root/trunk/lisp/textmodes/fill.el

;;; fill.el --- fill commands for Emacs         -*- coding: iso-2022-7bit -*-

;; Copyright (C) 1985, 1986, 1992, 1994, 1995, 1996, 1997, 1999, 2001, 2002,
;;   2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.

;; Maintainer: FSF
;; Keywords: wp

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 3, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;; All the commands for filling text.  These are documented in the Emacs
;; manual.

;;; Code:

(defgroup fill nil
  "Indenting and filling text."
  :link '(custom-manual "(emacs)Filling")
  :group 'editing)

(defcustom fill-individual-varying-indent nil
  "*Controls criterion for a new paragraph in `fill-individual-paragraphs'.
Non-nil means changing indent doesn't end a paragraph.
That mode can handle paragraphs with extra indentation on the first line,
but it requires separator lines between paragraphs.
A value of nil means that any change in indentation starts a new paragraph."
  :type 'boolean
  :group 'fill)

(defcustom colon-double-space nil
  "*Non-nil means put two spaces after a colon when filling."
  :type 'boolean
  :group 'fill)
;;;###autoload(put 'colon-double-space 'safe-local-variable 'booleanp)

(defvar fill-paragraph-function nil
  "Mode-specific function to fill a paragraph, or nil if there is none.
If the function returns nil, then `fill-paragraph' does its normal work.
A value of t means explicitly \"do nothing special\".")

(defvar fill-paragraph-handle-comment t
  "Non-nil means paragraph filling will try to pay attention to comments.")

(defcustom enable-kinsoku t
  "*Non-nil means enable \"kinsoku\" processing on filling paragraphs.
Kinsoku processing is designed to prevent certain characters from being
placed at the beginning or end of a line by filling.
See the documentation of `kinsoku' for more information."
  :type 'boolean
  :group 'fill)

(defun set-fill-prefix ()
  "Set the fill prefix to the current line up to point.
Filling expects lines to start with the fill prefix and
reinserts the fill prefix in each resulting line."
  (interactive)
  (let ((left-margin-pos (save-excursion (move-to-left-margin) (point))))
    (if (> (point) left-margin-pos)
        (progn
          (setq fill-prefix (buffer-substring left-margin-pos (point)))
          (if (equal fill-prefix "")
              (setq fill-prefix nil)))
      (setq fill-prefix nil)))
  (if fill-prefix
      (message "fill-prefix: \"%s\"" fill-prefix)
    (message "fill-prefix cancelled")))

(defcustom adaptive-fill-mode t
  "*Non-nil means determine a paragraph's fill prefix from its text."
  :type 'boolean
  :group 'fill)

(defcustom adaptive-fill-regexp
  ;; Added `!' for doxygen comments starting with `//!' or `/*!'.
  ;; Added `%' for TeX comments.
  ;; RMS: deleted the code to match `1.' and `(1)'.
  "[ \t]*\\([-!|#%;>*,A7$,1s"s#sC$,2"F(B]+[ \t]*\\)*"
  "*Regexp to match text at start of line that constitutes indentation.
If Adaptive Fill mode is enabled, a prefix matching this pattern
on the first and second lines of a paragraph is used as the
standard indentation for the whole paragraph.

If the paragraph has just one line, the indentation is taken from that
line, but in that case `adaptive-fill-first-line-regexp' also plays
a role."
  :type 'regexp
  :group 'fill)

(defcustom adaptive-fill-first-line-regexp "\\`[ \t]*\\'"
  "*Regexp specifying whether to set fill prefix from a one-line paragraph.
When a paragraph has just one line, then after `adaptive-fill-regexp'
finds the prefix at the beginning of the line, if it doesn't
match this regexp, it is replaced with whitespace.

By default, this regexp matches sequences of just spaces and tabs.

However, we never use a prefix from a one-line paragraph
if it would act as a paragraph-starter on the second line."
  :type 'regexp
  :group 'fill)

(defcustom adaptive-fill-function nil
  "Function to call to choose a fill prefix for a paragraph, or nil.
A nil value means the function has not determined the fill prefix."
  :type '(choice (const nil) function)
  :group 'fill)

(defvar fill-indent-according-to-mode nil ;Screws up CC-mode's filling tricks.
  "Whether or not filling should try to use the major mode's indentation.")

