/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2020, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://www.jfree.org/jfreechart/index.html
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 *
 * [Oracle and Java are registered trademarks of Oracle and/or its affiliates.
 * Other names may be trademarks of their respective owners.]
 *
 * ---------
 * Plot.java
 * ---------
 * (C) Copyright 2000-2020, by Object Refinery Limited and Contributors.
 *
 * Original Author:  David Gilbert (for Object Refinery Limited);
 * Contributor(s):   Sylvain Vieujot;
 *                   Jeremy Bowman;
 *                   Andreas Schneider;
 *                   Gideon Krause;
 *                   Nicolas Brodu;
 *                   Michal Krause;
 *                   Richard West, Advanced Micro Devices, Inc.;
 *                   Peter Kolb - patches 2603321, 2809117;
 * 
 */

package org.jfree.chart.plot;

import java.awt.AlphaComposite;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Composite;
import java.awt.Font;
import java.awt.GradientPaint;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Paint;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.Stroke;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

import javax.swing.event.EventListenerList;

import org.jfree.chart.JFreeChart;
import org.jfree.chart.LegendItemCollection;
import org.jfree.chart.LegendItemSource;
import org.jfree.chart.annotations.Annotation;
import org.jfree.chart.axis.AxisLocation;
import org.jfree.chart.entity.EntityCollection;
import org.jfree.chart.entity.PlotEntity;
import org.jfree.chart.event.AnnotationChangeEvent;
import org.jfree.chart.event.AnnotationChangeListener;
import org.jfree.chart.event.AxisChangeEvent;
import org.jfree.chart.event.AxisChangeListener;
import org.jfree.chart.event.ChartChangeEventType;
import org.jfree.chart.event.MarkerChangeEvent;
import org.jfree.chart.event.MarkerChangeListener;
import org.jfree.chart.event.PlotChangeEvent;
import org.jfree.chart.event.PlotChangeListener;
import org.jfree.chart.text.G2TextMeasurer;
import org.jfree.chart.text.TextBlock;
import org.jfree.chart.text.TextBlockAnchor;
import org.jfree.chart.text.TextUtils;
import org.jfree.chart.ui.Align;
import org.jfree.chart.ui.RectangleEdge;
import org.jfree.chart.ui.RectangleInsets;
import org.jfree.chart.util.ObjectUtils;
import org.jfree.chart.util.PaintUtils;
import org.jfree.chart.util.Args;
import org.jfree.chart.util.PublicCloneable;
import org.jfree.chart.util.SerialUtils;
import org.jfree.data.general.DatasetChangeEvent;
import org.jfree.data.general.DatasetChangeListener;
import org.jfree.data.general.DatasetGroup;

/**
 * The base class for all plots in JFreeChart.  The {@link JFreeChart} class
 * delegates the drawing of axes and data to the plot.  This base class
 * provides facilities common to most plot types.
 */
public abstract class Plot implements AxisChangeListener,
        DatasetChangeListener, AnnotationChangeListener, MarkerChangeListener,
        LegendItemSource, PublicCloneable, Cloneable, Serializable {

    /** For serialization. */
    private static final long serialVersionUID = -8831571430103671324L;

    /** Useful constant representing zero. */
    public static final Number ZERO = 0;

    /** The default insets. */
    public static final RectangleInsets DEFAULT_INSETS
            = new RectangleInsets(4.0, 8.0, 4.0, 8.0);

    /** The default outline stroke. */
    public static final Stroke DEFAULT_OUTLINE_STROKE = new BasicStroke(0.5f,
            BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);

    /** The default outline color. */
    public static final Paint DEFAULT_OUTLINE_PAINT = Color.GRAY;

    /** The default foreground alpha transparency. */
    public static final float DEFAULT_FOREGROUND_ALPHA = 1.0f;

    /** The default background alpha transparency. */
    public static final float DEFAULT_BACKGROUND_ALPHA = 1.0f;

    /** The default background color. */
    public static final Paint DEFAULT_BACKGROUND_PAINT = Color.WHITE;

    /** The minimum width at which the plot should be drawn. */
    public static final int MINIMUM_WIDTH_TO_DRAW = 10;

