bug#27775: footnotes mode hanging indent [CODE INCLUDED]

[Boruch Baum]

1] I find it preferable to have footnote text always left-justified to
   the beginning of the first character of text, while emacs
   auto-fills by default to column 1 and would require unwieldly
   toggling set-fill-prefix whenever moving between text body and
   footnotes.

   Here's what I've done for myself, so far, and if you like it in
   principle, you can have it. I'm available to tweak it some per your
   suggestions and my ability (eg. modify the footnote functions
   themselves instead advising after them).

2] Function `Footnote-add-footnote' in emacs25 defines an optional
   `arg', but it is never used.

3] The current default value for variable `footnote-body-tag-spacing'
   is 2, which is visually appealing, but doesn't persist upon
   `fill-paragraph'. I've tried replacing the space character with a
   non-breaking space (integer value 160), which you might want to
   consider, but it visually looks like an underscore which is
   un-appealing.


#+BEGIN_SRC emacs-lisp
(setq Footnote-align-to-fn-text t
      body-auto-fill-prefix nil)

(defun Footnote-calc-fn-alignment-column()
  (+ footnote-body-tag-spacing
    (length
       (concat footnote-start-tag  footnote-end-tag
         (Footnote-index-to-string
            (caar (last footnote-text-marker-alist)))))))

(defun Footnote-align-to-fn()
  (when Footnote-align-to-fn-text
    (setq body-auto-fill-prefix fill-prefix
          fill-prefix (make-string (Footnote-calc-fn-alignment-column) 32))))

(defun Footnote-align-to-body()
  (when (not Footnote-align-to-fn-text)
    (setq fill-prefix body-auto-fill-prefix)))

(defun Footnote-toggle-alignment()
  (interactive)
  (setq Footnote-align-to-fn-text (not Footnote-align-to-fn-text))
  (when footnote-text-marker-alist
    (if (>= (point) (cdr (first footnote-text-marker-alist)))
      (if Footnote-align-to-fn-text
        (Footnote-align-to-fn)
       (Footnote-align-to-body))))
  (if Footnote-align-to-fn-text
    (message "Footnotes will left-align to footnote text")
   (message "Footnotes will left-align to body text")))

(define-key footnote-mode-map
  (kbd "q") 'Footnote-toggle-alignment)

(defadvice Footnote-add-footnote (after update-auto-fill-prefix activate)
  (interactive)
  (Footnote-align-to-fn))

(defadvice Footnote-back-to-message (after restore-auto-fill-prefix
                                     activate)
  (interactive)
  (setq fill-prefix body-auto-fill-prefix))
#+END_SRC

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