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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
82c3d852 | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001, 2002 |
177c0ea7 | 4 | @c Free Software Foundation, Inc. |
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5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/display | |
969fe9b5 | 7 | @node Display, Calendar, Processes, Top |
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8 | @chapter Emacs Display |
9 | ||
10 | This chapter describes a number of features related to the display | |
11 | that Emacs presents to the user. | |
12 | ||
13 | @menu | |
14 | * Refresh Screen:: Clearing the screen and redrawing everything on it. | |
8241495d | 15 | * Forcing Redisplay:: Forcing redisplay. |
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16 | * Truncation:: Folding or wrapping long text lines. |
17 | * The Echo Area:: Where messages are displayed. | |
8a6ca431 | 18 | * Warnings:: Displaying warning messages for the user. |
276dd8a8 | 19 | * Progress:: Informing user about progress of a long operation. |
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20 | * Invisible Text:: Hiding part of the buffer text. |
21 | * Selective Display:: Hiding part of the buffer text (the old way). | |
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22 | * Overlay Arrow:: Display of an arrow to indicate position. |
23 | * Temporary Displays:: Displays that go away automatically. | |
02c77ee9 | 24 | * Overlays:: Use overlays to highlight parts of the buffer. |
a40d4712 | 25 | * Width:: How wide a character or string is on the screen. |
02c77ee9 | 26 | * Faces:: A face defines a graphics style for text characters: |
a40d4712 | 27 | font, colors, etc. |
8a6ca431 | 28 | * Fringes:: Controlling window fringes. |
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29 | * Fringe Bitmaps:: Displaying bitmaps in the window fringes. |
30 | * Customizing Bitmaps:: Specifying your own bitmaps to use in the fringes. | |
f6cad089 | 31 | * Scroll Bars:: Controlling vertical scroll bars. |
6db2bc02 | 32 | * Pointer Shape:: Controlling the mouse pointer shape. |
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33 | * Display Property:: Enabling special display features. |
34 | * Images:: Displaying images in Emacs buffers. | |
02c77ee9 | 35 | * Buttons:: Adding clickable buttons to Emacs buffers. |
42b85554 | 36 | * Blinking:: How Emacs shows the matching open parenthesis. |
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37 | * Inverse Video:: Specifying how the screen looks. |
38 | * Usual Display:: The usual conventions for displaying nonprinting chars. | |
39 | * Display Tables:: How to specify other conventions. | |
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40 | * Beeping:: Audible signal to the user. |
41 | * Window Systems:: Which window system is being used. | |
42 | @end menu | |
43 | ||
44 | @node Refresh Screen | |
45 | @section Refreshing the Screen | |
46 | ||
47 | The function @code{redraw-frame} redisplays the entire contents of a | |
1911e6e5 | 48 | given frame (@pxref{Frames}). |
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49 | |
50 | @c Emacs 19 feature | |
51 | @defun redraw-frame frame | |
52 | This function clears and redisplays frame @var{frame}. | |
53 | @end defun | |
54 | ||
55 | Even more powerful is @code{redraw-display}: | |
56 | ||
57 | @deffn Command redraw-display | |
58 | This function clears and redisplays all visible frames. | |
59 | @end deffn | |
60 | ||
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61 | This function forces certain windows to be redisplayed |
62 | but does not clear them. | |
63 | ||
64 | @defun force-window-update object | |
65 | This function forces redisplay of some or all windows. If | |
66 | @var{object} is a window, it forces redisplay of that window. If | |
67 | @var{object} is a buffer or buffer name, it forces redisplay of all | |
68 | windows displaying that buffer. If @var{object} is @code{nil}, it | |
69 | forces redisplay of all windows. | |
70 | @end defun | |
71 | ||
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72 | Processing user input takes absolute priority over redisplay. If you |
73 | call these functions when input is available, they do nothing | |
74 | immediately, but a full redisplay does happen eventually---after all the | |
75 | input has been processed. | |
76 | ||
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77 | Normally, suspending and resuming Emacs also refreshes the screen. |
78 | Some terminal emulators record separate contents for display-oriented | |
79 | programs such as Emacs and for ordinary sequential display. If you are | |
80 | using such a terminal, you might want to inhibit the redisplay on | |
78608595 | 81 | resumption. |
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82 | |
83 | @defvar no-redraw-on-reenter | |
84 | @cindex suspend (cf. @code{no-redraw-on-reenter}) | |
85 | @cindex resume (cf. @code{no-redraw-on-reenter}) | |
86 | This variable controls whether Emacs redraws the entire screen after it | |
f9f59935 | 87 | has been suspended and resumed. Non-@code{nil} means there is no need |
969fe9b5 | 88 | to redraw, @code{nil} means redrawing is needed. The default is @code{nil}. |
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89 | @end defvar |
90 | ||
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91 | @node Forcing Redisplay |
92 | @section Forcing Redisplay | |
93 | @cindex forcing redisplay | |
94 | ||
95 | Emacs redisplay normally stops if input arrives, and does not happen | |
96 | at all if input is available before it starts. Most of the time, this | |
97 | is exactly what you want. However, you can prevent preemption by | |
98 | binding @code{redisplay-dont-pause} to a non-@code{nil} value. | |
99 | ||
100 | @tindex redisplay-dont-pause | |
101 | @defvar redisplay-dont-pause | |
102 | If this variable is non-@code{nil}, pending input does not | |
103 | prevent or halt redisplay; redisplay occurs, and finishes, | |
104 | regardless of whether input is available. This feature is available | |
105 | as of Emacs 21. | |
106 | @end defvar | |
107 | ||
108 | You can request a display update, but only if no input is pending, | |
109 | with @code{(sit-for 0)}. To force a display update even when input is | |
110 | pending, do this: | |
111 | ||
112 | @example | |
113 | (let ((redisplay-dont-pause t)) | |
114 | (sit-for 0)) | |
115 | @end example | |
116 | ||
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117 | @node Truncation |
118 | @section Truncation | |
119 | @cindex line wrapping | |
120 | @cindex continuation lines | |
121 | @cindex @samp{$} in display | |
122 | @cindex @samp{\} in display | |
123 | ||
124 | When a line of text extends beyond the right edge of a window, the | |
125 | line can either be continued on the next screen line, or truncated to | |
126 | one screen line. The additional screen lines used to display a long | |
127 | text line are called @dfn{continuation} lines. Normally, a @samp{$} in | |
128 | the rightmost column of the window indicates truncation; a @samp{\} on | |
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129 | the rightmost column indicates a line that ``wraps'' onto the next line, |
130 | which is also called @dfn{continuing} the line. (The display table can | |
131 | specify alternative indicators; see @ref{Display Tables}.) | |
42b85554 | 132 | |
6e2391a8 | 133 | On a windowed display, the @samp{$} and @samp{\} indicators are |
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134 | replaced with graphics bitmaps displayed in the window fringes |
135 | (@pxref{Fringes}). | |
6e2391a8 | 136 | |
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137 | Note that continuation is different from filling; continuation happens |
138 | on the screen only, not in the buffer contents, and it breaks a line | |
139 | precisely at the right margin, not at a word boundary. @xref{Filling}. | |
140 | ||
141 | @defopt truncate-lines | |
142 | This buffer-local variable controls how Emacs displays lines that extend | |
143 | beyond the right edge of the window. The default is @code{nil}, which | |
144 | specifies continuation. If the value is non-@code{nil}, then these | |
145 | lines are truncated. | |
146 | ||
147 | If the variable @code{truncate-partial-width-windows} is non-@code{nil}, | |
148 | then truncation is always used for side-by-side windows (within one | |
149 | frame) regardless of the value of @code{truncate-lines}. | |
150 | @end defopt | |
151 | ||
bfe721d1 | 152 | @defopt default-truncate-lines |
42b85554 | 153 | This variable is the default value for @code{truncate-lines}, for |
969fe9b5 | 154 | buffers that do not have buffer-local values for it. |
bfe721d1 | 155 | @end defopt |
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156 | |
157 | @defopt truncate-partial-width-windows | |
158 | This variable controls display of lines that extend beyond the right | |
159 | edge of the window, in side-by-side windows (@pxref{Splitting Windows}). | |
160 | If it is non-@code{nil}, these lines are truncated; otherwise, | |
161 | @code{truncate-lines} says what to do with them. | |
162 | @end defopt | |
163 | ||
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164 | When horizontal scrolling (@pxref{Horizontal Scrolling}) is in use in |
165 | a window, that forces truncation. | |
166 | ||
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167 | You can override the glyphs that indicate continuation or truncation |
168 | using the display table; see @ref{Display Tables}. | |
42b85554 | 169 | |
1911e6e5 | 170 | If your buffer contains @emph{very} long lines, and you use |
22697dac | 171 | continuation to display them, just thinking about them can make Emacs |
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172 | redisplay slow. The column computation and indentation functions also |
173 | become slow. Then you might find it advisable to set | |
174 | @code{cache-long-line-scans} to @code{t}. | |
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175 | |
176 | @defvar cache-long-line-scans | |
177 | If this variable is non-@code{nil}, various indentation and motion | |
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178 | functions, and Emacs redisplay, cache the results of scanning the |
179 | buffer, and consult the cache to avoid rescanning regions of the buffer | |
180 | unless they are modified. | |
22697dac | 181 | |
bfe721d1 | 182 | Turning on the cache slows down processing of short lines somewhat. |
22697dac | 183 | |
969fe9b5 | 184 | This variable is automatically buffer-local in every buffer. |
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185 | @end defvar |
186 | ||
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187 | @node The Echo Area |
188 | @section The Echo Area | |
189 | @cindex error display | |
190 | @cindex echo area | |
191 | ||
22697dac | 192 | The @dfn{echo area} is used for displaying messages made with the |
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193 | @code{message} primitive, and for echoing keystrokes. It is not the |
194 | same as the minibuffer, despite the fact that the minibuffer appears | |
195 | (when active) in the same place on the screen as the echo area. The | |
196 | @cite{GNU Emacs Manual} specifies the rules for resolving conflicts | |
197 | between the echo area and the minibuffer for use of that screen space | |
198 | (@pxref{Minibuffer,, The Minibuffer, emacs, The GNU Emacs Manual}). | |
199 | Error messages appear in the echo area; see @ref{Errors}. | |
200 | ||
201 | You can write output in the echo area by using the Lisp printing | |
202 | functions with @code{t} as the stream (@pxref{Output Functions}), or as | |
203 | follows: | |
204 | ||
205 | @defun message string &rest arguments | |
a2f2ceaa | 206 | This function displays a message in the echo area. The |
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207 | argument @var{string} is similar to a C language @code{printf} control |
208 | string. See @code{format} in @ref{String Conversion}, for the details | |
209 | on the conversion specifications. @code{message} returns the | |
210 | constructed string. | |
211 | ||
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212 | In batch mode, @code{message} prints the message text on the standard |
213 | error stream, followed by a newline. | |
214 | ||
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215 | If @var{string}, or strings among the @var{arguments}, have @code{face} |
216 | text properties, these affect the way the message is displayed. | |
217 | ||
42b85554 | 218 | @c Emacs 19 feature |
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219 | If @var{string} is @code{nil}, @code{message} clears the echo area; if |
220 | the echo area has been expanded automatically, this brings it back to | |
221 | its normal size. If the minibuffer is active, this brings the | |
222 | minibuffer contents back onto the screen immediately. | |
b22f3a19 | 223 | |
a2f2ceaa | 224 | @vindex message-truncate-lines |
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225 | Normally, displaying a long message resizes the echo area to display |
226 | the entire message. But if the variable @code{message-truncate-lines} | |
227 | is non-@code{nil}, the echo area does not resize, and the message is | |
228 | truncated to fit it, as in Emacs 20 and before. | |
a2f2ceaa | 229 | |
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230 | @example |
231 | @group | |
232 | (message "Minibuffer depth is %d." | |
233 | (minibuffer-depth)) | |
234 | @print{} Minibuffer depth is 0. | |
235 | @result{} "Minibuffer depth is 0." | |
236 | @end group | |
237 | ||
238 | @group | |
239 | ---------- Echo Area ---------- | |
240 | Minibuffer depth is 0. | |
241 | ---------- Echo Area ---------- | |
242 | @end group | |
243 | @end example | |
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244 | |
245 | To automatically display a message in the echo area or in a pop-buffer, | |
246 | depending on its size, use @code{display-message-or-buffer}. | |
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247 | @end defun |
248 | ||
b6954afd RS |
249 | @tindex with-temp-message |
250 | @defmac with-temp-message message &rest body | |
251 | This construct displays a message in the echo area temporarily, during | |
252 | the execution of @var{body}. It displays @var{message}, executes | |
253 | @var{body}, then returns the value of the last body form while restoring | |
254 | the previous echo area contents. | |
255 | @end defmac | |
256 | ||
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257 | @defun message-or-box string &rest arguments |
258 | This function displays a message like @code{message}, but may display it | |
259 | in a dialog box instead of the echo area. If this function is called in | |
260 | a command that was invoked using the mouse---more precisely, if | |
261 | @code{last-nonmenu-event} (@pxref{Command Loop Info}) is either | |
262 | @code{nil} or a list---then it uses a dialog box or pop-up menu to | |
263 | display the message. Otherwise, it uses the echo area. (This is the | |
264 | same criterion that @code{y-or-n-p} uses to make a similar decision; see | |
265 | @ref{Yes-or-No Queries}.) | |
266 | ||
267 | You can force use of the mouse or of the echo area by binding | |
268 | @code{last-nonmenu-event} to a suitable value around the call. | |
269 | @end defun | |
270 | ||
271 | @defun message-box string &rest arguments | |
272 | This function displays a message like @code{message}, but uses a dialog | |
273 | box (or a pop-up menu) whenever that is possible. If it is impossible | |
274 | to use a dialog box or pop-up menu, because the terminal does not | |
275 | support them, then @code{message-box} uses the echo area, like | |
276 | @code{message}. | |
277 | @end defun | |
278 | ||
a43709e6 | 279 | @defun display-message-or-buffer message &optional buffer-name not-this-window frame |
26f42fed | 280 | @tindex display-message-or-buffer |
a43709e6 MB |
281 | This function displays the message @var{message}, which may be either a |
282 | string or a buffer. If it is shorter than the maximum height of the | |
283 | echo area, as defined by @code{max-mini-window-height}, it is displayed | |
284 | in the echo area, using @code{message}. Otherwise, | |
285 | @code{display-buffer} is used to show it in a pop-up buffer. | |
286 | ||
287 | Returns either the string shown in the echo area, or when a pop-up | |
288 | buffer is used, the window used to display it. | |
289 | ||
290 | If @var{message} is a string, then the optional argument | |
291 | @var{buffer-name} is the name of the buffer used to display it when a | |
292 | pop-up buffer is used, defaulting to @samp{*Message*}. In the case | |
293 | where @var{message} is a string and displayed in the echo area, it is | |
294 | not specified whether the contents are inserted into the buffer anyway. | |
295 | ||
296 | The optional arguments @var{not-this-window} and @var{frame} are as for | |
297 | @code{display-buffer}, and only used if a buffer is displayed. | |
298 | @end defun | |
299 | ||
f9f59935 RS |
300 | @defun current-message |
301 | This function returns the message currently being displayed in the | |
302 | echo area, or @code{nil} if there is none. | |
303 | @end defun | |
304 | ||
969fe9b5 RS |
305 | @defvar cursor-in-echo-area |
306 | This variable controls where the cursor appears when a message is | |
307 | displayed in the echo area. If it is non-@code{nil}, then the cursor | |
308 | appears at the end of the message. Otherwise, the cursor appears at | |
309 | point---not in the echo area at all. | |
310 | ||
311 | The value is normally @code{nil}; Lisp programs bind it to @code{t} | |
312 | for brief periods of time. | |
313 | @end defvar | |
314 | ||
f9f59935 RS |
315 | @defvar echo-area-clear-hook |
316 | This normal hook is run whenever the echo area is cleared---either by | |
317 | @code{(message nil)} or for any other reason. | |
318 | @end defvar | |
319 | ||
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320 | Almost all the messages displayed in the echo area are also recorded |
321 | in the @samp{*Messages*} buffer. | |
322 | ||
323 | @defopt message-log-max | |
324 | This variable specifies how many lines to keep in the @samp{*Messages*} | |
325 | buffer. The value @code{t} means there is no limit on how many lines to | |
326 | keep. The value @code{nil} disables message logging entirely. Here's | |
327 | how to display a message and prevent it from being logged: | |
328 | ||
329 | @example | |
330 | (let (message-log-max) | |
331 | (message @dots{})) | |
332 | @end example | |
333 | @end defopt | |
334 | ||
bfe721d1 KH |
335 | @defvar echo-keystrokes |
336 | This variable determines how much time should elapse before command | |
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337 | characters echo. Its value must be an integer or floating point number, |
338 | which specifies the | |
bfe721d1 KH |
339 | number of seconds to wait before echoing. If the user types a prefix |
340 | key (such as @kbd{C-x}) and then delays this many seconds before | |
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341 | continuing, the prefix key is echoed in the echo area. (Once echoing |
342 | begins in a key sequence, all subsequent characters in the same key | |
343 | sequence are echoed immediately.) | |
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344 | |
345 | If the value is zero, then command input is not echoed. | |
346 | @end defvar | |
347 | ||
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348 | @node Warnings |
349 | @section Reporting Warnings | |
350 | @cindex warnings | |
351 | ||
352 | @dfn{Warnings} are a facility for a program to inform the user of a | |
353 | possible problem, but continue running. | |
354 | ||
355 | @menu | |
356 | * Warning Basics:: Warnings concepts and functions to report them. | |
357 | * Warning Variables:: Variables programs bind to customize their warnings. | |
358 | * Warning Options:: Variables users set to control display of warnings. | |
359 | @end menu | |
360 | ||
361 | @node Warning Basics | |
362 | @subsection Warning Basics | |
363 | @cindex severity level | |
364 | ||
365 | Every warning has a textual message, which explains the problem for | |
366 | the user, and a @dfn{severity level} which is a symbol. Here are the | |
367 | possible severity levels, in order of decreasing severity, and their | |
368 | meanings: | |
369 | ||
370 | @table @code | |
371 | @item :emergency | |
372 | A problem that will seriously impair Emacs operation soon | |
373 | if you do not attend to it promptly. | |
374 | @item :error | |
375 | A report of data or circumstances that are inherently wrong. | |
376 | @item :warning | |
377 | A report of data or circumstances that are not inherently wrong, but | |
378 | raise suspicion of a possible problem. | |
379 | @item :debug | |
380 | A report of information that may be useful if you are debugging. | |
381 | @end table | |
382 | ||
383 | When your program encounters invalid input data, it can either | |
384 | signal a Lisp error by calling @code{error} or @code{signal} or report | |
385 | a warning with severity @code{:error}. Signaling a Lisp error is the | |
386 | easiest thing to do, but it means the program cannot continue | |
387 | processing. If you want to take the trouble to implement a way to | |
388 | continue processing despite the bad data, then reporting a warning of | |
389 | severity @code{:error} is the right way to inform the user of the | |
390 | problem. For instance, the Emacs Lisp byte compiler can report an | |
391 | error that way and continue compiling other functions. (If the | |
392 | program signals a Lisp error and then handles it with | |
393 | @code{condition-case}, the user won't see the error message; it could | |
394 | show the message to the user by reporting it as a warning.) | |
395 | ||
c00d3ba4 | 396 | @cindex warning type |
8a6ca431 RS |
397 | Each warning has a @dfn{warning type} to classify it. The type is a |
398 | list of symbols. The first symbol should be the custom group that you | |
399 | use for the program's user options. For example, byte compiler | |
400 | warnings use the warning type @code{(bytecomp)}. You can also | |
401 | subcategorize the warnings, if you wish, by using more symbols in the | |
402 | list. | |
403 | ||
404 | @defun display-warning type message &optional level buffer-name | |
405 | This function reports a warning, using @var{message} as the message | |
406 | and @var{type} as the warning type. @var{level} should be the | |
407 | severity level, with @code{:warning} being the default. | |
408 | ||
409 | @var{buffer-name}, if non-@code{nil}, specifies the name of the buffer | |
410 | for logging the warning. By default, it is @samp{*Warnings*}. | |
411 | @end defun | |
412 | ||
413 | @defun lwarn type level message &rest args | |
414 | This function reports a warning using the value of @code{(format | |
415 | @var{message} @var{args}...)} as the message. In other respects it is | |
416 | equivalent to @code{display-warning}. | |
417 | @end defun | |
418 | ||
419 | @defun warn message &rest args | |
420 | This function reports a warning using the value of @code{(format | |
421 | @var{message} @var{args}...)} as the message, @code{(emacs)} as the | |
422 | type, and @code{:warning} as the severity level. It exists for | |
423 | compatibility only; we recommend not using it, because you should | |
424 | specify a specific warning type. | |
425 | @end defun | |
426 | ||
427 | @node Warning Variables | |
428 | @subsection Warning Variables | |
429 | ||
430 | Programs can customize how their warnings appear by binding | |
431 | the variables described in this section. | |
432 | ||
433 | @defvar warning-levels | |
434 | This list defines the meaning and severity order of the warning | |
435 | severity levels. Each element defines one severity level, | |
436 | and they are arranged in order of decreasing severity. | |
437 | ||
438 | Each element has the form @code{(@var{level} @var{string} | |
439 | @var{function})}, where @var{level} is the severity level it defines. | |
440 | @var{string} specifies the textual description of this level. | |
441 | @var{string} should use @samp{%s} to specify where to put the warning | |
442 | type information, or it can omit the @samp{%s} so as not to include | |
443 | that information. | |
444 | ||
445 | The optional @var{function}, if non-@code{nil}, is a function to call | |
446 | with no arguments, to get the user's attention. | |
447 | ||
448 | Normally you should not change the value of this variable. | |
449 | @end defvar | |
450 | ||
451 | @defvar warning-prefix-function | |
812a2341 | 452 | If non-@code{nil}, the value is a function to generate prefix text for |
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453 | warnings. Programs can bind the variable to a suitable function. |
454 | @code{display-warning} calls this function with the warnings buffer | |
455 | current, and the function can insert text in it. That text becomes | |
456 | the beginning of the warning message. | |
457 | ||
458 | The function is called with two arguments, the severity level and its | |
459 | entry in @code{warning-levels}. It should return a list to use as the | |
460 | entry (this value need not be an actual member of | |
812a2341 | 461 | @code{warning-levels}). By constructing this value, the function can |
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462 | change the severity of the warning, or specify different handling for |
463 | a given severity level. | |
464 | ||
465 | If the variable's value is @code{nil} then there is no function | |
466 | to call. | |
467 | @end defvar | |
468 | ||
469 | @defvar warning-series | |
470 | Programs can bind this variable to @code{t} to say that the next | |
471 | warning should begin a series. When several warnings form a series, | |
472 | that means to leave point on the first warning of the series, rather | |
812a2341 | 473 | than keep moving it for each warning so that it appears on the last one. |
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474 | The series ends when the local binding is unbound and |
475 | @code{warning-series} becomes @code{nil} again. | |
476 | ||
477 | The value can also be a symbol with a function definition. That is | |
478 | equivalent to @code{t}, except that the next warning will also call | |
479 | the function with no arguments with the warnings buffer current. The | |
480 | function can insert text which will serve as a header for the series | |
481 | of warnings. | |
482 | ||
483 | Once a series has begun, the value is a marker which points to the | |
484 | buffer position in the warnings buffer of the start of the series. | |
485 | ||
486 | The variable's normal value is @code{nil}, which means to handle | |
487 | each warning separately. | |
488 | @end defvar | |
489 | ||
490 | @defvar warning-fill-prefix | |
491 | When this variable is non-@code{nil}, it specifies a fill prefix to | |
492 | use for filling each warning's text. | |
493 | @end defvar | |
494 | ||
495 | @defvar warning-type-format | |
496 | This variable specifies the format for displaying the warning type | |
497 | in the warning message. The result of formatting the type this way | |
498 | gets included in the message under the control of the string in the | |
499 | entry in @code{warning-levels}. The default value is @code{" (%s)"}. | |
500 | If you bind it to @code{""} then the warning type won't appear at | |
501 | all. | |
502 | @end defvar | |
503 | ||
504 | @node Warning Options | |
505 | @subsection Warning Options | |
506 | ||
507 | These variables are used by users to control what happens | |
508 | when a Lisp program reports a warning. | |
509 | ||
510 | @defopt warning-minimum-level | |
511 | This user option specifies the minimum severity level that should be | |
512 | shown immediately to the user. The default is @code{:warning}, which | |
513 | means to immediately display all warnings except @code{:debug} | |
514 | warnings. | |
515 | @end defopt | |
516 | ||
517 | @defopt warning-minimum-log-level | |
518 | This user option specifies the minimum severity level that should be | |
519 | logged in the warnings buffer. The default is @code{:warning}, which | |
520 | means to log all warnings except @code{:debug} warnings. | |
521 | @end defopt | |
522 | ||
523 | @defopt warning-suppress-types | |
524 | This list specifies which warning types should not be displayed | |
525 | immediately for the user. Each element of the list should be a list | |
526 | of symbols. If its elements match the first elements in a warning | |
527 | type, then that warning is not displayed immediately. | |
528 | @end defopt | |
529 | ||
530 | @defopt warning-suppress-log-types | |
531 | This list specifies which warning types should not be logged in the | |
532 | warnings buffer. Each element of the list should be a list of | |
533 | symbols. If it matches the first few elements in a warning type, then | |
534 | that warning is not logged. | |
535 | @end defopt | |
00b3c1cd | 536 | |
276dd8a8 EZ |
537 | @node Progress |
538 | @section Reporting Operation Progress | |
539 | @cindex progress reporting | |
540 | ||
541 | When an operation can take a while to finish, you should inform the | |
542 | user about the progress it makes. This way the user can estimate | |
543 | remaining time and clearly see that Emacs is busy working, not hung. | |
544 | ||
545 | Functions listed in this section provide simple and efficient way of | |
546 | reporting operation progress. Here is a working example that does | |
547 | nothing useful: | |
548 | ||
549 | @example | |
550 | (let ((progress-reporter | |
551 | (make-progress-reporter "Collecting some mana for Emacs..." | |
552 | 0 500))) | |
553 | (dotimes (k 500) | |
554 | (sit-for 0.01) | |
555 | (progress-reporter-update progress-reporter k)) | |
556 | (progress-reporter-done progress-reporter)) | |
557 | @end example | |
558 | ||
559 | @defun make-progress-reporter message min-value max-value &optional current-value min-change min-time | |
560 | This function creates a progress reporter---the object you will use as | |
