1 This is ../info/lispref.info, produced by makeinfo version 4.0b from
4 INFO-DIR-SECTION XEmacs Editor
6 * Lispref: (lispref). XEmacs Lisp Reference Manual.
11 GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU
12 Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid
13 Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994
14 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995
15 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp
16 Programmer's Manual (for 19.13) Third Edition, July 1995 XEmacs Lisp
17 Reference Manual (for 19.14 and 20.0) v3.1, March 1996 XEmacs Lisp
18 Reference Manual (for 19.15 and 20.1, 20.2, 20.3) v3.2, April, May,
19 November 1997 XEmacs Lisp Reference Manual (for 21.0) v3.3, April 1998
21 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software
22 Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc.
23 Copyright (C) 1995, 1996 Ben Wing.
25 Permission is granted to make and distribute verbatim copies of this
26 manual provided the copyright notice and this permission notice are
27 preserved on all copies.
29 Permission is granted to copy and distribute modified versions of
30 this manual under the conditions for verbatim copying, provided that the
31 entire resulting derived work is distributed under the terms of a
32 permission notice identical to this one.
34 Permission is granted to copy and distribute translations of this
35 manual into another language, under the above conditions for modified
36 versions, except that this permission notice may be stated in a
37 translation approved by the Foundation.
39 Permission is granted to copy and distribute modified versions of
40 this manual under the conditions for verbatim copying, provided also
41 that the section entitled "GNU General Public License" is included
42 exactly as in the original, and provided that the entire resulting
43 derived work is distributed under the terms of a permission notice
44 identical to this one.
46 Permission is granted to copy and distribute translations of this
47 manual into another language, under the above conditions for modified
48 versions, except that the section entitled "GNU General Public License"
49 may be included in a translation approved by the Free Software
50 Foundation instead of in the original English.
53 File: lispref.info, Node: Insertion, Next: Commands for Insertion, Prev: Comparing Text, Up: Text
58 "Insertion" means adding new text to a buffer. The inserted text
59 goes at point--between the character before point and the character
62 Insertion relocates markers that point at positions after the
63 insertion point, so that they stay with the surrounding text (*note
64 Markers::). When a marker points at the place of insertion, insertion
65 normally doesn't relocate the marker, so that it points to the
66 beginning of the inserted text; however, certain special functions such
67 as `insert-before-markers' relocate such markers to point after the
70 Some insertion functions leave point before the inserted text, while
71 other functions leave it after. We call the former insertion "after
72 point" and the latter insertion "before point".
74 If a string with non-`nil' extent data is inserted, the remembered
75 extents will also be inserted. *Note Duplicable Extents::.
77 Insertion functions signal an error if the current buffer is
80 These functions copy text characters from strings and buffers along
81 with their properties. The inserted characters have exactly the same
82 properties as the characters they were copied from. By contrast,
83 characters specified as separate arguments, not part of a string or
84 buffer, inherit their text properties from the neighboring text.
86 - Function: insert &rest args
87 This function inserts the strings and/or characters ARGS into the
88 current buffer, at point, moving point forward. In other words, it
89 inserts the text before point. An error is signaled unless all
90 ARGS are either strings or characters. The value is `nil'.
92 - Function: insert-before-markers &rest args
93 This function inserts the strings and/or characters ARGS into the
94 current buffer, at point, moving point forward. An error is
95 signaled unless all ARGS are either strings or characters. The
98 This function is unlike the other insertion functions in that it
99 relocates markers initially pointing at the insertion point, to
100 point after the inserted text.
102 - Function: insert-string string &optional buffer
103 This function inserts STRING into BUFFER before point. BUFFER
104 defaults to the current buffer if omitted. This function is
105 chiefly useful if you want to insert a string in a buffer other
106 than the current one (otherwise you could just use `insert').
108 - Function: insert-char character &optional count ignored buffer
109 This function inserts COUNT instances of CHARACTER into BUFFER
110 before point. COUNT must be a number, and CHARACTER must be a
113 If optional argument BUFFER is `nil', the current buffer is
114 assumed. (In FSF Emacs, the third argument is called INHERIT and
115 refers to text properties. In XEmacs, it is always ignored.)
117 This function always returns `nil'.
119 - Function: insert-buffer-substring from-buffer-or-name &optional
121 This function inserts a portion of buffer FROM-BUFFER-OR-NAME
122 (which must already exist) into the current buffer before point.
123 The text inserted is the region from START and END. (These
124 arguments default to the beginning and end of the accessible
125 portion of that buffer.) This function returns `nil'.
127 In this example, the form is executed with buffer `bar' as the
128 current buffer. We assume that buffer `bar' is initially empty.
