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, 2006 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 Here's an example which assumes Font-Lock mode is not enabled:
183 ---------- Buffer: foo ----------
184 This is the contents of buffer foo
186 ---------- Buffer: foo ----------
190 (buffer-substring 1 10)
191 @result{} "This is t"
194 (buffer-substring (point-max) 10)
195 @result{} "he contents of buffer foo\n"
199 If the text being copied has any text properties, these are copied into
200 the string along with the characters they belong to. @xref{Text
201 Properties}. However, overlays (@pxref{Overlays}) in the buffer and
202 their properties are ignored, not copied.
204 For example, if Font-Lock mode is enabled, you might get results like
209 (buffer-substring 1 10)
210 @result{} #("This is t" 0 1 (fontified t) 1 9 (fontified t))
215 @defun buffer-substring-no-properties start end
216 This is like @code{buffer-substring}, except that it does not copy text
217 properties, just the characters themselves. @xref{Text Properties}.
220 @defun filter-buffer-substring start end &optional delete noprops
221 This function passes the buffer text between @var{start} and @var{end}
222 through the filter functions specified by the variable
223 @code{buffer-substring-filters}, and returns the value from the last
224 filter function. If @code{buffer-substring-filters} is @code{nil},
225 the value is the unaltered text from the buffer, what
226 @code{buffer-substring} would return.
228 If @var{delete} is non-@code{nil}, this function deletes the text
229 between @var{start} and @var{end} after copying it, like
230 @code{delete-and-extract-region}.
232 If @var{noprops} is non-@code{nil}, the final string returned does not
233 include text properties, while the string passed through the filters
234 still includes text properties from the buffer text.
236 Lisp code should use this function instead of @code{buffer-substring},
237 @code{buffer-substring-no-properties},
238 or @code{delete-and-extract-region} when copying into user-accessible
239 data structures such as the kill-ring, X clipboard, and registers.
240 Major and minor modes can add functions to
241 @code{buffer-substring-filters} to alter such text as it is copied out
245 @defvar buffer-substring-filters
246 This variable should be a list of functions that accept a single
247 argument, a string, and return a string.
248 @code{filter-buffer-substring} passes the buffer substring to the
249 first function in this list, and the return value of each function is
250 passed to the next function. The return value of the last function is
251 used as the return value of @code{filter-buffer-substring}.
253 As a special convention, point is set to the start of the buffer text
254 being operated on (i.e., the @var{start} argument for
255 @code{filter-buffer-substring}) before these functions are called.
257 If this variable is @code{nil}, no filtering is performed.
261 This function returns the contents of the entire accessible portion of
262 the current buffer as a string. It is equivalent to
265 (buffer-substring (point-min) (point-max))
270 ---------- Buffer: foo ----------
271 This is the contents of buffer foo
273 ---------- Buffer: foo ----------
276 @result{} "This is the contents of buffer foo\n"
281 @defun current-word &optional strict really-word
282 This function returns the symbol (or word) at or near point, as a string.
283 The return value includes no text properties.
285 If the optional argument @var{really-word} is non-@code{nil}, it finds a
286 word; otherwise, it finds a symbol (which includes both word
287 characters and symbol constituent characters).
289 If the optional argument @var{strict} is non-@code{nil}, then point
290 must be in or next to the symbol or word---if no symbol or word is
291 there, the function returns @code{nil}. Otherwise, a nearby symbol or
292 word on the same line is acceptable.
295 @defun thing-at-point thing
296 Return the @var{thing} around or next to point, as a string.
298 The argument @var{thing} is a symbol which specifies a kind of syntactic
299 entity. Possibilities include @code{symbol}, @code{list}, @code{sexp},
300 @code{defun}, @code{filename}, @code{url}, @code{word}, @code{sentence},
301 @code{whitespace}, @code{line}, @code{page}, and others.
304 ---------- Buffer: foo ----------
305 Gentlemen may cry ``Pea@point{}ce! Peace!,''
306 but there is no peace.
307 ---------- Buffer: foo ----------
309 (thing-at-point 'word)
311 (thing-at-point 'line)
312 @result{} "Gentlemen may cry ``Peace! Peace!,''\n"
313 (thing-at-point 'whitespace)
319 @section Comparing Text
320 @cindex comparing buffer text
322 This function lets you compare portions of the text in a buffer, without
323 copying them into strings first.
325 @defun compare-buffer-substrings buffer1 start1 end1 buffer2 start2 end2
326 This function lets you compare two substrings of the same buffer or two
327 different buffers. The first three arguments specify one substring,
328 giving a buffer (or a buffer name) and two positions within the
329 buffer. The last three arguments specify the other substring in the
330 same way. You can use @code{nil} for @var{buffer1}, @var{buffer2}, or
331 both to stand for the current buffer.
333 The value is negative if the first substring is less, positive if the
334 first is greater, and zero if they are equal. The absolute value of
335 the result is one plus the index of the first differing characters
336 within the substrings.
338 This function ignores case when comparing characters
339 if @code{case-fold-search} is non-@code{nil}. It always ignores
342 Suppose the current buffer contains the text @samp{foobarbar
343 haha!rara!}; then in this example the two substrings are @samp{rbar }
344 and @samp{rara!}. The value is 2 because the first substring is greater
345 at the second character.
348 (compare-buffer-substrings nil 6 11 nil 16 21)
354 @section Inserting Text
355 @cindex insertion of text
356 @cindex text insertion
358 @cindex insertion before point
359 @cindex before point, insertion
360 @dfn{Insertion} means adding new text to a buffer. The inserted text
361 goes at point---between the character before point and the character
362 after point. Some insertion functions leave point before the inserted
363 text, while other functions leave it after. We call the former
364 insertion @dfn{after point} and the latter insertion @dfn{before point}.
366 Insertion relocates markers that point at positions after the
367 insertion point, so that they stay with the surrounding text
368 (@pxref{Markers}). When a marker points at the place of insertion,
369 insertion may or may not relocate the marker, depending on the marker's
370 insertion type (@pxref{Marker Insertion Types}). Certain special
371 functions such as @code{insert-before-markers} relocate all such markers
372 to point after the inserted text, regardless of the markers' insertion
375 Insertion functions signal an error if the current buffer is
376 read-only or if they insert within read-only text.
378 These functions copy text characters from strings and buffers along
379 with their properties. The inserted characters have exactly the same
380 properties as the characters they were copied from. By contrast,
381 characters specified as separate arguments, not part of a string or
382 buffer, inherit their text properties from the neighboring text.
384 The insertion functions convert text from unibyte to multibyte in
385 order to insert in a multibyte buffer, and vice versa---if the text
386 comes from a string or from a buffer. However, they do not convert
387 unibyte character codes 128 through 255 to multibyte characters, not
388 even if the current buffer is a multibyte buffer. @xref{Converting
391 @defun insert &rest args
392 This function inserts the strings and/or characters @var{args} into the
393 current buffer, at point, moving point forward. In other words, it
394 inserts the text before point. An error is signaled unless all
395 @var{args} are either strings or characters. The value is @code{nil}.
398 @defun insert-before-markers &rest args
399 This function inserts the strings and/or characters @var{args} into the
400 current buffer, at point, moving point forward. An error is signaled
401 unless all @var{args} are either strings or characters. The value is
404 This function is unlike the other insertion functions in that it
405 relocates markers initially pointing at the insertion point, to point
406 after the inserted text. If an overlay begins at the insertion point,
407 the inserted text falls outside the overlay; if a nonempty overlay
408 ends at the insertion point, the inserted text falls inside that
412 @defun insert-char character count &optional inherit
413 This function inserts @var{count} instances of @var{character} into the
414 current buffer before point. The argument @var{count} should be an
415 integer, and @var{character} must be a character. The value is @code{nil}.
417 This function does not convert unibyte character codes 128 through 255
418 to multibyte characters, not even if the current buffer is a multibyte
419 buffer. @xref{Converting Representations}.
421 If @var{inherit} is non-@code{nil}, then the inserted characters inherit
422 sticky text properties from the two characters before and after the
423 insertion point. @xref{Sticky Properties}.
426 @defun insert-buffer-substring from-buffer-or-name &optional start end
427 This function inserts a portion of buffer @var{from-buffer-or-name}
428 (which must already exist) into the current buffer before point. The
429 text inserted is the region between @var{start} and @var{end}. (These
430 arguments default to the beginning and end of the accessible portion of
431 that buffer.) This function returns @code{nil}.
433 In this example, the form is executed with buffer @samp{bar} as the
434 current buffer. We assume that buffer @samp{bar} is initially empty.
438 ---------- Buffer: foo ----------
439 We hold these truths to be self-evident, that all
440 ---------- Buffer: foo ----------
444 (insert-buffer-substring "foo" 1 20)
447 ---------- Buffer: bar ----------
448 We hold these truth@point{}
449 ---------- Buffer: bar ----------
454 @defun insert-buffer-substring-no-properties from-buffer-or-name &optional start end
455 This is like @code{insert-buffer-substring} except that it does not
456 copy any text properties.
459 @xref{Sticky Properties}, for other insertion functions that inherit
460 text properties from the nearby text in addition to inserting it.
461 Whitespace inserted by indentation functions also inherits text
464 @node Commands for Insertion
465 @section User-Level Insertion Commands
467 This section describes higher-level commands for inserting text,
468 commands intended primarily for the user but useful also in Lisp
471 @deffn Command insert-buffer from-buffer-or-name
472 This command inserts the entire accessible contents of
473 @var{from-buffer-or-name} (which must exist) into the current buffer
474 after point. It leaves the mark after the inserted text. The value
478 @deffn Command self-insert-command count
479 @cindex character insertion
480 @cindex self-insertion
481 This command inserts the last character typed; it does so @var{count}
482 times, before point, and returns @code{nil}. Most printing characters
483 are bound to this command. In routine use, @code{self-insert-command}
484 is the most frequently called function in Emacs, but programs rarely use
485 it except to install it on a keymap.
487 In an interactive call, @var{count} is the numeric prefix argument.
489 Self-insertion translates the input character through
490 @code{translation-table-for-input}. @xref{Translation of Characters}.
492 This command calls @code{auto-fill-function} whenever that is
493 non-@code{nil} and the character inserted is in the table
494 @code{auto-fill-chars} (@pxref{Auto Filling}).
496 @c Cross refs reworded to prevent overfull hbox. --rjc 15mar92
497 This command performs abbrev expansion if Abbrev mode is enabled and
498 the inserted character does not have word-constituent
499 syntax. (@xref{Abbrevs}, and @ref{Syntax Class Table}.) It is also
500 responsible for calling @code{blink-paren-function} when the inserted
501 character has close parenthesis syntax (@pxref{Blinking}).
503 Do not try substituting your own definition of
504 @code{self-insert-command} for the standard one. The editor command
505 loop handles this function specially.
508 @deffn Command newline &optional number-of-newlines
509 This command inserts newlines into the current buffer before point.
510 If @var{number-of-newlines} is supplied, that many newline characters
513 @cindex newline and Auto Fill mode
514 This function calls @code{auto-fill-function} if the current column
515 number is greater than the value of @code{fill-column} and
516 @var{number-of-newlines} is @code{nil}. Typically what
517 @code{auto-fill-function} does is insert a newline; thus, the overall
518 result in this case is to insert two newlines at different places: one
519 at point, and another earlier in the line. @code{newline} does not
520 auto-fill if @var{number-of-newlines} is non-@code{nil}.
522 This command indents to the left margin if that is not zero.
525 The value returned is @code{nil}. In an interactive call, @var{count}
526 is the numeric prefix argument.
529 @deffn Command split-line
530 This command splits the current line, moving the portion of the line
531 after point down vertically so that it is on the next line directly
532 below where it was before. Whitespace is inserted as needed at the
533 beginning of the lower line, using the @code{indent-to} function.
534 @code{split-line} returns the position of point.
536 Programs hardly ever use this function.
539 @defvar overwrite-mode
540 This variable controls whether overwrite mode is in effect. The value
541 should be @code{overwrite-mode-textual}, @code{overwrite-mode-binary},
542 or @code{nil}. @code{overwrite-mode-textual} specifies textual
543 overwrite mode (treats newlines and tabs specially), and
544 @code{overwrite-mode-binary} specifies binary overwrite mode (treats
545 newlines and tabs like any other characters).
549 @section Deleting Text
551 @cindex deletion vs killing
552 Deletion means removing part of the text in a buffer, without saving
553 it in the kill ring (@pxref{The Kill Ring}). Deleted text can't be
554 yanked, but can be reinserted using the undo mechanism (@pxref{Undo}).
555 Some deletion functions do save text in the kill ring in some special
558 All of the deletion functions operate on the current buffer.
560 @deffn Command erase-buffer
561 This function deletes the entire text of the current buffer
562 (@emph{not} just the accessible portion), leaving it
563 empty. If the buffer is read-only, it signals a @code{buffer-read-only}
564 error; if some of the text in it is read-only, it signals a
565 @code{text-read-only} error. Otherwise, it deletes the text without
566 asking for any confirmation. It returns @code{nil}.
568 Normally, deleting a large amount of text from a buffer inhibits further
569 auto-saving of that buffer ``because it has shrunk''. However,
570 @code{erase-buffer} does not do this, the idea being that the future
571 text is not really related to the former text, and its size should not
572 be compared with that of the former text.
575 @deffn Command delete-region start end
576 This command deletes the text between positions @var{start} and
577 @var{end} in the current buffer, and returns @code{nil}. If point was
578 inside the deleted region, its value afterward is @var{start}.
579 Otherwise, point relocates with the surrounding text, as markers do.
582 @defun delete-and-extract-region start end
583 This function deletes the text between positions @var{start} and
584 @var{end} in the current buffer, and returns a string containing the
587 If point was inside the deleted region, its value afterward is
588 @var{start}. Otherwise, point relocates with the surrounding text, as
592 @deffn Command delete-char count &optional killp
593 This command deletes @var{count} characters directly after point, or
594 before point if @var{count} is negative. If @var{killp} is
595 non-@code{nil}, then it saves the deleted characters in the kill ring.
597 In an interactive call, @var{count} is the numeric prefix argument, and
598 @var{killp} is the unprocessed prefix argument. Therefore, if a prefix
599 argument is supplied, the text is saved in the kill ring. If no prefix
600 argument is supplied, then one character is deleted, but not saved in
603 The value returned is always @code{nil}.
606 @deffn Command delete-backward-char count &optional killp
607 @cindex delete previous char
608 This command deletes @var{count} characters directly before point, or
609 after point if @var{count} is negative. If @var{killp} is
610 non-@code{nil}, then it saves the deleted characters in the kill ring.
612 In an interactive call, @var{count} is the numeric prefix argument, and
613 @var{killp} is the unprocessed prefix argument. Therefore, if a prefix
614 argument is supplied, the text is saved in the kill ring. If no prefix
615 argument is supplied, then one character is deleted, but not saved in
618 The value returned is always @code{nil}.
621 @deffn Command backward-delete-char-untabify count &optional killp
623 This command deletes @var{count} characters backward, changing tabs
624 into spaces. When the next character to be deleted is a tab, it is
625 first replaced with the proper number of spaces to preserve alignment
626 and then one of those spaces is deleted instead of the tab. If
627 @var{killp} is non-@code{nil}, then the command saves the deleted
628 characters in the kill ring.
630 Conversion of tabs to spaces happens only if @var{count} is positive.
631 If it is negative, exactly @minus{}@var{count} characters after point
634 In an interactive call, @var{count} is the numeric prefix argument, and
635 @var{killp} is the unprocessed prefix argument. Therefore, if a prefix
636 argument is supplied, the text is saved in the kill ring. If no prefix
637 argument is supplied, then one character is deleted, but not saved in
640 The value returned is always @code{nil}.
643 @defopt backward-delete-char-untabify-method
644 This option specifies how @code{backward-delete-char-untabify} should
645 deal with whitespace. Possible values include @code{untabify}, the
646 default, meaning convert a tab to many spaces and delete one;
647 @code{hungry}, meaning delete all tabs and spaces before point with
648 one command; @code{all} meaning delete all tabs, spaces and newlines
649 before point, and @code{nil}, meaning do nothing special for
650 whitespace characters.
653 @node User-Level Deletion
654 @section User-Level Deletion Commands
656 This section describes higher-level commands for deleting text,
657 commands intended primarily for the user but useful also in Lisp
660 @deffn Command delete-horizontal-space &optional backward-only
661 @cindex deleting whitespace
662 This function deletes all spaces and tabs around point. It returns
665 If @var{backward-only} is non-@code{nil}, the function deletes
666 spaces and tabs before point, but not after point.
668 In the following examples, we call @code{delete-horizontal-space} four
669 times, once on each line, with point between the second and third
670 characters on the line each time.
674 ---------- Buffer: foo ----------
679 ---------- Buffer: foo ----------
683 (delete-horizontal-space) ; @r{Four times.}
686 ---------- Buffer: foo ----------
691 ---------- Buffer: foo ----------
696 @deffn Command delete-indentation &optional join-following-p
697 This function joins the line point is on to the previous line, deleting
698 any whitespace at the join and in some cases replacing it with one
699 space. If @var{join-following-p} is non-@code{nil},
700 @code{delete-indentation} joins this line to the following line
701 instead. The function returns @code{nil}.
703 If there is a fill prefix, and the second of the lines being joined
704 starts with the prefix, then @code{delete-indentation} deletes the
705 fill prefix before joining the lines. @xref{Margins}.
707 In the example below, point is located on the line starting
708 @samp{events}, and it makes no difference if there are trailing spaces
709 in the preceding line.
713 ---------- Buffer: foo ----------
714 When in the course of human
715 @point{} events, it becomes necessary
716 ---------- Buffer: foo ----------
723 ---------- Buffer: foo ----------
724 When in the course of human@point{} events, it becomes necessary
725 ---------- Buffer: foo ----------
729 After the lines are joined, the function @code{fixup-whitespace} is
730 responsible for deciding whether to leave a space at the junction.
733 @deffn Command fixup-whitespace
734 This function replaces all the horizontal whitespace surrounding point
735 with either one space or no space, according to the context. It
738 At the beginning or end of a line, the appropriate amount of space is
739 none. Before a character with close parenthesis syntax, or after a
740 character with open parenthesis or expression-prefix syntax, no space is
741 also appropriate. Otherwise, one space is appropriate. @xref{Syntax
744 In the example below, @code{fixup-whitespace} is called the first time
745 with point before the word @samp{spaces} in the first line. For the
746 second invocation, point is directly after the @samp{(}.
