2 @c This is part of the GNU Emacs Lisp Reference Manual.
3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001,
4 @c 2002, 2005 Free Software Foundation, Inc.
5 @c See the file elisp.texi for copying conditions.
6 @setfilename ../info/display
7 @node Display, System Interface, Processes, Top
10 This chapter describes a number of features related to the display
11 that Emacs presents to the user.
14 * Refresh Screen:: Clearing the screen and redrawing everything on it.
15 * Forcing Redisplay:: Forcing redisplay.
16 * Truncation:: Folding or wrapping long text lines.
17 * The Echo Area:: Displaying messages at the bottom of the screen.
18 * Warnings:: Displaying warning messages for the user.
19 * Invisible Text:: Hiding part of the buffer text.
20 * Selective Display:: Hiding part of the buffer text (the old way).
21 * Temporary Displays:: Displays that go away automatically.
22 * Overlays:: Use overlays to highlight parts of the buffer.
23 * Width:: How wide a character or string is on the screen.
24 * Line Height:: Controlling the height of lines.
25 * Faces:: A face defines a graphics style for text characters:
27 * Fringes:: Controlling window fringes.
28 * Scroll Bars:: Controlling vertical scroll bars.
29 * Pointer Shape:: Controlling the mouse pointer shape.
30 * Display Property:: Enabling special display features.
31 * Images:: Displaying images in Emacs buffers.
32 * Buttons:: Adding clickable buttons to Emacs buffers.
33 * Blinking:: How Emacs shows the matching open parenthesis.
34 * Inverse Video:: Specifying how the screen looks.
35 * Usual Display:: The usual conventions for displaying nonprinting chars.
36 * Display Tables:: How to specify other conventions.
37 * Beeping:: Audible signal to the user.
38 * Window Systems:: Which window system is being used.
42 @section Refreshing the Screen
44 The function @code{redraw-frame} clears and redisplays the entire
45 contents of a given frame (@pxref{Frames}). This is useful if the
49 @defun redraw-frame frame
50 This function clears and redisplays frame @var{frame}.
53 Even more powerful is @code{redraw-display}:
55 @deffn Command redraw-display
56 This function clears and redisplays all visible frames.
59 This function calls for redisplay of certain windows, the next time
60 redisplay is done, but does not clear them first.
62 @defun force-window-update &optional object
63 This function forces redisplay of some or all windows. If
64 @var{object} is a window, it forces redisplay of that window. If
65 @var{object} is a buffer or buffer name, it forces redisplay of all
66 windows displaying that buffer. If @var{object} is @code{nil} (or
67 omitted), it forces redisplay of all windows.
70 Processing user input takes absolute priority over redisplay. If you
71 call these functions when input is available, they do nothing
72 immediately, but a full redisplay does happen eventually---after all the
73 input has been processed.
75 Normally, suspending and resuming Emacs also refreshes the screen.
76 Some terminal emulators record separate contents for display-oriented
77 programs such as Emacs and for ordinary sequential display. If you are
78 using such a terminal, you might want to inhibit the redisplay on
81 @defvar no-redraw-on-reenter
82 @cindex suspend (cf. @code{no-redraw-on-reenter})
83 @cindex resume (cf. @code{no-redraw-on-reenter})
84 This variable controls whether Emacs redraws the entire screen after it
85 has been suspended and resumed. Non-@code{nil} means there is no need
86 to redraw, @code{nil} means redrawing is needed. The default is @code{nil}.
89 @node Forcing Redisplay
90 @section Forcing Redisplay
91 @cindex forcing redisplay
93 Emacs redisplay normally stops if input arrives, and does not happen
94 at all if input is available before it starts. Most of the time, this
95 is exactly what you want. However, you can prevent preemption by
96 binding @code{redisplay-dont-pause} to a non-@code{nil} value.
98 @tindex redisplay-dont-pause
99 @defvar redisplay-dont-pause
100 If this variable is non-@code{nil}, pending input does not
101 prevent or halt redisplay; redisplay occurs, and finishes,
102 regardless of whether input is available.
105 You can request a display update, but only if no input is pending,
106 with @code{(sit-for 0)}. To force a display update even when input is
110 (let ((redisplay-dont-pause t))
116 @cindex line wrapping
117 @cindex continuation lines
118 @cindex @samp{$} in display
119 @cindex @samp{\} in display
121 When a line of text extends beyond the right edge of a window, the
122 line can either be continued on the next screen line, or truncated to
123 one screen line. The additional screen lines used to display a long
124 text line are called @dfn{continuation} lines. Normally, a @samp{$} in
125 the rightmost column of the window indicates truncation; a @samp{\} on
126 the rightmost column indicates a line that ``wraps'' onto the next line,
127 which is also called @dfn{continuing} the line. (The display table can
128 specify alternative indicators; see @ref{Display Tables}.)
130 On a window system display, the @samp{$} and @samp{\} indicators are
131 replaced with arrow images displayed in the window fringes
134 Note that continuation is different from filling; continuation happens
135 on the screen only, not in the buffer contents, and it breaks a line
136 precisely at the right margin, not at a word boundary. @xref{Filling}.
138 @defopt truncate-lines
139 This buffer-local variable controls how Emacs displays lines that extend
140 beyond the right edge of the window. The default is @code{nil}, which
141 specifies continuation. If the value is non-@code{nil}, then these
144 If the variable @code{truncate-partial-width-windows} is non-@code{nil},
145 then truncation is always used for side-by-side windows (within one
146 frame) regardless of the value of @code{truncate-lines}.
149 @defopt default-truncate-lines
150 This variable is the default value for @code{truncate-lines}, for
151 buffers that do not have buffer-local values for it.
154 @defopt truncate-partial-width-windows
155 This variable controls display of lines that extend beyond the right
156 edge of the window, in side-by-side windows (@pxref{Splitting Windows}).
157 If it is non-@code{nil}, these lines are truncated; otherwise,
158 @code{truncate-lines} says what to do with them.
161 When horizontal scrolling (@pxref{Horizontal Scrolling}) is in use in
162 a window, that forces truncation.
164 If your buffer contains @emph{very} long lines, and you use
165 continuation to display them, just thinking about them can make Emacs
166 redisplay slow. The column computation and indentation functions also
167 become slow. Then you might find it advisable to set
168 @code{cache-long-line-scans} to @code{t}.
170 @defvar cache-long-line-scans
171 If this variable is non-@code{nil}, various indentation and motion
172 functions, and Emacs redisplay, cache the results of scanning the
173 buffer, and consult the cache to avoid rescanning regions of the buffer
174 unless they are modified.
176 Turning on the cache slows down processing of short lines somewhat.
178 This variable is automatically buffer-local in every buffer.
182 @section The Echo Area
183 @cindex error display
186 The @dfn{echo area} is used for displaying error messages
187 (@pxref{Errors}), for messages made with the @code{message} primitive,
188 and for echoing keystrokes. It is not the same as the minibuffer,
189 despite the fact that the minibuffer appears (when active) in the same
190 place on the screen as the echo area. The @cite{GNU Emacs Manual}
191 specifies the rules for resolving conflicts between the echo area and
192 the minibuffer for use of that screen space (@pxref{Minibuffer,, The
193 Minibuffer, emacs, The GNU Emacs Manual}).
195 You can write output in the echo area by using the Lisp printing
196 functions with @code{t} as the stream (@pxref{Output Functions}), or
200 * Displaying Messages:: Explicitly displaying text in the echo area.
201 * Progress:: Informing user about progress of a long operation.
202 * Logging Messages:: Echo area messages are logged for the user.
203 * Echo Area Customization:: Controlling the echo area.
206 @node Displaying Messages
207 @subsection Displaying Messages in the Echo Area
209 This section describes the functions for explicitly producing echo
210 area messages. Many other Emacs features display messages there, too.
212 @defun message string &rest arguments
213 This function displays a message in the echo area. The
214 argument @var{string} is similar to a C language @code{printf} control
215 string. See @code{format} in @ref{Formatting Strings}, for the details
216 on the conversion specifications. @code{message} returns the
219 In batch mode, @code{message} prints the message text on the standard
220 error stream, followed by a newline.
222 If @var{string}, or strings among the @var{arguments}, have @code{face}
223 text properties, these affect the way the message is displayed.
226 If @var{string} is @code{nil}, @code{message} clears the echo area; if
227 the echo area has been expanded automatically, this brings it back to
228 its normal size. If the minibuffer is active, this brings the
229 minibuffer contents back onto the screen immediately.
233 (message "Minibuffer depth is %d."
235 @print{} Minibuffer depth is 0.
236 @result{} "Minibuffer depth is 0."
240 ---------- Echo Area ----------
241 Minibuffer depth is 0.
242 ---------- Echo Area ----------
246 To automatically display a message in the echo area or in a pop-buffer,
247 depending on its size, use @code{display-message-or-buffer} (see below).
250 @tindex with-temp-message
251 @defmac with-temp-message message &rest body
252 This construct displays a message in the echo area temporarily, during
253 the execution of @var{body}. It displays @var{message}, executes
254 @var{body}, then returns the value of the last body form while restoring
255 the previous echo area contents.
258 @defun message-or-box string &rest arguments
259 This function displays a message like @code{message}, but may display it
260 in a dialog box instead of the echo area. If this function is called in
261 a command that was invoked using the mouse---more precisely, if
262 @code{last-nonmenu-event} (@pxref{Command Loop Info}) is either
263 @code{nil} or a list---then it uses a dialog box or pop-up menu to
264 display the message. Otherwise, it uses the echo area. (This is the
265 same criterion that @code{y-or-n-p} uses to make a similar decision; see
266 @ref{Yes-or-No Queries}.)
268 You can force use of the mouse or of the echo area by binding
269 @code{last-nonmenu-event} to a suitable value around the call.
272 @defun message-box string &rest arguments
273 This function displays a message like @code{message}, but uses a dialog
274 box (or a pop-up menu) whenever that is possible. If it is impossible
275 to use a dialog box or pop-up menu, because the terminal does not
276 support them, then @code{message-box} uses the echo area, like
280 @defun display-message-or-buffer message &optional buffer-name not-this-window frame
281 @tindex display-message-or-buffer
282 This function displays the message @var{message}, which may be either a
283 string or a buffer. If it is shorter than the maximum height of the
284 echo area, as defined by @code{max-mini-window-height}, it is displayed
285 in the echo area, using @code{message}. Otherwise,
286 @code{display-buffer} is used to show it in a pop-up buffer.
288 Returns either the string shown in the echo area, or when a pop-up
289 buffer is used, the window used to display it.
291 If @var{message} is a string, then the optional argument
292 @var{buffer-name} is the name of the buffer used to display it when a
293 pop-up buffer is used, defaulting to @samp{*Message*}. In the case
294 where @var{message} is a string and displayed in the echo area, it is
295 not specified whether the contents are inserted into the buffer anyway.
297 The optional arguments @var{not-this-window} and @var{frame} are as for
298 @code{display-buffer}, and only used if a buffer is displayed.
301 @defun current-message
302 This function returns the message currently being displayed in the
303 echo area, or @code{nil} if there is none.
307 @subsection Reporting Operation Progress
308 @cindex progress reporting
310 When an operation can take a while to finish, you should inform the
311 user about the progress it makes. This way the user can estimate
312 remaining time and clearly see that Emacs is busy working, not hung.
314 Functions listed in this section provide simple and efficient way of
315 reporting operation progress. Here is a working example that does
319 (let ((progress-reporter
320 (make-progress-reporter "Collecting mana for Emacs..."
324 (progress-reporter-update progress-reporter k))
325 (progress-reporter-done progress-reporter))
328 @defun make-progress-reporter message min-value max-value &optional current-value min-change min-time
329 This function creates and returns a @dfn{progress reporter}---an
330 object you will use as an argument for all other functions listed
331 here. The idea is to precompute as much data as possible to make
332 progress reporting very fast.
334 When this progress reporter is subsequently used, it will display
335 @var{message} in the echo area, followed by progress percentage.
336 @var{message} is treated as a simple string. If you need it to depend
337 on a filename, for instance, use @code{format} before calling this
340 @var{min-value} and @var{max-value} arguments stand for starting and
341 final states of your operation. For instance, if you scan a buffer,
342 they should be the results of @code{point-min} and @code{point-max}
343 correspondingly. It is required that @var{max-value} is greater than
344 @var{min-value}. If you create progress reporter when some part of
345 the operation has already been completed, then specify
346 @var{current-value} argument. But normally you should omit it or set
347 it to @code{nil}---it will default to @var{min-value} then.
349 Remaining arguments control the rate of echo area updates. Progress
350 reporter will wait for at least @var{min-change} more percents of the
351 operation to be completed before printing next message.
352 @var{min-time} specifies the minimum time in seconds to pass between
353 successive prints. It can be fractional. Depending on Emacs and
354 system capabilities, progress reporter may or may not respect this
355 last argument or do it with varying precision. Default value for
356 @var{min-change} is 1 (one percent), for @var{min-time}---0.2
359 This function calls @code{progress-reporter-update}, so the first
360 message is printed immediately.
363 @defun progress-reporter-update reporter value
364 This function does the main work of reporting progress of your
365 operation. It displays the message of @var{reporter}, followed by
366 progress percentage determined by @var{value}. If percentage is zero,
367 or close enough according to the @var{min-change} and @var{min-time}
368 arguments, then it is omitted from the output.
370 @var{reporter} must be the result of a call to
371 @code{make-progress-reporter}. @var{value} specifies the current
372 state of your operation and must be between @var{min-value} and
373 @var{max-value} (inclusive) as passed to
374 @code{make-progress-reporter}. For instance, if you scan a buffer,
375 then @var{value} should be the result of a call to @code{point}.
377 This function respects @var{min-change} and @var{min-time} as passed
378 to @code{make-progress-reporter} and so does not output new messages
379 on every invocation. It is thus very fast and normally you should not
380 try to reduce the number of calls to it: resulting overhead will most
381 likely negate your effort.
384 @defun progress-reporter-force-update reporter value &optional new-message
385 This function is similar to @code{progress-reporter-update} except
386 that it prints a message in the echo area unconditionally.
388 The first two arguments have the same meaning as for
389 @code{progress-reporter-update}. Optional @var{new-message} allows
390 you to change the message of the @var{reporter}. Since this functions
391 always updates the echo area, such a change will be immediately
392 presented to the user.
395 @defun progress-reporter-done reporter
396 This function should be called when the operation is finished. It
397 prints the message of @var{reporter} followed by word ``done'' in the
400 You should always call this function and not hope for
401 @code{progress-reporter-update} to print ``100%.'' Firstly, it may
402 never print it, there are many good reasons for this not to happen.
403 Secondly, ``done'' is more explicit.
406 @defmac dotimes-with-progress-reporter (var count [result]) message body...
407 This is a convenience macro that works the same way as @code{dotimes}
408 does, but also reports loop progress using the functions described
409 above. It allows you to save some typing.
411 You can rewrite the example in the beginning of this node using
415 (dotimes-with-progress-reporter
417 "Collecting some mana for Emacs..."
422 @node Logging Messages
423 @subsection Logging Messages in @samp{*Messages*}
424 @cindex logging echo-area messages
426 Almost all the messages displayed in the echo area are also recorded
427 in the @samp{*Messages*} buffer so that the user can refer back to
428 them. This includes all the messages that are output with
431 @defopt message-log-max
432 This variable specifies how many lines to keep in the @samp{*Messages*}
433 buffer. The value @code{t} means there is no limit on how many lines to
434 keep. The value @code{nil} disables message logging entirely. Here's
435 how to display a message and prevent it from being logged:
438 (let (message-log-max)
443 To make @samp{*Messages*} more convenient for the user, the logging
444 facility combines successive identical messages. It also combines
445 successive related messages for the sake of two cases: question
446 followed by answer, and a series of progress messages.
448 A ``question followed by an answer'' means two messages like the
449 ones produced by @code{y-or-n-p}: the first is @samp{@var{question}},
450 and the second is @samp{@var{question}...@var{answer}}. The first
451 message conveys no additional information beyond what's in the second,
452 so logging the second message discards the first from the log.
454 A ``series of progress messages'' means successive messages like
455 those produced by @code{make-progress-reporter}. They have the form
456 @samp{@var{base}...@var{how-far}}, where @var{base} is the same each
457 time, while @var{how-far} varies. Logging each message in the series
458 discards the previous one, provided they are consecutive.
460 The functions @code{make-progress-reporter} and @code{y-or-n-p}
461 don't have to do anything special to activate the message log
462 combination feature. It operates whenever two consecutive messages
463 are logged that share a common prefix ending in @samp{...}.
465 @node Echo Area Customization
466 @subsection Echo Area Customization
468 These variables control details of how the echo area works.
470 @defvar cursor-in-echo-area
471 This variable controls where the cursor appears when a message is
472 displayed in the echo area. If it is non-@code{nil}, then the cursor
473 appears at the end of the message. Otherwise, the cursor appears at
474 point---not in the echo area at all.
476 The value is normally @code{nil}; Lisp programs bind it to @code{t}
477 for brief periods of time.
480 @defvar echo-area-clear-hook
481 This normal hook is run whenever the echo area is cleared---either by
482 @code{(message nil)} or for any other reason.
485 @defvar echo-keystrokes
486 This variable determines how much time should elapse before command
487 characters echo. Its value must be an integer or floating point number,
489 number of seconds to wait before echoing. If the user types a prefix
490 key (such as @kbd{C-x}) and then delays this many seconds before
491 continuing, the prefix key is echoed in the echo area. (Once echoing
492 begins in a key sequence, all subsequent characters in the same key
493 sequence are echoed immediately.)
495 If the value is zero, then command input is not echoed.
498 @defvar message-truncate-lines
499 Normally, displaying a long message resizes the echo area to display
500 the entire message. But if the variable @code{message-truncate-lines}
501 is non-@code{nil}, the echo area does not resize, and the message is
502 truncated to fit it, as in Emacs 20 and before.
505 The variable @code{max-mini-window-height}, which specifies the
506 maximum height for resizing minibuffer windows, also applies to the
507 echo area (which is really a special use of the minibuffer window.
508 @xref{Minibuffer Misc}.
511 @section Reporting Warnings
514 @dfn{Warnings} are a facility for a program to inform the user of a
515 possible problem, but continue running.
518 * Warning Basics:: Warnings concepts and functions to report them.
519 * Warning Variables:: Variables programs bind to customize their warnings.
520 * Warning Options:: Variables users set to control display of warnings.
524 @subsection Warning Basics
525 @cindex severity level
527 Every warning has a textual message, which explains the problem for
528 the user, and a @dfn{severity level} which is a symbol. Here are the
529 possible severity levels, in order of decreasing severity, and their
534 A problem that will seriously impair Emacs operation soon
535 if you do not attend to it promptly.
537 A report of data or circumstances that are inherently wrong.
539 A report of data or circumstances that are not inherently wrong, but
540 raise suspicion of a possible problem.
542 A report of information that may be useful if you are debugging.
545 When your program encounters invalid input data, it can either
546 signal a Lisp error by calling @code{error} or @code{signal} or report
547 a warning with severity @code{:error}. Signaling a Lisp error is the
548 easiest thing to do, but it means the program cannot continue
549 processing. If you want to take the trouble to implement a way to
550 continue processing despite the bad data, then reporting a warning of
551 severity @code{:error} is the right way to inform the user of the
552 problem. For instance, the Emacs Lisp byte compiler can report an
553 error that way and continue compiling other functions. (If the
554 program signals a Lisp error and then handles it with
555 @code{condition-case}, the user won't see the error message; it could
556 show the message to the user by reporting it as a warning.)
559 Each warning has a @dfn{warning type} to classify it. The type is a
560 list of symbols. The first symbol should be the custom group that you
561 use for the program's user options. For example, byte compiler
562 warnings use the warning type @code{(bytecomp)}. You can also
563 subcategorize the warnings, if you wish, by using more symbols in the
566 @defun display-warning type message &optional level buffer-name
567 This function reports a warning, using @var{message} as the message
568 and @var{type} as the warning type. @var{level} should be the
569 severity level, with @code{:warning} being the default.
571 @var{buffer-name}, if non-@code{nil}, specifies the name of the buffer
572 for logging the warning. By default, it is @samp{*Warnings*}.
575 @defun lwarn type level message &rest args
576 This function reports a warning using the value of @code{(format
577 @var{message} @var{args}...)} as the message. In other respects it is
578 equivalent to @code{display-warning}.
581 @defun warn message &rest args
582 This function reports a warning using the value of @code{(format
583 @var{message} @var{args}...)} as the message, @code{(emacs)} as the
584 type, and @code{:warning} as the severity level. It exists for
585 compatibility only; we recommend not using it, because you should
586 specify a specific warning type.
589 @node Warning Variables
590 @subsection Warning Variables
592 Programs can customize how their warnings appear by binding
593 the variables described in this section.
595 @defvar warning-levels
596 This list defines the meaning and severity order of the warning
597 severity levels. Each element defines one severity level,
598 and they are arranged in order of decreasing severity.
600 Each element has the form @code{(@var{level} @var{string}
601 @var{function})}, where @var{level} is the severity level it defines.
602 @var{string} specifies the textual description of this level.
603 @var{string} should use @samp{%s} to specify where to put the warning
604 type information, or it can omit the @samp{%s} so as not to include
607 The optional @var{function}, if non-@code{nil}, is a function to call
608 with no arguments, to get the user's attention.
610 Normally you should not change the value of this variable.
613 @defvar warning-prefix-function
614 If non-@code{nil}, the value is a function to generate prefix text for
615 warnings. Programs can bind the variable to a suitable function.
616 @code{display-warning} calls this function with the warnings buffer
617 current, and the function can insert text in it. That text becomes
618 the beginning of the warning message.
620 The function is called with two arguments, the severity level and its
621 entry in @code{warning-levels}. It should return a list to use as the
622 entry (this value need not be an actual member of
623 @code{warning-levels}). By constructing this value, the function can
624 change the severity of the warning, or specify different handling for
625 a given severity level.
