/*

 * CDDL HEADER START

 *

 * The contents of this file are subject to the terms of the

 * Common Development and Distribution License (the "License").

 * You may not use this file except in compliance with the License.

 *

 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE

 * or http://www.opensolaris.org/os/licensing.

 * See the License for the specific language governing permissions

 * and limitations under the License.

 *

 * When distributing Covered Code, include this CDDL HEADER in each

 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.

 * If applicable, add the following below this CDDL HEADER, with the

 * fields enclosed by brackets "[]" replaced with your own identifying

 * information: Portions Copyright [yyyy] [name of copyright owner]

 *

 * CDDL HEADER END

 */

/*

 * Copyright (c) 2010, 2012, Oracle and/or its affiliates. All rights reserved.

 */

package com.oracle.solaris.vp.util.swing;

import java.awt.Component;

import java.awt.event.*;

/**

 * When added as a {@code HierarchyListener}, the {@code ShowingListener} class

 * listens for changes in the showing property of a single {@code Component}.  A

 * single {@code ShowingListener} should NOT be added as a listener to more than

 * one {@code Component}.

 */

public class ShowingListener implements HierarchyListener {

    //

    // Instance data

    //

    private Boolean showing;

    //

    // HierarchyListener methods

    //

    @Override

    public void hierarchyChanged(HierarchyEvent e) {

	updateShowing(e.getComponent());

    }

    //

    // ShowingListener methods

    //

    /**

     * Calls {@link #componentHidden} or {@link #componentShown} if the

     * listening {@code Component}'s showing status has changed (or if neither

     * method has been called since this listener was registered).

     *

     * @param	    comp

     *		    the listening {@code Component}

     */

    public void updateShowing(Component comp) {

	boolean showing = comp.isShowing();

	if (this.showing == null || showing != this.showing) {

	    this.showing = showing;

	    if (showing) {

		componentShown();

	    } else {

		componentHidden();

	    }

	}

    }

    /**

     * Called when the listening {@code Component}'s showing status changes to

     * {@code false}.

     * </p>

     * This default implementation does nothing.

     */

    public void componentHidden() {

    }

    /**

     * Called when the listening {@code Component}'s showing status changes to

     * {@code true}.

     * </p>

     * This default implementation does nothing.

     */

    public void componentShown() {

    }

}