}). The resulting syntax | |
2076 | table is stored in @code{font-lock-syntax-table}. | |
2077 | ||
2078 | The fifth element, @var{syntax-begin}, specifies the value of | |
969fe9b5 | 2079 | @code{font-lock-beginning-of-syntax-function} (see below). |
f9f59935 | 2080 | |
a40d4712 PR |
2081 | All the remaining elements (if any) are collectively called |
2082 | @var{other-vars}. Each of these elements should have the form | |
2083 | @code{(@var{variable} . @var{value})}---which means, make @var{variable} | |
2084 | buffer-local and then set it to @var{value}. You can use these | |
2085 | @var{other-vars} to set other variables that affect fontification, | |
2086 | aside from those you can control with the first five elements. | |
f9f59935 RS |
2087 | @end defvar |
2088 | ||
2089 | @node Search-based Fontification | |
2090 | @subsection Search-based Fontification | |
2091 | ||
2092 | The most important variable for customizing Font Lock mode is | |
2093 | @code{font-lock-keywords}. It specifies the search criteria for | |
2094 | search-based fontification. | |
2095 | ||
2096 | @defvar font-lock-keywords | |
2097 | This variable's value is a list of the keywords to highlight. Be | |
969fe9b5 RS |
2098 | careful when composing regular expressions for this list; a poorly |
2099 | written pattern can dramatically slow things down! | |
f9f59935 RS |
2100 | @end defvar |
2101 | ||
2102 | Each element of @code{font-lock-keywords} specifies how to find | |
969fe9b5 RS |
2103 | certain cases of text, and how to highlight those cases. Font Lock mode |
2104 | processes the elements of @code{font-lock-keywords} one by one, and for | |
2105 | each element, it finds and handles all matches. Ordinarily, once | |
2106 | part of the text has been fontified already, this cannot be overridden | |
2107 | by a subsequent match in the same text; but you can specify different | |
2108 | behavior using the @var{override} element of a @var{highlighter}. | |
2109 | ||
2110 | Each element of @code{font-lock-keywords} should have one of these | |
2111 | forms: | |
f9f59935 RS |
2112 | |
2113 | @table @code | |
2114 | @item @var{regexp} | |
2115 | Highlight all matches for @var{regexp} using | |
2116 | @code{font-lock-keyword-face}. For example, | |
2117 | ||
2118 | @example | |
2119 | ;; @r{Highlight discrete occurrences of @samp{foo}} | |
2120 | ;; @r{using @code{font-lock-keyword-face}.} | |
2121 | "\\<foo\\>" | |
2122 | @end example | |
2123 | ||
969fe9b5 RS |
2124 | The function @code{regexp-opt} (@pxref{Syntax of Regexps}) is useful for |
2125 | calculating optimal regular expressions to match a number of different | |
2126 | keywords. | |
f9f59935 RS |
2127 | |
2128 | @item @var{function} | |
2129 | Find text by calling @var{function}, and highlight the matches | |
2130 | it finds using @code{font-lock-keyword-face}. | |
2131 | ||
2132 | When @var{function} is called, it receives one argument, the limit of | |
022cb162 | 2133 | the search; it should begin searching at point, and not search beyond the |
07f7b41c RS |
2134 | limit. It should return non-@code{nil} if it succeeds, and set the |
2135 | match data to describe the match that was found. Returning @code{nil} | |
2136 | indicates failure of the search. | |
2137 | ||
2138 | Fontification will call @var{function} repeatedly with the same limit, | |
2139 | and with point where the previous invocation left it, until | |
2140 | @var{function} fails. On failure, @var{function} need not reset point | |
2141 | in any particular way. | |
f9f59935 RS |
2142 | |
2143 | @item (@var{matcher} . @var{match}) | |
86494bd5 | 2144 | In this kind of element, @var{matcher} is either a regular |
f9f59935 RS |
2145 | expression or a function, as described above. The @sc{cdr}, |
2146 | @var{match}, specifies which subexpression of @var{matcher} should be | |
969fe9b5 | 2147 | highlighted (instead of the entire text that @var{matcher} matched). |
f9f59935 RS |
2148 | |
2149 | @example | |
8241495d | 2150 | ;; @r{Highlight the @samp{bar} in each occurrence of @samp{fubar},} |
f9f59935 RS |
2151 | ;; @r{using @code{font-lock-keyword-face}.} |
2152 | ("fu\\(bar\\)" . 1) | |
2153 | @end example | |
2154 | ||
969fe9b5 | 2155 | If you use @code{regexp-opt} to produce the regular expression |
f9f59935 RS |
2156 | @var{matcher}, then you can use @code{regexp-opt-depth} (@pxref{Syntax |
2157 | of Regexps}) to calculate the value for @var{match}. | |
2158 | ||
3ab66863 RS |
2159 | @item (@var{matcher} . @var{facespec}) |
2160 | In this kind of element, @var{facespec} is an object which specifies | |
2161 | the face variable to use for highlighting. In the simplest case, it | |