627 If the variable's value is @code{nil} then there is no function
631 @defvar warning-series
632 Programs can bind this variable to @code{t} to say that the next
633 warning should begin a series. When several warnings form a series,
634 that means to leave point on the first warning of the series, rather
635 than keep moving it for each warning so that it appears on the last one.
636 The series ends when the local binding is unbound and
637 @code{warning-series} becomes @code{nil} again.
639 The value can also be a symbol with a function definition. That is
640 equivalent to @code{t}, except that the next warning will also call
641 the function with no arguments with the warnings buffer current. The
642 function can insert text which will serve as a header for the series
645 Once a series has begun, the value is a marker which points to the
646 buffer position in the warnings buffer of the start of the series.
648 The variable's normal value is @code{nil}, which means to handle
649 each warning separately.
652 @defvar warning-fill-prefix
653 When this variable is non-@code{nil}, it specifies a fill prefix to
654 use for filling each warning's text.
657 @defvar warning-type-format
658 This variable specifies the format for displaying the warning type
659 in the warning message. The result of formatting the type this way
660 gets included in the message under the control of the string in the
661 entry in @code{warning-levels}. The default value is @code{" (%s)"}.
662 If you bind it to @code{""} then the warning type won't appear at
666 @node Warning Options
667 @subsection Warning Options
669 These variables are used by users to control what happens
670 when a Lisp program reports a warning.
672 @defopt warning-minimum-level
673 This user option specifies the minimum severity level that should be
674 shown immediately to the user. The default is @code{:warning}, which
675 means to immediately display all warnings except @code{:debug}
679 @defopt warning-minimum-log-level
680 This user option specifies the minimum severity level that should be
681 logged in the warnings buffer. The default is @code{:warning}, which
682 means to log all warnings except @code{:debug} warnings.
685 @defopt warning-suppress-types
686 This list specifies which warning types should not be displayed
687 immediately for the user. Each element of the list should be a list
688 of symbols. If its elements match the first elements in a warning
689 type, then that warning is not displayed immediately.
692 @defopt warning-suppress-log-types
693 This list specifies which warning types should not be logged in the
694 warnings buffer. Each element of the list should be a list of
695 symbols. If it matches the first few elements in a warning type, then
696 that warning is not logged.
700 @section Invisible Text
702 @cindex invisible text
703 You can make characters @dfn{invisible}, so that they do not appear on
704 the screen, with the @code{invisible} property. This can be either a
705 text property (@pxref{Text Properties}) or a property of an overlay
706 (@pxref{Overlays}). Cursor motion also partly ignores these
707 characters; if the command loop finds point within them, it moves
708 point to the other side of them.
710 In the simplest case, any non-@code{nil} @code{invisible} property makes
711 a character invisible. This is the default case---if you don't alter
712 the default value of @code{buffer-invisibility-spec}, this is how the
713 @code{invisible} property works. You should normally use @code{t}
714 as the value of the @code{invisible} property if you don't plan
715 to set @code{buffer-invisibility-spec} yourself.
717 More generally, you can use the variable @code{buffer-invisibility-spec}
718 to control which values of the @code{invisible} property make text
719 invisible. This permits you to classify the text into different subsets
720 in advance, by giving them different @code{invisible} values, and
721 subsequently make various subsets visible or invisible by changing the
722 value of @code{buffer-invisibility-spec}.
724 Controlling visibility with @code{buffer-invisibility-spec} is
725 especially useful in a program to display the list of entries in a
726 database. It permits the implementation of convenient filtering
727 commands to view just a part of the entries in the database. Setting
728 this variable is very fast, much faster than scanning all the text in
729 the buffer looking for properties to change.
731 @defvar buffer-invisibility-spec
732 This variable specifies which kinds of @code{invisible} properties
733 actually make a character invisible. Setting this variable makes it
738 A character is invisible if its @code{invisible} property is
739 non-@code{nil}. This is the default.
742 Each element of the list specifies a criterion for invisibility; if a
743 character's @code{invisible} property fits any one of these criteria,
744 the character is invisible. The list can have two kinds of elements:
748 A character is invisible if its @code{invisible} property value
749 is @var{atom} or if it is a list with @var{atom} as a member.
751 @item (@var{atom} . t)
752 A character is invisible if its @code{invisible} property value
753 is @var{atom} or if it is a list with @var{atom} as a member.
754 Moreover, if this character is at the end of a line and is followed
755 by a visible newline, it displays an ellipsis.
760 Two functions are specifically provided for adding elements to
761 @code{buffer-invisibility-spec} and removing elements from it.
763 @defun add-to-invisibility-spec element
764 This function adds the element @var{element} to
765 @code{buffer-invisibility-spec}. If @code{buffer-invisibility-spec}
766 was @code{t}, it changes to a list, @code{(t)}, so that text whose
767 @code{invisible} property is @code{t} remains invisible.
770 @defun remove-from-invisibility-spec element
771 This removes the element @var{element} from
772 @code{buffer-invisibility-spec}. This does nothing if @var{element}
776 A convention for use of @code{buffer-invisibility-spec} is that a
777 major mode should use the mode's own name as an element of
778 @code{buffer-invisibility-spec} and as the value of the
779 @code{invisible} property:
782 ;; @r{If you want to display an ellipsis:}
783 (add-to-invisibility-spec '(my-symbol . t))
784 ;; @r{If you don't want ellipsis:}
785 (add-to-invisibility-spec 'my-symbol)
787 (overlay-put (make-overlay beginning end)
788 'invisible 'my-symbol)
790 ;; @r{When done with the overlays:}
791 (remove-from-invisibility-spec '(my-symbol . t))
792 ;; @r{Or respectively:}
793 (remove-from-invisibility-spec 'my-symbol)
796 @vindex line-move-ignore-invisible
797 Ordinarily, functions that operate on text or move point do not care
798 whether the text is invisible. The user-level line motion commands
799 explicitly ignore invisible newlines if
800 @code{line-move-ignore-invisible} is non-@code{nil} (the default), but
801 only because they are explicitly programmed to do so.
803 However, if a command ends with point inside or immediately after
804 invisible text, the main editing loop moves point further forward or
805 further backward (in the same direction that the command already moved
806 it) until that condition is no longer true. Thus, if the command
807 moved point back into an invisible range, Emacs moves point back to
808 the beginning of that range, following the previous visible character.
809 If the command moved point forward into an invisible range, Emacs
810 moves point forward past the first visible character that follows the
813 Incremental search can make invisible overlays visible temporarily
814 and/or permanently when a match includes invisible text. To enable
815 this, the overlay should have a non-@code{nil}
816 @code{isearch-open-invisible} property. The property value should be a
817 function to be called with the overlay as an argument. This function
818 should make the overlay visible permanently; it is used when the match
819 overlaps the overlay on exit from the search.
821 During the search, such overlays are made temporarily visible by
822 temporarily modifying their invisible and intangible properties. If you
823 want this to be done differently for a certain overlay, give it an
824 @code{isearch-open-invisible-temporary} property which is a function.
825 The function is called with two arguments: the first is the overlay, and
826 the second is @code{nil} to make the overlay visible, or @code{t} to
827 make it invisible again.
829 @node Selective Display
830 @section Selective Display
831 @cindex selective display
833 @dfn{Selective display} refers to a pair of related features for
834 hiding certain lines on the screen.
836 The first variant, explicit selective display, is designed for use
837 in a Lisp program: it controls which lines are hidden by altering the
838 text. This kind of hiding in some ways resembles the effect of the
839 @code{invisible} property (@pxref{Invisible Text}), but the two
840 features are different and do not work the same way.
842 In the second variant, the choice of lines to hide is made
843 automatically based on indentation. This variant is designed to be a
846 The way you control explicit selective display is by replacing a
847 newline (control-j) with a carriage return (control-m). The text that
848 was formerly a line following that newline is now hidden. Strictly
849 speaking, it is temporarily no longer a line at all, since only
850 newlines can separate lines; it is now part of the previous line.
852 Selective display does not directly affect editing commands. For
853 example, @kbd{C-f} (@code{forward-char}) moves point unhesitatingly
854 into hidden text. However, the replacement of newline characters with
855 carriage return characters affects some editing commands. For
856 example, @code{next-line} skips hidden lines, since it searches only
857 for newlines. Modes that use selective display can also define
858 commands that take account of the newlines, or that control which
859 parts of the text are hidden.
861 When you write a selectively displayed buffer into a file, all the
862 control-m's are output as newlines. This means that when you next read
863 in the file, it looks OK, with nothing hidden. The selective display
864 effect is seen only within Emacs.
866 @defvar selective-display
867 This buffer-local variable enables selective display. This means that
868 lines, or portions of lines, may be made hidden.
872 If the value of @code{selective-display} is @code{t}, then the character
873 control-m marks the start of hidden text; the control-m, and the rest
874 of the line following it, are not displayed. This is explicit selective
878 If the value of @code{selective-display} is a positive integer, then
879 lines that start with more than that many columns of indentation are not
883 When some portion of a buffer is hidden, the vertical movement
884 commands operate as if that portion did not exist, allowing a single
885 @code{next-line} command to skip any number of hidden lines.
886 However, character movement commands (such as @code{forward-char}) do
887 not skip the hidden portion, and it is possible (if tricky) to insert
888 or delete text in an hidden portion.
890 In the examples below, we show the @emph{display appearance} of the
891 buffer @code{foo}, which changes with the value of
892 @code{selective-display}. The @emph{contents} of the buffer do not
897 (setq selective-display nil)
900 ---------- Buffer: foo ----------
907 ---------- Buffer: foo ----------
911 (setq selective-display 2)
914 ---------- Buffer: foo ----------
919 ---------- Buffer: foo ----------
924 @defvar selective-display-ellipses
925 If this buffer-local variable is non-@code{nil}, then Emacs displays
926 @samp{@dots{}} at the end of a line that is followed by hidden text.
927 This example is a continuation of the previous one.
931 (setq selective-display-ellipses t)
934 ---------- Buffer: foo ----------
939 ---------- Buffer: foo ----------
943 You can use a display table to substitute other text for the ellipsis
944 (@samp{@dots{}}). @xref{Display Tables}.
947 @node Temporary Displays
948 @section Temporary Displays
950 Temporary displays are used by Lisp programs to put output into a
951 buffer and then present it to the user for perusal rather than for
952 editing. Many help commands use this feature.
954 @defspec with-output-to-temp-buffer buffer-name forms@dots{}
955 This function executes @var{forms} while arranging to insert any output
956 they print into the buffer named @var{buffer-name}, which is first
957 created if necessary, and put into Help mode. Finally, the buffer is
958 displayed in some window, but not selected.
960 If the @var{forms} do not change the major mode in the output buffer,
961 so that it is still Help mode at the end of their execution, then
962 @code{with-output-to-temp-buffer} makes this buffer read-only at the
963 end, and also scans it for function and variable names to make them
964 into clickable cross-references. @xref{Docstring hyperlinks, , Tips
965 for Documentation Strings}, in particular the item on hyperlinks in
966 documentation strings, for more details.
968 The string @var{buffer-name} specifies the temporary buffer, which
969 need not already exist. The argument must be a string, not a buffer.
970 The buffer is erased initially (with no questions asked), and it is
971 marked as unmodified after @code{with-output-to-temp-buffer} exits.
973 @code{with-output-to-temp-buffer} binds @code{standard-output} to the
974 temporary buffer, then it evaluates the forms in @var{forms}. Output
975 using the Lisp output functions within @var{forms} goes by default to
976 that buffer (but screen display and messages in the echo area, although
977 they are ``output'' in the general sense of the word, are not affected).
978 @xref{Output Functions}.
980 Several hooks are available for customizing the behavior
981 of this construct; they are listed below.
983 The value of the last form in @var{forms} is returned.
987 ---------- Buffer: foo ----------
988 This is the contents of foo.
989 ---------- Buffer: foo ----------
993 (with-output-to-temp-buffer "foo"
995 (print standard-output))
996 @result{} #<buffer foo>
998 ---------- Buffer: foo ----------
1003 ---------- Buffer: foo ----------
1008 @defvar temp-buffer-show-function
1009 If this variable is non-@code{nil}, @code{with-output-to-temp-buffer}
1010 calls it as a function to do the job of displaying a help buffer. The
1011 function gets one argument, which is the buffer it should display.
1013 It is a good idea for this function to run @code{temp-buffer-show-hook}
1014 just as @code{with-output-to-temp-buffer} normally would, inside of
1015 @code{save-selected-window} and with the chosen window and buffer
1019 @defvar temp-buffer-setup-hook
1020 @tindex temp-buffer-setup-hook
1021 This normal hook is run by @code{with-output-to-temp-buffer} before
1022 evaluating @var{body}. When the hook runs, the temporary buffer is
1023 current. This hook is normally set up with a function to put the
1024 buffer in Help mode.
1027 @defvar temp-buffer-show-hook
1028 This normal hook is run by @code{with-output-to-temp-buffer} after
1029 displaying the temporary buffer. When the hook runs, the temporary buffer
1030 is current, and the window it was displayed in is selected. This hook
1031 is normally set up with a function to make the buffer read only, and
1032 find function names and variable names in it, provided the major mode
1036 @defun momentary-string-display string position &optional char message
1037 This function momentarily displays @var{string} in the current buffer at
1038 @var{position}. It has no effect on the undo list or on the buffer's
1039 modification status.
1041 The momentary display remains until the next input event. If the next
1042 input event is @var{char}, @code{momentary-string-display} ignores it
1043 and returns. Otherwise, that event remains buffered for subsequent use
1044 as input. Thus, typing @var{char} will simply remove the string from
1045 the display, while typing (say) @kbd{C-f} will remove the string from
1046 the display and later (presumably) move point forward. The argument
1047 @var{char} is a space by default.
1049 The return value of @code{momentary-string-display} is not meaningful.
1051 If the string @var{string} does not contain control characters, you can
1052 do the same job in a more general way by creating (and then subsequently
1053 deleting) an overlay with a @code{before-string} property.
1054 @xref{Overlay Properties}.
1056 If @var{message} is non-@code{nil}, it is displayed in the echo area
1057 while @var{string} is displayed in the buffer. If it is @code{nil}, a
1058 default message says to type @var{char} to continue.
1060 In this example, point is initially located at the beginning of the
1065 ---------- Buffer: foo ----------
1066 This is the contents of foo.
1067 @point{}Second line.
1068 ---------- Buffer: foo ----------
1072 (momentary-string-display
1073 "**** Important Message! ****"
1075 "Type RET when done reading")
1080 ---------- Buffer: foo ----------
1081 This is the contents of foo.
1082 **** Important Message! ****Second line.
1083 ---------- Buffer: foo ----------
1085 ---------- Echo Area ----------
1086 Type RET when done reading
1087 ---------- Echo Area ----------
1096 You can use @dfn{overlays} to alter the appearance of a buffer's text on
1097 the screen, for the sake of presentation features. An overlay is an
1098 object that belongs to a particular buffer, and has a specified
1099 beginning and end. It also has properties that you can examine and set;
1100 these affect the display of the text within the overlay.
1102 An overlays uses markers to record its beginning and end; thus,
1103 editing the text of the buffer adjusts the beginning and end of each
1104 overlay so that it stays with the text. When you create the overlay,
1105 you can specify whether text inserted at the beginning should be
1106 inside the overlay or outside, and likewise for the end of the overlay.
1109 * Managing Overlays:: Creating and moving overlays.
1110 * Overlay Properties:: How to read and set properties.
1111 What properties do to the screen display.
1112 * Finding Overlays:: Searching for overlays.
1115 @node Managing Overlays
1116 @subsection Managing Overlays
1118 This section describes the functions to create, delete and move
1119 overlays, and to examine their contents. Overlay changes are not
1120 recorded in the buffer's undo list, since the overlays are not
1121 part of the buffer's contents.
1123 @defun overlayp object
1124 This function returns @code{t} if @var{object} is an overlay.
1127 @defun make-overlay start end &optional buffer front-advance rear-advance
1128 This function creates and returns an overlay that belongs to
1129 @var{buffer} and ranges from @var{start} to @var{end}. Both @var{start}
1130 and @var{end} must specify buffer positions; they may be integers or
1131 markers. If @var{buffer} is omitted, the overlay is created in the
1134 The arguments @var{front-advance} and @var{rear-advance} specify the
1135 marker insertion type for the start of the overlay and for the end of
1136 the overlay, respectively. @xref{Marker Insertion Types}. If they
1137 are both @code{nil}, the default, then the overlay extends to include
1138 any text inserted at the beginning, but not text inserted at the end.
1139 If @var{front-advance} is non-@code{nil}, text inserted at the
1140 beginning of the overlay is excluded from the overlay. If
1141 @var{rear-advance} is non-@code{nil}, text inserted at the end of the
1142 overlay is included in the overlay.
1145 @defun overlay-start overlay
1146 This function returns the position at which @var{overlay} starts,
1150 @defun overlay-end overlay
1151 This function returns the position at which @var{overlay} ends,
1155 @defun overlay-buffer overlay
1156 This function returns the buffer that @var{overlay} belongs to. It
1157 returns @code{nil} if @var{overlay} has been deleted.
1160 @defun delete-overlay overlay
1161 This function deletes @var{overlay}. The overlay continues to exist as
1162 a Lisp object, and its property list is unchanged, but it ceases to be
1163 attached to the buffer it belonged to, and ceases to have any effect on
1166 A deleted overlay is not permanently disconnected. You can give it a
1167 position in a buffer again by calling @code{move-overlay}.
1170 @defun move-overlay overlay start end &optional buffer
1171 This function moves @var{overlay} to @var{buffer}, and places its bounds
1172 at @var{start} and @var{end}. Both arguments @var{start} and @var{end}
1173 must specify buffer positions; they may be integers or markers.
1175 If @var{buffer} is omitted, @var{overlay} stays in the same buffer it
1176 was already associated with; if @var{overlay} was deleted, it goes into
1179 The return value is @var{overlay}.
1181 This is the only valid way to change the endpoints of an overlay. Do
1182 not try modifying the markers in the overlay by hand, as that fails to
1183 update other vital data structures and can cause some overlays to be
1187 @defun remove-overlays &optional start end name value
1188 This function removes all the overlays between @var{start} and
1189 @var{end} whose property @var{name} has the value @var{value}. It can
1190 move the endpoints of the overlays in the region, or split them.
1192 If @var{name} is omitted or @code{nil}, it means to delete all overlays in
1193 the specified region. If @var{start} and/or @var{end} are omitted or
1194 @code{nil}, that means the beginning and end of the buffer respectively.
1195 Therefore, @code{(remove-overlays)} removes all the overlays in the
1199 Here are some examples:
1202 ;; @r{Create an overlay.}
1203 (setq foo (make-overlay 1 10))
1204 @result{} #<overlay from 1 to 10 in display.texi>
1209 (overlay-buffer foo)
1210 @result{} #<buffer display.texi>
1211 ;; @r{Give it a property we can check later.}
1212 (overlay-put foo 'happy t)
1214 ;; @r{Verify the property is present.}
1215 (overlay-get foo 'happy)
1217 ;; @r{Move the overlay.}
1218 (move-overlay foo 5 20)
1219 @result{} #<overlay from 5 to 20 in display.texi>
1224 ;; @r{Delete the overlay.}
1225 (delete-overlay foo)
1227 ;; @r{Verify it is deleted.}
1229 @result{} #<overlay in no buffer>
1230 ;; @r{A deleted overlay has no position.}
1235 (overlay-buffer foo)
1237 ;; @r{Undelete the overlay.}
1238 (move-overlay foo 1 20)
1239 @result{} #<overlay from 1 to 20 in display.texi>
1240 ;; @r{Verify the results.}
1245 (overlay-buffer foo)
1246 @result{} #<buffer display.texi>
1247 ;; @r{Moving and deleting the overlay does not change its properties.}
1248 (overlay-get foo 'happy)
1252 @node Overlay Properties
1253 @subsection Overlay Properties
1255 Overlay properties are like text properties in that the properties that
1256 alter how a character is displayed can come from either source. But in
1257 most respects they are different. @xref{Text Properties}, for comparison.
1259 Text properties are considered a part of the text; overlays and
1260 their properties are specifically considered not to be part of the
1261 text. Thus, copying text between various buffers and strings
1262 preserves text properties, but does not try to preserve overlays.
1263 Changing a buffer's text properties marks the buffer as modified,
1264 while moving an overlay or changing its properties does not. Unlike
1265 text property changes, overlay property changes are not recorded in
1266 the buffer's undo list.
1268 These functions read and set the properties of an overlay:
1270 @defun overlay-get overlay prop
1271 This function returns the value of property @var{prop} recorded in
1272 @var{overlay}, if any. If @var{overlay} does not record any value for
1273 that property, but it does have a @code{category} property which is a
1274 symbol, that symbol's @var{prop} property is used. Otherwise, the value
1278 @defun overlay-put overlay prop value
1279 This function sets the value of property @var{prop} recorded in
1280 @var{overlay} to @var{value}. It returns @var{value}.
1283 @defun overlay-properties overlay
1284 This returns a copy of the property list of @var{overlay}.
1287 See also the function @code{get-char-property} which checks both
1288 overlay properties and text properties for a given character.
1289 @xref{Examining Properties}.
1291 Many overlay properties have special meanings; here is a table
1296 @kindex priority @r{(overlay property)}
1297 This property's value (which should be a nonnegative integer number)
1298 determines the priority of the overlay. The priority matters when two
1299 or more overlays cover the same character and both specify the same
1300 property; the one whose @code{priority} value is larger takes priority
1301 over the other. For the @code{face} property, the higher priority
1302 value does not completely replace the other; instead, its face
1303 attributes override the face attributes of the lower priority
1304 @code{face} property.