750 ---------- Buffer: foo ----------
751 This has too many @point{}spaces
752 This has too many spaces at the start of (@point{} this list)
753 ---------- Buffer: foo ----------
764 ---------- Buffer: foo ----------
765 This has too many spaces
766 This has too many spaces at the start of (this list)
767 ---------- Buffer: foo ----------
772 @deffn Command just-one-space &optional n
773 @comment !!SourceFile simple.el
774 This command replaces any spaces and tabs around point with a single
775 space, or @var{n} spaces if @var{n} is specified. It returns
779 @deffn Command delete-blank-lines
780 This function deletes blank lines surrounding point. If point is on a
781 blank line with one or more blank lines before or after it, then all but
782 one of them are deleted. If point is on an isolated blank line, then it
783 is deleted. If point is on a nonblank line, the command deletes all
784 blank lines immediately following it.
786 A blank line is defined as a line containing only tabs and spaces.
788 @code{delete-blank-lines} returns @code{nil}.
792 @section The Kill Ring
795 @dfn{Kill functions} delete text like the deletion functions, but save
796 it so that the user can reinsert it by @dfn{yanking}. Most of these
797 functions have @samp{kill-} in their name. By contrast, the functions
798 whose names start with @samp{delete-} normally do not save text for
799 yanking (though they can still be undone); these are ``deletion''
802 Most of the kill commands are primarily for interactive use, and are
803 not described here. What we do describe are the functions provided for
804 use in writing such commands. You can use these functions to write
805 commands for killing text. When you need to delete text for internal
806 purposes within a Lisp function, you should normally use deletion
807 functions, so as not to disturb the kill ring contents.
810 Killed text is saved for later yanking in the @dfn{kill ring}. This
811 is a list that holds a number of recent kills, not just the last text
812 kill. We call this a ``ring'' because yanking treats it as having
813 elements in a cyclic order. The list is kept in the variable
814 @code{kill-ring}, and can be operated on with the usual functions for
815 lists; there are also specialized functions, described in this section,
816 that treat it as a ring.
818 Some people think this use of the word ``kill'' is unfortunate, since
819 it refers to operations that specifically @emph{do not} destroy the
820 entities ``killed''. This is in sharp contrast to ordinary life, in
821 which death is permanent and ``killed'' entities do not come back to
822 life. Therefore, other metaphors have been proposed. For example, the
823 term ``cut ring'' makes sense to people who, in pre-computer days, used
824 scissors and paste to cut up and rearrange manuscripts. However, it
825 would be difficult to change the terminology now.
828 * Kill Ring Concepts:: What text looks like in the kill ring.
829 * Kill Functions:: Functions that kill text.
830 * Yanking:: How yanking is done.
831 * Yank Commands:: Commands that access the kill ring.
832 * Low-Level Kill Ring:: Functions and variables for kill ring access.
833 * Internals of Kill Ring:: Variables that hold kill ring data.
836 @node Kill Ring Concepts
837 @comment node-name, next, previous, up
838 @subsection Kill Ring Concepts
840 The kill ring records killed text as strings in a list, most recent
841 first. A short kill ring, for example, might look like this:
844 ("some text" "a different piece of text" "even older text")
848 When the list reaches @code{kill-ring-max} entries in length, adding a
849 new entry automatically deletes the last entry.
851 When kill commands are interwoven with other commands, each kill
852 command makes a new entry in the kill ring. Multiple kill commands in
853 succession build up a single kill ring entry, which would be yanked as a
854 unit; the second and subsequent consecutive kill commands add text to
855 the entry made by the first one.
857 For yanking, one entry in the kill ring is designated the ``front'' of
858 the ring. Some yank commands ``rotate'' the ring by designating a
859 different element as the ``front.'' But this virtual rotation doesn't
860 change the list itself---the most recent entry always comes first in the
864 @comment node-name, next, previous, up
865 @subsection Functions for Killing
867 @code{kill-region} is the usual subroutine for killing text. Any
868 command that calls this function is a ``kill command'' (and should
869 probably have @samp{kill} in its name). @code{kill-region} puts the
870 newly killed text in a new element at the beginning of the kill ring or
871 adds it to the most recent element. It determines automatically (using
872 @code{last-command}) whether the previous command was a kill command,
873 and if so appends the killed text to the most recent entry.
875 @deffn Command kill-region start end &optional yank-handler
876 This function kills the text in the region defined by @var{start} and
877 @var{end}. The text is deleted but saved in the kill ring, along with
878 its text properties. The value is always @code{nil}.
880 In an interactive call, @var{start} and @var{end} are point and
884 If the buffer or text is read-only, @code{kill-region} modifies the kill
885 ring just the same, then signals an error without modifying the buffer.
886 This is convenient because it lets the user use a series of kill
887 commands to copy text from a read-only buffer into the kill ring.
889 If @var{yank-handler} is non-@code{nil}, this puts that value onto
890 the string of killed text, as a @code{yank-handler} text property.
891 @xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, any
892 @code{yank-handler} properties present on the killed text are copied
893 onto the kill ring, like other text properties.
896 @defopt kill-read-only-ok
897 If this option is non-@code{nil}, @code{kill-region} does not signal an
898 error if the buffer or text is read-only. Instead, it simply returns,
899 updating the kill ring but not changing the buffer.
902 @deffn Command copy-region-as-kill start end
903 This command saves the region defined by @var{start} and @var{end} on
904 the kill ring (including text properties), but does not delete the text
905 from the buffer. It returns @code{nil}.
907 The command does not set @code{this-command} to @code{kill-region}, so a
908 subsequent kill command does not append to the same kill ring entry.
910 Don't call @code{copy-region-as-kill} in Lisp programs unless you aim to
911 support Emacs 18. For newer Emacs versions, it is better to use
912 @code{kill-new} or @code{kill-append} instead. @xref{Low-Level Kill
919 Yanking means inserting text from the kill ring, but it does
920 not insert the text blindly. Yank commands and some other commands
921 use @code{insert-for-yank} to perform special processing on the
922 text that they copy into the buffer.
924 @defun insert-for-yank string
925 This function normally works like @code{insert} except that it doesn't
926 insert the text properties in the @code{yank-excluded-properties}
927 list. However, if any part of @var{string} has a non-@code{nil}
928 @code{yank-handler} text property, that property can do various
929 special processing on that part of the text being inserted.
932 @defun insert-buffer-substring-as-yank buf &optional start end
933 This function resembles @code{insert-buffer-substring} except that it
934 doesn't insert the text properties in the
935 @code{yank-excluded-properties} list.
938 You can put a @code{yank-handler} text property on all or part of
939 the text to control how it will be inserted if it is yanked. The
940 @code{insert-for-yank} function looks for that property. The property
941 value must be a list of one to four elements, with the following
942 format (where elements after the first may be omitted):
945 (@var{function} @var{param} @var{noexclude} @var{undo})
948 Here is what the elements do:
952 When @var{function} is present and non-@code{nil}, it is called instead of
953 @code{insert} to insert the string. @var{function} takes one
954 argument---the string to insert.
957 If @var{param} is present and non-@code{nil}, it replaces @var{string}
958 (or the part of @var{string} being processed) as the object passed to
959 @var{function} (or @code{insert}); for example, if @var{function} is
960 @code{yank-rectangle}, @var{param} should be a list of strings to
961 insert as a rectangle.
964 If @var{noexclude} is present and non-@code{nil}, the normal removal of the
965 yank-excluded-properties is not performed; instead @var{function} is
966 responsible for removing those properties. This may be necessary
967 if @var{function} adjusts point before or after inserting the object.
970 If @var{undo} is present and non-@code{nil}, it is a function that will be
971 called by @code{yank-pop} to undo the insertion of the current object.
972 It is called with two arguments, the start and end of the current
973 region. @var{function} can set @code{yank-undo-function} to override
974 the @var{undo} value.
978 @comment node-name, next, previous, up
979 @subsection Functions for Yanking
981 @dfn{Yanking} means reinserting an entry of previously killed text
982 from the kill ring. The text properties are copied too.
984 @deffn Command yank &optional arg
985 @cindex inserting killed text
986 This command inserts before point the text at the front of the
987 kill ring. It positions the mark at the beginning of that text, and
990 If @var{arg} is a non-@code{nil} list (which occurs interactively when
991 the user types @kbd{C-u} with no digits), then @code{yank} inserts the
992 text as described above, but puts point before the yanked text and
993 puts the mark after it.
995 If @var{arg} is a number, then @code{yank} inserts the @var{arg}th
996 most recently killed text---the @var{arg}th element of the kill ring
997 list, counted cyclically from the front, which is considered the
998 first element for this purpose.
1000 @code{yank} does not alter the contents of the kill ring, unless it
1001 used text provided by another program, in which case it pushes that text
1002 onto the kill ring. However if @var{arg} is an integer different from
1003 one, it rotates the kill ring to place the yanked string at the front.
1005 @code{yank} returns @code{nil}.
1008 @deffn Command yank-pop &optional arg
1009 This command replaces the just-yanked entry from the kill ring with a
1010 different entry from the kill ring.
1012 This is allowed only immediately after a @code{yank} or another
1013 @code{yank-pop}. At such a time, the region contains text that was just
1014 inserted by yanking. @code{yank-pop} deletes that text and inserts in
1015 its place a different piece of killed text. It does not add the deleted
1016 text to the kill ring, since it is already in the kill ring somewhere.
1017 It does however rotate the kill ring to place the newly yanked string at
1020 If @var{arg} is @code{nil}, then the replacement text is the previous
1021 element of the kill ring. If @var{arg} is numeric, the replacement is
1022 the @var{arg}th previous kill. If @var{arg} is negative, a more recent
1023 kill is the replacement.
1025 The sequence of kills in the kill ring wraps around, so that after the
1026 oldest one comes the newest one, and before the newest one goes the
1029 The return value is always @code{nil}.
1032 @defvar yank-undo-function
1033 If this variable is non-@code{nil}, the function @code{yank-pop} uses
1034 its value instead of @code{delete-region} to delete the text
1035 inserted by the previous @code{yank} or
1036 @code{yank-pop} command. The value must be a function of two
1037 arguments, the start and end of the current region.
1039 The function @code{insert-for-yank} automatically sets this variable
1040 according to the @var{undo} element of the @code{yank-handler}
1041 text property, if there is one.
1044 @node Low-Level Kill Ring
1045 @subsection Low-Level Kill Ring
1047 These functions and variables provide access to the kill ring at a
1048 lower level, but still convenient for use in Lisp programs, because they
1049 take care of interaction with window system selections
1050 (@pxref{Window System Selections}).
1052 @defun current-kill n &optional do-not-move
1053 The function @code{current-kill} rotates the yanking pointer, which
1054 designates the ``front'' of the kill ring, by @var{n} places (from newer
1055 kills to older ones), and returns the text at that place in the ring.
1057 If the optional second argument @var{do-not-move} is non-@code{nil},
1058 then @code{current-kill} doesn't alter the yanking pointer; it just
1059 returns the @var{n}th kill, counting from the current yanking pointer.
1061 If @var{n} is zero, indicating a request for the latest kill,
1062 @code{current-kill} calls the value of
1063 @code{interprogram-paste-function} (documented below) before
1064 consulting the kill ring. If that value is a function and calling it
1065 returns a string, @code{current-kill} pushes that string onto the kill
1066 ring and returns it. It also sets the yanking pointer to point to
1067 that new entry, regardless of the value of @var{do-not-move}.
1068 Otherwise, @code{current-kill} does not treat a zero value for @var{n}
1069 specially: it returns the entry pointed at by the yanking pointer and
1070 does not move the yanking pointer.
1073 @defun kill-new string &optional replace yank-handler
1074 This function pushes the text @var{string} onto the kill ring and
1075 makes the yanking pointer point to it. It discards the oldest entry
1076 if appropriate. It also invokes the value of
1077 @code{interprogram-cut-function} (see below).
1079 If @var{replace} is non-@code{nil}, then @code{kill-new} replaces the
1080 first element of the kill ring with @var{string}, rather than pushing
1081 @var{string} onto the kill ring.
1083 If @var{yank-handler} is non-@code{nil}, this puts that value onto
1084 the string of killed text, as a @code{yank-handler} property.
1085 @xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, then
1086 @code{kill-new} copies any @code{yank-handler} properties present on
1087 @var{string} onto the kill ring, as it does with other text properties.
1090 @defun kill-append string before-p &optional yank-handler
1091 This function appends the text @var{string} to the first entry in the
1092 kill ring and makes the yanking pointer point to the combined entry.
1093 Normally @var{string} goes at the end of the entry, but if
1094 @var{before-p} is non-@code{nil}, it goes at the beginning. This
1095 function also invokes the value of @code{interprogram-cut-function}
1096 (see below). This handles @var{yank-handler} just like
1097 @code{kill-new}, except that if @var{yank-handler} is different from
1098 the @code{yank-handler} property of the first entry of the kill ring,
1099 @code{kill-append} pushes the concatenated string onto the kill ring,
1100 instead of replacing the original first entry with it.
1103 @defvar interprogram-paste-function
1104 This variable provides a way of transferring killed text from other
1105 programs, when you are using a window system. Its value should be
1106 @code{nil} or a function of no arguments.
1108 If the value is a function, @code{current-kill} calls it to get the
1109 ``most recent kill''. If the function returns a non-@code{nil} value,
1110 then that value is used as the ``most recent kill''. If it returns
1111 @code{nil}, then the front of the kill ring is used.
1113 The normal use of this hook is to get the window system's primary
1114 selection as the most recent kill, even if the selection belongs to
1115 another application. @xref{Window System Selections}.
1118 @defvar interprogram-cut-function
1119 This variable provides a way of communicating killed text to other
1120 programs, when you are using a window system. Its value should be
1121 @code{nil} or a function of one required and one optional argument.
1123 If the value is a function, @code{kill-new} and @code{kill-append} call
1124 it with the new first element of the kill ring as the first argument.
1125 The second, optional, argument has the same meaning as the @var{push}
1126 argument to @code{x-set-cut-buffer} (@pxref{Definition of
1127 x-set-cut-buffer}) and only affects the second and later cut buffers.
1129 The normal use of this hook is to set the window system's primary
1130 selection (and first cut buffer) from the newly killed text.
1131 @xref{Window System Selections}.
1134 @node Internals of Kill Ring
1135 @comment node-name, next, previous, up
1136 @subsection Internals of the Kill Ring
1138 The variable @code{kill-ring} holds the kill ring contents, in the
1139 form of a list of strings. The most recent kill is always at the front
1142 The @code{kill-ring-yank-pointer} variable points to a link in the
1143 kill ring list, whose @sc{car} is the text to yank next. We say it
1144 identifies the ``front'' of the ring. Moving
1145 @code{kill-ring-yank-pointer} to a different link is called
1146 @dfn{rotating the kill ring}. We call the kill ring a ``ring'' because
1147 the functions that move the yank pointer wrap around from the end of the
1148 list to the beginning, or vice-versa. Rotation of the kill ring is
1149 virtual; it does not change the value of @code{kill-ring}.
1151 Both @code{kill-ring} and @code{kill-ring-yank-pointer} are Lisp
1152 variables whose values are normally lists. The word ``pointer'' in the
1153 name of the @code{kill-ring-yank-pointer} indicates that the variable's
1154 purpose is to identify one element of the list for use by the next yank
1157 The value of @code{kill-ring-yank-pointer} is always @code{eq} to one
1158 of the links in the kill ring list. The element it identifies is the
1159 @sc{car} of that link. Kill commands, which change the kill ring, also
1160 set this variable to the value of @code{kill-ring}. The effect is to
1161 rotate the ring so that the newly killed text is at the front.
1163 Here is a diagram that shows the variable @code{kill-ring-yank-pointer}
1164 pointing to the second entry in the kill ring @code{("some text" "a
1165 different piece of text" "yet older text")}.
1169 kill-ring ---- kill-ring-yank-pointer
1172 | --- --- --- --- --- ---
1173 --> | | |------> | | |--> | | |--> nil
1174 --- --- --- --- --- ---
1177 | | -->"yet older text"
1179 | --> "a different piece of text"
1186 This state of affairs might occur after @kbd{C-y} (@code{yank})
1187 immediately followed by @kbd{M-y} (@code{yank-pop}).
1190 This variable holds the list of killed text sequences, most recently
1194 @defvar kill-ring-yank-pointer
1195 This variable's value indicates which element of the kill ring is at the
1196 ``front'' of the ring for yanking. More precisely, the value is a tail
1197 of the value of @code{kill-ring}, and its @sc{car} is the kill string
1198 that @kbd{C-y} should yank.
1201 @defopt kill-ring-max
1202 The value of this variable is the maximum length to which the kill
1203 ring can grow, before elements are thrown away at the end. The default
1204 value for @code{kill-ring-max} is 60.
1208 @comment node-name, next, previous, up
1212 Most buffers have an @dfn{undo list}, which records all changes made
1213 to the buffer's text so that they can be undone. (The buffers that
1214 don't have one are usually special-purpose buffers for which Emacs
1215 assumes that undoing is not useful. In particular, any buffer whose
1216 name begins with a space has its undo recording off by default,
1217 see @ref{Buffer Names}.) All the primitives that modify the
1218 text in the buffer automatically add elements to the front of the undo
1219 list, which is in the variable @code{buffer-undo-list}.
1221 @defvar buffer-undo-list
1222 This buffer-local variable's value is the undo list of the current
1223 buffer. A value of @code{t} disables the recording of undo information.
1226 Here are the kinds of elements an undo list can have:
1229 @item @var{position}
1230 This kind of element records a previous value of point; undoing this
1231 element moves point to @var{position}. Ordinary cursor motion does not
1232 make any sort of undo record, but deletion operations use these entries
1233 to record where point was before the command.
1235 @item (@var{beg} . @var{end})
1236 This kind of element indicates how to delete text that was inserted.
1237 Upon insertion, the text occupied the range @var{beg}--@var{end} in the
1240 @item (@var{text} . @var{position})
1241 This kind of element indicates how to reinsert text that was deleted.
1242 The deleted text itself is the string @var{text}. The place to
1243 reinsert it is @code{(abs @var{position})}. If @var{position} is
1244 positive, point was at the beginning of the deleted text, otherwise it
1247 @item (t @var{high} . @var{low})
1248 This kind of element indicates that an unmodified buffer became
1249 modified. The elements @var{high} and @var{low} are two integers, each
1250 recording 16 bits of the visited file's modification time as of when it
1251 was previously visited or saved. @code{primitive-undo} uses those
1252 values to determine whether to mark the buffer as unmodified once again;
1253 it does so only if the file's modification time matches those numbers.
