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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
9db3a582 | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001 |
177c0ea7 | 4 | @c Free Software Foundation, Inc. |
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5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/text | |
f9f59935 | 7 | @node Text, Non-ASCII Characters, Markers, Top |
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8 | @chapter Text |
9 | @cindex text | |
10 | ||
11 | This chapter describes the functions that deal with the text in a | |
61cfa852 | 12 | buffer. Most examine, insert, or delete text in the current buffer, |
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13 | often operating at point or on text adjacent to point. Many are |
14 | interactive. All the functions that change the text provide for undoing | |
15 | the changes (@pxref{Undo}). | |
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16 | |
17 | Many text-related functions operate on a region of text defined by two | |
18 | buffer positions passed in arguments named @var{start} and @var{end}. | |
19 | These arguments should be either markers (@pxref{Markers}) or numeric | |
20 | character positions (@pxref{Positions}). The order of these arguments | |
21 | does not matter; it is all right for @var{start} to be the end of the | |
22 | region and @var{end} the beginning. For example, @code{(delete-region 1 | |
23 | 10)} and @code{(delete-region 10 1)} are equivalent. An | |
24 | @code{args-out-of-range} error is signaled if either @var{start} or | |
25 | @var{end} is outside the accessible portion of the buffer. In an | |
26 | interactive call, point and the mark are used for these arguments. | |
27 | ||
28 | @cindex buffer contents | |
29 | Throughout this chapter, ``text'' refers to the characters in the | |
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30 | buffer, together with their properties (when relevant). Keep in mind |
31 | that point is always between two characters, and the cursor appears on | |
32 | the character after point. | |
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33 | |
34 | @menu | |
35 | * Near Point:: Examining text in the vicinity of point. | |
36 | * Buffer Contents:: Examining text in a general fashion. | |
37 | * Comparing Text:: Comparing substrings of buffers. | |
38 | * Insertion:: Adding new text to a buffer. | |
39 | * Commands for Insertion:: User-level commands to insert text. | |
40 | * Deletion:: Removing text from a buffer. | |
41 | * User-Level Deletion:: User-level commands to delete text. | |
42 | * The Kill Ring:: Where removed text sometimes is saved for later use. | |
43 | * Undo:: Undoing changes to the text of a buffer. | |
44 | * Maintaining Undo:: How to enable and disable undo information. | |
45 | How to control how much information is kept. | |
46 | * Filling:: Functions for explicit filling. | |
bfe721d1 | 47 | * Margins:: How to specify margins for filling commands. |
e75ecfec | 48 | * Adaptive Fill:: Adaptive Fill mode chooses a fill prefix from context. |
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49 | * Auto Filling:: How auto-fill mode is implemented to break lines. |
50 | * Sorting:: Functions for sorting parts of the buffer. | |
51 | * Columns:: Computing horizontal positions, and using them. | |
52 | * Indentation:: Functions to insert or adjust indentation. | |
53 | * Case Changes:: Case conversion of parts of the buffer. | |
54 | * Text Properties:: Assigning Lisp property lists to text characters. | |
55 | * Substitution:: Replacing a given character wherever it appears. | |
b22f3a19 | 56 | * Transposition:: Swapping two portions of a buffer. |
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57 | * Registers:: How registers are implemented. Accessing the text or |
58 | position stored in a register. | |
b6954afd | 59 | * Base 64:: Conversion to or from base 64 encoding. |
944351c0 | 60 | * MD5 Checksum:: Compute the MD5 ``message digest''/``checksum''. |
d73eac4d | 61 | * Atomic Changes:: Installing several buffer changs ``atomically''. |
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62 | * Change Hooks:: Supplying functions to be run when text is changed. |
63 | @end menu | |
64 | ||
65 | @node Near Point | |
66 | @section Examining Text Near Point | |
67 | ||
68 | Many functions are provided to look at the characters around point. | |
69 | Several simple functions are described here. See also @code{looking-at} | |
70 | in @ref{Regexp Search}. | |
71 | ||
1911e6e5 | 72 | @defun char-after &optional position |
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73 | This function returns the character in the current buffer at (i.e., |
74 | immediately after) position @var{position}. If @var{position} is out of | |
75 | range for this purpose, either before the beginning of the buffer, or at | |
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76 | or beyond the end, then the value is @code{nil}. The default for |
77 | @var{position} is point. | |
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78 | |
79 | In the following example, assume that the first character in the | |
80 | buffer is @samp{@@}: | |
81 | ||
82 | @example | |
83 | @group | |
84 | (char-to-string (char-after 1)) | |
85 | @result{} "@@" | |
86 | @end group | |
87 | @end example | |
88 | @end defun | |
89 | ||
1911e6e5 | 90 | @defun char-before &optional position |
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91 | This function returns the character in the current buffer immediately |
92 | before position @var{position}. If @var{position} is out of range for | |
a3a349c4 | 93 | this purpose, either at or before the beginning of the buffer, or beyond |
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94 | the end, then the value is @code{nil}. The default for |
95 | @var{position} is point. | |
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96 | @end defun |
97 | ||
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98 | @defun following-char |
99 | This function returns the character following point in the current | |
100 | buffer. This is similar to @code{(char-after (point))}. However, if | |
101 | point is at the end of the buffer, then @code{following-char} returns 0. | |
102 | ||
103 | Remember that point is always between characters, and the terminal | |
104 | cursor normally appears over the character following point. Therefore, | |
105 | the character returned by @code{following-char} is the character the | |
106 | cursor is over. | |
107 | ||
108 | In this example, point is between the @samp{a} and the @samp{c}. | |
109 | ||
110 | @example | |
111 | @group | |
112 | ---------- Buffer: foo ---------- | |
113 | Gentlemen may cry ``Pea@point{}ce! Peace!,'' | |
114 | but there is no peace. | |
115 | ---------- Buffer: foo ---------- | |
116 | @end group | |
117 | ||
118 | @group | |
119 | (char-to-string (preceding-char)) | |
120 | @result{} "a" | |
121 | (char-to-string (following-char)) | |
122 | @result{} "c" | |
123 | @end group | |
124 | @end example | |
125 | @end defun | |
126 | ||
127 | @defun preceding-char | |
128 | This function returns the character preceding point in the current | |
129 | buffer. See above, under @code{following-char}, for an example. If | |
130 | point is at the beginning of the buffer, @code{preceding-char} returns | |
131 | 0. | |
132 | @end defun | |
133 | ||
134 | @defun bobp | |
135 | This function returns @code{t} if point is at the beginning of the | |
136 | buffer. If narrowing is in effect, this means the beginning of the | |
137 | accessible portion of the text. See also @code{point-min} in | |
138 | @ref{Point}. | |
139 | @end defun | |
140 | ||
141 | @defun eobp | |
142 | This function returns @code{t} if point is at the end of the buffer. | |
143 | If narrowing is in effect, this means the end of accessible portion of | |
144 | the text. See also @code{point-max} in @xref{Point}. | |
145 | @end defun | |
146 | ||
147 | @defun bolp | |
148 | This function returns @code{t} if point is at the beginning of a line. | |
f9f59935 | 149 | @xref{Text Lines}. The beginning of the buffer (or of its accessible |
61cfa852 | 150 | portion) always counts as the beginning of a line. |
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151 | @end defun |
152 | ||
153 | @defun eolp | |
154 | This function returns @code{t} if point is at the end of a line. The | |
155 | end of the buffer (or of its accessible portion) is always considered | |
156 | the end of a line. | |
157 | @end defun | |
158 | ||
159 | @node Buffer Contents | |
160 | @section Examining Buffer Contents | |
161 | ||
162 | This section describes two functions that allow a Lisp program to | |
163 | convert any portion of the text in the buffer into a string. | |
164 | ||
165 | @defun buffer-substring start end | |
166 | This function returns a string containing a copy of the text of the | |
167 | region defined by positions @var{start} and @var{end} in the current | |
168 | buffer. If the arguments are not positions in the accessible portion of | |
169 | the buffer, @code{buffer-substring} signals an @code{args-out-of-range} | |
170 | error. | |
171 | ||
172 | It is not necessary for @var{start} to be less than @var{end}; the | |
173 | arguments can be given in either order. But most often the smaller | |
174 | argument is written first. | |
175 | ||
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176 | If the text being copied has any text properties, these are copied into |
177 | the string along with the characters they belong to. @xref{Text | |
178 | Properties}. However, overlays (@pxref{Overlays}) in the buffer and | |
179 | their properties are ignored, not copied. | |
180 | ||
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181 | @example |
182 | @group | |
183 | ---------- Buffer: foo ---------- | |
184 | This is the contents of buffer foo | |
185 | ||
186 | ---------- Buffer: foo ---------- | |
187 | @end group | |
188 | ||
189 | @group | |
190 | (buffer-substring 1 10) | |
191 | @result{} "This is t" | |
192 | @end group | |
193 | @group | |
194 | (buffer-substring (point-max) 10) | |
195 | @result{} "he contents of buffer foo | |
196 | " | |
197 | @end group | |
198 | @end example | |
199 | @end defun | |
200 | ||
371f8cd0 | 201 | @defun buffer-substring-no-properties start end |
22697dac KH |
202 | This is like @code{buffer-substring}, except that it does not copy text |
203 | properties, just the characters themselves. @xref{Text Properties}. | |
22697dac KH |
204 | @end defun |
205 | ||
73804d4b | 206 | @defun buffer-string |
f9f59935 | 207 | This function returns the contents of the entire accessible portion of |
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208 | the current buffer as a string. It is equivalent to |
209 | ||
210 | @example | |
211 | (buffer-substring (point-min) (point-max)) | |
212 | @end example | |
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213 | |
214 | @example | |
215 | @group | |
216 | ---------- Buffer: foo ---------- | |
217 | This is the contents of buffer foo | |
218 | ||
219 | ---------- Buffer: foo ---------- | |
220 | ||
221 | (buffer-string) | |
222 | @result{} "This is the contents of buffer foo | |
223 | " | |
224 | @end group | |
225 | @end example | |
226 | @end defun | |
227 | ||
74eee906 RS |
228 | @tindex current-word |
229 | @defun current-word &optional strict really-word | |
230 | This function returns the symbol (or word) at or near point, as a string. | |
231 | The return value includes no text properties. | |
232 | ||
233 | The optional argument @var{really-word} is non-@code{nil}, it finds a | |
234 | word; otherwise, it finds a symbol (which includes word characters and | |
235 | both symbol constituent characters). | |
236 | ||
237 | If the optional argument @var{strict} is non-@code{nil}, then point | |
238 | must be in or next to the symbol or word---if no symbol or word is | |
239 | there, the function returns @code{nil}. Otherwise, a nearby symbol or | |
240 | word on the same line is acceptable. | |
241 | @end defun | |
242 | ||
f9f59935 RS |
243 | @defun thing-at-point thing |
244 | Return the @var{thing} around or next to point, as a string. | |
245 | ||
246 | The argument @var{thing} is a symbol which specifies a kind of syntactic | |
247 | entity. Possibilities include @code{symbol}, @code{list}, @code{sexp}, | |
248 | @code{defun}, @code{filename}, @code{url}, @code{word}, @code{sentence}, | |
249 | @code{whitespace}, @code{line}, @code{page}, and others. | |
250 | ||
251 | @example | |
252 | ---------- Buffer: foo ---------- | |
253 | Gentlemen may cry ``Pea@point{}ce! Peace!,'' | |
254 | but there is no peace. | |
255 | ---------- Buffer: foo ---------- | |
256 | ||
257 | (thing-at-point 'word) | |
258 | @result{} "Peace" | |
259 | (thing-at-point 'line) | |
260 | @result{} "Gentlemen may cry ``Peace! Peace!,''\n" | |
261 | (thing-at-point 'whitespace) | |
262 | @result{} nil | |
263 | @end example | |
264 | @end defun | |
265 | ||
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266 | @node Comparing Text |
267 | @section Comparing Text | |
268 | @cindex comparing buffer text | |
269 | ||
270 | This function lets you compare portions of the text in a buffer, without | |
271 | copying them into strings first. | |
272 | ||
273 | @defun compare-buffer-substrings buffer1 start1 end1 buffer2 start2 end2 | |
274 | This function lets you compare two substrings of the same buffer or two | |
275 | different buffers. The first three arguments specify one substring, | |
276 | giving a buffer and two positions within the buffer. The last three | |
277 | arguments specify the other substring in the same way. You can use | |
61cfa852 | 278 | @code{nil} for @var{buffer1}, @var{buffer2}, or both to stand for the |
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279 | current buffer. |
280 | ||
281 | The value is negative if the first substring is less, positive if the | |
282 | first is greater, and zero if they are equal. The absolute value of | |
283 | the result is one plus the index of the first differing characters | |
284 | within the substrings. | |
285 | ||
286 | This function ignores case when comparing characters | |
bfe721d1 KH |
287 | if @code{case-fold-search} is non-@code{nil}. It always ignores |
288 | text properties. | |
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289 | |
290 | Suppose the current buffer contains the text @samp{foobarbar | |
291 | haha!rara!}; then in this example the two substrings are @samp{rbar } | |
292 | and @samp{rara!}. The value is 2 because the first substring is greater | |
293 | at the second character. | |
294 | ||
295 | @example | |
8241495d | 296 | (compare-buffer-substrings nil 6 11 nil 16 21) |
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297 | @result{} 2 |
298 | @end example | |
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299 | @end defun |
300 | ||
301 | @node Insertion | |
bfe721d1 | 302 | @section Inserting Text |
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303 | @cindex insertion of text |
304 | @cindex text insertion | |
305 | ||
969fe9b5 RS |
306 | @cindex insertion before point |
307 | @cindex before point, insertion | |
73804d4b RS |
308 | @dfn{Insertion} means adding new text to a buffer. The inserted text |
309 | goes at point---between the character before point and the character | |
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310 | after point. Some insertion functions leave point before the inserted |
311 | text, while other functions leave it after. We call the former | |
312 | insertion @dfn{after point} and the latter insertion @dfn{before point}. | |
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313 | |
314 | Insertion relocates markers that point at positions after the | |
315 | insertion point, so that they stay with the surrounding text | |
316 | (@pxref{Markers}). When a marker points at the place of insertion, | |
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317 | insertion may or may not relocate the marker, depending on the marker's |
318 | insertion type (@pxref{Marker Insertion Types}). Certain special | |
319 | functions such as @code{insert-before-markers} relocate all such markers | |
320 | to point after the inserted text, regardless of the markers' insertion | |
321 | type. | |
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322 | |
323 | Insertion functions signal an error if the current buffer is | |
2468d0c0 | 324 | read-only or if they insert within read-only text. |
73804d4b | 325 | |
bfe721d1 KH |
326 | These functions copy text characters from strings and buffers along |
327 | with their properties. The inserted characters have exactly the same | |
328 | properties as the characters they were copied from. By contrast, | |
329 | characters specified as separate arguments, not part of a string or | |
330 | buffer, inherit their text properties from the neighboring text. | |
331 | ||
a9f0a989 RS |
332 | The insertion functions convert text from unibyte to multibyte in |
333 | order to insert in a multibyte buffer, and vice versa---if the text | |
334 | comes from a string or from a buffer. However, they do not convert | |
335 | unibyte character codes 128 through 255 to multibyte characters, not | |
336 | even if the current buffer is a multibyte buffer. @xref{Converting | |
337 | Representations}. | |
338 | ||
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339 | @defun insert &rest args |
340 | This function inserts the strings and/or characters @var{args} into the | |
61cfa852 RS |
341 | current buffer, at point, moving point forward. In other words, it |
342 | inserts the text before point. An error is signaled unless all | |
343 | @var{args} are either strings or characters. The value is @code{nil}. | |
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344 | @end defun |
345 | ||
346 | @defun insert-before-markers &rest args | |
347 | This function inserts the strings and/or characters @var{args} into the | |
348 | current buffer, at point, moving point forward. An error is signaled | |
349 | unless all @var{args} are either strings or characters. The value is | |
350 | @code{nil}. | |
351 | ||
352 | This function is unlike the other insertion functions in that it | |
353 | relocates markers initially pointing at the insertion point, to point | |
f9f59935 | 354 | after the inserted text. If an overlay begins the insertion point, the |
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355 | inserted text falls outside the overlay; if a nonempty overlay ends at |
356 | the insertion point, the inserted text falls inside that overlay. | |
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357 | @end defun |
358 | ||
9e3561d2 | 359 | @defun insert-char character count &optional inherit |
73804d4b | 360 | This function inserts @var{count} instances of @var{character} into the |
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361 | current buffer before point. The argument @var{count} should be a |
362 | number (@code{nil} means 1), and @var{character} must be a character. | |
363 | The value is @code{nil}. | |
33acbad2 | 364 | |
a9f0a989 RS |
365 | This function does not convert unibyte character codes 128 through 255 |
366 | to multibyte characters, not even if the current buffer is a multibyte | |
367 | buffer. @xref{Converting Representations}. | |
368 | ||
33acbad2 RS |
369 | If @var{inherit} is non-@code{nil}, then the inserted characters inherit |
370 | sticky text properties from the two characters before and after the | |
371 | insertion point. @xref{Sticky Properties}. | |
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372 | @end defun |
373 | ||
374 | @defun insert-buffer-substring from-buffer-or-name &optional start end | |
375 | This function inserts a portion of buffer @var{from-buffer-or-name} | |
376 | (which must already exist) into the current buffer before point. The | |
377 | text inserted is the region from @var{start} and @var{end}. (These | |
378 | arguments default to the beginning and end of the accessible portion of | |
379 | that buffer.) This function returns @code{nil}. | |
380 | ||
381 | In this example, the form is executed with buffer @samp{bar} as the | |
382 | current buffer. We assume that buffer @samp{bar} is initially empty. | |
383 | ||
384 | @example | |
385 | @group | |
386 | ---------- Buffer: foo ---------- | |
387 | We hold these truths to be self-evident, that all | |
388 | ---------- Buffer: foo ---------- | |
389 | @end group | |
390 | ||
391 | @group | |
392 | (insert-buffer-substring "foo" 1 20) | |
393 | @result{} nil | |
394 | ||
395 | ---------- Buffer: bar ---------- | |
61cfa852 | 396 | We hold these truth@point{} |
73804d4b RS |
397 | ---------- Buffer: bar ---------- |
398 | @end group | |
399 | @end example | |
d73eac4d RS |
400 | @end defun |
401 | ||
402 | @defun insert-buffer-substring-no-properties from-buffer-or-name &optional start end | |
403 | This is like @code{insert-buffer-substring} except that it does not | |
404 | copy any text properties. | |
73804d4b RS |
405 | @end defun |
406 | ||
407 | @xref{Sticky Properties}, for other insertion functions that inherit | |
61cfa852 | 408 | text properties from the nearby text in addition to inserting it. |
33acbad2 RS |
409 | Whitespace inserted by indentation functions also inherits text |
410 | properties. | |
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411 | |
412 | @node Commands for Insertion | |
413 | @section User-Level Insertion Commands | |
414 | ||
415 | This section describes higher-level commands for inserting text, | |
416 | commands intended primarily for the user but useful also in Lisp | |
417 | programs. | |
418 | ||
419 | @deffn Command insert-buffer from-buffer-or-name | |
420 | This command inserts the entire contents of @var{from-buffer-or-name} | |
421 | (which must exist) into the current buffer after point. It leaves | |
422 | the mark after the inserted text. The value is @code{nil}. | |
423 | @end deffn | |
424 | ||
425 | @deffn Command self-insert-command count | |
426 | @cindex character insertion | |
427 | @cindex self-insertion | |
61cfa852 RS |
428 | This command inserts the last character typed; it does so @var{count} |
429 | times, before point, and returns @code{nil}. Most printing characters | |
430 | are bound to this command. In routine use, @code{self-insert-command} | |
431 | is the most frequently called function in Emacs, but programs rarely use | |
432 | it except to install it on a keymap. | |
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433 | |
434 | In an interactive call, @var{count} is the numeric prefix argument. | |
435 | ||
22697dac | 436 | This command calls @code{auto-fill-function} whenever that is |
ca3be36e DL |
437 | non-@code{nil} and the character inserted is in the table |
438 | @code{auto-fill-chars} (@pxref{Auto Filling}). | |
73804d4b RS |
439 | |
440 | @c Cross refs reworded to prevent overfull hbox. --rjc 15mar92 | |
22697dac | 441 | This command performs abbrev expansion if Abbrev mode is enabled and |
73804d4b RS |
442 | the inserted character does not have word-constituent |
443 | syntax. (@xref{Abbrevs}, and @ref{Syntax Class Table}.) | |
444 | ||
22697dac KH |
445 | This is also responsible for calling @code{blink-paren-function} when |
446 | the inserted character has close parenthesis syntax (@pxref{Blinking}). | |
a40d4712 PR |
447 | |
448 | Do not try substituting your own definition of | |
449 | @code{self-insert-command} for the standard one. The editor command | |
450 | loop handles this function specially. | |
73804d4b RS |
451 | @end deffn |
452 | ||
177c0ea7 | 453 | @deffn Command newline &optional number-of-newlines |
73804d4b RS |
454 | This command inserts newlines into the current buffer before point. |
455 | If @var{number-of-newlines} is supplied, that many newline characters | |
456 | are inserted. | |
457 | ||
458 | @cindex newline and Auto Fill mode | |
61cfa852 RS |
459 | This function calls @code{auto-fill-function} if the current column |
460 | number is greater than the value of @code{fill-column} and | |
461 | @var{number-of-newlines} is @code{nil}. Typically what | |
462 | @code{auto-fill-function} does is insert a newline; thus, the overall | |
463 | result in this case is to insert two newlines at different places: one | |
464 | at point, and another earlier in the line. @code{newline} does not | |
465 | auto-fill if @var{number-of-newlines} is non-@code{nil}. | |
73804d4b | 466 | |
bfe721d1 KH |
467 | This command indents to the left margin if that is not zero. |
468 | @xref{Margins}. | |
469 | ||
73804d4b RS |
470 | The value returned is @code{nil}. In an interactive call, @var{count} |
471 | is the numeric prefix argument. | |
472 | @end deffn | |
473 | ||
474 | @deffn Command split-line | |
475 | This command splits the current line, moving the portion of the line | |
61cfa852 | 476 | after point down vertically so that it is on the next line directly |
73804d4b RS |
477 | below where it was before. Whitespace is inserted as needed at the |
478 | beginning of the lower line, using the @code{indent-to} function. | |
479 | @code{split-line} returns the position of point. | |
480 | ||
481 | Programs hardly ever use this function. | |
482 | @end deffn | |
483 | ||
484 | @defvar overwrite-mode | |
1911e6e5 RS |
485 | This variable controls whether overwrite mode is in effect. The value |
486 | should be @code{overwrite-mode-textual}, @code{overwrite-mode-binary}, | |
487 | or @code{nil}. @code{overwrite-mode-textual} specifies textual | |
488 | overwrite mode (treats newlines and tabs specially), and | |
489 | @code{overwrite-mode-binary} specifies binary overwrite mode (treats | |
490 | newlines and tabs like any other characters). | |
73804d4b RS |
491 | @end defvar |
492 | ||
493 | @node Deletion | |
bfe721d1 | 494 | @section Deleting Text |
73804d4b RS |
495 | |
496 | @cindex deletion vs killing | |
497 | Deletion means removing part of the text in a buffer, without saving | |
498 | it in the kill ring (@pxref{The Kill Ring}). Deleted text can't be | |
