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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
73b0cd50 | 3 | @c Copyright (C) 1990-1995, 1998-1999, 2001-2011 Free Software Foundation, Inc. |
b8d4c8d0 | 4 | @c See the file elisp.texi for copying conditions. |
6336d8c3 | 5 | @setfilename ../../info/markers |
b8d4c8d0 GM |
6 | @node Markers, Text, Positions, Top |
7 | @chapter Markers | |
8 | @cindex markers | |
9 | ||
10 | A @dfn{marker} is a Lisp object used to specify a position in a buffer | |
11 | relative to the surrounding text. A marker changes its offset from the | |
12 | beginning of the buffer automatically whenever text is inserted or | |
13 | deleted, so that it stays with the two characters on either side of it. | |
14 | ||
15 | @menu | |
16 | * Overview of Markers:: The components of a marker, and how it relocates. | |
17 | * Predicates on Markers:: Testing whether an object is a marker. | |
18 | * Creating Markers:: Making empty markers or markers at certain places. | |
19 | * Information from Markers:: Finding the marker's buffer or character position. | |
20 | * Marker Insertion Types:: Two ways a marker can relocate when you | |
21 | insert where it points. | |
22 | * Moving Markers:: Moving the marker to a new buffer or position. | |
23 | * The Mark:: How "the mark" is implemented with a marker. | |
24 | * The Region:: How to access "the region". | |
25 | @end menu | |
26 | ||
27 | @node Overview of Markers | |
28 | @section Overview of Markers | |
29 | ||
30 | A marker specifies a buffer and a position in that buffer. The | |
31 | marker can be used to represent a position in the functions that | |
32 | require one, just as an integer could be used. In that case, the | |
33 | marker's buffer is normally ignored. Of course, a marker used in this | |
34 | way usually points to a position in the buffer that the function | |
35 | operates on, but that is entirely the programmer's responsibility. | |
36 | @xref{Positions}, for a complete description of positions. | |
37 | ||
38 | A marker has three attributes: the marker position, the marker | |
39 | buffer, and the insertion type. The marker position is an integer | |
40 | that is equivalent (at a given time) to the marker as a position in | |
41 | that buffer. But the marker's position value can change often during | |
42 | the life of the marker. Insertion and deletion of text in the buffer | |
43 | relocate the marker. The idea is that a marker positioned between two | |
44 | characters remains between those two characters despite insertion and | |
45 | deletion elsewhere in the buffer. Relocation changes the integer | |
46 | 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 | |
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}). | |
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 | |
138 | This function returns @code{t} if @var{object} is a number (either | |
139 | integer or floating point) or a marker, @code{nil} otherwise. | |
140 | @end defun | |
141 | ||
142 | @node Creating Markers | |
143 | @section Functions that Create Markers | |
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 | ||
150 | The next four functions all return markers with insertion type | |
151 | @code{nil}. @xref{Marker Insertion Types}. | |
152 | ||
153 | @defun make-marker | |
154 | This function returns a newly created marker that does not point | |
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 | This function returns a new marker that points to the end of the | |
179 | accessible portion of the buffer. This will be the end of the buffer | |
180 | unless narrowing is in effect. @xref{Narrowing}. | |
181 | ||
182 | Here are examples of this function and @code{point-min-marker}, shown in | |
183 | a buffer containing a version of the source file for the text of this | |
184 | chapter. | |
185 | ||
186 | @example | |
187 | @group | |
188 | (point-min-marker) | |
189 | @result{} #<marker at 1 in markers.texi> | |
190 | (point-max-marker) | |
191 | @result{} #<marker at 15573 in markers.texi> | |
192 | @end group | |
193 | ||
194 | @group | |
195 | (narrow-to-region 100 200) | |
196 | @result{} nil | |
197 | @end group | |
198 | @group | |
199 | (point-min-marker) | |
