xemacs-beta: man/widget.texi comparison

comparison man/widget.texi @ 16:0293115a14e9 r19-15b91

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date	Mon, 13 Aug 2007 08:49:20 +0200
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children	859a2309aef8

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+\input texinfo.tex
+@c $Id: widget.texi,v 1.1 1997/02/02 04:58:52 steve Exp $
+@c %**start of header
+@setfilename widget
+@settitle The Emacs Widget Library
+@iftex
+@afourpaper
+@headings double
+@end iftex
+@c %**end of header
+@node Top, Introduction, (dir), (dir)
+@comment  node-name,  next,  previous,  up
+@top The Emacs Widget Library
+Version: 1.20
+@menu
+* Introduction::
+* User Interface::
+* Programming Example::
+* Setting Up the Buffer::
+* Basic Types::
+* Sexp Types::
+* Widget Properties::
+* Defining New Widgets::
+* Widget Wishlist.::
+@end menu
+@node  Introduction, User Interface, Top, Top
+@comment  node-name,  next,  previous,  up
+@section Introduction
+Most graphical user interface toolkits, such as Motif and XView, provide
+a number of standard user interface controls (sometimes known as
+`widgets' or `gadgets').  Emacs doesn't really support anything like
+this, except for an incredible powerful text ``widget''.  On the other
+hand, Emacs does provide the necessary primitives to implement many
+other widgets within a text buffer.  The @code{widget} package
+simplifies this task.
+The basic widgets are:
+@table @code
+@item link
+Areas of text with an associated action.  Intended for hypertext links
+embedded in text.
+@item push-button
+Like link, but intended for stand-alone buttons.
+@item editable-field
+An editable text field.  It can be either variable or fixed length.
+@item menu-choice
+Allows the user to choose one of multiple options from a menu, each
+option is itself a widget.  Only the selected option will be visible in
+the buffer.
+@item radio-button-choice
+Allows the user to choose one of multiple options by pushing radio
+buttons.  The options are implemented as widgets.  All options will be
+visible in the buffer.
+@item item
+A simple constant widget intended to be used in the @code{menu-choice} and
+@code{radio-button-choice} widgets.
+@item choice-item
+An button item only intended for use in choices.  When pushed, the user
+will be asked to select another option from the choice widget.
+@item toggle
+A simple @samp{on}/@samp{off} switch.
+@item checkbox
+A checkbox (@samp{[ ]}/@samp{[X]}).
+@item editable-list
+Create an editable list.  The user can insert or delete items in the
+list.  Each list item is itself a widget.
+@end table
+Now of what possible use can support for widgets be in a text editor?
+I'm glad you asked.  The answer is that widgets are useful for
+implementing forms.  A @dfn{form} in emacs is a buffer where the user is
+supposed to fill out a number of fields, each of which has a specific
+meaning.  The user is not supposed to change or delete any of the text
+between the fields.  Examples of forms in Emacs are the @file{forms}
+package (of course), the customize buffers, the mail and news compose
+modes, and the @sc{html} form support in the @file{w3} browser.
+The advantages for a programmer of using the @code{widget} package to
+implement forms are:
+@enumerate
+@item
+More complex field than just editable text are supported.
+@item
+You can give the user immediate feedback if he enters invalid data in a
+text field, and sometimes prevent entering invalid data.
+@item
+You can have fixed sized fields, thus allowing multiple field to be
+lined up in columns.
+@item
+It is simple to query or set the value of a field.
+@item
+Editing happens in buffer, not in the mini-buffer.
+@item
+Packages using the library get a uniform look, making them easier for
+the user to learn.
+@item
+As support for embedded graphics improve, the widget library will
+extended to support it.  This means that your code using the widget
+library will also use the new graphic features by automatic.
+@end enumerate
+In order to minimize the code that is loaded by users who does not
+create any widgets, the code has been split in two files:
+@table @file
+@item widget.el
+This will declare the user variables, define the function
+@code{widget-define}, and autoload the function @code{widget-create}.
+@item widget-edit.el
+Everything else is here, there is no reason to load it explicitly, as
+it will be autoloaded when needed.
+@end table
+@node User Interface, Programming Example, Introduction, Top
+@comment  node-name,  next,  previous,  up
+@section User Interface
+A form consist of read only text for documentation and some fields,
+where each the fields contain two parts, as tag and a value.  The tags
+are used to identify the fields, so the documentation can refer to the
+foo field, meaning the field tagged with @samp{Foo}. Here is an example
+form:
+@example
+Here is some documentation.
+Name: @i{My Name}     @strong{Choose}: This option
+Address:  @i{Some Place
+In some City
+Some country.}
+See also @b{_other work_} for more information.
+Numbers: count to three below
+@b{[INS]} @b{[DEL]} @i{One}
+@b{[INS]} @b{[DEL]} @i{Eh, two?}
+@b{[INS]} @b{[DEL]} @i{Five!}
+@b{[INS]}
+Select multiple:
+@b{[X]} This
+@b{[ ]} That
+@b{[X]} Thus
+Select one:
+@b{(*)} One
+@b{( )} Another One.
