Proposal of VAO class built on Bindable template.

src/Bindable.hpp

@@ -0,0 +1,66 @@
+#pragma once
+#include "glid.hpp"
+#include <boost/optional.hpp>
+
+namespace gldr {
+
+template<typename T>
+class ScopedBinder {
+    boost::optional<GLuint> id;
+
+public:
+    ScopedBinder(GLuint rebId)
+        : id(rebId)
+    { }
+    ScopedBinder(ScopedBinder && rhs) {
+        // workaround for lack of move constructor in boost::optional
+        id.swap(rhs.id);
+    }
+    ~ScopedBinder() {
+        if (id) {
+            T::bindObject(id.get());
+        }
+    }
+
+private:
+    ScopedBinder& operator=(ScopedBinder&) /* = delete*/;
+    ScopedBinder& operator=(ScopedBinder&&) /* = delete*/;
+    ScopedBinder(ScopedBinder&) /* = delete */;
+};
+
+template<typename T>
+class Bindable {
+protected:
+    Glid<T> id;
+
+public:
+    void bind() {
+        T::bindObject(id.get());
+    }
+
+    static void unbind() {
+        T::bindObject(0);
+    }
+
+    static ScopedBinder<T> createRebindToCurrent() {
+        return ScopedBinder<T>(T::getCurrentlyBound());
+    }
+
+    ScopedBinder<T> scopedBind() {
+        auto current = T::getCurrentlyBound();
+        bind();
+        return ScopedBinder<T>(current);
+    }
+
+    // For Visual Studio
+    Bindable() {
+    }
+    Bindable(Bindable&& rhs) 
+        : id(std::move(rhs.id)) {
+    }
+    Bindable& operator=(Bindable && rhs) {
+        id = std::move(rhs.id);
+    }
+};
+
+}

src/VertexAttributeArray.h

@@ -0,0 +1,102 @@
+#pragma once
+#include <utility>
+#include <stdexcept>
+
+#include "Bindable.hpp"
+#include "VertexBuffer.h"
+
+#define GLDR_HAS_DSA
+
+namespace gldr {
+
+enum class VertexAttributeType : GLenum {
+    Float = gl::FLOAT,
+    HalfFloat = gl::HALF_FLOAT,
+    Byte = gl::BYTE,
+    Short = gl::SHORT,
+    UShort = gl::UNSIGNED_SHORT,
+    Int = gl::INT,
+    UInt = gl::UNSIGNED_INT,
+    UByte = gl::UNSIGNED_BYTE
+};
+
+enum class VertexAttributeIntegerType : GLenum {
+    Byte = gl::BYTE,
+    Short = gl::SHORT,
+    UShort = gl::UNSIGNED_SHORT,
+    Int = gl::INT,
+    UInt = gl::UNSIGNED_INT,
+    UByte = gl::UNSIGNED_BYTE
+};
+
+class VertexAttributeArray : public Bindable<VertexAttributeArray> {
+
+public:
+    // creation and destruction
+    static GLuint create() {
+        GLuint id = 0;
+        gl::GenVertexArrays(1, &id);
+        if (!id)
+            throw std::runtime_error("Problem creating a vertex array");
+        return id;
+    }
+
+    static void destroy(GLuint id) {
+        gl::DeleteVertexArrays(1, &id);
+    }
+
+    static void bindObject(GLuint id) {
+        gl::BindVertexArray(id);
+    }
+
+    static GLuint getCurrentlyBound() {
+        GLint current;
+        gl::GetIntegerv(gl::VERTEX_ARRAY_BINDING, &current);
+        return current;
+    }
+
+    void directVertexAttribOffset(unsigned buffer, unsigned index, int size, VertexAttributeType type, bool normalized, unsigned stride, int offset) {
+    #ifdef GLDR_HAS_DSA
+        gl::VertexArrayVertexAttribOffsetEXT(id.get(), buffer, index, size, static_cast<GLenum>(type), normalized, stride, offset);
+    #else
+        auto vaoScope = scopedBind();
+        auto vboScope = VertexBuffer<VertexBufferType::ARRAY_BUFFER>::createRebindToCurrent();
+
+        gl::BindBuffer(gl::ARRAY_BUFFER, buffer);
+        gl::VertexAttribPointer(index, size, static_cast<GLenum>(type), normalized, stride, reinterpret_cast<void*>(offset));
+    #endif
+    }
+
+    void directVertexAttribIntegerOffset(unsigned buffer, unsigned index, int size, VertexAttributeIntegerType type, unsigned stride, int offset) {
+    #ifdef GLDR_HAS_DSA
+        gl::VertexArrayVertexAttribIOffsetEXT(id.get(), buffer, index, size, static_cast<GLenum>(type), stride, offset);
+    #else
+        auto vaoScope = scopedBind();
+        auto vboScope = VertexBuffer<VertexBufferType::ARRAY_BUFFER>::createRebindToCurrent();
+
+        gl::BindBuffer(gl::ARRAY_BUFFER, buffer);
+        gl::VertexAttribIPointer(index, size, static_cast<GLenum>(type), stride, reinterpret_cast<void*>(offset));
+    #endif
+    }
+
+    void VertexAttributeArray::enableAttributeArray(unsigned index) {
+    #ifdef GLDR_HAS_DSA
+        gl::EnableVertexArrayAttribEXT(id.get(), index);
+    #else
+        auto scope = scopedBind();
+        gl::EnableVertexAttribArray(index);
+    #endif
+    }
+
+    // static state queries
+    // TODO: MAX_VERTEX_ATTRIB_BINDINGS is a part of buffer specification, not VAO?
+    // Spec 4.3, 10.3.1-10.3.3
+    // TODO: is this too much of utility?
+    static unsigned getMaxVertexAttributes() {
+        GLint count;
+        gl::GetIntegerv(gl::MAX_VERTEX_ATTRIBS, &count);
+        return count;
+    }
+};
+
+} // namespace gldr