3 @setfilename ../../info/widget.info
4 @settitle The Emacs Widget Library
12 Copyright @copyright{} 2000--2019 Free Software Foundation, Inc.
15 Permission is granted to copy, distribute and/or modify this document
16 under the terms of the GNU Free Documentation License, Version 1.3 or
17 any later version published by the Free Software Foundation; with no
18 Invariant Sections, with the Front-Cover Texts being ``A GNU Manual'',
19 and with the Back-Cover Texts as in (a) below. A copy of the license
20 is included in the section entitled ``GNU Free Documentation License''.
22 (a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
23 modify this GNU manual.''
27 @dircategory Emacs lisp libraries
29 * Widget: (widget). The "widget" package used by the Emacs
30 Customization facility.
35 @title The Emacs Widget Library
37 @vskip 0pt plus 1filll
44 @top The Emacs Widget Library
51 * Programming Example::
52 * Setting Up the Buffer::
56 * Defining New Widgets::
61 * GNU Free Documentation License::
68 Most graphical user interface toolkits provide a number of standard
69 user interface controls (sometimes known as ``widgets'' or ``gadgets'').
70 Emacs doesn't really support anything like this, except for an
71 incredibly powerful text ``widget.'' On the other hand, Emacs does
72 provide the necessary primitives to implement many other widgets
73 within a text buffer. The @code{widget} package simplifies this task.
76 @cindex widgets, basic types
77 The basic widgets are:
81 Areas of text with an associated action. Intended for hypertext links
84 Like link, but intended for stand-alone buttons.
86 An editable text field. It can be either variable or fixed length.
88 Allows the user to choose one of multiple options from a menu, each
89 option is itself a widget. Only the selected option will be visible in
91 @item radio-button-choice
92 Allows the user to choose one of multiple options by activating radio
93 buttons. The options are implemented as widgets. All options will be
94 visible in the buffer.
96 A simple constant widget intended to be used in the @code{menu-choice} and
97 @code{radio-button-choice} widgets.
99 A button item only intended for use in choices. When invoked, the user
100 will be asked to select another option from the choice widget.
102 A simple @samp{on}/@samp{off} switch.
104 A checkbox (@samp{[ ]}/@samp{[X]}).
106 Create an editable list. The user can insert or delete items in the
107 list. Each list item is itself a widget.
110 Now, of what possible use can support for widgets be in a text editor?
111 I'm glad you asked. The answer is that widgets are useful for
112 implementing forms. A @dfn{form} in Emacs is a buffer where the user is
113 supposed to fill out a number of fields, each of which has a specific
114 meaning. The user is not supposed to change or delete any of the text
115 between the fields. Examples of forms in Emacs are the @file{forms}
116 package (of course), the customize buffers, the mail and news compose
117 modes, and the @acronym{HTML} form support in the @file{w3} browser.
119 @cindex widget library, why use it
120 The advantages for a programmer of using the @code{widget} package to
125 More complex fields than just editable text are supported.
127 You can give the users immediate feedback if they enter invalid data in a
128 text field, and sometimes prevent entering invalid data.
130 You can have fixed sized fields, thus allowing multiple fields to be
133 It is simple to query or set the value of a field.
135 Editing happens in the buffer, not in the mini-buffer.
137 Packages using the library get a uniform look, making them easier for
140 As support for embedded graphics improve, the widget library will be
141 extended to use the GUI features. This means that your code using the
142 widget library will also use the new graphic features automatically.
146 @chapter User Interface
148 A form consists of read only text for documentation and some fields,
149 where each field contains two parts, a tag and a value. The tags are
150 used to identify the fields, so the documentation can refer to the
151 @samp{foo field}, meaning the field tagged with @samp{Foo}. Here is an
155 Here is some documentation.
157 Name: @i{My Name} @strong{Choose}: This option
158 Address: @i{Some Place
162 See also @b{_other work_} for more information.
164 Numbers: count to three below
165 @b{[INS]} @b{[DEL]} @i{One}
166 @b{[INS]} @b{[DEL]} @i{Eh, two?}
167 @b{[INS]} @b{[DEL]} @i{Five!}
182 @b{[Apply Form]} @b{[Reset Form]}
185 The top level widgets in this example are tagged @samp{Name},
186 @samp{Choose}, @samp{Address}, @samp{_other work_}, @samp{Numbers},
187 @samp{Select multiple}, @samp{Select one}, @samp{[Apply Form]}, and
188 @samp{[Reset Form]}. There are basically two things the user can do
189 within a form, namely editing the editable text fields and activating
192 @section Editable Text Fields
194 In the example, the value for the @samp{Name} is most likely displayed
195 in an editable text field, and so are values for each of the members of
196 the @samp{Numbers} list. All the normal Emacs editing operations are
197 available for editing these fields. The only restriction is that each
198 change you make must be contained within a single editable text field.
199 For example, capitalizing all text from the middle of one field to the
200 middle of another field is prohibited.
202 Editable text fields are created by the @code{editable-field} widget.
204 @strong{Warning:} In an @code{editable-field} widget, the editable
205 field must not be adjacent to another widget---that won't work.
206 You must put some text in between. Either make this text part of
207 the @code{editable-field} widget itself, or insert it with
208 @code{widget-insert}.
210 The @code{:format} keyword is useful for generating the necessary
211 text; for instance, if you give it a value of @code{"Name: %v "},
212 the @samp{Name: } part will provide the necessary separating text
213 before the field and the trailing space will provide the
214 separating text after the field. If you don't include the
215 @code{:size} keyword, the field will extend to the end of the
216 line, and the terminating newline will provide separation after.
218 @strong{Warning:} In an @code{editable-field} widget, the @samp{%v} escape
219 must be preceded by some other text in the @code{:format} string
222 The editing text fields are highlighted with the
223 @code{widget-field-face} face, making them easy to find.
