lisp/textmodes/fill.el

   1 ;;; fill.el --- fill commands for Emacs
   2
   3 ;; Copyright (C) 1985, 86, 92, 94, 95, 96, 97, 1999 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: wp
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; All the commands for filling text.  These are documented in the Emacs
  28 ;; manual.
  29
  30 ;;; Code:
  31
  32 (defcustom fill-individual-varying-indent nil
  33   "*Controls criterion for a new paragraph in `fill-individual-paragraphs'.
  34 Non-nil means changing indent doesn't end a paragraph.
  35 That mode can handle paragraphs with extra indentation on the first line,
  36 but it requires separator lines between paragraphs.
  37 A value of nil means that any change in indentation starts a new paragraph."
  38   :type 'boolean
  39   :group 'fill)
  40
  41 (defcustom sentence-end-double-space t
  42   "*Non-nil means a single space does not end a sentence.
  43 This is relevant for filling.  See also `sentence-end-without-period'
  44 and `colon-double-space'.
  45
  46 If you change this, you should also change `sentence-end'.  See Info
  47 node `Sentences'."
  48   :type 'boolean
  49   :group 'fill)
  50
  51 (defcustom colon-double-space nil
  52   "*Non-nil means put two spaces after a colon when filling."
  53   :type 'boolean
  54   :group 'fill)
  55
  56 (defcustom sentence-end-without-period nil
  57   "*Non-nil means a sentence will end without a period.
  58 For example, a sentence in Thai text ends with double space but
  59 without a period."
  60   :type 'boolean
  61   :group 'fill)
  62
  63 (defvar fill-paragraph-function nil
  64   "Mode-specific function to fill a paragraph, or nil if there is none.
  65 If the function returns nil, then `fill-paragraph' does its normal work.")
  66
  67 (defvar enable-kinsoku t
  68   "*Non-nil means enable \"kinsoku\" processing on filling paragraph.
  69 Kinsoku processing is designed to prevent certain characters from being
  70 placed at the beginning or end of a line by filling.
  71 See the documentation of `kinsoku' for more information.")
  72
  73 (defun set-fill-prefix ()
  74   "Set the fill prefix to the current line up to point.
  75 Filling expects lines to start with the fill prefix and
  76 reinserts the fill prefix in each resulting line."
  77   (interactive)
  78   (let ((left-margin-pos (save-excursion (move-to-left-margin) (point))))
  79     (if (> (point) left-margin-pos)
  80         (progn
  81           (setq fill-prefix (buffer-substring left-margin-pos (point)))
  82           (if (equal fill-prefix "")
  83               (setq fill-prefix nil)))
  84       (setq fill-prefix nil)))
  85   (if fill-prefix
  86       (message "fill-prefix: \"%s\"" fill-prefix)
  87     (message "fill-prefix cancelled")))
  88
  89 (defcustom adaptive-fill-mode t
  90   "*Non-nil means determine a paragraph's fill prefix from its text."
  91   :type 'boolean
  92   :group 'fill)
  93
  94 (defcustom adaptive-fill-regexp
  95   (purecopy "[ \t]*\\([-|#;>*]+[ \t]*\\|(?[0-9]+[.)][ \t]*\\)*")
  96   "*Regexp to match text at start of line that constitutes indentation.
  97 If Adaptive Fill mode is enabled, a prefix matching this pattern
  98 on the first and second lines of a paragraph is used as the
  99 standard indentation for the whole paragraph.
 100
 101 If the paragraph has just one line, the indentation is taken from that
 102 line, but in that case `adaptive-fill-first-line-regexp' also plays
 103 a role."
 104   :type 'regexp
 105   :group 'fill)
 106
 107 (defcustom adaptive-fill-first-line-regexp "\\`[ \t]*\\'"
 108   "*Regexp specifying whether to set fill prefix from a one-line paragraph.
 109 When a paragraph has just one line, then after `adaptive-fill-regexp'
 110 finds the prefix at the beginning of the line, if it doesn't
 111 match this regexp, it is replaced with whitespace.
 112
 113 By default, this regexp matches sequences of just spaces and tabs.
 114
 115 However, we never use a prefix from a one-line paragraph
 116 if it would act as a paragraph-starter on the second line."
 117   :type 'regexp
 118   :group 'fill)
 119
 120 (defcustom adaptive-fill-function nil
 121   "*Function to call to choose a fill prefix for a paragraph, or nil.
 122 This function is used when `adaptive-fill-regexp' does not match."
 123   :type '(choice (const nil) function)
 124   :group 'fill)
 125
 126 (defvar fill-indent-according-to-mode nil
 127   "Whether or not filling should try to use the major mode's indentation.")
 128
 129 (defun current-fill-column ()
 130   "Return the fill-column to use for this line.
 131 The fill-column to use for a buffer is stored in the variable `fill-column',
 132 but can be locally modified by the `right-margin' text property, which is
 133 subtracted from `fill-column'.
 134
 135 The fill column to use for a line is the first column at which the column
 136 number equals or exceeds the local fill-column - right-margin difference."
 137   (save-excursion
 138     (if fill-column
 139         (let* ((here (progn (beginning-of-line) (point)))
 140                (here-col 0)
 141                (eol (progn (end-of-line) (point)))
 142                margin fill-col change col)
 143           ;; Look separately at each region of line with a different
 144           ;; right-margin.
 145           (while (and (setq margin (get-text-property here 'right-margin)
 146                             fill-col (- fill-column (or margin 0))
 147                             change (text-property-not-all
 148                                     here eol 'right-margin margin))
 149                       (progn (goto-char (1- change))
 150                              (setq col (current-column))
 151                              (< col fill-col)))
 152             (setq here change
 153                   here-col col))
 154           (max here-col fill-col)))))
 155
 156 (defun canonically-space-region (beg end)
 157   "Remove extra spaces between words in region.
 158 Leave one space between words, two at end of sentences or after colons
 159 \(depending on values of `sentence-end-double-space', `colon-double-space',
 160 and `sentence-end-without-period').
 161 Remove indentation from each line."
 162   (interactive "*r")
 163   (save-excursion
 164     (goto-char beg)
 165     ;; Nuke tabs; they get screwed up in a fill.
 166     ;; This is quick, but loses when a tab follows the end of a sentence.
 167     ;; Actually, it is difficult to tell that from "Mr.\tSmith".
 168     ;; Blame the typist.
 169     (subst-char-in-region beg end ?\t ?\ )
 170     (while (and (< (point) end)
 171                 (re-search-forward "   *" end t))
 172       (delete-region
 173        (+ (match-beginning 0)
 174           ;; Determine number of spaces to leave:
 175           (save-excursion
 176             (skip-chars-backward " ]})\"'")
 177             (cond ((and sentence-end-double-space
 178                         (or (memq (preceding-char) '(?. ?? ?!))