    /** The minimum height at which the plot should be drawn. */
    public static final int MINIMUM_HEIGHT_TO_DRAW = 10;

    /** A default box shape for legend items. */
    public static final Shape DEFAULT_LEGEND_ITEM_BOX
            = new Rectangle2D.Double(-4.0, -4.0, 8.0, 8.0);

    /** A default circle shape for legend items. */
    public static final Shape DEFAULT_LEGEND_ITEM_CIRCLE
            = new Ellipse2D.Double(-4.0, -4.0, 8.0, 8.0);

    /** 
     * The chart that the plot is assigned to.  It can be {@code null} if the
     * plot is not assigned to a chart yet, or if the plot is a subplot of a
     * another plot.
     * 
     * @since 1.0.20
     */
    private JFreeChart chart;
    
    /** The parent plot ({@code null} if this is the root plot). */
    private Plot parent;

    /** The dataset group (to be used for thread synchronisation). */
    private DatasetGroup datasetGroup;

    /** The message to display if no data is available. */
    private String noDataMessage;

    /** The font used to display the 'no data' message. */
    private Font noDataMessageFont;

    /** The paint used to draw the 'no data' message. */
    private transient Paint noDataMessagePaint;

    /** Amount of blank space around the plot area. */
    private RectangleInsets insets;

    /**
     * A flag that controls whether or not the plot outline is drawn.
     *
     * @since 1.0.6
     */
    private boolean outlineVisible;

    /** The Stroke used to draw an outline around the plot. */
    private transient Stroke outlineStroke;

    /** The Paint used to draw an outline around the plot. */
    private transient Paint outlinePaint;

    /** An optional color used to fill the plot background. */
    private transient Paint backgroundPaint;

    /** An optional image for the plot background. */
    private transient Image backgroundImage;  // not currently serialized

    /** The alignment for the background image. */
    private int backgroundImageAlignment = Align.FIT;

    /** The alpha value used to draw the background image. */
    private float backgroundImageAlpha = 0.5f;

    /** The alpha-transparency for the plot. */
    private float foregroundAlpha;

    /** The alpha transparency for the background paint. */
    private float backgroundAlpha;

    /** The drawing supplier. */
    private DrawingSupplier drawingSupplier;

    /** Storage for registered change listeners. */
    private transient EventListenerList listenerList;

    /**
     * A flag that controls whether or not the plot will notify listeners
     * of changes (defaults to true, but sometimes it is useful to disable
     * this).
     *
     * @since 1.0.13
     */
    private boolean notify;

    /**
     * Creates a new plot.
     */
    protected Plot() {
        this.chart = null;
        this.parent = null;
        this.insets = DEFAULT_INSETS;
        this.backgroundPaint = DEFAULT_BACKGROUND_PAINT;
        this.backgroundAlpha = DEFAULT_BACKGROUND_ALPHA;
        this.backgroundImage = null;
        this.outlineVisible = true;
        this.outlineStroke = DEFAULT_OUTLINE_STROKE;
        this.outlinePaint = DEFAULT_OUTLINE_PAINT;
        this.foregroundAlpha = DEFAULT_FOREGROUND_ALPHA;

        this.noDataMessage = null;
        this.noDataMessageFont = new Font("SansSerif", Font.PLAIN, 12);
        this.noDataMessagePaint = Color.BLACK;

        this.drawingSupplier = new DefaultDrawingSupplier();

        this.notify = true;
        this.listenerList = new EventListenerList();
    }
    
    /**
     * Returns the chart that this plot is assigned to.  This method can
     * return {@code null} if the plot is not yet assigned to a plot, or if the
     * plot is a subplot of another plot.
     * 
     * @return The chart (possibly {@code null}).
     * 
     * @since 1.0.20
     */
    public JFreeChart getChart() {
        return this.chart;
    }
    
    /**
     * Sets the chart that the plot is assigned to.  This method is not 
     * intended for external use.
     * 
     * @param chart  the chart ({@code null} permitted).
     * 
     * @since 1.0.20
     */
    public void setChart(JFreeChart chart) {
        this.chart = chart;
    }
    
