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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
fd897522 | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
177c0ea7 | 4 | @c Free Software Foundation, Inc. |
0abf66c5 RS |
5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/markers | |
7 | @node Markers, Text, Positions, Top | |
8 | @chapter Markers | |
9 | @cindex markers | |
10 | ||
11 | A @dfn{marker} is a Lisp object used to specify a position in a buffer | |
12 | relative to the surrounding text. A marker changes its offset from the | |
13 | beginning of the buffer automatically whenever text is inserted or | |
14 | deleted, so that it stays with the two characters on either side of it. | |
15 | ||
16 | @menu | |
17 | * Overview of Markers:: The components of a marker, and how it relocates. | |
18 | * Predicates on Markers:: Testing whether an object is a marker. | |
19 | * Creating Markers:: Making empty markers or markers at certain places. | |
20 | * Information from Markers:: Finding the marker's buffer or character position. | |
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21 | * Marker Insertion Types:: Two ways a marker can relocate when you |
22 | insert where it points. | |
23 | * Moving Markers:: Moving the marker to a new buffer or position. | |
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24 | * The Mark:: How ``the mark'' is implemented with a marker. |
25 | * The Region:: How to access ``the region''. | |
26 | @end menu | |
27 | ||
28 | @node Overview of Markers | |
29 | @section Overview of Markers | |
30 | ||
97ce05cf LT |
31 | A marker specifies a buffer and a position in that buffer. The |
32 | marker can be used to represent a position in the functions that | |
33 | require one, just as an integer could be used. In that case, the | |
34 | marker's buffer is normally ignored. Of course, a marker used in this | |
35 | way usually points to a position in the buffer that the function | |
36 | operates on, but that is entirely the programmer's responsibility. | |
37 | @xref{Positions}, for a complete description of positions. | |
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38 | |
39 | A marker has two attributes: the marker position, and the marker | |
29679a81 | 40 | buffer. The marker position is an integer that is equivalent (at a |
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41 | given time) to the marker as a position in that buffer. But the |
42 | marker's position value can change often during the life of the marker. | |
43 | Insertion and deletion of text in the buffer relocate the marker. The | |
44 | idea is that a marker positioned between two characters remains between | |
45 | those two characters despite insertion and deletion elsewhere in the | |
46 | buffer. Relocation changes the integer equivalent of the marker. | |
47 | ||
48 | @cindex marker relocation | |
49 | Deleting text around a marker's position leaves the marker between the | |
50 | characters immediately before and after the deleted text. Inserting | |
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51 | text at the position of a marker normally leaves the marker either in |
52 | front of or after the new text, depending on the marker's @dfn{insertion | |
53 | type} (@pxref{Marker Insertion Types})---unless the insertion is done | |
54 | with @code{insert-before-markers} (@pxref{Insertion}). | |
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55 | |
56 | @cindex marker garbage collection | |
57 | Insertion and deletion in a buffer must check all the markers and | |
58 | relocate them if necessary. This slows processing in a buffer with a | |
59 | large number of markers. For this reason, it is a good idea to make a | |
60 | marker point nowhere if you are sure you don't need it any more. | |
61 | Unreferenced markers are garbage collected eventually, but until then | |
62 | will continue to use time if they do point somewhere. | |
63 | ||
64 | @cindex markers as numbers | |
65 | Because it is common to perform arithmetic operations on a marker | |
66 | position, most of the arithmetic operations (including @code{+} and | |
67 | @code{-}) accept markers as arguments. In such cases, the marker | |