+@b{( )} A Final One.
+@b{[Apply Form]} @b{[Reset Form]}
+@end example
+The top level widgets in is example are tagged @samp{Name},
+@samp{Choose}, @samp{Address}, @samp{_other work_}, @samp{Numbers},
+@samp{Select multiple}, @samp{Select one}, @samp{[Apply Form]}, and
+@samp{[Reset Form]}.  There are basically two thing the user can do within
+a form, namely editing the editable text fields and activating the
+buttons.
+@subsection Editable Text Fields
+In the example, the value for the @samp{Name} is most likely displayed
+in an editable text field, and so are values for each of the members of
+the @samp{Numbers} list.  All the normal Emacs editing operations are
+available for editing these fields.  The only restriction is that each
+change you make must be contained within a single editable text field.
+For example, capitalizing all text from the middle of one field to the
+middle of another field is prohibited.
+Editing text fields are created by the @code{editable-field} widget.
+The editing text fields are highlighted with the
+@code{widget-field-face} face, making them easy to find.
+@deffn Face widget-field-face
+Face used for other editing fields.
+@end deffn
+@subsection Buttons
+Some portions of the buffer have an associated @dfn{action}, which can
+be @dfn{activated} by a standard key or mouse command.  These portions
+are called @dfn{buttons}.  The default commands for activating a button
+are:
+@table @kbd
+@item @key{RET}
+@deffn Command widget-button-press @var{pos} &optional @var{event}
+Activate the button at @var{pos}, defaulting to point.
+If point is not located on a button, activate the binding in
+@code{widget-global-map} (by default the global map).
+@end deffn
+@item mouse-2
+@deffn Command widget-button-click @var{event}
+Activate the button at the location of the mouse pointer.  If the mouse
+pointer is located in an editable text field, activate the binding in
+@code{widget-global-map} (by default the global map).
+@end deffn
+@end table
+There are several different kind of buttons, all of which are present in
+the example:
+@table @emph
+@item The Option Field Tags.
+When you activate one of these buttons, you will be asked to choose
+between a number of different options.  This is how you edit an option
+field.  Option fields are created by the @code{menu-choice} widget.  In
+the example, @samp{@b{Choose}} is an option field tag.
+@item The @samp{@b{[INS]}} and @samp{@b{[DEL]}} buttons.
+Activating these will insert or delete elements from a editable list.
+The list is created by the @code{editable-list} widget.
+@item Embedded Buttons.
+The @samp{@b{_other work_}} is an example of an embedded
+button. Embedded buttons are not associated with a fields, but can serve
+any purpose, such as implementing hypertext references.  They are
+usually created by the @code{link} widget.
+@item The @samp{@b{[ ]}} and @samp{@b{[X]}} buttons.
+Activating one of these will convert it to the other.  This is useful
+for implementing multiple-choice fields.  You can create it wit
+@item The @samp{@b{( )}} and @samp{@b{(*)}} buttons.
+Only one radio button in a @code{radio-button-choice} widget can be selected at any
+time.  When you push one of the unselected radio buttons, it will be
+selected and the previous selected radio button will become unselected.
+@item The @samp{@b{[Apply Form]}} @samp{@b{[Reset Form]}} buttons.
+These are explicit buttons made with the @code{push-button} widget.  The main
+difference from the @code{link} widget is that the buttons are intended
+to be displayed more like buttons in a GUI, once Emacs grows powerful
+enough.
+@end table
+To make them easier to locate, buttons are emphasized in the buffer.
+@deffn Face widget-button-face
+Face used for buttons.
+@end deffn
+@defopt widget-mouse-face
+Face used for buttons when the mouse pointer is above it.
+@end defopt
+@subsection Navigation
+You can use all the normal Emacs commands to move around in a form
+buffer, plus you will have these additional commands:
+@table @kbd
+@item @key{TAB}
+@deffn Command widget-forward &optional count
+Move point @var{count} buttons or editing fields forward.
+@end deffn
+@item @key{M-TAB}
+@deffn Command widget-backward &optional count
+Move point @var{count} buttons or editing fields backward.
+@end deffn
+@end table
+@node Programming Example, Setting Up the Buffer, User Interface, Top
+@comment  node-name,  next,  previous,  up
+@section Programming Example
+Here is the code to implement the user interface example (see @ref{User
+Interface}).
+@lisp
+(require 'widget)
+(eval-when-compile
+(require 'widget-edit))
+(defvar widget-example-repeat)
+(defun widget-example ()
+"Create the widgets from the Widget manual."
