@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990-1995, 1998-1999, 2001-2012 Free Software Foundation, Inc.
+@c Copyright (C) 1990-1995, 1998-1999, 2001-2012 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
-@setfilename ../../info/modes
-@node Modes, Documentation, Keymaps, Top
+@node Modes
@chapter Major and Minor Modes
@cindex mode
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.
+@xref{Standard Hooks}, for a list of some standard hook variables.
@cindex normal hook
Most of the hooks in Emacs are @dfn{normal hooks}. These variables
* Derived Modes:: Defining a new major mode based on another major
mode.
* Basic Major Modes:: Modes that other modes are often derived from.
+* Mode Hooks:: Hooks run at the end of major mode functions.
+* Tabulated List Mode:: Parent mode for buffers containing tabulated data.
* 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 commands.
* Example Major Modes:: Text mode and Lisp modes.
@end menu
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
+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
more buffer-local entries to the special hook
@code{completion-at-point-functions}. @xref{Completion in Buffers}.
-@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
-reinitialization could discard customizations made by the user.)
-
@item
@cindex buffer-local variables in modes
To make a buffer-local binding for an Emacs customization variable, use
@code{special} modes, Fundamental mode is used instead. Modes such as
Dired, Rmail, and Buffer List use this feature.
+The function @code{view-buffer} does not enable View mode in buffers
+whose mode-class is special, because such modes usually provide their
+own View-like bindings.
+
The @code{define-derived-mode} macro automatically marks the derived
mode as special if the parent mode is special. Special mode is a
convenient parent for such modes to inherit from; @xref{Basic Major
not autoload the mode command, it is sufficient to add the element in
the file that contains the mode definition.
-@item
-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
The top-level forms in the file defining the mode should be written so
that they may be evaluated more than once without adverse consequences.
+For instance, use @code{defvar} or @code{defcustom} to set mode-related
+variables, so that they are not reinitialized if they already have a
+value (@pxref{Defining Variables}).
+
@end itemize
@node Auto Major Mode
This function sets the major mode of @var{buffer} to the default value of
@code{major-mode}; if that 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
+if @var{buffer}'s name is @file{*scratch*}, it sets the mode to
@code{initial-major-mode}.
The low-level primitives for creating buffers do not use this function,
@end defun
@defopt initial-major-mode
-@cindex @samp{*scratch*}
+@cindex @file{*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
+@file{*scratch*} buffer. The value should be a symbol that is a major
mode command. The default value is @code{lisp-interaction-mode}.
@end defopt
variable @code{major-mode} (@pxref{Major Modes}), which is why every
major mode command needs to set that variable.
-@deffn Command describe-mode
-This function displays the documentation of the current major mode.
+@deffn Command describe-mode &optional buffer
+This command displays the documentation of the current buffer's major
+mode and minor modes. It uses the @code{documentation} function to
+retrieve the documentation strings of the major and minor mode
+commands (@pxref{Accessing Documentation}).
-The @code{describe-mode} function calls the @code{documentation}
-function using the value of @code{major-mode} as an argument. Thus, it
-displays the documentation string of the major mode command.
-(@xref{Accessing Documentation}.)
+If called from Lisp with a non-nil @var{buffer} argument, this
+function displays the documentation for that buffer's major and minor
+modes, rather than those of the current buffer.
@end deffn
@node Derived Modes
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},
+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
+documentation string. 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
@deffn Command special-mode
Special mode is a basic major mode for buffers containing text that is
-produced specially by Emacs, rather than from a file. Major modes
-derived from Special mode are given a @code{mode-class} property of
-@code{special} (@pxref{Major Mode Conventions}).
+produced specially by Emacs, rather than directly from a file. Major
+modes derived from Special mode are given a @code{mode-class} property
+of @code{special} (@pxref{Major Mode Conventions}).
Special mode sets the buffer to read-only. Its keymap defines several
common bindings, including @kbd{q} for @code{quit-window}, @kbd{z} for
(@pxref{Reverting}).
An example of a major mode derived from Special mode is Buffer Menu
-mode, which is used by the @samp{*Buffer List*} buffer. @xref{List
+mode, which is used by the @file{*Buffer List*} buffer. @xref{List
Buffers,,Listing Existing Buffers, emacs, The GNU Emacs Manual}.
@end deffn
-@cindex tables of data
-@deffn Command tabulated-list-mode
-Tabulated List mode is another mode that derives from Special mode. It
-displays tabulated data, i.e. a series of rows and columns, where each
-row represents a particular entry, whose properties are displayed in the
-various columns. It provides a general mechanism for sorting on
-columns. You can use Tabulated List mode as the basis for other modes
-that need to display lists. For example, the @samp{*Packages*} buffer
-uses this (@pxref{Packages,,, emacs, The GNU Emacs Manual}). The
-documentation of the @code{tabulated-list-mode} function explains what
-you need to do to use it. At a minimum, specify the column format via
-the @code{tabulated-list-format} variable.
-@end deffn
-
-@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. 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 defines a generic mode command named @var{mode} (a symbol,
-not quoted). The optional argument @var{docstring} is the
-documentation for the mode command. If you do not supply it,
-@code{define-generic-mode} generates one by default.
-
-The argument @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 mechanism has limitations
-about what comment starters and enders are actually possible.
-@xref{Syntax Tables}.
-
-The argument @var{keyword-list} is a list of keywords to highlight
-with @code{font-lock-keyword-face}. Each keyword should be a string.
-Meanwhile, @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}.