68 | stands for its current position. | |
69 | ||
70 | Here are examples of creating markers, setting markers, and moving point | |
71 | to markers: | |
72 | ||
73 | @example | |
74 | @group | |
75 | ;; @r{Make a new marker that initially does not point anywhere:} | |
76 | (setq m1 (make-marker)) | |
77 | @result{} #<marker in no buffer> | |
78 | @end group | |
79 | ||
80 | @group | |
81 | ;; @r{Set @code{m1} to point between the 99th and 100th characters} | |
82 | ;; @r{in the current buffer:} | |
83 | (set-marker m1 100) | |
84 | @result{} #<marker at 100 in markers.texi> | |
85 | @end group | |
86 | ||
87 | @group | |
88 | ;; @r{Now insert one character at the beginning of the buffer:} | |
89 | (goto-char (point-min)) | |
90 | @result{} 1 | |
91 | (insert "Q") | |
92 | @result{} nil | |
93 | @end group | |
94 | ||
95 | @group | |
96 | ;; @r{@code{m1} is updated appropriately.} | |
97 | m1 | |
98 | @result{} #<marker at 101 in markers.texi> | |
99 | @end group | |
100 | ||
101 | @group | |
102 | ;; @r{Two markers that point to the same position} | |
103 | ;; @r{are not @code{eq}, but they are @code{equal}.} | |
104 | (setq m2 (copy-marker m1)) | |
105 | @result{} #<marker at 101 in markers.texi> | |
106 | (eq m1 m2) | |
107 | @result{} nil | |
108 | (equal m1 m2) | |
109 | @result{} t | |
110 | @end group | |
111 | ||
112 | @group | |
113 | ;; @r{When you are finished using a marker, make it point nowhere.} | |
114 | (set-marker m1 nil) | |
115 | @result{} #<marker in no buffer> | |
116 | @end group | |
117 | @end example | |
118 | ||
119 | @node Predicates on Markers | |
120 | @section Predicates on Markers | |
121 | ||
122 | You can test an object to see whether it is a marker, or whether it is | |
123 | either an integer or a marker. The latter test is useful in connection | |
124 | with the arithmetic functions that work with both markers and integers. | |
125 | ||
126 | @defun markerp object | |
127 | This function returns @code{t} if @var{object} is a marker, @code{nil} | |
128 | otherwise. Note that integers are not markers, even though many | |
129 | functions will accept either a marker or an integer. | |
130 | @end defun | |
131 | ||
132 | @defun integer-or-marker-p object | |
133 | This function returns @code{t} if @var{object} is an integer or a marker, | |
134 | @code{nil} otherwise. | |
135 | @end defun | |
136 | ||
137 | @defun number-or-marker-p object | |
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138 | This function returns @code{t} if @var{object} is a number (either |
139 | integer or floating point) or a marker, @code{nil} otherwise. | |
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140 | @end defun |
141 | ||
142 | @node Creating Markers | |
8241495d | 143 | @section Functions that Create Markers |
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144 | |
145 | When you create a new marker, you can make it point nowhere, or point | |
146 | to the present position of point, or to the beginning or end of the | |
147 | accessible portion of the buffer, or to the same place as another given | |
148 | marker. | |
149 | ||
409edc05 LT |
150 | The next four functions all return markers with insertion type |
151 | @code{nil}. @xref{Marker Insertion Types}. | |
152 | ||
0abf66c5 | 153 | @defun make-marker |
a9f0a989 | 154 | This function returns a newly created marker that does not point |
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155 | anywhere. |
156 | ||
157 | @example | |
158 | @group | |
159 | (make-marker) | |
160 | @result{} #<marker in no buffer> | |
161 | @end group | |
162 | @end example | |
163 | @end defun | |
164 | ||
165 | @defun point-marker | |
166 | This function returns a new marker that points to the present position | |
167 | of point in the current buffer. @xref{Point}. For an example, see | |
168 | @code{copy-marker}, below. | |
169 | @end defun | |
170 | ||
171 | @defun point-min-marker | |
172 | This function returns a new marker that points to the beginning of the | |
173 | accessible portion of the buffer. This will be the beginning of the | |
174 | buffer unless narrowing is in effect. @xref{Narrowing}. | |
175 | @end defun | |
176 | ||
177 | @defun point-max-marker | |
178 | @cindex end of buffer marker | |
