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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
651f374c | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, |
8dc811d3 | 4 | @c 2003, 2004, 2005 Free Software Foundation, Inc. |
a44af9f2 RS |
5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/modes | |
3ebe0346 | 7 | @node Modes, Documentation, Keymaps, Top |
a44af9f2 RS |
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 | |
302691ab | 23 | * Hooks:: How to use hooks; how to write code that provides hooks. |
a44af9f2 RS |
24 | * Major Modes:: Defining major modes. |
25 | * Minor Modes:: Defining minor modes. | |
26 | * Mode Line Format:: Customizing the text that appears in the mode line. | |
f9f59935 RS |
27 | * Imenu:: How a mode can provide a menu |
28 | of definitions in the buffer. | |
29 | * Font Lock Mode:: How modes can highlight text according to syntax. | |
f730cc62 LH |
30 | * Desktop Save Mode:: How modes can have buffer state saved between |
31 | Emacs sessions. | |
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32 | @end menu |
33 | ||
302691ab LT |
34 | @node Hooks |
35 | @section Hooks | |
36 | @cindex hooks | |
37 | ||
38 | A @dfn{hook} is a variable where you can store a function or functions | |
39 | to be called on a particular occasion by an existing program. Emacs | |
40 | provides hooks for the sake of customization. Most often, hooks are set | |
41 | up in the init file (@pxref{Init File}), but Lisp programs can set them also. | |
42 | @xref{Standard Hooks}, for a list of standard hook variables. | |
43 | ||
44 | @cindex normal hook | |
45 | Most of the hooks in Emacs are @dfn{normal hooks}. These variables | |
46 | contain lists of functions to be called with no arguments. When the | |
47 | hook name ends in @samp{-hook}, that tells you it is normal. We try to | |
48 | make all hooks normal, as much as possible, so that you can use them in | |
49 | a uniform way. | |
50 | ||
51 | Every major mode function is supposed to run a normal hook called the | |
52 | @dfn{mode hook} as the last step of initialization. This makes it easy | |
53 | for a user to customize the behavior of the mode, by overriding the | |
54 | buffer-local variable assignments already made by the mode. Most | |
55 | minor modes also run a mode hook at their end. But hooks are used in | |
56 | other contexts too. For example, the hook @code{suspend-hook} runs | |
57 | just before Emacs suspends itself (@pxref{Suspending Emacs}). | |
58 | ||
59 | The recommended way to add a hook function to a normal hook is by | |
60 | calling @code{add-hook} (see below). The hook functions may be any of | |
61 | the valid kinds of functions that @code{funcall} accepts (@pxref{What | |
62 | Is a Function}). Most normal hook variables are initially void; | |
63 | @code{add-hook} knows how to deal with this. You can add hooks either | |
64 | globally or buffer-locally with @code{add-hook}. | |
65 | ||
66 | @cindex abnormal hook | |
67 | If the hook variable's name does not end with @samp{-hook}, that | |
68 | indicates it is probably an @dfn{abnormal hook}. Then you should look at its | |
69 | documentation to see how to use the hook properly. | |
70 | ||
71 | If the variable's name ends in @samp{-functions} or @samp{-hooks}, | |
72 | then the value is a list of functions, but it is abnormal in that either | |
73 | these functions are called with arguments or their values are used in | |
74 | some way. You can use @code{add-hook} to add a function to the list, | |
75 | but you must take care in writing the function. (A few of these | |
76 | variables, notably those ending in @samp{-hooks}, are actually | |
77 | normal hooks which were named before we established the convention of | |
78 | using @samp{-hook} for them.) | |
79 | ||
80 | If the variable's name ends in @samp{-function}, then its value | |
81 | is just a single function, not a list of functions. | |
82 | ||
83 | Here's an example that uses a mode hook to turn on Auto Fill mode when | |
84 | in Lisp Interaction mode: | |
85 | ||
86 | @example | |
87 | (add-hook 'lisp-interaction-mode-hook 'turn-on-auto-fill) | |
88 | @end example | |
89 | ||
90 | At the appropriate time, Emacs uses the @code{run-hooks} function to | |
b4a83bb8 | 91 | run particular hooks. |
302691ab LT |
92 | |
93 | @defun run-hooks &rest hookvars | |
94 | This function takes one or more normal hook variable names as | |
95 | arguments, and runs each hook in turn. Each argument should be a | |
96 | symbol that is a normal hook variable. These arguments are processed | |
97 | in the order specified. | |
98 | ||
99 | If a hook variable has a non-@code{nil} value, that value may be a | |
100 | function or a list of functions. (The former option is considered | |
101 | obsolete.) If the value is a function (either a lambda expression or | |
102 | a symbol with a function definition), it is called. If it is a list | |
103 | that isn't a function, its elements are called, consecutively. All | |
104 | the hook functions are called with no arguments. | |
105 | @end defun | |
106 | ||
107 | @defun run-hook-with-args hook &rest args | |
108 | This function is the way to run an abnormal hook and always call all | |
109 | of the hook functions. It calls each of the hook functions one by | |
110 | one, passing each of them the arguments @var{args}. | |
111 | @end defun | |
112 | ||
113 | @defun run-hook-with-args-until-failure hook &rest args | |
114 | This function is the way to run an abnormal hook until one of the hook | |
115 | functions fails. It calls each of the hook functions, passing each of | |
116 | them the arguments @var{args}, until some hook function returns | |
117 | @code{nil}. It then stops and returns @code{nil}. If none of the | |
118 | hook functions return @code{nil}, it returns a non-@code{nil} value. | |
119 | @end defun | |
120 | ||
121 | @defun run-hook-with-args-until-success hook &rest args | |
122 | This function is the way to run an abnormal hook until a hook function | |
123 | succeeds. It calls each of the hook functions, passing each of them | |
124 | the arguments @var{args}, until some hook function returns | |
125 | non-@code{nil}. Then it stops, and returns whatever was returned by | |
126 | the last hook function that was called. If all hook functions return | |
127 | @code{nil}, it returns @code{nil} as well. | |
128 | @end defun | |
129 | ||
130 | @defun add-hook hook function &optional append local | |
131 | This function is the handy way to add function @var{function} to hook | |
132 | variable @var{hook}. You can use it for abnormal hooks as well as for | |
133 | normal hooks. @var{function} can be any Lisp function that can accept | |
134 | the proper number of arguments for @var{hook}. For example, | |
135 | ||
136 | @example | |
137 | (add-hook 'text-mode-hook 'my-text-hook-function) | |
138 | @end example | |
139 | ||
140 | @noindent | |
141 | adds @code{my-text-hook-function} to the hook called @code{text-mode-hook}. | |
142 | ||
143 | If @var{function} is already present in @var{hook} (comparing using | |
144 | @code{equal}), then @code{add-hook} does not add it a second time. | |
145 | ||
146 | It is best to design your hook functions so that the order in which they | |
147 | are executed does not matter. Any dependence on the order is ``asking | |
148 | for trouble''. However, the order is predictable: normally, | |
149 | @var{function} goes at the front of the hook list, so it will be | |
150 | executed first (barring another @code{add-hook} call). If the optional | |
151 | argument @var{append} is non-@code{nil}, the new hook function goes at | |
152 | the end of the hook list and will be executed last. | |
153 | ||
154 | @code{add-hook} can handle the cases where @var{hook} is void or its | |
155 | value is a single function; it sets or changes the value to a list of | |
156 | functions. | |
157 | ||
158 | If @var{local} is non-@code{nil}, that says to add @var{function} to | |
159 | the buffer-local hook list instead of to the global hook list. If | |
160 | needed, this makes the hook buffer-local and adds @code{t} to the | |
161 | buffer-local value. The latter acts as a flag to run the hook | |
162 | functions in the default value as well as in the local value. | |
163 | @end defun | |
164 | ||
165 | @defun remove-hook hook function &optional local | |
166 | This function removes @var{function} from the hook variable | |
167 | @var{hook}. It compares @var{function} with elements of @var{hook} | |
168 | using @code{equal}, so it works for both symbols and lambda | |
169 | expressions. | |
170 | ||
171 | If @var{local} is non-@code{nil}, that says to remove @var{function} | |
172 | from the buffer-local hook list instead of from the global hook list. | |
173 | @end defun | |
174 | ||
a44af9f2 RS |
175 | @node Major Modes |
176 | @section Major Modes | |
177 | @cindex major mode | |
a44af9f2 RS |
178 | |
179 | Major modes specialize Emacs for editing particular kinds of text. | |
22c94cf2 RS |
180 | Each buffer has only one major mode at a time. For each major mode |
181 | there is a function to switch to that mode in the current buffer; its | |
182 | name should end in @samp{-mode}. These functions work by setting | |
183 | buffer-local variable bindings and other data associated with the | |
184 | buffer, such as a local keymap. The effect lasts until you switch | |
185 | to another major mode in the same buffer. | |
a44af9f2 | 186 | |
302691ab LT |
187 | @menu |
188 | * Major Mode Basics:: | |
189 | * Major Mode Conventions:: Coding conventions for keymaps, etc. | |
190 | * Example Major Modes:: Text mode and Lisp modes. | |
191 | * Auto Major Mode:: How Emacs chooses the major mode automatically. | |
192 | * Mode Help:: Finding out how to use a mode. | |
193 | * Derived Modes:: Defining a new major mode based on another major | |
194 | mode. | |
195 | * Generic Modes:: Defining a simple major mode that supports | |
196 | comment syntax and Font Lock mode. | |
197 | * Mode Hooks:: Hooks run at the end of major mode functions. | |
198 | @end menu | |
199 | ||
200 | @node Major Mode Basics | |
201 | @subsection Major Mode Basics | |
202 | @cindex Fundamental mode | |
203 | ||
a44af9f2 RS |
204 | The least specialized major mode is called @dfn{Fundamental mode}. |
205 | This mode has no mode-specific definitions or variable settings, so each | |
206 | Emacs command behaves in its default manner, and each option is in its | |
207 | default state. All other major modes redefine various keys and options. | |
208 | For example, Lisp Interaction mode provides special key bindings for | |
969fe9b5 | 209 | @kbd{C-j} (@code{eval-print-last-sexp}), @key{TAB} |
a44af9f2 RS |
210 | (@code{lisp-indent-line}), and other keys. |
211 | ||
212 | When you need to write several editing commands to help you perform a | |
213 | specialized editing task, creating a new major mode is usually a good | |
214 | idea. In practice, writing a major mode is easy (in contrast to | |
215 | writing a minor mode, which is often difficult). | |
216 | ||
217 | If the new mode is similar to an old one, it is often unwise to modify | |
218 | the old one to serve two purposes, since it may become harder to use and | |
219 | maintain. Instead, copy and rename an existing major mode definition | |
220 | and alter the copy---or define a @dfn{derived mode} (@pxref{Derived | |
221 | Modes}). For example, Rmail Edit mode, which is in | |
a40d4712 PR |
222 | @file{emacs/lisp/mail/rmailedit.el}, is a major mode that is very similar to |
223 | Text mode except that it provides two additional commands. Its | |
224 | definition is distinct from that of Text mode, but uses that of Text mode. | |
a44af9f2 | 225 | |
5858d11f | 226 | Even if the new mode is not an obvious derivative of any other mode, |
0b41c65c SM |
227 | it is convenient to use @code{define-derived-mode} with a @code{nil} |
228 | parent argument, since it automatically enforces the most important | |
229 | coding conventions for you. | |
5858d11f | 230 | |
44607ed4 | 231 | For a very simple programming language major mode that handles |
28e7aba4 LK |
232 | comments and fontification, you can use @code{define-generic-mode}. |
233 | @xref{Generic Modes}. | |
44607ed4 | 234 | |
969fe9b5 RS |
235 | Rmail Edit mode offers an example of changing the major mode |
236 | temporarily for a buffer, so it can be edited in a different way (with | |
1911e6e5 | 237 | ordinary Emacs commands rather than Rmail commands). In such cases, the |
8241495d | 238 | temporary major mode usually provides a command to switch back to the |
969fe9b5 RS |
239 | buffer's usual mode (Rmail mode, in this case). You might be tempted to |
240 | present the temporary redefinitions inside a recursive edit and restore | |
241 | the usual ones when the user exits; but this is a bad idea because it | |
242 | constrains the user's options when it is done in more than one buffer: | |
243 | recursive edits must be exited most-recently-entered first. Using an | |
244 | alternative major mode avoids this limitation. @xref{Recursive | |
a44af9f2 RS |
245 | Editing}. |
246 | ||
8241495d RS |
247 | The standard GNU Emacs Lisp library directory tree contains the code |
248 | for several major modes, in files such as @file{text-mode.el}, | |
a44af9f2 | 249 | @file{texinfo.el}, @file{lisp-mode.el}, @file{c-mode.el}, and |
a40d4712 PR |
250 | @file{rmail.el}. They are found in various subdirectories of the |
251 | @file{lisp} directory. You can study these libraries to see how modes | |
252 | are written. Text mode is perhaps the simplest major mode aside from | |
a44af9f2 RS |
253 | Fundamental mode. Rmail mode is a complicated and specialized mode. |
254 | ||
a44af9f2 RS |
255 | @node Major Mode Conventions |
256 | @subsection Major Mode Conventions | |
257 | ||
258 | The code for existing major modes follows various coding conventions, | |
259 | including conventions for local keymap and syntax table initialization, | |
260 | global names, and hooks. Please follow these conventions when you | |
008c5e26 RS |
261 | define a new major mode. |
262 | ||
263 | This list of conventions is only partial, because each major mode | |
264 | should aim for consistency in general with other Emacs major modes. | |
265 | This makes Emacs as a whole more coherent. It is impossible to list | |
266 | here all the possible points where this issue might come up; if the | |
267 | Emacs developers point out an area where your major mode deviates from | |
268 | the usual conventions, please make it compatible. | |
a44af9f2 RS |
269 | |
270 | @itemize @bullet | |
271 | @item | |
272 | Define a command whose name ends in @samp{-mode}, with no arguments, | |
273 | that switches to the new mode in the current buffer. This command | |
969fe9b5 RS |
274 | should set up the keymap, syntax table, and buffer-local variables in an |
275 | existing buffer, without changing the buffer's contents. | |
a44af9f2 RS |
276 | |
277 | @item | |
de9f0bd9 | 278 | Write a documentation string for this command that describes the |
a44af9f2 RS |
279 | special commands available in this mode. @kbd{C-h m} |
280 | (@code{describe-mode}) in your mode will display this string. | |
281 | ||
282 | The documentation string may include the special documentation | |
283 | substrings, @samp{\[@var{command}]}, @samp{\@{@var{keymap}@}}, and | |
86494bd5 | 284 | @samp{\<@var{keymap}>}, which enable the documentation to adapt |
a44af9f2 RS |
285 | automatically to the user's own key bindings. @xref{Keys in |
286 | Documentation}. | |
287 | ||
288 | @item | |
289 | The major mode command should start by calling | |
969fe9b5 RS |
290 | @code{kill-all-local-variables}. This is what gets rid of the |
291 | buffer-local variables of the major mode previously in effect. | |
a44af9f2 RS |
292 | |
293 | @item | |
294 | The major mode command should set the variable @code{major-mode} to the | |
295 | major mode command symbol. This is how @code{describe-mode} discovers | |
296 | which documentation to print. | |
297 | ||
298 | @item | |
299 | The major mode command should set the variable @code{mode-name} to the | |
969fe9b5 RS |
300 | ``pretty'' name of the mode, as a string. This string appears in the |
301 | mode line. | |
a44af9f2 RS |
302 | |
303 | @item | |
304 | @cindex functions in modes | |
305 | Since all global names are in the same name space, all the global | |
306 | variables, constants, and functions that are part of the mode should | |
307 | have names that start with the major mode name (or with an abbreviation | |
a4b12c74 | 308 | of it if the name is long). @xref{Coding Conventions}. |
a44af9f2 | 309 | |
008c5e26 RS |
310 | @item |
311 | In a major mode for editing some kind of structured text, such as a | |
312 | programming language, indentation of text according to structure is | |
313 | probably useful. So the mode should set @code{indent-line-function} | |
314 | to a suitable function, and probably customize other variables | |
315 | for indentation. | |
316 | ||
a44af9f2 RS |
317 | @item |
318 | @cindex keymaps in modes | |
319 | The major mode should usually have its own keymap, which is used as the | |
969fe9b5 RS |
320 | local keymap in all buffers in that mode. The major mode command should |
321 | call @code{use-local-map} to install this local map. @xref{Active | |
322 | Keymaps}, for more information. | |
a44af9f2 | 323 | |
969fe9b5 | 324 | This keymap should be stored permanently in a global variable named |
a44af9f2 | 325 | @code{@var{modename}-mode-map}. Normally the library that defines the |
de9f0bd9 | 326 | mode sets this variable. |
a44af9f2 | 327 | |
23ce41fc RS |
328 | @xref{Tips for Defining}, for advice about how to write the code to set |
329 | up the mode's keymap variable. | |
330 | ||
a4b12c74 RS |
331 | @item |
332 | The key sequences bound in a major mode keymap should usually start with | |
969fe9b5 | 333 | @kbd{C-c}, followed by a control character, a digit, or @kbd{@{}, |
a4b12c74 RS |
334 | @kbd{@}}, @kbd{<}, @kbd{>}, @kbd{:} or @kbd{;}. The other punctuation |
335 | characters are reserved for minor modes, and ordinary letters are | |
336 | reserved for users. | |
337 | ||
e0dbfecc RS |
338 | A major mode can also rebind the keys @kbd{M-n}, @kbd{M-p} and |
339 | @kbd{M-s}. The bindings for @kbd{M-n} and @kbd{M-p} should normally | |
340 | be some kind of ``moving forward and backward,'' but this does not | |
341 | necessarily mean cursor motion. | |
342 | ||
343 | It is legitimate for a major mode to rebind a standard key sequence if | |
344 | it provides a command that does ``the same job'' in a way better | |
345 | suited to the text this mode is used for. For example, a major mode | |
346 | for editing a programming language might redefine @kbd{C-M-a} to | |
347 | ``move to the beginning of a function'' in a way that works better for | |
348 | that language. | |
349 | ||
350 | It is also legitimate for a major mode to rebind a standard key | |
351 | sequence whose standard meaning is rarely useful in that mode. For | |
352 | instance, minibuffer modes rebind @kbd{M-r}, whose standard meaning is | |
353 | rarely of any use in the minibuffer. Major modes such as Dired or | |
354 | Rmail that do not allow self-insertion of text can reasonably redefine | |
355 | letters and other printing characters as special commands. | |
a4b12c74 | 356 | |
c2e903c0 RS |
357 | @item |
358 | Major modes must not define @key{RET} to do anything other than insert | |
359 | a newline. The command to insert a newline and then indent is | |
008c5e26 RS |
360 | @kbd{C-j}. Please keep this distinction uniform for all major modes. |
361 | ||
362 | @item | |
2a233172 | 363 | Major modes should not alter options that are primarily a matter of user |
008c5e26 RS |
364 | preference, such as whether Auto-Fill mode is enabled. Leave this to |
365 | each user to decide. However, a major mode should customize other | |
366 | variables so that Auto-Fill mode will work usefully @emph{if} the user | |
367 | decides to use it. | |
c2e903c0 | 368 | |
a44af9f2 RS |
369 | @item |
370 | @cindex syntax tables in modes | |
371 | The mode may have its own syntax table or may share one with other | |
