@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,
+@c 2003, 2004, 2005 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
@ref{Keymaps}, and @ref{Syntax Tables}.
@menu
+* Hooks:: How to use hooks; how to write code that provides hooks.
* Major Modes:: Defining major modes.
* Minor Modes:: Defining minor modes.
* Mode Line Format:: Customizing the text that appears in the mode line.
* Imenu:: How a mode can provide a menu
of definitions in the buffer.
* Font Lock Mode:: How modes can highlight text according to syntax.
-* Hooks:: How to use hooks; how to write code that provides hooks.
+* Desktop Save Mode:: How modes can have buffer state saved between
+ Emacs sessions.
@end menu
+@node Hooks
+@section Hooks
+@cindex 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 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
+ Most of the hooks in Emacs are @dfn{normal hooks}. These variables
+contain lists of functions to be called with no arguments. When the
+hook name ends in @samp{-hook}, that tells you it is normal. We try to
+make all hooks normal, as much as possible, so that you can use them in
+a uniform way.
+
+ Every major mode function is supposed to run a normal hook called the
+@dfn{mode hook} as the last step of initialization. This makes it easy
+for a user to customize the behavior of the mode, by overriding the
+buffer-local variable assignments already made by the mode. Most
+minor modes also run a mode hook at their end. But hooks are used in
+other contexts too. For example, the hook @code{suspend-hook} runs
+just before Emacs suspends itself (@pxref{Suspending Emacs}).
+
+ 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. 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}. 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},
+then the value is a list of functions, but it is abnormal in that either
+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, 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.
+
+ Here's an example that uses a mode hook to turn on Auto Fill mode when
+in Lisp Interaction mode:
+
+@example
+(add-hook 'lisp-interaction-mode-hook 'turn-on-auto-fill)
+@end example
+
+ At the appropriate time, Emacs uses the @code{run-hooks} function to
+run particular hooks.
+
+@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. (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.
+@end defun
+
+@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}. 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)
+@end example
+
+@noindent
+adds @code{my-text-hook-function} to the hook called @code{text-mode-hook}.
+
+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,
+@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.
+
+@code{add-hook} can handle the cases where @var{hook} is void or its
+value is a single function; it sets or changes the value to a list of
+functions.
+
+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}. 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.
+@end defun
+
@node Major Modes
@section Major Modes
@cindex major mode
-@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.
+
+@menu
+* Major Mode Basics::
+* Major Mode Conventions:: Coding conventions for keymaps, etc.
+* 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
+ mode.
+* Generic Modes:: Defining a simple major mode that supports
+ comment syntax and Font Lock mode.
+* Mode Hooks:: Hooks run at the end of major mode functions.
+@end menu
+
+@node Major Mode Basics
+@subsection Major Mode Basics
+@cindex Fundamental mode
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.
+
+ For a very simple programming language major mode that handles
+comments and fontification, you can use @code{define-generic-mode}.
+@xref{Generic Modes}.
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 commands). In such cases, the
-temporary major mode usually has a command to switch back to 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
-* Major Mode Conventions:: Coding conventions for keymaps, etc.
-* 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
- mode.
-@end menu
-
@node Major Mode Conventions
@subsection Major Mode Conventions
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
characters are reserved for minor modes, and ordinary letters are
reserved for users.
-It is reasonable for a major mode to rebind a key sequence with a
-standard meaning, if it implements a command that does ``the same job''
-in a way that fits the major mode better. For example, a major mode for
-editing a programming language might redefine @kbd{C-M-a} to ``move to
-the beginning of a function'' in a way that works better for that
-language.
+A major mode can also rebind the keys @kbd{M-n}, @kbd{M-p} and
+@kbd{M-s}. The bindings for @kbd{M-n} and @kbd{M-p} should normally
+be some kind of ``moving forward and backward,'' but this does not
+necessarily mean cursor motion.
+
+It is legitimate for a major mode to rebind a standard key sequence if
+it provides a command that does ``the same job'' in a way better
+suited to the text this mode is used for. For example, a major mode
+for editing a programming language might redefine @kbd{C-M-a} to
+``move to the beginning of a function'' in a way that works better for
+that language.
+
+It is also legitimate for a major mode to rebind a standard key
+sequence whose standard meaning is rarely useful in that mode. For
+instance, minibuffer modes rebind @kbd{M-r}, whose standard meaning is
+rarely of any use in the minibuffer. Major modes such as Dired or
+Rmail that do not allow self-insertion of text can reasonably redefine
+letters and other printing characters as special commands.
-Major modes such as Dired or Rmail that do not allow self-insertion of
-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
@item
@cindex abbrev tables in modes
The mode may have its own abbrev table or may share one with other
-related modes. If it has its own abbrev table, it should store this in
-a variable named @code{@var{modename}-mode-abbrev-table}. @xref{Abbrev
-Tables}.
+related modes. If it has its own abbrev table, it should store this
+in a variable named @code{@var{modename}-mode-abbrev-table}. If the
+major mode command defines any abbrevs itself, it should pass @code{t}
+for the @var{system-flag} argument to @code{define-abbrev}.
+@xref{Defining Abbrevs}.
@item
The mode should specify how to do highlighting for Font Lock mode, by
@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
+The mode can specify a local value for
+@code{eldoc-documentation-function} to tell ElDoc mode how to handle
+this mode.
+
@item
Use @code{defvar} or @code{defcustom} to set mode-related variables, so
that they are not reinitialized if they already have a value. (Such
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
-does. @xref{Hooks}.
+hook, with @code{run-mode-hooks}, as the very last thing it
+does. @xref{Mode 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) @emph{except} for the final call to
+@code{run-mode-hooks}, which runs the derived mode's hook. (Using
+@code{define-derived-mode} does this automatically.) @xref{Derived
+Modes}, and @ref{Mode Hooks}.
@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
-Funny mode should not inherit Funny mode. Modes such as Dired, Rmail,
+This tells Emacs that new buffers created while the current buffer is
+in Funny mode should not inherit Funny mode, in case
+@code{default-major-mode} is @code{nil}. Modes such as Dired, Rmail,
and Buffer List use this feature.
@item
If you want to make the new mode the default for files with certain
recognizable names, add an element to @code{auto-mode-alist} to select
-the mode for those file names. If you define the mode command to
-autoload, you should add this element in the same file that calls
-@code{autoload}. Otherwise, it is sufficient to add the element in the
-file that contains the mode definition. @xref{Auto Major Mode}.
+the mode for those file names (@pxref{Auto Major Mode}). If you
+define the mode command to autoload, you should add this element in
+the same file that calls @code{autoload}. If you use an autoload
+cookie for the mode command, you can also use an autoload cookie for
+the form that adds the element (@pxref{autoload cookie}). If you do
+not autoload the mode command, it is sufficient to add the element in
+the file that contains the mode definition.
@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.
+In the comments that document the file, 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 init files
+(@pxref{Init File}).
@item
@cindex mode loading
@smallexample
@group
-;; @r{Create mode-specific tables.}
-(defvar text-mode-syntax-table nil
- "Syntax table used while in text mode.")
+;; @r{Create the syntax table for this mode.}
+(defvar text-mode-syntax-table
+ (let ((st (make-syntax-table)))
+ (modify-syntax-entry ?\" ". " st)
+ (modify-syntax-entry ?\\ ". " st)
+ ;; We add `p' so that M-c on 'hello' leads to 'Hello' rather than 'hello'.
+ (modify-syntax-entry ?' "w p" st)
+ st)
+ "Syntax table used while in `text-mode'.")
@end group
+;; @r{Create the keymap for this mode.}
@group
-(if text-mode-syntax-table
- () ; @r{Do not change the table if it is already set up.}
- (setq text-mode-syntax-table (make-syntax-table))
- (modify-syntax-entry ?\" ". " text-mode-syntax-table)
- (modify-syntax-entry ?\\ ". " text-mode-syntax-table)
- (modify-syntax-entry ?' "w " text-mode-syntax-table))
+(defvar text-mode-map
+ (let ((map (make-sparse-keymap)))
+ (define-key map "\e\t" 'ispell-complete-word)
+ (define-key map "\es" 'center-line)
+ (define-key map "\eS" 'center-paragraph)
+ map)
+ "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.")
