@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2003
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/modes
-@node Modes, Documentation, Keymaps, Top
+@node Modes, Documentation, Keymaps, Top
@chapter Major and Minor Modes
@cindex mode
* Imenu:: How a mode can provide a menu
of definitions in the buffer.
* Font Lock Mode:: How modes can highlight text according to syntax.
+* Desktop Save Mode:: How modes can have buffer state saved between
+ Emacs sessions.
* Hooks:: How to use hooks; how to write code that provides hooks.
@end menu
@cindex Fundamental mode
Major modes specialize Emacs for editing particular kinds of text.
-Each buffer has only one major mode at a time.
+Each buffer has only one major mode at a time. For each major mode
+there is a function to switch to that mode in the current buffer; its
+name should end in @samp{-mode}. These functions work by setting
+buffer-local variable bindings and other data associated with the
+buffer, such as a local keymap. The effect lasts until you switch
+to another major mode in the same buffer.
The least specialized major mode is called @dfn{Fundamental mode}.
This mode has no mode-specific definitions or variable settings, so each
maintain. Instead, copy and rename an existing major mode definition
and alter the copy---or define a @dfn{derived mode} (@pxref{Derived
Modes}). For example, Rmail Edit mode, which is in
-@file{emacs/lisp/rmailedit.el}, is a major mode that is very similar to
-Text mode except that it provides three additional commands. Its
-definition is distinct from that of Text mode, but was derived from it.
+@file{emacs/lisp/mail/rmailedit.el}, is a major mode that is very similar to
+Text mode except that it provides two additional commands. Its
+definition is distinct from that of Text mode, but uses that of Text mode.
+
+ Even if the new mode is not an obvious derivative of any other mode,
+it is convenient to use @code{define-derived-mode} with a @code{nil}
+parent argument, since it automatically enforces the most important
+coding conventions for you.
+
+@findex define-generic-mode
+ For a very simple programming language major mode that handles
+comments and fontification, you can use @code{define-generic-mode}
+in @file{generic.el}.
Rmail Edit mode offers an example of changing the major mode
temporarily for a buffer, so it can be edited in a different way (with
-ordinary Emacs commands rather than Rmail). In such cases, the
-temporary major mode usually has a command to switch back to the
+ordinary Emacs commands rather than Rmail commands). In such cases, the
+temporary major mode usually provides a command to switch back to the
buffer's usual mode (Rmail mode, in this case). You might be tempted to
present the temporary redefinitions inside a recursive edit and restore
the usual ones when the user exits; but this is a bad idea because it
alternative major mode avoids this limitation. @xref{Recursive
Editing}.
- The standard GNU Emacs Lisp library directory contains the code for
-several major modes, in files such as @file{text-mode.el},
+ The standard GNU Emacs Lisp library directory tree contains the code
+for several major modes, in files such as @file{text-mode.el},
@file{texinfo.el}, @file{lisp-mode.el}, @file{c-mode.el}, and
-@file{rmail.el}. You can study these libraries to see how modes are
-written. Text mode is perhaps the simplest major mode aside from
+@file{rmail.el}. They are found in various subdirectories of the
+@file{lisp} directory. You can study these libraries to see how modes
+are written. Text mode is perhaps the simplest major mode aside from
Fundamental mode. Rmail mode is a complicated and specialized mode.
@menu
* Example Major Modes:: Text mode and Lisp modes.
* Auto Major Mode:: How Emacs chooses the major mode automatically.
* Mode Help:: Finding out how to use a mode.
-* Derived Modes:: Defining a new major mode based on another major
+* Derived Modes:: Defining a new major mode based on another major
mode.
@end menu
The code for existing major modes follows various coding conventions,
including conventions for local keymap and syntax table initialization,
global names, and hooks. Please follow these conventions when you
-define a new major mode:
+define a new major mode.
+
+ This list of conventions is only partial, because each major mode
+should aim for consistency in general with other Emacs major modes.
+This makes Emacs as a whole more coherent. It is impossible to list
+here all the possible points where this issue might come up; if the
+Emacs developers point out an area where your major mode deviates from
+the usual conventions, please make it compatible.
@itemize @bullet
@item
The documentation string may include the special documentation
substrings, @samp{\[@var{command}]}, @samp{\@{@var{keymap}@}}, and
-@samp{\<@var{keymap}>}, that enable the documentation to adapt
+@samp{\<@var{keymap}>}, which enable the documentation to adapt
automatically to the user's own key bindings. @xref{Keys in
Documentation}.
have names that start with the major mode name (or with an abbreviation
of it if the name is long). @xref{Coding Conventions}.
+@item
+In a major mode for editing some kind of structured text, such as a
+programming language, indentation of text according to structure is
+probably useful. So the mode should set @code{indent-line-function}
+to a suitable function, and probably customize other variables
+for indentation.
+
@item
@cindex keymaps in modes
The major mode should usually have its own keymap, which is used as the
text can reasonably redefine letters and other printing characters as
editing commands. Dired and Rmail both do this.
+@item
+Major modes must not define @key{RET} to do anything other than insert
+a newline. The command to insert a newline and then indent is
+@kbd{C-j}. Please keep this distinction uniform for all major modes.
+
+@item
+Major modes should not alter options that are primarily a matter of user
+preference, such as whether Auto-Fill mode is enabled. Leave this to
+each user to decide. However, a major mode should customize other
+variables so that Auto-Fill mode will work usefully @emph{if} the user
+decides to use it.
+
@item
@cindex syntax tables in modes
The mode may have its own syntax table or may share one with other
@item
The mode should specify how Imenu should find the definitions or
sections of a buffer, by setting up a buffer-local value for the
-variable @code{imenu-generic-expression} or
+variable @code{imenu-generic-expression}, for the pair of variables
+@code{imenu-prev-index-position-function} and
+@code{imenu-extract-index-name-function}, or for the variable
@code{imenu-create-index-function} (@pxref{Imenu}).
@item
would affect buffers that do not use this mode. It is undesirable for a
mode to have such global effects. @xref{Buffer-Local Variables}.
-It's OK to use @code{make-variable-buffer-local}, if you wish, for a
-variable used only within a single Lisp package.
+With rare exceptions, the only reasonable way to use
+@code{make-variable-buffer-local} in a Lisp package is for a variable
+which is used only within that package. Using it on a variable used by
+other packages would interfere with them.
@item
@cindex mode hook
@cindex major mode hook
Each major mode should have a @dfn{mode hook} named
@code{@var{modename}-mode-hook}. The major mode command should run that
-hook, with @code{run-hooks}, as the very last thing it
+hook, with @code{run-mode-hooks}, as the very last thing it
does. @xref{Hooks}.
@item
-The major mode command may also run the hooks of some more basic modes.
-For example, @code{indented-text-mode} runs @code{text-mode-hook} as
-well as @code{indented-text-mode-hook}. It may run these other hooks
-immediately before the mode's own hook (that is, after everything else),
-or it may run them earlier.
+The major mode command may start by calling some other major mode
+command (called the @dfn{parent mode}) and then alter some of its
+settings. A mode that does this is called a @dfn{derived mode}. The
+recommended way to define one is to use @code{define-derived-mode},
+but this is not required. Such a mode should use
+@code{delay-mode-hooks} around its entire body, including the call to
+the parent mode command and the final call to @code{run-mode-hooks}.
+(Using @code{define-derived-mode} does this automatically.)
@item
If something special should be done if the user switches a buffer from
major mode command symbol should have a property named @code{mode-class}
with value @code{special}, put on as follows:
-@cindex @code{mode-class} property
+@kindex mode-class @r{(property)}
@cindex @code{special}
@example
(put 'funny-mode 'mode-class 'special)
@end example
@noindent
-This tells Emacs that new buffers created while the current buffer has
+This tells Emacs that new buffers created while the current buffer is in
Funny mode should not inherit Funny mode. Modes such as Dired, Rmail,
and Buffer List use this feature.
file that contains the mode definition. @xref{Auto Major Mode}.
@item
-@cindex @file{.emacs} customization
In the documentation, you should provide a sample @code{autoload} form
and an example of how to add to @code{auto-mode-alist}, that users can
-include in their @file{.emacs} files.
+include in their init files (@pxref{Init File}).
@item
@cindex mode loading
@smallexample
@group
;; @r{Create mode-specific tables.}
-(defvar text-mode-syntax-table nil
+(defvar text-mode-syntax-table nil
"Syntax table used while in text mode.")
@end group
@end group
@group
-(defvar text-mode-map nil) ; @r{Create a mode-specific keymap.}
+(defvar text-mode-map nil ; @r{Create a mode-specific keymap.}
+ "Keymap for Text mode.
+Many other modes, such as Mail mode, Outline mode and Indented Text mode,
+inherit all the commands defined in this map.")
(if text-mode-map
() ; @r{Do not change the keymap if it is already set up.}
(setq text-mode-map (make-sparse-keymap))
- (define-key text-mode-map "\t" 'tab-to-tab-stop)
+ (define-key text-mode-map "\e\t" 'ispell-complete-word)
+ (define-key text-mode-map "\t" 'indent-relative)
(define-key text-mode-map "\es" 'center-line)
(define-key text-mode-map "\eS" 'center-paragraph))
@end group
@end smallexample
- Here is the complete major mode function definition for Text mode:
+ This was formerly the complete major mode function definition for Text mode:
@smallexample
@group
(defun text-mode ()
- "Major mode for editing text intended for humans to read@enddots{}
+ "Major mode for editing text intended for humans to read...