1255 @item (nil @var{property} @var{value} @var{beg} . @var{end})
1256 This kind of element records a change in a text property.
1257 Here's how you might undo the change:
1260 (put-text-property @var{beg} @var{end} @var{property} @var{value})
1263 @item (@var{marker} . @var{adjustment})
1264 This kind of element records the fact that the marker @var{marker} was
1265 relocated due to deletion of surrounding text, and that it moved
1266 @var{adjustment} character positions. Undoing this element moves
1267 @var{marker} @minus{} @var{adjustment} characters.
1269 @item (apply @var{funname} . @var{args})
1270 This is an extensible undo item, which is undone by calling
1271 @var{funname} with arguments @var{args}.
1273 @item (apply @var{delta} @var{beg} @var{end} @var{funname} . @var{args})
1274 This is an extensible undo item, which records a change limited to the
1275 range @var{beg} to @var{end}, which increased the size of the buffer
1276 by @var{delta}. It is undone by calling @var{funname} with arguments
1279 This kind of element enables undo limited to a region to determine
1280 whether the element pertains to that region.
1283 This element is a boundary. The elements between two boundaries are
1284 called a @dfn{change group}; normally, each change group corresponds to
1285 one keyboard command, and undo commands normally undo an entire group as
1289 @defun undo-boundary
1290 This function places a boundary element in the undo list. The undo
1291 command stops at such a boundary, and successive undo commands undo
1292 to earlier and earlier boundaries. This function returns @code{nil}.
1294 The editor command loop automatically creates an undo boundary before
1295 each key sequence is executed. Thus, each undo normally undoes the
1296 effects of one command. Self-inserting input characters are an
1297 exception. The command loop makes a boundary for the first such
1298 character; the next 19 consecutive self-inserting input characters do
1299 not make boundaries, and then the 20th does, and so on as long as
1300 self-inserting characters continue.
1302 All buffer modifications add a boundary whenever the previous undoable
1303 change was made in some other buffer. This is to ensure that
1304 each command makes a boundary in each buffer where it makes changes.
1306 Calling this function explicitly is useful for splitting the effects of
1307 a command into more than one unit. For example, @code{query-replace}
1308 calls @code{undo-boundary} after each replacement, so that the user can
1309 undo individual replacements one by one.
1312 @defvar undo-in-progress
1313 This variable is normally @code{nil}, but the undo commands bind it to
1314 @code{t}. This is so that various kinds of change hooks can tell when
1315 they're being called for the sake of undoing.
1318 @defun primitive-undo count list
1319 This is the basic function for undoing elements of an undo list.
1320 It undoes the first @var{count} elements of @var{list}, returning
1321 the rest of @var{list}. You could write this function in Lisp,
1322 but it is convenient to have it in C.
1324 @code{primitive-undo} adds elements to the buffer's undo list when it
1325 changes the buffer. Undo commands avoid confusion by saving the undo
1326 list value at the beginning of a sequence of undo operations. Then the
1327 undo operations use and update the saved value. The new elements added
1328 by undoing are not part of this saved value, so they don't interfere with
1331 This function does not bind @code{undo-in-progress}.
1334 @node Maintaining Undo
1335 @section Maintaining Undo Lists
1337 This section describes how to enable and disable undo information for
1338 a given buffer. It also explains how the undo list is truncated
1339 automatically so it doesn't get too big.
1341 Recording of undo information in a newly created buffer is normally
1342 enabled to start with; but if the buffer name starts with a space, the
1343 undo recording is initially disabled. You can explicitly enable or
1344 disable undo recording with the following two functions, or by setting
1345 @code{buffer-undo-list} yourself.
1347 @deffn Command buffer-enable-undo &optional buffer-or-name
1348 This command enables recording undo information for buffer
1349 @var{buffer-or-name}, so that subsequent changes can be undone. If no
1350 argument is supplied, then the current buffer is used. This function
1351 does nothing if undo recording is already enabled in the buffer. It
1354 In an interactive call, @var{buffer-or-name} is the current buffer.
1355 You cannot specify any other buffer.
1358 @deffn Command buffer-disable-undo &optional buffer-or-name
1359 @cindex disable undo
1360 This function discards the undo list of @var{buffer-or-name}, and disables
1361 further recording of undo information. As a result, it is no longer
1362 possible to undo either previous changes or any subsequent changes. If
1363 the undo list of @var{buffer-or-name} is already disabled, this function
1366 This function returns @code{nil}.
1369 As editing continues, undo lists get longer and longer. To prevent
1370 them from using up all available memory space, garbage collection trims
1371 them back to size limits you can set. (For this purpose, the ``size''
1372 of an undo list measures the cons cells that make up the list, plus the
1373 strings of deleted text.) Three variables control the range of acceptable
1374 sizes: @code{undo-limit}, @code{undo-strong-limit} and
1375 @code{undo-outer-limit}.
1378 This is the soft limit for the acceptable size of an undo list. The
1379 change group at which this size is exceeded is the last one kept.
1382 @defopt undo-strong-limit
1383 This is the upper limit for the acceptable size of an undo list. The
1384 change group at which this size is exceeded is discarded itself (along
1385 with all older change groups). There is one exception: the very latest
1386 change group is only discarded if it exceeds @code{undo-outer-limit}.
1389 @defopt undo-outer-limit
1390 If at garbage collection time the undo info for the current command
1391 exceeds this limit, Emacs discards the info and displays a warning.
1392 This is a last ditch limit to prevent memory overflow.
1396 @comment node-name, next, previous, up
1398 @cindex filling, explicit
1400 @dfn{Filling} means adjusting the lengths of lines (by moving the line
1401 breaks) so that they are nearly (but no greater than) a specified
1402 maximum width. Additionally, lines can be @dfn{justified}, which means
1403 inserting spaces to make the left and/or right margins line up
1404 precisely. The width is controlled by the variable @code{fill-column}.
1405 For ease of reading, lines should be no longer than 70 or so columns.
1407 You can use Auto Fill mode (@pxref{Auto Filling}) to fill text
1408 automatically as you insert it, but changes to existing text may leave
1409 it improperly filled. Then you must fill the text explicitly.
1411 Most of the commands in this section return values that are not
1412 meaningful. All the functions that do filling take note of the current
1413 left margin, current right margin, and current justification style
1414 (@pxref{Margins}). If the current justification style is
1415 @code{none}, the filling functions don't actually do anything.
1417 Several of the filling functions have an argument @var{justify}.
1418 If it is non-@code{nil}, that requests some kind of justification. It
1419 can be @code{left}, @code{right}, @code{full}, or @code{center}, to
1420 request a specific style of justification. If it is @code{t}, that
1421 means to use the current justification style for this part of the text
1422 (see @code{current-justification}, below). Any other value is treated
1425 When you call the filling functions interactively, using a prefix
1426 argument implies the value @code{full} for @var{justify}.
1428 @deffn Command fill-paragraph justify
1429 @cindex filling a paragraph
1430 This command fills the paragraph at or after point. If
1431 @var{justify} is non-@code{nil}, each line is justified as well.
1432 It uses the ordinary paragraph motion commands to find paragraph
1433 boundaries. @xref{Paragraphs,,, emacs, The GNU Emacs Manual}.
1436 @deffn Command fill-region start end &optional justify nosqueeze to-eop
1437 This command fills each of the paragraphs in the region from @var{start}
1438 to @var{end}. It justifies as well if @var{justify} is
1441 If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace
1442 other than line breaks untouched. If @var{to-eop} is non-@code{nil},
1443 that means to keep filling to the end of the paragraph---or the next hard
1444 newline, if @code{use-hard-newlines} is enabled (see below).
1446 The variable @code{paragraph-separate} controls how to distinguish
1447 paragraphs. @xref{Standard Regexps}.
1450 @deffn Command fill-individual-paragraphs start end &optional justify citation-regexp
1451 This command fills each paragraph in the region according to its
1452 individual fill prefix. Thus, if the lines of a paragraph were indented
1453 with spaces, the filled paragraph will remain indented in the same
1456 The first two arguments, @var{start} and @var{end}, are the beginning
1457 and end of the region to be filled. The third and fourth arguments,
1458 @var{justify} and @var{citation-regexp}, are optional. If
1459 @var{justify} is non-@code{nil}, the paragraphs are justified as
1460 well as filled. If @var{citation-regexp} is non-@code{nil}, it means the
1461 function is operating on a mail message and therefore should not fill
1462 the header lines. If @var{citation-regexp} is a string, it is used as
1463 a regular expression; if it matches the beginning of a line, that line
1464 is treated as a citation marker.
1466 Ordinarily, @code{fill-individual-paragraphs} regards each change in
1467 indentation as starting a new paragraph. If
1468 @code{fill-individual-varying-indent} is non-@code{nil}, then only
1469 separator lines separate paragraphs. That mode can handle indented
1470 paragraphs with additional indentation on the first line.
1473 @defopt fill-individual-varying-indent
1474 This variable alters the action of @code{fill-individual-paragraphs} as
1478 @deffn Command fill-region-as-paragraph start end &optional justify nosqueeze squeeze-after
1479 This command considers a region of text as a single paragraph and fills
1480 it. If the region was made up of many paragraphs, the blank lines
1481 between paragraphs are removed. This function justifies as well as
1482 filling when @var{justify} is non-@code{nil}.
1484 In an interactive call, any prefix argument requests justification.
1486 If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace
1487 other than line breaks untouched. If @var{squeeze-after} is
1488 non-@code{nil}, it specifies a position in the region, and means don't
1489 canonicalize spaces before that position.
1491 In Adaptive Fill mode, this command calls @code{fill-context-prefix} to
1492 choose a fill prefix by default. @xref{Adaptive Fill}.
1495 @deffn Command justify-current-line &optional how eop nosqueeze
1496 This command inserts spaces between the words of the current line so
1497 that the line ends exactly at @code{fill-column}. It returns
1500 The argument @var{how}, if non-@code{nil} specifies explicitly the style
1501 of justification. It can be @code{left}, @code{right}, @code{full},
1502 @code{center}, or @code{none}. If it is @code{t}, that means to do
1503 follow specified justification style (see @code{current-justification},
1504 below). @code{nil} means to do full justification.
1506 If @var{eop} is non-@code{nil}, that means do only left-justification
1507 if @code{current-justification} specifies full justification. This is
1508 used for the last line of a paragraph; even if the paragraph as a
1509 whole is fully justified, the last line should not be.
1511 If @var{nosqueeze} is non-@code{nil}, that means do not change interior
1515 @defopt default-justification
1516 This variable's value specifies the style of justification to use for
1517 text that doesn't specify a style with a text property. The possible
1518 values are @code{left}, @code{right}, @code{full}, @code{center}, or
1519 @code{none}. The default value is @code{left}.
1522 @defun current-justification
1523 This function returns the proper justification style to use for filling
1524 the text around point.
1527 @defopt sentence-end-double-space
1528 @anchor{Definition of sentence-end-double-space}
1529 If this variable is non-@code{nil}, a period followed by just one space
1530 does not count as the end of a sentence, and the filling functions
1531 avoid breaking the line at such a place.
1534 @defopt sentence-end-without-period
1535 If this variable is non-@code{nil}, a sentence can end without a
1536 period. This is used for languages like Thai, where sentences end
1537 with a double space but without a period.
1540 @defopt sentence-end-without-space
1541 If this variable is non-@code{nil}, it should be a string of
1542 characters that can end a sentence without following spaces.
1545 @defvar fill-paragraph-function
1546 This variable provides a way for major modes to override the filling of
1547 paragraphs. If the value is non-@code{nil}, @code{fill-paragraph} calls
1548 this function to do the work. If the function returns a non-@code{nil}
1549 value, @code{fill-paragraph} assumes the job is done, and immediately
1552 The usual use of this feature is to fill comments in programming
1553 language modes. If the function needs to fill a paragraph in the usual
1554 way, it can do so as follows:
1557 (let ((fill-paragraph-function nil))
1558 (fill-paragraph arg))
1562 @defvar use-hard-newlines
1563 If this variable is non-@code{nil}, the filling functions do not delete
1564 newlines that have the @code{hard} text property. These ``hard
1565 newlines'' act as paragraph separators.
1569 @section Margins for Filling
1572 This buffer-local variable specifies a string of text that appears at
1574 of normal text lines and should be disregarded when filling them. Any
1575 line that fails to start with the fill prefix is considered the start of
1576 a paragraph; so is any line that starts with the fill prefix followed by
1577 additional whitespace. Lines that start with the fill prefix but no
1578 additional whitespace are ordinary text lines that can be filled
1579 together. The resulting filled lines also start with the fill prefix.
1581 The fill prefix follows the left margin whitespace, if any.
1585 This buffer-local variable specifies the maximum width of filled lines.
1586 Its value should be an integer, which is a number of columns. All the
1587 filling, justification, and centering commands are affected by this
1588 variable, including Auto Fill mode (@pxref{Auto Filling}).
1590 As a practical matter, if you are writing text for other people to
1591 read, you should set @code{fill-column} to no more than 70. Otherwise
1592 the line will be too long for people to read comfortably, and this can
1593 make the text seem clumsy.
1596 @defvar default-fill-column
1597 The value of this variable is the default value for @code{fill-column} in
1598 buffers that do not override it. This is the same as
1599 @code{(default-value 'fill-column)}.
1601 The default value for @code{default-fill-column} is 70.
1604 @deffn Command set-left-margin from to margin
1605 This sets the @code{left-margin} property on the text from @var{from} to
1606 @var{to} to the value @var{margin}. If Auto Fill mode is enabled, this
1607 command also refills the region to fit the new margin.
1610 @deffn Command set-right-margin from to margin
1611 This sets the @code{right-margin} property on the text from @var{from}
1612 to @var{to} to the value @var{margin}. If Auto Fill mode is enabled,
1613 this command also refills the region to fit the new margin.
1616 @defun current-left-margin
1617 This function returns the proper left margin value to use for filling
1618 the text around point. The value is the sum of the @code{left-margin}
1619 property of the character at the start of the current line (or zero if
1620 none), and the value of the variable @code{left-margin}.
1623 @defun current-fill-column
1624 This function returns the proper fill column value to use for filling
1625 the text around point. The value is the value of the @code{fill-column}
1626 variable, minus the value of the @code{right-margin} property of the
1627 character after point.
1630 @deffn Command move-to-left-margin &optional n force
1631 This function moves point to the left margin of the current line. The
1632 column moved to is determined by calling the function
1633 @code{current-left-margin}. If the argument @var{n} is non-@code{nil},
1634 @code{move-to-left-margin} moves forward @var{n}@minus{}1 lines first.
1636 If @var{force} is non-@code{nil}, that says to fix the line's
1637 indentation if that doesn't match the left margin value.
1640 @defun delete-to-left-margin &optional from to
1641 This function removes left margin indentation from the text between
1642 @var{from} and @var{to}. The amount of indentation to delete is
1643 determined by calling @code{current-left-margin}. In no case does this
1644 function delete non-whitespace. If @var{from} and @var{to} are omitted,
1645 they default to the whole buffer.
1648 @defun indent-to-left-margin
1649 This is the default @code{indent-line-function}, used in Fundamental
1650 mode, Text mode, etc. Its effect is to adjust the indentation at the
1651 beginning of the current line to the value specified by the variable
1652 @code{left-margin}. This may involve either inserting or deleting
1657 This variable specifies the base left margin column. In Fundamental
1658 mode, @kbd{C-j} indents to this column. This variable automatically
1659 becomes buffer-local when set in any fashion.
1662 @defvar fill-nobreak-predicate
1663 This variable gives major modes a way to specify not to break a line
1664 at certain places. Its value should be a list of functions, but a
1665 single function is also supported for compatibility. Whenever filling
1666 considers breaking the line at a certain place in the buffer, it calls
1667 each of these functions with no arguments and with point located at
1668 that place. If any of the functions returns non-@code{nil}, then the
1669 line won't be broken there.
1673 @section Adaptive Fill Mode
1674 @cindex Adaptive Fill mode
1676 When @dfn{Adaptive Fill Mode} is enabled, Emacs determines the fill
1677 prefix automatically from the text in each paragraph being filled
1678 rather than using a predetermined value. During filling, this fill
1679 prefix gets inserted at the start of the second and subsequent lines
1680 of the paragraph as described in @ref{Filling}, and in @ref{Auto
1683 @defopt adaptive-fill-mode
1684 Adaptive Fill mode is enabled when this variable is non-@code{nil}.
1685 It is @code{t} by default.
1688 @defun fill-context-prefix from to
1689 This function implements the heart of Adaptive Fill mode; it chooses a
1690 fill prefix based on the text between @var{from} and @var{to},
1691 typically the start and end of a paragraph. It does this by looking
1692 at the first two lines of the paragraph, based on the variables
1694 @c The optional argument first-line-regexp is not documented
1695 @c because it exists for internal purposes and might be eliminated
1698 Usually, this function returns the fill prefix, a string. However,
1699 before doing this, the function makes a final check (not specially
1700 mentioned in the following) that a line starting with this prefix
1701 wouldn't look like the start of a paragraph. Should this happen, the
1702 function signals the anomaly by returning @code{nil} instead.
1704 In detail, @code{fill-context-prefix} does this:
1708 It takes a candidate for the fill prefix from the first line---it
1709 tries first the function in @code{adaptive-fill-function} (if any),
1710 then the regular expression @code{adaptive-fill-regexp} (see below).
1711 The first non-@code{nil} result of these, or the empty string if
1712 they're both @code{nil}, becomes the first line's candidate.
1714 If the paragraph has as yet only one line, the function tests the
1715 validity of the prefix candidate just found. The function then
1716 returns the candidate if it's valid, or a string of spaces otherwise.
1717 (see the description of @code{adaptive-fill-first-line-regexp} below).
1719 When the paragraph already has two lines, the function next looks for
1720 a prefix candidate on the second line, in just the same way it did for
1721 the first line. If it doesn't find one, it returns @code{nil}.
1723 The function now compares the two candidate prefixes heuristically: if
1724 the non-whitespace characters in the line 2 candidate occur in the
1725 same order in the line 1 candidate, the function returns the line 2
1726 candidate. Otherwise, it returns the largest initial substring which
1727 is common to both candidates (which might be the empty string).
1731 @defopt adaptive-fill-regexp
1732 Adaptive Fill mode matches this regular expression against the text
1733 starting after the left margin whitespace (if any) on a line; the
1734 characters it matches are that line's candidate for the fill prefix.
