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diff --git a/chickadee/render/blend.scm b/chickadee/render/blend.scm
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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))