 179                             (and sentence-end-without-period
 180                                  (= (char-syntax (preceding-char)) ?w)))) 2)
 181                   ((and colon-double-space
 182                         (= (preceding-char) ?:))  2)
 183                   ((char-equal (preceding-char) ?\n)  0)
 184                   (t 1))))
 185        (match-end 0)))
 186     ;; Make sure sentences ending at end of line get an extra space.
 187     ;; loses on split abbrevs ("Mr.\nSmith")
 188     (goto-char beg)
 189     (let ((eol-double-space-re (if colon-double-space
 190                                    "[.?!:][])}\"']*$"
 191                                  "[.?!][])}\"']*$")))
 192       (while (and (< (point) end)
 193                 (re-search-forward eol-double-space-re end t))
 194       ;; We insert before markers in case a caller such as
 195       ;; do-auto-fill has done a save-excursion with point at the end
 196       ;; of the line and wants it to stay at the end of the line.
 197       (insert-before-markers-and-inherit ? )))))
 198
 199 (defun fill-common-string-prefix (s1 s2)
 200   "Return the longest common prefix of strings S1 and S2, or nil if none."
 201   (let ((cmp (compare-strings s1 nil nil s2 nil nil)))
 202     (if (eq cmp t)
 203         s1
 204       (setq cmp (1- (abs cmp)))
 205       (unless (zerop cmp)
 206         (substring s1 0 cmp)))))
 207
 208 (defun fill-context-prefix (from to &optional first-line-regexp)
 209   "Compute a fill prefix from the text between FROM and TO.
 210 This uses the variables `adaptive-fill-regexp' and `adaptive-fill-function'
 211 and `adaptive-fill-first-line-regexp'.  `paragraph-start' also plays a role;
 212 we reject a prefix based on a one-line paragraph if that prefix would
 213 act as a paragraph-separator."
 214   (or first-line-regexp
 215       (setq first-line-regexp adaptive-fill-first-line-regexp))
 216   (save-excursion
 217     (goto-char from)
 218     (if (eolp) (forward-line 1))
 219     ;; Move to the second line unless there is just one.
 220     (let ((firstline (point))
 221           first-line-prefix
 222           ;; Non-nil if we are on the second line.
 223           at-second
 224           second-line-prefix
 225           start)
 226       (move-to-left-margin)
 227       (setq start (point))
 228       (setq first-line-prefix
 229             ;; We don't need to consider `paragraph-start' here since it
 230             ;; will be explicitly checked later on.
 231             ;; Also setting first-line-prefix to nil prevents
 232             ;; second-line-prefix from being used.
 233             (cond ;; ((looking-at paragraph-start) nil)
 234                   ((and adaptive-fill-regexp (looking-at adaptive-fill-regexp))
 235                    (buffer-substring-no-properties start (match-end 0)))
 236                   (adaptive-fill-function (funcall adaptive-fill-function))))
 237       (forward-line 1)
 238       (if (>= (point) to)
 239           (goto-char firstline)
 240         (setq at-second t)
 241         (move-to-left-margin)
 242         (setq start (point))
 243         (setq second-line-prefix
 244               (cond ((looking-at paragraph-start) nil)
 245                     ((and adaptive-fill-regexp
 246                           (looking-at adaptive-fill-regexp))
 247                      (buffer-substring-no-properties start (match-end 0)))
 248                     (adaptive-fill-function
 249                      (funcall adaptive-fill-function)))))
 250       (if at-second
 251           ;; If we get a fill prefix from the second line,
 252           ;; make sure it or something compatible is on the first line too.
 253           (and second-line-prefix first-line-prefix
 254                ;; If the first line has the second line prefix too, use it.
 255                (if (or (string-match (concat "\\`"
 256                                              (regexp-quote second-line-prefix)
 257                                              "\\(\\'\\|[ \t]\\)")
 258                                      first-line-prefix)
 259                        ;; If the second line prefix is whitespace, use it.
 260                        (string-match "\\`[ \t]+\\'" second-line-prefix))
 261                    second-line-prefix
 262
 263                  ;; If using the common prefix of first-line-prefix
 264                  ;; and second-line-prefix leads to problems, consider
 265                  ;; to restore the code below that's commented out,
 266                  ;; and document why a common prefix cannot be used.
 267
 268 ;                ;; If the second line has the first line prefix,
 269 ;                ;; plus whitespace, use the part that the first line shares.
 270 ;                (if (string-match (concat "\\`"
 271 ;                                            (regexp-quote first-line-prefix)
 272 ;                                            "[ \t]*\\'")
 273 ;                                  second-line-prefix)
 274 ;                    first-line-prefix)))
 275
 276                  ;; Use the longest common substring of both prefixes,
 277                  ;; if there is one.
 278                  (fill-common-string-prefix first-line-prefix
 279                                             second-line-prefix)))
 280         ;; If we get a fill prefix from a one-line paragraph,
 281         ;; maybe change it to whitespace,
 282         ;; and check that it isn't a paragraph starter.
 283         (if first-line-prefix
 284             (let ((result
 285                    ;; If first-line-prefix comes from the first line,
 286                    ;; see if it seems reasonable to use for all lines.
 287                    ;; If not, replace it with whitespace.
 288                    (if (or (and first-line-regexp
 289                                 (string-match first-line-regexp
 290                                               first-line-prefix))
 291                            (and comment-start-skip
 292                                 (string-match comment-start-skip
 293                                               first-line-prefix)))
 294                        first-line-prefix
 295                      (make-string (string-width first-line-prefix) ?\ ))))
 296               ;; But either way, reject it if it indicates the start
 297               ;; of a paragraph when text follows it.
 298               (if (not (eq 0 (string-match paragraph-start
 299                                            (concat result "a"))))
 300                   result)))))))
 301
 302 (defvar fill-nobreak-predicate nil
 303   "If non-nil, a predicate for recognizing places not to break a line.
 304 The predicate is called with no arguments, with point at the place
 305 to be tested.  If it returns t, fill commands do not break the line there.")
 306
 307 ;; Put `fill-find-break-point-function' property to charsets which
 308 ;; require special functions to find line breaking point.
 309 (let ((alist '((katakana-jisx0201 . kinsoku)
 310                (chinese-gb2312 . kinsoku)
 311                (japanese-jisx0208 . kinsoku)
 312                (japanese-jisx0212 . kinsoku)
 313                (chinese-big5-1 . kinsoku)
 314                (chinese-big5-2 . kinsoku))))
 315   (while alist
 316     (put-charset-property (car (car alist)) 'fill-find-break-point-function
 317                           (cdr (car alist)))
 318     (setq alist (cdr alist))))
 319
 320 (defun fill-find-break-point (limit)
 321   "Move point to a proper line breaking position of the current line.
 322 Don't move back past the buffer position LIMIT.
 323
 324 This function is called when we are going to break the current line
 325 after or before a non-ascii character.  If the charset of the
 326 character has the property `fill-find-break-point-function', this
 327 function calls the property value as a function with one arg LINEBEG.
