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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
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3 | @c Copyright (C) 1997, 1998, 1999, 2000, 2002, 2003, 2004, |
4 | @c 2005 Free Software Foundation, Inc. | |
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5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/customize | |
7 | @node Customization, Loading, Macros, Top | |
8 | @chapter Writing Customization Definitions | |
9 | ||
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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}). | |
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14 | |
15 | @menu | |
d5b3141d | 16 | * Common Keywords:: Common keyword arguments for all kinds of |
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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. | |
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21 | @end menu |
22 | ||
23 | @node Common Keywords | |
8241495d | 24 | @section Common Item Keywords |
cc6d0d2c | 25 | |
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26 | All kinds of customization declarations (for variables and groups, and |
27 | for faces) accept keyword arguments for specifying various information. | |
28 | This section describes some keywords that apply to all kinds. | |
cc6d0d2c | 29 | |
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30 | All of these keywords, except @code{:tag}, can be used more than once |
31 | in a given item. Each use of the keyword has an independent effect. | |
32 | The keyword @code{:tag} is an exception because any given item can only | |
33 | display one name. | |
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34 | |
35 | @table @code | |
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36 | @item :tag @var{label} |
37 | Use @var{label}, a string, instead of the item's name, to label the item | |
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38 | in customization menus and buffers. |
39 | ||
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40 | @item :group @var{group} |
41 | Put this customization item in group @var{group}. When you use | |
42 | @code{:group} in a @code{defgroup}, it makes the new group a subgroup of | |
43 | @var{group}. | |
44 | ||
45 | If you use this keyword more than once, you can put a single item into | |
46 | more than one group. Displaying any of those groups will show this | |
8241495d | 47 | item. Please don't overdo this, since the result would be annoying. |
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48 | |
49 | @item :link @var{link-data} | |
50 | Include an external link after the documentation string for this item. | |
51 | This is a sentence containing an active field which references some | |
52 | other documentation. | |
53 | ||
8f626a4c | 54 | There are four alternatives you can use for @var{link-data}: |
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55 | |
56 | @table @code | |
57 | @item (custom-manual @var{info-node}) | |
58 | Link to an Info node; @var{info-node} is a string which specifies the | |
59 | node name, as in @code{"(emacs)Top"}. The link appears as | |
60 | @samp{[manual]} in the customization buffer. | |
61 | ||
62 | @item (info-link @var{info-node}) | |
63 | Like @code{custom-manual} except that the link appears | |
64 | in the customization buffer with the Info node name. | |
65 | ||
66 | @item (url-link @var{url}) | |
ad800164 | 67 | Link to a web page; @var{url} is a string which specifies the @acronym{URL}. |
969fe9b5 | 68 | The link appears in the customization buffer as @var{url}. |
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69 | |
70 | @item (emacs-commentary-link @var{library}) | |
71 | Link to the commentary section of a library; @var{library} is a string | |
72 | which specifies the library name. | |
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73 | @end table |
74 | ||
75 | You can specify the text to use in the customization buffer by adding | |
76 | @code{:tag @var{name}} after the first element of the @var{link-data}; | |
77 | for example, @code{(info-link :tag "foo" "(emacs)Top")} makes a link to | |
78 | the Emacs manual which appears in the buffer as @samp{foo}. | |
79 | ||
80 | An item can have more than one external link; however, most items have | |
81 | none at all. | |
82 | ||
83 | @item :load @var{file} | |
84 | Load file @var{file} (a string) before displaying this customization | |
85 | item. Loading is done with @code{load-library}, and only if the file is | |
86 | not already loaded. | |
87 | ||
88 | @item :require @var{feature} | |
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89 | Execute @code{(require '@var{feature})} when your saved customizations |
90 | set the value of this item. @var{feature} should be a symbol. | |
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91 | |
92 | The most common reason to use @code{:require} is when a variable enables | |
93 | a feature such as a minor mode, and just setting the variable won't have | |
94 | any effect unless the code which implements the mode is loaded. | |
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95 | |
96 | @item :version @var{version} | |
97 | This option specifies that the item was first introduced in Emacs | |
98 | version @var{version}, or that its default value was changed in that | |
99 | version. The value @var{version} must be a string. | |
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100 | @end table |
101 | ||
102 | @node Group Definitions | |
103 | @section Defining Custom Groups | |
104 | ||
969fe9b5 | 105 | Each Emacs Lisp package should have one main customization group which |
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106 | contains all the options, faces and other groups in the package. If the |
107 | package has a small number of options and faces, use just one group and | |
108 | put everything in it. When there are more than twelve or so options and | |
109 | faces, then you should structure them into subgroups, and put the | |
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110 | subgroups under the package's main customization group. It is OK to |
111 | put some of the options and faces in the package's main group alongside | |
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112 | the subgroups. |
113 | ||
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114 | The package's main or only group should be a member of one or more of |
115 | the standard customization groups. (To display the full list of them, | |
116 | use @kbd{M-x customize}.) Choose one or more of them (but not too | |
117 | many), and add your group to each of them using the @code{:group} | |
118 | keyword. | |
cc6d0d2c | 119 | |
969fe9b5 | 120 | The way to declare new customization groups is with @code{defgroup}. |
cc6d0d2c | 121 | |
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122 | @defmac defgroup group members doc [keyword value]... |
123 | Declare @var{group} as a customization group containing @var{members}. | |
124 | Do not quote the symbol @var{group}. The argument @var{doc} specifies | |
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125 | the documentation string for the group. It should not start with a |
126 | @samp{*} as in @code{defcustom}; that convention is for variables only. | |
cc6d0d2c | 127 | |
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128 | The argument @var{members} is a list specifying an initial set of |
