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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. | |
4 | @c See the file elisp.texi for copying conditions. | |
5 | @setfilename ../info/text | |
6 | @node Text, Searching and Matching, Markers, Top | |
7 | @chapter Text | |
8 | @cindex text | |
9 | ||
10 | This chapter describes the functions that deal with the text in a | |
61cfa852 | 11 | buffer. Most examine, insert, or delete text in the current buffer, |
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12 | often in the vicinity of point. Many are interactive. All the |
13 | functions that change the text provide for undoing the changes | |
14 | (@pxref{Undo}). | |
15 | ||
16 | Many text-related functions operate on a region of text defined by two | |
17 | buffer positions passed in arguments named @var{start} and @var{end}. | |
18 | These arguments should be either markers (@pxref{Markers}) or numeric | |
19 | character positions (@pxref{Positions}). The order of these arguments | |
20 | does not matter; it is all right for @var{start} to be the end of the | |
21 | region and @var{end} the beginning. For example, @code{(delete-region 1 | |
22 | 10)} and @code{(delete-region 10 1)} are equivalent. An | |
23 | @code{args-out-of-range} error is signaled if either @var{start} or | |
24 | @var{end} is outside the accessible portion of the buffer. In an | |
25 | interactive call, point and the mark are used for these arguments. | |
26 | ||
27 | @cindex buffer contents | |
28 | Throughout this chapter, ``text'' refers to the characters in the | |
bfe721d1 | 29 | buffer, together with their properties (when relevant). |
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30 | |
31 | @menu | |
32 | * Near Point:: Examining text in the vicinity of point. | |
33 | * Buffer Contents:: Examining text in a general fashion. | |
34 | * Comparing Text:: Comparing substrings of buffers. | |
35 | * Insertion:: Adding new text to a buffer. | |
36 | * Commands for Insertion:: User-level commands to insert text. | |
37 | * Deletion:: Removing text from a buffer. | |
38 | * User-Level Deletion:: User-level commands to delete text. | |
39 | * The Kill Ring:: Where removed text sometimes is saved for later use. | |
40 | * Undo:: Undoing changes to the text of a buffer. | |
41 | * Maintaining Undo:: How to enable and disable undo information. | |
42 | How to control how much information is kept. | |
43 | * Filling:: Functions for explicit filling. | |
bfe721d1 | 44 | * Margins:: How to specify margins for filling commands. |
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45 | * Auto Filling:: How auto-fill mode is implemented to break lines. |
46 | * Sorting:: Functions for sorting parts of the buffer. | |
47 | * Columns:: Computing horizontal positions, and using them. | |
48 | * Indentation:: Functions to insert or adjust indentation. | |
49 | * Case Changes:: Case conversion of parts of the buffer. | |
50 | * Text Properties:: Assigning Lisp property lists to text characters. | |
51 | * Substitution:: Replacing a given character wherever it appears. | |
b22f3a19 | 52 | * Transposition:: Swapping two portions of a buffer. |
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53 | * Registers:: How registers are implemented. Accessing the text or |
54 | position stored in a register. | |
55 | * Change Hooks:: Supplying functions to be run when text is changed. | |
56 | @end menu | |
57 | ||
58 | @node Near Point | |
59 | @section Examining Text Near Point | |
60 | ||
61 | Many functions are provided to look at the characters around point. | |
62 | Several simple functions are described here. See also @code{looking-at} | |
63 | in @ref{Regexp Search}. | |
64 | ||
65 | @defun char-after position | |
66 | This function returns the character in the current buffer at (i.e., | |
67 | immediately after) position @var{position}. If @var{position} is out of | |
68 | range for this purpose, either before the beginning of the buffer, or at | |
69 | or beyond the end, then the value is @code{nil}. | |
70 | ||
71 | In the following example, assume that the first character in the | |
72 | buffer is @samp{@@}: | |
73 | ||
74 | @example | |
75 | @group | |
76 | (char-to-string (char-after 1)) | |
77 | @result{} "@@" | |
78 | @end group | |
79 | @end example | |
80 | @end defun | |
81 | ||
82 | @defun following-char | |
83 | This function returns the character following point in the current | |
84 | buffer. This is similar to @code{(char-after (point))}. However, if | |
85 | point is at the end of the buffer, then @code{following-char} returns 0. | |
86 | ||
87 | Remember that point is always between characters, and the terminal | |
88 | cursor normally appears over the character following point. Therefore, | |
89 | the character returned by @code{following-char} is the character the | |
90 | cursor is over. | |
91 | ||
92 | In this example, point is between the @samp{a} and the @samp{c}. | |
93 | ||
94 | @example | |
95 | @group | |
96 | ---------- Buffer: foo ---------- | |
97 | Gentlemen may cry ``Pea@point{}ce! Peace!,'' | |
98 | but there is no peace. | |
99 | ---------- Buffer: foo ---------- | |
100 | @end group | |
101 | ||
102 | @group | |
103 | (char-to-string (preceding-char)) | |
104 | @result{} "a" | |
105 | (char-to-string (following-char)) | |
106 | @result{} "c" | |
107 | @end group | |
108 | @end example | |
109 | @end defun | |
110 | ||
111 | @defun preceding-char | |
112 | This function returns the character preceding point in the current | |
113 | buffer. See above, under @code{following-char}, for an example. If | |
114 | point is at the beginning of the buffer, @code{preceding-char} returns | |
115 | 0. | |
116 | @end defun | |
117 | ||
118 | @defun bobp | |
119 | This function returns @code{t} if point is at the beginning of the | |
120 | buffer. If narrowing is in effect, this means the beginning of the | |
121 | accessible portion of the text. See also @code{point-min} in | |
122 | @ref{Point}. | |
123 | @end defun | |
124 | ||
125 | @defun eobp | |
126 | This function returns @code{t} if point is at the end of the buffer. | |
127 | If narrowing is in effect, this means the end of accessible portion of | |
128 | the text. See also @code{point-max} in @xref{Point}. | |
129 | @end defun | |
130 | ||
131 | @defun bolp | |
132 | This function returns @code{t} if point is at the beginning of a line. | |
133 | @xref{Text Lines}. The beginning of the buffer (or its accessible | |
61cfa852 | 134 | portion) always counts as the beginning of a line. |
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135 | @end defun |
136 | ||
137 | @defun eolp | |
138 | This function returns @code{t} if point is at the end of a line. The | |
139 | end of the buffer (or of its accessible portion) is always considered | |
140 | the end of a line. | |
141 | @end defun | |
142 | ||
143 | @node Buffer Contents | |
144 | @section Examining Buffer Contents | |
145 | ||
146 | This section describes two functions that allow a Lisp program to | |
147 | convert any portion of the text in the buffer into a string. | |
148 | ||
149 | @defun buffer-substring start end | |
150 | This function returns a string containing a copy of the text of the | |
151 | region defined by positions @var{start} and @var{end} in the current | |
152 | buffer. If the arguments are not positions in the accessible portion of | |
153 | the buffer, @code{buffer-substring} signals an @code{args-out-of-range} | |
154 | error. | |
155 | ||
156 | It is not necessary for @var{start} to be less than @var{end}; the | |
157 | arguments can be given in either order. But most often the smaller | |
158 | argument is written first. | |
159 | ||
22697dac KH |
160 | If the text being copied has any text properties, these are copied into |
161 | the string along with the characters they belong to. @xref{Text | |
162 | Properties}. However, overlays (@pxref{Overlays}) in the buffer and | |
163 | their properties are ignored, not copied. | |
164 | ||
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165 | @example |
166 | @group | |
167 | ---------- Buffer: foo ---------- | |
168 | This is the contents of buffer foo | |
169 | ||
170 | ---------- Buffer: foo ---------- | |
171 | @end group | |
172 | ||
173 | @group | |
174 | (buffer-substring 1 10) | |
175 | @result{} "This is t" | |
176 | @end group | |
177 | @group | |
178 | (buffer-substring (point-max) 10) | |
179 | @result{} "he contents of buffer foo | |
180 | " | |
181 | @end group | |
182 | @end example | |
183 | @end defun | |
184 | ||
371f8cd0 | 185 | @defun buffer-substring-no-properties start end |
22697dac KH |
186 | This is like @code{buffer-substring}, except that it does not copy text |
187 | properties, just the characters themselves. @xref{Text Properties}. | |
188 | Here's an example of using this function to get a word to look up in an | |
189 | alist: | |
190 | ||
191 | @example | |
192 | (setq flammable | |
193 | (assoc (buffer-substring start end) | |
194 | '(("wood" . t) ("paper" . t) | |
195 | ("steel" . nil) ("asbestos" . nil)))) | |
196 | @end example | |
197 | ||
198 | If this were written using @code{buffer-substring} instead, it would not | |
199 | work reliably; any text properties that happened to be in the word | |
200 | copied from the buffer would make the comparisons fail. | |
201 | @end defun | |
202 | ||
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203 | @defun buffer-string |
204 | This function returns the contents of the accessible portion of the | |
205 | current buffer as a string. This is the portion between | |
206 | @code{(point-min)} and @code{(point-max)} (@pxref{Narrowing}). | |
207 | ||
208 | @example | |
209 | @group | |
210 | ---------- Buffer: foo ---------- | |
211 | This is the contents of buffer foo | |
212 | ||
213 | ---------- Buffer: foo ---------- | |
214 | ||
215 | (buffer-string) | |
216 | @result{} "This is the contents of buffer foo | |
217 | " | |
218 | @end group | |
219 | @end example | |
220 | @end defun | |
221 | ||
222 | @node Comparing Text | |
223 | @section Comparing Text | |
224 | @cindex comparing buffer text | |
225 | ||
226 | This function lets you compare portions of the text in a buffer, without | |
227 | copying them into strings first. | |
228 | ||
229 | @defun compare-buffer-substrings buffer1 start1 end1 buffer2 start2 end2 | |
230 | This function lets you compare two substrings of the same buffer or two | |
231 | different buffers. The first three arguments specify one substring, | |
232 | giving a buffer and two positions within the buffer. The last three | |
233 | arguments specify the other substring in the same way. You can use | |
61cfa852 | 234 | @code{nil} for @var{buffer1}, @var{buffer2}, or both to stand for the |
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235 | current buffer. |
236 | ||
237 | The value is negative if the first substring is less, positive if the | |
238 | first is greater, and zero if they are equal. The absolute value of | |
239 | the result is one plus the index of the first differing characters | |
240 | within the substrings. | |
241 | ||
242 | This function ignores case when comparing characters | |
bfe721d1 KH |
243 | if @code{case-fold-search} is non-@code{nil}. It always ignores |
244 | text properties. | |
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245 | |
246 | Suppose the current buffer contains the text @samp{foobarbar | |
247 | haha!rara!}; then in this example the two substrings are @samp{rbar } | |
248 | and @samp{rara!}. The value is 2 because the first substring is greater | |
249 | at the second character. | |
250 | ||
251 | @example | |
252 | (compare-buffer-substring nil 6 11 nil 16 21) | |
253 | @result{} 2 | |
254 | @end example | |
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255 | @end defun |
256 | ||
257 | @node Insertion | |
bfe721d1 | 258 | @section Inserting Text |
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259 | @cindex insertion of text |
260 | @cindex text insertion | |
261 | ||
262 | @dfn{Insertion} means adding new text to a buffer. The inserted text | |
263 | goes at point---between the character before point and the character | |
264 | after point. | |
265 | ||
266 | Insertion relocates markers that point at positions after the | |
267 | insertion point, so that they stay with the surrounding text | |
268 | (@pxref{Markers}). When a marker points at the place of insertion, | |
269 | insertion normally doesn't relocate the marker, so that it points to the | |
270 | beginning of the inserted text; however, certain special functions such | |
271 | as @code{insert-before-markers} relocate such markers to point after the | |
272 | inserted text. | |
273 | ||
274 | @cindex insertion before point | |
275 | @cindex before point, insertion | |
276 | Some insertion functions leave point before the inserted text, while | |
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277 | other functions leave it after. We call the former insertion @dfn{after |
278 | point} and the latter insertion @dfn{before point}. | |
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279 | |
280 | Insertion functions signal an error if the current buffer is | |
281 | read-only. | |
282 | ||
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283 | These functions copy text characters from strings and buffers along |
284 | with their properties. The inserted characters have exactly the same | |
285 | properties as the characters they were copied from. By contrast, | |
286 | characters specified as separate arguments, not part of a string or | |
287 | buffer, inherit their text properties from the neighboring text. | |
288 | ||
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289 | @defun insert &rest args |
290 | This function inserts the strings and/or characters @var{args} into the | |
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291 | current buffer, at point, moving point forward. In other words, it |
292 | inserts the text before point. An error is signaled unless all | |
293 | @var{args} are either strings or characters. The value is @code{nil}. | |
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294 | @end defun |
295 | ||
296 | @defun insert-before-markers &rest args | |
297 | This function inserts the strings and/or characters @var{args} into the | |
298 | current buffer, at point, moving point forward. An error is signaled | |
299 | unless all @var{args} are either strings or characters. The value is | |
300 | @code{nil}. | |
301 | ||
302 | This function is unlike the other insertion functions in that it | |
303 | relocates markers initially pointing at the insertion point, to point | |
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304 | after the inserted text. If an overlat begins the insertion point, the |
305 | inserted text falls outside the overlay; if a nonempty overlay ends at | |
306 | the insertion point, the inserted text falls inside that overlay. | |
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307 | @end defun |
308 | ||
33acbad2 | 309 | @defun insert-char character count &optional inherit |
73804d4b RS |
310 | This function inserts @var{count} instances of @var{character} into the |
311 | current buffer before point. The argument @var{count} must be a number, | |
312 | and @var{character} must be a character. The value is @code{nil}. | |
313 | @c It's unfortunate that count comes second. Not like make-string, etc. | |
33acbad2 RS |
314 | |
315 | If @var{inherit} is non-@code{nil}, then the inserted characters inherit | |
316 | sticky text properties from the two characters before and after the | |
317 | insertion point. @xref{Sticky Properties}. | |
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318 | @end defun |
319 | ||
320 | @defun insert-buffer-substring from-buffer-or-name &optional start end | |
321 | This function inserts a portion of buffer @var{from-buffer-or-name} | |
322 | (which must already exist) into the current buffer before point. The | |
323 | text inserted is the region from @var{start} and @var{end}. (These | |
324 | arguments default to the beginning and end of the accessible portion of | |
325 | that buffer.) This function returns @code{nil}. | |
326 | ||
327 | In this example, the form is executed with buffer @samp{bar} as the | |
328 | current buffer. We assume that buffer @samp{bar} is initially empty. | |
329 | ||
330 | @example | |
331 | @group | |
332 | ---------- Buffer: foo ---------- | |
333 | We hold these truths to be self-evident, that all | |
334 | ---------- Buffer: foo ---------- | |
335 | @end group | |
336 | ||
337 | @group | |
338 | (insert-buffer-substring "foo" 1 20) | |
339 | @result{} nil | |
340 | ||
341 | ---------- Buffer: bar ---------- | |
61cfa852 | 342 | We hold these truth@point{} |
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343 | ---------- Buffer: bar ---------- |
344 | @end group | |
345 | @end example | |
346 | @end defun | |
347 | ||
348 | @xref{Sticky Properties}, for other insertion functions that inherit | |
61cfa852 | 349 | text properties from the nearby text in addition to inserting it. |
33acbad2 RS |
350 | Whitespace inserted by indentation functions also inherits text |
351 | properties. | |
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352 | |
353 | @node Commands for Insertion | |
354 | @section User-Level Insertion Commands | |
355 | ||
356 | This section describes higher-level commands for inserting text, | |
357 | commands intended primarily for the user but useful also in Lisp | |
358 | programs. | |
359 | ||
360 | @deffn Command insert-buffer from-buffer-or-name | |
361 | This command inserts the entire contents of @var{from-buffer-or-name} | |
362 | (which must exist) into the current buffer after point. It leaves | |
363 | the mark after the inserted text. The value is @code{nil}. | |
364 | @end deffn | |
365 | ||
366 | @deffn Command self-insert-command count | |
367 | @cindex character insertion | |
368 | @cindex self-insertion | |
61cfa852 RS |
369 | This command inserts the last character typed; it does so @var{count} |
370 | times, before point, and returns @code{nil}. Most printing characters | |
371 | are bound to this command. In routine use, @code{self-insert-command} | |
372 | is the most frequently called function in Emacs, but programs rarely use | |
373 | it except to install it on a keymap. | |
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374 | |
375 | In an interactive call, @var{count} is the numeric prefix argument. | |
376 | ||
22697dac KH |
377 | This command calls @code{auto-fill-function} whenever that is |
378 | non-@code{nil} and the character inserted is a space or a newline | |
379 | (@pxref{Auto Filling}). | |
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380 | |
381 | @c Cross refs reworded to prevent overfull hbox. --rjc 15mar92 | |
22697dac | 382 | This command performs abbrev expansion if Abbrev mode is enabled and |
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383 | the inserted character does not have word-constituent |
384 | syntax. (@xref{Abbrevs}, and @ref{Syntax Class Table}.) | |
385 | ||
22697dac KH |
386 | This is also responsible for calling @code{blink-paren-function} when |
387 | the inserted character has close parenthesis syntax (@pxref{Blinking}). | |
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388 | @end deffn |
389 | ||
390 | @deffn Command newline &optional number-of-newlines | |