Special commands: \\@{text-mode-map@}
@end group
@group
(setq paragraph-start (concat "[ \t]*$\\|" page-delimiter))
(make-local-variable 'paragraph-separate)
(setq paragraph-separate paragraph-start)
+ (make-local-variable 'indent-line-function)
+ (setq indent-line-function 'indent-relative-maybe)
@end group
@group
(setq mode-name "Text")
(setq major-mode 'text-mode)
- (run-hooks 'text-mode-hook)) ; @r{Finally, this permits the user to}
+ (run-mode-hooks 'text-mode-hook)) ; @r{Finally, this permits the user to}
; @r{customize the mode with a hook.}
@end group
@end smallexample
@smallexample
@group
;; @r{Create mode-specific table variables.}
-(defvar lisp-mode-syntax-table nil "")
+(defvar lisp-mode-syntax-table nil "")
(defvar emacs-lisp-mode-syntax-table nil "")
(defvar lisp-mode-abbrev-table nil "")
@end group
@group
;; @r{Set syntax of chars up to 0 to class of chars that are}
;; @r{part of symbol names but not words.}
- ;; @r{(The number 0 is @code{48} in the @sc{ASCII} character set.)}
- (while (< i ?0)
+ ;; @r{(The number 0 is @code{48} in the @acronym{ASCII} character set.)}
+ (while (< i ?0)
(modify-syntax-entry i "_ " emacs-lisp-mode-syntax-table)
(setq i (1+ i)))
@dots{}
(cond (lisp-syntax
(set-syntax-table lisp-mode-syntax-table)))
(setq local-abbrev-table lisp-mode-abbrev-table)
- @dots{})
+ @dots{}
@end group
@end smallexample
@group
(make-local-variable 'comment-indent-function)
(setq comment-indent-function 'lisp-comment-indent))
+ @dots{}
@end group
@end smallexample
@smallexample
@group
(defvar lisp-mode-map ()
- "Keymap for ordinary Lisp mode@enddots{}")
+ "Keymap for ordinary Lisp mode...")
(if lisp-mode-map
()
@end smallexample
Finally, here is the complete major mode function definition for
-Emacs Lisp mode.
+Lisp mode.
@smallexample
@group
@group
(setq imenu-case-fold-search t)
(set-syntax-table lisp-mode-syntax-table)
- (run-hooks 'lisp-mode-hook)) ; @r{This permits the user to use a}
+ (run-mode-hooks 'lisp-mode-hook)) ; @r{This permits the user to use a}
; @r{hook to customize the mode.}
@end group
@end smallexample
mode specification error}, followed by the original error message.
@end deffn
-@defopt enable-local-variables
-This variable controls processing of local variables lists in files
-being visited. A value of @code{t} means process the local variables
-lists unconditionally; @code{nil} means ignore them; anything else means
-ask the user what to do for each file. The default value is @code{t}.
-@end defopt
-
-@defvar ignored-local-variables
-This variable holds a list of variables that should not be
-set by a file's local variables list. Any value specified
-for one of these variables is ignored.
-@end defvar
-
-In addition to this list, any variable whose name has a non-@code{nil}
-@code{risky-local-variable} property is also ignored.
-
-@defopt enable-local-eval
-This variable controls processing of @samp{Eval:} in local variables
-lists in files being visited. A value of @code{t} means process them
-unconditionally; @code{nil} means ignore them; anything else means ask
-the user what to do for each file. The default value is @code{maybe}.
-@end defopt
-
@defun set-auto-mode
@cindex visited file mode
This function selects the major mode that is appropriate for the
How Major Modes are Chosen, emacs, The GNU Emacs Manual}.
@end defun
-@defopt default-major-mode
+@defopt default-major-mode
This variable holds the default major mode for new buffers. The
standard value is @code{fundamental-mode}.
@end group
@group
("\\.el\\'" . emacs-lisp-mode)
- ("\\.c\\'" . c-mode)
+ ("\\.c\\'" . c-mode)
("\\.h\\'" . c-mode)
@dots{})
@end group
Here is an example of how to prepend several pattern pairs to
@code{auto-mode-alist}. (You might use this sort of expression in your
-@file{.emacs} file.)
+init file.)
@smallexample
@group
(setq auto-mode-alist
- (append
+ (append
;; @r{File name (within directory) starts with a dot.}
- '(("/\\.[^/]*\\'" . fundamental-mode)
+ '(("/\\.[^/]*\\'" . fundamental-mode)
;; @r{File name has no dot.}
- ("[^\\./]*\\'" . fundamental-mode)
+ ("[^\\./]*\\'" . fundamental-mode)
;; @r{File name ends in @samp{.C}.}
("\\.C\\'" . c++-mode))
auto-mode-alist))
@defvar interpreter-mode-alist
This variable specifies major modes to use for scripts that specify a
-command interpreter in an @samp{#!} line. Its value is a list of
+command interpreter in a @samp{#!} line. Its value is a list of
elements of the form @code{(@var{interpreter} . @var{mode})}; for
example, @code{("perl" . perl-mode)} is one element present by default.
The element says to use mode @var{mode} if the file specifies
not indicate which major mode to use.
@end defvar
-@defun hack-local-variables &optional force
-This function parses, and binds or evaluates as appropriate, any local
-variables specified by the contents of the current buffer.
-
-The handling of @code{enable-local-variables} documented for
-@code{normal-mode} actually takes place here. The argument @var{force}
-usually comes from the argument @var{find-file} given to
-@code{normal-mode}.
-@end defun
-
@node Mode Help
@subsection Getting Help about a Major Mode
@cindex mode help
The new command @var{variant} is defined to call the function
@var{parent}, then override certain aspects of that parent mode:
-@itemize @bullet
+@itemize @bullet
@item
The new mode has its own keymap, named @code{@var{variant}-map}.
@code{define-derived-mode} initializes this map to inherit from
@item
The new mode has its own syntax table, kept in the variable
@code{@var{variant}-syntax-table}.
-@code{define-derived-mode} initializes this variable by copying
+@code{define-derived-mode} initializes this variable by copying
@code{@var{parent}-syntax-table}, if it is not already set.
@item
The new mode has its own abbrev table, kept in the variable
@code{@var{variant}-abbrev-table}.
-@code{define-derived-mode} initializes this variable by copying
+@code{define-derived-mode} initializes this variable by copying
@code{@var{parent}-abbrev-table}, if it is not already set.
@item
The new mode has its own mode hook, @code{@var{variant}-hook},
which it runs in standard fashion as the very last thing that it does.
-(The new mode also runs the mode hook of @var{parent} as part
+(The new mode also runs the mode hook of @var{parent} as part
of calling @var{parent}.)
@end itemize
In addition, you can specify how to override other aspects of
@var{parent} with @var{body}. The command @var{variant}
-evaluates the forms in @var{body} after setting up all its usual
+evaluates the forms in @var{body} after setting up all its usual
overrides, just before running @code{@var{variant}-hook}.
The argument @var{docstring} specifies the documentation string for the
(define-key hypertext-mode-map
[down-mouse-3] 'do-hyper-link)
@end example
+
+Do not write an @code{interactive} spec in the definition;
+@code{define-derived-mode} does that automatically.
@end defmac
@node Minor Modes
``generally available, optional feature modes,'' except that such a name
would be unwieldy.
- A minor mode is not usually a modification of single major mode. For
+ A minor mode is not usually meant as a variation of a single major mode.
+Usually they are general and can apply to many major modes. For
example, Auto Fill mode works with any major mode that permits text
insertion. To be general, a minor mode must be effectively independent
of the things major modes do.
way to insert the necessary hook into the rest of Emacs. Minor mode
keymaps make this easier than it used to be.
+@defvar minor-mode-list
+The value of this variable is a list of all minor mode commands.
+@end defvar
+
@menu
* Minor Mode Conventions:: Tips for writing a minor mode.
* Keymaps and Minor Modes:: How a minor mode can have its own keymap.
-* Easy-Mmode:: A convenient facility for defining minor modes.
+* Defining Minor Modes:: A convenient facility for defining minor modes.
@end menu
@node Minor Mode Conventions
Make a variable whose name ends in @samp{-mode} to control the minor
mode. We call this the @dfn{mode variable}. The minor mode command
should set this variable (@code{nil} to disable; anything else to
-enable.)
+enable).
-If it is possible, implement the mode so that setting the variable
+If possible, implement the mode so that setting the variable
automatically enables or disables the mode. Then the minor mode command
-does not need to do anything except the variable.
+does not need to do anything except set the variable.
This variable is used in conjunction with the @code{minor-mode-alist} to
display the minor mode name in the mode line. It can also enable
Its job is to enable and disable the mode by setting the variable.
The command should accept one optional argument. If the argument is
-@code{nil}, it should toggle the mode (turn it on if it is off, and off
-if it is on). Otherwise, it should turn the mode on if the argument is
-a positive integer, a symbol other than @code{nil} or @code{-}, or a
-list whose @sc{car} is such an integer or symbol; it should turn the
-mode off otherwise.
+@code{nil}, it should toggle the mode (turn it on if it is off, and
+off if it is on). It should turn the mode on if the argument is a
+positive integer, the symbol @code{t}, or a list whose @sc{car} is one
+of those. It should turn the mode off if the argument is a negative
+integer or zero, the symbol @code{-}, or a list whose @sc{car} is one
+of those. The meaning of other arguments is not specified.
Here is an example taken from the definition of @code{transient-mark-mode}.
It shows the use of @code{transient-mark-mode} as a variable that enables or
@smallexample
@group
-(or (assq 'leif-mode minor-mode-alist)
- (setq minor-mode-alist
- (cons '(leif-mode " Leif") minor-mode-alist)))
+(unless (assq 'leif-mode minor-mode-alist)
+ (setq minor-mode-alist
+ (cons '(leif-mode " Leif") minor-mode-alist)))
+@end group
+@end smallexample
+
+@noindent
+or like this, using @code{add-to-list} (@pxref{Setting Variables}):
+
+@smallexample
+@group
+(add-to-list 'minor-mode-alist '(leif-mode " Leif"))
@end group
@end smallexample
@end itemize
+ Global minor modes distributed with Emacs should if possible support
+enabling and disabling via Custom (@pxref{Customization}). To do this,
+the first step is to define the mode variable with @code{defcustom}, and
+specify @code{:type boolean}.
+
+ If just setting the variable is not sufficient to enable the mode, you
+should also specify a @code{:set} method which enables the mode by
+invoke the mode command. Note in the variable's documentation string that
+setting the variable other than via Custom may not take effect.
+
+ Also mark the definition with an autoload cookie (@pxref{Autoload}),
+and specify a @code{:require} so that customizing the variable will load
+the library that defines the mode. This will copy suitable definitions
+into @file{loaddefs.el} so that users can use @code{customize-option} to
+enable the mode. For example:
+
+@smallexample
+@group
+
+;;;###autoload
+(defcustom msb-mode nil
+ "Toggle msb-mode.
+Setting this variable directly does not take effect;
+use either \\[customize] or the function `msb-mode'."
