sclass AnimatedImageSurface > ImageSurface {

  double fps = 20;

  // We start & stop the timer by setting its frequency

  // to the actual frequency or 0, respectively.

  // (Don't want to close the timer as that is permanent.)

  FlexibleRateTimer animationTimer = new(0, l0 renderFrame).pileUp(false);

  void renderFrame {

    var img = makeImage();

    if (img != null)

      setImage(img);

  }

  selfType fps aka setFPS(double fps) {

    this.fps = fps;

    swing { updateTimer(isShowing()); }

    this;

  }

  swappable BufferedImage makeImage() {

    ret whiteImage(10, 10);

  }

  *() { init(); }

  *(IF0<BufferedImage> *makeImage) { init(); }

  *(double fps, IF0<BufferedImage> *makeImage) { setFPS(fps); init(); }

  *(Freq freq, IF0<BufferedImage> *makeImage) { setFPS(freq!); init(); }

  void updateTimer(bool showing) {

    animationTimer.setFrequencyImmediately(showing ? fps : 0.0);

  }

  void init {

    setDoubleBuffered(true);

    bindToComponent(this,

      -> { animationTimer.start(); updateTimer(true); },

      -> updateTimer(false));

  }

}