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Copyright (C) 2000 Free Software Foundation, Inc.
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INFO-DIR-SECTION Emacs
START-INFO-DIR-ENTRY
* Widget: (widget). Documenting the "widget" package used by the
Emacs Custom facility.
END-INFO-DIR-ENTRY
File: widget, Node: Top, Next: Introduction, Prev: (dir), Up: (dir)
The Emacs Widget Library
************************
* Menu:
* Introduction::
* User Interface::
* Programming Example::
* Setting Up the Buffer::
* Basic Types::
* Sexp Types::
* Widget Properties::
* Defining New Widgets::
* Widget Browser::
* Widget Minor Mode::
* Utilities::
* Widget Wishlist::
* Index::
File: widget, Node: Introduction, Next: User Interface, Prev: Top, Up: Top
Introduction
============
Most graphical user interface toolkits 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
incredibly powerful text "widget." On the other hand, Emacs does
provide the necessary primitives to implement many other widgets within
a text buffer. The `widget' package simplifies this task.
The basic widgets are:
`link'
Areas of text with an associated action. Intended for hypertext
links embedded in text.
`push-button'
Like link, but intended for stand-alone buttons.
`editable-field'
An editable text field. It can be either variable or fixed length.
`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.
`radio-button-choice'
Allows the user to choose one of multiple options by activating
radio buttons. The options are implemented as widgets. All
options will be visible in the buffer.
`item'
A simple constant widget intended to be used in the `menu-choice'
and `radio-button-choice' widgets.
`choice-item'
A button item only intended for use in choices. When invoked, the
user will be asked to select another option from the choice widget.
`toggle'
A simple `on'/`off' switch.
`checkbox'
A checkbox (`[ ]'/`[X]').
`editable-list'
Create an editable list. The user can insert or delete items in
the list. Each list item is itself a widget.
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 "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 `forms' package
(of course), the customize buffers, the mail and news compose modes,
and the HTML form support in the `w3' browser.
The advantages for a programmer of using the `widget' package to
implement forms are:
1. More complex fields than just editable text are supported.
2. You can give the users immediate feedback if they enter invalid
data in a text field, and sometimes prevent entering invalid data.
3. You can have fixed sized fields, thus allowing multiple fields to
be lined up in columns.
4. It is simple to query or set the value of a field.
5. Editing happens in the buffer, not in the mini-buffer.
6. Packages using the library get a uniform look, making them easier
for the user to learn.
7. As support for embedded graphics improve, the widget library will
be extended to use the GUI features. This means that your code
using the widget library will also use the new graphic features
automatically.
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:
`widget.el'
This will declare the user variables, define the function
`define-widget', and autoload the function `widget-create'.
`wid-edit.el'
Everything else is here, there is no reason to load it explicitly,
as it will be autoloaded when needed.
File: widget, Node: User Interface, Next: Programming Example, Prev: Introduction, Up: Top
User Interface
==============
A form consist of read only text for documentation and some fields,
where each field contains two parts, a 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 `Foo'. Here is an example form:
Here is some documentation.
Name: My Name *Choose*: This option
Address: Some Place
In some City
Some country.
See also _other work_ for more information.
Numbers: count to three below
[INS] [DEL] One
[INS] [DEL] Eh, two?
[INS] [DEL] Five!
[INS]
Select multiple:
[X] This
[ ] That
[X] Thus
Select one:
(*) One
( ) Another One.
( ) A Final One.
[Apply Form] [Reset Form]
The top level widgets in is example are tagged `Name', `Choose',
`Address', `_other work_', `Numbers', `Select multiple', `Select one',
`[Apply Form]', and `[Reset Form]'. There are basically two things the
user can do within a form, namely editing the editable text fields and
activating the buttons.
Editable Text Fields
--------------------
In the example, the value for the `Name' is most likely displayed in
an editable text field, and so are values for each of the members of
the `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 `editable-field' widget.
The editing text fields are highlighted with the `widget-field-face'
face, making them easy to find.
- Face: widget-field-face
Face used for other editing fields.
Buttons
-------
Some portions of the buffer have an associated "action", which can
be "invoked" by a standard key or mouse command. These portions are
called "buttons". The default commands for activating a button are:
`<RET>'
- Command: widget-button-press POS &optional EVENT
Invoke the button at POS, defaulting to point. If point is
not located on a button, invoke the binding in
`widget-global-map' (by default the global map).
`Mouse-2'
- Command: widget-button-click EVENT
Invoke the button at the location of the mouse pointer. If
the mouse pointer is located in an editable text field,
invoke the binding in `widget-global-map' (by default the
global map).
There are several different kind of buttons, all of which are
present in the example:
_The Option Field Tags_
When you invoke 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 `menu-choice'
widget. In the example, `Choose' is an option field tag.
_The `[INS]' and `[DEL]' buttons_
Activating these will insert or delete elements from an editable
list. The list is created by the `editable-list' widget.
_Embedded Buttons_
The `_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 `link' widget.
_The `[ ]' and `[X]' buttons_
Activating one of these will convert it to the other. This is
useful for implementing multiple-choice fields. You can create it
with the `checkbox' widget.
_The `( )' and `(*)' buttons_
Only one radio button in a `radio-button-choice' widget can be
selected at any time. When you invoke one of the unselected radio
buttons, it will be selected and the previous selected radio
button will become unselected.