225 @deffn Face widget-field-face
226 Face used for other editing fields.
231 @cindex widget buttons
232 @cindex button widgets
233 Some portions of the buffer have an associated @dfn{action}, which can
234 be @dfn{invoked} by a standard key or mouse command. These portions
235 are called @dfn{buttons}. The default commands for activating a button
240 @deffn Command widget-button-press @var{pos} &optional @var{event}
241 Invoke the button at @var{pos}, defaulting to point.
242 If point is not located on a button, invoke the binding in
243 @code{widget-global-map} (by default the global map).
246 @kindex mouse-2 @r{(on button widgets})
248 @deffn Command widget-button-click @var{event}
249 Invoke the button at the location of the mouse pointer. If the mouse
250 pointer is located in an editable text field, invoke the binding in
251 @code{widget-global-map} (by default the global map).
255 There are several different kind of buttons, all of which are present in
259 @cindex option field tag
260 @item The Option Field Tags
261 When you invoke one of these buttons, you will be asked to choose
262 between a number of different options. This is how you edit an option
263 field. Option fields are created by the @code{menu-choice} widget. In
264 the example, @samp{@b{Choose}} is an option field tag.
265 @item The @samp{@b{[INS]}} and @samp{@b{[DEL]}} buttons
266 Activating these will insert or delete elements from an editable list.
267 The list is created by the @code{editable-list} widget.
268 @cindex embedded buttons
269 @item Embedded Buttons
270 The @samp{@b{_other work_}} is an example of an embedded
271 button. Embedded buttons are not associated with any fields, but can serve
272 any purpose, such as implementing hypertext references. They are
273 usually created by the @code{link} widget.
274 @item The @samp{@b{[ ]}} and @samp{@b{[X]}} buttons
275 Activating one of these will convert it to the other. This is useful
276 for implementing multiple-choice fields. You can create them with the
277 @code{checkbox} widget.
278 @item The @samp{@b{( )}} and @samp{@b{(*)}} buttons
279 Only one radio button in a @code{radio-button-choice} widget can be
280 selected at any time. When you invoke one of the unselected radio
281 buttons, it will be selected and the previous selected radio button will
283 @item The @samp{@b{[Apply Form]}} and @samp{@b{[Reset Form]}} buttons
284 These are explicit buttons made with the @code{push-button} widget. The
285 main difference from the @code{link} widget is that the buttons will be
286 displayed as GUI buttons when possible.
289 To make them easier to locate, buttons are emphasized in the buffer.
291 @deffn Face widget-button-face
292 Face used for buttons.
295 @defopt widget-mouse-face
296 Face used for highlighting a button when the mouse pointer moves across
302 You can use all the normal Emacs commands to move around in a form
303 buffer, plus you will have these additional commands:
307 @deffn Command widget-forward &optional count
308 Move point @var{count} buttons or editing fields forward.
310 @item @kbd{M-@key{TAB}}
311 @itemx @kbd{S-@key{TAB}}
312 @deffn Command widget-backward &optional count
313 Move point @var{count} buttons or editing fields backward.
317 @node Programming Example
318 @chapter Programming Example
320 @cindex widgets, programming example
321 @cindex example of using widgets
322 Here is the code to implement the user interface example (@pxref{User
331 (defvar widget-example-repeat)
333 (defun widget-example ()
334 "Create the widgets from the Widget manual."
336 (switch-to-buffer "*Widget Example*")
337 (kill-all-local-variables)
338 (make-local-variable 'widget-example-repeat)
339 (let ((inhibit-read-only t))
342 (widget-insert "Here is some documentation.\n\n")
343 (widget-create 'editable-field
345 :format "Name: %v " ; Text after the field!
347 (widget-create 'menu-choice
350 :help-echo "Choose me, please!"
351 :notify (lambda (widget &rest ignore)
352 (message "%s is a good choice!"
353 (widget-value widget)))
354 '(item :tag "This option" :value "This")
355 '(choice-item "That option")
356 '(editable-field :menu-tag "No option" "Thus option"))
357 (widget-create 'editable-field
358 :format "Address: %v"
359 "Some Place\nIn some City\nSome country.")
360 (widget-insert "\nSee also ")
362 :notify (lambda (&rest ignore)
363 (widget-value-set widget-example-repeat
368 " for more information.\n\nNumbers: count to three below\n")
369 (setq widget-example-repeat
370 (widget-create 'editable-list
371 :entry-format "%i %d %v"
373 (lambda (widget &rest ignore)
374 (let ((old (widget-get widget
376 (new (length (widget-value widget))))
378 (widget-put widget ':example-length new)
379 (message "You can count to %d." new))))
380 :value '("One" "Eh, two?" "Five!")
381 '(editable-field :value "three")))
382 (widget-insert "\n\nSelect multiple:\n\n")
383 (widget-create 'checkbox t)
384 (widget-insert " This\n")
385 (widget-create 'checkbox nil)
386 (widget-insert " That\n")
387 (widget-create 'checkbox
388 :notify (lambda (&rest ignore) (message "Tickle"))
390 (widget-insert " Thus\n\nSelect one:\n\n")
391 (widget-create 'radio-button-choice
393 :notify (lambda (widget &rest ignore)
394 (message "You selected %s"
395 (widget-value widget)))
396 '(item "One") '(item "Another One.")
397 '(item "A Final One."))
399 (widget-create 'push-button
400 :notify (lambda (&rest ignore)
402 (widget-value widget-example-repeat))
404 (message "Congratulation!")
405 (error "Three was the count!")))
408 (widget-create 'push-button
409 :notify (lambda (&rest ignore)
413 (use-local-map widget-keymap)
417 @node Setting Up the Buffer
418 @chapter Setting Up the Buffer
420 Widgets are created with @code{widget-create}, which returns a
421 @dfn{widget} object. This object can be queried and manipulated by
422 other widget functions, until it is deleted with @code{widget-delete}.
423 After the widgets have been created, @code{widget-setup} must be called
426 @defun widget-create type [ keyword argument ]@dots{}
427 Create and return a widget of type @var{type}.
428 The syntax for the @var{type} argument is described in @ref{Basic Types}.
430 The keyword arguments can be used to overwrite the keyword arguments
431 that are part of @var{type}.
