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+;;; flow-fill.el --- interpret RFC2646 "flowed" text
+
+;; Copyright (C) 2000-2016 Free Software Foundation, Inc.
+
+;; Author: Simon Josefsson <jas@pdc.kth.se>
+;; Keywords: mail
+
+;; 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 of the License, 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. If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This implement decoding of RFC2646 formatted text, including the
+;; quoted-depth wins rules.
+
+;; Theory of operation: search for lines ending with SPC, save quote
+;; length of line, remove SPC and concatenate line with the following
+;; line if quote length of following line matches current line.
+
+;; When no further concatenations are possible, we've found a
+;; paragraph and we let `fill-region' fill the long line into several
+;; lines with the quote prefix as `fill-prefix'.
+
+;; Todo: implement basic `fill-region' (Emacs and XEmacs
+;; implementations differ..)
+
+;;; History:
+
+;; 2000-02-17 posted on ding mailing list
+;; 2000-02-19 use `point-at-{b,e}ol' in XEmacs
+;; 2000-03-11 no compile warnings for point-at-bol stuff
+;; 2000-03-26 committed to gnus cvs
+;; 2000-10-23 don't flow "-- " lines, make "quote-depth wins" rule
+;; work when first line is at level 0.
+;; 2002-01-12 probably incomplete encoding support
+;; 2003-12-08 started working on test harness.
+
+;;; Code:
+
+(eval-when-compile (require 'cl))
+
+(defcustom fill-flowed-display-column 'fill-column
+ "Column beyond which format=flowed lines are wrapped, when displayed.
+This can be a Lisp expression or an integer."
+ :version "22.1"
+ :group 'mime-display
+ :type '(choice (const :tag "Standard `fill-column'" fill-column)
+ (const :tag "Fit Window" (- (window-width) 5))
+ (sexp)
+ (integer)))
+
+(defcustom fill-flowed-encode-column 66
+ "Column beyond which format=flowed lines are wrapped, in outgoing messages.
+This can be a Lisp expression or an integer.
+RFC 2646 suggests 66 characters for readability."
+ :version "22.1"
+ :group 'mime-display
+ :type '(choice (const :tag "Standard fill-column" fill-column)
+ (const :tag "RFC 2646 default (66)" 66)
+ (sexp)
+ (integer)))
+
+;;;###autoload
+(defun fill-flowed-encode (&optional buffer)
+ (with-current-buffer (or buffer (current-buffer))
+ ;; No point in doing this unless hard newlines is used.
+ (when use-hard-newlines
+ (let ((start (point-min)) end)
+ ;; Go through each paragraph, filling it and adding SPC
+ ;; as the last character on each line.
+ (while (setq end (text-property-any start (point-max) 'hard 't))
+ (save-restriction
+ (narrow-to-region start end)
+ (let ((fill-column (eval fill-flowed-encode-column)))
+ (fill-flowed-fill-buffer))
+ (goto-char (point-min))
+ (while (re-search-forward "\n" nil t)
+ (replace-match " \n" t t))
+ (goto-char (setq start (1+ (point-max)))))))
+ t)))
+
+(defun fill-flowed-fill-buffer ()
+ (let ((prefix nil)
+ (prev-prefix nil)
+ (start (point-min)))
+ (goto-char (point-min))
+ (while (not (eobp))
+ (setq prefix (and (looking-at "[> ]+")
+ (match-string 0)))
+ (if (equal prefix prev-prefix)
+ (forward-line 1)
+ (save-restriction
+ (narrow-to-region start (point))
+ (let ((fill-prefix prev-prefix))
+ (fill-region (point-min) (point-max) t 'nosqueeze 'to-eop))
+ (goto-char (point-max)))
+ (setq prev-prefix prefix
+ start (point))))
+ (save-restriction
+ (narrow-to-region start (point))
+ (let ((fill-prefix prev-prefix))
+ (fill-region (point-min) (point-max) t 'nosqueeze 'to-eop)))))
+
+;;;###autoload
+(defun fill-flowed (&optional buffer delete-space)
+ (with-current-buffer (or (current-buffer) buffer)
+ (goto-char (point-min))
+ ;; Remove space stuffing.