391 | This command inserts newlines into the current buffer before point. | |
392 | If @var{number-of-newlines} is supplied, that many newline characters | |
393 | are inserted. | |
394 | ||
395 | @cindex newline and Auto Fill mode | |
61cfa852 RS |
396 | This function calls @code{auto-fill-function} if the current column |
397 | number is greater than the value of @code{fill-column} and | |
398 | @var{number-of-newlines} is @code{nil}. Typically what | |
399 | @code{auto-fill-function} does is insert a newline; thus, the overall | |
400 | result in this case is to insert two newlines at different places: one | |
401 | at point, and another earlier in the line. @code{newline} does not | |
402 | auto-fill if @var{number-of-newlines} is non-@code{nil}. | |
73804d4b | 403 | |
bfe721d1 KH |
404 | This command indents to the left margin if that is not zero. |
405 | @xref{Margins}. | |
406 | ||
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407 | The value returned is @code{nil}. In an interactive call, @var{count} |
408 | is the numeric prefix argument. | |
409 | @end deffn | |
410 | ||
411 | @deffn Command split-line | |
412 | This command splits the current line, moving the portion of the line | |
61cfa852 | 413 | after point down vertically so that it is on the next line directly |
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414 | below where it was before. Whitespace is inserted as needed at the |
415 | beginning of the lower line, using the @code{indent-to} function. | |
416 | @code{split-line} returns the position of point. | |
417 | ||
418 | Programs hardly ever use this function. | |
419 | @end deffn | |
420 | ||
421 | @defvar overwrite-mode | |
422 | This variable controls whether overwrite mode is in effect: a | |
423 | non-@code{nil} value enables the mode. It is automatically made | |
424 | buffer-local when set in any fashion. | |
425 | @end defvar | |
426 | ||
427 | @node Deletion | |
bfe721d1 | 428 | @section Deleting Text |
73804d4b RS |
429 | |
430 | @cindex deletion vs killing | |
431 | Deletion means removing part of the text in a buffer, without saving | |
432 | it in the kill ring (@pxref{The Kill Ring}). Deleted text can't be | |
433 | yanked, but can be reinserted using the undo mechanism (@pxref{Undo}). | |
61cfa852 RS |
434 | Some deletion functions do save text in the kill ring in some special |
435 | cases. | |
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436 | |
437 | All of the deletion functions operate on the current buffer, and all | |
438 | return a value of @code{nil}. | |
439 | ||
440 | @defun erase-buffer | |
441 | This function deletes the entire text of the current buffer, leaving it | |
442 | empty. If the buffer is read-only, it signals a @code{buffer-read-only} | |
443 | error. Otherwise, it deletes the text without asking for any | |
444 | confirmation. It returns @code{nil}. | |
445 | ||
446 | Normally, deleting a large amount of text from a buffer inhibits further | |
447 | auto-saving of that buffer ``because it has shrunk''. However, | |
448 | @code{erase-buffer} does not do this, the idea being that the future | |
449 | text is not really related to the former text, and its size should not | |
450 | be compared with that of the former text. | |
451 | @end defun | |
452 | ||
453 | @deffn Command delete-region start end | |
454 | This command deletes the text in the current buffer in the region | |
68002b5f RS |
455 | defined by @var{start} and @var{end}. The value is @code{nil}. If |
456 | point was inside the deleted region, its value afterward is @var{start}. | |
457 | Otherwise, point relocates with the surrounding text, as markers do. | |
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458 | @end deffn |
459 | ||
460 | @deffn Command delete-char count &optional killp | |
461 | This command deletes @var{count} characters directly after point, or | |
462 | before point if @var{count} is negative. If @var{killp} is | |
463 | non-@code{nil}, then it saves the deleted characters in the kill ring. | |
464 | ||
465 | In an interactive call, @var{count} is the numeric prefix argument, and | |
466 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix | |
467 | argument is supplied, the text is saved in the kill ring. If no prefix | |
468 | argument is supplied, then one character is deleted, but not saved in | |
469 | the kill ring. | |
470 | ||
471 | The value returned is always @code{nil}. | |
472 | @end deffn | |
473 | ||
474 | @deffn Command delete-backward-char count &optional killp | |
475 | @cindex delete previous char | |
476 | This command deletes @var{count} characters directly before point, or | |
477 | after point if @var{count} is negative. If @var{killp} is | |
478 | non-@code{nil}, then it saves the deleted characters in the kill ring. | |
479 | ||
480 | In an interactive call, @var{count} is the numeric prefix argument, and | |
481 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix | |
482 | argument is supplied, the text is saved in the kill ring. If no prefix | |
483 | argument is supplied, then one character is deleted, but not saved in | |
484 | the kill ring. | |
485 | ||
486 | The value returned is always @code{nil}. | |
487 | @end deffn | |
488 | ||
489 | @deffn Command backward-delete-char-untabify count &optional killp | |
490 | @cindex tab deletion | |
491 | This command deletes @var{count} characters backward, changing tabs | |
492 | into spaces. When the next character to be deleted is a tab, it is | |
493 | first replaced with the proper number of spaces to preserve alignment | |
494 | and then one of those spaces is deleted instead of the tab. If | |
495 | @var{killp} is non-@code{nil}, then the command saves the deleted | |
496 | characters in the kill ring. | |
497 | ||
498 | Conversion of tabs to spaces happens only if @var{count} is positive. | |
499 | If it is negative, exactly @minus{}@var{count} characters after point | |
500 | are deleted. | |
501 | ||
502 | In an interactive call, @var{count} is the numeric prefix argument, and | |
503 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix | |
504 | argument is supplied, the text is saved in the kill ring. If no prefix | |
505 | argument is supplied, then one character is deleted, but not saved in | |
506 | the kill ring. | |
507 | ||
508 | The value returned is always @code{nil}. | |
509 | @end deffn | |
510 | ||
511 | @node User-Level Deletion | |
512 | @section User-Level Deletion Commands | |
513 | ||
514 | This section describes higher-level commands for deleting text, | |
515 | commands intended primarily for the user but useful also in Lisp | |
516 | programs. | |
517 | ||
518 | @deffn Command delete-horizontal-space | |
519 | @cindex deleting whitespace | |
520 | This function deletes all spaces and tabs around point. It returns | |
521 | @code{nil}. | |
522 | ||
523 | In the following examples, we call @code{delete-horizontal-space} four | |
524 | times, once on each line, with point between the second and third | |
61cfa852 | 525 | characters on the line each time. |
73804d4b RS |
526 | |
527 | @example | |
528 | @group | |
529 | ---------- Buffer: foo ---------- | |
530 | I @point{}thought | |
531 | I @point{} thought | |
532 | We@point{} thought | |
533 | Yo@point{}u thought | |
534 | ---------- Buffer: foo ---------- | |
535 | @end group | |
536 | ||
537 | @group | |
538 | (delete-horizontal-space) ; @r{Four times.} | |
539 | @result{} nil | |
540 | ||
541 | ---------- Buffer: foo ---------- | |
542 | Ithought | |
543 | Ithought | |
544 | Wethought | |
545 | You thought | |
546 | ---------- Buffer: foo ---------- | |
547 | @end group | |
548 | @end example | |
549 | @end deffn | |
550 | ||
551 | @deffn Command delete-indentation &optional join-following-p | |
552 | This function joins the line point is on to the previous line, deleting | |
553 | any whitespace at the join and in some cases replacing it with one | |
554 | space. If @var{join-following-p} is non-@code{nil}, | |
555 | @code{delete-indentation} joins this line to the following line | |
556 | instead. The value is @code{nil}. | |
557 | ||
558 | If there is a fill prefix, and the second of the lines being joined | |
559 | starts with the prefix, then @code{delete-indentation} deletes the | |
bfe721d1 | 560 | fill prefix before joining the lines. @xref{Margins}. |
73804d4b RS |
561 | |
562 | In the example below, point is located on the line starting | |
563 | @samp{events}, and it makes no difference if there are trailing spaces | |
564 | in the preceding line. | |
565 | ||
566 | @smallexample | |
b22f3a19 | 567 | @group |
73804d4b RS |
568 | ---------- Buffer: foo ---------- |
569 | When in the course of human | |
570 | @point{} events, it becomes necessary | |
571 | ---------- Buffer: foo ---------- | |
b22f3a19 | 572 | @end group |
73804d4b RS |
573 | |
574 | (delete-indentation) | |
575 | @result{} nil | |
576 | ||
b22f3a19 | 577 | @group |
73804d4b RS |
578 | ---------- Buffer: foo ---------- |
579 | When in the course of human@point{} events, it becomes necessary | |
580 | ---------- Buffer: foo ---------- | |
b22f3a19 | 581 | @end group |
73804d4b RS |
582 | @end smallexample |
583 | ||
584 | After the lines are joined, the function @code{fixup-whitespace} is | |
585 | responsible for deciding whether to leave a space at the junction. | |
586 | @end deffn | |
587 | ||
588 | @defun fixup-whitespace | |
589 | This function replaces all the white space surrounding point with either | |
590 | one space or no space, according to the context. It returns @code{nil}. | |
591 | ||
592 | At the beginning or end of a line, the appropriate amount of space is | |
593 | none. Before a character with close parenthesis syntax, or after a | |
594 | character with open parenthesis or expression-prefix syntax, no space is | |
595 | also appropriate. Otherwise, one space is appropriate. @xref{Syntax | |
596 | Class Table}. | |
597 | ||
598 | In the example below, @code{fixup-whitespace} is called the first time | |
61cfa852 RS |
599 | with point before the word @samp{spaces} in the first line. For the |
600 | second invocation, point is directly after the @samp{(}. | |
73804d4b RS |
601 | |
602 | @smallexample | |
603 | @group | |
604 | ---------- Buffer: foo ---------- | |
605 | This has too many @point{}spaces | |
606 | This has too many spaces at the start of (@point{} this list) | |
607 | ---------- Buffer: foo ---------- | |
608 | @end group | |
609 | ||
610 | @group | |
611 | (fixup-whitespace) | |
612 | @result{} nil | |
613 | (fixup-whitespace) | |
614 | @result{} nil | |
615 | @end group | |
616 | ||
617 | @group | |
618 | ---------- Buffer: foo ---------- | |
619 | This has too many spaces | |
620 | This has too many spaces at the start of (this list) | |
621 | ---------- Buffer: foo ---------- | |
622 | @end group | |
623 | @end smallexample | |
624 | @end defun | |
625 | ||
626 | @deffn Command just-one-space | |
627 | @comment !!SourceFile simple.el | |
628 | This command replaces any spaces and tabs around point with a single | |
629 | space. It returns @code{nil}. | |
630 | @end deffn | |
631 | ||
632 | @deffn Command delete-blank-lines | |
633 | This function deletes blank lines surrounding point. If point is on a | |
634 | blank line with one or more blank lines before or after it, then all but | |
635 | one of them are deleted. If point is on an isolated blank line, then it | |
636 | is deleted. If point is on a nonblank line, the command deletes all | |
637 | blank lines following it. | |
638 | ||
639 | A blank line is defined as a line containing only tabs and spaces. | |
640 | ||
641 | @code{delete-blank-lines} returns @code{nil}. | |
642 | @end deffn | |
643 | ||
644 | @node The Kill Ring | |
645 | @section The Kill Ring | |
646 | @cindex kill ring | |
647 | ||
648 | @dfn{Kill} functions delete text like the deletion functions, but save | |
649 | it so that the user can reinsert it by @dfn{yanking}. Most of these | |
650 | functions have @samp{kill-} in their name. By contrast, the functions | |
651 | whose names start with @samp{delete-} normally do not save text for | |
652 | yanking (though they can still be undone); these are ``deletion'' | |
653 | functions. | |
654 | ||
655 | Most of the kill commands are primarily for interactive use, and are | |
656 | not described here. What we do describe are the functions provided for | |
657 | use in writing such commands. You can use these functions to write | |
61cfa852 | 658 | commands for killing text. When you need to delete text for internal |
73804d4b RS |
659 | purposes within a Lisp function, you should normally use deletion |
660 | functions, so as not to disturb the kill ring contents. | |
661 | @xref{Deletion}. | |
662 | ||
663 | Killed text is saved for later yanking in the @dfn{kill ring}. This | |
61cfa852 RS |
664 | is a list that holds a number of recent kills, not just the last text |
665 | kill. We call this a ``ring'' because yanking treats it as having | |
666 | elements in a cyclic order. The list is kept in the variable | |
667 | @code{kill-ring}, and can be operated on with the usual functions for | |
668 | lists; there are also specialized functions, described in this section, | |
669 | that treat it as a ring. | |
73804d4b RS |
670 | |
671 | Some people think this use of the word ``kill'' is unfortunate, since | |
61cfa852 | 672 | it refers to operations that specifically @emph{do not} destroy the |
73804d4b RS |
673 | entities ``killed''. This is in sharp contrast to ordinary life, in |
674 | which death is permanent and ``killed'' entities do not come back to | |
675 | life. Therefore, other metaphors have been proposed. For example, the | |
676 | term ``cut ring'' makes sense to people who, in pre-computer days, used | |
677 | scissors and paste to cut up and rearrange manuscripts. However, it | |
678 | would be difficult to change the terminology now. | |
679 | ||
680 | @menu | |
681 | * Kill Ring Concepts:: What text looks like in the kill ring. | |
682 | * Kill Functions:: Functions that kill text. | |
683 | * Yank Commands:: Commands that access the kill ring. | |
61cfa852 | 684 | * Low-Level Kill Ring:: Functions and variables for kill ring access. |
73804d4b RS |
685 | * Internals of Kill Ring:: Variables that hold kill-ring data. |
686 | @end menu | |
687 | ||
688 | @node Kill Ring Concepts | |
689 | @comment node-name, next, previous, up | |
690 | @subsection Kill Ring Concepts | |
691 | ||
692 | The kill ring records killed text as strings in a list, most recent | |
693 | first. A short kill ring, for example, might look like this: | |
694 | ||
695 | @example | |
696 | ("some text" "a different piece of text" "even older text") | |
697 | @end example | |
698 | ||
699 | @noindent | |
700 | When the list reaches @code{kill-ring-max} entries in length, adding a | |
701 | new entry automatically deletes the last entry. | |
702 | ||
703 | When kill commands are interwoven with other commands, each kill | |
704 | command makes a new entry in the kill ring. Multiple kill commands in | |
705 | succession build up a single entry in the kill ring, which would be | |
61cfa852 | 706 | yanked as a unit; the second and subsequent consecutive kill commands |
73804d4b RS |
707 | add text to the entry made by the first one. |
708 | ||
709 | For yanking, one entry in the kill ring is designated the ``front'' of | |
710 | the ring. Some yank commands ``rotate'' the ring by designating a | |
711 | different element as the ``front.'' But this virtual rotation doesn't | |
712 | change the list itself---the most recent entry always comes first in the | |
713 | list. | |
714 | ||
715 | @node Kill Functions | |
716 | @comment node-name, next, previous, up | |
717 | @subsection Functions for Killing | |
718 | ||
719 | @code{kill-region} is the usual subroutine for killing text. Any | |
720 | command that calls this function is a ``kill command'' (and should | |
721 | probably have @samp{kill} in its name). @code{kill-region} puts the | |
722 | newly killed text in a new element at the beginning of the kill ring or | |
723 | adds it to the most recent element. It uses the @code{last-command} | |
61cfa852 RS |
724 | variable to determine whether the previous command was a kill command, |
725 | and if so appends the killed text to the most recent entry. | |
73804d4b RS |
726 | |
727 | @deffn Command kill-region start end | |
728 | This function kills the text in the region defined by @var{start} and | |
bfe721d1 KH |
729 | @var{end}. The text is deleted but saved in the kill ring, along with |
730 | its text properties. The value is always @code{nil}. | |
73804d4b RS |
731 | |
732 | In an interactive call, @var{start} and @var{end} are point and | |
733 | the mark. | |
734 | ||
735 | @c Emacs 19 feature | |
736 | If the buffer is read-only, @code{kill-region} modifies the kill ring | |
737 | just the same, then signals an error without modifying the buffer. This | |
738 | is convenient because it lets the user use all the kill commands to copy | |
739 | text into the kill ring from a read-only buffer. | |
740 | @end deffn | |
741 | ||
742 | @deffn Command copy-region-as-kill start end | |
743 | This command saves the region defined by @var{start} and @var{end} on | |
bfe721d1 KH |
744 | the kill ring (including text properties), but does not delete the text |
745 | from the buffer. It returns @code{nil}. It also indicates the extent | |
746 | of the text copied by moving the cursor momentarily, or by displaying a | |
747 | message in the echo area. | |
73804d4b | 748 | |
22697dac KH |
749 | The command does not set @code{this-command} to @code{kill-region}, so a |
750 | subsequent kill command does not append to the same kill ring entry. | |
751 | ||
73804d4b RS |
752 | Don't call @code{copy-region-as-kill} in Lisp programs unless you aim to |
753 | support Emacs 18. For Emacs 19, it is better to use @code{kill-new} or | |
61cfa852 | 754 | @code{kill-append} instead. @xref{Low-Level Kill Ring}. |
73804d4b RS |
755 | @end deffn |
756 | ||
757 | @node Yank Commands | |
758 | @comment node-name, next, previous, up | |
759 | @subsection Functions for Yanking | |
760 | ||
761 | @dfn{Yanking} means reinserting an entry of previously killed text | |
bfe721d1 | 762 | from the kill ring. The text properties are copied too. |
73804d4b RS |
763 | |
764 | @deffn Command yank &optional arg | |
765 | @cindex inserting killed text | |
766 | This command inserts before point the text in the first entry in the | |
767 | kill ring. It positions the mark at the beginning of that text, and | |
768 | point at the end. | |
769 | ||
770 | If @var{arg} is a list (which occurs interactively when the user | |
771 | types @kbd{C-u} with no digits), then @code{yank} inserts the text as | |
772 | described above, but puts point before the yanked text and puts the mark | |
773 | after it. | |
774 | ||
775 | If @var{arg} is a number, then @code{yank} inserts the @var{arg}th most | |
776 | recently killed text---the @var{arg}th element of the kill ring list. | |
777 | ||
778 | @code{yank} does not alter the contents of the kill ring or rotate it. | |
779 | It returns @code{nil}. | |
780 | @end deffn | |
781 | ||
782 | @deffn Command yank-pop arg | |
783 | This command replaces the just-yanked entry from the kill ring with a | |
784 | different entry from the kill ring. | |
785 | ||
786 | This is allowed only immediately after a @code{yank} or another | |
787 | @code{yank-pop}. At such a time, the region contains text that was just | |
