pub type PFN_glCopyImageSubDataEXT = unsafe extern "system" fn(_srcName: GLuint, _srcTarget: GLenum, _srcLevel: GLint, _srcX: GLint, _srcY: GLint, _srcZ: GLint, _dstName: GLuint, _dstTarget: GLenum, _dstLevel: GLint, _dstX: GLint, _dstY: GLint, _dstZ: GLint, _srcWidth: GLsizei, _srcHeight: GLsizei, _srcDepth: GLsizei);