@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001,
+@c 2002, 2005 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/display
-@node Display, Calendar, System Interface, Top
+@node Display, System Interface, Processes, Top
@chapter Emacs Display
This chapter describes a number of features related to the display
@menu
* Refresh Screen:: Clearing the screen and redrawing everything on it.
-* Screen Size:: How big is the Emacs screen.
+* Forcing Redisplay:: Forcing redisplay.
* Truncation:: Folding or wrapping long text lines.
* The Echo Area:: Where messages are displayed.
-* Selective Display:: Hiding part of the buffer text.
-* Overlay Arrow:: Display of an arrow to indicate position.
+* Warnings:: Displaying warning messages for the user.
+* Progress:: Informing user about progress of a long operation.
+* 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.
-* Faces:: A face defines a graphics appearance: font, color, etc.
+* 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.
+* Pointer Shape:: Controlling the mouse pointer shape.
+* Display Property:: Enabling special display features.
+* Images:: Displaying images in Emacs buffers.
+* Buttons:: Adding clickable buttons to Emacs buffers.
* Blinking:: How Emacs shows the matching open parenthesis.
-* Inverse Video:: Specifying how the screen looks.
-* Usual Display:: The usual conventions for displaying nonprinting chars.
-* Display Tables:: How to specify other conventions.
+* Inverse Video:: Specifying how the screen looks.
+* 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.
@end menu
@node Refresh Screen
@section Refreshing the Screen
-The function @code{redraw-frame} redisplays the entire contents of a
-given frame. @xref{Frames}.
+ 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.
@c Emacs 19 feature
@defun redraw-frame frame
This function clears and redisplays frame @var{frame}.
@end defun
-Even more powerful is @code{redraw-display}:
+ Even more powerful is @code{redraw-display}:
@deffn Command redraw-display
This function clears and redisplays all visible frames.
@end deffn
+ This function calls for redisplay of certain windows, the next time
+redisplay is done, but does not clear them first.
+
+@defun force-window-update &optional object
+This function forces redisplay of some or all windows. If
+@var{object} is a window, it forces redisplay of that window. If
+@var{object} 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.
+@end 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. @xref{Suspending Emacs}.
+resumption.
@defvar no-redraw-on-reenter
@cindex suspend (cf. @code{no-redraw-on-reenter})
@cindex resume (cf. @code{no-redraw-on-reenter})
This variable controls whether Emacs redraws the entire screen after it
-has been suspended and resumed. Non-@code{nil} means yes, @code{nil}
-means no.
+has been suspended and resumed. Non-@code{nil} means there is no need
+to redraw, @code{nil} means redrawing is needed. The default is @code{nil}.
@end defvar
- 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.
-
-@node Screen Size
-@section Screen Size
-@cindex size of screen
-@cindex screen size
-@cindex display lines
-@cindex display columns
-@cindex resize redisplay
+@node Forcing Redisplay
+@section Forcing Redisplay
+@cindex forcing redisplay
- The screen size functions report or tell Emacs the height or width of
-the terminal. When you are using multiple frames, they apply to the
-selected frame (@pxref{Frames}).
+ 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 non-@code{nil} value.
-@defun screen-height
-This function returns the number of lines on the screen that are
-available for display.
-
-@example
-@group
-(screen-height)
- @result{} 50
-@end group
-@end example
-@end defun
+@tindex redisplay-dont-pause
+@defvar redisplay-dont-pause
+If this variable is non-@code{nil}, pending input does not
+prevent or halt redisplay; redisplay occurs, and finishes,
+regardless of whether input is available.
+@end defvar
-@defun screen-width
-This function returns the number of columns on the screen that are
-available for display.
+ You can request a display update, but only if no input is pending,
+with @code{(sit-for 0)}. To force a display update even when input is
+pending, do this:
@example
-@group
-(screen-width)
- @result{} 80
-@end group
+(let ((redisplay-dont-pause t))
+ (sit-for 0))
@end example
-@end defun
-
-@defun set-screen-height lines &optional not-actual-size
-This function declares that the terminal can display @var{lines} lines.
-The sizes of existing windows are altered proportionally to fit.
-
-If @var{not-actual-size} is non-@code{nil}, then Emacs displays
-@var{lines} lines of output, but does not change its value for the
-actual height of the screen. (Knowing the correct actual size may be
-necessary for correct cursor positioning.) Using a smaller height than
-the terminal actually implements may be useful to reproduce behavior
-observed on a smaller screen, or if the terminal malfunctions when using
-its whole screen.
-
-If @var{lines} is different from what it was previously, then the
-entire screen is cleared and redisplayed using the new size.
-
-This function returns @code{nil}.
-@end defun
-
-@defun set-screen-width columns &optional not-actual-size
-This function declares that the terminal can display @var{columns}
-columns. The details are as in @code{set-screen-height}.
-@end defun
@node Truncation
@section Truncation
one screen line. The additional screen lines used to display a long
text line are called @dfn{continuation} lines. Normally, a @samp{$} in
the rightmost column of the window indicates truncation; a @samp{\} on
-the rightmost column indicates a line that ``wraps'' or is continued
-onto the next line. (The display table can specify alternative
-indicators; see @ref{Display Tables}.)
+the rightmost column indicates a line that ``wraps'' onto the next line,
+which is also called @dfn{continuing} the line. (The display table can
+specify alternative indicators; see @ref{Display Tables}.)
+
+ On a window system display, the @samp{$} and @samp{\} indicators are
+replaced with arrow images displayed in the window fringes
+(@pxref{Fringes}).
Note that continuation is different from filling; continuation happens
on the screen only, not in the buffer contents, and it breaks a line
frame) regardless of the value of @code{truncate-lines}.
@end defopt
-@defvar default-truncate-lines
+@defopt default-truncate-lines
This variable is the default value for @code{truncate-lines}, for
-buffers that do not have local values for it.
-@end defvar
+buffers that do not have buffer-local values for it.
+@end defopt
@defopt truncate-partial-width-windows
This variable controls display of lines that extend beyond the right
@code{truncate-lines} says what to do with them.
@end defopt
- You can override the images that indicate continuation or truncation
-with the display table; see @ref{Display Tables}.
+ 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
+@code{cache-long-line-scans} to @code{t}.
+
+@defvar cache-long-line-scans
+If this variable is non-@code{nil}, 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.
+@end defvar
@node The Echo Area
@section The Echo Area
@cindex error display
@cindex echo area
- The @dfn{echo area} is used for displaying 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}).
-Error messages appear in the echo area; see @ref{Errors}.
+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 as
follows:
@defun message string &rest arguments
-This function prints a one-line message in the echo area. The
+This function displays a message in the echo area. The
argument @var{string} is similar to a C language @code{printf} control
-string. See @code{format} in @ref{String Conversion}, for the details
+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{string}, or strings among the @var{arguments}, have @code{face}
+text properties, these affect the way the message is displayed.
+
@c Emacs 19 feature
-If @var{string} is @code{nil}, @code{message} clears the echo area. If
-the minibuffer is active, this brings the minibuffer contents back onto
-the screen immediately.
+If @var{string} is @code{nil}, @code{message} 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.
+
+@vindex 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 non-@code{nil}, the echo area does not resize, and the message is
+truncated to fit it, as in Emacs 20 and before.
+
@example
@group
(message "Minibuffer depth is %d."
---------- Echo Area ----------
@end group
@end 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).
+@end defun
+
+@defopt max-mini-window-height
+This variable specifies the maximum height for resizing minibuffer
+windows. If a float, it specifies a fraction of the height of the
+frame. If an integer, it specifies a number of lines.
+@end defopt
+
+@tindex with-temp-message
+@defmac 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
+@var{body}, then returns the value of the last body form while restoring
+the previous echo area contents.
+@end defmac
+
+@defun message-or-box 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
+@code{last-nonmenu-event} (@pxref{Command Loop Info}) is either
+@code{nil} 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
+@ref{Yes-or-No Queries}.)
+
+You can force use of the mouse or of the echo area by binding
+@code{last-nonmenu-event} to a suitable value around the call.
+@end defun
+
+@defun message-box string &rest arguments
+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
+@code{message}.
+@end defun
+
+@defun display-message-or-buffer message &optional buffer-name not-this-window frame
+@tindex display-message-or-buffer
+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,
+@code{display-buffer} 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
+@var{buffer-name} 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
+@code{display-buffer}, and only used if a buffer is displayed.
+@end defun
+
+@defun current-message
+This function returns the message currently being displayed in the
+echo area, or @code{nil} if there is none.
@end defun
@defvar cursor-in-echo-area
for brief periods of time.
@end defvar
+@defvar echo-area-clear-hook
+This normal hook is run whenever the echo area is cleared---either by
+@code{(message nil)} or for any other reason.
+@end defvar
+
+Almost all the messages displayed in the echo area are also recorded
+in the @samp{*Messages*} buffer.
+
+@defopt 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:
+
+@example
+(let (message-log-max)
+ (message @dots{}))
+@end example
+@end defopt
+
+@defvar 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.
+@end defvar
+
+@node Warnings
+@section Reporting Warnings
+@cindex warnings
+
+ @dfn{Warnings} are a facility for a program to inform the user of a
+possible problem, but continue running.
+
+@menu
+* 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.
+@end menu
+
+@node Warning Basics
+@subsection Warning Basics
+@cindex 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:
+
+@table @code
+@item :emergency
+A problem that will seriously impair Emacs operation soon
+if you do not attend to it promptly.
+@item :error
+A report of data or circumstances that are inherently wrong.
+@item :warning
+A report of data or circumstances that are not inherently wrong, but
+raise suspicion of a possible problem.
+@item :debug
+A report of information that may be useful if you are debugging.
+@end 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
+@code{condition-case}, the user won't see the error message; it could
+show the message to the user by reporting it as a warning.)
+
+@cindex 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.
+
+@defun 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.
+
+@var{buffer-name}, if non-@code{nil}, specifies the name of the buffer
+for logging the warning. By default, it is @samp{*Warnings*}.
+@end defun
+
+@defun lwarn type level message &rest args
+This function reports a warning using the value of @code{(format
+@var{message} @var{args}...)} as the message. In other respects it is
+equivalent to @code{display-warning}.
+@end defun
+
+@defun warn message &rest args
+This function reports a warning using the value of @code{(format
+@var{message} @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.
+@end defun
+
+@node Warning Variables
+@subsection Warning Variables
+
+ Programs can customize how their warnings appear by binding
+the variables described in this section.
+
+@defvar 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}
+@var{function})}, where @var{level} is the severity level it defines.
+@var{string} specifies the textual description of this level.
+@var{string} 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 non-@code{nil}, is a function to call
+with no arguments, to get the user's attention.
+
+Normally you should not change the value of this variable.
+@end defvar
+
+@defvar warning-prefix-function
+If non-@code{nil}, the value is a function to generate prefix text for
+warnings. Programs can bind the variable to a suitable function.
+@code{display-warning} 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
+@code{warning-levels}). 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.
+@end defvar
+
+@defvar 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
+@code{warning-series} 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.
+@end defvar
+
+@defvar warning-fill-prefix
+When this variable is non-@code{nil}, it specifies a fill prefix to
+use for filling each warning's text.
+@end defvar
+
+@defvar 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.
+@end defvar
+
+@node Warning Options
+@subsection Warning Options
+
+ These variables are used by users to control what happens
+when a Lisp program reports a warning.
+
+@defopt 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.
+@end defopt
+
+@defopt 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.
+@end defopt
+
+@defopt 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.
+@end defopt
+
+@defopt 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.
+@end defopt
+
+@node Progress
+@section Reporting Operation Progress
+@cindex 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:
+
+@example
+(let ((progress-reporter
+ (make-progress-reporter "Collecting some mana for Emacs..."
+ 0 500)))
+ (dotimes (k 500)
+ (sit-for 0.01)
+ (progress-reporter-update progress-reporter k))
+ (progress-reporter-done progress-reporter))
+@end example
+
+@defun 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
+@var{message} in the echo area, followed by progress percentage.
+@var{message} is treated as a simple string. If you need it to depend
+on a filename, for instance, use @code{format} before calling this
+function.
+
+@var{min-value} 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
+@var{min-value}. If you create progress reporter when some part of
+the operation has already been completed, then specify
+@var{current-value} 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.
+@var{min-time} 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
+@var{min-change} 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.
+@end defun
+
+@defun 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.
+
+@var{reporter} must be the result of a call to
+@code{make-progress-reporter}. @var{value} specifies the current
+state of your operation and must be between @var{min-value} and
+@var{max-value} (inclusive) as passed to
+@code{make-progress-reporter}. 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.
+@end defun
+
+@defun 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
+@code{progress-reporter-update}. 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.
+@end defun
+
+@defun 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
+@code{progress-reporter-update} to print ``100%.'' Firstly, it may
+never print it, there are many good reasons for this not to happen.
+Secondly, ``done'' is more explicit.
+@end defun
+
+@defmac dotimes-with-progress-reporter (var count [result]) message body...