1306 Currently, all overlays take priority over text properties. Please
1307 avoid using negative priority values, as we have not yet decided just
1308 what they should mean.
1311 @kindex window @r{(overlay property)}
1312 If the @code{window} property is non-@code{nil}, then the overlay
1313 applies only on that window.
1316 @kindex category @r{(overlay property)}
1317 If an overlay has a @code{category} property, we call it the
1318 @dfn{category} of the overlay. It should be a symbol. The properties
1319 of the symbol serve as defaults for the properties of the overlay.
1322 @kindex face @r{(overlay property)}
1323 This property controls the way text is displayed---for example, which
1324 font and which colors. @xref{Faces}, for more information.
1326 In the simplest case, the value is a face name. It can also be a list;
1327 then each element can be any of these possibilities:
1331 A face name (a symbol or string).
1334 A property list of face attributes. This has the form (@var{keyword}
1335 @var{value} @dots{}), where each @var{keyword} is a face attribute
1336 name and @var{value} is a meaningful value for that attribute. With
1337 this feature, you do not need to create a face each time you want to
1338 specify a particular attribute for certain text. @xref{Face
1342 A cons cell of the form @code{(foreground-color . @var{color-name})} or
1343 @code{(background-color . @var{color-name})}. These elements specify
1344 just the foreground color or just the background color.
1346 @code{(foreground-color . @var{color-name})} has the same effect as
1347 @code{(:foreground @var{color-name})}; likewise for the background.
1351 @kindex mouse-face @r{(overlay property)}
1352 This property is used instead of @code{face} when the mouse is within
1353 the range of the overlay.
1356 @kindex display @r{(overlay property)}
1357 This property activates various features that change the
1358 way text is displayed. For example, it can make text appear taller
1359 or shorter, higher or lower, wider or narrower, or replaced with an image.
1360 @xref{Display Property}.
1363 @kindex help-echo @r{(overlay property)}
1364 If an overlay has a @code{help-echo} property, then when you move the
1365 mouse onto the text in the overlay, Emacs displays a help string in the
1366 echo area, or in the tooltip window. For details see @ref{Text
1369 @item modification-hooks
1370 @kindex modification-hooks @r{(overlay property)}
1371 This property's value is a list of functions to be called if any
1372 character within the overlay is changed or if text is inserted strictly
1375 The hook functions are called both before and after each change.
1376 If the functions save the information they receive, and compare notes
1377 between calls, they can determine exactly what change has been made
1380 When called before a change, each function receives four arguments: the
1381 overlay, @code{nil}, and the beginning and end of the text range to be
1384 When called after a change, each function receives five arguments: the
1385 overlay, @code{t}, the beginning and end of the text range just
1386 modified, and the length of the pre-change text replaced by that range.
1387 (For an insertion, the pre-change length is zero; for a deletion, that
1388 length is the number of characters deleted, and the post-change
1389 beginning and end are equal.)
1391 If these functions modify the buffer, they should bind
1392 @code{inhibit-modification-hooks} to @code{t} around doing so, to
1393 avoid confusing the internal mechanism that calls these hooks.
1395 @item insert-in-front-hooks
1396 @kindex insert-in-front-hooks @r{(overlay property)}
1397 This property's value is a list of functions to be called before and
1398 after inserting text right at the beginning of the overlay. The calling
1399 conventions are the same as for the @code{modification-hooks} functions.
1401 @item insert-behind-hooks
1402 @kindex insert-behind-hooks @r{(overlay property)}
1403 This property's value is a list of functions to be called before and
1404 after inserting text right at the end of the overlay. The calling
1405 conventions are the same as for the @code{modification-hooks} functions.
1408 @kindex invisible @r{(overlay property)}
1409 The @code{invisible} property can make the text in the overlay
1410 invisible, which means that it does not appear on the screen.
1411 @xref{Invisible Text}, for details.
1414 @kindex intangible @r{(overlay property)}
1415 The @code{intangible} property on an overlay works just like the
1416 @code{intangible} text property. @xref{Special Properties}, for details.
1418 @item isearch-open-invisible
1419 This property tells incremental search how to make an invisible overlay
1420 visible, permanently, if the final match overlaps it. @xref{Invisible
1423 @item isearch-open-invisible-temporary
1424 This property tells incremental search how to make an invisible overlay
1425 visible, temporarily, during the search. @xref{Invisible Text}.
1428 @kindex before-string @r{(overlay property)}
1429 This property's value is a string to add to the display at the beginning
1430 of the overlay. The string does not appear in the buffer in any
1431 sense---only on the screen.
1434 @kindex after-string @r{(overlay property)}
1435 This property's value is a string to add to the display at the end of
1436 the overlay. The string does not appear in the buffer in any
1437 sense---only on the screen.
1440 @kindex evaporate @r{(overlay property)}
1441 If this property is non-@code{nil}, the overlay is deleted automatically
1442 if it becomes empty (i.e., if its length becomes zero). If you give
1443 an empty overlay a non-@code{nil} @code{evaporate} property, that deletes
1447 @cindex keymap of character (and overlays)
1448 @kindex local-map @r{(overlay property)}
1449 If this property is non-@code{nil}, it specifies a keymap for a portion
1450 of the text. The property's value replaces the buffer's local map, when
1451 the character after point is within the overlay. @xref{Active Keymaps}.
1454 @kindex keymap @r{(overlay property)}
1455 The @code{keymap} property is similar to @code{local-map} but overrides the
1456 buffer's local map (and the map specified by the @code{local-map}
1457 property) rather than replacing it.
1460 @node Finding Overlays
1461 @subsection Searching for Overlays
1463 @defun overlays-at pos
1464 This function returns a list of all the overlays that cover the
1465 character at position @var{pos} in the current buffer. The list is in
1466 no particular order. An overlay contains position @var{pos} if it
1467 begins at or before @var{pos}, and ends after @var{pos}.
1469 To illustrate usage, here is a Lisp function that returns a list of the
1470 overlays that specify property @var{prop} for the character at point:
1473 (defun find-overlays-specifying (prop)
1474 (let ((overlays (overlays-at (point)))
1477 (let ((overlay (car overlays)))
1478 (if (overlay-get overlay prop)
1479 (setq found (cons overlay found))))
1480 (setq overlays (cdr overlays)))
1485 @defun overlays-in beg end
1486 This function returns a list of the overlays that overlap the region
1487 @var{beg} through @var{end}. ``Overlap'' means that at least one
1488 character is contained within the overlay and also contained within the
1489 specified region; however, empty overlays are included in the result if
1490 they are located at @var{beg}, or strictly between @var{beg} and @var{end}.
1493 @defun next-overlay-change pos
1494 This function returns the buffer position of the next beginning or end
1495 of an overlay, after @var{pos}. If there is none, it returns
1499 @defun previous-overlay-change pos
1500 This function returns the buffer position of the previous beginning or
1501 end of an overlay, before @var{pos}. If there is none, it returns
1505 Here's an easy way to use @code{next-overlay-change} to search for the
1506 next character which gets a non-@code{nil} @code{happy} property from
1507 either its overlays or its text properties (@pxref{Property Search}):
1510 (defun find-overlay-prop (prop)
1512 (while (and (not (eobp))
1513 (not (get-char-property (point) 'happy)))
1514 (goto-char (min (next-overlay-change (point))
1515 (next-single-property-change (point) 'happy))))
1522 Since not all characters have the same width, these functions let you
1523 check the width of a character. @xref{Primitive Indent}, and
1524 @ref{Screen Lines}, for related functions.
1526 @defun char-width char
1527 This function returns the width in columns of the character @var{char},
1528 if it were displayed in the current buffer and the selected window.
1531 @defun string-width string
1532 This function returns the width in columns of the string @var{string},
1533 if it were displayed in the current buffer and the selected window.
1536 @defun truncate-string-to-width string width &optional start-column padding ellipsis
1537 This function returns the part of @var{string} that fits within
1538 @var{width} columns, as a new string.
1540 If @var{string} does not reach @var{width}, then the result ends where
1541 @var{string} ends. If one multi-column character in @var{string}
1542 extends across the column @var{width}, that character is not included in
1543 the result. Thus, the result can fall short of @var{width} but cannot
1546 The optional argument @var{start-column} specifies the starting column.
1547 If this is non-@code{nil}, then the first @var{start-column} columns of
1548 the string are omitted from the value. If one multi-column character in
1549 @var{string} extends across the column @var{start-column}, that
1550 character is not included.
1552 The optional argument @var{padding}, if non-@code{nil}, is a padding
1553 character added at the beginning and end of the result string, to extend
1554 it to exactly @var{width} columns. The padding character is used at the
1555 end of the result if it falls short of @var{width}. It is also used at
1556 the beginning of the result if one multi-column character in
1557 @var{string} extends across the column @var{start-column}.
1559 If @var{ellipsis} is non-@code{nil}, it should be a string which will
1560 replace the end of @var{str} (including any padding) if it extends
1561 beyond @var{end-column}, unless the display width of @var{str} is
1562 equal to or less than the display width of @var{ellipsis}. If
1563 @var{ellipsis} is non-@code{nil} and not a string, it stands for
1567 (truncate-string-to-width "\tab\t" 12 4)
1569 (truncate-string-to-width "\tab\t" 12 4 ?\s)
1575 @section Line Height
1578 The total height of each display line consists of the height of the
1579 contents of the line, and additional vertical line spacing below the
1582 The height of the line contents is normally determined from the
1583 maximum height of any character or image on that display line,
1584 including the final newline if there is one. (A line that is
1585 continued doesn't include a final newline.) In the most common case,
1586 the line height equals the height of the default frame font.
1588 There are several ways to explicitly control or change the line
1589 height, either by specifying an absolute height for the display line,
1590 or by adding additional vertical space below one or all lines.
1592 @kindex line-height @r{(text property)}
1593 A newline can have a @code{line-height} text or overlay property
1594 that controls the total height of the display line ending in that
1597 If the property value is a list @code{(@var{height} @var{total})},
1598 then @var{height} is used as the actual property value for the
1599 @code{line-height}, and @var{total} specifies the total displayed
1600 height of the line, so the line spacing added below the line equals
1601 the @var{total} height minus the actual line height. In this case,
1602 the other ways to specify the line spacing are ignored.
1604 If the property value is @code{t}, the displayed height of the
1605 line is exactly what its contents demand; no line-spacing is added.
1606 This case is useful for tiling small images or image slices without
1607 adding blank areas between the images.
1609 If the property value is not @code{t}, it is a height spec. A height
1610 spec stands for a numeric height value; this height spec specifies the
1611 actual line height, @var{line-height}. There are several ways to
1612 write a height spec; here's how each of them translates into a numeric
1617 If the height spec is a positive integer, the height value is that integer.
1619 If the height spec is a float, @var{float}, the numeric height value
1620 is @var{float} times the frame's default line height.
1621 @item (@var{face} . @var{ratio})
1622 If the height spec is a cons of the format shown, the numeric height
1623 is @var{ratio} times the height of face @var{face}. @var{ratio} can
1624 be any type of number, or @code{nil} which means a ratio of 1.
1625 If @var{face} is @code{t}, it refers to the current face.
1626 @item (nil . @var{ratio})
1627 If the height spec is a cons of the format shown, the numeric height
1628 is @var{ratio} times the height of the contents of the line.
1631 Thus, any valid non-@code{t} property value specifies a height in pixels,
1632 @var{line-height}, one way or another. If the line contents' height
1633 is less than @var{line-height}, Emacs adds extra vertical space above
1634 the line to achieve the total height @var{line-height}. Otherwise,
1635 @var{line-height} has no effect.
1637 If you don't specify the @code{line-height} property, the line's
1638 height consists of the contents' height plus the line spacing.
1639 There are several ways to specify the line spacing for different
1640 parts of Emacs text.
1642 @vindex default-line-spacing
1643 You can specify the line spacing for all lines in a frame with the
1644 @code{line-spacing} frame parameter (@pxref{Layout Parameters}).
1645 However, if the variable @code{default-line-spacing} is
1646 non-@code{nil}, it overrides the frame's @code{line-spacing}
1647 parameter. An integer value specifies the number of pixels put below
1648 lines on window systems. A floating point number specifies the
1649 spacing relative to the frame's default line height.
1651 @vindex line-spacing
1652 You can specify the line spacing for all lines in a buffer via the
1653 buffer-local @code{line-spacing} variable. An integer value specifies
1654 the number of pixels put below lines on window systems. A floating
1655 point number specifies the spacing relative to the default frame line
1656 height. This overrides line spacings specified for the frame.
1658 @kindex line-spacing @r{(text property)}
1659 Finally, a newline can have a @code{line-spacing} text or overlay
1660 property that controls the height of the display line ending with that
1661 newline. The property value overrides the default frame line spacing
1662 and the buffer local @code{line-spacing} variable.
1664 One way or another, these mechanisms specify a Lisp value for the
1665 spacing of each line. The value is a height spec, and it translates
1666 into a Lisp value as described above. However, in this case the
1667 numeric height value specifies the line spacing, rather than the line
1674 A @dfn{face} is a named collection of graphical attributes: font
1675 family, foreground color, background color, optional underlining, and
1676 many others. Faces are used in Emacs to control the style of display of
1677 particular parts of the text or the frame.
1680 Each face has its own @dfn{face number}, which distinguishes faces at
1681 low levels within Emacs. However, for most purposes, you refer to
1682 faces in Lisp programs by the symbols that name them.
1685 This function returns @code{t} if @var{object} is a face name string
1686 or symbol (or if it is a vector of the kind used internally to record
1687 face data). It returns @code{nil} otherwise.
1690 Each face name is meaningful for all frames, and by default it has the
1691 same meaning in all frames. But you can arrange to give a particular
1692 face name a special meaning in one frame if you wish.
1695 * Standard Faces:: The faces Emacs normally comes with.
1696 * Defining Faces:: How to define a face with @code{defface}.
1697 * Face Attributes:: What is in a face?
1698 * Attribute Functions:: Functions to examine and set face attributes.
1699 * Displaying Faces:: How Emacs combines the faces specified for a character.
1700 * Font Selection:: Finding the best available font for a face.
1701 * Face Functions:: How to define and examine faces.
1702 * Auto Faces:: Hook for automatic face assignment.
1703 * Font Lookup:: Looking up the names of available fonts
1704 and information about them.
1705 * Fontsets:: A fontset is a collection of fonts
1706 that handle a range of character sets.
1709 @node Standard Faces
1710 @subsection Standard Faces
1712 This table lists all the standard faces and their uses. Most of them
1713 are used for displaying certain parts of the frames or certain kinds of
1714 text; you can control how those places look by customizing these faces.
1718 @kindex default @r{(face name)}
1719 This face is used for ordinary text.
1722 @kindex mode-line @r{(face name)}
1723 This face is used for the mode line of the selected window, and for
1724 menu bars when toolkit menus are not used.
1727 @kindex modeline @r{(face name)}
1728 This is an alias for the @code{mode-line} face, for compatibility with
1731 @item mode-line-inactive
1732 @kindex mode-line-inactive @r{(face name)}
1733 This face is used for mode lines of non-selected windows.
1734 This face inherits from @code{mode-line}, so changes
1735 in that face affect all windows.
1738 @kindex header-line @r{(face name)}
1739 This face is used for the header lines of windows that have them.
1742 This face controls the display of menus, both their colors and their
1743 font. (This works only on certain systems.)
1746 @kindex fringe @r{(face name)}
1747 This face controls the default colors of window fringes, the thin
1748 areas on either side that are used to display continuation and
1749 truncation glyphs. Other faces used to display bitmaps in the fringe
1750 are implicitly merged with this face.
1752 @item minibuffer-prompt
1753 @kindex minibuffer-prompt @r{(face name)}
1754 @vindex minibuffer-prompt-properties
1755 This face is used for the text of minibuffer prompts. By default,
1756 Emacs automatically adds this face to the value of
1757 @code{minibuffer-prompt-properties}, which is a list of text
1758 properties used to display the prompt text.
1761 @kindex scroll-bar @r{(face name)}
1762 This face controls the colors for display of scroll bars.
1765 @kindex tool-bar @r{(face name)}
1766 This face is used for display of the tool bar, if any.
1769 @kindex region @r{(face name)}
1770 This face is used for highlighting the region in Transient Mark mode.
1772 @item secondary-selection
1773 @kindex secondary-selection @r{(face name)}
1774 This face is used to show any secondary selection you have made.
1777 @kindex highlight @r{(face name)}
1778 This face is meant to be used for highlighting for various purposes.
1780 @item mode-line-highlight
1781 @kindex mode-line-highlight @r{(face name)}
1782 This face is used for highlighting something on @code{mode-line} or
1783 @code{header-line} for various purposes.
1785 @item trailing-whitespace
1786 @kindex trailing-whitespace @r{(face name)}
1787 This face is used to display excess whitespace at the end of a line,
1788 if @code{show-trailing-whitespace} is non-@code{nil}.
1791 @kindex escape-glyph @r{(face name)}
1792 This face is used to display control characters and escape glyphs.
1795 In contrast, these faces are provided to change the appearance of text
1796 in specific ways. You can use them on specific text, when you want
1797 the effects they produce.
1801 @kindex bold @r{(face name)}
1802 This face uses a bold font, if possible. It uses the bold variant of
1803 the frame's font, if it has one. It's up to you to choose a default
1804 font that has a bold variant, if you want to use one.
1807 @kindex italic @r{(face name)}
1808 This face uses the italic variant of the frame's font, if it has one.
1811 @kindex bold-italic @r{(face name)}
1812 This face uses the bold italic variant of the frame's font, if it has
1816 @kindex underline @r{(face name)}
1817 This face underlines text.
1820 @kindex fixed-pitch @r{(face name)}
1821 This face forces use of a particular fixed-width font.
1823 @item variable-pitch
1824 @kindex variable-pitch @r{(face name)}
1825 This face forces use of a particular variable-width font. It's
1826 reasonable to customize this to use a different variable-width font, if
1827 you like, but you should not make it a fixed-width font.
1830 @kindex shadow @r{(face name)}
1831 This face is used for making the text less noticeable than the
1832 surrounding ordinary text.
1835 @defvar show-trailing-whitespace
1836 @tindex show-trailing-whitespace
1837 If this variable is non-@code{nil}, Emacs uses the
1838 @code{trailing-whitespace} face to display any spaces and tabs at the
1842 @node Defining Faces
1843 @subsection Defining Faces
1845 The way to define a new face is with @code{defface}. This creates a
1846 kind of customization item (@pxref{Customization}) which the user can
1847 customize using the Customization buffer (@pxref{Easy Customization,,,
1848 emacs, The GNU Emacs Manual}).
1850 @defmac defface face spec doc [keyword value]...
1851 This declares @var{face} as a customizable face that defaults
1852 according to @var{spec}. You should not quote the symbol @var{face},
1853 and it should not end in @samp{-face} (that would be redundant). The
1854 argument @var{doc} specifies the face documentation. The keywords you
1855 can use in @code{defface} are the same as in @code{defgroup} and
1856 @code{defcustom} (@pxref{Common Keywords}).
1858 When @code{defface} executes, it defines the face according to
1859 @var{spec}, then uses any customizations that were read from the
1860 init file (@pxref{Init File}) to override that specification.
1862 The purpose of @var{spec} is to specify how the face should appear on
1863 different kinds of terminals. It should be an alist whose elements
1864 have the form @code{(@var{display} @var{atts})}. Each element's
1865 @sc{car}, @var{display}, specifies a class of terminals. (The first
1866 element, if it s @sc{car} is @code{default}, is special---it specifies
1867 defaults for the remaining elements). The element's @sc{cadr},
1868 @var{atts}, is a list of face attributes and their values; it
1869 specifies what the face should look like on that kind of terminal.
1870 The possible attributes are defined in the value of
1871 @code{custom-face-attributes}.
1873 The @var{display} part of an element of @var{spec} determines which
1874 frames the element matches. If more than one element of @var{spec}
1875 matches a given frame, the first element that matches is the one used
1876 for that frame. There are three possibilities for @var{display}:
1879 @item @code{default}
1880 This element of @var{spec} doesn't match any frames; instead, it
1881 specifies defaults that apply to all frames. This kind of element, if
1882 used, must be the first element of @var{spec}. Each of the following
1883 elements can override any or all of these defaults.
1886 This element of @var{spec} matches all frames. Therefore, any
1887 subsequent elements of @var{spec} are never used. Normally
1888 @code{t} is used in the last (or only) element of @var{spec}.
1891 If @var{display} is a list, each element should have the form
1892 @code{(@var{characteristic} @var{value}@dots{})}. Here
1893 @var{characteristic} specifies a way of classifying frames, and the
1894 @var{value}s are possible classifications which @var{display} should
1895 apply to. Here are the possible values of @var{characteristic}:
1899 The kind of window system the frame uses---either @code{graphic} (any
1900 graphics-capable display), @code{x}, @code{pc} (for the MS-DOS console),
1901 @code{w32} (for MS Windows 9X/NT), or @code{tty} (a non-graphics-capable
1905 What kinds of colors the frame supports---either @code{color},
1906 @code{grayscale}, or @code{mono}.
1909 The kind of background---either @code{light} or @code{dark}.
1912 An integer that represents the minimum number of colors the frame
1913 should support. This matches a frame if its
1914 @code{display-color-cells} value is at least the specified integer.
1917 Whether or not the frame can display the face attributes given in
1918 @var{value}@dots{} (@pxref{Face Attributes}). See the documentation
1919 for the function @code{display-supports-face-attributes-p} for more
1920 information on exactly how this testing is done. @xref{Display Face
1924 If an element of @var{display} specifies more than one @var{value} for a
1925 given @var{characteristic}, any of those values is acceptable. If
1926 @var{display} has more than one element, each element should specify a
1927 different @var{characteristic}; then @emph{each} characteristic of the
1928 frame must match one of the @var{value}s specified for it in
1933 Here's how the standard face @code{region} is defined:
1937 '((((class color) (min-colors 88) (background dark))
1938 :background "blue3")
1940 (((class color) (min-colors 88) (background light))
1941 :background "lightgoldenrod2")
1942 (((class color) (min-colors 16) (background dark))
1943 :background "blue3")
1944 (((class color) (min-colors 16) (background light))
1945 :background "lightgoldenrod2")
1946 (((class color) (min-colors 8))
1947 :background "blue" :foreground "white")
1948 (((type tty) (class mono))
1950 (t :background "gray"))
1952 "Basic face for highlighting the region."
