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[Emacs-diffs] Changes to display.texi
|
From: |
Glenn Morris |
|
Subject: |
[Emacs-diffs] Changes to display.texi |
|
Date: |
Thu, 06 Sep 2007 04:19:12 +0000 |
CVSROOT: /sources/emacs
Module name: emacs
Changes by: Glenn Morris <gm> 07/09/06 04:19:12
Index: display.texi
===================================================================
RCS file: display.texi
diff -N display.texi
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ display.texi 6 Sep 2007 04:19:12 -0000 1.1
@@ -0,0 +1,5442 @@
address@hidden -*-texinfo-*-
address@hidden This is part of the GNU Emacs Lisp Reference Manual.
address@hidden Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999,
2000, 2001,
address@hidden 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation,
Inc.
address@hidden See the file elisp.texi for copying conditions.
address@hidden ../info/display
address@hidden Display, System Interface, Processes, Top
address@hidden Emacs Display
+
+ This chapter describes a number of features related to the display
+that Emacs presents to the user.
+
address@hidden
+* Refresh Screen:: Clearing the screen and redrawing everything on it.
+* Forcing Redisplay:: Forcing redisplay.
+* Truncation:: Folding or wrapping long text lines.
+* The Echo Area:: Displaying messages at the bottom of the screen.
+* Warnings:: Displaying warning messages for the user.
+* Invisible Text:: Hiding part of the buffer text.
+* Selective Display:: Hiding part of the buffer text (the old way).
+* Temporary Displays:: Displays that go away automatically.
+* Overlays:: Use overlays to highlight parts of the buffer.
+* Width:: How wide a character or string is on the screen.
+* Line Height:: Controlling the height of lines.
+* Faces:: A face defines a graphics style for text characters:
+ font, colors, etc.
+* Fringes:: Controlling window fringes.
+* Scroll Bars:: Controlling vertical scroll bars.
+* Display Property:: Enabling special display features.
+* Images:: Displaying images in Emacs buffers.
+* Buttons:: Adding clickable buttons to Emacs buffers.
+* Abstract Display:: Emacs' Widget for Object Collections.
+* Blinking:: How Emacs shows the matching open parenthesis.
+* Usual Display:: The usual conventions for displaying nonprinting chars.
+* Display Tables:: How to specify other conventions.
+* Beeping:: Audible signal to the user.
+* Window Systems:: Which window system is being used.
address@hidden menu
+
address@hidden Refresh Screen
address@hidden Refreshing the Screen
+
+ The function @code{redraw-frame} clears and redisplays the entire
+contents of a given frame (@pxref{Frames}). This is useful if the
+screen is corrupted.
+
address@hidden Emacs 19 feature
address@hidden redraw-frame frame
+This function clears and redisplays frame @var{frame}.
address@hidden defun
+
+ Even more powerful is @code{redraw-display}:
+
address@hidden Command redraw-display
+This function clears and redisplays all visible frames.
address@hidden deffn
+
+ This function calls for redisplay of certain windows, the next time
+redisplay is done, but does not clear them first.
+
address@hidden force-window-update &optional object
+This function forces some or all windows to be updated on next redisplay.
+If @var{object} is a window, it forces redisplay of that window. If
address@hidden is a buffer or buffer name, it forces redisplay of all
+windows displaying that buffer. If @var{object} is @code{nil} (or
+omitted), it forces redisplay of all windows.
address@hidden defun
+
+ Processing user input takes absolute priority over redisplay. If you
+call these functions when input is available, they do nothing
+immediately, but a full redisplay does happen eventually---after all the
+input has been processed.
+
+ Normally, suspending and resuming Emacs also refreshes the screen.
+Some terminal emulators record separate contents for display-oriented
+programs such as Emacs and for ordinary sequential display. If you are
+using such a terminal, you might want to inhibit the redisplay on
+resumption.
+
address@hidden no-redraw-on-reenter
address@hidden suspend (cf. @code{no-redraw-on-reenter})
address@hidden resume (cf. @code{no-redraw-on-reenter})
+This variable controls whether Emacs redraws the entire screen after it
+has been suspended and resumed. address@hidden means there is no need
+to redraw, @code{nil} means redrawing is needed. The default is @code{nil}.
address@hidden defvar
+
address@hidden Forcing Redisplay
address@hidden Forcing Redisplay
address@hidden forcing redisplay
+
+ Emacs redisplay normally stops if input arrives, and does not happen
+at all if input is available before it starts. Most of the time, this
+is exactly what you want. However, you can prevent preemption by
+binding @code{redisplay-dont-pause} to a address@hidden value.
+
address@hidden redisplay-preemption-period
+This variable specifies how many seconds Emacs waits between checks
+for new input during redisplay. (The default is 0.1 seconds.) If
+input has arrived when Emacs checks, it pre-empts redisplay and
+processes the available input before trying again to redisplay.
+
+If this variable is @code{nil}, Emacs does not check for input during
+redisplay, and redisplay cannot be preempted by input.
+
+This variable is only obeyed on graphical terminals. For
+text terminals, see @ref{Terminal Output}.
address@hidden defvar
+
address@hidden redisplay-dont-pause
+If this variable is address@hidden, pending input does not
+prevent or halt redisplay; redisplay occurs, and finishes,
+regardless of whether input is available.
address@hidden defvar
+
address@hidden redisplay &optional force
+This function performs an immediate redisplay provided there are no
+pending input events. This is equivalent to @code{(sit-for 0)}.
+
+If the optional argument @var{force} is address@hidden, it forces an
+immediate and complete redisplay even if input is available.
+
+Returns @code{t} if redisplay was performed, or @code{nil} otherwise.
address@hidden defun
+
address@hidden Truncation
address@hidden Truncation
address@hidden line wrapping
address@hidden line truncation
address@hidden continuation lines
address@hidden @samp{$} in display
address@hidden @samp{\} in display
+
+ When a line of text extends beyond the right edge of a window, Emacs
+can @dfn{continue} the line (make it ``wrap'' to the next screen
+line), or @dfn{truncate} the line (limit it to one screen line). The
+additional screen lines used to display a long text line are called
address@hidden lines. Continuation is not the same as filling;
+continuation happens on the screen only, not in the buffer contents,
+and it breaks a line precisely at the right margin, not at a word
+boundary. @xref{Filling}.
+
+ On a graphical display, tiny arrow images in the window fringes
+indicate truncated and continued lines (@pxref{Fringes}). On a text
+terminal, a @samp{$} in the rightmost column of the window indicates
+truncation; a @samp{\} on the rightmost column indicates a line that
+``wraps.'' (The display table can specify alternate characters to use
+for this; @pxref{Display Tables}).
+
address@hidden truncate-lines
+This buffer-local variable controls how Emacs displays lines that extend
+beyond the right edge of the window. The default is @code{nil}, which
+specifies continuation. If the value is address@hidden, then these
+lines are truncated.
+
+If the variable @code{truncate-partial-width-windows} is address@hidden,
+then truncation is always used for side-by-side windows (within one
+frame) regardless of the value of @code{truncate-lines}.
address@hidden defopt
+
address@hidden default-truncate-lines
+This variable is the default value for @code{truncate-lines}, for
+buffers that do not have buffer-local values for it.
address@hidden defopt
+
address@hidden truncate-partial-width-windows
+This variable controls display of lines that extend beyond the right
+edge of the window, in side-by-side windows (@pxref{Splitting Windows}).
+If it is address@hidden, these lines are truncated; otherwise,
address@hidden says what to do with them.
address@hidden defopt
+
+ When horizontal scrolling (@pxref{Horizontal Scrolling}) is in use in
+a window, that forces truncation.
+
+ If your buffer contains @emph{very} long lines, and you use
+continuation to display them, just thinking about them can make Emacs
+redisplay slow. The column computation and indentation functions also
+become slow. Then you might find it advisable to set
address@hidden to @code{t}.
+
address@hidden cache-long-line-scans
+If this variable is address@hidden, various indentation and motion
+functions, and Emacs redisplay, cache the results of scanning the
+buffer, and consult the cache to avoid rescanning regions of the buffer
+unless they are modified.
+
+Turning on the cache slows down processing of short lines somewhat.
+
+This variable is automatically buffer-local in every buffer.
address@hidden defvar
+
address@hidden The Echo Area
address@hidden The Echo Area
address@hidden error display
address@hidden echo area
+
+ The @dfn{echo area} is used for displaying error messages
+(@pxref{Errors}), for messages made with the @code{message} primitive,
+and for echoing keystrokes. It is not the same as the minibuffer,
+despite the fact that the minibuffer appears (when active) in the same
+place on the screen as the echo area. The @cite{GNU Emacs Manual}
+specifies the rules for resolving conflicts between the echo area and
+the minibuffer for use of that screen space (@pxref{Minibuffer,, The
+Minibuffer, emacs, The GNU Emacs Manual}).
+
+ You can write output in the echo area by using the Lisp printing
+functions with @code{t} as the stream (@pxref{Output Functions}), or
+explicitly.
+
address@hidden
+* Displaying Messages:: Explicitly displaying text in the echo area.
+* Progress:: Informing user about progress of a long operation.
+* Logging Messages:: Echo area messages are logged for the user.
+* Echo Area Customization:: Controlling the echo area.
address@hidden menu
+
address@hidden Displaying Messages
address@hidden Displaying Messages in the Echo Area
address@hidden display message in echo area
+
+ This section describes the functions for explicitly producing echo
+area messages. Many other Emacs features display messages there, too.
+
address@hidden message format-string &rest arguments
+This function displays a message in the echo area. The argument
address@hidden is similar to a C language @code{printf} format
+string. See @code{format} in @ref{Formatting Strings}, for the details
+on the conversion specifications. @code{message} returns the
+constructed string.
+
+In batch mode, @code{message} prints the message text on the standard
+error stream, followed by a newline.
+
+If @var{format-string}, or strings among the @var{arguments}, have
address@hidden text properties, these affect the way the message is displayed.
+
address@hidden Emacs 19 feature
+If @var{format-string} is @code{nil} or the empty string,
address@hidden clears the echo area; if the echo area has been
+expanded automatically, this brings it back to its normal size.
+If the minibuffer is active, this brings the minibuffer contents back
+onto the screen immediately.
+
address@hidden
address@hidden
+(message "Minibuffer depth is %d."
+ (minibuffer-depth))
+ @print{} Minibuffer depth is 0.
address@hidden "Minibuffer depth is 0."
address@hidden group
+
address@hidden
+---------- Echo Area ----------
+Minibuffer depth is 0.
+---------- Echo Area ----------
address@hidden group
address@hidden example
+
+To automatically display a message in the echo area or in a pop-buffer,
+depending on its size, use @code{display-message-or-buffer} (see below).
address@hidden defun
+
address@hidden with-temp-message message &rest body
+This construct displays a message in the echo area temporarily, during
+the execution of @var{body}. It displays @var{message}, executes
address@hidden, then returns the value of the last body form while restoring
+the previous echo area contents.
address@hidden defmac
+
address@hidden message-or-box format-string &rest arguments
+This function displays a message like @code{message}, but may display it
+in a dialog box instead of the echo area. If this function is called in
+a command that was invoked using the mouse---more precisely, if
address@hidden (@pxref{Command Loop Info}) is either
address@hidden or a list---then it uses a dialog box or pop-up menu to
+display the message. Otherwise, it uses the echo area. (This is the
+same criterion that @code{y-or-n-p} uses to make a similar decision; see
address@hidden Queries}.)
+
+You can force use of the mouse or of the echo area by binding
address@hidden to a suitable value around the call.
address@hidden defun
+
address@hidden message-box format-string &rest arguments
address@hidden
+This function displays a message like @code{message}, but uses a dialog
+box (or a pop-up menu) whenever that is possible. If it is impossible
+to use a dialog box or pop-up menu, because the terminal does not
+support them, then @code{message-box} uses the echo area, like
address@hidden
address@hidden defun
+
address@hidden display-message-or-buffer message &optional buffer-name
not-this-window frame
+This function displays the message @var{message}, which may be either a
+string or a buffer. If it is shorter than the maximum height of the
+echo area, as defined by @code{max-mini-window-height}, it is displayed
+in the echo area, using @code{message}. Otherwise,
address@hidden is used to show it in a pop-up buffer.
+
+Returns either the string shown in the echo area, or when a pop-up
+buffer is used, the window used to display it.
+
+If @var{message} is a string, then the optional argument
address@hidden is the name of the buffer used to display it when a
+pop-up buffer is used, defaulting to @samp{*Message*}. In the case
+where @var{message} is a string and displayed in the echo area, it is
+not specified whether the contents are inserted into the buffer anyway.
+
+The optional arguments @var{not-this-window} and @var{frame} are as for
address@hidden, and only used if a buffer is displayed.
address@hidden defun
+
address@hidden current-message
+This function returns the message currently being displayed in the
+echo area, or @code{nil} if there is none.
address@hidden defun
+
address@hidden Progress
address@hidden Reporting Operation Progress
address@hidden progress reporting
+
+ When an operation can take a while to finish, you should inform the
+user about the progress it makes. This way the user can estimate
+remaining time and clearly see that Emacs is busy working, not hung.
+
+ Functions listed in this section provide simple and efficient way of
+reporting operation progress. Here is a working example that does
+nothing useful:
+
address@hidden
+(let ((progress-reporter
+ (make-progress-reporter "Collecting mana for Emacs..."
+ 0 500)))
+ (dotimes (k 500)
+ (sit-for 0.01)
+ (progress-reporter-update progress-reporter k))
+ (progress-reporter-done progress-reporter))
address@hidden smallexample
+
address@hidden make-progress-reporter message min-value max-value &optional
current-value min-change min-time
+This function creates and returns a @dfn{progress reporter}---an
+object you will use as an argument for all other functions listed
+here. The idea is to precompute as much data as possible to make
+progress reporting very fast.
+
+When this progress reporter is subsequently used, it will display
address@hidden in the echo area, followed by progress percentage.
address@hidden is treated as a simple string. If you need it to depend
+on a filename, for instance, use @code{format} before calling this
+function.
+
address@hidden and @var{max-value} arguments stand for starting and
+final states of your operation. For instance, if you scan a buffer,
+they should be the results of @code{point-min} and @code{point-max}
+correspondingly. It is required that @var{max-value} is greater than
address@hidden If you create progress reporter when some part of
+the operation has already been completed, then specify
address@hidden argument. But normally you should omit it or set
+it to @code{nil}---it will default to @var{min-value} then.
+
+Remaining arguments control the rate of echo area updates. Progress
+reporter will wait for at least @var{min-change} more percents of the
+operation to be completed before printing next message.
address@hidden specifies the minimum time in seconds to pass between
+successive prints. It can be fractional. Depending on Emacs and
+system capabilities, progress reporter may or may not respect this
+last argument or do it with varying precision. Default value for
address@hidden is 1 (one percent), for @var{min-time}---0.2
+(seconds.)
+
+This function calls @code{progress-reporter-update}, so the first
+message is printed immediately.
address@hidden defun
+
address@hidden progress-reporter-update reporter value
+This function does the main work of reporting progress of your
+operation. It displays the message of @var{reporter}, followed by
+progress percentage determined by @var{value}. If percentage is zero,
+or close enough according to the @var{min-change} and @var{min-time}
+arguments, then it is omitted from the output.
+
address@hidden must be the result of a call to
address@hidden @var{value} specifies the current
+state of your operation and must be between @var{min-value} and
address@hidden (inclusive) as passed to
address@hidden For instance, if you scan a buffer,
+then @var{value} should be the result of a call to @code{point}.
+
+This function respects @var{min-change} and @var{min-time} as passed
+to @code{make-progress-reporter} and so does not output new messages
+on every invocation. It is thus very fast and normally you should not
+try to reduce the number of calls to it: resulting overhead will most
+likely negate your effort.
address@hidden defun
+
address@hidden progress-reporter-force-update reporter value &optional
new-message
+This function is similar to @code{progress-reporter-update} except
+that it prints a message in the echo area unconditionally.
+
+The first two arguments have the same meaning as for
address@hidden Optional @var{new-message} allows
+you to change the message of the @var{reporter}. Since this functions
+always updates the echo area, such a change will be immediately
+presented to the user.
address@hidden defun
+
address@hidden progress-reporter-done reporter
+This function should be called when the operation is finished. It
+prints the message of @var{reporter} followed by word ``done'' in the
+echo area.
+
+You should always call this function and not hope for
address@hidden to print ``100%.'' Firstly, it may
+never print it, there are many good reasons for this not to happen.
+Secondly, ``done'' is more explicit.
address@hidden defun
+
address@hidden dotimes-with-progress-reporter (var count [result]) message
address@hidden
+This is a convenience macro that works the same way as @code{dotimes}
+does, but also reports loop progress using the functions described
+above. It allows you to save some typing.
+
+You can rewrite the example in the beginning of this node using
+this macro this way:
+
address@hidden
+(dotimes-with-progress-reporter
+ (k 500)
+ "Collecting some mana for Emacs..."
+ (sit-for 0.01))
address@hidden example
address@hidden defmac
+
address@hidden Logging Messages
address@hidden Logging Messages in @samp{*Messages*}
address@hidden logging echo-area messages
+
+ Almost all the messages displayed in the echo area are also recorded
+in the @samp{*Messages*} buffer so that the user can refer back to
+them. This includes all the messages that are output with
address@hidden
+
address@hidden message-log-max
+This variable specifies how many lines to keep in the @samp{*Messages*}
+buffer. The value @code{t} means there is no limit on how many lines to
+keep. The value @code{nil} disables message logging entirely. Here's
+how to display a message and prevent it from being logged:
+
address@hidden
+(let (message-log-max)
+ (message @dots{}))
address@hidden example
address@hidden defopt
+
+ To make @samp{*Messages*} more convenient for the user, the logging
+facility combines successive identical messages. It also combines
+successive related messages for the sake of two cases: question
+followed by answer, and a series of progress messages.
+
+ A ``question followed by an answer'' means two messages like the
+ones produced by @code{y-or-n-p}: the first is @address@hidden,
+and the second is @address@hidden@var{answer}}. The first
+message conveys no additional information beyond what's in the second,
+so logging the second message discards the first from the log.
+
+ A ``series of progress messages'' means successive messages like
+those produced by @code{make-progress-reporter}. They have the form
address@hidden@address@hidden, where @var{base} is the same each
+time, while @var{how-far} varies. Logging each message in the series
+discards the previous one, provided they are consecutive.
+
+ The functions @code{make-progress-reporter} and @code{y-or-n-p}
+don't have to do anything special to activate the message log
+combination feature. It operates whenever two consecutive messages
+are logged that share a common prefix ending in @samp{...}.
+
address@hidden Echo Area Customization
address@hidden Echo Area Customization
+
+ These variables control details of how the echo area works.
+
address@hidden cursor-in-echo-area
+This variable controls where the cursor appears when a message is
+displayed in the echo area. If it is address@hidden, then the cursor
+appears at the end of the message. Otherwise, the cursor appears at
+point---not in the echo area at all.
+
+The value is normally @code{nil}; Lisp programs bind it to @code{t}
+for brief periods of time.
address@hidden defvar
+
address@hidden echo-area-clear-hook
+This normal hook is run whenever the echo area is cleared---either by
address@hidden(message nil)} or for any other reason.
address@hidden defvar
+
address@hidden echo-keystrokes
+This variable determines how much time should elapse before command
+characters echo. Its value must be an integer or floating point number,
+which specifies the
+number of seconds to wait before echoing. If the user types a prefix
+key (such as @kbd{C-x}) and then delays this many seconds before
+continuing, the prefix key is echoed in the echo area. (Once echoing
+begins in a key sequence, all subsequent characters in the same key
+sequence are echoed immediately.)
+
+If the value is zero, then command input is not echoed.
address@hidden defvar
+
address@hidden message-truncate-lines
+Normally, displaying a long message resizes the echo area to display
+the entire message. But if the variable @code{message-truncate-lines}
+is address@hidden, the echo area does not resize, and the message is
+truncated to fit it, as in Emacs 20 and before.
address@hidden defvar
+
+ The variable @code{max-mini-window-height}, which specifies the
+maximum height for resizing minibuffer windows, also applies to the
+echo area (which is really a special use of the minibuffer window.
address@hidden Misc}.
+
address@hidden Warnings
address@hidden Reporting Warnings
address@hidden warnings
+
+ @dfn{Warnings} are a facility for a program to inform the user of a
+possible problem, but continue running.
+
address@hidden
+* Warning Basics:: Warnings concepts and functions to report them.
+* Warning Variables:: Variables programs bind to customize their warnings.
+* Warning Options:: Variables users set to control display of warnings.
address@hidden menu
+
address@hidden Warning Basics
address@hidden Warning Basics
address@hidden severity level
+
+ Every warning has a textual message, which explains the problem for
+the user, and a @dfn{severity level} which is a symbol. Here are the
+possible severity levels, in order of decreasing severity, and their
+meanings:
+
address@hidden @code
address@hidden :emergency
+A problem that will seriously impair Emacs operation soon
+if you do not attend to it promptly.
address@hidden :error
+A report of data or circumstances that are inherently wrong.
address@hidden :warning
+A report of data or circumstances that are not inherently wrong, but
+raise suspicion of a possible problem.
address@hidden :debug
+A report of information that may be useful if you are debugging.
address@hidden table
+
+ When your program encounters invalid input data, it can either
+signal a Lisp error by calling @code{error} or @code{signal} or report
+a warning with severity @code{:error}. Signaling a Lisp error is the
+easiest thing to do, but it means the program cannot continue
+processing. If you want to take the trouble to implement a way to
+continue processing despite the bad data, then reporting a warning of
+severity @code{:error} is the right way to inform the user of the
+problem. For instance, the Emacs Lisp byte compiler can report an
+error that way and continue compiling other functions. (If the
+program signals a Lisp error and then handles it with
address@hidden, the user won't see the error message; it could
+show the message to the user by reporting it as a warning.)
+
address@hidden warning type
+ Each warning has a @dfn{warning type} to classify it. The type is a
+list of symbols. The first symbol should be the custom group that you
+use for the program's user options. For example, byte compiler
+warnings use the warning type @code{(bytecomp)}. You can also
+subcategorize the warnings, if you wish, by using more symbols in the
+list.
+
address@hidden display-warning type message &optional level buffer-name
+This function reports a warning, using @var{message} as the message
+and @var{type} as the warning type. @var{level} should be the
+severity level, with @code{:warning} being the default.
+
address@hidden, if address@hidden, specifies the name of the buffer
+for logging the warning. By default, it is @samp{*Warnings*}.
address@hidden defun
+
address@hidden lwarn type level message &rest args
+This function reports a warning using the value of @code{(format
address@hidden @var{args}...)} as the message. In other respects it is
+equivalent to @code{display-warning}.
address@hidden defun
+
address@hidden warn message &rest args
+This function reports a warning using the value of @code{(format
address@hidden @var{args}...)} as the message, @code{(emacs)} as the
+type, and @code{:warning} as the severity level. It exists for
+compatibility only; we recommend not using it, because you should
+specify a specific warning type.
address@hidden defun
+
address@hidden Warning Variables
address@hidden Warning Variables
+
+ Programs can customize how their warnings appear by binding
+the variables described in this section.
+
address@hidden warning-levels
+This list defines the meaning and severity order of the warning
+severity levels. Each element defines one severity level,
+and they are arranged in order of decreasing severity.
+
+Each element has the form @code{(@var{level} @var{string}
address@hidden)}, where @var{level} is the severity level it defines.
address@hidden specifies the textual description of this level.
address@hidden should use @samp{%s} to specify where to put the warning
+type information, or it can omit the @samp{%s} so as not to include
+that information.
+
+The optional @var{function}, if address@hidden, is a function to call
+with no arguments, to get the user's attention.
+
+Normally you should not change the value of this variable.
address@hidden defvar
+
address@hidden warning-prefix-function
+If address@hidden, the value is a function to generate prefix text for
+warnings. Programs can bind the variable to a suitable function.
address@hidden calls this function with the warnings buffer
+current, and the function can insert text in it. That text becomes
+the beginning of the warning message.
+
+The function is called with two arguments, the severity level and its
+entry in @code{warning-levels}. It should return a list to use as the
+entry (this value need not be an actual member of
address@hidden). By constructing this value, the function can
+change the severity of the warning, or specify different handling for
+a given severity level.
+
+If the variable's value is @code{nil} then there is no function
+to call.
address@hidden defvar
+
address@hidden warning-series
+Programs can bind this variable to @code{t} to say that the next
+warning should begin a series. When several warnings form a series,
+that means to leave point on the first warning of the series, rather
+than keep moving it for each warning so that it appears on the last one.
+The series ends when the local binding is unbound and
address@hidden becomes @code{nil} again.