372 | related modes. If it has its own syntax table, it should store this in | |
de9f0bd9 | 373 | a variable named @code{@var{modename}-mode-syntax-table}. @xref{Syntax |
a44af9f2 RS |
374 | Tables}. |
375 | ||
be9345cf RS |
376 | @item |
377 | If the mode handles a language that has a syntax for comments, it should | |
378 | set the variables that define the comment syntax. @xref{Options for | |
379 | Comments,, Options Controlling Comments, emacs, The GNU Emacs Manual}. | |
380 | ||
a44af9f2 RS |
381 | @item |
382 | @cindex abbrev tables in modes | |
383 | The mode may have its own abbrev table or may share one with other | |
ec9b0882 RS |
384 | related modes. If it has its own abbrev table, it should store this |
385 | in a variable named @code{@var{modename}-mode-abbrev-table}. If the | |
386 | major mode command defines any abbrevs itself, it should pass @code{t} | |
387 | for the @var{system-flag} argument to @code{define-abbrev}. | |
302691ab | 388 | @xref{Defining Abbrevs}. |
a44af9f2 | 389 | |
be9345cf | 390 | @item |
be9345cf RS |
391 | The mode should specify how to do highlighting for Font Lock mode, by |
392 | setting up a buffer-local value for the variable | |
969fe9b5 | 393 | @code{font-lock-defaults} (@pxref{Font Lock Mode}). |
be9345cf RS |
394 | |
395 | @item | |
be9345cf RS |
396 | The mode should specify how Imenu should find the definitions or |
397 | sections of a buffer, by setting up a buffer-local value for the | |
342fd6cd | 398 | variable @code{imenu-generic-expression}, for the two variables |
10ee4e90 LK |
399 | @code{imenu-prev-index-position-function} and |
400 | @code{imenu-extract-index-name-function}, or for the variable | |
969fe9b5 | 401 | @code{imenu-create-index-function} (@pxref{Imenu}). |
be9345cf | 402 | |
e54eeb44 RS |
403 | @item |
404 | The mode can specify a local value for | |
405 | @code{eldoc-documentation-function} to tell ElDoc mode how to handle | |
406 | this mode. | |
407 | ||
de9f0bd9 | 408 | @item |
969fe9b5 RS |
409 | Use @code{defvar} or @code{defcustom} to set mode-related variables, so |
410 | that they are not reinitialized if they already have a value. (Such | |
411 | reinitialization could discard customizations made by the user.) | |
de9f0bd9 | 412 | |
a44af9f2 RS |
413 | @item |
414 | @cindex buffer-local variables in modes | |
415 | To make a buffer-local binding for an Emacs customization variable, use | |
416 | @code{make-local-variable} in the major mode command, not | |
417 | @code{make-variable-buffer-local}. The latter function would make the | |
418 | variable local to every buffer in which it is subsequently set, which | |
419 | would affect buffers that do not use this mode. It is undesirable for a | |
420 | mode to have such global effects. @xref{Buffer-Local Variables}. | |
421 | ||
177c0ea7 | 422 | With rare exceptions, the only reasonable way to use |
a40d4712 PR |
423 | @code{make-variable-buffer-local} in a Lisp package is for a variable |
424 | which is used only within that package. Using it on a variable used by | |
425 | other packages would interfere with them. | |
a44af9f2 RS |
426 | |
427 | @item | |
428 | @cindex mode hook | |
429 | @cindex major mode hook | |
430 | Each major mode should have a @dfn{mode hook} named | |
431 | @code{@var{modename}-mode-hook}. The major mode command should run that | |
fdba9ef4 | 432 | hook, with @code{run-mode-hooks}, as the very last thing it |
a3ee0299 | 433 | does. @xref{Mode Hooks}. |
a44af9f2 RS |
434 | |
435 | @item | |
fdba9ef4 RS |
436 | The major mode command may start by calling some other major mode |
437 | command (called the @dfn{parent mode}) and then alter some of its | |
438 | settings. A mode that does this is called a @dfn{derived mode}. The | |
439 | recommended way to define one is to use @code{define-derived-mode}, | |
01f52a87 LT |
440 | but this is not required. Such a mode should call the parent mode |
441 | command inside a @code{delay-mode-hooks} form. (Using | |
a3ee0299 LT |
442 | @code{define-derived-mode} does this automatically.) @xref{Derived |
443 | Modes}, and @ref{Mode Hooks}. | |
a44af9f2 RS |
444 | |
445 | @item | |
446 | If something special should be done if the user switches a buffer from | |
f9f59935 | 447 | this mode to any other major mode, this mode can set up a buffer-local |
969fe9b5 | 448 | value for @code{change-major-mode-hook} (@pxref{Creating Buffer-Local}). |
a44af9f2 RS |
449 | |
450 | @item | |
451 | If this mode is appropriate only for specially-prepared text, then the | |
452 | major mode command symbol should have a property named @code{mode-class} | |
453 | with value @code{special}, put on as follows: | |
454 | ||
ace41f7d | 455 | @kindex mode-class @r{(property)} |
a44af9f2 RS |
456 | @cindex @code{special} |
457 | @example | |
458 | (put 'funny-mode 'mode-class 'special) | |
459 | @end example | |
460 | ||
461 | @noindent | |
ec9b0882 RS |
462 | This tells Emacs that new buffers created while the current buffer is |
463 | in Funny mode should not inherit Funny mode, in case | |
464 | @code{default-major-mode} is @code{nil}. Modes such as Dired, Rmail, | |
a44af9f2 RS |
465 | and Buffer List use this feature. |
466 | ||
467 | @item | |
468 | If you want to make the new mode the default for files with certain | |
469 | recognizable names, add an element to @code{auto-mode-alist} to select | |
b4a83bb8 LT |
470 | the mode for those file names (@pxref{Auto Major Mode}). If you |
471 | define the mode command to autoload, you should add this element in | |
472 | the same file that calls @code{autoload}. If you use an autoload | |
473 | cookie for the mode command, you can also use an autoload cookie for | |
474 | the form that adds the element (@pxref{autoload cookie}). If you do | |
475 | not autoload the mode command, it is sufficient to add the element in | |
476 | the file that contains the mode definition. | |
a44af9f2 RS |
477 | |
478 | @item | |
ec9b0882 RS |
479 | In the comments that document the file, you should provide a sample |
480 | @code{autoload} form and an example of how to add to | |
481 | @code{auto-mode-alist}, that users can include in their init files | |
482 | (@pxref{Init File}). | |
a44af9f2 RS |
483 | |
484 | @item | |
485 | @cindex mode loading | |
de9f0bd9 | 486 | The top-level forms in the file defining the mode should be written so |
a44af9f2 RS |
487 | that they may be evaluated more than once without adverse consequences. |
488 | Even if you never load the file more than once, someone else will. | |
489 | @end itemize | |
490 | ||
a44af9f2 RS |
491 | @node Example Major Modes |
492 | @subsection Major Mode Examples | |
493 | ||
494 | Text mode is perhaps the simplest mode besides Fundamental mode. | |
495 | Here are excerpts from @file{text-mode.el} that illustrate many of | |
496 | the conventions listed above: | |
497 | ||
498 | @smallexample | |
499 | @group | |
ec9b0882 RS |
500 | ;; @r{Create the syntax table for this mode.} |
501 | (defvar text-mode-syntax-table | |
502 | (let ((st (make-syntax-table))) | |
503 | (modify-syntax-entry ?\" ". " st) | |
504 | (modify-syntax-entry ?\\ ". " st) | |
505 | ;; We add `p' so that M-c on 'hello' leads to 'Hello' rather than 'hello'. | |
506 | (modify-syntax-entry ?' "w p" st) | |
507 | st) | |
508 | "Syntax table used while in `text-mode'.") | |
a44af9f2 RS |
509 | @end group |
510 | ||
ec9b0882 | 511 | ;; @r{Create the keymap for this mode.} |
a44af9f2 | 512 | @group |
ec9b0882 RS |
513 | (defvar text-mode-map |
514 | (let ((map (make-sparse-keymap))) | |
515 | (define-key map "\e\t" 'ispell-complete-word) | |
516 | (define-key map "\es" 'center-line) | |
517 | (define-key map "\eS" 'center-paragraph) | |
518 | map) | |
519 | "Keymap for `text-mode'. | |
520 | Many other modes, such as `mail-mode', `outline-mode' and `indented-text-mode', | |
521 | inherit all the commands defined in this map.") | |
a44af9f2 | 522 | @end group |
ec9b0882 | 523 | @end smallexample |
a44af9f2 | 524 | |
ec9b0882 RS |
525 | Here is how the actual mode command is defined now: |
526 | ||
527 | @smallexample | |
a44af9f2 | 528 | @group |
ec9b0882 RS |
529 | (define-derived-mode text-mode nil "Text" |
530 | "Major mode for editing text written for humans to read. | |
531 | In this mode, paragraphs are delimited only by blank or white lines. | |
532 | You can thus get the full benefit of adaptive filling | |
533 | (see the variable `adaptive-fill-mode'). | |
1f9ad95a | 534 | \\@{text-mode-map@} |
ec9b0882 | 535 | Turning on Text mode runs the normal hook `text-mode-hook'." |
a44af9f2 | 536 | @end group |
a44af9f2 | 537 | @group |
ec9b0882 RS |
538 | (make-local-variable 'text-mode-variant) |
539 | (setq text-mode-variant t) | |
540 | ;; @r{These two lines are a feature added recently.} | |
541 | (set (make-local-variable 'require-final-newline) | |
542 | mode-require-final-newline) | |
543 | (set (make-local-variable 'indent-line-function) 'indent-relative)) | |
a44af9f2 RS |
544 | @end group |
545 | @end smallexample | |
546 | ||
ec9b0882 RS |
547 | But here is how it was defined formerly, before |
548 | @code{define-derived-mode} existed: | |
a44af9f2 RS |
549 | |
550 | @smallexample | |
ec9b0882 RS |
551 | @group |
552 | ;; @r{This isn't needed nowadays, since @code{define-derived-mode} does it.} | |
553 | (defvar text-mode-abbrev-table nil | |
554 | "Abbrev table used while in text mode.") | |
555 | (define-abbrev-table 'text-mode-abbrev-table ()) | |
556 | @end group | |
557 | ||
a44af9f2 RS |
558 | @group |
559 | (defun text-mode () | |
29b677db | 560 | "Major mode for editing text intended for humans to read... |
a44af9f2 RS |
561 | Special commands: \\@{text-mode-map@} |
562 | @end group | |
563 | @group | |
564 | Turning on text-mode runs the hook `text-mode-hook'." | |
565 | (interactive) | |
566 | (kill-all-local-variables) | |
969fe9b5 | 567 | (use-local-map text-mode-map) |
a44af9f2 RS |
568 | @end group |
569 | @group | |
a44af9f2 RS |
570 | (setq local-abbrev-table text-mode-abbrev-table) |
571 | (set-syntax-table text-mode-syntax-table) | |
969fe9b5 RS |
572 | @end group |
573 | @group | |
ec9b0882 RS |
574 | ;; @r{These four lines are absent from the current version} |
575 | ;; @r{not because this is done some other way, but rather} | |
576 | ;; @r{because nowadays Text mode uses the normal definition of paragraphs.} | |
969fe9b5 RS |
577 | (make-local-variable 'paragraph-start) |
578 | (setq paragraph-start (concat "[ \t]*$\\|" page-delimiter)) | |
579 | (make-local-variable 'paragraph-separate) | |
580 | (setq paragraph-separate paragraph-start) | |
a40d4712 PR |
581 | (make-local-variable 'indent-line-function) |
582 | (setq indent-line-function 'indent-relative-maybe) | |
969fe9b5 RS |
583 | @end group |
584 | @group | |
585 | (setq mode-name "Text") | |
586 | (setq major-mode 'text-mode) | |
fdba9ef4 | 587 | (run-mode-hooks 'text-mode-hook)) ; @r{Finally, this permits the user to} |
a44af9f2 RS |
588 | ; @r{customize the mode with a hook.} |
589 | @end group | |
590 | @end smallexample | |
591 | ||
592 | @cindex @file{lisp-mode.el} | |
593 | The three Lisp modes (Lisp mode, Emacs Lisp mode, and Lisp | |
594 | Interaction mode) have more features than Text mode and the code is | |
595 | correspondingly more complicated. Here are excerpts from | |
596 | @file{lisp-mode.el} that illustrate how these modes are written. | |
597 | ||
598 | @cindex syntax table example | |
599 | @smallexample | |
600 | @group | |
601 | ;; @r{Create mode-specific table variables.} | |
177c0ea7 | 602 | (defvar lisp-mode-syntax-table nil "") |
a44af9f2 RS |
603 | (defvar lisp-mode-abbrev-table nil "") |
604 | @end group | |
605 | ||
606 | @group | |
ec9b0882 RS |
607 | (defvar emacs-lisp-mode-syntax-table |
608 | (let ((table (make-syntax-table))) | |
a44af9f2 | 609 | (let ((i 0)) |
a44af9f2 RS |
610 | @end group |
611 | ||
612 | @group | |
ec9b0882 | 613 | ;; @r{Set syntax of chars up to @samp{0} to say they are} |
a44af9f2 | 614 | ;; @r{part of symbol names but not words.} |
ec9b0882 | 615 | ;; @r{(The digit @samp{0} is @code{48} in the @acronym{ASCII} character set.)} |
177c0ea7 | 616 | (while (< i ?0) |
ec9b0882 RS |
617 | (modify-syntax-entry i "_ " table) |
618 | (setq i (1+ i))) | |
619 | ;; @r{@dots{} similar code follows for other character ranges.} | |
a44af9f2 RS |
620 | @end group |
621 | @group | |
ec9b0882 RS |
622 | ;; @r{Then set the syntax codes for characters that are special in Lisp.} |
623 | (modify-syntax-entry ? " " table) | |
624 | (modify-syntax-entry ?\t " " table) | |
625 | (modify-syntax-entry ?\f " " table) | |
626 | (modify-syntax-entry ?\n "> " table) | |
a44af9f2 RS |
627 | @end group |
628 | @group | |
ec9b0882 RS |
629 | ;; @r{Give CR the same syntax as newline, for selective-display.} |
630 | (modify-syntax-entry ?\^m "> " table) | |
631 | (modify-syntax-entry ?\; "< " table) | |
632 | (modify-syntax-entry ?` "' " table) | |
633 | (modify-syntax-entry ?' "' " table) | |
634 | (modify-syntax-entry ?, "' " table) | |
635 | @end group | |
ec9b0882 RS |
636 | @group |
637 | ;; @r{@dots{}likewise for many other characters@dots{}} | |
638 | (modify-syntax-entry ?\( "() " table) | |
639 | (modify-syntax-entry ?\) ")( " table) | |
640 | (modify-syntax-entry ?\[ "(] " table) | |
641 | (modify-syntax-entry ?\] ")[ " table)) | |
642 | table)) | |
643 | @end group | |
1f9ad95a | 644 | @group |
a44af9f2 RS |
645 | ;; @r{Create an abbrev table for lisp-mode.} |
646 | (define-abbrev-table 'lisp-mode-abbrev-table ()) | |
647 | @end group | |
648 | @end smallexample | |
649 | ||
650 | Much code is shared among the three Lisp modes. The following | |
651 | function sets various variables; it is called by each of the major Lisp | |
652 | mode functions: | |
653 | ||
654 | @smallexample | |
655 | @group | |
656 | (defun lisp-mode-variables (lisp-syntax) | |
ec9b0882 RS |
657 | (when lisp-syntax |
658 | (set-syntax-table lisp-mode-syntax-table)) | |
a44af9f2 | 659 | (setq local-abbrev-table lisp-mode-abbrev-table) |
a9f0a989 | 660 | @dots{} |
a44af9f2 RS |
661 | @end group |
662 | @end smallexample | |
663 | ||
664 | Functions such as @code{forward-paragraph} use the value of the | |
665 | @code{paragraph-start} variable. Since Lisp code is different from | |
666 | ordinary text, the @code{paragraph-start} variable needs to be set | |
667 | specially to handle Lisp. Also, comments are indented in a special | |
668 | fashion in Lisp and the Lisp modes need their own mode-specific | |
669 | @code{comment-indent-function}. The code to set these variables is the | |
670 | rest of @code{lisp-mode-variables}. | |
671 | ||
672 | @smallexample | |
673 | @group | |
674 | (make-local-variable 'paragraph-start) | |
969fe9b5 RS |
675 | (setq paragraph-start (concat page-delimiter "\\|$" )) |
676 | (make-local-variable 'paragraph-separate) | |
677 | (setq paragraph-separate paragraph-start) | |
a44af9f2 RS |
678 | @dots{} |
679 | @end group | |
680 | @group | |
681 | (make-local-variable 'comment-indent-function) | |
682 | (setq comment-indent-function 'lisp-comment-indent)) | |
a40d4712 | 683 | @dots{} |
a44af9f2 RS |
684 | @end group |
685 | @end smallexample | |
686 | ||
687 | Each of the different Lisp modes has a slightly different keymap. For | |
f9f59935 | 688 | example, Lisp mode binds @kbd{C-c C-z} to @code{run-lisp}, but the other |
a44af9f2 | 689 | Lisp modes do not. However, all Lisp modes have some commands in |
969fe9b5 | 690 | common. The following code sets up the common commands: |
a44af9f2 RS |
691 | |
692 | @smallexample | |
693 | @group | |
969fe9b5 RS |
694 | (defvar shared-lisp-mode-map () |
695 | "Keymap for commands shared by all sorts of Lisp modes.") | |
696 | ||
ec9b0882 | 697 | ;; @r{Putting this @code{if} after the @code{defvar} is an older style.} |
969fe9b5 RS |
698 | (if shared-lisp-mode-map |
699 | () | |
700 | (setq shared-lisp-mode-map (make-sparse-keymap)) | |
701 | (define-key shared-lisp-mode-map "\e\C-q" 'indent-sexp) | |
702 | (define-key shared-lisp-mode-map "\177" | |
703 | 'backward-delete-char-untabify)) | |
a44af9f2 RS |
704 | @end group |
705 | @end smallexample | |
706 | ||
969fe9b5 RS |
707 | @noindent |
708 | And here is the code to set up the keymap for Lisp mode: | |
a44af9f2 RS |
709 | |
710 | @smallexample | |
711 | @group | |
969fe9b5 | 712 | (defvar lisp-mode-map () |
29b677db | 713 | "Keymap for ordinary Lisp mode...") |
969fe9b5 RS |
714 | |
715 | (if lisp-mode-map | |
a44af9f2 | 716 | () |
969fe9b5 RS |
717 | (setq lisp-mode-map (make-sparse-keymap)) |
718 | (set-keymap-parent lisp-mode-map shared-lisp-mode-map) | |
719 | (define-key lisp-mode-map "\e\C-x" 'lisp-eval-defun) | |
720 | (define-key lisp-mode-map "\C-c\C-z" 'run-lisp)) | |
a44af9f2 RS |
721 | @end group |
722 | @end smallexample | |
723 | ||
724 | Finally, here is the complete major mode function definition for | |
177c0ea7 | 725 | Lisp mode. |
a44af9f2 RS |
726 | |
727 | @smallexample | |
728 | @group | |
969fe9b5 RS |
729 | (defun lisp-mode () |
730 | "Major mode for editing Lisp code for Lisps other than GNU Emacs Lisp. | |
a44af9f2 RS |
731 | Commands: |
732 | Delete converts tabs to spaces as it moves back. | |
733 | Blank lines separate paragraphs. Semicolons start comments. | |
969fe9b5 RS |
734 | \\@{lisp-mode-map@} |
735 | Note that `run-lisp' may be used either to start an inferior Lisp job | |
736 | or to switch back to an existing one. | |
a44af9f2 | 737 | @end group |
969fe9b5 | 738 | |
a44af9f2 | 739 | @group |
969fe9b5 RS |
740 | Entry to this mode calls the value of `lisp-mode-hook' |
741 | if that value is non-nil." | |
a44af9f2 RS |
742 | (interactive) |
743 | (kill-all-local-variables) | |
a44af9f2 RS |
744 | @end group |
745 | @group | |
969fe9b5 RS |
746 | (use-local-map lisp-mode-map) ; @r{Select the mode's keymap.} |
747 | (setq major-mode 'lisp-mode) ; @r{This is how @code{describe-mode}} | |
a44af9f2 | 748 | ; @r{finds out what to describe.} |
969fe9b5 RS |
749 | (setq mode-name "Lisp") ; @r{This goes into the mode line.} |
750 | (lisp-mode-variables t) ; @r{This defines various variables.} | |
ec9b0882 RS |
751 | (make-local-variable 'comment-start-skip) |
752 | (setq comment-start-skip | |
753 | "\\(\\(^\\|[^\\\\\n]\\)\\(\\\\\\\\\\)*\\)\\(;+\\|#|\\) *") | |
754 | (make-local-variable 'font-lock-keywords-case-fold-search) | |
755 | (setq font-lock-keywords-case-fold-search t) | |
969fe9b5 RS |
756 | @end group |
757 | @group | |
758 | (setq imenu-case-fold-search t) | |
759 | (set-syntax-table lisp-mode-syntax-table) | |
fdba9ef4 | 760 | (run-mode-hooks 'lisp-mode-hook)) ; @r{This permits the user to use a} |
a44af9f2 RS |
761 | ; @r{hook to customize the mode.} |
762 | @end group | |
763 | @end smallexample | |
764 | ||
765 | @node Auto Major Mode | |
766 | @subsection How Emacs Chooses a Major Mode | |
767 | ||
768 | Based on information in the file name or in the file itself, Emacs | |
769 | automatically selects a major mode for the new buffer when a file is | |
969fe9b5 | 770 | visited. It also processes local variables specified in the file text. |
a44af9f2 RS |
771 | |
772 | @deffn Command fundamental-mode | |
773 | Fundamental mode is a major mode that is not specialized for anything | |
774 | in particular. Other major modes are defined in effect by comparison | |
775 | with this one---their definitions say what to change, starting from | |
776 | Fundamental mode. The @code{fundamental-mode} function does @emph{not} | |
a3ee0299 | 777 | run any mode hooks; you're not supposed to customize it. (If you want Emacs |
a44af9f2 RS |
778 | to behave differently in Fundamental mode, change the @emph{global} |
779 | state of Emacs.) | |
780 | @end deffn | |
781 | ||
782 | @deffn Command normal-mode &optional find-file | |
969fe9b5 | 783 | This function establishes the proper major mode and buffer-local variable |
302691ab LT |
784 | bindings for the current buffer. First it calls @code{set-auto-mode} |
785 | (see below), then it runs @code{hack-local-variables} to parse, and | |
786 | bind or evaluate as appropriate, the file's local variables | |
787 | (@pxref{File Local Variables}). | |
a44af9f2 | 788 | |
969fe9b5 RS |
789 | If the @var{find-file} argument to @code{normal-mode} is non-@code{nil}, |
790 | @code{normal-mode} assumes that the @code{find-file} function is calling | |