_The `[Apply Form]' `[Reset Form]' buttons_
These are explicit buttons made with the `push-button' widget. The
main difference from the `link' widget is that the buttons will be
displayed as GUI buttons when possible.
To make them easier to locate, buttons are emphasized in the buffer.
- Face: widget-button-face
Face used for buttons.
- User Option: widget-mouse-face
Face used for highlighting a button when the mouse pointer moves
across it.
Navigation
----------
You can use all the normal Emacs commands to move around in a form
buffer, plus you will have these additional commands:
`<TAB>'
- Command: widget-forward &optional count
Move point COUNT buttons or editing fields forward.
`<M-TAB>'
- Command: widget-backward &optional count
Move point COUNT buttons or editing fields backward.
File: widget, Node: Programming Example, Next: Setting Up the Buffer, Prev: User Interface, Up: Top
Programming Example
===================
Here is the code to implement the user interface example (*note User
Interface::).
(require 'widget)
(eval-when-compile
(require 'wid-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 "Another 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))
File: widget, Node: Setting Up the Buffer, Next: Basic Types, Prev: Programming Example, Up: Top
Setting Up the Buffer
=====================
Widgets are created with `widget-create', which returns a "widget"
object. This object can be queried and manipulated by other widget
functions, until it is deleted with `widget-delete'. After the widgets
have been created, `widget-setup' must be called to enable them.
- Function: widget-create type [ keyword argument ]...
Create and return a widget of type TYPE. The syntax for the TYPE
argument is described in *Note Basic Types::.
The keyword arguments can be used to overwrite the keyword
arguments that are part of TYPE.
- Function: widget-delete widget
Delete WIDGET and remove it from the buffer.
- Function: widget-setup
Set up a buffer to support widgets.
This should be called after creating all the widgets and before
allowing the user to edit them.
If you want to insert text outside the widgets in the form, the
recommended way to do that is with `widget-insert'.
- Function: widget-insert
Insert the arguments, either strings or characters, at point. The
inserted text will be read-only.
There is a standard widget keymap which you might find useful.
- Const: widget-keymap
A keymap with the global keymap as its parent.
<TAB> and `C-<TAB>' are bound to `widget-forward' and
`widget-backward', respectively. <RET> and `Mouse-2' are bound to
`widget-button-press' and `widget-button-click'.
- Variable: widget-global-map
Keymap used by `widget-button-press' and `widget-button-click'
when not on a button. By default this is `global-map'.
File: widget, Node: Basic Types, Next: Sexp Types, Prev: Setting Up the Buffer, Up: Top
Basic Types
===========
The syntax of a type specification is given below:
NAME ::= (NAME [KEYWORD ARGUMENT]... ARGS)
| NAME
Where, NAME is a widget name, KEYWORD is the name of a property,
ARGUMENT is the value of the property, and ARGS are interpreted in a
widget specific way.
The following keyword arguments that apply to all widgets:
`:value'
The initial value for widgets of this type.
`:format'
This string will be inserted in the buffer when you create a
widget. The following `%' escapes are available:
`%['
`%]'
The text inside will be marked as a button.
By default, the text will be shown in `widget-button-face',
and surrounded by brackets.
- User Option: widget-button-prefix
String to prefix buttons.
- User Option: widget-button-suffix
String to suffix buttons.
`%{'
`%}'
The text inside will be displayed with the face specified by
`:sample-face'.
`%v'
This will be replaced with the buffer representation of the
widget's value. What this is depends on the widget type.
`%d'
Insert the string specified by `:doc' here.
`%h'
Like `%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
`:doc' property in the widget, it will instead examine the
`: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.
`%t'
Insert the string specified by `:tag' here, or the `princ'
representation of the value if there is no tag.
`%%'
Insert a literal `%'.
`:button-face'
Face used to highlight text inside %[ %] in the format.
`:button-prefix'
`:button-suffix'
Text around %[ %] in the format.
These can be
_nil_
No text is inserted.
_a string_
The string is inserted literally.
_a symbol_
The value of the symbol is expanded according to this table.
`:doc'
The string inserted by the `%d' escape in the format string.
`:tag'
The string inserted by the `%t' escape in the format string.
`:tag-glyph'
Name of image to use instead of the string specified by `:tag' on
Emacsen that supports it.
`:help-echo'
Specifies how to display a message whenever you move to the widget
with either `widget-forward' or `widget-backward' or move the mouse
over it (using the standard `help-echo' mechanism). The argument
is either a string to display or a function of one argument, the
widget, which should return a string to display.
`:indent'
An integer indicating the absolute number of spaces to indent
children of this widget.
`:offset'
An integer indicating how many extra spaces to add to the widget's
grandchildren compared to this widget.
`:extra-offset'
An integer indicating how many extra spaces to add to the widget's
children compared to this widget.
`: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.
`:menu-tag'
Tag used in the menu when the widget is used as an option in a
`menu-choice' widget.
`:menu-tag-get'
Function used for finding the tag when the widget is used as an
option in a `menu-choice' widget. By default, the tag used will
be either the `:menu-tag' or `:tag' property if present, or the
`princ' representation of the `:value' property if not.
`: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.
