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2b71a73d | 1 | @c -*-texinfo-*- |
42b85554 | 2 | @c This is part of the GNU Emacs Lisp Reference Manual. |
f0d3d9fe | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001, |
4e6835db | 4 | @c 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc. |
42b85554 RS |
5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/display | |
8346b750 | 7 | @node Display, System Interface, Processes, Top |
42b85554 RS |
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. |
42b85554 | 16 | * Truncation:: Folding or wrapping long text lines. |
ac1d7a06 | 17 | * The Echo Area:: Displaying messages at the bottom of the screen. |
8a6ca431 | 18 | * Warnings:: Displaying warning messages for the user. |
22697dac KH |
19 | * Invisible Text:: Hiding part of the buffer text. |
20 | * Selective Display:: Hiding part of the buffer text (the old way). | |
42b85554 | 21 | * Temporary Displays:: Displays that go away automatically. |
02c77ee9 | 22 | * Overlays:: Use overlays to highlight parts of the buffer. |
a40d4712 | 23 | * Width:: How wide a character or string is on the screen. |
93449dd1 | 24 | * Line Height:: Controlling the height of lines. |
02c77ee9 | 25 | * Faces:: A face defines a graphics style for text characters: |
a40d4712 | 26 | font, colors, etc. |
8a6ca431 | 27 | * Fringes:: Controlling window fringes. |
f6cad089 | 28 | * Scroll Bars:: Controlling vertical scroll bars. |
8241495d RS |
29 | * Display Property:: Enabling special display features. |
30 | * Images:: Displaying images in Emacs buffers. | |
02c77ee9 | 31 | * Buttons:: Adding clickable buttons to Emacs buffers. |
f3dffabb | 32 | * Abstract Display:: Emacs' Widget for Object Collections. |
42b85554 | 33 | * Blinking:: How Emacs shows the matching open parenthesis. |
02c77ee9 MB |
34 | * Usual Display:: The usual conventions for displaying nonprinting chars. |
35 | * Display Tables:: How to specify other conventions. | |
42b85554 RS |
36 | * Beeping:: Audible signal to the user. |
37 | * Window Systems:: Which window system is being used. | |
38 | @end menu | |
39 | ||
40 | @node Refresh Screen | |
41 | @section Refreshing the Screen | |
42 | ||
c2579664 RS |
43 | The function @code{redraw-frame} clears and redisplays the entire |
44 | contents of a given frame (@pxref{Frames}). This is useful if the | |
45 | screen is corrupted. | |
42b85554 RS |
46 | |
47 | @c Emacs 19 feature | |
48 | @defun redraw-frame frame | |
49 | This function clears and redisplays frame @var{frame}. | |
50 | @end defun | |
51 | ||
c2579664 | 52 | Even more powerful is @code{redraw-display}: |
42b85554 RS |
53 | |
54 | @deffn Command redraw-display | |
55 | This function clears and redisplays all visible frames. | |
56 | @end deffn | |
57 | ||
c2579664 RS |
58 | This function calls for redisplay of certain windows, the next time |
59 | redisplay is done, but does not clear them first. | |
00b3c1cd | 60 | |
c2579664 | 61 | @defun force-window-update &optional object |
2735e109 KS |
62 | This function forces some or all windows to be updated on next redisplay. |
63 | If @var{object} is a window, it forces redisplay of that window. If | |
00b3c1cd | 64 | @var{object} is a buffer or buffer name, it forces redisplay of all |
c2579664 RS |
65 | windows displaying that buffer. If @var{object} is @code{nil} (or |
66 | omitted), it forces redisplay of all windows. | |
00b3c1cd RS |
67 | @end defun |
68 | ||
bfe721d1 KH |
69 | Processing user input takes absolute priority over redisplay. If you |
70 | call these functions when input is available, they do nothing | |
71 | immediately, but a full redisplay does happen eventually---after all the | |
72 | input has been processed. | |
73 | ||
42b85554 RS |
74 | Normally, suspending and resuming Emacs also refreshes the screen. |
75 | Some terminal emulators record separate contents for display-oriented | |
76 | programs such as Emacs and for ordinary sequential display. If you are | |
77 | using such a terminal, you might want to inhibit the redisplay on | |
78608595 | 78 | resumption. |
42b85554 RS |
79 | |
80 | @defvar no-redraw-on-reenter | |
81 | @cindex suspend (cf. @code{no-redraw-on-reenter}) | |
82 | @cindex resume (cf. @code{no-redraw-on-reenter}) | |
83 | This variable controls whether Emacs redraws the entire screen after it | |
f9f59935 | 84 | has been suspended and resumed. Non-@code{nil} means there is no need |
969fe9b5 | 85 | to redraw, @code{nil} means redrawing is needed. The default is @code{nil}. |
42b85554 RS |
86 | @end defvar |
87 | ||
8241495d RS |
88 | @node Forcing Redisplay |
89 | @section Forcing Redisplay | |
90 | @cindex forcing redisplay | |
91 | ||
92 | Emacs redisplay normally stops if input arrives, and does not happen | |
93 | at all if input is available before it starts. Most of the time, this | |
94 | is exactly what you want. However, you can prevent preemption by | |
95 | binding @code{redisplay-dont-pause} to a non-@code{nil} value. | |
96 | ||
a9d2c447 | 97 | @defvar redisplay-preemption-period |
c7484981 RS |
98 | This variable specifies how many seconds Emacs waits between checks |
99 | for new input during redisplay. (The default is 0.1 seconds.) If | |
100 | input has arrived when Emacs checks, it pre-empts redisplay and | |
101 | processes the available input before trying again to redisplay. | |
102 | ||
103 | If this variable is @code{nil}, Emacs does not check for input during | |
104 | redisplay, and redisplay cannot be preempted by input. | |
a9d2c447 | 105 | |
796660a5 KS |
106 | This variable is only obeyed on graphical terminals. For |
107 | text terminals, see @ref{Terminal Output}. | |
a9d2c447 KS |
108 | @end defvar |
109 | ||
8241495d RS |
110 | @defvar redisplay-dont-pause |
111 | If this variable is non-@code{nil}, pending input does not | |
112 | prevent or halt redisplay; redisplay occurs, and finishes, | |
911a7105 | 113 | regardless of whether input is available. |
8241495d RS |
114 | @end defvar |
115 | ||
a4df70f7 KS |
116 | @defun redisplay &optional force |
117 | This function performs an immediate redisplay provided there are no | |
118 | pending input events. This is equivalent to @code{(sit-for 0)}. | |
119 | ||
120 | If the optional argument @var{force} is non-@code{nil}, it forces an | |
121 | immediate and complete redisplay even if input is available. | |
cccdcb11 KS |
122 | |
123 | Returns @code{t} if redisplay was performed, or @code{nil} otherwise. | |
a4df70f7 | 124 | @end defun |
8241495d | 125 | |
42b85554 RS |
126 | @node Truncation |
127 | @section Truncation | |
128 | @cindex line wrapping | |
129 | @cindex continuation lines | |
130 | @cindex @samp{$} in display | |
131 | @cindex @samp{\} in display | |
132 | ||
b86be617 RS |
133 | When a line of text extends beyond the right edge of a window, Emacs |
134 | can @dfn{continue} the line (make it ``wrap'' to the next screen | |
135 | line), or @dfn{truncate} the line (limit it to one screen line). The | |
136 | additional screen lines used to display a long text line are called | |
137 | @dfn{continuation} lines. Continuation is not the same as filling; | |
138 | continuation happens on the screen only, not in the buffer contents, | |
139 | and it breaks a line precisely at the right margin, not at a word | |
140 | boundary. @xref{Filling}. | |
141 | ||
142 | On a graphical display, tiny arrow images in the window fringes | |
143 | indicate truncated and continued lines (@pxref{Fringes}). On a text | |
144 | terminal, a @samp{$} in the rightmost column of the window indicates | |
145 | truncation; a @samp{\} on the rightmost column indicates a line that | |
827b7ee7 | 146 | ``wraps.'' (The display table can specify alternate characters to use |
b86be617 | 147 | for this; @pxref{Display Tables}). |
42b85554 RS |
148 | |
149 | @defopt truncate-lines | |
150 | This buffer-local variable controls how Emacs displays lines that extend | |
151 | beyond the right edge of the window. The default is @code{nil}, which | |
152 | specifies continuation. If the value is non-@code{nil}, then these | |
153 | lines are truncated. | |
154 | ||
155 | If the variable @code{truncate-partial-width-windows} is non-@code{nil}, | |
156 | then truncation is always used for side-by-side windows (within one | |
157 | frame) regardless of the value of @code{truncate-lines}. | |
158 | @end defopt | |
159 | ||
bfe721d1 | 160 | @defopt default-truncate-lines |
42b85554 | 161 | This variable is the default value for @code{truncate-lines}, for |
969fe9b5 | 162 | buffers that do not have buffer-local values for it. |
bfe721d1 | 163 | @end defopt |
42b85554 RS |
164 | |
165 | @defopt truncate-partial-width-windows | |
166 | This variable controls display of lines that extend beyond the right | |
167 | edge of the window, in side-by-side windows (@pxref{Splitting Windows}). | |
168 | If it is non-@code{nil}, these lines are truncated; otherwise, | |
169 | @code{truncate-lines} says what to do with them. | |
170 | @end defopt | |
171 | ||
a9f0a989 RS |
172 | When horizontal scrolling (@pxref{Horizontal Scrolling}) is in use in |
173 | a window, that forces truncation. | |
174 | ||
1911e6e5 | 175 | If your buffer contains @emph{very} long lines, and you use |
22697dac | 176 | continuation to display them, just thinking about them can make Emacs |
bfe721d1 KH |
177 | redisplay slow. The column computation and indentation functions also |
178 | become slow. Then you might find it advisable to set | |
179 | @code{cache-long-line-scans} to @code{t}. | |
22697dac KH |
180 | |
181 | @defvar cache-long-line-scans | |
182 | If this variable is non-@code{nil}, various indentation and motion | |
bfe721d1 KH |
183 | functions, and Emacs redisplay, cache the results of scanning the |
184 | buffer, and consult the cache to avoid rescanning regions of the buffer | |
185 | unless they are modified. | |
22697dac | 186 | |
bfe721d1 | 187 | Turning on the cache slows down processing of short lines somewhat. |
22697dac | 188 | |
969fe9b5 | 189 | This variable is automatically buffer-local in every buffer. |
22697dac KH |
190 | @end defvar |
191 | ||
42b85554 RS |
192 | @node The Echo Area |
193 | @section The Echo Area | |
194 | @cindex error display | |
195 | @cindex echo area | |
196 | ||
ac1d7a06 | 197 | The @dfn{echo area} is used for displaying error messages |
c2579664 RS |
198 | (@pxref{Errors}), for messages made with the @code{message} primitive, |
199 | and for echoing keystrokes. It is not the same as the minibuffer, | |
200 | despite the fact that the minibuffer appears (when active) in the same | |
201 | place on the screen as the echo area. The @cite{GNU Emacs Manual} | |
202 | specifies the rules for resolving conflicts between the echo area and | |
203 | the minibuffer for use of that screen space (@pxref{Minibuffer,, The | |
204 | Minibuffer, emacs, The GNU Emacs Manual}). | |
42b85554 | 205 | |
ac1d7a06 RS |
206 | You can write output in the echo area by using the Lisp printing |
207 | functions with @code{t} as the stream (@pxref{Output Functions}), or | |
208 | explicitly. | |
209 | ||
210 | @menu | |
211 | * Displaying Messages:: Explicitly displaying text in the echo area. | |
7abe6d7a | 212 | * Progress:: Informing user about progress of a long operation. |
ac1d7a06 RS |
213 | * Logging Messages:: Echo area messages are logged for the user. |
214 | * Echo Area Customization:: Controlling the echo area. | |
215 | @end menu | |
216 | ||
217 | @node Displaying Messages | |
218 | @subsection Displaying Messages in the Echo Area | |
219 | ||
220 | This section describes the functions for explicitly producing echo | |
221 | area messages. Many other Emacs features display messages there, too. | |
42b85554 | 222 | |
1c145ce1 JL |
223 | @defun message format-string &rest arguments |
224 | This function displays a message in the echo area. The argument | |
225 | @var{format-string} is similar to a C language @code{printf} format | |
a3267c78 | 226 | string. See @code{format} in @ref{Formatting Strings}, for the details |
42b85554 RS |
227 | on the conversion specifications. @code{message} returns the |
228 | constructed string. | |
229 | ||
b22f3a19 RS |
230 | In batch mode, @code{message} prints the message text on the standard |
231 | error stream, followed by a newline. | |
232 | ||
1c145ce1 JL |
233 | If @var{format-string}, or strings among the @var{arguments}, have |
234 | @code{face} text properties, these affect the way the message is displayed. | |
8241495d | 235 | |
42b85554 | 236 | @c Emacs 19 feature |
1c145ce1 JL |
237 | If @var{format-string} is @code{nil} or the empty string, |
238 | @code{message} clears the echo area; if the echo area has been | |
239 | expanded automatically, this brings it back to its normal size. | |
240 | If the minibuffer is active, this brings the minibuffer contents back | |
241 | onto the screen immediately. | |
b22f3a19 | 242 | |
42b85554 RS |
243 | @example |
244 | @group | |
245 | (message "Minibuffer depth is %d." | |
246 | (minibuffer-depth)) | |
247 | @print{} Minibuffer depth is 0. | |
248 | @result{} "Minibuffer depth is 0." | |
249 | @end group | |
250 | ||
251 | @group | |
252 | ---------- Echo Area ---------- | |
253 | Minibuffer depth is 0. | |
254 | ---------- Echo Area ---------- | |
255 | @end group | |
256 | @end example | |
a43709e6 MB |
257 | |
258 | To automatically display a message in the echo area or in a pop-buffer, | |
c2579664 | 259 | depending on its size, use @code{display-message-or-buffer} (see below). |
42b85554 RS |
260 | @end defun |
261 | ||
b6954afd RS |
262 | @defmac with-temp-message message &rest body |
263 | This construct displays a message in the echo area temporarily, during | |
264 | the execution of @var{body}. It displays @var{message}, executes | |
265 | @var{body}, then returns the value of the last body form while restoring | |
266 | the previous echo area contents. | |
267 | @end defmac | |
268 | ||
1c145ce1 | 269 | @defun message-or-box format-string &rest arguments |
39d6d9bd RS |
270 | This function displays a message like @code{message}, but may display it |
271 | in a dialog box instead of the echo area. If this function is called in | |
272 | a command that was invoked using the mouse---more precisely, if | |
273 | @code{last-nonmenu-event} (@pxref{Command Loop Info}) is either | |
274 | @code{nil} or a list---then it uses a dialog box or pop-up menu to | |
275 | display the message. Otherwise, it uses the echo area. (This is the | |
276 | same criterion that @code{y-or-n-p} uses to make a similar decision; see | |
277 | @ref{Yes-or-No Queries}.) | |
278 | ||
279 | You can force use of the mouse or of the echo area by binding | |
280 | @code{last-nonmenu-event} to a suitable value around the call. | |
281 | @end defun | |
282 | ||
1c145ce1 | 283 | @defun message-box format-string &rest arguments |
b9602867 | 284 | @anchor{message-box} |
39d6d9bd RS |
285 | This function displays a message like @code{message}, but uses a dialog |
286 | box (or a pop-up menu) whenever that is possible. If it is impossible | |
287 | to use a dialog box or pop-up menu, because the terminal does not | |
288 | support them, then @code{message-box} uses the echo area, like | |
289 | @code{message}. | |
290 | @end defun | |
291 | ||
a43709e6 MB |
292 | @defun display-message-or-buffer message &optional buffer-name not-this-window frame |
293 | This function displays the message @var{message}, which may be either a | |
294 | string or a buffer. If it is shorter than the maximum height of the | |
295 | echo area, as defined by @code{max-mini-window-height}, it is displayed | |
296 | in the echo area, using @code{message}. Otherwise, | |
297 | @code{display-buffer} is used to show it in a pop-up buffer. | |
298 | ||
299 | Returns either the string shown in the echo area, or when a pop-up | |
300 | buffer is used, the window used to display it. | |
301 | ||
302 | If @var{message} is a string, then the optional argument | |
303 | @var{buffer-name} is the name of the buffer used to display it when a | |
304 | pop-up buffer is used, defaulting to @samp{*Message*}. In the case | |
305 | where @var{message} is a string and displayed in the echo area, it is | |
306 | not specified whether the contents are inserted into the buffer anyway. | |
307 | ||
308 | The optional arguments @var{not-this-window} and @var{frame} are as for | |
309 | @code{display-buffer}, and only used if a buffer is displayed. | |
310 | @end defun | |
311 | ||
f9f59935 RS |
312 | @defun current-message |
313 | This function returns the message currently being displayed in the | |
314 | echo area, or @code{nil} if there is none. | |
315 | @end defun | |
316 | ||
ac1d7a06 RS |
317 | @node Progress |
318 | @subsection Reporting Operation Progress | |
319 | @cindex progress reporting | |
969fe9b5 | 320 | |
ac1d7a06 RS |
321 | When an operation can take a while to finish, you should inform the |
322 | user about the progress it makes. This way the user can estimate | |
323 | remaining time and clearly see that Emacs is busy working, not hung. | |
969fe9b5 | 324 | |
ac1d7a06 RS |
325 | Functions listed in this section provide simple and efficient way of |
326 | reporting operation progress. Here is a working example that does | |
327 | nothing useful: | |
f9f59935 | 328 | |
ac1d7a06 RS |
329 | @smallexample |
330 | (let ((progress-reporter | |
331 | (make-progress-reporter "Collecting mana for Emacs..." | |
332 | 0 500))) | |
333 | (dotimes (k 500) | |
334 | (sit-for 0.01) | |
335 | (progress-reporter-update progress-reporter k)) | |
336 | (progress-reporter-done progress-reporter)) | |
337 | @end smallexample | |
338 | ||
339 | @defun make-progress-reporter message min-value max-value &optional current-value min-change min-time | |
340 | This function creates and returns a @dfn{progress reporter}---an | |
341 | object you will use as an argument for all other functions listed | |
342 | here. The idea is to precompute as much data as possible to make | |
343 | progress reporting very fast. | |
344 | ||
345 | When this progress reporter is subsequently used, it will display | |
346 | @var{message} in the echo area, followed by progress percentage. | |
347 | @var{message} is treated as a simple string. If you need it to depend | |
348 | on a filename, for instance, use @code{format} before calling this | |
349 | function. | |
350 | ||
351 | @var{min-value} and @var{max-value} arguments stand for starting and | |
352 | final states of your operation. For instance, if you scan a buffer, | |
353 | they should be the results of @code{point-min} and @code{point-max} | |
354 | correspondingly. It is required that @var{max-value} is greater than | |
355 | @var{min-value}. If you create progress reporter when some part of | |
356 | the operation has already been completed, then specify | |
357 | @var{current-value} argument. But normally you should omit it or set | |
358 | it to @code{nil}---it will default to @var{min-value} then. | |
359 | ||
360 | Remaining arguments control the rate of echo area updates. Progress | |
361 | reporter will wait for at least @var{min-change} more percents of the | |
362 | operation to be completed before printing next message. | |
363 | @var{min-time} specifies the minimum time in seconds to pass between | |
364 | successive prints. It can be fractional. Depending on Emacs and | |
365 | system capabilities, progress reporter may or may not respect this | |
366 | last argument or do it with varying precision. Default value for | |
367 | @var{min-change} is 1 (one percent), for @var{min-time}---0.2 | |
368 | (seconds.) | |
369 | ||
370 | This function calls @code{progress-reporter-update}, so the first | |
371 | message is printed immediately. | |
372 | @end defun | |
373 | ||
374 | @defun progress-reporter-update reporter value | |
375 | This function does the main work of reporting progress of your | |
376 | operation. It displays the message of @var{reporter}, followed by | |
377 | progress percentage determined by @var{value}. If percentage is zero, | |
378 | or close enough according to the @var{min-change} and @var{min-time} | |
379 | arguments, then it is omitted from the output. | |
380 | ||
381 | @var{reporter} must be the result of a call to | |
382 | @code{make-progress-reporter}. @var{value} specifies the current | |
383 | state of your operation and must be between @var{min-value} and | |
384 | @var{max-value} (inclusive) as passed to | |
385 | @code{make-progress-reporter}. For instance, if you scan a buffer, | |
386 | then @var{value} should be the result of a call to @code{point}. | |
387 | ||
388 | This function respects @var{min-change} and @var{min-time} as passed | |
389 | to @code{make-progress-reporter} and so does not output new messages | |
390 | on every invocation. It is thus very fast and normally you should not | |
391 | try to reduce the number of calls to it: resulting overhead will most | |
392 | likely negate your effort. | |
393 | @end defun | |
394 | ||
395 | @defun progress-reporter-force-update reporter value &optional new-message | |
396 | This function is similar to @code{progress-reporter-update} except | |
397 | that it prints a message in the echo area unconditionally. | |
398 | ||
399 | The first two arguments have the same meaning as for | |
400 | @code{progress-reporter-update}. Optional @var{new-message} allows | |
401 | you to change the message of the @var{reporter}. Since this functions | |
402 | always updates the echo area, such a change will be immediately | |
403 | presented to the user. | |
404 | @end defun | |
405 | ||
406 | @defun progress-reporter-done reporter | |
407 | This function should be called when the operation is finished. It | |
408 | prints the message of @var{reporter} followed by word ``done'' in the | |
409 | echo area. | |
410 | ||
411 | You should always call this function and not hope for | |
412 | @code{progress-reporter-update} to print ``100%.'' Firstly, it may | |
413 | never print it, there are many good reasons for this not to happen. | |
414 | Secondly, ``done'' is more explicit. | |
415 | @end defun | |
416 | ||
84ff884e | 417 | @defmac dotimes-with-progress-reporter (var count [result]) message body@dots{} |
ac1d7a06 RS |
418 | This is a convenience macro that works the same way as @code{dotimes} |
419 | does, but also reports loop progress using the functions described | |
420 | above. It allows you to save some typing. | |
421 | ||
422 | You can rewrite the example in the beginning of this node using | |
423 | this macro this way: | |
424 | ||
425 | @example | |
426 | (dotimes-with-progress-reporter | |
427 | (k 500) | |
428 | "Collecting some mana for Emacs..." | |
429 | (sit-for 0.01)) | |
430 | @end example | |
431 | @end defmac | |
432 | ||
433 | @node Logging Messages | |
434 | @subsection Logging Messages in @samp{*Messages*} | |
435 | @cindex logging echo-area messages | |
436 | ||
437 | Almost all the messages displayed in the echo area are also recorded | |
438 | in the @samp{*Messages*} buffer so that the user can refer back to | |
439 | them. This includes all the messages that are output with | |
440 | @code{message}. | |
22697dac KH |
441 | |
442 | @defopt message-log-max | |
443 | This variable specifies how many lines to keep in the @samp{*Messages*} | |
444 | buffer. The value @code{t} means there is no limit on how many lines to | |
445 | keep. The value @code{nil} disables message logging entirely. Here's | |
446 | how to display a message and prevent it from being logged: | |
447 | ||
448 | @example | |
449 | (let (message-log-max) | |
450 | (message @dots{})) | |
451 | @end example | |
452 | @end defopt | |
453 | ||
ac1d7a06 RS |
454 | To make @samp{*Messages*} more convenient for the user, the logging |
455 | facility combines successive identical messages. It also combines | |
456 | successive related messages for the sake of two cases: question | |
457 | followed by answer, and a series of progress messages. | |
458 | ||
459 | A ``question followed by an answer'' means two messages like the | |
460 | ones produced by @code{y-or-n-p}: the first is @samp{@var{question}}, | |
461 | and the second is @samp{@var{question}...@var{answer}}. The first | |
462 | message conveys no additional information beyond what's in the second, | |
463 | so logging the second message discards the first from the log. | |
464 | ||
465 | A ``series of progress messages'' means successive messages like | |
466 | those produced by @code{make-progress-reporter}. They have the form | |
467 | @samp{@var{base}...@var{how-far}}, where @var{base} is the same each | |
468 | time, while @var{how-far} varies. Logging each message in the series | |
469 | discards the previous one, provided they are consecutive. | |
470 | ||
471 | The functions @code{make-progress-reporter} and @code{y-or-n-p} | |
472 | don't have to do anything special to activate the message log | |
473 | combination feature. It operates whenever two consecutive messages | |
474 | are logged that share a common prefix ending in @samp{...}. | |
475 | ||
476 | @node Echo Area Customization | |
477 | @subsection Echo Area Customization | |
478 | ||
479 | These variables control details of how the echo area works. | |
480 | ||
481 | @defvar cursor-in-echo-area | |
482 | This variable controls where the cursor appears when a message is | |
483 | displayed in the echo area. If it is non-@code{nil}, then the cursor | |
484 | appears at the end of the message. Otherwise, the cursor appears at | |
485 | point---not in the echo area at all. | |
486 | ||
487 | The value is normally @code{nil}; Lisp programs bind it to @code{t} | |
488 | for brief periods of time. | |
489 | @end defvar | |
490 | ||
491 | @defvar echo-area-clear-hook | |
492 | This normal hook is run whenever the echo area is cleared---either by | |
493 | @code{(message nil)} or for any other reason. | |
494 | @end defvar | |
495 | ||
bfe721d1 KH |
496 | @defvar echo-keystrokes |
497 | This variable determines how much time should elapse before command | |
65e8b582 DL |
498 | characters echo. Its value must be an integer or floating point number, |
499 | which specifies the | |
bfe721d1 KH |
500 | number of seconds to wait before echoing. If the user types a prefix |
501 | key (such as @kbd{C-x}) and then delays this many seconds before | |
a9f0a989 RS |
502 | continuing, the prefix key is echoed in the echo area. (Once echoing |
503 | begins in a key sequence, all subsequent characters in the same key | |
504 | sequence are echoed immediately.) | |
bfe721d1 KH |
505 | |
506 | If the value is zero, then command input is not echoed. | |
507 | @end defvar | |
508 | ||
ac1d7a06 RS |
509 | @defvar message-truncate-lines |
510 | Normally, displaying a long message resizes the echo area to display | |
511 | the entire message. But if the variable @code{message-truncate-lines} | |
512 | is non-@code{nil}, the echo area does not resize, and the message is | |
513 | truncated to fit it, as in Emacs 20 and before. | |
514 | @end defvar | |
515 | ||
64230f2d RS |
516 | The variable @code{max-mini-window-height}, which specifies the |
517 | maximum height for resizing minibuffer windows, also applies to the | |
518 | echo area (which is really a special use of the minibuffer window. | |
519 | @xref{Minibuffer Misc}. | |
520 | ||
8a6ca431 RS |
521 | @node Warnings |
522 | @section Reporting Warnings | |
523 | @cindex warnings | |
524 | ||
525 | @dfn{Warnings} are a facility for a program to inform the user of a | |
526 | possible problem, but continue running. | |
527 | ||
528 | @menu | |
529 | * Warning Basics:: Warnings concepts and functions to report them. | |
530 | * Warning Variables:: Variables programs bind to customize their warnings. | |
531 | * Warning Options:: Variables users set to control display of warnings. | |
532 | @end menu | |
533 | ||
534 | @node Warning Basics | |
535 | @subsection Warning Basics | |
536 | @cindex severity level | |
537 | ||
538 | Every warning has a textual message, which explains the problem for | |
539 | the user, and a @dfn{severity level} which is a symbol. Here are the | |
540 | possible severity levels, in order of decreasing severity, and their | |
541 | meanings: | |
542 | ||
543 | @table @code | |
544 | @item :emergency | |
545 | A problem that will seriously impair Emacs operation soon | |
546 | if you do not attend to it promptly. | |
547 | @item :error | |
548 | A report of data or circumstances that are inherently wrong. | |
549 | @item :warning | |
550 | A report of data or circumstances that are not inherently wrong, but | |
551 | raise suspicion of a possible problem. | |
552 | @item :debug | |
553 | A report of information that may be useful if you are debugging. | |
554 | @end table | |
555 | ||
556 | When your program encounters invalid input data, it can either | |
557 | signal a Lisp error by calling @code{error} or @code{signal} or report | |
558 | a warning with severity @code{:error}. Signaling a Lisp error is the | |
559 | easiest thing to do, but it means the program cannot continue | |
560 | processing. If you want to take the trouble to implement a way to | |
561 | continue processing despite the bad data, then reporting a warning of | |
562 | severity @code{:error} is the right way to inform the user of the | |
563 | problem. For instance, the Emacs Lisp byte compiler can report an | |
564 | error that way and continue compiling other functions. (If the | |
565 | program signals a Lisp error and then handles it with | |
566 | @code{condition-case}, the user won't see the error message; it could | |
567 | show the message to the user by reporting it as a warning.) | |
568 | ||
c00d3ba4 | 569 | @cindex warning type |
8a6ca431 RS |
570 | Each warning has a @dfn{warning type} to classify it. The type is a |
571 | list of symbols. The first symbol should be the custom group that you | |
572 | use for the program's user options. For example, byte compiler | |
573 | warnings use the warning type @code{(bytecomp)}. You can also | |
574 | subcategorize the warnings, if you wish, by using more symbols in the | |
575 | list. | |
576 | ||
577 | @defun display-warning type message &optional level buffer-name | |
578 | This function reports a warning, using @var{message} as the message | |
579 | and @var{type} as the warning type. @var{level} should be the | |
580 | severity level, with @code{:warning} being the default. | |
581 | ||
582 | @var{buffer-name}, if non-@code{nil}, specifies the name of the buffer | |
583 | for logging the warning. By default, it is @samp{*Warnings*}. | |
584 | @end defun | |
585 | ||
586 | @defun lwarn type level message &rest args | |
587 | This function reports a warning using the value of @code{(format | |
588 | @var{message} @var{args}...)} as the message. In other respects it is | |
589 | equivalent to @code{display-warning}. | |
590 | @end defun | |
591 | ||
592 | @defun warn message &rest args | |
593 | This function reports a warning using the value of @code{(format | |
594 | @var{message} @var{args}...)} as the message, @code{(emacs)} as the | |
595 | type, and @code{:warning} as the severity level. It exists for | |
596 | compatibility only; we recommend not using it, because you should | |
597 | specify a specific warning type. | |
598 | @end defun | |
599 | ||
600 | @node Warning Variables | |
601 | @subsection Warning Variables | |
602 | ||
603 | Programs can customize how their warnings appear by binding | |
604 | the variables described in this section. | |
605 | ||
606 | @defvar warning-levels | |
607 | This list defines the meaning and severity order of the warning | |
608 | severity levels. Each element defines one severity level, | |
609 | and they are arranged in order of decreasing severity. | |
610 | ||
611 | Each element has the form @code{(@var{level} @var{string} | |
612 | @var{function})}, where @var{level} is the severity level it defines. | |
613 | @var{string} specifies the textual description of this level. | |
614 | @var{string} should use @samp{%s} to specify where to put the warning | |
615 | type information, or it can omit the @samp{%s} so as not to include | |
616 | that information. | |
617 | ||
618 | The optional @var{function}, if non-@code{nil}, is a function to call | |
619 | with no arguments, to get the user's attention. | |
620 | ||
621 | Normally you should not change the value of this variable. | |
622 | @end defvar | |
623 | ||
624 | @defvar warning-prefix-function | |
812a2341 | 625 | If non-@code{nil}, the value is a function to generate prefix text for |
8a6ca431 RS |
626 | warnings. Programs can bind the variable to a suitable function. |
627 | @code{display-warning} calls this function with the warnings buffer | |
628 | current, and the function can insert text in it. That text becomes | |
629 | the beginning of the warning message. | |
630 | ||
631 | The function is called with two arguments, the severity level and its | |
632 | entry in @code{warning-levels}. It should return a list to use as the | |
633 | entry (this value need not be an actual member of | |
812a2341 | 634 | @code{warning-levels}). By constructing this value, the function can |
8a6ca431 RS |
635 | change the severity of the warning, or specify different handling for |
636 | a given severity level. | |
637 | ||
638 | If the variable's value is @code{nil} then there is no function | |
639 | to call. | |
640 | @end defvar | |
641 | ||
642 | @defvar warning-series | |
643 | Programs can bind this variable to @code{t} to say that the next | |
644 | warning should begin a series. When several warnings form a series, | |
645 | that means to leave point on the first warning of the series, rather | |
812a2341 | 646 | than keep moving it for each warning so that it appears on the last one. |
8a6ca431 RS |
647 | The series ends when the local binding is unbound and |
648 | @code{warning-series} becomes @code{nil} again. | |
649 | ||
650 | The value can also be a symbol with a function definition. That is | |
651 | equivalent to @code{t}, except that the next warning will also call | |
652 | the function with no arguments with the warnings buffer current. The | |
653 | function can insert text which will serve as a header for the series | |
654 | of warnings. | |
655 | ||
656 | Once a series has begun, the value is a marker which points to the | |
657 | buffer position in the warnings buffer of the start of the series. | |
658 | ||
659 | The variable's normal value is @code{nil}, which means to handle | |
660 | each warning separately. | |
661 | @end defvar | |
662 | ||
663 | @defvar warning-fill-prefix | |
664 | When this variable is non-@code{nil}, it specifies a fill prefix to | |
665 | use for filling each warning's text. | |
666 | @end defvar | |
667 | ||
668 | @defvar warning-type-format | |
669 | This variable specifies the format for displaying the warning type | |
670 | in the warning message. The result of formatting the type this way | |
671 | gets included in the message under the control of the string in the | |
672 | entry in @code{warning-levels}. The default value is @code{" (%s)"}. | |