2162 | is a Lisp variable (a symbol), whose value should be a face name. | |
f9f59935 RS |
2163 | |
2164 | @example | |
2165 | ;; @r{Highlight occurrences of @samp{fubar},} | |
2166 | ;; @r{using the face which is the value of @code{fubar-face}.} | |
2167 | ("fubar" . fubar-face) | |
2168 | @end example | |
2169 | ||
3ab66863 | 2170 | However, @var{facespec} can also be a list of the form |
fdba9ef4 RS |
2171 | |
2172 | @example | |
2173 | (face @var{face} @var{prop1} @var{val1} @var{prop2} @var{val2}@dots{}) | |
2174 | @end example | |
2175 | ||
2176 | to specify various text properties to put on the text that matches. | |
2177 | If you do this, be sure to add the other text property names that you | |
2178 | set in this way to the value of @code{font-lock-extra-managed-props} | |
2179 | so that the properties will also be cleared out when they are no longer | |
2180 | appropriate. | |
2181 | ||
f9f59935 RS |
2182 | @item (@var{matcher} . @var{highlighter}) |
2183 | In this kind of element, @var{highlighter} is a list | |
2184 | which specifies how to highlight matches found by @var{matcher}. | |
2185 | It has the form | |
2186 | ||
2187 | @example | |
3ab66863 | 2188 | (@var{subexp} @var{facespec} @var{override} @var{laxmatch}) |
f9f59935 RS |
2189 | @end example |
2190 | ||
2191 | The @sc{car}, @var{subexp}, is an integer specifying which subexpression | |
969fe9b5 | 2192 | of the match to fontify (0 means the entire matching text). The second |
3ab66863 | 2193 | subelement, @var{facespec}, specifies the face, as described above. |
f9f59935 RS |
2194 | |
2195 | The last two values in @var{highlighter}, @var{override} and | |
bda7c6dd RS |
2196 | @var{laxmatch}, are flags. If @var{override} is @code{t}, this |
2197 | element can override existing fontification made by previous elements | |
2198 | of @code{font-lock-keywords}. If it is @code{keep}, then each | |
2199 | character is fontified if it has not been fontified already by some | |
3ab66863 RS |
2200 | other element. If it is @code{prepend}, the face specified by |
2201 | @var{facespec} is added to the beginning of the @code{font-lock-face} | |
2202 | property. If it is @code{append}, the face is added to the end of the | |
bda7c6dd | 2203 | @code{font-lock-face} property. |
f9f59935 RS |
2204 | |
2205 | If @var{laxmatch} is non-@code{nil}, it means there should be no error | |
2206 | if there is no subexpression numbered @var{subexp} in @var{matcher}. | |
99b62845 GM |
2207 | Obviously, fontification of the subexpression numbered @var{subexp} will |
2208 | not occur. However, fontification of other subexpressions (and other | |
2209 | regexps) will continue. If @var{laxmatch} is @code{nil}, and the | |
a3ee0299 | 2210 | specified subexpression is missing, then an error is signaled which |
99b62845 | 2211 | terminates search-based fontification. |
f9f59935 RS |
2212 | |
2213 | Here are some examples of elements of this kind, and what they do: | |
2214 | ||
2215 | @smallexample | |
2216 | ;; @r{Highlight occurrences of either @samp{foo} or @samp{bar},} | |
2217 | ;; @r{using @code{foo-bar-face}, even if they have already been highlighted.} | |
2218 | ;; @r{@code{foo-bar-face} should be a variable whose value is a face.} | |
2219 | ("foo\\|bar" 0 foo-bar-face t) | |
2220 | ||
8241495d | 2221 | ;; @r{Highlight the first subexpression within each occurrence} |
f9f59935 RS |
2222 | ;; @r{that the function @code{fubar-match} finds,} |
2223 | ;; @r{using the face which is the value of @code{fubar-face}.} | |
2224 | (fubar-match 1 fubar-face) | |
2225 | @end smallexample | |
2226 | ||
2227 | @item (@var{matcher} @var{highlighters}@dots{}) | |
2228 | This sort of element specifies several @var{highlighter} lists for a | |
2229 | single @var{matcher}. In order for this to be useful, each | |
2230 | @var{highlighter} should have a different value of @var{subexp}; that is, | |
2231 | each one should apply to a different subexpression of @var{matcher}. | |
2232 | ||
2233 | @ignore | |
2234 | @item (@var{matcher} . @var{anchored}) | |
2235 | In this kind of element, @var{anchored} acts much like a | |
2236 | @var{highlighter}, but it is more complex and can specify multiple | |
2237 | successive searches. | |
2238 | ||
2239 | For highlighting single items, typically only @var{highlighter} is | |
2240 | required. However, if an item or (typically) items are to be | |
2241 | highlighted following the instance of another item (the anchor) then | |
2242 | @var{anchored} may be required. | |
2243 | ||
2244 | It has this format: | |
2245 | ||
2246 | @example | |
2247 | (@var{submatcher} @var{pre-match-form} @var{post-match-form} @var{highlighters}@dots{}) | |