130 ---------- Buffer: foo ----------
131 We hold these truths to be self-evident, that all
132 ---------- Buffer: foo ----------
134 (insert-buffer-substring "foo" 1 20)
137 ---------- Buffer: bar ----------
138 We hold these truth-!-
139 ---------- Buffer: bar ----------
142 File: lispref.info, Node: Commands for Insertion, Next: Deletion, Prev: Insertion, Up: Text
144 User-Level Insertion Commands
145 =============================
147 This section describes higher-level commands for inserting text,
148 commands intended primarily for the user but useful also in Lisp
151 - Command: insert-buffer from-buffer-or-name
152 This command inserts the entire contents of FROM-BUFFER-OR-NAME
153 (which must exist) into the current buffer after point. It leaves
154 the mark after the inserted text. The value is `nil'.
156 - Command: self-insert-command count
157 This command inserts the last character typed; it does so COUNT
158 times, before point, and returns `nil'. Most printing characters
159 are bound to this command. In routine use, `self-insert-command'
160 is the most frequently called function in XEmacs, but programs
161 rarely use it except to install it on a keymap.
163 In an interactive call, COUNT is the numeric prefix argument.
165 This command calls `auto-fill-function' whenever that is non-`nil'
166 and the character inserted is a space or a newline (*note Auto
169 This command performs abbrev expansion if Abbrev mode is enabled
170 and the inserted character does not have word-constituent syntax.
171 (*Note Abbrevs::, and *Note Syntax Class Table::.)
173 This is also responsible for calling `blink-paren-function' when
174 the inserted character has close parenthesis syntax (*note
177 - Command: newline &optional count
178 This command inserts newlines into the current buffer before point.
179 If COUNT is supplied, that many newline characters are inserted.
181 This function calls `auto-fill-function' if the current column
182 number is greater than the value of `fill-column' and COUNT is
183 `nil'. Typically what `auto-fill-function' does is insert a
184 newline; thus, the overall result in this case is to insert two
185 newlines at different places: one at point, and another earlier in
186 the line. `newline' does not auto-fill if COUNT is non-`nil'.
188 This command indents to the left margin if that is not zero.
191 The value returned is `nil'. In an interactive call, COUNT is the
192 numeric prefix argument.
194 - Command: split-line
195 This command splits the current line, moving the portion of the
196 line after point down vertically so that it is on the next line
197 directly below where it was before. Whitespace is inserted as
198 needed at the beginning of the lower line, using the `indent-to'
199 function. `split-line' returns the position of point.
201 Programs hardly ever use this function.
203 - Variable: overwrite-mode
204 This variable controls whether overwrite mode is in effect: a
205 non-`nil' value enables the mode. It is automatically made
206 buffer-local when set in any fashion.
209 File: lispref.info, Node: Deletion, Next: User-Level Deletion, Prev: Commands for Insertion, Up: Text
214 Deletion means removing part of the text in a buffer, without saving
215 it in the kill ring (*note The Kill Ring::). Deleted text can't be
216 yanked, but can be reinserted using the undo mechanism (*note Undo::).
217 Some deletion functions do save text in the kill ring in some special
220 All of the deletion functions operate on the current buffer, and all
221 return a value of `nil'.
223 - Command: erase-buffer &optional buffer
224 This function deletes the entire text of BUFFER, leaving it empty.
225 If the buffer is read-only, it signals a `buffer-read-only'
226 error. Otherwise, it deletes the text without asking for any
227 confirmation. It returns `nil'. BUFFER defaults to the current
230 Normally, deleting a large amount of text from a buffer inhibits
231 further auto-saving of that buffer "because it has shrunk".
232 However, `erase-buffer' does not do this, the idea being that the
233 future text is not really related to the former text, and its size
234 should not be compared with that of the former text.
236 - Command: delete-region start end &optional buffer
237 This command deletes the text in BUFFER in the region defined by
238 START and END. The value is `nil'. If optional argument BUFFER
239 is `nil', the current buffer is assumed.
241 - Command: delete-char &optional count killp
242 This command deletes COUNT characters directly after point, or
243 before point if COUNT is negative. COUNT defaults to `1'. If
244 KILLP is non-`nil', then it saves the deleted characters in the
247 In an interactive call, COUNT is the numeric prefix argument, and
248 KILLP is the unprocessed prefix argument. Therefore, if a prefix
249 argument is supplied, the text is saved in the kill ring. If no
250 prefix argument is supplied, then one character is deleted, but
251 not saved in the kill ring.
253 The value returned is always `nil'.
255 - Command: delete-backward-char &optional count killp
256 This command deletes COUNT characters directly before point, or
257 after point if COUNT is negative. COUNT defaults to 1. If KILLP
258 is non-`nil', then it saves the deleted characters in the kill
261 In an interactive call, COUNT is the numeric prefix argument, and
262 KILLP is the unprocessed prefix argument. Therefore, if a prefix
263 argument is supplied, the text is saved in the kill ring. If no
264 prefix argument is supplied, then one character is deleted, but
265 not saved in the kill ring.
267 The value returned is always `nil'.
269 - Command: backward-delete-char-untabify count &optional killp
270 This command deletes COUNT characters backward, changing tabs into
271 spaces. When the next character to be deleted is a tab, it is
272 first replaced with the proper number of spaces to preserve
273 alignment and then one of those spaces is deleted instead of the
274 tab. If KILLP is non-`nil', then the command saves the deleted
275 characters in the kill ring.