+ :set (lambda (symbol value)
+ (msb-mode (or value 0)))
+ :initialize 'custom-initialize-default
+ :version "20.4"
+ :type 'boolean
+ :group 'msb
+ :require 'msb)
+@end group
+@end smallexample
+
@node Keymaps and Minor Modes
@subsection Keymaps and Minor Modes
The key sequences bound in a minor mode should consist of @kbd{C-c}
followed by a punctuation character @emph{other than} @kbd{@{},
-@kbd{@}}, @kbd{<}, @kbd{>}, @kbd{:} or @kbd{;}. (Those few punctuation
+@kbd{@}}, @kbd{<}, @kbd{>}, @kbd{:}, and @kbd{;}. (Those few punctuation
characters are reserved for major modes.)
-@node Easy-Mmode
-@subsection Easy-Mmode
-
- The easy-mmode package provides a convenient way of implementing a
-minor mode; with it, you can specify all about a simple minor mode in
-one self-contained definition.
+@node Defining Minor Modes
+@subsection Defining Minor Modes
-@tindex easy-mmode-define-minor-mode
-@defmac easy-mmode-define-minor-mode mode doc &optional init-value mode-indicator keymap
-This macro defines a new minor mode whose name is @var{mode} (a symbol).
+ The macro @code{define-minor-mode} offers a convenient way of
+implementing a mode in one self-contained definition. It supports only
+buffer-local minor modes, not global ones.
-This macro defines a command named @var{mode} which toggles the minor
-mode, and has @var{doc} as its documentation string.
+@defmac define-minor-mode mode doc [init-value [lighter [keymap keyword-args... body...]]]
+@tindex define-minor-mode
+This macro defines a new minor mode whose name is @var{mode} (a
+symbol). It defines a command named @var{mode} to toggle the minor
+mode, with @var{doc} as its documentation string. It also defines a
+variable named @var{mode}, which is set to @code{t} or @code{nil} by
+enabling or disabling the mode. The variable is initialized to
+@var{init-value}.
-It also defines a variable named @var{mode}, which is set to @code{t} or
-@code{nil} by enabling or disabling the mode. The variable is
-initialized to @var{init-value}.
-
-The string @var{mode-indicator} says what to display in the mode line
+The string @var{lighter} says what to display in the mode line
when the mode is enabled; if it is @code{nil}, the mode is not displayed
in the mode line.
@example
(@var{key-sequence} . @var{definition})
@end example
+
+The @var{keyword-args} consist of keywords followed by corresponding
+values. A few keywords have special meanings:
+
+@table @code
+@item :global @var{global}
+If non-@code{nil} specifies that the minor mode should be global.
+By default, minor modes are buffer-local.
+
+@item :init-value @var{init-value}
+This is equivalent to specifying @var{init-value} positionally.
+
+@item :lighter @var{lighter}
+This is equivalent to specifying @var{lighter} positionally.
+
+@item :keymap @var{keymap}
+This is equivalent to specifying @var{keymap} positionally.
+@end table
+
+Any other keyword arguments are passed passed directly to the
+@code{defcustom} generated for the variable @var{mode}.
+
+The command named @var{mode} finishes by executing the @var{body} forms,
+if any, after it has performed the standard actions such as setting
+the variable named @var{mode}.
@end defmac
- Here is an example of using @code{easy-mmode-define-minor-mode}:
+@findex easy-mmode-define-minor-mode
+ The name @code{easy-mmode-define-minor-mode} is an alias
+for this macro.
+
+ Here is an example of using @code{define-minor-mode}:
@smallexample
-(easy-mmode-define-minor-mode hungry-mode
+(define-minor-mode hungry-mode
"Toggle Hungry mode.
-With no argument, this command toggles the mode.
+With no argument, this command toggles the mode.
Non-null prefix argument turns on the mode.
Null prefix argument turns off the mode.
;; The minor mode bindings.
'(("\C-\^?" . hungry-electric-delete)
("\C-\M-\^?"
- . (lambda ()
+ . (lambda ()
(interactive)
- (hungry-electric-delete t)))))
+ (hungry-electric-delete t))))
+ :group 'hunger)
@end smallexample
@noindent
which indicates whether the mode is enabled, and a variable named
@code{hungry-mode-map} which holds the keymap that is active when the
mode is enabled. It initializes the keymap with key bindings for
-@kbd{C-@key{DEL}} and @kbd{C-M-@key{DEL}}.
+@kbd{C-@key{DEL}} and @kbd{C-M-@key{DEL}}. It puts the variable
+@code{hungry-mode} into custom group @code{hunger}. There are no
+@var{body} forms---many minor modes don't need any.
+
+ Here's an equivalent way to write it:
+
+@smallexample
+(define-minor-mode hungry-mode
+ "Toggle Hungry mode.
+With no argument, this command toggles the mode.
+Non-null prefix argument turns on the mode.
+Null prefix argument turns off the mode.
+
+When Hungry mode is enabled, the control delete key
+gobbles all preceding whitespace except the last.
+See the command \\[hungry-electric-delete]."
+ ;; The initial value.
+ :initial-value nil
+ ;; The indicator for the mode line.
+ :lighter " Hungry"
+ ;; The minor mode bindings.
+ :keymap
+ '(("\C-\^?" . hungry-electric-delete)
+ ("\C-\M-\^?"
+ . (lambda ()
+ (interactive)
+ (hungry-electric-delete t))))
+ :group 'hunger)
+@end smallexample
@node Mode Line Format
-@section Mode Line Format
+@section Mode-Line Format
@cindex mode line
- Each Emacs window (aside from minibuffer windows) includes a mode line,
-which displays status information about the buffer displayed in the
-window. The mode line contains information about the buffer, such as its
-name, associated file, depth of recursive editing, and the major and
-minor modes.
+ Each Emacs window (aside from minibuffer windows) typically has a mode
+line at the bottom, which displays status information about the buffer
+displayed in the window. The mode line contains information about the
+buffer, such as its name, associated file, depth of recursive editing,
+and major and minor modes. A window can also have a @dfn{header
+line}, which is much like the mode line but appears at the top of the
+window (starting in Emacs 21).
- This section describes how the contents of the mode line are
-controlled. We include it in this chapter because much of the
+ This section describes how to control the contents of the mode line
+and header line. We include it in this chapter because much of the
information displayed in the mode line relates to the enabled major and
minor modes.
@code{mode-line-format} is a buffer-local variable that holds a
template used to display the mode line of the current buffer. All
-windows for the same buffer use the same @code{mode-line-format} and
-their mode lines appear the same (except for scrolling percentages, and
-line and column numbers).
-
- The mode line of a window is normally updated whenever a different
-buffer is shown in the window, or when the buffer's modified-status
-changes from @code{nil} to @code{t} or vice-versa. If you modify any of
-the variables referenced by @code{mode-line-format} (@pxref{Mode Line
-Variables}), or any other variables and data structures that affect how
-text is displayed (@pxref{Display}), you may want to force an update of
-the mode line so as to display the new information or display it in
-the new way.
+windows for the same buffer use the same @code{mode-line-format}, so
+their mode lines appear the same---except for scrolling percentages, and
+line and column numbers, since those depend on point and on how the
+window is scrolled. @code{header-line-format} is used likewise for
+header lines.
+
+ For efficiency, Emacs does not recompute the mode line and header
+line of a window in every redisplay. It does so when circumstances
+appear to call for it---for instance, if you change the window
+configuration, switch buffers, narrow or widen the buffer, scroll, or
+change the buffer's modification status. If you modify any of the
+variables referenced by @code{mode-line-format} (@pxref{Mode Line
+Variables}), or any other variables and data structures that affect
+how text is displayed (@pxref{Display}), you may want to force an
+update of the mode line so as to display the new information or
+display it in the new way.
@c Emacs 19 feature
-@defun force-mode-line-update
-Force redisplay of the current buffer's mode line.
+@defun force-mode-line-update &optional all
+Force redisplay of the current buffer's mode line and header line.
+The next redisplay will update the mode line and header line based on
+the latest values of all relevant variables. With optional
+non-@code{nil} @var{all}, force redisplay of all mode lines and header
+lines.
+
+This function also forces recomputation of the menu bar menus
+and the frame title.
@end defun
The mode line is usually displayed in inverse video; see
@code{mode-line-inverse-video} in @ref{Inverse Video}.
+ A window that is just one line tall does not display either a mode
+line or a header line, even if the variables call for one. A window
+that is two lines tall cannot display both a mode line and a header
+line at once; if the variables call for both, only the mode line
+actually appears.
+
@menu
* Mode Line Data:: The data structure that controls the mode line.
* Mode Line Variables:: Variables used in that data structure.
* %-Constructs:: Putting information into a mode line.
+* Properties in Mode:: Using text properties in the mode line.
+* Header Lines:: Like a mode line, but at the top.
+* Emulating Mode Line:: Formatting text as the mode line would.
@end menu
@node Mode Line Data
@subsection The Data Structure of the Mode Line
-@cindex mode line construct
+@cindex mode-line construct
- The mode line contents are controlled by a data structure of lists,
-strings, symbols, and numbers kept in the buffer-local variable
-@code{mode-line-format}. The data structure is called a @dfn{mode line
-construct}, and it is built in recursive fashion out of simpler mode line
-constructs. The same data structure is used for constructing
-frame titles (@pxref{Frame Titles}).
+ The mode-line contents are controlled by a data structure of lists,
+strings, symbols, and numbers kept in buffer-local variables. The data
+structure is called a @dfn{mode-line construct}, and it is built in
+recursive fashion out of simpler mode-line constructs. The same data
+structure is used for constructing frame titles (@pxref{Frame Titles})
+and header lines (@pxref{Header Lines}).
@defvar mode-line-format
-The value of this variable is a mode line construct with overall
-responsibility for the mode line format. The value of this variable
-controls which other variables are used to form the mode line text, and
+The value of this variable is a mode-line construct with overall
+responsibility for the mode-line format. The value of this variable
+controls which other variables are used to form the mode-line text, and
where they appear.
+
+If you set this variable to @code{nil} in a buffer, that buffer does not
+have a mode line. (This feature was added in Emacs 21.)