673 | If you bind it to @code{""} then the warning type won't appear at | |
674 | all. | |
675 | @end defvar | |
676 | ||
677 | @node Warning Options | |
678 | @subsection Warning Options | |
679 | ||
680 | These variables are used by users to control what happens | |
681 | when a Lisp program reports a warning. | |
682 | ||
683 | @defopt warning-minimum-level | |
684 | This user option specifies the minimum severity level that should be | |
685 | shown immediately to the user. The default is @code{:warning}, which | |
686 | means to immediately display all warnings except @code{:debug} | |
687 | warnings. | |
688 | @end defopt | |
689 | ||
690 | @defopt warning-minimum-log-level | |
691 | This user option specifies the minimum severity level that should be | |
692 | logged in the warnings buffer. The default is @code{:warning}, which | |
693 | means to log all warnings except @code{:debug} warnings. | |
694 | @end defopt | |
695 | ||
696 | @defopt warning-suppress-types | |
697 | This list specifies which warning types should not be displayed | |
698 | immediately for the user. Each element of the list should be a list | |
699 | of symbols. If its elements match the first elements in a warning | |
700 | type, then that warning is not displayed immediately. | |
701 | @end defopt | |
702 | ||
703 | @defopt warning-suppress-log-types | |
704 | This list specifies which warning types should not be logged in the | |
705 | warnings buffer. Each element of the list should be a list of | |
706 | symbols. If it matches the first few elements in a warning type, then | |
707 | that warning is not logged. | |
708 | @end defopt | |
00b3c1cd | 709 | |
22697dac KH |
710 | @node Invisible Text |
711 | @section Invisible Text | |
712 | ||
713 | @cindex invisible text | |
714 | You can make characters @dfn{invisible}, so that they do not appear on | |
715 | the screen, with the @code{invisible} property. This can be either a | |
a9f0a989 | 716 | text property (@pxref{Text Properties}) or a property of an overlay |
c2579664 RS |
717 | (@pxref{Overlays}). Cursor motion also partly ignores these |
718 | characters; if the command loop finds point within them, it moves | |
719 | point to the other side of them. | |
22697dac KH |
720 | |
721 | In the simplest case, any non-@code{nil} @code{invisible} property makes | |
722 | a character invisible. This is the default case---if you don't alter | |
723 | the default value of @code{buffer-invisibility-spec}, this is how the | |
31b0520f RS |
724 | @code{invisible} property works. You should normally use @code{t} |
725 | as the value of the @code{invisible} property if you don't plan | |
726 | to set @code{buffer-invisibility-spec} yourself. | |
22697dac KH |
727 | |
728 | More generally, you can use the variable @code{buffer-invisibility-spec} | |
729 | to control which values of the @code{invisible} property make text | |
730 | invisible. This permits you to classify the text into different subsets | |
731 | in advance, by giving them different @code{invisible} values, and | |
732 | subsequently make various subsets visible or invisible by changing the | |
733 | value of @code{buffer-invisibility-spec}. | |
734 | ||
735 | Controlling visibility with @code{buffer-invisibility-spec} is | |
a40d4712 PR |
736 | especially useful in a program to display the list of entries in a |
737 | database. It permits the implementation of convenient filtering | |
738 | commands to view just a part of the entries in the database. Setting | |
739 | this variable is very fast, much faster than scanning all the text in | |
740 | the buffer looking for properties to change. | |
22697dac KH |
741 | |
742 | @defvar buffer-invisibility-spec | |
743 | This variable specifies which kinds of @code{invisible} properties | |
658f691f RS |
744 | actually make a character invisible. Setting this variable makes it |
745 | buffer-local. | |
22697dac KH |
746 | |
747 | @table @asis | |
748 | @item @code{t} | |
749 | A character is invisible if its @code{invisible} property is | |
750 | non-@code{nil}. This is the default. | |
751 | ||
752 | @item a list | |
969fe9b5 RS |
753 | Each element of the list specifies a criterion for invisibility; if a |
754 | character's @code{invisible} property fits any one of these criteria, | |
755 | the character is invisible. The list can have two kinds of elements: | |
22697dac KH |
756 | |
757 | @table @code | |
758 | @item @var{atom} | |
969fe9b5 | 759 | A character is invisible if its @code{invisible} property value |
22697dac KH |
760 | is @var{atom} or if it is a list with @var{atom} as a member. |
761 | ||
762 | @item (@var{atom} . t) | |
969fe9b5 | 763 | A character is invisible if its @code{invisible} property value |
22697dac KH |
764 | is @var{atom} or if it is a list with @var{atom} as a member. |
765 | Moreover, if this character is at the end of a line and is followed | |
766 | by a visible newline, it displays an ellipsis. | |
767 | @end table | |
768 | @end table | |
769 | @end defvar | |
770 | ||
f9f59935 RS |
771 | Two functions are specifically provided for adding elements to |
772 | @code{buffer-invisibility-spec} and removing elements from it. | |
773 | ||
f9f59935 | 774 | @defun add-to-invisibility-spec element |
31b0520f | 775 | This function adds the element @var{element} to |
332c6d4e RS |
776 | @code{buffer-invisibility-spec}. If @code{buffer-invisibility-spec} |
777 | was @code{t}, it changes to a list, @code{(t)}, so that text whose | |
778 | @code{invisible} property is @code{t} remains invisible. | |
f9f59935 RS |
779 | @end defun |
780 | ||
f9f59935 | 781 | @defun remove-from-invisibility-spec element |
812a2341 | 782 | This removes the element @var{element} from |
31b0520f RS |
783 | @code{buffer-invisibility-spec}. This does nothing if @var{element} |
784 | is not in the list. | |
f9f59935 RS |
785 | @end defun |
786 | ||
31b0520f RS |
787 | A convention for use of @code{buffer-invisibility-spec} is that a |
788 | major mode should use the mode's own name as an element of | |
789 | @code{buffer-invisibility-spec} and as the value of the | |
790 | @code{invisible} property: | |
f9f59935 RS |
791 | |
792 | @example | |
969fe9b5 | 793 | ;; @r{If you want to display an ellipsis:} |
177c0ea7 | 794 | (add-to-invisibility-spec '(my-symbol . t)) |
969fe9b5 | 795 | ;; @r{If you don't want ellipsis:} |
177c0ea7 | 796 | (add-to-invisibility-spec 'my-symbol) |
f9f59935 RS |
797 | |
798 | (overlay-put (make-overlay beginning end) | |
799 | 'invisible 'my-symbol) | |
800 | ||
969fe9b5 | 801 | ;; @r{When done with the overlays:} |
f9f59935 | 802 | (remove-from-invisibility-spec '(my-symbol . t)) |
969fe9b5 | 803 | ;; @r{Or respectively:} |
f9f59935 RS |
804 | (remove-from-invisibility-spec 'my-symbol) |
805 | @end example | |
806 | ||
5e8ae792 | 807 | @vindex line-move-ignore-invisible |
00b3c1cd | 808 | Ordinarily, functions that operate on text or move point do not care |
5e8ae792 RS |
809 | whether the text is invisible. The user-level line motion commands |
810 | explicitly ignore invisible newlines if | |
a93cc2b5 RS |
811 | @code{line-move-ignore-invisible} is non-@code{nil} (the default), but |
812 | only because they are explicitly programmed to do so. | |
bfe721d1 | 813 | |
7cd3712b | 814 | However, if a command ends with point inside or immediately before |
00b3c1cd RS |
815 | invisible text, the main editing loop moves point further forward or |
816 | further backward (in the same direction that the command already moved | |
817 | it) until that condition is no longer true. Thus, if the command | |
818 | moved point back into an invisible range, Emacs moves point back to | |
7cd3712b RS |
819 | the beginning of that range, and then back one more character. If the |
820 | command moved point forward into an invisible range, Emacs moves point | |
821 | forward up to the first visible character that follows the invisible | |
822 | text. | |
00b3c1cd | 823 | |
f9f59935 RS |
824 | Incremental search can make invisible overlays visible temporarily |
825 | and/or permanently when a match includes invisible text. To enable | |
826 | this, the overlay should have a non-@code{nil} | |
827 | @code{isearch-open-invisible} property. The property value should be a | |
828 | function to be called with the overlay as an argument. This function | |
829 | should make the overlay visible permanently; it is used when the match | |
830 | overlaps the overlay on exit from the search. | |
831 | ||
832 | During the search, such overlays are made temporarily visible by | |
833 | temporarily modifying their invisible and intangible properties. If you | |
ebc6903b | 834 | want this to be done differently for a certain overlay, give it an |
f9f59935 RS |
835 | @code{isearch-open-invisible-temporary} property which is a function. |
836 | The function is called with two arguments: the first is the overlay, and | |
f21b06b7 | 837 | the second is @code{nil} to make the overlay visible, or @code{t} to |
a9f0a989 | 838 | make it invisible again. |
f9f59935 | 839 | |
42b85554 RS |
840 | @node Selective Display |
841 | @section Selective Display | |
842 | @cindex selective display | |
843 | ||
969fe9b5 RS |
844 | @dfn{Selective display} refers to a pair of related features for |
845 | hiding certain lines on the screen. | |
42b85554 | 846 | |
c2579664 RS |
847 | The first variant, explicit selective display, is designed for use |
848 | in a Lisp program: it controls which lines are hidden by altering the | |
849 | text. This kind of hiding in some ways resembles the effect of the | |
850 | @code{invisible} property (@pxref{Invisible Text}), but the two | |
851 | features are different and do not work the same way. | |
22697dac KH |
852 | |
853 | In the second variant, the choice of lines to hide is made | |
bfe721d1 | 854 | automatically based on indentation. This variant is designed to be a |
22697dac | 855 | user-level feature. |
42b85554 RS |
856 | |
857 | The way you control explicit selective display is by replacing a | |
78608595 | 858 | newline (control-j) with a carriage return (control-m). The text that |
c2579664 RS |
859 | was formerly a line following that newline is now hidden. Strictly |
860 | speaking, it is temporarily no longer a line at all, since only | |
861 | newlines can separate lines; it is now part of the previous line. | |
42b85554 RS |
862 | |
863 | Selective display does not directly affect editing commands. For | |
c2579664 RS |
864 | example, @kbd{C-f} (@code{forward-char}) moves point unhesitatingly |
865 | into hidden text. However, the replacement of newline characters with | |
866 | carriage return characters affects some editing commands. For | |
867 | example, @code{next-line} skips hidden lines, since it searches only | |
868 | for newlines. Modes that use selective display can also define | |
869 | commands that take account of the newlines, or that control which | |
870 | parts of the text are hidden. | |
42b85554 RS |
871 | |
872 | When you write a selectively displayed buffer into a file, all the | |
873 | control-m's are output as newlines. This means that when you next read | |
c2579664 | 874 | in the file, it looks OK, with nothing hidden. The selective display |
42b85554 RS |
875 | effect is seen only within Emacs. |
876 | ||
877 | @defvar selective-display | |
878 | This buffer-local variable enables selective display. This means that | |
c2579664 | 879 | lines, or portions of lines, may be made hidden. |
42b85554 RS |
880 | |
881 | @itemize @bullet | |
882 | @item | |
a40d4712 | 883 | If the value of @code{selective-display} is @code{t}, then the character |
c2579664 | 884 | control-m marks the start of hidden text; the control-m, and the rest |
a40d4712 PR |
885 | of the line following it, are not displayed. This is explicit selective |
886 | display. | |
42b85554 RS |
887 | |
888 | @item | |
889 | If the value of @code{selective-display} is a positive integer, then | |
890 | lines that start with more than that many columns of indentation are not | |
891 | displayed. | |
892 | @end itemize | |
893 | ||
c2579664 | 894 | When some portion of a buffer is hidden, the vertical movement |
42b85554 | 895 | commands operate as if that portion did not exist, allowing a single |
c2579664 | 896 | @code{next-line} command to skip any number of hidden lines. |
42b85554 | 897 | However, character movement commands (such as @code{forward-char}) do |
c2579664 RS |
898 | not skip the hidden portion, and it is possible (if tricky) to insert |
899 | or delete text in an hidden portion. | |
42b85554 RS |
900 | |
901 | In the examples below, we show the @emph{display appearance} of the | |
902 | buffer @code{foo}, which changes with the value of | |
903 | @code{selective-display}. The @emph{contents} of the buffer do not | |
904 | change. | |
905 | ||
906 | @example | |
907 | @group | |
908 | (setq selective-display nil) | |
909 | @result{} nil | |
910 | ||
911 | ---------- Buffer: foo ---------- | |
912 | 1 on this column | |
913 | 2on this column | |
914 | 3n this column | |
915 | 3n this column | |
916 | 2on this column | |
917 | 1 on this column | |
918 | ---------- Buffer: foo ---------- | |
919 | @end group | |
920 | ||
921 | @group | |
922 | (setq selective-display 2) | |
923 | @result{} 2 | |
924 | ||
925 | ---------- Buffer: foo ---------- | |
926 | 1 on this column | |
927 | 2on this column | |
928 | 2on this column | |
929 | 1 on this column | |
930 | ---------- Buffer: foo ---------- | |
931 | @end group | |
932 | @end example | |
933 | @end defvar | |
934 | ||
935 | @defvar selective-display-ellipses | |
936 | If this buffer-local variable is non-@code{nil}, then Emacs displays | |
c2579664 | 937 | @samp{@dots{}} at the end of a line that is followed by hidden text. |
42b85554 RS |
938 | This example is a continuation of the previous one. |
939 | ||
940 | @example | |
941 | @group | |
942 | (setq selective-display-ellipses t) | |
943 | @result{} t | |
944 | ||
945 | ---------- Buffer: foo ---------- | |
946 | 1 on this column | |
947 | 2on this column ... | |
948 | 2on this column | |
949 | 1 on this column | |
950 | ---------- Buffer: foo ---------- | |
951 | @end group | |
952 | @end example | |
953 | ||
954 | You can use a display table to substitute other text for the ellipsis | |
955 | (@samp{@dots{}}). @xref{Display Tables}. | |
956 | @end defvar | |
957 | ||
42b85554 RS |
958 | @node Temporary Displays |
959 | @section Temporary Displays | |
960 | ||
969fe9b5 RS |
961 | Temporary displays are used by Lisp programs to put output into a |
962 | buffer and then present it to the user for perusal rather than for | |
963 | editing. Many help commands use this feature. | |
42b85554 RS |
964 | |
965 | @defspec with-output-to-temp-buffer buffer-name forms@dots{} | |
b6954afd RS |
966 | This function executes @var{forms} while arranging to insert any output |
967 | they print into the buffer named @var{buffer-name}, which is first | |
968 | created if necessary, and put into Help mode. Finally, the buffer is | |
969 | displayed in some window, but not selected. | |
970 | ||
d7cd58d7 LT |
971 | If the @var{forms} do not change the major mode in the output buffer, |
972 | so that it is still Help mode at the end of their execution, then | |
b6954afd | 973 | @code{with-output-to-temp-buffer} makes this buffer read-only at the |
d7cd58d7 | 974 | end, and also scans it for function and variable names to make them |
68e74f25 LT |
975 | into clickable cross-references. @xref{Docstring hyperlinks, , Tips |
976 | for Documentation Strings}, in particular the item on hyperlinks in | |
977 | documentation strings, for more details. | |
42b85554 RS |
978 | |
979 | The string @var{buffer-name} specifies the temporary buffer, which | |
980 | need not already exist. The argument must be a string, not a buffer. | |
981 | The buffer is erased initially (with no questions asked), and it is | |
982 | marked as unmodified after @code{with-output-to-temp-buffer} exits. | |
983 | ||
984 | @code{with-output-to-temp-buffer} binds @code{standard-output} to the | |
985 | temporary buffer, then it evaluates the forms in @var{forms}. Output | |
986 | using the Lisp output functions within @var{forms} goes by default to | |
987 | that buffer (but screen display and messages in the echo area, although | |
988 | they are ``output'' in the general sense of the word, are not affected). | |
989 | @xref{Output Functions}. | |
990 | ||
b6954afd RS |
991 | Several hooks are available for customizing the behavior |
992 | of this construct; they are listed below. | |
993 | ||
42b85554 RS |
994 | The value of the last form in @var{forms} is returned. |
995 | ||
996 | @example | |
997 | @group | |
998 | ---------- Buffer: foo ---------- | |
999 | This is the contents of foo. | |
1000 | ---------- Buffer: foo ---------- | |
1001 | @end group | |
1002 | ||
1003 | @group | |
1004 | (with-output-to-temp-buffer "foo" | |
1005 | (print 20) | |
1006 | (print standard-output)) | |
1007 | @result{} #<buffer foo> | |
1008 | ||
1009 | ---------- Buffer: foo ---------- | |
1010 | 20 | |
1011 | ||
1012 | #<buffer foo> | |
1013 | ||
1014 | ---------- Buffer: foo ---------- | |
1015 | @end group | |
1016 | @end example | |
1017 | @end defspec | |
1018 | ||
1019 | @defvar temp-buffer-show-function | |
78608595 | 1020 | If this variable is non-@code{nil}, @code{with-output-to-temp-buffer} |
42b85554 RS |
1021 | calls it as a function to do the job of displaying a help buffer. The |
1022 | function gets one argument, which is the buffer it should display. | |
a9f0a989 RS |
1023 | |
1024 | It is a good idea for this function to run @code{temp-buffer-show-hook} | |
1025 | just as @code{with-output-to-temp-buffer} normally would, inside of | |
b6954afd | 1026 | @code{save-selected-window} and with the chosen window and buffer |
a9f0a989 RS |
1027 | selected. |
1028 | @end defvar | |
1029 | ||
b6954afd | 1030 | @defvar temp-buffer-setup-hook |
b6954afd | 1031 | This normal hook is run by @code{with-output-to-temp-buffer} before |
13a8e917 RS |
1032 | evaluating @var{body}. When the hook runs, the temporary buffer is |
1033 | current. This hook is normally set up with a function to put the | |
1034 | buffer in Help mode. | |
b6954afd RS |
1035 | @end defvar |
1036 | ||
a9f0a989 RS |
1037 | @defvar temp-buffer-show-hook |
1038 | This normal hook is run by @code{with-output-to-temp-buffer} after | |
13a8e917 RS |
1039 | displaying the temporary buffer. When the hook runs, the temporary buffer |
1040 | is current, and the window it was displayed in is selected. This hook | |
1041 | is normally set up with a function to make the buffer read only, and | |
1042 | find function names and variable names in it, provided the major mode | |
1043 | is Help mode. | |
42b85554 RS |
1044 | @end defvar |
1045 | ||
1046 | @defun momentary-string-display string position &optional char message | |
1047 | This function momentarily displays @var{string} in the current buffer at | |
1048 | @var{position}. It has no effect on the undo list or on the buffer's | |
1049 | modification status. | |
1050 | ||
1051 | The momentary display remains until the next input event. If the next | |
1052 | input event is @var{char}, @code{momentary-string-display} ignores it | |
1053 | and returns. Otherwise, that event remains buffered for subsequent use | |
1054 | as input. Thus, typing @var{char} will simply remove the string from | |
1055 | the display, while typing (say) @kbd{C-f} will remove the string from | |
1056 | the display and later (presumably) move point forward. The argument | |
1057 | @var{char} is a space by default. | |
1058 | ||
1059 | The return value of @code{momentary-string-display} is not meaningful. | |
1060 | ||
bfe721d1 | 1061 | If the string @var{string} does not contain control characters, you can |
969fe9b5 RS |
1062 | do the same job in a more general way by creating (and then subsequently |
1063 | deleting) an overlay with a @code{before-string} property. | |
1064 | @xref{Overlay Properties}. | |
bfe721d1 | 1065 | |
42b85554 RS |
1066 | If @var{message} is non-@code{nil}, it is displayed in the echo area |
1067 | while @var{string} is displayed in the buffer. If it is @code{nil}, a | |
1068 | default message says to type @var{char} to continue. | |
1069 | ||
1070 | In this example, point is initially located at the beginning of the | |
1071 | second line: | |
1072 | ||
1073 | @example | |
1074 | @group | |
1075 | ---------- Buffer: foo ---------- | |
1076 | This is the contents of foo. | |
1077 | @point{}Second line. | |
1078 | ---------- Buffer: foo ---------- | |
1079 | @end group | |
1080 | ||
1081 | @group | |
1082 | (momentary-string-display | |
1083 | "**** Important Message! ****" | |
1084 | (point) ?\r | |
1085 | "Type RET when done reading") | |
1086 | @result{} t | |
1087 | @end group | |
1088 | ||
1089 | @group | |
1090 | ---------- Buffer: foo ---------- | |
1091 | This is the contents of foo. | |
1092 | **** Important Message! ****Second line. | |
1093 | ---------- Buffer: foo ---------- | |
1094 | ||
1095 | ---------- Echo Area ---------- | |
1096 | Type RET when done reading | |
1097 | ---------- Echo Area ---------- | |
1098 | @end group | |
1099 | @end example | |
1100 | @end defun | |
1101 | ||
1102 | @node Overlays | |
1103 | @section Overlays | |
1104 | @cindex overlays | |
1105 | ||
1106 | You can use @dfn{overlays} to alter the appearance of a buffer's text on | |
bfe721d1 KH |
1107 | the screen, for the sake of presentation features. An overlay is an |
1108 | object that belongs to a particular buffer, and has a specified | |
1109 | beginning and end. It also has properties that you can examine and set; | |
1110 | these affect the display of the text within the overlay. | |
42b85554 | 1111 | |
7fdc81ab | 1112 | An overlay uses markers to record its beginning and end; thus, |
812a2341 RS |
1113 | editing the text of the buffer adjusts the beginning and end of each |
1114 | overlay so that it stays with the text. When you create the overlay, | |
1115 | you can specify whether text inserted at the beginning should be | |
1116 | inside the overlay or outside, and likewise for the end of the overlay. | |
1117 | ||
42b85554 | 1118 | @menu |
c2579664 | 1119 | * Managing Overlays:: Creating and moving overlays. |
02c77ee9 | 1120 | * Overlay Properties:: How to read and set properties. |
42b85554 | 1121 | What properties do to the screen display. |
eda77a0f | 1122 | * Finding Overlays:: Searching for overlays. |
42b85554 RS |
1123 | @end menu |
1124 | ||
c2579664 RS |
1125 | @node Managing Overlays |
1126 | @subsection Managing Overlays | |
1127 | ||
1128 | This section describes the functions to create, delete and move | |
1129 | overlays, and to examine their contents. Overlay changes are not | |
1130 | recorded in the buffer's undo list, since the overlays are not | |
1131 | part of the buffer's contents. | |
1132 | ||
1133 | @defun overlayp object | |
1134 | This function returns @code{t} if @var{object} is an overlay. | |
1135 | @end defun | |
1136 | ||
1137 | @defun make-overlay start end &optional buffer front-advance rear-advance | |
1138 | This function creates and returns an overlay that belongs to | |
1139 | @var{buffer} and ranges from @var{start} to @var{end}. Both @var{start} | |
1140 | and @var{end} must specify buffer positions; they may be integers or | |
1141 | markers. If @var{buffer} is omitted, the overlay is created in the | |
1142 | current buffer. | |
1143 | ||
1144 | The arguments @var{front-advance} and @var{rear-advance} specify the | |
f209d77d RS |
1145 | marker insertion type for the start of the overlay and for the end of |
1146 | the overlay, respectively. @xref{Marker Insertion Types}. If they | |
1147 | are both @code{nil}, the default, then the overlay extends to include | |
1148 | any text inserted at the beginning, but not text inserted at the end. | |
1149 | If @var{front-advance} is non-@code{nil}, text inserted at the | |
1150 | beginning of the overlay is excluded from the overlay. If | |
1151 | @var{rear-advance} is non-@code{nil}, text inserted at the end of the | |
1152 | overlay is included in the overlay. | |
c2579664 RS |
1153 | @end defun |
1154 | ||
1155 | @defun overlay-start overlay | |
1156 | This function returns the position at which @var{overlay} starts, | |
1157 | as an integer. | |
1158 | @end defun | |
1159 | ||
1160 | @defun overlay-end overlay | |
1161 | This function returns the position at which @var{overlay} ends, | |
1162 | as an integer. | |
1163 | @end defun | |
1164 | ||
1165 | @defun overlay-buffer overlay | |
1166 | This function returns the buffer that @var{overlay} belongs to. It | |
1167 | returns @code{nil} if @var{overlay} has been deleted. | |
1168 | @end defun | |
1169 | ||
1170 | @defun delete-overlay overlay | |
1171 | This function deletes @var{overlay}. The overlay continues to exist as | |
1172 | a Lisp object, and its property list is unchanged, but it ceases to be | |
1173 | attached to the buffer it belonged to, and ceases to have any effect on | |
1174 | display. | |
1175 | ||
1176 | A deleted overlay is not permanently disconnected. You can give it a | |
1177 | position in a buffer again by calling @code{move-overlay}. | |
1178 | @end defun | |
1179 | ||
1180 | @defun move-overlay overlay start end &optional buffer | |
1181 | This function moves @var{overlay} to @var{buffer}, and places its bounds | |
1182 | at @var{start} and @var{end}. Both arguments @var{start} and @var{end} | |
1183 | must specify buffer positions; they may be integers or markers. | |
1184 | ||
1185 | If @var{buffer} is omitted, @var{overlay} stays in the same buffer it | |
1186 | was already associated with; if @var{overlay} was deleted, it goes into | |
1187 | the current buffer. | |
1188 | ||
1189 | The return value is @var{overlay}. | |
1190 | ||
1191 | This is the only valid way to change the endpoints of an overlay. Do | |
1192 | not try modifying the markers in the overlay by hand, as that fails to | |
1193 | update other vital data structures and can cause some overlays to be | |
827b7ee7 | 1194 | ``lost.'' |
a93cc2b5 RS |
1195 | @end defun |
1196 | ||
1197 | @defun remove-overlays &optional start end name value | |
1198 | This function removes all the overlays between @var{start} and | |
1199 | @var{end} whose property @var{name} has the value @var{value}. It can | |
1200 | move the endpoints of the overlays in the region, or split them. | |
1201 | ||
b2c8f143 | 1202 | If @var{name} is omitted or @code{nil}, it means to delete all overlays in |
a93cc2b5 | 1203 | the specified region. If @var{start} and/or @var{end} are omitted or |
b2c8f143 | 1204 | @code{nil}, that means the beginning and end of the buffer respectively. |
a93cc2b5 RS |
1205 | Therefore, @code{(remove-overlays)} removes all the overlays in the |
1206 | current buffer. | |
c2579664 RS |
1207 | @end defun |
1208 | ||
1209 | Here are some examples: | |
1210 | ||
1211 | @example | |
1212 | ;; @r{Create an overlay.} | |
1213 | (setq foo (make-overlay 1 10)) | |
1214 | @result{} #<overlay from 1 to 10 in display.texi> | |
1215 | (overlay-start foo) | |
1216 | @result{} 1 | |
1217 | (overlay-end foo) | |
1218 | @result{} 10 | |
1219 | (overlay-buffer foo) | |
1220 | @result{} #<buffer display.texi> | |
1221 | ;; @r{Give it a property we can check later.} | |
1222 | (overlay-put foo 'happy t) | |
1223 | @result{} t | |
1224 | ;; @r{Verify the property is present.} | |
1225 | (overlay-get foo 'happy) | |
1226 | @result{} t | |
1227 | ;; @r{Move the overlay.} | |
1228 | (move-overlay foo 5 20) | |
1229 | @result{} #<overlay from 5 to 20 in display.texi> | |
1230 | (overlay-start foo) | |
1231 | @result{} 5 | |
1232 | (overlay-end foo) | |
1233 | @result{} 20 | |
1234 | ;; @r{Delete the overlay.} | |
1235 | (delete-overlay foo) | |
1236 | @result{} nil | |
1237 | ;; @r{Verify it is deleted.} | |
1238 | foo | |
1239 | @result{} #<overlay in no buffer> | |
1240 | ;; @r{A deleted overlay has no position.} | |
1241 | (overlay-start foo) | |
1242 | @result{} nil | |
1243 | (overlay-end foo) | |
1244 | @result{} nil | |
1245 | (overlay-buffer foo) | |
1246 | @result{} nil | |
1247 | ;; @r{Undelete the overlay.} | |
1248 | (move-overlay foo 1 20) | |
1249 | @result{} #<overlay from 1 to 20 in display.texi> | |
1250 | ;; @r{Verify the results.} | |
1251 | (overlay-start foo) | |
1252 | @result{} 1 | |
1253 | (overlay-end foo) | |
1254 | @result{} 20 | |
1255 | (overlay-buffer foo) | |
1256 | @result{} #<buffer display.texi> | |
1257 | ;; @r{Moving and deleting the overlay does not change its properties.} | |
1258 | (overlay-get foo 'happy) | |
1259 | @result{} t | |
1260 | @end example | |
1261 | ||
7525356b RS |
1262 | Emacs stores the overlays of each buffer in two lists, divided |
1263 | around an arbitrary ``center position.'' One list extends backwards | |
1264 | through the buffer from that center position, and the other extends | |
1265 | forwards from that center position. The center position can be anywhere | |
1266 | in the buffer. | |
1267 | ||
1268 | @defun overlay-recenter pos | |
1269 | This function recenters the overlays of the current buffer around | |
1270 | position @var{pos}. That makes overlay lookup faster for positions | |
1271 | near @var{pos}, but slower for positions far away from @var{pos}. | |
1272 | @end defun | |
1273 | ||
1274 | A loop that scans the buffer forwards, creating overlays, can run | |
1275 | faster if you do @code{(overlay-recenter (point-max))} first. | |
1276 | ||
42b85554 RS |
1277 | @node Overlay Properties |
1278 | @subsection Overlay Properties | |
1279 | ||
8241495d | 1280 | Overlay properties are like text properties in that the properties that |
a9f0a989 | 1281 | alter how a character is displayed can come from either source. But in |
c2579664 RS |
1282 | most respects they are different. @xref{Text Properties}, for comparison. |
1283 | ||
1284 | Text properties are considered a part of the text; overlays and | |
1285 | their properties are specifically considered not to be part of the | |
1286 | text. Thus, copying text between various buffers and strings | |
1287 | preserves text properties, but does not try to preserve overlays. | |
1288 | Changing a buffer's text properties marks the buffer as modified, | |
1289 | while moving an overlay or changing its properties does not. Unlike | |
1290 | text property changes, overlay property changes are not recorded in | |
1291 | the buffer's undo list. | |
1292 | ||
1293 | These functions read and set the properties of an overlay: | |
8241495d RS |
1294 | |
1295 | @defun overlay-get overlay prop | |
1296 | This function returns the value of property @var{prop} recorded in | |
1297 | @var{overlay}, if any. If @var{overlay} does not record any value for | |
1298 | that property, but it does have a @code{category} property which is a | |
1299 | symbol, that symbol's @var{prop} property is used. Otherwise, the value | |
1300 | is @code{nil}. | |
1301 | @end defun | |
1302 | ||
1303 | @defun overlay-put overlay prop value | |
1304 | This function sets the value of property @var{prop} recorded in | |
1305 | @var{overlay} to @var{value}. It returns @var{value}. | |
00b3c1cd RS |
1306 | @end defun |
1307 | ||
1308 | @defun overlay-properties overlay | |
1309 | This returns a copy of the property list of @var{overlay}. | |
8241495d RS |
1310 | @end defun |
1311 | ||
1312 | See also the function @code{get-char-property} which checks both | |
1313 | overlay properties and text properties for a given character. | |
1314 | @xref{Examining Properties}. | |
1315 | ||
1316 | Many overlay properties have special meanings; here is a table | |
1317 | of them: | |
1318 | ||
42b85554 RS |
1319 | @table @code |
1320 | @item priority | |
1321 | @kindex priority @r{(overlay property)} | |
f1579f52 RS |
1322 | This property's value (which should be a nonnegative integer number) |
1323 | determines the priority of the overlay. The priority matters when two | |
1324 | or more overlays cover the same character and both specify the same | |
1325 | property; the one whose @code{priority} value is larger takes priority | |
1326 | over the other. For the @code{face} property, the higher priority | |
1327 | value does not completely replace the other; instead, its face | |
1328 | attributes override the face attributes of the lower priority | |
1329 | @code{face} property. | |
42b85554 RS |
1330 | |
1331 | Currently, all overlays take priority over text properties. Please | |
1332 | avoid using negative priority values, as we have not yet decided just | |
1333 | what they should mean. | |
1334 | ||
1335 | @item window | |
1336 | @kindex window @r{(overlay property)} | |
1337 | If the @code{window} property is non-@code{nil}, then the overlay | |
1338 | applies only on that window. | |
1339 | ||
22697dac KH |
1340 | @item category |
1341 | @kindex category @r{(overlay property)} | |
1342 | If an overlay has a @code{category} property, we call it the | |
bfe721d1 | 1343 | @dfn{category} of the overlay. It should be a symbol. The properties |
22697dac KH |
1344 | of the symbol serve as defaults for the properties of the overlay. |
1345 | ||
42b85554 RS |
1346 | @item face |
1347 | @kindex face @r{(overlay property)} | |
f9f59935 | 1348 | This property controls the way text is displayed---for example, which |
8241495d | 1349 | font and which colors. @xref{Faces}, for more information. |
f9f59935 | 1350 | |
8241495d | 1351 | In the simplest case, the value is a face name. It can also be a list; |
a40d4712 | 1352 | then each element can be any of these possibilities: |
8241495d RS |
1353 | |
1354 | @itemize @bullet | |
1355 | @item | |
1356 | A face name (a symbol or string). | |
1357 | ||
1358 | @item | |
911a7105 RS |
1359 | A property list of face attributes. This has the form (@var{keyword} |
1360 | @var{value} @dots{}), where each @var{keyword} is a face attribute | |
1361 | name and @var{value} is a meaningful value for that attribute. With | |
1362 | this feature, you do not need to create a face each time you want to | |
1363 | specify a particular attribute for certain text. @xref{Face | |
1364 | Attributes}. | |
8241495d RS |
1365 | |
1366 | @item | |
1367 | A cons cell of the form @code{(foreground-color . @var{color-name})} or | |
1368 | @code{(background-color . @var{color-name})}. These elements specify | |
1369 | just the foreground color or just the background color. | |
1370 | ||
342fd6cd RS |
1371 | @code{(foreground-color . @var{color-name})} has the same effect as |
1372 | @code{(:foreground @var{color-name})}; likewise for the background. | |
8241495d | 1373 | @end itemize |
42b85554 RS |
1374 | |
1375 | @item mouse-face | |
1376 | @kindex mouse-face @r{(overlay property)} | |
1377 | This property is used instead of @code{face} when the mouse is within | |
f9f59935 | 1378 | the range of the overlay. |
42b85554 | 1379 | |
8241495d RS |
1380 | @item display |
1381 | @kindex display @r{(overlay property)} | |
1382 | This property activates various features that change the | |