277 Conversion of tabs to spaces happens only if COUNT is positive.
278 If it is negative, exactly -COUNT characters after point are
281 In an interactive call, COUNT is the numeric prefix argument, and
282 KILLP is the unprocessed prefix argument. Therefore, if a prefix
283 argument is supplied, the text is saved in the kill ring. If no
284 prefix argument is supplied, then one character is deleted, but
285 not saved in the kill ring.
287 The value returned is always `nil'.
290 File: lispref.info, Node: User-Level Deletion, Next: The Kill Ring, Prev: Deletion, Up: Text
292 User-Level Deletion Commands
293 ============================
295 This section describes higher-level commands for deleting text,
296 commands intended primarily for the user but useful also in Lisp
299 - Command: delete-horizontal-space
300 This function deletes all spaces and tabs around point. It returns
303 In the following examples, we call `delete-horizontal-space' four
304 times, once on each line, with point between the second and third
305 characters on the line each time.
307 ---------- Buffer: foo ----------
312 ---------- Buffer: foo ----------
314 (delete-horizontal-space) ; Four times.
317 ---------- Buffer: foo ----------
322 ---------- Buffer: foo ----------
324 - Command: delete-indentation &optional join-following-p
325 This function joins the line point is on to the previous line,
326 deleting any whitespace at the join and in some cases replacing it
327 with one space. If JOIN-FOLLOWING-P is non-`nil',
328 `delete-indentation' joins this line to the following line
329 instead. The value is `nil'.
331 If there is a fill prefix, and the second of the lines being joined
332 starts with the prefix, then `delete-indentation' deletes the fill
333 prefix before joining the lines. *Note Margins::.
335 In the example below, point is located on the line starting
336 `events', and it makes no difference if there are trailing spaces
337 in the preceding line.
339 ---------- Buffer: foo ----------
340 When in the course of human
341 -!- events, it becomes necessary
342 ---------- Buffer: foo ----------
347 ---------- Buffer: foo ----------
348 When in the course of human-!- events, it becomes necessary
349 ---------- Buffer: foo ----------
351 After the lines are joined, the function `fixup-whitespace' is
352 responsible for deciding whether to leave a space at the junction.
354 - Command: fixup-whitespace
355 This function replaces all the white space surrounding point with
356 either one space or no space, according to the context. It
359 At the beginning or end of a line, the appropriate amount of space
360 is none. Before a character with close parenthesis syntax, or
361 after a character with open parenthesis or expression-prefix
362 syntax, no space is also appropriate. Otherwise, one space is
363 appropriate. *Note Syntax Class Table::.
365 In the example below, `fixup-whitespace' is called the first time
366 with point before the word `spaces' in the first line. For the
367 second invocation, point is directly after the `('.
369 ---------- Buffer: foo ----------
370 This has too many -!-spaces
371 This has too many spaces at the start of (-!- this list)
372 ---------- Buffer: foo ----------
379 ---------- Buffer: foo ----------
380 This has too many spaces
381 This has too many spaces at the start of (this list)
382 ---------- Buffer: foo ----------
384 - Command: just-one-space
385 This command replaces any spaces and tabs around point with a
386 single space. It returns `nil'.
388 - Command: delete-blank-lines
389 This function deletes blank lines surrounding point. If point is
390 on a blank line with one or more blank lines before or after it,
391 then all but one of them are deleted. If point is on an isolated
392 blank line, then it is deleted. If point is on a nonblank line,
393 the command deletes all blank lines following it.
395 A blank line is defined as a line containing only tabs and spaces.
397 `delete-blank-lines' returns `nil'.
400 File: lispref.info, Node: The Kill Ring, Next: Undo, Prev: User-Level Deletion, Up: Text
405 "Kill" functions delete text like the deletion functions, but save
406 it so that the user can reinsert it by "yanking". Most of these
407 functions have `kill-' in their name. By contrast, the functions whose
408 names start with `delete-' normally do not save text for yanking
409 (though they can still be undone); these are "deletion" functions.
411 Most of the kill commands are primarily for interactive use, and are
412 not described here. What we do describe are the functions provided for
413 use in writing such commands. You can use these functions to write
414 commands for killing text. When you need to delete text for internal
415 purposes within a Lisp function, you should normally use deletion
416 functions, so as not to disturb the kill ring contents. *Note
419 Killed text is saved for later yanking in the "kill ring". This is
420 a list that holds a number of recent kills, not just the last text
421 kill. We call this a "ring" because yanking treats it as having
422 elements in a cyclic order. The list is kept in the variable
423 `kill-ring', and can be operated on with the usual functions for lists;
424 there are also specialized functions, described in this section, that
427 Some people think this use of the word "kill" is unfortunate, since
428 it refers to operations that specifically _do not_ destroy the entities
429 "killed". This is in sharp contrast to ordinary life, in which death
430 is permanent and "killed" entities do not come back to life.
