public void rendererCheckboard(CPRect r) {
		CPRect rect = new CPRect(0, 0, width, height);
		rect.clip(r);
		for (int j = rect.top; j < rect.bottom; j++) {
			for (int i = rect.left; i < rect.right; i++) {
				if ((i & 0x8) != 0 ^ (j & 0x8) != 0) {
					data[i + j * width] = 0xffffffff;
				} else {
					data[i + j * width] = 0xffcccccc;
				}
			}
		}
	}