The Emacs Widget Library
Copyright © 2000–2024 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being “A GNU Manual”, and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License”.
(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”
Table of Contents
- 1 Introduction
- 2 User Interface
- 3 Programming Example
- 4 Widgets Basics
- 5 Setting Up the Buffer
- 6 Working with Widgets
- 7 Widgets and the Buffer
- 8 Widget Gallery
- 8.1 Basic Types
- 8.1.1 The
default
Widget - 8.1.2 The
item
Widget - 8.1.3 The
link
Widget - 8.1.4 The
url-link
Widget - 8.1.5 The
info-link
Widget - 8.1.6 The
function-link
Widget - 8.1.7 The
variable-link
Widget - 8.1.8 The
face-link
Widget - 8.1.9 The
file-link
Widget - 8.1.10 The
emacs-library-link
Widget - 8.1.11 The
emacs-commentary-link
Widget - 8.1.12 The
push-button
Widget - 8.1.13 The
editable-field
Widget - 8.1.14 The
text
Widget - 8.1.15 The
menu-choice
Widget - 8.1.16 The
radio-button-choice
Widget - 8.1.17 The
choice-item
Widget - 8.1.18 The
toggle
Widget - 8.1.19 The
radio-button-toggle
Widget - 8.1.20 The
checkbox
Widget - 8.1.21 The
checklist
Widget - 8.1.22 The
editable-list
Widget - 8.1.23 The
group
Widget - 8.1.24 The
documentation-string
Widget
- 8.1.1 The
- 8.2 Sexp Types
- 8.1 Basic Types
- 9 Defining New Widgets
- 10 Inspecting Widgets
- 11 Widget Minor Mode
- 12 Utilities
- 13 Customization
- 14 Wishlist
- Appendix A GNU Free Documentation License
- Index
Next: User Interface, Previous: The Emacs Widget Library, Up: The Emacs Widget Library [Contents][Index]
1 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, where each option is itself a widget. Only the selected option is 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 are visible in the buffer, with the selected one marked as chosen.
item
A simple constant widget intended to be used in the
menu-choice
andradio-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:
- More complex fields than just editable text are supported.
- You can give the users immediate feedback if they enter invalid data in a text field, and sometimes prevent entering invalid data.
- You can have fixed sized fields, thus allowing multiple fields to be lined up in columns.
- It is simple to query or set the value of a field.
- Editing happens in the buffer, not in the mini-buffer.
- Packages using the library get a uniform look, making them easier for the user to learn.
- 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.
Next: Programming Example, Previous: Introduction, Up: The Emacs Widget Library [Contents][Index]
2 User Interface
A form consists 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 this 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.
2.1 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.
Editable text fields are created by the editable-field
widget.
The :format
keyword is useful for generating the necessary
text; for instance, if you give it a value of "Name: %v "
,
the ‘Name: ’ part will provide the necessary separating text
before the field and the trailing space will provide the
separating text after the field. If you don’t include the
:size
keyword, the field will extend to the end of the
line, and the terminating newline will provide separation after.
The editing text fields are highlighted with the
widget-field-face
face, making them easy to find.
2.2 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 widget-button-press
and widget-button-click
. The
user typically interacts with the buttons with a key, like RET,
or with the mouse buttons.
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 any 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 them 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]’ and ‘[Reset Form]’ buttons
These are explicit buttons made with the
push-button
widget. The main difference from thelink
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
with a distinctive face, like widget-button-face
or
widget-mouse-face
.
Next: Widgets Basics, Previous: User Interface, Up: The Emacs Widget Library [Contents][Index]
3 Programming Example
Here is the code to implement the user interface example (see 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)) (remove-overlays) (widget-insert "Here is some documentation.\n\n") (widget-create 'editable-field :size 13 :format "Name: %v " ; Text after the field! "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-create 'editable-field :format "Address: %v" "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))
Next: Setting Up the Buffer, Previous: Programming Example, Up: The Emacs Widget Library [Contents][Index]
4 Widgets Basics
The Widget Library deals with widgets objects. A widget object has properties whose value may be anything, be it numbers, strings, symbols, functions, etc. Those properties are referred to as keywords and are responsible for the way a widget is represented in a buffer, and control the way a user or a program can interact with it.
The library defines several widget types, and gives you a way to
define new types as well. In addition, widgets can derive from other
types, creating a sort of widget inheritance. In fact, all widgets
defined in the Widget Library share a common parent, the default
widget. In this manual, when we talk about a default behavior, we
usually mean the behavior as defined by this default
widget.
See Widget Gallery, for a description of each defined widget.
Defining a new type that derives from a previous one is not mandatory to create widgets that work very different from a specified type. When creating a widget, you can override any default property, including functions, that control the widget. That is, you can specialize a widget on creation, without having to define it as a new type of widget.
In addition to the function for defining a widget, this library provides functions to create widgets, query and change its properties, respond to user events and destroy them. The following sections describe them.
One important property of a widget is its value. All widgets may have a value, which is stored in a so-called internal format. For the rest of Emacs, the widget presents its value in a so-called external format. Both formats can be equal or different, and each widget is responsible for defining how the conversion between each format should happen.
The value property is an important property for almost all widgets,
and perhaps more important for editable-field
widgets. This
type of widgets allow the user to edit them via the usual editing
commands in Emacs. They can also be edited programmatically.
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 the widget-put
and widget-get
functions. The
property names, as shown, are keywords, so they must begin with a
‘:’.
Next: Working with Widgets, Previous: Widgets Basics, Up: The Emacs Widget Library [Contents][Index]
5 Setting Up the Buffer
To show the widgets in a buffer, you have to create them. Widget creation is actually a two-step process: conversion and creation per se. With simple projects, usually the conversion step isn’t really important, and you only care about widget creation, so feel free to skip the conversion description until you really need to know it.
Widget conversion is the process that involves taking a widget specification and transforming it into a widget object, suitable to be created, queried and manipulated with other widget functions. Widget creation is the process that takes a widget object and actually inserts it in the buffer.
The simplest function to create a widget is widget-create
, which
gets a widget specification and returns a widget object.
- Function: widget-create type [ keyword argument ]… args ¶
Create and return a widget of type type, converting it.
type is a symbol that specifies a widget type. keyword may be one of the properties supported by the widget type, and argument specify the value for that property. These keyword arguments can be used to overwrite the keyword arguments that are part of type by default, as well as to provide other properties not present in type by default. args holds additional information for the creation of type and each widget type is responsible for handling that information in a specific way.
The syntax for the type argument is described in Widget Gallery, and in more detail in every widget where it’s relevant.
There are other functions for creating widgets, useful when you work with composite widgets. That is, widgets that are part of other widgets.
- Function: widget-create-child-and-convert parent type &rest args ¶
Create a widget of type type as a child of parent.
Before creating it, converts type using the keyword arguments provided in args. Adds the
:indent
property, unless it is already present, and sets it to the sum of the values of::indent
and:offset
from parent and:extra-offset
from type.Returns a widget object, with the property
:parent
set to PARENT.
