text.texi 119 KB
Newer Older
Richard M. Stallman's avatar
Richard M. Stallman committed
1 2 3 4 5 6 7 8 9 10
@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. 
@c See the file elisp.texi for copying conditions.
@setfilename ../info/text
@node Text, Searching and Matching, Markers, Top
@chapter Text
@cindex text

  This chapter describes the functions that deal with the text in a
11
buffer.  Most examine, insert, or delete text in the current buffer,
Richard M. Stallman's avatar
Richard M. Stallman committed
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
often in the vicinity of point.  Many are interactive.  All the
functions that change the text provide for undoing the changes
(@pxref{Undo}).

  Many text-related functions operate on a region of text defined by two
buffer positions passed in arguments named @var{start} and @var{end}.
These arguments should be either markers (@pxref{Markers}) or numeric
character positions (@pxref{Positions}).  The order of these arguments
does not matter; it is all right for @var{start} to be the end of the
region and @var{end} the beginning.  For example, @code{(delete-region 1
10)} and @code{(delete-region 10 1)} are equivalent.  An
@code{args-out-of-range} error is signaled if either @var{start} or
@var{end} is outside the accessible portion of the buffer.  In an
interactive call, point and the mark are used for these arguments.

@cindex buffer contents
  Throughout this chapter, ``text'' refers to the characters in the
Karl Heuer's avatar
Karl Heuer committed
29
buffer, together with their properties (when relevant).
Richard M. Stallman's avatar
Richard M. Stallman committed
30 31 32 33 34 35 36 37 38 39 40 41 42 43

@menu
* Near Point::       Examining text in the vicinity of point.
* Buffer Contents::  Examining text in a general fashion.
* Comparing Text::   Comparing substrings of buffers.
* Insertion::        Adding new text to a buffer.
* Commands for Insertion::  User-level commands to insert text.
* Deletion::         Removing text from a buffer.
* User-Level Deletion::     User-level commands to delete text.
* The Kill Ring::    Where removed text sometimes is saved for later use.
* Undo::             Undoing changes to the text of a buffer.
* Maintaining Undo:: How to enable and disable undo information.
			How to control how much information is kept.
* Filling::          Functions for explicit filling.
Karl Heuer's avatar
Karl Heuer committed
44
* Margins::          How to specify margins for filling commands.
Richard M. Stallman's avatar
Richard M. Stallman committed
45 46 47 48 49 50 51
* Auto Filling::     How auto-fill mode is implemented to break lines.
* Sorting::          Functions for sorting parts of the buffer.
* Columns::          Computing horizontal positions, and using them.
* Indentation::      Functions to insert or adjust indentation.
* Case Changes::     Case conversion of parts of the buffer.
* Text Properties::  Assigning Lisp property lists to text characters.
* Substitution::     Replacing a given character wherever it appears.
52
* Transposition::    Swapping two portions of a buffer.
Richard M. Stallman's avatar
Richard M. Stallman committed
53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133
* Registers::        How registers are implemented.  Accessing the text or
                       position stored in a register.
* Change Hooks::     Supplying functions to be run when text is changed.
@end menu

@node Near Point
@section Examining Text Near Point

  Many functions are provided to look at the characters around point.
Several simple functions are described here.  See also @code{looking-at}
in @ref{Regexp Search}.

@defun char-after position
This function returns the character in the current buffer at (i.e.,
immediately after) position @var{position}.  If @var{position} is out of
range for this purpose, either before the beginning of the buffer, or at
or beyond the end, then the value is @code{nil}.

In the following example, assume that the first character in the
buffer is @samp{@@}:

@example
@group
(char-to-string (char-after 1))
     @result{} "@@"
@end group
@end example
@end defun

@defun following-char
This function returns the character following point in the current
buffer.  This is similar to @code{(char-after (point))}.  However, if
point is at the end of the buffer, then @code{following-char} returns 0.

Remember that point is always between characters, and the terminal
cursor normally appears over the character following point.  Therefore,
the character returned by @code{following-char} is the character the
cursor is over.

In this example, point is between the @samp{a} and the @samp{c}.

@example
@group
---------- Buffer: foo ----------
Gentlemen may cry ``Pea@point{}ce! Peace!,''
but there is no peace.
---------- Buffer: foo ----------
@end group

@group
(char-to-string (preceding-char))
     @result{} "a"
(char-to-string (following-char))
     @result{} "c"
@end group
@end example
@end defun

@defun preceding-char
This function returns the character preceding point in the current
buffer.  See above, under @code{following-char}, for an example.  If
point is at the beginning of the buffer, @code{preceding-char} returns
0.
@end defun

@defun bobp
This function returns @code{t} if point is at the beginning of the
buffer.  If narrowing is in effect, this means the beginning of the
accessible portion of the text.  See also @code{point-min} in
@ref{Point}.
@end defun

@defun eobp
This function returns @code{t} if point is at the end of the buffer.
If narrowing is in effect, this means the end of accessible portion of
the text.  See also @code{point-max} in @xref{Point}.
@end defun

@defun bolp
This function returns @code{t} if point is at the beginning of a line.
@xref{Text Lines}.  The beginning of the buffer (or its accessible
134
portion) always counts as the beginning of a line.
Richard M. Stallman's avatar
Richard M. Stallman committed
135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159
@end defun

@defun eolp
This function returns @code{t} if point is at the end of a line.  The
end of the buffer (or of its accessible portion) is always considered
the end of a line.
@end defun

@node Buffer Contents
@section Examining Buffer Contents

  This section describes two functions that allow a Lisp program to
convert any portion of the text in the buffer into a string.

@defun buffer-substring start end
This function returns a string containing a copy of the text of the
region defined by positions @var{start} and @var{end} in the current
buffer.  If the arguments are not positions in the accessible portion of
the buffer, @code{buffer-substring} signals an @code{args-out-of-range}
error.

It is not necessary for @var{start} to be less than @var{end}; the
arguments can be given in either order.  But most often the smaller
argument is written first.

Karl Heuer's avatar
Karl Heuer committed
160 161 162 163 164
If the text being copied has any text properties, these are copied into
the string along with the characters they belong to.  @xref{Text
Properties}.  However, overlays (@pxref{Overlays}) in the buffer and
their properties are ignored, not copied.

Richard M. Stallman's avatar
Richard M. Stallman committed
165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184
@example
@group
---------- Buffer: foo ----------
This is the contents of buffer foo

---------- Buffer: foo ----------
@end group

@group
(buffer-substring 1 10)
@result{} "This is t"
@end group
@group
(buffer-substring (point-max) 10)
@result{} "he contents of buffer foo
"
@end group
@end example
@end defun

185
@defun buffer-substring-no-properties start end
Karl Heuer's avatar
Karl Heuer committed
186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202
This is like @code{buffer-substring}, except that it does not copy text
properties, just the characters themselves.  @xref{Text Properties}.
Here's an example of using this function to get a word to look up in an
alist:

@example
(setq flammable
      (assoc (buffer-substring start end)
             '(("wood" . t) ("paper" . t)
               ("steel" . nil) ("asbestos" . nil))))
@end example

If this were written using @code{buffer-substring} instead, it would not
work reliably; any text properties that happened to be in the word
copied from the buffer would make the comparisons fail.
@end defun

Richard M. Stallman's avatar
Richard M. Stallman committed
203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233
@defun buffer-string
This function returns the contents of the accessible portion of the
current buffer as a string.  This is the portion between
@code{(point-min)} and @code{(point-max)} (@pxref{Narrowing}).

@example
@group
---------- Buffer: foo ----------
This is the contents of buffer foo

---------- Buffer: foo ----------

(buffer-string)
     @result{} "This is the contents of buffer foo
"
@end group
@end example
@end defun

@node Comparing Text
@section Comparing Text
@cindex comparing buffer text

  This function lets you compare portions of the text in a buffer, without
copying them into strings first.

@defun compare-buffer-substrings buffer1 start1 end1 buffer2 start2 end2
This function lets you compare two substrings of the same buffer or two
different buffers.  The first three arguments specify one substring,
giving a buffer and two positions within the buffer.  The last three
arguments specify the other substring in the same way.  You can use
234
@code{nil} for @var{buffer1}, @var{buffer2}, or both to stand for the
Richard M. Stallman's avatar
Richard M. Stallman committed
235 236 237 238 239 240 241 242
current buffer.

The value is negative if the first substring is less, positive if the
first is greater, and zero if they are equal.  The absolute value of
the result is one plus the index of the first differing characters
within the substrings.

This function ignores case when comparing characters
Karl Heuer's avatar
Karl Heuer committed
243 244
if @code{case-fold-search} is non-@code{nil}.  It always ignores
text properties.
Richard M. Stallman's avatar
Richard M. Stallman committed
245 246 247 248 249 250 251 252 253 254 255 256 257

Suppose the current buffer contains the text @samp{foobarbar
haha!rara!}; then in this example the two substrings are @samp{rbar }
and @samp{rara!}.  The value is 2 because the first substring is greater
at the second character.

@example
(compare-buffer-substring nil 6 11 nil 16 21)
     @result{} 2
@end example
@end defun

@node Insertion
Karl Heuer's avatar
Karl Heuer committed
258
@section Inserting Text
Richard M. Stallman's avatar
Richard M. Stallman committed
259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276
@cindex insertion of text
@cindex text insertion

  @dfn{Insertion} means adding new text to a buffer.  The inserted text
goes at point---between the character before point and the character
after point.

