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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
73b0cd50 | 3 | @c Copyright (C) 1997-2011 Free Software Foundation, Inc. |
b8d4c8d0 | 4 | @c See the file elisp.texi for copying conditions. |
6336d8c3 | 5 | @setfilename ../../info/customize |
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6 | @node Customization, Loading, Macros, Top |
7 | @chapter Writing Customization Definitions | |
8 | ||
9 | @cindex customization definitions | |
10 | This chapter describes how to declare user options for customization, | |
11 | and also customization groups for classifying them. We use the term | |
12 | @dfn{customization item} to include both kinds of customization | |
13 | definitions---as well as face definitions (@pxref{Defining Faces}). | |
14 | ||
15 | @menu | |
16 | * Common Keywords:: Common keyword arguments for all kinds of | |
17 | customization declarations. | |
18 | * Group Definitions:: Writing customization group definitions. | |
19 | * Variable Definitions:: Declaring user options. | |
20 | * Customization Types:: Specifying the type of a user option. | |
21 | @end menu | |
22 | ||
23 | @node Common Keywords | |
24 | @section Common Item Keywords | |
25 | ||
26 | @cindex customization keywords | |
27 | All kinds of customization declarations (for variables and groups, and | |
28 | for faces) accept keyword arguments for specifying various information. | |
29 | This section describes some keywords that apply to all kinds. | |
30 | ||
31 | All of these keywords, except @code{:tag}, can be used more than once | |
32 | in a given item. Each use of the keyword has an independent effect. | |
33 | The keyword @code{:tag} is an exception because any given item can only | |
34 | display one name. | |
35 | ||
36 | @table @code | |
37 | @item :tag @var{label} | |
38 | @kindex tag@r{, customization keyword} | |
39 | Use @var{label}, a string, instead of the item's name, to label the | |
40 | item in customization menus and buffers. @strong{Don't use a tag | |
41 | which is substantially different from the item's real name; that would | |
0f631634 | 42 | cause confusion.} |
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43 | |
44 | @kindex group@r{, customization keyword} | |
45 | @item :group @var{group} | |
46 | Put this customization item in group @var{group}. When you use | |
47 | @code{:group} in a @code{defgroup}, it makes the new group a subgroup of | |
48 | @var{group}. | |
49 | ||
50 | If you use this keyword more than once, you can put a single item into | |
51 | more than one group. Displaying any of those groups will show this | |
52 | item. Please don't overdo this, since the result would be annoying. | |
53 | ||
54 | @item :link @var{link-data} | |
55 | @kindex link@r{, customization keyword} | |
56 | Include an external link after the documentation string for this item. | |
57 | This is a sentence containing an active field which references some | |
58 | other documentation. | |
59 | ||
60 | There are several alternatives you can use for @var{link-data}: | |
61 | ||
62 | @table @code | |
63 | @item (custom-manual @var{info-node}) | |
64 | Link to an Info node; @var{info-node} is a string which specifies the | |
65 | node name, as in @code{"(emacs)Top"}. The link appears as | |
66 | @samp{[Manual]} in the customization buffer and enters the built-in | |
67 | Info reader on @var{info-node}. | |
68 | ||
69 | @item (info-link @var{info-node}) | |
70 | Like @code{custom-manual} except that the link appears | |
71 | in the customization buffer with the Info node name. | |
72 | ||
73 | @item (url-link @var{url}) | |
74 | Link to a web page; @var{url} is a string which specifies the | |
75 | @acronym{URL}. The link appears in the customization buffer as | |
76 | @var{url} and invokes the WWW browser specified by | |
77 | @code{browse-url-browser-function}. | |
78 | ||
79 | @item (emacs-commentary-link @var{library}) | |
80 | Link to the commentary section of a library; @var{library} is a string | |
81 | which specifies the library name. | |
82 | ||
83 | @item (emacs-library-link @var{library}) | |
84 | Link to an Emacs Lisp library file; @var{library} is a string which | |
85 | specifies the library name. | |
86 | ||
87 | @item (file-link @var{file}) | |
88 | Link to a file; @var{file} is a string which specifies the name of the | |
89 | file to visit with @code{find-file} when the user invokes this link. | |
90 | ||
91 | @item (function-link @var{function}) | |
92 | Link to the documentation of a function; @var{function} is a string | |
93 | which specifies the name of the function to describe with | |
94 | @code{describe-function} when the user invokes this link. | |
95 | ||
96 | @item (variable-link @var{variable}) | |
97 | Link to the documentation of a variable; @var{variable} is a string | |
98 | which specifies the name of the variable to describe with | |
99 | @code{describe-variable} when the user invokes this link. | |
100 | ||
101 | @item (custom-group-link @var{group}) | |
102 | Link to another customization group. Invoking it creates a new | |
103 | customization buffer for @var{group}. | |
104 | @end table | |
105 | ||
106 | You can specify the text to use in the customization buffer by adding | |
107 | @code{:tag @var{name}} after the first element of the @var{link-data}; | |
108 | for example, @code{(info-link :tag "foo" "(emacs)Top")} makes a link to | |
109 | the Emacs manual which appears in the buffer as @samp{foo}. | |
110 | ||
111 | An item can have more than one external link; however, most items have | |
112 | none at all. | |
113 | ||
114 | @item :load @var{file} | |
115 | @kindex load@r{, customization keyword} | |
116 | Load file @var{file} (a string) before displaying this customization | |
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117 | item (@pxref{Loading}). Loading is done with @code{load}, and only if |
118 | the file is not already loaded. | |
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119 | |
120 | @item :require @var{feature} | |
121 | @kindex require@r{, customization keyword} | |
122 | Execute @code{(require '@var{feature})} when your saved customizations | |
123 | set the value of this item. @var{feature} should be a symbol. | |
124 | ||
125 | The most common reason to use @code{:require} is when a variable enables | |
126 | a feature such as a minor mode, and just setting the variable won't have | |
127 | any effect unless the code which implements the mode is loaded. | |
128 | ||
129 | @item :version @var{version} | |
130 | @kindex version@r{, customization keyword} | |
131 | This keyword specifies that the item was first introduced in Emacs | |
132 | version @var{version}, or that its default value was changed in that | |
133 | version. The value @var{version} must be a string. | |
134 | ||
135 | @item :package-version '(@var{package} . @var{version}) | |
136 | @kindex package-version@r{, customization keyword} | |
137 | This keyword specifies that the item was first introduced in | |
138 | @var{package} version @var{version}, or that its meaning or default | |
139 | value was changed in that version. The value of @var{package} is a | |
140 | symbol and @var{version} is a string. | |
141 | ||
142 | This keyword takes priority over @code{:version}. | |
143 | ||
144 | @var{package} should be the official name of the package, such as MH-E | |
145 | or Gnus. If the package @var{package} is released as part of Emacs, | |
146 | @var{package} and @var{version} should appear in the value of | |
147 | @code{customize-package-emacs-version-alist}. | |
148 | @end table | |
149 | ||
150 | Packages distributed as part of Emacs that use the | |
151 | @code{:package-version} keyword must also update the | |
152 | @code{customize-package-emacs-version-alist} variable. | |
153 | ||
154 | @defvar customize-package-emacs-version-alist | |
155 | This alist provides a mapping for the versions of Emacs that are | |
