More on format=flowed

[Yuri D'Elia <wavexx@users.sf.net>]

In my quest for format=flowed, I *think* I've come up with a workable
solution by using the following:

---

(defun harden-newlines ()
  (save-excursion
    (goto-char (point-min))
    (while (search-forward "\n" nil t)
      (put-text-property (1- (point)) (point) 'hard t))))

(setq fill-flowed-display-column nil)

(add-hook 'message-setup-hook
  (lambda ()
    (when message-this-is-mail
      (turn-off-auto-fill)
      (setq
	truncate-lines nil
	word-wrap t
	use-hard-newlines t))))

(add-hook 'message-send-hook
  (lambda ()
    (when use-hard-newlines
      (harden-newlines))))

(add-hook 'gnus-article-mode-hook
  (lambda ()
    (setq
      truncate-lines nil
      word-wrap t)))

---

The idea behind it:

- `fill-flowed-display-column' will unwrap flowed message as expected.
  Apparently, the current code in flow-fill.el has problems with long
  quoted text (not all lines are correctly unfolded, but this doesn't
  affect the usability of the message).

- `gnus-article-mode-hook' will wrap flowed messages using word-wrap
  instead. This works nicely.

- In `message-setup-hook' again we turn on the built-in worp-wrap,
  disable auto-fill and set use-hard-newlines silently. Those are set
  for mail messages only, though I've verified that flowed messages also
  work on gmane groups (gmane.test).

- The magic is really done i `message-send-hook', where all newlines are
  replaced with hard newlines. This way the existing message, and more
  importantly, pasted text lacking 'hard' newlines will be preserved.

  All long lines will be wrapped at `fill-flowed-encode-column' since
  `use-hard-newlines' was already turned on earlier.

That's *much* harder than calling (use-hard-newlines) to use
format=flowed all around. Yet, it seems to work. Maybe.

Comments?