434 @defun widget-delete widget
435 Delete @var{widget} and remove it from the buffer.
439 Set up a buffer to support widgets.
441 This should be called after creating all the widgets and before allowing
442 the user to edit them.
445 If you want to insert text outside the widgets in the form, the
446 recommended way to do that is with @code{widget-insert}.
449 Insert the arguments, either strings or characters, at point.
450 The inserted text will be read-only.
453 There is a standard widget keymap which you might find useful.
455 @findex widget-button-press
456 @findex widget-button-click
457 @defvr Const widget-keymap
458 @key{TAB} and @kbd{C-@key{TAB}} are bound to @code{widget-forward} and
459 @code{widget-backward}, respectively. @key{RET} and @kbd{mouse-2}
460 are bound to @code{widget-button-press} and
461 @code{widget-button-click}.
464 @defvar widget-global-map
465 Keymap used by @code{widget-button-press} and @code{widget-button-click}
466 when not on a button. By default this is @code{global-map}.
472 This is the general syntax of a type specification:
475 @var{name} ::= (@var{name} [@var{keyword} @var{argument}]... @var{args})
479 Where, @var{name} is a widget name, @var{keyword} is the name of a
480 property, @var{argument} is the value of the property, and @var{args}
481 are interpreted in a widget specific way.
483 @cindex keyword arguments
484 The following keyword arguments apply to all widgets:
487 @vindex value@r{ keyword}
489 The initial value for widgets of this type.
491 @vindex format@r{ keyword}
493 This string will be inserted in the buffer when you create a widget.
494 The following @samp{%} escapes are available:
499 The text inside will be marked as a button.
501 By default, the text will be shown in @code{widget-button-face}, and
502 surrounded by brackets.
504 @defopt widget-button-prefix
505 String to prefix buttons.
508 @defopt widget-button-suffix
509 String to suffix buttons.
514 The text inside will be displayed with the face specified by
518 This will be replaced with the buffer representation of the widget's
519 value. What this is depends on the widget type.
521 @strong{Warning:} In an @code{editable-field} widget, the @samp{%v} escape
522 must be preceded by some other text in the format string (if specified).
525 Insert the string specified by @code{:doc} here.
528 Like @samp{%d}, with the following modifications: If the documentation
529 string is more than one line, it will add a button which will toggle
530 between showing only the first line, and showing the full text.
531 Furthermore, if there is no @code{:doc} property in the widget, it will
532 instead examine the @code{:documentation-property} property. If it is a
533 lambda expression, it will be called with the widget's value as an
534 argument, and the result will be used as the documentation text.
537 Insert the string specified by @code{:tag} here, or the @code{princ}
538 representation of the value if there is no tag.
541 Insert a literal @samp{%}.
544 @vindex button-face@r{ keyword}
546 Face used to highlight text inside %[ %] in the format.
548 @vindex button-prefix@r{ keyword}
549 @vindex button-suffix@r{ keyword}
551 @itemx :button-suffix
552 Text around %[ %] in the format.
560 The string is inserted literally.
563 The value of the symbol is expanded according to this table.
566 @vindex doc@r{ keyword}
568 The string inserted by the @samp{%d} escape in the format
571 @vindex tag@r{ keyword}
573 The string inserted by the @samp{%t} escape in the format
576 @vindex tag-glyph@r{ keyword}
578 Name of image to use instead of the string specified by @code{:tag} on
579 Emacsen that supports it.
581 @vindex help-echo@r{ keyword}
583 Specifies how to display a message whenever you move to the widget with
584 either @code{widget-forward} or @code{widget-backward} or move the mouse
585 over it (using the standard @code{help-echo} mechanism). The argument
586 is either a string to display, a function of one argument, the widget,
587 which should return a string to display, or a form that evaluates to
590 @vindex follow-link@r{ keyword}
592 Specifies how to interpret a @key{mouse-1} click on the widget.
593 @xref{Clickable Text,, Defining Clickable Text, elisp, the Emacs Lisp Reference Manual}.
595 @vindex indent@r{ keyword}
597 An integer indicating the absolute number of spaces to indent children
600 @vindex offset@r{ keyword}
602 An integer indicating how many extra spaces to add to the widget's
603 grandchildren compared to this widget.
605 @vindex extra-offset@r{ keyword}
607 An integer indicating how many extra spaces to add to the widget's
608 children compared to this widget.
610 @vindex notify@r{ keyword}
612 A function called each time the widget or a nested widget is changed.
613 The function is called with two or three arguments. The first argument
614 is the widget itself, the second argument is the widget that was
615 changed, and the third argument is the event leading to the change, if
618 @vindex menu-tag@r{ keyword}
620 Tag used in the menu when the widget is used as an option in a
621 @code{menu-choice} widget.
623 @vindex menu-tag-get@r{ keyword}
625 Function used for finding the tag when the widget is used as an option
626 in a @code{menu-choice} widget. By default, the tag used will be either the
627 @code{:menu-tag} or @code{:tag} property if present, or the @code{princ}
628 representation of the @code{:value} property if not.
630 @vindex match@r{ keyword}
632 Should be a function called with two arguments, the widget and a value,
633 and returning non-@code{nil} if the widget can represent the specified value.
635 @vindex validate@r{ keyword}
637 A function which takes a widget as an argument, and returns @code{nil}
638 if the widget's current value is valid for the widget. Otherwise it
639 should return the widget containing the invalid data, and set that
640 widget's @code{:error} property to a string explaining the error.
642 The following predefined function can be used:
644 @defun widget-children-validate widget
645 All the @code{:children} of @var{widget} must be valid.
648 @vindex tab-order@r{ keyword}
650 Specify the order in which widgets are traversed with
651 @code{widget-forward} or @code{widget-backward}. This is only partially
656 Widgets with tabbing order @code{-1} are ignored.
659 (Unimplemented) When on a widget with tabbing order @var{n}, go to the
660 next widget in the buffer with tabbing order @var{n+1} or @code{nil},
661 whichever comes first.