2248 | @end example | |
2249 | ||
2250 | @c I can't parse this text -- rms | |
2251 | where @var{submatcher} is much like @var{matcher}, with one | |
2252 | exception---see below. @var{pre-match-form} and @var{post-match-form} | |
2253 | are evaluated before the first, and after the last, instance | |
2254 | @var{anchored}'s @var{submatcher} is used. Therefore they can be used | |
a9f0a989 | 2255 | to initialize before, and cleanup after, @var{submatcher} is used. |
f9f59935 RS |
2256 | Typically, @var{pre-match-form} is used to move to some position |
2257 | relative to the original @var{submatcher}, before starting with | |
2258 | @var{anchored}'s @var{submatcher}. @var{post-match-form} might be used | |
2259 | to move, before resuming with @var{anchored}'s parent's @var{matcher}. | |
2260 | ||
2261 | For example, an element of the form highlights (if not already highlighted): | |
2262 | ||
2263 | @example | |
2264 | ("\\<anchor\\>" (0 anchor-face) ("\\<item\\>" nil nil (0 item-face))) | |
2265 | @end example | |
2266 | ||
2267 | Discrete occurrences of @samp{anchor} in the value of | |
2268 | @code{anchor-face}, and subsequent discrete occurrences of @samp{item} | |
2269 | (on the same line) in the value of @code{item-face}. (Here | |
2270 | @var{pre-match-form} and @var{post-match-form} are @code{nil}. | |
2271 | Therefore @samp{item} is initially searched for starting from the end of | |
2272 | the match of @samp{anchor}, and searching for subsequent instance of | |
2273 | @samp{anchor} resumes from where searching for @samp{item} concluded.) | |
2274 | ||
2275 | The above-mentioned exception is as follows. The limit of the | |
2276 | @var{submatcher} search defaults to the end of the line after | |
2277 | @var{pre-match-form} is evaluated. However, if @var{pre-match-form} | |
2278 | returns a position greater than the position after @var{pre-match-form} | |
2279 | is evaluated, that position is used as the limit of the search. It is | |
2280 | generally a bad idea to return a position greater than the end of the | |
2281 | line; in other words, the @var{submatcher} search should not span lines. | |
2282 | ||
2283 | @item (@var{matcher} @var{highlighters-or-anchoreds} ...) | |
2284 | @end ignore | |
2285 | ||
2286 | @item (eval . @var{form}) | |
969fe9b5 | 2287 | Here @var{form} is an expression to be evaluated the first time |
f9f59935 | 2288 | this value of @code{font-lock-keywords} is used in a buffer. |
969fe9b5 | 2289 | Its value should have one of the forms described in this table. |
f9f59935 RS |
2290 | @end table |
2291 | ||
2292 | @strong{Warning:} Do not design an element of @code{font-lock-keywords} | |
2293 | to match text which spans lines; this does not work reliably. While | |
2294 | @code{font-lock-fontify-buffer} handles multi-line patterns correctly, | |
2295 | updating when you edit the buffer does not, since it considers text one | |
8ba2808b SM |
2296 | line at a time. If you have patterns that typically only span one |
2297 | line but can occasionally span two or three, such as | |
2298 | @samp{<title>...</title>}, you can ask font-lock to be more careful by | |
2299 | setting @code{font-lock-multiline} to @code{t}. But it still will not | |
2300 | work in all cases. | |
f9f59935 | 2301 | |
f9f59935 RS |
2302 | @node Other Font Lock Variables |
2303 | @subsection Other Font Lock Variables | |
2304 | ||
2305 | This section describes additional variables that a major mode | |
2306 | can set by means of @code{font-lock-defaults}. | |
2307 | ||
2308 | @defvar font-lock-keywords-only | |
2309 | Non-@code{nil} means Font Lock should not fontify comments or strings | |
969fe9b5 RS |
2310 | syntactically; it should only fontify based on |
2311 | @code{font-lock-keywords}. | |
f9f59935 RS |
2312 | @end defvar |
2313 | ||
2314 | @ignore | |
a9f0a989 | 2315 | Other variables include those for buffer-specialized fontification functions, |
f9f59935 RS |
2316 | `font-lock-fontify-buffer-function', `font-lock-unfontify-buffer-function', |
2317 | `font-lock-fontify-region-function', `font-lock-unfontify-region-function', | |
2318 | `font-lock-inhibit-thing-lock' and `font-lock-maximum-size'. | |
2319 | @end ignore | |
2320 | ||
2321 | @defvar font-lock-keywords-case-fold-search | |
969fe9b5 RS |
2322 | Non-@code{nil} means that regular expression matching for the sake of |
2323 | @code{font-lock-keywords} should be case-insensitive. | |
f9f59935 RS |
2324 | @end defvar |
2325 | ||
969fe9b5 RS |
2326 | @defvar font-lock-syntax-table |
2327 | This variable specifies the syntax table to use for fontification of | |
2328 | comments and strings. | |