1383 | way text is displayed. For example, it can make text appear taller | |
24eb6c0e | 1384 | or shorter, higher or lower, wider or narrower, or replaced with an image. |
8241495d RS |
1385 | @xref{Display Property}. |
1386 | ||
1387 | @item help-echo | |
d94f2aab | 1388 | @kindex help-echo @r{(overlay property)} |
e3b9fc91 DL |
1389 | If an overlay has a @code{help-echo} property, then when you move the |
1390 | mouse onto the text in the overlay, Emacs displays a help string in the | |
1391 | echo area, or in the tooltip window. For details see @ref{Text | |
2e46cd09 | 1392 | help-echo}. |
8241495d | 1393 | |
42b85554 RS |
1394 | @item modification-hooks |
1395 | @kindex modification-hooks @r{(overlay property)} | |
1396 | This property's value is a list of functions to be called if any | |
1397 | character within the overlay is changed or if text is inserted strictly | |
22697dac KH |
1398 | within the overlay. |
1399 | ||
1400 | The hook functions are called both before and after each change. | |
1401 | If the functions save the information they receive, and compare notes | |
1402 | between calls, they can determine exactly what change has been made | |
1403 | in the buffer text. | |
1404 | ||
1405 | When called before a change, each function receives four arguments: the | |
1406 | overlay, @code{nil}, and the beginning and end of the text range to be | |
a890e1b0 | 1407 | modified. |
42b85554 | 1408 | |
22697dac KH |
1409 | When called after a change, each function receives five arguments: the |
1410 | overlay, @code{t}, the beginning and end of the text range just | |
1411 | modified, and the length of the pre-change text replaced by that range. | |
1412 | (For an insertion, the pre-change length is zero; for a deletion, that | |
1413 | length is the number of characters deleted, and the post-change | |
bfe721d1 | 1414 | beginning and end are equal.) |
22697dac | 1415 | |
74502fa0 RS |
1416 | If these functions modify the buffer, they should bind |
1417 | @code{inhibit-modification-hooks} to @code{t} around doing so, to | |
1418 | avoid confusing the internal mechanism that calls these hooks. | |
1419 | ||
42b85554 RS |
1420 | @item insert-in-front-hooks |
1421 | @kindex insert-in-front-hooks @r{(overlay property)} | |
22697dac KH |
1422 | This property's value is a list of functions to be called before and |
1423 | after inserting text right at the beginning of the overlay. The calling | |
1424 | conventions are the same as for the @code{modification-hooks} functions. | |
42b85554 RS |
1425 | |
1426 | @item insert-behind-hooks | |
1427 | @kindex insert-behind-hooks @r{(overlay property)} | |
22697dac KH |
1428 | This property's value is a list of functions to be called before and |
1429 | after inserting text right at the end of the overlay. The calling | |
1430 | conventions are the same as for the @code{modification-hooks} functions. | |
42b85554 RS |
1431 | |
1432 | @item invisible | |
1433 | @kindex invisible @r{(overlay property)} | |
22697dac KH |
1434 | The @code{invisible} property can make the text in the overlay |
1435 | invisible, which means that it does not appear on the screen. | |
1436 | @xref{Invisible Text}, for details. | |
1437 | ||
1438 | @item intangible | |
1439 | @kindex intangible @r{(overlay property)} | |
1440 | The @code{intangible} property on an overlay works just like the | |
bfe721d1 | 1441 | @code{intangible} text property. @xref{Special Properties}, for details. |
f9f59935 RS |
1442 | |
1443 | @item isearch-open-invisible | |
a9f0a989 RS |
1444 | This property tells incremental search how to make an invisible overlay |
1445 | visible, permanently, if the final match overlaps it. @xref{Invisible | |
f9f59935 | 1446 | Text}. |
42b85554 | 1447 | |
a9f0a989 RS |
1448 | @item isearch-open-invisible-temporary |
1449 | This property tells incremental search how to make an invisible overlay | |
1450 | visible, temporarily, during the search. @xref{Invisible Text}. | |
1451 | ||
42b85554 RS |
1452 | @item before-string |
1453 | @kindex before-string @r{(overlay property)} | |
1454 | This property's value is a string to add to the display at the beginning | |
1455 | of the overlay. The string does not appear in the buffer in any | |
a40d4712 | 1456 | sense---only on the screen. |
42b85554 RS |
1457 | |
1458 | @item after-string | |
1459 | @kindex after-string @r{(overlay property)} | |
1460 | This property's value is a string to add to the display at the end of | |
1461 | the overlay. The string does not appear in the buffer in any | |
a40d4712 | 1462 | sense---only on the screen. |
22697dac KH |
1463 | |
1464 | @item evaporate | |
1465 | @kindex evaporate @r{(overlay property)} | |
1466 | If this property is non-@code{nil}, the overlay is deleted automatically | |
11cd6064 RS |
1467 | if it becomes empty (i.e., if its length becomes zero). If you give |
1468 | an empty overlay a non-@code{nil} @code{evaporate} property, that deletes | |
1469 | it immediately. | |
d2609065 | 1470 | |
ce75fd23 | 1471 | @item local-map |
969fe9b5 | 1472 | @cindex keymap of character (and overlays) |
ce75fd23 | 1473 | @kindex local-map @r{(overlay property)} |
d2609065 RS |
1474 | If this property is non-@code{nil}, it specifies a keymap for a portion |
1475 | of the text. The property's value replaces the buffer's local map, when | |
1476 | the character after point is within the overlay. @xref{Active Keymaps}. | |
62fb5c66 DL |
1477 | |
1478 | @item keymap | |
1479 | @kindex keymap @r{(overlay property)} | |
1480 | The @code{keymap} property is similar to @code{local-map} but overrides the | |
1481 | buffer's local map (and the map specified by the @code{local-map} | |
1482 | property) rather than replacing it. | |
42b85554 RS |
1483 | @end table |
1484 | ||
2468d0c0 DL |
1485 | @node Finding Overlays |
1486 | @subsection Searching for Overlays | |
1487 | ||
42b85554 | 1488 | @defun overlays-at pos |
2468d0c0 DL |
1489 | This function returns a list of all the overlays that cover the |
1490 | character at position @var{pos} in the current buffer. The list is in | |
1491 | no particular order. An overlay contains position @var{pos} if it | |
1492 | begins at or before @var{pos}, and ends after @var{pos}. | |
1493 | ||
1494 | To illustrate usage, here is a Lisp function that returns a list of the | |
1495 | overlays that specify property @var{prop} for the character at point: | |
1496 | ||
1497 | @smallexample | |
1498 | (defun find-overlays-specifying (prop) | |
1499 | (let ((overlays (overlays-at (point))) | |
1500 | found) | |
1501 | (while overlays | |
86b032fa | 1502 | (let ((overlay (car overlays))) |
2468d0c0 DL |
1503 | (if (overlay-get overlay prop) |
1504 | (setq found (cons overlay found)))) | |
1505 | (setq overlays (cdr overlays))) | |
1506 | found)) | |
1507 | @end smallexample | |
42b85554 RS |
1508 | @end defun |
1509 | ||
f9f59935 RS |
1510 | @defun overlays-in beg end |
1511 | This function returns a list of the overlays that overlap the region | |
1512 | @var{beg} through @var{end}. ``Overlap'' means that at least one | |
1513 | character is contained within the overlay and also contained within the | |
1514 | specified region; however, empty overlays are included in the result if | |
2468d0c0 | 1515 | they are located at @var{beg}, or strictly between @var{beg} and @var{end}. |
f9f59935 RS |
1516 | @end defun |
1517 | ||
42b85554 RS |
1518 | @defun next-overlay-change pos |
1519 | This function returns the buffer position of the next beginning or end | |
c2579664 RS |
1520 | of an overlay, after @var{pos}. If there is none, it returns |
1521 | @code{(point-max)}. | |
42b85554 RS |
1522 | @end defun |
1523 | ||
22697dac KH |
1524 | @defun previous-overlay-change pos |
1525 | This function returns the buffer position of the previous beginning or | |
c2579664 RS |
1526 | end of an overlay, before @var{pos}. If there is none, it returns |
1527 | @code{(point-min)}. | |
22697dac KH |
1528 | @end defun |
1529 | ||
7fdba705 RS |
1530 | Here's a function which uses @code{next-overlay-change} to search |
1531 | for the next character which gets a given property @code{prop} from | |
2468d0c0 DL |
1532 | either its overlays or its text properties (@pxref{Property Search}): |
1533 | ||
1534 | @smallexample | |
1535 | (defun find-overlay-prop (prop) | |
1536 | (save-excursion | |
1537 | (while (and (not (eobp)) | |
7fdba705 | 1538 | (not (get-char-property (point) prop))) |
2468d0c0 | 1539 | (goto-char (min (next-overlay-change (point)) |
7fdba705 | 1540 | (next-single-property-change (point) prop)))) |
2468d0c0 DL |
1541 | (point))) |
1542 | @end smallexample | |
1543 | ||
7fdba705 RS |
1544 | Now you can search for a @code{happy} property like this: |
1545 | ||
1546 | @smallexample | |
1547 | (find-overlay-prop 'happy) | |
1548 | @end smallexample | |
1549 | ||
f9f59935 RS |
1550 | @node Width |
1551 | @section Width | |
1552 | ||
1553 | Since not all characters have the same width, these functions let you | |
969fe9b5 RS |
1554 | check the width of a character. @xref{Primitive Indent}, and |
1555 | @ref{Screen Lines}, for related functions. | |
f9f59935 | 1556 | |
f9f59935 RS |
1557 | @defun char-width char |
1558 | This function returns the width in columns of the character @var{char}, | |
1559 | if it were displayed in the current buffer and the selected window. | |
1560 | @end defun | |
1561 | ||
f9f59935 RS |
1562 | @defun string-width string |
1563 | This function returns the width in columns of the string @var{string}, | |
1564 | if it were displayed in the current buffer and the selected window. | |
1565 | @end defun | |
1566 | ||
c2579664 | 1567 | @defun truncate-string-to-width string width &optional start-column padding ellipsis |
f9f59935 RS |
1568 | This function returns the part of @var{string} that fits within |
1569 | @var{width} columns, as a new string. | |
1570 | ||
1571 | If @var{string} does not reach @var{width}, then the result ends where | |
1572 | @var{string} ends. If one multi-column character in @var{string} | |
1573 | extends across the column @var{width}, that character is not included in | |
1574 | the result. Thus, the result can fall short of @var{width} but cannot | |
1575 | go beyond it. | |
1576 | ||
1577 | The optional argument @var{start-column} specifies the starting column. | |
1578 | If this is non-@code{nil}, then the first @var{start-column} columns of | |
1579 | the string are omitted from the value. If one multi-column character in | |
1580 | @var{string} extends across the column @var{start-column}, that | |
1581 | character is not included. | |
1582 | ||
1583 | The optional argument @var{padding}, if non-@code{nil}, is a padding | |
1584 | character added at the beginning and end of the result string, to extend | |
1585 | it to exactly @var{width} columns. The padding character is used at the | |
1586 | end of the result if it falls short of @var{width}. It is also used at | |
1587 | the beginning of the result if one multi-column character in | |
1588 | @var{string} extends across the column @var{start-column}. | |
1589 | ||
c2579664 RS |
1590 | If @var{ellipsis} is non-@code{nil}, it should be a string which will |
1591 | replace the end of @var{str} (including any padding) if it extends | |
1592 | beyond @var{end-column}, unless the display width of @var{str} is | |
1593 | equal to or less than the display width of @var{ellipsis}. If | |
1594 | @var{ellipsis} is non-@code{nil} and not a string, it stands for | |
1595 | @code{"..."}. | |
1596 | ||
f9f59935 RS |
1597 | @example |
1598 | (truncate-string-to-width "\tab\t" 12 4) | |
1599 | @result{} "ab" | |
6bc3abcb | 1600 | (truncate-string-to-width "\tab\t" 12 4 ?\s) |
f9f59935 RS |
1601 | @result{} " ab " |
1602 | @end example | |
1603 | @end defun | |
1604 | ||
93449dd1 KS |
1605 | @node Line Height |
1606 | @section Line Height | |
1607 | @cindex line height | |
1608 | ||
1609 | The total height of each display line consists of the height of the | |
6ac209a3 RS |
1610 | contents of the line, plus optional additional vertical line spacing |
1611 | above or below the display line. | |
93449dd1 | 1612 | |
6ac209a3 RS |
1613 | The height of the line contents is the maximum height of any |
1614 | character or image on that display line, including the final newline | |
1615 | if there is one. (A display line that is continued doesn't include a | |
1616 | final newline.) That is the default line height, if you do nothing to | |
1617 | specify a greater height. (In the most common case, this equals the | |
1618 | height of the default frame font.) | |
93449dd1 | 1619 | |
6ac209a3 RS |
1620 | There are several ways to explicitly specify a larger line height, |
1621 | either by specifying an absolute height for the display line, or by | |
1622 | specifying vertical space. However, no matter what you specify, the | |
1623 | actual line height can never be less than the default. | |
93449dd1 KS |
1624 | |
1625 | @kindex line-height @r{(text property)} | |
9eb8959a RS |
1626 | A newline can have a @code{line-height} text or overlay property |
1627 | that controls the total height of the display line ending in that | |
1225f637 KS |
1628 | newline. |
1629 | ||
6ac209a3 RS |
1630 | If the property value is @code{t}, the newline character has no |
1631 | effect on the displayed height of the line---the visible contents | |
1632 | alone determine the height. This is useful for tiling small images | |
1633 | (or image slices) without adding blank areas between the images. | |
1225f637 | 1634 | |
6ac209a3 RS |
1635 | If the property value is a list of the form @code{(@var{height} |
1636 | @var{total})}, that adds extra space @emph{below} the display line. | |
1637 | First Emacs uses @var{height} as a height spec to control extra space | |
1638 | @emph{above} the line; then it adds enough space @emph{below} the line | |
1639 | to bring the total line height up to @var{total}. In this case, the | |
1640 | other ways to specify the line spacing are ignored. | |
93449dd1 | 1641 | |
6ac209a3 RS |
1642 | Any other kind of property value is a height spec, which translates |
1643 | into a number---the specified line height. There are several ways to | |
1644 | write a height spec; here's how each of them translates into a number: | |
93449dd1 | 1645 | |
9eb8959a RS |
1646 | @table @code |
1647 | @item @var{integer} | |
af046edf | 1648 | If the height spec is a positive integer, the height value is that integer. |
9eb8959a | 1649 | @item @var{float} |
af046edf RS |
1650 | If the height spec is a float, @var{float}, the numeric height value |
1651 | is @var{float} times the frame's default line height. | |
1225f637 | 1652 | @item (@var{face} . @var{ratio}) |
af046edf RS |
1653 | If the height spec is a cons of the format shown, the numeric height |
1654 | is @var{ratio} times the height of face @var{face}. @var{ratio} can | |
1225f637 KS |
1655 | be any type of number, or @code{nil} which means a ratio of 1. |
1656 | If @var{face} is @code{t}, it refers to the current face. | |
b2c8f143 | 1657 | @item (nil . @var{ratio}) |
1225f637 KS |
1658 | If the height spec is a cons of the format shown, the numeric height |
1659 | is @var{ratio} times the height of the contents of the line. | |
9eb8959a | 1660 | @end table |
93449dd1 | 1661 | |
6ac209a3 RS |
1662 | Thus, any valid height spec determines the height in pixels, one way |
1663 | or another. If the line contents' height is less than that, Emacs | |
1664 | adds extra vertical space above the line to achieve the specified | |
1665 | total height. | |
93449dd1 | 1666 | |
b2c8f143 | 1667 | If you don't specify the @code{line-height} property, the line's |
9eb8959a | 1668 | height consists of the contents' height plus the line spacing. |
af046edf RS |
1669 | There are several ways to specify the line spacing for different |
1670 | parts of Emacs text. | |
93449dd1 KS |
1671 | |
1672 | @vindex default-line-spacing | |
9eb8959a | 1673 | You can specify the line spacing for all lines in a frame with the |
2adbd9b6 | 1674 | @code{line-spacing} frame parameter (@pxref{Layout Parameters}). |
9eb8959a | 1675 | However, if the variable @code{default-line-spacing} is |
93449dd1 KS |
1676 | non-@code{nil}, it overrides the frame's @code{line-spacing} |
1677 | parameter. An integer value specifies the number of pixels put below | |
ab7c5459 | 1678 | lines on graphical displays. A floating point number specifies the |
9eb8959a | 1679 | spacing relative to the frame's default line height. |
93449dd1 KS |
1680 | |
1681 | @vindex line-spacing | |
9eb8959a RS |
1682 | You can specify the line spacing for all lines in a buffer via the |
1683 | buffer-local @code{line-spacing} variable. An integer value specifies | |
ab7c5459 | 1684 | the number of pixels put below lines on graphical displays. A floating |
9eb8959a RS |
1685 | point number specifies the spacing relative to the default frame line |
1686 | height. This overrides line spacings specified for the frame. | |
93449dd1 KS |
1687 | |
1688 | @kindex line-spacing @r{(text property)} | |
1689 | Finally, a newline can have a @code{line-spacing} text or overlay | |
6ac209a3 RS |
1690 | property that overrides the default frame line spacing and the buffer |
1691 | local @code{line-spacing} variable, for the display line ending in | |
1692 | that newline. | |
9eb8959a | 1693 | |
af046edf RS |
1694 | One way or another, these mechanisms specify a Lisp value for the |
1695 | spacing of each line. The value is a height spec, and it translates | |
1696 | into a Lisp value as described above. However, in this case the | |
1697 | numeric height value specifies the line spacing, rather than the line | |
1698 | height. | |
1699 | ||
42b85554 RS |
1700 | @node Faces |
1701 | @section Faces | |
b9bc6c81 | 1702 | @cindex faces |
42b85554 | 1703 | |
8241495d RS |
1704 | A @dfn{face} is a named collection of graphical attributes: font |
1705 | family, foreground color, background color, optional underlining, and | |
1706 | many others. Faces are used in Emacs to control the style of display of | |
9ea1d6dc JL |
1707 | particular parts of the text or the frame. @xref{Standard Faces,,, |
1708 | emacs, The GNU Emacs Manual}, for the list of faces Emacs normally | |
1709 | comes with. | |
42b85554 RS |
1710 | |
1711 | @cindex face id | |
969fe9b5 | 1712 | Each face has its own @dfn{face number}, which distinguishes faces at |
8241495d | 1713 | low levels within Emacs. However, for most purposes, you refer to |
24ee714d | 1714 | faces in Lisp programs by the symbols that name them. |
42b85554 | 1715 | |
22697dac | 1716 | @defun facep object |
c3bf675d LT |
1717 | This function returns @code{t} if @var{object} is a face name string |
1718 | or symbol (or if it is a vector of the kind used internally to record | |
1719 | face data). It returns @code{nil} otherwise. | |
22697dac KH |
1720 | @end defun |
1721 | ||
42b85554 RS |
1722 | Each face name is meaningful for all frames, and by default it has the |
1723 | same meaning in all frames. But you can arrange to give a particular | |
1724 | face name a special meaning in one frame if you wish. | |
1725 | ||
1726 | @menu | |
969fe9b5 | 1727 | * Defining Faces:: How to define a face with @code{defface}. |
8241495d | 1728 | * Face Attributes:: What is in a face? |
02c77ee9 | 1729 | * Attribute Functions:: Functions to examine and set face attributes. |
6057489e | 1730 | * Displaying Faces:: How Emacs combines the faces specified for a character. |
8241495d | 1731 | * Font Selection:: Finding the best available font for a face. |
02c77ee9 | 1732 | * Face Functions:: How to define and examine faces. |
8241495d RS |
1733 | * Auto Faces:: Hook for automatic face assignment. |
1734 | * Font Lookup:: Looking up the names of available fonts | |
1735 | and information about them. | |
1736 | * Fontsets:: A fontset is a collection of fonts | |
1737 | that handle a range of character sets. | |
42b85554 RS |
1738 | @end menu |
1739 | ||
969fe9b5 | 1740 | @node Defining Faces |
a9f0a989 | 1741 | @subsection Defining Faces |
969fe9b5 RS |
1742 | |
1743 | The way to define a new face is with @code{defface}. This creates a | |
1744 | kind of customization item (@pxref{Customization}) which the user can | |
1745 | customize using the Customization buffer (@pxref{Easy Customization,,, | |
c3bf675d | 1746 | emacs, The GNU Emacs Manual}). |
969fe9b5 | 1747 | |
84ff884e | 1748 | @defmac defface face spec doc [keyword value]@dots{} |
b74f585b RS |
1749 | This declares @var{face} as a customizable face that defaults |
1750 | according to @var{spec}. You should not quote the symbol @var{face}, | |
1751 | and it should not end in @samp{-face} (that would be redundant). The | |
a40d4712 | 1752 | argument @var{doc} specifies the face documentation. The keywords you |
b74f585b RS |
1753 | can use in @code{defface} are the same as in @code{defgroup} and |
1754 | @code{defcustom} (@pxref{Common Keywords}). | |
969fe9b5 RS |
1755 | |
1756 | When @code{defface} executes, it defines the face according to | |
a9f0a989 | 1757 | @var{spec}, then uses any customizations that were read from the |
a40d4712 | 1758 | init file (@pxref{Init File}) to override that specification. |
969fe9b5 RS |
1759 | |
1760 | The purpose of @var{spec} is to specify how the face should appear on | |
2c705f25 RS |
1761 | different kinds of terminals. It should be an alist whose elements |
1762 | have the form @code{(@var{display} @var{atts})}. Each element's | |
1763 | @sc{car}, @var{display}, specifies a class of terminals. (The first | |
7fdc81ab | 1764 | element, if its @sc{car} is @code{default}, is special---it specifies |
2c705f25 RS |
1765 | defaults for the remaining elements). The element's @sc{cadr}, |
1766 | @var{atts}, is a list of face attributes and their values; it | |
1767 | specifies what the face should look like on that kind of terminal. | |
1768 | The possible attributes are defined in the value of | |
1769 | @code{custom-face-attributes}. | |
969fe9b5 RS |
1770 | |
1771 | The @var{display} part of an element of @var{spec} determines which | |
2c705f25 RS |
1772 | frames the element matches. If more than one element of @var{spec} |
1773 | matches a given frame, the first element that matches is the one used | |
1774 | for that frame. There are three possibilities for @var{display}: | |
969fe9b5 RS |
1775 | |
1776 | @table @asis | |
2c705f25 RS |
1777 | @item @code{default} |
1778 | This element of @var{spec} doesn't match any frames; instead, it | |
1779 | specifies defaults that apply to all frames. This kind of element, if | |
1780 | used, must be the first element of @var{spec}. Each of the following | |
1781 | elements can override any or all of these defaults. | |
1782 | ||
969fe9b5 RS |
1783 | @item @code{t} |
1784 | This element of @var{spec} matches all frames. Therefore, any | |
1785 | subsequent elements of @var{spec} are never used. Normally | |
1786 | @code{t} is used in the last (or only) element of @var{spec}. | |
1787 | ||
a9f0a989 | 1788 | @item a list |
1911e6e5 | 1789 | If @var{display} is a list, each element should have the form |
969fe9b5 RS |
1790 | @code{(@var{characteristic} @var{value}@dots{})}. Here |
1791 | @var{characteristic} specifies a way of classifying frames, and the | |
1792 | @var{value}s are possible classifications which @var{display} should | |
1793 | apply to. Here are the possible values of @var{characteristic}: | |
1794 | ||
1795 | @table @code | |
1796 | @item type | |
9a6b7dcd MB |
1797 | The kind of window system the frame uses---either @code{graphic} (any |
1798 | graphics-capable display), @code{x}, @code{pc} (for the MS-DOS console), | |
e1d01705 EZ |
1799 | @code{w32} (for MS Windows 9X/NT/2K/XP), @code{mac} (for the Macintosh |
1800 | display), or @code{tty} (a non-graphics-capable display). | |
1801 | @xref{Window Systems, window-system}. | |
969fe9b5 RS |
1802 | |
1803 | @item class | |
1804 | What kinds of colors the frame supports---either @code{color}, | |
1805 | @code{grayscale}, or @code{mono}. | |
1806 | ||
1807 | @item background | |
1911e6e5 | 1808 | The kind of background---either @code{light} or @code{dark}. |
82c3d852 | 1809 | |
9fe84db6 | 1810 | @item min-colors |
2c705f25 RS |
1811 | An integer that represents the minimum number of colors the frame |
1812 | should support. This matches a frame if its | |
1813 | @code{display-color-cells} value is at least the specified integer. | |
9fe84db6 | 1814 | |
82c3d852 | 1815 | @item supports |
95b5b933 MB |
1816 | Whether or not the frame can display the face attributes given in |
1817 | @var{value}@dots{} (@pxref{Face Attributes}). See the documentation | |
1818 | for the function @code{display-supports-face-attributes-p} for more | |
1819 | information on exactly how this testing is done. @xref{Display Face | |
1820 | Attribute Testing}. | |
969fe9b5 RS |
1821 | @end table |
1822 | ||
1823 | If an element of @var{display} specifies more than one @var{value} for a | |
1824 | given @var{characteristic}, any of those values is acceptable. If | |
1825 | @var{display} has more than one element, each element should specify a | |
1826 | different @var{characteristic}; then @emph{each} characteristic of the | |
1827 | frame must match one of the @var{value}s specified for it in | |
1828 | @var{display}. | |
1829 | @end table | |
1830 | @end defmac | |
1831 | ||
a40d4712 | 1832 | Here's how the standard face @code{region} is defined: |
969fe9b5 RS |
1833 | |
1834 | @example | |
a40d4712 | 1835 | @group |
9fe84db6 EZ |
1836 | '((((class color) (min-colors 88) (background dark)) |
1837 | :background "blue3") | |
a40d4712 | 1838 | @end group |
9fe84db6 EZ |
1839 | (((class color) (min-colors 88) (background light)) |
1840 | :background "lightgoldenrod2") | |
1841 | (((class color) (min-colors 16) (background dark)) | |
1842 | :background "blue3") | |
1843 | (((class color) (min-colors 16) (background light)) | |
1844 | :background "lightgoldenrod2") | |
1845 | (((class color) (min-colors 8)) | |
1846 | :background "blue" :foreground "white") | |
a40d4712 | 1847 | (((type tty) (class mono)) |
9fe84db6 EZ |
1848 | :inverse-video t) |
1849 | (t :background "gray")) | |
a40d4712 PR |
1850 | @group |
1851 | "Basic face for highlighting the region." | |
1852 | :group 'basic-faces) | |
1853 | @end group | |
969fe9b5 RS |
1854 | @end example |
1855 | ||
1856 | Internally, @code{defface} uses the symbol property | |
1857 | @code{face-defface-spec} to record the face attributes specified in | |
1858 | @code{defface}, @code{saved-face} for the attributes saved by the user | |
188e0f50 JL |
1859 | with the customization buffer, @code{customized-face} for the |
1860 | attributes customized by the user for the current session, but not | |
1861 | saved, and @code{face-documentation} for the documentation string. | |
969fe9b5 | 1862 | |
1911e6e5 RS |
1863 | @defopt frame-background-mode |
1864 | This option, if non-@code{nil}, specifies the background type to use for | |
1865 | interpreting face definitions. If it is @code{dark}, then Emacs treats | |
1866 | all frames as if they had a dark background, regardless of their actual | |
1867 | background colors. If it is @code{light}, then Emacs treats all frames | |
1868 | as if they had a light background. | |
1869 | @end defopt | |
1870 | ||
8241495d RS |
1871 | @node Face Attributes |
1872 | @subsection Face Attributes | |
1873 | @cindex face attributes | |
42b85554 | 1874 | |
8241495d RS |
1875 | The effect of using a face is determined by a fixed set of @dfn{face |
1876 | attributes}. This table lists all the face attributes, and what they | |
e3b4d849 RS |
1877 | mean. You can specify more than one face for a given piece of text; |
1878 | Emacs merges the attributes of all the faces to determine how to | |
1879 | display the text. @xref{Displaying Faces}. | |
42b85554 | 1880 | |
911a7105 RS |
1881 | Any attribute in a face can have the value @code{unspecified}. This |
1882 | means the face doesn't specify that attribute. In face merging, when | |
1883 | the first face fails to specify a particular attribute, that means the | |
1884 | next face gets a chance. However, the @code{default} face must | |
1885 | specify all attributes. | |
42b85554 | 1886 | |
a40d4712 PR |
1887 | Some of these font attributes are meaningful only on certain kinds of |
1888 | displays---if your display cannot handle a certain attribute, the | |
1889 | attribute is ignored. (The attributes @code{:family}, @code{:width}, | |
1890 | @code{:height}, @code{:weight}, and @code{:slant} correspond to parts of | |
1891 | an X Logical Font Descriptor.) | |
42b85554 | 1892 | |
8241495d RS |
1893 | @table @code |
1894 | @item :family | |
1895 | Font family name, or fontset name (@pxref{Fontsets}). If you specify a | |
a40d4712 PR |
1896 | font family name, the wild-card characters @samp{*} and @samp{?} are |
1897 | allowed. | |
8241495d RS |
1898 | |
1899 | @item :width | |
1900 | Relative proportionate width, also known as the character set width or | |
1901 | set width. This should be one of the symbols @code{ultra-condensed}, | |
1902 | @code{extra-condensed}, @code{condensed}, @code{semi-condensed}, | |
1903 | @code{normal}, @code{semi-expanded}, @code{expanded}, | |
1904 | @code{extra-expanded}, or @code{ultra-expanded}. | |
177c0ea7 | 1905 | |
8241495d | 1906 | @item :height |
96f71a49 MB |
1907 | Either the font height, an integer in units of 1/10 point, a floating |
1908 | point number specifying the amount by which to scale the height of any | |
1909 | underlying face, or a function, which is called with the old height | |
1910 | (from the underlying face), and should return the new height. | |
177c0ea7 | 1911 | |
8241495d RS |
1912 | @item :weight |
1913 | Font weight---a symbol from this series (from most dense to most faint): | |
1914 | @code{ultra-bold}, @code{extra-bold}, @code{bold}, @code{semi-bold}, | |
1915 | @code{normal}, @code{semi-light}, @code{light}, @code{extra-light}, | |
a40d4712 | 1916 | or @code{ultra-light}. |
66f54605 | 1917 | |
a40d4712 PR |
1918 | On a text-only terminal, any weight greater than normal is displayed as |
1919 | extra bright, and any weight less than normal is displayed as | |
1920 | half-bright (provided the terminal supports the feature). | |
1921 | ||
8241495d RS |
1922 | @item :slant |
1923 | Font slant---one of the symbols @code{italic}, @code{oblique}, @code{normal}, | |
1924 | @code{reverse-italic}, or @code{reverse-oblique}. | |
66f54605 PR |
1925 | |
1926 | On a text-only terminal, slanted text is displayed as half-bright, if | |
1927 | the terminal supports the feature. | |
1928 | ||
8241495d | 1929 | @item :foreground |
6057489e RS |
1930 | Foreground color, a string. The value can be a system-defined color |
1931 | name, or a hexadecimal color specification of the form | |
1932 | @samp{#@var{rr}@var{gg}@var{bb}}. (@samp{#000000} is black, | |
1933 | @samp{#ff0000} is red, @samp{#00ff00} is green, @samp{#0000ff} is | |
1934 | blue, and @samp{#ffffff} is white.) | |
177c0ea7 | 1935 | |
8241495d | 1936 | @item :background |
6057489e | 1937 | Background color, a string, like the foreground color. |
8241495d RS |
1938 | |
1939 | @item :inverse-video | |
1940 | Whether or not characters should be displayed in inverse video. The | |
1941 | value should be @code{t} (yes) or @code{nil} (no). | |
1942 | ||
1943 | @item :stipple | |
a40d4712 | 1944 | The background stipple, a bitmap. |
8241495d | 1945 | |
a40d4712 PR |
1946 | The value can be a string; that should be the name of a file containing |
1947 | external-format X bitmap data. The file is found in the directories | |
1948 | listed in the variable @code{x-bitmap-file-path}. | |
8241495d | 1949 | |
a3fbafe2 RS |
1950 | Alternatively, the value can specify the bitmap directly, with a list |
1951 | of the form @code{(@var{width} @var{height} @var{data})}. Here, | |
1952 | @var{width} and @var{height} specify the size in pixels, and | |
1953 | @var{data} is a string containing the raw bits of the bitmap, row by | |
1954 | row. Each row occupies @math{(@var{width} + 7) / 8} consecutive bytes | |
1955 | in the string (which should be a unibyte string for best results). | |
1956 | This means that each row always occupies at least one whole byte. | |
8241495d RS |
1957 | |
1958 | If the value is @code{nil}, that means use no stipple pattern. | |
1959 | ||
1960 | Normally you do not need to set the stipple attribute, because it is | |
1961 | used automatically to handle certain shades of gray. | |
1962 | ||
1963 | @item :underline | |
1964 | Whether or not characters should be underlined, and in what color. If | |
1965 | the value is @code{t}, underlining uses the foreground color of the | |
1966 | face. If the value is a string, underlining uses that color. The | |
1967 | value @code{nil} means do not underline. | |
1968 | ||
1969 | @item :overline | |
1970 | Whether or not characters should be overlined, and in what color. | |
1971 | The value is used like that of @code{:underline}. | |
1972 | ||
1973 | @item :strike-through | |
1974 | Whether or not characters should be strike-through, and in what | |
1975 | color. The value is used like that of @code{:underline}. | |
1976 | ||
96f71a49 MB |
1977 | @item :inherit |
1978 | The name of a face from which to inherit attributes, or a list of face | |
1979 | names. Attributes from inherited faces are merged into the face like an | |
1980 | underlying face would be, with higher priority than underlying faces. | |
e58b3620 RS |
1981 | If a list of faces is used, attributes from faces earlier in the list |
1982 | override those from later faces. | |
96f71a49 | 1983 | |
8241495d RS |
1984 | @item :box |
1985 | Whether or not a box should be drawn around characters, its color, the | |
a40d4712 | 1986 | width of the box lines, and 3D appearance. |
8241495d | 1987 | @end table |
42b85554 | 1988 | |
8241495d RS |
1989 | Here are the possible values of the @code{:box} attribute, and what |
1990 | they mean: | |
42b85554 | 1991 | |
8241495d RS |
1992 | @table @asis |
1993 | @item @code{nil} | |
1994 | Don't draw a box. | |
bfe721d1 | 1995 | |
8241495d RS |
1996 | @item @code{t} |
1997 | Draw a box with lines of width 1, in the foreground color. | |
42b85554 | 1998 | |
8241495d RS |
1999 | @item @var{color} |
2000 | Draw a box with lines of width 1, in color @var{color}. | |
42b85554 | 2001 | |
8241495d RS |
2002 | @item @code{(:line-width @var{width} :color @var{color} :style @var{style})} |
2003 | This way you can explicitly specify all aspects of the box. The value | |
2004 | @var{width} specifies the width of the lines to draw; it defaults to 1. | |
42b85554 | 2005 | |
8241495d RS |
2006 | The value @var{color} specifies the color to draw with. The default is |
2007 | the foreground color of the face for simple boxes, and the background | |
2008 | color of the face for 3D boxes. | |
42b85554 | 2009 | |
8241495d RS |
2010 | The value @var{style} specifies whether to draw a 3D box. If it is |
2011 | @code{released-button}, the box looks like a 3D button that is not being | |