664 When on a widget with no tabbing order specified, go to the next widget
665 in the buffer with a positive tabbing order, or @code{nil}
668 @vindex parent@r{ keyword}
670 The parent of a nested widget (e.g., a @code{menu-choice} item or an
671 element of a @code{editable-list} widget).
673 @vindex sibling-args@r{ keyword}
675 This keyword is only used for members of a @code{radio-button-choice} or
676 @code{checklist}. The value should be a list of extra keyword
677 arguments, which will be used when creating the @code{radio-button} or
678 @code{checkbox} associated with this item.
682 @deffn {User Option} widget-glyph-directory
683 Directory where glyphs are found.
684 Widget will look here for a file with the same name as specified for the
685 image, with either a @file{.xpm} (if supported) or @file{.xbm} extension.
688 @deffn{User Option} widget-glyph-enable
689 If non-@code{nil}, allow glyphs to appear on displays where they are supported.
701 * radio-button-choice::
712 @section The @code{link} Widget
713 @findex link@r{ widget}
718 @var{type} ::= (link [@var{keyword} @var{argument}]... [ @var{value} ])
721 The @var{value}, if present, is used to initialize the @code{:value}
722 property. The value should be a string, which will be inserted in the
725 By default the link will be shown in brackets.
727 @defopt widget-link-prefix
728 String to prefix links.
731 @defopt widget-link-suffix
732 String to suffix links.
736 @section The @code{url-link} Widget
737 @findex url-link@r{ widget}
742 @var{type} ::= (url-link [@var{keyword} @var{argument}]... @var{url})
745 @findex browse-url-browser-function@r{, and @code{url-link} widget}
746 When this link is invoked, the @acronym{WWW} browser specified by
747 @code{browse-url-browser-function} will be called with @var{url}.
750 @section The @code{info-link} Widget
751 @findex info-link@r{ widget}
756 @var{type} ::= (info-link [@var{keyword} @var{argument}]... @var{address})
759 When this link is invoked, the built-in Info reader is started on
763 @section The @code{push-button} Widget
764 @findex push-button@r{ widget}
769 @var{type} ::= (push-button [@var{keyword} @var{argument}]... [ @var{value} ])
772 The @var{value}, if present, is used to initialize the @code{:value}
773 property. The value should be a string, which will be inserted in the
776 By default the tag will be shown in brackets.
778 @defopt widget-push-button-prefix
779 String to prefix push buttons.
782 @defopt widget-push-button-suffix
783 String to suffix push buttons.
787 @section The @code{editable-field} Widget
788 @findex editable-field@r{ widget}
793 @var{type} ::= (editable-field [@var{keyword} @var{argument}]... [ @var{value} ])
796 The @var{value}, if present, is used to initialize the @code{:value}
797 property. The value should be a string, which will be inserted in the
798 field. This widget will match all string values.
800 The following extra properties are recognized:
803 @vindex size@r{ keyword}
805 The width of the editable field.@*
806 By default the field will reach to the end of the line.
808 @vindex value-face@r{ keyword}
810 Face used for highlighting the editable field. Default is
811 @code{widget-field-face}, see @ref{User Interface}.
813 @vindex secret@r{ keyword}
815 Character used to display the value. You can set this to, e.g., @code{?*}
816 if the field contains a password or other secret information. By
817 default, this is @code{nil}, and the value is not secret.
819 @vindex valid-regexp@r{ keyword}
821 By default the @code{:validate} function will match the content of the
822 field with the value of this attribute. The default value is @code{""}
823 which matches everything.
825 @vindex keymap@r{ keyword}
826 @vindex widget-field-keymap
828 Keymap used in the editable field. The default value is
829 @code{widget-field-keymap}, which allows you to use all the normal
830 editing commands, even if the buffer's major mode suppresses some of
831 them. Pressing @key{RET} invokes the function specified by
836 @section The @code{text} Widget
837 @findex text@r{ widget}
839 @vindex widget-text-keymap
840 This is just like @code{editable-field}, but intended for multiline text
841 fields. The default @code{:keymap} is @code{widget-text-keymap}, which
842 does not rebind the @key{RET} key.
845 @section The @code{menu-choice} Widget
846 @findex menu-choice@r{ widget}
851 @var{type} ::= (menu-choice [@var{keyword} @var{argument}]... @var{type} ... )
854 The @var{type} argument represents each possible choice. The widget's
855 value will be that of the chosen @var{type} argument. This widget will
856 match any value matching at least one of the specified @var{type}
860 @vindex void@r{ keyword}
862 Widget type used as a fallback when the value does not match any of the
863 specified @var{type} arguments.
865 @vindex case-fold@r{ keyword}
867 Set this to @code{nil} if you don't want to ignore case when prompting for a
868 choice through the minibuffer.
870 @vindex children@r{ keyword}
872 A list whose @sc{car} is the widget representing the currently chosen
875 @vindex choice@r{ keyword}
877 The current chosen type.
879 @vindex args@r{ keyword}
884 @node radio-button-choice
885 @section The @code{radio-button-choice} Widget
886 @findex radio-button-choice@r{ widget}
891 @var{type} ::= (radio-button-choice [@var{keyword} @var{argument}]... @var{type} ... )
894 The component types specify the choices, with one radio button for
895 each. The widget's value will be that of the chosen @var{type}
896 argument. This widget matches any value that matches at least one of
897 the specified @var{type} arguments.
899 The following extra properties are recognized.
902 @vindex entry-format@r{ keyword}
904 This string will be inserted for each entry in the list.
905 The following @samp{%} escapes are available:
908 Replace with the buffer representation of the @var{type} widget.
910 Replace with the radio button.
912 Insert a literal @samp{%}.
915 @vindex button-args@r{ keyword}
917 A list of keywords to pass to the radio buttons. Useful for setting,
918 e.g., the @samp{:help-echo} for each button.
