;;; big-lambda.el --- Display big lambda.

;; Copyright (C) 2007  Taiki SUGAWARA <buzz.taiki@gmail.com>

;; Author: Taiki SUGAWARA <buzz.taiki@gmail.com>
;; Keywords: lisp, convenience

;; This file is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; This file is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Installation:
;;
;; Put the following in your .emacs:
;; (require 'big-lambda)
;; (add-hook 'emacs-lisp-mode-hook 'big-lambda-mode-turn-on)
;; (add-hook 'lisp-mode-hook 'big-lambda-mode-turn-on)
;; (add-hook 'lisp-interaction-mode-hook 'big-lambda-mode-turn-on)

;;; Code:

(defvar big-lambda-image
  (create-image
   (base64-decode-string
    "/9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAsICAoIBwsKCQoNDAsNERwSEQ8PESIZGhQcKSQrKigk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")
   'jpeg t))

(defvar big-lambda-font-lock-keywords
  '((".+" (0 (prog1 nil
	       (big-lambda-remove-region
		(match-beginning 0) (match-end 0)))))
    ("(\\(lambda\\)\\>"
     (0 (prog1 nil
	  (big-lambda-region (match-beginning 1) (match-end 1)))))))

(defun big-lambda-remove-region (beg end)
  "Remove big lambda property in region between BEG and END."
  (let (pos)
    (while (setq pos (text-property-any beg end 'display big-lambda-image))
      (remove-text-properties
       pos
       (or (next-single-property-change pos 'display) end)
       '(display)))))

(defun big-lambda-region (beg end)
  "Add big lambda property in region between BEG and END."
  (put-text-property beg end 'display big-lambda-image))

(define-minor-mode big-lambda-mode
  "Display big lambda."
  nil " Lambda" nil
  (if big-lambda-mode
      (progn
	(save-restriction
	  (widen)
	  (let ((font-lock-keywords big-lambda-font-lock-keywords))
	    (font-lock-fontify-buffer)))
	(font-lock-add-keywords nil big-lambda-font-lock-keywords))
    (font-lock-remove-keywords nil big-lambda-font-lock-keywords)
    (save-restriction
      (widen)
      (let ((modified-p (buffer-modified-p)))
	(big-lambda-remove-region (point-min) (point-max))
	(set-buffer-modified-p modified-p)))))

(defun big-lambda-mode-turn-on ()
  "Turn on `big-lambda-mode'."
  (interactive)
  (big-lambda-mode 1))

(provide 'big-lambda)
;;; big-lambda.el ends here