@end group
+@end smallexample
+
+ Here is how the actual mode command is defined now:
+@smallexample
@group
-(defvar text-mode-abbrev-table nil
- "Abbrev table used while in text mode.")
-(define-abbrev-table 'text-mode-abbrev-table ())
+(define-derived-mode text-mode nil "Text"
+ "Major mode for editing text written for humans to read.
+In this mode, paragraphs are delimited only by blank or white lines.
+You can thus get the full benefit of adaptive filling
+ (see the variable `adaptive-fill-mode').
+\\@{text-mode-map@}
+Turning on Text mode runs the normal hook `text-mode-hook'."
@end group
-
@group
-(defvar text-mode-map nil) ; @r{Create a mode-specific keymap.}
-
-(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" 'indent-relative)
- (define-key text-mode-map "\es" 'center-line)
- (define-key text-mode-map "\eS" 'center-paragraph))
+ (make-local-variable 'text-mode-variant)
+ (setq text-mode-variant t)
+ ;; @r{These two lines are a feature added recently.}
+ (set (make-local-variable 'require-final-newline)
+ mode-require-final-newline)
+ (set (make-local-variable 'indent-line-function) 'indent-relative))
@end group
@end smallexample
- Here is the complete major mode function definition for Text mode:
+ But here is how it was defined formerly, before
+@code{define-derived-mode} existed:
@smallexample
+@group
+;; @r{This isn't needed nowadays, since @code{define-derived-mode} does it.}
+(defvar text-mode-abbrev-table nil
+ "Abbrev table used while in text mode.")
+(define-abbrev-table 'text-mode-abbrev-table ())
+@end group
+
@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
(set-syntax-table text-mode-syntax-table)
@end group
@group
+ ;; @r{These four lines are absent from the current version}
+ ;; @r{not because this is done some other way, but rather}
+ ;; @r{because nowadays Text mode uses the normal definition of paragraphs.}
(make-local-variable 'paragraph-start)
(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 emacs-lisp-mode-syntax-table nil "")
+(defvar lisp-mode-syntax-table nil "")
(defvar lisp-mode-abbrev-table nil "")
@end group
@group
-(if (not emacs-lisp-mode-syntax-table) ; @r{Do not change the table}
- ; @r{if it is already set.}
+(defvar emacs-lisp-mode-syntax-table
+ (let ((table (make-syntax-table)))
(let ((i 0))
- (setq emacs-lisp-mode-syntax-table (make-syntax-table))
@end group
@group
- ;; @r{Set syntax of chars up to 0 to class of chars that are}
+ ;; @r{Set syntax of chars up to @samp{0} to say they 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)
- (modify-syntax-entry i "_ " emacs-lisp-mode-syntax-table)
- (setq i (1+ i)))
- @dots{}
+ ;; @r{(The digit @samp{0} is @code{48} in the @acronym{ASCII} character set.)}
+ (while (< i ?0)
+ (modify-syntax-entry i "_ " table)
+ (setq i (1+ i)))
+ ;; @r{@dots{} similar code follows for other character ranges.}
+@end group
+@group
+ ;; @r{Then set the syntax codes for characters that are special in Lisp.}
+ (modify-syntax-entry ? " " table)
+ (modify-syntax-entry ?\t " " table)
+ (modify-syntax-entry ?\f " " table)
+ (modify-syntax-entry ?\n "> " table)
+@end group
+@group
+ ;; @r{Give CR the same syntax as newline, for selective-display.}
+ (modify-syntax-entry ?\^m "> " table)
+ (modify-syntax-entry ?\; "< " table)
+ (modify-syntax-entry ?` "' " table)
+ (modify-syntax-entry ?' "' " table)
+ (modify-syntax-entry ?, "' " table)
@end group
@group
- ;; @r{Set the syntax for other characters.}
- (modify-syntax-entry ? " " emacs-lisp-mode-syntax-table)
- (modify-syntax-entry ?\t " " emacs-lisp-mode-syntax-table)
- @dots{}
+ ;; @r{@dots{}likewise for many other characters@dots{}}
+ (modify-syntax-entry ?\( "() " table)
+ (modify-syntax-entry ?\) ")( " table)
+ (modify-syntax-entry ?\[ "(] " table)
+ (modify-syntax-entry ?\] ")[ " table))
+ table))
@end group
@group
- (modify-syntax-entry ?\( "() " emacs-lisp-mode-syntax-table)
- (modify-syntax-entry ?\) ")( " emacs-lisp-mode-syntax-table)
- @dots{}))
;; @r{Create an abbrev table for lisp-mode.}
(define-abbrev-table 'lisp-mode-abbrev-table ())
@end group
@smallexample
@group
(defun lisp-mode-variables (lisp-syntax)
- (cond (lisp-syntax
- (set-syntax-table lisp-mode-syntax-table)))
+ (when lisp-syntax
+ (set-syntax-table lisp-mode-syntax-table))
(setq local-abbrev-table lisp-mode-abbrev-table)
@dots{}
@end group
@group
(make-local-variable 'comment-indent-function)
(setq comment-indent-function 'lisp-comment-indent))
+ @dots{}
@end group
@end smallexample
(defvar shared-lisp-mode-map ()
"Keymap for commands shared by all sorts of Lisp modes.")
+;; @r{Putting this @code{if} after the @code{defvar} is an older style.}
(if shared-lisp-mode-map
()
(setq shared-lisp-mode-map (make-sparse-keymap))
@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
; @r{finds out what to describe.}
(setq mode-name "Lisp") ; @r{This goes into the mode line.}
(lisp-mode-variables t) ; @r{This defines various variables.}
+ (make-local-variable 'comment-start-skip)
+ (setq comment-start-skip
+ "\\(\\(^\\|[^\\\\\n]\\)\\(\\\\\\\\\\)*\\)\\(;+\\|#|\\) *")
+ (make-local-variable 'font-lock-keywords-case-fold-search)
+ (setq font-lock-keywords-case-fold-search t)
@end 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
in particular. Other major modes are defined in effect by comparison
with this one---their definitions say what to change, starting from
Fundamental mode. The @code{fundamental-mode} function does @emph{not}
-run any hooks; you're not supposed to customize it. (If you want Emacs
+run any mode hooks; you're not supposed to customize it. (If you want Emacs
to behave differently in Fundamental mode, change the @emph{global}
state of Emacs.)
@end deffn
@deffn Command normal-mode &optional find-file
This function establishes the proper major mode and buffer-local variable
-bindings for the current buffer. First it calls @code{set-auto-mode},
-then it runs @code{hack-local-variables} to parse, and bind or
-evaluate as appropriate, the file's local variables.
+bindings for the current buffer. First it calls @code{set-auto-mode}
+(see below), then it runs @code{hack-local-variables} to parse, and
+bind or evaluate as appropriate, the file's local variables
+(@pxref{File Local Variables}).
If the @var{find-file} argument to @code{normal-mode} is non-@code{nil},
@code{normal-mode} assumes that the @code{find-file} function is calling
-it. In this case, it may process a local variables list at the end of
-the file and in the @samp{-*-} line. The variable
+it. In this case, it may process local variables in the @samp{-*-}
+line or at the end of the file. The variable
@code{enable-local-variables} controls whether to do so. @xref{File
-variables, , Local Variables in Files, emacs, The GNU Emacs Manual}, for
-the syntax of the local variables section of a file.
+Variables, , Local Variables in Files, emacs, The GNU Emacs Manual},
+for the syntax of the local variables section of a file.
If you run @code{normal-mode} interactively, the argument
@var{find-file} is normally @code{nil}. In this case,
-@code{normal-mode} unconditionally processes any local variables list.
+@code{normal-mode} unconditionally processes any file local variables.
