@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
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/display
-@node Display, Calendar, System Interface, Top
+@node Display, Calendar, 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.
+* Invisible Text:: Hiding part of the buffer text.
+* Selective Display:: Hiding part of the buffer text (the old way).
* Overlay Arrow:: Display of an arrow to indicate position.
* 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.
+* Width:: How wide a character or string is on the screen.
+* Faces:: A face defines a graphics style for text characters:
+ font, colors, etc.
+* Display Property:: Enabling special display features.
+* Images:: Displaying images in 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.
@section Refreshing the Screen
The function @code{redraw-frame} redisplays the entire contents of a
-given frame. @xref{Frames}.
+given frame (@pxref{Frames}).
@c Emacs 19 feature
@defun redraw-frame frame
This function clears and redisplays all visible frames.
@end deffn
+ 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
@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
-
- The screen size functions access or specify the height or width of
-the terminal. When you are using multiple frames, they apply to the
-selected frame (@pxref{Frames}).
-
-@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
+@node Forcing Redisplay
+@section Forcing Redisplay
+@cindex forcing redisplay
+
+ Emacs redisplay normally stops if input arrives, and does not happen
+at all if input is available before it starts. Most of the time, this
+is exactly what you want. However, you can prevent preemption by
+binding @code{redisplay-dont-pause} to a non-@code{nil} value.
+
+@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. This feature is available
+as of Emacs 21.
+@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}.)
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.
+
+ You can override the glyphs that indicate continuation or truncation
+using the display table; see @ref{Display Tables}.
+
+ 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
+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
follows:
@defun message string &rest arguments
-This function prints a one-line message in the echo area. The
+This function displays a one-line 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
on the conversion specifications. @code{message} returns the
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.
@example
@group
---------- 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}.
+@end defun
+
+@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 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}).
+
+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.
+
+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.
+
+@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
+Add the element @var{element} to @code{buffer-invisibility-spec}
+(if it is not already present in that list).
+@end defun
+
+@defun remove-from-invisibility-spec element
+Remove the element @var{element} from @code{buffer-invisibility-spec}.
+This does nothing if @var{element} is not in the list.
+@end defun
+
+ One convention about the 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, commands 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}, but only because
+they are explicitly programmed to do so.
+
+ 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.
+a Lisp program: it controls which lines are hidden by altering the text.
+The invisible text feature (@pxref{Invisible Text}) has partially
+replaced this feature.
+
+ In the second variant, the choice of lines to hide is made
+automatically based on indentation. This variant is designed to be a
+user-level feature.
The way you control explicit selective display is by replacing a
newline (control-j) with a carriage return (control-m). The text that
@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 invisible 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
@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. The arrow text
+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
@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}.
+
@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.
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
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 help 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 help buffer. When the hook runs, the help 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
+still 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 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.
+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.
@menu
* Overlay Properties:: How to read and set properties.
What properties do to the screen display.
-* Managing Overlays:: Creating, moving, finding overlays.
+* Managing Overlays:: Creating and moving 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.
+ 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. 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 property
+changes, overlay changes are not recorded in the buffer's undo list.
+@xref{Text Properties}, for comparison.
+
+ These functions are used 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 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
+
+ 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
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 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.
+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
+Starting in Emacs 21, 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. This feature may be temporary, like
-@code{face}.
+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 narror, or replaced with an image.
+@xref{Display Property}.
+
+@item help-echo
+@kindex help-echo @r{(text 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}. This feature is available starting in Emacs 21.
@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
+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
-if text is inserted right at the beginning of the overlay.
+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 if text is
-inserted right at the end of the overlay.
+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)}
-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.
+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. This is not yet implemented, but will be.
+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. This is not yet implemented, but will be.
+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 ever becomes empty (i.e., if it spans no characters).
+
+@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
- 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.
-@defun make-overlay start end &optional buffer
+@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}.
@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
@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
+ 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 Finding Overlays
+@subsection Searching for Overlays
+
@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}.
+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 (cdr 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
of an overlay, after @var{pos}.
@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}.
+@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
+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}.
+
+@example
+(truncate-string-to-width "\tab\t" 12 4)
+ @result{} "ab"
+(truncate-string-to-width "\tab\t" 12 4 ?\ )
+ @result{} " ab "
+@end example
+@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.
+ 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 id number} which distinguishes faces at
-low levels within Emacs. However, for most purposes, you can refer to
+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.
-* Merging Faces:: How Emacs decides which face to use for a character.
+* 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.
+* Merging 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.
+ 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 mode lines, 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 face is used for mode lines and menu bars.
+This is an alias for the @code{mode-line} face, for compatibility with
+old Emacs versions.