129 | customization items to be members of the group. However, most often | |
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130 | @var{members} is @code{nil}, and you specify the group's members by |
131 | using the @code{:group} keyword when defining those members. | |
cc6d0d2c | 132 | |
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133 | If you want to specify group members through @var{members}, each element |
134 | should have the form @code{(@var{name} @var{widget})}. Here @var{name} | |
135 | is a symbol, and @var{widget} is a widget type for editing that symbol. | |
136 | Useful widgets are @code{custom-variable} for a variable, | |
137 | @code{custom-face} for a face, and @code{custom-group} for a group. | |
cc6d0d2c | 138 | |
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139 | When you introduce a new group into Emacs, use the @code{:version} |
140 | keyword in the @code{defgroup}; then you need not use it for | |
141 | the individual members of the group. | |
3d66f910 | 142 | |
cc6d0d2c | 143 | In addition to the common keywords (@pxref{Common Keywords}), you can |
3d66f910 | 144 | also use this keyword in @code{defgroup}: |
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145 | |
146 | @table @code | |
147 | @item :prefix @var{prefix} | |
148 | If the name of an item in the group starts with @var{prefix}, then the | |
149 | tag for that item is constructed (by default) by omitting @var{prefix}. | |
150 | ||
151 | One group can have any number of prefixes. | |
152 | @end table | |
153 | @end defmac | |
154 | ||
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155 | The prefix-discarding feature is currently turned off, which means |
156 | that @code{:prefix} currently has no effect. We did this because we | |
157 | found that discarding the specified prefixes often led to confusing | |
158 | names for options. This happened because the people who wrote the | |
159 | @code{defgroup} definitions for various groups added @code{:prefix} | |
160 | keywords whenever they make logical sense---that is, whenever the | |
161 | variables in the library have a common prefix. | |
162 | ||
163 | In order to obtain good results with @code{:prefix}, it would be | |
164 | necessary to check the specific effects of discarding a particular | |
165 | prefix, given the specific items in a group and their names and | |
166 | documentation. If the resulting text is not clear, then @code{:prefix} | |
167 | should not be used in that case. | |
168 | ||
169 | It should be possible to recheck all the customization groups, delete | |
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170 | the @code{:prefix} specifications which give unclear results, and then |
171 | turn this feature back on, if someone would like to do the work. | |
172 | ||
173 | @node Variable Definitions | |
174 | @section Defining Customization Variables | |
175 | ||
969fe9b5 | 176 | Use @code{defcustom} to declare user-editable variables. |
cc6d0d2c | 177 | |
4577e8cc | 178 | @defmac defcustom option default doc [keyword value]@dots{} |
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179 | Declare @var{option} as a customizable user option variable. Do not |
180 | quote @var{option}. The argument @var{doc} specifies the documentation | |
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181 | string for the variable. It should often start with a @samp{*} to mark |
182 | it as a @dfn{user option} (@pxref{Defining Variables}). Do not start | |
183 | the documentation string with @samp{*} for options which cannot or | |
184 | normally should not be set with @code{set-variable}; examples of the | |
185 | former are global minor mode options such as | |
186 | @code{global-font-lock-mode} and examples of the latter are hooks. | |
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187 | |
188 | If @var{option} is void, @code{defcustom} initializes it to | |
189 | @var{default}. @var{default} should be an expression to compute the | |
a9f0a989 | 190 | value; be careful in writing it, because it can be evaluated on more |
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191 | than one occasion. You should normally avoid using backquotes in |
192 | @var{default} because they are not expanded when editing the value, | |
193 | causing list values to appear to have the wrong structure. | |
8241495d | 194 | |
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195 | If you specify the @code{:set} option, to make the variable take other |
196 | special actions when set through the customization buffer, the | |
197 | variable's documentation string should tell the user specifically how | |
198 | to do the same job in hand-written Lisp code. | |
199 | ||
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200 | When you evaluate a @code{defcustom} form with @kbd{C-M-x} in Emacs Lisp |
201 | mode (@code{eval-defun}), a special feature of @code{eval-defun} | |
202 | arranges to set the variable unconditionally, without testing whether | |
203 | its value is void. (The same feature applies to @code{defvar}.) | |
204 | @xref{Defining Variables}. | |
7dd3d99f | 205 | @end defmac |
cc6d0d2c | 206 | |
7dd3d99f | 207 | @code{defcustom} accepts the following additional keywords: |
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208 | |
209 | @table @code | |
210 | @item :type @var{type} | |
211 | Use @var{type} as the data type for this option. It specifies which | |
212 | values are legitimate, and how to display the value. | |
213 | @xref{Customization Types}, for more information. | |
214 | ||
215 | @item :options @var{list} | |
216 | Specify @var{list} as the list of reasonable values for use in this | |
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217 | option. The user is not restricted to using only these values, but they |
218 | are offered as convenient alternatives. | |
cc6d0d2c | 219 | |
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220 | This is meaningful only for certain types, currently including |
221 | @code{hook}, @code{plist} and @code{alist}. See the definition of the | |
222 | individual types for a description of how to use @code{:options}. | |
cc6d0d2c | 223 | |
cc6d0d2c | 224 | @item :set @var{setfunction} |
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225 | Specify @var{setfunction} as the way to change the value of this |
226 | option. The function @var{setfunction} should take two arguments, a | |
227 | symbol (the option name) and the new value, and should do whatever is | |
228 | necessary to update the value properly for this option (which may not | |
229 | mean simply setting the option as a Lisp variable). The default for | |
230 | @var{setfunction} is @code{set-default}. | |
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231 | |
232 | @item :get @var{getfunction} | |
233 | Specify @var{getfunction} as the way to extract the value of this | |
234 | option. The function @var{getfunction} should take one argument, a | |
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235 | symbol, and should return whatever customize should use as the |
236 | ``current value'' for that symbol (which need not be the symbol's Lisp | |
237 | value). The default is @code{default-value}. | |
238 | ||
239 | You have to really understand the workings of Custom to use | |
240 | @code{:get} correctly. It is meant for values that are treated in | |
