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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001, | |
d24880de GM |
4 | @c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 |
5 | @c Free Software Foundation, Inc. | |
b8d4c8d0 | 6 | @c See the file elisp.texi for copying conditions. |
6336d8c3 | 7 | @setfilename ../../info/text |
b8d4c8d0 GM |
8 | @node Text, Non-ASCII Characters, Markers, Top |
9 | @chapter Text | |
10 | @cindex text | |
11 | ||
12 | This chapter describes the functions that deal with the text in a | |
13 | buffer. Most examine, insert, or delete text in the current buffer, | |
14 | often operating at point or on text adjacent to point. Many are | |
15 | interactive. All the functions that change the text provide for undoing | |
16 | the changes (@pxref{Undo}). | |
17 | ||
18 | Many text-related functions operate on a region of text defined by two | |
19 | buffer positions passed in arguments named @var{start} and @var{end}. | |
20 | These arguments should be either markers (@pxref{Markers}) or numeric | |
21 | character positions (@pxref{Positions}). The order of these arguments | |
22 | does not matter; it is all right for @var{start} to be the end of the | |
23 | region and @var{end} the beginning. For example, @code{(delete-region 1 | |
24 | 10)} and @code{(delete-region 10 1)} are equivalent. An | |
25 | @code{args-out-of-range} error is signaled if either @var{start} or | |
26 | @var{end} is outside the accessible portion of the buffer. In an | |
27 | interactive call, point and the mark are used for these arguments. | |
28 | ||
29 | @cindex buffer contents | |
30 | Throughout this chapter, ``text'' refers to the characters in the | |
31 | buffer, together with their properties (when relevant). Keep in mind | |
32 | that point is always between two characters, and the cursor appears on | |
33 | the character after point. | |
34 | ||
35 | @menu | |
36 | * Near Point:: Examining text in the vicinity of point. | |
37 | * Buffer Contents:: Examining text in a general fashion. | |
38 | * Comparing Text:: Comparing substrings of buffers. | |
39 | * Insertion:: Adding new text to a buffer. | |
40 | * Commands for Insertion:: User-level commands to insert text. | |
41 | * Deletion:: Removing text from a buffer. | |
42 | * User-Level Deletion:: User-level commands to delete text. | |
43 | * The Kill Ring:: Where removed text sometimes is saved for later use. | |
44 | * Undo:: Undoing changes to the text of a buffer. | |
45 | * Maintaining Undo:: How to enable and disable undo information. | |
d24880de | 46 | How to control how much information is kept. |
b8d4c8d0 GM |
47 | * Filling:: Functions for explicit filling. |
48 | * Margins:: How to specify margins for filling commands. | |
49 | * Adaptive Fill:: Adaptive Fill mode chooses a fill prefix from context. | |
50 | * Auto Filling:: How auto-fill mode is implemented to break lines. | |
51 | * Sorting:: Functions for sorting parts of the buffer. | |
52 | * Columns:: Computing horizontal positions, and using them. | |
53 | * Indentation:: Functions to insert or adjust indentation. | |
54 | * Case Changes:: Case conversion of parts of the buffer. | |
55 | * Text Properties:: Assigning Lisp property lists to text characters. | |
56 | * Substitution:: Replacing a given character wherever it appears. | |
57 | * Transposition:: Swapping two portions of a buffer. | |
58 | * Registers:: How registers are implemented. Accessing the text or | |
59 | position stored in a register. | |
60 | * Base 64:: Conversion to or from base 64 encoding. | |
61 | * MD5 Checksum:: Compute the MD5 "message digest"/"checksum". | |
381408e2 | 62 | * Parsing HTML:: Parsing HTML and XML. |
b8d4c8d0 GM |
63 | * Atomic Changes:: Installing several buffer changes "atomically". |
64 | * Change Hooks:: Supplying functions to be run when text is changed. | |
65 | @end menu | |
66 | ||
67 | @node Near Point | |
68 | @section Examining Text Near Point | |
69 | @cindex text near point | |
70 | ||
71 | Many functions are provided to look at the characters around point. | |
72 | Several simple functions are described here. See also @code{looking-at} | |
73 | in @ref{Regexp Search}. | |
74 | ||
75 | In the following four functions, ``beginning'' or ``end'' of buffer | |
76 | refers to the beginning or end of the accessible portion. | |
77 | ||
78 | @defun char-after &optional position | |
79 | This function returns the character in the current buffer at (i.e., | |
80 | immediately after) position @var{position}. If @var{position} is out of | |
81 | range for this purpose, either before the beginning of the buffer, or at | |
82 | or beyond the end, then the value is @code{nil}. The default for | |
83 | @var{position} is point. | |
84 | ||
85 | In the following example, assume that the first character in the | |
86 | buffer is @samp{@@}: | |
87 | ||
88 | @example | |
89 | @group | |
90 | (char-to-string (char-after 1)) | |
91 | @result{} "@@" | |
92 | @end group | |
93 | @end example | |
94 | @end defun | |
95 | ||
96 | @defun char-before &optional position | |
97 | This function returns the character in the current buffer immediately | |
98 | before position @var{position}. If @var{position} is out of range for | |
99 | this purpose, either at or before the beginning of the buffer, or beyond | |
100 | the end, then the value is @code{nil}. The default for | |
101 | @var{position} is point. | |
102 | @end defun | |
103 | ||
104 | @defun following-char | |
105 | This function returns the character following point in the current | |
106 | buffer. This is similar to @code{(char-after (point))}. However, if | |
107 | point is at the end of the buffer, then @code{following-char} returns 0. | |
108 | ||
109 | Remember that point is always between characters, and the cursor | |
110 | normally appears over the character following point. Therefore, the | |
111 | character returned by @code{following-char} is the character the | |
112 | cursor is over. | |
113 | ||
114 | In this example, point is between the @samp{a} and the @samp{c}. | |
115 | ||
116 | @example | |
117 | @group | |
118 | ---------- Buffer: foo ---------- | |
119 | Gentlemen may cry ``Pea@point{}ce! Peace!,'' | |
120 | but there is no peace. | |
121 | ---------- Buffer: foo ---------- | |
122 | @end group | |
123 | ||
124 | @group | |
125 | (char-to-string (preceding-char)) | |
126 | @result{} "a" | |
127 | (char-to-string (following-char)) | |
128 | @result{} "c" | |
129 | @end group | |
130 | @end example | |
131 | @end defun | |
132 | ||
133 | @defun preceding-char | |
134 | This function returns the character preceding point in the current | |
135 | buffer. See above, under @code{following-char}, for an example. If | |
136 | point is at the beginning of the buffer, @code{preceding-char} returns | |
137 | 0. | |
138 | @end defun | |
139 | ||
140 | @defun bobp | |
141 | This function returns @code{t} if point is at the beginning of the | |
142 | buffer. If narrowing is in effect, this means the beginning of the | |
143 | accessible portion of the text. See also @code{point-min} in | |
144 | @ref{Point}. | |
145 | @end defun | |
146 | ||
147 | @defun eobp | |
148 | This function returns @code{t} if point is at the end of the buffer. | |
149 | If narrowing is in effect, this means the end of accessible portion of | |
150 | the text. See also @code{point-max} in @xref{Point}. | |
151 | @end defun | |
152 | ||
153 | @defun bolp | |
154 | This function returns @code{t} if point is at the beginning of a line. | |
155 | @xref{Text Lines}. The beginning of the buffer (or of its accessible | |
156 | portion) always counts as the beginning of a line. | |
157 | @end defun | |
158 | ||
159 | @defun eolp | |
160 | This function returns @code{t} if point is at the end of a line. The | |
161 | end of the buffer (or of its accessible portion) is always considered | |
162 | the end of a line. | |
163 | @end defun | |
164 | ||
165 | @node Buffer Contents | |
166 | @section Examining Buffer Contents | |
167 | ||
168 | This section describes functions that allow a Lisp program to | |
169 | convert any portion of the text in the buffer into a string. | |
170 | ||
171 | @defun buffer-substring start end | |
172 | This function returns a string containing a copy of the text of the | |
173 | region defined by positions @var{start} and @var{end} in the current | |
174 | buffer. If the arguments are not positions in the accessible portion of | |
175 | the buffer, @code{buffer-substring} signals an @code{args-out-of-range} | |
176 | error. | |
177 | ||
178 | It is not necessary for @var{start} to be less than @var{end}; the | |
179 | arguments can be given in either order. But most often the smaller | |
180 | argument is written first. | |
181 | ||
182 | Here's an example which assumes Font-Lock mode is not enabled: | |
183 | ||
184 | @example | |
185 | @group | |
186 | ---------- Buffer: foo ---------- | |
187 | This is the contents of buffer foo | |
188 | ||
189 | ---------- Buffer: foo ---------- | |
190 | @end group | |
191 | ||
192 | @group | |
193 | (buffer-substring 1 10) | |
194 | @result{} "This is t" | |
195 | @end group | |
196 | @group | |
197 | (buffer-substring (point-max) 10) | |
198 | @result{} "he contents of buffer foo\n" | |
199 | @end group | |
200 | @end example | |
201 | ||
202 | If the text being copied has any text properties, these are copied into | |
203 | the string along with the characters they belong to. @xref{Text | |
204 | Properties}. However, overlays (@pxref{Overlays}) in the buffer and | |
205 | their properties are ignored, not copied. | |
206 | ||
207 | For example, if Font-Lock mode is enabled, you might get results like | |
208 | these: | |
209 | ||
210 | @example | |
211 | @group | |
212 | (buffer-substring 1 10) | |
213 | @result{} #("This is t" 0 1 (fontified t) 1 9 (fontified t)) | |
214 | @end group | |
215 | @end example | |
216 | @end defun | |
217 | ||
218 | @defun buffer-substring-no-properties start end | |
219 | This is like @code{buffer-substring}, except that it does not copy text | |
220 | properties, just the characters themselves. @xref{Text Properties}. | |
221 | @end defun | |
222 | ||
223 | @defun filter-buffer-substring start end &optional delete noprops | |
224 | This function passes the buffer text between @var{start} and @var{end} | |
225 | through the filter functions specified by the variable | |
226 | @code{buffer-substring-filters}, and returns the value from the last | |
227 | filter function. If @code{buffer-substring-filters} is @code{nil}, | |
228 | the value is the unaltered text from the buffer, what | |
229 | @code{buffer-substring} would return. | |
230 | ||
231 | If @var{delete} is non-@code{nil}, this function deletes the text | |
232 | between @var{start} and @var{end} after copying it, like | |
233 | @code{delete-and-extract-region}. | |
234 | ||
235 | If @var{noprops} is non-@code{nil}, the final string returned does not | |
236 | include text properties, while the string passed through the filters | |
237 | still includes text properties from the buffer text. | |
238 | ||
239 | Lisp code should use this function instead of @code{buffer-substring}, | |
240 | @code{buffer-substring-no-properties}, | |
241 | or @code{delete-and-extract-region} when copying into user-accessible | |
242 | data structures such as the kill-ring, X clipboard, and registers. | |
243 | Major and minor modes can add functions to | |
244 | @code{buffer-substring-filters} to alter such text as it is copied out | |
245 | of the buffer. | |
246 | @end defun | |
247 | ||
248 | @defvar buffer-substring-filters | |
249 | This variable should be a list of functions that accept a single | |
250 | argument, a string, and return a string. | |
251 | @code{filter-buffer-substring} passes the buffer substring to the | |
252 | first function in this list, and the return value of each function is | |
253 | passed to the next function. The return value of the last function is | |
254 | used as the return value of @code{filter-buffer-substring}. | |
255 | ||
256 | As a special convention, point is set to the start of the buffer text | |
257 | being operated on (i.e., the @var{start} argument for | |
258 | @code{filter-buffer-substring}) before these functions are called. | |
259 | ||
260 | If this variable is @code{nil}, no filtering is performed. | |
261 | @end defvar | |
262 | ||
263 | @defun buffer-string | |
264 | This function returns the contents of the entire accessible portion of | |
265 | the current buffer as a string. It is equivalent to | |
266 | ||
267 | @example | |
268 | (buffer-substring (point-min) (point-max)) | |
269 | @end example | |
270 | ||
271 | @example | |
272 | @group | |
273 | ---------- Buffer: foo ---------- | |
274 | This is the contents of buffer foo | |
275 | ||
276 | ---------- Buffer: foo ---------- | |
277 | ||
278 | (buffer-string) | |
279 | @result{} "This is the contents of buffer foo\n" | |
280 | @end group | |
281 | @end example | |
282 | @end defun | |
283 | ||
284 | @defun current-word &optional strict really-word | |
285 | This function returns the symbol (or word) at or near point, as a string. | |
286 | The return value includes no text properties. | |
287 | ||
288 | If the optional argument @var{really-word} is non-@code{nil}, it finds a | |
289 | word; otherwise, it finds a symbol (which includes both word | |
290 | characters and symbol constituent characters). | |
291 | ||
292 | If the optional argument @var{strict} is non-@code{nil}, then point | |
293 | must be in or next to the symbol or word---if no symbol or word is | |
294 | there, the function returns @code{nil}. Otherwise, a nearby symbol or | |
295 | word on the same line is acceptable. | |
296 | @end defun | |
297 | ||
298 | @defun thing-at-point thing | |
299 | Return the @var{thing} around or next to point, as a string. | |
300 | ||
301 | The argument @var{thing} is a symbol which specifies a kind of syntactic | |
302 | entity. Possibilities include @code{symbol}, @code{list}, @code{sexp}, | |
303 | @code{defun}, @code{filename}, @code{url}, @code{word}, @code{sentence}, | |
304 | @code{whitespace}, @code{line}, @code{page}, and others. | |
305 | ||
306 | @example | |
307 | ---------- Buffer: foo ---------- | |
308 | Gentlemen may cry ``Pea@point{}ce! Peace!,'' | |
309 | but there is no peace. | |
310 | ---------- Buffer: foo ---------- | |
311 | ||
312 | (thing-at-point 'word) | |
313 | @result{} "Peace" | |
314 | (thing-at-point 'line) | |
315 | @result{} "Gentlemen may cry ``Peace! Peace!,''\n" | |
316 | (thing-at-point 'whitespace) | |
317 | @result{} nil | |
318 | @end example | |
319 | @end defun | |
320 | ||
321 | @node Comparing Text | |
322 | @section Comparing Text | |
323 | @cindex comparing buffer text | |
324 | ||
325 | This function lets you compare portions of the text in a buffer, without | |
326 | copying them into strings first. | |
327 | ||
328 | @defun compare-buffer-substrings buffer1 start1 end1 buffer2 start2 end2 | |
329 | This function lets you compare two substrings of the same buffer or two | |
330 | different buffers. The first three arguments specify one substring, | |
331 | giving a buffer (or a buffer name) and two positions within the | |
332 | buffer. The last three arguments specify the other substring in the | |
333 | same way. You can use @code{nil} for @var{buffer1}, @var{buffer2}, or | |
334 | both to stand for the current buffer. | |
335 | ||
336 | The value is negative if the first substring is less, positive if the | |
337 | first is greater, and zero if they are equal. The absolute value of | |
338 | the result is one plus the index of the first differing characters | |
339 | within the substrings. | |
340 | ||
341 | This function ignores case when comparing characters | |
342 | if @code{case-fold-search} is non-@code{nil}. It always ignores | |
343 | text properties. | |
344 | ||
345 | Suppose the current buffer contains the text @samp{foobarbar | |
346 | haha!rara!}; then in this example the two substrings are @samp{rbar } | |
347 | and @samp{rara!}. The value is 2 because the first substring is greater | |
348 | at the second character. | |
349 | ||
350 | @example | |
351 | (compare-buffer-substrings nil 6 11 nil 16 21) | |
352 | @result{} 2 | |
353 | @end example | |
354 | @end defun | |
355 | ||
356 | @node Insertion | |
357 | @section Inserting Text | |
358 | @cindex insertion of text | |
359 | @cindex text insertion | |
360 | ||
361 | @cindex insertion before point | |
362 | @cindex before point, insertion | |
363 | @dfn{Insertion} means adding new text to a buffer. The inserted text | |
364 | goes at point---between the character before point and the character | |
365 | after point. Some insertion functions leave point before the inserted | |
366 | text, while other functions leave it after. We call the former | |
367 | insertion @dfn{after point} and the latter insertion @dfn{before point}. | |
368 | ||
369 | Insertion relocates markers that point at positions after the | |
370 | insertion point, so that they stay with the surrounding text | |
371 | (@pxref{Markers}). When a marker points at the place of insertion, | |
372 | insertion may or may not relocate the marker, depending on the marker's | |
373 | insertion type (@pxref{Marker Insertion Types}). Certain special | |
374 | functions such as @code{insert-before-markers} relocate all such markers | |
375 | to point after the inserted text, regardless of the markers' insertion | |
376 | type. | |
377 | ||
378 | Insertion functions signal an error if the current buffer is | |
379 | read-only or if they insert within read-only text. | |
380 | ||
381 | These functions copy text characters from strings and buffers along | |
382 | with their properties. The inserted characters have exactly the same | |
383 | properties as the characters they were copied from. By contrast, | |
384 | characters specified as separate arguments, not part of a string or | |
385 | buffer, inherit their text properties from the neighboring text. | |
386 | ||
387 | The insertion functions convert text from unibyte to multibyte in | |
388 | order to insert in a multibyte buffer, and vice versa---if the text | |
389 | comes from a string or from a buffer. However, they do not convert | |
390 | unibyte character codes 128 through 255 to multibyte characters, not | |
391 | even if the current buffer is a multibyte buffer. @xref{Converting | |
392 | Representations}. | |
393 | ||
394 | @defun insert &rest args | |
395 | This function inserts the strings and/or characters @var{args} into the | |
396 | current buffer, at point, moving point forward. In other words, it | |
397 | inserts the text before point. An error is signaled unless all | |
398 | @var{args} are either strings or characters. The value is @code{nil}. | |
399 | @end defun | |
400 | ||
401 | @defun insert-before-markers &rest args | |
402 | This function inserts the strings and/or characters @var{args} into the | |
403 | current buffer, at point, moving point forward. An error is signaled | |
404 | unless all @var{args} are either strings or characters. The value is | |
405 | @code{nil}. | |
406 | ||
407 | This function is unlike the other insertion functions in that it | |
408 | relocates markers initially pointing at the insertion point, to point | |
409 | after the inserted text. If an overlay begins at the insertion point, | |
410 | the inserted text falls outside the overlay; if a nonempty overlay | |
411 | ends at the insertion point, the inserted text falls inside that | |
412 | overlay. | |
413 | @end defun | |
414 | ||
415 | @defun insert-char character count &optional inherit | |
416 | This function inserts @var{count} instances of @var{character} into the | |
417 | current buffer before point. The argument @var{count} should be an | |
418 | integer, and @var{character} must be a character. The value is @code{nil}. | |
419 | ||
420 | This function does not convert unibyte character codes 128 through 255 | |
421 | to multibyte characters, not even if the current buffer is a multibyte | |
422 | buffer. @xref{Converting Representations}. | |
423 | ||
424 | If @var{inherit} is non-@code{nil}, then the inserted characters inherit | |
425 | sticky text properties from the two characters before and after the | |
426 | insertion point. @xref{Sticky Properties}. | |
427 | @end defun | |
428 | ||
429 | @defun insert-buffer-substring from-buffer-or-name &optional start end | |
430 | This function inserts a portion of buffer @var{from-buffer-or-name} | |
431 | (which must already exist) into the current buffer before point. The | |
432 | text inserted is the region between @var{start} and @var{end}. (These | |
433 | arguments default to the beginning and end of the accessible portion of | |
434 | that buffer.) This function returns @code{nil}. | |
435 | ||
436 | In this example, the form is executed with buffer @samp{bar} as the | |
437 | current buffer. We assume that buffer @samp{bar} is initially empty. | |
438 | ||
439 | @example | |
440 | @group | |
441 | ---------- Buffer: foo ---------- | |
442 | We hold these truths to be self-evident, that all | |
443 | ---------- Buffer: foo ---------- | |
444 | @end group | |
445 | ||
446 | @group | |
447 | (insert-buffer-substring "foo" 1 20) | |
448 | @result{} nil | |
449 | ||
450 | ---------- Buffer: bar ---------- | |
451 | We hold these truth@point{} | |
452 | ---------- Buffer: bar ---------- | |
453 | @end group | |
454 | @end example | |
455 | @end defun | |
456 | ||
457 | @defun insert-buffer-substring-no-properties from-buffer-or-name &optional start end | |
458 | This is like @code{insert-buffer-substring} except that it does not | |
459 | copy any text properties. | |
460 | @end defun | |
461 | ||
462 | @xref{Sticky Properties}, for other insertion functions that inherit | |
463 | text properties from the nearby text in addition to inserting it. | |
464 | Whitespace inserted by indentation functions also inherits text | |
465 | properties. | |
466 | ||
467 | @node Commands for Insertion | |
468 | @section User-Level Insertion Commands | |
469 | ||
470 | This section describes higher-level commands for inserting text, | |
471 | commands intended primarily for the user but useful also in Lisp | |
472 | programs. | |
473 | ||
474 | @deffn Command insert-buffer from-buffer-or-name | |
475 | This command inserts the entire accessible contents of | |
476 | @var{from-buffer-or-name} (which must exist) into the current buffer | |
477 | after point. It leaves the mark after the inserted text. The value | |
478 | is @code{nil}. | |
479 | @end deffn | |
480 | ||
481 | @deffn Command self-insert-command count | |
482 | @cindex character insertion | |
483 | @cindex self-insertion | |
484 | This command inserts the last character typed; it does so @var{count} | |
485 | times, before point, and returns @code{nil}. Most printing characters | |
486 | are bound to this command. In routine use, @code{self-insert-command} | |
487 | is the most frequently called function in Emacs, but programs rarely use | |
488 | it except to install it on a keymap. | |
489 | ||
490 | In an interactive call, @var{count} is the numeric prefix argument. | |
491 | ||
ab992d66 EZ |
492 | Self-insertion translates the input character through |
493 | @code{translation-table-for-input}. @xref{Translation of Characters}. | |
494 | ||
b8d4c8d0 GM |
495 | This command calls @code{auto-fill-function} whenever that is |
496 | non-@code{nil} and the character inserted is in the table | |
497 | @code{auto-fill-chars} (@pxref{Auto Filling}). | |
498 | ||
499 | @c Cross refs reworded to prevent overfull hbox. --rjc 15mar92 | |
500 | This command performs abbrev expansion if Abbrev mode is enabled and | |
501 | the inserted character does not have word-constituent | |
502 | syntax. (@xref{Abbrevs}, and @ref{Syntax Class Table}.) It is also | |
503 | responsible for calling @code{blink-paren-function} when the inserted | |
504 | character has close parenthesis syntax (@pxref{Blinking}). | |
505 | ||
506 | Do not try substituting your own definition of | |
507 | @code{self-insert-command} for the standard one. The editor command | |
508 | loop handles this function specially. | |
509 | @end deffn | |
510 | ||
511 | @deffn Command newline &optional number-of-newlines | |
512 | This command inserts newlines into the current buffer before point. | |
513 | If @var{number-of-newlines} is supplied, that many newline characters | |
514 | are inserted. | |
515 | ||
516 | @cindex newline and Auto Fill mode | |
517 | This function calls @code{auto-fill-function} if the current column | |
518 | number is greater than the value of @code{fill-column} and | |
519 | @var{number-of-newlines} is @code{nil}. Typically what | |
520 | @code{auto-fill-function} does is insert a newline; thus, the overall | |
521 | result in this case is to insert two newlines at different places: one | |
522 | at point, and another earlier in the line. @code{newline} does not | |
523 | auto-fill if @var{number-of-newlines} is non-@code{nil}. | |
524 | ||
525 | This command indents to the left margin if that is not zero. | |
526 | @xref{Margins}. | |
527 | ||
528 | The value returned is @code{nil}. In an interactive call, @var{count} | |
529 | is the numeric prefix argument. | |
530 | @end deffn | |
531 | ||
532 | @defvar overwrite-mode | |
533 | This variable controls whether overwrite mode is in effect. The value | |
534 | should be @code{overwrite-mode-textual}, @code{overwrite-mode-binary}, | |
535 | or @code{nil}. @code{overwrite-mode-textual} specifies textual | |
536 | overwrite mode (treats newlines and tabs specially), and | |
537 | @code{overwrite-mode-binary} specifies binary overwrite mode (treats | |
538 | newlines and tabs like any other characters). | |
539 | @end defvar | |
540 | ||
541 | @node Deletion | |
542 | @section Deleting Text | |
543 | @cindex text deletion | |
544 | ||
545 | @cindex deleting text vs killing | |
546 | Deletion means removing part of the text in a buffer, without saving | |
547 | it in the kill ring (@pxref{The Kill Ring}). Deleted text can't be | |
548 | yanked, but can be reinserted using the undo mechanism (@pxref{Undo}). | |
549 | Some deletion functions do save text in the kill ring in some special | |
550 | cases. | |
551 | ||
552 | All of the deletion functions operate on the current buffer. | |
553 | ||
554 | @deffn Command erase-buffer | |
555 | This function deletes the entire text of the current buffer | |
556 | (@emph{not} just the accessible portion), leaving it | |
557 | empty. If the buffer is read-only, it signals a @code{buffer-read-only} | |
558 | error; if some of the text in it is read-only, it signals a | |
559 | @code{text-read-only} error. Otherwise, it deletes the text without | |
560 | asking for any confirmation. It returns @code{nil}. | |
561 | ||
562 | Normally, deleting a large amount of text from a buffer inhibits further | |
563 | auto-saving of that buffer ``because it has shrunk.'' However, | |
564 | @code{erase-buffer} does not do this, the idea being that the future | |
565 | text is not really related to the former text, and its size should not | |
566 | be compared with that of the former text. | |
567 | @end deffn | |
568 | ||
569 | @deffn Command delete-region start end | |
570 | This command deletes the text between positions @var{start} and | |
571 | @var{end} in the current buffer, and returns @code{nil}. If point was | |
572 | inside the deleted region, its value afterward is @var{start}. | |
573 | Otherwise, point relocates with the surrounding text, as markers do. | |
574 | @end deffn | |