179 | This function returns a new marker that points to the end of the | |
180 | accessible portion of the buffer. This will be the end of the buffer | |
181 | unless narrowing is in effect. @xref{Narrowing}. | |
182 | ||
183 | Here are examples of this function and @code{point-min-marker}, shown in | |
184 | a buffer containing a version of the source file for the text of this | |
185 | chapter. | |
186 | ||
187 | @example | |
188 | @group | |
189 | (point-min-marker) | |
190 | @result{} #<marker at 1 in markers.texi> | |
191 | (point-max-marker) | |
192 | @result{} #<marker at 15573 in markers.texi> | |
193 | @end group | |
194 | ||
195 | @group | |
196 | (narrow-to-region 100 200) | |
197 | @result{} nil | |
198 | @end group | |
199 | @group | |
200 | (point-min-marker) | |
201 | @result{} #<marker at 100 in markers.texi> | |
202 | @end group | |
203 | @group | |
204 | (point-max-marker) | |
205 | @result{} #<marker at 200 in markers.texi> | |
206 | @end group | |
207 | @end example | |
208 | @end defun | |
209 | ||
409edc05 | 210 | @defun copy-marker marker-or-integer &optional insertion-type |
0abf66c5 RS |
211 | If passed a marker as its argument, @code{copy-marker} returns a |
212 | new marker that points to the same place and the same buffer as does | |
213 | @var{marker-or-integer}. If passed an integer as its argument, | |
214 | @code{copy-marker} returns a new marker that points to position | |
215 | @var{marker-or-integer} in the current buffer. | |
216 | ||
f9f59935 RS |
217 | The new marker's insertion type is specified by the argument |
218 | @var{insertion-type}. @xref{Marker Insertion Types}. | |
219 | ||
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220 | If passed an integer argument less than 1, @code{copy-marker} returns a |
221 | new marker that points to the beginning of the current buffer. If | |
222 | passed an integer argument greater than the length of the buffer, | |
223 | @code{copy-marker} returns a new marker that points to the end of the | |
224 | buffer. | |
225 | ||
a9f0a989 RS |
226 | @example |
227 | @group | |
228 | (copy-marker 0) | |
229 | @result{} #<marker at 1 in markers.texi> | |
230 | @end group | |
231 | ||
232 | @group | |
233 | (copy-marker 20000) | |
234 | @result{} #<marker at 7572 in markers.texi> | |
235 | @end group | |
236 | @end example | |
237 | ||
0abf66c5 RS |
238 | An error is signaled if @var{marker} is neither a marker nor an |
239 | integer. | |
a9f0a989 RS |
240 | @end defun |
241 | ||
242 | Two distinct markers are considered @code{equal} (even though not | |
243 | @code{eq}) to each other if they have the same position and buffer, or | |
244 | if they both point nowhere. | |
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245 | |
246 | @example | |
247 | @group | |
248 | (setq p (point-marker)) | |
249 | @result{} #<marker at 2139 in markers.texi> | |
250 | @end group | |
251 | ||
252 | @group | |
253 | (setq q (copy-marker p)) | |
254 | @result{} #<marker at 2139 in markers.texi> | |
255 | @end group | |
256 | ||
257 | @group | |
258 | (eq p q) | |
259 | @result{} nil | |
260 | @end group | |
261 | ||
262 | @group | |
263 | (equal p q) | |
264 | @result{} t | |
265 | @end group | |
0abf66c5 | 266 | @end example |
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267 | |
268 | @node Information from Markers | |
269 | @section Information from Markers | |
270 | ||
271 | This section describes the functions for accessing the components of a | |
272 | marker object. | |
273 | ||
274 | @defun marker-position marker | |
275 | This function returns the position that @var{marker} points to, or | |
276 | @code{nil} if it points nowhere. | |
277 | @end defun | |
278 | ||
279 | @defun marker-buffer marker | |
280 | This function returns the buffer that @var{marker} points into, or | |
281 | @code{nil} if it points nowhere. | |
282 | ||
283 | @example | |
284 | @group | |
285 | (setq m (make-marker)) | |
286 | @result{} #<marker in no buffer> | |
287 | @end group | |
288 | @group | |
289 | (marker-position m) | |
290 | @result{} nil | |
291 | @end group | |
292 | @group | |
293 | (marker-buffer m) | |
294 | @result{} nil | |
295 | @end group | |
296 | ||
297 | @group | |