241 | Custom as variables but are not actually stored in Lisp variables. It | |
242 | is almost surely a mistake to specify @code{getfunction} for a value | |
243 | that really is stored in a Lisp variable. | |
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244 | |
245 | @item :initialize @var{function} | |
937dbf8c RS |
246 | @var{function} should be a function used to initialize the variable |
247 | when the @code{defcustom} is evaluated. It should take two arguments, | |
248 | the option name (a symbol) and the value. Here are some predefined | |
249 | functions meant for use in this way: | |
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250 | |
251 | @table @code | |
252 | @item custom-initialize-set | |
969fe9b5 | 253 | Use the variable's @code{:set} function to initialize the variable, but |
7db0894f | 254 | do not reinitialize it if it is already non-void. |
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255 | |
256 | @item custom-initialize-default | |
969fe9b5 RS |
257 | Like @code{custom-initialize-set}, but use the function |
258 | @code{set-default} to set the variable, instead of the variable's | |
259 | @code{:set} function. This is the usual choice for a variable whose | |
260 | @code{:set} function enables or disables a minor mode; with this choice, | |
261 | defining the variable will not call the minor mode function, but | |
262 | customizing the variable will do so. | |
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263 | |
264 | @item custom-initialize-reset | |
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265 | Always use the @code{:set} function to initialize the variable. If |
266 | the variable is already non-void, reset it by calling the @code{:set} | |
969fe9b5 | 267 | function using the current value (returned by the @code{:get} method). |
7db0894f | 268 | This is the default @code{:initialize} function. |
cc6d0d2c RS |
269 | |
270 | @item custom-initialize-changed | |
969fe9b5 RS |
271 | Use the @code{:set} function to initialize the variable, if it is |
272 | already set or has been customized; otherwise, just use | |
273 | @code{set-default}. | |
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274 | |
275 | @item custom-initialize-safe-set | |
276 | @itemx custom-initialize-safe-default | |
277 | These functions behave like @code{custom-initialize-set} | |
278 | (@code{custom-initialize-default}, respectively), but catch errors. | |
279 | If an error occurs during initialization, they set the variable to | |
280 | @code{nil} using @code{set-default}, and throw no error. | |
281 | ||
282 | These two functions are only meant for options defined in pre-loaded | |
283 | files, where some variables or functions used to compute the option's | |
284 | value may not yet be defined. The option normally gets updated in | |
285 | @file{startup.el}, ignoring the previously computed value. Because of | |
286 | this typical usage, the value which these two functions compute | |
287 | normally only matters when, after startup, one unsets the option's | |
288 | value and then reevaluates the defcustom. By that time, the necessary | |
289 | variables and functions will be defined, so there will not be an error. | |
cc6d0d2c | 290 | @end table |
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291 | |
292 | @item :set-after @var{variables} | |
293 | When setting variables according to saved customizations, make sure to | |
294 | set the variables @var{variables} before this one; in other words, delay | |
295 | setting this variable until after those others have been handled. Use | |
296 | @code{:set-after} if setting this variable won't work properly unless | |
297 | those other variables already have their intended values. | |
969fe9b5 | 298 | @end table |
cc6d0d2c | 299 | |
969fe9b5 | 300 | The @code{:require} option is useful for an option that turns on the |
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301 | operation of a certain feature. Assuming that the package is coded to |
302 | check the value of the option, you still need to arrange for the package | |
969fe9b5 | 303 | to be loaded. You can do that with @code{:require}. @xref{Common |
1a60ceae | 304 | Keywords}. Here is an example, from the library @file{saveplace.el}: |
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305 | |
306 | @example | |
1a60ceae NR |
307 | (defcustom save-place nil |
308 | "*Non-nil means automatically save place in each file..." | |
969fe9b5 | 309 | :type 'boolean |
1a60ceae NR |
310 | :require 'saveplace |
311 | :group 'save-place) | |
969fe9b5 | 312 | @end example |
cc6d0d2c | 313 | |
b6954afd RS |
314 | If a customization item has a type such as @code{hook} or @code{alist}, |
315 | which supports @code{:options}, you can add additional options to the | |
316 | item, outside the @code{defcustom} declaration, by calling | |
317 | @code{custom-add-option}. For example, if you define a function | |
318 | @code{my-lisp-mode-initialization} intended to be called from | |
319 | @code{emacs-lisp-mode-hook}, you might want to add that to the list of | |
320 | options for @code{emacs-lisp-mode-hook}, but not by editing its | |
321 | definition. You can do it thus: | |
322 | ||
323 | @example | |
8241495d RS |
324 | (custom-add-option 'emacs-lisp-mode-hook |
325 | 'my-lisp-mode-initialization) | |
b6954afd | 326 | @end example |
cc6d0d2c RS |
327 | |
328 | @defun custom-add-option symbol option | |
b6954afd | 329 | To the customization @var{symbol}, add @var{option}. |
cc6d0d2c | 330 | |
b6954afd RS |
331 | The precise effect of adding @var{option} depends on the customization |
332 | type of @var{symbol}. | |
cc6d0d2c | 333 | @end defun |
cc6d0d2c RS |
334 | |
335 | Internally, @code{defcustom} uses the symbol property | |
336 | @code{standard-value} to record the expression for the default value, | |
337 | and @code{saved-value} to record the value saved by the user with the | |
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338 | customization buffer. Both properties are actually lists whose car is |
339 | an expression which evaluates to the value. | |
cc6d0d2c | 340 | |
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341 | @node Customization Types |
342 | @section Customization Types | |
343 | ||
344 | When you define a user option with @code{defcustom}, you must specify | |
969fe9b5 | 345 | its @dfn{customization type}. That is a Lisp object which describes (1) |
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346 | which values are legitimate and (2) how to display the value in the |
347 | customization buffer for editing. | |
348 | ||
349 | You specify the customization type in @code{defcustom} with the | |
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350 | @code{:type} keyword. The argument of @code{:type} is evaluated, but |
351 | only once when the @code{defcustom} is executed, so it isn't useful | |
352 | for the value to vary. Normally we use a quoted constant. For | |
353 | example: | |
cc6d0d2c RS |
354 | |
355 | @example | |
356 | (defcustom diff-command "diff" | |
357 | "*The command to use to run diff." | |
969fe9b5 | 358 | :type '(string) |
cc6d0d2c RS |
359 | :group 'diff) |
360 | @end example | |
361 | ||
969fe9b5 RS |
362 | In general, a customization type is a list whose first element is a |
363 | symbol, one of the customization type names defined in the following | |
364 | sections. After this symbol come a number of arguments, depending on | |