+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:
+
+@example
+(dotimes-with-progress-reporter
+ (k 500)
+ "Collecting some mana for Emacs..."
+ (sit-for 0.01))
+@end example
+@end defmac
+
+@node Invisible Text
+@section Invisible Text
+
+@cindex 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 non-@code{nil} @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
+@code{invisible} 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.
+
+@defvar buffer-invisibility-spec
+This variable specifies which kinds of @code{invisible} properties
+actually make a character invisible. Setting this variable makes it
+buffer-local.
+
+@table @asis
+@item @code{t}
+A character is invisible if its @code{invisible} property is
+non-@code{nil}. This is the default.
+
+@item 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:
+
+@table @code
+@item @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.
+
+@item (@var{atom} . t)
+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.
+Moreover, if this character is at the end of a line and is followed
+by a visible newline, it displays an ellipsis.
+@end table
+@end table
+@end defvar
+
+ Two functions are specifically provided for adding elements to
+@code{buffer-invisibility-spec} and removing elements from it.
+
+@defun add-to-invisibility-spec element
+This function adds the element @var{element} to
+@code{buffer-invisibility-spec}. If @code{buffer-invisibility-spec}
+was @code{t}, it changes to a list, @code{(t)}, so that text whose
+@code{invisible} property is @code{t} remains invisible.
+@end defun
+
+@defun remove-from-invisibility-spec element
+This removes the element @var{element} from
+@code{buffer-invisibility-spec}. This does nothing if @var{element}
+is not in the list.
+@end 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
+@code{buffer-invisibility-spec} and as the value of the
+@code{invisible} property:
+
+@example
+;; @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)
+@end example
+
+@vindex 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
+@code{line-move-ignore-invisible} is non-@code{nil} (the default), but
+only because they are explicitly programmed to do so.
+
+ However, if a command ends with point inside or immediately after
+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, following the previous visible character.
+If the command moved point forward into an invisible range, Emacs
+moves point forward past 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 non-@code{nil}
+@code{isearch-open-invisible} 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
+@code{isearch-open-invisible-temporary} 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.
+
@node Selective Display
@section Selective Display
@cindex selective display
- @dfn{Selective display} is a class of minor modes in which specially
-marked lines do not appear on the screen, or in which highly indented
-lines do not appear.
+ @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. The program controls which lines are hidden by altering
-the text. Outline mode uses this variant. In the second variant, the
-choice of lines to hide is made automatically based on indentation.
-This variant is designed as a user-level feature.
+ 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
+@code{invisible} 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 which
-was formerly a line following that newline is now invisible. 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.
+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
-invisible text. However, the replacement of newline characters with
-carriage return characters affects some editing commands. For example,
-@code{next-line} skips invisible lines, since it searches only for
-newlines. Modes that use selective display can also define commands
-that take account of the newlines, or that make parts of the text
-visible or invisible.
+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 invisible. The selective display
+in the file, it looks OK, with nothing hidden. The selective display
effect is seen only within Emacs.
@defvar selective-display
This buffer-local variable enables selective display. This means that
-lines, or portions of lines, may be made invisible.
+lines, or portions of lines, may be made hidden.
@itemize @bullet
@item
-If the value of @code{selective-display} is @code{t}, then any portion
-of a line that follows a control-m is not displayed.
+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.
@item
If the value of @code{selective-display} is a positive integer, then
displayed.
@end itemize
-When some portion of a buffer is invisible, the vertical movement
+When some portion of a buffer is hidden, the vertical movement
commands operate as if that portion did not exist, allowing a single
-@code{next-line} command to skip any number of invisible lines.
+@code{next-line} command to skip any number of hidden lines.
However, character movement commands (such as @code{forward-char}) do
-not skip the invisible portion, and it is possible (if tricky) to insert
-or delete text in an invisible portion.
+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
@defvar selective-display-ellipses
If this buffer-local variable is non-@code{nil}, then Emacs displays
-@samp{@dots{}} at the end of a line that is followed by invisible text.
+@samp{@dots{}} at the end of a line that is followed by hidden text.
This example is a continuation of the previous one.
@example
(@samp{@dots{}}). @xref{Display Tables}.
@end defvar
-@node Overlay Arrow
-@section The Overlay Arrow
-@cindex overlay arrow
-
- 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.
-
-@defvar overlay-arrow-string
-This variable holds the string to display as an arrow, or @code{nil} if
-the arrow feature is not in use.
-@end defvar
-
-@defvar overlay-arrow-position
-This variable holds a marker which indicates where to display the arrow.
-It should point at the beginning of a line. 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 string is displayed only in the buffer which this marker
-points into. Thus, only one buffer can have an overlay arrow at any
-given time.
-@c !!! overlay-arrow-position: but the overlay string may remain in the display
-@c of some other buffer until an update is required. This should be fixed
-@c now. Is it?
-@end defvar
-
@node Temporary Displays
@section Temporary Displays
- Temporary displays are used by commands to put output into a buffer
-and then present it to the user for perusal rather than for editing.
-Many of the help commands use this feature.
+ 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.
@defspec with-output-to-temp-buffer buffer-name forms@dots{}
-This function executes @var{forms} while arranging to insert any
-output they print into the buffer named @var{buffer-name}. The buffer
-is then shown in some window for viewing, displayed but not selected.
+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
+@code{with-output-to-temp-buffer} 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.
they are ``output'' in the general sense of the word, are not affected).
@xref{Output 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.
@example
@end defspec
@defvar temp-buffer-show-function
-If this variable, if non-@code{nil}, @code{with-output-to-temp-buffer}
+If this variable is non-@code{nil}, @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.
-In Emacs versions 18 and earlier, this variable was called
-@code{temp-buffer-show-hook}.
+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
+@code{save-selected-window} and with the chosen window and buffer
+selected.
+@end defvar
+
+@defvar temp-buffer-setup-hook
+@tindex 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.
+@end defvar
+
+@defvar 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.
@end defvar
@defun momentary-string-display string position &optional char message
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.
+@xref{Overlay Properties}.
+
If @var{message} is non-@code{nil}, 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.
@cindex overlays
You can use @dfn{overlays} to alter the appearance of a buffer's text on
-the screen. An overlay is an object which 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.
+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 overlays 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.
@menu
-* Overlay Properties:: How to read and set properties.
+* Managing Overlays:: Creating and moving overlays.
+* Overlay Properties:: How to read and set properties.
What properties do to the screen display.
-* Managing Overlays:: Creating, moving, finding overlays.
+* Finding Overlays:: Searching for overlays.
@end menu
-@node Overlay Properties
-@subsection Overlay Properties
-
-Overlay properties are like text properties in some respects, but the
-differences are more important than the similarities. Text properties
-are considered a part of the text; overlays 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 propery changes, overlay changes are not recorded in the
-buffer's undo list.
-
-@table @code
-@item priority
-@kindex priority @r{(overlay property)}
-This property's value (which should be a nonnegative number) determines
-the priority of the overlay. The priority matters when two or more
-overlays cover the same character and both specify a face for display;
-the one whose @code{priority} value is larger takes priority over the
-other, and its face attributes override the face attributes of the lower
-priority overlay.
-
-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.
-
-@item window
-@kindex window @r{(overlay property)}
-If the @code{window} property is non-@code{nil}, then the overlay
-applies only on that window.
-
-@item face
-@kindex face @r{(overlay property)}
-This property controls the font and color of text. @xref{Faces}, for
-more information. This feature is temporary; in the future, we may
-replace it with other ways of specifying how to display text.
-
-@item mouse-face
-@kindex mouse-face @r{(overlay property)}
-This property is used instead of @code{face} when the mouse is within
-the range of the overlay. This feature may be temporary, like
-@code{face}.
-
-@item modification-hooks
-@kindex 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. Each function receives three arguments: the
-overlay, and the beginning and end of the part of the buffer being
-modified.
-
-@item insert-in-front-hooks
-@kindex insert-in-front-hooks @r{(overlay property)}
-This property's value is a list of functions to be called
-if text is inserted right at the beginning of the overlay.
-
-@item insert-behind-hooks
-@kindex insert-behind-hooks @r{(overlay property)}
-This property's value is a list of functions to be called if text is
-inserted right at the end of the overlay.
-
-@item invisible
-@kindex invisible @r{(overlay property)}
-A non-@code{nil} @code{invisible} property means that the text in the
-overlay does not appear on the screen. This works much like selective
-display. Details of this feature are likely to change in future
-versions, so check the @file{etc/NEWS} file in the version you are
-using.
-
-@item before-string
-@kindex 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. This is not yet implemented, but will be.
-
-@item after-string
-@kindex 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. This is not yet implemented, but will be.
-@end table
-
- These are the functions for reading and writing the properties of an
-overlay.
-
-@defun overlay-get overlay prop
-This function returns the value of property @var{prop} recorded in
-@var{overlay}. If @var{overlay} does not record any value for that
-property, then the value is @code{nil}.
-@end defun
-
-@defun overlay-put overlay prop value
-This function sets the value of property @var{prop} recorded in
-@var{overlay} to @var{value}. It returns @var{value}.
-@end defun
-
- See also the function @code{get-char-property} which checks both
-overlay properties and text properties for a given character.
-@xref{Examining Properties}.
-
@node Managing Overlays
@subsection Managing Overlays
This section describes the functions to create, delete and move
-overlays, and to examine their contents.
+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.
-@defun make-overlay start end &optional buffer
-This function creates and returns an overlay which belongs to
+@defun overlayp object
+This function returns @code{t} if @var{object} is an overlay.
+@end defun
+
+@defun make-overlay start end &optional buffer front-advance rear-advance
+This function creates and returns an overlay that belongs to
@var{buffer} 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
+insertion type for the start of the overlay and for the end of the
+overlay, respectively. @xref{Marker Insertion Types}. If
+@var{front-advance} is non-@code{nil}, text inserted at the beginning
+of the overlay is excluded from the overlay. If @var{read-advance} is
+non-@code{nil}, text inserted at the beginning of the overlay is
+included in the overlay.
@end defun
@defun overlay-start overlay
-This function returns the position at which @var{overlay} starts.
+This function returns the position at which @var{overlay} starts,
+as an integer.
@end defun
@defun overlay-end overlay
-This function returns the position at which @var{overlay} ends.
+This function returns the position at which @var{overlay} ends,
+as an integer.
@end defun
@defun overlay-buffer overlay
-This function returns the buffer that @var{overlay} belongs to.
+This function returns the buffer that @var{overlay} belongs to. It
+returns @code{nil} if @var{overlay} has been deleted.
@end defun
@defun delete-overlay overlay
This function deletes @var{overlay}. The overlay continues to exist as
-a Lisp object, but ceases to be part of the buffer it belonged to, and
-ceases to have any effect on display.
+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}.
@end defun
@defun 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, the overlay stays in the same buffer.
+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}.
``lost''.
@end defun
-@defun overlays-at pos
-This function returns a list of all the overlays that contain 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}.
-@end defun
+@defun remove-overlays &optional start end name value
+This function removes all the overlays between @var{start} and
+@var{end} whose property @var{name} has the value @var{value}. It can
+move the endpoints of the overlays in the region, or split them.
-@defun next-overlay-change pos
-This function returns the buffer position of the next beginning or end
-of an overlay, after @var{pos}.
+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
+@code{nil}, that means the beginning and end of the buffer respectively.
+Therefore, @code{(remove-overlays)} removes all the overlays in the
+current buffer.
@end defun
-@node Faces
-@section Faces
-@cindex face
-
-A @dfn{face} is a named collection of graphical attributes: font,
-foreground color, background color and optional underlining. Faces
-control the display of text on the screen.
-
-@cindex face id
-Each face has its own @dfn{face id number} which distinguishes faces at
-low levels within Emacs. However, for most purposes, you can refer to
-faces in Lisp programs by their names.
-
-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.
+ Here are some examples:
+
+@example
+;; @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
+@end example
+
+@node Overlay Properties
+@subsection 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:
+
+@defun overlay-get overlay prop
+This function returns the value of property @var{prop} recorded in
+@var{overlay}, 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}.
+@end defun
+
+@defun overlay-put overlay prop value
+This function sets the value of property @var{prop} recorded in
+@var{overlay} to @var{value}. It returns @var{value}.
+@end defun
+
+@defun overlay-properties overlay
+This returns a copy of the property list of @var{overlay}.
+@end defun
+
+ See also the function @code{get-char-property} which checks both
+overlay properties and text properties for a given character.
+@xref{Examining Properties}.
+
+ Many overlay properties have special meanings; here is a table
+of them:
+
+@table @code
+@item priority
+@kindex 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
+@code{face} 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.
+
+@item window
+@kindex window @r{(overlay property)}
+If the @code{window} property is non-@code{nil}, then the overlay
+applies only on that window.
+
+@item category
+@kindex category @r{(overlay property)}
+If an overlay has a @code{category} property, we call it the
+@dfn{category} of the overlay. It should be a symbol. The properties
+of the symbol serve as defaults for the properties of the overlay.