+
+@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 colors of window fringes, the thin areas on
+either side that are used to display continuation and truncation glyphs.
+
+@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)}
@kindex highlight @r{(face name)}
This face is meant to be used for highlighting for various purposes.
-@item underline
-@kindex underline @r{(face name)}
-This face underlines text.
+@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}.
+@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
@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-patch
+@kindex fixed-patch @r{(face name)}
+This face forces use of a particular fixed-width font.
+
+@item variable-patch
+@kindex variable-patch @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
-@node Merging Faces
-@subsection Merging Faces for Display
+@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
- Here are all the ways to specify which face to use for display of text:
+@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 element's second element,
+@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 applies to. If more than one element of @var{spec}
+matches a given frame, the first matching element is the only one used
+for that frame. There are two possibilities for @var{display}:
-@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.
+@table @asis
+@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}:
-@item
-With text properties. A character may have a @code{face} property; if so,
-it is displayed with that face. @xref{Special Properties}.
+@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}.
+@end table
-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.
+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
-@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.
+ Here's how the standard face @code{region} is defined:
-@item
-With special glyphs. Each glyph can specify a particular face id
-number. @xref{Glyphs}.
-@end itemize
+@example
+@group
+(defface region
+ `((((type tty) (class color))
+ (:background "blue" :foreground "white"))
+@end group
+ (((type tty) (class mono))
+ (:inverse-video t))
+ (((class color) (background dark))
+ (:background "blue"))
+ (((class color) (background light))
+ (:background "lightblue"))
+ (t (:background "gray")))
+@group
+ "Basic face for highlighting the region."
+ :group 'basic-faces)
+@end group
+@end example
- 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.
+ 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
- When multiple overlays cover one character, an overlay with higher
-priority overrides those with lower priority. @xref{Overlays}.
+@node Face Attributes
+@subsection Face Attributes
+@cindex face attributes
- 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.
+ 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{Merging Faces}.
-@node Face Functions
-@subsection Functions for Working with Faces
+ In Emacs 21, 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.
- 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.
+ 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.)
- Here are the primitives for creating and changing faces.
+@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.
+
+@item :background
+Background color, a string.
+
+@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} consecutie bytes in the string
+(which should be a unibyte string for best results).
+
+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.
+
+@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
-@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
+ Here are the possible values of the @code{:box} attribute, and what
+they mean:
-@defun face-list
-This function returns a list of all defined face names.
-@end defun
+@table @asis
+@item @code{nil}
+Don't draw a box.
-@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.
+@item @code{t}
+Draw a box with lines of width 1, in the foreground color.
-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.
+@item @var{color}
+Draw a box with lines of width 1, in color @var{color}.
-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
+@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.
- 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.
+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.
-@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
+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
+
+ The attributes @code{:overline}, @code{:strike-through} and
+@code{:box} are new in Emacs 21. The attributes @code{:family},
+@code{:height}, @code{:width}, @code{:weight}, @code{:slant} are also
+new; previous versions used the following attributes, now semi-obsolete,
+to specify some of the same information:
+
+@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'' in Emacs 21,
+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}.
+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
+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.
+
+If @var{frame} is @code{t}, the value is the default for
+@var{face} for new frames.
+
+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.
+
+@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 @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}. The argument @var{font}
-should be a string.
+This function sets the font of face @var{face}.
+
+In Emacs 21, this actually sets the attributes @code{:family},
+@code{:width}, @code{:height}, @code{:weight}, and @code{:slant}
+according to the font name @var{font}.
+
+In Emacs 20, this sets the font attribute. Once you set the font
+explicitly, the bold and italic attributes cease to have any effect,
+because the precise font that you specified is used.
+@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.
+
+In Emacs 21, this sets the @code{:weight} attribute.
+In Emacs 20, it sets the @code{:bold} 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.
+
+In Emacs 21, this sets the @code{:slant} attribute.
+In Emacs 20, it sets the @code{:italic} attribute.
@end defun
@defun set-face-underline-p face underline-p &optional frame
@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,
-respectively.
+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
@defunx face-background face &optional frame
respectively) of face @var{face}, as a string.
@end defun
+@defun face-stipple face &optional frame
+This function returns the name of the background stipple pattern of face
+@var{face}, or @code{nil} if it doesn't have one.
+@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 underline attribute of face @var{face}.
+This function returns the @code{:underline} attribute of face @var{face}.
@end defun
-@defun face-id-number face
-This function returns the face id number of face @var{face}.
+@defun face-inverse-video-p face &optional frame
+This function returns the @code{:inverse-video} attribute of face @var{face}.
+@end defun
+
+@node Merging Faces
+@subsection Merging Faces for Display
+
+ 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.)