1953 :group 'basic-faces)
1957 Internally, @code{defface} uses the symbol property
1958 @code{face-defface-spec} to record the face attributes specified in
1959 @code{defface}, @code{saved-face} for the attributes saved by the user
1960 with the customization buffer, @code{customized-face} for the
1961 attributes customized by the user for the current session, but not
1962 saved, and @code{face-documentation} for the documentation string.
1964 @defopt frame-background-mode
1965 This option, if non-@code{nil}, specifies the background type to use for
1966 interpreting face definitions. If it is @code{dark}, then Emacs treats
1967 all frames as if they had a dark background, regardless of their actual
1968 background colors. If it is @code{light}, then Emacs treats all frames
1969 as if they had a light background.
1972 @node Face Attributes
1973 @subsection Face Attributes
1974 @cindex face attributes
1976 The effect of using a face is determined by a fixed set of @dfn{face
1977 attributes}. This table lists all the face attributes, and what they
1978 mean. Note that in general, more than one face can be specified for a
1979 given piece of text; when that happens, the attributes of all the faces
1980 are merged to specify how to display the text. @xref{Displaying Faces}.
1982 Any attribute in a face can have the value @code{unspecified}. This
1983 means the face doesn't specify that attribute. In face merging, when
1984 the first face fails to specify a particular attribute, that means the
1985 next face gets a chance. However, the @code{default} face must
1986 specify all attributes.
1988 Some of these font attributes are meaningful only on certain kinds of
1989 displays---if your display cannot handle a certain attribute, the
1990 attribute is ignored. (The attributes @code{:family}, @code{:width},
1991 @code{:height}, @code{:weight}, and @code{:slant} correspond to parts of
1992 an X Logical Font Descriptor.)
1996 Font family name, or fontset name (@pxref{Fontsets}). If you specify a
1997 font family name, the wild-card characters @samp{*} and @samp{?} are
2001 Relative proportionate width, also known as the character set width or
2002 set width. This should be one of the symbols @code{ultra-condensed},
2003 @code{extra-condensed}, @code{condensed}, @code{semi-condensed},
2004 @code{normal}, @code{semi-expanded}, @code{expanded},
2005 @code{extra-expanded}, or @code{ultra-expanded}.
2008 Either the font height, an integer in units of 1/10 point, a floating
2009 point number specifying the amount by which to scale the height of any
2010 underlying face, or a function, which is called with the old height
2011 (from the underlying face), and should return the new height.
2014 Font weight---a symbol from this series (from most dense to most faint):
2015 @code{ultra-bold}, @code{extra-bold}, @code{bold}, @code{semi-bold},
2016 @code{normal}, @code{semi-light}, @code{light}, @code{extra-light},
2017 or @code{ultra-light}.
2019 On a text-only terminal, any weight greater than normal is displayed as
2020 extra bright, and any weight less than normal is displayed as
2021 half-bright (provided the terminal supports the feature).
2024 Font slant---one of the symbols @code{italic}, @code{oblique}, @code{normal},
2025 @code{reverse-italic}, or @code{reverse-oblique}.
2027 On a text-only terminal, slanted text is displayed as half-bright, if
2028 the terminal supports the feature.
2031 Foreground color, a string. The value can be a system-defined color
2032 name, or a hexadecimal color specification of the form
2033 @samp{#@var{rr}@var{gg}@var{bb}}. (@samp{#000000} is black,
2034 @samp{#ff0000} is red, @samp{#00ff00} is green, @samp{#0000ff} is
2035 blue, and @samp{#ffffff} is white.)
2038 Background color, a string, like the foreground color.
2040 @item :inverse-video
2041 Whether or not characters should be displayed in inverse video. The
2042 value should be @code{t} (yes) or @code{nil} (no).
2045 The background stipple, a bitmap.
2047 The value can be a string; that should be the name of a file containing
2048 external-format X bitmap data. The file is found in the directories
2049 listed in the variable @code{x-bitmap-file-path}.
2051 Alternatively, the value can specify the bitmap directly, with a list
2052 of the form @code{(@var{width} @var{height} @var{data})}. Here,
2053 @var{width} and @var{height} specify the size in pixels, and
2054 @var{data} is a string containing the raw bits of the bitmap, row by
2055 row. Each row occupies @math{(@var{width} + 7) / 8} consecutive bytes
2056 in the string (which should be a unibyte string for best results).
2057 This means that each row always occupies at least one whole byte.
2059 If the value is @code{nil}, that means use no stipple pattern.
2061 Normally you do not need to set the stipple attribute, because it is
2062 used automatically to handle certain shades of gray.
2065 Whether or not characters should be underlined, and in what color. If
2066 the value is @code{t}, underlining uses the foreground color of the
2067 face. If the value is a string, underlining uses that color. The
2068 value @code{nil} means do not underline.
2071 Whether or not characters should be overlined, and in what color.
2072 The value is used like that of @code{:underline}.
2074 @item :strike-through
2075 Whether or not characters should be strike-through, and in what
2076 color. The value is used like that of @code{:underline}.
2079 The name of a face from which to inherit attributes, or a list of face
2080 names. Attributes from inherited faces are merged into the face like an
2081 underlying face would be, with higher priority than underlying faces.
2082 If a list of faces is used, attributes from faces earlier in the list
2083 override those from later faces.
2086 Whether or not a box should be drawn around characters, its color, the
2087 width of the box lines, and 3D appearance.
2090 Here are the possible values of the @code{:box} attribute, and what
2098 Draw a box with lines of width 1, in the foreground color.
2101 Draw a box with lines of width 1, in color @var{color}.
2103 @item @code{(:line-width @var{width} :color @var{color} :style @var{style})}
2104 This way you can explicitly specify all aspects of the box. The value
2105 @var{width} specifies the width of the lines to draw; it defaults to 1.
2107 The value @var{color} specifies the color to draw with. The default is
2108 the foreground color of the face for simple boxes, and the background
2109 color of the face for 3D boxes.
2111 The value @var{style} specifies whether to draw a 3D box. If it is
2112 @code{released-button}, the box looks like a 3D button that is not being
2113 pressed. If it is @code{pressed-button}, the box looks like a 3D button
2114 that is being pressed. If it is @code{nil} or omitted, a plain 2D box
2118 In older versions of Emacs, before @code{:family}, @code{:height},
2119 @code{:width}, @code{:weight}, and @code{:slant} existed, these
2120 attributes were used to specify the type face. They are now
2121 semi-obsolete, but they still work:
2125 This attribute specifies the font name.
2128 A non-@code{nil} value specifies a bold font.
2131 A non-@code{nil} value specifies an italic font.
2134 For compatibility, you can still set these ``attributes'', even
2135 though they are not real face attributes. Here is what that does:
2139 You can specify an X font name as the ``value'' of this ``attribute'';
2140 that sets the @code{:family}, @code{:width}, @code{:height},
2141 @code{:weight}, and @code{:slant} attributes according to the font name.
2143 If the value is a pattern with wildcards, the first font that matches
2144 the pattern is used to set these attributes.
2147 A non-@code{nil} makes the face bold; @code{nil} makes it normal.
2148 This actually works by setting the @code{:weight} attribute.
2151 A non-@code{nil} makes the face italic; @code{nil} makes it normal.
2152 This actually works by setting the @code{:slant} attribute.
2155 @defvar x-bitmap-file-path
2156 This variable specifies a list of directories for searching
2157 for bitmap files, for the @code{:stipple} attribute.
2160 @defun bitmap-spec-p object
2161 This returns @code{t} if @var{object} is a valid bitmap specification,
2162 suitable for use with @code{:stipple} (see above). It returns
2163 @code{nil} otherwise.
2166 @node Attribute Functions
2167 @subsection Face Attribute Functions
2169 You can modify the attributes of an existing face with the following
2170 functions. If you specify @var{frame}, they affect just that frame;
2171 otherwise, they affect all frames as well as the defaults that apply to
2174 @tindex set-face-attribute
2175 @defun set-face-attribute face frame &rest arguments
2176 This function sets one or more attributes of face @var{face}
2177 for frame @var{frame}. If @var{frame} is @code{nil}, it sets
2178 the attribute for all frames, and the defaults for new frames.
2180 The extra arguments @var{arguments} specify the attributes to set, and
2181 the values for them. They should consist of alternating attribute names
2182 (such as @code{:family} or @code{:underline}) and corresponding values.
2186 (set-face-attribute 'foo nil
2193 sets the attributes @code{:width}, @code{:weight} and @code{:underline}
2194 to the corresponding values.
2197 @tindex face-attribute
2198 @defun face-attribute face attribute &optional frame inherit
2199 This returns the value of the @var{attribute} attribute of face
2200 @var{face} on @var{frame}. If @var{frame} is @code{nil},
2201 that means the selected frame (@pxref{Input Focus}).
2203 If @var{frame} is @code{t}, the value is the default for
2204 @var{face} for new frames.
2206 If @var{inherit} is @code{nil}, only attributes directly defined by
2207 @var{face} are considered, so the return value may be
2208 @code{unspecified}, or a relative value. If @var{inherit} is
2209 non-@code{nil}, @var{face}'s definition of @var{attribute} is merged
2210 with the faces specified by its @code{:inherit} attribute; however the
2211 return value may still be @code{unspecified} or relative. If
2212 @var{inherit} is a face or a list of faces, then the result is further
2213 merged with that face (or faces), until it becomes specified and
2216 To ensure that the return value is always specified and absolute, use
2217 a value of @code{default} for @var{inherit}; this will resolve any
2218 unspecified or relative values by merging with the @code{default} face
2219 (which is always completely specified).
2224 (face-attribute 'bold :weight)
2229 The functions above did not exist before Emacs 21. For compatibility
2230 with older Emacs versions, you can use the following functions to set
2231 and examine the face attributes which existed in those versions.
2233 @tindex face-attribute-relative-p
2234 @defun face-attribute-relative-p attribute value
2235 This function returns non-@code{nil} if @var{value}, when used as
2236 the value of the face attribute @var{attribute}, is relative (that is,
2237 if it modifies an underlying or inherited value of @var{attribute}).
2240 @tindex merge-face-attribute
2241 @defun merge-face-attribute attribute value1 value2
2242 If @var{value1} is a relative value for the face attribute
2243 @var{attribute}, returns it merged with the underlying value
2244 @var{value2}; otherwise, if @var{value1} is an absolute value for the
2245 face attribute @var{attribute}, returns @var{value1} unchanged.
2248 @defun set-face-foreground face color &optional frame
2249 @defunx set-face-background face color &optional frame
2250 These functions set the foreground (or background, respectively) color
2251 of face @var{face} to @var{color}. The argument @var{color} should be a
2252 string, the name of a color.
2254 Certain shades of gray are implemented by stipple patterns on
2255 black-and-white screens.
2258 @defun set-face-stipple face pattern &optional frame
2259 This function sets the background stipple pattern of face @var{face}
2260 to @var{pattern}. The argument @var{pattern} should be the name of a
2261 stipple pattern defined by the X server, or actual bitmap data
2262 (@pxref{Face Attributes}), or @code{nil} meaning don't use stipple.
2264 Normally there is no need to pay attention to stipple patterns, because
2265 they are used automatically to handle certain shades of gray.
2268 @defun set-face-font face font &optional frame
2269 This function sets the font of face @var{face}. This actually sets
2270 the attributes @code{:family}, @code{:width}, @code{:height},
2271 @code{:weight}, and @code{:slant} according to the font name
2275 @defun set-face-bold-p face bold-p &optional frame
2276 This function specifies whether @var{face} should be bold. If
2277 @var{bold-p} is non-@code{nil}, that means yes; @code{nil} means no.
2278 This actually sets the @code{:weight} attribute.
2281 @defun set-face-italic-p face italic-p &optional frame
2282 This function specifies whether @var{face} should be italic. If
2283 @var{italic-p} is non-@code{nil}, that means yes; @code{nil} means no.
2284 This actually sets the @code{:slant} attribute.
2287 @defun set-face-underline-p face underline-p &optional frame
2288 This function sets the underline attribute of face @var{face}.
2289 Non-@code{nil} means do underline; @code{nil} means don't.
2292 @defun invert-face face &optional frame
2293 This function inverts the @code{:inverse-video} attribute of face
2294 @var{face}. If the attribute is @code{nil}, this function sets it to
2295 @code{t}, and vice versa.
2298 These functions examine the attributes of a face. If you don't
2299 specify @var{frame}, they refer to the default data for new frames.
2300 They return the symbol @code{unspecified} if the face doesn't define any
2301 value for that attribute.
2303 @defun face-foreground face &optional frame inherit
2304 @defunx face-background face &optional frame
2305 These functions return the foreground color (or background color,
2306 respectively) of face @var{face}, as a string.
2308 If @var{inherit} is @code{nil}, only a color directly defined by the face is
2309 returned. If @var{inherit} is non-@code{nil}, any faces specified by its
2310 @code{:inherit} attribute are considered as well, and if @var{inherit}
2311 is a face or a list of faces, then they are also considered, until a
2312 specified color is found. To ensure that the return value is always
2313 specified, use a value of @code{default} for @var{inherit}.
2316 @defun face-stipple face &optional frame inherit
2317 This function returns the name of the background stipple pattern of face
2318 @var{face}, or @code{nil} if it doesn't have one.
2320 If @var{inherit} is @code{nil}, only a stipple directly defined by the
2321 face is returned. If @var{inherit} is non-@code{nil}, any faces
2322 specified by its @code{:inherit} attribute are considered as well, and
2323 if @var{inherit} is a face or a list of faces, then they are also
2324 considered, until a specified stipple is found. To ensure that the
2325 return value is always specified, use a value of @code{default} for
2329 @defun face-font face &optional frame
2330 This function returns the name of the font of face @var{face}.
2333 @defun face-bold-p face &optional frame
2334 This function returns @code{t} if @var{face} is bold---that is, if it is
2335 bolder than normal. It returns @code{nil} otherwise.
2338 @defun face-italic-p face &optional frame
2339 This function returns @code{t} if @var{face} is italic or oblique,
2340 @code{nil} otherwise.
2343 @defun face-underline-p face &optional frame
2344 This function returns the @code{:underline} attribute of face @var{face}.
2347 @defun face-inverse-video-p face &optional frame
2348 This function returns the @code{:inverse-video} attribute of face @var{face}.
2351 @node Displaying Faces
2352 @subsection Displaying Faces
2354 Here are the ways to specify which faces to use for display of text:
2358 With defaults. The @code{default} face is used as the ultimate
2359 default for all text. (In Emacs 19 and 20, the @code{default}
2360 face is used only when no other face is specified.)
2363 For a mode line or header line, the face @code{mode-line} or
2364 @code{mode-line-inactive}, or @code{header-line}, is merged in just
2365 before @code{default}.
2368 With text properties. A character can have a @code{face} property; if
2369 so, the faces and face attributes specified there apply. @xref{Special
2372 If the character has a @code{mouse-face} property, that is used instead
2373 of the @code{face} property when the mouse is ``near enough'' to the
2377 With overlays. An overlay can have @code{face} and @code{mouse-face}
2378 properties too; they apply to all the text covered by the overlay.
2381 With a region that is active. In Transient Mark mode, the region is
2382 highlighted with the face @code{region} (@pxref{Standard Faces}).
2385 With special glyphs. Each glyph can specify a particular face
2386 number. @xref{Glyphs}.
2389 If these various sources together specify more than one face for a
2390 particular character, Emacs merges the attributes of the various faces
2391 specified. For each attribute, Emacs tries first the face of any
2392 special glyph; then the face for region highlighting, if appropriate;
2393 then the faces specified by overlays, followed by those specified by
2394 text properties, then the @code{mode-line} or
2395 @code{mode-line-inactive} or @code{header-line} face (if in a mode
2396 line or a header line), and last the @code{default} face.
2398 When multiple overlays cover one character, an overlay with higher
2399 priority overrides those with lower priority. @xref{Overlays}.
2401 @node Font Selection
2402 @subsection Font Selection
2404 @dfn{Selecting a font} means mapping the specified face attributes for
2405 a character to a font that is available on a particular display. The
2406 face attributes, as determined by face merging, specify most of the
2407 font choice, but not all. Part of the choice depends on what character
2410 If the face specifies a fontset name, that fontset determines a
2411 pattern for fonts of the given charset. If the face specifies a font
2412 family, a font pattern is constructed.
2414 Emacs tries to find an available font for the given face attributes
2415 and character's registry and encoding. If there is a font that matches
2416 exactly, it is used, of course. The hard case is when no available font
2417 exactly fits the specification. Then Emacs looks for one that is
2418 ``close''---one attribute at a time. You can specify the order to
2419 consider the attributes. In the case where a specified font family is
2420 not available, you can specify a set of mappings for alternatives to
2423 @defvar face-font-selection-order
2424 @tindex face-font-selection-order
2425 This variable specifies the order of importance of the face attributes
2426 @code{:width}, @code{:height}, @code{:weight}, and @code{:slant}. The
2427 value should be a list containing those four symbols, in order of
2428 decreasing importance.
2430 Font selection first finds the best available matches for the first
2431 attribute listed; then, among the fonts which are best in that way, it
2432 searches for the best matches in the second attribute, and so on.
2434 The attributes @code{:weight} and @code{:width} have symbolic values in
2435 a range centered around @code{normal}. Matches that are more extreme
2436 (farther from @code{normal}) are somewhat preferred to matches that are
2437 less extreme (closer to @code{normal}); this is designed to ensure that
2438 non-normal faces contrast with normal ones, whenever possible.
2440 The default is @code{(:width :height :weight :slant)}, which means first
2441 find the fonts closest to the specified @code{:width}, then---among the
2442 fonts with that width---find a best match for the specified font height,
2445 One example of a case where this variable makes a difference is when the
2446 default font has no italic equivalent. With the default ordering, the
2447 @code{italic} face will use a non-italic font that is similar to the
2448 default one. But if you put @code{:slant} before @code{:height}, the
2449 @code{italic} face will use an italic font, even if its height is not
2453 @defvar face-font-family-alternatives
2454 @tindex face-font-family-alternatives
2455 This variable lets you specify alternative font families to try, if a
2456 given family is specified and doesn't exist. Each element should have
2460 (@var{family} @var{alternate-families}@dots{})
2463 If @var{family} is specified but not available, Emacs will try the other
2464 families given in @var{alternate-families}, one by one, until it finds a
2465 family that does exist.
2468 @defvar face-font-registry-alternatives
2469 @tindex face-font-registry-alternatives
2470 This variable lets you specify alternative font registries to try, if a
2471 given registry is specified and doesn't exist. Each element should have
2475 (@var{registry} @var{alternate-registries}@dots{})
2478 If @var{registry} is specified but not available, Emacs will try the
2479 other registries given in @var{alternate-registries}, one by one,
2480 until it finds a registry that does exist.
2483 Emacs can make use of scalable fonts, but by default it does not use
2484 them, since the use of too many or too big scalable fonts can crash
2487 @defvar scalable-fonts-allowed
2488 @tindex scalable-fonts-allowed
2489 This variable controls which scalable fonts to use. A value of
2490 @code{nil}, the default, means do not use scalable fonts. @code{t}
2491 means to use any scalable font that seems appropriate for the text.
2493 Otherwise, the value must be a list of regular expressions. Then a
2494 scalable font is enabled for use if its name matches any regular
2495 expression in the list. For example,
2498 (setq scalable-fonts-allowed '("muleindian-2$"))
2502 allows the use of scalable fonts with registry @code{muleindian-2}.
2505 @defun clear-face-cache &optional unload-p
2506 @tindex clear-face-cache
2507 This function clears the face cache for all frames.
2508 If @var{unload-p} is non-@code{nil}, that means to unload
2509 all unused fonts as well.
2512 @defvar face-font-rescale-alist
2513 This variable specifies scaling for certain faces. Its value should
2514 be a list of elements of the form
2517 (@var{fontname-regexp} . @var{scale-factor})
2520 If @var{fontname-regexp} matches the font name that is about to be
2521 used, this says to choose a larger similar font according to the
2522 factor @var{scale-factor}. You would use this feature to normalize
2523 the font size if certain fonts are bigger or smaller than their
2524 nominal heights and widths would suggest.
2527 @node Face Functions
2528 @subsection Functions for Working with Faces
2530 Here are additional functions for creating and working with faces.
2532 @defun make-face name
2533 This function defines a new face named @var{name}, initially with all
2534 attributes @code{nil}. It does nothing if there is already a face named
2539 This function returns a list of all defined face names.
2542 @defun copy-face old-face new-name &optional frame new-frame
2543 This function defines a face named @var{new-name} as a copy of the existing
2544 face named @var{old-face}. It creates the face @var{new-name} if that
2545 doesn't already exist.
2547 If the optional argument @var{frame} is given, this function applies
2548 only to that frame. Otherwise it applies to each frame individually,
2549 copying attributes from @var{old-face} in each frame to @var{new-face}
2552 If the optional argument @var{new-frame} is given, then @code{copy-face}
2553 copies the attributes of @var{old-face} in @var{frame} to @var{new-name}
2558 This function returns the face number of face @var{face}.
2561 @defun face-documentation face
2562 This function returns the documentation string of face @var{face}, or
2563 @code{nil} if none was specified for it.
2566 @defun face-equal face1 face2 &optional frame
2567 This returns @code{t} if the faces @var{face1} and @var{face2} have the
2568 same attributes for display.
