gnu.app.displayhack.eraser.ThreeCircles Maven / Gradle / Ivy

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Escher is a collection of libraries for X Window System written purely in Java.

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package gnu.app.displayhack.eraser;


/**
 * Erase by three circles. 
 *
 * Modified from three_circle_wipe of erase.c
 * in xscreensaver by
 * Johannes Keukelaar .
 */
public class ThreeCircles extends Eraser {
  public ThreeCircles () { super ("three-circle-wipe"); }


  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 third = full / 3;
    int start = hack.random.nextInt (full);

    /* 200 = speed in {@link CircleWipe}
     * 3 = three circles
     * 2 = converge from two sides
     */
    int delta = (full/200/3/2) * hack.eraser_delta;

    /* 1 to offset rounding error
     * 3 = three circles
     * 2 = converge from two sides
     */
    int step_count = 1 + full/delta/3/2;

   
    for (int i=0; i