-
-The argument @var{auto-mode-list} is a list of regular expressions to
-add to the variable @code{auto-mode-alist}. They are added by the execution
-of the @code{define-generic-mode} form, not by expanding the macro call.
-
-Finally, @var{function-list} is a list of functions for the mode
-command to call for additional setup. It calls these functions just
-before it runs the mode hook variable @code{@var{mode}-hook}.
-@end defmac
+ In addition, modes for buffers of tabulated data can inherit from
+Tabulated List mode, which is in turn derived from Special mode.
+@xref{Tabulated List Mode}.
@node Mode Hooks
@subsection Mode Hooks
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 ``by hand,'' not using @code{define-derived-mode},
+define a major mode ``by hand'', not using @code{define-derived-mode},
use the following functions to handle these conventions automatically.
@defun run-mode-hooks &rest hookvars
very end of every properly-written major mode command.
@end defvar
+@node Tabulated List Mode
+@subsection Tabulated List mode
+@cindex Tabulated List mode
+
+ Tabulated List mode is a major mode for displaying tabulated data,
+i.e.@: data consisting of @dfn{entries}, each entry occupying one row of
+text with its contents divided into columns. Tabulated List mode
+provides facilities for pretty-printing rows and columns, and sorting
+the rows according to the values in each column. It is derived from
+Special mode (@pxref{Basic Major Modes}).
+
+ Tabulated List mode is intended to be used as a parent mode by a more
+specialized major mode. Examples include Process Menu mode
+(@pxref{Process Information}) and Package Menu mode (@pxref{Package
+Menu,,, emacs, The GNU Emacs Manual}).
+
+@findex tabulated-list-mode
+ Such a derived mode should use @code{define-derived-mode} in the usual
+way, specifying @code{tabulated-list-mode} as the second argument
+(@pxref{Derived Modes}). The body of the @code{define-derived-mode}
+form should specify the format of the tabulated data, by assigning
+values to the variables documented below; then, it should call the
+function @code{tabulated-list-init-header} to initialize the header
+line.
+
+ The derived mode should also define a @dfn{listing command}. This,
+not the mode command, is what the user calls (e.g.@: @kbd{M-x
+list-processes}). The listing command should create or switch to a
+buffer, turn on the derived mode, specify the tabulated data, and
+finally call @code{tabulated-list-print} to populate the buffer.
+
+@defvar tabulated-list-format
+This buffer-local variable specifies the format of the Tabulated List
+data. Its value should be a vector. Each element of the vector
+represents a data column, and should be a list @code{(@var{name}
+@var{width} @var{sort})}, where
+
+@itemize
+@item
+@var{name} is the column's name (a string).
+
+@item
+@var{width} is the width to reserve for the column (an integer). This
+is meaningless for the last column, which runs to the end of each line.
+
+@item
+@var{sort} specifies how to sort entries by the column. If @code{nil},
+the column cannot be used for sorting. If @code{t}, the column is
+sorted by comparing string values. Otherwise, this should be a
+predicate function for @code{sort} (@pxref{Rearrangement}), which
+accepts two arguments with the same form as the elements of
+@code{tabulated-list-entries} (see below).
+@end itemize
+@end defvar
+
+@defvar tabulated-list-entries
+This buffer-local variable specifies the entries displayed in the
+Tabulated List buffer. Its value should be either a list, or a
+function.
+
+If the value is a list, each list element corresponds to one entry, and
+should have the form @w{@code{(@var{id} @var{contents})}}, where
+
+@itemize
+@item
+@var{id} is either @code{nil}, or a Lisp object that identifies the
+entry. If the latter, the cursor stays on the ``same'' entry when
+re-sorting entries. Comparison is done with @code{equal}.
+
+@item
+@var{contents} is a vector with the same number of elements as
+@code{tabulated-list-format}. Each vector element is either a string,
+which is inserted into the buffer as-is, or a list @code{(@var{label}
+. @var{properties})}, which means to insert a text button by calling
+@code{insert-text-button} with @var{label} and @var{properties} as
+arguments (@pxref{Making Buttons}).
+
+There should be no newlines in any of these strings.
+@end itemize
+
+Otherwise, the value should be a function which returns a list of the
+above form when called with no arguments.
+@end defvar
+
+@defvar tabulated-list-revert-hook
+This normal hook is run prior to reverting a Tabulated List buffer. A
+derived mode can add a function to this hook to recompute
+@code{tabulated-list-entries}.
+@end defvar
+
+@defvar tabulated-list-printer
+The value of this variable is the function called to insert an entry at
+point, including its terminating newline. The function should accept
+two arguments, @var{id} and @var{contents}, having the same meanings as
+in @code{tabulated-list-entries}. The default value is a function which
+inserts an entry in a straightforward way; a mode which uses Tabulated
+List mode in a more complex way can specify another function.
+@end defvar
+
+@defvar tabulated-list-sort-key
+The value of this variable specifies the current sort key for the
+Tabulated List buffer. If it is @code{nil}, no sorting is done.
+Otherwise, it should have the form @code{(@var{name} . @var{flip})},
+where @var{name} is a string matching one of the column names in
+@code{tabulated-list-format}, and @var{flip}, if non-@code{nil}, means
+to invert the sort order.
+@end defvar
+
+@defun tabulated-list-init-header
+This function computes and sets @code{header-line-format} for the
+Tabulated List buffer (@pxref{Header Lines}), and assigns a keymap to
+the header line to allow sort entries by clicking on column headers.
+
+Modes derived from Tabulated List mode should call this after setting
+the above variables (in particular, only after setting
+@code{tabulated-list-format}).