2329 | @end defvar | |
f9f59935 | 2330 | |
969fe9b5 RS |
2331 | @defvar font-lock-beginning-of-syntax-function |
2332 | If this variable is non-@code{nil}, it should be a function to move | |
2333 | point back to a position that is syntactically at ``top level'' and | |
2334 | outside of strings or comments. Font Lock uses this when necessary | |
2335 | to get the right results for syntactic fontification. | |
f9f59935 RS |
2336 | |
2337 | This function is called with no arguments. It should leave point at the | |
2338 | beginning of any enclosing syntactic block. Typical values are | |
2339 | @code{beginning-of-line} (i.e., the start of the line is known to be | |
2340 | outside a syntactic block), or @code{beginning-of-defun} for programming | |
2341 | modes or @code{backward-paragraph} for textual modes (i.e., the | |
2342 | mode-dependent function is known to move outside a syntactic block). | |
2343 | ||
2344 | If the value is @code{nil}, the beginning of the buffer is used as a | |
969fe9b5 RS |
2345 | position outside of a syntactic block. This cannot be wrong, but it can |
2346 | be slow. | |
f9f59935 RS |
2347 | @end defvar |
2348 | ||
2349 | @defvar font-lock-mark-block-function | |
969fe9b5 RS |
2350 | If this variable is non-@code{nil}, it should be a function that is |
2351 | called with no arguments, to choose an enclosing range of text for | |
2352 | refontification for the command @kbd{M-g M-g} | |
2353 | (@code{font-lock-fontify-block}). | |
2354 | ||
2355 | The function should report its choice by placing the region around it. | |
2356 | A good choice is a range of text large enough to give proper results, | |
2357 | but not too large so that refontification becomes slow. Typical values | |
2358 | are @code{mark-defun} for programming modes or @code{mark-paragraph} for | |
2359 | textual modes. | |
f9f59935 RS |
2360 | @end defvar |
2361 | ||
fdba9ef4 | 2362 | @defvar font-lock-extra-managed-props |
bda7c6dd RS |
2363 | Additional properties (other than @code{font-lock-face}) that are |
2364 | being managed by Font Lock mode. Font Lock mode normally manages only | |
2365 | the @code{font-lock-face} property; if you want it to manage others as | |
3ab66863 | 2366 | well, you must specify them in a @var{facespec} in |
bda7c6dd | 2367 | @code{font-lock-keywords} as well as adding them to this list. |
fdba9ef4 RS |
2368 | @end defvar |
2369 | ||
8ba2808b SM |
2370 | @defvar font-lock-syntactic-face-function |
2371 | A function to determine which face to use for a given syntactic | |
2372 | element (a string or a comment). The function is called with one | |
2373 | argument, the parse state at point returned by | |
2374 | @code{parse-partial-sexp}, and should return a face. The default | |
2375 | value returns @code{font-lock-comment-face} for comments and | |
2376 | @code{font-lock-string-face} for strings. | |
2377 | ||
2378 | This can be used to highlighting different kinds of strings or | |
2379 | comments differently. It is also sometimes abused together with | |
2380 | @code{font-lock-syntactic-keywords} to highlight elements that span | |
2381 | multiple lines, but this is too obscure to document in this manual. | |
2382 | @end defvar | |
2383 | ||
3a05b1e4 RS |
2384 | @defvar font-lock-lines-before |
2385 | This variable specifies the number of extra lines to consider when | |
2386 | refontifying the buffer after each text change. Font lock begins | |
2387 | refontifying from that number of lines before the changed region. The | |
2388 | default is 1, but using a larger value can be useful for coping with | |
2389 | multi-line patterns. | |
2390 | @end defvar | |
2391 | ||
f9f59935 RS |
2392 | @node Levels of Font Lock |
2393 | @subsection Levels of Font Lock | |
2394 | ||
2395 | Many major modes offer three different levels of fontification. You | |
2396 | can define multiple levels by using a list of symbols for @var{keywords} | |
2397 | in @code{font-lock-defaults}. Each symbol specifies one level of | |
2398 | fontification; it is up to the user to choose one of these levels. The | |
2399 | chosen level's symbol value is used to initialize | |
2400 | @code{font-lock-keywords}. | |
2401 | ||
969fe9b5 RS |
2402 | Here are the conventions for how to define the levels of |
2403 | fontification: | |
2404 | ||
f9f59935 RS |
2405 | @itemize @bullet |
2406 | @item | |
2407 | Level 1: highlight function declarations, file directives (such as include or | |
2408 | import directives), strings and comments. The idea is speed, so only | |
2409 | the most important and top-level components are fontified. | |
2410 | ||
2411 | @item | |
969fe9b5 RS |