  Insertion relocates markers that point at positions after the
insertion point, so that they stay with the surrounding text
(@pxref{Markers}).  When a marker points at the place of insertion,
insertion normally doesn't relocate the marker, so that it points to the
beginning of the inserted text; however, certain special functions such
as @code{insert-before-markers} relocate such markers to point after the
inserted text.

@cindex insertion before point
@cindex before point, insertion
  Some insertion functions leave point before the inserted text, while
277 278
other functions leave it after.  We call the former insertion @dfn{after
point} and the latter insertion @dfn{before point}.
Richard M. Stallman's avatar
Richard M. Stallman committed
279 280 281 282

  Insertion functions signal an error if the current buffer is
read-only.

Karl Heuer's avatar
Karl Heuer committed
283 284 285 286 287 288
  These functions copy text characters from strings and buffers along
with their properties.  The inserted characters have exactly the same
properties as the characters they were copied from.  By contrast,
characters specified as separate arguments, not part of a string or
buffer, inherit their text properties from the neighboring text.

Richard M. Stallman's avatar
Richard M. Stallman committed
289 290
@defun insert &rest args
This function inserts the strings and/or characters @var{args} into the
291 292 293
current buffer, at point, moving point forward.  In other words, it
inserts the text before point.  An error is signaled unless all
@var{args} are either strings or characters.  The value is @code{nil}.
Richard M. Stallman's avatar
Richard M. Stallman committed
294 295 296 297 298 299 300 301 302 303
@end defun

@defun insert-before-markers &rest args
This function inserts the strings and/or characters @var{args} into the
current buffer, at point, moving point forward.  An error is signaled
unless all @var{args} are either strings or characters.  The value is
@code{nil}.

This function is unlike the other insertion functions in that it
relocates markers initially pointing at the insertion point, to point
304 305 306
after the inserted text.  If an overlat begins the insertion point, the
inserted text falls outside the overlay; if a nonempty overlay ends at
the insertion point, the inserted text falls inside that overlay.
Richard M. Stallman's avatar
Richard M. Stallman committed
307 308
@end defun

Richard M. Stallman's avatar
Richard M. Stallman committed
309
@defun insert-char character count &optional inherit
Richard M. Stallman's avatar
Richard M. Stallman committed
310 311 312 313
This function inserts @var{count} instances of @var{character} into the
current buffer before point.  The argument @var{count} must be a number,
and @var{character} must be a character.  The value is @code{nil}.
@c It's unfortunate that count comes second.  Not like make-string, etc.
Richard M. Stallman's avatar
Richard M. Stallman committed
314 315 316 317

If @var{inherit} is non-@code{nil}, then the inserted characters inherit
sticky text properties from the two characters before and after the
insertion point.  @xref{Sticky Properties}.
Richard M. Stallman's avatar
Richard M. Stallman committed
318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341
@end defun

@defun insert-buffer-substring from-buffer-or-name &optional start end
This function inserts a portion of buffer @var{from-buffer-or-name}
(which must already exist) into the current buffer before point.  The
text inserted is the region from @var{start} and @var{end}.  (These
arguments default to the beginning and end of the accessible portion of
that buffer.)  This function returns @code{nil}.

In this example, the form is executed with buffer @samp{bar} as the
current buffer.  We assume that buffer @samp{bar} is initially empty.

@example
@group
---------- Buffer: foo ----------
We hold these truths to be self-evident, that all
---------- Buffer: foo ----------
@end group

@group
(insert-buffer-substring "foo" 1 20)
     @result{} nil

---------- Buffer: bar ----------
342
We hold these truth@point{}
Richard M. Stallman's avatar
Richard M. Stallman committed
343 344 345 346 347 348
---------- Buffer: bar ----------
@end group
@end example
@end defun

  @xref{Sticky Properties}, for other insertion functions that inherit
349
text properties from the nearby text in addition to inserting it.
Richard M. Stallman's avatar
Richard M. Stallman committed
350 351
Whitespace inserted by indentation functions also inherits text
properties.
Richard M. Stallman's avatar
Richard M. Stallman committed
352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368

@node Commands for Insertion
@section User-Level Insertion Commands

  This section describes higher-level commands for inserting text,
commands intended primarily for the user but useful also in Lisp
programs.

@deffn Command insert-buffer from-buffer-or-name
This command inserts the entire contents of @var{from-buffer-or-name}
(which must exist) into the current buffer after point.  It leaves
the mark after the inserted text.  The value is @code{nil}.
@end deffn

@deffn Command self-insert-command count
@cindex character insertion
@cindex self-insertion
369 370 371 372 373
This command inserts the last character typed; it does so @var{count}
times, before point, and returns @code{nil}.  Most printing characters
are bound to this command.  In routine use, @code{self-insert-command}
is the most frequently called function in Emacs, but programs rarely use
it except to install it on a keymap.
Richard M. Stallman's avatar
Richard M. Stallman committed
374 375 376

In an interactive call, @var{count} is the numeric prefix argument.

Karl Heuer's avatar
Karl Heuer committed
377 378 379
This command calls @code{auto-fill-function} whenever that is
non-@code{nil} and the character inserted is a space or a newline
(@pxref{Auto Filling}).
Richard M. Stallman's avatar
Richard M. Stallman committed
380 381

@c Cross refs reworded to prevent overfull hbox.  --rjc 15mar92
Karl Heuer's avatar
Karl Heuer committed
382
This command performs abbrev expansion if Abbrev mode is enabled and
Richard M. Stallman's avatar
Richard M. Stallman committed
383 384 385
the inserted character does not have word-constituent
syntax. (@xref{Abbrevs}, and @ref{Syntax Class Table}.)

Karl Heuer's avatar
Karl Heuer committed
386 387
This is also responsible for calling @code{blink-paren-function} when
the inserted character has close parenthesis syntax (@pxref{Blinking}).
Richard M. Stallman's avatar
Richard M. Stallman committed
388 389 390 391 392 393 394 395
@end deffn

@deffn Command newline &optional number-of-newlines 
This command inserts newlines into the current buffer before point.
If @var{number-of-newlines} is supplied, that many newline characters
are inserted.

@cindex newline and Auto Fill mode
396 397 398 399 400 401 402
This function calls @code{auto-fill-function} if the current column
number is greater than the value of @code{fill-column} and
@var{number-of-newlines} is @code{nil}.  Typically what
@code{auto-fill-function} does is insert a newline; thus, the overall
result in this case is to insert two newlines at different places: one
at point, and another earlier in the line.  @code{newline} does not
auto-fill if @var{number-of-newlines} is non-@code{nil}.
Richard M. Stallman's avatar
Richard M. Stallman committed
403

Karl Heuer's avatar
Karl Heuer committed
404 405 406
This command indents to the left margin if that is not zero.
@xref{Margins}.

Richard M. Stallman's avatar
Richard M. Stallman committed
407 408 409 410 411 412
The value returned is @code{nil}.  In an interactive call, @var{count}
is the numeric prefix argument.
@end deffn

@deffn Command split-line
This command splits the current line, moving the portion of the line
413
after point down vertically so that it is on the next line directly
Richard M. Stallman's avatar
Richard M. Stallman committed
414 415 416 417 418 419 420 421 422 423 424 425 426 427
below where it was before.  Whitespace is inserted as needed at the
beginning of the lower line, using the @code{indent-to} function.
@code{split-line} returns the position of point.

Programs hardly ever use this function.
@end deffn

@defvar overwrite-mode
This variable controls whether overwrite mode is in effect: a
non-@code{nil} value enables the mode.  It is automatically made
buffer-local when set in any fashion.
@end defvar

@node Deletion
Karl Heuer's avatar
Karl Heuer committed
428
@section Deleting Text
Richard M. Stallman's avatar
Richard M. Stallman committed
429 430 431 432 433

@cindex deletion vs killing
  Deletion means removing part of the text in a buffer, without saving
it in the kill ring (@pxref{The Kill Ring}).  Deleted text can't be
yanked, but can be reinserted using the undo mechanism (@pxref{Undo}).
434 435
Some deletion functions do save text in the kill ring in some special
cases.
Richard M. Stallman's avatar
Richard M. Stallman committed
436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454

  All of the deletion functions operate on the current buffer, and all
return a value of @code{nil}.

@defun erase-buffer
This function deletes the entire text of the current buffer, leaving it
empty.  If the buffer is read-only, it signals a @code{buffer-read-only}
error.  Otherwise, it deletes the text without asking for any
confirmation.  It returns @code{nil}.

Normally, deleting a large amount of text from a buffer inhibits further
auto-saving of that buffer ``because it has shrunk''.  However,
@code{erase-buffer} does not do this, the idea being that the future
text is not really related to the former text, and its size should not
be compared with that of the former text.
@end defun

@deffn Command delete-region start end
This command deletes the text in the current buffer in the region
455 456 457
defined by @var{start} and @var{end}.  The value is @code{nil}.  If
point was inside the deleted region, its value afterward is @var{start}.
Otherwise, point relocates with the surrounding text, as markers do.
Richard M. Stallman's avatar
Richard M. Stallman committed
458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524
@end deffn

@deffn Command delete-char count &optional killp
This command deletes @var{count} characters directly after point, or
before point if @var{count} is negative.  If @var{killp} is
non-@code{nil}, then it saves the deleted characters in the kill ring.