499 | yanked, but can be reinserted using the undo mechanism (@pxref{Undo}). | |
61cfa852 RS |
500 | Some deletion functions do save text in the kill ring in some special |
501 | cases. | |
73804d4b RS |
502 | |
503 | All of the deletion functions operate on the current buffer, and all | |
504 | return a value of @code{nil}. | |
505 | ||
1911e6e5 | 506 | @deffn Command erase-buffer |
73804d4b RS |
507 | This function deletes the entire text of the current buffer, leaving it |
508 | empty. If the buffer is read-only, it signals a @code{buffer-read-only} | |
2468d0c0 DL |
509 | error; if some of the text in it is read-only, it signals a |
510 | @code{text-read-only} error. Otherwise, it deletes the text without | |
511 | asking for any confirmation. It returns @code{nil}. | |
8241495d | 512 | |
73804d4b RS |
513 | Normally, deleting a large amount of text from a buffer inhibits further |
514 | auto-saving of that buffer ``because it has shrunk''. However, | |
515 | @code{erase-buffer} does not do this, the idea being that the future | |
516 | text is not really related to the former text, and its size should not | |
517 | be compared with that of the former text. | |
1911e6e5 | 518 | @end deffn |
73804d4b RS |
519 | |
520 | @deffn Command delete-region start end | |
1dffc5db RS |
521 | This command deletes the text between positions @var{start} and |
522 | @var{end} in the current buffer, and returns @code{nil}. If point was | |
523 | inside the deleted region, its value afterward is @var{start}. | |
68002b5f | 524 | Otherwise, point relocates with the surrounding text, as markers do. |
73804d4b RS |
525 | @end deffn |
526 | ||
1dffc5db RS |
527 | @defun delete-and-extract-region start end |
528 | @tindex delete-and-extract-region | |
529 | This function deletes the text between positions @var{start} and | |
530 | @var{end} in the current buffer, and returns a string containing the | |
531 | text just deleted. | |
532 | ||
533 | If point was inside the deleted region, its value afterward is | |
534 | @var{start}. Otherwise, point relocates with the surrounding text, as | |
535 | markers do. | |
536 | @end defun | |
537 | ||
73804d4b RS |
538 | @deffn Command delete-char count &optional killp |
539 | This command deletes @var{count} characters directly after point, or | |
540 | before point if @var{count} is negative. If @var{killp} is | |
541 | non-@code{nil}, then it saves the deleted characters in the kill ring. | |
542 | ||
543 | In an interactive call, @var{count} is the numeric prefix argument, and | |
544 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix | |
545 | argument is supplied, the text is saved in the kill ring. If no prefix | |
546 | argument is supplied, then one character is deleted, but not saved in | |
547 | the kill ring. | |
548 | ||
549 | The value returned is always @code{nil}. | |
550 | @end deffn | |
551 | ||
552 | @deffn Command delete-backward-char count &optional killp | |
553 | @cindex delete previous char | |
554 | This command deletes @var{count} characters directly before point, or | |
555 | after point if @var{count} is negative. If @var{killp} is | |
556 | non-@code{nil}, then it saves the deleted characters in the kill ring. | |
557 | ||
558 | In an interactive call, @var{count} is the numeric prefix argument, and | |
559 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix | |
560 | argument is supplied, the text is saved in the kill ring. If no prefix | |
561 | argument is supplied, then one character is deleted, but not saved in | |
562 | the kill ring. | |
563 | ||
564 | The value returned is always @code{nil}. | |
565 | @end deffn | |
566 | ||
567 | @deffn Command backward-delete-char-untabify count &optional killp | |
568 | @cindex tab deletion | |
569 | This command deletes @var{count} characters backward, changing tabs | |
570 | into spaces. When the next character to be deleted is a tab, it is | |
571 | first replaced with the proper number of spaces to preserve alignment | |
572 | and then one of those spaces is deleted instead of the tab. If | |
573 | @var{killp} is non-@code{nil}, then the command saves the deleted | |
574 | characters in the kill ring. | |
575 | ||
576 | Conversion of tabs to spaces happens only if @var{count} is positive. | |
577 | If it is negative, exactly @minus{}@var{count} characters after point | |
578 | are deleted. | |
579 | ||
580 | In an interactive call, @var{count} is the numeric prefix argument, and | |
581 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix | |
582 | argument is supplied, the text is saved in the kill ring. If no prefix | |
583 | argument is supplied, then one character is deleted, but not saved in | |
584 | the kill ring. | |
585 | ||
586 | The value returned is always @code{nil}. | |
587 | @end deffn | |
588 | ||
969fe9b5 RS |
589 | @defopt backward-delete-char-untabify-method |
590 | This option specifies how @code{backward-delete-char-untabify} should | |
591 | deal with whitespace. Possible values include @code{untabify}, the | |
592 | default, meaning convert a tab to many spaces and delete one; | |
593 | @code{hungry}, meaning delete all the whitespace characters before point | |
594 | with one command, and @code{nil}, meaning do nothing special for | |
595 | whitespace characters. | |
596 | @end defopt | |
597 | ||
73804d4b RS |
598 | @node User-Level Deletion |
599 | @section User-Level Deletion Commands | |
600 | ||
601 | This section describes higher-level commands for deleting text, | |
602 | commands intended primarily for the user but useful also in Lisp | |
603 | programs. | |
604 | ||
605 | @deffn Command delete-horizontal-space | |
606 | @cindex deleting whitespace | |
607 | This function deletes all spaces and tabs around point. It returns | |
608 | @code{nil}. | |
609 | ||
610 | In the following examples, we call @code{delete-horizontal-space} four | |
611 | times, once on each line, with point between the second and third | |
61cfa852 | 612 | characters on the line each time. |
73804d4b RS |
613 | |
614 | @example | |
615 | @group | |
616 | ---------- Buffer: foo ---------- | |
617 | I @point{}thought | |
618 | I @point{} thought | |
619 | We@point{} thought | |
620 | Yo@point{}u thought | |
621 | ---------- Buffer: foo ---------- | |
622 | @end group | |
623 | ||
624 | @group | |
625 | (delete-horizontal-space) ; @r{Four times.} | |
626 | @result{} nil | |
627 | ||
628 | ---------- Buffer: foo ---------- | |
629 | Ithought | |
630 | Ithought | |
631 | Wethought | |
632 | You thought | |
633 | ---------- Buffer: foo ---------- | |
634 | @end group | |
635 | @end example | |
636 | @end deffn | |
637 | ||
177c0ea7 | 638 | @deffn Command delete-indentation &optional join-following-p |
73804d4b RS |
639 | This function joins the line point is on to the previous line, deleting |
640 | any whitespace at the join and in some cases replacing it with one | |
641 | space. If @var{join-following-p} is non-@code{nil}, | |
642 | @code{delete-indentation} joins this line to the following line | |
a9f0a989 | 643 | instead. The function returns @code{nil}. |
73804d4b RS |
644 | |
645 | If there is a fill prefix, and the second of the lines being joined | |
646 | starts with the prefix, then @code{delete-indentation} deletes the | |
bfe721d1 | 647 | fill prefix before joining the lines. @xref{Margins}. |
73804d4b RS |
648 | |
649 | In the example below, point is located on the line starting | |
650 | @samp{events}, and it makes no difference if there are trailing spaces | |
651 | in the preceding line. | |
652 | ||
653 | @smallexample | |
b22f3a19 | 654 | @group |
73804d4b RS |
655 | ---------- Buffer: foo ---------- |
656 | When in the course of human | |
657 | @point{} events, it becomes necessary | |
658 | ---------- Buffer: foo ---------- | |
b22f3a19 | 659 | @end group |
73804d4b RS |
660 | |
661 | (delete-indentation) | |
662 | @result{} nil | |
663 | ||
b22f3a19 | 664 | @group |
73804d4b RS |
665 | ---------- Buffer: foo ---------- |
666 | When in the course of human@point{} events, it becomes necessary | |
667 | ---------- Buffer: foo ---------- | |
b22f3a19 | 668 | @end group |
73804d4b RS |
669 | @end smallexample |
670 | ||
671 | After the lines are joined, the function @code{fixup-whitespace} is | |
672 | responsible for deciding whether to leave a space at the junction. | |
673 | @end deffn | |
674 | ||
675 | @defun fixup-whitespace | |
a9f0a989 | 676 | This function replaces all the whitespace surrounding point with either |
73804d4b RS |
677 | one space or no space, according to the context. It returns @code{nil}. |
678 | ||
679 | At the beginning or end of a line, the appropriate amount of space is | |
680 | none. Before a character with close parenthesis syntax, or after a | |
681 | character with open parenthesis or expression-prefix syntax, no space is | |
682 | also appropriate. Otherwise, one space is appropriate. @xref{Syntax | |
683 | Class Table}. | |
684 | ||
685 | In the example below, @code{fixup-whitespace} is called the first time | |
61cfa852 RS |
686 | with point before the word @samp{spaces} in the first line. For the |
687 | second invocation, point is directly after the @samp{(}. | |
73804d4b RS |
688 | |
689 | @smallexample | |
690 | @group | |
691 | ---------- Buffer: foo ---------- | |
692 | This has too many @point{}spaces | |
693 | This has too many spaces at the start of (@point{} this list) | |
694 | ---------- Buffer: foo ---------- | |
695 | @end group | |
696 | ||
697 | @group | |
698 | (fixup-whitespace) | |
699 | @result{} nil | |
700 | (fixup-whitespace) | |
701 | @result{} nil | |
702 | @end group | |
703 | ||
704 | @group | |
705 | ---------- Buffer: foo ---------- | |
706 | This has too many spaces | |
707 | This has too many spaces at the start of (this list) | |
708 | ---------- Buffer: foo ---------- | |
709 | @end group | |
710 | @end smallexample | |
711 | @end defun | |
712 | ||
713 | @deffn Command just-one-space | |
714 | @comment !!SourceFile simple.el | |
715 | This command replaces any spaces and tabs around point with a single | |
716 | space. It returns @code{nil}. | |
717 | @end deffn | |
718 | ||
719 | @deffn Command delete-blank-lines | |
720 | This function deletes blank lines surrounding point. If point is on a | |
721 | blank line with one or more blank lines before or after it, then all but | |
722 | one of them are deleted. If point is on an isolated blank line, then it | |
723 | is deleted. If point is on a nonblank line, the command deletes all | |
724 | blank lines following it. | |
725 | ||
726 | A blank line is defined as a line containing only tabs and spaces. | |
727 | ||
728 | @code{delete-blank-lines} returns @code{nil}. | |
729 | @end deffn | |
730 | ||
731 | @node The Kill Ring | |
732 | @section The Kill Ring | |
733 | @cindex kill ring | |
734 | ||
969fe9b5 | 735 | @dfn{Kill functions} delete text like the deletion functions, but save |
73804d4b RS |
736 | it so that the user can reinsert it by @dfn{yanking}. Most of these |
737 | functions have @samp{kill-} in their name. By contrast, the functions | |
738 | whose names start with @samp{delete-} normally do not save text for | |
739 | yanking (though they can still be undone); these are ``deletion'' | |
740 | functions. | |
741 | ||
742 | Most of the kill commands are primarily for interactive use, and are | |
743 | not described here. What we do describe are the functions provided for | |
744 | use in writing such commands. You can use these functions to write | |
61cfa852 | 745 | commands for killing text. When you need to delete text for internal |
73804d4b RS |
746 | purposes within a Lisp function, you should normally use deletion |
747 | functions, so as not to disturb the kill ring contents. | |
748 | @xref{Deletion}. | |
749 | ||
750 | Killed text is saved for later yanking in the @dfn{kill ring}. This | |
61cfa852 RS |
751 | is a list that holds a number of recent kills, not just the last text |
752 | kill. We call this a ``ring'' because yanking treats it as having | |
753 | elements in a cyclic order. The list is kept in the variable | |
754 | @code{kill-ring}, and can be operated on with the usual functions for | |
755 | lists; there are also specialized functions, described in this section, | |
756 | that treat it as a ring. | |
73804d4b RS |
757 | |
758 | Some people think this use of the word ``kill'' is unfortunate, since | |
61cfa852 | 759 | it refers to operations that specifically @emph{do not} destroy the |
73804d4b RS |
760 | entities ``killed''. This is in sharp contrast to ordinary life, in |
761 | which death is permanent and ``killed'' entities do not come back to | |
762 | life. Therefore, other metaphors have been proposed. For example, the | |
763 | term ``cut ring'' makes sense to people who, in pre-computer days, used | |
764 | scissors and paste to cut up and rearrange manuscripts. However, it | |
765 | would be difficult to change the terminology now. | |
766 | ||
767 | @menu | |
768 | * Kill Ring Concepts:: What text looks like in the kill ring. | |
769 | * Kill Functions:: Functions that kill text. | |
d73eac4d | 770 | * Yanking:: How yanking is done. |
73804d4b | 771 | * Yank Commands:: Commands that access the kill ring. |
61cfa852 | 772 | * Low-Level Kill Ring:: Functions and variables for kill ring access. |
73804d4b RS |
773 | * Internals of Kill Ring:: Variables that hold kill-ring data. |
774 | @end menu | |
775 | ||
776 | @node Kill Ring Concepts | |
777 | @comment node-name, next, previous, up | |
778 | @subsection Kill Ring Concepts | |
779 | ||
780 | The kill ring records killed text as strings in a list, most recent | |
781 | first. A short kill ring, for example, might look like this: | |
782 | ||
783 | @example | |
784 | ("some text" "a different piece of text" "even older text") | |
785 | @end example | |
786 | ||
787 | @noindent | |
788 | When the list reaches @code{kill-ring-max} entries in length, adding a | |
789 | new entry automatically deletes the last entry. | |
790 | ||
791 | When kill commands are interwoven with other commands, each kill | |
792 | command makes a new entry in the kill ring. Multiple kill commands in | |
a9f0a989 RS |
793 | succession build up a single kill-ring entry, which would be yanked as a |
794 | unit; the second and subsequent consecutive kill commands add text to | |
795 | the entry made by the first one. | |
73804d4b RS |
796 | |
797 | For yanking, one entry in the kill ring is designated the ``front'' of | |
798 | the ring. Some yank commands ``rotate'' the ring by designating a | |
799 | different element as the ``front.'' But this virtual rotation doesn't | |
800 | change the list itself---the most recent entry always comes first in the | |
801 | list. | |
802 | ||
803 | @node Kill Functions | |
804 | @comment node-name, next, previous, up | |
805 | @subsection Functions for Killing | |
806 | ||
807 | @code{kill-region} is the usual subroutine for killing text. Any | |
808 | command that calls this function is a ``kill command'' (and should | |
809 | probably have @samp{kill} in its name). @code{kill-region} puts the | |
810 | newly killed text in a new element at the beginning of the kill ring or | |
f9f59935 RS |
811 | adds it to the most recent element. It determines automatically (using |
812 | @code{last-command}) whether the previous command was a kill command, | |
61cfa852 | 813 | and if so appends the killed text to the most recent entry. |
73804d4b | 814 | |
d73eac4d | 815 | @deffn Command kill-region start end &optional yank-handler |
73804d4b | 816 | This function kills the text in the region defined by @var{start} and |
bfe721d1 KH |
817 | @var{end}. The text is deleted but saved in the kill ring, along with |
818 | its text properties. The value is always @code{nil}. | |
73804d4b RS |
819 | |
820 | In an interactive call, @var{start} and @var{end} are point and | |
821 | the mark. | |
822 | ||
823 | @c Emacs 19 feature | |
2468d0c0 DL |
824 | If the buffer or text is read-only, @code{kill-region} modifies the kill |
825 | ring just the same, then signals an error without modifying the buffer. | |
826 | This is convenient because it lets the user use a series of kill | |
827 | commands to copy text from a read-only buffer into the kill ring. | |
d73eac4d RS |
828 | |
829 | If @var{yank-handler} is non-@code{nil}, this puts that value onto | |
830 | the string of killed text, as a @code{yank-handler} property. | |
831 | @xref{Yanking}. | |
73804d4b RS |
832 | @end deffn |
833 | ||
1911e6e5 | 834 | @defopt kill-read-only-ok |
2468d0c0 DL |
835 | If this option is non-@code{nil}, @code{kill-region} does not signal an |
836 | error if the buffer or text is read-only. Instead, it simply returns, | |
837 | updating the kill ring but not changing the buffer. | |
1911e6e5 RS |
838 | @end defopt |
839 | ||
73804d4b RS |
840 | @deffn Command copy-region-as-kill start end |
841 | This command saves the region defined by @var{start} and @var{end} on | |
bfe721d1 KH |
842 | the kill ring (including text properties), but does not delete the text |
843 | from the buffer. It returns @code{nil}. It also indicates the extent | |
844 | of the text copied by moving the cursor momentarily, or by displaying a | |
845 | message in the echo area. | |
73804d4b | 846 | |
22697dac KH |
847 | The command does not set @code{this-command} to @code{kill-region}, so a |
848 | subsequent kill command does not append to the same kill ring entry. | |
849 | ||
73804d4b | 850 | Don't call @code{copy-region-as-kill} in Lisp programs unless you aim to |
f9f59935 RS |
851 | support Emacs 18. For newer Emacs versions, it is better to use |
852 | @code{kill-new} or @code{kill-append} instead. @xref{Low-Level Kill | |
853 | Ring}. | |
73804d4b RS |
854 | @end deffn |
855 | ||
d73eac4d RS |
856 | @node Yanking |
857 | @subsection Yanking | |
858 | ||
859 | Yanking means inserting text from the kill ring, but it does | |
860 | not insert the text blindly. Yank commands and some other commands | |
861 | use @code{insert-for-yank} to perform special processing on the | |
862 | text that they copy into the buffer. | |
863 | ||
864 | @defun insert-for-yank string | |
865 | This function normally works like @code{insert} except that it doesn't | |
866 | insert the text properties in the @code{yank-excluded-properties} | |
867 | list. However, if the first character of @var{string} has a | |
868 | non-@code{nil}@code{yank-handler} text property, that property | |
869 | can do various special processing on the text being inserted. | |
870 | @end defun | |
871 | ||
872 | @defun insert-buffer-substring-as-yank buf &optional start end | |
873 | This function resembles @code{insert-buffer-substring} except that it | |
874 | doesn't insert the text properties in the | |
875 | @code{yank-excluded-properties} list. | |
876 | @end defun | |
877 | ||
878 | You can put a @code{yank-handler} text property on the text to | |
879 | control how it will be inserted if it is yanked. The | |
880 | @code{insert-for-yank} function looks for a @code{yank-handler} | |
881 | property on the first character in its @var{string} argument. The | |
882 | property value must be a list of one to four elements, with the | |
883 | following format (where elements after the first may be omitted): | |
884 | ||
885 | @example | |
886 | (@var{function} @var{param} @var{noexclude} @var{undo}) | |
887 | @end example | |
888 | ||
889 | Here is what the elements do: | |
890 | ||
891 | @table @var | |
892 | @item function | |
893 | When @var{function} is present and non-nil, it is called instead of | |
894 | @code{insert} to insert the string. @var{function} takes one | |
895 | argument---the string to insert. | |
896 | ||
897 | @item param | |
898 | If @var{param} is present and non-@code{nil}, it replaces @var{string} | |
899 | as the object passed to @var{function} (or @code{insert}); for | |
900 | example, if @var{function} is @code{yank-rectangle}, @var{param} | |
901 | should be a list of strings to insert as a rectangle. | |
902 | ||
903 | @item noexclude | |
904 | If @var{noexclude} is present and non-@code{nil}, the normal removal of the | |
905 | yank-excluded-properties is not performed; instead @var{function} is | |
906 | responsible for removing those properties. This may be necessary | |
907 | if @var{function} adjusts point before or after inserting the object. | |
908 | ||
909 | @item undo | |
910 | If @var{undo} is present and non-nil, it is a function that will be | |
911 | called by @code{yank-pop} to undo the insertion of the current object. | |
912 | It is called with two arguments, the start and end of the current | |
913 | region. @var{function} can set @code{yank-undo-function} to override | |
914 | the @var{undo} value. | |
915 | @end table | |
916 | ||
73804d4b RS |
917 | @node Yank Commands |
918 | @comment node-name, next, previous, up | |
919 | @subsection Functions for Yanking | |
920 | ||
921 | @dfn{Yanking} means reinserting an entry of previously killed text | |
bfe721d1 | 922 | from the kill ring. The text properties are copied too. |
73804d4b RS |
923 | |
924 | @deffn Command yank &optional arg | |
925 | @cindex inserting killed text | |
926 | This command inserts before point the text in the first entry in the | |
927 | kill ring. It positions the mark at the beginning of that text, and | |
928 | point at the end. | |
929 | ||
930 | If @var{arg} is a list (which occurs interactively when the user | |
931 | types @kbd{C-u} with no digits), then @code{yank} inserts the text as | |
932 | described above, but puts point before the yanked text and puts the mark | |
933 | after it. | |
934 | ||
935 | If @var{arg} is a number, then @code{yank} inserts the @var{arg}th most | |
936 | recently killed text---the @var{arg}th element of the kill ring list. | |
937 | ||
938 | @code{yank} does not alter the contents of the kill ring or rotate it. | |
939 | It returns @code{nil}. | |
940 | @end deffn | |
941 | ||
942 | @deffn Command yank-pop arg | |
943 | This command replaces the just-yanked entry from the kill ring with a | |
944 | different entry from the kill ring. | |
945 | ||
946 | This is allowed only immediately after a @code{yank} or another | |
947 | @code{yank-pop}. At such a time, the region contains text that was just | |
948 | inserted by yanking. @code{yank-pop} deletes that text and inserts in | |
949 | its place a different piece of killed text. It does not add the deleted | |
950 | text to the kill ring, since it is already in the kill ring somewhere. | |
951 | ||
952 | If @var{arg} is @code{nil}, then the replacement text is the previous | |
953 | element of the kill ring. If @var{arg} is numeric, the replacement is | |
954 | the @var{arg}th previous kill. If @var{arg} is negative, a more recent | |
955 | kill is the replacement. | |
956 | ||
957 | The sequence of kills in the kill ring wraps around, so that after the | |
958 | oldest one comes the newest one, and before the newest one goes the | |
959 | oldest. | |
960 | ||
a9f0a989 | 961 | The return value is always @code{nil}. |
73804d4b RS |
962 | @end deffn |
963 | ||
d73eac4d RS |
964 | @defvar yank-undo-function |
965 | If this variable is non-@code{nil}, the function @code{yank-pop} uses | |
966 | its value instead of @code{delete-region} to delete the text | |
967 | inserted by the previous @code{yank} or | |
968 | @code{yank-pop} command. | |
969 | ||
970 | The function @code{insert-for-yank} automatically sets this variable | |
971 | according to the @var{undo} element of the @code{yank-handler} | |
972 | text property, if there is one. | |
973 | @end defvar | |
974 | ||
61cfa852 RS |
975 | @node Low-Level Kill Ring |
976 | @subsection Low-Level Kill Ring | |
73804d4b | 977 | |
969fe9b5 RS |
978 | These functions and variables provide access to the kill ring at a |
979 | lower level, but still convenient for use in Lisp programs, because they | |
980 | take care of interaction with window system selections | |
981 | (@pxref{Window System Selections}). | |
73804d4b RS |
982 | |
983 | @defun current-kill n &optional do-not-move | |
a9f0a989 RS |
984 | The function @code{current-kill} rotates the yanking pointer, which |
985 | designates the ``front'' of the kill ring, by @var{n} places (from newer | |
61cfa852 | 986 | kills to older ones), and returns the text at that place in the ring. |
73804d4b RS |
987 | |
988 | If the optional second argument @var{do-not-move} is non-@code{nil}, | |
989 | then @code{current-kill} doesn't alter the yanking pointer; it just | |
61cfa852 | 990 | returns the @var{n}th kill, counting from the current yanking pointer. |
73804d4b RS |
991 | |
992 | If @var{n} is zero, indicating a request for the latest kill, | |
993 | @code{current-kill} calls the value of | |
994 | @code{interprogram-paste-function} (documented below) before consulting | |
995 | the kill ring. | |
996 | @end defun | |
997 | ||
d73eac4d | 998 | @defun kill-new string &optional yank-handler |
73804d4b RS |
999 | This function puts the text @var{string} into the kill ring as a new |
1000 | entry at the front of the ring. It discards the oldest entry if | |
1001 | appropriate. It also invokes the value of | |
1002 | @code{interprogram-cut-function} (see below). | |
d73eac4d RS |
1003 | |
1004 | If @var{yank-handler} is non-@code{nil}, this puts that value onto | |
1005 | the string of killed text, as a @code{yank-handler} property. | |
1006 | @xref{Yanking}. | |
73804d4b RS |
1007 | @end defun |
1008 | ||
d73eac4d | 1009 | @defun kill-append string before-p &optional yank-handler |
73804d4b RS |
1010 | This function appends the text @var{string} to the first entry in the |
1011 | kill ring. Normally @var{string} goes at the end of the entry, but if | |
1012 | @var{before-p} is non-@code{nil}, it goes at the beginning. This | |
1013 | function also invokes the value of @code{interprogram-cut-function} (see | |
d73eac4d | 1014 | below). This handles @var{yank-handler} just like @code{kill-new}. |
73804d4b RS |
1015 | @end defun |
1016 | ||
1017 | @defvar interprogram-paste-function | |
1018 | This variable provides a way of transferring killed text from other | |