+(interactive)
+(switch-to-buffer "*Widget Example*")
+(kill-all-local-variables)
+(make-local-variable 'widget-example-repeat)
+(let ((inhibit-read-only t))
+(erase-buffer))
+(widget-insert "Here is some documentation.\n\nName: ")
+(widget-create 'editable-field
+		 :size 13
+		 "My Name")
+(widget-create 'menu-choice
+		 :tag "Choose"
+		 :value "This"
+		 :help-echo "Choose me, please!"
+		 :notify (lambda (widget &rest ignore)
+			   (message "%s is a good choice!"
+				    (widget-value widget)))
+		 '(item :tag "This option" :value "This")
+		 '(choice-item "That option")
+		 '(editable-field :menu-tag "No option" "Thus option"))
+(widget-insert "Address: ")
+(widget-create 'editable-field
+		 "Some Place\nIn some City\nSome country.")
+(widget-insert "\nSee also ")
+(widget-create 'link
+		 :notify (lambda (&rest ignore)
+			   (widget-value-set widget-example-repeat
+					     '("En" "To" "Tre"))
+			   (widget-setup))
+		 "other work")
+(widget-insert " for more information.\n\nNumbers: count to three below\n")
+(setq widget-example-repeat
+	(widget-create 'editable-list
+		       :entry-format "%i %d %v"
+		       :notify (lambda (widget &rest ignore)
+				 (let ((old (widget-get widget
+							':example-length))
+				       (new (length (widget-value widget))))
+				   (unless (eq old new)
+				     (widget-put widget ':example-length new)
+				     (message "You can count to %d." new))))
+		       :value '("One" "Eh, two?" "Five!")
+		       '(editable-field :value "three")))
+(widget-insert "\n\nSelect multiple:\n\n")
+(widget-create 'checkbox t)
+(widget-insert " This\n")
+(widget-create 'checkbox nil)
+(widget-insert " That\n")
+(widget-create 'checkbox
+		 :notify (lambda (&rest ignore) (message "Tickle"))
+		 t)
+(widget-insert " Thus\n\nSelect one:\n\n")
+(widget-create 'radio-button-choice
+		 :value "One"
+		 :notify (lambda (widget &rest ignore)
+			   (message "You selected %s"
+				    (widget-value widget)))
+		 '(item "One") '(item "Anthor One.") '(item "A Final One."))
+(widget-insert "\n")
+(widget-create 'push-button
+		 :notify (lambda (&rest ignore)
+			   (if (= (length (widget-value widget-example-repeat))
+				  3)
+			       (message "Congratulation!")
+			     (error "Three was the count!")))
+		 "Apply Form")
+(widget-insert " ")
+(widget-create 'push-button
+		 :notify (lambda (&rest ignore)
+			   (widget-example))
+		 "Reset Form")
+(widget-insert "\n")
+(use-local-map widget-keymap)
+(widget-setup))
+@end lisp
+@node Setting Up the Buffer, Basic Types, Programming Example, Top
+@comment  node-name,  next,  previous,  up
+@section Setting Up the Buffer
+Widgets are created with @code{widget-create}, which returns a
+@dfn{widget} object.  This object can be queried and manipulated by
+other widget functions, until it is deleted with @code{widget-delete}.
+After the widgets have been created, @code{widget-setup} must be called
+to enable them.
+@defun widget-create type [ keyword argument ]@dots{}
+Create and return a widget of type @var{type}.
+The syntax for the @var{type} argument is described in @ref{Basic Types}.
+The keyword arguments can be used to overwrite the keyword arguments
+that are part of @var{type}.
+@end defun
+@defun widget-delete widget
+Delete @var{widget} and remove it from the buffer.
+@end defun
+@defun widget-setup
+Setup a buffer to support widgets.
+This should be called after creating all the widgets and before allowing
+the user to edit them.
+@refill
+@end defun
+If you want to insert text outside the widgets in the form, the
+recommended way to do that is with @code{widget-insert}.
+@defun widget-insert
+Insert the arguments, either strings or characters, at point.
+The inserted text will be read only.
+@end defun
+There is a standard widget keymap which you might find useful.
+@defvr Const widget-keymap
+A keymap with the global keymap as its parent.@br
+@key{TAB} and @kbd{C-@key{TAB}} are bound to @code{widget-forward} and
+@code{widget-backward}, respectively.  @kbd{@key{RET}} and @kbd{mouse-2}
+are bound to @code{widget-button-press} and
+@code{widget-button-}.@refill
+@end defvr
+@defvar widget-global-map
+Keymap used by @code{widget-button-press} and @code{widget-button-click}
+when not on a button.  By default this is @code{global-map}.
+@end defvar
+@node Basic Types, Sexp Types, Setting Up the Buffer, Top
+@comment  node-name,  next,  previous,  up
+@section Basic Types
+The syntax of a type specification is given below:
+@example
+NAME ::= (NAME [KEYWORD ARGUMENT]... ARGS)
+|   NAME
+@end example
+Where, @var{name} is a widget name, @var{keyword} is the name of a
+property, @var{argument} is the value of the property, and @var{args}
+are interpreted in a widget specific way.