1736 @w{@code{"[ \t]*\\([-|#;>*]+[ \t]*\\|(?[0-9]+[.)][ \t]*\\)*"}} is the
1737 default value. This matches a number enclosed in parentheses or
1738 followed by a period, or certain punctuation characters, or any
1739 sequence of these intermingled with whitespace. In particular, it
1740 matches a sequence of whitespace, possibly empty.
1743 @defopt adaptive-fill-first-line-regexp
1744 Used only in one-line paragraphs, this regular expression acts as an
1745 additional check of the validity of the one available candidate fill
1746 prefix: the candidate must match this regular expression, or match
1747 @code{comment-start-skip}. If it doesn't, @code{fill-context-prefix}
1748 replaces the candidate with a string of spaces ``of the same width''
1751 The default value of this variable is @w{@code{"\\`[ \t]*\\'"}}, which
1752 matches only a string of whitespace. The effect of this default is to
1753 force the fill prefixes found in one-line paragraphs always to be pure
1757 @defopt adaptive-fill-function
1758 You can specify more complex ways of choosing a fill prefix
1759 automatically by setting this variable to a function. The function is
1760 called with point after the left margin (if any) of a line, and it
1761 must preserve point. It should return either ``that line's'' fill
1762 prefix or @code{nil}, meaning it has failed to determine a prefix.
1766 @comment node-name, next, previous, up
1767 @section Auto Filling
1768 @cindex filling, automatic
1769 @cindex Auto Fill mode
1771 Auto Fill mode is a minor mode that fills lines automatically as text
1772 is inserted. This section describes the hook used by Auto Fill mode.
1773 For a description of functions that you can call explicitly to fill and
1774 justify existing text, see @ref{Filling}.
1776 Auto Fill mode also enables the functions that change the margins and
1777 justification style to refill portions of the text. @xref{Margins}.
1779 @defvar auto-fill-function
1780 The value of this buffer-local variable should be a function (of no
1781 arguments) to be called after self-inserting a character from the table
1782 @code{auto-fill-chars}. It may be @code{nil}, in which case nothing
1783 special is done in that case.
1785 The value of @code{auto-fill-function} is @code{do-auto-fill} when
1786 Auto-Fill mode is enabled. That is a function whose sole purpose is to
1787 implement the usual strategy for breaking a line.
1790 In older Emacs versions, this variable was named @code{auto-fill-hook},
1791 but since it is not called with the standard convention for hooks, it
1792 was renamed to @code{auto-fill-function} in version 19.
1796 @defvar normal-auto-fill-function
1797 This variable specifies the function to use for
1798 @code{auto-fill-function}, if and when Auto Fill is turned on. Major
1799 modes can set buffer-local values for this variable to alter how Auto
1803 @defvar auto-fill-chars
1804 A char table of characters which invoke @code{auto-fill-function} when
1805 self-inserted---space and newline in most language environments. They
1806 have an entry @code{t} in the table.
1810 @section Sorting Text
1811 @cindex sorting text
1813 The sorting functions described in this section all rearrange text in
1814 a buffer. This is in contrast to the function @code{sort}, which
1815 rearranges the order of the elements of a list (@pxref{Rearrangement}).
1816 The values returned by these functions are not meaningful.
1818 @defun sort-subr reverse nextrecfun endrecfun &optional startkeyfun endkeyfun predicate
1819 This function is the general text-sorting routine that subdivides a
1820 buffer into records and then sorts them. Most of the commands in this
1821 section use this function.
1823 To understand how @code{sort-subr} works, consider the whole accessible
1824 portion of the buffer as being divided into disjoint pieces called
1825 @dfn{sort records}. The records may or may not be contiguous, but they
1826 must not overlap. A portion of each sort record (perhaps all of it) is
1827 designated as the sort key. Sorting rearranges the records in order by
1830 Usually, the records are rearranged in order of ascending sort key.
1831 If the first argument to the @code{sort-subr} function, @var{reverse},
1832 is non-@code{nil}, the sort records are rearranged in order of
1833 descending sort key.
1835 The next four arguments to @code{sort-subr} are functions that are
1836 called to move point across a sort record. They are called many times
1837 from within @code{sort-subr}.
1841 @var{nextrecfun} is called with point at the end of a record. This
1842 function moves point to the start of the next record. The first record
1843 is assumed to start at the position of point when @code{sort-subr} is
1844 called. Therefore, you should usually move point to the beginning of
1845 the buffer before calling @code{sort-subr}.
1847 This function can indicate there are no more sort records by leaving
1848 point at the end of the buffer.
1851 @var{endrecfun} is called with point within a record. It moves point to
1852 the end of the record.
1855 @var{startkeyfun} is called to move point from the start of a record to
1856 the start of the sort key. This argument is optional; if it is omitted,
1857 the whole record is the sort key. If supplied, the function should
1858 either return a non-@code{nil} value to be used as the sort key, or
1859 return @code{nil} to indicate that the sort key is in the buffer
1860 starting at point. In the latter case, @var{endkeyfun} is called to
1861 find the end of the sort key.
1864 @var{endkeyfun} is called to move point from the start of the sort key
1865 to the end of the sort key. This argument is optional. If
1866 @var{startkeyfun} returns @code{nil} and this argument is omitted (or
1867 @code{nil}), then the sort key extends to the end of the record. There
1868 is no need for @var{endkeyfun} if @var{startkeyfun} returns a
1869 non-@code{nil} value.
1872 The argument @var{predicate} is the function to use to compare keys.
1873 If keys are numbers, it defaults to @code{<}; otherwise it defaults to
1876 As an example of @code{sort-subr}, here is the complete function
1877 definition for @code{sort-lines}:
1881 ;; @r{Note that the first two lines of doc string}
1882 ;; @r{are effectively one line when viewed by a user.}
1883 (defun sort-lines (reverse beg end)
1884 "Sort lines in region alphabetically;\
1885 argument means descending order.
1886 Called from a program, there are three arguments:
1889 REVERSE (non-nil means reverse order),\
1890 BEG and END (region to sort).
1891 The variable `sort-fold-case' determines\
1892 whether alphabetic case affects
1896 (interactive "P\nr")
1899 (narrow-to-region beg end)
1900 (goto-char (point-min))
1901 (sort-subr reverse 'forward-line 'end-of-line))))
1905 Here @code{forward-line} moves point to the start of the next record,
1906 and @code{end-of-line} moves point to the end of record. We do not pass
1907 the arguments @var{startkeyfun} and @var{endkeyfun}, because the entire
1908 record is used as the sort key.
1910 The @code{sort-paragraphs} function is very much the same, except that
1911 its @code{sort-subr} call looks like this:
1918 (while (and (not (eobp))
1919 (looking-at paragraph-separate))
1925 Markers pointing into any sort records are left with no useful
1926 position after @code{sort-subr} returns.
1929 @defopt sort-fold-case
1930 If this variable is non-@code{nil}, @code{sort-subr} and the other
1931 buffer sorting functions ignore case when comparing strings.
1934 @deffn Command sort-regexp-fields reverse record-regexp key-regexp start end
1935 This command sorts the region between @var{start} and @var{end}
1936 alphabetically as specified by @var{record-regexp} and @var{key-regexp}.
1937 If @var{reverse} is a negative integer, then sorting is in reverse
1940 Alphabetical sorting means that two sort keys are compared by
1941 comparing the first characters of each, the second characters of each,
1942 and so on. If a mismatch is found, it means that the sort keys are
1943 unequal; the sort key whose character is less at the point of first
1944 mismatch is the lesser sort key. The individual characters are compared
1945 according to their numerical character codes in the Emacs character set.
1947 The value of the @var{record-regexp} argument specifies how to divide
1948 the buffer into sort records. At the end of each record, a search is
1949 done for this regular expression, and the text that matches it is taken
1950 as the next record. For example, the regular expression @samp{^.+$},
1951 which matches lines with at least one character besides a newline, would
1952 make each such line into a sort record. @xref{Regular Expressions}, for
1953 a description of the syntax and meaning of regular expressions.
1955 The value of the @var{key-regexp} argument specifies what part of each
1956 record is the sort key. The @var{key-regexp} could match the whole
1957 record, or only a part. In the latter case, the rest of the record has
1958 no effect on the sorted order of records, but it is carried along when
1959 the record moves to its new position.
1961 The @var{key-regexp} argument can refer to the text matched by a
1962 subexpression of @var{record-regexp}, or it can be a regular expression
1965 If @var{key-regexp} is:
1968 @item @samp{\@var{digit}}
1969 then the text matched by the @var{digit}th @samp{\(...\)} parenthesis
1970 grouping in @var{record-regexp} is the sort key.
1973 then the whole record is the sort key.
1975 @item a regular expression
1976 then @code{sort-regexp-fields} searches for a match for the regular
1977 expression within the record. If such a match is found, it is the sort
1978 key. If there is no match for @var{key-regexp} within a record then
1979 that record is ignored, which means its position in the buffer is not
1980 changed. (The other records may move around it.)
1983 For example, if you plan to sort all the lines in the region by the
1984 first word on each line starting with the letter @samp{f}, you should
1985 set @var{record-regexp} to @samp{^.*$} and set @var{key-regexp} to
1986 @samp{\<f\w*\>}. The resulting expression looks like this:
1990 (sort-regexp-fields nil "^.*$" "\\<f\\w*\\>"
1996 If you call @code{sort-regexp-fields} interactively, it prompts for
1997 @var{record-regexp} and @var{key-regexp} in the minibuffer.
2000 @deffn Command sort-lines reverse start end
2001 This command alphabetically sorts lines in the region between
2002 @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort
2003 is in reverse order.
2006 @deffn Command sort-paragraphs reverse start end
2007 This command alphabetically sorts paragraphs in the region between
2008 @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort
2009 is in reverse order.
2012 @deffn Command sort-pages reverse start end
2013 This command alphabetically sorts pages in the region between
2014 @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort
2015 is in reverse order.
2018 @deffn Command sort-fields field start end
2019 This command sorts lines in the region between @var{start} and
2020 @var{end}, comparing them alphabetically by the @var{field}th field
2021 of each line. Fields are separated by whitespace and numbered starting
2022 from 1. If @var{field} is negative, sorting is by the
2023 @w{@minus{}@var{field}th} field from the end of the line. This command
2024 is useful for sorting tables.
2027 @deffn Command sort-numeric-fields field start end
2028 This command sorts lines in the region between @var{start} and
2029 @var{end}, comparing them numerically by the @var{field}th field of
2030 each line. Fields are separated by whitespace and numbered starting
2031 from 1. The specified field must contain a number in each line of the
2032 region. Numbers starting with 0 are treated as octal, and numbers
2033 starting with @samp{0x} are treated as hexadecimal.
2035 If @var{field} is negative, sorting is by the
2036 @w{@minus{}@var{field}th} field from the end of the line. This
2037 command is useful for sorting tables.
2040 @defopt sort-numeric-base
2041 This variable specifies the default radix for
2042 @code{sort-numeric-fields} to parse numbers.
2045 @deffn Command sort-columns reverse &optional beg end
2046 This command sorts the lines in the region between @var{beg} and
2047 @var{end}, comparing them alphabetically by a certain range of
2048 columns. The column positions of @var{beg} and @var{end} bound the
2049 range of columns to sort on.
2051 If @var{reverse} is non-@code{nil}, the sort is in reverse order.
2053 One unusual thing about this command is that the entire line
2054 containing position @var{beg}, and the entire line containing position
2055 @var{end}, are included in the region sorted.
2057 Note that @code{sort-columns} uses the @code{sort} utility program,
2058 and so cannot work properly on text containing tab characters. Use
2059 @kbd{M-x untabify} to convert tabs to spaces before sorting.
2063 @comment node-name, next, previous, up
2064 @section Counting Columns
2066 @cindex counting columns
2067 @cindex horizontal position
2069 The column functions convert between a character position (counting
2070 characters from the beginning of the buffer) and a column position
2071 (counting screen characters from the beginning of a line).
2073 These functions count each character according to the number of
2074 columns it occupies on the screen. This means control characters count
2075 as occupying 2 or 4 columns, depending upon the value of
2076 @code{ctl-arrow}, and tabs count as occupying a number of columns that
2077 depends on the value of @code{tab-width} and on the column where the tab
2078 begins. @xref{Usual Display}.
2080 Column number computations ignore the width of the window and the
2081 amount of horizontal scrolling. Consequently, a column value can be
2082 arbitrarily high. The first (or leftmost) column is numbered 0. They
2083 also ignore overlays and text properties, aside from invisibility.
2085 @defun current-column
2086 This function returns the horizontal position of point, measured in
2087 columns, counting from 0 at the left margin. The column position is the
2088 sum of the widths of all the displayed representations of the characters
2089 between the start of the current line and point.
2091 For an example of using @code{current-column}, see the description of
2092 @code{count-lines} in @ref{Text Lines}.
2095 @defun move-to-column column &optional force
2096 This function moves point to @var{column} in the current line. The
2097 calculation of @var{column} takes into account the widths of the
2098 displayed representations of the characters between the start of the
2101 If column @var{column} is beyond the end of the line, point moves to the
2102 end of the line. If @var{column} is negative, point moves to the
2103 beginning of the line.
2105 If it is impossible to move to column @var{column} because that is in
2106 the middle of a multicolumn character such as a tab, point moves to the
2107 end of that character. However, if @var{force} is non-@code{nil}, and
2108 @var{column} is in the middle of a tab, then @code{move-to-column}
2109 converts the tab into spaces so that it can move precisely to column
2110 @var{column}. Other multicolumn characters can cause anomalies despite
2111 @var{force}, since there is no way to split them.
2113 The argument @var{force} also has an effect if the line isn't long
2114 enough to reach column @var{column}; if it is @code{t}, that means to
2115 add whitespace at the end of the line to reach that column.
2117 If @var{column} is not an integer, an error is signaled.
2119 The return value is the column number actually moved to.
2123 @section Indentation
2126 The indentation functions are used to examine, move to, and change
2127 whitespace that is at the beginning of a line. Some of the functions
2128 can also change whitespace elsewhere on a line. Columns and indentation
2129 count from zero at the left margin.
2132 * Primitive Indent:: Functions used to count and insert indentation.
2133 * Mode-Specific Indent:: Customize indentation for different modes.
2134 * Region Indent:: Indent all the lines in a region.
2135 * Relative Indent:: Indent the current line based on previous lines.
2136 * Indent Tabs:: Adjustable, typewriter-like tab stops.
2137 * Motion by Indent:: Move to first non-blank character.
2140 @node Primitive Indent
2141 @subsection Indentation Primitives
2143 This section describes the primitive functions used to count and
2144 insert indentation. The functions in the following sections use these
2145 primitives. @xref{Width}, for related functions.
2147 @defun current-indentation
2148 @comment !!Type Primitive Function
2149 @comment !!SourceFile indent.c
2150 This function returns the indentation of the current line, which is
2151 the horizontal position of the first nonblank character. If the
2152 contents are entirely blank, then this is the horizontal position of the
2156 @deffn Command indent-to column &optional minimum
2157 @comment !!Type Primitive Function
2158 @comment !!SourceFile indent.c
2159 This function indents from point with tabs and spaces until @var{column}
2160 is reached. If @var{minimum} is specified and non-@code{nil}, then at
2161 least that many spaces are inserted even if this requires going beyond
2162 @var{column}. Otherwise the function does nothing if point is already
2163 beyond @var{column}. The value is the column at which the inserted
2166 The inserted whitespace characters inherit text properties from the
2167 surrounding text (usually, from the preceding text only). @xref{Sticky
2171 @defopt indent-tabs-mode
2172 @comment !!SourceFile indent.c
2173 If this variable is non-@code{nil}, indentation functions can insert
2174 tabs as well as spaces. Otherwise, they insert only spaces. Setting
2175 this variable automatically makes it buffer-local in the current buffer.
2178 @node Mode-Specific Indent
2179 @subsection Indentation Controlled by Major Mode
2181 An important function of each major mode is to customize the @key{TAB}
2182 key to indent properly for the language being edited. This section
2183 describes the mechanism of the @key{TAB} key and how to control it.
2184 The functions in this section return unpredictable values.
2186 @defvar indent-line-function
2187 This variable's value is the function to be used by @key{TAB} (and
2188 various commands) to indent the current line. The command
2189 @code{indent-according-to-mode} does no more than call this function.
2191 In Lisp mode, the value is the symbol @code{lisp-indent-line}; in C
2192 mode, @code{c-indent-line}; in Fortran mode, @code{fortran-indent-line}.
2193 In Fundamental mode, Text mode, and many other modes with no standard
2194 for indentation, the value is @code{indent-to-left-margin} (which is the
2198 @deffn Command indent-according-to-mode
2199 This command calls the function in @code{indent-line-function} to
2200 indent the current line in a way appropriate for the current major mode.
2203 @deffn Command indent-for-tab-command
2204 This command calls the function in @code{indent-line-function} to indent
2205 the current line; however, if that function is
2206 @code{indent-to-left-margin}, @code{insert-tab} is called instead. (That
2207 is a trivial command that inserts a tab character.)
2210 @deffn Command newline-and-indent
2211 @comment !!SourceFile simple.el
2212 This function inserts a newline, then indents the new line (the one
2213 following the newline just inserted) according to the major mode.
2215 It does indentation by calling the current @code{indent-line-function}.
2216 In programming language modes, this is the same thing @key{TAB} does,
2217 but in some text modes, where @key{TAB} inserts a tab,
2218 @code{newline-and-indent} indents to the column specified by
2222 @deffn Command reindent-then-newline-and-indent
2223 @comment !!SourceFile simple.el
2224 This command reindents the current line, inserts a newline at point,
2225 and then indents the new line (the one following the newline just
2228 This command does indentation on both lines according to the current
2229 major mode, by calling the current value of @code{indent-line-function}.
2230 In programming language modes, this is the same thing @key{TAB} does,
2231 but in some text modes, where @key{TAB} inserts a tab,
2232 @code{reindent-then-newline-and-indent} indents to the column specified
2233 by @code{left-margin}.
2237 @subsection Indenting an Entire Region
2239 This section describes commands that indent all the lines in the
2240 region. They return unpredictable values.
2242 @deffn Command indent-region start end to-column
2243 This command indents each nonblank line starting between @var{start}
2244 (inclusive) and @var{end} (exclusive). If @var{to-column} is
2245 @code{nil}, @code{indent-region} indents each nonblank line by calling
2246 the current mode's indentation function, the value of
2247 @code{indent-line-function}.