@end defvar
- A mode line construct may be as simple as a fixed string of text, but
+ A mode-line construct may be as simple as a fixed string of text, but
it usually specifies how to use other variables to construct the text.
-Many of these variables are themselves defined to have mode line
+Many of these variables are themselves defined to have mode-line
constructs as their values.
The default value of @code{mode-line-format} incorporates the values
-of variables such as @code{mode-name} and @code{minor-mode-alist}.
-Because of this, very few modes need to alter @code{mode-line-format}
-itself. For most purposes, it is sufficient to alter some of the
-variables that @code{mode-line-format} refers to.
-
- A mode line construct may be a list, a symbol, or a string. If the
+of variables such as @code{mode-line-position} and
+@code{mode-line-modes} (which in turn incorporates the values of the
+variables @code{mode-name} and @code{minor-mode-alist}). Because of
+this, very few modes need to alter @code{mode-line-format} itself. For
+most purposes, it is sufficient to alter some of the variables that
+@code{mode-line-format} either directly or indirectly refers to.
+
+ A mode-line construct may be a list, a symbol, or a string. If the
value is a list, each element may be a list, a symbol, or a string.
+ The mode line can display various faces, if the strings that control
+it have the @code{face} property. @xref{Properties in Mode}. In
+addition, the face @code{mode-line} is used as a default for the whole
+mode line (@pxref{Standard Faces}).
+
@table @code
@cindex percent symbol in mode line
@item @var{string}
-A string as a mode line construct is displayed verbatim in the mode line
+A string as a mode-line construct is displayed verbatim in the mode line
except for @dfn{@code{%}-constructs}. Decimal digits after the @samp{%}
specify the field width for space filling on the right (i.e., the data
is left justified). @xref{%-Constructs}.
@item @var{symbol}
-A symbol as a mode line construct stands for its value. The value of
-@var{symbol} is used as a mode line construct, in place of @var{symbol}.
-However, the symbols @code{t} and @code{nil} are ignored; so is any
+A symbol as a mode-line construct stands for its value. The value of
+@var{symbol} is used as a mode-line construct, in place of @var{symbol}.
+However, the symbols @code{t} and @code{nil} are ignored, as is any
symbol whose value is void.
There is one exception: if the value of @var{symbol} is a string, it is
displayed verbatim: the @code{%}-constructs are not recognized.
+Unless @var{symbol} is marked as ``risky'' (i.e., it has a
+non-@code{nil} @code{risky-local-variable} property), all properties in
+any strings, as well as all @code{:eval} and @code{:propertize} forms in
+the value of that symbol will be ignored.
+
@item (@var{string} @var{rest}@dots{}) @r{or} (@var{list} @var{rest}@dots{})
A list whose first element is a string or list means to process all the
elements recursively and concatenate the results. This is the most
-common form of mode line construct.
+common form of mode-line construct.
+
+@item (:eval @var{form})
+A list whose first element is the symbol @code{:eval} says to evaluate
+@var{form}, and use the result as a string to display.
+(This feature is new as of Emacs 21.)
+
+@item (:propertize @var{elt} @var{props}@dots{})
+A list whose first element is the symbol @code{:propertize} says to
+process the mode-line construct @var{elt} recursively and add the text
+properties specified by @var{props} to the result. The argument
+@var{props} should consist of zero or more pairs @var{text-property}
+@var{value}. (This feature is new as of Emacs 21.4.)
+@c FIXME: This might be Emacs 21.5.
@item (@var{symbol} @var{then} @var{else})
-A list whose first element is a symbol is a conditional. Its meaning
-depends on the value of @var{symbol}. If the value is non-@code{nil},
-the second element, @var{then}, is processed recursively as a mode line
-element. But if the value of @var{symbol} is @code{nil}, the third
-element, @var{else}, is processed recursively. You may omit @var{else};
-then the mode line element displays nothing if the value of @var{symbol}
-is @code{nil}.
+A list whose first element is a symbol that is not a keyword specifies a
+conditional. Its meaning depends on the value of @var{symbol}. If the
+value is non-@code{nil}, the second element, @var{then}, is processed
+recursively as a mode-line element. But if the value of @var{symbol} is
+@code{nil}, the third element, @var{else}, is processed recursively.
+You may omit @var{else}; then the mode-line element displays nothing if
+the value of @var{symbol} is @code{nil}.
@item (@var{width} @var{rest}@dots{})
A list whose first element is an integer specifies truncation or
padding of the results of @var{rest}. The remaining elements
-@var{rest} are processed recursively as mode line constructs and
+@var{rest} are processed recursively as mode-line constructs and
concatenated together. Then the result is space filled (if
@var{width} is positive) or truncated (to @minus{}@var{width} columns,
if @var{width} is negative) on the right.
'mode-line-mule-info
'mode-line-modified
'mode-line-frame-identification
- "%b--"
+ "%b--"
@end group
@group
;; @r{Note that this is evaluated while making the list.}
- ;; @r{It makes a mode line construct which is just a string.}
+ ;; @r{It makes a mode-line construct which is just a string.}
(getenv "HOST")
@end group
- ":"
+ ":"
'default-directory
" "
'global-mode-string
" %[("
- 'mode-name
- 'mode-line-process
- 'minor-mode-alist
- "%n"
+ '(:eval (mode-line-mode-name))
+ 'mode-line-process
+ 'minor-mode-alist
+ "%n"
")%]--"
@group
'(which-func-mode ("" which-func-format "--"))
'(line-number-mode "L%l--")
'(column-number-mode "C%c--")
- '(-3 . "%p")
+ '(-3 "%p")
"-%-"))
@end group
@end example
+@noindent
+(The variables @code{line-number-mode}, @code{column-number-mode}
+and @code{which-func-mode} enable particular minor modes; as usual,
+these variable names are also the minor mode command names.)
+
@node Mode Line Variables
@subsection Variables Used in the Mode Line
other variables could have the same effects on the mode line if
@code{mode-line-format} were changed to use them.
-@tindex mode-line-mule-info
@defvar mode-line-mule-info
This variable holds the value of the mode-line construct that displays
information about the language environment, buffer coding system, and
-current input method. @xref{International,,, emacs, The GNU Emacs
-Manual}.
+current input method. @xref{Non-ASCII Characters}.
@end defvar
@defvar mode-line-modified
Changing this variable does not force an update of the mode line.
@end defvar
-@tindex mode-line-frame-identification
@defvar mode-line-frame-identification
This variable identifies the current frame. The default value is
-@code{" "} if you are using a window system which can show multiple
-frames, or @code{"-%F "} on an ordinary terminal which shows only one
+@code{" "} if you are using a window system which can show multiple
+frames, or @code{"-%F "} on an ordinary terminal which shows only one
frame at a time.
@end defvar
@defvar mode-line-buffer-identification
This variable identifies the buffer being displayed in the window. Its
-default value is @code{("%12b")}, which means that it usually
-displays @samp{Emacs:} followed by seventeen characters of the buffer
-name. (In a terminal frame, it displays the frame name instead of
-@samp{Emacs}; this has the effect of showing the frame number.) You may
-want to change this in modes such as Rmail that do not behave like a
-``normal'' Emacs.
+default value is @code{("%12b")}, which displays the buffer name, padded
+with spaces to at least 12 columns.
@end defvar
-@defvar global-mode-string
-This variable holds a mode line spec that appears in the mode line by
-default, just after the buffer name. The command @code{display-time}
-sets @code{global-mode-string} to refer to the variable
-@code{display-time-string}, which holds a string containing the time and
-load information.
+@defvar mode-line-position
+This variable indicates the position in the buffer. Here is a
+simplified version of its default value. The actual default value
+also specifies addition of the @code{help-echo} text property.
-The @samp{%M} construct substitutes the value of
-@code{global-mode-string}, but that is obsolete, since the variable is
-included in the mode line from @code{mode-line-format}.
+@example
+@group
+((-3 "%p")
+ (size-indication-mode (8 " of %I"))
+@end group
+@group
+ (line-number-mode
+ ((column-number-mode
+ (10 " (%l,%c)")
+ (6 " L%l")))
+ ((column-number-mode
+ (5 " C%c")))))
+@end group
+@end example
+
+This means that @code{mode-line-position} displays at least the buffer
+percentage and possibly the buffer size, the line number and the column
+number.
@end defvar
+@defvar vc-mode
+The variable @code{vc-mode}, buffer-local in each buffer, records
+whether the buffer's visited file is maintained with version control,
+and, if so, which kind. Its value is a string that appears in the mode
+line, or @code{nil} for no version control.
+@end defvar
+
+@defvar mode-line-modes
+This variable displays the buffer's major and minor modes. Here is a
+simplified version of its default value. The real default value also
+specifies addition of text properties.
+
+@example
+@group
+("%[(" mode-name
+ mode-line-process minor-mode-alist
+ "%n" ")%]--")
+@end group
+@end example
+
+So @code{mode-line-modes} normally also displays the recursive editing
+level, information on the process status and whether narrowing is in
+effect.
+@end defvar
+
+ The following three variables are used in @code{mode-line-modes}:
+
@defvar mode-name
This buffer-local variable holds the ``pretty'' name of the current
buffer's major mode. Each major mode should set this variable so that the
mode name will appear in the mode line.
@end defvar
+@defvar mode-line-process
+This buffer-local variable contains the mode-line information on process
+status in modes used for communicating with subprocesses. It is
+displayed immediately following the major mode name, with no intervening
+space. For example, its value in the @samp{*shell*} buffer is
+@code{(":%s")}, which allows the shell to display its status along
+with the major mode as: @samp{(Shell:run)}. Normally this variable
+is @code{nil}.
+@end defvar
+
@defvar minor-mode-alist
This variable holds an association list whose elements specify how the
mode line should indicate that a minor mode is active. Each element of
(@var{minor-mode-variable} @var{mode-line-string})
@end example
-More generally, @var{mode-line-string} can be any mode line spec. It
-appears in the mode line when the value of @var{minor-mode-variable} is
-non-@code{nil}, and not otherwise. These strings should begin with
+More generally, @var{mode-line-string} can be any mode-line spec. It
+appears in the mode line when the value of @var{minor-mode-variable}
+is non-@code{nil}, and not otherwise. These strings should begin with
spaces so that they don't run together. Conventionally, the
-@var{minor-mode-variable} for a specific mode is set to a non-@code{nil}
-value when that minor mode is activated.