920 @vindex buttons@r{ keyword}
922 The widgets representing the radio buttons.
924 @vindex children@r{ keyword}
926 The widgets representing each type.
928 @vindex choice@r{ keyword}
930 The current chosen type
932 @vindex args@r{ keyword}
937 You can add extra radio button items to a @code{radio-button-choice}
938 widget after it has been created with the function
939 @code{widget-radio-add-item}.
941 @defun widget-radio-add-item widget type
942 Add to @code{radio-button-choice} widget @var{widget} a new radio button
943 item of type @var{type}.
946 Please note that such items added after the @code{radio-button-choice}
947 widget has been created will @strong{not} be properly destructed when
948 you call @code{widget-delete}.
951 @section The @code{item} Widget
952 @findex item@r{ widget}
957 @var{item} ::= (item [@var{keyword} @var{argument}]... @var{value})
960 The @var{value}, if present, is used to initialize the @code{:value}
961 property. The value should be a string, which will be inserted in the
962 buffer. This widget will only match the specified value.
965 @section The @code{choice-item} Widget
966 @findex choice-item@r{ widget}
971 @var{item} ::= (choice-item [@var{keyword} @var{argument}]... @var{value})
974 The @var{value}, if present, is used to initialize the @code{:value}
975 property. The value should be a string, which will be inserted in the
976 buffer as a button. Activating the button of a @code{choice-item} is
977 equivalent to activating the parent widget. This widget will only match
981 @section The @code{toggle} Widget
982 @findex toggle@r{ widget}
987 @var{type} ::= (toggle [@var{keyword} @var{argument}]...)
990 The widget has two possible states, @samp{on} and @samp{off}, which
991 correspond to a @code{t} or @code{nil} value, respectively.
993 The following extra properties are recognized:
997 A string representing the @samp{on} state. By default the string
1000 A string representing the @samp{off} state. By default the string
1002 @vindex on-glyph@r{ keyword}
1004 Name of a glyph to be used instead of the @samp{:on} text string, on
1005 emacsen that supports this.
1006 @vindex off-glyph@r{ keyword}
1008 Name of a glyph to be used instead of the @samp{:off} text string, on
1009 emacsen that supports this.
1013 @section The @code{checkbox} Widget
1014 @findex checkbox@r{ widget}
1016 This widget has two possible states, @samp{selected} and
1017 @samp{unselected}, which corresponds to a @code{t} or @code{nil} value.
1022 @var{type} ::= (checkbox [@var{keyword} @var{argument}]...)
1026 @section The @code{checklist} Widget
1027 @findex checklist@r{ widget}
1032 @var{type} ::= (checklist [@var{keyword} @var{argument}]... @var{type} ... )
1035 The @var{type} arguments represent each checklist item. The widget's
1036 value will be a list containing the values of all checked @var{type}
1037 arguments. The checklist widget will match a list whose elements all
1038 match at least one of the specified @var{type} arguments.
1040 The following extra properties are recognized:
1043 @vindex entry-format@r{ keyword}
1045 This string will be inserted for each entry in the list.
1046 The following @samp{%} escapes are available:
1049 Replaced with the buffer representation of the @var{type} widget.
1051 Replace with the checkbox.
1053 Insert a literal @samp{%}.
1056 @vindex greedy@r{ keyword}
1058 Usually a checklist will only match if the items are in the exact
1059 sequence given in the specification. By setting @code{:greedy} to
1060 non-@code{nil}, it will allow the items to come in any sequence.
1061 However, if you extract the value they will be in the sequence given
1062 in the checklist, i.e., the original sequence is forgotten.
1064 @vindex button-args@r{ keyword}
1066 A list of keywords to pass to the checkboxes. Useful for setting,
1067 e.g., the @samp{:help-echo} for each checkbox.
1069 @vindex buttons@r{ keyword}
1071 The widgets representing the checkboxes.
1073 @vindex children@r{ keyword}
1075 The widgets representing each type.
1077 @vindex args@r{ keyword}
1083 @section The @code{editable-list} Widget
1084 @findex editable-list@r{ widget}
1089 @var{type} ::= (editable-list [@var{keyword} @var{argument}]... @var{type})
1092 The value is a list, where each member represents one widget of type
1095 The following extra properties are recognized:
1098 @vindex entry-format@r{ keyword}
1100 This string will be inserted for each entry in the list.
1101 The following @samp{%} escapes are available:
1104 This will be replaced with the buffer representation of the @var{type}
1107 Insert the @b{[INS]} button.
1109 Insert the @b{[DEL]} button.
1111 Insert a literal @samp{%}.
1114 @vindex insert-button-args@r{ keyword}
1115 @item :insert-button-args
1116 A list of keyword arguments to pass to the insert buttons.
1118 @vindex delete-button-args@r{ keyword}
1119 @item :delete-button-args
1120 A list of keyword arguments to pass to the delete buttons.
1122 @vindex append-button-args@r{ keyword}
1123 @item :append-button-args
1124 A list of keyword arguments to pass to the trailing insert button.
1126 @vindex buttons@r{ keyword}
1128 The widgets representing the insert and delete buttons.
1130 @vindex children@r{ keyword}
1132 The widgets representing the elements of the list.
1134 @vindex args@r{ keyword}
1136 List whose @sc{car} is the type of the list elements.
1140 @section The @code{group} Widget
1141 @findex group@r{ widget}
1143 This widget simply group other widgets together.
1148 @var{type} ::= (group [@var{keyword} @var{argument}]... @var{type}...)
1151 The value is a list, with one member for each @var{type}.
1157 A number of widgets for editing @dfn{s-expressions} (Lisp types), sexp
1158 for short, are also available. These basically fall in several
1159 categories described in this section.
1169 @section The Constant Widgets
1170 @cindex constant widgets
1172 The @code{const} widget can contain any Lisp expression, but the user is
1173 prohibited from editing it, which is mainly useful as a component of one
1174 of the composite widgets.
1176 The syntax for the @code{const} widget is:
1179 @var{type} ::= (const [@var{keyword} @var{argument}]... [ @var{value} ])
1182 The @var{value}, if present, is used to initialize the @code{:value}
1183 property and can be any s-expression.