788 | inserted by yanking. @code{yank-pop} deletes that text and inserts in | |
789 | its place a different piece of killed text. It does not add the deleted | |
790 | text to the kill ring, since it is already in the kill ring somewhere. | |
791 | ||
792 | If @var{arg} is @code{nil}, then the replacement text is the previous | |
793 | element of the kill ring. If @var{arg} is numeric, the replacement is | |
794 | the @var{arg}th previous kill. If @var{arg} is negative, a more recent | |
795 | kill is the replacement. | |
796 | ||
797 | The sequence of kills in the kill ring wraps around, so that after the | |
798 | oldest one comes the newest one, and before the newest one goes the | |
799 | oldest. | |
800 | ||
801 | The value is always @code{nil}. | |
802 | @end deffn | |
803 | ||
61cfa852 RS |
804 | @node Low-Level Kill Ring |
805 | @subsection Low-Level Kill Ring | |
73804d4b RS |
806 | |
807 | These functions and variables provide access to the kill ring at a lower | |
808 | level, but still convenient for use in Lisp programs. They take care of | |
809 | interaction with X Window selections. They do not exist in Emacs | |
810 | version 18. | |
811 | ||
812 | @defun current-kill n &optional do-not-move | |
61cfa852 RS |
813 | The function @code{current-kill} rotates the yanking pointer which |
814 | designates the ``front'' of the kill ring by @var{n} places (from newer | |
815 | kills to older ones), and returns the text at that place in the ring. | |
73804d4b RS |
816 | |
817 | If the optional second argument @var{do-not-move} is non-@code{nil}, | |
818 | then @code{current-kill} doesn't alter the yanking pointer; it just | |
61cfa852 | 819 | returns the @var{n}th kill, counting from the current yanking pointer. |
73804d4b RS |
820 | |
821 | If @var{n} is zero, indicating a request for the latest kill, | |
822 | @code{current-kill} calls the value of | |
823 | @code{interprogram-paste-function} (documented below) before consulting | |
824 | the kill ring. | |
825 | @end defun | |
826 | ||
827 | @defun kill-new string | |
828 | This function puts the text @var{string} into the kill ring as a new | |
829 | entry at the front of the ring. It discards the oldest entry if | |
830 | appropriate. It also invokes the value of | |
831 | @code{interprogram-cut-function} (see below). | |
832 | @end defun | |
833 | ||
834 | @defun kill-append string before-p | |
835 | This function appends the text @var{string} to the first entry in the | |
836 | kill ring. Normally @var{string} goes at the end of the entry, but if | |
837 | @var{before-p} is non-@code{nil}, it goes at the beginning. This | |
838 | function also invokes the value of @code{interprogram-cut-function} (see | |
839 | below). | |
840 | @end defun | |
841 | ||
842 | @defvar interprogram-paste-function | |
843 | This variable provides a way of transferring killed text from other | |
844 | programs, when you are using a window system. Its value should be | |
845 | @code{nil} or a function of no arguments. | |
846 | ||
847 | If the value is a function, @code{current-kill} calls it to get the | |
848 | ``most recent kill''. If the function returns a non-@code{nil} value, | |
849 | then that value is used as the ``most recent kill''. If it returns | |
850 | @code{nil}, then the first element of @code{kill-ring} is used. | |
851 | ||
852 | The normal use of this hook is to get the X server's primary selection | |
853 | as the most recent kill, even if the selection belongs to another X | |
854 | client. @xref{X Selections}. | |
855 | @end defvar | |
856 | ||
857 | @defvar interprogram-cut-function | |
61cfa852 RS |
858 | This variable provides a way of communicating killed text to other |
859 | programs, when you are using a window system. Its value should be | |
73804d4b RS |
860 | @code{nil} or a function of one argument. |
861 | ||
862 | If the value is a function, @code{kill-new} and @code{kill-append} call | |
863 | it with the new first element of the kill ring as an argument. | |
864 | ||
865 | The normal use of this hook is to set the X server's primary selection | |
866 | to the newly killed text. | |
867 | @end defvar | |
868 | ||
869 | @node Internals of Kill Ring | |
870 | @comment node-name, next, previous, up | |
871 | @subsection Internals of the Kill Ring | |
872 | ||
873 | The variable @code{kill-ring} holds the kill ring contents, in the | |
874 | form of a list of strings. The most recent kill is always at the front | |
875 | of the list. | |
876 | ||
877 | The @code{kill-ring-yank-pointer} variable points to a link in the | |
61cfa852 RS |
878 | kill ring list, whose @sc{car} is the text to yank next. We say it |
879 | identifies the ``front'' of the ring. Moving | |
73804d4b | 880 | @code{kill-ring-yank-pointer} to a different link is called |
61cfa852 RS |
881 | @dfn{rotating the kill ring}. We call the kill ring a ``ring'' because |
882 | the functions that move the yank pointer wrap around from the end of the | |
883 | list to the beginning, or vice-versa. Rotation of the kill ring is | |
884 | virtual; it does not change the value of @code{kill-ring}. | |
73804d4b RS |
885 | |
886 | Both @code{kill-ring} and @code{kill-ring-yank-pointer} are Lisp | |
887 | variables whose values are normally lists. The word ``pointer'' in the | |
888 | name of the @code{kill-ring-yank-pointer} indicates that the variable's | |
889 | purpose is to identify one element of the list for use by the next yank | |
890 | command. | |
891 | ||
892 | The value of @code{kill-ring-yank-pointer} is always @code{eq} to one | |
893 | of the links in the kill ring list. The element it identifies is the | |
894 | @sc{car} of that link. Kill commands, which change the kill ring, also | |
61cfa852 RS |
895 | set this variable to the value of @code{kill-ring}. The effect is to |
896 | rotate the ring so that the newly killed text is at the front. | |
73804d4b RS |
897 | |
898 | Here is a diagram that shows the variable @code{kill-ring-yank-pointer} | |
899 | pointing to the second entry in the kill ring @code{("some text" "a | |
900 | different piece of text" "yet older text")}. | |
901 | ||
902 | @example | |
903 | @group | |
904 | kill-ring kill-ring-yank-pointer | |
905 | | | | |
906 | | ___ ___ ---> ___ ___ ___ ___ | |
907 | --> |___|___|------> |___|___|--> |___|___|--> nil | |
908 | | | | | |
909 | | | | | |
910 | | | -->"yet older text" | |
911 | | | | |
912 | | --> "a different piece of text" | |
913 | | | |
914 | --> "some text" | |
915 | @end group | |
916 | @end example | |
917 | ||
918 | @noindent | |
919 | This state of affairs might occur after @kbd{C-y} (@code{yank}) | |
920 | immediately followed by @kbd{M-y} (@code{yank-pop}). | |
921 | ||
922 | @defvar kill-ring | |
61cfa852 RS |
923 | This variable holds the list of killed text sequences, most recently |
924 | killed first. | |
73804d4b RS |
925 | @end defvar |
926 | ||
927 | @defvar kill-ring-yank-pointer | |
928 | This variable's value indicates which element of the kill ring is at the | |
929 | ``front'' of the ring for yanking. More precisely, the value is a tail | |
930 | of the value of @code{kill-ring}, and its @sc{car} is the kill string | |
931 | that @kbd{C-y} should yank. | |
932 | @end defvar | |
933 | ||
934 | @defopt kill-ring-max | |
935 | The value of this variable is the maximum length to which the kill | |
936 | ring can grow, before elements are thrown away at the end. The default | |
937 | value for @code{kill-ring-max} is 30. | |
938 | @end defopt | |
939 | ||
940 | @node Undo | |
941 | @comment node-name, next, previous, up | |
942 | @section Undo | |
943 | @cindex redo | |
944 | ||
61cfa852 RS |
945 | Most buffers have an @dfn{undo list}, which records all changes made |
946 | to the buffer's text so that they can be undone. (The buffers that | |
947 | don't have one are usually special-purpose buffers for which Emacs | |
948 | assumes that undoing is not useful.) All the primitives that modify the | |
949 | text in the buffer automatically add elements to the front of the undo | |
950 | list, which is in the variable @code{buffer-undo-list}. | |
73804d4b RS |
951 | |
952 | @defvar buffer-undo-list | |
953 | This variable's value is the undo list of the current buffer. | |
954 | A value of @code{t} disables the recording of undo information. | |
955 | @end defvar | |
956 | ||
957 | Here are the kinds of elements an undo list can have: | |
958 | ||
959 | @table @code | |
960 | @item @var{integer} | |
961 | This kind of element records a previous value of point. Ordinary cursor | |
962 | motion does not get any sort of undo record, but deletion commands use | |
963 | these entries to record where point was before the command. | |
964 | ||
965 | @item (@var{beg} . @var{end}) | |
966 | This kind of element indicates how to delete text that was inserted. | |
967 | Upon insertion, the text occupied the range @var{beg}--@var{end} in the | |
968 | buffer. | |
969 | ||
d1756ab9 | 970 | @item (@var{text} . @var{position}) |
73804d4b | 971 | This kind of element indicates how to reinsert text that was deleted. |
d1756ab9 RS |
972 | The deleted text itself is the string @var{text}. The place to |
973 | reinsert it is @code{(abs @var{position})}. | |
73804d4b RS |
974 | |
975 | @item (t @var{high} . @var{low}) | |
976 | This kind of element indicates that an unmodified buffer became | |
977 | modified. The elements @var{high} and @var{low} are two integers, each | |
978 | recording 16 bits of the visited file's modification time as of when it | |
979 | was previously visited or saved. @code{primitive-undo} uses those | |
980 | values to determine whether to mark the buffer as unmodified once again; | |
981 | it does so only if the file's modification time matches those numbers. | |
982 | ||
983 | @item (nil @var{property} @var{value} @var{beg} . @var{end}) | |
984 | This kind of element records a change in a text property. | |
985 | Here's how you might undo the change: | |
986 | ||
987 | @example | |
988 | (put-text-property @var{beg} @var{end} @var{property} @var{value}) | |
989 | @end example | |
d1756ab9 | 990 | |
61ee3601 RS |
991 | @item (@var{marker} . @var{adjustment}) |
992 | This kind of element records the fact that the marker @var{marker} was | |
993 | relocated due to deletion of surrounding text, and that it moved | |
994 | @var{adjustment} character positions. Undoing this element moves | |
995 | @var{marker} @minus{} @var{adjustment} characters. | |
996 | ||
d1756ab9 | 997 | @item @var{position} |
bfe721d1 KH |
998 | This element indicates where point was at an earlier time. Undoing this |
999 | element sets point to @var{position}. Deletion normally creates an | |
1000 | element of this kind as well as a reinsertion element. | |
73804d4b RS |
1001 | |
1002 | @item nil | |
1003 | This element is a boundary. The elements between two boundaries are | |
1004 | called a @dfn{change group}; normally, each change group corresponds to | |
1005 | one keyboard command, and undo commands normally undo an entire group as | |
1006 | a unit. | |
1007 | @end table | |
1008 | ||
1009 | @defun undo-boundary | |
1010 | This function places a boundary element in the undo list. The undo | |
1011 | command stops at such a boundary, and successive undo commands undo | |
1012 | to earlier and earlier boundaries. This function returns @code{nil}. | |
1013 | ||
b6a786ce RS |
1014 | The editor command loop automatically creates an undo boundary before |
1015 | each key sequence is executed. Thus, each undo normally undoes the | |
1016 | effects of one command. Self-inserting input characters are an | |
1017 | exception. The command loop makes a boundary for the first such | |
1018 | character; the next 19 consecutive self-inserting input characters do | |
1019 | not make boundaries, and then the 20th does, and so on as long as | |
1020 | self-inserting characters continue. | |
1021 | ||
1022 | All buffer modifications add a boundary whenever the previous undoable | |
1023 | change was made in some other buffer. This way, a command that modifies | |
1024 | several buffers makes a boundary in each buffer it changes. | |
1025 | ||
1026 | Calling this function explicitly is useful for splitting the effects of | |
1027 | a command into more than one unit. For example, @code{query-replace} | |
1028 | calls @code{undo-boundary} after each replacement, so that the user can | |
1029 | undo individual replacements one by one. | |
73804d4b RS |
1030 | @end defun |
1031 | ||
1032 | @defun primitive-undo count list | |
1033 | This is the basic function for undoing elements of an undo list. | |
1034 | It undoes the first @var{count} elements of @var{list}, returning | |
1035 | the rest of @var{list}. You could write this function in Lisp, | |
1036 | but it is convenient to have it in C. | |
1037 | ||
1038 | @code{primitive-undo} adds elements to the buffer's undo list when it | |
1039 | changes the buffer. Undo commands avoid confusion by saving the undo | |
1040 | list value at the beginning of a sequence of undo operations. Then the | |
1041 | undo operations use and update the saved value. The new elements added | |
bfe721d1 | 1042 | by undoing are not part of this saved value, so they don't interfere with |
73804d4b RS |
1043 | continuing to undo. |
1044 | @end defun | |
1045 | ||
1046 | @node Maintaining Undo | |
1047 | @section Maintaining Undo Lists | |
1048 | ||
1049 | This section describes how to enable and disable undo information for | |
1050 | a given buffer. It also explains how the undo list is truncated | |
1051 | automatically so it doesn't get too big. | |
1052 | ||
1053 | Recording of undo information in a newly created buffer is normally | |
1054 | enabled to start with; but if the buffer name starts with a space, the | |
1055 | undo recording is initially disabled. You can explicitly enable or | |
1056 | disable undo recording with the following two functions, or by setting | |
1057 | @code{buffer-undo-list} yourself. | |
1058 | ||
1059 | @deffn Command buffer-enable-undo &optional buffer-or-name | |
1060 | This command enables recording undo information for buffer | |
1061 | @var{buffer-or-name}, so that subsequent changes can be undone. If no | |
1062 | argument is supplied, then the current buffer is used. This function | |
1063 | does nothing if undo recording is already enabled in the buffer. It | |
1064 | returns @code{nil}. | |
1065 | ||
1066 | In an interactive call, @var{buffer-or-name} is the current buffer. | |
1067 | You cannot specify any other buffer. | |
1068 | @end deffn | |
1069 | ||
1070 | @defun buffer-disable-undo &optional buffer | |
1071 | @defunx buffer-flush-undo &optional buffer | |
1072 | @cindex disable undo | |
1073 | This function discards the undo list of @var{buffer}, and disables | |
1074 | further recording of undo information. As a result, it is no longer | |
1075 | possible to undo either previous changes or any subsequent changes. If | |
1076 | the undo list of @var{buffer} is already disabled, this function | |
1077 | has no effect. | |
1078 | ||
1079 | This function returns @code{nil}. It cannot be called interactively. | |
1080 | ||
1081 | The name @code{buffer-flush-undo} is not considered obsolete, but the | |
1082 | preferred name @code{buffer-disable-undo} is new as of Emacs versions | |
1083 | 19. | |
1084 | @end defun | |
1085 | ||
1086 | As editing continues, undo lists get longer and longer. To prevent | |
1087 | them from using up all available memory space, garbage collection trims | |
1088 | them back to size limits you can set. (For this purpose, the ``size'' | |
1089 | of an undo list measures the cons cells that make up the list, plus the | |
1090 | strings of deleted text.) Two variables control the range of acceptable | |
1091 | sizes: @code{undo-limit} and @code{undo-strong-limit}. | |
1092 | ||
1093 | @defvar undo-limit | |
1094 | This is the soft limit for the acceptable size of an undo list. The | |
1095 | change group at which this size is exceeded is the last one kept. | |
1096 | @end defvar | |
1097 | ||
1098 | @defvar undo-strong-limit | |
61cfa852 RS |
1099 | This is the upper limit for the acceptable size of an undo list. The |
1100 | change group at which this size is exceeded is discarded itself (along | |
1101 | with all older change groups). There is one exception: the very latest | |
bda144f4 | 1102 | change group is never discarded no matter how big it is. |
73804d4b RS |
1103 | @end defvar |
1104 | ||
1105 | @node Filling | |
1106 | @comment node-name, next, previous, up | |
1107 | @section Filling | |
1108 | @cindex filling, explicit | |
1109 | ||
1110 | @dfn{Filling} means adjusting the lengths of lines (by moving the line | |
1111 | breaks) so that they are nearly (but no greater than) a specified | |
1112 | maximum width. Additionally, lines can be @dfn{justified}, which means | |
bfe721d1 KH |
1113 | inserting spaces to make the left and/or right margins line up |
1114 | precisely. The width is controlled by the variable @code{fill-column}. | |
1115 | For ease of reading, lines should be no longer than 70 or so columns. | |
73804d4b RS |
1116 | |
1117 | You can use Auto Fill mode (@pxref{Auto Filling}) to fill text | |
1118 | automatically as you insert it, but changes to existing text may leave | |
1119 | it improperly filled. Then you must fill the text explicitly. | |
1120 | ||
22697dac KH |
1121 | Most of the commands in this section return values that are not |
1122 | meaningful. All the functions that do filling take note of the current | |
bfe721d1 KH |
1123 | left margin, current right margin, and current justification style |
1124 | (@pxref{Margins}). If the current justification style is | |
1125 | @code{none}, the filling functions don't actually do anything. | |
1126 | ||
1127 | Several of the filling functions have an argument @var{justify}. | |
1128 | If it is non-@code{nil}, that requests some kind of justification. It | |
1129 | can be @code{left}, @code{right}, @code{full}, or @code{center}, to | |
1130 | request a specific style of justification. If it is @code{t}, that | |
1131 | means to use the current justification style for this part of the text | |
1132 | (see @code{current-justification}, below). | |
1133 | ||
1134 | When you call the filling functions interactively, using a prefix | |
1135 | argument implies the value @code{full} for @var{justify}. | |
73804d4b | 1136 | |
bfe721d1 | 1137 | @deffn Command fill-paragraph justify |
73804d4b RS |
1138 | @cindex filling a paragraph |
1139 | This command fills the paragraph at or after point. If | |
bfe721d1 | 1140 | @var{justify} is non-@code{nil}, each line is justified as well. |
73804d4b RS |
1141 | It uses the ordinary paragraph motion commands to find paragraph |
1142 | boundaries. @xref{Paragraphs,,, emacs, The Emacs Manual}. | |
1143 | @end deffn | |
1144 | ||
bfe721d1 | 1145 | @deffn Command fill-region start end &optional justify |
73804d4b | 1146 | This command fills each of the paragraphs in the region from @var{start} |
bfe721d1 | 1147 | to @var{end}. It justifies as well if @var{justify} is |
73804d4b RS |
1148 | non-@code{nil}. |
1149 | ||
1150 | The variable @code{paragraph-separate} controls how to distinguish | |
1151 | paragraphs. @xref{Standard Regexps}. | |
1152 | @end deffn | |
1153 | ||
bfe721d1 | 1154 | @deffn Command fill-individual-paragraphs start end &optional justify mail-flag |
73804d4b RS |
1155 | This command fills each paragraph in the region according to its |
