3 @c $Id: widget.texi,v 1.3 1996/12/14 09:53:45 steve Exp $
7 @settitle The Emacs Widget Library
14 @node Top, Introduction, (dir), (dir)
15 @comment node-name, next, previous, up
16 @top The Emacs Widget Library
23 * Programming Example::
24 * Setting Up the Buffer::
28 * Defining New Widgets::
32 @node Introduction, User Interface, Top, Top
33 @comment node-name, next, previous, up
36 Most graphical user interface toolkits, such as Motif and XView, provide
37 a number of standard user interface controls (sometimes known as
38 `widgets' or `gadgets'). Emacs doesn't really support anything like
39 this, except for an incredible powerful text ``widget''. On the other
40 hand, Emacs does provide the necessary primitives to implement many
41 other widgets within a text buffer. The @code{widget} package
44 The basic widgets are:
48 Areas of text with an associated action. Intended for hypertext links
51 Like link, but intended for stand-alone buttons.
53 An editable text field. It can be either variable or fixed length.
55 Allows the user to choose one of multiple options from a menu, each
56 option is itself a widget. Only the selected option will be visible in
58 @item radio-button-choice
59 Allows the user to choose one of multiple options by pushing radio
60 buttons. The options are implemented as widgets. All options will be
61 visible in the buffer.
63 A simple constant widget intended to be used in the @code{menu-choice} and
64 @code{radio-button-choice} widgets.
66 An button item only intended for use in choices. When pushed, the user
67 will be asked to select another option from the choice widget.
69 A simple @samp{on}/@samp{off} switch.
71 A checkbox (@samp{[ ]}/@samp{[X]}).
73 Create an editable list. The user can insert or delete items in the
74 list. Each list item is itself a widget.
77 Now of what possible use can support for widgets be in a text editor?
78 I'm glad you asked. The answer is that widgets are useful for
79 implementing forms. A @dfn{form} in emacs is a buffer where the user is
80 supposed to fill out a number of fields, each of which has a specific
81 meaning. The user is not supposed to change or delete any of the text
82 between the fields. Examples of forms in Emacs are the @file{forms}
83 package (of course), the customize buffers, the mail and news compose
84 modes, and the @sc{html} form support in the @file{w3} browser.
86 The advantages for a programmer of using the @code{widget} package to
91 More complex field than just editable text are supported.
93 You can give the user immediate feedback if he enters invalid data in a
94 text field, and sometimes prevent entering invalid data.
96 You can have fixed sized fields, thus allowing multiple field to be
99 It is simple to query or set the value of a field.
101 Editing happens in buffer, not in the mini-buffer.
103 Packages using the library get a uniform look, making them easier for
106 As support for embedded graphics improve, the widget library will
107 extended to support it. This means that your code using the widget
108 library will also use the new graphic features by automatic.
111 In order to minimize the code that is loaded by users who does not
112 create any widgets, the code has been split in two files:
116 This will declare the user variables, define the function
117 @code{widget-define}, and autoload the function @code{widget-create}.
119 Everything else is here, there is no reason to load it explicitly, as
120 it will be autoloaded when needed.
123 @node User Interface, Programming Example, Introduction, Top
124 @comment node-name, next, previous, up
125 @section User Interface
127 A form consist of read only text for documentation and some fields,
128 where each the fields contain two parts, as tag and a value. The tags
129 are used to identify the fields, so the documentation can refer to the
130 foo field, meaning the field tagged with @samp{Foo}. Here is an example
134 Here is some documentation.
136 Name: @i{My Name} @strong{Choose}: This option
137 Address: @i{Some Place
141 See also @b{_other work_} for more information.
143 Numbers: count to three below
144 @b{[INS]} @b{[DEL]} @i{One}
145 @b{[INS]} @b{[DEL]} @i{Eh, two?}
146 @b{[INS]} @b{[DEL]} @i{Five!}
161 @b{[Apply Form]} @b{[Reset Form]}
164 The top level widgets in is example are tagged @samp{Name},
165 @samp{Choose}, @samp{Address}, @samp{_other work_}, @samp{Numbers},
166 @samp{Select multiple}, @samp{Select one}, @samp{[Apply Form]}, and
167 @samp{[Reset Form]}. There are basically two thing the user can do within
168 a form, namely editing the editable text fields and activating the
171 @subsection Editable Text Fields
173 In the example, the value for the @samp{Name} is most likely displayed
174 in an editable text field, and so are values for each of the members of
175 the @samp{Numbers} list. All the normal Emacs editing operations are
176 available for editing these fields. The only restriction is that each
177 change you make must be contained within a single editable text field.