+There following keyword arguments that apply to all widgets:
+@table @code
+@item :value
+The initial value for widgets of this type.
+@item :format
+This string will be inserted in the buffer when you create a widget.
+The following @samp{%} escapes are available:
+@table @samp
+@item %[
+@itemx %]
+The text inside will be marked as a button.
+@item %@{
+@itemx %@}
+The text inside will be displayed with the face specified by
+@code{:sample-face}.
+@item %v
+This will be replaces with the buffer representation of the widgets
+value.  What this is depends on the widget type.
+@item %d
+Insert the string specified by @code{:doc} here.
+@item %h
+Like @samp{%d}, with the following modifications: If the documentation
+string is more than one line, it will add a button which will toggle
+between showing only the first line, and showing the full text.
+Furthermore, if there is no @code{:doc} property in the widget, it will
+instead examine the @code{:documentation-property} property.  If it is a
+lambda expression, it will be called with the widget's value as an
+argument, and the result will be used as the documentation text.
+@item %t
+Insert the string specified by @code{:tag} here, or the @code{princ}
+representation of the value if there is no tag.
+@item %%
+Insert a literal @samp{%}.
+@end table
+@item :button-face
+Face used to highlight text inside %[ %] in the format.
+@item :doc
+The string inserted by the @samp{%d} escape in the format
+string.
+@item :tag
+The string inserted by the @samp{%t} escape in the format
+string.
+@item :help-echo
+Message displayed whenever you move to the widget with either
+@code{widget-forward} or @code{widget-backward}.
+@item :indent
+An integer indicating the absolute number of spaces to indent children
+of this widget.
+@item :offset
+An integer indicating how many extra spaces to add to the widget's
+grandchildren compared to this widget.
+@item :extra-offset
+An integer indicating how many extra spaces to add to the widget's
+children compared to this widget.
+@item :notify
+A function called each time the widget or a nested widget is changed.
+The function is called with two or three arguments.  The first argument
+is the widget itself, the second argument is the widget that was
+changed, and the third argument is the event leading to the change, if
+any.
+@item :menu-tag
+Tag used in the menu when the widget is used as an option in a
+@code{menu-choice} widget.
+@item :menu-tag-get
+Function used for finding the tag when the widget is used as an option
+in a @code{menu-choice} widget.  By default, the tag used will be either the
+@code{:menu-tag} or @code{:tag} property if present, or the @code{princ}
+representation of the @code{:value} property if not.
+@item :match
+Should be a function called with two arguments, the widget and a value,
+and returning non-nil if the widget can represent the specified value.
+@item :validate
+A function which takes a widget as an argument, and return nil if the
+widgets current value is valid for the widget.  Otherwise, it should
+return the widget containing the invalid data, and set that widgets
+@code{:error} property to a string explaining the error.
+@item :parent
+The parent of a nested widget (e.g. a @code{menu-choice} item or an element of a
+@code{editable-list} widget).
+@end table
+@menu
+* link::
+* url-link::
+* info-link::
+* push-button::
+* editable-field::
+* text::
+* menu-choice::
+* radio-button-choice::
+* item::
+* choice-item::
+* toggle::
+* checkbox::
+* checklist::
+* editable-list::
+@end menu
+@node link, url-link, Basic Types, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{link} Widget
+Syntax:
+@example
+TYPE ::= (link [KEYWORD ARGUMENT]...  [ VALUE ])
+@end example
+The @var{value}, if present, is used to initialize the @code{:value}
+property.  The value should be a string, which will be inserted in the
+buffer.
+@node url-link, info-link, link, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{url-link} Widget
+Syntax:
+@example
+TYPE ::= (url-link [KEYWORD ARGUMENT]...  URL)
+@end example
+When this link is activated, the @sc{www} browser specified by
+@code{browse-url-browser-function} will be called with @var{url}.
+@node info-link, push-button, url-link, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{info-link} Widget
+Syntax:
+@example
+TYPE ::= (info-link [KEYWORD ARGUMENT]...  ADDRESS)
+@end example
+When this link is activated, the build-in info browser is started on
+@var{address}.
+@node  push-button, editable-field, info-link, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{push-button} Widget
+Syntax:
+@example
+TYPE ::= (push-button [KEYWORD ARGUMENT]...  [ VALUE ])
+@end example
+The @var{value}, if present, is used to initialize the @code{:value}
+property. The value should be a string, which will be inserted in the
+buffer.
+@node editable-field, text, push-button, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{editable-field} Widget
+Syntax:
+@example
+TYPE ::= (editable-field [KEYWORD ARGUMENT]... [ VALUE ])
+@end example
+The @var{value}, if present, is used to initialize the @code{:value}
+property.  The value should be a string, which will be inserted in
+field.  This widget will match all string values.
+The following extra properties are recognized.
+@table @code
+@item :size
+The width of the editable field.@br
+By default the field will reach to the end of the line.