`:validate'
A function which takes a widget as an argument, and returns `nil'
if the widget's current value is valid for the widget. Otherwise
it should return the widget containing the invalid data, and set
that widget's `:error' property to a string explaining the error.
The following predefined function can be used:
- Function: widget-children-validate widget
All the `:children' of WIDGET must be valid.
`:tab-order'
Specify the order in which widgets are traversed with
`widget-forward' or `widget-backward'. This is only partially
implemented.
a. Widgets with tabbing order `-1' are ignored.
b. (Unimplemented) When on a widget with tabbing order N, go to
the next widget in the buffer with tabbing order N+1 or `nil',
whichever comes first.
c. When on a widget with no tabbing order specified, go to the
next widget in the buffer with a positive tabbing order, or
`nil'
`:parent'
The parent of a nested widget (e.g. a `menu-choice' item or an
element of a `editable-list' widget).
`:sibling-args'
This keyword is only used for members of a `radio-button-choice' or
`checklist'. The value should be a list of extra keyword
arguments, which will be used when creating the `radio-button' or
`checkbox' associated with this item.
- User Option: widget-glyph-directory
Directory where glyphs are found. Widget will look here for a
file with the same name as specified for the image, with either a
`.xpm' (if supported) or `.xbm' extension.
- User Option: widget-glyph-enable
If non-nil, allow glyphs to appear on displays where they are
supported.
* Menu:
* link::
* url-link::
* info-link::
* push-button::
* editable-field::
* text::
* menu-choice::
* radio-button-choice::
* item::
* choice-item::
* toggle::
* checkbox::
* checklist::
* editable-list::
* group::
File: widget, Node: link, Next: url-link, Prev: Basic Types, Up: Basic Types
The `link' Widget
-----------------
Syntax:
TYPE ::= (link [KEYWORD ARGUMENT]... [ VALUE ])
The VALUE, if present, is used to initialize the `:value' property.
The value should be a string, which will be inserted in the buffer.
By default the link will be shown in brackets.
- User Option: widget-link-prefix
String to prefix links.
- User Option: widget-link-suffix
String to suffix links.
File: widget, Node: url-link, Next: info-link, Prev: link, Up: Basic Types
The `url-link' Widget
---------------------
Syntax:
TYPE ::= (url-link [KEYWORD ARGUMENT]... URL)
When this link is invoked, the WWW browser specified by
`browse-url-browser-function' will be called with URL.
File: widget, Node: info-link, Next: push-button, Prev: url-link, Up: Basic Types
The `info-link' Widget
----------------------
Syntax:
TYPE ::= (info-link [KEYWORD ARGUMENT]... ADDRESS)
When this link is invoked, the built-in Info reader is started on
ADDRESS.
File: widget, Node: push-button, Next: editable-field, Prev: info-link, Up: Basic Types
The `push-button' Widget
------------------------
Syntax:
TYPE ::= (push-button [KEYWORD ARGUMENT]... [ VALUE ])
The VALUE, if present, is used to initialize the `:value' property.
The value should be a string, which will be inserted in the buffer.
By default the tag will be shown in brackets.
- User Option: widget-push-button-prefix
String to prefix push buttons.
- User Option: widget-push-button-suffix
String to suffix push buttons.
File: widget, Node: editable-field, Next: text, Prev: push-button, Up: Basic Types
The `editable-field' Widget
---------------------------
Syntax:
TYPE ::= (editable-field [KEYWORD ARGUMENT]... [ VALUE ])
The VALUE, if present, is used to initialize the `: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:
`:size'
The width of the editable field.
By default the field will reach to the end of the line.
`:value-face'
Face used for highlighting the editable field. Default is
`widget-field-face', see *Note User Interface::.
`:secret'
Character used to display the value. You can set this to e.g. `?*'
if the field contains a password or other secret information. By
default, this is nil, and the value is not secret.
`:valid-regexp'
By default the `:validate' function will match the content of the
field with the value of this attribute. The default value is `""'
which matches everything.
`:keymap'
Keymap used in the editable field. The default value is
`widget-field-keymap', which allows you to use all the normal
editing commands, even if the buffer's major mode suppresses some
of them. Pressing <RET> invokes the function specified by
`:action'.
File: widget, Node: text, Next: menu-choice, Prev: editable-field, Up: Basic Types
The `text' Widget
-----------------
This is just like `editable-field', but intended for multiline text
fields. The default `:keymap' is `widget-text-keymap', which does not
rebind the <RET> key.
File: widget, Node: menu-choice, Next: radio-button-choice, Prev: text, Up: Basic Types
The `menu-choice' Widget
------------------------
Syntax:
TYPE ::= (menu-choice [KEYWORD ARGUMENT]... TYPE ... )
The TYPE argument represents each possible choice. The widget's
value will be that of the chosen TYPE argument. This widget will match
any value matching at least one of the specified TYPE arguments.
`:void'
Widget type used as a fallback when the value does not match any
of the specified TYPE arguments.
`:case-fold'
Set this to nil if you don't want to ignore case when prompting
for a choice through the minibuffer.
`:children'
A list whose `car' is the widget representing the currently chosen
type in the buffer.
`:choice'
The current chosen type.
`:args'
The list of types.
