From 9ff05910ecdaceed3b36aa29c75f99637a439cd0 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sat, 14 Nov 2015 22:36:53 -0500
Subject: render: shader: Remove 'attributes' field.

Attributes are fixed so the field is useless.

* sly/render/shader.scm (shader-program-attribute-location): Delete.
  (<shader-program>): Delete 'attributes' field.
  (make-shader-program): Remove 'attributes' argument.
  (load-shader-program): Likewise.  Change arguments from positional to
  keyword.
  (%default-shader): New variable.
  (load-default-shader): Reimplement in terms of promises.
---
 sly/render/shader.scm | 58 +++++++++++++++++++++++----------------------------
 1 file changed, 26 insertions(+), 32 deletions(-)

diff --git a/sly/render/shader.scm b/sly/render/shader.scm
index b736560..fe2eddd 100644
--- a/sly/render/shader.scm
+++ b/sly/render/shader.scm
@@ -49,7 +49,6 @@
             vertex-position-location
             vertex-texture-location
             shader-program-uniform-location
-            shader-program-attribute-location
             shader-program-id
             shader-program-uniforms
             shader-program-linked?
@@ -201,12 +200,13 @@ in the file FILENAME."
   (location attribute-location))
 
 (define-record-type <shader-program>
-  (%make-shader-program id uniforms attributes)
+  (%make-shader-program id uniforms)
   shader-program?
   (id shader-program-id)
-  (uniforms shader-program-uniforms)
-  (attributes shader-program-attributes))
+  (uniforms shader-program-uniforms))
 
+;; Hard-coded vertex attribute locations.  These are fixed so that all
+;; Sly shaders abide by the same interface.
 (define vertex-position-location 0)
 (define vertex-texture-location 1)
 
@@ -218,15 +218,6 @@ in the file FILENAME."
         (uniform-location uniform)
         (error "Uniform not found: " name))))
 
-(define (shader-program-attribute-location shader-program attribute-name)
-  (let ((attribute (find (match-lambda
-                          (($ <attribute> name _)
-                           (string=? attribute-name name)))
-                         (shader-program-attributes shader-program))))
-    (if attribute
-        (attribute-location attribute)
-        (error "Attribute not found: " attribute-name))))
-
 (define-guardian shader-program-guardian
   (lambda (shader-program)
     (false-if-exception
@@ -235,7 +226,7 @@ in the file FILENAME."
 (define-status shader-program-linked? glGetProgramiv link-status)
 (define-logger display-linking-error glGetProgramiv glGetProgramInfoLog)
 
-(define (make-shader-program vertex-shader fragment-shader uniforms attributes)
+(define (make-shader-program vertex-shader fragment-shader uniforms)
   "Create a new shader program that has been linked with the given
 VERTEX-SHADER and FRAGMENT-SHADER."
   (unless (and (vertex-shader? vertex-shader)
@@ -275,8 +266,7 @@ VERTEX-SHADER and FRAGMENT-SHADER."
                     (glDetachShader id (shader-id shader)))
                   shaders)
         (let* ((uniforms (map build-uniform uniforms))
-               (attributes (map string->attribute attributes))
-               (shader-program (%make-shader-program id uniforms attributes)))
+               (shader-program (%make-shader-program id uniforms)))
           (shader-program-guardian shader-program)
           shader-program))
       throw
@@ -284,14 +274,14 @@ VERTEX-SHADER and FRAGMENT-SHADER."
         ;; Make sure to delete program in case linking fails.
         (glDeleteProgram id)))))
 
-(define (load-shader-program vertex-shader-file-name fragment-shader-file-name
-                             uniforms attributes)
-  (make-shader-program (load-vertex-shader vertex-shader-file-name)
-                       (load-fragment-shader fragment-shader-file-name)
-                       uniforms attributes))
+(define* (load-shader-program #:key vertex-source fragment-source
+                              uniforms)
+  (make-shader-program (load-vertex-shader vertex-source)
+                       (load-fragment-shader fragment-source)
+                       uniforms))
 
 (define null-shader-program
-  (%make-shader-program 0 '() '()))
+  (%make-shader-program 0 '()))
 
 (define (apply-shader-program shader-program)
   (glUseProgram (shader-program-id shader-program)))
@@ -378,13 +368,17 @@ within SHADER-PROGRAM."
 ;;; Built-in Shaders
 ;;;
 
-(define load-default-shader
-  (memoize
-   (lambda ()
-     (load-shader-program
-      (string-append %datadir "/shaders/default-vertex.glsl")
-      (string-append %datadir "/shaders/default-fragment.glsl")
-      `((mvp "mvp" ,identity-transform)
-        (color "color" ,white)
-        (texture? "use_texture" #f))
-      '("position" "tex")))))
+;; Use lazy evaluation because shader loading will fail until there is
+;; an OpenGL context available.
+(define %default-shader
+  (delay
+    (load-shader-program
+     #:vertex-source (scope-datadir "/shaders/default-vertex.glsl")
+     #:fragment-source (scopre-datadir "/shaders/default-fragment.glsl")
+     #:uniforms `((mvp "mvp" ,identity-transform)
+                  (color "color" ,white)
+                  (texture? "use_texture" #f)))))
+
+(define (load-default-shader)
+  "Load and return the default shader program."
+  (force %default-shader))
-- 
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