431 Therefore, other metaphors have been proposed. For example, the term
432 "cut ring" makes sense to people who, in pre-computer days, used
433 scissors and paste to cut up and rearrange manuscripts. However, it
434 would be difficult to change the terminology now.
438 * Kill Ring Concepts:: What text looks like in the kill ring.
439 * Kill Functions:: Functions that kill text.
440 * Yank Commands:: Commands that access the kill ring.
441 * Low-Level Kill Ring:: Functions and variables for kill ring access.
442 * Internals of Kill Ring:: Variables that hold kill-ring data.
445 File: lispref.info, Node: Kill Ring Concepts, Next: Kill Functions, Up: The Kill Ring
450 The kill ring records killed text as strings in a list, most recent
451 first. A short kill ring, for example, might look like this:
453 ("some text" "a different piece of text" "even older text")
455 When the list reaches `kill-ring-max' entries in length, adding a new
456 entry automatically deletes the last entry.
458 When kill commands are interwoven with other commands, each kill
459 command makes a new entry in the kill ring. Multiple kill commands in
460 succession build up a single entry in the kill ring, which would be
461 yanked as a unit; the second and subsequent consecutive kill commands
462 add text to the entry made by the first one.
464 For yanking, one entry in the kill ring is designated the "front" of
465 the ring. Some yank commands "rotate" the ring by designating a
466 different element as the "front." But this virtual rotation doesn't
467 change the list itself--the most recent entry always comes first in the
471 File: lispref.info, Node: Kill Functions, Next: Yank Commands, Prev: Kill Ring Concepts, Up: The Kill Ring
473 Functions for Killing
474 ---------------------
476 `kill-region' is the usual subroutine for killing text. Any command
477 that calls this function is a "kill command" (and should probably have
478 `kill' in its name). `kill-region' puts the newly killed text in a new
479 element at the beginning of the kill ring or adds it to the most recent
480 element. It uses the `last-command' variable to determine whether the
481 previous command was a kill command, and if so appends the killed text
482 to the most recent entry.
484 - Command: kill-region start end &optional verbose
485 This function kills the text in the region defined by START and
486 END. The text is deleted but saved in the kill ring, along with
487 its text properties. The value is always `nil'.
489 In an interactive call, START and END are point and the mark.
491 If the buffer is read-only, `kill-region' modifies the kill ring
492 just the same, then signals an error without modifying the buffer.
493 This is convenient because it lets the user use all the kill
494 commands to copy text into the kill ring from a read-only buffer.
496 - Command: copy-region-as-kill start end
497 This command saves the region defined by START and END on the kill
498 ring (including text properties), but does not delete the text
499 from the buffer. It returns `nil'. It also indicates the extent
500 of the text copied by moving the cursor momentarily, or by
501 displaying a message in the echo area.
503 The command does not set `this-command' to `kill-region', so a
504 subsequent kill command does not append to the same kill ring
507 Don't call `copy-region-as-kill' in Lisp programs unless you aim to
508 support Emacs 18. For Emacs 19, it is better to use `kill-new' or
509 `kill-append' instead. *Note Low-Level Kill Ring::.
512 File: lispref.info, Node: Yank Commands, Next: Low-Level Kill Ring, Prev: Kill Functions, Up: The Kill Ring
514 Functions for Yanking
515 ---------------------
517 "Yanking" means reinserting an entry of previously killed text from
518 the kill ring. The text properties are copied too.
520 - Command: yank &optional arg
521 This command inserts before point the text in the first entry in
522 the kill ring. It positions the mark at the beginning of that
523 text, and point at the end.
525 If ARG is a list (which occurs interactively when the user types
526 `C-u' with no digits), then `yank' inserts the text as described
527 above, but puts point before the yanked text and puts the mark
530 If ARG is a number, then `yank' inserts the ARGth most recently
531 killed text--the ARGth element of the kill ring list.
533 `yank' does not alter the contents of the kill ring or rotate it.
536 - Command: yank-pop arg
537 This command replaces the just-yanked entry from the kill ring
538 with a different entry from the kill ring.
540 This is allowed only immediately after a `yank' or another
541 `yank-pop'. At such a time, the region contains text that was just
542 inserted by yanking. `yank-pop' deletes that text and inserts in
543 its place a different piece of killed text. It does not add the
544 deleted text to the kill ring, since it is already in the kill
547 If ARG is `nil', then the replacement text is the previous element
548 of the kill ring. If ARG is numeric, the replacement is the ARGth
549 previous kill. If ARG is negative, a more recent kill is the
552 The sequence of kills in the kill ring wraps around, so that after
553 the oldest one comes the newest one, and before the newest one
556 The value is always `nil'.
559 File: lispref.info, Node: Low-Level Kill Ring, Next: Internals of Kill Ring, Prev: Yank Commands, Up: The Kill Ring
564 These functions and variables provide access to the kill ring at a
565 lower level, but still convenient for use in Lisp programs. They take
566 care of interaction with X Window selections. They do not exist in
569 - Function: current-kill count &optional do-not-move
570 The function `current-kill' rotates the yanking pointer which
571 designates the "front" of the kill ring by COUNT places (from newer
572 kills to older ones), and returns the text at that place in the
575 If the optional second argument DO-NOT-MOVE is non-`nil', then
576 `current-kill' doesn't alter the yanking pointer; it just returns
577 the COUNTth kill, counting from the current yanking pointer.