2249 If @var{to-column} is non-@code{nil}, it should be an integer
2250 specifying the number of columns of indentation; then this function
2251 gives each line exactly that much indentation, by either adding or
2252 deleting whitespace.
2254 If there is a fill prefix, @code{indent-region} indents each line
2255 by making it start with the fill prefix.
2258 @defvar indent-region-function
2259 The value of this variable is a function that can be used by
2260 @code{indent-region} as a short cut. It should take two arguments, the
2261 start and end of the region. You should design the function so
2262 that it will produce the same results as indenting the lines of the
2263 region one by one, but presumably faster.
2265 If the value is @code{nil}, there is no short cut, and
2266 @code{indent-region} actually works line by line.
2268 A short-cut function is useful in modes such as C mode and Lisp mode,
2269 where the @code{indent-line-function} must scan from the beginning of
2270 the function definition: applying it to each line would be quadratic in
2271 time. The short cut can update the scan information as it moves through
2272 the lines indenting them; this takes linear time. In a mode where
2273 indenting a line individually is fast, there is no need for a short cut.
2275 @code{indent-region} with a non-@code{nil} argument @var{to-column} has
2276 a different meaning and does not use this variable.
2279 @deffn Command indent-rigidly start end count
2280 @comment !!SourceFile indent.el
2281 This command indents all lines starting between @var{start}
2282 (inclusive) and @var{end} (exclusive) sideways by @var{count} columns.
2283 This ``preserves the shape'' of the affected region, moving it as a
2284 rigid unit. Consequently, this command is useful not only for indenting
2285 regions of unindented text, but also for indenting regions of formatted
2288 For example, if @var{count} is 3, this command adds 3 columns of
2289 indentation to each of the lines beginning in the region specified.
2291 In Mail mode, @kbd{C-c C-y} (@code{mail-yank-original}) uses
2292 @code{indent-rigidly} to indent the text copied from the message being
2296 @defun indent-code-rigidly start end columns &optional nochange-regexp
2297 This is like @code{indent-rigidly}, except that it doesn't alter lines
2298 that start within strings or comments.
2300 In addition, it doesn't alter a line if @var{nochange-regexp} matches at
2301 the beginning of the line (if @var{nochange-regexp} is non-@code{nil}).
2304 @node Relative Indent
2305 @subsection Indentation Relative to Previous Lines
2307 This section describes two commands that indent the current line
2308 based on the contents of previous lines.
2310 @deffn Command indent-relative &optional unindented-ok
2311 This command inserts whitespace at point, extending to the same
2312 column as the next @dfn{indent point} of the previous nonblank line. An
2313 indent point is a non-whitespace character following whitespace. The
2314 next indent point is the first one at a column greater than the current
2315 column of point. For example, if point is underneath and to the left of
2316 the first non-blank character of a line of text, it moves to that column
2317 by inserting whitespace.
2319 If the previous nonblank line has no next indent point (i.e., none at a
2320 great enough column position), @code{indent-relative} either does
2321 nothing (if @var{unindented-ok} is non-@code{nil}) or calls
2322 @code{tab-to-tab-stop}. Thus, if point is underneath and to the right
2323 of the last column of a short line of text, this command ordinarily
2324 moves point to the next tab stop by inserting whitespace.
2326 The return value of @code{indent-relative} is unpredictable.
2328 In the following example, point is at the beginning of the second
2333 This line is indented twelve spaces.
2334 @point{}The quick brown fox jumped.
2339 Evaluation of the expression @code{(indent-relative nil)} produces the
2344 This line is indented twelve spaces.
2345 @point{}The quick brown fox jumped.
2349 In this next example, point is between the @samp{m} and @samp{p} of
2354 This line is indented twelve spaces.
2355 The quick brown fox jum@point{}ped.
2360 Evaluation of the expression @code{(indent-relative nil)} produces the
2365 This line is indented twelve spaces.
2366 The quick brown fox jum @point{}ped.
2371 @deffn Command indent-relative-maybe
2372 @comment !!SourceFile indent.el
2373 This command indents the current line like the previous nonblank line,
2374 by calling @code{indent-relative} with @code{t} as the
2375 @var{unindented-ok} argument. The return value is unpredictable.
2377 If the previous nonblank line has no indent points beyond the current
2378 column, this command does nothing.
2382 @comment node-name, next, previous, up
2383 @subsection Adjustable ``Tab Stops''
2384 @cindex tabs stops for indentation
2386 This section explains the mechanism for user-specified ``tab stops''
2387 and the mechanisms that use and set them. The name ``tab stops'' is
2388 used because the feature is similar to that of the tab stops on a
2389 typewriter. The feature works by inserting an appropriate number of
2390 spaces and tab characters to reach the next tab stop column; it does not
2391 affect the display of tab characters in the buffer (@pxref{Usual
2392 Display}). Note that the @key{TAB} character as input uses this tab
2393 stop feature only in a few major modes, such as Text mode.
2395 @deffn Command tab-to-tab-stop
2396 This command inserts spaces or tabs before point, up to the next tab
2397 stop column defined by @code{tab-stop-list}. It searches the list for
2398 an element greater than the current column number, and uses that element
2399 as the column to indent to. It does nothing if no such element is
2403 @defopt tab-stop-list
2404 This variable is the list of tab stop columns used by
2405 @code{tab-to-tab-stops}. The elements should be integers in increasing
2406 order. The tab stop columns need not be evenly spaced.
2408 Use @kbd{M-x edit-tab-stops} to edit the location of tab stops
2412 @node Motion by Indent
2413 @subsection Indentation-Based Motion Commands
2415 These commands, primarily for interactive use, act based on the
2416 indentation in the text.
2418 @deffn Command back-to-indentation
2419 @comment !!SourceFile simple.el
2420 This command moves point to the first non-whitespace character in the
2421 current line (which is the line in which point is located). It returns
2425 @deffn Command backward-to-indentation &optional arg
2426 @comment !!SourceFile simple.el
2427 This command moves point backward @var{arg} lines and then to the
2428 first nonblank character on that line. It returns @code{nil}.
2429 If @var{arg} is omitted or @code{nil}, it defaults to 1.
2432 @deffn Command forward-to-indentation &optional arg
2433 @comment !!SourceFile simple.el
2434 This command moves point forward @var{arg} lines and then to the first
2435 nonblank character on that line. It returns @code{nil}.
2436 If @var{arg} is omitted or @code{nil}, it defaults to 1.
2440 @comment node-name, next, previous, up
2441 @section Case Changes
2442 @cindex case conversion in buffers
2444 The case change commands described here work on text in the current
2445 buffer. @xref{Case Conversion}, for case conversion functions that work
2446 on strings and characters. @xref{Case Tables}, for how to customize
2447 which characters are upper or lower case and how to convert them.
2449 @deffn Command capitalize-region start end
2450 This function capitalizes all words in the region defined by
2451 @var{start} and @var{end}. To capitalize means to convert each word's
2452 first character to upper case and convert the rest of each word to lower
2453 case. The function returns @code{nil}.
2455 If one end of the region is in the middle of a word, the part of the
2456 word within the region is treated as an entire word.
2458 When @code{capitalize-region} is called interactively, @var{start} and
2459 @var{end} are point and the mark, with the smallest first.
2463 ---------- Buffer: foo ----------
2464 This is the contents of the 5th foo.
2465 ---------- Buffer: foo ----------
2469 (capitalize-region 1 44)
2472 ---------- Buffer: foo ----------
2473 This Is The Contents Of The 5th Foo.
2474 ---------- Buffer: foo ----------
2479 @deffn Command downcase-region start end
2480 This function converts all of the letters in the region defined by
2481 @var{start} and @var{end} to lower case. The function returns
2484 When @code{downcase-region} is called interactively, @var{start} and
2485 @var{end} are point and the mark, with the smallest first.
2488 @deffn Command upcase-region start end
2489 This function converts all of the letters in the region defined by
2490 @var{start} and @var{end} to upper case. The function returns
2493 When @code{upcase-region} is called interactively, @var{start} and
2494 @var{end} are point and the mark, with the smallest first.
2497 @deffn Command capitalize-word count
2498 This function capitalizes @var{count} words after point, moving point
2499 over as it does. To capitalize means to convert each word's first
2500 character to upper case and convert the rest of each word to lower case.
2501 If @var{count} is negative, the function capitalizes the
2502 @minus{}@var{count} previous words but does not move point. The value
2505 If point is in the middle of a word, the part of the word before point
2506 is ignored when moving forward. The rest is treated as an entire word.
2508 When @code{capitalize-word} is called interactively, @var{count} is
2509 set to the numeric prefix argument.
2512 @deffn Command downcase-word count
2513 This function converts the @var{count} words after point to all lower
2514 case, moving point over as it does. If @var{count} is negative, it
2515 converts the @minus{}@var{count} previous words but does not move point.
2516 The value is @code{nil}.
2518 When @code{downcase-word} is called interactively, @var{count} is set
2519 to the numeric prefix argument.
2522 @deffn Command upcase-word count
2523 This function converts the @var{count} words after point to all upper
2524 case, moving point over as it does. If @var{count} is negative, it
2525 converts the @minus{}@var{count} previous words but does not move point.
2526 The value is @code{nil}.
2528 When @code{upcase-word} is called interactively, @var{count} is set to
2529 the numeric prefix argument.
2532 @node Text Properties
2533 @section Text Properties
2534 @cindex text properties
2535 @cindex attributes of text
2536 @cindex properties of text
2538 Each character position in a buffer or a string can have a @dfn{text
2539 property list}, much like the property list of a symbol (@pxref{Property
2540 Lists}). The properties belong to a particular character at a
2541 particular place, such as, the letter @samp{T} at the beginning of this
2542 sentence or the first @samp{o} in @samp{foo}---if the same character
2543 occurs in two different places, the two occurrences in general have
2544 different properties.
2546 Each property has a name and a value. Both of these can be any Lisp
2547 object, but the name is normally a symbol. Typically each property
2548 name symbol is used for a particular purpose; for instance, the text
2549 property @code{face} specifies the faces for displaying the character
2550 (@pxref{Special Properties}). The usual way to access the property
2551 list is to specify a name and ask what value corresponds to it.
2553 If a character has a @code{category} property, we call it the
2554 @dfn{category} of the character. It should be a symbol. The properties
2555 of the symbol serve as defaults for the properties of the character.
2557 Copying text between strings and buffers preserves the properties
2558 along with the characters; this includes such diverse functions as
2559 @code{substring}, @code{insert}, and @code{buffer-substring}.
2562 * Examining Properties:: Looking at the properties of one character.
2563 * Changing Properties:: Setting the properties of a range of text.
2564 * Property Search:: Searching for where a property changes value.
2565 * Special Properties:: Particular properties with special meanings.
2566 * Format Properties:: Properties for representing formatting of text.
2567 * Sticky Properties:: How inserted text gets properties from
2569 * Saving Properties:: Saving text properties in files, and reading
2571 * Lazy Properties:: Computing text properties in a lazy fashion
2572 only when text is examined.
2573 * Clickable Text:: Using text properties to make regions of text
2574 do something when you click on them.
2575 * Links and Mouse-1:: How to make @key{Mouse-1} follow a link.
2576 * Fields:: The @code{field} property defines
2577 fields within the buffer.
2578 * Not Intervals:: Why text properties do not use
2579 Lisp-visible text intervals.
2582 @node Examining Properties
2583 @subsection Examining Text Properties
2585 The simplest way to examine text properties is to ask for the value of
2586 a particular property of a particular character. For that, use
2587 @code{get-text-property}. Use @code{text-properties-at} to get the
2588 entire property list of a character. @xref{Property Search}, for
2589 functions to examine the properties of a number of characters at once.
2591 These functions handle both strings and buffers. Keep in mind that
2592 positions in a string start from 0, whereas positions in a buffer start
2595 @defun get-text-property pos prop &optional object
2596 This function returns the value of the @var{prop} property of the
2597 character after position @var{pos} in @var{object} (a buffer or
2598 string). The argument @var{object} is optional and defaults to the
2601 If there is no @var{prop} property strictly speaking, but the character
2602 has a category that is a symbol, then @code{get-text-property} returns
2603 the @var{prop} property of that symbol.
2606 @defun get-char-property position prop &optional object
2607 This function is like @code{get-text-property}, except that it checks
2608 overlays first and then text properties. @xref{Overlays}.
2610 The argument @var{object} may be a string, a buffer, or a window. If it
2611 is a window, then the buffer displayed in that window is used for text
2612 properties and overlays, but only the overlays active for that window
2613 are considered. If @var{object} is a buffer, then all overlays in that
2614 buffer are considered, as well as text properties. If @var{object} is a
2615 string, only text properties are considered, since strings never have
2619 @defun get-char-property-and-overlay position prop &optional object
2620 This is like @code{get-char-property}, but gives extra information
2621 about the overlay that the property value comes from.
2623 Its value is a cons cell whose @sc{car} is the property value, the
2624 same value @code{get-char-property} would return with the same
2625 arguments. Its @sc{cdr} is the overlay in which the property was
2626 found, or @code{nil}, if it was found as a text property or not found
2629 If @var{position} is at the end of @var{object}, both the @sc{car} and
2630 the @sc{cdr} of the value are @code{nil}.
2633 @defvar char-property-alias-alist
2634 This variable holds an alist which maps property names to a list of
2635 alternative property names. If a character does not specify a direct
2636 value for a property, the alternative property names are consulted in
2637 order; the first non-@code{nil} value is used. This variable takes
2638 precedence over @code{default-text-properties}, and @code{category}
2639 properties take precedence over this variable.
2642 @defun text-properties-at position &optional object
2643 This function returns the entire property list of the character at
2644 @var{position} in the string or buffer @var{object}. If @var{object} is
2645 @code{nil}, it defaults to the current buffer.
2648 @defvar default-text-properties
2649 This variable holds a property list giving default values for text
2650 properties. Whenever a character does not specify a value for a
2651 property, neither directly, through a category symbol, or through
2652 @code{char-property-alias-alist}, the value stored in this list is
2653 used instead. Here is an example:
2656 (setq default-text-properties '(foo 69)
2657 char-property-alias-alist nil)
2658 ;; @r{Make sure character 1 has no properties of its own.}
2659 (set-text-properties 1 2 nil)
2660 ;; @r{What we get, when we ask, is the default value.}
2661 (get-text-property 1 'foo)
2666 @node Changing Properties
2667 @subsection Changing Text Properties
2669 The primitives for changing properties apply to a specified range of
2670 text in a buffer or string. The function @code{set-text-properties}
2671 (see end of section) sets the entire property list of the text in that
2672 range; more often, it is useful to add, change, or delete just certain
2673 properties specified by name.
2675 Since text properties are considered part of the contents of the
2676 buffer (or string), and can affect how a buffer looks on the screen,
2677 any change in buffer text properties marks the buffer as modified.
2678 Buffer text property changes are undoable also (@pxref{Undo}).
2679 Positions in a string start from 0, whereas positions in a buffer
2682 @defun put-text-property start end prop value &optional object
2683 This function sets the @var{prop} property to @var{value} for the text
2684 between @var{start} and @var{end} in the string or buffer @var{object}.
2685 If @var{object} is @code{nil}, it defaults to the current buffer.
2688 @defun add-text-properties start end props &optional object
2689 This function adds or overrides text properties for the text between
2690 @var{start} and @var{end} in the string or buffer @var{object}. If
2691 @var{object} is @code{nil}, it defaults to the current buffer.
2693 The argument @var{props} specifies which properties to add. It should
2694 have the form of a property list (@pxref{Property Lists}): a list whose
2695 elements include the property names followed alternately by the
2696 corresponding values.
2698 The return value is @code{t} if the function actually changed some
2699 property's value; @code{nil} otherwise (if @var{props} is @code{nil} or
2700 its values agree with those in the text).
2702 For example, here is how to set the @code{comment} and @code{face}
2703 properties of a range of text:
2706 (add-text-properties @var{start} @var{end}
2707 '(comment t face highlight))
2711 @defun remove-text-properties start end props &optional object
2712 This function deletes specified text properties from the text between
2713 @var{start} and @var{end} in the string or buffer @var{object}. If
2714 @var{object} is @code{nil}, it defaults to the current buffer.
2716 The argument @var{props} specifies which properties to delete. It
2717 should have the form of a property list (@pxref{Property Lists}): a list
2718 whose elements are property names alternating with corresponding values.
2719 But only the names matter---the values that accompany them are ignored.
2720 For example, here's how to remove the @code{face} property.
2723 (remove-text-properties @var{start} @var{end} '(face nil))
2726 The return value is @code{t} if the function actually changed some
2727 property's value; @code{nil} otherwise (if @var{props} is @code{nil} or
2728 if no character in the specified text had any of those properties).
2730 To remove all text properties from certain text, use
2731 @code{set-text-properties} and specify @code{nil} for the new property
2735 @defun remove-list-of-text-properties start end list-of-properties &optional object
2736 Like @code{remove-text-properties} except that
2737 @var{list-of-properties} is a list of property names only, not an
2738 alternating list of property names and values.
2741 @defun set-text-properties start end props &optional object
2742 This function completely replaces the text property list for the text
2743 between @var{start} and @var{end} in the string or buffer @var{object}.
2744 If @var{object} is @code{nil}, it defaults to the current buffer.
2746 The argument @var{props} is the new property list. It should be a list
2747 whose elements are property names alternating with corresponding values.
2749 After @code{set-text-properties} returns, all the characters in the
2750 specified range have identical properties.
2752 If @var{props} is @code{nil}, the effect is to get rid of all properties
2753 from the specified range of text. Here's an example:
2756 (set-text-properties @var{start} @var{end} nil)
2759 Do not rely on the return value of this function.
2762 The easiest way to make a string with text properties
2763 is with @code{propertize}:
2765 @defun propertize string &rest properties
2766 This function returns a copy of @var{string} which has the text
2767 properties @var{properties}. These properties apply to all the
2768 characters in the string that is returned. Here is an example that
2769 constructs a string with a @code{face} property and a @code{mouse-face}
2773 (propertize "foo" 'face 'italic
2774 'mouse-face 'bold-italic)
2775 @result{} #("foo" 0 3 (mouse-face bold-italic face italic))
2778 To put different properties on various parts of a string, you can
2779 construct each part with @code{propertize} and then combine them with
2784 (propertize "foo" 'face 'italic
2785 'mouse-face 'bold-italic)
2787 (propertize "bar" 'face 'italic
2788 'mouse-face 'bold-italic))
2789 @result{} #("foo and bar"
2790 0 3 (face italic mouse-face bold-italic)
2792 8 11 (face italic mouse-face bold-italic))
2796 See also the function @code{buffer-substring-no-properties}
2797 (@pxref{Buffer Contents}) which copies text from the buffer
2798 but does not copy its properties.