+
+The value can also be a symbol with a function definition. That is
+equivalent to @code{t}, except that the next warning will also call
+the function with no arguments with the warnings buffer current. The
+function can insert text which will serve as a header for the series
+of warnings.
+
+Once a series has begun, the value is a marker which points to the
+buffer position in the warnings buffer of the start of the series.
+
+The variable's normal value is @code{nil}, which means to handle
+each warning separately.
address@hidden defvar
+
address@hidden warning-fill-prefix
+When this variable is address@hidden, it specifies a fill prefix to
+use for filling each warning's text.
address@hidden defvar
+
address@hidden warning-type-format
+This variable specifies the format for displaying the warning type
+in the warning message. The result of formatting the type this way
+gets included in the message under the control of the string in the
+entry in @code{warning-levels}. The default value is @code{" (%s)"}.
+If you bind it to @code{""} then the warning type won't appear at
+all.
address@hidden defvar
+
address@hidden Warning Options
address@hidden Warning Options
+
+ These variables are used by users to control what happens
+when a Lisp program reports a warning.
+
address@hidden warning-minimum-level
+This user option specifies the minimum severity level that should be
+shown immediately to the user. The default is @code{:warning}, which
+means to immediately display all warnings except @code{:debug}
+warnings.
address@hidden defopt
+
address@hidden warning-minimum-log-level
+This user option specifies the minimum severity level that should be
+logged in the warnings buffer. The default is @code{:warning}, which
+means to log all warnings except @code{:debug} warnings.
address@hidden defopt
+
address@hidden warning-suppress-types
+This list specifies which warning types should not be displayed
+immediately for the user. Each element of the list should be a list
+of symbols. If its elements match the first elements in a warning
+type, then that warning is not displayed immediately.
address@hidden defopt
+
address@hidden warning-suppress-log-types
+This list specifies which warning types should not be logged in the
+warnings buffer. Each element of the list should be a list of
+symbols. If it matches the first few elements in a warning type, then
+that warning is not logged.
address@hidden defopt
+
address@hidden Invisible Text
address@hidden Invisible Text
+
address@hidden invisible text
+You can make characters @dfn{invisible}, so that they do not appear on
+the screen, with the @code{invisible} property. This can be either a
+text property (@pxref{Text Properties}) or a property of an overlay
+(@pxref{Overlays}). Cursor motion also partly ignores these
+characters; if the command loop finds point within them, it moves
+point to the other side of them.
+
+In the simplest case, any address@hidden @code{invisible} property makes
+a character invisible. This is the default case---if you don't alter
+the default value of @code{buffer-invisibility-spec}, this is how the
address@hidden property works. You should normally use @code{t}
+as the value of the @code{invisible} property if you don't plan
+to set @code{buffer-invisibility-spec} yourself.
+
+More generally, you can use the variable @code{buffer-invisibility-spec}
+to control which values of the @code{invisible} property make text
+invisible. This permits you to classify the text into different subsets
+in advance, by giving them different @code{invisible} values, and
+subsequently make various subsets visible or invisible by changing the
+value of @code{buffer-invisibility-spec}.
+
+Controlling visibility with @code{buffer-invisibility-spec} is
+especially useful in a program to display the list of entries in a
+database. It permits the implementation of convenient filtering
+commands to view just a part of the entries in the database. Setting
+this variable is very fast, much faster than scanning all the text in
+the buffer looking for properties to change.
+
address@hidden buffer-invisibility-spec
+This variable specifies which kinds of @code{invisible} properties
+actually make a character invisible. Setting this variable makes it
+buffer-local.
+
address@hidden @asis
address@hidden @code{t}
+A character is invisible if its @code{invisible} property is
address@hidden This is the default.
+
address@hidden a list
+Each element of the list specifies a criterion for invisibility; if a
+character's @code{invisible} property fits any one of these criteria,
+the character is invisible. The list can have two kinds of elements:
+
address@hidden @code
address@hidden @var{atom}
+A character is invisible if its @code{invisible} property value
+is @var{atom} or if it is a list with @var{atom} as a member.
+
address@hidden (@var{atom} . t)
+A character is invisible if its @code{invisible} property value is
address@hidden or if it is a list with @var{atom} as a member. Moreover,
+a sequence of such characters displays as an ellipsis.
address@hidden table
address@hidden table
address@hidden defvar
+
+ Two functions are specifically provided for adding elements to
address@hidden and removing elements from it.
+
address@hidden add-to-invisibility-spec element
+This function adds the element @var{element} to
address@hidden If @code{buffer-invisibility-spec}
+was @code{t}, it changes to a list, @code{(t)}, so that text whose
address@hidden property is @code{t} remains invisible.
address@hidden defun
+
address@hidden remove-from-invisibility-spec element
+This removes the element @var{element} from
address@hidden This does nothing if @var{element}
+is not in the list.
address@hidden defun
+
+ A convention for use of @code{buffer-invisibility-spec} is that a
+major mode should use the mode's own name as an element of
address@hidden and as the value of the
address@hidden property:
+
address@hidden
+;; @r{If you want to display an ellipsis:}
+(add-to-invisibility-spec '(my-symbol . t))
+;; @r{If you don't want ellipsis:}
+(add-to-invisibility-spec 'my-symbol)
+
+(overlay-put (make-overlay beginning end)
+ 'invisible 'my-symbol)
+
+;; @r{When done with the overlays:}
+(remove-from-invisibility-spec '(my-symbol . t))
+;; @r{Or respectively:}
+(remove-from-invisibility-spec 'my-symbol)
address@hidden example
+
address@hidden line-move-ignore-invisible
+ Ordinarily, functions that operate on text or move point do not care
+whether the text is invisible. The user-level line motion commands
+explicitly ignore invisible newlines if
address@hidden is address@hidden (the default), but
+only because they are explicitly programmed to do so.
+
+ However, if a command ends with point inside or immediately before
+invisible text, the main editing loop moves point further forward or
+further backward (in the same direction that the command already moved
+it) until that condition is no longer true. Thus, if the command
+moved point back into an invisible range, Emacs moves point back to
+the beginning of that range, and then back one more character. If the
+command moved point forward into an invisible range, Emacs moves point
+forward up to the first visible character that follows the invisible
+text.
+
+ Incremental search can make invisible overlays visible temporarily
+and/or permanently when a match includes invisible text. To enable
+this, the overlay should have a address@hidden
address@hidden property. The property value should be a
+function to be called with the overlay as an argument. This function
+should make the overlay visible permanently; it is used when the match
+overlaps the overlay on exit from the search.
+
+ During the search, such overlays are made temporarily visible by
+temporarily modifying their invisible and intangible properties. If you
+want this to be done differently for a certain overlay, give it an
address@hidden property which is a function.
+The function is called with two arguments: the first is the overlay, and
+the second is @code{nil} to make the overlay visible, or @code{t} to
+make it invisible again.
+
address@hidden Selective Display
address@hidden Selective Display
address@hidden @cindex selective display Duplicates selective-display
+
+ @dfn{Selective display} refers to a pair of related features for
+hiding certain lines on the screen.
+
+ The first variant, explicit selective display, is designed for use
+in a Lisp program: it controls which lines are hidden by altering the
+text. This kind of hiding in some ways resembles the effect of the
address@hidden property (@pxref{Invisible Text}), but the two
+features are different and do not work the same way.
+
+ In the second variant, the choice of lines to hide is made
+automatically based on indentation. This variant is designed to be a
+user-level feature.
+
+ The way you control explicit selective display is by replacing a
+newline (control-j) with a carriage return (control-m). The text that
+was formerly a line following that newline is now hidden. Strictly
+speaking, it is temporarily no longer a line at all, since only
+newlines can separate lines; it is now part of the previous line.
+
+ Selective display does not directly affect editing commands. For
+example, @kbd{C-f} (@code{forward-char}) moves point unhesitatingly
+into hidden text. However, the replacement of newline characters with
+carriage return characters affects some editing commands. For
+example, @code{next-line} skips hidden lines, since it searches only
+for newlines. Modes that use selective display can also define
+commands that take account of the newlines, or that control which
+parts of the text are hidden.
+
+ When you write a selectively displayed buffer into a file, all the
+control-m's are output as newlines. This means that when you next read
+in the file, it looks OK, with nothing hidden. The selective display
+effect is seen only within Emacs.
+
address@hidden selective-display
+This buffer-local variable enables selective display. This means that
+lines, or portions of lines, may be made hidden.
+
address@hidden @bullet
address@hidden
+If the value of @code{selective-display} is @code{t}, then the character
+control-m marks the start of hidden text; the control-m, and the rest
+of the line following it, are not displayed. This is explicit selective
+display.
+
address@hidden
+If the value of @code{selective-display} is a positive integer, then
+lines that start with more than that many columns of indentation are not
+displayed.
address@hidden itemize
+
+When some portion of a buffer is hidden, the vertical movement
+commands operate as if that portion did not exist, allowing a single
address@hidden command to skip any number of hidden lines.
+However, character movement commands (such as @code{forward-char}) do
+not skip the hidden portion, and it is possible (if tricky) to insert
+or delete text in an hidden portion.
+
+In the examples below, we show the @emph{display appearance} of the
+buffer @code{foo}, which changes with the value of
address@hidden The @emph{contents} of the buffer do not
+change.
+
address@hidden
address@hidden
+(setq selective-display nil)
+ @result{} nil
+
+---------- Buffer: foo ----------
+1 on this column
+ 2on this column
+ 3n this column
+ 3n this column
+ 2on this column
+1 on this column
+---------- Buffer: foo ----------
address@hidden group
+
address@hidden
+(setq selective-display 2)
+ @result{} 2
+
+---------- Buffer: foo ----------
+1 on this column
+ 2on this column
+ 2on this column
+1 on this column
+---------- Buffer: foo ----------
address@hidden group
address@hidden example
address@hidden defvar
+
address@hidden selective-display-ellipses
+If this buffer-local variable is address@hidden, then Emacs displays
address@hidden@dots{}} at the end of a line that is followed by hidden text.
+This example is a continuation of the previous one.
+
address@hidden
address@hidden
+(setq selective-display-ellipses t)
+ @result{} t
+
+---------- Buffer: foo ----------
+1 on this column
+ 2on this column ...
+ 2on this column
+1 on this column
+---------- Buffer: foo ----------
address@hidden group
address@hidden example
+
+You can use a display table to substitute other text for the ellipsis
+(@address@hidden). @xref{Display Tables}.
address@hidden defvar
+
address@hidden Temporary Displays
address@hidden Temporary Displays
+
+ Temporary displays are used by Lisp programs to put output into a
+buffer and then present it to the user for perusal rather than for
+editing. Many help commands use this feature.
+
address@hidden with-output-to-temp-buffer buffer-name address@hidden
+This function executes @var{forms} while arranging to insert any output
+they print into the buffer named @var{buffer-name}, which is first
+created if necessary, and put into Help mode. Finally, the buffer is
+displayed in some window, but not selected.
+
+If the @var{forms} do not change the major mode in the output buffer,
+so that it is still Help mode at the end of their execution, then
address@hidden makes this buffer read-only at the
+end, and also scans it for function and variable names to make them
+into clickable cross-references. @xref{Docstring hyperlinks, , Tips
+for Documentation Strings}, in particular the item on hyperlinks in
+documentation strings, for more details.
+
+The string @var{buffer-name} specifies the temporary buffer, which
+need not already exist. The argument must be a string, not a buffer.
+The buffer is erased initially (with no questions asked), and it is
+marked as unmodified after @code{with-output-to-temp-buffer} exits.
+
address@hidden binds @code{standard-output} to the
+temporary buffer, then it evaluates the forms in @var{forms}. Output
+using the Lisp output functions within @var{forms} goes by default to
+that buffer (but screen display and messages in the echo area, although
+they are ``output'' in the general sense of the word, are not affected).
address@hidden Functions}.
+
+Several hooks are available for customizing the behavior
+of this construct; they are listed below.
+
+The value of the last form in @var{forms} is returned.
+
address@hidden
address@hidden
+---------- Buffer: foo ----------
+ This is the contents of foo.
+---------- Buffer: foo ----------
address@hidden group
+
address@hidden
+(with-output-to-temp-buffer "foo"
+ (print 20)
+ (print standard-output))
address@hidden #<buffer foo>
+
+---------- Buffer: foo ----------
+20
+
+#<buffer foo>
+
+---------- Buffer: foo ----------
address@hidden group
address@hidden example
address@hidden defspec
+
address@hidden temp-buffer-show-function
+If this variable is address@hidden, @code{with-output-to-temp-buffer}
+calls it as a function to do the job of displaying a help buffer. The
+function gets one argument, which is the buffer it should display.
+
+It is a good idea for this function to run @code{temp-buffer-show-hook}
+just as @code{with-output-to-temp-buffer} normally would, inside of
address@hidden and with the chosen window and buffer
+selected.
address@hidden defvar
+
address@hidden temp-buffer-setup-hook
+This normal hook is run by @code{with-output-to-temp-buffer} before
+evaluating @var{body}. When the hook runs, the temporary buffer is
+current. This hook is normally set up with a function to put the
+buffer in Help mode.
address@hidden defvar
+
address@hidden temp-buffer-show-hook
+This normal hook is run by @code{with-output-to-temp-buffer} after
+displaying the temporary buffer. When the hook runs, the temporary buffer
+is current, and the window it was displayed in is selected. This hook
+is normally set up with a function to make the buffer read only, and
+find function names and variable names in it, provided the major mode
+is Help mode.
address@hidden defvar
+
address@hidden momentary-string-display string position &optional char message
+This function momentarily displays @var{string} in the current buffer at
address@hidden It has no effect on the undo list or on the buffer's
+modification status.
+
+The momentary display remains until the next input event. If the next
+input event is @var{char}, @code{momentary-string-display} ignores it
+and returns. Otherwise, that event remains buffered for subsequent use
+as input. Thus, typing @var{char} will simply remove the string from
+the display, while typing (say) @kbd{C-f} will remove the string from
+the display and later (presumably) move point forward. The argument
address@hidden is a space by default.
+
+The return value of @code{momentary-string-display} is not meaningful.
+
+If the string @var{string} does not contain control characters, you can
+do the same job in a more general way by creating (and then subsequently
+deleting) an overlay with a @code{before-string} property.
address@hidden Properties}.
+
+If @var{message} is address@hidden, it is displayed in the echo area
+while @var{string} is displayed in the buffer. If it is @code{nil}, a
+default message says to type @var{char} to continue.
+
+In this example, point is initially located at the beginning of the
+second line:
+
address@hidden
address@hidden
+---------- Buffer: foo ----------
+This is the contents of foo.
address@hidden line.
+---------- Buffer: foo ----------
address@hidden group
+
address@hidden
+(momentary-string-display
+ "**** Important Message! ****"
+ (point) ?\r
+ "Type RET when done reading")
address@hidden t
address@hidden group
+
address@hidden
+---------- Buffer: foo ----------
+This is the contents of foo.
+**** Important Message! ****Second line.
+---------- Buffer: foo ----------
+
+---------- Echo Area ----------
+Type RET when done reading
+---------- Echo Area ----------
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden Overlays
address@hidden Overlays
address@hidden overlays
+
+You can use @dfn{overlays} to alter the appearance of a buffer's text on
+the screen, for the sake of presentation features. An overlay is an
+object that belongs to a particular buffer, and has a specified
+beginning and end. It also has properties that you can examine and set;
+these affect the display of the text within the overlay.
+
+An overlay uses markers to record its beginning and end; thus,
+editing the text of the buffer adjusts the beginning and end of each
+overlay so that it stays with the text. When you create the overlay,
+you can specify whether text inserted at the beginning should be
+inside the overlay or outside, and likewise for the end of the overlay.
+
address@hidden
+* Managing Overlays:: Creating and moving overlays.
+* Overlay Properties:: How to read and set properties.
+ What properties do to the screen display.
+* Finding Overlays:: Searching for overlays.
address@hidden menu
+
address@hidden Managing Overlays
address@hidden Managing Overlays
+
+ This section describes the functions to create, delete and move
+overlays, and to examine their contents. Overlay changes are not
+recorded in the buffer's undo list, since the overlays are not
+part of the buffer's contents.
+
address@hidden overlayp object
+This function returns @code{t} if @var{object} is an overlay.
address@hidden defun
+
address@hidden make-overlay start end &optional buffer front-advance
rear-advance
+This function creates and returns an overlay that belongs to
address@hidden and ranges from @var{start} to @var{end}. Both @var{start}
+and @var{end} must specify buffer positions; they may be integers or
+markers. If @var{buffer} is omitted, the overlay is created in the
+current buffer.
+
+The arguments @var{front-advance} and @var{rear-advance} specify the
+marker insertion type for the start of the overlay and for the end of
+the overlay, respectively. @xref{Marker Insertion Types}. If they
+are both @code{nil}, the default, then the overlay extends to include
+any text inserted at the beginning, but not text inserted at the end.
+If @var{front-advance} is address@hidden, text inserted at the
+beginning of the overlay is excluded from the overlay. If
address@hidden is address@hidden, text inserted at the end of the
+overlay is included in the overlay.
address@hidden defun
+
address@hidden overlay-start overlay
+This function returns the position at which @var{overlay} starts,
+as an integer.
address@hidden defun
+
address@hidden overlay-end overlay
+This function returns the position at which @var{overlay} ends,
+as an integer.
address@hidden defun
+
address@hidden overlay-buffer overlay
+This function returns the buffer that @var{overlay} belongs to. It
+returns @code{nil} if @var{overlay} has been deleted.
address@hidden defun
+
address@hidden delete-overlay overlay
+This function deletes @var{overlay}. The overlay continues to exist as
+a Lisp object, and its property list is unchanged, but it ceases to be
+attached to the buffer it belonged to, and ceases to have any effect on
+display.
+
+A deleted overlay is not permanently disconnected. You can give it a
+position in a buffer again by calling @code{move-overlay}.
address@hidden defun
+
address@hidden move-overlay overlay start end &optional buffer
+This function moves @var{overlay} to @var{buffer}, and places its bounds
+at @var{start} and @var{end}. Both arguments @var{start} and @var{end}
+must specify buffer positions; they may be integers or markers.
+
+If @var{buffer} is omitted, @var{overlay} stays in the same buffer it
+was already associated with; if @var{overlay} was deleted, it goes into
+the current buffer.
+
+The return value is @var{overlay}.
+
+This is the only valid way to change the endpoints of an overlay. Do
+not try modifying the markers in the overlay by hand, as that fails to
+update other vital data structures and can cause some overlays to be
+``lost.''
address@hidden defun
+
address@hidden remove-overlays &optional start end name value
+This function removes all the overlays between @var{start} and
address@hidden whose property @var{name} has the value @var{value}. It can
+move the endpoints of the overlays in the region, or split them.
+
+If @var{name} is omitted or @code{nil}, it means to delete all overlays in
+the specified region. If @var{start} and/or @var{end} are omitted or
address@hidden, that means the beginning and end of the buffer respectively.
+Therefore, @code{(remove-overlays)} removes all the overlays in the
+current buffer.
address@hidden defun
+
+ Here are some examples:
+
address@hidden
+;; @r{Create an overlay.}
+(setq foo (make-overlay 1 10))
+ @result{} #<overlay from 1 to 10 in display.texi>
+(overlay-start foo)
+ @result{} 1
+(overlay-end foo)
+ @result{} 10
+(overlay-buffer foo)
+ @result{} #<buffer display.texi>
+;; @r{Give it a property we can check later.}
+(overlay-put foo 'happy t)
+ @result{} t
+;; @r{Verify the property is present.}
+(overlay-get foo 'happy)
+ @result{} t
+;; @r{Move the overlay.}
+(move-overlay foo 5 20)
+ @result{} #<overlay from 5 to 20 in display.texi>
+(overlay-start foo)
+ @result{} 5
+(overlay-end foo)
+ @result{} 20
+;; @r{Delete the overlay.}
+(delete-overlay foo)
+ @result{} nil
+;; @r{Verify it is deleted.}
+foo
+ @result{} #<overlay in no buffer>
+;; @r{A deleted overlay has no position.}
+(overlay-start foo)
+ @result{} nil
+(overlay-end foo)
+ @result{} nil
+(overlay-buffer foo)
+ @result{} nil
+;; @r{Undelete the overlay.}
+(move-overlay foo 1 20)
+ @result{} #<overlay from 1 to 20 in display.texi>
+;; @r{Verify the results.}
+(overlay-start foo)
+ @result{} 1
+(overlay-end foo)
+ @result{} 20
+(overlay-buffer foo)
+ @result{} #<buffer display.texi>
+;; @r{Moving and deleting the overlay does not change its properties.}
+(overlay-get foo 'happy)
+ @result{} t
address@hidden example
+
+ Emacs stores the overlays of each buffer in two lists, divided
+around an arbitrary ``center position.'' One list extends backwards
+through the buffer from that center position, and the other extends
+forwards from that center position. The center position can be anywhere
+in the buffer.
+
address@hidden overlay-recenter pos
+This function recenters the overlays of the current buffer around
+position @var{pos}. That makes overlay lookup faster for positions
+near @var{pos}, but slower for positions far away from @var{pos}.
address@hidden defun
+
+ A loop that scans the buffer forwards, creating overlays, can run
+faster if you do @code{(overlay-recenter (point-max))} first.
+
address@hidden Overlay Properties
address@hidden Overlay Properties
+
+ Overlay properties are like text properties in that the properties that
+alter how a character is displayed can come from either source. But in
+most respects they are different. @xref{Text Properties}, for comparison.
+
+ Text properties are considered a part of the text; overlays and
+their properties are specifically considered not to be part of the
+text. Thus, copying text between various buffers and strings
+preserves text properties, but does not try to preserve overlays.
+Changing a buffer's text properties marks the buffer as modified,
+while moving an overlay or changing its properties does not. Unlike
+text property changes, overlay property changes are not recorded in
+the buffer's undo list.
+
+ These functions read and set the properties of an overlay:
+
address@hidden overlay-get overlay prop
+This function returns the value of property @var{prop} recorded in
address@hidden, if any. If @var{overlay} does not record any value for
+that property, but it does have a @code{category} property which is a
+symbol, that symbol's @var{prop} property is used. Otherwise, the value
+is @code{nil}.
address@hidden defun
+
address@hidden overlay-put overlay prop value
+This function sets the value of property @var{prop} recorded in
address@hidden to @var{value}. It returns @var{value}.
address@hidden defun
+
address@hidden overlay-properties overlay
+This returns a copy of the property list of @var{overlay}.
address@hidden defun
+
+ See also the function @code{get-char-property} which checks both
+overlay properties and text properties for a given character.
address@hidden Properties}.
+
+ Many overlay properties have special meanings; here is a table
+of them:
+
address@hidden @code
address@hidden priority
address@hidden priority @r{(overlay property)}
+This property's value (which should be a nonnegative integer number)
+determines the priority of the overlay. The priority matters when two
+or more overlays cover the same character and both specify the same
+property; the one whose @code{priority} value is larger takes priority
+over the other. For the @code{face} property, the higher priority
+value does not completely replace the other; instead, its face
+attributes override the face attributes of the lower priority
address@hidden property.
+
+Currently, all overlays take priority over text properties. Please
+avoid using negative priority values, as we have not yet decided just
+what they should mean.
+
address@hidden window
address@hidden window @r{(overlay property)}
+If the @code{window} property is address@hidden, then the overlay
+applies only on that window.
+
address@hidden category
address@hidden category @r{(overlay property)}
+If an overlay has a @code{category} property, we call it the
address@hidden of the overlay. It should be a symbol. The properties
+of the symbol serve as defaults for the properties of the overlay.
+
address@hidden face
address@hidden face @r{(overlay property)}
+This property controls the way text is displayed---for example, which
+font and which colors. @xref{Faces}, for more information.
+
+In the simplest case, the value is a face name. It can also be a list;
+then each element can be any of these possibilities:
+
address@hidden @bullet
address@hidden
+A face name (a symbol or string).
+
address@hidden
+A property list of face attributes. This has the form (@var{keyword}
address@hidden @dots{}), where each @var{keyword} is a face attribute
+name and @var{value} is a meaningful value for that attribute. With
+this feature, you do not need to create a face each time you want to
+specify a particular attribute for certain text. @xref{Face
+Attributes}.
+
address@hidden
+A cons cell, either of the form @code{(foreground-color . @var{color-name})} or
address@hidden(background-color . @var{color-name})}. These elements specify
+just the foreground color or just the background color.
+
address@hidden(foreground-color . @var{color-name})} has the same effect as
address@hidden(:foreground @var{color-name})}; likewise for the background.
address@hidden itemize
+
address@hidden mouse-face
address@hidden mouse-face @r{(overlay property)}
+This property is used instead of @code{face} when the mouse is within
+the range of the overlay.