2012 | pressed. If it is @code{pressed-button}, the box looks like a 3D button | |
2013 | that is being pressed. If it is @code{nil} or omitted, a plain 2D box | |
2014 | is used. | |
2015 | @end table | |
42b85554 | 2016 | |
911a7105 RS |
2017 | In older versions of Emacs, before @code{:family}, @code{:height}, |
2018 | @code{:width}, @code{:weight}, and @code{:slant} existed, these | |
2019 | attributes were used to specify the type face. They are now | |
2020 | semi-obsolete, but they still work: | |
42b85554 | 2021 | |
8241495d RS |
2022 | @table @code |
2023 | @item :font | |
a40d4712 | 2024 | This attribute specifies the font name. |
42b85554 | 2025 | |
8241495d RS |
2026 | @item :bold |
2027 | A non-@code{nil} value specifies a bold font. | |
42b85554 | 2028 | |
8241495d RS |
2029 | @item :italic |
2030 | A non-@code{nil} value specifies an italic font. | |
2031 | @end table | |
42b85554 | 2032 | |
827b7ee7 | 2033 | For compatibility, you can still set these ``attributes,'' even |
911a7105 | 2034 | though they are not real face attributes. Here is what that does: |
42b85554 | 2035 | |
8241495d RS |
2036 | @table @code |
2037 | @item :font | |
a40d4712 PR |
2038 | You can specify an X font name as the ``value'' of this ``attribute''; |
2039 | that sets the @code{:family}, @code{:width}, @code{:height}, | |
2040 | @code{:weight}, and @code{:slant} attributes according to the font name. | |
8241495d RS |
2041 | |
2042 | If the value is a pattern with wildcards, the first font that matches | |
2043 | the pattern is used to set these attributes. | |
2044 | ||
2045 | @item :bold | |
2046 | A non-@code{nil} makes the face bold; @code{nil} makes it normal. | |
2047 | This actually works by setting the @code{:weight} attribute. | |
2048 | ||
2049 | @item :italic | |
2050 | A non-@code{nil} makes the face italic; @code{nil} makes it normal. | |
2051 | This actually works by setting the @code{:slant} attribute. | |
2052 | @end table | |
42b85554 | 2053 | |
8241495d RS |
2054 | @defvar x-bitmap-file-path |
2055 | This variable specifies a list of directories for searching | |
2056 | for bitmap files, for the @code{:stipple} attribute. | |
2057 | @end defvar | |
2058 | ||
ea7220f8 | 2059 | @defun bitmap-spec-p object |
2252bdcf RS |
2060 | This returns @code{t} if @var{object} is a valid bitmap specification, |
2061 | suitable for use with @code{:stipple} (see above). It returns | |
2062 | @code{nil} otherwise. | |
a40d4712 PR |
2063 | @end defun |
2064 | ||
8241495d RS |
2065 | @node Attribute Functions |
2066 | @subsection Face Attribute Functions | |
42b85554 | 2067 | |
47f6532e RS |
2068 | This section describes the functions for accessing and modifying the |
2069 | attributes of an existing face. | |
42b85554 | 2070 | |
8241495d | 2071 | @defun set-face-attribute face frame &rest arguments |
e3b4d849 RS |
2072 | This function sets one or more attributes of face @var{face} for frame |
2073 | @var{frame}. The attributes you specify this way override whatever | |
2074 | the @code{defface} says. | |
8241495d RS |
2075 | |
2076 | The extra arguments @var{arguments} specify the attributes to set, and | |
2077 | the values for them. They should consist of alternating attribute names | |
a40d4712 | 2078 | (such as @code{:family} or @code{:underline}) and corresponding values. |
8241495d RS |
2079 | Thus, |
2080 | ||
2081 | @example | |
2082 | (set-face-attribute 'foo nil | |
dbcff00c RS |
2083 | :width 'extended |
2084 | :weight 'bold | |
8241495d RS |
2085 | :underline "red") |
2086 | @end example | |
2087 | ||
2088 | @noindent | |
2089 | sets the attributes @code{:width}, @code{:weight} and @code{:underline} | |
2090 | to the corresponding values. | |
e3b4d849 | 2091 | |
47f6532e RS |
2092 | If @var{frame} is @code{t}, this function sets the default attributes |
2093 | for new frames. Default attribute values specified this way override | |
2094 | the @code{defface} for newly created frames. | |
2095 | ||
2096 | If @var{frame} is @code{nil}, this function sets the attributes for | |
2097 | all existing frames, and the default for new frames. | |
8241495d RS |
2098 | @end defun |
2099 | ||
35f23bbf | 2100 | @defun face-attribute face attribute &optional frame inherit |
8241495d RS |
2101 | This returns the value of the @var{attribute} attribute of face |
2102 | @var{face} on @var{frame}. If @var{frame} is @code{nil}, | |
8d82c597 | 2103 | that means the selected frame (@pxref{Input Focus}). |
8241495d | 2104 | |
e3b4d849 RS |
2105 | If @var{frame} is @code{t}, this returns whatever new-frames default |
2106 | value you previously specified with @code{set-face-attribute} for the | |
2107 | @var{attribute} attribute of @var{face}. If you have not specified | |
2108 | one, it returns @code{nil}. | |
8241495d | 2109 | |
9a8dc0d3 | 2110 | If @var{inherit} is @code{nil}, only attributes directly defined by |
35f23bbf | 2111 | @var{face} are considered, so the return value may be |
9a8dc0d3 RS |
2112 | @code{unspecified}, or a relative value. If @var{inherit} is |
2113 | non-@code{nil}, @var{face}'s definition of @var{attribute} is merged | |
2114 | with the faces specified by its @code{:inherit} attribute; however the | |
2115 | return value may still be @code{unspecified} or relative. If | |
2116 | @var{inherit} is a face or a list of faces, then the result is further | |
2117 | merged with that face (or faces), until it becomes specified and | |
2118 | absolute. | |
35f23bbf MB |
2119 | |
2120 | To ensure that the return value is always specified and absolute, use | |
2121 | a value of @code{default} for @var{inherit}; this will resolve any | |
2122 | unspecified or relative values by merging with the @code{default} face | |
2123 | (which is always completely specified). | |
2124 | ||
8241495d RS |
2125 | For example, |
2126 | ||
2127 | @example | |
2128 | (face-attribute 'bold :weight) | |
2129 | @result{} bold | |
2130 | @end example | |
2131 | @end defun | |
2132 | ||
35f23bbf | 2133 | @defun face-attribute-relative-p attribute value |
c5a83cf9 RS |
2134 | This function returns non-@code{nil} if @var{value}, when used as the |
2135 | value of the face attribute @var{attribute}, is relative. This means | |
2136 | it would modify, rather than completely override, any value that comes | |
2137 | from a subsequent face in the face list or that is inherited from | |
2138 | another face. | |
2139 | ||
2140 | @code{unspecified} is a relative value for all attributes. | |
2141 | For @code{:height}, floating point values are also relative. | |
2142 | ||
2143 | For example: | |
2144 | ||
2145 | @example | |
2146 | (read-face-name "Describe face" "= `default' face" t) | |
2147 | @end example | |
2148 | ||
2149 | prompts with @samp{Describe face (default = `default' face): }. | |
35f23bbf MB |
2150 | @end defun |
2151 | ||
35f23bbf MB |
2152 | @defun merge-face-attribute attribute value1 value2 |
2153 | If @var{value1} is a relative value for the face attribute | |
2154 | @var{attribute}, returns it merged with the underlying value | |
2155 | @var{value2}; otherwise, if @var{value1} is an absolute value for the | |
9ee1638e | 2156 | face attribute @var{attribute}, returns @var{value1} unchanged. |
35f23bbf MB |
2157 | @end defun |
2158 | ||
0d93030d RS |
2159 | The functions above did not exist before Emacs 21. For compatibility |
2160 | with older Emacs versions, you can use the following functions to set | |
2161 | and examine the face attributes which existed in those versions. | |
47f6532e RS |
2162 | They use values of @code{t} and @code{nil} for @var{frame} |
2163 | just like @code{set-face-attribute} and @code{face-attribute}. | |
0d93030d | 2164 | |
42b85554 RS |
2165 | @defun set-face-foreground face color &optional frame |
2166 | @defunx set-face-background face color &optional frame | |
78608595 RS |
2167 | These functions set the foreground (or background, respectively) color |
2168 | of face @var{face} to @var{color}. The argument @var{color} should be a | |
42b85554 | 2169 | string, the name of a color. |
bfe721d1 KH |
2170 | |
2171 | Certain shades of gray are implemented by stipple patterns on | |
2172 | black-and-white screens. | |
2173 | @end defun | |
2174 | ||
2175 | @defun set-face-stipple face pattern &optional frame | |
2252bdcf RS |
2176 | This function sets the background stipple pattern of face @var{face} |
2177 | to @var{pattern}. The argument @var{pattern} should be the name of a | |
2178 | stipple pattern defined by the X server, or actual bitmap data | |
2179 | (@pxref{Face Attributes}), or @code{nil} meaning don't use stipple. | |
bfe721d1 KH |
2180 | |
2181 | Normally there is no need to pay attention to stipple patterns, because | |
2182 | they are used automatically to handle certain shades of gray. | |
42b85554 RS |
2183 | @end defun |
2184 | ||
2185 | @defun set-face-font face font &optional frame | |
911a7105 RS |
2186 | This function sets the font of face @var{face}. This actually sets |
2187 | the attributes @code{:family}, @code{:width}, @code{:height}, | |
2188 | @code{:weight}, and @code{:slant} according to the font name | |
2189 | @var{font}. | |
21cffb83 RS |
2190 | @end defun |
2191 | ||
f9f59935 | 2192 | @defun set-face-bold-p face bold-p &optional frame |
8241495d RS |
2193 | This function specifies whether @var{face} should be bold. If |
2194 | @var{bold-p} is non-@code{nil}, that means yes; @code{nil} means no. | |
911a7105 | 2195 | This actually sets the @code{:weight} attribute. |
21cffb83 RS |
2196 | @end defun |
2197 | ||
f9f59935 | 2198 | @defun set-face-italic-p face italic-p &optional frame |
8241495d RS |
2199 | This function specifies whether @var{face} should be italic. If |
2200 | @var{italic-p} is non-@code{nil}, that means yes; @code{nil} means no. | |
911a7105 | 2201 | This actually sets the @code{:slant} attribute. |
42b85554 RS |
2202 | @end defun |
2203 | ||
969fe9b5 RS |
2204 | @defun set-face-underline-p face underline-p &optional frame |
2205 | This function sets the underline attribute of face @var{face}. | |
2206 | Non-@code{nil} means do underline; @code{nil} means don't. | |
2207 | @end defun | |
2208 | ||
79a8defb JL |
2209 | @defun set-face-inverse-video-p face inverse-video-p &optional frame |
2210 | This function sets the @code{:inverse-video} attribute of face | |
2211 | @var{face}. | |
2212 | @end defun | |
2213 | ||
42b85554 | 2214 | @defun invert-face face &optional frame |
79a8defb JL |
2215 | This function swaps the foreground and background colors of face |
2216 | @var{face}. | |
42b85554 RS |
2217 | @end defun |
2218 | ||
2219 | These functions examine the attributes of a face. If you don't | |
47f6532e RS |
2220 | specify @var{frame}, they refer to the selected frame; @code{t} refers |
2221 | to the default data for new frames. They return the symbol | |
2222 | @code{unspecified} if the face doesn't define any value for that | |
2223 | attribute. | |
42b85554 | 2224 | |
69137def | 2225 | @defun face-foreground face &optional frame inherit |
79a8defb | 2226 | @defunx face-background face &optional frame inherit |
78608595 RS |
2227 | These functions return the foreground color (or background color, |
2228 | respectively) of face @var{face}, as a string. | |
69137def | 2229 | |
00991494 JH |
2230 | If @var{inherit} is @code{nil}, only a color directly defined by the face is |
2231 | returned. If @var{inherit} is non-@code{nil}, any faces specified by its | |
69137def MB |
2232 | @code{:inherit} attribute are considered as well, and if @var{inherit} |
2233 | is a face or a list of faces, then they are also considered, until a | |
2234 | specified color is found. To ensure that the return value is always | |
2235 | specified, use a value of @code{default} for @var{inherit}. | |
42b85554 RS |
2236 | @end defun |
2237 | ||
69137def | 2238 | @defun face-stipple face &optional frame inherit |
bfe721d1 KH |
2239 | This function returns the name of the background stipple pattern of face |
2240 | @var{face}, or @code{nil} if it doesn't have one. | |
69137def | 2241 | |
9a8dc0d3 RS |
2242 | If @var{inherit} is @code{nil}, only a stipple directly defined by the |
2243 | face is returned. If @var{inherit} is non-@code{nil}, any faces | |
2244 | specified by its @code{:inherit} attribute are considered as well, and | |
2245 | if @var{inherit} is a face or a list of faces, then they are also | |
2246 | considered, until a specified stipple is found. To ensure that the | |
2247 | return value is always specified, use a value of @code{default} for | |
2248 | @var{inherit}. | |
bfe721d1 KH |
2249 | @end defun |
2250 | ||
42b85554 RS |
2251 | @defun face-font face &optional frame |
2252 | This function returns the name of the font of face @var{face}. | |
2253 | @end defun | |
2254 | ||
f9f59935 | 2255 | @defun face-bold-p face &optional frame |
8241495d RS |
2256 | This function returns @code{t} if @var{face} is bold---that is, if it is |
2257 | bolder than normal. It returns @code{nil} otherwise. | |
f9f59935 RS |
2258 | @end defun |
2259 | ||
f9f59935 | 2260 | @defun face-italic-p face &optional frame |
8241495d RS |
2261 | This function returns @code{t} if @var{face} is italic or oblique, |
2262 | @code{nil} otherwise. | |
f9f59935 RS |
2263 | @end defun |
2264 | ||
969fe9b5 | 2265 | @defun face-underline-p face &optional frame |
8241495d RS |
2266 | This function returns the @code{:underline} attribute of face @var{face}. |
2267 | @end defun | |
2268 | ||
2269 | @defun face-inverse-video-p face &optional frame | |
2270 | This function returns the @code{:inverse-video} attribute of face @var{face}. | |
2271 | @end defun | |
2272 | ||
6057489e RS |
2273 | @node Displaying Faces |
2274 | @subsection Displaying Faces | |
8241495d RS |
2275 | |
2276 | Here are the ways to specify which faces to use for display of text: | |
2277 | ||
2278 | @itemize @bullet | |
2279 | @item | |
2280 | With defaults. The @code{default} face is used as the ultimate | |
2281 | default for all text. (In Emacs 19 and 20, the @code{default} | |
2282 | face is used only when no other face is specified.) | |
2283 | ||
c2579664 RS |
2284 | @item |
2285 | For a mode line or header line, the face @code{mode-line} or | |
2286 | @code{mode-line-inactive}, or @code{header-line}, is merged in just | |
2287 | before @code{default}. | |
8241495d RS |
2288 | |
2289 | @item | |
2290 | With text properties. A character can have a @code{face} property; if | |
2291 | so, the faces and face attributes specified there apply. @xref{Special | |
2292 | Properties}. | |
2293 | ||
2294 | If the character has a @code{mouse-face} property, that is used instead | |
2295 | of the @code{face} property when the mouse is ``near enough'' to the | |
2296 | character. | |
2297 | ||
2298 | @item | |
2299 | With overlays. An overlay can have @code{face} and @code{mouse-face} | |
2300 | properties too; they apply to all the text covered by the overlay. | |
2301 | ||
2302 | @item | |
2303 | With a region that is active. In Transient Mark mode, the region is | |
9ea1d6dc JL |
2304 | highlighted with the face @code{region} (@pxref{Standard Faces,,, |
2305 | emacs, The GNU Emacs Manual}). | |
8241495d RS |
2306 | |
2307 | @item | |
177c0ea7 | 2308 | With special glyphs. Each glyph can specify a particular face |
8241495d RS |
2309 | number. @xref{Glyphs}. |
2310 | @end itemize | |
2311 | ||
2312 | If these various sources together specify more than one face for a | |
2313 | particular character, Emacs merges the attributes of the various faces | |
c2579664 RS |
2314 | specified. For each attribute, Emacs tries first the face of any |
2315 | special glyph; then the face for region highlighting, if appropriate; | |
2316 | then the faces specified by overlays, followed by those specified by | |
2317 | text properties, then the @code{mode-line} or | |
2318 | @code{mode-line-inactive} or @code{header-line} face (if in a mode | |
2319 | line or a header line), and last the @code{default} face. | |
8241495d RS |
2320 | |
2321 | When multiple overlays cover one character, an overlay with higher | |
2322 | priority overrides those with lower priority. @xref{Overlays}. | |
2323 | ||
8241495d RS |
2324 | @node Font Selection |
2325 | @subsection Font Selection | |
2326 | ||
2327 | @dfn{Selecting a font} means mapping the specified face attributes for | |
2328 | a character to a font that is available on a particular display. The | |
2329 | face attributes, as determined by face merging, specify most of the | |
2330 | font choice, but not all. Part of the choice depends on what character | |
2331 | it is. | |
2332 | ||
8241495d RS |
2333 | If the face specifies a fontset name, that fontset determines a |
2334 | pattern for fonts of the given charset. If the face specifies a font | |
2335 | family, a font pattern is constructed. | |
2336 | ||
2337 | Emacs tries to find an available font for the given face attributes | |
2338 | and character's registry and encoding. If there is a font that matches | |
2339 | exactly, it is used, of course. The hard case is when no available font | |
2340 | exactly fits the specification. Then Emacs looks for one that is | |
1dffc5db RS |
2341 | ``close''---one attribute at a time. You can specify the order to |
2342 | consider the attributes. In the case where a specified font family is | |
2343 | not available, you can specify a set of mappings for alternatives to | |
2344 | try. | |
8241495d RS |
2345 | |
2346 | @defvar face-font-selection-order | |
8241495d RS |
2347 | This variable specifies the order of importance of the face attributes |
2348 | @code{:width}, @code{:height}, @code{:weight}, and @code{:slant}. The | |
2349 | value should be a list containing those four symbols, in order of | |
2350 | decreasing importance. | |
2351 | ||
2352 | Font selection first finds the best available matches for the first | |
2353 | attribute listed; then, among the fonts which are best in that way, it | |
2354 | searches for the best matches in the second attribute, and so on. | |
2355 | ||
2356 | The attributes @code{:weight} and @code{:width} have symbolic values in | |
2357 | a range centered around @code{normal}. Matches that are more extreme | |
2358 | (farther from @code{normal}) are somewhat preferred to matches that are | |
2359 | less extreme (closer to @code{normal}); this is designed to ensure that | |
2360 | non-normal faces contrast with normal ones, whenever possible. | |
2361 | ||
2362 | The default is @code{(:width :height :weight :slant)}, which means first | |
2363 | find the fonts closest to the specified @code{:width}, then---among the | |
2364 | fonts with that width---find a best match for the specified font height, | |
2365 | and so on. | |
2366 | ||
2367 | One example of a case where this variable makes a difference is when the | |
2368 | default font has no italic equivalent. With the default ordering, the | |
2369 | @code{italic} face will use a non-italic font that is similar to the | |
2370 | default one. But if you put @code{:slant} before @code{:height}, the | |
2371 | @code{italic} face will use an italic font, even if its height is not | |
2372 | quite right. | |
2373 | @end defvar | |
2374 | ||
52d89894 | 2375 | @defvar face-font-family-alternatives |
8241495d RS |
2376 | This variable lets you specify alternative font families to try, if a |
2377 | given family is specified and doesn't exist. Each element should have | |
2378 | this form: | |
2379 | ||
2380 | @example | |
2381 | (@var{family} @var{alternate-families}@dots{}) | |
2382 | @end example | |
2383 | ||
2384 | If @var{family} is specified but not available, Emacs will try the other | |
2385 | families given in @var{alternate-families}, one by one, until it finds a | |
2386 | family that does exist. | |
52d89894 GM |
2387 | @end defvar |
2388 | ||
2389 | @defvar face-font-registry-alternatives | |
52d89894 GM |
2390 | This variable lets you specify alternative font registries to try, if a |
2391 | given registry is specified and doesn't exist. Each element should have | |
2392 | this form: | |
2393 | ||
2394 | @example | |
2395 | (@var{registry} @var{alternate-registries}@dots{}) | |
2396 | @end example | |
2397 | ||
2398 | If @var{registry} is specified but not available, Emacs will try the | |
2399 | other registries given in @var{alternate-registries}, one by one, | |
2400 | until it finds a registry that does exist. | |
8241495d RS |
2401 | @end defvar |
2402 | ||
2403 | Emacs can make use of scalable fonts, but by default it does not use | |
2404 | them, since the use of too many or too big scalable fonts can crash | |
2405 | XFree86 servers. | |
2406 | ||
2407 | @defvar scalable-fonts-allowed | |
8241495d RS |
2408 | This variable controls which scalable fonts to use. A value of |
2409 | @code{nil}, the default, means do not use scalable fonts. @code{t} | |
2410 | means to use any scalable font that seems appropriate for the text. | |
2411 | ||
2412 | Otherwise, the value must be a list of regular expressions. Then a | |
2413 | scalable font is enabled for use if its name matches any regular | |
2414 | expression in the list. For example, | |
2415 | ||
2416 | @example | |
2417 | (setq scalable-fonts-allowed '("muleindian-2$")) | |
2418 | @end example | |
2419 | ||
2420 | @noindent | |
2421 | allows the use of scalable fonts with registry @code{muleindian-2}. | |
eda77a0f | 2422 | @end defvar |
8241495d | 2423 | |
6bc3abcb RS |
2424 | @defvar face-font-rescale-alist |
2425 | This variable specifies scaling for certain faces. Its value should | |
2426 | be a list of elements of the form | |
2427 | ||
2428 | @example | |
2429 | (@var{fontname-regexp} . @var{scale-factor}) | |
2430 | @end example | |
2431 | ||
2432 | If @var{fontname-regexp} matches the font name that is about to be | |
2433 | used, this says to choose a larger similar font according to the | |
2434 | factor @var{scale-factor}. You would use this feature to normalize | |
2435 | the font size if certain fonts are bigger or smaller than their | |
2436 | nominal heights and widths would suggest. | |
2437 | @end defvar | |
2438 | ||
8241495d RS |
2439 | @node Face Functions |
2440 | @subsection Functions for Working with Faces | |
2441 | ||
2442 | Here are additional functions for creating and working with faces. | |
2443 | ||
2444 | @defun make-face name | |
2445 | This function defines a new face named @var{name}, initially with all | |
2446 | attributes @code{nil}. It does nothing if there is already a face named | |
2447 | @var{name}. | |
2448 | @end defun | |
2449 | ||
2450 | @defun face-list | |
2451 | This function returns a list of all defined face names. | |
2452 | @end defun | |
2453 | ||
2454 | @defun copy-face old-face new-name &optional frame new-frame | |
c2579664 | 2455 | This function defines a face named @var{new-name} as a copy of the existing |
8241495d RS |
2456 | face named @var{old-face}. It creates the face @var{new-name} if that |
2457 | doesn't already exist. | |
2458 | ||
2459 | If the optional argument @var{frame} is given, this function applies | |
2460 | only to that frame. Otherwise it applies to each frame individually, | |
2461 | copying attributes from @var{old-face} in each frame to @var{new-face} | |
2462 | in the same frame. | |
2463 | ||
2464 | If the optional argument @var{new-frame} is given, then @code{copy-face} | |
2465 | copies the attributes of @var{old-face} in @var{frame} to @var{new-name} | |
2466 | in @var{new-frame}. | |
969fe9b5 RS |
2467 | @end defun |
2468 | ||
bfe721d1 | 2469 | @defun face-id face |
969fe9b5 | 2470 | This function returns the face number of face @var{face}. |
42b85554 RS |
2471 | @end defun |
2472 | ||
f9f59935 RS |
2473 | @defun face-documentation face |
2474 | This function returns the documentation string of face @var{face}, or | |
2475 | @code{nil} if none was specified for it. | |
2476 | @end defun | |
2477 | ||
42b85554 RS |
2478 | @defun face-equal face1 face2 &optional frame |
2479 | This returns @code{t} if the faces @var{face1} and @var{face2} have the | |
2480 | same attributes for display. | |
2481 | @end defun | |
2482 | ||
2483 | @defun face-differs-from-default-p face &optional frame | |
7e07a66d MB |
2484 | This returns non-@code{nil} if the face @var{face} displays |
2485 | differently from the default face. | |
1911e6e5 RS |
2486 | @end defun |
2487 | ||
31c8b366 GM |
2488 | @cindex face alias |
2489 | A @dfn{face alias} provides an equivalent name for a face. You can | |
2490 | define a face alias by giving the alias symbol the @code{face-alias} | |
2491 | property, with a value of the target face name. The following example | |
b93e3c3b | 2492 | makes @code{modeline} an alias for the @code{mode-line} face. |
31c8b366 GM |
2493 | |
2494 | @example | |
2495 | (put 'modeline 'face-alias 'mode-line) | |
2496 | @end example | |
2497 | ||
2498 | ||
8241495d RS |
2499 | @node Auto Faces |
2500 | @subsection Automatic Face Assignment | |
2501 | @cindex automatic face assignment | |
2502 | @cindex faces, automatic choice | |
2503 | ||
2504 | @cindex Font-Lock mode | |
911a7105 RS |
2505 | This hook is used for automatically assigning faces to text in the |
2506 | buffer. It is part of the implementation of Font-Lock mode. | |
8241495d | 2507 | |
8241495d RS |
2508 | @defvar fontification-functions |
2509 | This variable holds a list of functions that are called by Emacs | |
2510 | redisplay as needed to assign faces automatically to text in the buffer. | |
2511 | ||
2512 | The functions are called in the order listed, with one argument, a | |
2513 | buffer position @var{pos}. Each function should attempt to assign faces | |
2514 | to the text in the current buffer starting at @var{pos}. | |
2515 | ||
2516 | Each function should record the faces they assign by setting the | |
2517 | @code{face} property. It should also add a non-@code{nil} | |
2518 | @code{fontified} property for all the text it has assigned faces to. | |
2519 | That property tells redisplay that faces have been assigned to that text | |
2520 | already. | |
2521 | ||
2522 | It is probably a good idea for each function to do nothing if the | |
2523 | character after @var{pos} already has a non-@code{nil} @code{fontified} | |
2524 | property, but this is not required. If one function overrides the | |
2525 | assignments made by a previous one, the properties as they are | |
2526 | after the last function finishes are the ones that really matter. | |
2527 | ||
2528 | For efficiency, we recommend writing these functions so that they | |
2529 | usually assign faces to around 400 to 600 characters at each call. | |
2530 | @end defvar | |
2531 | ||
2532 | @node Font Lookup | |
2533 | @subsection Looking Up Fonts | |
2534 | ||
2535 | @defun x-list-fonts pattern &optional face frame maximum | |
2536 | This function returns a list of available font names that match | |
2537 | @var{pattern}. If the optional arguments @var{face} and @var{frame} are | |
2538 | specified, then the list is limited to fonts that are the same size as | |
2539 | @var{face} currently is on @var{frame}. | |
2540 | ||
2541 | The argument @var{pattern} should be a string, perhaps with wildcard | |
2542 | characters: the @samp{*} character matches any substring, and the | |
2543 | @samp{?} character matches any single character. Pattern matching | |
2544 | of font names ignores case. | |
2545 | ||
2546 | If you specify @var{face} and @var{frame}, @var{face} should be a face name | |
2547 | (a symbol) and @var{frame} should be a frame. | |
2548 | ||
2549 | The optional argument @var{maximum} sets a limit on how many fonts to | |
2550 | return. If this is non-@code{nil}, then the return value is truncated | |
2551 | after the first @var{maximum} matching fonts. Specifying a small value | |
2552 | for @var{maximum} can make this function much faster, in cases where | |
2553 | many fonts match the pattern. | |
2554 | @end defun | |
2555 | ||
8241495d | 2556 | @defun x-family-fonts &optional family frame |
8241495d RS |
2557 | This function returns a list describing the available fonts for family |
2558 | @var{family} on @var{frame}. If @var{family} is omitted or @code{nil}, | |
2559 | this list applies to all families, and therefore, it contains all | |
2560 | available fonts. Otherwise, @var{family} must be a string; it may | |
2561 | contain the wildcards @samp{?} and @samp{*}. | |
2562 | ||
2563 | The list describes the display that @var{frame} is on; if @var{frame} is | |
8d82c597 EZ |
2564 | omitted or @code{nil}, it applies to the selected frame's display |
2565 | (@pxref{Input Focus}). | |
8241495d RS |
2566 | |
2567 | The list contains a vector of the following form for each font: | |
2568 | ||
2569 | @example | |
2570 | [@var{family} @var{width} @var{point-size} @var{weight} @var{slant} | |
2571 | @var{fixed-p} @var{full} @var{registry-and-encoding}] | |
2572 | @end example | |
2573 | ||
2574 | The first five elements correspond to face attributes; if you | |
2575 | specify these attributes for a face, it will use this font. | |
2576 | ||
2577 | The last three elements give additional information about the font. | |
9a8dc0d3 RS |
2578 | @var{fixed-p} is non-@code{nil} if the font is fixed-pitch. |
2579 | @var{full} is the full name of the font, and | |
2580 | @var{registry-and-encoding} is a string giving the registry and | |
2581 | encoding of the font. | |
8241495d RS |
2582 | |
2583 | The result list is sorted according to the current face font sort order. | |
2584 | @end defun | |
2585 | ||
2586 | @defun x-font-family-list &optional frame | |
8241495d RS |
2587 | This function returns a list of the font families available for |
2588 | @var{frame}'s display. If @var{frame} is omitted or @code{nil}, it | |
8d82c597 | 2589 | describes the selected frame's display (@pxref{Input Focus}). |
8241495d RS |
2590 | |
2591 | The value is a list of elements of this form: | |
2592 | ||
2593 | @example | |
2594 | (@var{family} . @var{fixed-p}) | |
2595 | @end example | |
2596 | ||
2597 | @noindent | |
2598 | Here @var{family} is a font family, and @var{fixed-p} is | |
2599 | non-@code{nil} if fonts of that family are fixed-pitch. | |
2600 | @end defun | |
2601 | ||
2602 | @defvar font-list-limit | |
8241495d RS |
2603 | This variable specifies maximum number of fonts to consider in font |
2604 | matching. The function @code{x-family-fonts} will not return more than | |
2605 | that many fonts, and font selection will consider only that many fonts | |
2606 | when searching a matching font for face attributes. The default is | |
2607 | currently 100. | |
2608 | @end defvar | |
2609 | ||
2610 | @node Fontsets | |
2611 | @subsection Fontsets | |
2612 | ||
2613 | A @dfn{fontset} is a list of fonts, each assigned to a range of | |
2614 | character codes. An individual font cannot display the whole range of | |
2615 | characters that Emacs supports, but a fontset can. Fontsets have names, | |
2616 | just as fonts do, and you can use a fontset name in place of a font name | |
2617 | when you specify the ``font'' for a frame or a face. Here is | |
2618 | information about defining a fontset under Lisp program control. | |
2619 | ||
2620 | @defun create-fontset-from-fontset-spec fontset-spec &optional style-variant-p noerror | |
2621 | This function defines a new fontset according to the specification | |
2622 | string @var{fontset-spec}. The string should have this format: | |
2623 | ||
2624 | @smallexample | |
2625 | @var{fontpattern}, @r{[}@var{charsetname}:@var{fontname}@r{]@dots{}} | |
2626 | @end smallexample | |
2627 | ||
2628 | @noindent | |
2629 | Whitespace characters before and after the commas are ignored. | |
2630 | ||
2631 | The first part of the string, @var{fontpattern}, should have the form of | |
2632 | a standard X font name, except that the last two fields should be | |
2633 | @samp{fontset-@var{alias}}. | |
2634 | ||
2635 | The new fontset has two names, one long and one short. The long name is | |
2636 | @var{fontpattern} in its entirety. The short name is | |
2637 | @samp{fontset-@var{alias}}. You can refer to the fontset by either | |
2638 | name. If a fontset with the same name already exists, an error is | |
2639 | signaled, unless @var{noerror} is non-@code{nil}, in which case this | |
2640 | function does nothing. | |
2641 | ||
2642 | If optional argument @var{style-variant-p} is non-@code{nil}, that says | |
2643 | to create bold, italic and bold-italic variants of the fontset as well. | |
2644 | These variant fontsets do not have a short name, only a long one, which | |
2645 | is made by altering @var{fontpattern} to indicate the bold or italic | |
2646 | status. | |
2647 | ||
2648 | The specification string also says which fonts to use in the fontset. | |
2649 | See below for the details. | |
2650 | @end defun | |
2651 | ||
2652 | The construct @samp{@var{charset}:@var{font}} specifies which font to | |
2653 | use (in this fontset) for one particular character set. Here, | |
2654 | @var{charset} is the name of a character set, and @var{font} is the font | |
2655 | to use for that character set. You can use this construct any number of | |
2656 | times in the specification string. | |
2657 | ||
2658 | For the remaining character sets, those that you don't specify | |
2659 | explicitly, Emacs chooses a font based on @var{fontpattern}: it replaces | |
2660 | @samp{fontset-@var{alias}} with a value that names one character set. | |
ad800164 | 2661 | For the @acronym{ASCII} character set, @samp{fontset-@var{alias}} is replaced |
8241495d RS |
2662 | with @samp{ISO8859-1}. |
2663 | ||
2664 | In addition, when several consecutive fields are wildcards, Emacs | |
2665 | collapses them into a single wildcard. This is to prevent use of | |
2666 | auto-scaled fonts. Fonts made by scaling larger fonts are not usable | |
2667 | for editing, and scaling a smaller font is not useful because it is | |
2668 | better to use the smaller font in its own size, which Emacs does. | |
2669 | ||
2670 | Thus if @var{fontpattern} is this, | |
2671 | ||
2672 | @example | |
2673 | -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24 | |
2674 | @end example | |
2675 | ||
2676 | @noindent | |
ad800164 | 2677 | the font specification for @acronym{ASCII} characters would be this: |
8241495d RS |
2678 | |
2679 | @example | |
2680 | -*-fixed-medium-r-normal-*-24-*-ISO8859-1 | |
2681 | @end example | |
2682 | ||
2683 | @noindent | |
2684 | and the font specification for Chinese GB2312 characters would be this: | |
2685 | ||
2686 | @example | |
2687 | -*-fixed-medium-r-normal-*-24-*-gb2312*-* | |
2688 | @end example | |
2689 | ||
2690 | You may not have any Chinese font matching the above font | |
2691 | specification. Most X distributions include only Chinese fonts that | |
2692 | have @samp{song ti} or @samp{fangsong ti} in the @var{family} field. In | |
2693 | such a case, @samp{Fontset-@var{n}} can be specified as below: | |
2694 | ||
2695 | @smallexample | |
2696 | Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\ | |
2697 | chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-* | |
2698 | @end smallexample | |
2699 | ||
2700 | @noindent | |