1156 | individual fill prefix. Thus, if the lines of a paragraph were indented | |
1157 | with spaces, the filled paragraph will remain indented in the same | |
1158 | fashion. | |
1159 | ||
1160 | The first two arguments, @var{start} and @var{end}, are the beginning | |
1161 | and end of the region to be filled. The third and fourth arguments, | |
bfe721d1 KH |
1162 | @var{justify} and @var{mail-flag}, are optional. If |
1163 | @var{justify} is non-@code{nil}, the paragraphs are justified as | |
73804d4b RS |
1164 | well as filled. If @var{mail-flag} is non-@code{nil}, it means the |
1165 | function is operating on a mail message and therefore should not fill | |
1166 | the header lines. | |
1167 | ||
1168 | Ordinarily, @code{fill-individual-paragraphs} regards each change in | |
1169 | indentation as starting a new paragraph. If | |
1170 | @code{fill-individual-varying-indent} is non-@code{nil}, then only | |
61cfa852 RS |
1171 | separator lines separate paragraphs. That mode can handle indented |
1172 | paragraphs with additional indentation on the first line. | |
73804d4b RS |
1173 | @end deffn |
1174 | ||
1175 | @defopt fill-individual-varying-indent | |
1176 | This variable alters the action of @code{fill-individual-paragraphs} as | |
1177 | described above. | |
1178 | @end defopt | |
1179 | ||
bfe721d1 | 1180 | @deffn Command fill-region-as-paragraph start end &optional justify |
73804d4b RS |
1181 | This command considers a region of text as a paragraph and fills it. If |
1182 | the region was made up of many paragraphs, the blank lines between | |
1183 | paragraphs are removed. This function justifies as well as filling when | |
bfe721d1 | 1184 | @var{justify} is non-@code{nil}. |
22697dac KH |
1185 | |
1186 | In an interactive call, any prefix argument requests justification. | |
73804d4b | 1187 | |
9e2b495b | 1188 | In Adaptive Fill mode, which is enabled by default, calling the function |
73804d4b RS |
1189 | @code{fill-region-as-paragraph} on an indented paragraph when there is |
1190 | no fill prefix uses the indentation of the second line of the paragraph | |
1191 | as the fill prefix. | |
1192 | @end deffn | |
1193 | ||
22697dac | 1194 | @deffn Command justify-current-line how eop nosqueeze |
73804d4b RS |
1195 | This command inserts spaces between the words of the current line so |
1196 | that the line ends exactly at @code{fill-column}. It returns | |
1197 | @code{nil}. | |
22697dac KH |
1198 | |
1199 | The argument @var{how}, if non-@code{nil} specifies explicitly the style | |
1200 | of justification. It can be @code{left}, @code{right}, @code{full}, | |
1201 | @code{center}, or @code{none}. If it is @code{t}, that means to do | |
1202 | follow specified justification style (see @code{current-justification}, | |
1203 | below). @code{nil} means to do full justification. | |
1204 | ||
9e2b495b | 1205 | If @var{eop} is non-@code{nil}, that means do left-justification if |
22697dac KH |
1206 | @code{current-justification} specifies full justification. This is used |
1207 | for the last line of a paragraph; even if the paragraph as a whole is | |
1208 | fully justified, the last line should not be. | |
1209 | ||
1210 | If @var{nosqueeze} is non-@code{nil}, that means do not change interior | |
1211 | whitespace. | |
73804d4b RS |
1212 | @end deffn |
1213 | ||
22697dac KH |
1214 | @defopt default-justification |
1215 | This variable's value specifies the style of justification to use for | |
1216 | text that doesn't specify a style with a text property. The possible | |
1217 | values are @code{left}, @code{right}, @code{full}, @code{center}, or | |
bfe721d1 | 1218 | @code{none}. The default value is @code{left}. |
22697dac KH |
1219 | @end defopt |
1220 | ||
1221 | @defun current-justification | |
1222 | This function returns the proper justification style to use for filling | |
1223 | the text around point. | |
1224 | @end defun | |
1225 | ||
bfe721d1 KH |
1226 | @defvar fill-paragraph-function |
1227 | This variable provides a way for major modes to override the filling of | |
1228 | paragraphs. If the value is non-@code{nil}, @code{fill-paragraph} calls | |
1229 | this function to do the work. If the function returns a non-@code{nil} | |
1230 | value, @code{fill-paragraph} assumes the job is done, and immediately | |
1231 | returns that value. | |
1232 | ||
1233 | The usual use of this feature is to fill comments in programming | |
1234 | language modes. If the function needs to fill a paragraph in the usual | |
1235 | way, it can do so as follows: | |
1236 | ||
1237 | @example | |
1238 | (let ((fill-paragraph-function nil)) | |
1239 | (fill-paragraph arg)) | |
1240 | @end example | |
1241 | @end defvar | |
1242 | ||
1243 | @defvar use-hard-newlines | |
1244 | If this variable is non-@code{nil}, the filling functions do not delete | |
1245 | newlines that have the @code{hard} text property. These ``hard | |
1246 | newlines'' act as paragraph separators. | |
1247 | @end defvar | |
1248 | ||
1249 | @node Margins | |
1250 | @section Margins for Filling | |
1251 | ||
61cfa852 RS |
1252 | @defopt fill-prefix |
1253 | This variable specifies a string of text that appears at the beginning | |
1254 | of normal text lines and should be disregarded when filling them. Any | |
1255 | line that fails to start with the fill prefix is considered the start of | |
1256 | a paragraph; so is any line that starts with the fill prefix followed by | |
1257 | additional whitespace. Lines that start with the fill prefix but no | |
1258 | additional whitespace are ordinary text lines that can be filled | |
1259 | together. The resulting filled lines also start with the fill prefix. | |
bfe721d1 KH |
1260 | |
1261 | The fill prefix follows the left margin whitespace, if any. | |
61cfa852 RS |
1262 | @end defopt |
1263 | ||
73804d4b RS |
1264 | @defopt fill-column |
1265 | This buffer-local variable specifies the maximum width of filled | |
1266 | lines. Its value should be an integer, which is a number of columns. | |
1267 | All the filling, justification and centering commands are affected by | |
1268 | this variable, including Auto Fill mode (@pxref{Auto Filling}). | |
1269 | ||
1270 | As a practical matter, if you are writing text for other people to | |
1271 | read, you should set @code{fill-column} to no more than 70. Otherwise | |
1272 | the line will be too long for people to read comfortably, and this can | |
1273 | make the text seem clumsy. | |
1274 | @end defopt | |
1275 | ||
1276 | @defvar default-fill-column | |
1277 | The value of this variable is the default value for @code{fill-column} in | |
1278 | buffers that do not override it. This is the same as | |
1279 | @code{(default-value 'fill-column)}. | |
1280 | ||
1281 | The default value for @code{default-fill-column} is 70. | |
1282 | @end defvar | |
1283 | ||
22697dac KH |
1284 | @deffn Command set-left-margin from to margin |
1285 | This sets the @code{left-margin} property on the text from @var{from} to | |
1286 | @var{to} to the value @var{margin}. If Auto Fill mode is enabled, this | |
1287 | command also refills the region to fit the new margin. | |
1288 | @end deffn | |
1289 | ||
1290 | @deffn Command set-right-margin from to margin | |
bfe721d1 KH |
1291 | This sets the @code{right-margin} property on the text from @var{from} |
1292 | to @var{to} to the value @var{margin}. If Auto Fill mode is enabled, | |
1293 | this command also refills the region to fit the new margin. | |
22697dac KH |
1294 | @end deffn |
1295 | ||
1296 | @defun current-left-margin | |
1297 | This function returns the proper left margin value to use for filling | |
1298 | the text around point. The value is the sum of the @code{left-margin} | |
1299 | property of the character at the start of the current line (or zero if | |
bfe721d1 | 1300 | none), and the value of the variable @code{left-margin}. |
22697dac KH |
1301 | @end defun |
1302 | ||
1303 | @defun current-fill-column | |
1304 | This function returns the proper fill column value to use for filling | |
1305 | the text around point. The value is the value of the @code{fill-column} | |
1306 | variable, minus the value of the @code{right-margin} property of the | |
1307 | character after point. | |
1308 | @end defun | |
1309 | ||
1310 | @deffn Command move-to-left-margin &optional n force | |
1311 | This function moves point to the left margin of the current line. The | |
1312 | column moved to is determined by calling the function | |
bfe721d1 | 1313 | @code{current-left-margin}. If the argument @var{n} is non-@code{nil}, |
22697dac KH |
1314 | @code{move-to-left-margin} moves forward @var{n}@minus{}1 lines first. |
1315 | ||
1316 | If @var{force} is non-@code{nil}, that says to fix the line's | |
1317 | indentation if that doesn't match the left margin value. | |
1318 | @end deffn | |
1319 | ||
1320 | @defun delete-to-left-margin from to | |
1321 | This function removes left margin indentation from the text | |
1322 | between @var{from} and @var{to}. The amount of indentation | |
1323 | to delete is determined by calling @code{current-left-margin}. | |
1324 | In no case does this function delete non-whitespace. | |
1325 | @end defun | |
1326 | ||
bfe721d1 KH |
1327 | @defun indent-to-left-margin |
1328 | This is the default @code{indent-line-function}, used in Fundamental | |
1329 | mode, Text mode, etc. Its effect is to adjust the indentation at the | |
1330 | beginning of the current line to the value specified by the variable | |
1331 | @code{left-margin}. This may involve either inserting or deleting | |
1332 | whitespace. | |
1333 | @end defun | |
1334 | ||
1335 | @defvar left-margin | |
1336 | This variable specifies the base left margin column. In Fundamental | |
1337 | mode, @key{LFD} indents to this column. This variable automatically | |
1338 | becomes buffer-local when set in any fashion. | |
1339 | @end defvar | |
1340 | ||
73804d4b RS |
1341 | @node Auto Filling |
1342 | @comment node-name, next, previous, up | |
1343 | @section Auto Filling | |
1344 | @cindex filling, automatic | |
1345 | @cindex Auto Fill mode | |
1346 | ||
61cfa852 | 1347 | Auto Fill mode is a minor mode that fills lines automatically as text |
bda144f4 | 1348 | is inserted. This section describes the hook used by Auto Fill mode. |
61cfa852 RS |
1349 | For a description of functions that you can call explicitly to fill and |
1350 | justify existing text, see @ref{Filling}. | |
73804d4b | 1351 | |
bfe721d1 KH |
1352 | Auto Fill mode also enables the functions that change the margins and |
1353 | justification style to refill portions of the text. @xref{Margins}. | |
1354 | ||
73804d4b | 1355 | @defvar auto-fill-function |
22697dac KH |
1356 | The value of this variable should be a function (of no arguments) to be |
1357 | called after self-inserting a space or a newline. It may be @code{nil}, | |
1358 | in which case nothing special is done in that case. | |
73804d4b RS |
1359 | |
1360 | The value of @code{auto-fill-function} is @code{do-auto-fill} when | |
1361 | Auto-Fill mode is enabled. That is a function whose sole purpose is to | |
1362 | implement the usual strategy for breaking a line. | |
1363 | ||
1364 | @quotation | |
1365 | In older Emacs versions, this variable was named @code{auto-fill-hook}, | |
1366 | but since it is not called with the standard convention for hooks, it | |
1367 | was renamed to @code{auto-fill-function} in version 19. | |
1368 | @end quotation | |
1369 | @end defvar | |
1370 | ||
910bc071 RS |
1371 | @defvar normal-auto-fill-function |
1372 | This variable specifies the function to use for | |
1373 | @code{auto-fill-function}, if and when Auto Fill is turned on. Major | |
1374 | modes can set this locally to alter how Auto Fill works. | |
1375 | @end defvar | |
1376 | ||
73804d4b RS |
1377 | @node Sorting |
1378 | @section Sorting Text | |
1379 | @cindex sorting text | |
1380 | ||
1381 | The sorting functions described in this section all rearrange text in | |
1382 | a buffer. This is in contrast to the function @code{sort}, which | |
1383 | rearranges the order of the elements of a list (@pxref{Rearrangement}). | |
1384 | The values returned by these functions are not meaningful. | |
1385 | ||
1386 | @defun sort-subr reverse nextrecfun endrecfun &optional startkeyfun endkeyfun | |
61cfa852 | 1387 | This function is the general text-sorting routine that divides a buffer |
73804d4b RS |
1388 | into records and sorts them. Most of the commands in this section use |
1389 | this function. | |
1390 | ||
1391 | To understand how @code{sort-subr} works, consider the whole accessible | |
1392 | portion of the buffer as being divided into disjoint pieces called | |
1393 | @dfn{sort records}. The records may or may not be contiguous; they may | |
1394 | not overlap. A portion of each sort record (perhaps all of it) is | |
1395 | designated as the sort key. Sorting rearranges the records in order by | |
1396 | their sort keys. | |
1397 | ||
1398 | Usually, the records are rearranged in order of ascending sort key. | |
1399 | If the first argument to the @code{sort-subr} function, @var{reverse}, | |
1400 | is non-@code{nil}, the sort records are rearranged in order of | |
1401 | descending sort key. | |
1402 | ||
1403 | The next four arguments to @code{sort-subr} are functions that are | |
1404 | called to move point across a sort record. They are called many times | |
1405 | from within @code{sort-subr}. | |
1406 | ||
1407 | @enumerate | |
1408 | @item | |
1409 | @var{nextrecfun} is called with point at the end of a record. This | |
1410 | function moves point to the start of the next record. The first record | |
1411 | is assumed to start at the position of point when @code{sort-subr} is | |
1412 | called. Therefore, you should usually move point to the beginning of | |
1413 | the buffer before calling @code{sort-subr}. | |
1414 | ||
1415 | This function can indicate there are no more sort records by leaving | |
1416 | point at the end of the buffer. | |
1417 | ||
1418 | @item | |
1419 | @var{endrecfun} is called with point within a record. It moves point to | |
1420 | the end of the record. | |
1421 | ||
1422 | @item | |
1423 | @var{startkeyfun} is called to move point from the start of a record to | |
1424 | the start of the sort key. This argument is optional; if it is omitted, | |
1425 | the whole record is the sort key. If supplied, the function should | |
1426 | either return a non-@code{nil} value to be used as the sort key, or | |
1427 | return @code{nil} to indicate that the sort key is in the buffer | |
1428 | starting at point. In the latter case, @var{endkeyfun} is called to | |
1429 | find the end of the sort key. | |
1430 | ||
1431 | @item | |
1432 | @var{endkeyfun} is called to move point from the start of the sort key | |
1433 | to the end of the sort key. This argument is optional. If | |
1434 | @var{startkeyfun} returns @code{nil} and this argument is omitted (or | |
1435 | @code{nil}), then the sort key extends to the end of the record. There | |
1436 | is no need for @var{endkeyfun} if @var{startkeyfun} returns a | |
1437 | non-@code{nil} value. | |
1438 | @end enumerate | |
1439 | ||
1440 | As an example of @code{sort-subr}, here is the complete function | |
1441 | definition for @code{sort-lines}: | |
1442 | ||
1443 | @example | |
1444 | @group | |
1445 | ;; @r{Note that the first two lines of doc string} | |
1446 | ;; @r{are effectively one line when viewed by a user.} | |
1447 | (defun sort-lines (reverse beg end) | |
1448 | "Sort lines in region alphabetically. | |
1449 | Called from a program, there are three arguments: | |
1450 | @end group | |
1451 | @group | |
1452 | REVERSE (non-nil means reverse order), | |
1453 | and BEG and END (the region to sort)." | |
1454 | (interactive "P\nr") | |
1455 | (save-restriction | |
1456 | (narrow-to-region beg end) | |
1457 | (goto-char (point-min)) | |
1458 | (sort-subr reverse | |
1459 | 'forward-line | |
1460 | 'end-of-line))) | |
1461 | @end group | |
1462 | @end example | |
1463 | ||
1464 | Here @code{forward-line} moves point to the start of the next record, | |
1465 | and @code{end-of-line} moves point to the end of record. We do not pass | |
1466 | the arguments @var{startkeyfun} and @var{endkeyfun}, because the entire | |
1467 | record is used as the sort key. | |
1468 | ||
1469 | The @code{sort-paragraphs} function is very much the same, except that | |
1470 | its @code{sort-subr} call looks like this: | |
1471 | ||
1472 | @example | |
1473 | @group | |
1474 | (sort-subr reverse | |
1475 | (function | |
1476 | (lambda () | |
1477 | (skip-chars-forward "\n \t\f"))) | |
1478 | 'forward-paragraph) | |
1479 | @end group | |
1480 | @end example | |
1481 | @end defun | |
1482 | ||
1483 | @deffn Command sort-regexp-fields reverse record-regexp key-regexp start end | |
1484 | This command sorts the region between @var{start} and @var{end} | |
1485 | alphabetically as specified by @var{record-regexp} and @var{key-regexp}. | |
1486 | If @var{reverse} is a negative integer, then sorting is in reverse | |
1487 | order. | |
1488 | ||
1489 | Alphabetical sorting means that two sort keys are compared by | |
1490 | comparing the first characters of each, the second characters of each, | |
1491 | and so on. If a mismatch is found, it means that the sort keys are | |
1492 | unequal; the sort key whose character is less at the point of first | |
1493 | mismatch is the lesser sort key. The individual characters are compared | |
1494 | according to their numerical values. Since Emacs uses the @sc{ASCII} | |
1495 | character set, the ordering in that set determines alphabetical order. | |
1496 | @c version 19 change | |
1497 | ||
1498 | The value of the @var{record-regexp} argument specifies how to divide | |
1499 | the buffer into sort records. At the end of each record, a search is | |
1500 | done for this regular expression, and the text that matches it is the | |
1501 | next record. For example, the regular expression @samp{^.+$}, which | |
1502 | matches lines with at least one character besides a newline, would make | |
1503 | each such line into a sort record. @xref{Regular Expressions}, for a | |
1504 | description of the syntax and meaning of regular expressions. | |
1505 | ||
1506 | The value of the @var{key-regexp} argument specifies what part of each | |
1507 | record is the sort key. The @var{key-regexp} could match the whole | |
1508 | record, or only a part. In the latter case, the rest of the record has | |
1509 | no effect on the sorted order of records, but it is carried along when | |
1510 | the record moves to its new position. | |
1511 | ||
1512 | The @var{key-regexp} argument can refer to the text matched by a | |
1513 | subexpression of @var{record-regexp}, or it can be a regular expression | |
1514 | on its own. | |
1515 | ||
1516 | If @var{key-regexp} is: | |
1517 | ||
1518 | @table @asis | |
1519 | @item @samp{\@var{digit}} | |
1520 | then the text matched by the @var{digit}th @samp{\(...\)} parenthesis | |
1521 | grouping in @var{record-regexp} is the sort key. | |
1522 | ||
1523 | @item @samp{\&} | |
1524 | then the whole record is the sort key. | |
1525 | ||
1526 | @item a regular expression | |
1527 | then @code{sort-regexp-fields} searches for a match for the regular | |
1528 | expression within the record. If such a match is found, it is the sort | |
1529 | key. If there is no match for @var{key-regexp} within a record then | |
1530 | that record is ignored, which means its position in the buffer is not | |