575 | ||
576 | @defun delete-and-extract-region start end | |
577 | This function deletes the text between positions @var{start} and | |
578 | @var{end} in the current buffer, and returns a string containing the | |
579 | text just deleted. | |
580 | ||
581 | If point was inside the deleted region, its value afterward is | |
582 | @var{start}. Otherwise, point relocates with the surrounding text, as | |
583 | markers do. | |
584 | @end defun | |
585 | ||
586 | @deffn Command delete-char count &optional killp | |
587 | This command deletes @var{count} characters directly after point, or | |
588 | before point if @var{count} is negative. If @var{killp} is | |
589 | non-@code{nil}, then it saves the deleted characters in the kill ring. | |
590 | ||
591 | In an interactive call, @var{count} is the numeric prefix argument, and | |
592 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix | |
593 | argument is supplied, the text is saved in the kill ring. If no prefix | |
594 | argument is supplied, then one character is deleted, but not saved in | |
595 | the kill ring. | |
596 | ||
597 | The value returned is always @code{nil}. | |
598 | @end deffn | |
599 | ||
600 | @deffn Command delete-backward-char count &optional killp | |
601 | @cindex deleting previous char | |
602 | This command deletes @var{count} characters directly before point, or | |
603 | after point if @var{count} is negative. If @var{killp} is | |
604 | non-@code{nil}, then it saves the deleted characters in the kill ring. | |
605 | ||
606 | In an interactive call, @var{count} is the numeric prefix argument, and | |
607 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix | |
608 | argument is supplied, the text is saved in the kill ring. If no prefix | |
609 | argument is supplied, then one character is deleted, but not saved in | |
610 | the kill ring. | |
611 | ||
612 | The value returned is always @code{nil}. | |
613 | @end deffn | |
614 | ||
615 | @deffn Command backward-delete-char-untabify count &optional killp | |
616 | @cindex tab deletion | |
617 | This command deletes @var{count} characters backward, changing tabs | |
618 | into spaces. When the next character to be deleted is a tab, it is | |
619 | first replaced with the proper number of spaces to preserve alignment | |
620 | and then one of those spaces is deleted instead of the tab. If | |
621 | @var{killp} is non-@code{nil}, then the command saves the deleted | |
622 | characters in the kill ring. | |
623 | ||
624 | Conversion of tabs to spaces happens only if @var{count} is positive. | |
625 | If it is negative, exactly @minus{}@var{count} characters after point | |
626 | are deleted. | |
627 | ||
628 | In an interactive call, @var{count} is the numeric prefix argument, and | |
629 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix | |
630 | argument is supplied, the text is saved in the kill ring. If no prefix | |
631 | argument is supplied, then one character is deleted, but not saved in | |
632 | the kill ring. | |
633 | ||
634 | The value returned is always @code{nil}. | |
635 | @end deffn | |
636 | ||
637 | @defopt backward-delete-char-untabify-method | |
638 | This option specifies how @code{backward-delete-char-untabify} should | |
639 | deal with whitespace. Possible values include @code{untabify}, the | |
640 | default, meaning convert a tab to many spaces and delete one; | |
641 | @code{hungry}, meaning delete all tabs and spaces before point with | |
642 | one command; @code{all} meaning delete all tabs, spaces and newlines | |
643 | before point, and @code{nil}, meaning do nothing special for | |
644 | whitespace characters. | |
645 | @end defopt | |
646 | ||
647 | @node User-Level Deletion | |
648 | @section User-Level Deletion Commands | |
649 | ||
650 | This section describes higher-level commands for deleting text, | |
651 | commands intended primarily for the user but useful also in Lisp | |
652 | programs. | |
653 | ||
654 | @deffn Command delete-horizontal-space &optional backward-only | |
655 | @cindex deleting whitespace | |
656 | This function deletes all spaces and tabs around point. It returns | |
657 | @code{nil}. | |
658 | ||
659 | If @var{backward-only} is non-@code{nil}, the function deletes | |
660 | spaces and tabs before point, but not after point. | |
661 | ||
662 | In the following examples, we call @code{delete-horizontal-space} four | |
663 | times, once on each line, with point between the second and third | |
664 | characters on the line each time. | |
665 | ||
666 | @example | |
667 | @group | |
668 | ---------- Buffer: foo ---------- | |
669 | I @point{}thought | |
670 | I @point{} thought | |
671 | We@point{} thought | |
672 | Yo@point{}u thought | |
673 | ---------- Buffer: foo ---------- | |
674 | @end group | |
675 | ||
676 | @group | |
677 | (delete-horizontal-space) ; @r{Four times.} | |
678 | @result{} nil | |
679 | ||
680 | ---------- Buffer: foo ---------- | |
681 | Ithought | |
682 | Ithought | |
683 | Wethought | |
684 | You thought | |
685 | ---------- Buffer: foo ---------- | |
686 | @end group | |
687 | @end example | |
688 | @end deffn | |
689 | ||
690 | @deffn Command delete-indentation &optional join-following-p | |
691 | This function joins the line point is on to the previous line, deleting | |
692 | any whitespace at the join and in some cases replacing it with one | |
693 | space. If @var{join-following-p} is non-@code{nil}, | |
694 | @code{delete-indentation} joins this line to the following line | |
695 | instead. The function returns @code{nil}. | |
696 | ||
697 | If there is a fill prefix, and the second of the lines being joined | |
698 | starts with the prefix, then @code{delete-indentation} deletes the | |
699 | fill prefix before joining the lines. @xref{Margins}. | |
700 | ||
701 | In the example below, point is located on the line starting | |
702 | @samp{events}, and it makes no difference if there are trailing spaces | |
703 | in the preceding line. | |
704 | ||
705 | @smallexample | |
706 | @group | |
707 | ---------- Buffer: foo ---------- | |
708 | When in the course of human | |
709 | @point{} events, it becomes necessary | |
710 | ---------- Buffer: foo ---------- | |
711 | @end group | |
712 | ||
713 | (delete-indentation) | |
714 | @result{} nil | |
715 | ||
716 | @group | |
717 | ---------- Buffer: foo ---------- | |
718 | When in the course of human@point{} events, it becomes necessary | |
719 | ---------- Buffer: foo ---------- | |
720 | @end group | |
721 | @end smallexample | |
722 | ||
723 | After the lines are joined, the function @code{fixup-whitespace} is | |
724 | responsible for deciding whether to leave a space at the junction. | |
725 | @end deffn | |
726 | ||
727 | @deffn Command fixup-whitespace | |
728 | This function replaces all the horizontal whitespace surrounding point | |
729 | with either one space or no space, according to the context. It | |
730 | returns @code{nil}. | |
731 | ||
732 | At the beginning or end of a line, the appropriate amount of space is | |
733 | none. Before a character with close parenthesis syntax, or after a | |
734 | character with open parenthesis or expression-prefix syntax, no space is | |
735 | also appropriate. Otherwise, one space is appropriate. @xref{Syntax | |
736 | Class Table}. | |
737 | ||
738 | In the example below, @code{fixup-whitespace} is called the first time | |
739 | with point before the word @samp{spaces} in the first line. For the | |
740 | second invocation, point is directly after the @samp{(}. | |
741 | ||
742 | @smallexample | |
743 | @group | |
744 | ---------- Buffer: foo ---------- | |
745 | This has too many @point{}spaces | |
746 | This has too many spaces at the start of (@point{} this list) | |
747 | ---------- Buffer: foo ---------- | |
748 | @end group | |
749 | ||
750 | @group | |
751 | (fixup-whitespace) | |
752 | @result{} nil | |
753 | (fixup-whitespace) | |
754 | @result{} nil | |
755 | @end group | |
756 | ||
757 | @group | |
758 | ---------- Buffer: foo ---------- | |
759 | This has too many spaces | |
760 | This has too many spaces at the start of (this list) | |
761 | ---------- Buffer: foo ---------- | |
762 | @end group | |
763 | @end smallexample | |
764 | @end deffn | |
765 | ||
766 | @deffn Command just-one-space &optional n | |
767 | @comment !!SourceFile simple.el | |
768 | This command replaces any spaces and tabs around point with a single | |
769 | space, or @var{n} spaces if @var{n} is specified. It returns | |
770 | @code{nil}. | |
771 | @end deffn | |
772 | ||
773 | @deffn Command delete-blank-lines | |
774 | This function deletes blank lines surrounding point. If point is on a | |
775 | blank line with one or more blank lines before or after it, then all but | |
776 | one of them are deleted. If point is on an isolated blank line, then it | |
777 | is deleted. If point is on a nonblank line, the command deletes all | |
778 | blank lines immediately following it. | |
779 | ||
780 | A blank line is defined as a line containing only tabs and spaces. | |
781 | ||
782 | @code{delete-blank-lines} returns @code{nil}. | |
783 | @end deffn | |
784 | ||
785 | @node The Kill Ring | |
786 | @section The Kill Ring | |
787 | @cindex kill ring | |
788 | ||
789 | @dfn{Kill functions} delete text like the deletion functions, but save | |
790 | it so that the user can reinsert it by @dfn{yanking}. Most of these | |
791 | functions have @samp{kill-} in their name. By contrast, the functions | |
792 | whose names start with @samp{delete-} normally do not save text for | |
793 | yanking (though they can still be undone); these are ``deletion'' | |
794 | functions. | |
795 | ||
796 | Most of the kill commands are primarily for interactive use, and are | |
797 | not described here. What we do describe are the functions provided for | |
798 | use in writing such commands. You can use these functions to write | |
799 | commands for killing text. When you need to delete text for internal | |
800 | purposes within a Lisp function, you should normally use deletion | |
801 | functions, so as not to disturb the kill ring contents. | |
802 | @xref{Deletion}. | |
803 | ||
804 | Killed text is saved for later yanking in the @dfn{kill ring}. This | |
805 | is a list that holds a number of recent kills, not just the last text | |
806 | kill. We call this a ``ring'' because yanking treats it as having | |
807 | elements in a cyclic order. The list is kept in the variable | |
808 | @code{kill-ring}, and can be operated on with the usual functions for | |
809 | lists; there are also specialized functions, described in this section, | |
810 | that treat it as a ring. | |
811 | ||
812 | Some people think this use of the word ``kill'' is unfortunate, since | |
813 | it refers to operations that specifically @emph{do not} destroy the | |
814 | entities ``killed.'' This is in sharp contrast to ordinary life, in | |
815 | which death is permanent and ``killed'' entities do not come back to | |
816 | life. Therefore, other metaphors have been proposed. For example, the | |
817 | term ``cut ring'' makes sense to people who, in pre-computer days, used | |
818 | scissors and paste to cut up and rearrange manuscripts. However, it | |
819 | would be difficult to change the terminology now. | |
820 | ||
821 | @menu | |
822 | * Kill Ring Concepts:: What text looks like in the kill ring. | |
823 | * Kill Functions:: Functions that kill text. | |
824 | * Yanking:: How yanking is done. | |
825 | * Yank Commands:: Commands that access the kill ring. | |
d24880de | 826 | * Low-Level Kill Ring:: Functions and variables for kill ring access. |
b8d4c8d0 GM |
827 | * Internals of Kill Ring:: Variables that hold kill ring data. |
828 | @end menu | |
829 | ||
830 | @node Kill Ring Concepts | |
831 | @comment node-name, next, previous, up | |
832 | @subsection Kill Ring Concepts | |
833 | ||
834 | The kill ring records killed text as strings in a list, most recent | |
835 | first. A short kill ring, for example, might look like this: | |
836 | ||
837 | @example | |
838 | ("some text" "a different piece of text" "even older text") | |
839 | @end example | |
840 | ||
841 | @noindent | |
842 | When the list reaches @code{kill-ring-max} entries in length, adding a | |
843 | new entry automatically deletes the last entry. | |
844 | ||
845 | When kill commands are interwoven with other commands, each kill | |
846 | command makes a new entry in the kill ring. Multiple kill commands in | |
847 | succession build up a single kill ring entry, which would be yanked as a | |
848 | unit; the second and subsequent consecutive kill commands add text to | |
849 | the entry made by the first one. | |
850 | ||
851 | For yanking, one entry in the kill ring is designated the ``front'' of | |
852 | the ring. Some yank commands ``rotate'' the ring by designating a | |
853 | different element as the ``front.'' But this virtual rotation doesn't | |
854 | change the list itself---the most recent entry always comes first in the | |
855 | list. | |
856 | ||
857 | @node Kill Functions | |
858 | @comment node-name, next, previous, up | |
859 | @subsection Functions for Killing | |
860 | ||
861 | @code{kill-region} is the usual subroutine for killing text. Any | |
862 | command that calls this function is a ``kill command'' (and should | |
863 | probably have @samp{kill} in its name). @code{kill-region} puts the | |
864 | newly killed text in a new element at the beginning of the kill ring or | |
865 | adds it to the most recent element. It determines automatically (using | |
866 | @code{last-command}) whether the previous command was a kill command, | |
867 | and if so appends the killed text to the most recent entry. | |
868 | ||
869 | @deffn Command kill-region start end &optional yank-handler | |
870 | This function kills the text in the region defined by @var{start} and | |
871 | @var{end}. The text is deleted but saved in the kill ring, along with | |
872 | its text properties. The value is always @code{nil}. | |
873 | ||
874 | In an interactive call, @var{start} and @var{end} are point and | |
875 | the mark. | |
876 | ||
877 | @c Emacs 19 feature | |
878 | If the buffer or text is read-only, @code{kill-region} modifies the kill | |
879 | ring just the same, then signals an error without modifying the buffer. | |
880 | This is convenient because it lets the user use a series of kill | |
881 | commands to copy text from a read-only buffer into the kill ring. | |
882 | ||
883 | If @var{yank-handler} is non-@code{nil}, this puts that value onto | |
884 | the string of killed text, as a @code{yank-handler} text property. | |
885 | @xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, any | |
886 | @code{yank-handler} properties present on the killed text are copied | |
887 | onto the kill ring, like other text properties. | |
888 | @end deffn | |
889 | ||
890 | @defopt kill-read-only-ok | |
891 | If this option is non-@code{nil}, @code{kill-region} does not signal an | |
892 | error if the buffer or text is read-only. Instead, it simply returns, | |
893 | updating the kill ring but not changing the buffer. | |
894 | @end defopt | |
895 | ||
896 | @deffn Command copy-region-as-kill start end | |
897 | This command saves the region defined by @var{start} and @var{end} on | |
898 | the kill ring (including text properties), but does not delete the text | |
899 | from the buffer. It returns @code{nil}. | |
900 | ||
901 | The command does not set @code{this-command} to @code{kill-region}, so a | |
902 | subsequent kill command does not append to the same kill ring entry. | |
903 | ||
904 | Don't call @code{copy-region-as-kill} in Lisp programs unless you aim to | |
905 | support Emacs 18. For newer Emacs versions, it is better to use | |
906 | @code{kill-new} or @code{kill-append} instead. @xref{Low-Level Kill | |
907 | Ring}. | |
908 | @end deffn | |
909 | ||
910 | @node Yanking | |
911 | @subsection Yanking | |
912 | ||
913 | Yanking means inserting text from the kill ring, but it does | |
914 | not insert the text blindly. Yank commands and some other commands | |
915 | use @code{insert-for-yank} to perform special processing on the | |
916 | text that they copy into the buffer. | |
917 | ||
918 | @defun insert-for-yank string | |
919 | This function normally works like @code{insert} except that it doesn't | |
920 | insert the text properties in the @code{yank-excluded-properties} | |
921 | list. However, if any part of @var{string} has a non-@code{nil} | |
922 | @code{yank-handler} text property, that property can do various | |
923 | special processing on that part of the text being inserted. | |
924 | @end defun | |
925 | ||
926 | @defun insert-buffer-substring-as-yank buf &optional start end | |
927 | This function resembles @code{insert-buffer-substring} except that it | |
928 | doesn't insert the text properties in the | |
929 | @code{yank-excluded-properties} list. | |
930 | @end defun | |
931 | ||
932 | You can put a @code{yank-handler} text property on all or part of | |
933 | the text to control how it will be inserted if it is yanked. The | |
934 | @code{insert-for-yank} function looks for that property. The property | |
935 | value must be a list of one to four elements, with the following | |
936 | format (where elements after the first may be omitted): | |
937 | ||
938 | @example | |
939 | (@var{function} @var{param} @var{noexclude} @var{undo}) | |
940 | @end example | |
941 | ||
942 | Here is what the elements do: | |
943 | ||
944 | @table @var | |
945 | @item function | |
946 | When @var{function} is present and non-@code{nil}, it is called instead of | |
947 | @code{insert} to insert the string. @var{function} takes one | |
948 | argument---the string to insert. | |
949 | ||
950 | @item param | |
951 | If @var{param} is present and non-@code{nil}, it replaces @var{string} | |
952 | (or the part of @var{string} being processed) as the object passed to | |
953 | @var{function} (or @code{insert}); for example, if @var{function} is | |
954 | @code{yank-rectangle}, @var{param} should be a list of strings to | |
955 | insert as a rectangle. | |
956 | ||
957 | @item noexclude | |
958 | If @var{noexclude} is present and non-@code{nil}, the normal removal of the | |
959 | yank-excluded-properties is not performed; instead @var{function} is | |
960 | responsible for removing those properties. This may be necessary | |
961 | if @var{function} adjusts point before or after inserting the object. | |
962 | ||
963 | @item undo | |
964 | If @var{undo} is present and non-@code{nil}, it is a function that will be | |
965 | called by @code{yank-pop} to undo the insertion of the current object. | |
966 | It is called with two arguments, the start and end of the current | |
967 | region. @var{function} can set @code{yank-undo-function} to override | |
968 | the @var{undo} value. | |
969 | @end table | |
970 | ||
971 | @node Yank Commands | |
972 | @comment node-name, next, previous, up | |
973 | @subsection Functions for Yanking | |
974 | ||
975 | This section describes higher-level commands for yanking, which are | |
976 | intended primarily for the user but useful also in Lisp programs. | |
977 | Both @code{yank} and @code{yank-pop} honor the | |
978 | @code{yank-excluded-properties} variable and @code{yank-handler} text | |
979 | property (@pxref{Yanking}). | |
980 | ||
981 | @deffn Command yank &optional arg | |
982 | @cindex inserting killed text | |
2bad3299 CY |
983 | This command inserts before point the text at the front of the kill |
984 | ring. It sets the mark at the beginning of that text, using | |
985 | @code{push-mark} (@pxref{The Mark}), and puts point at the end. | |
b8d4c8d0 GM |
986 | |
987 | If @var{arg} is a non-@code{nil} list (which occurs interactively when | |
988 | the user types @kbd{C-u} with no digits), then @code{yank} inserts the | |
989 | text as described above, but puts point before the yanked text and | |
2bad3299 | 990 | sets the mark after it. |
b8d4c8d0 GM |
991 | |
992 | If @var{arg} is a number, then @code{yank} inserts the @var{arg}th | |
993 | most recently killed text---the @var{arg}th element of the kill ring | |
994 | list, counted cyclically from the front, which is considered the | |
995 | first element for this purpose. | |
996 | ||
997 | @code{yank} does not alter the contents of the kill ring, unless it | |
998 | used text provided by another program, in which case it pushes that text | |
999 | onto the kill ring. However if @var{arg} is an integer different from | |
1000 | one, it rotates the kill ring to place the yanked string at the front. | |
1001 | ||
1002 | @code{yank} returns @code{nil}. | |
1003 | @end deffn | |
1004 | ||
1005 | @deffn Command yank-pop &optional arg | |
1006 | This command replaces the just-yanked entry from the kill ring with a | |
1007 | different entry from the kill ring. | |
1008 | ||
1009 | This is allowed only immediately after a @code{yank} or another | |
1010 | @code{yank-pop}. At such a time, the region contains text that was just | |
1011 | inserted by yanking. @code{yank-pop} deletes that text and inserts in | |
1012 | its place a different piece of killed text. It does not add the deleted | |
1013 | text to the kill ring, since it is already in the kill ring somewhere. | |
1014 | It does however rotate the kill ring to place the newly yanked string at | |
1015 | the front. | |
1016 | ||
1017 | If @var{arg} is @code{nil}, then the replacement text is the previous | |
1018 | element of the kill ring. If @var{arg} is numeric, the replacement is | |
1019 | the @var{arg}th previous kill. If @var{arg} is negative, a more recent | |
1020 | kill is the replacement. | |
1021 | ||
1022 | The sequence of kills in the kill ring wraps around, so that after the | |
1023 | oldest one comes the newest one, and before the newest one goes the | |
1024 | oldest. | |
1025 | ||
1026 | The return value is always @code{nil}. | |
1027 | @end deffn | |
1028 | ||
1029 | @defvar yank-undo-function | |
1030 | If this variable is non-@code{nil}, the function @code{yank-pop} uses | |
1031 | its value instead of @code{delete-region} to delete the text | |
1032 | inserted by the previous @code{yank} or | |
1033 | @code{yank-pop} command. The value must be a function of two | |
1034 | arguments, the start and end of the current region. | |
1035 | ||
1036 | The function @code{insert-for-yank} automatically sets this variable | |
1037 | according to the @var{undo} element of the @code{yank-handler} | |
1038 | text property, if there is one. | |
1039 | @end defvar | |
1040 | ||
1041 | @node Low-Level Kill Ring | |
1042 | @subsection Low-Level Kill Ring | |
1043 | ||
1044 | These functions and variables provide access to the kill ring at a | |
1045 | lower level, but still convenient for use in Lisp programs, because they | |
1046 | take care of interaction with window system selections | |
1047 | (@pxref{Window System Selections}). | |
1048 | ||
1049 | @defun current-kill n &optional do-not-move | |
1050 | The function @code{current-kill} rotates the yanking pointer, which | |
1051 | designates the ``front'' of the kill ring, by @var{n} places (from newer | |
1052 | kills to older ones), and returns the text at that place in the ring. | |
1053 | ||
1054 | If the optional second argument @var{do-not-move} is non-@code{nil}, | |
1055 | then @code{current-kill} doesn't alter the yanking pointer; it just | |
1056 | returns the @var{n}th kill, counting from the current yanking pointer. | |
1057 | ||
1058 | If @var{n} is zero, indicating a request for the latest kill, | |
1059 | @code{current-kill} calls the value of | |
1060 | @code{interprogram-paste-function} (documented below) before | |
1061 | consulting the kill ring. If that value is a function and calling it | |
8e8c1a72 EZ |
1062 | returns a string or a list of several string, @code{current-kill} |
1063 | pushes the strings onto the kill ring and returns the first string. | |
a053dae0 EZ |
1064 | It also sets the yanking pointer to point to the kill-ring entry of |
1065 | the first string returned by @code{interprogram-paste-function}, | |
8e8c1a72 EZ |
1066 | regardless of the value of @var{do-not-move}. Otherwise, |
1067 | @code{current-kill} does not treat a zero value for @var{n} specially: | |
1068 | it returns the entry pointed at by the yanking pointer and does not | |
1069 | move the yanking pointer. | |
b8d4c8d0 GM |
1070 | @end defun |
1071 | ||
1072 | @defun kill-new string &optional replace yank-handler | |
1073 | This function pushes the text @var{string} onto the kill ring and | |
1074 | makes the yanking pointer point to it. It discards the oldest entry | |
1075 | if appropriate. It also invokes the value of | |
1076 | @code{interprogram-cut-function} (see below). | |
1077 | ||
1078 | If @var{replace} is non-@code{nil}, then @code{kill-new} replaces the | |
1079 | first element of the kill ring with @var{string}, rather than pushing | |
1080 | @var{string} onto the kill ring. | |
1081 | ||
1082 | If @var{yank-handler} is non-@code{nil}, this puts that value onto | |
1083 | the string of killed text, as a @code{yank-handler} property. | |
1084 | @xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, then | |
1085 | @code{kill-new} copies any @code{yank-handler} properties present on | |
1086 | @var{string} onto the kill ring, as it does with other text properties. | |
1087 | @end defun | |
1088 | ||
1089 | @defun kill-append string before-p &optional yank-handler | |
1090 | This function appends the text @var{string} to the first entry in the | |
1091 | kill ring and makes the yanking pointer point to the combined entry. | |
1092 | Normally @var{string} goes at the end of the entry, but if | |
1093 | @var{before-p} is non-@code{nil}, it goes at the beginning. This | |
1094 | function also invokes the value of @code{interprogram-cut-function} | |
1095 | (see below). This handles @var{yank-handler} just like | |
1096 | @code{kill-new}, except that if @var{yank-handler} is different from | |
1097 | the @code{yank-handler} property of the first entry of the kill ring, | |
1098 | @code{kill-append} pushes the concatenated string onto the kill ring, | |
1099 | instead of replacing the original first entry with it. | |
1100 | @end defun | |
1101 | ||
1102 | @defvar interprogram-paste-function | |
1103 | This variable provides a way of transferring killed text from other | |
1104 | programs, when you are using a window system. Its value should be | |
1105 | @code{nil} or a function of no arguments. | |
1106 | ||
1107 | If the value is a function, @code{current-kill} calls it to get the | |
1108 | ``most recent kill.'' If the function returns a non-@code{nil} value, | |
1109 | then that value is used as the ``most recent kill.'' If it returns | |
1110 | @code{nil}, then the front of the kill ring is used. | |
1111 | ||
8e8c1a72 EZ |
1112 | To facilitate support for window systems that support multiple |
1113 | selections, this function may also return a list of strings. In that | |
1114 | case, the first string is used as the ``most recent kill'', and all | |
1115 | the other strings are pushed onto the kill ring, for easy access by | |
1116 | @code{yank-pop}. | |
1117 | ||
1118 | The normal use of this function is to get the window system's primary | |
b8d4c8d0 | 1119 | selection as the most recent kill, even if the selection belongs to |
8e8c1a72 EZ |
1120 | another application. @xref{Window System Selections}. However, if |
1121 | the selection was provided by the current Emacs session, this function | |
1122 | should return @code{nil}. (If it is hard to tell whether Emacs or | |
1123 | some other program provided the selection, it should be good enough to | |
