From 8c92224ff8d34503b0924a009afc516965143d10 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Sat, 3 Mar 2012 04:03:41 +0100
Subject: [PATCH] Type-safe shader attributes.

Now the data type is part of attribute definition, so user doesn't have
to guess / look up what data should be there when binding with
Mesh::bindAttribute().
---
 src/AbstractShaderProgram.h | 29 +++++++++++++++++++----------
 src/Mesh.h                  |  6 +++---
 src/Shaders/PhongShader.cpp |  4 ++--
 src/Shaders/PhongShader.h   |  7 ++-----
 4 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/src/AbstractShaderProgram.h b/src/AbstractShaderProgram.h
index b993db513..32c54e49d 100644
--- a/src/AbstractShaderProgram.h
+++ b/src/AbstractShaderProgram.h
@@ -31,14 +31,12 @@ namespace Magnum {
 
 This class is designed to be used via subclassing. Subclasses define these
 functions and properties:
- - <strong>Attribute location</strong> enum with indexes where the particular
-   attribute is bound, for example:
+ - <strong>Attribute location</strong> typedefs defining locations and types
+   for attribute binding with Mesh::bindAttribute(), for example:
 @code
-enum Attribute {
-    Vertex = 0,
-    Normal = 1,
-    TextureCoords = 2
-};
+typedef Attribute<0, Vector4> Vertex;
+typedef Attribute<1, Vector3> Normal;
+typedef Attribute<2, Vector2> TextureCoords;
 @endcode
    See also bindAttribute().
  - @b Constructor, which attaches particular shaders, links the program, binds
@@ -51,9 +49,9 @@ enum Attribute {
     attachShader(fragmentShader);
 
     // Bind attribute names to IDs
-    bindAttribute(Vertex, "vertex");
-    bindAttribute(Normal, "normal");
-    bindAttribute(TextureCoords, "textureCoords");
+    bindAttribute(Vertex::Location, "vertex");
+    bindAttribute(Normal::Location, "normal");
+    bindAttribute(TextureCoords::Location, "textureCoords");
 
     // Link, then delete now uneeded shaders
     link();
@@ -84,6 +82,17 @@ class MAGNUM_EXPORT AbstractShaderProgram {
     AbstractShaderProgram& operator=(AbstractShaderProgram&& other) = delete;
 
     public:
+        /**
+         * @brief Base struct for attribute location and type
+         *
+         * See AbstractShaderProgram documentation or Mesh::bindAttribute()
+         * for an example.
+         */
+        template<size_t i, class T> struct Attribute {
+            static const size_t Location = i;   /**< Location to which the attribute is bound */
+            typedef T Type;                     /**< Attribute type */
+        };
+
         /** @brief Default constructor */
         AbstractShaderProgram();
 
diff --git a/src/Mesh.h b/src/Mesh.h
index 1af71fc1d..7745b617a 100644
--- a/src/Mesh.h
+++ b/src/Mesh.h
@@ -162,17 +162,17 @@ class MAGNUM_EXPORT Mesh {
 
         /**
          * @brief Bind attribute
+         * @tparam attribute    Attribute, defined in the shader
          * @param buffer        Buffer where bind the attribute to (pointer
          *      returned by addBuffer())
-         * @param attribute     Attribute
          *
          * Binds attribute of given type with given buffer. If the attribute is
          * already bound, given buffer isn't managed with this mesh (wasn't
          * initialized with addBuffer) or the mesh was already drawn, the
          * function does nothing.
          */
-        template<class T> inline void bindAttribute(Buffer* buffer, GLuint attribute) {
-            bindAttribute(buffer, attribute, TypeTraits<T>::count(), TypeTraits<T>::glType());
+        template<class Attribute> inline void bindAttribute(Buffer* buffer) {
+            bindAttribute(buffer, Attribute::Location, TypeTraits<typename Attribute::Type>::count(), TypeTraits<typename Attribute::Type>::glType());
         }
 
         /**
diff --git a/src/Shaders/PhongShader.cpp b/src/Shaders/PhongShader.cpp
index ebec7e61d..299f1bc4b 100644
--- a/src/Shaders/PhongShader.cpp
+++ b/src/Shaders/PhongShader.cpp
@@ -28,8 +28,8 @@ PhongShader::PhongShader() {
     attachShader(vertexShader);
     attachShader(fragmentShader);
 
-    bindAttribute(Vertex, "vertex");
-    bindAttribute(Normal, "normal");
+    bindAttribute(Vertex::Location, "vertex");
+    bindAttribute(Normal::Location, "normal");
 
     link();
     delete vertexShader;
diff --git a/src/Shaders/PhongShader.h b/src/Shaders/PhongShader.h
index 2e347b26a..7c3f5331e 100644
--- a/src/Shaders/PhongShader.h
+++ b/src/Shaders/PhongShader.h
@@ -26,11 +26,8 @@ namespace Magnum { namespace Shaders {
 /** @brief Phong shader */
 class PhongShader: public AbstractShaderProgram {
     public:
-        /** @brief Attribute */
-        enum Attribute {
-            Vertex = 0,     /**< @brief Vertex position (four-component vector) */
-            Normal = 1      /**< @brief Normal direction (three-component vector) */
-        };
+        typedef Attribute<0, Vector4> Vertex;   /**< @brief Vertex position */
+        typedef Attribute<1, Vector3> Normal;   /**< @brief Normal direction */
 
         /** @brief Constructor */
         PhongShader();