Mercurial > hg > xemacs-beta
annotate man/lispref/modes.texi @ 5911:48386fd60fd0
GMP functions that take doubles choke on non-finite values, avoid that.
src/ChangeLog addition:
2015-05-10 Aidan Kehoe <kehoea@parhasard.net>
* floatfns.c (double_to_integer):
Rename this from float_to_int to fit our newer, bignum-compatible
terminology.
GMP can signal SIGFPE when asked to turn NaN or infinity into a
bignum, and we're not prepared to handle that signal if the OS float
library routines don't do that, so check for those values
explicitly.
* floatfns.c (ceiling_two_float):
* floatfns.c (ceiling_one_float):
* floatfns.c (floor_two_float):
* floatfns.c (floor_one_float):
* floatfns.c (round_two_float):
* floatfns.c (round_one_float):
* floatfns.c (truncate_two_float):
* floatfns.c (truncate_one_float):
Call double_to_integer() with its new name.
* number.c:
Don't use the {bignum,ratio,bigfloat}_set_double functions
directly here, with GMP they can choke when handed non-finite C
doubles, call Ftruncate() and the new float_to_bigfloat() from
floatfns.c. Maybe we should extend number-gmp.c with GMP-specific
implementations that check for non-finite values.
tests/ChangeLog addition:
2015-05-10 Aidan Kehoe <kehoea@parhasard.net>
* automated/lisp-tests.el:
Backslash a few parentheses in the first column for the sake of
fontification.
* automated/lisp-tests.el:
Check that the rounding functions signal Lisp errors correctly
when handed positive and negative infinity and NaN.
| author | Aidan Kehoe <kehoea@parhasard.net> |
|---|---|
| date | Sun, 10 May 2015 19:07:09 +0100 |
| parents | 9fae6227ede5 |
| children |
| rev | line source |
|---|---|
| 428 | 1 @c -*-texinfo-*- |
| 2 @c This is part of the XEmacs Lisp Reference Manual. | |
| 444 | 3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. |
| 428 | 4 @c See the file lispref.texi for copying conditions. |
| 5 @setfilename ../../info/modes.info | |
| 6 @node Modes, Documentation, Drag and Drop, Top | |
| 7 @chapter Major and Minor Modes | |
| 8 @cindex mode | |
| 9 | |
| 10 A @dfn{mode} is a set of definitions that customize XEmacs and can be | |
| 11 turned on and off while you edit. There are two varieties of modes: | |
| 12 @dfn{major modes}, which are mutually exclusive and used for editing | |
| 13 particular kinds of text, and @dfn{minor modes}, which provide features | |
| 14 that users can enable individually. | |
| 15 | |
| 16 This chapter describes how to write both major and minor modes, how to | |
| 17 indicate them in the modeline, and how they run hooks supplied by the | |
| 18 user. For related topics such as keymaps and syntax tables, see | |
| 19 @ref{Keymaps}, and @ref{Syntax Tables}. | |
| 20 | |
| 21 @menu | |
| 22 * Major Modes:: Defining major modes. | |
| 23 * Minor Modes:: Defining minor modes. | |
| 24 * Modeline Format:: Customizing the text that appears in the modeline. | |
| 25 * Hooks:: How to use hooks; how to write code that provides hooks. | |
| 26 @end menu | |
| 27 | |
|
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28 @node Major Modes, Minor Modes, Modes, Modes |
| 428 | 29 @section Major Modes |
| 30 @cindex major mode | |
| 31 @cindex Fundamental mode | |
| 32 | |
| 33 Major modes specialize XEmacs for editing particular kinds of text. | |
| 2135 | 34 Each buffer has only one major mode at a time. For each major mode |
| 35 there is a function to switch to that mode in the current buffer; its | |
| 36 name should end in @samp{-mode}. These functions work by setting | |
| 37 buffer-local variable bindings and other data associated with the | |
| 38 buffer, such as a local keymap. The effect lasts until you switch | |
| 39 to another major mode in the same buffer. | |
| 428 | 40 |
| 41 The least specialized major mode is called @dfn{Fundamental mode}. | |
| 42 This mode has no mode-specific definitions or variable settings, so each | |
| 43 XEmacs command behaves in its default manner, and each option is in its | |
| 44 default state. All other major modes redefine various keys and options. | |
| 45 For example, Lisp Interaction mode provides special key bindings for | |
| 46 @key{LFD} (@code{eval-print-last-sexp}), @key{TAB} | |
| 47 (@code{lisp-indent-line}), and other keys. | |
| 48 | |
| 49 When you need to write several editing commands to help you perform a | |
| 50 specialized editing task, creating a new major mode is usually a good | |
| 51 idea. In practice, writing a major mode is easy (in contrast to | |
| 52 writing a minor mode, which is often difficult). | |
| 53 | |
| 54 If the new mode is similar to an old one, it is often unwise to modify | |
| 55 the old one to serve two purposes, since it may become harder to use and | |
| 56 maintain. Instead, copy and rename an existing major mode definition | |
| 57 and alter the copy---or define a @dfn{derived mode} (@pxref{Derived | |
| 58 Modes}). For example, Rmail Edit mode, which is in | |
| 59 @file{emacs/lisp/rmailedit.el}, is a major mode that is very similar to | |
| 60 Text mode except that it provides three additional commands. Its | |
| 61 definition is distinct from that of Text mode, but was derived from it. | |
| 62 | |
| 2135 | 63 Even if the new mode is not an obvious derivative of any other mode, |
| 64 it is convenient to use @code{define-derived-mode} with a @code{nil} | |
| 65 parent argument, since it automatically enforces the most important | |
| 66 coding conventions for you. | |
| 67 | |
| 428 | 68 Rmail Edit mode is an example of a case where one piece of text is put |
| 69 temporarily into a different major mode so it can be edited in a | |
| 70 different way (with ordinary XEmacs commands rather than Rmail). In such | |
| 71 cases, the temporary major mode usually has a command to switch back to | |
| 72 the buffer's usual mode (Rmail mode, in this case). You might be | |
| 73 tempted to present the temporary redefinitions inside a recursive edit | |
| 74 and restore the usual ones when the user exits; but this is a bad idea | |
| 75 because it constrains the user's options when it is done in more than | |
| 76 one buffer: recursive edits must be exited most-recently-entered first. | |
| 77 Using alternative major modes avoids this limitation. @xref{Recursive | |
| 78 Editing}. | |
| 79 | |
| 80 The standard XEmacs Lisp library directory contains the code for | |
| 81 several major modes, in files including @file{text-mode.el}, | |
| 82 @file{texinfo.el}, @file{lisp-mode.el}, @file{c-mode.el}, and | |
| 83 @file{rmail.el}. You can look at these libraries to see how modes are | |
| 84 written. Text mode is perhaps the simplest major mode aside from | |
| 85 Fundamental mode. Rmail mode is a complicated and specialized mode. | |
| 86 | |
| 87 @menu | |
| 88 * Major Mode Conventions:: Coding conventions for keymaps, etc. | |
| 89 * Example Major Modes:: Text mode and Lisp modes. | |
| 90 * Auto Major Mode:: How XEmacs chooses the major mode automatically. | |
| 91 * Mode Help:: Finding out how to use a mode. | |
| 444 | 92 * Derived Modes:: Defining a new major mode based on another major |
| 428 | 93 mode. |
| 94 @end menu | |
| 95 | |
|
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96 @node Major Mode Conventions, Example Major Modes, Major Modes, Major Modes |
| 428 | 97 @subsection Major Mode Conventions |
| 98 | |
| 99 The code for existing major modes follows various coding conventions, | |
| 100 including conventions for local keymap and syntax table initialization, | |
| 101 global names, and hooks. Please follow these conventions when you | |
| 102 define a new major mode: | |
| 103 | |
| 104 @itemize @bullet | |
| 105 @item | |
| 106 Define a command whose name ends in @samp{-mode}, with no arguments, | |
| 107 that switches to the new mode in the current buffer. This command | |
| 108 should set up the keymap, syntax table, and local variables in an | |
| 109 existing buffer without changing the buffer's text. | |
| 110 | |
| 111 @item | |
| 112 Write a documentation string for this command that describes the | |
| 113 special commands available in this mode. @kbd{C-h m} | |
| 114 (@code{describe-mode}) in your mode will display this string. | |
| 115 | |
| 116 The documentation string may include the special documentation | |
| 117 substrings, @samp{\[@var{command}]}, @samp{\@{@var{keymap}@}}, and | |
| 118 @samp{\<@var{keymap}>}, that enable the documentation to adapt | |
| 119 automatically to the user's own key bindings. @xref{Keys in | |
| 120 Documentation}. | |
| 121 | |
| 122 @item | |
| 123 The major mode command should start by calling | |
| 124 @code{kill-all-local-variables}. This is what gets rid of the local | |
| 125 variables of the major mode previously in effect. | |
| 126 | |
| 127 @item | |
| 128 The major mode command should set the variable @code{major-mode} to the | |
| 129 major mode command symbol. This is how @code{describe-mode} discovers | |
| 130 which documentation to print. | |
| 131 | |
| 132 @item | |
| 133 The major mode command should set the variable @code{mode-name} to the | |
| 134 ``pretty'' name of the mode, as a string. This appears in the mode | |
| 135 line. | |
| 136 | |
| 137 @item | |
| 138 @cindex functions in modes | |
| 139 Since all global names are in the same name space, all the global | |
| 140 variables, constants, and functions that are part of the mode should | |