302691ab LT |
791 | it. In this case, it may process local variables in the @samp{-*-} |
792 | line or at the end of the file. The variable | |
969fe9b5 | 793 | @code{enable-local-variables} controls whether to do so. @xref{File |
302691ab LT |
794 | Variables, , Local Variables in Files, emacs, The GNU Emacs Manual}, |
795 | for the syntax of the local variables section of a file. | |
a44af9f2 | 796 | |
bfe721d1 | 797 | If you run @code{normal-mode} interactively, the argument |
a44af9f2 | 798 | @var{find-file} is normally @code{nil}. In this case, |
302691ab LT |
799 | @code{normal-mode} unconditionally processes any file local variables. |
800 | ||
801 | If @code{normal-mode} processes the local variables list and this list | |
802 | specifies a major mode, that mode overrides any mode chosen by | |
803 | @code{set-auto-mode}. If neither @code{set-auto-mode} nor | |
804 | @code{hack-local-variables} specify a major mode, the buffer stays in | |
805 | the major mode determined by @code{default-major-mode} (see below). | |
a44af9f2 RS |
806 | |
807 | @cindex file mode specification error | |
bfe721d1 | 808 | @code{normal-mode} uses @code{condition-case} around the call to the |
a44af9f2 RS |
809 | major mode function, so errors are caught and reported as a @samp{File |
810 | mode specification error}, followed by the original error message. | |
811 | @end deffn | |
812 | ||
302691ab | 813 | @defun set-auto-mode &optional keep-mode-if-same |
a44af9f2 RS |
814 | @cindex visited file mode |
815 | This function selects the major mode that is appropriate for the | |
302691ab LT |
816 | current buffer. It bases its decision (in order of precedence) on |
817 | the @w{@samp{-*-}} line, on the @w{@samp{#!}} line (using | |
818 | @code{interpreter-mode-alist}), on the text at the beginning of the | |
819 | buffer (using @code{magic-mode-alist}), and finally on the visited | |
820 | file name (using @code{auto-mode-alist}). @xref{Choosing Modes, , How | |
821 | Major Modes are Chosen, emacs, The GNU Emacs Manual}. However, this | |
822 | function does not look for the @samp{mode:} local variable near the | |
823 | end of a file; the @code{hack-local-variables} function does that. | |
824 | If @code{enable-local-variables} is @code{nil}, @code{set-auto-mode} | |
825 | does not check the @w{@samp{-*-}} line for a mode tag either. | |
826 | ||
827 | If @var{keep-mode-if-same} is non-@code{nil}, this function does not | |
828 | call the mode command if the buffer is already in the proper major | |
829 | mode. For instance, @code{set-visited-file-name} sets this to | |
830 | @code{t} to avoid killing buffer local variables that the user may | |
831 | have set. | |
a44af9f2 RS |
832 | @end defun |
833 | ||
177c0ea7 | 834 | @defopt default-major-mode |
969fe9b5 | 835 | This variable holds the default major mode for new buffers. The |
a44af9f2 RS |
836 | standard value is @code{fundamental-mode}. |
837 | ||
969fe9b5 | 838 | If the value of @code{default-major-mode} is @code{nil}, Emacs uses |
302691ab LT |
839 | the (previously) current buffer's major mode as the default major mode |
840 | of a new buffer. However, if that major mode symbol has a @code{mode-class} | |
a44af9f2 RS |
841 | property with value @code{special}, then it is not used for new buffers; |
842 | Fundamental mode is used instead. The modes that have this property are | |
843 | those such as Dired and Rmail that are useful only with text that has | |
844 | been specially prepared. | |
845 | @end defopt | |
846 | ||
22697dac KH |
847 | @defun set-buffer-major-mode buffer |
848 | This function sets the major mode of @var{buffer} to the value of | |
302691ab LT |
849 | @code{default-major-mode}; if that variable is @code{nil}, it uses the |
850 | current buffer's major mode (if that is suitable). As an exception, | |
851 | if @var{buffer}'s name is @samp{*scratch*}, it sets the mode to | |
852 | @code{initial-major-mode}. | |
22697dac KH |
853 | |
854 | The low-level primitives for creating buffers do not use this function, | |
bfe721d1 KH |
855 | but medium-level commands such as @code{switch-to-buffer} and |
856 | @code{find-file-noselect} use it whenever they create buffers. | |
22697dac KH |
857 | @end defun |
858 | ||
302691ab | 859 | @defopt initial-major-mode |
a44af9f2 RS |
860 | @cindex @samp{*scratch*} |
861 | The value of this variable determines the major mode of the initial | |
862 | @samp{*scratch*} buffer. The value should be a symbol that is a major | |
f9f59935 | 863 | mode command. The default value is @code{lisp-interaction-mode}. |
302691ab LT |
864 | @end defopt |
865 | ||
866 | @defvar interpreter-mode-alist | |
867 | This variable specifies major modes to use for scripts that specify a | |
868 | command interpreter in a @samp{#!} line. Its value is an alist with | |
869 | elements of the form @code{(@var{interpreter} . @var{mode})}; for | |
870 | example, @code{("perl" . perl-mode)} is one element present by | |
871 | default. The element says to use mode @var{mode} if the file | |
abd10ce8 | 872 | specifies an interpreter which matches @var{interpreter}. |
302691ab LT |
873 | @end defvar |
874 | ||
875 | @defvar magic-mode-alist | |
876 | This variable's value is an alist with elements of the form | |
877 | @code{(@var{regexp} . @var{function})}, where @var{regexp} is a | |
878 | regular expression and @var{function} is a function or @code{nil}. | |
879 | After visiting a file, @code{set-auto-mode} calls @var{function} if | |
880 | the text at the beginning of the buffer matches @var{regexp} and | |
881 | @var{function} is non-@code{nil}; if @var{function} is @code{nil}, | |
882 | @code{auto-mode-alist} gets to decide the mode. | |
a44af9f2 RS |
883 | @end defvar |
884 | ||
885 | @defvar auto-mode-alist | |
886 | This variable contains an association list of file name patterns | |
302691ab LT |
887 | (regular expressions) and corresponding major mode commands. Usually, |
888 | the file name patterns test for suffixes, such as @samp{.el} and | |
889 | @samp{.c}, but this need not be the case. An ordinary element of the | |
890 | alist looks like @code{(@var{regexp} . @var{mode-function})}. | |
a44af9f2 RS |
891 | |
892 | For example, | |
893 | ||
894 | @smallexample | |
895 | @group | |
969fe9b5 | 896 | (("\\`/tmp/fol/" . text-mode) |
24675e99 RS |
897 | ("\\.texinfo\\'" . texinfo-mode) |
898 | ("\\.texi\\'" . texinfo-mode) | |
a44af9f2 RS |
899 | @end group |
900 | @group | |
24675e99 | 901 | ("\\.el\\'" . emacs-lisp-mode) |
177c0ea7 | 902 | ("\\.c\\'" . c-mode) |
24675e99 | 903 | ("\\.h\\'" . c-mode) |
a44af9f2 RS |
904 | @dots{}) |
905 | @end group | |
906 | @end smallexample | |
907 | ||
908 | When you visit a file whose expanded file name (@pxref{File Name | |
302691ab LT |
909 | Expansion}), with version numbers and backup suffixes removed using |
910 | @code{file-name-sans-versions} (@pxref{File Name Components}), matches | |
911 | a @var{regexp}, @code{set-auto-mode} calls the corresponding | |
912 | @var{mode-function}. This feature enables Emacs to select the proper | |
913 | major mode for most files. | |
a44af9f2 RS |
914 | |
915 | If an element of @code{auto-mode-alist} has the form @code{(@var{regexp} | |
916 | @var{function} t)}, then after calling @var{function}, Emacs searches | |
917 | @code{auto-mode-alist} again for a match against the portion of the file | |
969fe9b5 RS |
918 | name that did not match before. This feature is useful for |
919 | uncompression packages: an entry of the form @code{("\\.gz\\'" | |
920 | @var{function} t)} can uncompress the file and then put the uncompressed | |
921 | file in the proper mode according to the name sans @samp{.gz}. | |
a44af9f2 RS |
922 | |
923 | Here is an example of how to prepend several pattern pairs to | |
924 | @code{auto-mode-alist}. (You might use this sort of expression in your | |
a40d4712 | 925 | init file.) |
a44af9f2 RS |
926 | |
927 | @smallexample | |
928 | @group | |
929 | (setq auto-mode-alist | |
177c0ea7 | 930 | (append |
f9f59935 | 931 | ;; @r{File name (within directory) starts with a dot.} |
177c0ea7 | 932 | '(("/\\.[^/]*\\'" . fundamental-mode) |
de9f0bd9 | 933 | ;; @r{File name has no dot.} |
177c0ea7 | 934 | ("[^\\./]*\\'" . fundamental-mode) |
de9f0bd9 | 935 | ;; @r{File name ends in @samp{.C}.} |
24675e99 | 936 | ("\\.C\\'" . c++-mode)) |
a44af9f2 RS |
937 | auto-mode-alist)) |
938 | @end group | |
939 | @end smallexample | |
940 | @end defvar | |
941 | ||
a44af9f2 RS |
942 | @node Mode Help |
943 | @subsection Getting Help about a Major Mode | |
944 | @cindex mode help | |
945 | @cindex help for major mode | |
946 | @cindex documentation for major mode | |
947 | ||
948 | The @code{describe-mode} function is used to provide information | |
949 | about major modes. It is normally called with @kbd{C-h m}. The | |
950 | @code{describe-mode} function uses the value of @code{major-mode}, | |
951 | which is why every major mode function needs to set the | |
952 | @code{major-mode} variable. | |
953 | ||
954 | @deffn Command describe-mode | |
955 | This function displays the documentation of the current major mode. | |
956 | ||
957 | The @code{describe-mode} function calls the @code{documentation} | |
958 | function using the value of @code{major-mode} as an argument. Thus, it | |
959 | displays the documentation string of the major mode function. | |
960 | (@xref{Accessing Documentation}.) | |
961 | @end deffn | |
962 | ||
963 | @defvar major-mode | |
475aab0d CY |
964 | This buffer-local variable holds the symbol for the current buffer's |
965 | major mode. This symbol should have a function definition that is the | |
966 | command to switch to that major mode. The @code{describe-mode} | |
967 | function uses the documentation string of the function as the | |
968 | documentation of the major mode. | |
a44af9f2 RS |
969 | @end defvar |
970 | ||
971 | @node Derived Modes | |
972 | @subsection Defining Derived Modes | |
010a3386 | 973 | @cindex derived mode |
a44af9f2 RS |
974 | |
975 | It's often useful to define a new major mode in terms of an existing | |
976 | one. An easy way to do this is to use @code{define-derived-mode}. | |
977 | ||
302691ab | 978 | @defmac define-derived-mode variant parent name docstring keyword-args@dots{} body@dots{} |
a44af9f2 | 979 | This construct defines @var{variant} as a major mode command, using |
302691ab LT |
980 | @var{name} as the string form of the mode name. @var{variant} and |
981 | @var{parent} should be unquoted symbols. | |
a44af9f2 | 982 | |
de9f0bd9 RS |
983 | The new command @var{variant} is defined to call the function |
984 | @var{parent}, then override certain aspects of that parent mode: | |
a44af9f2 | 985 | |
177c0ea7 | 986 | @itemize @bullet |
a44af9f2 | 987 | @item |
302691ab LT |
988 | The new mode has its own sparse keymap, named |
989 | @code{@var{variant}-map}. @code{define-derived-mode} | |
990 | makes the parent mode's keymap the parent of the new map, unless | |
991 | @code{@var{variant}-map} is already set and already has a parent. | |
a44af9f2 RS |
992 | |
993 | @item | |
de9f0bd9 | 994 | The new mode has its own syntax table, kept in the variable |
302691ab LT |
995 | @code{@var{variant}-syntax-table}, unless you override this using the |
996 | @code{:syntax-table} keyword (see below). @code{define-derived-mode} | |
997 | makes the parent mode's syntax-table the parent of | |
998 | @code{@var{variant}-syntax-table}, unless the latter is already set | |
703ba947 | 999 | and already has a parent different from the standard syntax table. |
a44af9f2 RS |
1000 | |
1001 | @item | |
de9f0bd9 | 1002 | The new mode has its own abbrev table, kept in the variable |
302691ab LT |
1003 | @code{@var{variant}-abbrev-table}, unless you override this using the |
1004 | @code{:abbrev-table} keyword (see below). | |
a44af9f2 RS |
1005 | |
1006 | @item | |
302691ab LT |
1007 | The new mode has its own mode hook, @code{@var{variant}-hook}. It |
1008 | runs this hook, after running the hooks of its ancestor modes, with | |
b4a83bb8 | 1009 | @code{run-mode-hooks}, as the last thing it does. @xref{Mode Hooks}. |
a44af9f2 RS |
1010 | @end itemize |
1011 | ||
1012 | In addition, you can specify how to override other aspects of | |
de9f0bd9 | 1013 | @var{parent} with @var{body}. The command @var{variant} |
177c0ea7 | 1014 | evaluates the forms in @var{body} after setting up all its usual |
b4a83bb8 | 1015 | overrides, just before running the mode hooks. |
a44af9f2 | 1016 | |
302691ab LT |
1017 | You can also specify @code{nil} for @var{parent}. This gives the new |
1018 | mode no parent. Then @code{define-derived-mode} behaves as described | |
1019 | above, but, of course, omits all actions connected with @var{parent}. | |
1020 | ||
1021 | The argument @var{docstring} specifies the documentation string for | |
1022 | the new mode. @code{define-derived-mode} adds some general | |
1023 | information about the mode's hook, followed by the mode's keymap, at | |
1024 | the end of this docstring. If you omit @var{docstring}, | |
1025 | @code{define-derived-mode} generates a documentation string. | |
1026 | ||
1027 | The @var{keyword-args} are pairs of keywords and values. The values | |
1028 | are evaluated. The following keywords are currently supported: | |
1029 | ||
1030 | @table @code | |
302691ab LT |
1031 | @item :syntax-table |
1032 | You can use this to explicitly specify a syntax table for the new | |
1033 | mode. If you specify a @code{nil} value, the new mode uses the same | |
703ba947 | 1034 | syntax table as @var{parent}, or the standard syntax table if |
302691ab LT |
1035 | @var{parent} is @code{nil}. (Note that this does @emph{not} follow |
1036 | the convention used for non-keyword arguments that a @code{nil} value | |
1037 | is equivalent with not specifying the argument.) | |
1038 | ||
1039 | @item :abbrev-table | |
1040 | You can use this to explicitly specify an abbrev table for the new | |
1041 | mode. If you specify a @code{nil} value, the new mode uses the same | |
7cefdf1d LT |
1042 | abbrev table as @var{parent}, or @code{fundamental-mode-abbrev-table} |
1043 | if @var{parent} is @code{nil}. (Again, a @code{nil} value is | |
302691ab | 1044 | @emph{not} equivalent to not specifying this keyword.) |
a217fa21 LT |
1045 | |
1046 | @item :group | |
1047 | If this is specified, the value should be the customization group for | |
1048 | this mode. (Not all major modes have one.) Only the (still | |
1049 | experimental and unadvertised) command @code{customize-mode} currently | |
1050 | uses this. @code{define-derived-mode} does @emph{not} automatically | |
1051 | define the specified customization group. | |
302691ab | 1052 | @end table |
a44af9f2 RS |
1053 | |
1054 | Here is a hypothetical example: | |
1055 | ||
1056 | @example | |
1057 | (define-derived-mode hypertext-mode | |
1058 | text-mode "Hypertext" | |
1059 | "Major mode for hypertext. | |
1060 | \\@{hypertext-mode-map@}" | |
1061 | (setq case-fold-search nil)) | |
1062 | ||
1063 | (define-key hypertext-mode-map | |
1064 | [down-mouse-3] 'do-hyper-link) | |
1065 | @end example | |
f140458b RS |
1066 | |
1067 | Do not write an @code{interactive} spec in the definition; | |
1068 | @code{define-derived-mode} does that automatically. | |
a44af9f2 RS |
1069 | @end defmac |
1070 | ||
010a3386 LK |
1071 | @node Generic Modes |
1072 | @subsection Generic Modes | |
1073 | @cindex generic mode | |
1074 | ||
1075 | @dfn{Generic modes} are simple major modes with basic support for | |
1076 | comment syntax and Font Lock mode. They are primarily useful for | |
1077 | configuration files. To define a generic mode, use the macro | |
1078 | @code{define-generic-mode}. See the file @file{generic-x.el} for some | |
1079 | examples of the use of @code{define-generic-mode}. | |
1080 | ||
28e7aba4 | 1081 | @defmac define-generic-mode mode comment-list keyword-list font-lock-list auto-mode-list function-list &optional docstring |
010a3386 LK |
1082 | This macro creates a new generic mode. The argument @var{mode} (an |
1083 | unquoted symbol) is the major mode command. The optional argument | |
1084 | @var{docstring} is the documentation for the mode command. If you do | |
1085 | not supply it, @code{define-generic-mode} uses a default documentation | |
1086 | string instead. | |
1087 | ||
1088 | @var{comment-list} is a list in which each element is either a | |
1089 | character, a string of one or two characters, or a cons cell. A | |
1090 | character or a string is set up in the mode's syntax table as a | |
1091 | ``comment starter.'' If the entry is a cons cell, the @sc{car} is set | |
1092 | up as a ``comment starter'' and the @sc{cdr} as a ``comment ender.'' | |
1093 | (Use @code{nil} for the latter if you want comments to end at the end | |
1094 | of the line.) Note that the syntax table has limitations about what | |
1095 | comment starters and enders are actually possible. @xref{Syntax | |
1096 | Tables}. | |
1097 | ||
1098 | @var{keyword-list} is a list of keywords to highlight with | |
1099 | @code{font-lock-keyword-face}. Each keyword should be a string. | |
1100 | @var{font-lock-list} is a list of additional expressions to highlight. | |
1101 | Each element of this list should have the same form as an element of | |
1102 | @code{font-lock-keywords}. @xref{Search-based Fontification}. | |
1103 | ||
1104 | @var{auto-mode-list} is a list of regular expressions to add to the | |
1105 | variable @code{auto-mode-alist}. These regular expressions are added | |
1106 | when Emacs runs the macro expansion. | |
1107 | ||
1108 | @var{function-list} is a list of functions to call to do some | |
1109 | additional setup. The mode command calls these functions just before | |
28e7aba4 | 1110 | it runs the mode hook variable @code{@var{mode}-hook}. |
010a3386 LK |
1111 | @end defmac |
1112 | ||
a3ee0299 LT |
1113 | @node Mode Hooks |
1114 | @subsection Mode Hooks | |
1115 | ||
801f0dc3 | 1116 | The two last things a major mode function should do is run its mode |
a3ee0299 LT |
1117 | hook and finally the mode independent normal hook |
1118 | @code{after-change-major-mode-hook}. If the major mode is a derived | |
1119 | mode, that is if it calls another major mode (the parent mode) in its | |
1120 | body, then the parent's mode hook is run just before the derived | |
1121 | mode's hook. Neither the parent's mode hook nor | |
1122 | @code{after-change-major-mode-hook} are run at the end of the actual | |
1123 | call to the parent mode. This applies recursively if the parent mode | |
801f0dc3 RS |
1124 | has itself a parent. That is, the mode hooks of all major modes |
1125 | called directly or indirectly by the major mode function are all run | |
1126 | in sequence at the end, just before | |
1127 | @code{after-change-major-mode-hook}. | |
1128 | ||
1129 | These conventions are new in Emacs 22, and some major modes | |
1130 | implemented by users do not follow them yet. So if you put a function | |
1131 | onto @code{after-change-major-mode-hook}, keep in mind that some modes | |
fbc6ab1a | 1132 | will fail to run it. If a user complains about that, you can respond, |
801f0dc3 RS |
1133 | ``That major mode fails to follow Emacs conventions, and that's why it |
1134 | fails to work. Please fix the major mode.'' In most cases, that is | |
1135 | good enough, so go ahead and use @code{after-change-major-mode-hook}. | |
1136 | However, if a certain feature needs to be completely reliable, | |
1137 | it should not use @code{after-change-major-mode-hook} as of yet. | |
1138 | ||
1139 | When you defined a major mode using @code{define-derived-mode}, it | |
1140 | automatically makes sure these conventions are followed. If you | |
1141 | define a major mode ``from scratch'', not using | |
1142 | @code{define-derived-mode}, make sure the major mode command follows | |
1143 | these and other conventions. @xref{Major Mode Conventions}. You use | |
1144 | these functions to do it properly. | |
a3ee0299 LT |
1145 | |
1146 | @defun run-mode-hooks &rest hookvars | |
1147 | Major modes should run their mode hook using this function. It is | |
801f0dc3 | 1148 | similar to @code{run-hooks} (@pxref{Hooks}), but it also runs |
a3ee0299 | 1149 | @code{after-change-major-mode-hook}. |