In an interactive call, @var{count} is the numeric prefix argument, and
@var{killp} is the unprocessed prefix argument.  Therefore, if a prefix
argument is supplied, the text is saved in the kill ring.  If no prefix
argument is supplied, then one character is deleted, but not saved in
the kill ring.

The value returned is always @code{nil}.
@end deffn

@deffn Command delete-backward-char count &optional killp
@cindex delete previous char
This command deletes @var{count} characters directly before point, or
after point if @var{count} is negative.  If @var{killp} is
non-@code{nil}, then it saves the deleted characters in the kill ring.

In an interactive call, @var{count} is the numeric prefix argument, and
@var{killp} is the unprocessed prefix argument.  Therefore, if a prefix
argument is supplied, the text is saved in the kill ring.  If no prefix
argument is supplied, then one character is deleted, but not saved in
the kill ring.

The value returned is always @code{nil}.
@end deffn

@deffn Command backward-delete-char-untabify count &optional killp
@cindex tab deletion
This command deletes @var{count} characters backward, changing tabs
into spaces.  When the next character to be deleted is a tab, it is
first replaced with the proper number of spaces to preserve alignment
and then one of those spaces is deleted instead of the tab.  If
@var{killp} is non-@code{nil}, then the command saves the deleted
characters in the kill ring.

Conversion of tabs to spaces happens only if @var{count} is positive.
If it is negative, exactly @minus{}@var{count} characters after point
are deleted.

In an interactive call, @var{count} is the numeric prefix argument, and
@var{killp} is the unprocessed prefix argument.  Therefore, if a prefix
argument is supplied, the text is saved in the kill ring.  If no prefix
argument is supplied, then one character is deleted, but not saved in
the kill ring.

The value returned is always @code{nil}.
@end deffn

@node User-Level Deletion
@section User-Level Deletion Commands

  This section describes higher-level commands for deleting text,
commands intended primarily for the user but useful also in Lisp
programs.

@deffn Command delete-horizontal-space
@cindex deleting whitespace
This function deletes all spaces and tabs around point.  It returns
@code{nil}.

In the following examples, we call @code{delete-horizontal-space} four
times, once on each line, with point between the second and third
525
characters on the line each time.
Richard M. Stallman's avatar
Richard M. Stallman committed
526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559

@example
@group
---------- Buffer: foo ----------
I @point{}thought
I @point{}     thought
We@point{} thought
Yo@point{}u thought
---------- Buffer: foo ----------
@end group

@group
(delete-horizontal-space)   ; @r{Four times.}
     @result{} nil

---------- Buffer: foo ----------
Ithought
Ithought
Wethought
You thought
---------- Buffer: foo ----------
@end group
@end example
@end deffn

@deffn Command delete-indentation &optional join-following-p 
This function joins the line point is on to the previous line, deleting
any whitespace at the join and in some cases replacing it with one
space.  If @var{join-following-p} is non-@code{nil},
@code{delete-indentation} joins this line to the following line
instead.  The value is @code{nil}.

If there is a fill prefix, and the second of the lines being joined
starts with the prefix, then @code{delete-indentation} deletes the
Karl Heuer's avatar
Karl Heuer committed
560
fill prefix before joining the lines.  @xref{Margins}.
Richard M. Stallman's avatar
Richard M. Stallman committed
561 562 563 564 565 566

In the example below, point is located on the line starting
@samp{events}, and it makes no difference if there are trailing spaces
in the preceding line.

@smallexample
567
@group
Richard M. Stallman's avatar
Richard M. Stallman committed
568 569 570 571
---------- Buffer: foo ----------
When in the course of human
@point{}    events, it becomes necessary
---------- Buffer: foo ----------
572
@end group
Richard M. Stallman's avatar
Richard M. Stallman committed
573 574 575 576

(delete-indentation)
     @result{} nil

577
@group
Richard M. Stallman's avatar
Richard M. Stallman committed
578 579 580
---------- Buffer: foo ----------
When in the course of human@point{} events, it becomes necessary
---------- Buffer: foo ----------
581
@end group
Richard M. Stallman's avatar
Richard M. Stallman committed
582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598
@end smallexample

After the lines are joined, the function @code{fixup-whitespace} is
responsible for deciding whether to leave a space at the junction.
@end deffn

@defun fixup-whitespace
This function replaces all the white space surrounding point with either
one space or no space, according to the context.  It returns @code{nil}.

At the beginning or end of a line, the appropriate amount of space is
none.  Before a character with close parenthesis syntax, or after a
character with open parenthesis or expression-prefix syntax, no space is
also appropriate.  Otherwise, one space is appropriate.  @xref{Syntax
Class Table}.

In the example below, @code{fixup-whitespace} is called the first time
599 600
with point before the word @samp{spaces} in the first line.  For the
second invocation, point is directly after the @samp{(}.
Richard M. Stallman's avatar
Richard M. Stallman committed
601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657

@smallexample
@group
---------- Buffer: foo ----------
This has too many     @point{}spaces
This has too many spaces at the start of (@point{}   this list)
---------- Buffer: foo ----------
@end group

@group
(fixup-whitespace)
     @result{} nil
(fixup-whitespace)
     @result{} nil
@end group

@group
---------- Buffer: foo ----------
This has too many spaces
This has too many spaces at the start of (this list)
---------- Buffer: foo ----------
@end group
@end smallexample
@end defun

@deffn Command just-one-space
@comment !!SourceFile simple.el
This command replaces any spaces and tabs around point with a single
space.  It returns @code{nil}.
@end deffn

@deffn Command delete-blank-lines
This function deletes blank lines surrounding point.  If point is on a
blank line with one or more blank lines before or after it, then all but
one of them are deleted.  If point is on an isolated blank line, then it
is deleted.  If point is on a nonblank line, the command deletes all
blank lines following it.

A blank line is defined as a line containing only tabs and spaces.

@code{delete-blank-lines} returns @code{nil}.
@end deffn

@node The Kill Ring
@section The Kill Ring
@cindex kill ring

  @dfn{Kill} functions delete text like the deletion functions, but save
it so that the user can reinsert it by @dfn{yanking}.  Most of these
functions have @samp{kill-} in their name.  By contrast, the functions
whose names start with @samp{delete-} normally do not save text for
yanking (though they can still be undone); these are ``deletion''
functions.

  Most of the kill commands are primarily for interactive use, and are
not described here.  What we do describe are the functions provided for
use in writing such commands.  You can use these functions to write
658
commands for killing text.  When you need to delete text for internal
Richard M. Stallman's avatar
Richard M. Stallman committed
659 660 661 662 663
purposes within a Lisp function, you should normally use deletion
functions, so as not to disturb the kill ring contents.
@xref{Deletion}.

  Killed text is saved for later yanking in the @dfn{kill ring}.  This
664 665 666 667 668 669
is a list that holds a number of recent kills, not just the last text
kill.  We call this a ``ring'' because yanking treats it as having
elements in a cyclic order.  The list is kept in the variable
@code{kill-ring}, and can be operated on with the usual functions for
lists; there are also specialized functions, described in this section,
that treat it as a ring.
Richard M. Stallman's avatar
Richard M. Stallman committed
670 671

  Some people think this use of the word ``kill'' is unfortunate, since
672
it refers to operations that specifically @emph{do not} destroy the
Richard M. Stallman's avatar
Richard M. Stallman committed
673 674 675 676 677 678 679 680 681 682 683
entities ``killed''.  This is in sharp contrast to ordinary life, in
which death is permanent and ``killed'' entities do not come back to
life.  Therefore, other metaphors have been proposed.  For example, the
term ``cut ring'' makes sense to people who, in pre-computer days, used
scissors and paste to cut up and rearrange manuscripts.  However, it
would be difficult to change the terminology now.

@menu
* Kill Ring Concepts::     What text looks like in the kill ring.
* Kill Functions::         Functions that kill text.
* Yank Commands::          Commands that access the kill ring.
684
* Low-Level Kill Ring::	   Functions and variables for kill ring access.
Richard M. Stallman's avatar
Richard M. Stallman committed
685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705
* Internals of Kill Ring:: Variables that hold kill-ring data.
@end menu

@node Kill Ring Concepts
@comment  node-name,  next,  previous,  up
@subsection Kill Ring Concepts

  The kill ring records killed text as strings in a list, most recent
first.  A short kill ring, for example, might look like this:

@example
("some text" "a different piece of text" "even older text")
@end example

@noindent
When the list reaches @code{kill-ring-max} entries in length, adding a
new entry automatically deletes the last entry.

  When kill commands are interwoven with other commands, each kill
command makes a new entry in the kill ring.  Multiple kill commands in
succession build up a single entry in the kill ring, which would be
706
yanked as a unit; the second and subsequent consecutive kill commands
Richard M. Stallman's avatar
Richard M. Stallman committed
707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723
add text to the entry made by the first one.

  For yanking, one entry in the kill ring is designated the ``front'' of
the ring.  Some yank commands ``rotate'' the ring by designating a
different element as the ``front.''  But this virtual rotation doesn't
change the list itself---the most recent entry always comes first in the
list.