156 | associated with versions of a package listed in the | |
157 | @code{:package-version} keyword. Its elements look like this: | |
158 | ||
159 | @example | |
160 | (@var{package} (@var{pversion} . @var{eversion})@dots{}) | |
161 | @end example | |
162 | ||
163 | For each @var{package}, which is a symbol, there are one or more | |
164 | elements that contain a package version @var{pversion} with an | |
165 | associated Emacs version @var{eversion}. These versions are strings. | |
166 | For example, the MH-E package updates this alist with the following: | |
167 | ||
168 | @smallexample | |
169 | (add-to-list 'customize-package-emacs-version-alist | |
170 | '(MH-E ("6.0" . "22.1") ("6.1" . "22.1") ("7.0" . "22.1") | |
171 | ("7.1" . "22.1") ("7.2" . "22.1") ("7.3" . "22.1") | |
172 | ("7.4" . "22.1") ("8.0" . "22.1"))) | |
173 | @end smallexample | |
174 | ||
175 | The value of @var{package} needs to be unique and it needs to match | |
176 | the @var{package} value appearing in the @code{:package-version} | |
35a30759 | 177 | keyword. Since the user might see the value in an error message, a good |
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178 | choice is the official name of the package, such as MH-E or Gnus. |
179 | @end defvar | |
180 | ||
181 | @node Group Definitions | |
182 | @section Defining Customization Groups | |
183 | @cindex define customization group | |
184 | @cindex customization groups, defining | |
185 | ||
186 | Each Emacs Lisp package should have one main customization group which | |
187 | contains all the options, faces and other groups in the package. If the | |
188 | package has a small number of options and faces, use just one group and | |
189 | put everything in it. When there are more than twelve or so options and | |
190 | faces, then you should structure them into subgroups, and put the | |
191 | subgroups under the package's main customization group. It is OK to | |
192 | put some of the options and faces in the package's main group alongside | |
193 | the subgroups. | |
194 | ||
195 | The package's main or only group should be a member of one or more of | |
196 | the standard customization groups. (To display the full list of them, | |
197 | use @kbd{M-x customize}.) Choose one or more of them (but not too | |
198 | many), and add your group to each of them using the @code{:group} | |
199 | keyword. | |
200 | ||
201 | The way to declare new customization groups is with @code{defgroup}. | |
202 | ||
203 | @defmac defgroup group members doc [keyword value]@dots{} | |
204 | Declare @var{group} as a customization group containing @var{members}. | |
205 | Do not quote the symbol @var{group}. The argument @var{doc} specifies | |
206 | the documentation string for the group. | |
207 | ||
208 | The argument @var{members} is a list specifying an initial set of | |
209 | customization items to be members of the group. However, most often | |
210 | @var{members} is @code{nil}, and you specify the group's members by | |
211 | using the @code{:group} keyword when defining those members. | |
212 | ||
213 | If you want to specify group members through @var{members}, each element | |
214 | should have the form @code{(@var{name} @var{widget})}. Here @var{name} | |
215 | is a symbol, and @var{widget} is a widget type for editing that symbol. | |
216 | Useful widgets are @code{custom-variable} for a variable, | |
217 | @code{custom-face} for a face, and @code{custom-group} for a group. | |
218 | ||
219 | When you introduce a new group into Emacs, use the @code{:version} | |
220 | keyword in the @code{defgroup}; then you need not use it for | |
221 | the individual members of the group. | |
222 | ||
223 | In addition to the common keywords (@pxref{Common Keywords}), you can | |
224 | also use this keyword in @code{defgroup}: | |
225 | ||
226 | @table @code | |
227 | @item :prefix @var{prefix} | |
228 | @kindex prefix@r{, @code{defgroup} keyword} | |
229 | If the name of an item in the group starts with @var{prefix}, then the | |
230 | tag for that item is constructed (by default) by omitting @var{prefix}. | |
231 | ||
232 | One group can have any number of prefixes. | |
233 | @end table | |
234 | @end defmac | |
235 | ||
236 | The prefix-discarding feature is currently turned off, which means | |
237 | that @code{:prefix} currently has no effect. We did this because we | |
238 | found that discarding the specified prefixes often led to confusing | |
239 | names for options. This happened because the people who wrote the | |
240 | @code{defgroup} definitions for various groups added @code{:prefix} | |
241 | keywords whenever they make logical sense---that is, whenever the | |
242 | variables in the library have a common prefix. | |
243 | ||
244 | In order to obtain good results with @code{:prefix}, it would be | |
245 | necessary to check the specific effects of discarding a particular | |
246 | prefix, given the specific items in a group and their names and | |
247 | documentation. If the resulting text is not clear, then @code{:prefix} | |
248 | should not be used in that case. | |
249 | ||
250 | It should be possible to recheck all the customization groups, delete | |
251 | the @code{:prefix} specifications which give unclear results, and then | |
252 | turn this feature back on, if someone would like to do the work. | |
253 | ||
254 | @node Variable Definitions | |
255 | @section Defining Customization Variables | |
256 | @cindex define customization options | |
257 | @cindex customization variables, how to define | |
258 | ||
259 | Use @code{defcustom} to declare user-customizable variables. | |
260 | ||
261 | @defmac defcustom option standard doc [keyword value]@dots{} | |
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262 | This macro declares @var{option} as a customizable @dfn{user option}. |
263 | You should not quote @var{option}. | |
264 | ||
265 | This causes the function @code{user-variable-p} to return @code{t} | |
266 | when given @var{option} as an argument. @xref{Defining Variables}. | |
267 | The argument @var{doc} specifies the documentation string for the | |
268 | variable. (Note that there is no need to start @var{doc} with a | |
269 | @samp{*}.) | |
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270 | |
271 | The argument @var{standard} is an expression that specifies the | |
272 | standard value for @var{option}. Evaluating the @code{defcustom} form | |
273 | evaluates @var{standard}, but does not necessarily install the | |
274 | standard value. If @var{option} already has a default value, | |
275 | @code{defcustom} does not change it. If the user has saved a | |
276 | customization for @var{option}, @code{defcustom} installs the user's | |
277 | customized value as @var{option}'s default value. If neither of those | |
278 | cases applies, @code{defcustom} installs the result of evaluating | |
279 | @var{standard} as the default value. | |
280 | ||
281 | The expression @var{standard} can be evaluated at various other times, | |
282 | too---whenever the customization facility needs to know @var{option}'s | |
283 | standard value. So be sure to use an expression which is harmless to | |
284 | evaluate at any time. We recommend avoiding backquotes in | |
285 | @var{standard}, because they are not expanded when editing the value, | |
286 | so list values will appear to have the wrong structure. | |
287 | ||
288 | Every @code{defcustom} should specify @code{:group} at least once. | |
289 | ||
290 | If you specify the @code{:set} keyword, to make the variable take other | |
291 | special actions when set through the customization buffer, the | |
292 | variable's documentation string should tell the user specifically how | |
293 | to do the same job in hand-written Lisp code. | |
294 | ||
295 | When you evaluate a @code{defcustom} form with @kbd{C-M-x} in Emacs Lisp | |
296 | mode (@code{eval-defun}), a special feature of @code{eval-defun} | |
297 | arranges to set the variable unconditionally, without testing whether | |