| 141 have names that start with the major mode name (or with an abbreviation | |
| 142 of it if the name is long). @xref{Style Tips}. | |
| 143 | |
| 144 @item | |
| 145 @cindex keymaps in modes | |
| 146 The major mode should usually have its own keymap, which is used as the | |
| 147 local keymap in all buffers in that mode. The major mode function | |
| 148 should call @code{use-local-map} to install this local map. | |
| 149 @xref{Active Keymaps}, for more information. | |
| 150 | |
| 151 This keymap should be kept in a global variable named | |
| 152 @code{@var{modename}-mode-map}. Normally the library that defines the | |
| 153 mode sets this variable. | |
| 154 | |
| 155 @item | |
| 156 @cindex syntax tables in modes | |
| 157 The mode may have its own syntax table or may share one with other | |
| 158 related modes. If it has its own syntax table, it should store this in | |
| 159 a variable named @code{@var{modename}-mode-syntax-table}. @xref{Syntax | |
| 160 Tables}. | |
| 161 | |
| 162 @item | |
| 163 @cindex abbrev tables in modes | |
| 164 The mode may have its own abbrev table or may share one with other | |
| 165 related modes. If it has its own abbrev table, it should store this in | |
| 166 a variable named @code{@var{modename}-mode-abbrev-table}. @xref{Abbrev | |
| 167 Tables}. | |
| 168 | |
| 169 @item | |
| 170 Use @code{defvar} to set mode-related variables, so that they are not | |
| 171 reinitialized if they already have a value. (Such reinitialization | |
| 172 could discard customizations made by the user.) | |
| 173 | |
| 174 @item | |
| 175 @cindex buffer-local variables in modes | |
| 176 To make a buffer-local binding for an Emacs customization variable, use | |
| 177 @code{make-local-variable} in the major mode command, not | |
| 178 @code{make-variable-buffer-local}. The latter function would make the | |
| 179 variable local to every buffer in which it is subsequently set, which | |
| 180 would affect buffers that do not use this mode. It is undesirable for a | |
| 181 mode to have such global effects. @xref{Buffer-Local Variables}. | |
| 182 | |
| 183 It's ok to use @code{make-variable-buffer-local}, if you wish, for a | |
| 184 variable used only within a single Lisp package. | |
| 185 | |
| 186 @item | |
| 187 @cindex mode hook | |
| 188 @cindex major mode hook | |
| 189 Each major mode should have a @dfn{mode hook} named | |
| 190 @code{@var{modename}-mode-hook}. The major mode command should run that | |
| 191 hook, with @code{run-hooks}, as the very last thing it | |
| 192 does. @xref{Hooks}. | |
| 193 | |
| 194 @item | |
| 195 The major mode command may also run the hooks of some more basic modes. | |
| 196 For example, @code{indented-text-mode} runs @code{text-mode-hook} as | |
| 197 well as @code{indented-text-mode-hook}. It may run these other hooks | |
| 198 immediately before the mode's own hook (that is, after everything else), | |
| 199 or it may run them earlier. | |
| 200 | |
| 201 @item | |
| 2135 | 202 The major mode command may start by calling some other major mode |
| 203 command (called the @dfn{parent mode}) and then alter some of its | |
| 204 settings. A mode that does this is called a @dfn{derived mode}. The | |
| 205 recommended way to define one is to use @code{define-derived-mode}, | |
| 206 but this is not required. Such a mode should use | |
| 207 @code{delay-mode-hooks} around its entire body, including the call to | |
| 208 the parent mode command and the final call to @code{run-mode-hooks}. | |
| 209 (Using @code{define-derived-mode} does this automatically.) | |
| 210 | |
| 211 @item | |
| 428 | 212 If something special should be done if the user switches a buffer from |
| 213 this mode to any other major mode, the mode can set a local value for | |
| 214 @code{change-major-mode-hook}. | |
| 215 | |
| 216 @item | |
| 217 If this mode is appropriate only for specially-prepared text, then the | |
| 218 major mode command symbol should have a property named @code{mode-class} | |
| 219 with value @code{special}, put on as follows: | |
| 220 | |
| 221 @cindex @code{mode-class} property | |
| 222 @cindex @code{special} | |
| 223 @example | |
| 224 (put 'funny-mode 'mode-class 'special) | |
| 225 @end example | |
| 226 | |
| 227 @noindent | |
| 228 This tells XEmacs that new buffers created while the current buffer has | |
| 229 Funny mode should not inherit Funny mode. Modes such as Dired, Rmail, | |
| 230 and Buffer List use this feature. | |
| 231 | |
| 232 @item | |
| 233 If you want to make the new mode the default for files with certain | |
| 234 recognizable names, add an element to @code{auto-mode-alist} to select | |
| 235 the mode for those file names. If you define the mode command to | |
| 236 autoload, you should add this element in the same file that calls | |
| 237 @code{autoload}. Otherwise, it is sufficient to add the element in the | |
| 238 file that contains the mode definition. @xref{Auto Major Mode}. | |
| 239 | |
| 240 @item | |
| 241 @cindex @file{.emacs} customization | |
| 242 In the documentation, you should provide a sample @code{autoload} form | |
| 243 and an example of how to add to @code{auto-mode-alist}, that users can | |
| 244 include in their @file{.emacs} files. | |
| 245 | |
| 246 @item | |
| 247 @cindex mode loading | |
| 248 The top-level forms in the file defining the mode should be written so | |
| 249 that they may be evaluated more than once without adverse consequences. | |
| 250 Even if you never load the file more than once, someone else will. | |
| 251 @end itemize | |
| 252 | |
| 253 @defvar change-major-mode-hook | |
| 254 This normal hook is run by @code{kill-all-local-variables} before it | |
| 255 does anything else. This gives major modes a way to arrange for | |
| 256 something special to be done if the user switches to a different major | |
| 257 mode. For best results, make this variable buffer-local, so that it | |
| 258 will disappear after doing its job and will not interfere with the | |
| 259 subsequent major mode. @xref{Hooks}. | |
| 260 @end defvar | |
| 261 | |
|
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|
262 @node Example Major Modes, Auto Major Mode, Major Mode Conventions, Major Modes |
| 428 | 263 @subsection Major Mode Examples |
| 264 | |
| 265 Text mode is perhaps the simplest mode besides Fundamental mode. | |
| 266 Here are excerpts from @file{text-mode.el} that illustrate many of | |
| 267 the conventions listed above: | |
| 268 | |
| 269 @smallexample | |
| 270 @group | |
| 271 ;; @r{Create mode-specific tables.} | |
| 444 | 272 (defvar text-mode-syntax-table nil |
| 428 | 273 "Syntax table used while in text mode.") |
| 274 @end group | |
| 275 | |
| 276 @group | |
| 277 (if text-mode-syntax-table | |
| 278 () ; @r{Do not change the table if it is already set up.} | |
| 279 (setq text-mode-syntax-table (make-syntax-table)) | |
| 280 (modify-syntax-entry ?\" ". " text-mode-syntax-table) | |
| 281 (modify-syntax-entry ?\\ ". " text-mode-syntax-table) | |
| 282 (modify-syntax-entry ?' "w " text-mode-syntax-table)) | |
| 283 @end group | |
| 284 | |
| 285 @group | |
| 286 (defvar text-mode-abbrev-table nil | |
| 287 "Abbrev table used while in text mode.") | |
| 288 (define-abbrev-table 'text-mode-abbrev-table ()) | |
| 289 @end group | |
| 290 | |
| 291 @group | |
| 292 (defvar text-mode-map nil) ; @r{Create a mode-specific keymap.} | |
| 293 | |
| 294 (if text-mode-map | |
| 295 () ; @r{Do not change the keymap if it is already set up.} | |
| 296 (setq text-mode-map (make-sparse-keymap)) | |
| 297 (define-key text-mode-map "\t" 'tab-to-tab-stop) | |
| 298 (define-key text-mode-map "\es" 'center-line) | |
| 299 (define-key text-mode-map "\eS" 'center-paragraph)) | |
| 300 @end group | |
| 301 @end smallexample | |
| 302 | |
| 303 Here is the complete major mode function definition for Text mode: | |
| 304 | |
| 305 @smallexample | |
| 306 @group | |
| 307 (defun text-mode () | |
| 444 | 308 "Major mode for editing text intended for humans to read. |
| 428 | 309 Special commands: \\@{text-mode-map@} |
| 310 @end group | |
| 311 @group | |
| 312 Turning on text-mode runs the hook `text-mode-hook'." | |
| 313 (interactive) | |
| 314 (kill-all-local-variables) | |
| 315 @end group | |
| 316 @group | |
| 317 (use-local-map text-mode-map) ; @r{This provides the local keymap.} | |
| 318 (setq mode-name "Text") ; @r{This name goes into the modeline.} | |
| 319 (setq major-mode 'text-mode) ; @r{This is how @code{describe-mode}} | |
| 320 ; @r{finds the doc string to print.} | |
| 321 (setq local-abbrev-table text-mode-abbrev-table) | |
| 322 (set-syntax-table text-mode-syntax-table) | |
| 323 (run-hooks 'text-mode-hook)) ; @r{Finally, this permits the user to} | |
| 324 ; @r{customize the mode with a hook.} | |
| 325 @end group | |
| 326 @end smallexample | |
| 327 | |
| 328 @cindex @file{lisp-mode.el} | |
| 329 The three Lisp modes (Lisp mode, Emacs Lisp mode, and Lisp | |
| 330 Interaction mode) have more features than Text mode and the code is | |
| 331 correspondingly more complicated. Here are excerpts from | |
| 332 @file{lisp-mode.el} that illustrate how these modes are written. | |
| 333 | |
| 334 @cindex syntax table example | |
| 335 @smallexample | |
| 336 @group | |
| 337 ;; @r{Create mode-specific table variables.} | |
| 444 | 338 (defvar lisp-mode-syntax-table nil "") |