298 | (set-marker m 3770 (current-buffer)) | |
299 | @result{} #<marker at 3770 in markers.texi> | |
300 | @end group | |
301 | @group | |
302 | (marker-buffer m) | |
303 | @result{} #<buffer markers.texi> | |
304 | @end group | |
305 | @group | |
306 | (marker-position m) | |
307 | @result{} 3770 | |
308 | @end group | |
309 | @end example | |
310 | @end defun | |
311 | ||
75f3230b GM |
312 | @defun buffer-has-markers-at position |
313 | @tindex buffer-has-markers-at | |
314 | This function returns @code{t} if one or more markers | |
315 | point at position @var{position} in the current buffer. | |
316 | @end defun | |
317 | ||
f9f59935 RS |
318 | @node Marker Insertion Types |
319 | @section Marker Insertion Types | |
320 | ||
321 | @cindex insertion type of a marker | |
322 | When you insert text directly at the place where a marker points, | |
323 | there are two possible ways to relocate that marker: it can point before | |
324 | the inserted text, or point after it. You can specify which one a given | |
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325 | marker should do by setting its @dfn{insertion type}. Note that use of |
326 | @code{insert-before-markers} ignores markers' insertion types, always | |
327 | relocating a marker to point after the inserted text. | |
f9f59935 | 328 | |
f9f59935 RS |
329 | @defun set-marker-insertion-type marker type |
330 | This function sets the insertion type of marker @var{marker} to | |
1911e6e5 RS |
331 | @var{type}. If @var{type} is @code{t}, @var{marker} will advance when |
332 | text is inserted at its position. If @var{type} is @code{nil}, | |
333 | @var{marker} does not advance when text is inserted there. | |
f9f59935 RS |
334 | @end defun |
335 | ||
f9f59935 RS |
336 | @defun marker-insertion-type marker |
337 | This function reports the current insertion type of @var{marker}. | |
338 | @end defun | |
339 | ||
3c028f5c LT |
340 | Most functions that create markers, without an argument allowing to |
341 | specify the insertion type, create them with insertion type | |
342 | @code{nil}. Also, the mark has, by default, insertion type | |
343 | @code{nil}. | |
d29edb21 | 344 | |
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345 | @node Moving Markers |
346 | @section Moving Marker Positions | |
0abf66c5 RS |
347 | |
348 | This section describes how to change the position of an existing | |
349 | marker. When you do this, be sure you know whether the marker is used | |
350 | outside of your program, and, if so, what effects will result from | |
351 | moving it---otherwise, confusing things may happen in other parts of | |
352 | Emacs. | |
353 | ||
354 | @defun set-marker marker position &optional buffer | |
355 | This function moves @var{marker} to @var{position} | |
356 | in @var{buffer}. If @var{buffer} is not provided, it defaults to | |
357 | the current buffer. | |
358 | ||
359 | If @var{position} is less than 1, @code{set-marker} moves @var{marker} | |
29679a81 RS |
360 | to the beginning of the buffer. If @var{position} is greater than the |
361 | size of the buffer, @code{set-marker} moves marker to the end of the | |
362 | buffer. If @var{position} is @code{nil} or a marker that points | |
363 | nowhere, then @var{marker} is set to point nowhere. | |
0abf66c5 RS |
364 | |
365 | The value returned is @var{marker}. | |
366 | ||
367 | @example | |
368 | @group | |
369 | (setq m (point-marker)) | |
370 | @result{} #<marker at 4714 in markers.texi> | |
371 | @end group | |
372 | @group | |
373 | (set-marker m 55) | |
374 | @result{} #<marker at 55 in markers.texi> | |
375 | @end group | |
376 | @group | |
377 | (setq b (get-buffer "foo")) | |
378 | @result{} #<buffer foo> | |
379 | @end group | |
380 | @group | |
381 | (set-marker m 0 b) | |
382 | @result{} #<marker at 1 in foo> | |
383 | @end group | |
384 | @end example | |
385 | @end defun | |
386 | ||
387 | @defun move-marker marker position &optional buffer | |
388 | This is another name for @code{set-marker}. | |
389 | @end defun | |
390 | ||
391 | @node The Mark | |
392 | @section The Mark | |
393 | @cindex mark, the | |
394 | @cindex mark ring | |
395 | ||
396 | One special marker in each buffer is designated @dfn{the mark}. It | |
