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, 2007, 2008 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 3, 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 ;;;###autoload
  79 (defun fill-flowed-encode (&optional buffer)
  80   (with-current-buffer (or buffer (current-buffer))
  81     ;; No point in doing this unless hard newlines is used.
  82     (when use-hard-newlines
  83       (let ((start (point-min)) end)
  84         ;; Go through each paragraph, filling it and adding SPC
  85         ;; as the last character on each line.
  86         (while (setq end (text-property-any start (point-max) 'hard 't))
  87           (let ((fill-column (eval fill-flowed-encode-column)))
  88             (fill-region start end t 'nosqueeze 'to-eop))
  89           (goto-char start)
  90           ;; `fill-region' probably distorted end.
  91           (setq end (text-property-any start (point-max) 'hard 't))
  92           (while (and (< (point) end)
  93                       (re-search-forward "$" (1- end) t))
  94             (insert " ")
  95             (setq end (1+ end))
  96             (forward-char))
  97           (goto-char (setq start (1+ end)))))
  98       t)))
  99
 100 ;;;###autoload
 101 (defun fill-flowed (&optional buffer delete-space)
 102   (save-excursion
 103     (set-buffer (or (current-buffer) buffer))
 104     (goto-char (point-min))
 105     ;; Remove space stuffing.
 106     (while (re-search-forward "^\\( \\|>+ $\\)" nil t)
 107       (delete-char -1)
 108       (forward-line 1))
 109     (goto-char (point-min))
 110     (while (re-search-forward " $" nil t)
 111       (when delete-space
 112         (delete-char -1))
 113       (when (save-excursion
 114               (beginning-of-line)
 115               (looking-at "^\\(>*\\)\\( ?\\)"))
 116         (let ((quote (match-string 1))
 117               sig)
 118           (if (string= quote "")
 119               (setq quote nil))
 120           (when (and quote (string= (match-string 2) ""))
 121             (save-excursion
 122               ;; insert SP after quote for pleasant reading of quoted lines
 123               (beginning-of-line)
 124               (when (> (skip-chars-forward ">") 0)
 125                 (insert " "))))
 126           ;; XXX slightly buggy handling of "-- "
 127           (while (and (save-excursion
 128                         (ignore-errors (backward-char 3))
 129                         (setq sig (looking-at "-- "))
 130                         (looking-at "[^-][^-] "))
 131                       (save-excursion
 132                         (unless (eobp)
 133                           (forward-char 1)
 134                           (looking-at (format "^\\(%s\\)\\([^>\n\r]\\)"
 135                                               (or quote " ?"))))))
 136             (save-excursion
 137               (replace-match (if (string= (match-string 2) " ")
 138                                  "" "\\2")))
 139             (backward-delete-char -1)
 140             (end-of-line))
 141           (unless sig
 142             (condition-case nil
 143                 (let ((fill-prefix (when quote (concat quote " ")))
 144                       (fill-column (eval fill-flowed-display-column))
 145                       filladapt-mode
 146                       adaptive-fill-mode)
 147                   (fill-region (point-at-bol)
 148                                (min (1+ (point-at-eol))
 149                                     (point-max))
 150                                'left 'nosqueeze))
 151               (error
 152                (forward-line 1)
 153                nil))))))))
 154
 155 ;; Test vectors.
 156
 157 (defvar show-trailing-whitespace)
 158
 159 (defvar fill-flowed-encode-tests
 160   `(
 161     ;; The syntax of each list element is:
 162     ;; (INPUT . EXPECTED-OUTPUT)
 163     (,(concat
 164        "> Thou villainous ill-breeding spongy dizzy-eyed \n"
 165        "> reeky elf-skinned pigeon-egg! \n"
 166        ">> Thou artless swag-bellied milk-livered \n"
 167        ">> dismal-dreaming idle-headed scut!\n"
 168        ">>> Thou errant folly-fallen spleeny reeling-ripe \n"
 169        ">>> unmuzzled ratsbane!\n"
 170        ">>>> Henceforth, the coding style is to be strictly \n"
 171        ">>>> enforced, including the use of only upper case.\n"
 172        ">>>>> I've noticed a lack of adherence to the coding \n"
 173        ">>>>> styles, of late.\n"
 174        ">>>>>> Any complaints?")
 175      .
 176      ,(concat
 177        "> Thou villainous ill-breeding spongy dizzy-eyed reeky elf-skinned\n"
 178        "> pigeon-egg! \n"
 179        ">> Thou artless swag-bellied milk-livered dismal-dreaming idle-headed\n"
 180        ">> scut!\n"
 181        ">>> Thou errant folly-fallen spleeny reeling-ripe unmuzzled ratsbane!\n"
 182        ">>>> Henceforth, the coding style is to be strictly enforced,\n"
 183        ">>>> including the use of only upper case.\n"
 184        ">>>>> I've noticed a lack of adherence to the coding styles, of late.\n"
 185        ">>>>>> Any complaints?\n"
 186        ))
 187     ;; (,(concat
 188     ;;    "\n"
 189     ;;    "> foo\n"
 190     ;;    "> \n"
 191     ;;    "> \n"
 192     ;;    "> bar\n")
 193     ;;  .
 194     ;;  ,(concat
 195     ;;    "\n"
 196     ;;    "> foo bar\n"))
 197     ))
 198
 199 (defun fill-flowed-test ()
 200   (interactive "")
 201   (switch-to-buffer (get-buffer-create "*Format=Flowed test output*"))
 202   (erase-buffer)
 203   (setq show-trailing-whitespace t)
 204   (dolist (test fill-flowed-encode-tests)
 205     (let (start output)
 206       (insert "***** BEGIN TEST INPUT *****\n")
 207       (insert (car test))
 208       (insert "***** END TEST INPUT *****\n\n")
 209       (insert "***** BEGIN TEST OUTPUT *****\n")
 210       (setq start (point))
 211       (insert (car test))
 212       (save-restriction
 213         (narrow-to-region start (point))
 214         (fill-flowed))
 215       (setq output (buffer-substring start (point-max)))
 216       (insert "***** END TEST OUTPUT *****\n")
 217       (unless (string= output (cdr test))
 218         (insert "\n***** BEGIN TEST EXPECTED OUTPUT *****\n")
 219         (insert (cdr test))
 220         (insert "***** END TEST EXPECTED OUTPUT *****\n"))
 221       (insert "\n\n")))
 222   (goto-char (point-max)))
 223
 224 (provide 'flow-fill)
 225
 226 ;; arch-tag: addc0040-bc53-4f17-b4bc-1eb44eed6f0b
 227 ;;; flow-fill.el ends here