@node Kill Functions
@comment  node-name,  next,  previous,  up
@subsection Functions for Killing

  @code{kill-region} is the usual subroutine for killing text.  Any
command that calls this function is a ``kill command'' (and should
probably have @samp{kill} in its name).  @code{kill-region} puts the
newly killed text in a new element at the beginning of the kill ring or
adds it to the most recent element.  It uses the @code{last-command}
724 725
variable to determine whether the previous command was a kill command,
and if so appends the killed text to the most recent entry.
Richard M. Stallman's avatar
Richard M. Stallman committed
726 727 728

@deffn Command kill-region start end
This function kills the text in the region defined by @var{start} and
Karl Heuer's avatar
Karl Heuer committed
729 730
@var{end}.  The text is deleted but saved in the kill ring, along with
its text properties.  The value is always @code{nil}.
Richard M. Stallman's avatar
Richard M. Stallman committed
731 732 733 734 735 736 737 738 739 740 741 742 743

In an interactive call, @var{start} and @var{end} are point and
the mark.

@c Emacs 19 feature
If the buffer is read-only, @code{kill-region} modifies the kill ring
just the same, then signals an error without modifying the buffer.  This
is convenient because it lets the user use all the kill commands to copy
text into the kill ring from a read-only buffer.
@end deffn

@deffn Command copy-region-as-kill start end
This command saves the region defined by @var{start} and @var{end} on
Karl Heuer's avatar
Karl Heuer committed
744 745 746 747
the kill ring (including text properties), but does not delete the text
from the buffer.  It returns @code{nil}.  It also indicates the extent
of the text copied by moving the cursor momentarily, or by displaying a
message in the echo area.
Richard M. Stallman's avatar
Richard M. Stallman committed
748

Karl Heuer's avatar
Karl Heuer committed
749 750 751
The command does not set @code{this-command} to @code{kill-region}, so a
subsequent kill command does not append to the same kill ring entry.

Richard M. Stallman's avatar
Richard M. Stallman committed
752 753
Don't call @code{copy-region-as-kill} in Lisp programs unless you aim to
support Emacs 18.  For Emacs 19, it is better to use @code{kill-new} or
754
@code{kill-append} instead.  @xref{Low-Level Kill Ring}.
Richard M. Stallman's avatar
Richard M. Stallman committed
755 756 757 758 759 760 761
@end deffn

@node Yank Commands
@comment  node-name,  next,  previous,  up
@subsection Functions for Yanking

  @dfn{Yanking} means reinserting an entry of previously killed text
Karl Heuer's avatar
Karl Heuer committed
762
from the kill ring.  The text properties are copied too.
Richard M. Stallman's avatar
Richard M. Stallman committed
763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803

@deffn Command yank &optional arg
@cindex inserting killed text
This command inserts before point the text in the first entry in the
kill ring.  It positions the mark at the beginning of that text, and
point at the end.

If @var{arg} is a list (which occurs interactively when the user
types @kbd{C-u} with no digits), then @code{yank} inserts the text as
described above, but puts point before the yanked text and puts the mark
after it.

If @var{arg} is a number, then @code{yank} inserts the @var{arg}th most
recently killed text---the @var{arg}th element of the kill ring list.

@code{yank} does not alter the contents of the kill ring or rotate it.
It returns @code{nil}.
@end deffn

@deffn Command yank-pop arg
This command replaces the just-yanked entry from the kill ring with a
different entry from the kill ring.

This is allowed only immediately after a @code{yank} or another
@code{yank-pop}.  At such a time, the region contains text that was just
inserted by yanking.  @code{yank-pop} deletes that text and inserts in
its place a different piece of killed text.  It does not add the deleted
text to the kill ring, since it is already in the kill ring somewhere.

If @var{arg} is @code{nil}, then the replacement text is the previous
element of the kill ring.  If @var{arg} is numeric, the replacement is
the @var{arg}th previous kill.  If @var{arg} is negative, a more recent
kill is the replacement.

The sequence of kills in the kill ring wraps around, so that after the
oldest one comes the newest one, and before the newest one goes the
oldest.

The value is always @code{nil}.
@end deffn

804 805
@node Low-Level Kill Ring
@subsection Low-Level Kill Ring
Richard M. Stallman's avatar
Richard M. Stallman committed
806 807 808 809 810 811 812

  These functions and variables provide access to the kill ring at a lower
level, but still convenient for use in Lisp programs.  They take care of
interaction with X Window selections.  They do not exist in Emacs
version 18.

@defun current-kill n &optional do-not-move
813 814 815
The function @code{current-kill} rotates the yanking pointer which
designates the ``front'' of the kill ring by @var{n} places (from newer
kills to older ones), and returns the text at that place in the ring.
Richard M. Stallman's avatar
Richard M. Stallman committed
816 817 818

If the optional second argument @var{do-not-move} is non-@code{nil},
then @code{current-kill} doesn't alter the yanking pointer; it just
819
returns the @var{n}th kill, counting from the current yanking pointer.
Richard M. Stallman's avatar
Richard M. Stallman committed
820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857

If @var{n} is zero, indicating a request for the latest kill,
@code{current-kill} calls the value of
@code{interprogram-paste-function} (documented below) before consulting
the kill ring.
@end defun

@defun kill-new string
This function puts the text @var{string} into the kill ring as a new
entry at the front of the ring.  It discards the oldest entry if
appropriate.  It also invokes the value of
@code{interprogram-cut-function} (see below).
@end defun

@defun kill-append string before-p
This function appends the text @var{string} to the first entry in the
kill ring.  Normally @var{string} goes at the end of the entry, but if
@var{before-p} is non-@code{nil}, it goes at the beginning.  This
function also invokes the value of @code{interprogram-cut-function} (see
below).
@end defun

@defvar interprogram-paste-function
This variable provides a way of transferring killed text from other
programs, when you are using a window system.  Its value should be
@code{nil} or a function of no arguments.

If the value is a function, @code{current-kill} calls it to get the
``most recent kill''.  If the function returns a non-@code{nil} value,
then that value is used as the ``most recent kill''.  If it returns
@code{nil}, then the first element of @code{kill-ring} is used.

The normal use of this hook is to get the X server's primary selection
as the most recent kill, even if the selection belongs to another X
client.  @xref{X Selections}.
@end defvar

@defvar interprogram-cut-function
858 859
This variable provides a way of communicating killed text to other
programs, when you are using a window system.  Its value should be
Richard M. Stallman's avatar
Richard M. Stallman committed
860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877
@code{nil} or a function of one argument.

If the value is a function, @code{kill-new} and @code{kill-append} call
it with the new first element of the kill ring as an argument.

The normal use of this hook is to set the X server's primary selection
to the newly killed text.
@end defvar

@node Internals of Kill Ring
@comment  node-name,  next,  previous,  up
@subsection Internals of the Kill Ring

  The variable @code{kill-ring} holds the kill ring contents, in the
form of a list of strings.  The most recent kill is always at the front
of the list. 

  The @code{kill-ring-yank-pointer} variable points to a link in the
878 879
kill ring list, whose @sc{car} is the text to yank next.  We say it
identifies the ``front'' of the ring.  Moving
Richard M. Stallman's avatar
Richard M. Stallman committed
880
@code{kill-ring-yank-pointer} to a different link is called
881 882 883 884
@dfn{rotating the kill ring}.  We call the kill ring a ``ring'' because
the functions that move the yank pointer wrap around from the end of the
list to the beginning, or vice-versa.  Rotation of the kill ring is
virtual; it does not change the value of @code{kill-ring}.
Richard M. Stallman's avatar
Richard M. Stallman committed
885 886 887 888 889 890 891 892 893 894

  Both @code{kill-ring} and @code{kill-ring-yank-pointer} are Lisp
variables whose values are normally lists.  The word ``pointer'' in the
name of the @code{kill-ring-yank-pointer} indicates that the variable's
purpose is to identify one element of the list for use by the next yank
command.

  The value of @code{kill-ring-yank-pointer} is always @code{eq} to one
of the links in the kill ring list.  The element it identifies is the
@sc{car} of that link.  Kill commands, which change the kill ring, also
895 896
set this variable to the value of @code{kill-ring}.  The effect is to
rotate the ring so that the newly killed text is at the front.
Richard M. Stallman's avatar
Richard M. Stallman committed
897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922

  Here is a diagram that shows the variable @code{kill-ring-yank-pointer}
pointing to the second entry in the kill ring @code{("some text" "a
different piece of text" "yet older text")}.  

@example
@group
kill-ring       kill-ring-yank-pointer
  |               |
  |     ___ ___    --->  ___ ___      ___ ___
   --> |___|___|------> |___|___|--> |___|___|--> nil
         |                |            |            
         |                |            |            
         |                |             -->"yet older text" 
         |                |
         |                 --> "a different piece of text" 
         |
          --> "some text"
@end group
@end example

@noindent
This state of affairs might occur after @kbd{C-y} (@code{yank})
immediately followed by @kbd{M-y} (@code{yank-pop}).

