lisp/textmodes/refill.el

   1 ;;; refill.el --- `auto-fill' by refilling paragraphs on changes
   2
   3 ;; Copyright (C) 2000 Free Software Foundation, Inc.
   4
   5 ;; Author: Dave Love <fx@gnu.org>
   6 ;; Keywords: wp
   7
   8 ;; This program is free software; you can redistribute it and/or modify
   9 ;; it under the terms of the GNU General Public License as published by
  10 ;; the Free Software Foundation; either version 2 of the License, or
  11 ;; (at your option) any later version.
  12 ;;
  13 ;; This program is distributed in the hope that it will be useful,
  14 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 ;; GNU General Public License for more details.
  17 ;;
  18 ;; You should have received a copy of the GNU General Public License
  19 ;; along with this program; if not, write to the
  20 ;; Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  21 ;; Boston, MA 02111-1307, USA.
  22
  23 ;;; Commentary:
  24
  25 ;; Provides a mode where paragraphs are refilled after changes in them
  26 ;; (using `after-change-functions').  This gives something akin to typical
  27 ;; word processor-style filling.  We restrict refilling due to
  28 ;; self-insertion to the characters which trigger auto-fill.
  29
  30 ;; It partly satisfies a todo item in enriched.el for some value of
  31 ;; `without slowing down editing too much'.  It doesn't attempt to do
  32 ;; anything (using `window-size-change-functions'?) about resizing
  33 ;; windows -- who cares?
  34
  35 ;; This implementation is probably fragile and missing some special
  36 ;; cases -- not extensively tested.  Yanking paragraph breaks, for
  37 ;; instance, won't DTRT by refilling all the relevant paragraphs.
  38
  39 ;; You could do it a bit more efficiently (and robustly?) with just an
  40 ;; auto-fill function, but that doesn't cope with changes other than
  41 ;; through self-insertion.  (Using auto-fill and after-change
  42 ;; functions together didn't seem winning.)  This could probably
  43 ;; benefit from a less-general and faster `fill-paragraph-function',
  44 ;; ideally as a primitive.
  45
  46 ;; The work is done in a local post-command hook but only if
  47 ;; `refill-doit' has been set by the after-change function.  Using
  48 ;; `post-command-hook' ensures simply that refilling only happens
  49 ;; once per command.
  50
  51 ;; [Per Abrahamsen's maniac.el does a similar thing, but operates from
  52 ;; post-command-hook.  I don't understand the statement in it that
  53 ;; after-change-functions don't work for this purpose; perhaps there was
  54 ;; some Emacs bug at the time.  ISTR maniac has problems with
  55 ;; whitespace at the end of paragraphs.]
  56
  57 ;;; Code:
  58
  59 (defun refill-fill-paragraph (arg)
  60   "Like `fill-paragraph' but don't delete whitespace at paragraph end."
  61   ;; Should probably use a text property indicating previously-filled
  62   ;; stuff to avoid filling before the point of change.
  63   (let ((before (point)))
  64     (save-excursion
  65       (forward-paragraph)
  66       (skip-syntax-backward "-")
  67       (let ((end (point))
  68             (beg (progn (backward-paragraph) (point))))
  69         (goto-char before)
  70         (save-restriction
  71           (if use-hard-newlines
  72               (fill-region beg end arg)
  73             (fill-region-as-paragraph beg end arg)))))))
  74
  75 (defvar refill-doit nil
  76   "Non-nil means that `refill-post-command-function' does its processing.
  77 Set by `refill-after-change-function' in `after-change-functions' and
  78 unset by `refill-post-command-function' in `post-command-hook'.  This
  79 ensures refilling is only done once per command that causes a change,
  80 regardless of the number of after-change calls from commands doing
  81 complex processing.")
  82 (make-variable-buffer-local 'refill-doit)
  83
  84 (defun refill-after-change-function (beg end len)
  85   "Function for `after-change-functions' which just sets `refill-doit'."
  86   (unless undo-in-progress
  87     (setq refill-doit t)))
  88
  89 (defun refill-post-command-function ()
  90   "Post-command function to do refilling (conditionally)."
  91   (when refill-doit             ; there was a change
  92     ;; There's probably scope for more special cases here...
  93     (cond
  94      ((eq this-command 'self-insert-command)
  95       ;; Respond to the same characters as auto-fill (other than
  96       ;; newline, covered below).
  97       (if (aref auto-fill-chars (char-before))
  98           (refill-fill-paragraph nil)))
  99      ((or (eq this-command 'quoted-insert)
 100           (eq this-command 'fill-paragraph)
 101           (eq this-command 'fill-region))
 102       nil)
 103      ((or (eq this-command 'newline)
 104           (eq this-command 'newline-and-indent)
 105           (eq this-command 'open-line))
 106       ;; Don't zap what was just inserted.
 107       (save-excursion
 108         (beginning-of-line)      ; for newline-and-indent
 109         (skip-chars-backward "\n")
 110         (save-restriction
 111           (narrow-to-region (point-min) (point))
 112           (refill-fill-paragraph nil)))
 113       (widen)
 114       (save-excursion
 115         (skip-chars-forward "\n")
 116         (save-restriction
 117           (narrow-to-region (line-beginning-position) (point-max))
 118           (refill-fill-paragraph nil))))
 119      (t (refill-fill-paragraph nil)))
 120     (setq refill-doit nil)))
 121
 122 (defvar refill-mode nil
 123   "Non-nil if Refill mode is active.  Use `refill-mode' to toggle it.")
 124 (make-variable-buffer-local 'refill-mode)
 125
 126 (defvar refill-mode-hook nil
 127   "Normal hook run by function `refill-mode'.")
 128
 129 (add-to-list 'minor-mode-alist '(refill-mode " Refill"))
 130
 131 ;;;###autoload
 132 (define-minor-mode refill-mode
 133   "Toggle Refill minor mode.
 134 With prefix arg, turn Refill mode on iff arg is positive.
 135
 136 When Refill mode is on, the current paragraph will be formatted when
 137 changes are made within it.  Self-inserting characters only cause
 138 refilling if they would cause auto-filling."
 139   nil " Refill" nil
 140   ;; This provides the test for recursive paragraph filling.
 141   (make-local-variable 'fill-paragraph-function)
 142   (if refill-mode
 143       (progn
 144         (add-hook 'after-change-functions 'refill-after-change-function nil t)
 145         (add-hook 'post-command-hook 'refill-post-command-function nil t)
 146         (set (make-local-variable 'fill-paragraph-function)
 147              'refill-fill-paragraph)
 148         (auto-fill-mode 0))
 149     (remove-hook 'after-change-functions 'refill-after-change-function t)
 150     (remove-hook 'post-command-hook 'refill-post-command-function t)
 151     (setq fill-paragraph-function nil)))
 152
 153 (provide 'refill)
 154
 155 ;;; refill.el ends here