    /**
     * Fetches the element hinting flag from the chart that this plot is 
     * assigned to.  If the plot is not assigned (directly or indirectly) to
     * a chart instance, this method will return {@code false}.
     * 
     * @return A boolean.
     * 
     * @since 1.0.20
     */
    public boolean fetchElementHintingFlag() {
        if (this.parent != null) {
            return this.parent.fetchElementHintingFlag();
        }
        if (this.chart != null) {
            return this.chart.getElementHinting();
        }
        return false;
    }

    /**
     * Returns the dataset group for the plot (not currently used).
     *
     * @return The dataset group.
     *
     * @see #setDatasetGroup(DatasetGroup)
     */
    public DatasetGroup getDatasetGroup() {
        return this.datasetGroup;
    }

    /**
     * Sets the dataset group (not currently used).
     *
     * @param group  the dataset group ({@code null} permitted).
     *
     * @see #getDatasetGroup()
     */
    protected void setDatasetGroup(DatasetGroup group) {
        this.datasetGroup = group;
    }

    /**
     * Returns the string that is displayed when the dataset is empty or
     * {@code null}.
     *
     * @return The 'no data' message ({@code null} possible).
     *
     * @see #setNoDataMessage(String)
     * @see #getNoDataMessageFont()
     * @see #getNoDataMessagePaint()
     */
    public String getNoDataMessage() {
        return this.noDataMessage;
    }

    /**
     * Sets the message that is displayed when the dataset is empty or
     * {@code null}, and sends a {@link PlotChangeEvent} to all registered
     * listeners.
     *
     * @param message  the message ({@code null} permitted).
     *
     * @see #getNoDataMessage()
     */
    public void setNoDataMessage(String message) {
        this.noDataMessage = message;
        fireChangeEvent();
    }

    /**
     * Returns the font used to display the 'no data' message.
     *
     * @return The font (never {@code null}).
     *
     * @see #setNoDataMessageFont(Font)
     * @see #getNoDataMessage()
     */
    public Font getNoDataMessageFont() {
        return this.noDataMessageFont;
    }

    /**
     * Sets the font used to display the 'no data' message and sends a
     * {@link PlotChangeEvent} to all registered listeners.
     *
     * @param font  the font ({@code null} not permitted).
     *
     * @see #getNoDataMessageFont()
     */
    public void setNoDataMessageFont(Font font) {
        Args.nullNotPermitted(font, "font");
        this.noDataMessageFont = font;
        fireChangeEvent();
    }

    /**
     * Returns the paint used to display the 'no data' message.
     *
     * @return The paint (never {@code null}).
     *
     * @see #setNoDataMessagePaint(Paint)
     * @see #getNoDataMessage()
     */
    public Paint getNoDataMessagePaint() {
        return this.noDataMessagePaint;
    }

    /**
     * Sets the paint used to display the 'no data' message and sends a
     * {@link PlotChangeEvent} to all registered listeners.
     *
     * @param paint  the paint ({@code null} not permitted).
     *
     * @see #getNoDataMessagePaint()
     */
    public void setNoDataMessagePaint(Paint paint) {
        Args.nullNotPermitted(paint, "paint");
        this.noDataMessagePaint = paint;
        fireChangeEvent();
    }

    /**
     * Returns a short string describing the plot type.
     * <P>
     * Note: this gets used in the chart property editing user interface,
     * but there needs to be a better mechanism for identifying the plot type.
     *
     * @return A short string describing the plot type (never
     *     {@code null}).
     */
    public abstract String getPlotType();

    /**
     * Returns the parent plot (or {@code null} if this plot is not part
     * of a combined plot).
     *
     * @return The parent plot.
     *
     * @see #setParent(Plot)
     * @see #getRootPlot()
     */
    public Plot getParent() {
        return this.parent;
    }

    /**
     * Sets the parent plot.  This method is intended for internal use, you
     * shouldn't need to call it directly.
     *
     * @param parent  the parent plot ({@code null} permitted).
     *
     * @see #getParent()
     */
    public void setParent(Plot parent) {
        this.parent = parent;
    }

    /**
     * Returns the root plot.
     *
     * @return The root plot.
     *
     * @see #getParent()
     */
    public Plot getRootPlot() {