2412 | Level 2: in addition to level 1, highlight all language keywords, |
2413 | including type names that act like keywords, as well as named constant | |
2414 | values. The idea is that all keywords (either syntactic or semantic) | |
2415 | should be fontified appropriately. | |
f9f59935 RS |
2416 | |
2417 | @item | |
969fe9b5 RS |
2418 | Level 3: in addition to level 2, highlight the symbols being defined in |
2419 | function and variable declarations, and all builtin function names, | |
2420 | wherever they appear. | |
f9f59935 RS |
2421 | @end itemize |
2422 | ||
651f7556 CW |
2423 | @node Precalculated Fontification |
2424 | @subsection Precalculated Fontification | |
2425 | ||
ec9b0882 | 2426 | In addition to using @code{font-lock-defaults} for search-based |
651f7556 CW |
2427 | fontification, you may use the special character property |
2428 | @code{font-lock-face} (@pxref{Special Properties}). This property | |
2429 | acts just like the explicit @code{face} property, but its activation | |
2430 | is toggled when the user calls @kbd{M-x font-lock-mode}. Using | |
06862374 | 2431 | @code{font-lock-face} is especially convenient for special modes |
651f7556 CW |
2432 | which construct their text programmatically, such as |
2433 | @code{list-buffers} and @code{occur}. | |
2434 | ||
0ab0c481 CW |
2435 | If your mode does not use any of the other machinery of Font Lock |
2436 | (i.e. it only uses the @code{font-lock-face} property), you can tell | |
2437 | Emacs not to load all of font-lock.el (unless it's already loaded), by | |
6fe50867 RS |
2438 | setting the variable @code{font-lock-core-only} to non-@code{nil} as |
2439 | part of the @code{font-lock-defaults} settings. Here is the canonical | |
2440 | way to do this: | |
0ab0c481 CW |
2441 | |
2442 | @example | |
2443 | (set (make-local-variable 'font-lock-defaults) | |
2444 | '(nil t nil nil nil (font-lock-core-only . t))) | |
2445 | @end example | |
2446 | ||
f9f59935 RS |
2447 | @node Faces for Font Lock |
2448 | @subsection Faces for Font Lock | |
2449 | ||
2450 | You can make Font Lock mode use any face, but several faces are | |
2451 | defined specifically for Font Lock mode. Each of these symbols is both | |
2452 | a face name, and a variable whose default value is the symbol itself. | |
2453 | Thus, the default value of @code{font-lock-comment-face} is | |
2454 | @code{font-lock-comment-face}. This means you can write | |
2455 | @code{font-lock-comment-face} in a context such as | |
2456 | @code{font-lock-keywords} where a face-name-valued expression is used. | |
2457 | ||
2458 | @table @code | |
2459 | @item font-lock-comment-face | |
2460 | @vindex font-lock-comment-face | |
f9f59935 RS |
2461 | Used (typically) for comments. |
2462 | ||
ec9b0882 RS |
2463 | @item font-lock-doc-face |
2464 | @vindex font-lock-doc-face | |
2465 | Used (typically) for documentation strings in the code. | |
2466 | ||
f9f59935 RS |
2467 | @item font-lock-string-face |
2468 | @vindex font-lock-string-face | |
f9f59935 RS |
2469 | Used (typically) for string constants. |
2470 | ||
2471 | @item font-lock-keyword-face | |
2472 | @vindex font-lock-keyword-face | |
f9f59935 RS |
2473 | Used (typically) for keywords---names that have special syntactic |
2474 | significance, like @code{for} and @code{if} in C. | |
2475 | ||
2476 | @item font-lock-builtin-face | |
2477 | @vindex font-lock-builtin-face | |
f9f59935 RS |
2478 | Used (typically) for built-in function names. |
2479 | ||
2480 | @item font-lock-function-name-face | |
2481 | @vindex font-lock-function-name-face | |
f9f59935 | 2482 | Used (typically) for the name of a function being defined or declared, |
177c0ea7 | 2483 | in a function definition or declaration. |
f9f59935 RS |
2484 | |
2485 | @item font-lock-variable-name-face | |
2486 | @vindex font-lock-variable-name-face | |
f9f59935 RS |
2487 | Used (typically) for the name of a variable being defined or declared, |
2488 | in a variable definition or declaration. | |
2489 | ||
2490 | @item font-lock-type-face | |
2491 | @vindex font-lock-type-face | |
f9f59935 RS |
2492 | Used (typically) for names of user-defined data types, |
2493 | where they are defined and where they are used. | |
2494 | ||
2495 | @item font-lock-constant-face | |
2496 | @vindex font-lock-constant-face | |
f9f59935 RS |
2497 | Used (typically) for constant names. |
2498 | ||
c22c5da6 LK |
2499 | @item font-lock-preprocessor-face |
2500 | @vindex font-lock-preprocessor-face | |
fdba9ef4 RS |
2501 | Used (typically) for preprocessor commands. |
2502 | ||
f9f59935 RS |
2503 | @item font-lock-warning-face |
2504 | @vindex font-lock-warning-face | |