+@end defun
+
+@defun tabulated-list-print &optional remember-pos
+This function populates the current buffer with entries. It should be
+called by the listing command. It erases the buffer, sorts the entries
+specified by @code{tabulated-list-entries} according to
+@code{tabulated-list-sort-key}, then calls the function specified by
+@code{tabulated-list-printer} to insert each entry.
+
+If the optional argument @var{remember-pos} is non-@code{nil}, this
+function looks for the @var{id} element on the current line, if any, and
+tries to move to that entry after all the entries are (re)inserted.
+@end defun
+
+@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. 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 defines a generic mode command named @var{mode} (a symbol,
+not quoted). The optional argument @var{docstring} is the
+documentation for the mode command. If you do not supply it,
+@code{define-generic-mode} generates one by default.
+
+The argument @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 mechanism has limitations
+about what comment starters and enders are actually possible.
+@xref{Syntax Tables}.
+
+The argument @var{keyword-list} is a list of keywords to highlight
+with @code{font-lock-keyword-face}. Each keyword should be a string.
+Meanwhile, @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}.
+
+The argument @var{auto-mode-list} is a list of regular expressions to
+add to the variable @code{auto-mode-alist}. They are added by the execution
+of the @code{define-generic-mode} form, not by expanding the macro call.
+
+Finally, @var{function-list} is a list of functions for the mode
+command to call for additional setup. It calls these functions just
+before it runs the mode hook variable @code{@var{mode}-hook}.
+@end defmac
+
@node Example Major Modes
@subsection Major Mode Examples
@smallexample
@group
-(defun lisp-mode-variables (&optional lisp-syntax keywords-case-insensitive)
- (when lisp-syntax
+(defun lisp-mode-variables (&optional syntax keywords-case-insensitive)
+ (when syntax
(set-syntax-table lisp-mode-syntax-table))
(setq local-abbrev-table lisp-mode-abbrev-table)
@dots{}
Entry to this mode calls the value of `lisp-mode-hook'
if that value is non-nil."
(lisp-mode-variables nil t)
- (set (make-local-variable 'find-tag-default-function) 'lisp-find-tag-default)
- (make-local-variable 'comment-start-skip)
- (setq comment-start-skip
+ (set (make-local-variable 'find-tag-default-function)
+ 'lisp-find-tag-default)
+ (set (make-local-variable 'comment-start-skip)
"\\(\\(^\\|[^\\\\\n]\\)\\(\\\\\\\\\\)*\\)\\(;+\\|#|\\) *")
(setq imenu-case-fold-search t))
@end group
@section Minor Modes
@cindex minor mode
- A @dfn{minor mode} provides features that users may enable or disable
-independently of the choice of major mode. Minor modes can be enabled
-individually or in combination. Minor modes would be better named
-``generally available, optional feature modes,'' except that such a name
-would be unwieldy.
-
- 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.
+ A @dfn{minor mode} provides optional features that users may enable or
+disable independently of the choice of major mode. Minor modes can be
+enabled individually or in combination.
- A minor mode is often much more difficult to implement than a major
-mode. One reason is that you should be able to activate and deactivate
-minor modes in any order. A minor mode should be able to have its
-desired effect regardless of the major mode and regardless of the other
-minor modes in effect.
+ Most minor modes implement features that are independent of the major
+mode, and can thus be used with most major modes. For example, Auto
+Fill mode works with any major mode that permits text insertion. A few
+minor modes, however, are specific to a particular major mode. For
+example, Diff Auto Refine mode is a minor mode that is intended to be
+used only with Diff mode.
- Often the biggest problem in implementing a minor mode is finding a
-way to insert the necessary hook into the rest of Emacs. Minor mode
-keymaps make this easier than it used to be.
+ Ideally, a minor mode should have its desired effect regardless of the
+other minor modes in effect. It should be possible to activate and
+deactivate minor modes in any order.
@defvar minor-mode-list
The value of this variable is a list of all minor mode commands.
@cindex conventions for writing minor modes
There are conventions for writing minor modes just as there are for
-major modes. Several of the major mode conventions apply to minor
-modes as well: those regarding the name of the mode initialization
-function, the names of global symbols, the use of a hook at the end of
-the initialization function, and the use of keymaps and other tables.
-
- In addition, there are several conventions that are specific to
-minor modes. (The easiest way to follow all the conventions is to use
-the macro @code{define-minor-mode}; @ref{Defining Minor Modes}.)
+major modes. These conventions are described below. The easiest way to
+follow them is to use the macro @code{define-minor-mode}.
+@xref{Defining Minor Modes}.
@itemize @bullet
@item
@cindex mode variable
-Make a variable whose name ends in @samp{-mode} to control the minor
-mode. We call this the @dfn{mode variable}. The minor mode command
-should set this variable (@code{nil} to disable; anything else to
-enable).
-
-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.
+Define a variable whose name ends in @samp{-mode}. We call this the
+@dfn{mode variable}. The minor mode command should set this variable.
+The value will be @code{nil} is the mode is disabled, and non-@code{nil}
+if the mode is enabled. The variable should be buffer-local if the
+minor mode is buffer-local.
This variable is used in conjunction with the @code{minor-mode-alist} to
-display the minor mode name in the mode line. It can also enable
-or disable a minor mode keymap. Individual commands or hooks can also
-check the variable's value.
-
-If you want the minor mode to be enabled separately in each buffer,
-make the variable buffer-local.
+display the minor mode name in the mode line. It also determines
+whether the minor mode keymap is active, via @code{minor-mode-map-alist}
+(@pxref{Controlling Active Maps}). Individual commands or hooks can
+also check its value.