397 | records a position for the user for the sake of commands such as | |
a9f0a989 RS |
398 | @code{kill-region} and @code{indent-rigidly}. Lisp programs should set |
399 | the mark only to values that have a potential use to the user, and never | |
400 | for their own internal purposes. For example, the @code{replace-regexp} | |
0abf66c5 RS |
401 | command sets the mark to the value of point before doing any |
402 | replacements, because this enables the user to move back there | |
403 | conveniently after the replace is finished. | |
404 | ||
405 | Many commands are designed so that when called interactively they | |
406 | operate on the text between point and the mark. If you are writing such | |
407 | a command, don't examine the mark directly; instead, use | |
408 | @code{interactive} with the @samp{r} specification. This provides the | |
409 | values of point and the mark as arguments to the command in an | |
410 | interactive call, but permits other Lisp programs to specify arguments | |
411 | explicitly. @xref{Interactive Codes}. | |
412 | ||
413 | Each buffer has its own value of the mark that is independent of the | |
414 | value of the mark in other buffers. When a buffer is created, the mark | |
415 | exists but does not point anywhere. We consider this state as ``the | |
29679a81 | 416 | absence of a mark in that buffer.'' |
0abf66c5 RS |
417 | |
418 | Once the mark ``exists'' in a buffer, it normally never ceases to | |
419 | exist. However, it may become @dfn{inactive}, if Transient Mark mode is | |
969fe9b5 RS |
420 | enabled. The variable @code{mark-active}, which is always buffer-local |
421 | in all buffers, indicates whether the mark is active: non-@code{nil} | |
422 | means yes. A command can request deactivation of the mark upon return | |
423 | to the editor command loop by setting @code{deactivate-mark} to a | |
424 | non-@code{nil} value (but this causes deactivation only if Transient | |
425 | Mark mode is enabled). | |
0abf66c5 RS |
426 | |
427 | The main motivation for using Transient Mark mode is that this mode | |
428 | also enables highlighting of the region when the mark is active. | |
429 | @xref{Display}. | |
430 | ||
431 | In addition to the mark, each buffer has a @dfn{mark ring} which is a | |
432 | list of markers containing previous values of the mark. When editing | |
433 | commands change the mark, they should normally save the old value of the | |
434 | mark on the mark ring. The variable @code{mark-ring-max} specifies the | |
435 | maximum number of entries in the mark ring; once the list becomes this | |
436 | long, adding a new element deletes the last element. | |
437 | ||
75f3230b GM |
438 | There is also a separate global mark ring, but that is used only in a |
439 | few particular user-level commands, and is not relevant to Lisp | |
440 | programming. So we do not describe it here. | |
441 | ||
0abf66c5 RS |
442 | @defun mark &optional force |
443 | @cindex current buffer mark | |
444 | This function returns the current buffer's mark position as an integer. | |
445 | ||
409edc05 LT |
446 | If Transient Mark mode is enabled, @code{mark-even-if-inactive} is |
447 | @code{nil} and and the mark is inactive, @code{mark} normally signals | |
448 | an error. However, if @var{force} is non-@code{nil}, then @code{mark} | |
449 | returns the mark position anyway---or @code{nil}, if the mark is not | |
450 | yet set for this buffer. | |
0abf66c5 RS |
451 | @end defun |
452 | ||
453 | @defun mark-marker | |
454 | This function returns the current buffer's mark. This is the very marker | |
29679a81 | 455 | that records the mark location inside Emacs, not a copy. Therefore, |
0abf66c5 RS |
456 | changing this marker's position will directly affect the position of the mark. |
457 | Don't do it unless that is the effect you want. | |
458 | ||
459 | @example | |
460 | @group | |
461 | (setq m (mark-marker)) | |
462 | @result{} #<marker at 3420 in markers.texi> | |
463 | @end group | |
464 | @group | |
465 | (set-marker m 100) | |
466 | @result{} #<marker at 100 in markers.texi> | |
467 | @end group | |
468 | @group | |
469 | (mark-marker) | |
470 | @result{} #<marker at 100 in markers.texi> | |
471 | @end group | |
472 | @end example | |
473 | ||