- Function: widget-create-child parent type ¶
Create a widget of type type as a child of parent.
This function is like
widget-create-child-and-convert
but it doesn’t convert type, so it expects an already converted widget.
- Function: widget-create-child-value parent type value ¶
Create a widget of type type as a child of parent with value value.
This function is like
widget-create-child
, but it lets you specify a value for the widget.Converts value to the internal format, as specified by type, and stores it into the
:value
property of type. That means, value should be in the external format, as specified by type.
All these creating functions described here use the function stored in
the :create
property. So, to modify the creation logic for a
widget, you can provide a different :create
function.
When you’re done creating widgets and you’re ready for the user to
interact with the buffer, use the function widget-setup
.
- Function: widget-setup ¶
Setup the current buffer, so that editable widgets can be edited.
This should be called after creating all the widgets and before allowing the user to edit them.
As mentioned, all these functions return a widget object. That widget object can be queried and manipulated with widget functions that take widgets as arguments, until deleting it with the widgets functions available to delete widgets. Even if you don’t save the returned widget object, you still can interact programmatically with the widget. See Working with Widgets.
- Function: widget-delete widget ¶
Delete the widget widget and remove it from the buffer.
- Function: widget-children-value-delete widget ¶
Delete all children and buttons in widget widget.
This function does not delete widget itself, only the widgets stored in the
:children
and:buttons
properties. It also sets those properties tonil
.
As with the creation mechanism, the function stored in :delete
controls the deletion mechanism for a widget.
Additionally, the library provides a way to make a copy of a widget.
- Function: widget-copy widget ¶
Makes a copy of widget widget and returns it.
It uses the function stored in the
:copy
property of widget and returns the widget that that function returns.
As discussed, there is a conversion step when creating a widget. To
do the conversion without actually creating the widget, you can use
the widget-convert
function.
- Function: widget-convert type &rest args ¶
Convert type to a widget object, using keyword arguments args.
Returns a widget object, suitable for creation. It calls the function stored in the
:convert-widget
property, after putting into the:args
property the arguments that the widget in question needs. If type has a:value
property, either originally or after doing the conversion, this function converts the value stored in:value
to the internal format, and stores it into:value
.
Apart from only creating widgets in the buffer, It’s useful to have
plain text. For inserting text, the recommended way is with the
widget-insert
function.
- Function: widget-insert &rest args ¶
Insert args, either strings or characters, at point.
Uses
insert
to perform the insertion, passing args as argument. See Insertion in the Emacs Lisp Reference Manual, for more information about args.The resulting text will be read-only.
Next: Widgets and the Buffer, Previous: Setting Up the Buffer, Up: The Emacs Widget Library [Contents][Index]
6 Working with Widgets
This section covers the more important functions needed to query and manipulate widgets in a generic way. Widgets may have additional functions for interacting with them, those are described in the description for each widget. See Widget Gallery.
- Function: widgetp widget ¶
Non-
nil
if widget is a widget.
- Function: widget-type widget ¶
Return the type of widget widget, a symbol.
This function is useful to find out which kind of widget widget represents, i.e., the name of the widget type when the widget was created.
- Function: widget-member widget property ¶
Non-
nil
if widget widget has a value (evennil
) for property property.
- Function: widget-get widget property ¶
For widget widget, return the value of the property property.
property should be a keyword, and the value is what was last set by
widget-put
for property.
- Function: widget-put widget property value ¶
For widget widget, set the property property to value. property should be a keyword, while value can be anything.
- Function: widget-at &optional pos ¶
Return the widget at position pos, or at point if pos is
nil
.
- Function: widget-field-at pos ¶
Return the widget field at position POS, or
nil
if there is none.
- Function: widget-apply widget property &rest args ¶
Apply the function stored in property to widget, passing args as additional arguments to the function.
Returns the result of that function call.
- Function: widget-value widget ¶
Return the current value contained in widget.
Note that the value returned by this function might differ from what’s stored in the
:value
property of widget. This is because this function extracts the current value of widget from the buffer, taking editions into account.The value returned is in the external format, after getting it with the
:value-get
function.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.
Converts value to the internal format, and then sets it by applying the
:value-set
function.It is an error to call this function with an invalid value, that is, a value that widget cannot represent.
- Function: widget-default-get widget ¶
Return the default external value of widget widget.
The default value is the one stored in
:value
or the result of applying the:default-get
function to the arguments of widget, as stored in:args
. A value ofnil
is ignored by default, so in order for a widget to respectnil
as a value, it has to override the:default-get
function.
- Function: widget-type-default-get widget ¶
Convert the
:type
attribute in widget and return its default value.
- Function: widget-child-value-get widget ¶
Return the value of the first member of
:children
in widget.
- Function: widget-child-value-inline widget ¶
Return the inline value of the first member of
:children
in widget.The inline value is whatever the function stored in
:value-inline
returns.
- Function: widget-type-value-create widget ¶
Create a child widget for widget, of type stored in
:type
.Creates the child widget taking the value from the
:value
property and stores the newly created widget in the:children
property of widget.The value stored in
:type
should be an unconverted widget type.
- Function: widget-value-convert-widget widget ¶
Initializes the
:value
property of widget from:args
.Sets
:args
tonil
and returns the modified widget widget.
- Function: widget-value-value-get widget ¶
Return the value stored in
:value
for widget widget.This is different to getting the current value for widget with
widget-value
, since that function extracts the value from the buffer.
- Function: widget-apply-action widget &optional event ¶
Apply the function stored in
:action
to widget, in response to event.It is an error to call this function with an inactive widget.
- Function: widget-parent-action widget &optional event ¶
Tell
:parent
of widget to handle event.Optional event is the event that triggered the action.
- Function: widget-child-validate widget ¶
Check that the first member of
:children
in widget is valid.To be valid means that the widget value passes the checks that the function stored in
:validate
makes.
- Function: widget-children-validate widget ¶
Check that all
:children
in widget are valid.Returns
nil
on success, or the first child that isn’t valid.
- Function: widget-type-match widget value ¶
Return non-
nil
if VALUE matches the value for the:type
widget.As with the other type functions, the widget stored in
:type
should be an unconverted widget.
- Function: widget-types-copy widget ¶
Copy the
:args
value in widget and store them in:args
.Makes the copies by calling
widget-copy
on each element present in:args
. Returns the modified widget widget.
- Function: widget-types-convert-widget widget ¶
Convert the
:args
value in widget and store them inargs
.Returns the modified widget widget.
Next: Widget Gallery, Previous: Working with Widgets, Up: The Emacs Widget Library [Contents][Index]
7 Widgets and the Buffer
This chapter describes commands that are specific to buffers that contain widgets.
- Variable: widget-keymap ¶
Keymap containing useful bindings for buffers containing widgets.
Binds TAB to
widget-forward
and both S-TAB and M-TAB towidget-backward
. It also binds RET towidget-button-press
and both down-mouse-1 and down-mouse-2 towidget-button-click
.