+
+If @code{normal-mode} processes the local variables list and this list
+specifies a major mode, that mode overrides any mode chosen by
+@code{set-auto-mode}. If neither @code{set-auto-mode} nor
+@code{hack-local-variables} specify a major mode, the buffer stays in
+the major mode determined by @code{default-major-mode} (see below).
@cindex file mode specification error
@code{normal-mode} uses @code{condition-case} around the call to the
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
+@defun set-auto-mode &optional keep-mode-if-same
@cindex visited file mode
This function selects the major mode that is appropriate for the
-current buffer. It may base its decision on the value of the @w{@samp{-*-}}
-line, on the visited file name (using @code{auto-mode-alist}), on the
-@w{@samp{#!}} line (using @code{interpreter-mode-alist}), or on the
-file's local variables list. However, this function does not look for
-the @samp{mode:} local variable near the end of a file; the
-@code{hack-local-variables} function does that. @xref{Choosing Modes, ,
-How Major Modes are Chosen, emacs, The GNU Emacs Manual}.
+current buffer. It bases its decision (in order of precedence) on
+the @w{@samp{-*-}} line, on the @w{@samp{#!}} line (using
+@code{interpreter-mode-alist}), on the text at the beginning of the
+buffer (using @code{magic-mode-alist}), and finally on the visited
+file name (using @code{auto-mode-alist}). @xref{Choosing Modes, , How
+Major Modes are Chosen, emacs, The GNU Emacs Manual}. However, this
+function does not look for the @samp{mode:} local variable near the
+end of a file; the @code{hack-local-variables} function does that.
+If @code{enable-local-variables} is @code{nil}, @code{set-auto-mode}
+does not check the @w{@samp{-*-}} line for a mode tag either.
+
+If @var{keep-mode-if-same} is non-@code{nil}, this function does not
+call the mode command if the buffer is already in the proper major
+mode. For instance, @code{set-visited-file-name} sets this to
+@code{t} to avoid killing buffer local variables that the user may
+have set.
@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}.
If the value of @code{default-major-mode} is @code{nil}, Emacs uses
-the (previously) current buffer's major mode for the major mode of a new
-buffer. However, if that major mode symbol has a @code{mode-class}
+the (previously) current buffer's major mode as the default major mode
+of a new buffer. However, if that major mode symbol has a @code{mode-class}
property with value @code{special}, then it is not used for new buffers;
Fundamental mode is used instead. The modes that have this property are
those such as Dired and Rmail that are useful only with text that has
@defun set-buffer-major-mode buffer
This function sets the major mode of @var{buffer} to the value of
-@code{default-major-mode}. If that variable is @code{nil}, it uses
-the current buffer's major mode (if that is suitable).
+@code{default-major-mode}; if that variable is @code{nil}, it uses the
+current buffer's major mode (if that is suitable). As an exception,
+if @var{buffer}'s name is @samp{*scratch*}, it sets the mode to
+@code{initial-major-mode}.
The low-level primitives for creating buffers do not use this function,
but medium-level commands such as @code{switch-to-buffer} and
@code{find-file-noselect} use it whenever they create buffers.
@end defun
-@defvar initial-major-mode
+@defopt initial-major-mode
@cindex @samp{*scratch*}
The value of this variable determines the major mode of the initial
@samp{*scratch*} buffer. The value should be a symbol that is a major
mode command. The default value is @code{lisp-interaction-mode}.
+@end defopt
+
+@defvar interpreter-mode-alist
+This variable specifies major modes to use for scripts that specify a
+command interpreter in a @samp{#!} line. Its value is an alist with
+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 an interpreter which matches @var{interpreter}. The value
+of @var{interpreter} is actually a regular expression. @xref{Regular
+Expressions}.
+@end defvar
+
+@defvar magic-mode-alist
+This variable's value is an alist with elements of the form
+@code{(@var{regexp} . @var{function})}, where @var{regexp} is a
+regular expression and @var{function} is a function or @code{nil}.
+After visiting a file, @code{set-auto-mode} calls @var{function} if
+the text at the beginning of the buffer matches @var{regexp} and
+@var{function} is non-@code{nil}; if @var{function} is @code{nil},
+@code{auto-mode-alist} gets to decide the mode.
@end defvar
@defvar auto-mode-alist
This variable contains an association list of file name patterns
-(regular expressions; @pxref{Regular Expressions}) and corresponding
-major mode commands. Usually, the file name patterns test for suffixes,
-such as @samp{.el} and @samp{.c}, but this need not be the case. An
-ordinary element of the alist looks like @code{(@var{regexp} .
-@var{mode-function})}.
+(regular expressions) and corresponding major mode commands. Usually,
+the file name patterns test for suffixes, such as @samp{.el} and
+@samp{.c}, but this need not be the case. An ordinary element of the
+alist looks like @code{(@var{regexp} . @var{mode-function})}.
For example,
@end group
@group
("\\.el\\'" . emacs-lisp-mode)
- ("\\.c\\'" . c-mode)
+ ("\\.c\\'" . c-mode)
("\\.h\\'" . c-mode)
@dots{})
@end group
@end smallexample
When you visit a file whose expanded file name (@pxref{File Name
-Expansion}) matches a @var{regexp}, @code{set-auto-mode} calls the
-corresponding @var{mode-function}. This feature enables Emacs to select
-the proper major mode for most files.
+Expansion}), with version numbers and backup suffixes removed using
+@code{file-name-sans-versions} (@pxref{File Name Components}), matches
+a @var{regexp}, @code{set-auto-mode} calls the corresponding
+@var{mode-function}. This feature enables Emacs to select the proper
+major mode for most files.
If an element of @code{auto-mode-alist} has the form @code{(@var{regexp}
@var{function} t)}, then after calling @var{function}, Emacs searches
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))
@end smallexample
@end defvar
-@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
-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
-an interpreter which matches @var{interpreter}. The value of
-@var{interpreter} is actually a regular expression.
-
-This variable is applicable only when the @code{auto-mode-alist} does
-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
@node Derived Modes
@subsection Defining Derived Modes
+@cindex derived mode
It's often useful to define a new major mode in terms of an existing
one. An easy way to do this is to use @code{define-derived-mode}.
-@defmac define-derived-mode variant parent name docstring body@dots{}
+@defmac define-derived-mode variant parent name docstring keyword-args@dots{} body@dots{}
This construct defines @var{variant} as a major mode command, using
-@var{name} as the string form of the mode name.
+@var{name} as the string form of the mode name. @var{variant} and
+@var{parent} should be unquoted symbols.
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
-@code{@var{parent}-map}, if it is not already set.
+The new mode has its own sparse keymap, named
+@code{@var{variant}-map}. @code{define-derived-mode}
+makes the parent mode's keymap the parent of the new map, unless
+@code{@var{variant}-map} is already set and already has a parent.
@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{@var{parent}-syntax-table}, if it is not already set.
+@code{@var{variant}-syntax-table}, unless you override this using the
+@code{:syntax-table} keyword (see below). @code{define-derived-mode}
+makes the parent mode's syntax-table the parent of
+@code{@var{variant}-syntax-table}, unless the latter is already set
+and already has a parent different from the standard syntax table.
@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{@var{parent}-abbrev-table}, if it is not already set.
+@code{@var{variant}-abbrev-table}, unless you override this using the
+@code{:abbrev-table} keyword (see below).
@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
-of calling @var{parent}.)
+The new mode has its own mode hook, @code{@var{variant}-hook}. It
+runs this hook, after running the hooks of its ancestor modes, with
+@code{run-mode-hooks}, as the last thing it does. @xref{Mode Hooks}.
@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
-overrides, just before running @code{@var{variant}-hook}.
+evaluates the forms in @var{body} after setting up all its usual
+overrides, just before running the mode hooks.
+
+You can also specify @code{nil} for @var{parent}. This gives the new
+mode no parent. Then @code{define-derived-mode} behaves as described
+above, but, of course, omits all actions connected with @var{parent}.