+
+For a mode line or header line, the face @code{modeline} or
+@code{header-line} is used 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. The attributes of the faces of special glyphs come first;
+then comes the face for region highlighting, if appropriate;
+then come attributes of faces from overlays, followed by those from text
+properties, and last the default face.
+
+ When multiple overlays cover one character, an overlay with higher
+priority overrides those with lower priority. @xref{Overlays}.
+
+ In Emacs 20, 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. In newer Emacs versions, this cannot happen, because the
+@code{default} face specifies all attributes---in fact, the frame's own
+font and colors are synonymous with those of the default face.
+
+@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.
+
+ For multibyte characters, typically each font covers only one
+character set. So each character set (@pxref{Character Sets}) specifies
+a registry and encoding to use, with the character set's
+@code{x-charset-registry} property. Its value is a string containing
+the registry and the encoding, with a dash between them:
+
+@example
+(plist-get (charset-plist 'latin-iso8859-1)
+ 'x-charset-registry)
+ @result{} "ISO8859-1"
+@end example
+
+ Unibyte text does not have character sets, so displaying a unibyte
+character takes the registry and encoding from the variable
+@code{face-default-registry}.
+
+@defvar face-default-registry
+This variable specifies which registry and encoding to use in choosing
+fonts for unibyte characters. The value is initialized at Emacs startup
+time from the font the user specified for Emacs.
+@end defvar
+
+ 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
+
+@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 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.
+
+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
@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).
+the default face. A face is considered to be ``the same'' as the
+default face if each attribute is either the same as that of the default
+face, or unspecified (meaning to inherit from the default).
@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.
+@node Auto Faces
+@subsection Automatic Face Assignment
+@cindex automatic face assignment
+@cindex faces, automatic choice
+
+@cindex Font-Lock mode
+ Starting with Emacs 21, a hook is available for automatically
+assigning faces to text in the buffer. This hook is used for 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
-Normally, the value is the id number of the face named @code{region}.
+@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
+
+ These additional functions are available starting in Emacs 21.
+
+@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.
+
+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-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.
+
+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 @sc{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 @sc{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.
+
+@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. These features are available starting in Emacs 21. The value
+of the @code{display} property should be a display specification, or a
+list or vector containing several display specifications. 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.
+* 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.
+* Conditional Display:: Making any of the above features conditional
+ depending on some Lisp expression.
+@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 to specify the weight of the space:
+
+@table @code
+@item :width @var{width}
+Specifies that the space width should be @var{width} times the normal
+character width. @var{width} can be an integer or floating point
+number.
+
+@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}. The
+value @var{hpos} is measured in units of the normal character width. It
+may be an interer or a floating point number.
+@end table
+
+ Exactly one of the above properties should be used. You can also
+specify the height of the space, with other properties:
+
+@table @code
+@item :height @var{height}
+Specifies the height of the space, as @var{height},
+measured in terms of the normal line height.
+
+@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}
+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 value of @var{ascent} must be a non-negative number no
+greater than 100.
+@end table
+
+ You should not use both @code{:height} and @code{:relative-height}
+together.
+
+@node Other Display Specs
+@subsection Other Display Specifications
+
+@table @code
+@item (image . @var{image-props})
+This is in fact 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 ((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}).
+
+@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
+
+@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.
+
+ 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 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.
+@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 Conditional Display
+@subsection Conditional Display Specifications
+@cindex conditional display specifications
+
+ 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, point is temporarily set at the end position of the text
+having this conditional display specification.
+
+@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}). Like the
+@code{display} property, this feature is available starting in Emacs 21.
+
+ Emacs can display a number of different image formats; some of them
+are supported only if particular support libraries are installed on your
+machine. The supported image formats include XBM, XPM (needing the
+libraries @code{libXpm} version 3.4k and @code{libz}), GIF (needing
+@code{libungif} 4.1.0), Postscript, PBM, JPEG (needing the
+@code{libjpeg} library version v6a), TIFF (needing @code{libtiff} v3.4),
+and PNG (needing @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
+supported in the current configuration.
+@end defvar
+
+@menu
+* 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 Image Descriptors
+@subsection Image Descriptors
+@cindex image descriptor
+
+ An image description is a list of the form @code{(image
+. @var{props})}, where @var{props} is a property list containing
+alternating keyword symbols (symbols whose names start with a colon) and
+their values. You can use any Lisp object as a property, but the only
+properties that have any special meaning are certain symbols, all of
+them keywords.
+
+ Every image descriptor must contain the property @code{:type
+@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.
+
+ Here is a list of other properties that are meaningful for all image
+types:
+
+@table @code
+@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 :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; if it is not specified, the default is zero.
+
+@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 :algorithm @var{algorithm}
+The @code{:algorithm} 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.