200 | @result{} #<marker at 100 in markers.texi> | |
201 | @end group | |
202 | @group | |
203 | (point-max-marker) | |
204 | @result{} #<marker at 200 in markers.texi> | |
205 | @end group | |
206 | @end example | |
207 | @end defun | |
208 | ||
209 | @defun copy-marker marker-or-integer &optional insertion-type | |
210 | If passed a marker as its argument, @code{copy-marker} returns a | |
211 | new marker that points to the same place and the same buffer as does | |
212 | @var{marker-or-integer}. If passed an integer as its argument, | |
213 | @code{copy-marker} returns a new marker that points to position | |
214 | @var{marker-or-integer} in the current buffer. | |
215 | ||
216 | The new marker's insertion type is specified by the argument | |
217 | @var{insertion-type}. @xref{Marker Insertion Types}. | |
218 | ||
219 | If passed an integer argument less than 1, @code{copy-marker} returns a | |
220 | new marker that points to the beginning of the current buffer. If | |
221 | passed an integer argument greater than the length of the buffer, | |
222 | @code{copy-marker} returns a new marker that points to the end of the | |
223 | buffer. | |
224 | ||
225 | @example | |
226 | @group | |
227 | (copy-marker 0) | |
228 | @result{} #<marker at 1 in markers.texi> | |
229 | @end group | |
230 | ||
231 | @group | |
232 | (copy-marker 20000) | |
233 | @result{} #<marker at 7572 in markers.texi> | |
234 | @end group | |
235 | @end example | |
236 | ||
237 | An error is signaled if @var{marker} is neither a marker nor an | |
238 | integer. | |
239 | @end defun | |
240 | ||
241 | Two distinct markers are considered @code{equal} (even though not | |
242 | @code{eq}) to each other if they have the same position and buffer, or | |
243 | if they both point nowhere. | |
244 | ||
245 | @example | |
246 | @group | |
247 | (setq p (point-marker)) | |
248 | @result{} #<marker at 2139 in markers.texi> | |
249 | @end group | |
250 | ||
251 | @group | |
252 | (setq q (copy-marker p)) | |
253 | @result{} #<marker at 2139 in markers.texi> | |
254 | @end group | |
255 | ||
256 | @group | |
257 | (eq p q) | |
258 | @result{} nil | |
259 | @end group | |
260 | ||
261 | @group | |
262 | (equal p q) | |
263 | @result{} t | |
264 | @end group | |
265 | @end example | |
266 | ||
267 | @node Information from Markers | |
268 | @section Information from Markers | |
269 | ||
270 | This section describes the functions for accessing the components of a | |
271 | marker object. | |
272 | ||
273 | @defun marker-position marker | |
274 | This function returns the position that @var{marker} points to, or | |
275 | @code{nil} if it points nowhere. | |
276 | @end defun | |
277 | ||
278 | @defun marker-buffer marker | |
279 | This function returns the buffer that @var{marker} points into, or | |
280 | @code{nil} if it points nowhere. | |
281 | ||
282 | @example | |
283 | @group | |
284 | (setq m (make-marker)) | |
285 | @result{} #<marker in no buffer> | |
286 | @end group | |
287 | @group | |
288 | (marker-position m) | |
289 | @result{} nil | |
290 | @end group | |
291 | @group | |
292 | (marker-buffer m) | |
293 | @result{} nil | |
294 | @end group | |
295 | ||
296 | @group | |
297 | (set-marker m 3770 (current-buffer)) | |
298 | @result{} #<marker at 3770 in markers.texi> | |
299 | @end group | |
300 | @group | |
301 | (marker-buffer m) | |
302 | @result{} #<buffer markers.texi> | |
303 | @end group | |
304 | @group | |
305 | (marker-position m) | |
306 | @result{} 3770 | |
307 | @end group | |
308 | @end example | |
309 | @end defun | |
310 | ||
311 | @defun buffer-has-markers-at position | |
312 | This function returns @code{t} if one or more markers | |
313 | point at position @var{position} in the current buffer. | |
314 | @end defun | |
315 | ||
316 | @node Marker Insertion Types | |
317 | @section Marker Insertion Types | |
318 | ||
319 | @cindex insertion type of a marker | |
320 | When you insert text directly at the place where a marker points, | |
321 | there are two possible ways to relocate that marker: it can point before | |
322 | the inserted text, or point after it. You can specify which one a given | |
323 | marker should do by setting its @dfn{insertion type}. Note that use of | |
