sclass CirclesRelater extends MouseAdapter {
  Canvas canvas;
  CirclesAndLines cal;
  Circle circle;

  *(Canvas *canvas, CirclesAndLines *cal) {
    if (containsInstance(canvas.tools, CirclesRelater)) ret;
    canvas.tools.add(this);
    canvas.addMouseListener(this);
    canvas.addMouseMotionListener(this);
  }

  public void mousePressed(MouseEvent e) {
    if (e.getButton() == MouseEvent.BUTTON2)
      circle = findCircle(canvas.pointFromEvent(e));
  }

  public void mouseDragged(MouseEvent e) {
  }

  public void mouseReleased(MouseEvent e) {
    mouseDragged(e);
    if (circle != null) {
      final Circle circle2 = findCircle(canvas.pointFromEvent(e));
      final Circle circle1 = circle;
      if (circle != circle2 && circle2 != null) {
        final JTextField tf = jTextField();
        showFormTitled("Link nodes",
          "Node 1", circle1.text,
          "Node 2", circle2.text,
          "Connection Name", tf, r {
            cal.arrow(circle, getTextTrim(tf), circle2);
            canvas.update();
          });
      }
    }
    circle = null;
  }
  
  Circle findCircle(Pt p) { ret cal.findCircle(canvas, p); }
}