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, 2009 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 of the License, or
  14 ;; (at your option) 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.  If not, see <http://www.gnu.org/licenses/>.
  23
  24 ;;; Commentary:
  25
  26 ;; This implement decoding of RFC2646 formatted text, including the
  27 ;; quoted-depth wins rules.
  28
  29 ;; Theory of operation: search for lines ending with SPC, save quote
  30 ;; length of line, remove SPC and concatenate line with the following
  31 ;; line if quote length of following line matches current line.
  32
  33 ;; When no further concatenations are possible, we've found a
  34 ;; paragraph and we let `fill-region' fill the long line into several
  35 ;; lines with the quote prefix as `fill-prefix'.
  36
  37 ;; Todo: implement basic `fill-region' (Emacs and XEmacs
  38 ;;       implementations differ..)
  39
  40 ;;; History:
  41
  42 ;; 2000-02-17  posted on ding mailing list
  43 ;; 2000-02-19  use `point-at-{b,e}ol' in XEmacs
  44 ;; 2000-03-11  no compile warnings for point-at-bol stuff
  45 ;; 2000-03-26  committed to gnus cvs
  46 ;; 2000-10-23  don't flow "-- " lines, make "quote-depth wins" rule
  47 ;;             work when first line is at level 0.
  48 ;; 2002-01-12  probably incomplete encoding support
  49 ;; 2003-12-08  started working on test harness.
  50
  51 ;;; Code:
  52
  53 (eval-when-compile (require 'cl))
  54
  55 (defcustom fill-flowed-display-column 'fill-column
  56   "Column beyond which format=flowed lines are wrapped, when displayed.
  57 This can be a Lisp expression or an integer."
  58   :version "22.1"
  59   :group 'mime-display
  60   :type '(choice (const :tag "Standard `fill-column'" fill-column)
  61                  (const :tag "Fit Window" (- (window-width) 5))
  62                  (sexp)
  63                  (integer)))
  64
  65 (defcustom fill-flowed-encode-column 66
  66   "Column beyond which format=flowed lines are wrapped, in outgoing messages.
  67 This can be a Lisp expression or an integer.
  68 RFC 2646 suggests 66 characters for readability."
  69   :version "22.1"
  70   :group 'mime-display
  71   :type '(choice (const :tag "Standard fill-column" fill-column)
  72                  (const :tag "RFC 2646 default (66)" 66)
  73                  (sexp)
  74                  (integer)))
  75
  76 ;;;###autoload
  77 (defun fill-flowed-encode (&optional buffer)
  78   (with-current-buffer (or buffer (current-buffer))
  79     ;; No point in doing this unless hard newlines is used.
  80     (when use-hard-newlines
  81       (let ((start (point-min)) end)
  82         ;; Go through each paragraph, filling it and adding SPC
  83         ;; as the last character on each line.
  84         (while (setq end (text-property-any start (point-max) 'hard 't))
  85           (let ((fill-column (eval fill-flowed-encode-column)))
  86             (fill-region start end t 'nosqueeze 'to-eop))
  87           (goto-char start)
  88           ;; `fill-region' probably distorted end.
  89           (setq end (text-property-any start (point-max) 'hard 't))
  90           (while (and (< (point) end)
  91                       (re-search-forward "$" (1- end) t))
  92             (insert " ")
  93             (setq end (1+ end))
  94             (forward-char))
  95           (goto-char (setq start (1+ end)))))
  96       t)))
  97
  98 ;;;###autoload
  99 (defun fill-flowed (&optional buffer delete-space)
 100   (save-excursion
 101     (set-buffer (or (current-buffer) buffer))
 102     (goto-char (point-min))
 103     ;; Remove space stuffing.
 104     (while (re-search-forward "^\\( \\|>+ $\\)" nil t)
 105       (delete-char -1)
 106       (forward-line 1))
 107     (goto-char (point-min))
 108     (while (re-search-forward " $" nil t)
 109       (when delete-space
 110         (delete-char -1))
 111       (when (save-excursion
 112               (beginning-of-line)
 113               (looking-at "^\\(>*\\)\\( ?\\)"))
 114         (let ((quote (match-string 1))
 115               sig)
 116           (if (string= quote "")
 117               (setq quote nil))
 118           (when (and quote (string= (match-string 2) ""))
 119             (save-excursion
 120               ;; insert SP after quote for pleasant reading of quoted lines
 121               (beginning-of-line)
 122               (when (> (skip-chars-forward ">") 0)
 123                 (insert " "))))
 124           ;; XXX slightly buggy handling of "-- "
 125           (while (and (save-excursion
 126                         (ignore-errors (backward-char 3))
 127                         (setq sig (looking-at "-- "))
 128                         (looking-at "[^-][^-] "))
 129                       (save-excursion
 130                         (unless (eobp)
 131                           (forward-char 1)
 132                           (looking-at (format "^\\(%s\\)\\([^>\n\r]\\)"
 133                                               (or quote " ?"))))))