+@item :value-face
+Face used for highlighting the editable field.  Default is
+@code{widget-field-face}.
+@item :keymap
+Keymap used in the editable field.  @code{widget-keymap} will allow you
+to use normal editing commands, even if these has been suppressed in the
+current buffer.
+@item :hide-front-space
+@itemx :hide-rear-space
+In order to keep track of the editable field, emacs places an invisible
+space character in front of the field, and for fixed sized fields also
+in the rear end of the field.  For fields that extent to the end of the
+line, the terminating linefeed serves that purpose instead.
+Emacs will try to make the spaces intangible when it is safe to do so.
+Intangible means that the cursor motion commands will skip over the
+character as if it didn't exist.  This is safe to do when the text
+preceding or following the widget cannot possible change during the
+lifetime of the @code{editable-field} widget.  The preferred way to tell
+Emacs this, is to add text to the @code{:format} property around the
+value.  For example @code{:format "Tag: %v "}.
+You can overwrite the internal safety check by setting the
+@code{:hide-front-space} or @code{:hide-rear-space} properties to
+non-nil.  This is not recommended.  For example, @emph{all} text that
+belongs to a widget (i.e. is created from its @code{:format} string) will
+change whenever the widget changes its value.
+@end table
+@node text, menu-choice, editable-field, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{text} Widget
+This is just like @code{editable-field}, but intended for multiline text
+fields.
+@node menu-choice, radio-button-choice, text, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{menu-choice} Widget
+Syntax:
+@example
+TYPE ::= (menu-choice [KEYWORD ARGUMENT]... TYPE ... )
+@end example
+The @var{type} arguments represents each possible choice.  The widgets
+value of will be the value of the chosen @var{type} argument.  This
+widget will match any value that matches at least one of the specified
+@var{type} arguments.
+@table @code
+@item :void
+Widget type used as a fallback when the value does not match any of the
+specified @var{type} arguments.
+@item :case-fold
+Set this to nil if you don't want to ignore case when prompting for a
+choice through the minibuffer.
+@item :children
+A list whose car is the widget representing the currently chosen type in
+the buffer.
+@item :choice
+The current chosen type
+@item :args
+The list of types.
+@end table
+@node radio-button-choice, item, menu-choice, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{radio-button-choice} Widget
+Syntax:
+@example
+TYPE ::= (radio-button-choice [KEYWORD ARGUMENT]...  TYPE ... )
+@end example
+The @var{type} arguments represents each possible choice.  The widgets
+value of will be the value of the chosen @var{type} argument.  This
+widget will match any value that matches at least one of the specified
+@var{type} arguments.
+The following extra properties are recognized.
+@table @code
+@item :entry-format
+This string will be inserted for each entry in the list.
+The following @samp{%} escapes are available:
+@table @samp
+@item %v
+Replaced with the buffer representation of the @var{type} widget.
+@item %b
+Replace with the radio button.
+@item %%
+Insert a literal @samp{%}.
+@end table
+@item :buttons
+The widgets representing the radio buttons.
+@item :children
+The widgets representing each type.
+@item :choice
+The current chosen type
+@item :args
+The list of types.
+@end table
+You can add extra radio button items to a @code{radio-button-choice}
+widget after it has been created with the function
+@code{widget-radio-add-item}.
+@defun widget-radio-add-item widget type
+Add to @code{radio-button-choice} widget @var{widget} a new radio button item of type
+@var{type}.
+@end defun
+Please note that such items added after the @code{radio-button-choice}
+widget has been created will @strong{not} be properly destructed when
+you call @code{widget-delete}.
+@node item, choice-item, radio-button-choice, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{item} Widget
+Syntax:
+@example
+ITEM ::= (item [KEYWORD ARGUMENT]... VALUE)
+@end example
+The @var{value}, if present, is used to initialize the @code{:value}
+property.  The value should be a string, which will be inserted in the
+buffer.  This widget will only match the specified value.
+@node choice-item, toggle, item, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{choice-item} Widget
+Syntax:
+@example
+ITEM ::= (choice-item [KEYWORD ARGUMENT]... VALUE)
+@end example
+The @var{value}, if present, is used to initialize the @code{:value}
+property.  The value should be a string, which will be inserted in the
+buffer as a button.  Activating the button of a @code{choice-item} is
+equivalent to activating the parent widget.  This widget will only match
+the specified value.
+@node toggle, checkbox, choice-item, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{toggle} Widget
+Syntax:
+@example
+TYPE ::= (toggle [KEYWORD ARGUMENT]...)
+@end example
+The widget has two possible states, `on' and `off', which corresponds to
+a @code{t} or @code{nil} value.
+The following extra properties are recognized.
+@table @code
+@item :on
+String representing the `on' state.  By default the string @samp{on}.
+@item :off
+String representing the `off' state.  By default the string @samp{off}.
+@item :on-type
+Type representing the `on' state.  By default an `item' widget displaying
+the string specified with the @code{:on} keyword.
