From e74f4e6d4ffcbf3923c597e75acbc5f0260516f8 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Thu, 22 May 2014 19:29:05 -0400
Subject: Add explicit vertex/fragment shader parameters to
 make-shader-program.

* 2d/shader.scm (make-shader-program): Change parameter list.
  (vertex-shader?, fragment-shader?): New procedures.
---
 2d/shader.scm | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

(limited to '2d')

diff --git a/2d/shader.scm b/2d/shader.scm
index 094b929..d8b165e 100644
--- a/2d/shader.scm
+++ b/2d/shader.scm
@@ -36,6 +36,8 @@
             load-vertex-shader
             load-fragment-shader
             shader?
+            vertex-shader?
+            fragment-shader?
             shader-compiled?
             shader-type
             shader-id
@@ -76,6 +78,14 @@
   (type shader-type)
   (id shader-id))
 
+(define (vertex-shader? shader)
+  "Return #t if SHADER is a vertex shader, #f otherwise."
+  (eq? (shader-type shader) 'vertex))
+
+(define (fragment-shader? shader)
+  "Return #t if SHADER is a fragment shader, #f otherwise."
+  (eq? (shader-type shader) 'fragment))
+
 (define-guardian shader-guardian
   (lambda (shader)
     (false-if-exception
@@ -183,11 +193,16 @@ shaders or #f otherwise."
 (define (display-linking-error shader-program)
   (%display-linking-error (shader-program-id shader-program)))
 
-(define (make-shader-program . shaders)
+(define (make-shader-program vertex-shader fragment-shader)
   "Create a new shader program that has been linked with the given
-SHADERS."
+VERTEX-SHADER and FRAGMENT-SHADER."
+  (unless (and (vertex-shader? vertex-shader)
+               (fragment-shader? fragment-shader))
+    (error "Expected a vertex shader and fragment shader"
+           vertex-shader fragment-shader))
   (let* ((id (glCreateProgram))
-         (shader-program (%make-shader-program id)))
+         (shader-program (%make-shader-program id))
+         (shaders (list vertex-shader fragment-shader)))
     (shader-program-guardian shader-program)
     (for-each (lambda (shader)
                 (glAttachShader id (shader-id shader)))
-- 
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