+
address@hidden display
address@hidden display @r{(overlay property)}
+This property activates various features that change the
+way text is displayed. For example, it can make text appear taller
+or shorter, higher or lower, wider or narrower, or replaced with an image.
address@hidden Property}.
+
address@hidden help-echo
address@hidden help-echo @r{(overlay property)}
+If an overlay has a @code{help-echo} property, then when you move the
+mouse onto the text in the overlay, Emacs displays a help string in the
+echo area, or in the tooltip window. For details see @ref{Text
+help-echo}.
+
address@hidden modification-hooks
address@hidden modification-hooks @r{(overlay property)}
+This property's value is a list of functions to be called if any
+character within the overlay is changed or if text is inserted strictly
+within the overlay.
+
+The hook functions are called both before and after each change.
+If the functions save the information they receive, and compare notes
+between calls, they can determine exactly what change has been made
+in the buffer text.
+
+When called before a change, each function receives four arguments: the
+overlay, @code{nil}, and the beginning and end of the text range to be
+modified.
+
+When called after a change, each function receives five arguments: the
+overlay, @code{t}, the beginning and end of the text range just
+modified, and the length of the pre-change text replaced by that range.
+(For an insertion, the pre-change length is zero; for a deletion, that
+length is the number of characters deleted, and the post-change
+beginning and end are equal.)
+
+If these functions modify the buffer, they should bind
address@hidden to @code{t} around doing so, to
+avoid confusing the internal mechanism that calls these hooks.
+
+Text properties also support the @code{modification-hooks} property,
+but the details are somewhat different (@pxref{Special Properties}).
+
address@hidden insert-in-front-hooks
address@hidden insert-in-front-hooks @r{(overlay property)}
+This property's value is a list of functions to be called before and
+after inserting text right at the beginning of the overlay. The calling
+conventions are the same as for the @code{modification-hooks} functions.
+
address@hidden insert-behind-hooks
address@hidden insert-behind-hooks @r{(overlay property)}
+This property's value is a list of functions to be called before and
+after inserting text right at the end of the overlay. The calling
+conventions are the same as for the @code{modification-hooks} functions.
+
address@hidden invisible
address@hidden invisible @r{(overlay property)}
+The @code{invisible} property can make the text in the overlay
+invisible, which means that it does not appear on the screen.
address@hidden Text}, for details.
+
address@hidden intangible
address@hidden intangible @r{(overlay property)}
+The @code{intangible} property on an overlay works just like the
address@hidden text property. @xref{Special Properties}, for details.
+
address@hidden isearch-open-invisible
+This property tells incremental search how to make an invisible overlay
+visible, permanently, if the final match overlaps it. @xref{Invisible
+Text}.
+
address@hidden isearch-open-invisible-temporary
+This property tells incremental search how to make an invisible overlay
+visible, temporarily, during the search. @xref{Invisible Text}.
+
address@hidden before-string
address@hidden before-string @r{(overlay property)}
+This property's value is a string to add to the display at the beginning
+of the overlay. The string does not appear in the buffer in any
+sense---only on the screen.
+
address@hidden after-string
address@hidden after-string @r{(overlay property)}
+This property's value is a string to add to the display at the end of
+the overlay. The string does not appear in the buffer in any
+sense---only on the screen.
+
address@hidden evaporate
address@hidden evaporate @r{(overlay property)}
+If this property is address@hidden, the overlay is deleted automatically
+if it becomes empty (i.e., if its length becomes zero). If you give
+an empty overlay a address@hidden @code{evaporate} property, that deletes
+it immediately.
+
address@hidden local-map
address@hidden keymap of character (and overlays)
address@hidden local-map @r{(overlay property)}
+If this property is address@hidden, it specifies a keymap for a portion
+of the text. The property's value replaces the buffer's local map, when
+the character after point is within the overlay. @xref{Active Keymaps}.
+
address@hidden keymap
address@hidden keymap @r{(overlay property)}
+The @code{keymap} property is similar to @code{local-map} but overrides the
+buffer's local map (and the map specified by the @code{local-map}
+property) rather than replacing it.
address@hidden table
+
address@hidden Finding Overlays
address@hidden Searching for Overlays
+
address@hidden overlays-at pos
+This function returns a list of all the overlays that cover the
+character at position @var{pos} in the current buffer. The list is in
+no particular order. An overlay contains position @var{pos} if it
+begins at or before @var{pos}, and ends after @var{pos}.
+
+To illustrate usage, here is a Lisp function that returns a list of the
+overlays that specify property @var{prop} for the character at point:
+
address@hidden
+(defun find-overlays-specifying (prop)
+ (let ((overlays (overlays-at (point)))
+ found)
+ (while overlays
+ (let ((overlay (car overlays)))
+ (if (overlay-get overlay prop)
+ (setq found (cons overlay found))))
+ (setq overlays (cdr overlays)))
+ found))
address@hidden smallexample
address@hidden defun
+
address@hidden overlays-in beg end
+This function returns a list of the overlays that overlap the region
address@hidden through @var{end}. ``Overlap'' means that at least one
+character is contained within the overlay and also contained within the
+specified region; however, empty overlays are included in the result if
+they are located at @var{beg}, or strictly between @var{beg} and @var{end}.
address@hidden defun
+
address@hidden next-overlay-change pos
+This function returns the buffer position of the next beginning or end
+of an overlay, after @var{pos}. If there is none, it returns
address@hidden(point-max)}.
address@hidden defun
+
address@hidden previous-overlay-change pos
+This function returns the buffer position of the previous beginning or
+end of an overlay, before @var{pos}. If there is none, it returns
address@hidden(point-min)}.
address@hidden defun
+
+ As an example, here's a simplified (and inefficient) version of the
+primitive function @code{next-single-char-property-change}
+(@pxref{Property Search}). It searches forward from position
address@hidden for the next position where the value of a given property
address@hidden, as obtained from either overlays or text properties,
+changes.
+
address@hidden
+(defun next-single-char-property-change (position prop)
+ (save-excursion
+ (goto-char position)
+ (let ((propval (get-char-property (point) prop)))
+ (while (and (not (eobp))
+ (eq (get-char-property (point) prop) propval))
+ (goto-char (min (next-overlay-change (point))
+ (next-single-property-change (point) prop)))))
+ (point)))
address@hidden smallexample
+
address@hidden Width
address@hidden Width
+
+Since not all characters have the same width, these functions let you
+check the width of a character. @xref{Primitive Indent}, and
address@hidden Lines}, for related functions.
+
address@hidden char-width char
+This function returns the width in columns of the character @var{char},
+if it were displayed in the current buffer and the selected window.
address@hidden defun
+
address@hidden string-width string
+This function returns the width in columns of the string @var{string},
+if it were displayed in the current buffer and the selected window.
address@hidden defun
+
address@hidden truncate-string-to-width string width &optional start-column
padding ellipsis
+This function returns the part of @var{string} that fits within
address@hidden columns, as a new string.
+
+If @var{string} does not reach @var{width}, then the result ends where
address@hidden ends. If one multi-column character in @var{string}
+extends across the column @var{width}, that character is not included in
+the result. Thus, the result can fall short of @var{width} but cannot
+go beyond it.
+
+The optional argument @var{start-column} specifies the starting column.
+If this is address@hidden, then the first @var{start-column} columns of
+the string are omitted from the value. If one multi-column character in
address@hidden extends across the column @var{start-column}, that
+character is not included.
+
+The optional argument @var{padding}, if address@hidden, is a padding
+character added at the beginning and end of the result string, to extend
+it to exactly @var{width} columns. The padding character is used at the
+end of the result if it falls short of @var{width}. It is also used at
+the beginning of the result if one multi-column character in
address@hidden extends across the column @var{start-column}.
+
+If @var{ellipsis} is address@hidden, it should be a string which will
+replace the end of @var{str} (including any padding) if it extends
+beyond @var{end-column}, unless the display width of @var{str} is
+equal to or less than the display width of @var{ellipsis}. If
address@hidden is address@hidden and not a string, it stands for
address@hidden"..."}.
+
address@hidden
+(truncate-string-to-width "\tab\t" 12 4)
+ @result{} "ab"
+(truncate-string-to-width "\tab\t" 12 4 ?\s)
+ @result{} " ab "
address@hidden example
address@hidden defun
+
address@hidden Line Height
address@hidden Line Height
address@hidden line height
+
+ The total height of each display line consists of the height of the
+contents of the line, plus optional additional vertical line spacing
+above or below the display line.
+
+ The height of the line contents is the maximum height of any
+character or image on that display line, including the final newline
+if there is one. (A display line that is continued doesn't include a
+final newline.) That is the default line height, if you do nothing to
+specify a greater height. (In the most common case, this equals the
+height of the default frame font.)
+
+ There are several ways to explicitly specify a larger line height,
+either by specifying an absolute height for the display line, or by
+specifying vertical space. However, no matter what you specify, the
+actual line height can never be less than the default.
+
address@hidden line-height @r{(text property)}
+ A newline can have a @code{line-height} text or overlay property
+that controls the total height of the display line ending in that
+newline.
+
+ If the property value is @code{t}, the newline character has no
+effect on the displayed height of the line---the visible contents
+alone determine the height. This is useful for tiling small images
+(or image slices) without adding blank areas between the images.
+
+ If the property value is a list of the form @code{(@var{height}
address@hidden)}, that adds extra space @emph{below} the display line.
+First Emacs uses @var{height} as a height spec to control extra space
address@hidden the line; then it adds enough space @emph{below} the line
+to bring the total line height up to @var{total}. In this case, the
+other ways to specify the line spacing are ignored.
+
+ Any other kind of property value is a height spec, which translates
+into a number---the specified line height. There are several ways to
+write a height spec; here's how each of them translates into a number:
+
address@hidden @code
address@hidden @var{integer}
+If the height spec is a positive integer, the height value is that integer.
address@hidden @var{float}
+If the height spec is a float, @var{float}, the numeric height value
+is @var{float} times the frame's default line height.
address@hidden (@var{face} . @var{ratio})
+If the height spec is a cons of the format shown, the numeric height
+is @var{ratio} times the height of face @var{face}. @var{ratio} can
+be any type of number, or @code{nil} which means a ratio of 1.
+If @var{face} is @code{t}, it refers to the current face.
address@hidden (nil . @var{ratio})
+If the height spec is a cons of the format shown, the numeric height
+is @var{ratio} times the height of the contents of the line.
address@hidden table
+
+ Thus, any valid height spec determines the height in pixels, one way
+or another. If the line contents' height is less than that, Emacs
+adds extra vertical space above the line to achieve the specified
+total height.
+
+ If you don't specify the @code{line-height} property, the line's
+height consists of the contents' height plus the line spacing.
+There are several ways to specify the line spacing for different
+parts of Emacs text.
+
address@hidden default-line-spacing
+ You can specify the line spacing for all lines in a frame with the
address@hidden frame parameter (@pxref{Layout Parameters}).
+However, if the variable @code{default-line-spacing} is
address@hidden, it overrides the frame's @code{line-spacing}
+parameter. An integer value specifies the number of pixels put below
+lines on graphical displays. A floating point number specifies the
+spacing relative to the frame's default line height.
+
address@hidden line-spacing
+ You can specify the line spacing for all lines in a buffer via the
+buffer-local @code{line-spacing} variable. An integer value specifies
+the number of pixels put below lines on graphical displays. A floating
+point number specifies the spacing relative to the default frame line
+height. This overrides line spacings specified for the frame.
+
address@hidden line-spacing @r{(text property)}
+ Finally, a newline can have a @code{line-spacing} text or overlay
+property that overrides the default frame line spacing and the buffer
+local @code{line-spacing} variable, for the display line ending in
+that newline.
+
+ One way or another, these mechanisms specify a Lisp value for the
+spacing of each line. The value is a height spec, and it translates
+into a Lisp value as described above. However, in this case the
+numeric height value specifies the line spacing, rather than the line
+height.
+
address@hidden Faces
address@hidden Faces
address@hidden faces
+
+ A @dfn{face} is a named collection of graphical attributes: font
+family, foreground color, background color, optional underlining, and
+many others. Faces are used in Emacs to control the style of display of
+particular parts of the text or the frame. @xref{Standard Faces,,,
+emacs, The GNU Emacs Manual}, for the list of faces Emacs normally
+comes with.
+
address@hidden face id
+Each face has its own @dfn{face number}, which distinguishes faces at
+low levels within Emacs. However, for most purposes, you refer to
+faces in Lisp programs by the symbols that name them.
+
address@hidden facep object
+This function returns @code{t} if @var{object} is a face name string
+or symbol (or if it is a vector of the kind used internally to record
+face data). It returns @code{nil} otherwise.
address@hidden defun
+
+Each face name is meaningful for all frames, and by default it has the
+same meaning in all frames. But you can arrange to give a particular
+face name a special meaning in one frame if you wish.
+
address@hidden
+* Defining Faces:: How to define a face with @code{defface}.
+* Face Attributes:: What is in a face?
+* Attribute Functions:: Functions to examine and set face attributes.
+* Displaying Faces:: How Emacs combines the faces specified for a
character.
+* Font Selection:: Finding the best available font for a face.
+* Face Functions:: How to define and examine faces.
+* Auto Faces:: Hook for automatic face assignment.
+* Font Lookup:: Looking up the names of available fonts
+ and information about them.
+* Fontsets:: A fontset is a collection of fonts
+ that handle a range of character sets.
address@hidden menu
+
address@hidden Defining Faces
address@hidden Defining Faces
+
+ The way to define a new face is with @code{defface}. This creates a
+kind of customization item (@pxref{Customization}) which the user can
+customize using the Customization buffer (@pxref{Easy Customization,,,
+emacs, The GNU Emacs Manual}).
+
address@hidden defface face spec doc [keyword address@hidden
+This declares @var{face} as a customizable face that defaults
+according to @var{spec}. You should not quote the symbol @var{face},
+and it should not end in @samp{-face} (that would be redundant). The
+argument @var{doc} specifies the face documentation. The keywords you
+can use in @code{defface} are the same as in @code{defgroup} and
address@hidden (@pxref{Common Keywords}).
+
+When @code{defface} executes, it defines the face according to
address@hidden, then uses any customizations that were read from the
+init file (@pxref{Init File}) to override that specification.
+
+When you evaluate a @code{defface} form with @kbd{C-M-x} in Emacs
+Lisp mode (@code{eval-defun}), a special feature of @code{eval-defun}
+overrides any customizations of the face. This way, the face reflects
+exactly what the @code{defface} says.
+
+The purpose of @var{spec} is to specify how the face should appear on
+different kinds of terminals. It should be an alist whose elements
+have the form @code{(@var{display} @var{atts})}. Each element's
address@hidden, @var{display}, specifies a class of terminals. (The first
+element, if its @sc{car} is @code{default}, is special---it specifies
+defaults for the remaining elements). The element's @sc{cadr},
address@hidden, is a list of face attributes and their values; it
+specifies what the face should look like on that kind of terminal.
+The possible attributes are defined in the value of
address@hidden
+
+The @var{display} part of an element of @var{spec} determines which
+frames the element matches. If more than one element of @var{spec}
+matches a given frame, the first element that matches is the one used
+for that frame. There are three possibilities for @var{display}:
+
address@hidden @asis
address@hidden @code{default}
+This element of @var{spec} doesn't match any frames; instead, it
+specifies defaults that apply to all frames. This kind of element, if
+used, must be the first element of @var{spec}. Each of the following
+elements can override any or all of these defaults.
+
address@hidden @code{t}
+This element of @var{spec} matches all frames. Therefore, any
+subsequent elements of @var{spec} are never used. Normally
address@hidden is used in the last (or only) element of @var{spec}.
+
address@hidden a list
+If @var{display} is a list, each element should have the form
address@hidden(@var{characteristic} @address@hidden)}. Here
address@hidden specifies a way of classifying frames, and the
address@hidden are possible classifications which @var{display} should
+apply to. Here are the possible values of @var{characteristic}:
+
address@hidden @code
address@hidden type
+The kind of window system the frame uses---either @code{graphic} (any
+graphics-capable display), @code{x}, @code{pc} (for the MS-DOS console),
address@hidden (for MS Windows 9X/NT/2K/XP), @code{mac} (for the Macintosh
+display), or @code{tty} (a non-graphics-capable display).
address@hidden Systems, window-system}.
+
address@hidden class
+What kinds of colors the frame supports---either @code{color},
address@hidden, or @code{mono}.
+
address@hidden background
+The kind of background---either @code{light} or @code{dark}.
+
address@hidden min-colors
+An integer that represents the minimum number of colors the frame
+should support. This matches a frame if its
address@hidden value is at least the specified integer.
+
address@hidden supports
+Whether or not the frame can display the face attributes given in
address@hidden@dots{} (@pxref{Face Attributes}). See the documentation
+for the function @code{display-supports-face-attributes-p} for more
+information on exactly how this testing is done. @xref{Display Face
+Attribute Testing}.
address@hidden table
+
+If an element of @var{display} specifies more than one @var{value} for a
+given @var{characteristic}, any of those values is acceptable. If
address@hidden has more than one element, each element should specify a
+different @var{characteristic}; then @emph{each} characteristic of the
+frame must match one of the @var{value}s specified for it in
address@hidden
address@hidden table
address@hidden defmac
+
+ Here's how the standard face @code{region} is defined:
+
address@hidden
address@hidden
+(defface region
+ '((((class color) (min-colors 88) (background dark))
+ :background "blue3")
address@hidden group
+ (((class color) (min-colors 88) (background light))
+ :background "lightgoldenrod2")
+ (((class color) (min-colors 16) (background dark))
+ :background "blue3")
+ (((class color) (min-colors 16) (background light))
+ :background "lightgoldenrod2")
+ (((class color) (min-colors 8))
+ :background "blue" :foreground "white")
+ (((type tty) (class mono))
+ :inverse-video t)
+ (t :background "gray"))
address@hidden
+ "Basic face for highlighting the region."
+ :group 'basic-faces)
address@hidden group
address@hidden example
+
+ Internally, @code{defface} uses the symbol property
address@hidden to record the face attributes specified in
address@hidden, @code{saved-face} for the attributes saved by the user
+with the customization buffer, @code{customized-face} for the
+attributes customized by the user for the current session, but not
+saved, and @code{face-documentation} for the documentation string.
+
address@hidden frame-background-mode
+This option, if address@hidden, specifies the background type to use for
+interpreting face definitions. If it is @code{dark}, then Emacs treats
+all frames as if they had a dark background, regardless of their actual
+background colors. If it is @code{light}, then Emacs treats all frames
+as if they had a light background.
address@hidden defopt
+
address@hidden Face Attributes
address@hidden Face Attributes
address@hidden face attributes
+
+ The effect of using a face is determined by a fixed set of @dfn{face
+attributes}. This table lists all the face attributes, and what they
+mean. You can specify more than one face for a given piece of text;
+Emacs merges the attributes of all the faces to determine how to
+display the text. @xref{Displaying Faces}.
+
+ Any attribute in a face can have the value @code{unspecified}. This
+means the face doesn't specify that attribute. In face merging, when
+the first face fails to specify a particular attribute, that means the
+next face gets a chance. However, the @code{default} face must
+specify all attributes.
+
+ Some of these font attributes are meaningful only on certain kinds of
+displays---if your display cannot handle a certain attribute, the
+attribute is ignored. (The attributes @code{:family}, @code{:width},
address@hidden:height}, @code{:weight}, and @code{:slant} correspond to parts of
+an X Logical Font Descriptor.)
+
address@hidden @code
address@hidden :family
+Font family name, or fontset name (@pxref{Fontsets}). If you specify a
+font family name, the wild-card characters @samp{*} and @samp{?} are
+allowed.
+
address@hidden :width
+Relative proportionate width, also known as the character set width or
+set width. This should be one of the symbols @code{ultra-condensed},
address@hidden, @code{condensed}, @code{semi-condensed},
address@hidden, @code{semi-expanded}, @code{expanded},
address@hidden, or @code{ultra-expanded}.
+
address@hidden :height
+Either the font height, an integer in units of 1/10 point, a floating
+point number specifying the amount by which to scale the height of any
+underlying face, or a function, which is called with the old height
+(from the underlying face), and should return the new height.
+
address@hidden :weight
+Font weight---a symbol from this series (from most dense to most faint):
address@hidden, @code{extra-bold}, @code{bold}, @code{semi-bold},
address@hidden, @code{semi-light}, @code{light}, @code{extra-light},
+or @code{ultra-light}.
+
+On a text-only terminal, any weight greater than normal is displayed as
+extra bright, and any weight less than normal is displayed as
+half-bright (provided the terminal supports the feature).
+
address@hidden :slant
+Font slant---one of the symbols @code{italic}, @code{oblique}, @code{normal},
address@hidden, or @code{reverse-oblique}.
+
+On a text-only terminal, slanted text is displayed as half-bright, if
+the terminal supports the feature.
+
address@hidden :foreground
+Foreground color, a string. The value can be a system-defined color
+name, or a hexadecimal color specification of the form
address@hidden@address@hidden@var{bb}}. (@samp{#000000} is black,
address@hidden is red, @samp{#00ff00} is green, @samp{#0000ff} is
+blue, and @samp{#ffffff} is white.)
+
address@hidden :background
+Background color, a string, like the foreground color.
+
address@hidden :inverse-video
+Whether or not characters should be displayed in inverse video. The
+value should be @code{t} (yes) or @code{nil} (no).
+
address@hidden :stipple
+The background stipple, a bitmap.
+
+The value can be a string; that should be the name of a file containing
+external-format X bitmap data. The file is found in the directories
+listed in the variable @code{x-bitmap-file-path}.
+
+Alternatively, the value can specify the bitmap directly, with a list
+of the form @code{(@var{width} @var{height} @var{data})}. Here,
address@hidden and @var{height} specify the size in pixels, and
address@hidden is a string containing the raw bits of the bitmap, row by
+row. Each row occupies @math{(@var{width} + 7) / 8} consecutive bytes
+in the string (which should be a unibyte string for best results).
+This means that each row always occupies at least one whole byte.
+
+If the value is @code{nil}, that means use no stipple pattern.
+
+Normally you do not need to set the stipple attribute, because it is
+used automatically to handle certain shades of gray.
+
address@hidden :underline
+Whether or not characters should be underlined, and in what color. If
+the value is @code{t}, underlining uses the foreground color of the
+face. If the value is a string, underlining uses that color. The
+value @code{nil} means do not underline.
+
address@hidden :overline
+Whether or not characters should be overlined, and in what color.
+The value is used like that of @code{:underline}.
+
address@hidden :strike-through
+Whether or not characters should be strike-through, and in what
+color. The value is used like that of @code{:underline}.
+
address@hidden :inherit
+The name of a face from which to inherit attributes, or a list of face
+names. Attributes from inherited faces are merged into the face like an
+underlying face would be, with higher priority than underlying faces.
+If a list of faces is used, attributes from faces earlier in the list
+override those from later faces.
+
address@hidden :box
+Whether or not a box should be drawn around characters, its color, the
+width of the box lines, and 3D appearance.
address@hidden table
+
+ Here are the possible values of the @code{:box} attribute, and what
+they mean:
+
address@hidden @asis
address@hidden @code{nil}
+Don't draw a box.
+
address@hidden @code{t}
+Draw a box with lines of width 1, in the foreground color.
+
address@hidden @var{color}
+Draw a box with lines of width 1, in color @var{color}.
+
address@hidden @code{(:line-width @var{width} :color @var{color} :style
@var{style})}
+This way you can explicitly specify all aspects of the box. The value
address@hidden specifies the width of the lines to draw; it defaults to 1.
+
+The value @var{color} specifies the color to draw with. The default is
+the foreground color of the face for simple boxes, and the background
+color of the face for 3D boxes.
+
+The value @var{style} specifies whether to draw a 3D box. If it is
address@hidden, the box looks like a 3D button that is not being
+pressed. If it is @code{pressed-button}, the box looks like a 3D button
+that is being pressed. If it is @code{nil} or omitted, a plain 2D box
+is used.
address@hidden table
+
+ In older versions of Emacs, before @code{:family}, @code{:height},
address@hidden:width}, @code{:weight}, and @code{:slant} existed, these
+attributes were used to specify the type face. They are now
+semi-obsolete, but they still work:
+
address@hidden @code
address@hidden :font
+This attribute specifies the font name.
+
address@hidden :bold
+A address@hidden value specifies a bold font.
+
address@hidden :italic
+A address@hidden value specifies an italic font.
address@hidden table
+
+ For compatibility, you can still set these ``attributes,'' even
+though they are not real face attributes. Here is what that does:
+
address@hidden @code
address@hidden :font
+You can specify an X font name as the ``value'' of this ``attribute'';
+that sets the @code{:family}, @code{:width}, @code{:height},
address@hidden:weight}, and @code{:slant} attributes according to the font name.
