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,
4 @c 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
5 @c See the file elisp.texi for copying conditions.
6 @setfilename ../info/text
7 @node Text, Non-ASCII Characters, Markers, Top
11 This chapter describes the functions that deal with the text in a
12 buffer. Most examine, insert, or delete text in the current buffer,
13 often operating at point or on text adjacent to point. Many are
14 interactive. All the functions that change the text provide for undoing
15 the changes (@pxref{Undo}).
17 Many text-related functions operate on a region of text defined by two
18 buffer positions passed in arguments named @var{start} and @var{end}.
19 These arguments should be either markers (@pxref{Markers}) or numeric
20 character positions (@pxref{Positions}). The order of these arguments
21 does not matter; it is all right for @var{start} to be the end of the
22 region and @var{end} the beginning. For example, @code{(delete-region 1
23 10)} and @code{(delete-region 10 1)} are equivalent. An
24 @code{args-out-of-range} error is signaled if either @var{start} or
25 @var{end} is outside the accessible portion of the buffer. In an
26 interactive call, point and the mark are used for these arguments.
28 @cindex buffer contents
29 Throughout this chapter, ``text'' refers to the characters in the
30 buffer, together with their properties (when relevant). Keep in mind
31 that point is always between two characters, and the cursor appears on
32 the character after point.
35 * Near Point:: Examining text in the vicinity of point.
36 * Buffer Contents:: Examining text in a general fashion.
37 * Comparing Text:: Comparing substrings of buffers.
38 * Insertion:: Adding new text to a buffer.
39 * Commands for Insertion:: User-level commands to insert text.
40 * Deletion:: Removing text from a buffer.
41 * User-Level Deletion:: User-level commands to delete text.
42 * The Kill Ring:: Where removed text sometimes is saved for later use.
43 * Undo:: Undoing changes to the text of a buffer.
44 * Maintaining Undo:: How to enable and disable undo information.
45 How to control how much information is kept.
46 * Filling:: Functions for explicit filling.
47 * Margins:: How to specify margins for filling commands.
48 * Adaptive Fill:: Adaptive Fill mode chooses a fill prefix from context.
49 * Auto Filling:: How auto-fill mode is implemented to break lines.
50 * Sorting:: Functions for sorting parts of the buffer.
51 * Columns:: Computing horizontal positions, and using them.
52 * Indentation:: Functions to insert or adjust indentation.
53 * Case Changes:: Case conversion of parts of the buffer.
54 * Text Properties:: Assigning Lisp property lists to text characters.
55 * Substitution:: Replacing a given character wherever it appears.
56 * Transposition:: Swapping two portions of a buffer.
57 * Registers:: How registers are implemented. Accessing the text or
58 position stored in a register.
59 * Base 64:: Conversion to or from base 64 encoding.
60 * MD5 Checksum:: Compute the MD5 ``message digest''/``checksum''.
61 * Atomic Changes:: Installing several buffer changes ``atomically''.
62 * Change Hooks:: Supplying functions to be run when text is changed.
66 @section Examining Text Near Point
68 Many functions are provided to look at the characters around point.
69 Several simple functions are described here. See also @code{looking-at}
70 in @ref{Regexp Search}.
72 In the following four functions, ``beginning'' or ``end'' of buffer
73 refers to the beginning or end of the accessible portion.
75 @defun char-after &optional position
76 This function returns the character in the current buffer at (i.e.,
77 immediately after) position @var{position}. If @var{position} is out of
78 range for this purpose, either before the beginning of the buffer, or at
79 or beyond the end, then the value is @code{nil}. The default for
80 @var{position} is point.
82 In the following example, assume that the first character in the
87 (char-to-string (char-after 1))
93 @defun char-before &optional position
94 This function returns the character in the current buffer immediately
95 before position @var{position}. If @var{position} is out of range for
96 this purpose, either at or before the beginning of the buffer, or beyond
97 the end, then the value is @code{nil}. The default for
98 @var{position} is point.
101 @defun following-char
102 This function returns the character following point in the current
103 buffer. This is similar to @code{(char-after (point))}. However, if
104 point is at the end of the buffer, then @code{following-char} returns 0.
106 Remember that point is always between characters, and the terminal
107 cursor normally appears over the character following point. Therefore,
108 the character returned by @code{following-char} is the character the
111 In this example, point is between the @samp{a} and the @samp{c}.
115 ---------- Buffer: foo ----------
116 Gentlemen may cry ``Pea@point{}ce! Peace!,''
117 but there is no peace.
118 ---------- Buffer: foo ----------
122 (char-to-string (preceding-char))
124 (char-to-string (following-char))
130 @defun preceding-char
131 This function returns the character preceding point in the current
132 buffer. See above, under @code{following-char}, for an example. If
133 point is at the beginning of the buffer, @code{preceding-char} returns
138 This function returns @code{t} if point is at the beginning of the
139 buffer. If narrowing is in effect, this means the beginning of the
140 accessible portion of the text. See also @code{point-min} in
145 This function returns @code{t} if point is at the end of the buffer.
146 If narrowing is in effect, this means the end of accessible portion of
147 the text. See also @code{point-max} in @xref{Point}.
151 This function returns @code{t} if point is at the beginning of a line.
152 @xref{Text Lines}. The beginning of the buffer (or of its accessible
153 portion) always counts as the beginning of a line.
157 This function returns @code{t} if point is at the end of a line. The
158 end of the buffer (or of its accessible portion) is always considered
162 @node Buffer Contents
163 @section Examining Buffer Contents
165 This section describes functions that allow a Lisp program to
166 convert any portion of the text in the buffer into a string.
168 @defun buffer-substring start end
169 This function returns a string containing a copy of the text of the
170 region defined by positions @var{start} and @var{end} in the current
171 buffer. If the arguments are not positions in the accessible portion of
172 the buffer, @code{buffer-substring} signals an @code{args-out-of-range}
175 It is not necessary for @var{start} to be less than @var{end}; the
176 arguments can be given in either order. But most often the smaller
177 argument is written first.
179 If the text being copied has any text properties, these are copied into
180 the string along with the characters they belong to. @xref{Text
181 Properties}. However, overlays (@pxref{Overlays}) in the buffer and
182 their properties are ignored, not copied.
186 ---------- Buffer: foo ----------
187 This is the contents of buffer foo
189 ---------- Buffer: foo ----------
193 (buffer-substring 1 10)
194 @result{} "This is t"
197 (buffer-substring (point-max) 10)
198 @result{} "he contents of buffer foo\n"
203 @defun buffer-substring-no-properties start end
204 This is like @code{buffer-substring}, except that it does not copy text
205 properties, just the characters themselves. @xref{Text Properties}.
208 @defun filter-buffer-substring start end &optional delete
209 This function passes the buffer text between @var{start} and @var{end}
210 through the filter functions specified by the variable
211 @code{buffer-substring-filters}, and returns the value from the last
212 filter function. If @code{buffer-substring-filters} is @code{nil},
213 the value is the unaltered text from the buffer, what
214 @code{buffer-substring} would return.
216 If @var{delete} is non-@code{nil}, this function deletes the text
217 between @var{start} and @var{end} after copying it, like
218 @code{delete-and-extract-region}.
220 Lisp code should use this function instead of @code{buffer-substring}
221 or @code{delete-and-extract-region} when copying into user-accessible
222 data structures such as the kill-ring, X clipboard, and registers.
223 Major and minor modes can add functions to
224 @code{buffer-substring-filters} to alter such text as it is copied out
228 @defvar buffer-substring-filters
229 This variable should be a list of functions that accept a single
230 argument, a string, and return a string.
231 @code{filter-buffer-substring} passes the buffer substring to the
232 first function in this list, and the return value of each function is
233 passed to the next function. The return value of the last function is
234 used as the return value of @code{filter-buffer-substring}.
236 As a special convention, point is set to the start of the buffer text
237 being operated on (i.e., the @var{start} argument for
238 @code{filter-buffer-substring}) before these functions are called.
240 If this variable is @code{nil}, no filtering is performed.
244 This function returns the contents of the entire accessible portion of
245 the current buffer as a string. It is equivalent to
248 (buffer-substring (point-min) (point-max))
253 ---------- Buffer: foo ----------
254 This is the contents of buffer foo
256 ---------- Buffer: foo ----------
259 @result{} "This is the contents of buffer foo\n"
265 @defun current-word &optional strict really-word
266 This function returns the symbol (or word) at or near point, as a string.
267 The return value includes no text properties.
269 If the optional argument @var{really-word} is non-@code{nil}, it finds a
270 word; otherwise, it finds a symbol (which includes both word
271 characters and symbol constituent characters).
273 If the optional argument @var{strict} is non-@code{nil}, then point
274 must be in or next to the symbol or word---if no symbol or word is
275 there, the function returns @code{nil}. Otherwise, a nearby symbol or
276 word on the same line is acceptable.
279 @defun thing-at-point thing
280 Return the @var{thing} around or next to point, as a string.
282 The argument @var{thing} is a symbol which specifies a kind of syntactic
283 entity. Possibilities include @code{symbol}, @code{list}, @code{sexp},
284 @code{defun}, @code{filename}, @code{url}, @code{word}, @code{sentence},
285 @code{whitespace}, @code{line}, @code{page}, and others.
288 ---------- Buffer: foo ----------
289 Gentlemen may cry ``Pea@point{}ce! Peace!,''
290 but there is no peace.
291 ---------- Buffer: foo ----------
293 (thing-at-point 'word)
295 (thing-at-point 'line)
296 @result{} "Gentlemen may cry ``Peace! Peace!,''\n"
297 (thing-at-point 'whitespace)
303 @section Comparing Text
304 @cindex comparing buffer text
306 This function lets you compare portions of the text in a buffer, without
307 copying them into strings first.
309 @defun compare-buffer-substrings buffer1 start1 end1 buffer2 start2 end2
310 This function lets you compare two substrings of the same buffer or two
311 different buffers. The first three arguments specify one substring,
312 giving a buffer (or a buffer name) and two positions within the
313 buffer. The last three arguments specify the other substring in the
314 same way. You can use @code{nil} for @var{buffer1}, @var{buffer2}, or
315 both to stand for the current buffer.
317 The value is negative if the first substring is less, positive if the
318 first is greater, and zero if they are equal. The absolute value of
319 the result is one plus the index of the first differing characters
320 within the substrings.
322 This function ignores case when comparing characters
323 if @code{case-fold-search} is non-@code{nil}. It always ignores
326 Suppose the current buffer contains the text @samp{foobarbar
327 haha!rara!}; then in this example the two substrings are @samp{rbar }
328 and @samp{rara!}. The value is 2 because the first substring is greater
329 at the second character.
332 (compare-buffer-substrings nil 6 11 nil 16 21)
338 @section Inserting Text
339 @cindex insertion of text
340 @cindex text insertion
342 @cindex insertion before point
343 @cindex before point, insertion
344 @dfn{Insertion} means adding new text to a buffer. The inserted text
345 goes at point---between the character before point and the character
346 after point. Some insertion functions leave point before the inserted
347 text, while other functions leave it after. We call the former
348 insertion @dfn{after point} and the latter insertion @dfn{before point}.
350 Insertion relocates markers that point at positions after the
351 insertion point, so that they stay with the surrounding text
352 (@pxref{Markers}). When a marker points at the place of insertion,
353 insertion may or may not relocate the marker, depending on the marker's
354 insertion type (@pxref{Marker Insertion Types}). Certain special
355 functions such as @code{insert-before-markers} relocate all such markers
356 to point after the inserted text, regardless of the markers' insertion
359 Insertion functions signal an error if the current buffer is
360 read-only or if they insert within read-only text.
362 These functions copy text characters from strings and buffers along
363 with their properties. The inserted characters have exactly the same
364 properties as the characters they were copied from. By contrast,
365 characters specified as separate arguments, not part of a string or
366 buffer, inherit their text properties from the neighboring text.
368 The insertion functions convert text from unibyte to multibyte in
369 order to insert in a multibyte buffer, and vice versa---if the text
370 comes from a string or from a buffer. However, they do not convert
371 unibyte character codes 128 through 255 to multibyte characters, not
372 even if the current buffer is a multibyte buffer. @xref{Converting
375 @defun insert &rest args
376 This function inserts the strings and/or characters @var{args} into the
377 current buffer, at point, moving point forward. In other words, it
378 inserts the text before point. An error is signaled unless all
379 @var{args} are either strings or characters. The value is @code{nil}.
382 @defun insert-before-markers &rest args
383 This function inserts the strings and/or characters @var{args} into the
384 current buffer, at point, moving point forward. An error is signaled
385 unless all @var{args} are either strings or characters. The value is
388 This function is unlike the other insertion functions in that it
389 relocates markers initially pointing at the insertion point, to point
390 after the inserted text. If an overlay begins at the insertion point,
391 the inserted text falls outside the overlay; if a nonempty overlay
392 ends at the insertion point, the inserted text falls inside that
396 @defun insert-char character count &optional inherit
397 This function inserts @var{count} instances of @var{character} into the
398 current buffer before point. The argument @var{count} should be an
399 integer, and @var{character} must be a character. The value is @code{nil}.
401 This function does not convert unibyte character codes 128 through 255
402 to multibyte characters, not even if the current buffer is a multibyte
403 buffer. @xref{Converting Representations}.
405 If @var{inherit} is non-@code{nil}, then the inserted characters inherit
406 sticky text properties from the two characters before and after the
407 insertion point. @xref{Sticky Properties}.
410 @defun insert-buffer-substring from-buffer-or-name &optional start end
411 This function inserts a portion of buffer @var{from-buffer-or-name}
412 (which must already exist) into the current buffer before point. The
413 text inserted is the region between @var{start} and @var{end}. (These
414 arguments default to the beginning and end of the accessible portion of
415 that buffer.) This function returns @code{nil}.
417 In this example, the form is executed with buffer @samp{bar} as the
418 current buffer. We assume that buffer @samp{bar} is initially empty.
422 ---------- Buffer: foo ----------
423 We hold these truths to be self-evident, that all
424 ---------- Buffer: foo ----------
428 (insert-buffer-substring "foo" 1 20)
431 ---------- Buffer: bar ----------
432 We hold these truth@point{}
433 ---------- Buffer: bar ----------
438 @defun insert-buffer-substring-no-properties from-buffer-or-name &optional start end
439 This is like @code{insert-buffer-substring} except that it does not
440 copy any text properties.
443 @xref{Sticky Properties}, for other insertion functions that inherit
444 text properties from the nearby text in addition to inserting it.
445 Whitespace inserted by indentation functions also inherits text
448 @node Commands for Insertion
449 @section User-Level Insertion Commands
451 This section describes higher-level commands for inserting text,
452 commands intended primarily for the user but useful also in Lisp
455 @deffn Command insert-buffer from-buffer-or-name
456 This command inserts the entire accessible contents of
457 @var{from-buffer-or-name} (which must exist) into the current buffer
458 after point. It leaves the mark after the inserted text. The value
462 @deffn Command self-insert-command count
463 @cindex character insertion
464 @cindex self-insertion
465 This command inserts the last character typed; it does so @var{count}
466 times, before point, and returns @code{nil}. Most printing characters
467 are bound to this command. In routine use, @code{self-insert-command}
468 is the most frequently called function in Emacs, but programs rarely use
469 it except to install it on a keymap.
471 In an interactive call, @var{count} is the numeric prefix argument.
473 This command calls @code{auto-fill-function} whenever that is
474 non-@code{nil} and the character inserted is in the table
475 @code{auto-fill-chars} (@pxref{Auto Filling}).
477 @c Cross refs reworded to prevent overfull hbox. --rjc 15mar92
478 This command performs abbrev expansion if Abbrev mode is enabled and
479 the inserted character does not have word-constituent
480 syntax. (@xref{Abbrevs}, and @ref{Syntax Class Table}.)
482 This is also responsible for calling @code{blink-paren-function} when
483 the inserted character has close parenthesis syntax (@pxref{Blinking}).
485 Do not try substituting your own definition of
486 @code{self-insert-command} for the standard one. The editor command
487 loop handles this function specially.
490 @deffn Command newline &optional number-of-newlines
491 This command inserts newlines into the current buffer before point.
492 If @var{number-of-newlines} is supplied, that many newline characters
495 @cindex newline and Auto Fill mode
496 This function calls @code{auto-fill-function} if the current column
497 number is greater than the value of @code{fill-column} and
498 @var{number-of-newlines} is @code{nil}. Typically what
499 @code{auto-fill-function} does is insert a newline; thus, the overall
500 result in this case is to insert two newlines at different places: one
501 at point, and another earlier in the line. @code{newline} does not
502 auto-fill if @var{number-of-newlines} is non-@code{nil}.
504 This command indents to the left margin if that is not zero.
507 The value returned is @code{nil}. In an interactive call, @var{count}
508 is the numeric prefix argument.
511 @deffn Command split-line
512 This command splits the current line, moving the portion of the line
513 after point down vertically so that it is on the next line directly
514 below where it was before. Whitespace is inserted as needed at the
515 beginning of the lower line, using the @code{indent-to} function.
516 @code{split-line} returns the position of point.
518 Programs hardly ever use this function.
521 @defvar overwrite-mode
522 This variable controls whether overwrite mode is in effect. The value
523 should be @code{overwrite-mode-textual}, @code{overwrite-mode-binary},
524 or @code{nil}. @code{overwrite-mode-textual} specifies textual
525 overwrite mode (treats newlines and tabs specially), and
526 @code{overwrite-mode-binary} specifies binary overwrite mode (treats
527 newlines and tabs like any other characters).
531 @section Deleting Text
533 @cindex deletion vs killing
534 Deletion means removing part of the text in a buffer, without saving
535 it in the kill ring (@pxref{The Kill Ring}). Deleted text can't be
536 yanked, but can be reinserted using the undo mechanism (@pxref{Undo}).
537 Some deletion functions do save text in the kill ring in some special
540 All of the deletion functions operate on the current buffer.
542 @deffn Command erase-buffer
543 This function deletes the entire text of the current buffer
544 (@emph{not} just the accessible portion), leaving it
545 empty. If the buffer is read-only, it signals a @code{buffer-read-only}
546 error; if some of the text in it is read-only, it signals a
547 @code{text-read-only} error. Otherwise, it deletes the text without
548 asking for any confirmation. It returns @code{nil}.
550 Normally, deleting a large amount of text from a buffer inhibits further
551 auto-saving of that buffer ``because it has shrunk''. However,
552 @code{erase-buffer} does not do this, the idea being that the future
553 text is not really related to the former text, and its size should not
554 be compared with that of the former text.
557 @deffn Command delete-region start end
558 This command deletes the text between positions @var{start} and
559 @var{end} in the current buffer, and returns @code{nil}. If point was
560 inside the deleted region, its value afterward is @var{start}.
561 Otherwise, point relocates with the surrounding text, as markers do.
564 @defun delete-and-extract-region start end
565 @tindex delete-and-extract-region
566 This function deletes the text between positions @var{start} and
567 @var{end} in the current buffer, and returns a string containing the
570 If point was inside the deleted region, its value afterward is
571 @var{start}. Otherwise, point relocates with the surrounding text, as
575 @deffn Command delete-char count &optional killp
576 This command deletes @var{count} characters directly after point, or
577 before point if @var{count} is negative. If @var{killp} is
578 non-@code{nil}, then it saves the deleted characters in the kill ring.