324 | @code{insert-before-markers} ignores markers' insertion types, always | |
325 | relocating a marker to point after the inserted text. | |
326 | ||
327 | @defun set-marker-insertion-type marker type | |
328 | This function sets the insertion type of marker @var{marker} to | |
329 | @var{type}. If @var{type} is @code{t}, @var{marker} will advance when | |
330 | text is inserted at its position. If @var{type} is @code{nil}, | |
331 | @var{marker} does not advance when text is inserted there. | |
332 | @end defun | |
333 | ||
334 | @defun marker-insertion-type marker | |
335 | This function reports the current insertion type of @var{marker}. | |
336 | @end defun | |
337 | ||
338 | Most functions that create markers, without an argument allowing to | |
339 | specify the insertion type, create them with insertion type | |
340 | @code{nil}. Also, the mark has, by default, insertion type | |
341 | @code{nil}. | |
342 | ||
343 | @node Moving Markers | |
344 | @section Moving Marker Positions | |
345 | ||
346 | This section describes how to change the position of an existing | |
347 | marker. When you do this, be sure you know whether the marker is used | |
348 | outside of your program, and, if so, what effects will result from | |
349 | moving it---otherwise, confusing things may happen in other parts of | |
350 | Emacs. | |
351 | ||
352 | @defun set-marker marker position &optional buffer | |
353 | This function moves @var{marker} to @var{position} | |
354 | in @var{buffer}. If @var{buffer} is not provided, it defaults to | |
355 | the current buffer. | |
356 | ||
357 | If @var{position} is less than 1, @code{set-marker} moves @var{marker} | |
358 | to the beginning of the buffer. If @var{position} is greater than the | |
359 | size of the buffer, @code{set-marker} moves marker to the end of the | |
360 | buffer. If @var{position} is @code{nil} or a marker that points | |
361 | nowhere, then @var{marker} is set to point nowhere. | |
362 | ||
363 | The value returned is @var{marker}. | |
364 | ||
365 | @example | |
366 | @group | |
367 | (setq m (point-marker)) | |
368 | @result{} #<marker at 4714 in markers.texi> | |
369 | @end group | |
370 | @group | |
371 | (set-marker m 55) | |
372 | @result{} #<marker at 55 in markers.texi> | |
373 | @end group | |
374 | @group | |
375 | (setq b (get-buffer "foo")) | |
376 | @result{} #<buffer foo> | |
377 | @end group | |
378 | @group | |
379 | (set-marker m 0 b) | |
380 | @result{} #<marker at 1 in foo> | |
381 | @end group | |
382 | @end example | |
383 | @end defun | |
384 | ||
385 | @defun move-marker marker position &optional buffer | |
386 | This is another name for @code{set-marker}. | |
387 | @end defun | |
388 | ||
389 | @node The Mark | |
390 | @section The Mark | |
391 | @cindex mark, the | |
392 | @cindex mark ring | |
393 | ||
47af2f4b CY |
394 | Each buffer has a special marker, which is designated @dfn{the |
395 | mark}. When a buffer is newly created, this marker exists but does | |
396 | not point anywhere; this means that the mark ``doesn't exist'' in that | |
397 | buffer yet. Subsequent commands can set the mark. | |
398 | ||
399 | The mark specifies a position to bound a range of text for many | |
400 | commands, such as @code{kill-region} and @code{indent-rigidly}. These | |
401 | commands typically act on the text between point and the mark, which | |
402 | is called the @dfn{region}. If you are writing a command that | |
403 | operates on the region, don't examine the mark directly; instead, use | |
b8d4c8d0 GM |
404 | @code{interactive} with the @samp{r} specification. This provides the |
405 | values of point and the mark as arguments to the command in an | |
406 | interactive call, but permits other Lisp programs to specify arguments | |
407 | explicitly. @xref{Interactive Codes}. | |
408 | ||
47af2f4b CY |
409 | Some commands set the mark as a side-effect. Commands should do |
410 | this only if it has a potential use to the user, and never for their | |
411 | own internal purposes. For example, the @code{replace-regexp} command | |
412 | sets the mark to the value of point before doing any replacements, | |
413 | because this enables the user to move back there conveniently after | |