@defvar kill-ring
923 924
This variable holds the list of killed text sequences, most recently
killed first.
Richard M. Stallman's avatar
Richard M. Stallman committed
925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944
@end defvar

@defvar kill-ring-yank-pointer
This variable's value indicates which element of the kill ring is at the
``front'' of the ring for yanking.  More precisely, the value is a tail
of the value of @code{kill-ring}, and its @sc{car} is the kill string
that @kbd{C-y} should yank.
@end defvar

@defopt kill-ring-max
The value of this variable is the maximum length to which the kill
ring can grow, before elements are thrown away at the end.  The default
value for @code{kill-ring-max} is 30.
@end defopt

@node Undo
@comment  node-name,  next,  previous,  up
@section Undo
@cindex redo

945 946 947 948 949 950
  Most buffers have an @dfn{undo list}, which records all changes made
to the buffer's text so that they can be undone.  (The buffers that
don't have one are usually special-purpose buffers for which Emacs
assumes that undoing is not useful.)  All the primitives that modify the
text in the buffer automatically add elements to the front of the undo
list, which is in the variable @code{buffer-undo-list}.
Richard M. Stallman's avatar
Richard M. Stallman committed
951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969

@defvar buffer-undo-list
This variable's value is the undo list of the current buffer.
A value of @code{t} disables the recording of undo information.
@end defvar

Here are the kinds of elements an undo list can have:

@table @code
@item @var{integer}
This kind of element records a previous value of point.  Ordinary cursor
motion does not get any sort of undo record, but deletion commands use
these entries to record where point was before the command.

@item (@var{beg} . @var{end})
This kind of element indicates how to delete text that was inserted.
Upon insertion, the text occupied the range @var{beg}--@var{end} in the 
buffer.

Richard M. Stallman's avatar
Richard M. Stallman committed
970
@item (@var{text} . @var{position})
Richard M. Stallman's avatar
Richard M. Stallman committed
971
This kind of element indicates how to reinsert text that was deleted.
Richard M. Stallman's avatar
Richard M. Stallman committed
972 973
The deleted text itself is the string @var{text}.  The place to
reinsert it is @code{(abs @var{position})}.
Richard M. Stallman's avatar
Richard M. Stallman committed
974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989

@item (t @var{high} . @var{low})
This kind of element indicates that an unmodified buffer became
modified.  The elements @var{high} and @var{low} are two integers, each
recording 16 bits of the visited file's modification time as of when it
was previously visited or saved.  @code{primitive-undo} uses those
values to determine whether to mark the buffer as unmodified once again;
it does so only if the file's modification time matches those numbers.

@item (nil @var{property} @var{value} @var{beg} . @var{end})
This kind of element records a change in a text property.
Here's how you might undo the change:

@example
(put-text-property @var{beg} @var{end} @var{property} @var{value})
@end example
Richard M. Stallman's avatar
Richard M. Stallman committed
990

991 992 993 994 995 996
@item (@var{marker} . @var{adjustment})
This kind of element records the fact that the marker @var{marker} was
relocated due to deletion of surrounding text, and that it moved
@var{adjustment} character positions.  Undoing this element moves
@var{marker} @minus{} @var{adjustment} characters.

Richard M. Stallman's avatar
Richard M. Stallman committed
997
@item @var{position}
Karl Heuer's avatar
Karl Heuer committed
998 999 1000
This element indicates where point was at an earlier time.  Undoing this
element sets point to @var{position}.  Deletion normally creates an
element of this kind as well as a reinsertion element.
Richard M. Stallman's avatar
Richard M. Stallman committed
1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013

@item nil
This element is a boundary.  The elements between two boundaries are
called a @dfn{change group}; normally, each change group corresponds to
one keyboard command, and undo commands normally undo an entire group as
a unit.
@end table

@defun undo-boundary
This function places a boundary element in the undo list.  The undo
command stops at such a boundary, and successive undo commands undo
to earlier and earlier boundaries.  This function returns @code{nil}.

1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029
The editor command loop automatically creates an undo boundary before
each key sequence is executed.  Thus, each undo normally undoes the
effects of one command.  Self-inserting input characters are an
exception.  The command loop makes a boundary for the first such
character; the next 19 consecutive self-inserting input characters do
not make boundaries, and then the 20th does, and so on as long as
self-inserting characters continue.

All buffer modifications add a boundary whenever the previous undoable
change was made in some other buffer.  This way, a command that modifies
several buffers makes a boundary in each buffer it changes.

Calling this function explicitly is useful for splitting the effects of
a command into more than one unit.  For example, @code{query-replace}
calls @code{undo-boundary} after each replacement, so that the user can
undo individual replacements one by one.
Richard M. Stallman's avatar
Richard M. Stallman committed
1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041
@end defun

@defun primitive-undo count list
This is the basic function for undoing elements of an undo list.
It undoes the first @var{count} elements of @var{list}, returning
the rest of @var{list}.  You could write this function in Lisp,
but it is convenient to have it in C.

@code{primitive-undo} adds elements to the buffer's undo list when it
changes the buffer.  Undo commands avoid confusion by saving the undo
list value at the beginning of a sequence of undo operations.  Then the
undo operations use and update the saved value.  The new elements added
Karl Heuer's avatar
Karl Heuer committed
1042
by undoing are not part of this saved value, so they don't interfere with
Richard M. Stallman's avatar
Richard M. Stallman committed
1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098
continuing to undo.
@end defun

@node Maintaining Undo
@section Maintaining Undo Lists

  This section describes how to enable and disable undo information for
a given buffer.  It also explains how the undo list is truncated
automatically so it doesn't get too big.

  Recording of undo information in a newly created buffer is normally
enabled to start with; but if the buffer name starts with a space, the
undo recording is initially disabled.  You can explicitly enable or
disable undo recording with the following two functions, or by setting
@code{buffer-undo-list} yourself.

@deffn Command buffer-enable-undo &optional buffer-or-name
This command enables recording undo information for buffer
@var{buffer-or-name}, so that subsequent changes can be undone.  If no
argument is supplied, then the current buffer is used.  This function
does nothing if undo recording is already enabled in the buffer.  It
returns @code{nil}.

In an interactive call, @var{buffer-or-name} is the current buffer.
You cannot specify any other buffer.
@end deffn

@defun buffer-disable-undo &optional buffer
@defunx buffer-flush-undo &optional buffer
@cindex disable undo
This function discards the undo list of @var{buffer}, and disables
further recording of undo information.  As a result, it is no longer
possible to undo either previous changes or any subsequent changes.  If
the undo list of @var{buffer} is already disabled, this function
has no effect.

This function returns @code{nil}.  It cannot be called interactively.

The name @code{buffer-flush-undo} is not considered obsolete, but the
preferred name @code{buffer-disable-undo} is new as of Emacs versions
19.
@end defun

  As editing continues, undo lists get longer and longer.  To prevent
them from using up all available memory space, garbage collection trims
them back to size limits you can set.  (For this purpose, the ``size''
of an undo list measures the cons cells that make up the list, plus the
strings of deleted text.)  Two variables control the range of acceptable
sizes: @code{undo-limit} and @code{undo-strong-limit}.

@defvar undo-limit
This is the soft limit for the acceptable size of an undo list.  The
change group at which this size is exceeded is the last one kept.
@end defvar

@defvar undo-strong-limit
1099 1100 1101
This is the upper limit for the acceptable size of an undo list.  The
change group at which this size is exceeded is discarded itself (along
with all older change groups).  There is one exception: the very latest
1102
change group is never discarded no matter how big it is.
Richard M. Stallman's avatar
Richard M. Stallman committed
1103 1104 1105 1106 1107 1108 1109 1110 1111 1112
@end defvar

@node Filling
@comment  node-name,  next,  previous,  up
@section Filling
@cindex filling, explicit

  @dfn{Filling} means adjusting the lengths of lines (by moving the line
breaks) so that they are nearly (but no greater than) a specified
maximum width.  Additionally, lines can be @dfn{justified}, which means
Karl Heuer's avatar
Karl Heuer committed
1113 1114 1115
inserting spaces to make the left and/or right margins line up
precisely.  The width is controlled by the variable @code{fill-column}.
For ease of reading, lines should be no longer than 70 or so columns.
Richard M. Stallman's avatar
Richard M. Stallman committed
1116 1117 1118 1119 1120

  You can use Auto Fill mode (@pxref{Auto Filling}) to fill text
automatically as you insert it, but changes to existing text may leave
it improperly filled.  Then you must fill the text explicitly.

Karl Heuer's avatar
Karl Heuer committed
1121 1122
  Most of the commands in this section return values that are not
meaningful.  All the functions that do filling take note of the current
Karl Heuer's avatar
Karl Heuer committed
1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135
left margin, current right margin, and current justification style
(@pxref{Margins}).  If the current justification style is
@code{none}, the filling functions don't actually do anything.

  Several of the filling functions have an argument @var{justify}.
If it is non-@code{nil}, that requests some kind of justification.  It
can be @code{left}, @code{right}, @code{full}, or @code{center}, to
request a specific style of justification.  If it is @code{t}, that
means to use the current justification style for this part of the text
(see @code{current-justification}, below).