2571 @defun face-differs-from-default-p face &optional frame
2572 This returns non-@code{nil} if the face @var{face} displays
2573 differently from the default face.
2577 A @dfn{face alias} provides an equivalent name for a face. You can
2578 define a face alias by giving the alias symbol the @code{face-alias}
2579 property, with a value of the target face name. The following example
2580 makes @code{modeline} an alias for the @code{mode-line} face.
2583 (put 'modeline 'face-alias 'mode-line)
2588 @subsection Automatic Face Assignment
2589 @cindex automatic face assignment
2590 @cindex faces, automatic choice
2592 @cindex Font-Lock mode
2593 This hook is used for automatically assigning faces to text in the
2594 buffer. It is part of the implementation of Font-Lock mode.
2596 @tindex fontification-functions
2597 @defvar fontification-functions
2598 This variable holds a list of functions that are called by Emacs
2599 redisplay as needed to assign faces automatically to text in the buffer.
2601 The functions are called in the order listed, with one argument, a
2602 buffer position @var{pos}. Each function should attempt to assign faces
2603 to the text in the current buffer starting at @var{pos}.
2605 Each function should record the faces they assign by setting the
2606 @code{face} property. It should also add a non-@code{nil}
2607 @code{fontified} property for all the text it has assigned faces to.
2608 That property tells redisplay that faces have been assigned to that text
2611 It is probably a good idea for each function to do nothing if the
2612 character after @var{pos} already has a non-@code{nil} @code{fontified}
2613 property, but this is not required. If one function overrides the
2614 assignments made by a previous one, the properties as they are
2615 after the last function finishes are the ones that really matter.
2617 For efficiency, we recommend writing these functions so that they
2618 usually assign faces to around 400 to 600 characters at each call.
2622 @subsection Looking Up Fonts
2624 @defun x-list-fonts pattern &optional face frame maximum
2625 This function returns a list of available font names that match
2626 @var{pattern}. If the optional arguments @var{face} and @var{frame} are
2627 specified, then the list is limited to fonts that are the same size as
2628 @var{face} currently is on @var{frame}.
2630 The argument @var{pattern} should be a string, perhaps with wildcard
2631 characters: the @samp{*} character matches any substring, and the
2632 @samp{?} character matches any single character. Pattern matching
2633 of font names ignores case.
2635 If you specify @var{face} and @var{frame}, @var{face} should be a face name
2636 (a symbol) and @var{frame} should be a frame.
2638 The optional argument @var{maximum} sets a limit on how many fonts to
2639 return. If this is non-@code{nil}, then the return value is truncated
2640 after the first @var{maximum} matching fonts. Specifying a small value
2641 for @var{maximum} can make this function much faster, in cases where
2642 many fonts match the pattern.
2645 @defun x-family-fonts &optional family frame
2646 @tindex x-family-fonts
2647 This function returns a list describing the available fonts for family
2648 @var{family} on @var{frame}. If @var{family} is omitted or @code{nil},
2649 this list applies to all families, and therefore, it contains all
2650 available fonts. Otherwise, @var{family} must be a string; it may
2651 contain the wildcards @samp{?} and @samp{*}.
2653 The list describes the display that @var{frame} is on; if @var{frame} is
2654 omitted or @code{nil}, it applies to the selected frame's display
2655 (@pxref{Input Focus}).
2657 The list contains a vector of the following form for each font:
2660 [@var{family} @var{width} @var{point-size} @var{weight} @var{slant}
2661 @var{fixed-p} @var{full} @var{registry-and-encoding}]
2664 The first five elements correspond to face attributes; if you
2665 specify these attributes for a face, it will use this font.
2667 The last three elements give additional information about the font.
2668 @var{fixed-p} is non-@code{nil} if the font is fixed-pitch.
2669 @var{full} is the full name of the font, and
2670 @var{registry-and-encoding} is a string giving the registry and
2671 encoding of the font.
2673 The result list is sorted according to the current face font sort order.
2676 @defun x-font-family-list &optional frame
2677 @tindex x-font-family-list
2678 This function returns a list of the font families available for
2679 @var{frame}'s display. If @var{frame} is omitted or @code{nil}, it
2680 describes the selected frame's display (@pxref{Input Focus}).
2682 The value is a list of elements of this form:
2685 (@var{family} . @var{fixed-p})
2689 Here @var{family} is a font family, and @var{fixed-p} is
2690 non-@code{nil} if fonts of that family are fixed-pitch.
2693 @defvar font-list-limit
2694 @tindex font-list-limit
2695 This variable specifies maximum number of fonts to consider in font
2696 matching. The function @code{x-family-fonts} will not return more than
2697 that many fonts, and font selection will consider only that many fonts
2698 when searching a matching font for face attributes. The default is
2703 @subsection Fontsets
2705 A @dfn{fontset} is a list of fonts, each assigned to a range of
2706 character codes. An individual font cannot display the whole range of
2707 characters that Emacs supports, but a fontset can. Fontsets have names,
2708 just as fonts do, and you can use a fontset name in place of a font name
2709 when you specify the ``font'' for a frame or a face. Here is
2710 information about defining a fontset under Lisp program control.
2712 @defun create-fontset-from-fontset-spec fontset-spec &optional style-variant-p noerror
2713 This function defines a new fontset according to the specification
2714 string @var{fontset-spec}. The string should have this format:
2717 @var{fontpattern}, @r{[}@var{charsetname}:@var{fontname}@r{]@dots{}}
2721 Whitespace characters before and after the commas are ignored.
2723 The first part of the string, @var{fontpattern}, should have the form of
2724 a standard X font name, except that the last two fields should be
2725 @samp{fontset-@var{alias}}.
2727 The new fontset has two names, one long and one short. The long name is
2728 @var{fontpattern} in its entirety. The short name is
2729 @samp{fontset-@var{alias}}. You can refer to the fontset by either
2730 name. If a fontset with the same name already exists, an error is
2731 signaled, unless @var{noerror} is non-@code{nil}, in which case this
2732 function does nothing.
2734 If optional argument @var{style-variant-p} is non-@code{nil}, that says
2735 to create bold, italic and bold-italic variants of the fontset as well.
2736 These variant fontsets do not have a short name, only a long one, which
2737 is made by altering @var{fontpattern} to indicate the bold or italic
2740 The specification string also says which fonts to use in the fontset.
2741 See below for the details.
2744 The construct @samp{@var{charset}:@var{font}} specifies which font to
2745 use (in this fontset) for one particular character set. Here,
2746 @var{charset} is the name of a character set, and @var{font} is the font
2747 to use for that character set. You can use this construct any number of
2748 times in the specification string.
2750 For the remaining character sets, those that you don't specify
2751 explicitly, Emacs chooses a font based on @var{fontpattern}: it replaces
2752 @samp{fontset-@var{alias}} with a value that names one character set.
2753 For the @acronym{ASCII} character set, @samp{fontset-@var{alias}} is replaced
2754 with @samp{ISO8859-1}.
2756 In addition, when several consecutive fields are wildcards, Emacs
2757 collapses them into a single wildcard. This is to prevent use of
2758 auto-scaled fonts. Fonts made by scaling larger fonts are not usable
2759 for editing, and scaling a smaller font is not useful because it is
2760 better to use the smaller font in its own size, which Emacs does.
2762 Thus if @var{fontpattern} is this,
2765 -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24
2769 the font specification for @acronym{ASCII} characters would be this:
2772 -*-fixed-medium-r-normal-*-24-*-ISO8859-1
2776 and the font specification for Chinese GB2312 characters would be this:
2779 -*-fixed-medium-r-normal-*-24-*-gb2312*-*
2782 You may not have any Chinese font matching the above font
2783 specification. Most X distributions include only Chinese fonts that
2784 have @samp{song ti} or @samp{fangsong ti} in the @var{family} field. In
2785 such a case, @samp{Fontset-@var{n}} can be specified as below:
2788 Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\
2789 chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-*
2793 Then, the font specifications for all but Chinese GB2312 characters have
2794 @samp{fixed} in the @var{family} field, and the font specification for
2795 Chinese GB2312 characters has a wild card @samp{*} in the @var{family}
2798 @defun set-fontset-font name character fontname &optional frame
2799 This function modifies the existing fontset @var{name} to
2800 use the font name @var{fontname} for the character @var{character}.
2802 If @var{name} is @code{nil}, this function modifies the default
2803 fontset, whose short name is @samp{fontset-default}.
2805 @var{character} may be a cons; @code{(@var{from} . @var{to})}, where
2806 @var{from} and @var{to} are non-generic characters. In that case, use
2807 @var{fontname} for all characters in the range @var{from} and @var{to}
2810 @var{character} may be a charset. In that case, use
2811 @var{fontname} for all character in the charsets.
2813 @var{fontname} may be a cons; @code{(@var{family} . @var{registry})},
2814 where @var{family} is a family name of a font (possibly including a
2815 foundry name at the head), @var{registry} is a registry name of a font
2816 (possibly including an encoding name at the tail).
2818 For instance, this changes the default fontset to use a font of which
2819 registry name is @samp{JISX0208.1983} for all characters belonging to
2820 the charset @code{japanese-jisx0208}.
2823 (set-fontset-font nil 'japanese-jisx0208 '(nil . "JISX0208.1983"))
2827 @defun char-displayable-p char
2828 This function returns @code{t} if Emacs ought to be able to display
2829 @var{char}. More precisely, if the selected frame's fontset has a
2830 font to display the character set that @var{char} belongs to.
2832 Fontsets can specify a font on a per-character basis; when the fontset
2833 does that, this function's value may not be accurate.
2840 The @dfn{fringes} of a window are thin vertical strips down the
2841 sides that are used for displaying bitmaps that indicate truncation,
2842 continuation, horizontal scrolling, and the overlay arrow.
2845 * Fringe Size/Pos:: Specifying where to put the window fringes.
2846 * Fringe Bitmaps:: Displaying bitmaps in the window fringes.
2847 * Customizing Bitmaps:: Specifying your own bitmaps to use in the fringes.
2848 * Overlay Arrow:: Display of an arrow to indicate position.
2851 @node Fringe Size/Pos
2852 @subsection Fringe Size and Position
2854 Here's how to control the position and width of the window fringes.
2856 @defvar fringes-outside-margins
2857 If the value is non-@code{nil}, the frames appear outside the display
2858 margins. The fringes normally appear between the display margins and
2859 the window text. It works to set @code{fringes-outside-margins}
2860 buffer-locally. @xref{Display Margins}.
2863 @defvar left-fringe-width
2864 This variable, if non-@code{nil}, specifies the width of the left
2868 @defvar right-fringe-width
2869 This variable, if non-@code{nil}, specifies the width of the right
2873 The values of these variables take effect when you display the
2874 buffer in a window. If you change them while the buffer is visible,
2875 you can call @code{set-window-buffer} to display it once again in the
2876 same window, to make the changes take effect.
2878 @defun set-window-fringes window left &optional right outside-margins
2879 This function sets the fringe widths of window @var{window}.
2880 If @var{window} is @code{nil}, the selected window is used.
2882 The argument @var{left} specifies the width in pixels of the left
2883 fringe, and likewise @var{right} for the right fringe. A value of
2884 @code{nil} for either one stands for the default width. If
2885 @var{outside-margins} is non-@code{nil}, that specifies that fringes
2886 should appear outside of the display margins.
2889 @defun window-fringes &optional window
2890 This function returns information about the fringes of a window
2891 @var{window}. If @var{window} is omitted or @code{nil}, the selected
2892 window is used. The value has the form @code{(@var{left-width}
2893 @var{right-width} @var{outside-margins})}.
2896 @defvar overflow-newline-into-fringe
2897 If this is non-@code{nil}, lines exactly as wide as the window (not
2898 counting the final newline character) are not continued. Instead,
2899 when point is at the end of the line, the cursor appears in the right
2903 @node Fringe Bitmaps
2904 @subsection Fringe Bitmaps
2905 @cindex fringe bitmaps
2906 @cindex bitmaps, fringe
2908 The @dfn{fringe bitmaps} are tiny icons Emacs displays in the window
2909 fringe (on a graphic display) to indicate truncated or continued
2910 lines, buffer boundaries, overlay arrow, etc. The fringe bitmaps are
2911 shared by all frames and windows. You can redefine the built-in
2912 fringe bitmaps, and you can define new fringe bitmaps.
2914 The way to display a bitmap in the left or right fringes for a given
2915 line in a window is by specifying the @code{display} property for one
2916 of the characters that appears in it. Use a display specification of
2917 the form @code{(left-fringe @var{bitmap} [@var{face}])} or
2918 @code{(right-fringe @var{bitmap} [@var{face}])} (@pxref{Display
2919 Property}). Here, @var{bitmap} is a symbol identifying the bitmap you
2920 want, and @var{face} (which is optional) is the name of the face whose
2921 colors should be used for displaying the bitmap, instead of the
2922 default @code{fringe} face. @var{face} is automatically merged with
2923 the @code{fringe} face, so normally @var{face} need only specify the
2924 foreground color for the bitmap.
2926 These symbols identify the standard fringe bitmaps. Evaluate
2927 @code{(require 'fringe)} to define them. Fringe bitmap symbols have
2928 their own name space.
2931 @item Truncation and continuation line bitmaps:
2932 @code{left-truncation}, @code{right-truncation},
2933 @code{continued-line}, @code{continuation-line}.
2935 @item Buffer indication bitmaps:
2936 @code{up-arrow}, @code{down-arrow},
2937 @code{top-left-angle}, @code{top-right-angle},
2938 @code{bottom-left-angle}, @code{bottom-right-angle},
2939 @code{left-bracket}, @code{right-bracket}.
2941 @item Empty line indication bitmap:
2944 @item Overlay arrow bitmap:
2945 @code{overlay-arrow}.
2947 @item Bitmaps for displaying the cursor in right fringe:
2948 @code{filled-box-cursor}, @code{hollow-box-cursor}, @code{hollow-square},
2949 @code{bar-cursor}, @code{hbar-cursor}.
2952 @defun fringe-bitmaps-at-pos &optional pos window
2953 This function returns the fringe bitmaps of the display line
2954 containing position @var{pos} in window @var{window}. The return
2955 value has the form @code{(@var{left} @var{right} @var{ov})}, where @var{left}
2956 is the symbol for the fringe bitmap in the left fringe (or @code{nil}
2957 if no bitmap), @var{right} is similar for the right fringe, and @var{ov}
2958 is non-@code{nil} if there is an overlay arrow in the left fringe.
2960 The value is @code{nil} if @var{pos} is not visible in @var{window}.
2961 If @var{window} is @code{nil}, that stands for the selected window.
2962 If @var{pos} is @code{nil}, that stands for the value of point in
2966 @node Customizing Bitmaps
2967 @subsection Customizing Fringe Bitmaps
2969 @defun define-fringe-bitmap bitmap bits &optional height width align
2970 This function defines the symbol @var{bitmap} as a new fringe bitmap,
2971 or replaces an existing bitmap with that name.
2973 The argument @var{bits} specifies the image to use. It should be
2974 either a string or a vector of integers, where each element (an
2975 integer) corresponds to one row of the bitmap. Each bit of an integer
2976 corresponds to one pixel of the bitmap, where the low bit corresponds
2977 to the rightmost pixel of the bitmap.
2979 The height is normally the length of @var{bits}. However, you
2980 can specify a different height with non-@code{nil} @var{height}. The width
2981 is normally 8, but you can specify a different width with non-@code{nil}
2982 @var{width}. The width must be an integer between 1 and 16.
2984 The argument @var{align} specifies the positioning of the bitmap
2985 relative to the range of rows where it is used; the default is to
2986 center the bitmap. The allowed values are @code{top}, @code{center},
2989 The @var{align} argument may also be a list @code{(@var{align}
2990 @var{periodic})} where @var{align} is interpreted as described above.
2991 If @var{periodic} is non-@code{nil}, it specifies that the rows in
2992 @code{bits} should be repeated enough times to reach the specified
2995 The return value on success is an integer identifying the new bitmap.
2996 You should save that integer in a variable so it can be used to select
2999 This function signals an error if there are no more free bitmap slots.
3002 @defun destroy-fringe-bitmap bitmap
3003 This function destroy the fringe bitmap identified by @var{bitmap}.
3004 If @var{bitmap} identifies a standard fringe bitmap, it actually
3005 restores the standard definition of that bitmap, instead of
3006 eliminating it entirely.
3009 @defun set-fringe-bitmap-face bitmap &optional face
3010 This sets the face for the fringe bitmap @var{bitmap} to @var{face}.
3011 If @var{face} is @code{nil}, it selects the @code{fringe} face. The
3012 bitmap's face controls the color to draw it in.
3014 @var{face} is merged with the @code{fringe} face, so normally
3015 @var{face} should specify only the foreground color.
3019 @subsection The Overlay Arrow
3020 @cindex overlay arrow
3022 The @dfn{overlay arrow} is useful for directing the user's attention
3023 to a particular line in a buffer. For example, in the modes used for
3024 interface to debuggers, the overlay arrow indicates the line of code
3025 about to be executed. This feature has nothing to do with
3026 @dfn{overlays} (@pxref{Overlays}).
3028 @defvar overlay-arrow-string
3029 This variable holds the string to display to call attention to a
3030 particular line, or @code{nil} if the arrow feature is not in use.
3031 On a graphical display the contents of the string are ignored; instead a
3032 glyph is displayed in the fringe area to the left of the display area.
3035 @defvar overlay-arrow-position
3036 This variable holds a marker that indicates where to display the overlay
3037 arrow. It should point at the beginning of a line. On a non-graphical
3038 display the arrow text
3039 appears at the beginning of that line, overlaying any text that would
3040 otherwise appear. Since the arrow is usually short, and the line
3041 usually begins with indentation, normally nothing significant is
3044 The overlay string is displayed only in the buffer that this marker
3045 points into. Thus, only one buffer can have an overlay arrow at any
3047 @c !!! overlay-arrow-position: but the overlay string may remain in the display
3048 @c of some other buffer until an update is required. This should be fixed
3052 You can do a similar job by creating an overlay with a
3053 @code{before-string} property. @xref{Overlay Properties}.
3055 You can define multiple overlay arrows via the variable
3056 @code{overlay-arrow-variable-list}.
3058 @defvar overlay-arrow-variable-list
3059 This variable's value is a list of variables, each of which specifies
3060 the position of an overlay arrow. The variable
3061 @code{overlay-arrow-position} has its normal meaning because it is on
3065 Each variable on this list can have properties
3066 @code{overlay-arrow-string} and @code{overlay-arrow-bitmap} that
3067 specify an overlay arrow string (for text-only terminals) or fringe
3068 bitmap (for graphical terminals) to display at the corresponding
3069 overlay arrow position. If either property is not set, the default
3070 (@code{overlay-arrow-string} or @code{overlay-arrow-fringe-bitmap}) is
3074 @section Scroll Bars
3076 Normally the frame parameter @code{vertical-scroll-bars} controls
3077 whether the windows in the frame have vertical scroll bars, and
3078 whether they are on the left or right. The frame parameter
3079 @code{scroll-bar-width} specifies how wide they are (@code{nil}
3080 meaning the default). @xref{Layout Parameters}.
3082 @defun frame-current-scroll-bars &optional frame
3083 This function reports the scroll bar type settings for frame
3084 @var{frame}. The value is a cons cell
3085 @code{(@var{vertical-type} .@: @var{horizontal-type})}, where
3086 @var{vertical-type} is either @code{left}, @code{right}, or @code{nil}
3087 (which means no scroll bar.) @var{horizontal-type} is meant to
3088 specify the horizontal scroll bar type, but since they are not
3089 implemented, it is always @code{nil}.
3092 @vindex vertical-scroll-bar
3093 You can enable or disable scroll bars for a particular buffer,
3094 by setting the variable @code{vertical-scroll-bar}. This variable
3095 automatically becomes buffer-local when set. The possible values are
3096 @code{left}, @code{right}, @code{t}, which means to use the
3097 frame's default, and @code{nil} for no scroll bar.
3099 You can also control this for individual windows. Call the function
3100 @code{set-window-scroll-bars} to specify what to do for a specific window:
3102 @defun set-window-scroll-bars window width &optional vertical-type horizontal-type
3103 This function sets the width and type of scroll bars for window
3106 @var{width} specifies the scroll bar width in pixels (@code{nil} means
3107 use the width specified for the frame). @var{vertical-type} specifies
3108 whether to have a vertical scroll bar and, if so, where. The possible
3109 values are @code{left}, @code{right} and @code{nil}, just like the
3110 values of the @code{vertical-scroll-bars} frame parameter.
3112 The argument @var{horizontal-type} is meant to specify whether and
3113 where to have horizontal scroll bars, but since they are not
3114 implemented, it has no effect. If @var{window} is @code{nil}, the
3115 selected window is used.
3118 @defun window-scroll-bars &optional window
3119 Report the width and type of scroll bars specified for @var{window}.
3120 If @var{window} is omitted or @code{nil}, the selected window is used.
3121 The value is a list of the form @code{(@var{width}
3122 @var{cols} @var{vertical-type} @var{horizontal-type})}. The value
3123 @var{width} is the value that was specified for the width (which may
3124 be @code{nil}); @var{cols} is the number of columns that the scroll
3125 bar actually occupies.
3127 @var{horizontal-type} is not actually meaningful.
3130 If you don't specify these values for a window with
3131 @code{set-window-scroll-bars}, the buffer-local variables
3132 @code{scroll-bar-mode} and @code{scroll-bar-width} in the buffer being
3133 displayed control the window's vertical scroll bars. The function
3134 @code{set-window-buffer} examines these variables. If you change them
3135 in a buffer that is already visible in a window, you can make the
3136 window take note of the new values by calling @code{set-window-buffer}
3137 specifying the same buffer that is already displayed.