| 428 | 339 (defvar emacs-lisp-mode-syntax-table nil "") |
| 340 (defvar lisp-mode-abbrev-table nil "") | |
| 341 @end group | |
| 342 | |
| 343 @group | |
| 344 (if (not emacs-lisp-mode-syntax-table) ; @r{Do not change the table} | |
| 345 ; @r{if it is already set.} | |
| 346 (let ((i 0)) | |
| 347 (setq emacs-lisp-mode-syntax-table (make-syntax-table)) | |
| 348 @end group | |
| 349 | |
| 350 @group | |
| 351 ;; @r{Set syntax of chars up to 0 to class of chars that are} | |
| 352 ;; @r{part of symbol names but not words.} | |
| 353 ;; @r{(The number 0 is @code{48} in the @sc{ascii} character set.)} | |
| 444 | 354 (while (< i ?0) |
| 428 | 355 (modify-syntax-entry i "_ " emacs-lisp-mode-syntax-table) |
| 356 (setq i (1+ i))) | |
| 357 @dots{} | |
| 358 @end group | |
| 359 @group | |
| 360 ;; @r{Set the syntax for other characters.} | |
| 361 (modify-syntax-entry ? " " emacs-lisp-mode-syntax-table) | |
| 362 (modify-syntax-entry ?\t " " emacs-lisp-mode-syntax-table) | |
| 363 @dots{} | |
| 364 @end group | |
| 365 @group | |
| 366 (modify-syntax-entry ?\( "() " emacs-lisp-mode-syntax-table) | |
| 367 (modify-syntax-entry ?\) ")( " emacs-lisp-mode-syntax-table) | |
| 368 @dots{})) | |
| 369 ;; @r{Create an abbrev table for lisp-mode.} | |
| 370 (define-abbrev-table 'lisp-mode-abbrev-table ()) | |
| 371 @end group | |
| 372 @end smallexample | |
| 373 | |
| 374 Much code is shared among the three Lisp modes. The following | |
| 375 function sets various variables; it is called by each of the major Lisp | |
| 376 mode functions: | |
| 377 | |
| 378 @smallexample | |
| 379 @group | |
| 380 (defun lisp-mode-variables (lisp-syntax) | |
| 381 ;; @r{The @code{lisp-syntax} argument is @code{nil} in Emacs Lisp mode,} | |
| 382 ;; @r{and @code{t} in the other two Lisp modes.} | |
| 383 (cond (lisp-syntax | |
| 384 (if (not lisp-mode-syntax-table) | |
| 385 ;; @r{The Emacs Lisp mode syntax table always exists, but} | |
| 386 ;; @r{the Lisp Mode syntax table is created the first time a} | |
| 387 ;; @r{mode that needs it is called. This is to save space.} | |
| 388 @end group | |
| 389 @group | |
| 390 (progn (setq lisp-mode-syntax-table | |
| 391 (copy-syntax-table emacs-lisp-mode-syntax-table)) | |
| 392 ;; @r{Change some entries for Lisp mode.} | |
| 393 (modify-syntax-entry ?\| "\" " | |
| 394 lisp-mode-syntax-table) | |
| 395 (modify-syntax-entry ?\[ "_ " | |
| 396 lisp-mode-syntax-table) | |
| 397 (modify-syntax-entry ?\] "_ " | |
| 398 lisp-mode-syntax-table))) | |
| 399 @end group | |
| 400 @group | |
| 401 (set-syntax-table lisp-mode-syntax-table))) | |
| 402 (setq local-abbrev-table lisp-mode-abbrev-table) | |
| 403 @dots{}) | |
| 404 @end group | |
| 405 @end smallexample | |
| 406 | |
| 407 Functions such as @code{forward-paragraph} use the value of the | |
| 408 @code{paragraph-start} variable. Since Lisp code is different from | |
| 409 ordinary text, the @code{paragraph-start} variable needs to be set | |
| 410 specially to handle Lisp. Also, comments are indented in a special | |
| 411 fashion in Lisp and the Lisp modes need their own mode-specific | |
| 412 @code{comment-indent-function}. The code to set these variables is the | |
| 413 rest of @code{lisp-mode-variables}. | |
| 414 | |
| 415 @smallexample | |
| 416 @group | |
| 417 (make-local-variable 'paragraph-start) | |
| 418 ;; @r{Having @samp{^} is not clean, but @code{page-delimiter}} | |
| 419 ;; @r{has them too, and removing those is a pain.} | |
| 420 (setq paragraph-start (concat "^$\\|" page-delimiter)) | |
| 421 @dots{} | |
| 422 @end group | |
| 423 @group | |
| 424 (make-local-variable 'comment-indent-function) | |
| 425 (setq comment-indent-function 'lisp-comment-indent)) | |
| 426 @end group | |
| 427 @end smallexample | |
| 428 | |
| 429 Each of the different Lisp modes has a slightly different keymap. For | |
| 430 example, Lisp mode binds @kbd{C-c C-l} to @code{run-lisp}, but the other | |
| 431 Lisp modes do not. However, all Lisp modes have some commands in | |
| 432 common. The following function adds these common commands to a given | |
| 433 keymap. | |
| 434 | |
| 435 @smallexample | |
| 436 @group | |
| 437 (defun lisp-mode-commands (map) | |
| 438 (define-key map "\e\C-q" 'indent-sexp) | |
| 439 (define-key map "\177" 'backward-delete-char-untabify) | |
| 440 (define-key map "\t" 'lisp-indent-line)) | |
| 441 @end group | |
| 442 @end smallexample | |
| 443 | |
| 444 Here is an example of using @code{lisp-mode-commands} to initialize a | |
| 445 keymap, as part of the code for Emacs Lisp mode. First we declare a | |
| 446 variable with @code{defvar} to hold the mode-specific keymap. When this | |
| 447 @code{defvar} executes, it sets the variable to @code{nil} if it was | |
| 448 void. Then we set up the keymap if the variable is @code{nil}. | |
| 449 | |
| 450 This code avoids changing the keymap or the variable if it is already | |
| 451 set up. This lets the user customize the keymap. | |
| 452 | |
| 453 @smallexample | |
| 454 @group | |
| 444 | 455 (defvar emacs-lisp-mode-map () "") |
| 428 | 456 (if emacs-lisp-mode-map |
| 457 () | |
| 458 (setq emacs-lisp-mode-map (make-sparse-keymap)) | |
| 459 (define-key emacs-lisp-mode-map "\e\C-x" 'eval-defun) | |
| 460 (lisp-mode-commands emacs-lisp-mode-map)) | |
| 461 @end group | |
| 462 @end smallexample | |
| 463 | |
| 464 Finally, here is the complete major mode function definition for | |
| 444 | 465 Emacs Lisp mode. |
| 428 | 466 |
| 467 @smallexample | |
| 468 @group | |
| 469 (defun emacs-lisp-mode () | |
| 470 "Major mode for editing Lisp code to run in XEmacs. | |
| 471 Commands: | |
| 472 Delete converts tabs to spaces as it moves back. | |
| 473 Blank lines separate paragraphs. Semicolons start comments. | |
| 474 \\@{emacs-lisp-mode-map@} | |
| 475 @end group | |
| 476 @group | |
| 477 Entry to this mode runs the hook `emacs-lisp-mode-hook'." | |
| 478 (interactive) | |
| 479 (kill-all-local-variables) | |
| 480 (use-local-map emacs-lisp-mode-map) ; @r{This provides the local keymap.} | |
| 481 (set-syntax-table emacs-lisp-mode-syntax-table) | |
| 482 @end group | |
| 483 @group | |
| 484 (setq major-mode 'emacs-lisp-mode) ; @r{This is how @code{describe-mode}} | |
| 485 ; @r{finds out what to describe.} | |
| 486 (setq mode-name "Emacs-Lisp") ; @r{This goes into the modeline.} | |
| 487 (lisp-mode-variables nil) ; @r{This defines various variables.} | |
| 488 (run-hooks 'emacs-lisp-mode-hook)) ; @r{This permits the user to use a} | |
| 489 ; @r{hook to customize the mode.} | |
| 490 @end group | |
| 491 @end smallexample | |
| 492 | |
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493 @node Auto Major Mode, Mode Help, Example Major Modes, Major Modes |
| 428 | 494 @subsection How XEmacs Chooses a Major Mode |
| 495 | |
| 496 Based on information in the file name or in the file itself, XEmacs | |
| 497 automatically selects a major mode for the new buffer when a file is | |
| 498 visited. | |
| 499 | |
| 500 @deffn Command fundamental-mode | |
| 501 Fundamental mode is a major mode that is not specialized for anything | |
| 502 in particular. Other major modes are defined in effect by comparison | |
| 503 with this one---their definitions say what to change, starting from | |
| 504 Fundamental mode. The @code{fundamental-mode} function does @emph{not} | |
| 505 run any hooks; you're not supposed to customize it. (If you want Emacs | |
| 506 to behave differently in Fundamental mode, change the @emph{global} | |
| 507 state of Emacs.) | |
| 508 @end deffn | |
| 509 | |
| 510 @deffn Command normal-mode &optional find-file | |
| 511 This function establishes the proper major mode and local variable | |
| 512 bindings for the current buffer. First it calls @code{set-auto-mode}, | |
| 513 then it runs @code{hack-local-variables} to parse, and bind or | |
| 514 evaluate as appropriate, any local variables. | |
| 515 | |
| 516 If the @var{find-file} argument to @code{normal-mode} is | |
| 517 non-@code{nil}, @code{normal-mode} assumes that the @code{find-file} | |
| 518 function is calling it. In this case, it may process a local variables | |
| 519 list at the end of the file and in the @samp{-*-} line. The variable | |
| 520 @code{enable-local-variables} controls whether to do so. | |
| 521 | |
| 522 If you run @code{normal-mode} interactively, the argument | |
| 523 @var{find-file} is normally @code{nil}. In this case, | |
| 524 @code{normal-mode} unconditionally processes any local variables list. | |
| 446 | 525 @xref{File variables, , Local Variables in Files, xemacs, The XEmacs |
| 428 | 526 Reference Manual}, for the syntax of the local variables section of a file. |
| 527 | |
| 528 @cindex file mode specification error | |
| 529 @code{normal-mode} uses @code{condition-case} around the call to the | |
| 530 major mode function, so errors are caught and reported as a @samp{File | |
| 531 mode specification error}, followed by the original error message. | |
| 532 @end deffn | |
| 533 | |
| 534 @defopt enable-local-variables | |
| 535 This variable controls processing of local variables lists in files | |
| 536 being visited. A value of @code{t} means process the local variables | |
| 537 lists unconditionally; @code{nil} means ignore them; anything else means | |
| 538 ask the user what to do for each file. The default value is @code{t}. | |
| 539 @end defopt | |