+
+The argument @var{docstring} specifies the documentation string for
+the new mode. @code{define-derived-mode} adds some general
+information about the mode's hook, followed by the mode's keymap, at
+the end of this docstring. If you omit @var{docstring},
+@code{define-derived-mode} generates a documentation string.
+
+The @var{keyword-args} are pairs of keywords and values. The values
+are evaluated. The following keywords are currently supported:
-The argument @var{docstring} specifies the documentation string for the
-new mode. If you omit @var{docstring}, @code{define-derived-mode}
-generates a documentation string.
+@table @code
+@item :syntax-table
+You can use this to explicitly specify a syntax table for the new
+mode. If you specify a @code{nil} value, the new mode uses the same
+syntax table as @var{parent}, or the standard syntax table if
+@var{parent} is @code{nil}. (Note that this does @emph{not} follow
+the convention used for non-keyword arguments that a @code{nil} value
+is equivalent with not specifying the argument.)
+
+@item :abbrev-table
+You can use this to explicitly specify an abbrev table for the new
+mode. If you specify a @code{nil} value, the new mode uses the same
+abbrev table as @var{parent}, or @code{fundamental-mode-abbrev-table}
+if @var{parent} is @code{nil}. (Again, a @code{nil} value is
+@emph{not} equivalent to not specifying this keyword.)
+
+@item :group
+If this is specified, the value should be the customization group for
+this mode. (Not all major modes have one.) Only the (still
+experimental and unadvertised) command @code{customize-mode} currently
+uses this. @code{define-derived-mode} does @emph{not} automatically
+define the specified customization group.
+@end table
Here is a hypothetical example:
(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 Generic Modes
+@subsection Generic Modes
+@cindex generic mode
+
+@dfn{Generic modes} are simple major modes with basic support for
+comment syntax and Font Lock mode. They are primarily useful for
+configuration files. To define a generic mode, use the macro
+@code{define-generic-mode}. See the file @file{generic-x.el} for some
+examples of the use of @code{define-generic-mode}.
+
+@defmac define-generic-mode mode comment-list keyword-list font-lock-list auto-mode-list function-list &optional docstring
+This macro creates a new generic mode. The argument @var{mode} (an
+unquoted symbol) is the major mode command. The optional argument
+@var{docstring} is the documentation for the mode command. If you do
+not supply it, @code{define-generic-mode} uses a default documentation
+string instead.
+
+@var{comment-list} is a list in which each element is either a
+character, a string of one or two characters, or a cons cell. A
+character or a string is set up in the mode's syntax table as a
+``comment starter.'' If the entry is a cons cell, the @sc{car} is set
+up as a ``comment starter'' and the @sc{cdr} as a ``comment ender.''
+(Use @code{nil} for the latter if you want comments to end at the end
+of the line.) Note that the syntax table has limitations about what
+comment starters and enders are actually possible. @xref{Syntax
+Tables}.
+
+@var{keyword-list} is a list of keywords to highlight with
+@code{font-lock-keyword-face}. Each keyword should be a string.
+@var{font-lock-list} is a list of additional expressions to highlight.
+Each element of this list should have the same form as an element of
+@code{font-lock-keywords}. @xref{Search-based Fontification}.
+
+@var{auto-mode-list} is a list of regular expressions to add to the
+variable @code{auto-mode-alist}. These regular expressions are added
+when Emacs runs the macro expansion.
+
+@var{function-list} is a list of functions to call to do some
+additional setup. The mode command calls these functions just before
+it runs the mode hook variable @code{@var{mode}-hook}.
+@end defmac
+
+@node Mode Hooks
+@subsection Mode Hooks
+
+The two last things a major mode function does is to run its mode
+hook and finally the mode independent normal hook
+@code{after-change-major-mode-hook}. If the major mode is a derived
+mode, that is if it calls another major mode (the parent mode) in its
+body, then the parent's mode hook is run just before the derived
+mode's hook. Neither the parent's mode hook nor
+@code{after-change-major-mode-hook} are run at the end of the actual
+call to the parent mode. This applies recursively if the parent mode
+has itself a parent. That is, the mode hooks of all major modes called
+directly or indirectly by the major mode function are all run in
+sequence at the end, just before @code{after-change-major-mode-hook}.
+
+If you are customizing a major mode, rather than defining one, the
+above is all you need to know about the hooks run at the end of a
+major mode. This also applies if you use @code{define-derived-mode}
+to define a major mode, because that macro will automatically
+implement the above for you.
+
+Programmers wishing to define a major mode without using
+@code{define-derived-mode}, should make sure that their major mode
+follows the above conventions. @xref{Major Mode Conventions}, for how
+this should be accomplished. Below, we give some implementation
+details.
+
+@defun run-mode-hooks &rest hookvars
+Major modes should run their mode hook using this function. It is
+similar to @code{run-hooks} (@pxref{Hooks}), but if run inside a
+@code{delay-mode-hooks} form, this function does not run any hooks.
+Instead, it arranges for @var{hookvars} to be run at a later call to
+the function. Otherwise, @code{run-mode-hooks} runs any delayed hooks
+in order, then @var{hookvars} and finally
+@code{after-change-major-mode-hook}.
+@end defun
+
+@defmac delay-mode-hooks body...
+This macro executes @var{body} like @code{progn}, but all calls to
+@code{run-mode-hooks} inside @var{body} delay running their hooks.
+They will be run by the first call to @code{run-mode-hooks} after exit
+from @code{delay-mode-hooks}.
@end defmac
+@defvar after-change-major-mode-hook
+Every major mode function should run this normal hook at its very end.
+It normally does not need to do so explicitly. Indeed, a major mode
+function should normally run its mode hook with @code{run-mode-hooks}
+as the very last thing it does and @code{run-mode-hooks} runs
+@code{after-change-major-mode-hook} at its very end.
+@end defvar
+
@node Minor Modes
@section Minor Modes
@cindex minor mode
``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
other tables.
In addition, there are several conventions that are specific to
-minor modes.
+minor modes. (The easiest way to follow all the conventions is to use
+the macro @code{define-minor-mode}; @ref{Defining Minor Modes}.)
@itemize @bullet
@item
should set this variable (@code{nil} to disable; anything else to
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 set the variable.
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 a
+negative integer or zero. 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
@item
Add an element to @code{minor-mode-alist} for each minor mode
-(@pxref{Mode Line Variables}), if you want to indicate the minor mode in
-the mode line. This element should be a list of the following form:
+(@pxref{Definition of minor-mode-alist}), if you want to indicate the
+minor mode in the mode line. This element should be a list of the
+following form:
@smallexample
(@var{mode-variable} @var{string})
@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
- You can also use @code{add-to-list} to add an element to this list
-just once (@pxref{Setting Variables}).
+ 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
+invoking 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 cookie}),
+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
Each minor mode can have its own keymap, which is active when the mode
is enabled. To set up a keymap for a minor mode, add an element to the
-alist @code{minor-mode-map-alist}. @xref{Active Keymaps}.
+alist @code{minor-mode-map-alist}. @xref{Definition of minor-mode-map-alist}.
@cindex @code{self-insert-command}, minor modes
One use of minor mode keymaps is to modify the behavior of certain
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.
-
-@defmac easy-mmode-define-minor-mode mode doc &optional init-value mode-indicator keymap
-@tindex easy-mmode-define-minor-mode
-This macro defines a new minor mode whose name is @var{mode} (a symbol).
+@node Defining Minor Modes
+@subsection Defining Minor Modes
-This macro defines a command named @var{mode} which toggles the minor
-mode, and has @var{doc} as its documentation string.
+ The macro @code{define-minor-mode} offers a convenient way of
+implementing a mode in one self-contained definition.
-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}.
+@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}.
-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 above three arguments @var{init-value}, @var{lighter}, and
+@var{keymap} can be (partially) omitted when @var{keyword-args} are
+used. The @var{keyword-args} consist of keywords followed by
+corresponding values. A few keywords have special meanings:
+
+@table @code
+@item :group @var{group}
+Custom group name to use in all generated @code{defcustom} forms.