801f0dc3 RS |
1150 | |
1151 | When the call to this function is dynamically inside a | |
1152 | @code{delay-mode-hooks} form, this function does not run any hooks. | |
1153 | Instead, it arranges for the next call to @code{run-mode-hooks} to run | |
1154 | @var{hookvars}. | |
a3ee0299 LT |
1155 | @end defun |
1156 | ||
3389865a | 1157 | @defmac delay-mode-hooks body@dots{} |
a3ee0299 LT |
1158 | This macro executes @var{body} like @code{progn}, but all calls to |
1159 | @code{run-mode-hooks} inside @var{body} delay running their hooks. | |
1160 | They will be run by the first call to @code{run-mode-hooks} after exit | |
801f0dc3 RS |
1161 | from @code{delay-mode-hooks}. This is the proper way for a major mode |
1162 | command to invoke its parent mode. | |
a3ee0299 LT |
1163 | @end defmac |
1164 | ||
1165 | @defvar after-change-major-mode-hook | |
1166 | Every major mode function should run this normal hook at its very end. | |
1167 | It normally does not need to do so explicitly. Indeed, a major mode | |
1168 | function should normally run its mode hook with @code{run-mode-hooks} | |
801f0dc3 RS |
1169 | as the very last thing it does, and the last thing |
1170 | @code{run-mode-hooks} does is run @code{after-change-major-mode-hook}. | |
a3ee0299 LT |
1171 | @end defvar |
1172 | ||
a44af9f2 RS |
1173 | @node Minor Modes |
1174 | @section Minor Modes | |
1175 | @cindex minor mode | |
1176 | ||
1177 | A @dfn{minor mode} provides features that users may enable or disable | |
1178 | independently of the choice of major mode. Minor modes can be enabled | |
1179 | individually or in combination. Minor modes would be better named | |
969fe9b5 RS |
1180 | ``generally available, optional feature modes,'' except that such a name |
1181 | would be unwieldy. | |
a44af9f2 | 1182 | |
8241495d RS |
1183 | A minor mode is not usually meant as a variation of a single major mode. |
1184 | Usually they are general and can apply to many major modes. For | |
969fe9b5 | 1185 | example, Auto Fill mode works with any major mode that permits text |
a44af9f2 RS |
1186 | insertion. To be general, a minor mode must be effectively independent |
1187 | of the things major modes do. | |
1188 | ||
1189 | A minor mode is often much more difficult to implement than a major | |
1190 | mode. One reason is that you should be able to activate and deactivate | |
de9f0bd9 RS |
1191 | minor modes in any order. A minor mode should be able to have its |
1192 | desired effect regardless of the major mode and regardless of the other | |
1193 | minor modes in effect. | |
a44af9f2 RS |
1194 | |
1195 | Often the biggest problem in implementing a minor mode is finding a | |
1196 | way to insert the necessary hook into the rest of Emacs. Minor mode | |
bfe721d1 | 1197 | keymaps make this easier than it used to be. |
a44af9f2 | 1198 | |
fdba9ef4 RS |
1199 | @defvar minor-mode-list |
1200 | The value of this variable is a list of all minor mode commands. | |
1201 | @end defvar | |
1202 | ||
a44af9f2 RS |
1203 | @menu |
1204 | * Minor Mode Conventions:: Tips for writing a minor mode. | |
1205 | * Keymaps and Minor Modes:: How a minor mode can have its own keymap. | |
2468d0c0 | 1206 | * Defining Minor Modes:: A convenient facility for defining minor modes. |
a44af9f2 RS |
1207 | @end menu |
1208 | ||
1209 | @node Minor Mode Conventions | |
1210 | @subsection Conventions for Writing Minor Modes | |
1211 | @cindex minor mode conventions | |
1212 | @cindex conventions for writing minor modes | |
1213 | ||
1214 | There are conventions for writing minor modes just as there are for | |
1215 | major modes. Several of the major mode conventions apply to minor | |
1216 | modes as well: those regarding the name of the mode initialization | |
16b4c38b SM |
1217 | function, the names of global symbols, the use of a hook at the end of |
1218 | the initialization function, and the use of keymaps and other tables. | |
a44af9f2 RS |
1219 | |
1220 | In addition, there are several conventions that are specific to | |
ec9b0882 RS |
1221 | minor modes. (The easiest way to follow all the conventions is to use |
1222 | the macro @code{define-minor-mode}; @ref{Defining Minor Modes}.) | |
a44af9f2 RS |
1223 | |
1224 | @itemize @bullet | |
1225 | @item | |
1226 | @cindex mode variable | |
969fe9b5 RS |
1227 | Make a variable whose name ends in @samp{-mode} to control the minor |
1228 | mode. We call this the @dfn{mode variable}. The minor mode command | |
1229 | should set this variable (@code{nil} to disable; anything else to | |
1911e6e5 | 1230 | enable). |
969fe9b5 | 1231 | |
8241495d | 1232 | If possible, implement the mode so that setting the variable |
969fe9b5 | 1233 | automatically enables or disables the mode. Then the minor mode command |
1911e6e5 | 1234 | does not need to do anything except set the variable. |
a44af9f2 RS |
1235 | |
1236 | This variable is used in conjunction with the @code{minor-mode-alist} to | |
1237 | display the minor mode name in the mode line. It can also enable | |
1238 | or disable a minor mode keymap. Individual commands or hooks can also | |
1239 | check the variable's value. | |
1240 | ||
1241 | If you want the minor mode to be enabled separately in each buffer, | |
1242 | make the variable buffer-local. | |
1243 | ||
1244 | @item | |
1245 | Define a command whose name is the same as the mode variable. | |
1246 | Its job is to enable and disable the mode by setting the variable. | |
1247 | ||
1248 | The command should accept one optional argument. If the argument is | |
8cd4f018 RS |
1249 | @code{nil}, it should toggle the mode (turn it on if it is off, and |
1250 | off if it is on). It should turn the mode on if the argument is a | |
1251 | positive integer, the symbol @code{t}, or a list whose @sc{car} is one | |
1252 | of those. It should turn the mode off if the argument is a negative | |
4d386728 RS |
1253 | integer or zero, the symbol @code{-}, or a list whose @sc{car} is a |
1254 | negative integer or zero. The meaning of other arguments is not | |
1255 | specified. | |
a44af9f2 | 1256 | |
bfe721d1 KH |
1257 | Here is an example taken from the definition of @code{transient-mark-mode}. |
1258 | It shows the use of @code{transient-mark-mode} as a variable that enables or | |
de9f0bd9 RS |
1259 | disables the mode's behavior, and also shows the proper way to toggle, |
1260 | enable or disable the minor mode based on the raw prefix argument value. | |
a44af9f2 RS |
1261 | |
1262 | @smallexample | |
1263 | @group | |
bfe721d1 KH |
1264 | (setq transient-mark-mode |
1265 | (if (null arg) (not transient-mark-mode) | |
a44af9f2 RS |
1266 | (> (prefix-numeric-value arg) 0))) |
1267 | @end group | |
1268 | @end smallexample | |
1269 | ||
1270 | @item | |
1271 | Add an element to @code{minor-mode-alist} for each minor mode | |
b4a83bb8 LT |
1272 | (@pxref{Definition of minor-mode-alist}), if you want to indicate the |
1273 | minor mode in the mode line. This element should be a list of the | |
1274 | following form: | |
a44af9f2 RS |
1275 | |
1276 | @smallexample | |
1277 | (@var{mode-variable} @var{string}) | |
1278 | @end smallexample | |
1279 | ||
de9f0bd9 | 1280 | Here @var{mode-variable} is the variable that controls enabling of the |
a44af9f2 RS |
1281 | minor mode, and @var{string} is a short string, starting with a space, |
1282 | to represent the mode in the mode line. These strings must be short so | |
1283 | that there is room for several of them at once. | |
1284 | ||
1285 | When you add an element to @code{minor-mode-alist}, use @code{assq} to | |
1286 | check for an existing element, to avoid duplication. For example: | |
1287 | ||
1288 | @smallexample | |
1289 | @group | |
a40d4712 PR |
1290 | (unless (assq 'leif-mode minor-mode-alist) |
1291 | (setq minor-mode-alist | |
1292 | (cons '(leif-mode " Leif") minor-mode-alist))) | |
a44af9f2 RS |
1293 | @end group |
1294 | @end smallexample | |
a44af9f2 | 1295 | |
a40d4712 PR |
1296 | @noindent |
1297 | or like this, using @code{add-to-list} (@pxref{Setting Variables}): | |
1298 | ||
1299 | @smallexample | |
1300 | @group | |
1301 | (add-to-list 'minor-mode-alist '(leif-mode " Leif")) | |
1302 | @end group | |
1303 | @end smallexample | |
1304 | @end itemize | |
1911e6e5 | 1305 | |
8241495d RS |
1306 | Global minor modes distributed with Emacs should if possible support |
1307 | enabling and disabling via Custom (@pxref{Customization}). To do this, | |
1308 | the first step is to define the mode variable with @code{defcustom}, and | |
1309 | specify @code{:type boolean}. | |
1310 | ||
1311 | If just setting the variable is not sufficient to enable the mode, you | |
1312 | should also specify a @code{:set} method which enables the mode by | |
ec9b0882 | 1313 | invoking the mode command. Note in the variable's documentation string that |
8241495d RS |
1314 | setting the variable other than via Custom may not take effect. |
1315 | ||
b4a83bb8 | 1316 | Also mark the definition with an autoload cookie (@pxref{autoload cookie}), |
8241495d RS |
1317 | and specify a @code{:require} so that customizing the variable will load |
1318 | the library that defines the mode. This will copy suitable definitions | |
1319 | into @file{loaddefs.el} so that users can use @code{customize-option} to | |
1320 | enable the mode. For example: | |
1321 | ||
1322 | @smallexample | |
1323 | @group | |
1324 | ||
1325 | ;;;###autoload | |
1326 | (defcustom msb-mode nil | |
1327 | "Toggle msb-mode. | |
1328 | Setting this variable directly does not take effect; | |
1329 | use either \\[customize] or the function `msb-mode'." | |
cbad4a9e | 1330 | :set 'custom-set-minor-mode |
8241495d RS |
1331 | :initialize 'custom-initialize-default |
1332 | :version "20.4" | |
1333 | :type 'boolean | |
1334 | :group 'msb | |
1335 | :require 'msb) | |
1336 | @end group | |
1337 | @end smallexample | |
1338 | ||
a44af9f2 RS |
1339 | @node Keymaps and Minor Modes |
1340 | @subsection Keymaps and Minor Modes | |
1341 | ||
bfe721d1 KH |
1342 | Each minor mode can have its own keymap, which is active when the mode |
1343 | is enabled. To set up a keymap for a minor mode, add an element to the | |
b4a83bb8 | 1344 | alist @code{minor-mode-map-alist}. @xref{Definition of minor-mode-map-alist}. |
a44af9f2 RS |
1345 | |
1346 | @cindex @code{self-insert-command}, minor modes | |
f9f59935 | 1347 | One use of minor mode keymaps is to modify the behavior of certain |
a44af9f2 RS |
1348 | self-inserting characters so that they do something else as well as |
1349 | self-insert. In general, this is the only way to do that, since the | |
1350 | facilities for customizing @code{self-insert-command} are limited to | |
1351 | special cases (designed for abbrevs and Auto Fill mode). (Do not try | |
1352 | substituting your own definition of @code{self-insert-command} for the | |
1353 | standard one. The editor command loop handles this function specially.) | |
1354 | ||
a4b12c74 RS |
1355 | The key sequences bound in a minor mode should consist of @kbd{C-c} |
1356 | followed by a punctuation character @emph{other than} @kbd{@{}, | |
8241495d | 1357 | @kbd{@}}, @kbd{<}, @kbd{>}, @kbd{:}, and @kbd{;}. (Those few punctuation |
a4b12c74 RS |
1358 | characters are reserved for major modes.) |
1359 | ||
2468d0c0 DL |
1360 | @node Defining Minor Modes |
1361 | @subsection Defining Minor Modes | |
f9f59935 | 1362 | |
2468d0c0 | 1363 | The macro @code{define-minor-mode} offers a convenient way of |
8dc811d3 | 1364 | implementing a mode in one self-contained definition. |
f9f59935 | 1365 | |
3389865a | 1366 | @defmac define-minor-mode mode doc [init-value [lighter [keymap]]] keyword-args@dots{} body@dots{} |
2468d0c0 | 1367 | @tindex define-minor-mode |
fdba9ef4 RS |
1368 | This macro defines a new minor mode whose name is @var{mode} (a |
1369 | symbol). It defines a command named @var{mode} to toggle the minor | |
2468d0c0 DL |
1370 | mode, with @var{doc} as its documentation string. It also defines a |
1371 | variable named @var{mode}, which is set to @code{t} or @code{nil} by | |
1372 | enabling or disabling the mode. The variable is initialized to | |
32808f83 RS |
1373 | @var{init-value}. Except in unusual circumstances (see below), this |
1374 | value must be @code{nil}. | |
f9f59935 | 1375 | |
fdba9ef4 | 1376 | The string @var{lighter} says what to display in the mode line |
f9f59935 RS |
1377 | when the mode is enabled; if it is @code{nil}, the mode is not displayed |
1378 | in the mode line. | |
1379 | ||
1380 | The optional argument @var{keymap} specifies the keymap for the minor mode. | |
1381 | It can be a variable name, whose value is the keymap, or it can be an alist | |
1382 | specifying bindings in this form: | |
1383 | ||
1384 | @example | |
1385 | (@var{key-sequence} . @var{definition}) | |
1386 | @end example | |
fdba9ef4 | 1387 | |
f24be0a7 LK |
1388 | The above three arguments @var{init-value}, @var{lighter}, and |
1389 | @var{keymap} can be (partially) omitted when @var{keyword-args} are | |
1390 | used. The @var{keyword-args} consist of keywords followed by | |
1391 | corresponding values. A few keywords have special meanings: | |
fdba9ef4 RS |
1392 | |
1393 | @table @code | |
bfa54668 LK |
1394 | @item :group @var{group} |
1395 | Custom group name to use in all generated @code{defcustom} forms. | |
4f45f65e LK |
1396 | Defaults to @var{mode} without the possible trailing @samp{-mode}. |
1397 | @strong{Warning:} don't use this default group name unless you have | |
1398 | written a @code{defgroup} to define that group properly. @xref{Group | |
1399 | Definitions}. | |
bfa54668 | 1400 | |
fdba9ef4 | 1401 | @item :global @var{global} |
cbb8b77d RS |
1402 | If non-@code{nil} specifies that the minor mode should be global. By |
1403 | default, minor modes defined with @code{define-minor-mode} are | |
1404 | buffer-local. | |
fdba9ef4 RS |
1405 | |
1406 | @item :init-value @var{init-value} | |
1407 | This is equivalent to specifying @var{init-value} positionally. | |
1408 | ||
1409 | @item :lighter @var{lighter} | |
1410 | This is equivalent to specifying @var{lighter} positionally. | |
1411 | ||
1412 | @item :keymap @var{keymap} | |
1413 | This is equivalent to specifying @var{keymap} positionally. | |
1414 | @end table | |
1415 | ||
2cde13e4 | 1416 | Any other keyword arguments are passed directly to the |
fdba9ef4 RS |
1417 | @code{defcustom} generated for the variable @var{mode}. |
1418 | ||
82ecc38a LK |
1419 | The command named @var{mode} first performs the standard actions such |
1420 | as setting the variable named @var{mode} and then executes the | |
1421 | @var{body} forms, if any. It finishes by running the mode hook | |
1422 | variable @code{@var{mode}-hook}. | |
f9f59935 RS |
1423 | @end defmac |
1424 | ||
32808f83 RS |
1425 | The initial value must be @code{nil} except in cases where (1) the |
1426 | mode is preloaded in Emacs, or (2) it is painless to for loading to | |
1427 | enable the mode even though the user did not request it. For | |
1428 | instance, if the mode has no effect unless something else is enabled, | |
1429 | and will always be loaded by that time, enabling it by default is | |
1430 | harmless. But these are unusual circumstances. Normally, the | |
1431 | initial value must be @code{nil}. | |
1432 | ||
fdba9ef4 RS |
1433 | @findex easy-mmode-define-minor-mode |
1434 | The name @code{easy-mmode-define-minor-mode} is an alias | |
1435 | for this macro. | |
1436 | ||
2468d0c0 | 1437 | Here is an example of using @code{define-minor-mode}: |
f9f59935 RS |
1438 | |
1439 | @smallexample | |
2468d0c0 | 1440 | (define-minor-mode hungry-mode |
969fe9b5 | 1441 | "Toggle Hungry mode. |
177c0ea7 | 1442 | With no argument, this command toggles the mode. |
f9f59935 RS |
1443 | Non-null prefix argument turns on the mode. |
1444 | Null prefix argument turns off the mode. | |
1445 | ||
1446 | When Hungry mode is enabled, the control delete key | |
1447 | gobbles all preceding whitespace except the last. | |
1448 | See the command \\[hungry-electric-delete]." | |
1449 | ;; The initial value. | |
1450 | nil | |
1451 | ;; The indicator for the mode line. | |
1452 | " Hungry" | |
1453 | ;; The minor mode bindings. | |
ec9b0882 | 1454 | '(("\C-\^?" . hungry-electric-delete)) |
fdba9ef4 | 1455 | :group 'hunger) |
f9f59935 RS |
1456 | @end smallexample |
1457 | ||
1458 | @noindent | |
1459 | This defines a minor mode named ``Hungry mode'', a command named | |
1460 | @code{hungry-mode} to toggle it, a variable named @code{hungry-mode} | |
1461 | which indicates whether the mode is enabled, and a variable named | |
1462 | @code{hungry-mode-map} which holds the keymap that is active when the | |
ec9b0882 RS |
1463 | mode is enabled. It initializes the keymap with a key binding for |
1464 | @kbd{C-@key{DEL}}. It puts the variable @code{hungry-mode} into | |
1465 | custom group @code{hunger}. There are no @var{body} forms---many | |
1466 | minor modes don't need any. | |
f9f59935 | 1467 | |
fdba9ef4 | 1468 | Here's an equivalent way to write it: |
2468d0c0 | 1469 | |
fdba9ef4 RS |
1470 | @smallexample |
1471 | (define-minor-mode hungry-mode | |
1472 | "Toggle Hungry mode. | |
1473 | With no argument, this command toggles the mode. | |
1474 | Non-null prefix argument turns on the mode. | |
1475 | Null prefix argument turns off the mode. | |
1476 | ||
1477 | When Hungry mode is enabled, the control delete key | |
1478 | gobbles all preceding whitespace except the last. | |
1479 | See the command \\[hungry-electric-delete]." | |
1480 | ;; The initial value. | |
e890842c | 1481 | :init-value nil |
fdba9ef4 RS |
1482 | ;; The indicator for the mode line. |
1483 | :lighter " Hungry" | |
1484 | ;; The minor mode bindings. | |
1485 | :keymap | |
1486 | '(("\C-\^?" . hungry-electric-delete) | |
1487 | ("\C-\M-\^?" | |
1488 | . (lambda () | |
1489 | (interactive) | |
1490 | (hungry-electric-delete t)))) | |
1491 | :group 'hunger) | |
1492 | @end smallexample | |
2468d0c0 | 1493 | |
3389865a | 1494 | @defmac define-global-minor-mode global-mode mode turn-on keyword-args@dots{} |
cbb8b77d RS |
1495 | This defines a global minor mode named @var{global-mode} whose meaning |
1496 | is to enable the buffer-local minor mode @var{mode} in every buffer. | |
1497 | To turn on the minor mode in a buffer, it uses the function | |
1498 | @var{turn-on}; to turn off the minor mode, it calls @code{mode} with | |
1499 | @minus{}1 as argument. | |
1500 | ||
1501 | Use @code{:group @var{group}} in @var{keyword-args} to specify the | |
1502 | custom group for the mode variable of the global minor mode. | |
1503 | @end defmac | |
1504 | ||
a44af9f2 | 1505 | @node Mode Line Format |
06862374 | 1506 | @section Mode-Line Format |
a44af9f2 RS |
1507 | @cindex mode line |
1508 | ||
8241495d RS |
1509 | Each Emacs window (aside from minibuffer windows) typically has a mode |
1510 | line at the bottom, which displays status information about the buffer | |
1511 | displayed in the window. The mode line contains information about the | |
1512 | buffer, such as its name, associated file, depth of recursive editing, | |
1513 | and major and minor modes. A window can also have a @dfn{header | |
1514 | line}, which is much like the mode line but appears at the top of the | |
8caa1356 | 1515 | window. |
a44af9f2 | 1516 | |
8241495d RS |
1517 | This section describes how to control the contents of the mode line |
1518 | and header line. We include it in this chapter because much of the | |
a44af9f2 RS |
1519 | information displayed in the mode line relates to the enabled major and |
1520 | minor modes. | |
1521 | ||
302691ab LT |
1522 | @menu |
1523 | * Mode Line Basics:: | |
1524 | * Mode Line Data:: The data structure that controls the mode line. | |
1525 | * Mode Line Variables:: Variables used in that data structure. | |
1526 | * %-Constructs:: Putting information into a mode line. | |
1527 | * Properties in Mode:: Using text properties in the mode line. | |
1528 | * Header Lines:: Like a mode line, but at the top. | |
1529 | * Emulating Mode Line:: Formatting text as the mode line would. | |
1530 | @end menu | |
1531 | ||
1532 | @node Mode Line Basics | |
1533 | @subsection Mode Line Basics | |
1534 | ||
a44af9f2 RS |
1535 | @code{mode-line-format} is a buffer-local variable that holds a |