| 540 | |
| 541 @defvar ignored-local-variables | |
| 542 This variable holds a list of variables that should not be | |
| 543 set by a local variables list. Any value specified | |
| 544 for one of these variables is ignored. | |
| 545 @end defvar | |
| 546 | |
| 547 In addition to this list, any variable whose name has a non-@code{nil} | |
| 548 @code{risky-local-variable} property is also ignored. | |
| 549 | |
| 550 @defopt enable-local-eval | |
| 551 This variable controls processing of @samp{Eval:} in local variables | |
| 552 lists in files being visited. A value of @code{t} means process them | |
| 553 unconditionally; @code{nil} means ignore them; anything else means ask | |
| 554 the user what to do for each file. The default value is @code{maybe}. | |
| 555 @end defopt | |
| 556 | |
| 557 @defun set-auto-mode | |
| 558 @cindex visited file mode | |
| 559 This function selects the major mode that is appropriate for the | |
| 560 current buffer. It may base its decision on the value of the @w{@samp{-*-}} | |
| 561 line, on the visited file name (using @code{auto-mode-alist}), or on the | |
| 562 value of a local variable. However, this function does not look for | |
| 563 the @samp{mode:} local variable near the end of a file; the | |
| 564 @code{hack-local-variables} function does that. @xref{Choosing Modes, , | |
| 446 | 565 How Major Modes are Chosen, xemacs, The XEmacs Lisp Reference Manual}. |
| 428 | 566 @end defun |
| 567 | |
| 444 | 568 @defopt default-major-mode |
| 428 | 569 This variable holds the default major mode for new buffers. The |
| 570 standard value is @code{fundamental-mode}. | |
| 571 | |
| 572 If the value of @code{default-major-mode} is @code{nil}, XEmacs uses | |
| 573 the (previously) current buffer's major mode for the major mode of a new | |
| 574 buffer. However, if the major mode symbol has a @code{mode-class} | |
| 575 property with value @code{special}, then it is not used for new buffers; | |
| 576 Fundamental mode is used instead. The modes that have this property are | |
| 577 those such as Dired and Rmail that are useful only with text that has | |
| 578 been specially prepared. | |
| 579 @end defopt | |
| 580 | |
| 581 @defun set-buffer-major-mode buffer | |
| 582 This function sets the major mode of @var{buffer} to the value of | |
| 583 @code{default-major-mode}. If that variable is @code{nil}, it uses | |
| 584 the current buffer's major mode (if that is suitable). | |
| 585 | |
| 586 The low-level primitives for creating buffers do not use this function, | |
| 587 but medium-level commands such as @code{switch-to-buffer} and | |
| 588 @code{find-file-noselect} use it whenever they create buffers. | |
| 589 @end defun | |
| 590 | |
| 591 @defvar initial-major-mode | |
| 592 @cindex @samp{*scratch*} | |
| 593 The value of this variable determines the major mode of the initial | |
| 594 @samp{*scratch*} buffer. The value should be a symbol that is a major | |
| 595 mode command name. The default value is @code{lisp-interaction-mode}. | |
| 596 @end defvar | |
| 597 | |
| 598 @defvar auto-mode-alist | |
| 599 This variable contains an association list of file name patterns | |
| 600 (regular expressions; @pxref{Regular Expressions}) and corresponding | |
| 601 major mode functions. Usually, the file name patterns test for | |
| 602 suffixes, such as @samp{.el} and @samp{.c}, but this need not be the | |
| 603 case. An ordinary element of the alist looks like @code{(@var{regexp} . | |
| 604 @var{mode-function})}. | |
| 605 | |
| 606 For example, | |
| 607 | |
| 608 @smallexample | |
| 609 @group | |
| 610 (("^/tmp/fol/" . text-mode) | |
| 611 ("\\.texinfo\\'" . texinfo-mode) | |
| 612 ("\\.texi\\'" . texinfo-mode) | |
| 613 @end group | |
| 614 @group | |
| 615 ("\\.el\\'" . emacs-lisp-mode) | |
| 444 | 616 ("\\.c\\'" . c-mode) |
| 428 | 617 ("\\.h\\'" . c-mode) |
| 618 @dots{}) | |
| 619 @end group | |
| 620 @end smallexample | |
| 621 | |
| 622 When you visit a file whose expanded file name (@pxref{File Name | |
| 623 Expansion}) matches a @var{regexp}, @code{set-auto-mode} calls the | |
| 624 corresponding @var{mode-function}. This feature enables XEmacs to select | |
| 625 the proper major mode for most files. | |
| 626 | |
| 627 If an element of @code{auto-mode-alist} has the form @code{(@var{regexp} | |
| 628 @var{function} t)}, then after calling @var{function}, XEmacs searches | |
| 629 @code{auto-mode-alist} again for a match against the portion of the file | |
| 630 name that did not match before. | |
| 631 | |
| 632 This match-again feature is useful for uncompression packages: an entry | |
| 633 of the form @code{("\\.gz\\'" . @var{function})} can uncompress the file | |
| 634 and then put the uncompressed file in the proper mode according to the | |
| 635 name sans @samp{.gz}. | |
| 636 | |
| 637 Here is an example of how to prepend several pattern pairs to | |
| 638 @code{auto-mode-alist}. (You might use this sort of expression in your | |
| 639 @file{.emacs} file.) | |
| 640 | |
| 641 @smallexample | |
| 642 @group | |
| 643 (setq auto-mode-alist | |
| 444 | 644 (append |
| 428 | 645 ;; @r{File name starts with a dot.} |
| 444 | 646 '(("/\\.[^/]*\\'" . fundamental-mode) |
| 428 | 647 ;; @r{File name has no dot.} |
| 444 | 648 ("[^\\./]*\\'" . fundamental-mode) |
| 428 | 649 ;; @r{File name ends in @samp{.C}.} |
| 650 ("\\.C\\'" . c++-mode)) | |
| 651 auto-mode-alist)) | |
| 652 @end group | |
| 653 @end smallexample | |
| 654 @end defvar | |
| 655 | |
| 656 @defvar interpreter-mode-alist | |
| 657 This variable specifies major modes to use for scripts that specify a | |
| 658 command interpreter in an @samp{#!} line. Its value is a list of | |
| 659 elements of the form @code{(@var{interpreter} . @var{mode})}; for | |
| 660 example, @code{("perl" . perl-mode)} is one element present by default. | |
| 661 The element says to use mode @var{mode} if the file specifies | |
| 662 @var{interpreter}. | |
| 663 | |
| 664 This variable is applicable only when the @code{auto-mode-alist} does | |
| 665 not indicate which major mode to use. | |
| 666 @end defvar | |
| 667 | |
| 668 @defun hack-local-variables &optional force | |
| 669 This function parses, and binds or evaluates as appropriate, any local | |
| 670 variables for the current buffer. | |
| 671 | |
| 672 The handling of @code{enable-local-variables} documented for | |
| 673 @code{normal-mode} actually takes place here. The argument @var{force} | |
| 674 usually comes from the argument @var{find-file} given to | |
| 675 @code{normal-mode}. | |
| 676 @end defun | |
| 677 | |
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678 @node Mode Help, Derived Modes, Auto Major Mode, Major Modes |
| 428 | 679 @subsection Getting Help about a Major Mode |
| 680 @cindex mode help | |
| 681 @cindex help for major mode | |
| 682 @cindex documentation for major mode | |
| 683 | |
| 684 The @code{describe-mode} function is used to provide information | |
| 685 about major modes. It is normally called with @kbd{C-h m}. The | |
| 686 @code{describe-mode} function uses the value of @code{major-mode}, | |
| 687 which is why every major mode function needs to set the | |
| 688 @code{major-mode} variable. | |
| 689 | |
| 690 @deffn Command describe-mode | |
| 691 This function displays the documentation of the current major mode. | |
| 692 | |
| 693 The @code{describe-mode} function calls the @code{documentation} | |
| 694 function using the value of @code{major-mode} as an argument. Thus, it | |
| 695 displays the documentation string of the major mode function. | |
| 696 (@xref{Accessing Documentation}.) | |
| 697 @end deffn | |
| 698 | |
| 699 @defvar major-mode | |
| 700 This variable holds the symbol for the current buffer's major mode. | |
| 701 This symbol should have a function definition that is the command to | |
| 702 switch to that major mode. The @code{describe-mode} function uses the | |
| 703 documentation string of the function as the documentation of the major | |
| 704 mode. | |
| 705 @end defvar | |
| 706 | |
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707 @node Derived Modes, , Mode Help, Major Modes |
| 428 | 708 @subsection Defining Derived Modes |
| 709 | |
| 710 It's often useful to define a new major mode in terms of an existing | |
| 711 one. An easy way to do this is to use @code{define-derived-mode}. | |
| 712 | |
| 713 @defmac define-derived-mode variant parent name docstring body@dots{} | |
| 714 This construct defines @var{variant} as a major mode command, using | |
| 715 @var{name} as the string form of the mode name. | |
| 716 | |
| 717 The new command @var{variant} is defined to call the function | |
| 718 @var{parent}, then override certain aspects of that parent mode: | |
| 719 | |
| 444 | 720 @itemize @bullet |
| 428 | 721 @item |
| 722 The new mode has its own keymap, named @code{@var{variant}-map}. | |
| 723 @code{define-derived-mode} initializes this map to inherit from | |
| 724 @code{@var{parent}-map}, if it is not already set. | |
| 725 | |
| 726 @item | |
| 727 The new mode has its own syntax table, kept in the variable | |
| 728 @code{@var{variant}-syntax-table}. | |
| 444 | 729 @code{define-derived-mode} initializes this variable by copying |
| 428 | 730 @code{@var{parent}-syntax-table}, if it is not already set. |
| 731 | |
| 732 @item | |