561 | an argument for all other functions listed here. The idea is to | |
562 | precompute as much data as possible to make progress reporting very | |
563 | fast. | |
564 | ||
565 | The @var{message} will be displayed in the echo area, followed by | |
566 | progress percentage. @var{message} is treated as a simple string. If | |
567 | you need it to depend on a filename, for instance, use @code{format} | |
568 | before calling this function. | |
569 | ||
570 | @var{min-value} and @var{max-value} arguments stand for starting and | |
571 | final states of your operation. For instance, if you scan a buffer, | |
572 | they should be the results of @code{point-min} and @code{point-max} | |
573 | correspondingly. It is required that @var{max-value} is greater than | |
574 | @var{min-value}. If you create progress reporter when some part of | |
575 | the operation has already been completed, then specify | |
576 | @var{current-value} argument. But normally you should omit it or set | |
577 | it to @code{nil}---it will default to @var{min-value} then. | |
578 | ||
579 | Remaining arguments control the rate of echo area updates. Progress | |
580 | reporter will wait for at least @var{min-change} more percents of the | |
581 | operation to be completed before printing next message. | |
582 | @var{min-time} specifies the minimum time in seconds to pass between | |
583 | successive prints. It can be fractional. Depending on Emacs and | |
584 | system capabilities, progress reporter may or may not respect this | |
585 | last argument or do it with varying precision. Default value for | |
586 | @var{min-change} is 1 (one percent), for @var{min-time}---0.2 | |
587 | (seconds.) | |
588 | ||
589 | This function calls @code{progress-reporter-update}, so the first | |
590 | message is printed immediately. | |
591 | @end defun | |
592 | ||
593 | @defun progress-reporter-update reporter value | |
594 | This function does the main work of reporting progress of your | |
595 | operation. It print the message of @var{reporter} followed by | |
596 | progress percentage determined by @var{value}. If percentage is zero, | |
597 | then it is not printed at all. | |
598 | ||
599 | @var{reporter} must be the result of a call to | |
600 | @code{make-progress-reporter}. @var{value} specifies the current | |
601 | state of your operation and must be between @var{min-value} and | |
602 | @var{max-value} (inclusive) as passed to | |
603 | @code{make-progress-reporter}. For instance, if you scan a buffer, | |
604 | then @var{value} should be the result of a call to @code{point}. | |
605 | ||
606 | This function respects @var{min-change} and @var{min-time} as passed | |
607 | to @code{make-progress-reporter} and so does not output new messages | |
608 | on every invocation. It is thus very fast and normally you should not | |
609 | try to reduce the number of calls to it: resulting overhead will most | |
610 | likely negate your effort. | |
611 | @end defun | |
612 | ||
613 | @defun progress-reporter-force-update reporter value &optional new-message | |
614 | This function is similar to @code{progress-reporter-update} except | |
615 | that it prints a message in the echo area unconditionally. | |
616 | ||
617 | The first two arguments have the same meaning as for | |
618 | @code{progress-reporter-update}. Optional @var{new-message} allows | |
619 | you to change the message of the @var{reporter}. Since this functions | |
620 | always updates the echo area, such a change will be immediately | |
621 | presented to the user. | |
622 | @end defun | |
623 | ||
624 | @defun progress-reporter-done reporter | |
625 | This function should be called when the operation is finished. It | |
626 | prints the message of @var{reporter} followed by word ``done'' in the | |
627 | echo area. | |
628 | ||
629 | You should always call this function and not hope for | |
630 | @code{progress-reporter-update} to print ``100%.'' Firstly, it may | |
631 | never print it, there are many good reasons for this not to happen. | |
632 | Secondly, ``done'' is more explicit. | |
633 | @end defun | |
634 | ||
22697dac KH |
635 | @node Invisible Text |
636 | @section Invisible Text | |
637 | ||
638 | @cindex invisible text | |
639 | You can make characters @dfn{invisible}, so that they do not appear on | |
640 | the screen, with the @code{invisible} property. This can be either a | |
a9f0a989 RS |
641 | text property (@pxref{Text Properties}) or a property of an overlay |
642 | (@pxref{Overlays}). | |
22697dac KH |
643 | |
644 | In the simplest case, any non-@code{nil} @code{invisible} property makes | |
645 | a character invisible. This is the default case---if you don't alter | |
646 | the default value of @code{buffer-invisibility-spec}, this is how the | |
31b0520f RS |
647 | @code{invisible} property works. You should normally use @code{t} |
648 | as the value of the @code{invisible} property if you don't plan | |
649 | to set @code{buffer-invisibility-spec} yourself. | |
22697dac KH |
650 | |
651 | More generally, you can use the variable @code{buffer-invisibility-spec} | |
652 | to control which values of the @code{invisible} property make text | |
653 | invisible. This permits you to classify the text into different subsets | |
654 | in advance, by giving them different @code{invisible} values, and | |
655 | subsequently make various subsets visible or invisible by changing the | |
656 | value of @code{buffer-invisibility-spec}. | |
657 | ||
658 | Controlling visibility with @code{buffer-invisibility-spec} is | |
a40d4712 PR |
659 | especially useful in a program to display the list of entries in a |
660 | database. It permits the implementation of convenient filtering | |
661 | commands to view just a part of the entries in the database. Setting | |
662 | this variable is very fast, much faster than scanning all the text in | |
663 | the buffer looking for properties to change. | |
22697dac KH |
664 | |
665 | @defvar buffer-invisibility-spec | |
666 | This variable specifies which kinds of @code{invisible} properties | |
658f691f RS |
667 | actually make a character invisible. Setting this variable makes it |
668 | buffer-local. | |
22697dac KH |
669 | |
670 | @table @asis | |
671 | @item @code{t} | |
672 | A character is invisible if its @code{invisible} property is | |
673 | non-@code{nil}. This is the default. | |
674 | ||
675 | @item a list | |
969fe9b5 RS |
676 | Each element of the list specifies a criterion for invisibility; if a |
677 | character's @code{invisible} property fits any one of these criteria, | |
678 | the character is invisible. The list can have two kinds of elements: | |
22697dac KH |
679 | |
680 | @table @code | |
681 | @item @var{atom} | |
969fe9b5 | 682 | A character is invisible if its @code{invisible} property value |
22697dac KH |
683 | is @var{atom} or if it is a list with @var{atom} as a member. |
684 | ||
685 | @item (@var{atom} . t) | |
969fe9b5 | 686 | A character is invisible if its @code{invisible} property value |
22697dac KH |
687 | is @var{atom} or if it is a list with @var{atom} as a member. |
688 | Moreover, if this character is at the end of a line and is followed | |
689 | by a visible newline, it displays an ellipsis. | |
690 | @end table | |
691 | @end table | |
692 | @end defvar | |
693 | ||
f9f59935 RS |
694 | Two functions are specifically provided for adding elements to |
695 | @code{buffer-invisibility-spec} and removing elements from it. | |
696 | ||
f9f59935 | 697 | @defun add-to-invisibility-spec element |
31b0520f RS |
698 | This function adds the element @var{element} to |
699 | @code{buffer-invisibility-spec} (if it is not already present in that | |
700 | list). If @code{buffer-invisibility-spec} was @code{t}, it changes to | |
701 | a list, @code{(t)}, so that text whose @code{invisible} property | |
702 | is @code{t} remains invisible. | |
f9f59935 RS |
703 | @end defun |
704 | ||
f9f59935 | 705 | @defun remove-from-invisibility-spec element |
812a2341 | 706 | This removes the element @var{element} from |
31b0520f RS |
707 | @code{buffer-invisibility-spec}. This does nothing if @var{element} |
708 | is not in the list. | |
f9f59935 RS |
709 | @end defun |
710 | ||
31b0520f RS |
711 | A convention for use of @code{buffer-invisibility-spec} is that a |
712 | major mode should use the mode's own name as an element of | |
713 | @code{buffer-invisibility-spec} and as the value of the | |
714 | @code{invisible} property: | |
f9f59935 RS |
715 | |
716 | @example | |
969fe9b5 | 717 | ;; @r{If you want to display an ellipsis:} |
177c0ea7 | 718 | (add-to-invisibility-spec '(my-symbol . t)) |
969fe9b5 | 719 | ;; @r{If you don't want ellipsis:} |
177c0ea7 | 720 | (add-to-invisibility-spec 'my-symbol) |
f9f59935 RS |
721 | |
722 | (overlay-put (make-overlay beginning end) | |
723 | 'invisible 'my-symbol) | |
724 | ||
969fe9b5 | 725 | ;; @r{When done with the overlays:} |
f9f59935 | 726 | (remove-from-invisibility-spec '(my-symbol . t)) |
969fe9b5 | 727 | ;; @r{Or respectively:} |
f9f59935 RS |
728 | (remove-from-invisibility-spec 'my-symbol) |
729 | @end example | |
730 | ||
5e8ae792 | 731 | @vindex line-move-ignore-invisible |
00b3c1cd | 732 | Ordinarily, functions that operate on text or move point do not care |
5e8ae792 RS |
733 | whether the text is invisible. The user-level line motion commands |
734 | explicitly ignore invisible newlines if | |
735 | @code{line-move-ignore-invisible} is non-@code{nil}, but only because | |
736 | they are explicitly programmed to do so. | |
bfe721d1 | 737 | |
00b3c1cd RS |
738 | However, if a command ends with point inside or immediately after |
739 | invisible text, the main editing loop moves point further forward or | |
740 | further backward (in the same direction that the command already moved | |
741 | it) until that condition is no longer true. Thus, if the command | |
742 | moved point back into an invisible range, Emacs moves point back to | |
743 | the beginning of that range, following the previous visible character. | |
744 | If the command moved point forward into an invisible range, Emacs | |
745 | moves point forward past the first visible character that follows the | |
746 | invisible text. | |
747 | ||
f9f59935 RS |
748 | Incremental search can make invisible overlays visible temporarily |
749 | and/or permanently when a match includes invisible text. To enable | |
750 | this, the overlay should have a non-@code{nil} | |
751 | @code{isearch-open-invisible} property. The property value should be a | |
752 | function to be called with the overlay as an argument. This function | |
753 | should make the overlay visible permanently; it is used when the match | |
754 | overlaps the overlay on exit from the search. | |
755 | ||
756 | During the search, such overlays are made temporarily visible by | |
757 | temporarily modifying their invisible and intangible properties. If you | |
ebc6903b | 758 | want this to be done differently for a certain overlay, give it an |
f9f59935 RS |
759 | @code{isearch-open-invisible-temporary} property which is a function. |
760 | The function is called with two arguments: the first is the overlay, and | |
f21b06b7 | 761 | the second is @code{nil} to make the overlay visible, or @code{t} to |
a9f0a989 | 762 | make it invisible again. |
f9f59935 | 763 | |
42b85554 RS |
764 | @node Selective Display |
765 | @section Selective Display | |
766 | @cindex selective display | |
767 | ||
969fe9b5 RS |
768 | @dfn{Selective display} refers to a pair of related features for |
769 | hiding certain lines on the screen. | |
42b85554 RS |
770 | |
771 | The first variant, explicit selective display, is designed for use in | |
969fe9b5 RS |
772 | a Lisp program: it controls which lines are hidden by altering the text. |
773 | The invisible text feature (@pxref{Invisible Text}) has partially | |
774 | replaced this feature. | |
22697dac KH |
775 | |
776 | In the second variant, the choice of lines to hide is made | |
bfe721d1 | 777 | automatically based on indentation. This variant is designed to be a |
22697dac | 778 | user-level feature. |
42b85554 RS |
779 | |
780 | The way you control explicit selective display is by replacing a | |
78608595 | 781 | newline (control-j) with a carriage return (control-m). The text that |
42b85554 RS |
782 | was formerly a line following that newline is now invisible. Strictly |
783 | speaking, it is temporarily no longer a line at all, since only newlines | |
784 | can separate lines; it is now part of the previous line. | |
785 | ||
786 | Selective display does not directly affect editing commands. For | |
787 | example, @kbd{C-f} (@code{forward-char}) moves point unhesitatingly into | |
788 | invisible text. However, the replacement of newline characters with | |
789 | carriage return characters affects some editing commands. For example, | |
790 | @code{next-line} skips invisible lines, since it searches only for | |
791 | newlines. Modes that use selective display can also define commands | |
792 | that take account of the newlines, or that make parts of the text | |
793 | visible or invisible. | |
794 | ||
795 | When you write a selectively displayed buffer into a file, all the | |
796 | control-m's are output as newlines. This means that when you next read | |
797 | in the file, it looks OK, with nothing invisible. The selective display | |
798 | effect is seen only within Emacs. | |
799 | ||
800 | @defvar selective-display | |
801 | This buffer-local variable enables selective display. This means that | |
177c0ea7 | 802 | lines, or portions of lines, may be made invisible. |
42b85554 RS |
803 | |
804 | @itemize @bullet | |
805 | @item | |
a40d4712 PR |
806 | If the value of @code{selective-display} is @code{t}, then the character |
807 | control-m marks the start of invisible text; the control-m, and the rest | |
808 | of the line following it, are not displayed. This is explicit selective | |
809 | display. | |
42b85554 RS |
810 | |
811 | @item | |
812 | If the value of @code{selective-display} is a positive integer, then | |
813 | lines that start with more than that many columns of indentation are not | |
814 | displayed. | |
815 | @end itemize | |
816 | ||
817 | When some portion of a buffer is invisible, the vertical movement | |
818 | commands operate as if that portion did not exist, allowing a single | |
819 | @code{next-line} command to skip any number of invisible lines. | |
820 | However, character movement commands (such as @code{forward-char}) do | |
821 | not skip the invisible portion, and it is possible (if tricky) to insert | |
822 | or delete text in an invisible portion. | |
823 | ||
824 | In the examples below, we show the @emph{display appearance} of the | |
825 | buffer @code{foo}, which changes with the value of | |
826 | @code{selective-display}. The @emph{contents} of the buffer do not | |
827 | change. | |
828 | ||
829 | @example | |
830 | @group | |
831 | (setq selective-display nil) | |
832 | @result{} nil | |
833 | ||
834 | ---------- Buffer: foo ---------- | |
835 | 1 on this column | |
836 | 2on this column | |
837 | 3n this column | |
838 | 3n this column | |
839 | 2on this column | |
840 | 1 on this column | |
841 | ---------- Buffer: foo ---------- | |
842 | @end group | |
843 | ||
844 | @group | |
845 | (setq selective-display 2) | |
846 | @result{} 2 | |
847 | ||
848 | ---------- Buffer: foo ---------- | |
849 | 1 on this column | |
850 | 2on this column | |
851 | 2on this column | |
852 | 1 on this column | |
853 | ---------- Buffer: foo ---------- | |
854 | @end group | |
855 | @end example | |
856 | @end defvar | |
857 | ||
858 | @defvar selective-display-ellipses | |
859 | If this buffer-local variable is non-@code{nil}, then Emacs displays | |
860 | @samp{@dots{}} at the end of a line that is followed by invisible text. | |
861 | This example is a continuation of the previous one. | |
862 | ||
863 | @example | |
864 | @group | |
865 | (setq selective-display-ellipses t) | |
866 | @result{} t | |
867 | ||
868 | ---------- Buffer: foo ---------- | |
869 | 1 on this column | |
870 | 2on this column ... | |
871 | 2on this column | |
872 | 1 on this column | |
873 | ---------- Buffer: foo ---------- | |
874 | @end group | |
875 | @end example | |
876 | ||
877 | You can use a display table to substitute other text for the ellipsis | |
878 | (@samp{@dots{}}). @xref{Display Tables}. | |
879 | @end defvar | |
880 | ||
881 | @node Overlay Arrow | |
882 | @section The Overlay Arrow | |
883 | @cindex overlay arrow | |
884 | ||
885 | The @dfn{overlay arrow} is useful for directing the user's attention | |
886 | to a particular line in a buffer. For example, in the modes used for | |
887 | interface to debuggers, the overlay arrow indicates the line of code | |
888 | about to be executed. | |
889 | ||
890 | @defvar overlay-arrow-string | |
78608595 RS |
891 | This variable holds the string to display to call attention to a |
892 | particular line, or @code{nil} if the arrow feature is not in use. | |
bb2337f5 DL |
893 | On a graphical display the contents of the string are ignored; instead a |
894 | glyph is displayed in the fringe area to the left of the display area. | |
42b85554 RS |
895 | @end defvar |
896 | ||
897 | @defvar overlay-arrow-position | |
78608595 | 898 | This variable holds a marker that indicates where to display the overlay |
bb2337f5 DL |
899 | arrow. It should point at the beginning of a line. On a non-graphical |
900 | display the arrow text | |
78608595 RS |
901 | appears at the beginning of that line, overlaying any text that would |
902 | otherwise appear. Since the arrow is usually short, and the line | |
903 | usually begins with indentation, normally nothing significant is | |
904 | overwritten. | |
905 | ||
906 | The overlay string is displayed only in the buffer that this marker | |
42b85554 RS |
907 | points into. Thus, only one buffer can have an overlay arrow at any |
908 | given time. | |
909 | @c !!! overlay-arrow-position: but the overlay string may remain in the display | |
910 | @c of some other buffer until an update is required. This should be fixed | |
911 | @c now. Is it? | |
912 | @end defvar | |
913 | ||
969fe9b5 | 914 | You can do a similar job by creating an overlay with a |
22697dac KH |
915 | @code{before-string} property. @xref{Overlay Properties}. |
916 | ||
42b85554 RS |
917 | @node Temporary Displays |
918 | @section Temporary Displays | |
919 | ||
969fe9b5 RS |
920 | Temporary displays are used by Lisp programs to put output into a |
921 | buffer and then present it to the user for perusal rather than for | |
922 | editing. Many help commands use this feature. | |
42b85554 RS |
923 | |
924 | @defspec with-output-to-temp-buffer buffer-name forms@dots{} | |
b6954afd RS |
925 | This function executes @var{forms} while arranging to insert any output |
926 | they print into the buffer named @var{buffer-name}, which is first | |
927 | created if necessary, and put into Help mode. Finally, the buffer is | |
928 | displayed in some window, but not selected. | |
929 | ||
d7cd58d7 LT |
930 | If the @var{forms} do not change the major mode in the output buffer, |
931 | so that it is still Help mode at the end of their execution, then | |
b6954afd | 932 | @code{with-output-to-temp-buffer} makes this buffer read-only at the |
d7cd58d7 | 933 | end, and also scans it for function and variable names to make them |
68e74f25 LT |
934 | into clickable cross-references. @xref{Docstring hyperlinks, , Tips |
935 | for Documentation Strings}, in particular the item on hyperlinks in | |
936 | documentation strings, for more details. | |
42b85554 RS |
937 | |
938 | The string @var{buffer-name} specifies the temporary buffer, which | |
939 | need not already exist. The argument must be a string, not a buffer. | |
940 | The buffer is erased initially (with no questions asked), and it is | |
941 | marked as unmodified after @code{with-output-to-temp-buffer} exits. | |
942 | ||
943 | @code{with-output-to-temp-buffer} binds @code{standard-output} to the | |
944 | temporary buffer, then it evaluates the forms in @var{forms}. Output | |
945 | using the Lisp output functions within @var{forms} goes by default to | |
946 | that buffer (but screen display and messages in the echo area, although | |
947 | they are ``output'' in the general sense of the word, are not affected). | |
948 | @xref{Output Functions}. | |
949 | ||
b6954afd RS |
950 | Several hooks are available for customizing the behavior |
951 | of this construct; they are listed below. | |
952 | ||
42b85554 RS |
953 | The value of the last form in @var{forms} is returned. |
954 | ||
955 | @example | |
956 | @group | |
957 | ---------- Buffer: foo ---------- | |
958 | This is the contents of foo. | |
959 | ---------- Buffer: foo ---------- | |
960 | @end group | |
961 | ||
962 | @group | |
963 | (with-output-to-temp-buffer "foo" | |
964 | (print 20) | |
965 | (print standard-output)) | |
966 | @result{} #<buffer foo> | |
967 | ||
968 | ---------- Buffer: foo ---------- | |
969 | 20 | |
970 | ||
971 | #<buffer foo> | |
972 | ||
973 | ---------- Buffer: foo ---------- | |
974 | @end group | |
975 | @end example | |
976 | @end defspec | |
977 | ||
978 | @defvar temp-buffer-show-function | |
78608595 | 979 | If this variable is non-@code{nil}, @code{with-output-to-temp-buffer} |
42b85554 RS |
980 | calls it as a function to do the job of displaying a help buffer. The |
981 | function gets one argument, which is the buffer it should display. | |
a9f0a989 RS |
982 | |
983 | It is a good idea for this function to run @code{temp-buffer-show-hook} | |
984 | just as @code{with-output-to-temp-buffer} normally would, inside of | |
b6954afd | 985 | @code{save-selected-window} and with the chosen window and buffer |
a9f0a989 RS |
986 | selected. |
987 | @end defvar | |
988 | ||
b6954afd RS |
989 | @defvar temp-buffer-setup-hook |
990 | @tindex temp-buffer-setup-hook | |
991 | This normal hook is run by @code{with-output-to-temp-buffer} before | |
13a8e917 RS |
992 | evaluating @var{body}. When the hook runs, the temporary buffer is |
993 | current. This hook is normally set up with a function to put the | |
994 | buffer in Help mode. | |
b6954afd RS |
995 | @end defvar |
996 | ||
a9f0a989 RS |
997 | @defvar temp-buffer-show-hook |
998 | This normal hook is run by @code{with-output-to-temp-buffer} after | |
13a8e917 RS |
999 | displaying the temporary buffer. When the hook runs, the temporary buffer |
1000 | is current, and the window it was displayed in is selected. This hook | |
1001 | is normally set up with a function to make the buffer read only, and | |
1002 | find function names and variable names in it, provided the major mode | |
1003 | is Help mode. | |
42b85554 RS |
1004 | @end defvar |
1005 | ||
1006 | @defun momentary-string-display string position &optional char message | |
1007 | This function momentarily displays @var{string} in the current buffer at | |
1008 | @var{position}. It has no effect on the undo list or on the buffer's | |
1009 | modification status. | |
1010 | ||
1011 | The momentary display remains until the next input event. If the next | |
1012 | input event is @var{char}, @code{momentary-string-display} ignores it | |
1013 | and returns. Otherwise, that event remains buffered for subsequent use | |
1014 | as input. Thus, typing @var{char} will simply remove the string from | |
1015 | the display, while typing (say) @kbd{C-f} will remove the string from | |
1016 | the display and later (presumably) move point forward. The argument | |
1017 | @var{char} is a space by default. | |
1018 | ||
1019 | The return value of @code{momentary-string-display} is not meaningful. | |
1020 | ||
bfe721d1 | 1021 | If the string @var{string} does not contain control characters, you can |
969fe9b5 RS |
1022 | do the same job in a more general way by creating (and then subsequently |
1023 | deleting) an overlay with a @code{before-string} property. | |
1024 | @xref{Overlay Properties}. | |
bfe721d1 | 1025 | |
42b85554 RS |
1026 | If @var{message} is non-@code{nil}, it is displayed in the echo area |
1027 | while @var{string} is displayed in the buffer. If it is @code{nil}, a | |
1028 | default message says to type @var{char} to continue. | |
1029 | ||
1030 | In this example, point is initially located at the beginning of the | |
1031 | second line: | |
1032 | ||
1033 | @example | |
1034 | @group | |
1035 | ---------- Buffer: foo ---------- | |
1036 | This is the contents of foo. | |
1037 | @point{}Second line. | |
1038 | ---------- Buffer: foo ---------- | |
1039 | @end group | |
1040 | ||
1041 | @group | |
1042 | (momentary-string-display | |
1043 | "**** Important Message! ****" | |
1044 | (point) ?\r | |
1045 | "Type RET when done reading") | |
1046 | @result{} t | |
1047 | @end group | |
1048 | ||
1049 | @group | |
1050 | ---------- Buffer: foo ---------- | |
1051 | This is the contents of foo. | |
1052 | **** Important Message! ****Second line. | |
1053 | ---------- Buffer: foo ---------- | |
1054 | ||
1055 | ---------- Echo Area ---------- | |
1056 | Type RET when done reading | |
1057 | ---------- Echo Area ---------- | |
1058 | @end group | |
1059 | @end example | |
1060 | @end defun | |
1061 | ||
1062 | @node Overlays | |
1063 | @section Overlays | |
1064 | @cindex overlays | |
1065 | ||
1066 | You can use @dfn{overlays} to alter the appearance of a buffer's text on | |
bfe721d1 KH |
1067 | the screen, for the sake of presentation features. An overlay is an |
1068 | object that belongs to a particular buffer, and has a specified | |
1069 | beginning and end. It also has properties that you can examine and set; | |
1070 | these affect the display of the text within the overlay. | |
42b85554 | 1071 | |
812a2341 RS |
1072 | An overlays uses markers to record its beginning and end; thus, |
1073 | editing the text of the buffer adjusts the beginning and end of each | |
1074 | overlay so that it stays with the text. When you create the overlay, | |
1075 | you can specify whether text inserted at the beginning should be | |
1076 | inside the overlay or outside, and likewise for the end of the overlay. | |
1077 | ||
42b85554 | 1078 | @menu |
02c77ee9 | 1079 | * Overlay Properties:: How to read and set properties. |
42b85554 | 1080 | What properties do to the screen display. |
eda77a0f DL |
1081 | * Managing Overlays:: Creating and moving overlays. |
1082 | * Finding Overlays:: Searching for overlays. | |
42b85554 RS |
1083 | @end menu |
1084 | ||
1085 | @node Overlay Properties | |
1086 | @subsection Overlay Properties | |
1087 | ||
8241495d | 1088 | Overlay properties are like text properties in that the properties that |
a9f0a989 RS |
1089 | alter how a character is displayed can come from either source. But in |
1090 | most respects they are different. Text properties are considered a part | |
1091 | of the text; overlays are specifically considered not to be part of the | |
1092 | text. Thus, copying text between various buffers and strings preserves | |
1093 | text properties, but does not try to preserve overlays. Changing a | |
1094 | buffer's text properties marks the buffer as modified, while moving an | |
1095 | overlay or changing its properties does not. Unlike text property | |
1096 | changes, overlay changes are not recorded in the buffer's undo list. | |
1097 | @xref{Text Properties}, for comparison. | |
42b85554 | 1098 | |
8241495d RS |
1099 | These functions are used for reading and writing the properties of an |
1100 | overlay: | |
1101 | ||
1102 | @defun overlay-get overlay prop | |
1103 | This function returns the value of property @var{prop} recorded in | |
1104 | @var{overlay}, if any. If @var{overlay} does not record any value for | |
1105 | that property, but it does have a @code{category} property which is a | |
1106 | symbol, that symbol's @var{prop} property is used. Otherwise, the value | |
1107 | is @code{nil}. | |
1108 | @end defun | |
1109 | ||
1110 | @defun overlay-put overlay prop value | |
1111 | This function sets the value of property @var{prop} recorded in | |
1112 | @var{overlay} to @var{value}. It returns @var{value}. | |
00b3c1cd RS |
1113 | @end defun |
1114 | ||
1115 | @defun overlay-properties overlay | |
1116 | This returns a copy of the property list of @var{overlay}. | |
8241495d RS |
1117 | @end defun |
1118 | ||
1119 | See also the function @code{get-char-property} which checks both | |
1120 | overlay properties and text properties for a given character. | |
1121 | @xref{Examining Properties}. | |
1122 | ||
1123 | Many overlay properties have special meanings; here is a table | |
1124 | of them: | |
1125 | ||
42b85554 RS |
1126 | @table @code |
1127 | @item priority | |
1128 | @kindex priority @r{(overlay property)} | |
f1579f52 RS |
1129 | This property's value (which should be a nonnegative integer number) |
1130 | determines the priority of the overlay. The priority matters when two | |
1131 | or more overlays cover the same character and both specify the same | |
1132 | property; the one whose @code{priority} value is larger takes priority | |
1133 | over the other. For the @code{face} property, the higher priority | |
1134 | value does not completely replace the other; instead, its face | |
1135 | attributes override the face attributes of the lower priority | |
1136 | @code{face} property. | |
42b85554 RS |
1137 | |
1138 | Currently, all overlays take priority over text properties. Please | |
1139 | avoid using negative priority values, as we have not yet decided just | |
1140 | what they should mean. | |
1141 | ||
1142 | @item window | |
1143 | @kindex window @r{(overlay property)} | |
1144 | If the @code{window} property is non-@code{nil}, then the overlay | |
1145 | applies only on that window. | |
1146 | ||
22697dac KH |
1147 | @item category |
1148 | @kindex category @r{(overlay property)} | |
1149 | If an overlay has a @code{category} property, we call it the | |
bfe721d1 | 1150 | @dfn{category} of the overlay. It should be a symbol. The properties |
22697dac KH |
1151 | of the symbol serve as defaults for the properties of the overlay. |
1152 | ||
42b85554 RS |
1153 | @item face |
1154 | @kindex face @r{(overlay property)} | |
f9f59935 | 1155 | This property controls the way text is displayed---for example, which |
8241495d | 1156 | font and which colors. @xref{Faces}, for more information. |
