static JVolatileImageSurface volatileImageSurfaceDemo() {
  ret new JVolatileImageSurface {
    void renderVolatile(int w, int h, Graphics2D g) {
      g.setColor(Color.green);
      g.fillRect(0, 0, w, h);
      fillCircle(g, w/2, h/2, w/4, Color.blue);
    }
  };
}