+Defaults to @var{mode} without the possible trailing @samp{-mode}.
+@strong{Warning:} don't use this default group name unless you have
+written a @code{defgroup} to define that group properly. @xref{Group
+Definitions}.
+
+@item :global @var{global}
+If non-@code{nil} specifies that the minor mode should be global. By
+default, minor modes defined with @code{define-minor-mode} 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} first performs the standard actions such
+as setting the variable named @var{mode} and then executes the
+@var{body} forms, if any. It finishes by running the mode hook
+variable @code{@var{mode}-hook}.
@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 indicator for the mode line.
" Hungry"
;; The minor mode bindings.
- '(("\C-\^?" . hungry-electric-delete)
- ("\C-\M-\^?"
- . (lambda ()
- (interactive)
- (hungry-electric-delete t)))))
+ '(("\C-\^?" . hungry-electric-delete))
+ :group 'hunger)
@end smallexample
@noindent
@code{hungry-mode} to toggle it, a variable named @code{hungry-mode}
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}}.
+mode is enabled. It initializes the keymap with a key binding for
+@kbd{C-@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
+
+@defmac define-global-minor-mode global-mode mode turn-on keyword-args...
+This defines a global minor mode named @var{global-mode} whose meaning
+is to enable the buffer-local minor mode @var{mode} in every buffer.
+To turn on the minor mode in a buffer, it uses the function
+@var{turn-on}; to turn off the minor mode, it calls @code{mode} with
+@minus{}1 as argument.
+
+Use @code{:group @var{group}} in @var{keyword-args} to specify the
+custom group for the mode variable of the global minor mode.
+@end defmac
@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.
- 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.
+@menu
+* Mode Line Basics::
+* 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 Basics
+@subsection Mode Line Basics
+
@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}.
+ The selected window's mode line is usually displayed in a different
+color using the face @code{mode-line}. Other windows' mode lines
+appear in the face @code{mode-line-inactive} instead. @xref{Faces}.
-@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.
-@end menu
+ 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.
@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.
@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. Make sure this
+evaluation cannot load any files, as doing so could cause infinite
+recursion.
+
+@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 22.1.)
@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
-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.
+@var{rest} are processed recursively as mode-line constructs and
+concatenated together. When @var{width} is positive, the result is
+space filled on the right if its width is less than @var{width}. When
+@var{width} is negative, the result is truncated on the right to
+@minus{}@var{width} columns if its width exceeds @minus{}@var{width}.
For example, the usual way to show what percentage of a buffer is above
the top of the window is to use a list like this: @code{(-3 "%p")}.
'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
@code{mode-line-format} were changed to use them.
@defvar mode-line-mule-info
-@tindex 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{Non-ASCII Characters}.
@end defvar
@defvar mode-line-frame-identification
-@tindex 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
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}.
-@end defvar
+@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
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
+@anchor{Definition of 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
the @code{minor-mode-alist} should be a two-element list:
(@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 following table lists the recognized @code{%}-constructs and what
they mean. In any construct except @samp{%%}, you can add a decimal
-integer after the @samp{%} to specify how many characters to display.
+integer after the @samp{%} to specify a minimum field width. If the
+width is less, the field is padded with spaces to the right.
@table @code
@item %b
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
+
+ Certain text properties are meaningful in the
+mode line. The @code{face} property affects the appearance of text; the
+@code{help-echo} property associates 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.
+
+ When the mode line refers to a variable which does not have a
+non-@code{nil} @code{risky-local-variable} property, any text
+properties given or specified within that variable's values are
+ignored. This is because such properties could otherwise specify
+functions to be called, and those functions could come from file
+local variables.
+
+@node Header Lines
+@subsection Window Header Lines
+@cindex header line (of a window)
+@cindex window header line
+
+ 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 a certain mode-line specification.
+
+@defun format-mode-line format &optional face window buffer
+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. The argument @var{window} defaults to the
+selected window. If @var{buffer} is non-@code{nil}, all the
+information used is taken from @var{buffer}; by default, it comes from
+@var{window}'s buffer.
+
+The value string normally has text properties that correspond to the
+faces, keymaps, etc., that the mode line would have. And any character
+for which no @code{face} property is specified gets a default
+value which is usually @var{face}. (If @var{face} is @code{t},
+that stands for either @code{mode-line} if @var{window} is selected,
+otherwise @code{mode-line-inactive}. If @var{face} is @code{nil} or
+omitted, that stands for no face property.)
+
+However, if @var{face} is an integer, the value has no text properties.
+
+For example, @code{(format-mode-line header-line-format)} returns the
+text that would appear in the selected window's header line (@code{""}
+if it has no header line). @code{(format-mode-line header-line-format
+'header-line)} returns the same text, with each character
+carrying the face that it will have in the header line itself.
+@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. Major modes can add a menu
+bar item to use Imenu using @code{imenu-add-to-menubar}.
+
+@defun imenu-add-to-menubar name
+This function defines a local menu bar item named @var{name}
+to run Imenu.
+@end defun
+
+ 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
@end defvar
@defvar imenu-case-fold-search
-This variable controls whether matching against
-@var{imenu-generic-expression} is case-sensitive: @code{t}, the default,
-means matching should ignore case.
+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
For example, Fortran mode uses it this way:
@example
- (setq imenu-syntax-alist '(("_$" . "w")))
+(setq imenu-syntax-alist '(("_$" . "w")))
@end example
-The @code{imenu-generic-expression} patterns can then use @samp{\\sw+}
-instead of @samp{\\(\\sw\\|\\s_\\)+}. Note that this technique may be
-inconvenient to use 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.
+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
+
+Selecting a simple element has the effect of moving to position
+@var{index-position} in the buffer. Special elements look like this:
+
+@example
+(@var{index-name} @var{index-position} @var{function} @var{arguments}@dots{})
+@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 special element performs:
-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
+(funcall @var{function}
+ @var{index-name} @var{index-position} @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
+A nested sub-alist element looks like this:
@example
-(funcall @var{function} @var{index-name} @var{position} @var{arguments}@dots{})
+(@var{menu-title} @var{sub-alist})
@end example
-A nested sub-alist element looks like @code{(@var{index-name}
-@var{sub-alist})}.
+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.
+ 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.
+Search-based fontification happens second.
@menu
-* Font Lock Basics::
-* Search-based Fontification::
-* Other Font Lock Variables::
-* Levels of Font Lock::
-* Faces for Font Lock::
-* Syntactic Font Lock::
+* Font Lock Basics:: Overview of customizing Font Lock.
+* Search-based Fontification:: Fontification based on regexps.
+* Other Font Lock Variables:: Additional customization facilities.
+* Levels of Font Lock:: Each mode can define alternative levels
+ so that the user can select more or less.
+* Precalculated Fontification:: How Lisp programs that produce the buffer
+ contents can also specify how to fontify it.
+* Faces for Font Lock:: Special faces specifically for Font Lock.
+* Syntactic Font Lock:: Fontification based on syntax tables.
+* Setting Syntax Properties:: Defining character syntax based on context
+ using the Font Lock mechanism.
@end menu
@node Font Lock Basics
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.
@defvar font-lock-defaults
This variable is set by major modes, as a buffer-local variable, to
-specify how to fontify text in that mode. The value should look like
-this:
+specify how to fontify text in that mode. It automatically becomes
+buffer-local when you set it. The value should look like this:
@example
-(@var{keywords} @var{keywords-only} @var{case-fold}
- @var{syntax-alist} @var{syntax-begin} @var{other-vars}@dots{})
+(@var{keywords} [@var{keywords-only} [@var{case-fold}
+ [@var{syntax-alist} [@var{syntax-begin} @var{other-vars}@dots{}]]]])
@end example
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
-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.
+@code{font-lock-keywords} which directs search-based fontification.
+It can be a symbol, a variable or a function whose value 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. @xref{Levels of Font Lock}.