1124 | use @code{string=} to compare it with the last text Emacs provided.) | |
b8d4c8d0 GM |
1125 | @end defvar |
1126 | ||
1127 | @defvar interprogram-cut-function | |
1128 | This variable provides a way of communicating killed text to other | |
1129 | programs, when you are using a window system. Its value should be | |
45240125 | 1130 | @code{nil} or a function of one required argument. |
b8d4c8d0 GM |
1131 | |
1132 | If the value is a function, @code{kill-new} and @code{kill-append} call | |
45240125 | 1133 | it with the new first element of the kill ring as the argument. |
b8d4c8d0 | 1134 | |
8e8c1a72 | 1135 | The normal use of this function is to set the window system's primary |
45240125 | 1136 | selection from the newly killed text. |
b8d4c8d0 GM |
1137 | @xref{Window System Selections}. |
1138 | @end defvar | |
1139 | ||
1140 | @node Internals of Kill Ring | |
1141 | @comment node-name, next, previous, up | |
1142 | @subsection Internals of the Kill Ring | |
1143 | ||
1144 | The variable @code{kill-ring} holds the kill ring contents, in the | |
1145 | form of a list of strings. The most recent kill is always at the front | |
1146 | of the list. | |
1147 | ||
1148 | The @code{kill-ring-yank-pointer} variable points to a link in the | |
1149 | kill ring list, whose @sc{car} is the text to yank next. We say it | |
1150 | identifies the ``front'' of the ring. Moving | |
1151 | @code{kill-ring-yank-pointer} to a different link is called | |
1152 | @dfn{rotating the kill ring}. We call the kill ring a ``ring'' because | |
1153 | the functions that move the yank pointer wrap around from the end of the | |
1154 | list to the beginning, or vice-versa. Rotation of the kill ring is | |
1155 | virtual; it does not change the value of @code{kill-ring}. | |
1156 | ||
1157 | Both @code{kill-ring} and @code{kill-ring-yank-pointer} are Lisp | |
1158 | variables whose values are normally lists. The word ``pointer'' in the | |
1159 | name of the @code{kill-ring-yank-pointer} indicates that the variable's | |
1160 | purpose is to identify one element of the list for use by the next yank | |
1161 | command. | |
1162 | ||
1163 | The value of @code{kill-ring-yank-pointer} is always @code{eq} to one | |
1164 | of the links in the kill ring list. The element it identifies is the | |
1165 | @sc{car} of that link. Kill commands, which change the kill ring, also | |
1166 | set this variable to the value of @code{kill-ring}. The effect is to | |
1167 | rotate the ring so that the newly killed text is at the front. | |
1168 | ||
1169 | Here is a diagram that shows the variable @code{kill-ring-yank-pointer} | |
1170 | pointing to the second entry in the kill ring @code{("some text" "a | |
1171 | different piece of text" "yet older text")}. | |
1172 | ||
1173 | @example | |
1174 | @group | |
1175 | kill-ring ---- kill-ring-yank-pointer | |
1176 | | | | |
1177 | | v | |
1178 | | --- --- --- --- --- --- | |
1179 | --> | | |------> | | |--> | | |--> nil | |
1180 | --- --- --- --- --- --- | |
1181 | | | | | |
1182 | | | | | |
1183 | | | -->"yet older text" | |
1184 | | | | |
1185 | | --> "a different piece of text" | |
1186 | | | |
1187 | --> "some text" | |
1188 | @end group | |
1189 | @end example | |
1190 | ||
1191 | @noindent | |
1192 | This state of affairs might occur after @kbd{C-y} (@code{yank}) | |
1193 | immediately followed by @kbd{M-y} (@code{yank-pop}). | |
1194 | ||
1195 | @defvar kill-ring | |
1196 | This variable holds the list of killed text sequences, most recently | |
1197 | killed first. | |
1198 | @end defvar | |
1199 | ||
1200 | @defvar kill-ring-yank-pointer | |
1201 | This variable's value indicates which element of the kill ring is at the | |
1202 | ``front'' of the ring for yanking. More precisely, the value is a tail | |
1203 | of the value of @code{kill-ring}, and its @sc{car} is the kill string | |
1204 | that @kbd{C-y} should yank. | |
1205 | @end defvar | |
1206 | ||
1207 | @defopt kill-ring-max | |
1208 | The value of this variable is the maximum length to which the kill | |
1209 | ring can grow, before elements are thrown away at the end. The default | |
1210 | value for @code{kill-ring-max} is 60. | |
1211 | @end defopt | |
1212 | ||
1213 | @node Undo | |
1214 | @comment node-name, next, previous, up | |
1215 | @section Undo | |
1216 | @cindex redo | |
1217 | ||
1218 | Most buffers have an @dfn{undo list}, which records all changes made | |
1219 | to the buffer's text so that they can be undone. (The buffers that | |
1220 | don't have one are usually special-purpose buffers for which Emacs | |
1221 | assumes that undoing is not useful. In particular, any buffer whose | |
1222 | name begins with a space has its undo recording off by default; | |
1223 | see @ref{Buffer Names}.) All the primitives that modify the | |
1224 | text in the buffer automatically add elements to the front of the undo | |
1225 | list, which is in the variable @code{buffer-undo-list}. | |
1226 | ||
1227 | @defvar buffer-undo-list | |
1228 | This buffer-local variable's value is the undo list of the current | |
1229 | buffer. A value of @code{t} disables the recording of undo information. | |
1230 | @end defvar | |
1231 | ||
1232 | Here are the kinds of elements an undo list can have: | |
1233 | ||
1234 | @table @code | |
1235 | @item @var{position} | |
1236 | This kind of element records a previous value of point; undoing this | |
1237 | element moves point to @var{position}. Ordinary cursor motion does not | |
1238 | make any sort of undo record, but deletion operations use these entries | |
1239 | to record where point was before the command. | |
1240 | ||
1241 | @item (@var{beg} . @var{end}) | |
1242 | This kind of element indicates how to delete text that was inserted. | |
1243 | Upon insertion, the text occupied the range @var{beg}--@var{end} in the | |
1244 | buffer. | |
1245 | ||
1246 | @item (@var{text} . @var{position}) | |
1247 | This kind of element indicates how to reinsert text that was deleted. | |
1248 | The deleted text itself is the string @var{text}. The place to | |
1249 | reinsert it is @code{(abs @var{position})}. If @var{position} is | |
1250 | positive, point was at the beginning of the deleted text, otherwise it | |
1251 | was at the end. | |
1252 | ||
1253 | @item (t @var{high} . @var{low}) | |
1254 | This kind of element indicates that an unmodified buffer became | |
1255 | modified. The elements @var{high} and @var{low} are two integers, each | |
1256 | recording 16 bits of the visited file's modification time as of when it | |
1257 | was previously visited or saved. @code{primitive-undo} uses those | |
1258 | values to determine whether to mark the buffer as unmodified once again; | |
1259 | it does so only if the file's modification time matches those numbers. | |
1260 | ||
1261 | @item (nil @var{property} @var{value} @var{beg} . @var{end}) | |
1262 | This kind of element records a change in a text property. | |
1263 | Here's how you might undo the change: | |
1264 | ||
1265 | @example | |
1266 | (put-text-property @var{beg} @var{end} @var{property} @var{value}) | |
1267 | @end example | |
1268 | ||
1269 | @item (@var{marker} . @var{adjustment}) | |
1270 | This kind of element records the fact that the marker @var{marker} was | |
1271 | relocated due to deletion of surrounding text, and that it moved | |
1272 | @var{adjustment} character positions. Undoing this element moves | |
1273 | @var{marker} @minus{} @var{adjustment} characters. | |
1274 | ||
1275 | @item (apply @var{funname} . @var{args}) | |
1276 | This is an extensible undo item, which is undone by calling | |
1277 | @var{funname} with arguments @var{args}. | |
1278 | ||
1279 | @item (apply @var{delta} @var{beg} @var{end} @var{funname} . @var{args}) | |
1280 | This is an extensible undo item, which records a change limited to the | |
1281 | range @var{beg} to @var{end}, which increased the size of the buffer | |
1282 | by @var{delta}. It is undone by calling @var{funname} with arguments | |
1283 | @var{args}. | |
1284 | ||
1285 | This kind of element enables undo limited to a region to determine | |
1286 | whether the element pertains to that region. | |
1287 | ||
1288 | @item nil | |
1289 | This element is a boundary. The elements between two boundaries are | |
1290 | called a @dfn{change group}; normally, each change group corresponds to | |
1291 | one keyboard command, and undo commands normally undo an entire group as | |
1292 | a unit. | |
1293 | @end table | |
1294 | ||
1295 | @defun undo-boundary | |
1296 | This function places a boundary element in the undo list. The undo | |
1297 | command stops at such a boundary, and successive undo commands undo | |
1298 | to earlier and earlier boundaries. This function returns @code{nil}. | |
1299 | ||
51422d6d CY |
1300 | The editor command loop automatically calls @code{undo-boundary} just |
1301 | before executing each key sequence, so that each undo normally undoes | |
1302 | the effects of one command. As an exception, the command | |
1303 | @code{self-insert-command}, which produces self-inserting input | |
1304 | characters (@pxref{Commands for Insertion}), may remove the boundary | |
1305 | inserted by the command loop: a boundary is accepted for the first | |
1306 | such character, the next 19 consecutive self-inserting input | |
1307 | characters do not have boundaries, and then the 20th does; and so on | |
1308 | as long as the self-inserting characters continue. Hence, sequences | |
1309 | of consecutive character insertions can be undone as a group. | |
b8d4c8d0 GM |
1310 | |
1311 | All buffer modifications add a boundary whenever the previous undoable | |
1312 | change was made in some other buffer. This is to ensure that | |
1313 | each command makes a boundary in each buffer where it makes changes. | |
1314 | ||
1315 | Calling this function explicitly is useful for splitting the effects of | |
1316 | a command into more than one unit. For example, @code{query-replace} | |
1317 | calls @code{undo-boundary} after each replacement, so that the user can | |
1318 | undo individual replacements one by one. | |
1319 | @end defun | |
1320 | ||
1321 | @defvar undo-in-progress | |
1322 | This variable is normally @code{nil}, but the undo commands bind it to | |
1323 | @code{t}. This is so that various kinds of change hooks can tell when | |
1324 | they're being called for the sake of undoing. | |
1325 | @end defvar | |
1326 | ||
1327 | @defun primitive-undo count list | |
1328 | This is the basic function for undoing elements of an undo list. | |
1329 | It undoes the first @var{count} elements of @var{list}, returning | |
1330 | the rest of @var{list}. | |
1331 | ||
1332 | @code{primitive-undo} adds elements to the buffer's undo list when it | |
1333 | changes the buffer. Undo commands avoid confusion by saving the undo | |
1334 | list value at the beginning of a sequence of undo operations. Then the | |
1335 | undo operations use and update the saved value. The new elements added | |
1336 | by undoing are not part of this saved value, so they don't interfere with | |
1337 | continuing to undo. | |
1338 | ||
1339 | This function does not bind @code{undo-in-progress}. | |
1340 | @end defun | |
1341 | ||
1342 | @node Maintaining Undo | |
1343 | @section Maintaining Undo Lists | |
1344 | ||
1345 | This section describes how to enable and disable undo information for | |
1346 | a given buffer. It also explains how the undo list is truncated | |
1347 | automatically so it doesn't get too big. | |
1348 | ||
1349 | Recording of undo information in a newly created buffer is normally | |
1350 | enabled to start with; but if the buffer name starts with a space, the | |
1351 | undo recording is initially disabled. You can explicitly enable or | |
1352 | disable undo recording with the following two functions, or by setting | |
1353 | @code{buffer-undo-list} yourself. | |
1354 | ||
1355 | @deffn Command buffer-enable-undo &optional buffer-or-name | |
1356 | This command enables recording undo information for buffer | |
1357 | @var{buffer-or-name}, so that subsequent changes can be undone. If no | |
1358 | argument is supplied, then the current buffer is used. This function | |
1359 | does nothing if undo recording is already enabled in the buffer. It | |
1360 | returns @code{nil}. | |
1361 | ||
1362 | In an interactive call, @var{buffer-or-name} is the current buffer. | |
1363 | You cannot specify any other buffer. | |
1364 | @end deffn | |
1365 | ||
1366 | @deffn Command buffer-disable-undo &optional buffer-or-name | |
1367 | @cindex disabling undo | |
1368 | This function discards the undo list of @var{buffer-or-name}, and disables | |
1369 | further recording of undo information. As a result, it is no longer | |
1370 | possible to undo either previous changes or any subsequent changes. If | |
1371 | the undo list of @var{buffer-or-name} is already disabled, this function | |
1372 | has no effect. | |
1373 | ||
1374 | This function returns @code{nil}. | |
1375 | @end deffn | |
1376 | ||
1377 | As editing continues, undo lists get longer and longer. To prevent | |
1378 | them from using up all available memory space, garbage collection trims | |
1379 | them back to size limits you can set. (For this purpose, the ``size'' | |
1380 | of an undo list measures the cons cells that make up the list, plus the | |
1381 | strings of deleted text.) Three variables control the range of acceptable | |
1382 | sizes: @code{undo-limit}, @code{undo-strong-limit} and | |
1383 | @code{undo-outer-limit}. In these variables, size is counted as the | |
1384 | number of bytes occupied, which includes both saved text and other | |
1385 | data. | |
1386 | ||
1387 | @defopt undo-limit | |
1388 | This is the soft limit for the acceptable size of an undo list. The | |
1389 | change group at which this size is exceeded is the last one kept. | |
1390 | @end defopt | |
1391 | ||
1392 | @defopt undo-strong-limit | |
1393 | This is the upper limit for the acceptable size of an undo list. The | |
1394 | change group at which this size is exceeded is discarded itself (along | |
1395 | with all older change groups). There is one exception: the very latest | |
1396 | change group is only discarded if it exceeds @code{undo-outer-limit}. | |
1397 | @end defopt | |
1398 | ||
1399 | @defopt undo-outer-limit | |
1400 | If at garbage collection time the undo info for the current command | |
1401 | exceeds this limit, Emacs discards the info and displays a warning. | |
1402 | This is a last ditch limit to prevent memory overflow. | |
1403 | @end defopt | |
1404 | ||
1405 | @defopt undo-ask-before-discard | |
1406 | If this variable is non-@code{nil}, when the undo info exceeds | |
1407 | @code{undo-outer-limit}, Emacs asks in the echo area whether to | |
1408 | discard the info. The default value is @code{nil}, which means to | |
1409 | discard it automatically. | |
1410 | ||
1411 | This option is mainly intended for debugging. Garbage collection is | |
1412 | inhibited while the question is asked, which means that Emacs might | |
1413 | leak memory if the user waits too long before answering the question. | |
1414 | @end defopt | |
1415 | ||
1416 | @node Filling | |
1417 | @comment node-name, next, previous, up | |
1418 | @section Filling | |
1419 | @cindex filling text | |
1420 | ||
1421 | @dfn{Filling} means adjusting the lengths of lines (by moving the line | |
1422 | breaks) so that they are nearly (but no greater than) a specified | |
1423 | maximum width. Additionally, lines can be @dfn{justified}, which means | |
1424 | inserting spaces to make the left and/or right margins line up | |
1425 | precisely. The width is controlled by the variable @code{fill-column}. | |
1426 | For ease of reading, lines should be no longer than 70 or so columns. | |
1427 | ||
1428 | You can use Auto Fill mode (@pxref{Auto Filling}) to fill text | |
1429 | automatically as you insert it, but changes to existing text may leave | |
1430 | it improperly filled. Then you must fill the text explicitly. | |
1431 | ||
1432 | Most of the commands in this section return values that are not | |
1433 | meaningful. All the functions that do filling take note of the current | |
1434 | left margin, current right margin, and current justification style | |
1435 | (@pxref{Margins}). If the current justification style is | |
1436 | @code{none}, the filling functions don't actually do anything. | |
1437 | ||
1438 | Several of the filling functions have an argument @var{justify}. | |
1439 | If it is non-@code{nil}, that requests some kind of justification. It | |
1440 | can be @code{left}, @code{right}, @code{full}, or @code{center}, to | |
1441 | request a specific style of justification. If it is @code{t}, that | |
1442 | means to use the current justification style for this part of the text | |
1443 | (see @code{current-justification}, below). Any other value is treated | |
1444 | as @code{full}. | |
1445 | ||
1446 | When you call the filling functions interactively, using a prefix | |
1447 | argument implies the value @code{full} for @var{justify}. | |
1448 | ||
65ced25f | 1449 | @deffn Command fill-paragraph &optional justify region |
b8d4c8d0 GM |
1450 | This command fills the paragraph at or after point. If |
1451 | @var{justify} is non-@code{nil}, each line is justified as well. | |
1452 | It uses the ordinary paragraph motion commands to find paragraph | |
1453 | boundaries. @xref{Paragraphs,,, emacs, The GNU Emacs Manual}. | |
2bad3299 CY |
1454 | |
1455 | When @var{region} is non-@code{nil}, then if Transient Mark mode is | |
1456 | enabled and the mark is active, this command calls @code{fill-region} | |
1457 | to fill all the paragraphs in the region, instead of filling only the | |
1458 | current paragraph. When this command is called interactively, | |
1459 | @var{region} is @code{t}. | |
b8d4c8d0 GM |
1460 | @end deffn |
1461 | ||
1462 | @deffn Command fill-region start end &optional justify nosqueeze to-eop | |
1463 | This command fills each of the paragraphs in the region from @var{start} | |
1464 | to @var{end}. It justifies as well if @var{justify} is | |
1465 | non-@code{nil}. | |
1466 | ||
1467 | If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace | |
1468 | other than line breaks untouched. If @var{to-eop} is non-@code{nil}, | |
1469 | that means to keep filling to the end of the paragraph---or the next hard | |
1470 | newline, if @code{use-hard-newlines} is enabled (see below). | |
1471 | ||
1472 | The variable @code{paragraph-separate} controls how to distinguish | |
1473 | paragraphs. @xref{Standard Regexps}. | |
1474 | @end deffn | |
1475 | ||
1476 | @deffn Command fill-individual-paragraphs start end &optional justify citation-regexp | |
1477 | This command fills each paragraph in the region according to its | |
1478 | individual fill prefix. Thus, if the lines of a paragraph were indented | |
1479 | with spaces, the filled paragraph will remain indented in the same | |
1480 | fashion. | |
1481 | ||
1482 | The first two arguments, @var{start} and @var{end}, are the beginning | |
1483 | and end of the region to be filled. The third and fourth arguments, | |
1484 | @var{justify} and @var{citation-regexp}, are optional. If | |
1485 | @var{justify} is non-@code{nil}, the paragraphs are justified as | |
1486 | well as filled. If @var{citation-regexp} is non-@code{nil}, it means the | |
1487 | function is operating on a mail message and therefore should not fill | |
1488 | the header lines. If @var{citation-regexp} is a string, it is used as | |
1489 | a regular expression; if it matches the beginning of a line, that line | |
1490 | is treated as a citation marker. | |
1491 | ||
1492 | Ordinarily, @code{fill-individual-paragraphs} regards each change in | |
1493 | indentation as starting a new paragraph. If | |
1494 | @code{fill-individual-varying-indent} is non-@code{nil}, then only | |
1495 | separator lines separate paragraphs. That mode can handle indented | |
1496 | paragraphs with additional indentation on the first line. | |
1497 | @end deffn | |
1498 | ||
1499 | @defopt fill-individual-varying-indent | |
1500 | This variable alters the action of @code{fill-individual-paragraphs} as | |
1501 | described above. | |
1502 | @end defopt | |
1503 | ||
1504 | @deffn Command fill-region-as-paragraph start end &optional justify nosqueeze squeeze-after | |
1505 | This command considers a region of text as a single paragraph and fills | |
1506 | it. If the region was made up of many paragraphs, the blank lines | |
1507 | between paragraphs are removed. This function justifies as well as | |
1508 | filling when @var{justify} is non-@code{nil}. | |
1509 | ||
1510 | If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace | |
1511 | other than line breaks untouched. If @var{squeeze-after} is | |
1512 | non-@code{nil}, it specifies a position in the region, and means don't | |
1513 | canonicalize spaces before that position. | |
1514 | ||
1515 | In Adaptive Fill mode, this command calls @code{fill-context-prefix} to | |
1516 | choose a fill prefix by default. @xref{Adaptive Fill}. | |
1517 | @end deffn | |
1518 | ||
1519 | @deffn Command justify-current-line &optional how eop nosqueeze | |
1520 | This command inserts spaces between the words of the current line so | |
1521 | that the line ends exactly at @code{fill-column}. It returns | |
1522 | @code{nil}. | |
1523 | ||
1524 | The argument @var{how}, if non-@code{nil} specifies explicitly the style | |
1525 | of justification. It can be @code{left}, @code{right}, @code{full}, | |
1526 | @code{center}, or @code{none}. If it is @code{t}, that means to do | |
1527 | follow specified justification style (see @code{current-justification}, | |
1528 | below). @code{nil} means to do full justification. | |
1529 | ||
1530 | If @var{eop} is non-@code{nil}, that means do only left-justification | |
1531 | if @code{current-justification} specifies full justification. This is | |
1532 | used for the last line of a paragraph; even if the paragraph as a | |
1533 | whole is fully justified, the last line should not be. | |
1534 | ||
1535 | If @var{nosqueeze} is non-@code{nil}, that means do not change interior | |
1536 | whitespace. | |
1537 | @end deffn | |
1538 | ||
1539 | @defopt default-justification | |
1540 | This variable's value specifies the style of justification to use for | |
1541 | text that doesn't specify a style with a text property. The possible | |
1542 | values are @code{left}, @code{right}, @code{full}, @code{center}, or | |
1543 | @code{none}. The default value is @code{left}. | |
1544 | @end defopt | |
1545 | ||
1546 | @defun current-justification | |
1547 | This function returns the proper justification style to use for filling | |
1548 | the text around point. | |
1549 | ||
1550 | This returns the value of the @code{justification} text property at | |
1551 | point, or the variable @var{default-justification} if there is no such | |
1552 | text property. However, it returns @code{nil} rather than @code{none} | |
1553 | to mean ``don't justify''. | |
1554 | @end defun | |
1555 | ||
1556 | @defopt sentence-end-double-space | |
1557 | @anchor{Definition of sentence-end-double-space} | |
1558 | If this variable is non-@code{nil}, a period followed by just one space | |
1559 | does not count as the end of a sentence, and the filling functions | |
1560 | avoid breaking the line at such a place. | |
1561 | @end defopt | |
1562 | ||
1563 | @defopt sentence-end-without-period | |
1564 | If this variable is non-@code{nil}, a sentence can end without a | |
1565 | period. This is used for languages like Thai, where sentences end | |
1566 | with a double space but without a period. | |
1567 | @end defopt | |
1568 | ||
1569 | @defopt sentence-end-without-space | |
1570 | If this variable is non-@code{nil}, it should be a string of | |
1571 | characters that can end a sentence without following spaces. | |
1572 | @end defopt | |
1573 | ||
1574 | @defvar fill-paragraph-function | |
2bad3299 CY |
1575 | This variable provides a way to override the filling of paragraphs. |
1576 | If its value is non-@code{nil}, @code{fill-paragraph} calls this | |
1577 | function to do the work. If the function returns a non-@code{nil} | |
b8d4c8d0 GM |
1578 | value, @code{fill-paragraph} assumes the job is done, and immediately |
1579 | returns that value. | |
1580 | ||
1581 | The usual use of this feature is to fill comments in programming | |
1582 | language modes. If the function needs to fill a paragraph in the usual | |
1583 | way, it can do so as follows: | |
1584 | ||
1585 | @example | |
1586 | (let ((fill-paragraph-function nil)) | |
1587 | (fill-paragraph arg)) | |
1588 | @end example | |
1589 | @end defvar | |
1590 | ||
2bad3299 CY |
1591 | @defvar fill-forward-paragraph-function |
1592 | This variable provides a way to override how the filling functions, | |
1593 | such as @code{fill-region} and @code{fill-paragraph}, move forward to | |
1594 | the next paragraph. Its value should be a function, which is called | |
1595 | with a single argument @var{n}, the number of paragraphs to move, and | |
1596 | should return the difference between @var{n} and the number of | |
1597 | paragraphs actually moved. The default value of this variable is | |
1598 | @code{forward-paragraph}. @xref{Paragraphs,,, emacs, The GNU Emacs | |
1599 | Manual}. | |
1600 | @end defvar | |
1601 | ||
b8d4c8d0 GM |
1602 | @defvar use-hard-newlines |
1603 | If this variable is non-@code{nil}, the filling functions do not delete | |
1604 | newlines that have the @code{hard} text property. These ``hard | |
1605 | newlines'' act as paragraph separators. | |
1606 | @end defvar | |
1607 | ||
1608 | @node Margins | |
1609 | @section Margins for Filling | |
1610 | ||
1611 | @defopt fill-prefix | |
1612 | This buffer-local variable, if non-@code{nil}, specifies a string of | |
1613 | text that appears at the beginning of normal text lines and should be | |
1614 | disregarded when filling them. Any line that fails to start with the | |
1615 | fill prefix is considered the start of a paragraph; so is any line | |
1616 | that starts with the fill prefix followed by additional whitespace. | |
1617 | Lines that start with the fill prefix but no additional whitespace are | |
1618 | ordinary text lines that can be filled together. The resulting filled | |
1619 | lines also start with the fill prefix. | |
1620 | ||
1621 | The fill prefix follows the left margin whitespace, if any. | |
1622 | @end defopt | |
1623 | ||
1624 | @defopt fill-column | |
1625 | This buffer-local variable specifies the maximum width of filled lines. | |
1626 | Its value should be an integer, which is a number of columns. All the | |
1627 | filling, justification, and centering commands are affected by this | |
1628 | variable, including Auto Fill mode (@pxref{Auto Filling}). | |
1629 | ||
1630 | As a practical matter, if you are writing text for other people to | |
1631 | read, you should set @code{fill-column} to no more than 70. Otherwise | |
1632 | the line will be too long for people to read comfortably, and this can | |
1633 | make the text seem clumsy. | |
b8d4c8d0 | 1634 | |
4e3b4528 SM |
1635 | The default value for @code{fill-column} is 70. |
1636 | @end defopt | |
b8d4c8d0 GM |
1637 | |
1638 | @deffn Command set-left-margin from to margin | |
1639 | This sets the @code{left-margin} property on the text from @var{from} to | |
1640 | @var{to} to the value @var{margin}. If Auto Fill mode is enabled, this | |
1641 | command also refills the region to fit the new margin. | |
1642 | @end deffn | |
1643 | ||