 328 If the charset has no such property, do nothing."
 329   (let* ((ch (following-char))
 330          (charset (char-charset ch))
 331          func)
 332     (if (eq charset 'ascii)
 333         (setq ch (preceding-char)
 334               charset (char-charset ch)))
 335     (if (charsetp charset)
 336         (setq func
 337               (get-charset-property charset 'fill-find-break-point-function)))
 338     (if (and func (fboundp func))
 339         (funcall func limit))))
 340
 341 (defun fill-region-as-paragraph (from to &optional justify
 342                                       nosqueeze squeeze-after)
 343   "Fill the region as one paragraph.
 344 It removes any paragraph breaks in the region and extra newlines at the end,
 345 indents and fills lines between the margins given by the
 346 `current-left-margin' and `current-fill-column' functions.
 347 \(In most cases, the variable `fill-column' controls the width.)
 348 It leaves point at the beginning of the line following the paragraph.
 349
 350 Normally performs justification according to the `current-justification'
 351 function, but with a prefix arg, does full justification instead.
 352
 353 From a program, optional third arg JUSTIFY can specify any type of
 354 justification.  Fourth arg NOSQUEEZE non-nil means not to make spaces
 355 between words canonical before filling.  Fifth arg SQUEEZE-AFTER, if non-nil,
 356 means don't canonicalize spaces before that position.
 357
 358 Return the fill-prefix used for filling.
 359
 360 If `sentence-end-double-space' is non-nil, then period followed by one
 361 space does not end a sentence, so don't break a line there."
 362   (interactive (progn
 363                  (barf-if-buffer-read-only)
 364                  (list (region-beginning) (region-end)
 365                        (if current-prefix-arg 'full))))
 366   (unless (memq justify '(t nil none full center left right))
 367     (setq justify 'full))
 368   ;; Arrange for undoing the fill to restore point.
 369   (if (and buffer-undo-list (not (eq buffer-undo-list t)))
 370       (setq buffer-undo-list (cons (point) buffer-undo-list)))
 371
 372   ;; Make sure "to" is the endpoint.
 373   (goto-char (min from to))
 374   (setq to   (max from to))
 375   ;; Ignore blank lines at beginning of region.
 376   (skip-chars-forward " \t\n")
 377
 378   (let ((from-plus-indent (point))
 379         (oneleft nil))
 380
 381     (beginning-of-line)
 382     (setq from (point))
 383
 384     ;; Delete all but one soft newline at end of region.
 385     ;; And leave TO before that one.
 386     (goto-char to)
 387     (while (and (> (point) from) (eq ?\n (char-after (1- (point)))))
 388       (if (and oneleft
 389                (not (and use-hard-newlines
 390                          (get-text-property (1- (point)) 'hard))))
 391           (delete-backward-char 1)
 392         (backward-char 1)
 393         (setq oneleft t)))
 394     (setq to (point))
 395     ;; ;; If there was no newline, and there is text in the paragraph, then
 396     ;; ;; create a newline.
 397     ;; (if (and (not oneleft) (> to from-plus-indent))
 398     ;;  (newline))
 399     (goto-char from-plus-indent))
 400
 401   (if (not (> to (point)))
 402       nil ; There is no paragraph, only whitespace: exit now.
 403
 404     (or justify (setq justify (current-justification)))
 405
 406     ;; Don't let Adaptive Fill mode alter the fill prefix permanently.
 407     (let ((fill-prefix fill-prefix))
 408       ;; Figure out how this paragraph is indented, if desired.
 409       (if (and adaptive-fill-mode
 410                (or (null fill-prefix) (string= fill-prefix "")))
 411           (setq fill-prefix (fill-context-prefix from to)))
 412
 413       (save-restriction
 414         (goto-char from)
 415         (beginning-of-line)
 416         (narrow-to-region (point) to)
 417
 418         (if (not justify)           ; filling disabled: just check indentation
 419             (progn
 420               (goto-char from)
 421               (while (not (eobp))
 422                 (if (and (not (eolp))
 423                          (< (current-indentation) (current-left-margin)))
 424                     (indent-to-left-margin))
 425                 (forward-line 1)))
 426
 427           (if use-hard-newlines
 428               (remove-text-properties from (point-max) '(hard nil)))
 429           ;; Make sure first line is indented (at least) to left margin...
 430           (if (or (memq justify '(right center))
 431                   (< (current-indentation) (current-left-margin)))
 432               (indent-to-left-margin))
 433           ;; Delete the fill prefix from every line except the first.
 434           ;; The first line may not even have a fill prefix.
 435           (goto-char from)
 436           (let ((fpre (and fill-prefix (not (equal fill-prefix ""))
 437                            (concat "[ \t]*"
 438                                    (regexp-quote fill-prefix)
 439                                    "[ \t]*"))))
 440             (and fpre
 441                  (progn
 442                    (if (>= (+ (current-left-margin) (length fill-prefix))
 443                            (current-fill-column))
 444                        (error "fill-prefix too long for specified width"))
 445                    (goto-char from)
 446                    (forward-line 1)
 447                    (while (not (eobp))
 448                      (if (looking-at fpre)
 449                          (delete-region (point) (match-end 0)))
 450                      (forward-line 1))
 451                    (goto-char from)
 452                    (if (looking-at fpre)
 453                        (goto-char (match-end 0)))
 454                    (setq from (point)))))
 455           ;; Remove indentation from lines other than the first.
 456           (beginning-of-line 2)
 457           (indent-region (point) (point-max) 0)
 458           (goto-char from)
 459
 460           ;; FROM, and point, are now before the text to fill,
 461           ;; but after any fill prefix on the first line.
 462
 463           ;; Make sure sentences ending at end of line get an extra space.
 464           ;; loses on split abbrevs ("Mr.\nSmith")
 465           (let ((eol-double-space-re (if colon-double-space
 466                                          "[.?!:][])}\"']*$"
 467                                        "[.?!][])}\"']*$")))
 468             (while (re-search-forward eol-double-space-re nil t)
 469               (or (eobp) (insert-and-inherit ?\ ))))
 470
 471           (goto-char from)
 472           (if enable-multibyte-characters
 473               ;; Delete unnecessay newlines surrounded by words.  The
 474               ;; character category `|' means that we can break a line
 475               ;; at the character.  And, charset property
 476               ;; `nospace-between-words' tells how to concatenate
 477               ;; words.  If the value is non-nil, never put spaces
 478               ;; between words, thus delete a newline between them.
 479               ;; If the value is nil, delete a newline only when a
 480               ;; character preceding a newline has text property
 481               ;; `nospace-between-words'.
 482               (while (search-forward "\n" nil t)
 483                 (let ((prev (char-before (match-beginning 0)))
 484                       (next (following-char)))
 485                   (if (and (or (aref (char-category-set next) ?|)
 486                                (aref (char-category-set prev) ?|))
 487                            (or (get-charset-property (char-charset prev)
 488                                                      'nospace-between-words)
 489                                (get-text-property (1- (match-beginning 0))
 490                                                   'nospace-between-words)))
 491                       (delete-char -1)))))
 492
 493           (goto-char from)
 494           (skip-chars-forward " \t")
 495           ;; Then change all newlines to spaces.