580 In an interactive call, @var{count} is the numeric prefix argument, and
581 @var{killp} is the unprocessed prefix argument. Therefore, if a prefix
582 argument is supplied, the text is saved in the kill ring. If no prefix
583 argument is supplied, then one character is deleted, but not saved in
586 The value returned is always @code{nil}.
589 @deffn Command delete-backward-char count &optional killp
590 @cindex delete previous char
591 This command deletes @var{count} characters directly before point, or
592 after point if @var{count} is negative. If @var{killp} is
593 non-@code{nil}, then it saves the deleted characters in the kill ring.
595 In an interactive call, @var{count} is the numeric prefix argument, and
596 @var{killp} is the unprocessed prefix argument. Therefore, if a prefix
597 argument is supplied, the text is saved in the kill ring. If no prefix
598 argument is supplied, then one character is deleted, but not saved in
601 The value returned is always @code{nil}.
604 @deffn Command backward-delete-char-untabify count &optional killp
606 This command deletes @var{count} characters backward, changing tabs
607 into spaces. When the next character to be deleted is a tab, it is
608 first replaced with the proper number of spaces to preserve alignment
609 and then one of those spaces is deleted instead of the tab. If
610 @var{killp} is non-@code{nil}, then the command saves the deleted
611 characters in the kill ring.
613 Conversion of tabs to spaces happens only if @var{count} is positive.
614 If it is negative, exactly @minus{}@var{count} characters after point
617 In an interactive call, @var{count} is the numeric prefix argument, and
618 @var{killp} is the unprocessed prefix argument. Therefore, if a prefix
619 argument is supplied, the text is saved in the kill ring. If no prefix
620 argument is supplied, then one character is deleted, but not saved in
623 The value returned is always @code{nil}.
626 @defopt backward-delete-char-untabify-method
627 This option specifies how @code{backward-delete-char-untabify} should
628 deal with whitespace. Possible values include @code{untabify}, the
629 default, meaning convert a tab to many spaces and delete one;
630 @code{hungry}, meaning delete all tabs and spaces before point with
631 one command; @code{all} meaning delete all tabs, spaces and newlines
632 before point, and @code{nil}, meaning do nothing special for
633 whitespace characters.
636 @node User-Level Deletion
637 @section User-Level Deletion Commands
639 This section describes higher-level commands for deleting text,
640 commands intended primarily for the user but useful also in Lisp
643 @deffn Command delete-horizontal-space &optional backward-only
644 @cindex deleting whitespace
645 This function deletes all spaces and tabs around point. It returns
648 If @var{backward-only} is non-@code{nil}, the function deletes
649 spaces and tabs before point, but not after point.
651 In the following examples, we call @code{delete-horizontal-space} four
652 times, once on each line, with point between the second and third
653 characters on the line each time.
657 ---------- Buffer: foo ----------
662 ---------- Buffer: foo ----------
666 (delete-horizontal-space) ; @r{Four times.}
669 ---------- Buffer: foo ----------
674 ---------- Buffer: foo ----------
679 @deffn Command delete-indentation &optional join-following-p
680 This function joins the line point is on to the previous line, deleting
681 any whitespace at the join and in some cases replacing it with one
682 space. If @var{join-following-p} is non-@code{nil},
683 @code{delete-indentation} joins this line to the following line
684 instead. The function returns @code{nil}.
686 If there is a fill prefix, and the second of the lines being joined
687 starts with the prefix, then @code{delete-indentation} deletes the
688 fill prefix before joining the lines. @xref{Margins}.
690 In the example below, point is located on the line starting
691 @samp{events}, and it makes no difference if there are trailing spaces
692 in the preceding line.
696 ---------- Buffer: foo ----------
697 When in the course of human
698 @point{} events, it becomes necessary
699 ---------- Buffer: foo ----------
706 ---------- Buffer: foo ----------
707 When in the course of human@point{} events, it becomes necessary
708 ---------- Buffer: foo ----------
712 After the lines are joined, the function @code{fixup-whitespace} is
713 responsible for deciding whether to leave a space at the junction.
716 @deffn Command fixup-whitespace
717 This function replaces all the horizontal whitespace surrounding point
718 with either one space or no space, according to the context. It
721 At the beginning or end of a line, the appropriate amount of space is
722 none. Before a character with close parenthesis syntax, or after a
723 character with open parenthesis or expression-prefix syntax, no space is
724 also appropriate. Otherwise, one space is appropriate. @xref{Syntax
727 In the example below, @code{fixup-whitespace} is called the first time
728 with point before the word @samp{spaces} in the first line. For the
729 second invocation, point is directly after the @samp{(}.
733 ---------- Buffer: foo ----------
734 This has too many @point{}spaces
735 This has too many spaces at the start of (@point{} this list)
736 ---------- Buffer: foo ----------
747 ---------- Buffer: foo ----------
748 This has too many spaces
749 This has too many spaces at the start of (this list)
750 ---------- Buffer: foo ----------
755 @deffn Command just-one-space &optional n
756 @comment !!SourceFile simple.el
757 This command replaces any spaces and tabs around point with a single
758 space, or @var{n} spaces if @var{n} is specified. It returns
762 @deffn Command delete-blank-lines
763 This function deletes blank lines surrounding point. If point is on a
764 blank line with one or more blank lines before or after it, then all but
765 one of them are deleted. If point is on an isolated blank line, then it
766 is deleted. If point is on a nonblank line, the command deletes all
767 blank lines immediately following it.
769 A blank line is defined as a line containing only tabs and spaces.
771 @code{delete-blank-lines} returns @code{nil}.
775 @section The Kill Ring
778 @dfn{Kill functions} delete text like the deletion functions, but save
779 it so that the user can reinsert it by @dfn{yanking}. Most of these
780 functions have @samp{kill-} in their name. By contrast, the functions
781 whose names start with @samp{delete-} normally do not save text for
782 yanking (though they can still be undone); these are ``deletion''
785 Most of the kill commands are primarily for interactive use, and are
786 not described here. What we do describe are the functions provided for
787 use in writing such commands. You can use these functions to write
788 commands for killing text. When you need to delete text for internal
789 purposes within a Lisp function, you should normally use deletion
790 functions, so as not to disturb the kill ring contents.
793 Killed text is saved for later yanking in the @dfn{kill ring}. This
794 is a list that holds a number of recent kills, not just the last text
795 kill. We call this a ``ring'' because yanking treats it as having
796 elements in a cyclic order. The list is kept in the variable
797 @code{kill-ring}, and can be operated on with the usual functions for
798 lists; there are also specialized functions, described in this section,
799 that treat it as a ring.
801 Some people think this use of the word ``kill'' is unfortunate, since
802 it refers to operations that specifically @emph{do not} destroy the
803 entities ``killed''. This is in sharp contrast to ordinary life, in
804 which death is permanent and ``killed'' entities do not come back to
805 life. Therefore, other metaphors have been proposed. For example, the
806 term ``cut ring'' makes sense to people who, in pre-computer days, used
807 scissors and paste to cut up and rearrange manuscripts. However, it
808 would be difficult to change the terminology now.
811 * Kill Ring Concepts:: What text looks like in the kill ring.
812 * Kill Functions:: Functions that kill text.
813 * Yanking:: How yanking is done.
814 * Yank Commands:: Commands that access the kill ring.
815 * Low-Level Kill Ring:: Functions and variables for kill ring access.
816 * Internals of Kill Ring:: Variables that hold kill ring data.
819 @node Kill Ring Concepts
820 @comment node-name, next, previous, up
821 @subsection Kill Ring Concepts
823 The kill ring records killed text as strings in a list, most recent
824 first. A short kill ring, for example, might look like this:
827 ("some text" "a different piece of text" "even older text")
831 When the list reaches @code{kill-ring-max} entries in length, adding a
832 new entry automatically deletes the last entry.
834 When kill commands are interwoven with other commands, each kill
835 command makes a new entry in the kill ring. Multiple kill commands in
836 succession build up a single kill ring entry, which would be yanked as a
837 unit; the second and subsequent consecutive kill commands add text to
838 the entry made by the first one.
840 For yanking, one entry in the kill ring is designated the ``front'' of
841 the ring. Some yank commands ``rotate'' the ring by designating a
842 different element as the ``front.'' But this virtual rotation doesn't
843 change the list itself---the most recent entry always comes first in the
847 @comment node-name, next, previous, up
848 @subsection Functions for Killing
850 @code{kill-region} is the usual subroutine for killing text. Any
851 command that calls this function is a ``kill command'' (and should
852 probably have @samp{kill} in its name). @code{kill-region} puts the
853 newly killed text in a new element at the beginning of the kill ring or
854 adds it to the most recent element. It determines automatically (using
855 @code{last-command}) whether the previous command was a kill command,
856 and if so appends the killed text to the most recent entry.
858 @deffn Command kill-region start end &optional yank-handler
859 This function kills the text in the region defined by @var{start} and
860 @var{end}. The text is deleted but saved in the kill ring, along with
861 its text properties. The value is always @code{nil}.
863 In an interactive call, @var{start} and @var{end} are point and
867 If the buffer or text is read-only, @code{kill-region} modifies the kill
868 ring just the same, then signals an error without modifying the buffer.
869 This is convenient because it lets the user use a series of kill
870 commands to copy text from a read-only buffer into the kill ring.
872 If @var{yank-handler} is non-@code{nil}, this puts that value onto
873 the string of killed text, as a @code{yank-handler} text property.
874 @xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, any
875 @code{yank-handler} properties present on the killed text are copied
876 onto the kill ring, like other text properties.
879 @defopt kill-read-only-ok
880 If this option is non-@code{nil}, @code{kill-region} does not signal an
881 error if the buffer or text is read-only. Instead, it simply returns,
882 updating the kill ring but not changing the buffer.
885 @deffn Command copy-region-as-kill start end
886 This command saves the region defined by @var{start} and @var{end} on
887 the kill ring (including text properties), but does not delete the text
888 from the buffer. It returns @code{nil}.
890 The command does not set @code{this-command} to @code{kill-region}, so a
891 subsequent kill command does not append to the same kill ring entry.
893 Don't call @code{copy-region-as-kill} in Lisp programs unless you aim to
894 support Emacs 18. For newer Emacs versions, it is better to use
895 @code{kill-new} or @code{kill-append} instead. @xref{Low-Level Kill
902 Yanking means inserting text from the kill ring, but it does
903 not insert the text blindly. Yank commands and some other commands
904 use @code{insert-for-yank} to perform special processing on the
905 text that they copy into the buffer.
907 @defun insert-for-yank string
908 This function normally works like @code{insert} except that it doesn't
909 insert the text properties in the @code{yank-excluded-properties}
910 list. However, if any part of @var{string} has a non-@code{nil}
911 @code{yank-handler} text property, that property can do various
912 special processing on that part of the text being inserted.
915 @defun insert-buffer-substring-as-yank buf &optional start end
916 This function resembles @code{insert-buffer-substring} except that it
917 doesn't insert the text properties in the
918 @code{yank-excluded-properties} list.
921 You can put a @code{yank-handler} text property on all or part of
922 the text to control how it will be inserted if it is yanked. The
923 @code{insert-for-yank} function looks for that property. The property
924 value must be a list of one to four elements, with the following
925 format (where elements after the first may be omitted):
928 (@var{function} @var{param} @var{noexclude} @var{undo})
931 Here is what the elements do:
935 When @var{function} is present and non-@code{nil}, it is called instead of
936 @code{insert} to insert the string. @var{function} takes one
937 argument---the string to insert.
940 If @var{param} is present and non-@code{nil}, it replaces @var{string}
941 (or the part of @var{string} being processed) as the object passed to
942 @var{function} (or @code{insert}); for example, if @var{function} is
943 @code{yank-rectangle}, @var{param} should be a list of strings to
944 insert as a rectangle.
947 If @var{noexclude} is present and non-@code{nil}, the normal removal of the
948 yank-excluded-properties is not performed; instead @var{function} is
949 responsible for removing those properties. This may be necessary
950 if @var{function} adjusts point before or after inserting the object.
953 If @var{undo} is present and non-@code{nil}, it is a function that will be
954 called by @code{yank-pop} to undo the insertion of the current object.
955 It is called with two arguments, the start and end of the current
956 region. @var{function} can set @code{yank-undo-function} to override
957 the @var{undo} value.
961 @comment node-name, next, previous, up
962 @subsection Functions for Yanking
964 @dfn{Yanking} means reinserting an entry of previously killed text
965 from the kill ring. The text properties are copied too.
967 @deffn Command yank &optional arg
968 @cindex inserting killed text
969 This command inserts before point the text at the front of the
970 kill ring. It positions the mark at the beginning of that text, and
973 If @var{arg} is a non-@code{nil} list (which occurs interactively when
974 the user types @kbd{C-u} with no digits), then @code{yank} inserts the
975 text as described above, but puts point before the yanked text and
976 puts the mark after it.
978 If @var{arg} is a number, then @code{yank} inserts the @var{arg}th
979 most recently killed text---the @var{arg}th element of the kill ring
980 list, counted cyclically from the front, which is considered the
981 first element for this purpose.
983 @code{yank} does not alter the contents of the kill ring, unless it
984 used text provided by another program, in which case it pushes that text
985 onto the kill ring. However if @var{arg} is an integer different from
986 one, it rotates the kill ring to place the yanked string at the front.
988 @code{yank} returns @code{nil}.
991 @deffn Command yank-pop &optional arg
992 This command replaces the just-yanked entry from the kill ring with a
993 different entry from the kill ring.
995 This is allowed only immediately after a @code{yank} or another
996 @code{yank-pop}. At such a time, the region contains text that was just
997 inserted by yanking. @code{yank-pop} deletes that text and inserts in
998 its place a different piece of killed text. It does not add the deleted
999 text to the kill ring, since it is already in the kill ring somewhere.
1000 It does however rotate the kill ring to place the newly yanked string at
1003 If @var{arg} is @code{nil}, then the replacement text is the previous
1004 element of the kill ring. If @var{arg} is numeric, the replacement is
1005 the @var{arg}th previous kill. If @var{arg} is negative, a more recent
1006 kill is the replacement.
1008 The sequence of kills in the kill ring wraps around, so that after the
1009 oldest one comes the newest one, and before the newest one goes the
1012 The return value is always @code{nil}.
1015 @defvar yank-undo-function
1016 If this variable is non-@code{nil}, the function @code{yank-pop} uses
1017 its value instead of @code{delete-region} to delete the text
1018 inserted by the previous @code{yank} or
1019 @code{yank-pop} command. The value must be a function of two
1020 arguments, the start and end of the current region.
1022 The function @code{insert-for-yank} automatically sets this variable
1023 according to the @var{undo} element of the @code{yank-handler}
1024 text property, if there is one.
1027 @node Low-Level Kill Ring
1028 @subsection Low-Level Kill Ring
1030 These functions and variables provide access to the kill ring at a
1031 lower level, but still convenient for use in Lisp programs, because they
1032 take care of interaction with window system selections
1033 (@pxref{Window System Selections}).
1035 @defun current-kill n &optional do-not-move
1036 The function @code{current-kill} rotates the yanking pointer, which
1037 designates the ``front'' of the kill ring, by @var{n} places (from newer
1038 kills to older ones), and returns the text at that place in the ring.
1040 If the optional second argument @var{do-not-move} is non-@code{nil},
1041 then @code{current-kill} doesn't alter the yanking pointer; it just
1042 returns the @var{n}th kill, counting from the current yanking pointer.
1044 If @var{n} is zero, indicating a request for the latest kill,
1045 @code{current-kill} calls the value of
1046 @code{interprogram-paste-function} (documented below) before
1047 consulting the kill ring. If that value is a function and calling it
1048 returns a string, @code{current-kill} pushes that string onto the kill
1049 ring and returns it. It also sets the yanking pointer to point to
1050 that new entry, regardless of the value of @var{do-not-move}.
1051 Otherwise, @code{current-kill} does not treat a zero value for @var{n}
1052 specially: it returns the entry pointed at by the yanking pointer and
1053 does not move the yanking pointer.
1056 @defun kill-new string &optional replace yank-handler
1057 This function pushes the text @var{string} onto the kill ring and
1058 makes the yanking pointer point to it. It discards the oldest entry
1059 if appropriate. It also invokes the value of
1060 @code{interprogram-cut-function} (see below).
1062 If @var{replace} is non-@code{nil}, then @code{kill-new} replaces the
1063 first element of the kill ring with @var{string}, rather than pushing
1064 @var{string} onto the kill ring.
1066 If @var{yank-handler} is non-@code{nil}, this puts that value onto
1067 the string of killed text, as a @code{yank-handler} property.
1068 @xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, then
1069 @code{kill-new} copies any @code{yank-handler} properties present on
1070 @var{string} onto the kill ring, as it does with other text properties.
1073 @defun kill-append string before-p &optional yank-handler
1074 This function appends the text @var{string} to the first entry in the
1075 kill ring and makes the yanking pointer point to the combined entry.
1076 Normally @var{string} goes at the end of the entry, but if
1077 @var{before-p} is non-@code{nil}, it goes at the beginning. This
1078 function also invokes the value of @code{interprogram-cut-function}
1079 (see below). This handles @var{yank-handler} just like
1080 @code{kill-new}, except that if @var{yank-handler} is different from
1081 the @code{yank-handler} property of the first entry of the kill ring,
1082 @code{kill-append} pushes the concatenated string onto the kill ring,
1083 instead of replacing the original first entry with it.
1086 @defvar interprogram-paste-function
1087 This variable provides a way of transferring killed text from other
1088 programs, when you are using a window system. Its value should be
1089 @code{nil} or a function of no arguments.
1091 If the value is a function, @code{current-kill} calls it to get the
1092 ``most recent kill''. If the function returns a non-@code{nil} value,
1093 then that value is used as the ``most recent kill''. If it returns
1094 @code{nil}, then the front of the kill ring is used.
1096 The normal use of this hook is to get the window system's primary
1097 selection as the most recent kill, even if the selection belongs to
1098 another application. @xref{Window System Selections}.
1101 @defvar interprogram-cut-function
1102 This variable provides a way of communicating killed text to other
1103 programs, when you are using a window system. Its value should be
1104 @code{nil} or a function of one required and one optional argument.
1106 If the value is a function, @code{kill-new} and @code{kill-append} call
1107 it with the new first element of the kill ring as the first argument.
1108 The second, optional, argument has the same meaning as the @var{push}
1109 argument to @code{x-set-cut-buffer} (@pxref{Definition of
1110 x-set-cut-buffer}) and only affects the second and later cut buffers.
1112 The normal use of this hook is to set the window system's primary
1113 selection (and first cut buffer) from the newly killed text.
1114 @xref{Window System Selections}.
