From 09fd03e14729ea929ecc3428ccfe091fa8c8deba Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Wed, 11 Mar 2015 19:56:14 -0400
Subject: render: context: Add GL parameter type.

* sly/render/context.scm (<gl-parameter>): New record type.
  (%make-gl-parameter, make-gl-parameter, gl-parameter?,
  gl-parameter-default, gl-parameter-bind, gl-parameter-ref,
  %gl-parameter-set!, gl-parameter-set!, gl-parameter-reset!): New
  procedures.

Fixup gl-parameter
---
 sly/render/context.scm | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/sly/render/context.scm b/sly/render/context.scm
index 0e96e26..aec04b0 100644
--- a/sly/render/context.scm
+++ b/sly/render/context.scm
@@ -43,6 +43,24 @@
             render-context-shader set-render-context-shader!
             render-context-mesh set-render-context-mesh!))
 
+(define-record-type <gl-parameter>
+  (%make-gl-parameter default bind value)
+  gl-parameter?
+  (default gl-parameter-default)
+  (bind gl-parameter-bind)
+  (value gl-parameter-ref %gl-parameter-set!))
+
+(define (make-gl-parameter default bind)
+  (%make-gl-parameter default bind default))
+
+(define* (gl-parameter-set! parameter value #:optional force?)
+  (unless (and (not force?) (equal? (gl-parameter-ref parameter) value))
+    (%gl-parameter-set! parameter value)
+    ((gl-parameter-bind parameter) value)))
+
+(define (gl-parameter-reset! parameter)
+  (gl-parameter-set! parameter (gl-parameter-default parameter) #t))
+
 (define-record-type <render-context>
   (%make-render-context blend-mode depth-test? texture shader
                         mesh transform-stack)
-- 
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