1644 | @deffn Command set-right-margin from to margin | |
1645 | This sets the @code{right-margin} property on the text from @var{from} | |
1646 | to @var{to} to the value @var{margin}. If Auto Fill mode is enabled, | |
1647 | this command also refills the region to fit the new margin. | |
1648 | @end deffn | |
1649 | ||
1650 | @defun current-left-margin | |
1651 | This function returns the proper left margin value to use for filling | |
1652 | the text around point. The value is the sum of the @code{left-margin} | |
1653 | property of the character at the start of the current line (or zero if | |
1654 | none), and the value of the variable @code{left-margin}. | |
1655 | @end defun | |
1656 | ||
1657 | @defun current-fill-column | |
1658 | This function returns the proper fill column value to use for filling | |
1659 | the text around point. The value is the value of the @code{fill-column} | |
1660 | variable, minus the value of the @code{right-margin} property of the | |
1661 | character after point. | |
1662 | @end defun | |
1663 | ||
1664 | @deffn Command move-to-left-margin &optional n force | |
1665 | This function moves point to the left margin of the current line. The | |
1666 | column moved to is determined by calling the function | |
1667 | @code{current-left-margin}. If the argument @var{n} is non-@code{nil}, | |
1668 | @code{move-to-left-margin} moves forward @var{n}@minus{}1 lines first. | |
1669 | ||
1670 | If @var{force} is non-@code{nil}, that says to fix the line's | |
1671 | indentation if that doesn't match the left margin value. | |
1672 | @end deffn | |
1673 | ||
1674 | @defun delete-to-left-margin &optional from to | |
1675 | This function removes left margin indentation from the text between | |
1676 | @var{from} and @var{to}. The amount of indentation to delete is | |
1677 | determined by calling @code{current-left-margin}. In no case does this | |
1678 | function delete non-whitespace. If @var{from} and @var{to} are omitted, | |
1679 | they default to the whole buffer. | |
1680 | @end defun | |
1681 | ||
1682 | @defun indent-to-left-margin | |
1683 | This function adjusts the indentation at the beginning of the current | |
1684 | line to the value specified by the variable @code{left-margin}. (That | |
1685 | may involve either inserting or deleting whitespace.) This function | |
1686 | is value of @code{indent-line-function} in Paragraph-Indent Text mode. | |
1687 | @end defun | |
1688 | ||
01f17ae2 | 1689 | @defopt left-margin |
b8d4c8d0 GM |
1690 | This variable specifies the base left margin column. In Fundamental |
1691 | mode, @kbd{C-j} indents to this column. This variable automatically | |
1692 | becomes buffer-local when set in any fashion. | |
01f17ae2 | 1693 | @end defopt |
b8d4c8d0 | 1694 | |
01f17ae2 | 1695 | @defopt fill-nobreak-predicate |
b8d4c8d0 GM |
1696 | This variable gives major modes a way to specify not to break a line |
1697 | at certain places. Its value should be a list of functions. Whenever | |
1698 | filling considers breaking the line at a certain place in the buffer, | |
1699 | it calls each of these functions with no arguments and with point | |
1700 | located at that place. If any of the functions returns | |
1701 | non-@code{nil}, then the line won't be broken there. | |
01f17ae2 | 1702 | @end defopt |
b8d4c8d0 GM |
1703 | |
1704 | @node Adaptive Fill | |
1705 | @section Adaptive Fill Mode | |
1706 | @c @cindex Adaptive Fill mode "adaptive-fill-mode" is adjacent. | |
1707 | ||
1708 | When @dfn{Adaptive Fill Mode} is enabled, Emacs determines the fill | |
1709 | prefix automatically from the text in each paragraph being filled | |
1710 | rather than using a predetermined value. During filling, this fill | |
1711 | prefix gets inserted at the start of the second and subsequent lines | |
1712 | of the paragraph as described in @ref{Filling}, and in @ref{Auto | |
1713 | Filling}. | |
1714 | ||
1715 | @defopt adaptive-fill-mode | |
1716 | Adaptive Fill mode is enabled when this variable is non-@code{nil}. | |
1717 | It is @code{t} by default. | |
1718 | @end defopt | |
1719 | ||
1720 | @defun fill-context-prefix from to | |
1721 | This function implements the heart of Adaptive Fill mode; it chooses a | |
1722 | fill prefix based on the text between @var{from} and @var{to}, | |
1723 | typically the start and end of a paragraph. It does this by looking | |
1724 | at the first two lines of the paragraph, based on the variables | |
1725 | described below. | |
1726 | @c The optional argument first-line-regexp is not documented | |
1727 | @c because it exists for internal purposes and might be eliminated | |
1728 | @c in the future. | |
1729 | ||
1730 | Usually, this function returns the fill prefix, a string. However, | |
1731 | before doing this, the function makes a final check (not specially | |
1732 | mentioned in the following) that a line starting with this prefix | |
1733 | wouldn't look like the start of a paragraph. Should this happen, the | |
1734 | function signals the anomaly by returning @code{nil} instead. | |
1735 | ||
1736 | In detail, @code{fill-context-prefix} does this: | |
1737 | ||
1738 | @enumerate | |
1739 | @item | |
1740 | It takes a candidate for the fill prefix from the first line---it | |
1741 | tries first the function in @code{adaptive-fill-function} (if any), | |
1742 | then the regular expression @code{adaptive-fill-regexp} (see below). | |
1743 | The first non-@code{nil} result of these, or the empty string if | |
1744 | they're both @code{nil}, becomes the first line's candidate. | |
1745 | @item | |
1746 | If the paragraph has as yet only one line, the function tests the | |
1747 | validity of the prefix candidate just found. The function then | |
1748 | returns the candidate if it's valid, or a string of spaces otherwise. | |
1749 | (see the description of @code{adaptive-fill-first-line-regexp} below). | |
1750 | @item | |
1751 | When the paragraph already has two lines, the function next looks for | |
1752 | a prefix candidate on the second line, in just the same way it did for | |
1753 | the first line. If it doesn't find one, it returns @code{nil}. | |
1754 | @item | |
1755 | The function now compares the two candidate prefixes heuristically: if | |
1756 | the non-whitespace characters in the line 2 candidate occur in the | |
1757 | same order in the line 1 candidate, the function returns the line 2 | |
1758 | candidate. Otherwise, it returns the largest initial substring which | |
1759 | is common to both candidates (which might be the empty string). | |
1760 | @end enumerate | |
1761 | @end defun | |
1762 | ||
1763 | @defopt adaptive-fill-regexp | |
1764 | Adaptive Fill mode matches this regular expression against the text | |
1765 | starting after the left margin whitespace (if any) on a line; the | |
1766 | characters it matches are that line's candidate for the fill prefix. | |
1767 | ||
1768 | The default value matches whitespace with certain punctuation | |
1769 | characters intermingled. | |
1770 | @end defopt | |
1771 | ||
1772 | @defopt adaptive-fill-first-line-regexp | |
1773 | Used only in one-line paragraphs, this regular expression acts as an | |
1774 | additional check of the validity of the one available candidate fill | |
1775 | prefix: the candidate must match this regular expression, or match | |
1776 | @code{comment-start-skip}. If it doesn't, @code{fill-context-prefix} | |
1777 | replaces the candidate with a string of spaces ``of the same width'' | |
1778 | as it. | |
1779 | ||
1780 | The default value of this variable is @w{@code{"\\`[ \t]*\\'"}}, which | |
1781 | matches only a string of whitespace. The effect of this default is to | |
1782 | force the fill prefixes found in one-line paragraphs always to be pure | |
1783 | whitespace. | |
1784 | @end defopt | |
1785 | ||
1786 | @defopt adaptive-fill-function | |
1787 | You can specify more complex ways of choosing a fill prefix | |
1788 | automatically by setting this variable to a function. The function is | |
1789 | called with point after the left margin (if any) of a line, and it | |
1790 | must preserve point. It should return either ``that line's'' fill | |
1791 | prefix or @code{nil}, meaning it has failed to determine a prefix. | |
1792 | @end defopt | |
1793 | ||
1794 | @node Auto Filling | |
1795 | @comment node-name, next, previous, up | |
1796 | @section Auto Filling | |
1797 | @cindex filling, automatic | |
1798 | @cindex Auto Fill mode | |
1799 | ||
1800 | Auto Fill mode is a minor mode that fills lines automatically as text | |
1801 | is inserted. This section describes the hook used by Auto Fill mode. | |
1802 | For a description of functions that you can call explicitly to fill and | |
1803 | justify existing text, see @ref{Filling}. | |
1804 | ||
1805 | Auto Fill mode also enables the functions that change the margins and | |
1806 | justification style to refill portions of the text. @xref{Margins}. | |
1807 | ||
1808 | @defvar auto-fill-function | |
1809 | The value of this buffer-local variable should be a function (of no | |
1810 | arguments) to be called after self-inserting a character from the table | |
1811 | @code{auto-fill-chars}. It may be @code{nil}, in which case nothing | |
1812 | special is done in that case. | |
1813 | ||
1814 | The value of @code{auto-fill-function} is @code{do-auto-fill} when | |
1815 | Auto-Fill mode is enabled. That is a function whose sole purpose is to | |
1816 | implement the usual strategy for breaking a line. | |
1817 | ||
1818 | @quotation | |
1819 | In older Emacs versions, this variable was named @code{auto-fill-hook}, | |
1820 | but since it is not called with the standard convention for hooks, it | |
1821 | was renamed to @code{auto-fill-function} in version 19. | |
1822 | @end quotation | |
1823 | @end defvar | |
1824 | ||
1825 | @defvar normal-auto-fill-function | |
1826 | This variable specifies the function to use for | |
1827 | @code{auto-fill-function}, if and when Auto Fill is turned on. Major | |
1828 | modes can set buffer-local values for this variable to alter how Auto | |
1829 | Fill works. | |
1830 | @end defvar | |
1831 | ||
1832 | @defvar auto-fill-chars | |
1833 | A char table of characters which invoke @code{auto-fill-function} when | |
1834 | self-inserted---space and newline in most language environments. They | |
1835 | have an entry @code{t} in the table. | |
1836 | @end defvar | |
1837 | ||
1838 | @node Sorting | |
1839 | @section Sorting Text | |
1840 | @cindex sorting text | |
1841 | ||
1842 | The sorting functions described in this section all rearrange text in | |
1843 | a buffer. This is in contrast to the function @code{sort}, which | |
1844 | rearranges the order of the elements of a list (@pxref{Rearrangement}). | |
1845 | The values returned by these functions are not meaningful. | |
1846 | ||
1847 | @defun sort-subr reverse nextrecfun endrecfun &optional startkeyfun endkeyfun predicate | |
1848 | This function is the general text-sorting routine that subdivides a | |
1849 | buffer into records and then sorts them. Most of the commands in this | |
1850 | section use this function. | |
1851 | ||
1852 | To understand how @code{sort-subr} works, consider the whole accessible | |
1853 | portion of the buffer as being divided into disjoint pieces called | |
1854 | @dfn{sort records}. The records may or may not be contiguous, but they | |
1855 | must not overlap. A portion of each sort record (perhaps all of it) is | |
1856 | designated as the sort key. Sorting rearranges the records in order by | |
1857 | their sort keys. | |
1858 | ||
1859 | Usually, the records are rearranged in order of ascending sort key. | |
1860 | If the first argument to the @code{sort-subr} function, @var{reverse}, | |
1861 | is non-@code{nil}, the sort records are rearranged in order of | |
1862 | descending sort key. | |
1863 | ||
1864 | The next four arguments to @code{sort-subr} are functions that are | |
1865 | called to move point across a sort record. They are called many times | |
1866 | from within @code{sort-subr}. | |
1867 | ||
1868 | @enumerate | |
1869 | @item | |
1870 | @var{nextrecfun} is called with point at the end of a record. This | |
1871 | function moves point to the start of the next record. The first record | |
1872 | is assumed to start at the position of point when @code{sort-subr} is | |
1873 | called. Therefore, you should usually move point to the beginning of | |
1874 | the buffer before calling @code{sort-subr}. | |
1875 | ||
1876 | This function can indicate there are no more sort records by leaving | |
1877 | point at the end of the buffer. | |
1878 | ||
1879 | @item | |
1880 | @var{endrecfun} is called with point within a record. It moves point to | |
1881 | the end of the record. | |
1882 | ||
1883 | @item | |
1884 | @var{startkeyfun} is called to move point from the start of a record to | |
1885 | the start of the sort key. This argument is optional; if it is omitted, | |
1886 | the whole record is the sort key. If supplied, the function should | |
1887 | either return a non-@code{nil} value to be used as the sort key, or | |
1888 | return @code{nil} to indicate that the sort key is in the buffer | |
1889 | starting at point. In the latter case, @var{endkeyfun} is called to | |
1890 | find the end of the sort key. | |
1891 | ||
1892 | @item | |
1893 | @var{endkeyfun} is called to move point from the start of the sort key | |
1894 | to the end of the sort key. This argument is optional. If | |
1895 | @var{startkeyfun} returns @code{nil} and this argument is omitted (or | |
1896 | @code{nil}), then the sort key extends to the end of the record. There | |
1897 | is no need for @var{endkeyfun} if @var{startkeyfun} returns a | |
1898 | non-@code{nil} value. | |
1899 | @end enumerate | |
1900 | ||
1901 | The argument @var{predicate} is the function to use to compare keys. | |
1902 | If keys are numbers, it defaults to @code{<}; otherwise it defaults to | |
1903 | @code{string<}. | |
1904 | ||
1905 | As an example of @code{sort-subr}, here is the complete function | |
1906 | definition for @code{sort-lines}: | |
1907 | ||
1908 | @example | |
1909 | @group | |
1910 | ;; @r{Note that the first two lines of doc string} | |
1911 | ;; @r{are effectively one line when viewed by a user.} | |
1912 | (defun sort-lines (reverse beg end) | |
1913 | "Sort lines in region alphabetically;\ | |
1914 | argument means descending order. | |
1915 | Called from a program, there are three arguments: | |
1916 | @end group | |
1917 | @group | |
1918 | REVERSE (non-nil means reverse order),\ | |
1919 | BEG and END (region to sort). | |
1920 | The variable `sort-fold-case' determines\ | |
1921 | whether alphabetic case affects | |
1922 | the sort order." | |
1923 | @end group | |
1924 | @group | |
1925 | (interactive "P\nr") | |
1926 | (save-excursion | |
1927 | (save-restriction | |
1928 | (narrow-to-region beg end) | |
1929 | (goto-char (point-min)) | |
1930 | (let ((inhibit-field-text-motion t)) | |
1931 | (sort-subr reverse 'forward-line 'end-of-line))))) | |
1932 | @end group | |
1933 | @end example | |
1934 | ||
1935 | Here @code{forward-line} moves point to the start of the next record, | |
1936 | and @code{end-of-line} moves point to the end of record. We do not pass | |
1937 | the arguments @var{startkeyfun} and @var{endkeyfun}, because the entire | |
1938 | record is used as the sort key. | |
1939 | ||
1940 | The @code{sort-paragraphs} function is very much the same, except that | |
1941 | its @code{sort-subr} call looks like this: | |
1942 | ||
1943 | @example | |
1944 | @group | |
1945 | (sort-subr reverse | |
1946 | (function | |
1947 | (lambda () | |
1948 | (while (and (not (eobp)) | |
1949 | (looking-at paragraph-separate)) | |
1950 | (forward-line 1)))) | |
1951 | 'forward-paragraph) | |
1952 | @end group | |
1953 | @end example | |
1954 | ||
1955 | Markers pointing into any sort records are left with no useful | |
1956 | position after @code{sort-subr} returns. | |
1957 | @end defun | |
1958 | ||
1959 | @defopt sort-fold-case | |
1960 | If this variable is non-@code{nil}, @code{sort-subr} and the other | |
1961 | buffer sorting functions ignore case when comparing strings. | |
1962 | @end defopt | |
1963 | ||
1964 | @deffn Command sort-regexp-fields reverse record-regexp key-regexp start end | |
1965 | This command sorts the region between @var{start} and @var{end} | |
1966 | alphabetically as specified by @var{record-regexp} and @var{key-regexp}. | |
1967 | If @var{reverse} is a negative integer, then sorting is in reverse | |
1968 | order. | |
1969 | ||
1970 | Alphabetical sorting means that two sort keys are compared by | |
1971 | comparing the first characters of each, the second characters of each, | |
1972 | and so on. If a mismatch is found, it means that the sort keys are | |
1973 | unequal; the sort key whose character is less at the point of first | |
1974 | mismatch is the lesser sort key. The individual characters are compared | |
1975 | according to their numerical character codes in the Emacs character set. | |
1976 | ||
1977 | The value of the @var{record-regexp} argument specifies how to divide | |
1978 | the buffer into sort records. At the end of each record, a search is | |
1979 | done for this regular expression, and the text that matches it is taken | |
1980 | as the next record. For example, the regular expression @samp{^.+$}, | |
1981 | which matches lines with at least one character besides a newline, would | |
1982 | make each such line into a sort record. @xref{Regular Expressions}, for | |
1983 | a description of the syntax and meaning of regular expressions. | |
1984 | ||
1985 | The value of the @var{key-regexp} argument specifies what part of each | |
1986 | record is the sort key. The @var{key-regexp} could match the whole | |
1987 | record, or only a part. In the latter case, the rest of the record has | |
1988 | no effect on the sorted order of records, but it is carried along when | |
1989 | the record moves to its new position. | |
1990 | ||
1991 | The @var{key-regexp} argument can refer to the text matched by a | |
1992 | subexpression of @var{record-regexp}, or it can be a regular expression | |
1993 | on its own. | |
1994 | ||
1995 | If @var{key-regexp} is: | |
1996 | ||
1997 | @table @asis | |
1998 | @item @samp{\@var{digit}} | |
1999 | then the text matched by the @var{digit}th @samp{\(...\)} parenthesis | |
2000 | grouping in @var{record-regexp} is the sort key. | |
2001 | ||
2002 | @item @samp{\&} | |
2003 | then the whole record is the sort key. | |
2004 | ||
2005 | @item a regular expression | |
2006 | then @code{sort-regexp-fields} searches for a match for the regular | |
2007 | expression within the record. If such a match is found, it is the sort | |
2008 | key. If there is no match for @var{key-regexp} within a record then | |
2009 | that record is ignored, which means its position in the buffer is not | |
2010 | changed. (The other records may move around it.) | |
2011 | @end table | |
2012 | ||
2013 | For example, if you plan to sort all the lines in the region by the | |
2014 | first word on each line starting with the letter @samp{f}, you should | |
2015 | set @var{record-regexp} to @samp{^.*$} and set @var{key-regexp} to | |
2016 | @samp{\<f\w*\>}. The resulting expression looks like this: | |
2017 | ||
2018 | @example | |
2019 | @group | |
2020 | (sort-regexp-fields nil "^.*$" "\\<f\\w*\\>" | |
2021 | (region-beginning) | |
2022 | (region-end)) | |
2023 | @end group | |
2024 | @end example | |
2025 | ||
2026 | If you call @code{sort-regexp-fields} interactively, it prompts for | |
2027 | @var{record-regexp} and @var{key-regexp} in the minibuffer. | |
2028 | @end deffn | |
2029 | ||
2030 | @deffn Command sort-lines reverse start end | |
2031 | This command alphabetically sorts lines in the region between | |
2032 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort | |
2033 | is in reverse order. | |
2034 | @end deffn | |
2035 | ||
2036 | @deffn Command sort-paragraphs reverse start end | |
2037 | This command alphabetically sorts paragraphs in the region between | |
2038 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort | |
2039 | is in reverse order. | |
2040 | @end deffn | |
2041 | ||
2042 | @deffn Command sort-pages reverse start end | |
2043 | This command alphabetically sorts pages in the region between | |
2044 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort | |
2045 | is in reverse order. | |
2046 | @end deffn | |
2047 | ||
2048 | @deffn Command sort-fields field start end | |
2049 | This command sorts lines in the region between @var{start} and | |
2050 | @var{end}, comparing them alphabetically by the @var{field}th field | |
2051 | of each line. Fields are separated by whitespace and numbered starting | |
2052 | from 1. If @var{field} is negative, sorting is by the | |
2053 | @w{@minus{}@var{field}th} field from the end of the line. This command | |
2054 | is useful for sorting tables. | |
2055 | @end deffn | |
2056 | ||
2057 | @deffn Command sort-numeric-fields field start end | |
2058 | This command sorts lines in the region between @var{start} and | |
2059 | @var{end}, comparing them numerically by the @var{field}th field of | |
2060 | each line. Fields are separated by whitespace and numbered starting | |
2061 | from 1. The specified field must contain a number in each line of the | |
2062 | region. Numbers starting with 0 are treated as octal, and numbers | |
2063 | starting with @samp{0x} are treated as hexadecimal. | |
2064 | ||
2065 | If @var{field} is negative, sorting is by the | |
2066 | @w{@minus{}@var{field}th} field from the end of the line. This | |
2067 | command is useful for sorting tables. | |
2068 | @end deffn | |
2069 | ||
2070 | @defopt sort-numeric-base | |
2071 | This variable specifies the default radix for | |
2072 | @code{sort-numeric-fields} to parse numbers. | |
2073 | @end defopt | |
2074 | ||
2075 | @deffn Command sort-columns reverse &optional beg end | |
2076 | This command sorts the lines in the region between @var{beg} and | |
2077 | @var{end}, comparing them alphabetically by a certain range of | |
2078 | columns. The column positions of @var{beg} and @var{end} bound the | |
2079 | range of columns to sort on. | |
2080 | ||
2081 | If @var{reverse} is non-@code{nil}, the sort is in reverse order. | |
2082 | ||
2083 | One unusual thing about this command is that the entire line | |
2084 | containing position @var{beg}, and the entire line containing position | |
2085 | @var{end}, are included in the region sorted. | |
2086 | ||
2087 | Note that @code{sort-columns} rejects text that contains tabs, because | |
2088 | tabs could be split across the specified columns. Use @kbd{M-x | |
2089 | untabify} to convert tabs to spaces before sorting. | |
2090 | ||
2091 | When possible, this command actually works by calling the @code{sort} | |
2092 | utility program. | |
2093 | @end deffn | |
2094 | ||
2095 | @node Columns | |
2096 | @comment node-name, next, previous, up | |
2097 | @section Counting Columns | |
2098 | @cindex columns | |
2099 | @cindex counting columns | |
2100 | @cindex horizontal position | |
2101 | ||
2102 | The column functions convert between a character position (counting | |
2103 | characters from the beginning of the buffer) and a column position | |
2104 | (counting screen characters from the beginning of a line). | |
2105 | ||
2106 | These functions count each character according to the number of | |
2107 | columns it occupies on the screen. This means control characters count | |
2108 | as occupying 2 or 4 columns, depending upon the value of | |
2109 | @code{ctl-arrow}, and tabs count as occupying a number of columns that | |
2110 | depends on the value of @code{tab-width} and on the column where the tab | |
2111 | begins. @xref{Usual Display}. | |
2112 | ||
2113 | Column number computations ignore the width of the window and the | |
2114 | amount of horizontal scrolling. Consequently, a column value can be | |
2115 | arbitrarily high. The first (or leftmost) column is numbered 0. They | |
2116 | also ignore overlays and text properties, aside from invisibility. | |
2117 | ||
2118 | @defun current-column | |
2119 | This function returns the horizontal position of point, measured in | |
2120 | columns, counting from 0 at the left margin. The column position is the | |
2121 | sum of the widths of all the displayed representations of the characters | |
2122 | between the start of the current line and point. | |
2123 | ||
2124 | For an example of using @code{current-column}, see the description of | |
2125 | @code{count-lines} in @ref{Text Lines}. | |
2126 | @end defun | |
2127 | ||
106e6894 | 2128 | @deffn Command move-to-column column &optional force |
b8d4c8d0 GM |
2129 | This function moves point to @var{column} in the current line. The |
2130 | calculation of @var{column} takes into account the widths of the | |
2131 | displayed representations of the characters between the start of the | |
2132 | line and point. | |
2133 | ||
106e6894 CY |
2134 | When called interactively, @var{column} is the value of prefix numeric |
2135 | argument. If @var{column} is not an integer, an error is signaled. | |
2136 | ||
2137 | If column @var{column} is beyond the end of the line, point moves to | |
2138 | the end of the line. If @var{column} is negative, point moves to the | |
b8d4c8d0 GM |
2139 | beginning of the line. |
2140 | ||
2141 | If it is impossible to move to column @var{column} because that is in | |
2142 | the middle of a multicolumn character such as a tab, point moves to the | |
2143 | end of that character. However, if @var{force} is non-@code{nil}, and | |
2144 | @var{column} is in the middle of a tab, then @code{move-to-column} | |
2145 | converts the tab into spaces so that it can move precisely to column | |
2146 | @var{column}. Other multicolumn characters can cause anomalies despite | |
2147 | @var{force}, since there is no way to split them. | |
2148 | ||
2149 | The argument @var{force} also has an effect if the line isn't long | |
2150 | enough to reach column @var{column}; if it is @code{t}, that means to | |
2151 | add whitespace at the end of the line to reach that column. | |
2152 | ||
b8d4c8d0 | 2153 | The return value is the column number actually moved to. |
106e6894 | 2154 | @end deffn |
b8d4c8d0 GM |
2155 | |
2156 | @node Indentation | |
2157 | @section Indentation | |
2158 | @cindex indentation | |
2159 | ||
2160 | The indentation functions are used to examine, move to, and change | |
2161 | whitespace that is at the beginning of a line. Some of the functions | |
2162 | can also change whitespace elsewhere on a line. Columns and indentation | |
2163 | count from zero at the left margin. | |
2164 | ||
2165 | @menu | |
2166 | * Primitive Indent:: Functions used to count and insert indentation. | |
2167 | * Mode-Specific Indent:: Customize indentation for different modes. | |
2168 | * Region Indent:: Indent all the lines in a region. | |
2169 | * Relative Indent:: Indent the current line based on previous lines. | |
2170 | * Indent Tabs:: Adjustable, typewriter-like tab stops. | |
2171 | * Motion by Indent:: Move to first non-blank character. | |
2172 | @end menu | |
2173 | ||
2174 | @node Primitive Indent | |
2175 | @subsection Indentation Primitives | |
2176 | ||
2177 | This section describes the primitive functions used to count and | |
2178 | insert indentation. The functions in the following sections use these | |
2179 | primitives. @xref{Width}, for related functions. | |
2180 | ||
2181 | @defun current-indentation | |
2182 | @comment !!Type Primitive Function | |
2183 | @comment !!SourceFile indent.c | |
