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;;; flow-fill.el --- interpret RFC2646 "flowed" text -*- lexical-binding:t -*-
;; Copyright (C) 2000-2019 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 <https://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:
(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
|