+
+@item face
+@kindex 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:
+
+@itemize @bullet
+@item
+A face name (a symbol or string).
+
+@item
+A property list of face attributes. This has the form (@var{keyword}
+@var{value} @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}.
+
+@item
+A cons cell of the form @code{(foreground-color . @var{color-name})} or
+@code{(background-color . @var{color-name})}. These elements specify
+just the foreground color or just the background color.
+
+@code{(foreground-color . @var{color-name})} is equivalent to
+@code{(:foreground @var{color-name})}, and likewise for the background.
+@end itemize
+
+@item mouse-face
+@kindex mouse-face @r{(overlay property)}
+This property is used instead of @code{face} when the mouse is within
+the range of the overlay.
+
+@item display
+@kindex 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.
+@xref{Display Property}.
+
+@item help-echo
+@kindex 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}.
+
+@item modification-hooks
+@kindex 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.)
+
+@item insert-in-front-hooks
+@kindex 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.
+
+@item insert-behind-hooks
+@kindex 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.
+
+@item invisible
+@kindex 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.
+@xref{Invisible Text}, for details.
+
+@item intangible
+@kindex intangible @r{(overlay property)}
+The @code{intangible} property on an overlay works just like the
+@code{intangible} text property. @xref{Special Properties}, for details.
+
+@item 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}.
+
+@item isearch-open-invisible-temporary
+This property tells incremental search how to make an invisible overlay
+visible, temporarily, during the search. @xref{Invisible Text}.
+
+@item before-string
+@kindex 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.
+
+@item after-string
+@kindex 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.
+
+@item evaporate
+@kindex evaporate @r{(overlay property)}
+If this property is non-@code{nil}, the overlay is deleted automatically
+if it becomes empty (i.e., if its length becomes zero). If you give
+an empty overlay a non-@code{nil} @code{evaporate} property, that deletes
+it immediately.
+
+@item local-map
+@cindex keymap of character (and overlays)
+@kindex local-map @r{(overlay property)}
+If this property is non-@code{nil}, 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}.
+
+@item keymap
+@kindex 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.
+@end table
+
+@node Finding Overlays
+@subsection Searching for Overlays
+
+@defun 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:
+
+@smallexample
+(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))
+@end smallexample
+@end defun
+
+@defun overlays-in beg end
+This function returns a list of the overlays that overlap the region
+@var{beg} 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}.
+@end defun
+
+@defun 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
+@code{(point-max)}.
+@end defun
+
+@defun 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
+@code{(point-min)}.
+@end defun
+
+ Here's an easy way to use @code{next-overlay-change} to search for the
+next character which gets a non-@code{nil} @code{happy} property from
+either its overlays or its text properties (@pxref{Property Search}):
+
+@smallexample
+(defun find-overlay-prop (prop)
+ (save-excursion
+ (while (and (not (eobp))
+ (not (get-char-property (point) 'happy)))
+ (goto-char (min (next-overlay-change (point))
+ (next-single-property-change (point) 'happy))))
+ (point)))
+@end smallexample
+
+@node Width
+@section Width
+
+Since not all characters have the same width, these functions let you
+check the width of a character. @xref{Primitive Indent}, and
+@ref{Screen Lines}, for related functions.
+
+@defun 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.
+@end defun
+
+@defun 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.
+@end defun
+
+@defun truncate-string-to-width string width &optional start-column padding ellipsis
+This function returns the part of @var{string} that fits within
+@var{width} columns, as a new string.
+
+If @var{string} does not reach @var{width}, then the result ends where
+@var{string} 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 non-@code{nil}, then the first @var{start-column} columns of
+the string are omitted from the value. If one multi-column character in
+@var{string} extends across the column @var{start-column}, that
+character is not included.
+
+The optional argument @var{padding}, if non-@code{nil}, 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
+@var{string} extends across the column @var{start-column}.
+
+If @var{ellipsis} is non-@code{nil}, 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
+@var{ellipsis} is non-@code{nil} and not a string, it stands for
+@code{"..."}.
+
+@example
+(truncate-string-to-width "\tab\t" 12 4)
+ @result{} "ab"
+(truncate-string-to-width "\tab\t" 12 4 ?\s)
+ @result{} " ab "
+@end example
+@end defun
+
+@node Line Height
+@section Line Height
+@cindex line height
+
+ The total height of each display line consists of the height of the
+contents of the line, and additional vertical line spacing below the
+display row.
+
+ The height of the line contents is normally determined from the
+maximum height of any character or image on that display line,
+including the final newline if there is one. (A line that is
+continued doesn't include a final newline.) In the most common case,
+the line height equals the height of the default frame font.
+
+ There are several ways to explicitly control or change the line
+height, either by specifying an absolute height for the display line,
+or by adding additional vertical space below one or all lines.
+
+@kindex 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 a list @code{(@var{height} @var{total})},
+then @var{height} is used as the actual property value for the
+@code{line-height}, and @var{total} specifies the total displayed
+height of the line, so the line spacing added below the line equals
+the @var{total} height minus the actual line height. In this case,
+the other ways to specify the line spacing are ignored.
+
+ If the property value is @code{t}, the displayed height of the
+line is exactly what its contents demand; no line-spacing is added.
+This case is useful for tiling small images or image slices without
+adding blank areas between the images.
+
+ If the property value is not @code{t}, it is a height spec. A height
+spec stands for a numeric height value; this height spec specifies the
+actual line height, @var{line-height}. There are several ways to
+write a height spec; here's how each of them translates into a numeric
+height:
+
+@table @code
+@item @var{integer}
+If the height spec is a positive integer, the height value is that integer.
+@item @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.
+@item (@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.
+@item (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.
+@end table
+
+ Thus, any valid non-@code{t} property value specifies a height in pixels,
+@var{line-height}, one way or another. If the line contents' height
+is less than @var{line-height}, Emacs adds extra vertical space above
+the line to achieve the total height @var{line-height}. Otherwise,
+@var{line-height} has no effect.
+
+ 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.
+
+@vindex default-line-spacing
+ You can specify the line spacing for all lines in a frame with the
+@code{line-spacing} frame parameter, @xref{Window Frame Parameters}.
+However, if the variable @code{default-line-spacing} is
+non-@code{nil}, it overrides the frame's @code{line-spacing}
+parameter. An integer value specifies the number of pixels put below
+lines on window systems. A floating point number specifies the
+spacing relative to the frame's default line height.
+
+@vindex 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 window systems. A floating
+point number specifies the spacing relative to the default frame line
+height. This overrides line spacings specified for the frame.
+
+@kindex line-spacing @r{(text property)}
+ Finally, a newline can have a @code{line-spacing} text or overlay
+property that controls the height of the display line ending with that
+newline. The property value overrides the default frame line spacing
+and the buffer local @code{line-spacing} variable.
+
+ 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.
+
+@node Faces
+@section Faces
+@cindex 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.
+
+@cindex 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 their names.
+
+@defun facep object
+This function returns @code{t} if @var{object} is a face name symbol (or
+if it is a vector of the kind used internally to record face data). It
+returns @code{nil} otherwise.
+@end 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.
+
+@menu
+* Standard Faces:: The faces Emacs normally comes with.
+* 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.
+@end menu
+
+@node Standard Faces
+@subsection Standard Faces
+
+ This table lists all the standard faces and their uses. Most of them
+are used for displaying certain parts of the frames or certain kinds of
+text; you can control how those places look by customizing these faces.
+
+@table @code
+@item default
+@kindex default @r{(face name)}
+This face is used for ordinary text.
+
+@item mode-line
+@kindex mode-line @r{(face name)}
+This face is used for the mode line of the selected window, and for
+menu bars when toolkit menus are not used---but only if
+@code{mode-line-inverse-video} is non-@code{nil}.
+
+@item modeline
+@kindex modeline @r{(face name)}
+This is an alias for the @code{mode-line} face, for compatibility with
+old Emacs versions.
+
+@item mode-line-inactive
+@kindex mode-line-inactive @r{(face name)}
+This face is used for mode lines of non-selected windows.
+This face inherits from @code{mode-line}, so changes
+in that face affect all windows.
+
+@item header-line
+@kindex header-line @r{(face name)}
+This face is used for the header lines of windows that have them.
+
+@item menu
+This face controls the display of menus, both their colors and their
+font. (This works only on certain systems.)
+
+@item fringe
+@kindex fringe @r{(face name)}
+This face controls the default colors of window fringes, the thin
+areas on either side that are used to display continuation and
+truncation glyphs. Other faces used to display bitmaps in the fringe
+are implicitly merged with this face.
+
+@item minibuffer-prompt
+@kindex minibuffer-prompt @r{(face name)}
+@vindex minibuffer-prompt-properties
+This face is used for the text of minibuffer prompts. By default,
+Emacs automatically adds this face to the value of
+@code{minibuffer-prompt-properties}, which is a list of text
+properties used to display the prompt text.
+
+@item scroll-bar
+@kindex scroll-bar @r{(face name)}
+This face controls the colors for display of scroll bars.
+
+@item tool-bar
+@kindex tool-bar @r{(face name)}
+This face is used for display of the tool bar, if any.
+
+@item region
+@kindex region @r{(face name)}
+This face is used for highlighting the region in Transient Mark mode.
+
+@item secondary-selection
+@kindex secondary-selection @r{(face name)}
+This face is used to show any secondary selection you have made.
+
+@item highlight
+@kindex highlight @r{(face name)}
+This face is meant to be used for highlighting for various purposes.
+
+@item mode-line-highlight
+@kindex mode-line-highlight @r{(face name)}
+This face is used for highlighting something on @code{mode-line} or
+@code{header-line} for various purposes.
+
+@item trailing-whitespace
+@kindex trailing-whitespace @r{(face name)}
+This face is used to display excess whitespace at the end of a line,
+if @code{show-trailing-whitespace} is non-@code{nil}.
+
+@item escape-glyph
+@kindex escape-glyph @r{(face name)}
+This face is used to display control characters and escape glyphs.
+@end table
+
+ In contrast, these faces are provided to change the appearance of text
+in specific ways. You can use them on specific text, when you want
+the effects they produce.
+
+@table @code
+@item bold
+@kindex bold @r{(face name)}
+This face uses a bold font, if possible. It uses the bold variant of
+the frame's font, if it has one. It's up to you to choose a default
+font that has a bold variant, if you want to use one.
+
+@item italic
+@kindex italic @r{(face name)}
+This face uses the italic variant of the frame's font, if it has one.
+
+@item bold-italic
+@kindex bold-italic @r{(face name)}
+This face uses the bold italic variant of the frame's font, if it has
+one.
+
+@item underline
+@kindex underline @r{(face name)}
+This face underlines text.
+
+@item fixed-pitch
+@kindex fixed-pitch @r{(face name)}
+This face forces use of a particular fixed-width font.
+
+@item variable-pitch
+@kindex variable-pitch @r{(face name)}
+This face forces use of a particular variable-width font. It's
+reasonable to customize this to use a different variable-width font, if
+you like, but you should not make it a fixed-width font.
+@end table
+
+@defvar show-trailing-whitespace
+@tindex show-trailing-whitespace
+If this variable is non-@code{nil}, Emacs uses the
+@code{trailing-whitespace} face to display any spaces and tabs at the
+end of a line.
+@end defvar
+
+@node Defining Faces
+@subsection 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}).
+
+@defmac defface face spec doc [keyword value]...
+This declares @var{face} as a customizable face that defaults according
+to @var{spec}. You should not quote the symbol @var{face}. The
+argument @var{doc} specifies the face documentation. The keywords you
+can use in @code{defface} are the same ones that are meaningful in both
+@code{defgroup} and @code{defcustom} (@pxref{Common Keywords}).
+
+When @code{defface} executes, it defines the face according to
+@var{spec}, then uses any customizations that were read from the
+init file (@pxref{Init File}) to override that specification.
+
+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
+@sc{car}, @var{display}, specifies a class of terminals. (The first
+element, if it s @sc{car} is @code{default}, is special---it specifies
+defaults for the remaining elements). The element's @sc{cadr},
+@var{atts}, 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
+@code{custom-face-attributes}.
+
+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}:
+
+@table @asis
+@item @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.
+
+@item @code{t}
+This element of @var{spec} matches all frames. Therefore, any
+subsequent elements of @var{spec} are never used. Normally
+@code{t} is used in the last (or only) element of @var{spec}.
+
+@item a list
+If @var{display} is a list, each element should have the form
+@code{(@var{characteristic} @var{value}@dots{})}. Here
+@var{characteristic} specifies a way of classifying frames, and the
+@var{value}s are possible classifications which @var{display} should
+apply to. Here are the possible values of @var{characteristic}:
+
+@table @code
+@item 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),
+@code{w32} (for MS Windows 9X/NT), or @code{tty} (a non-graphics-capable
+display).
+
+@item class
+What kinds of colors the frame supports---either @code{color},
+@code{grayscale}, or @code{mono}.