 496           (subst-char-in-region from (point-max) ?\n ?\ )
 497           (if (and nosqueeze (not (eq justify 'full)))
 498               nil
 499             (canonically-space-region (or squeeze-after (point)) (point-max))
 500             (goto-char (point-max))
 501             (delete-horizontal-space)
 502             (insert-and-inherit " "))
 503           (goto-char (point-min))
 504
 505           ;; This is the actual filling loop.
 506           (let ((prefixcol 0) linebeg)
 507             (while (not (eobp))
 508               (setq linebeg (point))
 509               (move-to-column (1+ (current-fill-column)))
 510               (if (eobp)
 511                   (or nosqueeze (delete-horizontal-space))
 512                 ;; Move back to the point where we can break the line
 513                 ;; at.  We break the line between word or after/before
 514                 ;; the character which has character category `|'.  We
 515                 ;; search space, \c| followed by a character, or \c|
 516                 ;; following a character.  If not found, place
 517                 ;; the point at linebeg.
 518                 (if (re-search-backward " \\|\\c|.\\|.\\c|" linebeg 0)
 519                     ;; In case of space, we place the point at next to
 520                     ;; the point where the break occurs acutually,
 521                     ;; because we don't want to change the following
 522                     ;; logic of original Emacs.  In case of \c|, the
 523                     ;; point is at the place where the break occurs.
 524                     (forward-char 1))
 525                 ;; Don't break after a period followed by just one space.
 526                 ;; Move back to the previous place to break.
 527                 ;; The reason is that if a period ends up at the end of a line,
 528                 ;; further fills will assume it ends a sentence.
 529                 ;; If we now know it does not end a sentence,
 530                 ;; avoid putting it at the end of the line.
 531                 (while (and (> (point) linebeg)
 532                             (or (and sentence-end-double-space
 533                                      (> (point) (+ linebeg 2))
 534                                      (eq (preceding-char) ?\ )
 535                                      (not (eq (following-char) ?\ ))
 536                                      (eq (char-after (- (point) 2)) ?\.)
 537                                      (progn (forward-char -2) t))
 538                                 (and fill-nobreak-predicate
 539                                      (funcall fill-nobreak-predicate)
 540                                      (skip-chars-backward " \t"))))
 541                   (if (re-search-backward " \\|\\c|.\\|.\\c|" linebeg 0)
 542                       (forward-char 1)))
 543                 ;; If the left margin and fill prefix by themselves
 544                 ;; pass the fill-column. or if they are zero
 545                 ;; but we have no room for even one word,
 546                 ;; keep at least one word or a character which has
 547                 ;; category `|'anyway .
 548                 ;; This handles ALL BUT the first line of the paragraph.
 549                 (if (if (zerop prefixcol)
 550                         (save-excursion
 551                           (skip-chars-backward " \t" linebeg)
 552                           (bolp))
 553                       (>= prefixcol (current-column)))
 554                     ;; Ok, skip at least one word or one \c| character.
 555                     ;; Meanwhile, don't stop at a period followed by one space.
 556                     (let ((first t))
 557                       (move-to-column prefixcol)
 558                       (while (and (not (eobp))
 559                                   (or first
 560                                       (and (not (bobp))
 561                                            sentence-end-double-space
 562                                            (save-excursion
 563                                              (forward-char -1)
 564                                              (and (looking-at "\\. ")
 565                                                   (not (looking-at "\\.  ")))))
 566                                       (and fill-nobreak-predicate
 567                                            (funcall fill-nobreak-predicate))))
 568                         ;; Find a breakable point while ignoring the
 569                         ;; following spaces.
 570                         (skip-chars-forward " \t")
 571                         (if (looking-at "\\c|")
 572                             (forward-char 1)
 573                           (let ((pos (save-excursion
 574                                        (skip-chars-forward "^ \n\t")
 575                                        (point))))
 576                             (if (re-search-forward "\\c|" pos t)
 577                                 (forward-char -1)
 578                               (goto-char pos))))
 579                         (setq first nil)))
 580                   ;; Normally, move back over the single space between
 581                   ;; the words.
 582                   (if (= (preceding-char) ?\ ) (forward-char -1))
 583
 584                   (if enable-multibyte-characters
 585                       ;; If we are going to break the line after or
 586                       ;; before a non-ascii character, we may have to
 587                       ;; run a special function for the charset of the
 588                       ;; character to find the correct break point.
 589                       (if (not (and (eq (charset-after (1- (point))) 'ascii)
 590                                     (eq (charset-after (point)) 'ascii)))
 591                           ;; Make sure we take SOMETHING after the
 592                           ;; fill prefix if any.
 593                           (fill-find-break-point
 594                            (save-excursion
 595                              (goto-char linebeg)
 596                              (move-to-column prefixcol)
 597                              (point))))))
 598
 599                 ;; If the left margin and fill prefix by themselves
 600                 ;; pass the fill-column, keep at least one word.
 601                 ;; This handles the first line of the paragraph.
 602                 (if (and (zerop prefixcol)
 603                          (let ((fill-point (point)) nchars)
 604                            (save-excursion
 605                              (move-to-left-margin)
 606                              (setq nchars (- fill-point (point)))
 607                              (or (< nchars 0)
 608                                  (and fill-prefix
 609                                       (< nchars (length fill-prefix))
 610                                       (string= (buffer-substring (point)
 611                                                                  fill-point)
 612                                                (substring fill-prefix
 613                                                           0 nchars)))))))
 614                     ;; Ok, skip at least one word.  But
 615                     ;; don't stop at a period followed by just one space.
 616                     (let ((first t))
 617                       (while (and (not (eobp))
 618                                   (or first
 619                                       (and (not (bobp))
 620                                            sentence-end-double-space
 621                                            (save-excursion
 622                                              (forward-char -1)
 623                                              (and (looking-at "\\. ")
 624                                                   (not (looking-at "\\.  ")))))
 625                                       (and fill-nobreak-predicate
 626                                            (funcall fill-nobreak-predicate))))
 627                         ;; Find a breakable point while ignoring the
 628                         ;; following spaces.
 629                         (skip-chars-forward " \t")
 630                         (if (looking-at "\\c|")
 631                             (forward-char 1)
 632                           (let ((pos (save-excursion
 633                                        (skip-chars-forward "^ \n\t")
 634                                        (point))))
 635                             (if (re-search-forward "\\c|" pos t)
 636                                 (forward-char -1)
 637                               (goto-char pos))))
 638                         (setq first nil))))
 639                 ;; Check again to see if we got to the end of the paragraph.
 640                 (if (save-excursion (skip-chars-forward " \t") (eobp))
 641                     (or nosqueeze (delete-horizontal-space))
 642                   ;; Replace whitespace here with one newline, then
 643                   ;; indent to left margin.