178 For example, capitalizing all text from the middle of one field to the
179 middle of another field is prohibited.
181 Editing text fields are created by the @code{editable-field} widget.
183 The editing text fields are highlighted with the
184 @code{widget-field-face} face, making them easy to find.
186 @deffn Face widget-field-face
187 Face used for other editing fields.
192 Some portions of the buffer have an associated @dfn{action}, which can
193 be @dfn{activated} by a standard key or mouse command. These portions
194 are called @dfn{buttons}. The default commands for activating a button
199 @deffn Command widget-button-press @var{pos} &optional @var{event}
200 Activate the button at @var{pos}, defaulting to point.
201 If point is not located on a button, activate the binding in
202 @code{widget-global-map} (by default the global map).
206 @deffn Command widget-button-click @var{event}
207 Activate the button at the location of the mouse pointer. If the mouse
208 pointer is located in an editable text field, activate the binding in
209 @code{widget-global-map} (by default the global map).
213 There are several different kind of buttons, all of which are present in
217 @item The Option Field Tags.
218 When you activate one of these buttons, you will be asked to choose
219 between a number of different options. This is how you edit an option
220 field. Option fields are created by the @code{menu-choice} widget. In
221 the example, @samp{@b{Choose}} is an option field tag.
222 @item The @samp{@b{[INS]}} and @samp{@b{[DEL]}} buttons.
223 Activating these will insert or delete elements from a editable list.
224 The list is created by the @code{editable-list} widget.
225 @item Embedded Buttons.
226 The @samp{@b{_other work_}} is an example of an embedded
227 button. Embedded buttons are not associated with a fields, but can serve
228 any purpose, such as implementing hypertext references. They are
229 usually created by the @code{link} widget.
230 @item The @samp{@b{[ ]}} and @samp{@b{[X]}} buttons.
231 Activating one of these will convert it to the other. This is useful
232 for implementing multiple-choice fields. You can create it wit
233 @item The @samp{@b{( )}} and @samp{@b{(*)}} buttons.
234 Only one radio button in a @code{radio-button-choice} widget can be selected at any
235 time. When you push one of the unselected radio buttons, it will be
236 selected and the previous selected radio button will become unselected.
237 @item The @samp{@b{[Apply Form]}} @samp{@b{[Reset Form]}} buttons.
238 These are explicit buttons made with the @code{push-button} widget. The main
239 difference from the @code{link} widget is that the buttons are intended
240 to be displayed more like buttons in a GUI, once Emacs grows powerful
244 To make them easier to locate, buttons are emphasized in the buffer.
246 @deffn Face widget-button-face
247 Face used for buttons.
250 @defopt widget-mouse-face
251 Face used for buttons when the mouse pointer is above it.
254 @subsection Navigation
256 You can use all the normal Emacs commands to move around in a form
257 buffer, plus you will have these additional commands:
261 @deffn Command widget-forward &optional count
262 Move point @var{count} buttons or editing fields forward.
265 @deffn Command widget-backward &optional count
266 Move point @var{count} buttons or editing fields backward.
270 @node Programming Example, Setting Up the Buffer, User Interface, Top
271 @comment node-name, next, previous, up
272 @section Programming Example
274 Here is the code to implement the user interface example (see @ref{User
281 (require 'widget-edit))
283 (defvar widget-example-repeat)
285 (defun widget-example ()
286 "Create the widgets from the Widget manual."
288 (switch-to-buffer "*Widget Example*")
289 (kill-all-local-variables)
290 (make-local-variable 'widget-example-repeat)
291 (let ((inhibit-read-only t))
293 (widget-insert "Here is some documentation.\n\nName: ")
294 (widget-create 'editable-field
297 (widget-create 'menu-choice
300 :help-echo "Choose me, please!"
301 :notify (lambda (widget &rest ignore)
302 (message "%s is a good choice!"