2800 @node Property Search
2801 @subsection Text Property Search Functions
2803 In typical use of text properties, most of the time several or many
2804 consecutive characters have the same value for a property. Rather than
2805 writing your programs to examine characters one by one, it is much
2806 faster to process chunks of text that have the same property value.
2808 Here are functions you can use to do this. They use @code{eq} for
2809 comparing property values. In all cases, @var{object} defaults to the
2812 For high performance, it's very important to use the @var{limit}
2813 argument to these functions, especially the ones that search for a
2814 single property---otherwise, they may spend a long time scanning to the
2815 end of the buffer, if the property you are interested in does not change.
2817 These functions do not move point; instead, they return a position (or
2818 @code{nil}). Remember that a position is always between two characters;
2819 the position returned by these functions is between two characters with
2820 different properties.
2822 @defun next-property-change pos &optional object limit
2823 The function scans the text forward from position @var{pos} in the
2824 string or buffer @var{object} till it finds a change in some text
2825 property, then returns the position of the change. In other words, it
2826 returns the position of the first character beyond @var{pos} whose
2827 properties are not identical to those of the character just after
2830 If @var{limit} is non-@code{nil}, then the scan ends at position
2831 @var{limit}. If there is no property change before that point,
2832 @code{next-property-change} returns @var{limit}.
2834 The value is @code{nil} if the properties remain unchanged all the way
2835 to the end of @var{object} and @var{limit} is @code{nil}. If the value
2836 is non-@code{nil}, it is a position greater than or equal to @var{pos}.
2837 The value equals @var{pos} only when @var{limit} equals @var{pos}.
2839 Here is an example of how to scan the buffer by chunks of text within
2840 which all properties are constant:
2844 (let ((plist (text-properties-at (point)))
2846 (or (next-property-change (point) (current-buffer))
2848 @r{Process text from point to @var{next-change}@dots{}}
2849 (goto-char next-change)))
2853 @defun previous-property-change pos &optional object limit
2854 This is like @code{next-property-change}, but scans back from @var{pos}
2855 instead of forward. If the value is non-@code{nil}, it is a position
2856 less than or equal to @var{pos}; it equals @var{pos} only if @var{limit}
2860 @defun next-single-property-change pos prop &optional object limit
2861 The function scans text for a change in the @var{prop} property, then
2862 returns the position of the change. The scan goes forward from
2863 position @var{pos} in the string or buffer @var{object}. In other
2864 words, this function returns the position of the first character
2865 beyond @var{pos} whose @var{prop} property differs from that of the
2866 character just after @var{pos}.
2868 If @var{limit} is non-@code{nil}, then the scan ends at position
2869 @var{limit}. If there is no property change before that point,
2870 @code{next-single-property-change} returns @var{limit}.
2872 The value is @code{nil} if the property remains unchanged all the way to
2873 the end of @var{object} and @var{limit} is @code{nil}. If the value is
2874 non-@code{nil}, it is a position greater than or equal to @var{pos}; it
2875 equals @var{pos} only if @var{limit} equals @var{pos}.
2878 @defun previous-single-property-change pos prop &optional object limit
2879 This is like @code{next-single-property-change}, but scans back from
2880 @var{pos} instead of forward. If the value is non-@code{nil}, it is a
2881 position less than or equal to @var{pos}; it equals @var{pos} only if
2882 @var{limit} equals @var{pos}.
2885 @defun next-char-property-change pos &optional limit
2886 This is like @code{next-property-change} except that it considers
2887 overlay properties as well as text properties, and if no change is
2888 found before the end of the buffer, it returns the maximum buffer
2889 position rather than @code{nil} (in this sense, it resembles the
2890 corresponding overlay function @code{next-overlay-change}, rather than
2891 @code{next-property-change}). There is no @var{object} operand
2892 because this function operates only on the current buffer. It returns
2893 the next address at which either kind of property changes.
2896 @defun previous-char-property-change pos &optional limit
2897 This is like @code{next-char-property-change}, but scans back from
2898 @var{pos} instead of forward, and returns the minimum buffer
2899 position if no change is found.
2902 @defun next-single-char-property-change pos prop &optional object limit
2903 This is like @code{next-single-property-change} except that it
2904 considers overlay properties as well as text properties, and if no
2905 change is found before the end of the @var{object}, it returns the
2906 maximum valid position in @var{object} rather than @code{nil}. Unlike
2907 @code{next-char-property-change}, this function @emph{does} have an
2908 @var{object} operand; if @var{object} is not a buffer, only
2909 text-properties are considered.
2912 @defun previous-single-char-property-change pos prop &optional object limit
2913 This is like @code{next-single-char-property-change}, but scans back
2914 from @var{pos} instead of forward, and returns the minimum valid
2915 position in @var{object} if no change is found.
2918 @defun text-property-any start end prop value &optional object
2919 This function returns non-@code{nil} if at least one character between
2920 @var{start} and @var{end} has a property @var{prop} whose value is
2921 @var{value}. More precisely, it returns the position of the first such
2922 character. Otherwise, it returns @code{nil}.
2924 The optional fifth argument, @var{object}, specifies the string or
2925 buffer to scan. Positions are relative to @var{object}. The default
2926 for @var{object} is the current buffer.
2929 @defun text-property-not-all start end prop value &optional object
2930 This function returns non-@code{nil} if at least one character between
2931 @var{start} and @var{end} does not have a property @var{prop} with value
2932 @var{value}. More precisely, it returns the position of the first such
2933 character. Otherwise, it returns @code{nil}.
2935 The optional fifth argument, @var{object}, specifies the string or
2936 buffer to scan. Positions are relative to @var{object}. The default
2937 for @var{object} is the current buffer.
2940 @node Special Properties
2941 @subsection Properties with Special Meanings
2943 Here is a table of text property names that have special built-in
2944 meanings. The following sections list a few additional special property
2945 names that control filling and property inheritance. All other names
2946 have no standard meaning, and you can use them as you like.
2949 @cindex category of text character
2950 @kindex category @r{(text property)}
2952 If a character has a @code{category} property, we call it the
2953 @dfn{category} of the character. It should be a symbol. The properties
2954 of the symbol serve as defaults for the properties of the character.
2957 @cindex face codes of text
2958 @kindex face @r{(text property)}
2959 You can use the property @code{face} to control the font and color of
2960 text. @xref{Faces}, for more information.
2962 In the simplest case, the value is a face name. It can also be a list;
2963 then each element can be any of these possibilities;
2967 A face name (a symbol or string).
2970 A property list of face attributes. This has the
2971 form (@var{keyword} @var{value} @dots{}), where each @var{keyword} is a
2972 face attribute name and @var{value} is a meaningful value for that
2973 attribute. With this feature, you do not need to create a face each
2974 time you want to specify a particular attribute for certain text.
2975 @xref{Face Attributes}.
2978 A cons cell of the form @code{(foreground-color . @var{color-name})} or
2979 @code{(background-color . @var{color-name})}. These elements specify
2980 just the foreground color or just the background color. @xref{Color
2981 Names}, for the supported forms of @var{color-name}.
2983 @code{(foreground-color . @var{color-name})} is equivalent to
2984 specifying @code{(:foreground @var{color-name})}, and likewise for the
2988 You can use Font Lock Mode (@pxref{Font Lock Mode}), to dynamically
2989 update @code{face} properties based on the contents of the text.
2991 @item font-lock-face
2992 @kindex font-lock-face @r{(text property)}
2993 The @code{font-lock-face} property is the same in all respects as the
2994 @code{face} property, but its state of activation is controlled by
2995 @code{font-lock-mode}. This can be advantageous for special buffers
2996 which are not intended to be user-editable, or for static areas of
2997 text which are always fontified in the same way.
2998 @xref{Precalculated Fontification}.
3000 Strictly speaking, @code{font-lock-face} is not a built-in text
3001 property; rather, it is implemented in Font Lock mode using
3002 @code{char-property-alias-alist}. @xref{Examining Properties}.
3004 This property is new in Emacs 22.1.
3007 @kindex mouse-face @r{(text property)}
3008 The property @code{mouse-face} is used instead of @code{face} when the
3009 mouse is on or near the character. For this purpose, ``near'' means
3010 that all text between the character and where the mouse is have the same
3011 @code{mouse-face} property value.
3014 @kindex fontified @r{(text property)}
3015 This property says whether the text has had faces assigned to it by
3016 font locking. The display engine tests it to decide whether a buffer
3017 portion needs refontifying before display. @xref{Auto Faces}. It
3018 takes one of these three values---other values are invalid:
3022 Font locking is disabled, or the @code{face} properties on the text,
3023 if any, are invalid.
3025 @item The symbol @code{defer}
3026 This value states that the text's @code{face} properties are invalid
3027 and marks it for deferred fontification. It is used only when ``just
3028 in time'' font locking is enabled.
3031 The @code{face} properties, or lack of them, on the text are currently
3036 @kindex display @r{(text property)}
3037 This property activates various features that change the
3038 way text is displayed. For example, it can make text appear taller
3039 or shorter, higher or lower, wider or narrow, or replaced with an image.
3040 @xref{Display Property}.
3043 @kindex help-echo @r{(text property)}
3045 @anchor{Text help-echo}
3046 If text has a string as its @code{help-echo} property, then when you
3047 move the mouse onto that text, Emacs displays that string in the echo
3048 area, or in the tooltip window (@pxref{Tooltips,,, emacs, The GNU Emacs
3051 If the value of the @code{help-echo} property is a function, that
3052 function is called with three arguments, @var{window}, @var{object} and
3053 @var{pos} and should return a help string or @code{nil} for
3054 none. The first argument, @var{window} is the window in which
3055 the help was found. The second, @var{object}, is the buffer, overlay or
3056 string which had the @code{help-echo} property. The @var{pos}
3057 argument is as follows:
3061 If @var{object} is a buffer, @var{pos} is the position in the buffer
3062 where the @code{help-echo} text property was found.
3064 If @var{object} is an overlay, that overlay has a @code{help-echo}
3065 property, and @var{pos} is the position in the overlay's buffer under
3068 If @var{object} is a string (an overlay string or a string displayed
3069 with the @code{display} property), @var{pos} is the position in that
3070 string under the mouse.
3073 If the value of the @code{help-echo} property is neither a function nor
3074 a string, it is evaluated to obtain a help string.
3076 You can alter the way help text is displayed by setting the variable
3077 @code{show-help-function} (@pxref{Help display}).
3079 This feature is used in the mode line and for other active text.
3082 @cindex keymap of character
3083 @kindex keymap @r{(text property)}
3084 The @code{keymap} property specifies an additional keymap for
3085 commands. The property's value for the character before point applies
3086 if it is non-@code{nil} and rear-sticky, and the property's value for
3087 the character after point applies if it is non-@code{nil} and
3088 front-sticky. (For mouse clicks, the position of the click is used
3089 instead of the position of point.) If the property value is a symbol,
3090 the symbol's function definition is used as the keymap.
3092 When this keymap applies, it is used for key lookup before the minor
3093 mode keymaps and before the buffer's local map. @xref{Active
3097 @kindex local-map @r{(text property)}
3098 This property works like @code{keymap} except that it specifies a
3099 keymap to use @emph{instead of} the buffer's local map. For most
3100 purposes (perhaps all purposes), the @code{keymap} is superior.
3103 The @code{syntax-table} property overrides what the syntax table says
3104 about this particular character. @xref{Syntax Properties}.
3107 @cindex read-only character
3108 @kindex read-only @r{(text property)}
3109 If a character has the property @code{read-only}, then modifying that
3110 character is not allowed. Any command that would do so gets an error,
3111 @code{text-read-only}. If the property value is a string, that string
3112 is used as the error message.
3114 Insertion next to a read-only character is an error if inserting
3115 ordinary text there would inherit the @code{read-only} property due to
3116 stickiness. Thus, you can control permission to insert next to
3117 read-only text by controlling the stickiness. @xref{Sticky Properties}.
3119 Since changing properties counts as modifying the buffer, it is not
3120 possible to remove a @code{read-only} property unless you know the
3121 special trick: bind @code{inhibit-read-only} to a non-@code{nil} value
3122 and then remove the property. @xref{Read Only Buffers}.
3125 @kindex invisible @r{(text property)}
3126 A non-@code{nil} @code{invisible} property can make a character invisible
3127 on the screen. @xref{Invisible Text}, for details.
3130 @kindex intangible @r{(text property)}
3131 If a group of consecutive characters have equal and non-@code{nil}
3132 @code{intangible} properties, then you cannot place point between them.
3133 If you try to move point forward into the group, point actually moves to
3134 the end of the group. If you try to move point backward into the group,
3135 point actually moves to the start of the group.
3137 When the variable @code{inhibit-point-motion-hooks} is non-@code{nil},
3138 the @code{intangible} property is ignored.
3141 @kindex field @r{(text property)}
3142 Consecutive characters with the same @code{field} property constitute a
3143 @dfn{field}. Some motion functions including @code{forward-word} and
3144 @code{beginning-of-line} stop moving at a field boundary.
3148 @kindex cursor @r{(text property)}
3149 Normally, the cursor is displayed at the end of any overlay and text
3150 property strings present at the current window position. You can
3151 place the cursor on any desired character of these strings by giving
3152 that character a non-@code{nil} @var{cursor} text property.
3155 @kindex pointer @r{(text property)}
3156 This specifies a specific pointer shape when the mouse pointer is over
3157 this text or image. @xref{Pointer Shape}, for possible pointer
3161 @kindex line-spacing @r{(text property)}
3162 A newline can have a @code{line-spacing} text or overlay property that
3163 controls the height of the display line ending with that newline. The
3164 property value overrides the default frame line spacing and the buffer
3165 local @code{line-spacing} variable. @xref{Line Height}.
3168 @kindex line-height @r{(text property)}
3169 A newline can have a @code{line-height} text or overlay property that
3170 controls the total height of the display line ending in that newline.
3173 @item modification-hooks
3174 @cindex change hooks for a character
3175 @cindex hooks for changing a character
3176 @kindex modification-hooks @r{(text property)}
3177 If a character has the property @code{modification-hooks}, then its
3178 value should be a list of functions; modifying that character calls all
3179 of those functions. Each function receives two arguments: the beginning
3180 and end of the part of the buffer being modified. Note that if a
3181 particular modification hook function appears on several characters
3182 being modified by a single primitive, you can't predict how many times
3183 the function will be called.
3185 If these functions modify the buffer, they should bind
3186 @code{inhibit-modification-hooks} to @code{t} around doing so, to
3187 avoid confusing the internal mechanism that calls these hooks.
3189 @item insert-in-front-hooks
3190 @itemx insert-behind-hooks
3191 @kindex insert-in-front-hooks @r{(text property)}
3192 @kindex insert-behind-hooks @r{(text property)}
3193 The operation of inserting text in a buffer also calls the functions
3194 listed in the @code{insert-in-front-hooks} property of the following
3195 character and in the @code{insert-behind-hooks} property of the
3196 preceding character. These functions receive two arguments, the
3197 beginning and end of the inserted text. The functions are called
3198 @emph{after} the actual insertion takes place.
3200 See also @ref{Change Hooks}, for other hooks that are called
3201 when you change text in a buffer.
3205 @cindex hooks for motion of point
3206 @kindex point-entered @r{(text property)}
3207 @kindex point-left @r{(text property)}
3208 The special properties @code{point-entered} and @code{point-left}
3209 record hook functions that report motion of point. Each time point
3210 moves, Emacs compares these two property values:
3214 the @code{point-left} property of the character after the old location,
3217 the @code{point-entered} property of the character after the new
3222 If these two values differ, each of them is called (if not @code{nil})
3223 with two arguments: the old value of point, and the new one.
3225 The same comparison is made for the characters before the old and new
3226 locations. The result may be to execute two @code{point-left} functions
3227 (which may be the same function) and/or two @code{point-entered}
3228 functions (which may be the same function). In any case, all the
3229 @code{point-left} functions are called first, followed by all the
3230 @code{point-entered} functions.
3232 It is possible with @code{char-after} to examine characters at various
3233 buffer positions without moving point to those positions. Only an
3234 actual change in the value of point runs these hook functions.
3237 @defvar inhibit-point-motion-hooks
3238 When this variable is non-@code{nil}, @code{point-left} and
3239 @code{point-entered} hooks are not run, and the @code{intangible}
3240 property has no effect. Do not set this variable globally; bind it with
3244 @defvar show-help-function
3245 @anchor{Help display} If this variable is non-@code{nil}, it specifies a
3246 function called to display help strings. These may be @code{help-echo}
3247 properties, menu help strings (@pxref{Simple Menu Items},
3248 @pxref{Extended Menu Items}), or tool bar help strings (@pxref{Tool
3249 Bar}). The specified function is called with one argument, the help
3250 string to display. Tooltip mode (@pxref{Tooltips,,, emacs, The GNU Emacs
3251 Manual}) provides an example.
3254 @node Format Properties
3255 @subsection Formatted Text Properties
3257 These text properties affect the behavior of the fill commands. They
3258 are used for representing formatted text. @xref{Filling}, and
3263 If a newline character has this property, it is a ``hard'' newline.
3264 The fill commands do not alter hard newlines and do not move words
3265 across them. However, this property takes effect only if the
3266 @code{use-hard-newlines} minor mode is enabled. @xref{Hard and Soft
3267 Newlines,, Hard and Soft Newlines, emacs, The GNU Emacs Manual}.
3270 This property specifies an extra right margin for filling this part of the
3274 This property specifies an extra left margin for filling this part of the
3278 This property specifies the style of justification for filling this part
3282 @node Sticky Properties
3283 @subsection Stickiness of Text Properties
3284 @cindex sticky text properties
3285 @cindex inheritance of text properties
3287 Self-inserting characters normally take on the same properties as the
3288 preceding character. This is called @dfn{inheritance} of properties.
3290 In a Lisp program, you can do insertion with inheritance or without,
3291 depending on your choice of insertion primitive. The ordinary text
3292 insertion functions such as @code{insert} do not inherit any properties.
3293 They insert text with precisely the properties of the string being
3294 inserted, and no others. This is correct for programs that copy text
3295 from one context to another---for example, into or out of the kill ring.
3296 To insert with inheritance, use the special primitives described in this
3297 section. Self-inserting characters inherit properties because they work
3298 using these primitives.