@item
-Define a command whose name is the same as the mode variable.
-Its job is to enable and disable the mode by setting the variable.
+Define a command, called the @dfn{mode command}, whose name is the same
+as the mode variable. Its job is to set the value of the mode variable,
+plus anything else that needs to be done to actually enable or disable
+the mode's features.
-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). 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.
+The mode command should accept one optional argument. If called
+interactively with no prefix argument, it should toggle the mode
+(i.e.@: enable if it is disabled, and disable if it is enabled). If
+called interactively with a prefix argument, it should enable the mode
+if the argument is positive and disable it otherwise.
-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
-disables the mode's behavior, and also shows the proper way to toggle,
-enable or disable the minor mode based on the raw prefix argument value.
+If the mode command is called from Lisp (i.e.@: non-interactively), it
+should enable the mode if the argument is omitted or @code{nil}; it
+should toggle the mode if the argument is the symbol @code{toggle};
+otherwise it should treat the argument in the same way as for an
+interactive call with a numeric prefix argument, as described above.
-@smallexample
-@group
-(setq transient-mark-mode
- (if (null arg) (not transient-mark-mode)
- (> (prefix-numeric-value arg) 0)))
-@end group
-@end smallexample
+The following example shows how to implement this behavior (it is
+similar to the code generated by the @code{define-minor-mode} macro):
+
+@example
+(interactive (list (or current-prefix-arg 'toggle)))
+(let ((enable (if (eq arg 'toggle)
+ (not foo-mode) ; @r{this mode's mode variable}
+ (> (prefix-numeric-value arg) 0))))
+ (if enable
+ @var{do-enable}
+ @var{do-disable}))
+@end example
+
+The reason for this somewhat complex behavior is that it lets users
+easily toggle the minor mode interactively, and also lets the minor mode
+be easily enabled in a mode hook, like this:
+
+@example
+(add-hook 'text-mode-hook 'foo-mode)
+@end example
+
+@noindent
+This behaves correctly whether or not @code{foo-mode} was already
+enabled, since the @code{foo-mode} mode command unconditionally enables
+the minor mode when it is called from Lisp with no argument. Disabling
+a minor mode in a mode hook is a little uglier:
+
+@example
+(add-hook 'text-mode-hook (lambda () (foo-mode -1)))
+@end example
+
+@noindent
+However, this is not very commonly done.
@item
Add an element to @code{minor-mode-alist} for each minor mode
@smallexample
@group
(unless (assq 'leif-mode minor-mode-alist)
- (setq minor-mode-alist
- (cons '(leif-mode " Leif") minor-mode-alist)))
+ (push '(leif-mode " Leif") minor-mode-alist))
@end group
@end smallexample
@end smallexample
@end itemize
- Global minor modes distributed with Emacs should if possible support
-enabling and disabling via Custom (@pxref{Customization}). To do this,
-the first step is to define the mode variable with @code{defcustom}, and
-specify @code{:type 'boolean}.
+ In addition, several major mode conventions apply to minor modes as
+well: those regarding the names of global symbols, the use of a hook at
+the end of the initialization function, and the use of keymaps and other
+tables.
- If just setting the variable is not sufficient to enable the mode, you
+ The minor mode should, if possible, support enabling and disabling via
+Custom (@pxref{Customization}). To do this, the mode variable should be
+defined with @code{defcustom}, usually with @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:
+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. For example:
@smallexample
@group
-
;;;###autoload
(defcustom msb-mode nil
"Toggle msb-mode.
One of the effects of making a minor mode global is that the
@var{mode} variable becomes a customization variable. Toggling it
-through the Custom interface turns the mode on and off, and its value
-can be saved for future Emacs sessions (@pxref{Saving
+through the Customize interface turns the mode on and off, and its
+value can be saved for future Emacs sessions (@pxref{Saving
Customizations,,, emacs, The GNU Emacs Manual}. For the saved
variable to work, you should ensure that the @code{define-minor-mode}
form is evaluated each time Emacs starts; for packages that are not
@var{place} can also be a cons @code{(@var{get} . @var{set})},
where @var{get} is an expression that returns the current state,
and @var{set} is a function of one argument (a state) that sets it.
+
+@item :after-hook @var{after-hook}
+This defines a single Lisp form which is evaluated after the mode hooks
+have run. It should not be quoted.
@end table
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
-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}.
+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 then runs the mode hook variable
+@code{@var{mode}-hook} and finishes by evaluating any form in
+@code{:after-hook}.
@end defmac
The initial value must be @code{nil} except in cases where (1) the
@end smallexample
@noindent
-This defines a minor mode named ``Hungry mode,'' a command named
+This defines a minor mode named ``Hungry mode'', a command named
@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
in Fundamental mode.
This defines the customization option @var{global-mode} (@pxref{Customization}),
-which can be toggled in the Custom interface to turn the minor mode on
+which can be toggled in the Customize interface to turn the minor mode on
and off. As with @code{define-minor-mode}, you should ensure that the
@code{define-globalized-minor-mode} form is evaluated each time Emacs
starts, for example by providing a @code{:require} keyword.