+
+@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 :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 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 :file @var{file}
+The @code{:file} property specifies 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 specifies 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}.
+@end table
+
+@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.
+@end defun
+
+@node XBM Images
+@subsection XBM Images
+@cindex XBM
+
+ To use XBM format, specify @code{xbm} as the image type. This image
+format doesn't require an external library, so images of this type are
+always supported.
+
+ Additional image properties supported for the @code{xbm} image type are:
+
+@table @code
+@item :foreground @var{foreground}
+The value, @var{foreground}, should be a string specifying the image
+foreground 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. This color is used for each pixel in the XBM that is
+0. The default is the frame's background color.
+@end table
+
+ If you specify an XBM image using data within Emacs instead of an
+external file, use the following three properties:
+
+@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
+A vector of strings or bool-vectors, each specifying one line of the
+image. Do specify @code{:height} and @code{:width}.
+
+@item
+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
+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
+
+@item :width @var{width}
+The value, @var{width}, specifies the width of the image, in pixels.
+
+@item :height @var{height}
+The value, @var{height}, specifies the height of the image, in pixels.
+@end table
+
+@node XPM Images
+@subsection XPM Images
+@cindex XPM
+
+ To use XPM format, specify @code{xpm} as the image type. The
+additional image property @code{:color-symbols} is also meaningful with
+the @code{xpm} image type:
+
+@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
+
+@node GIF Images
+@subsection GIF Images
+@cindex GIF
+
+ For GIF images, specify image type @code{gif}. Because of the patents
+in the US covering the LZW algorithm, the continued use of GIF format is
+a problem for the whole Internet; to end this problem, it is a good idea
+for everyone, even outside the US, to stop using GIFS right away
+(@uref{http://www.burnallgifs.org/}). But if you still want to use
+them, Emacs can display them.
+
+@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. An error is signaled if the GIF file
+doesn't contain an image with index @var{index}.
+@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. 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. 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 &optional type &rest props
+@tindex create-image
+This function creates and returns an image descriptor which uses the
+data in @var{file}.
+
+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 :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
+
+@defmac defimage variable doc &rest specs
+@tindex defimage
+This macro defines @var{variable} as an image name. The second argument,
+@var{doc}, is an optional documentation string. The remaining
+arguments, @var{specs}, specify alternative ways to display the image.
+
+Each argument in @var{specs} has the form of a property list, and each
+one should specify at least the @code{:type} property and the
+@code{:file} property. 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 the variable @var{variable}.
+
+If none of the alternatives will work, then @var{variable} 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
+
+@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
+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.
+
+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 inserts @var{string} in the buffer, and gives
+it a @code{display} property which specifies @var{image}. @xref{Display
+Property}.
+@end defun
+
+@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
+
+@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.
+
+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 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-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.
+@end defun
+
+@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
+
@node Blinking
@section Blinking Parentheses
@cindex parenthesis matching
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
+inverse video. Otherwise, these lines are displayed normally, just like
+other text. The default is @code{t}.
+
+For window frames, this feature actually applies the face named
+@code{mode-line}; that face is normally set up as the inverse of the
+default face, unless you change it.
@end defopt
@node Usual Display
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
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 @sc{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-@sc{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 @sc{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
buffers that do not override it. @xref{Default Value}.
@end defvar
+@defopt indicate-empty-lines
+@tindex indicate-empty-lines
+When this is non-@code{nil}, Emacs displays a special glyph in
+each empty line at the end of the buffer, on terminals that
+support it (window systems).
+@end defopt
+
@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
@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 @sc{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.
@end menu
@node Display Table Format
@subsection Display Table Format
- A display table is actually an array of 262 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}). Note that the
-display table has no effect on the tab and newline characters; they are
-always displayed as whitespace in their usual special fashion.
+ 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 six 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}. Newer Emacs versions, on some platforms,
+display arrows to indicate truncation---the display table has no effect
+in these situations.
+@item 1
The glyph for the end of a continued line (the default is @samp{\}).
-@item 258
+Newer Emacs versions, on some platforms, display curved arrows to
+indicate truncation---the display table has no effect in these
+situations.
+@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 261
+@item 5
The glyph used to draw the border between side-by-side windows (the
-default is @samp{|}). @xref{Splitting Windows}.
+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
@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
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; see below.
@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. On an ordinary terminal, the glyph code mod
+524288 is the character to output. In a window system, the glyph code
+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}.
@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 that displays the other
-ISO characters as explanatory 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 under X windows, and on a character-only terminal provided
-the terminal's Termcap entry defines the visible bell capability
-(@samp{vb}).
+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
HCoop / bpt / emacs.git / blobdiff