3139 @defvar scroll-bar-mode
3140 This variable, always local in all buffers, controls whether and where
3141 to put scroll bars in windows displaying the buffer. The possible values
3142 are @code{nil} for no scroll bar, @code{left} to put a scroll bar on
3143 the left, and @code{right} to put a scroll bar on the right.
3146 @defun window-current-scroll-bars &optional window
3147 This function reports the scroll bar type for window @var{window}.
3148 If @var{window} is omitted or @code{nil}, the selected window is used.
3149 The value is a cons cell
3150 @code{(@var{vertical-type} .@: @var{horizontal-type})}. Unlike
3151 @code{window-scroll-bars}, this reports the scroll bar type actually
3152 used, once frame defaults and @code{scroll-bar-mode} are taken into
3156 @defvar scroll-bar-width
3157 This variable, always local in all buffers, specifies the width of the
3158 buffer's scroll bars, measured in pixels. A value of @code{nil} means
3159 to use the value specified by the frame.
3163 @section Pointer Shape
3165 Normally, the mouse pointer has the @code{text} shape over text and
3166 the @code{arrow} shape over window areas which do not correspond to
3167 any buffer text. You can specify the mouse pointer shape over text or
3168 images via the @code{pointer} text property, and for images with the
3169 @code{:pointer} and @code{:map} image properties.
3171 The available pointer shapes are: @code{text} (or @code{nil}),
3172 @code{arrow}, @code{hand}, @code{vdrag}, @code{hdrag},
3173 @code{modeline}, and @code{hourglass}.
3175 @defvar void-text-area-pointer
3176 @tindex void-text-area-pointer
3177 This variable specifies the mouse pointer shape in void text areas,
3178 i.e. the areas after the end of a line or below the last line in the
3179 buffer. The default is to use the @code{arrow} (non-text) pointer.
3182 @node Display Property
3183 @section The @code{display} Property
3184 @cindex display specification
3185 @kindex display @r{(text property)}
3187 The @code{display} text property (or overlay property) is used to
3188 insert images into text, and also control other aspects of how text
3189 displays. The value of the @code{display} property should be a
3190 display specification, or a list or vector containing several display
3193 Some kinds of @code{display} properties specify something to display
3194 instead of the text that has the property. In this case, ``the text''
3195 means all the consecutive characters that have the same Lisp object as
3196 their @code{display} property; these characters are replaced as a
3197 single unit. By contrast, characters that have similar but distinct
3198 Lisp objects as their @code{display} properties are handled
3199 separately. Here's a function that illustrates this point:
3203 (goto-char (point-min))
3205 (let ((string (concat "A")))
3206 (put-text-property (point) (1+ (point)) 'display string)
3208 (put-text-property (point) (1+ (point)) 'display string)
3213 It gives each of the first ten characters in the buffer string
3214 @code{"A"} as the @code{display} property, but they don't all get the
3215 same string. The first two characters get the same string, so they
3216 together are replaced with one @samp{A}. The next two characters get
3217 a second string, so they together are replaced with one @samp{A}.
3218 Likewise for each following pair of characters. Thus, the ten
3219 characters appear as five A's. This function would have the same
3224 (goto-char (point-min))
3226 (let ((string (concat "A")))
3227 (put-text-property (point) (2+ (point)) 'display string)
3228 (put-text-property (point) (1+ (point)) 'display string)
3233 This illustrates that what matters is the property value for
3234 each character. If two consecutive characters have the same
3235 object as the @code{display} property value, it's irrelevant
3236 whether they got this property from a single call to
3237 @code{put-text-property} or from two different calls.
3239 The rest of this section describes several kinds of
3240 display specifications and what they mean.
3243 * Specified Space:: Displaying one space with a specified width.
3244 * Pixel Specification:: Specifying space width or height in pixels.
3245 * Other Display Specs:: Displaying an image; magnifying text; moving it
3246 up or down on the page; adjusting the width
3247 of spaces within text.
3248 * Display Margins:: Displaying text or images to the side of the main text.
3251 @node Specified Space
3252 @subsection Specified Spaces
3253 @cindex spaces, specified height or width
3254 @cindex specified spaces
3255 @cindex variable-width spaces
3257 To display a space of specified width and/or height, use a display
3258 specification of the form @code{(space . @var{props})}, where
3259 @var{props} is a property list (a list of alternating properties and
3260 values). You can put this property on one or more consecutive
3261 characters; a space of the specified height and width is displayed in
3262 place of @emph{all} of those characters. These are the properties you
3263 can use in @var{props} to specify the weight of the space:
3266 @item :width @var{width}
3267 If @var{width} is an integer or floating point number, it specifies
3268 that the space width should be @var{width} times the normal character
3269 width. @var{width} can also be a @dfn{pixel width} specification
3270 (@pxref{Pixel Specification}).
3272 @item :relative-width @var{factor}
3273 Specifies that the width of the stretch should be computed from the
3274 first character in the group of consecutive characters that have the
3275 same @code{display} property. The space width is the width of that
3276 character, multiplied by @var{factor}.
3278 @item :align-to @var{hpos}
3279 Specifies that the space should be wide enough to reach @var{hpos}.
3280 If @var{hpos} is a number, it is measured in units of the normal
3281 character width. @var{hpos} can also be a @dfn{pixel width}
3282 specification (@pxref{Pixel Specification}).
3285 You should use one and only one of the above properties. You can
3286 also specify the height of the space, with these properties:
3289 @item :height @var{height}
3290 Specifies the height of the space.
3291 If @var{height} is an integer or floating point number, it specifies
3292 that the space height should be @var{height} times the normal character
3293 height. The @var{height} may also be a @dfn{pixel height} specification
3294 (@pxref{Pixel Specification}).
3296 @item :relative-height @var{factor}
3297 Specifies the height of the space, multiplying the ordinary height
3298 of the text having this display specification by @var{factor}.
3300 @item :ascent @var{ascent}
3301 If the value of @var{ascent} is a non-negative number no greater than
3302 100, it specifies that @var{ascent} percent of the height of the space
3303 should be considered as the ascent of the space---that is, the part
3304 above the baseline. The ascent may also be specified in pixel units
3305 with a @dfn{pixel ascent} specification (@pxref{Pixel Specification}).
3309 Don't use both @code{:height} and @code{:relative-height} together.
3311 The @code{:width} and @code{:align-to} properties are supported on
3312 non-graphic terminals, but the other space properties in this section
3315 @node Pixel Specification
3316 @subsection Pixel Specification for Spaces
3317 @cindex spaces, pixel specification
3319 The value of the @code{:width}, @code{:align-to}, @code{:height},
3320 and @code{:ascent} properties can be a special kind of expression that
3321 is evaluated during redisplay. The result of the evaluation is used
3322 as an absolute number of pixels.
3324 The following expressions are supported:
3328 @var{expr} ::= @var{num} | (@var{num}) | @var{unit} | @var{elem} | @var{pos} | @var{image} | @var{form}
3329 @var{num} ::= @var{integer} | @var{float} | @var{symbol}
3330 @var{unit} ::= in | mm | cm | width | height
3333 @var{elem} ::= left-fringe | right-fringe | left-margin | right-margin
3335 @var{pos} ::= left | center | right
3336 @var{form} ::= (@var{num} . @var{expr}) | (@var{op} @var{expr} ...)
3341 The form @var{num} specifies a fraction of the default frame font
3342 height or width. The form @code{(@var{num})} specifies an absolute
3343 number of pixels. If @var{num} is a symbol, @var{symbol}, its
3344 buffer-local variable binding is used.
3346 The @code{in}, @code{mm}, and @code{cm} units specify the number of
3347 pixels per inch, millimeter, and centimeter, respectively. The
3348 @code{width} and @code{height} units correspond to the default width
3349 and height of the current face. An image specification @code{image}
3350 corresponds to the width or height of the image.
3352 The @code{left-fringe}, @code{right-fringe}, @code{left-margin},
3353 @code{right-margin}, @code{scroll-bar}, and @code{text} elements
3354 specify to the width of the corresponding area of the window.
3356 The @code{left}, @code{center}, and @code{right} positions can be
3357 used with @code{:align-to} to specify a position relative to the left
3358 edge, center, or right edge of the text area.
3360 Any of the above window elements (except @code{text}) can also be
3361 used with @code{:align-to} to specify that the position is relative to
3362 the left edge of the given area. Once the base offset for a relative
3363 position has been set (by the first occurrence of one of these
3364 symbols), further occurrences of these symbols are interpreted as the
3365 width of the specified area. For example, to align to the center of
3366 the left-margin, use
3369 :align-to (+ left-margin (0.5 . left-margin))
3372 If no specific base offset is set for alignment, it is always relative
3373 to the left edge of the text area. For example, @samp{:align-to 0} in a
3374 header-line aligns with the first text column in the text area.
3376 A value of the form @code{(@var{num} . @var{expr})} stands for the
3377 product of the values of @var{num} and @var{expr}. For example,
3378 @code{(2 . in)} specifies a width of 2 inches, while @code{(0.5 .
3379 @var{image})} specifies half the width (or height) of the specified
3382 The form @code{(+ @var{expr} ...)} adds up the value of the
3383 expressions. The form @code{(- @var{expr} ...)} negates or subtracts
3384 the value of the expressions.
3386 @node Other Display Specs
3387 @subsection Other Display Specifications
3389 Here are the other sorts of display specifications that you can use
3390 in the @code{display} text property.
3394 Display @var{string} instead of the text that has this property.
3396 @item (image . @var{image-props})
3397 This kind of display specification is an image descriptor (@pxref{Images}).
3398 When used as a display specification, it means to display the image
3399 instead of the text that has the display specification.
3401 @item (slice @var{x} @var{y} @var{width} @var{height})
3402 This specification together with @code{image} specifies a @dfn{slice}
3403 (a partial area) of the image to display. The elements @var{y} and
3404 @var{x} specify the top left corner of the slice, within the image;
3405 @var{width} and @var{height} specify the width and height of the
3406 slice. Integer values are numbers of pixels. A floating point number
3407 in the range 0.0--1.0 stands for that fraction of the width or height
3408 of the entire image.
3410 @item ((margin nil) @var{string})
3412 A display specification of this form means to display @var{string}
3413 instead of the text that has the display specification, at the same
3414 position as that text. This is a special case of marginal display
3415 (@pxref{Display Margins}).
3417 Recursive display specifications are not supported---string display
3418 specifications must not have @code{display} properties themselves.
3420 @item (space-width @var{factor})
3421 This display specification affects all the space characters within the
3422 text that has the specification. It displays all of these spaces
3423 @var{factor} times as wide as normal. The element @var{factor} should
3424 be an integer or float. Characters other than spaces are not affected
3425 at all; in particular, this has no effect on tab characters.
3427 @item (height @var{height})
3428 This display specification makes the text taller or shorter.
3429 Here are the possibilities for @var{height}:
3432 @item @code{(+ @var{n})}
3433 This means to use a font that is @var{n} steps larger. A ``step'' is
3434 defined by the set of available fonts---specifically, those that match
3435 what was otherwise specified for this text, in all attributes except
3436 height. Each size for which a suitable font is available counts as
3437 another step. @var{n} should be an integer.
3439 @item @code{(- @var{n})}
3440 This means to use a font that is @var{n} steps smaller.
3442 @item a number, @var{factor}
3443 A number, @var{factor}, means to use a font that is @var{factor} times
3444 as tall as the default font.
3446 @item a symbol, @var{function}
3447 A symbol is a function to compute the height. It is called with the
3448 current height as argument, and should return the new height to use.
3450 @item anything else, @var{form}
3451 If the @var{height} value doesn't fit the previous possibilities, it is
3452 a form. Emacs evaluates it to get the new height, with the symbol
3453 @code{height} bound to the current specified font height.
3456 @item (raise @var{factor})
3457 This kind of display specification raises or lowers the text
3458 it applies to, relative to the baseline of the line.
3460 @var{factor} must be a number, which is interpreted as a multiple of the
3461 height of the affected text. If it is positive, that means to display
3462 the characters raised. If it is negative, that means to display them
3465 If the text also has a @code{height} display specification, that does
3466 not affect the amount of raising or lowering, which is based on the
3467 faces used for the text.
3470 You can make any display specification conditional. To do that,
3471 package it in another list of the form @code{(when @var{condition} .
3472 @var{spec})}. Then the specification @var{spec} applies only when
3473 @var{condition} evaluates to a non-@code{nil} value. During the
3474 evaluation, @code{object} is bound to the string or buffer having the
3475 conditional @code{display} property. @code{position} and
3476 @code{buffer-position} are bound to the position within @code{object}
3477 and the buffer position where the @code{display} property was found,
3478 respectively. Both positions can be different when @code{object} is a
3481 @node Display Margins
3482 @subsection Displaying in the Margins
3483 @cindex display margins
3484 @cindex margins, display
3486 A buffer can have blank areas called @dfn{display margins} on the left
3487 and on the right. Ordinary text never appears in these areas, but you
3488 can put things into the display margins using the @code{display}
3491 To put text in the left or right display margin of the window, use a
3492 display specification of the form @code{(margin right-margin)} or
3493 @code{(margin left-margin)} on it. To put an image in a display margin,
3494 use that display specification along with the display specification for
3495 the image. Unfortunately, there is currently no way to make
3496 text or images in the margin mouse-sensitive.
3498 If you put such a display specification directly on text in the
3499 buffer, the specified margin display appears @emph{instead of} that
3500 buffer text itself. To put something in the margin @emph{in
3501 association with} certain buffer text without preventing or altering
3502 the display of that text, put a @code{before-string} property on the
3503 text and put the display specification on the contents of the
3506 Before the display margins can display anything, you must give
3507 them a nonzero width. The usual way to do that is to set these
3510 @defvar left-margin-width
3511 @tindex left-margin-width
3512 This variable specifies the width of the left margin.
3513 It is buffer-local in all buffers.
3516 @defvar right-margin-width
3517 @tindex right-margin-width
3518 This variable specifies the width of the right margin.
3519 It is buffer-local in all buffers.
3522 Setting these variables does not immediately affect the window. These
3523 variables are checked when a new buffer is displayed in the window.
3524 Thus, you can make changes take effect by calling
3525 @code{set-window-buffer}.
3527 You can also set the margin widths immediately.
3529 @defun set-window-margins window left &optional right
3530 @tindex set-window-margins
3531 This function specifies the margin widths for window @var{window}.
3532 The argument @var{left} controls the left margin and
3533 @var{right} controls the right margin (default @code{0}).
3536 @defun window-margins &optional window
3537 @tindex window-margins
3538 This function returns the left and right margins of @var{window}
3539 as a cons cell of the form @code{(@var{left} . @var{right})}.
3540 If @var{window} is @code{nil}, the selected window is used.
3545 @cindex images in buffers
3547 To display an image in an Emacs buffer, you must first create an image
3548 descriptor, then use it as a display specifier in the @code{display}
3549 property of text that is displayed (@pxref{Display Property}).
3551 Emacs can display a number of different image formats; some of them
3552 are supported only if particular support libraries are installed on
3553 your machine. In some environments, Emacs can load image
3554 libraries on demand; if so, the variable @code{image-library-alist}
3555 can be used to modify the set of known names for these dynamic
3556 libraries (though it is not possible to add new image formats).
3558 The supported image formats include XBM, XPM (this requires the
3559 libraries @code{libXpm} version 3.4k and @code{libz}), GIF (requiring
3560 @code{libungif} 4.1.0), Postscript, PBM, JPEG (requiring the
3561 @code{libjpeg} library version v6a), TIFF (requiring @code{libtiff}
3562 v3.4), and PNG (requiring @code{libpng} 1.0.2).
3564 You specify one of these formats with an image type symbol. The image
3565 type symbols are @code{xbm}, @code{xpm}, @code{gif}, @code{postscript},
3566 @code{pbm}, @code{jpeg}, @code{tiff}, and @code{png}.
3569 This variable contains a list of those image type symbols that are
3570 potentially supported in the current configuration.
3571 @emph{Potentially} here means that Emacs knows about the image types,
3572 not necessarily that they can be loaded (they could depend on
3573 unavailable dynamic libraries, for example).
3575 To know which image types are really available, use
3576 @code{image-type-available-p}.
3579 @defvar image-library-alist
3580 This in an alist of image types vs external libraries needed to
3583 Each element is a list @code{(@var{image-type} @var{library}...)},
3584 where the car is a supported image format from @code{image-types}, and
3585 the rest are strings giving alternate filenames for the corresponding
3586 external libraries to load.
3588 Emacs tries to load the libraries in the order they appear on the
3589 list; if none is loaded, the running session of Emacs won't support
3590 the image type. @code{pbm} and @code{xbm} don't need to be listed;
3591 they're always supported.
3593 This variable is ignored if the image libraries are statically linked
3597 @defun image-type-available-p type
3598 @findex image-type-available-p
3600 This function returns non-@code{nil} if image type @var{type} is
3601 available, i.e., if images of this type can be loaded and displayed in
3602 Emacs. @var{type} should be one of the types contained in
3605 For image types whose support libraries are statically linked, this
3606 function always returns @code{t}; for other image types, it returns
3607 @code{t} if the dynamic library could be loaded, @code{nil} otherwise.
3611 * Image Descriptors:: How to specify an image for use in @code{:display}.
3612 * XBM Images:: Special features for XBM format.
3613 * XPM Images:: Special features for XPM format.
3614 * GIF Images:: Special features for GIF format.
3615 * Postscript Images:: Special features for Postscript format.
3616 * Other Image Types:: Various other formats are supported.
3617 * Defining Images:: Convenient ways to define an image for later use.
3618 * Showing Images:: Convenient ways to display an image once it is defined.
3619 * Image Cache:: Internal mechanisms of image display.
3622 @node Image Descriptors
3623 @subsection Image Descriptors
3624 @cindex image descriptor
3626 An image description is a list of the form @code{(image
3627 . @var{props})}, where @var{props} is a property list containing
3628 alternating keyword symbols (symbols whose names start with a colon) and
3629 their values. You can use any Lisp object as a property, but the only
3630 properties that have any special meaning are certain symbols, all of
3633 Every image descriptor must contain the property @code{:type
3634 @var{type}} to specify the format of the image. The value of @var{type}
3635 should be an image type symbol; for example, @code{xpm} for an image in
3638 Here is a list of other properties that are meaningful for all image
3642 @item :file @var{file}
3643 The @code{:file} property says to load the image from file
3644 @var{file}. If @var{file} is not an absolute file name, it is expanded
3645 in @code{data-directory}.
3647 @item :data @var{data}
3648 The @code{:data} property says the actual contents of the image.
3649 Each image must use either @code{:data} or @code{:file}, but not both.
3650 For most image types, the value of the @code{:data} property should be a
3651 string containing the image data; we recommend using a unibyte string.
3653 Before using @code{:data}, look for further information in the section
3654 below describing the specific image format. For some image types,
3655 @code{:data} may not be supported; for some, it allows other data types;
3656 for some, @code{:data} alone is not enough, so you need to use other
3657 image properties along with @code{:data}.
3659 @item :margin @var{margin}
3660 The @code{:margin} property specifies how many pixels to add as an
3661 extra margin around the image. The value, @var{margin}, must be a
3662 non-negative number, or a pair @code{(@var{x} . @var{y})} of such
3663 numbers. If it is a pair, @var{x} specifies how many pixels to add
3664 horizontally, and @var{y} specifies how many pixels to add vertically.
3665 If @code{:margin} is not specified, the default is zero.
3667 @item :ascent @var{ascent}
3668 The @code{:ascent} property specifies the amount of the image's
3669 height to use for its ascent---that is, the part above the baseline.
3670 The value, @var{ascent}, must be a number in the range 0 to 100, or
3671 the symbol @code{center}.
3673 If @var{ascent} is a number, that percentage of the image's height is
3674 used for its ascent.
3676 If @var{ascent} is @code{center}, the image is vertically centered
3677 around a centerline which would be the vertical centerline of text drawn
3678 at the position of the image, in the manner specified by the text
3679 properties and overlays that apply to the image.
3681 If this property is omitted, it defaults to 50.
3683 @item :relief @var{relief}
3684 The @code{:relief} property, if non-@code{nil}, adds a shadow rectangle
3685 around the image. The value, @var{relief}, specifies the width of the
3686 shadow lines, in pixels. If @var{relief} is negative, shadows are drawn
3687 so that the image appears as a pressed button; otherwise, it appears as
3688 an unpressed button.
3690 @item :conversion @var{algorithm}
3691 The @code{:conversion} property, if non-@code{nil}, specifies a
3692 conversion algorithm that should be applied to the image before it is
3693 displayed; the value, @var{algorithm}, specifies which algorithm.
3698 Specifies the Laplace edge detection algorithm, which blurs out small
3699 differences in color while highlighting larger differences. People
3700 sometimes consider this useful for displaying the image for a
3701 ``disabled'' button.
3703 @item (edge-detection :matrix @var{matrix} :color-adjust @var{adjust})
3704 Specifies a general edge-detection algorithm. @var{matrix} must be
3705 either a nine-element list or a nine-element vector of numbers. A pixel
3706 at position @math{x/y} in the transformed image is computed from
3707 original pixels around that position. @var{matrix} specifies, for each
3708 pixel in the neighborhood of @math{x/y}, a factor with which that pixel
3709 will influence the transformed pixel; element @math{0} specifies the
3710 factor for the pixel at @math{x-1/y-1}, element @math{1} the factor for
3711 the pixel at @math{x/y-1} etc., as shown below:
3714 $$\pmatrix{x-1/y-1 & x/y-1 & x+1/y-1 \cr
3715 x-1/y & x/y & x+1/y \cr
3716 x-1/y+1& x/y+1 & x+1/y+1 \cr}$$
3721 (x-1/y-1 x/y-1 x+1/y-1
3723 x-1/y+1 x/y+1 x+1/y+1)
3727 The resulting pixel is computed from the color intensity of the color
3728 resulting from summing up the RGB values of surrounding pixels,
3729 multiplied by the specified factors, and dividing that sum by the sum
3730 of the factors' absolute values.