2701 | Then, the font specifications for all but Chinese GB2312 characters have | |
2702 | @samp{fixed} in the @var{family} field, and the font specification for | |
2703 | Chinese GB2312 characters has a wild card @samp{*} in the @var{family} | |
2704 | field. | |
2705 | ||
885fef7c KH |
2706 | @defun set-fontset-font name character fontname &optional frame |
2707 | This function modifies the existing fontset @var{name} to | |
2708 | use the font name @var{fontname} for the character @var{character}. | |
2709 | ||
a2296bf9 | 2710 | If @var{name} is @code{nil}, this function modifies the default |
812a2341 | 2711 | fontset, whose short name is @samp{fontset-default}. |
885fef7c | 2712 | |
a2296bf9 KH |
2713 | @var{character} may be a cons; @code{(@var{from} . @var{to})}, where |
2714 | @var{from} and @var{to} are non-generic characters. In that case, use | |
2715 | @var{fontname} for all characters in the range @var{from} and @var{to} | |
2716 | (inclusive). | |
885fef7c KH |
2717 | |
2718 | @var{character} may be a charset. In that case, use | |
2719 | @var{fontname} for all character in the charsets. | |
2720 | ||
a2296bf9 KH |
2721 | @var{fontname} may be a cons; @code{(@var{family} . @var{registry})}, |
2722 | where @var{family} is a family name of a font (possibly including a | |
2723 | foundry name at the head), @var{registry} is a registry name of a font | |
2724 | (possibly including an encoding name at the tail). | |
885fef7c | 2725 | |
a2296bf9 KH |
2726 | For instance, this changes the default fontset to use a font of which |
2727 | registry name is @samp{JISX0208.1983} for all characters belonging to | |
2728 | the charset @code{japanese-jisx0208}. | |
885fef7c | 2729 | |
342fd6cd | 2730 | @smallexample |
885fef7c | 2731 | (set-fontset-font nil 'japanese-jisx0208 '(nil . "JISX0208.1983")) |
342fd6cd | 2732 | @end smallexample |
885fef7c KH |
2733 | @end defun |
2734 | ||
f6cad089 RS |
2735 | @defun char-displayable-p char |
2736 | This function returns @code{t} if Emacs ought to be able to display | |
2737 | @var{char}. More precisely, if the selected frame's fontset has a | |
2738 | font to display the character set that @var{char} belongs to. | |
2739 | ||
2740 | Fontsets can specify a font on a per-character basis; when the fontset | |
2741 | does that, this function's value may not be accurate. | |
2742 | @end defun | |
2743 | ||
8a6ca431 RS |
2744 | @node Fringes |
2745 | @section Fringes | |
2746 | @cindex Fringes | |
2747 | ||
2748 | The @dfn{fringes} of a window are thin vertical strips down the | |
2749 | sides that are used for displaying bitmaps that indicate truncation, | |
c2579664 RS |
2750 | continuation, horizontal scrolling, and the overlay arrow. |
2751 | ||
2752 | @menu | |
2753 | * Fringe Size/Pos:: Specifying where to put the window fringes. | |
01bc0451 KS |
2754 | * Fringe Indicators:: Displaying indicator icons in the window fringes. |
2755 | * Fringe Cursors:: Displaying cursors in the right fringe. | |
2756 | * Fringe Bitmaps:: Specifying bitmaps for fringe indicators. | |
c2579664 RS |
2757 | * Customizing Bitmaps:: Specifying your own bitmaps to use in the fringes. |
2758 | * Overlay Arrow:: Display of an arrow to indicate position. | |
2759 | @end menu | |
2760 | ||
2761 | @node Fringe Size/Pos | |
2762 | @subsection Fringe Size and Position | |
2763 | ||
70a08278 NR |
2764 | The following buffer-local variables control the position and width |
2765 | of the window fringes. | |
8a6ca431 RS |
2766 | |
2767 | @defvar fringes-outside-margins | |
70a08278 NR |
2768 | The fringes normally appear between the display margins and the window |
2769 | text. If the value is non-@code{nil}, they appear outside the display | |
2770 | margins. @xref{Display Margins}. | |
8a6ca431 RS |
2771 | @end defvar |
2772 | ||
2773 | @defvar left-fringe-width | |
2774 | This variable, if non-@code{nil}, specifies the width of the left | |
70a08278 NR |
2775 | fringe in pixels. A value of @code{nil} means to use the left fringe |
2776 | width from the window's frame. | |
8a6ca431 RS |
2777 | @end defvar |
2778 | ||
2779 | @defvar right-fringe-width | |
2780 | This variable, if non-@code{nil}, specifies the width of the right | |
70a08278 NR |
2781 | fringe in pixels. A value of @code{nil} means to use the right fringe |
2782 | width from the window's frame. | |
8a6ca431 RS |
2783 | @end defvar |
2784 | ||
2785 | The values of these variables take effect when you display the | |
2786 | buffer in a window. If you change them while the buffer is visible, | |
812a2341 RS |
2787 | you can call @code{set-window-buffer} to display it once again in the |
2788 | same window, to make the changes take effect. | |
8a6ca431 RS |
2789 | |
2790 | @defun set-window-fringes window left &optional right outside-margins | |
812a2341 | 2791 | This function sets the fringe widths of window @var{window}. |
479dbc9d | 2792 | If @var{window} is @code{nil}, the selected window is used. |
8a6ca431 RS |
2793 | |
2794 | The argument @var{left} specifies the width in pixels of the left | |
2795 | fringe, and likewise @var{right} for the right fringe. A value of | |
2796 | @code{nil} for either one stands for the default width. If | |
2797 | @var{outside-margins} is non-@code{nil}, that specifies that fringes | |
2798 | should appear outside of the display margins. | |
2799 | @end defun | |
2800 | ||
479dbc9d | 2801 | @defun window-fringes &optional window |
8a6ca431 | 2802 | This function returns information about the fringes of a window |
479dbc9d KS |
2803 | @var{window}. If @var{window} is omitted or @code{nil}, the selected |
2804 | window is used. The value has the form @code{(@var{left-width} | |
c2579664 | 2805 | @var{right-width} @var{outside-margins})}. |
8a6ca431 RS |
2806 | @end defun |
2807 | ||
01bc0451 KS |
2808 | |
2809 | @node Fringe Indicators | |
2810 | @subsection Fringe Indicators | |
2811 | @cindex fringe indicators | |
2812 | @cindex indicators, fringe | |
2813 | ||
2814 | The @dfn{fringe indicators} are tiny icons Emacs displays in the | |
2815 | window fringe (on a graphic display) to indicate truncated or | |
2816 | continued lines, buffer boundaries, overlay arrow, etc. | |
2817 | ||
2818 | @defopt indicate-empty-lines | |
01bc0451 KS |
2819 | @cindex fringes, and empty line indication |
2820 | When this is non-@code{nil}, Emacs displays a special glyph in the | |
2821 | fringe of each empty line at the end of the buffer, on graphical | |
2822 | displays. @xref{Fringes}. This variable is automatically | |
2823 | buffer-local in every buffer. | |
2824 | @end defopt | |
2825 | ||
2826 | @defvar indicate-buffer-boundaries | |
2827 | This buffer-local variable controls how the buffer boundaries and | |
2828 | window scrolling are indicated in the window fringes. | |
2829 | ||
2830 | Emacs can indicate the buffer boundaries---that is, the first and last | |
2831 | line in the buffer---with angle icons when they appear on the screen. | |
2832 | In addition, Emacs can display an up-arrow in the fringe to show | |
2833 | that there is text above the screen, and a down-arrow to show | |
2834 | there is text below the screen. | |
2835 | ||
ab1ea94e | 2836 | There are three kinds of basic values: |
01bc0451 KS |
2837 | |
2838 | @table @asis | |
2839 | @item @code{nil} | |
ab1ea94e | 2840 | Don't display any of these fringe icons. |
01bc0451 | 2841 | @item @code{left} |
ab1ea94e | 2842 | Display the angle icons and arrows in the left fringe. |
01bc0451 | 2843 | @item @code{right} |
ab1ea94e RS |
2844 | Display the angle icons and arrows in the right fringe. |
2845 | @item any non-alist | |
2846 | Display the angle icons in the left fringe | |
2847 | and don't display the arrows. | |
01bc0451 KS |
2848 | @end table |
2849 | ||
ab1ea94e RS |
2850 | Otherwise the value should be an alist that specifies which fringe |
2851 | indicators to display and where. Each element of the alist should | |
2852 | have the form @code{(@var{indicator} . @var{position})}. Here, | |
2853 | @var{indicator} is one of @code{top}, @code{bottom}, @code{up}, | |
2854 | @code{down}, and @code{t} (which covers all the icons not yet | |
2855 | specified), while @var{position} is one of @code{left}, @code{right} | |
2856 | and @code{nil}. | |
2857 | ||
2858 | For example, @code{((top . left) (t . right))} places the top angle | |
2859 | bitmap in left fringe, and the bottom angle bitmap as well as both | |
2860 | arrow bitmaps in right fringe. To show the angle bitmaps in the left | |
2861 | fringe, and no arrow bitmaps, use @code{((top . left) (bottom . left))}. | |
01bc0451 KS |
2862 | @end defvar |
2863 | ||
2864 | @defvar default-indicate-buffer-boundaries | |
2865 | The value of this variable is the default value for | |
2866 | @code{indicate-buffer-boundaries} in buffers that do not override it. | |
2867 | @end defvar | |
2868 | ||
2869 | @defvar fringe-indicator-alist | |
2870 | This buffer-local variable specifies the mapping from logical fringe | |
2871 | indicators to the actual bitmaps displayed in the window fringes. | |
2872 | ||
2873 | These symbols identify the logical fringe indicators: | |
2874 | ||
2875 | @table @asis | |
2876 | @item Truncation and continuation line indicators: | |
2877 | @code{truncation}, @code{continuation}. | |
2878 | ||
2879 | @item Buffer position indicators: | |
2880 | @code{up}, @code{down}, | |
2881 | @code{top}, @code{bottom}, | |
2882 | @code{top-bottom}. | |
2883 | ||
2884 | @item Empty line indicator: | |
2885 | @code{empty-line}. | |
2886 | ||
2887 | @item Overlay arrow indicator: | |
2888 | @code{overlay-arrow}. | |
2889 | ||
2890 | @item Unknown bitmap indicator: | |
2891 | @code{unknown}. | |
2892 | @end table | |
2893 | ||
2894 | The value is an alist where each element @code{(@var{indicator} . @var{bitmaps})} | |
2895 | specifies the fringe bitmaps used to display a specific logical | |
2896 | fringe indicator. | |
2897 | ||
2898 | Here, @var{indicator} specifies the logical indicator type, and | |
2899 | @var{bitmaps} is list of symbols @code{(@var{left} @var{right} | |
2900 | [@var{left1} @var{right1}])} which specifies the actual bitmap shown | |
2901 | in the left or right fringe for the logical indicator. | |
2902 | ||
2903 | The @var{left} and @var{right} symbols specify the bitmaps shown in | |
2904 | the left and/or right fringe for the specific indicator. The | |
2905 | @var{left1} or @var{right1} bitmaps are used only for the `bottom' and | |
2906 | `top-bottom indicators when the last (only) line in has no final | |
2907 | newline. Alternatively, @var{bitmaps} may be a single symbol which is | |
2908 | used in both left and right fringes. | |
2909 | ||
2910 | When @code{fringe-indicator-alist} has a buffer-local value, and there | |
2911 | is no bitmap defined for a logical indicator, or the bitmap is | |
2912 | @code{t}, the corresponding value from the (non-local) | |
7704f61d | 2913 | @code{default-fringe-indicator-alist} is used. |
01bc0451 KS |
2914 | |
2915 | To completely hide a specific indicator, set the bitmap to @code{nil}. | |
2916 | @end defvar | |
2917 | ||
7704f61d | 2918 | @defvar default-fringe-indicator-alist |
01bc0451 KS |
2919 | The value of this variable is the default value for |
2920 | @code{fringe-indicator-alist} in buffers that do not override it. | |
2921 | @end defvar | |
2922 | ||
42b50684 KB |
2923 | Standard fringe bitmaps for indicators: |
2924 | @example | |
2925 | left-arrow right-arrow up-arrow down-arrow | |
2926 | left-curly-arrow right-curly-arrow | |
2927 | left-triangle right-triangle | |
2928 | top-left-angle top-right-angle | |
2929 | bottom-left-angle bottom-right-angle | |
2930 | left-bracket right-bracket | |
2931 | filled-rectangle hollow-rectangle | |
2932 | filled-square hollow-square | |
2933 | vertical-bar horizontal-bar | |
2934 | empty-line question-mark | |
2935 | @end example | |
01bc0451 KS |
2936 | |
2937 | @node Fringe Cursors | |
2938 | @subsection Fringe Cursors | |
2939 | @cindex fringe cursors | |
2940 | @cindex cursor, fringe | |
2941 | ||
2942 | When a line is exactly as wide as the window, Emacs displays the | |
2943 | cursor in the right fringe instead of using two lines. Different | |
2944 | bitmaps are used to represent the cursor in the fringe depending on | |
2945 | the current buffer's cursor type. | |
2946 | ||
2947 | @table @asis | |
2948 | @item Logical cursor types: | |
2949 | @code{box} , @code{hollow}, @code{bar}, | |
2950 | @code{hbar}, @code{hollow-small}. | |
2951 | @end table | |
2952 | ||
2953 | The @code{hollow-small} type is used instead of @code{hollow} when the | |
2954 | normal @code{hollow-rectangle} bitmap is too tall to fit on a specific | |
2955 | display line. | |
2956 | ||
9b6e4bc3 | 2957 | @defvar overflow-newline-into-fringe |
26b76360 RS |
2958 | If this is non-@code{nil}, lines exactly as wide as the window (not |
2959 | counting the final newline character) are not continued. Instead, | |
2960 | when point is at the end of the line, the cursor appears in the right | |
2961 | fringe. | |
9b6e4bc3 KS |
2962 | @end defvar |
2963 | ||
01bc0451 KS |
2964 | @defvar fringe-cursor-alist |
2965 | This variable specifies the mapping from logical cursor type to the | |
2966 | actual fringe bitmaps displayed in the right fringe. The value is an | |
1daf0dde | 2967 | alist where each element @code{(@var{cursor} . @var{bitmap})} specifies |
01bc0451 KS |
2968 | the fringe bitmaps used to display a specific logical cursor type in |
2969 | the fringe. Here, @var{cursor} specifies the logical cursor type and | |
2970 | @var{bitmap} is a symbol specifying the fringe bitmap to be displayed | |
2971 | for that logical cursor type. | |
2972 | ||
2973 | When @code{fringe-cursor-alist} has a buffer-local value, and there is | |
2974 | no bitmap defined for a cursor type, the corresponding value from the | |
2975 | (non-local) @code{default-fringes-indicator-alist} is used. | |
2976 | @end defvar | |
2977 | ||
2978 | @defvar default-fringes-cursor-alist | |
2979 | The value of this variable is the default value for | |
2980 | @code{fringe-cursor-alist} in buffers that do not override it. | |
2981 | @end defvar | |
2982 | ||
42b50684 KB |
2983 | Standard bitmaps for displaying the cursor in right fringe: |
2984 | @example | |
2985 | filled-rectangle hollow-rectangle filled-square hollow-square | |
2986 | vertical-bar horizontal-bar | |
2987 | @end example | |
01bc0451 KS |
2988 | |
2989 | ||
9b6e4bc3 | 2990 | @node Fringe Bitmaps |
c2579664 | 2991 | @subsection Fringe Bitmaps |
26b76360 RS |
2992 | @cindex fringe bitmaps |
2993 | @cindex bitmaps, fringe | |
2994 | ||
01bc0451 KS |
2995 | The @dfn{fringe bitmaps} are the actual bitmaps which represent the |
2996 | logical fringe indicators for truncated or continued lines, buffer | |
2997 | boundaries, overlay arrow, etc. Fringe bitmap symbols have their own | |
2998 | name space. The fringe bitmaps are shared by all frames and windows. | |
2999 | You can redefine the built-in fringe bitmaps, and you can define new | |
3000 | fringe bitmaps. | |
26b76360 RS |
3001 | |
3002 | The way to display a bitmap in the left or right fringes for a given | |
3003 | line in a window is by specifying the @code{display} property for one | |
3004 | of the characters that appears in it. Use a display specification of | |
3005 | the form @code{(left-fringe @var{bitmap} [@var{face}])} or | |
3006 | @code{(right-fringe @var{bitmap} [@var{face}])} (@pxref{Display | |
e58b3620 RS |
3007 | Property}). Here, @var{bitmap} is a symbol identifying the bitmap you |
3008 | want, and @var{face} (which is optional) is the name of the face whose | |
3009 | colors should be used for displaying the bitmap, instead of the | |
3010 | default @code{fringe} face. @var{face} is automatically merged with | |
3011 | the @code{fringe} face, so normally @var{face} need only specify the | |
3012 | foreground color for the bitmap. | |
26b76360 | 3013 | |
26b76360 RS |
3014 | @defun fringe-bitmaps-at-pos &optional pos window |
3015 | This function returns the fringe bitmaps of the display line | |
3016 | containing position @var{pos} in window @var{window}. The return | |
cf6d43ae | 3017 | value has the form @code{(@var{left} @var{right} @var{ov})}, where @var{left} |
90801c68 | 3018 | is the symbol for the fringe bitmap in the left fringe (or @code{nil} |
cf6d43ae KS |
3019 | if no bitmap), @var{right} is similar for the right fringe, and @var{ov} |
3020 | is non-@code{nil} if there is an overlay arrow in the left fringe. | |
26b76360 RS |
3021 | |
3022 | The value is @code{nil} if @var{pos} is not visible in @var{window}. | |
3023 | If @var{window} is @code{nil}, that stands for the selected window. | |
3024 | If @var{pos} is @code{nil}, that stands for the value of point in | |
3025 | @var{window}. | |
3026 | @end defun | |
9b6e4bc3 | 3027 | |
26b76360 | 3028 | @node Customizing Bitmaps |
c2579664 | 3029 | @subsection Customizing Fringe Bitmaps |
26b76360 | 3030 | |
90801c68 KS |
3031 | @defun define-fringe-bitmap bitmap bits &optional height width align |
3032 | This function defines the symbol @var{bitmap} as a new fringe bitmap, | |
3033 | or replaces an existing bitmap with that name. | |
9b6e4bc3 | 3034 | |
26b76360 RS |
3035 | The argument @var{bits} specifies the image to use. It should be |
3036 | either a string or a vector of integers, where each element (an | |
3037 | integer) corresponds to one row of the bitmap. Each bit of an integer | |
90801c68 KS |
3038 | corresponds to one pixel of the bitmap, where the low bit corresponds |
3039 | to the rightmost pixel of the bitmap. | |
9b6e4bc3 | 3040 | |
26b76360 RS |
3041 | The height is normally the length of @var{bits}. However, you |
3042 | can specify a different height with non-@code{nil} @var{height}. The width | |
3043 | is normally 8, but you can specify a different width with non-@code{nil} | |
3044 | @var{width}. The width must be an integer between 1 and 16. | |
9b6e4bc3 | 3045 | |
26b76360 RS |
3046 | The argument @var{align} specifies the positioning of the bitmap |
3047 | relative to the range of rows where it is used; the default is to | |
3048 | center the bitmap. The allowed values are @code{top}, @code{center}, | |
3049 | or @code{bottom}. | |
9b6e4bc3 | 3050 | |
26b76360 | 3051 | The @var{align} argument may also be a list @code{(@var{align} |
17234906 | 3052 | @var{periodic})} where @var{align} is interpreted as described above. |
26b76360 RS |
3053 | If @var{periodic} is non-@code{nil}, it specifies that the rows in |
3054 | @code{bits} should be repeated enough times to reach the specified | |
3055 | height. | |
9b6e4bc3 KS |
3056 | @end defun |
3057 | ||
3058 | @defun destroy-fringe-bitmap bitmap | |
26b76360 RS |
3059 | This function destroy the fringe bitmap identified by @var{bitmap}. |
3060 | If @var{bitmap} identifies a standard fringe bitmap, it actually | |
3061 | restores the standard definition of that bitmap, instead of | |
3062 | eliminating it entirely. | |
9b6e4bc3 KS |
3063 | @end defun |
3064 | ||
3065 | @defun set-fringe-bitmap-face bitmap &optional face | |
26b76360 RS |
3066 | This sets the face for the fringe bitmap @var{bitmap} to @var{face}. |
3067 | If @var{face} is @code{nil}, it selects the @code{fringe} face. The | |
3068 | bitmap's face controls the color to draw it in. | |
9b6e4bc3 | 3069 | |
e58b3620 RS |
3070 | @var{face} is merged with the @code{fringe} face, so normally |
3071 | @var{face} should specify only the foreground color. | |
9b6e4bc3 KS |
3072 | @end defun |
3073 | ||
c2579664 RS |
3074 | @node Overlay Arrow |
3075 | @subsection The Overlay Arrow | |
3076 | @cindex overlay arrow | |
3077 | ||
3078 | The @dfn{overlay arrow} is useful for directing the user's attention | |
3079 | to a particular line in a buffer. For example, in the modes used for | |
3080 | interface to debuggers, the overlay arrow indicates the line of code | |
3081 | about to be executed. This feature has nothing to do with | |
3082 | @dfn{overlays} (@pxref{Overlays}). | |
3083 | ||
3084 | @defvar overlay-arrow-string | |
3085 | This variable holds the string to display to call attention to a | |
3086 | particular line, or @code{nil} if the arrow feature is not in use. | |
3087 | On a graphical display the contents of the string are ignored; instead a | |
3088 | glyph is displayed in the fringe area to the left of the display area. | |
3089 | @end defvar | |
3090 | ||
3091 | @defvar overlay-arrow-position | |
3092 | This variable holds a marker that indicates where to display the overlay | |
3093 | arrow. It should point at the beginning of a line. On a non-graphical | |
3094 | display the arrow text | |
3095 | appears at the beginning of that line, overlaying any text that would | |
3096 | otherwise appear. Since the arrow is usually short, and the line | |
3097 | usually begins with indentation, normally nothing significant is | |
3098 | overwritten. | |
3099 | ||
751fc7d9 RS |
3100 | The overlay-arrow string is displayed in any given buffer if the value |
3101 | of @code{overlay-arrow-position} in that buffer points into that | |
3102 | buffer. Thus, it works to can display multiple overlay arrow strings | |
3103 | by creating buffer-local bindings of @code{overlay-arrow-position}. | |
3104 | However, it is usually cleaner to use | |
3105 | @code{overlay-arrow-variable-list} to achieve this result. | |
c2579664 RS |
3106 | @c !!! overlay-arrow-position: but the overlay string may remain in the display |
3107 | @c of some other buffer until an update is required. This should be fixed | |
3108 | @c now. Is it? | |
3109 | @end defvar | |
3110 | ||
3111 | You can do a similar job by creating an overlay with a | |
3112 | @code{before-string} property. @xref{Overlay Properties}. | |
3113 | ||
3114 | You can define multiple overlay arrows via the variable | |
3115 | @code{overlay-arrow-variable-list}. | |
3116 | ||
3117 | @defvar overlay-arrow-variable-list | |
b2c8f143 | 3118 | This variable's value is a list of variables, each of which specifies |
c2579664 RS |
3119 | the position of an overlay arrow. The variable |
3120 | @code{overlay-arrow-position} has its normal meaning because it is on | |
3121 | this list. | |
3122 | @end defvar | |
3123 | ||
3124 | Each variable on this list can have properties | |
3125 | @code{overlay-arrow-string} and @code{overlay-arrow-bitmap} that | |
3126 | specify an overlay arrow string (for text-only terminals) or fringe | |
3127 | bitmap (for graphical terminals) to display at the corresponding | |
3128 | overlay arrow position. If either property is not set, the default | |
1daf0dde KS |
3129 | @code{overlay-arrow-string} or @code{overlay-arrow} fringe indicator |
3130 | is used. | |
c2579664 | 3131 | |
f6cad089 RS |
3132 | @node Scroll Bars |
3133 | @section Scroll Bars | |
3134 | ||
3135 | Normally the frame parameter @code{vertical-scroll-bars} controls | |
e58b3620 RS |
3136 | whether the windows in the frame have vertical scroll bars, and |
3137 | whether they are on the left or right. The frame parameter | |
f6cad089 | 3138 | @code{scroll-bar-width} specifies how wide they are (@code{nil} |
2adbd9b6 | 3139 | meaning the default). @xref{Layout Parameters}. |
f6cad089 | 3140 | |
e58b3620 RS |
3141 | @defun frame-current-scroll-bars &optional frame |
3142 | This function reports the scroll bar type settings for frame | |
3143 | @var{frame}. The value is a cons cell | |
3144 | @code{(@var{vertical-type} .@: @var{horizontal-type})}, where | |
3145 | @var{vertical-type} is either @code{left}, @code{right}, or @code{nil} | |
3146 | (which means no scroll bar.) @var{horizontal-type} is meant to | |
3147 | specify the horizontal scroll bar type, but since they are not | |
3148 | implemented, it is always @code{nil}. | |
3149 | @end defun | |
3150 | ||
93449dd1 KS |
3151 | @vindex vertical-scroll-bar |
3152 | You can enable or disable scroll bars for a particular buffer, | |
3153 | by setting the variable @code{vertical-scroll-bar}. This variable | |
3154 | automatically becomes buffer-local when set. The possible values are | |
3155 | @code{left}, @code{right}, @code{t}, which means to use the | |
3156 | frame's default, and @code{nil} for no scroll bar. | |
3157 | ||
3158 | You can also control this for individual windows. Call the function | |
f6cad089 RS |
3159 | @code{set-window-scroll-bars} to specify what to do for a specific window: |
3160 | ||
3161 | @defun set-window-scroll-bars window width &optional vertical-type horizontal-type | |
26b76360 RS |
3162 | This function sets the width and type of scroll bars for window |
3163 | @var{window}. | |
3164 | ||
f6cad089 | 3165 | @var{width} specifies the scroll bar width in pixels (@code{nil} means |
26b76360 RS |
3166 | use the width specified for the frame). @var{vertical-type} specifies |
3167 | whether to have a vertical scroll bar and, if so, where. The possible | |
3168 | values are @code{left}, @code{right} and @code{nil}, just like the | |
3169 | values of the @code{vertical-scroll-bars} frame parameter. | |
f6cad089 RS |
3170 | |
3171 | The argument @var{horizontal-type} is meant to specify whether and | |
3172 | where to have horizontal scroll bars, but since they are not | |
26b76360 RS |
3173 | implemented, it has no effect. If @var{window} is @code{nil}, the |
3174 | selected window is used. | |
f6cad089 RS |
3175 | @end defun |
3176 | ||
3177 | @defun window-scroll-bars &optional window | |
3178 | Report the width and type of scroll bars specified for @var{window}. | |
479dbc9d KS |
3179 | If @var{window} is omitted or @code{nil}, the selected window is used. |
3180 | The value is a list of the form @code{(@var{width} | |
f6cad089 RS |
3181 | @var{cols} @var{vertical-type} @var{horizontal-type})}. The value |
3182 | @var{width} is the value that was specified for the width (which may | |
3183 | be @code{nil}); @var{cols} is the number of columns that the scroll | |
3184 | bar actually occupies. | |
3185 | ||
3186 | @var{horizontal-type} is not actually meaningful. | |
3187 | @end defun | |
3188 | ||
3189 | If you don't specify these values for a window with | |
3190 | @code{set-window-scroll-bars}, the buffer-local variables | |
3191 | @code{scroll-bar-mode} and @code{scroll-bar-width} in the buffer being | |
3192 | displayed control the window's vertical scroll bars. The function | |
3193 | @code{set-window-buffer} examines these variables. If you change them | |
3194 | in a buffer that is already visible in a window, you can make the | |
3195 | window take note of the new values by calling @code{set-window-buffer} | |
3196 | specifying the same buffer that is already displayed. | |
3197 | ||
fe8d1469 RS |
3198 | @defvar scroll-bar-mode |
3199 | This variable, always local in all buffers, controls whether and where | |
3200 | to put scroll bars in windows displaying the buffer. The possible values | |
3201 | are @code{nil} for no scroll bar, @code{left} to put a scroll bar on | |
3202 | the left, and @code{right} to put a scroll bar on the right. | |
3203 | @end defvar | |
3204 | ||
e58b3620 RS |
3205 | @defun window-current-scroll-bars &optional window |
3206 | This function reports the scroll bar type for window @var{window}. | |
3207 | If @var{window} is omitted or @code{nil}, the selected window is used. | |
3208 | The value is a cons cell | |
3209 | @code{(@var{vertical-type} .@: @var{horizontal-type})}. Unlike | |
3210 | @code{window-scroll-bars}, this reports the scroll bar type actually | |
3211 | used, once frame defaults and @code{scroll-bar-mode} are taken into | |
3212 | account. | |
3213 | @end defun | |
3214 | ||
fe8d1469 RS |
3215 | @defvar scroll-bar-width |
3216 | This variable, always local in all buffers, specifies the width of the | |
3217 | buffer's scroll bars, measured in pixels. A value of @code{nil} means | |
3218 | to use the value specified by the frame. | |
3219 | @end defvar | |
3220 | ||
8241495d RS |
3221 | @node Display Property |
3222 | @section The @code{display} Property | |
3223 | @cindex display specification | |
3224 | @kindex display @r{(text property)} | |
3225 | ||
a40d4712 PR |
3226 | The @code{display} text property (or overlay property) is used to |
3227 | insert images into text, and also control other aspects of how text | |
911a7105 RS |
3228 | displays. The value of the @code{display} property should be a |
3229 | display specification, or a list or vector containing several display | |
4db6da64 RS |
3230 | specifications. |
3231 | ||
3232 | Some kinds of @code{display} properties specify something to display | |
3233 | instead of the text that has the property. In this case, ``the text'' | |
3234 | means all the consecutive characters that have the same Lisp object as | |
3235 | their @code{display} property; these characters are replaced as a | |
3236 | single unit. By contrast, characters that have similar but distinct | |
3237 | Lisp objects as their @code{display} properties are handled | |
3238 | separately. Here's a function that illustrates this point: | |
3239 | ||
342fd6cd | 3240 | @smallexample |
4db6da64 RS |
3241 | (defun foo () |
3242 | (goto-char (point-min)) | |
3243 | (dotimes (i 5) | |
3244 | (let ((string (concat "A"))) | |
3245 | (put-text-property (point) (1+ (point)) 'display string) | |
3246 | (forward-char 1) | |
3247 | (put-text-property (point) (1+ (point)) 'display string) | |
3248 | (forward-char 1)))) | |
342fd6cd | 3249 | @end smallexample |
4db6da64 RS |
3250 | |
3251 | @noindent | |
3252 | It gives each of the first ten characters in the buffer string | |
3253 | @code{"A"} as the @code{display} property, but they don't all get the | |
3254 | same string. The first two characters get the same string, so they | |
3255 | together are replaced with one @samp{A}. The next two characters get | |
3256 | a second string, so they together are replaced with one @samp{A}. | |
3257 | Likewise for each following pair of characters. Thus, the ten | |
3258 | characters appear as five A's. This function would have the same | |
3259 | results: | |
3260 | ||
342fd6cd | 3261 | @smallexample |
4db6da64 RS |
3262 | (defun foo () |
3263 | (goto-char (point-min)) | |
3264 | (dotimes (i 5) | |
3265 | (let ((string (concat "A"))) | |
3266 | (put-text-property (point) (2+ (point)) 'display string) | |
3267 | (put-text-property (point) (1+ (point)) 'display string) | |
3268 | (forward-char 2)))) | |
342fd6cd | 3269 | @end smallexample |
4db6da64 RS |
3270 | |
3271 | @noindent | |
3272 | This illustrates that what matters is the property value for | |
3273 | each character. If two consecutive characters have the same | |
b2c8f143 | 3274 | object as the @code{display} property value, it's irrelevant |
4db6da64 RS |
3275 | whether they got this property from a single call to |
3276 | @code{put-text-property} or from two different calls. | |
3277 | ||
3278 | The rest of this section describes several kinds of | |
911a7105 | 3279 | display specifications and what they mean. |
8241495d RS |
3280 | |
3281 | @menu | |
02c77ee9 | 3282 | * Specified Space:: Displaying one space with a specified width. |
9b6e4bc3 | 3283 | * Pixel Specification:: Specifying space width or height in pixels. |
02c77ee9 | 3284 | * Other Display Specs:: Displaying an image; magnifying text; moving it |
177c0ea7 | 3285 | up or down on the page; adjusting the width |
a40d4712 PR |
3286 | of spaces within text. |
3287 | * Display Margins:: Displaying text or images to the side of the main text. | |
8241495d RS |
3288 | @end menu |
3289 | ||
3290 | @node Specified Space | |
3291 | @subsection Specified Spaces | |
3292 | @cindex spaces, specified height or width | |
3293 | @cindex specified spaces | |
3294 | @cindex variable-width spaces | |
3295 | ||
3296 | To display a space of specified width and/or height, use a display | |
a40d4712 PR |
3297 | specification of the form @code{(space . @var{props})}, where |
3298 | @var{props} is a property list (a list of alternating properties and | |
3299 | values). You can put this property on one or more consecutive | |
3300 | characters; a space of the specified height and width is displayed in | |
3301 | place of @emph{all} of those characters. These are the properties you | |
0b0e8041 | 3302 | can use in @var{props} to specify the weight of the space: |
8241495d RS |
3303 | |
3304 | @table @code | |
3305 | @item :width @var{width} | |
9b6e4bc3 KS |
3306 | If @var{width} is an integer or floating point number, it specifies |
3307 | that the space width should be @var{width} times the normal character | |
26b76360 | 3308 | width. @var{width} can also be a @dfn{pixel width} specification |
9b6e4bc3 | 3309 | (@pxref{Pixel Specification}). |
8241495d RS |
3310 | |
3311 | @item :relative-width @var{factor} | |
3312 | Specifies that the width of the stretch should be computed from the | |
3313 | first character in the group of consecutive characters that have the | |
3314 | same @code{display} property. The space width is the width of that | |
3315 | character, multiplied by @var{factor}. | |
3316 | ||
3317 | @item :align-to @var{hpos} | |
9b6e4bc3 | 3318 | Specifies that the space should be wide enough to reach @var{hpos}. |
26b76360 RS |
3319 | If @var{hpos} is a number, it is measured in units of the normal |
3320 | character width. @var{hpos} can also be a @dfn{pixel width} | |
3321 | specification (@pxref{Pixel Specification}). | |
8241495d RS |
3322 | @end table |
3323 | ||
0b0e8041 | 3324 | You should use one and only one of the above properties. You can |
26b76360 | 3325 | also specify the height of the space, with these properties: |
8241495d RS |
3326 | |
3327 | @table @code | |
3328 | @item :height @var{height} | |
9b6e4bc3 KS |
3329 | Specifies the height of the space. |
3330 | If @var{height} is an integer or floating point number, it specifies | |
3331 | that the space height should be @var{height} times the normal character | |
3332 | height. The @var{height} may also be a @dfn{pixel height} specification | |
3333 | (@pxref{Pixel Specification}). | |
8241495d RS |
3334 | |
3335 | @item :relative-height @var{factor} | |
3336 | Specifies the height of the space, multiplying the ordinary height | |
3337 | of the text having this display specification by @var{factor}. | |
3338 | ||
3339 | @item :ascent @var{ascent} | |
9b6e4bc3 KS |
3340 | If the value of @var{ascent} is a non-negative number no greater than |
3341 | 100, it specifies that @var{ascent} percent of the height of the space | |
3342 | should be considered as the ascent of the space---that is, the part | |
3343 | above the baseline. The ascent may also be specified in pixel units | |
3344 | with a @dfn{pixel ascent} specification (@pxref{Pixel Specification}). | |
3345 | ||
8241495d RS |
3346 | @end table |
3347 | ||
0b0e8041 | 3348 | Don't use both @code{:height} and @code{:relative-height} together. |
8241495d | 3349 | |
5fc1299d | 3350 | The @code{:width} and @code{:align-to} properties are supported on |
26b76360 RS |
3351 | non-graphic terminals, but the other space properties in this section |
3352 | are not. | |
3353 | ||
9b6e4bc3 KS |
3354 | @node Pixel Specification |