        Plot p = getParent();
        if (p == null) {
            return this;
        }
        return p.getRootPlot();

    }

    /**
     * Returns {@code true} if this plot is part of a combined plot
     * structure (that is, {@link #getParent()} returns a non-{@code null}
     * value), and {@code false} otherwise.
     *
     * @return {@code true} if this plot is part of a combined plot
     *         structure.
     *
     * @see #getParent()
     */
    public boolean isSubplot() {
        return (getParent() != null);
    }

    /**
     * Returns the insets for the plot area.
     *
     * @return The insets (never {@code null}).
     *
     * @see #setInsets(RectangleInsets)
     */
    public RectangleInsets getInsets() {
        return this.insets;
    }

    /**
     * Sets the insets for the plot and sends a {@link PlotChangeEvent} to
     * all registered listeners.
     *
     * @param insets  the new insets ({@code null} not permitted).
     *
     * @see #getInsets()
     * @see #setInsets(RectangleInsets, boolean)
     */
    public void setInsets(RectangleInsets insets) {
        setInsets(insets, true);
    }

    /**
     * Sets the insets for the plot and, if requested,  and sends a
     * {@link PlotChangeEvent} to all registered listeners.
     *
     * @param insets  the new insets ({@code null} not permitted).
     * @param notify  a flag that controls whether the registered listeners are
     *                notified.
     *
     * @see #getInsets()
     * @see #setInsets(RectangleInsets)
     */
    public void setInsets(RectangleInsets insets, boolean notify) {
        Args.nullNotPermitted(insets, "insets");
        if (!this.insets.equals(insets)) {
            this.insets = insets;
            if (notify) {
                fireChangeEvent();
            }
        }

    }

    /**
     * Returns the background color of the plot area.
     *
     * @return The paint (possibly {@code null}).
     *
     * @see #setBackgroundPaint(Paint)
     */
    public Paint getBackgroundPaint() {
        return this.backgroundPaint;
    }

    /**
     * Sets the background color of the plot area and sends a
     * {@link PlotChangeEvent} to all registered listeners.
     *
     * @param paint  the paint ({@code null} permitted).
     *
     * @see #getBackgroundPaint()
     */
    public void setBackgroundPaint(Paint paint) {

        if (paint == null) {
            if (this.backgroundPaint != null) {
                this.backgroundPaint = null;
                fireChangeEvent();
            }
        }
        else {
            if (this.backgroundPaint != null) {
                if (this.backgroundPaint.equals(paint)) {
                    return;  // nothing to do
                }
            }
            this.backgroundPaint = paint;
            fireChangeEvent();
        }

    }

    /**
     * Returns the alpha transparency of the plot area background.
     *
     * @return The alpha transparency.
     *
     * @see #setBackgroundAlpha(float)
     */
    public float getBackgroundAlpha() {
        return this.backgroundAlpha;
    }

    /**
     * Sets the alpha transparency of the plot area background, and notifies
     * registered listeners that the plot has been modified.
     *
     * @param alpha the new alpha value (in the range 0.0f to 1.0f).
     *
     * @see #getBackgroundAlpha()
     */
    public void setBackgroundAlpha(float alpha) {
        if (this.backgroundAlpha != alpha) {
            this.backgroundAlpha = alpha;
            fireChangeEvent();
        }
    }

    /**
     * Returns the drawing supplier for the plot.
     *
     * @return The drawing supplier (possibly {@code null}).
     *
     * @see #setDrawingSupplier(DrawingSupplier)
     */
    public DrawingSupplier getDrawingSupplier() {
        DrawingSupplier result;
        Plot p = getParent();
        if (p != null) {
            result = p.getDrawingSupplier();
        }
        else {
            result = this.drawingSupplier;
        }
        return result;
    }

    /**
     * Sets the drawing supplier for the plot and sends a
     * {@link PlotChangeEvent} to all registered listeners.  The drawing
     * supplier is responsible for supplying a limitless (possibly repeating)
     * sequence of {@code Paint}, {@code Stroke} and
     * {@code Shape} objects that the plot's renderer(s) can use to
     * populate its (their) tables.
     *
     * @param supplier  the new supplier.
     *
     * @see #getDrawingSupplier()
     */
    public void setDrawingSupplier(DrawingSupplier supplier) {
        this.drawingSupplier = supplier;
        fireChangeEvent();
    }