3732 Laplace edge-detection currently uses a matrix of
3735 $$\pmatrix{1 & 0 & 0 \cr
3748 Emboss edge-detection uses a matrix of
3751 $$\pmatrix{ 2 & -1 & 0 \cr
3765 Specifies transforming the image so that it looks ``disabled''.
3768 @item :mask @var{mask}
3769 If @var{mask} is @code{heuristic} or @code{(heuristic @var{bg})}, build
3770 a clipping mask for the image, so that the background of a frame is
3771 visible behind the image. If @var{bg} is not specified, or if @var{bg}
3772 is @code{t}, determine the background color of the image by looking at
3773 the four corners of the image, assuming the most frequently occurring
3774 color from the corners is the background color of the image. Otherwise,
3775 @var{bg} must be a list @code{(@var{red} @var{green} @var{blue})}
3776 specifying the color to assume for the background of the image.
3778 If @var{mask} is @code{nil}, remove a mask from the image, if it has
3779 one. Images in some formats include a mask which can be removed by
3780 specifying @code{:mask nil}.
3782 @item :pointer @var{shape}
3783 This specifies the pointer shape when the mouse pointer is over this
3784 image. @xref{Pointer Shape}, for available pointer shapes.
3786 @item :map @var{map}
3787 This associates an image map of @dfn{hot spots} with this image.
3789 An image map is an alist where each element has the format
3790 @code{(@var{area} @var{id} @var{plist})}. An @var{area} is specified
3791 as either a rectangle, a circle, or a polygon.
3793 A rectangle is a cons
3794 @code{(rect . ((@var{x0} . @var{y0}) . (@var{x1} . @var{y1})))}
3795 which specifies the pixel coordinates of the upper left and bottom right
3796 corners of the rectangle area.
3799 @code{(circle . ((@var{x0} . @var{y0}) . @var{r}))}
3800 which specifies the center and the radius of the circle; @var{r} may
3801 be a float or integer.
3804 @code{(poly . [@var{x0} @var{y0} @var{x1} @var{y1} ...])}
3805 where each pair in the vector describes one corner in the polygon.
3807 When the mouse pointer is above a hot-spot area of an image, the
3808 @var{plist} of that hot-spot is consulted; if it contains a @code{help-echo}
3809 property it defines a tool-tip for the hot-spot, and if it contains
3810 a @code{pointer} property, it defines the shape of the mouse cursor when
3811 it is over the hot-spot.
3812 @xref{Pointer Shape}, for available pointer shapes.
3814 When you click the mouse when the mouse pointer is over a hot-spot, an
3815 event is composed by combining the @var{id} of the hot-spot with the
3816 mouse event; for instance, @code{[area4 mouse-1]} if the hot-spot's
3817 @var{id} is @code{area4}.
3820 @defun image-mask-p spec &optional frame
3821 @tindex image-mask-p
3822 This function returns @code{t} if image @var{spec} has a mask bitmap.
3823 @var{frame} is the frame on which the image will be displayed.
3824 @var{frame} @code{nil} or omitted means to use the selected frame
3825 (@pxref{Input Focus}).
3829 @subsection XBM Images
3832 To use XBM format, specify @code{xbm} as the image type. This image
3833 format doesn't require an external library, so images of this type are
3836 Additional image properties supported for the @code{xbm} image type are:
3839 @item :foreground @var{foreground}
3840 The value, @var{foreground}, should be a string specifying the image
3841 foreground color, or @code{nil} for the default color. This color is
3842 used for each pixel in the XBM that is 1. The default is the frame's
3845 @item :background @var{background}
3846 The value, @var{background}, should be a string specifying the image
3847 background color, or @code{nil} for the default color. This color is
3848 used for each pixel in the XBM that is 0. The default is the frame's
3852 If you specify an XBM image using data within Emacs instead of an
3853 external file, use the following three properties:
3856 @item :data @var{data}
3857 The value, @var{data}, specifies the contents of the image.
3858 There are three formats you can use for @var{data}:
3862 A vector of strings or bool-vectors, each specifying one line of the
3863 image. Do specify @code{:height} and @code{:width}.
3866 A string containing the same byte sequence as an XBM file would contain.
3867 You must not specify @code{:height} and @code{:width} in this case,
3868 because omitting them is what indicates the data has the format of an
3869 XBM file. The file contents specify the height and width of the image.
3872 A string or a bool-vector containing the bits of the image (plus perhaps
3873 some extra bits at the end that will not be used). It should contain at
3874 least @var{width} * @code{height} bits. In this case, you must specify
3875 @code{:height} and @code{:width}, both to indicate that the string
3876 contains just the bits rather than a whole XBM file, and to specify the
3880 @item :width @var{width}
3881 The value, @var{width}, specifies the width of the image, in pixels.
3883 @item :height @var{height}
3884 The value, @var{height}, specifies the height of the image, in pixels.
3888 @subsection XPM Images
3891 To use XPM format, specify @code{xpm} as the image type. The
3892 additional image property @code{:color-symbols} is also meaningful with
3893 the @code{xpm} image type:
3896 @item :color-symbols @var{symbols}
3897 The value, @var{symbols}, should be an alist whose elements have the
3898 form @code{(@var{name} . @var{color})}. In each element, @var{name} is
3899 the name of a color as it appears in the image file, and @var{color}
3900 specifies the actual color to use for displaying that name.
3904 @subsection GIF Images
3907 For GIF images, specify image type @code{gif}.
3910 @item :index @var{index}
3911 You can use @code{:index} to specify one image from a GIF file that
3912 contains more than one image. This property specifies use of image
3913 number @var{index} from the file. If the GIF file doesn't contain an
3914 image with index @var{index}, the image displays as a hollow box.
3918 This could be used to implement limited support for animated GIFs.
3919 For example, the following function displays a multi-image GIF file
3920 at point-min in the current buffer, switching between sub-images
3923 (defun show-anim (file max)
3924 "Display multi-image GIF file FILE which contains MAX subimages."
3925 (display-anim (current-buffer) file 0 max t))
3927 (defun display-anim (buffer file idx max first-time)
3930 (let ((img (create-image file nil :image idx)))
3933 (goto-char (point-min))
3934 (unless first-time (delete-char 1))
3936 (run-with-timer 0.1 nil 'display-anim buffer file (1+ idx) max nil)))
3939 @node Postscript Images
3940 @subsection Postscript Images
3941 @cindex Postscript images
3943 To use Postscript for an image, specify image type @code{postscript}.
3944 This works only if you have Ghostscript installed. You must always use
3945 these three properties:
3948 @item :pt-width @var{width}
3949 The value, @var{width}, specifies the width of the image measured in
3950 points (1/72 inch). @var{width} must be an integer.
3952 @item :pt-height @var{height}
3953 The value, @var{height}, specifies the height of the image in points
3954 (1/72 inch). @var{height} must be an integer.
3956 @item :bounding-box @var{box}
3957 The value, @var{box}, must be a list or vector of four integers, which
3958 specifying the bounding box of the Postscript image, analogous to the
3959 @samp{BoundingBox} comment found in Postscript files.
3962 %%BoundingBox: 22 171 567 738
3966 Displaying Postscript images from Lisp data is not currently
3967 implemented, but it may be implemented by the time you read this.
3968 See the @file{etc/NEWS} file to make sure.
3970 @node Other Image Types
3971 @subsection Other Image Types
3974 For PBM images, specify image type @code{pbm}. Color, gray-scale and
3975 monochromatic images are supported. For mono PBM images, two additional
3976 image properties are supported.
3979 @item :foreground @var{foreground}
3980 The value, @var{foreground}, should be a string specifying the image
3981 foreground color, or @code{nil} for the default color. This color is
3982 used for each pixel in the XBM that is 1. The default is the frame's
3985 @item :background @var{background}
3986 The value, @var{background}, should be a string specifying the image
3987 background color, or @code{nil} for the default color. This color is
3988 used for each pixel in the XBM that is 0. The default is the frame's
3992 For JPEG images, specify image type @code{jpeg}.
3994 For TIFF images, specify image type @code{tiff}.
3996 For PNG images, specify image type @code{png}.
3998 @node Defining Images
3999 @subsection Defining Images
4001 The functions @code{create-image}, @code{defimage} and
4002 @code{find-image} provide convenient ways to create image descriptors.
4004 @defun create-image file-or-data &optional type data-p &rest props
4005 @tindex create-image
4006 This function creates and returns an image descriptor which uses the
4007 data in @var{file-or-data}. @var{file-or-data} can be a file name or
4008 a string containing the image data; @var{data-p} should be @code{nil}
4009 for the former case, non-@code{nil} for the latter case.
4011 The optional argument @var{type} is a symbol specifying the image type.
4012 If @var{type} is omitted or @code{nil}, @code{create-image} tries to
4013 determine the image type from the file's first few bytes, or else
4014 from the file's name.
4016 The remaining arguments, @var{props}, specify additional image
4017 properties---for example,
4020 (create-image "foo.xpm" 'xpm nil :heuristic-mask t)
4023 The function returns @code{nil} if images of this type are not
4024 supported. Otherwise it returns an image descriptor.
4027 @defmac defimage symbol specs &optional doc
4029 This macro defines @var{symbol} as an image name. The arguments
4030 @var{specs} is a list which specifies how to display the image.
4031 The third argument, @var{doc}, is an optional documentation string.
4033 Each argument in @var{specs} has the form of a property list, and each
4034 one should specify at least the @code{:type} property and either the
4035 @code{:file} or the @code{:data} property. The value of @code{:type}
4036 should be a symbol specifying the image type, the value of
4037 @code{:file} is the file to load the image from, and the value of
4038 @code{:data} is a string containing the actual image data. Here is an
4042 (defimage test-image
4043 ((:type xpm :file "~/test1.xpm")
4044 (:type xbm :file "~/test1.xbm")))
4047 @code{defimage} tests each argument, one by one, to see if it is
4048 usable---that is, if the type is supported and the file exists. The
4049 first usable argument is used to make an image descriptor which is
4050 stored in @var{symbol}.
4052 If none of the alternatives will work, then @var{symbol} is defined
4056 @defun find-image specs
4058 This function provides a convenient way to find an image satisfying one
4059 of a list of image specifications @var{specs}.
4061 Each specification in @var{specs} is a property list with contents
4062 depending on image type. All specifications must at least contain the
4063 properties @code{:type @var{type}} and either @w{@code{:file @var{file}}}
4064 or @w{@code{:data @var{DATA}}}, where @var{type} is a symbol specifying
4065 the image type, e.g.@: @code{xbm}, @var{file} is the file to load the
4066 image from, and @var{data} is a string containing the actual image data.
4067 The first specification in the list whose @var{type} is supported, and
4068 @var{file} exists, is used to construct the image specification to be
4069 returned. If no specification is satisfied, @code{nil} is returned.
4071 The image is looked for first on @code{load-path} and then in
4072 @code{data-directory}.
4075 @node Showing Images
4076 @subsection Showing Images
4078 You can use an image descriptor by setting up the @code{display}
4079 property yourself, but it is easier to use the functions in this
4082 @defun insert-image image &optional string area slice
4083 This function inserts @var{image} in the current buffer at point. The
4084 value @var{image} should be an image descriptor; it could be a value
4085 returned by @code{create-image}, or the value of a symbol defined with
4086 @code{defimage}. The argument @var{string} specifies the text to put
4087 in the buffer to hold the image. If it is omitted or @code{nil},
4088 @code{insert-image} uses @code{" "} by default.
4090 The argument @var{area} specifies whether to put the image in a margin.
4091 If it is @code{left-margin}, the image appears in the left margin;
4092 @code{right-margin} specifies the right margin. If @var{area} is
4093 @code{nil} or omitted, the image is displayed at point within the
4096 The argument @var{slice} specifies a slice of the image to insert. If
4097 @var{slice} is @code{nil} or omitted the whole image is inserted.
4098 Otherwise, @var{slice} is a list @code{(@var{x} @var{y} @var{width}
4099 @var{height})} which specifies the @var{x} and @var{y} positions and
4100 @var{width} and @var{height} of the image area to insert. Integer
4101 values are in units of pixels. A floating point number in the range
4102 0.0--1.0 stands for that fraction of the width or height of the entire
4105 Internally, this function inserts @var{string} in the buffer, and gives
4106 it a @code{display} property which specifies @var{image}. @xref{Display
4110 @defun insert-sliced-image image &optional string area rows cols
4111 This function inserts @var{image} in the current buffer at point, like
4112 @code{insert-image}, but splits the image into @var{rows}x@var{cols}
4113 equally sized slices.
4116 @defun put-image image pos &optional string area
4117 This function puts image @var{image} in front of @var{pos} in the
4118 current buffer. The argument @var{pos} should be an integer or a
4119 marker. It specifies the buffer position where the image should appear.
4120 The argument @var{string} specifies the text that should hold the image
4121 as an alternative to the default.
4123 The argument @var{image} must be an image descriptor, perhaps returned
4124 by @code{create-image} or stored by @code{defimage}.
4126 The argument @var{area} specifies whether to put the image in a margin.
4127 If it is @code{left-margin}, the image appears in the left margin;
4128 @code{right-margin} specifies the right margin. If @var{area} is
4129 @code{nil} or omitted, the image is displayed at point within the
4132 Internally, this function creates an overlay, and gives it a
4133 @code{before-string} property containing text that has a @code{display}
4134 property whose value is the image. (Whew!)
4137 @defun remove-images start end &optional buffer
4138 This function removes images in @var{buffer} between positions
4139 @var{start} and @var{end}. If @var{buffer} is omitted or @code{nil},
4140 images are removed from the current buffer.
4142 This removes only images that were put into @var{buffer} the way
4143 @code{put-image} does it, not images that were inserted with
4144 @code{insert-image} or in other ways.
4147 @defun image-size spec &optional pixels frame
4149 This function returns the size of an image as a pair
4150 @w{@code{(@var{width} . @var{height})}}. @var{spec} is an image
4151 specification. @var{pixels} non-@code{nil} means return sizes
4152 measured in pixels, otherwise return sizes measured in canonical
4153 character units (fractions of the width/height of the frame's default
4154 font). @var{frame} is the frame on which the image will be displayed.
4155 @var{frame} null or omitted means use the selected frame (@pxref{Input
4160 @subsection Image Cache
4162 Emacs stores images in an image cache when it displays them, so it can
4163 display them again more efficiently. It removes an image from the cache
4164 when it hasn't been displayed for a specified period of time.
4166 When an image is looked up in the cache, its specification is compared
4167 with cached image specifications using @code{equal}. This means that
4168 all images with equal specifications share the same image in the cache.
4170 @defvar image-cache-eviction-delay
4171 @tindex image-cache-eviction-delay
4172 This variable specifies the number of seconds an image can remain in the
4173 cache without being displayed. When an image is not displayed for this
4174 length of time, Emacs removes it from the image cache.
4176 If the value is @code{nil}, Emacs does not remove images from the cache
4177 except when you explicitly clear it. This mode can be useful for
4181 @defun clear-image-cache &optional frame
4182 @tindex clear-image-cache
4183 This function clears the image cache. If @var{frame} is non-@code{nil},
4184 only the cache for that frame is cleared. Otherwise all frames' caches
4191 @cindex buttons in buffers
4192 @cindex clickable buttons in buffers
4194 The @emph{button} package defines functions for inserting and
4195 manipulating clickable (with the mouse, or via keyboard commands)
4196 buttons in Emacs buffers, such as might be used for help hyper-links,
4197 etc. Emacs uses buttons for the hyper-links in help text and the like.
4199 A button is essentially a set of properties attached (via text
4200 properties or overlays) to a region of text in an Emacs buffer. These
4201 properties are called @dfn{button properties}.
4203 One of the these properties (@code{action}) is a function, which will
4204 be called when the user invokes it using the keyboard or the mouse.
4205 The invoked function may then examine the button and use its other
4206 properties as desired.
4208 In some ways the Emacs button package duplicates functionality offered
4209 by the widget package (@pxref{Top, , Introduction, widget, The Emacs
4210 Widget Library}), but the button package has the advantage that it is
4211 much faster, much smaller, and much simpler to use (for elisp
4212 programmers---for users, the result is about the same). The extra
4213 speed and space savings are useful mainly if you need to create many
4214 buttons in a buffer (for instance an @code{*Apropos*} buffer uses
4215 buttons to make entries clickable, and may contain many thousands of
4219 * Button Properties:: Button properties with special meanings.
4220 * Button Types:: Defining common properties for classes of buttons.
4221 * Making Buttons:: Adding buttons to Emacs buffers.
4222 * Manipulating Buttons:: Getting and setting properties of buttons.
4223 * Button Buffer Commands:: Buffer-wide commands and bindings for buttons.
4226 @node Button Properties
4227 @subsection Button Properties
4228 @cindex button properties
4230 Buttons have an associated list of properties defining their
4231 appearance and behavior, and other arbitrary properties may be used
4232 for application specific purposes. Some properties that have special
4233 meaning to the button package include:
4237 @kindex action @r{(button property)}
4238 The function to call when the user invokes the button, which is passed
4239 the single argument @var{button}. By default this is @code{ignore},
4243 @kindex mouse-action @r{(button property)}
4244 This is similar to @code{action}, and when present, will be used
4245 instead of @code{action} for button invocations resulting from
4246 mouse-clicks (instead of the user hitting @key{RET}). If not
4247 present, mouse-clicks use @code{action} instead.
4250 @kindex face @r{(button property)}
4251 This is an Emacs face controlling how buttons of this type are
4252 displayed; by default this is the @code{button} face.
4255 @kindex mouse-face @r{(button property)}
4256 This is an additional face which controls appearance during
4257 mouse-overs (merged with the usual button face); by default this is
4258 the usual Emacs @code{highlight} face.
4261 @kindex keymap @r{(button property)}
4262 The button's keymap, defining bindings active within the button
4263 region. By default this is the usual button region keymap, stored
4264 in the variable @code{button-map}, which defines @key{RET} and
4265 @key{mouse-2} to invoke the button.
4268 @kindex type @r{(button property)}
4269 The button-type of the button. When creating a button, this is
4270 usually specified using the @code{:type} keyword argument.
4271 @xref{Button Types}.
4274 @kindex help-index @r{(button property)}
4275 A string displayed by the Emacs tool-tip help system; by default,
4276 @code{"mouse-2, RET: Push this button"}.
4279 @kindex follow-link @r{(button property)}
4280 The follow-link property, defining how a @key{Mouse-1} click behaves
4281 on this button, @xref{Links and Mouse-1}.
4284 @kindex button @r{(button property)}
4285 All buttons have a non-@code{nil} @code{button} property, which may be useful
4286 in finding regions of text that comprise buttons (which is what the
4287 standard button functions do).
4290 There are other properties defined for the regions of text in a
4291 button, but these are not generally interesting for typical uses.
4294 @subsection Button Types
4295 @cindex button types
4297 Every button has a button @emph{type}, which defines default values
4298 for the button's properties. Button types are arranged in a
4299 hierarchy, with specialized types inheriting from more general types,
4300 so that it's easy to define special-purpose types of buttons for
4303 @defun define-button-type name &rest properties
4304 @tindex define-button-type
4305 Define a `button type' called @var{name}. The remaining arguments
4306 form a sequence of @var{property value} pairs, specifying default
4307 property values for buttons with this type (a button's type may be set
4308 by giving it a @code{type} property when creating the button, using
4309 the @code{:type} keyword argument).
4311 In addition, the keyword argument @code{:supertype} may be used to
4312 specify a button-type from which @var{name} inherits its default
4313 property values. Note that this inheritance happens only when
4314 @var{name} is defined; subsequent changes to a supertype are not
4315 reflected in its subtypes.
4318 Using @code{define-button-type} to define default properties for
4319 buttons is not necessary---buttons without any specified type use the
4320 built-in button-type @code{button}---but it is encouraged, since
4321 doing so usually makes the resulting code clearer and more efficient.
4323 @node Making Buttons
4324 @subsection Making Buttons
4325 @cindex making buttons
4327 Buttons are associated with a region of text, using an overlay or
4328 text properties to hold button-specific information, all of which are
4329 initialized from the button's type (which defaults to the built-in
4330 button type @code{button}). Like all Emacs text, the appearance of
4331 the button is governed by the @code{face} property; by default (via
4332 the @code{face} property inherited from the @code{button} button-type)
4333 this is a simple underline, like a typical web-page link.
4335 For convenience, there are two sorts of button-creation functions,
4336 those that add button properties to an existing region of a buffer,
4337 called @code{make-...button}, and those also insert the button text,
4338 called @code{insert-...button}.
4340 The button-creation functions all take the @code{&rest} argument
4341 @var{properties}, which should be a sequence of @var{property value}
4342 pairs, specifying properties to add to the button; see @ref{Button
4343 Properties}. In addition, the keyword argument @code{:type} may be
4344 used to specify a button-type from which to inherit other properties;
4345 see @ref{Button Types}. Any properties not explicitly specified
4346 during creation will be inherited from the button's type (if the type
4347 defines such a property).
4349 The following functions add a button using an overlay
4350 (@pxref{Overlays}) to hold the button properties:
4352 @defun make-button beg end &rest properties
4354 This makes a button from @var{beg} to @var{end} in the
4355 current buffer, and returns it.