365 | the symbol. Between the type symbol and its arguments, you can | |
366 | optionally write keyword-value pairs (@pxref{Type Keywords}). | |
cc6d0d2c | 367 | |
969fe9b5 RS |
368 | Some of the type symbols do not use any arguments; those are called |
369 | @dfn{simple types}. For a simple type, if you do not use any | |
370 | keyword-value pairs, you can omit the parentheses around the type | |
371 | symbol. For example just @code{string} as a customization type is | |
372 | equivalent to @code{(string)}. | |
cc6d0d2c RS |
373 | |
374 | @menu | |
375 | * Simple Types:: | |
376 | * Composite Types:: | |
377 | * Splicing into Lists:: | |
378 | * Type Keywords:: | |
cfa921fd | 379 | * Defining New Types:: |
cc6d0d2c RS |
380 | @end menu |
381 | ||
c5c36e02 | 382 | All customization types are implemented as widgets; see @ref{Top, , |
333c5fc5 | 383 | Introduction, widget, The Emacs Widget Library}, for details. |
c5c36e02 | 384 | |
cc6d0d2c RS |
385 | @node Simple Types |
386 | @subsection Simple Types | |
387 | ||
388 | This section describes all the simple customization types. | |
389 | ||
390 | @table @code | |
391 | @item sexp | |
392 | The value may be any Lisp object that can be printed and read back. You | |
393 | can use @code{sexp} as a fall-back for any option, if you don't want to | |
394 | take the time to work out a more specific type to use. | |
395 | ||
396 | @item integer | |
397 | The value must be an integer, and is represented textually | |
398 | in the customization buffer. | |
399 | ||
400 | @item number | |
177f790c MR |
401 | The value must be a number (floating point or integer), and is |
402 | represented textually in the customization buffer. | |
403 | ||
404 | @item float | |
405 | The value must be a floating point number, and is represented | |
406 | textually in the customization buffer. | |
cc6d0d2c RS |
407 | |
408 | @item string | |
409 | The value must be a string, and the customization buffer shows just the | |
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410 | contents, with no delimiting @samp{"} characters and no quoting with |
411 | @samp{\}. | |
cc6d0d2c RS |
412 | |
413 | @item regexp | |
969fe9b5 RS |
414 | Like @code{string} except that the string must be a valid regular |
415 | expression. | |
cc6d0d2c RS |
416 | |
417 | @item character | |
418 | The value must be a character code. A character code is actually an | |
419 | integer, but this type shows the value by inserting the character in the | |
420 | buffer, rather than by showing the number. | |
421 | ||
422 | @item file | |
423 | The value must be a file name, and you can do completion with | |
424 | @kbd{M-@key{TAB}}. | |
425 | ||
426 | @item (file :must-match t) | |
427 | The value must be a file name for an existing file, and you can do | |
428 | completion with @kbd{M-@key{TAB}}. | |
429 | ||
430 | @item directory | |
431 | The value must be a directory name, and you can do completion with | |
432 | @kbd{M-@key{TAB}}. | |
433 | ||
a9f0a989 RS |
434 | @item hook |
435 | The value must be a list of functions (or a single function, but that is | |
436 | obsolete usage). This customization type is used for hook variables. | |
1911e6e5 RS |
437 | You can use the @code{:options} keyword in a hook variable's |
438 | @code{defcustom} to specify a list of functions recommended for use in | |
439 | the hook; see @ref{Variable Definitions}. | |
a9f0a989 | 440 | |
b6954afd | 441 | @item alist |
08f0f5e9 KH |
442 | The value must be a list of cons-cells, the @sc{car} of each cell |
443 | representing a key, and the @sc{cdr} of the same cell representing an | |
444 | associated value. The user can add and delete key/value pairs, and | |
b6954afd RS |
445 | edit both the key and the value of each pair. |
446 | ||
447 | You can specify the key and value types like this: | |
448 | ||
8241495d RS |
449 | @smallexample |
450 | (alist :key-type @var{key-type} :value-type @var{value-type}) | |
451 | @end smallexample | |
b6954afd RS |
452 | |
453 | @noindent | |
454 | where @var{key-type} and @var{value-type} are customization type | |
455 | specifications. The default key type is @code{sexp}, and the default | |
456 | value type is @code{sexp}. | |
457 | ||
458 | The user can add any key matching the specified key type, but you can | |
459 | give some keys a preferential treatment by specifying them with the | |
460 | @code{:options} (see @ref{Variable Definitions}). The specified keys | |
461 | will always be shown in the customize buffer (together with a suitable | |
462 | value), with a checkbox to include or exclude or disable the key/value | |
463 | pair from the alist. The user will not be able to edit the keys | |
464 | specified by the @code{:options} keyword argument. | |
465 | ||
466 | The argument to the @code{:options} keywords should be a list of option | |
467 | specifications. Ordinarily, the options are simply atoms, which are the | |
468 | specified keys. For example: | |
469 | ||
8241495d | 470 | @smallexample |
b6954afd | 471 | :options '("foo" "bar" "baz") |
8241495d | 472 | @end smallexample |
b6954afd RS |
473 | |
474 | @noindent | |
475 | specifies that there are three ``known'' keys, namely @code{"foo"}, | |
476 | @code{"bar"} and @code{"baz"}, which will always be shown first. | |
477 | ||
478 | You may want to restrict the value type for specific keys, for example, | |
479 | the value associated with the @code{"bar"} key can only be an integer. | |
480 | You can specify this by using a list instead of an atom in the option | |
481 | specification. The first element will specify the key, like before, | |
482 | while the second element will specify the value type. | |
483 | ||
8241495d | 484 | @smallexample |
b6954afd | 485 | :options '("foo" ("bar" integer) "baz") |
8241495d | 486 | @end smallexample |
b6954afd RS |
487 | |
488 | Finally, you may want to change how the key is presented. By default, | |
489 | the key is simply shown as a @code{const}, since the user cannot change | |
490 | the special keys specified with the @code{:options} keyword. However, | |
491 | you may want to use a more specialized type for presenting the key, like | |
492 | @code{function-item} if you know it is a symbol with a function binding. | |
493 | This is done by using a customization type specification instead of a | |
494 | symbol for the key. | |
495 | ||
8241495d | 496 | @smallexample |
b6954afd | 497 | :options '("foo" ((function-item some-function) integer) "baz") |
8241495d | 498 | @end smallexample |
b6954afd | 499 | |
08f0f5e9 | 500 | Many alists use lists with two elements, instead of cons cells. For |
b6954afd RS |
501 | example, |
502 | ||
8241495d | 503 | @smallexample |
b6954afd RS |
504 | (defcustom list-alist '(("foo" 1) ("bar" 2) ("baz" 3)) |
505 | "Each element is a list of the form (KEY VALUE).") | |
8241495d | 506 | @end smallexample |
b6954afd RS |
507 | |
508 | @noindent | |
177c0ea7 | 509 | instead of |
b6954afd | 510 | |
8241495d | 511 | @smallexample |
b6954afd RS |
512 | (defcustom cons-alist '(("foo" . 1) ("bar" . 2) ("baz" . 3)) |
513 | "Each element is a cons-cell (KEY . VALUE).") | |
8241495d | 514 | @end smallexample |
b6954afd RS |
515 | |
516 | Because of the way lists are implemented on top of cons cells, you can | |
517 | treat @code{list-alist} in the example above as a cons cell alist, where | |
518 | the value type is a list with a single element containing the real | |
519 | value. | |
520 | ||
8241495d | 521 | @smallexample |