298 | its value is void. (The same feature applies to @code{defvar}.) | |
299 | @xref{Defining Variables}. | |
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300 | |
301 | If you put a @code{defcustom} in a file that is preloaded at dump time | |
302 | (@pxref{Building Emacs}), and the standard value installed for the | |
303 | variable at that time might not be correct, use | |
304 | @code{custom-reevaluate-setting}, described below, to re-evaluate the | |
305 | standard value during or after Emacs startup. | |
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306 | @end defmac |
307 | ||
308 | @code{defcustom} accepts the following additional keywords: | |
309 | ||
310 | @table @code | |
311 | @item :type @var{type} | |
312 | Use @var{type} as the data type for this option. It specifies which | |
313 | values are legitimate, and how to display the value. | |
314 | @xref{Customization Types}, for more information. | |
315 | ||
316 | @item :options @var{value-list} | |
317 | @kindex options@r{, @code{defcustom} keyword} | |
318 | Specify the list of reasonable values for use in this | |
319 | option. The user is not restricted to using only these values, but they | |
320 | are offered as convenient alternatives. | |
321 | ||
322 | This is meaningful only for certain types, currently including | |
323 | @code{hook}, @code{plist} and @code{alist}. See the definition of the | |
324 | individual types for a description of how to use @code{:options}. | |
325 | ||
326 | @item :set @var{setfunction} | |
327 | @kindex set@r{, @code{defcustom} keyword} | |
328 | Specify @var{setfunction} as the way to change the value of this | |
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329 | option when using the Customize user interface. The function |
330 | @var{setfunction} should take two arguments, a symbol (the option | |
331 | name) and the new value, and should do whatever is necessary to update | |
332 | the value properly for this option (which may not mean simply setting | |
333 | the option as a Lisp variable). The default for @var{setfunction} is | |
334 | @code{set-default}. | |
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335 | |
336 | @item :get @var{getfunction} | |
337 | @kindex get@r{, @code{defcustom} keyword} | |
338 | Specify @var{getfunction} as the way to extract the value of this | |
339 | option. The function @var{getfunction} should take one argument, a | |
340 | symbol, and should return whatever customize should use as the | |
341 | ``current value'' for that symbol (which need not be the symbol's Lisp | |
342 | value). The default is @code{default-value}. | |
343 | ||
344 | You have to really understand the workings of Custom to use | |
345 | @code{:get} correctly. It is meant for values that are treated in | |
346 | Custom as variables but are not actually stored in Lisp variables. It | |
347 | is almost surely a mistake to specify @code{getfunction} for a value | |
348 | that really is stored in a Lisp variable. | |
349 | ||
350 | @item :initialize @var{function} | |
351 | @kindex initialize@r{, @code{defcustom} keyword} | |
352 | @var{function} should be a function used to initialize the variable | |
353 | when the @code{defcustom} is evaluated. It should take two arguments, | |
354 | the option name (a symbol) and the value. Here are some predefined | |
355 | functions meant for use in this way: | |
356 | ||
357 | @table @code | |
358 | @item custom-initialize-set | |
359 | Use the variable's @code{:set} function to initialize the variable, but | |
360 | do not reinitialize it if it is already non-void. | |
361 | ||
362 | @item custom-initialize-default | |
363 | Like @code{custom-initialize-set}, but use the function | |
364 | @code{set-default} to set the variable, instead of the variable's | |
365 | @code{:set} function. This is the usual choice for a variable whose | |
366 | @code{:set} function enables or disables a minor mode; with this choice, | |
367 | defining the variable will not call the minor mode function, but | |
368 | customizing the variable will do so. | |
369 | ||
370 | @item custom-initialize-reset | |
371 | Always use the @code{:set} function to initialize the variable. If | |
372 | the variable is already non-void, reset it by calling the @code{:set} | |
373 | function using the current value (returned by the @code{:get} method). | |
374 | This is the default @code{:initialize} function. | |
375 | ||
376 | @item custom-initialize-changed | |
377 | Use the @code{:set} function to initialize the variable, if it is | |
378 | already set or has been customized; otherwise, just use | |
379 | @code{set-default}. | |
380 | ||
381 | @item custom-initialize-safe-set | |
382 | @itemx custom-initialize-safe-default | |
383 | These functions behave like @code{custom-initialize-set} | |
384 | (@code{custom-initialize-default}, respectively), but catch errors. | |
385 | If an error occurs during initialization, they set the variable to | |
386 | @code{nil} using @code{set-default}, and throw no error. | |
387 | ||
388 | These two functions are only meant for options defined in pre-loaded | |
389 | files, where some variables or functions used to compute the option's | |
390 | value may not yet be defined. The option normally gets updated in | |
391 | @file{startup.el}, ignoring the previously computed value. Because of | |
392 | this typical usage, the value which these two functions compute | |
393 | normally only matters when, after startup, one unsets the option's | |
394 | value and then reevaluates the defcustom. By that time, the necessary | |
395 | variables and functions will be defined, so there will not be an error. | |
396 | @end table | |
397 | ||
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398 | @item :risky @var{value} |
399 | @kindex risky@r{, @code{defcustom} keyword} | |
95ddd36f | 400 | Set the variable's @code{risky-local-variable} property to |
0f631634 | 401 | @var{value} (@pxref{File Local Variables}). |
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402 | |
403 | @item :safe @var{function} | |
404 | @kindex safe@r{, @code{defcustom} keyword} | |
95ddd36f | 405 | Set the variable's @code{safe-local-variable} property to |
0f631634 | 406 | @var{function} (@pxref{File Local Variables}). |
db21122c | 407 | |
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408 | @item :set-after @var{variables} |
409 | @kindex set-after@r{, @code{defcustom} keyword} | |
410 | When setting variables according to saved customizations, make sure to | |
411 | set the variables @var{variables} before this one; in other words, delay | |
412 | setting this variable until after those others have been handled. Use | |
413 | @code{:set-after} if setting this variable won't work properly unless | |
414 | those other variables already have their intended values. | |
415 | @end table | |
416 | ||
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417 | It is useful to specify the @code{:require} keyword for an option |
418 | that ``turns on'' a certain feature. This causes Emacs to load the | |
419 | feature, if it is not already loaded, whenever the option is set. | |
420 | @xref{Common Keywords}. Here is an example, from the library | |
421 | @file{saveplace.el}: | |
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422 | |
423 | @example | |
424 | (defcustom save-place nil | |
425 | "Non-nil means automatically save place in each file..." | |
426 | :type 'boolean | |
427 | :require 'saveplace | |
428 | :group 'save-place) | |
429 | @end example | |
430 | ||
431 | If a customization item has a type such as @code{hook} or | |
432 | @code{alist}, which supports @code{:options}, you can add additional | |
433 | values to the list from outside the @code{defcustom} declaration by | |
434 | calling @code{custom-add-frequent-value}. For example, if you define a | |
435 | function @code{my-lisp-mode-initialization} intended to be called from | |