(defun current-fill-column ()
  "Return the fill-column to use for this line.
The fill-column to use for a buffer is stored in the variable `fill-column',
but can be locally modified by the `right-margin' text property, which is
subtracted from `fill-column'.

The fill column to use for a line is the first column at which the column
number equals or exceeds the local fill-column - right-margin difference."
  (save-excursion
    (if fill-column
        (let* ((here (progn (beginning-of-line) (point)))
               (here-col 0)
               (eol (progn (end-of-line) (point)))
               margin fill-col change col)
          ;; Look separately at each region of line with a different
          ;; right-margin.
          (while (and (setq margin (get-text-property here 'right-margin)
                            fill-col (- fill-column (or margin 0))
                            change (text-property-not-all
                                    here eol 'right-margin margin))
                      (progn (goto-char (1- change))
                             (setq col (current-column))
                             (< col fill-col)))
            (setq here change
                  here-col col))
          (max here-col fill-col)))))

(defun canonically-space-region (beg end)
  "Remove extra spaces between words in region.
Leave one space between words, two at end of sentences or after colons
\(depending on values of `sentence-end-double-space', `colon-double-space',
and `sentence-end-without-period').
Remove indentation from each line."
  (interactive "*r")
  ;; Ideally, we'd want to scan the text from the end, so that changes to
  ;; text don't affect the boundary, but the regexp we match against does
  ;; not match as eagerly when matching backward, so we instead use
  ;; a marker.
  (unless (markerp end) (setq end (copy-marker end t)))
  (let ((end-spc-re (concat "\\(" (sentence-end) "\\) *\\|  +")))
    (save-excursion
      (goto-char beg)
      ;; Nuke tabs; they get screwed up in a fill.
      ;; This is quick, but loses when a tab follows the end of a sentence.
      ;; Actually, it is difficult to tell that from "Mr.\tSmith".
      ;; Blame the typist.
      (subst-char-in-region beg end ?\t ?\s)
      (while (and (< (point) end)
                  (re-search-forward end-spc-re end t))
        (delete-region
         (cond
          ;; `sentence-end' matched and did not match all spaces.
          ;; I.e. it only matched the number of spaces it needs: drop the rest.
          ((and (match-end 1) (> (match-end 0) (match-end 1)))  (match-end 1))
          ;; `sentence-end' matched but with nothing left.  Either that means
          ;; nothing should be removed, or it means it's the "old-style"
          ;; sentence-end which matches all it can.  Keep only 2 spaces.
          ;; We probably don't even need to check `sentence-end-double-space'.
          ((match-end 1)
           (min (match-end 0)
                (+ (if sentence-end-double-space 2 1)
                   (save-excursion (goto-char (match-end 0))
                                   (skip-chars-backward " ")
                                   (point)))))
          (t ;; It's not an end of sentence.
           (+ (match-beginning 0)
              ;; Determine number of spaces to leave:
              (save-excursion
                (skip-chars-backward " ]})\"'")
                (cond ((and sentence-end-double-space
                            (or (memq (preceding-char) '(?. ?? ?!))
                                (and sentence-end-without-period
                                     (= (char-syntax (preceding-char)) ?w)))) 2)
                      ((and colon-double-space
                            (= (preceding-char) ?:))  2)
                      ((char-equal (preceding-char) ?\n)  0)
                      (t 1))))))
         (match-end 0))))))

(defun fill-common-string-prefix (s1 s2)
  "Return the longest common prefix of strings S1 and S2, or nil if none."
  (let ((cmp (compare-strings s1 nil nil s2 nil nil)))
    (if (eq cmp t)
        s1
      (setq cmp (1- (abs cmp)))
      (unless (zerop cmp)
        (substring s1 0 cmp)))))

(defun fill-match-adaptive-prefix ()
  (let ((str (or
              (and adaptive-fill-function (funcall adaptive-fill-function))
              (and adaptive-fill-regexp (looking-at adaptive-fill-regexp)
                   (match-string-no-properties 0)))))
    (if (>= (+ (current-left-margin) (length str)) (current-fill-column))
        ;; Death to insanely long prefixes.
        nil
      str)))