@node Mode Line Format
-@section Mode-Line Format
+@section Mode Line Format
@cindex mode line
Each Emacs window (aside from minibuffer windows) typically has a mode
@node Mode Line Basics
@subsection Mode Line Basics
- @code{mode-line-format} is a buffer-local variable that holds a
-@dfn{mode line construct}, a kind of template, which controls what is
-displayed on the mode line of the current buffer. The value of
-@code{header-line-format} specifies the buffer's header line in the
-same way. All windows for the same buffer use the same
+ The contents of each mode line are specified by the buffer-local
+variable @code{mode-line-format} (@pxref{Mode Line Top}). This variable
+holds a @dfn{mode line construct}: a template that controls what is
+displayed on the buffer's mode line. The value of
+@code{header-line-format} specifies the buffer's header line in the same
+way. All windows for the same buffer use the same
@code{mode-line-format} and @code{header-line-format}.
- For efficiency, Emacs does not continuously recompute the mode
-line and header line of a window. 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.
+ For efficiency, Emacs does not continuously recompute each window's
+mode line and header line. 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 modify the buffer. If
+you alter any of the variables referenced by @code{mode-line-format} or
+@code{header-line-format} (@pxref{Mode Line Variables}), or any other
+data structures that affect how text is displayed (@pxref{Display}), you
+should use the function @code{force-mode-line-update} to update the
+display.
@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.
+This function forces Emacs to update the current buffer's mode line and
+header line, based on the latest values of all relevant variables,
+during its next redisplay cycle. If the optional argument @var{all} is
+non-@code{nil}, it forces an update for all mode lines and header lines.
+
+This function also forces an update of the menu bar and frame title.
@end defun
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}.
+color using the face @code{mode-line}. Other windows' mode lines appear
+in the face @code{mode-line-inactive} instead. @xref{Faces}.
@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 called a
-@dfn{mode-line construct}, made up of lists, strings, symbols, and
+ The mode line contents are controlled by a data structure called a
+@dfn{mode line construct}, made up of lists, strings, symbols, and
numbers kept in buffer-local variables. Each data type has a specific
-meaning for the mode-line appearance, as described below. The same
-data structure is used for constructing frame titles (@pxref{Frame
-Titles}) and header lines (@pxref{Header Lines}).
+meaning for the mode line appearance, as described below. The same data
+structure is used for constructing frame titles (@pxref{Frame Titles})
+and header lines (@pxref{Header Lines}).
- A mode-line construct may be as simple as a fixed string of text,
+ A mode line construct may be as simple as a fixed string of text,
but it usually specifies how to combine fixed strings with variables'
values to construct the text. Many of these variables are themselves
-defined to have mode-line constructs as their values.
+defined to have mode line constructs as their values.
- Here are the meanings of various data types as mode-line constructs:
+ Here are the meanings of various data types as mode line constructs:
@table @code
@cindex percent symbol in mode line
@item @var{string}
-A string as a mode-line construct appears verbatim except for
+A string as a mode line construct appears verbatim except for
@dfn{@code{%}-constructs} in it. These stand for substitution of
other data; see @ref{%-Constructs}.
special meanings. @xref{Properties in Mode}.
@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}.
+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.
Unless @var{symbol} is marked as ``risky'' (i.e., it has a
non-@code{nil} @code{risky-local-variable} property), all text
-properties specified in @var{symbol}'s value are ignored. This
-includes the text properties of strings in @var{symbol}'s value, as
-well as all @code{:eval} and @code{:propertize} forms in it. (The
-reason for this is security: non-risky variables could be set
-automatically from file variables without prompting the user.)
+properties specified in @var{symbol}'s value are ignored. This includes
+the text properties of strings in @var{symbol}'s value, as well as all
+@code{:eval} and @code{:propertize} forms in it. (The reason for this
+is security: non-risky variables could be set automatically from file
+variables without prompting the user.)
@item (@var{string} @var{rest}@dots{})
@itemx (@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
@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, then add the text
+process the mode line construct @var{elt} recursively, then 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.)
+@var{value}.
@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
@var{symbol} has a non-@code{nil} value, the second element,
-@var{then}, is processed recursively as a mode-line element.
+@var{then}, is processed recursively as a mode line construct.
Otherwise, the third element, @var{else}, is processed recursively.
-You may omit @var{else}; then the mode-line element displays nothing
+You may omit @var{else}; then the mode line construct 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
padding of the results of @var{rest}. The remaining elements
-@var{rest} are processed recursively as mode-line constructs and
+@var{rest} are processed recursively as mode line constructs and
concatenated together. 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
@code{mode-line-format}.
@defopt mode-line-format
-The value of this variable is a mode-line construct that controls the
+The value of this variable is a mode line construct that controls the
contents of the mode-line. It is always buffer-local in all buffers.
-If you set this variable to @code{nil} in a buffer, that buffer does
-not have a mode line. (A window that is just one line tall never
-displays a mode line.)
+If you set this variable to @code{nil} in a buffer, that buffer does not
+have a mode line. (A window that is just one line tall also does not
+display a mode line.)
@end defopt
The default value of @code{mode-line-format} is designed to use the
the user or by Lisp programs (such as @code{display-time} and major
modes) via changes to those variables remain effective.
- Here is an example of a @code{mode-line-format} that might be
-useful for @code{shell-mode}, since it contains the host name and default
-directory.
+ Here is a hypothetical example of a @code{mode-line-format} that might
+be useful for Shell mode (in reality, Shell mode does not set
+@code{mode-line-format}):
@example
@group
@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
":"
'(which-func-mode ("" which-func-format "--"))
'(line-number-mode "L%l--")
'(column-number-mode "C%c--")
- '(-3 "%p")
- "-%-"))
+ '(-3 "%p")))
@end group
@end example
@node Mode Line Variables
@subsection Variables Used in the Mode Line
- This section describes variables incorporated by the standard value
-of @code{mode-line-format} into the text of the mode line. There is
+ This section describes variables incorporated by the standard value of
+@code{mode-line-format} into the text of the mode line. There is
nothing inherently special about these variables; any other variables
-could have the same effects on the mode line if
-@code{mode-line-format}'s value were changed to use them. However,
-various parts of Emacs set these variables on the understanding that
-they will control parts of the mode line; therefore, practically
-speaking, it is essential for the mode line to use them.