f9f59935 RS |
2505 | Used (typically) for constructs that are peculiar, or that greatly |
2506 | change the meaning of other text. For example, this is used for | |
2507 | @samp{;;;###autoload} cookies in Emacs Lisp, and for @code{#error} | |
2508 | directives in C. | |
2509 | @end table | |
2510 | ||
969fe9b5 RS |
2511 | @node Syntactic Font Lock |
2512 | @subsection Syntactic Font Lock | |
2513 | ||
2514 | Font Lock mode can be used to update @code{syntax-table} properties | |
2515 | automatically. This is useful in languages for which a single syntax | |
2516 | table by itself is not sufficient. | |
2517 | ||
2518 | @defvar font-lock-syntactic-keywords | |
f8cecb20 DL |
2519 | This variable enables and controls syntactic Font Lock. It is |
2520 | normally set via @code{font-lock-defaults}. Its value should be a | |
2521 | list of elements of this form: | |
969fe9b5 RS |
2522 | |
2523 | @example | |
2524 | (@var{matcher} @var{subexp} @var{syntax} @var{override} @var{laxmatch}) | |
2525 | @end example | |
2526 | ||
2527 | The parts of this element have the same meanings as in the corresponding | |
2528 | sort of element of @code{font-lock-keywords}, | |
2529 | ||
2530 | @example | |
2531 | (@var{matcher} @var{subexp} @var{facename} @var{override} @var{laxmatch}) | |
2532 | @end example | |
2533 | ||
2534 | However, instead of specifying the value @var{facename} to use for the | |
f8cecb20 DL |
2535 | @code{face} property, it specifies the value @var{syntax} to use for |
2536 | the @code{syntax-table} property. Here, @var{syntax} can be a string | |
2537 | (as taken by @code{modify-syntax-entry}), a syntax table, a cons cell | |
2538 | (as returned by @code{string-to-syntax}), or an expression whose value | |
2539 | is one of those two types. @var{override} cannot be @code{prepend} or | |
2540 | @code{append}. | |
2541 | ||
2542 | For example, an element of the form: | |
2543 | ||
2544 | @example | |
2545 | ("\\$\\(#\\)" 1 ".") | |
2546 | @end example | |
2547 | ||
2548 | highlights syntactically a hash character when following a dollar | |
2549 | character, with a SYNTAX of @code{"."} (meaning punctuation syntax). | |
2550 | Assuming that the buffer syntax table specifies hash characters to | |
2551 | have comment start syntax, the element will only highlight hash | |
2552 | characters that do not follow dollar characters as comments | |
2553 | syntactically. | |
2554 | ||
2555 | An element of the form: | |
2556 | ||
2557 | @example | |
2558 | ("\\('\\).\\('\\)" | |
2559 | (1 "\"") | |
2560 | (2 "\"")) | |
2561 | @end example | |
2562 | ||
2563 | highlights syntactically both single quotes which surround a single | |
2564 | character, with a SYNTAX of @code{"\""} (meaning string quote syntax). | |
2565 | Assuming that the buffer syntax table does not specify single quotes | |
2566 | to have quote syntax, the element will only highlight single quotes of | |
2567 | the form @samp{'@var{c}'} as strings syntactically. Other forms, such | |
2568 | as @samp{foo'bar} or @samp{'fubar'}, will not be highlighted as | |
2569 | strings. | |
2570 | ||
969fe9b5 RS |
2571 | @end defvar |
2572 | ||
f730cc62 LH |
2573 | @node Desktop Save Mode |
2574 | @section Desktop Save Mode | |
2575 | @cindex desktop save mode | |
2576 | ||
2577 | @dfn{Desktop Save Mode} is a feature to save the state of Emacs from | |
2578 | one session to another. The user-level commands for using Desktop | |
2579 | Save Mode are described in the GNU Emacs Manual (@pxref{Saving Emacs | |
2580 | Sessions,,, emacs, the GNU Emacs Manual}). Modes whose buffers visit | |
2581 | a file, don't have to do anything to use this feature. | |
2582 | ||
2583 | For buffers not visiting a file to have their state saved, the major | |
2584 | mode must bind the buffer local variable @code{desktop-save-buffer} to | |
a3ee0299 | 2585 | a non-@code{nil} value. |
f730cc62 LH |
2586 | |
2587 | @defvar desktop-save-buffer | |
2588 | If this buffer-local variable is non-@code{nil}, the buffer will have | |
2589 | its state saved in the desktop file at desktop save. If the value is | |
2590 | a function, it is called at desktop save with argument | |
2591 | @var{desktop-dirname}, and its value is saved in the desktop file along | |
2592 | with the state of the buffer for which it was called. When file names | |
2593 | are returned as part of the auxiliary information, they should be | |
2594 | formatted using the call | |
2595 | ||
2596 | @example | |
2597 | (desktop-file-name @var{file-name} @var{desktop-dirname}) | |
2598 | @end example | |
2599 | ||
2600 | @end defvar | |
2601 | ||
2602 | For buffers not visiting a file to be restored, the major mode must | |