f9f59935 | 1157 | |
8241495d | 1158 | In the simplest case, the value is a face name. It can also be a list; |
a40d4712 | 1159 | then each element can be any of these possibilities: |
8241495d RS |
1160 | |
1161 | @itemize @bullet | |
1162 | @item | |
1163 | A face name (a symbol or string). | |
1164 | ||
1165 | @item | |
1166 | Starting in Emacs 21, a property list of face attributes. This has the | |
1167 | form (@var{keyword} @var{value} @dots{}), where each @var{keyword} is a | |
1168 | face attribute name and @var{value} is a meaningful value for that | |
1169 | attribute. With this feature, you do not need to create a face each | |
1170 | time you want to specify a particular attribute for certain text. | |
1171 | @xref{Face Attributes}. | |
1172 | ||
1173 | @item | |
1174 | A cons cell of the form @code{(foreground-color . @var{color-name})} or | |
1175 | @code{(background-color . @var{color-name})}. These elements specify | |
1176 | just the foreground color or just the background color. | |
1177 | ||
1178 | @code{(foreground-color . @var{color-name})} is equivalent to | |
1179 | @code{(:foreground @var{color-name})}, and likewise for the background. | |
1180 | @end itemize | |
42b85554 RS |
1181 | |
1182 | @item mouse-face | |
1183 | @kindex mouse-face @r{(overlay property)} | |
1184 | This property is used instead of @code{face} when the mouse is within | |
f9f59935 | 1185 | the range of the overlay. |
42b85554 | 1186 | |
8241495d RS |
1187 | @item display |
1188 | @kindex display @r{(overlay property)} | |
1189 | This property activates various features that change the | |
1190 | way text is displayed. For example, it can make text appear taller | |
24eb6c0e | 1191 | or shorter, higher or lower, wider or narrower, or replaced with an image. |
8241495d RS |
1192 | @xref{Display Property}. |
1193 | ||
1194 | @item help-echo | |
1195 | @kindex help-echo @r{(text property)} | |
e3b9fc91 DL |
1196 | If an overlay has a @code{help-echo} property, then when you move the |
1197 | mouse onto the text in the overlay, Emacs displays a help string in the | |
1198 | echo area, or in the tooltip window. For details see @ref{Text | |
2e46cd09 | 1199 | help-echo}. |
8241495d | 1200 | |
42b85554 RS |
1201 | @item modification-hooks |
1202 | @kindex modification-hooks @r{(overlay property)} | |
1203 | This property's value is a list of functions to be called if any | |
1204 | character within the overlay is changed or if text is inserted strictly | |
22697dac KH |
1205 | within the overlay. |
1206 | ||
1207 | The hook functions are called both before and after each change. | |
1208 | If the functions save the information they receive, and compare notes | |
1209 | between calls, they can determine exactly what change has been made | |
1210 | in the buffer text. | |
1211 | ||
1212 | When called before a change, each function receives four arguments: the | |
1213 | overlay, @code{nil}, and the beginning and end of the text range to be | |
a890e1b0 | 1214 | modified. |
42b85554 | 1215 | |
22697dac KH |
1216 | When called after a change, each function receives five arguments: the |
1217 | overlay, @code{t}, the beginning and end of the text range just | |
1218 | modified, and the length of the pre-change text replaced by that range. | |
1219 | (For an insertion, the pre-change length is zero; for a deletion, that | |
1220 | length is the number of characters deleted, and the post-change | |
bfe721d1 | 1221 | beginning and end are equal.) |
22697dac | 1222 | |
42b85554 RS |
1223 | @item insert-in-front-hooks |
1224 | @kindex insert-in-front-hooks @r{(overlay property)} | |
22697dac KH |
1225 | This property's value is a list of functions to be called before and |
1226 | after inserting text right at the beginning of the overlay. The calling | |
1227 | conventions are the same as for the @code{modification-hooks} functions. | |
42b85554 RS |
1228 | |
1229 | @item insert-behind-hooks | |
1230 | @kindex insert-behind-hooks @r{(overlay property)} | |
22697dac KH |
1231 | This property's value is a list of functions to be called before and |
1232 | after inserting text right at the end of the overlay. The calling | |
1233 | conventions are the same as for the @code{modification-hooks} functions. | |
42b85554 RS |
1234 | |
1235 | @item invisible | |
1236 | @kindex invisible @r{(overlay property)} | |
22697dac KH |
1237 | The @code{invisible} property can make the text in the overlay |
1238 | invisible, which means that it does not appear on the screen. | |
1239 | @xref{Invisible Text}, for details. | |
1240 | ||
1241 | @item intangible | |
1242 | @kindex intangible @r{(overlay property)} | |
1243 | The @code{intangible} property on an overlay works just like the | |
bfe721d1 | 1244 | @code{intangible} text property. @xref{Special Properties}, for details. |
f9f59935 RS |
1245 | |
1246 | @item isearch-open-invisible | |
a9f0a989 RS |
1247 | This property tells incremental search how to make an invisible overlay |
1248 | visible, permanently, if the final match overlaps it. @xref{Invisible | |
f9f59935 | 1249 | Text}. |
42b85554 | 1250 | |
a9f0a989 RS |
1251 | @item isearch-open-invisible-temporary |
1252 | This property tells incremental search how to make an invisible overlay | |
1253 | visible, temporarily, during the search. @xref{Invisible Text}. | |
1254 | ||
42b85554 RS |
1255 | @item before-string |
1256 | @kindex before-string @r{(overlay property)} | |
1257 | This property's value is a string to add to the display at the beginning | |
1258 | of the overlay. The string does not appear in the buffer in any | |
a40d4712 | 1259 | sense---only on the screen. |
42b85554 RS |
1260 | |
1261 | @item after-string | |
1262 | @kindex after-string @r{(overlay property)} | |
1263 | This property's value is a string to add to the display at the end of | |
1264 | the overlay. The string does not appear in the buffer in any | |
a40d4712 | 1265 | sense---only on the screen. |
22697dac KH |
1266 | |
1267 | @item evaporate | |
1268 | @kindex evaporate @r{(overlay property)} | |
1269 | If this property is non-@code{nil}, the overlay is deleted automatically | |
11cd6064 RS |
1270 | if it becomes empty (i.e., if its length becomes zero). If you give |
1271 | an empty overlay a non-@code{nil} @code{evaporate} property, that deletes | |
1272 | it immediately. | |
d2609065 | 1273 | |
ce75fd23 | 1274 | @item local-map |
969fe9b5 | 1275 | @cindex keymap of character (and overlays) |
ce75fd23 | 1276 | @kindex local-map @r{(overlay property)} |
d2609065 RS |
1277 | If this property is non-@code{nil}, it specifies a keymap for a portion |
1278 | of the text. The property's value replaces the buffer's local map, when | |
1279 | the character after point is within the overlay. @xref{Active Keymaps}. | |
62fb5c66 DL |
1280 | |
1281 | @item keymap | |
1282 | @kindex keymap @r{(overlay property)} | |
1283 | The @code{keymap} property is similar to @code{local-map} but overrides the | |
1284 | buffer's local map (and the map specified by the @code{local-map} | |
1285 | property) rather than replacing it. | |
42b85554 RS |
1286 | @end table |
1287 | ||
42b85554 RS |
1288 | @node Managing Overlays |
1289 | @subsection Managing Overlays | |
1290 | ||
1291 | This section describes the functions to create, delete and move | |
1292 | overlays, and to examine their contents. | |
1293 | ||
00b3c1cd RS |
1294 | @defun overlayp object |
1295 | This function returns @code{t} if @var{object} is an overlay. | |
1296 | @end defun | |
1297 | ||
f9f59935 | 1298 | @defun make-overlay start end &optional buffer front-advance rear-advance |
78608595 | 1299 | This function creates and returns an overlay that belongs to |
42b85554 RS |
1300 | @var{buffer} and ranges from @var{start} to @var{end}. Both @var{start} |
1301 | and @var{end} must specify buffer positions; they may be integers or | |
1302 | markers. If @var{buffer} is omitted, the overlay is created in the | |
1303 | current buffer. | |
f9f59935 RS |
1304 | |
1305 | The arguments @var{front-advance} and @var{rear-advance} specify the | |
1306 | insertion type for the start of the overlay and for the end of the | |
812a2341 RS |
1307 | overlay, respectively. @xref{Marker Insertion Types}. If |
1308 | @var{front-advance} is non-@code{nil}, text inserted at the beginning | |
1309 | of the overlay is excluded from the overlay. If @var{read-advance} is | |
1310 | non-@code{nil}, text inserted at the beginning of the overlay is | |
1311 | included in the overlay. | |
42b85554 RS |
1312 | @end defun |
1313 | ||
1314 | @defun overlay-start overlay | |
f9f59935 RS |
1315 | This function returns the position at which @var{overlay} starts, |
1316 | as an integer. | |
42b85554 RS |
1317 | @end defun |
1318 | ||
1319 | @defun overlay-end overlay | |
f9f59935 RS |
1320 | This function returns the position at which @var{overlay} ends, |
1321 | as an integer. | |
42b85554 RS |
1322 | @end defun |
1323 | ||
1324 | @defun overlay-buffer overlay | |
1325 | This function returns the buffer that @var{overlay} belongs to. | |
1326 | @end defun | |
1327 | ||
1328 | @defun delete-overlay overlay | |
1329 | This function deletes @var{overlay}. The overlay continues to exist as | |
2468d0c0 DL |
1330 | a Lisp object, and its property list is unchanged, but it ceases to be |
1331 | attached to the buffer it belonged to, and ceases to have any effect on | |
1332 | display. | |
a9f0a989 | 1333 | |
2468d0c0 DL |
1334 | A deleted overlay is not permanently disconnected. You can give it a |
1335 | position in a buffer again by calling @code{move-overlay}. | |
42b85554 RS |
1336 | @end defun |
1337 | ||
1338 | @defun move-overlay overlay start end &optional buffer | |
1339 | This function moves @var{overlay} to @var{buffer}, and places its bounds | |
1340 | at @var{start} and @var{end}. Both arguments @var{start} and @var{end} | |
2468d0c0 DL |
1341 | must specify buffer positions; they may be integers or markers. |
1342 | ||
1343 | If @var{buffer} is omitted, @var{overlay} stays in the same buffer it | |
1344 | was already associated with; if @var{overlay} was deleted, it goes into | |
1345 | the current buffer. | |
42b85554 RS |
1346 | |
1347 | The return value is @var{overlay}. | |
1348 | ||
1349 | This is the only valid way to change the endpoints of an overlay. Do | |
1350 | not try modifying the markers in the overlay by hand, as that fails to | |
1351 | update other vital data structures and can cause some overlays to be | |
1352 | ``lost''. | |
1353 | @end defun | |
1354 | ||
2468d0c0 DL |
1355 | Here are some examples: |
1356 | ||
1357 | @example | |
1358 | ;; @r{Create an overlay.} | |
1359 | (setq foo (make-overlay 1 10)) | |
1360 | @result{} #<overlay from 1 to 10 in display.texi> | |
1361 | (overlay-start foo) | |
1362 | @result{} 1 | |
1363 | (overlay-end foo) | |
1364 | @result{} 10 | |
1365 | (overlay-buffer foo) | |
1366 | @result{} #<buffer display.texi> | |
1367 | ;; @r{Give it a property we can check later.} | |
1368 | (overlay-put foo 'happy t) | |
1369 | @result{} t | |
1370 | ;; @r{Verify the property is present.} | |
1371 | (overlay-get foo 'happy) | |
1372 | @result{} t | |
1373 | ;; @r{Move the overlay.} | |
1374 | (move-overlay foo 5 20) | |
1375 | @result{} #<overlay from 5 to 20 in display.texi> | |
1376 | (overlay-start foo) | |
1377 | @result{} 5 | |
1378 | (overlay-end foo) | |
1379 | @result{} 20 | |
1380 | ;; @r{Delete the overlay.} | |
1381 | (delete-overlay foo) | |
1382 | @result{} nil | |
1383 | ;; @r{Verify it is deleted.} | |
1384 | foo | |
1385 | @result{} #<overlay in no buffer> | |
1386 | ;; @r{A deleted overlay has no position.} | |
1387 | (overlay-start foo) | |
1388 | @result{} nil | |
1389 | (overlay-end foo) | |
1390 | @result{} nil | |
1391 | (overlay-buffer foo) | |
1392 | @result{} nil | |
1393 | ;; @r{Undelete the overlay.} | |
1394 | (move-overlay foo 1 20) | |
1395 | @result{} #<overlay from 1 to 20 in display.texi> | |
1396 | ;; @r{Verify the results.} | |
1397 | (overlay-start foo) | |
1398 | @result{} 1 | |
1399 | (overlay-end foo) | |
1400 | @result{} 20 | |
1401 | (overlay-buffer foo) | |
1402 | @result{} #<buffer display.texi> | |
05aea714 | 1403 | ;; @r{Moving and deleting the overlay does not change its properties.} |
2468d0c0 DL |
1404 | (overlay-get foo 'happy) |
1405 | @result{} t | |
1406 | @end example | |
1407 | ||
1408 | @node Finding Overlays | |
1409 | @subsection Searching for Overlays | |
1410 | ||
42b85554 | 1411 | @defun overlays-at pos |
2468d0c0 DL |
1412 | This function returns a list of all the overlays that cover the |
1413 | character at position @var{pos} in the current buffer. The list is in | |
1414 | no particular order. An overlay contains position @var{pos} if it | |
1415 | begins at or before @var{pos}, and ends after @var{pos}. | |
1416 | ||
1417 | To illustrate usage, here is a Lisp function that returns a list of the | |
1418 | overlays that specify property @var{prop} for the character at point: | |
1419 | ||
1420 | @smallexample | |
1421 | (defun find-overlays-specifying (prop) | |
1422 | (let ((overlays (overlays-at (point))) | |
1423 | found) | |
1424 | (while overlays | |
86b032fa | 1425 | (let ((overlay (car overlays))) |
2468d0c0 DL |
1426 | (if (overlay-get overlay prop) |
1427 | (setq found (cons overlay found)))) | |
1428 | (setq overlays (cdr overlays))) | |
1429 | found)) | |
1430 | @end smallexample | |
42b85554 RS |
1431 | @end defun |
1432 | ||
f9f59935 RS |
1433 | @defun overlays-in beg end |
1434 | This function returns a list of the overlays that overlap the region | |
1435 | @var{beg} through @var{end}. ``Overlap'' means that at least one | |
1436 | character is contained within the overlay and also contained within the | |
1437 | specified region; however, empty overlays are included in the result if | |
2468d0c0 | 1438 | they are located at @var{beg}, or strictly between @var{beg} and @var{end}. |
f9f59935 RS |
1439 | @end defun |
1440 | ||
42b85554 RS |
1441 | @defun next-overlay-change pos |
1442 | This function returns the buffer position of the next beginning or end | |
1443 | of an overlay, after @var{pos}. | |
1444 | @end defun | |
1445 | ||
22697dac KH |
1446 | @defun previous-overlay-change pos |
1447 | This function returns the buffer position of the previous beginning or | |
1448 | end of an overlay, before @var{pos}. | |
1449 | @end defun | |
1450 | ||
2468d0c0 DL |
1451 | Here's an easy way to use @code{next-overlay-change} to search for the |
1452 | next character which gets a non-@code{nil} @code{happy} property from | |
1453 | either its overlays or its text properties (@pxref{Property Search}): | |
1454 | ||
1455 | @smallexample | |
1456 | (defun find-overlay-prop (prop) | |
1457 | (save-excursion | |
1458 | (while (and (not (eobp)) | |
1459 | (not (get-char-property (point) 'happy))) | |
1460 | (goto-char (min (next-overlay-change (point)) | |
1461 | (next-single-property-change (point) 'happy)))) | |
1462 | (point))) | |
1463 | @end smallexample | |
1464 | ||
f9f59935 RS |
1465 | @node Width |
1466 | @section Width | |
1467 | ||
1468 | Since not all characters have the same width, these functions let you | |
969fe9b5 RS |
1469 | check the width of a character. @xref{Primitive Indent}, and |
1470 | @ref{Screen Lines}, for related functions. | |
f9f59935 | 1471 | |
f9f59935 RS |
1472 | @defun char-width char |
1473 | This function returns the width in columns of the character @var{char}, | |
1474 | if it were displayed in the current buffer and the selected window. | |
1475 | @end defun | |
1476 | ||
f9f59935 RS |
1477 | @defun string-width string |
1478 | This function returns the width in columns of the string @var{string}, | |
1479 | if it were displayed in the current buffer and the selected window. | |
1480 | @end defun | |
1481 | ||
f9f59935 RS |
1482 | @defun truncate-string-to-width string width &optional start-column padding |
1483 | This function returns the part of @var{string} that fits within | |
1484 | @var{width} columns, as a new string. | |
1485 | ||
1486 | If @var{string} does not reach @var{width}, then the result ends where | |
1487 | @var{string} ends. If one multi-column character in @var{string} | |
1488 | extends across the column @var{width}, that character is not included in | |
1489 | the result. Thus, the result can fall short of @var{width} but cannot | |
1490 | go beyond it. | |
1491 | ||
1492 | The optional argument @var{start-column} specifies the starting column. | |
1493 | If this is non-@code{nil}, then the first @var{start-column} columns of | |
1494 | the string are omitted from the value. If one multi-column character in | |
1495 | @var{string} extends across the column @var{start-column}, that | |
1496 | character is not included. | |
1497 | ||
1498 | The optional argument @var{padding}, if non-@code{nil}, is a padding | |
1499 | character added at the beginning and end of the result string, to extend | |
1500 | it to exactly @var{width} columns. The padding character is used at the | |
1501 | end of the result if it falls short of @var{width}. It is also used at | |
1502 | the beginning of the result if one multi-column character in | |
1503 | @var{string} extends across the column @var{start-column}. | |
1504 | ||
1505 | @example | |
1506 | (truncate-string-to-width "\tab\t" 12 4) | |
1507 | @result{} "ab" | |
6bc3abcb | 1508 | (truncate-string-to-width "\tab\t" 12 4 ?\s) |
f9f59935 RS |
1509 | @result{} " ab " |
1510 | @end example | |
1511 | @end defun | |
1512 | ||
42b85554 RS |
1513 | @node Faces |
1514 | @section Faces | |
b9bc6c81 | 1515 | @cindex faces |
42b85554 | 1516 | |
8241495d RS |
1517 | A @dfn{face} is a named collection of graphical attributes: font |
1518 | family, foreground color, background color, optional underlining, and | |
1519 | many others. Faces are used in Emacs to control the style of display of | |
1520 | particular parts of the text or the frame. | |
42b85554 RS |
1521 | |
1522 | @cindex face id | |
969fe9b5 | 1523 | Each face has its own @dfn{face number}, which distinguishes faces at |
8241495d | 1524 | low levels within Emacs. However, for most purposes, you refer to |
42b85554 RS |
1525 | faces in Lisp programs by their names. |
1526 | ||
22697dac KH |
1527 | @defun facep object |
1528 | This function returns @code{t} if @var{object} is a face name symbol (or | |
1529 | if it is a vector of the kind used internally to record face data). It | |
1530 | returns @code{nil} otherwise. | |
1531 | @end defun | |
1532 | ||
42b85554 RS |
1533 | Each face name is meaningful for all frames, and by default it has the |
1534 | same meaning in all frames. But you can arrange to give a particular | |
1535 | face name a special meaning in one frame if you wish. | |
1536 | ||
1537 | @menu | |
1538 | * Standard Faces:: The faces Emacs normally comes with. | |
969fe9b5 | 1539 | * Defining Faces:: How to define a face with @code{defface}. |
8241495d | 1540 | * Face Attributes:: What is in a face? |
02c77ee9 MB |
1541 | * Attribute Functions:: Functions to examine and set face attributes. |
1542 | * Merging Faces:: How Emacs combines the faces specified for a character. | |
8241495d | 1543 | * Font Selection:: Finding the best available font for a face. |
02c77ee9 | 1544 | * Face Functions:: How to define and examine faces. |
8241495d RS |
1545 | * Auto Faces:: Hook for automatic face assignment. |
1546 | * Font Lookup:: Looking up the names of available fonts | |
1547 | and information about them. | |
1548 | * Fontsets:: A fontset is a collection of fonts | |
1549 | that handle a range of character sets. | |
42b85554 RS |
1550 | @end menu |
1551 | ||
1552 | @node Standard Faces | |
1553 | @subsection Standard Faces | |
1554 | ||
8241495d RS |
1555 | This table lists all the standard faces and their uses. Most of them |
1556 | are used for displaying certain parts of the frames or certain kinds of | |
1557 | text; you can control how those places look by customizing these faces. | |
42b85554 RS |
1558 | |
1559 | @table @code | |
1560 | @item default | |
1561 | @kindex default @r{(face name)} | |
1562 | This face is used for ordinary text. | |
1563 | ||
8241495d RS |
1564 | @item mode-line |
1565 | @kindex mode-line @r{(face name)} | |
d211eec7 EZ |
1566 | This face is used for the mode line of the selected window, and for |
1567 | menu bars when toolkit menus are not used---but only if | |
1568 | @code{mode-line-inverse-video} is non-@code{nil}. | |
8241495d | 1569 | |
42b85554 RS |
1570 | @item modeline |
1571 | @kindex modeline @r{(face name)} | |
8241495d RS |
1572 | This is an alias for the @code{mode-line} face, for compatibility with |
1573 | old Emacs versions. | |
1574 | ||
d211eec7 EZ |
1575 | @item mode-line-inactive |
1576 | @kindex mode-line-inactive @r{(face name)} | |
1577 | This face is used for mode lines of non-selected windows. | |
9b9d845d RS |
1578 | This face inherits from @code{mode-line}, so changes |
1579 | in that face affect all windows. | |
d211eec7 | 1580 | |
8241495d RS |
1581 | @item header-line |
1582 | @kindex header-line @r{(face name)} | |
1583 | This face is used for the header lines of windows that have them. | |
1584 | ||
a40d4712 PR |
1585 | @item menu |
1586 | This face controls the display of menus, both their colors and their | |
1587 | font. (This works only on certain systems.) | |
1588 | ||
8241495d RS |
1589 | @item fringe |
1590 | @kindex fringe @r{(face name)} | |
9b6e4bc3 | 1591 | This face controls the default colors of window fringes, the thin areas on |
8241495d RS |
1592 | either side that are used to display continuation and truncation glyphs. |
1593 | ||
2811080b EZ |
1594 | @item minibuffer-prompt |
1595 | @kindex minibuffer-prompt @r{(face name)} | |
1596 | @vindex minibuffer-prompt-properties | |
1597 | This face is used for the text of minibuffer prompts. By default, | |
1598 | Emacs automatically adds this face to the value of | |
1599 | @code{minibuffer-prompt-properties}, which is a list of text | |
1600 | properties used to display the prompt text. | |
1601 | ||
8241495d RS |
1602 | @item scroll-bar |
1603 | @kindex scroll-bar @r{(face name)} | |
1604 | This face controls the colors for display of scroll bars. | |
1605 | ||
1606 | @item tool-bar | |
1607 | @kindex tool-bar @r{(face name)} | |
1608 | This face is used for display of the tool bar, if any. | |
42b85554 RS |
1609 | |
1610 | @item region | |
1611 | @kindex region @r{(face name)} | |
1612 | This face is used for highlighting the region in Transient Mark mode. | |
1613 | ||
1614 | @item secondary-selection | |
1615 | @kindex secondary-selection @r{(face name)} | |
1616 | This face is used to show any secondary selection you have made. | |
1617 | ||
1618 | @item highlight | |
1619 | @kindex highlight @r{(face name)} | |
1620 | This face is meant to be used for highlighting for various purposes. | |
1621 | ||
8241495d RS |
1622 | @item trailing-whitespace |
1623 | @kindex trailing-whitespace @r{(face name)} | |
a40d4712 PR |
1624 | This face is used to display excess whitespace at the end of a line, |
1625 | if @code{show-trailing-whitespace} is non-@code{nil}. | |
8241495d | 1626 | @end table |
42b85554 | 1627 | |
8241495d RS |
1628 | In contrast, these faces are provided to change the appearance of text |
1629 | in specific ways. You can use them on specific text, when you want | |
1630 | the effects they produce. | |
1631 | ||
1632 | @table @code | |
42b85554 RS |
1633 | @item bold |
1634 | @kindex bold @r{(face name)} | |
1635 | This face uses a bold font, if possible. It uses the bold variant of | |
1636 | the frame's font, if it has one. It's up to you to choose a default | |
1637 | font that has a bold variant, if you want to use one. | |
1638 | ||
1639 | @item italic | |
1640 | @kindex italic @r{(face name)} | |
1641 | This face uses the italic variant of the frame's font, if it has one. | |
1642 | ||
1643 | @item bold-italic | |
1644 | @kindex bold-italic @r{(face name)} | |
1645 | This face uses the bold italic variant of the frame's font, if it has | |
1646 | one. | |
8241495d RS |
1647 | |
1648 | @item underline | |
1649 | @kindex underline @r{(face name)} | |
1650 | This face underlines text. | |
1651 | ||
24eb6c0e GM |
1652 | @item fixed-pitch |
1653 | @kindex fixed-pitch @r{(face name)} | |
8241495d RS |
1654 | This face forces use of a particular fixed-width font. |
1655 | ||
24eb6c0e GM |
1656 | @item variable-pitch |
1657 | @kindex variable-pitch @r{(face name)} | |
8241495d | 1658 | This face forces use of a particular variable-width font. It's |
a40d4712 | 1659 | reasonable to customize this to use a different variable-width font, if |
8241495d | 1660 | you like, but you should not make it a fixed-width font. |
42b85554 RS |
1661 | @end table |
1662 | ||
a40d4712 PR |
1663 | @defvar show-trailing-whitespace |
1664 | @tindex show-trailing-whitespace | |
1665 | If this variable is non-@code{nil}, Emacs uses the | |
1666 | @code{trailing-whitespace} face to display any spaces and tabs at the | |
1667 | end of a line. | |
1668 | @end defvar | |
1669 | ||
969fe9b5 | 1670 | @node Defining Faces |
a9f0a989 | 1671 | @subsection Defining Faces |
969fe9b5 RS |
1672 | |
1673 | The way to define a new face is with @code{defface}. This creates a | |
1674 | kind of customization item (@pxref{Customization}) which the user can | |
1675 | customize using the Customization buffer (@pxref{Easy Customization,,, | |
1676 | emacs, The GNU Emacs Manual}). | |
1677 | ||
177c0ea7 | 1678 | @defmac defface face spec doc [keyword value]... |
a40d4712 PR |
1679 | This declares @var{face} as a customizable face that defaults according |
1680 | to @var{spec}. You should not quote the symbol @var{face}. The | |
1681 | argument @var{doc} specifies the face documentation. The keywords you | |
1682 | can use in @code{defface} are the same ones that are meaningful in both | |
1683 | @code{defgroup} and @code{defcustom} (@pxref{Common Keywords}). | |
969fe9b5 RS |
1684 | |
1685 | When @code{defface} executes, it defines the face according to | |
a9f0a989 | 1686 | @var{spec}, then uses any customizations that were read from the |
a40d4712 | 1687 | init file (@pxref{Init File}) to override that specification. |
969fe9b5 RS |
1688 | |
1689 | The purpose of @var{spec} is to specify how the face should appear on | |
1690 | different kinds of terminals. It should be an alist whose elements have | |
a40d4712 PR |
1691 | the form @code{(@var{display} @var{atts})}. Each element's @sc{car}, |
1692 | @var{display}, specifies a class of terminals. The element's second element, | |
969fe9b5 RS |
1693 | @var{atts}, is a list of face attributes and their values; it specifies |
1694 | what the face should look like on that kind of terminal. The possible | |
1695 | attributes are defined in the value of @code{custom-face-attributes}. | |
1696 | ||
1697 | The @var{display} part of an element of @var{spec} determines which | |
1698 | frames the element applies to. If more than one element of @var{spec} | |
1699 | matches a given frame, the first matching element is the only one used | |
1700 | for that frame. There are two possibilities for @var{display}: | |
1701 | ||
1702 | @table @asis | |
1703 | @item @code{t} | |
1704 | This element of @var{spec} matches all frames. Therefore, any | |
1705 | subsequent elements of @var{spec} are never used. Normally | |
1706 | @code{t} is used in the last (or only) element of @var{spec}. | |
1707 | ||
a9f0a989 | 1708 | @item a list |
1911e6e5 | 1709 | If @var{display} is a list, each element should have the form |
969fe9b5 RS |
1710 | @code{(@var{characteristic} @var{value}@dots{})}. Here |
1711 | @var{characteristic} specifies a way of classifying frames, and the | |
1712 | @var{value}s are possible classifications which @var{display} should | |
1713 | apply to. Here are the possible values of @var{characteristic}: | |
1714 | ||
1715 | @table @code | |
1716 | @item type | |
9a6b7dcd MB |
1717 | The kind of window system the frame uses---either @code{graphic} (any |
1718 | graphics-capable display), @code{x}, @code{pc} (for the MS-DOS console), | |
1719 | @code{w32} (for MS Windows 9X/NT), or @code{tty} (a non-graphics-capable | |
1720 | display). | |
969fe9b5 RS |
1721 | |
1722 | @item class | |
1723 | What kinds of colors the frame supports---either @code{color}, | |
1724 | @code{grayscale}, or @code{mono}. | |
1725 | ||
1726 | @item background | |
1911e6e5 | 1727 | The kind of background---either @code{light} or @code{dark}. |
82c3d852 | 1728 | |
9fe84db6 EZ |
1729 | @item min-colors |
1730 | An integer that represents the minimum number of colors the frame should | |
1731 | support, it is compared with the result of @code{display-color-cells}. | |
1732 | ||
82c3d852 | 1733 | @item supports |
95b5b933 MB |
1734 | Whether or not the frame can display the face attributes given in |
1735 | @var{value}@dots{} (@pxref{Face Attributes}). See the documentation | |
1736 | for the function @code{display-supports-face-attributes-p} for more | |
1737 | information on exactly how this testing is done. @xref{Display Face | |
1738 | Attribute Testing}. | |
969fe9b5 RS |
1739 | @end table |
1740 | ||
1741 | If an element of @var{display} specifies more than one @var{value} for a | |
1742 | given @var{characteristic}, any of those values is acceptable. If | |
1743 | @var{display} has more than one element, each element should specify a | |
1744 | different @var{characteristic}; then @emph{each} characteristic of the | |
1745 | frame must match one of the @var{value}s specified for it in | |
1746 | @var{display}. | |
1747 | @end table | |
1748 | @end defmac | |
1749 | ||
a40d4712 | 1750 | Here's how the standard face @code{region} is defined: |
969fe9b5 RS |
1751 | |
1752 | @example | |
a40d4712 | 1753 | @group |
9fe84db6 EZ |
1754 | '((((class color) (min-colors 88) (background dark)) |
1755 | :background "blue3") | |
a40d4712 | 1756 | @end group |
9fe84db6 EZ |
1757 | (((class color) (min-colors 88) (background light)) |
1758 | :background "lightgoldenrod2") | |
1759 | (((class color) (min-colors 16) (background dark)) | |
1760 | :background "blue3") | |
1761 | (((class color) (min-colors 16) (background light)) | |
1762 | :background "lightgoldenrod2") | |
1763 | (((class color) (min-colors 8)) | |
1764 | :background "blue" :foreground "white") | |
a40d4712 | 1765 | (((type tty) (class mono)) |