(defun fill-context-prefix (from to &optional first-line-regexp)
  "Compute a fill prefix from the text between FROM and TO.
This uses the variables `adaptive-fill-regexp' and `adaptive-fill-function'
and `adaptive-fill-first-line-regexp'.  `paragraph-start' also plays a role;
we reject a prefix based on a one-line paragraph if that prefix would
act as a paragraph-separator."
  (or first-line-regexp
      (setq first-line-regexp adaptive-fill-first-line-regexp))
  (save-excursion
    (goto-char from)
    (if (eolp) (forward-line 1))
    ;; Move to the second line unless there is just one.
    (move-to-left-margin)
    (let (first-line-prefix
          ;; Non-nil if we are on the second line.
          second-line-prefix)
      (setq first-line-prefix
            ;; We don't need to consider `paragraph-start' here since it
            ;; will be explicitly checked later on.
            ;; Also setting first-line-prefix to nil prevents
            ;; second-line-prefix from being used.
            ;; ((looking-at paragraph-start) nil)
            (fill-match-adaptive-prefix))
      (forward-line 1)
      (if (< (point) to)
          (progn
            (move-to-left-margin)
            (setq second-line-prefix
                  (cond ((looking-at paragraph-start) nil) ;Can it happen? -Stef
                        (t (fill-match-adaptive-prefix))))
            ;; If we get a fill prefix from the second line,
            ;; make sure it or something compatible is on the first line too.
            (when second-line-prefix
              (unless first-line-prefix (setq first-line-prefix ""))
              ;; If the non-whitespace chars match the first line,
              ;; just use it (this subsumes the 2 checks used previously).
              ;; Used when first line is `/* ...' and second-line is
              ;; ` * ...'.
              (let ((tmp second-line-prefix)
                    (re "\\`"))
                (while (string-match "\\`[ \t]*\\([^ \t]+\\)" tmp)
                  (setq re (concat re ".*" (regexp-quote (match-string 1 tmp))))
                  (setq tmp (substring tmp (match-end 0))))
                ;; (assert (string-match "\\`[ \t]*\\'" tmp))

                (if (string-match re first-line-prefix)
                    second-line-prefix

                  ;; Use the longest common substring of both prefixes,
                  ;; if there is one.
                  (fill-common-string-prefix first-line-prefix
                                             second-line-prefix)))))
        ;; If we get a fill prefix from a one-line paragraph,
        ;; maybe change it to whitespace,
        ;; and check that it isn't a paragraph starter.
        (if first-line-prefix
            (let ((result
                   ;; If first-line-prefix comes from the first line,
                   ;; see if it seems reasonable to use for all lines.
                   ;; If not, replace it with whitespace.
                   (if (or (and first-line-regexp
                                (string-match first-line-regexp
                                              first-line-prefix))
                           (and comment-start-skip
                                (string-match comment-start-skip
                                              first-line-prefix)))
                       first-line-prefix
                     (make-string (string-width first-line-prefix) ?\s))))
              ;; But either way, reject it if it indicates the start
              ;; of a paragraph when text follows it.
              (if (not (eq 0 (string-match paragraph-start
                                           (concat result "a"))))
                  result)))))))

(defun fill-single-word-nobreak-p ()
  "Don't break a line after the first or before the last word of a sentence."
  ;; Actually, allow breaking before the last word of a sentence, so long as
  ;; it's not the last word of the paragraph.
  (or (looking-at (concat "[ \t]*\\sw+" "\\(?:" (sentence-end) "\\)[ \t]*$"))
      (save-excursion
        (skip-chars-backward " \t")
        (and (/= (skip-syntax-backward "w") 0)
             (/= (skip-chars-backward " \t") 0)
             (/= (skip-chars-backward ".?!:") 0)
             (looking-at (sentence-end))))))

(defun fill-french-nobreak-p ()
  "Return nil if French style allows breaking the line at point.
This is used in `fill-nobreak-predicate' to prevent breaking lines just
after an opening paren or just before a closing paren or a punctuation
mark such as `?' or `:'.  It is common in French writing to put a space
at such places, which would normally allow breaking the line at those
places."
  (or (looking-at "[ \t]*[])},A;,b;(B?!;:-]")
      (save-excursion
        (skip-chars-backward " \t")
        (unless (bolp)
          (backward-char 1)
          (or (looking-at "[([{,A+,b+(B]")
              ;; Don't cut right after a single-letter word.
              (and (memq (preceding-char) '(?\t ?\s))
                   (eq (char-syntax (following-char)) ?w)))))))