2184 | This function returns the indentation of the current line, which is | |
2185 | the horizontal position of the first nonblank character. If the | |
2186 | contents are entirely blank, then this is the horizontal position of the | |
2187 | end of the line. | |
2188 | @end defun | |
2189 | ||
2190 | @deffn Command indent-to column &optional minimum | |
2191 | @comment !!Type Primitive Function | |
2192 | @comment !!SourceFile indent.c | |
2193 | This function indents from point with tabs and spaces until @var{column} | |
2194 | is reached. If @var{minimum} is specified and non-@code{nil}, then at | |
2195 | least that many spaces are inserted even if this requires going beyond | |
2196 | @var{column}. Otherwise the function does nothing if point is already | |
2197 | beyond @var{column}. The value is the column at which the inserted | |
2198 | indentation ends. | |
2199 | ||
2200 | The inserted whitespace characters inherit text properties from the | |
2201 | surrounding text (usually, from the preceding text only). @xref{Sticky | |
2202 | Properties}. | |
2203 | @end deffn | |
2204 | ||
2205 | @defopt indent-tabs-mode | |
2206 | @comment !!SourceFile indent.c | |
2207 | If this variable is non-@code{nil}, indentation functions can insert | |
2208 | tabs as well as spaces. Otherwise, they insert only spaces. Setting | |
2209 | this variable automatically makes it buffer-local in the current buffer. | |
2210 | @end defopt | |
2211 | ||
2212 | @node Mode-Specific Indent | |
2213 | @subsection Indentation Controlled by Major Mode | |
2214 | ||
2215 | An important function of each major mode is to customize the @key{TAB} | |
2216 | key to indent properly for the language being edited. This section | |
2217 | describes the mechanism of the @key{TAB} key and how to control it. | |
2218 | The functions in this section return unpredictable values. | |
2219 | ||
2220 | @defvar indent-line-function | |
2221 | This variable's value is the function to be used by @key{TAB} (and | |
2222 | various commands) to indent the current line. The command | |
2223 | @code{indent-according-to-mode} does no more than call this function. | |
2224 | ||
2225 | In Lisp mode, the value is the symbol @code{lisp-indent-line}; in C | |
2226 | mode, @code{c-indent-line}; in Fortran mode, @code{fortran-indent-line}. | |
2227 | The default value is @code{indent-relative}. | |
2228 | @end defvar | |
2229 | ||
2230 | @deffn Command indent-according-to-mode | |
2231 | This command calls the function in @code{indent-line-function} to | |
2232 | indent the current line in a way appropriate for the current major mode. | |
2233 | @end deffn | |
2234 | ||
106e6894 CY |
2235 | @deffn Command indent-for-tab-command &optional rigid |
2236 | This command calls the function in @code{indent-line-function} to | |
2237 | indent the current line; however, if that function is | |
2238 | @code{indent-to-left-margin}, @code{insert-tab} is called instead. | |
2239 | (That is a trivial command that inserts a tab character.) If | |
2240 | @var{rigid} is non-@code{nil}, this function also rigidly indents the | |
2241 | entire balanced expression that starts at the beginning of the current | |
2242 | line, to reflect change in indentation of the current line. | |
b8d4c8d0 GM |
2243 | @end deffn |
2244 | ||
2245 | @deffn Command newline-and-indent | |
b8d4c8d0 GM |
2246 | This function inserts a newline, then indents the new line (the one |
2247 | following the newline just inserted) according to the major mode. | |
2248 | ||
2249 | It does indentation by calling the current @code{indent-line-function}. | |
2250 | In programming language modes, this is the same thing @key{TAB} does, | |
2251 | but in some text modes, where @key{TAB} inserts a tab, | |
2252 | @code{newline-and-indent} indents to the column specified by | |
2253 | @code{left-margin}. | |
2254 | @end deffn | |
2255 | ||
2256 | @deffn Command reindent-then-newline-and-indent | |
2257 | @comment !!SourceFile simple.el | |
2258 | This command reindents the current line, inserts a newline at point, | |
2259 | and then indents the new line (the one following the newline just | |
2260 | inserted). | |
2261 | ||
2262 | This command does indentation on both lines according to the current | |
2263 | major mode, by calling the current value of @code{indent-line-function}. | |
2264 | In programming language modes, this is the same thing @key{TAB} does, | |
2265 | but in some text modes, where @key{TAB} inserts a tab, | |
2266 | @code{reindent-then-newline-and-indent} indents to the column specified | |
2267 | by @code{left-margin}. | |
2268 | @end deffn | |
2269 | ||
2270 | @node Region Indent | |
2271 | @subsection Indenting an Entire Region | |
2272 | ||
2273 | This section describes commands that indent all the lines in the | |
2274 | region. They return unpredictable values. | |
2275 | ||
106e6894 | 2276 | @deffn Command indent-region start end &optional to-column |
b8d4c8d0 GM |
2277 | This command indents each nonblank line starting between @var{start} |
2278 | (inclusive) and @var{end} (exclusive). If @var{to-column} is | |
2279 | @code{nil}, @code{indent-region} indents each nonblank line by calling | |
2280 | the current mode's indentation function, the value of | |
2281 | @code{indent-line-function}. | |
2282 | ||
2283 | If @var{to-column} is non-@code{nil}, it should be an integer | |
2284 | specifying the number of columns of indentation; then this function | |
2285 | gives each line exactly that much indentation, by either adding or | |
2286 | deleting whitespace. | |
2287 | ||
2288 | If there is a fill prefix, @code{indent-region} indents each line | |
2289 | by making it start with the fill prefix. | |
2290 | @end deffn | |
2291 | ||
2292 | @defvar indent-region-function | |
2293 | The value of this variable is a function that can be used by | |
2294 | @code{indent-region} as a short cut. It should take two arguments, the | |
2295 | start and end of the region. You should design the function so | |
2296 | that it will produce the same results as indenting the lines of the | |
2297 | region one by one, but presumably faster. | |
2298 | ||
2299 | If the value is @code{nil}, there is no short cut, and | |
2300 | @code{indent-region} actually works line by line. | |
2301 | ||
2302 | A short-cut function is useful in modes such as C mode and Lisp mode, | |
2303 | where the @code{indent-line-function} must scan from the beginning of | |
2304 | the function definition: applying it to each line would be quadratic in | |
2305 | time. The short cut can update the scan information as it moves through | |
2306 | the lines indenting them; this takes linear time. In a mode where | |
2307 | indenting a line individually is fast, there is no need for a short cut. | |
2308 | ||
2309 | @code{indent-region} with a non-@code{nil} argument @var{to-column} has | |
2310 | a different meaning and does not use this variable. | |
2311 | @end defvar | |
2312 | ||
2313 | @deffn Command indent-rigidly start end count | |
b8d4c8d0 GM |
2314 | This command indents all lines starting between @var{start} |
2315 | (inclusive) and @var{end} (exclusive) sideways by @var{count} columns. | |
2316 | This ``preserves the shape'' of the affected region, moving it as a | |
2317 | rigid unit. Consequently, this command is useful not only for indenting | |
2318 | regions of unindented text, but also for indenting regions of formatted | |
2319 | code. | |
2320 | ||
2321 | For example, if @var{count} is 3, this command adds 3 columns of | |
2322 | indentation to each of the lines beginning in the region specified. | |
2323 | ||
2324 | In Mail mode, @kbd{C-c C-y} (@code{mail-yank-original}) uses | |
2325 | @code{indent-rigidly} to indent the text copied from the message being | |
2326 | replied to. | |
2327 | @end deffn | |
2328 | ||
106e6894 | 2329 | @deffn Command indent-code-rigidly start end columns &optional nochange-regexp |
b8d4c8d0 GM |
2330 | This is like @code{indent-rigidly}, except that it doesn't alter lines |
2331 | that start within strings or comments. | |
2332 | ||
2333 | In addition, it doesn't alter a line if @var{nochange-regexp} matches at | |
2334 | the beginning of the line (if @var{nochange-regexp} is non-@code{nil}). | |
106e6894 | 2335 | @end deffn |
b8d4c8d0 GM |
2336 | |
2337 | @node Relative Indent | |
2338 | @subsection Indentation Relative to Previous Lines | |
2339 | ||
2340 | This section describes two commands that indent the current line | |
2341 | based on the contents of previous lines. | |
2342 | ||
2343 | @deffn Command indent-relative &optional unindented-ok | |
2344 | This command inserts whitespace at point, extending to the same | |
2345 | column as the next @dfn{indent point} of the previous nonblank line. An | |
2346 | indent point is a non-whitespace character following whitespace. The | |
2347 | next indent point is the first one at a column greater than the current | |
2348 | column of point. For example, if point is underneath and to the left of | |
2349 | the first non-blank character of a line of text, it moves to that column | |
2350 | by inserting whitespace. | |
2351 | ||
2352 | If the previous nonblank line has no next indent point (i.e., none at a | |
2353 | great enough column position), @code{indent-relative} either does | |
2354 | nothing (if @var{unindented-ok} is non-@code{nil}) or calls | |
2355 | @code{tab-to-tab-stop}. Thus, if point is underneath and to the right | |
2356 | of the last column of a short line of text, this command ordinarily | |
2357 | moves point to the next tab stop by inserting whitespace. | |
2358 | ||
2359 | The return value of @code{indent-relative} is unpredictable. | |
2360 | ||
2361 | In the following example, point is at the beginning of the second | |
2362 | line: | |
2363 | ||
2364 | @example | |
2365 | @group | |
2366 | This line is indented twelve spaces. | |
2367 | @point{}The quick brown fox jumped. | |
2368 | @end group | |
2369 | @end example | |
2370 | ||
2371 | @noindent | |
2372 | Evaluation of the expression @code{(indent-relative nil)} produces the | |
2373 | following: | |
2374 | ||
2375 | @example | |
2376 | @group | |
2377 | This line is indented twelve spaces. | |
2378 | @point{}The quick brown fox jumped. | |
2379 | @end group | |
2380 | @end example | |
2381 | ||
2382 | In this next example, point is between the @samp{m} and @samp{p} of | |
2383 | @samp{jumped}: | |
2384 | ||
2385 | @example | |
2386 | @group | |
2387 | This line is indented twelve spaces. | |
2388 | The quick brown fox jum@point{}ped. | |
2389 | @end group | |
2390 | @end example | |
2391 | ||
2392 | @noindent | |
2393 | Evaluation of the expression @code{(indent-relative nil)} produces the | |
2394 | following: | |
2395 | ||
2396 | @example | |
2397 | @group | |
2398 | This line is indented twelve spaces. | |
2399 | The quick brown fox jum @point{}ped. | |
2400 | @end group | |
2401 | @end example | |
2402 | @end deffn | |
2403 | ||
2404 | @deffn Command indent-relative-maybe | |
2405 | @comment !!SourceFile indent.el | |
2406 | This command indents the current line like the previous nonblank line, | |
2407 | by calling @code{indent-relative} with @code{t} as the | |
2408 | @var{unindented-ok} argument. The return value is unpredictable. | |
2409 | ||
2410 | If the previous nonblank line has no indent points beyond the current | |
2411 | column, this command does nothing. | |
2412 | @end deffn | |
2413 | ||
2414 | @node Indent Tabs | |
2415 | @comment node-name, next, previous, up | |
2416 | @subsection Adjustable ``Tab Stops'' | |
2417 | @cindex tabs stops for indentation | |
2418 | ||
2419 | This section explains the mechanism for user-specified ``tab stops'' | |
2420 | and the mechanisms that use and set them. The name ``tab stops'' is | |
2421 | used because the feature is similar to that of the tab stops on a | |
2422 | typewriter. The feature works by inserting an appropriate number of | |
2423 | spaces and tab characters to reach the next tab stop column; it does not | |
2424 | affect the display of tab characters in the buffer (@pxref{Usual | |
2425 | Display}). Note that the @key{TAB} character as input uses this tab | |
2426 | stop feature only in a few major modes, such as Text mode. | |
2427 | @xref{Tab Stops,,, emacs, The GNU Emacs Manual}. | |
2428 | ||
2429 | @deffn Command tab-to-tab-stop | |
2430 | This command inserts spaces or tabs before point, up to the next tab | |
2431 | stop column defined by @code{tab-stop-list}. It searches the list for | |
2432 | an element greater than the current column number, and uses that element | |
2433 | as the column to indent to. It does nothing if no such element is | |
2434 | found. | |
2435 | @end deffn | |
2436 | ||
2437 | @defopt tab-stop-list | |
2438 | This variable is the list of tab stop columns used by | |
2439 | @code{tab-to-tab-stops}. The elements should be integers in increasing | |
2440 | order. The tab stop columns need not be evenly spaced. | |
2441 | ||
2442 | Use @kbd{M-x edit-tab-stops} to edit the location of tab stops | |
2443 | interactively. | |
2444 | @end defopt | |
2445 | ||
2446 | @node Motion by Indent | |
2447 | @subsection Indentation-Based Motion Commands | |
2448 | ||
2449 | These commands, primarily for interactive use, act based on the | |
2450 | indentation in the text. | |
2451 | ||
2452 | @deffn Command back-to-indentation | |
2453 | @comment !!SourceFile simple.el | |
2454 | This command moves point to the first non-whitespace character in the | |
2455 | current line (which is the line in which point is located). It returns | |
2456 | @code{nil}. | |
2457 | @end deffn | |
2458 | ||
2459 | @deffn Command backward-to-indentation &optional arg | |
2460 | @comment !!SourceFile simple.el | |
2461 | This command moves point backward @var{arg} lines and then to the | |
2462 | first nonblank character on that line. It returns @code{nil}. | |
2463 | If @var{arg} is omitted or @code{nil}, it defaults to 1. | |
2464 | @end deffn | |
2465 | ||
2466 | @deffn Command forward-to-indentation &optional arg | |
2467 | @comment !!SourceFile simple.el | |
2468 | This command moves point forward @var{arg} lines and then to the first | |
2469 | nonblank character on that line. It returns @code{nil}. | |
2470 | If @var{arg} is omitted or @code{nil}, it defaults to 1. | |
2471 | @end deffn | |
2472 | ||
2473 | @node Case Changes | |
2474 | @comment node-name, next, previous, up | |
2475 | @section Case Changes | |
2476 | @cindex case conversion in buffers | |
2477 | ||
2478 | The case change commands described here work on text in the current | |
2479 | buffer. @xref{Case Conversion}, for case conversion functions that work | |
2480 | on strings and characters. @xref{Case Tables}, for how to customize | |
2481 | which characters are upper or lower case and how to convert them. | |
2482 | ||
2483 | @deffn Command capitalize-region start end | |
2484 | This function capitalizes all words in the region defined by | |
2485 | @var{start} and @var{end}. To capitalize means to convert each word's | |
2486 | first character to upper case and convert the rest of each word to lower | |
2487 | case. The function returns @code{nil}. | |
2488 | ||
2489 | If one end of the region is in the middle of a word, the part of the | |
2490 | word within the region is treated as an entire word. | |
2491 | ||
2492 | When @code{capitalize-region} is called interactively, @var{start} and | |
2493 | @var{end} are point and the mark, with the smallest first. | |
2494 | ||
2495 | @example | |
2496 | @group | |
2497 | ---------- Buffer: foo ---------- | |
2498 | This is the contents of the 5th foo. | |
2499 | ---------- Buffer: foo ---------- | |
2500 | @end group | |
2501 | ||
2502 | @group | |
2503 | (capitalize-region 1 44) | |
2504 | @result{} nil | |
2505 | ||
2506 | ---------- Buffer: foo ---------- | |
2507 | This Is The Contents Of The 5th Foo. | |
2508 | ---------- Buffer: foo ---------- | |
2509 | @end group | |
2510 | @end example | |
2511 | @end deffn | |
2512 | ||
2513 | @deffn Command downcase-region start end | |
2514 | This function converts all of the letters in the region defined by | |
2515 | @var{start} and @var{end} to lower case. The function returns | |
2516 | @code{nil}. | |
2517 | ||
2518 | When @code{downcase-region} is called interactively, @var{start} and | |
2519 | @var{end} are point and the mark, with the smallest first. | |
2520 | @end deffn | |
2521 | ||
2522 | @deffn Command upcase-region start end | |
2523 | This function converts all of the letters in the region defined by | |
2524 | @var{start} and @var{end} to upper case. The function returns | |
2525 | @code{nil}. | |
2526 | ||
2527 | When @code{upcase-region} is called interactively, @var{start} and | |
2528 | @var{end} are point and the mark, with the smallest first. | |
2529 | @end deffn | |
2530 | ||
2531 | @deffn Command capitalize-word count | |
2532 | This function capitalizes @var{count} words after point, moving point | |
2533 | over as it does. To capitalize means to convert each word's first | |
2534 | character to upper case and convert the rest of each word to lower case. | |
2535 | If @var{count} is negative, the function capitalizes the | |
2536 | @minus{}@var{count} previous words but does not move point. The value | |
2537 | is @code{nil}. | |
2538 | ||
2539 | If point is in the middle of a word, the part of the word before point | |
2540 | is ignored when moving forward. The rest is treated as an entire word. | |
2541 | ||
2542 | When @code{capitalize-word} is called interactively, @var{count} is | |
2543 | set to the numeric prefix argument. | |
2544 | @end deffn | |
2545 | ||
2546 | @deffn Command downcase-word count | |
2547 | This function converts the @var{count} words after point to all lower | |
2548 | case, moving point over as it does. If @var{count} is negative, it | |
2549 | converts the @minus{}@var{count} previous words but does not move point. | |
2550 | The value is @code{nil}. | |
2551 | ||
2552 | When @code{downcase-word} is called interactively, @var{count} is set | |
2553 | to the numeric prefix argument. | |
2554 | @end deffn | |
2555 | ||
2556 | @deffn Command upcase-word count | |
2557 | This function converts the @var{count} words after point to all upper | |
2558 | case, moving point over as it does. If @var{count} is negative, it | |
2559 | converts the @minus{}@var{count} previous words but does not move point. | |
2560 | The value is @code{nil}. | |
2561 | ||
2562 | When @code{upcase-word} is called interactively, @var{count} is set to | |
2563 | the numeric prefix argument. | |
2564 | @end deffn | |
2565 | ||
2566 | @node Text Properties | |
2567 | @section Text Properties | |
2568 | @cindex text properties | |
2569 | @cindex attributes of text | |
2570 | @cindex properties of text | |
2571 | ||
2572 | Each character position in a buffer or a string can have a @dfn{text | |
2573 | property list}, much like the property list of a symbol (@pxref{Property | |
2574 | Lists}). The properties belong to a particular character at a | |
2575 | particular place, such as, the letter @samp{T} at the beginning of this | |
2576 | sentence or the first @samp{o} in @samp{foo}---if the same character | |
2577 | occurs in two different places, the two occurrences in general have | |
2578 | different properties. | |
2579 | ||
2580 | Each property has a name and a value. Both of these can be any Lisp | |
2581 | object, but the name is normally a symbol. Typically each property | |
2582 | name symbol is used for a particular purpose; for instance, the text | |
2583 | property @code{face} specifies the faces for displaying the character | |
2584 | (@pxref{Special Properties}). The usual way to access the property | |
2585 | list is to specify a name and ask what value corresponds to it. | |
2586 | ||
2587 | If a character has a @code{category} property, we call it the | |
2588 | @dfn{property category} of the character. It should be a symbol. The | |
2589 | properties of the symbol serve as defaults for the properties of the | |
2590 | character. | |
2591 | ||
2592 | Copying text between strings and buffers preserves the properties | |
2593 | along with the characters; this includes such diverse functions as | |
2594 | @code{substring}, @code{insert}, and @code{buffer-substring}. | |
2595 | ||
2596 | @menu | |
2597 | * Examining Properties:: Looking at the properties of one character. | |
d24880de GM |
2598 | * Changing Properties:: Setting the properties of a range of text. |
2599 | * Property Search:: Searching for where a property changes value. | |
2600 | * Special Properties:: Particular properties with special meanings. | |
b8d4c8d0 GM |
2601 | * Format Properties:: Properties for representing formatting of text. |
2602 | * Sticky Properties:: How inserted text gets properties from | |
2603 | neighboring text. | |
2604 | * Lazy Properties:: Computing text properties in a lazy fashion | |
2605 | only when text is examined. | |
2606 | * Clickable Text:: Using text properties to make regions of text | |
2607 | do something when you click on them. | |
b8d4c8d0 GM |
2608 | * Fields:: The @code{field} property defines |
2609 | fields within the buffer. | |
d24880de GM |
2610 | * Not Intervals:: Why text properties do not use |
2611 | Lisp-visible text intervals. | |
b8d4c8d0 GM |
2612 | @end menu |
2613 | ||
2614 | @node Examining Properties | |
2615 | @subsection Examining Text Properties | |
2616 | ||
2617 | The simplest way to examine text properties is to ask for the value of | |
2618 | a particular property of a particular character. For that, use | |
2619 | @code{get-text-property}. Use @code{text-properties-at} to get the | |
2620 | entire property list of a character. @xref{Property Search}, for | |
2621 | functions to examine the properties of a number of characters at once. | |
2622 | ||
2623 | These functions handle both strings and buffers. Keep in mind that | |
2624 | positions in a string start from 0, whereas positions in a buffer start | |
2625 | from 1. | |
2626 | ||
2627 | @defun get-text-property pos prop &optional object | |
2628 | This function returns the value of the @var{prop} property of the | |
2629 | character after position @var{pos} in @var{object} (a buffer or | |
2630 | string). The argument @var{object} is optional and defaults to the | |
2631 | current buffer. | |
2632 | ||
2633 | If there is no @var{prop} property strictly speaking, but the character | |
2634 | has a property category that is a symbol, then @code{get-text-property} returns | |
2635 | the @var{prop} property of that symbol. | |
2636 | @end defun | |
2637 | ||
2638 | @defun get-char-property position prop &optional object | |
2639 | This function is like @code{get-text-property}, except that it checks | |
2640 | overlays first and then text properties. @xref{Overlays}. | |
2641 | ||
af23e1e8 RS |
2642 | The argument @var{object} may be a string, a buffer, or a window. If |
2643 | it is a window, then the buffer displayed in that window is used for | |
2644 | text properties and overlays, but only the overlays active for that | |
2645 | window are considered. If @var{object} is a buffer, then overlays in | |
2646 | that buffer are considered first, in order of decreasing priority, | |
2647 | followed by the text properties. If @var{object} is a string, only | |
2648 | text properties are considered, since strings never have overlays. | |
b8d4c8d0 GM |
2649 | @end defun |
2650 | ||
2651 | @defun get-char-property-and-overlay position prop &optional object | |
2652 | This is like @code{get-char-property}, but gives extra information | |
2653 | about the overlay that the property value comes from. | |
2654 | ||
2655 | Its value is a cons cell whose @sc{car} is the property value, the | |
2656 | same value @code{get-char-property} would return with the same | |
2657 | arguments. Its @sc{cdr} is the overlay in which the property was | |
2658 | found, or @code{nil}, if it was found as a text property or not found | |
2659 | at all. | |
2660 | ||
2661 | If @var{position} is at the end of @var{object}, both the @sc{car} and | |
2662 | the @sc{cdr} of the value are @code{nil}. | |
2663 | @end defun | |
2664 | ||
2665 | @defvar char-property-alias-alist | |
2666 | This variable holds an alist which maps property names to a list of | |
2667 | alternative property names. If a character does not specify a direct | |
2668 | value for a property, the alternative property names are consulted in | |
2669 | order; the first non-@code{nil} value is used. This variable takes | |
2670 | precedence over @code{default-text-properties}, and @code{category} | |
2671 | properties take precedence over this variable. | |
2672 | @end defvar | |
2673 | ||
2674 | @defun text-properties-at position &optional object | |
2675 | This function returns the entire property list of the character at | |
2676 | @var{position} in the string or buffer @var{object}. If @var{object} is | |
2677 | @code{nil}, it defaults to the current buffer. | |
2678 | @end defun | |
2679 | ||
2680 | @defvar default-text-properties | |
2681 | This variable holds a property list giving default values for text | |
2682 | properties. Whenever a character does not specify a value for a | |
2683 | property, neither directly, through a category symbol, or through | |
2684 | @code{char-property-alias-alist}, the value stored in this list is | |
2685 | used instead. Here is an example: | |
2686 | ||
2687 | @example | |
2688 | (setq default-text-properties '(foo 69) | |
2689 | char-property-alias-alist nil) | |
2690 | ;; @r{Make sure character 1 has no properties of its own.} | |
2691 | (set-text-properties 1 2 nil) | |
2692 | ;; @r{What we get, when we ask, is the default value.} | |
2693 | (get-text-property 1 'foo) | |
2694 | @result{} 69 | |
2695 | @end example | |
2696 | @end defvar | |
2697 | ||
2698 | @node Changing Properties | |
2699 | @subsection Changing Text Properties | |
2700 | ||
2701 | The primitives for changing properties apply to a specified range of | |
2702 | text in a buffer or string. The function @code{set-text-properties} | |
2703 | (see end of section) sets the entire property list of the text in that | |
2704 | range; more often, it is useful to add, change, or delete just certain | |
2705 | properties specified by name. | |
2706 | ||
2707 | Since text properties are considered part of the contents of the | |
2708 | buffer (or string), and can affect how a buffer looks on the screen, | |
2709 | any change in buffer text properties marks the buffer as modified. | |
2710 | Buffer text property changes are undoable also (@pxref{Undo}). | |
2711 | Positions in a string start from 0, whereas positions in a buffer | |
2712 | start from 1. | |
2713 | ||
2714 | @defun put-text-property start end prop value &optional object | |
2715 | This function sets the @var{prop} property to @var{value} for the text | |
2716 | between @var{start} and @var{end} in the string or buffer @var{object}. | |
2717 | If @var{object} is @code{nil}, it defaults to the current buffer. | |
2718 | @end defun | |
2719 | ||
2720 | @defun add-text-properties start end props &optional object | |
2721 | This function adds or overrides text properties for the text between | |
2722 | @var{start} and @var{end} in the string or buffer @var{object}. If | |
2723 | @var{object} is @code{nil}, it defaults to the current buffer. | |
2724 | ||
2725 | The argument @var{props} specifies which properties to add. It should | |
2726 | have the form of a property list (@pxref{Property Lists}): a list whose | |
2727 | elements include the property names followed alternately by the | |