+ (while (re-search-forward "^\\( \\|>+ $\\)" nil t)
+ (delete-char -1)
+ (forward-line 1))
+ (goto-char (point-min))
+ (while (re-search-forward " $" nil t)
+ (when (save-excursion
+ (beginning-of-line)
+ (looking-at "^\\(>*\\)\\( ?\\)"))
+ (let ((quote (match-string 1))
+ sig)
+ (if (string= quote "")
+ (setq quote nil))
+ (when (and quote (string= (match-string 2) ""))
+ (save-excursion
+ ;; insert SP after quote for pleasant reading of quoted lines
+ (beginning-of-line)
+ (when (> (skip-chars-forward ">") 0)
+ (insert " "))))
+ ;; XXX slightly buggy handling of "-- "
+ (while (and (save-excursion
+ (ignore-errors (backward-char 3))
+ (setq sig (looking-at "-- "))
+ (looking-at "[^-][^-] "))
+ (save-excursion
+ (unless (eobp)
+ (forward-char 1)
+ (looking-at (format "^\\(%s\\)\\([^>\n\r]\\)"
+ (or quote " ?"))))))
+ (save-excursion
+ (replace-match (if (string= (match-string 2) " ")
+ "" "\\2")))
+ (backward-delete-char -1)
+ (when delete-space
+ (delete-char -1))
+ (end-of-line))
+ (unless sig
+ (condition-case nil
+ (let ((fill-prefix (when quote (concat quote " ")))
+ (fill-column (eval fill-flowed-display-column))
+ adaptive-fill-mode)
+ (fill-region (point-at-bol)
+ (min (1+ (point-at-eol))
+ (point-max))
+ 'left 'nosqueeze))
+ (error
+ (forward-line 1)
+ nil))))))))
+
+;; Test vectors.
+
+(defvar show-trailing-whitespace)
+
+(defvar fill-flowed-encode-tests
+ `(
+ ;; The syntax of each list element is:
+ ;; (INPUT . EXPECTED-OUTPUT)
+ (,(concat
+ "> Thou villainous ill-breeding spongy dizzy-eyed \n"
+ "> reeky elf-skinned pigeon-egg! \n"
+ ">> Thou artless swag-bellied milk-livered \n"
+ ">> dismal-dreaming idle-headed scut!\n"
+ ">>> Thou errant folly-fallen spleeny reeling-ripe \n"
+ ">>> unmuzzled ratsbane!\n"
+ ">>>> Henceforth, the coding style is to be strictly \n"
+ ">>>> enforced, including the use of only upper case.\n"
+ ">>>>> I've noticed a lack of adherence to the coding \n"
+ ">>>>> styles, of late.\n"
+ ">>>>>> Any complaints?")
+ .
+ ,(concat
+ "> Thou villainous ill-breeding spongy dizzy-eyed reeky elf-skinned\n"
+ "> pigeon-egg! \n"
+ ">> Thou artless swag-bellied milk-livered dismal-dreaming idle-headed\n"
+ ">> scut!\n"
+ ">>> Thou errant folly-fallen spleeny reeling-ripe unmuzzled ratsbane!\n"
+ ">>>> Henceforth, the coding style is to be strictly enforced,\n"
+ ">>>> including the use of only upper case.\n"
+ ">>>>> I've noticed a lack of adherence to the coding styles, of late.\n"
+ ">>>>>> Any complaints?\n"
+ ))
+ ;; (,(concat
+ ;; "\n"
+ ;; "> foo\n"
+ ;; "> \n"
+ ;; "> \n"
+ ;; "> bar\n")
+ ;; .
+ ;; ,(concat
+ ;; "\n"
+ ;; "> foo bar\n"))
+ ))
+
+(defun fill-flowed-test ()
+ (interactive "")
+ (switch-to-buffer (get-buffer-create "*Format=Flowed test output*"))
+ (erase-buffer)
+ (setq show-trailing-whitespace t)
+ (dolist (test fill-flowed-encode-tests)
+ (let (start output)
+ (insert "***** BEGIN TEST INPUT *****\n")
+ (insert (car test))
+ (insert "***** END TEST INPUT *****\n\n")
+ (insert "***** BEGIN TEST OUTPUT *****\n")
+ (setq start (point))
+ (insert (car test))
+ (save-restriction
+ (narrow-to-region start (point))
+ (fill-flowed))
+ (setq output (buffer-substring start (point-max)))
+ (insert "***** END TEST OUTPUT *****\n")
+ (unless (string= output (cdr test))
+ (insert "\n***** BEGIN TEST EXPECTED OUTPUT *****\n")
+ (insert (cdr test))
+ (insert "***** END TEST EXPECTED OUTPUT *****\n"))
+ (insert "\n\n")))
+ (goto-char (point-max)))
+
+(provide 'flow-fill)
+
+;;; flow-fill.el ends here
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