[emacs-wiki-discuss] semi-colons and filling

[Jim Ottaway]

I have come across some anomalous cases of paragraph filling involving
text with semi-colons in it.  For example, this text

Markets, then, are an interface between different calculative agencies; they
supply a structure within which differences between strangers may be brought
into some sort of a relation, and into a relation which is ordered.

ends up like this

Markets, then, are an interface between different calculative agencies;
                                                                      ; they
                                                                      ; supply
                                                                      ; a
                                                                      ; 
structure
                                                                      ; within
                                                                      ; which
                                                                      ; 
differences
                                                                      ; between
                                                                      ; 
strangers
                                                                      ; may

... etc., etc. Clearly, the text after the semi-colon is being handled as if
it were a comment.

This happens when the fill-column is greater than the end of the
comment-start string in the line, which is '; ' for muse mode.

It also appears that if the fill-column is less than the beginning position
of the comment-start string that an error is raised: "fill-delete-prefix:
fill-prefix too long for specified width".

I am tremendously fond of the semi-colon, so I have come up with this
solution. I implemented it as a hook to muse-mode; it could easily be
worked into the muse-mode function itself.

(defun muse-fill-paragraph (arg)
  (unless
      (save-excursion
        (goto-char (muse-line-beginning-position))
        (looking-at comment-start))
    (let ((fill-paragraph-handle-comment nil)
          (fill-paragraph-function nil))
      (fill-paragraph arg))))

(defun muse-mode-fix-paragraph-filling ()
  (set (make-local-variable 'fill-paragraph-function) #'muse-fill-paragraph))

(add-hook 'muse-mode-hook #'muse-mode-fix-paragraph-filling)

Regards,

-- 
Jim Ottaway