579 If COUNT is zero, indicating a request for the latest kill,
580 `current-kill' calls the value of `interprogram-paste-function'
581 (documented below) before consulting the kill ring.
583 - Function: kill-new string &optional replace
584 This function makes the text STRING the latest entry in the kill
585 ring, and sets `kill-ring-yank-pointer' to point to it.
587 Normally, STRING is added to the front of the kill ring as a new
588 entry. However, if optional argument REPLACE is non-`nil', the
589 entry previously at the front of the kill ring is discarded, and
592 This function runs the functions on `kill-hooks', and also invokes
593 the value of `interprogram-cut-function' (see below).
595 - Function: kill-append string before-p
596 This function appends the text STRING to the first entry in the
597 kill ring. Normally STRING goes at the end of the entry, but if
598 BEFORE-P is non-`nil', it goes at the beginning. This function
599 also invokes the value of `interprogram-cut-function' (see below).
601 - Variable: interprogram-paste-function
602 This variable provides a way of transferring killed text from other
603 programs, when you are using a window system. Its value should be
604 `nil' or a function of no arguments.
606 If the value is a function, `current-kill' calls it to get the
607 "most recent kill". If the function returns a non-`nil' value,
608 then that value is used as the "most recent kill". If it returns
609 `nil', then the first element of `kill-ring' is used.
611 The normal use of this hook is to get the X server's primary
612 selection as the most recent kill, even if the selection belongs
613 to another X client. *Note X Selections::.
615 - Variable: interprogram-cut-function
616 This variable provides a way of communicating killed text to other
617 programs, when you are using a window system. Its value should be
618 `nil' or a function of one argument.
620 If the value is a function, `kill-new' and `kill-append' call it
621 with the new first element of the kill ring as an argument.
623 The normal use of this hook is to set the X server's primary
624 selection to the newly killed text.
627 File: lispref.info, Node: Internals of Kill Ring, Prev: Low-Level Kill Ring, Up: The Kill Ring
629 Internals of the Kill Ring
630 --------------------------
632 The variable `kill-ring' holds the kill ring contents, in the form
633 of a list of strings. The most recent kill is always at the front of
636 The `kill-ring-yank-pointer' variable points to a link in the kill
637 ring list, whose CAR is the text to yank next. We say it identifies
638 the "front" of the ring. Moving `kill-ring-yank-pointer' to a
639 different link is called "rotating the kill ring". We call the kill
640 ring a "ring" because the functions that move the yank pointer wrap
641 around from the end of the list to the beginning, or vice-versa.
642 Rotation of the kill ring is virtual; it does not change the value of
645 Both `kill-ring' and `kill-ring-yank-pointer' are Lisp variables
646 whose values are normally lists. The word "pointer" in the name of the
647 `kill-ring-yank-pointer' indicates that the variable's purpose is to
648 identify one element of the list for use by the next yank command.
650 The value of `kill-ring-yank-pointer' is always `eq' to one of the
651 links in the kill ring list. The element it identifies is the CAR of
652 that link. Kill commands, which change the kill ring, also set this
653 variable to the value of `kill-ring'. The effect is to rotate the ring
654 so that the newly killed text is at the front.
656 Here is a diagram that shows the variable `kill-ring-yank-pointer'
657 pointing to the second entry in the kill ring `("some text" "a
658 different piece of text" "yet older text")'.
660 kill-ring kill-ring-yank-pointer
662 | ___ ___ ---> ___ ___ ___ ___
663 --> |___|___|------> |___|___|--> |___|___|--> nil
666 | | -->"yet older text"
668 | --> "a different piece of text"
672 This state of affairs might occur after `C-y' (`yank') immediately
673 followed by `M-y' (`yank-pop').
675 - Variable: kill-ring
676 This variable holds the list of killed text sequences, most
677 recently killed first.
679 - Variable: kill-ring-yank-pointer
680 This variable's value indicates which element of the kill ring is
681 at the "front" of the ring for yanking. More precisely, the value
682 is a tail of the value of `kill-ring', and its CAR is the kill
683 string that `C-y' should yank.
685 - User Option: kill-ring-max
686 The value of this variable is the maximum length to which the kill
687 ring can grow, before elements are thrown away at the end. The
688 default value for `kill-ring-max' is 30.
691 File: lispref.info, Node: Undo, Next: Maintaining Undo, Prev: The Kill Ring, Up: Text
696 Most buffers have an "undo list", which records all changes made to
697 the buffer's text so that they can be undone. (The buffers that don't
698 have one are usually special-purpose buffers for which XEmacs assumes
699 that undoing is not useful.) All the primitives that modify the text
700 in the buffer automatically add elements to the front of the undo list,
701 which is in the variable `buffer-undo-list'.