| 733 The new mode has its own abbrev table, kept in the variable | |
| 734 @code{@var{variant}-abbrev-table}. | |
| 444 | 735 @code{define-derived-mode} initializes this variable by copying |
| 428 | 736 @code{@var{parent}-abbrev-table}, if it is not already set. |
| 737 | |
| 738 @item | |
| 739 The new mode has its own mode hook, @code{@var{variant}-hook}, | |
| 740 which it runs in standard fashion as the very last thing that it does. | |
| 444 | 741 (The new mode also runs the mode hook of @var{parent} as part |
| 428 | 742 of calling @var{parent}.) |
| 743 @end itemize | |
| 744 | |
| 745 In addition, you can specify how to override other aspects of | |
| 746 @var{parent} with @var{body}. The command @var{variant} | |
| 444 | 747 evaluates the forms in @var{body} after setting up all its usual |
| 428 | 748 overrides, just before running @code{@var{variant}-hook}. |
| 749 | |
| 750 The argument @var{docstring} specifies the documentation string for the | |
| 751 new mode. If you omit @var{docstring}, @code{define-derived-mode} | |
| 752 generates a documentation string. | |
| 753 | |
| 754 Here is a hypothetical example: | |
| 755 | |
| 756 @example | |
| 757 (define-derived-mode hypertext-mode | |
| 758 text-mode "Hypertext" | |
| 759 "Major mode for hypertext. | |
| 760 \\@{hypertext-mode-map@}" | |
| 761 (setq case-fold-search nil)) | |
| 762 | |
| 763 (define-key hypertext-mode-map | |
| 764 [down-mouse-3] 'do-hyper-link) | |
| 765 @end example | |
| 2135 | 766 |
| 767 Do not write an @code{interactive} spec in the definition; | |
| 768 @code{define-derived-mode} does that automatically. | |
| 428 | 769 @end defmac |
| 770 | |
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771 @node Minor Modes, Modeline Format, Major Modes, Modes |
| 428 | 772 @section Minor Modes |
| 773 @cindex minor mode | |
| 774 | |
| 775 A @dfn{minor mode} provides features that users may enable or disable | |
| 776 independently of the choice of major mode. Minor modes can be enabled | |
| 777 individually or in combination. Minor modes would be better named | |
| 778 ``Generally available, optional feature modes'' except that such a name is | |
| 779 unwieldy. | |
| 780 | |
| 781 A minor mode is not usually a modification of single major mode. For | |
| 782 example, Auto Fill mode may be used in any major mode that permits text | |
| 783 insertion. To be general, a minor mode must be effectively independent | |
| 784 of the things major modes do. | |
| 785 | |
| 786 A minor mode is often much more difficult to implement than a major | |
| 787 mode. One reason is that you should be able to activate and deactivate | |
| 788 minor modes in any order. A minor mode should be able to have its | |
| 789 desired effect regardless of the major mode and regardless of the other | |
| 790 minor modes in effect. | |
| 791 | |
| 792 Often the biggest problem in implementing a minor mode is finding a | |
| 793 way to insert the necessary hook into the rest of XEmacs. Minor mode | |
| 794 keymaps make this easier than it used to be. | |
| 795 | |
| 796 @menu | |
| 797 * Minor Mode Conventions:: Tips for writing a minor mode. | |
| 798 * Keymaps and Minor Modes:: How a minor mode can have its own keymap. | |
| 799 @end menu | |
| 800 | |
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801 @node Minor Mode Conventions, Keymaps and Minor Modes, Minor Modes, Minor Modes |
| 428 | 802 @subsection Conventions for Writing Minor Modes |
| 803 @cindex minor mode conventions | |
| 804 @cindex conventions for writing minor modes | |
| 805 | |
| 806 There are conventions for writing minor modes just as there are for | |
| 807 major modes. Several of the major mode conventions apply to minor | |
| 808 modes as well: those regarding the name of the mode initialization | |
| 809 function, the names of global symbols, and the use of keymaps and | |
| 810 other tables. | |
| 811 | |
| 812 In addition, there are several conventions that are specific to | |
| 813 minor modes. | |
| 814 | |
| 815 @itemize @bullet | |
| 816 @item | |
| 817 @cindex mode variable | |
| 818 Make a variable whose name ends in @samp{-mode} to represent the minor | |
| 819 mode. Its value should enable or disable the mode (@code{nil} to | |
| 820 disable; anything else to enable.) We call this the @dfn{mode | |
| 821 variable}. | |
| 822 | |
| 823 This variable is used in conjunction with the @code{minor-mode-alist} to | |
| 824 display the minor mode name in the modeline. It can also enable | |
| 825 or disable a minor mode keymap. Individual commands or hooks can also | |
| 826 check the variable's value. | |
| 827 | |
| 828 If you want the minor mode to be enabled separately in each buffer, | |
| 829 make the variable buffer-local. | |
| 830 | |
| 831 @item | |
| 832 Define a command whose name is the same as the mode variable. | |
| 833 Its job is to enable and disable the mode by setting the variable. | |
| 834 | |
| 835 The command should accept one optional argument. If the argument is | |
| 836 @code{nil}, it should toggle the mode (turn it on if it is off, and off | |
| 837 if it is on). Otherwise, it should turn the mode on if the argument is | |
| 838 a positive integer, a symbol other than @code{nil} or @code{-}, or a | |
| 839 list whose @sc{car} is such an integer or symbol; it should turn the | |
| 840 mode off otherwise. | |
| 841 | |
| 842 Here is an example taken from the definition of @code{transient-mark-mode}. | |
| 843 It shows the use of @code{transient-mark-mode} as a variable that enables or | |
| 844 disables the mode's behavior, and also shows the proper way to toggle, | |
| 845 enable or disable the minor mode based on the raw prefix argument value. | |
| 846 | |
| 847 @smallexample | |
| 848 @group | |
| 849 (setq transient-mark-mode | |
| 850 (if (null arg) (not transient-mark-mode) | |
| 851 (> (prefix-numeric-value arg) 0))) | |
| 852 @end group | |
| 853 @end smallexample | |
| 854 | |
| 855 @item | |
| 856 Add an element to @code{minor-mode-alist} for each minor mode | |
| 857 (@pxref{Modeline Variables}). This element should be a list of the | |
| 858 following form: | |
| 859 | |
| 860 @smallexample | |
| 861 (@var{mode-variable} @var{string}) | |
| 862 @end smallexample | |
| 863 | |
| 864 Here @var{mode-variable} is the variable that controls enabling of the | |
| 865 minor mode, and @var{string} is a short string, starting with a space, | |
| 866 to represent the mode in the modeline. These strings must be short so | |
| 867 that there is room for several of them at once. | |
| 868 | |
| 869 When you add an element to @code{minor-mode-alist}, use @code{assq} to | |
| 870 check for an existing element, to avoid duplication. For example: | |
| 871 | |
| 872 @smallexample | |
| 873 @group | |
| 874 (or (assq 'leif-mode minor-mode-alist) | |
| 875 (setq minor-mode-alist | |
| 876 (cons '(leif-mode " Leif") minor-mode-alist))) | |
| 877 @end group | |
| 878 @end smallexample | |
| 879 @end itemize | |
| 880 | |
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881 @node Keymaps and Minor Modes, , Minor Mode Conventions, Minor Modes |
| 428 | 882 @subsection Keymaps and Minor Modes |
| 883 | |
| 884 Each minor mode can have its own keymap, which is active when the mode | |
| 885 is enabled. To set up a keymap for a minor mode, add an element to the | |
| 886 alist @code{minor-mode-map-alist}. @xref{Active Keymaps}. | |
| 887 | |
| 888 @cindex @code{self-insert-command}, minor modes | |
| 889 One use of minor mode keymaps is to modify the behavior of certain | |
| 890 self-inserting characters so that they do something else as well as | |
| 891 self-insert. In general, this is the only way to do that, since the | |
| 892 facilities for customizing @code{self-insert-command} are limited to | |
| 893 special cases (designed for abbrevs and Auto Fill mode). (Do not try | |
| 894 substituting your own definition of @code{self-insert-command} for the | |
| 895 standard one. The editor command loop handles this function specially.) | |
| 896 | |
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897 @node Modeline Format, Hooks, Minor Modes, Modes |
| 428 | 898 @section Modeline Format |
| 899 @cindex modeline | |
| 900 | |
| 901 Each Emacs window (aside from minibuffer windows) includes a modeline, | |
| 902 which displays status information about the buffer displayed in the | |
| 903 window. The modeline contains information about the buffer, such as its | |
| 904 name, associated file, depth of recursive editing, and the major and | |
| 905 minor modes. | |
| 906 | |
| 907 This section describes how the contents of the modeline are | |
| 908 controlled. It is in the chapter on modes because much of the | |
| 909 information displayed in the modeline relates to the enabled major and | |
| 910 minor modes. | |
| 911 | |
| 912 @code{modeline-format} is a buffer-local variable that holds a | |
| 913 template used to display the modeline of the current buffer. All | |
| 914 windows for the same buffer use the same @code{modeline-format} and | |
| 915 their modelines appear the same (except for scrolling percentages and | |
| 916 line numbers). | |
| 917 | |
| 918 The modeline of a window is normally updated whenever a different | |
| 919 buffer is shown in the window, or when the buffer's modified-status | |
| 920 changes from @code{nil} to @code{t} or vice-versa. If you modify any of | |