1117 @node Internals of Kill Ring
1118 @comment node-name, next, previous, up
1119 @subsection Internals of the Kill Ring
1121 The variable @code{kill-ring} holds the kill ring contents, in the
1122 form of a list of strings. The most recent kill is always at the front
1125 The @code{kill-ring-yank-pointer} variable points to a link in the
1126 kill ring list, whose @sc{car} is the text to yank next. We say it
1127 identifies the ``front'' of the ring. Moving
1128 @code{kill-ring-yank-pointer} to a different link is called
1129 @dfn{rotating the kill ring}. We call the kill ring a ``ring'' because
1130 the functions that move the yank pointer wrap around from the end of the
1131 list to the beginning, or vice-versa. Rotation of the kill ring is
1132 virtual; it does not change the value of @code{kill-ring}.
1134 Both @code{kill-ring} and @code{kill-ring-yank-pointer} are Lisp
1135 variables whose values are normally lists. The word ``pointer'' in the
1136 name of the @code{kill-ring-yank-pointer} indicates that the variable's
1137 purpose is to identify one element of the list for use by the next yank
1140 The value of @code{kill-ring-yank-pointer} is always @code{eq} to one
1141 of the links in the kill ring list. The element it identifies is the
1142 @sc{car} of that link. Kill commands, which change the kill ring, also
1143 set this variable to the value of @code{kill-ring}. The effect is to
1144 rotate the ring so that the newly killed text is at the front.
1146 Here is a diagram that shows the variable @code{kill-ring-yank-pointer}
1147 pointing to the second entry in the kill ring @code{("some text" "a
1148 different piece of text" "yet older text")}.
1152 kill-ring ---- kill-ring-yank-pointer
1155 | --- --- --- --- --- ---
1156 --> | | |------> | | |--> | | |--> nil
1157 --- --- --- --- --- ---
1160 | | -->"yet older text"
1162 | --> "a different piece of text"
1169 This state of affairs might occur after @kbd{C-y} (@code{yank})
1170 immediately followed by @kbd{M-y} (@code{yank-pop}).
1173 This variable holds the list of killed text sequences, most recently
1177 @defvar kill-ring-yank-pointer
1178 This variable's value indicates which element of the kill ring is at the
1179 ``front'' of the ring for yanking. More precisely, the value is a tail
1180 of the value of @code{kill-ring}, and its @sc{car} is the kill string
1181 that @kbd{C-y} should yank.
1184 @defopt kill-ring-max
1185 The value of this variable is the maximum length to which the kill
1186 ring can grow, before elements are thrown away at the end. The default
1187 value for @code{kill-ring-max} is 60.
1191 @comment node-name, next, previous, up
1195 Most buffers have an @dfn{undo list}, which records all changes made
1196 to the buffer's text so that they can be undone. (The buffers that
1197 don't have one are usually special-purpose buffers for which Emacs
1198 assumes that undoing is not useful.) All the primitives that modify the
1199 text in the buffer automatically add elements to the front of the undo
1200 list, which is in the variable @code{buffer-undo-list}.
1202 @defvar buffer-undo-list
1203 This variable's value is the undo list of the current buffer.
1204 A value of @code{t} disables the recording of undo information.
1207 Here are the kinds of elements an undo list can have:
1210 @item @var{position}
1211 This kind of element records a previous value of point; undoing this
1212 element moves point to @var{position}. Ordinary cursor motion does not
1213 make any sort of undo record, but deletion operations use these entries
1214 to record where point was before the command.
1216 @item (@var{beg} . @var{end})
1217 This kind of element indicates how to delete text that was inserted.
1218 Upon insertion, the text occupied the range @var{beg}--@var{end} in the
1221 @item (@var{text} . @var{position})
1222 This kind of element indicates how to reinsert text that was deleted.
1223 The deleted text itself is the string @var{text}. The place to
1224 reinsert it is @code{(abs @var{position})}. If @var{position} is
1225 positive, point was at the beginning of the deleted text, otherwise it
1228 @item (t @var{high} . @var{low})
1229 This kind of element indicates that an unmodified buffer became
1230 modified. The elements @var{high} and @var{low} are two integers, each
1231 recording 16 bits of the visited file's modification time as of when it
1232 was previously visited or saved. @code{primitive-undo} uses those
1233 values to determine whether to mark the buffer as unmodified once again;
1234 it does so only if the file's modification time matches those numbers.
1236 @item (nil @var{property} @var{value} @var{beg} . @var{end})
1237 This kind of element records a change in a text property.
1238 Here's how you might undo the change:
1241 (put-text-property @var{beg} @var{end} @var{property} @var{value})
1244 @item (apply @var{funname} . @var{args})
1245 This kind of element records a change that can be undone by evaluating
1246 (@code{apply} @var{funname} @var{args}).
1248 @item (apply @var{delta} @var{beg} @var{end} @var{funname} . @var{args})
1249 This kind of element records a change that can be undone by evaluating
1250 (@code{apply} @var{funname} @var{args}). The integer values @var{beg}
1251 and @var{end} is buffer positions of the range affected by this change
1252 and @var{delta} is an integer value which is the number of bytes added
1253 or deleted in that range by this change. This kind of element
1254 enables undo limited to a region to determine whether the element
1255 pertains to that region.
1257 @item (@var{marker} . @var{adjustment})
1258 This kind of element records the fact that the marker @var{marker} was
1259 relocated due to deletion of surrounding text, and that it moved
1260 @var{adjustment} character positions. Undoing this element moves
1261 @var{marker} @minus{} @var{adjustment} characters.
1263 @item (apply @var{funname} . @var{args})
1264 This is an extensible undo item, which is undone by calling
1265 @var{funname} with arguments @var{args}.
1267 @item (apply @var{delta} @var{beg} @var{end} @var{funname} . @var{args})
1268 This is an extensible undo item, which records a change limited to the
1269 range @var{beg} to @var{end}, which increased the size of the buffer
1270 by @var{delta}. It is undone by calling @var{funname} with arguments
1274 This element is a boundary. The elements between two boundaries are
1275 called a @dfn{change group}; normally, each change group corresponds to
1276 one keyboard command, and undo commands normally undo an entire group as
1280 @defun undo-boundary
1281 This function places a boundary element in the undo list. The undo
1282 command stops at such a boundary, and successive undo commands undo
1283 to earlier and earlier boundaries. This function returns @code{nil}.
1285 The editor command loop automatically creates an undo boundary before
1286 each key sequence is executed. Thus, each undo normally undoes the
1287 effects of one command. Self-inserting input characters are an
1288 exception. The command loop makes a boundary for the first such
1289 character; the next 19 consecutive self-inserting input characters do
1290 not make boundaries, and then the 20th does, and so on as long as
1291 self-inserting characters continue.
1293 All buffer modifications add a boundary whenever the previous undoable
1294 change was made in some other buffer. This is to ensure that
1295 each command makes a boundary in each buffer where it makes changes.
1297 Calling this function explicitly is useful for splitting the effects of
1298 a command into more than one unit. For example, @code{query-replace}
1299 calls @code{undo-boundary} after each replacement, so that the user can
1300 undo individual replacements one by one.
1303 @defvar undo-in-progress
1304 This variable is normally @code{nil}, but the undo commands bind it to
1305 @code{t}. This is so that various kinds of change hooks can tell when
1306 they're being called for the sake of undoing.
1309 @defun primitive-undo count list
1310 This is the basic function for undoing elements of an undo list.
1311 It undoes the first @var{count} elements of @var{list}, returning
1312 the rest of @var{list}. You could write this function in Lisp,
1313 but it is convenient to have it in C.
1315 @code{primitive-undo} adds elements to the buffer's undo list when it
1316 changes the buffer. Undo commands avoid confusion by saving the undo
1317 list value at the beginning of a sequence of undo operations. Then the
1318 undo operations use and update the saved value. The new elements added
1319 by undoing are not part of this saved value, so they don't interfere with
1322 This function does not bind @code{undo-in-progress}.
1325 @node Maintaining Undo
1326 @section Maintaining Undo Lists
1328 This section describes how to enable and disable undo information for
1329 a given buffer. It also explains how the undo list is truncated
1330 automatically so it doesn't get too big.
1332 Recording of undo information in a newly created buffer is normally
1333 enabled to start with; but if the buffer name starts with a space, the
1334 undo recording is initially disabled. You can explicitly enable or
1335 disable undo recording with the following two functions, or by setting
1336 @code{buffer-undo-list} yourself.
1338 @deffn Command buffer-enable-undo &optional buffer-or-name
1339 This command enables recording undo information for buffer
1340 @var{buffer-or-name}, so that subsequent changes can be undone. If no
1341 argument is supplied, then the current buffer is used. This function
1342 does nothing if undo recording is already enabled in the buffer. It
1345 In an interactive call, @var{buffer-or-name} is the current buffer.
1346 You cannot specify any other buffer.
1349 @deffn Command buffer-disable-undo &optional buffer-or-name
1350 @cindex disable undo
1351 This function discards the undo list of @var{buffer-or-name}, and disables
1352 further recording of undo information. As a result, it is no longer
1353 possible to undo either previous changes or any subsequent changes. If
1354 the undo list of @var{buffer-or-name} is already disabled, this function
1357 This function returns @code{nil}.
1360 As editing continues, undo lists get longer and longer. To prevent
1361 them from using up all available memory space, garbage collection trims
1362 them back to size limits you can set. (For this purpose, the ``size''
1363 of an undo list measures the cons cells that make up the list, plus the
1364 strings of deleted text.) Three variables control the range of acceptable
1365 sizes: @code{undo-limit}, @code{undo-strong-limit} and
1366 @code{undo-outer-limit}.
1369 This is the soft limit for the acceptable size of an undo list. The
1370 change group at which this size is exceeded is the last one kept.
1373 @defopt undo-strong-limit
1374 This is the upper limit for the acceptable size of an undo list. The
1375 change group at which this size is exceeded is discarded itself (along
1376 with all older change groups). There is one exception: the very latest
1377 change group is only discarded if it exceeds @code{undo-outer-limit}.
1380 @defopt undo-outer-limit
1381 If at garbage collection time the undo info for the current command
1382 exceeds this limit, Emacs discards the info and displays a warning.
1383 This is a last ditch limit to prevent memory overflow.
1387 @comment node-name, next, previous, up
1389 @cindex filling, explicit
1391 @dfn{Filling} means adjusting the lengths of lines (by moving the line
1392 breaks) so that they are nearly (but no greater than) a specified
1393 maximum width. Additionally, lines can be @dfn{justified}, which means
1394 inserting spaces to make the left and/or right margins line up
1395 precisely. The width is controlled by the variable @code{fill-column}.
1396 For ease of reading, lines should be no longer than 70 or so columns.
1398 You can use Auto Fill mode (@pxref{Auto Filling}) to fill text
1399 automatically as you insert it, but changes to existing text may leave
1400 it improperly filled. Then you must fill the text explicitly.
1402 Most of the commands in this section return values that are not
1403 meaningful. All the functions that do filling take note of the current
1404 left margin, current right margin, and current justification style
1405 (@pxref{Margins}). If the current justification style is
1406 @code{none}, the filling functions don't actually do anything.
1408 Several of the filling functions have an argument @var{justify}.
1409 If it is non-@code{nil}, that requests some kind of justification. It
1410 can be @code{left}, @code{right}, @code{full}, or @code{center}, to
1411 request a specific style of justification. If it is @code{t}, that
1412 means to use the current justification style for this part of the text
1413 (see @code{current-justification}, below). Any other value is treated
1416 When you call the filling functions interactively, using a prefix
1417 argument implies the value @code{full} for @var{justify}.
1419 @deffn Command fill-paragraph justify
1420 @cindex filling a paragraph
1421 This command fills the paragraph at or after point. If
1422 @var{justify} is non-@code{nil}, each line is justified as well.
1423 It uses the ordinary paragraph motion commands to find paragraph
1424 boundaries. @xref{Paragraphs,,, emacs, The GNU Emacs Manual}.
1427 @deffn Command fill-region start end &optional justify nosqueeze to-eop
1428 This command fills each of the paragraphs in the region from @var{start}
1429 to @var{end}. It justifies as well if @var{justify} is
1432 If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace
1433 other than line breaks untouched. If @var{to-eop} is non-@code{nil},
1434 that means to keep filling to the end of the paragraph---or the next hard
1435 newline, if @code{use-hard-newlines} is enabled (see below).
1437 The variable @code{paragraph-separate} controls how to distinguish
1438 paragraphs. @xref{Standard Regexps}.
1441 @deffn Command fill-individual-paragraphs start end &optional justify citation-regexp
1442 This command fills each paragraph in the region according to its
1443 individual fill prefix. Thus, if the lines of a paragraph were indented
1444 with spaces, the filled paragraph will remain indented in the same
1447 The first two arguments, @var{start} and @var{end}, are the beginning
1448 and end of the region to be filled. The third and fourth arguments,
1449 @var{justify} and @var{citation-regexp}, are optional. If
1450 @var{justify} is non-@code{nil}, the paragraphs are justified as
1451 well as filled. If @var{citation-regexp} is non-@code{nil}, it means the
1452 function is operating on a mail message and therefore should not fill
1453 the header lines. If @var{citation-regexp} is a string, it is used as
1454 a regular expression; if it matches the beginning of a line, that line
1455 is treated as a citation marker.
1457 Ordinarily, @code{fill-individual-paragraphs} regards each change in
1458 indentation as starting a new paragraph. If
1459 @code{fill-individual-varying-indent} is non-@code{nil}, then only
1460 separator lines separate paragraphs. That mode can handle indented
1461 paragraphs with additional indentation on the first line.
1464 @defopt fill-individual-varying-indent
1465 This variable alters the action of @code{fill-individual-paragraphs} as
1469 @deffn Command fill-region-as-paragraph start end &optional justify nosqueeze squeeze-after
1470 This command considers a region of text as a single paragraph and fills
1471 it. If the region was made up of many paragraphs, the blank lines
1472 between paragraphs are removed. This function justifies as well as
1473 filling when @var{justify} is non-@code{nil}.
1475 In an interactive call, any prefix argument requests justification.
1477 If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace
1478 other than line breaks untouched. If @var{squeeze-after} is
1479 non-@code{nil}, it specifies a position in the region, and means don't
1480 canonicalize spaces before that position.
1482 In Adaptive Fill mode, this command calls @code{fill-context-prefix} to
1483 choose a fill prefix by default. @xref{Adaptive Fill}.
1486 @deffn Command justify-current-line &optional how eop nosqueeze
1487 This command inserts spaces between the words of the current line so
1488 that the line ends exactly at @code{fill-column}. It returns
1491 The argument @var{how}, if non-@code{nil} specifies explicitly the style
1492 of justification. It can be @code{left}, @code{right}, @code{full},
1493 @code{center}, or @code{none}. If it is @code{t}, that means to do
1494 follow specified justification style (see @code{current-justification},
1495 below). @code{nil} means to do full justification.
1497 If @var{eop} is non-@code{nil}, that means do only left-justification
1498 if @code{current-justification} specifies full justification. This is
1499 used for the last line of a paragraph; even if the paragraph as a
1500 whole is fully justified, the last line should not be.
1502 If @var{nosqueeze} is non-@code{nil}, that means do not change interior
1506 @defopt default-justification
1507 This variable's value specifies the style of justification to use for
1508 text that doesn't specify a style with a text property. The possible
1509 values are @code{left}, @code{right}, @code{full}, @code{center}, or
1510 @code{none}. The default value is @code{left}.
1513 @defun current-justification
1514 This function returns the proper justification style to use for filling
1515 the text around point.
1518 @defopt sentence-end-double-space
1519 @anchor{Definition of sentence-end-double-space}
1520 If this variable is non-@code{nil}, a period followed by just one space
1521 does not count as the end of a sentence, and the filling functions
1522 avoid breaking the line at such a place.
1525 @defopt sentence-end-without-period
1526 If this variable is non-@code{nil}, a sentence can end without a
1527 period. This is used for languages like Thai, where sentences end
1528 with a double space but without a period.
1531 @defopt sentence-end-without-space
1532 If this variable is non-@code{nil}, it should be a string of
1533 characters that can end a sentence without following spaces.
1536 @defvar fill-paragraph-function
1537 This variable provides a way for major modes to override the filling of
1538 paragraphs. If the value is non-@code{nil}, @code{fill-paragraph} calls
1539 this function to do the work. If the function returns a non-@code{nil}
1540 value, @code{fill-paragraph} assumes the job is done, and immediately
1543 The usual use of this feature is to fill comments in programming
1544 language modes. If the function needs to fill a paragraph in the usual
1545 way, it can do so as follows:
1548 (let ((fill-paragraph-function nil))
1549 (fill-paragraph arg))
1553 @defvar use-hard-newlines
1554 If this variable is non-@code{nil}, the filling functions do not delete
1555 newlines that have the @code{hard} text property. These ``hard
1556 newlines'' act as paragraph separators.
1560 @section Margins for Filling
1563 This buffer-local variable specifies a string of text that appears at
1565 of normal text lines and should be disregarded when filling them. Any
1566 line that fails to start with the fill prefix is considered the start of
1567 a paragraph; so is any line that starts with the fill prefix followed by
1568 additional whitespace. Lines that start with the fill prefix but no
1569 additional whitespace are ordinary text lines that can be filled
1570 together. The resulting filled lines also start with the fill prefix.
1572 The fill prefix follows the left margin whitespace, if any.
1576 This buffer-local variable specifies the maximum width of filled lines.
1577 Its value should be an integer, which is a number of columns. All the
1578 filling, justification, and centering commands are affected by this
1579 variable, including Auto Fill mode (@pxref{Auto Filling}).
1581 As a practical matter, if you are writing text for other people to
1582 read, you should set @code{fill-column} to no more than 70. Otherwise
1583 the line will be too long for people to read comfortably, and this can
1584 make the text seem clumsy.
1587 @defvar default-fill-column
1588 The value of this variable is the default value for @code{fill-column} in
1589 buffers that do not override it. This is the same as
1590 @code{(default-value 'fill-column)}.
1592 The default value for @code{default-fill-column} is 70.
1595 @deffn Command set-left-margin from to margin
1596 This sets the @code{left-margin} property on the text from @var{from} to
1597 @var{to} to the value @var{margin}. If Auto Fill mode is enabled, this
1598 command also refills the region to fit the new margin.
1601 @deffn Command set-right-margin from to margin
1602 This sets the @code{right-margin} property on the text from @var{from}
1603 to @var{to} to the value @var{margin}. If Auto Fill mode is enabled,
1604 this command also refills the region to fit the new margin.
1607 @defun current-left-margin
1608 This function returns the proper left margin value to use for filling
1609 the text around point. The value is the sum of the @code{left-margin}
1610 property of the character at the start of the current line (or zero if
1611 none), and the value of the variable @code{left-margin}.
1614 @defun current-fill-column
1615 This function returns the proper fill column value to use for filling
1616 the text around point. The value is the value of the @code{fill-column}
1617 variable, minus the value of the @code{right-margin} property of the
1618 character after point.
1621 @deffn Command move-to-left-margin &optional n force
1622 This function moves point to the left margin of the current line. The
1623 column moved to is determined by calling the function
1624 @code{current-left-margin}. If the argument @var{n} is non-@code{nil},
1625 @code{move-to-left-margin} moves forward @var{n}@minus{}1 lines first.
1627 If @var{force} is non-@code{nil}, that says to fix the line's
1628 indentation if that doesn't match the left margin value.