1186 This will display any valid s-expression in an immutable part of the
1190 There are two variations of the @code{const} widget, namely
1191 @code{variable-item} and @code{function-item}. These should contain a
1192 symbol with a variable or function binding. The major difference from
1193 the @code{const} widget is that they will allow the user to see the
1194 variable or function documentation for the symbol.
1196 @deffn Widget variable-item
1197 An immutable symbol that is bound as a variable.
1200 @deffn Widget function-item
1201 An immutable symbol that is bound as a function.
1205 @section Generic Sexp Widget
1206 @cindex generic sexp widget
1208 The @code{sexp} widget can contain any Lisp expression, and allows the
1209 user to edit it inline in the buffer.
1211 The syntax for the @code{sexp} widget is:
1214 @var{type} ::= (sexp [@var{keyword} @var{argument}]... [ @var{value} ])
1218 This will allow you to edit any valid s-expression in an editable buffer
1221 The @code{sexp} widget takes the same keyword arguments as the
1222 @code{editable-field} widget. @xref{editable-field}.
1226 @section Atomic Sexp Widgets
1227 @cindex atomic sexp widget
1229 The atoms are s-expressions that do not consist of other s-expressions.
1230 For example, a string, a file name, or a symbol are atoms, while a list
1231 is a composite type. You can edit the value of an atom with the
1234 The syntax for all the atoms are:
1237 @var{type} ::= (@var{construct} [@var{keyword} @var{argument}]... [ @var{value} ])
1240 The @var{value}, if present, is used to initialize the @code{:value}
1241 property and must be an expression of the same type as the widget.
1242 That is, the string widget can only be initialized with a string.
1244 All the atom widgets take the same keyword arguments as the
1245 @code{editable-field} widget. @xref{editable-field}.
1247 @deffn Widget string
1248 Allows you to edit a string in an editable field.
1251 @deffn Widget regexp
1252 Allows you to edit a regular expression in an editable field.
1255 @deffn Widget character
1256 Allows you to enter a character in an editable field.
1260 Allows you to edit a file name in an editable field.
1264 @vindex must-match@r{ keyword}
1266 If this is set to non-@code{nil}, only existing file names will be
1267 allowed in the minibuffer.
1271 @deffn Widget directory
1272 Allows you to edit a directory name in an editable field.
1273 Similar to the @code{file} widget.
1276 @deffn Widget symbol
1277 Allows you to edit a Lisp symbol in an editable field.
1280 @deffn Widget function
1281 Allows you to edit a lambda expression, or a function name with completion.
1284 @deffn Widget variable
1285 Allows you to edit a variable name, with completion.
1288 @deffn Widget integer
1289 Allows you to edit an integer in an editable field.
1292 @deffn Widget number
1293 Allows you to edit a number in an editable field.
1296 @deffn Widget boolean
1297 Allows you to edit a boolean. In Lisp this means a variable which is
1298 either @code{nil} meaning false, or non-@code{nil} meaning true.
1303 @section Composite Sexp Widgets
1304 @cindex composite sexp widgets
1306 The syntax for the composite widget construct is:
1309 @var{type} ::= (@var{construct} [@var{keyword} @var{argument}]... @var{component}...)
1313 where each @var{component} must be a widget type. Each component widget
1314 will be displayed in the buffer, and will be editable by the user.
1317 The value of a @code{cons} widget must be a cons-cell whose @sc{car}
1318 and @sc{cdr} have two specified types. It uses this syntax:
1321 @var{type} ::= (cons [@var{keyword} @var{argument}]... @var{car-type} @var{cdr-type})
1325 @deffn Widget choice
1326 The value matched by a @code{choice} widget must have one of a fixed
1327 set of types. The widget's syntax is as follows:
1330 @var{type} ::= (choice [@var{keyword} @var{argument}]... @var{type} ... )
1333 The value of a @code{choice} widget can be anything that matches any of the
1338 The value of a @code{list} widget must be a list whose element types
1339 match the specified component types:
1342 @var{type} ::= (list [@var{keyword} @var{argument}]... @var{component-type}...)
1345 Thus, @code{(list string number)} matches lists of two elements,
1346 the first being a string and the second being a number.
1349 @deffn Widget vector
1350 The @code{vector} widget is like the @code{list} widget but matches
1351 vectors instead of lists. Thus, @code{(vector string number)} matches
1352 vectors of two elements, the first being a string and the second being
1356 The above suffice for specifying fixed size lists and vectors. To get
1357 variable length lists and vectors, you can use a @code{choice},
1358 @code{set}, or @code{repeat} widget together with the @code{:inline}
1359 keyword. If any component of a composite widget has the
1360 @code{:inline} keyword set, its value must be a list which will then
1361 be spliced into the composite. For example, to specify a list whose
1362 first element must be a file name, and whose remaining elements should
1363 either be the symbol @code{t} or two strings (file names), you can use
1364 the following widget specification:
1370 :value ("foo" "bar")
1374 The value of a widget of this type will either have the form
1375 @code{(file t)} or @code{(file @var{string} @var{string})}.
1377 This concept of @code{:inline} may be hard to understand. It was
1378 certainly hard to implement, so instead of confusing you more by
1379 trying to explain it here, I'll just suggest you meditate over it for
1383 Specifies a type whose values are the lists whose elements all belong
1384 to a given set. The order of elements of the list is not significant.
1388 @var{type} ::= (set [@var{keyword} @var{argument}]... @var{permitted-element} ... )
1391 Use @code{const} to specify each permitted element, like this:
1392 @code{(set (const a) (const b))}.
1395 @deffn Widget repeat
1396 Specifies a list of any number of elements that fit a certain type.
1399 @var{type} ::= (repeat [@var{keyword} @var{argument}]... @var{type})
1403 @node Widget Properties
1405 @cindex properties of widgets
1406 @cindex widget properties
1408 You can examine or set the value of a widget by using the widget object
1409 that was returned by @code{widget-create}.
