;; To use, load this file
;;         turn on balloon-help-mode
;;         run footnote-balloons, or have it run automatically, e.g.,
;;         (add-hook 'gnus-article-display-hook 'footnote-balloons t)

;; Limitations: Currently, the program may make an extraneous balloon
;; here and there (e.g., if there is a footnote reference in a
;; citation which uses the same numbering scheme).

(require 'balloon-help)

(setq balloon-help-timeout 200)

(defvar footnote-extent-face 'red)
(defvar footnote-balloon-regexp "\\[[^\]\n]+\\]")
;; The following might have been more appropriate, but who knows
;; what people will dream up for footnote markers.
;(defvar footnote-balloon-regexp "\\[\\([0-9]+\\|[a-z]\\|[ixv]+\\)\\]")


(defun get-foot-string ()
	(let (start end foot-string ; ext
							)
		(while (looking-at "[ \t]")
			(forward-char))
		(setq start (point))
		;; Find the end of the footnote.
		(re-search-forward (concat "\\\n\\\n\\|\\'\\|"
															 footnote-balloon-regexp) nil t)
		(beginning-of-line)
		(while (looking-at "^")
			(backward-char))
		(setq end (point))
		(setq foot-string (buffer-substring start end))
	  ;; Superfluous colorizing of the footnotes.
    ; (setq ext (make-extent start end))
    ; (set-extent-property ext 'footnote t)
    ; (set-extent-face ext 'green)
		foot-string))

(defun footnote-balloons ()
	"Make references to footnotes pop up a help balloon
containing the text of the footnote."
	(interactive)
	(map-extents (lambda (extent ignore)
								 (when (extent-property extent 'footnote)
									 (delete-extent extent))))
	(save-excursion
	(let (ref-beg ref-end ext footnum note)
		(goto-char (point-min))
		;; Looking for footnote refs in the text.
		(while (re-search-forward footnote-balloon-regexp nil t)
			(setq ref-beg (match-beginning 0))
			(setq ref-end (match-end 0))
			(setq footnum (buffer-substring ref-beg ref-end))
			(goto-char (point-max))
			;; Now find the footnote itself.
;			(when (search-forward footnum nil t)
			(when (search-backward footnum ref-end t)
				(search-forward footnum nil t)
				(setq note (get-foot-string))
				(setq ext (make-extent ref-beg ref-end))
				(set-extent-face ext footnote-extent-face)
				(set-extent-property ext 'footnote t)
				(set-extent-property ext 'balloon-help note)
			)
			(goto-char ref-end)))))