3300 When you do insertion with inheritance, @emph{which} properties are
3301 inherited, and from where, depends on which properties are @dfn{sticky}.
3302 Insertion after a character inherits those of its properties that are
3303 @dfn{rear-sticky}. Insertion before a character inherits those of its
3304 properties that are @dfn{front-sticky}. When both sides offer different
3305 sticky values for the same property, the previous character's value
3308 By default, a text property is rear-sticky but not front-sticky; thus,
3309 the default is to inherit all the properties of the preceding character,
3310 and nothing from the following character.
3312 You can control the stickiness of various text properties with two
3313 specific text properties, @code{front-sticky} and @code{rear-nonsticky},
3314 and with the variable @code{text-property-default-nonsticky}. You can
3315 use the variable to specify a different default for a given property.
3316 You can use those two text properties to make any specific properties
3317 sticky or nonsticky in any particular part of the text.
3319 If a character's @code{front-sticky} property is @code{t}, then all
3320 its properties are front-sticky. If the @code{front-sticky} property is
3321 a list, then the sticky properties of the character are those whose
3322 names are in the list. For example, if a character has a
3323 @code{front-sticky} property whose value is @code{(face read-only)},
3324 then insertion before the character can inherit its @code{face} property
3325 and its @code{read-only} property, but no others.
3327 The @code{rear-nonsticky} property works the opposite way. Most
3328 properties are rear-sticky by default, so the @code{rear-nonsticky}
3329 property says which properties are @emph{not} rear-sticky. If a
3330 character's @code{rear-nonsticky} property is @code{t}, then none of its
3331 properties are rear-sticky. If the @code{rear-nonsticky} property is a
3332 list, properties are rear-sticky @emph{unless} their names are in the
3335 @defvar text-property-default-nonsticky
3336 This variable holds an alist which defines the default rear-stickiness
3337 of various text properties. Each element has the form
3338 @code{(@var{property} . @var{nonstickiness})}, and it defines the
3339 stickiness of a particular text property, @var{property}.
3341 If @var{nonstickiness} is non-@code{nil}, this means that the property
3342 @var{property} is rear-nonsticky by default. Since all properties are
3343 front-nonsticky by default, this makes @var{property} nonsticky in both
3344 directions by default.
3346 The text properties @code{front-sticky} and @code{rear-nonsticky}, when
3347 used, take precedence over the default @var{nonstickiness} specified in
3348 @code{text-property-default-nonsticky}.
3351 Here are the functions that insert text with inheritance of properties:
3353 @defun insert-and-inherit &rest strings
3354 Insert the strings @var{strings}, just like the function @code{insert},
3355 but inherit any sticky properties from the adjoining text.
3358 @defun insert-before-markers-and-inherit &rest strings
3359 Insert the strings @var{strings}, just like the function
3360 @code{insert-before-markers}, but inherit any sticky properties from the
3364 @xref{Insertion}, for the ordinary insertion functions which do not
3367 @node Saving Properties
3368 @subsection Saving Text Properties in Files
3369 @cindex text properties in files
3370 @cindex saving text properties
3372 You can save text properties in files (along with the text itself),
3373 and restore the same text properties when visiting or inserting the
3374 files, using these two hooks:
3376 @defvar write-region-annotate-functions
3377 This variable's value is a list of functions for @code{write-region} to
3378 run to encode text properties in some fashion as annotations to the text
3379 being written in the file. @xref{Writing to Files}.
3381 Each function in the list is called with two arguments: the start and
3382 end of the region to be written. These functions should not alter the
3383 contents of the buffer. Instead, they should return lists indicating
3384 annotations to write in the file in addition to the text in the
3387 Each function should return a list of elements of the form
3388 @code{(@var{position} . @var{string})}, where @var{position} is an
3389 integer specifying the relative position within the text to be written,
3390 and @var{string} is the annotation to add there.
3392 Each list returned by one of these functions must be already sorted in
3393 increasing order by @var{position}. If there is more than one function,
3394 @code{write-region} merges the lists destructively into one sorted list.
3396 When @code{write-region} actually writes the text from the buffer to the
3397 file, it intermixes the specified annotations at the corresponding
3398 positions. All this takes place without modifying the buffer.
3401 @defvar after-insert-file-functions
3402 This variable holds a list of functions for @code{insert-file-contents}
3403 to call after inserting a file's contents. These functions should scan
3404 the inserted text for annotations, and convert them to the text
3405 properties they stand for.
3407 Each function receives one argument, the length of the inserted text;
3408 point indicates the start of that text. The function should scan that
3409 text for annotations, delete them, and create the text properties that
3410 the annotations specify. The function should return the updated length
3411 of the inserted text, as it stands after those changes. The value
3412 returned by one function becomes the argument to the next function.
3414 These functions should always return with point at the beginning of
3417 The intended use of @code{after-insert-file-functions} is for converting
3418 some sort of textual annotations into actual text properties. But other
3419 uses may be possible.
3422 We invite users to write Lisp programs to store and retrieve text
3423 properties in files, using these hooks, and thus to experiment with
3424 various data formats and find good ones. Eventually we hope users
3425 will produce good, general extensions we can install in Emacs.
3427 We suggest not trying to handle arbitrary Lisp objects as text property
3428 names or values---because a program that general is probably difficult
3429 to write, and slow. Instead, choose a set of possible data types that
3430 are reasonably flexible, and not too hard to encode.
3432 @xref{Format Conversion}, for a related feature.
3434 @c ??? In next edition, merge this info Format Conversion.
3436 @node Lazy Properties
3437 @subsection Lazy Computation of Text Properties
3439 Instead of computing text properties for all the text in the buffer,
3440 you can arrange to compute the text properties for parts of the text
3441 when and if something depends on them.
3443 The primitive that extracts text from the buffer along with its
3444 properties is @code{buffer-substring}. Before examining the properties,
3445 this function runs the abnormal hook @code{buffer-access-fontify-functions}.
3447 @defvar buffer-access-fontify-functions
3448 This variable holds a list of functions for computing text properties.
3449 Before @code{buffer-substring} copies the text and text properties for a
3450 portion of the buffer, it calls all the functions in this list. Each of
3451 the functions receives two arguments that specify the range of the
3452 buffer being accessed. (The buffer itself is always the current
3456 The function @code{buffer-substring-no-properties} does not call these
3457 functions, since it ignores text properties anyway.
3459 In order to prevent the hook functions from being called more than
3460 once for the same part of the buffer, you can use the variable
3461 @code{buffer-access-fontified-property}.
3463 @defvar buffer-access-fontified-property
3464 If this value's variable is non-@code{nil}, it is a symbol which is used
3465 as a text property name. A non-@code{nil} value for that text property
3466 means, ``the other text properties for this character have already been
3469 If all the characters in the range specified for @code{buffer-substring}
3470 have a non-@code{nil} value for this property, @code{buffer-substring}
3471 does not call the @code{buffer-access-fontify-functions} functions. It
3472 assumes these characters already have the right text properties, and
3473 just copies the properties they already have.
3475 The normal way to use this feature is that the
3476 @code{buffer-access-fontify-functions} functions add this property, as
3477 well as others, to the characters they operate on. That way, they avoid
3478 being called over and over for the same text.
3481 @node Clickable Text
3482 @subsection Defining Clickable Text
3483 @cindex clickable text
3485 There are two ways to set up @dfn{clickable text} in a buffer.
3486 There are typically two parts of this: to make the text highlight
3487 when the mouse is over it, and to make a mouse button do something
3488 when you click it on that part of the text.
3490 Highlighting is done with the @code{mouse-face} text property.
3491 Here is an example of how Dired does it:
3495 (if (dired-move-to-filename)
3496 (put-text-property (point)
3498 (dired-move-to-end-of-filename)
3500 'mouse-face 'highlight))
3505 The first two arguments to @code{put-text-property} specify the
3506 beginning and end of the text.
3508 The usual way to make the mouse do something when you click it
3509 on this text is to define @code{mouse-2} in the major mode's
3510 keymap. The job of checking whether the click was on clickable text
3511 is done by the command definition. Here is how Dired does it:
3514 (defun dired-mouse-find-file-other-window (event)
3515 "In dired, visit the file or directory name you click on."
3519 (set-buffer (window-buffer (posn-window (event-end event))))
3521 (goto-char (posn-point (event-end event)))
3522 (setq file (dired-get-filename))))
3523 (select-window (posn-window (event-end event)))
3524 (find-file-other-window (file-name-sans-versions file t))))
3528 The reason for the outer @code{save-excursion} construct is to avoid
3529 changing the current buffer; the reason for the inner one is to avoid
3530 permanently altering point in the buffer you click on. In this case,
3531 Dired uses the function @code{dired-get-filename} to determine which
3532 file to visit, based on the position found in the event.
3534 Instead of defining a mouse command for the major mode, you can define
3535 a key binding for the clickable text itself, using the @code{keymap}
3539 (let ((map (make-sparse-keymap)))
3540 (define-key map [mouse-2] 'operate-this-button)
3541 (put-text-property (point)
3543 (dired-move-to-end-of-filename)
3549 This method makes it possible to define different commands for various
3550 clickable pieces of text. Also, the major mode definition (or the
3551 global definition) remains available for the rest of the text in the
3554 @node Links and Mouse-1
3555 @subsection Links and Mouse-1
3556 @cindex follow links
3559 The normal Emacs command for activating text in read-only buffers is
3560 @key{Mouse-2}, which includes following textual links. However, most
3561 graphical applications use @key{Mouse-1} for following links. For
3562 compatibility, @key{Mouse-1} follows links in Emacs too, when you
3563 click on a link quickly without moving the mouse. The user can
3564 customize this behavior through the variable
3565 @code{mouse-1-click-follows-link}.
3567 To define text as a link at the Lisp level, you should bind the
3568 @code{mouse-2} event to a command to follow the link. Then, to indicate that
3569 @key{Mouse-1} should also follow the link, you should specify a
3570 @code{follow-link} condition either as a text property or as a key
3574 @item @code{follow-link} property
3575 If the clickable text has a non-@code{nil} @code{follow-link} text or overlay
3576 property, that specifies the condition.
3578 @item @code{follow-link} event
3579 If there is a binding for the @code{follow-link} event, either on the
3580 clickable text or in the local keymap, the binding is the condition.
3583 Regardless of how you set the @code{follow-link} condition, its
3584 value is used as follows to determine whether the given position is
3585 inside a link, and (if so) to compute an @dfn{action code} saying how
3586 @key{Mouse-1} should handle the link.
3589 @item @code{mouse-face}
3590 If the condition is @code{mouse-face}, a position is inside a link if
3591 there is a non-@code{nil} @code{mouse-face} property at that position.
3592 The action code is always @code{t}.
3594 For example, here is how Info mode handles @key{Mouse-1}:
3597 (define-key Info-mode-map [follow-link] 'mouse-face)
3601 If the condition is a valid function, @var{func}, then a position
3602 @var{pos} is inside a link if @code{(@var{func} @var{pos})} evaluates
3603 to non-@code{nil}. The value returned by @var{func} serves as the
3606 For example, here is how pcvs enables @key{Mouse-1} to follow links on
3610 (define-key map [follow-link]
3612 (eq (get-char-property pos 'face) 'cvs-filename-face)))
3616 If the condition value is anything else, then the position is inside a
3617 link and the condition itself is the action code. Clearly you should
3618 only specify this kind of condition on the text that constitutes a
3623 The action code tells @key{Mouse-1} how to follow the link:
3626 @item a string or vector
3627 If the action code is a string or vector, the @key{Mouse-1} event is
3628 translated into the first element of the string or vector; i.e., the
3629 action of the @key{Mouse-1} click is the local or global binding of
3630 that character or symbol. Thus, if the action code is @code{"foo"},
3631 @key{Mouse-1} translates into @kbd{f}. If it is @code{[foo]},
3632 @key{Mouse-1} translates into @key{foo}.
3635 For any other non-@code{nil} action code, the @code{mouse-1} event is
3636 translated into a @code{mouse-2} event at the same position.
3639 To define @key{Mouse-1} to activate a button defined with
3640 @code{define-button-type}, give the button a @code{follow-link}
3641 property with a value as specified above to determine how to follow
3642 the link. For example, here is how Help mode handles @key{Mouse-1}:
3645 (define-button-type 'help-xref
3647 'action #'help-button-action)
3650 To define @key{Mouse-1} on a widget defined with
3651 @code{define-widget}, give the widget a @code{:follow-link} property
3652 with a value as specified above to determine how to follow the link.
3654 For example, here is how the @code{link} widget specifies that
3655 a @key{Mouse-1} click shall be translated to @key{RET}:
3658 (define-widget 'link 'item
3660 :button-prefix 'widget-link-prefix
3661 :button-suffix 'widget-link-suffix
3663 :help-echo "Follow the link."
3667 @defun mouse-on-link-p pos
3668 This function returns non-@code{nil} if position @var{pos} in the
3669 current buffer is on a link.
3673 @subsection Defining and Using Fields
3676 A field is a range of consecutive characters in the buffer that are
3677 identified by having the same value (comparing with @code{eq}) of the
3678 @code{field} property (either a text-property or an overlay property).
3679 This section describes special functions that are available for
3680 operating on fields.
3682 You specify a field with a buffer position, @var{pos}. We think of
3683 each field as containing a range of buffer positions, so the position
3684 you specify stands for the field containing that position.
3686 When the characters before and after @var{pos} are part of the same
3687 field, there is no doubt which field contains @var{pos}: the one those
3688 characters both belong to. When @var{pos} is at a boundary between
3689 fields, which field it belongs to depends on the stickiness of the
3690 @code{field} properties of the two surrounding characters (@pxref{Sticky
3691 Properties}). The field whose property would be inherited by text
3692 inserted at @var{pos} is the field that contains @var{pos}.
3694 There is an anomalous case where newly inserted text at @var{pos}
3695 would not inherit the @code{field} property from either side. This
3696 happens if the previous character's @code{field} property is not
3697 rear-sticky, and the following character's @code{field} property is not
3698 front-sticky. In this case, @var{pos} belongs to neither the preceding
3699 field nor the following field; the field functions treat it as belonging
3700 to an empty field whose beginning and end are both at @var{pos}.
3702 In all of these functions, if @var{pos} is omitted or @code{nil}, the
3703 value of point is used by default.
3705 @defun field-beginning &optional pos escape-from-edge limit
3706 This function returns the beginning of the field specified by @var{pos}.
3708 If @var{pos} is at the beginning of its field, and
3709 @var{escape-from-edge} is non-@code{nil}, then the return value is
3710 always the beginning of the preceding field that @emph{ends} at @var{pos},
3711 regardless of the stickiness of the @code{field} properties around
3714 If @var{limit} is non-@code{nil}, it is a buffer position; if the
3715 beginning of the field is before @var{limit}, then @var{limit} will be
3719 @defun field-end &optional pos escape-from-edge limit
3720 This function returns the end of the field specified by @var{pos}.
3722 If @var{pos} is at the end of its field, and @var{escape-from-edge} is
3723 non-@code{nil}, then the return value is always the end of the following
3724 field that @emph{begins} at @var{pos}, regardless of the stickiness of
3725 the @code{field} properties around @var{pos}.
3727 If @var{limit} is non-@code{nil}, it is a buffer position; if the end
3728 of the field is after @var{limit}, then @var{limit} will be returned
3732 @defun field-string &optional pos
3733 This function returns the contents of the field specified by @var{pos},
3737 @defun field-string-no-properties &optional pos
3738 This function returns the contents of the field specified by @var{pos},
3739 as a string, discarding text properties.
3742 @defun delete-field &optional pos
3743 This function deletes the text of the field specified by @var{pos}.
3746 @defun constrain-to-field new-pos old-pos &optional escape-from-edge only-in-line inhibit-capture-property
3747 This function ``constrains'' @var{new-pos} to the field that
3748 @var{old-pos} belongs to---in other words, it returns the position
3749 closest to @var{new-pos} that is in the same field as @var{old-pos}.
3751 If @var{new-pos} is @code{nil}, then @code{constrain-to-field} uses
3752 the value of point instead, and moves point to the resulting position.
3754 If @var{old-pos} is at the boundary of two fields, then the acceptable
3755 positions for @var{new-pos} depend on the value of the optional argument
3756 @var{escape-from-edge}. If @var{escape-from-edge} is @code{nil}, then
3757 @var{new-pos} is constrained to the field that has the same @code{field}
3758 property (either a text-property or an overlay property) that new
3759 characters inserted at @var{old-pos} would get. (This depends on the
3760 stickiness of the @code{field} property for the characters before and
3761 after @var{old-pos}.) If @var{escape-from-edge} is non-@code{nil},
3762 @var{new-pos} is constrained to the union of the two adjacent fields.
3763 Additionally, if two fields are separated by another field with the
3764 special value @code{boundary}, then any point within this special field
3765 is also considered to be ``on the boundary.''
3767 If the optional argument @var{only-in-line} is non-@code{nil}, and
3768 constraining @var{new-pos} in the usual way would move it to a different
3769 line, @var{new-pos} is returned unconstrained. This used in commands
3770 that move by line, such as @code{next-line} and
3771 @code{beginning-of-line}, so that they respect field boundaries only in
3772 the case where they can still move to the right line.
3774 If the optional argument @var{inhibit-capture-property} is
3775 non-@code{nil}, and @var{old-pos} has a non-@code{nil} property of that
3776 name, then any field boundaries are ignored.
3778 You can cause @code{constrain-to-field} to ignore all field boundaries
3779 (and so never constrain anything) by binding the variable
3780 @code{inhibit-field-text-motion} to a non-@code{nil} value.
3784 @subsection Why Text Properties are not Intervals
3787 Some editors that support adding attributes to text in the buffer do
3788 so by letting the user specify ``intervals'' within the text, and adding
3789 the properties to the intervals. Those editors permit the user or the
3790 programmer to determine where individual intervals start and end. We
3791 deliberately provided a different sort of interface in Emacs Lisp to
3792 avoid certain paradoxical behavior associated with text modification.
3794 If the actual subdivision into intervals is meaningful, that means you
3795 can distinguish between a buffer that is just one interval with a
3796 certain property, and a buffer containing the same text subdivided into
3797 two intervals, both of which have that property.
3799 Suppose you take the buffer with just one interval and kill part of
3800 the text. The text remaining in the buffer is one interval, and the
3801 copy in the kill ring (and the undo list) becomes a separate interval.
3802 Then if you yank back the killed text, you get two intervals with the
3803 same properties. Thus, editing does not preserve the distinction
3804 between one interval and two.