  When you call the filling functions interactively, using a prefix
argument implies the value @code{full} for @var{justify}.
Richard M. Stallman's avatar
Richard M. Stallman committed
1136

Karl Heuer's avatar
Karl Heuer committed
1137
@deffn Command fill-paragraph justify
Richard M. Stallman's avatar
Richard M. Stallman committed
1138 1139
@cindex filling a paragraph
This command fills the paragraph at or after point.  If
Karl Heuer's avatar
Karl Heuer committed
1140
@var{justify} is non-@code{nil}, each line is justified as well.
Richard M. Stallman's avatar
Richard M. Stallman committed
1141 1142 1143 1144
It uses the ordinary paragraph motion commands to find paragraph
boundaries.  @xref{Paragraphs,,, emacs, The Emacs Manual}.
@end deffn

Karl Heuer's avatar
Karl Heuer committed
1145
@deffn Command fill-region start end &optional justify
Richard M. Stallman's avatar
Richard M. Stallman committed
1146
This command fills each of the paragraphs in the region from @var{start}
Karl Heuer's avatar
Karl Heuer committed
1147
to @var{end}.  It justifies as well if @var{justify} is
Richard M. Stallman's avatar
Richard M. Stallman committed
1148 1149 1150 1151 1152 1153
non-@code{nil}.

The variable @code{paragraph-separate} controls how to distinguish
paragraphs.  @xref{Standard Regexps}.
@end deffn

Karl Heuer's avatar
Karl Heuer committed
1154
@deffn Command fill-individual-paragraphs start end &optional justify mail-flag
Richard M. Stallman's avatar
Richard M. Stallman committed
1155 1156 1157 1158 1159 1160 1161
This command fills each paragraph in the region according to its
individual fill prefix.  Thus, if the lines of a paragraph were indented
with spaces, the filled paragraph will remain indented in the same
fashion.

The first two arguments, @var{start} and @var{end}, are the beginning
and end of the region to be filled.  The third and fourth arguments,
Karl Heuer's avatar
Karl Heuer committed
1162 1163
@var{justify} and @var{mail-flag}, are optional.  If
@var{justify} is non-@code{nil}, the paragraphs are justified as
Richard M. Stallman's avatar
Richard M. Stallman committed
1164 1165 1166 1167 1168 1169 1170
well as filled.  If @var{mail-flag} is non-@code{nil}, it means the
function is operating on a mail message and therefore should not fill
the header lines.

Ordinarily, @code{fill-individual-paragraphs} regards each change in
indentation as starting a new paragraph.  If
@code{fill-individual-varying-indent} is non-@code{nil}, then only
1171 1172
separator lines separate paragraphs.  That mode can handle indented
paragraphs with additional indentation on the first line.
Richard M. Stallman's avatar
Richard M. Stallman committed
1173 1174 1175 1176 1177 1178 1179
@end deffn

@defopt fill-individual-varying-indent
This variable alters the action of @code{fill-individual-paragraphs} as
described above.
@end defopt

Karl Heuer's avatar
Karl Heuer committed
1180
@deffn Command fill-region-as-paragraph start end &optional justify
Richard M. Stallman's avatar
Richard M. Stallman committed
1181 1182 1183
This command considers a region of text as a paragraph and fills it.  If
the region was made up of many paragraphs, the blank lines between
paragraphs are removed.  This function justifies as well as filling when
Karl Heuer's avatar
Karl Heuer committed
1184
@var{justify} is non-@code{nil}.
Karl Heuer's avatar
Karl Heuer committed
1185 1186

In an interactive call, any prefix argument requests justification.
Richard M. Stallman's avatar
Richard M. Stallman committed
1187

1188
In Adaptive Fill mode, which is enabled by default, calling the function
Richard M. Stallman's avatar
Richard M. Stallman committed
1189 1190 1191 1192 1193
@code{fill-region-as-paragraph} on an indented paragraph when there is
no fill prefix uses the indentation of the second line of the paragraph
as the fill prefix.
@end deffn

Karl Heuer's avatar
Karl Heuer committed
1194
@deffn Command justify-current-line how eop nosqueeze
Richard M. Stallman's avatar
Richard M. Stallman committed
1195 1196 1197
This command inserts spaces between the words of the current line so
that the line ends exactly at @code{fill-column}.  It returns
@code{nil}.
Karl Heuer's avatar
Karl Heuer committed
1198 1199 1200 1201 1202 1203 1204

The argument @var{how}, if non-@code{nil} specifies explicitly the style
of justification.  It can be @code{left}, @code{right}, @code{full},
@code{center}, or @code{none}.  If it is @code{t}, that means to do
follow specified justification style (see @code{current-justification},
below).  @code{nil} means to do full justification.

1205
If @var{eop} is non-@code{nil}, that means do left-justification if
Karl Heuer's avatar
Karl Heuer committed
1206 1207 1208 1209 1210 1211
@code{current-justification} specifies full justification.  This is used
for the last line of a paragraph; even if the paragraph as a whole is
fully justified, the last line should not be.

If @var{nosqueeze} is non-@code{nil}, that means do not change interior
whitespace.
Richard M. Stallman's avatar
Richard M. Stallman committed
1212 1213
@end deffn

Karl Heuer's avatar
Karl Heuer committed
1214 1215 1216 1217
@defopt default-justification
This variable's value specifies the style of justification to use for
text that doesn't specify a style with a text property.  The possible
values are @code{left}, @code{right}, @code{full}, @code{center}, or
Karl Heuer's avatar
Karl Heuer committed
1218
@code{none}.  The default value is @code{left}.
Karl Heuer's avatar
Karl Heuer committed
1219 1220 1221 1222 1223 1224 1225
@end defopt

@defun current-justification
This function returns the proper justification style to use for filling
the text around point.
@end defun

Karl Heuer's avatar
Karl Heuer committed
1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251
@defvar fill-paragraph-function
This variable provides a way for major modes to override the filling of
paragraphs.  If the value is non-@code{nil}, @code{fill-paragraph} calls
this function to do the work.  If the function returns a non-@code{nil}
value, @code{fill-paragraph} assumes the job is done, and immediately
returns that value.

The usual use of this feature is to fill comments in programming
language modes.  If the function needs to fill a paragraph in the usual
way, it can do so as follows:

@example
(let ((fill-paragraph-function nil))
  (fill-paragraph arg))
@end example
@end defvar

@defvar use-hard-newlines
If this variable is non-@code{nil}, the filling functions do not delete
newlines that have the @code{hard} text property.  These ``hard
newlines'' act as paragraph separators.
@end defvar

@node Margins
@section Margins for Filling

1252 1253 1254 1255 1256 1257 1258 1259
@defopt fill-prefix
This variable specifies a string of text that appears at the beginning
of normal text lines and should be disregarded when filling them.  Any
line that fails to start with the fill prefix is considered the start of
a paragraph; so is any line that starts with the fill prefix followed by
additional whitespace.  Lines that start with the fill prefix but no
additional whitespace are ordinary text lines that can be filled
together.  The resulting filled lines also start with the fill prefix.
Karl Heuer's avatar
Karl Heuer committed
1260 1261

The fill prefix follows the left margin whitespace, if any.
1262 1263
@end defopt

Richard M. Stallman's avatar
Richard M. Stallman committed
1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283
@defopt fill-column
This buffer-local variable specifies the maximum width of filled
lines.  Its value should be an integer, which is a number of columns.
All the filling, justification and centering commands are affected by
this variable, including Auto Fill mode (@pxref{Auto Filling}).

As a practical matter, if you are writing text for other people to
read, you should set @code{fill-column} to no more than 70.  Otherwise
the line will be too long for people to read comfortably, and this can
make the text seem clumsy.
@end defopt

@defvar default-fill-column
The value of this variable is the default value for @code{fill-column} in
buffers that do not override it.  This is the same as
@code{(default-value 'fill-column)}.

The default value for @code{default-fill-column} is 70.
@end defvar

Karl Heuer's avatar
Karl Heuer committed
1284 1285 1286 1287 1288 1289 1290
@deffn Command set-left-margin from to margin
This sets the @code{left-margin} property on the text from @var{from} to
@var{to} to the value @var{margin}.  If Auto Fill mode is enabled, this
command also refills the region to fit the new margin.
@end deffn

@deffn Command set-right-margin from to margin
Karl Heuer's avatar
Karl Heuer committed
1291 1292 1293
This sets the @code{right-margin} property on the text from @var{from}
to @var{to} to the value @var{margin}.  If Auto Fill mode is enabled,
this command also refills the region to fit the new margin.
Karl Heuer's avatar
Karl Heuer committed
1294 1295 1296 1297 1298 1299
@end deffn

@defun current-left-margin
This function returns the proper left margin value to use for filling
the text around point.  The value is the sum of the @code{left-margin}
property of the character at the start of the current line (or zero if
Karl Heuer's avatar
Karl Heuer committed
1300
none), and the value of the variable @code{left-margin}.
Karl Heuer's avatar
Karl Heuer committed
1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312
@end defun

@defun current-fill-column
This function returns the proper fill column value to use for filling
the text around point.  The value is the value of the @code{fill-column}
variable, minus the value of the @code{right-margin} property of the
character after point.
@end defun

@deffn Command move-to-left-margin &optional n force
This function moves point to the left margin of the current line.  The
column moved to is determined by calling the function
Karl Heuer's avatar
Karl Heuer committed
1313
@code{current-left-margin}.  If the argument @var{n} is non-@code{nil},
Karl Heuer's avatar
Karl Heuer committed
1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326
@code{move-to-left-margin} moves forward @var{n}@minus{}1 lines first.