| 921 the variables referenced by @code{modeline-format} (@pxref{Modeline | |
| 922 Variables}), you may want to force an update of the modeline so as to | |
| 923 display the new information. | |
| 924 | |
| 925 @c Emacs 19 feature | |
| 926 @defun redraw-modeline &optional all | |
| 927 Force redisplay of the current buffer's modeline. If @var{all} is | |
| 928 non-@code{nil}, then force redisplay of all modelines. | |
| 929 @end defun | |
| 930 | |
| 931 The modeline is usually displayed in inverse video. This | |
| 932 is controlled using the @code{modeline} face. @xref{Faces}. | |
| 933 | |
| 934 @menu | |
| 935 * Modeline Data:: The data structure that controls the modeline. | |
| 936 * Modeline Variables:: Variables used in that data structure. | |
| 937 * %-Constructs:: Putting information into a modeline. | |
| 938 @end menu | |
| 939 | |
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940 @node Modeline Data, Modeline Variables, Modeline Format, Modeline Format |
| 428 | 941 @subsection The Data Structure of the Modeline |
| 942 @cindex modeline construct | |
| 943 | |
| 944 The modeline contents are controlled by a data structure of lists, | |
| 945 strings, symbols, and numbers kept in the buffer-local variable | |
| 442 | 946 @code{modeline-format}. The data structure is called a @dfn{modeline |
| 428 | 947 construct}, and it is built in recursive fashion out of simpler modeline |
| 948 constructs. The same data structure is used for constructing | |
| 949 frame titles (@pxref{Frame Titles}). | |
| 950 | |
| 951 @defvar modeline-format | |
| 952 The value of this variable is a modeline construct with overall | |
| 953 responsibility for the modeline format. The value of this variable | |
| 954 controls which other variables are used to form the modeline text, and | |
| 955 where they appear. | |
| 956 @end defvar | |
| 957 | |
| 958 A modeline construct may be as simple as a fixed string of text, but | |
| 959 it usually specifies how to use other variables to construct the text. | |
| 960 Many of these variables are themselves defined to have modeline | |
| 961 constructs as their values. | |
| 962 | |
| 963 The default value of @code{modeline-format} incorporates the values | |
| 964 of variables such as @code{mode-name} and @code{minor-mode-alist}. | |
| 965 Because of this, very few modes need to alter @code{modeline-format}. | |
| 966 For most purposes, it is sufficient to alter the variables referenced by | |
| 967 @code{modeline-format}. | |
| 968 | |
| 442 | 969 A modeline construct may be a string, symbol, glyph, generic |
| 970 specifier, list or cons cell. | |
| 428 | 971 |
| 972 @table @code | |
| 973 @cindex percent symbol in modeline | |
| 974 @item @var{string} | |
| 975 A string as a modeline construct is displayed verbatim in the mode line | |
| 976 except for @dfn{@code{%}-constructs}. Decimal digits after the @samp{%} | |
| 977 specify the field width for space filling on the right (i.e., the data | |
| 978 is left justified). @xref{%-Constructs}. | |
| 979 | |
| 980 @item @var{symbol} | |
| 981 A symbol as a modeline construct stands for its value. The value of | |
| 442 | 982 @var{symbol} is processed as a modeline construct, in place of |
| 983 @var{symbol}. However, the symbols @code{t} and @code{nil} are ignored; | |
| 984 so is any symbol whose value is void. | |
| 428 | 985 |
| 986 There is one exception: if the value of @var{symbol} is a string, it is | |
| 987 displayed verbatim: the @code{%}-constructs are not recognized. | |
| 988 | |
| 442 | 989 @item @var{glyph} |
| 990 A glyph is displayed as is. | |
| 991 | |
| 992 @item @var{generic-specifier} | |
| 993 A @var{generic-specifier} (i.e. a specifier of type @code{generic}) | |
| 994 stands for its instance. The instance of @var{generic-specifier} is | |
| 995 computed in the current window using the equivalent of | |
| 996 @code{specifier-instance} and the value is processed. | |
| 997 | |
| 428 | 998 @item (@var{string} @var{rest}@dots{}) @r{or} (@var{list} @var{rest}@dots{}) |
| 999 A list whose first element is a string or list means to process all the | |
| 1000 elements recursively and concatenate the results. This is the most | |
| 1001 common form of mode line construct. | |
| 1002 | |
| 1003 @item (@var{symbol} @var{then} @var{else}) | |
| 1004 A list whose first element is a symbol is a conditional. Its meaning | |
| 1005 depends on the value of @var{symbol}. If the value is non-@code{nil}, | |
| 1006 the second element, @var{then}, is processed recursively as a modeline | |
| 1007 element. But if the value of @var{symbol} is @code{nil}, the third | |
| 1008 element, @var{else}, is processed recursively. You may omit @var{else}; | |
| 1009 then the mode line element displays nothing if the value of @var{symbol} | |
| 1010 is @code{nil}. | |
| 1011 | |
| 1012 @item (@var{width} @var{rest}@dots{}) | |
| 1013 A list whose first element is an integer specifies truncation or | |
| 1014 padding of the results of @var{rest}. The remaining elements | |
| 1015 @var{rest} are processed recursively as modeline constructs and | |
| 1016 concatenated together. Then the result is space filled (if | |
| 1017 @var{width} is positive) or truncated (to @minus{}@var{width} columns, | |
| 1018 if @var{width} is negative) on the right. | |
| 1019 | |
| 1020 For example, the usual way to show what percentage of a buffer is above | |
| 1021 the top of the window is to use a list like this: @code{(-3 "%p")}. | |
| 442 | 1022 |
| 1023 @item (@var{extent} @var{rest}@dots{}) | |
| 1024 | |
| 1025 A list whose car is an extent means the cdr of the list is processed | |
| 1026 normally but the results are displayed using the face of the extent, and | |
| 1027 mouse clicks over this section are processed using the keymap of the | |
| 1028 extent. (In addition, if the extent has a help-echo property, that | |
| 1029 string will be echoed when the mouse moves over this section.) If | |
| 1030 extents are nested, all keymaps are properly consulted when processing | |
| 1031 mouse clicks, but multiple faces are not correctly merged (only the | |
| 1032 first face is used), and lists of faces are not correctly handled. | |
| 1033 @c #### Document generate-modeline-string. | |
| 1034 @c See `generated-modeline-string' for more information. | |
| 428 | 1035 @end table |
| 1036 | |
| 1037 If you do alter @code{modeline-format} itself, the new value should | |
| 1038 use the same variables that appear in the default value (@pxref{Modeline | |
| 1039 Variables}), rather than duplicating their contents or displaying | |
| 1040 the information in another fashion. This way, customizations made by | |
| 1041 the user or by Lisp programs (such as @code{display-time} and major | |
| 1042 modes) via changes to those variables remain effective. | |
| 1043 | |
| 1044 @cindex Shell mode @code{modeline-format} | |
| 1045 Here is an example of a @code{modeline-format} that might be | |
| 1046 useful for @code{shell-mode}, since it contains the hostname and default | |
| 1047 directory. | |
| 1048 | |
| 1049 @example | |
| 1050 @group | |
| 1051 (setq modeline-format | |
| 1052 (list "" | |
| 1053 'modeline-modified | |
| 444 | 1054 "%b--" |
| 428 | 1055 @end group |
| 1056 (getenv "HOST") ; @r{One element is not constant.} | |
| 444 | 1057 ":" |
| 428 | 1058 'default-directory |
| 1059 " " | |
| 1060 'global-mode-string | |
| 1061 " %[(" | |
| 444 | 1062 'mode-name |
| 1063 'modeline-process | |
| 1064 'minor-mode-alist | |
| 1065 "%n" | |
| 428 | 1066 ")%]----" |
| 1067 @group | |
| 1068 '(line-number-mode "L%l--") | |
| 1069 '(-3 . "%p") | |
| 1070 "-%-")) | |
| 1071 @end group | |
| 1072 @end example | |
| 1073 | |
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1074 @node Modeline Variables, %-Constructs, Modeline Data, Modeline Format |
| 428 | 1075 @subsection Variables Used in the Modeline |
| 1076 | |
| 1077 This section describes variables incorporated by the | |
| 1078 standard value of @code{modeline-format} into the text of the mode | |
| 1079 line. There is nothing inherently special about these variables; any | |
| 1080 other variables could have the same effects on the modeline if | |
| 1081 @code{modeline-format} were changed to use them. | |
| 1082 | |
| 1083 @defvar modeline-modified | |
| 1084 This variable holds the value of the modeline construct that displays | |
| 1085 whether the current buffer is modified. | |
| 1086 | |
| 1087 The default value of @code{modeline-modified} is @code{("--%1*%1+-")}. | |
| 1088 This means that the modeline displays @samp{--**-} if the buffer is | |
| 1089 modified, @samp{-----} if the buffer is not modified, @samp{--%%-} if | |
| 1090 the buffer is read only, and @samp{--%*--} if the buffer is read only | |
| 1091 and modified. | |
| 1092 | |
| 1093 Changing this variable does not force an update of the modeline. | |
| 1094 @end defvar | |
| 1095 | |
| 1096 @defvar modeline-buffer-identification | |
| 1097 This variable identifies the buffer being displayed in the window. Its | |
| 1098 default value is @code{("%F: %17b")}, which means that it usually | |
| 1099 displays @samp{Emacs:} followed by seventeen characters of the buffer | |
| 1100 name. (In a terminal frame, it displays the frame name instead of | |
| 1101 @samp{Emacs}; this has the effect of showing the frame number.) You may | |