414 | the replace is finished. | |
b8d4c8d0 GM |
415 | |
416 | Once the mark ``exists'' in a buffer, it normally never ceases to | |
47af2f4b CY |
417 | exist. However, it may become @dfn{inactive}, if Transient Mark mode |
418 | is enabled. The buffer-local variable @code{mark-active}, if | |
419 | non-@code{nil}, means that the mark is active. A command can call the | |
420 | function @code{deactivate-mark} to deactivate the mark directly, or it | |
421 | can request deactivation of the mark upon return to the editor command | |
422 | loop by setting the variable @code{deactivate-mark} to a | |
423 | non-@code{nil} value. | |
424 | ||
425 | If Transient Mode is enabled, certain editing commands that normally | |
426 | apply to text near point, apply instead to the region when the mark is | |
2de17c73 | 427 | active. This is the main motivation for using Transient Mark mode. |
47af2f4b CY |
428 | (Another is that this enables highlighting of the region when the mark |
429 | is active. @xref{Display}.) | |
b8d4c8d0 GM |
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 | ||
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 | ||
442 | @defun mark &optional force | |
443 | @cindex current buffer mark | |
444 | This function returns the current buffer's mark position as an integer, | |
445 | or @code{nil} if no mark has ever been set in this buffer. | |
446 | ||
447 | If Transient Mark mode is enabled, and @code{mark-even-if-inactive} is | |
448 | @code{nil}, @code{mark} signals an error if the mark is inactive. | |
449 | However, if @var{force} is non-@code{nil}, then @code{mark} disregards | |
47af2f4b CY |
450 | inactivity of the mark, and returns the mark position (or @code{nil}) |
451 | anyway. | |
b8d4c8d0 GM |
452 | @end defun |
453 | ||
454 | @defun mark-marker | |
455 | This function returns the marker that represents the current buffer's | |
456 | mark. It is not a copy, it is the marker used internally. Therefore, | |
457 | changing this marker's position will directly affect the buffer's | |
458 | mark. Don't do that unless that is the effect you want. | |
459 | ||
460 | @example | |
461 | @group | |
462 | (setq m (mark-marker)) | |
463 | @result{} #<marker at 3420 in markers.texi> | |
464 | @end group | |
465 | @group | |
466 | (set-marker m 100) | |
467 | @result{} #<marker at 100 in markers.texi> | |
468 | @end group | |
469 | @group | |
470 | (mark-marker) | |
471 | @result{} #<marker at 100 in markers.texi> | |
472 | @end group | |
473 | @end example | |
474 | ||
475 | Like any marker, this marker can be set to point at any buffer you | |
476 | like. If you make it point at any buffer other than the one of which | |
477 | it is the mark, it will yield perfectly consistent, but rather odd, | |
478 | results. We recommend that you not do it! | |
479 | @end defun | |
480 | ||
b8d4c8d0 GM |
481 | @defun set-mark position |
482 | This function sets the mark to @var{position}, and activates the mark. | |
483 | The old value of the mark is @emph{not} pushed onto the mark ring. | |
484 | ||
485 | @strong{Please note:} Use this function only if you want the user to | |
486 | see that the mark has moved, and you want the previous mark position to | |
487 | be lost. Normally, when a new mark is set, the old one should go on the | |
488 | @code{mark-ring}. For this reason, most applications should use | |
489 | @code{push-mark} and @code{pop-mark}, not @code{set-mark}. | |
490 | ||
491 | Novice Emacs Lisp programmers often try to use the mark for the wrong | |
492 | purposes. The mark saves a location for the user's convenience. An | |
493 | editing command should not alter the mark unless altering the mark is | |
494 | part of the user-level functionality of the command. (And, in that | |
495 | case, this effect should be documented.) To remember a location for | |
496 | internal use in the Lisp program, store it in a Lisp variable. For | |
497 | example: | |
498 | ||
499 | @example | |
500 | @group | |
501 | (let ((beg (point))) | |
502 | (forward-line 1) | |
503 | (delete-region beg (point))). | |
504 | @end group | |
505 | @end example | |
506 | @end defun | |
507 | ||
b8d4c8d0 GM |
508 | @defun push-mark &optional position nomsg activate |