File: widget, Node: radio-button-choice, Next: item, Prev: menu-choice, Up: Basic Types
The `radio-button-choice' Widget
--------------------------------
Syntax:
TYPE ::= (radio-button-choice [KEYWORD ARGUMENT]... TYPE ... )
The TYPE argument represents each possible choice. The widget's
value will be that of the chosen TYPE argument. This widget will match
any value matching at least one of the specified TYPE arguments.
The following extra properties are recognized.
`:entry-format'
This string will be inserted for each entry in the list. The
following `%' escapes are available:
`%v'
Replace with the buffer representation of the TYPE widget.
`%b'
Replace with the radio button.
`%%'
Insert a literal `%'.
`:button-args'
A list of keywords to pass to the radio buttons. Useful for
setting e.g. the `:help-echo' for each button.
`:buttons'
The widgets representing the radio buttons.
`:children'
The widgets representing each type.
`:choice'
The current chosen type
`:args'
The list of types.
You can add extra radio button items to a `radio-button-choice'
widget after it has been created with the function
`widget-radio-add-item'.
- Function: widget-radio-add-item widget type
Add to `radio-button-choice' widget WIDGET a new radio button item
of type TYPE.
Please note that such items added after the `radio-button-choice'
widget has been created will *not* be properly destructed when you call
`widget-delete'.
File: widget, Node: item, Next: choice-item, Prev: radio-button-choice, Up: Basic Types
The `item' Widget
-----------------
Syntax:
ITEM ::= (item [KEYWORD ARGUMENT]... VALUE)
The VALUE, if present, is used to initialize the `:value' property.
The value should be a string, which will be inserted in the buffer.
This widget will only match the specified value.
File: widget, Node: choice-item, Next: toggle, Prev: item, Up: Basic Types
The `choice-item' Widget
------------------------
Syntax:
ITEM ::= (choice-item [KEYWORD ARGUMENT]... VALUE)
The VALUE, if present, is used to initialize the `:value' property.
The value should be a string, which will be inserted in the buffer as a
button. Activating the button of a `choice-item' is equivalent to
activating the parent widget. This widget will only match the
specified value.
File: widget, Node: toggle, Next: checkbox, Prev: choice-item, Up: Basic Types
The `toggle' Widget
-------------------
Syntax:
TYPE ::= (toggle [KEYWORD ARGUMENT]...)
The widget has two possible states, `on' and `off', which correspond
to a `t' or `nil' value, respectively.
The following extra properties are recognized:
`:on'
A string representing the `on' state. By default the string `on'.
`:off'
A string representing the `off' state. By default the string
`off'.
`:on-glyph'
Name of a glyph to be used instead of the `:on' text string, on
emacsen that supports this.
`:off-glyph'
Name of a glyph to be used instead of the `:off' text string, on
emacsen that supports this.
File: widget, Node: checkbox, Next: checklist, Prev: toggle, Up: Basic Types
The `checkbox' Widget
---------------------
This widget has two possible states, `selected' and `unselected',
which corresponds to a `t' or `nil' value.
Syntax:
TYPE ::= (checkbox [KEYWORD ARGUMENT]...)
File: widget, Node: checklist, Next: editable-list, Prev: checkbox, Up: Basic Types
The `checklist' Widget
----------------------
Syntax:
TYPE ::= (checklist [KEYWORD ARGUMENT]... TYPE ... )
The TYPE arguments represent each checklist item. The widget's
value will be a list containing the values of all checked TYPE
arguments. The checklist widget will match a list whose elements all
match at least one of the specified TYPE arguments.
The following extra properties are recognized:
`:entry-format'
This string will be inserted for each entry in the list. The
following `%' escapes are available:
`%v'
Replaced with the buffer representation of the TYPE widget.
`%b'
Replace with the checkbox.
`%%'
Insert a literal `%'.
`:greedy'
Usually a checklist will only match if the items are in the exact
sequence given in the specification. By setting `:greedy' to
non-nil, it will allow the items to come in any sequence.
However, if you extract the value they will be in the sequence
given in the checklist, i.e. the original sequence is forgotten.
`:button-args'
A list of keywords to pass to the checkboxes. Useful for setting
e.g. the `:help-echo' for each checkbox.
`:buttons'
The widgets representing the checkboxes.
`:children'
The widgets representing each type.
`:args'
The list of types.
File: widget, Node: editable-list, Next: group, Prev: checklist, Up: Basic Types
The `editable-list' Widget
--------------------------
Syntax:
TYPE ::= (editable-list [KEYWORD ARGUMENT]... TYPE)
The value is a list, where each member represents one widget of type
TYPE.
The following extra properties are recognized:
`:entry-format'
This string will be inserted for each entry in the list. The
following `%' escapes are available:
`%v'
This will be replaced with the buffer representation of the
TYPE widget.
`%i'
Insert the [INS] button.
`%d'
Insert the [DEL] button.
`%%'
Insert a literal `%'.
`:insert-button-args'
A list of keyword arguments to pass to the insert buttons.
`:delete-button-args'
A list of keyword arguments to pass to the delete buttons.
`:append-button-args'
A list of keyword arguments to pass to the trailing insert button.
`:buttons'
The widgets representing the insert and delete buttons.
`:children'
The widgets representing the elements of the list.
`:args'
List whose `car' is the type of the list elements.