1531 | changed. (The other records may move around it.) | |
1532 | @end table | |
1533 | ||
1534 | For example, if you plan to sort all the lines in the region by the | |
1535 | first word on each line starting with the letter @samp{f}, you should | |
1536 | set @var{record-regexp} to @samp{^.*$} and set @var{key-regexp} to | |
1537 | @samp{\<f\w*\>}. The resulting expression looks like this: | |
1538 | ||
1539 | @example | |
1540 | @group | |
1541 | (sort-regexp-fields nil "^.*$" "\\<f\\w*\\>" | |
1542 | (region-beginning) | |
1543 | (region-end)) | |
1544 | @end group | |
1545 | @end example | |
1546 | ||
1547 | If you call @code{sort-regexp-fields} interactively, it prompts for | |
1548 | @var{record-regexp} and @var{key-regexp} in the minibuffer. | |
1549 | @end deffn | |
1550 | ||
1551 | @deffn Command sort-lines reverse start end | |
1552 | This command alphabetically sorts lines in the region between | |
1553 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort | |
1554 | is in reverse order. | |
1555 | @end deffn | |
1556 | ||
1557 | @deffn Command sort-paragraphs reverse start end | |
1558 | This command alphabetically sorts paragraphs in the region between | |
1559 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort | |
1560 | is in reverse order. | |
1561 | @end deffn | |
1562 | ||
1563 | @deffn Command sort-pages reverse start end | |
1564 | This command alphabetically sorts pages in the region between | |
1565 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort | |
1566 | is in reverse order. | |
1567 | @end deffn | |
1568 | ||
1569 | @deffn Command sort-fields field start end | |
1570 | This command sorts lines in the region between @var{start} and | |
1571 | @var{end}, comparing them alphabetically by the @var{field}th field | |
1572 | of each line. Fields are separated by whitespace and numbered starting | |
1573 | from 1. If @var{field} is negative, sorting is by the | |
1574 | @w{@minus{}@var{field}th} field from the end of the line. This command | |
1575 | is useful for sorting tables. | |
1576 | @end deffn | |
1577 | ||
1578 | @deffn Command sort-numeric-fields field start end | |
1579 | This command sorts lines in the region between @var{start} and | |
1580 | @var{end}, comparing them numerically by the @var{field}th field of each | |
1581 | line. The specified field must contain a number in each line of the | |
1582 | region. Fields are separated by whitespace and numbered starting from | |
1583 | 1. If @var{field} is negative, sorting is by the | |
1584 | @w{@minus{}@var{field}th} field from the end of the line. This command | |
1585 | is useful for sorting tables. | |
1586 | @end deffn | |
1587 | ||
1588 | @deffn Command sort-columns reverse &optional beg end | |
1589 | This command sorts the lines in the region between @var{beg} and | |
1590 | @var{end}, comparing them alphabetically by a certain range of columns. | |
1591 | The column positions of @var{beg} and @var{end} bound the range of | |
1592 | columns to sort on. | |
1593 | ||
1594 | If @var{reverse} is non-@code{nil}, the sort is in reverse order. | |
1595 | ||
1596 | One unusual thing about this command is that the entire line | |
1597 | containing position @var{beg}, and the entire line containing position | |
1598 | @var{end}, are included in the region sorted. | |
1599 | ||
1600 | Note that @code{sort-columns} uses the @code{sort} utility program, | |
1601 | and so cannot work properly on text containing tab characters. Use | |
1602 | @kbd{M-x @code{untabify}} to convert tabs to spaces before sorting. | |
73804d4b RS |
1603 | @end deffn |
1604 | ||
1605 | @node Columns | |
1606 | @comment node-name, next, previous, up | |
1607 | @section Counting Columns | |
1608 | @cindex columns | |
1609 | @cindex counting columns | |
1610 | @cindex horizontal position | |
1611 | ||
1612 | The column functions convert between a character position (counting | |
1613 | characters from the beginning of the buffer) and a column position | |
1614 | (counting screen characters from the beginning of a line). | |
1615 | ||
1616 | A character counts according to the number of columns it occupies on | |
1617 | the screen. This means control characters count as occupying 2 or 4 | |
1618 | columns, depending upon the value of @code{ctl-arrow}, and tabs count as | |
1619 | occupying a number of columns that depends on the value of | |
1620 | @code{tab-width} and on the column where the tab begins. @xref{Usual Display}. | |
1621 | ||
1622 | Column number computations ignore the width of the window and the | |
1623 | amount of horizontal scrolling. Consequently, a column value can be | |
1624 | arbitrarily high. The first (or leftmost) column is numbered 0. | |
1625 | ||
1626 | @defun current-column | |
1627 | This function returns the horizontal position of point, measured in | |
1628 | columns, counting from 0 at the left margin. The column position is the | |
1629 | sum of the widths of all the displayed representations of the characters | |
1630 | between the start of the current line and point. | |
1631 | ||
1632 | For an example of using @code{current-column}, see the description of | |
1633 | @code{count-lines} in @ref{Text Lines}. | |
1634 | @end defun | |
1635 | ||
1636 | @defun move-to-column column &optional force | |
1637 | This function moves point to @var{column} in the current line. The | |
1638 | calculation of @var{column} takes into account the widths of the | |
1639 | displayed representations of the characters between the start of the | |
1640 | line and point. | |
1641 | ||
1642 | If column @var{column} is beyond the end of the line, point moves to the | |
1643 | end of the line. If @var{column} is negative, point moves to the | |
1644 | beginning of the line. | |
1645 | ||
1646 | If it is impossible to move to column @var{column} because that is in | |
1647 | the middle of a multicolumn character such as a tab, point moves to the | |
1648 | end of that character. However, if @var{force} is non-@code{nil}, and | |
1649 | @var{column} is in the middle of a tab, then @code{move-to-column} | |
1650 | converts the tab into spaces so that it can move precisely to column | |
1651 | @var{column}. Other multicolumn characters can cause anomalies despite | |
1652 | @var{force}, since there is no way to split them. | |
1653 | ||
1654 | The argument @var{force} also has an effect if the line isn't long | |
61cfa852 RS |
1655 | enough to reach column @var{column}; in that case, it says to add |
1656 | whitespace at the end of the line to reach that column. | |
73804d4b RS |
1657 | |
1658 | If @var{column} is not an integer, an error is signaled. | |
1659 | ||
1660 | The return value is the column number actually moved to. | |
1661 | @end defun | |
1662 | ||
1663 | @node Indentation | |
1664 | @section Indentation | |
1665 | @cindex indentation | |
1666 | ||
1667 | The indentation functions are used to examine, move to, and change | |
1668 | whitespace that is at the beginning of a line. Some of the functions | |
1669 | can also change whitespace elsewhere on a line. Columns and indentation | |
1670 | count from zero at the left margin. | |
1671 | ||
1672 | @menu | |
1673 | * Primitive Indent:: Functions used to count and insert indentation. | |
1674 | * Mode-Specific Indent:: Customize indentation for different modes. | |
1675 | * Region Indent:: Indent all the lines in a region. | |
1676 | * Relative Indent:: Indent the current line based on previous lines. | |
1677 | * Indent Tabs:: Adjustable, typewriter-like tab stops. | |
1678 | * Motion by Indent:: Move to first non-blank character. | |
1679 | @end menu | |
1680 | ||
1681 | @node Primitive Indent | |
1682 | @subsection Indentation Primitives | |
1683 | ||
1684 | This section describes the primitive functions used to count and | |
1685 | insert indentation. The functions in the following sections use these | |
1686 | primitives. | |
1687 | ||
1688 | @defun current-indentation | |
1689 | @comment !!Type Primitive Function | |
1690 | @comment !!SourceFile indent.c | |
1691 | This function returns the indentation of the current line, which is | |
1692 | the horizontal position of the first nonblank character. If the | |
1693 | contents are entirely blank, then this is the horizontal position of the | |
1694 | end of the line. | |
1695 | @end defun | |
1696 | ||
1697 | @deffn Command indent-to column &optional minimum | |
1698 | @comment !!Type Primitive Function | |
1699 | @comment !!SourceFile indent.c | |
61cfa852 RS |
1700 | This function indents from point with tabs and spaces until @var{column} |
1701 | is reached. If @var{minimum} is specified and non-@code{nil}, then at | |
1702 | least that many spaces are inserted even if this requires going beyond | |
1703 | @var{column}. Otherwise the function does nothing if point is already | |
1704 | beyond @var{column}. The value is the column at which the inserted | |
1705 | indentation ends. | |
33acbad2 RS |
1706 | |
1707 | The inserted whitespace characters inherit text properties from the | |
1708 | surrounding text (usually, from the preceding text only). @xref{Sticky | |
1709 | Properties}. | |
73804d4b RS |
1710 | @end deffn |
1711 | ||
1712 | @defopt indent-tabs-mode | |
1713 | @comment !!SourceFile indent.c | |
1714 | If this variable is non-@code{nil}, indentation functions can insert | |
1715 | tabs as well as spaces. Otherwise, they insert only spaces. Setting | |
1716 | this variable automatically makes it local to the current buffer. | |
1717 | @end defopt | |
1718 | ||
1719 | @node Mode-Specific Indent | |
1720 | @subsection Indentation Controlled by Major Mode | |
1721 | ||
1722 | An important function of each major mode is to customize the @key{TAB} | |
1723 | key to indent properly for the language being edited. This section | |
1724 | describes the mechanism of the @key{TAB} key and how to control it. | |
1725 | The functions in this section return unpredictable values. | |
1726 | ||
1727 | @defvar indent-line-function | |
1728 | This variable's value is the function to be used by @key{TAB} (and | |
1729 | various commands) to indent the current line. The command | |
1730 | @code{indent-according-to-mode} does no more than call this function. | |
1731 | ||
1732 | In Lisp mode, the value is the symbol @code{lisp-indent-line}; in C | |
1733 | mode, @code{c-indent-line}; in Fortran mode, @code{fortran-indent-line}. | |
1734 | In Fundamental mode, Text mode, and many other modes with no standard | |
1735 | for indentation, the value is @code{indent-to-left-margin} (which is the | |
1736 | default value). | |
1737 | @end defvar | |
1738 | ||
1739 | @deffn Command indent-according-to-mode | |
1740 | This command calls the function in @code{indent-line-function} to | |
1741 | indent the current line in a way appropriate for the current major mode. | |
1742 | @end deffn | |
1743 | ||
1744 | @deffn Command indent-for-tab-command | |
1745 | This command calls the function in @code{indent-line-function} to indent | |
1746 | the current line; except that if that function is | |
1747 | @code{indent-to-left-margin}, it calls @code{insert-tab} instead. (That | |
61cfa852 | 1748 | is a trivial command that inserts a tab character.) |
73804d4b RS |
1749 | @end deffn |
1750 | ||
73804d4b RS |
1751 | @deffn Command newline-and-indent |
1752 | @comment !!SourceFile simple.el | |
1753 | This function inserts a newline, then indents the new line (the one | |
1754 | following the newline just inserted) according to the major mode. | |
1755 | ||
1756 | It does indentation by calling the current @code{indent-line-function}. | |
1757 | In programming language modes, this is the same thing @key{TAB} does, | |
1758 | but in some text modes, where @key{TAB} inserts a tab, | |
1759 | @code{newline-and-indent} indents to the column specified by | |
1760 | @code{left-margin}. | |
1761 | @end deffn | |
1762 | ||
1763 | @deffn Command reindent-then-newline-and-indent | |
1764 | @comment !!SourceFile simple.el | |
1765 | This command reindents the current line, inserts a newline at point, | |
1766 | and then reindents the new line (the one following the newline just | |
1767 | inserted). | |
1768 | ||
1769 | This command does indentation on both lines according to the current | |
1770 | major mode, by calling the current value of @code{indent-line-function}. | |
1771 | In programming language modes, this is the same thing @key{TAB} does, | |
1772 | but in some text modes, where @key{TAB} inserts a tab, | |
1773 | @code{reindent-then-newline-and-indent} indents to the column specified | |
1774 | by @code{left-margin}. | |
1775 | @end deffn | |
1776 | ||
1777 | @node Region Indent | |
1778 | @subsection Indenting an Entire Region | |
1779 | ||
61cfa852 | 1780 | This section describes commands that indent all the lines in the |
73804d4b RS |
1781 | region. They return unpredictable values. |
1782 | ||
1783 | @deffn Command indent-region start end to-column | |
1784 | This command indents each nonblank line starting between @var{start} | |
1785 | (inclusive) and @var{end} (exclusive). If @var{to-column} is | |
1786 | @code{nil}, @code{indent-region} indents each nonblank line by calling | |
1787 | the current mode's indentation function, the value of | |
1788 | @code{indent-line-function}. | |
1789 | ||
1790 | If @var{to-column} is non-@code{nil}, it should be an integer | |
1791 | specifying the number of columns of indentation; then this function | |
1792 | gives each line exactly that much indentation, by either adding or | |
1793 | deleting whitespace. | |
1794 | ||
1795 | If there is a fill prefix, @code{indent-region} indents each line | |
1796 | by making it start with the fill prefix. | |
1797 | @end deffn | |
1798 | ||
1799 | @defvar indent-region-function | |
1800 | The value of this variable is a function that can be used by | |
1801 | @code{indent-region} as a short cut. You should design the function so | |
1802 | that it will produce the same results as indenting the lines of the | |
1803 | region one by one, but presumably faster. | |
1804 | ||
1805 | If the value is @code{nil}, there is no short cut, and | |
1806 | @code{indent-region} actually works line by line. | |
1807 | ||
61cfa852 | 1808 | A short-cut function is useful in modes such as C mode and Lisp mode, |
73804d4b | 1809 | where the @code{indent-line-function} must scan from the beginning of |
61cfa852 RS |
1810 | the function definition: applying it to each line would be quadratic in |
1811 | time. The short cut can update the scan information as it moves through | |
1812 | the lines indenting them; this takes linear time. In a mode where | |
1813 | indenting a line individually is fast, there is no need for a short cut. | |
73804d4b | 1814 | |
61cfa852 RS |
1815 | @code{indent-region} with a non-@code{nil} argument @var{to-column} has |
1816 | a different meaning and does not use this variable. | |
73804d4b RS |
1817 | @end defvar |
1818 | ||
1819 | @deffn Command indent-rigidly start end count | |
1820 | @comment !!SourceFile indent.el | |
1821 | This command indents all lines starting between @var{start} | |
1822 | (inclusive) and @var{end} (exclusive) sideways by @var{count} columns. | |
1823 | This ``preserves the shape'' of the affected region, moving it as a | |
1824 | rigid unit. Consequently, this command is useful not only for indenting | |
1825 | regions of unindented text, but also for indenting regions of formatted | |
1826 | code. | |
1827 | ||
1828 | For example, if @var{count} is 3, this command adds 3 columns of | |
1829 | indentation to each of the lines beginning in the region specified. | |
1830 | ||
1831 | In Mail mode, @kbd{C-c C-y} (@code{mail-yank-original}) uses | |
1832 | @code{indent-rigidly} to indent the text copied from the message being | |
1833 | replied to. | |
1834 | @end deffn | |
1835 | ||
1836 | @defun indent-code-rigidly start end columns &optional nochange-regexp | |
1837 | This is like @code{indent-rigidly}, except that it doesn't alter lines | |
1838 | that start within strings or comments. | |
1839 | ||
1840 | In addition, it doesn't alter a line if @var{nochange-regexp} matches at | |
1841 | the beginning of the line (if @var{nochange-regexp} is non-@code{nil}). | |
1842 | @end defun | |
1843 | ||
1844 | @node Relative Indent | |
1845 | @subsection Indentation Relative to Previous Lines | |
1846 | ||
61cfa852 | 1847 | This section describes two commands that indent the current line |
73804d4b RS |
1848 | based on the contents of previous lines. |
1849 | ||
1850 | @deffn Command indent-relative &optional unindented-ok | |
1851 | This command inserts whitespace at point, extending to the same | |
1852 | column as the next @dfn{indent point} of the previous nonblank line. An | |
1853 | indent point is a non-whitespace character following whitespace. The | |
1854 | next indent point is the first one at a column greater than the current | |
1855 | column of point. For example, if point is underneath and to the left of | |
1856 | the first non-blank character of a line of text, it moves to that column | |
1857 | by inserting whitespace. | |
1858 | ||
1859 | If the previous nonblank line has no next indent point (i.e., none at a | |
1860 | great enough column position), @code{indent-relative} either does | |
1861 | nothing (if @var{unindented-ok} is non-@code{nil}) or calls | |
1862 | @code{tab-to-tab-stop}. Thus, if point is underneath and to the right | |
1863 | of the last column of a short line of text, this command ordinarily | |
1864 | moves point to the next tab stop by inserting whitespace. | |
1865 | ||
1866 | The return value of @code{indent-relative} is unpredictable. | |
1867 | ||
1868 | In the following example, point is at the beginning of the second | |
1869 | line: | |
1870 | ||
1871 | @example | |
1872 | @group | |
1873 | This line is indented twelve spaces. | |
1874 | @point{}The quick brown fox jumped. | |
1875 | @end group | |
1876 | @end example | |
1877 | ||
1878 | @noindent | |
1879 | Evaluation of the expression @code{(indent-relative nil)} produces the | |
1880 | following: | |
1881 | ||
1882 | @example | |
1883 | @group | |
1884 | This line is indented twelve spaces. | |
1885 | @point{}The quick brown fox jumped. | |
1886 | @end group | |
1887 | @end example | |
1888 | ||
1889 | In this example, point is between the @samp{m} and @samp{p} of | |
1890 | @samp{jumped}: | |
1891 | ||
1892 | @example | |
1893 | @group | |
1894 | This line is indented twelve spaces. | |
1895 | The quick brown fox jum@point{}ped. | |
1896 | @end group | |
1897 | @end example | |
1898 | ||
1899 | @noindent | |
1900 | Evaluation of the expression @code{(indent-relative nil)} produces the | |
1901 | following: | |
1902 | ||
1903 | @example | |
1904 | @group | |
1905 | This line is indented twelve spaces. | |
1906 | The quick brown fox jum @point{}ped. | |
1907 | @end group | |
1908 | @end example | |
1909 | @end deffn | |
1910 | ||
1911 | @deffn Command indent-relative-maybe | |
1912 | @comment !!SourceFile indent.el | |
1913 | This command indents the current line like the previous nonblank line. | |
1914 | It calls @code{indent-relative} with @code{t} as the @var{unindented-ok} | |
1915 | argument. The return value is unpredictable. | |
1916 | ||
1917 | If the previous nonblank line has no indent points beyond the current | |
1918 | column, this command does nothing. | |
1919 | @end deffn | |
1920 | ||
1921 | @node Indent Tabs | |
1922 | @comment node-name, next, previous, up | |
1923 | @subsection Adjustable ``Tab Stops'' | |