1411 @defun widget-value widget
1412 Return the current value contained in @var{widget}.
1413 It is an error to call this function on an uninitialized widget.
1416 @defun widget-value-set widget value
1417 Set the value contained in @var{widget} to @var{value}.
1418 It is an error to call this function with an invalid @var{value}.
1421 @strong{Important:} You @emph{must} call @code{widget-setup} after
1422 modifying the value of a widget before the user is allowed to edit the
1423 widget again. It is enough to call @code{widget-setup} once if you
1424 modify multiple widgets. This is currently only necessary if the widget
1425 contains an editing field, but may be necessary for other widgets in the
1428 If your application needs to associate some information with the widget
1429 objects, for example a reference to the item being edited, it can be
1430 done with @code{widget-put} and @code{widget-get}. The property names
1431 must begin with a @samp{:}.
1433 @defun widget-put widget property value
1434 In @var{widget} set @var{property} to @var{value}.
1435 @var{property} should be a symbol, while @var{value} can be anything.
1438 @defun widget-get widget property
1439 In @var{widget} return the value for @var{property}.
1440 @var{property} should be a symbol, the value is what was last set by
1441 @code{widget-put} for @var{property}.
1444 @defun widget-member widget property
1445 Non-@code{nil} if @var{widget} has a value (even @code{nil}) for
1446 property @var{property}.
1449 @defun widget-apply widget property &rest args
1450 Apply the value of @var{property} to @var{widget}, passing @var{args}
1451 as additional arguments to the function. Return the result of that
1455 Occasionally it can be useful to know which kind of widget you have,
1456 i.e., the name of the widget type you gave when the widget was created.
1458 @defun widget-type widget
1459 Return the name of @var{widget}, a symbol.
1462 @cindex active widget
1463 @cindex inactive widget
1464 @cindex activate a widget
1465 @cindex deactivate a widget
1466 Widgets can be in two states: active, which means they are modifiable by
1467 the user, or inactive, which means they cannot be modified by the user.
1468 You can query or set the state with the following code:
1471 ;; Examine if @var{widget} is active or not.
1472 (if (widget-apply @var{widget} :active)
1473 (message "Widget is active.")
1474 (message "Widget is inactive.")
1476 ;; Make @var{widget} inactive.
1477 (widget-apply @var{widget} :deactivate)
1479 ;; Make @var{widget} active.
1480 (widget-apply @var{widget} :activate)
1483 A widget is inactive if it, or any of its ancestors (found by
1484 following the @code{:parent} link), have been deactivated. To make sure
1485 a widget is really active, you must therefore activate both it and
1490 (widget-apply widget :activate)
1491 (setq widget (widget-get widget :parent)))
1494 You can check if a widget has been made inactive by examining the value
1495 of the @code{:inactive} keyword. If this is non-@code{nil}, the widget itself
1496 has been deactivated. This is different from using the @code{:active}
1497 keyword, in that the latter tells you if the widget @strong{or} any of
1498 its ancestors have been deactivated. Do not attempt to set the
1499 @code{:inactive} keyword directly. Use the @code{:activate}
1500 @code{:deactivate} keywords instead.
1503 @node Defining New Widgets
1504 @chapter Defining New Widgets
1506 @cindex defining new widgets
1508 You can define specialized widgets with @code{define-widget}. It allows
1509 you to create a shorthand for more complex widgets, including specifying
1510 component widgets and new default values for the keyword
1513 @defun define-widget name class doc &rest args
1514 Define a new widget type named @var{name} from @code{class}.
1516 @var{name} and class should both be symbols, @code{class} should be one
1517 of the existing widget types.
1519 The third argument @var{doc} is a documentation string for the widget.
1521 After the new widget has been defined, the following two calls will
1522 create identical widgets:
1527 (widget-create @var{name})
1532 (apply widget-create @var{class} @var{args})
1538 Using @code{define-widget} just stores the definition of the widget type
1539 in the @code{widget-type} property of @var{name}, which is what
1540 @code{widget-create} uses.
1542 If you only want to specify defaults for keywords with no complex
1543 conversions, you can use @code{identity} as your conversion function.
1545 The following additional keyword arguments are useful when defining new
1548 @vindex convert-widget@r{ keyword}
1549 @item :convert-widget
1550 Function to convert a widget type before creating a widget of that
1551 type. It takes a widget type as an argument, and returns the converted
1552 widget type. When a widget is created, this function is called for the
1553 widget type and all the widget's parent types, most derived first.
1555 The following predefined functions can be used here:
1557 @defun widget-types-convert-widget widget
1558 Convert @code{:args} as widget types in @var{widget}.
1561 @defun widget-value-convert-widget widget
1562 Initialize @code{:value} from @code{:args} in @var{widget}.
1565 @vindex copy@r{ keyword}
1567 Function to deep copy a widget type. It takes a shallow copy of the
1568 widget type as an argument (made by @code{copy-sequence}), and returns a
1569 deep copy. The purpose of this is to avoid having different instances
1570 of combined widgets share nested attributes.
1572 The following predefined functions can be used here:
1574 @defun widget-types-copy widget
1575 Copy @code{:args} as widget types in @var{widget}.
1578 @vindex value-to-internal@r{ keyword}
1579 @item :value-to-internal
1580 Function to convert the value to the internal format. The function
1581 takes two arguments, a widget and an external value, and returns the
1582 internal value. The function is called on the present @code{:value}
1583 when the widget is created, and on any value set later with
1584 @code{widget-value-set}.
1586 @vindex value-to-external@r{ keyword}
1587 @item :value-to-external
1588 Function to convert the value to the external format. The function
1589 takes two arguments, a widget and an internal value, and returns the
1590 external value. The function is called on the present @code{:value}
1591 when the widget is created, and on any value set later with
1592 @code{widget-value-set}.
1594 @vindex create@r{ keyword}
1596 Function to create a widget from scratch. The function takes one
1597 argument, a widget type, and creates a widget of that type, inserts it
1598 in the buffer, and returns a widget object.
1600 @vindex delete@r{ keyword}
1602 Function to delete a widget. The function takes one argument, a widget,
1603 and should remove all traces of the widget from the buffer.