+could have the same effects on the mode line if the value of
+@code{mode-line-format} is changed to use them. However, various parts
+of Emacs set these variables on the understanding that they will control
+parts of the mode line; therefore, practically speaking, it is essential
+for the mode line to use them.
@defvar mode-line-mule-info
-This variable holds the value of the mode-line construct that displays
+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-modified
-This variable holds the value of the mode-line construct that displays
+This variable holds the value of the mode line construct that displays
whether the current buffer is modified. Its default value displays
@samp{**} if the buffer is modified, @samp{--} if the buffer is not
modified, @samp{%%} if the buffer is read only, and @samp{%*} if the
on the process status, and whether narrowing is in effect.
@end defopt
-@defopt mode-line-remote
+@defvar mode-line-remote
This variable is used to show whether @code{default-directory} for the
current buffer is remote.
-@end defopt
+@end defvar
-@defopt mode-line-client
+@defvar mode-line-client
This variable is used to identify @code{emacsclient} frames.
-@end defopt
+@end defvar
The following three variables are used in @code{mode-line-modes}:
@end defvar
@defvar mode-line-process
-This buffer-local variable contains the mode-line information on 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
+space. For example, its value in the @file{*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}.
(@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}
+More generally, @var{mode-line-string} can be any mode line construct.
+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.
+@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
@end defvar
@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.
+This variable holds a mode line construct 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
@node %-Constructs
@subsection @code{%}-Constructs in the Mode Line
- Strings used as mode-line constructs can use certain
+ Strings used as mode line constructs can use certain
@code{%}-constructs to substitute various kinds of data. Here is a
list of the defined @code{%}-constructs, and what they mean. In any
construct except @samp{%%}, you can add a decimal integer after the
@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.
+@samp{Top}, @samp{Bottom} or @samp{All}. Note that the default mode
+line construct truncates this to three characters.
@item %P
The percentage of the buffer text that is above the @strong{bottom} of
@enumerate
@item
-Put a string with a text property directly into the mode-line data
+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
+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
give @var{elt} a text property specified by @var{props}.
@item
-Use a list containing @code{:eval @var{form}} in the mode-line data
+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
@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.
+ 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
+@code{header-line-format}:
@defvar header-line-format
This variable, local in every buffer, specifies how to display the
header line.
@node Emulating Mode Line
-@subsection Emulating Mode-Line Formatting
+@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.
+ 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 construct.
@defun format-mode-line format &optional face window buffer
This function formats a line of text according to @var{format} as if it
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
+@deffn Command imenu-add-to-menubar name
This function defines a local menu bar item named @var{name}
to run Imenu.
-@end defun
+@end deffn
The user-level commands for using Imenu are described in the Emacs
Manual (@pxref{Imenu,, Imenu, emacs, the Emacs Manual}). This section
@section Font Lock Mode
@cindex 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
-which contexts. This section explains how to customize Font Lock for a
-particular major mode.
+ @dfn{Font Lock mode} is a buffer-local minor mode 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 which contexts. This section explains how to customize Font Lock for
+a particular major mode.
Font Lock mode finds text to highlight in two ways: through
syntactic parsing based on the syntax table, and through searching
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.
* Multiline Font Lock:: How to coerce Font Lock into properly
highlighting multiline constructs.
@end menu
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. It automatically becomes
-buffer-local when you set it. If its value is @code{nil}, Font-Lock
-mode does no highlighting, and you can use the @samp{Faces} menu
-(under @samp{Edit} and then @samp{Text Properties} in the menu bar) to
-assign faces explicitly to text in the buffer.
+This variable is set by major modes to specify how to fontify text in
+that mode. It automatically becomes buffer-local when set. If its
+value is @code{nil}, Font Lock mode does no highlighting, and you can
+use the @samp{Faces} menu (under @samp{Edit} and then @samp{Text
+Properties} in the menu bar) to assign faces explicitly to text in the
+buffer.
If non-@code{nil}, the value should look like this:
The second element, @var{keywords-only}, specifies the value of the
variable @code{font-lock-keywords-only}. If this is omitted or
@code{nil}, syntactic fontification (of strings and comments) is also
-performed. If this is non-@code{nil}, such fontification is not
+performed. If this is non-@code{nil}, syntactic fontification is not
performed. @xref{Syntactic Font Lock}.
The third element, @var{case-fold}, specifies the value of
@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}.
+Font Lock mode ignores case during search-based fontification.
-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
-syntactic fontification (@pxref{Syntax Table Functions}). The
-resulting syntax table is stored in @code{font-lock-syntax-table}.
+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 syntactic
+fontification; the resulting syntax table is stored in
+@code{font-lock-syntax-table}. If @var{syntax-alist} is omitted or
+@code{nil}, syntactic fontification uses the syntax table returned by
+the @code{syntax-table} function. @xref{Syntax Table Functions}.
The fifth element, @var{syntax-begin}, specifies the value of
@code{font-lock-beginning-of-syntax-function}. We recommend setting
@node Search-based Fontification
@subsection 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. You should specify the value of this
-variable with @var{keywords} in @code{font-lock-defaults}.
+ The variable which directly controls search-based fontification is
+@code{font-lock-keywords}, which is typically specified via the
+@var{keywords} element in @code{font-lock-defaults}.