1536 | template used to display the mode line of the current buffer. All | |
8241495d RS |
1537 | windows for the same buffer use the same @code{mode-line-format}, so |
1538 | their mode lines appear the same---except for scrolling percentages, and | |
1539 | line and column numbers, since those depend on point and on how the | |
1540 | window is scrolled. @code{header-line-format} is used likewise for | |
1541 | header lines. | |
1542 | ||
8e0f7b5b RS |
1543 | For efficiency, Emacs does not recompute the mode line and header |
1544 | line of a window in every redisplay. It does so when circumstances | |
1545 | appear to call for it---for instance, if you change the window | |
1546 | configuration, switch buffers, narrow or widen the buffer, scroll, or | |
1547 | change the buffer's modification status. If you modify any of the | |
1548 | variables referenced by @code{mode-line-format} (@pxref{Mode Line | |
1549 | Variables}), or any other variables and data structures that affect | |
1550 | how text is displayed (@pxref{Display}), you may want to force an | |
1551 | update of the mode line so as to display the new information or | |
1552 | display it in the new way. | |
a44af9f2 RS |
1553 | |
1554 | @c Emacs 19 feature | |
0ad8cce8 | 1555 | @defun force-mode-line-update &optional all |
8241495d | 1556 | Force redisplay of the current buffer's mode line and header line. |
8e0f7b5b | 1557 | The next redisplay will update the mode line and header line based on |
0ad8cce8 LK |
1558 | the latest values of all relevant variables. With optional |
1559 | non-@code{nil} @var{all}, force redisplay of all mode lines and header | |
1560 | lines. | |
8e0f7b5b RS |
1561 | |
1562 | This function also forces recomputation of the menu bar menus | |
1563 | and the frame title. | |
a44af9f2 RS |
1564 | @end defun |
1565 | ||
ec9b0882 RS |
1566 | The selected window's mode line is usually displayed in a different |
1567 | color using the face @code{mode-line}. Other windows' mode lines | |
1568 | appear in the face @code{mode-line-inactive} instead. @xref{Faces}. | |
a44af9f2 | 1569 | |
a1112b37 RS |
1570 | A window that is just one line tall does not display either a mode |
1571 | line or a header line, even if the variables call for one. A window | |
1572 | that is two lines tall cannot display both a mode line and a header | |
1573 | line at once; if the variables call for both, only the mode line | |
1574 | actually appears. | |
1575 | ||
a44af9f2 RS |
1576 | @node Mode Line Data |
1577 | @subsection The Data Structure of the Mode Line | |
06862374 | 1578 | @cindex mode-line construct |
a44af9f2 | 1579 | |
06862374 | 1580 | The mode-line contents are controlled by a data structure of lists, |
a40d4712 | 1581 | strings, symbols, and numbers kept in buffer-local variables. The data |
06862374 LK |
1582 | structure is called a @dfn{mode-line construct}, and it is built in |
1583 | recursive fashion out of simpler mode-line constructs. The same data | |
a40d4712 PR |
1584 | structure is used for constructing frame titles (@pxref{Frame Titles}) |
1585 | and header lines (@pxref{Header Lines}). | |
a44af9f2 RS |
1586 | |
1587 | @defvar mode-line-format | |
06862374 LK |
1588 | The value of this variable is a mode-line construct with overall |
1589 | responsibility for the mode-line format. The value of this variable | |
1590 | controls which other variables are used to form the mode-line text, and | |
a44af9f2 | 1591 | where they appear. |
8241495d RS |
1592 | |
1593 | If you set this variable to @code{nil} in a buffer, that buffer does not | |
8caa1356 | 1594 | have a mode line. |
a44af9f2 RS |
1595 | @end defvar |
1596 | ||
06862374 | 1597 | A mode-line construct may be as simple as a fixed string of text, but |
a44af9f2 | 1598 | it usually specifies how to use other variables to construct the text. |
06862374 | 1599 | Many of these variables are themselves defined to have mode-line |
a44af9f2 RS |
1600 | constructs as their values. |
1601 | ||
1602 | The default value of @code{mode-line-format} incorporates the values | |
06862374 LK |
1603 | of variables such as @code{mode-line-position} and |
1604 | @code{mode-line-modes} (which in turn incorporates the values of the | |
1605 | variables @code{mode-name} and @code{minor-mode-alist}). Because of | |
1606 | this, very few modes need to alter @code{mode-line-format} itself. For | |
1607 | most purposes, it is sufficient to alter some of the variables that | |
1608 | @code{mode-line-format} either directly or indirectly refers to. | |
1609 | ||
1610 | A mode-line construct may be a list, a symbol, or a string. If the | |
de9f0bd9 | 1611 | value is a list, each element may be a list, a symbol, or a string. |
a44af9f2 | 1612 | |
8241495d RS |
1613 | The mode line can display various faces, if the strings that control |
1614 | it have the @code{face} property. @xref{Properties in Mode}. In | |
1615 | addition, the face @code{mode-line} is used as a default for the whole | |
c29a63fd | 1616 | mode line (@pxref{Standard Faces,,, emacs, The GNU Emacs Manual}). |
8241495d | 1617 | |
a44af9f2 RS |
1618 | @table @code |
1619 | @cindex percent symbol in mode line | |
1620 | @item @var{string} | |
06862374 | 1621 | A string as a mode-line construct is displayed verbatim in the mode line |
bfe721d1 | 1622 | except for @dfn{@code{%}-constructs}. Decimal digits after the @samp{%} |
a44af9f2 RS |
1623 | specify the field width for space filling on the right (i.e., the data |
1624 | is left justified). @xref{%-Constructs}. | |
1625 | ||
1626 | @item @var{symbol} | |
06862374 LK |
1627 | A symbol as a mode-line construct stands for its value. The value of |
1628 | @var{symbol} is used as a mode-line construct, in place of @var{symbol}. | |
8241495d | 1629 | However, the symbols @code{t} and @code{nil} are ignored, as is any |
de9f0bd9 | 1630 | symbol whose value is void. |
a44af9f2 RS |
1631 | |
1632 | There is one exception: if the value of @var{symbol} is a string, it is | |
de9f0bd9 | 1633 | displayed verbatim: the @code{%}-constructs are not recognized. |
a44af9f2 | 1634 | |
a232a240 LK |
1635 | Unless @var{symbol} is marked as ``risky'' (i.e., it has a |
1636 | non-@code{nil} @code{risky-local-variable} property), all properties in | |
1637 | any strings, as well as all @code{:eval} and @code{:propertize} forms in | |
1638 | the value of that symbol will be ignored. | |
1639 | ||
a44af9f2 | 1640 | @item (@var{string} @var{rest}@dots{}) @r{or} (@var{list} @var{rest}@dots{}) |
de9f0bd9 RS |
1641 | A list whose first element is a string or list means to process all the |
1642 | elements recursively and concatenate the results. This is the most | |
06862374 | 1643 | common form of mode-line construct. |
a44af9f2 | 1644 | |
8241495d RS |
1645 | @item (:eval @var{form}) |
1646 | A list whose first element is the symbol @code{:eval} says to evaluate | |
b4a83bb8 LT |
1647 | @var{form}, and use the result as a string to display. Make sure this |
1648 | evaluation cannot load any files, as doing so could cause infinite | |
1649 | recursion. | |
8241495d | 1650 | |
06862374 LK |
1651 | @item (:propertize @var{elt} @var{props}@dots{}) |
1652 | A list whose first element is the symbol @code{:propertize} says to | |
1653 | process the mode-line construct @var{elt} recursively and add the text | |
1654 | properties specified by @var{props} to the result. The argument | |
1655 | @var{props} should consist of zero or more pairs @var{text-property} | |
bf247b6e | 1656 | @var{value}. (This feature is new as of Emacs 22.1.) |
06862374 | 1657 | |
a44af9f2 | 1658 | @item (@var{symbol} @var{then} @var{else}) |
03de4399 RS |
1659 | A list whose first element is a symbol that is not a keyword specifies |
1660 | a conditional. Its meaning depends on the value of @var{symbol}. If | |
1661 | @var{symbol} has a non-@code{nil} value, the second element, | |
1662 | @var{then}, is processed recursively as a mode-line element. | |
1663 | Otherwise, the third element, @var{else}, is processed recursively. | |
1664 | You may omit @var{else}; then the mode-line element displays nothing | |
1665 | if the value of @var{symbol} is @code{nil} or void. | |
a44af9f2 RS |
1666 | |
1667 | @item (@var{width} @var{rest}@dots{}) | |
1668 | A list whose first element is an integer specifies truncation or | |
1669 | padding of the results of @var{rest}. The remaining elements | |
06862374 | 1670 | @var{rest} are processed recursively as mode-line constructs and |
b4a83bb8 LT |
1671 | concatenated together. When @var{width} is positive, the result is |
1672 | space filled on the right if its width is less than @var{width}. When | |
1673 | @var{width} is negative, the result is truncated on the right to | |
1674 | @minus{}@var{width} columns if its width exceeds @minus{}@var{width}. | |
a44af9f2 RS |
1675 | |
1676 | For example, the usual way to show what percentage of a buffer is above | |
de9f0bd9 | 1677 | the top of the window is to use a list like this: @code{(-3 "%p")}. |
a44af9f2 RS |
1678 | @end table |
1679 | ||
1680 | If you do alter @code{mode-line-format} itself, the new value should | |
de9f0bd9 RS |
1681 | use the same variables that appear in the default value (@pxref{Mode |
1682 | Line Variables}), rather than duplicating their contents or displaying | |
1683 | the information in another fashion. This way, customizations made by | |
bfe721d1 KH |
1684 | the user or by Lisp programs (such as @code{display-time} and major |
1685 | modes) via changes to those variables remain effective. | |
a44af9f2 RS |
1686 | |
1687 | @cindex Shell mode @code{mode-line-format} | |
1688 | Here is an example of a @code{mode-line-format} that might be | |
969fe9b5 | 1689 | useful for @code{shell-mode}, since it contains the host name and default |
a44af9f2 RS |
1690 | directory. |
1691 | ||
1692 | @example | |
1693 | @group | |
1694 | (setq mode-line-format | |
969fe9b5 RS |
1695 | (list "-" |
1696 | 'mode-line-mule-info | |
a44af9f2 | 1697 | 'mode-line-modified |
969fe9b5 | 1698 | 'mode-line-frame-identification |
177c0ea7 | 1699 | "%b--" |
a44af9f2 | 1700 | @end group |
f9f59935 RS |
1701 | @group |
1702 | ;; @r{Note that this is evaluated while making the list.} | |
06862374 | 1703 | ;; @r{It makes a mode-line construct which is just a string.} |
f9f59935 RS |
1704 | (getenv "HOST") |
1705 | @end group | |
177c0ea7 | 1706 | ":" |
a44af9f2 RS |
1707 | 'default-directory |
1708 | " " | |
1709 | 'global-mode-string | |
de9f0bd9 | 1710 | " %[(" |
8241495d | 1711 | '(:eval (mode-line-mode-name)) |
177c0ea7 JB |
1712 | 'mode-line-process |
1713 | 'minor-mode-alist | |
1714 | "%n" | |
969fe9b5 | 1715 | ")%]--" |
a44af9f2 | 1716 | @group |
969fe9b5 | 1717 | '(which-func-mode ("" which-func-format "--")) |
bfe721d1 | 1718 | '(line-number-mode "L%l--") |
969fe9b5 | 1719 | '(column-number-mode "C%c--") |
a232a240 | 1720 | '(-3 "%p") |
a44af9f2 RS |
1721 | "-%-")) |
1722 | @end group | |
1723 | @end example | |
1724 | ||
1911e6e5 RS |
1725 | @noindent |
1726 | (The variables @code{line-number-mode}, @code{column-number-mode} | |
1727 | and @code{which-func-mode} enable particular minor modes; as usual, | |
1728 | these variable names are also the minor mode command names.) | |
1729 | ||
a44af9f2 RS |
1730 | @node Mode Line Variables |
1731 | @subsection Variables Used in the Mode Line | |
1732 | ||
1733 | This section describes variables incorporated by the | |
1734 | standard value of @code{mode-line-format} into the text of the mode | |
1735 | line. There is nothing inherently special about these variables; any | |
1736 | other variables could have the same effects on the mode line if | |
1737 | @code{mode-line-format} were changed to use them. | |
1738 | ||
969fe9b5 RS |
1739 | @defvar mode-line-mule-info |
1740 | This variable holds the value of the mode-line construct that displays | |
1741 | information about the language environment, buffer coding system, and | |
a9f0a989 | 1742 | current input method. @xref{Non-ASCII Characters}. |
969fe9b5 RS |
1743 | @end defvar |
1744 | ||
a44af9f2 | 1745 | @defvar mode-line-modified |
de9f0bd9 | 1746 | This variable holds the value of the mode-line construct that displays |
a44af9f2 RS |
1747 | whether the current buffer is modified. |
1748 | ||
969fe9b5 RS |
1749 | The default value of @code{mode-line-modified} is @code{("%1*%1+")}. |
1750 | This means that the mode line displays @samp{**} if the buffer is | |
1751 | modified, @samp{--} if the buffer is not modified, @samp{%%} if the | |
1752 | buffer is read only, and @samp{%*} if the buffer is read only and | |
1753 | modified. | |
a44af9f2 RS |
1754 | |
1755 | Changing this variable does not force an update of the mode line. | |
1756 | @end defvar | |
1757 | ||
969fe9b5 RS |
1758 | @defvar mode-line-frame-identification |
1759 | This variable identifies the current frame. The default value is | |
06862374 LK |
1760 | @code{" "} if you are using a window system which can show multiple |
1761 | frames, or @code{"-%F "} on an ordinary terminal which shows only one | |
969fe9b5 RS |
1762 | frame at a time. |
1763 | @end defvar | |
1764 | ||
a44af9f2 | 1765 | @defvar mode-line-buffer-identification |
de9f0bd9 | 1766 | This variable identifies the buffer being displayed in the window. Its |
ebc6903b RS |
1767 | default value is @code{("%12b")}, which displays the buffer name, padded |
1768 | with spaces to at least 12 columns. | |
a44af9f2 RS |
1769 | @end defvar |
1770 | ||
06862374 LK |
1771 | @defvar mode-line-position |
1772 | This variable indicates the position in the buffer. Here is a | |
1773 | simplified version of its default value. The actual default value | |
1774 | also specifies addition of the @code{help-echo} text property. | |
a44af9f2 | 1775 | |
06862374 LK |
1776 | @example |
1777 | @group | |
a232a240 | 1778 | ((-3 "%p") |
06862374 LK |
1779 | (size-indication-mode (8 " of %I")) |
1780 | @end group | |
1781 | @group | |
1782 | (line-number-mode | |
1783 | ((column-number-mode | |
1784 | (10 " (%l,%c)") | |
1785 | (6 " L%l"))) | |
1786 | ((column-number-mode | |
1787 | (5 " C%c"))))) | |
1788 | @end group | |
1789 | @end example | |
1790 | ||
1791 | This means that @code{mode-line-position} displays at least the buffer | |
1792 | percentage and possibly the buffer size, the line number and the column | |
1793 | number. | |
1794 | @end defvar | |
1795 | ||
1796 | @defvar vc-mode | |
1797 | The variable @code{vc-mode}, buffer-local in each buffer, records | |
1798 | whether the buffer's visited file is maintained with version control, | |
1799 | and, if so, which kind. Its value is a string that appears in the mode | |
1800 | line, or @code{nil} for no version control. | |
a44af9f2 RS |
1801 | @end defvar |
1802 | ||
06862374 LK |
1803 | @defvar mode-line-modes |
1804 | This variable displays the buffer's major and minor modes. Here is a | |
1805 | simplified version of its default value. The real default value also | |
1806 | specifies addition of text properties. | |
1807 | ||
1808 | @example | |
1809 | @group | |
1810 | ("%[(" mode-name | |
1811 | mode-line-process minor-mode-alist | |
1812 | "%n" ")%]--") | |
1813 | @end group | |
1814 | @end example | |
1815 | ||
1816 | So @code{mode-line-modes} normally also displays the recursive editing | |
1817 | level, information on the process status and whether narrowing is in | |
1818 | effect. | |
1819 | @end defvar | |
1820 | ||
1821 | The following three variables are used in @code{mode-line-modes}: | |
1822 | ||
a44af9f2 | 1823 | @defvar mode-name |
de9f0bd9 | 1824 | This buffer-local variable holds the ``pretty'' name of the current |
a44af9f2 RS |
1825 | buffer's major mode. Each major mode should set this variable so that the |
1826 | mode name will appear in the mode line. | |
1827 | @end defvar | |
1828 | ||
06862374 LK |
1829 | @defvar mode-line-process |
1830 | This buffer-local variable contains the mode-line information on process | |
1831 | status in modes used for communicating with subprocesses. It is | |
1832 | displayed immediately following the major mode name, with no intervening | |
1833 | space. For example, its value in the @samp{*shell*} buffer is | |
1834 | @code{(":%s")}, which allows the shell to display its status along | |
1835 | with the major mode as: @samp{(Shell:run)}. Normally this variable | |
1836 | is @code{nil}. | |
1837 | @end defvar | |
1838 | ||
a44af9f2 | 1839 | @defvar minor-mode-alist |
b4a83bb8 | 1840 | @anchor{Definition of minor-mode-alist} |
de9f0bd9 | 1841 | This variable holds an association list whose elements specify how the |
a44af9f2 RS |
1842 | mode line should indicate that a minor mode is active. Each element of |
1843 | the @code{minor-mode-alist} should be a two-element list: | |
1844 | ||
1845 | @example | |
1846 | (@var{minor-mode-variable} @var{mode-line-string}) | |
1847 | @end example | |
1848 | ||
06862374 LK |
1849 | More generally, @var{mode-line-string} can be any mode-line spec. It |
1850 | appears in the mode line when the value of @var{minor-mode-variable} | |
1851 | is non-@code{nil}, and not otherwise. These strings should begin with | |
a44af9f2 | 1852 | spaces so that they don't run together. Conventionally, the |
06862374 LK |
1853 | @var{minor-mode-variable} for a specific mode is set to a |
1854 | non-@code{nil} value when that minor mode is activated. | |
a44af9f2 | 1855 | |
f9f59935 RS |
1856 | @code{minor-mode-alist} itself is not buffer-local. Each variable |
1857 | mentioned in the alist should be buffer-local if its minor mode can be | |
1858 | enabled separately in each buffer. | |
a44af9f2 RS |
1859 | @end defvar |
1860 | ||
06862374 | 1861 | @defvar global-mode-string |
1074a881 JB |
1862 | This variable holds a mode-line spec that, by default, appears in the |
1863 | mode line just after the @code{which-func-mode} minor mode if set, | |
1864 | else after @code{mode-line-modes}. The command @code{display-time} | |
06862374 | 1865 | sets @code{global-mode-string} to refer to the variable |
1074a881 JB |
1866 | @code{display-time-string}, which holds a string containing the time |
1867 | and load information. | |
a40d4712 | 1868 | |
06862374 LK |
1869 | The @samp{%M} construct substitutes the value of |
1870 | @code{global-mode-string}, but that is obsolete, since the variable is | |
1871 | included in the mode line from @code{mode-line-format}. | |
a40d4712 PR |
1872 | @end defvar |
1873 | ||
1874 | The variable @code{default-mode-line-format} is where | |
1875 | @code{mode-line-format} usually gets its value: | |
1876 | ||
a44af9f2 | 1877 | @defvar default-mode-line-format |
de9f0bd9 | 1878 | This variable holds the default @code{mode-line-format} for buffers |
a44af9f2 RS |
1879 | that do not override it. This is the same as @code{(default-value |
1880 | 'mode-line-format)}. | |
1881 | ||
06862374 LK |
1882 | Here is a simplified version of the default value of |
1883 | @code{default-mode-line-format}. The real default value also | |
1884 | specifies addition of text properties. | |
a44af9f2 RS |
1885 | |
1886 | @example | |
1887 | @group | |
f9f59935 RS |
1888 | ("-" |
1889 | mode-line-mule-info | |
a44af9f2 | 1890 | mode-line-modified |
f9f59935 | 1891 | mode-line-frame-identification |
a44af9f2 | 1892 | mode-line-buffer-identification |
f9f59935 | 1893 | @end group |
a44af9f2 | 1894 | " " |
06862374 LK |
1895 | mode-line-position |
1896 | (vc-mode vc-mode) | |
1897 | " " | |
f9f59935 | 1898 | @group |
06862374 | 1899 | mode-line-modes |
f9f59935 | 1900 | (which-func-mode ("" which-func-format "--")) |
06862374 | 1901 | (global-mode-string ("--" global-mode-string)) |
a44af9f2 RS |
1902 | "-%-") |
1903 | @end group | |
1904 | @end example | |
1905 | @end defvar | |
1906 | ||
1907 | @node %-Constructs | |
1908 | @subsection @code{%}-Constructs in the Mode Line | |
1909 | ||
1910 | The following table lists the recognized @code{%}-constructs and what | |
de9f0bd9 | 1911 | they mean. In any construct except @samp{%%}, you can add a decimal |
b4a83bb8 LT |
1912 | integer after the @samp{%} to specify a minimum field width. If the |
1913 | width is less, the field is padded with spaces to the right. | |
a44af9f2 RS |
1914 | |
1915 | @table @code | |
1916 | @item %b | |