    /**
     * Sets the drawing supplier for the plot and, if requested, sends a
     * {@link PlotChangeEvent} to all registered listeners.  The drawing
     * supplier is responsible for supplying a limitless (possibly repeating)
     * sequence of {@code Paint}, {@code Stroke} and
     * {@code Shape} objects that the plot's renderer(s) can use to
     * populate its (their) tables.
     *
     * @param supplier  the new supplier.
     * @param notify  notify listeners?
     *
     * @see #getDrawingSupplier()
     *
     * @since 1.0.11
     */
    public void setDrawingSupplier(DrawingSupplier supplier, boolean notify) {
        this.drawingSupplier = supplier;
        if (notify) {
            fireChangeEvent();
        }
    }

    /**
     * Returns the background image that is used to fill the plot's background
     * area.
     *
     * @return The image (possibly {@code null}).
     *
     * @see #setBackgroundImage(Image)
     */
    public Image getBackgroundImage() {
        return this.backgroundImage;
    }

    /**
     * Sets the background image for the plot and sends a
     * {@link PlotChangeEvent} to all registered listeners.
     *
     * @param image  the image ({@code null} permitted).
     *
     * @see #getBackgroundImage()
     */
    public void setBackgroundImage(Image image) {
        this.backgroundImage = image;
        fireChangeEvent();
    }

    /**
     * Returns the background image alignment. Alignment constants are defined
     * in the {@code Align} class.
     *
     * @return The alignment.
     *
     * @see #setBackgroundImageAlignment(int)
     */
    public int getBackgroundImageAlignment() {
        return this.backgroundImageAlignment;
    }

    /**
     * Sets the alignment for the background image and sends a
     * {@link PlotChangeEvent} to all registered listeners.  Alignment options
     * are defined by the {@link org.jfree.chart.ui.Align} class.
     *
     * @param alignment  the alignment.
     *
     * @see #getBackgroundImageAlignment()
     */
    public void setBackgroundImageAlignment(int alignment) {
        if (this.backgroundImageAlignment != alignment) {
            this.backgroundImageAlignment = alignment;
            fireChangeEvent();
        }
    }

    /**
     * Returns the alpha transparency used to draw the background image.  This
     * is a value in the range 0.0f to 1.0f, where 0.0f is fully transparent
     * and 1.0f is fully opaque.
     *
     * @return The alpha transparency.
     *
     * @see #setBackgroundImageAlpha(float)
     */
    public float getBackgroundImageAlpha() {
        return this.backgroundImageAlpha;
    }

    /**
     * Sets the alpha transparency used when drawing the background image.
     *
     * @param alpha  the alpha transparency (in the range 0.0f to 1.0f, where
     *     0.0f is fully transparent, and 1.0f is fully opaque).
     *
     * @throws IllegalArgumentException if {@code alpha} is not within
     *     the specified range.
     *
     * @see #getBackgroundImageAlpha()
     */
    public void setBackgroundImageAlpha(float alpha) {
        if (alpha < 0.0f || alpha > 1.0f) {
            throw new IllegalArgumentException(
                    "The 'alpha' value must be in the range 0.0f to 1.0f.");
        }
        if (this.backgroundImageAlpha != alpha) {
            this.backgroundImageAlpha = alpha;
            fireChangeEvent();
        }
    }

    /**
     * Returns the flag that controls whether or not the plot outline is
     * drawn.  The default value is {@code true}.  Note that for
     * historical reasons, the plot's outline paint and stroke can take on
     * {@code null} values, in which case the outline will not be drawn
     * even if this flag is set to {@code true}.
     *
     * @return The outline visibility flag.
     *
     * @since 1.0.6
     *
     * @see #setOutlineVisible(boolean)
     */
    public boolean isOutlineVisible() {
        return this.outlineVisible;
    }

