static void blinkWindowUsingShape(final JWindow w, final Shape shape) {
  awtEveryAndNow(w, 1000, new Runnable {
    bool on;
    
    public void run() {
      w.setShape((on = !on) ? shape :
        new Rectangle2D.Double(-10, -10, 1, 1));
      if (on) w.repaint();
    }
  });
}

Began life as a copy of #1013340