436 | @code{emacs-lisp-mode-hook}, you might want to add that to the list of | |
437 | reasonable values for @code{emacs-lisp-mode-hook}, but not by editing | |
438 | its definition. You can do it thus: | |
439 | ||
440 | @example | |
441 | (custom-add-frequent-value 'emacs-lisp-mode-hook | |
442 | 'my-lisp-mode-initialization) | |
443 | @end example | |
444 | ||
445 | @defun custom-add-frequent-value symbol value | |
446 | For the customization option @var{symbol}, add @var{value} to the | |
447 | list of reasonable values. | |
448 | ||
449 | The precise effect of adding a value depends on the customization type | |
450 | of @var{symbol}. | |
451 | @end defun | |
452 | ||
453 | Internally, @code{defcustom} uses the symbol property | |
454 | @code{standard-value} to record the expression for the standard value, | |
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455 | @code{saved-value} to record the value saved by the user with the |
456 | customization buffer, and @code{customized-value} to record the value | |
457 | set by the user with the customization buffer, but not saved. | |
458 | @xref{Property Lists}. These properties are lists, the car of which | |
459 | is an expression that evaluates to the value. | |
b8d4c8d0 | 460 | |
437706cd | 461 | @defun custom-reevaluate-setting symbol |
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462 | This function re-evaluates the standard value of @var{symbol}, which |
463 | should be a user option declared via @code{defcustom}. (If the | |
464 | variable was customized, this function re-evaluates the saved value | |
465 | instead.) This is useful for customizable options that are defined | |
466 | before their value could be computed correctly, such as variables | |
467 | defined in packages that are loaded at dump time, but depend on the | |
468 | run-time information. For example, the value could be a file whose | |
469 | precise name depends on the hierarchy of files when Emacs runs, or a | |
470 | name of a program that needs to be searched at run time. | |
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471 | |
472 | A good place to put calls to this function is in the function | |
473 | @code{command-line} that is run during startup (@pxref{Startup Summary}) | |
474 | or in the various hooks it calls. | |
475 | @end defun | |
476 | ||
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477 | @node Customization Types |
478 | @section Customization Types | |
479 | ||
480 | @cindex customization types | |
481 | When you define a user option with @code{defcustom}, you must specify | |
482 | its @dfn{customization type}. That is a Lisp object which describes (1) | |
483 | which values are legitimate and (2) how to display the value in the | |
484 | customization buffer for editing. | |
485 | ||
486 | @kindex type@r{, @code{defcustom} keyword} | |
487 | You specify the customization type in @code{defcustom} with the | |
488 | @code{:type} keyword. The argument of @code{:type} is evaluated, but | |
489 | only once when the @code{defcustom} is executed, so it isn't useful | |
490 | for the value to vary. Normally we use a quoted constant. For | |
491 | example: | |
492 | ||
493 | @example | |
494 | (defcustom diff-command "diff" | |
495 | "The command to use to run diff." | |
496 | :type '(string) | |
497 | :group 'diff) | |
498 | @end example | |
499 | ||
500 | In general, a customization type is a list whose first element is a | |
501 | symbol, one of the customization type names defined in the following | |
502 | sections. After this symbol come a number of arguments, depending on | |
503 | the symbol. Between the type symbol and its arguments, you can | |
504 | optionally write keyword-value pairs (@pxref{Type Keywords}). | |
505 | ||
0f631634 | 506 | Some type symbols do not use any arguments; those are called |
b8d4c8d0 GM |
507 | @dfn{simple types}. For a simple type, if you do not use any |
508 | keyword-value pairs, you can omit the parentheses around the type | |
509 | symbol. For example just @code{string} as a customization type is | |
510 | equivalent to @code{(string)}. | |
511 | ||
0f631634 CY |
512 | All customization types are implemented as widgets; see @ref{Top, , |
513 | Introduction, widget, The Emacs Widget Library}, for details. | |
514 | ||
b8d4c8d0 | 515 | @menu |
3deead93 | 516 | * Simple Types:: Simple customization types: sexp, integer, etc. |
51d9979c GM |
517 | * Composite Types:: Build new types from other types or data. |
518 | * Splicing into Lists:: Splice elements into list with @code{:inline}. | |
519 | * Type Keywords:: Keyword-argument pairs in a customization type. | |
520 | * Defining New Types:: Give your type a name. | |
b8d4c8d0 GM |
521 | @end menu |
522 | ||
b8d4c8d0 GM |
523 | @node Simple Types |
524 | @subsection Simple Types | |
525 | ||
526 | This section describes all the simple customization types. | |
527 | ||
528 | @table @code | |
529 | @item sexp | |
530 | The value may be any Lisp object that can be printed and read back. You | |
531 | can use @code{sexp} as a fall-back for any option, if you don't want to | |
532 | take the time to work out a more specific type to use. | |
533 | ||
534 | @item integer | |
535 | The value must be an integer, and is represented textually | |
536 | in the customization buffer. | |
537 | ||
538 | @item number | |
539 | The value must be a number (floating point or integer), and is | |
540 | represented textually in the customization buffer. | |
541 | ||
542 | @item float | |
543 | The value must be a floating point number, and is represented | |
544 | textually in the customization buffer. | |
545 | ||
546 | @item string | |
547 | The value must be a string, and the customization buffer shows just the | |
548 | contents, with no delimiting @samp{"} characters and no quoting with | |
549 | @samp{\}. | |
550 | ||
551 | @item regexp | |
552 | Like @code{string} except that the string must be a valid regular | |
553 | expression. | |
554 | ||
555 | @item character | |
556 | The value must be a character code. A character code is actually an | |
557 | integer, but this type shows the value by inserting the character in the | |
558 | buffer, rather than by showing the number. | |
559 | ||
560 | @item file | |
561 | The value must be a file name, and you can do completion with | |
562 | @kbd{M-@key{TAB}}. | |
563 | ||
564 | @item (file :must-match t) | |
565 | The value must be a file name for an existing file, and you can do | |
566 | completion with @kbd{M-@key{TAB}}. | |
567 | ||
568 | @item directory | |
569 | The value must be a directory name, and you can do completion with | |
570 | @kbd{M-@key{TAB}}. | |
571 | ||
572 | @item hook | |
573 | The value must be a list of functions (or a single function, but that is | |
574 | obsolete usage). This customization type is used for hook variables. | |
575 | You can use the @code{:options} keyword in a hook variable's | |
576 | @code{defcustom} to specify a list of functions recommended for use in | |
577 | the hook; see @ref{Variable Definitions}. | |
578 | ||
3deead93 CY |
579 | @item symbol |
580 | The value must be a symbol. It appears in the customization buffer as | |
581 | the name of the symbol. | |
b8d4c8d0 | 582 | |
3deead93 CY |
583 | @item function |
584 | The value must be either a lambda expression or a function name. When | |
585 | it is a function name, you can do completion with @kbd{M-@key{TAB}}. | |
b8d4c8d0 | 586 | |
3deead93 CY |
587 | @item variable |
588 | The value must be a variable name, and you can do completion with | |
589 | @kbd{M-@key{TAB}}. | |
590 | ||
591 | @item face | |
592 | The value must be a symbol which is a face name, and you can do | |
593 | completion with @kbd{M-@key{TAB}}. | |
594 | ||
595 | @item boolean | |
596 | The value is boolean---either @code{nil} or @code{t}. Note that by | |
597 | using @code{choice} and @code{const} together (see the next section), | |
598 | you can specify that the value must be @code{nil} or @code{t}, but also | |