1019 | programs, when you are using a window system. Its value should be | |
1020 | @code{nil} or a function of no arguments. | |
1021 | ||
1022 | If the value is a function, @code{current-kill} calls it to get the | |
1023 | ``most recent kill''. If the function returns a non-@code{nil} value, | |
1024 | then that value is used as the ``most recent kill''. If it returns | |
1025 | @code{nil}, then the first element of @code{kill-ring} is used. | |
1026 | ||
969fe9b5 RS |
1027 | The normal use of this hook is to get the window system's primary |
1028 | selection as the most recent kill, even if the selection belongs to | |
1029 | another application. @xref{Window System Selections}. | |
73804d4b RS |
1030 | @end defvar |
1031 | ||
1032 | @defvar interprogram-cut-function | |
61cfa852 RS |
1033 | This variable provides a way of communicating killed text to other |
1034 | programs, when you are using a window system. Its value should be | |
73804d4b RS |
1035 | @code{nil} or a function of one argument. |
1036 | ||
1037 | If the value is a function, @code{kill-new} and @code{kill-append} call | |
1038 | it with the new first element of the kill ring as an argument. | |
1039 | ||
969fe9b5 RS |
1040 | The normal use of this hook is to set the window system's primary |
1041 | selection from the newly killed text. @xref{Window System Selections}. | |
73804d4b RS |
1042 | @end defvar |
1043 | ||
1044 | @node Internals of Kill Ring | |
1045 | @comment node-name, next, previous, up | |
1046 | @subsection Internals of the Kill Ring | |
1047 | ||
1048 | The variable @code{kill-ring} holds the kill ring contents, in the | |
1049 | form of a list of strings. The most recent kill is always at the front | |
177c0ea7 | 1050 | of the list. |
73804d4b RS |
1051 | |
1052 | The @code{kill-ring-yank-pointer} variable points to a link in the | |
61cfa852 RS |
1053 | kill ring list, whose @sc{car} is the text to yank next. We say it |
1054 | identifies the ``front'' of the ring. Moving | |
73804d4b | 1055 | @code{kill-ring-yank-pointer} to a different link is called |
61cfa852 RS |
1056 | @dfn{rotating the kill ring}. We call the kill ring a ``ring'' because |
1057 | the functions that move the yank pointer wrap around from the end of the | |
1058 | list to the beginning, or vice-versa. Rotation of the kill ring is | |
1059 | virtual; it does not change the value of @code{kill-ring}. | |
73804d4b RS |
1060 | |
1061 | Both @code{kill-ring} and @code{kill-ring-yank-pointer} are Lisp | |
1062 | variables whose values are normally lists. The word ``pointer'' in the | |
1063 | name of the @code{kill-ring-yank-pointer} indicates that the variable's | |
1064 | purpose is to identify one element of the list for use by the next yank | |
1065 | command. | |
1066 | ||
1067 | The value of @code{kill-ring-yank-pointer} is always @code{eq} to one | |
1068 | of the links in the kill ring list. The element it identifies is the | |
1069 | @sc{car} of that link. Kill commands, which change the kill ring, also | |
61cfa852 RS |
1070 | set this variable to the value of @code{kill-ring}. The effect is to |
1071 | rotate the ring so that the newly killed text is at the front. | |
73804d4b RS |
1072 | |
1073 | Here is a diagram that shows the variable @code{kill-ring-yank-pointer} | |
1074 | pointing to the second entry in the kill ring @code{("some text" "a | |
177c0ea7 | 1075 | different piece of text" "yet older text")}. |
73804d4b RS |
1076 | |
1077 | @example | |
1078 | @group | |
969fe9b5 RS |
1079 | kill-ring ---- kill-ring-yank-pointer |
1080 | | | | |
1081 | | v | |
1082 | | --- --- --- --- --- --- | |
1083 | --> | | |------> | | |--> | | |--> nil | |
1084 | --- --- --- --- --- --- | |
177c0ea7 JB |
1085 | | | | |
1086 | | | | | |
1087 | | | -->"yet older text" | |
73804d4b | 1088 | | | |
177c0ea7 | 1089 | | --> "a different piece of text" |
73804d4b RS |
1090 | | |
1091 | --> "some text" | |
1092 | @end group | |
1093 | @end example | |
1094 | ||
1095 | @noindent | |
1096 | This state of affairs might occur after @kbd{C-y} (@code{yank}) | |
1097 | immediately followed by @kbd{M-y} (@code{yank-pop}). | |
1098 | ||
1099 | @defvar kill-ring | |
61cfa852 RS |
1100 | This variable holds the list of killed text sequences, most recently |
1101 | killed first. | |
73804d4b RS |
1102 | @end defvar |
1103 | ||
1104 | @defvar kill-ring-yank-pointer | |
1105 | This variable's value indicates which element of the kill ring is at the | |
1106 | ``front'' of the ring for yanking. More precisely, the value is a tail | |
1107 | of the value of @code{kill-ring}, and its @sc{car} is the kill string | |
1108 | that @kbd{C-y} should yank. | |
1109 | @end defvar | |
1110 | ||
1111 | @defopt kill-ring-max | |
1112 | The value of this variable is the maximum length to which the kill | |
1113 | ring can grow, before elements are thrown away at the end. The default | |
1114 | value for @code{kill-ring-max} is 30. | |
1115 | @end defopt | |
1116 | ||
1117 | @node Undo | |
1118 | @comment node-name, next, previous, up | |
1119 | @section Undo | |
1120 | @cindex redo | |
1121 | ||
61cfa852 RS |
1122 | Most buffers have an @dfn{undo list}, which records all changes made |
1123 | to the buffer's text so that they can be undone. (The buffers that | |
1124 | don't have one are usually special-purpose buffers for which Emacs | |
1125 | assumes that undoing is not useful.) All the primitives that modify the | |
1126 | text in the buffer automatically add elements to the front of the undo | |
1127 | list, which is in the variable @code{buffer-undo-list}. | |
73804d4b RS |
1128 | |
1129 | @defvar buffer-undo-list | |
1130 | This variable's value is the undo list of the current buffer. | |
1131 | A value of @code{t} disables the recording of undo information. | |
1132 | @end defvar | |
1133 | ||
1134 | Here are the kinds of elements an undo list can have: | |
1135 | ||
1136 | @table @code | |
1911e6e5 RS |
1137 | @item @var{position} |
1138 | This kind of element records a previous value of point; undoing this | |
1139 | element moves point to @var{position}. Ordinary cursor motion does not | |
1140 | make any sort of undo record, but deletion operations use these entries | |
1141 | to record where point was before the command. | |
73804d4b RS |
1142 | |
1143 | @item (@var{beg} . @var{end}) | |
1144 | This kind of element indicates how to delete text that was inserted. | |
177c0ea7 | 1145 | Upon insertion, the text occupied the range @var{beg}--@var{end} in the |
73804d4b RS |
1146 | buffer. |
1147 | ||
d1756ab9 | 1148 | @item (@var{text} . @var{position}) |
73804d4b | 1149 | This kind of element indicates how to reinsert text that was deleted. |
d1756ab9 RS |
1150 | The deleted text itself is the string @var{text}. The place to |
1151 | reinsert it is @code{(abs @var{position})}. | |
73804d4b RS |
1152 | |
1153 | @item (t @var{high} . @var{low}) | |
1154 | This kind of element indicates that an unmodified buffer became | |
1155 | modified. The elements @var{high} and @var{low} are two integers, each | |
1156 | recording 16 bits of the visited file's modification time as of when it | |
1157 | was previously visited or saved. @code{primitive-undo} uses those | |
1158 | values to determine whether to mark the buffer as unmodified once again; | |
1159 | it does so only if the file's modification time matches those numbers. | |
1160 | ||
1161 | @item (nil @var{property} @var{value} @var{beg} . @var{end}) | |
1162 | This kind of element records a change in a text property. | |
1163 | Here's how you might undo the change: | |
1164 | ||
1165 | @example | |
1166 | (put-text-property @var{beg} @var{end} @var{property} @var{value}) | |
1167 | @end example | |
d1756ab9 | 1168 | |
61ee3601 RS |
1169 | @item (@var{marker} . @var{adjustment}) |
1170 | This kind of element records the fact that the marker @var{marker} was | |
1171 | relocated due to deletion of surrounding text, and that it moved | |
1172 | @var{adjustment} character positions. Undoing this element moves | |
1173 | @var{marker} @minus{} @var{adjustment} characters. | |
1174 | ||
73804d4b RS |
1175 | @item nil |
1176 | This element is a boundary. The elements between two boundaries are | |
1177 | called a @dfn{change group}; normally, each change group corresponds to | |
1178 | one keyboard command, and undo commands normally undo an entire group as | |
1179 | a unit. | |
1180 | @end table | |
1181 | ||
1182 | @defun undo-boundary | |
1183 | This function places a boundary element in the undo list. The undo | |
1184 | command stops at such a boundary, and successive undo commands undo | |
1185 | to earlier and earlier boundaries. This function returns @code{nil}. | |
1186 | ||
b6a786ce RS |
1187 | The editor command loop automatically creates an undo boundary before |
1188 | each key sequence is executed. Thus, each undo normally undoes the | |
1189 | effects of one command. Self-inserting input characters are an | |
1190 | exception. The command loop makes a boundary for the first such | |
1191 | character; the next 19 consecutive self-inserting input characters do | |
1192 | not make boundaries, and then the 20th does, and so on as long as | |
1193 | self-inserting characters continue. | |
1194 | ||
1195 | All buffer modifications add a boundary whenever the previous undoable | |
a9f0a989 RS |
1196 | change was made in some other buffer. This is to ensure that |
1197 | each command makes a boundary in each buffer where it makes changes. | |
b6a786ce RS |
1198 | |
1199 | Calling this function explicitly is useful for splitting the effects of | |
1200 | a command into more than one unit. For example, @code{query-replace} | |
1201 | calls @code{undo-boundary} after each replacement, so that the user can | |
1202 | undo individual replacements one by one. | |
73804d4b RS |
1203 | @end defun |
1204 | ||
1205 | @defun primitive-undo count list | |
1206 | This is the basic function for undoing elements of an undo list. | |
1207 | It undoes the first @var{count} elements of @var{list}, returning | |
1208 | the rest of @var{list}. You could write this function in Lisp, | |
1209 | but it is convenient to have it in C. | |
1210 | ||
1211 | @code{primitive-undo} adds elements to the buffer's undo list when it | |
1212 | changes the buffer. Undo commands avoid confusion by saving the undo | |
1213 | list value at the beginning of a sequence of undo operations. Then the | |
1214 | undo operations use and update the saved value. The new elements added | |
bfe721d1 | 1215 | by undoing are not part of this saved value, so they don't interfere with |
73804d4b RS |
1216 | continuing to undo. |
1217 | @end defun | |
1218 | ||
1219 | @node Maintaining Undo | |
1220 | @section Maintaining Undo Lists | |
1221 | ||
1222 | This section describes how to enable and disable undo information for | |
1223 | a given buffer. It also explains how the undo list is truncated | |
1224 | automatically so it doesn't get too big. | |
1225 | ||
1226 | Recording of undo information in a newly created buffer is normally | |
1227 | enabled to start with; but if the buffer name starts with a space, the | |
1228 | undo recording is initially disabled. You can explicitly enable or | |
1229 | disable undo recording with the following two functions, or by setting | |
1230 | @code{buffer-undo-list} yourself. | |
1231 | ||
1232 | @deffn Command buffer-enable-undo &optional buffer-or-name | |
1233 | This command enables recording undo information for buffer | |
1234 | @var{buffer-or-name}, so that subsequent changes can be undone. If no | |
1235 | argument is supplied, then the current buffer is used. This function | |
1236 | does nothing if undo recording is already enabled in the buffer. It | |
1237 | returns @code{nil}. | |
1238 | ||
1239 | In an interactive call, @var{buffer-or-name} is the current buffer. | |
1240 | You cannot specify any other buffer. | |
1241 | @end deffn | |
1242 | ||
a9f0a989 RS |
1243 | @deffn Command buffer-disable-undo &optional buffer |
1244 | @deffnx Command buffer-flush-undo &optional buffer | |
73804d4b RS |
1245 | @cindex disable undo |
1246 | This function discards the undo list of @var{buffer}, and disables | |
1247 | further recording of undo information. As a result, it is no longer | |
1248 | possible to undo either previous changes or any subsequent changes. If | |
1249 | the undo list of @var{buffer} is already disabled, this function | |
1250 | has no effect. | |
1251 | ||
a9f0a989 | 1252 | This function returns @code{nil}. |
73804d4b RS |
1253 | |
1254 | The name @code{buffer-flush-undo} is not considered obsolete, but the | |
969fe9b5 | 1255 | preferred name is @code{buffer-disable-undo}. |
a9f0a989 | 1256 | @end deffn |
73804d4b RS |
1257 | |
1258 | As editing continues, undo lists get longer and longer. To prevent | |
1259 | them from using up all available memory space, garbage collection trims | |
1260 | them back to size limits you can set. (For this purpose, the ``size'' | |
1261 | of an undo list measures the cons cells that make up the list, plus the | |
1262 | strings of deleted text.) Two variables control the range of acceptable | |
1263 | sizes: @code{undo-limit} and @code{undo-strong-limit}. | |
1264 | ||
1265 | @defvar undo-limit | |
1266 | This is the soft limit for the acceptable size of an undo list. The | |
1267 | change group at which this size is exceeded is the last one kept. | |
1268 | @end defvar | |
1269 | ||
1270 | @defvar undo-strong-limit | |
61cfa852 RS |
1271 | This is the upper limit for the acceptable size of an undo list. The |
1272 | change group at which this size is exceeded is discarded itself (along | |
1273 | with all older change groups). There is one exception: the very latest | |
bda144f4 | 1274 | change group is never discarded no matter how big it is. |
73804d4b RS |
1275 | @end defvar |
1276 | ||
1277 | @node Filling | |
1278 | @comment node-name, next, previous, up | |
1279 | @section Filling | |
1280 | @cindex filling, explicit | |
1281 | ||
1282 | @dfn{Filling} means adjusting the lengths of lines (by moving the line | |
1283 | breaks) so that they are nearly (but no greater than) a specified | |
1284 | maximum width. Additionally, lines can be @dfn{justified}, which means | |
bfe721d1 KH |
1285 | inserting spaces to make the left and/or right margins line up |
1286 | precisely. The width is controlled by the variable @code{fill-column}. | |
1287 | For ease of reading, lines should be no longer than 70 or so columns. | |
73804d4b RS |
1288 | |
1289 | You can use Auto Fill mode (@pxref{Auto Filling}) to fill text | |
1290 | automatically as you insert it, but changes to existing text may leave | |
1291 | it improperly filled. Then you must fill the text explicitly. | |
1292 | ||
22697dac KH |
1293 | Most of the commands in this section return values that are not |
1294 | meaningful. All the functions that do filling take note of the current | |
bfe721d1 KH |
1295 | left margin, current right margin, and current justification style |
1296 | (@pxref{Margins}). If the current justification style is | |
1297 | @code{none}, the filling functions don't actually do anything. | |
1298 | ||
1299 | Several of the filling functions have an argument @var{justify}. | |
1300 | If it is non-@code{nil}, that requests some kind of justification. It | |
1301 | can be @code{left}, @code{right}, @code{full}, or @code{center}, to | |
1302 | request a specific style of justification. If it is @code{t}, that | |
1303 | means to use the current justification style for this part of the text | |
969fe9b5 RS |
1304 | (see @code{current-justification}, below). Any other value is treated |
1305 | as @code{full}. | |
bfe721d1 KH |
1306 | |
1307 | When you call the filling functions interactively, using a prefix | |
1308 | argument implies the value @code{full} for @var{justify}. | |
73804d4b | 1309 | |
bfe721d1 | 1310 | @deffn Command fill-paragraph justify |
73804d4b RS |
1311 | @cindex filling a paragraph |
1312 | This command fills the paragraph at or after point. If | |
bfe721d1 | 1313 | @var{justify} is non-@code{nil}, each line is justified as well. |
73804d4b | 1314 | It uses the ordinary paragraph motion commands to find paragraph |
0b2fb045 | 1315 | boundaries. @xref{Paragraphs,,, emacs, The GNU Emacs Manual}. |
73804d4b RS |
1316 | @end deffn |
1317 | ||
15da7853 | 1318 | @deffn Command fill-region start end &optional justify nosqueeze to-eop |
73804d4b | 1319 | This command fills each of the paragraphs in the region from @var{start} |
bfe721d1 | 1320 | to @var{end}. It justifies as well if @var{justify} is |
73804d4b RS |
1321 | non-@code{nil}. |
1322 | ||
1911e6e5 RS |
1323 | If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace |
1324 | other than line breaks untouched. If @var{to-eop} is non-@code{nil}, | |
ebc6903b | 1325 | that means to keep filling to the end of the paragraph---or the next hard |
1911e6e5 RS |
1326 | newline, if @code{use-hard-newlines} is enabled (see below). |
1327 | ||
73804d4b RS |
1328 | The variable @code{paragraph-separate} controls how to distinguish |
1329 | paragraphs. @xref{Standard Regexps}. | |
1330 | @end deffn | |
1331 | ||
2468d0c0 | 1332 | @deffn Command fill-individual-paragraphs start end &optional justify citation-regexp |
73804d4b RS |
1333 | This command fills each paragraph in the region according to its |
1334 | individual fill prefix. Thus, if the lines of a paragraph were indented | |
1335 | with spaces, the filled paragraph will remain indented in the same | |
1336 | fashion. | |
1337 | ||
1338 | The first two arguments, @var{start} and @var{end}, are the beginning | |
1339 | and end of the region to be filled. The third and fourth arguments, | |
2468d0c0 | 1340 | @var{justify} and @var{citation-regexp}, are optional. If |
bfe721d1 | 1341 | @var{justify} is non-@code{nil}, the paragraphs are justified as |
2468d0c0 | 1342 | well as filled. If @var{citation-regexp} is non-@code{nil}, it means the |
73804d4b | 1343 | function is operating on a mail message and therefore should not fill |
2468d0c0 DL |
1344 | the header lines. If @var{citation-regexp} is a string, it is used as |
1345 | a regular expression; if it matches the beginning of a line, that line | |
1346 | is treated as a citation marker. | |
73804d4b RS |
1347 | |
1348 | Ordinarily, @code{fill-individual-paragraphs} regards each change in | |
1349 | indentation as starting a new paragraph. If | |
1350 | @code{fill-individual-varying-indent} is non-@code{nil}, then only | |
61cfa852 RS |
1351 | separator lines separate paragraphs. That mode can handle indented |
1352 | paragraphs with additional indentation on the first line. | |
73804d4b RS |
1353 | @end deffn |
1354 | ||
1355 | @defopt fill-individual-varying-indent | |
1356 | This variable alters the action of @code{fill-individual-paragraphs} as | |
1357 | described above. | |
1358 | @end defopt | |
1359 | ||
1911e6e5 | 1360 | @deffn Command fill-region-as-paragraph start end &optional justify nosqueeze squeeze-after |
f9f59935 RS |
1361 | This command considers a region of text as a single paragraph and fills |
1362 | it. If the region was made up of many paragraphs, the blank lines | |
1363 | between paragraphs are removed. This function justifies as well as | |
1364 | filling when @var{justify} is non-@code{nil}. | |
22697dac KH |
1365 | |
1366 | In an interactive call, any prefix argument requests justification. | |
73804d4b | 1367 | |
1911e6e5 RS |
1368 | If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace |
1369 | other than line breaks untouched. If @var{squeeze-after} is | |
ebc6903b | 1370 | non-@code{nil}, it specifies a position in the region, and means don't |
1911e6e5 RS |
1371 | canonicalize spaces before that position. |
1372 | ||
1373 | In Adaptive Fill mode, this command calls @code{fill-context-prefix} to | |
1374 | choose a fill prefix by default. @xref{Adaptive Fill}. | |
73804d4b RS |
1375 | @end deffn |
1376 | ||
2468d0c0 | 1377 | @deffn Command justify-current-line &optional how eop nosqueeze |
73804d4b RS |
1378 | This command inserts spaces between the words of the current line so |
1379 | that the line ends exactly at @code{fill-column}. It returns | |
1380 | @code{nil}. | |
22697dac KH |
1381 | |
1382 | The argument @var{how}, if non-@code{nil} specifies explicitly the style | |
1383 | of justification. It can be @code{left}, @code{right}, @code{full}, | |
1384 | @code{center}, or @code{none}. If it is @code{t}, that means to do | |
1385 | follow specified justification style (see @code{current-justification}, | |
1386 | below). @code{nil} means to do full justification. | |
1387 | ||
9e2b495b | 1388 | If @var{eop} is non-@code{nil}, that means do left-justification if |
22697dac KH |
1389 | @code{current-justification} specifies full justification. This is used |
1390 | for the last line of a paragraph; even if the paragraph as a whole is | |
1391 | fully justified, the last line should not be. | |
1392 | ||
1393 | If @var{nosqueeze} is non-@code{nil}, that means do not change interior | |
1394 | whitespace. | |
73804d4b RS |
1395 | @end deffn |
1396 | ||
22697dac KH |
1397 | @defopt default-justification |
1398 | This variable's value specifies the style of justification to use for | |
1399 | text that doesn't specify a style with a text property. The possible | |
1400 | values are @code{left}, @code{right}, @code{full}, @code{center}, or | |
bfe721d1 | 1401 | @code{none}. The default value is @code{left}. |
22697dac KH |
1402 | @end defopt |
1403 | ||
1404 | @defun current-justification | |
1405 | This function returns the proper justification style to use for filling | |
1406 | the text around point. | |
1407 | @end defun | |
1408 | ||
1911e6e5 RS |
1409 | @defopt sentence-end-double-space |
1410 | If this variable is non-@code{nil}, a period followed by just one space | |
1411 | does not count as the end of a sentence, and the filling functions | |
1412 | avoid breaking the line at such a place. | |
1413 | @end defopt | |
1414 | ||
bfe721d1 KH |
1415 | @defvar fill-paragraph-function |
1416 | This variable provides a way for major modes to override the filling of | |
1417 | paragraphs. If the value is non-@code{nil}, @code{fill-paragraph} calls | |
1418 | this function to do the work. If the function returns a non-@code{nil} | |
1419 | value, @code{fill-paragraph} assumes the job is done, and immediately | |
1420 | returns that value. | |
1421 | ||
1422 | The usual use of this feature is to fill comments in programming | |
1423 | language modes. If the function needs to fill a paragraph in the usual | |
1424 | way, it can do so as follows: | |
1425 | ||
1426 | @example | |
1427 | (let ((fill-paragraph-function nil)) | |
1428 | (fill-paragraph arg)) | |
1429 | @end example | |
1430 | @end defvar | |
1431 | ||
1432 | @defvar use-hard-newlines | |
1433 | If this variable is non-@code{nil}, the filling functions do not delete | |
1434 | newlines that have the @code{hard} text property. These ``hard | |
1435 | newlines'' act as paragraph separators. | |
1436 | @end defvar | |
1437 | ||
1438 | @node Margins | |
1439 | @section Margins for Filling | |
1440 | ||
61cfa852 | 1441 | @defopt fill-prefix |
a9f0a989 RS |
1442 | This buffer-local variable specifies a string of text that appears at |
1443 | the beginning | |
61cfa852 RS |
1444 | of normal text lines and should be disregarded when filling them. Any |
1445 | line that fails to start with the fill prefix is considered the start of | |
1446 | a paragraph; so is any line that starts with the fill prefix followed by | |
1447 | additional whitespace. Lines that start with the fill prefix but no | |
1448 | additional whitespace are ordinary text lines that can be filled | |
1449 | together. The resulting filled lines also start with the fill prefix. | |
bfe721d1 KH |
1450 | |
1451 | The fill prefix follows the left margin whitespace, if any. | |
61cfa852 RS |
1452 | @end defopt |
1453 | ||
1911e6e5 | 1454 | @defopt fill-column |
f9f59935 RS |
1455 | This buffer-local variable specifies the maximum width of filled lines. |
1456 | Its value should be an integer, which is a number of columns. All the | |
1457 | filling, justification, and centering commands are affected by this | |
1458 | variable, including Auto Fill mode (@pxref{Auto Filling}). | |
73804d4b RS |
1459 | |
1460 | As a practical matter, if you are writing text for other people to | |
1461 | read, you should set @code{fill-column} to no more than 70. Otherwise | |
1462 | the line will be too long for people to read comfortably, and this can | |
1463 | make the text seem clumsy. | |
1911e6e5 | 1464 | @end defopt |
73804d4b RS |
1465 | |
1466 | @defvar default-fill-column | |
1467 | The value of this variable is the default value for @code{fill-column} in | |
1468 | buffers that do not override it. This is the same as | |
1469 | @code{(default-value 'fill-column)}. | |
1470 | ||
1471 | The default value for @code{default-fill-column} is 70. | |
1472 | @end defvar | |
1473 | ||
22697dac KH |
1474 | @deffn Command set-left-margin from to margin |
1475 | This sets the @code{left-margin} property on the text from @var{from} to | |
1476 | @var{to} to the value @var{margin}. If Auto Fill mode is enabled, this | |
1477 | command also refills the region to fit the new margin. | |
1478 | @end deffn | |
1479 | ||
1480 | @deffn Command set-right-margin from to margin | |
bfe721d1 KH |
1481 | This sets the @code{right-margin} property on the text from @var{from} |
1482 | to @var{to} to the value @var{margin}. If Auto Fill mode is enabled, | |
1483 | this command also refills the region to fit the new margin. | |
22697dac KH |
1484 | @end deffn |
1485 | ||
1486 | @defun current-left-margin | |
1487 | This function returns the proper left margin value to use for filling | |
1488 | the text around point. The value is the sum of the @code{left-margin} | |
1489 | property of the character at the start of the current line (or zero if | |
bfe721d1 | 1490 | none), and the value of the variable @code{left-margin}. |
22697dac KH |
1491 | @end defun |
1492 | ||
1493 | @defun current-fill-column | |
