public void erase(gnu.app.displayhack.DisplayHack hack) {
gnu.x11.Window window = hack.window;
/* Minimum radius = L/sqrt(2) ~= 0.707*L,
* where L = max(width, heigth)
* sqrt(2) = 1.414213562373095
*
* Take radius = L for faster (easier) computation.
*/
int radius = Math.max(window.width, window.height);
int full = 360 * 64;
int delta = (full / 200) * hack.eraser_delta;
int step_count = (int) Math.ceil(1 + full / delta);
int start = hack.random.nextInt(full);
// clockwise or counter-clockwise
if (hack.random.nextBoolean()) delta = -delta;
for (int i = 0; i < step_count; i++) {
window.fill_arc(
hack.display.default_gc,
window.width / 2 - radius,
window.height / 2 - radius,
2 * radius,
2 * radius,
(start + i * delta) % full,
delta);
if (sleep(hack)) return;
}
hack.sleep(hack.delay / 2); // before next screen
}