(defcustom fill-nobreak-predicate nil
  "List of predicates for recognizing places not to break a line.
The predicates are called with no arguments, with point at the place to
be tested.  If it returns t, fill commands do not break the line there."
  :group 'fill
  :type 'hook
  :options '(fill-french-nobreak-p fill-single-word-nobreak-p))

(defcustom fill-nobreak-invisible nil
  "Non-nil means that fill commands do not break lines in invisible text."
  :type 'boolean
  :group 'fill)

(defun fill-nobreak-p ()
  "Return nil if breaking the line at point is allowed.
Can be customized with the variables `fill-nobreak-predicate'
and `fill-nobreak-invisible'."
  (or
   (and fill-nobreak-invisible (line-move-invisible-p (point)))
   (unless (bolp)
    (or
     ;; Don't break after a period followed by just one space.
     ;; Move back to the previous place to break.
     ;; The reason is that if a period ends up at the end of a
     ;; line, further fills will assume it ends a sentence.
     ;; If we now know it does not end a sentence, avoid putting
     ;; it at the end of the line.
     (and sentence-end-double-space
          (save-excursion
            (skip-chars-backward " ")
            (and (eq (preceding-char) ?.)
                 (looking-at " \\([^ ]\\|$\\)"))))
     ;; Another approach to the same problem.
     (save-excursion
       (skip-chars-backward " ")
       (and (eq (preceding-char) ?.)
            (not (progn (forward-char -1) (looking-at (sentence-end))))))
     ;; Don't split a line if the rest would look like a new paragraph.
     (unless use-hard-newlines
       (save-excursion
         (skip-chars-forward " \t")
         ;; If this break point is at the end of the line,
         ;; which can occur for auto-fill, don't consider the newline
         ;; which follows as a reason to return t.
         (and (not (eolp))
              (looking-at paragraph-start))))
     (run-hook-with-args-until-success 'fill-nobreak-predicate)))))

;; Put `fill-find-break-point-function' property to charsets which
;; require special functions to find line breaking point.
(dolist (pair '((katakana-jisx0201 . kinsoku)
                (chinese-gb2312 . kinsoku)
                (japanese-jisx0208 . kinsoku)
                (japanese-jisx0212 . kinsoku)
                (chinese-big5-1 . kinsoku)
                (chinese-big5-2 . kinsoku)))
  (put-charset-property (car pair) 'fill-find-break-point-function (cdr pair)))

(defun fill-find-break-point (limit)
  "Move point to a proper line breaking position of the current line.
Don't move back past the buffer position LIMIT.

This function is called when we are going to break the current line
after or before a non-ASCII character.  If the charset of the
character has the property `fill-find-break-point-function', this
function calls the property value as a function with one arg LIMIT.
If the charset has no such property, do nothing."
  (let* ((ch (following-char))
         (charset (char-charset ch))
         func)
    (if (eq charset 'ascii)
        (setq ch (preceding-char)
              charset (char-charset ch)))
    (if (charsetp charset)
        (setq func
              (get-charset-property charset 'fill-find-break-point-function)))
    (if (and func (fboundp func))
        (funcall func limit))))

(defun fill-delete-prefix (from to prefix)
  "Delete the fill prefix from every line except the first.
The first line may not even have a fill prefix.
Point is moved to just past the fill prefix on the first line."
  (let ((fpre (if (and prefix (not (string-match "\\`[ \t]*\\'" prefix)))
                  (concat "[ \t]*\\("
                          (replace-regexp-in-string
                           "[ \t]+" "[ \t]*"
                           (regexp-quote prefix))
                          "\\)?[ \t]*")
                "[ \t]*")))
    (goto-char from)
    ;; Why signal an error here?  The problem needs to be caught elsewhere.
    ;; (if (>= (+ (current-left-margin) (length prefix))
    ;;         (current-fill-column))
    ;;     (error "fill-prefix too long for specified width"))
    (forward-line 1)
    (while (< (point) to)
      (if (looking-at fpre)
          (delete-region (point) (match-end 0)))
      (forward-line 1))
    (goto-char from)
    (if (looking-at fpre)
        (goto-char (match-end 0)))
    (point)))

