sclass RegionBoundingBoxPainter > RegionPainter {
  settable Color outerColor = Color.red;
  settable Color innerColor = Color.green;

  void drawRegion {
    Rect r = bounds();
    r = growRect(r);
    drawRect(g, innerColor, r);
    r = growRect(r);
    drawRect(g, outerColor, r);
  }
}