-
-The default value of @code{minor-mode-alist} is:
-
-@example
-@group
-minor-mode-alist
-@result{} ((vc-mode vc-mode)
- (abbrev-mode " Abbrev")
- (overwrite-mode overwrite-mode)
- (auto-fill-function " Fill")
- (defining-kbd-macro " Def")
- (isearch-mode isearch-mode))
-@end group
-@end example
+@var{minor-mode-variable} for a specific mode is set to a
+non-@code{nil} value when that minor mode is activated.
@code{minor-mode-alist} itself is not buffer-local. Each variable
mentioned in the alist should be buffer-local if its minor mode can be
enabled separately in each buffer.
@end defvar
-@defvar mode-line-process
-This buffer-local variable contains the mode line information on process
-status in modes used for communicating with subprocesses. It is
-displayed immediately following the major mode name, with no intervening
-space. For example, its value in the @samp{*shell*} buffer is
-@code{(":@: %s")}, which allows the shell to display its status along
-with the major mode as: @samp{(Shell:@: run)}. Normally this variable
-is @code{nil}.
+@defvar global-mode-string
+This variable holds a mode-line spec that, by default, appears in the
+mode line just after the @code{which-func-mode} minor mode if set,
+else after @code{mode-line-modes}. The command @code{display-time}
+sets @code{global-mode-string} to refer to the variable
+@code{display-time-string}, which holds a string containing the time
+and load information.
+
+The @samp{%M} construct substitutes the value of
+@code{global-mode-string}, but that is obsolete, since the variable is
+included in the mode line from @code{mode-line-format}.
@end defvar
+ The variable @code{default-mode-line-format} is where
+@code{mode-line-format} usually gets its value:
+
@defvar default-mode-line-format
This variable holds the default @code{mode-line-format} for buffers
that do not override it. This is the same as @code{(default-value
'mode-line-format)}.
-The default value of @code{default-mode-line-format} is this list:
+Here is a simplified version of the default value of
+@code{default-mode-line-format}. The real default value also
+specifies addition of text properties.
@example
@group
mode-line-buffer-identification
@end group
" "
- global-mode-string
-@group
- " %[("
- mode-name
- mode-line-process
- minor-mode-alist
- "%n"
- ")%]--"
-@end group
+ mode-line-position
+ (vc-mode vc-mode)
+ " "
@group
+ mode-line-modes
(which-func-mode ("" which-func-format "--"))
- (line-number-mode "L%l--")
- (column-number-mode "C%c--")
- (-3 . "%p")
+ (global-mode-string ("--" global-mode-string))
"-%-")
@end group
@end example
@end defvar
-@defvar vc-mode
-The variable @code{vc-mode}, buffer-local in each buffer, records
-whether the buffer's visited file is maintained with version control,
-and, if so, which kind. Its value is @code{nil} for no version control,
-or a string that appears in the mode line.
-@end defvar
-
@node %-Constructs
@subsection @code{%}-Constructs in the Mode Line
The current buffer name, obtained with the @code{buffer-name} function.
@xref{Buffer Names}.
+@item %c
+The current column number of point.
+
@item %f
The visited file name, obtained with the @code{buffer-file-name}
function. @xref{Buffer File Name}.
The title (only on a window system) or the name of the selected frame.
@xref{Window Frame Parameters}.
-@item %c
-The current column number of point.
+@item %i
+The size of the accessible part of the current buffer; basically
+@code{(- (point-max) (point-min))}.
+
+@item %I
+Like @samp{%i}, but the size is printed in a more readable way by using
+@samp{k} for 10^3, @samp{M} for 10^6, @samp{G} for 10^9, etc., to
+abbreviate.
@item %l
-The current line number of point.
+The current line number of point, counting within the accessible portion
+of the buffer.
+
+@item %n
+@samp{Narrow} when narrowing is in effect; nothing otherwise (see
+@code{narrow-to-region} in @ref{Narrowing}).
+
+@item %p
+The percentage of the buffer text above the @strong{top} of window, or
+@samp{Top}, @samp{Bottom} or @samp{All}. Note that the default
+mode-line specification truncates this to three characters.
+
+@item %P
+The percentage of the buffer text that is above the @strong{bottom} of
+the window (which includes the text visible in the window, as well as
+the text above the top), plus @samp{Top} if the top of the buffer is
+visible on screen; or @samp{Bottom} or @samp{All}.
+
+@item %s
+The status of the subprocess belonging to the current buffer, obtained with
+@code{process-status}. @xref{Process Information}.
+
+@item %t
+Whether the visited file is a text file or a binary file. This is a
+meaningful distinction only on certain operating systems (@pxref{MS-DOS
+File Types}).
@item %*
@samp{%} if the buffer is read only (see @code{buffer-read-only}); @*
@item %&
@samp{*} if the buffer is modified, and @samp{-} otherwise.
-@item %s
-The status of the subprocess belonging to the current buffer, obtained with
-@code{process-status}. @xref{Process Information}.
-
-@item %t
-Whether the visited file is a text file or a binary file. (This is a
-meaningful distinction only on certain operating systems.)
-
-@item %p
-The percentage of the buffer text above the @strong{top} of window, or
-@samp{Top}, @samp{Bottom} or @samp{All}.
-
-@item %P
-The percentage of the buffer text that is above the @strong{bottom} of
-the window (which includes the text visible in the window, as well as
-the text above the top), plus @samp{Top} if the top of the buffer is
-visible on screen; or @samp{Bottom} or @samp{All}.
-
-@item %n
-@samp{Narrow} when narrowing is in effect; nothing otherwise (see
-@code{narrow-to-region} in @ref{Narrowing}).
-
@item %[
An indication of the depth of recursive editing levels (not counting
minibuffer levels): one @samp{[} for each editing level.
One @samp{]} for each recursive editing level (not counting minibuffer
levels).
+@item %-
+Dashes sufficient to fill the remainder of the mode line.
+
@item %%
The character @samp{%}---this is how to include a literal @samp{%} in a
string in which @code{%}-constructs are allowed.
-
-@item %-
-Dashes sufficient to fill the remainder of the mode line.
@end table
The following two @code{%}-constructs are still supported, but they are
@code{display-time} modifies the value of @code{global-mode-string}.
@end table
+@node Properties in Mode
+@subsection Properties in the Mode Line
+@cindex text properties in the mode line
+
+ Starting in Emacs 21, certain text properties are meaningful in the
+mode line. The @code{face} property affects the appearance of text; the
+@code{help-echo} property associate help strings with the text, and
+@code{local-map} can make the text mouse-sensitive.
+
+ There are four ways to specify text properties for text in the mode
+line:
+
+@enumerate
+@item
+Put a string with a text property directly into the mode-line data
+structure.
+
+@item
+Put a text property on a mode-line %-construct such as @samp{%12b}; then
+the expansion of the %-construct will have that same text property.
+
+@item
+Use a @code{(:propertize @var{elt} @var{props}@dots{})} construct to
+give @var{elt} a text property specified by @var{props}.
+
+@item
+Use a list containing @code{:eval @var{form}} in the mode-line data
+structure, and make @var{form} evaluate to a string that has a text
+property.
+@end enumerate
+
+ You use the @code{local-map} property to specify a keymap. Like any
+keymap, it can bind character keys and function keys; but that has no
+effect, since it is impossible to move point into the mode line. This
+keymap can only take real effect for mouse clicks.
+
+@node Header Lines
+@subsection Window Header Lines
+@cindex header line (of a window)
+@cindex window header line
+
+ Starting in Emacs 21, a window can have a @dfn{header line} at the
+top, just as it can have a mode line at the bottom. The header line
+feature works just like the mode-line feature, except that it's
+controlled by different variables.
+
+@tindex header-line-format
+@defvar header-line-format
+This variable, local in every buffer, specifies how to display the
+header line, for windows displaying the buffer. The format of the value
+is the same as for @code{mode-line-format} (@pxref{Mode Line Data}).
+@end defvar
+
+@tindex default-header-line-format
+@defvar default-header-line-format
+This variable holds the default @code{header-line-format} for buffers
+that do not override it. This is the same as @code{(default-value
+'header-line-format)}.
+
+It is normally @code{nil}, so that ordinary buffers have no header line.
+@end defvar
+
+@node Emulating Mode Line
+@subsection Emulating Mode-Line Formatting
+
+ You can use the function @code{format-mode-line} to compute
+the text that would appear in a mode line or header line
+based on certain mode-line specification.
+
+@defun format-mode-line &optional format window no-props
+This function formats a line of text according to @var{format} as if
+it were generating the mode line for @var{window}, but instead of
+displaying the text in the mode line or the header line, it returns
+the text as a string.
+
+If @var{format} is @code{nil}, that means to use
+@code{mode-line-format} and return the text that would appear in the
+mode line. If @var{format} is @code{t}, that means to use
+@code{header-line-format} so as to return the text that would appear
+in the header line (@code{""} if the window has no header line).
+The argument @var{window} defaults to the selected window.
+
+The value string normally has text properties that correspond to the
+faces, keymaps, etc., that the mode line would have. If
+@var{no-props} is non-@code{nil}, the value has no text properties.
+@end defun
+
@node Imenu
@section Imenu
@cindex Imenu
@dfn{Imenu} is a feature that lets users select a definition or
section in the buffer, from a menu which lists all of them, to go
-directly to that location in the buffer. Imenu works by constructing a
-buffer index which lists the names and positions of the definitions or
-portions of in the buffer, so the user can pick one of them to move to.
-This section explains how to customize Imenu for a major mode.
+directly to that location in the buffer. Imenu works by constructing
+a buffer index which lists the names and buffer positions of the
+definitions, or other named portions of the buffer; then the user can
+choose one of them and move point to it. The user-level commands for
+using Imenu are described in the Emacs Manual (@pxref{Imenu,, Imenu,
+emacs, the Emacs Manual}). This section explains how to customize
+Imenu's method of finding definitions or buffer portions for a
+particular major mode.