+
+@item background
+The kind of background---either @code{light} or @code{dark}.
+
+@item min-colors
+An integer that represents the minimum number of colors the frame
+should support. This matches a frame if its
+@code{display-color-cells} value is at least the specified integer.
+
+@item supports
+Whether or not the frame can display the face attributes given in
+@var{value}@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}.
+@end 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
+@var{display} 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
+@var{display}.
+@end table
+@end defmac
+
+ Here's how the standard face @code{region} is defined:
+
+@example
+@group
+ '((((class color) (min-colors 88) (background dark))
+ :background "blue3")
+@end 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"))
+@group
+ "Basic face for highlighting the region."
+ :group 'basic-faces)
+@end group
+@end example
+
+ Internally, @code{defface} uses the symbol property
+@code{face-defface-spec} to record the face attributes specified in
+@code{defface}, @code{saved-face} for the attributes saved by the user
+with the customization buffer, and @code{face-documentation} for the
+documentation string.
+
+@defopt frame-background-mode
+This option, if non-@code{nil}, 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.
+@end defopt
+
+@node Face Attributes
+@subsection Face Attributes
+@cindex 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. Note that in general, more than one face can be specified for a
+given piece of text; when that happens, the attributes of all the faces
+are merged to specify 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},
+@code{:height}, @code{:weight}, and @code{:slant} correspond to parts of
+an X Logical Font Descriptor.)
+
+@table @code
+@item :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.
+
+@item :width
+Relative proportionate width, also known as the character set width or
+set width. This should be one of the symbols @code{ultra-condensed},
+@code{extra-condensed}, @code{condensed}, @code{semi-condensed},
+@code{normal}, @code{semi-expanded}, @code{expanded},
+@code{extra-expanded}, or @code{ultra-expanded}.
+
+@item :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.
+
+@item :weight
+Font weight---a symbol from this series (from most dense to most faint):
+@code{ultra-bold}, @code{extra-bold}, @code{bold}, @code{semi-bold},
+@code{normal}, @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).
+
+@item :slant
+Font slant---one of the symbols @code{italic}, @code{oblique}, @code{normal},
+@code{reverse-italic}, or @code{reverse-oblique}.
+
+On a text-only terminal, slanted text is displayed as half-bright, if
+the terminal supports the feature.
+
+@item :foreground
+Foreground color, a string. The value can be a system-defined color
+name, or a hexadecimal color specification of the form
+@samp{#@var{rr}@var{gg}@var{bb}}. (@samp{#000000} is black,
+@samp{#ff0000} is red, @samp{#00ff00} is green, @samp{#0000ff} is
+blue, and @samp{#ffffff} is white.)
+
+@item :background
+Background color, a string, like the foreground color.
+
+@item :inverse-video
+Whether or not characters should be displayed in inverse video. The
+value should be @code{t} (yes) or @code{nil} (no).
+
+@item :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,
+@var{width} and @var{height} specify the size in pixels, and
+@var{data} 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.
+
+@item :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.
+
+@item :overline
+Whether or not characters should be overlined, and in what color.
+The value is used like that of @code{:underline}.
+
+@item :strike-through
+Whether or not characters should be strike-through, and in what
+color. The value is used like that of @code{:underline}.
+
+@item :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.
+
+@item :box
+Whether or not a box should be drawn around characters, its color, the
+width of the box lines, and 3D appearance.
+@end table
+
+ Here are the possible values of the @code{:box} attribute, and what
+they mean:
+
+@table @asis
+@item @code{nil}
+Don't draw a box.
+
+@item @code{t}
+Draw a box with lines of width 1, in the foreground color.
+
+@item @var{color}
+Draw a box with lines of width 1, in color @var{color}.
+
+@item @code{(:line-width @var{width} :color @var{color} :style @var{style})}
+This way you can explicitly specify all aspects of the box. The value
+@var{width} 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
+@code{released-button}, 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.
+@end table
+
+ In older versions of Emacs, before @code{:family}, @code{:height},
+@code{: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:
+
+@table @code
+@item :font
+This attribute specifies the font name.
+
+@item :bold
+A non-@code{nil} value specifies a bold font.
+
+@item :italic
+A non-@code{nil} value specifies an italic font.
+@end table
+
+ For compatibility, you can still set these ``attributes'', even
+though they are not real face attributes. Here is what that does:
+
+@table @code
+@item :font
+You can specify an X font name as the ``value'' of this ``attribute'';
+that sets the @code{:family}, @code{:width}, @code{:height},
+@code{: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.
+
+@item :bold
+A non-@code{nil} makes the face bold; @code{nil} makes it normal.
+This actually works by setting the @code{:weight} attribute.
+
+@item :italic
+A non-@code{nil} makes the face italic; @code{nil} makes it normal.
+This actually works by setting the @code{:slant} attribute.
+@end table
+
+@defvar x-bitmap-file-path
+This variable specifies a list of directories for searching
+for bitmap files, for the @code{:stipple} attribute.
+@end defvar
+
+@defun 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
+@code{nil} otherwise.
+@end defun
+
+@node Attribute Functions
+@subsection Face Attribute Functions
+
+ You can modify the attributes of an existing face with the following
+functions. If you specify @var{frame}, they affect just that frame;
+otherwise, they affect all frames as well as the defaults that apply to
+new frames.
+
+@tindex set-face-attribute
+@defun set-face-attribute face frame &rest arguments
+This function sets one or more attributes of face @var{face}
+for frame @var{frame}. If @var{frame} is @code{nil}, it sets
+the attribute for all frames, and the defaults for new frames.
+
+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,
+
+@example
+(set-face-attribute 'foo nil
+ :width 'extended
+ :weight 'bold
+ :underline "red")
+@end example
+
+@noindent
+sets the attributes @code{:width}, @code{:weight} and @code{:underline}
+to the corresponding values.
+@end defun
+
+@tindex face-attribute
+@defun face-attribute face attribute &optional frame inherit
+This returns the value of the @var{attribute} attribute of face
+@var{face} on @var{frame}. If @var{frame} is @code{nil},
+that means the selected frame (@pxref{Input Focus}).
+
+If @var{frame} is @code{t}, the value is the default for
+@var{face} for new frames.
+
+If @var{inherit} is @code{nil}, only attributes directly defined by
+@var{face} are considered, so the return value may be
+@code{unspecified}, or a relative value. If @var{inherit} is
+non-@code{nil}, @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
+@var{inherit} 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,
+
+@example
+(face-attribute 'bold :weight)
+ @result{} bold
+@end example
+@end 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.
+
+@tindex face-attribute-relative-p
+@defun face-attribute-relative-p attribute value
+This function returns non-@code{nil} if @var{value}, when used as
+the value of the face attribute @var{attribute}, is relative (that is,
+if it modifies an underlying or inherited value of @var{attribute}).
+@end defun
+
+@tindex merge-face-attribute
+@defun merge-face-attribute attribute value1 value2
+If @var{value1} is a relative value for the face attribute
+@var{attribute}, returns it merged with the underlying value
+@var{value2}; otherwise, if @var{value1} is an absolute value for the
+face attribute @var{attribute}, returns @var{value1} unchanged.
+@end defun
+
+@defun set-face-foreground face color &optional frame
+@defunx 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.
+@end defun
+
+@defun 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.
+@end defun
+
+@defun 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},
+@code{:weight}, and @code{:slant} according to the font name
+@var{font}.
+@end defun
+
+@defun set-face-bold-p face bold-p &optional frame
+This function specifies whether @var{face} should be bold. If
+@var{bold-p} is non-@code{nil}, that means yes; @code{nil} means no.
+This actually sets the @code{:weight} attribute.
+@end defun
+
+@defun set-face-italic-p face italic-p &optional frame
+This function specifies whether @var{face} should be italic. If
+@var{italic-p} is non-@code{nil}, that means yes; @code{nil} means no.
+This actually sets the @code{:slant} attribute.
+@end defun
+
+@defun set-face-underline-p face underline-p &optional frame
+This function sets the underline attribute of face @var{face}.
+Non-@code{nil} means do underline; @code{nil} means don't.
+@end defun
+
+@defun invert-face face &optional frame
+This function inverts the @code{:inverse-video} attribute of face
+@var{face}. If the attribute is @code{nil}, this function sets it to
+@code{t}, and vice versa.
+@end defun
+
+ These functions examine the attributes of a face. If you don't
+specify @var{frame}, they refer to the default data for new frames.
+They return the symbol @code{unspecified} if the face doesn't define any
+value for that attribute.
+
+@defun face-foreground face &optional frame inherit
+@defunx face-background face &optional frame
+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 non-@code{nil}, 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 color is found. To ensure that the return value is always
+specified, use a value of @code{default} for @var{inherit}.
+@end defun
+
+@defun face-stipple face &optional frame inherit
+This function returns the name of the background stipple pattern of face
+@var{face}, 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 non-@code{nil}, 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
+@var{inherit}.
+@end defun
+
+@defun face-font face &optional frame
+This function returns the name of the font of face @var{face}.
+@end defun
+
+@defun 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.
+@end defun
+
+@defun face-italic-p face &optional frame
+This function returns @code{t} if @var{face} is italic or oblique,
+@code{nil} otherwise.
+@end defun
+
+@defun face-underline-p face &optional frame
+This function returns the @code{:underline} attribute of face @var{face}.
+@end defun
+
+@defun face-inverse-video-p face &optional frame
+This function returns the @code{:inverse-video} attribute of face @var{face}.
+@end defun
+
+@node Displaying Faces
+@subsection Displaying Faces
+
+ Here are the ways to specify which faces to use for display of text:
+
+@itemize @bullet
+@item
+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.)
+
+@item
+For a mode line or header line, the face @code{mode-line} or
+@code{mode-line-inactive}, or @code{header-line}, is merged in just
+before @code{default}.
+
+@item
+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.
+
+@item
+With overlays. An overlay can have @code{face} and @code{mouse-face}
+properties too; they apply to all the text covered by the overlay.
+
+@item
+With a region that is active. In Transient Mark mode, the region is
+highlighted with the face @code{region} (@pxref{Standard Faces}).
+
+@item
+With special glyphs. Each glyph can specify a particular face
+number. @xref{Glyphs}.
+@end 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
+@code{mode-line-inactive} 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}.
+
+@node Font Selection
+@subsection 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.
+
+@defvar face-font-selection-order
+@tindex face-font-selection-order
+This variable specifies the order of importance of the face attributes
+@code{: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
+@code{italic} face will use a non-italic font that is similar to the
+default one. But if you put @code{:slant} before @code{:height}, the
+@code{italic} face will use an italic font, even if its height is not
+quite right.
+@end defvar
+
+@defvar face-font-family-alternatives
+@tindex 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:
+
+@example
+(@var{family} @var{alternate-families}@dots{})
+@end 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.
+@end defvar
+
+@defvar face-font-registry-alternatives
+@tindex 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:
+
+@example
+(@var{registry} @var{alternate-registries}@dots{})
+@end 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.
+@end 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.
+
+@defvar scalable-fonts-allowed
+@tindex scalable-fonts-allowed
+This variable controls which scalable fonts to use. A value of
+@code{nil}, 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,
+
+@example
+(setq scalable-fonts-allowed '("muleindian-2$"))
+@end example
+
+@noindent
+allows the use of scalable fonts with registry @code{muleindian-2}.
+@end defvar
+
+@defun clear-face-cache &optional unload-p
+@tindex clear-face-cache
+This function clears the face cache for all frames.
+If @var{unload-p} is non-@code{nil}, that means to unload
+all unused fonts as well.
+@end defun
+
+@defvar face-font-rescale-alist
+This variable specifies scaling for certain faces. Its value should
+be a list of elements of the form
+
+@example
+(@var{fontname-regexp} . @var{scale-factor})
+@end 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.
+@end defvar
+
+@node Face Functions
+@subsection Functions for Working with Faces
+
+ Here are additional functions for creating and working with faces.
+
+@defun 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
+@var{name}.
+@end defun
+
+@defun face-list
+This function returns a list of all defined face names.
+@end defun
+
+@defun 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}.
+@end defun
+
+@defun face-id face
+This function returns the face number of face @var{face}.
+@end defun
+
+@defun face-documentation face
+This function returns the documentation string of face @var{face}, or
+@code{nil} if none was specified for it.
+@end defun
+
+@defun face-equal face1 face2 &optional frame
+This returns @code{t} if the faces @var{face1} and @var{face2} have the
+same attributes for display.
+@end defun
+
+@defun face-differs-from-default-p face &optional frame
+This returns non-@code{nil} if the face @var{face} displays
+differently from the default face.
+@end defun
+
+@node Auto Faces
+@subsection Automatic Face Assignment
+@cindex automatic face assignment
+@cindex faces, automatic choice
+
+@cindex Font-Lock mode
+ This hook is used for automatically assigning faces to text in the
+buffer. It is part of the implementation of Font-Lock mode.