File: widget, Node: group, Prev: editable-list, Up: Basic Types
The `group' Widget
------------------
This widget simply group other widgets together.
Syntax:
TYPE ::= (group [KEYWORD ARGUMENT]... TYPE...)
The value is a list, with one member for each TYPE.
File: widget, Node: Sexp Types, Next: Widget Properties, Prev: Basic Types, Up: Top
Sexp Types
==========
A number of widgets for editing "s-expressions" (lisp types), sexp
for short, are also available. These basically fall in several
categories described in this section.
* Menu:
* constants::
* generic::
* atoms::
* composite::
File: widget, Node: constants, Next: generic, Prev: Sexp Types, Up: Sexp Types
The Constant Widgets
--------------------
The `const' widget can contain any lisp expression, but the user is
prohibited from editing it, which is mainly useful as a component of one
of the composite widgets.
The syntax for the `const' widget is:
TYPE ::= (const [KEYWORD ARGUMENT]... [ VALUE ])
The VALUE, if present, is used to initialize the `:value' property
and can be any s-expression.
- Widget: const
This will display any valid s-expression in an immutable part of
the buffer.
There are two variations of the `const' widget, namely
`variable-item' and `function-item'. These should contain a symbol
with a variable or function binding. The major difference from the
`const' widget is that they will allow the user to see the variable or
function documentation for the symbol.
- Widget: variable-item
An immutable symbol that is bound as a variable.
- Widget: function-item
An immutable symbol that is bound as a function.
File: widget, Node: generic, Next: atoms, Prev: constants, Up: Sexp Types
Generic Sexp Widget
-------------------
The `sexp' widget can contain any lisp expression, and allows the
user to edit it inline in the buffer.
The syntax for the `sexp' widget is:
TYPE ::= (sexp [KEYWORD ARGUMENT]... [ VALUE ])
- Widget: sexp
This will allow you to edit any valid s-expression in an editable
buffer field.
The `sexp' widget takes the same keyword arguments as the
`editable-field' widget. *Note editable-field::.
File: widget, Node: atoms, Next: composite, Prev: generic, Up: Sexp Types
Atomic Sexp Widgets
-------------------
The atoms are s-expressions that do not consist of other
s-expressions. For example, a string, a file name, or a symbol are
atoms, 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:
TYPE ::= (NAME [KEYWORD ARGUMENT]... [ VALUE ])
The VALUE, if present, is used to initialize the `:value' property
and must be an expression of the same type as the widget. That is, the
string widget can only be initialized with a string.
All the atom widgets take the same keyword arguments as the
`editable-field' widget. *Note editable-field::.
- Widget: string
Allows you to edit a string in an editable field.
- Widget: regexp
Allows you to edit a regular expression in an editable field.
- Widget: character
Allows you to enter a character in an editable field.
- Widget: file
Allows you to edit a file name in an editable field. If you invoke
the tag button, you can edit the file name in the mini-buffer with
completion.
Keywords:
`:must-match'
If this is set to non-nil, only existing file names will be
allowed in the minibuffer.
- Widget: directory
Allows you to edit a directory name in an editable field. Similar
to the `file' widget.
- Widget: symbol
Allows you to edit a lisp symbol in an editable field.
- Widget: function
Allows you to edit a lambda expression, or a function name with
completion.
- Widget: variable
Allows you to edit a variable name, with completion.
- Widget: integer
Allows you to edit an integer in an editable field.
- Widget: number
Allows you to edit a number in an editable field.
- 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.
File: widget, Node: composite, Prev: atoms, Up: Sexp Types
Composite Sexp Widgets
----------------------
The syntax for the composite widget is:
TYPE ::= (NAME [KEYWORD ARGUMENT]... COMPONENT...)
where each COMPONENT must be a widget type. Each component widget will
be displayed in the buffer, and will be editable by the user.
- Widget: cons
The value of a `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.
- Widget: list
The value of a `list' widget is a list containing the value of
each of its component.
- Widget: vector
The value of a `vector' widget is a vector containing the value of
each of its component.
The above suffice for specifying fixed size lists and vectors. To
get variable length lists and vectors, you can use a `choice', `set',
or `repeat' widgets together with the `:inline' keywords. If any
component of a composite widget has the `: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 `t' or two
files, you can use the following widget specification:
(list file
(choice (const t)
(list :inline t
:value ("foo" "bar")
string string)))
The value of a widget of this type will either have the form `(file
t)' or `(file string string)'.
This concept of inline is probably hard to understand. It was
certainly hard to implement, so instead of confusing you more by trying
to explain it here, I'll just suggest you meditate over it for a while.
- Widget: choice
Allows you to edit a sexp which may have one of a fixed set of
types. It is currently implemented with the `choice-menu' basic
widget, and has a similar syntax.
- 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 are not
significant. This is implemented on top of the `checklist' basic
widget, and has a similar syntax.
- 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.
File: widget, Node: Widget Properties, Next: Defining New Widgets, Prev: Sexp Types, Up: Top
Properties
==========
You can examine or set the value of a widget by using the widget
object that was returned by `widget-create'.
- Function: widget-value widget
Return the current value contained in WIDGET. It is an error to
call this function on an uninitialized widget.