1917 | The current buffer name, obtained with the @code{buffer-name} function. | |
1918 | @xref{Buffer Names}. | |
1919 | ||
a40d4712 PR |
1920 | @item %c |
1921 | The current column number of point. | |
1922 | ||
a44af9f2 RS |
1923 | @item %f |
1924 | The visited file name, obtained with the @code{buffer-file-name} | |
1925 | function. @xref{Buffer File Name}. | |
1926 | ||
22697dac | 1927 | @item %F |
969fe9b5 | 1928 | The title (only on a window system) or the name of the selected frame. |
8deadbd4 | 1929 | @xref{Basic Parameters}. |
22697dac | 1930 | |
08622028 LK |
1931 | @item %i |
1932 | The size of the accessible part of the current buffer; basically | |
1933 | @code{(- (point-max) (point-min))}. | |
1934 | ||
1935 | @item %I | |
1936 | Like @samp{%i}, but the size is printed in a more readable way by using | |
1937 | @samp{k} for 10^3, @samp{M} for 10^6, @samp{G} for 10^9, etc., to | |
1938 | abbreviate. | |
1939 | ||
22697dac | 1940 | @item %l |
8241495d RS |
1941 | The current line number of point, counting within the accessible portion |
1942 | of the buffer. | |
22697dac | 1943 | |
a40d4712 PR |
1944 | @item %n |
1945 | @samp{Narrow} when narrowing is in effect; nothing otherwise (see | |
1946 | @code{narrow-to-region} in @ref{Narrowing}). | |
1947 | ||
1948 | @item %p | |
1949 | The percentage of the buffer text above the @strong{top} of window, or | |
1950 | @samp{Top}, @samp{Bottom} or @samp{All}. Note that the default | |
1951 | mode-line specification truncates this to three characters. | |
1952 | ||
1953 | @item %P | |
1954 | The percentage of the buffer text that is above the @strong{bottom} of | |
1955 | the window (which includes the text visible in the window, as well as | |
1956 | the text above the top), plus @samp{Top} if the top of the buffer is | |
1957 | visible on screen; or @samp{Bottom} or @samp{All}. | |
1958 | ||
1959 | @item %s | |
1960 | The status of the subprocess belonging to the current buffer, obtained with | |
1961 | @code{process-status}. @xref{Process Information}. | |
1962 | ||
1963 | @item %t | |
1964 | Whether the visited file is a text file or a binary file. This is a | |
1965 | meaningful distinction only on certain operating systems (@pxref{MS-DOS | |
1966 | File Types}). | |
1967 | ||
a44af9f2 RS |
1968 | @item %* |
1969 | @samp{%} if the buffer is read only (see @code{buffer-read-only}); @* | |
1970 | @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @* | |
1971 | @samp{-} otherwise. @xref{Buffer Modification}. | |
1972 | ||
1973 | @item %+ | |
22697dac KH |
1974 | @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @* |
1975 | @samp{%} if the buffer is read only (see @code{buffer-read-only}); @* | |
1976 | @samp{-} otherwise. This differs from @samp{%*} only for a modified | |
1977 | read-only buffer. @xref{Buffer Modification}. | |
1978 | ||
1979 | @item %& | |
de9f0bd9 | 1980 | @samp{*} if the buffer is modified, and @samp{-} otherwise. |
a44af9f2 | 1981 | |
a44af9f2 RS |
1982 | @item %[ |
1983 | An indication of the depth of recursive editing levels (not counting | |
1984 | minibuffer levels): one @samp{[} for each editing level. | |
1985 | @xref{Recursive Editing}. | |
1986 | ||
1987 | @item %] | |
1988 | One @samp{]} for each recursive editing level (not counting minibuffer | |
1989 | levels). | |
1990 | ||
a40d4712 PR |
1991 | @item %- |
1992 | Dashes sufficient to fill the remainder of the mode line. | |
1993 | ||
a44af9f2 RS |
1994 | @item %% |
1995 | The character @samp{%}---this is how to include a literal @samp{%} in a | |
1996 | string in which @code{%}-constructs are allowed. | |
a44af9f2 RS |
1997 | @end table |
1998 | ||
1999 | The following two @code{%}-constructs are still supported, but they are | |
2000 | obsolete, since you can get the same results with the variables | |
2001 | @code{mode-name} and @code{global-mode-string}. | |
2002 | ||
2003 | @table @code | |
2004 | @item %m | |
2005 | The value of @code{mode-name}. | |
2006 | ||
2007 | @item %M | |
2008 | The value of @code{global-mode-string}. Currently, only | |
2009 | @code{display-time} modifies the value of @code{global-mode-string}. | |
2010 | @end table | |
2011 | ||
8241495d RS |
2012 | @node Properties in Mode |
2013 | @subsection Properties in the Mode Line | |
06862374 | 2014 | @cindex text properties in the mode line |
8241495d | 2015 | |
8caa1356 | 2016 | Certain text properties are meaningful in the |
8241495d | 2017 | mode line. The @code{face} property affects the appearance of text; the |
b4a83bb8 | 2018 | @code{help-echo} property associates help strings with the text, and |
ce75fd23 | 2019 | @code{local-map} can make the text mouse-sensitive. |
8241495d | 2020 | |
06862374 | 2021 | There are four ways to specify text properties for text in the mode |
8241495d RS |
2022 | line: |
2023 | ||
2024 | @enumerate | |
2025 | @item | |
06862374 LK |
2026 | Put a string with a text property directly into the mode-line data |
2027 | structure. | |
2028 | ||
2029 | @item | |
2030 | Put a text property on a mode-line %-construct such as @samp{%12b}; then | |
2031 | the expansion of the %-construct will have that same text property. | |
8241495d RS |
2032 | |
2033 | @item | |
06862374 LK |
2034 | Use a @code{(:propertize @var{elt} @var{props}@dots{})} construct to |
2035 | give @var{elt} a text property specified by @var{props}. | |
8241495d RS |
2036 | |
2037 | @item | |
2038 | Use a list containing @code{:eval @var{form}} in the mode-line data | |
06862374 LK |
2039 | structure, and make @var{form} evaluate to a string that has a text |
2040 | property. | |
8241495d RS |
2041 | @end enumerate |
2042 | ||
ce75fd23 | 2043 | You use the @code{local-map} property to specify a keymap. Like any |
8241495d | 2044 | keymap, it can bind character keys and function keys; but that has no |
a40d4712 | 2045 | effect, since it is impossible to move point into the mode line. This |
8241495d RS |
2046 | keymap can only take real effect for mouse clicks. |
2047 | ||
ec9b0882 RS |
2048 | When the mode line refers to a variable which does not have a |
2049 | non-@code{nil} @code{risky-local-variable} property, any text | |
2050 | properties given or specified within that variable's values are | |
2051 | ignored. This is because such properties could otherwise specify | |
2052 | functions to be called, and those functions could come from file | |
2053 | local variables. | |
2054 | ||
8241495d RS |
2055 | @node Header Lines |
2056 | @subsection Window Header Lines | |
2057 | @cindex header line (of a window) | |
2058 | @cindex window header line | |
2059 | ||
8caa1356 | 2060 | A window can have a @dfn{header line} at the |
8241495d | 2061 | top, just as it can have a mode line at the bottom. The header line |
06862374 | 2062 | feature works just like the mode-line feature, except that it's |
8241495d RS |
2063 | controlled by different variables. |
2064 | ||
2065 | @tindex header-line-format | |
2066 | @defvar header-line-format | |
2067 | This variable, local in every buffer, specifies how to display the | |
2068 | header line, for windows displaying the buffer. The format of the value | |
13ede7fc | 2069 | is the same as for @code{mode-line-format} (@pxref{Mode Line Data}). |
8241495d RS |
2070 | @end defvar |
2071 | ||
2072 | @tindex default-header-line-format | |
2073 | @defvar default-header-line-format | |
2074 | This variable holds the default @code{header-line-format} for buffers | |
2075 | that do not override it. This is the same as @code{(default-value | |
2076 | 'header-line-format)}. | |
2077 | ||
2078 | It is normally @code{nil}, so that ordinary buffers have no header line. | |
2079 | @end defvar | |
2080 | ||
bda7c6dd | 2081 | @node Emulating Mode Line |
06862374 | 2082 | @subsection Emulating Mode-Line Formatting |
bda7c6dd RS |
2083 | |
2084 | You can use the function @code{format-mode-line} to compute | |
2085 | the text that would appear in a mode line or header line | |
b4a83bb8 | 2086 | based on a certain mode-line specification. |
bda7c6dd | 2087 | |
f2dfc856 | 2088 | @defun format-mode-line format &optional face window buffer |
bda7c6dd RS |
2089 | This function formats a line of text according to @var{format} as if |
2090 | it were generating the mode line for @var{window}, but instead of | |
2091 | displaying the text in the mode line or the header line, it returns | |
0a54d76e RS |
2092 | the text as a string. The argument @var{window} defaults to the |
2093 | selected window. If @var{buffer} is non-@code{nil}, all the | |
2094 | information used is taken from @var{buffer}; by default, it comes from | |
2095 | @var{window}'s buffer. | |
bda7c6dd RS |
2096 | |
2097 | The value string normally has text properties that correspond to the | |
0fee24ae RS |
2098 | faces, keymaps, etc., that the mode line would have. And any character |
2099 | for which no @code{face} property is specified gets a default | |
2100 | value which is usually @var{face}. (If @var{face} is @code{t}, | |
2101 | that stands for either @code{mode-line} if @var{window} is selected, | |
b4a83bb8 LT |
2102 | otherwise @code{mode-line-inactive}. If @var{face} is @code{nil} or |
2103 | omitted, that stands for no face property.) | |
0fee24ae | 2104 | |
f2dfc856 | 2105 | However, if @var{face} is an integer, the value has no text properties. |
0a54d76e RS |
2106 | |
2107 | For example, @code{(format-mode-line header-line-format)} returns the | |
2108 | text that would appear in the selected window's header line (@code{""} | |
0fee24ae | 2109 | if it has no header line). @code{(format-mode-line header-line-format |
f2dfc856 | 2110 | 'header-line)} returns the same text, with each character |
0fee24ae | 2111 | carrying the face that it will have in the header line itself. |
bda7c6dd RS |
2112 | @end defun |
2113 | ||
f9f59935 RS |
2114 | @node Imenu |
2115 | @section Imenu | |
2116 | ||
2117 | @cindex Imenu | |
969fe9b5 RS |
2118 | @dfn{Imenu} is a feature that lets users select a definition or |
2119 | section in the buffer, from a menu which lists all of them, to go | |
5a5d2aec RS |
2120 | directly to that location in the buffer. Imenu works by constructing |
2121 | a buffer index which lists the names and buffer positions of the | |
a40d4712 | 2122 | definitions, or other named portions of the buffer; then the user can |
ec9b0882 RS |
2123 | choose one of them and move point to it. Major modes can add a menu |
2124 | bar item to use Imenu using @code{imenu-add-to-menubar}. | |
2125 | ||
2126 | @defun imenu-add-to-menubar name | |
2127 | This function defines a local menu bar item named @var{name} | |
2128 | to run Imenu. | |
2129 | @end defun | |
2130 | ||
2131 | The user-level commands for using Imenu are described in the Emacs | |
2132 | Manual (@pxref{Imenu,, Imenu, emacs, the Emacs Manual}). This section | |
2133 | explains how to customize Imenu's method of finding definitions or | |
2134 | buffer portions for a particular major mode. | |
969fe9b5 RS |
2135 | |
2136 | The usual and simplest way is to set the variable | |
2137 | @code{imenu-generic-expression}: | |
f9f59935 RS |
2138 | |
2139 | @defvar imenu-generic-expression | |
10ee4e90 LK |
2140 | This variable, if non-@code{nil}, is a list that specifies regular |
2141 | expressions for finding definitions for Imenu. Simple elements of | |
2142 | @code{imenu-generic-expression} look like this: | |
f9f59935 RS |
2143 | |
2144 | @example | |
10ee4e90 | 2145 | (@var{menu-title} @var{regexp} @var{index}) |
f9f59935 RS |
2146 | @end example |
2147 | ||
2148 | Here, if @var{menu-title} is non-@code{nil}, it says that the matches | |
2149 | for this element should go in a submenu of the buffer index; | |
2150 | @var{menu-title} itself specifies the name for the submenu. If | |
2151 | @var{menu-title} is @code{nil}, the matches for this element go directly | |
2152 | in the top level of the buffer index. | |
2153 | ||
2154 | The second item in the list, @var{regexp}, is a regular expression | |
10ee4e90 LK |
2155 | (@pxref{Regular Expressions}); anything in the buffer that it matches |
2156 | is considered a definition, something to mention in the buffer index. | |
2157 | The third item, @var{index}, is a non-negative integer that indicates | |
2158 | which subexpression in @var{regexp} matches the definition's name. | |
f9f59935 RS |
2159 | |
2160 | An element can also look like this: | |
2161 | ||
2162 | @example | |
2163 | (@var{menu-title} @var{regexp} @var{index} @var{function} @var{arguments}@dots{}) | |
2164 | @end example | |
2165 | ||
10ee4e90 LK |
2166 | Like in the previous case, each match for this element creates an |
2167 | index item. However, if this index item is selected by the user, it | |
2168 | calls @var{function} with arguments consisting of the item name, the | |
2169 | buffer position, and @var{arguments}. | |
f9f59935 | 2170 | |
10ee4e90 LK |
2171 | For Emacs Lisp mode, @code{imenu-generic-expression} could look like |
2172 | this: | |
f9f59935 | 2173 | |
a9f0a989 | 2174 | @c should probably use imenu-syntax-alist and \\sw rather than [-A-Za-z0-9+] |
f9f59935 RS |
2175 | @example |
2176 | @group | |
2177 | ((nil "^\\s-*(def\\(un\\|subst\\|macro\\|advice\\)\ | |
2178 | \\s-+\\([-A-Za-z0-9+]+\\)" 2) | |
2179 | @end group | |
2180 | @group | |
2181 | ("*Vars*" "^\\s-*(def\\(var\\|const\\)\ | |
2182 | \\s-+\\([-A-Za-z0-9+]+\\)" 2) | |
2183 | @end group | |
2184 | @group | |
2185 | ("*Types*" | |
a9f0a989 RS |
2186 | "^\\s-*\ |
2187 | (def\\(type\\|struct\\|class\\|ine-condition\\)\ | |
f9f59935 RS |
2188 | \\s-+\\([-A-Za-z0-9+]+\\)" 2)) |
2189 | @end group | |
2190 | @end example | |
2191 | ||
969fe9b5 | 2192 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
2193 | @end defvar |
2194 | ||
2195 | @defvar imenu-case-fold-search | |
10ee4e90 LK |
2196 | This variable controls whether matching against the regular |
2197 | expressions in the value of @code{imenu-generic-expression} is | |
2198 | case-sensitive: @code{t}, the default, means matching should ignore | |
2199 | case. | |
a9f0a989 RS |
2200 | |
2201 | Setting this variable makes it buffer-local in the current buffer. | |
2202 | @end defvar | |
2203 | ||
2204 | @defvar imenu-syntax-alist | |
2205 | This variable is an alist of syntax table modifiers to use while | |
1911e6e5 RS |
2206 | processing @code{imenu-generic-expression}, to override the syntax table |
2207 | of the current buffer. Each element should have this form: | |
a9f0a989 RS |
2208 | |
2209 | @example | |
2210 | (@var{characters} . @var{syntax-description}) | |
2211 | @end example | |
2212 | ||
2213 | The @sc{car}, @var{characters}, can be either a character or a string. | |
2214 | The element says to give that character or characters the syntax | |
2215 | specified by @var{syntax-description}, which is passed to | |
2216 | @code{modify-syntax-entry} (@pxref{Syntax Table Functions}). | |
2217 | ||
2218 | This feature is typically used to give word syntax to characters which | |
2219 | normally have symbol syntax, and thus to simplify | |
2220 | @code{imenu-generic-expression} and speed up matching. | |
2221 | For example, Fortran mode uses it this way: | |
2222 | ||
2223 | @example | |
5a5d2aec | 2224 | (setq imenu-syntax-alist '(("_$" . "w"))) |
a9f0a989 RS |
2225 | @end example |
2226 | ||
10ee4e90 LK |
2227 | The @code{imenu-generic-expression} regular expressions can then use |
2228 | @samp{\\sw+} instead of @samp{\\(\\sw\\|\\s_\\)+}. Note that this | |
2229 | technique may be inconvenient when the mode needs to limit the initial | |
2230 | character of a name to a smaller set of characters than are allowed in | |
2231 | the rest of a name. | |
f9f59935 | 2232 | |
969fe9b5 | 2233 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
2234 | @end defvar |
2235 | ||
2236 | Another way to customize Imenu for a major mode is to set the | |
2237 | variables @code{imenu-prev-index-position-function} and | |
969fe9b5 | 2238 | @code{imenu-extract-index-name-function}: |
f9f59935 RS |
2239 | |
2240 | @defvar imenu-prev-index-position-function | |
05aea714 | 2241 | If this variable is non-@code{nil}, its value should be a function that |
a40d4712 PR |
2242 | finds the next ``definition'' to put in the buffer index, scanning |
2243 | backward in the buffer from point. It should return @code{nil} if it | |
5fe3b9bc | 2244 | doesn't find another ``definition'' before point. Otherwise it should |
a40d4712 PR |
2245 | leave point at the place it finds a ``definition,'' and return any |
2246 | non-@code{nil} value. | |
f9f59935 | 2247 | |
969fe9b5 | 2248 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
2249 | @end defvar |
2250 | ||
2251 | @defvar imenu-extract-index-name-function | |
2252 | If this variable is non-@code{nil}, its value should be a function to | |
969fe9b5 RS |
2253 | return the name for a definition, assuming point is in that definition |
2254 | as the @code{imenu-prev-index-position-function} function would leave | |
2255 | it. | |
f9f59935 | 2256 | |
969fe9b5 | 2257 | Setting this variable makes it buffer-local in the current buffer. |
f9f59935 RS |
2258 | @end defvar |
2259 | ||
969fe9b5 | 2260 | The last way to customize Imenu for a major mode is to set the |
a40d4712 | 2261 | variable @code{imenu-create-index-function}: |
969fe9b5 | 2262 | |
f9f59935 | 2263 | @defvar imenu-create-index-function |
10ee4e90 LK |
2264 | This variable specifies the function to use for creating a buffer |
2265 | index. The function should take no arguments, and return an index | |
2266 | alist for the current buffer. It is called within | |
2267 | @code{save-excursion}, so where it leaves point makes no difference. | |
f9f59935 | 2268 | |
10ee4e90 LK |
2269 | The index alist can have three types of elements. Simple elements |
2270 | look like this: | |
f9f59935 | 2271 | |
10ee4e90 LK |
2272 | @example |
2273 | (@var{index-name} . @var{index-position}) | |
2274 | @end example | |
f9f59935 | 2275 | |
10ee4e90 LK |
2276 | Selecting a simple element has the effect of moving to position |
2277 | @var{index-position} in the buffer. Special elements look like this: | |
f9f59935 | 2278 | |
10ee4e90 LK |
2279 | @example |
2280 | (@var{index-name} @var{index-position} @var{function} @var{arguments}@dots{}) | |
2281 | @end example | |
f9f59935 | 2282 | |
10ee4e90 | 2283 | Selecting a special element performs: |
f9f59935 RS |
2284 | |
2285 | @example | |
c22c5da6 | 2286 | (funcall @var{function} |
10ee4e90 | 2287 | @var{index-name} @var{index-position} @var{arguments}@dots{}) |
f9f59935 RS |
2288 | @end example |
2289 | ||
10ee4e90 LK |
2290 | A nested sub-alist element looks like this: |
2291 | ||
2292 | @example | |
f008b925 | 2293 | (@var{menu-title} @var{sub-alist}) |
10ee4e90 LK |
2294 | @end example |
2295 | ||
f008b925 | 2296 | It creates the submenu @var{menu-title} specified by @var{sub-alist}. |
10ee4e90 | 2297 | |
f008b925 | 2298 | The default value of @code{imenu-create-index-function} is |
342fd6cd RS |
2299 | @code{imenu-default-create-index-function}. This function calls the |
2300 | value of @code{imenu-prev-index-position-function} and the value of | |
10ee4e90 LK |
2301 | @code{imenu-extract-index-name-function} to produce the index alist. |
2302 | However, if either of these two variables is @code{nil}, the default | |
2303 | function uses @code{imenu-generic-expression} instead. | |
2304 | ||
2305 | Setting this variable makes it buffer-local in the current buffer. | |
f9f59935 RS |
2306 | @end defvar |
2307 | ||
2308 | @node Font Lock Mode | |
2309 | @section Font Lock Mode | |
2310 | @cindex Font Lock Mode | |
2311 | ||
2312 | @dfn{Font Lock mode} is a feature that automatically attaches | |
2313 | @code{face} properties to certain parts of the buffer based on their | |
2314 | syntactic role. How it parses the buffer depends on the major mode; | |
a40d4712 | 2315 | most major modes define syntactic criteria for which faces to use in |
969fe9b5 | 2316 | which contexts. This section explains how to customize Font Lock for a |
a40d4712 | 2317 | particular major mode. |
f9f59935 | 2318 | |
4f45f65e LK |
2319 | Font Lock mode finds text to highlight in two ways: through |
2320 | syntactic parsing based on the syntax table, and through searching | |
2321 | (usually for regular expressions). Syntactic fontification happens | |