509 | This function sets the current buffer's mark to @var{position}, and | |
510 | pushes a copy of the previous mark onto @code{mark-ring}. If | |
511 | @var{position} is @code{nil}, then the value of point is used. | |
512 | @code{push-mark} returns @code{nil}. | |
513 | ||
514 | The function @code{push-mark} normally @emph{does not} activate the | |
515 | mark. To do that, specify @code{t} for the argument @var{activate}. | |
516 | ||
517 | A @samp{Mark set} message is displayed unless @var{nomsg} is | |
518 | non-@code{nil}. | |
519 | @end defun | |
520 | ||
521 | @defun pop-mark | |
522 | This function pops off the top element of @code{mark-ring} and makes | |
523 | that mark become the buffer's actual mark. This does not move point in | |
524 | the buffer, and it does nothing if @code{mark-ring} is empty. It | |
525 | deactivates the mark. | |
526 | ||
527 | The return value is not meaningful. | |
528 | @end defun | |
529 | ||
530 | @defopt transient-mark-mode | |
47af2f4b CY |
531 | This variable, if non-@code{nil}, enables Transient Mark mode. In |
532 | Transient Mark mode, every buffer-modifying primitive sets | |
533 | @code{deactivate-mark}. As a consequence, most commands that modify | |
534 | the buffer also deactivate the mark. | |
b8d4c8d0 | 535 | |
47af2f4b CY |
536 | When Transient Mark mode is enabled and the mark is active, many |
537 | commands that normally apply to the text near point instead apply to | |
538 | the region. Such commands should use the function @code{use-region-p} | |
539 | to test whether they should operate on the region. @xref{The Region}. | |
2de17c73 | 540 | |
16624be8 EZ |
541 | Lisp programs can set @code{transient-mark-mode} to non-@code{nil}, |
542 | non-@code{t} values to enable Transient Mark mode temporarily. If the | |
66e3cca6 | 543 | value is @code{lambda}, Transient Mark mode is automatically turned |
16624be8 EZ |
544 | off after any action, such as buffer modification, that would normally |
545 | deactivate the mark. If the value is @w{@code{(only . @var{oldval})}}, | |
546 | then @code{transient-mark-mode} is set to the value @var{oldval} after | |
547 | any subsequent command that moves point and is not shift-translated | |
548 | (@pxref{Key Sequence Input, shift-translation}), or after any other | |
549 | action that would normally deactivate the mark. | |
b8d4c8d0 GM |
550 | @end defopt |
551 | ||
552 | @defopt mark-even-if-inactive | |
553 | If this is non-@code{nil}, Lisp programs and the Emacs user can use the | |
554 | mark even when it is inactive. This option affects the behavior of | |
555 | Transient Mark mode. When the option is non-@code{nil}, deactivation of | |
556 | the mark turns off region highlighting, but commands that use the mark | |
557 | behave as if the mark were still active. | |
558 | @end defopt | |
559 | ||
560 | @defvar deactivate-mark | |
561 | If an editor command sets this variable non-@code{nil}, then the editor | |
562 | command loop deactivates the mark after the command returns (if | |
563 | Transient Mark mode is enabled). All the primitives that change the | |
564 | buffer set @code{deactivate-mark}, to deactivate the mark when the | |
565 | command is finished. | |
566 | ||
567 | To write Lisp code that modifies the buffer without causing | |
568 | deactivation of the mark at the end of the command, bind | |
569 | @code{deactivate-mark} to @code{nil} around the code that does the | |
570 | modification. For example: | |
571 | ||
572 | @example | |
573 | (let (deactivate-mark) | |
574 | (insert " ")) | |
575 | @end example | |
576 | @end defvar | |
577 | ||
6bbd4600 | 578 | @defun deactivate-mark &optional force |
b40c84b0 CY |
579 | If Transient Mark mode is enabled or @var{force} is non-@code{nil}, |
580 | this function deactivates the mark and runs the normal hook | |
581 | @code{deactivate-mark-hook}. Otherwise, it does nothing. | |
b8d4c8d0 GM |
582 | @end defun |
583 | ||
584 | @defvar mark-active | |
2de17c73 EZ |
585 | The mark is active when this variable is non-@code{nil}. This |
586 | variable is always buffer-local in each buffer. Do @emph{not} use the | |
587 | value of this variable to decide whether a command that normally | |