;; The `fill-space' property carries the string with which a newline
;; should be replaced when unbreaking a line (in fill-delete-newlines).
;; It is added to newline characters by fill-newline when the default
;; behavior of fill-delete-newlines is not what we want.
(add-to-list 'text-property-default-nonsticky '(fill-space . t))

(defun fill-delete-newlines (from to justify nosqueeze squeeze-after)
  (goto-char from)
  ;; Make sure sentences ending at end of line get an extra space.
  ;; loses on split abbrevs ("Mr.\nSmith")
  (let ((eol-double-space-re
         (cond
          ((not colon-double-space) (concat (sentence-end) "$"))
          ;; Try to add the : inside the `sentence-end' regexp.
          ((string-match "\\[[^][]*\\(\\.\\)[^][]*\\]" (sentence-end))
           (concat (replace-match ".:" nil nil (sentence-end) 1) "$"))
          ;; Can't find the right spot to insert the colon.
          (t "[.?!:][])}\"']*$")))
        (sentence-end-without-space-list
         (string-to-list sentence-end-without-space)))
    (while (re-search-forward eol-double-space-re to t)
      (or (>= (point) to) (memq (char-before) '(?\t ?\s))
          (memq (char-after (match-beginning 0))
                sentence-end-without-space-list)
          (insert-and-inherit ?\s))))

  (goto-char from)
  (if enable-multibyte-characters
      ;; Delete unnecessay newlines surrounded by words.  The
      ;; character category `|' means that we can break a line
      ;; at the character.  And, charset property
      ;; `nospace-between-words' tells how to concatenate
      ;; words.  If the value is non-nil, never put spaces
      ;; between words, thus delete a newline between them.
      ;; If the value is nil, delete a newline only when a
      ;; character preceding a newline has text property
      ;; `nospace-between-words'.
      (while (search-forward "\n" to t)
        (if (get-text-property (match-beginning 0) 'fill-space)
            (replace-match (get-text-property (match-beginning 0) 'fill-space))
          (let ((prev (char-before (match-beginning 0)))
                (next (following-char)))
            (if (and (or (aref (char-category-set next) ?|)
                         (aref (char-category-set prev) ?|))
                     (or (get-charset-property (char-charset prev)
                                               'nospace-between-words)
                         (get-text-property (1- (match-beginning 0))
                                            'nospace-between-words)))
                (delete-char -1))))))

  (goto-char from)
  (skip-chars-forward " \t")
  ;; Then change all newlines to spaces.
  (subst-char-in-region from to ?\n ?\s)
  (if (and nosqueeze (not (eq justify 'full)))
      nil
    (canonically-space-region (or squeeze-after (point)) to)
    ;; Remove trailing whitespace.
    ;; Maybe canonically-space-region should do that.
    (goto-char to) (delete-char (- (skip-chars-backward " \t"))))
  (goto-char from))

(defun fill-move-to-break-point (linebeg)
  "Move to the position where the line should be broken.
The break position will be always after LINEBEG and generally before point."
  ;; If the fill column is before linebeg, move to linebeg.
  (if (> linebeg (point)) (goto-char linebeg))
  ;; Move back to the point where we can break the line
  ;; at.  We break the line between word or after/before
  ;; the character which has character category `|'.  We
  ;; search space, \c| followed by a character, or \c|
  ;; following a character.  If not found, place
  ;; the point at linebeg.
  (while
      (when (re-search-backward "[ \t]\\|\\c|.\\|.\\c|" linebeg 0)
        ;; In case of space, we place the point at next to
        ;; the point where the break occurs actually,
        ;; because we don't want to change the following
        ;; logic of original Emacs.  In case of \c|, the
        ;; point is at the place where the break occurs.
        (forward-char 1)
        (when (fill-nobreak-p) (skip-chars-backward " \t" linebeg))))

  ;; Move back over the single space between the words.
  (skip-chars-backward " \t")

  ;; If the left margin and fill prefix by themselves
  ;; pass the fill-column. or if they are zero
  ;; but we have no room for even one word,
  ;; keep at least one word or a character which has
  ;; category `|' anyway.
  (if (>= linebeg (point))
      ;; Ok, skip at least one word or one \c| character.
      ;; Meanwhile, don't stop at a period followed by one space.
      (let ((to (line-end-position))
            (first t))
        (goto-char linebeg)
        (while (and (< (point) to) (or first (fill-nobreak-p)))
          ;; Find a breakable point while ignoring the
          ;; following spaces.
          (skip-chars-forward " \t")
          (if (looking-at "\\c|")
              (forward-char 1)
            (let ((pos (save-excursion
                         (skip-chars-forward "^ \n\t")
                         (point))))
              (if (re-search-forward "\\c|" pos t)
                  (forward-char -1)
                (goto-char pos))))
          (setq first nil)))