+
+If the value is a pattern with wildcards, the first font that matches
+the pattern is used to set these attributes.
+
address@hidden :bold
+A address@hidden makes the face bold; @code{nil} makes it normal.
+This actually works by setting the @code{:weight} attribute.
+
address@hidden :italic
+A address@hidden makes the face italic; @code{nil} makes it normal.
+This actually works by setting the @code{:slant} attribute.
address@hidden table
+
address@hidden x-bitmap-file-path
+This variable specifies a list of directories for searching
+for bitmap files, for the @code{:stipple} attribute.
address@hidden defvar
+
address@hidden bitmap-spec-p object
+This returns @code{t} if @var{object} is a valid bitmap specification,
+suitable for use with @code{:stipple} (see above). It returns
address@hidden otherwise.
address@hidden defun
+
address@hidden Attribute Functions
address@hidden Face Attribute Functions
+
+ This section describes the functions for accessing and modifying the
+attributes of an existing face.
+
address@hidden set-face-attribute face frame &rest arguments
+This function sets one or more attributes of face @var{face} for frame
address@hidden The attributes you specify this way override whatever
+the @code{defface} says.
+
+The extra arguments @var{arguments} specify the attributes to set, and
+the values for them. They should consist of alternating attribute names
+(such as @code{:family} or @code{:underline}) and corresponding values.
+Thus,
+
address@hidden
+(set-face-attribute 'foo nil
+ :width 'extended
+ :weight 'bold
+ :underline "red")
address@hidden example
+
address@hidden
+sets the attributes @code{:width}, @code{:weight} and @code{:underline}
+to the corresponding values.
+
+If @var{frame} is @code{t}, this function sets the default attributes
+for new frames. Default attribute values specified this way override
+the @code{defface} for newly created frames.
+
+If @var{frame} is @code{nil}, this function sets the attributes for
+all existing frames, and the default for new frames.
address@hidden defun
+
address@hidden face-attribute face attribute &optional frame inherit
+This returns the value of the @var{attribute} attribute of face
address@hidden on @var{frame}. If @var{frame} is @code{nil},
+that means the selected frame (@pxref{Input Focus}).
+
+If @var{frame} is @code{t}, this returns whatever new-frames default
+value you previously specified with @code{set-face-attribute} for the
address@hidden attribute of @var{face}. If you have not specified
+one, it returns @code{nil}.
+
+If @var{inherit} is @code{nil}, only attributes directly defined by
address@hidden are considered, so the return value may be
address@hidden, or a relative value. If @var{inherit} is
address@hidden, @var{face}'s definition of @var{attribute} is merged
+with the faces specified by its @code{:inherit} attribute; however the
+return value may still be @code{unspecified} or relative. If
address@hidden is a face or a list of faces, then the result is further
+merged with that face (or faces), until it becomes specified and
+absolute.
+
+To ensure that the return value is always specified and absolute, use
+a value of @code{default} for @var{inherit}; this will resolve any
+unspecified or relative values by merging with the @code{default} face
+(which is always completely specified).
+
+For example,
+
address@hidden
+(face-attribute 'bold :weight)
+ @result{} bold
address@hidden example
address@hidden defun
+
address@hidden face-attribute-relative-p attribute value
+This function returns address@hidden if @var{value}, when used as the
+value of the face attribute @var{attribute}, is relative. This means
+it would modify, rather than completely override, any value that comes
+from a subsequent face in the face list or that is inherited from
+another face.
+
address@hidden is a relative value for all attributes.
+For @code{:height}, floating point values are also relative.
+
+For example:
+
address@hidden
+(face-attribute-relative-p :height 2.0)
+ @result{} t
address@hidden example
address@hidden defun
+
address@hidden merge-face-attribute attribute value1 value2
+If @var{value1} is a relative value for the face attribute
address@hidden, returns it merged with the underlying value
address@hidden; otherwise, if @var{value1} is an absolute value for the
+face attribute @var{attribute}, returns @var{value1} unchanged.
address@hidden defun
+
+ The functions above did not exist before Emacs 21. For compatibility
+with older Emacs versions, you can use the following functions to set
+and examine the face attributes which existed in those versions.
+They use values of @code{t} and @code{nil} for @var{frame}
+just like @code{set-face-attribute} and @code{face-attribute}.
+
address@hidden set-face-foreground face color &optional frame
address@hidden set-face-background face color &optional frame
+These functions set the foreground (or background, respectively) color
+of face @var{face} to @var{color}. The argument @var{color} should be a
+string, the name of a color.
+
+Certain shades of gray are implemented by stipple patterns on
+black-and-white screens.
address@hidden defun
+
address@hidden set-face-stipple face pattern &optional frame
+This function sets the background stipple pattern of face @var{face}
+to @var{pattern}. The argument @var{pattern} should be the name of a
+stipple pattern defined by the X server, or actual bitmap data
+(@pxref{Face Attributes}), or @code{nil} meaning don't use stipple.
+
+Normally there is no need to pay attention to stipple patterns, because
+they are used automatically to handle certain shades of gray.
address@hidden defun
+
address@hidden set-face-font face font &optional frame
+This function sets the font of face @var{face}. This actually sets
+the attributes @code{:family}, @code{:width}, @code{:height},
address@hidden:weight}, and @code{:slant} according to the font name
address@hidden
address@hidden defun
+
address@hidden set-face-bold-p face bold-p &optional frame
+This function specifies whether @var{face} should be bold. If
address@hidden is address@hidden, that means yes; @code{nil} means no.
+This actually sets the @code{:weight} attribute.
address@hidden defun
+
address@hidden set-face-italic-p face italic-p &optional frame
+This function specifies whether @var{face} should be italic. If
address@hidden is address@hidden, that means yes; @code{nil} means no.
+This actually sets the @code{:slant} attribute.
address@hidden defun
+
address@hidden set-face-underline-p face underline &optional frame
+This function sets the underline attribute of face @var{face}.
address@hidden means do underline; @code{nil} means don't.
+If @var{underline} is a string, underline with that color.
address@hidden defun
+
address@hidden set-face-inverse-video-p face inverse-video-p &optional frame
+This function sets the @code{:inverse-video} attribute of face
address@hidden
address@hidden defun
+
address@hidden invert-face face &optional frame
+This function swaps the foreground and background colors of face
address@hidden
address@hidden defun
+
+ These functions examine the attributes of a face. If you don't
+specify @var{frame}, they refer to the selected frame; @code{t} refers
+to the default data for new frames. They return the symbol
address@hidden if the face doesn't define any value for that
+attribute.
+
address@hidden face-foreground face &optional frame inherit
address@hidden face-background face &optional frame inherit
+These functions return the foreground color (or background color,
+respectively) of face @var{face}, as a string.
+
+If @var{inherit} is @code{nil}, only a color directly defined by the face is
+returned. If @var{inherit} is address@hidden, any faces specified by its
address@hidden:inherit} attribute are considered as well, and if @var{inherit}
+is a face or a list of faces, then they are also considered, until a
+specified color is found. To ensure that the return value is always
+specified, use a value of @code{default} for @var{inherit}.
address@hidden defun
+
address@hidden face-stipple face &optional frame inherit
+This function returns the name of the background stipple pattern of face
address@hidden, or @code{nil} if it doesn't have one.
+
+If @var{inherit} is @code{nil}, only a stipple directly defined by the
+face is returned. If @var{inherit} is address@hidden, any faces
+specified by its @code{:inherit} attribute are considered as well, and
+if @var{inherit} is a face or a list of faces, then they are also
+considered, until a specified stipple is found. To ensure that the
+return value is always specified, use a value of @code{default} for
address@hidden
address@hidden defun
+
address@hidden face-font face &optional frame
+This function returns the name of the font of face @var{face}.
address@hidden defun
+
address@hidden face-bold-p face &optional frame
+This function returns @code{t} if @var{face} is bold---that is, if it is
+bolder than normal. It returns @code{nil} otherwise.
address@hidden defun
+
address@hidden face-italic-p face &optional frame
+This function returns @code{t} if @var{face} is italic or oblique,
address@hidden otherwise.
address@hidden defun
+
address@hidden face-underline-p face &optional frame
+This function returns the @code{:underline} attribute of face @var{face}.
address@hidden defun
+
address@hidden face-inverse-video-p face &optional frame
+This function returns the @code{:inverse-video} attribute of face @var{face}.
address@hidden defun
+
address@hidden Displaying Faces
address@hidden Displaying Faces
+
+ Here are the ways to specify which faces to use for display of text:
+
address@hidden @bullet
address@hidden
+With defaults. The @code{default} face is used as the ultimate
+default for all text. (In Emacs 19 and 20, the @code{default}
+face is used only when no other face is specified.)
+
address@hidden
+For a mode line or header line, the face @code{mode-line} or
address@hidden, or @code{header-line}, is merged in just
+before @code{default}.
+
address@hidden
+With text properties. A character can have a @code{face} property; if
+so, the faces and face attributes specified there apply. @xref{Special
+Properties}.
+
+If the character has a @code{mouse-face} property, that is used instead
+of the @code{face} property when the mouse is ``near enough'' to the
+character.
+
address@hidden
+With overlays. An overlay can have @code{face} and @code{mouse-face}
+properties too; they apply to all the text covered by the overlay.
+
address@hidden
+With a region that is active. In Transient Mark mode, the region is
+highlighted with the face @code{region} (@pxref{Standard Faces,,,
+emacs, The GNU Emacs Manual}).
+
address@hidden
+With special glyphs. Each glyph can specify a particular face
+number. @xref{Glyphs}.
address@hidden itemize
+
+ If these various sources together specify more than one face for a
+particular character, Emacs merges the attributes of the various faces
+specified. For each attribute, Emacs tries first the face of any
+special glyph; then the face for region highlighting, if appropriate;
+then the faces specified by overlays, followed by those specified by
+text properties, then the @code{mode-line} or
address@hidden or @code{header-line} face (if in a mode
+line or a header line), and last the @code{default} face.
+
+ When multiple overlays cover one character, an overlay with higher
+priority overrides those with lower priority. @xref{Overlays}.
+
address@hidden Font Selection
address@hidden Font Selection
+
+ @dfn{Selecting a font} means mapping the specified face attributes for
+a character to a font that is available on a particular display. The
+face attributes, as determined by face merging, specify most of the
+font choice, but not all. Part of the choice depends on what character
+it is.
+
+ If the face specifies a fontset name, that fontset determines a
+pattern for fonts of the given charset. If the face specifies a font
+family, a font pattern is constructed.
+
+ Emacs tries to find an available font for the given face attributes
+and character's registry and encoding. If there is a font that matches
+exactly, it is used, of course. The hard case is when no available font
+exactly fits the specification. Then Emacs looks for one that is
+``close''---one attribute at a time. You can specify the order to
+consider the attributes. In the case where a specified font family is
+not available, you can specify a set of mappings for alternatives to
+try.
+
address@hidden face-font-selection-order
+This variable specifies the order of importance of the face attributes
address@hidden:width}, @code{:height}, @code{:weight}, and @code{:slant}. The
+value should be a list containing those four symbols, in order of
+decreasing importance.
+
+Font selection first finds the best available matches for the first
+attribute listed; then, among the fonts which are best in that way, it
+searches for the best matches in the second attribute, and so on.
+
+The attributes @code{:weight} and @code{:width} have symbolic values in
+a range centered around @code{normal}. Matches that are more extreme
+(farther from @code{normal}) are somewhat preferred to matches that are
+less extreme (closer to @code{normal}); this is designed to ensure that
+non-normal faces contrast with normal ones, whenever possible.
+
+The default is @code{(:width :height :weight :slant)}, which means first
+find the fonts closest to the specified @code{:width}, then---among the
+fonts with that width---find a best match for the specified font height,
+and so on.
+
+One example of a case where this variable makes a difference is when the
+default font has no italic equivalent. With the default ordering, the
address@hidden face will use a non-italic font that is similar to the
+default one. But if you put @code{:slant} before @code{:height}, the
address@hidden face will use an italic font, even if its height is not
+quite right.
address@hidden defvar
+
address@hidden face-font-family-alternatives
+This variable lets you specify alternative font families to try, if a
+given family is specified and doesn't exist. Each element should have
+this form:
+
address@hidden
+(@var{family} @address@hidden)
address@hidden example
+
+If @var{family} is specified but not available, Emacs will try the other
+families given in @var{alternate-families}, one by one, until it finds a
+family that does exist.
address@hidden defvar
+
address@hidden face-font-registry-alternatives
+This variable lets you specify alternative font registries to try, if a
+given registry is specified and doesn't exist. Each element should have
+this form:
+
address@hidden
+(@var{registry} @address@hidden)
address@hidden example
+
+If @var{registry} is specified but not available, Emacs will try the
+other registries given in @var{alternate-registries}, one by one,
+until it finds a registry that does exist.
address@hidden defvar
+
+ Emacs can make use of scalable fonts, but by default it does not use
+them, since the use of too many or too big scalable fonts can crash
+XFree86 servers.
+
address@hidden scalable-fonts-allowed
+This variable controls which scalable fonts to use. A value of
address@hidden, the default, means do not use scalable fonts. @code{t}
+means to use any scalable font that seems appropriate for the text.
+
+Otherwise, the value must be a list of regular expressions. Then a
+scalable font is enabled for use if its name matches any regular
+expression in the list. For example,
+
address@hidden
+(setq scalable-fonts-allowed '("muleindian-2$"))
address@hidden example
+
address@hidden
+allows the use of scalable fonts with registry @code{muleindian-2}.
address@hidden defvar
+
address@hidden face-font-rescale-alist
+This variable specifies scaling for certain faces. Its value should
+be a list of elements of the form
+
address@hidden
+(@var{fontname-regexp} . @var{scale-factor})
address@hidden example
+
+If @var{fontname-regexp} matches the font name that is about to be
+used, this says to choose a larger similar font according to the
+factor @var{scale-factor}. You would use this feature to normalize
+the font size if certain fonts are bigger or smaller than their
+nominal heights and widths would suggest.
address@hidden defvar
+
address@hidden Face Functions
address@hidden Functions for Working with Faces
+
+ Here are additional functions for creating and working with faces.
+
address@hidden make-face name
+This function defines a new face named @var{name}, initially with all
+attributes @code{nil}. It does nothing if there is already a face named
address@hidden
address@hidden defun
+
address@hidden face-list
+This function returns a list of all defined face names.
address@hidden defun
+
address@hidden copy-face old-face new-name &optional frame new-frame
+This function defines a face named @var{new-name} as a copy of the existing
+face named @var{old-face}. It creates the face @var{new-name} if that
+doesn't already exist.
+
+If the optional argument @var{frame} is given, this function applies
+only to that frame. Otherwise it applies to each frame individually,
+copying attributes from @var{old-face} in each frame to @var{new-face}
+in the same frame.
+
+If the optional argument @var{new-frame} is given, then @code{copy-face}
+copies the attributes of @var{old-face} in @var{frame} to @var{new-name}
+in @var{new-frame}.
address@hidden defun
+
address@hidden face-id face
+This function returns the face number of face @var{face}.
address@hidden defun
+
address@hidden face-documentation face
+This function returns the documentation string of face @var{face}, or
address@hidden if none was specified for it.
address@hidden defun
+
address@hidden face-equal face1 face2 &optional frame
+This returns @code{t} if the faces @var{face1} and @var{face2} have the
+same attributes for display.
address@hidden defun
+
address@hidden face-differs-from-default-p face &optional frame
+This returns address@hidden if the face @var{face} displays
+differently from the default face.
address@hidden defun
+
address@hidden face alias
+A @dfn{face alias} provides an equivalent name for a face. You can
+define a face alias by giving the alias symbol the @code{face-alias}
+property, with a value of the target face name. The following example
+makes @code{modeline} an alias for the @code{mode-line} face.
+
address@hidden
+(put 'modeline 'face-alias 'mode-line)
address@hidden example
+
+
address@hidden Auto Faces
address@hidden Automatic Face Assignment
address@hidden automatic face assignment
address@hidden faces, automatic choice
+
+ This hook is used for automatically assigning facesto text in the
+buffer. It is part of the implementation of Jit-Lock mode, used by
+Font-Lock.
+
address@hidden fontification-functions
+This variable holds a list of functions that are called by Emacs
+redisplay as needed to assign faces automatically to text in the buffer.
+
+The functions are called in the order listed, with one argument, a
+buffer position @var{pos}. Each function should attempt to assign faces
+to the text in the current buffer starting at @var{pos}.
+
+Each function should record the faces they assign by setting the
address@hidden property. It should also add a address@hidden
address@hidden property for all the text it has assigned faces to.
+That property tells redisplay that faces have been assigned to that text
+already.
+
+It is probably a good idea for each function to do nothing if the
+character after @var{pos} already has a address@hidden @code{fontified}
+property, but this is not required. If one function overrides the
+assignments made by a previous one, the properties as they are
+after the last function finishes are the ones that really matter.
+
+For efficiency, we recommend writing these functions so that they
+usually assign faces to around 400 to 600 characters at each call.
address@hidden defvar
+
address@hidden Font Lookup
address@hidden Looking Up Fonts
+
address@hidden x-list-fonts pattern &optional face frame maximum
+This function returns a list of available font names that match
address@hidden If the optional arguments @var{face} and @var{frame} are
+specified, then the list is limited to fonts that are the same size as
address@hidden currently is on @var{frame}.
+
+The argument @var{pattern} should be a string, perhaps with wildcard
+characters: the @samp{*} character matches any substring, and the
address@hidden character matches any single character. Pattern matching
+of font names ignores case.
+
+If you specify @var{face} and @var{frame}, @var{face} should be a face name
+(a symbol) and @var{frame} should be a frame.
+
+The optional argument @var{maximum} sets a limit on how many fonts to
+return. If this is address@hidden, then the return value is truncated
+after the first @var{maximum} matching fonts. Specifying a small value
+for @var{maximum} can make this function much faster, in cases where
+many fonts match the pattern.
address@hidden defun
+
address@hidden x-family-fonts &optional family frame
+This function returns a list describing the available fonts for family
address@hidden on @var{frame}. If @var{family} is omitted or @code{nil},
+this list applies to all families, and therefore, it contains all
+available fonts. Otherwise, @var{family} must be a string; it may
+contain the wildcards @samp{?} and @samp{*}.
+
+The list describes the display that @var{frame} is on; if @var{frame} is
+omitted or @code{nil}, it applies to the selected frame's display
+(@pxref{Input Focus}).
+
+The list contains a vector of the following form for each font:
+
address@hidden
address@hidden @var{width} @var{point-size} @var{weight} @var{slant}
+ @var{fixed-p} @var{full} @var{registry-and-encoding}]
address@hidden example
+
+The first five elements correspond to face attributes; if you
+specify these attributes for a face, it will use this font.
+
+The last three elements give additional information about the font.
address@hidden is address@hidden if the font is fixed-pitch.
address@hidden is the full name of the font, and
address@hidden is a string giving the registry and
+encoding of the font.
+
+The result list is sorted according to the current face font sort order.
address@hidden defun
+
address@hidden x-font-family-list &optional frame
+This function returns a list of the font families available for
address@hidden's display. If @var{frame} is omitted or @code{nil}, it
+describes the selected frame's display (@pxref{Input Focus}).
+
+The value is a list of elements of this form:
+
address@hidden
+(@var{family} . @var{fixed-p})
address@hidden example
+
address@hidden
+Here @var{family} is a font family, and @var{fixed-p} is
address@hidden if fonts of that family are fixed-pitch.
address@hidden defun
+
address@hidden font-list-limit
+This variable specifies maximum number of fonts to consider in font
+matching. The function @code{x-family-fonts} will not return more than
+that many fonts, and font selection will consider only that many fonts
+when searching a matching font for face attributes. The default is
+currently 100.
address@hidden defvar
+
address@hidden Fontsets
address@hidden Fontsets
+
+ A @dfn{fontset} is a list of fonts, each assigned to a range of
+character codes. An individual font cannot display the whole range of
+characters that Emacs supports, but a fontset can. Fontsets have names,
+just as fonts do, and you can use a fontset name in place of a font name
+when you specify the ``font'' for a frame or a face. Here is
+information about defining a fontset under Lisp program control.
+
address@hidden create-fontset-from-fontset-spec fontset-spec &optional
style-variant-p noerror
+This function defines a new fontset according to the specification
+string @var{fontset-spec}. The string should have this format:
+
address@hidden
address@hidden, @address@hidden:@address@hidden@dots{}}
address@hidden smallexample
+
address@hidden
+Whitespace characters before and after the commas are ignored.
+
+The first part of the string, @var{fontpattern}, should have the form of
+a standard X font name, except that the last two fields should be
address@hidden@var{alias}}.
+
+The new fontset has two names, one long and one short. The long name is
address@hidden in its entirety. The short name is
address@hidden@var{alias}}. You can refer to the fontset by either
+name. If a fontset with the same name already exists, an error is
+signaled, unless @var{noerror} is address@hidden, in which case this
+function does nothing.
+
+If optional argument @var{style-variant-p} is address@hidden, that says
+to create bold, italic and bold-italic variants of the fontset as well.
+These variant fontsets do not have a short name, only a long one, which
+is made by altering @var{fontpattern} to indicate the bold or italic
+status.
+
+The specification string also says which fonts to use in the fontset.
+See below for the details.
address@hidden defun
+
+ The construct @address@hidden:@var{font}} specifies which font to
+use (in this fontset) for one particular character set. Here,
address@hidden is the name of a character set, and @var{font} is the font
+to use for that character set. You can use this construct any number of
+times in the specification string.
+
+ For the remaining character sets, those that you don't specify
+explicitly, Emacs chooses a font based on @var{fontpattern}: it replaces
address@hidden@var{alias}} with a value that names one character set.
+For the @acronym{ASCII} character set, @address@hidden is replaced
+with @samp{ISO8859-1}.
+
+ In addition, when several consecutive fields are wildcards, Emacs
+collapses them into a single wildcard. This is to prevent use of
+auto-scaled fonts. Fonts made by scaling larger fonts are not usable
+for editing, and scaling a smaller font is not useful because it is
+better to use the smaller font in its own size, which Emacs does.
+
+ Thus if @var{fontpattern} is this,
+
address@hidden
+-*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24
address@hidden example
+
address@hidden
+the font specification for @acronym{ASCII} characters would be this:
+
address@hidden
+-*-fixed-medium-r-normal-*-24-*-ISO8859-1
address@hidden example
+
address@hidden
+and the font specification for Chinese GB2312 characters would be this:
+
address@hidden
+-*-fixed-medium-r-normal-*-24-*-gb2312*-*
address@hidden example
+
+ You may not have any Chinese font matching the above font
+specification. Most X distributions include only Chinese fonts that
+have @samp{song ti} or @samp{fangsong ti} in the @var{family} field. In
+such a case, @address@hidden can be specified as below:
+
address@hidden
+Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\
+ chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-*
address@hidden smallexample
+
address@hidden
+Then, the font specifications for all but Chinese GB2312 characters have
address@hidden in the @var{family} field, and the font specification for
+Chinese GB2312 characters has a wild card @samp{*} in the @var{family}
+field.
+
address@hidden set-fontset-font name character fontname &optional frame
+This function modifies the existing fontset @var{name} to
+use the font name @var{fontname} for the character @var{character}.
+
+If @var{name} is @code{nil}, this function modifies the default
+fontset, whose short name is @samp{fontset-default}.
+
address@hidden may be a cons; @code{(@var{from} . @var{to})}, where
address@hidden and @var{to} are non-generic characters. In that case, use
address@hidden for all characters in the range @var{from} and @var{to}
+(inclusive).
+
address@hidden may be a charset. In that case, use
address@hidden for all character in the charsets.
+
address@hidden may be a cons; @code{(@var{family} . @var{registry})},
+where @var{family} is a family name of a font (possibly including a
+foundry name at the head), @var{registry} is a registry name of a font
+(possibly including an encoding name at the tail).
+
+For instance, this changes the default fontset to use a font of which
+registry name is @samp{JISX0208.1983} for all characters belonging to
+the charset @code{japanese-jisx0208}.
+
address@hidden
+(set-fontset-font nil 'japanese-jisx0208 '(nil . "JISX0208.1983"))
address@hidden smallexample
address@hidden defun
+
address@hidden char-displayable-p char
+This function returns @code{t} if Emacs ought to be able to display
address@hidden More precisely, if the selected frame's fontset has a
+font to display the character set that @var{char} belongs to.
+
+Fontsets can specify a font on a per-character basis; when the fontset
+does that, this function's value may not be accurate.
address@hidden defun
+
address@hidden Fringes
address@hidden Fringes
address@hidden fringes
+
+ The @dfn{fringes} of a window are thin vertical strips down the
+sides that are used for displaying bitmaps that indicate truncation,
+continuation, horizontal scrolling, and the overlay arrow.