9fe84db6 EZ |
1766 | :inverse-video t) |
1767 | (t :background "gray")) | |
a40d4712 PR |
1768 | @group |
1769 | "Basic face for highlighting the region." | |
1770 | :group 'basic-faces) | |
1771 | @end group | |
969fe9b5 RS |
1772 | @end example |
1773 | ||
1774 | Internally, @code{defface} uses the symbol property | |
1775 | @code{face-defface-spec} to record the face attributes specified in | |
1776 | @code{defface}, @code{saved-face} for the attributes saved by the user | |
1777 | with the customization buffer, and @code{face-documentation} for the | |
1778 | documentation string. | |
1779 | ||
1911e6e5 RS |
1780 | @defopt frame-background-mode |
1781 | This option, if non-@code{nil}, specifies the background type to use for | |
1782 | interpreting face definitions. If it is @code{dark}, then Emacs treats | |
1783 | all frames as if they had a dark background, regardless of their actual | |
1784 | background colors. If it is @code{light}, then Emacs treats all frames | |
1785 | as if they had a light background. | |
1786 | @end defopt | |
1787 | ||
8241495d RS |
1788 | @node Face Attributes |
1789 | @subsection Face Attributes | |
1790 | @cindex face attributes | |
42b85554 | 1791 | |
8241495d RS |
1792 | The effect of using a face is determined by a fixed set of @dfn{face |
1793 | attributes}. This table lists all the face attributes, and what they | |
a40d4712 PR |
1794 | mean. Note that in general, more than one face can be specified for a |
1795 | given piece of text; when that happens, the attributes of all the faces | |
1796 | are merged to specify how to display the text. @xref{Merging Faces}. | |
42b85554 | 1797 | |
8241495d RS |
1798 | In Emacs 21, any attribute in a face can have the value |
1799 | @code{unspecified}. This means the face doesn't specify that attribute. | |
1800 | In face merging, when the first face fails to specify a particular | |
1801 | attribute, that means the next face gets a chance. However, the | |
1802 | @code{default} face must specify all attributes. | |
42b85554 | 1803 | |
a40d4712 PR |
1804 | Some of these font attributes are meaningful only on certain kinds of |
1805 | displays---if your display cannot handle a certain attribute, the | |
1806 | attribute is ignored. (The attributes @code{:family}, @code{:width}, | |
1807 | @code{:height}, @code{:weight}, and @code{:slant} correspond to parts of | |
1808 | an X Logical Font Descriptor.) | |
42b85554 | 1809 | |
8241495d RS |
1810 | @table @code |
1811 | @item :family | |
1812 | Font family name, or fontset name (@pxref{Fontsets}). If you specify a | |
a40d4712 PR |
1813 | font family name, the wild-card characters @samp{*} and @samp{?} are |
1814 | allowed. | |
8241495d RS |
1815 | |
1816 | @item :width | |
1817 | Relative proportionate width, also known as the character set width or | |
1818 | set width. This should be one of the symbols @code{ultra-condensed}, | |
1819 | @code{extra-condensed}, @code{condensed}, @code{semi-condensed}, | |
1820 | @code{normal}, @code{semi-expanded}, @code{expanded}, | |
1821 | @code{extra-expanded}, or @code{ultra-expanded}. | |
177c0ea7 | 1822 | |
8241495d | 1823 | @item :height |
96f71a49 MB |
1824 | Either the font height, an integer in units of 1/10 point, a floating |
1825 | point number specifying the amount by which to scale the height of any | |
1826 | underlying face, or a function, which is called with the old height | |
1827 | (from the underlying face), and should return the new height. | |
177c0ea7 | 1828 | |
8241495d RS |
1829 | @item :weight |
1830 | Font weight---a symbol from this series (from most dense to most faint): | |
1831 | @code{ultra-bold}, @code{extra-bold}, @code{bold}, @code{semi-bold}, | |
1832 | @code{normal}, @code{semi-light}, @code{light}, @code{extra-light}, | |
a40d4712 | 1833 | or @code{ultra-light}. |
66f54605 | 1834 | |
a40d4712 PR |
1835 | On a text-only terminal, any weight greater than normal is displayed as |
1836 | extra bright, and any weight less than normal is displayed as | |
1837 | half-bright (provided the terminal supports the feature). | |
1838 | ||
8241495d RS |
1839 | @item :slant |
1840 | Font slant---one of the symbols @code{italic}, @code{oblique}, @code{normal}, | |
1841 | @code{reverse-italic}, or @code{reverse-oblique}. | |
66f54605 PR |
1842 | |
1843 | On a text-only terminal, slanted text is displayed as half-bright, if | |
1844 | the terminal supports the feature. | |
1845 | ||
8241495d RS |
1846 | @item :foreground |
1847 | Foreground color, a string. | |
177c0ea7 | 1848 | |
8241495d RS |
1849 | @item :background |
1850 | Background color, a string. | |
1851 | ||
1852 | @item :inverse-video | |
1853 | Whether or not characters should be displayed in inverse video. The | |
1854 | value should be @code{t} (yes) or @code{nil} (no). | |
1855 | ||
1856 | @item :stipple | |
a40d4712 | 1857 | The background stipple, a bitmap. |
8241495d | 1858 | |
a40d4712 PR |
1859 | The value can be a string; that should be the name of a file containing |
1860 | external-format X bitmap data. The file is found in the directories | |
1861 | listed in the variable @code{x-bitmap-file-path}. | |
8241495d | 1862 | |
a3fbafe2 RS |
1863 | Alternatively, the value can specify the bitmap directly, with a list |
1864 | of the form @code{(@var{width} @var{height} @var{data})}. Here, | |
1865 | @var{width} and @var{height} specify the size in pixels, and | |
1866 | @var{data} is a string containing the raw bits of the bitmap, row by | |
1867 | row. Each row occupies @math{(@var{width} + 7) / 8} consecutive bytes | |
1868 | in the string (which should be a unibyte string for best results). | |
1869 | This means that each row always occupies at least one whole byte. | |
8241495d RS |
1870 | |
1871 | If the value is @code{nil}, that means use no stipple pattern. | |
1872 | ||
1873 | Normally you do not need to set the stipple attribute, because it is | |
1874 | used automatically to handle certain shades of gray. | |
1875 | ||
1876 | @item :underline | |
1877 | Whether or not characters should be underlined, and in what color. If | |
1878 | the value is @code{t}, underlining uses the foreground color of the | |
1879 | face. If the value is a string, underlining uses that color. The | |
1880 | value @code{nil} means do not underline. | |
1881 | ||
1882 | @item :overline | |
1883 | Whether or not characters should be overlined, and in what color. | |
1884 | The value is used like that of @code{:underline}. | |
1885 | ||
1886 | @item :strike-through | |
1887 | Whether or not characters should be strike-through, and in what | |
1888 | color. The value is used like that of @code{:underline}. | |
1889 | ||
96f71a49 MB |
1890 | @item :inherit |
1891 | The name of a face from which to inherit attributes, or a list of face | |
1892 | names. Attributes from inherited faces are merged into the face like an | |
1893 | underlying face would be, with higher priority than underlying faces. | |
1894 | ||
8241495d RS |
1895 | @item :box |
1896 | Whether or not a box should be drawn around characters, its color, the | |
a40d4712 | 1897 | width of the box lines, and 3D appearance. |
8241495d | 1898 | @end table |
42b85554 | 1899 | |
8241495d RS |
1900 | Here are the possible values of the @code{:box} attribute, and what |
1901 | they mean: | |
42b85554 | 1902 | |
8241495d RS |
1903 | @table @asis |
1904 | @item @code{nil} | |
1905 | Don't draw a box. | |
bfe721d1 | 1906 | |
8241495d RS |
1907 | @item @code{t} |
1908 | Draw a box with lines of width 1, in the foreground color. | |
42b85554 | 1909 | |
8241495d RS |
1910 | @item @var{color} |
1911 | Draw a box with lines of width 1, in color @var{color}. | |
42b85554 | 1912 | |
8241495d RS |
1913 | @item @code{(:line-width @var{width} :color @var{color} :style @var{style})} |
1914 | This way you can explicitly specify all aspects of the box. The value | |
1915 | @var{width} specifies the width of the lines to draw; it defaults to 1. | |
42b85554 | 1916 | |
8241495d RS |
1917 | The value @var{color} specifies the color to draw with. The default is |
1918 | the foreground color of the face for simple boxes, and the background | |
1919 | color of the face for 3D boxes. | |
42b85554 | 1920 | |
8241495d RS |
1921 | The value @var{style} specifies whether to draw a 3D box. If it is |
1922 | @code{released-button}, the box looks like a 3D button that is not being | |
1923 | pressed. If it is @code{pressed-button}, the box looks like a 3D button | |
1924 | that is being pressed. If it is @code{nil} or omitted, a plain 2D box | |
1925 | is used. | |
1926 | @end table | |
42b85554 | 1927 | |
8241495d RS |
1928 | The attributes @code{:overline}, @code{:strike-through} and |
1929 | @code{:box} are new in Emacs 21. The attributes @code{:family}, | |
1930 | @code{:height}, @code{:width}, @code{:weight}, @code{:slant} are also | |
a40d4712 PR |
1931 | new; previous versions used the following attributes, now semi-obsolete, |
1932 | to specify some of the same information: | |
42b85554 | 1933 | |
8241495d RS |
1934 | @table @code |
1935 | @item :font | |
a40d4712 | 1936 | This attribute specifies the font name. |
42b85554 | 1937 | |
8241495d RS |
1938 | @item :bold |
1939 | A non-@code{nil} value specifies a bold font. | |
42b85554 | 1940 | |
8241495d RS |
1941 | @item :italic |
1942 | A non-@code{nil} value specifies an italic font. | |
1943 | @end table | |
42b85554 | 1944 | |
8241495d RS |
1945 | For compatibility, you can still set these ``attributes'' in Emacs 21, |
1946 | even though they are not real face attributes. Here is what that does: | |
42b85554 | 1947 | |
8241495d RS |
1948 | @table @code |
1949 | @item :font | |
a40d4712 PR |
1950 | You can specify an X font name as the ``value'' of this ``attribute''; |
1951 | that sets the @code{:family}, @code{:width}, @code{:height}, | |
1952 | @code{:weight}, and @code{:slant} attributes according to the font name. | |
8241495d RS |
1953 | |
1954 | If the value is a pattern with wildcards, the first font that matches | |
1955 | the pattern is used to set these attributes. | |
1956 | ||
1957 | @item :bold | |
1958 | A non-@code{nil} makes the face bold; @code{nil} makes it normal. | |
1959 | This actually works by setting the @code{:weight} attribute. | |
1960 | ||
1961 | @item :italic | |
1962 | A non-@code{nil} makes the face italic; @code{nil} makes it normal. | |
1963 | This actually works by setting the @code{:slant} attribute. | |
1964 | @end table | |
42b85554 | 1965 | |
8241495d RS |
1966 | @defvar x-bitmap-file-path |
1967 | This variable specifies a list of directories for searching | |
1968 | for bitmap files, for the @code{:stipple} attribute. | |
1969 | @end defvar | |
1970 | ||
ea7220f8 | 1971 | @defun bitmap-spec-p object |
2252bdcf RS |
1972 | This returns @code{t} if @var{object} is a valid bitmap specification, |
1973 | suitable for use with @code{:stipple} (see above). It returns | |
1974 | @code{nil} otherwise. | |
a40d4712 PR |
1975 | @end defun |
1976 | ||
8241495d RS |
1977 | @node Attribute Functions |
1978 | @subsection Face Attribute Functions | |
42b85554 RS |
1979 | |
1980 | You can modify the attributes of an existing face with the following | |
1981 | functions. If you specify @var{frame}, they affect just that frame; | |
1982 | otherwise, they affect all frames as well as the defaults that apply to | |
1983 | new frames. | |
1984 | ||
8241495d RS |
1985 | @tindex set-face-attribute |
1986 | @defun set-face-attribute face frame &rest arguments | |
1987 | This function sets one or more attributes of face @var{face} | |
1988 | for frame @var{frame}. If @var{frame} is @code{nil}, it sets | |
1989 | the attribute for all frames, and the defaults for new frames. | |
1990 | ||
1991 | The extra arguments @var{arguments} specify the attributes to set, and | |
1992 | the values for them. They should consist of alternating attribute names | |
a40d4712 | 1993 | (such as @code{:family} or @code{:underline}) and corresponding values. |
8241495d RS |
1994 | Thus, |
1995 | ||
1996 | @example | |
1997 | (set-face-attribute 'foo nil | |
dbcff00c RS |
1998 | :width 'extended |
1999 | :weight 'bold | |
8241495d RS |
2000 | :underline "red") |
2001 | @end example | |
2002 | ||
2003 | @noindent | |
2004 | sets the attributes @code{:width}, @code{:weight} and @code{:underline} | |
2005 | to the corresponding values. | |
2006 | @end defun | |
2007 | ||
2008 | @tindex face-attribute | |
35f23bbf | 2009 | @defun face-attribute face attribute &optional frame inherit |
8241495d RS |
2010 | This returns the value of the @var{attribute} attribute of face |
2011 | @var{face} on @var{frame}. If @var{frame} is @code{nil}, | |
8d82c597 | 2012 | that means the selected frame (@pxref{Input Focus}). |
8241495d RS |
2013 | |
2014 | If @var{frame} is @code{t}, the value is the default for | |
2015 | @var{face} for new frames. | |
2016 | ||
9a8dc0d3 | 2017 | If @var{inherit} is @code{nil}, only attributes directly defined by |
35f23bbf | 2018 | @var{face} are considered, so the return value may be |
9a8dc0d3 RS |
2019 | @code{unspecified}, or a relative value. If @var{inherit} is |
2020 | non-@code{nil}, @var{face}'s definition of @var{attribute} is merged | |
2021 | with the faces specified by its @code{:inherit} attribute; however the | |
2022 | return value may still be @code{unspecified} or relative. If | |
2023 | @var{inherit} is a face or a list of faces, then the result is further | |
2024 | merged with that face (or faces), until it becomes specified and | |
2025 | absolute. | |
35f23bbf MB |
2026 | |
2027 | To ensure that the return value is always specified and absolute, use | |
2028 | a value of @code{default} for @var{inherit}; this will resolve any | |
2029 | unspecified or relative values by merging with the @code{default} face | |
2030 | (which is always completely specified). | |
2031 | ||
8241495d RS |
2032 | For example, |
2033 | ||
2034 | @example | |
2035 | (face-attribute 'bold :weight) | |
2036 | @result{} bold | |
2037 | @end example | |
2038 | @end defun | |
2039 | ||
a40d4712 PR |
2040 | The functions above did not exist before Emacs 21. For compatibility |
2041 | with older Emacs versions, you can use the following functions to set | |
8241495d RS |
2042 | and examine the face attributes which existed in those versions. |
2043 | ||
35f23bbf MB |
2044 | @tindex face-attribute-relative-p |
2045 | @defun face-attribute-relative-p attribute value | |
812a2341 | 2046 | This function returns non-@code{nil} if @var{value}, when used as |
35f23bbf MB |
2047 | the value of the face attribute @var{attribute}, is relative (that is, |
2048 | if it modifies an underlying or inherited value of @var{attribute}). | |
2049 | @end defun | |
2050 | ||
2051 | @tindex merge-face-attribute | |
2052 | @defun merge-face-attribute attribute value1 value2 | |
2053 | If @var{value1} is a relative value for the face attribute | |
2054 | @var{attribute}, returns it merged with the underlying value | |
2055 | @var{value2}; otherwise, if @var{value1} is an absolute value for the | |
9ee1638e | 2056 | face attribute @var{attribute}, returns @var{value1} unchanged. |
35f23bbf MB |
2057 | @end defun |
2058 | ||
42b85554 RS |
2059 | @defun set-face-foreground face color &optional frame |
2060 | @defunx set-face-background face color &optional frame | |
78608595 RS |
2061 | These functions set the foreground (or background, respectively) color |
2062 | of face @var{face} to @var{color}. The argument @var{color} should be a | |
42b85554 | 2063 | string, the name of a color. |
bfe721d1 KH |
2064 | |
2065 | Certain shades of gray are implemented by stipple patterns on | |
2066 | black-and-white screens. | |
2067 | @end defun | |
2068 | ||
2069 | @defun set-face-stipple face pattern &optional frame | |
2252bdcf RS |
2070 | This function sets the background stipple pattern of face @var{face} |
2071 | to @var{pattern}. The argument @var{pattern} should be the name of a | |
2072 | stipple pattern defined by the X server, or actual bitmap data | |
2073 | (@pxref{Face Attributes}), or @code{nil} meaning don't use stipple. | |
bfe721d1 KH |
2074 | |
2075 | Normally there is no need to pay attention to stipple patterns, because | |
2076 | they are used automatically to handle certain shades of gray. | |
42b85554 RS |
2077 | @end defun |
2078 | ||
2079 | @defun set-face-font face font &optional frame | |
8241495d RS |
2080 | This function sets the font of face @var{face}. |
2081 | ||
2082 | In Emacs 21, this actually sets the attributes @code{:family}, | |
2083 | @code{:width}, @code{:height}, @code{:weight}, and @code{:slant} | |
2084 | according to the font name @var{font}. | |
2085 | ||
2086 | In Emacs 20, this sets the font attribute. Once you set the font | |
a9f0a989 | 2087 | explicitly, the bold and italic attributes cease to have any effect, |
8241495d | 2088 | because the precise font that you specified is used. |
21cffb83 RS |
2089 | @end defun |
2090 | ||
f9f59935 | 2091 | @defun set-face-bold-p face bold-p &optional frame |
8241495d RS |
2092 | This function specifies whether @var{face} should be bold. If |
2093 | @var{bold-p} is non-@code{nil}, that means yes; @code{nil} means no. | |
2094 | ||
2095 | In Emacs 21, this sets the @code{:weight} attribute. | |
2096 | In Emacs 20, it sets the @code{:bold} attribute. | |
21cffb83 RS |
2097 | @end defun |
2098 | ||
f9f59935 | 2099 | @defun set-face-italic-p face italic-p &optional frame |
8241495d RS |
2100 | This function specifies whether @var{face} should be italic. If |
2101 | @var{italic-p} is non-@code{nil}, that means yes; @code{nil} means no. | |
2102 | ||
2103 | In Emacs 21, this sets the @code{:slant} attribute. | |
2104 | In Emacs 20, it sets the @code{:italic} attribute. | |
42b85554 RS |
2105 | @end defun |
2106 | ||
969fe9b5 RS |
2107 | @defun set-face-underline-p face underline-p &optional frame |
2108 | This function sets the underline attribute of face @var{face}. | |
2109 | Non-@code{nil} means do underline; @code{nil} means don't. | |
2110 | @end defun | |
2111 | ||
42b85554 | 2112 | @defun invert-face face &optional frame |
8241495d RS |
2113 | This function inverts the @code{:inverse-video} attribute of face |
2114 | @var{face}. If the attribute is @code{nil}, this function sets it to | |
2115 | @code{t}, and vice versa. | |
42b85554 RS |
2116 | @end defun |
2117 | ||
2118 | These functions examine the attributes of a face. If you don't | |
2119 | specify @var{frame}, they refer to the default data for new frames. | |
a40d4712 PR |
2120 | They return the symbol @code{unspecified} if the face doesn't define any |
2121 | value for that attribute. | |
42b85554 | 2122 | |
69137def | 2123 | @defun face-foreground face &optional frame inherit |
42b85554 | 2124 | @defunx face-background face &optional frame |
78608595 RS |
2125 | These functions return the foreground color (or background color, |
2126 | respectively) of face @var{face}, as a string. | |
69137def | 2127 | |
00991494 JH |
2128 | If @var{inherit} is @code{nil}, only a color directly defined by the face is |
2129 | returned. If @var{inherit} is non-@code{nil}, any faces specified by its | |
69137def MB |
2130 | @code{:inherit} attribute are considered as well, and if @var{inherit} |
2131 | is a face or a list of faces, then they are also considered, until a | |
2132 | specified color is found. To ensure that the return value is always | |
2133 | specified, use a value of @code{default} for @var{inherit}. | |
42b85554 RS |
2134 | @end defun |
2135 | ||
69137def | 2136 | @defun face-stipple face &optional frame inherit |
bfe721d1 KH |
2137 | This function returns the name of the background stipple pattern of face |
2138 | @var{face}, or @code{nil} if it doesn't have one. | |
69137def | 2139 | |
9a8dc0d3 RS |
2140 | If @var{inherit} is @code{nil}, only a stipple directly defined by the |
2141 | face is returned. If @var{inherit} is non-@code{nil}, any faces | |
2142 | specified by its @code{:inherit} attribute are considered as well, and | |
2143 | if @var{inherit} is a face or a list of faces, then they are also | |
2144 | considered, until a specified stipple is found. To ensure that the | |
2145 | return value is always specified, use a value of @code{default} for | |
2146 | @var{inherit}. | |
bfe721d1 KH |
2147 | @end defun |
2148 | ||
42b85554 RS |
2149 | @defun face-font face &optional frame |
2150 | This function returns the name of the font of face @var{face}. | |
2151 | @end defun | |
2152 | ||
f9f59935 | 2153 | @defun face-bold-p face &optional frame |
8241495d RS |
2154 | This function returns @code{t} if @var{face} is bold---that is, if it is |
2155 | bolder than normal. It returns @code{nil} otherwise. | |
f9f59935 RS |
2156 | @end defun |
2157 | ||
f9f59935 | 2158 | @defun face-italic-p face &optional frame |
8241495d RS |
2159 | This function returns @code{t} if @var{face} is italic or oblique, |
2160 | @code{nil} otherwise. | |
f9f59935 RS |
2161 | @end defun |
2162 | ||
969fe9b5 | 2163 | @defun face-underline-p face &optional frame |
8241495d RS |
2164 | This function returns the @code{:underline} attribute of face @var{face}. |
2165 | @end defun | |
2166 | ||
2167 | @defun face-inverse-video-p face &optional frame | |
2168 | This function returns the @code{:inverse-video} attribute of face @var{face}. | |
2169 | @end defun | |
2170 | ||
2171 | @node Merging Faces | |
2172 | @subsection Merging Faces for Display | |
2173 | ||
2174 | Here are the ways to specify which faces to use for display of text: | |
2175 | ||
2176 | @itemize @bullet | |
2177 | @item | |
2178 | With defaults. The @code{default} face is used as the ultimate | |
2179 | default for all text. (In Emacs 19 and 20, the @code{default} | |
2180 | face is used only when no other face is specified.) | |
2181 | ||
2182 | For a mode line or header line, the face @code{modeline} or | |
2183 | @code{header-line} is used just before @code{default}. | |
2184 | ||
2185 | @item | |
2186 | With text properties. A character can have a @code{face} property; if | |
2187 | so, the faces and face attributes specified there apply. @xref{Special | |
2188 | Properties}. | |
2189 | ||
2190 | If the character has a @code{mouse-face} property, that is used instead | |
2191 | of the @code{face} property when the mouse is ``near enough'' to the | |
2192 | character. | |
2193 | ||
2194 | @item | |
2195 | With overlays. An overlay can have @code{face} and @code{mouse-face} | |
2196 | properties too; they apply to all the text covered by the overlay. | |
2197 | ||
2198 | @item | |
2199 | With a region that is active. In Transient Mark mode, the region is | |
2200 | highlighted with the face @code{region} (@pxref{Standard Faces}). | |
2201 | ||
2202 | @item | |
177c0ea7 | 2203 | With special glyphs. Each glyph can specify a particular face |
8241495d RS |
2204 | number. @xref{Glyphs}. |
2205 | @end itemize | |
2206 | ||
2207 | If these various sources together specify more than one face for a | |
2208 | particular character, Emacs merges the attributes of the various faces | |
2209 | specified. The attributes of the faces of special glyphs come first; | |
2210 | then comes the face for region highlighting, if appropriate; | |
2211 | then come attributes of faces from overlays, followed by those from text | |
2212 | properties, and last the default face. | |
2213 | ||
2214 | When multiple overlays cover one character, an overlay with higher | |
2215 | priority overrides those with lower priority. @xref{Overlays}. | |
2216 | ||
2217 | In Emacs 20, if an attribute such as the font or a color is not | |
2218 | specified in any of the above ways, the frame's own font or color is | |
2219 | used. In newer Emacs versions, this cannot happen, because the | |
2220 | @code{default} face specifies all attributes---in fact, the frame's own | |
2221 | font and colors are synonymous with those of the default face. | |
2222 | ||
2223 | @node Font Selection | |
2224 | @subsection Font Selection | |
2225 | ||
2226 | @dfn{Selecting a font} means mapping the specified face attributes for | |
2227 | a character to a font that is available on a particular display. The | |
2228 | face attributes, as determined by face merging, specify most of the | |
2229 | font choice, but not all. Part of the choice depends on what character | |
2230 | it is. | |
2231 | ||
8241495d RS |
2232 | If the face specifies a fontset name, that fontset determines a |
2233 | pattern for fonts of the given charset. If the face specifies a font | |
2234 | family, a font pattern is constructed. | |
2235 | ||
2236 | Emacs tries to find an available font for the given face attributes | |
2237 | and character's registry and encoding. If there is a font that matches | |
2238 | exactly, it is used, of course. The hard case is when no available font | |
2239 | exactly fits the specification. Then Emacs looks for one that is | |
1dffc5db RS |
2240 | ``close''---one attribute at a time. You can specify the order to |
2241 | consider the attributes. In the case where a specified font family is | |
2242 | not available, you can specify a set of mappings for alternatives to | |
2243 | try. | |
8241495d RS |
2244 | |
2245 | @defvar face-font-selection-order | |
2246 | @tindex face-font-selection-order | |
2247 | This variable specifies the order of importance of the face attributes | |
2248 | @code{:width}, @code{:height}, @code{:weight}, and @code{:slant}. The | |
2249 | value should be a list containing those four symbols, in order of | |
2250 | decreasing importance. | |
2251 | ||
2252 | Font selection first finds the best available matches for the first | |
2253 | attribute listed; then, among the fonts which are best in that way, it | |
2254 | searches for the best matches in the second attribute, and so on. | |
2255 | ||
2256 | The attributes @code{:weight} and @code{:width} have symbolic values in | |
2257 | a range centered around @code{normal}. Matches that are more extreme | |
2258 | (farther from @code{normal}) are somewhat preferred to matches that are | |
2259 | less extreme (closer to @code{normal}); this is designed to ensure that | |
2260 | non-normal faces contrast with normal ones, whenever possible. | |
2261 | ||
2262 | The default is @code{(:width :height :weight :slant)}, which means first | |
2263 | find the fonts closest to the specified @code{:width}, then---among the | |
2264 | fonts with that width---find a best match for the specified font height, | |
2265 | and so on. | |
2266 | ||
2267 | One example of a case where this variable makes a difference is when the | |
2268 | default font has no italic equivalent. With the default ordering, the | |
2269 | @code{italic} face will use a non-italic font that is similar to the | |
2270 | default one. But if you put @code{:slant} before @code{:height}, the | |
2271 | @code{italic} face will use an italic font, even if its height is not | |
2272 | quite right. | |
2273 | @end defvar | |
2274 | ||
52d89894 GM |
2275 | @defvar face-font-family-alternatives |
2276 | @tindex face-font-family-alternatives | |
8241495d RS |
2277 | This variable lets you specify alternative font families to try, if a |
2278 | given family is specified and doesn't exist. Each element should have | |
2279 | this form: | |
2280 | ||
2281 | @example | |
2282 | (@var{family} @var{alternate-families}@dots{}) | |
2283 | @end example | |
2284 | ||
2285 | If @var{family} is specified but not available, Emacs will try the other | |
2286 | families given in @var{alternate-families}, one by one, until it finds a | |
2287 | family that does exist. | |
52d89894 GM |
2288 | @end defvar |
2289 | ||
2290 | @defvar face-font-registry-alternatives | |
2291 | @tindex face-font-registry-alternatives | |
2292 | This variable lets you specify alternative font registries to try, if a | |
2293 | given registry is specified and doesn't exist. Each element should have | |
2294 | this form: | |
2295 | ||
2296 | @example | |
2297 | (@var{registry} @var{alternate-registries}@dots{}) | |
2298 | @end example | |
2299 | ||
2300 | If @var{registry} is specified but not available, Emacs will try the | |
2301 | other registries given in @var{alternate-registries}, one by one, | |
2302 | until it finds a registry that does exist. | |
8241495d RS |
2303 | @end defvar |
2304 | ||
2305 | Emacs can make use of scalable fonts, but by default it does not use | |
2306 | them, since the use of too many or too big scalable fonts can crash | |
2307 | XFree86 servers. | |
2308 | ||
2309 | @defvar scalable-fonts-allowed | |
2310 | @tindex scalable-fonts-allowed | |
2311 | This variable controls which scalable fonts to use. A value of | |
2312 | @code{nil}, the default, means do not use scalable fonts. @code{t} | |
2313 | means to use any scalable font that seems appropriate for the text. | |
2314 | ||
2315 | Otherwise, the value must be a list of regular expressions. Then a | |
2316 | scalable font is enabled for use if its name matches any regular | |
2317 | expression in the list. For example, | |
2318 | ||
2319 | @example | |
2320 | (setq scalable-fonts-allowed '("muleindian-2$")) | |
2321 | @end example | |
2322 | ||
2323 | @noindent | |
2324 | allows the use of scalable fonts with registry @code{muleindian-2}. | |
eda77a0f | 2325 | @end defvar |
8241495d RS |
2326 | |
2327 | @defun clear-face-cache &optional unload-p | |
2328 | @tindex clear-face-cache | |
2329 | This function clears the face cache for all frames. | |
2330 | If @var{unload-p} is non-@code{nil}, that means to unload | |
2331 | all unused fonts as well. | |
2332 | @end defun | |
2333 | ||
6bc3abcb RS |
2334 | @defvar face-font-rescale-alist |
2335 | This variable specifies scaling for certain faces. Its value should | |
2336 | be a list of elements of the form | |
2337 | ||
2338 | @example | |
2339 | (@var{fontname-regexp} . @var{scale-factor}) | |
2340 | @end example | |
2341 | ||
2342 | If @var{fontname-regexp} matches the font name that is about to be | |
2343 | used, this says to choose a larger similar font according to the | |
2344 | factor @var{scale-factor}. You would use this feature to normalize | |
2345 | the font size if certain fonts are bigger or smaller than their | |
2346 | nominal heights and widths would suggest. | |
2347 | @end defvar | |
2348 | ||
8241495d RS |
2349 | @node Face Functions |