| 1102 want to change this in modes such as Rmail that do not behave like a | |
| 1103 ``normal'' XEmacs. | |
| 1104 @end defvar | |
| 1105 | |
| 1106 @defvar global-mode-string | |
| 1107 This variable holds a modeline spec that appears in the mode line by | |
| 1108 default, just after the buffer name. The command @code{display-time} | |
| 1109 sets @code{global-mode-string} to refer to the variable | |
| 1110 @code{display-time-string}, which holds a string containing the time and | |
| 1111 load information. | |
| 1112 | |
| 1113 The @samp{%M} construct substitutes the value of | |
| 1114 @code{global-mode-string}, but this is obsolete, since the variable is | |
| 1115 included directly in the modeline. | |
| 1116 @end defvar | |
| 1117 | |
| 1118 @defvar mode-name | |
| 1119 This buffer-local variable holds the ``pretty'' name of the current | |
| 1120 buffer's major mode. Each major mode should set this variable so that the | |
| 1121 mode name will appear in the modeline. | |
| 1122 @end defvar | |
| 1123 | |
| 1124 @defvar minor-mode-alist | |
| 1125 This variable holds an association list whose elements specify how the | |
| 1126 modeline should indicate that a minor mode is active. Each element of | |
| 1127 the @code{minor-mode-alist} should be a two-element list: | |
| 1128 | |
| 1129 @example | |
| 1130 (@var{minor-mode-variable} @var{modeline-string}) | |
| 1131 @end example | |
| 1132 | |
| 1133 More generally, @var{modeline-string} can be any mode line spec. It | |
| 1134 appears in the mode line when the value of @var{minor-mode-variable} is | |
| 1135 non-@code{nil}, and not otherwise. These strings should begin with | |
| 1136 spaces so that they don't run together. Conventionally, the | |
| 1137 @var{minor-mode-variable} for a specific mode is set to a non-@code{nil} | |
| 1138 value when that minor mode is activated. | |
| 1139 | |
| 1140 The default value of @code{minor-mode-alist} is: | |
| 1141 | |
| 1142 @example | |
| 1143 @group | |
| 1144 minor-mode-alist | |
| 1145 @result{} ((vc-mode vc-mode) | |
| 444 | 1146 (abbrev-mode " Abbrev") |
| 1147 (overwrite-mode overwrite-mode) | |
| 1148 (auto-fill-function " Fill") | |
| 428 | 1149 (defining-kbd-macro " Def") |
| 1150 (isearch-mode isearch-mode)) | |
| 1151 @end group | |
| 1152 @end example | |
| 1153 | |
| 1154 @code{minor-mode-alist} is not buffer-local. The variables mentioned | |
| 1155 in the alist should be buffer-local if the minor mode can be enabled | |
| 1156 separately in each buffer. | |
| 1157 @end defvar | |
| 1158 | |
| 1159 @defvar modeline-process | |
| 1160 This buffer-local variable contains the modeline information on process | |
| 1161 status in modes used for communicating with subprocesses. It is | |
| 1162 displayed immediately following the major mode name, with no intervening | |
| 1163 space. For example, its value in the @samp{*shell*} buffer is | |
| 1164 @code{(":@: %s")}, which allows the shell to display its status along | |
| 1165 with the major mode as: @samp{(Shell:@: run)}. Normally this variable | |
| 1166 is @code{nil}. | |
| 1167 @end defvar | |
| 1168 | |
| 1169 @defvar default-modeline-format | |
| 1170 This variable holds the default @code{modeline-format} for buffers | |
| 1171 that do not override it. This is the same as @code{(default-value | |
| 1172 'modeline-format)}. | |
| 1173 | |
| 1174 The default value of @code{default-modeline-format} is: | |
| 1175 | |
| 1176 @example | |
| 1177 @group | |
| 1178 ("" | |
| 1179 modeline-modified | |
| 1180 modeline-buffer-identification | |
| 1181 " " | |
| 1182 global-mode-string | |
| 1183 " %[(" | |
| 444 | 1184 mode-name |
| 428 | 1185 @end group |
| 1186 @group | |
| 1187 modeline-process | |
| 444 | 1188 minor-mode-alist |
| 1189 "%n" | |
| 428 | 1190 ")%]----" |
| 1191 (line-number-mode "L%l--") | |
| 1192 (-3 . "%p") | |
| 1193 "-%-") | |
| 1194 @end group | |
| 1195 @end example | |
| 1196 @end defvar | |
| 1197 | |
| 1198 @defvar vc-mode | |
| 1199 The variable @code{vc-mode}, local in each buffer, records whether the | |
| 1200 buffer's visited file is maintained with version control, and, if so, | |
| 1201 which kind. Its value is @code{nil} for no version control, or a string | |
| 1202 that appears in the mode line. | |
| 1203 @end defvar | |
| 1204 | |
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1205 @node %-Constructs, , Modeline Variables, Modeline Format |
| 428 | 1206 @subsection @code{%}-Constructs in the ModeLine |
| 1207 | |
| 1208 The following table lists the recognized @code{%}-constructs and what | |
| 1209 they mean. In any construct except @samp{%%}, you can add a decimal | |
| 1210 integer after the @samp{%} to specify how many characters to display. | |
| 1211 | |
| 1212 @table @code | |
| 1213 @item %b | |
| 1214 The current buffer name, obtained with the @code{buffer-name} function. | |
| 1215 @xref{Buffer Names}. | |
| 1216 | |
| 1217 @item %f | |
| 1218 The visited file name, obtained with the @code{buffer-file-name} | |
| 1219 function. @xref{Buffer File Name}. | |
| 1220 | |
| 1221 @item %F | |
| 1222 The name of the selected frame. | |
| 1223 | |
| 1224 @item %c | |
| 1225 The current column number of point. | |
| 1226 | |
| 1227 @item %l | |
| 1228 The current line number of point. | |
| 1229 | |
| 1230 @item %* | |
| 1231 @samp{%} if the buffer is read only (see @code{buffer-read-only}); @* | |
| 1232 @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @* | |
| 1233 @samp{-} otherwise. @xref{Buffer Modification}. | |
| 1234 | |
| 1235 @item %+ | |
| 1236 @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @* | |
| 1237 @samp{%} if the buffer is read only (see @code{buffer-read-only}); @* | |
| 1238 @samp{-} otherwise. This differs from @samp{%*} only for a modified | |
| 1239 read-only buffer. @xref{Buffer Modification}. | |
| 1240 | |
| 1241 @item %& | |
| 1242 @samp{*} if the buffer is modified, and @samp{-} otherwise. | |
| 1243 | |
| 1244 @item %s | |
| 1245 The status of the subprocess belonging to the current buffer, obtained with | |
| 1246 @code{process-status}. @xref{Process Information}. | |
| 1247 | |
| 1248 @c The following two may only apply in XEmacs. | |
| 1249 @item %l | |
| 442 | 1250 The current line number. |
| 428 | 1251 |
| 1252 @item %S | |
| 442 | 1253 The name of the selected frame; this is only meaningful under the |
| 428 | 1254 X Window System. @xref{Frame Name}. |
| 1255 | |
| 1256 @item %t | |
| 1257 Whether the visited file is a text file or a binary file. (This is a | |
| 1258 meaningful distinction only on certain operating systems.) | |
| 1259 | |
| 1260 @item %p | |
| 1261 The percentage of the buffer text above the @strong{top} of window, or | |
| 1262 @samp{Top}, @samp{Bottom} or @samp{All}. | |
| 1263 | |
| 1264 @item %P | |
| 1265 The percentage of the buffer text that is above the @strong{bottom} of | |
| 1266 the window (which includes the text visible in the window, as well as | |
| 1267 the text above the top), plus @samp{Top} if the top of the buffer is | |
| 1268 visible on screen; or @samp{Bottom} or @samp{All}. | |
| 1269 | |
| 1270 @item %n | |
| 1271 @samp{Narrow} when narrowing is in effect; nothing otherwise (see | |
| 1272 @code{narrow-to-region} in @ref{Narrowing}). | |
| 1273 | |
| 442 | 1274 @item %C |
| 1275 Under XEmacs/mule, the mnemonic for @code{buffer-file-coding-system}. | |
| 1276 | |
| 428 | 1277 @item %[ |
| 1278 An indication of the depth of recursive editing levels (not counting | |
| 1279 minibuffer levels): one @samp{[} for each editing level. | |
| 1280 @xref{Recursive Editing}. | |
| 1281 | |
| 1282 @item %] | |
| 1283 One @samp{]} for each recursive editing level (not counting minibuffer | |
| 1284 levels). | |
| 1285 | |
| 1286 @item %% | |
| 1287 The character @samp{%}---this is how to include a literal @samp{%} in a | |
| 1288 string in which @code{%}-constructs are allowed. | |
| 1289 | |
| 1290 @item %- | |
| 1291 Dashes sufficient to fill the remainder of the modeline. | |
| 1292 @end table | |
| 1293 | |
| 1294 The following two @code{%}-constructs are still supported, but they are | |
| 1295 obsolete, since you can get the same results with the variables | |
| 1296 @code{mode-name} and @code{global-mode-string}. | |
| 1297 | |
| 1298 @table @code | |
| 1299 @item %m | |
| 1300 The value of @code{mode-name}. | |
| 1301 | |
| 1302 @item %M | |
| 1303 The value of @code{global-mode-string}. Currently, only | |
| 1304 @code{display-time} modifies the value of @code{global-mode-string}. | |
| 1305 @end table | |
| 1306 | |
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1307 @node Hooks, , Modeline Format, Modes |
| 428 | 1308 @section Hooks |
| 1309 @cindex hooks | |
| 1310 | |
| 1311 A @dfn{hook} is a variable where you can store a function or functions | |
| 1312 to be called on a particular occasion by an existing program. XEmacs | |
| 1313 provides hooks for the sake of customization. Most often, hooks are set | |
| 1314 up in the @file{.emacs} file, but Lisp programs can set them also. | |
| 1315 @xref{Standard Hooks}, for a list of standard hook variables. | |
| 1316 | |
| 1317 Most of the hooks in XEmacs are @dfn{normal hooks}. These variables | |
| 1318 contain lists of functions to be called with no arguments. The reason | |
| 1319 most hooks are normal hooks is so that you can use them in a uniform | |
