func BlendFunc(sfactor uint32, dfactor uint32) {
	C.glowBlendFunc(gpBlendFunc, (C.GLenum)(sfactor), (C.GLenum)(dfactor))
}
func BlendFunc(sfactor uint32, dfactor uint32) {
	C.glowBlendFunc(gpBlendFunc, (C.GLenum)(sfactor), (C.GLenum)(dfactor))
}
// specify pixel arithmetic