    /**
     * Sets the flag that controls whether or not the plot's outline is
     * drawn, and sends a {@link PlotChangeEvent} to all registered listeners.
     *
     * @param visible  the new flag value.
     *
     * @since 1.0.6
     *
     * @see #isOutlineVisible()
     */
    public void setOutlineVisible(boolean visible) {
        this.outlineVisible = visible;
        fireChangeEvent();
    }

    /**
     * Returns the stroke used to outline the plot area.
     *
     * @return The stroke (possibly {@code null}).
     *
     * @see #setOutlineStroke(Stroke)
     */
    public Stroke getOutlineStroke() {
        return this.outlineStroke;
    }

    /**
     * Sets the stroke used to outline the plot area and sends a
     * {@link PlotChangeEvent} to all registered listeners. If you set this
     * attribute to {@code null}, no outline will be drawn.
     *
     * @param stroke  the stroke ({@code null} permitted).
     *
     * @see #getOutlineStroke()
     */
    public void setOutlineStroke(Stroke stroke) {
        if (stroke == null) {
            if (this.outlineStroke != null) {
                this.outlineStroke = null;
                fireChangeEvent();
            }
        }
        else {
            if (this.outlineStroke != null) {
                if (this.outlineStroke.equals(stroke)) {
                    return;  // nothing to do
                }
            }
            this.outlineStroke = stroke;
            fireChangeEvent();
        }
    }

    /**
     * Returns the color used to draw the outline of the plot area.
     *
     * @return The color (possibly {@code null}).
     *
     * @see #setOutlinePaint(Paint)
     */
    public Paint getOutlinePaint() {
        return this.outlinePaint;
    }

    /**
     * Sets the paint used to draw the outline of the plot area and sends a
     * {@link PlotChangeEvent} to all registered listeners.  If you set this
     * attribute to {@code null}, no outline will be drawn.
     *
     * @param paint  the paint ({@code null} permitted).
     *
     * @see #getOutlinePaint()
     */
    public void setOutlinePaint(Paint paint) {
        if (paint == null) {
            if (this.outlinePaint != null) {
                this.outlinePaint = null;
                fireChangeEvent();
            }
        }
        else {
            if (this.outlinePaint != null) {
                if (this.outlinePaint.equals(paint)) {
                    return;  // nothing to do
                }
            }
            this.outlinePaint = paint;
            fireChangeEvent();
        }
    }

    /**
     * Returns the alpha-transparency for the plot foreground.
     *
     * @return The alpha-transparency.
     *
     * @see #setForegroundAlpha(float)
     */
    public float getForegroundAlpha() {
        return this.foregroundAlpha;
    }

    /**
     * Sets the alpha-transparency for the plot and sends a
     * {@link PlotChangeEvent} to all registered listeners.
     *
     * @param alpha  the new alpha transparency.
     *
     * @see #getForegroundAlpha()
     */
    public void setForegroundAlpha(float alpha) {
        if (this.foregroundAlpha != alpha) {
            this.foregroundAlpha = alpha;
            fireChangeEvent();
        }
    }

    /**
     * Returns the legend items for the plot.  By default, this method returns
     * {@code null}.  Subclasses should override to return a
     * {@link LegendItemCollection}.
     *
     * @return The legend items for the plot (possibly {@code null}).
     */
    @Override
    public LegendItemCollection getLegendItems() {
        return null;
    }

    /**
     * Returns a flag that controls whether or not change events are sent to
     * registered listeners.
     *
     * @return A boolean.
     *
     * @see #setNotify(boolean)
     *
     * @since 1.0.13
     */
    public boolean isNotify() {
        return this.notify;
    }

    /**
     * Sets a flag that controls whether or not listeners receive
     * {@link PlotChangeEvent} notifications.
     *
     * @param notify  a boolean.
     *
     * @see #isNotify()
     *
     * @since 1.0.13
     */
    public void setNotify(boolean notify) {
        this.notify = notify;
        // if the flag is being set to true, there may be queued up changes...
        if (notify) {
            notifyListeners(new PlotChangeEvent(this));
        }
    }

    /**
     * Registers an object for notification of changes to the plot.
     *
     * @param listener  the object to be registered.
     *
     * @see #removeChangeListener(PlotChangeListener)
     */
    public void addChangeListener(PlotChangeListener listener) {
        this.listenerList.add(PlotChangeListener.class, listener);
    }