@defvar font-lock-keywords
-This variable's value is a list of the keywords to highlight. Be
-careful when composing regular expressions for this list; a poorly
-written pattern can dramatically slow things down!
+The value of this variable is a list of the keywords to highlight. Lisp
+programs should not set this variable directly. Normally, the value is
+automatically set by Font Lock mode, using the @var{keywords} element in
+@code{font-lock-defaults}. The value can also be altered using the
+functions @code{font-lock-add-keywords} and
+@code{font-lock-remove-keywords} (@pxref{Customizing Keywords}).
@end defvar
Each element of @code{font-lock-keywords} specifies how to find
"\\<foo\\>"
@end example
-The function @code{regexp-opt} (@pxref{Regexp Functions}) is useful
-for calculating optimal regular expressions to match a number of
-different keywords.
+Be careful when composing these regular expressions; a poorly written
+pattern can dramatically slow things down! The function
+@code{regexp-opt} (@pxref{Regexp Functions}) is useful for calculating
+optimal regular expressions to match several keywords.
@item @var{function}
Find text by calling @var{function}, and highlight the matches
@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 commands must not call
+@strong{Warning:} Major mode commands 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
@code{font-lock-add-keywords} apply here too.
@end defun
- For example, this code
+ For example, the following code 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.
@smallexample
(font-lock-add-keywords 'c-mode
@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.
-
-@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:
+This example affects only C mode proper. To add the same patterns to C
+mode @emph{and} all modes derived from it, do this instead:
@smallexample
(add-hook 'c-mode-hook
@node Levels of Font Lock
@subsection Levels of Font Lock
- Many major modes offer three different levels of fontification. You
+ Some major modes offer three different levels of fontification. You
can define multiple levels by using a list of symbols for @var{keywords}
in @code{font-lock-defaults}. Each symbol specifies one level of
fontification; it is up to the user to choose one of these levels,
normally by setting @code{font-lock-maximum-decoration} (@pxref{Font
-Lock,,, emacs, the GNU Emacs Manual}). The chosen level's symbol
-value is used to initialize @code{font-lock-keywords}.
+Lock,,, emacs, the GNU Emacs Manual}). The chosen level's symbol value
+is used to initialize @code{font-lock-keywords}.
Here are the conventions for how to define the levels of
fontification:
@cindex font lock faces
Font Lock mode can highlight using any face, but Emacs defines several
-faces specifically for syntactic highlighting. These @dfn{Font Lock
-faces} are listed below. They can also be used by major modes for
-syntactic highlighting outside of Font Lock mode (@pxref{Major Mode
-Conventions}).
+faces specifically for Font Lock to use to highlight text. These
+@dfn{Font Lock faces} are listed below. They can also be used by major
+modes for syntactic highlighting outside of Font Lock mode (@pxref{Major
+Mode Conventions}).
Each of these symbols is both a face name, and a variable whose
default value is the symbol itself. Thus, the default value of
@subsection Syntactic Font Lock
@cindex 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}), or whatever
-@code{font-lock-syntactic-face-function} chooses. There are several
-variables that affect syntactic fontification; you should set them by
-means of @code{font-lock-defaults} (@pxref{Font Lock Basics}).
+Syntactic fontification uses a syntax table (@pxref{Syntax Tables}) to
+find and highlight syntactically relevant text. If enabled, it runs
+prior to search-based fontification. The variable
+@code{font-lock-syntactic-face-function}, documented below, determines
+which syntactic constructs to highlight. There are several variables
+that affect syntactic fontification; you should set them by means of
+@code{font-lock-defaults} (@pxref{Font Lock Basics}).
+
+ Whenever Font Lock mode performs syntactic fontification on a stretch
+of text, it first calls the function specified by
+@code{syntax-propertize-function}. Major modes can use this to apply
+@code{syntax-table} text properties to override the buffer's syntax
+table in special cases. @xref{Syntax Properties}.
@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}.
+If the value of this variable is non-@code{nil}, Font Lock does not do
+syntactic fontification, only search-based fontification based on
+@code{font-lock-keywords}. It is normally set by Font Lock mode based
+on the @var{keywords-only} element 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}. If this is @code{nil}, fontification uses
-the buffer's syntax table.
+comments and strings. It is normally set by Font Lock mode based on the
+@var{syntax-alist} element in @code{font-lock-defaults}. If this value
+is @code{nil}, syntactic fontification uses the buffer's syntax table
+(the value returned by the function @code{syntax-table}; @pxref{Syntax
+Table Functions}).
@end defvar
@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
+outside of strings or comments. The value is normally set through an
+@var{other-vars} element in @code{font-lock-defaults}. If it is
+@code{nil}, Font Lock uses @code{syntax-begin-function} to move back
+outside of any comment, string, or sexp (@pxref{Position Parse}).
+
+This variable is semi-obsolete; we usually recommend setting
+@code{syntax-begin-function} instead. One of its uses is to tune the
+behavior of syntactic fontification, e.g.@: to ensure that different
+kinds of strings or comments are highlighted differently.
+
+The specified 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}, Font Lock uses
-@code{syntax-begin-function} to move back outside of any comment,
-string, or sexp. This variable is semi-obsolete; we recommend setting
-@code{syntax-begin-function} instead.
-
-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 constructs that span
-multiple lines, but this is too esoteric to document here.
-
-Specify this variable using @var{other-vars} in
+If this variable is non-@code{nil}, it should be a function to determine
+which face to use for a given syntactic element (a string or a comment).