There’s also a keymap for events that the Widget library doesn’t need to handle.
- Variable: widget-global-map ¶
Keymap used by
widget-button-press
andwidget-button-click
when not on a button. By default this isglobal-map
.
In addition to these two keymaps, each widget might define a keymap of its own, active when events happen at that widget.
The following navigation commands are available:
- TAB
- Command: widget-forward &optional count ¶
Move point count buttons or editing fields forward.
- M-TAB
- S-TAB
- Command: widget-backward &optional count ¶
Move point count buttons or editing fields backward.
When editing an editable-field
widget, the following commands
are available:
- C-e
- Command: widget-end-of-line ¶
Move point to the end of field or end of line, whichever is first.
- C-k
- Command: widget-kill-line ¶
Kill to end of field or end of line, whichever is first.
- M-TAB
- C-M-i
- Command: widget-complete ¶
Complete the content of the editable field at point.
- C-m
- RET
- Command: widget-field-activate ¶
Invoke the editable field at point.
The following two commands can execute the action associated with a button widget (e.g., a radio button or checkbox):
- C-m
Invoke the button at pos, defaulting to point.
Invocation means to run the function stored in the
:action
property.If point is not located on a button, invoke the binding in
widget-global-map
(by default the global map).
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).In case the mouse-click is on a widget, calls the function stored in the
:mouse-down-action
property.
Next: Defining New Widgets, Previous: Widgets and the Buffer, Up: The Emacs Widget Library [Contents][Index]
8 Widget Gallery
All widgets can be created from a type specification. The general syntax of a type specification is:
name ::= (name [keyword argument]... args) | name
Where name is a widget name, as defined with
define-widget
, keyword is the name of a property and
argument is the value for that property, and args are
interpreted in a widget specific way. See Defining New Widgets.
Next: Sexp Types, Up: Widget Gallery [Contents][Index]
8.1 Basic Types
- The
default
Widget - The
item
Widget - The
link
Widget - The
url-link
Widget - The
info-link
Widget - The
function-link
Widget - The
variable-link
Widget - The
face-link
Widget - The
file-link
Widget - The
emacs-library-link
Widget - The
emacs-commentary-link
Widget - The
push-button
Widget - The
editable-field
Widget - The
text
Widget - The
menu-choice
Widget - The
radio-button-choice
Widget - The
choice-item
Widget - The
toggle
Widget - The
radio-button-toggle
Widget - The
checkbox
Widget - The
checklist
Widget - The
editable-list
Widget - The
group
Widget - The
documentation-string
Widget
Next: The item
Widget, Up: Basic Types [Contents][Index]
8.1.1 The default
Widget
The most basic widget in the Widget Library is the default widget. It provides the basic behavior for all other widgets, and all its properties are present by default in derived widgets. You’re seldom (if ever) going to effectively create a default widget, but here we describe its properties and behavior, so that we can describe other widgets only by mentioning the properties and behavior those other widgets specialize.
- 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. If you want to define a new widget from scratch, use the
default
widget as its base.
The following keyword arguments apply to all widgets:
: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.
By default, it inserts the widget at point, using the format provided in the
:format
property.:delete
Function to delete a widget.
The function should take one argument, a widget, and should remove all traces of the widget from the buffer.
The default value is:
- Function: widget-default-delete widget ¶
Remove widget from the buffer. Delete all
:children
and:buttons
in widget.
In most cases you should not change this value, but instead use
:value-delete
to make any additional cleanup.:value
The initial value for widgets of this type.
Typically, a widget represents its value in two formats: external and internal. The external format is the value as the rest of Emacs sees it, and the internal format is a representation that the widget defines and uses in a widget specific way.
Both formats might be the same for certain widgets and might differ for others, and there is no guarantee about which format the value stored in the
:value
property has. However, when creating a widget or defining a new one (see Defining New Widgets), the:value
should be in the external format.: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 withwidget-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 value in the external format.
: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
A function that 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 these are not listed in
:children
or:buttons
.By default, it’s a no-op.
:value-get
Function to extract the value of a widget, as it is displayed in the buffer.
:value-set
Function that takes a widget and a value as arguments, and recreates it.
The value must already be in the internal format for widget. By default, it deletes the widget with the
:delete
function and creates it again with the:create
function.:value-inline
Function that takes a widget and returns its value, inlined.
Inlined means that if the widget is not inline (i.e., its
:inline
property isnil
), the return value is wrapped in a list.:default-get
Function that takes a widget and returns its default value.
By default, it just returns the value stored in
:value
.: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.- ‘%{’
- ‘%}’
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 theprinc
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
Strings used as prefix and suffix for widgets that are buttons.
By default, the values are
widget-button-prefix
andwidget-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
orwidget-backward
or move the mouse over it (using the standardhelp-echo
mechanism).The value is either a string to display, or a function of one argument, the widget. If a function, it should return a string to display, or a form that evaluates to such a string.
:follow-link
Specifies how to interpret a mouse-1 click on the widget. See Defining Clickable Text in the Emacs Lisp Reference Manual.
:indent
An integer indicating the absolute number of spaces to indent children of this widget. Its value might be
nil
too, which corresponds to a value of 0.The default
:create
functions and the functions that create the value per se use this property as a rudimentary layout mechanism for the widgets.: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.
:menu-tag
Tag used in the menu when the widget is used as an option in a
menu-choice
widget.:menu-tag-get
Function that takes a widget and returns 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 theprinc
representation of the:value
property if not.:match
Should be a function called with two arguments, the widget and an external value, and should return 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.By default, it always returns
nil
.:tab-order
Specify the order in which widgets are traversed with
widget-forward
orwidget-backward
. This is only partially implemented.- Widgets with tabbing order
-1
are ignored. - (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. - When on a widget with no tabbing order specified, go to the next widget
in the buffer with a positive tabbing order, or
nil
- Widgets with tabbing order
:parent
The parent of a nested widget (e.g., a
menu-choice
item or an element of aeditable-list
widget).:sibling-args
This keyword is only used for members of a
radio-button-choice
orchecklist
. The value should be a list of extra keyword arguments, which will be used when creating theradio-button
orcheckbox
associated with this item.:completions-function
Function that takes a widget and returns completion data for that widget, like
completion-at-point-functions
would. See Completion in the Emacs Lisp Reference Manual. It’s used byeditable-field
widgets to provide completions.By default, it looks into the property
:completions
, which should be a completion table. If:completions
isnil
, then it calls the function stored either in the:complete
or:complete-function
property.:format-handler
Function to handle unknown ‘%’ escapes in the format string.
It takes a widget and the character that follows the ‘%’ as arguments. You can set this to allow your widget to handle non-standard escapes in your own specialized widgets.
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.:button-face-get
Function to return the face used to fontify a widget button.
Takes a widget and returns an appropriate face for the widget. By default, it either returns the face stored in the
:button-face
property, or calls the:button-face-get
function from the parent of the widget, if it has one.:mouse-face-get
Function to return the face used to fontify a widget when the mouse pointer hovers over it.