599 | specify the text to describe each value in a way that fits the specific | |
600 | meaning of the alternative. | |
601 | ||
602 | @item coding-system | |
603 | The value must be a coding-system name, and you can do completion with | |
604 | @kbd{M-@key{TAB}}. | |
605 | ||
606 | @item color | |
607 | The value must be a valid color name, and you can do completion with | |
608 | @kbd{M-@key{TAB}}. A sample is provided. | |
609 | @end table | |
610 | ||
611 | @node Composite Types | |
612 | @subsection Composite Types | |
613 | @cindex composite types (customization) | |
614 | ||
615 | When none of the simple types is appropriate, you can use composite | |
616 | types, which build new types from other types or from specified data. | |
617 | The specified types or data are called the @dfn{arguments} of the | |
618 | composite type. The composite type normally looks like this: | |
619 | ||
620 | @example | |
621 | (@var{constructor} @var{arguments}@dots{}) | |
622 | @end example | |
b8d4c8d0 GM |
623 | |
624 | @noindent | |
3deead93 CY |
625 | but you can also add keyword-value pairs before the arguments, like |
626 | this: | |
627 | ||
628 | @example | |
629 | (@var{constructor} @r{@{}@var{keyword} @var{value}@r{@}}@dots{} @var{arguments}@dots{}) | |
630 | @end example | |
631 | ||
632 | Here is a table of constructors and how to use them to write | |
633 | composite types: | |
634 | ||
635 | @table @code | |
636 | @item (cons @var{car-type} @var{cdr-type}) | |
637 | The value must be a cons cell, its @sc{car} must fit @var{car-type}, and | |
638 | its @sc{cdr} must fit @var{cdr-type}. For example, @code{(cons string | |
639 | symbol)} is a customization type which matches values such as | |
640 | @code{("foo" . foo)}. | |
641 | ||
642 | In the customization buffer, the @sc{car} and the @sc{cdr} are | |
643 | displayed and edited separately, each according to the type | |
644 | that you specify for it. | |
645 | ||
646 | @item (list @var{element-types}@dots{}) | |
647 | The value must be a list with exactly as many elements as the | |
648 | @var{element-types} given; and each element must fit the | |
649 | corresponding @var{element-type}. | |
650 | ||
651 | For example, @code{(list integer string function)} describes a list of | |
652 | three elements; the first element must be an integer, the second a | |
653 | string, and the third a function. | |
654 | ||
655 | In the customization buffer, each element is displayed and edited | |
656 | separately, according to the type specified for it. | |
657 | ||
658 | @item (group @var{element-types}@dots{}) | |
659 | This works like @code{list} except for the formatting | |
660 | of text in the Custom buffer. @code{list} labels each | |
661 | element value with its tag; @code{group} does not. | |
662 | ||
663 | @item (vector @var{element-types}@dots{}) | |
664 | Like @code{list} except that the value must be a vector instead of a | |
665 | list. The elements work the same as in @code{list}. | |
666 | ||
667 | @item (alist :key-type @var{key-type} :value-type @var{value-type}) | |
668 | The value must be a list of cons-cells, the @sc{car} of each cell | |
669 | representing a key of customization type @var{key-type}, and the | |
670 | @sc{cdr} of the same cell representing a value of customization type | |
671 | @var{value-type}. The user can add and delete key/value pairs, and | |
672 | edit both the key and the value of each pair. | |
673 | ||
674 | If omitted, @var{key-type} and @var{value-type} default to | |
675 | @code{sexp}. | |
b8d4c8d0 GM |
676 | |
677 | The user can add any key matching the specified key type, but you can | |
678 | give some keys a preferential treatment by specifying them with the | |
679 | @code{:options} (see @ref{Variable Definitions}). The specified keys | |
680 | will always be shown in the customize buffer (together with a suitable | |
681 | value), with a checkbox to include or exclude or disable the key/value | |
682 | pair from the alist. The user will not be able to edit the keys | |
683 | specified by the @code{:options} keyword argument. | |
684 | ||
685 | The argument to the @code{:options} keywords should be a list of | |
686 | specifications for reasonable keys in the alist. Ordinarily, they are | |
687 | simply atoms, which stand for themselves as. For example: | |
688 | ||
689 | @smallexample | |
690 | :options '("foo" "bar" "baz") | |
691 | @end smallexample | |
692 | ||
693 | @noindent | |
694 | specifies that there are three ``known'' keys, namely @code{"foo"}, | |
695 | @code{"bar"} and @code{"baz"}, which will always be shown first. | |
696 | ||
697 | You may want to restrict the value type for specific keys, for | |
698 | example, the value associated with the @code{"bar"} key can only be an | |
699 | integer. You can specify this by using a list instead of an atom in | |
700 | the list. The first element will specify the key, like before, while | |
701 | the second element will specify the value type. For example: | |
702 | ||
703 | @smallexample | |
704 | :options '("foo" ("bar" integer) "baz") | |
705 | @end smallexample | |
706 | ||
707 | Finally, you may want to change how the key is presented. By default, | |
708 | the key is simply shown as a @code{const}, since the user cannot change | |
709 | the special keys specified with the @code{:options} keyword. However, | |
710 | you may want to use a more specialized type for presenting the key, like | |
711 | @code{function-item} if you know it is a symbol with a function binding. | |
712 | This is done by using a customization type specification instead of a | |
713 | symbol for the key. | |
714 | ||
715 | @smallexample | |
716 | :options '("foo" ((function-item some-function) integer) | |
717 | "baz") | |
718 | @end smallexample | |
719 | ||
720 | Many alists use lists with two elements, instead of cons cells. For | |
721 | example, | |
722 | ||
723 | @smallexample | |
724 | (defcustom list-alist '(("foo" 1) ("bar" 2) ("baz" 3)) | |
725 | "Each element is a list of the form (KEY VALUE).") | |
726 | @end smallexample | |
727 | ||
728 | @noindent | |
729 | instead of | |
730 | ||
731 | @smallexample | |
732 | (defcustom cons-alist '(("foo" . 1) ("bar" . 2) ("baz" . 3)) | |
733 | "Each element is a cons-cell (KEY . VALUE).") | |
734 | @end smallexample | |
735 | ||
736 | Because of the way lists are implemented on top of cons cells, you can | |
737 | treat @code{list-alist} in the example above as a cons cell alist, where | |
738 | the value type is a list with a single element containing the real | |
739 | value. | |
740 | ||
741 | @smallexample | |
742 | (defcustom list-alist '(("foo" 1) ("bar" 2) ("baz" 3)) | |
743 | "Each element is a list of the form (KEY VALUE)." | |
744 | :type '(alist :value-type (group integer))) | |
745 | @end smallexample | |
746 | ||
747 | The @code{group} widget is used here instead of @code{list} only because | |
748 | the formatting is better suited for the purpose. | |
749 | ||
750 | Similarly, you can have alists with more values associated with each | |
751 | key, using variations of this trick: | |
752 | ||
753 | @smallexample | |
754 | (defcustom person-data '(("brian" 50 t) | |
755 | ("dorith" 55 nil) | |
756 | ("ken" 52 t)) | |
757 | "Alist of basic info about people. | |
758 | Each element has the form (NAME AGE MALE-FLAG)." | |
759 | :type '(alist :value-type (group integer boolean))) | |
760 | ||
761 | (defcustom pets '(("brian") | |
762 | ("dorith" "dog" "guppy") | |
763 | ("ken" "cat")) | |
764 | "Alist of people's pets. | |
765 | In an element (KEY . VALUE), KEY is the person's name, | |
766 | and the VALUE is a list of that person's pets." | |
767 | :type '(alist :value-type (repeat string))) | |
768 | @end smallexample | |
769 | ||
3deead93 CY |
770 | @item (plist :key-type @var{key-type} :value-type @var{value-type}) |
771 | This customization type is similar to @code{alist} (see above), except | |
