sclass CircleDoubleClicker extends MouseAdapter {
  CirclesAndLines cal;
  Canvas canvas;
  O onClick;

  *(CirclesAndLines *cal, Canvas *canvas, O *onClick) {
    if (containsInstance(canvas.tools, CircleDoubleClicker)) ret;
    canvas.tools.add(this);
    canvas.addMouseListener(this);
  }

  public void mouseClicked(MouseEvent e) {
    if (e.getButton() == MouseEvent.BUTTON1 && e.getClickCount() == 2) {
      Pt p = canvas.pointFromEvent(e);
      Circle c = cal.findCircle(canvas, p);
      if (c != null)
        pcallF(onClick, c);
    }
  }
}