+
+@tindex fontification-functions
+@defvar 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
+@code{face} property. It should also add a non-@code{nil}
+@code{fontified} 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 non-@code{nil} @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.
+@end defvar
+
+@node Font Lookup
+@subsection Looking Up Fonts
+
+@defun x-list-fonts pattern &optional face frame maximum
+This function returns a list of available font names that match
+@var{pattern}. If the optional arguments @var{face} and @var{frame} are
+specified, then the list is limited to fonts that are the same size as
+@var{face} 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
+@samp{?} 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 non-@code{nil}, 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.
+@end defun
+
+@defun x-family-fonts &optional family frame
+@tindex x-family-fonts
+This function returns a list describing the available fonts for family
+@var{family} 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:
+
+@example
+[@var{family} @var{width} @var{point-size} @var{weight} @var{slant}
+ @var{fixed-p} @var{full} @var{registry-and-encoding}]
+@end 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.
+@var{fixed-p} is non-@code{nil} if the font is fixed-pitch.
+@var{full} is the full name of the font, and
+@var{registry-and-encoding} is a string giving the registry and
+encoding of the font.
+
+The result list is sorted according to the current face font sort order.
+@end defun
+
+@defun x-font-family-list &optional frame
+@tindex x-font-family-list
+This function returns a list of the font families available for
+@var{frame}'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:
+
+@example
+(@var{family} . @var{fixed-p})
+@end example
+
+@noindent
+Here @var{family} is a font family, and @var{fixed-p} is
+non-@code{nil} if fonts of that family are fixed-pitch.
+@end defun
+
+@defvar font-list-limit
+@tindex 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.
+@end defvar
+
+@node Fontsets
+@subsection 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.
+
+@defun 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:
+
+@smallexample
+@var{fontpattern}, @r{[}@var{charsetname}:@var{fontname}@r{]@dots{}}
+@end smallexample
+
+@noindent
+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
+@samp{fontset-@var{alias}}.
+
+The new fontset has two names, one long and one short. The long name is
+@var{fontpattern} in its entirety. The short name is
+@samp{fontset-@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 non-@code{nil}, in which case this
+function does nothing.
+
+If optional argument @var{style-variant-p} is non-@code{nil}, 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.
+@end defun
+
+ The construct @samp{@var{charset}:@var{font}} specifies which font to
+use (in this fontset) for one particular character set. Here,
+@var{charset} 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
+@samp{fontset-@var{alias}} with a value that names one character set.
+For the @acronym{ASCII} character set, @samp{fontset-@var{alias}} 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,
+
+@example
+-*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24
+@end example
+
+@noindent
+the font specification for @acronym{ASCII} characters would be this:
+
+@example
+-*-fixed-medium-r-normal-*-24-*-ISO8859-1
+@end example
+
+@noindent
+and the font specification for Chinese GB2312 characters would be this:
+
+@example
+-*-fixed-medium-r-normal-*-24-*-gb2312*-*
+@end 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, @samp{Fontset-@var{n}} can be specified as below:
+
+@smallexample
+Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\
+ chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-*
+@end smallexample
+
+@noindent
+Then, the font specifications for all but Chinese GB2312 characters have
+@samp{fixed} in the @var{family} field, and the font specification for
+Chinese GB2312 characters has a wild card @samp{*} in the @var{family}
+field.
+
+@defun 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}.
+
+@var{character} may be a cons; @code{(@var{from} . @var{to})}, where
+@var{from} and @var{to} are non-generic characters. In that case, use
+@var{fontname} for all characters in the range @var{from} and @var{to}
+(inclusive).
+
+@var{character} may be a charset. In that case, use
+@var{fontname} for all character in the charsets.
+
+@var{fontname} 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}.
+
+@example
+(set-fontset-font nil 'japanese-jisx0208 '(nil . "JISX0208.1983"))
+@end example
+
+@end defun
+
+@defun char-displayable-p char
+This function returns @code{t} if Emacs ought to be able to display
+@var{char}. 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.
+@end defun
+
+@node Fringes
+@section Fringes
+@cindex 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.
+
+@menu
+* Fringe Size/Pos:: Specifying where to put the window fringes.
+* Fringe Bitmaps:: Displaying bitmaps in the window fringes.
+* Customizing Bitmaps:: Specifying your own bitmaps to use in the fringes.
+* Overlay Arrow:: Display of an arrow to indicate position.
+@end menu
+
+@node Fringe Size/Pos
+@subsection Fringe Size and Position
+
+ Here's how to control the position and width of the window fringes.
+
+@defvar fringes-outside-margins
+If the value is non-@code{nil}, the frames appear outside the display
+margins. The fringes normally appear between the display margins and
+the window text. It works to set @code{fringes-outside-margins}
+buffer-locally. @xref{Display Margins}.
+@end defvar
+
+@defvar left-fringe-width
+This variable, if non-@code{nil}, specifies the width of the left
+fringe in pixels.
+@end defvar
+
+@defvar right-fringe-width
+This variable, if non-@code{nil}, specifies the width of the right
+fringe in pixels.
+@end 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.
+
+@defun 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
+@code{nil} for either one stands for the default width. If
+@var{outside-margins} is non-@code{nil}, that specifies that fringes
+should appear outside of the display margins.
+@end defun
+
+@defun window-fringes &optional window
+This function returns information about the fringes of a window
+@var{window}. If @var{window} is omitted or @code{nil}, the selected
+window is used. The value has the form @code{(@var{left-width}
+@var{right-width} @var{outside-margins})}.
+@end defun
+
+@defvar overflow-newline-into-fringe
+If this is non-@code{nil}, 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.
+@end defvar
+
+@node Fringe Bitmaps
+@subsection Fringe Bitmaps
+@cindex fringe bitmaps
+@cindex bitmaps, fringe
+
+ The @dfn{fringe bitmaps} are tiny icons Emacs displays in the window
+fringe (on a graphic display) to indicate truncated or continued
+lines, buffer boundaries, overlay arrow, etc. 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} [@var{face}])} or
+@code{(right-fringe @var{bitmap} [@var{face}])} (@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.
+
+ These are the symbols identify the standard fringe bitmaps.
+Evaluate @code{(require 'fringe)} to define them. Fringe bitmap
+symbols have their own name space.
+
+@table @asis
+@item Truncation and continuation line bitmaps:
+@code{left-truncation}, @code{right-truncation},
+@code{continued-line}, @code{continuation-line}.
+
+@item Buffer indication bitmaps:
+@code{up-arrow}, @code{down-arrow},
+@code{top-left-angle}, @code{top-right-angle},
+@code{bottom-left-angle}, @code{bottom-right-angle},
+@code{left-bracket}, @code{right-bracket}.
+
+@item Empty line indication bitmap:
+@code{empty-line}.
+
+@item Overlay arrow bitmap:
+@code{overlay-arrow}.
+
+@item Bitmaps for displaying the cursor in right fringe:
+@code{filled-box-cursor}, @code{hollow-box-cursor}, @code{hollow-square},
+@code{bar-cursor}, @code{hbar-cursor}.
+@end table
+
+@defun 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 non-@code{nil} 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
+@var{window}.
+@end defun
+
+@node Customizing Bitmaps
+@subsection Customizing Fringe Bitmaps
+
+@defun 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 non-@code{nil} @var{height}. The width
+is normally 8, but you can specify a different width with non-@code{nil}
+@var{width}. 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}
+@var{periodic})} where @var{align} is interpreted as described above.
+If @var{periodic} is non-@code{nil}, it specifies that the rows in
+@code{bits} should be repeated enough times to reach the specified
+height.
+
+The return value on success is an integer identifying the new bitmap.
+You should save that integer in a variable so it can be used to select
+this bitmap.
+
+This function signals an error if there are no more free bitmap slots.
+@end defun
+
+@defun 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.
+@end defun
+
+@defun 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.
+
+@var{face} is merged with the @code{fringe} face, so normally
+@var{face} should specify only the foreground color.
+@end defun
+
+@node Overlay Arrow
+@subsection The Overlay Arrow
+@cindex overlay arrow
+
+ 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
+@dfn{overlays} (@pxref{Overlays}).
+
+@defvar 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.
+@end defvar
+
+@defvar 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 string is displayed only in the buffer that this marker
+points into. Thus, only one buffer can have an overlay arrow at any
+given time.
+@c !!! overlay-arrow-position: but the overlay string may remain in the display
+@c of some other buffer until an update is required. This should be fixed
+@c now. Is it?
+@end defvar
+
+ You can do a similar job by creating an overlay with a
+@code{before-string} property. @xref{Overlay Properties}.
+
+ You can define multiple overlay arrows via the variable
+@code{overlay-arrow-variable-list}.
+
+@defvar 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
+@code{overlay-arrow-position} has its normal meaning because it is on
+this list.
+@end defvar
+
+Each variable on this list can have properties
+@code{overlay-arrow-string} 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
+(@code{overlay-arrow-string} or @code{overlay-arrow-fringe-bitmap}) is
+used.
+
+@node Scroll Bars
+@section 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
+@code{scroll-bar-width} specifies how wide they are (@code{nil}
+meaning the default). @xref{Window Frame Parameters}.
+
+@defun frame-current-scroll-bars &optional frame
+This function reports the scroll bar type settings for frame
+@var{frame}. The value is a cons cell
+@code{(@var{vertical-type} .@: @var{horizontal-type})}, where
+@var{vertical-type} 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}.
+@end defun
+
+@vindex 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
+@code{left}, @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
+@code{set-window-scroll-bars} to specify what to do for a specific window:
+
+@defun set-window-scroll-bars window width &optional vertical-type horizontal-type
+This function sets the width and type of scroll bars for window
+@var{window}.
+
+@var{width} 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.
+@end defun
+
+@defun 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}
+@var{cols} @var{vertical-type} @var{horizontal-type})}. The value
+@var{width} 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.
+
+@var{horizontal-type} is not actually meaningful.
+@end defun
+
+If you don't specify these values for a window with
+@code{set-window-scroll-bars}, the buffer-local variables
+@code{scroll-bar-mode} and @code{scroll-bar-width} in the buffer being
+displayed control the window's vertical scroll bars. The function
+@code{set-window-buffer} 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.
+
+@defvar 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.
+@end defvar
+
+@defun 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
+@code{(@var{vertical-type} .@: @var{horizontal-type})}. Unlike
+@code{window-scroll-bars}, this reports the scroll bar type actually
+used, once frame defaults and @code{scroll-bar-mode} are taken into
+account.
+@end defun
+
+@defvar 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.
+@end defvar
+
+@node Pointer Shape
+@section Pointer Shape
+
+ Normally, the mouse pointer has the @code{text} shape over text and
+the @code{arrow} shape over window areas which do not correspond to
+any buffer text. You can specify the mouse pointer shape over text or
+images via the @code{pointer} text property, and for images with the
+@code{:pointer} and @code{:map} image properties.
+
+ The available pointer shapes are: @code{text} (or @code{nil}),
+@code{arrow}, @code{hand}, @code{vdrag}, @code{hdrag},
+@code{modeline}, and @code{hourglass}.
+
+@defvar void-text-area-pointer
+@tindex void-text-area-pointer
+This variable specifies the mouse pointer shape in void text areas,
+i.e. the areas after the end of a line or below the last line in the
+buffer. The default is to use the @code{arrow} (non-text) pointer.
+@end defvar
+
+@node Display Property
+@section The @code{display} Property
+@cindex display specification
+@kindex 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:
+
+@example
+(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))))
+@end example
+
+@noindent
+It gives each of the first ten characters in the buffer string
+@code{"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:
+
+@example
+(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))))
+@end example
+
+@noindent
+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
+@code{put-text-property} or from two different calls.
+
+ The rest of this section describes several kinds of
+display specifications and what they mean.
+
+@menu
+* 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.
+@end menu
+
+@node Specified Space
+@subsection Specified Spaces
+@cindex spaces, specified height or width
+@cindex specified spaces
+@cindex 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
+@var{props} 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:
+
+@table @code
+@item :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}).
+
+@item :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}.
+
+@item :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}).
+@end table
+
+ You should use one and only one of the above properties. You can
+also specify the height of the space, with these properties:
+
+@table @code
+@item :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}).
+
+@item :relative-height @var{factor}
+Specifies the height of the space, multiplying the ordinary height
+of the text having this display specification by @var{factor}.
+
+@item :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}).
+
+@end 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.
+
+@node Pixel Specification
+@subsection Pixel Specification for Spaces
+@cindex 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:
+
+@example
+@group
+ @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
+ @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} ::= + | -
+@end group
+@end example
+
+ 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
+@code{width} 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},
+@code{right-margin}, @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
+
+@example
+:align-to (+ left-margin (0.5 . left-margin))
+@end 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,
+@code{(2 . in)} specifies a width of 2 inches, while @code{(0.5 .
+@var{image})} 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.
+
+@node Other Display Specs
+@subsection Other Display Specifications
+
+ Here are the other sorts of display specifications that you can use
+in the @code{display} text property.