The second element, @var{keywords-only}, specifies the value of the
variable @code{font-lock-keywords-only}. If this is non-@code{nil},
syntactic fontification (of strings and comments) is not performed.
+@xref{Syntactic Font Lock}.
The third element, @var{case-fold}, specifies the value of
-@code{font-lock-case-fold-search}. If it is non-@code{nil}, Font Lock
-mode ignores case when searching as directed by
+@code{font-lock-keywords-case-fold-search}. If it is non-@code{nil},
+Font Lock mode ignores case when searching as directed by
@code{font-lock-keywords}.
-If the fourth element, @var{syntax-alist}, is non-@code{nil}, it should be
-a list of cons cells of the form @code{(@var{char-or-string}
+If the fourth element, @var{syntax-alist}, is non-@code{nil}, it
+should be a list of cons cells of the form @code{(@var{char-or-string}
. @var{string})}. These are used to set up a syntax table for
-fontification (@pxref{Syntax Table Functions}). The resulting syntax
-table is stored in @code{font-lock-syntax-table}.
+syntactic fontification (@pxref{Syntax Table Functions}). The
+resulting syntax table is stored in @code{font-lock-syntax-table}.
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.
+@code{font-lock-beginning-of-syntax-function}.
+
+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. @xref{Other Font Lock Variables}.
@end defvar
@node Search-based Fontification
The most important variable for customizing Font Lock mode is
@code{font-lock-keywords}. It specifies the search criteria for
-search-based fontification.
+search-based fontification. You should specify the value of this
+variable with @var{keywords} in @code{font-lock-defaults}.
@defvar font-lock-keywords
This variable's value is a list of the keywords to highlight. Be
each element, it finds and handles all matches. Ordinarily, once
part of the text has been fontified already, this cannot be overridden
by a subsequent match in the same text; but you can specify different
-behavior using the @var{override} element of a @var{highlighter}.
+behavior using the @var{override} element of a @var{subexp-highlighter}.
Each element of @code{font-lock-keywords} should have one of these
forms:
@code{font-lock-keyword-face}. For example,
@example
-;; @r{Highlight discrete occurrences of @samp{foo}}
+;; @r{Highlight occurrences of the word @samp{foo}}
;; @r{using @code{font-lock-keyword-face}.}
"\\<foo\\>"
@end example
-The function @code{regexp-opt} (@pxref{Syntax of Regexps}) is useful for
-calculating optimal regular expressions to match a number of different
-keywords.
+The function @code{regexp-opt} (@pxref{Regexp Functions}) is useful
+for calculating optimal regular expressions to match a number of
+different keywords.
@item @var{function}
Find text by calling @var{function}, and highlight the matches
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.
-
-@item (@var{matcher} . @var{match})
-In this kind of element, @var{matcher} stands for either a regular
+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{subexp})
+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
+@var{subexp}, 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
If you use @code{regexp-opt} to produce the regular expression
-@var{matcher}, then you can use @code{regexp-opt-depth} (@pxref{Syntax
-of Regexps}) to calculate the value for @var{match}.
+@var{matcher}, then you can use @code{regexp-opt-depth} (@pxref{Regexp
+Functions}) to calculate the value for @var{subexp}.
-@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 expression whose value
+specifies the face to use for highlighting. In the simplest case,
+@var{facespec} is a Lisp variable (a symbol) whose value is a face
+name.
@example
;; @r{Highlight occurrences of @samp{fubar},}
("fubar" . fubar-face)
@end example
-@item (@var{matcher} . @var{highlighter})
-In this kind of element, @var{highlighter} is a list
+However, @var{facespec} can also evaluate to a list of this form:
+
+@example
+(face @var{face} @var{prop1} @var{val1} @var{prop2} @var{val2}@dots{})
+@end example
+
+@noindent
+to specify the face @var{face} and various additional 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. Alternatively,
+you can set the variable @code{font-lock-unfontify-region-function} to
+a function that clears these properties. @xref{Other Font Lock
+Variables}.
+
+@item (@var{matcher} . @var{subexp-highlighter})
+In this kind of element, @var{subexp-highlighter} is a list
which specifies how to highlight matches found by @var{matcher}.
-It has the form
+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.
-
-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.
+subelement, @var{facespec}, is an expression whose value specifies the
+face, as described above.
+
+The last two values in @var{subexp-highlighter}, @var{override} and
+@var{laxmatch}, are optional 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 signaled which
+terminates search-based fontification.
Here are some examples of elements of this kind, and what they do:
@smallexample
-;; @r{Highlight occurrences of either @samp{foo} or @samp{bar},}
-;; @r{using @code{foo-bar-face}, even if they have already been highlighted.}
+;; @r{Highlight occurrences of either @samp{foo} or @samp{bar}, using}
+;; @r{@code{foo-bar-face}, even if they have already been highlighted.}
;; @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)
@end smallexample
-@item (@var{matcher} @var{highlighters}@dots{})
-This sort of element specifies several @var{highlighter} lists for a
-single @var{matcher}. In order for this to be useful, each
-@var{highlighter} should have a different value of @var{subexp}; that is,
-each one should apply to a different subexpression of @var{matcher}.
+@item (@var{matcher} . @var{anchored-highlighter})
+In this kind of element, @var{anchored-highlighter} specifies how to
+highlight text that follows a match found by @var{matcher}. So a
+match found by @var{matcher} acts as the anchor for further searches
+specified by @var{anchored-highlighter}. @var{anchored-highlighter}
+is a list of the following form:
-@ignore
-@item (@var{matcher} . @var{anchored})
-In this kind of element, @var{anchored} acts much like a
-@var{highlighter}, but it is more complex and can specify multiple
-successive searches.
+@example
+(@var{anchored-matcher} @var{pre-form} @var{post-form}
+ @var{subexp-highlighters}@dots{})
+@end example
-For highlighting single items, typically only @var{highlighter} is
-required. However, if an item or (typically) items are to be
-highlighted following the instance of another item (the anchor) then
-@var{anchored} may be required.
+Here, @var{anchored-matcher}, like @var{matcher}, is either a regular
+expression or a function. After a match of @var{matcher} is found,
+point is at the end of the match. Now, Font Lock evaluates the form
+@var{pre-form}. Then it searches for matches of
+@var{anchored-matcher} and uses @var{subexp-highlighters} to highlight
+these. A @var{subexp-highlighter} is as described above. Finally,
+Font Lock evaluates @var{post-form}.
+
+The forms @var{pre-form} and @var{post-form} can be used to initialize
+before, and cleanup after, @var{anchored-matcher} is used. Typically,
+@var{pre-form} is used to move point to some position relative to the
+match of @var{matcher}, before starting with @var{anchored-matcher}.
+@var{post-form} might be used to move back, before resuming with
+@var{matcher}.
+
+After Font Lock evaluates @var{pre-form}, it does not search for
+@var{anchored-matcher} beyond the end of the line. However, if
+@var{pre-form} returns a buffer position that is greater than the
+position of point after @var{pre-form} is evaluated, then the position
+returned by @var{pre-form} is used as the limit of the search instead.
+It is generally a bad idea to return a position greater than the end
+of the line; in other words, the @var{anchored-matcher} search should
+not span lines.
-It has this format:
+For example,
-@example
-(@var{submatcher} @var{pre-match-form} @var{post-match-form} @var{highlighters}@dots{})
-@end example
+@smallexample
+;; @r{Highlight occurrences of the word @samp{item} following}
+;; @r{an occurrence of the word @samp{anchor} (on the same line)}
+;; @r{in the value of @code{item-face}.}
+("\\<anchor\\>" "\\<item\\>" nil nil (0 item-face))
+@end smallexample
-@c I can't parse this text -- rms
-where @var{submatcher} is much like @var{matcher}, with one
-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 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 move, before resuming with @var{anchored}'s parent's @var{matcher}.