2350 | @subsection Functions for Working with Faces | |
2351 | ||
2352 | Here are additional functions for creating and working with faces. | |
2353 | ||
2354 | @defun make-face name | |
2355 | This function defines a new face named @var{name}, initially with all | |
2356 | attributes @code{nil}. It does nothing if there is already a face named | |
2357 | @var{name}. | |
2358 | @end defun | |
2359 | ||
2360 | @defun face-list | |
2361 | This function returns a list of all defined face names. | |
2362 | @end defun | |
2363 | ||
2364 | @defun copy-face old-face new-name &optional frame new-frame | |
2365 | This function defines the face @var{new-name} as a copy of the existing | |
2366 | face named @var{old-face}. It creates the face @var{new-name} if that | |
2367 | doesn't already exist. | |
2368 | ||
2369 | If the optional argument @var{frame} is given, this function applies | |
2370 | only to that frame. Otherwise it applies to each frame individually, | |
2371 | copying attributes from @var{old-face} in each frame to @var{new-face} | |
2372 | in the same frame. | |
2373 | ||
2374 | If the optional argument @var{new-frame} is given, then @code{copy-face} | |
2375 | copies the attributes of @var{old-face} in @var{frame} to @var{new-name} | |
2376 | in @var{new-frame}. | |
969fe9b5 RS |
2377 | @end defun |
2378 | ||
bfe721d1 | 2379 | @defun face-id face |
969fe9b5 | 2380 | This function returns the face number of face @var{face}. |
42b85554 RS |
2381 | @end defun |
2382 | ||
f9f59935 RS |
2383 | @defun face-documentation face |
2384 | This function returns the documentation string of face @var{face}, or | |
2385 | @code{nil} if none was specified for it. | |
2386 | @end defun | |
2387 | ||
42b85554 RS |
2388 | @defun face-equal face1 face2 &optional frame |
2389 | This returns @code{t} if the faces @var{face1} and @var{face2} have the | |
2390 | same attributes for display. | |
2391 | @end defun | |
2392 | ||
2393 | @defun face-differs-from-default-p face &optional frame | |
7e07a66d MB |
2394 | This returns non-@code{nil} if the face @var{face} displays |
2395 | differently from the default face. | |
1911e6e5 RS |
2396 | @end defun |
2397 | ||
8241495d RS |
2398 | @node Auto Faces |
2399 | @subsection Automatic Face Assignment | |
2400 | @cindex automatic face assignment | |
2401 | @cindex faces, automatic choice | |
2402 | ||
2403 | @cindex Font-Lock mode | |
2404 | Starting with Emacs 21, a hook is available for automatically | |
2405 | assigning faces to text in the buffer. This hook is used for part of | |
2406 | the implementation of Font-Lock mode. | |
2407 | ||
2408 | @tindex fontification-functions | |
2409 | @defvar fontification-functions | |
2410 | This variable holds a list of functions that are called by Emacs | |
2411 | redisplay as needed to assign faces automatically to text in the buffer. | |
2412 | ||
2413 | The functions are called in the order listed, with one argument, a | |
2414 | buffer position @var{pos}. Each function should attempt to assign faces | |
2415 | to the text in the current buffer starting at @var{pos}. | |
2416 | ||
2417 | Each function should record the faces they assign by setting the | |
2418 | @code{face} property. It should also add a non-@code{nil} | |
2419 | @code{fontified} property for all the text it has assigned faces to. | |
2420 | That property tells redisplay that faces have been assigned to that text | |
2421 | already. | |
2422 | ||
2423 | It is probably a good idea for each function to do nothing if the | |
2424 | character after @var{pos} already has a non-@code{nil} @code{fontified} | |
2425 | property, but this is not required. If one function overrides the | |
2426 | assignments made by a previous one, the properties as they are | |
2427 | after the last function finishes are the ones that really matter. | |
2428 | ||
2429 | For efficiency, we recommend writing these functions so that they | |
2430 | usually assign faces to around 400 to 600 characters at each call. | |
2431 | @end defvar | |
2432 | ||
2433 | @node Font Lookup | |
2434 | @subsection Looking Up Fonts | |
2435 | ||
2436 | @defun x-list-fonts pattern &optional face frame maximum | |
2437 | This function returns a list of available font names that match | |
2438 | @var{pattern}. If the optional arguments @var{face} and @var{frame} are | |
2439 | specified, then the list is limited to fonts that are the same size as | |
2440 | @var{face} currently is on @var{frame}. | |
2441 | ||
2442 | The argument @var{pattern} should be a string, perhaps with wildcard | |
2443 | characters: the @samp{*} character matches any substring, and the | |
2444 | @samp{?} character matches any single character. Pattern matching | |
2445 | of font names ignores case. | |
2446 | ||
2447 | If you specify @var{face} and @var{frame}, @var{face} should be a face name | |
2448 | (a symbol) and @var{frame} should be a frame. | |
2449 | ||
2450 | The optional argument @var{maximum} sets a limit on how many fonts to | |
2451 | return. If this is non-@code{nil}, then the return value is truncated | |
2452 | after the first @var{maximum} matching fonts. Specifying a small value | |
2453 | for @var{maximum} can make this function much faster, in cases where | |
2454 | many fonts match the pattern. | |
2455 | @end defun | |
2456 | ||
2457 | These additional functions are available starting in Emacs 21. | |
2458 | ||
2459 | @defun x-family-fonts &optional family frame | |
2460 | @tindex x-family-fonts | |
2461 | This function returns a list describing the available fonts for family | |
2462 | @var{family} on @var{frame}. If @var{family} is omitted or @code{nil}, | |
2463 | this list applies to all families, and therefore, it contains all | |
2464 | available fonts. Otherwise, @var{family} must be a string; it may | |
2465 | contain the wildcards @samp{?} and @samp{*}. | |
2466 | ||
2467 | The list describes the display that @var{frame} is on; if @var{frame} is | |
8d82c597 EZ |
2468 | omitted or @code{nil}, it applies to the selected frame's display |
2469 | (@pxref{Input Focus}). | |
8241495d RS |
2470 | |
2471 | The list contains a vector of the following form for each font: | |
2472 | ||
2473 | @example | |
2474 | [@var{family} @var{width} @var{point-size} @var{weight} @var{slant} | |
2475 | @var{fixed-p} @var{full} @var{registry-and-encoding}] | |
2476 | @end example | |
2477 | ||
2478 | The first five elements correspond to face attributes; if you | |
2479 | specify these attributes for a face, it will use this font. | |
2480 | ||
2481 | The last three elements give additional information about the font. | |
9a8dc0d3 RS |
2482 | @var{fixed-p} is non-@code{nil} if the font is fixed-pitch. |
2483 | @var{full} is the full name of the font, and | |
2484 | @var{registry-and-encoding} is a string giving the registry and | |
2485 | encoding of the font. | |
8241495d RS |
2486 | |
2487 | The result list is sorted according to the current face font sort order. | |
2488 | @end defun | |
2489 | ||
2490 | @defun x-font-family-list &optional frame | |
2491 | @tindex x-font-family-list | |
2492 | This function returns a list of the font families available for | |
2493 | @var{frame}'s display. If @var{frame} is omitted or @code{nil}, it | |
8d82c597 | 2494 | describes the selected frame's display (@pxref{Input Focus}). |
8241495d RS |
2495 | |
2496 | The value is a list of elements of this form: | |
2497 | ||
2498 | @example | |
2499 | (@var{family} . @var{fixed-p}) | |
2500 | @end example | |
2501 | ||
2502 | @noindent | |
2503 | Here @var{family} is a font family, and @var{fixed-p} is | |
2504 | non-@code{nil} if fonts of that family are fixed-pitch. | |
2505 | @end defun | |
2506 | ||
2507 | @defvar font-list-limit | |
2508 | @tindex font-list-limit | |
2509 | This variable specifies maximum number of fonts to consider in font | |
2510 | matching. The function @code{x-family-fonts} will not return more than | |
2511 | that many fonts, and font selection will consider only that many fonts | |
2512 | when searching a matching font for face attributes. The default is | |
2513 | currently 100. | |
2514 | @end defvar | |
2515 | ||
2516 | @node Fontsets | |
2517 | @subsection Fontsets | |
2518 | ||
2519 | A @dfn{fontset} is a list of fonts, each assigned to a range of | |
2520 | character codes. An individual font cannot display the whole range of | |
2521 | characters that Emacs supports, but a fontset can. Fontsets have names, | |
2522 | just as fonts do, and you can use a fontset name in place of a font name | |
2523 | when you specify the ``font'' for a frame or a face. Here is | |
2524 | information about defining a fontset under Lisp program control. | |
2525 | ||
2526 | @defun create-fontset-from-fontset-spec fontset-spec &optional style-variant-p noerror | |
2527 | This function defines a new fontset according to the specification | |
2528 | string @var{fontset-spec}. The string should have this format: | |
2529 | ||
2530 | @smallexample | |
2531 | @var{fontpattern}, @r{[}@var{charsetname}:@var{fontname}@r{]@dots{}} | |
2532 | @end smallexample | |
2533 | ||
2534 | @noindent | |
2535 | Whitespace characters before and after the commas are ignored. | |
2536 | ||
2537 | The first part of the string, @var{fontpattern}, should have the form of | |
2538 | a standard X font name, except that the last two fields should be | |
2539 | @samp{fontset-@var{alias}}. | |
2540 | ||
2541 | The new fontset has two names, one long and one short. The long name is | |
2542 | @var{fontpattern} in its entirety. The short name is | |
2543 | @samp{fontset-@var{alias}}. You can refer to the fontset by either | |
2544 | name. If a fontset with the same name already exists, an error is | |
2545 | signaled, unless @var{noerror} is non-@code{nil}, in which case this | |
2546 | function does nothing. | |
2547 | ||
2548 | If optional argument @var{style-variant-p} is non-@code{nil}, that says | |
2549 | to create bold, italic and bold-italic variants of the fontset as well. | |
2550 | These variant fontsets do not have a short name, only a long one, which | |
2551 | is made by altering @var{fontpattern} to indicate the bold or italic | |
2552 | status. | |
2553 | ||
2554 | The specification string also says which fonts to use in the fontset. | |
2555 | See below for the details. | |
2556 | @end defun | |
2557 | ||
2558 | The construct @samp{@var{charset}:@var{font}} specifies which font to | |
2559 | use (in this fontset) for one particular character set. Here, | |
2560 | @var{charset} is the name of a character set, and @var{font} is the font | |
2561 | to use for that character set. You can use this construct any number of | |
2562 | times in the specification string. | |
2563 | ||
2564 | For the remaining character sets, those that you don't specify | |
2565 | explicitly, Emacs chooses a font based on @var{fontpattern}: it replaces | |
2566 | @samp{fontset-@var{alias}} with a value that names one character set. | |
ad800164 | 2567 | For the @acronym{ASCII} character set, @samp{fontset-@var{alias}} is replaced |
8241495d RS |
2568 | with @samp{ISO8859-1}. |
2569 | ||
2570 | In addition, when several consecutive fields are wildcards, Emacs | |
2571 | collapses them into a single wildcard. This is to prevent use of | |
2572 | auto-scaled fonts. Fonts made by scaling larger fonts are not usable | |
2573 | for editing, and scaling a smaller font is not useful because it is | |
2574 | better to use the smaller font in its own size, which Emacs does. | |
2575 | ||
2576 | Thus if @var{fontpattern} is this, | |
2577 | ||
2578 | @example | |
2579 | -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24 | |
2580 | @end example | |
2581 | ||
2582 | @noindent | |
ad800164 | 2583 | the font specification for @acronym{ASCII} characters would be this: |
8241495d RS |
2584 | |
2585 | @example | |
2586 | -*-fixed-medium-r-normal-*-24-*-ISO8859-1 | |
2587 | @end example | |
2588 | ||
2589 | @noindent | |
2590 | and the font specification for Chinese GB2312 characters would be this: | |
2591 | ||
2592 | @example | |
2593 | -*-fixed-medium-r-normal-*-24-*-gb2312*-* | |
2594 | @end example | |
2595 | ||
2596 | You may not have any Chinese font matching the above font | |
2597 | specification. Most X distributions include only Chinese fonts that | |
2598 | have @samp{song ti} or @samp{fangsong ti} in the @var{family} field. In | |
2599 | such a case, @samp{Fontset-@var{n}} can be specified as below: | |
2600 | ||
2601 | @smallexample | |
2602 | Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\ | |
2603 | chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-* | |
2604 | @end smallexample | |
2605 | ||
2606 | @noindent | |
2607 | Then, the font specifications for all but Chinese GB2312 characters have | |
2608 | @samp{fixed} in the @var{family} field, and the font specification for | |
2609 | Chinese GB2312 characters has a wild card @samp{*} in the @var{family} | |
2610 | field. | |
2611 | ||
885fef7c KH |
2612 | @defun set-fontset-font name character fontname &optional frame |
2613 | This function modifies the existing fontset @var{name} to | |
2614 | use the font name @var{fontname} for the character @var{character}. | |
2615 | ||
a2296bf9 | 2616 | If @var{name} is @code{nil}, this function modifies the default |
812a2341 | 2617 | fontset, whose short name is @samp{fontset-default}. |
885fef7c | 2618 | |
a2296bf9 KH |
2619 | @var{character} may be a cons; @code{(@var{from} . @var{to})}, where |
2620 | @var{from} and @var{to} are non-generic characters. In that case, use | |
2621 | @var{fontname} for all characters in the range @var{from} and @var{to} | |
2622 | (inclusive). | |
885fef7c KH |
2623 | |
2624 | @var{character} may be a charset. In that case, use | |
2625 | @var{fontname} for all character in the charsets. | |
2626 | ||
a2296bf9 KH |
2627 | @var{fontname} may be a cons; @code{(@var{family} . @var{registry})}, |
2628 | where @var{family} is a family name of a font (possibly including a | |
2629 | foundry name at the head), @var{registry} is a registry name of a font | |
2630 | (possibly including an encoding name at the tail). | |
885fef7c | 2631 | |
a2296bf9 KH |
2632 | For instance, this changes the default fontset to use a font of which |
2633 | registry name is @samp{JISX0208.1983} for all characters belonging to | |
2634 | the charset @code{japanese-jisx0208}. | |
885fef7c KH |
2635 | |
2636 | @example | |
2637 | (set-fontset-font nil 'japanese-jisx0208 '(nil . "JISX0208.1983")) | |
2638 | @end example | |
2639 | ||
2640 | @end defun | |
2641 | ||
f6cad089 RS |
2642 | @defun char-displayable-p char |
2643 | This function returns @code{t} if Emacs ought to be able to display | |
2644 | @var{char}. More precisely, if the selected frame's fontset has a | |
2645 | font to display the character set that @var{char} belongs to. | |
2646 | ||
2647 | Fontsets can specify a font on a per-character basis; when the fontset | |
2648 | does that, this function's value may not be accurate. | |
2649 | @end defun | |
2650 | ||
8a6ca431 RS |
2651 | @node Fringes |
2652 | @section Fringes | |
2653 | @cindex Fringes | |
2654 | ||
2655 | The @dfn{fringes} of a window are thin vertical strips down the | |
2656 | sides that are used for displaying bitmaps that indicate truncation, | |
812a2341 | 2657 | continuation, horizontal scrolling, and the overlay arrow. The |
8a6ca431 RS |
2658 | fringes normally appear between the display margins and the window |
2659 | text, but you can put them outside the display margins for a specific | |
2660 | buffer by setting @code{fringes-outside-margins} buffer-locally to a | |
2661 | non-@code{nil} value. | |
2662 | ||
2663 | @defvar fringes-outside-margins | |
2664 | If the value is non-@code{nil}, the frames appear outside | |
9b6e4bc3 | 2665 | the display margins. |
8a6ca431 RS |
2666 | @end defvar |
2667 | ||
2668 | @defvar left-fringe-width | |
2669 | This variable, if non-@code{nil}, specifies the width of the left | |
2670 | fringe in pixels. | |
2671 | @end defvar | |
2672 | ||
2673 | @defvar right-fringe-width | |
2674 | This variable, if non-@code{nil}, specifies the width of the right | |
2675 | fringe in pixels. | |
2676 | @end defvar | |
2677 | ||
2678 | The values of these variables take effect when you display the | |
2679 | buffer in a window. If you change them while the buffer is visible, | |
812a2341 RS |
2680 | you can call @code{set-window-buffer} to display it once again in the |
2681 | same window, to make the changes take effect. | |
8a6ca431 RS |
2682 | |
2683 | @defun set-window-fringes window left &optional right outside-margins | |
812a2341 | 2684 | This function sets the fringe widths of window @var{window}. |
479dbc9d | 2685 | If @var{window} is @code{nil}, the selected window is used. |
8a6ca431 RS |
2686 | |
2687 | The argument @var{left} specifies the width in pixels of the left | |
2688 | fringe, and likewise @var{right} for the right fringe. A value of | |
2689 | @code{nil} for either one stands for the default width. If | |
2690 | @var{outside-margins} is non-@code{nil}, that specifies that fringes | |
2691 | should appear outside of the display margins. | |
2692 | @end defun | |
2693 | ||
479dbc9d | 2694 | @defun window-fringes &optional window |
8a6ca431 | 2695 | This function returns information about the fringes of a window |
479dbc9d KS |
2696 | @var{window}. If @var{window} is omitted or @code{nil}, the selected |
2697 | window is used. The value has the form @code{(@var{left-width} | |
c00d3ba4 | 2698 | @var{right-width} @var{frames-outside-margins})}. |
8a6ca431 RS |
2699 | @end defun |
2700 | ||
9b6e4bc3 | 2701 | @defvar overflow-newline-into-fringe |
26b76360 RS |
2702 | If this is non-@code{nil}, lines exactly as wide as the window (not |
2703 | counting the final newline character) are not continued. Instead, | |
2704 | when point is at the end of the line, the cursor appears in the right | |
2705 | fringe. | |
9b6e4bc3 KS |
2706 | @end defvar |
2707 | ||
2708 | @node Fringe Bitmaps | |
2709 | @section Fringe Bitmaps | |
26b76360 RS |
2710 | @cindex fringe bitmaps |
2711 | @cindex bitmaps, fringe | |
2712 | ||
2713 | The @dfn{fringe bitmaps} are tiny icons Emacs displays in the window | |
2714 | fringe (on a graphic display) to indicate truncated or continued | |
2715 | lines, buffer boundaries, overlay arrow, etc. The fringe bitmaps are | |
2716 | shared by all frames and windows. You can redefine the built-in | |
90801c68 | 2717 | fringe bitmaps, and you can define new fringe bitmaps. |
26b76360 RS |
2718 | |
2719 | The way to display a bitmap in the left or right fringes for a given | |
2720 | line in a window is by specifying the @code{display} property for one | |
2721 | of the characters that appears in it. Use a display specification of | |
2722 | the form @code{(left-fringe @var{bitmap} [@var{face}])} or | |
2723 | @code{(right-fringe @var{bitmap} [@var{face}])} (@pxref{Display | |
90801c68 | 2724 | Property}). Here, @var{bitmap} is a symbol identifying the bitmap |
26b76360 RS |
2725 | you want, and @var{face} (which is optional) is the name of the face |
2726 | whose colors should be used for displaying the bitmap. | |
26b76360 RS |
2727 | |
2728 | These are the symbols identify the standard fringe bitmaps. | |
90801c68 KS |
2729 | Evaluate @code{(require 'fringe)} to define them. Fringe bitmap |
2730 | symbols have their own name space. | |
9b6e4bc3 | 2731 | |
26b76360 RS |
2732 | @table @asis |
2733 | @item Truncation and continuation line bitmaps: | |
90801c68 KS |
2734 | @code{left-truncation}, @code{right-truncation}, |
2735 | @code{continued-line}, @code{continuation-line}. | |
9b6e4bc3 | 2736 | |
26b76360 | 2737 | @item Buffer indication bitmaps: |
90801c68 KS |
2738 | @code{up-arrow}, @code{down-arrow}, |
2739 | @code{top-left-angle}, @code{top-right-angle}, | |
2740 | @code{bottom-left-angle}, @code{bottom-right-angle}, | |
2741 | @code{left-bracket}, @code{right-bracket}. | |
9b6e4bc3 | 2742 | |
26b76360 | 2743 | @item Empty line indication bitmap: |
90801c68 | 2744 | @code{empty-line}. |
9b6e4bc3 | 2745 | |
26b76360 | 2746 | @item Overlay arrow bitmap: |
90801c68 | 2747 | @code{overlay-arrow}. |
9b6e4bc3 | 2748 | |
26b76360 | 2749 | @item Bitmaps for displaying the cursor in right fringe: |
90801c68 KS |
2750 | @code{filled-box-cursor}, @code{hollow-box-cursor}, @code{hollow-square}, |
2751 | @code{bar-cursor}, @code{hbar-cursor}. | |
26b76360 | 2752 | @end table |
9b6e4bc3 | 2753 | |
26b76360 RS |
2754 | @defun fringe-bitmaps-at-pos &optional pos window |
2755 | This function returns the fringe bitmaps of the display line | |
2756 | containing position @var{pos} in window @var{window}. The return | |
cf6d43ae | 2757 | value has the form @code{(@var{left} @var{right} @var{ov})}, where @var{left} |
90801c68 | 2758 | is the symbol for the fringe bitmap in the left fringe (or @code{nil} |
cf6d43ae KS |
2759 | if no bitmap), @var{right} is similar for the right fringe, and @var{ov} |
2760 | is non-@code{nil} if there is an overlay arrow in the left fringe. | |
26b76360 RS |
2761 | |
2762 | The value is @code{nil} if @var{pos} is not visible in @var{window}. | |
2763 | If @var{window} is @code{nil}, that stands for the selected window. | |
2764 | If @var{pos} is @code{nil}, that stands for the value of point in | |
2765 | @var{window}. | |
2766 | @end defun | |
9b6e4bc3 | 2767 | |
26b76360 RS |
2768 | @node Customizing Bitmaps |
2769 | @section Customizing Fringe Bitmaps | |
2770 | ||
90801c68 KS |
2771 | @defun define-fringe-bitmap bitmap bits &optional height width align |
2772 | This function defines the symbol @var{bitmap} as a new fringe bitmap, | |
2773 | or replaces an existing bitmap with that name. | |
9b6e4bc3 | 2774 | |
26b76360 RS |
2775 | The argument @var{bits} specifies the image to use. It should be |
2776 | either a string or a vector of integers, where each element (an | |
2777 | integer) corresponds to one row of the bitmap. Each bit of an integer | |
90801c68 KS |
2778 | corresponds to one pixel of the bitmap, where the low bit corresponds |
2779 | to the rightmost pixel of the bitmap. | |
9b6e4bc3 | 2780 | |
26b76360 RS |
2781 | The height is normally the length of @var{bits}. However, you |
2782 | can specify a different height with non-@code{nil} @var{height}. The width | |
2783 | is normally 8, but you can specify a different width with non-@code{nil} | |
2784 | @var{width}. The width must be an integer between 1 and 16. | |
9b6e4bc3 | 2785 | |
26b76360 RS |
2786 | The argument @var{align} specifies the positioning of the bitmap |
2787 | relative to the range of rows where it is used; the default is to | |
2788 | center the bitmap. The allowed values are @code{top}, @code{center}, | |
2789 | or @code{bottom}. | |
9b6e4bc3 | 2790 | |
26b76360 | 2791 | The @var{align} argument may also be a list @code{(@var{align} |
17234906 | 2792 | @var{periodic})} where @var{align} is interpreted as described above. |
26b76360 RS |
2793 | If @var{periodic} is non-@code{nil}, it specifies that the rows in |
2794 | @code{bits} should be repeated enough times to reach the specified | |
2795 | height. | |
9b6e4bc3 | 2796 | |
26b76360 RS |
2797 | The return value on success is an integer identifying the new bitmap. |
2798 | You should save that integer in a variable so it can be used to select | |
90801c68 KS |
2799 | this bitmap. |
2800 | ||
2801 | This function signals an error if there are no more free bitmap slots. | |
9b6e4bc3 KS |
2802 | @end defun |
2803 | ||
2804 | @defun destroy-fringe-bitmap bitmap | |
26b76360 RS |
2805 | This function destroy the fringe bitmap identified by @var{bitmap}. |
2806 | If @var{bitmap} identifies a standard fringe bitmap, it actually | |
2807 | restores the standard definition of that bitmap, instead of | |
2808 | eliminating it entirely. | |
9b6e4bc3 KS |
2809 | @end defun |
2810 | ||
2811 | @defun set-fringe-bitmap-face bitmap &optional face | |
26b76360 RS |
2812 | This sets the face for the fringe bitmap @var{bitmap} to @var{face}. |
2813 | If @var{face} is @code{nil}, it selects the @code{fringe} face. The | |
2814 | bitmap's face controls the color to draw it in. | |
9b6e4bc3 | 2815 | |
26b76360 RS |
2816 | The face you use here should be derived from @code{fringe}, and should |
2817 | specify only the foreground color. | |
9b6e4bc3 KS |
2818 | @end defun |
2819 | ||
26b76360 RS |
2820 | @defvar indicate-buffer-boundaries |
2821 | This buffer-local variable controls how the buffer boundaries and | |
2822 | window scrolling are indicated in the window fringes. | |
2823 | ||
2824 | Emacs can indicate the buffer boundaries---that is, the first and last | |
2825 | line in the buffer---with angle icons when they appear on the screen. | |
2826 | In addition, Emacs can display an up-arrow in the fringe to show | |
2827 | that there is text above the screen, and a down-arrow to show | |
2828 | there is text below the screen. | |
2829 | ||
2830 | There are four kinds of basic values: | |
2831 | ||
2832 | @table @asis | |
2833 | @item @code{nil} | |
2834 | Don't display the icons. | |
2835 | @item @code{left} | |
2836 | Display them in the left fringe. | |
2837 | @item @code{right} | |
2838 | Display them in the right fringe. | |
2839 | @item @var{anything-else} | |
2840 | Display the icon at the top of the window top in the left fringe, and other | |
2841 | in the right fringe. | |
2842 | @end table | |
2843 | ||
2844 | If value is a cons @code{(@var{angles} . @var{arrows})}, @var{angles} | |
2845 | controls the angle icons, and @var{arrows} controls the arrows. Both | |
2846 | @var{angles} and @var{arrows} work according to the table above. | |
2847 | Thus, @code{(t . right)} places the top angle icon in the left | |
2848 | fringe, the bottom angle icon in the right fringe, and both arrows in | |
2849 | the right fringe. | |
2850 | @end defvar | |
2851 | ||
2852 | @defvar default-indicate-buffer-boundaries | |
2853 | The value of this variable is the default value for | |
2854 | @code{indicate-buffer-boundaries} in buffers that do not override it. | |
2855 | @end defvar | |
2856 | ||
f6cad089 RS |
2857 | @node Scroll Bars |
2858 | @section Scroll Bars | |
2859 | ||
2860 | Normally the frame parameter @code{vertical-scroll-bars} controls | |
2861 | whether the windows in the frame have vertical scroll bars. A | |
2862 | non-@code{nil} parameter value means they do. The frame parameter | |
2863 | @code{scroll-bar-width} specifies how wide they are (@code{nil} | |
2864 | meaning the default). @xref{Window Frame Parameters}. | |
2865 | ||
2866 | You can also control this for individual windows. Call the function | |
2867 | @code{set-window-scroll-bars} to specify what to do for a specific window: | |
2868 | ||
2869 | @defun set-window-scroll-bars window width &optional vertical-type horizontal-type | |
26b76360 RS |
2870 | This function sets the width and type of scroll bars for window |
2871 | @var{window}. | |
2872 | ||
f6cad089 | 2873 | @var{width} specifies the scroll bar width in pixels (@code{nil} means |
26b76360 RS |
2874 | use the width specified for the frame). @var{vertical-type} specifies |
2875 | whether to have a vertical scroll bar and, if so, where. The possible | |
2876 | values are @code{left}, @code{right} and @code{nil}, just like the | |
2877 | values of the @code{vertical-scroll-bars} frame parameter. | |
f6cad089 RS |
2878 | |
2879 | The argument @var{horizontal-type} is meant to specify whether and | |
2880 | where to have horizontal scroll bars, but since they are not | |
26b76360 RS |
2881 | implemented, it has no effect. If @var{window} is @code{nil}, the |
2882 | selected window is used. | |
f6cad089 RS |
2883 | @end defun |
2884 | ||
2885 | @defun window-scroll-bars &optional window | |
2886 | Report the width and type of scroll bars specified for @var{window}. | |
479dbc9d KS |
2887 | If @var{window} is omitted or @code{nil}, the selected window is used. |
2888 | The value is a list of the form @code{(@var{width} | |
f6cad089 RS |
2889 | @var{cols} @var{vertical-type} @var{horizontal-type})}. The value |
2890 | @var{width} is the value that was specified for the width (which may | |
2891 | be @code{nil}); @var{cols} is the number of columns that the scroll | |
2892 | bar actually occupies. | |
2893 | ||
2894 | @var{horizontal-type} is not actually meaningful. | |
2895 | @end defun | |
2896 | ||
2897 | If you don't specify these values for a window with | |
2898 | @code{set-window-scroll-bars}, the buffer-local variables | |
2899 | @code{scroll-bar-mode} and @code{scroll-bar-width} in the buffer being | |
2900 | displayed control the window's vertical scroll bars. The function | |
2901 | @code{set-window-buffer} examines these variables. If you change them | |
2902 | in a buffer that is already visible in a window, you can make the | |
2903 | window take note of the new values by calling @code{set-window-buffer} | |
2904 | specifying the same buffer that is already displayed. | |
2905 | ||
61e74968 LT |
2906 | @node Pointer Shape |
2907 | @section Pointer Shape | |
9b6e4bc3 | 2908 | |
26b76360 | 2909 | Normally, the mouse pointer has the @code{text} shape over text and |
9b6e4bc3 | 2910 | the @code{arrow} shape over window areas which do not correspond to |
26b76360 RS |
2911 | any buffer text. You can specify the mouse pointer shape over text or |
2912 | images via the @code{pointer} text property, and for images with the | |
2913 | @code{:pointer} and @code{:map} image properties. | |
9b6e4bc3 | 2914 | |
26b76360 | 2915 | The available pointer shapes are: @code{text} (or @code{nil}), |
9b6e4bc3 KS |
2916 | @code{arrow}, @code{hand}, @code{vdrag}, @code{hdrag}, |
2917 | @code{modeline}, and @code{hourglass}. | |
2918 | ||
9b6e4bc3 KS |
2919 | @defvar void-text-area-pointer |
2920 | @tindex void-text-area-pointer | |
2921 | This variable specifies the mouse pointer shape in void text areas, | |
2922 | i.e. the areas after the end of a line or below the last line in the | |
2923 | buffer. The default is to use the @code{arrow} (non-text) pointer. | |
2924 | @end defvar | |
2925 | ||
8241495d RS |
2926 | @node Display Property |
2927 | @section The @code{display} Property | |
2928 | @cindex display specification | |
2929 | @kindex display @r{(text property)} | |
2930 | ||
a40d4712 PR |
2931 | The @code{display} text property (or overlay property) is used to |