If @var{force} is non-@code{nil}, that says to fix the line's
indentation if that doesn't match the left margin value.
@end deffn

@defun delete-to-left-margin from to
This function removes left margin indentation from the text
between @var{from} and @var{to}.  The amount of indentation
to delete is determined by calling @code{current-left-margin}.
In no case does this function delete non-whitespace.
@end defun

Karl Heuer's avatar
Karl Heuer committed
1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340
@defun indent-to-left-margin
This is the default @code{indent-line-function}, used in Fundamental
mode, Text mode, etc.  Its effect is to adjust the indentation at the
beginning of the current line to the value specified by the variable
@code{left-margin}.  This may involve either inserting or deleting
whitespace.
@end defun

@defvar left-margin
This variable specifies the base left margin column.  In Fundamental
mode, @key{LFD} indents to this column.  This variable automatically
becomes buffer-local when set in any fashion.
@end defvar

Richard M. Stallman's avatar
Richard M. Stallman committed
1341 1342 1343 1344 1345 1346
@node Auto Filling
@comment  node-name,  next,  previous,  up
@section Auto Filling
@cindex filling, automatic
@cindex Auto Fill mode

1347
  Auto Fill mode is a minor mode that fills lines automatically as text
1348
is inserted.  This section describes the hook used by Auto Fill mode.
1349 1350
For a description of functions that you can call explicitly to fill and
justify existing text, see @ref{Filling}.
Richard M. Stallman's avatar
Richard M. Stallman committed
1351

Karl Heuer's avatar
Karl Heuer committed
1352 1353 1354
  Auto Fill mode also enables the functions that change the margins and
justification style to refill portions of the text.  @xref{Margins}.

Richard M. Stallman's avatar
Richard M. Stallman committed
1355
@defvar auto-fill-function
Karl Heuer's avatar
Karl Heuer committed
1356 1357 1358
The value of this variable should be a function (of no arguments) to be
called after self-inserting a space or a newline.  It may be @code{nil},
in which case nothing special is done in that case.
Richard M. Stallman's avatar
Richard M. Stallman committed
1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370

The value of @code{auto-fill-function} is @code{do-auto-fill} when
Auto-Fill mode is enabled.  That is a function whose sole purpose is to
implement the usual strategy for breaking a line.

@quotation
In older Emacs versions, this variable was named @code{auto-fill-hook},
but since it is not called with the standard convention for hooks, it
was renamed to @code{auto-fill-function} in version 19.
@end quotation
@end defvar

1371 1372 1373 1374 1375 1376
@defvar normal-auto-fill-function
This variable specifies the function to use for
@code{auto-fill-function}, if and when Auto Fill is turned on.  Major
modes can set this locally to alter how Auto Fill works.
@end defvar

Richard M. Stallman's avatar
Richard M. Stallman committed
1377 1378 1379 1380 1381 1382 1383 1384 1385 1386
@node Sorting
@section Sorting Text
@cindex sorting text

  The sorting functions described in this section all rearrange text in
a buffer.  This is in contrast to the function @code{sort}, which
rearranges the order of the elements of a list (@pxref{Rearrangement}).
The values returned by these functions are not meaningful.

@defun sort-subr reverse nextrecfun endrecfun &optional startkeyfun endkeyfun
1387
This function is the general text-sorting routine that divides a buffer
Richard M. Stallman's avatar
Richard M. Stallman committed
1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654
into records and sorts them.  Most of the commands in this section use
this function.

To understand how @code{sort-subr} works, consider the whole accessible
portion of the buffer as being divided into disjoint pieces called
@dfn{sort records}.  The records may or may not be contiguous; they may
not overlap.  A portion of each sort record (perhaps all of it) is
designated as the sort key.  Sorting rearranges the records in order by
their sort keys.

Usually, the records are rearranged in order of ascending sort key.
If the first argument to the @code{sort-subr} function, @var{reverse},
is non-@code{nil}, the sort records are rearranged in order of
descending sort key.

The next four arguments to @code{sort-subr} are functions that are
called to move point across a sort record.  They are called many times
from within @code{sort-subr}.

@enumerate
@item
@var{nextrecfun} is called with point at the end of a record.  This
function moves point to the start of the next record.  The first record
is assumed to start at the position of point when @code{sort-subr} is
called.  Therefore, you should usually move point to the beginning of
the buffer before calling @code{sort-subr}.

This function can indicate there are no more sort records by leaving
point at the end of the buffer.

@item
@var{endrecfun} is called with point within a record.  It moves point to
the end of the record.

@item
@var{startkeyfun} is called to move point from the start of a record to
the start of the sort key.  This argument is optional; if it is omitted,
the whole record is the sort key.  If supplied, the function should
either return a non-@code{nil} value to be used as the sort key, or
return @code{nil} to indicate that the sort key is in the buffer
starting at point.  In the latter case, @var{endkeyfun} is called to
find the end of the sort key.

@item
@var{endkeyfun} is called to move point from the start of the sort key
to the end of the sort key.  This argument is optional.  If
@var{startkeyfun} returns @code{nil} and this argument is omitted (or
@code{nil}), then the sort key extends to the end of the record.  There
is no need for @var{endkeyfun} if @var{startkeyfun} returns a
non-@code{nil} value.
@end enumerate

As an example of @code{sort-subr}, here is the complete function
definition for @code{sort-lines}:

@example
@group
;; @r{Note that the first two lines of doc string}
;; @r{are effectively one line when viewed by a user.}
(defun sort-lines (reverse beg end)
  "Sort lines in region alphabetically.
Called from a program, there are three arguments:
@end group
@group
REVERSE (non-nil means reverse order),
and BEG and END (the region to sort)."
  (interactive "P\nr")
  (save-restriction
    (narrow-to-region beg end)
    (goto-char (point-min))
    (sort-subr reverse
               'forward-line
               'end-of-line)))
@end group
@end example

Here @code{forward-line} moves point to the start of the next record,
and @code{end-of-line} moves point to the end of record.  We do not pass
the arguments @var{startkeyfun} and @var{endkeyfun}, because the entire
record is used as the sort key.

The @code{sort-paragraphs} function is very much the same, except that
its @code{sort-subr} call looks like this:

@example
@group
(sort-subr reverse
           (function 
            (lambda () 
              (skip-chars-forward "\n \t\f")))
           'forward-paragraph)
@end group
@end example
@end defun

@deffn Command sort-regexp-fields reverse record-regexp key-regexp start end
This command sorts the region between @var{start} and @var{end}
alphabetically as specified by @var{record-regexp} and @var{key-regexp}.
If @var{reverse} is a negative integer, then sorting is in reverse
order.

Alphabetical sorting means that two sort keys are compared by
comparing the first characters of each, the second characters of each,
and so on.  If a mismatch is found, it means that the sort keys are
unequal; the sort key whose character is less at the point of first
mismatch is the lesser sort key.  The individual characters are compared
according to their numerical values.  Since Emacs uses the @sc{ASCII}
character set, the ordering in that set determines alphabetical order.
@c version 19 change

The value of the @var{record-regexp} argument specifies how to divide
the buffer into sort records.  At the end of each record, a search is
done for this regular expression, and the text that matches it is the
next record.  For example, the regular expression @samp{^.+$}, which
matches lines with at least one character besides a newline, would make
each such line into a sort record.  @xref{Regular Expressions}, for a
description of the syntax and meaning of regular expressions.

The value of the @var{key-regexp} argument specifies what part of each
record is the sort key.  The @var{key-regexp} could match the whole
record, or only a part.  In the latter case, the rest of the record has
no effect on the sorted order of records, but it is carried along when
the record moves to its new position.

The @var{key-regexp} argument can refer to the text matched by a
subexpression of @var{record-regexp}, or it can be a regular expression
on its own.

If @var{key-regexp} is:

@table @asis
@item @samp{\@var{digit}}
then the text matched by the @var{digit}th @samp{\(...\)} parenthesis
grouping in @var{record-regexp} is the sort key.

@item @samp{\&}
then the whole record is the sort key.

@item a regular expression
then @code{sort-regexp-fields} searches for a match for the regular
expression within the record.  If such a match is found, it is the sort
key.  If there is no match for @var{key-regexp} within a record then
that record is ignored, which means its position in the buffer is not
changed.  (The other records may move around it.)
@end table

For example, if you plan to sort all the lines in the region by the
first word on each line starting with the letter @samp{f}, you should
set @var{record-regexp} to @samp{^.*$} and set @var{key-regexp} to
@samp{\<f\w*\>}.  The resulting expression looks like this:

@example
@group
(sort-regexp-fields nil "^.*$" "\\<f\\w*\\>"
                    (region-beginning)
                    (region-end))
@end group
@end example

If you call @code{sort-regexp-fields} interactively, it prompts for
@var{record-regexp} and @var{key-regexp} in the minibuffer.
@end deffn

@deffn Command sort-lines reverse start end
This command alphabetically sorts lines in the region between
@var{start} and @var{end}.  If @var{reverse} is non-@code{nil}, the sort
is in reverse order.
@end deffn

@deffn Command sort-paragraphs reverse start end
This command alphabetically sorts paragraphs in the region between
@var{start} and @var{end}.  If @var{reverse} is non-@code{nil}, the sort
is in reverse order.
@end deffn

@deffn Command sort-pages reverse start end
This command alphabetically sorts pages in the region between
@var{start} and @var{end}.  If @var{reverse} is non-@code{nil}, the sort
is in reverse order.
@end deffn

@deffn Command sort-fields field start end
This command sorts lines in the region between @var{start} and
@var{end}, comparing them alphabetically by the @var{field}th field
of each line.  Fields are separated by whitespace and numbered starting
from 1.  If @var{field} is negative, sorting is by the
@w{@minus{}@var{field}th} field from the end of the line.  This command
is useful for sorting tables.
@end deffn

@deffn Command sort-numeric-fields field start end
This command sorts lines in the region between @var{start} and
@var{end}, comparing them numerically by the @var{field}th field of each
line.  The specified field must contain a number in each line of the
region.  Fields are separated by whitespace and numbered starting from
1.  If @var{field} is negative, sorting is by the
@w{@minus{}@var{field}th} field from the end of the line.  This command
is useful for sorting tables.
@end deffn

@deffn Command sort-columns reverse &optional beg end
This command sorts the lines in the region between @var{beg} and
@var{end}, comparing them alphabetically by a certain range of columns.
The column positions of @var{beg} and @var{end} bound the range of
columns to sort on.