2728 | corresponding values. | |
2729 | ||
2730 | The return value is @code{t} if the function actually changed some | |
2731 | property's value; @code{nil} otherwise (if @var{props} is @code{nil} or | |
2732 | its values agree with those in the text). | |
2733 | ||
2734 | For example, here is how to set the @code{comment} and @code{face} | |
2735 | properties of a range of text: | |
2736 | ||
2737 | @example | |
2738 | (add-text-properties @var{start} @var{end} | |
2739 | '(comment t face highlight)) | |
2740 | @end example | |
2741 | @end defun | |
2742 | ||
2743 | @defun remove-text-properties start end props &optional object | |
2744 | This function deletes specified text properties from the text between | |
2745 | @var{start} and @var{end} in the string or buffer @var{object}. If | |
2746 | @var{object} is @code{nil}, it defaults to the current buffer. | |
2747 | ||
2748 | The argument @var{props} specifies which properties to delete. It | |
2749 | should have the form of a property list (@pxref{Property Lists}): a list | |
2750 | whose elements are property names alternating with corresponding values. | |
2751 | But only the names matter---the values that accompany them are ignored. | |
2752 | For example, here's how to remove the @code{face} property. | |
2753 | ||
2754 | @example | |
2755 | (remove-text-properties @var{start} @var{end} '(face nil)) | |
2756 | @end example | |
2757 | ||
2758 | The return value is @code{t} if the function actually changed some | |
2759 | property's value; @code{nil} otherwise (if @var{props} is @code{nil} or | |
2760 | if no character in the specified text had any of those properties). | |
2761 | ||
2762 | To remove all text properties from certain text, use | |
2763 | @code{set-text-properties} and specify @code{nil} for the new property | |
2764 | list. | |
2765 | @end defun | |
2766 | ||
2767 | @defun remove-list-of-text-properties start end list-of-properties &optional object | |
2768 | Like @code{remove-text-properties} except that | |
2769 | @var{list-of-properties} is a list of property names only, not an | |
2770 | alternating list of property names and values. | |
2771 | @end defun | |
2772 | ||
2773 | @defun set-text-properties start end props &optional object | |
2774 | This function completely replaces the text property list for the text | |
2775 | between @var{start} and @var{end} in the string or buffer @var{object}. | |
2776 | If @var{object} is @code{nil}, it defaults to the current buffer. | |
2777 | ||
2778 | The argument @var{props} is the new property list. It should be a list | |
2779 | whose elements are property names alternating with corresponding values. | |
2780 | ||
2781 | After @code{set-text-properties} returns, all the characters in the | |
2782 | specified range have identical properties. | |
2783 | ||
2784 | If @var{props} is @code{nil}, the effect is to get rid of all properties | |
2785 | from the specified range of text. Here's an example: | |
2786 | ||
2787 | @example | |
2788 | (set-text-properties @var{start} @var{end} nil) | |
2789 | @end example | |
2790 | ||
2791 | Do not rely on the return value of this function. | |
2792 | @end defun | |
2793 | ||
2794 | The easiest way to make a string with text properties | |
2795 | is with @code{propertize}: | |
2796 | ||
2797 | @defun propertize string &rest properties | |
2798 | This function returns a copy of @var{string} which has the text | |
2799 | properties @var{properties}. These properties apply to all the | |
2800 | characters in the string that is returned. Here is an example that | |
2801 | constructs a string with a @code{face} property and a @code{mouse-face} | |
2802 | property: | |
2803 | ||
2804 | @smallexample | |
2805 | (propertize "foo" 'face 'italic | |
2806 | 'mouse-face 'bold-italic) | |
2807 | @result{} #("foo" 0 3 (mouse-face bold-italic face italic)) | |
2808 | @end smallexample | |
2809 | ||
2810 | To put different properties on various parts of a string, you can | |
2811 | construct each part with @code{propertize} and then combine them with | |
2812 | @code{concat}: | |
2813 | ||
2814 | @smallexample | |
2815 | (concat | |
2816 | (propertize "foo" 'face 'italic | |
2817 | 'mouse-face 'bold-italic) | |
2818 | " and " | |
2819 | (propertize "bar" 'face 'italic | |
2820 | 'mouse-face 'bold-italic)) | |
2821 | @result{} #("foo and bar" | |
2822 | 0 3 (face italic mouse-face bold-italic) | |
2823 | 3 8 nil | |
2824 | 8 11 (face italic mouse-face bold-italic)) | |
2825 | @end smallexample | |
2826 | @end defun | |
2827 | ||
2828 | See also the function @code{buffer-substring-no-properties} | |
2829 | (@pxref{Buffer Contents}) which copies text from the buffer | |
2830 | but does not copy its properties. | |
2831 | ||
2832 | @node Property Search | |
2833 | @subsection Text Property Search Functions | |
2834 | ||
2835 | In typical use of text properties, most of the time several or many | |
2836 | consecutive characters have the same value for a property. Rather than | |
2837 | writing your programs to examine characters one by one, it is much | |
2838 | faster to process chunks of text that have the same property value. | |
2839 | ||
2840 | Here are functions you can use to do this. They use @code{eq} for | |
2841 | comparing property values. In all cases, @var{object} defaults to the | |
2842 | current buffer. | |
2843 | ||
2844 | For high performance, it's very important to use the @var{limit} | |
2845 | argument to these functions, especially the ones that search for a | |
2846 | single property---otherwise, they may spend a long time scanning to the | |
2847 | end of the buffer, if the property you are interested in does not change. | |
2848 | ||
2849 | These functions do not move point; instead, they return a position (or | |
2850 | @code{nil}). Remember that a position is always between two characters; | |
2851 | the position returned by these functions is between two characters with | |
2852 | different properties. | |
2853 | ||
2854 | @defun next-property-change pos &optional object limit | |
2855 | The function scans the text forward from position @var{pos} in the | |
2856 | string or buffer @var{object} till it finds a change in some text | |
2857 | property, then returns the position of the change. In other words, it | |
2858 | returns the position of the first character beyond @var{pos} whose | |
2859 | properties are not identical to those of the character just after | |
2860 | @var{pos}. | |
2861 | ||
2862 | If @var{limit} is non-@code{nil}, then the scan ends at position | |
2863 | @var{limit}. If there is no property change before that point, | |
2864 | @code{next-property-change} returns @var{limit}. | |
2865 | ||
2866 | The value is @code{nil} if the properties remain unchanged all the way | |
2867 | to the end of @var{object} and @var{limit} is @code{nil}. If the value | |
2868 | is non-@code{nil}, it is a position greater than or equal to @var{pos}. | |
2869 | The value equals @var{pos} only when @var{limit} equals @var{pos}. | |
2870 | ||
2871 | Here is an example of how to scan the buffer by chunks of text within | |
2872 | which all properties are constant: | |
2873 | ||
2874 | @smallexample | |
2875 | (while (not (eobp)) | |
2876 | (let ((plist (text-properties-at (point))) | |
2877 | (next-change | |
2878 | (or (next-property-change (point) (current-buffer)) | |
2879 | (point-max)))) | |
2880 | @r{Process text from point to @var{next-change}@dots{}} | |
2881 | (goto-char next-change))) | |
2882 | @end smallexample | |
2883 | @end defun | |
2884 | ||
2885 | @defun previous-property-change pos &optional object limit | |
2886 | This is like @code{next-property-change}, but scans back from @var{pos} | |
2887 | instead of forward. If the value is non-@code{nil}, it is a position | |
2888 | less than or equal to @var{pos}; it equals @var{pos} only if @var{limit} | |
2889 | equals @var{pos}. | |
2890 | @end defun | |
2891 | ||
2892 | @defun next-single-property-change pos prop &optional object limit | |
2893 | The function scans text for a change in the @var{prop} property, then | |
2894 | returns the position of the change. The scan goes forward from | |
2895 | position @var{pos} in the string or buffer @var{object}. In other | |
2896 | words, this function returns the position of the first character | |
2897 | beyond @var{pos} whose @var{prop} property differs from that of the | |
2898 | character just after @var{pos}. | |
2899 | ||
2900 | If @var{limit} is non-@code{nil}, then the scan ends at position | |
2901 | @var{limit}. If there is no property change before that point, | |
2902 | @code{next-single-property-change} returns @var{limit}. | |
2903 | ||
2904 | The value is @code{nil} if the property remains unchanged all the way to | |
2905 | the end of @var{object} and @var{limit} is @code{nil}. If the value is | |
2906 | non-@code{nil}, it is a position greater than or equal to @var{pos}; it | |
2907 | equals @var{pos} only if @var{limit} equals @var{pos}. | |
2908 | @end defun | |
2909 | ||
2910 | @defun previous-single-property-change pos prop &optional object limit | |
2911 | This is like @code{next-single-property-change}, but scans back from | |
2912 | @var{pos} instead of forward. If the value is non-@code{nil}, it is a | |
2913 | position less than or equal to @var{pos}; it equals @var{pos} only if | |
2914 | @var{limit} equals @var{pos}. | |
2915 | @end defun | |
2916 | ||
2917 | @defun next-char-property-change pos &optional limit | |
2918 | This is like @code{next-property-change} except that it considers | |
2919 | overlay properties as well as text properties, and if no change is | |
2920 | found before the end of the buffer, it returns the maximum buffer | |
2921 | position rather than @code{nil} (in this sense, it resembles the | |
2922 | corresponding overlay function @code{next-overlay-change}, rather than | |
2923 | @code{next-property-change}). There is no @var{object} operand | |
2924 | because this function operates only on the current buffer. It returns | |
2925 | the next address at which either kind of property changes. | |
2926 | @end defun | |
2927 | ||
2928 | @defun previous-char-property-change pos &optional limit | |
2929 | This is like @code{next-char-property-change}, but scans back from | |
2930 | @var{pos} instead of forward, and returns the minimum buffer | |
2931 | position if no change is found. | |
2932 | @end defun | |
2933 | ||
2934 | @defun next-single-char-property-change pos prop &optional object limit | |
2935 | This is like @code{next-single-property-change} except that it | |
2936 | considers overlay properties as well as text properties, and if no | |
2937 | change is found before the end of the @var{object}, it returns the | |
2938 | maximum valid position in @var{object} rather than @code{nil}. Unlike | |
2939 | @code{next-char-property-change}, this function @emph{does} have an | |
2940 | @var{object} operand; if @var{object} is not a buffer, only | |
2941 | text-properties are considered. | |
2942 | @end defun | |
2943 | ||
2944 | @defun previous-single-char-property-change pos prop &optional object limit | |
2945 | This is like @code{next-single-char-property-change}, but scans back | |
2946 | from @var{pos} instead of forward, and returns the minimum valid | |
2947 | position in @var{object} if no change is found. | |
2948 | @end defun | |
2949 | ||
2950 | @defun text-property-any start end prop value &optional object | |
2951 | This function returns non-@code{nil} if at least one character between | |
2952 | @var{start} and @var{end} has a property @var{prop} whose value is | |
2953 | @var{value}. More precisely, it returns the position of the first such | |
2954 | character. Otherwise, it returns @code{nil}. | |
2955 | ||
2956 | The optional fifth argument, @var{object}, specifies the string or | |
2957 | buffer to scan. Positions are relative to @var{object}. The default | |
2958 | for @var{object} is the current buffer. | |
2959 | @end defun | |
2960 | ||
2961 | @defun text-property-not-all start end prop value &optional object | |
2962 | This function returns non-@code{nil} if at least one character between | |
2963 | @var{start} and @var{end} does not have a property @var{prop} with value | |
2964 | @var{value}. More precisely, it returns the position of the first such | |
2965 | character. Otherwise, it returns @code{nil}. | |
2966 | ||
2967 | The optional fifth argument, @var{object}, specifies the string or | |
2968 | buffer to scan. Positions are relative to @var{object}. The default | |
2969 | for @var{object} is the current buffer. | |
2970 | @end defun | |
2971 | ||
2972 | @node Special Properties | |
2973 | @subsection Properties with Special Meanings | |
2974 | ||
2975 | Here is a table of text property names that have special built-in | |
2976 | meanings. The following sections list a few additional special property | |
2977 | names that control filling and property inheritance. All other names | |
2978 | have no standard meaning, and you can use them as you like. | |
2979 | ||
2980 | Note: the properties @code{composition}, @code{display}, | |
2981 | @code{invisible} and @code{intangible} can also cause point to move to | |
2982 | an acceptable place, after each Emacs command. @xref{Adjusting | |
2983 | Point}. | |
2984 | ||
2985 | @table @code | |
2986 | @cindex property category of text character | |
2987 | @kindex category @r{(text property)} | |
2988 | @item category | |
2989 | If a character has a @code{category} property, we call it the | |
2990 | @dfn{property category} of the character. It should be a symbol. The | |
2991 | properties of this symbol serve as defaults for the properties of the | |
2992 | character. | |
2993 | ||
2994 | @item face | |
2995 | @cindex face codes of text | |
2996 | @kindex face @r{(text property)} | |
2997 | You can use the property @code{face} to control the font and color of | |
2998 | text. @xref{Faces}, for more information. | |
2999 | ||
3000 | In the simplest case, the value is a face name. It can also be a list; | |
3001 | then each element can be any of these possibilities; | |
3002 | ||
3003 | @itemize @bullet | |
3004 | @item | |
3005 | A face name (a symbol or string). | |
3006 | ||
3007 | @item | |
3008 | A property list of face attributes. This has the | |
3009 | form (@var{keyword} @var{value} @dots{}), where each @var{keyword} is a | |
3010 | face attribute name and @var{value} is a meaningful value for that | |
3011 | attribute. With this feature, you do not need to create a face each | |
3012 | time you want to specify a particular attribute for certain text. | |
3013 | @xref{Face Attributes}. | |
3014 | ||
3015 | @item | |
db3625ba | 3016 | A cons cell with the form @code{(foreground-color . @var{color-name})} |
57eedec1 | 3017 | or @code{(background-color . @var{color-name})}. These are old, |
db3625ba RS |
3018 | deprecated equivalents for @code{(:foreground @var{color-name})} and |
3019 | @code{(:background @var{color-name})}. Please convert code that uses | |
3020 | them. | |
b8d4c8d0 GM |
3021 | @end itemize |
3022 | ||
db3625ba RS |
3023 | It works to use the latter two forms directly as the value |
3024 | of the @code{face} property. | |
3025 | ||
3026 | Font Lock mode (@pxref{Font Lock Mode}) works in most buffers by | |
3027 | dynamically updating the @code{face} property of characters based on | |
3028 | the context. | |
b8d4c8d0 GM |
3029 | |
3030 | @item font-lock-face | |
3031 | @kindex font-lock-face @r{(text property)} | |
db3625ba RS |
3032 | The @code{font-lock-face} property is equivalent to the @code{face} |
3033 | property when Font Lock mode is enabled. When Font Lock mode is disabled, | |
3034 | @code{font-lock-face} has no effect. | |
b8d4c8d0 | 3035 | |
1c84bc7a | 3036 | The @code{font-lock-face} property is useful for special modes that |
db3625ba | 3037 | implement their own highlighting. @xref{Precalculated Fontification}. |
b8d4c8d0 | 3038 | |
b8d4c8d0 GM |
3039 | @item mouse-face |
3040 | @kindex mouse-face @r{(text property)} | |
3041 | The property @code{mouse-face} is used instead of @code{face} when the | |
3042 | mouse is on or near the character. For this purpose, ``near'' means | |
3043 | that all text between the character and where the mouse is have the same | |
3044 | @code{mouse-face} property value. | |
3045 | ||
3046 | @item fontified | |
3047 | @kindex fontified @r{(text property)} | |
3048 | This property says whether the text is ready for display. If | |
3049 | @code{nil}, Emacs's redisplay routine calls the functions in | |
3050 | @code{fontification-functions} (@pxref{Auto Faces}) to prepare this | |
3051 | part of the buffer before it is displayed. It is used internally by | |
3052 | the ``just in time'' font locking code. | |
3053 | ||
3054 | @item display | |
3055 | This property activates various features that change the | |
3056 | way text is displayed. For example, it can make text appear taller | |
3057 | or shorter, higher or lower, wider or narrow, or replaced with an image. | |
3058 | @xref{Display Property}. | |
3059 | ||
3060 | @item help-echo | |
3061 | @kindex help-echo @r{(text property)} | |
3062 | @cindex tooltip | |
3063 | @anchor{Text help-echo} | |
3064 | If text has a string as its @code{help-echo} property, then when you | |
3065 | move the mouse onto that text, Emacs displays that string in the echo | |
3066 | area, or in the tooltip window (@pxref{Tooltips,,, emacs, The GNU Emacs | |
3067 | Manual}). | |
3068 | ||
3069 | If the value of the @code{help-echo} property is a function, that | |
3070 | function is called with three arguments, @var{window}, @var{object} and | |
3071 | @var{pos} and should return a help string or @code{nil} for | |
3072 | none. The first argument, @var{window} is the window in which | |
3073 | the help was found. The second, @var{object}, is the buffer, overlay or | |
3074 | string which had the @code{help-echo} property. The @var{pos} | |
3075 | argument is as follows: | |
3076 | ||
3077 | @itemize @bullet{} | |
3078 | @item | |
3079 | If @var{object} is a buffer, @var{pos} is the position in the buffer. | |
3080 | @item | |
3081 | If @var{object} is an overlay, that overlay has a @code{help-echo} | |
3082 | property, and @var{pos} is the position in the overlay's buffer. | |
3083 | @item | |
3084 | If @var{object} is a string (an overlay string or a string displayed | |
3085 | with the @code{display} property), @var{pos} is the position in that | |
3086 | string. | |
3087 | @end itemize | |
3088 | ||
3089 | If the value of the @code{help-echo} property is neither a function nor | |
3090 | a string, it is evaluated to obtain a help string. | |
3091 | ||
3092 | You can alter the way help text is displayed by setting the variable | |
3093 | @code{show-help-function} (@pxref{Help display}). | |
3094 | ||
3095 | This feature is used in the mode line and for other active text. | |
3096 | ||
3097 | @item keymap | |
3098 | @cindex keymap of character | |
3099 | @kindex keymap @r{(text property)} | |
3100 | The @code{keymap} property specifies an additional keymap for | |
3101 | commands. When this keymap applies, it is used for key lookup before | |
3102 | the minor mode keymaps and before the buffer's local map. | |
3103 | @xref{Active Keymaps}. If the property value is a symbol, the | |
3104 | symbol's function definition is used as the keymap. | |
3105 | ||
3106 | The property's value for the character before point applies if it is | |
3107 | non-@code{nil} and rear-sticky, and the property's value for the | |
3108 | character after point applies if it is non-@code{nil} and | |
3109 | front-sticky. (For mouse clicks, the position of the click is used | |
3110 | instead of the position of point.) | |
3111 | ||
3112 | @item local-map | |
3113 | @kindex local-map @r{(text property)} | |
3114 | This property works like @code{keymap} except that it specifies a | |
3115 | keymap to use @emph{instead of} the buffer's local map. For most | |
3116 | purposes (perhaps all purposes), it is better to use the @code{keymap} | |
3117 | property. | |
3118 | ||
3119 | @item syntax-table | |
3120 | The @code{syntax-table} property overrides what the syntax table says | |
3121 | about this particular character. @xref{Syntax Properties}. | |
3122 | ||
3123 | @item read-only | |
3124 | @cindex read-only character | |
3125 | @kindex read-only @r{(text property)} | |
3126 | If a character has the property @code{read-only}, then modifying that | |
3127 | character is not allowed. Any command that would do so gets an error, | |
3128 | @code{text-read-only}. If the property value is a string, that string | |
3129 | is used as the error message. | |
3130 | ||
3131 | Insertion next to a read-only character is an error if inserting | |
3132 | ordinary text there would inherit the @code{read-only} property due to | |
3133 | stickiness. Thus, you can control permission to insert next to | |
3134 | read-only text by controlling the stickiness. @xref{Sticky Properties}. | |
3135 | ||
3136 | Since changing properties counts as modifying the buffer, it is not | |
3137 | possible to remove a @code{read-only} property unless you know the | |
3138 | special trick: bind @code{inhibit-read-only} to a non-@code{nil} value | |
3139 | and then remove the property. @xref{Read Only Buffers}. | |
3140 | ||
3141 | @item invisible | |
3142 | @kindex invisible @r{(text property)} | |
3143 | A non-@code{nil} @code{invisible} property can make a character invisible | |
3144 | on the screen. @xref{Invisible Text}, for details. | |
3145 | ||
3146 | @item intangible | |
3147 | @kindex intangible @r{(text property)} | |
3148 | If a group of consecutive characters have equal and non-@code{nil} | |
3149 | @code{intangible} properties, then you cannot place point between them. | |
3150 | If you try to move point forward into the group, point actually moves to | |
3151 | the end of the group. If you try to move point backward into the group, | |
3152 | point actually moves to the start of the group. | |
3153 | ||
3154 | If consecutive characters have unequal non-@code{nil} | |
3155 | @code{intangible} properties, they belong to separate groups; each | |
3156 | group is separately treated as described above. | |
3157 | ||
3158 | When the variable @code{inhibit-point-motion-hooks} is non-@code{nil}, | |
3159 | the @code{intangible} property is ignored. | |
3160 | ||
3161 | @item field | |
3162 | @kindex field @r{(text property)} | |
3163 | Consecutive characters with the same @code{field} property constitute a | |
3164 | @dfn{field}. Some motion functions including @code{forward-word} and | |
3165 | @code{beginning-of-line} stop moving at a field boundary. | |
3166 | @xref{Fields}. | |
3167 | ||
3168 | @item cursor | |
3169 | @kindex cursor @r{(text property)} | |
3170 | Normally, the cursor is displayed at the end of any overlay and text | |
b640eb52 | 3171 | property strings present at the current buffer position. You can |
b8d4c8d0 | 3172 | place the cursor on any desired character of these strings by giving |
b640eb52 EZ |
3173 | that character a non-@code{nil} @code{cursor} text property. In |
3174 | addition, if the value of the @code{cursor} property of an overlay | |
3175 | string is an integer number, it specifies the number of buffer's | |
3176 | character positions associated with the overlay string; this way, | |
3177 | Emacs will display the cursor on the character with that property | |
3178 | regardless of whether the current buffer position is actually covered | |
3179 | by the overlay. Specifically, if the value of the @code{cursor} | |
3180 | property of a character is the number @var{n}, the cursor will be | |
3181 | displayed on this character for any buffer position in the range | |
3182 | @code{[@var{ovpos}..@var{ovpos}+@var{n}]}, where @var{ovpos} is the | |
3183 | starting buffer position covered by the overlay (@pxref{Managing | |
3184 | Overlays}). | |
b8d4c8d0 GM |
3185 | |
3186 | @item pointer | |
3187 | @kindex pointer @r{(text property)} | |
3188 | This specifies a specific pointer shape when the mouse pointer is over | |
3189 | this text or image. @xref{Pointer Shape}, for possible pointer | |
3190 | shapes. | |
3191 | ||
3192 | @item line-spacing | |
3193 | @kindex line-spacing @r{(text property)} | |
3194 | A newline can have a @code{line-spacing} text or overlay property that | |
3195 | controls the height of the display line ending with that newline. The | |
3196 | property value overrides the default frame line spacing and the buffer | |
3197 | local @code{line-spacing} variable. @xref{Line Height}. | |
3198 | ||
3199 | @item line-height | |
3200 | @kindex line-height @r{(text property)} | |
3201 | A newline can have a @code{line-height} text or overlay property that | |
3202 | controls the total height of the display line ending in that newline. | |
3203 | @xref{Line Height}. | |
3204 | ||
c4f4682b MB |
3205 | @item wrap-prefix |
3206 | If text has a @code{wrap-prefix} property, the prefix it defines will | |
3207 | be added at display-time to the beginning of every continuation line | |
3208 | due to text wrapping (so if lines are truncated, the wrap-prefix is | |
3209 | never used). It may be a string, an image, or a stretch-glyph such as | |
3210 | used by the @code{display} text-property. @xref{Display Property}. | |
3211 | ||
3212 | A wrap-prefix may also be specified for an entire buffer using the | |
3213 | @code{wrap-prefix} buffer-local variable (however, a | |
3214 | @code{wrap-prefix} text-property takes precedence over the value of | |
3215 | the @code{wrap-prefix} variable). @xref{Truncation}. | |
3216 | ||
3217 | @item line-prefix | |
3218 | If text has a @code{line-prefix} property, the prefix it defines will | |
3219 | be added at display-time to the beginning of every non-continuation | |
3220 | line. It may be a string, an image, or a stretch-glyph such as used | |
3221 | by the @code{display} text-property. @xref{Display Property}. | |
3222 | ||
3223 | A line-prefix may also be specified for an entire buffer using the | |
3224 | @code{line-prefix} buffer-local variable (however, a | |
3225 | @code{line-prefix} text-property takes precedence over the value of | |
3226 | the @code{line-prefix} variable). @xref{Truncation}. | |
3227 | ||
b8d4c8d0 GM |
3228 | @item modification-hooks |
3229 | @cindex change hooks for a character | |
3230 | @cindex hooks for changing a character | |
3231 | @kindex modification-hooks @r{(text property)} | |
3232 | If a character has the property @code{modification-hooks}, then its | |
3233 | value should be a list of functions; modifying that character calls all | |
3234 | of those functions. Each function receives two arguments: the beginning | |
3235 | and end of the part of the buffer being modified. Note that if a | |
3236 | particular modification hook function appears on several characters | |
3237 | being modified by a single primitive, you can't predict how many times | |
3238 | the function will be called. | |
3239 | ||
3240 | If these functions modify the buffer, they should bind | |
3241 | @code{inhibit-modification-hooks} to @code{t} around doing so, to | |
3242 | avoid confusing the internal mechanism that calls these hooks. | |
3243 | ||
3244 | Overlays also support the @code{modification-hooks} property, but the | |
3245 | details are somewhat different (@pxref{Overlay Properties}). | |
3246 | ||
3247 | @item insert-in-front-hooks | |
3248 | @itemx insert-behind-hooks | |
3249 | @kindex insert-in-front-hooks @r{(text property)} | |
3250 | @kindex insert-behind-hooks @r{(text property)} | |
3251 | The operation of inserting text in a buffer also calls the functions | |