+
address@hidden
+* Fringe Size/Pos:: Specifying where to put the window fringes.
+* Fringe Indicators:: Displaying indicator icons in the window fringes.
+* Fringe Cursors:: Displaying cursors in the right fringe.
+* Fringe Bitmaps:: Specifying bitmaps for fringe indicators.
+* Customizing Bitmaps:: Specifying your own bitmaps to use in the fringes.
+* Overlay Arrow:: Display of an arrow to indicate position.
address@hidden menu
+
address@hidden Fringe Size/Pos
address@hidden Fringe Size and Position
+
+ The following buffer-local variables control the position and width
+of the window fringes.
+
address@hidden fringes-outside-margins
+The fringes normally appear between the display margins and the window
+text. If the value is address@hidden, they appear outside the display
+margins. @xref{Display Margins}.
address@hidden defvar
+
address@hidden left-fringe-width
+This variable, if address@hidden, specifies the width of the left
+fringe in pixels. A value of @code{nil} means to use the left fringe
+width from the window's frame.
address@hidden defvar
+
address@hidden right-fringe-width
+This variable, if address@hidden, specifies the width of the right
+fringe in pixels. A value of @code{nil} means to use the right fringe
+width from the window's frame.
address@hidden defvar
+
+ The values of these variables take effect when you display the
+buffer in a window. If you change them while the buffer is visible,
+you can call @code{set-window-buffer} to display it once again in the
+same window, to make the changes take effect.
+
address@hidden set-window-fringes window left &optional right outside-margins
+This function sets the fringe widths of window @var{window}.
+If @var{window} is @code{nil}, the selected window is used.
+
+The argument @var{left} specifies the width in pixels of the left
+fringe, and likewise @var{right} for the right fringe. A value of
address@hidden for either one stands for the default width. If
address@hidden is address@hidden, that specifies that fringes
+should appear outside of the display margins.
address@hidden defun
+
address@hidden window-fringes &optional window
+This function returns information about the fringes of a window
address@hidden If @var{window} is omitted or @code{nil}, the selected
+window is used. The value has the form @code{(@var{left-width}
address@hidden @var{outside-margins})}.
address@hidden defun
+
+
address@hidden Fringe Indicators
address@hidden Fringe Indicators
address@hidden fringe indicators
address@hidden indicators, fringe
+
+ The @dfn{fringe indicators} are tiny icons Emacs displays in the
+window fringe (on a graphic display) to indicate truncated or
+continued lines, buffer boundaries, overlay arrow, etc.
+
address@hidden indicate-empty-lines
address@hidden fringes, and empty line indication
+When this is address@hidden, Emacs displays a special glyph in the
+fringe of each empty line at the end of the buffer, on graphical
+displays. @xref{Fringes}. This variable is automatically
+buffer-local in every buffer.
address@hidden defopt
+
address@hidden indicate-buffer-boundaries
+This buffer-local variable controls how the buffer boundaries and
+window scrolling are indicated in the window fringes.
+
+Emacs can indicate the buffer boundaries---that is, the first and last
+line in the buffer---with angle icons when they appear on the screen.
+In addition, Emacs can display an up-arrow in the fringe to show
+that there is text above the screen, and a down-arrow to show
+there is text below the screen.
+
+There are three kinds of basic values:
+
address@hidden @asis
address@hidden @code{nil}
+Don't display any of these fringe icons.
address@hidden @code{left}
+Display the angle icons and arrows in the left fringe.
address@hidden @code{right}
+Display the angle icons and arrows in the right fringe.
address@hidden any non-alist
+Display the angle icons in the left fringe
+and don't display the arrows.
address@hidden table
+
+Otherwise the value should be an alist that specifies which fringe
+indicators to display and where. Each element of the alist should
+have the form @code{(@var{indicator} . @var{position})}. Here,
address@hidden is one of @code{top}, @code{bottom}, @code{up},
address@hidden, and @code{t} (which covers all the icons not yet
+specified), while @var{position} is one of @code{left}, @code{right}
+and @code{nil}.
+
+For example, @code{((top . left) (t . right))} places the top angle
+bitmap in left fringe, and the bottom angle bitmap as well as both
+arrow bitmaps in right fringe. To show the angle bitmaps in the left
+fringe, and no arrow bitmaps, use @code{((top . left) (bottom . left))}.
address@hidden defvar
+
address@hidden default-indicate-buffer-boundaries
+The value of this variable is the default value for
address@hidden in buffers that do not override it.
address@hidden defvar
+
address@hidden fringe-indicator-alist
+This buffer-local variable specifies the mapping from logical fringe
+indicators to the actual bitmaps displayed in the window fringes.
+
+These symbols identify the logical fringe indicators:
+
address@hidden @asis
address@hidden Truncation and continuation line indicators:
address@hidden, @code{continuation}.
+
address@hidden Buffer position indicators:
address@hidden, @code{down},
address@hidden, @code{bottom},
address@hidden
+
address@hidden Empty line indicator:
address@hidden
+
address@hidden Overlay arrow indicator:
address@hidden
+
address@hidden Unknown bitmap indicator:
address@hidden
address@hidden table
+
+ The value is an alist where each element @code{(@var{indicator} .
@var{bitmaps})}
+specifies the fringe bitmaps used to display a specific logical
+fringe indicator.
+
+Here, @var{indicator} specifies the logical indicator type, and
address@hidden is list of symbols @code{(@var{left} @var{right}
address@hidden @var{right1}])} which specifies the actual bitmap shown
+in the left or right fringe for the logical indicator.
+
+The @var{left} and @var{right} symbols specify the bitmaps shown in
+the left and/or right fringe for the specific indicator. The
address@hidden or @var{right1} bitmaps are used only for the `bottom' and
+`top-bottom indicators when the last (only) line in has no final
+newline. Alternatively, @var{bitmaps} may be a single symbol which is
+used in both left and right fringes.
+
+When @code{fringe-indicator-alist} has a buffer-local value, and there
+is no bitmap defined for a logical indicator, or the bitmap is
address@hidden, the corresponding value from the (non-local)
address@hidden is used.
+
+To completely hide a specific indicator, set the bitmap to @code{nil}.
address@hidden defvar
+
address@hidden default-fringe-indicator-alist
+The value of this variable is the default value for
address@hidden in buffers that do not override it.
address@hidden defvar
+
+Standard fringe bitmaps for indicators:
address@hidden
+left-arrow right-arrow up-arrow down-arrow
+left-curly-arrow right-curly-arrow
+left-triangle right-triangle
+top-left-angle top-right-angle
+bottom-left-angle bottom-right-angle
+left-bracket right-bracket
+filled-rectangle hollow-rectangle
+filled-square hollow-square
+vertical-bar horizontal-bar
+empty-line question-mark
address@hidden example
+
address@hidden Fringe Cursors
address@hidden Fringe Cursors
address@hidden fringe cursors
address@hidden cursor, fringe
+
+ When a line is exactly as wide as the window, Emacs displays the
+cursor in the right fringe instead of using two lines. Different
+bitmaps are used to represent the cursor in the fringe depending on
+the current buffer's cursor type.
+
address@hidden @asis
address@hidden Logical cursor types:
address@hidden , @code{hollow}, @code{bar},
address@hidden, @code{hollow-small}.
address@hidden table
+
+The @code{hollow-small} type is used instead of @code{hollow} when the
+normal @code{hollow-rectangle} bitmap is too tall to fit on a specific
+display line.
+
address@hidden overflow-newline-into-fringe
+If this is address@hidden, lines exactly as wide as the window (not
+counting the final newline character) are not continued. Instead,
+when point is at the end of the line, the cursor appears in the right
+fringe.
address@hidden defvar
+
address@hidden fringe-cursor-alist
+This variable specifies the mapping from logical cursor type to the
+actual fringe bitmaps displayed in the right fringe. The value is an
+alist where each element @code{(@var{cursor} . @var{bitmap})} specifies
+the fringe bitmaps used to display a specific logical cursor type in
+the fringe. Here, @var{cursor} specifies the logical cursor type and
address@hidden is a symbol specifying the fringe bitmap to be displayed
+for that logical cursor type.
+
+When @code{fringe-cursor-alist} has a buffer-local value, and there is
+no bitmap defined for a cursor type, the corresponding value from the
+(non-local) @code{default-fringes-indicator-alist} is used.
address@hidden defvar
+
address@hidden default-fringes-cursor-alist
+The value of this variable is the default value for
address@hidden in buffers that do not override it.
address@hidden defvar
+
+Standard bitmaps for displaying the cursor in right fringe:
address@hidden
+filled-rectangle hollow-rectangle filled-square hollow-square
+vertical-bar horizontal-bar
address@hidden example
+
+
address@hidden Fringe Bitmaps
address@hidden Fringe Bitmaps
address@hidden fringe bitmaps
address@hidden bitmaps, fringe
+
+ The @dfn{fringe bitmaps} are the actual bitmaps which represent the
+logical fringe indicators for truncated or continued lines, buffer
+boundaries, overlay arrow, etc. Fringe bitmap symbols have their own
+name space. The fringe bitmaps are shared by all frames and windows.
+You can redefine the built-in fringe bitmaps, and you can define new
+fringe bitmaps.
+
+ The way to display a bitmap in the left or right fringes for a given
+line in a window is by specifying the @code{display} property for one
+of the characters that appears in it. Use a display specification of
+the form @code{(left-fringe @var{bitmap} address@hidden)} or
address@hidden(right-fringe @var{bitmap} address@hidden)} (@pxref{Display
+Property}). Here, @var{bitmap} is a symbol identifying the bitmap you
+want, and @var{face} (which is optional) is the name of the face whose
+colors should be used for displaying the bitmap, instead of the
+default @code{fringe} face. @var{face} is automatically merged with
+the @code{fringe} face, so normally @var{face} need only specify the
+foreground color for the bitmap.
+
address@hidden fringe-bitmaps-at-pos &optional pos window
+This function returns the fringe bitmaps of the display line
+containing position @var{pos} in window @var{window}. The return
+value has the form @code{(@var{left} @var{right} @var{ov})}, where @var{left}
+is the symbol for the fringe bitmap in the left fringe (or @code{nil}
+if no bitmap), @var{right} is similar for the right fringe, and @var{ov}
+is address@hidden if there is an overlay arrow in the left fringe.
+
+The value is @code{nil} if @var{pos} is not visible in @var{window}.
+If @var{window} is @code{nil}, that stands for the selected window.
+If @var{pos} is @code{nil}, that stands for the value of point in
address@hidden
address@hidden defun
+
address@hidden Customizing Bitmaps
address@hidden Customizing Fringe Bitmaps
+
address@hidden define-fringe-bitmap bitmap bits &optional height width align
+This function defines the symbol @var{bitmap} as a new fringe bitmap,
+or replaces an existing bitmap with that name.
+
+The argument @var{bits} specifies the image to use. It should be
+either a string or a vector of integers, where each element (an
+integer) corresponds to one row of the bitmap. Each bit of an integer
+corresponds to one pixel of the bitmap, where the low bit corresponds
+to the rightmost pixel of the bitmap.
+
+The height is normally the length of @var{bits}. However, you
+can specify a different height with address@hidden @var{height}. The width
+is normally 8, but you can specify a different width with address@hidden
address@hidden The width must be an integer between 1 and 16.
+
+The argument @var{align} specifies the positioning of the bitmap
+relative to the range of rows where it is used; the default is to
+center the bitmap. The allowed values are @code{top}, @code{center},
+or @code{bottom}.
+
+The @var{align} argument may also be a list @code{(@var{align}
address@hidden)} where @var{align} is interpreted as described above.
+If @var{periodic} is address@hidden, it specifies that the rows in
address@hidden should be repeated enough times to reach the specified
+height.
address@hidden defun
+
address@hidden destroy-fringe-bitmap bitmap
+This function destroy the fringe bitmap identified by @var{bitmap}.
+If @var{bitmap} identifies a standard fringe bitmap, it actually
+restores the standard definition of that bitmap, instead of
+eliminating it entirely.
address@hidden defun
+
address@hidden set-fringe-bitmap-face bitmap &optional face
+This sets the face for the fringe bitmap @var{bitmap} to @var{face}.
+If @var{face} is @code{nil}, it selects the @code{fringe} face. The
+bitmap's face controls the color to draw it in.
+
address@hidden is merged with the @code{fringe} face, so normally
address@hidden should specify only the foreground color.
address@hidden defun
+
address@hidden Overlay Arrow
address@hidden The Overlay Arrow
address@hidden @cindex overlay arrow Duplicates variable names
+
+ The @dfn{overlay arrow} is useful for directing the user's attention
+to a particular line in a buffer. For example, in the modes used for
+interface to debuggers, the overlay arrow indicates the line of code
+about to be executed. This feature has nothing to do with
address@hidden (@pxref{Overlays}).
+
address@hidden overlay-arrow-string
+This variable holds the string to display to call attention to a
+particular line, or @code{nil} if the arrow feature is not in use.
+On a graphical display the contents of the string are ignored; instead a
+glyph is displayed in the fringe area to the left of the display area.
address@hidden defvar
+
address@hidden overlay-arrow-position
+This variable holds a marker that indicates where to display the overlay
+arrow. It should point at the beginning of a line. On a non-graphical
+display the arrow text
+appears at the beginning of that line, overlaying any text that would
+otherwise appear. Since the arrow is usually short, and the line
+usually begins with indentation, normally nothing significant is
+overwritten.
+
+The overlay-arrow string is displayed in any given buffer if the value
+of @code{overlay-arrow-position} in that buffer points into that
+buffer. Thus, it is possible to display multiple overlay arrow strings
+by creating buffer-local bindings of @code{overlay-arrow-position}.
+However, it is usually cleaner to use
address@hidden to achieve this result.
address@hidden !!! overlay-arrow-position: but the overlay string may remain in
the display
address@hidden of some other buffer until an update is required. This should
be fixed
address@hidden now. Is it?
address@hidden defvar
+
+ You can do a similar job by creating an overlay with a
address@hidden property. @xref{Overlay Properties}.
+
+ You can define multiple overlay arrows via the variable
address@hidden
+
address@hidden overlay-arrow-variable-list
+This variable's value is a list of variables, each of which specifies
+the position of an overlay arrow. The variable
address@hidden has its normal meaning because it is on
+this list.
address@hidden defvar
+
+Each variable on this list can have properties
address@hidden and @code{overlay-arrow-bitmap} that
+specify an overlay arrow string (for text-only terminals) or fringe
+bitmap (for graphical terminals) to display at the corresponding
+overlay arrow position. If either property is not set, the default
address@hidden or @code{overlay-arrow} fringe indicator
+is used.
+
address@hidden Scroll Bars
address@hidden Scroll Bars
address@hidden scroll bars
+
+Normally the frame parameter @code{vertical-scroll-bars} controls
+whether the windows in the frame have vertical scroll bars, and
+whether they are on the left or right. The frame parameter
address@hidden specifies how wide they are (@code{nil}
+meaning the default). @xref{Layout Parameters}.
+
address@hidden frame-current-scroll-bars &optional frame
+This function reports the scroll bar type settings for frame
address@hidden The value is a cons cell
address@hidden(@var{vertical-type} .@: @var{horizontal-type})}, where
address@hidden is either @code{left}, @code{right}, or @code{nil}
+(which means no scroll bar.) @var{horizontal-type} is meant to
+specify the horizontal scroll bar type, but since they are not
+implemented, it is always @code{nil}.
address@hidden defun
+
address@hidden vertical-scroll-bar
+ You can enable or disable scroll bars for a particular buffer,
+by setting the variable @code{vertical-scroll-bar}. This variable
+automatically becomes buffer-local when set. The possible values are
address@hidden, @code{right}, @code{t}, which means to use the
+frame's default, and @code{nil} for no scroll bar.
+
+ You can also control this for individual windows. Call the function
address@hidden to specify what to do for a specific window:
+
address@hidden set-window-scroll-bars window width &optional vertical-type
horizontal-type
+This function sets the width and type of scroll bars for window
address@hidden
+
address@hidden specifies the scroll bar width in pixels (@code{nil} means
+use the width specified for the frame). @var{vertical-type} specifies
+whether to have a vertical scroll bar and, if so, where. The possible
+values are @code{left}, @code{right} and @code{nil}, just like the
+values of the @code{vertical-scroll-bars} frame parameter.
+
+The argument @var{horizontal-type} is meant to specify whether and
+where to have horizontal scroll bars, but since they are not
+implemented, it has no effect. If @var{window} is @code{nil}, the
+selected window is used.
address@hidden defun
+
address@hidden window-scroll-bars &optional window
+Report the width and type of scroll bars specified for @var{window}.
+If @var{window} is omitted or @code{nil}, the selected window is used.
+The value is a list of the form @code{(@var{width}
address@hidden @var{vertical-type} @var{horizontal-type})}. The value
address@hidden is the value that was specified for the width (which may
+be @code{nil}); @var{cols} is the number of columns that the scroll
+bar actually occupies.
+
address@hidden is not actually meaningful.
address@hidden defun
+
+If you don't specify these values for a window with
address@hidden, the buffer-local variables
address@hidden and @code{scroll-bar-width} in the buffer being
+displayed control the window's vertical scroll bars. The function
address@hidden examines these variables. If you change them
+in a buffer that is already visible in a window, you can make the
+window take note of the new values by calling @code{set-window-buffer}
+specifying the same buffer that is already displayed.
+
address@hidden scroll-bar-mode
+This variable, always local in all buffers, controls whether and where
+to put scroll bars in windows displaying the buffer. The possible values
+are @code{nil} for no scroll bar, @code{left} to put a scroll bar on
+the left, and @code{right} to put a scroll bar on the right.
address@hidden defvar
+
address@hidden window-current-scroll-bars &optional window
+This function reports the scroll bar type for window @var{window}.
+If @var{window} is omitted or @code{nil}, the selected window is used.
+The value is a cons cell
address@hidden(@var{vertical-type} .@: @var{horizontal-type})}. Unlike
address@hidden, this reports the scroll bar type actually
+used, once frame defaults and @code{scroll-bar-mode} are taken into
+account.
address@hidden defun
+
address@hidden scroll-bar-width
+This variable, always local in all buffers, specifies the width of the
+buffer's scroll bars, measured in pixels. A value of @code{nil} means
+to use the value specified by the frame.
address@hidden defvar
+
address@hidden Display Property
address@hidden The @code{display} Property
address@hidden display specification
address@hidden display @r{(text property)}
+
+ The @code{display} text property (or overlay property) is used to
+insert images into text, and also control other aspects of how text
+displays. The value of the @code{display} property should be a
+display specification, or a list or vector containing several display
+specifications.
+
+ Some kinds of @code{display} properties specify something to display
+instead of the text that has the property. In this case, ``the text''
+means all the consecutive characters that have the same Lisp object as
+their @code{display} property; these characters are replaced as a
+single unit. By contrast, characters that have similar but distinct
+Lisp objects as their @code{display} properties are handled
+separately. Here's a function that illustrates this point:
+
address@hidden
+(defun foo ()
+ (goto-char (point-min))
+ (dotimes (i 5)
+ (let ((string (concat "A")))
+ (put-text-property (point) (1+ (point)) 'display string)
+ (forward-char 1)
+ (put-text-property (point) (1+ (point)) 'display string)
+ (forward-char 1))))
address@hidden smallexample
+
address@hidden
+It gives each of the first ten characters in the buffer string
address@hidden"A"} as the @code{display} property, but they don't all get the
+same string. The first two characters get the same string, so they
+together are replaced with one @samp{A}. The next two characters get
+a second string, so they together are replaced with one @samp{A}.
+Likewise for each following pair of characters. Thus, the ten
+characters appear as five A's. This function would have the same
+results:
+
address@hidden
+(defun foo ()
+ (goto-char (point-min))
+ (dotimes (i 5)
+ (let ((string (concat "A")))
+ (put-text-property (point) (2+ (point)) 'display string)
+ (put-text-property (point) (1+ (point)) 'display string)
+ (forward-char 2))))
address@hidden smallexample
+
address@hidden
+This illustrates that what matters is the property value for
+each character. If two consecutive characters have the same
+object as the @code{display} property value, it's irrelevant
+whether they got this property from a single call to
address@hidden or from two different calls.
+
+ The rest of this section describes several kinds of
+display specifications and what they mean.
+
address@hidden
+* Specified Space:: Displaying one space with a specified width.
+* Pixel Specification:: Specifying space width or height in pixels.
+* Other Display Specs:: Displaying an image; magnifying text; moving it
+ up or down on the page; adjusting the width
+ of spaces within text.
+* Display Margins:: Displaying text or images to the side of the main text.
address@hidden menu
+
address@hidden Specified Space
address@hidden Specified Spaces
address@hidden spaces, specified height or width
address@hidden variable-width spaces
+
+ To display a space of specified width and/or height, use a display
+specification of the form @code{(space . @var{props})}, where
address@hidden is a property list (a list of alternating properties and
+values). You can put this property on one or more consecutive
+characters; a space of the specified height and width is displayed in
+place of @emph{all} of those characters. These are the properties you
+can use in @var{props} to specify the weight of the space:
+
address@hidden @code
address@hidden :width @var{width}
+If @var{width} is an integer or floating point number, it specifies
+that the space width should be @var{width} times the normal character
+width. @var{width} can also be a @dfn{pixel width} specification
+(@pxref{Pixel Specification}).
+
address@hidden :relative-width @var{factor}
+Specifies that the width of the stretch should be computed from the
+first character in the group of consecutive characters that have the
+same @code{display} property. The space width is the width of that
+character, multiplied by @var{factor}.
+
address@hidden :align-to @var{hpos}
+Specifies that the space should be wide enough to reach @var{hpos}.
+If @var{hpos} is a number, it is measured in units of the normal
+character width. @var{hpos} can also be a @dfn{pixel width}
+specification (@pxref{Pixel Specification}).
address@hidden table
+
+ You should use one and only one of the above properties. You can
+also specify the height of the space, with these properties:
+
address@hidden @code
address@hidden :height @var{height}
+Specifies the height of the space.
+If @var{height} is an integer or floating point number, it specifies
+that the space height should be @var{height} times the normal character
+height. The @var{height} may also be a @dfn{pixel height} specification
+(@pxref{Pixel Specification}).
+
address@hidden :relative-height @var{factor}
+Specifies the height of the space, multiplying the ordinary height
+of the text having this display specification by @var{factor}.
+
address@hidden :ascent @var{ascent}
+If the value of @var{ascent} is a non-negative number no greater than
+100, it specifies that @var{ascent} percent of the height of the space
+should be considered as the ascent of the space---that is, the part
+above the baseline. The ascent may also be specified in pixel units
+with a @dfn{pixel ascent} specification (@pxref{Pixel Specification}).
+
address@hidden table
+
+ Don't use both @code{:height} and @code{:relative-height} together.
+
+ The @code{:width} and @code{:align-to} properties are supported on
+non-graphic terminals, but the other space properties in this section
+are not.
+
address@hidden Pixel Specification
address@hidden Pixel Specification for Spaces
address@hidden spaces, pixel specification
+
+ The value of the @code{:width}, @code{:align-to}, @code{:height},
+and @code{:ascent} properties can be a special kind of expression that
+is evaluated during redisplay. The result of the evaluation is used
+as an absolute number of pixels.
+
+ The following expressions are supported:
+
address@hidden
address@hidden
+ @var{expr} ::= @var{num} | (@var{num}) | @var{unit} | @var{elem} | @var{pos}
| @var{image} | @var{form}
+ @var{num} ::= @var{integer} | @var{float} | @var{symbol}
+ @var{unit} ::= in | mm | cm | width | height
address@hidden group
address@hidden
+ @var{elem} ::= left-fringe | right-fringe | left-margin | right-margin
+ | scroll-bar | text
+ @var{pos} ::= left | center | right
+ @var{form} ::= (@var{num} . @var{expr}) | (@var{op} @var{expr} ...)
+ @var{op} ::= + | -
address@hidden group
address@hidden smallexample
+
+ The form @var{num} specifies a fraction of the default frame font
+height or width. The form @code{(@var{num})} specifies an absolute
+number of pixels. If @var{num} is a symbol, @var{symbol}, its
+buffer-local variable binding is used.
+
+ The @code{in}, @code{mm}, and @code{cm} units specify the number of
+pixels per inch, millimeter, and centimeter, respectively. The
address@hidden and @code{height} units correspond to the default width
+and height of the current face. An image specification @code{image}
+corresponds to the width or height of the image.
+
+ The @code{left-fringe}, @code{right-fringe}, @code{left-margin},
address@hidden, @code{scroll-bar}, and @code{text} elements
+specify to the width of the corresponding area of the window.
+
+ The @code{left}, @code{center}, and @code{right} positions can be
+used with @code{:align-to} to specify a position relative to the left
+edge, center, or right edge of the text area.