If @var{reverse} is non-@code{nil}, the sort is in reverse order.

One unusual thing about this command is that the entire line
containing position @var{beg}, and the entire line containing position
@var{end}, are included in the region sorted.

Note that @code{sort-columns} uses the @code{sort} utility program,
and so cannot work properly on text containing tab characters.  Use
@kbd{M-x @code{untabify}} to convert tabs to spaces before sorting.
@end deffn

@node Columns
@comment  node-name,  next,  previous,  up
@section Counting Columns
@cindex columns
@cindex counting columns
@cindex horizontal position

  The column functions convert between a character position (counting
characters from the beginning of the buffer) and a column position
(counting screen characters from the beginning of a line).

  A character counts according to the number of columns it occupies on
the screen.  This means control characters count as occupying 2 or 4
columns, depending upon the value of @code{ctl-arrow}, and tabs count as
occupying a number of columns that depends on the value of
@code{tab-width} and on the column where the tab begins.  @xref{Usual Display}.

  Column number computations ignore the width of the window and the
amount of horizontal scrolling.  Consequently, a column value can be
arbitrarily high.  The first (or leftmost) column is numbered 0.

@defun current-column
This function returns the horizontal position of point, measured in
columns, counting from 0 at the left margin.  The column position is the
sum of the widths of all the displayed representations of the characters
between the start of the current line and point.

For an example of using @code{current-column}, see the description of
@code{count-lines} in @ref{Text Lines}.
@end defun

@defun move-to-column column &optional force
This function moves point to @var{column} in the current line.  The
calculation of @var{column} takes into account the widths of the
displayed representations of the characters between the start of the
line and point.

If column @var{column} is beyond the end of the line, point moves to the
end of the line.  If @var{column} is negative, point moves to the
beginning of the line.

If it is impossible to move to column @var{column} because that is in
the middle of a multicolumn character such as a tab, point moves to the
end of that character.  However, if @var{force} is non-@code{nil}, and
@var{column} is in the middle of a tab, then @code{move-to-column}
converts the tab into spaces so that it can move precisely to column
@var{column}.  Other multicolumn characters can cause anomalies despite
@var{force}, since there is no way to split them.

The argument @var{force} also has an effect if the line isn't long
1655 1656
enough to reach column @var{column}; in that case, it says to add
whitespace at the end of the line to reach that column.
Richard M. Stallman's avatar
Richard M. Stallman committed
1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699

If @var{column} is not an integer, an error is signaled.

The return value is the column number actually moved to.
@end defun

@node Indentation
@section Indentation
@cindex indentation

  The indentation functions are used to examine, move to, and change
whitespace that is at the beginning of a line.  Some of the functions
can also change whitespace elsewhere on a line.  Columns and indentation
count from zero at the left margin.

@menu
* Primitive Indent::      Functions used to count and insert indentation.
* Mode-Specific Indent::  Customize indentation for different modes.
* Region Indent::         Indent all the lines in a region.
* Relative Indent::       Indent the current line based on previous lines.
* Indent Tabs::           Adjustable, typewriter-like tab stops.
* Motion by Indent::      Move to first non-blank character.
@end menu

@node Primitive Indent
@subsection Indentation Primitives

  This section describes the primitive functions used to count and
insert indentation.  The functions in the following sections use these
primitives.

@defun current-indentation
@comment !!Type Primitive Function
@comment !!SourceFile indent.c
This function returns the indentation of the current line, which is
the horizontal position of the first nonblank character.  If the
contents are entirely blank, then this is the horizontal position of the
end of the line.
@end defun

@deffn Command indent-to column &optional minimum
@comment !!Type Primitive Function
@comment !!SourceFile indent.c
1700 1701 1702 1703 1704 1705
This function indents from point with tabs and spaces until @var{column}
is reached.  If @var{minimum} is specified and non-@code{nil}, then at
least that many spaces are inserted even if this requires going beyond
@var{column}.  Otherwise the function does nothing if point is already
beyond @var{column}.  The value is the column at which the inserted
indentation ends.
Richard M. Stallman's avatar
Richard M. Stallman committed
1706 1707 1708 1709

The inserted whitespace characters inherit text properties from the
surrounding text (usually, from the preceding text only).  @xref{Sticky
Properties}.
Richard M. Stallman's avatar
Richard M. Stallman committed
1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747
@end deffn

@defopt indent-tabs-mode
@comment !!SourceFile indent.c
If this variable is non-@code{nil}, indentation functions can insert
tabs as well as spaces.  Otherwise, they insert only spaces.  Setting
this variable automatically makes it local to the current buffer.
@end defopt

@node Mode-Specific Indent
@subsection Indentation Controlled by Major Mode

  An important function of each major mode is to customize the @key{TAB}
key to indent properly for the language being edited.  This section
describes the mechanism of the @key{TAB} key and how to control it.
The functions in this section return unpredictable values.

@defvar indent-line-function
This variable's value is the function to be used by @key{TAB} (and
various commands) to indent the current line.  The command
@code{indent-according-to-mode} does no more than call this function.

In Lisp mode, the value is the symbol @code{lisp-indent-line}; in C
mode, @code{c-indent-line}; in Fortran mode, @code{fortran-indent-line}.
In Fundamental mode, Text mode, and many other modes with no standard
for indentation, the value is @code{indent-to-left-margin} (which is the
default value).
@end defvar

@deffn Command indent-according-to-mode
This command calls the function in @code{indent-line-function} to
indent the current line in a way appropriate for the current major mode.
@end deffn

@deffn Command indent-for-tab-command
This command calls the function in @code{indent-line-function} to indent
the current line; except that if that function is
@code{indent-to-left-margin}, it calls @code{insert-tab} instead.  (That
1748
is a trivial command that inserts a tab character.)
Richard M. Stallman's avatar
Richard M. Stallman committed
1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779
@end deffn

@deffn Command newline-and-indent
@comment !!SourceFile simple.el
This function inserts a newline, then indents the new line (the one
following the newline just inserted) according to the major mode.

It does indentation by calling the current @code{indent-line-function}.
In programming language modes, this is the same thing @key{TAB} does,
but in some text modes, where @key{TAB} inserts a tab,
@code{newline-and-indent} indents to the column specified by
@code{left-margin}.
@end deffn

@deffn Command reindent-then-newline-and-indent
@comment !!SourceFile simple.el
This command reindents the current line, inserts a newline at point,
and then reindents the new line (the one following the newline just
inserted).

This command does indentation on both lines according to the current
major mode, by calling the current value of @code{indent-line-function}.
In programming language modes, this is the same thing @key{TAB} does,
but in some text modes, where @key{TAB} inserts a tab,
@code{reindent-then-newline-and-indent} indents to the column specified
by @code{left-margin}.
@end deffn

@node Region Indent
@subsection Indenting an Entire Region

1780
  This section describes commands that indent all the lines in the
Richard M. Stallman's avatar
Richard M. Stallman committed
1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807
region.  They return unpredictable values.

@deffn Command indent-region start end to-column
This command indents each nonblank line starting between @var{start}
(inclusive) and @var{end} (exclusive).  If @var{to-column} is
@code{nil}, @code{indent-region} indents each nonblank line by calling
the current mode's indentation function, the value of
@code{indent-line-function}.

If @var{to-column} is non-@code{nil}, it should be an integer
specifying the number of columns of indentation; then this function
gives each line exactly that much indentation, by either adding or
deleting whitespace.

If there is a fill prefix, @code{indent-region} indents each line
by making it start with the fill prefix.
@end deffn

@defvar indent-region-function
The value of this variable is a function that can be used by
@code{indent-region} as a short cut.  You should design the function so
that it will produce the same results as indenting the lines of the
region one by one, but presumably faster.

If the value is @code{nil}, there is no short cut, and
@code{indent-region} actually works line by line.

1808
A short-cut function is useful in modes such as C mode and Lisp mode,
Richard M. Stallman's avatar
Richard M. Stallman committed
1809
where the @code{indent-line-function} must scan from the beginning of
1810 1811 1812 1813
the function definition: applying it to each line would be quadratic in
time.  The short cut can update the scan information as it moves through
the lines indenting them; this takes linear time.  In a mode where
indenting a line individually is fast, there is no need for a short cut.
Richard M. Stallman's avatar
Richard M. Stallman committed
1814