2322 | first; it finds comments and string constants and highlights them. | |
2323 | Search-based fontification happens second. | |
f9f59935 RS |
2324 | |
2325 | @menu | |
ec9b0882 RS |
2326 | * Font Lock Basics:: Overview of customizing Font Lock. |
2327 | * Search-based Fontification:: Fontification based on regexps. | |
03de4399 | 2328 | * Customizing Keywords:: Customizing search-based fontification. |
ec9b0882 RS |
2329 | * Other Font Lock Variables:: Additional customization facilities. |
2330 | * Levels of Font Lock:: Each mode can define alternative levels | |
2331 | so that the user can select more or less. | |
2332 | * Precalculated Fontification:: How Lisp programs that produce the buffer | |
2333 | contents can also specify how to fontify it. | |
2334 | * Faces for Font Lock:: Special faces specifically for Font Lock. | |
4f45f65e LK |
2335 | * Syntactic Font Lock:: Fontification based on syntax tables. |
2336 | * Setting Syntax Properties:: Defining character syntax based on context | |
ec9b0882 | 2337 | using the Font Lock mechanism. |
f9f59935 RS |
2338 | @end menu |
2339 | ||
2340 | @node Font Lock Basics | |
2341 | @subsection Font Lock Basics | |
2342 | ||
2343 | There are several variables that control how Font Lock mode highlights | |
2344 | text. But major modes should not set any of these variables directly. | |
86494bd5 | 2345 | Instead, they should set @code{font-lock-defaults} as a buffer-local |
969fe9b5 RS |
2346 | variable. The value assigned to this variable is used, if and when Font |
2347 | Lock mode is enabled, to set all the other variables. | |
f9f59935 RS |
2348 | |
2349 | @defvar font-lock-defaults | |
2350 | This variable is set by major modes, as a buffer-local variable, to | |
4f45f65e LK |
2351 | specify how to fontify text in that mode. It automatically becomes |
2352 | buffer-local when you set it. The value should look like this: | |
f9f59935 RS |
2353 | |
2354 | @example | |
4f45f65e LK |
2355 | (@var{keywords} [@var{keywords-only} [@var{case-fold} |
2356 | [@var{syntax-alist} [@var{syntax-begin} @var{other-vars}@dots{}]]]]) | |
f9f59935 RS |
2357 | @end example |
2358 | ||
2359 | The first element, @var{keywords}, indirectly specifies the value of | |
4f45f65e LK |
2360 | @code{font-lock-keywords} which directs search-based fontification. |
2361 | It can be a symbol, a variable or a function whose value is the list | |
2362 | to use for @code{font-lock-keywords}. It can also be a list of | |
2363 | several such symbols, one for each possible level of fontification. | |
2364 | The first symbol specifies how to do level 1 fontification, the second | |
2365 | symbol how to do level 2, and so on. @xref{Levels of Font Lock}. | |
f9f59935 RS |
2366 | |
2367 | The second element, @var{keywords-only}, specifies the value of the | |
a9f0a989 | 2368 | variable @code{font-lock-keywords-only}. If this is non-@code{nil}, |
969fe9b5 | 2369 | syntactic fontification (of strings and comments) is not performed. |
4f45f65e | 2370 | @xref{Syntactic Font Lock}. |
f9f59935 RS |
2371 | |
2372 | The third element, @var{case-fold}, specifies the value of | |
4f45f65e LK |
2373 | @code{font-lock-keywords-case-fold-search}. If it is non-@code{nil}, |
2374 | Font Lock mode ignores case when searching as directed by | |
969fe9b5 | 2375 | @code{font-lock-keywords}. |
f9f59935 | 2376 | |
4f45f65e LK |
2377 | If the fourth element, @var{syntax-alist}, is non-@code{nil}, it |
2378 | should be a list of cons cells of the form @code{(@var{char-or-string} | |
f9f59935 | 2379 | . @var{string})}. These are used to set up a syntax table for |
4f45f65e LK |
2380 | syntactic fontification (@pxref{Syntax Table Functions}). The |
2381 | resulting syntax table is stored in @code{font-lock-syntax-table}. | |
f9f59935 RS |
2382 | |
2383 | The fifth element, @var{syntax-begin}, specifies the value of | |
3c8572f5 LK |
2384 | @code{font-lock-beginning-of-syntax-function}. We recommend setting |
2385 | this variable to @code{nil} and using @code{syntax-begin-function} | |
2386 | instead. | |
f9f59935 | 2387 | |
a40d4712 PR |
2388 | All the remaining elements (if any) are collectively called |
2389 | @var{other-vars}. Each of these elements should have the form | |
4f45f65e LK |
2390 | @code{(@var{variable} . @var{value})}---which means, make |
2391 | @var{variable} buffer-local and then set it to @var{value}. You can | |
2392 | use these @var{other-vars} to set other variables that affect | |
2393 | fontification, aside from those you can control with the first five | |
2394 | elements. @xref{Other Font Lock Variables}. | |
f9f59935 RS |
2395 | @end defvar |
2396 | ||
2397 | @node Search-based Fontification | |
2398 | @subsection Search-based Fontification | |
2399 | ||
2400 | The most important variable for customizing Font Lock mode is | |
2401 | @code{font-lock-keywords}. It specifies the search criteria for | |
4f45f65e LK |
2402 | search-based fontification. You should specify the value of this |
2403 | variable with @var{keywords} in @code{font-lock-defaults}. | |
f9f59935 RS |
2404 | |
2405 | @defvar font-lock-keywords | |
2406 | This variable's value is a list of the keywords to highlight. Be | |
969fe9b5 RS |
2407 | careful when composing regular expressions for this list; a poorly |
2408 | written pattern can dramatically slow things down! | |
f9f59935 RS |
2409 | @end defvar |
2410 | ||
2411 | Each element of @code{font-lock-keywords} specifies how to find | |
969fe9b5 RS |
2412 | certain cases of text, and how to highlight those cases. Font Lock mode |
2413 | processes the elements of @code{font-lock-keywords} one by one, and for | |
2414 | each element, it finds and handles all matches. Ordinarily, once | |
2415 | part of the text has been fontified already, this cannot be overridden | |
2416 | by a subsequent match in the same text; but you can specify different | |
199bb209 | 2417 | behavior using the @var{override} element of a @var{subexp-highlighter}. |
969fe9b5 RS |
2418 | |
2419 | Each element of @code{font-lock-keywords} should have one of these | |
2420 | forms: | |
f9f59935 RS |
2421 | |
2422 | @table @code | |
2423 | @item @var{regexp} | |
2424 | Highlight all matches for @var{regexp} using | |
2425 | @code{font-lock-keyword-face}. For example, | |
2426 | ||
2427 | @example | |
199bb209 | 2428 | ;; @r{Highlight occurrences of the word @samp{foo}} |
f9f59935 RS |
2429 | ;; @r{using @code{font-lock-keyword-face}.} |
2430 | "\\<foo\\>" | |
2431 | @end example | |
2432 | ||
199bb209 LK |
2433 | The function @code{regexp-opt} (@pxref{Regexp Functions}) is useful |
2434 | for calculating optimal regular expressions to match a number of | |
2435 | different keywords. | |
f9f59935 RS |
2436 | |
2437 | @item @var{function} | |
2438 | Find text by calling @var{function}, and highlight the matches | |
2439 | it finds using @code{font-lock-keyword-face}. | |
2440 | ||
2441 | When @var{function} is called, it receives one argument, the limit of | |
022cb162 | 2442 | the search; it should begin searching at point, and not search beyond the |
07f7b41c RS |
2443 | limit. It should return non-@code{nil} if it succeeds, and set the |
2444 | match data to describe the match that was found. Returning @code{nil} | |
2445 | indicates failure of the search. | |
2446 | ||
2447 | Fontification will call @var{function} repeatedly with the same limit, | |
2448 | and with point where the previous invocation left it, until | |
2449 | @var{function} fails. On failure, @var{function} need not reset point | |
2450 | in any particular way. | |
f9f59935 | 2451 | |
199bb209 | 2452 | @item (@var{matcher} . @var{subexp}) |
86494bd5 | 2453 | In this kind of element, @var{matcher} is either a regular |
f9f59935 | 2454 | expression or a function, as described above. The @sc{cdr}, |
199bb209 | 2455 | @var{subexp}, specifies which subexpression of @var{matcher} should be |
969fe9b5 | 2456 | highlighted (instead of the entire text that @var{matcher} matched). |
f9f59935 RS |
2457 | |
2458 | @example | |
8241495d | 2459 | ;; @r{Highlight the @samp{bar} in each occurrence of @samp{fubar},} |
f9f59935 RS |
2460 | ;; @r{using @code{font-lock-keyword-face}.} |
2461 | ("fu\\(bar\\)" . 1) | |
2462 | @end example | |
2463 | ||
969fe9b5 | 2464 | If you use @code{regexp-opt} to produce the regular expression |
342fd6cd | 2465 | @var{matcher}, you can use @code{regexp-opt-depth} (@pxref{Regexp |
199bb209 | 2466 | Functions}) to calculate the value for @var{subexp}. |
f9f59935 | 2467 | |
3ab66863 | 2468 | @item (@var{matcher} . @var{facespec}) |
ed35c736 RS |
2469 | In this kind of element, @var{facespec} is an expression whose value |
2470 | specifies the face to use for highlighting. In the simplest case, | |
2471 | @var{facespec} is a Lisp variable (a symbol) whose value is a face | |
2472 | name. | |
f9f59935 RS |
2473 | |
2474 | @example | |
2475 | ;; @r{Highlight occurrences of @samp{fubar},} | |
2476 | ;; @r{using the face which is the value of @code{fubar-face}.} | |
2477 | ("fubar" . fubar-face) | |
2478 | @end example | |
2479 | ||
ed35c736 | 2480 | However, @var{facespec} can also evaluate to a list of this form: |
fdba9ef4 RS |
2481 | |
2482 | @example | |
2483 | (face @var{face} @var{prop1} @var{val1} @var{prop2} @var{val2}@dots{}) | |
2484 | @end example | |
2485 | ||
ed35c736 | 2486 | @noindent |
199bb209 LK |
2487 | to specify the face @var{face} and various additional text properties |
2488 | to put on the text that matches. If you do this, be sure to add the | |
2489 | other text property names that you set in this way to the value of | |
2490 | @code{font-lock-extra-managed-props} so that the properties will also | |
2491 | be cleared out when they are no longer appropriate. Alternatively, | |
2492 | you can set the variable @code{font-lock-unfontify-region-function} to | |
4f45f65e LK |
2493 | a function that clears these properties. @xref{Other Font Lock |
2494 | Variables}. | |
fdba9ef4 | 2495 | |
199bb209 LK |
2496 | @item (@var{matcher} . @var{subexp-highlighter}) |
2497 | In this kind of element, @var{subexp-highlighter} is a list | |
f9f59935 | 2498 | which specifies how to highlight matches found by @var{matcher}. |
199bb209 | 2499 | It has the form: |
f9f59935 RS |
2500 | |
2501 | @example | |
199bb209 | 2502 | (@var{subexp} @var{facespec} [[@var{override} [@var{laxmatch}]]) |
f9f59935 RS |
2503 | @end example |
2504 | ||
2505 | The @sc{car}, @var{subexp}, is an integer specifying which subexpression | |
969fe9b5 | 2506 | of the match to fontify (0 means the entire matching text). The second |
ed35c736 RS |
2507 | subelement, @var{facespec}, is an expression whose value specifies the |
2508 | face, as described above. | |
f9f59935 | 2509 | |
199bb209 LK |
2510 | The last two values in @var{subexp-highlighter}, @var{override} and |
2511 | @var{laxmatch}, are optional flags. If @var{override} is @code{t}, | |
2512 | this element can override existing fontification made by previous | |
2513 | elements of @code{font-lock-keywords}. If it is @code{keep}, then | |
2514 | each character is fontified if it has not been fontified already by | |
2515 | some other element. If it is @code{prepend}, the face specified by | |
3ab66863 RS |
2516 | @var{facespec} is added to the beginning of the @code{font-lock-face} |
2517 | property. If it is @code{append}, the face is added to the end of the | |
bda7c6dd | 2518 | @code{font-lock-face} property. |
f9f59935 RS |
2519 | |
2520 | If @var{laxmatch} is non-@code{nil}, it means there should be no error | |
2521 | if there is no subexpression numbered @var{subexp} in @var{matcher}. | |
99b62845 GM |
2522 | Obviously, fontification of the subexpression numbered @var{subexp} will |
2523 | not occur. However, fontification of other subexpressions (and other | |
2524 | regexps) will continue. If @var{laxmatch} is @code{nil}, and the | |
a3ee0299 | 2525 | specified subexpression is missing, then an error is signaled which |
99b62845 | 2526 | terminates search-based fontification. |
f9f59935 RS |
2527 | |
2528 | Here are some examples of elements of this kind, and what they do: | |
2529 | ||
2530 | @smallexample | |
199bb209 LK |
2531 | ;; @r{Highlight occurrences of either @samp{foo} or @samp{bar}, using} |
2532 | ;; @r{@code{foo-bar-face}, even if they have already been highlighted.} | |
f9f59935 RS |
2533 | ;; @r{@code{foo-bar-face} should be a variable whose value is a face.} |
2534 | ("foo\\|bar" 0 foo-bar-face t) | |
2535 | ||
8241495d | 2536 | ;; @r{Highlight the first subexpression within each occurrence} |
f9f59935 RS |
2537 | ;; @r{that the function @code{fubar-match} finds,} |
2538 | ;; @r{using the face which is the value of @code{fubar-face}.} | |
2539 | (fubar-match 1 fubar-face) | |
2540 | @end smallexample | |
2541 | ||
199bb209 LK |
2542 | @item (@var{matcher} . @var{anchored-highlighter}) |
2543 | In this kind of element, @var{anchored-highlighter} specifies how to | |
2544 | highlight text that follows a match found by @var{matcher}. So a | |
2545 | match found by @var{matcher} acts as the anchor for further searches | |
2546 | specified by @var{anchored-highlighter}. @var{anchored-highlighter} | |
2547 | is a list of the following form: | |
f9f59935 | 2548 | |
199bb209 LK |
2549 | @example |
2550 | (@var{anchored-matcher} @var{pre-form} @var{post-form} | |
2551 | @var{subexp-highlighters}@dots{}) | |
2552 | @end example | |
f9f59935 | 2553 | |
199bb209 LK |
2554 | Here, @var{anchored-matcher}, like @var{matcher}, is either a regular |
2555 | expression or a function. After a match of @var{matcher} is found, | |
2556 | point is at the end of the match. Now, Font Lock evaluates the form | |
2557 | @var{pre-form}. Then it searches for matches of | |
2558 | @var{anchored-matcher} and uses @var{subexp-highlighters} to highlight | |
2559 | these. A @var{subexp-highlighter} is as described above. Finally, | |
2560 | Font Lock evaluates @var{post-form}. | |
2561 | ||
2562 | The forms @var{pre-form} and @var{post-form} can be used to initialize | |
2563 | before, and cleanup after, @var{anchored-matcher} is used. Typically, | |
2564 | @var{pre-form} is used to move point to some position relative to the | |
2565 | match of @var{matcher}, before starting with @var{anchored-matcher}. | |
2566 | @var{post-form} might be used to move back, before resuming with | |
2567 | @var{matcher}. | |
2568 | ||
2569 | After Font Lock evaluates @var{pre-form}, it does not search for | |
2570 | @var{anchored-matcher} beyond the end of the line. However, if | |
2571 | @var{pre-form} returns a buffer position that is greater than the | |
2572 | position of point after @var{pre-form} is evaluated, then the position | |
2573 | returned by @var{pre-form} is used as the limit of the search instead. | |
2574 | It is generally a bad idea to return a position greater than the end | |
2575 | of the line; in other words, the @var{anchored-matcher} search should | |
2576 | not span lines. | |
f9f59935 | 2577 | |
199bb209 | 2578 | For example, |
f9f59935 | 2579 | |
199bb209 LK |
2580 | @smallexample |
2581 | ;; @r{Highlight occurrences of the word @samp{item} following} | |
2582 | ;; @r{an occurrence of the word @samp{anchor} (on the same line)} | |
2583 | ;; @r{in the value of @code{item-face}.} | |
2584 | ("\\<anchor\\>" "\\<item\\>" nil nil (0 item-face)) | |
2585 | @end smallexample | |
f9f59935 | 2586 | |
199bb209 LK |
2587 | Here, @var{pre-form} and @var{post-form} are @code{nil}. Therefore |
2588 | searching for @samp{item} starts at the end of the match of | |
2589 | @samp{anchor}, and searching for subsequent instances of @samp{anchor} | |
2590 | resumes from where searching for @samp{item} concluded. | |
f9f59935 | 2591 | |
199bb209 LK |
2592 | @item (@var{matcher} @var{highlighters}@dots{}) |
2593 | This sort of element specifies several @var{highlighter} lists for a | |
2594 | single @var{matcher}. A @var{highlighter} list can be of the type | |
2595 | @var{subexp-highlighter} or @var{anchored-highlighter} as described | |
2596 | above. | |
f9f59935 | 2597 | |
199bb209 | 2598 | For example, |
f9f59935 | 2599 | |
199bb209 LK |
2600 | @smallexample |
2601 | ;; @r{Highlight occurrences of the word @samp{anchor} in the value} | |
2602 | ;; @r{of @code{anchor-face}, and subsequent occurrences of the word} | |
2603 | ;; @r{@samp{item} (on the same line) in the value of @code{item-face}.} | |
2604 | ("\\<anchor\\>" (0 anchor-face) | |
2605 | ("\\<item\\>" nil nil (0 item-face))) | |
2606 | @end smallexample | |
f9f59935 RS |
2607 | |
2608 | @item (eval . @var{form}) | |
969fe9b5 | 2609 | Here @var{form} is an expression to be evaluated the first time |
f9f59935 | 2610 | this value of @code{font-lock-keywords} is used in a buffer. |
969fe9b5 | 2611 | Its value should have one of the forms described in this table. |
f9f59935 RS |
2612 | @end table |
2613 | ||
4f45f65e | 2614 | @vindex font-lock-multiline |
f9f59935 RS |
2615 | @strong{Warning:} Do not design an element of @code{font-lock-keywords} |
2616 | to match text which spans lines; this does not work reliably. While | |
2617 | @code{font-lock-fontify-buffer} handles multi-line patterns correctly, | |
2618 | updating when you edit the buffer does not, since it considers text one | |
8ba2808b SM |
2619 | line at a time. If you have patterns that typically only span one |
2620 | line but can occasionally span two or three, such as | |
199bb209 | 2621 | @samp{<title>...</title>}, you can ask Font Lock to be more careful by |
8ba2808b SM |
2622 | setting @code{font-lock-multiline} to @code{t}. But it still will not |
2623 | work in all cases. | |
f9f59935 | 2624 | |
4f45f65e LK |
2625 | You can use @var{case-fold} in @code{font-lock-defaults} to specify |
2626 | the value of @code{font-lock-keywords-case-fold-search} which says | |
2627 | whether search-based fontification should be case-insensitive. | |
f9f59935 RS |
2628 | |
2629 | @defvar font-lock-keywords-case-fold-search | |
969fe9b5 RS |
2630 | Non-@code{nil} means that regular expression matching for the sake of |
2631 | @code{font-lock-keywords} should be case-insensitive. | |
f9f59935 RS |
2632 | @end defvar |
2633 | ||
03de4399 RS |
2634 | @node Customizing Keywords |
2635 | @subsection Customizing Search-Based Fontification | |
2636 | ||
2637 | You can use @code{font-lock-add-keywords} to add additional | |
4f45f65e LK |
2638 | search-based fontification rules to a major mode, and |
2639 | @code{font-lock-remove-keywords} to removes rules. | |
2640 | ||
2641 | @defun font-lock-add-keywords mode keywords &optional append | |
03de4399 RS |
2642 | This function adds highlighting @var{keywords}, for the current buffer |
2643 | or for major mode @var{mode}. The argument @var{keywords} should be a | |
2644 | list with the same format as the variable @code{font-lock-keywords}. | |
2645 | ||
2646 | If @var{mode} is a symbol which is a major mode command name, such as | |
2647 | @code{c-mode}, the effect is that enabling Font Lock mode in | |
2648 | @var{mode} will add @var{keywords} to @code{font-lock-keywords}. | |
2649 | Calling with a non-@code{nil} value of @var{mode} is correct only in | |
2650 | your @file{~/.emacs} file. | |
2651 | ||
2652 | If @var{mode} is @code{nil}, this function adds @var{keywords} to | |
2653 | @code{font-lock-keywords} in the current buffer. This way of calling | |
2654 | @code{font-lock-add-keywords} is usually used in mode hook functions. | |
4f45f65e LK |
2655 | |
2656 | By default, @var{keywords} are added at the beginning of | |
2657 | @code{font-lock-keywords}. If the optional argument @var{append} is | |
2658 | @code{set}, they are used to replace the value of | |
2659 | @code{font-lock-keywords}. If @var{append} is any other | |
2660 | non-@code{nil} value, they are added at the end of | |
2661 | @code{font-lock-keywords}. | |
f9f59935 | 2662 | |
03de4399 RS |
2663 | Some modes provide specialized support you can use in additional |
2664 | highlighting patterns. See the variables | |
2665 | @code{c-font-lock-extra-types}, @code{c++-font-lock-extra-types}, | |
342fd6cd | 2666 | and @code{java-font-lock-extra-types}, for example. |
03de4399 RS |
2667 | |
2668 | @strong{Warning:} major mode functions must not call | |
2669 | @code{font-lock-add-keywords} under any circumstances, either directly | |