+
+@table @code
+@item @var{string}
+Display @var{string} instead of the text that has this property.
+
+@item (image . @var{image-props})
+This 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.
+
+@item (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
+@var{x} specify the top left corner of the slice, within the image;
+@var{width} 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.
+
+@item ((margin nil) @var{string})
+@itemx @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. This is a special case of marginal display
+(@pxref{Display Margins}).
+
+Recursive display specifications are not supported---string display
+specifications must not have @code{display} properties themselves.
+
+@item (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
+@var{factor} 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.
+
+@item (height @var{height})
+This display specification makes the text taller or shorter.
+Here are the possibilities for @var{height}:
+
+@table @asis
+@item @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.
+
+@item @code{(- @var{n})}
+This means to use a font that is @var{n} steps smaller.
+
+@item a number, @var{factor}
+A number, @var{factor}, means to use a font that is @var{factor} times
+as tall as the default font.
+
+@item 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.
+
+@item 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
+@code{height} bound to the current specified font height.
+@end table
+
+@item (raise @var{factor})
+This kind of display specification raises or lowers the text
+it applies to, relative to the baseline of the line.
+
+@var{factor} 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.
+@end table
+
+ You can make any display specification conditional. To do that,
+package it in another list of the form @code{(when @var{condition} .
+@var{spec})}. Then the specification @var{spec} applies only when
+@var{condition} evaluates to a non-@code{nil} value. During the
+evaluation, @code{object} is bound to the string or buffer having the
+conditional @code{display} property. @code{position} and
+@code{buffer-position} 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.
+
+@node Display Margins
+@subsection Displaying in the Margins
+@cindex display margins
+@cindex 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
+@code{(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:
+
+@defvar left-margin-width
+@tindex left-margin-width
+This variable specifies the width of the left margin.
+It is buffer-local in all buffers.
+@end defvar
+
+@defvar right-margin-width
+@tindex right-margin-width
+This variable specifies the width of the right margin.
+It is buffer-local in all buffers.
+@end 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
+@code{set-window-buffer}.
+
+ You can also set the margin widths immediately.
+
+@defun set-window-margins window left &optional right
+@tindex set-window-margins
+This function specifies the margin widths for window @var{window}.
+The argument @var{left} controls the left margin and
+@var{right} controls the right margin (default @code{0}).
+@end defun
+
+@defun window-margins &optional window
+@tindex window-margins
+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.
+@end defun
+
+@node Images
+@section Images
+@cindex 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 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
+@code{libungif} 4.1.0), Postscript, PBM, JPEG (requiring the
+@code{libjpeg} library version v6a), TIFF (requiring @code{libtiff}
+v3.4), and PNG (requiring @code{libpng} 1.0.2).
+
+ You specify one of these formats with an image type symbol. The image
+type symbols are @code{xbm}, @code{xpm}, @code{gif}, @code{postscript},
+@code{pbm}, @code{jpeg}, @code{tiff}, and @code{png}.
+
+@defvar image-types
+This variable contains a list of those image type symbols that are
+potentially supported in the current configuration.
+@emph{Potentially} 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
+@code{image-type-available-p}.
+@end defvar
+
+@defvar 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.
+@end defvar
+
+@defun image-type-available-p type
+@findex image-type-available-p
+
+This function returns non-@code{nil} 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
+@code{image-types}.
+
+For image types whose support libraries are statically linked, this
+function always returns @code{t}; for other image types, it returns
+@code{t} if the dynamic library could be loaded, @code{nil} otherwise.
+@end defun
@menu
-* Standard Faces:: The faces Emacs normally comes with.
-* Merging Faces:: How Emacs decides which face to use for a character.
-* Face Functions:: How to define and examine faces.
+* 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.
@end menu
-@node Standard Faces
-@subsection Standard Faces
+@node Image Descriptors
+@subsection Image Descriptors
+@cindex image descriptor
- This table lists all the standard faces and their uses.
+ 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.
-@table @code
-@item default
-@kindex default @r{(face name)}
-This face is used for ordinary text.
+ Every image descriptor must contain the property @code{:type
+@var{type}} 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.
-@item modeline
-@kindex modeline @r{(face name)}
-This face is used for mode lines and menu bars.
+ Here is a list of other properties that are meaningful for all image
+types:
-@item region
-@kindex region @r{(face name)}
-This face is used for highlighting the region in Transient Mark mode.
+@table @code
+@item :file @var{file}
+The @code{:file} property says to load the image from file
+@var{file}. If @var{file} is not an absolute file name, it is expanded
+in @code{data-directory}.
+
+@item :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,
+@code{: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}.
+
+@item :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.
+
+@item :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.
+
+@item :relief @var{relief}
+The @code{:relief} property, if non-@code{nil}, 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.
+
+@item :conversion @var{algorithm}
+The @code{:conversion} property, if non-@code{nil}, specifies a
+conversion algorithm that should be applied to the image before it is
+displayed; the value, @var{algorithm}, specifies which algorithm.
-@item secondary-selection
-@kindex secondary-selection @r{(face name)}
-This face is used to show any secondary selection you have made.
+@table @code
+@item laplace
+@itemx 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.
+
+@item (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:
+@iftex
+@tex
+$$\pmatrix{x-1/y-1 & x/y-1 & x+1/y-1 \cr
+ x-1/y & x/y & x+1/y \cr
+ x-1/y+1& x/y+1 & x+1/y+1 \cr}$$
+@end tex
+@end iftex
+@ifnottex
+@display
+ (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)
+@end display
+@end 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
+@iftex
+@tex
+$$\pmatrix{1 & 0 & 0 \cr
+ 0& 0 & 0 \cr
+ 9 & 9 & -1 \cr}$$
+@end tex
+@end iftex
+@ifnottex
+@display
+ (1 0 0
+ 0 0 0
+ 9 9 -1)
+@end display
+@end ifnottex
+
+Emboss edge-detection uses a matrix of
+@iftex
+@tex
+$$\pmatrix{ 2 & -1 & 0 \cr
+ -1 & 0 & 1 \cr
+ 0 & 1 & -2 \cr}$$
+@end tex
+@end iftex
+@ifnottex
+@display
+ ( 2 -1 0
+ -1 0 1
+ 0 1 -2)
+@end display
+@end ifnottex
+
+@item disabled
+Specifies transforming the image so that it looks ``disabled''.
+@end table
-@item highlight
-@kindex highlight @r{(face name)}
-This face is meant to be used for highlighting for various purposes.
+@item :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,
+@var{bg} 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}.
+
+@item :pointer @var{shape}
+This specifies the pointer shape when the mouse pointer is over this
+image. @xref{Pointer Shape}, for available pointer shapes.
+
+@item :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
+@code{(@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
+@code{(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
+@code{(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
+@code{(poly . [@var{x0} @var{y0} @var{x1} @var{y1} ...])}
+where each pair in the vector describes one corner in the polygon.
+
+When the mouse pointer is above a hot-spot area of an image, the
+@var{plist} of that hot-spot is consulted; if it contains a @code{help-echo}
+property it defines a tool-tip for the hot-spot, and if it contains
+a @code{pointer} property, it defines the shape of the mouse cursor when
+it is over the hot-spot.
+@xref{Pointer 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
+@var{id} is @code{area4}.
+@end table
-@item underline
-@kindex underline @r{(face name)}
-This face underlines text.
+@defun image-mask-p spec &optional frame
+@tindex image-mask-p
+This function returns @code{t} if image @var{spec} has a mask bitmap.
+@var{frame} is the frame on which the image will be displayed.
+@var{frame} @code{nil} or omitted means to use the selected frame
+(@pxref{Input Focus}).
+@end defun
-@item bold
-@kindex bold @r{(face name)}
-This face uses a bold font, if possible. It uses the bold variant of
-the frame's font, if it has one. It's up to you to choose a default
-font that has a bold variant, if you want to use one.
+@node XBM Images
+@subsection XBM Images
+@cindex XBM
-@item italic
-@kindex italic @r{(face name)}
-This face uses the italic variant of the frame's font, if it has one.
+ 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.
-@item bold-italic
-@kindex bold-italic @r{(face name)}
-This face uses the bold italic variant of the frame's font, if it has
-one.
+ Additional image properties supported for the @code{xbm} image type are:
+
+@table @code
+@item :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.
+
+@item :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.
@end table
-@node Merging Faces
-@subsection Merging Faces for Display
+ If you specify an XBM image using data within Emacs instead of an
+external file, use the following three properties:
- Here are all the ways to specify which face to use for display of text:
+@table @code
+@item :data @var{data}
+The value, @var{data}, specifies the contents of the image.
+There are three formats you can use for @var{data}:
@itemize @bullet
@item
-With defaults. Each frame has a @dfn{default face}, whose id number is
-zero, which is used for all text that doesn't somehow specify another
-face.
-
-@item
-With text properties. A character may have a @code{face} property; if so,
-it's displayed with that face. @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.
+A vector of strings or bool-vectors, each specifying one line of the
+image. Do specify @code{:height} and @code{:width}.
@item
-With overlays. An overlay may have @code{face} and @code{mouse-face}
-properties too; they apply to all the text covered by the overlay.
+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.
@item
-With special glyphs. Each glyph can specify a particular face id
-number. @xref{Glyphs}.
+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
+@code{: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.
@end itemize
- If these various sources together specify more than one face for a
-particular character, Emacs merges the attributes of the various faces
-specified. The attributes of the faces of special glyphs come first;
-then come attributes of faces from overlays, followed by those from text
-properties, and last the default face.
+@item :width @var{width}
+The value, @var{width}, specifies the width of the image, in pixels.
- When multiple overlays cover one character, an overlay with higher
-priority overrides those with lower priority. @xref{Overlays}.
+@item :height @var{height}
+The value, @var{height}, specifies the height of the image, in pixels.
+@end table
- If an attribute such as the font or a color is not specified in any of
-the above ways, the frame's own font or color is used.
+@node XPM Images
+@subsection XPM Images
+@cindex XPM
-@node Face Functions
-@subsection Functions for Working with Faces
+ 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:
- The attributes a face can specify include the font, the foreground
-color, the background color, and underlining. The face can also leave
-these unspecified by giving the value @code{nil} for them.
+@table @code
+@item :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.
+@end table
- Here are the primitives for creating and changing faces.
+@node GIF Images
+@subsection GIF Images
+@cindex GIF
-@defun 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
-@var{name}.
+ For GIF images, specify image type @code{gif}.
+
+@table @code
+@item :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.
+@end table
+
+@ignore
+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)))
+@end ignore
+
+@node Postscript Images
+@subsection Postscript Images
+@cindex 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:
+
+@table @code
+@item :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.
+
+@item :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.
+
+@item :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
+@samp{BoundingBox} comment found in Postscript files.
+
+@example
+%%BoundingBox: 22 171 567 738
+@end example
+@end 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.
+
+@node Other Image Types
+@subsection Other Image Types
+@cindex 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.
+
+@table @code
+@item :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.
+
+@item :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.
+@end 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}.
+
+@node Defining Images
+@subsection Defining Images
+
+ The functions @code{create-image}, @code{defimage} and
+@code{find-image} provide convenient ways to create image descriptors.
+
+@defun create-image file-or-data &optional type data-p &rest props
+@tindex create-image
+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, non-@code{nil} 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,
+
+@example
+(create-image "foo.xpm" 'xpm nil :heuristic-mask t)
+@end example
+
+The function returns @code{nil} if images of this type are not
+supported. Otherwise it returns an image descriptor.
@end defun
-@defun face-list
-This function returns a list of all defined face names.
+@defmac defimage symbol specs &optional doc
+@tindex defimage
+This macro defines @var{symbol} as an image name. The arguments
+@var{specs} 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
+@code{:file} or the @code{:data} property. The value of @code{:type}
+should be a symbol specifying the image type, the value of
+@code{:file} is the file to load the image from, and the value of
+@code{:data} is a string containing the actual image data. Here is an
+example:
+
+@example
+(defimage test-image
+ ((:type xpm :file "~/test1.xpm")
+ (:type xbm :file "~/test1.xbm")))
+@end example
+
+@code{defimage} 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}.
+@end defmac
+
+@defun find-image specs
+@tindex find-image
+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 @w{@code{:file @var{file}}}
+or @w{@code{: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
+@var{file} 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 first on @code{load-path} and then in
+@code{data-directory}.
@end defun
-@defun copy-face old-face new-name &optional frame new-frame
-This function defines the face @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.
+@node Showing Images
+@subsection 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.
+
+@defun 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
+@code{defimage}. The argument @var{string} specifies the text to put
+in the buffer to hold the image. If it is omitted or @code{nil},
+@code{insert-image} 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;
+@code{right-margin} specifies the right margin. If @var{area} is
+@code{nil} 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
+@var{slice} is @code{nil} or omitted the whole image is inserted.
+Otherwise, @var{slice} is a list @code{(@var{x} @var{y} @var{width}
+@var{height})} which specifies the @var{x} and @var{y} positions and
+@var{width} 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}.