3252 | listed in the @code{insert-in-front-hooks} property of the following | |
3253 | character and in the @code{insert-behind-hooks} property of the | |
3254 | preceding character. These functions receive two arguments, the | |
3255 | beginning and end of the inserted text. The functions are called | |
3256 | @emph{after} the actual insertion takes place. | |
3257 | ||
3258 | See also @ref{Change Hooks}, for other hooks that are called | |
3259 | when you change text in a buffer. | |
3260 | ||
3261 | @item point-entered | |
3262 | @itemx point-left | |
3263 | @cindex hooks for motion of point | |
3264 | @kindex point-entered @r{(text property)} | |
3265 | @kindex point-left @r{(text property)} | |
3266 | The special properties @code{point-entered} and @code{point-left} | |
3267 | record hook functions that report motion of point. Each time point | |
3268 | moves, Emacs compares these two property values: | |
3269 | ||
3270 | @itemize @bullet | |
3271 | @item | |
3272 | the @code{point-left} property of the character after the old location, | |
3273 | and | |
3274 | @item | |
3275 | the @code{point-entered} property of the character after the new | |
3276 | location. | |
3277 | @end itemize | |
3278 | ||
3279 | @noindent | |
3280 | If these two values differ, each of them is called (if not @code{nil}) | |
3281 | with two arguments: the old value of point, and the new one. | |
3282 | ||
3283 | The same comparison is made for the characters before the old and new | |
3284 | locations. The result may be to execute two @code{point-left} functions | |
3285 | (which may be the same function) and/or two @code{point-entered} | |
3286 | functions (which may be the same function). In any case, all the | |
3287 | @code{point-left} functions are called first, followed by all the | |
3288 | @code{point-entered} functions. | |
3289 | ||
3290 | It is possible with @code{char-after} to examine characters at various | |
3291 | buffer positions without moving point to those positions. Only an | |
3292 | actual change in the value of point runs these hook functions. | |
3293 | ||
3294 | @defvar inhibit-point-motion-hooks | |
3295 | When this variable is non-@code{nil}, @code{point-left} and | |
3296 | @code{point-entered} hooks are not run, and the @code{intangible} | |
3297 | property has no effect. Do not set this variable globally; bind it with | |
3298 | @code{let}. | |
3299 | @end defvar | |
3300 | ||
3301 | @defvar show-help-function | |
3302 | @anchor{Help display} If this variable is non-@code{nil}, it specifies a | |
3303 | function called to display help strings. These may be @code{help-echo} | |
3304 | properties, menu help strings (@pxref{Simple Menu Items}, | |
3305 | @pxref{Extended Menu Items}), or tool bar help strings (@pxref{Tool | |
3306 | Bar}). The specified function is called with one argument, the help | |
3307 | string to display. Tooltip mode (@pxref{Tooltips,,, emacs, The GNU Emacs | |
3308 | Manual}) provides an example. | |
3309 | @end defvar | |
3310 | ||
3311 | @item composition | |
3312 | @kindex composition @r{(text property)} | |
3313 | This text property is used to display a sequence of characters as a | |
3314 | single glyph composed from components. But the value of the property | |
3315 | itself is completely internal to Emacs and should not be manipulated | |
3316 | directly by, for instance, @code{put-text-property}. | |
3317 | ||
3318 | @end table | |
3319 | ||
3320 | @node Format Properties | |
3321 | @subsection Formatted Text Properties | |
3322 | ||
3323 | These text properties affect the behavior of the fill commands. They | |
3324 | are used for representing formatted text. @xref{Filling}, and | |
3325 | @ref{Margins}. | |
3326 | ||
3327 | @table @code | |
3328 | @item hard | |
3329 | If a newline character has this property, it is a ``hard'' newline. | |
3330 | The fill commands do not alter hard newlines and do not move words | |
3331 | across them. However, this property takes effect only if the | |
3332 | @code{use-hard-newlines} minor mode is enabled. @xref{Hard and Soft | |
3333 | Newlines,, Hard and Soft Newlines, emacs, The GNU Emacs Manual}. | |
3334 | ||
3335 | @item right-margin | |
3336 | This property specifies an extra right margin for filling this part of the | |
3337 | text. | |
3338 | ||
3339 | @item left-margin | |
3340 | This property specifies an extra left margin for filling this part of the | |
3341 | text. | |
3342 | ||
3343 | @item justification | |
3344 | This property specifies the style of justification for filling this part | |
3345 | of the text. | |
3346 | @end table | |
3347 | ||
3348 | @node Sticky Properties | |
3349 | @subsection Stickiness of Text Properties | |
3350 | @cindex sticky text properties | |
3351 | @cindex inheritance of text properties | |
3352 | ||
3353 | Self-inserting characters normally take on the same properties as the | |
3354 | preceding character. This is called @dfn{inheritance} of properties. | |
3355 | ||
3356 | In a Lisp program, you can do insertion with inheritance or without, | |
3357 | depending on your choice of insertion primitive. The ordinary text | |
3358 | insertion functions such as @code{insert} do not inherit any properties. | |
3359 | They insert text with precisely the properties of the string being | |
3360 | inserted, and no others. This is correct for programs that copy text | |
3361 | from one context to another---for example, into or out of the kill ring. | |
3362 | To insert with inheritance, use the special primitives described in this | |
3363 | section. Self-inserting characters inherit properties because they work | |
3364 | using these primitives. | |
3365 | ||
3366 | When you do insertion with inheritance, @emph{which} properties are | |
3367 | inherited, and from where, depends on which properties are @dfn{sticky}. | |
3368 | Insertion after a character inherits those of its properties that are | |
3369 | @dfn{rear-sticky}. Insertion before a character inherits those of its | |
3370 | properties that are @dfn{front-sticky}. When both sides offer different | |
3371 | sticky values for the same property, the previous character's value | |
3372 | takes precedence. | |
3373 | ||
3374 | By default, a text property is rear-sticky but not front-sticky; thus, | |
3375 | the default is to inherit all the properties of the preceding character, | |
3376 | and nothing from the following character. | |
3377 | ||
3378 | You can control the stickiness of various text properties with two | |
3379 | specific text properties, @code{front-sticky} and @code{rear-nonsticky}, | |
3380 | and with the variable @code{text-property-default-nonsticky}. You can | |
3381 | use the variable to specify a different default for a given property. | |
3382 | You can use those two text properties to make any specific properties | |
3383 | sticky or nonsticky in any particular part of the text. | |
3384 | ||
3385 | If a character's @code{front-sticky} property is @code{t}, then all | |
3386 | its properties are front-sticky. If the @code{front-sticky} property is | |
3387 | a list, then the sticky properties of the character are those whose | |
3388 | names are in the list. For example, if a character has a | |
3389 | @code{front-sticky} property whose value is @code{(face read-only)}, | |
3390 | then insertion before the character can inherit its @code{face} property | |
3391 | and its @code{read-only} property, but no others. | |
3392 | ||
3393 | The @code{rear-nonsticky} property works the opposite way. Most | |
3394 | properties are rear-sticky by default, so the @code{rear-nonsticky} | |
3395 | property says which properties are @emph{not} rear-sticky. If a | |
3396 | character's @code{rear-nonsticky} property is @code{t}, then none of its | |
3397 | properties are rear-sticky. If the @code{rear-nonsticky} property is a | |
3398 | list, properties are rear-sticky @emph{unless} their names are in the | |
3399 | list. | |
3400 | ||
3401 | @defvar text-property-default-nonsticky | |
3402 | This variable holds an alist which defines the default rear-stickiness | |
3403 | of various text properties. Each element has the form | |
3404 | @code{(@var{property} . @var{nonstickiness})}, and it defines the | |
3405 | stickiness of a particular text property, @var{property}. | |
3406 | ||
3407 | If @var{nonstickiness} is non-@code{nil}, this means that the property | |
3408 | @var{property} is rear-nonsticky by default. Since all properties are | |
3409 | front-nonsticky by default, this makes @var{property} nonsticky in both | |
3410 | directions by default. | |
3411 | ||
3412 | The text properties @code{front-sticky} and @code{rear-nonsticky}, when | |
3413 | used, take precedence over the default @var{nonstickiness} specified in | |
3414 | @code{text-property-default-nonsticky}. | |
3415 | @end defvar | |
3416 | ||
3417 | Here are the functions that insert text with inheritance of properties: | |
3418 | ||
3419 | @defun insert-and-inherit &rest strings | |
3420 | Insert the strings @var{strings}, just like the function @code{insert}, | |
3421 | but inherit any sticky properties from the adjoining text. | |
3422 | @end defun | |
3423 | ||
3424 | @defun insert-before-markers-and-inherit &rest strings | |
3425 | Insert the strings @var{strings}, just like the function | |
3426 | @code{insert-before-markers}, but inherit any sticky properties from the | |
3427 | adjoining text. | |
3428 | @end defun | |
3429 | ||
3430 | @xref{Insertion}, for the ordinary insertion functions which do not | |
3431 | inherit. | |
3432 | ||
3433 | @node Lazy Properties | |
3434 | @subsection Lazy Computation of Text Properties | |
3435 | ||
3436 | Instead of computing text properties for all the text in the buffer, | |
3437 | you can arrange to compute the text properties for parts of the text | |
3438 | when and if something depends on them. | |
3439 | ||
3440 | The primitive that extracts text from the buffer along with its | |
3441 | properties is @code{buffer-substring}. Before examining the properties, | |
3442 | this function runs the abnormal hook @code{buffer-access-fontify-functions}. | |
3443 | ||
3444 | @defvar buffer-access-fontify-functions | |
3445 | This variable holds a list of functions for computing text properties. | |
3446 | Before @code{buffer-substring} copies the text and text properties for a | |
3447 | portion of the buffer, it calls all the functions in this list. Each of | |
3448 | the functions receives two arguments that specify the range of the | |
3449 | buffer being accessed. (The buffer itself is always the current | |
3450 | buffer.) | |
3451 | @end defvar | |
3452 | ||
3453 | The function @code{buffer-substring-no-properties} does not call these | |
3454 | functions, since it ignores text properties anyway. | |
3455 | ||
3456 | In order to prevent the hook functions from being called more than | |
3457 | once for the same part of the buffer, you can use the variable | |
3458 | @code{buffer-access-fontified-property}. | |
3459 | ||
3460 | @defvar buffer-access-fontified-property | |
3461 | If this variable's value is non-@code{nil}, it is a symbol which is used | |
3462 | as a text property name. A non-@code{nil} value for that text property | |
3463 | means, ``the other text properties for this character have already been | |
3464 | computed.'' | |
3465 | ||
3466 | If all the characters in the range specified for @code{buffer-substring} | |
3467 | have a non-@code{nil} value for this property, @code{buffer-substring} | |
3468 | does not call the @code{buffer-access-fontify-functions} functions. It | |
3469 | assumes these characters already have the right text properties, and | |
3470 | just copies the properties they already have. | |
3471 | ||
3472 | The normal way to use this feature is that the | |
3473 | @code{buffer-access-fontify-functions} functions add this property, as | |
3474 | well as others, to the characters they operate on. That way, they avoid | |
3475 | being called over and over for the same text. | |
3476 | @end defvar | |
3477 | ||
3478 | @node Clickable Text | |
3479 | @subsection Defining Clickable Text | |
3480 | @cindex clickable text | |
2bad3299 CY |
3481 | @cindex follow links |
3482 | @cindex mouse-1 | |
b8d4c8d0 GM |
3483 | |
3484 | @dfn{Clickable text} is text that can be clicked, with either the | |
2bad3299 CY |
3485 | mouse or via a keyboard command, to produce some result. Many major |
3486 | modes use clickable text to implement textual hyper-links, or | |
3487 | @dfn{links} for short. | |
3488 | ||
3489 | The easiest way to insert and manipulate links is to use the | |
3490 | @code{button} package. @xref{Buttons}. In this section, we will | |
3491 | explain how to manually set up clickable text in a buffer, using text | |
3492 | properties. For simplicity, we will refer to the clickable text as a | |
3493 | @dfn{link}. | |
3494 | ||
3495 | Implementing a link involves three separate steps: (1) indicating | |
3496 | clickability when the mouse moves over the link; (2) making @kbd{RET} | |
3497 | or @kbd{Mouse-2} on that link do something; and (3) setting up a | |
3498 | @code{follow-link} condition so that the link obeys | |
3499 | @code{mouse-1-click-follows-link}. | |
3500 | ||
3501 | To indicate clickability, add the @code{mouse-face} text property to | |
3502 | the text of the link; then Emacs will highlight the link when the | |
3503 | mouse moves over it. In addition, you should define a tooltip or echo | |
3504 | area message, using the @code{help-echo} text property. @xref{Special | |
3505 | Properties}. For instance, here is how Dired indicates that file | |
3506 | names are clickable: | |
b8d4c8d0 GM |
3507 | |
3508 | @smallexample | |
2bad3299 CY |
3509 | (if (dired-move-to-filename) |
3510 | (add-text-properties | |
3511 | (point) | |
3512 | (save-excursion | |
3513 | (dired-move-to-end-of-filename) | |
3514 | (point)) | |
3515 | '(mouse-face highlight | |
3516 | help-echo "mouse-2: visit this file in other window"))) | |
b8d4c8d0 GM |
3517 | @end smallexample |
3518 | ||
2bad3299 CY |
3519 | To make the link clickable, bind @key{RET} and @kbd{Mouse-2} to |
3520 | commands that perform the desired action. Each command should check | |
3521 | to see whether it was called on a link, and act accordingly. For | |
3522 | instance, Dired's major mode keymap binds @kbd{Mouse-2} to the | |
3523 | following command: | |
b8d4c8d0 GM |
3524 | |
3525 | @smallexample | |
3526 | (defun dired-mouse-find-file-other-window (event) | |
3527 | "In Dired, visit the file or directory name you click on." | |
3528 | (interactive "e") | |
c57008f6 SM |
3529 | (let ((window (posn-window (event-end event))) |
3530 | (pos (posn-point (event-end event))) | |
3531 | file) | |
3532 | (if (not (windowp window)) | |
3533 | (error "No file chosen")) | |
3534 | (with-current-buffer (window-buffer window) | |
b8d4c8d0 GM |
3535 | (goto-char pos) |
3536 | (setq file (dired-get-file-for-visit))) | |
3537 | (if (file-directory-p file) | |
3538 | (or (and (cdr dired-subdir-alist) | |
3539 | (dired-goto-subdir file)) | |
3540 | (progn | |
3541 | (select-window window) | |
3542 | (dired-other-window file))) | |
3543 | (select-window window) | |
3544 | (find-file-other-window (file-name-sans-versions file t))))) | |
3545 | @end smallexample | |
3546 | ||
3547 | @noindent | |
2bad3299 CY |
3548 | This command uses the functions @code{posn-window} and |
3549 | @code{posn-point} to determine where the click occurred, and | |
3550 | @code{dired-get-file-for-visit} to determine which file to visit. | |
b8d4c8d0 | 3551 | |
2bad3299 CY |
3552 | Instead of binding the mouse command in a major mode keymap, you can |
3553 | bind it within the link text, using the @code{keymap} text property | |
3554 | (@pxref{Special Properties}). For instance: | |
b8d4c8d0 GM |
3555 | |
3556 | @example | |
3557 | (let ((map (make-sparse-keymap))) | |
3558 | (define-key map [mouse-2] 'operate-this-button) | |
2bad3299 | 3559 | (put-text-property link-start link-end 'keymap map)) |
b8d4c8d0 GM |
3560 | @end example |
3561 | ||
3562 | @noindent | |
2bad3299 CY |
3563 | With this method, you can easily define different commands for |
3564 | different links. Furthermore, the global definition of @key{RET} and | |
3565 | @kbd{Mouse-2} remain available for the rest of the text in the buffer. | |
3566 | ||
3567 | @vindex mouse-1-click-follows-link | |
3568 | The basic Emacs command for clicking on links is @kbd{Mouse-2}. | |
3569 | However, for compatibility with other graphical applications, Emacs | |
3570 | also recognizes @kbd{Mouse-1} clicks on links, provided the user | |
3571 | clicks on the link quickly without moving the mouse. This behavior is | |
3572 | controlled by the user option @code{mouse-1-click-follows-link}. | |
3573 | @xref{Mouse References,,, emacs, The GNU Emacs Manual}. | |
3574 | ||
3575 | To set up the link so that it obeys | |
3576 | @code{mouse-1-click-follows-link}, you must either (1) apply a | |
3577 | @code{follow-link} text or overlay property to the link text, or (2) | |
3578 | bind the @code{follow-link} event to a keymap (which can be a major | |
3579 | mode keymap or a local keymap specified via the @code{keymap} text | |
3580 | property). The value of the @code{follow-link} property, or the | |
3581 | binding for the @code{follow-link} event, acts as a ``condition'' for | |
3582 | the link action. This condition tells Emacs two things: the | |
3583 | circumstances under which a @kbd{Mouse-1} click should be regarded as | |
3584 | occurring ``inside'' the link, and how to compute an ``action code'' | |
3585 | that says what to translate the @kbd{Mouse-1} click into. The link | |
3586 | action condition can be one of the following: | |
b8d4c8d0 GM |
3587 | |
3588 | @table @asis | |
3589 | @item @code{mouse-face} | |
2bad3299 CY |
3590 | If the condition is the symbol @code{mouse-face}, a position is inside |
3591 | a link if there is a non-@code{nil} @code{mouse-face} property at that | |
3592 | position. The action code is always @code{t}. | |
b8d4c8d0 GM |
3593 | |
3594 | For example, here is how Info mode handles @key{Mouse-1}: | |
3595 | ||
3596 | @smallexample | |
3597 | (define-key Info-mode-map [follow-link] 'mouse-face) | |
3598 | @end smallexample | |
3599 | ||
3600 | @item a function | |
2bad3299 CY |
3601 | If the condition is a function, @var{func}, then a position @var{pos} |
3602 | is inside a link if @code{(@var{func} @var{pos})} evaluates to | |
3603 | non-@code{nil}. The value returned by @var{func} serves as the action | |
3604 | code. | |
b8d4c8d0 | 3605 | |
2bad3299 | 3606 | For example, here is how pcvs enables @kbd{Mouse-1} to follow links on |
b8d4c8d0 GM |
3607 | file names only: |
3608 | ||
3609 | @smallexample | |
3610 | (define-key map [follow-link] | |
3611 | (lambda (pos) | |
3612 | (eq (get-char-property pos 'face) 'cvs-filename-face))) | |
3613 | @end smallexample | |
3614 | ||
3615 | @item anything else | |
3616 | If the condition value is anything else, then the position is inside a | |
2bad3299 CY |
3617 | link and the condition itself is the action code. Clearly, you should |
3618 | specify this kind of condition only when applying the condition via a | |
3619 | text or property overlay on the link text (so that it does not apply | |
3620 | to the entire buffer). | |
b8d4c8d0 GM |
3621 | @end table |
3622 | ||
3623 | @noindent | |
2bad3299 | 3624 | The action code tells @kbd{Mouse-1} how to follow the link: |
b8d4c8d0 GM |
3625 | |
3626 | @table @asis | |
3627 | @item a string or vector | |
2bad3299 | 3628 | If the action code is a string or vector, the @kbd{Mouse-1} event is |
b8d4c8d0 | 3629 | translated into the first element of the string or vector; i.e., the |
2bad3299 | 3630 | action of the @kbd{Mouse-1} click is the local or global binding of |
b8d4c8d0 | 3631 | that character or symbol. Thus, if the action code is @code{"foo"}, |
2bad3299 CY |
3632 | @kbd{Mouse-1} translates into @kbd{f}. If it is @code{[foo]}, |
3633 | @kbd{Mouse-1} translates into @key{foo}. | |
b8d4c8d0 GM |
3634 | |
3635 | @item anything else | |
2bad3299 CY |
3636 | For any other non-@code{nil} action code, the @kbd{Mouse-1} event is |
3637 | translated into a @kbd{Mouse-2} event at the same position. | |
b8d4c8d0 GM |
3638 | @end table |
3639 | ||
2bad3299 | 3640 | To define @kbd{Mouse-1} to activate a button defined with |
b8d4c8d0 | 3641 | @code{define-button-type}, give the button a @code{follow-link} |
2bad3299 CY |
3642 | property. The property value should be a link action condition, as |
3643 | described above. @xref{Buttons}. For example, here is how Help mode | |
3644 | handles @kbd{Mouse-1}: | |
b8d4c8d0 GM |
3645 | |
3646 | @smallexample | |
3647 | (define-button-type 'help-xref | |
3648 | 'follow-link t | |
3649 | 'action #'help-button-action) | |
3650 | @end smallexample | |
3651 | ||
2bad3299 CY |
3652 | To define @kbd{Mouse-1} on a widget defined with |
3653 | @code{define-widget}, give the widget a @code{:follow-link} property. | |
3654 | The property value should be a link action condition, as described | |
3655 | above. For example, here is how the @code{link} widget specifies that | |
b8d4c8d0 GM |
3656 | a @key{Mouse-1} click shall be translated to @key{RET}: |
3657 | ||
3658 | @smallexample | |
3659 | (define-widget 'link 'item | |
3660 | "An embedded link." | |
3661 | :button-prefix 'widget-link-prefix | |
3662 | :button-suffix 'widget-link-suffix | |
3663 | :follow-link "\C-m" | |
3664 | :help-echo "Follow the link." | |
3665 | :format "%[%t%]") | |
3666 | @end smallexample | |
3667 | ||
3668 | @defun mouse-on-link-p pos | |
3669 | This function returns non-@code{nil} if position @var{pos} in the | |
3670 | current buffer is on a link. @var{pos} can also be a mouse event | |
db3625ba | 3671 | location, as returned by @code{event-start} (@pxref{Accessing Mouse}). |
b8d4c8d0 GM |
3672 | @end defun |
3673 | ||
3674 | @node Fields | |
3675 | @subsection Defining and Using Fields | |
3676 | @cindex fields | |
3677 | ||
3678 | A field is a range of consecutive characters in the buffer that are | |
3679 | identified by having the same value (comparing with @code{eq}) of the | |
3680 | @code{field} property (either a text-property or an overlay property). | |
3681 | This section describes special functions that are available for | |
3682 | operating on fields. | |
3683 | ||
3684 | You specify a field with a buffer position, @var{pos}. We think of | |
3685 | each field as containing a range of buffer positions, so the position | |
3686 | you specify stands for the field containing that position. | |
3687 | ||
3688 | When the characters before and after @var{pos} are part of the same | |
3689 | field, there is no doubt which field contains @var{pos}: the one those | |
3690 | characters both belong to. When @var{pos} is at a boundary between | |
3691 | fields, which field it belongs to depends on the stickiness of the | |
3692 | @code{field} properties of the two surrounding characters (@pxref{Sticky | |
3693 | Properties}). The field whose property would be inherited by text | |
3694 | inserted at @var{pos} is the field that contains @var{pos}. | |
3695 | ||
3696 | There is an anomalous case where newly inserted text at @var{pos} | |
3697 | would not inherit the @code{field} property from either side. This | |
3698 | happens if the previous character's @code{field} property is not | |
3699 | rear-sticky, and the following character's @code{field} property is not | |
3700 | front-sticky. In this case, @var{pos} belongs to neither the preceding | |
3701 | field nor the following field; the field functions treat it as belonging | |
3702 | to an empty field whose beginning and end are both at @var{pos}. | |
3703 | ||
3704 | In all of these functions, if @var{pos} is omitted or @code{nil}, the | |
3705 | value of point is used by default. If narrowing is in effect, then | |
3706 | @var{pos} should fall within the accessible portion. @xref{Narrowing}. | |
3707 | ||
3708 | @defun field-beginning &optional pos escape-from-edge limit | |
3709 | This function returns the beginning of the field specified by @var{pos}. | |
3710 | ||
3711 | If @var{pos} is at the beginning of its field, and | |
3712 | @var{escape-from-edge} is non-@code{nil}, then the return value is | |
3713 | always the beginning of the preceding field that @emph{ends} at @var{pos}, | |
3714 | regardless of the stickiness of the @code{field} properties around | |
3715 | @var{pos}. | |
3716 | ||
3717 | If @var{limit} is non-@code{nil}, it is a buffer position; if the | |
3718 | beginning of the field is before @var{limit}, then @var{limit} will be | |
3719 | returned instead. | |
3720 | @end defun | |
3721 | ||
3722 | @defun field-end &optional pos escape-from-edge limit | |
3723 | This function returns the end of the field specified by @var{pos}. | |
3724 | ||
3725 | If @var{pos} is at the end of its field, and @var{escape-from-edge} is | |
3726 | non-@code{nil}, then the return value is always the end of the following | |
3727 | field that @emph{begins} at @var{pos}, regardless of the stickiness of | |
3728 | the @code{field} properties around @var{pos}. | |
3729 | ||
3730 | If @var{limit} is non-@code{nil}, it is a buffer position; if the end | |
3731 | of the field is after @var{limit}, then @var{limit} will be returned | |
3732 | instead. | |
3733 | @end defun | |
3734 | ||
3735 | @defun field-string &optional pos | |
3736 | This function returns the contents of the field specified by @var{pos}, | |
3737 | as a string. | |
3738 | @end defun | |
3739 | ||
3740 | @defun field-string-no-properties &optional pos | |
3741 | This function returns the contents of the field specified by @var{pos}, | |
3742 | as a string, discarding text properties. | |
3743 | @end defun | |
3744 | ||
3745 | @defun delete-field &optional pos | |
3746 | This function deletes the text of the field specified by @var{pos}. | |
3747 | @end defun | |
3748 | ||
3749 | @defun constrain-to-field new-pos old-pos &optional escape-from-edge only-in-line inhibit-capture-property | |
3750 | This function ``constrains'' @var{new-pos} to the field that | |
3751 | @var{old-pos} belongs to---in other words, it returns the position | |
3752 | closest to @var{new-pos} that is in the same field as @var{old-pos}. | |
3753 | ||
3754 | If @var{new-pos} is @code{nil}, then @code{constrain-to-field} uses | |
3755 | the value of point instead, and moves point to the resulting position | |
3756 | as well as returning it. | |
3757 | ||
3758 | If @var{old-pos} is at the boundary of two fields, then the acceptable | |
3759 | final positions depend on the argument @var{escape-from-edge}. If | |
3760 | @var{escape-from-edge} is @code{nil}, then @var{new-pos} must be in | |
3761 | the field whose @code{field} property equals what new characters | |
3762 | inserted at @var{old-pos} would inherit. (This depends on the | |
3763 | stickiness of the @code{field} property for the characters before and | |
3764 | after @var{old-pos}.) If @var{escape-from-edge} is non-@code{nil}, | |
3765 | @var{new-pos} can be anywhere in the two adjacent fields. | |
3766 | Additionally, if two fields are separated by another field with the | |
3767 | special value @code{boundary}, then any point within this special | |
3768 | field is also considered to be ``on the boundary.'' | |
3769 | ||
3770 | Commands like @kbd{C-a} with no argumemt, that normally move backward | |
3771 | to a specific kind of location and stay there once there, probably | |
3772 | should specify @code{nil} for @var{escape-from-edge}. Other motion | |
3773 | commands that check fields should probably pass @code{t}. | |
3774 | ||