772 | that (i) the information is stored as a property list, | |
773 | (@pxref{Property Lists}), and (ii) @var{key-type}, if omitted, | |
774 | defaults to @code{symbol} rather than @code{sexp}. | |
b8d4c8d0 GM |
775 | |
776 | @item (choice @var{alternative-types}@dots{}) | |
777 | The value must fit at least one of @var{alternative-types}. | |
778 | For example, @code{(choice integer string)} allows either an | |
779 | integer or a string. | |
780 | ||
781 | In the customization buffer, the user selects an alternative | |
782 | using a menu, and can then edit the value in the usual way for that | |
783 | alternative. | |
784 | ||
785 | Normally the strings in this menu are determined automatically from the | |
786 | choices; however, you can specify different strings for the menu by | |
787 | including the @code{:tag} keyword in the alternatives. For example, if | |
788 | an integer stands for a number of spaces, while a string is text to use | |
789 | verbatim, you might write the customization type this way, | |
790 | ||
791 | @example | |
792 | (choice (integer :tag "Number of spaces") | |
793 | (string :tag "Literal text")) | |
794 | @end example | |
795 | ||
796 | @noindent | |
797 | so that the menu offers @samp{Number of spaces} and @samp{Literal text}. | |
798 | ||
799 | In any alternative for which @code{nil} is not a valid value, other than | |
800 | a @code{const}, you should specify a valid default for that alternative | |
801 | using the @code{:value} keyword. @xref{Type Keywords}. | |
802 | ||
803 | If some values are covered by more than one of the alternatives, | |
804 | customize will choose the first alternative that the value fits. This | |
805 | means you should always list the most specific types first, and the | |
806 | most general last. Here's an example of proper usage: | |
807 | ||
808 | @example | |
809 | (choice (const :tag "Off" nil) | |
810 | symbol (sexp :tag "Other")) | |
811 | @end example | |
812 | ||
813 | @noindent | |
814 | This way, the special value @code{nil} is not treated like other | |
815 | symbols, and symbols are not treated like other Lisp expressions. | |
816 | ||
817 | @item (radio @var{element-types}@dots{}) | |
818 | This is similar to @code{choice}, except that the choices are displayed | |
819 | using `radio buttons' rather than a menu. This has the advantage of | |
820 | displaying documentation for the choices when applicable and so is often | |
821 | a good choice for a choice between constant functions | |
822 | (@code{function-item} customization types). | |
823 | ||
824 | @item (const @var{value}) | |
825 | The value must be @var{value}---nothing else is allowed. | |
826 | ||
827 | The main use of @code{const} is inside of @code{choice}. For example, | |
828 | @code{(choice integer (const nil))} allows either an integer or | |
829 | @code{nil}. | |
830 | ||
831 | @code{:tag} is often used with @code{const}, inside of @code{choice}. | |
832 | For example, | |
833 | ||
834 | @example | |
835 | (choice (const :tag "Yes" t) | |
836 | (const :tag "No" nil) | |
837 | (const :tag "Ask" foo)) | |
838 | @end example | |
839 | ||
840 | @noindent | |
841 | describes a variable for which @code{t} means yes, @code{nil} means no, | |
842 | and @code{foo} means ``ask.'' | |
843 | ||
844 | @item (other @var{value}) | |
845 | This alternative can match any Lisp value, but if the user chooses this | |
846 | alternative, that selects the value @var{value}. | |
847 | ||
848 | The main use of @code{other} is as the last element of @code{choice}. | |
849 | For example, | |
850 | ||
851 | @example | |
852 | (choice (const :tag "Yes" t) | |
853 | (const :tag "No" nil) | |
854 | (other :tag "Ask" foo)) | |
855 | @end example | |
856 | ||
857 | @noindent | |
858 | describes a variable for which @code{t} means yes, @code{nil} means no, | |
859 | and anything else means ``ask.'' If the user chooses @samp{Ask} from | |
860 | the menu of alternatives, that specifies the value @code{foo}; but any | |
861 | other value (not @code{t}, @code{nil} or @code{foo}) displays as | |
862 | @samp{Ask}, just like @code{foo}. | |
863 | ||
864 | @item (function-item @var{function}) | |
865 | Like @code{const}, but used for values which are functions. This | |
866 | displays the documentation string as well as the function name. | |
867 | The documentation string is either the one you specify with | |
868 | @code{:doc}, or @var{function}'s own documentation string. | |
869 | ||
870 | @item (variable-item @var{variable}) | |
871 | Like @code{const}, but used for values which are variable names. This | |
872 | displays the documentation string as well as the variable name. The | |
873 | documentation string is either the one you specify with @code{:doc}, or | |
874 | @var{variable}'s own documentation string. | |
875 | ||
876 | @item (set @var{types}@dots{}) | |
877 | The value must be a list, and each element of the list must match one of | |
878 | the @var{types} specified. | |
879 | ||
880 | This appears in the customization buffer as a checklist, so that each of | |
881 | @var{types} may have either one corresponding element or none. It is | |
882 | not possible to specify two different elements that match the same one | |
883 | of @var{types}. For example, @code{(set integer symbol)} allows one | |
884 | integer and/or one symbol in the list; it does not allow multiple | |
885 | integers or multiple symbols. As a result, it is rare to use | |
886 | nonspecific types such as @code{integer} in a @code{set}. | |
887 | ||
888 | Most often, the @var{types} in a @code{set} are @code{const} types, as | |
889 | shown here: | |
890 | ||
891 | @example | |
892 | (set (const :bold) (const :italic)) | |
893 | @end example | |
894 | ||
895 | Sometimes they describe possible elements in an alist: | |
896 | ||
897 | @example | |
898 | (set (cons :tag "Height" (const height) integer) | |
899 | (cons :tag "Width" (const width) integer)) | |
900 | @end example | |
901 | ||
902 | @noindent | |
903 | That lets the user specify a height value optionally | |
904 | and a width value optionally. | |
905 | ||
906 | @item (repeat @var{element-type}) | |
907 | The value must be a list and each element of the list must fit the type | |
908 | @var{element-type}. This appears in the customization buffer as a | |
909 | list of elements, with @samp{[INS]} and @samp{[DEL]} buttons for adding | |
910 | more elements or removing elements. | |
911 | ||
912 | @item (restricted-sexp :match-alternatives @var{criteria}) | |
913 | This is the most general composite type construct. The value may be | |
914 | any Lisp object that satisfies one of @var{criteria}. @var{criteria} | |
915 | should be a list, and each element should be one of these | |
916 | possibilities: | |
917 | ||
918 | @itemize @bullet | |
919 | @item | |
920 | A predicate---that is, a function of one argument that has no side | |
921 | effects, and returns either @code{nil} or non-@code{nil} according to | |
922 | the argument. Using a predicate in the list says that objects for which | |
923 | the predicate returns non-@code{nil} are acceptable. | |
924 | ||
925 | @item | |
926 | A quoted constant---that is, @code{'@var{object}}. This sort of element | |
927 | in the list says that @var{object} itself is an acceptable value. | |
928 | @end itemize | |
929 | ||
930 | For example, | |
931 | ||
932 | @example | |
933 | (restricted-sexp :match-alternatives | |
934 | (integerp 't 'nil)) | |
935 | @end example | |
936 | ||
937 | @noindent | |
938 | allows integers, @code{t} and @code{nil} as legitimate values. | |
939 | ||
940 | The customization buffer shows all legitimate values using their read | |
941 | syntax, and the user edits them textually. | |
942 | @end table | |
943 | ||
944 | Here is a table of the keywords you can use in keyword-value pairs | |
945 | in a composite type: | |
946 | ||
947 | @table @code | |
948 | @item :tag @var{tag} | |
949 | Use @var{tag} as the name of this alternative, for user communication | |