b6954afd RS |
522 | (defcustom list-alist '(("foo" 1) ("bar" 2) ("baz" 3)) |
523 | "Each element is a list of the form (KEY VALUE)." | |
524 | :type '(alist :value-type (group integer))) | |
8241495d | 525 | @end smallexample |
b6954afd RS |
526 | |
527 | The @code{group} widget is used here instead of @code{list} only because | |
528 | the formatting is better suited for the purpose. | |
529 | ||
38c7d6d5 | 530 | Similarly, you can have alists with more values associated with each |
b6954afd RS |
531 | key, using variations of this trick: |
532 | ||
8241495d | 533 | @smallexample |
177c0ea7 | 534 | (defcustom person-data '(("brian" 50 t) |
b6954afd RS |
535 | ("dorith" 55 nil) |
536 | ("ken" 52 t)) | |
3d3df9e1 RS |
537 | "Alist of basic info about people. |
538 | Each element has the form (NAME AGE MALE-FLAG)." | |
38c7d6d5 | 539 | :type '(alist :value-type (group integer boolean))) |
b6954afd | 540 | |
177c0ea7 | 541 | (defcustom pets '(("brian") |
b6954afd RS |
542 | ("dorith" "dog" "guppy") |
543 | ("ken" "cat")) | |
3d3df9e1 RS |
544 | "Alist of people's pets. |
545 | In an element (KEY . VALUE), KEY is the person's name, | |
546 | and the VALUE is a list of that person's pets." | |
b6954afd | 547 | :type '(alist :value-type (repeat string))) |
8241495d | 548 | @end smallexample |
b6954afd RS |
549 | |
550 | @item plist | |
551 | The @code{plist} custom type is similar to the @code{alist} (see above), | |
552 | except that the information is stored as a property list, i.e. a list of | |
553 | this form: | |
554 | ||
8241495d | 555 | @smallexample |
b6954afd | 556 | (@var{key} @var{value} @var{key} @var{value} @var{key} @var{value} @dots{}) |
8241495d | 557 | @end smallexample |
b6954afd RS |
558 | |
559 | The default @code{:key-type} for @code{plist} is @code{symbol}, | |
560 | rather than @code{sexp}. | |
561 | ||
cc6d0d2c RS |
562 | @item symbol |
563 | The value must be a symbol. It appears in the customization buffer as | |
564 | the name of the symbol. | |
565 | ||
566 | @item function | |
567 | The value must be either a lambda expression or a function name. When | |
568 | it is a function name, you can do completion with @kbd{M-@key{TAB}}. | |
569 | ||
570 | @item variable | |
571 | The value must be a variable name, and you can do completion with | |
572 | @kbd{M-@key{TAB}}. | |
573 | ||
a9f0a989 RS |
574 | @item face |
575 | The value must be a symbol which is a face name, and you can do | |
576 | completion with @kbd{M-@key{TAB}}. | |
577 | ||
cc6d0d2c | 578 | @item boolean |
969fe9b5 RS |
579 | The value is boolean---either @code{nil} or @code{t}. Note that by |
580 | using @code{choice} and @code{const} together (see the next section), | |
581 | you can specify that the value must be @code{nil} or @code{t}, but also | |
582 | specify the text to describe each value in a way that fits the specific | |
583 | meaning of the alternative. | |
5e0c8a23 DL |
584 | |
585 | @item coding-system | |
586 | The value must be a coding-system name, and you can do completion with | |
587 | @kbd{M-@key{TAB}}. | |
588 | ||
589 | @item color | |
590 | The value must be a valid color name, and you can do completion with | |
97073664 | 591 | @kbd{M-@key{TAB}}. A sample is provided. |
cc6d0d2c RS |
592 | @end table |
593 | ||
594 | @node Composite Types | |
595 | @subsection Composite Types | |
608dc417 | 596 | @cindex arguments (of composite type) |
cc6d0d2c RS |
597 | |
598 | When none of the simple types is appropriate, you can use composite | |
608dc417 RS |
599 | types, which build new types from other types or from specified data. |
600 | The specified types or data are called the @dfn{arguments} of the | |
601 | composite type. The composite type normally looks like this: | |
cc6d0d2c RS |
602 | |
603 | @example | |
608dc417 | 604 | (@var{constructor} @var{arguments}@dots{}) |
cc6d0d2c RS |
605 | @end example |
606 | ||
607 | @noindent | |
608dc417 RS |
608 | but you can also add keyword-value pairs before the arguments, like |
609 | this: | |
cc6d0d2c | 610 | |
608dc417 RS |
611 | @example |
612 | (@var{constructor} @r{@{}@var{keyword} @var{value}@r{@}}@dots{} @var{arguments}@dots{}) | |
613 | @end example | |
cc6d0d2c | 614 | |
608dc417 RS |
615 | Here is a table of constructors and how to use them to write |
616 | composite types: | |
617 | ||
618 | @table @code | |
cc6d0d2c RS |
619 | @item (cons @var{car-type} @var{cdr-type}) |
620 | The value must be a cons cell, its @sc{car} must fit @var{car-type}, and | |
a9f0a989 | 621 | its @sc{cdr} must fit @var{cdr-type}. For example, @code{(cons string |
cc6d0d2c RS |
622 | symbol)} is a customization type which matches values such as |
623 | @code{("foo" . foo)}. | |
624 | ||
969fe9b5 | 625 | In the customization buffer, the @sc{car} and the @sc{cdr} are |
cc6d0d2c RS |
626 | displayed and edited separately, each according to the type |
627 | that you specify for it. | |
628 | ||
629 | @item (list @var{element-types}@dots{}) | |
630 | The value must be a list with exactly as many elements as the | |
631 | @var{element-types} you have specified; and each element must fit the | |
632 | corresponding @var{element-type}. | |
633 | ||
634 | For example, @code{(list integer string function)} describes a list of | |
635 | three elements; the first element must be an integer, the second a | |
636 | string, and the third a function. | |
637 | ||
a9f0a989 | 638 | In the customization buffer, each element is displayed and edited |
cc6d0d2c RS |
639 | separately, according to the type specified for it. |
640 | ||
641 | @item (vector @var{element-types}@dots{}) | |
642 | Like @code{list} except that the value must be a vector instead of a | |
643 | list. The elements work the same as in @code{list}. | |
644 | ||
4577e8cc | 645 | @item (choice @var{alternative-types}@dots{}) |
cc6d0d2c RS |
646 | The value must fit at least one of @var{alternative-types}. |
647 | For example, @code{(choice integer string)} allows either an | |
648 | integer or a string. | |
649 | ||
650 | In the customization buffer, the user selects one of the alternatives | |
651 | using a menu, and can then edit the value in the usual way for that | |
652 | alternative. | |
653 | ||
654 | Normally the strings in this menu are determined automatically from the | |
655 | choices; however, you can specify different strings for the menu by | |
656 | including the @code{:tag} keyword in the alternatives. For example, if | |
657 | an integer stands for a number of spaces, while a string is text to use | |
658 | verbatim, you might write the customization type this way, | |
659 | ||
a9f0a989 | 660 | @example |
cc6d0d2c RS |
661 | (choice (integer :tag "Number of spaces") |
662 | (string :tag "Literal text")) | |
a9f0a989 | 663 | @end example |
cc6d0d2c RS |
664 | |
665 | @noindent | |
38c7d6d5 | 666 | so that the menu offers @samp{Number of spaces} and @samp{Literal text}. |
cc6d0d2c | 667 | |
969fe9b5 RS |
668 | In any alternative for which @code{nil} is not a valid value, other than |
669 | a @code{const}, you should specify a valid default for that alternative | |
670 | using the @code{:value} keyword. @xref{Type Keywords}. | |
671 | ||
b56f98ab RS |
672 | If some values are covered by more than one of the alternatives, |
673 | customize will choose the first alternative that the value fits. This | |
674 | means you should always list the most specific types first, and the | |
675 | most general last. Here's an example of proper usage: | |