 644                   (skip-chars-backward " \t")
 645                   (if (and (= (following-char) ?\ )
 646                            (or (aref (char-category-set (preceding-char)) ?|)
 647                                (looking-at "[ \t]+\\c|")))
 648                       ;; We need one space at end of line so that
 649                       ;; further filling won't delete it.  NOTE: We
 650                       ;; intentionally leave this one space to
 651                       ;; distingush the case that user wants to put
 652                       ;; space between \c| characters.
 653                       (forward-char 1))
 654                   (insert ?\n)
 655                   ;; Give newline the properties of the space(s) it replaces
 656                   (set-text-properties (1- (point)) (point)
 657                                        (text-properties-at (point)))
 658                   (if (or fill-prefix
 659                           (not fill-indent-according-to-mode)
 660                           (memq indent-line-function
 661                                 ;; Brain dead "indenting" functions.
 662                                 '(indent-relative-maybe indent-relative)))
 663                       (indent-to-left-margin)
 664                     (indent-according-to-mode))
 665                   ;; Insert the fill prefix after indentation.
 666                   ;; Set prefixcol so whitespace in the prefix won't get lost.
 667                   (and fill-prefix (not (equal fill-prefix ""))
 668                        (progn
 669                          (insert-and-inherit fill-prefix)
 670                          (setq prefixcol (current-column))))))
 671               ;; Justify the line just ended, if desired.
 672               (if justify
 673                 (if (save-excursion (skip-chars-forward " \t") (eobp))
 674                     (progn
 675                       (delete-horizontal-space)
 676                       (justify-current-line justify t t))
 677                     (forward-line -1)
 678                     (justify-current-line justify nil t)
 679                     (forward-line 1))))))
 680         ;; Leave point after final newline.
 681         (goto-char (point-max)))
 682       (unless (eobp)
 683         (forward-char 1))
 684       ;; Return the fill-prefix we used
 685       fill-prefix)))
 686
 687 (defsubst skip-line-prefix (prefix)
 688   "If point is inside the string PREFIX at the beginning of line, move past it."
 689   (when (and prefix
 690              (< (- (point) (line-beginning-position)) (length prefix))
 691              (save-excursion
 692                (beginning-of-line)
 693                (looking-at (regexp-quote prefix))))
 694     (goto-char (match-end 0))))
 695
 696 (defun fill-paragraph (arg)
 697   "Fill paragraph at or after point.  Prefix ARG means justify as well.
 698 If `sentence-end-double-space' is non-nil, then period followed by one
 699 space does not end a sentence, so don't break a line there.
 700 the variable `fill-column' controls the width for filling.
 701
 702 If `fill-paragraph-function' is non-nil, we call it (passing our
 703 argument to it), and if it returns non-nil, we simply return its value.
 704
 705 If `fill-paragraph-function' is nil, return the `fill-prefix' used for filling."
 706   (interactive (progn
 707                  (barf-if-buffer-read-only)
 708                  (list (if current-prefix-arg 'full))))
 709   (or (and fill-paragraph-function
 710            (let ((function fill-paragraph-function)
 711                  fill-paragraph-function)
 712              (funcall function arg)))
 713       (let ((before (point))
 714             ;; Fill prefix used for filling the paragraph
 715             fill-pfx
 716             ;; If fill-paragraph is called recursively,
 717             ;; don't give fill-paragraph-function a second chance.
 718             fill-paragraph-function)
 719         (save-excursion
 720           (forward-paragraph)
 721           (or (bolp) (newline 1))
 722           (let ((end (point))
 723                 (beg (progn (backward-paragraph) (point))))
 724             (goto-char before)
 725             (setq fill-pfx
 726                   (if use-hard-newlines
 727                       ;; Can't use fill-region-as-paragraph, since this
 728                       ;; paragraph may still contain hard newlines.  See
 729                       ;; fill-region.
 730                       (fill-region beg end arg)
 731                     (fill-region-as-paragraph beg end arg)))))
 732         ;; See if point ended up inside the fill-prefix, and if so, move
 733         ;; past it.
 734         (skip-line-prefix fill-pfx)
 735         fill-pfx)))
 736
 737 (defun fill-region (from to &optional justify nosqueeze to-eop)
 738   "Fill each of the paragraphs in the region.
 739 A prefix arg means justify as well.
 740 Ordinarily the variable `fill-column' controls the width.
 741
 742 Noninteractively, the third argument JUSTIFY specifies which
 743 kind of justification to do: `full', `left', `right', `center',
 744 or `none' (equivalent to nil).  t means handle each paragraph
 745 as specified by its text properties.
 746
 747 The fourth arg NOSQUEEZE non-nil means to leave
 748 whitespace other than line breaks untouched, and fifth arg TO-EOP
 749 non-nil means to keep filling to the end of the paragraph (or next
 750 hard newline, if `use-hard-newlines' is on).
 751
 752 Return the fill-prefix used for filling the last paragraph.
 753
 754 If `sentence-end-double-space' is non-nil, then period followed by one
 755 space does not end a sentence, so don't break a line there."
 756   (interactive (progn
 757                  (barf-if-buffer-read-only)
 758                  (list (region-beginning) (region-end)
 759                        (if current-prefix-arg 'full))))
 760   (unless (memq justify '(t nil none full center left right))
 761     (setq justify 'full))
 762   (let (end beg fill-pfx)
 763     (save-restriction
 764       (goto-char (max from to))
 765       (when to-eop
 766         (skip-chars-backward "\n")
 767         (forward-paragraph))
 768       (setq end (point))
 769       (goto-char (setq beg (min from to)))
 770       (beginning-of-line)
 771       (narrow-to-region (point) end)
 772       (while (not (eobp))
 773         (let ((initial (point))
 774               end)
 775           ;; If using hard newlines, break at every one for filling
 776           ;; purposes rather than using paragraph breaks.
 777           (if use-hard-newlines
 778               (progn
 779                 (while (and (setq end (text-property-any (point) (point-max)
 780                                                          'hard t))
 781                             (not (= ?\n (char-after end)))
 782                             (not (= end (point-max))))
 783                   (goto-char (1+ end)))
 784                 (setq end (if end (min (point-max) (1+ end)) (point-max)))
 785                 (goto-char initial))
 786             (forward-paragraph 1)
 787             (setq end (point))
 788             (forward-paragraph -1))
 789           (if (< (point) beg)
 790               (goto-char beg))
 791           (if (>= (point) initial)
 792               (setq fill-pfx
 793                     (fill-region-as-paragraph (point) end justify nosqueeze))
 794             (goto-char end))))
 795       fill-pfx)))
 796
 797 \f
 798 (defcustom default-justification 'left
 799   "*Method of justifying text not otherwise specified.
 800 Possible values are `left', `right', `full', `center', or `none'.
 801 The requested kind of justification is done whenever lines are filled.
 802 The `justification' text-property  can locally override this variable.
 803 This variable automatically becomes buffer-local when set in any fashion."
 804   :type '(choice (const left)
 805                  (const right)
 806                  (const full)
 807                  (const center)
 808                  (const none))
 809   :group 'fill)
 810 (make-variable-buffer-local 'default-justification)
 811
 812 (defun current-justification ()
 813   "How should we justify this line?