1631 @defun delete-to-left-margin &optional from to
1632 This function removes left margin indentation from the text between
1633 @var{from} and @var{to}. The amount of indentation to delete is
1634 determined by calling @code{current-left-margin}. In no case does this
1635 function delete non-whitespace. If @var{from} and @var{to} are omitted,
1636 they default to the whole buffer.
1639 @defun indent-to-left-margin
1640 This is the default @code{indent-line-function}, used in Fundamental
1641 mode, Text mode, etc. Its effect is to adjust the indentation at the
1642 beginning of the current line to the value specified by the variable
1643 @code{left-margin}. This may involve either inserting or deleting
1648 This variable specifies the base left margin column. In Fundamental
1649 mode, @kbd{C-j} indents to this column. This variable automatically
1650 becomes buffer-local when set in any fashion.
1653 @defvar fill-nobreak-predicate
1654 This variable gives major modes a way to specify not to break a line
1655 at certain places. Its value should be a list of functions, but a
1656 single function is also supported for compatibility. Whenever filling
1657 considers breaking the line at a certain place in the buffer, it calls
1658 each of these functions with no arguments and with point located at
1659 that place. If any of the functions returns non-@code{nil}, then the
1660 line won't be broken there.
1664 @section Adaptive Fill Mode
1665 @cindex Adaptive Fill mode
1667 When @dfn{Adaptive Fill Mode} is enabled, Emacs determines the fill
1668 prefix automatically from the text in each paragraph being filled
1669 rather than using a predetermined value. During filling, this fill
1670 prefix gets inserted at the start of the second and subsequent lines
1671 of the paragraph as described in @ref{Filling}, and in @ref{Auto
1674 @defopt adaptive-fill-mode
1675 Adaptive Fill mode is enabled when this variable is non-@code{nil}.
1676 It is @code{t} by default.
1679 @defun fill-context-prefix from to
1680 This function implements the heart of Adaptive Fill mode; it chooses a
1681 fill prefix based on the text between @var{from} and @var{to},
1682 typically the start and end of a paragraph. It does this by looking
1683 at the first two lines of the paragraph, based on the variables
1685 @c The optional argument first-line-regexp is not documented
1686 @c because it exists for internal purposes and might be eliminated
1689 Usually, this function returns the fill prefix, a string. However,
1690 before doing this, the function makes a final check (not specially
1691 mentioned in the following) that a line starting with this prefix
1692 wouldn't look like the start of a paragraph. Should this happen, the
1693 function signals the anomaly by returning @code{nil} instead.
1695 In detail, @code{fill-context-prefix} does this:
1699 It takes a candidate for the fill prefix from the first line---it
1700 tries first the function in @code{adaptive-fill-function} (if any),
1701 then the regular expression @code{adaptive-fill-regexp} (see below).
1702 The first non-@code{nil} result of these, or the empty string if
1703 they're both @code{nil}, becomes the first line's candidate.
1705 If the paragraph has as yet only one line, the function tests the
1706 validity of the prefix candidate just found. The function then
1707 returns the candidate if it's valid, or a string of spaces otherwise.
1708 (see the description of @code{adaptive-fill-first-line-regexp} below).
1710 When the paragraph already has two lines, the function next looks for
1711 a prefix candidate on the second line, in just the same way it did for
1712 the first line. If it doesn't find one, it returns @code{nil}.
1714 The function now compares the two candidate prefixes heuristically: if
1715 the non-whitespace characters in the line 2 candidate occur in the
1716 same order in the line 1 candidate, the function returns the line 2
1717 candidate. Otherwise, it returns the largest initial substring which
1718 is common to both candidates (which might be the empty string).
1722 @defopt adaptive-fill-regexp
1723 Adaptive Fill mode matches this regular expression against the text
1724 starting after the left margin whitespace (if any) on a line; the
1725 characters it matches are that line's candidate for the fill prefix.
1727 @w{@samp{"[ \t]*\\([-|#;>*]+[ \t]*\\|(?[0-9]+[.)][ \t]*\\)*"}} is the
1728 default value. This matches a number enclosed in parentheses or
1729 followed by a period, or certain punctuation characters, or any
1730 sequence of these intermingled with whitespace. In particular, it
1731 matches a sequence of whitespace, possibly empty.
1734 @defopt adaptive-fill-first-line-regexp
1735 Used only in one-line paragraphs, this regular expression acts as an
1736 additional check of the validity of the one available candidate fill
1737 prefix: the candidate must match this regular expression, or match
1738 @code{comment-start-skip}. If it doesn't, @code{fill-context-prefix}
1739 replaces the candidate with a string of spaces ``of the same width''
1742 The default value of this variable is @w{@samp{"\\`[ \t]*\\'"}}, which
1743 matches only a string of whitespace. The effect of this default is to
1744 force the fill prefixes found in one-line paragraphs always to be pure
1748 @defopt adaptive-fill-function
1749 You can specify more complex ways of choosing a fill prefix
1750 automatically by setting this variable to a function. The function is
1751 called with point after the left margin (if any) of a line, and it
1752 must preserve point. It should return either ``that line's'' fill
1753 prefix or @code{nil}, meaning it has failed to determine a prefix.
1757 @comment node-name, next, previous, up
1758 @section Auto Filling
1759 @cindex filling, automatic
1760 @cindex Auto Fill mode
1762 Auto Fill mode is a minor mode that fills lines automatically as text
1763 is inserted. This section describes the hook used by Auto Fill mode.
1764 For a description of functions that you can call explicitly to fill and
1765 justify existing text, see @ref{Filling}.
1767 Auto Fill mode also enables the functions that change the margins and
1768 justification style to refill portions of the text. @xref{Margins}.
1770 @defvar auto-fill-function
1771 The value of this variable should be a function (of no arguments) to be
1772 called after self-inserting a character from the table
1773 @code{auto-fill-chars}. It may be @code{nil}, in which case nothing
1774 special is done in that case.
1776 The value of @code{auto-fill-function} is @code{do-auto-fill} when
1777 Auto-Fill mode is enabled. That is a function whose sole purpose is to
1778 implement the usual strategy for breaking a line.
1781 In older Emacs versions, this variable was named @code{auto-fill-hook},
1782 but since it is not called with the standard convention for hooks, it
1783 was renamed to @code{auto-fill-function} in version 19.
1787 @defvar normal-auto-fill-function
1788 This variable specifies the function to use for
1789 @code{auto-fill-function}, if and when Auto Fill is turned on. Major
1790 modes can set buffer-local values for this variable to alter how Auto
1794 @defvar auto-fill-chars
1795 A char table of characters which invoke @code{auto-fill-function} when
1796 self-inserted---space and newline in most language environments. They
1797 have an entry @code{t} in the table.
1801 @section Sorting Text
1802 @cindex sorting text
1804 The sorting functions described in this section all rearrange text in
1805 a buffer. This is in contrast to the function @code{sort}, which
1806 rearranges the order of the elements of a list (@pxref{Rearrangement}).
1807 The values returned by these functions are not meaningful.
1809 @defun sort-subr reverse nextrecfun endrecfun &optional startkeyfun endkeyfun
1810 This function is the general text-sorting routine that subdivides a
1811 buffer into records and then sorts them. Most of the commands in this
1812 section use this function.
1814 To understand how @code{sort-subr} works, consider the whole accessible
1815 portion of the buffer as being divided into disjoint pieces called
1816 @dfn{sort records}. The records may or may not be contiguous, but they
1817 must not overlap. A portion of each sort record (perhaps all of it) is
1818 designated as the sort key. Sorting rearranges the records in order by
1821 Usually, the records are rearranged in order of ascending sort key.
1822 If the first argument to the @code{sort-subr} function, @var{reverse},
1823 is non-@code{nil}, the sort records are rearranged in order of
1824 descending sort key.
1826 The next four arguments to @code{sort-subr} are functions that are
1827 called to move point across a sort record. They are called many times
1828 from within @code{sort-subr}.
1832 @var{nextrecfun} is called with point at the end of a record. This
1833 function moves point to the start of the next record. The first record
1834 is assumed to start at the position of point when @code{sort-subr} is
1835 called. Therefore, you should usually move point to the beginning of
1836 the buffer before calling @code{sort-subr}.
1838 This function can indicate there are no more sort records by leaving
1839 point at the end of the buffer.
1842 @var{endrecfun} is called with point within a record. It moves point to
1843 the end of the record.
1846 @var{startkeyfun} is called to move point from the start of a record to
1847 the start of the sort key. This argument is optional; if it is omitted,
1848 the whole record is the sort key. If supplied, the function should
1849 either return a non-@code{nil} value to be used as the sort key, or
1850 return @code{nil} to indicate that the sort key is in the buffer
1851 starting at point. In the latter case, @var{endkeyfun} is called to
1852 find the end of the sort key.
1855 @var{endkeyfun} is called to move point from the start of the sort key
1856 to the end of the sort key. This argument is optional. If
1857 @var{startkeyfun} returns @code{nil} and this argument is omitted (or
1858 @code{nil}), then the sort key extends to the end of the record. There
1859 is no need for @var{endkeyfun} if @var{startkeyfun} returns a
1860 non-@code{nil} value.
1863 As an example of @code{sort-subr}, here is the complete function
1864 definition for @code{sort-lines}:
1868 ;; @r{Note that the first two lines of doc string}
1869 ;; @r{are effectively one line when viewed by a user.}
1870 (defun sort-lines (reverse beg end)
1871 "Sort lines in region alphabetically;\
1872 argument means descending order.
1873 Called from a program, there are three arguments:
1876 REVERSE (non-nil means reverse order),\
1877 BEG and END (region to sort).
1878 The variable `sort-fold-case' determines\
1879 whether alphabetic case affects
1883 (interactive "P\nr")
1886 (narrow-to-region beg end)
1887 (goto-char (point-min))
1888 (sort-subr reverse 'forward-line 'end-of-line))))
1892 Here @code{forward-line} moves point to the start of the next record,
1893 and @code{end-of-line} moves point to the end of record. We do not pass
1894 the arguments @var{startkeyfun} and @var{endkeyfun}, because the entire
1895 record is used as the sort key.
1897 The @code{sort-paragraphs} function is very much the same, except that
1898 its @code{sort-subr} call looks like this:
1905 (while (and (not (eobp))
1906 (looking-at paragraph-separate))
1912 Markers pointing into any sort records are left with no useful
1913 position after @code{sort-subr} returns.
1916 @defopt sort-fold-case
1917 If this variable is non-@code{nil}, @code{sort-subr} and the other
1918 buffer sorting functions ignore case when comparing strings.
1921 @deffn Command sort-regexp-fields reverse record-regexp key-regexp start end
1922 This command sorts the region between @var{start} and @var{end}
1923 alphabetically as specified by @var{record-regexp} and @var{key-regexp}.
1924 If @var{reverse} is a negative integer, then sorting is in reverse
1927 Alphabetical sorting means that two sort keys are compared by
1928 comparing the first characters of each, the second characters of each,
1929 and so on. If a mismatch is found, it means that the sort keys are
1930 unequal; the sort key whose character is less at the point of first
1931 mismatch is the lesser sort key. The individual characters are compared
1932 according to their numerical character codes in the Emacs character set.
1934 The value of the @var{record-regexp} argument specifies how to divide
1935 the buffer into sort records. At the end of each record, a search is
1936 done for this regular expression, and the text that matches it is taken
1937 as the next record. For example, the regular expression @samp{^.+$},
1938 which matches lines with at least one character besides a newline, would
1939 make each such line into a sort record. @xref{Regular Expressions}, for
1940 a description of the syntax and meaning of regular expressions.
1942 The value of the @var{key-regexp} argument specifies what part of each
1943 record is the sort key. The @var{key-regexp} could match the whole
1944 record, or only a part. In the latter case, the rest of the record has
1945 no effect on the sorted order of records, but it is carried along when
1946 the record moves to its new position.
1948 The @var{key-regexp} argument can refer to the text matched by a
1949 subexpression of @var{record-regexp}, or it can be a regular expression
1952 If @var{key-regexp} is:
1955 @item @samp{\@var{digit}}
1956 then the text matched by the @var{digit}th @samp{\(...\)} parenthesis
1957 grouping in @var{record-regexp} is the sort key.
1960 then the whole record is the sort key.
1962 @item a regular expression
1963 then @code{sort-regexp-fields} searches for a match for the regular
1964 expression within the record. If such a match is found, it is the sort
1965 key. If there is no match for @var{key-regexp} within a record then
1966 that record is ignored, which means its position in the buffer is not
1967 changed. (The other records may move around it.)
1970 For example, if you plan to sort all the lines in the region by the
1971 first word on each line starting with the letter @samp{f}, you should
1972 set @var{record-regexp} to @samp{^.*$} and set @var{key-regexp} to
1973 @samp{\<f\w*\>}. The resulting expression looks like this:
1977 (sort-regexp-fields nil "^.*$" "\\<f\\w*\\>"
1983 If you call @code{sort-regexp-fields} interactively, it prompts for
1984 @var{record-regexp} and @var{key-regexp} in the minibuffer.
1987 @deffn Command sort-lines reverse start end
1988 This command alphabetically sorts lines in the region between
1989 @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort
1990 is in reverse order.
1993 @deffn Command sort-paragraphs reverse start end
1994 This command alphabetically sorts paragraphs in the region between
1995 @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort
1996 is in reverse order.
1999 @deffn Command sort-pages reverse start end
2000 This command alphabetically sorts pages in the region between
2001 @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort
2002 is in reverse order.
2005 @deffn Command sort-fields field start end
2006 This command sorts lines in the region between @var{start} and
2007 @var{end}, comparing them alphabetically by the @var{field}th field
2008 of each line. Fields are separated by whitespace and numbered starting
2009 from 1. If @var{field} is negative, sorting is by the
2010 @w{@minus{}@var{field}th} field from the end of the line. This command
2011 is useful for sorting tables.
2014 @deffn Command sort-numeric-fields field start end
2015 This command sorts lines in the region between @var{start} and
2016 @var{end}, comparing them numerically by the @var{field}th field of
2017 each line. Fields are separated by whitespace and numbered starting
2018 from 1. The specified field must contain a number in each line of the
2019 region. Numbers starting with 0 are treated as octal, and numbers
2020 starting with @samp{0x} are treated as hexadecimal.
2022 If @var{field} is negative, sorting is by the
2023 @w{@minus{}@var{field}th} field from the end of the line. This
2024 command is useful for sorting tables.
2027 @defopt sort-numeric-base
2028 This variable specifies the default radix for
2029 @code{sort-numeric-fields} to parse numbers.
2032 @deffn Command sort-columns reverse &optional beg end
2033 This command sorts the lines in the region between @var{beg} and
2034 @var{end}, comparing them alphabetically by a certain range of
2035 columns. The column positions of @var{beg} and @var{end} bound the
2036 range of columns to sort on.
2038 If @var{reverse} is non-@code{nil}, the sort is in reverse order.
2040 One unusual thing about this command is that the entire line
2041 containing position @var{beg}, and the entire line containing position
2042 @var{end}, are included in the region sorted.
2044 Note that @code{sort-columns} uses the @code{sort} utility program,
2045 and so cannot work properly on text containing tab characters. Use
2046 @kbd{M-x untabify} to convert tabs to spaces before sorting.
2050 @comment node-name, next, previous, up
2051 @section Counting Columns
2053 @cindex counting columns
2054 @cindex horizontal position
2056 The column functions convert between a character position (counting
2057 characters from the beginning of the buffer) and a column position
2058 (counting screen characters from the beginning of a line).
2060 These functions count each character according to the number of
2061 columns it occupies on the screen. This means control characters count
2062 as occupying 2 or 4 columns, depending upon the value of
2063 @code{ctl-arrow}, and tabs count as occupying a number of columns that
2064 depends on the value of @code{tab-width} and on the column where the tab
2065 begins. @xref{Usual Display}.
2067 Column number computations ignore the width of the window and the
2068 amount of horizontal scrolling. Consequently, a column value can be
2069 arbitrarily high. The first (or leftmost) column is numbered 0. They
2070 also ignore overlays and text properties, aside from invisibility.
2072 @defun current-column
2073 This function returns the horizontal position of point, measured in
2074 columns, counting from 0 at the left margin. The column position is the
2075 sum of the widths of all the displayed representations of the characters
2076 between the start of the current line and point.
2078 For an example of using @code{current-column}, see the description of
2079 @code{count-lines} in @ref{Text Lines}.
2082 @defun move-to-column column &optional force
2083 This function moves point to @var{column} in the current line. The
2084 calculation of @var{column} takes into account the widths of the
2085 displayed representations of the characters between the start of the
2088 If column @var{column} is beyond the end of the line, point moves to the
2089 end of the line. If @var{column} is negative, point moves to the
2090 beginning of the line.
2092 If it is impossible to move to column @var{column} because that is in
2093 the middle of a multicolumn character such as a tab, point moves to the
2094 end of that character. However, if @var{force} is non-@code{nil}, and
2095 @var{column} is in the middle of a tab, then @code{move-to-column}
2096 converts the tab into spaces so that it can move precisely to column
2097 @var{column}. Other multicolumn characters can cause anomalies despite
2098 @var{force}, since there is no way to split them.
2100 The argument @var{force} also has an effect if the line isn't long
2101 enough to reach column @var{column}; if it is @code{t}, that means to
2102 add whitespace at the end of the line to reach that column.
2104 If @var{column} is not an integer, an error is signaled.
2106 The return value is the column number actually moved to.
2110 @section Indentation
2113 The indentation functions are used to examine, move to, and change
2114 whitespace that is at the beginning of a line. Some of the functions
2115 can also change whitespace elsewhere on a line. Columns and indentation
2116 count from zero at the left margin.
2119 * Primitive Indent:: Functions used to count and insert indentation.
2120 * Mode-Specific Indent:: Customize indentation for different modes.
2121 * Region Indent:: Indent all the lines in a region.
2122 * Relative Indent:: Indent the current line based on previous lines.
2123 * Indent Tabs:: Adjustable, typewriter-like tab stops.
2124 * Motion by Indent:: Move to first non-blank character.
2127 @node Primitive Indent
2128 @subsection Indentation Primitives
2130 This section describes the primitive functions used to count and
2131 insert indentation. The functions in the following sections use these
2132 primitives. @xref{Width}, for related functions.
2134 @defun current-indentation
2135 @comment !!Type Primitive Function
2136 @comment !!SourceFile indent.c
2137 This function returns the indentation of the current line, which is
2138 the horizontal position of the first nonblank character. If the
2139 contents are entirely blank, then this is the horizontal position of the
2143 @deffn Command indent-to column &optional minimum
2144 @comment !!Type Primitive Function
2145 @comment !!SourceFile indent.c
2146 This function indents from point with tabs and spaces until @var{column}
2147 is reached. If @var{minimum} is specified and non-@code{nil}, then at
2148 least that many spaces are inserted even if this requires going beyond
2149 @var{column}. Otherwise the function does nothing if point is already
2150 beyond @var{column}. The value is the column at which the inserted
2153 The inserted whitespace characters inherit text properties from the
2154 surrounding text (usually, from the preceding text only). @xref{Sticky
2158 @defopt indent-tabs-mode
2159 @comment !!SourceFile indent.c
2160 If this variable is non-@code{nil}, indentation functions can insert
2161 tabs as well as spaces. Otherwise, they insert only spaces. Setting
2162 this variable automatically makes it buffer-local in the current buffer.