676 | ||
677 | @example | |
342fd6cd RS |
678 | (choice (const :tag "Off" nil) |
679 | symbol (sexp :tag "Other")) | |
b56f98ab RS |
680 | @end example |
681 | ||
682 | @noindent | |
683 | This way, the special value @code{nil} is not treated like other | |
684 | symbols, and symbols are not treated like other Lisp expressions. | |
685 | ||
4577e8cc DL |
686 | @item (radio @var{element-types}@dots{}) |
687 | This is similar to @code{choice}, except that the choices are displayed | |
688 | using `radio buttons' rather than a menu. This has the advantage of | |
689 | displaying documentation for the choices when applicable and so is often | |
690 | a good choice for a choice between constant functions | |
691 | (@code{function-item} customization types). | |
692 | ||
cc6d0d2c RS |
693 | @item (const @var{value}) |
694 | The value must be @var{value}---nothing else is allowed. | |
695 | ||
696 | The main use of @code{const} is inside of @code{choice}. For example, | |
697 | @code{(choice integer (const nil))} allows either an integer or | |
969fe9b5 RS |
698 | @code{nil}. |
699 | ||
700 | @code{:tag} is often used with @code{const}, inside of @code{choice}. | |
701 | For example, | |
702 | ||
a9f0a989 | 703 | @example |
969fe9b5 RS |
704 | (choice (const :tag "Yes" t) |
705 | (const :tag "No" nil) | |
706 | (const :tag "Ask" foo)) | |
a9f0a989 | 707 | @end example |
cc6d0d2c | 708 | |
da03dc1d RS |
709 | @noindent |
710 | describes a variable for which @code{t} means yes, @code{nil} means no, | |
711 | and @code{foo} means ``ask.'' | |
712 | ||
713 | @item (other @var{value}) | |
714 | This alternative can match any Lisp value, but if the user chooses this | |
715 | alternative, that selects the value @var{value}. | |
716 | ||
717 | The main use of @code{other} is as the last element of @code{choice}. | |
718 | For example, | |
719 | ||
720 | @example | |
721 | (choice (const :tag "Yes" t) | |
722 | (const :tag "No" nil) | |
723 | (other :tag "Ask" foo)) | |
724 | @end example | |
725 | ||
726 | @noindent | |
727 | describes a variable for which @code{t} means yes, @code{nil} means no, | |
728 | and anything else means ``ask.'' If the user chooses @samp{Ask} from | |
729 | the menu of alternatives, that specifies the value @code{foo}; but any | |
730 | other value (not @code{t}, @code{nil} or @code{foo}) displays as | |
731 | @samp{Ask}, just like @code{foo}. | |
732 | ||
cc6d0d2c RS |
733 | @item (function-item @var{function}) |
734 | Like @code{const}, but used for values which are functions. This | |
969fe9b5 RS |
735 | displays the documentation string as well as the function name. |
736 | The documentation string is either the one you specify with | |
737 | @code{:doc}, or @var{function}'s own documentation string. | |
cc6d0d2c RS |
738 | |
739 | @item (variable-item @var{variable}) | |
740 | Like @code{const}, but used for values which are variable names. This | |
969fe9b5 RS |
741 | displays the documentation string as well as the variable name. The |
742 | documentation string is either the one you specify with @code{:doc}, or | |
743 | @var{variable}'s own documentation string. | |
cc6d0d2c | 744 | |
1f447a50 KH |
745 | @item (set @var{types}@dots{}) |
746 | The value must be a list, and each element of the list must match one of | |
747 | the @var{types} specified. | |
748 | ||
749 | This appears in the customization buffer as a checklist, so that each of | |
750 | @var{types} may have either one corresponding element or none. It is | |
751 | not possible to specify two different elements that match the same one | |
752 | of @var{types}. For example, @code{(set integer symbol)} allows one | |
753 | integer and/or one symbol in the list; it does not allow multiple | |
754 | integers or multiple symbols. As a result, it is rare to use | |
755 | nonspecific types such as @code{integer} in a @code{set}. | |
756 | ||
757 | Most often, the @var{types} in a @code{set} are @code{const} types, as | |
758 | shown here: | |
759 | ||
760 | @example | |
761 | (set (const :bold) (const :italic)) | |
762 | @end example | |
763 | ||
764 | Sometimes they describe possible elements in an alist: | |
765 | ||
766 | @example | |
767 | (set (cons :tag "Height" (const height) integer) | |
768 | (cons :tag "Width" (const width) integer)) | |
769 | @end example | |
770 | ||
771 | @noindent | |
772 | That lets the user specify a height value optionally | |
773 | and a width value optionally. | |
cc6d0d2c RS |
774 | |
775 | @item (repeat @var{element-type}) | |
776 | The value must be a list and each element of the list must fit the type | |
777 | @var{element-type}. This appears in the customization buffer as a | |
778 | list of elements, with @samp{[INS]} and @samp{[DEL]} buttons for adding | |
779 | more elements or removing elements. | |
608dc417 RS |
780 | |
781 | @item (restricted-sexp :match-alternatives @var{criteria}) | |
782 | This is the most general composite type construct. The value may be | |
783 | any Lisp object that satisfies one of @var{criteria}. @var{criteria} | |
784 | should be a list, and each element should be one of these | |
785 | possibilities: | |
786 | ||
787 | @itemize @bullet | |
788 | @item | |
789 | A predicate---that is, a function of one argument that has no side | |
790 | effects, and returns either @code{nil} or non-@code{nil} according to | |
791 | the argument. Using a predicate in the list says that objects for which | |
792 | the predicate returns non-@code{nil} are acceptable. | |
793 | ||
794 | @item | |
795 | A quoted constant---that is, @code{'@var{object}}. This sort of element | |
796 | in the list says that @var{object} itself is an acceptable value. | |
797 | @end itemize | |
798 | ||
799 | For example, | |
800 | ||
801 | @example | |
802 | (restricted-sexp :match-alternatives | |
803 | (integerp 't 'nil)) | |
804 | @end example | |
805 | ||
806 | @noindent | |
807 | allows integers, @code{t} and @code{nil} as legitimate values. | |
808 | ||
809 | The customization buffer shows all legitimate values using their read | |
810 | syntax, and the user edits them textually. | |
811 | @end table | |
812 | ||
813 | Here is a table of the keywords you can use in keyword-value pairs | |
814 | in a composite type: | |
815 | ||
816 | @table @code | |
817 | @item :tag @var{tag} | |
818 | Use @var{tag} as the name of this alternative, for user communication | |
819 | purposes. This is useful for a type that appears inside of a | |
820 | @code{choice}. | |
821 | ||
822 | @item :match-alternatives @var{criteria} | |
823 | Use @var{criteria} to match possible values. This is used only in | |
824 | @code{restricted-sexp}. | |
825 | ||
38c7d6d5 RS |
826 | @item :args @var{argument-list} |
827 | Use the elements of @var{argument-list} as the arguments of the type | |
608dc417 RS |
828 | construct. For instance, @code{(const :args (foo))} is equivalent to |
829 | @code{(const foo)}. You rarely need to write @code{:args} explicitly, | |
830 | because normally the arguments are recognized automatically as | |
831 | whatever follows the last keyword-value pair. | |
cc6d0d2c RS |
832 | @end table |
833 | ||
834 | @node Splicing into Lists | |
835 | @subsection Splicing into Lists | |
836 | ||
837 | The @code{:inline} feature lets you splice a variable number of | |
838 | elements into the middle of a list or vector. You use it in a | |
839 | @code{set}, @code{choice} or @code{repeat} type which appears among the | |