474 | Like any marker, this marker can be set to point at any buffer you like. | |
475 | We don't recommend that you make it point at any buffer other than the | |
476 | one of which it is the mark. If you do, it will yield perfectly | |
477 | consistent, but rather odd, results. | |
478 | @end defun | |
479 | ||
480 | @ignore | |
481 | @deffn Command set-mark-command jump | |
482 | If @var{jump} is @code{nil}, this command sets the mark to the value | |
483 | of point and pushes the previous value of the mark on the mark ring. The | |
484 | message @samp{Mark set} is also displayed in the echo area. | |
485 | ||
486 | If @var{jump} is not @code{nil}, this command sets point to the value | |
487 | of the mark, and sets the mark to the previous saved mark value, which | |
488 | is popped off the mark ring. | |
489 | ||
490 | This function is @emph{only} intended for interactive use. | |
491 | @end deffn | |
492 | @end ignore | |
493 | ||
494 | @defun set-mark position | |
495 | This function sets the mark to @var{position}, and activates the mark. | |
496 | The old value of the mark is @emph{not} pushed onto the mark ring. | |
497 | ||
ec221d13 | 498 | @strong{Please note:} Use this function only if you want the user to |
0abf66c5 RS |
499 | see that the mark has moved, and you want the previous mark position to |
500 | be lost. Normally, when a new mark is set, the old one should go on the | |
501 | @code{mark-ring}. For this reason, most applications should use | |
502 | @code{push-mark} and @code{pop-mark}, not @code{set-mark}. | |
503 | ||
504 | Novice Emacs Lisp programmers often try to use the mark for the wrong | |
505 | purposes. The mark saves a location for the user's convenience. An | |
506 | editing command should not alter the mark unless altering the mark is | |
507 | part of the user-level functionality of the command. (And, in that | |
508 | case, this effect should be documented.) To remember a location for | |
509 | internal use in the Lisp program, store it in a Lisp variable. For | |
510 | example: | |
511 | ||
512 | @example | |
513 | @group | |
514 | (let ((beg (point))) | |
515 | (forward-line 1) | |
516 | (delete-region beg (point))). | |
517 | @end group | |
518 | @end example | |
519 | @end defun | |
520 | ||
521 | @c for interactive use only | |
522 | @ignore | |
523 | @deffn Command exchange-point-and-mark | |
524 | This function exchanges the positions of point and the mark. | |
525 | It is intended for interactive use. | |
526 | @end deffn | |
527 | @end ignore | |
528 | ||
529 | @defun push-mark &optional position nomsg activate | |
530 | This function sets the current buffer's mark to @var{position}, and | |
531 | pushes a copy of the previous mark onto @code{mark-ring}. If | |
532 | @var{position} is @code{nil}, then the value of point is used. | |
533 | @code{push-mark} returns @code{nil}. | |
534 | ||
535 | The function @code{push-mark} normally @emph{does not} activate the | |
536 | mark. To do that, specify @code{t} for the argument @var{activate}. | |
537 | ||
538 | A @samp{Mark set} message is displayed unless @var{nomsg} is | |
539 | non-@code{nil}. | |
540 | @end defun | |
541 | ||
542 | @defun pop-mark | |
543 | This function pops off the top element of @code{mark-ring} and makes | |
544 | that mark become the buffer's actual mark. This does not move point in | |
545 | the buffer, and it does nothing if @code{mark-ring} is empty. It | |
546 | deactivates the mark. | |
547 | ||
548 | The return value is not meaningful. | |
549 | @end defun | |
550 | ||
551 | @defopt transient-mark-mode | |
552 | @cindex Transient Mark mode | |
bfe721d1 KH |
553 | This variable if non-@code{nil} enables Transient Mark mode, in which |
554 | every buffer-modifying primitive sets @code{deactivate-mark}. The | |
555 | consequence of this is that commands that modify the buffer normally | |
556 | make the mark inactive. | |
0abf66c5 RS |
557 | @end defopt |
558 | ||
969fe9b5 RS |
559 | @defopt mark-even-if-inactive |
560 | If this is non-@code{nil}, Lisp programs and the Emacs user can use the | |
561 | mark even when it is inactive. This option affects the behavior of | |
562 | Transient Mark mode. When the option is non-@code{nil}, deactivation of | |