1494 | This function returns the proper fill column value to use for filling | |
1495 | the text around point. The value is the value of the @code{fill-column} | |
1496 | variable, minus the value of the @code{right-margin} property of the | |
1497 | character after point. | |
1498 | @end defun | |
1499 | ||
1500 | @deffn Command move-to-left-margin &optional n force | |
1501 | This function moves point to the left margin of the current line. The | |
1502 | column moved to is determined by calling the function | |
bfe721d1 | 1503 | @code{current-left-margin}. If the argument @var{n} is non-@code{nil}, |
22697dac KH |
1504 | @code{move-to-left-margin} moves forward @var{n}@minus{}1 lines first. |
1505 | ||
1506 | If @var{force} is non-@code{nil}, that says to fix the line's | |
1507 | indentation if that doesn't match the left margin value. | |
1508 | @end deffn | |
1509 | ||
2468d0c0 DL |
1510 | @defun delete-to-left-margin &optional from to |
1511 | This function removes left margin indentation from the text between | |
1512 | @var{from} and @var{to}. The amount of indentation to delete is | |
1513 | determined by calling @code{current-left-margin}. In no case does this | |
1514 | function delete non-whitespace. If @var{from} and @var{to} are omitted, | |
1515 | they default to the whole buffer. | |
22697dac KH |
1516 | @end defun |
1517 | ||
bfe721d1 KH |
1518 | @defun indent-to-left-margin |
1519 | This is the default @code{indent-line-function}, used in Fundamental | |
1520 | mode, Text mode, etc. Its effect is to adjust the indentation at the | |
1521 | beginning of the current line to the value specified by the variable | |
1522 | @code{left-margin}. This may involve either inserting or deleting | |
1523 | whitespace. | |
1524 | @end defun | |
1525 | ||
1526 | @defvar left-margin | |
1527 | This variable specifies the base left margin column. In Fundamental | |
969fe9b5 | 1528 | mode, @kbd{C-j} indents to this column. This variable automatically |
bfe721d1 KH |
1529 | becomes buffer-local when set in any fashion. |
1530 | @end defvar | |
1531 | ||
969fe9b5 RS |
1532 | @defvar fill-nobreak-predicate |
1533 | This variable gives major modes a way to specify not to break a line at | |
1534 | certain places. Its value should be a function. This function is | |
1535 | called during filling, with no arguments and with point located at the | |
1536 | place where a break is being considered. If the function returns | |
1537 | non-@code{nil}, then the line won't be broken there. | |
1538 | @end defvar | |
1539 | ||
1911e6e5 RS |
1540 | @node Adaptive Fill |
1541 | @section Adaptive Fill Mode | |
1542 | @cindex Adaptive Fill mode | |
1543 | ||
1544 | Adaptive Fill mode chooses a fill prefix automatically from the text | |
1545 | in each paragraph being filled. | |
1546 | ||
1547 | @defopt adaptive-fill-mode | |
1548 | Adaptive Fill mode is enabled when this variable is non-@code{nil}. | |
1549 | It is @code{t} by default. | |
1550 | @end defopt | |
1551 | ||
1552 | @defun fill-context-prefix from to | |
1553 | This function implements the heart of Adaptive Fill mode; it chooses a | |
1554 | fill prefix based on the text between @var{from} and @var{to}. It does | |
1555 | this by looking at the first two lines of the paragraph, based on the | |
1556 | variables described below. | |
2468d0c0 DL |
1557 | @c The optional argument first-line-regexp is not documented |
1558 | @c because it exists for internal purposes and might be eliminated | |
1559 | @c in the future. | |
1911e6e5 RS |
1560 | @end defun |
1561 | ||
1562 | @defopt adaptive-fill-regexp | |
1563 | This variable holds a regular expression to control Adaptive Fill mode. | |
ebc6903b RS |
1564 | Adaptive Fill mode matches this regular expression against the text |
1565 | starting after the left margin whitespace (if any) on a line; the | |
1566 | characters it matches are that line's candidate for the fill prefix. | |
1911e6e5 RS |
1567 | @end defopt |
1568 | ||
1569 | @defopt adaptive-fill-first-line-regexp | |
ebc6903b RS |
1570 | In a one-line paragraph, if the candidate fill prefix matches this |
1571 | regular expression, or if it matches @code{comment-start-skip}, then it | |
1572 | is used---otherwise, spaces amounting to the same width are used | |
1573 | instead. | |
1911e6e5 RS |
1574 | |
1575 | However, the fill prefix is never taken from a one-line paragraph | |
1576 | if it would act as a paragraph starter on subsequent lines. | |
1577 | @end defopt | |
1578 | ||
1579 | @defopt adaptive-fill-function | |
1580 | You can specify more complex ways of choosing a fill prefix | |
1581 | automatically by setting this variable to a function. The function is | |
1582 | called when @code{adaptive-fill-regexp} does not match, with point after | |
1583 | the left margin of a line, and it should return the appropriate fill | |
1584 | prefix based on that line. If it returns @code{nil}, that means it sees | |
1585 | no fill prefix in that line. | |
1586 | @end defopt | |
1587 | ||
73804d4b RS |
1588 | @node Auto Filling |
1589 | @comment node-name, next, previous, up | |
1590 | @section Auto Filling | |
1591 | @cindex filling, automatic | |
1592 | @cindex Auto Fill mode | |
1593 | ||
61cfa852 | 1594 | Auto Fill mode is a minor mode that fills lines automatically as text |
bda144f4 | 1595 | is inserted. This section describes the hook used by Auto Fill mode. |
61cfa852 RS |
1596 | For a description of functions that you can call explicitly to fill and |
1597 | justify existing text, see @ref{Filling}. | |
73804d4b | 1598 | |
bfe721d1 KH |
1599 | Auto Fill mode also enables the functions that change the margins and |
1600 | justification style to refill portions of the text. @xref{Margins}. | |
1601 | ||
73804d4b | 1602 | @defvar auto-fill-function |
22697dac | 1603 | The value of this variable should be a function (of no arguments) to be |
ca3be36e DL |
1604 | called after self-inserting a character from the table |
1605 | @code{auto-fill-chars}. It may be @code{nil}, in which case nothing | |
1606 | special is done in that case. | |
73804d4b RS |
1607 | |
1608 | The value of @code{auto-fill-function} is @code{do-auto-fill} when | |
1609 | Auto-Fill mode is enabled. That is a function whose sole purpose is to | |
1610 | implement the usual strategy for breaking a line. | |
1611 | ||
1612 | @quotation | |
1613 | In older Emacs versions, this variable was named @code{auto-fill-hook}, | |
1614 | but since it is not called with the standard convention for hooks, it | |
1615 | was renamed to @code{auto-fill-function} in version 19. | |
1616 | @end quotation | |
1617 | @end defvar | |
1618 | ||
910bc071 RS |
1619 | @defvar normal-auto-fill-function |
1620 | This variable specifies the function to use for | |
1621 | @code{auto-fill-function}, if and when Auto Fill is turned on. Major | |
969fe9b5 RS |
1622 | modes can set buffer-local values for this variable to alter how Auto |
1623 | Fill works. | |
910bc071 RS |
1624 | @end defvar |
1625 | ||
ca3be36e DL |
1626 | @defvar auto-fill-chars |
1627 | A char table of characters which invoke @code{auto-fill-function} when | |
1628 | self-inserted---space and newline in most language environments. They | |
1629 | have an entry @code{t} in the table. | |
1630 | @end defvar | |
1631 | ||
73804d4b RS |
1632 | @node Sorting |
1633 | @section Sorting Text | |
1634 | @cindex sorting text | |
1635 | ||
1636 | The sorting functions described in this section all rearrange text in | |
1637 | a buffer. This is in contrast to the function @code{sort}, which | |
1638 | rearranges the order of the elements of a list (@pxref{Rearrangement}). | |
1639 | The values returned by these functions are not meaningful. | |
1640 | ||
1641 | @defun sort-subr reverse nextrecfun endrecfun &optional startkeyfun endkeyfun | |
f9f59935 RS |
1642 | This function is the general text-sorting routine that subdivides a |
1643 | buffer into records and then sorts them. Most of the commands in this | |
1644 | section use this function. | |
73804d4b RS |
1645 | |
1646 | To understand how @code{sort-subr} works, consider the whole accessible | |
1647 | portion of the buffer as being divided into disjoint pieces called | |
f9f59935 RS |
1648 | @dfn{sort records}. The records may or may not be contiguous, but they |
1649 | must not overlap. A portion of each sort record (perhaps all of it) is | |
73804d4b RS |
1650 | designated as the sort key. Sorting rearranges the records in order by |
1651 | their sort keys. | |
1652 | ||
1653 | Usually, the records are rearranged in order of ascending sort key. | |
1654 | If the first argument to the @code{sort-subr} function, @var{reverse}, | |
1655 | is non-@code{nil}, the sort records are rearranged in order of | |
1656 | descending sort key. | |
1657 | ||
1658 | The next four arguments to @code{sort-subr} are functions that are | |
1659 | called to move point across a sort record. They are called many times | |
1660 | from within @code{sort-subr}. | |
1661 | ||
1662 | @enumerate | |
1663 | @item | |
1664 | @var{nextrecfun} is called with point at the end of a record. This | |
1665 | function moves point to the start of the next record. The first record | |
1666 | is assumed to start at the position of point when @code{sort-subr} is | |
1667 | called. Therefore, you should usually move point to the beginning of | |
1668 | the buffer before calling @code{sort-subr}. | |
1669 | ||
1670 | This function can indicate there are no more sort records by leaving | |
1671 | point at the end of the buffer. | |
1672 | ||
1673 | @item | |
1674 | @var{endrecfun} is called with point within a record. It moves point to | |
1675 | the end of the record. | |
1676 | ||
1677 | @item | |
1678 | @var{startkeyfun} is called to move point from the start of a record to | |
1679 | the start of the sort key. This argument is optional; if it is omitted, | |
1680 | the whole record is the sort key. If supplied, the function should | |
1681 | either return a non-@code{nil} value to be used as the sort key, or | |
1682 | return @code{nil} to indicate that the sort key is in the buffer | |
1683 | starting at point. In the latter case, @var{endkeyfun} is called to | |
1684 | find the end of the sort key. | |
1685 | ||
1686 | @item | |
1687 | @var{endkeyfun} is called to move point from the start of the sort key | |
1688 | to the end of the sort key. This argument is optional. If | |
1689 | @var{startkeyfun} returns @code{nil} and this argument is omitted (or | |
1690 | @code{nil}), then the sort key extends to the end of the record. There | |
1691 | is no need for @var{endkeyfun} if @var{startkeyfun} returns a | |
1692 | non-@code{nil} value. | |
1693 | @end enumerate | |
1694 | ||
1695 | As an example of @code{sort-subr}, here is the complete function | |
1696 | definition for @code{sort-lines}: | |
1697 | ||
1698 | @example | |
1699 | @group | |
1700 | ;; @r{Note that the first two lines of doc string} | |
1701 | ;; @r{are effectively one line when viewed by a user.} | |
1702 | (defun sort-lines (reverse beg end) | |
f9f59935 RS |
1703 | "Sort lines in region alphabetically;\ |
1704 | argument means descending order. | |
73804d4b RS |
1705 | Called from a program, there are three arguments: |
1706 | @end group | |
1707 | @group | |
f9f59935 RS |
1708 | REVERSE (non-nil means reverse order),\ |
1709 | BEG and END (region to sort). | |
1710 | The variable `sort-fold-case' determines\ | |
1711 | whether alphabetic case affects | |
1712 | the sort order. | |
1713 | @end group | |
1714 | @group | |
73804d4b | 1715 | (interactive "P\nr") |
1911e6e5 RS |
1716 | (save-excursion |
1717 | (save-restriction | |
1718 | (narrow-to-region beg end) | |
1719 | (goto-char (point-min)) | |
1720 | (sort-subr reverse 'forward-line 'end-of-line)))) | |
73804d4b RS |
1721 | @end group |
1722 | @end example | |
1723 | ||
1724 | Here @code{forward-line} moves point to the start of the next record, | |
1725 | and @code{end-of-line} moves point to the end of record. We do not pass | |
1726 | the arguments @var{startkeyfun} and @var{endkeyfun}, because the entire | |
1727 | record is used as the sort key. | |
1728 | ||
1729 | The @code{sort-paragraphs} function is very much the same, except that | |
1730 | its @code{sort-subr} call looks like this: | |
1731 | ||
1732 | @example | |
1733 | @group | |
1734 | (sort-subr reverse | |
1911e6e5 RS |
1735 | (function |
1736 | (lambda () | |
1737 | (while (and (not (eobp)) | |
1738 | (looking-at paragraph-separate)) | |
1739 | (forward-line 1)))) | |
73804d4b RS |
1740 | 'forward-paragraph) |
1741 | @end group | |
1742 | @end example | |
f9f59935 RS |
1743 | |
1744 | Markers pointing into any sort records are left with no useful | |
1745 | position after @code{sort-subr} returns. | |
73804d4b RS |
1746 | @end defun |
1747 | ||
1911e6e5 RS |
1748 | @defopt sort-fold-case |
1749 | If this variable is non-@code{nil}, @code{sort-subr} and the other | |
1750 | buffer sorting functions ignore case when comparing strings. | |
1751 | @end defopt | |
1752 | ||
73804d4b RS |
1753 | @deffn Command sort-regexp-fields reverse record-regexp key-regexp start end |
1754 | This command sorts the region between @var{start} and @var{end} | |
1755 | alphabetically as specified by @var{record-regexp} and @var{key-regexp}. | |
1756 | If @var{reverse} is a negative integer, then sorting is in reverse | |
1757 | order. | |
1758 | ||
1759 | Alphabetical sorting means that two sort keys are compared by | |
1760 | comparing the first characters of each, the second characters of each, | |
1761 | and so on. If a mismatch is found, it means that the sort keys are | |
1762 | unequal; the sort key whose character is less at the point of first | |
1763 | mismatch is the lesser sort key. The individual characters are compared | |
f9f59935 | 1764 | according to their numerical character codes in the Emacs character set. |
73804d4b RS |
1765 | |
1766 | The value of the @var{record-regexp} argument specifies how to divide | |
1767 | the buffer into sort records. At the end of each record, a search is | |
f9f59935 RS |
1768 | done for this regular expression, and the text that matches it is taken |
1769 | as the next record. For example, the regular expression @samp{^.+$}, | |
1770 | which matches lines with at least one character besides a newline, would | |
1771 | make each such line into a sort record. @xref{Regular Expressions}, for | |
1772 | a description of the syntax and meaning of regular expressions. | |
73804d4b RS |
1773 | |
1774 | The value of the @var{key-regexp} argument specifies what part of each | |
1775 | record is the sort key. The @var{key-regexp} could match the whole | |
1776 | record, or only a part. In the latter case, the rest of the record has | |
1777 | no effect on the sorted order of records, but it is carried along when | |
1778 | the record moves to its new position. | |
1779 | ||
1780 | The @var{key-regexp} argument can refer to the text matched by a | |
1781 | subexpression of @var{record-regexp}, or it can be a regular expression | |
1782 | on its own. | |
1783 | ||
1784 | If @var{key-regexp} is: | |
1785 | ||
1786 | @table @asis | |
1787 | @item @samp{\@var{digit}} | |
1788 | then the text matched by the @var{digit}th @samp{\(...\)} parenthesis | |
1789 | grouping in @var{record-regexp} is the sort key. | |
1790 | ||
1791 | @item @samp{\&} | |
1792 | then the whole record is the sort key. | |
1793 | ||
1794 | @item a regular expression | |
1795 | then @code{sort-regexp-fields} searches for a match for the regular | |
1796 | expression within the record. If such a match is found, it is the sort | |
1797 | key. If there is no match for @var{key-regexp} within a record then | |
1798 | that record is ignored, which means its position in the buffer is not | |
1799 | changed. (The other records may move around it.) | |
1800 | @end table | |
1801 | ||
1802 | For example, if you plan to sort all the lines in the region by the | |
1803 | first word on each line starting with the letter @samp{f}, you should | |
1804 | set @var{record-regexp} to @samp{^.*$} and set @var{key-regexp} to | |
1805 | @samp{\<f\w*\>}. The resulting expression looks like this: | |
1806 | ||
1807 | @example | |
1808 | @group | |
1809 | (sort-regexp-fields nil "^.*$" "\\<f\\w*\\>" | |
1810 | (region-beginning) | |
1811 | (region-end)) | |
1812 | @end group | |
1813 | @end example | |
1814 | ||
1815 | If you call @code{sort-regexp-fields} interactively, it prompts for | |
1816 | @var{record-regexp} and @var{key-regexp} in the minibuffer. | |
1817 | @end deffn | |
1818 | ||
1819 | @deffn Command sort-lines reverse start end | |
1820 | This command alphabetically sorts lines in the region between | |
1821 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort | |
1822 | is in reverse order. | |
1823 | @end deffn | |
1824 | ||
1825 | @deffn Command sort-paragraphs reverse start end | |
1826 | This command alphabetically sorts paragraphs in the region between | |
1827 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort | |
1828 | is in reverse order. | |
1829 | @end deffn | |
1830 | ||
1831 | @deffn Command sort-pages reverse start end | |
1832 | This command alphabetically sorts pages in the region between | |
1833 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort | |
1834 | is in reverse order. | |
1835 | @end deffn | |
1836 | ||
1837 | @deffn Command sort-fields field start end | |
1838 | This command sorts lines in the region between @var{start} and | |
1839 | @var{end}, comparing them alphabetically by the @var{field}th field | |
1840 | of each line. Fields are separated by whitespace and numbered starting | |
1841 | from 1. If @var{field} is negative, sorting is by the | |
1842 | @w{@minus{}@var{field}th} field from the end of the line. This command | |
1843 | is useful for sorting tables. | |
1844 | @end deffn | |
1845 | ||
1846 | @deffn Command sort-numeric-fields field start end | |
1847 | This command sorts lines in the region between @var{start} and | |
1848 | @var{end}, comparing them numerically by the @var{field}th field of each | |
1849 | line. The specified field must contain a number in each line of the | |
1850 | region. Fields are separated by whitespace and numbered starting from | |
1851 | 1. If @var{field} is negative, sorting is by the | |
1852 | @w{@minus{}@var{field}th} field from the end of the line. This command | |
1853 | is useful for sorting tables. | |
1854 | @end deffn | |
1855 | ||
1856 | @deffn Command sort-columns reverse &optional beg end | |
1857 | This command sorts the lines in the region between @var{beg} and | |
1858 | @var{end}, comparing them alphabetically by a certain range of columns. | |
1859 | The column positions of @var{beg} and @var{end} bound the range of | |
1860 | columns to sort on. | |
1861 | ||
1862 | If @var{reverse} is non-@code{nil}, the sort is in reverse order. | |
1863 | ||
1864 | One unusual thing about this command is that the entire line | |
1865 | containing position @var{beg}, and the entire line containing position | |
1866 | @var{end}, are included in the region sorted. | |
1867 | ||
1868 | Note that @code{sort-columns} uses the @code{sort} utility program, | |
1869 | and so cannot work properly on text containing tab characters. Use | |
969fe9b5 | 1870 | @kbd{M-x untabify} to convert tabs to spaces before sorting. |
73804d4b RS |
1871 | @end deffn |
1872 | ||
1873 | @node Columns | |
1874 | @comment node-name, next, previous, up | |
1875 | @section Counting Columns | |
1876 | @cindex columns | |
1877 | @cindex counting columns | |
1878 | @cindex horizontal position | |
1879 | ||
1880 | The column functions convert between a character position (counting | |
1881 | characters from the beginning of the buffer) and a column position | |
1882 | (counting screen characters from the beginning of a line). | |
1883 | ||
f9f59935 RS |
1884 | These functions count each character according to the number of |
1885 | columns it occupies on the screen. This means control characters count | |
1886 | as occupying 2 or 4 columns, depending upon the value of | |
1887 | @code{ctl-arrow}, and tabs count as occupying a number of columns that | |
1888 | depends on the value of @code{tab-width} and on the column where the tab | |
1889 | begins. @xref{Usual Display}. | |
73804d4b RS |
1890 | |
1891 | Column number computations ignore the width of the window and the | |
1892 | amount of horizontal scrolling. Consequently, a column value can be | |
1893 | arbitrarily high. The first (or leftmost) column is numbered 0. | |
1894 | ||
1895 | @defun current-column | |
1896 | This function returns the horizontal position of point, measured in | |
1897 | columns, counting from 0 at the left margin. The column position is the | |
1898 | sum of the widths of all the displayed representations of the characters | |
1899 | between the start of the current line and point. | |
1900 | ||
1901 | For an example of using @code{current-column}, see the description of | |
1902 | @code{count-lines} in @ref{Text Lines}. | |
1903 | @end defun | |
1904 | ||
1905 | @defun move-to-column column &optional force | |
1906 | This function moves point to @var{column} in the current line. The | |
1907 | calculation of @var{column} takes into account the widths of the | |
1908 | displayed representations of the characters between the start of the | |
1909 | line and point. | |
1910 | ||
1911 | If column @var{column} is beyond the end of the line, point moves to the | |
1912 | end of the line. If @var{column} is negative, point moves to the | |
1913 | beginning of the line. | |
1914 | ||
1915 | If it is impossible to move to column @var{column} because that is in | |
1916 | the middle of a multicolumn character such as a tab, point moves to the | |
1917 | end of that character. However, if @var{force} is non-@code{nil}, and | |
1918 | @var{column} is in the middle of a tab, then @code{move-to-column} | |
1919 | converts the tab into spaces so that it can move precisely to column | |
1920 | @var{column}. Other multicolumn characters can cause anomalies despite | |
1921 | @var{force}, since there is no way to split them. | |
1922 | ||
1923 | The argument @var{force} also has an effect if the line isn't long | |
8241495d RS |
1924 | enough to reach column @var{column}; if it is @code{t}, that means to |
1925 | add whitespace at the end of the line to reach that column. | |
73804d4b RS |
1926 | |
1927 | If @var{column} is not an integer, an error is signaled. | |
1928 | ||
1929 | The return value is the column number actually moved to. | |
1930 | @end defun | |
1931 | ||
1932 | @node Indentation | |
1933 | @section Indentation | |
1934 | @cindex indentation | |
1935 | ||
1936 | The indentation functions are used to examine, move to, and change | |
1937 | whitespace that is at the beginning of a line. Some of the functions | |
1938 | can also change whitespace elsewhere on a line. Columns and indentation | |
1939 | count from zero at the left margin. | |
1940 | ||
1941 | @menu | |
1942 | * Primitive Indent:: Functions used to count and insert indentation. | |
1943 | * Mode-Specific Indent:: Customize indentation for different modes. | |
1944 | * Region Indent:: Indent all the lines in a region. | |
1945 | * Relative Indent:: Indent the current line based on previous lines. | |
1946 | * Indent Tabs:: Adjustable, typewriter-like tab stops. | |
1947 | * Motion by Indent:: Move to first non-blank character. | |
1948 | @end menu | |
1949 | ||
1950 | @node Primitive Indent | |
1951 | @subsection Indentation Primitives | |
1952 | ||
1953 | This section describes the primitive functions used to count and | |
1954 | insert indentation. The functions in the following sections use these | |
969fe9b5 | 1955 | primitives. @xref{Width}, for related functions. |
73804d4b RS |
1956 | |
1957 | @defun current-indentation | |
1958 | @comment !!Type Primitive Function | |
1959 | @comment !!SourceFile indent.c | |
1960 | This function returns the indentation of the current line, which is | |
1961 | the horizontal position of the first nonblank character. If the | |
1962 | contents are entirely blank, then this is the horizontal position of the | |
1963 | end of the line. | |
1964 | @end defun | |
1965 | ||
1966 | @deffn Command indent-to column &optional minimum | |
1967 | @comment !!Type Primitive Function | |
1968 | @comment !!SourceFile indent.c | |
61cfa852 RS |
1969 | This function indents from point with tabs and spaces until @var{column} |
1970 | is reached. If @var{minimum} is specified and non-@code{nil}, then at | |
1971 | least that many spaces are inserted even if this requires going beyond | |
1972 | @var{column}. Otherwise the function does nothing if point is already | |
1973 | beyond @var{column}. The value is the column at which the inserted | |
1974 | indentation ends. | |
33acbad2 RS |
1975 | |
1976 | The inserted whitespace characters inherit text properties from the | |
1977 | surrounding text (usually, from the preceding text only). @xref{Sticky | |
1978 | Properties}. | |
73804d4b RS |
1979 | @end deffn |
1980 | ||
1981 | @defopt indent-tabs-mode | |
1982 | @comment !!SourceFile indent.c | |
1983 | If this variable is non-@code{nil}, indentation functions can insert | |
1984 | tabs as well as spaces. Otherwise, they insert only spaces. Setting | |
969fe9b5 | 1985 | this variable automatically makes it buffer-local in the current buffer. |
73804d4b RS |
1986 | @end defopt |
1987 | ||
1988 | @node Mode-Specific Indent | |
1989 | @subsection Indentation Controlled by Major Mode | |
1990 | ||
1991 | An important function of each major mode is to customize the @key{TAB} | |
1992 | key to indent properly for the language being edited. This section | |
1993 | describes the mechanism of the @key{TAB} key and how to control it. | |
1994 | The functions in this section return unpredictable values. | |
1995 | ||
1996 | @defvar indent-line-function | |
1997 | This variable's value is the function to be used by @key{TAB} (and | |
1998 | various commands) to indent the current line. The command | |
1999 | @code{indent-according-to-mode} does no more than call this function. | |
2000 | ||