+Here, @var{pre-form} and @var{post-form} are @code{nil}. Therefore
+searching for @samp{item} starts at the end of the match of
+@samp{anchor}, and searching for subsequent instances of @samp{anchor}
+resumes from where searching for @samp{item} concluded.
-For example, an element of the form highlights (if not already highlighted):
+@item (@var{matcher} @var{highlighters}@dots{})
+This sort of element specifies several @var{highlighter} lists for a
+single @var{matcher}. A @var{highlighter} list can be of the type
+@var{subexp-highlighter} or @var{anchored-highlighter} as described
+above.
-@example
-("\\<anchor\\>" (0 anchor-face) ("\\<item\\>" nil nil (0 item-face)))
-@end example
+For example,
-Discrete occurrences of @samp{anchor} in the value of
-@code{anchor-face}, and subsequent discrete occurrences of @samp{item}
-(on the same line) in the value of @code{item-face}. (Here
-@var{pre-match-form} and @var{post-match-form} are @code{nil}.
-Therefore @samp{item} is initially searched for starting from the end of
-the match of @samp{anchor}, and searching for subsequent instance of
-@samp{anchor} resumes from where searching for @samp{item} concluded.)
-
-The above-mentioned exception is as follows. The limit of the
-@var{submatcher} search defaults to the end of the line after
-@var{pre-match-form} is evaluated. However, if @var{pre-match-form}
-returns a position greater than the position after @var{pre-match-form}
-is evaluated, that position is used as the limit of the search. It is
-generally a bad idea to return a position greater than the end of the
-line; in other words, the @var{submatcher} search should not span lines.
-
-@item (@var{matcher} @var{highlighters-or-anchoreds} ...)
-@end ignore
+@smallexample
+;; @r{Highlight occurrences of the word @samp{anchor} in the value}
+;; @r{of @code{anchor-face}, and subsequent occurrences of the word}
+;; @r{@samp{item} (on the same line) in the value of @code{item-face}.}
+("\\<anchor\\>" (0 anchor-face)
+ ("\\<item\\>" nil nil (0 item-face)))
+@end smallexample
@item (eval . @var{form})
Here @var{form} is an expression to be evaluated the first time
Its value should have one of the forms described in this table.
@end table
+@vindex font-lock-multiline
@strong{Warning:} Do not design an element of @code{font-lock-keywords}
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.
-
-@node Other Font Lock Variables
-@subsection Other Font Lock Variables
+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.
- This section describes additional variables that a major mode
-can set by means of @code{font-lock-defaults}.
-
-@defvar font-lock-keywords-only
-Non-@code{nil} means Font Lock should not fontify comments or strings
-syntactically; it should only fontify based on
-@code{font-lock-keywords}.
-@end defvar
-
-@ignore
-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'.
-@end ignore
+You can use @var{case-fold} in @code{font-lock-defaults} to specify
+the value of @code{font-lock-keywords-case-fold-search} which says
+whether search-based fontification should be case-insensitive.
@defvar font-lock-keywords-case-fold-search
Non-@code{nil} means that regular expression matching for the sake of
@code{font-lock-keywords} should be case-insensitive.
@end defvar
-@defvar font-lock-syntax-table
-This variable specifies the syntax table to use for fontification of
-comments and strings.
-@end defvar
+You can use @code{font-lock-add-keywords} to add additional
+search-based fontification rules to a major mode, and
+@code{font-lock-remove-keywords} to removes rules.
+
+@defun font-lock-add-keywords mode keywords &optional append
+This function adds highlighting @var{keywords} for @var{mode}. The
+argument @var{keywords} should be a list with the same format as the
+variable @code{font-lock-keywords}. @var{mode} should be a symbol,
+the major mode command name, such as @code{c-mode}. When Font Lock
+mode is turned on in @var{mode}, it adds @var{keywords} to
+@code{font-lock-keywords}. @var{mode} can also be @code{nil}; the
+highlighting @var{keywords} are immediately added to
+@code{font-lock-keywords} in the current buffer in that case.
+
+By default, @var{keywords} are added at the beginning of
+@code{font-lock-keywords}. If the optional argument @var{append} is
+@code{set}, they are used to replace the value of
+@code{font-lock-keywords}. If @var{append} is any other
+non-@code{nil} value, they are added at the end of
+@code{font-lock-keywords}.
-@defvar font-lock-beginning-of-syntax-function
-If this variable is non-@code{nil}, it should be a function to move
-point back to a position that is syntactically at ``top level'' and
-outside of strings or comments. Font Lock uses this when necessary
-to get the right results for syntactic fontification.
+For example:
-This function is called with no arguments. It should leave point at the
-beginning of any enclosing syntactic block. Typical values are
-@code{beginning-of-line} (i.e., the start of the line is known to be
-outside a syntactic block), or @code{beginning-of-defun} for programming
-modes or @code{backward-paragraph} for textual modes (i.e., the
-mode-dependent function is known to move outside a syntactic block).
+@smallexample
+(font-lock-add-keywords 'c-mode
+ '(("\\<\\(FIXME\\):" 1 font-lock-warning-face prepend)
+ ("\\<\\(and\\|or\\|not\\)\\>" . font-lock-keyword-face)))
+@end smallexample
-If the value is @code{nil}, the beginning of the buffer is used as a
-position outside of a syntactic block. This cannot be wrong, but it can
-be slow.
-@end defvar
+adds two fontification patterns for C mode: one to fontify the word
+@samp{FIXME}, even in comments, and another to fontify the words
+@samp{and}, @samp{or} and @samp{not} as keywords.
+
+Some modes have specialized support for additional patterns. See the
+variables @code{c-font-lock-extra-types},
+@code{c++-font-lock-extra-types}, @code{objc-font-lock-extra-types}
+and @code{java-font-lock-extra-types}, for example.
+@end defun
+
+@defun font-lock-remove-keywords mode keywords
+This function removes highlighting @var{keywords} for @var{mode}. As
+in @code{font-lock-add-keywords}, @var{mode} should be a major mode
+command name or @code{nil}. If @code{nil}, the highlighting
+@var{keywords} are immediately removed in the current buffer.
+@end defun
+
+@strong{Warning:} Only use a non-@code{nil} @var{mode} argument when
+you use @code{font-lock-add-keywords} or
+@code{font-lock-remove-keywords} in your @file{.emacs} file. When you
+use these functions from a Lisp program (such as a minor mode), we
+recommend that you use @code{nil} for @var{mode} (and place the call
+on a hook) to avoid subtle problems due to the details of the
+implementation.
+
+@node Other Font Lock Variables
+@subsection Other Font Lock Variables
+
+ This section describes additional variables that a major mode can
+set by means of @var{other-vars} in @code{font-lock-defaults}
+(@pxref{Font Lock Basics}).
@defvar font-lock-mark-block-function
If this variable is non-@code{nil}, it should be a function that is
called with no arguments, to choose an enclosing range of text for
-refontification for the command @kbd{M-g M-g}
+refontification for the command @kbd{M-o M-o}
(@code{font-lock-fontify-block}).
The function should report its choice by placing the region around it.
textual modes.
@end defvar
+@defvar font-lock-extra-managed-props
+This variable specifies additional properties (other than
+@code{font-lock-face}) that are being managed by Font Lock mode. It
+is used by @code{font-lock-default-unfontify-region}, which normally
+only manages the @code{font-lock-face} property. If you want Font
+Lock to manage other properties as well, you must specify them in a
+@var{facespec} in @code{font-lock-keywords} as well as add them to
+this list. @xref{Search-based Fontification}.
+@end defvar
+
+@defvar font-lock-fontify-buffer-function
+Function to use for fontifying the buffer. The default value is
+@code{font-lock-default-fontify-buffer}.
+@end defvar
+
+@defvar font-lock-unfontify-buffer-function
+Function to use for unfontifying the buffer. This is used when
+turning off Font Lock mode. The default value is
+@code{font-lock-default-unfontify-buffer}.