+@item :off-type
+Type representing the `off' state.  By default an `item' widget
+displaying the string specified with the @code{:off} keyword.
+@end table
+@node checkbox, checklist, toggle, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{checkbox} Widget
+The widget has two possible states, `selected' and `unselected', which
+corresponds to a @code{t} or @code{nil} value.
+Syntax:
+@example
+TYPE ::= (checkbox [KEYWORD ARGUMENT]...)
+@end example
+@node checklist, editable-list, checkbox, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{checklist} Widget
+Syntax:
+@example
+TYPE ::= (checklist [KEYWORD ARGUMENT]...  TYPE ... )
+@end example
+The @var{type} arguments represents each checklist item.  The widgets
+value of will be a list containing the value of each ticked @var{type}
+argument.  The checklist widget will match a list whose elements all
+matches at least one of the specified @var{type} arguments.
+The following extra properties are recognized.
+@table @code
+@item :entry-format
+This string will be inserted for each entry in the list.
+The following @samp{%} escapes are available:
+@table @samp
+@item %v
+Replaced with the buffer representation of the @var{type} widget.
+@item %b
+Replace with the checkbox.
+@item %%
+Insert a literal @samp{%}.
+@end table
+@item :buttons
+The widgets representing the checkboxes.
+@item :children
+The widgets representing each type.
+@item :args
+The list of types.
+@end table
+@node editable-list,  , checklist, Basic Types
+@comment  node-name,  next,  previous,  up
+@subsection The @code{editable-list} Widget
+Syntax:
+@example
+TYPE ::= (editable-list [KEYWORD ARGUMENT]... TYPE)
+@end example
+The value is a list, where each member represent one widget of type
+@var{type}.
+The following extra properties are recognized.
+@table @code
+@item :entry-format
+This string will be inserted for each entry in the list.
+The following @samp{%} escapes are available:
+@table @samp
+@item %v
+This will be replaced with the buffer representation of the @var{type}
+widget.
+@item %i
+Insert the @b{[INS]} button.
+@item %d
+Insert the @b{[DEL]} button.
+@item %%
+Insert a literal @samp{%}.
+@end table
+@item :buttons
+The widgets representing the insert and delete buttons.
+@item :children
+The widgets representing the elements of the list.
+@item :args
+List whose car is the type of the list elements.
+@end table
+@node Sexp Types, Widget Properties, Basic Types, Top
+@comment
+@section Sexp Types
+A number of widgets for editing s-expressions (lisp types) are also
+available.  These basically fall in three categories: @dfn{atoms},
+@dfn{composite types}, and @dfn{generic}.
+@menu
+* generic::
+* atoms::
+* composite::
+@end menu
+@node generic, atoms, Sexp Types, Sexp Types
+@comment  node-name,  next,  previous,  up
+@subsection The Generic Widget.
+The @code{const} and @code{sexp} widgets can contain any lisp
+expression.  In the case of the @code{const} widget the user is
+prohibited from editing edit it, which is mainly useful as a component
+of one of the composite widgets.
+The syntax for the generic widgets is
+@example
+TYPE ::= (const [KEYWORD ARGUMENT]...  [ VALUE ])
+@end example
+The @var{value}, if present, is used to initialize the @code{:value}
+property and can be any s-expression.
+@deffn Widget const
+This will display any valid s-expression in an immutable part of the
+buffer.
+@end deffn
+@deffn Widget sexp
+This will allow you to edit any valid s-expression in an editable buffer
+field.
+The @code{sexp} widget takes the same keyword arguments as the
+@code{editable-field} widget.
+@end deffn
+@node atoms, composite, generic, Sexp Types
+@comment  node-name,  next,  previous,  up
+@subsection Atomic Sexp Widgets.
+The atoms are s-expressions that does not consist of other
+s-expressions.  A string is an atom, while a list is a composite type.
+You can edit the value of an atom with the following widgets.
+The syntax for all the atoms are
+@example
+TYPE ::= (NAME [KEYWORD ARGUMENT]...  [ VALUE ])
+@end example
+The @var{value}, if present, is used to initialize the @code{:value}
+property and must be an expression of the same type as the widget.
+I.e. the string widget can only be initialized with a string.
+All the atom widgets take the same keyword arguments as the @code{editable-field}
+widget.
+@deffn Widget string
+Allows you to edit a string in an editable field.
+@end deffn
+@deffn Widget file
+Allows you to edit a file name in an editable field.  You you activate
+the tag button, you can edit the file name in the mini-buffer with
+completion.
+Keywords:
+@table @code
+@item :must-match
+If this is set to non-nil, only existing file names will be allowed in
+the minibuffer.
+@end table
+@end deffn
+@deffn Widget directory
+Allows you to edit a directory name in an editable field.
+Similar to the @code{file} widget.
+@end deffn
+@deffn Widget symbol
+Allows you to edit a lisp symbol in an editable field.
+@end deffn
+@deffn Widget integer
+Allows you to edit an integer in an editable field.