3355 | @subsection Pixel Specification for Spaces | |
3356 | @cindex spaces, pixel specification | |
3357 | ||
3358 | The value of the @code{:width}, @code{:align-to}, @code{:height}, | |
26b76360 RS |
3359 | and @code{:ascent} properties can be a special kind of expression that |
3360 | is evaluated during redisplay. The result of the evaluation is used | |
3361 | as an absolute number of pixels. | |
9b6e4bc3 KS |
3362 | |
3363 | The following expressions are supported: | |
3364 | ||
342fd6cd | 3365 | @smallexample |
9b6e4bc3 | 3366 | @group |
90801c68 | 3367 | @var{expr} ::= @var{num} | (@var{num}) | @var{unit} | @var{elem} | @var{pos} | @var{image} | @var{form} |
26b76360 RS |
3368 | @var{num} ::= @var{integer} | @var{float} | @var{symbol} |
3369 | @var{unit} ::= in | mm | cm | width | height | |
342fd6cd RS |
3370 | @end group |
3371 | @group | |
26b76360 | 3372 | @var{elem} ::= left-fringe | right-fringe | left-margin | right-margin |
9b6e4bc3 | 3373 | | scroll-bar | text |
26b76360 RS |
3374 | @var{pos} ::= left | center | right |
3375 | @var{form} ::= (@var{num} . @var{expr}) | (@var{op} @var{expr} ...) | |
3376 | @var{op} ::= + | - | |
9b6e4bc3 | 3377 | @end group |
342fd6cd | 3378 | @end smallexample |
9b6e4bc3 | 3379 | |
26b76360 RS |
3380 | The form @var{num} specifies a fraction of the default frame font |
3381 | height or width. The form @code{(@var{num})} specifies an absolute | |
3382 | number of pixels. If @var{num} is a symbol, @var{symbol}, its | |
9b6e4bc3 KS |
3383 | buffer-local variable binding is used. |
3384 | ||
26b76360 RS |
3385 | The @code{in}, @code{mm}, and @code{cm} units specify the number of |
3386 | pixels per inch, millimeter, and centimeter, respectively. The | |
3387 | @code{width} and @code{height} units correspond to the default width | |
90801c68 | 3388 | and height of the current face. An image specification @code{image} |
9b6e4bc3 KS |
3389 | corresponds to the width or height of the image. |
3390 | ||
3391 | The @code{left-fringe}, @code{right-fringe}, @code{left-margin}, | |
3392 | @code{right-margin}, @code{scroll-bar}, and @code{text} elements | |
3393 | specify to the width of the corresponding area of the window. | |
3394 | ||
3395 | The @code{left}, @code{center}, and @code{right} positions can be | |
3396 | used with @code{:align-to} to specify a position relative to the left | |
3397 | edge, center, or right edge of the text area. | |
3398 | ||
26b76360 | 3399 | Any of the above window elements (except @code{text}) can also be |
9b6e4bc3 KS |
3400 | used with @code{:align-to} to specify that the position is relative to |
3401 | the left edge of the given area. Once the base offset for a relative | |
3402 | position has been set (by the first occurrence of one of these | |
17234906 | 3403 | symbols), further occurrences of these symbols are interpreted as the |
9b6e4bc3 KS |
3404 | width of the specified area. For example, to align to the center of |
3405 | the left-margin, use | |
3406 | ||
3407 | @example | |
3408 | :align-to (+ left-margin (0.5 . left-margin)) | |
3409 | @end example | |
3410 | ||
3411 | If no specific base offset is set for alignment, it is always relative | |
3412 | to the left edge of the text area. For example, @samp{:align-to 0} in a | |
3413 | header-line aligns with the first text column in the text area. | |
3414 | ||
c2579664 RS |
3415 | A value of the form @code{(@var{num} . @var{expr})} stands for the |
3416 | product of the values of @var{num} and @var{expr}. For example, | |
26b76360 | 3417 | @code{(2 . in)} specifies a width of 2 inches, while @code{(0.5 . |
c2579664 RS |
3418 | @var{image})} specifies half the width (or height) of the specified |
3419 | image. | |
9b6e4bc3 | 3420 | |
26b76360 RS |
3421 | The form @code{(+ @var{expr} ...)} adds up the value of the |
3422 | expressions. The form @code{(- @var{expr} ...)} negates or subtracts | |
9b6e4bc3 KS |
3423 | the value of the expressions. |
3424 | ||
8241495d RS |
3425 | @node Other Display Specs |
3426 | @subsection Other Display Specifications | |
3427 | ||
26b76360 RS |
3428 | Here are the other sorts of display specifications that you can use |
3429 | in the @code{display} text property. | |
3430 | ||
8241495d | 3431 | @table @code |
4db6da64 RS |
3432 | @item @var{string} |
3433 | Display @var{string} instead of the text that has this property. | |
3434 | ||
215576f1 RS |
3435 | Recursive display specifications are not supported---@var{string}'s |
3436 | @code{display} properties, if any, are not used. | |
3437 | ||
0f5fe5cc | 3438 | @item (image . @var{image-props}) |
342fd6cd | 3439 | This kind of display specification is an image descriptor (@pxref{Images}). |
c2579664 RS |
3440 | When used as a display specification, it means to display the image |
3441 | instead of the text that has the display specification. | |
8241495d | 3442 | |
9b6e4bc3 | 3443 | @item (slice @var{x} @var{y} @var{width} @var{height}) |
26b76360 RS |
3444 | This specification together with @code{image} specifies a @dfn{slice} |
3445 | (a partial area) of the image to display. The elements @var{y} and | |
3446 | @var{x} specify the top left corner of the slice, within the image; | |
3447 | @var{width} and @var{height} specify the width and height of the | |
3448 | slice. Integer values are numbers of pixels. A floating point number | |
3449 | in the range 0.0--1.0 stands for that fraction of the width or height | |
3450 | of the entire image. | |
9b6e4bc3 | 3451 | |
1574933b | 3452 | @item ((margin nil) @var{string}) |
1574933b DL |
3453 | A display specification of this form means to display @var{string} |
3454 | instead of the text that has the display specification, at the same | |
215576f1 RS |
3455 | position as that text. It is equivalent to using just @var{string}, |
3456 | but it is done as a special case of marginal display (@pxref{Display | |
3457 | Margins}). | |
5143d8a4 | 3458 | |
8241495d | 3459 | @item (space-width @var{factor}) |
a40d4712 PR |
3460 | This display specification affects all the space characters within the |
3461 | text that has the specification. It displays all of these spaces | |
3462 | @var{factor} times as wide as normal. The element @var{factor} should | |
3463 | be an integer or float. Characters other than spaces are not affected | |
3464 | at all; in particular, this has no effect on tab characters. | |
8241495d RS |
3465 | |
3466 | @item (height @var{height}) | |
3467 | This display specification makes the text taller or shorter. | |
3468 | Here are the possibilities for @var{height}: | |
3469 | ||
3470 | @table @asis | |
3471 | @item @code{(+ @var{n})} | |
3472 | This means to use a font that is @var{n} steps larger. A ``step'' is | |
a40d4712 PR |
3473 | defined by the set of available fonts---specifically, those that match |
3474 | what was otherwise specified for this text, in all attributes except | |
3475 | height. Each size for which a suitable font is available counts as | |
3476 | another step. @var{n} should be an integer. | |
8241495d RS |
3477 | |
3478 | @item @code{(- @var{n})} | |
3479 | This means to use a font that is @var{n} steps smaller. | |
3480 | ||
3481 | @item a number, @var{factor} | |
3482 | A number, @var{factor}, means to use a font that is @var{factor} times | |
3483 | as tall as the default font. | |
3484 | ||
3485 | @item a symbol, @var{function} | |
3486 | A symbol is a function to compute the height. It is called with the | |
3487 | current height as argument, and should return the new height to use. | |
3488 | ||
3489 | @item anything else, @var{form} | |
3490 | If the @var{height} value doesn't fit the previous possibilities, it is | |
3491 | a form. Emacs evaluates it to get the new height, with the symbol | |
3492 | @code{height} bound to the current specified font height. | |
3493 | @end table | |
3494 | ||
3495 | @item (raise @var{factor}) | |
3496 | This kind of display specification raises or lowers the text | |
3497 | it applies to, relative to the baseline of the line. | |
3498 | ||
3499 | @var{factor} must be a number, which is interpreted as a multiple of the | |
3500 | height of the affected text. If it is positive, that means to display | |
3501 | the characters raised. If it is negative, that means to display them | |
3502 | lower down. | |
3503 | ||
3504 | If the text also has a @code{height} display specification, that does | |
3505 | not affect the amount of raising or lowering, which is based on the | |
3506 | faces used for the text. | |
3507 | @end table | |
3508 | ||
4f815b29 TTN |
3509 | @c We put all the `@code{(when ...)}' on one line to encourage |
3510 | @c makeinfo's end-of-sentence heuristics to DTRT. Previously, the dot | |
3511 | @c was at eol; the info file ended up w/ two spaces rendered after it. | |
c2579664 | 3512 | You can make any display specification conditional. To do that, |
4f815b29 TTN |
3513 | package it in another list of the form |
3514 | @code{(when @var{condition} . @var{spec})}. | |
3515 | Then the specification @var{spec} applies only when | |
c2579664 RS |
3516 | @var{condition} evaluates to a non-@code{nil} value. During the |
3517 | evaluation, @code{object} is bound to the string or buffer having the | |
3518 | conditional @code{display} property. @code{position} and | |
3519 | @code{buffer-position} are bound to the position within @code{object} | |
3520 | and the buffer position where the @code{display} property was found, | |
3521 | respectively. Both positions can be different when @code{object} is a | |
3522 | string. | |
3523 | ||
8241495d RS |
3524 | @node Display Margins |
3525 | @subsection Displaying in the Margins | |
3526 | @cindex display margins | |
3527 | @cindex margins, display | |
3528 | ||
3529 | A buffer can have blank areas called @dfn{display margins} on the left | |
3530 | and on the right. Ordinary text never appears in these areas, but you | |
3531 | can put things into the display margins using the @code{display} | |
3532 | property. | |
3533 | ||
3534 | To put text in the left or right display margin of the window, use a | |
3535 | display specification of the form @code{(margin right-margin)} or | |
3536 | @code{(margin left-margin)} on it. To put an image in a display margin, | |
3537 | use that display specification along with the display specification for | |
a8e171ce RS |
3538 | the image. Unfortunately, there is currently no way to make |
3539 | text or images in the margin mouse-sensitive. | |
8241495d | 3540 | |
78263139 RS |
3541 | If you put such a display specification directly on text in the |
3542 | buffer, the specified margin display appears @emph{instead of} that | |
3543 | buffer text itself. To put something in the margin @emph{in | |
3544 | association with} certain buffer text without preventing or altering | |
3545 | the display of that text, put a @code{before-string} property on the | |
3546 | text and put the display specification on the contents of the | |
3547 | before-string. | |
3548 | ||
8241495d RS |
3549 | Before the display margins can display anything, you must give |
3550 | them a nonzero width. The usual way to do that is to set these | |
3551 | variables: | |
3552 | ||
3553 | @defvar left-margin-width | |
8241495d RS |
3554 | This variable specifies the width of the left margin. |
3555 | It is buffer-local in all buffers. | |
3556 | @end defvar | |
3557 | ||
3558 | @defvar right-margin-width | |
8241495d RS |
3559 | This variable specifies the width of the right margin. |
3560 | It is buffer-local in all buffers. | |
3561 | @end defvar | |
3562 | ||
3563 | Setting these variables does not immediately affect the window. These | |
3564 | variables are checked when a new buffer is displayed in the window. | |
3565 | Thus, you can make changes take effect by calling | |
3566 | @code{set-window-buffer}. | |
3567 | ||
3568 | You can also set the margin widths immediately. | |
3569 | ||
5143d8a4 | 3570 | @defun set-window-margins window left &optional right |
8241495d | 3571 | This function specifies the margin widths for window @var{window}. |
177c0ea7 | 3572 | The argument @var{left} controls the left margin and |
5143d8a4 | 3573 | @var{right} controls the right margin (default @code{0}). |
8241495d RS |
3574 | @end defun |
3575 | ||
3576 | @defun window-margins &optional window | |
8241495d RS |
3577 | This function returns the left and right margins of @var{window} |
3578 | as a cons cell of the form @code{(@var{left} . @var{right})}. | |
3579 | If @var{window} is @code{nil}, the selected window is used. | |
3580 | @end defun | |
3581 | ||
8241495d RS |
3582 | @node Images |
3583 | @section Images | |
3584 | @cindex images in buffers | |
3585 | ||
3586 | To display an image in an Emacs buffer, you must first create an image | |
3587 | descriptor, then use it as a display specifier in the @code{display} | |
911a7105 | 3588 | property of text that is displayed (@pxref{Display Property}). |
8241495d | 3589 | |
bda420a3 CY |
3590 | Emacs is usually able to display images when it is run on a |
3591 | graphical terminal. Images cannot be displayed in a text terminal, on | |
3592 | certain graphical terminals that lack the support for this, or if | |
3593 | Emacs is compiled without image support. You can use the function | |
3594 | @code{display-images-p} to determine if images can in principle be | |
3595 | displayed (@pxref{Display Feature Testing}). | |
3596 | ||
8241495d | 3597 | Emacs can display a number of different image formats; some of them |
da4b7798 | 3598 | are supported only if particular support libraries are installed on |
c2579664 | 3599 | your machine. In some environments, Emacs can load image |
da4b7798 JB |
3600 | libraries on demand; if so, the variable @code{image-library-alist} |
3601 | can be used to modify the set of known names for these dynamic | |
17234906 | 3602 | libraries (though it is not possible to add new image formats). |
da4b7798 | 3603 | |
c2579664 RS |
3604 | The supported image formats include XBM, XPM (this requires the |
3605 | libraries @code{libXpm} version 3.4k and @code{libz}), GIF (requiring | |
3606 | @code{libungif} 4.1.0), Postscript, PBM, JPEG (requiring the | |
3607 | @code{libjpeg} library version v6a), TIFF (requiring @code{libtiff} | |
3608 | v3.4), and PNG (requiring @code{libpng} 1.0.2). | |
8241495d RS |
3609 | |
3610 | You specify one of these formats with an image type symbol. The image | |
3611 | type symbols are @code{xbm}, @code{xpm}, @code{gif}, @code{postscript}, | |
3612 | @code{pbm}, @code{jpeg}, @code{tiff}, and @code{png}. | |
3613 | ||
3614 | @defvar image-types | |
3615 | This variable contains a list of those image type symbols that are | |
da4b7798 JB |
3616 | potentially supported in the current configuration. |
3617 | @emph{Potentially} here means that Emacs knows about the image types, | |
3618 | not necessarily that they can be loaded (they could depend on | |
3619 | unavailable dynamic libraries, for example). | |
3620 | ||
3621 | To know which image types are really available, use | |
3622 | @code{image-type-available-p}. | |
8241495d RS |
3623 | @end defvar |
3624 | ||
da4b7798 | 3625 | @defvar image-library-alist |
da4b7798 JB |
3626 | This in an alist of image types vs external libraries needed to |
3627 | display them. | |
3628 | ||
aa0e4da8 | 3629 | Each element is a list @code{(@var{image-type} @var{library}...)}, |
da4b7798 JB |
3630 | where the car is a supported image format from @code{image-types}, and |
3631 | the rest are strings giving alternate filenames for the corresponding | |
3632 | external libraries to load. | |
3633 | ||
e6263643 JB |
3634 | Emacs tries to load the libraries in the order they appear on the |
3635 | list; if none is loaded, the running session of Emacs won't support | |
3636 | the image type. @code{pbm} and @code{xbm} don't need to be listed; | |
da4b7798 JB |
3637 | they're always supported. |
3638 | ||
3639 | This variable is ignored if the image libraries are statically linked | |
3640 | into Emacs. | |
3641 | @end defvar | |
3642 | ||
3643 | @defun image-type-available-p type | |
3644 | @findex image-type-available-p | |
3645 | ||
aa0e4da8 JB |
3646 | This function returns non-@code{nil} if image type @var{type} is |
3647 | available, i.e., if images of this type can be loaded and displayed in | |
3648 | Emacs. @var{type} should be one of the types contained in | |
3649 | @code{image-types}. | |
da4b7798 JB |
3650 | |
3651 | For image types whose support libraries are statically linked, this | |
3652 | function always returns @code{t}; for other image types, it returns | |
3653 | @code{t} if the dynamic library could be loaded, @code{nil} otherwise. | |
3654 | @end defun | |
3655 | ||
8241495d | 3656 | @menu |
a40d4712 PR |
3657 | * Image Descriptors:: How to specify an image for use in @code{:display}. |
3658 | * XBM Images:: Special features for XBM format. | |
3659 | * XPM Images:: Special features for XPM format. | |
3660 | * GIF Images:: Special features for GIF format. | |
3661 | * Postscript Images:: Special features for Postscript format. | |
3662 | * Other Image Types:: Various other formats are supported. | |
3663 | * Defining Images:: Convenient ways to define an image for later use. | |
3664 | * Showing Images:: Convenient ways to display an image once it is defined. | |
3665 | * Image Cache:: Internal mechanisms of image display. | |
8241495d RS |
3666 | @end menu |
3667 | ||
3668 | @node Image Descriptors | |
3669 | @subsection Image Descriptors | |
3670 | @cindex image descriptor | |
3671 | ||
0f5fe5cc LT |
3672 | An image description is a list of the form @code{(image . @var{props})}, |
3673 | where @var{props} is a property list containing alternating keyword | |
3674 | symbols (symbols whose names start with a colon) and their values. | |
3675 | You can use any Lisp object as a property, but the only properties | |
3676 | that have any special meaning are certain symbols, all of them keywords. | |
14ac7224 GM |
3677 | |
3678 | Every image descriptor must contain the property @code{:type | |
3679 | @var{type}} to specify the format of the image. The value of @var{type} | |
3680 | should be an image type symbol; for example, @code{xpm} for an image in | |
3681 | XPM format. | |
8241495d RS |
3682 | |
3683 | Here is a list of other properties that are meaningful for all image | |
3684 | types: | |
3685 | ||
3686 | @table @code | |
2cd8656e | 3687 | @item :file @var{file} |
c2579664 | 3688 | The @code{:file} property says to load the image from file |
2cd8656e RS |
3689 | @var{file}. If @var{file} is not an absolute file name, it is expanded |
3690 | in @code{data-directory}. | |
3691 | ||
3692 | @item :data @var{data} | |
c2579664 | 3693 | The @code{:data} property says the actual contents of the image. |
2cd8656e RS |
3694 | Each image must use either @code{:data} or @code{:file}, but not both. |
3695 | For most image types, the value of the @code{:data} property should be a | |
3696 | string containing the image data; we recommend using a unibyte string. | |
3697 | ||
3698 | Before using @code{:data}, look for further information in the section | |
3699 | below describing the specific image format. For some image types, | |
3700 | @code{:data} may not be supported; for some, it allows other data types; | |
3701 | for some, @code{:data} alone is not enough, so you need to use other | |
3702 | image properties along with @code{:data}. | |
3703 | ||
3704 | @item :margin @var{margin} | |
3705 | The @code{:margin} property specifies how many pixels to add as an | |
9ee1638e | 3706 | extra margin around the image. The value, @var{margin}, must be a |
2cd8656e RS |
3707 | non-negative number, or a pair @code{(@var{x} . @var{y})} of such |
3708 | numbers. If it is a pair, @var{x} specifies how many pixels to add | |
3709 | horizontally, and @var{y} specifies how many pixels to add vertically. | |
3710 | If @code{:margin} is not specified, the default is zero. | |
3711 | ||
8241495d | 3712 | @item :ascent @var{ascent} |
04545643 GM |
3713 | The @code{:ascent} property specifies the amount of the image's |
3714 | height to use for its ascent---that is, the part above the baseline. | |
3715 | The value, @var{ascent}, must be a number in the range 0 to 100, or | |
3716 | the symbol @code{center}. | |
3717 | ||
3718 | If @var{ascent} is a number, that percentage of the image's height is | |
3719 | used for its ascent. | |
3720 | ||
3721 | If @var{ascent} is @code{center}, the image is vertically centered | |
3722 | around a centerline which would be the vertical centerline of text drawn | |
3723 | at the position of the image, in the manner specified by the text | |
3724 | properties and overlays that apply to the image. | |
3725 | ||
3726 | If this property is omitted, it defaults to 50. | |
8241495d | 3727 | |
8241495d RS |
3728 | @item :relief @var{relief} |
3729 | The @code{:relief} property, if non-@code{nil}, adds a shadow rectangle | |
3730 | around the image. The value, @var{relief}, specifies the width of the | |
3731 | shadow lines, in pixels. If @var{relief} is negative, shadows are drawn | |
3732 | so that the image appears as a pressed button; otherwise, it appears as | |
3733 | an unpressed button. | |
3734 | ||
f864120f GM |
3735 | @item :conversion @var{algorithm} |
3736 | The @code{:conversion} property, if non-@code{nil}, specifies a | |
8241495d RS |
3737 | conversion algorithm that should be applied to the image before it is |
3738 | displayed; the value, @var{algorithm}, specifies which algorithm. | |
3739 | ||
62fb5c66 DL |
3740 | @table @code |
3741 | @item laplace | |
3742 | @itemx emboss | |
3743 | Specifies the Laplace edge detection algorithm, which blurs out small | |
3744 | differences in color while highlighting larger differences. People | |
3745 | sometimes consider this useful for displaying the image for a | |
3746 | ``disabled'' button. | |
3747 | ||
3748 | @item (edge-detection :matrix @var{matrix} :color-adjust @var{adjust}) | |
3749 | Specifies a general edge-detection algorithm. @var{matrix} must be | |
3750 | either a nine-element list or a nine-element vector of numbers. A pixel | |
3751 | at position @math{x/y} in the transformed image is computed from | |
3752 | original pixels around that position. @var{matrix} specifies, for each | |
3753 | pixel in the neighborhood of @math{x/y}, a factor with which that pixel | |
3754 | will influence the transformed pixel; element @math{0} specifies the | |
3755 | factor for the pixel at @math{x-1/y-1}, element @math{1} the factor for | |
3756 | the pixel at @math{x/y-1} etc., as shown below: | |
3757 | @iftex | |
3758 | @tex | |
3759 | $$\pmatrix{x-1/y-1 & x/y-1 & x+1/y-1 \cr | |
3760 | x-1/y & x/y & x+1/y \cr | |
3761 | x-1/y+1& x/y+1 & x+1/y+1 \cr}$$ | |
3762 | @end tex | |
3763 | @end iftex | |
3764 | @ifnottex | |
3765 | @display | |
3766 | (x-1/y-1 x/y-1 x+1/y-1 | |
3767 | x-1/y x/y x+1/y | |
3768 | x-1/y+1 x/y+1 x+1/y+1) | |
3769 | @end display | |
3770 | @end ifnottex | |
3771 | ||
3772 | The resulting pixel is computed from the color intensity of the color | |
3773 | resulting from summing up the RGB values of surrounding pixels, | |
3774 | multiplied by the specified factors, and dividing that sum by the sum | |
3775 | of the factors' absolute values. | |
3776 | ||
3777 | Laplace edge-detection currently uses a matrix of | |
3778 | @iftex | |
3779 | @tex | |
3780 | $$\pmatrix{1 & 0 & 0 \cr | |
3781 | 0& 0 & 0 \cr | |
3782 | 9 & 9 & -1 \cr}$$ | |
3783 | @end tex | |
3784 | @end iftex | |
3785 | @ifnottex | |
3786 | @display | |
3787 | (1 0 0 | |
3788 | 0 0 0 | |
3789 | 9 9 -1) | |
3790 | @end display | |
3791 | @end ifnottex | |
3792 | ||
3793 | Emboss edge-detection uses a matrix of | |
3794 | @iftex | |
3795 | @tex | |
3796 | $$\pmatrix{ 2 & -1 & 0 \cr | |
3797 | -1 & 0 & 1 \cr | |
3798 | 0 & 1 & -2 \cr}$$ | |
3799 | @end tex | |
3800 | @end iftex | |
3801 | @ifnottex | |
3802 | @display | |
3803 | ( 2 -1 0 | |
3804 | -1 0 1 | |
3805 | 0 1 -2) | |
3806 | @end display | |
3807 | @end ifnottex | |
3808 | ||
3809 | @item disabled | |
827b7ee7 | 3810 | Specifies transforming the image so that it looks ``disabled.'' |
62fb5c66 | 3811 | @end table |
8241495d | 3812 | |
62fb5c66 DL |
3813 | @item :mask @var{mask} |
3814 | If @var{mask} is @code{heuristic} or @code{(heuristic @var{bg})}, build | |
3815 | a clipping mask for the image, so that the background of a frame is | |
3816 | visible behind the image. If @var{bg} is not specified, or if @var{bg} | |
3817 | is @code{t}, determine the background color of the image by looking at | |
3818 | the four corners of the image, assuming the most frequently occurring | |
3819 | color from the corners is the background color of the image. Otherwise, | |
3820 | @var{bg} must be a list @code{(@var{red} @var{green} @var{blue})} | |
3821 | specifying the color to assume for the background of the image. | |
8241495d | 3822 | |
9a8dc0d3 RS |
3823 | If @var{mask} is @code{nil}, remove a mask from the image, if it has |
3824 | one. Images in some formats include a mask which can be removed by | |
3825 | specifying @code{:mask nil}. | |
9b6e4bc3 KS |
3826 | |
3827 | @item :pointer @var{shape} | |
3828 | This specifies the pointer shape when the mouse pointer is over this | |
17234906 | 3829 | image. @xref{Pointer Shape}, for available pointer shapes. |
9b6e4bc3 KS |
3830 | |
3831 | @item :map @var{map} | |
3832 | This associates an image map of @dfn{hot spots} with this image. | |
3833 | ||
3834 | An image map is an alist where each element has the format | |
3835 | @code{(@var{area} @var{id} @var{plist})}. An @var{area} is specified | |
3836 | as either a rectangle, a circle, or a polygon. | |
3837 | ||
3838 | A rectangle is a cons | |
3839 | @code{(rect . ((@var{x0} . @var{y0}) . (@var{x1} . @var{y1})))} | |
3840 | which specifies the pixel coordinates of the upper left and bottom right | |
3841 | corners of the rectangle area. | |
3842 | ||
3843 | A circle is a cons | |
3844 | @code{(circle . ((@var{x0} . @var{y0}) . @var{r}))} | |
3845 | which specifies the center and the radius of the circle; @var{r} may | |
3846 | be a float or integer. | |
3847 | ||
3848 | A polygon is a cons | |
61e74968 | 3849 | @code{(poly . [@var{x0} @var{y0} @var{x1} @var{y1} ...])} |
9b6e4bc3 KS |
3850 | where each pair in the vector describes one corner in the polygon. |
3851 | ||
032fd62a | 3852 | When the mouse pointer lies on a hot-spot area of an image, the |
9b6e4bc3 | 3853 | @var{plist} of that hot-spot is consulted; if it contains a @code{help-echo} |
032fd62a RS |
3854 | property, that defines a tool-tip for the hot-spot, and if it contains |
3855 | a @code{pointer} property, that defines the shape of the mouse cursor when | |
3856 | it is on the hot-spot. | |
17234906 | 3857 | @xref{Pointer Shape}, for available pointer shapes. |
9b6e4bc3 KS |
3858 | |
3859 | When you click the mouse when the mouse pointer is over a hot-spot, an | |
3860 | event is composed by combining the @var{id} of the hot-spot with the | |
26b76360 RS |
3861 | mouse event; for instance, @code{[area4 mouse-1]} if the hot-spot's |
3862 | @var{id} is @code{area4}. | |
8241495d RS |
3863 | @end table |
3864 | ||
62fb5c66 | 3865 | @defun image-mask-p spec &optional frame |
62fb5c66 DL |
3866 | This function returns @code{t} if image @var{spec} has a mask bitmap. |
3867 | @var{frame} is the frame on which the image will be displayed. | |
8d82c597 EZ |
3868 | @var{frame} @code{nil} or omitted means to use the selected frame |
3869 | (@pxref{Input Focus}). | |
62fb5c66 DL |
3870 | @end defun |
3871 | ||
8241495d RS |
3872 | @node XBM Images |
3873 | @subsection XBM Images | |
3874 | @cindex XBM | |
3875 | ||
3876 | To use XBM format, specify @code{xbm} as the image type. This image | |
3877 | format doesn't require an external library, so images of this type are | |
3878 | always supported. | |
3879 | ||
3880 | Additional image properties supported for the @code{xbm} image type are: | |
3881 | ||
3882 | @table @code | |
3883 | @item :foreground @var{foreground} | |
3884 | The value, @var{foreground}, should be a string specifying the image | |
0d88b7d0 GM |
3885 | foreground color, or @code{nil} for the default color. This color is |
3886 | used for each pixel in the XBM that is 1. The default is the frame's | |
3887 | foreground color. | |
8241495d RS |
3888 | |
3889 | @item :background @var{background} | |
3890 | The value, @var{background}, should be a string specifying the image | |
0d88b7d0 GM |
3891 | background color, or @code{nil} for the default color. This color is |
3892 | used for each pixel in the XBM that is 0. The default is the frame's | |
3893 | background color. | |
8241495d RS |
3894 | @end table |
3895 | ||
72821190 | 3896 | If you specify an XBM image using data within Emacs instead of an |
96f66dc5 | 3897 | external file, use the following three properties: |
8241495d RS |
3898 | |
3899 | @table @code | |
96f66dc5 GM |
3900 | @item :data @var{data} |
3901 | The value, @var{data}, specifies the contents of the image. | |
3902 | There are three formats you can use for @var{data}: | |
8241495d | 3903 | |
96f66dc5 GM |
3904 | @itemize @bullet |
3905 | @item | |
3906 | A vector of strings or bool-vectors, each specifying one line of the | |
3907 | image. Do specify @code{:height} and @code{:width}. | |
8241495d | 3908 | |
96f66dc5 GM |
3909 | @item |
3910 | A string containing the same byte sequence as an XBM file would contain. | |
3911 | You must not specify @code{:height} and @code{:width} in this case, | |
3912 | because omitting them is what indicates the data has the format of an | |
3913 | XBM file. The file contents specify the height and width of the image. | |
8241495d | 3914 | |
96f66dc5 GM |
3915 | @item |
3916 | A string or a bool-vector containing the bits of the image (plus perhaps | |
3917 | some extra bits at the end that will not be used). It should contain at | |
3918 | least @var{width} * @code{height} bits. In this case, you must specify | |
3919 | @code{:height} and @code{:width}, both to indicate that the string | |
3920 | contains just the bits rather than a whole XBM file, and to specify the | |
3921 | size of the image. | |
3922 | @end itemize | |
3923 | ||
3924 | @item :width @var{width} | |
3925 | The value, @var{width}, specifies the width of the image, in pixels. | |
3926 | ||
3927 | @item :height @var{height} | |
3928 | The value, @var{height}, specifies the height of the image, in pixels. | |
8241495d RS |
3929 | @end table |
3930 | ||
3931 | @node XPM Images | |
3932 | @subsection XPM Images | |
3933 | @cindex XPM | |
3934 | ||
72821190 RS |
3935 | To use XPM format, specify @code{xpm} as the image type. The |
3936 | additional image property @code{:color-symbols} is also meaningful with | |
3937 | the @code{xpm} image type: | |
8241495d RS |
3938 | |
3939 | @table @code | |
3940 | @item :color-symbols @var{symbols} | |
3941 | The value, @var{symbols}, should be an alist whose elements have the | |
3942 | form @code{(@var{name} . @var{color})}. In each element, @var{name} is | |
3943 | the name of a color as it appears in the image file, and @var{color} | |
3944 | specifies the actual color to use for displaying that name. | |
8241495d RS |
3945 | @end table |
3946 | ||
3947 | @node GIF Images | |
3948 | @subsection GIF Images | |
3949 | @cindex GIF | |
3950 | ||
c2579664 | 3951 | For GIF images, specify image type @code{gif}. |
8241495d RS |
3952 | |
3953 | @table @code | |
3954 | @item :index @var{index} | |
3955 | You can use @code{:index} to specify one image from a GIF file that | |
3956 | contains more than one image. This property specifies use of image | |
00b3c1cd RS |
3957 | number @var{index} from the file. If the GIF file doesn't contain an |
3958 | image with index @var{index}, the image displays as a hollow box. | |
8241495d RS |
3959 | @end table |
3960 | ||
3961 | @ignore | |
3962 | This could be used to implement limited support for animated GIFs. | |
3963 | For example, the following function displays a multi-image GIF file | |
3964 | at point-min in the current buffer, switching between sub-images | |
3965 | every 0.1 seconds. | |
3966 | ||
3967 | (defun show-anim (file max) | |
3968 | "Display multi-image GIF file FILE which contains MAX subimages." | |
3969 | (display-anim (current-buffer) file 0 max t)) | |
3970 | ||
3971 | (defun display-anim (buffer file idx max first-time) | |
3972 | (when (= idx max) | |
3973 | (setq idx 0)) | |
3974 | (let ((img (create-image file nil :image idx))) | |
3975 | (save-excursion | |
3976 | (set-buffer buffer) | |
3977 | (goto-char (point-min)) | |
3978 | (unless first-time (delete-char 1)) | |
3979 | (insert-image img)) | |
3980 | (run-with-timer 0.1 nil 'display-anim buffer file (1+ idx) max nil))) | |
3981 | @end ignore | |
3982 | ||
3983 | @node Postscript Images | |
3984 | @subsection Postscript Images | |
3985 | @cindex Postscript images | |
3986 | ||
3987 | To use Postscript for an image, specify image type @code{postscript}. | |
3988 | This works only if you have Ghostscript installed. You must always use | |
3989 | these three properties: | |
3990 | ||
3991 | @table @code | |
3992 | @item :pt-width @var{width} | |
3993 | The value, @var{width}, specifies the width of the image measured in | |
3994 | points (1/72 inch). @var{width} must be an integer. | |
3995 | ||
3996 | @item :pt-height @var{height} | |
3997 | The value, @var{height}, specifies the height of the image in points | |
3998 | (1/72 inch). @var{height} must be an integer. | |
3999 | ||
4000 | @item :bounding-box @var{box} | |
4001 | The value, @var{box}, must be a list or vector of four integers, which | |
4002 | specifying the bounding box of the Postscript image, analogous to the | |
4003 | @samp{BoundingBox} comment found in Postscript files. | |
4004 | ||
4005 | @example | |
4006 | %%BoundingBox: 22 171 567 738 | |
4007 | @end example | |
4008 | @end table | |
4009 | ||
72821190 RS |
4010 | Displaying Postscript images from Lisp data is not currently |
4011 | implemented, but it may be implemented by the time you read this. | |
4012 | See the @file{etc/NEWS} file to make sure. | |
4013 | ||
8241495d RS |
4014 | @node Other Image Types |
4015 | @subsection Other Image Types | |
4016 | @cindex PBM | |
4017 | ||
4018 | For PBM images, specify image type @code{pbm}. Color, gray-scale and | |
7ccd82bd GM |
4019 | monochromatic images are supported. For mono PBM images, two additional |
4020 | image properties are supported. | |
4021 | ||
4022 | @table @code | |
4023 | @item :foreground @var{foreground} | |
4024 | The value, @var{foreground}, should be a string specifying the image | |
0d88b7d0 GM |
4025 | foreground color, or @code{nil} for the default color. This color is |
4026 | used for each pixel in the XBM that is 1. The default is the frame's | |
4027 | foreground color. | |
7ccd82bd GM |
4028 | |
4029 | @item :background @var{background} | |
4030 | The value, @var{background}, should be a string specifying the image | |
0d88b7d0 GM |
4031 | background color, or @code{nil} for the default color. This color is |