2001 | In Lisp mode, the value is the symbol @code{lisp-indent-line}; in C | |
2002 | mode, @code{c-indent-line}; in Fortran mode, @code{fortran-indent-line}. | |
2003 | In Fundamental mode, Text mode, and many other modes with no standard | |
2004 | for indentation, the value is @code{indent-to-left-margin} (which is the | |
2005 | default value). | |
2006 | @end defvar | |
2007 | ||
2008 | @deffn Command indent-according-to-mode | |
2009 | This command calls the function in @code{indent-line-function} to | |
2010 | indent the current line in a way appropriate for the current major mode. | |
2011 | @end deffn | |
2012 | ||
2013 | @deffn Command indent-for-tab-command | |
2014 | This command calls the function in @code{indent-line-function} to indent | |
a9f0a989 RS |
2015 | the current line; however, if that function is |
2016 | @code{indent-to-left-margin}, @code{insert-tab} is called instead. (That | |
61cfa852 | 2017 | is a trivial command that inserts a tab character.) |
73804d4b RS |
2018 | @end deffn |
2019 | ||
73804d4b RS |
2020 | @deffn Command newline-and-indent |
2021 | @comment !!SourceFile simple.el | |
2022 | This function inserts a newline, then indents the new line (the one | |
2023 | following the newline just inserted) according to the major mode. | |
2024 | ||
2025 | It does indentation by calling the current @code{indent-line-function}. | |
2026 | In programming language modes, this is the same thing @key{TAB} does, | |
2027 | but in some text modes, where @key{TAB} inserts a tab, | |
2028 | @code{newline-and-indent} indents to the column specified by | |
2029 | @code{left-margin}. | |
2030 | @end deffn | |
2031 | ||
2032 | @deffn Command reindent-then-newline-and-indent | |
2033 | @comment !!SourceFile simple.el | |
2034 | This command reindents the current line, inserts a newline at point, | |
1911e6e5 | 2035 | and then indents the new line (the one following the newline just |
73804d4b RS |
2036 | inserted). |
2037 | ||
2038 | This command does indentation on both lines according to the current | |
2039 | major mode, by calling the current value of @code{indent-line-function}. | |
2040 | In programming language modes, this is the same thing @key{TAB} does, | |
2041 | but in some text modes, where @key{TAB} inserts a tab, | |
2042 | @code{reindent-then-newline-and-indent} indents to the column specified | |
2043 | by @code{left-margin}. | |
2044 | @end deffn | |
2045 | ||
2046 | @node Region Indent | |
2047 | @subsection Indenting an Entire Region | |
2048 | ||
61cfa852 | 2049 | This section describes commands that indent all the lines in the |
73804d4b RS |
2050 | region. They return unpredictable values. |
2051 | ||
2052 | @deffn Command indent-region start end to-column | |
2053 | This command indents each nonblank line starting between @var{start} | |
2054 | (inclusive) and @var{end} (exclusive). If @var{to-column} is | |
2055 | @code{nil}, @code{indent-region} indents each nonblank line by calling | |
2056 | the current mode's indentation function, the value of | |
2057 | @code{indent-line-function}. | |
2058 | ||
2059 | If @var{to-column} is non-@code{nil}, it should be an integer | |
2060 | specifying the number of columns of indentation; then this function | |
2061 | gives each line exactly that much indentation, by either adding or | |
2062 | deleting whitespace. | |
2063 | ||
2064 | If there is a fill prefix, @code{indent-region} indents each line | |
2065 | by making it start with the fill prefix. | |
2066 | @end deffn | |
2067 | ||
2068 | @defvar indent-region-function | |
2069 | The value of this variable is a function that can be used by | |
a9f0a989 RS |
2070 | @code{indent-region} as a short cut. It should take two arguments, the |
2071 | start and end of the region. You should design the function so | |
73804d4b RS |
2072 | that it will produce the same results as indenting the lines of the |
2073 | region one by one, but presumably faster. | |
2074 | ||
2075 | If the value is @code{nil}, there is no short cut, and | |
2076 | @code{indent-region} actually works line by line. | |
2077 | ||
61cfa852 | 2078 | A short-cut function is useful in modes such as C mode and Lisp mode, |
73804d4b | 2079 | where the @code{indent-line-function} must scan from the beginning of |
61cfa852 RS |
2080 | the function definition: applying it to each line would be quadratic in |
2081 | time. The short cut can update the scan information as it moves through | |
2082 | the lines indenting them; this takes linear time. In a mode where | |
2083 | indenting a line individually is fast, there is no need for a short cut. | |
73804d4b | 2084 | |
61cfa852 RS |
2085 | @code{indent-region} with a non-@code{nil} argument @var{to-column} has |
2086 | a different meaning and does not use this variable. | |
73804d4b RS |
2087 | @end defvar |
2088 | ||
2089 | @deffn Command indent-rigidly start end count | |
2090 | @comment !!SourceFile indent.el | |
2091 | This command indents all lines starting between @var{start} | |
2092 | (inclusive) and @var{end} (exclusive) sideways by @var{count} columns. | |
2093 | This ``preserves the shape'' of the affected region, moving it as a | |
2094 | rigid unit. Consequently, this command is useful not only for indenting | |
2095 | regions of unindented text, but also for indenting regions of formatted | |
2096 | code. | |
2097 | ||
2098 | For example, if @var{count} is 3, this command adds 3 columns of | |
2099 | indentation to each of the lines beginning in the region specified. | |
2100 | ||
2101 | In Mail mode, @kbd{C-c C-y} (@code{mail-yank-original}) uses | |
2102 | @code{indent-rigidly} to indent the text copied from the message being | |
2103 | replied to. | |
2104 | @end deffn | |
2105 | ||
2106 | @defun indent-code-rigidly start end columns &optional nochange-regexp | |
2107 | This is like @code{indent-rigidly}, except that it doesn't alter lines | |
2108 | that start within strings or comments. | |
2109 | ||
2110 | In addition, it doesn't alter a line if @var{nochange-regexp} matches at | |
2111 | the beginning of the line (if @var{nochange-regexp} is non-@code{nil}). | |
2112 | @end defun | |
2113 | ||
2114 | @node Relative Indent | |
2115 | @subsection Indentation Relative to Previous Lines | |
2116 | ||
61cfa852 | 2117 | This section describes two commands that indent the current line |
73804d4b RS |
2118 | based on the contents of previous lines. |
2119 | ||
2120 | @deffn Command indent-relative &optional unindented-ok | |
2121 | This command inserts whitespace at point, extending to the same | |
2122 | column as the next @dfn{indent point} of the previous nonblank line. An | |
2123 | indent point is a non-whitespace character following whitespace. The | |
2124 | next indent point is the first one at a column greater than the current | |
2125 | column of point. For example, if point is underneath and to the left of | |
2126 | the first non-blank character of a line of text, it moves to that column | |
2127 | by inserting whitespace. | |
2128 | ||
2129 | If the previous nonblank line has no next indent point (i.e., none at a | |
2130 | great enough column position), @code{indent-relative} either does | |
2131 | nothing (if @var{unindented-ok} is non-@code{nil}) or calls | |
2132 | @code{tab-to-tab-stop}. Thus, if point is underneath and to the right | |
2133 | of the last column of a short line of text, this command ordinarily | |
2134 | moves point to the next tab stop by inserting whitespace. | |
2135 | ||
2136 | The return value of @code{indent-relative} is unpredictable. | |
2137 | ||
2138 | In the following example, point is at the beginning of the second | |
2139 | line: | |
2140 | ||
2141 | @example | |
2142 | @group | |
2143 | This line is indented twelve spaces. | |
2144 | @point{}The quick brown fox jumped. | |
2145 | @end group | |
2146 | @end example | |
2147 | ||
2148 | @noindent | |
2149 | Evaluation of the expression @code{(indent-relative nil)} produces the | |
2150 | following: | |
2151 | ||
2152 | @example | |
2153 | @group | |
2154 | This line is indented twelve spaces. | |
2155 | @point{}The quick brown fox jumped. | |
2156 | @end group | |
2157 | @end example | |
2158 | ||
f9f59935 | 2159 | In this next example, point is between the @samp{m} and @samp{p} of |
73804d4b RS |
2160 | @samp{jumped}: |
2161 | ||
2162 | @example | |
2163 | @group | |
2164 | This line is indented twelve spaces. | |
2165 | The quick brown fox jum@point{}ped. | |
2166 | @end group | |
2167 | @end example | |
2168 | ||
2169 | @noindent | |
2170 | Evaluation of the expression @code{(indent-relative nil)} produces the | |
2171 | following: | |
2172 | ||
2173 | @example | |
2174 | @group | |
2175 | This line is indented twelve spaces. | |
2176 | The quick brown fox jum @point{}ped. | |
2177 | @end group | |
2178 | @end example | |
2179 | @end deffn | |
2180 | ||
2181 | @deffn Command indent-relative-maybe | |
2182 | @comment !!SourceFile indent.el | |
f9f59935 RS |
2183 | This command indents the current line like the previous nonblank line, |
2184 | by calling @code{indent-relative} with @code{t} as the | |
2185 | @var{unindented-ok} argument. The return value is unpredictable. | |
73804d4b RS |
2186 | |
2187 | If the previous nonblank line has no indent points beyond the current | |
2188 | column, this command does nothing. | |
2189 | @end deffn | |
2190 | ||
2191 | @node Indent Tabs | |
2192 | @comment node-name, next, previous, up | |
2193 | @subsection Adjustable ``Tab Stops'' | |
2194 | @cindex tabs stops for indentation | |
2195 | ||
2196 | This section explains the mechanism for user-specified ``tab stops'' | |
61cfa852 | 2197 | and the mechanisms that use and set them. The name ``tab stops'' is |
73804d4b RS |
2198 | used because the feature is similar to that of the tab stops on a |
2199 | typewriter. The feature works by inserting an appropriate number of | |
2200 | spaces and tab characters to reach the next tab stop column; it does not | |
2201 | affect the display of tab characters in the buffer (@pxref{Usual | |
2202 | Display}). Note that the @key{TAB} character as input uses this tab | |
2203 | stop feature only in a few major modes, such as Text mode. | |
2204 | ||
2205 | @deffn Command tab-to-tab-stop | |
f9f59935 RS |
2206 | This command inserts spaces or tabs before point, up to the next tab |
2207 | stop column defined by @code{tab-stop-list}. It searches the list for | |
2208 | an element greater than the current column number, and uses that element | |
2209 | as the column to indent to. It does nothing if no such element is | |
2210 | found. | |
73804d4b RS |
2211 | @end deffn |
2212 | ||
2213 | @defopt tab-stop-list | |
2214 | This variable is the list of tab stop columns used by | |
2215 | @code{tab-to-tab-stops}. The elements should be integers in increasing | |
2216 | order. The tab stop columns need not be evenly spaced. | |
2217 | ||
2218 | Use @kbd{M-x edit-tab-stops} to edit the location of tab stops | |
2219 | interactively. | |
2220 | @end defopt | |
2221 | ||
2222 | @node Motion by Indent | |
2223 | @subsection Indentation-Based Motion Commands | |
2224 | ||
2225 | These commands, primarily for interactive use, act based on the | |
2226 | indentation in the text. | |
2227 | ||
177c0ea7 | 2228 | @deffn Command back-to-indentation |
73804d4b RS |
2229 | @comment !!SourceFile simple.el |
2230 | This command moves point to the first non-whitespace character in the | |
2231 | current line (which is the line in which point is located). It returns | |
2232 | @code{nil}. | |
2233 | @end deffn | |
2234 | ||
2235 | @deffn Command backward-to-indentation arg | |
2236 | @comment !!SourceFile simple.el | |
2237 | This command moves point backward @var{arg} lines and then to the | |
2238 | first nonblank character on that line. It returns @code{nil}. | |
2239 | @end deffn | |
2240 | ||
2241 | @deffn Command forward-to-indentation arg | |
2242 | @comment !!SourceFile simple.el | |
2243 | This command moves point forward @var{arg} lines and then to the first | |
2244 | nonblank character on that line. It returns @code{nil}. | |
2245 | @end deffn | |
2246 | ||
2247 | @node Case Changes | |
2248 | @comment node-name, next, previous, up | |
2249 | @section Case Changes | |
969fe9b5 | 2250 | @cindex case conversion in buffers |
73804d4b RS |
2251 | |
2252 | The case change commands described here work on text in the current | |
969fe9b5 RS |
2253 | buffer. @xref{Case Conversion}, for case conversion functions that work |
2254 | on strings and characters. @xref{Case Tables}, for how to customize | |
73804d4b RS |
2255 | which characters are upper or lower case and how to convert them. |
2256 | ||
2257 | @deffn Command capitalize-region start end | |
2258 | This function capitalizes all words in the region defined by | |
2259 | @var{start} and @var{end}. To capitalize means to convert each word's | |
2260 | first character to upper case and convert the rest of each word to lower | |
2261 | case. The function returns @code{nil}. | |
2262 | ||
2263 | If one end of the region is in the middle of a word, the part of the | |
2264 | word within the region is treated as an entire word. | |
2265 | ||
2266 | When @code{capitalize-region} is called interactively, @var{start} and | |
2267 | @var{end} are point and the mark, with the smallest first. | |
2268 | ||
2269 | @example | |
2270 | @group | |
2271 | ---------- Buffer: foo ---------- | |
2272 | This is the contents of the 5th foo. | |
2273 | ---------- Buffer: foo ---------- | |
2274 | @end group | |
2275 | ||
2276 | @group | |
2277 | (capitalize-region 1 44) | |
2278 | @result{} nil | |
2279 | ||
2280 | ---------- Buffer: foo ---------- | |
2281 | This Is The Contents Of The 5th Foo. | |
2282 | ---------- Buffer: foo ---------- | |
2283 | @end group | |
2284 | @end example | |
2285 | @end deffn | |
2286 | ||
2287 | @deffn Command downcase-region start end | |
2288 | This function converts all of the letters in the region defined by | |
2289 | @var{start} and @var{end} to lower case. The function returns | |
2290 | @code{nil}. | |
2291 | ||
2292 | When @code{downcase-region} is called interactively, @var{start} and | |
2293 | @var{end} are point and the mark, with the smallest first. | |
2294 | @end deffn | |
2295 | ||
2296 | @deffn Command upcase-region start end | |
2297 | This function converts all of the letters in the region defined by | |
2298 | @var{start} and @var{end} to upper case. The function returns | |
2299 | @code{nil}. | |
2300 | ||
2301 | When @code{upcase-region} is called interactively, @var{start} and | |
2302 | @var{end} are point and the mark, with the smallest first. | |
2303 | @end deffn | |
2304 | ||
2305 | @deffn Command capitalize-word count | |
2306 | This function capitalizes @var{count} words after point, moving point | |
2307 | over as it does. To capitalize means to convert each word's first | |
2308 | character to upper case and convert the rest of each word to lower case. | |
2309 | If @var{count} is negative, the function capitalizes the | |
2310 | @minus{}@var{count} previous words but does not move point. The value | |
2311 | is @code{nil}. | |
2312 | ||
61cfa852 RS |
2313 | If point is in the middle of a word, the part of the word before point |
2314 | is ignored when moving forward. The rest is treated as an entire word. | |
73804d4b RS |
2315 | |
2316 | When @code{capitalize-word} is called interactively, @var{count} is | |
2317 | set to the numeric prefix argument. | |
2318 | @end deffn | |
2319 | ||
2320 | @deffn Command downcase-word count | |
2321 | This function converts the @var{count} words after point to all lower | |
2322 | case, moving point over as it does. If @var{count} is negative, it | |
2323 | converts the @minus{}@var{count} previous words but does not move point. | |
2324 | The value is @code{nil}. | |
2325 | ||
2326 | When @code{downcase-word} is called interactively, @var{count} is set | |
2327 | to the numeric prefix argument. | |
2328 | @end deffn | |
2329 | ||
2330 | @deffn Command upcase-word count | |
2331 | This function converts the @var{count} words after point to all upper | |
2332 | case, moving point over as it does. If @var{count} is negative, it | |
2333 | converts the @minus{}@var{count} previous words but does not move point. | |
2334 | The value is @code{nil}. | |
2335 | ||
2336 | When @code{upcase-word} is called interactively, @var{count} is set to | |
2337 | the numeric prefix argument. | |
2338 | @end deffn | |
2339 | ||
2340 | @node Text Properties | |
2341 | @section Text Properties | |
2342 | @cindex text properties | |
2343 | @cindex attributes of text | |
2344 | @cindex properties of text | |
2345 | ||
2346 | Each character position in a buffer or a string can have a @dfn{text | |
2347 | property list}, much like the property list of a symbol (@pxref{Property | |
2348 | Lists}). The properties belong to a particular character at a | |
2349 | particular place, such as, the letter @samp{T} at the beginning of this | |
2350 | sentence or the first @samp{o} in @samp{foo}---if the same character | |
2351 | occurs in two different places, the two occurrences generally have | |
2352 | different properties. | |
2353 | ||
2354 | Each property has a name and a value. Both of these can be any Lisp | |
2355 | object, but the name is normally a symbol. The usual way to access the | |
2356 | property list is to specify a name and ask what value corresponds to it. | |
2357 | ||
2358 | If a character has a @code{category} property, we call it the | |
2359 | @dfn{category} of the character. It should be a symbol. The properties | |
2360 | of the symbol serve as defaults for the properties of the character. | |
2361 | ||
2362 | Copying text between strings and buffers preserves the properties | |
2363 | along with the characters; this includes such diverse functions as | |
2364 | @code{substring}, @code{insert}, and @code{buffer-substring}. | |
2365 | ||
2366 | @menu | |
a6b73788 RS |
2367 | * Examining Properties:: Looking at the properties of one character. |
2368 | * Changing Properties:: Setting the properties of a range of text. | |
2369 | * Property Search:: Searching for where a property changes value. | |
2370 | * Special Properties:: Particular properties with special meanings. | |
2371 | * Format Properties:: Properties for representing formatting of text. | |
2372 | * Sticky Properties:: How inserted text gets properties from | |
2373 | neighboring text. | |
2374 | * Saving Properties:: Saving text properties in files, and reading | |
2375 | them back. | |
2376 | * Lazy Properties:: Computing text properties in a lazy fashion | |
2377 | only when text is examined. | |
2378 | * Clickable Text:: Using text properties to make regions of text | |
2379 | do something when you click on them. | |
2380 | * Fields:: The @code{field} property defines | |
2381 | fields within the buffer. | |
2382 | * Not Intervals:: Why text properties do not use | |
2383 | Lisp-visible text intervals. | |
73804d4b RS |
2384 | @end menu |
2385 | ||
2386 | @node Examining Properties | |
2387 | @subsection Examining Text Properties | |
2388 | ||
2389 | The simplest way to examine text properties is to ask for the value of | |
2390 | a particular property of a particular character. For that, use | |
2391 | @code{get-text-property}. Use @code{text-properties-at} to get the | |
2392 | entire property list of a character. @xref{Property Search}, for | |
2393 | functions to examine the properties of a number of characters at once. | |
2394 | ||
2395 | These functions handle both strings and buffers. Keep in mind that | |
2396 | positions in a string start from 0, whereas positions in a buffer start | |
2397 | from 1. | |
2398 | ||
2399 | @defun get-text-property pos prop &optional object | |
2400 | This function returns the value of the @var{prop} property of the | |
2401 | character after position @var{pos} in @var{object} (a buffer or | |
2402 | string). The argument @var{object} is optional and defaults to the | |
2403 | current buffer. | |
2404 | ||
2405 | If there is no @var{prop} property strictly speaking, but the character | |
61cfa852 | 2406 | has a category that is a symbol, then @code{get-text-property} returns |
73804d4b RS |
2407 | the @var{prop} property of that symbol. |
2408 | @end defun | |
2409 | ||
2410 | @defun get-char-property pos prop &optional object | |
2411 | This function is like @code{get-text-property}, except that it checks | |
2412 | overlays first and then text properties. @xref{Overlays}. | |
2413 | ||
2414 | The argument @var{object} may be a string, a buffer, or a window. If it | |
2415 | is a window, then the buffer displayed in that window is used for text | |
2416 | properties and overlays, but only the overlays active for that window | |
2417 | are considered. If @var{object} is a buffer, then all overlays in that | |
2418 | buffer are considered, as well as text properties. If @var{object} is a | |
2419 | string, only text properties are considered, since strings never have | |
2420 | overlays. | |
2421 | @end defun | |
2422 | ||
1f63f814 CW |
2423 | @defvar char-property-alias-alist |
2424 | This variable holds an alist which maps property names to a list of | |
2425 | alternative property names. If a character does not specify a direct | |
2426 | value for a property, the alternative property names are consulted in | |
74eee906 | 2427 | order; the first non-@code{nil} value is used. This variable takes |
1f63f814 CW |
2428 | precedence over @code{default-text-properties}, and @code{category} |
2429 | properties take precedence over this variable. | |
2430 | @end defvar | |
2431 | ||
73804d4b RS |
2432 | @defun text-properties-at position &optional object |
2433 | This function returns the entire property list of the character at | |
2434 | @var{position} in the string or buffer @var{object}. If @var{object} is | |
2435 | @code{nil}, it defaults to the current buffer. | |
2436 | @end defun | |
2437 | ||
22697dac KH |
2438 | @defvar default-text-properties |
2439 | This variable holds a property list giving default values for text | |
2440 | properties. Whenever a character does not specify a value for a | |
1f63f814 CW |
2441 | property, neither directly, through a category symbol, or through |
2442 | @code{char-property-alias-alist}, the value stored in this list is | |
2443 | used instead. Here is an example: | |
22697dac KH |
2444 | |
2445 | @example | |
1f63f814 CW |
2446 | (setq default-text-properties '(foo 69) |
2447 | char-property-alias-alist nil) | |
22697dac KH |
2448 | ;; @r{Make sure character 1 has no properties of its own.} |
2449 | (set-text-properties 1 2 nil) | |
2450 | ;; @r{What we get, when we ask, is the default value.} | |
2451 | (get-text-property 1 'foo) | |
2452 | @result{} 69 | |
2453 | @end example | |
2454 | @end defvar | |
2455 | ||
73804d4b RS |
2456 | @node Changing Properties |
2457 | @subsection Changing Text Properties | |
2458 | ||
2459 | The primitives for changing properties apply to a specified range of | |
e78ea3db RS |
2460 | text in a buffer or string. The function @code{set-text-properties} |
2461 | (see end of section) sets the entire property list of the text in that | |
2462 | range; more often, it is useful to add, change, or delete just certain | |
2463 | properties specified by name. | |
73804d4b | 2464 | |
e78ea3db | 2465 | Since text properties are considered part of the contents of the |
9a36dd51 RS |
2466 | buffer (or string), and can affect how a buffer looks on the screen, |
2467 | any change in buffer text properties marks the buffer as modified. | |
2468 | Buffer text property changes are undoable also (@pxref{Undo}). | |
2469 | Positions in a string start from 0, whereas positions in a buffer | |
2470 | start from 1. | |
73804d4b | 2471 | |
bfe721d1 KH |
2472 | @defun put-text-property start end prop value &optional object |
2473 | This function sets the @var{prop} property to @var{value} for the text | |
2474 | between @var{start} and @var{end} in the string or buffer @var{object}. | |
2475 | If @var{object} is @code{nil}, it defaults to the current buffer. | |
2476 | @end defun | |
2477 | ||
73804d4b | 2478 | @defun add-text-properties start end props &optional object |
f9f59935 | 2479 | This function adds or overrides text properties for the text between |
73804d4b RS |
2480 | @var{start} and @var{end} in the string or buffer @var{object}. If |
2481 | @var{object} is @code{nil}, it defaults to the current buffer. | |
2482 | ||
f9f59935 RS |
2483 | The argument @var{props} specifies which properties to add. It should |
2484 | have the form of a property list (@pxref{Property Lists}): a list whose | |
2485 | elements include the property names followed alternately by the | |
73804d4b RS |
2486 | corresponding values. |
2487 | ||
2488 | The return value is @code{t} if the function actually changed some | |
2489 | property's value; @code{nil} otherwise (if @var{props} is @code{nil} or | |
2490 | its values agree with those in the text). | |
2491 | ||
2492 | For example, here is how to set the @code{comment} and @code{face} | |
2493 | properties of a range of text: | |
2494 | ||
2495 | @example | |
2496 | (add-text-properties @var{start} @var{end} | |
2497 | '(comment t face highlight)) | |
2498 | @end example | |
2499 | @end defun | |
2500 | ||
73804d4b RS |
2501 | @defun remove-text-properties start end props &optional object |
2502 | This function deletes specified text properties from the text between | |
2503 | @var{start} and @var{end} in the string or buffer @var{object}. If | |
2504 | @var{object} is @code{nil}, it defaults to the current buffer. | |
2505 | ||
2506 | The argument @var{props} specifies which properties to delete. It | |
2507 | should have the form of a property list (@pxref{Property Lists}): a list | |
2508 | whose elements are property names alternating with corresponding values. | |
2509 | But only the names matter---the values that accompany them are ignored. | |
2510 | For example, here's how to remove the @code{face} property. | |
2511 | ||
2512 | @example | |
2513 | (remove-text-properties @var{start} @var{end} '(face nil)) | |
2514 | @end example | |
2515 | ||