+
+ Any of the above window elements (except @code{text}) can also be
+used with @code{:align-to} to specify that the position is relative to
+the left edge of the given area. Once the base offset for a relative
+position has been set (by the first occurrence of one of these
+symbols), further occurrences of these symbols are interpreted as the
+width of the specified area. For example, to align to the center of
+the left-margin, use
+
address@hidden
+:align-to (+ left-margin (0.5 . left-margin))
address@hidden example
+
+ If no specific base offset is set for alignment, it is always relative
+to the left edge of the text area. For example, @samp{:align-to 0} in a
+header-line aligns with the first text column in the text area.
+
+ A value of the form @code{(@var{num} . @var{expr})} stands for the
+product of the values of @var{num} and @var{expr}. For example,
address@hidden(2 . in)} specifies a width of 2 inches, while @code{(0.5 .
address@hidden)} specifies half the width (or height) of the specified
+image.
+
+ The form @code{(+ @var{expr} ...)} adds up the value of the
+expressions. The form @code{(- @var{expr} ...)} negates or subtracts
+the value of the expressions.
+
address@hidden Other Display Specs
address@hidden Other Display Specifications
+
+ Here are the other sorts of display specifications that you can use
+in the @code{display} text property.
+
address@hidden @code
address@hidden @var{string}
+Display @var{string} instead of the text that has this property.
+
+Recursive display specifications are not address@hidden's
address@hidden properties, if any, are not used.
+
address@hidden (image . @var{image-props})
+This kind of display specification is an image descriptor (@pxref{Images}).
+When used as a display specification, it means to display the image
+instead of the text that has the display specification.
+
address@hidden (slice @var{x} @var{y} @var{width} @var{height})
+This specification together with @code{image} specifies a @dfn{slice}
+(a partial area) of the image to display. The elements @var{y} and
address@hidden specify the top left corner of the slice, within the image;
address@hidden and @var{height} specify the width and height of the
+slice. Integer values are numbers of pixels. A floating point number
+in the range 0.0--1.0 stands for that fraction of the width or height
+of the entire image.
+
address@hidden ((margin nil) @var{string})
+A display specification of this form means to display @var{string}
+instead of the text that has the display specification, at the same
+position as that text. It is equivalent to using just @var{string},
+but it is done as a special case of marginal display (@pxref{Display
+Margins}).
+
address@hidden (space-width @var{factor})
+This display specification affects all the space characters within the
+text that has the specification. It displays all of these spaces
address@hidden times as wide as normal. The element @var{factor} should
+be an integer or float. Characters other than spaces are not affected
+at all; in particular, this has no effect on tab characters.
+
address@hidden (height @var{height})
+This display specification makes the text taller or shorter.
+Here are the possibilities for @var{height}:
+
address@hidden @asis
address@hidden @code{(+ @var{n})}
+This means to use a font that is @var{n} steps larger. A ``step'' is
+defined by the set of available fonts---specifically, those that match
+what was otherwise specified for this text, in all attributes except
+height. Each size for which a suitable font is available counts as
+another step. @var{n} should be an integer.
+
address@hidden @code{(- @var{n})}
+This means to use a font that is @var{n} steps smaller.
+
address@hidden a number, @var{factor}
+A number, @var{factor}, means to use a font that is @var{factor} times
+as tall as the default font.
+
address@hidden a symbol, @var{function}
+A symbol is a function to compute the height. It is called with the
+current height as argument, and should return the new height to use.
+
address@hidden anything else, @var{form}
+If the @var{height} value doesn't fit the previous possibilities, it is
+a form. Emacs evaluates it to get the new height, with the symbol
address@hidden bound to the current specified font height.
address@hidden table
+
address@hidden (raise @var{factor})
+This kind of display specification raises or lowers the text
+it applies to, relative to the baseline of the line.
+
address@hidden must be a number, which is interpreted as a multiple of the
+height of the affected text. If it is positive, that means to display
+the characters raised. If it is negative, that means to display them
+lower down.
+
+If the text also has a @code{height} display specification, that does
+not affect the amount of raising or lowering, which is based on the
+faces used for the text.
address@hidden table
+
address@hidden We put all the address@hidden(when ...)}' on one line to
encourage
address@hidden makeinfo's end-of-sentence heuristics to DTRT. Previously, the
dot
address@hidden was at eol; the info file ended up w/ two spaces rendered after
it.
+ You can make any display specification conditional. To do that,
+package it in another list of the form
address@hidden(when @var{condition} . @var{spec})}.
+Then the specification @var{spec} applies only when
address@hidden evaluates to a address@hidden value. During the
+evaluation, @code{object} is bound to the string or buffer having the
+conditional @code{display} property. @code{position} and
address@hidden are bound to the position within @code{object}
+and the buffer position where the @code{display} property was found,
+respectively. Both positions can be different when @code{object} is a
+string.
+
address@hidden Display Margins
address@hidden Displaying in the Margins
address@hidden display margins
address@hidden margins, display
+
+ A buffer can have blank areas called @dfn{display margins} on the left
+and on the right. Ordinary text never appears in these areas, but you
+can put things into the display margins using the @code{display}
+property.
+
+ To put text in the left or right display margin of the window, use a
+display specification of the form @code{(margin right-margin)} or
address@hidden(margin left-margin)} on it. To put an image in a display margin,
+use that display specification along with the display specification for
+the image. Unfortunately, there is currently no way to make
+text or images in the margin mouse-sensitive.
+
+ If you put such a display specification directly on text in the
+buffer, the specified margin display appears @emph{instead of} that
+buffer text itself. To put something in the margin @emph{in
+association with} certain buffer text without preventing or altering
+the display of that text, put a @code{before-string} property on the
+text and put the display specification on the contents of the
+before-string.
+
+ Before the display margins can display anything, you must give
+them a nonzero width. The usual way to do that is to set these
+variables:
+
address@hidden left-margin-width
+This variable specifies the width of the left margin.
+It is buffer-local in all buffers.
address@hidden defvar
+
address@hidden right-margin-width
+This variable specifies the width of the right margin.
+It is buffer-local in all buffers.
address@hidden defvar
+
+ Setting these variables does not immediately affect the window. These
+variables are checked when a new buffer is displayed in the window.
+Thus, you can make changes take effect by calling
address@hidden
+
+ You can also set the margin widths immediately.
+
address@hidden set-window-margins window left &optional right
+This function specifies the margin widths for window @var{window}.
+The argument @var{left} controls the left margin and
address@hidden controls the right margin (default @code{0}).
address@hidden defun
+
address@hidden window-margins &optional window
+This function returns the left and right margins of @var{window}
+as a cons cell of the form @code{(@var{left} . @var{right})}.
+If @var{window} is @code{nil}, the selected window is used.
address@hidden defun
+
address@hidden Images
address@hidden Images
address@hidden images in buffers
+
+ To display an image in an Emacs buffer, you must first create an image
+descriptor, then use it as a display specifier in the @code{display}
+property of text that is displayed (@pxref{Display Property}).
+
+ Emacs is usually able to display images when it is run on a
+graphical terminal. Images cannot be displayed in a text terminal, on
+certain graphical terminals that lack the support for this, or if
+Emacs is compiled without image support. You can use the function
address@hidden to determine if images can in principle be
+displayed (@pxref{Display Feature Testing}).
+
address@hidden
+* Image Formats:: Supported image formats.
+* Image Descriptors:: How to specify an image for use in @code{:display}.
+* XBM Images:: Special features for XBM format.
+* XPM Images:: Special features for XPM format.
+* GIF Images:: Special features for GIF format.
+* PostScript Images:: Special features for PostScript format.
+* Other Image Types:: Various other formats are supported.
+* Defining Images:: Convenient ways to define an image for later use.
+* Showing Images:: Convenient ways to display an image once it is defined.
+* Image Cache:: Internal mechanisms of image display.
address@hidden menu
+
address@hidden Image Formats
address@hidden Image Formats
address@hidden image formats
address@hidden image types
+
+ Emacs can display a number of different image formats; some of them
+are supported only if particular support libraries are installed on
+your machine. In some environments, Emacs can load image
+libraries on demand; if so, the variable @code{image-library-alist}
+can be used to modify the set of known names for these dynamic
+libraries (though it is not possible to add new image formats).
+
+ The supported image formats include XBM, XPM (this requires the
+libraries @code{libXpm} version 3.4k and @code{libz}), GIF (requiring
address@hidden 4.1.0), PostScript, PBM, JPEG (requiring the
address@hidden library version v6a), TIFF (requiring @code{libtiff}
+v3.4), PNG (requiring @code{libpng} 1.0.2), and SVG (requiring
address@hidden 2.0.0).
+
+ You specify one of these formats with an image type symbol. The image
+type symbols are @code{xbm}, @code{xpm}, @code{gif}, @code{postscript},
address@hidden, @code{jpeg}, @code{tiff}, @code{png}, and @code{svg}.
+
address@hidden image-types
+This variable contains a list of those image type symbols that are
+potentially supported in the current configuration.
address@hidden here means that Emacs knows about the image types,
+not necessarily that they can be loaded (they could depend on
+unavailable dynamic libraries, for example).
+
+To know which image types are really available, use
address@hidden
address@hidden defvar
+
address@hidden image-library-alist
+This in an alist of image types vs external libraries needed to
+display them.
+
+Each element is a list @code{(@var{image-type} @var{library}...)},
+where the car is a supported image format from @code{image-types}, and
+the rest are strings giving alternate filenames for the corresponding
+external libraries to load.
+
+Emacs tries to load the libraries in the order they appear on the
+list; if none is loaded, the running session of Emacs won't support
+the image type. @code{pbm} and @code{xbm} don't need to be listed;
+they're always supported.
+
+This variable is ignored if the image libraries are statically linked
+into Emacs.
address@hidden defvar
+
address@hidden image-type-available-p type
+This function returns address@hidden if image type @var{type} is
+available, i.e., if images of this type can be loaded and displayed in
+Emacs. @var{type} should be one of the types contained in
address@hidden
+
+For image types whose support libraries are statically linked, this
+function always returns @code{t}; for other image types, it returns
address@hidden if the dynamic library could be loaded, @code{nil} otherwise.
address@hidden defun
+
address@hidden Image Descriptors
address@hidden Image Descriptors
address@hidden image descriptor
+
+ An image description is a list of the form @code{(image . @var{props})},
+where @var{props} is a property list containing alternating keyword
+symbols (symbols whose names start with a colon) and their values.
+You can use any Lisp object as a property, but the only properties
+that have any special meaning are certain symbols, all of them keywords.
+
+ Every image descriptor must contain the property @code{:type
address@hidden to specify the format of the image. The value of @var{type}
+should be an image type symbol; for example, @code{xpm} for an image in
+XPM format.
+
+ Here is a list of other properties that are meaningful for all image
+types:
+
address@hidden @code
address@hidden :file @var{file}
+The @code{:file} property says to load the image from file
address@hidden If @var{file} is not an absolute file name, it is expanded
+in @code{data-directory}.
+
address@hidden :data @var{data}
+The @code{:data} property says the actual contents of the image.
+Each image must use either @code{:data} or @code{:file}, but not both.
+For most image types, the value of the @code{:data} property should be a
+string containing the image data; we recommend using a unibyte string.
+
+Before using @code{:data}, look for further information in the section
+below describing the specific image format. For some image types,
address@hidden:data} may not be supported; for some, it allows other data types;
+for some, @code{:data} alone is not enough, so you need to use other
+image properties along with @code{:data}.
+
address@hidden :margin @var{margin}
+The @code{:margin} property specifies how many pixels to add as an
+extra margin around the image. The value, @var{margin}, must be a
+non-negative number, or a pair @code{(@var{x} . @var{y})} of such
+numbers. If it is a pair, @var{x} specifies how many pixels to add
+horizontally, and @var{y} specifies how many pixels to add vertically.
+If @code{:margin} is not specified, the default is zero.
+
address@hidden :ascent @var{ascent}
+The @code{:ascent} property specifies the amount of the image's
+height to use for its ascent---that is, the part above the baseline.
+The value, @var{ascent}, must be a number in the range 0 to 100, or
+the symbol @code{center}.
+
+If @var{ascent} is a number, that percentage of the image's height is
+used for its ascent.
+
+If @var{ascent} is @code{center}, the image is vertically centered
+around a centerline which would be the vertical centerline of text drawn
+at the position of the image, in the manner specified by the text
+properties and overlays that apply to the image.
+
+If this property is omitted, it defaults to 50.
+
address@hidden :relief @var{relief}
+The @code{:relief} property, if address@hidden, adds a shadow rectangle
+around the image. The value, @var{relief}, specifies the width of the
+shadow lines, in pixels. If @var{relief} is negative, shadows are drawn
+so that the image appears as a pressed button; otherwise, it appears as
+an unpressed button.
+
address@hidden :conversion @var{algorithm}
+The @code{:conversion} property, if address@hidden, specifies a
+conversion algorithm that should be applied to the image before it is
+displayed; the value, @var{algorithm}, specifies which algorithm.
+
address@hidden @code
address@hidden laplace
address@hidden emboss
+Specifies the Laplace edge detection algorithm, which blurs out small
+differences in color while highlighting larger differences. People
+sometimes consider this useful for displaying the image for a
+``disabled'' button.
+
address@hidden (edge-detection :matrix @var{matrix} :color-adjust @var{adjust})
+Specifies a general edge-detection algorithm. @var{matrix} must be
+either a nine-element list or a nine-element vector of numbers. A pixel
+at position @math{x/y} in the transformed image is computed from
+original pixels around that position. @var{matrix} specifies, for each
+pixel in the neighborhood of @math{x/y}, a factor with which that pixel
+will influence the transformed pixel; element @math{0} specifies the
+factor for the pixel at @math{x-1/y-1}, element @math{1} the factor for
+the pixel at @math{x/y-1} etc., as shown below:
address@hidden
address@hidden
+$$\pmatrix{x-1/y-1 & x/y-1 & x+1/y-1 \cr
+ x-1/y & x/y & x+1/y \cr
+ x-1/y+1& x/y+1 & x+1/y+1 \cr}$$
address@hidden tex
address@hidden iftex
address@hidden
address@hidden
+ (x-1/y-1 x/y-1 x+1/y-1
+ x-1/y x/y x+1/y
+ x-1/y+1 x/y+1 x+1/y+1)
address@hidden display
address@hidden ifnottex
+
+The resulting pixel is computed from the color intensity of the color
+resulting from summing up the RGB values of surrounding pixels,
+multiplied by the specified factors, and dividing that sum by the sum
+of the factors' absolute values.
+
+Laplace edge-detection currently uses a matrix of
address@hidden
address@hidden
+$$\pmatrix{1 & 0 & 0 \cr
+ 0& 0 & 0 \cr
+ 9 & 9 & -1 \cr}$$
address@hidden tex
address@hidden iftex
address@hidden
address@hidden
+ (1 0 0
+ 0 0 0
+ 9 9 -1)
address@hidden display
address@hidden ifnottex
+
+Emboss edge-detection uses a matrix of
address@hidden
address@hidden
+$$\pmatrix{ 2 & -1 & 0 \cr
+ -1 & 0 & 1 \cr
+ 0 & 1 & -2 \cr}$$
address@hidden tex
address@hidden iftex
address@hidden
address@hidden
+ ( 2 -1 0
+ -1 0 1
+ 0 1 -2)
address@hidden display
address@hidden ifnottex
+
address@hidden disabled
+Specifies transforming the image so that it looks ``disabled.''
address@hidden table
+
address@hidden :mask @var{mask}
+If @var{mask} is @code{heuristic} or @code{(heuristic @var{bg})}, build
+a clipping mask for the image, so that the background of a frame is
+visible behind the image. If @var{bg} is not specified, or if @var{bg}
+is @code{t}, determine the background color of the image by looking at
+the four corners of the image, assuming the most frequently occurring
+color from the corners is the background color of the image. Otherwise,
address@hidden must be a list @code{(@var{red} @var{green} @var{blue})}
+specifying the color to assume for the background of the image.
+
+If @var{mask} is @code{nil}, remove a mask from the image, if it has
+one. Images in some formats include a mask which can be removed by
+specifying @code{:mask nil}.
+
address@hidden :pointer @var{shape}
+This specifies the pointer shape when the mouse pointer is over this
+image. @xref{Pointer Shape}, for available pointer shapes.
+
address@hidden :map @var{map}
+This associates an image map of @dfn{hot spots} with this image.
+
+An image map is an alist where each element has the format
address@hidden(@var{area} @var{id} @var{plist})}. An @var{area} is specified
+as either a rectangle, a circle, or a polygon.
+
+A rectangle is a cons
address@hidden(rect . ((@var{x0} . @var{y0}) . (@var{x1} . @var{y1})))}
+which specifies the pixel coordinates of the upper left and bottom right
+corners of the rectangle area.
+
+A circle is a cons
address@hidden(circle . ((@var{x0} . @var{y0}) . @var{r}))}
+which specifies the center and the radius of the circle; @var{r} may
+be a float or integer.
+
+A polygon is a cons
address@hidden(poly . address@hidden @var{y0} @var{x1} @var{y1} ...])}
+where each pair in the vector describes one corner in the polygon.
+
+When the mouse pointer lies on a hot-spot area of an image, the
address@hidden of that hot-spot is consulted; if it contains a @code{help-echo}
+property, that defines a tool-tip for the hot-spot, and if it contains
+a @code{pointer} property, that defines the shape of the mouse cursor when
+it is on the hot-spot.
address@hidden Shape}, for available pointer shapes.
+
+When you click the mouse when the mouse pointer is over a hot-spot, an
+event is composed by combining the @var{id} of the hot-spot with the
+mouse event; for instance, @code{[area4 mouse-1]} if the hot-spot's
address@hidden is @code{area4}.
address@hidden table
+
address@hidden image-mask-p spec &optional frame
+This function returns @code{t} if image @var{spec} has a mask bitmap.
address@hidden is the frame on which the image will be displayed.
address@hidden @code{nil} or omitted means to use the selected frame
+(@pxref{Input Focus}).
address@hidden defun
+
address@hidden XBM Images
address@hidden XBM Images
address@hidden XBM
+
+ To use XBM format, specify @code{xbm} as the image type. This image
+format doesn't require an external library, so images of this type are
+always supported.
+
+ Additional image properties supported for the @code{xbm} image type are:
+
address@hidden @code
address@hidden :foreground @var{foreground}
+The value, @var{foreground}, should be a string specifying the image
+foreground color, or @code{nil} for the default color. This color is
+used for each pixel in the XBM that is 1. The default is the frame's
+foreground color.
+
address@hidden :background @var{background}
+The value, @var{background}, should be a string specifying the image
+background color, or @code{nil} for the default color. This color is
+used for each pixel in the XBM that is 0. The default is the frame's
+background color.
address@hidden table
+
+ If you specify an XBM image using data within Emacs instead of an
+external file, use the following three properties:
+
address@hidden @code
address@hidden :data @var{data}
+The value, @var{data}, specifies the contents of the image.
+There are three formats you can use for @var{data}:
+
address@hidden @bullet
address@hidden
+A vector of strings or bool-vectors, each specifying one line of the
+image. Do specify @code{:height} and @code{:width}.
+
address@hidden
+A string containing the same byte sequence as an XBM file would contain.
+You must not specify @code{:height} and @code{:width} in this case,
+because omitting them is what indicates the data has the format of an
+XBM file. The file contents specify the height and width of the image.
+
address@hidden
+A string or a bool-vector containing the bits of the image (plus perhaps
+some extra bits at the end that will not be used). It should contain at
+least @var{width} * @code{height} bits. In this case, you must specify
address@hidden:height} and @code{:width}, both to indicate that the string
+contains just the bits rather than a whole XBM file, and to specify the
+size of the image.
address@hidden itemize
+
address@hidden :width @var{width}
+The value, @var{width}, specifies the width of the image, in pixels.
+
address@hidden :height @var{height}
+The value, @var{height}, specifies the height of the image, in pixels.
address@hidden table
+
address@hidden XPM Images
address@hidden XPM Images
address@hidden XPM
+
+ To use XPM format, specify @code{xpm} as the image type. The
+additional image property @code{:color-symbols} is also meaningful with
+the @code{xpm} image type:
+
address@hidden @code
address@hidden :color-symbols @var{symbols}
+The value, @var{symbols}, should be an alist whose elements have the
+form @code{(@var{name} . @var{color})}. In each element, @var{name} is
+the name of a color as it appears in the image file, and @var{color}
+specifies the actual color to use for displaying that name.
address@hidden table
+
address@hidden GIF Images
address@hidden GIF Images
address@hidden GIF
+
+ For GIF images, specify image type @code{gif}.
+
address@hidden @code
address@hidden :index @var{index}
+You can use @code{:index} to specify one image from a GIF file that
+contains more than one image. This property specifies use of image
+number @var{index} from the file. If the GIF file doesn't contain an
+image with index @var{index}, the image displays as a hollow box.
address@hidden table
+
address@hidden
+This could be used to implement limited support for animated GIFs.
+For example, the following function displays a multi-image GIF file
+at point-min in the current buffer, switching between sub-images
+every 0.1 seconds.
+
+(defun show-anim (file max)
+ "Display multi-image GIF file FILE which contains MAX subimages."
+ (display-anim (current-buffer) file 0 max t))
+
+(defun display-anim (buffer file idx max first-time)
+ (when (= idx max)
+ (setq idx 0))
+ (let ((img (create-image file nil :image idx)))
+ (save-excursion
+ (set-buffer buffer)
+ (goto-char (point-min))
+ (unless first-time (delete-char 1))
+ (insert-image img))
+ (run-with-timer 0.1 nil 'display-anim buffer file (1+ idx) max nil)))
address@hidden ignore
+
address@hidden PostScript Images
address@hidden PostScript Images
address@hidden postscript images
+
+ To use PostScript for an image, specify image type @code{postscript}.
+This works only if you have Ghostscript installed. You must always use
+these three properties:
+
address@hidden @code
address@hidden :pt-width @var{width}
+The value, @var{width}, specifies the width of the image measured in
+points (1/72 inch). @var{width} must be an integer.
+
address@hidden :pt-height @var{height}
+The value, @var{height}, specifies the height of the image in points
+(1/72 inch). @var{height} must be an integer.
+
address@hidden :bounding-box @var{box}
+The value, @var{box}, must be a list or vector of four integers, which
+specifying the bounding box of the PostScript image, analogous to the
address@hidden comment found in PostScript files.
+
address@hidden
+%%BoundingBox: 22 171 567 738
address@hidden example
address@hidden table
+
+ Displaying PostScript images from Lisp data is not currently
+implemented, but it may be implemented by the time you read this.
+See the @file{etc/NEWS} file to make sure.
+
address@hidden Other Image Types
address@hidden Other Image Types
address@hidden PBM
+
+ For PBM images, specify image type @code{pbm}. Color, gray-scale and
+monochromatic images are supported. For mono PBM images, two additional
+image properties are supported.
+
address@hidden @code
address@hidden :foreground @var{foreground}
+The value, @var{foreground}, should be a string specifying the image
+foreground color, or @code{nil} for the default color. This color is
+used for each pixel in the XBM that is 1. The default is the frame's
+foreground color.
+
address@hidden :background @var{background}
+The value, @var{background}, should be a string specifying the image
+background color, or @code{nil} for the default color. This color is
+used for each pixel in the XBM that is 0. The default is the frame's
+background color.
address@hidden table
+
+ For JPEG images, specify image type @code{jpeg}.
+
+ For TIFF images, specify image type @code{tiff}.
+
+ For PNG images, specify image type @code{png}.
+
+ For SVG images, specify image type @code{svg}.
+
address@hidden Defining Images
address@hidden Defining Images
+
+ The functions @code{create-image}, @code{defimage} and
address@hidden provide convenient ways to create image descriptors.
+
address@hidden create-image file-or-data &optional type data-p &rest props
+This function creates and returns an image descriptor which uses the
+data in @var{file-or-data}. @var{file-or-data} can be a file name or
+a string containing the image data; @var{data-p} should be @code{nil}
+for the former case, address@hidden for the latter case.
+
+The optional argument @var{type} is a symbol specifying the image type.
+If @var{type} is omitted or @code{nil}, @code{create-image} tries to
+determine the image type from the file's first few bytes, or else
+from the file's name.
+
+The remaining arguments, @var{props}, specify additional image
+properties---for example,
+
address@hidden
+(create-image "foo.xpm" 'xpm nil :heuristic-mask t)
address@hidden example
+
+The function returns @code{nil} if images of this type are not
+supported. Otherwise it returns an image descriptor.
address@hidden defun
+
address@hidden defimage symbol specs &optional doc
+This macro defines @var{symbol} as an image name. The arguments
address@hidden is a list which specifies how to display the image.
