sclass ImageSurface_PositionToolTip > ImageSurfaceMouseHandler {
  *(ImageSurface is) {
    if (containsInstance(is.tools, ImageSurface_PositionToolTip)) ret;
    register(is);
  }

  public void mouseMoved aka mouseDragged(MouseEvent e) {
    setToolTip(is, getPt(e));
  }
}