2165 @node Mode-Specific Indent
2166 @subsection Indentation Controlled by Major Mode
2168 An important function of each major mode is to customize the @key{TAB}
2169 key to indent properly for the language being edited. This section
2170 describes the mechanism of the @key{TAB} key and how to control it.
2171 The functions in this section return unpredictable values.
2173 @defvar indent-line-function
2174 This variable's value is the function to be used by @key{TAB} (and
2175 various commands) to indent the current line. The command
2176 @code{indent-according-to-mode} does no more than call this function.
2178 In Lisp mode, the value is the symbol @code{lisp-indent-line}; in C
2179 mode, @code{c-indent-line}; in Fortran mode, @code{fortran-indent-line}.
2180 In Fundamental mode, Text mode, and many other modes with no standard
2181 for indentation, the value is @code{indent-to-left-margin} (which is the
2185 @deffn Command indent-according-to-mode
2186 This command calls the function in @code{indent-line-function} to
2187 indent the current line in a way appropriate for the current major mode.
2190 @deffn Command indent-for-tab-command
2191 This command calls the function in @code{indent-line-function} to indent
2192 the current line; however, if that function is
2193 @code{indent-to-left-margin}, @code{insert-tab} is called instead. (That
2194 is a trivial command that inserts a tab character.)
2197 @deffn Command newline-and-indent
2198 @comment !!SourceFile simple.el
2199 This function inserts a newline, then indents the new line (the one
2200 following the newline just inserted) according to the major mode.
2202 It does indentation by calling the current @code{indent-line-function}.
2203 In programming language modes, this is the same thing @key{TAB} does,
2204 but in some text modes, where @key{TAB} inserts a tab,
2205 @code{newline-and-indent} indents to the column specified by
2209 @deffn Command reindent-then-newline-and-indent
2210 @comment !!SourceFile simple.el
2211 This command reindents the current line, inserts a newline at point,
2212 and then indents the new line (the one following the newline just
2215 This command does indentation on both lines according to the current
2216 major mode, by calling the current value of @code{indent-line-function}.
2217 In programming language modes, this is the same thing @key{TAB} does,
2218 but in some text modes, where @key{TAB} inserts a tab,
2219 @code{reindent-then-newline-and-indent} indents to the column specified
2220 by @code{left-margin}.
2224 @subsection Indenting an Entire Region
2226 This section describes commands that indent all the lines in the
2227 region. They return unpredictable values.
2229 @deffn Command indent-region start end to-column
2230 This command indents each nonblank line starting between @var{start}
2231 (inclusive) and @var{end} (exclusive). If @var{to-column} is
2232 @code{nil}, @code{indent-region} indents each nonblank line by calling
2233 the current mode's indentation function, the value of
2234 @code{indent-line-function}.
2236 If @var{to-column} is non-@code{nil}, it should be an integer
2237 specifying the number of columns of indentation; then this function
2238 gives each line exactly that much indentation, by either adding or
2239 deleting whitespace.
2241 If there is a fill prefix, @code{indent-region} indents each line
2242 by making it start with the fill prefix.
2245 @defvar indent-region-function
2246 The value of this variable is a function that can be used by
2247 @code{indent-region} as a short cut. It should take two arguments, the
2248 start and end of the region. You should design the function so
2249 that it will produce the same results as indenting the lines of the
2250 region one by one, but presumably faster.
2252 If the value is @code{nil}, there is no short cut, and
2253 @code{indent-region} actually works line by line.
2255 A short-cut function is useful in modes such as C mode and Lisp mode,
2256 where the @code{indent-line-function} must scan from the beginning of
2257 the function definition: applying it to each line would be quadratic in
2258 time. The short cut can update the scan information as it moves through
2259 the lines indenting them; this takes linear time. In a mode where
2260 indenting a line individually is fast, there is no need for a short cut.
2262 @code{indent-region} with a non-@code{nil} argument @var{to-column} has
2263 a different meaning and does not use this variable.
2266 @deffn Command indent-rigidly start end count
2267 @comment !!SourceFile indent.el
2268 This command indents all lines starting between @var{start}
2269 (inclusive) and @var{end} (exclusive) sideways by @var{count} columns.
2270 This ``preserves the shape'' of the affected region, moving it as a
2271 rigid unit. Consequently, this command is useful not only for indenting
2272 regions of unindented text, but also for indenting regions of formatted
2275 For example, if @var{count} is 3, this command adds 3 columns of
2276 indentation to each of the lines beginning in the region specified.
2278 In Mail mode, @kbd{C-c C-y} (@code{mail-yank-original}) uses
2279 @code{indent-rigidly} to indent the text copied from the message being
2283 @defun indent-code-rigidly start end columns &optional nochange-regexp
2284 This is like @code{indent-rigidly}, except that it doesn't alter lines
2285 that start within strings or comments.
2287 In addition, it doesn't alter a line if @var{nochange-regexp} matches at
2288 the beginning of the line (if @var{nochange-regexp} is non-@code{nil}).
2291 @node Relative Indent
2292 @subsection Indentation Relative to Previous Lines
2294 This section describes two commands that indent the current line
2295 based on the contents of previous lines.
2297 @deffn Command indent-relative &optional unindented-ok
2298 This command inserts whitespace at point, extending to the same
2299 column as the next @dfn{indent point} of the previous nonblank line. An
2300 indent point is a non-whitespace character following whitespace. The
2301 next indent point is the first one at a column greater than the current
2302 column of point. For example, if point is underneath and to the left of
2303 the first non-blank character of a line of text, it moves to that column
2304 by inserting whitespace.
2306 If the previous nonblank line has no next indent point (i.e., none at a
2307 great enough column position), @code{indent-relative} either does
2308 nothing (if @var{unindented-ok} is non-@code{nil}) or calls
2309 @code{tab-to-tab-stop}. Thus, if point is underneath and to the right
2310 of the last column of a short line of text, this command ordinarily
2311 moves point to the next tab stop by inserting whitespace.
2313 The return value of @code{indent-relative} is unpredictable.
2315 In the following example, point is at the beginning of the second
2320 This line is indented twelve spaces.
2321 @point{}The quick brown fox jumped.
2326 Evaluation of the expression @code{(indent-relative nil)} produces the
2331 This line is indented twelve spaces.
2332 @point{}The quick brown fox jumped.
2336 In this next example, point is between the @samp{m} and @samp{p} of
2341 This line is indented twelve spaces.
2342 The quick brown fox jum@point{}ped.
2347 Evaluation of the expression @code{(indent-relative nil)} produces the
2352 This line is indented twelve spaces.
2353 The quick brown fox jum @point{}ped.
2358 @deffn Command indent-relative-maybe
2359 @comment !!SourceFile indent.el
2360 This command indents the current line like the previous nonblank line,
2361 by calling @code{indent-relative} with @code{t} as the
2362 @var{unindented-ok} argument. The return value is unpredictable.
2364 If the previous nonblank line has no indent points beyond the current
2365 column, this command does nothing.
2369 @comment node-name, next, previous, up
2370 @subsection Adjustable ``Tab Stops''
2371 @cindex tabs stops for indentation
2373 This section explains the mechanism for user-specified ``tab stops''
2374 and the mechanisms that use and set them. The name ``tab stops'' is
2375 used because the feature is similar to that of the tab stops on a
2376 typewriter. The feature works by inserting an appropriate number of
2377 spaces and tab characters to reach the next tab stop column; it does not
2378 affect the display of tab characters in the buffer (@pxref{Usual
2379 Display}). Note that the @key{TAB} character as input uses this tab
2380 stop feature only in a few major modes, such as Text mode.
2382 @deffn Command tab-to-tab-stop
2383 This command inserts spaces or tabs before point, up to the next tab
2384 stop column defined by @code{tab-stop-list}. It searches the list for
2385 an element greater than the current column number, and uses that element
2386 as the column to indent to. It does nothing if no such element is
2390 @defopt tab-stop-list
2391 This variable is the list of tab stop columns used by
2392 @code{tab-to-tab-stops}. The elements should be integers in increasing
2393 order. The tab stop columns need not be evenly spaced.
2395 Use @kbd{M-x edit-tab-stops} to edit the location of tab stops
2399 @node Motion by Indent
2400 @subsection Indentation-Based Motion Commands
2402 These commands, primarily for interactive use, act based on the
2403 indentation in the text.
2405 @deffn Command back-to-indentation
2406 @comment !!SourceFile simple.el
2407 This command moves point to the first non-whitespace character in the
2408 current line (which is the line in which point is located). It returns
2412 @deffn Command backward-to-indentation &optional arg
2413 @comment !!SourceFile simple.el
2414 This command moves point backward @var{arg} lines and then to the
2415 first nonblank character on that line. It returns @code{nil}.
2416 If @var{arg} is omitted or @code{nil}, it defaults to 1.
2419 @deffn Command forward-to-indentation &optional arg
2420 @comment !!SourceFile simple.el
2421 This command moves point forward @var{arg} lines and then to the first
2422 nonblank character on that line. It returns @code{nil}.
2423 If @var{arg} is omitted or @code{nil}, it defaults to 1.
2427 @comment node-name, next, previous, up
2428 @section Case Changes
2429 @cindex case conversion in buffers
2431 The case change commands described here work on text in the current
2432 buffer. @xref{Case Conversion}, for case conversion functions that work
2433 on strings and characters. @xref{Case Tables}, for how to customize
2434 which characters are upper or lower case and how to convert them.
2436 @deffn Command capitalize-region start end
2437 This function capitalizes all words in the region defined by
2438 @var{start} and @var{end}. To capitalize means to convert each word's
2439 first character to upper case and convert the rest of each word to lower
2440 case. The function returns @code{nil}.
2442 If one end of the region is in the middle of a word, the part of the
2443 word within the region is treated as an entire word.
2445 When @code{capitalize-region} is called interactively, @var{start} and
2446 @var{end} are point and the mark, with the smallest first.
2450 ---------- Buffer: foo ----------
2451 This is the contents of the 5th foo.
2452 ---------- Buffer: foo ----------
2456 (capitalize-region 1 44)
2459 ---------- Buffer: foo ----------
2460 This Is The Contents Of The 5th Foo.
2461 ---------- Buffer: foo ----------
2466 @deffn Command downcase-region start end
2467 This function converts all of the letters in the region defined by
2468 @var{start} and @var{end} to lower case. The function returns
2471 When @code{downcase-region} is called interactively, @var{start} and
2472 @var{end} are point and the mark, with the smallest first.
2475 @deffn Command upcase-region start end
2476 This function converts all of the letters in the region defined by
2477 @var{start} and @var{end} to upper case. The function returns
2480 When @code{upcase-region} is called interactively, @var{start} and
2481 @var{end} are point and the mark, with the smallest first.
2484 @deffn Command capitalize-word count
2485 This function capitalizes @var{count} words after point, moving point
2486 over as it does. To capitalize means to convert each word's first
2487 character to upper case and convert the rest of each word to lower case.
2488 If @var{count} is negative, the function capitalizes the
2489 @minus{}@var{count} previous words but does not move point. The value
2492 If point is in the middle of a word, the part of the word before point
2493 is ignored when moving forward. The rest is treated as an entire word.
2495 When @code{capitalize-word} is called interactively, @var{count} is
2496 set to the numeric prefix argument.
2499 @deffn Command downcase-word count
2500 This function converts the @var{count} words after point to all lower
2501 case, moving point over as it does. If @var{count} is negative, it
2502 converts the @minus{}@var{count} previous words but does not move point.
2503 The value is @code{nil}.
2505 When @code{downcase-word} is called interactively, @var{count} is set
2506 to the numeric prefix argument.
2509 @deffn Command upcase-word count
2510 This function converts the @var{count} words after point to all upper
2511 case, moving point over as it does. If @var{count} is negative, it
2512 converts the @minus{}@var{count} previous words but does not move point.
2513 The value is @code{nil}.
2515 When @code{upcase-word} is called interactively, @var{count} is set to
2516 the numeric prefix argument.
2519 @node Text Properties
2520 @section Text Properties
2521 @cindex text properties
2522 @cindex attributes of text
2523 @cindex properties of text
2525 Each character position in a buffer or a string can have a @dfn{text
2526 property list}, much like the property list of a symbol (@pxref{Property
2527 Lists}). The properties belong to a particular character at a
2528 particular place, such as, the letter @samp{T} at the beginning of this
2529 sentence or the first @samp{o} in @samp{foo}---if the same character
2530 occurs in two different places, the two occurrences generally have
2531 different properties.
2533 Each property has a name and a value. Both of these can be any Lisp
2534 object, but the name is normally a symbol. The usual way to access the
2535 property list is to specify a name and ask what value corresponds to it.
2537 If a character has a @code{category} property, we call it the
2538 @dfn{category} of the character. It should be a symbol. The properties
2539 of the symbol serve as defaults for the properties of the character.
2541 Copying text between strings and buffers preserves the properties
2542 along with the characters; this includes such diverse functions as
2543 @code{substring}, @code{insert}, and @code{buffer-substring}.
2546 * Examining Properties:: Looking at the properties of one character.
2547 * Changing Properties:: Setting the properties of a range of text.
2548 * Property Search:: Searching for where a property changes value.
2549 * Special Properties:: Particular properties with special meanings.
2550 * Format Properties:: Properties for representing formatting of text.
2551 * Sticky Properties:: How inserted text gets properties from
2553 * Saving Properties:: Saving text properties in files, and reading
2555 * Lazy Properties:: Computing text properties in a lazy fashion
2556 only when text is examined.
2557 * Clickable Text:: Using text properties to make regions of text
2558 do something when you click on them.
2559 * Links and Mouse-1:: How to make @key{Mouse-1} follow a link.
2560 * Fields:: The @code{field} property defines
2561 fields within the buffer.
2562 * Not Intervals:: Why text properties do not use
2563 Lisp-visible text intervals.
2566 @node Examining Properties
2567 @subsection Examining Text Properties
2569 The simplest way to examine text properties is to ask for the value of
2570 a particular property of a particular character. For that, use
2571 @code{get-text-property}. Use @code{text-properties-at} to get the
2572 entire property list of a character. @xref{Property Search}, for
2573 functions to examine the properties of a number of characters at once.
2575 These functions handle both strings and buffers. Keep in mind that
2576 positions in a string start from 0, whereas positions in a buffer start
2579 @defun get-text-property pos prop &optional object
2580 This function returns the value of the @var{prop} property of the
2581 character after position @var{pos} in @var{object} (a buffer or
2582 string). The argument @var{object} is optional and defaults to the
2585 If there is no @var{prop} property strictly speaking, but the character
2586 has a category that is a symbol, then @code{get-text-property} returns
2587 the @var{prop} property of that symbol.
2590 @defun get-char-property position prop &optional object
2591 This function is like @code{get-text-property}, except that it checks
2592 overlays first and then text properties. @xref{Overlays}.
2594 The argument @var{object} may be a string, a buffer, or a window. If it
2595 is a window, then the buffer displayed in that window is used for text
2596 properties and overlays, but only the overlays active for that window
2597 are considered. If @var{object} is a buffer, then all overlays in that
2598 buffer are considered, as well as text properties. If @var{object} is a
2599 string, only text properties are considered, since strings never have
2603 @defun get-char-property-and-overlay position prop &optional object
2604 This is like @code{get-char-property}, but gives extra information
2605 about the overlay that the property value comes from.
2607 Its value is a cons cell whose @sc{car} is the property value, the
2608 same value @code{get-char-property} would return with the same
2609 arguments. Its @sc{cdr} is the overlay in which the property was
2610 found, or @code{nil}, if it was found as a text property or not found
2613 If @var{position} is at the end of @var{object}, both the @sc{car} and
2614 the @sc{cdr} of the value are @code{nil}.
2617 @defvar char-property-alias-alist
2618 This variable holds an alist which maps property names to a list of
2619 alternative property names. If a character does not specify a direct
2620 value for a property, the alternative property names are consulted in
2621 order; the first non-@code{nil} value is used. This variable takes
2622 precedence over @code{default-text-properties}, and @code{category}
2623 properties take precedence over this variable.
2626 @defun text-properties-at position &optional object
2627 This function returns the entire property list of the character at
2628 @var{position} in the string or buffer @var{object}. If @var{object} is
2629 @code{nil}, it defaults to the current buffer.
2632 @defvar default-text-properties
2633 This variable holds a property list giving default values for text
2634 properties. Whenever a character does not specify a value for a
2635 property, neither directly, through a category symbol, or through
2636 @code{char-property-alias-alist}, the value stored in this list is
2637 used instead. Here is an example:
2640 (setq default-text-properties '(foo 69)
2641 char-property-alias-alist nil)
2642 ;; @r{Make sure character 1 has no properties of its own.}
2643 (set-text-properties 1 2 nil)
2644 ;; @r{What we get, when we ask, is the default value.}
2645 (get-text-property 1 'foo)
2650 @node Changing Properties
2651 @subsection Changing Text Properties
2653 The primitives for changing properties apply to a specified range of
2654 text in a buffer or string. The function @code{set-text-properties}
2655 (see end of section) sets the entire property list of the text in that
2656 range; more often, it is useful to add, change, or delete just certain
2657 properties specified by name.
2659 Since text properties are considered part of the contents of the
2660 buffer (or string), and can affect how a buffer looks on the screen,
2661 any change in buffer text properties marks the buffer as modified.
2662 Buffer text property changes are undoable also (@pxref{Undo}).
2663 Positions in a string start from 0, whereas positions in a buffer
2666 @defun put-text-property start end prop value &optional object
2667 This function sets the @var{prop} property to @var{value} for the text
2668 between @var{start} and @var{end} in the string or buffer @var{object}.
2669 If @var{object} is @code{nil}, it defaults to the current buffer.
2672 @defun add-text-properties start end props &optional object
2673 This function adds or overrides text properties for the text between
2674 @var{start} and @var{end} in the string or buffer @var{object}. If
2675 @var{object} is @code{nil}, it defaults to the current buffer.
2677 The argument @var{props} specifies which properties to add. It should
2678 have the form of a property list (@pxref{Property Lists}): a list whose
2679 elements include the property names followed alternately by the
2680 corresponding values.
2682 The return value is @code{t} if the function actually changed some
2683 property's value; @code{nil} otherwise (if @var{props} is @code{nil} or
2684 its values agree with those in the text).
2686 For example, here is how to set the @code{comment} and @code{face}
2687 properties of a range of text:
2690 (add-text-properties @var{start} @var{end}
2691 '(comment t face highlight))
2695 @defun remove-text-properties start end props &optional object
2696 This function deletes specified text properties from the text between
2697 @var{start} and @var{end} in the string or buffer @var{object}. If
2698 @var{object} is @code{nil}, it defaults to the current buffer.
2700 The argument @var{props} specifies which properties to delete. It
2701 should have the form of a property list (@pxref{Property Lists}): a list
2702 whose elements are property names alternating with corresponding values.