2932 | insert images into text, and also control other aspects of how text | |
2933 | displays. These features are available starting in Emacs 21. The value | |
2934 | of the @code{display} property should be a display specification, or a | |
2935 | list or vector containing several display specifications. The rest of | |
2936 | this section describes several kinds of display specifications and what | |
2937 | they mean. | |
8241495d RS |
2938 | |
2939 | @menu | |
02c77ee9 | 2940 | * Specified Space:: Displaying one space with a specified width. |
9b6e4bc3 | 2941 | * Pixel Specification:: Specifying space width or height in pixels. |
02c77ee9 | 2942 | * Other Display Specs:: Displaying an image; magnifying text; moving it |
177c0ea7 | 2943 | up or down on the page; adjusting the width |
a40d4712 PR |
2944 | of spaces within text. |
2945 | * Display Margins:: Displaying text or images to the side of the main text. | |
02c77ee9 | 2946 | * Conditional Display:: Making any of the above features conditional |
a40d4712 | 2947 | depending on some Lisp expression. |
8241495d RS |
2948 | @end menu |
2949 | ||
2950 | @node Specified Space | |
2951 | @subsection Specified Spaces | |
2952 | @cindex spaces, specified height or width | |
2953 | @cindex specified spaces | |
2954 | @cindex variable-width spaces | |
2955 | ||
2956 | To display a space of specified width and/or height, use a display | |
a40d4712 PR |
2957 | specification of the form @code{(space . @var{props})}, where |
2958 | @var{props} is a property list (a list of alternating properties and | |
2959 | values). You can put this property on one or more consecutive | |
2960 | characters; a space of the specified height and width is displayed in | |
2961 | place of @emph{all} of those characters. These are the properties you | |
0b0e8041 | 2962 | can use in @var{props} to specify the weight of the space: |
8241495d RS |
2963 | |
2964 | @table @code | |
2965 | @item :width @var{width} | |
9b6e4bc3 KS |
2966 | If @var{width} is an integer or floating point number, it specifies |
2967 | that the space width should be @var{width} times the normal character | |
26b76360 | 2968 | width. @var{width} can also be a @dfn{pixel width} specification |
9b6e4bc3 | 2969 | (@pxref{Pixel Specification}). |
8241495d RS |
2970 | |
2971 | @item :relative-width @var{factor} | |
2972 | Specifies that the width of the stretch should be computed from the | |
2973 | first character in the group of consecutive characters that have the | |
2974 | same @code{display} property. The space width is the width of that | |
2975 | character, multiplied by @var{factor}. | |
2976 | ||
2977 | @item :align-to @var{hpos} | |
9b6e4bc3 | 2978 | Specifies that the space should be wide enough to reach @var{hpos}. |
26b76360 RS |
2979 | If @var{hpos} is a number, it is measured in units of the normal |
2980 | character width. @var{hpos} can also be a @dfn{pixel width} | |
2981 | specification (@pxref{Pixel Specification}). | |
8241495d RS |
2982 | @end table |
2983 | ||
0b0e8041 | 2984 | You should use one and only one of the above properties. You can |
26b76360 | 2985 | also specify the height of the space, with these properties: |
8241495d RS |
2986 | |
2987 | @table @code | |
2988 | @item :height @var{height} | |
9b6e4bc3 KS |
2989 | Specifies the height of the space. |
2990 | If @var{height} is an integer or floating point number, it specifies | |
2991 | that the space height should be @var{height} times the normal character | |
2992 | height. The @var{height} may also be a @dfn{pixel height} specification | |
2993 | (@pxref{Pixel Specification}). | |
8241495d RS |
2994 | |
2995 | @item :relative-height @var{factor} | |
2996 | Specifies the height of the space, multiplying the ordinary height | |
2997 | of the text having this display specification by @var{factor}. | |
2998 | ||
2999 | @item :ascent @var{ascent} | |
9b6e4bc3 KS |
3000 | If the value of @var{ascent} is a non-negative number no greater than |
3001 | 100, it specifies that @var{ascent} percent of the height of the space | |
3002 | should be considered as the ascent of the space---that is, the part | |
3003 | above the baseline. The ascent may also be specified in pixel units | |
3004 | with a @dfn{pixel ascent} specification (@pxref{Pixel Specification}). | |
3005 | ||
8241495d RS |
3006 | @end table |
3007 | ||
0b0e8041 | 3008 | Don't use both @code{:height} and @code{:relative-height} together. |
8241495d | 3009 | |
26b76360 RS |
3010 | The @code{:height} and @code{:align-to} properties are supported on |
3011 | non-graphic terminals, but the other space properties in this section | |
3012 | are not. | |
3013 | ||
9b6e4bc3 KS |
3014 | @node Pixel Specification |
3015 | @subsection Pixel Specification for Spaces | |
3016 | @cindex spaces, pixel specification | |
3017 | ||
3018 | The value of the @code{:width}, @code{:align-to}, @code{:height}, | |
26b76360 RS |
3019 | and @code{:ascent} properties can be a special kind of expression that |
3020 | is evaluated during redisplay. The result of the evaluation is used | |
3021 | as an absolute number of pixels. | |
9b6e4bc3 KS |
3022 | |
3023 | The following expressions are supported: | |
3024 | ||
3025 | @example | |
3026 | @group | |
90801c68 | 3027 | @var{expr} ::= @var{num} | (@var{num}) | @var{unit} | @var{elem} | @var{pos} | @var{image} | @var{form} |
26b76360 RS |
3028 | @var{num} ::= @var{integer} | @var{float} | @var{symbol} |
3029 | @var{unit} ::= in | mm | cm | width | height | |
3030 | @var{elem} ::= left-fringe | right-fringe | left-margin | right-margin | |
9b6e4bc3 | 3031 | | scroll-bar | text |
26b76360 RS |
3032 | @var{pos} ::= left | center | right |
3033 | @var{form} ::= (@var{num} . @var{expr}) | (@var{op} @var{expr} ...) | |
3034 | @var{op} ::= + | - | |
9b6e4bc3 KS |
3035 | @end group |
3036 | @end example | |
3037 | ||
26b76360 RS |
3038 | The form @var{num} specifies a fraction of the default frame font |
3039 | height or width. The form @code{(@var{num})} specifies an absolute | |
3040 | number of pixels. If @var{num} is a symbol, @var{symbol}, its | |
9b6e4bc3 KS |
3041 | buffer-local variable binding is used. |
3042 | ||
26b76360 RS |
3043 | The @code{in}, @code{mm}, and @code{cm} units specify the number of |
3044 | pixels per inch, millimeter, and centimeter, respectively. The | |
3045 | @code{width} and @code{height} units correspond to the default width | |
90801c68 | 3046 | and height of the current face. An image specification @code{image} |
9b6e4bc3 KS |
3047 | corresponds to the width or height of the image. |
3048 | ||
3049 | The @code{left-fringe}, @code{right-fringe}, @code{left-margin}, | |
3050 | @code{right-margin}, @code{scroll-bar}, and @code{text} elements | |
3051 | specify to the width of the corresponding area of the window. | |
3052 | ||
3053 | The @code{left}, @code{center}, and @code{right} positions can be | |
3054 | used with @code{:align-to} to specify a position relative to the left | |
3055 | edge, center, or right edge of the text area. | |
3056 | ||
26b76360 | 3057 | Any of the above window elements (except @code{text}) can also be |
9b6e4bc3 KS |
3058 | used with @code{:align-to} to specify that the position is relative to |
3059 | the left edge of the given area. Once the base offset for a relative | |
3060 | position has been set (by the first occurrence of one of these | |
17234906 | 3061 | symbols), further occurrences of these symbols are interpreted as the |
9b6e4bc3 KS |
3062 | width of the specified area. For example, to align to the center of |
3063 | the left-margin, use | |
3064 | ||
3065 | @example | |
3066 | :align-to (+ left-margin (0.5 . left-margin)) | |
3067 | @end example | |
3068 | ||
3069 | If no specific base offset is set for alignment, it is always relative | |
3070 | to the left edge of the text area. For example, @samp{:align-to 0} in a | |
3071 | header-line aligns with the first text column in the text area. | |
3072 | ||
26b76360 RS |
3073 | A value of the form @code{(@var{num} . @var{expr})} stands |
3074 | multiplying the values of @var{num} and @var{expr}. For example, | |
3075 | @code{(2 . in)} specifies a width of 2 inches, while @code{(0.5 . | |
90801c68 | 3076 | @var{image})} specifies half the width (or height) of the specified image. |
9b6e4bc3 | 3077 | |
26b76360 RS |
3078 | The form @code{(+ @var{expr} ...)} adds up the value of the |
3079 | expressions. The form @code{(- @var{expr} ...)} negates or subtracts | |
9b6e4bc3 KS |
3080 | the value of the expressions. |
3081 | ||
8241495d RS |
3082 | @node Other Display Specs |
3083 | @subsection Other Display Specifications | |
3084 | ||
26b76360 RS |
3085 | Here are the other sorts of display specifications that you can use |
3086 | in the @code{display} text property. | |
3087 | ||
8241495d RS |
3088 | @table @code |
3089 | @item (image . @var{image-props}) | |
3090 | This is in fact an image descriptor (@pxref{Images}). When used as a | |
3091 | display specification, it means to display the image instead of the text | |
3092 | that has the display specification. | |
3093 | ||
9b6e4bc3 | 3094 | @item (slice @var{x} @var{y} @var{width} @var{height}) |
26b76360 RS |
3095 | This specification together with @code{image} specifies a @dfn{slice} |
3096 | (a partial area) of the image to display. The elements @var{y} and | |
3097 | @var{x} specify the top left corner of the slice, within the image; | |
3098 | @var{width} and @var{height} specify the width and height of the | |
3099 | slice. Integer values are numbers of pixels. A floating point number | |
3100 | in the range 0.0--1.0 stands for that fraction of the width or height | |
3101 | of the entire image. | |
9b6e4bc3 | 3102 | |
1574933b DL |
3103 | @item ((margin nil) @var{string}) |
3104 | @itemx @var{string} | |
3105 | A display specification of this form means to display @var{string} | |
3106 | instead of the text that has the display specification, at the same | |
3107 | position as that text. This is a special case of marginal display | |
3108 | (@pxref{Display Margins}). | |
3109 | ||
0b0e8041 RS |
3110 | Recursive display specifications are not supported---string display |
3111 | specifications must not have @code{display} properties themselves. | |
5143d8a4 | 3112 | |
8241495d | 3113 | @item (space-width @var{factor}) |
a40d4712 PR |
3114 | This display specification affects all the space characters within the |
3115 | text that has the specification. It displays all of these spaces | |
3116 | @var{factor} times as wide as normal. The element @var{factor} should | |
3117 | be an integer or float. Characters other than spaces are not affected | |
3118 | at all; in particular, this has no effect on tab characters. | |
8241495d RS |
3119 | |
3120 | @item (height @var{height}) | |
3121 | This display specification makes the text taller or shorter. | |
3122 | Here are the possibilities for @var{height}: | |
3123 | ||
3124 | @table @asis | |
3125 | @item @code{(+ @var{n})} | |
3126 | This means to use a font that is @var{n} steps larger. A ``step'' is | |
a40d4712 PR |
3127 | defined by the set of available fonts---specifically, those that match |
3128 | what was otherwise specified for this text, in all attributes except | |
3129 | height. Each size for which a suitable font is available counts as | |
3130 | another step. @var{n} should be an integer. | |
8241495d RS |
3131 | |
3132 | @item @code{(- @var{n})} | |
3133 | This means to use a font that is @var{n} steps smaller. | |
3134 | ||
3135 | @item a number, @var{factor} | |
3136 | A number, @var{factor}, means to use a font that is @var{factor} times | |
3137 | as tall as the default font. | |
3138 | ||
3139 | @item a symbol, @var{function} | |
3140 | A symbol is a function to compute the height. It is called with the | |
3141 | current height as argument, and should return the new height to use. | |
3142 | ||
3143 | @item anything else, @var{form} | |
3144 | If the @var{height} value doesn't fit the previous possibilities, it is | |
3145 | a form. Emacs evaluates it to get the new height, with the symbol | |
3146 | @code{height} bound to the current specified font height. | |
3147 | @end table | |
3148 | ||
3149 | @item (raise @var{factor}) | |
3150 | This kind of display specification raises or lowers the text | |
3151 | it applies to, relative to the baseline of the line. | |
3152 | ||
3153 | @var{factor} must be a number, which is interpreted as a multiple of the | |
3154 | height of the affected text. If it is positive, that means to display | |
3155 | the characters raised. If it is negative, that means to display them | |
3156 | lower down. | |
3157 | ||
3158 | If the text also has a @code{height} display specification, that does | |
3159 | not affect the amount of raising or lowering, which is based on the | |
3160 | faces used for the text. | |
3161 | @end table | |
3162 | ||
3163 | @node Display Margins | |
3164 | @subsection Displaying in the Margins | |
3165 | @cindex display margins | |
3166 | @cindex margins, display | |
3167 | ||
3168 | A buffer can have blank areas called @dfn{display margins} on the left | |
3169 | and on the right. Ordinary text never appears in these areas, but you | |
3170 | can put things into the display margins using the @code{display} | |
3171 | property. | |
3172 | ||
3173 | To put text in the left or right display margin of the window, use a | |
3174 | display specification of the form @code{(margin right-margin)} or | |
3175 | @code{(margin left-margin)} on it. To put an image in a display margin, | |
3176 | use that display specification along with the display specification for | |
a8e171ce RS |
3177 | the image. Unfortunately, there is currently no way to make |
3178 | text or images in the margin mouse-sensitive. | |
8241495d | 3179 | |
78263139 RS |
3180 | If you put such a display specification directly on text in the |
3181 | buffer, the specified margin display appears @emph{instead of} that | |
3182 | buffer text itself. To put something in the margin @emph{in | |
3183 | association with} certain buffer text without preventing or altering | |
3184 | the display of that text, put a @code{before-string} property on the | |
3185 | text and put the display specification on the contents of the | |
3186 | before-string. | |
3187 | ||
8241495d RS |
3188 | Before the display margins can display anything, you must give |
3189 | them a nonzero width. The usual way to do that is to set these | |
3190 | variables: | |
3191 | ||
3192 | @defvar left-margin-width | |
3193 | @tindex left-margin-width | |
3194 | This variable specifies the width of the left margin. | |
3195 | It is buffer-local in all buffers. | |
3196 | @end defvar | |
3197 | ||
3198 | @defvar right-margin-width | |
3199 | @tindex right-margin-width | |
3200 | This variable specifies the width of the right margin. | |
3201 | It is buffer-local in all buffers. | |
3202 | @end defvar | |
3203 | ||
3204 | Setting these variables does not immediately affect the window. These | |
3205 | variables are checked when a new buffer is displayed in the window. | |
3206 | Thus, you can make changes take effect by calling | |
3207 | @code{set-window-buffer}. | |
3208 | ||
3209 | You can also set the margin widths immediately. | |
3210 | ||
5143d8a4 | 3211 | @defun set-window-margins window left &optional right |
8241495d RS |
3212 | @tindex set-window-margins |
3213 | This function specifies the margin widths for window @var{window}. | |
177c0ea7 | 3214 | The argument @var{left} controls the left margin and |
5143d8a4 | 3215 | @var{right} controls the right margin (default @code{0}). |
8241495d RS |
3216 | @end defun |
3217 | ||
3218 | @defun window-margins &optional window | |
3219 | @tindex window-margins | |
3220 | This function returns the left and right margins of @var{window} | |
3221 | as a cons cell of the form @code{(@var{left} . @var{right})}. | |
3222 | If @var{window} is @code{nil}, the selected window is used. | |
3223 | @end defun | |
3224 | ||
3225 | @node Conditional Display | |
3226 | @subsection Conditional Display Specifications | |
3227 | @cindex conditional display specifications | |
3228 | ||
3229 | You can make any display specification conditional. To do that, | |
bb2337f5 | 3230 | package it in another list of the form @code{(when @var{condition} . |
8241495d RS |
3231 | @var{spec})}. Then the specification @var{spec} applies only when |
3232 | @var{condition} evaluates to a non-@code{nil} value. During the | |
5fd2dcb8 GM |
3233 | evaluation, @code{object} is bound to the string or buffer having the |
3234 | conditional @code{display} property. @code{position} and | |
3235 | @code{buffer-position} are bound to the position within @code{object} | |
3236 | and the buffer position where the @code{display} property was found, | |
3237 | respectively. Both positions can be different when @code{object} is a | |
3238 | string. | |
8241495d RS |
3239 | |
3240 | @node Images | |
3241 | @section Images | |
3242 | @cindex images in buffers | |
3243 | ||
3244 | To display an image in an Emacs buffer, you must first create an image | |
3245 | descriptor, then use it as a display specifier in the @code{display} | |
3246 | property of text that is displayed (@pxref{Display Property}). Like the | |
3247 | @code{display} property, this feature is available starting in Emacs 21. | |
3248 | ||
3249 | Emacs can display a number of different image formats; some of them | |
da4b7798 JB |
3250 | are supported only if particular support libraries are installed on |
3251 | your machine. In some environments, Emacs allows loading image | |
3252 | libraries on demand; if so, the variable @code{image-library-alist} | |
3253 | can be used to modify the set of known names for these dynamic | |
17234906 | 3254 | libraries (though it is not possible to add new image formats). |
da4b7798 JB |
3255 | |
3256 | The supported image formats include XBM, XPM (needing the | |
8241495d RS |
3257 | libraries @code{libXpm} version 3.4k and @code{libz}), GIF (needing |
3258 | @code{libungif} 4.1.0), Postscript, PBM, JPEG (needing the | |
3259 | @code{libjpeg} library version v6a), TIFF (needing @code{libtiff} v3.4), | |
3260 | and PNG (needing @code{libpng} 1.0.2). | |
3261 | ||
3262 | You specify one of these formats with an image type symbol. The image | |
3263 | type symbols are @code{xbm}, @code{xpm}, @code{gif}, @code{postscript}, | |
3264 | @code{pbm}, @code{jpeg}, @code{tiff}, and @code{png}. | |
3265 | ||
3266 | @defvar image-types | |
3267 | This variable contains a list of those image type symbols that are | |
da4b7798 JB |
3268 | potentially supported in the current configuration. |
3269 | @emph{Potentially} here means that Emacs knows about the image types, | |
3270 | not necessarily that they can be loaded (they could depend on | |
3271 | unavailable dynamic libraries, for example). | |
3272 | ||
3273 | To know which image types are really available, use | |
3274 | @code{image-type-available-p}. | |
8241495d RS |
3275 | @end defvar |
3276 | ||
da4b7798 | 3277 | @defvar image-library-alist |
da4b7798 JB |
3278 | This in an alist of image types vs external libraries needed to |
3279 | display them. | |
3280 | ||
aa0e4da8 | 3281 | Each element is a list @code{(@var{image-type} @var{library}...)}, |
da4b7798 JB |
3282 | where the car is a supported image format from @code{image-types}, and |
3283 | the rest are strings giving alternate filenames for the corresponding | |
3284 | external libraries to load. | |
3285 | ||
e6263643 JB |
3286 | Emacs tries to load the libraries in the order they appear on the |
3287 | list; if none is loaded, the running session of Emacs won't support | |
3288 | the image type. @code{pbm} and @code{xbm} don't need to be listed; | |
da4b7798 JB |
3289 | they're always supported. |
3290 | ||
3291 | This variable is ignored if the image libraries are statically linked | |
3292 | into Emacs. | |
3293 | @end defvar | |
3294 | ||
3295 | @defun image-type-available-p type | |
3296 | @findex image-type-available-p | |
3297 | ||
aa0e4da8 JB |
3298 | This function returns non-@code{nil} if image type @var{type} is |
3299 | available, i.e., if images of this type can be loaded and displayed in | |
3300 | Emacs. @var{type} should be one of the types contained in | |
3301 | @code{image-types}. | |
da4b7798 JB |
3302 | |
3303 | For image types whose support libraries are statically linked, this | |
3304 | function always returns @code{t}; for other image types, it returns | |
3305 | @code{t} if the dynamic library could be loaded, @code{nil} otherwise. | |
3306 | @end defun | |
3307 | ||
8241495d | 3308 | @menu |
a40d4712 PR |
3309 | * Image Descriptors:: How to specify an image for use in @code{:display}. |
3310 | * XBM Images:: Special features for XBM format. | |
3311 | * XPM Images:: Special features for XPM format. | |
3312 | * GIF Images:: Special features for GIF format. | |
3313 | * Postscript Images:: Special features for Postscript format. | |
3314 | * Other Image Types:: Various other formats are supported. | |
3315 | * Defining Images:: Convenient ways to define an image for later use. | |
3316 | * Showing Images:: Convenient ways to display an image once it is defined. | |
3317 | * Image Cache:: Internal mechanisms of image display. | |
8241495d RS |
3318 | @end menu |
3319 | ||
3320 | @node Image Descriptors | |
3321 | @subsection Image Descriptors | |
3322 | @cindex image descriptor | |
3323 | ||
3324 | An image description is a list of the form @code{(image | |
3325 | . @var{props})}, where @var{props} is a property list containing | |
3326 | alternating keyword symbols (symbols whose names start with a colon) and | |
14ac7224 GM |
3327 | their values. You can use any Lisp object as a property, but the only |
3328 | properties that have any special meaning are certain symbols, all of | |
3329 | them keywords. | |
3330 | ||
3331 | Every image descriptor must contain the property @code{:type | |
3332 | @var{type}} to specify the format of the image. The value of @var{type} | |
3333 | should be an image type symbol; for example, @code{xpm} for an image in | |
3334 | XPM format. | |
8241495d RS |
3335 | |
3336 | Here is a list of other properties that are meaningful for all image | |
3337 | types: | |
3338 | ||
3339 | @table @code | |
2cd8656e RS |
3340 | @item :file @var{file} |
3341 | The @code{:file} property specifies to load the image from file | |
3342 | @var{file}. If @var{file} is not an absolute file name, it is expanded | |
3343 | in @code{data-directory}. | |
3344 | ||
3345 | @item :data @var{data} | |
3346 | The @code{:data} property specifies the actual contents of the image. | |
3347 | Each image must use either @code{:data} or @code{:file}, but not both. | |
3348 | For most image types, the value of the @code{:data} property should be a | |
3349 | string containing the image data; we recommend using a unibyte string. | |
3350 | ||
3351 | Before using @code{:data}, look for further information in the section | |
3352 | below describing the specific image format. For some image types, | |
3353 | @code{:data} may not be supported; for some, it allows other data types; | |
3354 | for some, @code{:data} alone is not enough, so you need to use other | |
3355 | image properties along with @code{:data}. | |
3356 | ||
3357 | @item :margin @var{margin} | |
3358 | The @code{:margin} property specifies how many pixels to add as an | |
9ee1638e | 3359 | extra margin around the image. The value, @var{margin}, must be a |
2cd8656e RS |
3360 | non-negative number, or a pair @code{(@var{x} . @var{y})} of such |
3361 | numbers. If it is a pair, @var{x} specifies how many pixels to add | |
3362 | horizontally, and @var{y} specifies how many pixels to add vertically. | |
3363 | If @code{:margin} is not specified, the default is zero. | |
3364 | ||
8241495d | 3365 | @item :ascent @var{ascent} |
04545643 GM |
3366 | The @code{:ascent} property specifies the amount of the image's |
3367 | height to use for its ascent---that is, the part above the baseline. | |
3368 | The value, @var{ascent}, must be a number in the range 0 to 100, or | |
3369 | the symbol @code{center}. | |
3370 | ||
3371 | If @var{ascent} is a number, that percentage of the image's height is | |
3372 | used for its ascent. | |
3373 | ||
3374 | If @var{ascent} is @code{center}, the image is vertically centered | |
3375 | around a centerline which would be the vertical centerline of text drawn | |
3376 | at the position of the image, in the manner specified by the text | |
3377 | properties and overlays that apply to the image. | |
3378 | ||
3379 | If this property is omitted, it defaults to 50. | |
8241495d | 3380 | |
8241495d RS |
3381 | @item :relief @var{relief} |
3382 | The @code{:relief} property, if non-@code{nil}, adds a shadow rectangle | |
3383 | around the image. The value, @var{relief}, specifies the width of the | |
3384 | shadow lines, in pixels. If @var{relief} is negative, shadows are drawn | |
3385 | so that the image appears as a pressed button; otherwise, it appears as | |
3386 | an unpressed button. | |
3387 | ||
f864120f GM |
3388 | @item :conversion @var{algorithm} |
3389 | The @code{:conversion} property, if non-@code{nil}, specifies a | |
8241495d RS |
3390 | conversion algorithm that should be applied to the image before it is |
3391 | displayed; the value, @var{algorithm}, specifies which algorithm. | |
3392 | ||
62fb5c66 DL |
3393 | @table @code |
3394 | @item laplace | |
3395 | @itemx emboss | |
3396 | Specifies the Laplace edge detection algorithm, which blurs out small | |
3397 | differences in color while highlighting larger differences. People | |
3398 | sometimes consider this useful for displaying the image for a | |
3399 | ``disabled'' button. | |
3400 | ||
3401 | @item (edge-detection :matrix @var{matrix} :color-adjust @var{adjust}) | |
3402 | Specifies a general edge-detection algorithm. @var{matrix} must be | |
3403 | either a nine-element list or a nine-element vector of numbers. A pixel | |
3404 | at position @math{x/y} in the transformed image is computed from | |
3405 | original pixels around that position. @var{matrix} specifies, for each | |
3406 | pixel in the neighborhood of @math{x/y}, a factor with which that pixel | |
3407 | will influence the transformed pixel; element @math{0} specifies the | |
3408 | factor for the pixel at @math{x-1/y-1}, element @math{1} the factor for | |
3409 | the pixel at @math{x/y-1} etc., as shown below: | |
3410 | @iftex | |
3411 | @tex | |
3412 | $$\pmatrix{x-1/y-1 & x/y-1 & x+1/y-1 \cr | |
3413 | x-1/y & x/y & x+1/y \cr | |
3414 | x-1/y+1& x/y+1 & x+1/y+1 \cr}$$ | |
3415 | @end tex | |
3416 | @end iftex | |
3417 | @ifnottex | |
3418 | @display | |
3419 | (x-1/y-1 x/y-1 x+1/y-1 | |
3420 | x-1/y x/y x+1/y | |
3421 | x-1/y+1 x/y+1 x+1/y+1) | |
3422 | @end display | |
3423 | @end ifnottex | |
3424 | ||
3425 | The resulting pixel is computed from the color intensity of the color | |
3426 | resulting from summing up the RGB values of surrounding pixels, | |
3427 | multiplied by the specified factors, and dividing that sum by the sum | |
3428 | of the factors' absolute values. | |
3429 | ||
3430 | Laplace edge-detection currently uses a matrix of | |
3431 | @iftex | |
3432 | @tex | |
3433 | $$\pmatrix{1 & 0 & 0 \cr | |
3434 | 0& 0 & 0 \cr | |
3435 | 9 & 9 & -1 \cr}$$ | |
3436 | @end tex | |
3437 | @end iftex | |
3438 | @ifnottex | |
3439 | @display | |
3440 | (1 0 0 | |
3441 | 0 0 0 | |
3442 | 9 9 -1) | |
3443 | @end display | |
3444 | @end ifnottex | |
3445 | ||
3446 | Emboss edge-detection uses a matrix of | |
3447 | @iftex | |
3448 | @tex | |
3449 | $$\pmatrix{ 2 & -1 & 0 \cr | |
3450 | -1 & 0 & 1 \cr | |
3451 | 0 & 1 & -2 \cr}$$ | |
3452 | @end tex | |
3453 | @end iftex | |
3454 | @ifnottex | |
3455 | @display | |
3456 | ( 2 -1 0 | |
3457 | -1 0 1 | |
3458 | 0 1 -2) | |
3459 | @end display | |
3460 | @end ifnottex | |
3461 | ||
3462 | @item disabled | |
3463 | Specifies transforming the image so that it looks ``disabled''. | |
3464 | @end table | |
8241495d | 3465 | |
62fb5c66 DL |
3466 | @item :mask @var{mask} |
3467 | If @var{mask} is @code{heuristic} or @code{(heuristic @var{bg})}, build | |
3468 | a clipping mask for the image, so that the background of a frame is | |
3469 | visible behind the image. If @var{bg} is not specified, or if @var{bg} | |
3470 | is @code{t}, determine the background color of the image by looking at | |
3471 | the four corners of the image, assuming the most frequently occurring | |
3472 | color from the corners is the background color of the image. Otherwise, | |
3473 | @var{bg} must be a list @code{(@var{red} @var{green} @var{blue})} | |
3474 | specifying the color to assume for the background of the image. | |
8241495d | 3475 | |
9a8dc0d3 RS |
3476 | If @var{mask} is @code{nil}, remove a mask from the image, if it has |
3477 | one. Images in some formats include a mask which can be removed by | |
3478 | specifying @code{:mask nil}. | |
9b6e4bc3 KS |
3479 | |
3480 | @item :pointer @var{shape} | |
3481 | This specifies the pointer shape when the mouse pointer is over this | |
17234906 | 3482 | image. @xref{Pointer Shape}, for available pointer shapes. |
9b6e4bc3 KS |
3483 | |
3484 | @item :map @var{map} | |
3485 | This associates an image map of @dfn{hot spots} with this image. | |
3486 | ||
3487 | An image map is an alist where each element has the format | |
3488 | @code{(@var{area} @var{id} @var{plist})}. An @var{area} is specified | |
3489 | as either a rectangle, a circle, or a polygon. | |
3490 | ||
3491 | A rectangle is a cons | |
3492 | @code{(rect . ((@var{x0} . @var{y0}) . (@var{x1} . @var{y1})))} | |
3493 | which specifies the pixel coordinates of the upper left and bottom right | |
3494 | corners of the rectangle area. | |
3495 | ||
3496 | A circle is a cons | |
3497 | @code{(circle . ((@var{x0} . @var{y0}) . @var{r}))} | |
3498 | which specifies the center and the radius of the circle; @var{r} may | |
3499 | be a float or integer. | |
3500 | ||
3501 | A polygon is a cons | |
61e74968 | 3502 | @code{(poly . [@var{x0} @var{y0} @var{x1} @var{y1} ...])} |
9b6e4bc3 KS |
3503 | where each pair in the vector describes one corner in the polygon. |
3504 | ||
3505 | When the mouse pointer is above a hot-spot area of an image, the | |
3506 | @var{plist} of that hot-spot is consulted; if it contains a @code{help-echo} | |