1924 | @cindex tabs stops for indentation | |
1925 | ||
1926 | This section explains the mechanism for user-specified ``tab stops'' | |
61cfa852 | 1927 | and the mechanisms that use and set them. The name ``tab stops'' is |
73804d4b RS |
1928 | used because the feature is similar to that of the tab stops on a |
1929 | typewriter. The feature works by inserting an appropriate number of | |
1930 | spaces and tab characters to reach the next tab stop column; it does not | |
1931 | affect the display of tab characters in the buffer (@pxref{Usual | |
1932 | Display}). Note that the @key{TAB} character as input uses this tab | |
1933 | stop feature only in a few major modes, such as Text mode. | |
1934 | ||
1935 | @deffn Command tab-to-tab-stop | |
1936 | This command inserts spaces or tabs up to the next tab stop column | |
1937 | defined by @code{tab-stop-list}. It searches the list for an element | |
1938 | greater than the current column number, and uses that element as the | |
1939 | column to indent to. It does nothing if no such element is found. | |
1940 | @end deffn | |
1941 | ||
1942 | @defopt tab-stop-list | |
1943 | This variable is the list of tab stop columns used by | |
1944 | @code{tab-to-tab-stops}. The elements should be integers in increasing | |
1945 | order. The tab stop columns need not be evenly spaced. | |
1946 | ||
1947 | Use @kbd{M-x edit-tab-stops} to edit the location of tab stops | |
1948 | interactively. | |
1949 | @end defopt | |
1950 | ||
1951 | @node Motion by Indent | |
1952 | @subsection Indentation-Based Motion Commands | |
1953 | ||
1954 | These commands, primarily for interactive use, act based on the | |
1955 | indentation in the text. | |
1956 | ||
1957 | @deffn Command back-to-indentation | |
1958 | @comment !!SourceFile simple.el | |
1959 | This command moves point to the first non-whitespace character in the | |
1960 | current line (which is the line in which point is located). It returns | |
1961 | @code{nil}. | |
1962 | @end deffn | |
1963 | ||
1964 | @deffn Command backward-to-indentation arg | |
1965 | @comment !!SourceFile simple.el | |
1966 | This command moves point backward @var{arg} lines and then to the | |
1967 | first nonblank character on that line. It returns @code{nil}. | |
1968 | @end deffn | |
1969 | ||
1970 | @deffn Command forward-to-indentation arg | |
1971 | @comment !!SourceFile simple.el | |
1972 | This command moves point forward @var{arg} lines and then to the first | |
1973 | nonblank character on that line. It returns @code{nil}. | |
1974 | @end deffn | |
1975 | ||
1976 | @node Case Changes | |
1977 | @comment node-name, next, previous, up | |
1978 | @section Case Changes | |
1979 | @cindex case changes | |
1980 | ||
1981 | The case change commands described here work on text in the current | |
1982 | buffer. @xref{Character Case}, for case conversion commands that work | |
1983 | on strings and characters. @xref{Case Table}, for how to customize | |
1984 | which characters are upper or lower case and how to convert them. | |
1985 | ||
1986 | @deffn Command capitalize-region start end | |
1987 | This function capitalizes all words in the region defined by | |
1988 | @var{start} and @var{end}. To capitalize means to convert each word's | |
1989 | first character to upper case and convert the rest of each word to lower | |
1990 | case. The function returns @code{nil}. | |
1991 | ||
1992 | If one end of the region is in the middle of a word, the part of the | |
1993 | word within the region is treated as an entire word. | |
1994 | ||
1995 | When @code{capitalize-region} is called interactively, @var{start} and | |
1996 | @var{end} are point and the mark, with the smallest first. | |
1997 | ||
1998 | @example | |
1999 | @group | |
2000 | ---------- Buffer: foo ---------- | |
2001 | This is the contents of the 5th foo. | |
2002 | ---------- Buffer: foo ---------- | |
2003 | @end group | |
2004 | ||
2005 | @group | |
2006 | (capitalize-region 1 44) | |
2007 | @result{} nil | |
2008 | ||
2009 | ---------- Buffer: foo ---------- | |
2010 | This Is The Contents Of The 5th Foo. | |
2011 | ---------- Buffer: foo ---------- | |
2012 | @end group | |
2013 | @end example | |
2014 | @end deffn | |
2015 | ||
2016 | @deffn Command downcase-region start end | |
2017 | This function converts all of the letters in the region defined by | |
2018 | @var{start} and @var{end} to lower case. The function returns | |
2019 | @code{nil}. | |
2020 | ||
2021 | When @code{downcase-region} is called interactively, @var{start} and | |
2022 | @var{end} are point and the mark, with the smallest first. | |
2023 | @end deffn | |
2024 | ||
2025 | @deffn Command upcase-region start end | |
2026 | This function converts all of the letters in the region defined by | |
2027 | @var{start} and @var{end} to upper case. The function returns | |
2028 | @code{nil}. | |
2029 | ||
2030 | When @code{upcase-region} is called interactively, @var{start} and | |
2031 | @var{end} are point and the mark, with the smallest first. | |
2032 | @end deffn | |
2033 | ||
2034 | @deffn Command capitalize-word count | |
2035 | This function capitalizes @var{count} words after point, moving point | |
2036 | over as it does. To capitalize means to convert each word's first | |
2037 | character to upper case and convert the rest of each word to lower case. | |
2038 | If @var{count} is negative, the function capitalizes the | |
2039 | @minus{}@var{count} previous words but does not move point. The value | |
2040 | is @code{nil}. | |
2041 | ||
61cfa852 RS |
2042 | If point is in the middle of a word, the part of the word before point |
2043 | is ignored when moving forward. The rest is treated as an entire word. | |
73804d4b RS |
2044 | |
2045 | When @code{capitalize-word} is called interactively, @var{count} is | |
2046 | set to the numeric prefix argument. | |
2047 | @end deffn | |
2048 | ||
2049 | @deffn Command downcase-word count | |
2050 | This function converts the @var{count} words after point to all lower | |
2051 | case, moving point over as it does. If @var{count} is negative, it | |
2052 | converts the @minus{}@var{count} previous words but does not move point. | |
2053 | The value is @code{nil}. | |
2054 | ||
2055 | When @code{downcase-word} is called interactively, @var{count} is set | |
2056 | to the numeric prefix argument. | |
2057 | @end deffn | |
2058 | ||
2059 | @deffn Command upcase-word count | |
2060 | This function converts the @var{count} words after point to all upper | |
2061 | case, moving point over as it does. If @var{count} is negative, it | |
2062 | converts the @minus{}@var{count} previous words but does not move point. | |
2063 | The value is @code{nil}. | |
2064 | ||
2065 | When @code{upcase-word} is called interactively, @var{count} is set to | |
2066 | the numeric prefix argument. | |
2067 | @end deffn | |
2068 | ||
2069 | @node Text Properties | |
2070 | @section Text Properties | |
2071 | @cindex text properties | |
2072 | @cindex attributes of text | |
2073 | @cindex properties of text | |
2074 | ||
2075 | Each character position in a buffer or a string can have a @dfn{text | |
2076 | property list}, much like the property list of a symbol (@pxref{Property | |
2077 | Lists}). The properties belong to a particular character at a | |
2078 | particular place, such as, the letter @samp{T} at the beginning of this | |
2079 | sentence or the first @samp{o} in @samp{foo}---if the same character | |
2080 | occurs in two different places, the two occurrences generally have | |
2081 | different properties. | |
2082 | ||
2083 | Each property has a name and a value. Both of these can be any Lisp | |
2084 | object, but the name is normally a symbol. The usual way to access the | |
2085 | property list is to specify a name and ask what value corresponds to it. | |
2086 | ||
2087 | If a character has a @code{category} property, we call it the | |
2088 | @dfn{category} of the character. It should be a symbol. The properties | |
2089 | of the symbol serve as defaults for the properties of the character. | |
2090 | ||
2091 | Copying text between strings and buffers preserves the properties | |
2092 | along with the characters; this includes such diverse functions as | |
2093 | @code{substring}, @code{insert}, and @code{buffer-substring}. | |
2094 | ||
2095 | @menu | |
2096 | * Examining Properties:: Looking at the properties of one character. | |
2097 | * Changing Properties:: Setting the properties of a range of text. | |
2098 | * Property Search:: Searching for where a property changes value. | |
2099 | * Special Properties:: Particular properties with special meanings. | |
22697dac | 2100 | * Format Properties:: Properties for representing formatting of text. |
73804d4b RS |
2101 | * Sticky Properties:: How inserted text gets properties from |
2102 | neighboring text. | |
2103 | * Saving Properties:: Saving text properties in files, and reading | |
2104 | them back. | |
61ee3601 RS |
2105 | * Lazy Properties:: Computing text properties in a lazy fashion |
2106 | only when text is examined. | |
73804d4b RS |
2107 | * Not Intervals:: Why text properties do not use |
2108 | Lisp-visible text intervals. | |
2109 | @end menu | |
2110 | ||
2111 | @node Examining Properties | |
2112 | @subsection Examining Text Properties | |
2113 | ||
2114 | The simplest way to examine text properties is to ask for the value of | |
2115 | a particular property of a particular character. For that, use | |
2116 | @code{get-text-property}. Use @code{text-properties-at} to get the | |
2117 | entire property list of a character. @xref{Property Search}, for | |
2118 | functions to examine the properties of a number of characters at once. | |
2119 | ||
2120 | These functions handle both strings and buffers. Keep in mind that | |
2121 | positions in a string start from 0, whereas positions in a buffer start | |
2122 | from 1. | |
2123 | ||
2124 | @defun get-text-property pos prop &optional object | |
2125 | This function returns the value of the @var{prop} property of the | |
2126 | character after position @var{pos} in @var{object} (a buffer or | |
2127 | string). The argument @var{object} is optional and defaults to the | |
2128 | current buffer. | |
2129 | ||
2130 | If there is no @var{prop} property strictly speaking, but the character | |
61cfa852 | 2131 | has a category that is a symbol, then @code{get-text-property} returns |
73804d4b RS |
2132 | the @var{prop} property of that symbol. |
2133 | @end defun | |
2134 | ||
2135 | @defun get-char-property pos prop &optional object | |
2136 | This function is like @code{get-text-property}, except that it checks | |
2137 | overlays first and then text properties. @xref{Overlays}. | |
2138 | ||
2139 | The argument @var{object} may be a string, a buffer, or a window. If it | |
2140 | is a window, then the buffer displayed in that window is used for text | |
2141 | properties and overlays, but only the overlays active for that window | |
2142 | are considered. If @var{object} is a buffer, then all overlays in that | |
2143 | buffer are considered, as well as text properties. If @var{object} is a | |
2144 | string, only text properties are considered, since strings never have | |
2145 | overlays. | |
2146 | @end defun | |
2147 | ||
2148 | @defun text-properties-at position &optional object | |
2149 | This function returns the entire property list of the character at | |
2150 | @var{position} in the string or buffer @var{object}. If @var{object} is | |
2151 | @code{nil}, it defaults to the current buffer. | |
2152 | @end defun | |
2153 | ||
22697dac KH |
2154 | @defvar default-text-properties |
2155 | This variable holds a property list giving default values for text | |
2156 | properties. Whenever a character does not specify a value for a | |
bfe721d1 KH |
2157 | property, neither directly nor through a category symbol, the value |
2158 | stored in this list is used instead. Here is an example: | |
22697dac KH |
2159 | |
2160 | @example | |
2161 | (setq default-text-properties '(foo 69)) | |
2162 | ;; @r{Make sure character 1 has no properties of its own.} | |
2163 | (set-text-properties 1 2 nil) | |
2164 | ;; @r{What we get, when we ask, is the default value.} | |
2165 | (get-text-property 1 'foo) | |
2166 | @result{} 69 | |
2167 | @end example | |
2168 | @end defvar | |
2169 | ||
73804d4b RS |
2170 | @node Changing Properties |
2171 | @subsection Changing Text Properties | |
2172 | ||
2173 | The primitives for changing properties apply to a specified range of | |
e78ea3db RS |
2174 | text in a buffer or string. The function @code{set-text-properties} |
2175 | (see end of section) sets the entire property list of the text in that | |
2176 | range; more often, it is useful to add, change, or delete just certain | |
2177 | properties specified by name. | |
73804d4b | 2178 | |
e78ea3db RS |
2179 | Since text properties are considered part of the contents of the |
2180 | buffer (or string), and can affect how a buffer looks on the screen, any | |
2181 | change in buffer text properties mark the buffer as modified. Buffer | |
2182 | text property changes are undoable also (@pxref{Undo}). | |
73804d4b | 2183 | |
bfe721d1 KH |
2184 | @defun put-text-property start end prop value &optional object |
2185 | This function sets the @var{prop} property to @var{value} for the text | |
2186 | between @var{start} and @var{end} in the string or buffer @var{object}. | |
2187 | If @var{object} is @code{nil}, it defaults to the current buffer. | |
2188 | @end defun | |
2189 | ||
73804d4b RS |
2190 | @defun add-text-properties start end props &optional object |
2191 | This function modifies the text properties for the text between | |
2192 | @var{start} and @var{end} in the string or buffer @var{object}. If | |
2193 | @var{object} is @code{nil}, it defaults to the current buffer. | |
2194 | ||
2195 | The argument @var{props} specifies which properties to change. It | |
2196 | should have the form of a property list (@pxref{Property Lists}): a list | |
2197 | whose elements include the property names followed alternately by the | |
2198 | corresponding values. | |
2199 | ||
2200 | The return value is @code{t} if the function actually changed some | |
2201 | property's value; @code{nil} otherwise (if @var{props} is @code{nil} or | |
2202 | its values agree with those in the text). | |
2203 | ||
2204 | For example, here is how to set the @code{comment} and @code{face} | |
2205 | properties of a range of text: | |
2206 | ||
2207 | @example | |
2208 | (add-text-properties @var{start} @var{end} | |
2209 | '(comment t face highlight)) | |
2210 | @end example | |
2211 | @end defun | |
2212 | ||
73804d4b RS |
2213 | @defun remove-text-properties start end props &optional object |
2214 | This function deletes specified text properties from the text between | |
2215 | @var{start} and @var{end} in the string or buffer @var{object}. If | |
2216 | @var{object} is @code{nil}, it defaults to the current buffer. | |
2217 | ||
2218 | The argument @var{props} specifies which properties to delete. It | |
2219 | should have the form of a property list (@pxref{Property Lists}): a list | |
2220 | whose elements are property names alternating with corresponding values. | |
2221 | But only the names matter---the values that accompany them are ignored. | |
2222 | For example, here's how to remove the @code{face} property. | |
2223 | ||
2224 | @example | |
2225 | (remove-text-properties @var{start} @var{end} '(face nil)) | |
2226 | @end example | |
2227 | ||
2228 | The return value is @code{t} if the function actually changed some | |
2229 | property's value; @code{nil} otherwise (if @var{props} is @code{nil} or | |
2230 | if no character in the specified text had any of those properties). | |
e78ea3db RS |
2231 | |
2232 | To remove all text properties from certain text, use | |
2233 | @code{set-text-properties} and specify @code{nil} for the new property | |
2234 | list. | |
73804d4b RS |
2235 | @end defun |
2236 | ||
2237 | @defun set-text-properties start end props &optional object | |
2238 | This function completely replaces the text property list for the text | |
2239 | between @var{start} and @var{end} in the string or buffer @var{object}. | |
2240 | If @var{object} is @code{nil}, it defaults to the current buffer. | |
2241 | ||
2242 | The argument @var{props} is the new property list. It should be a list | |
2243 | whose elements are property names alternating with corresponding values. | |
2244 | ||
2245 | After @code{set-text-properties} returns, all the characters in the | |
2246 | specified range have identical properties. | |
2247 | ||
2248 | If @var{props} is @code{nil}, the effect is to get rid of all properties | |
2249 | from the specified range of text. Here's an example: | |
2250 | ||
2251 | @example | |
2252 | (set-text-properties @var{start} @var{end} nil) | |
2253 | @end example | |
2254 | @end defun | |
2255 | ||
371f8cd0 | 2256 | See also the function @code{buffer-substring-no-properties} |
22697dac KH |
2257 | (@pxref{Buffer Contents}) which copies text from the buffer |
2258 | but does not copy its properties. | |
2259 | ||
73804d4b RS |
2260 | @node Property Search |
2261 | @subsection Property Search Functions | |
2262 | ||
2263 | In typical use of text properties, most of the time several or many | |
2264 | consecutive characters have the same value for a property. Rather than | |
2265 | writing your programs to examine characters one by one, it is much | |
2266 | faster to process chunks of text that have the same property value. | |
2267 | ||
bfe721d1 KH |
2268 | Here are functions you can use to do this. They use @code{eq} for |
2269 | comparing property values. In all cases, @var{object} defaults to the | |
2270 | current buffer. | |
73804d4b RS |
2271 | |
2272 | For high performance, it's very important to use the @var{limit} | |
2273 | argument to these functions, especially the ones that search for a | |
bfe721d1 KH |
2274 | single property---otherwise, they may spend a long time scanning to the |
2275 | end of the buffer, if the property you are interested in does not change. | |
73804d4b | 2276 | |
61cfa852 RS |
2277 | Remember that a position is always between two characters; the position |
2278 | returned by these functions is between two characters with different | |
2279 | properties. | |
2280 | ||
73804d4b RS |
2281 | @defun next-property-change pos &optional object limit |
2282 | The function scans the text forward from position @var{pos} in the | |
2283 | string or buffer @var{object} till it finds a change in some text | |
2284 | property, then returns the position of the change. In other words, it | |
2285 | returns the position of the first character beyond @var{pos} whose | |
2286 | properties are not identical to those of the character just after | |
2287 | @var{pos}. | |
2288 | ||
2289 | If @var{limit} is non-@code{nil}, then the scan ends at position | |
2290 | @var{limit}. If there is no property change before that point, | |
2291 | @code{next-property-change} returns @var{limit}. | |
2292 | ||
2293 | The value is @code{nil} if the properties remain unchanged all the way | |
61cfa852 RS |
2294 | to the end of @var{object} and @var{limit} is @code{nil}. If the value |
2295 | is non-@code{nil}, it is a position greater than or equal to @var{pos}. | |
2296 | The value equals @var{pos} only when @var{limit} equals @var{pos}. | |
73804d4b RS |
2297 | |
2298 | Here is an example of how to scan the buffer by chunks of text within | |