2703 But only the names matter---the values that accompany them are ignored.
2704 For example, here's how to remove the @code{face} property.
2707 (remove-text-properties @var{start} @var{end} '(face nil))
2710 The return value is @code{t} if the function actually changed some
2711 property's value; @code{nil} otherwise (if @var{props} is @code{nil} or
2712 if no character in the specified text had any of those properties).
2714 To remove all text properties from certain text, use
2715 @code{set-text-properties} and specify @code{nil} for the new property
2719 @defun remove-list-of-text-properties start end list-of-properties &optional object
2720 Like @code{remove-text-properties} except that
2721 @var{list-of-properties} is a list property names only, not an
2722 alternating list of property names and values.
2725 @defun set-text-properties start end props &optional object
2726 This function completely replaces the text property list for the text
2727 between @var{start} and @var{end} in the string or buffer @var{object}.
2728 If @var{object} is @code{nil}, it defaults to the current buffer.
2730 The argument @var{props} is the new property list. It should be a list
2731 whose elements are property names alternating with corresponding values.
2733 After @code{set-text-properties} returns, all the characters in the
2734 specified range have identical properties.
2736 If @var{props} is @code{nil}, the effect is to get rid of all properties
2737 from the specified range of text. Here's an example:
2740 (set-text-properties @var{start} @var{end} nil)
2744 The easiest way to make a string with text properties
2745 is with @code{propertize}:
2747 @defun propertize string &rest properties
2749 This function returns a copy of @var{string} which has the text
2750 properties @var{properties}. These properties apply to all the
2751 characters in the string that is returned. Here is an example that
2752 constructs a string with a @code{face} property and a @code{mouse-face}
2756 (propertize "foo" 'face 'italic
2757 'mouse-face 'bold-italic)
2758 @result{} #("foo" 0 3 (mouse-face bold-italic face italic))
2761 To put different properties on various parts of a string, you can
2762 construct each part with @code{propertize} and then combine them with
2767 (propertize "foo" 'face 'italic
2768 'mouse-face 'bold-italic)
2770 (propertize "bar" 'face 'italic
2771 'mouse-face 'bold-italic))
2772 @result{} #("foo and bar"
2773 0 3 (face italic mouse-face bold-italic)
2775 8 11 (face italic mouse-face bold-italic))
2779 See also the function @code{buffer-substring-no-properties}
2780 (@pxref{Buffer Contents}) which copies text from the buffer
2781 but does not copy its properties.
2783 @node Property Search
2784 @subsection Text Property Search Functions
2786 In typical use of text properties, most of the time several or many
2787 consecutive characters have the same value for a property. Rather than
2788 writing your programs to examine characters one by one, it is much
2789 faster to process chunks of text that have the same property value.
2791 Here are functions you can use to do this. They use @code{eq} for
2792 comparing property values. In all cases, @var{object} defaults to the
2795 For high performance, it's very important to use the @var{limit}
2796 argument to these functions, especially the ones that search for a
2797 single property---otherwise, they may spend a long time scanning to the
2798 end of the buffer, if the property you are interested in does not change.
2800 These functions do not move point; instead, they return a position (or
2801 @code{nil}). Remember that a position is always between two characters;
2802 the position returned by these functions is between two characters with
2803 different properties.
2805 @defun next-property-change pos &optional object limit
2806 The function scans the text forward from position @var{pos} in the
2807 string or buffer @var{object} till it finds a change in some text
2808 property, then returns the position of the change. In other words, it
2809 returns the position of the first character beyond @var{pos} whose
2810 properties are not identical to those of the character just after
2813 If @var{limit} is non-@code{nil}, then the scan ends at position
2814 @var{limit}. If there is no property change before that point,
2815 @code{next-property-change} returns @var{limit}.
2817 The value is @code{nil} if the properties remain unchanged all the way
2818 to the end of @var{object} and @var{limit} is @code{nil}. If the value
2819 is non-@code{nil}, it is a position greater than or equal to @var{pos}.
2820 The value equals @var{pos} only when @var{limit} equals @var{pos}.
2822 Here is an example of how to scan the buffer by chunks of text within
2823 which all properties are constant:
2827 (let ((plist (text-properties-at (point)))
2829 (or (next-property-change (point) (current-buffer))
2831 @r{Process text from point to @var{next-change}@dots{}}
2832 (goto-char next-change)))
2836 @defun next-single-property-change pos prop &optional object limit
2837 The function scans the text forward from position @var{pos} in the
2838 string or buffer @var{object} till it finds a change in the @var{prop}
2839 property, then returns the position of the change. In other words, it
2840 returns the position of the first character beyond @var{pos} whose
2841 @var{prop} property differs from that of the character just after
2844 If @var{limit} is non-@code{nil}, then the scan ends at position
2845 @var{limit}. If there is no property change before that point,
2846 @code{next-single-property-change} returns @var{limit}.
2848 The value is @code{nil} if the property remains unchanged all the way to
2849 the end of @var{object} and @var{limit} is @code{nil}. If the value is
2850 non-@code{nil}, it is a position greater than or equal to @var{pos}; it
2851 equals @var{pos} only if @var{limit} equals @var{pos}.
2854 @defun previous-property-change pos &optional object limit
2855 This is like @code{next-property-change}, but scans back from @var{pos}
2856 instead of forward. If the value is non-@code{nil}, it is a position
2857 less than or equal to @var{pos}; it equals @var{pos} only if @var{limit}
2861 @defun previous-single-property-change pos prop &optional object limit
2862 This is like @code{next-single-property-change}, but scans back from
2863 @var{pos} instead of forward. If the value is non-@code{nil}, it is a
2864 position less than or equal to @var{pos}; it equals @var{pos} only if
2865 @var{limit} equals @var{pos}.
2868 @defun next-char-property-change pos &optional limit
2869 This is like @code{next-property-change} except that it considers
2870 overlay properties as well as text properties, and if no change is
2871 found before the end of the buffer, it returns the maximum buffer
2872 position rather than @code{nil} (in this sense, it resembles the
2873 corresponding overlay function @code{next-overlay-change}, rather than
2874 @code{next-property-change}). There is no @var{object} operand
2875 because this function operates only on the current buffer. It returns
2876 the next address at which either kind of property changes.
2879 @defun previous-char-property-change pos &optional limit
2880 This is like @code{next-char-property-change}, but scans back from
2881 @var{pos} instead of forward, and returns the minimum buffer
2882 position if no change is found.
2885 @defun next-single-char-property-change pos prop &optional object limit
2886 @tindex next-single-char-property-change
2887 This is like @code{next-single-property-change} except that it
2888 considers overlay properties as well as text properties, and if no
2889 change is found before the end of the @var{object}, it returns the
2890 maximum valid position in @var{object} rather than @code{nil}. Unlike
2891 @code{next-char-property-change}, this function @emph{does} have an
2892 @var{object} operand; if @var{object} is not a buffer, only
2893 text-properties are considered.
2896 @defun previous-single-char-property-change pos prop &optional object limit
2897 @tindex previous-single-char-property-change
2898 This is like @code{next-single-char-property-change}, but scans back
2899 from @var{pos} instead of forward, and returns the minimum valid
2900 position in @var{object} if no change is found.
2903 @defun text-property-any start end prop value &optional object
2904 This function returns non-@code{nil} if at least one character between
2905 @var{start} and @var{end} has a property @var{prop} whose value is
2906 @var{value}. More precisely, it returns the position of the first such
2907 character. Otherwise, it returns @code{nil}.
2909 The optional fifth argument, @var{object}, specifies the string or
2910 buffer to scan. Positions are relative to @var{object}. The default
2911 for @var{object} is the current buffer.
2914 @defun text-property-not-all start end prop value &optional object
2915 This function returns non-@code{nil} if at least one character between
2916 @var{start} and @var{end} does not have a property @var{prop} with value
2917 @var{value}. More precisely, it returns the position of the first such
2918 character. Otherwise, it returns @code{nil}.
2920 The optional fifth argument, @var{object}, specifies the string or
2921 buffer to scan. Positions are relative to @var{object}. The default
2922 for @var{object} is the current buffer.
2925 @node Special Properties
2926 @subsection Properties with Special Meanings
2928 Here is a table of text property names that have special built-in
2929 meanings. The following sections list a few additional special property
2930 names that control filling and property inheritance. All other names
2931 have no standard meaning, and you can use them as you like.
2934 @cindex category of text character
2935 @kindex category @r{(text property)}
2937 If a character has a @code{category} property, we call it the
2938 @dfn{category} of the character. It should be a symbol. The properties
2939 of the symbol serve as defaults for the properties of the character.
2942 @cindex face codes of text
2943 @kindex face @r{(text property)}
2944 You can use the property @code{face} to control the font and color of
2945 text. @xref{Faces}, for more information.
2947 In the simplest case, the value is a face name. It can also be a list;
2948 then each element can be any of these possibilities;
2952 A face name (a symbol or string).
2955 A property list of face attributes. This has the
2956 form (@var{keyword} @var{value} @dots{}), where each @var{keyword} is a
2957 face attribute name and @var{value} is a meaningful value for that
2958 attribute. With this feature, you do not need to create a face each
2959 time you want to specify a particular attribute for certain text.
2960 @xref{Face Attributes}.
2963 A cons cell of the form @code{(foreground-color . @var{color-name})} or
2964 @code{(background-color . @var{color-name})}. These elements specify
2965 just the foreground color or just the background color.
2967 @code{(foreground-color . @var{color-name})} is equivalent to
2968 specifying @code{(:foreground @var{color-name})}, and likewise for the
2972 You can use Font Lock Mode (@pxref{Font Lock Mode}), to dynamically
2973 update @code{face} properties based on the contents of the text.
2975 @item font-lock-face
2976 @kindex font-lock-face @r{(text property)}
2977 The @code{font-lock-face} property is the same in all respects as the
2978 @code{face} property, but its state of activation is controlled by
2979 @code{font-lock-mode}. This can be advantageous for special buffers
2980 which are not intended to be user-editable, or for static areas of
2981 text which are always fontified in the same way.
2982 @xref{Precalculated Fontification}.
2984 Strictly speaking, @code{font-lock-face} is not a built-in text
2985 property; rather, it is implemented in Font Lock mode using
2986 @code{char-property-alias-alist}. @xref{Examining Properties}.
2988 This property is new in Emacs 22.1.
2991 @kindex mouse-face @r{(text property)}
2992 The property @code{mouse-face} is used instead of @code{face} when the
2993 mouse is on or near the character. For this purpose, ``near'' means
2994 that all text between the character and where the mouse is have the same
2995 @code{mouse-face} property value.
2998 @kindex fontified @r{(text property)}
2999 This property, if non-@code{nil}, says that text in the buffer has
3000 had faces assigned automatically by a feature such as Font-Lock mode.
3004 @kindex display @r{(text property)}
3005 This property activates various features that change the
3006 way text is displayed. For example, it can make text appear taller
3007 or shorter, higher or lower, wider or narrow, or replaced with an image.
3008 @xref{Display Property}.
3011 @kindex help-echo @r{(text property)}
3013 @anchor{Text help-echo}
3014 If text has a string as its @code{help-echo} property, then when you
3015 move the mouse onto that text, Emacs displays that string in the echo
3016 area, or in the tooltip window (@pxref{Tooltips,,, emacs, The GNU Emacs
3019 If the value of the @code{help-echo} property is a function, that
3020 function is called with three arguments, @var{window}, @var{object} and
3021 @var{pos} and should return a help string or @code{nil} for
3022 none. The first argument, @var{window} is the window in which
3023 the help was found. The second, @var{object}, is the buffer, overlay or
3024 string which had the @code{help-echo} property. The @var{pos}
3025 argument is as follows:
3029 If @var{object} is a buffer, @var{pos} is the position in the buffer
3030 where the @code{help-echo} text property was found.
3032 If @var{object} is an overlay, that overlay has a @code{help-echo}
3033 property, and @var{pos} is the position in the overlay's buffer under
3036 If @var{object} is a string (an overlay string or a string displayed
3037 with the @code{display} property), @var{pos} is the position in that
3038 string under the mouse.
3041 If the value of the @code{help-echo} property is neither a function nor
3042 a string, it is evaluated to obtain a help string.
3044 You can alter the way help text is displayed by setting the variable
3045 @code{show-help-function} (@pxref{Help display}).
3047 This feature is used in the mode line and for other active text.
3050 @cindex keymap of character
3051 @kindex keymap @r{(text property)}
3052 The @code{keymap} property specifies an additional keymap for
3053 commands. The property's value for the character before point applies
3054 if it is non-@code{nil} and rear-sticky, and the property's value for
3055 the character after point applies if it is non-@code{nil} and
3056 front-sticky. (For mouse clicks, the position of the click is used
3057 instead of the position of point.) If the property value is a symbol,
3058 the symbol's function definition is used as the keymap.
3060 When this keymap applies, it is used for key lookup before the minor
3061 mode keymaps and before the buffer's local map. @xref{Active
3065 @kindex local-map @r{(text property)}
3066 This property works like @code{keymap} except that it specifies a
3067 keymap to use @emph{instead of} the buffer's local map. For most
3068 purposes (perhaps all purposes), the @code{keymap} is superior.
3071 The @code{syntax-table} property overrides what the syntax table says
3072 about this particular character. @xref{Syntax Properties}.
3075 @cindex read-only character
3076 @kindex read-only @r{(text property)}
3077 If a character has the property @code{read-only}, then modifying that
3078 character is not allowed. Any command that would do so gets an error,
3079 @code{text-read-only}.
3081 Insertion next to a read-only character is an error if inserting
3082 ordinary text there would inherit the @code{read-only} property due to
3083 stickiness. Thus, you can control permission to insert next to
3084 read-only text by controlling the stickiness. @xref{Sticky Properties}.
3086 Since changing properties counts as modifying the buffer, it is not
3087 possible to remove a @code{read-only} property unless you know the
3088 special trick: bind @code{inhibit-read-only} to a non-@code{nil} value
3089 and then remove the property. @xref{Read Only Buffers}.
3092 @kindex invisible @r{(text property)}
3093 A non-@code{nil} @code{invisible} property can make a character invisible
3094 on the screen. @xref{Invisible Text}, for details.
3097 @kindex intangible @r{(text property)}
3098 If a group of consecutive characters have equal and non-@code{nil}
3099 @code{intangible} properties, then you cannot place point between them.
3100 If you try to move point forward into the group, point actually moves to
3101 the end of the group. If you try to move point backward into the group,
3102 point actually moves to the start of the group.
3104 When the variable @code{inhibit-point-motion-hooks} is non-@code{nil},
3105 the @code{intangible} property is ignored.
3108 @kindex field @r{(text property)}
3109 Consecutive characters with the same @code{field} property constitute a
3110 @dfn{field}. Some motion functions including @code{forward-word} and
3111 @code{beginning-of-line} stop moving at a field boundary.
3115 @kindex cursor @r{(text property)}
3116 Normally, the cursor is displayed at the end of any overlay and text
3117 property strings present at the current window position. You can
3118 place the cursor on any desired character of these strings by giving
3119 that character a non-@code{nil} @var{cursor} text property.
3122 @kindex pointer @r{(text property)}
3123 This specifies a specific pointer shape when the mouse pointer is over
3124 this text or image. @xref{Pointer Shape}, for possible pointer
3128 @kindex line-spacing @r{(text property)}
3129 A newline can have a @code{line-spacing} text or overlay property that
3130 controls the height of the display line ending with that newline. The
3131 property value overrides the default frame line spacing and the buffer
3132 local @code{line-spacing} variable. @xref{Line Height}.
3135 @kindex line-height @r{(text property)}
3136 A newline can have a @code{line-height} text or overlay property that
3137 controls the total height of the display line ending in that newline.
3140 @item modification-hooks
3141 @cindex change hooks for a character
3142 @cindex hooks for changing a character
3143 @kindex modification-hooks @r{(text property)}
3144 If a character has the property @code{modification-hooks}, then its
3145 value should be a list of functions; modifying that character calls all
3146 of those functions. Each function receives two arguments: the beginning
3147 and end of the part of the buffer being modified. Note that if a
3148 particular modification hook function appears on several characters
3149 being modified by a single primitive, you can't predict how many times
3150 the function will be called.
3152 If these functions modify the buffer, they should bind
3153 @code{inhibit-modification-hooks} to @code{t} around doing so, to
3154 avoid confusing the internal mechanism that calls these hooks.
3156 @item insert-in-front-hooks
3157 @itemx insert-behind-hooks
3158 @kindex insert-in-front-hooks @r{(text property)}
3159 @kindex insert-behind-hooks @r{(text property)}
3160 The operation of inserting text in a buffer also calls the functions
3161 listed in the @code{insert-in-front-hooks} property of the following
3162 character and in the @code{insert-behind-hooks} property of the
3163 preceding character. These functions receive two arguments, the
3164 beginning and end of the inserted text. The functions are called
3165 @emph{after} the actual insertion takes place.
3167 See also @ref{Change Hooks}, for other hooks that are called
3168 when you change text in a buffer.
3172 @cindex hooks for motion of point
3173 @kindex point-entered @r{(text property)}
3174 @kindex point-left @r{(text property)}
3175 The special properties @code{point-entered} and @code{point-left}
3176 record hook functions that report motion of point. Each time point
3177 moves, Emacs compares these two property values:
3181 the @code{point-left} property of the character after the old location,
3184 the @code{point-entered} property of the character after the new
3189 If these two values differ, each of them is called (if not @code{nil})
3190 with two arguments: the old value of point, and the new one.
3192 The same comparison is made for the characters before the old and new
3193 locations. The result may be to execute two @code{point-left} functions
3194 (which may be the same function) and/or two @code{point-entered}
3195 functions (which may be the same function). In any case, all the
3196 @code{point-left} functions are called first, followed by all the
3197 @code{point-entered} functions.
3199 It is possible with @code{char-after} to examine characters at various
3200 buffer positions without moving point to those positions. Only an
3201 actual change in the value of point runs these hook functions.
3204 @defvar inhibit-point-motion-hooks
3205 When this variable is non-@code{nil}, @code{point-left} and
3206 @code{point-entered} hooks are not run, and the @code{intangible}
3207 property has no effect. Do not set this variable globally; bind it with
3211 @defvar show-help-function
3212 @tindex show-help-function
3213 @anchor{Help display} If this variable is non-@code{nil}, it specifies a
3214 function called to display help strings. These may be @code{help-echo}
3215 properties, menu help strings (@pxref{Simple Menu Items},
3216 @pxref{Extended Menu Items}), or tool bar help strings (@pxref{Tool
3217 Bar}). The specified function is called with one argument, the help
3218 string to display. Tooltip mode (@pxref{Tooltips,,, emacs, The GNU Emacs
3219 Manual}) provides an example.
3222 @node Format Properties
3223 @subsection Formatted Text Properties
3225 These text properties affect the behavior of the fill commands. They
3226 are used for representing formatted text. @xref{Filling}, and
3231 If a newline character has this property, it is a ``hard'' newline.
3232 The fill commands do not alter hard newlines and do not move words
3233 across them. However, this property takes effect only if the
3234 @code{use-hard-newlines} minor mode is enabled. @xref{Hard and Soft
3235 Newlines,, Hard and Soft Newlines, emacs, The GNU Emacs Manual}.
3238 This property specifies an extra right margin for filling this part of the
3242 This property specifies an extra left margin for filling this part of the
3246 This property specifies the style of justification for filling this part
3250 @node Sticky Properties
3251 @subsection Stickiness of Text Properties
3252 @cindex sticky text properties
3253 @cindex inheritance of text properties
3255 Self-inserting characters normally take on the same properties as the
3256 preceding character. This is called @dfn{inheritance} of properties.