588 | operates on text near point should operate on the region instead. Use | |
47af2f4b | 589 | the function @code{use-region-p} for that (@pxref{The Region}). |
b8d4c8d0 GM |
590 | @end defvar |
591 | ||
592 | @defvar activate-mark-hook | |
593 | @defvarx deactivate-mark-hook | |
594 | These normal hooks are run, respectively, when the mark becomes active | |
595 | and when it becomes inactive. The hook @code{activate-mark-hook} is | |
596 | also run at the end of a command if the mark is active and it is | |
597 | possible that the region may have changed. | |
598 | @end defvar | |
599 | ||
47af2f4b CY |
600 | @defun handle-shift-selection |
601 | This function implements the ``shift-selection'' behavior of | |
602 | point-motion commands. @xref{Shift Selection,,, emacs, The GNU Emacs | |
603 | Manual}. It is called automatically by the Emacs command loop | |
604 | whenever a command with a @samp{^} character in its @code{interactive} | |
605 | spec is invoked, before the command itself is executed | |
606 | (@pxref{Interactive Codes, ^}). | |
607 | ||
608 | If @code{shift-select-mode} is non-@code{nil} and the current command | |
609 | was invoked via shift translation (@pxref{Key Sequence Input, | |
610 | shift-translation}), this function sets the mark and temporarily | |
611 | activates the region, unless the region was already temporarily | |
612 | activated in this way. Otherwise, if the region has been activated | |
613 | temporarily, it deactivates the mark and restores the variable | |
614 | @code{transient-mark-mode} to its earlier value. | |
615 | @end defun | |
616 | ||
b8d4c8d0 GM |
617 | @defvar mark-ring |
618 | The value of this buffer-local variable is the list of saved former | |
619 | marks of the current buffer, most recent first. | |
620 | ||
621 | @example | |
622 | @group | |
623 | mark-ring | |
624 | @result{} (#<marker at 11050 in markers.texi> | |
625 | #<marker at 10832 in markers.texi> | |
626 | @dots{}) | |
627 | @end group | |
628 | @end example | |
629 | @end defvar | |
630 | ||
631 | @defopt mark-ring-max | |
632 | The value of this variable is the maximum size of @code{mark-ring}. If | |
633 | more marks than this are pushed onto the @code{mark-ring}, | |
634 | @code{push-mark} discards an old mark when it adds a new one. | |
635 | @end defopt | |
636 | ||
637 | @node The Region | |
638 | @section The Region | |
639 | @cindex region (between point and mark) | |
640 | ||
641 | The text between point and the mark is known as @dfn{the region}. | |
642 | Various functions operate on text delimited by point and the mark, but | |
643 | only those functions specifically related to the region itself are | |
644 | described here. | |
645 | ||
646 | The next two functions signal an error if the mark does not point | |
647 | anywhere. If Transient Mark mode is enabled and | |
648 | @code{mark-even-if-inactive} is @code{nil}, they also signal an error | |
649 | if the mark is inactive. | |
650 | ||
651 | @defun region-beginning | |
652 | This function returns the position of the beginning of the region (as | |
653 | an integer). This is the position of either point or the mark, | |
654 | whichever is smaller. | |
655 | @end defun | |
656 | ||
657 | @defun region-end | |
658 | This function returns the position of the end of the region (as an | |
659 | integer). This is the position of either point or the mark, whichever is | |
660 | larger. | |
661 | @end defun | |
662 | ||
663 | Few programs need to use the @code{region-beginning} and | |
664 | @code{region-end} functions. A command designed to operate on a region | |
665 | should normally use @code{interactive} with the @samp{r} specification | |
666 | to find the beginning and end of the region. This lets other Lisp | |
667 | programs specify the bounds explicitly as arguments. (@xref{Interactive | |
668 | Codes}.) | |
669 | ||
47af2f4b CY |
670 | @defun use-region-p |
671 | This function returns @code{t} if Transient Mark mode is enabled, the | |
672 | mark is active, and there's a valid region in the buffer. Commands | |
673 | that operate on the region (instead of on text near point) when | |
674 | there's an active mark should use this to test whether to do that. | |
675 | @end defun |