    /**
     * Unregisters an object for notification of changes to the plot.
     *
     * @param listener  the object to be unregistered.
     *
     * @see #addChangeListener(PlotChangeListener)
     */
    public void removeChangeListener(PlotChangeListener listener) {
        this.listenerList.remove(PlotChangeListener.class, listener);
    }

    /**
     * Notifies all registered listeners that the plot has been modified.
     *
     * @param event  information about the change event.
     */
    public void notifyListeners(PlotChangeEvent event) {
        // if the 'notify' flag has been switched to false, we don't notify
        // the listeners
        if (!this.notify) {
            return;
        }
        Object[] listeners = this.listenerList.getListenerList();
        for (int i = listeners.length - 2; i >= 0; i -= 2) {
            if (listeners[i] == PlotChangeListener.class) {
                ((PlotChangeListener) listeners[i + 1]).plotChanged(event);
            }
        }
    }

    /**
     * Sends a {@link PlotChangeEvent} to all registered listeners.
     *
     * @since 1.0.10
     */
    protected void fireChangeEvent() {
        notifyListeners(new PlotChangeEvent(this));
    }

    /**
     * Draws the plot within the specified area.  The anchor is a point on the
     * chart that is specified externally (for instance, it may be the last
     * point of the last mouse click performed by the user) - plots can use or
     * ignore this value as they see fit.
     * <br><br>
     * Subclasses need to provide an implementation of this method, obviously.
     *
     * @param g2  the graphics device.
     * @param area  the plot area.
     * @param anchor  the anchor point ({@code null} permitted).
     * @param parentState  the parent state (if any, {@code null} permitted).
     * @param info  carries back plot rendering info.
     */
    public abstract void draw(Graphics2D g2, Rectangle2D area, Point2D anchor,
            PlotState parentState, PlotRenderingInfo info);

    /**
     * Draws the plot background (the background color and/or image).
     * <P>
     * This method will be called during the chart drawing process and is
     * declared public so that it can be accessed by the renderers used by
     * certain subclasses.  You shouldn't need to call this method directly.
     *
     * @param g2  the graphics device.
     * @param area  the area within which the plot should be drawn.
     */
    public void drawBackground(Graphics2D g2, Rectangle2D area) {
        // some subclasses override this method completely, so don't put
        // anything here that *must* be done
        fillBackground(g2, area);
        drawBackgroundImage(g2, area);
    }

    /**
     * Fills the specified area with the background paint.
     *
     * @param g2  the graphics device.
     * @param area  the area.
     *
     * @see #getBackgroundPaint()
     * @see #getBackgroundAlpha()
     * @see #fillBackground(Graphics2D, Rectangle2D, PlotOrientation)
     */
    protected void fillBackground(Graphics2D g2, Rectangle2D area) {
        fillBackground(g2, area, PlotOrientation.VERTICAL);
    }

    /**
     * Fills the specified area with the background paint.  If the background
     * paint is an instance of {@code GradientPaint}, the gradient will
     * run in the direction suggested by the plot's orientation.
     *
     * @param g2  the graphics target.
     * @param area  the plot area.
     * @param orientation  the plot orientation ({@code null} not
     *         permitted).
     *
     * @since 1.0.6
     */
    protected void fillBackground(Graphics2D g2, Rectangle2D area,
            PlotOrientation orientation) {
        Args.nullNotPermitted(orientation, "orientation");
        if (this.backgroundPaint == null) {
            return;
        }
        Paint p = this.backgroundPaint;
        if (p instanceof GradientPaint) {
            GradientPaint gp = (GradientPaint) p;
            if (orientation == PlotOrientation.VERTICAL) {
                p = new GradientPaint((float) area.getCenterX(),
                        (float) area.getMaxY(), gp.getColor1(),
                        (float) area.getCenterX(), (float) area.getMinY(),
                        gp.getColor2());
            }
            else if (orientation == PlotOrientation.HORIZONTAL) {
                p = new GradientPaint((float) area.getMinX(),
                        (float) area.getCenterY(), gp.getColor1(),
                        (float) area.getMaxX(), (float) area.getCenterY(),
                        gp.getColor2());
            }
        }
        Composite originalComposite = g2.getComposite();
        g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER,
                this.backgroundAlpha));
        g2.setPaint(p);
        g2.fill(area);
        g2.setComposite(originalComposite);
    }

