001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2022, 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 2009-2022, by David Gilbert.
031 *
032 * Original Author:  David Gilbert;
033 * Contributor(s):   -;
034 *
035 */
036
037package org.jfree.chart.swing;
038
039import java.awt.Graphics2D;
040
041/**
042 * An {@code Overlay} is anything that can be drawn over top of a chart to add
043 * additional information to the chart.  This interface defines the operations
044 * that must be supported for an overlay that can be added to a 
045 * {@link ChartPanel} in Swing.
046 * <br><br>
047 * Note: if you are using JavaFX rather than Swing, then you need to look at 
048 * the {@code OverlayFX} interface in the <b>JFreeChart-FX</b> project.
049 */
050public interface Overlay {
051
052    /**
053     * Paints the visual representation of the overlay.  This method will be
054     * called by the {@link ChartPanel} after the underlying chart has been 
055     * fully rendered.  When implementing this method, the {@code chartPanel} 
056     * argument can be used to get state information from the chart (you can, 
057     * for example, extract the axis ranges for the chart).
058     *
059     * @param g2  the graphics target (never {@code null}).
060     * @param chartPanel  the chart panel (never {@code null}).
061     */
062    void paintOverlay(Graphics2D g2, ChartPanel chartPanel);
063
064    /**
065     * Registers a change listener with the overlay.  Typically this method
066     * not be called by user code, it exists so that the {@link ChartPanel}
067     * can register and receive notification of changes to the overlay (such
068     * changes will trigger an automatic repaint of the chart).
069     * 
070     * @param listener  the listener ({@code null} not permitted).
071     * 
072     * @see #removeChangeListener(org.jfree.chart.event.OverlayChangeListener) 
073     */
074    void addChangeListener(OverlayChangeListener listener);
075
076    /**
077     * Deregisters a listener from the overlay.
078     * 
079     * @param listener  the listener ({@code null} not permitted).
080     * 
081     * @see #addChangeListener(org.jfree.chart.event.OverlayChangeListener) 
082     */
083    void removeChangeListener(OverlayChangeListener listener);
084
085}