    (if enable-multibyte-characters
        ;; If we are going to break the line after or
        ;; before a non-ascii character, we may have to
        ;; run a special function for the charset of the
        ;; character to find the correct break point.
        (if (not (and (eq (charset-after (1- (point))) 'ascii)
                      (eq (charset-after (point)) 'ascii)))
            ;; Make sure we take SOMETHING after the fill prefix if any.
            (fill-find-break-point linebeg)))))

;; Like text-properties-at but don't include `composition' property.
(defun fill-text-properties-at (pos)
  (let ((l (text-properties-at pos))
        prop-list)
    (while l
      (unless (eq (car l) 'composition)
        (setq prop-list
              (cons (car l) (cons (cadr l) prop-list))))
      (setq l (cddr l)))
    prop-list))

(defun fill-newline ()
  ;; Replace whitespace here with one newline, then
  ;; indent to left margin.
  (skip-chars-backward " \t")
  (insert ?\n)
  ;; Give newline the properties of the space(s) it replaces
  (set-text-properties (1- (point)) (point)
                       (fill-text-properties-at (point)))
  (and (looking-at "\\( [ \t]*\\)\\(\\c|\\)?")
       (or (aref (char-category-set (or (char-before (1- (point))) ?\000)) ?|)
           (match-end 2))
       ;; When refilling later on, this newline would normally not be replaced
       ;; by a space, so we need to mark it specially to re-install the space
       ;; when we unfill.
       (put-text-property (1- (point)) (point) 'fill-space (match-string 1)))
  ;; If we don't want breaks in invisible text, don't insert
  ;; an invisible newline.
  (if fill-nobreak-invisible
      (remove-text-properties (1- (point)) (point)
                              '(invisible t)))
  (if (or fill-prefix
          (not fill-indent-according-to-mode))
      (fill-indent-to-left-margin)
    (indent-according-to-mode))
  ;; Insert the fill prefix after indentation.
  (and fill-prefix (not (equal fill-prefix ""))
       ;; Markers that were after the whitespace are now at point: insert
       ;; before them so they don't get stuck before the prefix.
       (insert-before-markers-and-inherit fill-prefix)))

(defun fill-indent-to-left-margin ()
  "Indent current line to the column given by `current-left-margin'."
  (let ((beg (point)))
    (indent-line-to (current-left-margin))
    (put-text-property beg (point) 'face 'default)))

(defun fill-region-as-paragraph (from to &optional justify
                                      nosqueeze squeeze-after)
  "Fill the region as one paragraph.
It removes any paragraph breaks in the region and extra newlines at the end,
indents and fills lines between the margins given by the
`current-left-margin' and `current-fill-column' functions.
\(In most cases, the variable `fill-column' controls the width.)
It leaves point at the beginning of the line following the paragraph.

Normally performs justification according to the `current-justification'
function, but with a prefix arg, does full justification instead.

From a program, optional third arg JUSTIFY can specify any type of
justification.  Fourth arg NOSQUEEZE non-nil means not to make spaces
between words canonical before filling.  Fifth arg SQUEEZE-AFTER, if non-nil,
means don't canonicalize spaces before that position.

Return the `fill-prefix' used for filling.

If `sentence-end-double-space' is non-nil, then period followed by one
space does not end a sentence, so don't break a line there."
  (interactive (progn
                 (barf-if-buffer-read-only)
                 (list (region-beginning) (region-end)
                       (if current-prefix-arg 'full))))
  (unless (memq justify '(t nil none full center left right))
    (setq justify 'full))

  ;; Make sure "to" is the endpoint.
  (goto-char (min from to))
  (setq to   (max from to))
  ;; Ignore blank lines at beginning of region.
  (skip-chars-forward " \t\n")

  (let ((from-plus-indent (point))
        (oneleft nil))

