001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-present, by David Gilbert and Contributors.
006 *
007 * Project Info:  http://www.jfree.org/jfreechart/index.html
008 *
009 * This library is free software; you can redistribute it and/or modify it
010 * under the terms of the GNU Lesser General Public License as published by
011 * the Free Software Foundation; either version 2.1 of the License, or
012 * (at your option) any later version.
013 *
014 * This library is distributed in the hope that it will be useful, but
015 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
016 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
017 * License for more details.
018 *
019 * You should have received a copy of the GNU Lesser General Public
020 * License along with this library; if not, write to the Free Software
021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
022 * USA.
023 *
024 * [Oracle and Java are registered trademarks of Oracle and/or its affiliates. 
025 * Other names may be trademarks of their respective owners.]
026 *
027 * ------------
028 * Overlay.java
029 * ------------
030 * (C) Copyright 2009-present, by David Gilbert.
031 *
032 * Original Author:  David Gilbert;
033 * Contributor(s):   -;
034 *
035 */
036package org.jfree.chart.panel;
037
038import java.awt.Graphics2D;
039import org.jfree.chart.ChartPanel;
040import org.jfree.chart.event.OverlayChangeListener;
041
042/**
043 * Defines the interface for an overlay that can be added to a
044 * {@link ChartPanel}.
045 */
046public interface Overlay {
047
048    /**
049     * Paints the crosshairs in the layer.
050     *
051     * @param g2  the graphics target.
052     * @param chartPanel  the chart panel.
053     */
054    void paintOverlay(Graphics2D g2, ChartPanel chartPanel);
055
056    /**
057     * Registers a change listener with the overlay.
058     * 
059     * @param listener  the listener.
060     */
061    void addChangeListener(OverlayChangeListener listener);
062
063    /**
064     * Deregisters a listener from the overlay.
065     * 
066     * @param listener  the listener.
067     */
068    void removeChangeListener(OverlayChangeListener listener);
069
070}