+@end defun
-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.
+@defun insert-sliced-image image &optional string area rows cols
+This function inserts @var{image} in the current buffer at point, like
+@code{insert-image}, but splits the image into @var{rows}x@var{cols}
+equally sized slices.
+@end defun
-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}.
+@defun 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;
+@code{right-margin} specifies the right margin. If @var{area} is
+@code{nil} or omitted, the image is displayed at point within the
+buffer's text.
+
+Internally, this function creates an overlay, and gives it a
+@code{before-string} property containing text that has a @code{display}
+property whose value is the image. (Whew!)
@end defun
- You can modify the attributes of an existing face with the following
-functions. If you specify @var{frame}, they affect just that frame;
-otherwise, they affect all frames as well as the defaults that apply to
-new frames.
+@defun remove-images start end &optional buffer
+This function removes images in @var{buffer} between positions
+@var{start} and @var{end}. If @var{buffer} is omitted or @code{nil},
+images are removed from the current buffer.
-@defun set-face-foreground face color &optional frame
-@defunx set-face-background face color &optional frame
-These functions set the foreground (respectively, background) color of
-face @var{face} to @var{color}. The argument @var{color} should be a
-string, the name of a color.
+This removes only images that were put into @var{buffer} the way
+@code{put-image} does it, not images that were inserted with
+@code{insert-image} or in other ways.
@end defun
-@defun set-face-font face font &optional frame
-This function sets the font of face @var{face}. The argument @var{font}
-should be a string.
+@defun image-size spec &optional pixels frame
+@tindex image-size
+This function returns the size of an image as a pair
+@w{@code{(@var{width} . @var{height})}}. @var{spec} is an image
+specification. @var{pixels} non-@code{nil} 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.
+@var{frame} null or omitted means use the selected frame (@pxref{Input
+Focus}).
@end defun
-@defun set-face-underline-p face underline-p &optional frame
-This function sets the underline attribute of face @var{face}.
-Non-@code{nil} means do underline; @code{nil} means don't.
+@node Image Cache
+@subsection Image Cache
+
+ Emacs stores images in an image cache when it displays them, so it can
+display them again more efficiently. It removes an image from the cache
+when it hasn't been displayed for a specified period of time.
+
+When an image is looked up in the cache, its specification is compared
+with cached image specifications using @code{equal}. This means that
+all images with equal specifications share the same image in the cache.
+
+@defvar image-cache-eviction-delay
+@tindex 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.
+@end defvar
+
+@defun clear-image-cache &optional frame
+@tindex clear-image-cache
+This function clears the image cache. If @var{frame} is non-@code{nil},
+only the cache for that frame is cleared. Otherwise all frames' caches
+are cleared.
@end defun
-@defun invert-face face &optional frame
-Swap the foreground and background colors of face @var{face}. If the
-face doesn't specify both foreground and background, then its foreground
-and background are set to the default background and foreground.
+@node Buttons
+@section Buttons
+@cindex buttons
+@cindex buttons in buffers
+@cindex 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 the 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).
+
+@menu
+* 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.
+@end menu
+
+@node Button Properties
+@subsection Button Properties
+@cindex 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:
+
+@table @code
+@item action
+@kindex 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.
+
+@item mouse-action
+@kindex 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.
+
+@item face
+@kindex 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.
+
+@item mouse-face
+@kindex 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.
+
+@item keymap
+@kindex 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
+@key{mouse-2} to invoke the button.
+
+@item type
+@kindex type @r{(button property)}
+The button-type of the button. When creating a button, this is
+usually specified using the @code{:type} keyword argument.
+@xref{Button Types}.
+
+@item help-echo
+@kindex help-index @r{(button property)}
+A string displayed by the Emacs tool-tip help system; by default,
+@code{"mouse-2, RET: Push this button"}.
+
+@item follow-link
+@kindex 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}.
+
+@item button
+@kindex button @r{(button property)}
+All buttons have a non-@code{nil} @code{button} property, which may be useful
+in finding regions of text that comprise buttons (which is what the
+standard button functions do).
+@end table
+
+ There are other properties defined for the regions of text in a
+button, but these are not generally interesting for typical uses.
+
+@node Button Types
+@subsection Button Types
+@cindex 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.
+
+@defun define-button-type name &rest properties
+@tindex define-button-type
+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
+@var{name} is defined; subsequent changes to a supertype are not
+reflected in its subtypes.
@end defun
- These functions examine the attributes of a face. If you don't
-specify @var{frame}, they refer to the default data for new frames.
+ 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.
+
+@node Making Buttons
+@subsection Making Buttons
+@cindex 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 also insert the button text,
+called @code{insert-...button}.
+
+ The button-creation functions all take the @code{&rest} argument
+@var{properties}, 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:
+
+@defun make-button beg end &rest properties
+@tindex make-button
+This makes a button from @var{beg} to @var{end} in the
+current buffer, and returns it.
+@end defun
-@defun face-foreground face &optional frame
-@defunx face-background face &optional frame
-These functions return the foreground (respectively, background) color
-of face @var{face}, as a string.
+@defun insert-button label &rest properties
+@tindex insert-button
+This insert a button with the label @var{label} at point,
+and returns it.
@end defun
-@defun face-font face &optional frame
-This function returns the name of the font of face @var{face}.
+ 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:
+
+@defun make-text-button beg end &rest properties
+@tindex make-text-button
+This makes a button from @var{beg} to @var{end} in the current buffer, using
+text properties.
@end defun
-@defun face-underline-p face &optional frame
-This function returns the underline attribute of face @var{face}.
+@defun insert-text-button label &rest properties
+@tindex insert-text-button
+This inserts a button with the label @var{label} at point, using text
+properties.
+@end defun
+
+@node Manipulating Buttons
+@subsection Manipulating Buttons
+@cindex 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.
+
+@defun button-start button
+@tindex button-start
+Return the position at which @var{button} starts.
@end defun
-@defun face-id-number face
-This function returns the face id number of face @var{face}.
+@defun button-end button
+@tindex button-end
+Return the position at which @var{button} ends.
@end defun
-@defun face-equal face1 face2 &optional frame
-This returns @code{t} if the faces @var{face1} and @var{face2} have the
-same attributes for display.
+@defun button-get button prop
+@tindex button-get
+Get the property of button @var{button} named @var{prop}.
@end defun
-@defun face-differs-from-default-p face &optional frame
-This returns @code{t} if the face @var{face} displays differently from
-the default face. A face is considered to be ``the same'' as the normal
-face if each attribute is either the same as that of the default face or
-@code{nil} (meaning to inherit from the default).
+@defun button-put button prop val
+@tindex button-put
+Set @var{button}'s @var{prop} property to @var{val}.
@end defun
-@defvar region-face
-This variable's value specifies the face id to use to display characters
-in the region when it is active (in Transient Mark mode only). The face
-thus specified takes precedence over all faces that come from text
-properties and overlays, for characters in the region. @xref{The Mark},
-for more information about Transient Mark mode.
+@defun button-activate button &optional use-mouse-action
+@tindex button-activate
+Call @var{button}'s @code{action} property (i.e., invoke it). If
+@var{use-mouse-action} is non-@code{nil}, try to invoke the button's
+@code{mouse-action} property instead of @code{action}; if the button
+has no @code{mouse-action} property, use @code{action} as normal.
+@end defun
-Normally, the value is the id number of the face named @code{region}.
-@end defvar
+@defun button-label button
+@tindex button-label
+Return @var{button}'s text label.
+@end defun
+
+@defun button-type button
+@tindex button-type
+Return @var{button}'s button-type.
+@end defun
+
+@defun button-has-type-p button type
+@tindex button-has-type-p
+Return @code{t} if @var{button} has button-type @var{type}, or one of
+@var{type}'s subtypes.
+@end defun
+
+@defun button-at pos
+@tindex button-at
+Return the button at position @var{pos} in the current buffer, or @code{nil}.
+@end defun
+
+@defun button-type-put type prop val
+@tindex button-type-put
+Set the button-type @var{type}'s @var{prop} property to @var{val}.
+@end defun
+
+@defun button-type-get type prop
+@tindex button-type-get
+Get the property of button-type @var{type} named @var{prop}.
+@end defun
+
+@defun button-type-subtype-p type supertype
+@tindex button-type-subtype-p
+Return @code{t} if button-type @var{type} is a subtype of @var{supertype}.
+@end defun
+
+@node Button Buffer Commands
+@subsection Button Buffer Commands
+@cindex button buffer commands
+
+These are commands and functions for locating and operating on
+buttons in an Emacs buffer.
+
+@code{push-button} 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
+@code{forward-button} 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 non-@code{nil} @code{follow-link} property, and
+@var{mouse-1-click-follows-link} is set, a quick @key{Mouse-1} click
+will also activate the @code{push-button} command.
+@xref{Links and Mouse-1}.
+
+@deffn Command push-button &optional pos use-mouse-action
+@tindex push-button
+Perform the action specified by a button at location @var{pos}.
+@var{pos} may be either a buffer position or a mouse-event. If
+@var{use-mouse-action} is non-@code{nil}, or @var{pos} is a
+mouse-event (@pxref{Mouse Events}), try to invoke the button's
+@code{mouse-action} property instead of @code{action}; if the button
+has no @code{mouse-action} property, use @code{action} as normal.
+@var{pos} 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}.
+@end deffn
+
+@deffn Command forward-button n &optional wrap display-message
+@tindex forward-button
+Move to the @var{n}th next button, or @var{n}th previous button if
+@var{n} is negative. If @var{n} is zero, move to the start of any
+button at point. If @var{wrap} is non-@code{nil}, moving past either
+end of the buffer continues from the other end. If
+@var{display-message} is non-@code{nil}, the button's help-echo string
+is displayed. Any button with a non-@code{nil} @code{skip} property
+is skipped over. Returns the button found.
+@end deffn
+
+@deffn Command backward-button n &optional wrap display-message
+@tindex backward-button
+Move to the @var{n}th previous button, or @var{n}th next button if
+@var{n} is negative. If @var{n} is zero, move to the start of any
+button at point. If @var{wrap} is non-@code{nil}, moving past either
+end of the buffer continues from the other end. If
+@var{display-message} is non-@code{nil}, the button's help-echo string
+is displayed. Any button with a non-@code{nil} @code{skip} property
+is skipped over. Returns the button found.
+@end deffn
+
+@defun next-button pos &optional count-current
+@tindex next-button
+Return the next button after position @var{pos} in the current buffer.
+If @var{count-current} is non-@code{nil}, count any button at
+@var{pos} in the search, instead of starting at the next button.
+@end defun
+
+@defun previous-button pos &optional count-current
+@tindex previous-button
+Return the @var{n}th button before position @var{pos} in the current
+buffer. If @var{count-current} is non-@code{nil}, count any button at
+@var{pos} in the search, instead of starting at the next button.
+@end defun
@node Blinking
@section Blinking Parentheses
This section describes the mechanism by which Emacs shows a matching
open parenthesis when the user inserts a close parenthesis.
-@vindex blink-paren-hook
@defvar 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.
-
-@quotation
-@strong{Please note:} this variable was named @code{blink-paren-hook} in
-older Emacs versions, but since it is not called with the standard
-convention for hooks, it was renamed to @code{blink-paren-function} in
-version 19.
-@end quotation
@end defvar
-@defvar blink-matching-paren
+@defopt blink-matching-paren
If this variable is @code{nil}, then @code{blink-matching-open} does
nothing.
-@end defvar
+@end defopt
-@defvar blink-matching-paren-distance
+@defopt blink-matching-paren-distance
This variable specifies the maximum distance to scan for a matching
parenthesis before giving up.
-@end defvar
+@end defopt
+
+@defopt 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.
+@end defopt
-@defun blink-matching-open
+@deffn 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
(blink-matching-open)))
@end group
@end smallexample
-@end defun
+@end deffn
@node Inverse Video
@section Inverse Video
@end defopt
@defopt mode-line-inverse-video
-This variable controls the use of inverse video for mode lines. If it
-is non-@code{nil}, then mode lines are displayed in inverse video (under
-X, this uses the face named @code{modeline}, which you can set as you
-wish). Otherwise, mode lines are displayed normally, just like text.
-The default is @code{t}.
+This variable controls the use of inverse video for mode lines and
+menu bars. If it is non-@code{nil}, then these lines are displayed in
+the face @code{mode-line}. Otherwise, these lines are displayed
+normally, just like other text. The default is @code{t}.
@end defopt
@node Usual Display
@item
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 is
+of two ways according to the value of @code{ctl-arrow}. If it is
non-@code{nil}, these codes map to sequences of two glyphs, where the
-first glyph is the @sc{ASCII} code for @samp{^}. (A display table can
+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 non-@acronym{ASCII} characters
+that the MS-DOS terminal doesn't support. @xref{MS-DOS and MULE,,,
+emacs, The GNU Emacs Manual}.