2516 | The return value is @code{t} if the function actually changed some | |
2517 | property's value; @code{nil} otherwise (if @var{props} is @code{nil} or | |
2518 | if no character in the specified text had any of those properties). | |
e78ea3db RS |
2519 | |
2520 | To remove all text properties from certain text, use | |
2521 | @code{set-text-properties} and specify @code{nil} for the new property | |
2522 | list. | |
73804d4b RS |
2523 | @end defun |
2524 | ||
d73eac4d RS |
2525 | @defun remove-list-of-text-properties start end list-of-properties &optional object |
2526 | Like @code{remove-list-properties} except that | |
2527 | @var{list-of-properties} is a list property names only, not an | |
2528 | alternating list of property values. | |
2529 | @end defun | |
2530 | ||
73804d4b RS |
2531 | @defun set-text-properties start end props &optional object |
2532 | This function completely replaces the text property list for the text | |
2533 | between @var{start} and @var{end} in the string or buffer @var{object}. | |
2534 | If @var{object} is @code{nil}, it defaults to the current buffer. | |
2535 | ||
2536 | The argument @var{props} is the new property list. It should be a list | |
2537 | whose elements are property names alternating with corresponding values. | |
2538 | ||
2539 | After @code{set-text-properties} returns, all the characters in the | |
2540 | specified range have identical properties. | |
2541 | ||
2542 | If @var{props} is @code{nil}, the effect is to get rid of all properties | |
2543 | from the specified range of text. Here's an example: | |
2544 | ||
2545 | @example | |
2546 | (set-text-properties @var{start} @var{end} nil) | |
2547 | @end example | |
a40d4712 PR |
2548 | @end defun |
2549 | ||
2550 | The easiest way to make a string with text properties | |
2551 | is with @code{propertize}: | |
2552 | ||
2553 | @defun propertize string &rest properties | |
2554 | @tindex propertize | |
2555 | This function returns a copy of @var{string} which has the text | |
2556 | properties @var{properties}. These properties apply to all the | |
2557 | characters in the string that is returned. Here is an example that | |
2558 | constructs a string with a @code{face} property and a @code{mouse-face} | |
2559 | property: | |
2560 | ||
2561 | @smallexample | |
2562 | (propertize "foo" 'face 'italic | |
2563 | 'mouse-face 'bold-italic) | |
2564 | @result{} #("foo" 0 3 (mouse-face bold-italic face italic)) | |
2565 | @end smallexample | |
2566 | ||
2567 | To put different properties on various parts of a string, you can | |
2568 | construct each part with @code{propertize} and then combine them with | |
2569 | @code{concat}: | |
2570 | ||
2571 | @smallexample | |
2572 | (concat | |
2573 | (propertize "foo" 'face 'italic | |
2574 | 'mouse-face 'bold-italic) | |
2575 | " and " | |
2576 | (propertize "bar" 'face 'italic | |
2577 | 'mouse-face 'bold-italic)) | |
2578 | @result{} #("foo and bar" | |
2579 | 0 3 (face italic mouse-face bold-italic) | |
2580 | 3 8 nil | |
2581 | 8 11 (face italic mouse-face bold-italic)) | |
2582 | @end smallexample | |
73804d4b RS |
2583 | @end defun |
2584 | ||
f9f59935 | 2585 | See also the function @code{buffer-substring-no-properties} |
22697dac KH |
2586 | (@pxref{Buffer Contents}) which copies text from the buffer |
2587 | but does not copy its properties. | |
2588 | ||
73804d4b | 2589 | @node Property Search |
f9f59935 | 2590 | @subsection Text Property Search Functions |
73804d4b | 2591 | |
f9f59935 | 2592 | In typical use of text properties, most of the time several or many |
73804d4b RS |
2593 | consecutive characters have the same value for a property. Rather than |
2594 | writing your programs to examine characters one by one, it is much | |
2595 | faster to process chunks of text that have the same property value. | |
2596 | ||
f9f59935 | 2597 | Here are functions you can use to do this. They use @code{eq} for |
bfe721d1 KH |
2598 | comparing property values. In all cases, @var{object} defaults to the |
2599 | current buffer. | |
73804d4b | 2600 | |
f9f59935 | 2601 | For high performance, it's very important to use the @var{limit} |
73804d4b | 2602 | argument to these functions, especially the ones that search for a |
bfe721d1 KH |
2603 | single property---otherwise, they may spend a long time scanning to the |
2604 | end of the buffer, if the property you are interested in does not change. | |
73804d4b | 2605 | |
f9f59935 RS |
2606 | These functions do not move point; instead, they return a position (or |
2607 | @code{nil}). Remember that a position is always between two characters; | |
2608 | the position returned by these functions is between two characters with | |
2609 | different properties. | |
61cfa852 | 2610 | |
73804d4b RS |
2611 | @defun next-property-change pos &optional object limit |
2612 | The function scans the text forward from position @var{pos} in the | |
2613 | string or buffer @var{object} till it finds a change in some text | |
2614 | property, then returns the position of the change. In other words, it | |
2615 | returns the position of the first character beyond @var{pos} whose | |
2616 | properties are not identical to those of the character just after | |
2617 | @var{pos}. | |
2618 | ||
2619 | If @var{limit} is non-@code{nil}, then the scan ends at position | |
177c0ea7 | 2620 | @var{limit}. If there is no property change before that point, |
73804d4b RS |
2621 | @code{next-property-change} returns @var{limit}. |
2622 | ||
2623 | The value is @code{nil} if the properties remain unchanged all the way | |
61cfa852 RS |
2624 | to the end of @var{object} and @var{limit} is @code{nil}. If the value |
2625 | is non-@code{nil}, it is a position greater than or equal to @var{pos}. | |
2626 | The value equals @var{pos} only when @var{limit} equals @var{pos}. | |
73804d4b RS |
2627 | |
2628 | Here is an example of how to scan the buffer by chunks of text within | |
2629 | which all properties are constant: | |
2630 | ||
2631 | @smallexample | |
2632 | (while (not (eobp)) | |
2633 | (let ((plist (text-properties-at (point))) | |
2634 | (next-change | |
2635 | (or (next-property-change (point) (current-buffer)) | |
2636 | (point-max)))) | |
2637 | @r{Process text from point to @var{next-change}@dots{}} | |
2638 | (goto-char next-change))) | |
2639 | @end smallexample | |
2640 | @end defun | |
2641 | ||
2642 | @defun next-single-property-change pos prop &optional object limit | |
2643 | The function scans the text forward from position @var{pos} in the | |
2644 | string or buffer @var{object} till it finds a change in the @var{prop} | |
2645 | property, then returns the position of the change. In other words, it | |
2646 | returns the position of the first character beyond @var{pos} whose | |
2647 | @var{prop} property differs from that of the character just after | |
2648 | @var{pos}. | |
2649 | ||
2650 | If @var{limit} is non-@code{nil}, then the scan ends at position | |
177c0ea7 | 2651 | @var{limit}. If there is no property change before that point, |
73804d4b RS |
2652 | @code{next-single-property-change} returns @var{limit}. |
2653 | ||
2654 | The value is @code{nil} if the property remains unchanged all the way to | |
2655 | the end of @var{object} and @var{limit} is @code{nil}. If the value is | |
2656 | non-@code{nil}, it is a position greater than or equal to @var{pos}; it | |
2657 | equals @var{pos} only if @var{limit} equals @var{pos}. | |
2658 | @end defun | |
2659 | ||
2660 | @defun previous-property-change pos &optional object limit | |
2661 | This is like @code{next-property-change}, but scans back from @var{pos} | |
2662 | instead of forward. If the value is non-@code{nil}, it is a position | |
2663 | less than or equal to @var{pos}; it equals @var{pos} only if @var{limit} | |
2664 | equals @var{pos}. | |
73804d4b RS |
2665 | @end defun |
2666 | ||
2667 | @defun previous-single-property-change pos prop &optional object limit | |
61cfa852 RS |
2668 | This is like @code{next-single-property-change}, but scans back from |
2669 | @var{pos} instead of forward. If the value is non-@code{nil}, it is a | |
2670 | position less than or equal to @var{pos}; it equals @var{pos} only if | |
2671 | @var{limit} equals @var{pos}. | |
73804d4b RS |
2672 | @end defun |
2673 | ||
9db3a582 | 2674 | @defun next-char-property-change pos &optional limit |
f9f59935 | 2675 | This is like @code{next-property-change} except that it considers |
9db3a582 MB |
2676 | overlay properties as well as text properties, and if no change is |
2677 | found before the end of the buffer, it returns the maximum buffer | |
2678 | position rather than @code{nil} (in this sense, it resembles the | |
2679 | corresponding overlay function @code{next-overlay-change}, rather than | |
2680 | @code{next-property-change}). There is no @var{object} operand | |
2681 | because this function operates only on the current buffer. It returns | |
2682 | the next address at which either kind of property changes. | |
f9f59935 RS |
2683 | @end defun |
2684 | ||
9db3a582 | 2685 | @defun previous-char-property-change pos &optional limit |
f9f59935 | 2686 | This is like @code{next-char-property-change}, but scans back from |
9db3a582 MB |
2687 | @var{pos} instead of forward, and returns the minimum buffer |
2688 | position if no change is found. | |
2689 | @end defun | |
2690 | ||
2691 | @defun next-single-char-property-change pos prop &optional object limit | |
adce7d83 | 2692 | @tindex next-single-char-property-change |
9db3a582 MB |
2693 | This is like @code{next-single-property-change} except that it |
2694 | considers overlay properties as well as text properties, and if no | |
2695 | change is found before the end of the @var{object}, it returns the | |
2696 | maximum valid position in @var{object} rather than @code{nil}. Unlike | |
2697 | @code{next-char-property-change}, this function @emph{does} have an | |
2698 | @var{object} operand; if @var{object} is not a buffer, only | |
2699 | text-properties are considered. | |
2700 | @end defun | |
2701 | ||
2702 | @defun previous-single-char-property-change pos prop &optional object limit | |
adce7d83 | 2703 | @tindex previous-single-char-property-change |
9db3a582 MB |
2704 | This is like @code{next-single-char-property-change}, but scans back |
2705 | from @var{pos} instead of forward, and returns the minimum valid | |
2706 | position in @var{object} if no change is found. | |
f9f59935 RS |
2707 | @end defun |
2708 | ||
73804d4b RS |
2709 | @defun text-property-any start end prop value &optional object |
2710 | This function returns non-@code{nil} if at least one character between | |
2711 | @var{start} and @var{end} has a property @var{prop} whose value is | |
2712 | @var{value}. More precisely, it returns the position of the first such | |
2713 | character. Otherwise, it returns @code{nil}. | |
2714 | ||
2715 | The optional fifth argument, @var{object}, specifies the string or | |
2716 | buffer to scan. Positions are relative to @var{object}. The default | |
2717 | for @var{object} is the current buffer. | |
2718 | @end defun | |
2719 | ||
2720 | @defun text-property-not-all start end prop value &optional object | |
2721 | This function returns non-@code{nil} if at least one character between | |
f9f59935 RS |
2722 | @var{start} and @var{end} does not have a property @var{prop} with value |
2723 | @var{value}. More precisely, it returns the position of the first such | |
2724 | character. Otherwise, it returns @code{nil}. | |
73804d4b RS |
2725 | |
2726 | The optional fifth argument, @var{object}, specifies the string or | |
2727 | buffer to scan. Positions are relative to @var{object}. The default | |
2728 | for @var{object} is the current buffer. | |
2729 | @end defun | |
2730 | ||
2731 | @node Special Properties | |
2732 | @subsection Properties with Special Meanings | |
2733 | ||
bfe721d1 | 2734 | Here is a table of text property names that have special built-in |
969fe9b5 RS |
2735 | meanings. The following sections list a few additional special property |
2736 | names that control filling and property inheritance. All other names | |
2737 | have no standard meaning, and you can use them as you like. | |
bfe721d1 | 2738 | |
73804d4b RS |
2739 | @table @code |
2740 | @cindex category of text character | |
2741 | @kindex category @r{(text property)} | |
2742 | @item category | |
2743 | If a character has a @code{category} property, we call it the | |
2744 | @dfn{category} of the character. It should be a symbol. The properties | |
2745 | of the symbol serve as defaults for the properties of the character. | |
2746 | ||
2747 | @item face | |
2748 | @cindex face codes of text | |
2749 | @kindex face @r{(text property)} | |
2750 | You can use the property @code{face} to control the font and color of | |
8241495d RS |
2751 | text. @xref{Faces}, for more information. |
2752 | ||
2753 | In the simplest case, the value is a face name. It can also be a list; | |
2754 | then each element can be any of these possibilities; | |
2755 | ||
2756 | @itemize @bullet | |
2757 | @item | |
2758 | A face name (a symbol or string). | |
f9f59935 | 2759 | |
8241495d RS |
2760 | @item |
2761 | Starting in Emacs 21, a property list of face attributes. This has the | |
2762 | form (@var{keyword} @var{value} @dots{}), where each @var{keyword} is a | |
2763 | face attribute name and @var{value} is a meaningful value for that | |
2764 | attribute. With this feature, you do not need to create a face each | |
2765 | time you want to specify a particular attribute for certain text. | |
2766 | @xref{Face Attributes}. | |
2767 | ||
2768 | @item | |
2769 | A cons cell of the form @code{(foreground-color . @var{color-name})} or | |
2770 | @code{(background-color . @var{color-name})}. These elements specify | |
2771 | just the foreground color or just the background color. | |
2772 | ||
2773 | @code{(foreground-color . @var{color-name})} is equivalent to | |
2774 | @code{(:foreground @var{color-name})}, and likewise for the background. | |
2775 | @end itemize | |
f9f59935 | 2776 | |
1f63f814 CW |
2777 | You can use Font Lock Mode (@pxref{Font Lock Mode}), to dynamically |
2778 | update @code{face} properties based on the contents of the text. | |
2779 | ||
2780 | @item font-lock-face | |
2781 | @kindex font-lock-face @r{(text property)} | |
2782 | The @code{font-lock-face} property is the same in all respects as the | |
2783 | @code{face} property, but its state of activation is controlled by | |
2784 | @code{font-lock-mode}. This can be advantageous for special buffers | |
2785 | which are not intended to be user-editable, or for static areas of | |
2786 | text which are always fontified in the same way. | |
2787 | @xref{Precalculated Fontification}. | |
2788 | ||
2789 | Strictly speaking, @code{font-lock-face} is not a built-in text | |
2790 | property; rather, it is implemented in Font Lock mode using | |
2791 | @code{char-property-alias-alist}. @xref{Examining Properties}. | |
2792 | ||
2793 | This property is new in Emacs 21.4. | |
73804d4b RS |
2794 | |
2795 | @item mouse-face | |
2796 | @kindex mouse-face @r{(text property)} | |
2797 | The property @code{mouse-face} is used instead of @code{face} when the | |
2798 | mouse is on or near the character. For this purpose, ``near'' means | |
2799 | that all text between the character and where the mouse is have the same | |
2800 | @code{mouse-face} property value. | |
2801 | ||
8241495d RS |
2802 | @item fontified |
2803 | @kindex fontified @r{(text property)} | |
2804 | This property, if non-@code{nil}, says that text in the buffer has | |
2805 | had faces assigned automatically by a feature such as Font-Lock mode. | |
2806 | @xref{Auto Faces}. | |
2807 | ||
2808 | @item display | |
2809 | @kindex display @r{(text property)} | |
2810 | This property activates various features that change the | |
2811 | way text is displayed. For example, it can make text appear taller | |
75708135 | 2812 | or shorter, higher or lower, wider or narrow, or replaced with an image. |
8241495d RS |
2813 | @xref{Display Property}. |
2814 | ||
2815 | @item help-echo | |
2816 | @kindex help-echo @r{(text property)} | |
85378c3f | 2817 | @cindex tooltip |
b6dd5963 | 2818 | @anchor{Text help-echo} |
8241495d RS |
2819 | If text has a string as its @code{help-echo} property, then when you |
2820 | move the mouse onto that text, Emacs displays that string in the echo | |
85378c3f RS |
2821 | area, or in the tooltip window (@pxref{Tooltips,,, emacs, The GNU Emacs |
2822 | Manual}). | |
b6dd5963 | 2823 | |
05cae5d0 | 2824 | If the value of the @code{help-echo} property is a function, that |
b6dd5963 | 2825 | function is called with three arguments, @var{window}, @var{object} and |
05cae5d0 | 2826 | @var{position} and should return a help string or @var{nil} for |
b6dd5963 DL |
2827 | none. The first argument, @var{window} is the window in which |
2828 | the help was found. The second, @var{object}, is the buffer, overlay or | |
2829 | string which had the @code{help-echo} property. The @var{position} | |
2830 | argument is as follows: | |
2831 | ||
2832 | @itemize @bullet{} | |
2833 | @item | |
2834 | If @var{object} is a buffer, @var{pos} is the position in the buffer | |
2835 | where the @code{help-echo} text property was found. | |
2836 | @item | |
2837 | If @var{object} is an overlay, that overlay has a @code{help-echo} | |
2838 | property, and @var{pos} is the position in the overlay's buffer under | |
2839 | the mouse. | |
2840 | @item | |
2841 | If @var{object} is a string (an overlay string or a string displayed | |
05cae5d0 | 2842 | with the @code{display} property), @var{pos} is the position in that |
b6dd5963 DL |
2843 | string under the mouse. |
2844 | @end itemize | |
2845 | ||
2846 | If the value of the @code{help-echo} property is neither a function nor | |
2847 | a string, it is evaluated to obtain a help string. | |
2848 | ||
05cae5d0 DL |
2849 | You can alter the way help text is displayed by setting the variable |
2850 | @code{show-help-function} (@pxref{Help display}). | |
b6dd5963 | 2851 | |
2e46cd09 | 2852 | This feature is used in the mode line and for other active text. |
8241495d | 2853 | |
0b3da4ec | 2854 | @item keymap |
1bd2023a | 2855 | @cindex keymap of character |
0b3da4ec | 2856 | @kindex keymap @r{(text property)} |
1bd2023a | 2857 | The @code{keymap} property specifies an additional keymap for |
41332983 RS |
2858 | commands. The property's value for the character before point applies |
2859 | if it is non-@code{nil} and rear-sticky, and the property's value for | |
2860 | the character after point applies if it is non-@code{nil} and | |
2861 | front-sticky. When the value applies, it is used for key lookup | |
2862 | before the buffer's local map. (For mouse clicks, the position of the | |
2863 | click is used instead of the position of point.) If the property | |
2864 | value is a symbol, the symbol's function definition is used as the | |
2865 | keymap. @xref{Active Keymaps}. | |
1bd2023a RS |
2866 | |
2867 | @item local-map | |
2868 | @kindex local-map @r{(text property)} | |
41332983 RS |
2869 | This property works like @code{keymap} except that it specifies a |
2870 | keymap to use @emph{instead of} the buffer's local map. For most | |
2871 | purposes (perhaps all purposes), the @code{keymap} is superior. | |
0b3da4ec | 2872 | |
f9f59935 RS |
2873 | @item syntax-table |
2874 | The @code{syntax-table} property overrides what the syntax table says | |
2875 | about this particular character. @xref{Syntax Properties}. | |
73804d4b RS |
2876 | |
2877 | @item read-only | |
2878 | @cindex read-only character | |
2879 | @kindex read-only @r{(text property)} | |
2880 | If a character has the property @code{read-only}, then modifying that | |
2468d0c0 DL |
2881 | character is not allowed. Any command that would do so gets an error, |
2882 | @code{text-read-only}. | |
73804d4b RS |
2883 | |
2884 | Insertion next to a read-only character is an error if inserting | |
2885 | ordinary text there would inherit the @code{read-only} property due to | |
2886 | stickiness. Thus, you can control permission to insert next to | |
2887 | read-only text by controlling the stickiness. @xref{Sticky Properties}. | |
2888 | ||
2889 | Since changing properties counts as modifying the buffer, it is not | |
2890 | possible to remove a @code{read-only} property unless you know the | |
2891 | special trick: bind @code{inhibit-read-only} to a non-@code{nil} value | |
2892 | and then remove the property. @xref{Read Only Buffers}. | |
2893 | ||
2894 | @item invisible | |
2895 | @kindex invisible @r{(text property)} | |
22697dac KH |
2896 | A non-@code{nil} @code{invisible} property can make a character invisible |
2897 | on the screen. @xref{Invisible Text}, for details. | |
73804d4b | 2898 | |
72654a3c RS |
2899 | @item intangible |
2900 | @kindex intangible @r{(text property)} | |
22697dac KH |
2901 | If a group of consecutive characters have equal and non-@code{nil} |
2902 | @code{intangible} properties, then you cannot place point between them. | |
bfe721d1 KH |
2903 | If you try to move point forward into the group, point actually moves to |
2904 | the end of the group. If you try to move point backward into the group, | |
22697dac KH |
2905 | point actually moves to the start of the group. |
2906 | ||
2907 | When the variable @code{inhibit-point-motion-hooks} is non-@code{nil}, | |
2908 | the @code{intangible} property is ignored. | |
72654a3c | 2909 | |
2468d0c0 DL |
2910 | @item field |
2911 | @kindex field @r{(text property)} | |
2912 | Consecutive characters with the same @code{field} property constitute a | |
2913 | @dfn{field}. Some motion functions including @code{forward-word} and | |
2914 | @code{beginning-of-line} stop moving at a field boundary. | |
2915 | @xref{Fields}. | |
2916 | ||
73804d4b RS |
2917 | @item modification-hooks |
2918 | @cindex change hooks for a character | |
2919 | @cindex hooks for changing a character | |
2920 | @kindex modification-hooks @r{(text property)} | |
2921 | If a character has the property @code{modification-hooks}, then its | |
2922 | value should be a list of functions; modifying that character calls all | |
2923 | of those functions. Each function receives two arguments: the beginning | |
2924 | and end of the part of the buffer being modified. Note that if a | |
2925 | particular modification hook function appears on several characters | |
2926 | being modified by a single primitive, you can't predict how many times | |
2927 | the function will be called. | |
2928 | ||
2929 | @item insert-in-front-hooks | |
2930 | @itemx insert-behind-hooks | |
2931 | @kindex insert-in-front-hooks @r{(text property)} | |
2932 | @kindex insert-behind-hooks @r{(text property)} | |
9ea65df9 RS |
2933 | The operation of inserting text in a buffer also calls the functions |
2934 | listed in the @code{insert-in-front-hooks} property of the following | |
2935 | character and in the @code{insert-behind-hooks} property of the | |
2936 | preceding character. These functions receive two arguments, the | |
2937 | beginning and end of the inserted text. The functions are called | |
2938 | @emph{after} the actual insertion takes place. | |
73804d4b RS |
2939 | |
2940 | See also @ref{Change Hooks}, for other hooks that are called | |
2941 | when you change text in a buffer. | |
2942 | ||
2943 | @item point-entered | |
2944 | @itemx point-left | |
2945 | @cindex hooks for motion of point | |
2946 | @kindex point-entered @r{(text property)} | |
2947 | @kindex point-left @r{(text property)} | |
2948 | The special properties @code{point-entered} and @code{point-left} | |
2949 | record hook functions that report motion of point. Each time point | |
2950 | moves, Emacs compares these two property values: | |
2951 | ||
2952 | @itemize @bullet | |
2953 | @item | |
2954 | the @code{point-left} property of the character after the old location, | |
2955 | and | |
2956 | @item | |
2957 | the @code{point-entered} property of the character after the new | |
2958 | location. | |
2959 | @end itemize | |
2960 | ||
2961 | @noindent | |
2962 | If these two values differ, each of them is called (if not @code{nil}) | |
2963 | with two arguments: the old value of point, and the new one. | |
2964 | ||
2965 | The same comparison is made for the characters before the old and new | |
2966 | locations. The result may be to execute two @code{point-left} functions | |
2967 | (which may be the same function) and/or two @code{point-entered} | |
61cfa852 RS |
2968 | functions (which may be the same function). In any case, all the |
2969 | @code{point-left} functions are called first, followed by all the | |
2970 | @code{point-entered} functions. | |
73804d4b | 2971 | |
f9f59935 RS |
2972 | It is possible using @code{char-after} to examine characters at various |
2973 | positions without moving point to those positions. Only an actual | |
2974 | change in the value of point runs these hook functions. | |
73804d4b RS |
2975 | @end table |
2976 | ||
2977 | @defvar inhibit-point-motion-hooks | |
2978 | When this variable is non-@code{nil}, @code{point-left} and | |
22697dac | 2979 | @code{point-entered} hooks are not run, and the @code{intangible} |
f9f59935 RS |
2980 | property has no effect. Do not set this variable globally; bind it with |
2981 | @code{let}. | |
73804d4b RS |
2982 | @end defvar |
2983 | ||
b6dd5963 DL |
2984 | @defvar show-help-function |
2985 | @tindex show-help-function | |
05cae5d0 DL |
2986 | @anchor{Help display} If this variable is non-@code{nil}, it specifies a |
2987 | function called to display help strings. These may be @code{help-echo} | |
2988 | properties, menu help strings (@pxref{Simple Menu Items}, | |
2989 | @pxref{Extended Menu Items}), or tool bar help strings (@pxref{Tool | |
2990 | Bar}). The specified function is called with one argument, the help | |
0b2fb045 WL |
2991 | string to display. Tooltip mode (@pxref{Tooltips,,, emacs, The GNU Emacs |
2992 | Manual}) provides an example. | |
b6dd5963 DL |
2993 | @end defvar |
2994 | ||
22697dac | 2995 | @node Format Properties |
bfe721d1 | 2996 | @subsection Formatted Text Properties |