4358 @defun insert-button label &rest properties
4359 @tindex insert-button
4360 This insert a button with the label @var{label} at point,
4364 The following functions are similar, but use Emacs text properties
4365 (@pxref{Text Properties}) to hold the button properties, making the
4366 button actually part of the text instead of being a property of the
4367 buffer. Buttons using text properties do not create markers into the
4368 buffer, which is important for speed when you use extremely large
4369 numbers of buttons. Both functions return the position of the start
4372 @defun make-text-button beg end &rest properties
4373 @tindex make-text-button
4374 This makes a button from @var{beg} to @var{end} in the current buffer, using
4378 @defun insert-text-button label &rest properties
4379 @tindex insert-text-button
4380 This inserts a button with the label @var{label} at point, using text
4384 @node Manipulating Buttons
4385 @subsection Manipulating Buttons
4386 @cindex manipulating buttons
4388 These are functions for getting and setting properties of buttons.
4389 Often these are used by a button's invocation function to determine
4392 Where a @var{button} parameter is specified, it means an object
4393 referring to a specific button, either an overlay (for overlay
4394 buttons), or a buffer-position or marker (for text property buttons).
4395 Such an object is passed as the first argument to a button's
4396 invocation function when it is invoked.
4398 @defun button-start button
4399 @tindex button-start
4400 Return the position at which @var{button} starts.
4403 @defun button-end button
4405 Return the position at which @var{button} ends.
4408 @defun button-get button prop
4410 Get the property of button @var{button} named @var{prop}.
4413 @defun button-put button prop val
4415 Set @var{button}'s @var{prop} property to @var{val}.
4418 @defun button-activate button &optional use-mouse-action
4419 @tindex button-activate
4420 Call @var{button}'s @code{action} property (i.e., invoke it). If
4421 @var{use-mouse-action} is non-@code{nil}, try to invoke the button's
4422 @code{mouse-action} property instead of @code{action}; if the button
4423 has no @code{mouse-action} property, use @code{action} as normal.
4426 @defun button-label button
4427 @tindex button-label
4428 Return @var{button}'s text label.
4431 @defun button-type button
4433 Return @var{button}'s button-type.
4436 @defun button-has-type-p button type
4437 @tindex button-has-type-p
4438 Return @code{t} if @var{button} has button-type @var{type}, or one of
4439 @var{type}'s subtypes.
4442 @defun button-at pos
4444 Return the button at position @var{pos} in the current buffer, or @code{nil}.
4447 @defun button-type-put type prop val
4448 @tindex button-type-put
4449 Set the button-type @var{type}'s @var{prop} property to @var{val}.
4452 @defun button-type-get type prop
4453 @tindex button-type-get
4454 Get the property of button-type @var{type} named @var{prop}.
4457 @defun button-type-subtype-p type supertype
4458 @tindex button-type-subtype-p
4459 Return @code{t} if button-type @var{type} is a subtype of @var{supertype}.
4462 @node Button Buffer Commands
4463 @subsection Button Buffer Commands
4464 @cindex button buffer commands
4466 These are commands and functions for locating and operating on
4467 buttons in an Emacs buffer.
4469 @code{push-button} is the command that a user uses to actually `push'
4470 a button, and is bound by default in the button itself to @key{RET}
4471 and to @key{mouse-2} using a region-specific keymap. Commands
4472 that are useful outside the buttons itself, such as
4473 @code{forward-button} and @code{backward-button} are additionally
4474 available in the keymap stored in @code{button-buffer-map}; a mode
4475 which uses buttons may want to use @code{button-buffer-map} as a
4476 parent keymap for its keymap.
4478 If the button has a non-@code{nil} @code{follow-link} property, and
4479 @var{mouse-1-click-follows-link} is set, a quick @key{Mouse-1} click
4480 will also activate the @code{push-button} command.
4481 @xref{Links and Mouse-1}.
4483 @deffn Command push-button &optional pos use-mouse-action
4485 Perform the action specified by a button at location @var{pos}.
4486 @var{pos} may be either a buffer position or a mouse-event. If
4487 @var{use-mouse-action} is non-@code{nil}, or @var{pos} is a
4488 mouse-event (@pxref{Mouse Events}), try to invoke the button's
4489 @code{mouse-action} property instead of @code{action}; if the button
4490 has no @code{mouse-action} property, use @code{action} as normal.
4491 @var{pos} defaults to point, except when @code{push-button} is invoked
4492 interactively as the result of a mouse-event, in which case, the mouse
4493 event's position is used. If there's no button at @var{pos}, do
4494 nothing and return @code{nil}, otherwise return @code{t}.
4497 @deffn Command forward-button n &optional wrap display-message
4498 @tindex forward-button
4499 Move to the @var{n}th next button, or @var{n}th previous button if
4500 @var{n} is negative. If @var{n} is zero, move to the start of any
4501 button at point. If @var{wrap} is non-@code{nil}, moving past either
4502 end of the buffer continues from the other end. If
4503 @var{display-message} is non-@code{nil}, the button's help-echo string
4504 is displayed. Any button with a non-@code{nil} @code{skip} property
4505 is skipped over. Returns the button found.
4508 @deffn Command backward-button n &optional wrap display-message
4509 @tindex backward-button
4510 Move to the @var{n}th previous button, or @var{n}th next button if
4511 @var{n} is negative. If @var{n} is zero, move to the start of any
4512 button at point. If @var{wrap} is non-@code{nil}, moving past either
4513 end of the buffer continues from the other end. If
4514 @var{display-message} is non-@code{nil}, the button's help-echo string
4515 is displayed. Any button with a non-@code{nil} @code{skip} property
4516 is skipped over. Returns the button found.
4519 @defun next-button pos &optional count-current
4521 Return the next button after position @var{pos} in the current buffer.
4522 If @var{count-current} is non-@code{nil}, count any button at
4523 @var{pos} in the search, instead of starting at the next button.
4526 @defun previous-button pos &optional count-current
4527 @tindex previous-button
4528 Return the @var{n}th button before position @var{pos} in the current
4529 buffer. If @var{count-current} is non-@code{nil}, count any button at
4530 @var{pos} in the search, instead of starting at the next button.
4534 @section Blinking Parentheses
4535 @cindex parenthesis matching
4537 @cindex balancing parentheses
4538 @cindex close parenthesis
4540 This section describes the mechanism by which Emacs shows a matching
4541 open parenthesis when the user inserts a close parenthesis.
4543 @defvar blink-paren-function
4544 The value of this variable should be a function (of no arguments) to
4545 be called whenever a character with close parenthesis syntax is inserted.
4546 The value of @code{blink-paren-function} may be @code{nil}, in which
4547 case nothing is done.
4550 @defopt blink-matching-paren
4551 If this variable is @code{nil}, then @code{blink-matching-open} does
4555 @defopt blink-matching-paren-distance
4556 This variable specifies the maximum distance to scan for a matching
4557 parenthesis before giving up.
4560 @defopt blink-matching-delay
4561 This variable specifies the number of seconds for the cursor to remain
4562 at the matching parenthesis. A fraction of a second often gives
4563 good results, but the default is 1, which works on all systems.
4566 @deffn Command blink-matching-open
4567 This function is the default value of @code{blink-paren-function}. It
4568 assumes that point follows a character with close parenthesis syntax and
4569 moves the cursor momentarily to the matching opening character. If that
4570 character is not already on the screen, it displays the character's
4571 context in the echo area. To avoid long delays, this function does not
4572 search farther than @code{blink-matching-paren-distance} characters.
4574 Here is an example of calling this function explicitly.
4578 (defun interactive-blink-matching-open ()
4579 @c Do not break this line! -- rms.
4580 @c The first line of a doc string
4581 @c must stand alone.
4582 "Indicate momentarily the start of sexp before point."
4586 (let ((blink-matching-paren-distance
4588 (blink-matching-paren t))
4589 (blink-matching-open)))
4595 @section Inverse Video
4596 @cindex Inverse Video
4598 @defopt inverse-video
4599 @cindex highlighting
4600 This variable controls whether Emacs uses inverse video for all text
4601 on the screen. Non-@code{nil} means yes, @code{nil} means no. The
4602 default is @code{nil}.
4606 @section Usual Display Conventions
4608 The usual display conventions define how to display each character
4609 code. You can override these conventions by setting up a display table
4610 (@pxref{Display Tables}). Here are the usual display conventions:
4614 Character codes 32 through 126 map to glyph codes 32 through 126.
4615 Normally this means they display as themselves.
4618 Character code 9 is a horizontal tab. It displays as whitespace
4619 up to a position determined by @code{tab-width}.
4622 Character code 10 is a newline.
4625 All other codes in the range 0 through 31, and code 127, display in one
4626 of two ways according to the value of @code{ctl-arrow}. If it is
4627 non-@code{nil}, these codes map to sequences of two glyphs, where the
4628 first glyph is the @acronym{ASCII} code for @samp{^}. (A display table can
4629 specify a glyph to use instead of @samp{^}.) Otherwise, these codes map
4630 just like the codes in the range 128 to 255.
4632 On MS-DOS terminals, Emacs arranges by default for the character code
4633 127 to be mapped to the glyph code 127, which normally displays as an
4634 empty polygon. This glyph is used to display non-@acronym{ASCII} characters
4635 that the MS-DOS terminal doesn't support. @xref{MS-DOS and MULE,,,
4636 emacs, The GNU Emacs Manual}.
4639 Character codes 128 through 255 map to sequences of four glyphs, where
4640 the first glyph is the @acronym{ASCII} code for @samp{\}, and the others are
4641 digit characters representing the character code in octal. (A display
4642 table can specify a glyph to use instead of @samp{\}.)
4645 Multibyte character codes above 256 are displayed as themselves, or as a
4646 question mark or empty box if the terminal cannot display that
4650 The usual display conventions apply even when there is a display
4651 table, for any character whose entry in the active display table is
4652 @code{nil}. Thus, when you set up a display table, you need only
4653 specify the characters for which you want special behavior.
4655 These display rules apply to carriage return (character code 13), when
4656 it appears in the buffer. But that character may not appear in the
4657 buffer where you expect it, if it was eliminated as part of end-of-line
4658 conversion (@pxref{Coding System Basics}).
4660 These variables affect the way certain characters are displayed on the
4661 screen. Since they change the number of columns the characters occupy,
4662 they also affect the indentation functions. These variables also affect
4663 how the mode line is displayed; if you want to force redisplay of the
4664 mode line using the new values, call the function
4665 @code{force-mode-line-update} (@pxref{Mode Line Format}).
4668 @cindex control characters in display
4669 This buffer-local variable controls how control characters are
4670 displayed. If it is non-@code{nil}, they are displayed as a caret
4671 followed by the character: @samp{^A}. If it is @code{nil}, they are
4672 displayed as a backslash followed by three octal digits: @samp{\001}.
4675 @c Following may have overfull hbox.
4676 @defvar default-ctl-arrow
4677 The value of this variable is the default value for @code{ctl-arrow} in
4678 buffers that do not override it. @xref{Default Value}.
4682 The value of this variable is the spacing between tab stops used for
4683 displaying tab characters in Emacs buffers. The value is in units of
4684 columns, and the default is 8. Note that this feature is completely
4685 independent of the user-settable tab stops used by the command
4686 @code{tab-to-tab-stop}. @xref{Indent Tabs}.
4689 @defopt indicate-empty-lines
4690 @tindex indicate-empty-lines
4691 @cindex fringes, and empty line indication
4692 When this is non-@code{nil}, Emacs displays a special glyph in the
4693 fringe of each empty line at the end of the buffer, on terminals that
4694 support it (window systems). @xref{Fringes}.
4697 @defvar indicate-buffer-boundaries
4698 This buffer-local variable controls how the buffer boundaries and
4699 window scrolling are indicated in the window fringes.
4701 Emacs can indicate the buffer boundaries---that is, the first and last
4702 line in the buffer---with angle icons when they appear on the screen.
4703 In addition, Emacs can display an up-arrow in the fringe to show
4704 that there is text above the screen, and a down-arrow to show
4705 there is text below the screen.
4707 There are four kinds of basic values:
4711 Don't display the icons.
4713 Display them in the left fringe.
4715 Display them in the right fringe.
4716 @item @var{anything-else}
4717 Display the icon at the top of the window top in the left fringe, and other
4718 in the right fringe.
4721 If value is a cons @code{(@var{angles} . @var{arrows})}, @var{angles}
4722 controls the angle icons, and @var{arrows} controls the arrows. Both
4723 @var{angles} and @var{arrows} work according to the table above.
4724 Thus, @code{(t . right)} places the top angle icon in the left
4725 fringe, the bottom angle icon in the right fringe, and both arrows in
4729 @defvar default-indicate-buffer-boundaries
4730 The value of this variable is the default value for
4731 @code{indicate-buffer-boundaries} in buffers that do not override it.
4734 @node Display Tables
4735 @section Display Tables
4737 @cindex display table
4738 You can use the @dfn{display table} feature to control how all possible
4739 character codes display on the screen. This is useful for displaying
4740 European languages that have letters not in the @acronym{ASCII} character
4743 The display table maps each character code into a sequence of
4744 @dfn{glyphs}, each glyph being a graphic that takes up one character
4745 position on the screen. You can also define how to display each glyph
4746 on your terminal, using the @dfn{glyph table}.
4748 Display tables affect how the mode line is displayed; if you want to
4749 force redisplay of the mode line using a new display table, call
4750 @code{force-mode-line-update} (@pxref{Mode Line Format}).
4753 * Display Table Format:: What a display table consists of.
4754 * Active Display Table:: How Emacs selects a display table to use.
4755 * Glyphs:: How to define a glyph, and what glyphs mean.
4758 @node Display Table Format
4759 @subsection Display Table Format
4761 A display table is actually a char-table (@pxref{Char-Tables}) with
4762 @code{display-table} as its subtype.
4764 @defun make-display-table
4765 This creates and returns a display table. The table initially has
4766 @code{nil} in all elements.
4769 The ordinary elements of the display table are indexed by character
4770 codes; the element at index @var{c} says how to display the character
4771 code @var{c}. The value should be @code{nil} or a vector of glyph
4772 values (@pxref{Glyphs}). If an element is @code{nil}, it says to
4773 display that character according to the usual display conventions
4774 (@pxref{Usual Display}).
4776 If you use the display table to change the display of newline
4777 characters, the whole buffer will be displayed as one long ``line.''
4779 The display table also has six ``extra slots'' which serve special
4780 purposes. Here is a table of their meanings; @code{nil} in any slot
4781 means to use the default for that slot, as stated below.
4785 The glyph for the end of a truncated screen line (the default for this
4786 is @samp{$}). @xref{Glyphs}. On graphical terminals, Emacs uses
4787 arrows in the fringes to indicate truncation, so the display table has
4791 The glyph for the end of a continued line (the default is @samp{\}).
4792 On graphical terminals, Emacs uses curved arrows in the fringes to
4793 indicate continuation, so the display table has no effect.
4796 The glyph for indicating a character displayed as an octal character
4797 code (the default is @samp{\}).
4800 The glyph for indicating a control character (the default is @samp{^}).
4803 A vector of glyphs for indicating the presence of invisible lines (the
4804 default is @samp{...}). @xref{Selective Display}.
4807 The glyph used to draw the border between side-by-side windows (the
4808 default is @samp{|}). @xref{Splitting Windows}. This takes effect only
4809 when there are no scroll bars; if scroll bars are supported and in use,
4810 a scroll bar separates the two windows.
4813 For example, here is how to construct a display table that mimics the
4814 effect of setting @code{ctl-arrow} to a non-@code{nil} value:
4817 (setq disptab (make-display-table))
4820 (or (= i ?\t) (= i ?\n)
4821 (aset disptab i (vector ?^ (+ i 64))))
4823 (aset disptab 127 (vector ?^ ??)))
4826 @defun display-table-slot display-table slot
4827 This function returns the value of the extra slot @var{slot} of
4828 @var{display-table}. The argument @var{slot} may be a number from 0 to
4829 5 inclusive, or a slot name (symbol). Valid symbols are
4830 @code{truncation}, @code{wrap}, @code{escape}, @code{control},
4831 @code{selective-display}, and @code{vertical-border}.
4834 @defun set-display-table-slot display-table slot value
4835 This function stores @var{value} in the extra slot @var{slot} of
4836 @var{display-table}. The argument @var{slot} may be a number from 0 to
4837 5 inclusive, or a slot name (symbol). Valid symbols are
4838 @code{truncation}, @code{wrap}, @code{escape}, @code{control},
4839 @code{selective-display}, and @code{vertical-border}.
4842 @defun describe-display-table display-table
4843 @tindex describe-display-table
4844 This function displays a description of the display table
4845 @var{display-table} in a help buffer.
4848 @deffn Command describe-current-display-table
4849 @tindex describe-current-display-table
4850 This command displays a description of the current display table in a
4854 @node Active Display Table
4855 @subsection Active Display Table
4856 @cindex active display table
4858 Each window can specify a display table, and so can each buffer. When
4859 a buffer @var{b} is displayed in window @var{w}, display uses the
4860 display table for window @var{w} if it has one; otherwise, the display
4861 table for buffer @var{b} if it has one; otherwise, the standard display
4862 table if any. The display table chosen is called the @dfn{active}
4865 @defun window-display-table &optional window
4866 This function returns @var{window}'s display table, or @code{nil}
4867 if @var{window} does not have an assigned display table. The default
4868 for @var{window} is the selected window.
4871 @defun set-window-display-table window table
4872 This function sets the display table of @var{window} to @var{table}.
4873 The argument @var{table} should be either a display table or
4877 @defvar buffer-display-table
4878 This variable is automatically buffer-local in all buffers; its value in
4879 a particular buffer specifies the display table for that buffer. If it
4880 is @code{nil}, that means the buffer does not have an assigned display
4884 @defvar standard-display-table
4885 This variable's value is the default display table, used whenever a
4886 window has no display table and neither does the buffer displayed in
4887 that window. This variable is @code{nil} by default.
4890 If there is no display table to use for a particular window---that is,
4891 if the window specifies none, its buffer specifies none, and
4892 @code{standard-display-table} is @code{nil}---then Emacs uses the usual
4893 display conventions for all character codes in that window. @xref{Usual
4896 A number of functions for changing the standard display table
4897 are defined in the library @file{disp-table}.
4903 A @dfn{glyph} is a generalization of a character; it stands for an
4904 image that takes up a single character position on the screen. Glyphs
4905 are represented in Lisp as integers, just as characters are. Normally
4906 Emacs finds glyphs in the display table (@pxref{Display Tables}).
4908 A glyph can be @dfn{simple} or it can be defined by the @dfn{glyph
4909 table}. A simple glyph is just a way of specifying a character and a
4910 face to output it in. The glyph code for a simple glyph, mod 524288,
4911 is the character to output, and the glyph code divided by 524288
4912 specifies the face number (@pxref{Face Functions}) to use while
4913 outputting it. (524288 is
4922 On character terminals, you can set up a @dfn{glyph table} to define
4923 the meaning of glyph codes. The glyph codes is the value of the
4924 variable @code{glyph-table}.
4927 The value of this variable is the current glyph table. It should be a
4928 vector; the @var{g}th element defines glyph code @var{g}.
4930 If a glyph code is greater than or equal to the length of the glyph
4931 table, that code is automatically simple. If the value of
4932 @code{glyph-table} is @code{nil} instead of a vector, then all glyphs
4933 are simple. The glyph table is not used on graphical displays, only
4934 on character terminals. On graphical displays, all glyphs are simple.
4937 Here are the possible types of elements in the glyph table:
4941 Send the characters in @var{string} to the terminal to output
4942 this glyph. This alternative is available on character terminals,
4943 but not under a window system.
4946 Define this glyph code as an alias for glyph code @var{integer}. You
4947 can use an alias to specify a face code for the glyph and use a small
4951 This glyph is simple.
4954 @defun create-glyph string
4955 @tindex create-glyph
4956 This function returns a newly-allocated glyph code which is set up to
4957 display by sending @var{string} to the terminal.
4965 This section describes how to make Emacs ring the bell (or blink the
4966 screen) to attract the user's attention. Be conservative about how
4967 often you do this; frequent bells can become irritating. Also be
4968 careful not to use just beeping when signaling an error is more
4969 appropriate. (@xref{Errors}.)
4971 @defun ding &optional do-not-terminate
4972 @cindex keyboard macro termination
4973 This function beeps, or flashes the screen (see @code{visible-bell} below).
4974 It also terminates any keyboard macro currently executing unless
4975 @var{do-not-terminate} is non-@code{nil}.
4978 @defun beep &optional do-not-terminate
4979 This is a synonym for @code{ding}.
4982 @defopt visible-bell
4983 This variable determines whether Emacs should flash the screen to
4984 represent a bell. Non-@code{nil} means yes, @code{nil} means no. This
4985 is effective on a window system, and on a character-only terminal
4986 provided the terminal's Termcap entry defines the visible bell
4987 capability (@samp{vb}).
4990 @defvar ring-bell-function
4991 If this is non-@code{nil}, it specifies how Emacs should ``ring the
4992 bell.'' Its value should be a function of no arguments. If this is
4993 non-@code{nil}, it takes precedence over the @code{visible-bell}
4997 @node Window Systems
4998 @section Window Systems
5000 Emacs works with several window systems, most notably the X Window
5001 System. Both Emacs and X use the term ``window'', but use it
5002 differently. An Emacs frame is a single window as far as X is
5003 concerned; the individual Emacs windows are not known to X at all.
5005 @defvar window-system
5006 This variable tells Lisp programs what window system Emacs is running
5007 under. The possible values are
5011 @cindex X Window System
5012 Emacs is displaying using X.
5014 Emacs is displaying using MS-DOS.
5016 Emacs is displaying using Windows.
5018 Emacs is displaying using a Macintosh.
5020 Emacs is using a character-based terminal.
5024 @defvar window-setup-hook
5025 This variable is a normal hook which Emacs runs after handling the
5026 initialization files. Emacs runs this hook after it has completed
5027 loading your init file, the default initialization file (if
5028 any), and the terminal-specific Lisp code, and running the hook
5029 @code{term-setup-hook}.
5031 This hook is used for internal purposes: setting up communication with
5032 the window system, and creating the initial window. Users should not
5037 arch-tag: ffdf5714-7ecf-415b-9023-fbc6b409c2c6