sclass JPaintTool is Swingable {
  transient BufferedImage image;
  transient ImageSurface imageSurface = jImageSurface();
  transient Pt defaultImageSize = new(heightToWidth(480), 480);
  
  void init {
    if (image == null)
      image = newImage(defaultImageSize);
  }
  
  visualize {
    init();
    ret jscroll_center_borderless(imageSurface);
  }
}