+The value is normally set through an @var{other-vars} element 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 (@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 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})
-@end example
-
-The parts of this element have the same meanings as in the corresponding
-sort of element of @code{font-lock-keywords},
-
-@example
-(@var{matcher} @var{subexp} @var{facespec} @var{override} @var{laxmatch})
-@end example
-
-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}.
-
-For example, an element of the form:
-
-@example
-("\\$\\(#\\)" 1 ".")
-@end example
-
-highlights syntactically a hash character when following a dollar
-character, with a SYNTAX of @code{"."} (meaning punctuation syntax).
-Assuming that the buffer syntax table specifies hash characters to
-have comment start syntax, the element will only highlight hash
-characters that do not follow dollar characters as comments
-syntactically.
-
-An element of the form:
-
-@example
- ("\\('\\).\\('\\)"
- (1 "\"")
- (2 "\""))
-@end example
-
-highlights syntactically both single quotes which surround a single
-character, with a SYNTAX of @code{"\""} (meaning string quote syntax).
-Assuming that the buffer syntax table does not specify single quotes
-to have quote syntax, the element will only highlight single quotes of
-the form @samp{'@var{c}'} as strings syntactically. Other forms, such
-as @samp{foo'bar} or @samp{'fubar'}, will not be highlighted as
-strings.
-
-Major modes normally set this variable with @var{other-vars} in
-@code{font-lock-defaults}.
+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 (@pxref{Faces for Font Lock}).
@end defvar
@node Multiline Font Lock
The @code{font-lock-multiline} property is meant to ensure proper
refontification; it does not automatically identify new multiline
-constructs. Identifying the requires that Font-Lock operate on large
-enough chunks at a time. This will happen by accident on many cases,
-which may give the impression that multiline constructs magically work.
-If you set the @code{font-lock-multiline} variable non-@code{nil},
-this impression will be even stronger, since the highlighting of those
-constructs which are found will be properly updated from then on.
-But that does not work reliably.
-
- To find multiline constructs reliably, you must either manually
-place the @code{font-lock-multiline} property on the text before
-Font-Lock looks at it, or use
-@code{font-lock-fontify-region-function}.
+constructs. Identifying the requires that Font Lock mode operate on
+large enough chunks at a time. This will happen by accident on many
+cases, which may give the impression that multiline constructs magically
+work. If you set the @code{font-lock-multiline} variable
+non-@code{nil}, this impression will be even stronger, since the
+highlighting of those constructs which are found will be properly
+updated from then on. But that does not work reliably.
+
+ To find multiline constructs reliably, you must either manually place
+the @code{font-lock-multiline} property on the text before Font Lock
+mode looks at it, or use @code{font-lock-fontify-region-function}.
@node Region to Refontify
@subsubsection Region to Fontify after a Buffer Change
the following variable:
@defvar font-lock-extend-after-change-region-function
-This buffer-local variable is either @code{nil} or a function for
-Font-Lock to call to determine the region to scan and fontify.
+This buffer-local variable is either @code{nil} or a function for Font
+Lock mode to call to determine the region to scan and fontify.
The function is given three parameters, the standard @var{beg},
@var{end}, and @var{old-len} from @code{after-change-functions}
@end defvar
@node Auto-Indentation
-@section Auto-indentation of code
+@section Automatic Indentation of code
For programming languages, an important feature of a major mode is to
provide automatic indentation. This is controlled in Emacs by
indentation code will want to be somewhat friendly to syntactically
incorrect code.
-Good maintainable indentation functions usually fall into 2 categories:
+Good maintainable indentation functions usually fall into two categories:
either parsing forward from some ``safe'' starting point until the
position of interest, or parsing backward from the position of interest.
Neither of the two is a clearly better choice than the other: parsing
of Lisp sexps and adapts it to non-Lisp languages.
@menu
-* SMIE:: A simple minded indentation engine
+* SMIE:: A simple minded indentation engine.
@end menu
@node SMIE
resorting to some special tricks (@pxref{SMIE Tricks}).
@menu
-* SMIE setup:: SMIE setup and features
-* Operator Precedence Grammars:: A very simple parsing technique
-* SMIE Grammar:: Defining the grammar of a language
-* SMIE Lexer:: Defining tokens
-* SMIE Tricks:: Working around the parser's limitations
-* SMIE Indentation:: Specifying indentation rules
-* SMIE Indentation Helpers:: Helper functions for indentation rules
-* SMIE Indentation Example:: Sample indentation rules
+* SMIE setup:: SMIE setup and features.
+* Operator Precedence Grammars:: A very simple parsing technique.
+* SMIE Grammar:: Defining the grammar of a language.
+* SMIE Lexer:: Defining tokens.
+* SMIE Tricks:: Working around the parser's limitations.
+* SMIE Indentation:: Specifying indentation rules.
+* SMIE Indentation Helpers:: Helper functions for indentation rules.
+* SMIE Indentation Example:: Sample indentation rules.
@end menu
@node SMIE setup
@end defun
@defun smie-rule-sibling-p
-Return non-nil if the current token's parent is actually a sibling.
-This is the case for example when the parent of a @code{","} is just the
-previous @code{","}.
+Return non-@code{nil} if the current token's parent is actually a
+sibling. This is the case for example when the parent of a @code{","}
+is just the previous @code{","}.
@end defun
@defun smie-rule-parent &optional offset
optionally bound to @code{desktop-save-buffer}.
@end defvar
-@ignore
- Local Variables:
- fill-column: 72
- End:
-@end ignore
HCoop / bpt / emacs.git / blobdiff