2603 | define a function to do the job, and that function must be listed in | |
2604 | the alist @code{desktop-buffer-mode-handlers}. | |
2605 | ||
2606 | @defvar desktop-buffer-mode-handlers | |
2607 | Alist with elements | |
2608 | ||
2609 | @example | |
2610 | (@var{major-mode} . @var{restore-buffer-function}) | |
2611 | @end example | |
2612 | ||
2613 | The function @var{restore-buffer-function} will be called with | |
2614 | argument list | |
2615 | ||
2616 | @example | |
2617 | (@var{buffer-file-name} @var{buffer-name} @var{desktop-buffer-misc}) | |
2618 | @end example | |
2619 | ||
2620 | and it should return the restored buffer. | |
2621 | Here @var{desktop-buffer-misc} is the value returned by the function | |
2622 | optionally bound to @code{desktop-save-buffer}. | |
2623 | ||
2624 | @end defvar | |
2625 | ||
a44af9f2 RS |
2626 | @node Hooks |
2627 | @section Hooks | |
2628 | @cindex hooks | |
2629 | ||
2630 | A @dfn{hook} is a variable where you can store a function or functions | |
2631 | to be called on a particular occasion by an existing program. Emacs | |
2632 | provides hooks for the sake of customization. Most often, hooks are set | |
a40d4712 | 2633 | up in the init file (@pxref{Init File}), but Lisp programs can set them also. |
a44af9f2 RS |
2634 | @xref{Standard Hooks}, for a list of standard hook variables. |
2635 | ||
f9f59935 | 2636 | @cindex normal hook |
a44af9f2 | 2637 | Most of the hooks in Emacs are @dfn{normal hooks}. These variables |
dd73b091 RS |
2638 | contain lists of functions to be called with no arguments. When the |
2639 | hook name ends in @samp{-hook}, that tells you it is normal. We try to | |
2640 | make all hooks normal, as much as possible, so that you can use them in | |
2641 | a uniform way. | |
2642 | ||
2643 | Every major mode function is supposed to run a normal hook called the | |
2644 | @dfn{mode hook} as the last step of initialization. This makes it easy | |
2645 | for a user to customize the behavior of the mode, by overriding the | |
969fe9b5 RS |
2646 | buffer-local variable assignments already made by the mode. But hooks |
2647 | are used in other contexts too. For example, the hook | |
2648 | @code{suspend-hook} runs just before Emacs suspends itself | |
2649 | (@pxref{Suspending Emacs}). | |
a44af9f2 RS |
2650 | |
2651 | The recommended way to add a hook function to a normal hook is by | |
2652 | calling @code{add-hook} (see below). The hook functions may be any of | |
da3178e2 RS |
2653 | the valid kinds of functions that @code{funcall} accepts (@pxref{What |
2654 | Is a Function}). Most normal hook variables are initially void; | |
2655 | @code{add-hook} knows how to deal with this. You can add hooks either | |
2656 | globally or buffer-locally with @code{add-hook}. | |
c22c5da6 | 2657 | |
f9f59935 | 2658 | @cindex abnormal hook |
dd73b091 | 2659 | If the hook variable's name does not end with @samp{-hook}, that |
a40d4712 | 2660 | indicates it is probably an @dfn{abnormal hook}. Then you should look at its |
dd73b091 RS |
2661 | documentation to see how to use the hook properly. |
2662 | ||
2663 | If the variable's name ends in @samp{-functions} or @samp{-hooks}, | |
2664 | then the value is a list of functions, but it is abnormal in that either | |
2665 | these functions are called with arguments or their values are used in | |
2666 | some way. You can use @code{add-hook} to add a function to the list, | |
2667 | but you must take care in writing the function. (A few of these | |
89cda0c5 SM |
2668 | variables, notably those ending in @samp{-hooks}, are actually |
2669 | normal hooks which were named before we established the convention of | |
2670 | using @samp{-hook} for them.) | |
dd73b091 RS |
2671 | |
2672 | If the variable's name ends in @samp{-function}, then its value | |
2673 | is just a single function, not a list of functions. | |
a44af9f2 | 2674 | |
969fe9b5 RS |
2675 | Here's an example that uses a mode hook to turn on Auto Fill mode when |
2676 | in Lisp Interaction mode: | |
a44af9f2 RS |
2677 | |
2678 | @example | |
2679 | (add-hook 'lisp-interaction-mode-hook 'turn-on-auto-fill) | |
a44af9f2 RS |
2680 | @end example |
2681 | ||
2682 | At the appropriate time, Emacs uses the @code{run-hooks} function to | |
bfe721d1 KH |
2683 | run particular hooks. This function calls the hook functions that have |
2684 | been added with @code{add-hook}. | |
a44af9f2 | 2685 | |
a40d4712 | 2686 | @defun run-hooks &rest hookvars |
c22c5da6 LK |
2687 | This function takes one or more normal hook variable names as |
2688 | arguments, and runs each hook in turn. Each argument should be a | |