Takes a widget and returns an appropriate face. By default, it either returns the face stored in the
:mouse-face
property, or calls the:button-face-get
function from the parent of the widget, if it has one.:copy
Function to deep copy a widget type.
It takes a shallow copy of the widget type as an argument (made by
copy-sequence
), and returns a deep copy. The purpose of this is to avoid having different instances of combined widgets share nested attributes.Its value by default is
identity
.:active
Function that takes a widget and returns
t
if it is active.A widget might be effectively always active, if its
:always-active
property ist
.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
functions instead.:activate
Function that takes a widget and makes it active for user modifications.
:deactivate
Function that takes a widget and makes it inactive for user modifications.
:action
Function that takes a widget and optionally an event, and handles a user initiated event.
By default, uses the
:notify
function to notify the widget’s parent about the event.:mouse-down-action
Function that takes a widget and optionally an event, and handles a mouse click on the widget.
By default, it does nothing.
: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.
By default, it passes the notification to the widget’s parent.
:prompt-value
Function to prompt for a value in the minibuffer.
The function should take four arguments, a widget, a prompt (a string), a value and a boolean, and should return a value for the widget, entered by the user.
The prompt is the prompt to use. The value is the default value to use, unless the fourtha argument 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.
Next: The link
Widget, Previous: The default
Widget, Up: Basic Types [Contents][Index]
8.1.2 The item
Widget
Syntax:
type ::= (item [keyword argument]... value)
A useful widget that holds a constant value, and can be included in
other widgets. Its super is the default
widget.
As can be seen in the syntax, the item
widget is one of the
widget that handles the args argument to widget-create
in
a specific way. If present, value is used to initialize the
:value
property. When created, it inserts the value as a
string in the buffer.
Example:
(widget-create 'item :tag "Today is" :format "%t: %v\n" (format-time-string "%d-%m-%Y"))
By default, it has the following properties:
:convert-widget
The function that allows it to handle value.
:value-create
Prints the representation of
:value
in the buffer.:value-get
Returns the value stored in
:value
.:match
A value matches the
item
widget if it’sequal
to its:value
.:match-inline
Inline values match the
item
widget if:value
is a sublist of values.:action
The
item
widget notifies itself of an event.:format
By default, the
item
widget inserts its tag in the buffer.
Next: The url-link
Widget, Previous: The item
Widget, Up: Basic Types [Contents][Index]
8.1.3 The link
Widget
Syntax:
type ::= (link [keyword argument]... [ value ])
A widget to represent an embedded link. Its super is the item
widget.
The value, if present, is used to initialize the :value
property. The value should be a string, which will be inserted in the
buffer.
Example:
(widget-create 'link :button-prefix "" :button-suffix "" :tag "Mail yourself" :action #'(lambda (widget &optional _event) (compose-mail-other-window (widget-value widget))) user-mail-address)
By default, it has the following properties:
:button-prefix
The value of
widget-link-prefix
.:button-suffix
The value of
widget-link-suffix
.:keymap
A custom keymap for the link widget, so that it can respond to mouse clicks.
:follow-link
This property allows the link to respect the value of
mouse-1-click-follows-link
. See Clickable Text in the Emacs Lisp Reference Manual.:format
Buttonizes the link, to make it clickable.
If you override this property, you should make sure to provide the ‘%[’ and ‘%]’ escape sequences, so that the link is clickable.
By default the link will be shown in brackets.
Next: The info-link
Widget, Previous: The link
Widget, Up: Basic Types [Contents][Index]
8.1.4 The url-link
Widget
Syntax:
type ::= (url-link [keyword argument]... url)
A widget to represent a link to a web page. Its super is the
link
widget.
It overrides the :action
property to open up the url
specified.
Example:
(widget-create 'url-link :button-prefix "" :button-suffix "" ;; Return appropriate face. :button-face-get (lambda (widget) (if (widget-get widget :visited) 'link-visited 'link)) :format "%[%t%]" :tag "Browse this manual" :action (lambda (widget &optional _event) (widget-put widget :visited t) ;; Takes care of redrawing the widget. (widget-value-set widget (widget-value widget)) ;; And then call the original function. (widget-url-link-action widget)) "https://www.gnu.org/software/emacs/manual/html_mono/widget.html")
Next: The function-link
Widget, Previous: The url-link
Widget, Up: Basic Types [Contents][Index]
8.1.5 The info-link
Widget
Syntax:
type ::= (info-link [keyword argument]... address)
A widget to represent a link to an info file. Its super is the
link
widget.
It overrides the :action
property, to a function to start the
built-in Info reader on address, when invoked.
Example:
(widget-create 'info-link :button-prefix "" :button-suffix "" :tag "Browse this manual" "(widget) info-link")))
Next: The variable-link
Widget, Previous: The info-link
Widget, Up: Basic Types [Contents][Index]
8.1.6 The function-link
Widget
Syntax:
type ::= (function-link [keyword argument]... function)
A widget to represent a link to an Emacs function. Its super is the
link
widget.
It overrides the :action
property, to a function to describe
function.
Example:
(widget-create 'function-link :button-prefix "" :button-suffix "" :tag "Describe the function that gets called" #'widget-function-link-action)
Next: The face-link
Widget, Previous: The function-link
Widget, Up: Basic Types [Contents][Index]
8.1.7 The variable-link
Widget
Syntax:
type ::= (variable-link [keyword argument]... var)
A widget to represent a link to an Emacs variable. Its super is the
link
widget.
It overrides the :action
property, to a function to describe
var.
Example:
(widget-create 'variable-link :button-prefix "" :button-suffix "" :tag "What setting controls button-prefix?" 'widget-button-prefix)
Next: The file-link
Widget, Previous: The variable-link
Widget, Up: Basic Types [Contents][Index]
8.1.8 The face-link
Widget
Syntax:
type ::= (face-link [keyword argument]... face)
A widget to represent a link to an Emacs face. Its super is the
link
widget.
It overrides the :action
property, to a function to describe
face.
Example:
(widget-create 'face-link :button-prefix "" :button-suffix "" :tag "Which face is this one?" 'widget-button)
Next: The emacs-library-link
Widget, Previous: The face-link
Widget, Up: Basic Types [Contents][Index]
8.1.9 The file-link
Widget
Syntax:
type ::= (file-link [keyword argument]... file)
A widget to represent a link to a file. Its super is the
link
widget.
It overrides the :action
property, to a function to find the file
file.
Example:
(let ((elisp-files (directory-files user-emacs-directory t ".el$"))) (dolist (file elisp-files) (widget-create 'file-link :button-prefix "" :button-suffix "" file) (widget-insert "\n")))
Next: The emacs-commentary-link
Widget, Previous: The file-link
Widget, Up: Basic Types [Contents][Index]
8.1.10 The emacs-library-link
Widget
Syntax:
type ::= (emacs-library-link [keyword argument]... file)
A widget to represent a link to an Emacs Lisp file. Its super is the
link
widget.
It overrides the :action
property, to a function to find the file
file.