 814 This returns the value of the text-property `justification',
 815 or the variable `default-justification' if there is no text-property.
 816 However, it returns nil rather than `none' to mean \"don't justify\"."
 817   (let ((j (or (get-text-property
 818                 ;; Make sure we're looking at paragraph body.
 819                 (save-excursion (skip-chars-forward " \t")
 820                                 (if (and (eobp) (not (bobp)))
 821                                     (1- (point)) (point)))
 822                 'justification)
 823                default-justification)))
 824     (if (eq 'none j)
 825         nil
 826       j)))
 827
 828 (defun set-justification (begin end value &optional whole-par)
 829   "Set the region's justification style.
 830 The kind of justification to use is prompted for.
 831 If the mark is not active, this command operates on the current paragraph.
 832 If the mark is active, the region is used.  However, if the beginning and end
 833 of the region are not at paragraph breaks, they are moved to the beginning and
 834 end of the paragraphs they are in.
 835 If `use-hard-newlines' is true, all hard newlines are taken to be paragraph
 836 breaks.
 837
 838 When calling from a program, operates just on region between BEGIN and END,
 839 unless optional fourth arg WHOLE-PAR is non-nil.  In that case bounds are
 840 extended to include entire paragraphs as in the interactive command."
 841   (interactive (list (if mark-active (region-beginning) (point))
 842                      (if mark-active (region-end) (point))
 843                      (let ((s (completing-read
 844                                "Set justification to: "
 845                                '(("left") ("right") ("full")
 846                                  ("center") ("none"))
 847                                nil t)))
 848                        (if (equal s "") (error ""))
 849                        (intern s))
 850                      t))
 851   (save-excursion
 852     (save-restriction
 853       (if whole-par
 854           (let ((paragraph-start (if use-hard-newlines "." paragraph-start))
 855                 (paragraph-ignore-fill-prefix (if use-hard-newlines t
 856                                                 paragraph-ignore-fill-prefix)))
 857             (goto-char begin)
 858             (while (and (bolp) (not (eobp))) (forward-char 1))
 859             (backward-paragraph)
 860             (setq begin (point))
 861             (goto-char end)
 862             (skip-chars-backward " \t\n" begin)
 863             (forward-paragraph)
 864             (setq end (point))))
 865
 866       (narrow-to-region (point-min) end)
 867       (unjustify-region begin (point-max))
 868       (put-text-property begin (point-max) 'justification value)
 869       (fill-region begin (point-max) nil t))))
 870
 871 (defun set-justification-none (b e)
 872   "Disable automatic filling for paragraphs in the region.
 873 If the mark is not active, this applies to the current paragraph."
 874   (interactive (list (if mark-active (region-beginning) (point))
 875                      (if mark-active (region-end) (point))))
 876   (set-justification b e 'none t))
 877
 878 (defun set-justification-left (b e)
 879   "Make paragraphs in the region left-justified.
 880 This is usually the default, but see the variable `default-justification'.
 881 If the mark is not active, this applies to the current paragraph."
 882   (interactive (list (if mark-active (region-beginning) (point))
 883                      (if mark-active (region-end) (point))))
 884   (set-justification b e 'left t))
 885
 886 (defun set-justification-right (b e)
 887   "Make paragraphs in the region right-justified:
 888 Flush at the right margin and ragged on the left.
 889 If the mark is not active, this applies to the current paragraph."
 890   (interactive (list (if mark-active (region-beginning) (point))
 891                      (if mark-active (region-end) (point))))
 892   (set-justification b e 'right t))
 893
 894 (defun set-justification-full (b e)
 895   "Make paragraphs in the region fully justified:
 896 This makes lines flush on both margins by inserting spaces between words.
 897 If the mark is not active, this applies to the current paragraph."
 898   (interactive (list (if mark-active (region-beginning) (point))
 899                      (if mark-active (region-end) (point))))
 900   (set-justification b e 'full t))
 901
 902 (defun set-justification-center (b e)
 903   "Make paragraphs in the region centered.
 904 If the mark is not active, this applies to the current paragraph."
 905   (interactive (list (if mark-active (region-beginning) (point))
 906                      (if mark-active (region-end) (point))))
 907   (set-justification b e 'center t))
 908
 909 ;; A line has up to six parts:
 910 ;;
 911 ;;           >>>                    hello.
 912 ;; [Indent-1][FP][    Indent-2     ][text][trailing whitespace][newline]
 913 ;;
 914 ;; "Indent-1" is the left-margin indentation; normally it ends at column
 915 ;;     given by the `current-left-margin' function.
 916 ;; "FP" is the fill-prefix.  It can be any string, including whitespace.
 917 ;; "Indent-2" is added to justify a line if the `current-justification' is
 918 ;;     `center' or `right'.  In `left' and `full' justification regions, any
 919 ;;     whitespace there is part of the line's text, and should not be changed.
 920 ;; Trailing whitespace is not counted as part of the line length when
 921 ;; center- or right-justifying.
 922 ;;
 923 ;; All parts of the line are optional, although the final newline can
 924 ;;     only be missing on the last line of the buffer.
 925
 926 (defun justify-current-line (&optional how eop nosqueeze)
 927   "Do some kind of justification on this line.
 928 Normally does full justification: adds spaces to the line to make it end at
 929 the column given by `current-fill-column'.
 930 Optional first argument HOW specifies alternate type of justification:
 931 it can be `left', `right', `full', `center', or `none'.
 932 If HOW is t, will justify however the `current-justification' function says to.
 933 If HOW is nil or missing, full justification is done by default.
 934 Second arg EOP non-nil means that this is the last line of the paragraph, so
 935 it will not be stretched by full justification.
 936 Third arg NOSQUEEZE non-nil means to leave interior whitespace unchanged,
 937 otherwise it is made canonical."
 938   (interactive "*")
 939   (if (eq t how) (setq how (or (current-justification) 'none))
 940     (if (null how) (setq how 'full)
 941       (or (memq how '(none left right center))
 942           (setq how 'full))))
 943   (or (memq how '(none left))  ; No action required for these.
 944       (let ((fc (current-fill-column))
 945             (pos (point-marker))
 946             fp-end                      ; point at end of fill prefix
 947             beg                         ; point at beginning of line's text
 948             end                         ; point at end of line's text
 949             indent                      ; column of `beg'
 950             endcol                      ; column of `end'
 951             ncols                       ; new indent point or offset
 952             (nspaces 0)                 ; number of spaces between words
 953                                         ; in line (not space characters)
 954             fracspace                   ; fractional amount of space to be
 955                                         ; added between each words
 956             (curr-fracspace 0)          ; current fractional space amount
 957             count)
 958         (end-of-line)
 959         ;; Check if this is the last line of the paragraph.