The usual and simplest way is to set the variable
@code{imenu-generic-expression}:
@defvar imenu-generic-expression
-This variable, if non-@code{nil}, specifies regular expressions for
-finding definitions for Imenu. In the simplest case, elements should
-look like this:
+This variable, if non-@code{nil}, is a list that specifies regular
+expressions for finding definitions for Imenu. Simple elements of
+@code{imenu-generic-expression} look like this:
@example
-(@var{menu-title} @var{regexp} @var{subexp})
+(@var{menu-title} @var{regexp} @var{index})
@end example
Here, if @var{menu-title} is non-@code{nil}, it says that the matches
in the top level of the buffer index.
The second item in the list, @var{regexp}, is a regular expression
-(@pxref{Regular Expressions}); wherever it matches, that is a definition
-to mention in the buffer index. The third item, @var{subexp}, indicates
+(@pxref{Regular Expressions}); anything in the buffer that it matches
+is considered a definition, something to mention in the buffer index.
+The third item, @var{index}, is a non-negative integer that indicates
which subexpression in @var{regexp} matches the definition's name.
An element can also look like this:
(@var{menu-title} @var{regexp} @var{index} @var{function} @var{arguments}@dots{})
@end example
-Each match for this element creates a special index item which, if
-selected by the user, calls @var{function} with arguments
-@var{item-name}, the buffer position, and @var{arguments}.
+Like in the previous case, each match for this element creates an
+index item. However, if this index item is selected by the user, it
+calls @var{function} with arguments consisting of the item name, the
+buffer position, and @var{arguments}.
-For Emacs Lisp mode, @var{pattern} could look like this:
+For Emacs Lisp mode, @code{imenu-generic-expression} could look like
+this:
+@c should probably use imenu-syntax-alist and \\sw rather than [-A-Za-z0-9+]
@example
@group
((nil "^\\s-*(def\\(un\\|subst\\|macro\\|advice\\)\
@end group
@group
("*Types*"
- "^\\s-*(def\\(type\\|struct\\|class\\|ine-condition\\)\
+ "^\\s-*\
+(def\\(type\\|struct\\|class\\|ine-condition\\)\
\\s-+\\([-A-Za-z0-9+]+\\)" 2))
@end group
@end example
@end defvar
@defvar imenu-case-fold-search
-This variable controls whether the regular expression matching for Imenu
-is case-sensitive: @code{t}, the default, means matching should ignore
+This variable controls whether matching against the regular
+expressions in the value of @code{imenu-generic-expression} is
+case-sensitive: @code{t}, the default, means matching should ignore
case.
+Setting this variable makes it buffer-local in the current buffer.
+@end defvar
+
+@defvar imenu-syntax-alist
+This variable is an alist of syntax table modifiers to use while
+processing @code{imenu-generic-expression}, to override the syntax table
+of the current buffer. Each element should have this form:
+
+@example
+(@var{characters} . @var{syntax-description})
+@end example
+
+The @sc{car}, @var{characters}, can be either a character or a string.
+The element says to give that character or characters the syntax
+specified by @var{syntax-description}, which is passed to
+@code{modify-syntax-entry} (@pxref{Syntax Table Functions}).
+
+This feature is typically used to give word syntax to characters which
+normally have symbol syntax, and thus to simplify
+@code{imenu-generic-expression} and speed up matching.
+For example, Fortran mode uses it this way:
+
+@example
+(setq imenu-syntax-alist '(("_$" . "w")))
+@end example
+
+The @code{imenu-generic-expression} regular expressions can then use
+@samp{\\sw+} instead of @samp{\\(\\sw\\|\\s_\\)+}. Note that this
+technique may be inconvenient when the mode needs to limit the initial
+character of a name to a smaller set of characters than are allowed in
+the rest of a name.
+
Setting this variable makes it buffer-local in the current buffer.
@end defvar
@code{imenu-extract-index-name-function}:
@defvar imenu-prev-index-position-function
-If this variable is non-@code{nil}, its value should be a function for
-finding the next definition to mention in the buffer index, moving
-backwards in the file.
-
-The function should leave point at the place to be connected to the
-index item; it should return @code{nil} if it doesn't find another item.
+If this variable is non-@code{nil}, its value should be a function that
+finds the next ``definition'' to put in the buffer index, scanning
+backward in the buffer from point. It should return @code{nil} if it
+doesn't find another ``definition'' before point. Otherwise it should
+leave point at the place it finds a ``definition,'' and return any
+non-@code{nil} value.
Setting this variable makes it buffer-local in the current buffer.
@end defvar
@end defvar
The last way to customize Imenu for a major mode is to set the
-variables @code{imenu-create-index-function}:
+variable @code{imenu-create-index-function}:
@defvar imenu-create-index-function
-This variable specifies the function to use for creating a buffer index.
-The function should take no arguments, and return an index for the
-current buffer. It is called within @code{save-excursion}, so where it
-leaves point makes no difference.
+This variable specifies the function to use for creating a buffer
+index. The function should take no arguments, and return an index
+alist for the current buffer. It is called within
+@code{save-excursion}, so where it leaves point makes no difference.
-The default value is a function that uses
-@code{imenu-generic-expression} to produce the index alist. If you
-specify a different function, then @code{imenu-generic-expression} is
-not used.
+The index alist can have three types of elements. Simple elements
+look like this:
-Setting this variable makes it buffer-local in the current buffer.
-@end defvar
+@example
+(@var{index-name} . @var{index-position})
+@end example
-@defvar imenu-index-alist
-This variable holds the index alist for the current buffer.
-Setting it makes it buffer-local in the current buffer.
+Selecting a simple element has the effect of moving to position
+@var{index-position} in the buffer. Special elements look like this:
-Simple elements in the alist look like @code{(@var{index-name}
-. @var{index-position})}. Selecting a simple element has the effect of
-moving to position @var{index-position} in the buffer.
+@example
+(@var{index-name} @var{index-position} @var{function} @var{arguments}@dots{})
+@end example
-Special elements look like @code{(@var{index-name} @var{position}
-@var{function} @var{arguments}@dots{})}. Selecting a special element
-performs
+Selecting a special element performs:
@example
-(funcall @var{function} @var{index-name} @var{position} @var{arguments}@dots{})
+(funcall @var{function}
+ @var{index-name} @var{index-position} @var{arguments}@dots{})
@end example
-A nested sub-alist element looks like @code{(@var{index-name}
-@var{sub-alist})}.
+A nested sub-alist element looks like this:
+
+@example
+(@var{menu-title} @var{sub-alist})
+@end example
+
+It creates the submenu @var{menu-title} specified by @var{sub-alist}.
+
+The default value of @code{imenu-create-index-function} is
+@code{imenu-default-create-index-function}. This function uses
+@code{imenu-prev-index-position-function} and
+@code{imenu-extract-index-name-function} to produce the index alist.
+However, if either of these two variables is @code{nil}, the default
+function uses @code{imenu-generic-expression} instead.
+
+Setting this variable makes it buffer-local in the current buffer.
@end defvar
@node Font Lock Mode
@dfn{Font Lock mode} is a feature that automatically attaches
@code{face} properties to certain parts of the buffer based on their
syntactic role. How it parses the buffer depends on the major mode;
-most major modes define syntactic criteria for which faces to use, in
+most major modes define syntactic criteria for which faces to use in
which contexts. This section explains how to customize Font Lock for a
-particular language---in other words, for a particular major mode.
+particular major mode.
Font Lock mode finds text to highlight in two ways: through syntactic
parsing based on the syntax table, and through searching (usually for
regular expressions). Syntactic fontification happens first; it finds
comments and string constants, and highlights them using
@code{font-lock-comment-face} and @code{font-lock-string-face}
-(@pxref{Faces for Font Lock}); search-based fontification follows.
+(@pxref{Faces for Font Lock}). Search-based fontification follows.
@menu
* Font Lock Basics::
* Search-based Fontification::
* Other Font Lock Variables::
* Levels of Font Lock::
+* Precalculated Fontification::
* Faces for Font Lock::
* Syntactic Font Lock::
@end menu
There are several variables that control how Font Lock mode highlights
text. But major modes should not set any of these variables directly.
-Instead, it should set @code{font-lock-defaults} as a buffer-local
+Instead, they should set @code{font-lock-defaults} as a buffer-local
variable. The value assigned to this variable is used, if and when Font
Lock mode is enabled, to set all the other variables.
The first element, @var{keywords}, indirectly specifies the value of
@code{font-lock-keywords}. It can be a symbol, a variable whose value
-is list to use for @code{font-lock-keywords}. It can also be a list of
+is the list to use for @code{font-lock-keywords}. It can also be a list of
several such symbols, one for each possible level of fontification. The
first symbol specifies how to do level 1 fontification, the second
symbol how to do level 2, and so on.
The second element, @var{keywords-only}, specifies the value of the
-variable @code{font-lock-keywords-only}. If this is is non-@code{nil},
+variable @code{font-lock-keywords-only}. If this is non-@code{nil},
syntactic fontification (of strings and comments) is not performed.
The third element, @var{case-fold}, specifies the value of
The fifth element, @var{syntax-begin}, specifies the value of
@code{font-lock-beginning-of-syntax-function} (see below).
-Any further elements @var{other-vars} are have form
-@code{(@var{variable} . @var{value})}. This kind of element means to
-make @var{variable} buffer-local and then set it to @var{value}. This
-is used to set other variables that affect fontification.
+All the remaining elements (if any) are collectively called
+@var{other-vars}. Each of these elements should have the form
+@code{(@var{variable} . @var{value})}---which means, make @var{variable}
+buffer-local and then set it to @var{value}. You can use these
+@var{other-vars} to set other variables that affect fontification,
+aside from those you can control with the first five elements.
@end defvar
@node Search-based Fontification
it finds using @code{font-lock-keyword-face}.
When @var{function} is called, it receives one argument, the limit of
-the search. It should return non-@code{nil} if it succeeds, and set the
-match data to describe the match that was found.
+the search; it should begin searching at point, and not search beyond the
+limit. It should return non-@code{nil} if it succeeds, and set the
+match data to describe the match that was found. Returning @code{nil}
+indicates failure of the search.
+
+Fontification will call @var{function} repeatedly with the same limit,
+and with point where the previous invocation left it, until
+@var{function} fails. On failure, @var{function} need not reset point
+in any particular way.