Example:
(widget-create 'emacs-library-link :button-prefix "" :button-suffix "" :tag "Show yourself, Widget Library!" "wid-edit.el")
Next: The push-button
Widget, Previous: The emacs-library-link
Widget, Up: Basic Types [Contents][Index]
8.1.11 The emacs-commentary-link
Widget
Syntax:
type ::= (emacs-commentary-link [keyword argument]... file)
A widget to represent a link to the Comment section of an Emacs Lisp
file. Its super is the link
widget.
It overrides the :action
property, to a function to find the file
file and put point in the Comment section.
Example:
(widget-create 'emacs-commentary-link :button-prefix "" :button-suffix "" :tag "Check our good friend Customize" "cus-edit.el")
Next: The editable-field
Widget, Previous: The emacs-commentary-link
Widget, Up: Basic Types [Contents][Index]
8.1.12 The push-button
Widget
Syntax:
type ::= (push-button [keyword argument]... [ value ])
A widget that acts as a pushable button. Its super is the item
widget.
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, it has the following properties:
:button-prefix
The empty string.
:button-suffix
The empty string.
:value-create
Inserts a representation of the “on” and “off” states for the push button.
The representation might be an image, stored in the
:tag-glyph
property, or text. If it is text, it might be the value of the:tag
property, or the:value
of the widget, surrounded withwidget-push-button-prefix
andwidget-push-button-suffix
. See Customization.:format
Buttonizes the widget, to make it clickable.
Next: The text
Widget, Previous: The push-button
Widget, Up: Basic Types [Contents][Index]
8.1.13 The editable-field
Widget
Syntax:
type ::= (editable-field [keyword argument]... [ value ])
A widget that can be edited by the user. Its super is the
default
widget.
The value, if present, is used to initialize the :value
property. The value should be a string, which will be inserted in the
field. If not present, :value
is the empty string.
Warning: In an editable-field
widget, the editable
field must not be adjacent to another widget—that won’t work.
You must put some text in between. Either make this text part of
the editable-field
widget itself, or insert it with
widget-insert
.
This widget either overrides or adds the following properties:
:convert-widget
Just like the
item
widget, this function allows it to initialize:value
from value.:keymap
Keymap used in the editable field.
The default value is
widget-field-keymap
, which allows the user 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
.:format
By default, it specifies to insert only the widget’s value.
Warning: In an
editable-field
widget, the ‘%v’ escape must be preceded by some other text in the:format
string (if specified).: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 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 isnil
, 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.:validate
Returns
nil
if the current value of the widget matches the:valid-regexp
value.:prompt-internal
A function to read a value for widget, used by the
:prompt-value
function.:prompt-history
A variable that holds the history of field minibuffer edits.
:prompt-value
A function that uses the
:prompt-internal
function and the:prompt-history
value to prompt for a string, and return the user response in the external format.:action
When invoked, moves point to the next field.
:value-create
Function that takes care of creating the widget, respecting its
:size
and:value
.:value-set
Function to use to modify programmatically the current value of the widget.
:value-delete
Function that removes the widget so it cannot be edited anymore.
:value-get
Function to return the current text in the widget.
It takes an optional argument, no-truncate. If no-truncate is nil, truncates trailing spaces.
:match
Function that makes the widget match any string value.
Next: The menu-choice
Widget, Previous: The editable-field
Widget, Up: Basic Types [Contents][Index]
8.1.14 The text
Widget
Syntax:
type ::= (text [keyword argument]... [ value ])
A widget just like the editable-field
widget, but intended for
multiline text fields. Its super is the editable-field
widget.
It overrides the following properties:
:format
By default, prints a tag and the value.
:keymap
The default is
widget-text-keymap
, which does not rebind the RET key.
Next: The choice-item
Widget, Previous: The menu-choice
Widget, Up: Basic Types [Contents][Index]
8.1.16 The radio-button-choice
Widget
Syntax:
type ::= (radio-button-choice [keyword argument]... type ... )
A widget to represent a choice from multiple options. Its super is
the default
widget.
The component types specify the choices, with one radio button for each. The widget’s value will be that of the chosen type argument.
It overrides the following properties:
:convert-widget
As other composite widgets, a function that takes care of converting each available choice.
:copy
A function to copy each available choice.
:action
A function that checks if any radio button was pressed and activates the pressed one, possibly deactivating an old one. Then, it notifies itself.
: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 ‘%’.
:format
By default, it inserts its value.
: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.
:value-create
A function to insert all available choices.
:value-get
Returns the value for the chosen widget.
:value-set
A function to set the value to one of its available options.
:value-inline
A function that returns the inline value of the child widget.
:offset
By default, this widget has an offset of 4.
:validate
The widget validates if the current value is valid for one of its children.
:match
This widget matches any value that matches at least one of the specified type arguments.
:match-inline
Like the
:match
function, but taking into account inline values.
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
.
Next: The toggle
Widget, Previous: The radio-button-choice
Widget, Up: Basic Types [Contents][Index]
8.1.17 The choice-item
Widget
Syntax:
item ::= (choice-item [keyword argument]... value)
A widget to represent a choice in a menu-choice
widget. Its
super is the item
widget.
The value, if present, is used to initialize the :value
property.
It overrides the following properties:
:action
Activating the button of a
choice-item
is equivalent to activating the parent widget.:format
By default, it buttonizes the tag (i.e., its value) and adds a newline character at the end of the widget.
Next: The radio-button-toggle
Widget, Previous: The choice-item
Widget, Up: Basic Types [Contents][Index]
8.1.18 The toggle
Widget
Syntax:
type ::= (toggle [keyword argument]...)
A widget that can toggle between two states. Its super is the
item
widget.
The widget has two possible states, ‘on’ and ‘off’, which
correspond to a t
or nil
value, respectively.
Example:
(widget-insert "Press the button to activate/deactivate the field: ") (widget-create 'toggle :notify (lambda (widget &rest _ignored) (widget-apply widget-example-field (if (widget-value widget) :activate :deactivate)))) (widget-insert "\n")
(setq widget-example-field (widget-create 'editable-field :deactivate (lambda (widget) (widget-specify-inactive widget (widget-field-start widget) (widget-get widget :to))))) (widget-apply widget-example-field :deactivate)))
It either overrides or adds the following properties:
:format
By default, it buttonizes the value and adds a newline at the end of the widget.
: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.
:value-create
A function for creating the widget’s value, according to its ‘:on’ or ‘:off’ state.
:action
Function to toggle the state of the widget. After toggling, it notifies itself.
:match
This widget matches anything.
Next: The checkbox
Widget, Previous: The toggle
Widget, Up: Basic Types [Contents][Index]
8.1.19 The radio-button-toggle
Widget
Syntax:
type ::= (radio-button-toggle [keyword argument]...)
A toggle to use in the radio
widget.
It overrides the following properties:
:button-prefix
The empty string.
:button-suffix
The empty string.
:on
The string “(*)”, to represent the ‘on’ state.
