void showTip(String msg, int x, int y, int time) {
		if (tipPopupMenu == null) {
			tipPopupMenu = new JPopupMenu("Tip");
			tipPopupMenu.setBorder(BorderFactory.createLineBorder(Color.black));
			tipPopupMenu.setBackground(SystemColor.info);
			JLabel l = new JLabel(msg);
			l.setFont(ViewAttribute.SMALL_FONT);
			l.setBorder(BorderFactory.createEmptyBorder(2, 4, 2, 4));
			tipPopupMenu.add(l);
		} else {
			((JLabel) tipPopupMenu.getComponent(0)).setText(msg);
		}
		tipPopupMenu.show(this, x, y);
		if (time > 0) {
			Timer timer = new Timer(time, new ActionListener() {
				public void actionPerformed(ActionEvent e) {
					tipPopupMenu.setVisible(false);
				}
			});
			timer.setRepeats(false);
			timer.setInitialDelay(time);
			timer.start();
		}
	}