3258 In a Lisp program, you can do insertion with inheritance or without,
3259 depending on your choice of insertion primitive. The ordinary text
3260 insertion functions such as @code{insert} do not inherit any properties.
3261 They insert text with precisely the properties of the string being
3262 inserted, and no others. This is correct for programs that copy text
3263 from one context to another---for example, into or out of the kill ring.
3264 To insert with inheritance, use the special primitives described in this
3265 section. Self-inserting characters inherit properties because they work
3266 using these primitives.
3268 When you do insertion with inheritance, @emph{which} properties are
3269 inherited, and from where, depends on which properties are @dfn{sticky}.
3270 Insertion after a character inherits those of its properties that are
3271 @dfn{rear-sticky}. Insertion before a character inherits those of its
3272 properties that are @dfn{front-sticky}. When both sides offer different
3273 sticky values for the same property, the previous character's value
3276 By default, a text property is rear-sticky but not front-sticky; thus,
3277 the default is to inherit all the properties of the preceding character,
3278 and nothing from the following character.
3280 You can control the stickiness of various text properties with two
3281 specific text properties, @code{front-sticky} and @code{rear-nonsticky},
3282 and with the variable @code{text-property-default-nonsticky}. You can
3283 use the variable to specify a different default for a given property.
3284 You can use those two text properties to make any specific properties
3285 sticky or nonsticky in any particular part of the text.
3287 If a character's @code{front-sticky} property is @code{t}, then all
3288 its properties are front-sticky. If the @code{front-sticky} property is
3289 a list, then the sticky properties of the character are those whose
3290 names are in the list. For example, if a character has a
3291 @code{front-sticky} property whose value is @code{(face read-only)},
3292 then insertion before the character can inherit its @code{face} property
3293 and its @code{read-only} property, but no others.
3295 The @code{rear-nonsticky} property works the opposite way. Most
3296 properties are rear-sticky by default, so the @code{rear-nonsticky}
3297 property says which properties are @emph{not} rear-sticky. If a
3298 character's @code{rear-nonsticky} property is @code{t}, then none of its
3299 properties are rear-sticky. If the @code{rear-nonsticky} property is a
3300 list, properties are rear-sticky @emph{unless} their names are in the
3303 @defvar text-property-default-nonsticky
3304 @tindex text-property-default-nonsticky
3305 This variable holds an alist which defines the default rear-stickiness
3306 of various text properties. Each element has the form
3307 @code{(@var{property} . @var{nonstickiness})}, and it defines the
3308 stickiness of a particular text property, @var{property}.
3310 If @var{nonstickiness} is non-@code{nil}, this means that the property
3311 @var{property} is rear-nonsticky by default. Since all properties are
3312 front-nonsticky by default, this makes @var{property} nonsticky in both
3313 directions by default.
3315 The text properties @code{front-sticky} and @code{rear-nonsticky}, when
3316 used, take precedence over the default @var{nonstickiness} specified in
3317 @code{text-property-default-nonsticky}.
3320 Here are the functions that insert text with inheritance of properties:
3322 @defun insert-and-inherit &rest strings
3323 Insert the strings @var{strings}, just like the function @code{insert},
3324 but inherit any sticky properties from the adjoining text.
3327 @defun insert-before-markers-and-inherit &rest strings
3328 Insert the strings @var{strings}, just like the function
3329 @code{insert-before-markers}, but inherit any sticky properties from the
3333 @xref{Insertion}, for the ordinary insertion functions which do not
3336 @node Saving Properties
3337 @subsection Saving Text Properties in Files
3338 @cindex text properties in files
3339 @cindex saving text properties
3341 You can save text properties in files (along with the text itself),
3342 and restore the same text properties when visiting or inserting the
3343 files, using these two hooks:
3345 @defvar write-region-annotate-functions
3346 This variable's value is a list of functions for @code{write-region} to
3347 run to encode text properties in some fashion as annotations to the text
3348 being written in the file. @xref{Writing to Files}.
3350 Each function in the list is called with two arguments: the start and
3351 end of the region to be written. These functions should not alter the
3352 contents of the buffer. Instead, they should return lists indicating
3353 annotations to write in the file in addition to the text in the
3356 Each function should return a list of elements of the form
3357 @code{(@var{position} . @var{string})}, where @var{position} is an
3358 integer specifying the relative position within the text to be written,
3359 and @var{string} is the annotation to add there.
3361 Each list returned by one of these functions must be already sorted in
3362 increasing order by @var{position}. If there is more than one function,
3363 @code{write-region} merges the lists destructively into one sorted list.
3365 When @code{write-region} actually writes the text from the buffer to the
3366 file, it intermixes the specified annotations at the corresponding
3367 positions. All this takes place without modifying the buffer.
3370 @defvar after-insert-file-functions
3371 This variable holds a list of functions for @code{insert-file-contents}
3372 to call after inserting a file's contents. These functions should scan
3373 the inserted text for annotations, and convert them to the text
3374 properties they stand for.
3376 Each function receives one argument, the length of the inserted text;
3377 point indicates the start of that text. The function should scan that
3378 text for annotations, delete them, and create the text properties that
3379 the annotations specify. The function should return the updated length
3380 of the inserted text, as it stands after those changes. The value
3381 returned by one function becomes the argument to the next function.
3383 These functions should always return with point at the beginning of
3386 The intended use of @code{after-insert-file-functions} is for converting
3387 some sort of textual annotations into actual text properties. But other
3388 uses may be possible.
3391 We invite users to write Lisp programs to store and retrieve text
3392 properties in files, using these hooks, and thus to experiment with
3393 various data formats and find good ones. Eventually we hope users
3394 will produce good, general extensions we can install in Emacs.
3396 We suggest not trying to handle arbitrary Lisp objects as text property
3397 names or values---because a program that general is probably difficult
3398 to write, and slow. Instead, choose a set of possible data types that
3399 are reasonably flexible, and not too hard to encode.
3401 @xref{Format Conversion}, for a related feature.
3403 @c ??? In next edition, merge this info Format Conversion.
3405 @node Lazy Properties
3406 @subsection Lazy Computation of Text Properties
3408 Instead of computing text properties for all the text in the buffer,
3409 you can arrange to compute the text properties for parts of the text
3410 when and if something depends on them.
3412 The primitive that extracts text from the buffer along with its
3413 properties is @code{buffer-substring}. Before examining the properties,
3414 this function runs the abnormal hook @code{buffer-access-fontify-functions}.
3416 @defvar buffer-access-fontify-functions
3417 This variable holds a list of functions for computing text properties.
3418 Before @code{buffer-substring} copies the text and text properties for a
3419 portion of the buffer, it calls all the functions in this list. Each of
3420 the functions receives two arguments that specify the range of the
3421 buffer being accessed. (The buffer itself is always the current
3425 The function @code{buffer-substring-no-properties} does not call these
3426 functions, since it ignores text properties anyway.
3428 In order to prevent the hook functions from being called more than
3429 once for the same part of the buffer, you can use the variable
3430 @code{buffer-access-fontified-property}.
3432 @defvar buffer-access-fontified-property
3433 If this value's variable is non-@code{nil}, it is a symbol which is used
3434 as a text property name. A non-@code{nil} value for that text property
3435 means, ``the other text properties for this character have already been
3438 If all the characters in the range specified for @code{buffer-substring}
3439 have a non-@code{nil} value for this property, @code{buffer-substring}
3440 does not call the @code{buffer-access-fontify-functions} functions. It
3441 assumes these characters already have the right text properties, and
3442 just copies the properties they already have.
3444 The normal way to use this feature is that the
3445 @code{buffer-access-fontify-functions} functions add this property, as
3446 well as others, to the characters they operate on. That way, they avoid
3447 being called over and over for the same text.
3450 @node Clickable Text
3451 @subsection Defining Clickable Text
3452 @cindex clickable text
3454 There are two ways to set up @dfn{clickable text} in a buffer.
3455 There are typically two parts of this: to make the text highlight
3456 when the mouse is over it, and to make a mouse button do something
3457 when you click it on that part of the text.
3459 Highlighting is done with the @code{mouse-face} text property.
3460 Here is an example of how Dired does it:
3464 (if (dired-move-to-filename)
3465 (put-text-property (point)
3467 (dired-move-to-end-of-filename)
3469 'mouse-face 'highlight))
3474 The first two arguments to @code{put-text-property} specify the
3475 beginning and end of the text.
3477 The usual way to make the mouse do something when you click it
3478 on this text is to define @code{mouse-2} in the major mode's
3479 keymap. The job of checking whether the click was on clickable text
3480 is done by the command definition. Here is how Dired does it:
3483 (defun dired-mouse-find-file-other-window (event)
3484 "In dired, visit the file or directory name you click on."
3488 (set-buffer (window-buffer (posn-window (event-end event))))
3490 (goto-char (posn-point (event-end event)))
3491 (setq file (dired-get-filename))))
3492 (select-window (posn-window (event-end event)))
3493 (find-file-other-window (file-name-sans-versions file t))))
3497 The reason for the outer @code{save-excursion} construct is to avoid
3498 changing the current buffer; the reason for the inner one is to avoid
3499 permanently altering point in the buffer you click on. In this case,
3500 Dired uses the function @code{dired-get-filename} to determine which
3501 file to visit, based on the position found in the event.
3503 Instead of defining a mouse command for the major mode, you can define
3504 a key binding for the clickable text itself, using the @code{keymap}
3508 (let ((map (make-sparse-keymap)))
3509 (define-key map [mouse-2] 'operate-this-button)
3510 (put-text-property (point)
3512 (dired-move-to-end-of-filename)
3518 This method makes it possible to define different commands for various
3519 clickable pieces of text. Also, the major mode definition (or the
3520 global definition) remains available for the rest of the text in the
3523 @node Links and Mouse-1
3524 @subsection Links and Mouse-1
3525 @cindex follow links
3528 The normal Emacs command for activating text in read-only buffers is
3529 @key{Mouse-2}, which includes following textual links. However, most
3530 graphical applications use @key{Mouse-1} for following links. For
3531 compatibility, @key{Mouse-1} follows links in Emacs too, when you
3532 click on a link quickly without moving the mouse. The user can
3533 customize this behavior through the variable
3534 @code{mouse-1-click-follows-link}.
3536 To define text as a link at the Lisp level, you should bind the
3537 @code{mouse-2} event to a command to follow the link. Then, to indicate that
3538 @key{Mouse-1} should also follow the link, you should specify a
3539 @code{follow-link} condition either as a text property or as a key
3543 @item @code{follow-link} property
3544 If the clickable text has a non-@code{nil} @code{follow-link} text or overlay
3545 property, that specifies the condition.
3547 @item @code{follow-link} event
3548 If there is a binding for the @code{follow-link} event, either on the
3549 clickable text or in the local keymap, the binding is the condition.
3552 Regardless of how you set the @code{follow-link} condition, its
3553 value is used as follows to determine whether the given position is
3554 inside a link, and (if so) to compute an @dfn{action code} saying how
3555 @key{Mouse-1} should handle the link.
3558 @item @code{mouse-face}
3559 If the condition is @code{mouse-face}, a position is inside a link if
3560 there is a non-@code{nil} @code{mouse-face} property at that position.
3561 The action code is always @code{t}.
3563 For example, here is how Info mode handles @key{Mouse-1}:
3566 (define-key Info-mode-map [follow-link] 'mouse-face)
3570 If the condition is a valid function, @var{func}, then a position
3571 @var{pos} is inside a link if @code{(@var{func} @var{pos})} evaluates
3572 to non-@code{nil}. The value returned by @var{func} serves as the
3575 For example, here is how pcvs enables @key{Mouse-1} to follow links on
3579 (define-key map [follow-link]
3581 (eq (get-char-property pos 'face) 'cvs-filename-face)))
3585 If the condition value is anything else, then the position is inside a
3586 link and the condition itself is the action code. Clearly you should
3587 only specify this kind of condition on the text that constitutes a
3592 The action code tells @key{Mouse-1} how to follow the link:
3595 @item a string or vector
3596 If the action code is a string or vector, the @key{Mouse-1} event is
3597 translated into the first element of the string or vector; i.e., the
3598 action of the @key{Mouse-1} click is the local or global binding of
3599 that character or symbol. Thus, if the action code is @code{"foo"},
3600 @key{Mouse-1} translates into @kbd{f}. If it is @code{[foo]},
3601 @key{Mouse-1} translates into @key{foo}.
3604 For any other non-@code{nil} action code, the @code{mouse-1} event is
3605 translated into a @code{mouse-2} event at the same position.
3608 To define @key{Mouse-1} to activate a button defined with
3609 @code{define-button-type}, give the button a @code{follow-link}
3610 property with a value as specified above to determine how to follow
3611 the link. For example, here is how Help mode handles @key{Mouse-1}:
3614 (define-button-type 'help-xref
3616 'action #'help-button-action)
3619 To define @key{Mouse-1} on a widget defined with
3620 @code{define-widget}, give the widget a @code{:follow-link} property
3621 with a value as specified above to determine how to follow the link.
3623 For example, here is how the @code{link} widget specifies that
3624 a @key{Mouse-1} click shall be translated to @key{RET}:
3627 (define-widget 'link 'item
3629 :button-prefix 'widget-link-prefix
3630 :button-suffix 'widget-link-suffix
3632 :help-echo "Follow the link."
3636 @defun mouse-on-link-p pos
3637 @tindex mouse-on-link-p
3638 This function returns non-@code{nil} if position @var{pos} in the
3639 current buffer is on a link.
3643 @subsection Defining and Using Fields
3646 A field is a range of consecutive characters in the buffer that are
3647 identified by having the same value (comparing with @code{eq}) of the
3648 @code{field} property (either a text-property or an overlay property).
3649 This section describes special functions that are available for
3650 operating on fields.
3652 You specify a field with a buffer position, @var{pos}. We think of
3653 each field as containing a range of buffer positions, so the position
3654 you specify stands for the field containing that position.
3656 When the characters before and after @var{pos} are part of the same
3657 field, there is no doubt which field contains @var{pos}: the one those
3658 characters both belong to. When @var{pos} is at a boundary between
3659 fields, which field it belongs to depends on the stickiness of the
3660 @code{field} properties of the two surrounding characters (@pxref{Sticky
3661 Properties}). The field whose property would be inherited by text
3662 inserted at @var{pos} is the field that contains @var{pos}.
3664 There is an anomalous case where newly inserted text at @var{pos}
3665 would not inherit the @code{field} property from either side. This
3666 happens if the previous character's @code{field} property is not
3667 rear-sticky, and the following character's @code{field} property is not
3668 front-sticky. In this case, @var{pos} belongs to neither the preceding
3669 field nor the following field; the field functions treat it as belonging
3670 to an empty field whose beginning and end are both at @var{pos}.
3672 In all of these functions, if @var{pos} is omitted or @code{nil}, the
3673 value of point is used by default.
3675 @defun field-beginning &optional pos escape-from-edge limit
3676 @tindex field-beginning
3677 This function returns the beginning of the field specified by @var{pos}.
3679 If @var{pos} is at the beginning of its field, and
3680 @var{escape-from-edge} is non-@code{nil}, then the return value is
3681 always the beginning of the preceding field that @emph{ends} at @var{pos},
3682 regardless of the stickiness of the @code{field} properties around
3685 If @var{limit} is non-@code{nil}, it is a buffer position; if the
3686 beginning of the field is before @var{limit}, then @var{limit} will be
3690 @defun field-end &optional pos escape-from-edge limit
3692 This function returns the end of the field specified by @var{pos}.
3694 If @var{pos} is at the end of its field, and @var{escape-from-edge} is
3695 non-@code{nil}, then the return value is always the end of the following
3696 field that @emph{begins} at @var{pos}, regardless of the stickiness of
3697 the @code{field} properties around @var{pos}.
3699 If @var{limit} is non-@code{nil}, it is a buffer position; if the end
3700 of the field is after @var{limit}, then @var{limit} will be returned
3704 @defun field-string &optional pos
3705 @tindex field-string
3706 This function returns the contents of the field specified by @var{pos},
3710 @defun field-string-no-properties &optional pos
3711 @tindex field-string-no-properties
3712 This function returns the contents of the field specified by @var{pos},
3713 as a string, discarding text properties.
3716 @defun delete-field &optional pos
3717 @tindex delete-field
3718 This function deletes the text of the field specified by @var{pos}.
3721 @defun constrain-to-field new-pos old-pos &optional escape-from-edge only-in-line inhibit-capture-property
3722 @tindex constrain-to-field
3723 This function ``constrains'' @var{new-pos} to the field that
3724 @var{old-pos} belongs to---in other words, it returns the position
3725 closest to @var{new-pos} that is in the same field as @var{old-pos}.
3727 If @var{new-pos} is @code{nil}, then @code{constrain-to-field} uses
3728 the value of point instead, and moves point to the resulting position.
3730 If @var{old-pos} is at the boundary of two fields, then the acceptable
3731 positions for @var{new-pos} depend on the value of the optional argument
3732 @var{escape-from-edge}. If @var{escape-from-edge} is @code{nil}, then
3733 @var{new-pos} is constrained to the field that has the same @code{field}
3734 property (either a text-property or an overlay property) that new
3735 characters inserted at @var{old-pos} would get. (This depends on the
3736 stickiness of the @code{field} property for the characters before and
3737 after @var{old-pos}.) If @var{escape-from-edge} is non-@code{nil},
3738 @var{new-pos} is constrained to the union of the two adjacent fields.
3739 Additionally, if two fields are separated by another field with the
3740 special value @code{boundary}, then any point within this special field
3741 is also considered to be ``on the boundary.''
3743 If the optional argument @var{only-in-line} is non-@code{nil}, and
3744 constraining @var{new-pos} in the usual way would move it to a different
3745 line, @var{new-pos} is returned unconstrained. This used in commands
3746 that move by line, such as @code{next-line} and
3747 @code{beginning-of-line}, so that they respect field boundaries only in
3748 the case where they can still move to the right line.
3750 If the optional argument @var{inhibit-capture-property} is
3751 non-@code{nil}, and @var{old-pos} has a non-@code{nil} property of that
3752 name, then any field boundaries are ignored.
3754 You can cause @code{constrain-to-field} to ignore all field boundaries
3755 (and so never constrain anything) by binding the variable
3756 @code{inhibit-field-text-motion} to a non-@code{nil} value.
3760 @subsection Why Text Properties are not Intervals
3763 Some editors that support adding attributes to text in the buffer do
3764 so by letting the user specify ``intervals'' within the text, and adding
3765 the properties to the intervals. Those editors permit the user or the
3766 programmer to determine where individual intervals start and end. We
3767 deliberately provided a different sort of interface in Emacs Lisp to
3768 avoid certain paradoxical behavior associated with text modification.