22697dac KH |
2997 | |
2998 | These text properties affect the behavior of the fill commands. They | |
bfe721d1 KH |
2999 | are used for representing formatted text. @xref{Filling}, and |
3000 | @ref{Margins}. | |
22697dac | 3001 | |
bfe721d1 | 3002 | @table @code |
22697dac KH |
3003 | @item hard |
3004 | If a newline character has this property, it is a ``hard'' newline. | |
3005 | The fill commands do not alter hard newlines and do not move words | |
3006 | across them. However, this property takes effect only if the variable | |
3007 | @code{use-hard-newlines} is non-@code{nil}. | |
3008 | ||
3009 | @item right-margin | |
bfe721d1 | 3010 | This property specifies an extra right margin for filling this part of the |
22697dac KH |
3011 | text. |
3012 | ||
3013 | @item left-margin | |
bfe721d1 | 3014 | This property specifies an extra left margin for filling this part of the |
22697dac KH |
3015 | text. |
3016 | ||
3017 | @item justification | |
3018 | This property specifies the style of justification for filling this part | |
3019 | of the text. | |
3020 | @end table | |
3021 | ||
73804d4b RS |
3022 | @node Sticky Properties |
3023 | @subsection Stickiness of Text Properties | |
3024 | @cindex sticky text properties | |
3025 | @cindex inheritance of text properties | |
3026 | ||
3027 | Self-inserting characters normally take on the same properties as the | |
3028 | preceding character. This is called @dfn{inheritance} of properties. | |
3029 | ||
3030 | In a Lisp program, you can do insertion with inheritance or without, | |
3031 | depending on your choice of insertion primitive. The ordinary text | |
3032 | insertion functions such as @code{insert} do not inherit any properties. | |
3033 | They insert text with precisely the properties of the string being | |
3034 | inserted, and no others. This is correct for programs that copy text | |
61cfa852 RS |
3035 | from one context to another---for example, into or out of the kill ring. |
3036 | To insert with inheritance, use the special primitives described in this | |
3037 | section. Self-inserting characters inherit properties because they work | |
3038 | using these primitives. | |
73804d4b RS |
3039 | |
3040 | When you do insertion with inheritance, @emph{which} properties are | |
2468d0c0 DL |
3041 | inherited, and from where, depends on which properties are @dfn{sticky}. |
3042 | Insertion after a character inherits those of its properties that are | |
73804d4b | 3043 | @dfn{rear-sticky}. Insertion before a character inherits those of its |
2468d0c0 DL |
3044 | properties that are @dfn{front-sticky}. When both sides offer different |
3045 | sticky values for the same property, the previous character's value | |
3046 | takes precedence. | |
3047 | ||
3048 | By default, a text property is rear-sticky but not front-sticky; thus, | |
3049 | the default is to inherit all the properties of the preceding character, | |
3050 | and nothing from the following character. | |
3051 | ||
3052 | You can control the stickiness of various text properties with two | |
3053 | specific text properties, @code{front-sticky} and @code{rear-nonsticky}, | |
3054 | and with the variable @code{text-property-default-nonsticky}. You can | |
3055 | use the variable to specify a different default for a given property. | |
3056 | You can use those two text properties to make any specific properties | |
3057 | sticky or nonsticky in any particular part of the text. | |
73804d4b RS |
3058 | |
3059 | If a character's @code{front-sticky} property is @code{t}, then all | |
3060 | its properties are front-sticky. If the @code{front-sticky} property is | |
3061 | a list, then the sticky properties of the character are those whose | |
3062 | names are in the list. For example, if a character has a | |
3063 | @code{front-sticky} property whose value is @code{(face read-only)}, | |
3064 | then insertion before the character can inherit its @code{face} property | |
3065 | and its @code{read-only} property, but no others. | |
3066 | ||
75708135 RS |
3067 | The @code{rear-nonsticky} property works the opposite way. Most |
3068 | properties are rear-sticky by default, so the @code{rear-nonsticky} | |
3069 | property says which properties are @emph{not} rear-sticky. If a | |
3070 | character's @code{rear-nonsticky} property is @code{t}, then none of its | |
3071 | properties are rear-sticky. If the @code{rear-nonsticky} property is a | |
3072 | list, properties are rear-sticky @emph{unless} their names are in the | |
3073 | list. | |
73804d4b | 3074 | |
2468d0c0 DL |
3075 | @defvar text-property-default-nonsticky |
3076 | @tindex text-property-default-nonsticky | |
3077 | This variable holds an alist which defines the default rear-stickiness | |
3078 | of various text properties. Each element has the form | |
3079 | @code{(@var{property} . @var{nonstickiness})}, and it defines the | |
3080 | stickiness of a particular text property, @var{property}. | |
3081 | ||
3082 | If @var{nonstickiness} is non-@code{nil}, this means that the property | |
3083 | @var{property} is rear-nonsticky by default. Since all properties are | |
3084 | front-nonsticky by default, this makes @var{property} nonsticky in both | |
3085 | directions by default. | |
3086 | ||
3087 | The text properties @code{front-sticky} and @code{rear-nonsticky}, when | |
8b6c1445 | 3088 | used, take precedence over the default @var{nonstickiness} specified in |
2468d0c0 DL |
3089 | @code{text-property-default-nonsticky}. |
3090 | @end defvar | |
73804d4b RS |
3091 | |
3092 | Here are the functions that insert text with inheritance of properties: | |
3093 | ||
3094 | @defun insert-and-inherit &rest strings | |
3095 | Insert the strings @var{strings}, just like the function @code{insert}, | |
3096 | but inherit any sticky properties from the adjoining text. | |
3097 | @end defun | |
3098 | ||
3099 | @defun insert-before-markers-and-inherit &rest strings | |
3100 | Insert the strings @var{strings}, just like the function | |
3101 | @code{insert-before-markers}, but inherit any sticky properties from the | |
3102 | adjoining text. | |
3103 | @end defun | |
3104 | ||
f9f59935 RS |
3105 | @xref{Insertion}, for the ordinary insertion functions which do not |
3106 | inherit. | |
3107 | ||
73804d4b | 3108 | @node Saving Properties |
61cfa852 | 3109 | @subsection Saving Text Properties in Files |
73804d4b RS |
3110 | @cindex text properties in files |
3111 | @cindex saving text properties | |
3112 | ||
f9f59935 RS |
3113 | You can save text properties in files (along with the text itself), |
3114 | and restore the same text properties when visiting or inserting the | |
3115 | files, using these two hooks: | |
73804d4b | 3116 | |
bfe721d1 | 3117 | @defvar write-region-annotate-functions |
73804d4b RS |
3118 | This variable's value is a list of functions for @code{write-region} to |
3119 | run to encode text properties in some fashion as annotations to the text | |
3120 | being written in the file. @xref{Writing to Files}. | |
3121 | ||
3122 | Each function in the list is called with two arguments: the start and | |
3123 | end of the region to be written. These functions should not alter the | |
3124 | contents of the buffer. Instead, they should return lists indicating | |
3125 | annotations to write in the file in addition to the text in the | |
3126 | buffer. | |
3127 | ||
3128 | Each function should return a list of elements of the form | |
3129 | @code{(@var{position} . @var{string})}, where @var{position} is an | |
f9f59935 RS |
3130 | integer specifying the relative position within the text to be written, |
3131 | and @var{string} is the annotation to add there. | |
73804d4b RS |
3132 | |
3133 | Each list returned by one of these functions must be already sorted in | |
3134 | increasing order by @var{position}. If there is more than one function, | |
3135 | @code{write-region} merges the lists destructively into one sorted list. | |
3136 | ||
3137 | When @code{write-region} actually writes the text from the buffer to the | |
3138 | file, it intermixes the specified annotations at the corresponding | |
3139 | positions. All this takes place without modifying the buffer. | |
3140 | @end defvar | |
3141 | ||
3142 | @defvar after-insert-file-functions | |
3143 | This variable holds a list of functions for @code{insert-file-contents} | |
3144 | to call after inserting a file's contents. These functions should scan | |
3145 | the inserted text for annotations, and convert them to the text | |
3146 | properties they stand for. | |
3147 | ||
3148 | Each function receives one argument, the length of the inserted text; | |
3149 | point indicates the start of that text. The function should scan that | |
3150 | text for annotations, delete them, and create the text properties that | |
3151 | the annotations specify. The function should return the updated length | |
3152 | of the inserted text, as it stands after those changes. The value | |
3153 | returned by one function becomes the argument to the next function. | |
3154 | ||
3155 | These functions should always return with point at the beginning of | |
3156 | the inserted text. | |
3157 | ||
3158 | The intended use of @code{after-insert-file-functions} is for converting | |
3159 | some sort of textual annotations into actual text properties. But other | |
3160 | uses may be possible. | |
3161 | @end defvar | |
3162 | ||
3163 | We invite users to write Lisp programs to store and retrieve text | |
3164 | properties in files, using these hooks, and thus to experiment with | |
177c0ea7 | 3165 | various data formats and find good ones. Eventually we hope users |
73804d4b RS |
3166 | will produce good, general extensions we can install in Emacs. |
3167 | ||
f9f59935 RS |
3168 | We suggest not trying to handle arbitrary Lisp objects as text property |
3169 | names or values---because a program that general is probably difficult | |
3170 | to write, and slow. Instead, choose a set of possible data types that | |
3171 | are reasonably flexible, and not too hard to encode. | |
73804d4b | 3172 | |
bfe721d1 KH |
3173 | @xref{Format Conversion}, for a related feature. |
3174 | ||
3175 | @c ??? In next edition, merge this info Format Conversion. | |
3176 | ||
61ee3601 RS |
3177 | @node Lazy Properties |
3178 | @subsection Lazy Computation of Text Properties | |
3179 | ||
3180 | Instead of computing text properties for all the text in the buffer, | |
3181 | you can arrange to compute the text properties for parts of the text | |
3182 | when and if something depends on them. | |
3183 | ||
3184 | The primitive that extracts text from the buffer along with its | |
3185 | properties is @code{buffer-substring}. Before examining the properties, | |
3186 | this function runs the abnormal hook @code{buffer-access-fontify-functions}. | |
3187 | ||
3188 | @defvar buffer-access-fontify-functions | |
3189 | This variable holds a list of functions for computing text properties. | |
3190 | Before @code{buffer-substring} copies the text and text properties for a | |
3191 | portion of the buffer, it calls all the functions in this list. Each of | |
3192 | the functions receives two arguments that specify the range of the | |
3193 | buffer being accessed. (The buffer itself is always the current | |
3194 | buffer.) | |
3195 | @end defvar | |
3196 | ||
3197 | The function @code{buffer-substring-no-properties} does not call these | |
3198 | functions, since it ignores text properties anyway. | |
3199 | ||
3200 | In order to prevent the hook functions from being called more than | |
3201 | once for the same part of the buffer, you can use the variable | |
3202 | @code{buffer-access-fontified-property}. | |
3203 | ||
3204 | @defvar buffer-access-fontified-property | |
3205 | If this value's variable is non-@code{nil}, it is a symbol which is used | |
3206 | as a text property name. A non-@code{nil} value for that text property | |
3207 | means, ``the other text properties for this character have already been | |
3208 | computed.'' | |
3209 | ||
3210 | If all the characters in the range specified for @code{buffer-substring} | |
3211 | have a non-@code{nil} value for this property, @code{buffer-substring} | |
3212 | does not call the @code{buffer-access-fontify-functions} functions. It | |
3213 | assumes these characters already have the right text properties, and | |
3214 | just copies the properties they already have. | |
3215 | ||
3216 | The normal way to use this feature is that the | |
3217 | @code{buffer-access-fontify-functions} functions add this property, as | |
3218 | well as others, to the characters they operate on. That way, they avoid | |
3219 | being called over and over for the same text. | |
3220 | @end defvar | |
3221 | ||
f9f59935 RS |
3222 | @node Clickable Text |
3223 | @subsection Defining Clickable Text | |
3224 | @cindex clickable text | |
3225 | ||
3226 | There are two ways to set up @dfn{clickable text} in a buffer. | |
3227 | There are typically two parts of this: to make the text highlight | |
3228 | when the mouse is over it, and to make a mouse button do something | |
3229 | when you click it on that part of the text. | |
3230 | ||
3231 | Highlighting is done with the @code{mouse-face} text property. | |
3232 | Here is an example of how Dired does it: | |
3233 | ||
3234 | @smallexample | |
3235 | (condition-case nil | |
3236 | (if (dired-move-to-filename) | |
3237 | (put-text-property (point) | |
3238 | (save-excursion | |
3239 | (dired-move-to-end-of-filename) | |
3240 | (point)) | |
3241 | 'mouse-face 'highlight)) | |
3242 | (error nil)) | |
3243 | @end smallexample | |
3244 | ||
3245 | @noindent | |
3246 | The first two arguments to @code{put-text-property} specify the | |
3247 | beginning and end of the text. | |
3248 | ||
3249 | The usual way to make the mouse do something when you click it | |
3250 | on this text is to define @code{mouse-2} in the major mode's | |
3251 | keymap. The job of checking whether the click was on clickable text | |
3252 | is done by the command definition. Here is how Dired does it: | |
3253 | ||
3254 | @smallexample | |
3255 | (defun dired-mouse-find-file-other-window (event) | |
3256 | "In dired, visit the file or directory name you click on." | |
3257 | (interactive "e") | |
3258 | (let (file) | |
3259 | (save-excursion | |
3260 | (set-buffer (window-buffer (posn-window (event-end event)))) | |
3261 | (save-excursion | |
969fe9b5 RS |
3262 | (goto-char (posn-point (event-end event))) |
3263 | (setq file (dired-get-filename)))) | |
f9f59935 RS |
3264 | (select-window (posn-window (event-end event))) |
3265 | (find-file-other-window (file-name-sans-versions file t)))) | |
3266 | @end smallexample | |
3267 | ||
3268 | @noindent | |
3269 | The reason for the outer @code{save-excursion} construct is to avoid | |
3270 | changing the current buffer; the reason for the inner one is to avoid | |
3271 | permanently altering point in the buffer you click on. In this case, | |
3272 | Dired uses the function @code{dired-get-filename} to determine which | |
3273 | file to visit, based on the position found in the event. | |
3274 | ||
3275 | Instead of defining a mouse command for the major mode, you can define | |
c26a99e8 | 3276 | a key binding for the clickable text itself, using the @code{keymap} |
ce75fd23 | 3277 | text property: |
f9f59935 RS |
3278 | |
3279 | @example | |
3280 | (let ((map (make-sparse-keymap))) | |
c26a99e8 | 3281 | (define-key map [mouse-2] 'operate-this-button) |
f9f59935 RS |
3282 | (put-text-property (point) |
3283 | (save-excursion | |
3284 | (dired-move-to-end-of-filename) | |
3285 | (point)) | |
c26a99e8 | 3286 | 'keymap map)) |
f9f59935 RS |
3287 | @end example |
3288 | ||
3289 | @noindent | |
3290 | This method makes it possible to define different commands for various | |
3291 | clickable pieces of text. Also, the major mode definition (or the | |
3292 | global definition) remains available for the rest of the text in the | |
3293 | buffer. | |
3294 | ||
2468d0c0 DL |
3295 | @node Fields |
3296 | @subsection Defining and Using Fields | |
3297 | @cindex fields | |
3298 | ||
3299 | A field is a range of consecutive characters in the buffer that are | |
3300 | identified by having the same value (comparing with @code{eq}) of the | |
35627f72 MB |
3301 | @code{field} property (either a text-property or an overlay property). |
3302 | This section describes special functions that are available for | |
3303 | operating on fields. | |
2468d0c0 DL |
3304 | |
3305 | You specify a field with a buffer position, @var{pos}. We think of | |
3306 | each field as containing a range of buffer positions, so the position | |
3307 | you specify stands for the field containing that position. | |
3308 | ||
3309 | When the characters before and after @var{pos} are part of the same | |
3310 | field, there is no doubt which field contains @var{pos}: the one those | |
3311 | characters both belong to. When @var{pos} is at a boundary between | |
3312 | fields, which field it belongs to depends on the stickiness of the | |
3313 | @code{field} properties of the two surrounding characters (@pxref{Sticky | |
3314 | Properties}). The field whose property would be inherited by text | |
3315 | inserted at @var{pos} is the field that contains @var{pos}. | |
3316 | ||
3317 | There is an anomalous case where newly inserted text at @var{pos} | |
3318 | would not inherit the @code{field} property from either side. This | |
3319 | happens if the previous character's @code{field} property is not | |
3320 | rear-sticky, and the following character's @code{field} property is not | |
3321 | front-sticky. In this case, @var{pos} belongs to neither the preceding | |
3322 | field nor the following field; the field functions treat it as belonging | |
3323 | to an empty field whose beginning and end are both at @var{pos}. | |
3324 | ||
3325 | In all of these functions, if @var{pos} is omitted or @code{nil}, the | |
3326 | value of point is used by default. | |
3327 | ||
9c7fce05 | 3328 | @defun field-beginning &optional pos escape-from-edge limit |
2468d0c0 DL |
3329 | @tindex field-beginning |
3330 | This function returns the beginning of the field specified by @var{pos}. | |
3331 | ||
35627f72 MB |
3332 | If @var{pos} is at the beginning of its field, and |
3333 | @var{escape-from-edge} is non-@code{nil}, then the return value is | |
3334 | always the beginning of the preceding field that @emph{ends} at @var{pos}, | |
3335 | regardless of the stickiness of the @code{field} properties around | |
3336 | @var{pos}. | |
9c7fce05 MB |
3337 | |
3338 | If @var{limit} is non-@code{nil}, it is a buffer position; if the | |
3339 | beginning of the field is before @var{limit}, then @var{limit} will be | |
3340 | returned instead. | |
2468d0c0 DL |
3341 | @end defun |
3342 | ||
9c7fce05 | 3343 | @defun field-end &optional pos escape-from-edge limit |
2468d0c0 DL |
3344 | @tindex field-end |
3345 | This function returns the end of the field specified by @var{pos}. | |
3346 | ||
35627f72 MB |
3347 | If @var{pos} is at the end of its field, and @var{escape-from-edge} is |
3348 | non-@code{nil}, then the return value is always the end of the following | |
3349 | field that @emph{begins} at @var{pos}, regardless of the stickiness of | |
3350 | the @code{field} properties around @var{pos}. | |
9c7fce05 MB |
3351 | |
3352 | If @var{limit} is non-@code{nil}, it is a buffer position; if the end | |
3353 | of the field is after @var{limit}, then @var{limit} will be returned | |
3354 | instead. | |
2468d0c0 DL |
3355 | @end defun |
3356 | ||
3357 | @defun field-string &optional pos | |
3358 | @tindex field-string | |
3359 | This function returns the contents of the field specified by @var{pos}, | |
3360 | as a string. | |
3361 | @end defun | |
3362 | ||
3363 | @defun field-string-no-properties &optional pos | |
3364 | @tindex field-string-no-properties | |
3365 | This function returns the contents of the field specified by @var{pos}, | |
3366 | as a string, discarding text properties. | |
3367 | @end defun | |
3368 | ||
3369 | @defun delete-field &optional pos | |
3370 | @tindex delete-field | |
3371 | This function deletes the text of the field specified by @var{pos}. | |
3372 | @end defun | |
3373 | ||
35627f72 | 3374 | @defun constrain-to-field new-pos old-pos &optional escape-from-edge only-in-line inhibit-capture-property |
2468d0c0 DL |
3375 | @tindex constrain-to-field |
3376 | This function ``constrains'' @var{new-pos} to the field that | |
3377 | @var{old-pos} belongs to---in other words, it returns the position | |
3378 | closest to @var{new-pos} that is in the same field as @var{old-pos}. | |
3379 | ||
3380 | If @var{new-pos} is @code{nil}, then @code{constrain-to-field} uses | |
3381 | the value of point instead, and moves point to the resulting position. | |
3382 | ||
75708135 RS |
3383 | If @var{old-pos} is at the boundary of two fields, then the acceptable |
3384 | positions for @var{new-pos} depend on the value of the optional argument | |
3385 | @var{escape-from-edge}. If @var{escape-from-edge} is @code{nil}, then | |
3386 | @var{new-pos} is constrained to the field that has the same @code{field} | |
35627f72 MB |
3387 | property (either a text-property or an overlay property) that new |
3388 | characters inserted at @var{old-pos} would get. (This depends on the | |
3389 | stickiness of the @code{field} property for the characters before and | |
3390 | after @var{old-pos}.) If @var{escape-from-edge} is non-@code{nil}, | |
3391 | @var{new-pos} is constrained to the union of the two adjacent fields. | |
3392 | Additionally, if two fields are separated by another field with the | |
3393 | special value @code{boundary}, then any point within this special field | |
3394 | is also considered to be ``on the boundary.'' | |
2468d0c0 DL |
3395 | |
3396 | If the optional argument @var{only-in-line} is non-@code{nil}, and | |
3397 | constraining @var{new-pos} in the usual way would move it to a different | |
3398 | line, @var{new-pos} is returned unconstrained. This used in commands | |
3399 | that move by line, such as @code{next-line} and | |
3400 | @code{beginning-of-line}, so that they respect field boundaries only in | |
3401 | the case where they can still move to the right line. | |
35627f72 MB |
3402 | |
3403 | If the optional argument @var{inhibit-capture-property} is | |
3404 | non-@code{nil}, and @var{old-pos} has a non-@code{nil} property of that | |
3405 | name, then any field boundaries are ignored. | |
3406 | ||
3407 | You can cause @code{constrain-to-field} to ignore all field boundaries | |
3408 | (and so never constrain anything) by binding the variable | |
74eee906 | 3409 | @code{inhibit-field-text-motion} to a non-@code{nil} value. |
2468d0c0 DL |
3410 | @end defun |
3411 | ||
73804d4b RS |
3412 | @node Not Intervals |
3413 | @subsection Why Text Properties are not Intervals | |
3414 | @cindex intervals | |
3415 | ||
3416 | Some editors that support adding attributes to text in the buffer do | |
3417 | so by letting the user specify ``intervals'' within the text, and adding | |
3418 | the properties to the intervals. Those editors permit the user or the | |
3419 | programmer to determine where individual intervals start and end. We | |
3420 | deliberately provided a different sort of interface in Emacs Lisp to | |
3421 | avoid certain paradoxical behavior associated with text modification. | |
3422 | ||
3423 | If the actual subdivision into intervals is meaningful, that means you | |
3424 | can distinguish between a buffer that is just one interval with a | |
3425 | certain property, and a buffer containing the same text subdivided into | |
3426 | two intervals, both of which have that property. | |
3427 | ||
3428 | Suppose you take the buffer with just one interval and kill part of | |
3429 | the text. The text remaining in the buffer is one interval, and the | |
3430 | copy in the kill ring (and the undo list) becomes a separate interval. | |
3431 | Then if you yank back the killed text, you get two intervals with the | |
3432 | same properties. Thus, editing does not preserve the distinction | |
3433 | between one interval and two. | |
3434 | ||
3435 | Suppose we ``fix'' this problem by coalescing the two intervals when | |
3436 | the text is inserted. That works fine if the buffer originally was a | |
3437 | single interval. But suppose instead that we have two adjacent | |
3438 | intervals with the same properties, and we kill the text of one interval | |
3439 | and yank it back. The same interval-coalescence feature that rescues | |
3440 | the other case causes trouble in this one: after yanking, we have just | |
3441 | one interval. One again, editing does not preserve the distinction | |
3442 | between one interval and two. | |
3443 | ||
3444 | Insertion of text at the border between intervals also raises | |
3445 | questions that have no satisfactory answer. | |
3446 | ||
3447 | However, it is easy to arrange for editing to behave consistently for | |
3448 | questions of the form, ``What are the properties of this character?'' | |
3449 | So we have decided these are the only questions that make sense; we have | |
3450 | not implemented asking questions about where intervals start or end. | |
3451 | ||
f9f59935 | 3452 | In practice, you can usually use the text property search functions in |
73804d4b RS |
3453 | place of explicit interval boundaries. You can think of them as finding |
3454 | the boundaries of intervals, assuming that intervals are always | |
3455 | coalesced whenever possible. @xref{Property Search}. | |
3456 | ||
3457 | Emacs also provides explicit intervals as a presentation feature; see | |
3458 | @ref{Overlays}. | |
3459 | ||
3460 | @node Substitution | |
3461 | @section Substituting for a Character Code | |
3462 | ||
3463 | The following functions replace characters within a specified region | |
3464 | based on their character codes. | |
3465 | ||
3466 | @defun subst-char-in-region start end old-char new-char &optional noundo | |
3467 | @cindex replace characters | |
3468 | This function replaces all occurrences of the character @var{old-char} | |
3469 | with the character @var{new-char} in the region of the current buffer | |