@item (@var{matcher} . @var{match})
-In this kind of element, @var{matcher} stands for either a regular
+In this kind of element, @var{matcher} is either a regular
expression or a function, as described above. The @sc{cdr},
@var{match}, specifies which subexpression of @var{matcher} should be
highlighted (instead of the entire text that @var{matcher} matched).
@example
-;; @r{Highlight the @samp{bar} in each occurrences of @samp{fubar},}
+;; @r{Highlight the @samp{bar} in each occurrence of @samp{fubar},}
;; @r{using @code{font-lock-keyword-face}.}
("fu\\(bar\\)" . 1)
@end example
@var{matcher}, then you can use @code{regexp-opt-depth} (@pxref{Syntax
of Regexps}) to calculate the value for @var{match}.
-@item (@var{matcher} . @var{facename})
-In this kind of element, @var{facename} is an expression whose value
-specifies the face name to use for highlighting.
+@item (@var{matcher} . @var{facespec})
+In this kind of element, @var{facespec} is an object which specifies
+the face variable to use for highlighting. In the simplest case, it
+is a Lisp variable (a symbol), whose value should be a face name.
@example
;; @r{Highlight occurrences of @samp{fubar},}
("fubar" . fubar-face)
@end example
+However, @var{facespec} can also be a list of the form
+
+@example
+(face @var{face} @var{prop1} @var{val1} @var{prop2} @var{val2}@dots{})
+@end example
+
+to specify various text properties to put on the text that matches.
+If you do this, be sure to add the other text property names that you
+set in this way to the value of @code{font-lock-extra-managed-props}
+so that the properties will also be cleared out when they are no longer
+appropriate.
+
@item (@var{matcher} . @var{highlighter})
In this kind of element, @var{highlighter} is a list
which specifies how to highlight matches found by @var{matcher}.
It has the form
@example
-(@var{subexp} @var{facename} @var{override} @var{laxmatch})
+(@var{subexp} @var{facespec} @var{override} @var{laxmatch})
@end example
The @sc{car}, @var{subexp}, is an integer specifying which subexpression
of the match to fontify (0 means the entire matching text). The second
-subelement, @var{facename}, specifies the face, as described above.
+subelement, @var{facespec}, specifies the face, as described above.
The last two values in @var{highlighter}, @var{override} and
-@var{laxmatch}, are flags. If @var{override} is @code{t}, this element
-can override existing fontification made by previous elements of
-@code{font-lock-keywords}. If it is @code{keep}, then each character is
-fontified if it has not been fontified already by some other element.
-If it is @code{prepend}, the face @var{facename} is added to the
-beginning of the @code{face} property. If it is @code{append}, the face
-@var{facename} is added to the end of the @code{face} property.
+@var{laxmatch}, are flags. If @var{override} is @code{t}, this
+element can override existing fontification made by previous elements
+of @code{font-lock-keywords}. If it is @code{keep}, then each
+character is fontified if it has not been fontified already by some
+other element. If it is @code{prepend}, the face specified by
+@var{facespec} is added to the beginning of the @code{font-lock-face}
+property. If it is @code{append}, the face is added to the end of the
+@code{font-lock-face} property.
If @var{laxmatch} is non-@code{nil}, it means there should be no error
if there is no subexpression numbered @var{subexp} in @var{matcher}.
+Obviously, fontification of the subexpression numbered @var{subexp} will
+not occur. However, fontification of other subexpressions (and other
+regexps) will continue. If @var{laxmatch} is @code{nil}, and the
+specified subexpression is missing, then an error is signalled which
+terminates search-based fontification.
Here are some examples of elements of this kind, and what they do:
;; @r{@code{foo-bar-face} should be a variable whose value is a face.}
("foo\\|bar" 0 foo-bar-face t)
-;; @r{Highlight the first subexpression within each occurrences}
+;; @r{Highlight the first subexpression within each occurrence}
;; @r{that the function @code{fubar-match} finds,}
;; @r{using the face which is the value of @code{fubar-face}.}
(fubar-match 1 fubar-face)
exception---see below. @var{pre-match-form} and @var{post-match-form}
are evaluated before the first, and after the last, instance
@var{anchored}'s @var{submatcher} is used. Therefore they can be used
-to initialise before, and cleanup after, @var{submatcher} is used.
+to initialize before, and cleanup after, @var{submatcher} is used.
Typically, @var{pre-match-form} is used to move to some position
relative to the original @var{submatcher}, before starting with
@var{anchored}'s @var{submatcher}. @var{post-match-form} might be used
to match text which spans lines; this does not work reliably. While
@code{font-lock-fontify-buffer} handles multi-line patterns correctly,
updating when you edit the buffer does not, since it considers text one
-line at a time.
+line at a time. If you have patterns that typically only span one
+line but can occasionally span two or three, such as
+@samp{<title>...</title>}, you can ask font-lock to be more careful by
+setting @code{font-lock-multiline} to @code{t}. But it still will not
+work in all cases.
@node Other Font Lock Variables
@subsection Other Font Lock Variables
@end defvar
@ignore
-Other variables include those for buffer-specialised fontification functions,
+Other variables include those for buffer-specialized fontification functions,
`font-lock-fontify-buffer-function', `font-lock-unfontify-buffer-function',
`font-lock-fontify-region-function', `font-lock-unfontify-region-function',
`font-lock-inhibit-thing-lock' and `font-lock-maximum-size'.
textual modes.
@end defvar
+@defvar font-lock-extra-managed-props
+Additional properties (other than @code{font-lock-face}) that are
+being managed by Font Lock mode. Font Lock mode normally manages only
+the @code{font-lock-face} property; if you want it to manage others as
+well, you must specify them in a @var{facespec} in
+@code{font-lock-keywords} as well as adding them to this list.
+@end defvar
+
+@defvar font-lock-syntactic-face-function
+A function to determine which face to use for a given syntactic
+element (a string or a comment). The function is called with one
+argument, the parse state at point returned by
+@code{parse-partial-sexp}, and should return a face. The default
+value returns @code{font-lock-comment-face} for comments and
+@code{font-lock-string-face} for strings.
+
+This can be used to highlighting different kinds of strings or
+comments differently. It is also sometimes abused together with
+@code{font-lock-syntactic-keywords} to highlight elements that span
+multiple lines, but this is too obscure to document in this manual.
+@end defvar
+
@node Levels of Font Lock
@subsection Levels of Font Lock
wherever they appear.
@end itemize
+@node Precalculated Fontification
+@subsection Precalculated Fontification
+
+In addition to using @code{font-lock-defaults} for search-based
+fontification, you may use the special character property
+@code{font-lock-face} (@pxref{Special Properties}). This property
+acts just like the explicit @code{face} property, but its activation
+is toggled when the user calls @kbd{M-x font-lock-mode}. Using
+@code{font-lock-face} is especially convenient for special modes
+which construct their text programmatically, such as
+@code{list-buffers} and @code{occur}.
+
+If your mode does not use any of the other machinery of Font Lock
+(i.e. it only uses the @code{font-lock-face} property), you can tell
+Emacs not to load all of font-lock.el (unless it's already loaded), by
+setting the variable @code{font-lock-core-only} to non-@code{nil} as
+part of the @code{font-lock-defaults} settings. Here is the canonical
+way to do this:
+
+@example
+(set (make-local-variable 'font-lock-defaults)
+ '(nil t nil nil nil (font-lock-core-only . t)))
+@end example
+
@node Faces for Font Lock
@subsection Faces for Font Lock
@table @code
@item font-lock-comment-face
@vindex font-lock-comment-face
-@kindex font-lock-comment-face @r{(face name)}
Used (typically) for comments.
@item font-lock-string-face
@vindex font-lock-string-face
-@kindex font-lock-string-face @r{(face name)}
Used (typically) for string constants.
@item font-lock-keyword-face
@vindex font-lock-keyword-face
-@kindex font-lock-keyword-face @r{(face name)}
Used (typically) for keywords---names that have special syntactic
significance, like @code{for} and @code{if} in C.
@item font-lock-builtin-face
@vindex font-lock-builtin-face
-@kindex font-lock-builtin-face @r{(face name)}
Used (typically) for built-in function names.
@item font-lock-function-name-face
@vindex font-lock-function-name-face
-@kindex font-lock-function-name-face @r{(face name)}
Used (typically) for the name of a function being defined or declared,
-in a function definition or declaration.
+in a function definition or declaration.
@item font-lock-variable-name-face
@vindex font-lock-variable-name-face
-@kindex font-lock-variable-name-face @r{(face name)}
Used (typically) for the name of a variable being defined or declared,
in a variable definition or declaration.
@item font-lock-type-face
@vindex font-lock-type-face
-@kindex font-lock-type-face @r{(face name)}
Used (typically) for names of user-defined data types,
where they are defined and where they are used.
@item font-lock-constant-face
@vindex font-lock-constant-face
-@kindex font-lock-constant-face @r{(face name)}
Used (typically) for constant names.
+@item font-lock-preprocessor-face
+@vindex font-lock-preprocessor-face
+Used (typically) for preprocessor commands.
+
@item font-lock-warning-face
@vindex font-lock-warning-face
-@kindex font-lock-warning-face @r{(face name)}
Used (typically) for constructs that are peculiar, or that greatly
change the meaning of other text. For example, this is used for
@samp{;;;###autoload} cookies in Emacs Lisp, and for @code{#error}
table by itself is not sufficient.
@defvar font-lock-syntactic-keywords
-This variable enables and controls syntactic Font Lock. Its value
-should be a list of elements of this form:
+This variable enables and controls syntactic Font Lock. It is
+normally set via @code{font-lock-defaults}. Its value should be a
+list of elements of this form:
@example
(@var{matcher} @var{subexp} @var{syntax} @var{override} @var{laxmatch})
@end example
However, instead of specifying the value @var{facename} to use for the
-@code{face} property, it specifies the value @var{syntax} to use for the
-@code{syntax-table} property. Here, @var{syntax} can be a variable
-whose value is a syntax table, a syntax entry of the form
-@code{(@var{syntax-code} . @var{matching-char})}, or an expression whose
-value is one of those two types.
+@code{face} property, it specifies the value @var{syntax} to use for
+the @code{syntax-table} property. Here, @var{syntax} can be a string
+(as taken by @code{modify-syntax-entry}), a syntax table, a cons cell
+(as returned by @code{string-to-syntax}), or an expression whose value
+is one of those two types. @var{override} cannot be @code{prepend} or
+@code{append}.