950 | purposes. This is useful for a type that appears inside of a | |
951 | @code{choice}. | |
952 | ||
953 | @item :match-alternatives @var{criteria} | |
954 | @kindex match-alternatives@r{, customization keyword} | |
955 | Use @var{criteria} to match possible values. This is used only in | |
956 | @code{restricted-sexp}. | |
957 | ||
958 | @item :args @var{argument-list} | |
959 | @kindex args@r{, customization keyword} | |
960 | Use the elements of @var{argument-list} as the arguments of the type | |
961 | construct. For instance, @code{(const :args (foo))} is equivalent to | |
962 | @code{(const foo)}. You rarely need to write @code{:args} explicitly, | |
963 | because normally the arguments are recognized automatically as | |
964 | whatever follows the last keyword-value pair. | |
965 | @end table | |
966 | ||
967 | @node Splicing into Lists | |
968 | @subsection Splicing into Lists | |
969 | ||
970 | The @code{:inline} feature lets you splice a variable number of | |
971 | elements into the middle of a list or vector. You use it in a | |
972 | @code{set}, @code{choice} or @code{repeat} type which appears among the | |
973 | element-types of a @code{list} or @code{vector}. | |
974 | ||
975 | Normally, each of the element-types in a @code{list} or @code{vector} | |
976 | describes one and only one element of the list or vector. Thus, if an | |
977 | element-type is a @code{repeat}, that specifies a list of unspecified | |
978 | length which appears as one element. | |
979 | ||
980 | But when the element-type uses @code{:inline}, the value it matches is | |
981 | merged directly into the containing sequence. For example, if it | |
982 | matches a list with three elements, those become three elements of the | |
983 | overall sequence. This is analogous to using @samp{,@@} in the backquote | |
984 | construct. | |
985 | ||
986 | For example, to specify a list whose first element must be @code{baz} | |
987 | and whose remaining arguments should be zero or more of @code{foo} and | |
988 | @code{bar}, use this customization type: | |
989 | ||
990 | @example | |
991 | (list (const baz) (set :inline t (const foo) (const bar))) | |
992 | @end example | |
993 | ||
994 | @noindent | |
995 | This matches values such as @code{(baz)}, @code{(baz foo)}, @code{(baz bar)} | |
996 | and @code{(baz foo bar)}. | |
997 | ||
998 | When the element-type is a @code{choice}, you use @code{:inline} not | |
999 | in the @code{choice} itself, but in (some of) the alternatives of the | |
1000 | @code{choice}. For example, to match a list which must start with a | |
1001 | file name, followed either by the symbol @code{t} or two strings, use | |
1002 | this customization type: | |
1003 | ||
1004 | @example | |
1005 | (list file | |
1006 | (choice (const t) | |
1007 | (list :inline t string string))) | |
1008 | @end example | |
1009 | ||
1010 | @noindent | |
1011 | If the user chooses the first alternative in the choice, then the | |
1012 | overall list has two elements and the second element is @code{t}. If | |
1013 | the user chooses the second alternative, then the overall list has three | |
1014 | elements and the second and third must be strings. | |
1015 | ||
1016 | @node Type Keywords | |
1017 | @subsection Type Keywords | |
1018 | ||
1019 | You can specify keyword-argument pairs in a customization type after the | |
1020 | type name symbol. Here are the keywords you can use, and their | |
1021 | meanings: | |
1022 | ||
1023 | @table @code | |
1024 | @item :value @var{default} | |
0ec389b9 LMI |
1025 | Provide a default value. |
1026 | ||
1027 | If @code{nil} is not a valid value for the alternative, then it is | |
1028 | essential to specify a valid default with @code{:value}. | |
1029 | ||
1030 | If you use this for a type that appears as an alternative inside of | |
b8d4c8d0 GM |
1031 | @code{choice}; it specifies the default value to use, at first, if and |
1032 | when the user selects this alternative with the menu in the | |
1033 | customization buffer. | |
1034 | ||
1035 | Of course, if the actual value of the option fits this alternative, it | |
1036 | will appear showing the actual value, not @var{default}. | |
1037 | ||
b8d4c8d0 GM |
1038 | @item :format @var{format-string} |
1039 | @kindex format@r{, customization keyword} | |
1040 | This string will be inserted in the buffer to represent the value | |
1041 | corresponding to the type. The following @samp{%} escapes are available | |
1042 | for use in @var{format-string}: | |
1043 | ||
1044 | @table @samp | |
1045 | @item %[@var{button}%] | |
1046 | Display the text @var{button} marked as a button. The @code{:action} | |
1047 | attribute specifies what the button will do if the user invokes it; | |
1048 | its value is a function which takes two arguments---the widget which | |
1049 | the button appears in, and the event. | |
1050 | ||
1051 | There is no way to specify two different buttons with different | |
1052 | actions. | |
1053 | ||
1054 | @item %@{@var{sample}%@} | |
1055 | Show @var{sample} in a special face specified by @code{:sample-face}. | |
1056 | ||
1057 | @item %v | |
1058 | Substitute the item's value. How the value is represented depends on | |
1059 | the kind of item, and (for variables) on the customization type. | |
1060 | ||
1061 | @item %d | |
1062 | Substitute the item's documentation string. | |
1063 | ||
1064 | @item %h | |
1065 | Like @samp{%d}, but if the documentation string is more than one line, | |
1066 | add an active field to control whether to show all of it or just the | |
1067 | first line. | |
1068 | ||
1069 | @item %t | |
1070 | Substitute the tag here. You specify the tag with the @code{:tag} | |
1071 | keyword. | |
1072 | ||
1073 | @item %% | |
1074 | Display a literal @samp{%}. | |
1075 | @end table | |
1076 | ||
1077 | @item :action @var{action} | |
1078 | @kindex action@r{, customization keyword} | |
1079 | Perform @var{action} if the user clicks on a button. | |
1080 | ||
1081 | @item :button-face @var{face} | |
1082 | @kindex button-face@r{, customization keyword} | |
1083 | Use the face @var{face} (a face name or a list of face names) for button | |
1084 | text displayed with @samp{%[@dots{}%]}. | |
1085 | ||
1086 | @item :button-prefix @var{prefix} | |
1087 | @itemx :button-suffix @var{suffix} | |
1088 | @kindex button-prefix@r{, customization keyword} | |
1089 | @kindex button-suffix@r{, customization keyword} | |
1090 | These specify the text to display before and after a button. | |
1091 | Each can be: | |
1092 | ||
1093 | @table @asis | |
1094 | @item @code{nil} | |
1095 | No text is inserted. | |
1096 | ||
1097 | @item a string | |
1098 | The string is inserted literally. | |
1099 | ||
1100 | @item a symbol | |
1101 | The symbol's value is used. | |
1102 | @end table | |
1103 | ||
1104 | @item :tag @var{tag} | |
1105 | Use @var{tag} (a string) as the tag for the value (or part of the value) | |
1106 | that corresponds to this type. | |
1107 | ||
1108 | @item :doc @var{doc} | |
1109 | @kindex doc@r{, customization keyword} | |
1110 | Use @var{doc} as the documentation string for this value (or part of the | |
1111 | value) that corresponds to this type. In order for this to work, you | |
1112 | must specify a value for @code{:format}, and use @samp{%d} or @samp{%h} | |
1113 | in that value. | |
1114 | ||
1115 | The usual reason to specify a documentation string for a type is to | |
1116 | provide more information about the meanings of alternatives inside a | |
1117 | @code{:choice} type or the parts of some other composite type. | |
1118 | ||
1119 | @item :help-echo @var{motion-doc} | |
1120 | @kindex help-echo@r{, customization keyword} | |
1121 | When you move to this item with @code{widget-forward} or | |
1122 | @code{widget-backward}, it will display the string @var{motion-doc} in | |
1123 | the echo area. In addition, @var{motion-doc} is used as the mouse | |
1124 | @code{help-echo} string and may actually be a function or form evaluated | |