+@end deffn
+@deffn Widget number
+Allows you to edit a number in an editable field.
+@end deffn
+@deffn Widget boolean
+Allows you to edit a boolean.  In lisp this means a variable which is
+either nil meaning false, or non-nil meaning true.
+@end deffn
+@node composite,  , atoms, Sexp Types
+@comment  node-name,  next,  previous,  up
+@subsection Composite Sexp Widgets.
+The syntax for the composite are
+@example
+TYPE ::= (NAME [KEYWORD ARGUMENT]...  COMPONENT...)
+@end example
+Where each @var{component} must be a widget type.  Each component widget
+will be displayed in the buffer, and be editable to the user.
+@deffn Widget cons
+The value of a @code{cons} widget is a cons-cell where the car is the
+value of the first component and the cdr is the value of the second
+component.  There must be exactly two components.
+@end deffn
+@deffn Widget lisp
+The value of a @code{lisp} widget is a list containing the value of
+each of its component.
+@end deffn
+@deffn Widget vector
+The value of a @code{vector} widget is a vector containing the value of
+each of its component.
+@end deffn
+The above suffice for specifying fixed size lists and vectors.  To get
+variable length lists and vectors, you can use a @code{choice},
+@code{set} or @code{repeat} widgets together with the @code{:inline}
+keywords.  If any component of a composite widget has the @code{:inline}
+keyword set, its value must be a list which will then be spliced into
+the composite.  For example, to specify a list whose first element must
+be a file name, and whose remaining arguments should either by the
+symbol @code{t} or two files, you can use the following widget
+specification:
+@example
+(list file
+(choice (const t)
+(list :inline t
+:value ("foo" "bar")
+string string)))
+@end example
+The value of a widget of this type will either have the form
+@samp{(file t)} or @code{(file string string)}.
+This concept of inline is probably hard to understand.  It was certainly
+hard to implement so instead of confuse you more by trying to explain it
+here, I'll just suggest you meditate over it for a while.
+@deffn Widget choice
+Allows you to edit a sexp which may have one of fixed set of types.  It
+is currently implemented with the @code{choice-menu} basic widget, and
+has a similar syntax.
+@end deffn
+@deffn Widget set
+Allows you to specify a type which must be a list whose elements all
+belong to given set.  The elements of the list is not significant.  This
+is implemented on top of the @code{checklist} basic widget, and has a
+similar syntax.
+@end deffn
+@deffn Widget repeat
+Allows you to specify a variable length list whose members are all of
+the same type.  Implemented on top of the `editable-list' basic widget,
+and has a similar syntax.
+@end deffn
+@node Widget Properties, Defining New Widgets, Sexp Types, Top
+@comment  node-name,  next,  previous,  up
+@section Properties
+You can examine or set this value by using the widget object that was
+returned by @code{widget-create}.
+@defun widget-value widget
+Return the current value contained in @var{widget}.
+It is an error to call this function on an uninitialized widget.
+@end defun
+@defun widget-value-set widget value
+Set the value contained in @var{widget} to @var{value}.
+It is an error to call this function with an invalid @var{value}.
+@end defun
+@strong{Important:} You @emph{must} call @code{widget-setup} after
+modifying the value of a widget before the user is allowed to edit the
+widget again.  It is enough to call @code{widget-setup} once if you
+modify multiple widgets.  This is currently only necessary if the widget
+contains an editing field, but may be necessary for other widgets in the
+future.
+If your application needs to associate some information with the widget
+objects, for example a reference to the item being edited, it can be
+done with @code{widget-put} and @code{widget-get}.  The property names
+must begin with a @samp{:}.
+@defun widget-put widget property value
+In @var{widget} set @var{property} to @var{value}.
+@var{property} should be a symbol, while @var{value} can be anything.
+@end defun
+@defun widget-get widget property
+In @var{widget} return the value for @var{property}.
+@var{property} should be a symbol, the value is what was last set by
+@code{widget-put} for @var{property}.
+@end defun
+@defun widget-member widget property
+Non-nil if @var{widget} has a value (even nil) for property @var{property}.
+@end defun
+@node Defining New Widgets, Widget Wishlist., Widget Properties, Top
+@comment  node-name,  next,  previous,  up
+@section Defining New Widgets
+You can define specialized widgets with @code{define-widget}.  It allows
+you to create a shorthand for more complex widgets, including specifying
+component widgets and default new default values for the keyword
+arguments.
+@defun widget-define name class doc &rest args
+Define a new widget type named @var{name} from @code{class}.
+@var{name} and class should both be symbols, @code{class} should be one
+of the existing widget types.
+The third argument @var{DOC} is a documentation string for the widget.
+After the new widget has been defined, the following two calls will
+create identical widgets:
+@itemize @bullet
+@item
+@lisp
+(widget-create @var{name})
+@end lisp
+@item
+@lisp
+(apply widget-create @var{class} @var{args})
+@end lisp
+@end itemize
+@end defun
+Using @code{widget-define} does just store the definition of the widget
+type in the @code{widget-type} property of @var{name}, which is what
+@code{widget-create} uses.