+
@item
Character codes 128 through 255 map to sequences of four glyphs, where
-the first glyph is the @sc{ASCII} code for @samp{\}, and the others are
-digit characters representing the code in octal. (A display table can
-specify a glyph to use instead of @samp{\}.)
+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{\}.)
+
+@item
+Multibyte character codes above 256 are displayed as themselves, or as a
+question mark or empty box if the terminal cannot display that
+character.
@end itemize
The usual display conventions apply even when there is a display
table, for any character whose entry in the active display table is
@code{nil}. Thus, when you set up a display table, you need only
-specify the the characters for which you want unusual behavior.
+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.
+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
+@code{force-mode-line-update} (@pxref{Mode Line Format}).
@defopt ctl-arrow
@cindex control characters in display
@defopt tab-width
The value of this variable is the spacing between tab stops used for
-displaying tab characters in Emacs buffers. The default is 8. Note
-that this feature is completely independent from the user-settable tab
-stops used by the command @code{tab-to-tab-stop}. @xref{Indent Tabs}.
+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}.
+@end defopt
+
+@defopt indicate-empty-lines
+@tindex indicate-empty-lines
+@cindex fringes, and empty line indication
+When this is non-@code{nil}, Emacs displays a special glyph in the
+fringe of each empty line at the end of the buffer, on terminals that
+support it (window systems). @xref{Fringes}.
@end defopt
+@defvar 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 four kinds of basic values:
+
+@table @asis
+@item @code{nil}
+Don't display the icons.
+@item @code{left}
+Display them in the left fringe.
+@item @code{right}
+Display them in the right fringe.
+@item @var{anything-else}
+Display the icon at the top of the window top in the left fringe, and other
+in the right fringe.
+@end table
+
+If value is a cons @code{(@var{angles} . @var{arrows})}, @var{angles}
+controls the angle icons, and @var{arrows} controls the arrows. Both
+@var{angles} and @var{arrows} work according to the table above.
+Thus, @code{(t . right)} places the top angle icon in the left
+fringe, the bottom angle icon in the right fringe, and both arrows in
+the right fringe.
+@end defvar
+
+@defvar default-indicate-buffer-boundaries
+The value of this variable is the default value for
+@code{indicate-buffer-boundaries} in buffers that do not override it.
+@end defvar
+
@node Display Tables
@section Display Tables
@cindex display table
-You can use the @dfn{display table} feature to control how all 256
-possible character codes display on the screen. This is useful for
-displaying European languages that have letters not in the @sc{ASCII}
-character set.
+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
-@dfn{glyphs}, each glyph being an image that takes up one character
+@dfn{glyphs}, 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
+@code{force-mode-line-update} (@pxref{Mode Line Format}).
+
@menu
-* 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.
-* ISO Latin 1:: How to use display tables
- to support the ISO Latin 1 character set.
+* 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.
@end menu
@node Display Table Format
@subsection Display Table Format
- A display table is actually an array of 261 elements.
+ A display table is actually a char-table (@pxref{Char-Tables}) with
+@code{display-table} as its subtype.
@defun make-display-table
This creates and returns a display table. The table initially has
@code{nil} in all elements.
@end defun
- The first 256 elements correspond to character codes; the @var{n}th
-element says how to display the character code @var{n}. The value
-should be @code{nil} or a vector of glyph values (@pxref{Glyphs}). If
-an element is @code{nil}, it says to display that character according to
-the usual display conventions (@pxref{Usual Display}).
+ 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 glyph
+values (@pxref{Glyphs}). If an element is @code{nil}, it says to
+display that character according to the usual display conventions
+(@pxref{Usual Display}).
+
+ If you use the display table to change the display of newline
+characters, the whole buffer will be displayed as one long ``line.''
- The remaining five elements of a display table serve special purposes,
-and @code{nil} means use the default stated below.
+ 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.
@table @asis
-@item 256
+@item 0
The glyph for the end of a truncated screen line (the default for this
-is @samp{$}). @xref{Glyphs}.
-@item 257
+is @samp{$}). @xref{Glyphs}. On graphical terminals, Emacs uses
+arrows in the fringes to indicate truncation, so the display table has
+no effect.
+
+@item 1
The glyph for the end of a continued line (the default is @samp{\}).
-@item 258
+On graphical terminals, Emacs uses curved arrows in the fringes to
+indicate continuation, so the display table has no effect.
+
+@item 2
The glyph for indicating a character displayed as an octal character
code (the default is @samp{\}).
-@item 259
+
+@item 3
The glyph for indicating a control character (the default is @samp{^}).
-@item 260
+
+@item 4
A vector of glyphs for indicating the presence of invisible lines (the
default is @samp{...}). @xref{Selective Display}.
+
+@item 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.
@end table
For example, here is how to construct a display table that mimics the
(aset disptab 127 (vector ?^ ??)))
@end example
+@defun display-table-slot display-table slot
+This function returns the value of the extra slot @var{slot} of
+@var{display-table}. The argument @var{slot} may be a number from 0 to
+5 inclusive, or a slot name (symbol). Valid symbols are
+@code{truncation}, @code{wrap}, @code{escape}, @code{control},
+@code{selective-display}, and @code{vertical-border}.
+@end defun
+
+@defun set-display-table-slot display-table slot value
+This function stores @var{value} in the extra slot @var{slot} of
+@var{display-table}. The argument @var{slot} may be a number from 0 to
+5 inclusive, or a slot name (symbol). Valid symbols are
+@code{truncation}, @code{wrap}, @code{escape}, @code{control},
+@code{selective-display}, and @code{vertical-border}.
+@end defun
+
+@defun describe-display-table display-table
+@tindex describe-display-table
+This function displays a description of the display table
+@var{display-table} in a help buffer.
+@end defun
+
+@deffn Command describe-current-display-table
+@tindex describe-current-display-table
+This command displays a description of the current display table in a
+help buffer.
+@end deffn
+
@node Active Display Table
@subsection Active Display Table
@cindex active display table
table if any. The display table chosen is called the @dfn{active}
display table.
-@defun window-display-table window
+@defun 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.
+if @var{window} does not have an assigned display table. The default
+for @var{window} is the selected window.
@end defun
@defun set-window-display-table window table
@end defun
@defvar buffer-display-table
-This variable is automatically local in all buffers; its value in a
-particular buffer is the display table for that buffer, or @code{nil} if
-the buffer does not have an assigned 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.
@end defvar
@defvar standard-display-table
@end defvar
If there is no display table to use for a particular window---that is,
-if the window has none, its buffer has none, and
-@code{standard-display-table} has none---then Emacs uses the usual
+if the window specifies none, its buffer specifies none, and
+@code{standard-display-table} 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}.
+
@node Glyphs
@subsection Glyphs
@cindex 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. Glyphs
-are represented in Lisp as integers, just as characters are.
-
-@cindex glyph table
- The meaning of each integer, as a glyph, is defined by the glyph
-table, which is the value of the variable @code{glyph-table}.
+are represented in Lisp as integers, just as characters are. Normally
+Emacs finds glyphs in the display table (@pxref{Display Tables}).
+
+ A glyph can be @dfn{simple} or it can be defined by the @dfn{glyph
+table}. A simple glyph is just a way of specifying a character and a
+face to output it in. The glyph code for a simple glyph, mod 524288,
+is the character to output, and the glyph code divided by 524288
+specifies the face number (@pxref{Face Functions}) to use while
+outputting it. (524288 is
+@ifnottex
+2**19.)
+@end ifnottex
+@tex
+$2^{19}$.)
+@end tex
+@xref{Faces}.
+
+ On character terminals, you can set up a @dfn{glyph table} to define
+the meaning of glyph codes. The glyph codes is the value of the
+variable @code{glyph-table}.
@defvar glyph-table
The value of this variable is the current glyph table. It should be a
-vector; the @var{g}th element defines glyph code @var{g}. If the value
-is @code{nil} instead of a vector, then all glyphs are simple (see
-below).
+vector; the @var{g}th element defines glyph code @var{g}.
+
+If a glyph code is greater than or equal to the length of the glyph
+table, that code is automatically simple. If the value of
+@code{glyph-table} is @code{nil} instead of a vector, then all glyphs
+are simple. The glyph table is not used on graphical displays, only
+on character terminals. On graphical displays, all glyphs are simple.
@end defvar
Here are the possible types of elements in the glyph table:
-@table @var
-@item string
+@table @asis
+@item @var{string}
Send the characters in @var{string} to the terminal to output
this glyph. This alternative is available on character terminals,
-but not under X.
+but not under a window system.
-@item integer
-Define this glyph code as an alias for code @var{integer}. You can use
-an alias to specify a face code for the glyph; see below.
+@item @var{integer}
+Define this glyph code as an alias for glyph code @var{integer}. You
+can use an alias to specify a face code for the glyph and use a small
+number as its code.
@item @code{nil}
-This glyph is simple. On an ordinary terminal, the glyph code mod 256
-is the character to output. With X, the glyph code mod 256 is the
-character to output, and the glyph code divided by 256 specifies the
-@dfn{face id number} to use while outputting it. @xref{Faces}.
+This glyph is simple.
@end table
- If a glyph code is greater than or equal to the length of the glyph
-table, that code is automatically simple.
-
-@node ISO Latin 1
-@subsection ISO Latin 1
-
-If you have a terminal that can handle the entire ISO Latin 1 character
-set, you can arrange to use that character set as follows:
-
-@example
-(require 'disp-table)
-;; @r{Set char codes 160--255 to display as themselves.}
-;; @r{(Codes 128--159 are the additional control characters.)}
-(standard-display-8bit 160 255)
-@end example
-
-If you are editing buffers written in the ISO Latin 1 character set and
-your terminal doesn't handle anything but @sc{ASCII}, you can load the file
-@file{iso-ascii} to set up a display table which makes the other ISO
-characters display as sequences of @sc{ASCII} characters. For example, the
-character ``o with umlaut'' displays as @samp{@{"o@}}.
-
-Some European countries have terminals that don't support ISO Latin 1
-but do support the special characters for that country's language. You
-can define a display table to work one language using such terminals.
-For an example, see @file{lisp/iso-swed.el}, which handles certain
-Swedish terminals.
-
-You can load the appropriate display table for your terminal
-automatically by writing a terminal-specific Lisp file for the terminal
-type.
+@defun create-glyph string
+@tindex create-glyph
+This function returns a newly-allocated glyph code which is set up to
+display by sending @var{string} to the terminal.
+@end defun
@node Beeping
@section Beeping
@cindex beeping
@cindex bell
- You can make Emacs ring a 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 beeping alone
-when signaling an error is appropriate. (@xref{Errors}.)
+ 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}.)
-@defun ding &optional dont-terminate
+@defun ding &optional do-not-terminate
@cindex keyboard macro termination
This function beeps, or flashes the screen (see @code{visible-bell} below).
It also terminates any keyboard macro currently executing unless
-@var{dont-terminate} is non-@code{nil}.
+@var{do-not-terminate} is non-@code{nil}.
@end defun
-@defun beep &optional dont-terminate
+@defun beep &optional do-not-terminate
This is a synonym for @code{ding}.
@end defun
-@defvar visible-bell
+@defopt visible-bell
This variable determines whether Emacs should flash the screen to
represent a bell. Non-@code{nil} means yes, @code{nil} means no. This
-is effective only if the Termcap entry for the terminal in use has the
-visible bell flag (@samp{vb}) set.
+is effective on a window system, and on a character-only terminal
+provided the terminal's Termcap entry defines the visible bell
+capability (@samp{vb}).
+@end defopt
+
+@defvar ring-bell-function
+If this is non-@code{nil}, it specifies how Emacs should ``ring the
+bell.'' Its value should be a function of no arguments. If this is
+non-@code{nil}, it takes precedence over the @code{visible-bell}
+variable.
@end defvar
@node Window Systems
concerned; the individual Emacs windows are not known to X at all.
@defvar window-system
-@cindex X Window System
This variable tells Lisp programs what window system Emacs is running
-under. Its value should be a symbol such as @code{x} (if Emacs is
-running under X) or @code{nil} (if Emacs is running on an ordinary
-terminal).
-@end defvar
+under. The possible values are
-@defvar window-system-version
-This variable distinguishes between different versions of the X Window
-System. Its value is 10 or 11 when using X; @code{nil} otherwise.
+@table @code
+@item x
+@cindex X Window System
+Emacs is displaying using X.
+@item pc
+Emacs is displaying using MS-DOS.
+@item w32
+Emacs is displaying using Windows.
+@item mac
+Emacs is displaying using a Macintosh.
+@item nil
+Emacs is using a character-based terminal.
+@end table
@end defvar
@defvar window-setup-hook
-This variable is a normal hook which Emacs runs after loading your
-@file{.emacs} file and the default initialization file (if any), after
-loading terminal-specific Lisp code, and after running the 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
@code{term-setup-hook}.
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.
@end defvar
+
+@ignore
+ arch-tag: ffdf5714-7ecf-415b-9023-fbc6b409c2c6
+@end ignore