1125 | to yield a help string. If it is a function, it is called with one | |
1126 | argument, the widget. | |
1127 | ||
1128 | @item :match @var{function} | |
1129 | @kindex match@r{, customization keyword} | |
1130 | Specify how to decide whether a value matches the type. The | |
1131 | corresponding value, @var{function}, should be a function that accepts | |
1132 | two arguments, a widget and a value; it should return non-@code{nil} if | |
1133 | the value is acceptable. | |
1134 | ||
72b7e664 RS |
1135 | @item :validate @var{function} |
1136 | Specify a validation function for input. @var{function} takes a | |
1137 | widget as an argument, and should return @code{nil} if the widget's | |
1138 | current value is valid for the widget. Otherwise, it should return | |
1139 | the widget containing the invalid data, and set that widget's | |
1140 | @code{:error} property to a string explaining the error. | |
1141 | ||
b8d4c8d0 GM |
1142 | @ignore |
1143 | @item :indent @var{columns} | |
1144 | Indent this item by @var{columns} columns. The indentation is used for | |
1145 | @samp{%n}, and automatically for group names, for checklists and radio | |
1146 | buttons, and for editable lists. It affects the whole of the | |
1147 | item except for the first line. | |
1148 | ||
72b7e664 RS |
1149 | @item :offset @var{extra} |
1150 | Indent the subitems of this item @var{extra} columns more than this | |
1151 | item itself. By default, subitems are indented the same as their | |
1152 | parent. | |
b8d4c8d0 | 1153 | |
72b7e664 RS |
1154 | @item :extra-offset @var{n} |
1155 | Add @var{n} extra spaces to this item's indentation, compared to its | |
1156 | parent's indentation. | |
b8d4c8d0 | 1157 | |
72b7e664 RS |
1158 | @item :notify @var{function} |
1159 | Call @var{function} each time the item or a subitem is changed. The | |
1160 | function gets two or three arguments. The first argument is the item | |
1161 | itself, the second argument is the item that was changed, and the | |
1162 | third argument is the event leading to the change, if any. | |
b8d4c8d0 | 1163 | |
72b7e664 RS |
1164 | @item :menu-tag @var{tag-string} |
1165 | Use @var{tag-string} in the menu when the widget is used as an option | |
1166 | in a @code{menu-choice} widget. | |
b8d4c8d0 GM |
1167 | |
1168 | @item :menu-tag-get | |
1169 | A function used for finding the tag when the widget is used as an option | |
1170 | in a @code{menu-choice} widget. By default, the tag used will be either the | |
1171 | @code{:menu-tag} or @code{:tag} property if present, or the @code{princ} | |
1172 | representation of the @code{:value} property if not. | |
1173 | ||
b8d4c8d0 GM |
1174 | @item :tab-order |
1175 | Specify the order in which widgets are traversed with | |
1176 | @code{widget-forward} or @code{widget-backward}. This is only partially | |
1177 | implemented. | |
1178 | ||
1179 | @enumerate a | |
1180 | @item | |
1181 | Widgets with tabbing order @code{-1} are ignored. | |
1182 | ||
1183 | @item | |
1184 | (Unimplemented) When on a widget with tabbing order @var{n}, go to the | |
1185 | next widget in the buffer with tabbing order @var{n+1} or @code{nil}, | |
1186 | whichever comes first. | |
1187 | ||
1188 | @item | |
1189 | When on a widget with no tabbing order specified, go to the next widget | |
1190 | in the buffer with a positive tabbing order, or @code{nil} | |
1191 | @end enumerate | |
1192 | ||
1193 | @item :parent | |
1194 | The parent of a nested widget (e.g., a @code{menu-choice} item or an | |
1195 | element of a @code{editable-list} widget). | |
1196 | ||
1197 | @item :sibling-args | |
1198 | This keyword is only used for members of a @code{radio-button-choice} or | |
1199 | @code{checklist}. The value should be a list of extra keyword | |
1200 | arguments, which will be used when creating the @code{radio-button} or | |
1201 | @code{checkbox} associated with this item. | |
1202 | @end ignore | |
1203 | @end table | |
1204 | ||
1205 | @node Defining New Types | |
1206 | @subsection Defining New Types | |
1207 | ||
1208 | In the previous sections we have described how to construct elaborate | |
1209 | type specifications for @code{defcustom}. In some cases you may want | |
1210 | to give such a type specification a name. The obvious case is when | |
1211 | you are using the same type for many user options: rather than repeat | |
1212 | the specification for each option, you can give the type specification | |
1213 | a name, and use that name each @code{defcustom}. The other case is | |
1214 | when a user option's value is a recursive data structure. To make it | |
1215 | possible for a datatype to refer to itself, it needs to have a name. | |
1216 | ||
1217 | Since custom types are implemented as widgets, the way to define a new | |
1218 | customize type is to define a new widget. We are not going to describe | |
1219 | the widget interface here in details, see @ref{Top, , Introduction, | |
1220 | widget, The Emacs Widget Library}, for that. Instead we are going to | |
1221 | demonstrate the minimal functionality needed for defining new customize | |
1222 | types by a simple example. | |
1223 | ||
1224 | @example | |
1225 | (define-widget 'binary-tree-of-string 'lazy | |
1226 | "A binary tree made of cons-cells and strings." | |
1227 | :offset 4 | |
1228 | :tag "Node" | |
1229 | :type '(choice (string :tag "Leaf" :value "") | |
1230 | (cons :tag "Interior" | |
1231 | :value ("" . "") | |
1232 | binary-tree-of-string | |
1233 | binary-tree-of-string))) | |
1234 | ||
1235 | (defcustom foo-bar "" | |
1236 | "Sample variable holding a binary tree of strings." | |
1237 | :type 'binary-tree-of-string) | |
1238 | @end example | |
1239 | ||
1240 | The function to define a new widget is called @code{define-widget}. The | |
1241 | first argument is the symbol we want to make a new widget type. The | |
1242 | second argument is a symbol representing an existing widget, the new | |
1243 | widget is going to be defined in terms of difference from the existing | |
1244 | widget. For the purpose of defining new customization types, the | |
1245 | @code{lazy} widget is perfect, because it accepts a @code{:type} keyword | |
1246 | argument with the same syntax as the keyword argument to | |
1247 | @code{defcustom} with the same name. The third argument is a | |
1248 | documentation string for the new widget. You will be able to see that | |
1249 | string with the @kbd{M-x widget-browse @key{RET} binary-tree-of-string | |
1250 | @key{RET}} command. | |
1251 | ||
1252 | After these mandatory arguments follow the keyword arguments. The most | |
1253 | important is @code{:type}, which describes the data type we want to match | |
1254 | with this widget. Here a @code{binary-tree-of-string} is described as | |
1255 | being either a string, or a cons-cell whose car and cdr are themselves | |
1256 | both @code{binary-tree-of-string}. Note the reference to the widget | |
1257 | type we are currently in the process of defining. The @code{:tag} | |
1258 | attribute is a string to name the widget in the user interface, and the | |
1259 | @code{:offset} argument is there to ensure that child nodes are | |
1260 | indented four spaces relative to the parent node, making the tree | |
1261 | structure apparent in the customization buffer. | |
1262 | ||
1263 | The @code{defcustom} shows how the new widget can be used as an ordinary | |
1264 | customization type. | |
1265 | ||
1266 | The reason for the name @code{lazy} is that the other composite | |
1267 | widgets convert their inferior widgets to internal form when the | |
1268 | widget is instantiated in a buffer. This conversion is recursive, so | |
1269 | the inferior widgets will convert @emph{their} inferior widgets. If | |
1270 | the data structure is itself recursive, this conversion is an infinite | |
1271 | recursion. The @code{lazy} widget prevents the recursion: it convert | |
1272 | its @code{:type} argument only when needed. |