3507 | property it defines a tool-tip for the hot-spot, and if it contains | |
3508 | a @code{pointer} property, it defines the shape of the mouse cursor when | |
3509 | it is over the hot-spot. | |
17234906 | 3510 | @xref{Pointer Shape}, for available pointer shapes. |
9b6e4bc3 KS |
3511 | |
3512 | When you click the mouse when the mouse pointer is over a hot-spot, an | |
3513 | event is composed by combining the @var{id} of the hot-spot with the | |
26b76360 RS |
3514 | mouse event; for instance, @code{[area4 mouse-1]} if the hot-spot's |
3515 | @var{id} is @code{area4}. | |
8241495d RS |
3516 | @end table |
3517 | ||
62fb5c66 DL |
3518 | @defun image-mask-p spec &optional frame |
3519 | @tindex image-mask-p | |
3520 | This function returns @code{t} if image @var{spec} has a mask bitmap. | |
3521 | @var{frame} is the frame on which the image will be displayed. | |
8d82c597 EZ |
3522 | @var{frame} @code{nil} or omitted means to use the selected frame |
3523 | (@pxref{Input Focus}). | |
62fb5c66 DL |
3524 | @end defun |
3525 | ||
8241495d RS |
3526 | @node XBM Images |
3527 | @subsection XBM Images | |
3528 | @cindex XBM | |
3529 | ||
3530 | To use XBM format, specify @code{xbm} as the image type. This image | |
3531 | format doesn't require an external library, so images of this type are | |
3532 | always supported. | |
3533 | ||
3534 | Additional image properties supported for the @code{xbm} image type are: | |
3535 | ||
3536 | @table @code | |
3537 | @item :foreground @var{foreground} | |
3538 | The value, @var{foreground}, should be a string specifying the image | |
0d88b7d0 GM |
3539 | foreground color, or @code{nil} for the default color. This color is |
3540 | used for each pixel in the XBM that is 1. The default is the frame's | |
3541 | foreground color. | |
8241495d RS |
3542 | |
3543 | @item :background @var{background} | |
3544 | The value, @var{background}, should be a string specifying the image | |
0d88b7d0 GM |
3545 | background color, or @code{nil} for the default color. This color is |
3546 | used for each pixel in the XBM that is 0. The default is the frame's | |
3547 | background color. | |
8241495d RS |
3548 | @end table |
3549 | ||
72821190 | 3550 | If you specify an XBM image using data within Emacs instead of an |
96f66dc5 | 3551 | external file, use the following three properties: |
8241495d RS |
3552 | |
3553 | @table @code | |
96f66dc5 GM |
3554 | @item :data @var{data} |
3555 | The value, @var{data}, specifies the contents of the image. | |
3556 | There are three formats you can use for @var{data}: | |
8241495d | 3557 | |
96f66dc5 GM |
3558 | @itemize @bullet |
3559 | @item | |
3560 | A vector of strings or bool-vectors, each specifying one line of the | |
3561 | image. Do specify @code{:height} and @code{:width}. | |
8241495d | 3562 | |
96f66dc5 GM |
3563 | @item |
3564 | A string containing the same byte sequence as an XBM file would contain. | |
3565 | You must not specify @code{:height} and @code{:width} in this case, | |
3566 | because omitting them is what indicates the data has the format of an | |
3567 | XBM file. The file contents specify the height and width of the image. | |
8241495d | 3568 | |
96f66dc5 GM |
3569 | @item |
3570 | A string or a bool-vector containing the bits of the image (plus perhaps | |
3571 | some extra bits at the end that will not be used). It should contain at | |
3572 | least @var{width} * @code{height} bits. In this case, you must specify | |
3573 | @code{:height} and @code{:width}, both to indicate that the string | |
3574 | contains just the bits rather than a whole XBM file, and to specify the | |
3575 | size of the image. | |
3576 | @end itemize | |
3577 | ||
3578 | @item :width @var{width} | |
3579 | The value, @var{width}, specifies the width of the image, in pixels. | |
3580 | ||
3581 | @item :height @var{height} | |
3582 | The value, @var{height}, specifies the height of the image, in pixels. | |
8241495d RS |
3583 | @end table |
3584 | ||
3585 | @node XPM Images | |
3586 | @subsection XPM Images | |
3587 | @cindex XPM | |
3588 | ||
72821190 RS |
3589 | To use XPM format, specify @code{xpm} as the image type. The |
3590 | additional image property @code{:color-symbols} is also meaningful with | |
3591 | the @code{xpm} image type: | |
8241495d RS |
3592 | |
3593 | @table @code | |
3594 | @item :color-symbols @var{symbols} | |
3595 | The value, @var{symbols}, should be an alist whose elements have the | |
3596 | form @code{(@var{name} . @var{color})}. In each element, @var{name} is | |
3597 | the name of a color as it appears in the image file, and @var{color} | |
3598 | specifies the actual color to use for displaying that name. | |
8241495d RS |
3599 | @end table |
3600 | ||
3601 | @node GIF Images | |
3602 | @subsection GIF Images | |
3603 | @cindex GIF | |
3604 | ||
3605 | For GIF images, specify image type @code{gif}. Because of the patents | |
3606 | in the US covering the LZW algorithm, the continued use of GIF format is | |
3607 | a problem for the whole Internet; to end this problem, it is a good idea | |
572fd5aa | 3608 | for everyone, even outside the US, to stop using GIFs right away |
8241495d RS |
3609 | (@uref{http://www.burnallgifs.org/}). But if you still want to use |
3610 | them, Emacs can display them. | |
3611 | ||
3612 | @table @code | |
3613 | @item :index @var{index} | |
3614 | You can use @code{:index} to specify one image from a GIF file that | |
3615 | contains more than one image. This property specifies use of image | |
00b3c1cd RS |
3616 | number @var{index} from the file. If the GIF file doesn't contain an |
3617 | image with index @var{index}, the image displays as a hollow box. | |
8241495d RS |
3618 | @end table |
3619 | ||
3620 | @ignore | |
3621 | This could be used to implement limited support for animated GIFs. | |
3622 | For example, the following function displays a multi-image GIF file | |
3623 | at point-min in the current buffer, switching between sub-images | |
3624 | every 0.1 seconds. | |
3625 | ||
3626 | (defun show-anim (file max) | |
3627 | "Display multi-image GIF file FILE which contains MAX subimages." | |
3628 | (display-anim (current-buffer) file 0 max t)) | |
3629 | ||
3630 | (defun display-anim (buffer file idx max first-time) | |
3631 | (when (= idx max) | |
3632 | (setq idx 0)) | |
3633 | (let ((img (create-image file nil :image idx))) | |
3634 | (save-excursion | |
3635 | (set-buffer buffer) | |
3636 | (goto-char (point-min)) | |
3637 | (unless first-time (delete-char 1)) | |
3638 | (insert-image img)) | |
3639 | (run-with-timer 0.1 nil 'display-anim buffer file (1+ idx) max nil))) | |
3640 | @end ignore | |
3641 | ||
3642 | @node Postscript Images | |
3643 | @subsection Postscript Images | |
3644 | @cindex Postscript images | |
3645 | ||
3646 | To use Postscript for an image, specify image type @code{postscript}. | |
3647 | This works only if you have Ghostscript installed. You must always use | |
3648 | these three properties: | |
3649 | ||
3650 | @table @code | |
3651 | @item :pt-width @var{width} | |
3652 | The value, @var{width}, specifies the width of the image measured in | |
3653 | points (1/72 inch). @var{width} must be an integer. | |
3654 | ||
3655 | @item :pt-height @var{height} | |
3656 | The value, @var{height}, specifies the height of the image in points | |
3657 | (1/72 inch). @var{height} must be an integer. | |
3658 | ||
3659 | @item :bounding-box @var{box} | |
3660 | The value, @var{box}, must be a list or vector of four integers, which | |
3661 | specifying the bounding box of the Postscript image, analogous to the | |
3662 | @samp{BoundingBox} comment found in Postscript files. | |
3663 | ||
3664 | @example | |
3665 | %%BoundingBox: 22 171 567 738 | |
3666 | @end example | |
3667 | @end table | |
3668 | ||
72821190 RS |
3669 | Displaying Postscript images from Lisp data is not currently |
3670 | implemented, but it may be implemented by the time you read this. | |
3671 | See the @file{etc/NEWS} file to make sure. | |
3672 | ||
8241495d RS |
3673 | @node Other Image Types |
3674 | @subsection Other Image Types | |
3675 | @cindex PBM | |
3676 | ||
3677 | For PBM images, specify image type @code{pbm}. Color, gray-scale and | |
7ccd82bd GM |
3678 | monochromatic images are supported. For mono PBM images, two additional |
3679 | image properties are supported. | |
3680 | ||
3681 | @table @code | |
3682 | @item :foreground @var{foreground} | |
3683 | The value, @var{foreground}, should be a string specifying the image | |
0d88b7d0 GM |
3684 | foreground color, or @code{nil} for the default color. This color is |
3685 | used for each pixel in the XBM that is 1. The default is the frame's | |
3686 | foreground color. | |
7ccd82bd GM |
3687 | |
3688 | @item :background @var{background} | |
3689 | The value, @var{background}, should be a string specifying the image | |
0d88b7d0 GM |
3690 | background color, or @code{nil} for the default color. This color is |
3691 | used for each pixel in the XBM that is 0. The default is the frame's | |
3692 | background color. | |
7ccd82bd | 3693 | @end table |
8241495d | 3694 | |
72821190 | 3695 | For JPEG images, specify image type @code{jpeg}. |
8241495d RS |
3696 | |
3697 | For TIFF images, specify image type @code{tiff}. | |
3698 | ||
3699 | For PNG images, specify image type @code{png}. | |
3700 | ||
3701 | @node Defining Images | |
3702 | @subsection Defining Images | |
3703 | ||
e3b9fc91 DL |
3704 | The functions @code{create-image}, @code{defimage} and |
3705 | @code{find-image} provide convenient ways to create image descriptors. | |
8241495d RS |
3706 | |
3707 | @defun create-image file &optional type &rest props | |
3708 | @tindex create-image | |
3709 | This function creates and returns an image descriptor which uses the | |
3710 | data in @var{file}. | |
3711 | ||
3712 | The optional argument @var{type} is a symbol specifying the image type. | |
3713 | If @var{type} is omitted or @code{nil}, @code{create-image} tries to | |
3714 | determine the image type from the file's first few bytes, or else | |
3715 | from the file's name. | |
3716 | ||
3717 | The remaining arguments, @var{props}, specify additional image | |
3718 | properties---for example, | |
3719 | ||
3720 | @example | |
3721 | (create-image "foo.xpm" 'xpm :heuristic-mask t) | |
3722 | @end example | |
3723 | ||
3724 | The function returns @code{nil} if images of this type are not | |
3725 | supported. Otherwise it returns an image descriptor. | |
3726 | @end defun | |
3727 | ||
11519a5e | 3728 | @defmac defimage symbol specs &optional doc |
8241495d | 3729 | @tindex defimage |
11519a5e EZ |
3730 | This macro defines @var{symbol} as an image name. The arguments |
3731 | @var{specs} is a list which specifies how to display the image. | |
3732 | The third argument, @var{doc}, is an optional documentation string. | |
8241495d RS |
3733 | |
3734 | Each argument in @var{specs} has the form of a property list, and each | |
11519a5e EZ |
3735 | one should specify at least the @code{:type} property and either the |
3736 | @code{:file} or the @code{:data} property. The value of @code{:type} | |
3737 | should be a symbol specifying the image type, the value of | |
3738 | @code{:file} is the file to load the image from, and the value of | |
3739 | @code{:data} is a string containing the actual image data. Here is an | |
3740 | example: | |
8241495d | 3741 | |
a40d4712 PR |
3742 | @example |
3743 | (defimage test-image | |
f43c34a0 RS |
3744 | ((:type xpm :file "~/test1.xpm") |
3745 | (:type xbm :file "~/test1.xbm"))) | |
a40d4712 | 3746 | @end example |
8241495d RS |
3747 | |
3748 | @code{defimage} tests each argument, one by one, to see if it is | |
3749 | usable---that is, if the type is supported and the file exists. The | |
3750 | first usable argument is used to make an image descriptor which is | |
11519a5e | 3751 | stored in @var{symbol}. |
8241495d | 3752 | |
11519a5e | 3753 | If none of the alternatives will work, then @var{symbol} is defined |
8241495d RS |
3754 | as @code{nil}. |
3755 | @end defmac | |
3756 | ||
e3b9fc91 DL |
3757 | @defun find-image specs |
3758 | @tindex find-image | |
3759 | This function provides a convenient way to find an image satisfying one | |
3760 | of a list of image specifications @var{specs}. | |
3761 | ||
3762 | Each specification in @var{specs} is a property list with contents | |
3763 | depending on image type. All specifications must at least contain the | |
3764 | properties @code{:type @var{type}} and either @w{@code{:file @var{file}}} | |
3765 | or @w{@code{:data @var{DATA}}}, where @var{type} is a symbol specifying | |
3766 | the image type, e.g.@: @code{xbm}, @var{file} is the file to load the | |
3767 | image from, and @var{data} is a string containing the actual image data. | |
3768 | The first specification in the list whose @var{type} is supported, and | |
3769 | @var{file} exists, is used to construct the image specification to be | |
3770 | returned. If no specification is satisfied, @code{nil} is returned. | |
3771 | ||
3772 | The image is looked for first on @code{load-path} and then in | |
3773 | @code{data-directory}. | |
3774 | @end defun | |
3775 | ||
8241495d RS |
3776 | @node Showing Images |
3777 | @subsection Showing Images | |
3778 | ||
3779 | You can use an image descriptor by setting up the @code{display} | |
3780 | property yourself, but it is easier to use the functions in this | |
3781 | section. | |
3782 | ||
9b6e4bc3 | 3783 | @defun insert-image image &optional string area slice |
8241495d RS |
3784 | This function inserts @var{image} in the current buffer at point. The |
3785 | value @var{image} should be an image descriptor; it could be a value | |
3786 | returned by @code{create-image}, or the value of a symbol defined with | |
a40d4712 PR |
3787 | @code{defimage}. The argument @var{string} specifies the text to put in |
3788 | the buffer to hold the image. | |
8241495d RS |
3789 | |
3790 | The argument @var{area} specifies whether to put the image in a margin. | |
3791 | If it is @code{left-margin}, the image appears in the left margin; | |
3792 | @code{right-margin} specifies the right margin. If @var{area} is | |
3793 | @code{nil} or omitted, the image is displayed at point within the | |
3794 | buffer's text. | |
3795 | ||
9b6e4bc3 KS |
3796 | The argument @var{slice} specifies a slice of the image to insert. If |
3797 | @var{slice} is @code{nil} or omitted the whole image is inserted. | |
26b76360 RS |
3798 | Otherwise, @var{slice} is a list @code{(@var{x} @var{y} @var{width} |
3799 | @var{height})} which specifies the @var{x} and @var{y} positions and | |
9b6e4bc3 | 3800 | @var{width} and @var{height} of the image area to insert. Integer |
26b76360 RS |
3801 | values are in units of pixels. A floating point number in the range |
3802 | 0.0--1.0 stands for that fraction of the width or height of the entire | |
3803 | image. | |
9b6e4bc3 | 3804 | |
a40d4712 PR |
3805 | Internally, this function inserts @var{string} in the buffer, and gives |
3806 | it a @code{display} property which specifies @var{image}. @xref{Display | |
8241495d RS |
3807 | Property}. |
3808 | @end defun | |
3809 | ||
9b6e4bc3 | 3810 | @defun insert-sliced-image image &optional string area rows cols |
26b76360 RS |
3811 | This function inserts @var{image} in the current buffer at point, like |
3812 | @code{insert-image}, but splits the image into @var{rows}x@var{cols} | |
3813 | equally sized slices. | |
9b6e4bc3 KS |
3814 | @end defun |
3815 | ||
bb2337f5 | 3816 | @defun put-image image pos &optional string area |
8241495d RS |
3817 | This function puts image @var{image} in front of @var{pos} in the |
3818 | current buffer. The argument @var{pos} should be an integer or a | |
3819 | marker. It specifies the buffer position where the image should appear. | |
bb2337f5 DL |
3820 | The argument @var{string} specifies the text that should hold the image |
3821 | as an alternative to the default. | |
8241495d RS |
3822 | |
3823 | The argument @var{image} must be an image descriptor, perhaps returned | |
3824 | by @code{create-image} or stored by @code{defimage}. | |
3825 | ||
3826 | The argument @var{area} specifies whether to put the image in a margin. | |
3827 | If it is @code{left-margin}, the image appears in the left margin; | |
3828 | @code{right-margin} specifies the right margin. If @var{area} is | |
3829 | @code{nil} or omitted, the image is displayed at point within the | |
3830 | buffer's text. | |
3831 | ||
3832 | Internally, this function creates an overlay, and gives it a | |
3833 | @code{before-string} property containing text that has a @code{display} | |
3834 | property whose value is the image. (Whew!) | |
3835 | @end defun | |
3836 | ||
3837 | @defun remove-images start end &optional buffer | |
3838 | This function removes images in @var{buffer} between positions | |
3839 | @var{start} and @var{end}. If @var{buffer} is omitted or @code{nil}, | |
3840 | images are removed from the current buffer. | |
3841 | ||
05aea714 | 3842 | This removes only images that were put into @var{buffer} the way |
8241495d RS |
3843 | @code{put-image} does it, not images that were inserted with |
3844 | @code{insert-image} or in other ways. | |
3845 | @end defun | |
3846 | ||
e3b9fc91 DL |
3847 | @defun image-size spec &optional pixels frame |
3848 | @tindex image-size | |
3849 | This function returns the size of an image as a pair | |
3850 | @w{@code{(@var{width} . @var{height})}}. @var{spec} is an image | |
9a8dc0d3 RS |
3851 | specification. @var{pixels} non-@code{nil} means return sizes |
3852 | measured in pixels, otherwise return sizes measured in canonical | |
3853 | character units (fractions of the width/height of the frame's default | |
3854 | font). @var{frame} is the frame on which the image will be displayed. | |
8d82c597 EZ |
3855 | @var{frame} null or omitted means use the selected frame (@pxref{Input |
3856 | Focus}). | |
e3b9fc91 DL |
3857 | @end defun |
3858 | ||
8241495d RS |
3859 | @node Image Cache |
3860 | @subsection Image Cache | |
3861 | ||
3862 | Emacs stores images in an image cache when it displays them, so it can | |
3863 | display them again more efficiently. It removes an image from the cache | |
3864 | when it hasn't been displayed for a specified period of time. | |
3865 | ||
3e8b2a01 GM |
3866 | When an image is looked up in the cache, its specification is compared |
3867 | with cached image specifications using @code{equal}. This means that | |
3868 | all images with equal specifications share the same image in the cache. | |
3869 | ||
8241495d RS |
3870 | @defvar image-cache-eviction-delay |
3871 | @tindex image-cache-eviction-delay | |
3872 | This variable specifies the number of seconds an image can remain in the | |
3873 | cache without being displayed. When an image is not displayed for this | |
3874 | length of time, Emacs removes it from the image cache. | |
3875 | ||
3876 | If the value is @code{nil}, Emacs does not remove images from the cache | |
3877 | except when you explicitly clear it. This mode can be useful for | |
3878 | debugging. | |
3879 | @end defvar | |
3880 | ||
3881 | @defun clear-image-cache &optional frame | |
3882 | @tindex clear-image-cache | |
3883 | This function clears the image cache. If @var{frame} is non-@code{nil}, | |
3884 | only the cache for that frame is cleared. Otherwise all frames' caches | |
3885 | are cleared. | |
3886 | @end defun | |
a065c889 | 3887 | |
02c77ee9 MB |
3888 | @node Buttons |
3889 | @section Buttons | |
a3cb3b2e | 3890 | @cindex buttons |
02c77ee9 MB |
3891 | @cindex buttons in buffers |
3892 | @cindex clickable buttons in buffers | |
3893 | ||
3894 | The @emph{button} package defines functions for inserting and | |
3895 | manipulating clickable (with the mouse, or via keyboard commands) | |
a3cb3b2e MB |
3896 | buttons in Emacs buffers, such as might be used for help hyper-links, |
3897 | etc. Emacs uses buttons for the hyper-links in help text and the like. | |
02c77ee9 MB |
3898 | |
3899 | A button is essentially a set of properties attached (via text | |
058296d3 | 3900 | properties or overlays) to a region of text in an Emacs buffer, which |
02c77ee9 MB |
3901 | are called its button properties. @xref{Button Properties}. |
3902 | ||
3903 | One of the these properties (@code{action}) is a function, which will | |
3904 | be called when the user invokes it using the keyboard or the mouse. | |
3905 | The invoked function may then examine the button and use its other | |
3906 | properties as desired. | |
3907 | ||
058296d3 | 3908 | In some ways the Emacs button package duplicates functionality offered |
02c77ee9 MB |
3909 | by the widget package (@pxref{Top, , Introduction, widget, The Emacs |
3910 | Widget Library}), but the button package has the advantage that it is | |
3911 | much faster, much smaller, and much simpler to use (for elisp | |
3912 | programmers---for users, the result is about the same). The extra | |
3913 | speed and space savings are useful mainly if you need to create many | |
3914 | buttons in a buffer (for instance an @code{*Apropos*} buffer uses | |
3915 | buttons to make entries clickable, and may contain many thousands of | |
3916 | entries). | |
3917 | ||
3918 | @menu | |
3919 | * Button Properties:: Button properties with special meanings. | |
3920 | * Button Types:: Defining common properties for classes of buttons. | |
058296d3 | 3921 | * Making Buttons:: Adding buttons to Emacs buffers. |
02c77ee9 MB |
3922 | * Manipulating Buttons:: Getting and setting properties of buttons. |
3923 | * Button Buffer Commands:: Buffer-wide commands and bindings for buttons. | |
9b6e4bc3 | 3924 | * Manipulating Button Types:: |
02c77ee9 MB |
3925 | @end menu |
3926 | ||
3927 | @node Button Properties | |
3928 | @subsection Button Properties | |
3929 | @cindex button properties | |
3930 | ||
3931 | Buttons have an associated list of properties defining their | |
3932 | appearance and behavior, and other arbitrary properties may be used | |
3933 | for application specific purposes. | |
3934 | ||
3935 | Some properties that have special meaning to the button package | |
3936 | include: | |
3937 | ||
3938 | @table @code | |
3939 | ||
3940 | @item action | |
a3cb3b2e | 3941 | @kindex action @r{(button property)} |
02c77ee9 MB |
3942 | The function to call when the user invokes the button, which is passed |
3943 | the single argument @var{button}. By default this is @code{ignore}, | |
3944 | which does nothing. | |
3945 | ||
3946 | @item mouse-action | |
a3cb3b2e | 3947 | @kindex mouse-action @r{(button property)} |
02c77ee9 MB |
3948 | This is similar to @code{action}, and when present, will be used |
3949 | instead of @code{action} for button invocations resulting from | |
3950 | mouse-clicks (instead of the user hitting @key{RET}). If not | |
3951 | present, mouse-clicks use @code{action} instead. | |
3952 | ||
3953 | @item face | |
a3cb3b2e | 3954 | @kindex face @r{(button property)} |
058296d3 | 3955 | This is an Emacs face controlling how buttons of this type are |
02c77ee9 MB |
3956 | displayed; by default this is the @code{button} face. |
3957 | ||
3958 | @item mouse-face | |
a3cb3b2e | 3959 | @kindex mouse-face @r{(button property)} |
02c77ee9 MB |
3960 | This is an additional face which controls appearance during |
3961 | mouse-overs (merged with the usual button face); by default this is | |
058296d3 | 3962 | the usual Emacs @code{highlight} face. |
02c77ee9 MB |
3963 | |
3964 | @item keymap | |
a3cb3b2e | 3965 | @kindex keymap @r{(button property)} |
02c77ee9 MB |
3966 | The button's keymap, defining bindings active within the button |
3967 | region. By default this is the usual button region keymap, stored | |
3968 | in the variable @code{button-map}, which defines @key{RET} and | |
eb3c144c | 3969 | @key{mouse-2} to invoke the button. |
02c77ee9 MB |
3970 | |
3971 | @item type | |
a3cb3b2e | 3972 | @kindex type @r{(button property)} |
02c77ee9 MB |
3973 | The button-type of the button. When creating a button, this is |
3974 | usually specified using the @code{:type} keyword argument. | |
3975 | @xref{Button Types}. | |
3976 | ||
3977 | @item help-echo | |
a3cb3b2e | 3978 | @kindex help-index @r{(button property)} |
058296d3 | 3979 | A string displayed by the Emacs tool-tip help system; by default, |
02c77ee9 MB |
3980 | @code{"mouse-2, RET: Push this button"}. |
3981 | ||
3982 | @item button | |
a3cb3b2e | 3983 | @kindex button @r{(button property)} |
02c77ee9 MB |
3984 | All buttons have a non-@code{nil} @code{button} property, which may be useful |
3985 | in finding regions of text that comprise buttons (which is what the | |
3986 | standard button functions do). | |
3987 | @end table | |
3988 | ||
3989 | There are other properties defined for the regions of text in a | |
3990 | button, but these are not generally interesting for typical uses. | |
3991 | ||
3992 | @node Button Types | |
3993 | @subsection Button Types | |
3994 | @cindex button types | |
3995 | ||
3996 | Every button has a button @emph{type}, which defines default values | |
a3cb3b2e MB |
3997 | for the button's properties. Button types are arranged in a |
3998 | hierarchy, with specialized types inheriting from more general types, | |
3999 | so that it's easy to define special-purpose types of buttons for | |
4000 | specific tasks. | |
02c77ee9 MB |
4001 | |
4002 | @defun define-button-type name &rest properties | |
4003 | @tindex define-button-type | |
4004 | Define a `button type' called @var{name}. The remaining arguments | |
4005 | form a sequence of @var{property value} pairs, specifying default | |
4006 | property values for buttons with this type (a button's type may be set | |
4007 | by giving it a @code{type} property when creating the button, using | |
4008 | the @code{:type} keyword argument). | |
4009 | ||
4010 | In addition, the keyword argument @code{:supertype} may be used to | |
4011 | specify a button-type from which @var{name} inherits its default | |
4012 | property values. Note that this inheritance happens only when | |
4013 | @var{name} is defined; subsequent changes to a supertype are not | |
4014 | reflected in its subtypes. | |
4015 | @end defun | |
4016 | ||
4017 | Using @code{define-button-type} to define default properties for | |
a3cb3b2e MB |
4018 | buttons is not necessary---buttons without any specified type use the |
4019 | built-in button-type @code{button}---but it is is encouraged, since | |
4020 | doing so usually makes the resulting code clearer and more efficient. | |
02c77ee9 | 4021 | |
a3cb3b2e MB |
4022 | @node Making Buttons |
4023 | @subsection Making Buttons | |
02c77ee9 MB |
4024 | @cindex making buttons |
4025 | ||
4026 | Buttons are associated with a region of text, using an overlay or | |
4027 | text-properties to hold button-specific information, all of which are | |
4028 | initialized from the button's type (which defaults to the built-in | |
058296d3 | 4029 | button type @code{button}). Like all Emacs text, the appearance of |
02c77ee9 MB |
4030 | the button is governed by the @code{face} property; by default (via |
4031 | the @code{face} property inherited from the @code{button} button-type) | |
4032 | this is a simple underline, like a typical web-page link. | |
4033 | ||
4034 | For convenience, there are two sorts of button-creation functions, | |
4035 | those that add button properties to an existing region of a buffer, | |
4036 | called @code{make-...button}, and those also insert the button text, | |
4037 | called @code{insert-...button}. | |
4038 | ||
4039 | The button-creation functions all take the @code{&rest} argument | |
4040 | @var{properties}, which should be a sequence of @var{property value} | |
4041 | pairs, specifying properties to add to the button; see @ref{Button | |
4042 | Properties}. In addition, the keyword argument @code{:type} may be | |
4043 | used to specify a button-type from which to inherit other properties; | |
4044 | see @ref{Button Types}. Any properties not explicitly specified | |
4045 | during creation will be inherited from the button's type (if the type | |
4046 | defines such a property). | |
4047 | ||
4048 | The following functions add a button using an overlay | |
4049 | (@pxref{Overlays}) to hold the button properties: | |
4050 | ||
4051 | @defun make-button beg end &rest properties | |
4052 | @tindex make-button | |
4053 | Make a button from @var{beg} to @var{end} in the current buffer. | |
4054 | @end defun | |
4055 | ||
4056 | @defun insert-button label &rest properties | |
4057 | @tindex insert-button | |
4058 | Insert a button with the label @var{label}. | |
4059 | @end defun | |
4060 | ||
058296d3 | 4061 | The following functions are similar, but use Emacs text-properties |
02c77ee9 MB |
4062 | (@pxref{Text Properties}) to hold the button properties, making the |
4063 | button actually part of the text instead of being a property of the | |
4064 | buffer (using text-properties is usually faster than using overlays, | |
4065 | so this may be preferable when creating large numbers of buttons): | |
4066 | ||
4067 | @defun make-text-button beg end &rest properties | |
4068 | @tindex make-text-button | |
4069 | Make a button from @var{beg} to @var{end} in the current buffer, using | |
4070 | text-properties. | |
4071 | @end defun | |
4072 | ||
4073 | @defun insert-text-button label &rest properties | |
4074 | @tindex insert-text-button | |
4075 | Insert a button with the label @var{label}, using text-properties. | |
4076 | @end defun | |
4077 | ||
4078 | Buttons using text-properties retain no markers into the buffer are | |
4079 | retained, which is important for speed in cases where there are | |
4080 | extremely large numbers of buttons. | |
4081 | ||
4082 | @node Manipulating Buttons | |
4083 | @subsection Manipulating Buttons | |
4084 | @cindex manipulating buttons | |
4085 | ||
4086 | These are functions for getting and setting properties of buttons. | |
4087 | Often these are used by a button's invocation function to determine | |
4088 | what to do. | |
4089 | ||
4090 | Where a @var{button} parameter is specified, it means an object | |
4091 | referring to a specific button, either an overlay (for overlay | |
4092 | buttons), or a buffer-position or marker (for text property buttons). | |
4093 | Such an object is passed as the first argument to a button's | |