| 444 | 1320 way. You can usually tell when a hook is a normal hook, because its |
| 428 | 1321 name ends in @samp{-hook}. |
| 1322 | |
| 1323 The recommended way to add a hook function to a normal hook is by | |
| 1324 calling @code{add-hook} (see below). The hook functions may be any of | |
| 1325 the valid kinds of functions that @code{funcall} accepts (@pxref{What Is | |
| 1326 a Function}). Most normal hook variables are initially void; | |
| 1327 @code{add-hook} knows how to deal with this. | |
| 1328 | |
| 1329 As for abnormal hooks, those whose names end in @samp{-function} have | |
| 1330 a value that is a single function. Those whose names end in | |
| 1331 @samp{-hooks} have a value that is a list of functions. Any hook that | |
| 1332 is abnormal is abnormal because a normal hook won't do the job; either | |
| 1333 the functions are called with arguments, or their values are meaningful. | |
| 1334 The name shows you that the hook is abnormal and that you should look at | |
| 1335 its documentation string to see how to use it properly. | |
| 1336 | |
| 1337 Major mode functions are supposed to run a hook called the @dfn{mode | |
| 1338 hook} as the last step of initialization. This makes it easy for a user | |
| 1339 to customize the behavior of the mode, by overriding the local variable | |
| 1340 assignments already made by the mode. But hooks are used in other | |
| 1341 contexts too. For example, the hook @code{suspend-hook} runs just | |
| 1342 before XEmacs suspends itself (@pxref{Suspending XEmacs}). | |
| 1343 | |
| 1344 Here's an expression that uses a mode hook to turn on Auto Fill mode | |
| 1345 when in Lisp Interaction mode: | |
| 1346 | |
| 1347 @example | |
| 1348 (add-hook 'lisp-interaction-mode-hook 'turn-on-auto-fill) | |
| 1349 @end example | |
| 1350 | |
| 1351 The next example shows how to use a hook to customize the way XEmacs | |
| 1352 formats C code. (People often have strong personal preferences for one | |
| 1353 format or another.) Here the hook function is an anonymous lambda | |
| 1354 expression. | |
| 1355 | |
| 1356 @cindex lambda expression in hook | |
| 1357 @example | |
| 1358 @group | |
| 444 | 1359 (add-hook 'c-mode-hook |
| 428 | 1360 (function (lambda () |
| 1361 (setq c-indent-level 4 | |
| 1362 c-argdecl-indent 0 | |
| 1363 c-label-offset -4 | |
| 1364 @end group | |
| 1365 @group | |
| 1366 c-continued-statement-indent 0 | |
| 1367 c-brace-offset 0 | |
| 1368 comment-column 40)))) | |
| 1369 | |
| 1370 (setq c++-mode-hook c-mode-hook) | |
| 1371 @end group | |
| 1372 @end example | |
| 1373 | |
| 1374 The final example shows how the appearance of the modeline can be | |
| 1375 modified for a particular class of buffers only. | |
| 1376 | |
| 1377 @example | |
| 1378 @group | |
| 1379 (add-hook 'text-mode-hook | |
| 1380 (function (lambda () | |
| 1381 (setq modeline-format | |
| 1382 '(modeline-modified | |
| 1383 "Emacs: %14b" | |
| 444 | 1384 " " |
| 428 | 1385 @end group |
| 1386 @group | |
| 1387 default-directory | |
| 1388 " " | |
| 1389 global-mode-string | |
| 444 | 1390 "%[(" |
| 1391 mode-name | |
| 1392 minor-mode-alist | |
| 1393 "%n" | |
| 1394 modeline-process | |
| 428 | 1395 ") %]---" |
| 1396 (-3 . "%p") | |
| 1397 "-%-"))))) | |
| 1398 @end group | |
| 1399 @end example | |
| 1400 | |
| 1401 At the appropriate time, XEmacs uses the @code{run-hooks} function to | |
| 1402 run particular hooks. This function calls the hook functions you have | |
| 1403 added with @code{add-hooks}. | |
| 1404 | |
| 1405 @defun run-hooks &rest hookvar | |
| 1406 This function takes one or more hook variable names as arguments, and | |
| 1407 runs each hook in turn. Each @var{hookvar} argument should be a symbol | |
| 1408 that is a hook variable. These arguments are processed in the order | |
| 1409 specified. | |
| 1410 | |
| 1411 If a hook variable has a non-@code{nil} value, that value may be a | |
| 1412 function or a list of functions. If the value is a function (either a | |
| 1413 lambda expression or a symbol with a function definition), it is | |
| 1414 called. If it is a list, the elements are called, in order. | |
| 1415 The hook functions are called with no arguments. | |
| 1416 | |
| 1417 For example, here's how @code{emacs-lisp-mode} runs its mode hook: | |
| 1418 | |
| 1419 @example | |
| 1420 (run-hooks 'emacs-lisp-mode-hook) | |
| 1421 @end example | |
| 1422 @end defun | |
| 1423 | |
| 2135 | 1424 @defun run-mode-hooks &rest hookvars |
| 1425 Like @code{run-hooks}, but is affected by the @code{delay-mode-hooks} | |
| 1426 macro. | |
| 1427 @end defun | |
| 1428 | |
| 1429 @defmac delay-mode-hooks body... | |
| 1430 This macro executes the @var{body} forms but defers all calls to | |
| 1431 @code{run-mode-hooks} within them until the end of @var{body}. | |
| 1432 This macro enables a derived mode to arrange not to run | |
| 1433 its parent modes' mode hooks until the end. | |
| 1434 @end defmac | |
| 1435 | |
| 1436 @defun run-hook-with-args hook &rest args | |
| 1437 This function is the way to run an abnormal hook and always call all | |
| 1438 of the hook functions. It calls each of the hook functions one by | |
| 1439 one, passing each of them the arguments @var{args}. | |
| 1440 @end defun | |
| 1441 | |
| 1442 @defun run-hook-with-args-until-failure hook &rest args | |
| 1443 This function is the way to run an abnormal hook until one of the hook | |
| 1444 functions fails. It calls each of the hook functions, passing each of | |
| 1445 them the arguments @var{args}, until some hook function returns | |
| 1446 @code{nil}. It then stops and returns @code{nil}. If none of the | |
| 1447 hook functions return @code{nil}, it returns a non-@code{nil} value. | |
| 1448 @end defun | |
| 1449 | |
| 1450 @defun run-hook-with-args-until-success hook &rest args | |
| 1451 This function is the way to run an abnormal hook until a hook function | |
| 1452 succeeds. It calls each of the hook functions, passing each of them | |
| 1453 the arguments @var{args}, until some hook function returns | |
| 1454 non-@code{nil}. Then it stops, and returns whatever was returned by | |
| 1455 the last hook function that was called. If all hook functions return | |
| 1456 @code{nil}, it returns @code{nil} as well. | |
| 1457 @end defun | |
| 1458 | |
| 428 | 1459 @defun add-hook hook function &optional append local |
| 1460 This function is the handy way to add function @var{function} to hook | |
| 1461 variable @var{hook}. The argument @var{function} may be any valid Lisp | |
| 1462 function with the proper number of arguments. For example, | |
| 1463 | |
| 1464 @example | |
| 1465 (add-hook 'text-mode-hook 'my-text-hook-function) | |
| 1466 @end example | |
| 1467 | |
| 1468 @noindent | |
| 1469 adds @code{my-text-hook-function} to the hook called @code{text-mode-hook}. | |
| 1470 | |
| 1471 You can use @code{add-hook} for abnormal hooks as well as for normal | |
| 1472 hooks. | |
| 1473 | |
| 1474 It is best to design your hook functions so that the order in which they | |
| 1475 are executed does not matter. Any dependence on the order is ``asking | |
| 1476 for trouble.'' However, the order is predictable: normally, | |
| 1477 @var{function} goes at the front of the hook list, so it will be | |
| 1478 executed first (barring another @code{add-hook} call). | |
| 1479 | |
| 1480 If the optional argument @var{append} is non-@code{nil}, the new hook | |
| 1481 function goes at the end of the hook list and will be executed last. | |
| 1482 | |
| 1483 If @var{local} is non-@code{nil}, that says to make the new hook | |
| 1484 function local to the current buffer. Before you can do this, you must | |
| 1485 make the hook itself buffer-local by calling @code{make-local-hook} | |
| 1486 (@strong{not} @code{make-local-variable}). If the hook itself is not | |
| 1487 buffer-local, then the value of @var{local} makes no difference---the | |
| 1488 hook function is always global. | |
| 1489 @end defun | |
| 1490 | |
| 1491 @defun remove-hook hook function &optional local | |
| 1492 This function removes @var{function} from the hook variable @var{hook}. | |
| 1493 | |
| 1494 If @var{local} is non-@code{nil}, that says to remove @var{function} | |
| 1495 from the local hook list instead of from the global hook list. If the | |
| 1496 hook itself is not buffer-local, then the value of @var{local} makes no | |
| 1497 difference. | |
| 1498 @end defun | |
| 1499 | |
| 1500 @defun make-local-hook hook | |
| 444 | 1501 This function makes the hook variable @var{hook} local to the current |
| 428 | 1502 buffer. When a hook variable is local, it can have local and global |
| 1503 hook functions, and @code{run-hooks} runs all of them. | |
| 1504 | |
| 1505 This function works by making @code{t} an element of the buffer-local | |
| 1506 value. That serves as a flag to use the hook functions in the default | |
| 1507 value of the hook variable as well as those in the local value. Since | |
| 1508 @code{run-hooks} understands this flag, @code{make-local-hook} works | |
| 1509 with all normal hooks. It works for only some non-normal hooks---those | |
| 1510 whose callers have been updated to understand this meaning of @code{t}. | |
| 1511 | |
| 1512 Do not use @code{make-local-variable} directly for hook variables; it is | |
| 1513 not sufficient. | |
| 1514 @end defun |