lisp/gnus/flow-fill.el

   1 ;;; flow-fill.el --- interpret RFC2646 "flowed" text
   2
   3 ;; Copyright (C) 2000, 2001, 2002, 2003, 2004,
   4 ;;   2005, 2006 Free Software Foundation, Inc.
   5
   6 ;; Author: Simon Josefsson <jas@pdc.kth.se>
   7 ;; Keywords: mail
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  24 ;; Boston, MA 02110-1301, USA.
  25
  26 ;;; Commentary:
  27
  28 ;; This implement decoding of RFC2646 formatted text, including the
  29 ;; quoted-depth wins rules.
  30
  31 ;; Theory of operation: search for lines ending with SPC, save quote
  32 ;; length of line, remove SPC and concatenate line with the following
  33 ;; line if quote length of following line matches current line.
  34
  35 ;; When no further concatenations are possible, we've found a
  36 ;; paragraph and we let `fill-region' fill the long line into several
  37 ;; lines with the quote prefix as `fill-prefix'.
  38
  39 ;; Todo: implement basic `fill-region' (Emacs and XEmacs
  40 ;;       implementations differ..)
  41
  42 ;;; History:
  43
  44 ;; 2000-02-17  posted on ding mailing list
  45 ;; 2000-02-19  use `point-at-{b,e}ol' in XEmacs
  46 ;; 2000-03-11  no compile warnings for point-at-bol stuff
  47 ;; 2000-03-26  committed to gnus cvs
  48 ;; 2000-10-23  don't flow "-- " lines, make "quote-depth wins" rule
  49 ;;             work when first line is at level 0.
  50 ;; 2002-01-12  probably incomplete encoding support
  51 ;; 2003-12-08  started working on test harness.
  52
  53 ;;; Code:
  54
  55 (eval-when-compile (require 'cl))
  56
  57 (defcustom fill-flowed-display-column 'fill-column
  58   "Column beyond which format=flowed lines are wrapped, when displayed.
  59 This can be a Lisp expression or an integer."
  60   :version "22.1"
  61   :group 'mime-display
  62   :type '(choice (const :tag "Standard `fill-column'" fill-column)
  63                  (const :tag "Fit Window" (- (window-width) 5))
  64                  (sexp)
  65                  (integer)))
  66
  67 (defcustom fill-flowed-encode-column 66
  68   "Column beyond which format=flowed lines are wrapped, in outgoing messages.
  69 This can be a Lisp expression or an integer.
  70 RFC 2646 suggests 66 characters for readability."
  71   :version "22.1"
  72   :group 'mime-display
  73   :type '(choice (const :tag "Standard fill-column" fill-column)
  74                  (const :tag "RFC 2646 default (66)" 66)
  75                  (sexp)
  76                  (integer)))
  77
  78 (eval-and-compile
  79   (defalias 'fill-flowed-point-at-bol
  80         (if (fboundp 'point-at-bol)
  81             'point-at-bol
  82           'line-beginning-position))
  83
  84    (defalias 'fill-flowed-point-at-eol
  85         (if (fboundp 'point-at-eol)
  86             'point-at-eol
  87           'line-end-position)))
  88
  89 ;;;###autoload
  90 (defun fill-flowed-encode (&optional buffer)
  91   (with-current-buffer (or buffer (current-buffer))
  92     ;; No point in doing this unless hard newlines is used.
  93     (when use-hard-newlines
  94       (let ((start (point-min)) end)
  95         ;; Go through each paragraph, filling it and adding SPC
  96         ;; as the last character on each line.
  97         (while (setq end (text-property-any start (point-max) 'hard 't))
  98           (let ((fill-column (eval fill-flowed-encode-column)))
  99             (fill-region start end t 'nosqueeze 'to-eop))
 100           (goto-char start)
 101           ;; `fill-region' probably distorted end.
 102           (setq end (text-property-any start (point-max) 'hard 't))
 103           (while (and (< (point) end)
 104                       (re-search-forward "$" (1- end) t))
 105             (insert " ")
 106             (setq end (1+ end))
 107             (forward-char))
 108           (goto-char (setq start (1+ end)))))
 109       t)))
 110
 111 ;;;###autoload
 112 (defun fill-flowed (&optional buffer)
 113   (save-excursion
 114     (set-buffer (or (current-buffer) buffer))
 115     (goto-char (point-min))
 116     ;; Remove space stuffing.
