/*
 This file is part of the software framework JStatCom, 
 a library for building applications for data based analysis.

 Copyright (C) 2000-2005  Markus Kraetzig

 This library is free software; you can redistribute it and/or modify
 it under the terms of the GNU Lesser General Public License as
 published by the Free Software Foundation; either version 2.1 of the
 License, or (at your option) any later version.

 This library is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 USA
 */

package com.jstatcom.component;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

import javax.swing.JMenu;
import javax.swing.JMenuItem;

/**
 * This class provides a JMenu that gets enabled
 * if at least one item belonging to it becomes enabled. It
 * gets disabled if none of its menu items is enabled.
 * The default initial state of this component is disabled.
 * 
 * @author A. Benkwitz, Markus Kraetzig
 */
public final class AutoEnableMenu
	extends JMenu
	implements PropertyChangeListener {
	/**
	 * See JMenu default constructor.
	 */
	public AutoEnableMenu() {
		super();
		setEnabled(false);
	}

	/**
	 * See JMenu(String s) constructor.
	 */
	public AutoEnableMenu(String s) {
		super(s);
		setEnabled(false);
	}

	/**
	 * See JMenu(String s, boolean b) constructor.
	 */
	public AutoEnableMenu(String s, boolean b) {
		super(s, b);
		setEnabled(false);
	}

	/**
	 * Overwrites superclass method to register itself as
	 * property change listener to newly added menus.
	 *
	 * @param item the item to add to this menu
	 */
	public JMenuItem add(JMenuItem item) {
		super.add(item);
		if (item.isEnabled())
			setEnabled(true);
		item.addPropertyChangeListener(this);
		return item;
	}

	/**
	 * Checks, whether there are any enabled items
	 * and disables/enables this menu accordingly.
	 *
	 * @param e a property change event, responds only to
	 *          enabled property
	 */
	public void propertyChange(PropertyChangeEvent e) {

		if (e.getPropertyName().equals("enabled")) {
			boolean __enabled = false;
			int n = getItemCount();
			int i = 0;
			while (!__enabled && i < n) {
				JMenuItem item = getItem(i++);
				if (!item.equals(this)) {
					__enabled = item.isEnabled();
				}
			}
			setEnabled(__enabled);
		}
	}
}