3806 Suppose we ``fix'' this problem by coalescing the two intervals when
3807 the text is inserted. That works fine if the buffer originally was a
3808 single interval. But suppose instead that we have two adjacent
3809 intervals with the same properties, and we kill the text of one interval
3810 and yank it back. The same interval-coalescence feature that rescues
3811 the other case causes trouble in this one: after yanking, we have just
3812 one interval. One again, editing does not preserve the distinction
3813 between one interval and two.
3815 Insertion of text at the border between intervals also raises
3816 questions that have no satisfactory answer.
3818 However, it is easy to arrange for editing to behave consistently for
3819 questions of the form, ``What are the properties of this character?''
3820 So we have decided these are the only questions that make sense; we have
3821 not implemented asking questions about where intervals start or end.
3823 In practice, you can usually use the text property search functions in
3824 place of explicit interval boundaries. You can think of them as finding
3825 the boundaries of intervals, assuming that intervals are always
3826 coalesced whenever possible. @xref{Property Search}.
3828 Emacs also provides explicit intervals as a presentation feature; see
3832 @section Substituting for a Character Code
3834 The following functions replace characters within a specified region
3835 based on their character codes.
3837 @defun subst-char-in-region start end old-char new-char &optional noundo
3838 @cindex replace characters
3839 This function replaces all occurrences of the character @var{old-char}
3840 with the character @var{new-char} in the region of the current buffer
3841 defined by @var{start} and @var{end}.
3843 @cindex undo avoidance
3844 If @var{noundo} is non-@code{nil}, then @code{subst-char-in-region} does
3845 not record the change for undo and does not mark the buffer as modified.
3846 This was useful for controlling the old selective display feature
3847 (@pxref{Selective Display}).
3849 @code{subst-char-in-region} does not move point and returns
3854 ---------- Buffer: foo ----------
3855 This is the contents of the buffer before.
3856 ---------- Buffer: foo ----------
3860 (subst-char-in-region 1 20 ?i ?X)
3863 ---------- Buffer: foo ----------
3864 ThXs Xs the contents of the buffer before.
3865 ---------- Buffer: foo ----------
3870 @defun translate-region start end table
3871 This function applies a translation table to the characters in the
3872 buffer between positions @var{start} and @var{end}.
3874 The translation table @var{table} is a string or a char-table;
3875 @code{(aref @var{table} @var{ochar})} gives the translated character
3876 corresponding to @var{ochar}. If @var{table} is a string, any
3877 characters with codes larger than the length of @var{table} are not
3878 altered by the translation.
3880 The return value of @code{translate-region} is the number of
3881 characters that were actually changed by the translation. This does
3882 not count characters that were mapped into themselves in the
3890 A register is a sort of variable used in Emacs editing that can hold a
3891 variety of different kinds of values. Each register is named by a
3892 single character. All @acronym{ASCII} characters and their meta variants
3893 (but with the exception of @kbd{C-g}) can be used to name registers.
3894 Thus, there are 255 possible registers. A register is designated in
3895 Emacs Lisp by the character that is its name.
3897 @defvar register-alist
3898 This variable is an alist of elements of the form @code{(@var{name} .
3899 @var{contents})}. Normally, there is one element for each Emacs
3900 register that has been used.
3902 The object @var{name} is a character (an integer) identifying the
3906 The @var{contents} of a register can have several possible types:
3910 A number stands for itself. If @code{insert-register} finds a number
3911 in the register, it converts the number to decimal.
3914 A marker represents a buffer position to jump to.
3917 A string is text saved in the register.
3920 A rectangle is represented by a list of strings.
3922 @item @code{(@var{window-configuration} @var{position})}
3923 This represents a window configuration to restore in one frame, and a
3924 position to jump to in the current buffer.
3926 @item @code{(@var{frame-configuration} @var{position})}
3927 This represents a frame configuration to restore, and a position
3928 to jump to in the current buffer.
3930 @item (file @var{filename})
3931 This represents a file to visit; jumping to this value visits file
3934 @item (file-query @var{filename} @var{position})
3935 This represents a file to visit and a position in it; jumping to this
3936 value visits file @var{filename} and goes to buffer position
3937 @var{position}. Restoring this type of position asks the user for
3941 The functions in this section return unpredictable values unless
3944 @defun get-register reg
3945 This function returns the contents of the register
3946 @var{reg}, or @code{nil} if it has no contents.
3949 @defun set-register reg value
3950 This function sets the contents of register @var{reg} to @var{value}.
3951 A register can be set to any value, but the other register functions
3952 expect only certain data types. The return value is @var{value}.
3955 @deffn Command view-register reg
3956 This command displays what is contained in register @var{reg}.
3960 @deffn Command point-to-register reg
3961 This command stores both the current location of point and the current
3962 buffer in register @var{reg} as a marker.
3965 @deffn Command jump-to-register reg
3966 @deffnx Command register-to-point reg
3967 @comment !!SourceFile register.el
3968 This command restores the status recorded in register @var{reg}.
3970 If @var{reg} contains a marker, it moves point to the position stored in
3971 the marker. Since both the buffer and the location within the buffer
3972 are stored by the @code{point-to-register} function, this command can
3973 switch you to another buffer.
3975 If @var{reg} contains a window configuration or a frame configuration.
3976 @code{jump-to-register} restores that configuration.
3980 @deffn Command insert-register reg &optional beforep
3981 This command inserts contents of register @var{reg} into the current
3984 Normally, this command puts point before the inserted text, and the
3985 mark after it. However, if the optional second argument @var{beforep}
3986 is non-@code{nil}, it puts the mark before and point after.
3987 You can pass a non-@code{nil} second argument @var{beforep} to this
3988 function interactively by supplying any prefix argument.
3990 If the register contains a rectangle, then the rectangle is inserted
3991 with its upper left corner at point. This means that text is inserted
3992 in the current line and underneath it on successive lines.
3994 If the register contains something other than saved text (a string) or
3995 a rectangle (a list), currently useless things happen. This may be
3996 changed in the future.
4000 @deffn Command copy-to-register reg start end &optional delete-flag
4001 This command copies the region from @var{start} to @var{end} into
4002 register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes
4003 the region from the buffer after copying it into the register.
4006 @deffn Command prepend-to-register reg start end &optional delete-flag
4007 This command prepends the region from @var{start} to @var{end} into
4008 register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes
4009 the region from the buffer after copying it to the register.
4012 @deffn Command append-to-register reg start end &optional delete-flag
4013 This command appends the region from @var{start} to @var{end} to the
4014 text already in register @var{reg}. If @var{delete-flag} is
4015 non-@code{nil}, it deletes the region from the buffer after copying it
4019 @deffn Command copy-rectangle-to-register reg start end &optional delete-flag
4020 This command copies a rectangular region from @var{start} to @var{end}
4021 into register @var{reg}. If @var{delete-flag} is non-@code{nil}, it
4022 deletes the region from the buffer after copying it to the register.
4025 @deffn Command window-configuration-to-register reg
4026 This function stores the window configuration of the selected frame in
4030 @deffn Command frame-configuration-to-register reg
4031 This function stores the current frame configuration in register
4037 @section Transposition of Text
4039 This subroutine is used by the transposition commands.
4041 @defun transpose-regions start1 end1 start2 end2 &optional leave-markers
4042 This function exchanges two nonoverlapping portions of the buffer.
4043 Arguments @var{start1} and @var{end1} specify the bounds of one portion
4044 and arguments @var{start2} and @var{end2} specify the bounds of the
4047 Normally, @code{transpose-regions} relocates markers with the transposed
4048 text; a marker previously positioned within one of the two transposed
4049 portions moves along with that portion, thus remaining between the same
4050 two characters in their new position. However, if @var{leave-markers}
4051 is non-@code{nil}, @code{transpose-regions} does not do this---it leaves
4052 all markers unrelocated.
4056 @section Base 64 Encoding
4057 @cindex base 64 encoding
4059 Base 64 code is used in email to encode a sequence of 8-bit bytes as
4060 a longer sequence of @acronym{ASCII} graphic characters. It is defined in
4061 Internet RFC@footnote{
4062 An RFC, an acronym for @dfn{Request for Comments}, is a numbered
4063 Internet informational document describing a standard. RFCs are
4064 usually written by technical experts acting on their own initiative,
4065 and are traditionally written in a pragmatic, experience-driven
4067 }2045. This section describes the functions for
4068 converting to and from this code.
4070 @defun base64-encode-region beg end &optional no-line-break
4071 This function converts the region from @var{beg} to @var{end} into base
4072 64 code. It returns the length of the encoded text. An error is
4073 signaled if a character in the region is multibyte, i.e.@: in a
4074 multibyte buffer the region must contain only characters from the
4075 charsets @code{ascii}, @code{eight-bit-control} and
4076 @code{eight-bit-graphic}.
4078 Normally, this function inserts newline characters into the encoded
4079 text, to avoid overlong lines. However, if the optional argument
4080 @var{no-line-break} is non-@code{nil}, these newlines are not added, so
4081 the output is just one long line.
4084 @defun base64-encode-string string &optional no-line-break
4085 This function converts the string @var{string} into base 64 code. It
4086 returns a string containing the encoded text. As for
4087 @code{base64-encode-region}, an error is signaled if a character in the
4088 string is multibyte.
4090 Normally, this function inserts newline characters into the encoded
4091 text, to avoid overlong lines. However, if the optional argument
4092 @var{no-line-break} is non-@code{nil}, these newlines are not added, so
4093 the result string is just one long line.
4096 @defun base64-decode-region beg end
4097 This function converts the region from @var{beg} to @var{end} from base
4098 64 code into the corresponding decoded text. It returns the length of
4101 The decoding functions ignore newline characters in the encoded text.
4104 @defun base64-decode-string string
4105 This function converts the string @var{string} from base 64 code into
4106 the corresponding decoded text. It returns a unibyte string containing the
4109 The decoding functions ignore newline characters in the encoded text.
4113 @section MD5 Checksum
4114 @cindex MD5 checksum
4115 @cindex message digest computation
4117 MD5 cryptographic checksums, or @dfn{message digests}, are 128-bit
4118 ``fingerprints'' of a document or program. They are used to verify
4119 that you have an exact and unaltered copy of the data. The algorithm
4120 to calculate the MD5 message digest is defined in Internet
4122 For an explanation of what is an RFC, see the footnote in @ref{Base
4124 }1321. This section describes the Emacs facilities for computing
4127 @defun md5 object &optional start end coding-system noerror
4128 This function returns the MD5 message digest of @var{object}, which
4129 should be a buffer or a string.
4131 The two optional arguments @var{start} and @var{end} are character
4132 positions specifying the portion of @var{object} to compute the
4133 message digest for. If they are @code{nil} or omitted, the digest is
4134 computed for the whole of @var{object}.
4136 The function @code{md5} does not compute the message digest directly
4137 from the internal Emacs representation of the text (@pxref{Text
4138 Representations}). Instead, it encodes the text using a coding
4139 system, and computes the message digest from the encoded text. The
4140 optional fourth argument @var{coding-system} specifies which coding
4141 system to use for encoding the text. It should be the same coding
4142 system that you used to read the text, or that you used or will use
4143 when saving or sending the text. @xref{Coding Systems}, for more
4144 information about coding systems.
4146 If @var{coding-system} is @code{nil} or omitted, the default depends
4147 on @var{object}. If @var{object} is a buffer, the default for
4148 @var{coding-system} is whatever coding system would be chosen by
4149 default for writing this text into a file. If @var{object} is a
4150 string, the user's most preferred coding system (@pxref{Recognize
4151 Coding, prefer-coding-system, the description of
4152 @code{prefer-coding-system}, emacs, GNU Emacs Manual}) is used.
4154 Normally, @code{md5} signals an error if the text can't be encoded
4155 using the specified or chosen coding system. However, if
4156 @var{noerror} is non-@code{nil}, it silently uses @code{raw-text}
4160 @node Atomic Changes
4161 @section Atomic Change Groups
4162 @cindex atomic changes
4164 In data base terminology, an @dfn{atomic} change is an indivisible
4165 change---it can succeed entirely or it can fail entirely, but it
4166 cannot partly succeed. A Lisp program can make a series of changes to
4167 one or several buffers as an @dfn{atomic change group}, meaning that
4168 either the entire series of changes will be installed in their buffers
4169 or, in case of an error, none of them will be.
4171 To do this for one buffer, the one already current, simply write a
4172 call to @code{atomic-change-group} around the code that makes the
4176 (atomic-change-group
4178 (delete-region x y))
4182 If an error (or other nonlocal exit) occurs inside the body of
4183 @code{atomic-change-group}, it unmakes all the changes in that buffer
4184 that were during the execution of the body. This kind of change group
4185 has no effect on any other buffers---any such changes remain.
4187 If you need something more sophisticated, such as to make changes in
4188 various buffers constitute one atomic group, you must directly call
4189 lower-level functions that @code{atomic-change-group} uses.
4191 @defun prepare-change-group &optional buffer
4192 This function sets up a change group for buffer @var{buffer}, which
4193 defaults to the current buffer. It returns a ``handle'' that
4194 represents the change group. You must use this handle to activate the
4195 change group and subsequently to finish it.
4198 To use the change group, you must @dfn{activate} it. You must do
4199 this before making any changes in the text of @var{buffer}.
4201 @defun activate-change-group handle
4202 This function activates the change group that @var{handle} designates.
4205 After you activate the change group, any changes you make in that
4206 buffer become part of it. Once you have made all the desired changes
4207 in the buffer, you must @dfn{finish} the change group. There are two
4208 ways to do this: you can either accept (and finalize) all the changes,
4211 @defun accept-change-group handle
4212 This function accepts all the changes in the change group specified by
4213 @var{handle}, making them final.
4216 @defun cancel-change-group handle
4217 This function cancels and undoes all the changes in the change group
4218 specified by @var{handle}.
4221 Your code should use @code{unwind-protect} to make sure the group is
4222 always finished. The call to @code{activate-change-group} should be
4223 inside the @code{unwind-protect}, in case the user types @kbd{C-g}
4224 just after it runs. (This is one reason why
4225 @code{prepare-change-group} and @code{activate-change-group} are
4226 separate functions, because normally you would call
4227 @code{prepare-change-group} before the start of that
4228 @code{unwind-protect}.) Once you finish the group, don't use the
4229 handle again---in particular, don't try to finish the same group
4232 To make a multibuffer change group, call @code{prepare-change-group}
4233 once for each buffer you want to cover, then use @code{nconc} to
4234 combine the returned values, like this:
4237 (nconc (prepare-change-group buffer-1)
4238 (prepare-change-group buffer-2))
4241 You can then activate the multibuffer change group with a single call
4242 to @code{activate-change-group}, and finish it with a single call to
4243 @code{accept-change-group} or @code{cancel-change-group}.
4245 Nested use of several change groups for the same buffer works as you
4246 would expect. Non-nested use of change groups for the same buffer
4247 will get Emacs confused, so don't let it happen; the first change
4248 group you start for any given buffer should be the last one finished.
4251 @section Change Hooks
4252 @cindex change hooks
4253 @cindex hooks for text changes
4255 These hook variables let you arrange to take notice of all changes in
4256 all buffers (or in a particular buffer, if you make them buffer-local).
4257 See also @ref{Special Properties}, for how to detect changes to specific
4260 The functions you use in these hooks should save and restore the match
4261 data if they do anything that uses regular expressions; otherwise, they
4262 will interfere in bizarre ways with the editing operations that call
4265 @defvar before-change-functions
4266 This variable holds a list of functions to call before any buffer
4267 modification. Each function gets two arguments, the beginning and end
4268 of the region that is about to change, represented as integers. The
4269 buffer that is about to change is always the current buffer.
4272 @defvar after-change-functions
4273 This variable holds a list of functions to call after any buffer
4274 modification. Each function receives three arguments: the beginning and
4275 end of the region just changed, and the length of the text that existed
4276 before the change. All three arguments are integers. The buffer that's
4277 about to change is always the current buffer.
4279 The length of the old text is the difference between the buffer positions
4280 before and after that text as it was before the change. As for the
4281 changed text, its length is simply the difference between the first two
4285 Output of messages into the @samp{*Messages*} buffer does not
4286 call these functions.
4288 @defmac combine-after-change-calls body@dots{}
4289 The macro executes @var{body} normally, but arranges to call the
4290 after-change functions just once for a series of several changes---if
4293 If a program makes several text changes in the same area of the buffer,
4294 using the macro @code{combine-after-change-calls} around that part of
4295 the program can make it run considerably faster when after-change hooks
4296 are in use. When the after-change hooks are ultimately called, the
4297 arguments specify a portion of the buffer including all of the changes
4298 made within the @code{combine-after-change-calls} body.
4300 @strong{Warning:} You must not alter the values of
4301 @code{after-change-functions} within
4302 the body of a @code{combine-after-change-calls} form.
4304 @strong{Warning:} if the changes you combine occur in widely scattered
4305 parts of the buffer, this will still work, but it is not advisable,
4306 because it may lead to inefficient behavior for some change hook
4310 The two variables above are temporarily bound to @code{nil} during the
4311 time that any of these functions is running. This means that if one of
4312 these functions changes the buffer, that change won't run these
4313 functions. If you do want a hook function to make changes that run
4314 these functions, make it bind these variables back to their usual
4317 One inconvenient result of this protective feature is that you cannot
4318 have a function in @code{after-change-functions} or
4319 @code{before-change-functions} which changes the value of that variable.
4320 But that's not a real limitation. If you want those functions to change
4321 the list of functions to run, simply add one fixed function to the hook,
4322 and code that function to look in another variable for other functions
4323 to call. Here is an example:
4326 (setq my-own-after-change-functions nil)
4327 (defun indirect-after-change-function (beg end len)
4328 (let ((list my-own-after-change-functions))
4330 (funcall (car list) beg end len)
4331 (setq list (cdr list)))))
4334 (add-hooks 'after-change-functions
4335 'indirect-after-change-function)
4339 @defvar first-change-hook
4340 This variable is a normal hook that is run whenever a buffer is changed
4341 that was previously in the unmodified state.
4344 @defvar inhibit-modification-hooks
4345 If this variable is non-@code{nil}, all of the change hooks are
4346 disabled; none of them run. This affects all the hook variables
4347 described above in this section, as well as the hooks attached to
4348 certain special text properties (@pxref{Special Properties}) and overlay
4349 properties (@pxref{Overlay Properties}).
4353 arch-tag: 3721e738-a1cb-4085-bc1a-6cb8d8e1d32b