[Bug-gforth] [bug #55867] Bug in forth-fill-paragraph, and fix

[Reuben Thomas]

URL:
  <https://savannah.gnu.org/bugs/?55867>

                 Summary: Bug in forth-fill-paragraph, and fix
                 Project: Gforth
            Submitted by: rrt
            Submitted on: Fri 08 Mar 2019 05:21:09 PM UTC
                Category: None
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

This bug report supersedes #54866.

The bug is that forth-fill-paragraph globally sets fill-prefix.

While investigating this bug, I discovered that an assertion (that it's not
possible to use `fill-paragraph`) is (no longer?) true, which led to a much
simpler definition:

(defun forth-fill-paragraph () 
  "Fill comments starting with '\\' which start a line; do not fill code."
  ;; Something like lisp-fill-paragraph may be better.
  (interactive)
  (save-excursion
    (beginning-of-line)
    (if (looking-at "[ \t]*\\\\g?[ \t]+")
        (fill-paragraph))))

This also fixes another problem: it does not reformat a comment that ends on
the line above point. However, this is presumably not backwards compatible to
very old Emacsen.

A fix that is more backwards-compatible (but only fixes the first problem)
goes like this:

(defun forth-fill-paragraph () 
  "Fill comments starting with '\\' which start a line; do not fill code."
  ;; Something like lisp-fill-paragraph may be better.
  (interactive)
  (save-excursion
    (beginning-of-line)
    (while (and (= (forward-line -1) 0)
                (looking-at "[ \t]*\\\\g?[ \t]+")))
    (if (not (looking-at "[ \t]*\\\\g?[ \t]+"))
        (forward-line 1))
    (let ((from (point))
          (to (save-excursion (forward-paragraph) (point))))
      (if (looking-at "[ \t]*\\\\g?[ \t]+")
          (progn (goto-char (match-end 0))
                 (let ((fill-prefix-save fill-prefix))
                   (set-fill-prefix)
                   (fill-region from to nil)
                   (setq fill-prefix fill-prefix-save)))))))

(This is an example of why I would like to maintain a version of gforth.el
that is compatible with only current Emacsen; see #54559!)




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