da3178e2 RS |
2689 | symbol that is a normal hook variable. These arguments are processed |
2690 | in the order specified. | |
a44af9f2 RS |
2691 | |
2692 | If a hook variable has a non-@code{nil} value, that value may be a | |
da3178e2 RS |
2693 | function or a list of functions. (The former option is considered |
2694 | obsolete.) If the value is a function (either a lambda expression or | |
2695 | a symbol with a function definition), it is called. If it is a list | |
2696 | that isn't a function, its elements are called, consecutively. All | |
2697 | the hook functions are called with no arguments. | |
a44af9f2 RS |
2698 | @end defun |
2699 | ||
a9f0a989 | 2700 | @defun run-hook-with-args hook &rest args |
da3178e2 RS |
2701 | This function is the way to run an abnormal hook and always call all |
2702 | of the hook functions. It calls each of the hook functions one by | |
2703 | one, passing each of them the arguments @var{args}. | |
a9f0a989 RS |
2704 | @end defun |
2705 | ||
2706 | @defun run-hook-with-args-until-failure hook &rest args | |
c22c5da6 LK |
2707 | This function is the way to run an abnormal hook until one of the hook |
2708 | functions fails. It calls each of the hook functions, passing each of | |
2709 | them the arguments @var{args}, until some hook function returns | |
2710 | @code{nil}. It then stops and returns @code{nil}. If none of the | |
2711 | hook functions return @code{nil}, it returns a non-@code{nil} value. | |
a9f0a989 RS |
2712 | @end defun |
2713 | ||
2714 | @defun run-hook-with-args-until-success hook &rest args | |
c22c5da6 LK |
2715 | This function is the way to run an abnormal hook until a hook function |
2716 | succeeds. It calls each of the hook functions, passing each of them | |
2717 | the arguments @var{args}, until some hook function returns | |
2718 | non-@code{nil}. Then it stops, and returns whatever was returned by | |
2719 | the last hook function that was called. If all hook functions return | |
2720 | @code{nil}, it returns @code{nil} as well. | |
a9f0a989 RS |
2721 | @end defun |
2722 | ||
22697dac | 2723 | @defun add-hook hook function &optional append local |
a44af9f2 | 2724 | This function is the handy way to add function @var{function} to hook |
da3178e2 RS |
2725 | variable @var{hook}. You can use it for abnormal hooks as well as for |
2726 | normal hooks. @var{function} can be any Lisp function that can accept | |
2727 | the proper number of arguments for @var{hook}. For example, | |
a44af9f2 RS |
2728 | |
2729 | @example | |
2730 | (add-hook 'text-mode-hook 'my-text-hook-function) | |
2731 | @end example | |
2732 | ||
2733 | @noindent | |
2734 | adds @code{my-text-hook-function} to the hook called @code{text-mode-hook}. | |
2735 | ||
da3178e2 RS |
2736 | If @var{function} is already present in @var{hook} (comparing using |
2737 | @code{equal}), then @code{add-hook} does not add it a second time. | |
de9f0bd9 | 2738 | |
a44af9f2 RS |
2739 | It is best to design your hook functions so that the order in which they |
2740 | are executed does not matter. Any dependence on the order is ``asking | |
c22c5da6 | 2741 | for trouble''. However, the order is predictable: normally, |
a44af9f2 | 2742 | @var{function} goes at the front of the hook list, so it will be |
969fe9b5 RS |
2743 | executed first (barring another @code{add-hook} call). If the optional |
2744 | argument @var{append} is non-@code{nil}, the new hook function goes at | |
2745 | the end of the hook list and will be executed last. | |
22697dac | 2746 | |
c22c5da6 LK |
2747 | If @var{local} is non-@code{nil}, that says to add @var{function} to |
2748 | the buffer-local hook list instead of to the global hook list. If | |
2749 | needed, this makes the hook buffer-local and adds @code{t} to the | |
2750 | buffer-local value. The latter acts as a flag to run the hook | |
2751 | functions in the default value as well as in the local value. | |
a44af9f2 RS |
2752 | @end defun |
2753 | ||
22697dac | 2754 | @defun remove-hook hook function &optional local |
c22c5da6 | 2755 | This function removes @var{function} from the hook variable |
da3178e2 RS |
2756 | @var{hook}. It compares @var{function} with elements of @var{hook} |
2757 | using @code{equal}, so it works for both symbols and lambda | |
2758 | expressions. | |
c44d2ced | 2759 | |
22697dac | 2760 | If @var{local} is non-@code{nil}, that says to remove @var{function} |
969fe9b5 | 2761 | from the buffer-local hook list instead of from the global hook list. |
22697dac | 2762 | @end defun |
ab5796a9 MB |
2763 | |
2764 | @ignore | |
2765 | arch-tag: 4c7bff41-36e6-4da6-9e7f-9b9289e27c8e | |
2766 | @end ignore |