2299 | which all properties are constant: | |
2300 | ||
2301 | @smallexample | |
2302 | (while (not (eobp)) | |
2303 | (let ((plist (text-properties-at (point))) | |
2304 | (next-change | |
2305 | (or (next-property-change (point) (current-buffer)) | |
2306 | (point-max)))) | |
2307 | @r{Process text from point to @var{next-change}@dots{}} | |
2308 | (goto-char next-change))) | |
2309 | @end smallexample | |
2310 | @end defun | |
2311 | ||
2312 | @defun next-single-property-change pos prop &optional object limit | |
2313 | The function scans the text forward from position @var{pos} in the | |
2314 | string or buffer @var{object} till it finds a change in the @var{prop} | |
2315 | property, then returns the position of the change. In other words, it | |
2316 | returns the position of the first character beyond @var{pos} whose | |
2317 | @var{prop} property differs from that of the character just after | |
2318 | @var{pos}. | |
2319 | ||
2320 | If @var{limit} is non-@code{nil}, then the scan ends at position | |
2321 | @var{limit}. If there is no property change before that point, | |
2322 | @code{next-single-property-change} returns @var{limit}. | |
2323 | ||
2324 | The value is @code{nil} if the property remains unchanged all the way to | |
2325 | the end of @var{object} and @var{limit} is @code{nil}. If the value is | |
2326 | non-@code{nil}, it is a position greater than or equal to @var{pos}; it | |
2327 | equals @var{pos} only if @var{limit} equals @var{pos}. | |
2328 | @end defun | |
2329 | ||
2330 | @defun previous-property-change pos &optional object limit | |
2331 | This is like @code{next-property-change}, but scans back from @var{pos} | |
2332 | instead of forward. If the value is non-@code{nil}, it is a position | |
2333 | less than or equal to @var{pos}; it equals @var{pos} only if @var{limit} | |
2334 | equals @var{pos}. | |
73804d4b RS |
2335 | @end defun |
2336 | ||
2337 | @defun previous-single-property-change pos prop &optional object limit | |
61cfa852 RS |
2338 | This is like @code{next-single-property-change}, but scans back from |
2339 | @var{pos} instead of forward. If the value is non-@code{nil}, it is a | |
2340 | position less than or equal to @var{pos}; it equals @var{pos} only if | |
2341 | @var{limit} equals @var{pos}. | |
73804d4b RS |
2342 | @end defun |
2343 | ||
2344 | @defun text-property-any start end prop value &optional object | |
2345 | This function returns non-@code{nil} if at least one character between | |
2346 | @var{start} and @var{end} has a property @var{prop} whose value is | |
2347 | @var{value}. More precisely, it returns the position of the first such | |
2348 | character. Otherwise, it returns @code{nil}. | |
2349 | ||
2350 | The optional fifth argument, @var{object}, specifies the string or | |
2351 | buffer to scan. Positions are relative to @var{object}. The default | |
2352 | for @var{object} is the current buffer. | |
2353 | @end defun | |
2354 | ||
2355 | @defun text-property-not-all start end prop value &optional object | |
2356 | This function returns non-@code{nil} if at least one character between | |
2357 | @var{start} and @var{end} has a property @var{prop} whose value differs | |
2358 | from @var{value}. More precisely, it returns the position of the | |
2359 | first such character. Otherwise, it returns @code{nil}. | |
2360 | ||
2361 | The optional fifth argument, @var{object}, specifies the string or | |
2362 | buffer to scan. Positions are relative to @var{object}. The default | |
2363 | for @var{object} is the current buffer. | |
2364 | @end defun | |
2365 | ||
2366 | @node Special Properties | |
2367 | @subsection Properties with Special Meanings | |
2368 | ||
bfe721d1 KH |
2369 | Here is a table of text property names that have special built-in |
2370 | meanings. The following section lists a few more special property names | |
2371 | that are used to control filling. All other names have no standard | |
2372 | meaning, and you can use them as you like. | |
2373 | ||
73804d4b RS |
2374 | @table @code |
2375 | @cindex category of text character | |
2376 | @kindex category @r{(text property)} | |
2377 | @item category | |
2378 | If a character has a @code{category} property, we call it the | |
2379 | @dfn{category} of the character. It should be a symbol. The properties | |
2380 | of the symbol serve as defaults for the properties of the character. | |
2381 | ||
2382 | @item face | |
2383 | @cindex face codes of text | |
2384 | @kindex face @r{(text property)} | |
2385 | You can use the property @code{face} to control the font and color of | |
22697dac KH |
2386 | text. Its value is a face name or a list of face names. @xref{Faces}, |
2387 | for more information. This feature may be temporary; in the future, we | |
2388 | may replace it with other ways of specifying how to display text. | |
73804d4b RS |
2389 | |
2390 | @item mouse-face | |
2391 | @kindex mouse-face @r{(text property)} | |
2392 | The property @code{mouse-face} is used instead of @code{face} when the | |
2393 | mouse is on or near the character. For this purpose, ``near'' means | |
2394 | that all text between the character and where the mouse is have the same | |
2395 | @code{mouse-face} property value. | |
2396 | ||
2397 | @item local-map | |
2398 | @cindex keymap of character | |
2399 | @kindex local-map @r{(text property)} | |
61cfa852 RS |
2400 | You can specify a different keymap for a portion of the text by means of |
2401 | a @code{local-map} property. The property's value for the character | |
2402 | after point, if non-@code{nil}, replaces the buffer's local map. | |
2403 | @xref{Active Keymaps}. | |
73804d4b RS |
2404 | |
2405 | @item read-only | |
2406 | @cindex read-only character | |
2407 | @kindex read-only @r{(text property)} | |
2408 | If a character has the property @code{read-only}, then modifying that | |
2409 | character is not allowed. Any command that would do so gets an error. | |
2410 | ||
2411 | Insertion next to a read-only character is an error if inserting | |
2412 | ordinary text there would inherit the @code{read-only} property due to | |
2413 | stickiness. Thus, you can control permission to insert next to | |
2414 | read-only text by controlling the stickiness. @xref{Sticky Properties}. | |
2415 | ||
2416 | Since changing properties counts as modifying the buffer, it is not | |
2417 | possible to remove a @code{read-only} property unless you know the | |
2418 | special trick: bind @code{inhibit-read-only} to a non-@code{nil} value | |
2419 | and then remove the property. @xref{Read Only Buffers}. | |
2420 | ||
2421 | @item invisible | |
2422 | @kindex invisible @r{(text property)} | |
22697dac KH |
2423 | A non-@code{nil} @code{invisible} property can make a character invisible |
2424 | on the screen. @xref{Invisible Text}, for details. | |
73804d4b | 2425 | |
72654a3c RS |
2426 | @item intangible |
2427 | @kindex intangible @r{(text property)} | |
22697dac KH |
2428 | If a group of consecutive characters have equal and non-@code{nil} |
2429 | @code{intangible} properties, then you cannot place point between them. | |
bfe721d1 KH |
2430 | If you try to move point forward into the group, point actually moves to |
2431 | the end of the group. If you try to move point backward into the group, | |
22697dac KH |
2432 | point actually moves to the start of the group. |
2433 | ||
2434 | When the variable @code{inhibit-point-motion-hooks} is non-@code{nil}, | |
2435 | the @code{intangible} property is ignored. | |
72654a3c | 2436 | |
73804d4b RS |
2437 | @item modification-hooks |
2438 | @cindex change hooks for a character | |
2439 | @cindex hooks for changing a character | |
2440 | @kindex modification-hooks @r{(text property)} | |
2441 | If a character has the property @code{modification-hooks}, then its | |
2442 | value should be a list of functions; modifying that character calls all | |
2443 | of those functions. Each function receives two arguments: the beginning | |
2444 | and end of the part of the buffer being modified. Note that if a | |
2445 | particular modification hook function appears on several characters | |
2446 | being modified by a single primitive, you can't predict how many times | |
2447 | the function will be called. | |
2448 | ||
2449 | @item insert-in-front-hooks | |
2450 | @itemx insert-behind-hooks | |
2451 | @kindex insert-in-front-hooks @r{(text property)} | |
2452 | @kindex insert-behind-hooks @r{(text property)} | |
9ea65df9 RS |
2453 | The operation of inserting text in a buffer also calls the functions |
2454 | listed in the @code{insert-in-front-hooks} property of the following | |
2455 | character and in the @code{insert-behind-hooks} property of the | |
2456 | preceding character. These functions receive two arguments, the | |
2457 | beginning and end of the inserted text. The functions are called | |
2458 | @emph{after} the actual insertion takes place. | |
73804d4b RS |
2459 | |
2460 | See also @ref{Change Hooks}, for other hooks that are called | |
2461 | when you change text in a buffer. | |
2462 | ||
2463 | @item point-entered | |
2464 | @itemx point-left | |
2465 | @cindex hooks for motion of point | |
2466 | @kindex point-entered @r{(text property)} | |
2467 | @kindex point-left @r{(text property)} | |
2468 | The special properties @code{point-entered} and @code{point-left} | |
2469 | record hook functions that report motion of point. Each time point | |
2470 | moves, Emacs compares these two property values: | |
2471 | ||
2472 | @itemize @bullet | |
2473 | @item | |
2474 | the @code{point-left} property of the character after the old location, | |
2475 | and | |
2476 | @item | |
2477 | the @code{point-entered} property of the character after the new | |
2478 | location. | |
2479 | @end itemize | |
2480 | ||
2481 | @noindent | |
2482 | If these two values differ, each of them is called (if not @code{nil}) | |
2483 | with two arguments: the old value of point, and the new one. | |
2484 | ||
2485 | The same comparison is made for the characters before the old and new | |
2486 | locations. The result may be to execute two @code{point-left} functions | |
2487 | (which may be the same function) and/or two @code{point-entered} | |
61cfa852 RS |
2488 | functions (which may be the same function). In any case, all the |
2489 | @code{point-left} functions are called first, followed by all the | |
2490 | @code{point-entered} functions. | |
73804d4b RS |
2491 | |
2492 | A primitive function may examine characters at various positions | |
2493 | without moving point to those positions. Only an actual change in the | |
2494 | value of point runs these hook functions. | |
2495 | @end table | |
2496 | ||
2497 | @defvar inhibit-point-motion-hooks | |
2498 | When this variable is non-@code{nil}, @code{point-left} and | |
22697dac KH |
2499 | @code{point-entered} hooks are not run, and the @code{intangible} |
2500 | property has no effect. | |
73804d4b RS |
2501 | @end defvar |
2502 | ||
22697dac | 2503 | @node Format Properties |
bfe721d1 | 2504 | @subsection Formatted Text Properties |
22697dac KH |
2505 | |
2506 | These text properties affect the behavior of the fill commands. They | |
bfe721d1 KH |
2507 | are used for representing formatted text. @xref{Filling}, and |
2508 | @ref{Margins}. | |
22697dac | 2509 | |
bfe721d1 | 2510 | @table @code |
22697dac KH |
2511 | @item hard |
2512 | If a newline character has this property, it is a ``hard'' newline. | |
2513 | The fill commands do not alter hard newlines and do not move words | |
2514 | across them. However, this property takes effect only if the variable | |
2515 | @code{use-hard-newlines} is non-@code{nil}. | |
2516 | ||
2517 | @item right-margin | |
bfe721d1 | 2518 | This property specifies an extra right margin for filling this part of the |
22697dac KH |
2519 | text. |
2520 | ||
2521 | @item left-margin | |
bfe721d1 | 2522 | This property specifies an extra left margin for filling this part of the |
22697dac KH |
2523 | text. |
2524 | ||
2525 | @item justification | |
2526 | This property specifies the style of justification for filling this part | |
2527 | of the text. | |
2528 | @end table | |
2529 | ||
73804d4b RS |
2530 | @node Sticky Properties |
2531 | @subsection Stickiness of Text Properties | |
2532 | @cindex sticky text properties | |
2533 | @cindex inheritance of text properties | |
2534 | ||
2535 | Self-inserting characters normally take on the same properties as the | |
2536 | preceding character. This is called @dfn{inheritance} of properties. | |
2537 | ||
2538 | In a Lisp program, you can do insertion with inheritance or without, | |
2539 | depending on your choice of insertion primitive. The ordinary text | |
2540 | insertion functions such as @code{insert} do not inherit any properties. | |
2541 | They insert text with precisely the properties of the string being | |
2542 | inserted, and no others. This is correct for programs that copy text | |
61cfa852 RS |
2543 | from one context to another---for example, into or out of the kill ring. |
2544 | To insert with inheritance, use the special primitives described in this | |
2545 | section. Self-inserting characters inherit properties because they work | |
2546 | using these primitives. | |
73804d4b RS |
2547 | |
2548 | When you do insertion with inheritance, @emph{which} properties are | |
2549 | inherited depends on two specific properties: @code{front-sticky} and | |
2550 | @code{rear-nonsticky}. | |
2551 | ||
2552 | Insertion after a character inherits those of its properties that are | |
2553 | @dfn{rear-sticky}. Insertion before a character inherits those of its | |
2554 | properties that are @dfn{front-sticky}. By default, a text property is | |
2555 | rear-sticky but not front-sticky. Thus, the default is to inherit all | |
2556 | the properties of the preceding character, and nothing from the | |
2557 | following character. You can request different behavior by specifying | |
2558 | the stickiness of certain properties. | |
2559 | ||
2560 | If a character's @code{front-sticky} property is @code{t}, then all | |
2561 | its properties are front-sticky. If the @code{front-sticky} property is | |
2562 | a list, then the sticky properties of the character are those whose | |
2563 | names are in the list. For example, if a character has a | |
2564 | @code{front-sticky} property whose value is @code{(face read-only)}, | |
2565 | then insertion before the character can inherit its @code{face} property | |
2566 | and its @code{read-only} property, but no others. | |
2567 | ||
2568 | The @code{rear-nonsticky} works the opposite way. Every property is | |
2569 | rear-sticky by default, so the @code{rear-nonsticky} property says which | |
2570 | properties are @emph{not} rear-sticky. If a character's | |
2571 | @code{rear-nonsticky} property is @code{t}, then none of its properties | |
2572 | are rear-sticky. If the @code{rear-nonsticky} property is a list, | |
2573 | properties are rear-sticky @emph{unless} their names are in the list. | |
2574 | ||
2575 | When you insert text with inheritance, it inherits all the rear-sticky | |
2576 | properties of the preceding character, and all the front-sticky | |
2577 | properties of the following character. The previous character's | |
2578 | properties take precedence when both sides offer different sticky values | |
2579 | for the same property. | |
2580 | ||
2581 | Here are the functions that insert text with inheritance of properties: | |
2582 | ||
2583 | @defun insert-and-inherit &rest strings | |
2584 | Insert the strings @var{strings}, just like the function @code{insert}, | |
2585 | but inherit any sticky properties from the adjoining text. | |
2586 | @end defun | |
2587 | ||
2588 | @defun insert-before-markers-and-inherit &rest strings | |
2589 | Insert the strings @var{strings}, just like the function | |
2590 | @code{insert-before-markers}, but inherit any sticky properties from the | |
2591 | adjoining text. | |
2592 | @end defun | |
2593 | ||
2594 | @node Saving Properties | |
61cfa852 | 2595 | @subsection Saving Text Properties in Files |
73804d4b RS |
2596 | @cindex text properties in files |
2597 | @cindex saving text properties | |
2598 | ||
2599 | You can save text properties in files, and restore text properties | |
2600 | when inserting the files, using these two hooks: | |
2601 | ||
bfe721d1 | 2602 | @defvar write-region-annotate-functions |
73804d4b RS |
2603 | This variable's value is a list of functions for @code{write-region} to |
2604 | run to encode text properties in some fashion as annotations to the text | |
2605 | being written in the file. @xref{Writing to Files}. | |
2606 | ||
2607 | Each function in the list is called with two arguments: the start and | |
2608 | end of the region to be written. These functions should not alter the | |
2609 | contents of the buffer. Instead, they should return lists indicating | |
2610 | annotations to write in the file in addition to the text in the | |
2611 | buffer. | |
2612 | ||
2613 | Each function should return a list of elements of the form | |
2614 | @code{(@var{position} . @var{string})}, where @var{position} is an | |
2615 | integer specifying the relative position in the text to be written, and | |
2616 | @var{string} is the annotation to add there. | |
2617 | ||
2618 | Each list returned by one of these functions must be already sorted in | |
2619 | increasing order by @var{position}. If there is more than one function, | |
2620 | @code{write-region} merges the lists destructively into one sorted list. | |
2621 | ||
2622 | When @code{write-region} actually writes the text from the buffer to the | |
2623 | file, it intermixes the specified annotations at the corresponding | |
2624 | positions. All this takes place without modifying the buffer. | |
2625 | @end defvar | |
2626 | ||
2627 | @defvar after-insert-file-functions | |
2628 | This variable holds a list of functions for @code{insert-file-contents} | |
2629 | to call after inserting a file's contents. These functions should scan | |
2630 | the inserted text for annotations, and convert them to the text | |
2631 | properties they stand for. | |
2632 | ||
2633 | Each function receives one argument, the length of the inserted text; | |
2634 | point indicates the start of that text. The function should scan that | |
2635 | text for annotations, delete them, and create the text properties that | |
2636 | the annotations specify. The function should return the updated length | |
2637 | of the inserted text, as it stands after those changes. The value | |
2638 | returned by one function becomes the argument to the next function. | |
2639 | ||
2640 | These functions should always return with point at the beginning of | |
2641 | the inserted text. | |
2642 | ||
2643 | The intended use of @code{after-insert-file-functions} is for converting | |
2644 | some sort of textual annotations into actual text properties. But other | |
2645 | uses may be possible. | |
2646 | @end defvar | |
2647 | ||
2648 | We invite users to write Lisp programs to store and retrieve text | |
2649 | properties in files, using these hooks, and thus to experiment with | |
2650 | various data formats and find good ones. Eventually we hope users | |
2651 | will produce good, general extensions we can install in Emacs. | |
2652 | ||
2653 | We suggest not trying to handle arbitrary Lisp objects as property | |
2654 | names or property values---because a program that general is probably | |
2655 | difficult to write, and slow. Instead, choose a set of possible data | |
