func PointSize(size float32) {
	syscall.Syscall(gpPointSize, 1, uintptr(math.Float32bits(size)), 0, 0)
}
func PointSize(size float32) {
	syscall.Syscall(gpPointSize, 1, uintptr(math.Float32bits(size)), 0, 0)
}
func PointSize ( size float32 ) { syscall . Syscall ( gpPointSize , 1 , uintptr ( math . Float32bits ( size ) ) , 0 , 0 ) }
// specify the diameter of rasterized points
specify the diameter of rasterized points