703 - Variable: buffer-undo-list
704 This variable's value is the undo list of the current buffer. A
705 value of `t' disables the recording of undo information.
707 Here are the kinds of elements an undo list can have:
710 This kind of element records a previous value of point. Ordinary
711 cursor motion does not get any sort of undo record, but deletion
712 commands use these entries to record where point was before the
716 This kind of element indicates how to delete text that was
717 inserted. Upon insertion, the text occupied the range START-END
721 This kind of element indicates how to reinsert text that was
722 deleted. The deleted text itself is the string TEXT. The place to
723 reinsert it is `(abs POSITION)'.
726 This kind of element indicates that an unmodified buffer became
727 modified. The elements HIGH and LOW are two integers, each
728 recording 16 bits of the visited file's modification time as of
729 when it was previously visited or saved. `primitive-undo' uses
730 those values to determine whether to mark the buffer as unmodified
731 once again; it does so only if the file's modification time
732 matches those numbers.
734 `(nil PROPERTY VALUE START . END)'
735 This kind of element records a change in a text property. Here's
736 how you might undo the change:
738 (put-text-property START END PROPERTY VALUE)
741 This element indicates where point was at an earlier time.
742 Undoing this element sets point to POSITION. Deletion normally
743 creates an element of this kind as well as a reinsertion element.
746 This element is a boundary. The elements between two boundaries
747 are called a "change group"; normally, each change group
748 corresponds to one keyboard command, and undo commands normally
749 undo an entire group as a unit.
751 - Function: undo-boundary
752 This function places a boundary element in the undo list. The undo
753 command stops at such a boundary, and successive undo commands undo
754 to earlier and earlier boundaries. This function returns `nil'.
756 The editor command loop automatically creates an undo boundary
757 before each key sequence is executed. Thus, each undo normally
758 undoes the effects of one command. Self-inserting input
759 characters are an exception. The command loop makes a boundary
760 for the first such character; the next 19 consecutive
761 self-inserting input characters do not make boundaries, and then
762 the 20th does, and so on as long as self-inserting characters
765 All buffer modifications add a boundary whenever the previous
766 undoable change was made in some other buffer. This way, a
767 command that modifies several buffers makes a boundary in each
770 Calling this function explicitly is useful for splitting the
771 effects of a command into more than one unit. For example,
772 `query-replace' calls `undo-boundary' after each replacement, so
773 that the user can undo individual replacements one by one.
775 - Function: primitive-undo count list
776 This is the basic function for undoing elements of an undo list.
777 It undoes the first COUNT elements of LIST, returning the rest of
778 LIST. You could write this function in Lisp, but it is convenient
781 `primitive-undo' adds elements to the buffer's undo list when it
782 changes the buffer. Undo commands avoid confusion by saving the
783 undo list value at the beginning of a sequence of undo operations.
784 Then the undo operations use and update the saved value. The new
785 elements added by undoing are not part of this saved value, so
786 they don't interfere with continuing to undo.
789 File: lispref.info, Node: Maintaining Undo, Next: Filling, Prev: Undo, Up: Text
791 Maintaining Undo Lists
792 ======================
794 This section describes how to enable and disable undo information for
795 a given buffer. It also explains how the undo list is truncated
796 automatically so it doesn't get too big.
798 Recording of undo information in a newly created buffer is normally
799 enabled to start with; but if the buffer name starts with a space, the
800 undo recording is initially disabled. You can explicitly enable or
801 disable undo recording with the following two functions, or by setting
802 `buffer-undo-list' yourself.
804 - Command: buffer-enable-undo &optional buffer-or-name
805 This command enables recording undo information for buffer
806 BUFFER-OR-NAME, so that subsequent changes can be undone. If no
807 argument is supplied, then the current buffer is used. This
808 function does nothing if undo recording is already enabled in the
809 buffer. It returns `nil'.
811 In an interactive call, BUFFER-OR-NAME is the current buffer. You
812 cannot specify any other buffer.
814 - Command: buffer-disable-undo &optional buffer
815 - Command: buffer-flush-undo &optional buffer
816 This function discards the undo list of BUFFER, and disables
817 further recording of undo information. As a result, it is no
818 longer possible to undo either previous changes or any subsequent
819 changes. If the undo list of BUFFER is already disabled, this
820 function has no effect.
822 This function returns `nil'. It cannot be called interactively.
824 The name `buffer-flush-undo' is not considered obsolete, but the
825 preferred name `buffer-disable-undo' is new as of Emacs versions
828 As editing continues, undo lists get longer and longer. To prevent
829 them from using up all available memory space, garbage collection trims
830 them back to size limits you can set. (For this purpose, the "size" of
831 an undo list measures the cons cells that make up the list, plus the
832 strings of deleted text.) Two variables control the range of acceptable
833 sizes: `undo-limit' and `undo-strong-limit'.