+
+For example, an element of the form:
+
+@example
+("\\$\\(#\\)" 1 ".")
+@end example
+
+highlights syntactically a hash character when following a dollar
+character, with a SYNTAX of @code{"."} (meaning punctuation syntax).
+Assuming that the buffer syntax table specifies hash characters to
+have comment start syntax, the element will only highlight hash
+characters that do not follow dollar characters as comments
+syntactically.
+
+An element of the form:
+
+@example
+ ("\\('\\).\\('\\)"
+ (1 "\"")
+ (2 "\""))
+@end example
+
+highlights syntactically both single quotes which surround a single
+character, with a SYNTAX of @code{"\""} (meaning string quote syntax).
+Assuming that the buffer syntax table does not specify single quotes
+to have quote syntax, the element will only highlight single quotes of
+the form @samp{'@var{c}'} as strings syntactically. Other forms, such
+as @samp{foo'bar} or @samp{'fubar'}, will not be highlighted as
+strings.
+
+@end defvar
+
+@node Desktop Save Mode
+@section Desktop Save Mode
+@cindex desktop save mode
+
+@dfn{Desktop Save Mode} is a feature to save the state of Emacs from
+one session to another. The user-level commands for using Desktop
+Save Mode are described in the GNU Emacs Manual (@pxref{Saving Emacs
+Sessions,,, emacs, the GNU Emacs Manual}). Modes whose buffers visit
+a file, don't have to do anything to use this feature.
+
+For buffers not visiting a file to have their state saved, the major
+mode must bind the buffer local variable @code{desktop-save-buffer} to
+a non-nil value.
+
+@defvar desktop-save-buffer
+If this buffer-local variable is non-@code{nil}, the buffer will have
+its state saved in the desktop file at desktop save. If the value is
+a function, it is called at desktop save with argument
+@var{desktop-dirname}, and its value is saved in the desktop file along
+with the state of the buffer for which it was called. When file names
+are returned as part of the auxiliary information, they should be
+formatted using the call
+
+@example
+(desktop-file-name @var{file-name} @var{desktop-dirname})
+@end example
+
+@end defvar
+
+For buffers not visiting a file to be restored, the major mode must
+define a function to do the job, and that function must be listed in
+the alist @code{desktop-buffer-mode-handlers}.
+
+@defvar desktop-buffer-mode-handlers
+Alist with elements
+
+@example
+(@var{major-mode} . @var{restore-buffer-function})
+@end example
+
+The function @var{restore-buffer-function} will be called with
+argument list
+
+@example
+(@var{buffer-file-name} @var{buffer-name} @var{desktop-buffer-misc})
+@end example
+
+and it should return the restored buffer.
+Here @var{desktop-buffer-misc} is the value returned by the function
+optionally bound to @code{desktop-save-buffer}.
+
@end defvar
@node Hooks
A @dfn{hook} is a variable where you can store a function or functions
to be called on a particular occasion by an existing program. Emacs
provides hooks for the sake of customization. Most often, hooks are set
-up in the @file{.emacs} file, but Lisp programs can set them also.
+up in the init file (@pxref{Init File}), but Lisp programs can set them also.
@xref{Standard Hooks}, for a list of standard hook variables.
@cindex normal hook
The recommended way to add a hook function to a normal hook is by
calling @code{add-hook} (see below). The hook functions may be any of
-the valid kinds of functions that @code{funcall} accepts (@pxref{What Is
-a Function}). Most normal hook variables are initially void;
-@code{add-hook} knows how to deal with this.
+the valid kinds of functions that @code{funcall} accepts (@pxref{What
+Is a Function}). Most normal hook variables are initially void;
+@code{add-hook} knows how to deal with this. You can add hooks either
+globally or buffer-locally with @code{add-hook}.
@cindex abnormal hook
If the hook variable's name does not end with @samp{-hook}, that
-indicates it is probably an @dfn{abnormal hook}; you should look at its
+indicates it is probably an @dfn{abnormal hook}. Then you should look at its
documentation to see how to use the hook properly.
If the variable's name ends in @samp{-functions} or @samp{-hooks},
these functions are called with arguments or their values are used in
some way. You can use @code{add-hook} to add a function to the list,
but you must take care in writing the function. (A few of these
-variables are actually normal hooks which were named before we
-established the convention of using @samp{-hook} for them.)
+variables, notably those ending in @samp{-hooks}, are actually
+normal hooks which were named before we established the convention of
+using @samp{-hook} for them.)
If the variable's name ends in @samp{-function}, then its value
is just a single function, not a list of functions.
run particular hooks. This function calls the hook functions that have
been added with @code{add-hook}.
-@defun run-hooks &rest hookvar
-This function takes one or more hook variable names as arguments, and
-runs each hook in turn. Each @var{hookvar} argument should be a symbol
-that is a hook variable. These arguments are processed in the order
-specified.
+@defun run-hooks &rest hookvars
+This function takes one or more normal hook variable names as
+arguments, and runs each hook in turn. Each argument should be a
+symbol that is a normal hook variable. These arguments are processed
+in the order specified.
If a hook variable has a non-@code{nil} value, that value may be a
-function or a list of functions. If the value is a function (either a
-lambda expression or a symbol with a function definition), it is called.
-If it is a list, the elements are called, in order. The hook functions
-are called with no arguments. Nowadays, storing a single function in
-the hook variable is semi-obsolete; you should always use a list of
-functions.
+function or a list of functions. (The former option is considered
+obsolete.) If the value is a function (either a lambda expression or
+a symbol with a function definition), it is called. If it is a list
+that isn't a function, its elements are called, consecutively. All
+the hook functions are called with no arguments.
For example, here's how @code{emacs-lisp-mode} runs its mode hook:
@end example
@end defun
+@defun run-mode-hooks &rest hookvars
+Like @code{run-hooks}, but is affected by the @code{delay-mode-hooks}
+macro.
+@end defun
+
+@defmac delay-mode-hooks body...
+This macro executes the @var{body} forms but defers all calls to
+@code{run-mode-hooks} within them until the end of @var{body}.
+This macro enables a derived mode to arrange not to run
+its parent modes' mode hooks until the end.
+@end defmac
+
+@defun run-hook-with-args hook &rest args
+This function is the way to run an abnormal hook and always call all
+of the hook functions. It calls each of the hook functions one by
+one, passing each of them the arguments @var{args}.
+@end defun
+
+@defun run-hook-with-args-until-failure hook &rest args
+This function is the way to run an abnormal hook until one of the hook
+functions fails. It calls each of the hook functions, passing each of
+them the arguments @var{args}, until some hook function returns
+@code{nil}. It then stops and returns @code{nil}. If none of the
+hook functions return @code{nil}, it returns a non-@code{nil} value.
+@end defun
+
+@defun run-hook-with-args-until-success hook &rest args
+This function is the way to run an abnormal hook until a hook function
+succeeds. It calls each of the hook functions, passing each of them
+the arguments @var{args}, until some hook function returns
+non-@code{nil}. Then it stops, and returns whatever was returned by
+the last hook function that was called. If all hook functions return
+@code{nil}, it returns @code{nil} as well.
+@end defun
+
@defun add-hook hook function &optional append local
This function is the handy way to add function @var{function} to hook
-variable @var{hook}. The argument @var{function} may be any valid Lisp
-function with the proper number of arguments. For example,
+variable @var{hook}. You can use it for abnormal hooks as well as for
+normal hooks. @var{function} can be any Lisp function that can accept
+the proper number of arguments for @var{hook}. For example,
@example
(add-hook 'text-mode-hook 'my-text-hook-function)
@noindent
adds @code{my-text-hook-function} to the hook called @code{text-mode-hook}.
-You can use @code{add-hook} for abnormal hooks as well as for normal
-hooks.
+If @var{function} is already present in @var{hook} (comparing using
+@code{equal}), then @code{add-hook} does not add it a second time.
It is best to design your hook functions so that the order in which they
are executed does not matter. Any dependence on the order is ``asking
-for trouble.'' However, the order is predictable: normally,
+for trouble''. However, the order is predictable: normally,
@var{function} goes at the front of the hook list, so it will be
executed first (barring another @code{add-hook} call). If the optional
argument @var{append} is non-@code{nil}, the new hook function goes at
the end of the hook list and will be executed last.
-If @var{local} is non-@code{nil}, that says to make the new hook
-function buffer-local in the current buffer. Before you can do this, you must
-make the hook itself buffer-local by calling @code{make-local-hook}
-(@strong{not} @code{make-local-variable}). If the hook itself is not
-buffer-local, then the value of @var{local} makes no difference---the
-hook function is always global.
+If @var{local} is non-@code{nil}, that says to add @var{function} to
+the buffer-local hook list instead of to the global hook list. If
+needed, this makes the hook buffer-local and adds @code{t} to the
+buffer-local value. The latter acts as a flag to run the hook
+functions in the default value as well as in the local value.
@end defun
@defun remove-hook hook function &optional local
-This function removes @var{function} from the hook variable @var{hook}.
+This function removes @var{function} from the hook variable
+@var{hook}. It compares @var{function} with elements of @var{hook}
+using @code{equal}, so it works for both symbols and lambda
+expressions.
If @var{local} is non-@code{nil}, that says to remove @var{function}
from the buffer-local hook list instead of from the global hook list.
-If the hook variable itself is not buffer-local, then the value of
-@var{local} makes no difference.
@end defun
-@defun make-local-hook hook
-This function makes the hook variable @code{hook} buffer-local in the
-current buffer. When a hook variable is buffer-local, it can have
-buffer-local and global hook functions, and @code{run-hooks} runs all of
-them.
-
-This function works by making @code{t} an element of the buffer-local
-value. That serves as a flag to use the hook functions in the default
-value of the hook variable as well as those in the buffer-local value.
-Since @code{run-hooks} understands this flag, @code{make-local-hook}
-works with all normal hooks. It works for only some non-normal
-hooks---those whose callers have been updated to understand this meaning
-of @code{t}.
-
-Do not use @code{make-local-variable} directly for hook variables; it is
-not sufficient.
-@end defun
+@ignore
+ arch-tag: 4c7bff41-36e6-4da6-9e7f-9b9289e27c8e
+@end ignore