+The third argument, @var{doc}, is an optional documentation string.
+
+Each argument in @var{specs} has the form of a property list, and each
+one should specify at least the @code{:type} property and either the
address@hidden:file} or the @code{:data} property. The value of @code{:type}
+should be a symbol specifying the image type, the value of
address@hidden:file} is the file to load the image from, and the value of
address@hidden:data} is a string containing the actual image data. Here is an
+example:
+
address@hidden
+(defimage test-image
+ ((:type xpm :file "~/test1.xpm")
+ (:type xbm :file "~/test1.xbm")))
address@hidden example
+
address@hidden tests each argument, one by one, to see if it is
+usable---that is, if the type is supported and the file exists. The
+first usable argument is used to make an image descriptor which is
+stored in @var{symbol}.
+
+If none of the alternatives will work, then @var{symbol} is defined
+as @code{nil}.
address@hidden defmac
+
address@hidden find-image specs
+This function provides a convenient way to find an image satisfying one
+of a list of image specifications @var{specs}.
+
+Each specification in @var{specs} is a property list with contents
+depending on image type. All specifications must at least contain the
+properties @code{:type @var{type}} and either @address@hidden:file @var{file}}}
+or @address@hidden:data @var{DATA}}}, where @var{type} is a symbol specifying
+the image type, e.g.@: @code{xbm}, @var{file} is the file to load the
+image from, and @var{data} is a string containing the actual image data.
+The first specification in the list whose @var{type} is supported, and
address@hidden exists, is used to construct the image specification to be
+returned. If no specification is satisfied, @code{nil} is returned.
+
+The image is looked for in @code{image-load-path}.
address@hidden defun
+
address@hidden image-load-path
+This variable's value is a list of locations in which to search for
+image files. If an element is a string or a variable symbol whose
+value is a string, the string is taken to be the name of a directory
+to search. If an element is a variable symbol whose value is a list,
+that is taken to be a list of directory names to search.
+
+The default is to search in the @file{images} subdirectory of the
+directory specified by @code{data-directory}, then the directory
+specified by @code{data-directory}, and finally in the directories in
address@hidden Subdirectories are not automatically included in
+the search, so if you put an image file in a subdirectory, you have to
+supply the subdirectory name explicitly. For example, to find the
+image @file{images/foo/bar.xpm} within @code{data-directory}, you
+should specify the image as follows:
+
address@hidden
+(defimage foo-image '((:type xpm :file "foo/bar.xpm")))
address@hidden example
address@hidden defvar
+
address@hidden image-load-path-for-library library image &optional path no-error
+This function returns a suitable search path for images used by the
+Lisp package @var{library}.
+
+The function searches for @var{image} first using @code{image-load-path},
+excluding @address@hidden/images}, and then in
address@hidden, followed by a path suitable for @var{library}, which
+includes @file{../../etc/images} and @file{../etc/images} relative to
+the library file itself, and finally in
address@hidden@code{data-directory}/images}.
+
+Then this function returns a list of directories which contains first
+the directory in which @var{image} was found, followed by the value of
address@hidden If @var{path} is given, it is used instead of
address@hidden
+
+If @var{no-error} is address@hidden and a suitable path can't be
+found, don't signal an error. Instead, return a list of directories as
+before, except that @code{nil} appears in place of the image directory.
+
+Here is an example that uses a common idiom to provide compatibility
+with versions of Emacs that lack the variable @code{image-load-path}:
+
address@hidden
+(defvar image-load-path) ; shush compiler
+(let* ((load-path (image-load-path-for-library
+ "mh-e" "mh-logo.xpm"))
+ (image-load-path (cons (car load-path)
+ (when (boundp 'image-load-path)
+ image-load-path))))
+ (mh-tool-bar-folder-buttons-init))
address@hidden example
address@hidden defun
+
address@hidden Showing Images
address@hidden Showing Images
+
+ You can use an image descriptor by setting up the @code{display}
+property yourself, but it is easier to use the functions in this
+section.
+
address@hidden insert-image image &optional string area slice
+This function inserts @var{image} in the current buffer at point. The
+value @var{image} should be an image descriptor; it could be a value
+returned by @code{create-image}, or the value of a symbol defined with
address@hidden The argument @var{string} specifies the text to put
+in the buffer to hold the image. If it is omitted or @code{nil},
address@hidden uses @code{" "} by default.
+
+The argument @var{area} specifies whether to put the image in a margin.
+If it is @code{left-margin}, the image appears in the left margin;
address@hidden specifies the right margin. If @var{area} is
address@hidden or omitted, the image is displayed at point within the
+buffer's text.
+
+The argument @var{slice} specifies a slice of the image to insert. If
address@hidden is @code{nil} or omitted the whole image is inserted.
+Otherwise, @var{slice} is a list @code{(@var{x} @var{y} @var{width}
address@hidden)} which specifies the @var{x} and @var{y} positions and
address@hidden and @var{height} of the image area to insert. Integer
+values are in units of pixels. A floating point number in the range
+0.0--1.0 stands for that fraction of the width or height of the entire
+image.
+
+Internally, this function inserts @var{string} in the buffer, and gives
+it a @code{display} property which specifies @var{image}. @xref{Display
+Property}.
address@hidden defun
+
address@hidden insert-sliced-image image &optional string area rows cols
+This function inserts @var{image} in the current buffer at point, like
address@hidden, but splits the image into @address@hidden
+equally sized slices.
address@hidden defun
+
address@hidden put-image image pos &optional string area
+This function puts image @var{image} in front of @var{pos} in the
+current buffer. The argument @var{pos} should be an integer or a
+marker. It specifies the buffer position where the image should appear.
+The argument @var{string} specifies the text that should hold the image
+as an alternative to the default.
+
+The argument @var{image} must be an image descriptor, perhaps returned
+by @code{create-image} or stored by @code{defimage}.
+
+The argument @var{area} specifies whether to put the image in a margin.
+If it is @code{left-margin}, the image appears in the left margin;
address@hidden specifies the right margin. If @var{area} is
address@hidden or omitted, the image is displayed at point within the
+buffer's text.
+
+Internally, this function creates an overlay, and gives it a
address@hidden property containing text that has a @code{display}
+property whose value is the image. (Whew!)
address@hidden defun
+
address@hidden remove-images start end &optional buffer
+This function removes images in @var{buffer} between positions
address@hidden and @var{end}. If @var{buffer} is omitted or @code{nil},
+images are removed from the current buffer.
+
+This removes only images that were put into @var{buffer} the way
address@hidden does it, not images that were inserted with
address@hidden or in other ways.
address@hidden defun
+
address@hidden image-size spec &optional pixels frame
+This function returns the size of an image as a pair
address@hidden@code{(@var{width} . @var{height})}}. @var{spec} is an image
+specification. @var{pixels} address@hidden means return sizes
+measured in pixels, otherwise return sizes measured in canonical
+character units (fractions of the width/height of the frame's default
+font). @var{frame} is the frame on which the image will be displayed.
address@hidden null or omitted means use the selected frame (@pxref{Input
+Focus}).
address@hidden defun
+
address@hidden max-image-size
+This variable is used to define the maximum size of image that Emacs
+will load. Emacs will refuse to load (and display) any image that is
+larger than this limit.
+
+If the value is an integer, it directly specifies the maximum
+image height and width, measured in pixels. If it is a floating
+point number, it specifies the maximum image height and width
+as a ratio to the frame height and width. If the value is
+non-numeric, there is no explicit limit on the size of images.
+
+The purpose of this variable is to prevent unreasonably large images
+from accidentally being loaded into Emacs. It only takes effect the
+first time an image is loaded. Once an image is placed in the image
+cache, it can always be displayed, even if the value of
address@hidden is subsequently changed (@pxref{Image Cache}).
address@hidden defvar
+
address@hidden Image Cache
address@hidden Image Cache
address@hidden image cache
+
+ Emacs stores images in an image cache so that it can display them
+again more efficiently. When Emacs displays an image, it searches the
+image cache for an existing image specification @code{equal} to the
+desired specification. If a match is found, the image is displayed
+from the cache; otherwise, Emacs loads the image normally.
+
+ Occasionally, you may need to tell Emacs to refresh the images
+associated with a given image specification. For example, suppose you
+display an image using a specification that contains a @code{:file}
+property. The image is loaded from the given file and stored in the
+image cache. If you later display the image again, using the same
+image specification, the image is displayed from the image cache.
+Normally, this is not a problem. However, if the image file has
+changed in the meantime, Emacs would be displaying the old version of
+the image. In such a situation, it is necessary to ``refresh'' the
+image using @code{image-refresh}.
+
address@hidden image-refresh spec &optional frame
+This function refreshes any images having image specifications
address@hidden to @var{spec} on frame @var{frame}. If @var{frame} is
address@hidden, the selected frame is used. If @var{frame} is @code{t},
+the refresh is applied to all existing frames.
+
+This works by removing all image with image specifications matching
address@hidden from the image cache. Thus, the next time the image is
+displayed, Emacs will load the image again.
address@hidden defun
+
address@hidden clear-image-cache &optional frame
+This function clears the entire image cache. If @var{frame} is
address@hidden, only the cache for that frame is cleared. Otherwise,
+all frames' caches are cleared.
address@hidden defun
+
+If an image in the image cache has not been displayed for a specified
+period of time, Emacs removes it from the cache and frees the
+associated memory.
+
address@hidden image-cache-eviction-delay
+This variable specifies the number of seconds an image can remain in the
+cache without being displayed. When an image is not displayed for this
+length of time, Emacs removes it from the image cache.
+
+If the value is @code{nil}, Emacs does not remove images from the cache
+except when you explicitly clear it. This mode can be useful for
+debugging.
address@hidden defvar
+
address@hidden Buttons
address@hidden Buttons
address@hidden buttons in buffers
address@hidden clickable buttons in buffers
+
+ The @emph{button} package defines functions for inserting and
+manipulating clickable (with the mouse, or via keyboard commands)
+buttons in Emacs buffers, such as might be used for help hyper-links,
+etc. Emacs uses buttons for the hyper-links in help text and the like.
+
+ A button is essentially a set of properties attached (via text
+properties or overlays) to a region of text in an Emacs buffer. These
+properties are called @dfn{button properties}.
+
+ One of these properties (@code{action}) is a function, which will
+be called when the user invokes it using the keyboard or the mouse.
+The invoked function may then examine the button and use its other
+properties as desired.
+
+ In some ways the Emacs button package duplicates functionality offered
+by the widget package (@pxref{Top, , Introduction, widget, The Emacs
+Widget Library}), but the button package has the advantage that it is
+much faster, much smaller, and much simpler to use (for elisp
+programmers---for users, the result is about the same). The extra
+speed and space savings are useful mainly if you need to create many
+buttons in a buffer (for instance an @code{*Apropos*} buffer uses
+buttons to make entries clickable, and may contain many thousands of
+entries).
+
address@hidden
+* Button Properties:: Button properties with special meanings.
+* Button Types:: Defining common properties for classes of buttons.
+* Making Buttons:: Adding buttons to Emacs buffers.
+* Manipulating Buttons:: Getting and setting properties of buttons.
+* Button Buffer Commands:: Buffer-wide commands and bindings for buttons.
address@hidden menu
+
address@hidden Button Properties
address@hidden Button Properties
address@hidden button properties
+
+ Buttons have an associated list of properties defining their
+appearance and behavior, and other arbitrary properties may be used
+for application specific purposes. Some properties that have special
+meaning to the button package include:
+
address@hidden @code
address@hidden action
address@hidden action @r{(button property)}
+The function to call when the user invokes the button, which is passed
+the single argument @var{button}. By default this is @code{ignore},
+which does nothing.
+
address@hidden mouse-action
address@hidden mouse-action @r{(button property)}
+This is similar to @code{action}, and when present, will be used
+instead of @code{action} for button invocations resulting from
+mouse-clicks (instead of the user hitting @key{RET}). If not
+present, mouse-clicks use @code{action} instead.
+
address@hidden face
address@hidden face @r{(button property)}
+This is an Emacs face controlling how buttons of this type are
+displayed; by default this is the @code{button} face.
+
address@hidden mouse-face
address@hidden mouse-face @r{(button property)}
+This is an additional face which controls appearance during
+mouse-overs (merged with the usual button face); by default this is
+the usual Emacs @code{highlight} face.
+
address@hidden keymap
address@hidden keymap @r{(button property)}
+The button's keymap, defining bindings active within the button
+region. By default this is the usual button region keymap, stored
+in the variable @code{button-map}, which defines @key{RET} and
address@hidden to invoke the button.
+
address@hidden type
address@hidden type @r{(button property)}
+The button-type of the button. When creating a button, this is
+usually specified using the @code{:type} keyword argument.
address@hidden Types}.
+
address@hidden help-echo
address@hidden help-index @r{(button property)}
+A string displayed by the Emacs tool-tip help system; by default,
address@hidden"mouse-2, RET: Push this button"}.
+
address@hidden follow-link
address@hidden follow-link @r{(button property)}
+The follow-link property, defining how a @key{Mouse-1} click behaves
+on this button, @xref{Links and Mouse-1}.
+
address@hidden button
address@hidden button @r{(button property)}
+All buttons have a address@hidden @code{button} property, which may be useful
+in finding regions of text that comprise buttons (which is what the
+standard button functions do).
address@hidden table
+
+ There are other properties defined for the regions of text in a
+button, but these are not generally interesting for typical uses.
+
address@hidden Button Types
address@hidden Button Types
address@hidden button types
+
+ Every button has a button @emph{type}, which defines default values
+for the button's properties. Button types are arranged in a
+hierarchy, with specialized types inheriting from more general types,
+so that it's easy to define special-purpose types of buttons for
+specific tasks.
+
address@hidden define-button-type name &rest properties
+Define a `button type' called @var{name}. The remaining arguments
+form a sequence of @var{property value} pairs, specifying default
+property values for buttons with this type (a button's type may be set
+by giving it a @code{type} property when creating the button, using
+the @code{:type} keyword argument).
+
+In addition, the keyword argument @code{:supertype} may be used to
+specify a button-type from which @var{name} inherits its default
+property values. Note that this inheritance happens only when
address@hidden is defined; subsequent changes to a supertype are not
+reflected in its subtypes.
address@hidden defun
+
+ Using @code{define-button-type} to define default properties for
+buttons is not necessary---buttons without any specified type use the
+built-in button-type @code{button}---but it is encouraged, since
+doing so usually makes the resulting code clearer and more efficient.
+
address@hidden Making Buttons
address@hidden Making Buttons
address@hidden making buttons
+
+ Buttons are associated with a region of text, using an overlay or
+text properties to hold button-specific information, all of which are
+initialized from the button's type (which defaults to the built-in
+button type @code{button}). Like all Emacs text, the appearance of
+the button is governed by the @code{face} property; by default (via
+the @code{face} property inherited from the @code{button} button-type)
+this is a simple underline, like a typical web-page link.
+
+ For convenience, there are two sorts of button-creation functions,
+those that add button properties to an existing region of a buffer,
+called @code{make-...button}, and those that also insert the button
+text, called @code{insert-...button}.
+
+ The button-creation functions all take the @code{&rest} argument
address@hidden, which should be a sequence of @var{property value}
+pairs, specifying properties to add to the button; see @ref{Button
+Properties}. In addition, the keyword argument @code{:type} may be
+used to specify a button-type from which to inherit other properties;
+see @ref{Button Types}. Any properties not explicitly specified
+during creation will be inherited from the button's type (if the type
+defines such a property).
+
+ The following functions add a button using an overlay
+(@pxref{Overlays}) to hold the button properties:
+
address@hidden make-button beg end &rest properties
+This makes a button from @var{beg} to @var{end} in the
+current buffer, and returns it.
address@hidden defun
+
address@hidden insert-button label &rest properties
+This insert a button with the label @var{label} at point,
+and returns it.
address@hidden defun
+
+ The following functions are similar, but use Emacs text properties
+(@pxref{Text Properties}) to hold the button properties, making the
+button actually part of the text instead of being a property of the
+buffer. Buttons using text properties do not create markers into the
+buffer, which is important for speed when you use extremely large
+numbers of buttons. Both functions return the position of the start
+of the new button:
+
address@hidden make-text-button beg end &rest properties
+This makes a button from @var{beg} to @var{end} in the current buffer, using
+text properties.
address@hidden defun
+
address@hidden insert-text-button label &rest properties
+This inserts a button with the label @var{label} at point, using text
+properties.
address@hidden defun
+
address@hidden Manipulating Buttons
address@hidden Manipulating Buttons
address@hidden manipulating buttons
+
+These are functions for getting and setting properties of buttons.
+Often these are used by a button's invocation function to determine
+what to do.
+
+Where a @var{button} parameter is specified, it means an object
+referring to a specific button, either an overlay (for overlay
+buttons), or a buffer-position or marker (for text property buttons).
+Such an object is passed as the first argument to a button's
+invocation function when it is invoked.
+
address@hidden button-start button
+Return the position at which @var{button} starts.
address@hidden defun
+
address@hidden button-end button
+Return the position at which @var{button} ends.
address@hidden defun
+
address@hidden button-get button prop
+Get the property of button @var{button} named @var{prop}.
address@hidden defun
+
address@hidden button-put button prop val
+Set @var{button}'s @var{prop} property to @var{val}.
address@hidden defun
+
address@hidden button-activate button &optional use-mouse-action
+Call @var{button}'s @code{action} property (i.e., invoke it). If
address@hidden is address@hidden, try to invoke the button's
address@hidden property instead of @code{action}; if the button
+has no @code{mouse-action} property, use @code{action} as normal.
address@hidden defun
+
address@hidden button-label button
+Return @var{button}'s text label.
address@hidden defun
+
address@hidden button-type button
+Return @var{button}'s button-type.
address@hidden defun
+
address@hidden button-has-type-p button type
+Return @code{t} if @var{button} has button-type @var{type}, or one of
address@hidden's subtypes.
address@hidden defun
+
address@hidden button-at pos
+Return the button at position @var{pos} in the current buffer, or @code{nil}.
address@hidden defun
+
address@hidden button-type-put type prop val
+Set the button-type @var{type}'s @var{prop} property to @var{val}.
address@hidden defun
+
address@hidden button-type-get type prop
+Get the property of button-type @var{type} named @var{prop}.
address@hidden defun
+
address@hidden button-type-subtype-p type supertype
+Return @code{t} if button-type @var{type} is a subtype of @var{supertype}.
address@hidden defun
+
address@hidden Button Buffer Commands
address@hidden Button Buffer Commands
address@hidden button buffer commands
+
+These are commands and functions for locating and operating on
+buttons in an Emacs buffer.
+
address@hidden is the command that a user uses to actually `push'
+a button, and is bound by default in the button itself to @key{RET}
+and to @key{mouse-2} using a region-specific keymap. Commands
+that are useful outside the buttons itself, such as
address@hidden and @code{backward-button} are additionally
+available in the keymap stored in @code{button-buffer-map}; a mode
+which uses buttons may want to use @code{button-buffer-map} as a
+parent keymap for its keymap.
+
+If the button has a address@hidden @code{follow-link} property, and
address@hidden is set, a quick @key{Mouse-1} click
+will also activate the @code{push-button} command.
address@hidden and Mouse-1}.
+
address@hidden Command push-button &optional pos use-mouse-action
+Perform the action specified by a button at location @var{pos}.
address@hidden may be either a buffer position or a mouse-event. If
address@hidden is address@hidden, or @var{pos} is a
+mouse-event (@pxref{Mouse Events}), try to invoke the button's
address@hidden property instead of @code{action}; if the button
+has no @code{mouse-action} property, use @code{action} as normal.
address@hidden defaults to point, except when @code{push-button} is invoked
+interactively as the result of a mouse-event, in which case, the mouse
+event's position is used. If there's no button at @var{pos}, do
+nothing and return @code{nil}, otherwise return @code{t}.
address@hidden deffn
+
address@hidden Command forward-button n &optional wrap display-message
+Move to the @var{n}th next button, or @var{n}th previous button if
address@hidden is negative. If @var{n} is zero, move to the start of any
+button at point. If @var{wrap} is address@hidden, moving past either
+end of the buffer continues from the other end. If
address@hidden is address@hidden, the button's help-echo string
+is displayed. Any button with a address@hidden @code{skip} property
+is skipped over. Returns the button found.
address@hidden deffn
+
address@hidden Command backward-button n &optional wrap display-message
+Move to the @var{n}th previous button, or @var{n}th next button if
address@hidden is negative. If @var{n} is zero, move to the start of any
+button at point. If @var{wrap} is address@hidden, moving past either
+end of the buffer continues from the other end. If
address@hidden is address@hidden, the button's help-echo string
+is displayed. Any button with a address@hidden @code{skip} property
+is skipped over. Returns the button found.
address@hidden deffn
+
address@hidden next-button pos &optional count-current
address@hidden previous-button pos &optional count-current
+Return the next button after (for @code{next-button} or before (for
address@hidden) position @var{pos} in the current buffer. If
address@hidden is address@hidden, count any button at @var{pos}
+in the search, instead of starting at the next button.
address@hidden defun
+
address@hidden Abstract Display
address@hidden Abstract Display
address@hidden ewoc
address@hidden display, abstract
address@hidden display, arbitrary objects
address@hidden model/view/controller
address@hidden view part, model/view/controller
+
+ The Ewoc package constructs buffer text that represents a structure
+of Lisp objects, and updates the text to follow changes in that
+structure. This is like the ``view'' component in the
+``model/view/controller'' design paradigm.
+
+ An @dfn{ewoc} is a structure that organizes information required to
+construct buffer text that represents certain Lisp data. The buffer
+text of the ewoc has three parts, in order: first, fixed @dfn{header}
+text; next, textual descriptions of a series of data elements (Lisp
+objects that you specify); and last, fixed @dfn{footer} text.
+Specifically, an ewoc contains information on:
+
address@hidden @bullet
address@hidden
+The buffer which its text is generated in.
+
address@hidden
+The text's start position in the buffer.
+
address@hidden
+The header and footer strings.
+
address@hidden
+A doubly-linked chain of @dfn{nodes}, each of which contains:
+
address@hidden
address@hidden
+A @dfn{data element}, a single Lisp object.
+
address@hidden
+Links to the preceding and following nodes in the chain.
address@hidden itemize
+
address@hidden
+A @dfn{pretty-printer} function which is responsible for
+inserting the textual representation of a data
+element value into the current buffer.
address@hidden itemize
+
+ Typically, you define an ewoc with @code{ewoc-create}, and then pass
+the resulting ewoc structure to other functions in the Ewoc package to
+build nodes within it, and display it in the buffer. Once it is
+displayed in the buffer, other functions determine the correspondance
+between buffer positions and nodes, move point from one node's textual
+representation to another, and so forth. @xref{Abstract Display
+Functions}.
+
+ A node @dfn{encapsulates} a data element much the way a variable
+holds a value. Normally, encapsulation occurs as a part of adding a
+node to the ewoc. You can retrieve the data element value and place a
+new value in its place, like so:
+
address@hidden
+(ewoc-data @var{node})
address@hidden value
+
+(ewoc-set-data @var{node} @var{new-value})
address@hidden @var{new-value}
address@hidden lisp
+
address@hidden
+You can also use, as the data element value, a Lisp object (list or
+vector) that is a container for the ``real'' value, or an index into
+some other structure. The example (@pxref{Abstract Display Example})
+uses the latter approach.
+
+ When the data changes, you will want to update the text in the
+buffer. You can update all nodes by calling @code{ewoc-refresh}, or
+just specific nodes using @code{ewoc-invalidate}, or all nodes
+satisfying a predicate using @code{ewoc-map}. Alternatively, you can
+delete invalid nodes using @code{ewoc-delete} or @code{ewoc-filter},
+and add new nodes in their place. Deleting a node from an ewoc deletes
+its associated textual description from buffer, as well.
+
address@hidden
+* Abstract Display Functions::
+* Abstract Display Example::
address@hidden menu
+
address@hidden Abstract Display Functions
address@hidden Abstract Display Functions
+
+ In this subsection, @var{ewoc} and @var{node} stand for the
+structures described above (@pxref{Abstract Display}), while
address@hidden stands for an arbitrary Lisp object used as a data element.
+
address@hidden ewoc-create pretty-printer &optional header footer nosep
+This constructs and returns a new ewoc, with no nodes (and thus no data
+elements). @var{pretty-printer} should be a function that takes one
+argument, a data element of the sort you plan to use in this ewoc, and
+inserts its textual description at point using @code{insert} (and never
address@hidden, because that would interfere with the
+Ewoc package's internal mechanisms).
+
+Normally, a newline is automatically inserted after the header,
+the footer and every node's textual description. If @var{nosep}
+is address@hidden, no newline is inserted. This may be useful for
+displaying an entire ewoc on a single line, for example, or for
+making nodes ``invisible'' by arranging for @var{pretty-printer}
+to do nothing for those nodes.