303 (widget-value widget)))
304 '(item :tag "This option" :value "This")
305 '(choice-item "That option")
306 '(editable-field :menu-tag "No option" "Thus option"))
307 (widget-insert "Address: ")
308 (widget-create 'editable-field
309 "Some Place\nIn some City\nSome country.")
310 (widget-insert "\nSee also ")
312 :notify (lambda (&rest ignore)
313 (widget-value-set widget-example-repeat
317 (widget-insert " for more information.\n\nNumbers: count to three below\n")
318 (setq widget-example-repeat
319 (widget-create 'editable-list
320 :entry-format "%i %d %v"
321 :notify (lambda (widget &rest ignore)
322 (let ((old (widget-get widget
324 (new (length (widget-value widget))))
326 (widget-put widget ':example-length new)
327 (message "You can count to %d." new))))
328 :value '("One" "Eh, two?" "Five!")
329 '(editable-field :value "three")))
330 (widget-insert "\n\nSelect multiple:\n\n")
331 (widget-create 'checkbox t)
332 (widget-insert " This\n")
333 (widget-create 'checkbox nil)
334 (widget-insert " That\n")
335 (widget-create 'checkbox
336 :notify (lambda (&rest ignore) (message "Tickle"))
338 (widget-insert " Thus\n\nSelect one:\n\n")
339 (widget-create 'radio-button-choice
341 :notify (lambda (widget &rest ignore)
342 (message "You selected %s"
343 (widget-value widget)))
344 '(item "One") '(item "Anthor One.") '(item "A Final One."))
346 (widget-create 'push-button
347 :notify (lambda (&rest ignore)
348 (if (= (length (widget-value widget-example-repeat))
350 (message "Congratulation!")
351 (error "Three was the count!")))
354 (widget-create 'push-button
355 :notify (lambda (&rest ignore)
359 (use-local-map widget-keymap)
363 @node Setting Up the Buffer, Basic Types, Programming Example, Top
364 @comment node-name, next, previous, up
365 @section Setting Up the Buffer
367 Widgets are created with @code{widget-create}, which returns a
368 @dfn{widget} object. This object can be queried and manipulated by
369 other widget functions, until it is deleted with @code{widget-delete}.
370 After the widgets have been created, @code{widget-setup} must be called
373 @defun widget-create type [ keyword argument ]@dots{}
374 Create and return a widget of type @var{type}.
375 The syntax for the @var{type} argument is described in @ref{Basic Types}.
377 The keyword arguments can be used to overwrite the keyword arguments
378 that are part of @var{type}.
381 @defun widget-delete widget
382 Delete @var{widget} and remove it from the buffer.
386 Setup a buffer to support widgets.
388 This should be called after creating all the widgets and before allowing
389 the user to edit them.
393 If you want to insert text outside the widgets in the form, the
394 recommended way to do that is with @code{widget-insert}.
397 Insert the arguments, either strings or characters, at point.
398 The inserted text will be read only.
401 There is a standard widget keymap which you might find useful.
403 @defvr Const widget-keymap
404 A keymap with the global keymap as its parent.@br
405 @key{TAB} and @kbd{C-@key{TAB}} are bound to @code{widget-forward} and
406 @code{widget-backward}, respectively. @kbd{@key{RET}} and @kbd{mouse-2}
407 are bound to @code{widget-button-press} and
408 @code{widget-button-}.@refill
411 @defvar widget-global-map
412 Keymap used by @code{widget-button-press} and @code{widget-button-click}
413 when not on a button. By default this is @code{global-map}.
416 @node Basic Types, Sexp Types, Setting Up the Buffer, Top
417 @comment node-name, next, previous, up
420 The syntax of a type specification is given below:
423 NAME ::= (NAME [KEYWORD ARGUMENT]... ARGS)
427 Where, @var{name} is a widget name, @var{keyword} is the name of a
428 property, @var{argument} is the value of the property, and @var{args}
429 are interpreted in a widget specific way.
431 There following keyword arguments that apply to all widgets:
435 The initial value for widgets of this type.
438 This string will be inserted in the buffer when you create a widget.
439 The following @samp{%} escapes are available:
444 The text inside will be marked as a button.
447 This will be replaces with the buffer representation of the widgets
448 value. What this is depends on the widget type.
451 Insert the string specified by @code{:doc} here.
454 Like @samp{%d}, with the following modifications: If the documentation
455 string is more than one line, it will add a button which will toggle
456 between showing only the first line, and showing the full text.