1605 The default value is:
1607 @defun widget-default-delete widget
1608 Remove @var{widget} from the buffer.
1609 Delete all @code{:children} and @code{:buttons} in @var{widget}.
1612 In most cases you should not change this value, but instead use
1613 @code{:value-delete} to make any additional cleanup.
1615 @vindex value-create@r{ keyword}
1617 Function to expand the @samp{%v} escape in the format string. It will
1618 be called with the widget as its argument and should insert a
1619 representation of the widget's value in the buffer.
1621 Nested widgets should be listed in @code{:children} or @code{:buttons}
1622 to make sure they are automatically deleted.
1624 @vindex value-delete@r{ keyword}
1626 Should remove the representation of the widget's value from the buffer.
1627 It will be called with the widget as its argument. It doesn't have to
1628 remove the text, but it should release markers and delete nested widgets
1629 if these are not listed in @code{:children} or @code{:buttons}.
1631 @vindex value-get@r{ keyword}
1633 Function to extract the value of a widget, as it is displayed in the
1636 The following predefined function can be used here:
1638 @defun widget-value-value-get widget
1639 Return the @code{:value} property of @var{widget}.
1642 @vindex format-handler@r{ keyword}
1643 @item :format-handler
1644 Function to handle unknown @samp{%} escapes in the format string. It
1645 will be called with the widget and the character that follows the
1646 @samp{%} as arguments. You can set this to allow your widget to handle
1647 non-standard escapes.
1649 @findex widget-default-format-handler
1650 You should end up calling @code{widget-default-format-handler} to handle
1651 unknown escape sequences, which will handle the @samp{%h} and any future
1652 escape sequences, as well as give an error for unknown escapes.
1654 @vindex action@r{ keyword}
1656 Function to handle user initiated events. By default, @code{:notify}
1659 The following predefined function can be used here:
1661 @defun widget-parent-action widget &optional event
1662 Tell @code{:parent} of @var{widget} to handle the @code{:action}.
1663 Optional @var{event} is the event that triggered the action.
1666 @vindex prompt-value@r{ keyword}
1668 Function to prompt for a value in the minibuffer. The function should
1669 take four arguments, @var{widget}, @var{prompt}, @var{value}, and
1670 @var{unbound} and should return a value for widget entered by the user.
1671 @var{prompt} is the prompt to use. @var{value} is the default value to
1672 use, unless @var{unbound} is non-@code{nil}, in which case there is no default
1673 value. The function should read the value using the method most natural
1674 for this widget, and does not have to check that it matches.
1677 If you want to define a new widget from scratch, use the @code{default}
1680 @deffn Widget default
1681 Widget used as a base for other widgets.
1683 It provides most of the functionality that is referred to as ``by
1684 default'' in this text.
1687 @node Widget Browser
1688 @chapter Widget Browser
1689 @cindex widget browser
1691 There is a separate package to browse widgets. This is intended to help
1692 programmers who want to examine the content of a widget. The browser
1693 shows the value of each keyword, but uses links for certain keywords
1694 such as @samp{:parent}, which avoids printing cyclic structures.
1696 @deffn Command widget-browse @var{widget}
1697 Create a widget browser for @var{widget}.
1698 When called interactively, prompt for @var{widget}.
1701 @deffn Command widget-browse-other-window @var{widget}
1702 Create a widget browser for @var{widget} and show it in another window.
1703 When called interactively, prompt for @var{widget}.
1706 @deffn Command widget-browse-at @var{pos}
1707 Create a widget browser for the widget at @var{pos}.
1708 When called interactively, use the position of point.
1711 @node Widget Minor Mode
1712 @chapter Widget Minor Mode
1713 @cindex widget minor mode
1715 There is a minor mode for manipulating widgets in major modes that
1716 don't provide any support for widgets themselves. This is mostly
1717 intended to be useful for programmers doing experiments.
1719 @deffn Command widget-minor-mode
1720 Toggle minor mode for traversing widgets.
1721 With arg, turn widget mode on if and only if arg is positive.
1724 @defvar widget-minor-mode-keymap
1725 Keymap used in @code{widget-minor-mode}.
1730 @cindex utility functions for widgets
1732 @defun widget-prompt-value widget prompt [ value unbound ]
1733 Prompt for a value matching @var{widget}, using @var{prompt}.
1734 The current value is assumed to be @var{value}, unless @var{unbound} is
1738 @defun widget-get-sibling widget
1739 Get the item which @var{widget} is assumed to toggle.
1740 This is only meaningful for radio buttons or checkboxes in a list.
1743 @node Widget Wishlist
1749 It should be possible to add or remove items from a list with @kbd{C-k}
1750 and @kbd{C-o} (suggested by @sc{rms}).
1753 The @samp{[INS]} and @samp{[DEL]} buttons should be replaced by a single
1754 dash (@samp{-}). The dash should be a button that, when invoked, asks
1755 whether you want to add or delete an item (@sc{rms} wanted to git rid of
1756 the ugly buttons, the dash is my idea).
1759 The @code{menu-choice} tag should be prettier, something like the abbreviated
1763 Finish @code{:tab-order}.
1766 Make indentation work with glyphs and proportional fonts.
1769 Add commands to show overview of object and class hierarchies to the
1773 Find a way to disable mouse highlight for inactive widgets.
1776 Find a way to make glyphs look inactive.
1779 Add @code{property-list} widget.
1782 Add @code{association-list} widget.
1785 Add @code{key-binding} widget.
1788 Add @code{widget} widget for editing widget specifications.
1791 Find clean way to implement variable length list.
1792 See @code{TeX-printer-list} for an explanation.
1795 @kbd{C-h} in @code{widget-prompt-value} should give type specific help.
1798 Add a @code{mailto} widget.
1801 @node GNU Free Documentation License
1802 @appendix GNU Free Documentation License
1803 @include doclicense.texi
1808 This is an alphabetical listing of all concepts, functions, commands,
1809 variables, and widgets described in this manual.