- Function: widget-value-set widget value
Set the value contained in WIDGET to VALUE. It is an error to
call this function with an invalid VALUE.
*Important:* You _must_ call `widget-setup' after modifying the
value of a widget before the user is allowed to edit the widget again.
It is enough to call `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 `widget-put' and `widget-get'. The property names
must begin with a `:'.
- Function: widget-put widget property value
In WIDGET set PROPERTY to VALUE. PROPERTY should be a symbol,
while VALUE can be anything.
- Function: widget-get widget property
In WIDGET return the value for PROPERTY. PROPERTY should be a
symbol, the value is what was last set by `widget-put' for
PROPERTY.
- Function: widget-member widget property
Non-nil if WIDGET has a value (even nil) for property PROPERTY.
Occasionally it can be useful to know which kind of widget you have,
i.e. the name of the widget type you gave when the widget was created.
- Function: widget-type widget
Return the name of WIDGET, a symbol.
Widgets can be in two states: active, which means they are
modifiable by the user, or inactive, which means they cannot be
modified by the user. You can query or set the state with the
following code:
;; Examine if WIDGET is active or not.
(if (widget-apply WIDGET :active)
(message "Widget is active.")
(message "Widget is inactive.")
;; Make WIDGET inactive.
(widget-apply WIDGET :deactivate)
;; Make WIDGET active.
(widget-apply WIDGET :activate)
A widget is inactive if it, or any of its ancestors (found by
following the `:parent' link), have been deactivated. To make sure a
widget is really active, you must therefore activate both it and all
its ancestors.
(while widget
(widget-apply widget :activate)
(setq widget (widget-get widget :parent)))
You can check if a widget has been made inactive by examining the
value of the `:inactive' keyword. If this is non-nil, the widget itself
has been deactivated. This is different from using the `:active'
keyword, in that the latter tells you if the widget *or* any of its
ancestors have been deactivated. Do not attempt to set the `:inactive'
keyword directly. Use the `:activate' `:deactivate' keywords instead.
File: widget, Node: Defining New Widgets, Next: Widget Browser, Prev: Widget Properties, Up: Top
Defining New Widgets
====================
You can define specialized widgets with `define-widget'. It allows
you to create a shorthand for more complex widgets, including specifying
component widgets and new default values for the keyword arguments.
- Function: define-widget name class doc &rest args
Define a new widget type named NAME from `class'.
NAME and class should both be symbols, `class' should be one of
the existing widget types.
The third argument DOC is a documentation string for the widget.
After the new widget has been defined, the following two calls will
create identical widgets:
* (widget-create NAME)
* (apply widget-create CLASS ARGS)
Using `define-widget' just stores the definition of the widget type
in the `widget-type' property of NAME, which is what `widget-create'
uses.
If you only want to specify defaults for keywords with no complex
conversions, you can use `identity' as your conversion function.
The following additional keyword arguments are useful when defining
new widgets:
`: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 widget's parent types, most
derived first.
The following predefined functions can be used here:
- Function: widget-types-convert-widget widget
Convert `:args' as widget types in WIDGET.
- Function: widget-value-convert-widget widget
Initialize `:value' from `:args' in WIDGET.
`: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 `:value'
when the widget is created, and on any value set later with
`widget-value-set'.
`: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 external value. The function is called on the present `:value'
when the widget is created, and on any value set later with
`widget-value-set'.
`:create'
Function to create a widget from scratch. The function takes one
argument, a widget type, and creates a widget of that type,
inserts it in the buffer, and returns a widget object.
`:delete'
Function to delete a widget. The function takes one argument, a
widget, and should remove all traces of the widget from the buffer.
`:value-create'
Function to expand the `%v' escape in the format string. It will
be called with the widget as its argument and should insert a
representation of the widget's value in the buffer.
`:value-delete'
Should remove the representation of the widget's 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 have been used.
The following predefined function can be used here:
- Function: widget-children-value-delete widget
Delete all `:children' and `:buttons' in WIDGET.
`:value-get'
Function to extract the value of a widget, as it is displayed in
the buffer.
The following predefined function can be used here:
- Function: widget-value-value-get widget
Return the `:value' property of WIDGET.
`:format-handler'
Function to handle unknown `%' escapes in the format string. It
will be called with the widget and the character that follows the
`%' as arguments. You can set this to allow your widget to handle
non-standard escapes.
You should end up calling `widget-default-format-handler' to handle
unknown escape sequences, which will handle the `%h' and any future
escape sequences, as well as give an error for unknown escapes.
`:action'
Function to handle user initiated events. By default, `:notify'
the parent.
The following predefined function can be used here:
- Function: widget-parent-action widget &optional event
Tell `:parent' of WIDGET to handle the `:action'. Optional
EVENT is the event that triggered the action.
`:prompt-value'
Function to prompt for a value in the minibuffer. The function
should take four arguments, WIDGET, PROMPT, VALUE, and UNBOUND and
should return a value for widget entered by the user. PROMPT is
the prompt to use. VALUE is the default value to use, unless
UNBOUND is non-nil, in which case there is no default value. The
function should read the value using the method most natural for
this widget, and does not have to check that it matches.
If you want to define a new widget from scratch, use the `default'
widget as its base.
- Widget: default
Widget used as a base for other widgets.
It provides most of the functionality that is referred to as "by
default" in this text.