 960         (if (and use-hard-newlines (null eop)
 961                  (get-text-property (point) 'hard))
 962             (setq eop t))
 963         (skip-chars-backward " \t")
 964         ;; Quick exit if it appears to be properly justified already
 965         ;; or there is no text.
 966         (if (or (bolp)
 967                 (and (memq how '(full right))
 968                      (= (current-column) fc)))
 969             nil
 970           (setq end (point))
 971           (beginning-of-line)
 972           (skip-chars-forward " \t")
 973           ;; Skip over fill-prefix.
 974           (if (and fill-prefix
 975                    (not (string-equal fill-prefix ""))
 976                    (equal fill-prefix
 977                           (buffer-substring
 978                            (point) (min (point-max) (+ (length fill-prefix)
 979                                                        (point))))))
 980               (forward-char (length fill-prefix))
 981             (if (and adaptive-fill-mode
 982                      (looking-at adaptive-fill-regexp))
 983                 (goto-char (match-end 0))))
 984           (setq fp-end (point))
 985           (skip-chars-forward " \t")
 986           ;; This is beginning of the line's text.
 987           (setq indent (current-column))
 988           (setq beg (point))
 989           (goto-char end)
 990           (setq endcol (current-column))
 991
 992           ;; HOW can't be null or left--we would have exited already
 993           (cond ((eq 'right how)
 994                  (setq ncols (- fc endcol))
 995                  (if (< ncols 0)
 996                      ;; Need to remove some indentation
 997                      (delete-region
 998                       (progn (goto-char fp-end)
 999                              (if (< (current-column) (+ indent ncols))
1000                                  (move-to-column (+ indent ncols) t))
1001                              (point))
1002                       (progn (move-to-column indent) (point)))
1003                    ;; Need to add some
1004                    (goto-char beg)
1005                    (indent-to (+ indent ncols))
1006                    ;; If point was at beginning of text, keep it there.
1007                    (if (= beg pos)
1008                        (move-marker pos (point)))))
1009
1010                 ((eq 'center how)
1011                  ;; Figure out how much indentation is needed
1012                  (setq ncols (+ (current-left-margin)
1013                                 (/ (- fc (current-left-margin) ;avail. space
1014                                       (- endcol indent)) ;text width
1015                                    2)))
1016                  (if (< ncols indent)
1017                      ;; Have too much indentation - remove some
1018                      (delete-region
1019                       (progn (goto-char fp-end)
1020                              (if (< (current-column) ncols)
1021                                  (move-to-column ncols t))
1022                              (point))
1023                       (progn (move-to-column indent) (point)))
1024                    ;; Have too little - add some
1025                    (goto-char beg)
1026                    (indent-to ncols)
1027                    ;; If point was at beginning of text, keep it there.
1028                    (if (= beg pos)
1029                        (move-marker pos (point)))))
1030
1031                 ((eq 'full how)
1032                  ;; Insert extra spaces between words to justify line
1033                  (save-restriction
1034                    (narrow-to-region beg end)
1035                    (or nosqueeze
1036                        (canonically-space-region beg end))
1037                    (goto-char (point-max))
1038                    ;; count word spaces in line
1039                    (while (search-backward " " nil t)
1040                      (setq nspaces (1+ nspaces))
1041                      (skip-chars-backward " "))
1042                    (setq ncols (- fc endcol))
1043                    ;; Ncols is number of additional space chars needed
1044                    (if (and (> ncols 0) (> nspaces 0) (not eop))
1045                        (progn
1046                          (setq curr-fracspace (+ ncols (/ (1+ nspaces) 2))
1047                                count nspaces)
1048                          (while (> count 0)
1049                            (skip-chars-forward " ")
1050                            (insert-and-inherit
1051                             (make-string (/ curr-fracspace nspaces) ?\ ))
1052                            (search-forward " " nil t)
1053                            (setq count (1- count)
1054                                  curr-fracspace
1055                                    (+ (% curr-fracspace nspaces) ncols)))))))
1056                 (t (error "Unknown justification value"))))
1057         (goto-char pos)
1058         (move-marker pos nil)))
1059   nil)
1060
1061 (defun unjustify-current-line ()
1062   "Remove justification whitespace from current line.
1063 If the line is centered or right-justified, this function removes any
1064 indentation past the left margin.  If the line is full-justified, it removes
1065 extra spaces between words.  It does nothing in other justification modes."
1066   (let ((justify (current-justification)))
1067     (cond ((eq 'left justify) nil)
1068           ((eq  nil  justify) nil)
1069           ((eq 'full justify)           ; full justify: remove extra spaces
1070            (beginning-of-line-text)
1071            (canonically-space-region (point) (line-end-position)))
1072           ((memq justify '(center right))
1073            (save-excursion
1074              (move-to-left-margin nil t)
1075              ;; Position ourselves after any fill-prefix.
1076              (if (and fill-prefix
1077                       (not (string-equal fill-prefix ""))
1078                       (equal fill-prefix
1079                              (buffer-substring
1080                               (point) (min (point-max) (+ (length fill-prefix)
1081                                                           (point))))))
1082                  (forward-char (length fill-prefix)))
1083              (delete-region (point) (progn (skip-chars-forward " \t")
1084                                            (point))))))))
1085
1086 (defun unjustify-region (&optional begin end)
1087   "Remove justification whitespace from region.
1088 For centered or right-justified regions, this function removes any indentation
1089 past the left margin from each line.  For full-justified lines, it removes
1090 extra spaces between words.  It does nothing in other justification modes.
1091 Arguments BEGIN and END are optional; default is the whole buffer."
1092   (save-excursion
1093     (save-restriction
1094       (if end (narrow-to-region (point-min) end))
1095       (goto-char (or begin (point-min)))
1096       (while (not (eobp))
1097         (unjustify-current-line)
1098         (forward-line 1)))))
1099
1100 \f
1101 (defun fill-nonuniform-paragraphs (min max &optional justifyp citation-regexp)
1102   "Fill paragraphs within the region, allowing varying indentation within each.
1103 This command divides the region into \"paragraphs\",
1104 only at paragraph-separator lines, then fills each paragraph
1105 using as the fill prefix the smallest indentation of any line
1106 in the paragraph.
1107
1108 When calling from a program, pass range to fill as first two arguments.
1109
1110 Optional third and fourth arguments JUSTIFY and MAIL-FLAG:
1111 JUSTIFY to justify paragraphs (prefix arg),
1112 When filling a mail message, pass a regexp for CITATION-REGEXP
1113 which will match the prefix of a line which is a citation marker
1114 plus whitespace, but no other kind of prefix.
1115 Also, if CITATION-REGEXP is non-nil,  don't fill header lines."
1116   (interactive (progn
1117                  (barf-if-buffer-read-only)
1118                  (list (region-beginning) (region-end)
1119                        (if current-prefix-arg 'full))))
1120   (let ((fill-individual-varying-indent t))
1121     (fill-individual-paragraphs min max justifyp citation-regexp)))
1122
1123 (defun fill-individual-paragraphs (min max &optional justify citation-regexp)
1124   "Fill paragraphs of uniform indentation within the region.