457 Furthermore, if there is no @code{:doc} property in the widget, it will
458 instead examine the @code{:documentation-property} property. If it is a
459 lambda expression, it will be called with the widget's value as an
460 argument, and the result will be used as the documentation text.
463 Insert the string specified by @code{:tag} here, or the @code{princ}
464 representation of the value if there is no tag.
467 Insert a literal @samp{%}.
471 Face used to highlight text inside %[ %] in the format.
474 The string inserted by the @samp{%d} escape in the format
478 The string inserted by the @samp{%t} escape in the format
482 Message displayed whenever you move to the widget with either
483 @code{widget-forward} or @code{widget-backward}.
486 An integer indicating the absolute number of spaces to indent children
490 An integer indicating how many extra spaces to add to the widget's
491 grandchildren compared to this widget.
494 An integer indicating how many extra spaces to add to the widget's
495 children compared to this widget.
498 A function called each time the widget or a nested widget is changed.
499 The function is called with two or three arguments. The first argument
500 is the widget itself, the second argument is the widget that was
501 changed, and the third argument is the event leading to the change, if
505 Tag used in the menu when the widget is used as an option in a
506 @code{menu-choice} widget.
509 Function used for finding the tag when the widget is used as an option
510 in a @code{menu-choice} widget. By default, the tag used will be either the
511 @code{:menu-tag} or @code{:tag} property if present, or the @code{princ}
512 representation of the @code{:value} property if not.
515 Should be a function called with two arguments, the widget and a value,
516 and returning non-nil if the widget can represent the specified value.
519 A function which takes a widget as an argument, and return nil if the
520 widgets current value is valid for the widget. Otherwise, it should
521 return the widget containing the invalid data, and set that widgets
522 @code{:error} property to a string explaining the error.
525 The parent of a nested widget (e.g. a @code{menu-choice} item or an element of a
526 @code{editable-list} widget).
537 * radio-button-choice::
546 @node link, url-link, Basic Types, Basic Types
547 @comment node-name, next, previous, up
548 @subsection The @code{link} Widget
553 TYPE ::= (link [KEYWORD ARGUMENT]... [ VALUE ])
556 The @var{value}, if present, is used to initialize the @code{:value}
557 property. The value should be a string, which will be inserted in the
560 @node url-link, info-link, link, Basic Types
561 @comment node-name, next, previous, up
562 @subsection The @code{url-link} Widget
567 TYPE ::= (url-link [KEYWORD ARGUMENT]... URL)
570 When this link is activated, the @sc{www} browser specified by
571 @code{browse-url-browser-function} will be called with @var{url}.
573 @node info-link, push-button, url-link, Basic Types
574 @comment node-name, next, previous, up
575 @subsection The @code{info-link} Widget
580 TYPE ::= (info-link [KEYWORD ARGUMENT]... ADDRESS)
583 When this link is activated, the build-in info browser is started on
586 @node push-button, editable-field, info-link, Basic Types
587 @comment node-name, next, previous, up
588 @subsection The @code{push-button} Widget
593 TYPE ::= (push-button [KEYWORD ARGUMENT]... [ VALUE ])
596 The @var{value}, if present, is used to initialize the @code{:value}
597 property. The value should be a string, which will be inserted in the
600 @node editable-field, text, push-button, Basic Types
601 @comment node-name, next, previous, up
602 @subsection The @code{editable-field} Widget
607 TYPE ::= (editable-field [KEYWORD ARGUMENT]... [ VALUE ])
610 The @var{value}, if present, is used to initialize the @code{:value}
611 property. The value should be a string, which will be inserted in
612 field. This widget will match all string values.
614 The following extra properties are recognized.
618 The width of the editable field.@br
619 By default the field will reach to the end of the line.
622 Face used for highlighting the editable field. Default is
623 @code{widget-field-face}.
626 Keymap used in the editable field. @code{widget-keymap} will allow you
627 to use normal editing commands, even if these has been suppressed in the
630 @item :hide-front-space
631 @itemx :hide-rear-space
632 In order to keep track of the editable field, emacs places an invisible
633 space character in front of the field, and for fixed sized fields also
634 in the rear end of the field. For fields that extent to the end of the
635 line, the terminating linefeed serves that purpose instead.