2656 | types that are reasonably flexible, and not too hard to encode. | |
2657 | ||
bfe721d1 KH |
2658 | @xref{Format Conversion}, for a related feature. |
2659 | ||
2660 | @c ??? In next edition, merge this info Format Conversion. | |
2661 | ||
61ee3601 RS |
2662 | @node Lazy Properties |
2663 | @subsection Lazy Computation of Text Properties | |
2664 | ||
2665 | Instead of computing text properties for all the text in the buffer, | |
2666 | you can arrange to compute the text properties for parts of the text | |
2667 | when and if something depends on them. | |
2668 | ||
2669 | The primitive that extracts text from the buffer along with its | |
2670 | properties is @code{buffer-substring}. Before examining the properties, | |
2671 | this function runs the abnormal hook @code{buffer-access-fontify-functions}. | |
2672 | ||
2673 | @defvar buffer-access-fontify-functions | |
2674 | This variable holds a list of functions for computing text properties. | |
2675 | Before @code{buffer-substring} copies the text and text properties for a | |
2676 | portion of the buffer, it calls all the functions in this list. Each of | |
2677 | the functions receives two arguments that specify the range of the | |
2678 | buffer being accessed. (The buffer itself is always the current | |
2679 | buffer.) | |
2680 | @end defvar | |
2681 | ||
2682 | The function @code{buffer-substring-no-properties} does not call these | |
2683 | functions, since it ignores text properties anyway. | |
2684 | ||
2685 | In order to prevent the hook functions from being called more than | |
2686 | once for the same part of the buffer, you can use the variable | |
2687 | @code{buffer-access-fontified-property}. | |
2688 | ||
2689 | @defvar buffer-access-fontified-property | |
2690 | If this value's variable is non-@code{nil}, it is a symbol which is used | |
2691 | as a text property name. A non-@code{nil} value for that text property | |
2692 | means, ``the other text properties for this character have already been | |
2693 | computed.'' | |
2694 | ||
2695 | If all the characters in the range specified for @code{buffer-substring} | |
2696 | have a non-@code{nil} value for this property, @code{buffer-substring} | |
2697 | does not call the @code{buffer-access-fontify-functions} functions. It | |
2698 | assumes these characters already have the right text properties, and | |
2699 | just copies the properties they already have. | |
2700 | ||
2701 | The normal way to use this feature is that the | |
2702 | @code{buffer-access-fontify-functions} functions add this property, as | |
2703 | well as others, to the characters they operate on. That way, they avoid | |
2704 | being called over and over for the same text. | |
2705 | @end defvar | |
2706 | ||
73804d4b RS |
2707 | @node Not Intervals |
2708 | @subsection Why Text Properties are not Intervals | |
2709 | @cindex intervals | |
2710 | ||
2711 | Some editors that support adding attributes to text in the buffer do | |
2712 | so by letting the user specify ``intervals'' within the text, and adding | |
2713 | the properties to the intervals. Those editors permit the user or the | |
2714 | programmer to determine where individual intervals start and end. We | |
2715 | deliberately provided a different sort of interface in Emacs Lisp to | |
2716 | avoid certain paradoxical behavior associated with text modification. | |
2717 | ||
2718 | If the actual subdivision into intervals is meaningful, that means you | |
2719 | can distinguish between a buffer that is just one interval with a | |
2720 | certain property, and a buffer containing the same text subdivided into | |
2721 | two intervals, both of which have that property. | |
2722 | ||
2723 | Suppose you take the buffer with just one interval and kill part of | |
2724 | the text. The text remaining in the buffer is one interval, and the | |
2725 | copy in the kill ring (and the undo list) becomes a separate interval. | |
2726 | Then if you yank back the killed text, you get two intervals with the | |
2727 | same properties. Thus, editing does not preserve the distinction | |
2728 | between one interval and two. | |
2729 | ||
2730 | Suppose we ``fix'' this problem by coalescing the two intervals when | |
2731 | the text is inserted. That works fine if the buffer originally was a | |
2732 | single interval. But suppose instead that we have two adjacent | |
2733 | intervals with the same properties, and we kill the text of one interval | |
2734 | and yank it back. The same interval-coalescence feature that rescues | |
2735 | the other case causes trouble in this one: after yanking, we have just | |
2736 | one interval. One again, editing does not preserve the distinction | |
2737 | between one interval and two. | |
2738 | ||
2739 | Insertion of text at the border between intervals also raises | |
2740 | questions that have no satisfactory answer. | |
2741 | ||
2742 | However, it is easy to arrange for editing to behave consistently for | |
2743 | questions of the form, ``What are the properties of this character?'' | |
2744 | So we have decided these are the only questions that make sense; we have | |
2745 | not implemented asking questions about where intervals start or end. | |
2746 | ||
2747 | In practice, you can usually use the property search functions in | |
2748 | place of explicit interval boundaries. You can think of them as finding | |
2749 | the boundaries of intervals, assuming that intervals are always | |
2750 | coalesced whenever possible. @xref{Property Search}. | |
2751 | ||
2752 | Emacs also provides explicit intervals as a presentation feature; see | |
2753 | @ref{Overlays}. | |
2754 | ||
2755 | @node Substitution | |
2756 | @section Substituting for a Character Code | |
2757 | ||
2758 | The following functions replace characters within a specified region | |
2759 | based on their character codes. | |
2760 | ||
2761 | @defun subst-char-in-region start end old-char new-char &optional noundo | |
2762 | @cindex replace characters | |
2763 | This function replaces all occurrences of the character @var{old-char} | |
2764 | with the character @var{new-char} in the region of the current buffer | |
2765 | defined by @var{start} and @var{end}. | |
2766 | ||
2767 | @cindex Outline mode | |
2768 | @cindex undo avoidance | |
bfe721d1 KH |
2769 | If @var{noundo} is non-@code{nil}, then @code{subst-char-in-region} does |
2770 | not record the change for undo and does not mark the buffer as modified. | |
2771 | This feature is used for controlling selective display (@pxref{Selective | |
2772 | Display}). | |
73804d4b RS |
2773 | |
2774 | @code{subst-char-in-region} does not move point and returns | |
2775 | @code{nil}. | |
2776 | ||
2777 | @example | |
2778 | @group | |
2779 | ---------- Buffer: foo ---------- | |
2780 | This is the contents of the buffer before. | |
2781 | ---------- Buffer: foo ---------- | |
2782 | @end group | |
2783 | ||
2784 | @group | |
2785 | (subst-char-in-region 1 20 ?i ?X) | |
2786 | @result{} nil | |
2787 | ||
2788 | ---------- Buffer: foo ---------- | |
2789 | ThXs Xs the contents of the buffer before. | |
2790 | ---------- Buffer: foo ---------- | |
2791 | @end group | |
2792 | @end example | |
2793 | @end defun | |
2794 | ||
2795 | @defun translate-region start end table | |
2796 | This function applies a translation table to the characters in the | |
2797 | buffer between positions @var{start} and @var{end}. | |
2798 | ||
2799 | The translation table @var{table} is a string; @code{(aref @var{table} | |
2800 | @var{ochar})} gives the translated character corresponding to | |
2801 | @var{ochar}. If the length of @var{table} is less than 256, any | |
2802 | characters with codes larger than the length of @var{table} are not | |
2803 | altered by the translation. | |
2804 | ||
2805 | The return value of @code{translate-region} is the number of | |
61cfa852 RS |
2806 | characters that were actually changed by the translation. This does |
2807 | not count characters that were mapped into themselves in the | |
73804d4b | 2808 | translation table. |
73804d4b RS |
2809 | @end defun |
2810 | ||
2811 | @node Registers | |
2812 | @section Registers | |
2813 | @cindex registers | |
2814 | ||
2815 | A register is a sort of variable used in Emacs editing that can hold a | |
2816 | marker, a string, a rectangle, a window configuration (of one frame), or | |
2817 | a frame configuration (of all frames). Each register is named by a | |
2818 | single character. All characters, including control and meta characters | |
2819 | (but with the exception of @kbd{C-g}), can be used to name registers. | |
2820 | Thus, there are 255 possible registers. A register is designated in | |
61cfa852 | 2821 | Emacs Lisp by a character that is its name. |
73804d4b RS |
2822 | |
2823 | The functions in this section return unpredictable values unless | |
2824 | otherwise stated. | |
2825 | @c Will change in version 19 | |
2826 | ||
2827 | @defvar register-alist | |
2828 | This variable is an alist of elements of the form @code{(@var{name} . | |
2829 | @var{contents})}. Normally, there is one element for each Emacs | |
2830 | register that has been used. | |
2831 | ||
2832 | The object @var{name} is a character (an integer) identifying the | |
2833 | register. The object @var{contents} is a string, marker, or list | |
2834 | representing the register contents. A string represents text stored in | |
2835 | the register. A marker represents a position. A list represents a | |
2836 | rectangle; its elements are strings, one per line of the rectangle. | |
2837 | @end defvar | |
2838 | ||
2839 | @defun get-register reg | |
2840 | This function returns the contents of the register | |
2841 | @var{reg}, or @code{nil} if it has no contents. | |
2842 | @end defun | |
2843 | ||
2844 | @defun set-register reg value | |
2845 | This function sets the contents of register @var{reg} to @var{value}. | |
2846 | A register can be set to any value, but the other register functions | |
2847 | expect only certain data types. The return value is @var{value}. | |
2848 | @end defun | |
2849 | ||
2850 | @deffn Command view-register reg | |
2851 | This command displays what is contained in register @var{reg}. | |
2852 | @end deffn | |
2853 | ||
2854 | @ignore | |
2855 | @deffn Command point-to-register reg | |
2856 | This command stores both the current location of point and the current | |
2857 | buffer in register @var{reg} as a marker. | |
2858 | @end deffn | |
2859 | ||
2860 | @deffn Command jump-to-register reg | |
2861 | @deffnx Command register-to-point reg | |
2862 | @comment !!SourceFile register.el | |
2863 | This command restores the status recorded in register @var{reg}. | |
2864 | ||
2865 | If @var{reg} contains a marker, it moves point to the position stored in | |
2866 | the marker. Since both the buffer and the location within the buffer | |
2867 | are stored by the @code{point-to-register} function, this command can | |
2868 | switch you to another buffer. | |
2869 | ||
2870 | If @var{reg} contains a window configuration or a frame configuration. | |
2871 | @code{jump-to-register} restores that configuration. | |
2872 | @end deffn | |
2873 | @end ignore | |
2874 | ||
2875 | @deffn Command insert-register reg &optional beforep | |
2876 | This command inserts contents of register @var{reg} into the current | |
2877 | buffer. | |
2878 | ||
2879 | Normally, this command puts point before the inserted text, and the | |
2880 | mark after it. However, if the optional second argument @var{beforep} | |
2881 | is non-@code{nil}, it puts the mark before and point after. | |
2882 | You can pass a non-@code{nil} second argument @var{beforep} to this | |
2883 | function interactively by supplying any prefix argument. | |
2884 | ||
2885 | If the register contains a rectangle, then the rectangle is inserted | |
2886 | with its upper left corner at point. This means that text is inserted | |
2887 | in the current line and underneath it on successive lines. | |
2888 | ||
2889 | If the register contains something other than saved text (a string) or | |
2890 | a rectangle (a list), currently useless things happen. This may be | |
2891 | changed in the future. | |
2892 | @end deffn | |
2893 | ||
2894 | @ignore | |
2895 | @deffn Command copy-to-register reg start end &optional delete-flag | |
2896 | This command copies the region from @var{start} to @var{end} into | |
2897 | register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes | |
2898 | the region from the buffer after copying it into the register. | |
2899 | @end deffn | |
2900 | ||
2901 | @deffn Command prepend-to-register reg start end &optional delete-flag | |
2902 | This command prepends the region from @var{start} to @var{end} into | |
2903 | register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes | |
2904 | the region from the buffer after copying it to the register. | |
2905 | @end deffn | |
2906 | ||
2907 | @deffn Command append-to-register reg start end &optional delete-flag | |
2908 | This command appends the region from @var{start} to @var{end} to the | |
2909 | text already in register @var{reg}. If @var{delete-flag} is | |
2910 | non-@code{nil}, it deletes the region from the buffer after copying it | |
2911 | to the register. | |
2912 | @end deffn | |
2913 | ||
2914 | @deffn Command copy-rectangle-to-register reg start end &optional delete-flag | |
2915 | This command copies a rectangular region from @var{start} to @var{end} | |
2916 | into register @var{reg}. If @var{delete-flag} is non-@code{nil}, it | |
2917 | deletes the region from the buffer after copying it to the register. | |
2918 | @end deffn | |
2919 | ||
2920 | @deffn Command window-configuration-to-register reg | |
2921 | This function stores the window configuration of the selected frame in | |
2922 | register @var{reg}. | |
2923 | @end deffn | |
2924 | ||
2925 | @deffn Command frame-configuration-to-register reg | |
2926 | This function stores the current frame configuration in register | |
2927 | @var{reg}. | |
2928 | @end deffn | |
2929 | @end ignore | |
2930 | ||
b22f3a19 RS |
2931 | @node Transposition |
2932 | @section Transposition of Text | |
2933 | ||
2934 | This subroutine is used by the transposition commands. | |
2935 | ||
2936 | @defun transpose-regions start1 end1 start2 end2 &optional leave-markers | |
2937 | This function exchanges two nonoverlapping portions of the buffer. | |
2938 | Arguments @var{start1} and @var{end1} specify the bounds of one portion | |
2939 | and arguments @var{start2} and @var{end2} specify the bounds of the | |
2940 | other portion. | |
2941 | ||
2942 | Normally, @code{transpose-regions} relocates markers with the transposed | |
2943 | text; a marker previously positioned within one of the two transposed | |
2944 | portions moves along with that portion, thus remaining between the same | |
2945 | two characters in their new position. However, if @var{leave-markers} | |
2946 | is non-@code{nil}, @code{transpose-regions} does not do this---it leaves | |
2947 | all markers unrelocated. | |
2948 | @end defun | |
2949 | ||
73804d4b RS |
2950 | @node Change Hooks |
2951 | @section Change Hooks | |
2952 | @cindex change hooks | |
2953 | @cindex hooks for text changes | |
2954 | ||
2955 | These hook variables let you arrange to take notice of all changes in | |
2956 | all buffers (or in a particular buffer, if you make them buffer-local). | |
2957 | See also @ref{Special Properties}, for how to detect changes to specific | |
2958 | parts of the text. | |
2959 | ||
2960 | The functions you use in these hooks should save and restore the match | |
2961 | data if they do anything that uses regular expressions; otherwise, they | |
2962 | will interfere in bizarre ways with the editing operations that call | |
2963 | them. | |
2964 | ||
72654a3c RS |
2965 | @defvar before-change-functions |
2966 | This variable holds a list of a functions to call before any buffer | |
2967 | modification. Each function gets two arguments, the beginning and end | |
2968 | of the region that is about to change, represented as integers. The | |
2969 | buffer that is about to change is always the current buffer. | |
2970 | @end defvar | |
2971 | ||
2972 | @defvar after-change-functions | |
2973 | This variable holds a list of a functions to call after any buffer | |
2974 | modification. Each function receives three arguments: the beginning and | |
2975 | end of the region just changed, and the length of the text that existed | |
584b8104 RS |
2976 | before the change. All three arguments are integers. The buffer that's |
2977 | about to change is always the current buffer. | |
2978 | ||
2979 | The length of the old text is measured in bytes; it is the difference | |
2980 | between the buffer positions before and after that text, before the | |
2981 | change. As for the changed text, its length in bytes is simply the | |
2982 | difference between the first two arguments. If you want the length | |
2983 | in @emph{characters} of the text before the change, you should use | |
2984 | a @code{before-change-functions} function that calls @code{chars-in-region} | |
2985 | (@pxref{Chars and Bytes}). | |
72654a3c RS |
2986 | @end defvar |
2987 | ||
73804d4b | 2988 | @defvar before-change-function |
bfe721d1 KH |
2989 | This obsolete variable holds one function to call before any buffer |
2990 | modification (or @code{nil} for no function). It is called just like | |
2991 | the functions in @code{before-change-functions}. | |
73804d4b RS |
2992 | @end defvar |
2993 | ||
2994 | @defvar after-change-function | |
bfe721d1 | 2995 | This obsolete variable holds one function to call after any buffer modification |
72654a3c RS |
2996 | (or @code{nil} for no function). It is called just like the functions in |
2997 | @code{after-change-functions}. | |
73804d4b RS |
2998 | @end defvar |
2999 | ||
72654a3c RS |
3000 | The four variables above are temporarily bound to @code{nil} during the |
3001 | time that any of these functions is running. This means that if one of | |
73804d4b | 3002 | these functions changes the buffer, that change won't run these |
72654a3c RS |
3003 | functions. If you do want a hook function to make changes that run |
3004 | these functions, make it bind these variables back to their usual | |
73804d4b RS |
3005 | values. |
3006 | ||
b22f3a19 RS |
3007 | One inconvenient result of this protective feature is that you cannot |
3008 | have a function in @code{after-change-functions} or | |
3009 | @code{before-change-functions} which changes the value of that variable. | |
3010 | But that's not a real limitation. If you want those functions to change | |
3011 | the list of functions to run, simply add one fixed function to the hook, | |
3012 | and code that function to look in another variable for other functions | |
3013 | to call. Here is an example: | |
3014 | ||
3015 | @example | |
3016 | (setq my-own-after-change-functions nil) | |
3017 | (defun indirect-after-change-function (beg end len) | |
3018 | (let ((list my-own-after-change-functions)) | |
3019 | (while list | |
3020 | (funcall (car list) beg end len) | |
3021 | (setq list (cdr list))))) | |
3022 | (add-hooks 'after-change-functions | |
3023 | 'indirect-after-change-function) | |
3024 | @end example | |
3025 | ||
73804d4b RS |
3026 | @defvar first-change-hook |
3027 | This variable is a normal hook that is run whenever a buffer is changed | |
3028 | that was previously in the unmodified state. | |
3029 | @end defvar |