840 | element-types of a @code{list} or @code{vector}. | |
841 | ||
842 | Normally, each of the element-types in a @code{list} or @code{vector} | |
843 | describes one and only one element of the list or vector. Thus, if an | |
844 | element-type is a @code{repeat}, that specifies a list of unspecified | |
845 | length which appears as one element. | |
846 | ||
847 | But when the element-type uses @code{:inline}, the value it matches is | |
848 | merged directly into the containing sequence. For example, if it | |
849 | matches a list with three elements, those become three elements of the | |
850 | overall sequence. This is analogous to using @samp{,@@} in the backquote | |
851 | construct. | |
852 | ||
241f79af | 853 | For example, to specify a list whose first element must be @code{baz} |
cc6d0d2c RS |
854 | and whose remaining arguments should be zero or more of @code{foo} and |
855 | @code{bar}, use this customization type: | |
856 | ||
857 | @example | |
241f79af | 858 | (list (const baz) (set :inline t (const foo) (const bar))) |
cc6d0d2c RS |
859 | @end example |
860 | ||
861 | @noindent | |
241f79af PA |
862 | This matches values such as @code{(baz)}, @code{(baz foo)}, @code{(baz bar)} |
863 | and @code{(baz foo bar)}. | |
cc6d0d2c RS |
864 | |
865 | When the element-type is a @code{choice}, you use @code{:inline} not | |
866 | in the @code{choice} itself, but in (some of) the alternatives of the | |
867 | @code{choice}. For example, to match a list which must start with a | |
868 | file name, followed either by the symbol @code{t} or two strings, use | |
869 | this customization type: | |
870 | ||
871 | @example | |
872 | (list file | |
873 | (choice (const t) | |
874 | (list :inline t string string))) | |
875 | @end example | |
876 | ||
877 | @noindent | |
878 | If the user chooses the first alternative in the choice, then the | |
879 | overall list has two elements and the second element is @code{t}. If | |
880 | the user chooses the second alternative, then the overall list has three | |
881 | elements and the second and third must be strings. | |
882 | ||
883 | @node Type Keywords | |
884 | @subsection Type Keywords | |
885 | ||
886 | You can specify keyword-argument pairs in a customization type after the | |
887 | type name symbol. Here are the keywords you can use, and their | |
888 | meanings: | |
889 | ||
890 | @table @code | |
891 | @item :value @var{default} | |
892 | This is used for a type that appears as an alternative inside of | |
969fe9b5 | 893 | @code{choice}; it specifies the default value to use, at first, if and |
cc6d0d2c RS |
894 | when the user selects this alternative with the menu in the |
895 | customization buffer. | |
896 | ||
897 | Of course, if the actual value of the option fits this alternative, it | |
898 | will appear showing the actual value, not @var{default}. | |
899 | ||
969fe9b5 RS |
900 | If @code{nil} is not a valid value for the alternative, then it is |
901 | essential to specify a valid default with @code{:value}. | |
902 | ||
cc6d0d2c RS |
903 | @item :format @var{format-string} |
904 | This string will be inserted in the buffer to represent the value | |
905 | corresponding to the type. The following @samp{%} escapes are available | |
906 | for use in @var{format-string}: | |
907 | ||
908 | @table @samp | |
cc6d0d2c RS |
909 | @item %[@var{button}%] |
910 | Display the text @var{button} marked as a button. The @code{:action} | |
911 | attribute specifies what the button will do if the user invokes it; | |
912 | its value is a function which takes two arguments---the widget which | |
913 | the button appears in, and the event. | |
914 | ||
915 | There is no way to specify two different buttons with different | |
969fe9b5 | 916 | actions. |
cc6d0d2c RS |
917 | |
918 | @item %@{@var{sample}%@} | |
919 | Show @var{sample} in a special face specified by @code{:sample-face}. | |
920 | ||
921 | @item %v | |
922 | Substitute the item's value. How the value is represented depends on | |
923 | the kind of item, and (for variables) on the customization type. | |
924 | ||
925 | @item %d | |
926 | Substitute the item's documentation string. | |
927 | ||
928 | @item %h | |
929 | Like @samp{%d}, but if the documentation string is more than one line, | |
930 | add an active field to control whether to show all of it or just the | |
931 | first line. | |
932 | ||
933 | @item %t | |
934 | Substitute the tag here. You specify the tag with the @code{:tag} | |
935 | keyword. | |
936 | ||
937 | @item %% | |
177c0ea7 | 938 | Display a literal @samp{%}. |
cc6d0d2c RS |
939 | @end table |
940 | ||
969fe9b5 RS |
941 | @item :action @var{action} |
942 | Perform @var{action} if the user clicks on a button. | |
943 | ||
cc6d0d2c | 944 | @item :button-face @var{face} |
969fe9b5 RS |
945 | Use the face @var{face} (a face name or a list of face names) for button |
946 | text displayed with @samp{%[@dots{}%]}. | |
cc6d0d2c | 947 | |
969fe9b5 RS |
948 | @item :button-prefix @var{prefix} |
949 | @itemx :button-suffix @var{suffix} | |
cc6d0d2c RS |
950 | These specify the text to display before and after a button. |
951 | Each can be: | |
952 | ||
953 | @table @asis | |
954 | @item @code{nil} | |
955 | No text is inserted. | |
956 | ||
957 | @item a string | |
958 | The string is inserted literally. | |
959 | ||
960 | @item a symbol | |
961 | The symbol's value is used. | |
962 | @end table | |
963 | ||
969fe9b5 RS |
964 | @item :tag @var{tag} |
965 | Use @var{tag} (a string) as the tag for the value (or part of the value) | |
966 | that corresponds to this type. | |
967 | ||
cc6d0d2c | 968 | @item :doc @var{doc} |
969fe9b5 RS |
969 | Use @var{doc} as the documentation string for this value (or part of the |
970 | value) that corresponds to this type. In order for this to work, you | |
971 | must specify a value for @code{:format}, and use @samp{%d} or @samp{%h} | |
972 | in that value. | |
cc6d0d2c | 973 | |
969fe9b5 RS |
974 | The usual reason to specify a documentation string for a type is to |
975 | provide more information about the meanings of alternatives inside a | |
976 | @code{:choice} type or the parts of some other composite type. | |
cc6d0d2c RS |
977 | |
978 | @item :help-echo @var{motion-doc} | |
979 | When you move to this item with @code{widget-forward} or | |
19182f77 DL |
980 | @code{widget-backward}, it will display the string @var{motion-doc} in |
981 | the echo area. In addition, @var{motion-doc} is used as the mouse | |
982 | @code{help-echo} string and may actually be a function or form evaluated | |
17458c91 LT |
983 | to yield a help string. If it is a function, it is called with one |
984 | argument, the widget. | |
9172ffcd | 985 | @xref{Text help-echo}. |
cc6d0d2c RS |
986 | |
987 | @item :match @var{function} | |
969fe9b5 RS |
988 | Specify how to decide whether a value matches the type. The |
989 | corresponding value, @var{function}, should be a function that accepts | |
990 | two arguments, a widget and a value; it should return non-@code{nil} if | |
991 | the value is acceptable. | |
cc6d0d2c RS |
992 | |
993 | @ignore | |
994 | @item :indent @var{columns} | |
995 | Indent this item by @var{columns} columns. The indentation is used for | |
996 | @samp{%n}, and automatically for group names, for checklists and radio | |
997 | buttons, and for editable lists. It affects the whole of the | |
998 | item except for the first line. | |
999 | ||
1000 | @item :offset @var{columns} | |