+@end defvar
+
+@defvar font-lock-fontify-region-function
+Function to use for fontifying a region. It should take two
+arguments, the beginning and end of the region, and an optional third
+argument @var{verbose}. If @var{verbose} is non-@code{nil}, the
+function should print status messages. The default value is
+@code{font-lock-default-fontify-region}.
+@end defvar
+
+@defvar font-lock-unfontify-region-function
+Function to use for unfontifying a region. It should take two
+arguments, the beginning and end of the region. The default value is
+@code{font-lock-default-unfontify-region}.
+@end defvar
+
+@defvar font-lock-lines-before
+This variable specifies the number of extra lines to consider when
+refontifying the buffer after each text change. Font lock begins
+refontifying from that number of lines before the changed region. The
+default is 1, but using a larger value can be useful for coping with
+multi-line patterns.
+@end defvar
+
+@ignore
+@defvar font-lock-inhibit-thing-lock
+List of Font Lock mode related modes that should not be turned on.
+Currently, valid mode names are @code{fast-lock-mode},
+@code{jit-lock-mode} and @code{lazy-lock-mode}.
+@end defvar
+@end ignore
+
@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), it should not
+set the variable @code{font-lock-defaults}. That way, it will not
+cause loading of the @file{font-lock} library.
+
@node Faces for Font Lock
@subsection Faces for Font Lock
@vindex font-lock-comment-face
Used (typically) for comments.
+@item font-lock-comment-delimiter-face
+@vindex font-lock-comment-delimiter-face
+Used (typically) for comments delimiters.
+
+@item font-lock-doc-face
+@vindex font-lock-doc-face
+Used (typically) for documentation strings in the code.
+
@item font-lock-string-face
@vindex font-lock-string-face
Used (typically) for string constants.
@item font-lock-function-name-face
@vindex font-lock-function-name-face
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
@vindex font-lock-constant-face
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
Used (typically) for constructs that are peculiar, or that greatly
@node Syntactic Font Lock
@subsection Syntactic Font Lock
+Syntactic fontification uses the syntax table to find comments and
+string constants (@pxref{Syntax Tables}). It highlights them using
+@code{font-lock-comment-face} and @code{font-lock-string-face}
+(@pxref{Faces for Font Lock}). There are several variables that
+affect syntactic fontification; you should set them by means of
+@code{font-lock-defaults} (@pxref{Font Lock Basics}).
+
+@defvar font-lock-keywords-only
+Non-@code{nil} means Font Lock should not do syntactic fontification;
+it should only fontify based on @code{font-lock-keywords}. The normal
+way for a mode to set this variable to @code{t} is with
+@var{keywords-only} in @code{font-lock-defaults}.
+@end defvar
+
+@defvar font-lock-syntax-table
+This variable holds the syntax table to use for fontification of
+comments and strings. Specify it using @var{syntax-alist} in
+@code{font-lock-defaults}.
+@end defvar
+
+@c ???
+@c The docstring says that font-lock-syntax-table is semi-obsolete.
+@c How the alternative should be used is not clear. --lute
+
+@defvar font-lock-beginning-of-syntax-function
+If this variable is non-@code{nil}, it should be a function to move
+point back to a position that is syntactically at ``top level'' and
+outside of strings or comments. Font Lock uses this when necessary
+to get the right results for syntactic fontification.
+
+This function is called with no arguments. It should leave point at
+the beginning of any enclosing syntactic block. Typical values are
+@code{beginning-of-line} (used when the start of the line is known to
+be outside a syntactic block), or @code{beginning-of-defun} for
+programming modes, or @code{backward-paragraph} for textual modes.
+
+If the value is @code{nil}, the beginning of the buffer is used as a
+position outside of a syntactic block. This cannot be wrong, but it
+can be slow.
+
+Specify this variable using @var{syntax-begin} in
+@code{font-lock-defaults}.
+@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.
+
+Specify this variable using @var{other-vars} in
+@code{font-lock-defaults}.
+@end defvar
+
+@node Setting Syntax Properties
+@subsection Setting Syntax Properties
+
Font Lock mode can be used to update @code{syntax-table} properties
-automatically. This is useful in languages for which a single syntax
-table by itself is not sufficient.
+automatically (@pxref{Syntax Properties}). This is useful in
+languages for which a single syntax 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 updating @code{syntax-table}
+properties by Font Lock. Its value should be a list of elements of
+this form:
@example
(@var{matcher} @var{subexp} @var{syntax} @var{override} @var{laxmatch})
sort of element of @code{font-lock-keywords},
@example
-(@var{matcher} @var{subexp} @var{facename} @var{override} @var{laxmatch})
+(@var{matcher} @var{subexp} @var{facespec} @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.
-@end defvar
+However, instead of specifying the value @var{facespec} 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 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}.
-@node Hooks
-@section Hooks
-@cindex 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.
-@xref{Standard Hooks}, for a list of standard hook variables.
+For example, an element of the form:
-@cindex normal hook
- Most of the hooks in Emacs are @dfn{normal hooks}. These variables
-contain lists of functions to be called with no arguments. When the
-hook name ends in @samp{-hook}, that tells you it is normal. We try to
-make all hooks normal, as much as possible, so that you can use them in
-a uniform way.
-
- Every major mode function is supposed to run a normal hook called the
-@dfn{mode hook} as the last step of initialization. This makes it easy
-for a user to customize the behavior of the mode, by overriding the
-buffer-local variable assignments already made by the mode. But hooks
-are used in other contexts too. For example, the hook
-@code{suspend-hook} runs just before Emacs suspends itself
-(@pxref{Suspending Emacs}).
-
- 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.
-
-@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
-documentation to see how to use the hook properly.
-
- If the variable's name ends in @samp{-functions} or @samp{-hooks},
-then the value is a list of functions, but it is abnormal in that either
-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.)
+@example
+("\\$\\(#\\)" 1 ".")
+@end example
- If the variable's name ends in @samp{-function}, then its value
-is just a single function, not a list of functions.
+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.
- Here's an example that uses a mode hook to turn on Auto Fill mode when
-in Lisp Interaction mode:
+An element of the form:
@example
-(add-hook 'lisp-interaction-mode-hook 'turn-on-auto-fill)
+ ("\\('\\).\\('\\)"
+ (1 "\"")
+ (2 "\""))
@end example
- At the appropriate time, Emacs uses the @code{run-hooks} function to
-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.
+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.
-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.
+Major modes normally set this variable with @var{other-vars} in
+@code{font-lock-defaults}.
+@end defvar
-For example, here's how @code{emacs-lisp-mode} runs its mode hook:
+@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-@code{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
-(run-hooks 'emacs-lisp-mode-hook)
+(desktop-file-name @var{file-name} @var{desktop-dirname})
@end example
-@end defun
-
-@defun run-hook-with-args hook &rest args
-This function is the way to run an abnormal hook which passes arguments
-to the hook functions. It calls each of the hook functions, 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 which passes arguments
-to the hook functions, and stops as soon as any hook function fails. It
-calls each of the hook functions, passing each of them the arguments
-@var{args}, until some hook function returns @code{nil}. Then it stops,
-and returns @code{nil} if some hook function did, and otherwise
-returns a non-@code{nil} value.
-@end defun
+@end defvar
-@defun run-hook-with-args-until-success hook &rest args
-This function is the way to run an abnormal hook which passes arguments
-to the hook functions, and stops as soon as any 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.
-@end defun
+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}.
-@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,
+@defvar desktop-buffer-mode-handlers
+Alist with elements
@example
-(add-hook 'text-mode-hook 'my-text-hook-function)
+(@var{major-mode} . @var{restore-buffer-function})
@end example
-@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.
-
-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,
-@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.
-@end defun
+The function @var{restore-buffer-function} will be called with
+argument list
-@defun remove-hook hook function &optional local
-This function removes @var{function} from the hook variable @var{hook}.
+@example
+(@var{buffer-file-name} @var{buffer-name} @var{desktop-buffer-misc})
+@end example
-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
+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
-@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
HCoop / bpt / emacs.git / blobdiff