public void itemStateChanged(ItemEvent e) {
				boolean b = e.getStateChange() == ItemEvent.SELECTED;
				if (b && !jmolContainer.jmol.viewer.getPerspectiveDepth()) {
					JOptionPane.showMessageDialog(JOptionPane.getFrameForComponent(jmolContainer),
							"Perspective depth is required for the navigation mode. It will be turned on.");
					miPerspectiveDepth.setSelected(true);
				}
				jmolContainer.changeNavigationMode(b);
				jmolContainer.notifyChange();
			}