+
+An ewoc maintains its text in the buffer that is current when
+you create it, so switch to the intended buffer before calling
address@hidden
address@hidden defun
+
address@hidden ewoc-buffer ewoc
+This returns the buffer where @var{ewoc} maintains its text.
address@hidden defun
+
address@hidden ewoc-get-hf ewoc
+This returns a cons cell @code{(@var{header} . @var{footer})}
+made from @var{ewoc}'s header and footer.
address@hidden defun
+
address@hidden ewoc-set-hf ewoc header footer
+This sets the header and footer of @var{ewoc} to the strings
address@hidden and @var{footer}, respectively.
address@hidden defun
+
address@hidden ewoc-enter-first ewoc data
address@hidden ewoc-enter-last ewoc data
+These add a new node encapsulating @var{data}, putting it, respectively,
+at the beginning or end of @var{ewoc}'s chain of nodes.
address@hidden defun
+
address@hidden ewoc-enter-before ewoc node data
address@hidden ewoc-enter-after ewoc node data
+These add a new node encapsulating @var{data}, adding it to
address@hidden before or after @var{node}, respectively.
address@hidden defun
+
address@hidden ewoc-prev ewoc node
address@hidden ewoc-next ewoc node
+These return, respectively, the previous node and the next node of @var{node}
+in @var{ewoc}.
address@hidden defun
+
address@hidden ewoc-nth ewoc n
+This returns the node in @var{ewoc} found at zero-based index @var{n}.
+A negative @var{n} means count from the end. @code{ewoc-nth} returns
address@hidden if @var{n} is out of range.
address@hidden defun
+
address@hidden ewoc-data node
+This extracts the data encapsulated by @var{node} and returns it.
address@hidden defun
+
address@hidden ewoc-set-data node data
+This sets the data encapsulated by @var{node} to @var{data}.
address@hidden defun
+
address@hidden ewoc-locate ewoc &optional pos guess
+This determines the node in @var{ewoc} which contains point (or
address@hidden if specified), and returns that node. If @var{ewoc} has no
+nodes, it returns @code{nil}. If @var{pos} is before the first node,
+it returns the first node; if @var{pos} is after the last node, it returns
+the last node. The optional third arg @var{guess}
+should be a node that is likely to be near @var{pos}; this doesn't
+alter the result, but makes the function run faster.
address@hidden defun
+
address@hidden ewoc-location node
+This returns the start position of @var{node}.
address@hidden defun
+
address@hidden ewoc-goto-prev ewoc arg
address@hidden ewoc-goto-next ewoc arg
+These move point to the previous or next, respectively, @var{arg}th node
+in @var{ewoc}. @code{ewoc-goto-prev} does not move if it is already at
+the first node or if @var{ewoc} is empty, whereas @code{ewoc-goto-next}
+moves past the last node, returning @code{nil}. Excepting this special
+case, these functions return the node moved to.
address@hidden defun
+
address@hidden ewoc-goto-node ewoc node
+This moves point to the start of @var{node} in @var{ewoc}.
address@hidden defun
+
address@hidden ewoc-refresh ewoc
+This function regenerates the text of @var{ewoc}. It works by
+deleting the text between the header and the footer, i.e., all the
+data elements' representations, and then calling the pretty-printer
+function for each node, one by one, in order.
address@hidden defun
+
address@hidden ewoc-invalidate ewoc &rest nodes
+This is similar to @code{ewoc-refresh}, except that only @var{nodes} in
address@hidden are updated instead of the entire set.
address@hidden defun
+
address@hidden ewoc-delete ewoc &rest nodes
+This deletes each node in @var{nodes} from @var{ewoc}.
address@hidden defun
+
address@hidden ewoc-filter ewoc predicate &rest args
+This calls @var{predicate} for each data element in @var{ewoc} and
+deletes those nodes for which @var{predicate} returns @code{nil}.
+Any @var{args} are passed to @var{predicate}.
address@hidden defun
+
address@hidden ewoc-collect ewoc predicate &rest args
+This calls @var{predicate} for each data element in @var{ewoc}
+and returns a list of those elements for which @var{predicate}
+returns address@hidden The elements in the list are ordered
+as in the buffer. Any @var{args} are passed to @var{predicate}.
address@hidden defun
+
address@hidden ewoc-map map-function ewoc &rest args
+This calls @var{map-function} for each data element in @var{ewoc} and
+updates those nodes for which @var{map-function} returns address@hidden
+Any @var{args} are passed to @var{map-function}.
address@hidden defun
+
address@hidden Abstract Display Example
address@hidden Abstract Display Example
+
+ Here is a simple example using functions of the ewoc package to
+implement a ``color components display,'' an area in a buffer that
+represents a vector of three integers (itself representing a 24-bit RGB
+value) in various ways.
+
address@hidden
+(setq colorcomp-ewoc nil
+ colorcomp-data nil
+ colorcomp-mode-map nil
+ colorcomp-labels ["Red" "Green" "Blue"])
+
+(defun colorcomp-pp (data)
+ (if data
+ (let ((comp (aref colorcomp-data data)))
+ (insert (aref colorcomp-labels data) "\t: #x"
+ (format "%02X" comp) " "
+ (make-string (ash comp -2) ?#) "\n"))
+ (let ((cstr (format "#%02X%02X%02X"
+ (aref colorcomp-data 0)
+ (aref colorcomp-data 1)
+ (aref colorcomp-data 2)))
+ (samp " (sample text) "))
+ (insert "Color\t: "
+ (propertize samp 'face `(foreground-color . ,cstr))
+ (propertize samp 'face `(background-color . ,cstr))
+ "\n"))))
+
+(defun colorcomp (color)
+ "Allow fiddling with COLOR in a new buffer.
+The buffer is in Color Components mode."
+ (interactive "sColor (name or #RGB or #RRGGBB): ")
+ (when (string= "" color)
+ (setq color "green"))
+ (unless (color-values color)
+ (error "No such color: %S" color))
+ (switch-to-buffer
+ (generate-new-buffer (format "originally: %s" color)))
+ (kill-all-local-variables)
+ (setq major-mode 'colorcomp-mode
+ mode-name "Color Components")
+ (use-local-map colorcomp-mode-map)
+ (erase-buffer)
+ (buffer-disable-undo)
+ (let ((data (apply 'vector (mapcar (lambda (n) (ash n -8))
+ (color-values color))))
+ (ewoc (ewoc-create 'colorcomp-pp
+ "\nColor Components\n\n"
+ (substitute-command-keys
+ "address@hidden@}"))))
+ (set (make-local-variable 'colorcomp-data) data)
+ (set (make-local-variable 'colorcomp-ewoc) ewoc)
+ (ewoc-enter-last ewoc 0)
+ (ewoc-enter-last ewoc 1)
+ (ewoc-enter-last ewoc 2)
+ (ewoc-enter-last ewoc nil)))
address@hidden example
+
address@hidden controller part, model/view/controller
+ This example can be extended to be a ``color selection widget'' (in
+other words, the controller part of the ``model/view/controller''
+design paradigm) by defining commands to modify @code{colorcomp-data}
+and to ``finish'' the selection process, and a keymap to tie it all
+together conveniently.
+
address@hidden
+(defun colorcomp-mod (index limit delta)
+ (let ((cur (aref colorcomp-data index)))
+ (unless (= limit cur)
+ (aset colorcomp-data index (+ cur delta)))
+ (ewoc-invalidate
+ colorcomp-ewoc
+ (ewoc-nth colorcomp-ewoc index)
+ (ewoc-nth colorcomp-ewoc -1))))
+
+(defun colorcomp-R-more () (interactive) (colorcomp-mod 0 255 1))
+(defun colorcomp-G-more () (interactive) (colorcomp-mod 1 255 1))
+(defun colorcomp-B-more () (interactive) (colorcomp-mod 2 255 1))
+(defun colorcomp-R-less () (interactive) (colorcomp-mod 0 0 -1))
+(defun colorcomp-G-less () (interactive) (colorcomp-mod 1 0 -1))
+(defun colorcomp-B-less () (interactive) (colorcomp-mod 2 0 -1))
+
+(defun colorcomp-copy-as-kill-and-exit ()
+ "Copy the color components into the kill ring and kill the buffer.
+The string is formatted #RRGGBB (hash followed by six hex digits)."
+ (interactive)
+ (kill-new (format "#%02X%02X%02X"
+ (aref colorcomp-data 0)
+ (aref colorcomp-data 1)
+ (aref colorcomp-data 2)))
+ (kill-buffer nil))
+
+(setq colorcomp-mode-map
+ (let ((m (make-sparse-keymap)))
+ (suppress-keymap m)
+ (define-key m "i" 'colorcomp-R-less)
+ (define-key m "o" 'colorcomp-R-more)
+ (define-key m "k" 'colorcomp-G-less)
+ (define-key m "l" 'colorcomp-G-more)
+ (define-key m "," 'colorcomp-B-less)
+ (define-key m "." 'colorcomp-B-more)
+ (define-key m " " 'colorcomp-copy-as-kill-and-exit)
+ m))
address@hidden smallexample
+
+Note that we never modify the data in each node, which is fixed when the
+ewoc is created to be either @code{nil} or an index into the vector
address@hidden, the actual color components.
+
address@hidden Blinking
address@hidden Blinking Parentheses
address@hidden parenthesis matching
address@hidden blinking parentheses
address@hidden balancing parentheses
+
+ This section describes the mechanism by which Emacs shows a matching
+open parenthesis when the user inserts a close parenthesis.
+
address@hidden blink-paren-function
+The value of this variable should be a function (of no arguments) to
+be called whenever a character with close parenthesis syntax is inserted.
+The value of @code{blink-paren-function} may be @code{nil}, in which
+case nothing is done.
address@hidden defvar
+
address@hidden blink-matching-paren
+If this variable is @code{nil}, then @code{blink-matching-open} does
+nothing.
address@hidden defopt
+
address@hidden blink-matching-paren-distance
+This variable specifies the maximum distance to scan for a matching
+parenthesis before giving up.
address@hidden defopt
+
address@hidden blink-matching-delay
+This variable specifies the number of seconds for the cursor to remain
+at the matching parenthesis. A fraction of a second often gives
+good results, but the default is 1, which works on all systems.
address@hidden defopt
+
address@hidden Command blink-matching-open
+This function is the default value of @code{blink-paren-function}. It
+assumes that point follows a character with close parenthesis syntax and
+moves the cursor momentarily to the matching opening character. If that
+character is not already on the screen, it displays the character's
+context in the echo area. To avoid long delays, this function does not
+search farther than @code{blink-matching-paren-distance} characters.
+
+Here is an example of calling this function explicitly.
+
address@hidden
address@hidden
+(defun interactive-blink-matching-open ()
address@hidden Do not break this line! -- rms.
address@hidden The first line of a doc string
address@hidden must stand alone.
+ "Indicate momentarily the start of sexp before point."
+ (interactive)
address@hidden group
address@hidden
+ (let ((blink-matching-paren-distance
+ (buffer-size))
+ (blink-matching-paren t))
+ (blink-matching-open)))
address@hidden group
address@hidden smallexample
address@hidden deffn
+
address@hidden Usual Display
address@hidden Usual Display Conventions
+
+ The usual display conventions define how to display each character
+code. You can override these conventions by setting up a display table
+(@pxref{Display Tables}). Here are the usual display conventions:
+
address@hidden @bullet
address@hidden
+Character codes 32 through 126 map to glyph codes 32 through 126.
+Normally this means they display as themselves.
+
address@hidden
+Character code 9 is a horizontal tab. It displays as whitespace
+up to a position determined by @code{tab-width}.
+
address@hidden
+Character code 10 is a newline.
+
address@hidden
+All other codes in the range 0 through 31, and code 127, display in one
+of two ways according to the value of @code{ctl-arrow}. If it is
address@hidden, these codes map to sequences of two glyphs, where the
+first glyph is the @acronym{ASCII} code for @samp{^}. (A display table can
+specify a glyph to use instead of @samp{^}.) Otherwise, these codes map
+just like the codes in the range 128 to 255.
+
+On MS-DOS terminals, Emacs arranges by default for the character code
+127 to be mapped to the glyph code 127, which normally displays as an
+empty polygon. This glyph is used to display address@hidden characters
+that the MS-DOS terminal doesn't support. @xref{MS-DOS and MULE,,,
+emacs, The GNU Emacs Manual}.
+
address@hidden
+Character codes 128 through 255 map to sequences of four glyphs, where
+the first glyph is the @acronym{ASCII} code for @samp{\}, and the others are
+digit characters representing the character code in octal. (A display
+table can specify a glyph to use instead of @samp{\}.)
+
address@hidden
+Multibyte character codes above 256 are displayed as themselves, or as a
+question mark or empty box if the terminal cannot display that
+character.
address@hidden itemize
+
+ The usual display conventions apply even when there is a display
+table, for any character whose entry in the active display table is
address@hidden Thus, when you set up a display table, you need only
+specify the characters for which you want special behavior.
+
+ These display rules apply to carriage return (character code 13), when
+it appears in the buffer. But that character may not appear in the
+buffer where you expect it, if it was eliminated as part of end-of-line
+conversion (@pxref{Coding System Basics}).
+
+ These variables affect the way certain characters are displayed on the
+screen. Since they change the number of columns the characters occupy,
+they also affect the indentation functions. These variables also affect
+how the mode line is displayed; if you want to force redisplay of the
+mode line using the new values, call the function
address@hidden (@pxref{Mode Line Format}).
+
address@hidden ctl-arrow
address@hidden control characters in display
+This buffer-local variable controls how control characters are
+displayed. If it is address@hidden, they are displayed as a caret
+followed by the character: @samp{^A}. If it is @code{nil}, they are
+displayed as a backslash followed by three octal digits: @samp{\001}.
address@hidden defopt
+
address@hidden Following may have overfull hbox.
address@hidden default-ctl-arrow
+The value of this variable is the default value for @code{ctl-arrow} in
+buffers that do not override it. @xref{Default Value}.
address@hidden defvar
+
address@hidden tab-width
+The value of this buffer-local variable is the spacing between tab
+stops used for displaying tab characters in Emacs buffers. The value
+is in units of columns, and the default is 8. Note that this feature
+is completely independent of the user-settable tab stops used by the
+command @code{tab-to-tab-stop}. @xref{Indent Tabs}.
address@hidden defopt
+
address@hidden Display Tables
address@hidden Display Tables
+
address@hidden display table
+You can use the @dfn{display table} feature to control how all possible
+character codes display on the screen. This is useful for displaying
+European languages that have letters not in the @acronym{ASCII} character
+set.
+
+The display table maps each character code into a sequence of
address@hidden, each glyph being a graphic that takes up one character
+position on the screen. You can also define how to display each glyph
+on your terminal, using the @dfn{glyph table}.
+
+Display tables affect how the mode line is displayed; if you want to
+force redisplay of the mode line using a new display table, call
address@hidden (@pxref{Mode Line Format}).
+
address@hidden
+* Display Table Format:: What a display table consists of.
+* Active Display Table:: How Emacs selects a display table to use.
+* Glyphs:: How to define a glyph, and what glyphs mean.
address@hidden menu
+
address@hidden Display Table Format
address@hidden Display Table Format
+
+ A display table is actually a char-table (@pxref{Char-Tables}) with
address@hidden as its subtype.
+
address@hidden make-display-table
+This creates and returns a display table. The table initially has
address@hidden in all elements.
address@hidden defun
+
+ The ordinary elements of the display table are indexed by character
+codes; the element at index @var{c} says how to display the character
+code @var{c}. The value should be @code{nil} or a vector of the
+glyphs to be output (@pxref{Glyphs}). @code{nil} says to display the
+character @var{c} according to the usual display conventions
+(@pxref{Usual Display}).
+
+ @strong{Warning:} if you use the display table to change the display
+of newline characters, the whole buffer will be displayed as one long
+``line.''
+
+ The display table also has six ``extra slots'' which serve special
+purposes. Here is a table of their meanings; @code{nil} in any slot
+means to use the default for that slot, as stated below.
+
address@hidden @asis
address@hidden 0
+The glyph for the end of a truncated screen line (the default for this
+is @samp{$}). @xref{Glyphs}. On graphical terminals, Emacs uses
+arrows in the fringes to indicate truncation, so the display table has
+no effect.
+
address@hidden 1
+The glyph for the end of a continued line (the default is @samp{\}).
+On graphical terminals, Emacs uses curved arrows in the fringes to
+indicate continuation, so the display table has no effect.
+
address@hidden 2
+The glyph for indicating a character displayed as an octal character
+code (the default is @samp{\}).
+
address@hidden 3
+The glyph for indicating a control character (the default is @samp{^}).
+
address@hidden 4
+A vector of glyphs for indicating the presence of invisible lines (the
+default is @samp{...}). @xref{Selective Display}.
+
address@hidden 5
+The glyph used to draw the border between side-by-side windows (the
+default is @samp{|}). @xref{Splitting Windows}. This takes effect only
+when there are no scroll bars; if scroll bars are supported and in use,
+a scroll bar separates the two windows.
address@hidden table
+
+ For example, here is how to construct a display table that mimics the
+effect of setting @code{ctl-arrow} to a address@hidden value:
+
address@hidden
+(setq disptab (make-display-table))
+(let ((i 0))
+ (while (< i 32)
+ (or (= i ?\t) (= i ?\n)
+ (aset disptab i (vector ?^ (+ i 64))))
+ (setq i (1+ i)))
+ (aset disptab 127 (vector ?^ ??)))
address@hidden example
+
address@hidden display-table-slot display-table slot
+This function returns the value of the extra slot @var{slot} of
address@hidden The argument @var{slot} may be a number from 0 to
+5 inclusive, or a slot name (symbol). Valid symbols are
address@hidden, @code{wrap}, @code{escape}, @code{control},
address@hidden, and @code{vertical-border}.
address@hidden defun
+
address@hidden set-display-table-slot display-table slot value
+This function stores @var{value} in the extra slot @var{slot} of
address@hidden The argument @var{slot} may be a number from 0 to
+5 inclusive, or a slot name (symbol). Valid symbols are
address@hidden, @code{wrap}, @code{escape}, @code{control},
address@hidden, and @code{vertical-border}.
address@hidden defun
+
address@hidden describe-display-table display-table
+This function displays a description of the display table
address@hidden in a help buffer.
address@hidden defun
+
address@hidden Command describe-current-display-table
+This command displays a description of the current display table in a
+help buffer.
address@hidden deffn
+
address@hidden Active Display Table
address@hidden Active Display Table
address@hidden active display table
+
+ Each window can specify a display table, and so can each buffer. When
+a buffer @var{b} is displayed in window @var{w}, display uses the
+display table for window @var{w} if it has one; otherwise, the display
+table for buffer @var{b} if it has one; otherwise, the standard display
+table if any. The display table chosen is called the @dfn{active}
+display table.
+
address@hidden window-display-table &optional window
+This function returns @var{window}'s display table, or @code{nil}
+if @var{window} does not have an assigned display table. The default
+for @var{window} is the selected window.
address@hidden defun
+
address@hidden set-window-display-table window table
+This function sets the display table of @var{window} to @var{table}.
+The argument @var{table} should be either a display table or
address@hidden
address@hidden defun
+
address@hidden buffer-display-table
+This variable is automatically buffer-local in all buffers; its value in
+a particular buffer specifies the display table for that buffer. If it
+is @code{nil}, that means the buffer does not have an assigned display
+table.
address@hidden defvar
+
address@hidden standard-display-table
+This variable's value is the default display table, used whenever a
+window has no display table and neither does the buffer displayed in
+that window. This variable is @code{nil} by default.
address@hidden defvar
+
+ If there is no display table to use for a particular window---that is,
+if the window specifies none, its buffer specifies none, and
address@hidden is @code{nil}---then Emacs uses the usual
+display conventions for all character codes in that window. @xref{Usual
+Display}.
+
+A number of functions for changing the standard display table
+are defined in the library @file{disp-table}.
+
address@hidden Glyphs
address@hidden Glyphs
+
address@hidden glyph
+ A @dfn{glyph} is a generalization of a character; it stands for an
+image that takes up a single character position on the screen. Normally
+glyphs come from vectors in the display table (@pxref{Display Tables}).
+
+ A glyph is represented in Lisp as a @dfn{glyph code}. A glyph code
+can be @dfn{simple} or it can be defined by the @dfn{glyph table}. A
+simple glyph code is just a way of specifying a character and a face
+to output it in. @xref{Faces}.
+
+ The following functions are used to manipulate simple glyph codes:
+
address@hidden make-glyph-code char &optional face
+This function returns a simple glyph code representing char @var{char}
+with face @var{face}.
address@hidden defun
+
address@hidden glyph-char glyph
+This function returns the character of simple glyph code @var{glyph}.
address@hidden defun
+
address@hidden glyph-face glyph
+This function returns face of simple glyph code @var{glyph}, or
address@hidden if @var{glyph} has the default face (face-id 0).
address@hidden defun
+
+ On character terminals, you can set up a @dfn{glyph table} to define
+the meaning of glyph codes (represented as small integers).
+
address@hidden glyph-table
+The value of this variable is the current glyph table. It should be
address@hidden or a vector whose @var{g}th element defines glyph code
address@hidden
+
+If a glyph code is greater than or equal to the length of the glyph
+table, that code is automatically simple. If @code{glyph-table} is
address@hidden then all glyph codes are simple.
+
+The glyph table is used only on character terminals. On graphical
+displays, all glyph codes are simple.
address@hidden defvar
+
+ Here are the meaningful types of elements in the glyph table:
+
address@hidden @asis
address@hidden @var{string}
+Send the characters in @var{string} to the terminal to output
+this glyph code.
+
address@hidden @var{code}
+Define this glyph code as an alias for glyph code @var{code} created
+by @code{make-glyph-code}. You can use such an alias to define a
+small-numbered glyph code which specifies a character with a face.
+
address@hidden @code{nil}
+This glyph code is simple.
address@hidden table
+
address@hidden create-glyph string
+This function returns a newly-allocated glyph code which is set up to
+display by sending @var{string} to the terminal.
address@hidden defun
+
address@hidden Beeping
address@hidden Beeping
address@hidden @cindex beeping "beep" is adjacent
address@hidden bell
+
+ This section describes how to make Emacs ring the bell (or blink the
+screen) to attract the user's attention. Be conservative about how
+often you do this; frequent bells can become irritating. Also be
+careful not to use just beeping when signaling an error is more
+appropriate. (@xref{Errors}.)
+
address@hidden ding &optional do-not-terminate
address@hidden keyboard macro termination
+This function beeps, or flashes the screen (see @code{visible-bell} below).
+It also terminates any keyboard macro currently executing unless
address@hidden is address@hidden
address@hidden defun
+
address@hidden beep &optional do-not-terminate
+This is a synonym for @code{ding}.
address@hidden defun
+
address@hidden visible-bell
+This variable determines whether Emacs should flash the screen to
+represent a bell. address@hidden means yes, @code{nil} means no. This
+is effective on graphical displays, and on text-only terminals
+provided the terminal's Termcap entry defines the visible bell
+capability (@samp{vb}).
address@hidden defopt
+
address@hidden ring-bell-function
+If this is address@hidden, it specifies how Emacs should ``ring the
+bell.'' Its value should be a function of no arguments. If this is
address@hidden, it takes precedence over the @code{visible-bell}
+variable.
address@hidden defvar
+
address@hidden Window Systems
address@hidden Window Systems
+
+ Emacs works with several window systems, most notably the X Window
+System. Both Emacs and X use the term ``window,'' but use it
+differently. An Emacs frame is a single window as far as X is
+concerned; the individual Emacs windows are not known to X at all.
+
address@hidden window-system
+This variable tells Lisp programs what window system Emacs is running
+under. The possible values are
+
address@hidden @code
address@hidden x
address@hidden X Window System
+Emacs is displaying using X.
address@hidden pc
+Emacs is displaying using MS-DOS.
address@hidden w32
+Emacs is displaying using Windows.
address@hidden mac
+Emacs is displaying using a Macintosh.
address@hidden nil
+Emacs is using a character-based terminal.
address@hidden table
address@hidden defvar
+
address@hidden window-setup-hook
+This variable is a normal hook which Emacs runs after handling the
+initialization files. Emacs runs this hook after it has completed
+loading your init file, the default initialization file (if
+any), and the terminal-specific Lisp code, and running the hook
address@hidden
+
+This hook is used for internal purposes: setting up communication with
+the window system, and creating the initial window. Users should not
+interfere with it.
address@hidden defvar
+
address@hidden
+ arch-tag: ffdf5714-7ecf-415b-9023-fbc6b409c2c6
address@hidden ignore