sclass JMaxSpeedAnimation is Swingable {
  settable IF0<BufferedImage> renderFrame;
  gettable new ImageSurface imageSurface;
  gettable new DoubleFPSCounter fps;
  
  *() {}
  *(IF0<BufferedImage> *renderFrame) {}
  
  cachedVisualize {
    imageSurface.pixelate(true);
    imageSurface.autoZoomToDisplay(true);
    awtCalcContinuously(imageSurface, -> {
      var img = renderFrame!;
      fps.inc();
      displayNewImage(img);
    });
    ret jscroll_center_borderless(imageSurface);
  }
  
  // image may be null (=no update)
  swappable void displayNewImage(BufferedImage image) {
    if (image != null) imageSurface.setImage(image);
  }
}

Began life as a copy of #1035609