563 | the mark turns off region highlighting, but commands that use the mark | |
564 | behave as if the mark were still active. | |
565 | @end defopt | |
566 | ||
0abf66c5 RS |
567 | @defvar deactivate-mark |
568 | If an editor command sets this variable non-@code{nil}, then the editor | |
969fe9b5 RS |
569 | command loop deactivates the mark after the command returns (if |
570 | Transient Mark mode is enabled). All the primitives that change the | |
571 | buffer set @code{deactivate-mark}, to deactivate the mark when the | |
572 | command is finished. | |
ce218967 RS |
573 | |
574 | To write Lisp code that modifies the buffer without causing | |
575 | deactivation of the mark at the end of the command, bind | |
576 | @code{deactivate-mark} to @code{nil} around the code that does the | |
577 | modification. For example: | |
578 | ||
579 | @example | |
580 | (let (deactivate-mark) | |
581 | (insert " ")) | |
582 | @end example | |
0abf66c5 RS |
583 | @end defvar |
584 | ||
29679a81 | 585 | @defun deactivate-mark |
969fe9b5 RS |
586 | This function deactivates the mark, if Transient Mark mode is enabled. |
587 | Otherwise it does nothing. | |
29679a81 RS |
588 | @end defun |
589 | ||
0abf66c5 RS |
590 | @defvar mark-active |
591 | The mark is active when this variable is non-@code{nil}. This variable | |
969fe9b5 | 592 | is always buffer-local in each buffer. |
0abf66c5 RS |
593 | @end defvar |
594 | ||
595 | @defvar activate-mark-hook | |
596 | @defvarx deactivate-mark-hook | |
597 | These normal hooks are run, respectively, when the mark becomes active | |
f9f59935 RS |
598 | and when it becomes inactive. The hook @code{activate-mark-hook} is |
599 | also run at the end of a command if the mark is active and it is | |
600 | possible that the region may have changed. | |
0abf66c5 RS |
601 | @end defvar |
602 | ||
603 | @defvar mark-ring | |
604 | The value of this buffer-local variable is the list of saved former | |
605 | marks of the current buffer, most recent first. | |
606 | ||
607 | @example | |
608 | @group | |
609 | mark-ring | |
177c0ea7 | 610 | @result{} (#<marker at 11050 in markers.texi> |
0abf66c5 RS |
611 | #<marker at 10832 in markers.texi> |
612 | @dots{}) | |
613 | @end group | |
614 | @end example | |
615 | @end defvar | |
616 | ||
617 | @defopt mark-ring-max | |
618 | The value of this variable is the maximum size of @code{mark-ring}. If | |
619 | more marks than this are pushed onto the @code{mark-ring}, | |
620 | @code{push-mark} discards an old mark when it adds a new one. | |
621 | @end defopt | |
622 | ||
623 | @node The Region | |
624 | @section The Region | |
625 | @cindex region, the | |
626 | ||
627 | The text between point and the mark is known as @dfn{the region}. | |
628 | Various functions operate on text delimited by point and the mark, but | |
629 | only those functions specifically related to the region itself are | |
630 | described here. | |
631 | ||
409edc05 LT |
632 | The next two functions signal an error if the mark does not point |
633 | anywhere. If Transient Mark mode is enabled and | |
634 | @code{mark-even-if-inactive} is @code{nil}, they also signal an error | |
635 | if the mark is inactive. | |
636 | ||
0abf66c5 RS |
637 | @defun region-beginning |
638 | This function returns the position of the beginning of the region (as | |
639 | an integer). This is the position of either point or the mark, | |
640 | whichever is smaller. | |
0abf66c5 RS |
641 | @end defun |
642 | ||
643 | @defun region-end | |
644 | This function returns the position of the end of the region (as an | |
645 | integer). This is the position of either point or the mark, whichever is | |
646 | larger. | |
0abf66c5 RS |
647 | @end defun |
648 | ||
649 | Few programs need to use the @code{region-beginning} and | |
650 | @code{region-end} functions. A command designed to operate on a region | |
651 | should normally use @code{interactive} with the @samp{r} specification | |
652 | to find the beginning and end of the region. This lets other Lisp | |
653 | programs specify the bounds explicitly as arguments. (@xref{Interactive | |
654 | Codes}.) | |
ab5796a9 MB |
655 | |
656 | @ignore | |
657 | arch-tag: b1ba2e7a-a0f3-4c5e-875c-7d8e22d73299 | |
658 | @end ignore |