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#ifndef OSD_GL_DRAW_CONTEXT_H
#define OSD_GL_DRAW_CONTEXT_H

#if defined(__APPLE__)
    #include "TargetConditionals.h"
    #if TARGET_OS_IPHONE or TARGET_IPHONE_SIMULATOR
        #include <OpenGLES/ES2/gl.h>
    #else
        #include <OpenGL/gl3.h>
    #endif
#elif defined(ANDROID)
    #include <GLES2/gl2.h>
#else
    #if defined(_WIN32)
        #include <windows.h>
    #endif
    #include <GL/gl.h>
#endif

#include "../version.h"

#include "../far/mesh.h"
#include "../osd/drawContext.h"
#include "../osd/drawRegistry.h"
#include "../osd/vertex.h"

#include <map>

namespace OpenSubdiv {
namespace OPENSUBDIV_VERSION {

/// \brief OpenGL specialized DrawContext class
///
/// OsdGLDrawContext implements the OSD drawing interface with the OpenGL API.
/// Some functionality may be disabled depending on compile and run-time driver
/// support.
///
/// Contexts interface the serialized topological data pertaining to the 
/// geometric primitives with the capabilities of the selected discrete 
/// compute device.
///
class OsdGLDrawContext : public OsdDrawContext {
public:
    typedef GLuint VertexBufferBinding;

    virtual ~OsdGLDrawContext();

    /// \brief Create an OsdGLDraContext from FarPatchTables
    ///
    /// @param patchTables      a valid set of FarPatchTables
    ///
    /// @param requireFVarData  set to true to enable face-varying data to be 
    ///                         carried over from the Far data structures.
    ///
    static OsdGLDrawContext * Create(FarPatchTables const * patchTables, bool requireFVarData);

    /// Set vbo as a vertex texture (for gregory patch drawing)
    ///
    /// @param vbo  the vertex buffer object to update
    ///
    template<class VERTEX_BUFFER>
    void UpdateVertexTexture(VERTEX_BUFFER *vbo) {
        updateVertexTexture(vbo->BindVBO(), vbo->GetNumElements());
    }

    /// true if the GL version detected supports shader tessellation
    static bool SupportsAdaptiveTessellation();

    GLuint patchIndexBuffer;

#if defined(GL_ES_VERSION_2_0)
    GLuint patchTrianglesIndexBuffer;
#endif

    GLuint ptexCoordinateTextureBuffer;
    GLuint fvarDataTextureBuffer;

    GLuint vertexTextureBuffer;
    GLuint vertexValenceTextureBuffer;
    GLuint quadOffsetTextureBuffer;

protected:
    OsdGLDrawContext();

    // allocate buffers from patchTables
    bool create(FarPatchTables const *patchTables, bool requireFVarData);

    void updateVertexTexture(GLuint vbo, int numElements);
};

} // end namespace OPENSUBDIV_VERSION
using namespace OPENSUBDIV_VERSION;

} // end namespace OpenSubdiv

#endif /* OSD_DRAW_CONTEXT_H */