 117     (while (re-search-forward "^\\( \\|>+ $\\)" nil t)
 118       (delete-char -1)
 119       (forward-line 1))
 120     (goto-char (point-min))
 121     (while (re-search-forward " $" nil t)
 122       (when (save-excursion
 123               (beginning-of-line)
 124               (looking-at "^\\(>*\\)\\( ?\\)"))
 125         (let ((quote (match-string 1))
 126               sig)
 127           (if (string= quote "")
 128               (setq quote nil))
 129           (when (and quote (string= (match-string 2) ""))
 130             (save-excursion
 131               ;; insert SP after quote for pleasant reading of quoted lines
 132               (beginning-of-line)
 133               (when (> (skip-chars-forward ">") 0)
 134                 (insert " "))))
 135           ;; XXX slightly buggy handling of "-- "
 136           (while (and (save-excursion
 137                         (ignore-errors (backward-char 3))
 138                         (setq sig (looking-at "-- "))
 139                         (looking-at "[^-][^-] "))
 140                       (save-excursion
 141                         (unless (eobp)
 142                           (forward-char 1)
 143                           (looking-at (format "^\\(%s\\)\\([^>\n\r]\\)"
 144                                               (or quote " ?"))))))
 145             (save-excursion
 146               (replace-match (if (string= (match-string 2) " ")
 147                                  "" "\\2")))
 148             (backward-delete-char -1)
 149             (end-of-line))
 150           (unless sig
 151             (condition-case nil
 152                 (let ((fill-prefix (when quote (concat quote " ")))
 153                       (fill-column (eval fill-flowed-display-column))
 154                       filladapt-mode
 155                       adaptive-fill-mode)
 156                   (fill-region (fill-flowed-point-at-bol)
 157                                (min (1+ (fill-flowed-point-at-eol))
 158                                     (point-max))
 159                                'left 'nosqueeze))
 160               (error
 161                (forward-line 1)
 162                nil))))))))
 163
 164 ;; Test vectors.
 165
 166 (eval-when-compile
 167   (defvar show-trailing-whitespace))
 168
 169 (defvar fill-flowed-encode-tests
 170   `(
 171     ;; The syntax of each list element is:
 172     ;; (INPUT . EXPECTED-OUTPUT)
 173     (,(concat
 174        "> Thou villainous ill-breeding spongy dizzy-eyed \n"
 175        "> reeky elf-skinned pigeon-egg! \n"
 176        ">> Thou artless swag-bellied milk-livered \n"
 177        ">> dismal-dreaming idle-headed scut!\n"
 178        ">>> Thou errant folly-fallen spleeny reeling-ripe \n"
 179        ">>> unmuzzled ratsbane!\n"
 180        ">>>> Henceforth, the coding style is to be strictly \n"
 181        ">>>> enforced, including the use of only upper case.\n"
 182        ">>>>> I've noticed a lack of adherence to the coding \n"
 183        ">>>>> styles, of late.\n"
 184        ">>>>>> Any complaints?")
 185      .
 186      ,(concat
 187        "> Thou villainous ill-breeding spongy dizzy-eyed reeky elf-skinned\n"
 188        "> pigeon-egg! \n"
 189        ">> Thou artless swag-bellied milk-livered dismal-dreaming idle-headed\n"
 190        ">> scut!\n"
 191        ">>> Thou errant folly-fallen spleeny reeling-ripe unmuzzled ratsbane!\n"
 192        ">>>> Henceforth, the coding style is to be strictly enforced,\n"
 193        ">>>> including the use of only upper case.\n"
 194        ">>>>> I've noticed a lack of adherence to the coding styles, of late.\n"
 195        ">>>>>> Any complaints?\n"
 196        ))
 197     ;; (,(concat
 198     ;;    "\n"
 199     ;;    "> foo\n"
 200     ;;    "> \n"
 201     ;;    "> \n"
 202     ;;    "> bar\n")
 203     ;;  .
 204     ;;  ,(concat
 205     ;;    "\n"
 206     ;;    "> foo bar\n"))
 207     ))
 208
 209 (defun fill-flowed-test ()
 210   (interactive "")
 211   (switch-to-buffer (get-buffer-create "*Format=Flowed test output*"))
 212   (erase-buffer)
 213   (setq show-trailing-whitespace t)
 214   (dolist (test fill-flowed-encode-tests)
 215     (let (start output)
 216       (insert "***** BEGIN TEST INPUT *****\n")
 217       (insert (car test))
 218       (insert "***** END TEST INPUT *****\n\n")
 219       (insert "***** BEGIN TEST OUTPUT *****\n")
 220       (setq start (point))
 221       (insert (car test))
 222       (save-restriction
 223         (narrow-to-region start (point))
 224         (fill-flowed))
 225       (setq output (buffer-substring start (point-max)))
 226       (insert "***** END TEST OUTPUT *****\n")
 227       (unless (string= output (cdr test))
 228         (insert "\n***** BEGIN TEST EXPECTED OUTPUT *****\n")
 229         (insert (cdr test))
 230         (insert "***** END TEST EXPECTED OUTPUT *****\n"))
 231       (insert "\n\n")))
 232   (goto-char (point-max)))
 233
 234 (provide 'flow-fill)
 235
 236 ;;; arch-tag: addc0040-bc53-4f17-b4bc-1eb44eed6f0b
 237 ;;; flow-fill.el ends here