3770 If the actual subdivision into intervals is meaningful, that means you
3771 can distinguish between a buffer that is just one interval with a
3772 certain property, and a buffer containing the same text subdivided into
3773 two intervals, both of which have that property.
3775 Suppose you take the buffer with just one interval and kill part of
3776 the text. The text remaining in the buffer is one interval, and the
3777 copy in the kill ring (and the undo list) becomes a separate interval.
3778 Then if you yank back the killed text, you get two intervals with the
3779 same properties. Thus, editing does not preserve the distinction
3780 between one interval and two.
3782 Suppose we ``fix'' this problem by coalescing the two intervals when
3783 the text is inserted. That works fine if the buffer originally was a
3784 single interval. But suppose instead that we have two adjacent
3785 intervals with the same properties, and we kill the text of one interval
3786 and yank it back. The same interval-coalescence feature that rescues
3787 the other case causes trouble in this one: after yanking, we have just
3788 one interval. One again, editing does not preserve the distinction
3789 between one interval and two.
3791 Insertion of text at the border between intervals also raises
3792 questions that have no satisfactory answer.
3794 However, it is easy to arrange for editing to behave consistently for
3795 questions of the form, ``What are the properties of this character?''
3796 So we have decided these are the only questions that make sense; we have
3797 not implemented asking questions about where intervals start or end.
3799 In practice, you can usually use the text property search functions in
3800 place of explicit interval boundaries. You can think of them as finding
3801 the boundaries of intervals, assuming that intervals are always
3802 coalesced whenever possible. @xref{Property Search}.
3804 Emacs also provides explicit intervals as a presentation feature; see
3808 @section Substituting for a Character Code
3810 The following functions replace characters within a specified region
3811 based on their character codes.
3813 @defun subst-char-in-region start end old-char new-char &optional noundo
3814 @cindex replace characters
3815 This function replaces all occurrences of the character @var{old-char}
3816 with the character @var{new-char} in the region of the current buffer
3817 defined by @var{start} and @var{end}.
3819 @cindex undo avoidance
3820 If @var{noundo} is non-@code{nil}, then @code{subst-char-in-region} does
3821 not record the change for undo and does not mark the buffer as modified.
3822 This was useful for controlling the old selective display feature
3823 (@pxref{Selective Display}).
3825 @code{subst-char-in-region} does not move point and returns
3830 ---------- Buffer: foo ----------
3831 This is the contents of the buffer before.
3832 ---------- Buffer: foo ----------
3836 (subst-char-in-region 1 20 ?i ?X)
3839 ---------- Buffer: foo ----------
3840 ThXs Xs the contents of the buffer before.
3841 ---------- Buffer: foo ----------
3846 @defun translate-region start end table
3847 This function applies a translation table to the characters in the
3848 buffer between positions @var{start} and @var{end}.
3850 The translation table @var{table} is a string or a char-table;
3851 @code{(aref @var{table} @var{ochar})} gives the translated character
3852 corresponding to @var{ochar}. If @var{table} is a string, any
3853 characters with codes larger than the length of @var{table} are not
3854 altered by the translation.
3856 The return value of @code{translate-region} is the number of
3857 characters that were actually changed by the translation. This does
3858 not count characters that were mapped into themselves in the
3866 A register is a sort of variable used in Emacs editing that can hold a
3867 variety of different kinds of values. Each register is named by a
3868 single character. All @acronym{ASCII} characters and their meta variants
3869 (but with the exception of @kbd{C-g}) can be used to name registers.
3870 Thus, there are 255 possible registers. A register is designated in
3871 Emacs Lisp by the character that is its name.
3873 @defvar register-alist
3874 This variable is an alist of elements of the form @code{(@var{name} .
3875 @var{contents})}. Normally, there is one element for each Emacs
3876 register that has been used.
3878 The object @var{name} is a character (an integer) identifying the
3882 The @var{contents} of a register can have several possible types:
3886 A number stands for itself. If @code{insert-register} finds a number
3887 in the register, it converts the number to decimal.
3890 A marker represents a buffer position to jump to.
3893 A string is text saved in the register.
3896 A rectangle is represented by a list of strings.
3898 @item @code{(@var{window-configuration} @var{position})}
3899 This represents a window configuration to restore in one frame, and a
3900 position to jump to in the current buffer.
3902 @item @code{(@var{frame-configuration} @var{position})}
3903 This represents a frame configuration to restore, and a position
3904 to jump to in the current buffer.
3906 @item (file @var{filename})
3907 This represents a file to visit; jumping to this value visits file
3910 @item (file-query @var{filename} @var{position})
3911 This represents a file to visit and a position in it; jumping to this
3912 value visits file @var{filename} and goes to buffer position
3913 @var{position}. Restoring this type of position asks the user for
3917 The functions in this section return unpredictable values unless
3920 @defun get-register reg
3921 This function returns the contents of the register
3922 @var{reg}, or @code{nil} if it has no contents.
3925 @defun set-register reg value
3926 This function sets the contents of register @var{reg} to @var{value}.
3927 A register can be set to any value, but the other register functions
3928 expect only certain data types. The return value is @var{value}.
3931 @deffn Command view-register reg
3932 This command displays what is contained in register @var{reg}.
3936 @deffn Command point-to-register reg
3937 This command stores both the current location of point and the current
3938 buffer in register @var{reg} as a marker.
3941 @deffn Command jump-to-register reg
3942 @deffnx Command register-to-point reg
3943 @comment !!SourceFile register.el
3944 This command restores the status recorded in register @var{reg}.
3946 If @var{reg} contains a marker, it moves point to the position stored in
3947 the marker. Since both the buffer and the location within the buffer
3948 are stored by the @code{point-to-register} function, this command can
3949 switch you to another buffer.
3951 If @var{reg} contains a window configuration or a frame configuration.
3952 @code{jump-to-register} restores that configuration.
3956 @deffn Command insert-register reg &optional beforep
3957 This command inserts contents of register @var{reg} into the current
3960 Normally, this command puts point before the inserted text, and the
3961 mark after it. However, if the optional second argument @var{beforep}
3962 is non-@code{nil}, it puts the mark before and point after.
3963 You can pass a non-@code{nil} second argument @var{beforep} to this
3964 function interactively by supplying any prefix argument.
3966 If the register contains a rectangle, then the rectangle is inserted
3967 with its upper left corner at point. This means that text is inserted
3968 in the current line and underneath it on successive lines.
3970 If the register contains something other than saved text (a string) or
3971 a rectangle (a list), currently useless things happen. This may be
3972 changed in the future.
3976 @deffn Command copy-to-register reg start end &optional delete-flag
3977 This command copies the region from @var{start} to @var{end} into
3978 register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes
3979 the region from the buffer after copying it into the register.
3982 @deffn Command prepend-to-register reg start end &optional delete-flag
3983 This command prepends the region from @var{start} to @var{end} into
3984 register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes
3985 the region from the buffer after copying it to the register.
3988 @deffn Command append-to-register reg start end &optional delete-flag
3989 This command appends the region from @var{start} to @var{end} to the
3990 text already in register @var{reg}. If @var{delete-flag} is
3991 non-@code{nil}, it deletes the region from the buffer after copying it
3995 @deffn Command copy-rectangle-to-register reg start end &optional delete-flag
3996 This command copies a rectangular region from @var{start} to @var{end}
3997 into register @var{reg}. If @var{delete-flag} is non-@code{nil}, it
3998 deletes the region from the buffer after copying it to the register.
4001 @deffn Command window-configuration-to-register reg
4002 This function stores the window configuration of the selected frame in
4006 @deffn Command frame-configuration-to-register reg
4007 This function stores the current frame configuration in register
4013 @section Transposition of Text
4015 This subroutine is used by the transposition commands.
4017 @defun transpose-regions start1 end1 start2 end2 &optional leave-markers
4018 This function exchanges two nonoverlapping portions of the buffer.
4019 Arguments @var{start1} and @var{end1} specify the bounds of one portion
4020 and arguments @var{start2} and @var{end2} specify the bounds of the
4023 Normally, @code{transpose-regions} relocates markers with the transposed
4024 text; a marker previously positioned within one of the two transposed
4025 portions moves along with that portion, thus remaining between the same
4026 two characters in their new position. However, if @var{leave-markers}
4027 is non-@code{nil}, @code{transpose-regions} does not do this---it leaves
4028 all markers unrelocated.
4032 @section Base 64 Encoding
4033 @cindex base 64 encoding
4035 Base 64 code is used in email to encode a sequence of 8-bit bytes as
4036 a longer sequence of @acronym{ASCII} graphic characters. It is defined in
4037 Internet RFC@footnote{
4038 An RFC, an acronym for @dfn{Request for Comments}, is a numbered
4039 Internet informational document describing a standard. RFCs are
4040 usually written by technical experts acting on their own initiative,
4041 and are traditionally written in a pragmatic, experience-driven
4043 }2045. This section describes the functions for
4044 converting to and from this code.
4046 @defun base64-encode-region beg end &optional no-line-break
4047 @tindex base64-encode-region
4048 This function converts the region from @var{beg} to @var{end} into base
4049 64 code. It returns the length of the encoded text. An error is
4050 signaled if a character in the region is multibyte, i.e.@: in a
4051 multibyte buffer the region must contain only characters from the
4052 charsets @code{ascii}, @code{eight-bit-control} and
4053 @code{eight-bit-graphic}.
4055 Normally, this function inserts newline characters into the encoded
4056 text, to avoid overlong lines. However, if the optional argument
4057 @var{no-line-break} is non-@code{nil}, these newlines are not added, so
4058 the output is just one long line.
4061 @defun base64-encode-string string &optional no-line-break
4062 @tindex base64-encode-string
4063 This function converts the string @var{string} into base 64 code. It
4064 returns a string containing the encoded text. As for
4065 @code{base64-encode-region}, an error is signaled if a character in the
4066 string is multibyte.
4068 Normally, this function inserts newline characters into the encoded
4069 text, to avoid overlong lines. However, if the optional argument
4070 @var{no-line-break} is non-@code{nil}, these newlines are not added, so
4071 the result string is just one long line.
4074 @defun base64-decode-region beg end
4075 @tindex base64-decode-region
4076 This function converts the region from @var{beg} to @var{end} from base
4077 64 code into the corresponding decoded text. It returns the length of
4080 The decoding functions ignore newline characters in the encoded text.
4083 @defun base64-decode-string string
4084 @tindex base64-decode-string
4085 This function converts the string @var{string} from base 64 code into
4086 the corresponding decoded text. It returns a unibyte string containing the
4089 The decoding functions ignore newline characters in the encoded text.
4093 @section MD5 Checksum
4094 @cindex MD5 checksum
4095 @cindex message digest computation
4097 MD5 cryptographic checksums, or @dfn{message digests}, are 128-bit
4098 ``fingerprints'' of a document or program. They are used to verify
4099 that you have an exact and unaltered copy of the data. The algorithm
4100 to calculate the MD5 message digest is defined in Internet
4102 For an explanation of what is an RFC, see the footnote in @ref{Base
4104 }1321. This section describes the Emacs facilities for computing
4107 @defun md5 object &optional start end coding-system noerror
4108 This function returns the MD5 message digest of @var{object}, which
4109 should be a buffer or a string.
4111 The two optional arguments @var{start} and @var{end} are character
4112 positions specifying the portion of @var{object} to compute the
4113 message digest for. If they are @code{nil} or omitted, the digest is
4114 computed for the whole of @var{object}.
4116 The function @code{md5} does not compute the message digest directly
4117 from the internal Emacs representation of the text (@pxref{Text
4118 Representations}). Instead, it encodes the text using a coding
4119 system, and computes the message digest from the encoded text. The
4120 optional fourth argument @var{coding-system} specifies which coding
4121 system to use for encoding the text. It should be the same coding
4122 system that you used to read the text, or that you used or will use
4123 when saving or sending the text. @xref{Coding Systems}, for more
4124 information about coding systems.
4126 If @var{coding-system} is @code{nil} or omitted, the default depends
4127 on @var{object}. If @var{object} is a buffer, the default for
4128 @var{coding-system} is whatever coding system would be chosen by
4129 default for writing this text into a file. If @var{object} is a
4130 string, the user's most preferred coding system (@pxref{Recognize
4131 Coding, prefer-coding-system, the description of
4132 @code{prefer-coding-system}, emacs, GNU Emacs Manual}) is used.
4134 Normally, @code{md5} signals an error if the text can't be encoded
4135 using the specified or chosen coding system. However, if
4136 @var{noerror} is non-@code{nil}, it silently uses @code{raw-text}
4140 @node Atomic Changes
4141 @section Atomic Change Groups
4142 @cindex atomic changes
4144 In data base terminology, an @dfn{atomic} change is an indivisible
4145 change---it can succeed entirely or it can fail entirely, but it
4146 cannot partly succeed. A Lisp program can make a series of changes to
4147 one or several buffers as an @dfn{atomic change group}, meaning that
4148 either the entire series of changes will be installed in their buffers
4149 or, in case of an error, none of them will be.
4151 To do this for one buffer, the one already current, simply write a
4152 call to @code{atomic-change-group} around the code that makes the
4156 (atomic-change-group
4158 (delete-region x y))
4162 If an error (or other nonlocal exit) occurs inside the body of
4163 @code{atomic-change-group}, it unmakes all the changes in that buffer
4164 that were during the execution of the body. This kind of change group
4165 has no effect on any other buffers---any such changes remain.
4167 If you need something more sophisticated, such as to make changes in
4168 various buffers constitute one atomic group, you must directly call
4169 lower-level functions that @code{atomic-change-group} uses.
4171 @defun prepare-change-group &optional buffer
4172 This function sets up a change group for buffer @var{buffer}, which
4173 defaults to the current buffer. It returns a ``handle'' that
4174 represents the change group. You must use this handle to activate the
4175 change group and subsequently to finish it.
4178 To use the change group, you must @dfn{activate} it. You must do
4179 this before making any changes in the text of @var{buffer}.
4181 @defun activate-change-group handle
4182 This function activates the change group that @var{handle} designates.
4185 After you activate the change group, any changes you make in that
4186 buffer become part of it. Once you have made all the desired changes
4187 in the buffer, you must @dfn{finish} the change group. There are two
4188 ways to do this: you can either accept (and finalize) all the changes,
4191 @defun accept-change-group handle
4192 This function accepts all the changes in the change group specified by
4193 @var{handle}, making them final.
4196 @defun cancel-change-group handle
4197 This function cancels and undoes all the changes in the change group
4198 specified by @var{handle}.
4201 Your code should use @code{unwind-protect} to make sure the group is
4202 always finished. The call to @code{activate-change-group} should be
4203 inside the @code{unwind-protect}, in case the user types @kbd{C-g}
4204 just after it runs. (This is one reason why
4205 @code{prepare-change-group} and @code{activate-change-group} are
4206 separate functions, because normally you would call
4207 @code{prepare-change-group} before the start of that
4208 @code{unwind-protect}.) Once you finish the group, don't use the
4209 handle again---in particular, don't try to finish the same group
4212 To make a multibuffer change group, call @code{prepare-change-group}
4213 once for each buffer you want to cover, then use @code{nconc} to
4214 combine the returned values, like this:
4217 (nconc (prepare-change-group buffer-1)
4218 (prepare-change-group buffer-2))
4221 You can then activate the multibuffer change group with a single call
4222 to @code{activate-change-group}, and finish it with a single call to
4223 @code{accept-change-group} or @code{cancel-change-group}.
4225 Nested use of several change groups for the same buffer works as you
4226 would expect. Non-nested use of change groups for the same buffer
4227 will get Emacs confused, so don't let it happen; the first change
4228 group you start for any given buffer should be the last one finished.
4231 @section Change Hooks
4232 @cindex change hooks
4233 @cindex hooks for text changes
4235 These hook variables let you arrange to take notice of all changes in
4236 all buffers (or in a particular buffer, if you make them buffer-local).
4237 See also @ref{Special Properties}, for how to detect changes to specific
4240 The functions you use in these hooks should save and restore the match
4241 data if they do anything that uses regular expressions; otherwise, they
4242 will interfere in bizarre ways with the editing operations that call
4245 @defvar before-change-functions
4246 This variable holds a list of functions to call before any buffer
4247 modification. Each function gets two arguments, the beginning and end
4248 of the region that is about to change, represented as integers. The
4249 buffer that is about to change is always the current buffer.
4252 @defvar after-change-functions
4253 This variable holds a list of functions to call after any buffer
4254 modification. Each function receives three arguments: the beginning and
4255 end of the region just changed, and the length of the text that existed
4256 before the change. All three arguments are integers. The buffer that's
4257 about to change is always the current buffer.
4259 The length of the old text is the difference between the buffer positions
4260 before and after that text as it was before the change. As for the
4261 changed text, its length is simply the difference between the first two
4265 Output of messages into the @samp{*Messages*} buffer does not
4266 call these functions.
4268 @defmac combine-after-change-calls body...
4269 The macro executes @var{body} normally, but arranges to call the
4270 after-change functions just once for a series of several changes---if
4273 If a program makes several text changes in the same area of the buffer,
4274 using the macro @code{combine-after-change-calls} around that part of
4275 the program can make it run considerably faster when after-change hooks
4276 are in use. When the after-change hooks are ultimately called, the
4277 arguments specify a portion of the buffer including all of the changes
4278 made within the @code{combine-after-change-calls} body.
4280 @strong{Warning:} You must not alter the values of
4281 @code{after-change-functions} within
4282 the body of a @code{combine-after-change-calls} form.
4284 @strong{Warning:} if the changes you combine occur in widely scattered
4285 parts of the buffer, this will still work, but it is not advisable,
4286 because it may lead to inefficient behavior for some change hook
4290 The two variables above are temporarily bound to @code{nil} during the
4291 time that any of these functions is running. This means that if one of
4292 these functions changes the buffer, that change won't run these
4293 functions. If you do want a hook function to make changes that run
4294 these functions, make it bind these variables back to their usual
4297 One inconvenient result of this protective feature is that you cannot
4298 have a function in @code{after-change-functions} or
4299 @code{before-change-functions} which changes the value of that variable.
4300 But that's not a real limitation. If you want those functions to change
4301 the list of functions to run, simply add one fixed function to the hook,
4302 and code that function to look in another variable for other functions
4303 to call. Here is an example:
4306 (setq my-own-after-change-functions nil)
4307 (defun indirect-after-change-function (beg end len)
4308 (let ((list my-own-after-change-functions))
4310 (funcall (car list) beg end len)
4311 (setq list (cdr list)))))
4314 (add-hooks 'after-change-functions
4315 'indirect-after-change-function)
4319 @defvar first-change-hook
4320 This variable is a normal hook that is run whenever a buffer is changed
4321 that was previously in the unmodified state.
4324 @defvar inhibit-modification-hooks
4325 @tindex inhibit-modification-hooks
4326 If this variable is non-@code{nil}, all of the change hooks are
4327 disabled; none of them run. This affects all the hook variables
4328 described above in this section, as well as the hooks attached to
4329 certain special text properties (@pxref{Special Properties}) and overlay
4330 properties (@pxref{Overlay Properties}).
4334 arch-tag: 3721e738-a1cb-4085-bc1a-6cb8d8e1d32b