4032 | used for each pixel in the XBM that is 0. The default is the frame's | |
4033 | background color. | |
7ccd82bd | 4034 | @end table |
8241495d | 4035 | |
72821190 | 4036 | For JPEG images, specify image type @code{jpeg}. |
8241495d RS |
4037 | |
4038 | For TIFF images, specify image type @code{tiff}. | |
4039 | ||
4040 | For PNG images, specify image type @code{png}. | |
4041 | ||
4042 | @node Defining Images | |
4043 | @subsection Defining Images | |
4044 | ||
e3b9fc91 DL |
4045 | The functions @code{create-image}, @code{defimage} and |
4046 | @code{find-image} provide convenient ways to create image descriptors. | |
8241495d | 4047 | |
5092b644 | 4048 | @defun create-image file-or-data &optional type data-p &rest props |
8241495d | 4049 | This function creates and returns an image descriptor which uses the |
5092b644 RS |
4050 | data in @var{file-or-data}. @var{file-or-data} can be a file name or |
4051 | a string containing the image data; @var{data-p} should be @code{nil} | |
4052 | for the former case, non-@code{nil} for the latter case. | |
8241495d RS |
4053 | |
4054 | The optional argument @var{type} is a symbol specifying the image type. | |
4055 | If @var{type} is omitted or @code{nil}, @code{create-image} tries to | |
4056 | determine the image type from the file's first few bytes, or else | |
4057 | from the file's name. | |
4058 | ||
4059 | The remaining arguments, @var{props}, specify additional image | |
4060 | properties---for example, | |
4061 | ||
4062 | @example | |
5092b644 | 4063 | (create-image "foo.xpm" 'xpm nil :heuristic-mask t) |
8241495d RS |
4064 | @end example |
4065 | ||
4066 | The function returns @code{nil} if images of this type are not | |
4067 | supported. Otherwise it returns an image descriptor. | |
4068 | @end defun | |
4069 | ||
11519a5e | 4070 | @defmac defimage symbol specs &optional doc |
11519a5e EZ |
4071 | This macro defines @var{symbol} as an image name. The arguments |
4072 | @var{specs} is a list which specifies how to display the image. | |
4073 | The third argument, @var{doc}, is an optional documentation string. | |
8241495d RS |
4074 | |
4075 | Each argument in @var{specs} has the form of a property list, and each | |
11519a5e EZ |
4076 | one should specify at least the @code{:type} property and either the |
4077 | @code{:file} or the @code{:data} property. The value of @code{:type} | |
4078 | should be a symbol specifying the image type, the value of | |
4079 | @code{:file} is the file to load the image from, and the value of | |
4080 | @code{:data} is a string containing the actual image data. Here is an | |
4081 | example: | |
8241495d | 4082 | |
a40d4712 PR |
4083 | @example |
4084 | (defimage test-image | |
f43c34a0 RS |
4085 | ((:type xpm :file "~/test1.xpm") |
4086 | (:type xbm :file "~/test1.xbm"))) | |
a40d4712 | 4087 | @end example |
8241495d RS |
4088 | |
4089 | @code{defimage} tests each argument, one by one, to see if it is | |
4090 | usable---that is, if the type is supported and the file exists. The | |
4091 | first usable argument is used to make an image descriptor which is | |
11519a5e | 4092 | stored in @var{symbol}. |
8241495d | 4093 | |
11519a5e | 4094 | If none of the alternatives will work, then @var{symbol} is defined |
8241495d RS |
4095 | as @code{nil}. |
4096 | @end defmac | |
4097 | ||
e3b9fc91 | 4098 | @defun find-image specs |
e3b9fc91 DL |
4099 | This function provides a convenient way to find an image satisfying one |
4100 | of a list of image specifications @var{specs}. | |
4101 | ||
4102 | Each specification in @var{specs} is a property list with contents | |
4103 | depending on image type. All specifications must at least contain the | |
4104 | properties @code{:type @var{type}} and either @w{@code{:file @var{file}}} | |
4105 | or @w{@code{:data @var{DATA}}}, where @var{type} is a symbol specifying | |
4106 | the image type, e.g.@: @code{xbm}, @var{file} is the file to load the | |
4107 | image from, and @var{data} is a string containing the actual image data. | |
4108 | The first specification in the list whose @var{type} is supported, and | |
4109 | @var{file} exists, is used to construct the image specification to be | |
4110 | returned. If no specification is satisfied, @code{nil} is returned. | |
4111 | ||
5b51c037 | 4112 | The image is looked for in @code{image-load-path}. |
e3b9fc91 DL |
4113 | @end defun |
4114 | ||
5b51c037 | 4115 | @defvar image-load-path |
5b51c037 | 4116 | This variable's value is a list of locations in which to search for |
906320ec CY |
4117 | image files. If an element is a string or a variable symbol whose |
4118 | value is a string, the string is taken to be the name of a directory | |
4119 | to search. If an element is a variable symbol whose value is a list, | |
4120 | that is taken to be a list of directory names to search. | |
5b51c037 | 4121 | |
cc1f9806 RS |
4122 | The default is to search in the @file{images} subdirectory of the |
4123 | directory specified by @code{data-directory}, then the directory | |
4124 | specified by @code{data-directory}, and finally in the directories in | |
5b51c037 CY |
4125 | @code{load-path}. Subdirectories are not automatically included in |
4126 | the search, so if you put an image file in a subdirectory, you have to | |
cc1f9806 | 4127 | supply the subdirectory name explicitly. For example, to find the |
906320ec | 4128 | image @file{images/foo/bar.xpm} within @code{data-directory}, you |
cc1f9806 | 4129 | should specify the image as follows: |
5b51c037 CY |
4130 | |
4131 | @example | |
cc1f9806 | 4132 | (defimage foo-image '((:type xpm :file "foo/bar.xpm"))) |
5b51c037 CY |
4133 | @end example |
4134 | @end defvar | |
4135 | ||
2c676341 | 4136 | @defun image-load-path-for-library library image &optional path no-error |
e8a5f60b RS |
4137 | This function returns a suitable search path for images used by the |
4138 | Lisp package @var{library}. | |
7cd3712b | 4139 | |
42b50684 KB |
4140 | The function searches for @var{image} first in @code{image-load-path} |
4141 | (excluding @file{@code{data-directory}/images}) and then in | |
4142 | @code{load-path}, followed by a path suitable for @var{library}, which | |
4143 | includes @file{../../etc/images} and @file{../etc/images} relative to | |
4144 | the library file itself, and finally in | |
4145 | @file{@code{data-directory}/images}. | |
7cd3712b | 4146 | |
2e556b3f RS |
4147 | Then this function returns a list of directories which contains first |
4148 | the directory in which @var{image} was found, followed by the value of | |
4149 | @code{load-path}. If @var{path} is given, it is used instead of | |
70949f30 | 4150 | @code{load-path}. |
7cd3712b | 4151 | |
70949f30 BW |
4152 | If @var{no-error} is non-@code{nil} and a suitable path can't be |
4153 | found, don't signal an error. Instead, return a list of directories as | |
4154 | before, except that @code{nil} appears in place of the image directory. | |
2c676341 BW |
4155 | |
4156 | Here is an example that uses a common idiom to provide compatibility | |
4157 | with versions of Emacs that lack the variable @code{image-load-path}: | |
4158 | ||
4159 | @example | |
42b50684 KB |
4160 | (defvar image-load-path) ; shush compiler |
4161 | (let* ((load-path (image-load-path-for-library | |
4162 | "mh-e" "mh-logo.xpm")) | |
874a6ef8 BW |
4163 | (image-load-path (cons (car load-path) |
4164 | (when (boundp 'image-load-path) | |
4165 | image-load-path)))) | |
2c676341 BW |
4166 | (mh-tool-bar-folder-buttons-init)) |
4167 | @end example | |
4168 | @end defun | |
4169 | ||
8241495d RS |
4170 | @node Showing Images |
4171 | @subsection Showing Images | |
4172 | ||
4173 | You can use an image descriptor by setting up the @code{display} | |
4174 | property yourself, but it is easier to use the functions in this | |
4175 | section. | |
4176 | ||
9b6e4bc3 | 4177 | @defun insert-image image &optional string area slice |
8241495d RS |
4178 | This function inserts @var{image} in the current buffer at point. The |
4179 | value @var{image} should be an image descriptor; it could be a value | |
4180 | returned by @code{create-image}, or the value of a symbol defined with | |
c2579664 RS |
4181 | @code{defimage}. The argument @var{string} specifies the text to put |
4182 | in the buffer to hold the image. If it is omitted or @code{nil}, | |
4183 | @code{insert-image} uses @code{" "} by default. | |
8241495d RS |
4184 | |
4185 | The argument @var{area} specifies whether to put the image in a margin. | |
4186 | If it is @code{left-margin}, the image appears in the left margin; | |
4187 | @code{right-margin} specifies the right margin. If @var{area} is | |
4188 | @code{nil} or omitted, the image is displayed at point within the | |
4189 | buffer's text. | |
4190 | ||
9b6e4bc3 KS |
4191 | The argument @var{slice} specifies a slice of the image to insert. If |
4192 | @var{slice} is @code{nil} or omitted the whole image is inserted. | |
26b76360 RS |
4193 | Otherwise, @var{slice} is a list @code{(@var{x} @var{y} @var{width} |
4194 | @var{height})} which specifies the @var{x} and @var{y} positions and | |
9b6e4bc3 | 4195 | @var{width} and @var{height} of the image area to insert. Integer |
26b76360 RS |
4196 | values are in units of pixels. A floating point number in the range |
4197 | 0.0--1.0 stands for that fraction of the width or height of the entire | |
4198 | image. | |
9b6e4bc3 | 4199 | |
a40d4712 PR |
4200 | Internally, this function inserts @var{string} in the buffer, and gives |
4201 | it a @code{display} property which specifies @var{image}. @xref{Display | |
8241495d RS |
4202 | Property}. |
4203 | @end defun | |
4204 | ||
9b6e4bc3 | 4205 | @defun insert-sliced-image image &optional string area rows cols |
26b76360 RS |
4206 | This function inserts @var{image} in the current buffer at point, like |
4207 | @code{insert-image}, but splits the image into @var{rows}x@var{cols} | |
4208 | equally sized slices. | |
9b6e4bc3 KS |
4209 | @end defun |
4210 | ||
bb2337f5 | 4211 | @defun put-image image pos &optional string area |
8241495d RS |
4212 | This function puts image @var{image} in front of @var{pos} in the |
4213 | current buffer. The argument @var{pos} should be an integer or a | |
4214 | marker. It specifies the buffer position where the image should appear. | |
bb2337f5 DL |
4215 | The argument @var{string} specifies the text that should hold the image |
4216 | as an alternative to the default. | |
8241495d RS |
4217 | |
4218 | The argument @var{image} must be an image descriptor, perhaps returned | |
4219 | by @code{create-image} or stored by @code{defimage}. | |
4220 | ||
4221 | The argument @var{area} specifies whether to put the image in a margin. | |
4222 | If it is @code{left-margin}, the image appears in the left margin; | |
4223 | @code{right-margin} specifies the right margin. If @var{area} is | |
4224 | @code{nil} or omitted, the image is displayed at point within the | |
4225 | buffer's text. | |
4226 | ||
4227 | Internally, this function creates an overlay, and gives it a | |
4228 | @code{before-string} property containing text that has a @code{display} | |
4229 | property whose value is the image. (Whew!) | |
4230 | @end defun | |
4231 | ||
4232 | @defun remove-images start end &optional buffer | |
4233 | This function removes images in @var{buffer} between positions | |
4234 | @var{start} and @var{end}. If @var{buffer} is omitted or @code{nil}, | |
4235 | images are removed from the current buffer. | |
4236 | ||
05aea714 | 4237 | This removes only images that were put into @var{buffer} the way |
8241495d RS |
4238 | @code{put-image} does it, not images that were inserted with |
4239 | @code{insert-image} or in other ways. | |
4240 | @end defun | |
4241 | ||
e3b9fc91 | 4242 | @defun image-size spec &optional pixels frame |
e3b9fc91 DL |
4243 | This function returns the size of an image as a pair |
4244 | @w{@code{(@var{width} . @var{height})}}. @var{spec} is an image | |
9a8dc0d3 RS |
4245 | specification. @var{pixels} non-@code{nil} means return sizes |
4246 | measured in pixels, otherwise return sizes measured in canonical | |
4247 | character units (fractions of the width/height of the frame's default | |
4248 | font). @var{frame} is the frame on which the image will be displayed. | |
8d82c597 EZ |
4249 | @var{frame} null or omitted means use the selected frame (@pxref{Input |
4250 | Focus}). | |
e3b9fc91 DL |
4251 | @end defun |
4252 | ||
63ab30d0 | 4253 | @defvar max-image-size |
63ab30d0 | 4254 | This variable is used to define the maximum size of image that Emacs |
1ac3cfd8 KS |
4255 | will load. Emacs will refuse to load (and display) any image that is |
4256 | larger than this limit. | |
4257 | ||
4258 | If the value is an integer, it directly specifies the maximum | |
4259 | image height and width, measured in pixels. If it is a floating | |
4260 | point number, it specifies the maximum image height and width | |
4261 | as a ratio to the frame height and width. If the value is | |
4262 | non-numeric, there is no explicit limit on the size of images. | |
63ab30d0 CY |
4263 | |
4264 | The purpose of this variable is to prevent unreasonably large images | |
4265 | from accidentally being loaded into Emacs. It only takes effect the | |
4266 | first time an image is loaded. Once an image is placed in the image | |
4267 | cache, it can always be displayed, even if the value of | |
4268 | @var{max-image-size} is subsequently changed (@pxref{Image Cache}). | |
4269 | @end defvar | |
4270 | ||
8241495d RS |
4271 | @node Image Cache |
4272 | @subsection Image Cache | |
4273 | ||
4274 | Emacs stores images in an image cache when it displays them, so it can | |
4275 | display them again more efficiently. It removes an image from the cache | |
4276 | when it hasn't been displayed for a specified period of time. | |
4277 | ||
3e8b2a01 GM |
4278 | When an image is looked up in the cache, its specification is compared |
4279 | with cached image specifications using @code{equal}. This means that | |
4280 | all images with equal specifications share the same image in the cache. | |
4281 | ||
8241495d | 4282 | @defvar image-cache-eviction-delay |
8241495d RS |
4283 | This variable specifies the number of seconds an image can remain in the |
4284 | cache without being displayed. When an image is not displayed for this | |
4285 | length of time, Emacs removes it from the image cache. | |
4286 | ||
4287 | If the value is @code{nil}, Emacs does not remove images from the cache | |
4288 | except when you explicitly clear it. This mode can be useful for | |
4289 | debugging. | |
4290 | @end defvar | |
4291 | ||
4292 | @defun clear-image-cache &optional frame | |
8241495d RS |
4293 | This function clears the image cache. If @var{frame} is non-@code{nil}, |
4294 | only the cache for that frame is cleared. Otherwise all frames' caches | |
4295 | are cleared. | |
4296 | @end defun | |
a065c889 | 4297 | |
02c77ee9 MB |
4298 | @node Buttons |
4299 | @section Buttons | |
a3cb3b2e | 4300 | @cindex buttons |
02c77ee9 MB |
4301 | @cindex buttons in buffers |
4302 | @cindex clickable buttons in buffers | |
4303 | ||
4304 | The @emph{button} package defines functions for inserting and | |
4305 | manipulating clickable (with the mouse, or via keyboard commands) | |
a3cb3b2e MB |
4306 | buttons in Emacs buffers, such as might be used for help hyper-links, |
4307 | etc. Emacs uses buttons for the hyper-links in help text and the like. | |
02c77ee9 | 4308 | |
c2579664 RS |
4309 | A button is essentially a set of properties attached (via text |
4310 | properties or overlays) to a region of text in an Emacs buffer. These | |
4311 | properties are called @dfn{button properties}. | |
02c77ee9 | 4312 | |
d9e8a964 | 4313 | One of these properties (@code{action}) is a function, which will |
02c77ee9 MB |
4314 | be called when the user invokes it using the keyboard or the mouse. |
4315 | The invoked function may then examine the button and use its other | |
4316 | properties as desired. | |
4317 | ||
c2579664 | 4318 | In some ways the Emacs button package duplicates functionality offered |
02c77ee9 MB |
4319 | by the widget package (@pxref{Top, , Introduction, widget, The Emacs |
4320 | Widget Library}), but the button package has the advantage that it is | |
4321 | much faster, much smaller, and much simpler to use (for elisp | |
4322 | programmers---for users, the result is about the same). The extra | |
4323 | speed and space savings are useful mainly if you need to create many | |
4324 | buttons in a buffer (for instance an @code{*Apropos*} buffer uses | |
4325 | buttons to make entries clickable, and may contain many thousands of | |
4326 | entries). | |
4327 | ||
4328 | @menu | |
4329 | * Button Properties:: Button properties with special meanings. | |
4330 | * Button Types:: Defining common properties for classes of buttons. | |
058296d3 | 4331 | * Making Buttons:: Adding buttons to Emacs buffers. |
02c77ee9 MB |
4332 | * Manipulating Buttons:: Getting and setting properties of buttons. |
4333 | * Button Buffer Commands:: Buffer-wide commands and bindings for buttons. | |
02c77ee9 MB |
4334 | @end menu |
4335 | ||
4336 | @node Button Properties | |
4337 | @subsection Button Properties | |
4338 | @cindex button properties | |
4339 | ||
4340 | Buttons have an associated list of properties defining their | |
4341 | appearance and behavior, and other arbitrary properties may be used | |
c2579664 RS |
4342 | for application specific purposes. Some properties that have special |
4343 | meaning to the button package include: | |
02c77ee9 MB |
4344 | |
4345 | @table @code | |
02c77ee9 | 4346 | @item action |
a3cb3b2e | 4347 | @kindex action @r{(button property)} |
02c77ee9 MB |
4348 | The function to call when the user invokes the button, which is passed |
4349 | the single argument @var{button}. By default this is @code{ignore}, | |
4350 | which does nothing. | |
4351 | ||
4352 | @item mouse-action | |
a3cb3b2e | 4353 | @kindex mouse-action @r{(button property)} |
02c77ee9 MB |
4354 | This is similar to @code{action}, and when present, will be used |
4355 | instead of @code{action} for button invocations resulting from | |
4356 | mouse-clicks (instead of the user hitting @key{RET}). If not | |
4357 | present, mouse-clicks use @code{action} instead. | |
4358 | ||
4359 | @item face | |
a3cb3b2e | 4360 | @kindex face @r{(button property)} |
058296d3 | 4361 | This is an Emacs face controlling how buttons of this type are |
02c77ee9 MB |
4362 | displayed; by default this is the @code{button} face. |
4363 | ||
4364 | @item mouse-face | |
a3cb3b2e | 4365 | @kindex mouse-face @r{(button property)} |
02c77ee9 MB |
4366 | This is an additional face which controls appearance during |
4367 | mouse-overs (merged with the usual button face); by default this is | |
058296d3 | 4368 | the usual Emacs @code{highlight} face. |
02c77ee9 MB |
4369 | |
4370 | @item keymap | |
a3cb3b2e | 4371 | @kindex keymap @r{(button property)} |
02c77ee9 MB |
4372 | The button's keymap, defining bindings active within the button |
4373 | region. By default this is the usual button region keymap, stored | |
51d40dab KS |
4374 | in the variable @code{button-map}, which defines @key{RET} and |
4375 | @key{mouse-2} to invoke the button. | |
02c77ee9 MB |
4376 | |
4377 | @item type | |
a3cb3b2e | 4378 | @kindex type @r{(button property)} |
02c77ee9 MB |
4379 | The button-type of the button. When creating a button, this is |
4380 | usually specified using the @code{:type} keyword argument. | |
4381 | @xref{Button Types}. | |
4382 | ||
4383 | @item help-echo | |
a3cb3b2e | 4384 | @kindex help-index @r{(button property)} |
058296d3 | 4385 | A string displayed by the Emacs tool-tip help system; by default, |
02c77ee9 MB |
4386 | @code{"mouse-2, RET: Push this button"}. |
4387 | ||
91106113 KS |
4388 | @item follow-link |
4389 | @kindex follow-link @r{(button property)} | |
51d40dab KS |
4390 | The follow-link property, defining how a @key{Mouse-1} click behaves |
4391 | on this button, @xref{Links and Mouse-1}. | |
4392 | ||
02c77ee9 | 4393 | @item button |
a3cb3b2e | 4394 | @kindex button @r{(button property)} |
02c77ee9 MB |
4395 | All buttons have a non-@code{nil} @code{button} property, which may be useful |
4396 | in finding regions of text that comprise buttons (which is what the | |
4397 | standard button functions do). | |
4398 | @end table | |
4399 | ||
c2579664 | 4400 | There are other properties defined for the regions of text in a |
02c77ee9 MB |
4401 | button, but these are not generally interesting for typical uses. |
4402 | ||
4403 | @node Button Types | |
4404 | @subsection Button Types | |
4405 | @cindex button types | |
4406 | ||
4407 | Every button has a button @emph{type}, which defines default values | |
a3cb3b2e MB |
4408 | for the button's properties. Button types are arranged in a |
4409 | hierarchy, with specialized types inheriting from more general types, | |
4410 | so that it's easy to define special-purpose types of buttons for | |
4411 | specific tasks. | |
02c77ee9 MB |
4412 | |
4413 | @defun define-button-type name &rest properties | |
02c77ee9 MB |
4414 | Define a `button type' called @var{name}. The remaining arguments |
4415 | form a sequence of @var{property value} pairs, specifying default | |
4416 | property values for buttons with this type (a button's type may be set | |
4417 | by giving it a @code{type} property when creating the button, using | |
4418 | the @code{:type} keyword argument). | |
4419 | ||
4420 | In addition, the keyword argument @code{:supertype} may be used to | |
4421 | specify a button-type from which @var{name} inherits its default | |
4422 | property values. Note that this inheritance happens only when | |
4423 | @var{name} is defined; subsequent changes to a supertype are not | |
4424 | reflected in its subtypes. | |
4425 | @end defun | |
4426 | ||
c2579664 | 4427 | Using @code{define-button-type} to define default properties for |
a3cb3b2e | 4428 | buttons is not necessary---buttons without any specified type use the |
c2579664 | 4429 | built-in button-type @code{button}---but it is encouraged, since |
a3cb3b2e | 4430 | doing so usually makes the resulting code clearer and more efficient. |
02c77ee9 | 4431 | |
a3cb3b2e MB |
4432 | @node Making Buttons |
4433 | @subsection Making Buttons | |
02c77ee9 MB |
4434 | @cindex making buttons |
4435 | ||
4436 | Buttons are associated with a region of text, using an overlay or | |
c2579664 | 4437 | text properties to hold button-specific information, all of which are |
02c77ee9 | 4438 | initialized from the button's type (which defaults to the built-in |
058296d3 | 4439 | button type @code{button}). Like all Emacs text, the appearance of |
02c77ee9 MB |
4440 | the button is governed by the @code{face} property; by default (via |
4441 | the @code{face} property inherited from the @code{button} button-type) | |
4442 | this is a simple underline, like a typical web-page link. | |
4443 | ||
c2579664 | 4444 | For convenience, there are two sorts of button-creation functions, |
02c77ee9 | 4445 | those that add button properties to an existing region of a buffer, |
7fdc81ab EZ |
4446 | called @code{make-...button}, and those that also insert the button |
4447 | text, called @code{insert-...button}. | |
02c77ee9 | 4448 | |
c2579664 | 4449 | The button-creation functions all take the @code{&rest} argument |
02c77ee9 MB |
4450 | @var{properties}, which should be a sequence of @var{property value} |
4451 | pairs, specifying properties to add to the button; see @ref{Button | |
4452 | Properties}. In addition, the keyword argument @code{:type} may be | |
4453 | used to specify a button-type from which to inherit other properties; | |
4454 | see @ref{Button Types}. Any properties not explicitly specified | |
4455 | during creation will be inherited from the button's type (if the type | |
4456 | defines such a property). | |
4457 | ||
c2579664 | 4458 | The following functions add a button using an overlay |
02c77ee9 MB |
4459 | (@pxref{Overlays}) to hold the button properties: |
4460 | ||
4461 | @defun make-button beg end &rest properties | |
c2579664 RS |
4462 | This makes a button from @var{beg} to @var{end} in the |
4463 | current buffer, and returns it. | |
02c77ee9 MB |
4464 | @end defun |
4465 | ||
4466 | @defun insert-button label &rest properties | |
c2579664 RS |
4467 | This insert a button with the label @var{label} at point, |
4468 | and returns it. | |
02c77ee9 MB |
4469 | @end defun |
4470 | ||
c2579664 | 4471 | The following functions are similar, but use Emacs text properties |
02c77ee9 MB |
4472 | (@pxref{Text Properties}) to hold the button properties, making the |
4473 | button actually part of the text instead of being a property of the | |
c2579664 RS |
4474 | buffer. Buttons using text properties do not create markers into the |
4475 | buffer, which is important for speed when you use extremely large | |
4476 | numbers of buttons. Both functions return the position of the start | |
4477 | of the new button: | |
02c77ee9 MB |
4478 | |
4479 | @defun make-text-button beg end &rest properties | |
c2579664 RS |
4480 | This makes a button from @var{beg} to @var{end} in the current buffer, using |
4481 | text properties. | |
02c77ee9 MB |
4482 | @end defun |
4483 | ||
4484 | @defun insert-text-button label &rest properties | |
c2579664 RS |
4485 | This inserts a button with the label @var{label} at point, using text |
4486 | properties. | |
02c77ee9 MB |
4487 | @end defun |
4488 | ||
02c77ee9 MB |
4489 | @node Manipulating Buttons |
4490 | @subsection Manipulating Buttons | |
4491 | @cindex manipulating buttons | |
4492 | ||
4493 | These are functions for getting and setting properties of buttons. | |
4494 | Often these are used by a button's invocation function to determine | |
4495 | what to do. | |
4496 | ||
4497 | Where a @var{button} parameter is specified, it means an object | |
4498 | referring to a specific button, either an overlay (for overlay | |
4499 | buttons), or a buffer-position or marker (for text property buttons). | |
4500 | Such an object is passed as the first argument to a button's | |
4501 | invocation function when it is invoked. | |
4502 | ||
4503 | @defun button-start button | |
02c77ee9 MB |
4504 | Return the position at which @var{button} starts. |
4505 | @end defun | |
4506 | ||
4507 | @defun button-end button | |
02c77ee9 MB |
4508 | Return the position at which @var{button} ends. |
4509 | @end defun | |
4510 | ||
4511 | @defun button-get button prop | |
02c77ee9 MB |
4512 | Get the property of button @var{button} named @var{prop}. |
4513 | @end defun | |
4514 | ||
4515 | @defun button-put button prop val | |
02c77ee9 MB |
4516 | Set @var{button}'s @var{prop} property to @var{val}. |
4517 | @end defun | |
4518 | ||
4519 | @defun button-activate button &optional use-mouse-action | |
02c77ee9 MB |
4520 | Call @var{button}'s @code{action} property (i.e., invoke it). If |
4521 | @var{use-mouse-action} is non-@code{nil}, try to invoke the button's | |
a3cb3b2e MB |
4522 | @code{mouse-action} property instead of @code{action}; if the button |
4523 | has no @code{mouse-action} property, use @code{action} as normal. | |
02c77ee9 MB |
4524 | @end defun |
4525 | ||
4526 | @defun button-label button | |
02c77ee9 MB |
4527 | Return @var{button}'s text label. |
4528 | @end defun | |
4529 | ||
4530 | @defun button-type button | |
02c77ee9 MB |
4531 | Return @var{button}'s button-type. |
4532 | @end defun | |
4533 | ||
4534 | @defun button-has-type-p button type | |
02c77ee9 MB |
4535 | Return @code{t} if @var{button} has button-type @var{type}, or one of |
4536 | @var{type}'s subtypes. | |
4537 | @end defun | |
4538 | ||
4539 | @defun button-at pos | |
02c77ee9 MB |
4540 | Return the button at position @var{pos} in the current buffer, or @code{nil}. |
4541 | @end defun | |
4542 | ||
c2579664 | 4543 | @defun button-type-put type prop val |
c2579664 RS |
4544 | Set the button-type @var{type}'s @var{prop} property to @var{val}. |
4545 | @end defun | |
4546 | ||
4547 | @defun button-type-get type prop | |
c2579664 RS |
4548 | Get the property of button-type @var{type} named @var{prop}. |
4549 | @end defun | |
4550 | ||
4551 | @defun button-type-subtype-p type supertype | |
c2579664 RS |
4552 | Return @code{t} if button-type @var{type} is a subtype of @var{supertype}. |
4553 | @end defun | |
4554 | ||
02c77ee9 MB |
4555 | @node Button Buffer Commands |
4556 | @subsection Button Buffer Commands | |
4557 | @cindex button buffer commands | |
4558 | ||
4559 | These are commands and functions for locating and operating on | |
058296d3 | 4560 | buttons in an Emacs buffer. |
02c77ee9 MB |
4561 | |
4562 | @code{push-button} is the command that a user uses to actually `push' | |
51d40dab | 4563 | a button, and is bound by default in the button itself to @key{RET} |
eb3c144c | 4564 | and to @key{mouse-2} using a region-specific keymap. Commands |
02c77ee9 MB |
4565 | that are useful outside the buttons itself, such as |
4566 | @code{forward-button} and @code{backward-button} are additionally | |
4567 | available in the keymap stored in @code{button-buffer-map}; a mode | |
4568 | which uses buttons may want to use @code{button-buffer-map} as a | |
4569 | parent keymap for its keymap. | |
4570 | ||
51d40dab | 4571 | If the button has a non-@code{nil} @code{follow-link} property, and |
c2579664 RS |
4572 | @var{mouse-1-click-follows-link} is set, a quick @key{Mouse-1} click |
4573 | will also activate the @code{push-button} command. | |
4574 | @xref{Links and Mouse-1}. | |
51d40dab | 4575 | |
02c77ee9 | 4576 | @deffn Command push-button &optional pos use-mouse-action |
02c77ee9 MB |
4577 | Perform the action specified by a button at location @var{pos}. |
4578 | @var{pos} may be either a buffer position or a mouse-event. If | |
a3cb3b2e MB |
4579 | @var{use-mouse-action} is non-@code{nil}, or @var{pos} is a |
4580 | mouse-event (@pxref{Mouse Events}), try to invoke the button's | |
4581 | @code{mouse-action} property instead of @code{action}; if the button | |
4582 | has no @code{mouse-action} property, use @code{action} as normal. | |
4583 | @var{pos} defaults to point, except when @code{push-button} is invoked | |
4584 | interactively as the result of a mouse-event, in which case, the mouse | |
4585 | event's position is used. If there's no button at @var{pos}, do | |
02c77ee9 MB |
4586 | nothing and return @code{nil}, otherwise return @code{t}. |
4587 | @end deffn | |
4588 | ||
4589 | @deffn Command forward-button n &optional wrap display-message | |
02c77ee9 MB |
4590 | Move to the @var{n}th next button, or @var{n}th previous button if |
4591 | @var{n} is negative. If @var{n} is zero, move to the start of any | |
4592 | button at point. If @var{wrap} is non-@code{nil}, moving past either | |
4593 | end of the buffer continues from the other end. If | |
4594 | @var{display-message} is non-@code{nil}, the button's help-echo string | |
a3cb3b2e MB |
4595 | is displayed. Any button with a non-@code{nil} @code{skip} property |
4596 | is skipped over. Returns the button found. | |
02c77ee9 MB |
4597 | @end deffn |
4598 | ||
4599 | @deffn Command backward-button n &optional wrap display-message | |
02c77ee9 MB |
4600 | Move to the @var{n}th previous button, or @var{n}th next button if |
4601 | @var{n} is negative. If @var{n} is zero, move to the start of any | |
4602 | button at point. If @var{wrap} is non-@code{nil}, moving past either | |
4603 | end of the buffer continues from the other end. If | |
4604 | @var{display-message} is non-@code{nil}, the button's help-echo string | |
a3cb3b2e MB |
4605 | is displayed. Any button with a non-@code{nil} @code{skip} property |
4606 | is skipped over. Returns the button found. | |
02c77ee9 MB |
4607 | @end deffn |
4608 | ||
4609 | @defun next-button pos &optional count-current | |
02c77ee9 MB |
4610 | Return the next button after position @var{pos} in the current buffer. |
4611 | If @var{count-current} is non-@code{nil}, count any button at | |
4612 | @var{pos} in the search, instead of starting at the next button. | |
4613 | @end defun | |
4614 | ||
4615 | @defun previous-button pos &optional count-current | |
02c77ee9 MB |
4616 | Return the @var{n}th button before position @var{pos} in the current |
4617 | buffer. If @var{count-current} is non-@code{nil}, count any button at | |
4618 | @var{pos} in the search, instead of starting at the next button. | |
4619 | @end defun | |
4620 | ||
f3dffabb TTN |
4621 | @node Abstract Display |
4622 | @section Abstract Display | |
4623 | @cindex ewoc | |
4624 | @cindex display, abstract | |
4625 | @cindex display, arbitrary objects | |
4626 | @cindex model/view/controller | |
4627 | @cindex view part, model/view/controller | |
4628 | ||
4629 | The Ewoc package constructs buffer text that represents a structure | |
4630 | of Lisp objects, and updates the text to follow changes in that | |
71ee3e04 | 4631 | structure. This is like the ``view'' component in the |
f3dffabb TTN |
4632 | ``model/view/controller'' design paradigm. |
4633 | ||
4634 | An @dfn{ewoc} is a structure that organizes information required to | |
4635 | construct buffer text that represents certain Lisp data. The buffer | |
4636 | text of the ewoc has three parts, in order: first, fixed @dfn{header} | |
4637 | text; next, textual descriptions of a series of data elements (Lisp | |
4638 | objects that you specify); and last, fixed @dfn{footer} text. | |
4639 | Specifically, an ewoc contains information on: | |
4640 | ||
4641 | @itemize @bullet | |
4642 | @item | |
4643 | The buffer which its text is generated in. | |
4644 | ||
4645 | @item | |
4646 | The text's start position in the buffer. | |
4647 | ||
4648 | @item | |
4649 | The header and footer strings. | |
4650 | ||
4651 | @item | |
4652 | A doubly-linked chain of @dfn{nodes}, each of which contains: | |
4653 | ||
4654 | @itemize | |
4655 | @item | |
4656 | A @dfn{data element}, a single Lisp object. | |
4657 | ||
4658 | @item | |
4659 | Links to the preceding and following nodes in the chain. | |
4660 | @end itemize | |
4661 | ||
4662 | @item | |
4663 | A @dfn{pretty-printer} function which is responsible for | |
4664 | inserting the textual representation of a data | |
4665 | element value into the current buffer. | |
4666 | @end itemize | |
4667 | ||
4668 | Typically, you define an ewoc with @code{ewoc-create}, and then pass | |
4669 | the resulting ewoc structure to other functions in the Ewoc package to | |
4670 | build nodes within it, and display it in the buffer. Once it is | |
4671 | displayed in the buffer, other functions determine the correspondance | |
4672 | between buffer positions and nodes, move point from one node's textual | |
4673 | representation to another, and so forth. @xref{Abstract Display | |
4674 | Functions}. | |
4675 | ||
4676 | A node @dfn{encapsulates} a data element much the way a variable | |
4677 | holds a value. Normally, encapsulation occurs as a part of adding a | |
4678 | node to the ewoc. You can retrieve the data element value and place a | |
4679 | new value in its place, like so: | |