    (beginning-of-line)
    ;; We used to round up to whole line, but that prevents us from
    ;; correctly handling filling of mixed code-and-comment where we do want
    ;; to fill the comment but not the code.  So only use (point) if it's
    ;; further than `from', which means that `from' is followed by some
    ;; number of empty lines.
    (setq from (max (point) from))

    ;; Delete all but one soft newline at end of region.
    ;; And leave TO before that one.
    (goto-char to)
    (while (and (> (point) from) (eq ?\n (char-after (1- (point)))))
      (if (and oneleft
               (not (and use-hard-newlines
                         (get-text-property (1- (point)) 'hard))))
          (delete-backward-char 1)
        (backward-char 1)
        (setq oneleft t)))
    (setq to (copy-marker (point) t))
    ;; ;; If there was no newline, and there is text in the paragraph, then
    ;; ;; create a newline.
    ;; (if (and (not oneleft) (> to from-plus-indent))
    ;;  (newline))
    (goto-char from-plus-indent))

  (if (not (> to (point)))
      nil ;; There is no paragraph, only whitespace: exit now.

    (or justify (setq justify (current-justification)))

    ;; Don't let Adaptive Fill mode alter the fill prefix permanently.
    (let ((fill-prefix fill-prefix))
      ;; Figure out how this paragraph is indented, if desired.
      (when (and adaptive-fill-mode
                 (or (null fill-prefix) (string= fill-prefix "")))
        (setq fill-prefix (fill-context-prefix from to))
        ;; Ignore a white-space only fill-prefix
        ;; if we indent-according-to-mode.
        (when (and fill-prefix fill-indent-according-to-mode
                   (string-match "\\`[ \t]*\\'" fill-prefix))
          (setq fill-prefix nil)))

      (goto-char from)
      (beginning-of-line)

      (if (not justify)   ; filling disabled: just check indentation
          (progn
            (goto-char from)
            (while (< (point) to)
              (if (and (not (eolp))
                       (< (current-indentation) (current-left-margin)))
                  (fill-indent-to-left-margin))
              (forward-line 1)))

        (if use-hard-newlines
            (remove-list-of-text-properties from to '(hard)))
        ;; Make sure first line is indented (at least) to left margin...
        (if (or (memq justify '(right center))
                (< (current-indentation) (current-left-margin)))
            (fill-indent-to-left-margin))
        ;; Delete the fill-prefix from every line.
        (fill-delete-prefix from to fill-prefix)
        (setq from (point))

        ;; FROM, and point, are now before the text to fill,
        ;; but after any fill prefix on the first line.

        (fill-delete-newlines from to justify nosqueeze squeeze-after)

        ;; This is the actual filling loop.
        (goto-char from)
        (let (linebeg)
          (while (< (point) to)
            (setq linebeg (point))
            (move-to-column (current-fill-column))
            (if (when (< (point) to)
                  ;; Find the position where we'll break the line.
                  (forward-char 1) ;Use an immediately following space, if any.
                  (fill-move-to-break-point linebeg)
                  ;; Check again to see if we got to the end of
                  ;; the paragraph.
                  (skip-chars-forward " \t")
                  (< (point) to))
                ;; Found a place to cut.
                (progn
                  (fill-newline)
                  (when justify
                    ;; Justify the line just ended, if desired.
                    (save-excursion
                      (forward-line -1)
                      (justify-current-line justify nil t))))

              (goto-char to)
              ;; Justify this last line, if desired.
              (if justify (justify-current-line justify t t))))))
      ;; Leave point after final newline.
      (goto-char to)
      (unless (eobp) (forward-char 1))
      ;; Return the fill-prefix we used
      fill-prefix)))

(defsubst skip-line-prefix (prefix)
  "If point is inside the string PREFIX at the beginning of line, move past it."
  (when (and prefix
             (< (- (point) (line-beginning-position)) (length prefix))
             (save-excursion
               (beginning-of-line)
               (looking-at (regexp-quote prefix))))
    (goto-char (match-end 0))))

(defun fill-minibuffer-function (arg)
  "Fill a paragraph in the minibuffer, ignoring the prompt."
  (save-restriction
    (narrow-to-region (minibuffer-prompt-end) (point-max))
    (fill-paragraph arg)))

(defun fill-paragraph (arg)
  "Fill paragraph at or after point.

If ARG is non-nil (interactively, with prefix argument), justify as well.
If `sentence-end-double-space' is non-nil, then period followed by one