3470 | defined by @var{start} and @var{end}. | |
3471 | ||
73804d4b | 3472 | @cindex undo avoidance |
bfe721d1 KH |
3473 | If @var{noundo} is non-@code{nil}, then @code{subst-char-in-region} does |
3474 | not record the change for undo and does not mark the buffer as modified. | |
2468d0c0 DL |
3475 | This was useful for controlling the old selective display feature |
3476 | (@pxref{Selective Display}). | |
73804d4b RS |
3477 | |
3478 | @code{subst-char-in-region} does not move point and returns | |
3479 | @code{nil}. | |
3480 | ||
3481 | @example | |
3482 | @group | |
3483 | ---------- Buffer: foo ---------- | |
3484 | This is the contents of the buffer before. | |
3485 | ---------- Buffer: foo ---------- | |
3486 | @end group | |
3487 | ||
3488 | @group | |
3489 | (subst-char-in-region 1 20 ?i ?X) | |
3490 | @result{} nil | |
3491 | ||
3492 | ---------- Buffer: foo ---------- | |
3493 | ThXs Xs the contents of the buffer before. | |
3494 | ---------- Buffer: foo ---------- | |
3495 | @end group | |
3496 | @end example | |
3497 | @end defun | |
3498 | ||
3499 | @defun translate-region start end table | |
3500 | This function applies a translation table to the characters in the | |
3501 | buffer between positions @var{start} and @var{end}. | |
3502 | ||
3503 | The translation table @var{table} is a string; @code{(aref @var{table} | |
3504 | @var{ochar})} gives the translated character corresponding to | |
3505 | @var{ochar}. If the length of @var{table} is less than 256, any | |
3506 | characters with codes larger than the length of @var{table} are not | |
3507 | altered by the translation. | |
3508 | ||
3509 | The return value of @code{translate-region} is the number of | |
61cfa852 RS |
3510 | characters that were actually changed by the translation. This does |
3511 | not count characters that were mapped into themselves in the | |
73804d4b | 3512 | translation table. |
73804d4b RS |
3513 | @end defun |
3514 | ||
3515 | @node Registers | |
3516 | @section Registers | |
3517 | @cindex registers | |
3518 | ||
3519 | A register is a sort of variable used in Emacs editing that can hold a | |
969fe9b5 | 3520 | variety of different kinds of values. Each register is named by a |
75708135 RS |
3521 | single character. All @sc{ascii} characters and their meta variants |
3522 | (but with the exception of @kbd{C-g}) can be used to name registers. | |
3523 | Thus, there are 255 possible registers. A register is designated in | |
3524 | Emacs Lisp by the character that is its name. | |
73804d4b RS |
3525 | |
3526 | @defvar register-alist | |
3527 | This variable is an alist of elements of the form @code{(@var{name} . | |
3528 | @var{contents})}. Normally, there is one element for each Emacs | |
3529 | register that has been used. | |
3530 | ||
3531 | The object @var{name} is a character (an integer) identifying the | |
969fe9b5 | 3532 | register. |
73804d4b RS |
3533 | @end defvar |
3534 | ||
969fe9b5 RS |
3535 | The @var{contents} of a register can have several possible types: |
3536 | ||
3537 | @table @asis | |
3538 | @item a number | |
3539 | A number stands for itself. If @code{insert-register} finds a number | |
3540 | in the register, it converts the number to decimal. | |
3541 | ||
3542 | @item a marker | |
3543 | A marker represents a buffer position to jump to. | |
3544 | ||
3545 | @item a string | |
3546 | A string is text saved in the register. | |
3547 | ||
3548 | @item a rectangle | |
3549 | A rectangle is represented by a list of strings. | |
3550 | ||
3551 | @item @code{(@var{window-configuration} @var{position})} | |
3552 | This represents a window configuration to restore in one frame, and a | |
3553 | position to jump to in the current buffer. | |
3554 | ||
3555 | @item @code{(@var{frame-configuration} @var{position})} | |
3556 | This represents a frame configuration to restore, and a position | |
3557 | to jump to in the current buffer. | |
3558 | ||
3559 | @item (file @var{filename}) | |
3560 | This represents a file to visit; jumping to this value visits file | |
3561 | @var{filename}. | |
3562 | ||
3563 | @item (file-query @var{filename} @var{position}) | |
3564 | This represents a file to visit and a position in it; jumping to this | |
3565 | value visits file @var{filename} and goes to buffer position | |
3566 | @var{position}. Restoring this type of position asks the user for | |
3567 | confirmation first. | |
3568 | @end table | |
3569 | ||
3570 | The functions in this section return unpredictable values unless | |
3571 | otherwise stated. | |
3572 | ||
73804d4b RS |
3573 | @defun get-register reg |
3574 | This function returns the contents of the register | |
3575 | @var{reg}, or @code{nil} if it has no contents. | |
3576 | @end defun | |
3577 | ||
3578 | @defun set-register reg value | |
3579 | This function sets the contents of register @var{reg} to @var{value}. | |
3580 | A register can be set to any value, but the other register functions | |
3581 | expect only certain data types. The return value is @var{value}. | |
3582 | @end defun | |
3583 | ||
3584 | @deffn Command view-register reg | |
3585 | This command displays what is contained in register @var{reg}. | |
3586 | @end deffn | |
3587 | ||
3588 | @ignore | |
3589 | @deffn Command point-to-register reg | |
3590 | This command stores both the current location of point and the current | |
3591 | buffer in register @var{reg} as a marker. | |
3592 | @end deffn | |
3593 | ||
3594 | @deffn Command jump-to-register reg | |
3595 | @deffnx Command register-to-point reg | |
3596 | @comment !!SourceFile register.el | |
3597 | This command restores the status recorded in register @var{reg}. | |
3598 | ||
3599 | If @var{reg} contains a marker, it moves point to the position stored in | |
3600 | the marker. Since both the buffer and the location within the buffer | |
3601 | are stored by the @code{point-to-register} function, this command can | |
3602 | switch you to another buffer. | |
3603 | ||
3604 | If @var{reg} contains a window configuration or a frame configuration. | |
3605 | @code{jump-to-register} restores that configuration. | |
3606 | @end deffn | |
3607 | @end ignore | |
3608 | ||
3609 | @deffn Command insert-register reg &optional beforep | |
3610 | This command inserts contents of register @var{reg} into the current | |
3611 | buffer. | |
3612 | ||
3613 | Normally, this command puts point before the inserted text, and the | |
3614 | mark after it. However, if the optional second argument @var{beforep} | |
3615 | is non-@code{nil}, it puts the mark before and point after. | |
3616 | You can pass a non-@code{nil} second argument @var{beforep} to this | |
3617 | function interactively by supplying any prefix argument. | |
3618 | ||
3619 | If the register contains a rectangle, then the rectangle is inserted | |
3620 | with its upper left corner at point. This means that text is inserted | |
3621 | in the current line and underneath it on successive lines. | |
3622 | ||
3623 | If the register contains something other than saved text (a string) or | |
3624 | a rectangle (a list), currently useless things happen. This may be | |
3625 | changed in the future. | |
3626 | @end deffn | |
3627 | ||
3628 | @ignore | |
3629 | @deffn Command copy-to-register reg start end &optional delete-flag | |
3630 | This command copies the region from @var{start} to @var{end} into | |
3631 | register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes | |
3632 | the region from the buffer after copying it into the register. | |
3633 | @end deffn | |
3634 | ||
3635 | @deffn Command prepend-to-register reg start end &optional delete-flag | |
3636 | This command prepends the region from @var{start} to @var{end} into | |
3637 | register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes | |
3638 | the region from the buffer after copying it to the register. | |
3639 | @end deffn | |
3640 | ||
3641 | @deffn Command append-to-register reg start end &optional delete-flag | |
3642 | This command appends the region from @var{start} to @var{end} to the | |
3643 | text already in register @var{reg}. If @var{delete-flag} is | |
3644 | non-@code{nil}, it deletes the region from the buffer after copying it | |
3645 | to the register. | |
3646 | @end deffn | |
3647 | ||
3648 | @deffn Command copy-rectangle-to-register reg start end &optional delete-flag | |
3649 | This command copies a rectangular region from @var{start} to @var{end} | |
3650 | into register @var{reg}. If @var{delete-flag} is non-@code{nil}, it | |
3651 | deletes the region from the buffer after copying it to the register. | |
3652 | @end deffn | |
3653 | ||
3654 | @deffn Command window-configuration-to-register reg | |
3655 | This function stores the window configuration of the selected frame in | |
3656 | register @var{reg}. | |
3657 | @end deffn | |
3658 | ||
3659 | @deffn Command frame-configuration-to-register reg | |
3660 | This function stores the current frame configuration in register | |
3661 | @var{reg}. | |
3662 | @end deffn | |
3663 | @end ignore | |
3664 | ||
b22f3a19 RS |
3665 | @node Transposition |
3666 | @section Transposition of Text | |
3667 | ||
3668 | This subroutine is used by the transposition commands. | |
3669 | ||
3670 | @defun transpose-regions start1 end1 start2 end2 &optional leave-markers | |
3671 | This function exchanges two nonoverlapping portions of the buffer. | |
3672 | Arguments @var{start1} and @var{end1} specify the bounds of one portion | |
3673 | and arguments @var{start2} and @var{end2} specify the bounds of the | |
3674 | other portion. | |
3675 | ||
3676 | Normally, @code{transpose-regions} relocates markers with the transposed | |
3677 | text; a marker previously positioned within one of the two transposed | |
3678 | portions moves along with that portion, thus remaining between the same | |
3679 | two characters in their new position. However, if @var{leave-markers} | |
3680 | is non-@code{nil}, @code{transpose-regions} does not do this---it leaves | |
3681 | all markers unrelocated. | |
3682 | @end defun | |
3683 | ||
b6954afd RS |
3684 | @node Base 64 |
3685 | @section Base 64 Encoding | |
3686 | @cindex base 64 encoding | |
3687 | ||
ae9b6b4a RS |
3688 | Base 64 code is used in email to encode a sequence of 8-bit bytes as |
3689 | a longer sequence of @sc{ascii} graphic characters. It is defined in | |
944351c0 EZ |
3690 | Internet RFC@footnote{ |
3691 | An RFC, an acronym for @dfn{Request for Comments}, is a numbered | |
3692 | Internet informational document describing a standard. RFCs are | |
3693 | usually written by technical experts acting on their own initiative, | |
3694 | and are traditionally written in a pragmatic, experience-driven | |
3695 | manner. | |
3696 | }2045. This section describes the functions for | |
ae9b6b4a | 3697 | converting to and from this code. |
b6954afd RS |
3698 | |
3699 | @defun base64-encode-region beg end &optional no-line-break | |
3700 | @tindex base64-encode-region | |
b25e2fb5 DL |
3701 | This function converts the region from @var{beg} to @var{end} into base |
3702 | 64 code. It returns the length of the encoded text. An error is | |
3703 | signaled if a character in the region is multibyte, i.e.@: in a | |
3704 | multibyte buffer the region must contain only characters from the | |
3705 | charsets @code{ascii}, @code{eight-bit-control} and | |
3706 | @code{eight-bit-graphic}. | |
b6954afd RS |
3707 | |
3708 | Normally, this function inserts newline characters into the encoded | |
3709 | text, to avoid overlong lines. However, if the optional argument | |
3710 | @var{no-line-break} is non-@code{nil}, these newlines are not added, so | |
3711 | the output is just one long line. | |
3712 | @end defun | |
3713 | ||
3714 | @defun base64-encode-string string &optional no-line-break | |
3715 | @tindex base64-encode-string | |
3716 | This function converts the string @var{string} into base 64 code. It | |
b25e2fb5 DL |
3717 | returns a string containing the encoded text. As for |
3718 | @code{base64-encode-region}, an error is signaled if a character in the | |
3719 | string is multibyte. | |
b6954afd RS |
3720 | |
3721 | Normally, this function inserts newline characters into the encoded | |
3722 | text, to avoid overlong lines. However, if the optional argument | |
3723 | @var{no-line-break} is non-@code{nil}, these newlines are not added, so | |
3724 | the result string is just one long line. | |
3725 | @end defun | |
3726 | ||
3727 | @defun base64-decode-region beg end | |
3728 | @tindex base64-decode-region | |
3729 | This function converts the region from @var{beg} to @var{end} from base | |
3730 | 64 code into the corresponding decoded text. It returns the length of | |
3731 | the decoded text. | |
3732 | ||
3733 | The decoding functions ignore newline characters in the encoded text. | |
3734 | @end defun | |
3735 | ||
3736 | @defun base64-decode-string string | |
3737 | @tindex base64-decode-string | |
3738 | This function converts the string @var{string} from base 64 code into | |
54f7f2a4 | 3739 | the corresponding decoded text. It returns a unibyte string containing the |
b6954afd RS |
3740 | decoded text. |
3741 | ||
3742 | The decoding functions ignore newline characters in the encoded text. | |
3743 | @end defun | |
3744 | ||
944351c0 EZ |
3745 | @node MD5 Checksum |
3746 | @section MD5 Checksum | |
3747 | @cindex MD5 checksum | |
3748 | @cindex message digest computation | |
3749 | ||
3750 | MD5 cryptographic checksums, or @dfn{message digests}, are 128-bit | |
3751 | ``fingerprints'' of a document or program. They are used to verify | |
3752 | that you have an exact and unaltered copy of the data. The algorithm | |
3753 | to calculate the MD5 message digest is defined in Internet | |
3754 | RFC@footnote{ | |
3755 | For an explanation of what is an RFC, see the footnote in @ref{Base | |
3756 | 64}. | |
3757 | }1321. This section describes the Emacs facilities for computing | |
3758 | message digests. | |
3759 | ||
3760 | @defun md5 object &optional start end coding-system noerror | |
3761 | This function returns the MD5 message digest of @var{object}, which | |
3762 | should be a buffer or a string. | |
3763 | ||
3764 | The two optional arguments @var{start} and @var{end} are character | |
3765 | positions specifying the portion of @var{object} to compute the | |
3766 | message digest for. If they are @code{nil} or omitted, the digest is | |
3767 | computed for the whole of @var{object}. | |
3768 | ||
3769 | The function @code{md5} does not compute the message digest directly | |
3770 | from the internal Emacs representation of the text (@pxref{Text | |
3771 | Representations}). Instead, it encodes the text using a coding | |
3772 | system, and computes the message digest from the encoded text. The | |
3773 | optional fourth argument @var{coding-system} specifies which coding | |
3774 | system to use for encoding the text. It should be the same coding | |
3775 | system that you used to read the text, or that you used or will use | |
3776 | when saving or sending the text. @xref{Coding Systems}, for more | |
3777 | information about coding systems. | |
3778 | ||
3779 | If @var{coding-system} is @code{nil} or omitted, the default depends | |
3780 | on @var{object}. If @var{object} is a buffer, the default for | |
3781 | @var{coding-system} is whatever coding system would be chosen by | |
3782 | default for writing this text into a file. If @var{object} is a | |
3783 | string, the user's most preferred coding system (@pxref{Recognize | |
3784 | Coding, prefer-coding-system, the description of | |
3785 | @code{prefer-coding-system}, emacs, GNU Emacs Manual}) is used. | |
3786 | ||
3787 | Normally, @code{md5} signals an error if the text can't be encoded | |
3788 | using the specified or chosen coding system. However, if | |
3789 | @var{noerror} is non-@code{nil}, it silently uses @code{raw-text} | |
3790 | coding instead. | |
3791 | @end defun | |
3792 | ||
d73eac4d RS |
3793 | @node Atomic Changes |
3794 | @section Atomic Change Groups | |
3795 | @cindex atomic changes | |
3796 | ||
3797 | In data base terminology, an @dfn{atomic} change is an indivisible | |
3798 | change---it can succeed entirely or it can fail entirely, but it | |
3799 | cannot partly succeed. A Lisp program can make a series of changes to | |
3800 | one or several buffers as an @dfn{atomic change group}, meaning that | |
3801 | either the entire series of changes will be installed in their buffers | |
3802 | or, in case of an error, none of them will be. | |
3803 | ||
3804 | To do this for one buffer, the one already current, simply write a | |
3805 | call to @code{atomic-change-group} around the code that makes the | |
3806 | changes, like this: | |
3807 | ||
3808 | @example | |
3809 | (atomic-change-group | |
3810 | (insert foo) | |
3811 | (delete-region x y)) | |
3812 | @end example | |
3813 | ||
3814 | @noindent | |
3815 | If an error (or other nonlocal exit) occurs inside the body of | |
3816 | @code{atomic-change-group}, it unmakes all the changes in that buffer | |
3817 | that were during the execution of the body. This kind of change group | |
3818 | has no effect on any other buffers--any such changes remain. | |
3819 | ||
3820 | If you need something more sophisticated, such as to make changes in | |
3821 | various buffers constitute one atomic group, you must directly call | |
3822 | lower-level functions that @code{atomic-change-group} uses. | |
3823 | ||
3824 | @defun prepare-change-group &optional buffer | |
3825 | This function sets up a change group for buffer @var{buffer}, which | |
3826 | defaults to the current buffer. It returns a ``handle'' that | |
3827 | represents the change group. You must use this handle to activate the | |
3828 | change group and subsequently to finish it. | |
3829 | @end defun | |
3830 | ||
3831 | To use the change group, you must @dfn{activate} it. You must do | |
3832 | this before making any changes in the text of @var{buffer}. | |
3833 | ||
3834 | @defun activate-change-group handle | |
3835 | This function activates the change group that @var{handle} designates. | |
3836 | @end defun | |
3837 | ||
3838 | After you activate the change group, any changes you make in that | |
3839 | buffer become part of it. Once you have made all the desired changes | |
3840 | in the buffer, you must @dfn{finish} the change group. There are two | |
3841 | ways to do this: you can either accept (and finalize) all the changes, | |
3842 | or cancel them all. | |
3843 | ||
3844 | @defun accept-change-group handle | |
3845 | This function accepts all the changes in the change group specified by | |
3846 | @var{handle}, making them final. | |
3847 | @end defun | |
3848 | ||
3849 | @defun cancel-change-group handle | |
3850 | This function cancels and undoes all the changes in the change group | |
3851 | specified by @var{handle}. | |
3852 | @end defun | |
3853 | ||
3854 | Your code should use @code{unwind-protect} to make sure the group is | |
3855 | always finished. The call to @code{activate-change-group} should be | |
3856 | inside the @code{unwind-protect}, in case the user types @kbd{C-g} | |
3857 | just after it runs. (This is one reason why | |
3858 | @code{prepare-change-group} and @code{activate-change-group} are | |
3859 | separate functions, because normally you would call | |
3860 | @code{prepare-change-group} before the start of that | |
3861 | @code{unwind-protect}.) Once you finish the group, don't use the | |
3862 | handle again---in particular, don't try to finish the same group | |
3863 | twice. | |
3864 | ||
3865 | To make a multibuffer change group, call @code{prepare-change-group} | |
3866 | once for each buffer you want to cover, then use @code{nconc} to | |
3867 | combine the returned values, like this: | |
3868 | ||
3869 | @example | |
3870 | (nconc (prepare-change-group buffer-1) | |
3871 | (prepare-change-group buffer-2)) | |
3872 | @end example | |
3873 | ||
3874 | You can then activate the multibuffer change group with a single call | |
3875 | to @code{activate-change-group}, and finish it with a single call to | |
3876 | @code{accept-change-group} or @code{cancel-change-group}. | |
3877 | ||
3878 | Nested use of several change groups for the same buffer works as you | |
3879 | would expect. Non-nested use of change groups for the same buffer | |
3880 | will get Emacs confused, so don't let it happen; the first change | |
3881 | group you start for any given buffer should be the last one finished. | |
3882 | ||
73804d4b RS |
3883 | @node Change Hooks |
3884 | @section Change Hooks | |
3885 | @cindex change hooks | |
3886 | @cindex hooks for text changes | |
3887 | ||
3888 | These hook variables let you arrange to take notice of all changes in | |
3889 | all buffers (or in a particular buffer, if you make them buffer-local). | |
3890 | See also @ref{Special Properties}, for how to detect changes to specific | |
3891 | parts of the text. | |
3892 | ||
3893 | The functions you use in these hooks should save and restore the match | |
3894 | data if they do anything that uses regular expressions; otherwise, they | |
3895 | will interfere in bizarre ways with the editing operations that call | |
3896 | them. | |
3897 | ||
72654a3c | 3898 | @defvar before-change-functions |
f9f59935 | 3899 | This variable holds a list of functions to call before any buffer |
72654a3c RS |
3900 | modification. Each function gets two arguments, the beginning and end |
3901 | of the region that is about to change, represented as integers. The | |
3902 | buffer that is about to change is always the current buffer. | |
3903 | @end defvar | |
3904 | ||
3905 | @defvar after-change-functions | |
f9f59935 | 3906 | This variable holds a list of functions to call after any buffer |
72654a3c RS |
3907 | modification. Each function receives three arguments: the beginning and |
3908 | end of the region just changed, and the length of the text that existed | |
584b8104 RS |
3909 | before the change. All three arguments are integers. The buffer that's |
3910 | about to change is always the current buffer. | |
3911 | ||
1911e6e5 | 3912 | The length of the old text is the difference between the buffer positions |
a9f0a989 RS |
3913 | before and after that text as it was before the change. As for the |
3914 | changed text, its length is simply the difference between the first two | |
3915 | arguments. | |
72654a3c RS |
3916 | @end defvar |
3917 | ||
74eee906 RS |
3918 | Output of messges into the @samp{*Messages*} buffer does not |
3919 | call these functions. | |
3920 | ||
f9f59935 RS |
3921 | @defmac combine-after-change-calls body... |
3922 | The macro executes @var{body} normally, but arranges to call the | |
3923 | after-change functions just once for a series of several changes---if | |
3924 | that seems safe. | |
3925 | ||
3926 | If a program makes several text changes in the same area of the buffer, | |
3927 | using the macro @code{combine-after-change-calls} around that part of | |
3928 | the program can make it run considerably faster when after-change hooks | |
969fe9b5 RS |
3929 | are in use. When the after-change hooks are ultimately called, the |
3930 | arguments specify a portion of the buffer including all of the changes | |
3931 | made within the @code{combine-after-change-calls} body. | |
f9f59935 RS |
3932 | |
3933 | @strong{Warning:} You must not alter the values of | |
b6dd5963 | 3934 | @code{after-change-functions} within |
f9f59935 | 3935 | the body of a @code{combine-after-change-calls} form. |
969fe9b5 RS |
3936 | |
3937 | @strong{Note:} If the changes you combine occur in widely scattered | |
3938 | parts of the buffer, this will still work, but it is not advisable, | |
3939 | because it may lead to inefficient behavior for some change hook | |
3940 | functions. | |
f9f59935 RS |
3941 | @end defmac |
3942 | ||
b6dd5963 | 3943 | The two variables above are temporarily bound to @code{nil} during the |
72654a3c | 3944 | time that any of these functions is running. This means that if one of |
73804d4b | 3945 | these functions changes the buffer, that change won't run these |
72654a3c RS |
3946 | functions. If you do want a hook function to make changes that run |
3947 | these functions, make it bind these variables back to their usual | |
73804d4b RS |
3948 | values. |
3949 | ||
b22f3a19 RS |
3950 | One inconvenient result of this protective feature is that you cannot |
3951 | have a function in @code{after-change-functions} or | |
3952 | @code{before-change-functions} which changes the value of that variable. | |
3953 | But that's not a real limitation. If you want those functions to change | |
3954 | the list of functions to run, simply add one fixed function to the hook, | |
3955 | and code that function to look in another variable for other functions | |
3956 | to call. Here is an example: | |
3957 | ||
3958 | @example | |
3959 | (setq my-own-after-change-functions nil) | |
3960 | (defun indirect-after-change-function (beg end len) | |
3961 | (let ((list my-own-after-change-functions)) | |
3962 | (while list | |
3963 | (funcall (car list) beg end len) | |
3964 | (setq list (cdr list))))) | |
969fe9b5 RS |
3965 | |
3966 | @group | |
b22f3a19 RS |
3967 | (add-hooks 'after-change-functions |
3968 | 'indirect-after-change-function) | |
969fe9b5 | 3969 | @end group |
b22f3a19 RS |
3970 | @end example |
3971 | ||
73804d4b RS |
3972 | @defvar first-change-hook |
3973 | This variable is a normal hook that is run whenever a buffer is changed | |
3974 | that was previously in the unmodified state. | |
3975 | @end defvar | |
8241495d RS |
3976 | |
3977 | @defvar inhibit-modification-hooks | |
3978 | @tindex inhibit-modification-hooks | |
3979 | If this variable is non-@code{nil}, all of the change hooks are | |
3980 | disabled; none of them run. This affects all the hook variables | |
3981 | described above in this section, as well as the hooks attached to | |
3982 | certain special text properties (@pxref{Special Properties}) and overlay | |
3983 | properties (@pxref{Overlay Properties}). | |
3984 | ||
3985 | This variable is available starting in Emacs 21. | |
3986 | @end defvar |