@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999,
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002,
@c 2003, 2004, 2005 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/modes
@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}, for the pair of variables
+variable @code{imenu-generic-expression}, for the two 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}).
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
+but this is not required. Such a mode should call the parent mode
+command inside a @code{delay-mode-hooks} form. (Using
@code{define-derived-mode} does this automatically.) @xref{Derived
Modes}, and @ref{Mode Hooks}.
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}.
+specifies an interpreter which matches @var{interpreter}.
@end defvar
@defvar magic-mode-alist
@node Mode Hooks
@subsection Mode Hooks
-The two last things a major mode function does is to run its mode
+ The two last things a major mode function should do is 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
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.
+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}.
+
+ These conventions are new in Emacs 22, and some major modes
+implemented by users do not follow them yet. So if you put a function
+onto @code{after-change-major-mode-hook}, keep in mind that some modes
+will fail to run it. If a user complains about that, you can respond,
+``That major mode fails to follow Emacs conventions, and that's why it
+fails to work. Please fix the major mode.'' In most cases, that is
+good enough, so go ahead and use @code{after-change-major-mode-hook}.
+However, if a certain feature needs to be completely reliable,
+it should not use @code{after-change-major-mode-hook} as of yet.
+
+ When you defined a major mode using @code{define-derived-mode}, it
+automatically makes sure these conventions are followed. If you
+define a major mode ``from scratch'', not using
+@code{define-derived-mode}, make sure the major mode command follows
+these and other conventions. @xref{Major Mode Conventions}. You use
+these functions to do it properly.
@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
+similar to @code{run-hooks} (@pxref{Hooks}), but it also runs
@code{after-change-major-mode-hook}.
+
+When the call to this function is dynamically inside a
+@code{delay-mode-hooks} form, this function does not run any hooks.
+Instead, it arranges for the next call to @code{run-mode-hooks} to run
+@var{hookvars}.
@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}.
+from @code{delay-mode-hooks}. This is the proper way for a major mode
+command to invoke its parent mode.
@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.
+as the very last thing it does, and the last thing
+@code{run-mode-hooks} does is run @code{after-change-major-mode-hook}.
@end defvar
@node Minor Modes
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}.
+@var{init-value}. Except in unusual circumstances (see below), this
+value must be @code{nil}.
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
This is equivalent to specifying @var{keymap} positionally.
@end table
-Any other keyword arguments are passed passed directly to the
+Any other keyword arguments are passed directly to the
@code{defcustom} generated for the variable @var{mode}.
The command named @var{mode} first performs the standard actions such
variable @code{@var{mode}-hook}.
@end defmac
+ The initial value must be @code{nil} except in cases where (1) the
+mode is preloaded in Emacs, or (2) it is painless to for loading to
+enable the mode even though the user did not request it. For
+instance, if the mode has no effect unless something else is enabled,
+and will always be loaded by that time, enabling it by default is
+harmless. But these are unusual circumstances. Normally, the
+initial value must be @code{nil}.
+
@findex easy-mmode-define-minor-mode
The name @code{easy-mmode-define-minor-mode} is an alias
for this macro.
gobbles all preceding whitespace except the last.
See the command \\[hungry-electric-delete]."
;; The initial value.
- :initial-value nil
+ :init-value nil
;; The indicator for the mode line.
:lighter " Hungry"
;; The minor mode bindings.
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}).
+mode line (@pxref{Standard Faces,,, emacs, The GNU Emacs Manual}).
@table @code
@cindex percent symbol in mode line
@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 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}.
+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
+@var{symbol} has a non-@code{nil} value, the second element,
+@var{then}, is processed recursively as a mode-line element.
+Otherwise, 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} or void.
@item (@var{width} @var{rest}@dots{})
A list whose first element is an integer specifies truncation or
@item %F
The title (only on a window system) or the name of the selected frame.
-@xref{Window Frame Parameters}.
+@xref{Basic Parameters}.
@item %i
The size of the accessible part of the current buffer; basically
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-default-create-index-function}. This function calls the
+value of @code{imenu-prev-index-position-function} and the value of
@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.
@menu
* Font Lock Basics:: Overview of customizing Font Lock.
* Search-based Fontification:: Fontification based on regexps.
+* Customizing Keywords:: Customizing search-based fontification.
* 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.
@end example
If you use @code{regexp-opt} to produce the regular expression
-@var{matcher}, then you can use @code{regexp-opt-depth} (@pxref{Regexp
+@var{matcher}, you can use @code{regexp-opt-depth} (@pxref{Regexp
Functions}) to calculate the value for @var{subexp}.
@item (@var{matcher} . @var{facespec})
@code{font-lock-keywords} should be case-insensitive.
@end defvar
-You can use @code{font-lock-add-keywords} to add additional
+@node Customizing Keywords
+@subsection Customizing Search-Based Fontification
+
+ 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.
+This function adds highlighting @var{keywords}, for the current buffer
+or for major mode @var{mode}. The argument @var{keywords} should be a
+list with the same format as the variable @code{font-lock-keywords}.
+
+If @var{mode} is a symbol which is a major mode command name, such as
+@code{c-mode}, the effect is that enabling Font Lock mode in
+@var{mode} will add @var{keywords} to @code{font-lock-keywords}.
+Calling with a non-@code{nil} value of @var{mode} is correct only in
+your @file{~/.emacs} file.
+
+If @var{mode} is @code{nil}, this function adds @var{keywords} to
+@code{font-lock-keywords} in the current buffer. This way of calling
+@code{font-lock-add-keywords} is usually used in mode hook functions.
By default, @var{keywords} are added at the beginning of
@code{font-lock-keywords}. If the optional argument @var{append} is
non-@code{nil} value, they are added at the end of
@code{font-lock-keywords}.
-For example:
+Some modes provide specialized support you can use in additional
+highlighting patterns. See the variables
+@code{c-font-lock-extra-types}, @code{c++-font-lock-extra-types},
+and @code{java-font-lock-extra-types}, for example.
+
+@strong{Warning:} major mode functions must not call
+@code{font-lock-add-keywords} under any circumstances, either directly
+or indirectly, except through their mode hooks. (Doing so would lead
+to incorrect behavior for some minor modes.) They should set up their
+rules for search-based fontification by setting
+@code{font-lock-keywords}.
+@end defun
+
+@defun font-lock-remove-keywords mode keywords
+This function removes @var{keywords} from @code{font-lock-keywords}
+for the current buffer or for major mode @var{mode}. As in
+@code{font-lock-add-keywords}, @var{mode} should be a major mode
+command name or @code{nil}. All the caveats and requirments for
+@code{font-lock-add-keywords} apply here too.
+@end defun
+
+ For example, this code
@smallexample
(font-lock-add-keywords 'c-mode
("\\<\\(and\\|or\\|not\\)\\>" . font-lock-keyword-face)))
@end smallexample
+@noindent
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
+@noindent
+That example affects only C mode proper. To add the same patterns to
+C mode @emph{and} all modes derived from it, do this instead:
-@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.
+@smallexample
+(add-hook 'c-mode-hook
+ (lambda ()
+ (font-lock-add-keywords nil
+ '(("\\<\\(FIXME\\):" 1 font-lock-warning-face prepend)
+ ("\\<\\(and\\|or\\|not\\)\\>" .
+ font-lock-keyword-face)))))
+@end smallexample
@node Other Font Lock Variables
@subsection Other Font Lock Variables