4680 | ||
4681 | @lisp | |
4682 | (ewoc-data @var{node}) | |
4683 | @result{} value | |
4684 | ||
4685 | (ewoc-set-data @var{node} @var{new-value}) | |
4686 | @result{} @var{new-value} | |
4687 | @end lisp | |
4688 | ||
4689 | @noindent | |
4690 | You can also use, as the data element value, a Lisp object (list or | |
4691 | vector) that is a container for the ``real'' value, or an index into | |
4692 | some other structure. The example (@pxref{Abstract Display Example}) | |
4693 | uses the latter approach. | |
4694 | ||
4695 | When the data changes, you will want to update the text in the | |
4696 | buffer. You can update all nodes by calling @code{ewoc-refresh}, or | |
4697 | just specific nodes using @code{ewoc-invalidate}, or all nodes | |
4698 | satisfying a predicate using @code{ewoc-map}. Alternatively, you can | |
4699 | delete invalid nodes using @code{ewoc-delete} or @code{ewoc-filter}, | |
4700 | and add new nodes in their place. Deleting a node from an ewoc deletes | |
4701 | its associated textual description from buffer, as well. | |
4702 | ||
4703 | @menu | |
4704 | * Abstract Display Functions:: | |
4705 | * Abstract Display Example:: | |
4706 | @end menu | |
4707 | ||
4708 | @node Abstract Display Functions | |
4709 | @subsection Abstract Display Functions | |
4710 | ||
4711 | In this subsection, @var{ewoc} and @var{node} stand for the | |
4712 | structures described above (@pxref{Abstract Display}), while | |
4713 | @var{data} stands for an arbitrary Lisp object used as a data element. | |
4714 | ||
4715 | @defun ewoc-create pretty-printer &optional header footer nosep | |
4716 | This constructs and returns a new ewoc, with no nodes (and thus no data | |
4717 | elements). @var{pretty-printer} should be a function that takes one | |
4718 | argument, a data element of the sort you plan to use in this ewoc, and | |
4719 | inserts its textual description at point using @code{insert} (and never | |
4720 | @code{insert-before-markers}, because that would interfere with the | |
4721 | Ewoc package's internal mechanisms). | |
4722 | ||
4723 | Normally, a newline is automatically inserted after the header, | |
4724 | the footer and every node's textual description. If @var{nosep} | |
4725 | is non-@code{nil}, no newline is inserted. This may be useful for | |
4726 | displaying an entire ewoc on a single line, for example, or for | |
4727 | making nodes ``invisible'' by arranging for @var{pretty-printer} | |
4728 | to do nothing for those nodes. | |
4729 | ||
4730 | An ewoc maintains its text in the buffer that is current when | |
4731 | you create it, so switch to the intended buffer before calling | |
4732 | @code{ewoc-create}. | |
4733 | @end defun | |
4734 | ||
4735 | @defun ewoc-buffer ewoc | |
4736 | This returns the buffer where @var{ewoc} maintains its text. | |
4737 | @end defun | |
4738 | ||
4739 | @defun ewoc-get-hf ewoc | |
4740 | This returns a cons cell @code{(@var{header} . @var{footer})} | |
4741 | made from @var{ewoc}'s header and footer. | |
4742 | @end defun | |
4743 | ||
4744 | @defun ewoc-set-hf ewoc header footer | |
4745 | This sets the header and footer of @var{ewoc} to the strings | |
4746 | @var{header} and @var{footer}, respectively. | |
4747 | @end defun | |
4748 | ||
4749 | @defun ewoc-enter-first ewoc data | |
4750 | @defunx ewoc-enter-last ewoc data | |
4751 | These add a new node encapsulating @var{data}, putting it, respectively, | |
4752 | at the beginning or end of @var{ewoc}'s chain of nodes. | |
4753 | @end defun | |
4754 | ||
4755 | @defun ewoc-enter-before ewoc node data | |
4756 | @defunx ewoc-enter-after ewoc node data | |
4757 | These add a new node encapsulating @var{data}, adding it to | |
4758 | @var{ewoc} before or after @var{node}, respectively. | |
4759 | @end defun | |
4760 | ||
4761 | @defun ewoc-prev ewoc node | |
4762 | @defunx ewoc-next ewoc node | |
4763 | These return, respectively, the previous node and the next node of @var{node} | |
4764 | in @var{ewoc}. | |
4765 | @end defun | |
4766 | ||
4767 | @defun ewoc-nth ewoc n | |
4768 | This returns the node in @var{ewoc} found at zero-based index @var{n}. | |
4769 | A negative @var{n} means count from the end. @code{ewoc-nth} returns | |
4770 | @code{nil} if @var{n} is out of range. | |
4771 | @end defun | |
4772 | ||
4773 | @defun ewoc-data node | |
4774 | This extracts the data encapsulated by @var{node} and returns it. | |
4775 | @end defun | |
4776 | ||
4777 | @defun ewoc-set-data node data | |
4778 | This sets the data encapsulated by @var{node} to @var{data}. | |
4779 | @end defun | |
4780 | ||
4781 | @defun ewoc-locate ewoc &optional pos guess | |
4782 | This determines the node in @var{ewoc} which contains point (or | |
4783 | @var{pos} if specified), and returns that node. If @var{ewoc} has no | |
4784 | nodes, it returns @code{nil}. If @var{pos} is before the first node, | |
4785 | it returns the first node; if @var{pos} is after the last node, it returns | |
4786 | the last node. The optional third arg @var{guess} | |
4787 | should be a node that is likely to be near @var{pos}; this doesn't | |
4788 | alter the result, but makes the function run faster. | |
4789 | @end defun | |
4790 | ||
4791 | @defun ewoc-location node | |
4792 | This returns the start position of @var{node}. | |
4793 | @end defun | |
4794 | ||
4795 | @defun ewoc-goto-prev ewoc arg | |
4796 | @defunx ewoc-goto-next ewoc arg | |
4797 | These move point to the previous or next, respectively, @var{arg}th node | |
4798 | in @var{ewoc}. @code{ewoc-goto-prev} does not move if it is already at | |
4799 | the first node or if @var{ewoc} is empty, whereas @code{ewoc-goto-next} | |
4800 | moves past the last node, returning @code{nil}. Excepting this special | |
4801 | case, these functions return the node moved to. | |
4802 | @end defun | |
4803 | ||
4804 | @defun ewoc-goto-node ewoc node | |
4805 | This moves point to the start of @var{node} in @var{ewoc}. | |
4806 | @end defun | |
4807 | ||
4808 | @defun ewoc-refresh ewoc | |
4809 | This function regenerates the text of @var{ewoc}. It works by | |
4810 | deleting the text between the header and the footer, i.e., all the | |
4811 | data elements' representations, and then calling the pretty-printer | |
4812 | function for each node, one by one, in order. | |
4813 | @end defun | |
4814 | ||
4815 | @defun ewoc-invalidate ewoc &rest nodes | |
4816 | This is similar to @code{ewoc-refresh}, except that only @var{nodes} in | |
4817 | @var{ewoc} are updated instead of the entire set. | |
4818 | @end defun | |
4819 | ||
4820 | @defun ewoc-delete ewoc &rest nodes | |
4821 | This deletes each node in @var{nodes} from @var{ewoc}. | |
4822 | @end defun | |
4823 | ||
4824 | @defun ewoc-filter ewoc predicate &rest args | |
4825 | This calls @var{predicate} for each data element in @var{ewoc} and | |
4826 | deletes those nodes for which @var{predicate} returns @code{nil}. | |
4827 | Any @var{args} are passed to @var{predicate}. | |
4828 | @end defun | |
4829 | ||
4830 | @defun ewoc-collect ewoc predicate &rest args | |
4831 | This calls @var{predicate} for each data element in @var{ewoc} | |
4832 | and returns a list of those elements for which @var{predicate} | |
4833 | returns non-@code{nil}. The elements in the list are ordered | |
4834 | as in the buffer. Any @var{args} are passed to @var{predicate}. | |
4835 | @end defun | |
4836 | ||
4837 | @defun ewoc-map map-function ewoc &rest args | |
4838 | This calls @var{map-function} for each data element in @var{ewoc} and | |
4839 | updates those nodes for which @var{map-function} returns non-@code{nil}. | |
4840 | Any @var{args} are passed to @var{map-function}. | |
4841 | @end defun | |
4842 | ||
4843 | @node Abstract Display Example | |
4844 | @subsection Abstract Display Example | |
4845 | ||
4846 | Here is a simple example using functions of the ewoc package to | |
827b7ee7 | 4847 | implement a ``color components display,'' an area in a buffer that |
f3dffabb TTN |
4848 | represents a vector of three integers (itself representing a 24-bit RGB |
4849 | value) in various ways. | |
4850 | ||
4851 | @example | |
4852 | (setq colorcomp-ewoc nil | |
4853 | colorcomp-data nil | |
4854 | colorcomp-mode-map nil | |
4855 | colorcomp-labels ["Red" "Green" "Blue"]) | |
4856 | ||
4857 | (defun colorcomp-pp (data) | |
4858 | (if data | |
4859 | (let ((comp (aref colorcomp-data data))) | |
4860 | (insert (aref colorcomp-labels data) "\t: #x" | |
4861 | (format "%02X" comp) " " | |
4862 | (make-string (ash comp -2) ?#) "\n")) | |
4863 | (let ((cstr (format "#%02X%02X%02X" | |
4864 | (aref colorcomp-data 0) | |
4865 | (aref colorcomp-data 1) | |
4866 | (aref colorcomp-data 2))) | |
4867 | (samp " (sample text) ")) | |
4868 | (insert "Color\t: " | |
4869 | (propertize samp 'face `(foreground-color . ,cstr)) | |
4870 | (propertize samp 'face `(background-color . ,cstr)) | |
4871 | "\n")))) | |
4872 | ||
4873 | (defun colorcomp (color) | |
4874 | "Allow fiddling with COLOR in a new buffer. | |
4875 | The buffer is in Color Components mode." | |
4876 | (interactive "sColor (name or #RGB or #RRGGBB): ") | |
4877 | (when (string= "" color) | |
4878 | (setq color "green")) | |
4879 | (unless (color-values color) | |
4880 | (error "No such color: %S" color)) | |
4881 | (switch-to-buffer | |
4882 | (generate-new-buffer (format "originally: %s" color))) | |
4883 | (kill-all-local-variables) | |
4884 | (setq major-mode 'colorcomp-mode | |
4885 | mode-name "Color Components") | |
4886 | (use-local-map colorcomp-mode-map) | |
4887 | (erase-buffer) | |
4888 | (buffer-disable-undo) | |
4889 | (let ((data (apply 'vector (mapcar (lambda (n) (ash n -8)) | |
4890 | (color-values color)))) | |
4891 | (ewoc (ewoc-create 'colorcomp-pp | |
4892 | "\nColor Components\n\n" | |
4893 | (substitute-command-keys | |
4894 | "\n\\@{colorcomp-mode-map@}")))) | |
4895 | (set (make-local-variable 'colorcomp-data) data) | |
4896 | (set (make-local-variable 'colorcomp-ewoc) ewoc) | |
4897 | (ewoc-enter-last ewoc 0) | |
4898 | (ewoc-enter-last ewoc 1) | |
4899 | (ewoc-enter-last ewoc 2) | |
4900 | (ewoc-enter-last ewoc nil))) | |
4901 | @end example | |
4902 | ||
4903 | @cindex controller part, model/view/controller | |
4904 | This example can be extended to be a ``color selection widget'' (in | |
4905 | other words, the controller part of the ``model/view/controller'' | |
4906 | design paradigm) by defining commands to modify @code{colorcomp-data} | |
4907 | and to ``finish'' the selection process, and a keymap to tie it all | |
4908 | together conveniently. | |
4909 | ||
42b50684 | 4910 | @smallexample |
f3dffabb TTN |
4911 | (defun colorcomp-mod (index limit delta) |
4912 | (let ((cur (aref colorcomp-data index))) | |
4913 | (unless (= limit cur) | |
4914 | (aset colorcomp-data index (+ cur delta))) | |
4915 | (ewoc-invalidate | |
4916 | colorcomp-ewoc | |
4917 | (ewoc-nth colorcomp-ewoc index) | |
4918 | (ewoc-nth colorcomp-ewoc -1)))) | |
4919 | ||
4920 | (defun colorcomp-R-more () (interactive) (colorcomp-mod 0 255 1)) | |
4921 | (defun colorcomp-G-more () (interactive) (colorcomp-mod 1 255 1)) | |
4922 | (defun colorcomp-B-more () (interactive) (colorcomp-mod 2 255 1)) | |
4923 | (defun colorcomp-R-less () (interactive) (colorcomp-mod 0 0 -1)) | |
4924 | (defun colorcomp-G-less () (interactive) (colorcomp-mod 1 0 -1)) | |
4925 | (defun colorcomp-B-less () (interactive) (colorcomp-mod 2 0 -1)) | |
4926 | ||
4927 | (defun colorcomp-copy-as-kill-and-exit () | |
4928 | "Copy the color components into the kill ring and kill the buffer. | |
4929 | The string is formatted #RRGGBB (hash followed by six hex digits)." | |
4930 | (interactive) | |
4931 | (kill-new (format "#%02X%02X%02X" | |
4932 | (aref colorcomp-data 0) | |
4933 | (aref colorcomp-data 1) | |
4934 | (aref colorcomp-data 2))) | |
4935 | (kill-buffer nil)) | |
4936 | ||
4937 | (setq colorcomp-mode-map | |
4938 | (let ((m (make-sparse-keymap))) | |
4939 | (suppress-keymap m) | |
4940 | (define-key m "i" 'colorcomp-R-less) | |
4941 | (define-key m "o" 'colorcomp-R-more) | |
4942 | (define-key m "k" 'colorcomp-G-less) | |
4943 | (define-key m "l" 'colorcomp-G-more) | |
4944 | (define-key m "," 'colorcomp-B-less) | |
4945 | (define-key m "." 'colorcomp-B-more) | |
4946 | (define-key m " " 'colorcomp-copy-as-kill-and-exit) | |
4947 | m)) | |
42b50684 | 4948 | @end smallexample |
f3dffabb TTN |
4949 | |
4950 | Note that we never modify the data in each node, which is fixed when the | |
4951 | ewoc is created to be either @code{nil} or an index into the vector | |
4952 | @code{colorcomp-data}, the actual color components. | |
4953 | ||
42b85554 RS |
4954 | @node Blinking |
4955 | @section Blinking Parentheses | |
4956 | @cindex parenthesis matching | |
4957 | @cindex blinking | |
4958 | @cindex balancing parentheses | |
4959 | @cindex close parenthesis | |
4960 | ||
4961 | This section describes the mechanism by which Emacs shows a matching | |
4962 | open parenthesis when the user inserts a close parenthesis. | |
4963 | ||
42b85554 RS |
4964 | @defvar blink-paren-function |
4965 | The value of this variable should be a function (of no arguments) to | |
4966 | be called whenever a character with close parenthesis syntax is inserted. | |
4967 | The value of @code{blink-paren-function} may be @code{nil}, in which | |
4968 | case nothing is done. | |
42b85554 RS |
4969 | @end defvar |
4970 | ||
1911e6e5 | 4971 | @defopt blink-matching-paren |
42b85554 RS |
4972 | If this variable is @code{nil}, then @code{blink-matching-open} does |
4973 | nothing. | |
1911e6e5 | 4974 | @end defopt |
42b85554 | 4975 | |
1911e6e5 | 4976 | @defopt blink-matching-paren-distance |
42b85554 RS |
4977 | This variable specifies the maximum distance to scan for a matching |
4978 | parenthesis before giving up. | |
1911e6e5 | 4979 | @end defopt |
42b85554 | 4980 | |
1911e6e5 | 4981 | @defopt blink-matching-delay |
bfe721d1 KH |
4982 | This variable specifies the number of seconds for the cursor to remain |
4983 | at the matching parenthesis. A fraction of a second often gives | |
4984 | good results, but the default is 1, which works on all systems. | |
1911e6e5 | 4985 | @end defopt |
bfe721d1 | 4986 | |
1911e6e5 | 4987 | @deffn Command blink-matching-open |
42b85554 RS |
4988 | This function is the default value of @code{blink-paren-function}. It |
4989 | assumes that point follows a character with close parenthesis syntax and | |
4990 | moves the cursor momentarily to the matching opening character. If that | |
4991 | character is not already on the screen, it displays the character's | |
4992 | context in the echo area. To avoid long delays, this function does not | |
4993 | search farther than @code{blink-matching-paren-distance} characters. | |
4994 | ||
4995 | Here is an example of calling this function explicitly. | |
4996 | ||
4997 | @smallexample | |
4998 | @group | |
4999 | (defun interactive-blink-matching-open () | |
5000 | @c Do not break this line! -- rms. | |
5001 | @c The first line of a doc string | |
5002 | @c must stand alone. | |
5003 | "Indicate momentarily the start of sexp before point." | |
5004 | (interactive) | |
5005 | @end group | |
5006 | @group | |
5007 | (let ((blink-matching-paren-distance | |
5008 | (buffer-size)) | |
5009 | (blink-matching-paren t)) | |
5010 | (blink-matching-open))) | |
5011 | @end group | |
5012 | @end smallexample | |
1911e6e5 | 5013 | @end deffn |
42b85554 | 5014 | |
42b85554 RS |
5015 | @node Usual Display |
5016 | @section Usual Display Conventions | |
5017 | ||
5018 | The usual display conventions define how to display each character | |
5019 | code. You can override these conventions by setting up a display table | |
5020 | (@pxref{Display Tables}). Here are the usual display conventions: | |
5021 | ||
5022 | @itemize @bullet | |
5023 | @item | |
5024 | Character codes 32 through 126 map to glyph codes 32 through 126. | |
5025 | Normally this means they display as themselves. | |
5026 | ||
5027 | @item | |
5028 | Character code 9 is a horizontal tab. It displays as whitespace | |
5029 | up to a position determined by @code{tab-width}. | |
5030 | ||
5031 | @item | |
5032 | Character code 10 is a newline. | |
5033 | ||
5034 | @item | |
5035 | All other codes in the range 0 through 31, and code 127, display in one | |
78608595 | 5036 | of two ways according to the value of @code{ctl-arrow}. If it is |
42b85554 | 5037 | non-@code{nil}, these codes map to sequences of two glyphs, where the |
ad800164 | 5038 | first glyph is the @acronym{ASCII} code for @samp{^}. (A display table can |
42b85554 RS |
5039 | specify a glyph to use instead of @samp{^}.) Otherwise, these codes map |
5040 | just like the codes in the range 128 to 255. | |
5041 | ||
8241495d RS |
5042 | On MS-DOS terminals, Emacs arranges by default for the character code |
5043 | 127 to be mapped to the glyph code 127, which normally displays as an | |
ad800164 | 5044 | empty polygon. This glyph is used to display non-@acronym{ASCII} characters |
8241495d RS |
5045 | that the MS-DOS terminal doesn't support. @xref{MS-DOS and MULE,,, |
5046 | emacs, The GNU Emacs Manual}. | |
5047 | ||
42b85554 RS |
5048 | @item |
5049 | Character codes 128 through 255 map to sequences of four glyphs, where | |
ad800164 | 5050 | the first glyph is the @acronym{ASCII} code for @samp{\}, and the others are |
a9f0a989 | 5051 | digit characters representing the character code in octal. (A display |
969fe9b5 RS |
5052 | table can specify a glyph to use instead of @samp{\}.) |
5053 | ||
5054 | @item | |
5055 | Multibyte character codes above 256 are displayed as themselves, or as a | |
5056 | question mark or empty box if the terminal cannot display that | |
5057 | character. | |
42b85554 RS |
5058 | @end itemize |
5059 | ||
5060 | The usual display conventions apply even when there is a display | |
5061 | table, for any character whose entry in the active display table is | |
5062 | @code{nil}. Thus, when you set up a display table, you need only | |
969fe9b5 | 5063 | specify the characters for which you want special behavior. |
42b85554 | 5064 | |
b6954afd RS |
5065 | These display rules apply to carriage return (character code 13), when |
5066 | it appears in the buffer. But that character may not appear in the | |
5067 | buffer where you expect it, if it was eliminated as part of end-of-line | |
15da7853 | 5068 | conversion (@pxref{Coding System Basics}). |
b6954afd | 5069 | |
42b85554 RS |
5070 | These variables affect the way certain characters are displayed on the |
5071 | screen. Since they change the number of columns the characters occupy, | |
f9f59935 RS |
5072 | they also affect the indentation functions. These variables also affect |
5073 | how the mode line is displayed; if you want to force redisplay of the | |
5074 | mode line using the new values, call the function | |
5075 | @code{force-mode-line-update} (@pxref{Mode Line Format}). | |
42b85554 RS |
5076 | |
5077 | @defopt ctl-arrow | |
5078 | @cindex control characters in display | |
5079 | This buffer-local variable controls how control characters are | |
5080 | displayed. If it is non-@code{nil}, they are displayed as a caret | |
5081 | followed by the character: @samp{^A}. If it is @code{nil}, they are | |
5082 | displayed as a backslash followed by three octal digits: @samp{\001}. | |
5083 | @end defopt | |
5084 | ||
5085 | @c Following may have overfull hbox. | |
5086 | @defvar default-ctl-arrow | |
5087 | The value of this variable is the default value for @code{ctl-arrow} in | |
5088 | buffers that do not override it. @xref{Default Value}. | |
5089 | @end defvar | |
5090 | ||
fe8d1469 | 5091 | @defopt tab-width |
475aab0d CY |
5092 | The value of this buffer-local variable is the spacing between tab |
5093 | stops used for displaying tab characters in Emacs buffers. The value | |
5094 | is in units of columns, and the default is 8. Note that this feature | |
5095 | is completely independent of the user-settable tab stops used by the | |
5096 | command @code{tab-to-tab-stop}. @xref{Indent Tabs}. | |
fe8d1469 RS |
5097 | @end defopt |
5098 | ||
42b85554 RS |
5099 | @node Display Tables |
5100 | @section Display Tables | |
5101 | ||
5102 | @cindex display table | |
969fe9b5 RS |
5103 | You can use the @dfn{display table} feature to control how all possible |
5104 | character codes display on the screen. This is useful for displaying | |
ad800164 | 5105 | European languages that have letters not in the @acronym{ASCII} character |
969fe9b5 | 5106 | set. |
42b85554 RS |
5107 | |
5108 | The display table maps each character code into a sequence of | |
8241495d | 5109 | @dfn{glyphs}, each glyph being a graphic that takes up one character |
42b85554 RS |
5110 | position on the screen. You can also define how to display each glyph |
5111 | on your terminal, using the @dfn{glyph table}. | |
5112 | ||
f9f59935 RS |
5113 | Display tables affect how the mode line is displayed; if you want to |
5114 | force redisplay of the mode line using a new display table, call | |
5115 | @code{force-mode-line-update} (@pxref{Mode Line Format}). | |
5116 | ||
42b85554 | 5117 | @menu |
02c77ee9 MB |
5118 | * Display Table Format:: What a display table consists of. |
5119 | * Active Display Table:: How Emacs selects a display table to use. | |
5120 | * Glyphs:: How to define a glyph, and what glyphs mean. | |
42b85554 RS |
5121 | @end menu |
5122 | ||
5123 | @node Display Table Format | |
5124 | @subsection Display Table Format | |
5125 | ||
a9f0a989 RS |
5126 | A display table is actually a char-table (@pxref{Char-Tables}) with |
5127 | @code{display-table} as its subtype. | |
42b85554 RS |
5128 | |
5129 | @defun make-display-table | |
5130 | This creates and returns a display table. The table initially has | |
5131 | @code{nil} in all elements. | |
5132 | @end defun | |
5133 | ||
f9f59935 RS |
5134 | The ordinary elements of the display table are indexed by character |
5135 | codes; the element at index @var{c} says how to display the character | |
8b170b82 RS |
5136 | code @var{c}. The value should be @code{nil} or a vector of the |
5137 | glyphs to be output (@pxref{Glyphs}). @code{nil} says to display the | |
5138 | character @var{c} according to the usual display conventions | |
f9f59935 | 5139 | (@pxref{Usual Display}). |
22697dac | 5140 | |
8b170b82 RS |
5141 | @strong{Warning:} if you use the display table to change the display |
5142 | of newline characters, the whole buffer will be displayed as one long | |
5143 | ``line.'' | |
42b85554 | 5144 | |
f9f59935 | 5145 | The display table also has six ``extra slots'' which serve special |
969fe9b5 RS |
5146 | purposes. Here is a table of their meanings; @code{nil} in any slot |
5147 | means to use the default for that slot, as stated below. | |
42b85554 RS |
5148 | |
5149 | @table @asis | |
f9f59935 | 5150 | @item 0 |
42b85554 | 5151 | The glyph for the end of a truncated screen line (the default for this |
c2579664 RS |
5152 | is @samp{$}). @xref{Glyphs}. On graphical terminals, Emacs uses |
5153 | arrows in the fringes to indicate truncation, so the display table has | |
5154 | no effect. | |
5155 | ||
f9f59935 | 5156 | @item 1 |
42b85554 | 5157 | The glyph for the end of a continued line (the default is @samp{\}). |
c2579664 RS |
5158 | On graphical terminals, Emacs uses curved arrows in the fringes to |
5159 | indicate continuation, so the display table has no effect. | |
5160 | ||
f9f59935 | 5161 | @item 2 |
42b85554 RS |
5162 | The glyph for indicating a character displayed as an octal character |
5163 | code (the default is @samp{\}). | |
c2579664 | 5164 | |
f9f59935 | 5165 | @item 3 |
42b85554 | 5166 | The glyph for indicating a control character (the default is @samp{^}). |
c2579664 | 5167 | |
f9f59935 | 5168 | @item 4 |
42b85554 RS |
5169 | A vector of glyphs for indicating the presence of invisible lines (the |
5170 | default is @samp{...}). @xref{Selective Display}. | |
c2579664 | 5171 | |
f9f59935 | 5172 | @item 5 |
50b04c36 | 5173 | The glyph used to draw the border between side-by-side windows (the |
8241495d RS |
5174 | default is @samp{|}). @xref{Splitting Windows}. This takes effect only |
5175 | when there are no scroll bars; if scroll bars are supported and in use, | |
5176 | a scroll bar separates the two windows. | |
42b85554 RS |
5177 | @end table |
5178 | ||
5179 | For example, here is how to construct a display table that mimics the | |
5180 | effect of setting @code{ctl-arrow} to a non-@code{nil} value: | |
5181 | ||
5182 | @example | |
5183 | (setq disptab (make-display-table)) | |
5184 | (let ((i 0)) | |
5185 | (while (< i 32) | |
5186 | (or (= i ?\t) (= i ?\n) | |
5187 | (aset disptab i (vector ?^ (+ i 64)))) | |
5188 | (setq i (1+ i))) | |
5189 | (aset disptab 127 (vector ?^ ??))) | |
5190 | @end example | |
5191 | ||
f9f59935 RS |
5192 | @defun display-table-slot display-table slot |
5193 | This function returns the value of the extra slot @var{slot} of | |
5194 | @var{display-table}. The argument @var{slot} may be a number from 0 to | |
5195 | 5 inclusive, or a slot name (symbol). Valid symbols are | |
5196 | @code{truncation}, @code{wrap}, @code{escape}, @code{control}, | |
5197 | @code{selective-display}, and @code{vertical-border}. | |
5198 | @end defun | |
5199 | ||
f9f59935 RS |
5200 | @defun set-display-table-slot display-table slot value |
5201 | This function stores @var{value} in the extra slot @var{slot} of | |
5202 | @var{display-table}. The argument @var{slot} may be a number from 0 to | |
5203 | 5 inclusive, or a slot name (symbol). Valid symbols are | |
5204 | @code{truncation}, @code{wrap}, @code{escape}, @code{control}, | |
5205 | @code{selective-display}, and @code{vertical-border}. | |
5206 | @end defun | |
5207 | ||
8241495d | 5208 | @defun describe-display-table display-table |
8241495d RS |
5209 | This function displays a description of the display table |
5210 | @var{display-table} in a help buffer. | |
5211 | @end defun | |
5212 | ||
5213 | @deffn Command describe-current-display-table | |
8241495d RS |
5214 | This command displays a description of the current display table in a |
5215 | help buffer. | |
5216 | @end deffn | |
5217 | ||
42b85554 RS |
5218 | @node Active Display Table |
5219 | @subsection Active Display Table | |
5220 | @cindex active display table | |
5221 | ||
5222 | Each window can specify a display table, and so can each buffer. When | |
5223 | a buffer @var{b} is displayed in window @var{w}, display uses the | |
5224 | display table for window @var{w} if it has one; otherwise, the display | |
5225 | table for buffer @var{b} if it has one; otherwise, the standard display | |
5226 | table if any. The display table chosen is called the @dfn{active} | |
5227 | display table. | |
5228 | ||
c2579664 | 5229 | @defun window-display-table &optional window |
42b85554 | 5230 | This function returns @var{window}'s display table, or @code{nil} |
c2579664 RS |
5231 | if @var{window} does not have an assigned display table. The default |
5232 | for @var{window} is the selected window. | |
42b85554 RS |
5233 | @end defun |
5234 | ||
5235 | @defun set-window-display-table window table | |
5236 | This function sets the display table of @var{window} to @var{table}. | |
5237 | The argument @var{table} should be either a display table or | |
5238 | @code{nil}. | |
5239 | @end defun | |
5240 | ||
5241 | @defvar buffer-display-table | |
969fe9b5 RS |
5242 | This variable is automatically buffer-local in all buffers; its value in |
5243 | a particular buffer specifies the display table for that buffer. If it | |
5244 | is @code{nil}, that means the buffer does not have an assigned display | |
5245 | table. | |
42b85554 RS |
5246 | @end defvar |
5247 | ||
5248 | @defvar standard-display-table | |
5249 | This variable's value is the default display table, used whenever a | |
5250 | window has no display table and neither does the buffer displayed in | |
5251 | that window. This variable is @code{nil} by default. | |
5252 | @end defvar | |
5253 | ||
5254 | If there is no display table to use for a particular window---that is, | |
f9f59935 RS |
5255 | if the window specifies none, its buffer specifies none, and |
5256 | @code{standard-display-table} is @code{nil}---then Emacs uses the usual | |
42b85554 RS |
5257 | display conventions for all character codes in that window. @xref{Usual |
5258 | Display}. | |
5259 | ||
8241495d RS |
5260 | A number of functions for changing the standard display table |
5261 | are defined in the library @file{disp-table}. | |
5262 | ||
42b85554 RS |
5263 | @node Glyphs |
5264 | @subsection Glyphs | |
5265 | ||
5266 | @cindex glyph | |
5267 | A @dfn{glyph} is a generalization of a character; it stands for an | |
5268 | image that takes up a single character position on the screen. Glyphs | |
bbf77fe8 | 5269 | are represented in Lisp as integers, just as characters are. Normally |
c5b0bab9 RS |
5270 | glyph come from vectors in the display table (@pxref{Display Tables}). |
5271 | ||
5272 | A glyph code can be @dfn{simple} or it can be defined by the | |
5273 | @dfn{glyph table}. A simple glyph code is just a way of specifying a | |
5274 | character and a face to output it in. When a glyph code is simple, | |
5275 | the code, mod 524288, is the character to output, and the code divided | |
5276 | by 524288 specifies the face number (@pxref{Face Functions}) to use | |
5277 | while outputting it. (524288 is | |
bbf77fe8 RS |
5278 | @ifnottex |
5279 | 2**19.) | |
5280 | @end ifnottex | |
5281 | @tex | |
5282 | $2^{19}$.) | |
5283 | @end tex | |
5284 | @xref{Faces}. | |
42b85554 | 5285 | |
bbf77fe8 | 5286 | On character terminals, you can set up a @dfn{glyph table} to define |
c5b0bab9 | 5287 | the meaning of glyph codes. |
42b85554 RS |
5288 | |
5289 | @defvar glyph-table | |
c5b0bab9 RS |
5290 | The value of this variable is the current glyph table. It should be |
5291 | @code{nil} or a vector whose @var{g}th element defines glyph code | |
5292 | @var{g}. | |
bbf77fe8 RS |
5293 | |
5294 | If a glyph code is greater than or equal to the length of the glyph | |
c5b0bab9 RS |
5295 | table, that code is automatically simple. If @code{glyph-table} is |
5296 | @code{nil} then all glyph codes are simple. | |
5297 | ||
5298 | The glyph table is used only on character terminals. On graphical | |
5299 | displays, all glyph codes are simple. | |
42b85554 RS |
5300 | @end defvar |
5301 | ||
c5b0bab9 | 5302 | Here are the meaningful types of elements in the glyph table: |
42b85554 | 5303 | |
1911e6e5 RS |
5304 | @table @asis |
5305 | @item @var{string} | |
42b85554 | 5306 | Send the characters in @var{string} to the terminal to output |
c5b0bab9 | 5307 | this glyph code. |
42b85554 | 5308 | |
1911e6e5 | 5309 | @item @var{integer} |
969fe9b5 | 5310 | Define this glyph code as an alias for glyph code @var{integer}. You |
c5b0bab9 RS |
5311 | can use such an alias to define a small-numbered glyph code which |
5312 | specifies a face. | |
42b85554 RS |
5313 | |
5314 | @item @code{nil} | |
c5b0bab9 | 5315 | This glyph code is simple. |
42b85554 RS |
5316 | @end table |
5317 | ||
8241495d | 5318 | @defun create-glyph string |
8241495d RS |
5319 | This function returns a newly-allocated glyph code which is set up to |
5320 | display by sending @var{string} to the terminal. | |
5321 | @end defun | |
5322 | ||
42b85554 RS |
5323 | @node Beeping |
5324 | @section Beeping | |
5325 | @cindex beeping | |
5326 | @cindex bell | |
5327 | ||
f9f59935 RS |
5328 | This section describes how to make Emacs ring the bell (or blink the |
5329 | screen) to attract the user's attention. Be conservative about how | |
5330 | often you do this; frequent bells can become irritating. Also be | |
5331 | careful not to use just beeping when signaling an error is more | |
cf6e4adc | 5332 | appropriate. (@xref{Errors}.) |
42b85554 | 5333 | |
a9f0a989 | 5334 | @defun ding &optional do-not-terminate |
42b85554 RS |
5335 | @cindex keyboard macro termination |
5336 | This function beeps, or flashes the screen (see @code{visible-bell} below). | |
5337 | It also terminates any keyboard macro currently executing unless | |
a9f0a989 | 5338 | @var{do-not-terminate} is non-@code{nil}. |
42b85554 RS |
5339 | @end defun |
5340 | ||
a9f0a989 | 5341 | @defun beep &optional do-not-terminate |
42b85554 RS |
5342 | This is a synonym for @code{ding}. |
5343 | @end defun | |
5344 | ||
1911e6e5 | 5345 | @defopt visible-bell |
42b85554 RS |
5346 | This variable determines whether Emacs should flash the screen to |
5347 | represent a bell. Non-@code{nil} means yes, @code{nil} means no. This | |
ab7c5459 | 5348 | is effective on graphical displays, and on text-only terminals |
969fe9b5 RS |
5349 | provided the terminal's Termcap entry defines the visible bell |
5350 | capability (@samp{vb}). | |
1911e6e5 | 5351 | @end defopt |
42b85554 | 5352 | |
f9f59935 RS |
5353 | @defvar ring-bell-function |
5354 | If this is non-@code{nil}, it specifies how Emacs should ``ring the | |
a40d4712 PR |
5355 | bell.'' Its value should be a function of no arguments. If this is |
5356 | non-@code{nil}, it takes precedence over the @code{visible-bell} | |
5357 | variable. | |
f9f59935 RS |
5358 | @end defvar |
5359 | ||
42b85554 RS |
5360 | @node Window Systems |
5361 | @section Window Systems | |
5362 | ||
5363 | Emacs works with several window systems, most notably the X Window | |
827b7ee7 | 5364 | System. Both Emacs and X use the term ``window,'' but use it |
42b85554 RS |
5365 | differently. An Emacs frame is a single window as far as X is |
5366 | concerned; the individual Emacs windows are not known to X at all. | |
5367 | ||
5368 | @defvar window-system | |
42b85554 | 5369 | This variable tells Lisp programs what window system Emacs is running |
1911e6e5 RS |
5370 | under. The possible values are |
5371 | ||
5372 | @table @code | |
5373 | @item x | |
5374 | @cindex X Window System | |
5375 | Emacs is displaying using X. | |
5376 | @item pc | |
8241495d | 5377 | Emacs is displaying using MS-DOS. |
1911e6e5 | 5378 | @item w32 |
05aea714 | 5379 | Emacs is displaying using Windows. |
8241495d RS |
5380 | @item mac |
5381 | Emacs is displaying using a Macintosh. | |
1911e6e5 RS |
5382 | @item nil |
5383 | Emacs is using a character-based terminal. | |
5384 | @end table | |
42b85554 RS |
5385 | @end defvar |
5386 | ||
42b85554 | 5387 | @defvar window-setup-hook |
f9f59935 RS |
5388 | This variable is a normal hook which Emacs runs after handling the |
5389 | initialization files. Emacs runs this hook after it has completed | |
a40d4712 | 5390 | loading your init file, the default initialization file (if |
a9f0a989 | 5391 | any), and the terminal-specific Lisp code, and running the hook |
42b85554 RS |
5392 | @code{term-setup-hook}. |
5393 | ||
5394 | This hook is used for internal purposes: setting up communication with | |
5395 | the window system, and creating the initial window. Users should not | |
5396 | interfere with it. | |
5397 | @end defvar | |
ab5796a9 MB |
5398 | |
5399 | @ignore | |
5400 | arch-tag: ffdf5714-7ecf-415b-9023-fbc6b409c2c6 | |
5401 | @end ignore |