File: widget, Node: Widget Browser, Next: Widget Minor Mode, Prev: Defining New Widgets, Up: Top
Widget Browser
==============
There is a separate package to browse widgets. This is intended to
help programmers who want to examine the content of a widget. The
browser shows the value of each keyword, but uses links for certain
keywords such as `:parent', which avoids printing cyclic structures.
- Command: widget-browse WIDGET
Create a widget browser for WIDGET. When called interactively,
prompt for WIDGET.
- Command: widget-browse-other-window WIDGET
Create a widget browser for WIDGET and show it in another window.
When called interactively, prompt for WIDGET.
- Command: widget-browse-at POS
Create a widget browser for the widget at POS. When called
interactively, use the position of point.
File: widget, Node: Widget Minor Mode, Next: Utilities, Prev: Widget Browser, Up: Top
Widget Minor Mode
=================
There is a minor mode for manipulating widgets in major modes that
don't provide any support for widgets themselves. This is mostly
intended to be useful for programmers doing experiments.
- Command: widget-minor-mode
Toggle minor mode for traversing widgets. With arg, turn widget
mode on if and only if arg is positive.
- Variable: widget-minor-mode-keymap
Keymap used in `widget-minor-mode'.
File: widget, Node: Utilities, Next: Widget Wishlist, Prev: Widget Minor Mode, Up: Top
Utilities.
==========
- Function: widget-prompt-value widget prompt [ value unbound ]
Prompt for a value matching WIDGET, using PROMPT. The current
value is assumed to be VALUE, unless UNBOUND is non-nil.
- Function: widget-get-sibling widget
Get the item which WIDGET is assumed to toggle. This is only
meaningful for radio buttons or checkboxes in a list.
File: widget, Node: Widget Wishlist, Next: Index, Prev: Utilities, Up: Top
Wishlist
========
* It should be possible to add or remove items from a list with `C-k'
and `C-o' (suggested by RMS).
* The `[INS]' and `[DEL]' buttons should be replaced by a single
dash (`-'). The dash should be a button that, when invoked, asks
whether you want to add or delete an item (RMS wanted to git rid of
the ugly buttons, the dash is my idea).
* The `menu-choice' tag should be prettier, something like the
abbreviated menus in Open Look.
* Finish `:tab-order'.
* Make indentation work with glyphs and proportional fonts.
* Add commands to show overview of object and class hierarchies to
the browser.
* Find a way to disable mouse highlight for inactive widgets.
* Find a way to make glyphs look inactive.
* Add `property-list' widget.
* Add `association-list' widget.
* Add `key-binding' widget.
* Add `widget' widget for editing widget specifications.
* Find clean way to implement variable length list. See
`TeX-printer-list' for an explanation.
* `C-h' in `widget-prompt-value' should give type specific help.
* Add a `mailto' widget.
File: widget, Node: Index, Prev: Widget Wishlist, Up: Top
Index
*****
This is an alphabetical listing of all concepts, functions, commands,
variables, and widgets described in this manual.
* Menu:
* action keyword: Defining New Widgets.
* activate a widget: Widget Properties.
* active widget: Widget Properties.
* append-button-args keyword: editable-list.
* args keyword <1>: checklist.
* args keyword <2>: editable-list.
* args keyword <3>: menu-choice.
* args keyword: radio-button-choice.
* atomic sexp widget: atoms.
* basic widgets: Introduction.
* boolean: atoms.
* browse-url-browser-function, and url-link widget: url-link.
* button widgets: User Interface.
* button-args keyword <1>: checklist.
* button-args keyword: radio-button-choice.
* button-face keyword: Basic Types.
* button-prefix keyword: Basic Types.
* button-suffix keyword: Basic Types.
* buttons keyword <1>: checklist.
* buttons keyword <2>: editable-list.
* buttons keyword: radio-button-choice.
* case-fold keyword: menu-choice.
* character: atoms.
* checkbox widget: checkbox.
* checklist widget: checklist.
* children keyword <1>: menu-choice.
* children keyword <2>: editable-list.
* children keyword <3>: checklist.
* children keyword: radio-button-choice.
* choice: composite.
* choice keyword <1>: menu-choice.
* choice keyword: radio-button-choice.
* choice-item widget: choice-item.
* composite sexp widgets: composite.
* cons: composite.
* const: constants.
* constant widgets: constants.
* convert-widget keyword: Defining New Widgets.
* create keyword: Defining New Widgets.
* deactivate a widget: Widget Properties.
* default: Defining New Widgets.
* define-widget: Defining New Widgets.
* defining new widgets: Defining New Widgets.
* delete keyword: Defining New Widgets.
* delete-button-args keyword: editable-list.
* directory: atoms.
* doc keyword: Basic Types.
* editable-field widget: editable-field.
* editable-list widget: editable-list.
* embedded buttons: User Interface.
* entry-format keyword <1>: radio-button-choice.
* entry-format keyword <2>: checklist.
* entry-format keyword: editable-list.
* example of using widgets: Programming Example.
* extra-offset keyword: Basic Types.
* file: atoms.
* format keyword: Basic Types.
* format-handler keyword: Defining New Widgets.
* function: atoms.
* function-item: constants.
* generic sexp widget: generic.
* greedy keyword: checklist.