835 - Variable: undo-limit
836 This is the soft limit for the acceptable size of an undo list.
837 The change group at which this size is exceeded is the last one
840 - Variable: undo-strong-limit
841 This is the upper limit for the acceptable size of an undo list.
842 The change group at which this size is exceeded is discarded
843 itself (along with all older change groups). There is one
844 exception: the very latest change group is never discarded no
845 matter how big it is.
848 File: lispref.info, Node: Filling, Next: Margins, Prev: Maintaining Undo, Up: Text
853 "Filling" means adjusting the lengths of lines (by moving the line
854 breaks) so that they are nearly (but no greater than) a specified
855 maximum width. Additionally, lines can be "justified", which means
856 inserting spaces to make the left and/or right margins line up
857 precisely. The width is controlled by the variable `fill-column'. For
858 ease of reading, lines should be no longer than 70 or so columns.
860 You can use Auto Fill mode (*note Auto Filling::) to fill text
861 automatically as you insert it, but changes to existing text may leave
862 it improperly filled. Then you must fill the text explicitly.
864 Most of the commands in this section return values that are not
865 meaningful. All the functions that do filling take note of the current
866 left margin, current right margin, and current justification style
867 (*note Margins::). If the current justification style is `none', the
868 filling functions don't actually do anything.
870 Several of the filling functions have an argument JUSTIFY. If it is
871 non-`nil', that requests some kind of justification. It can be `left',
872 `right', `full', or `center', to request a specific style of
873 justification. If it is `t', that means to use the current
874 justification style for this part of the text (see
875 `current-justification', below).
877 When you call the filling functions interactively, using a prefix
878 argument implies the value `full' for JUSTIFY.
880 - Command: fill-paragraph justify
881 This command fills the paragraph at or after point. If JUSTIFY is
882 non-`nil', each line is justified as well. It uses the ordinary
883 paragraph motion commands to find paragraph boundaries. *Note
884 Paragraphs: (xemacs)Paragraphs.
886 - Command: fill-region start end &optional justify
887 This command fills each of the paragraphs in the region from START
888 to END. It justifies as well if JUSTIFY is non-`nil'.
890 The variable `paragraph-separate' controls how to distinguish
891 paragraphs. *Note Standard Regexps::.
893 - Command: fill-individual-paragraphs start end &optional justify
895 This command fills each paragraph in the region according to its
896 individual fill prefix. Thus, if the lines of a paragraph were
897 indented with spaces, the filled paragraph will remain indented in
900 The first two arguments, START and END, are the beginning and end
901 of the region to be filled. The third and fourth arguments,
902 JUSTIFY and MAIL-FLAG, are optional. If JUSTIFY is non-`nil', the
903 paragraphs are justified as well as filled. If MAIL-FLAG is
904 non-`nil', it means the function is operating on a mail message
905 and therefore should not fill the header lines.
907 Ordinarily, `fill-individual-paragraphs' regards each change in
908 indentation as starting a new paragraph. If
909 `fill-individual-varying-indent' is non-`nil', then only separator
910 lines separate paragraphs. That mode can handle indented
911 paragraphs with additional indentation on the first line.
913 - User Option: fill-individual-varying-indent
914 This variable alters the action of `fill-individual-paragraphs' as
917 - Command: fill-region-as-paragraph start end &optional justify
918 This command considers a region of text as a paragraph and fills
919 it. If the region was made up of many paragraphs, the blank lines
920 between paragraphs are removed. This function justifies as well
921 as filling when JUSTIFY is non-`nil'.
923 In an interactive call, any prefix argument requests justification.
925 In Adaptive Fill mode, which is enabled by default,
926 `fill-region-as-paragraph' on an indented paragraph when there is
927 no fill prefix uses the indentation of the second line of the
928 paragraph as the fill prefix.
930 - Command: justify-current-line how eop nosqueeze
931 This command inserts spaces between the words of the current line
932 so that the line ends exactly at `fill-column'. It returns `nil'.
934 The argument HOW, if non-`nil' specifies explicitly the style of
935 justification. It can be `left', `right', `full', `center', or
936 `none'. If it is `t', that means to do follow specified
937 justification style (see `current-justification', below). `nil'
938 means to do full justification.
940 If EOP is non-`nil', that means do left-justification when
941 `current-justification' specifies full justification. This is used
942 for the last line of a paragraph; even if the paragraph as a whole
943 is fully justified, the last line should not be.
945 If NOSQUEEZE is non-`nil', that means do not change interior
948 - User Option: default-justification
949 This variable's value specifies the style of justification to use
950 for text that doesn't specify a style with a text property. The
951 possible values are `left', `right', `full', `center', or `none'.
952 The default value is `left'.
954 - Function: current-justification
955 This function returns the proper justification style to use for
956 filling the text around point.
958 - Variable: fill-paragraph-function
959 This variable provides a way for major modes to override the
960 filling of paragraphs. If the value is non-`nil',
961 `fill-paragraph' calls this function to do the work. If the
962 function returns a non-`nil' value, `fill-paragraph' assumes the
963 job is done, and immediately returns that value.