:off
The string “( )”, to represent the ‘off’ state.
:on-glyph
The name of an image to represent the ‘on’ state.
:off-glpyh
The name of an image to represent the ‘off’ state.
:format
By default, it buttonizes its value.
:notify
A function to notify its parent.
Next: The checklist
Widget, Previous: The radio-button-toggle
Widget, Up: Basic Types [Contents][Index]
8.1.20 The checkbox
Widget
Syntax:
type ::= (checkbox [keyword argument]...)
A widget to represent a toggle widget, with a checkbox. Its super is
the toggle
widget.
This widget has two possible states, ‘selected’ and
‘unselected’, which corresponds to a t
or nil
value, respectively.
It either overrides or adds the following properties:
:button-prefix
The empty string.
:button-suffix
The empty string.
:format
By default, buttonizes the value.
:on
By default, the string “[X]”.
:off
By default, the string “[ ]”.
:on-glyph
The name of the image to use when the state is ‘on’.
:off-glyph
The name of the image to use when the state is ‘off’.
:action
A function that toggles the checkbox, notifies the parents and in the ‘on’ state, activates its siblings.
Next: The editable-list
Widget, Previous: The checkbox
Widget, Up: Basic Types [Contents][Index]
8.1.21 The checklist
Widget
Syntax:
type ::= (checklist [keyword argument]... type ... )
A widget to represent a multiplice choice. Its super is the
default
widget.
The type arguments represent each checklist item. The widget’s value will be a list containing the values of all checked type arguments.
Example:
(widget-create 'checklist :notify (lambda (widget child &optional _event) (funcall (widget-value (widget-get-sibling child)) 'toggle)) :value (list 'tool-bar-mode 'menu-bar-mode) '(item :tag "Tool-bar" tool-bar-mode) '(item :tag "Menu-bar" menu-bar-mode))))
It either overrides or adds the following properties:
:convert-widget
As other composite widgets, a function that takes care of converting each checklist item.
:copy
A function to copy each checklist item.
:format
By default, it inserts its value.
: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 ‘%’.
: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.
:value-create
The function that takes care of inserting all values.
:value-get
A function that returns all values of selected items.
:validate
A function that ensures all selected children are valid.
:match
The checklist widget will match a list whose elements all match at least one of the specified type arguments.
:match-inline
Like the
:match
function, but taking into account the:inline
property.: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.
Next: The group
Widget, Previous: The checklist
Widget, Up: Basic Types [Contents][Index]
8.1.22 The editable-list
Widget
Syntax:
type ::= (editable-list [keyword argument]... type)
A widget that can hold a variable list of widgets of the same type,
represented by type. Its super is the default
widget.
It either overrides or adds the following properties:
:convert-widget
As other composite widgets, a function that takes care of converting each type in type.
:copy
A function to copy the types given in type.
: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, a widget of type
insert-button
.- ‘%d’
Insert the [DEL] button, a widget of type
delete-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.
:format
By default, insert its value and at the and adds an insert button.
This is useful so that new elements can be added to the list upon user request.
:format-handler
A function that recognize the escape for inserting an insert button.
:offset
By default, this widget has an offset of 12.
:children
The widgets representing the elements of the list.
:args
List whose CAR is the type of the list elements.
:insert-before
Function to insert a new widget as a child of the
editable-list
widget.This function inserts a recently deleted child, if there is one. That is useful, so that the user can move elements in a list easily. If there is not a recently deleted child, it inserts a child with its default value.
:delete-at
Function to delete a child from the widget, and store it into the
:last-deleted
list, so that it can be reinserted when the:insert-before
function executes.:value-create
The function that takes care of inserting all values.
:value-get
Function that returns a list with the value of the child widgets.
:validate
This widget validates if all children validate.
:match
To match, the value must be a list and all the list members must match the specified type.
:match-inline
Like the
:match
function, but taking into account inline values and widgets.
Next: The documentation-string
Widget, Previous: The editable-list
Widget, Up: Basic Types [Contents][Index]
8.1.23 The group
Widget
Syntax:
type ::= (group [keyword argument]... type...)
A widget to group other widgets. Its super is the default
widget.
Its value is a list, with one member for each type.
It overrides the following properties:
:convert-widget
As other composite widgets, a function that takes care of converting each widget in type.
:copy
A function to copy the types given in type.
:format
By default, displays a newline character and its value.
:value-create
A function to create each of its components.
:value-get
The same function used by the
editable-list
widget.:default-get
A function that returns a list whose members are the default values of each widget it groups.
:validate
This widget validates if all of its children validate.
:match
This widget matches a value that matches each of its components.
:match-inline
As
:match
, but taking into account widgets and values that are inline.
Previous: The group
Widget, Up: Basic Types [Contents][Index]
8.1.24 The documentation-string
Widget
Syntax:
type ::= (documentation-string [keyword argument]... value)
A widget to represent a documentation string. Its super is the
item
widget.
It either overrides or adds the following properties:
:format
By default, insert its value.
:value-create
Function to insert a documentation string, possibly hiding part of the documentation if its large.
To show or hide the rest of the documentation, uses a
visibility
widget.:action
Function to toggle showing the documentation upon an event.
:visibility-widget
A symbol, the type of the widget to use for the visibility widget.
This is, by default, the symbol
visibility
.
Previous: Basic Types, Up: Widget Gallery [Contents][Index]
8.2 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.
Next: Generic Sexp Widget, Up: Sexp Types [Contents][Index]
8.2.1 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 ])
Its super is the item
widget. 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.
It overrides the
:prompt-value
function, to avoid prompting and just return the widget’s value.
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, respectively. The major
difference from the const
widget is that they will allow the
user to see the variable or function documentation for the symbol.
This is accomplished via using the ‘%h’ format escape, and adding
an appropriate :documentation-property
function for each widget.
- Widget: variable-item ¶
An immutable symbol that is bound as a variable.
- Widget: function-item ¶
An immutable symbol that is bound as a function.
Next: Atomic Sexp Widgets, Previous: The Constant Widgets, Up: Sexp Types [Contents][Index]
8.2.2 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 widget represents an editable field that’s useful to edit any valid s-expression.
The
sexp
widget takes the same keyword arguments as theeditable-field
widget. See Theeditable-field
Widget.Its default value is
nil
.
- Widget: restricted-sexp ¶
A widget to edit Lisp expressions restricted to certain values or types. Its super is the
sexp
widget.It works just like the sexp widget, but it overrides the
:match
function to match for certain values. To use this widget, either you must define a:match
function or give a:match-alternatives
property. The:match-alternatives
property holds a list of predicate functions to call when checking if a given value matches the widget. Each predicate function will be called with one argument, the value to be matched, and should return non-nil
on success.As an example, the
integer
widget overrides:match-alternatives
to(integerp)
.
Next: Composite Sexp Widgets, Previous: Generic Sexp Widget, Up: Sexp Types [Contents][Index]
8.2.3 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 widgets described in this section.
The syntax for all the atoms is:
type ::= (construct [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, for example, the string widget can only be initialized with a
string.