 134             (save-excursion
 135               (replace-match (if (string= (match-string 2) " ")
 136                                  "" "\\2")))
 137             (backward-delete-char -1)
 138             (end-of-line))
 139           (unless sig
 140             (condition-case nil
 141                 (let ((fill-prefix (when quote (concat quote " ")))
 142                       (fill-column (eval fill-flowed-display-column))
 143                       filladapt-mode
 144                       adaptive-fill-mode)
 145                   (fill-region (point-at-bol)
 146                                (min (1+ (point-at-eol))
 147                                     (point-max))
 148                                'left 'nosqueeze))
 149               (error
 150                (forward-line 1)
 151                nil))))))))
 152
 153 ;; Test vectors.
 154
 155 (defvar show-trailing-whitespace)
 156
 157 (defvar fill-flowed-encode-tests
 158   `(
 159     ;; The syntax of each list element is:
 160     ;; (INPUT . EXPECTED-OUTPUT)
 161     (,(concat
 162        "> Thou villainous ill-breeding spongy dizzy-eyed \n"
 163        "> reeky elf-skinned pigeon-egg! \n"
 164        ">> Thou artless swag-bellied milk-livered \n"
 165        ">> dismal-dreaming idle-headed scut!\n"
 166        ">>> Thou errant folly-fallen spleeny reeling-ripe \n"
 167        ">>> unmuzzled ratsbane!\n"
 168        ">>>> Henceforth, the coding style is to be strictly \n"
 169        ">>>> enforced, including the use of only upper case.\n"
 170        ">>>>> I've noticed a lack of adherence to the coding \n"
 171        ">>>>> styles, of late.\n"
 172        ">>>>>> Any complaints?")
 173      .
 174      ,(concat
 175        "> Thou villainous ill-breeding spongy dizzy-eyed reeky elf-skinned\n"
 176        "> pigeon-egg! \n"
 177        ">> Thou artless swag-bellied milk-livered dismal-dreaming idle-headed\n"
 178        ">> scut!\n"
 179        ">>> Thou errant folly-fallen spleeny reeling-ripe unmuzzled ratsbane!\n"
 180        ">>>> Henceforth, the coding style is to be strictly enforced,\n"
 181        ">>>> including the use of only upper case.\n"
 182        ">>>>> I've noticed a lack of adherence to the coding styles, of late.\n"
 183        ">>>>>> Any complaints?\n"
 184        ))
 185     ;; (,(concat
 186     ;;    "\n"
 187     ;;    "> foo\n"
 188     ;;    "> \n"
 189     ;;    "> \n"
 190     ;;    "> bar\n")
 191     ;;  .
 192     ;;  ,(concat
 193     ;;    "\n"
 194     ;;    "> foo bar\n"))
 195     ))
 196
 197 (defun fill-flowed-test ()
 198   (interactive "")
 199   (switch-to-buffer (get-buffer-create "*Format=Flowed test output*"))
 200   (erase-buffer)
 201   (setq show-trailing-whitespace t)
 202   (dolist (test fill-flowed-encode-tests)
 203     (let (start output)
 204       (insert "***** BEGIN TEST INPUT *****\n")
 205       (insert (car test))
 206       (insert "***** END TEST INPUT *****\n\n")
 207       (insert "***** BEGIN TEST OUTPUT *****\n")
 208       (setq start (point))
 209       (insert (car test))
 210       (save-restriction
 211         (narrow-to-region start (point))
 212         (fill-flowed))
 213       (setq output (buffer-substring start (point-max)))
 214       (insert "***** END TEST OUTPUT *****\n")
 215       (unless (string= output (cdr test))
 216         (insert "\n***** BEGIN TEST EXPECTED OUTPUT *****\n")
 217         (insert (cdr test))
 218         (insert "***** END TEST EXPECTED OUTPUT *****\n"))
 219       (insert "\n\n")))
 220   (goto-char (point-max)))
 221
 222 (provide 'flow-fill)
 223
 224 ;; arch-tag: addc0040-bc53-4f17-b4bc-1eb44eed6f0b
 225 ;;; flow-fill.el ends here