3775 | If the optional argument @var{only-in-line} is non-@code{nil}, and | |
3776 | constraining @var{new-pos} in the usual way would move it to a different | |
3777 | line, @var{new-pos} is returned unconstrained. This used in commands | |
3778 | that move by line, such as @code{next-line} and | |
3779 | @code{beginning-of-line}, so that they respect field boundaries only in | |
3780 | the case where they can still move to the right line. | |
3781 | ||
3782 | If the optional argument @var{inhibit-capture-property} is | |
3783 | non-@code{nil}, and @var{old-pos} has a non-@code{nil} property of that | |
3784 | name, then any field boundaries are ignored. | |
3785 | ||
3786 | You can cause @code{constrain-to-field} to ignore all field boundaries | |
3787 | (and so never constrain anything) by binding the variable | |
3788 | @code{inhibit-field-text-motion} to a non-@code{nil} value. | |
3789 | @end defun | |
3790 | ||
3791 | @node Not Intervals | |
3792 | @subsection Why Text Properties are not Intervals | |
3793 | @cindex intervals | |
3794 | ||
3795 | Some editors that support adding attributes to text in the buffer do | |
3796 | so by letting the user specify ``intervals'' within the text, and adding | |
3797 | the properties to the intervals. Those editors permit the user or the | |
3798 | programmer to determine where individual intervals start and end. We | |
3799 | deliberately provided a different sort of interface in Emacs Lisp to | |
3800 | avoid certain paradoxical behavior associated with text modification. | |
3801 | ||
3802 | If the actual subdivision into intervals is meaningful, that means you | |
3803 | can distinguish between a buffer that is just one interval with a | |
3804 | certain property, and a buffer containing the same text subdivided into | |
3805 | two intervals, both of which have that property. | |
3806 | ||
3807 | Suppose you take the buffer with just one interval and kill part of | |
3808 | the text. The text remaining in the buffer is one interval, and the | |
3809 | copy in the kill ring (and the undo list) becomes a separate interval. | |
3810 | Then if you yank back the killed text, you get two intervals with the | |
3811 | same properties. Thus, editing does not preserve the distinction | |
3812 | between one interval and two. | |
3813 | ||
3814 | Suppose we ``fix'' this problem by coalescing the two intervals when | |
3815 | the text is inserted. That works fine if the buffer originally was a | |
3816 | single interval. But suppose instead that we have two adjacent | |
3817 | intervals with the same properties, and we kill the text of one interval | |
3818 | and yank it back. The same interval-coalescence feature that rescues | |
3819 | the other case causes trouble in this one: after yanking, we have just | |
3820 | one interval. One again, editing does not preserve the distinction | |
3821 | between one interval and two. | |
3822 | ||
3823 | Insertion of text at the border between intervals also raises | |
3824 | questions that have no satisfactory answer. | |
3825 | ||
3826 | However, it is easy to arrange for editing to behave consistently for | |
3827 | questions of the form, ``What are the properties of this character?'' | |
3828 | So we have decided these are the only questions that make sense; we have | |
3829 | not implemented asking questions about where intervals start or end. | |
3830 | ||
3831 | In practice, you can usually use the text property search functions in | |
3832 | place of explicit interval boundaries. You can think of them as finding | |
3833 | the boundaries of intervals, assuming that intervals are always | |
3834 | coalesced whenever possible. @xref{Property Search}. | |
3835 | ||
3836 | Emacs also provides explicit intervals as a presentation feature; see | |
3837 | @ref{Overlays}. | |
3838 | ||
3839 | @node Substitution | |
3840 | @section Substituting for a Character Code | |
3841 | ||
3842 | The following functions replace characters within a specified region | |
3843 | based on their character codes. | |
3844 | ||
3845 | @defun subst-char-in-region start end old-char new-char &optional noundo | |
3846 | @cindex replace characters | |
3847 | This function replaces all occurrences of the character @var{old-char} | |
3848 | with the character @var{new-char} in the region of the current buffer | |
3849 | defined by @var{start} and @var{end}. | |
3850 | ||
3851 | @cindex undo avoidance | |
3852 | If @var{noundo} is non-@code{nil}, then @code{subst-char-in-region} does | |
3853 | not record the change for undo and does not mark the buffer as modified. | |
3854 | This was useful for controlling the old selective display feature | |
3855 | (@pxref{Selective Display}). | |
3856 | ||
3857 | @code{subst-char-in-region} does not move point and returns | |
3858 | @code{nil}. | |
3859 | ||
3860 | @example | |
3861 | @group | |
3862 | ---------- Buffer: foo ---------- | |
3863 | This is the contents of the buffer before. | |
3864 | ---------- Buffer: foo ---------- | |
3865 | @end group | |
3866 | ||
3867 | @group | |
3868 | (subst-char-in-region 1 20 ?i ?X) | |
3869 | @result{} nil | |
3870 | ||
3871 | ---------- Buffer: foo ---------- | |
3872 | ThXs Xs the contents of the buffer before. | |
3873 | ---------- Buffer: foo ---------- | |
3874 | @end group | |
3875 | @end example | |
3876 | @end defun | |
3877 | ||
106e6894 | 3878 | @deffn Command translate-region start end table |
b8d4c8d0 GM |
3879 | This function applies a translation table to the characters in the |
3880 | buffer between positions @var{start} and @var{end}. | |
3881 | ||
3882 | The translation table @var{table} is a string or a char-table; | |
3883 | @code{(aref @var{table} @var{ochar})} gives the translated character | |
3884 | corresponding to @var{ochar}. If @var{table} is a string, any | |
3885 | characters with codes larger than the length of @var{table} are not | |
3886 | altered by the translation. | |
3887 | ||
3888 | The return value of @code{translate-region} is the number of | |
3889 | characters that were actually changed by the translation. This does | |
3890 | not count characters that were mapped into themselves in the | |
3891 | translation table. | |
106e6894 | 3892 | @end deffn |
b8d4c8d0 GM |
3893 | |
3894 | @node Registers | |
3895 | @section Registers | |
3896 | @cindex registers | |
3897 | ||
3898 | A register is a sort of variable used in Emacs editing that can hold a | |
3899 | variety of different kinds of values. Each register is named by a | |
3900 | single character. All @acronym{ASCII} characters and their meta variants | |
3901 | (but with the exception of @kbd{C-g}) can be used to name registers. | |
3902 | Thus, there are 255 possible registers. A register is designated in | |
3903 | Emacs Lisp by the character that is its name. | |
3904 | ||
3905 | @defvar register-alist | |
3906 | This variable is an alist of elements of the form @code{(@var{name} . | |
3907 | @var{contents})}. Normally, there is one element for each Emacs | |
3908 | register that has been used. | |
3909 | ||
3910 | The object @var{name} is a character (an integer) identifying the | |
3911 | register. | |
3912 | @end defvar | |
3913 | ||
3914 | The @var{contents} of a register can have several possible types: | |
3915 | ||
3916 | @table @asis | |
3917 | @item a number | |
3918 | A number stands for itself. If @code{insert-register} finds a number | |
3919 | in the register, it converts the number to decimal. | |
3920 | ||
3921 | @item a marker | |
3922 | A marker represents a buffer position to jump to. | |
3923 | ||
3924 | @item a string | |
3925 | A string is text saved in the register. | |
3926 | ||
3927 | @item a rectangle | |
3928 | A rectangle is represented by a list of strings. | |
3929 | ||
3930 | @item @code{(@var{window-configuration} @var{position})} | |
3931 | This represents a window configuration to restore in one frame, and a | |
3932 | position to jump to in the current buffer. | |
3933 | ||
3934 | @item @code{(@var{frame-configuration} @var{position})} | |
3935 | This represents a frame configuration to restore, and a position | |
3936 | to jump to in the current buffer. | |
3937 | ||
3938 | @item (file @var{filename}) | |
3939 | This represents a file to visit; jumping to this value visits file | |
3940 | @var{filename}. | |
3941 | ||
3942 | @item (file-query @var{filename} @var{position}) | |
3943 | This represents a file to visit and a position in it; jumping to this | |
3944 | value visits file @var{filename} and goes to buffer position | |
3945 | @var{position}. Restoring this type of position asks the user for | |
3946 | confirmation first. | |
3947 | @end table | |
3948 | ||
3949 | The functions in this section return unpredictable values unless | |
3950 | otherwise stated. | |
3951 | ||
3952 | @defun get-register reg | |
3953 | This function returns the contents of the register | |
3954 | @var{reg}, or @code{nil} if it has no contents. | |
3955 | @end defun | |
3956 | ||
3957 | @defun set-register reg value | |
3958 | This function sets the contents of register @var{reg} to @var{value}. | |
3959 | A register can be set to any value, but the other register functions | |
3960 | expect only certain data types. The return value is @var{value}. | |
3961 | @end defun | |
3962 | ||
3963 | @deffn Command view-register reg | |
3964 | This command displays what is contained in register @var{reg}. | |
3965 | @end deffn | |
3966 | ||
b8d4c8d0 GM |
3967 | @deffn Command insert-register reg &optional beforep |
3968 | This command inserts contents of register @var{reg} into the current | |
3969 | buffer. | |
3970 | ||
3971 | Normally, this command puts point before the inserted text, and the | |
3972 | mark after it. However, if the optional second argument @var{beforep} | |
3973 | is non-@code{nil}, it puts the mark before and point after. | |
3974 | You can pass a non-@code{nil} second argument @var{beforep} to this | |
3975 | function interactively by supplying any prefix argument. | |
3976 | ||
3977 | If the register contains a rectangle, then the rectangle is inserted | |
3978 | with its upper left corner at point. This means that text is inserted | |
3979 | in the current line and underneath it on successive lines. | |
3980 | ||
3981 | If the register contains something other than saved text (a string) or | |
3982 | a rectangle (a list), currently useless things happen. This may be | |
3983 | changed in the future. | |
3984 | @end deffn | |
3985 | ||
b8d4c8d0 GM |
3986 | @node Transposition |
3987 | @section Transposition of Text | |
3988 | ||
3989 | This subroutine is used by the transposition commands. | |
3990 | ||
3991 | @defun transpose-regions start1 end1 start2 end2 &optional leave-markers | |
3992 | This function exchanges two nonoverlapping portions of the buffer. | |
3993 | Arguments @var{start1} and @var{end1} specify the bounds of one portion | |
3994 | and arguments @var{start2} and @var{end2} specify the bounds of the | |
3995 | other portion. | |
3996 | ||
3997 | Normally, @code{transpose-regions} relocates markers with the transposed | |
3998 | text; a marker previously positioned within one of the two transposed | |
3999 | portions moves along with that portion, thus remaining between the same | |
4000 | two characters in their new position. However, if @var{leave-markers} | |
4001 | is non-@code{nil}, @code{transpose-regions} does not do this---it leaves | |
4002 | all markers unrelocated. | |
4003 | @end defun | |
4004 | ||
4005 | @node Base 64 | |
4006 | @section Base 64 Encoding | |
4007 | @cindex base 64 encoding | |
4008 | ||
4009 | Base 64 code is used in email to encode a sequence of 8-bit bytes as | |
4010 | a longer sequence of @acronym{ASCII} graphic characters. It is defined in | |
4011 | Internet RFC@footnote{ | |
4012 | An RFC, an acronym for @dfn{Request for Comments}, is a numbered | |
4013 | Internet informational document describing a standard. RFCs are | |
4014 | usually written by technical experts acting on their own initiative, | |
4015 | and are traditionally written in a pragmatic, experience-driven | |
4016 | manner. | |
4017 | }2045. This section describes the functions for | |
4018 | converting to and from this code. | |
4019 | ||
106e6894 | 4020 | @deffn Command base64-encode-region beg end &optional no-line-break |
b8d4c8d0 GM |
4021 | This function converts the region from @var{beg} to @var{end} into base |
4022 | 64 code. It returns the length of the encoded text. An error is | |
4023 | signaled if a character in the region is multibyte, i.e.@: in a | |
4024 | multibyte buffer the region must contain only characters from the | |
4025 | charsets @code{ascii}, @code{eight-bit-control} and | |
4026 | @code{eight-bit-graphic}. | |
4027 | ||
4028 | Normally, this function inserts newline characters into the encoded | |
4029 | text, to avoid overlong lines. However, if the optional argument | |
4030 | @var{no-line-break} is non-@code{nil}, these newlines are not added, so | |
4031 | the output is just one long line. | |
106e6894 | 4032 | @end deffn |
b8d4c8d0 | 4033 | |
106e6894 | 4034 | @deffn Command base64-encode-string string &optional no-line-break |
b8d4c8d0 GM |
4035 | This function converts the string @var{string} into base 64 code. It |
4036 | returns a string containing the encoded text. As for | |
4037 | @code{base64-encode-region}, an error is signaled if a character in the | |
4038 | string is multibyte. | |
4039 | ||
4040 | Normally, this function inserts newline characters into the encoded | |
4041 | text, to avoid overlong lines. However, if the optional argument | |
4042 | @var{no-line-break} is non-@code{nil}, these newlines are not added, so | |
4043 | the result string is just one long line. | |
106e6894 | 4044 | @end deffn |
b8d4c8d0 GM |
4045 | |
4046 | @defun base64-decode-region beg end | |
4047 | This function converts the region from @var{beg} to @var{end} from base | |
4048 | 64 code into the corresponding decoded text. It returns the length of | |
4049 | the decoded text. | |
4050 | ||
4051 | The decoding functions ignore newline characters in the encoded text. | |
4052 | @end defun | |
4053 | ||
4054 | @defun base64-decode-string string | |
4055 | This function converts the string @var{string} from base 64 code into | |
4056 | the corresponding decoded text. It returns a unibyte string containing the | |
4057 | decoded text. | |
4058 | ||
4059 | The decoding functions ignore newline characters in the encoded text. | |
4060 | @end defun | |
4061 | ||
4062 | @node MD5 Checksum | |
4063 | @section MD5 Checksum | |
4064 | @cindex MD5 checksum | |
4065 | @cindex message digest computation | |
4066 | ||
4067 | MD5 cryptographic checksums, or @dfn{message digests}, are 128-bit | |
4068 | ``fingerprints'' of a document or program. They are used to verify | |
4069 | that you have an exact and unaltered copy of the data. The algorithm | |
4070 | to calculate the MD5 message digest is defined in Internet | |
4071 | RFC@footnote{ | |
4072 | For an explanation of what is an RFC, see the footnote in @ref{Base | |
4073 | 64}. | |
4074 | }1321. This section describes the Emacs facilities for computing | |
4075 | message digests. | |
4076 | ||
4077 | @defun md5 object &optional start end coding-system noerror | |
4078 | This function returns the MD5 message digest of @var{object}, which | |
4079 | should be a buffer or a string. | |
4080 | ||
4081 | The two optional arguments @var{start} and @var{end} are character | |
4082 | positions specifying the portion of @var{object} to compute the | |
4083 | message digest for. If they are @code{nil} or omitted, the digest is | |
4084 | computed for the whole of @var{object}. | |
4085 | ||
4086 | The function @code{md5} does not compute the message digest directly | |
4087 | from the internal Emacs representation of the text (@pxref{Text | |
4088 | Representations}). Instead, it encodes the text using a coding | |
4089 | system, and computes the message digest from the encoded text. The | |
4090 | optional fourth argument @var{coding-system} specifies which coding | |
4091 | system to use for encoding the text. It should be the same coding | |
4092 | system that you used to read the text, or that you used or will use | |
4093 | when saving or sending the text. @xref{Coding Systems}, for more | |
4094 | information about coding systems. | |
4095 | ||
4096 | If @var{coding-system} is @code{nil} or omitted, the default depends | |
4097 | on @var{object}. If @var{object} is a buffer, the default for | |
4098 | @var{coding-system} is whatever coding system would be chosen by | |
4099 | default for writing this text into a file. If @var{object} is a | |
4100 | string, the user's most preferred coding system (@pxref{Recognize | |
4101 | Coding, prefer-coding-system, the description of | |
4102 | @code{prefer-coding-system}, emacs, GNU Emacs Manual}) is used. | |
4103 | ||
4104 | Normally, @code{md5} signals an error if the text can't be encoded | |
4105 | using the specified or chosen coding system. However, if | |
4106 | @var{noerror} is non-@code{nil}, it silently uses @code{raw-text} | |
4107 | coding instead. | |
4108 | @end defun | |
4109 | ||
381408e2 LMI |
4110 | @node Parsing HTML |
4111 | @section Parsing HTML | |
4112 | @cindex parsing html | |
4113 | @cindex parsing xml | |
4114 | ||
4115 | Emacs provides an interface to the @code{libxml2} library via two | |
4116 | functions: @code{html-parse-buffer} and @code{xml-parse-buffer}. The | |
4117 | HTML function will parse ``real world'' HTML and try to return a | |
4118 | sensible parse tree, while the XML function is somewhat stricter about | |
4119 | syntax. | |
4120 | ||
4121 | They both take a two optional parameter. The first is a buffer, and | |
4122 | the second is a base URL to be used to expand relative URLs in the | |
4123 | document, if any. | |
4124 | ||
4125 | Here's an example demonstrating the structure of the parsed data you | |
4126 | get out. Given this HTML document: | |
4127 | ||
4128 | @example | |
4129 | <html><hEad></head><body width=101><div class=thing>Foo<div>Yes | |
4130 | @end example | |
4131 | ||
4132 | You get this parse tree: | |
4133 | ||
4134 | @example | |
4135 | (html | |
4136 | (head) | |
4137 | (body | |
4138 | (:width . "101") | |
4139 | (div | |
4140 | (:class . "thing") | |
4141 | (text . "Foo") | |
4142 | (div | |
4143 | (text . "Yes\n"))))) | |
4144 | @end example | |
4145 | ||
4146 | It's a simple tree structure, where the @code{car} for each node is | |
4147 | the name of the node, and the @code{cdr} is the value, or the list of | |
4148 | values. | |
4149 | ||
4150 | Attributes are coded the same way as child nodes, but with @samp{:} as | |
4151 | the first character. | |
4152 | ||
b8d4c8d0 GM |
4153 | @node Atomic Changes |
4154 | @section Atomic Change Groups | |
4155 | @cindex atomic changes | |
4156 | ||
4157 | In data base terminology, an @dfn{atomic} change is an indivisible | |
4158 | change---it can succeed entirely or it can fail entirely, but it | |
4159 | cannot partly succeed. A Lisp program can make a series of changes to | |
4160 | one or several buffers as an @dfn{atomic change group}, meaning that | |
4161 | either the entire series of changes will be installed in their buffers | |
4162 | or, in case of an error, none of them will be. | |
4163 | ||
4164 | To do this for one buffer, the one already current, simply write a | |
4165 | call to @code{atomic-change-group} around the code that makes the | |
4166 | changes, like this: | |
4167 | ||
4168 | @example | |
4169 | (atomic-change-group | |
4170 | (insert foo) | |
4171 | (delete-region x y)) | |
4172 | @end example | |
4173 | ||
4174 | @noindent | |
4175 | If an error (or other nonlocal exit) occurs inside the body of | |
4176 | @code{atomic-change-group}, it unmakes all the changes in that buffer | |
4177 | that were during the execution of the body. This kind of change group | |
4178 | has no effect on any other buffers---any such changes remain. | |
4179 | ||
4180 | If you need something more sophisticated, such as to make changes in | |
4181 | various buffers constitute one atomic group, you must directly call | |
4182 | lower-level functions that @code{atomic-change-group} uses. | |
4183 | ||
4184 | @defun prepare-change-group &optional buffer | |
4185 | This function sets up a change group for buffer @var{buffer}, which | |
4186 | defaults to the current buffer. It returns a ``handle'' that | |
4187 | represents the change group. You must use this handle to activate the | |
4188 | change group and subsequently to finish it. | |
4189 | @end defun | |
4190 | ||
4191 | To use the change group, you must @dfn{activate} it. You must do | |
4192 | this before making any changes in the text of @var{buffer}. | |
4193 | ||
4194 | @defun activate-change-group handle | |
4195 | This function activates the change group that @var{handle} designates. | |
4196 | @end defun | |
4197 | ||
4198 | After you activate the change group, any changes you make in that | |
4199 | buffer become part of it. Once you have made all the desired changes | |
4200 | in the buffer, you must @dfn{finish} the change group. There are two | |
4201 | ways to do this: you can either accept (and finalize) all the changes, | |
4202 | or cancel them all. | |
4203 | ||
4204 | @defun accept-change-group handle | |
4205 | This function accepts all the changes in the change group specified by | |
4206 | @var{handle}, making them final. | |
4207 | @end defun | |
4208 | ||
4209 | @defun cancel-change-group handle | |
4210 | This function cancels and undoes all the changes in the change group | |
4211 | specified by @var{handle}. | |
4212 | @end defun | |
4213 | ||
4214 | Your code should use @code{unwind-protect} to make sure the group is | |
4215 | always finished. The call to @code{activate-change-group} should be | |
4216 | inside the @code{unwind-protect}, in case the user types @kbd{C-g} | |
4217 | just after it runs. (This is one reason why | |
4218 | @code{prepare-change-group} and @code{activate-change-group} are | |
4219 | separate functions, because normally you would call | |
4220 | @code{prepare-change-group} before the start of that | |
4221 | @code{unwind-protect}.) Once you finish the group, don't use the | |
4222 | handle again---in particular, don't try to finish the same group | |
4223 | twice. | |
4224 | ||
4225 | To make a multibuffer change group, call @code{prepare-change-group} | |
4226 | once for each buffer you want to cover, then use @code{nconc} to | |
4227 | combine the returned values, like this: | |
4228 | ||
4229 | @example | |
4230 | (nconc (prepare-change-group buffer-1) | |
4231 | (prepare-change-group buffer-2)) | |
4232 | @end example | |
4233 | ||
4234 | You can then activate the multibuffer change group with a single call | |
4235 | to @code{activate-change-group}, and finish it with a single call to | |
4236 | @code{accept-change-group} or @code{cancel-change-group}. | |
4237 | ||
4238 | Nested use of several change groups for the same buffer works as you | |
4239 | would expect. Non-nested use of change groups for the same buffer | |
4240 | will get Emacs confused, so don't let it happen; the first change | |
4241 | group you start for any given buffer should be the last one finished. | |
4242 | ||
4243 | @node Change Hooks | |
4244 | @section Change Hooks | |
4245 | @cindex change hooks | |
4246 | @cindex hooks for text changes | |
4247 | ||
4248 | These hook variables let you arrange to take notice of all changes in | |
4249 | all buffers (or in a particular buffer, if you make them buffer-local). | |
4250 | See also @ref{Special Properties}, for how to detect changes to specific | |
4251 | parts of the text. | |
4252 | ||
4253 | The functions you use in these hooks should save and restore the match | |
4254 | data if they do anything that uses regular expressions; otherwise, they | |
4255 | will interfere in bizarre ways with the editing operations that call | |
4256 | them. | |
4257 | ||
4258 | @defvar before-change-functions | |
4259 | This variable holds a list of functions to call before any buffer | |
4260 | modification. Each function gets two arguments, the beginning and end | |
4261 | of the region that is about to change, represented as integers. The | |
4262 | buffer that is about to change is always the current buffer. | |
4263 | @end defvar | |
4264 | ||
4265 | @defvar after-change-functions | |
4266 | This variable holds a list of functions to call after any buffer | |
4267 | modification. Each function receives three arguments: the beginning and | |
4268 | end of the region just changed, and the length of the text that existed | |
4269 | before the change. All three arguments are integers. The buffer that's | |
4270 | about to change is always the current buffer. | |
4271 | ||
4272 | The length of the old text is the difference between the buffer positions | |
4273 | before and after that text as it was before the change. As for the | |
4274 | changed text, its length is simply the difference between the first two | |
4275 | arguments. | |
4276 | @end defvar | |
4277 | ||
4278 | Output of messages into the @samp{*Messages*} buffer does not | |
4279 | call these functions. | |
4280 | ||
4281 | @defmac combine-after-change-calls body@dots{} | |
4282 | The macro executes @var{body} normally, but arranges to call the | |
4283 | after-change functions just once for a series of several changes---if | |
4284 | that seems safe. | |
4285 | ||
4286 | If a program makes several text changes in the same area of the buffer, | |
4287 | using the macro @code{combine-after-change-calls} around that part of | |
4288 | the program can make it run considerably faster when after-change hooks | |
4289 | are in use. When the after-change hooks are ultimately called, the | |
4290 | arguments specify a portion of the buffer including all of the changes | |
4291 | made within the @code{combine-after-change-calls} body. | |
4292 | ||
4293 | @strong{Warning:} You must not alter the values of | |
4294 | @code{after-change-functions} within | |
4295 | the body of a @code{combine-after-change-calls} form. | |
4296 | ||
4297 | @strong{Warning:} if the changes you combine occur in widely scattered | |
4298 | parts of the buffer, this will still work, but it is not advisable, | |
4299 | because it may lead to inefficient behavior for some change hook | |
4300 | functions. | |
4301 | @end defmac | |
4302 | ||
4303 | @defvar first-change-hook | |
4304 | This variable is a normal hook that is run whenever a buffer is changed | |
4305 | that was previously in the unmodified state. | |
4306 | @end defvar | |
4307 | ||
4308 | @defvar inhibit-modification-hooks | |
4309 | If this variable is non-@code{nil}, all of the change hooks are | |
4310 | disabled; none of them run. This affects all the hook variables | |
4311 | described above in this section, as well as the hooks attached to | |
4312 | certain special text properties (@pxref{Special Properties}) and overlay | |
4313 | properties (@pxref{Overlay Properties}). | |
4314 | ||
4315 | Also, this variable is bound to non-@code{nil} while running those | |
4316 | same hook variables, so that by default modifying the buffer from | |
4317 | a modification hook does not cause other modification hooks to be run. | |
4318 | If you do want modification hooks to be run in a particular piece of | |
4319 | code that is itself run from a modification hook, then rebind locally | |
4320 | @code{inhibit-modification-hooks} to @code{nil}. | |
4321 | @end defvar | |
4322 | ||
4323 | @ignore | |
4324 | arch-tag: 3721e738-a1cb-4085-bc1a-6cb8d8e1d32b | |
4325 | @end ignore |