1125 This command divides the region into \"paragraphs\",
1126 treating every change in indentation level or prefix as a paragraph boundary,
1127 then fills each paragraph using its indentation level as the fill prefix.
1128
1129 There is one special case where a change in indentation does not start
1130 a new paragraph.  This is for text of this form:
1131
1132    foo>    This line with extra indentation starts
1133    foo> a paragraph that continues on more lines.
1134
1135 These lines are filled together.
1136
1137 When calling from a program, pass the range to fill
1138 as the first two arguments.
1139
1140 Optional third and fourth arguments JUSTIFY and MAIL-FLAG:
1141 JUSTIFY to justify paragraphs (prefix arg),
1142 When filling a mail message, pass a regexp for CITATION-REGEXP
1143 which will match the prefix of a line which is a citation marker
1144 plus whitespace, but no other kind of prefix.
1145 Also, if CITATION-REGEXP is non-nil,  don't fill header lines."
1146   (interactive (progn
1147                  (barf-if-buffer-read-only)
1148                  (list (region-beginning) (region-end)
1149                        (if current-prefix-arg 'full))))
1150   (save-restriction
1151     (save-excursion
1152       (goto-char min)
1153       (beginning-of-line)
1154       (narrow-to-region (point) max)
1155       (if citation-regexp
1156           (while (and (not (eobp))
1157                       (or (looking-at "[ \t]*[^ \t\n]+:")
1158                           (looking-at "[ \t]*$")))
1159             (if (looking-at "[ \t]*[^ \t\n]+:")
1160                 (search-forward "\n\n" nil 'move)
1161               (forward-line 1))))
1162       (narrow-to-region (point) max)
1163       ;; Loop over paragraphs.
1164       (while (let ((here (point)))
1165                ;; Skip over all paragraph-separating lines
1166                ;; so as to not include them in any paragraph.
1167                (while (and (not (eobp))
1168                            (progn (move-to-left-margin)
1169                                   (and (not (eobp))
1170                                        (looking-at paragraph-separate))))
1171                  (forward-line 1))
1172                (skip-chars-forward " \t\n") (not (eobp)))
1173         (move-to-left-margin)
1174         (let ((start (point))
1175               fill-prefix fill-prefix-regexp)
1176           ;; Find end of paragraph, and compute the smallest fill-prefix
1177           ;; that fits all the lines in this paragraph.
1178           (while (progn
1179                    ;; Update the fill-prefix on the first line
1180                    ;; and whenever the prefix good so far is too long.
1181                    (if (not (and fill-prefix
1182                                  (looking-at fill-prefix-regexp)))
1183                        (setq fill-prefix
1184                              (fill-individual-paragraphs-prefix
1185                               citation-regexp)
1186                              fill-prefix-regexp (regexp-quote fill-prefix)))
1187                    (forward-line 1)
1188                    (if (bolp)
1189                        ;; If forward-line went past a newline,
1190                        ;; move further to the left margin.
1191                        (move-to-left-margin))
1192                    ;; Now stop the loop if end of paragraph.
1193                    (and (not (eobp))
1194                         (if fill-individual-varying-indent
1195                             ;; If this line is a separator line, with or
1196                             ;; without prefix, end the paragraph.
1197                             (and
1198                              (not (looking-at paragraph-separate))
1199                              (save-excursion
1200                                (not (and (looking-at fill-prefix-regexp)
1201                                          (progn (forward-char
1202                                                  (length fill-prefix))
1203                                                 (looking-at
1204                                                  paragraph-separate))))))
1205                           ;; If this line has more or less indent
1206                           ;; than the fill prefix wants, end the paragraph.
1207                           (and (looking-at fill-prefix-regexp)
1208                                ;; If fill prefix is shorter than a new
1209                                ;; fill prefix computed here, end paragraph.
1210                                (let ((this-line-fill-prefix
1211                                       (fill-individual-paragraphs-prefix
1212                                        citation-regexp)))
1213                                  (>= (length fill-prefix)
1214                                      (length this-line-fill-prefix)))
1215                                (save-excursion
1216                                  (not (progn (forward-char
1217                                               (length fill-prefix))
1218                                              (or (looking-at "[ \t]")
1219                                                  (looking-at paragraph-separate)
1220                                                  (looking-at paragraph-start)))))
1221                                (not (and (equal fill-prefix "")
1222                                          citation-regexp
1223                                          (looking-at citation-regexp))))))))
1224           ;; Fill this paragraph, but don't add a newline at the end.
1225           (let ((had-newline (bolp)))
1226             (fill-region-as-paragraph start (point) justify)
1227             (if (and (bolp) (not had-newline))
1228                 (delete-char -1))))))))
1229
1230 (defun fill-individual-paragraphs-prefix (citation-regexp)
1231   (or (let ((adaptive-fill-first-line-regexp "")
1232             just-one-line-prefix
1233             two-lines-prefix
1234             one-line-citation-part
1235             two-lines-citation-part
1236             adjusted-two-lines-citation-part)
1237         (setq just-one-line-prefix
1238               (fill-context-prefix
1239                (point)
1240                (line-beginning-position 2)))
1241         (setq two-lines-prefix
1242               (fill-context-prefix
1243                (point)
1244                (line-beginning-position 3)))
1245         (when just-one-line-prefix
1246           (setq one-line-citation-part
1247                 (if citation-regexp
1248                     (fill-individual-paragraphs-citation just-one-line-prefix
1249                                                          citation-regexp)
1250                   just-one-line-prefix)))
1251         (when two-lines-prefix
1252           (setq two-lines-citation-part
1253                 (if citation-regexp
1254                     (fill-individual-paragraphs-citation two-lines-prefix
1255                                                          citation-regexp)
1256                   just-one-line-prefix))
1257           (or two-lines-citation-part (setq two-lines-citation-part ""))
1258           (setq adjusted-two-lines-citation-part
1259                 (substring two-lines-citation-part 0
1260                            (string-match "[ \t]*\\'"
1261                                          two-lines-citation-part))))
1262         ;; See if the citation part of JUST-ONE-LINE-PREFIX
1263         ;; is the same as that of TWO-LINES-PREFIX,
1264         ;; except perhaps with longer whitespace.
1265         (if (and just-one-line-prefix
1266                  two-lines-prefix
1267                  (string-match (concat "\\`"
1268                                        (regexp-quote
1269                                         adjusted-two-lines-citation-part)
1270                                        "[ \t]*\\'")
1271                                one-line-citation-part)
1272                  (>= (string-width one-line-citation-part)
1273                      (string-width two-lines-citation-part)))
1274             two-lines-prefix
1275           just-one-line-prefix))
1276       (buffer-substring
1277        (point)
1278        (save-excursion (skip-chars-forward " \t")
1279                        (point)))))
1280
1281 (defun fill-individual-paragraphs-citation (string citation-regexp)
1282   (string-match citation-regexp
1283                 string)
1284   (match-string 0 string))
1285
1286 ;;; fill.el ends here