All the atom widgets take the same keyword arguments as the
editable-field
widget. See The editable-field
Widget.
- Widget: string ¶
An editable field widget that can represent any Lisp string.
It offers completion via the ispell library and the
:complete
property.
- Widget: regexp ¶
An editable field widget that can represent a regular expression.
Overrides the
:match
and the:validate
properties to check that the value is a valid regexp.
- Widget: character ¶
An editable field widget that can represent a character.
The character widget represents some characters (like the newline character) in a special manner, to make it easier for the user to see what’s the content of the character field.
- Widget: file ¶
A widget for editing file names.
Keywords:
:completions
Offers file name completion to the user.
:prompt-value
A function to read a file name from the minibuffer.
:must-match
If this is set to non-
nil
, only existing file names are allowed when prompting for a value in the minibuffer.:match
The widget matches if the value is a string, and the file whose name is that string is an existing file, or if
:must-match
isnil
.:validate
The widget is valid if its value matches.
- Widget: directory ¶
A widget for editing directory names.
Its super is the
file
widget, and it overrides the:completions
property, to offer completions only for directories.
- Widget: symbol ¶
A widget for editing a Lisp symbol.
Its value by default is
nil
.
- Widget: function ¶
A widget for editing a lambda expression, or a function name, offering completion. Its super is the
restricted-sexp
widget.
- Widget: variable ¶
A widget for editing variable names, offering completion. Its super is the
symbol
widget.
- Widget: integer ¶
A widget for editing integers in an editable field. Its super is the
restricted-sexp
widget.It has a default
:value
of 0.
- Widget: natnum ¶
A widget for editing non-negative integers. Its super is the
restricted-sexp
widget.It has a default
:value
of 0.
- Widget: float ¶
A widget for editing a floating point number. Its super is the
restricted-sexp
widget.It has a default
:value
of 0.0.
- Widget: number ¶
A widget for editing a number, either floating point or integer. Its super is the
restricted-sexp
widget.It has a default
:value
of 0.0.
- Widget: boolean ¶
A widget for editing a boolean value. Its super is the
toggle
widget.Its value may be
nil
, meaning false, or non-nil
, meaning true.
- Widget: color ¶
A widget to edit a color name.
In addition, shows a sample that shows the selected color, if any.
- Widget: other ¶
A widget useful as the last item in a
choice
widget, since it matches any value.Its super is the
sexp
widget, and its:value
isother
, by default.
- Widget: coding-system ¶
A widget that can represent a coding system name, offering completions. See Coding Systems in the Emacs Lisp Reference Manual. Its super is the
symbol
widget.It has a default value of
undecided
.
- Widget: key ¶
A widget to represent a key sequence.
It uses a special keymap as the
:keymap
.
Previous: Atomic Sexp Widgets, Up: Sexp Types [Contents][Index]
8.2.4 Composite Sexp Widgets
The syntax for the composite widget construct is:
type ::= (construct [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 ¶
A widget to edit cons-cell values. Its super is the
group
widget.The value of a
cons
widget must be a cons-cell whose CAR and CDR have two specified types. It uses this syntax:type ::= (cons [keyword argument]... car-type cdr-type)
- Widget: choice ¶
A widget to hold a value of one of a fixed set of types. Its super is the
menu-choice
widget.The widget’s syntax is as follows:
type ::= (choice [keyword argument]... type ... )
The value of a
choice
widget can be anything that matches any of the types.This widget only displays the widget that corresponds to the current choice.
- Widget: radio ¶
A widget to hold a value of one of a fixed set of options. Its super is the
radio-button-choice
widget.
- Widget: list ¶
A widget to edit a list value. Its super is the
group
widget.The value of a
list
widget must be a list whose element types match the specified component types:type ::= (list [keyword argument]... component-type...)
Thus, for example,
(list string number)
matches lists of two elements, the first being a string and the second being a number.
- Widget: vector ¶
A widget to edit a vector value. Its super is the
group
widget.The
vector
widget is like thelist
widget but matches vectors instead of lists. Thus, for example,(vector string number)
matches vectors of two elements, the first being a string and the second being a number.
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
widget together with the :inline
keyword. 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 elements should
either be the symbol t
or two strings (file names), 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
may be 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: set ¶
A widget to hold a list of members from a fixed set. Its super is the
checklist
widget.Its value is a list where the elements all belong to a given set. The order of elements of the list is not significant.
Here’s the syntax:
type ::= (set [keyword argument]... permitted-element ... )
Use
const
to specify each permitted element, like this:(set (const a) (const b))
.
- Widget: repeat ¶
Specifies a list of any number of elements that fit a certain type. Its super is the
editable-list
widget.type ::= (repeat [keyword argument]... type)
- Widget: plist ¶
A widget to edit property lists. Its super is the
list
widget.It recognizes the following properties:
:options
A given set of recommended key-value values for the
plist
widget. Each option shows up as a checklist item.:key-type
The widget type to use for the plist keys. By default, it uses the
symbol
widget.:value-type
The widget type to use for the plist values. By default, it uses the
sexp
widget.
- Widget: alist ¶
A widget to edit association lists. Its super is the
list
widget.It recognizes the same properties that the
plist
widget, with the difference that the:key-type
uses by default asexp
widget.
Most composite widgets do not allow for recursion. That is, none of
the contained widgets may be of the same type that is currently being
defined. To allow for this kind of widgets, there’s the lazy
widget.
- Widget: lazy ¶
A base widget for recursive data structures. Its super is the
default
widget.When instantiated, it contains a single inferior widget of the widget type specified in the
:type
property. Its value is the same as the value of this inferior widget.
Next: Inspecting Widgets, Previous: Widget Gallery, Up: The Emacs Widget Library [Contents][Index]
9 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 that derives from class.
name and class should both be symbols, and class should be one of the existing widget types.
The third argument doc is a documentation string for the widget.
args should be key-value pairs, overriding keyword values of class, or adding new recognized keywords for name.
Usually, you’ll want to derive from an existing widget type, like the
editable-field
widget, or thedefault
widget, but it’s also possible to derive from nothing, by passing a value ofnil
as class. Note that if you do this, you’re entirely responsible for defining a whole new default behavior for your widgets.After using this function, 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.
When defining new widgets, the :convert-widget
property might
be useful:
: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 predefined functions
widget-types-convert-widget
andwidget-value-convert-widget
can be used here.
