void startImageTracking() {
      collectImages(getUI().getRootView(this));
      boolean update = false;
      for (Image image : myImages) {
        IMAGE_MANAGER.setCompletionListener(image, this::scheduleRepaint);
        update |= image.getWidth(myImageObserver) >= 0 || image.getHeight(myImageObserver) >= 0;
      }
      if (update) {
        myImageObserver.imageUpdate(null, WIDTH | HEIGHT, 0, 0, 0, 0);
      }
    }
void startImageTracking()