From 68fc1480bfcd38747e1cf27943e6dbd3e63e37b9 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Wed, 11 Mar 2015 22:15:38 -0400
Subject: render: utils: Improve apply-blend-mode.

* sly/render/utils.scm (apply-blend-mode): Enable/disable blending when
  necessary.
---
 sly/render/utils.scm | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/sly/render/utils.scm b/sly/render/utils.scm
index 0146b49..802eca7 100644
--- a/sly/render/utils.scm
+++ b/sly/render/utils.scm
@@ -26,7 +26,7 @@
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-9)
   #:use-module (gl low-level)
-  #:use-module (gl enums)
+  #:use-module (gl)
   #:export (make-blend-mode blend-mode?
             blend-mode-source blend-mode-destination
             default-blend-mode
@@ -78,5 +78,10 @@
    ('one-minus-constant-alpha 32772)))
 
 (define (apply-blend-mode blend-mode)
-  (glBlendFunc (source-blend-function (blend-mode-source blend-mode))
-               (destination-blend-function (blend-mode-destination blend-mode))))
+  (if blend-mode
+      (begin
+        (gl-enable (enable-cap blend))
+        (glBlendFunc (source-blend-function (blend-mode-source blend-mode))
+                     (destination-blend-function
+                      (blend-mode-destination blend-mode))))
+      (gl-disable (enable-cap blend))))
-- 
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