4094 | invocation function when it is invoked. | |
4095 | ||
4096 | @defun button-start button | |
4097 | @tindex button-start | |
4098 | Return the position at which @var{button} starts. | |
4099 | @end defun | |
4100 | ||
4101 | @defun button-end button | |
4102 | @tindex button-end | |
4103 | Return the position at which @var{button} ends. | |
4104 | @end defun | |
4105 | ||
4106 | @defun button-get button prop | |
4107 | @tindex button-get | |
4108 | Get the property of button @var{button} named @var{prop}. | |
4109 | @end defun | |
4110 | ||
4111 | @defun button-put button prop val | |
4112 | @tindex button-put | |
4113 | Set @var{button}'s @var{prop} property to @var{val}. | |
4114 | @end defun | |
4115 | ||
4116 | @defun button-activate button &optional use-mouse-action | |
4117 | @tindex button-activate | |
4118 | Call @var{button}'s @code{action} property (i.e., invoke it). If | |
4119 | @var{use-mouse-action} is non-@code{nil}, try to invoke the button's | |
a3cb3b2e MB |
4120 | @code{mouse-action} property instead of @code{action}; if the button |
4121 | has no @code{mouse-action} property, use @code{action} as normal. | |
02c77ee9 MB |
4122 | @end defun |
4123 | ||
4124 | @defun button-label button | |
4125 | @tindex button-label | |
4126 | Return @var{button}'s text label. | |
4127 | @end defun | |
4128 | ||
4129 | @defun button-type button | |
4130 | @tindex button-type | |
4131 | Return @var{button}'s button-type. | |
4132 | @end defun | |
4133 | ||
4134 | @defun button-has-type-p button type | |
4135 | @tindex button-has-type-p | |
4136 | Return @code{t} if @var{button} has button-type @var{type}, or one of | |
4137 | @var{type}'s subtypes. | |
4138 | @end defun | |
4139 | ||
4140 | @defun button-at pos | |
4141 | @tindex button-at | |
4142 | Return the button at position @var{pos} in the current buffer, or @code{nil}. | |
4143 | @end defun | |
4144 | ||
4145 | @node Button Buffer Commands | |
4146 | @subsection Button Buffer Commands | |
4147 | @cindex button buffer commands | |
4148 | ||
4149 | These are commands and functions for locating and operating on | |
058296d3 | 4150 | buttons in an Emacs buffer. |
02c77ee9 MB |
4151 | |
4152 | @code{push-button} is the command that a user uses to actually `push' | |
4153 | a button, and is bound by default in the button itself to @key{RET} | |
eb3c144c | 4154 | and to @key{mouse-2} using a region-specific keymap. Commands |
02c77ee9 MB |
4155 | that are useful outside the buttons itself, such as |
4156 | @code{forward-button} and @code{backward-button} are additionally | |
4157 | available in the keymap stored in @code{button-buffer-map}; a mode | |
4158 | which uses buttons may want to use @code{button-buffer-map} as a | |
4159 | parent keymap for its keymap. | |
4160 | ||
4161 | @deffn Command push-button &optional pos use-mouse-action | |
4162 | @tindex push-button | |
4163 | Perform the action specified by a button at location @var{pos}. | |
4164 | @var{pos} may be either a buffer position or a mouse-event. If | |
a3cb3b2e MB |
4165 | @var{use-mouse-action} is non-@code{nil}, or @var{pos} is a |
4166 | mouse-event (@pxref{Mouse Events}), try to invoke the button's | |
4167 | @code{mouse-action} property instead of @code{action}; if the button | |
4168 | has no @code{mouse-action} property, use @code{action} as normal. | |
4169 | @var{pos} defaults to point, except when @code{push-button} is invoked | |
4170 | interactively as the result of a mouse-event, in which case, the mouse | |
4171 | event's position is used. If there's no button at @var{pos}, do | |
02c77ee9 MB |
4172 | nothing and return @code{nil}, otherwise return @code{t}. |
4173 | @end deffn | |
4174 | ||
4175 | @deffn Command forward-button n &optional wrap display-message | |
4176 | @tindex forward-button | |
4177 | Move to the @var{n}th next button, or @var{n}th previous button if | |
4178 | @var{n} is negative. If @var{n} is zero, move to the start of any | |
4179 | button at point. If @var{wrap} is non-@code{nil}, moving past either | |
4180 | end of the buffer continues from the other end. If | |
4181 | @var{display-message} is non-@code{nil}, the button's help-echo string | |
a3cb3b2e MB |
4182 | is displayed. Any button with a non-@code{nil} @code{skip} property |
4183 | is skipped over. Returns the button found. | |
02c77ee9 MB |
4184 | @end deffn |
4185 | ||
4186 | @deffn Command backward-button n &optional wrap display-message | |
4187 | @tindex backward-button | |
4188 | Move to the @var{n}th previous button, or @var{n}th next button if | |
4189 | @var{n} is negative. If @var{n} is zero, move to the start of any | |
4190 | button at point. If @var{wrap} is non-@code{nil}, moving past either | |
4191 | end of the buffer continues from the other end. If | |
4192 | @var{display-message} is non-@code{nil}, the button's help-echo string | |
a3cb3b2e MB |
4193 | is displayed. Any button with a non-@code{nil} @code{skip} property |
4194 | is skipped over. Returns the button found. | |
02c77ee9 MB |
4195 | @end deffn |
4196 | ||
4197 | @defun next-button pos &optional count-current | |
4198 | @tindex next-button | |
4199 | Return the next button after position @var{pos} in the current buffer. | |
4200 | If @var{count-current} is non-@code{nil}, count any button at | |
4201 | @var{pos} in the search, instead of starting at the next button. | |
4202 | @end defun | |
4203 | ||
4204 | @defun previous-button pos &optional count-current | |
4205 | @tindex previous-button | |
4206 | Return the @var{n}th button before position @var{pos} in the current | |
4207 | buffer. If @var{count-current} is non-@code{nil}, count any button at | |
4208 | @var{pos} in the search, instead of starting at the next button. | |
4209 | @end defun | |
4210 | ||
4211 | @node Manipulating Button Types | |
4212 | @subsection Manipulating Button Types | |
4213 | @cindex manipulating button types | |
4214 | ||
4215 | @defun button-type-put type prop val | |
4216 | @tindex button-type-put | |
4217 | Set the button-type @var{type}'s @var{prop} property to @var{val}. | |
4218 | @end defun | |
4219 | ||
4220 | @defun button-type-get type prop | |
4221 | @tindex button-type-get | |
4222 | Get the property of button-type @var{type} named @var{prop}. | |
4223 | @end defun | |
4224 | ||
4225 | @defun button-type-subtype-p type supertype | |
4226 | @tindex button-type-subtype-p | |
4227 | Return @code{t} if button-type @var{type} is a subtype of @var{supertype}. | |
4228 | @end defun | |
4229 | ||
42b85554 RS |
4230 | @node Blinking |
4231 | @section Blinking Parentheses | |
4232 | @cindex parenthesis matching | |
4233 | @cindex blinking | |
4234 | @cindex balancing parentheses | |
4235 | @cindex close parenthesis | |
4236 | ||
4237 | This section describes the mechanism by which Emacs shows a matching | |
4238 | open parenthesis when the user inserts a close parenthesis. | |
4239 | ||
42b85554 RS |
4240 | @defvar blink-paren-function |
4241 | The value of this variable should be a function (of no arguments) to | |
4242 | be called whenever a character with close parenthesis syntax is inserted. | |
4243 | The value of @code{blink-paren-function} may be @code{nil}, in which | |
4244 | case nothing is done. | |
42b85554 RS |
4245 | @end defvar |
4246 | ||
1911e6e5 | 4247 | @defopt blink-matching-paren |
42b85554 RS |
4248 | If this variable is @code{nil}, then @code{blink-matching-open} does |
4249 | nothing. | |
1911e6e5 | 4250 | @end defopt |
42b85554 | 4251 | |
1911e6e5 | 4252 | @defopt blink-matching-paren-distance |
42b85554 RS |
4253 | This variable specifies the maximum distance to scan for a matching |
4254 | parenthesis before giving up. | |
1911e6e5 | 4255 | @end defopt |
42b85554 | 4256 | |
1911e6e5 | 4257 | @defopt blink-matching-delay |
bfe721d1 KH |
4258 | This variable specifies the number of seconds for the cursor to remain |
4259 | at the matching parenthesis. A fraction of a second often gives | |
4260 | good results, but the default is 1, which works on all systems. | |
1911e6e5 | 4261 | @end defopt |
bfe721d1 | 4262 | |
1911e6e5 | 4263 | @deffn Command blink-matching-open |
42b85554 RS |
4264 | This function is the default value of @code{blink-paren-function}. It |
4265 | assumes that point follows a character with close parenthesis syntax and | |
4266 | moves the cursor momentarily to the matching opening character. If that | |
4267 | character is not already on the screen, it displays the character's | |
4268 | context in the echo area. To avoid long delays, this function does not | |
4269 | search farther than @code{blink-matching-paren-distance} characters. | |
4270 | ||
4271 | Here is an example of calling this function explicitly. | |
4272 | ||
4273 | @smallexample | |
4274 | @group | |
4275 | (defun interactive-blink-matching-open () | |
4276 | @c Do not break this line! -- rms. | |
4277 | @c The first line of a doc string | |
4278 | @c must stand alone. | |
4279 | "Indicate momentarily the start of sexp before point." | |
4280 | (interactive) | |
4281 | @end group | |
4282 | @group | |
4283 | (let ((blink-matching-paren-distance | |
4284 | (buffer-size)) | |
4285 | (blink-matching-paren t)) | |
4286 | (blink-matching-open))) | |
4287 | @end group | |
4288 | @end smallexample | |
1911e6e5 | 4289 | @end deffn |
42b85554 RS |
4290 | |
4291 | @node Inverse Video | |
4292 | @section Inverse Video | |
4293 | @cindex Inverse Video | |
4294 | ||
4295 | @defopt inverse-video | |
4296 | @cindex highlighting | |
4297 | This variable controls whether Emacs uses inverse video for all text | |
4298 | on the screen. Non-@code{nil} means yes, @code{nil} means no. The | |
4299 | default is @code{nil}. | |
4300 | @end defopt | |
4301 | ||
4302 | @defopt mode-line-inverse-video | |
a40d4712 PR |
4303 | This variable controls the use of inverse video for mode lines and menu |
4304 | bars. If it is non-@code{nil}, then these lines are displayed in | |
05aea714 | 4305 | inverse video. Otherwise, these lines are displayed normally, just like |
a40d4712 PR |
4306 | other text. The default is @code{t}. |
4307 | ||
4308 | For window frames, this feature actually applies the face named | |
4309 | @code{mode-line}; that face is normally set up as the inverse of the | |
4310 | default face, unless you change it. | |
42b85554 RS |
4311 | @end defopt |
4312 | ||
4313 | @node Usual Display | |
4314 | @section Usual Display Conventions | |
4315 | ||
4316 | The usual display conventions define how to display each character | |
4317 | code. You can override these conventions by setting up a display table | |
4318 | (@pxref{Display Tables}). Here are the usual display conventions: | |
4319 | ||
4320 | @itemize @bullet | |
4321 | @item | |
4322 | Character codes 32 through 126 map to glyph codes 32 through 126. | |
4323 | Normally this means they display as themselves. | |
4324 | ||
4325 | @item | |
4326 | Character code 9 is a horizontal tab. It displays as whitespace | |
4327 | up to a position determined by @code{tab-width}. | |
4328 | ||
4329 | @item | |
4330 | Character code 10 is a newline. | |
4331 | ||
4332 | @item | |
4333 | All other codes in the range 0 through 31, and code 127, display in one | |
78608595 | 4334 | of two ways according to the value of @code{ctl-arrow}. If it is |
42b85554 | 4335 | non-@code{nil}, these codes map to sequences of two glyphs, where the |
ad800164 | 4336 | first glyph is the @acronym{ASCII} code for @samp{^}. (A display table can |
42b85554 RS |
4337 | specify a glyph to use instead of @samp{^}.) Otherwise, these codes map |
4338 | just like the codes in the range 128 to 255. | |
4339 | ||
8241495d RS |
4340 | On MS-DOS terminals, Emacs arranges by default for the character code |
4341 | 127 to be mapped to the glyph code 127, which normally displays as an | |
ad800164 | 4342 | empty polygon. This glyph is used to display non-@acronym{ASCII} characters |
8241495d RS |
4343 | that the MS-DOS terminal doesn't support. @xref{MS-DOS and MULE,,, |
4344 | emacs, The GNU Emacs Manual}. | |
4345 | ||
42b85554 RS |
4346 | @item |
4347 | Character codes 128 through 255 map to sequences of four glyphs, where | |
ad800164 | 4348 | the first glyph is the @acronym{ASCII} code for @samp{\}, and the others are |
a9f0a989 | 4349 | digit characters representing the character code in octal. (A display |
969fe9b5 RS |
4350 | table can specify a glyph to use instead of @samp{\}.) |
4351 | ||
4352 | @item | |
4353 | Multibyte character codes above 256 are displayed as themselves, or as a | |
4354 | question mark or empty box if the terminal cannot display that | |
4355 | character. | |
42b85554 RS |
4356 | @end itemize |
4357 | ||
4358 | The usual display conventions apply even when there is a display | |
4359 | table, for any character whose entry in the active display table is | |
4360 | @code{nil}. Thus, when you set up a display table, you need only | |
969fe9b5 | 4361 | specify the characters for which you want special behavior. |
42b85554 | 4362 | |
b6954afd RS |
4363 | These display rules apply to carriage return (character code 13), when |
4364 | it appears in the buffer. But that character may not appear in the | |
4365 | buffer where you expect it, if it was eliminated as part of end-of-line | |
15da7853 | 4366 | conversion (@pxref{Coding System Basics}). |
b6954afd | 4367 | |
42b85554 RS |
4368 | These variables affect the way certain characters are displayed on the |
4369 | screen. Since they change the number of columns the characters occupy, | |
f9f59935 RS |
4370 | they also affect the indentation functions. These variables also affect |
4371 | how the mode line is displayed; if you want to force redisplay of the | |
4372 | mode line using the new values, call the function | |
4373 | @code{force-mode-line-update} (@pxref{Mode Line Format}). | |
42b85554 RS |
4374 | |
4375 | @defopt ctl-arrow | |
4376 | @cindex control characters in display | |
4377 | This buffer-local variable controls how control characters are | |
4378 | displayed. If it is non-@code{nil}, they are displayed as a caret | |
4379 | followed by the character: @samp{^A}. If it is @code{nil}, they are | |
4380 | displayed as a backslash followed by three octal digits: @samp{\001}. | |
4381 | @end defopt | |
4382 | ||
4383 | @c Following may have overfull hbox. | |
4384 | @defvar default-ctl-arrow | |
4385 | The value of this variable is the default value for @code{ctl-arrow} in | |
4386 | buffers that do not override it. @xref{Default Value}. | |
4387 | @end defvar | |
4388 | ||
2468d0c0 DL |
4389 | @defopt indicate-empty-lines |
4390 | @tindex indicate-empty-lines | |
6e2391a8 | 4391 | @cindex fringes, and empty line indication |
8a6ca431 RS |
4392 | When this is non-@code{nil}, Emacs displays a special glyph in the |
4393 | fringe of each empty line at the end of the buffer, on terminals that | |
4394 | support it (window systems). @xref{Fringes}. | |
2468d0c0 DL |
4395 | @end defopt |
4396 | ||
42b85554 RS |
4397 | @defopt tab-width |
4398 | The value of this variable is the spacing between tab stops used for | |
a40d4712 PR |
4399 | displaying tab characters in Emacs buffers. The value is in units of |
4400 | columns, and the default is 8. Note that this feature is completely | |
4401 | independent of the user-settable tab stops used by the command | |
4402 | @code{tab-to-tab-stop}. @xref{Indent Tabs}. | |
42b85554 RS |
4403 | @end defopt |
4404 | ||
4405 | @node Display Tables | |
4406 | @section Display Tables | |
4407 | ||
4408 | @cindex display table | |
969fe9b5 RS |
4409 | You can use the @dfn{display table} feature to control how all possible |
4410 | character codes display on the screen. This is useful for displaying | |
ad800164 | 4411 | European languages that have letters not in the @acronym{ASCII} character |
969fe9b5 | 4412 | set. |
42b85554 RS |
4413 | |
4414 | The display table maps each character code into a sequence of | |
8241495d | 4415 | @dfn{glyphs}, each glyph being a graphic that takes up one character |
42b85554 RS |
4416 | position on the screen. You can also define how to display each glyph |
4417 | on your terminal, using the @dfn{glyph table}. | |
4418 | ||
f9f59935 RS |
4419 | Display tables affect how the mode line is displayed; if you want to |
4420 | force redisplay of the mode line using a new display table, call | |
4421 | @code{force-mode-line-update} (@pxref{Mode Line Format}). | |
4422 | ||
42b85554 | 4423 | @menu |
02c77ee9 MB |
4424 | * Display Table Format:: What a display table consists of. |
4425 | * Active Display Table:: How Emacs selects a display table to use. | |
4426 | * Glyphs:: How to define a glyph, and what glyphs mean. | |
42b85554 RS |
4427 | @end menu |
4428 | ||
4429 | @node Display Table Format | |
4430 | @subsection Display Table Format | |
4431 | ||
a9f0a989 RS |
4432 | A display table is actually a char-table (@pxref{Char-Tables}) with |
4433 | @code{display-table} as its subtype. | |
42b85554 RS |
4434 | |
4435 | @defun make-display-table | |
4436 | This creates and returns a display table. The table initially has | |
4437 | @code{nil} in all elements. | |
4438 | @end defun | |
4439 | ||
f9f59935 RS |
4440 | The ordinary elements of the display table are indexed by character |
4441 | codes; the element at index @var{c} says how to display the character | |
4442 | code @var{c}. The value should be @code{nil} or a vector of glyph | |
4443 | values (@pxref{Glyphs}). If an element is @code{nil}, it says to | |
4444 | display that character according to the usual display conventions | |
4445 | (@pxref{Usual Display}). | |
22697dac KH |
4446 | |
4447 | If you use the display table to change the display of newline | |
4448 | characters, the whole buffer will be displayed as one long ``line.'' | |
42b85554 | 4449 | |
f9f59935 | 4450 | The display table also has six ``extra slots'' which serve special |
969fe9b5 RS |
4451 | purposes. Here is a table of their meanings; @code{nil} in any slot |
4452 | means to use the default for that slot, as stated below. | |
42b85554 RS |
4453 | |
4454 | @table @asis | |
f9f59935 | 4455 | @item 0 |
42b85554 | 4456 | The glyph for the end of a truncated screen line (the default for this |
8241495d RS |
4457 | is @samp{$}). @xref{Glyphs}. Newer Emacs versions, on some platforms, |
4458 | display arrows to indicate truncation---the display table has no effect | |
4459 | in these situations. | |
f9f59935 | 4460 | @item 1 |
42b85554 | 4461 | The glyph for the end of a continued line (the default is @samp{\}). |
8241495d | 4462 | Newer Emacs versions, on some platforms, display curved arrows to |
c2efe6c0 | 4463 | indicate continuation---the display table has no effect in these |
8241495d | 4464 | situations. |
f9f59935 | 4465 | @item 2 |
42b85554 RS |
4466 | The glyph for indicating a character displayed as an octal character |
4467 | code (the default is @samp{\}). | |
f9f59935 | 4468 | @item 3 |
42b85554 | 4469 | The glyph for indicating a control character (the default is @samp{^}). |
f9f59935 | 4470 | @item 4 |
42b85554 RS |
4471 | A vector of glyphs for indicating the presence of invisible lines (the |
4472 | default is @samp{...}). @xref{Selective Display}. | |
f9f59935 | 4473 | @item 5 |
50b04c36 | 4474 | The glyph used to draw the border between side-by-side windows (the |
8241495d RS |
4475 | default is @samp{|}). @xref{Splitting Windows}. This takes effect only |
4476 | when there are no scroll bars; if scroll bars are supported and in use, | |
4477 | a scroll bar separates the two windows. | |
42b85554 RS |
4478 | @end table |
4479 | ||
4480 | For example, here is how to construct a display table that mimics the | |
4481 | effect of setting @code{ctl-arrow} to a non-@code{nil} value: | |
4482 | ||
4483 | @example | |
4484 | (setq disptab (make-display-table)) | |
4485 | (let ((i 0)) | |
4486 | (while (< i 32) | |
4487 | (or (= i ?\t) (= i ?\n) | |
4488 | (aset disptab i (vector ?^ (+ i 64)))) | |
4489 | (setq i (1+ i))) | |
4490 | (aset disptab 127 (vector ?^ ??))) | |
4491 | @end example | |
4492 | ||
f9f59935 RS |
4493 | @defun display-table-slot display-table slot |
4494 | This function returns the value of the extra slot @var{slot} of | |
4495 | @var{display-table}. The argument @var{slot} may be a number from 0 to | |
4496 | 5 inclusive, or a slot name (symbol). Valid symbols are | |
4497 | @code{truncation}, @code{wrap}, @code{escape}, @code{control}, | |
4498 | @code{selective-display}, and @code{vertical-border}. | |
4499 | @end defun | |
4500 | ||
f9f59935 RS |
4501 | @defun set-display-table-slot display-table slot value |
4502 | This function stores @var{value} in the extra slot @var{slot} of | |
4503 | @var{display-table}. The argument @var{slot} may be a number from 0 to | |
4504 | 5 inclusive, or a slot name (symbol). Valid symbols are | |
4505 | @code{truncation}, @code{wrap}, @code{escape}, @code{control}, | |
4506 | @code{selective-display}, and @code{vertical-border}. | |
4507 | @end defun | |
4508 | ||
8241495d RS |
4509 | @defun describe-display-table display-table |
4510 | @tindex describe-display-table | |
4511 | This function displays a description of the display table | |
4512 | @var{display-table} in a help buffer. | |
4513 | @end defun | |
4514 | ||
4515 | @deffn Command describe-current-display-table | |
4516 | @tindex describe-current-display-table | |
4517 | This command displays a description of the current display table in a | |
4518 | help buffer. | |
4519 | @end deffn | |
4520 | ||
42b85554 RS |
4521 | @node Active Display Table |
4522 | @subsection Active Display Table | |
4523 | @cindex active display table | |
4524 | ||
4525 | Each window can specify a display table, and so can each buffer. When | |
4526 | a buffer @var{b} is displayed in window @var{w}, display uses the | |
4527 | display table for window @var{w} if it has one; otherwise, the display | |
4528 | table for buffer @var{b} if it has one; otherwise, the standard display | |
4529 | table if any. The display table chosen is called the @dfn{active} | |
4530 | display table. | |
4531 | ||
4532 | @defun window-display-table window | |
4533 | This function returns @var{window}'s display table, or @code{nil} | |
4534 | if @var{window} does not have an assigned display table. | |
4535 | @end defun | |
4536 | ||
4537 | @defun set-window-display-table window table | |
4538 | This function sets the display table of @var{window} to @var{table}. | |
4539 | The argument @var{table} should be either a display table or | |
4540 | @code{nil}. | |
4541 | @end defun | |
4542 | ||
4543 | @defvar buffer-display-table | |
969fe9b5 RS |
4544 | This variable is automatically buffer-local in all buffers; its value in |
4545 | a particular buffer specifies the display table for that buffer. If it | |
4546 | is @code{nil}, that means the buffer does not have an assigned display | |
4547 | table. | |
42b85554 RS |
4548 | @end defvar |
4549 | ||
4550 | @defvar standard-display-table | |
4551 | This variable's value is the default display table, used whenever a | |
4552 | window has no display table and neither does the buffer displayed in | |
4553 | that window. This variable is @code{nil} by default. | |
4554 | @end defvar | |
4555 | ||
4556 | If there is no display table to use for a particular window---that is, | |
f9f59935 RS |
4557 | if the window specifies none, its buffer specifies none, and |
4558 | @code{standard-display-table} is @code{nil}---then Emacs uses the usual | |
42b85554 RS |
4559 | display conventions for all character codes in that window. @xref{Usual |
4560 | Display}. | |
4561 | ||
8241495d RS |
4562 | A number of functions for changing the standard display table |
4563 | are defined in the library @file{disp-table}. | |
4564 | ||
42b85554 RS |
4565 | @node Glyphs |
4566 | @subsection Glyphs | |
4567 | ||
4568 | @cindex glyph | |
4569 | A @dfn{glyph} is a generalization of a character; it stands for an | |
4570 | image that takes up a single character position on the screen. Glyphs | |
bbf77fe8 RS |
4571 | are represented in Lisp as integers, just as characters are. Normally |
4572 | Emacs finds glyphs in the display table (@pxref{Display Tables}). | |
4573 | ||
4574 | A glyph can be @dfn{simple} or it can be defined by the @dfn{glyph | |
4575 | table}. A simple glyph is just a way of specifying a character and a | |
4576 | face to output it in. The glyph code for a simple glyph, mod 524288, | |
4577 | is the character to output, and the glyph code divided by 524288 | |
4578 | specifies the face number (@pxref{Face Functions}) to use while | |
4579 | outputting it. (524288 is | |
4580 | @ifnottex | |
4581 | 2**19.) | |
4582 | @end ifnottex | |
4583 | @tex | |
4584 | $2^{19}$.) | |
4585 | @end tex | |
4586 | @xref{Faces}. | |
42b85554 | 4587 | |
bbf77fe8 RS |
4588 | On character terminals, you can set up a @dfn{glyph table} to define |
4589 | the meaning of glyph codes. The glyph codes is the value of the | |
4590 | variable @code{glyph-table}. | |
42b85554 RS |
4591 | |
4592 | @defvar glyph-table | |
4593 | The value of this variable is the current glyph table. It should be a | |
177c0ea7 | 4594 | vector; the @var{g}th element defines glyph code @var{g}. |
bbf77fe8 RS |
4595 | |
4596 | If a glyph code is greater than or equal to the length of the glyph | |
4597 | table, that code is automatically simple. If the value of | |
4598 | @code{glyph-table} is @code{nil} instead of a vector, then all glyphs | |
4599 | are simple. The glyph table is not used on graphical displays, only | |
4600 | on character terminals. On graphical displays, all glyphs are simple. | |
42b85554 RS |
4601 | @end defvar |
4602 | ||
4603 | Here are the possible types of elements in the glyph table: | |
4604 | ||
1911e6e5 RS |
4605 | @table @asis |
4606 | @item @var{string} | |
42b85554 RS |
4607 | Send the characters in @var{string} to the terminal to output |
4608 | this glyph. This alternative is available on character terminals, | |
969fe9b5 | 4609 | but not under a window system. |
42b85554 | 4610 | |
1911e6e5 | 4611 | @item @var{integer} |
969fe9b5 | 4612 | Define this glyph code as an alias for glyph code @var{integer}. You |
bbf77fe8 RS |
4613 | can use an alias to specify a face code for the glyph and use a small |
4614 | number as its code. | |
42b85554 RS |
4615 | |
4616 | @item @code{nil} | |
bbf77fe8 | 4617 | This glyph is simple. |
42b85554 RS |
4618 | @end table |
4619 | ||
8241495d RS |
4620 | @defun create-glyph string |
4621 | @tindex create-glyph | |
4622 | This function returns a newly-allocated glyph code which is set up to | |
4623 | display by sending @var{string} to the terminal. | |
4624 | @end defun | |
4625 | ||
42b85554 RS |
4626 | @node Beeping |
4627 | @section Beeping | |
4628 | @cindex beeping | |
4629 | @cindex bell | |
4630 | ||
f9f59935 RS |
4631 | This section describes how to make Emacs ring the bell (or blink the |
4632 | screen) to attract the user's attention. Be conservative about how | |
4633 | often you do this; frequent bells can become irritating. Also be | |
4634 | careful not to use just beeping when signaling an error is more | |
4635 | appropriate. (@xref{Errors}.) | |
42b85554 | 4636 | |
a9f0a989 | 4637 | @defun ding &optional do-not-terminate |
42b85554 RS |
4638 | @cindex keyboard macro termination |
4639 | This function beeps, or flashes the screen (see @code{visible-bell} below). | |
4640 | It also terminates any keyboard macro currently executing unless | |
a9f0a989 | 4641 | @var{do-not-terminate} is non-@code{nil}. |
42b85554 RS |
4642 | @end defun |
4643 | ||
a9f0a989 | 4644 | @defun beep &optional do-not-terminate |
42b85554 RS |
4645 | This is a synonym for @code{ding}. |
4646 | @end defun | |
4647 | ||
1911e6e5 | 4648 | @defopt visible-bell |
42b85554 RS |
4649 | This variable determines whether Emacs should flash the screen to |
4650 | represent a bell. Non-@code{nil} means yes, @code{nil} means no. This | |
969fe9b5 RS |
4651 | is effective on a window system, and on a character-only terminal |
4652 | provided the terminal's Termcap entry defines the visible bell | |
4653 | capability (@samp{vb}). | |
1911e6e5 | 4654 | @end defopt |
42b85554 | 4655 | |
f9f59935 RS |
4656 | @defvar ring-bell-function |
4657 | If this is non-@code{nil}, it specifies how Emacs should ``ring the | |
a40d4712 PR |
4658 | bell.'' Its value should be a function of no arguments. If this is |
4659 | non-@code{nil}, it takes precedence over the @code{visible-bell} | |
4660 | variable. | |
f9f59935 RS |
4661 | @end defvar |
4662 | ||
42b85554 RS |
4663 | @node Window Systems |
4664 | @section Window Systems | |
4665 | ||
4666 | Emacs works with several window systems, most notably the X Window | |
4667 | System. Both Emacs and X use the term ``window'', but use it | |
4668 | differently. An Emacs frame is a single window as far as X is | |
4669 | concerned; the individual Emacs windows are not known to X at all. | |
4670 | ||
4671 | @defvar window-system | |
42b85554 | 4672 | This variable tells Lisp programs what window system Emacs is running |
1911e6e5 RS |
4673 | under. The possible values are |
4674 | ||
4675 | @table @code | |
4676 | @item x | |
4677 | @cindex X Window System | |
4678 | Emacs is displaying using X. | |
4679 | @item pc | |
8241495d | 4680 | Emacs is displaying using MS-DOS. |
1911e6e5 | 4681 | @item w32 |
05aea714 | 4682 | Emacs is displaying using Windows. |
8241495d RS |
4683 | @item mac |
4684 | Emacs is displaying using a Macintosh. | |
1911e6e5 RS |
4685 | @item nil |
4686 | Emacs is using a character-based terminal. | |
4687 | @end table | |
42b85554 RS |
4688 | @end defvar |
4689 | ||
42b85554 | 4690 | @defvar window-setup-hook |
f9f59935 RS |
4691 | This variable is a normal hook which Emacs runs after handling the |
4692 | initialization files. Emacs runs this hook after it has completed | |
a40d4712 | 4693 | loading your init file, the default initialization file (if |
a9f0a989 | 4694 | any), and the terminal-specific Lisp code, and running the hook |
42b85554 RS |
4695 | @code{term-setup-hook}. |
4696 | ||
4697 | This hook is used for internal purposes: setting up communication with | |
4698 | the window system, and creating the initial window. Users should not | |
4699 | interfere with it. | |
4700 | @end defvar | |
ab5796a9 MB |
4701 | |
4702 | @ignore | |
4703 | arch-tag: ffdf5714-7ecf-415b-9023-fbc6b409c2c6 | |
4704 | @end ignore |