* group widget: group.
* help-echo keyword: Basic Types.
* inactive widget: Widget Properties.
* indent keyword: Basic Types.
* info-link widget: info-link.
* insert-button-args keyword: editable-list.
* integer: atoms.
* item widget: item.
* keymap keyword: editable-field.
* keyword arguments: Basic Types.
* link widget: link.
* list: composite.
* match keyword: Basic Types.
* menu-choice widget: menu-choice.
* menu-tag keyword: Basic Types.
* menu-tag-get keyword: Basic Types.
* Mouse-2 (on button widgets): User Interface.
* must-match keyword: atoms.
* new widgets: Defining New Widgets.
* notify keyword: Basic Types.
* number: atoms.
* off-glyph keyword: toggle.
* offset keyword: Basic Types.
* on-glyph keyword: toggle.
* option field tag: User Interface.
* parent keyword: Basic Types.
* prompt-value keyword: Defining New Widgets.
* properties of widgets: Widget Properties.
* push-button widget: push-button.
* radio-button-choice widget: radio-button-choice.
* regexp: atoms.
* repeat: composite.
* secret keyword: editable-field.
* set: composite.
* sexp: generic.
* sexp types: Sexp Types.
* sibling-args keyword: Basic Types.
* size keyword: editable-field.
* string: atoms.
* symbol: atoms.
* tab-order keyword: Basic Types.
* tag keyword: Basic Types.
* tag-glyph keyword: Basic Types.
* text widget: text.
* todo: Widget Wishlist.
* toggle widget: toggle.
* url-link widget: url-link.
* utility functions for widgets: Utilities.
* valid-regexp keyword: editable-field.
* validate keyword: Basic Types.
* value keyword: Basic Types.
* value-create keyword: Defining New Widgets.
* value-delete keyword: Defining New Widgets.
* value-face keyword: editable-field.
* value-get keyword: Defining New Widgets.
* value-to-external keyword: Defining New Widgets.
* value-to-internal keyword: Defining New Widgets.
* variable: atoms.
* variable-item: constants.
* vector: composite.
* void keyword: menu-choice.
* widget browser: Widget Browser.
* widget buttons: User Interface.
* widget library, files: Introduction.
* widget library, why use it: Introduction.
* widget minor mode: Widget Minor Mode.
* widget properties: Widget Properties.
* widget-backward: User Interface.
* widget-browse: Widget Browser.
* widget-browse-at: Widget Browser.
* widget-browse-other-window: Widget Browser.
* widget-button-click <1>: User Interface.
* widget-button-click: Setting Up the Buffer.
* widget-button-face: User Interface.
* widget-button-prefix: Basic Types.
* widget-button-press <1>: Setting Up the Buffer.
* widget-button-press: User Interface.
* widget-button-suffix: Basic Types.
* widget-children-validate: Basic Types.
* widget-children-value-delete: Defining New Widgets.
* widget-create: Setting Up the Buffer.
* widget-default-format-handler: Defining New Widgets.
* widget-delete: Setting Up the Buffer.
* widget-field-face: User Interface.
* widget-field-keymap: editable-field.
* widget-forward: User Interface.
* widget-get: Widget Properties.
* widget-get-sibling: Utilities.
* widget-global-map: Setting Up the Buffer.
* widget-glyph-directory: Basic Types.
* widget-glyph-enable: Basic Types.
* widget-insert: Setting Up the Buffer.
* widget-keymap: Setting Up the Buffer.
* widget-link-prefix: link.
* widget-link-suffix: link.
* widget-member: Widget Properties.
* widget-minor-mode: Widget Minor Mode.
* widget-minor-mode-keymap: Widget Minor Mode.
* widget-mouse-face: User Interface.
* widget-parent-action: Defining New Widgets.
* widget-prompt-value: Utilities.
* widget-push-button-prefix: push-button.
* widget-push-button-suffix: push-button.
* widget-put: Widget Properties.
* widget-radio-add-item: radio-button-choice.
* widget-setup: Setting Up the Buffer.
* widget-text-keymap: text.
* widget-type: Widget Properties.
* widget-types-convert-widget: Defining New Widgets.
* widget-value: Widget Properties.
* widget-value-convert-widget: Defining New Widgets.
* widget-value-set: Widget Properties.
* widget-value-value-get: Defining New Widgets.
* widgets, basic types: Introduction.
* widgets, programming example: Programming Example.
Tag Table:
Node: Top1301
Node: Introduction1686
Node: User Interface5160
Node: Programming Example10079
Node: Setting Up the Buffer13377
Node: Basic Types15093
Node: link21365
Node: url-link21874
Node: info-link22181
Node: push-button22466
Node: editable-field23034
Node: text24420
Node: menu-choice24712
Node: radio-button-choice25563
Node: item27125
Node: choice-item27508
Node: toggle28001
Node: checkbox28747
Node: checklist29049
Node: editable-list30485
Node: group31664
Node: Sexp Types31947
Node: constants32294
Node: generic33362
Node: atoms33914
Node: composite35921
Node: Widget Properties38400
Node: Defining New Widgets41454
Node: Widget Browser46761
Node: Widget Minor Mode47614
Node: Utilities48164
Node: Widget Wishlist48643
Node: Index49875
End Tag Table