637 Emacs will try to make the spaces intangible when it is safe to do so.
638 Intangible means that the cursor motion commands will skip over the
639 character as if it didn't exist. This is safe to do when the text
640 preceding or following the widget cannot possible change during the
641 lifetime of the @code{editable-field} widget. The preferred way to tell
642 Emacs this, is to add text to the @code{:format} property around the
643 value. For example @code{:format "Tag: %v "}.
645 You can overwrite the internal safety check by setting the
646 @code{:hide-front-space} or @code{:hide-rear-space} properties to
647 non-nil. This is not recommended. For example, @emph{all} text that
648 belongs to a widget (i.e. is created from its @code{:format} string) will
649 change whenever the widget changes its value.
653 @node text, menu-choice, editable-field, Basic Types
654 @comment node-name, next, previous, up
655 @subsection The @code{text} Widget
657 This is just like @code{editable-field}, but intended for multiline text
660 @node menu-choice, radio-button-choice, text, Basic Types
661 @comment node-name, next, previous, up
662 @subsection The @code{menu-choice} Widget
667 TYPE ::= (menu-choice [KEYWORD ARGUMENT]... TYPE ... )
670 The @var{type} arguments represents each possible choice. The widgets
671 value of will be the value of the chosen @var{type} argument. This
672 widget will match any value that matches at least one of the specified
673 @var{type} arguments.
677 Widget type used as a fallback when the value does not match any of the
678 specified @var{type} arguments.
681 Set this to nil if you don't want to ignore case when prompting for a
682 choice through the minibuffer.
685 A list whose car is the widget representing the currently chosen type in
689 The current chosen type
695 @node radio-button-choice, item, menu-choice, Basic Types
696 @comment node-name, next, previous, up
697 @subsection The @code{radio-button-choice} Widget
702 TYPE ::= (radio-button-choice [KEYWORD ARGUMENT]... TYPE ... )
705 The @var{type} arguments represents each possible choice. The widgets
706 value of will be the value of the chosen @var{type} argument. This
707 widget will match any value that matches at least one of the specified
708 @var{type} arguments.
710 The following extra properties are recognized.
714 This string will be inserted for each entry in the list.
715 The following @samp{%} escapes are available:
718 Replaced with the buffer representation of the @var{type} widget.
720 Replace with the radio button.
722 Insert a literal @samp{%}.
726 The widgets representing the radio buttons.
729 The widgets representing each type.
732 The current chosen type
738 You can add extra radio button items to a @code{radio-button-choice}
739 widget after it has been created with the function
740 @code{widget-radio-add-item}.
742 @defun widget-radio-add-item widget type
743 Add to @code{radio-button-choice} widget @var{widget} a new radio button item of type
747 Please note that such items added after the @code{radio-button-choice}
748 widget has been created will @strong{not} be properly destructed when
749 you call @code{widget-delete}.
751 @node item, choice-item, radio-button-choice, Basic Types
752 @comment node-name, next, previous, up
753 @subsection The @code{item} Widget
758 ITEM ::= (item [KEYWORD ARGUMENT]... VALUE)
761 The @var{value}, if present, is used to initialize the @code{:value}
762 property. The value should be a string, which will be inserted in the
763 buffer. This widget will only match the specified value.
765 @node choice-item, toggle, item, Basic Types
766 @comment node-name, next, previous, up
767 @subsection The @code{choice-item} Widget
772 ITEM ::= (choice-item [KEYWORD ARGUMENT]... VALUE)
775 The @var{value}, if present, is used to initialize the @code{:value}
776 property. The value should be a string, which will be inserted in the
777 buffer as a button. Activating the button of a @code{choice-item} is
778 equivalent to activating the parent widget. This widget will only match
781 @node toggle, checkbox, choice-item, Basic Types
782 @comment node-name, next, previous, up
783 @subsection The @code{toggle} Widget
788 TYPE ::= (toggle [KEYWORD ARGUMENT]...)
791 The widget has two possible states, `on' and `off', which corresponds to
792 a @code{t} or @code{nil} value.
794 The following extra properties are recognized.
798 String representing the `on' state. By default the string @samp{on}.
800 String representing the `off' state. By default the string @samp{off}.
802 Type representing the `on' state. By default an `item' widget displaying
803 the string specified with the @code{:on} keyword.