+If you just want to specify defaults for keywords with no complex
+conversions, you can use @code{identity} as your conversion function.
+The following additional keyword arguments are useful when defining new
+widgets:
+@table @code
+@item :convert-widget
+Function to convert a widget type before creating a widget of that
+type.  It takes a widget type as an argument, and returns the converted
+widget type.  When a widget is created, this function is called for the
+widget type and all the widgets parent types, most derived first.
+@item :value-to-internal
+Function to convert the value to the internal format.  The function
+takes two arguments, a widget and an external value, and returns the
+internal value.  The function is called on the present @code{:value}
+when the widget is created, and on any value set later with
+@code{widget-value-set}.
+@item :value-to-external
+Function to convert the value to the external format.  The function
+takes two arguments, a widget and an internal value, and returns the
+internal value.  The function is called on the present @code{:value}
+when the widget is created, and on any value set later with
+@code{widget-value-set}.
+@item :create
+Function to create a widget from scratch.  The function takes one
+argument, a widget type, and create a widget of that type, insert it in
+the buffer, and return a widget object.
+@item :delete
+Function to delete a widget.  The function takes one argument, a widget,
+and should remove all traces of the widget from the buffer.
+@item :value-create
+Function to expand the @samp{%v} escape in the format string.  It will
+be called with the widget as its argument.  Should
+insert a representation of the widgets value in the buffer.
+@item :value-delete
+Should remove the representation of the widgets value from the buffer.
+It will be called with the widget as its argument.  It doesn't have to
+remove the text, but it should release markers and delete nested widgets
+if such has been used.
+@item :format-handler
+Function to handle unknown @samp{%} escapes in the format string.  It
+will be called with the widget and the escape character as arguments.
+You can set this to allow your widget to handle non-standard escapes.
+You should end up calling @code{widget-default-format-handler} to handle
+unknown escape sequences, which will handle the @samp{%h} and any future
+escape sequences, as well as give an error for unknown escapes.
+@end table
+If you want to define a new widget from scratch, use the @code{default}
+widget as its base.
+@deffn Widget default [ keyword argument ]
+Widget used as a base for other widgets.
+It provides most of the functionality that is referred to as ``by
+default'' in this text.
+@end deffn
+@node  Widget Wishlist.,  , Defining New Widgets, Top
+@comment  node-name,  next,  previous,  up
+@section Wishlist.
+@itemize @bullet
+@item
+In general, we need @strong{much} better support for keyboard
+operations.
+@itemize -
+@item
+It should be possible to add or remove items from a list with @kbd{C-k}
+and @kbd{C-o} (suggested by @sc{rms}).
+@item
+@kbd{C-k} should kill to end of field or end of line, whatever come
+first.
+@item
+Commands to move to the beginning/end of a field.
+@end itemize
+@item
+The @samp{[INS]} and @samp{[DEL]} buttons should be replaced by a single
+dash (@samp{-}).  The dash should be a button that, when activated, ask
+whether you want to add or delete an item (@sc{rms} wanted to git rid of
+the ugly buttons, the dash is my idea).
+@item
+Use graphical versions of the widgets for emacsen that can do that.
+I.e. real radio buttons and checkmarks instead of their @sc{ascii}
+equivalents.
+@item
+There should be support for browsing the widget documentation.
+@item
+There should be a way to specify that @key{RET} in a field will call the
+@code{:activate} function.  This should be used by widgets such as
+@code{file} and @code{symbol} prompt with completion.
+@item
+The @code{menu-choice} tag should be prettier, something like the abbreviated
+menus in Open Look.
+@item
+The functions used in many widgets, like
+@code{widget-item-convert-widget}, should not have names that are
+specific to the first widget where I used them.
+@item
+Unchecked items in a @code{radio-button-choice} or @code{checklist}
+should be grayed out, and the subwidgets should somehow become inactive.
+This could perhaps be implemented by binding @code{widget-inactive} to t
+when inserting the grayed out subwidget, and let the widget-specify
+functions check that variable.
+@item
+Flag to make @code{widget-move} skip a specified button.
+@item
+Document `helper' functions for defining new widgets.
+@item
+Show button menus on mouse down.
+@item
+Activate the item this is below the mouse when the button is
+released, not the item this is below the mouse when the button is
+pressed.  Dired and grep gets this right.
+@item
+Use @samp{@@deffn Widget} to document widgets.
+@item
+Document global keywords in one place.
+Document keywords particular to a specific widget in the widget
+definition.
+Document the `default' widget first.
+Split, when needed, keywords into those useful for normal
+customization, those primarily useful when deriving, and those who
+represent runtime information.
+@end itemize
+@contents
+@bye

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comparison man/widget.texi @ 16:0293115a14e9 r19-15b91