;;; transparency.el --- a viewing mode for books and novels.  -*- lexical-binding: t; -*-

;; Copyright (C) 2019 Robert Rose

;; Author: Robert Rose <overclucker@gmail.com>
;; Keywords: lisp eww novel book
;; Version: 0.0.1
;; Package-Requires ((emacs "24"))

;; This program 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 3 of the License, or
;; (at your option) any later version.

;; This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Toggles transparency on and off with `transparency-toggle'. Customize how it looks in `transparency'
;; custom group.

;;; Code:

(defvar transparency-state nil
  "Reflects the current state of transparency.")

(defvar transparency-original-faces '()
  "Stores original faces while transparency is enable.")

(defgroup transparency nil
  "Custom group for transparency package.")

(defcustom transparency-alpha 50
  "The level of transparency used."
  :type 'integer
  :group 'transparency)

(defcustom transparency-faces
  '((default :background "#444")
    (default :foreground "grey75")
    (fringe :background "#444")
    (mode-line :background "#444")
    (mode-line :foreground "grey75")
    (mode-line :box nil)
    (mode-line-inactive :background "#444")
    (mode-line-inactive :foreground "grey50")
    (mode-line-inactive :box nil))
  "Faces used when transparency is enabled."
  :type '(alist face)
  :group 'transparency)


(setq alpha-prop (if (>= emacs-major-version 29) 
                        'alpha-background 
                      'alpha))

(defun transparency-modface (FPV)
  "Sets new and returns old FPV"
  (let* ((face (pop FPV))
	 (prop (pop FPV))
	 (val (pop FPV))
	 (prev (face-attribute face prop)))    
    (set-face-attribute face nil prop val)
    `(,face ,prop ,prev)))

(defun transparency-toggle ()
  "better alpha toggle transparency"
  (interactive)
  (if transparency-state
      (progn
	(set-frame-parameter nil alpha-prop 100)
	;; (set-frame-parameter nil 'alpha-background 100)
	(mapcar 'transparency-modface transparency-original-faces)
	(setq transparency-state nil))
    (set-frame-parameter nil alpha-prop transparency-alpha)
    (setq transparency-original-faces
	  (mapcar 'transparency-modface transparency-faces))
    (setq transparency-state t)))

(provide 'transparency)

;;; transparency.el ends here