805 Type representing the `off' state. By default an `item' widget
806 displaying the string specified with the @code{:off} keyword.
809 @node checkbox, checklist, toggle, Basic Types
810 @comment node-name, next, previous, up
811 @subsection The @code{checkbox} Widget
813 The widget has two possible states, `selected' and `unselected', which
814 corresponds to a @code{t} or @code{nil} value.
819 TYPE ::= (checkbox [KEYWORD ARGUMENT]...)
822 @node checklist, editable-list, checkbox, Basic Types
823 @comment node-name, next, previous, up
824 @subsection The @code{checklist} Widget
829 TYPE ::= (checklist [KEYWORD ARGUMENT]... TYPE ... )
832 The @var{type} arguments represents each checklist item. The widgets
833 value of will be a list containing the value of each ticked @var{type}
834 argument. The checklist widget will match a list whose elements all
835 matches at least one of the specified @var{type} arguments.
837 The following extra properties are recognized.
841 This string will be inserted for each entry in the list.
842 The following @samp{%} escapes are available:
845 Replaced with the buffer representation of the @var{type} widget.
847 Replace with the checkbox.
849 Insert a literal @samp{%}.
853 The widgets representing the checkboxes.
856 The widgets representing each type.
862 @node editable-list, , checklist, Basic Types
863 @comment node-name, next, previous, up
864 @subsection The @code{editable-list} Widget
869 TYPE ::= (editable-list [KEYWORD ARGUMENT]... TYPE)
872 The value is a list, where each member represent one widget of type
875 The following extra properties are recognized.
879 This string will be inserted for each entry in the list.
880 The following @samp{%} escapes are available:
883 This will be replaced with the buffer representation of the @var{type}
886 Insert the @b{[INS]} button.
888 Insert the @b{[DEL]} button.
890 Insert a literal @samp{%}.
894 The widgets representing the insert and delete buttons.
897 The widgets representing the elements of the list.
900 List whose car is the type of the list elements.
904 @node Sexp Types, Widget Properties, Basic Types, Top
908 A number of widgets for editing s-expressions (lisp types) are also
909 available. These basically fall in three categories: @dfn{atoms},
910 @dfn{composite types}, and @dfn{generic}.
918 @node generic, atoms, Sexp Types, Sexp Types
919 @comment node-name, next, previous, up
920 @subsection The Generic Widget.
922 The @code{const} and @code{sexp} widgets can contain any lisp
923 expression. In the case of the @code{const} widget the user is
924 prohibited from editing edit it, which is mainly useful as a component
925 of one of the composite widgets.
927 The syntax for the generic widgets is
930 TYPE ::= (const [KEYWORD ARGUMENT]... [ VALUE ])
933 The @var{value}, if present, is used to initialize the @code{:value}
934 property and can be any s-expression.
937 This will display any valid s-expression in an immutable part of the
942 This will allow you to edit any valid s-expression in an editable buffer
945 The @code{sexp} widget takes the same keyword arguments as the
946 @code{editable-field} widget.
949 @node atoms, composite, generic, Sexp Types
950 @comment node-name, next, previous, up
951 @subsection Atomic Sexp Widgets.
953 The atoms are s-expressions that does not consist of other
954 s-expressions. A string is an atom, while a list is a composite type.
955 You can edit the value of an atom with the following widgets.
957 The syntax for all the atoms are
960 TYPE ::= (NAME [KEYWORD ARGUMENT]... [ VALUE ])
963 The @var{value}, if present, is used to initialize the @code{:value}
964 property and must be an expression of the same type as the widget.
965 I.e. the string widget can only be initialized with a string.
967 All the atom widgets take the same keyword arguments as the @code{editable-field}
971 Allows you to edit a string in an editable field.
975 Allows you to edit a file name in an editable field. You you activate
976 the tag button, you can edit the file name in the mini-buffer with
982 If this is set to non-nil, only existing file names will be allowed in
987 @deffn Widget directory
988 Allows you to edit a directory name in an editable field.
989 Similar to the @code{file} widget.
993 Allows you to edit a lisp symbol in an editable field.
996 @deffn Widget integer
997 Allows you to edit an integer in an editable field.
1000 @deffn Widget number
1001 Allows you to edit a number in an editable field.
1004 @deffn Widget boolean
1005 Allows you to edit a boolean. In lisp this means a variable which is
1006 either nil meaning false, or non-nil meaning true.