Example:
(defvar widget-ranged-integer-map (let ((map (copy-keymap widget-keymap))) (define-key map [up] #'widget-ranged-integer-increase) (define-key map [down] #'widget-ranged-integer-decrease) map))
(define-widget 'ranged-integer 'integer "A ranged integer widget." :min-value most-negative-fixnum :max-value most-positive-fixnum :keymap widget-ranged-integer-map)
(defun widget-ranged-integer-change (widget how) "Change the value of the ranged-integer WIDGET, according to HOW." (let* ((value (widget-value widget)) (newval (cond ((eq how 'up) (if (< (1+ value) (widget-get widget :max-value)) (1+ value) (widget-get widget :max-value))) ((eq how 'down) (if (> (1- value) (widget-get widget :min-value)) (1- value) (widget-get widget :min-value))) (t (error "HOW has a bad value")))) (inhibit-read-only t)) (widget-value-set widget newval)))
(defun widget-ranged-integer-increase (widget) "Increase the value of the ranged-integer WIDGET." (interactive (list (widget-at))) (widget-ranged-integer-change widget 'up))
(defun widget-ranged-integer-decrease (widget) "Decrease the value of the ranged-integer WIDGET." (interactive (list (widget-at))) (widget-ranged-integer-change widget 'down))
Next: Widget Minor Mode, Previous: Defining New Widgets, Up: The Emacs Widget Library [Contents][Index]
10 Inspecting Widgets
There is a separate package to browse widgets, in ‘wid-browse.el’. 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.
In addition, there’s a function to describe the widget at point.
- Command: widget-describe &optional widget-or-pos ¶
Describe the widget at point.
When called from Lisp, widget-or-pos might be the widget to describe or a buffer position where a widget is present. If widget-or-pos is
nil
, the widget to describe is the widget at point.This command sets up a help buffer for providing information about the widget, mainly its
:action
and:mouse-down-action
functions, and provides links to describe it in more detail using thewidget-browse
commands described above.
Next: Utilities, Previous: Inspecting Widgets, Up: The Emacs Widget Library [Contents][Index]
11 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
.
Next: Customization, Previous: Widget Minor Mode, Up: The Emacs Widget Library [Contents][Index]
12 Utilities
Here we describe some utility functions that don’t really have a place earlier in this manual.
- 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
.Converts widget before prompting, and for prompting it uses the
:prompt-value
function. This function returns the user “answer”, and it’s an error if that answer doesn’t match the widget, as with the:match
function.If the answer matches the widget, returns the answer.
- Function: widget-get-sibling widget ¶
Get the item which widget should toggle. This is only meaningful for radio buttons or checkboxes in a list.
- Function: widget-choose title items &optional event ¶
Prompt the user to choose an item from a list of options.
title is the name of the list of options. items should be a menu, with its items in the simple format or in the extended format. See Defining Menus in the Emacs Lisp Reference Manual. Independently of the format, you don’t have to provide a title for the menu, just pass the desired title in title. The optional event is an input event. If event is a mouse event and the number of elements in items is less than the user option
widget-menu-max-size
, thenwidget-choose
uses a popup menu to prompt the user. Otherwise,widget-choose
uses the minibuffer.When items is a keymap menu, the returned value is the symbol in the key vector, as in the argument of
define-key
(see Changing Key Bindings in the Emacs Lisp Reference Manual). When items is a list whose selectable items are of the form (name . value) (i.e., the simplified format), then the return value is the value of the chosen element.
- Function: widget-image-find image ¶
Create a graphical button from image, an image or a file name sans extension.
If image is a file name, the file should be in
widget-image-directory
, or in a place wherefind-image
will find it.
- Function: widget-image-insert widget tag image ¶
As part of widget, insert the text tag or, if supported, the image image.
image should be as described in
widget-image-find
.
- Function: widget-echo-help pos ¶
Display help-echo text for the widget at pos.
Uses the value of
:help-echo
. If it is a function, it calls it to get a string. Otherwise, iteval
s it.
Next: Wishlist, Previous: Utilities, Up: The Emacs Widget Library [Contents][Index]
13 Customization
This chapter is about the customization options for the Widget library, for the end user.
- Face: widget-documentation ¶
Face used for documentation text.
- Face: widget-field ¶
Face used for editable fields.
Face used for buttons.
Face used for pressed buttons.
- Face: widget-inactive ¶
Face used for inactive widgets.
- User Option: widget-mouse-face ¶
Face used for highlighting a button when the mouse pointer moves across it.
The default value is
highlight
.
- User Option: widget-image-directory ¶
Directory where Widget should look for images.
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-image-enable ¶
If non-
nil
, allow images to appear on displays where they are supported.
- User Option: widget-image-conversion ¶
An alist to convert symbols from image formats to file name suffixes.
Each element is a cons cell (format . suffix), where format is a symbol that represents an image format and suffix is its correspondent suffix.
String to prefix buttons.
String to suffix buttons.
String to prefix push buttons.
String to suffix push buttons.
- User Option: widget-link-prefix ¶
String to prefix links.
- User Option: widget-link-suffix ¶
String to suffix links.
- User Option: widget-choice-toggle ¶
If non-
nil
, toggle when there are just two options.By default, its value is
nil
.
- User Option: widget-documentation-links ¶
If non-
nil
, add hyperlinks to documentation strings.
- User Option: widget-documentation-link-regexp ¶
A regexp that matches potential links in documentation strings. The link itself should match to the first group.
- User Option: widget-documentation-link-p ¶
A predicate function to test if a string is useful as a link. The function is called with one argument, a string, and should return non-
nil
if there should be a link for that string.By default, the value is
intern-soft
.
- User Option: widget-documentation-link-type ¶
A symbol that represents a widget type to use for links in documentation strings.
By default, the value is
documentation-link
.
Maximum size for a popup menu. By default, its value is 40.
If a function ask you to choose from a menu that is larger than this value, it will use the minibuffer.
Largest number of items for which it works to choose one with a character.
For a larger number, use the minibuffer.
Whether to use the minibuffer to ask for a choice.
If
nil
, the default, read a single character.
Next: GNU Free Documentation License, Previous: Customization, Up: The Emacs Widget Library [Contents][Index]
14 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
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.
Next: Index, Previous: Wishlist, Up: The Emacs Widget Library [Contents][Index]
Appendix A GNU Free Documentation License
Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. https://fsf.org/ Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
- PREAMBLE
The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.
This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.
We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.
- APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.
A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.
A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.
The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.
The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.
A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.
Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.
The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.
The “publisher” means any person or entity that distributes copies of the Document to the public.
A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.
The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.
- VERBATIM COPYING
You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and you may publicly display copies.
- COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.
If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.
- MODIFICATIONS
You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:
- Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
- List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
- State on the Title page the name of the publisher of the Modified Version, as the publisher.
- Preserve all the copyright notices of the Document.
- Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
- Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
- Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.
- Include an unaltered copy of this License.
- Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
- Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
- For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
- Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
- Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
- Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
- Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.
You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.
- COMBINING DOCUMENTS
You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”
- COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.
- AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.
- TRANSLATION
Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.
If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.
- TERMINATION
You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.
Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.
- FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See https://www.gnu.org/licenses/.
Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.
- RELICENSING
“Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.
“CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.
“Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.
An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.
ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:
Copyright (C) year your name. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:
with the Invariant Sections being list their titles, with the Front-Cover Texts being list, and with the Back-Cover Texts being list.
If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.
Previous: GNU Free Documentation License, Up: The Emacs Widget Library [Contents][Index]
Index
This is an alphabetical listing of all concepts, functions, commands, variables, and widgets described in this manual.
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