965 The usual use of this feature is to fill comments in programming
966 language modes. If the function needs to fill a paragraph in the
967 usual way, it can do so as follows:
969 (let ((fill-paragraph-function nil))
970 (fill-paragraph arg))
972 - Variable: use-hard-newlines
973 If this variable is non-`nil', the filling functions do not delete
974 newlines that have the `hard' text property. These "hard
975 newlines" act as paragraph separators.
978 File: lispref.info, Node: Margins, Next: Auto Filling, Prev: Filling, Up: Text
983 - User Option: fill-prefix
984 This variable specifies a string of text that appears at the
985 beginning of normal text lines and should be disregarded when
986 filling them. Any line that fails to start with the fill prefix
987 is considered the start of a paragraph; so is any line that starts
988 with the fill prefix followed by additional whitespace. Lines
989 that start with the fill prefix but no additional whitespace are
990 ordinary text lines that can be filled together. The resulting
991 filled lines also start with the fill prefix.
993 The fill prefix follows the left margin whitespace, if any.
995 - User Option: fill-column
996 This buffer-local variable specifies the maximum width of filled
997 lines. Its value should be an integer, which is a number of
998 columns. All the filling, justification and centering commands
999 are affected by this variable, including Auto Fill mode (*note
1002 As a practical matter, if you are writing text for other people to
1003 read, you should set `fill-column' to no more than 70. Otherwise
1004 the line will be too long for people to read comfortably, and this
1005 can make the text seem clumsy.
1007 - Variable: default-fill-column
1008 The value of this variable is the default value for `fill-column'
1009 in buffers that do not override it. This is the same as
1010 `(default-value 'fill-column)'.
1012 The default value for `default-fill-column' is 70.
1014 - Command: set-left-margin from to margin
1015 This sets the `left-margin' property on the text from FROM to TO
1016 to the value MARGIN. If Auto Fill mode is enabled, this command
1017 also refills the region to fit the new margin.
1019 - Command: set-right-margin from to margin
1020 This sets the `right-margin' property on the text from FROM to TO
1021 to the value MARGIN. If Auto Fill mode is enabled, this command
1022 also refills the region to fit the new margin.
1024 - Function: current-left-margin
1025 This function returns the proper left margin value to use for
1026 filling the text around point. The value is the sum of the
1027 `left-margin' property of the character at the start of the
1028 current line (or zero if none), and the value of the variable
1031 - Function: current-fill-column
1032 This function returns the proper fill column value to use for
1033 filling the text around point. The value is the value of the
1034 `fill-column' variable, minus the value of the `right-margin'
1035 property of the character after point.
1037 - Command: move-to-left-margin &optional n force
1038 This function moves point to the left margin of the current line.
1039 The column moved to is determined by calling the function
1040 `current-left-margin'. If the argument N is non-`nil',
1041 `move-to-left-margin' moves forward N-1 lines first.
1043 If FORCE is non-`nil', that says to fix the line's indentation if
1044 that doesn't match the left margin value.
1046 - Function: delete-to-left-margin &optional from to
1047 This function removes left margin indentation from the text
1048 between FROM and TO. The amount of indentation to delete is
1049 determined by calling `current-left-margin'. In no case does this
1050 function delete non-whitespace.
1052 The arguments FROM and TO are optional; the default is the whole
1055 - Function: indent-to-left-margin
1056 This is the default `indent-line-function', used in Fundamental
1057 mode, Text mode, etc. Its effect is to adjust the indentation at
1058 the beginning of the current line to the value specified by the
1059 variable `left-margin'. This may involve either inserting or
1060 deleting whitespace.
1062 - Variable: left-margin
1063 This variable specifies the base left margin column. In
1064 Fundamental mode, <LFD> indents to this column. This variable
1065 automatically becomes buffer-local when set in any fashion.
1068 File: lispref.info, Node: Auto Filling, Next: Sorting, Prev: Margins, Up: Text
1073 Auto Fill mode is a minor mode that fills lines automatically as text
1074 is inserted. This section describes the hook used by Auto Fill mode.
1075 For a description of functions that you can call explicitly to fill and
1076 justify existing text, see *Note Filling::.
1078 Auto Fill mode also enables the functions that change the margins and
1079 justification style to refill portions of the text. *Note Margins::.
1081 - Variable: auto-fill-function
1082 The value of this variable should be a function (of no arguments)
1083 to be called after self-inserting a space or a newline. It may be
1084 `nil', in which case nothing special is done in that case.
1086 The value of `auto-fill-function' is `do-auto-fill' when Auto-Fill
1087 mode is enabled. That is a function whose sole purpose is to
1088 implement the usual strategy for breaking a line.
1090 In older Emacs versions, this variable was named
1091 `auto-fill-hook', but since it is not called with the
1092 standard convention for hooks, it was renamed to
1093 `auto-fill-function' in version 19.
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