1010 @node composite, , atoms, Sexp Types
1011 @comment node-name, next, previous, up
1012 @subsection Composite Sexp Widgets.
1014 The syntax for the composite are
1017 TYPE ::= (NAME [KEYWORD ARGUMENT]... COMPONENT...)
1020 Where each @var{component} must be a widget type. Each component widget
1021 will be displayed in the buffer, and be editable to the user.
1024 The value of a @code{cons} widget is a cons-cell where the car is the
1025 value of the first component and the cdr is the value of the second
1026 component. There must be exactly two components.
1030 The value of a @code{lisp} widget is a list containing the value of
1031 each of its component.
1034 @deffn Widget vector
1035 The value of a @code{vector} widget is a vector containing the value of
1036 each of its component.
1039 The above suffice for specifying fixed size lists and vectors. To get
1040 variable length lists and vectors, you can use a @code{choice},
1041 @code{set} or @code{repeat} widgets together with the @code{:inline}
1042 keywords. If any component of a composite widget has the @code{:inline}
1043 keyword set, its value must be a list which will then be spliced into
1044 the composite. For example, to specify a list whose first element must
1045 be a file name, and whose remaining arguments should either by the
1046 symbol @code{t} or two files, you can use the following widget
1053 :value ("foo" "bar")
1057 The value of a widget of this type will either have the form
1058 @samp{(file t)} or @code{(file string string)}.
1060 This concept of inline is probably hard to understand. It was certainly
1061 hard to implement so instead of confuse you more by trying to explain it
1062 here, I'll just suggest you meditate over it for a while.
1064 @deffn Widget choice
1065 Allows you to edit a sexp which may have one of fixed set of types. It
1066 is currently implemented with the @code{choice-menu} basic widget, and
1067 has a similar syntax.
1071 Allows you to specify a type which must be a list whose elements all
1072 belong to given set. The elements of the list is not significant. This
1073 is implemented on top of the @code{checklist} basic widget, and has a
1077 @deffn Widget repeat
1078 Allows you to specify a variable length list whose members are all of
1079 the same type. Implemented on top of the `editable-list' basic widget,
1080 and has a similar syntax.
1083 @node Widget Properties, Defining New Widgets, Sexp Types, Top
1084 @comment node-name, next, previous, up
1087 You can examine or set this value by using the widget object that was
1088 returned by @code{widget-create}.
1090 @defun widget-value widget
1091 Return the current value contained in @var{widget}.
1092 It is an error to call this function on an uninitialized widget.
1095 @defun widget-value-set widget value
1096 Set the value contained in @var{widget} to @var{value}.
1097 It is an error to call this function with an invalid @var{value}.
1100 @strong{Important:} You @emph{must} call @code{widget-setup} after
1101 modifying the value of a widget before the user is allowed to edit the
1102 widget again. It is enough to call @code{widget-setup} once if you
1103 modify multiple widgets. This is currently only necessary if the widget
1104 contains an editing field, but may be necessary for other widgets in the
1107 If your application needs to associate some information with the widget
1108 objects, for example a reference to the item being edited, it can be
1109 done with @code{widget-put} and @code{widget-get}. The property names
1110 must begin with a @samp{:}.
1112 @defun widget-put widget property value
1113 In @var{widget} set @var{property} to @var{value}.
1114 @var{property} should be a symbol, while @var{value} can be anything.
1117 @defun widget-get widget property
1118 In @var{widget} return the value for @var{property}.
1119 @var{property} should be a symbol, the value is what was last set by
1120 @code{widget-put} for @var{property}.
1123 @defun widget-member widget property
1124 Non-nil if @var{widget} has a value (even nil) for property @var{property}.
1127 @node Defining New Widgets, Widget Wishlist., Widget Properties, Top
1128 @comment node-name, next, previous, up
1129 @section Defining New Widgets
1131 You can define specialized widgets with @code{define-widget}. It allows
1132 you to create a shorthand for more complex widgets, including specifying
1133 component widgets and default new default values for the keyword
1136 @defun widget-define name class doc &rest args
1137 Define a new widget type named @var{name} from @code{class}.
1139 @var{name} and class should both be symbols, @code{class} should be one
1140 of the existing widget types.