2670 | or indirectly, except through their mode hooks. (Doing so would lead | |
2671 | to incorrect behavior for some minor modes.) They should set up their | |
2672 | rules for search-based fontification by setting | |
2673 | @code{font-lock-keywords}. | |
2674 | @end defun | |
2675 | ||
2676 | @defun font-lock-remove-keywords mode keywords | |
2677 | This function removes @var{keywords} from @code{font-lock-keywords} | |
2678 | for the current buffer or for major mode @var{mode}. As in | |
2679 | @code{font-lock-add-keywords}, @var{mode} should be a major mode | |
2680 | command name or @code{nil}. All the caveats and requirments for | |
2681 | @code{font-lock-add-keywords} apply here too. | |
2682 | @end defun | |
2683 | ||
2684 | For example, this code | |
f9f59935 | 2685 | |
4f45f65e LK |
2686 | @smallexample |
2687 | (font-lock-add-keywords 'c-mode | |
2688 | '(("\\<\\(FIXME\\):" 1 font-lock-warning-face prepend) | |
2689 | ("\\<\\(and\\|or\\|not\\)\\>" . font-lock-keyword-face))) | |
2690 | @end smallexample | |
f9f59935 | 2691 | |
03de4399 | 2692 | @noindent |
4f45f65e LK |
2693 | adds two fontification patterns for C mode: one to fontify the word |
2694 | @samp{FIXME}, even in comments, and another to fontify the words | |
2695 | @samp{and}, @samp{or} and @samp{not} as keywords. | |
2696 | ||
03de4399 RS |
2697 | @noindent |
2698 | That example affects only C mode proper. To add the same patterns to | |
2699 | C mode @emph{and} all modes derived from it, do this instead: | |
4f45f65e | 2700 | |
03de4399 RS |
2701 | @smallexample |
2702 | (add-hook 'c-mode-hook | |
2703 | (lambda () | |
2704 | (font-lock-add-keywords nil | |
2705 | '(("\\<\\(FIXME\\):" 1 font-lock-warning-face prepend) | |
2706 | ("\\<\\(and\\|or\\|not\\)\\>" . | |
2707 | font-lock-keyword-face))))) | |
2708 | @end smallexample | |
4f45f65e LK |
2709 | |
2710 | @node Other Font Lock Variables | |
2711 | @subsection Other Font Lock Variables | |
2712 | ||
2713 | This section describes additional variables that a major mode can | |
2714 | set by means of @var{other-vars} in @code{font-lock-defaults} | |
2715 | (@pxref{Font Lock Basics}). | |
f9f59935 RS |
2716 | |
2717 | @defvar font-lock-mark-block-function | |
969fe9b5 RS |
2718 | If this variable is non-@code{nil}, it should be a function that is |
2719 | called with no arguments, to choose an enclosing range of text for | |
aaac1251 | 2720 | refontification for the command @kbd{M-o M-o} |
969fe9b5 RS |
2721 | (@code{font-lock-fontify-block}). |
2722 | ||
2723 | The function should report its choice by placing the region around it. | |
2724 | A good choice is a range of text large enough to give proper results, | |
2725 | but not too large so that refontification becomes slow. Typical values | |
2726 | are @code{mark-defun} for programming modes or @code{mark-paragraph} for | |
2727 | textual modes. | |
f9f59935 RS |
2728 | @end defvar |
2729 | ||
fdba9ef4 | 2730 | @defvar font-lock-extra-managed-props |
4f45f65e LK |
2731 | This variable specifies additional properties (other than |
2732 | @code{font-lock-face}) that are being managed by Font Lock mode. It | |
2733 | is used by @code{font-lock-default-unfontify-region}, which normally | |
2734 | only manages the @code{font-lock-face} property. If you want Font | |
2735 | Lock to manage other properties as well, you must specify them in a | |
2736 | @var{facespec} in @code{font-lock-keywords} as well as add them to | |
2737 | this list. @xref{Search-based Fontification}. | |
fdba9ef4 RS |
2738 | @end defvar |
2739 | ||
4f45f65e LK |
2740 | @defvar font-lock-fontify-buffer-function |
2741 | Function to use for fontifying the buffer. The default value is | |
2742 | @code{font-lock-default-fontify-buffer}. | |
2743 | @end defvar | |
8ba2808b | 2744 | |
4f45f65e LK |
2745 | @defvar font-lock-unfontify-buffer-function |
2746 | Function to use for unfontifying the buffer. This is used when | |
2747 | turning off Font Lock mode. The default value is | |
2748 | @code{font-lock-default-unfontify-buffer}. | |
2749 | @end defvar | |
2750 | ||
2751 | @defvar font-lock-fontify-region-function | |
2752 | Function to use for fontifying a region. It should take two | |
2753 | arguments, the beginning and end of the region, and an optional third | |
2754 | argument @var{verbose}. If @var{verbose} is non-@code{nil}, the | |
2755 | function should print status messages. The default value is | |
2756 | @code{font-lock-default-fontify-region}. | |
2757 | @end defvar | |
2758 | ||
2759 | @defvar font-lock-unfontify-region-function | |
2760 | Function to use for unfontifying a region. It should take two | |
2761 | arguments, the beginning and end of the region. The default value is | |
2762 | @code{font-lock-default-unfontify-region}. | |
8ba2808b SM |
2763 | @end defvar |
2764 | ||
3a05b1e4 RS |
2765 | @defvar font-lock-lines-before |
2766 | This variable specifies the number of extra lines to consider when | |
2767 | refontifying the buffer after each text change. Font lock begins | |
2768 | refontifying from that number of lines before the changed region. The | |
34b50776 | 2769 | default is 0, but using a larger value can be useful for coping with |
3a05b1e4 RS |
2770 | multi-line patterns. |
2771 | @end defvar | |
2772 | ||
4f45f65e LK |
2773 | @ignore |
2774 | @defvar font-lock-inhibit-thing-lock | |
2775 | List of Font Lock mode related modes that should not be turned on. | |
2776 | Currently, valid mode names are @code{fast-lock-mode}, | |
2777 | @code{jit-lock-mode} and @code{lazy-lock-mode}. | |
2778 | @end defvar | |
2779 | @end ignore | |
2780 | ||
f9f59935 RS |
2781 | @node Levels of Font Lock |
2782 | @subsection Levels of Font Lock | |
2783 | ||
2784 | Many major modes offer three different levels of fontification. You | |
2785 | can define multiple levels by using a list of symbols for @var{keywords} | |
2786 | in @code{font-lock-defaults}. Each symbol specifies one level of | |
2787 | fontification; it is up to the user to choose one of these levels. The | |
2788 | chosen level's symbol value is used to initialize | |
2789 | @code{font-lock-keywords}. | |
2790 | ||
969fe9b5 RS |
2791 | Here are the conventions for how to define the levels of |
2792 | fontification: | |
2793 | ||
f9f59935 RS |
2794 | @itemize @bullet |
2795 | @item | |
2796 | Level 1: highlight function declarations, file directives (such as include or | |
2797 | import directives), strings and comments. The idea is speed, so only | |
2798 | the most important and top-level components are fontified. | |
2799 | ||
2800 | @item | |
969fe9b5 RS |
2801 | Level 2: in addition to level 1, highlight all language keywords, |
2802 | including type names that act like keywords, as well as named constant | |
2803 | values. The idea is that all keywords (either syntactic or semantic) | |
2804 | should be fontified appropriately. | |
f9f59935 RS |
2805 | |
2806 | @item | |
969fe9b5 RS |
2807 | Level 3: in addition to level 2, highlight the symbols being defined in |
2808 | function and variable declarations, and all builtin function names, | |
2809 | wherever they appear. | |
f9f59935 RS |
2810 | @end itemize |
2811 | ||
651f7556 CW |
2812 | @node Precalculated Fontification |
2813 | @subsection Precalculated Fontification | |
2814 | ||
ec9b0882 | 2815 | In addition to using @code{font-lock-defaults} for search-based |
651f7556 CW |
2816 | fontification, you may use the special character property |
2817 | @code{font-lock-face} (@pxref{Special Properties}). This property | |
2818 | acts just like the explicit @code{face} property, but its activation | |
2819 | is toggled when the user calls @kbd{M-x font-lock-mode}. Using | |
06862374 | 2820 | @code{font-lock-face} is especially convenient for special modes |
651f7556 CW |
2821 | which construct their text programmatically, such as |
2822 | @code{list-buffers} and @code{occur}. | |
2823 | ||
0ab0c481 | 2824 | If your mode does not use any of the other machinery of Font Lock |
4f45f65e LK |
2825 | (i.e. it only uses the @code{font-lock-face} property), it should not |
2826 | set the variable @code{font-lock-defaults}. That way, it will not | |
2827 | cause loading of the @file{font-lock} library. | |
0ab0c481 | 2828 | |
f9f59935 RS |
2829 | @node Faces for Font Lock |
2830 | @subsection Faces for Font Lock | |
2831 | ||
2832 | You can make Font Lock mode use any face, but several faces are | |
2833 | defined specifically for Font Lock mode. Each of these symbols is both | |
2834 | a face name, and a variable whose default value is the symbol itself. | |
2835 | Thus, the default value of @code{font-lock-comment-face} is | |
2836 | @code{font-lock-comment-face}. This means you can write | |
2837 | @code{font-lock-comment-face} in a context such as | |
2838 | @code{font-lock-keywords} where a face-name-valued expression is used. | |
2839 | ||
2840 | @table @code | |
2841 | @item font-lock-comment-face | |
2842 | @vindex font-lock-comment-face | |
f9f59935 RS |
2843 | Used (typically) for comments. |
2844 | ||
4f45f65e LK |
2845 | @item font-lock-comment-delimiter-face |
2846 | @vindex font-lock-comment-delimiter-face | |
2847 | Used (typically) for comments delimiters. | |
2848 | ||
ec9b0882 RS |
2849 | @item font-lock-doc-face |
2850 | @vindex font-lock-doc-face | |
2851 | Used (typically) for documentation strings in the code. | |
2852 | ||
f9f59935 RS |
2853 | @item font-lock-string-face |
2854 | @vindex font-lock-string-face | |
f9f59935 RS |
2855 | Used (typically) for string constants. |
2856 | ||
2857 | @item font-lock-keyword-face | |
2858 | @vindex font-lock-keyword-face | |
f9f59935 RS |
2859 | Used (typically) for keywords---names that have special syntactic |
2860 | significance, like @code{for} and @code{if} in C. | |
2861 | ||
2862 | @item font-lock-builtin-face | |
2863 | @vindex font-lock-builtin-face | |
f9f59935 RS |
2864 | Used (typically) for built-in function names. |
2865 | ||
2866 | @item font-lock-function-name-face | |
2867 | @vindex font-lock-function-name-face | |
f9f59935 | 2868 | Used (typically) for the name of a function being defined or declared, |
177c0ea7 | 2869 | in a function definition or declaration. |
f9f59935 RS |
2870 | |
2871 | @item font-lock-variable-name-face | |
2872 | @vindex font-lock-variable-name-face | |
f9f59935 RS |
2873 | Used (typically) for the name of a variable being defined or declared, |
2874 | in a variable definition or declaration. | |
2875 | ||
2876 | @item font-lock-type-face | |
2877 | @vindex font-lock-type-face | |
f9f59935 RS |
2878 | Used (typically) for names of user-defined data types, |
2879 | where they are defined and where they are used. | |
2880 | ||
2881 | @item font-lock-constant-face | |
2882 | @vindex font-lock-constant-face | |
f9f59935 RS |
2883 | Used (typically) for constant names. |
2884 | ||
c22c5da6 LK |
2885 | @item font-lock-preprocessor-face |
2886 | @vindex font-lock-preprocessor-face | |
fdba9ef4 RS |
2887 | Used (typically) for preprocessor commands. |
2888 | ||
f9f59935 RS |
2889 | @item font-lock-warning-face |
2890 | @vindex font-lock-warning-face | |
f9f59935 RS |
2891 | Used (typically) for constructs that are peculiar, or that greatly |
2892 | change the meaning of other text. For example, this is used for | |
2893 | @samp{;;;###autoload} cookies in Emacs Lisp, and for @code{#error} | |
2894 | directives in C. | |
2895 | @end table | |
2896 | ||
969fe9b5 RS |
2897 | @node Syntactic Font Lock |
2898 | @subsection Syntactic Font Lock | |
2899 | ||
4f45f65e LK |
2900 | Syntactic fontification uses the syntax table to find comments and |
2901 | string constants (@pxref{Syntax Tables}). It highlights them using | |
2902 | @code{font-lock-comment-face} and @code{font-lock-string-face} | |
2903 | (@pxref{Faces for Font Lock}). There are several variables that | |
2904 | affect syntactic fontification; you should set them by means of | |
2905 | @code{font-lock-defaults} (@pxref{Font Lock Basics}). | |
2906 | ||
2907 | @defvar font-lock-keywords-only | |
2908 | Non-@code{nil} means Font Lock should not do syntactic fontification; | |
2909 | it should only fontify based on @code{font-lock-keywords}. The normal | |
2910 | way for a mode to set this variable to @code{t} is with | |
2911 | @var{keywords-only} in @code{font-lock-defaults}. | |
2912 | @end defvar | |
2913 | ||
2914 | @defvar font-lock-syntax-table | |
2915 | This variable holds the syntax table to use for fontification of | |
2916 | comments and strings. Specify it using @var{syntax-alist} in | |
2917 | @code{font-lock-defaults}. | |
2918 | @end defvar | |
2919 | ||
4f45f65e LK |
2920 | @defvar font-lock-beginning-of-syntax-function |
2921 | If this variable is non-@code{nil}, it should be a function to move | |
2922 | point back to a position that is syntactically at ``top level'' and | |
2923 | outside of strings or comments. Font Lock uses this when necessary | |
2924 | to get the right results for syntactic fontification. | |
2925 | ||
2926 | This function is called with no arguments. It should leave point at | |
2927 | the beginning of any enclosing syntactic block. Typical values are | |
2928 | @code{beginning-of-line} (used when the start of the line is known to | |
2929 | be outside a syntactic block), or @code{beginning-of-defun} for | |
2930 | programming modes, or @code{backward-paragraph} for textual modes. | |
2931 | ||
3c8572f5 LK |
2932 | If the value is @code{nil}, Font Lock uses |
2933 | @code{syntax-begin-function} to move back outside of any comment, | |
2934 | string, or sexp. This variable is semi-obsolete; we recommend setting | |
2935 | @code{syntax-begin-function} instead. | |
4f45f65e LK |
2936 | |
2937 | Specify this variable using @var{syntax-begin} in | |
2938 | @code{font-lock-defaults}. | |
2939 | @end defvar | |
2940 | ||
2941 | @defvar font-lock-syntactic-face-function | |
2942 | A function to determine which face to use for a given syntactic | |
2943 | element (a string or a comment). The function is called with one | |
2944 | argument, the parse state at point returned by | |
2945 | @code{parse-partial-sexp}, and should return a face. The default | |
2946 | value returns @code{font-lock-comment-face} for comments and | |
2947 | @code{font-lock-string-face} for strings. | |
2948 | ||
2949 | This can be used to highlighting different kinds of strings or | |
2950 | comments differently. It is also sometimes abused together with | |
2951 | @code{font-lock-syntactic-keywords} to highlight elements that span | |
2952 | multiple lines, but this is too obscure to document in this manual. | |
2953 | ||
2954 | Specify this variable using @var{other-vars} in | |
2955 | @code{font-lock-defaults}. | |
2956 | @end defvar | |
2957 | ||
2958 | @node Setting Syntax Properties | |
2959 | @subsection Setting Syntax Properties | |
2960 | ||
969fe9b5 | 2961 | Font Lock mode can be used to update @code{syntax-table} properties |
4f45f65e LK |
2962 | automatically (@pxref{Syntax Properties}). This is useful in |
2963 | languages for which a single syntax table by itself is not sufficient. | |
969fe9b5 RS |
2964 | |
2965 | @defvar font-lock-syntactic-keywords | |
4f45f65e LK |
2966 | This variable enables and controls updating @code{syntax-table} |
2967 | properties by Font Lock. Its value should be a list of elements of | |
2968 | this form: | |
969fe9b5 RS |
2969 | |
2970 | @example | |
2971 | (@var{matcher} @var{subexp} @var{syntax} @var{override} @var{laxmatch}) | |
2972 | @end example | |
2973 | ||
2974 | The parts of this element have the same meanings as in the corresponding | |
2975 | sort of element of @code{font-lock-keywords}, | |
2976 | ||
2977 | @example | |
4f45f65e | 2978 | (@var{matcher} @var{subexp} @var{facespec} @var{override} @var{laxmatch}) |
969fe9b5 RS |
2979 | @end example |
2980 | ||
4f45f65e | 2981 | However, instead of specifying the value @var{facespec} to use for the |
f8cecb20 DL |
2982 | @code{face} property, it specifies the value @var{syntax} to use for |
2983 | the @code{syntax-table} property. Here, @var{syntax} can be a string | |
2984 | (as taken by @code{modify-syntax-entry}), a syntax table, a cons cell | |
2985 | (as returned by @code{string-to-syntax}), or an expression whose value | |
2986 | is one of those two types. @var{override} cannot be @code{prepend} or | |
2987 | @code{append}. | |
2988 | ||
2989 | For example, an element of the form: | |
2990 | ||
2991 | @example | |
2992 | ("\\$\\(#\\)" 1 ".") | |
2993 | @end example | |
2994 | ||
2995 | highlights syntactically a hash character when following a dollar | |
2996 | character, with a SYNTAX of @code{"."} (meaning punctuation syntax). | |
2997 | Assuming that the buffer syntax table specifies hash characters to | |
2998 | have comment start syntax, the element will only highlight hash | |
2999 | characters that do not follow dollar characters as comments | |
3000 | syntactically. | |
3001 | ||
3002 | An element of the form: | |
3003 | ||
3004 | @example | |
3005 | ("\\('\\).\\('\\)" | |
3006 | (1 "\"") | |
3007 | (2 "\"")) | |
3008 | @end example | |
3009 | ||
3010 | highlights syntactically both single quotes which surround a single | |
3011 | character, with a SYNTAX of @code{"\""} (meaning string quote syntax). | |
3012 | Assuming that the buffer syntax table does not specify single quotes | |
3013 | to have quote syntax, the element will only highlight single quotes of | |
3014 | the form @samp{'@var{c}'} as strings syntactically. Other forms, such | |
3015 | as @samp{foo'bar} or @samp{'fubar'}, will not be highlighted as | |
3016 | strings. | |
3017 | ||
4f45f65e LK |
3018 | Major modes normally set this variable with @var{other-vars} in |
3019 | @code{font-lock-defaults}. | |
969fe9b5 RS |
3020 | @end defvar |
3021 | ||
f730cc62 LH |
3022 | @node Desktop Save Mode |
3023 | @section Desktop Save Mode | |
3024 | @cindex desktop save mode | |
3025 | ||
3026 | @dfn{Desktop Save Mode} is a feature to save the state of Emacs from | |
3027 | one session to another. The user-level commands for using Desktop | |
3028 | Save Mode are described in the GNU Emacs Manual (@pxref{Saving Emacs | |
3029 | Sessions,,, emacs, the GNU Emacs Manual}). Modes whose buffers visit | |
3030 | a file, don't have to do anything to use this feature. | |
3031 | ||
3032 | For buffers not visiting a file to have their state saved, the major | |
3033 | mode must bind the buffer local variable @code{desktop-save-buffer} to | |
a3ee0299 | 3034 | a non-@code{nil} value. |
f730cc62 LH |
3035 | |
3036 | @defvar desktop-save-buffer | |
3037 | If this buffer-local variable is non-@code{nil}, the buffer will have | |
3038 | its state saved in the desktop file at desktop save. If the value is | |
3039 | a function, it is called at desktop save with argument | |
3040 | @var{desktop-dirname}, and its value is saved in the desktop file along | |
3041 | with the state of the buffer for which it was called. When file names | |
3042 | are returned as part of the auxiliary information, they should be | |
3043 | formatted using the call | |
3044 | ||
3045 | @example | |
3046 | (desktop-file-name @var{file-name} @var{desktop-dirname}) | |
3047 | @end example | |
3048 | ||
3049 | @end defvar | |
3050 | ||
3051 | For buffers not visiting a file to be restored, the major mode must | |
3052 | define a function to do the job, and that function must be listed in | |
3053 | the alist @code{desktop-buffer-mode-handlers}. | |
3054 | ||
3055 | @defvar desktop-buffer-mode-handlers | |
3056 | Alist with elements | |
3057 | ||
3058 | @example | |
3059 | (@var{major-mode} . @var{restore-buffer-function}) | |
3060 | @end example | |
3061 | ||
3062 | The function @var{restore-buffer-function} will be called with | |
3063 | argument list | |
3064 | ||
3065 | @example | |
3066 | (@var{buffer-file-name} @var{buffer-name} @var{desktop-buffer-misc}) | |
3067 | @end example | |
3068 | ||
3069 | and it should return the restored buffer. | |
3070 | Here @var{desktop-buffer-misc} is the value returned by the function | |
3071 | optionally bound to @code{desktop-save-buffer}. | |
f730cc62 LH |
3072 | @end defvar |
3073 | ||
ab5796a9 MB |
3074 | @ignore |
3075 | arch-tag: 4c7bff41-36e6-4da6-9e7f-9b9289e27c8e | |
3076 | @end ignore |