1001 | An integer indicating how many extra spaces to indent the subitems of | |
1002 | this item. By default, subitems are indented the same as their parent. | |
1003 | ||
1004 | @item :extra-offset | |
1005 | An integer indicating how many extra spaces to add to this item's | |
1006 | indentation, compared to its parent. | |
1007 | ||
1008 | @item :notify | |
1009 | A function called each time the item or a subitem is changed. The | |
1010 | function is called with two or three arguments. The first argument is | |
1011 | the item itself, the second argument is the item that was changed, and | |
1012 | the third argument is the event leading to the change, if any. | |
1013 | ||
1014 | @item :menu-tag | |
35208b42 | 1015 | A tag used in the menu when the widget is used as an option in a |
cc6d0d2c RS |
1016 | @code{menu-choice} widget. |
1017 | ||
1018 | @item :menu-tag-get | |
35208b42 | 1019 | A function used for finding the tag when the widget is used as an option |
cc6d0d2c RS |
1020 | in a @code{menu-choice} widget. By default, the tag used will be either the |
1021 | @code{:menu-tag} or @code{:tag} property if present, or the @code{princ} | |
1022 | representation of the @code{:value} property if not. | |
1023 | ||
1024 | @item :validate | |
35208b42 RS |
1025 | A function which takes a widget as an argument, and return @code{nil} |
1026 | if the widget's current value is valid for the widget. Otherwise, it | |
1027 | should return the widget containing the invalid data, and set that | |
1028 | widget's @code{:error} property to a string explaining the error. | |
cc6d0d2c RS |
1029 | |
1030 | You can use the function @code{widget-children-validate} for this job; | |
1031 | it tests that all children of @var{widget} are valid. | |
1032 | ||
1033 | @item :tab-order | |
1034 | Specify the order in which widgets are traversed with | |
1035 | @code{widget-forward} or @code{widget-backward}. This is only partially | |
1036 | implemented. | |
1037 | ||
1038 | @enumerate a | |
1039 | @item | |
1040 | Widgets with tabbing order @code{-1} are ignored. | |
1041 | ||
177c0ea7 | 1042 | @item |
cc6d0d2c RS |
1043 | (Unimplemented) When on a widget with tabbing order @var{n}, go to the |
1044 | next widget in the buffer with tabbing order @var{n+1} or @code{nil}, | |
1045 | whichever comes first. | |
1046 | ||
1047 | @item | |
1048 | When on a widget with no tabbing order specified, go to the next widget | |
1049 | in the buffer with a positive tabbing order, or @code{nil} | |
1050 | @end enumerate | |
1051 | ||
1052 | @item :parent | |
a9f0a989 | 1053 | The parent of a nested widget (e.g., a @code{menu-choice} item or an |
cc6d0d2c RS |
1054 | element of a @code{editable-list} widget). |
1055 | ||
1056 | @item :sibling-args | |
1057 | This keyword is only used for members of a @code{radio-button-choice} or | |
1058 | @code{checklist}. The value should be a list of extra keyword | |
1059 | arguments, which will be used when creating the @code{radio-button} or | |
1060 | @code{checkbox} associated with this item. | |
1061 | @end ignore | |
1062 | @end table | |
ab5796a9 | 1063 | |
cfa921fd PA |
1064 | @node Defining New Types |
1065 | @subsection Defining New Types | |
1066 | ||
1067 | In the previous sections we have described how to construct elaborate | |
38c7d6d5 RS |
1068 | type specifications for @code{defcustom}. In some cases you may want |
1069 | to give such a type specification a name. The obvious case is when | |
1070 | you are using the same type for many user options: rather than repeat | |
1071 | the specification for each option, you can give the type specification | |
1072 | a name, and use that name each @code{defcustom}. The other case is | |
1073 | when a user option's value is a recursive data structure. To make it | |
cfa921fd PA |
1074 | possible for a datatype to refer to itself, it needs to have a name. |
1075 | ||
1076 | Since custom types are implemented as widgets, the way to define a new | |
1077 | customize type is to define a new widget. We are not going to describe | |
1078 | the widget interface here in details, see @ref{Top, , Introduction, | |
1079 | widget, The Emacs Widget Library}, for that. Instead we are going to | |
1080 | demonstrate the minimal functionality needed for defining new customize | |
1081 | types by a simple example. | |
1082 | ||
1083 | @example | |
1084 | (define-widget 'binary-tree-of-string 'lazy | |
1085 | "A binary tree made of cons-cells and strings." | |
1086 | :offset 4 | |
1087 | :tag "Node" | |
1088 | :type '(choice (string :tag "Leaf" :value "") | |
1089 | (cons :tag "Interior" | |
97073664 | 1090 | :value ("" . "") |
cfa921fd PA |
1091 | binary-tree-of-string |
1092 | binary-tree-of-string))) | |
1093 | ||
1094 | (defcustom foo-bar "" | |
1095 | "Sample variable holding a binary tree of strings." | |
1096 | :type 'binary-tree-of-string) | |
1097 | @end example | |
1098 | ||
38c7d6d5 | 1099 | The function to define a new widget is called @code{define-widget}. The |
cfa921fd PA |
1100 | first argument is the symbol we want to make a new widget type. The |
1101 | second argument is a symbol representing an existing widget, the new | |
1102 | widget is going to be defined in terms of difference from the existing | |
1103 | widget. For the purpose of defining new customization types, the | |
38c7d6d5 | 1104 | @code{lazy} widget is perfect, because it accepts a @code{:type} keyword |
cfa921fd PA |
1105 | argument with the same syntax as the keyword argument to |
1106 | @code{defcustom} with the same name. The third argument is a | |
1107 | documentation string for the new widget. You will be able to see that | |
d5b3141d LT |
1108 | string with the @kbd{M-x widget-browse @key{RET} binary-tree-of-string |
1109 | @key{RET}} command. | |
cfa921fd | 1110 | |
38c7d6d5 RS |
1111 | After these mandatory arguments follow the keyword arguments. The most |
1112 | important is @code{:type}, which describes the data type we want to match | |
cfa921fd PA |
1113 | with this widget. Here a @code{binary-tree-of-string} is described as |
1114 | being either a string, or a cons-cell whose car and cdr are themselves | |
1115 | both @code{binary-tree-of-string}. Note the reference to the widget | |
1116 | type we are currently in the process of defining. The @code{:tag} | |
1117 | attribute is a string to name the widget in the user interface, and the | |
38c7d6d5 RS |
1118 | @code{:offset} argument is there to ensure that child nodes are |
1119 | indented four spaces relative to the parent node, making the tree | |
cfa921fd PA |
1120 | structure apparent in the customization buffer. |
1121 | ||
1122 | The @code{defcustom} shows how the new widget can be used as an ordinary | |
97073664 | 1123 | customization type. |
cfa921fd | 1124 | |
38c7d6d5 RS |
1125 | The reason for the name @code{lazy} is that the other composite |
1126 | widgets convert their inferior widgets to internal form when the | |
1127 | widget is instantiated in a buffer. This conversion is recursive, so | |
1128 | the inferior widgets will convert @emph{their} inferior widgets. If | |
1129 | the data structure is itself recursive, this conversion is an infinite | |
1130 | recursion. The @code{lazy} widget prevents the recursion: it convert | |
1131 | its @code{:type} argument only when needed. | |
cfa921fd | 1132 | |
ab5796a9 MB |
1133 | @ignore |
1134 | arch-tag: d1b8fad3-f48c-4ce4-a402-f73b5ef19bd2 | |
1135 | @end ignore |