More code restructuring.

Move all love.graphics functionality that doesn’t call OpenGL out of the OpenGL backend Graphics class.

--HG--
branch : minor

src/modules/graphics/vertex.h

@@ -32,6 +32,25 @@ namespace love
 namespace graphics
 {
 
+// Vertex attribute indices used in shaders by LOVE. The values map to OpenGL
+// generic vertex attribute indices.
+enum VertexAttribID
+{
+	ATTRIB_POS = 0,
+	ATTRIB_TEXCOORD,
+	ATTRIB_COLOR,
+	ATTRIB_CONSTANTCOLOR,
+	ATTRIB_MAX_ENUM
+};
+
+enum VertexAttribFlags
+{
+	ATTRIBFLAG_POS = 1 << ATTRIB_POS,
+	ATTRIBFLAG_TEXCOORD = 1 << ATTRIB_TEXCOORD,
+	ATTRIBFLAG_COLOR = 1 << ATTRIB_COLOR,
+	ATTRIBFLAG_CONSTANTCOLOR = 1 << ATTRIB_CONSTANTCOLOR
+};
+
 enum BufferType
 {
 	BUFFER_VERTEX = 0,
@@ -42,6 +61,15 @@ enum BufferType
 namespace vertex
 {
 
+// The expected usage pattern of vertex data.
+enum Usage
+{
+	USAGE_STREAM,
+	USAGE_DYNAMIC,
+	USAGE_STATIC,
+	USAGE_MAX_ENUM
+};
+
 enum class PrimitiveMode
 {
 	TRIANGLES,
@@ -93,6 +121,9 @@ int getIndexCount(TriangleIndexMode mode, int vertexCount);
 void fillIndices(TriangleIndexMode mode, uint16 vertexStart, uint16 vertexCount, uint16 *indices);
 void fillIndices(TriangleIndexMode mode, uint32 vertexStart, uint32 vertexCount, uint32 *indices);
 
+bool getConstant(const char *in, Usage &out);
+bool getConstant(Usage in, const char *&out);
+
 } // vertex
 
 typedef vertex::XYf_STf_RGBAub Vertex;