1142 The third argument @var{DOC} is a documentation string for the widget.
1144 After the new widget has been defined, the following two calls will
1145 create identical widgets:
1150 (widget-create @var{name})
1155 (apply widget-create @var{class} @var{args})
1161 Using @code{widget-define} does just store the definition of the widget
1162 type in the @code{widget-type} property of @var{name}, which is what
1163 @code{widget-create} uses.
1165 If you just want to specify defaults for keywords with no complex
1166 conversions, you can use @code{identity} as your conversion function.
1168 The following additional keyword arguments are useful when defining new
1171 @item :convert-widget
1172 Function to convert a widget type before creating a widget of that
1173 type. It takes a widget type as an argument, and returns the converted
1174 widget type. When a widget is created, this function is called for the
1175 widget type and all the widgets parent types, most derived first.
1177 @item :value-to-internal
1178 Function to convert the value to the internal format. The function
1179 takes two arguments, a widget and an external value, and returns the
1180 internal value. The function is called on the present @code{:value}
1181 when the widget is created, and on any value set later with
1182 @code{widget-value-set}.
1184 @item :value-to-external
1185 Function to convert the value to the external format. The function
1186 takes two arguments, a widget and an internal value, and returns the
1187 internal value. The function is called on the present @code{:value}
1188 when the widget is created, and on any value set later with
1189 @code{widget-value-set}.
1192 Function to create a widget from scratch. The function takes one
1193 argument, a widget type, and create a widget of that type, insert it in
1194 the buffer, and return a widget object.
1197 Function to delete a widget. The function takes one argument, a widget,
1198 and should remove all traces of the widget from the buffer.
1201 Function to expand the @samp{%v} escape in the format string. It will
1202 be called with the widget as its argument. Should
1203 insert a representation of the widgets value in the buffer.
1206 Should remove the representation of the widgets value from the buffer.
1207 It will be called with the widget as its argument. It doesn't have to
1208 remove the text, but it should release markers and delete nested widgets
1209 if such has been used.
1211 @item :format-handler
1212 Function to handle unknown @samp{%} escapes in the format string. It
1213 will be called with the widget and the escape character as arguments.
1214 You can set this to allow your widget to handle non-standard escapes.
1216 You should end up calling @code{widget-default-format-handler} to handle
1217 unknown escape sequences, which will handle the @samp{%h} and any future
1218 escape sequences, as well as give an error for unknown escapes.
1221 If you want to define a new widget from scratch, use the @code{default}
1224 @deffn Widget default [ keyword argument ]
1225 Widget used as a base for other widgets.
1227 It provides most of the functionality that is referred to as ``by
1228 default'' in this text.
1231 @node Widget Wishlist., , Defining New Widgets, Top
1232 @comment node-name, next, previous, up
1237 In general, we need @strong{much} better support for keyboard
1242 It should be possible to add or remove items from a list with @kbd{C-k}
1243 and @kbd{C-o} (suggested by @sc{rms}).
1246 @kbd{C-k} should kill to end of field or end of line, whatever come
1250 Commands to move to the beginning/end of a field.
1255 The @samp{[INS]} and @samp{[DEL]} buttons should be replaced by a single
1256 dash (@samp{-}). The dash should be a button that, when activated, ask
1257 whether you want to add or delete an item (@sc{rms} wanted to git rid of
1258 the ugly buttons, the dash is my idea).
1261 Use graphical versions of the widgets for emacsen that can do that.
1262 I.e. real radio buttons and checkmarks instead of their @sc{ascii}
1266 There should be support for browsing the widget documentation.
1269 There should be a way to specify that @key{RET} in a field will call the
1270 @code{:activate} function. This should be used by widgets such as
1271 @code{file} and @code{symbol} prompt with completion.
1274 The @code{menu-choice} tag should be prettier, something like the abbreviated
1278 The functions used in many widgets, like
1279 @code{widget-item-convert-widget}, should not have names that are
1280 specific to the first widget where I used them.
1283 Unchecked items in a @code{radio-button-choice} or @code{checklist}
1284 should be grayed out, and the subwidgets should somehow become inactive.
1285 This could perhaps be implemented by binding @code{widget-inactive} to t
1286 when inserting the grayed out subwidget, and let the widget-specify
1287 functions check that variable.