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;;; Chickadee Game Toolkit
;;; Copyright © 2016 David Thompson <davet@gnu.org>
;;;
;;; Chickadee 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.
;;;
;;; Chickadee 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/>.
(define-module (chickadee render blend)
#:use-module (ice-9 match)
#:use-module (gl)
#:use-module (chickadee render gl)
#:use-module (chickadee render gpu)
#:export (*blend-mode-state*
*depth-test-state*))
(define (apply-blend-mode blend-mode)
(if blend-mode
(begin
(gl-enable (enable-cap blend))
(match blend-mode
('alpha
(gl-blend-equation (blend-equation-mode-ext func-add-ext))
(gl-blend-func (blending-factor-src src-alpha)
(blending-factor-dest one-minus-src-alpha)))
('multiply
(gl-blend-equation (blend-equation-mode-ext func-add-ext))
(gl-blend-func (blending-factor-src dst-color)
(blending-factor-dest zero)))
('subtract
(gl-blend-equation
(blend-equation-mode-ext func-reverse-subtract-ext))
(gl-blend-func (blending-factor-src one)
(blending-factor-dest zero)))
('add
(gl-blend-equation (blend-equation-mode-ext func-add-ext))
(gl-blend-func (blending-factor-src one)
(blending-factor-dest zero)))
('lighten
(gl-blend-equation (blend-equation-mode-ext max-ext))
(gl-blend-func (blending-factor-src one)
(blending-factor-dest zero)))
('darken
(gl-blend-equation (blend-equation-mode-ext min-ext))
(gl-blend-func (blending-factor-src one)
(blending-factor-dest zero)))
('screen
(gl-blend-equation (blend-equation-mode-ext func-add-ext))
(gl-blend-func (blending-factor-src one)
(blending-factor-dest one-minus-src-color)))
('replace
(gl-blend-equation (blend-equation-mode-ext func-add-ext))
(gl-blend-func (blending-factor-src one)
(blending-factor-dest zero)))))
(gl-disable (enable-cap blend))))
(define *blend-mode-state* (make-gpu-state apply-blend-mode 'replace))
(define (apply-depth-test depth-test?)
(if depth-test?
(gl-enable (enable-cap depth-test))
(gl-disable (enable-cap depth-test))))
(define *depth-test-state* (make-gpu-state apply-depth-test #f))
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