    /**
     * Draws the background image (if there is one) aligned within the
     * specified area.
     *
     * @param g2  the graphics device.
     * @param area  the area.
     *
     * @see #getBackgroundImage()
     * @see #getBackgroundImageAlignment()
     * @see #getBackgroundImageAlpha()
     */
    public void drawBackgroundImage(Graphics2D g2, Rectangle2D area) {
        if (this.backgroundImage == null) {
            return;  // nothing to do
        }
        Composite savedComposite = g2.getComposite();
        g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER,
                this.backgroundImageAlpha));
        Rectangle2D dest = new Rectangle2D.Double(0.0, 0.0,
                this.backgroundImage.getWidth(null),
                this.backgroundImage.getHeight(null));
        Align.align(dest, area, this.backgroundImageAlignment);
        Shape savedClip = g2.getClip();
        g2.clip(area);
        g2.drawImage(this.backgroundImage, (int) dest.getX(),
                (int) dest.getY(), (int) dest.getWidth() + 1,
                (int) dest.getHeight() + 1, null);
        g2.setClip(savedClip);
        g2.setComposite(savedComposite);
    }

    /**
     * Draws the plot outline.  This method will be called during the chart
     * drawing process and is declared public so that it can be accessed by the
     * renderers used by certain subclasses. You shouldn't need to call this
     * method directly.
     *
     * @param g2  the graphics device.
     * @param area  the area within which the plot should be drawn.
     */
    public void drawOutline(Graphics2D g2, Rectangle2D area) {
        if (!this.outlineVisible) {
            return;
        }
        if ((this.outlineStroke != null) && (this.outlinePaint != null)) {
            g2.setStroke(this.outlineStroke);
            g2.setPaint(this.outlinePaint);
            Object saved = g2.getRenderingHint(RenderingHints.KEY_STROKE_CONTROL);
            g2.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_NORMALIZE);
            g2.draw(area);
            g2.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, saved);
        }
    }

    /**
     * Draws a message to state that there is no data to plot.
     *
     * @param g2  the graphics device.
     * @param area  the area within which the plot should be drawn.
     */
    protected void drawNoDataMessage(Graphics2D g2, Rectangle2D area) {
        Shape savedClip = g2.getClip();
        g2.clip(area);
        String message = this.noDataMessage;
        if (message != null) {
            g2.setFont(this.noDataMessageFont);
            g2.setPaint(this.noDataMessagePaint);
            TextBlock block = TextUtils.createTextBlock(
                    this.noDataMessage, this.noDataMessageFont,
                    this.noDataMessagePaint, 0.9f * (float) area.getWidth(),
                    new G2TextMeasurer(g2));
            block.draw(g2, (float) area.getCenterX(),
                    (float) area.getCenterY(), TextBlockAnchor.CENTER);
        }
        g2.setClip(savedClip);
    }

    /**
     * Creates a plot entity that contains a reference to the plot and the
     * data area as shape.
     *
     * @param dataArea  the data area used as hot spot for the entity.
     * @param plotState  the plot rendering info containing a reference to the
     *     EntityCollection.
     * @param toolTip  the tool tip (defined in the respective Plot
     *     subclass) ({@code null} permitted).
     * @param urlText  the url (defined in the respective Plot subclass)
     *     ({@code null} permitted).
     *
     *  @since 1.0.13
     */
    protected void createAndAddEntity(Rectangle2D dataArea,
            PlotRenderingInfo plotState, String toolTip, String urlText) {
        if (plotState != null && plotState.getOwner() != null) {
            EntityCollection e = plotState.getOwner().getEntityCollection();
            if (e != null) {
                e.add(new PlotEntity(dataArea, this, toolTip, urlText));
            }
        }
    }

    /**
     * Handles a 'click' on the plot.  Since the plot does not maintain any
     * information about where it has been drawn, the plot rendering info is
     * supplied as an argument so that the plot dimensions can be determined.
     *
     * @param x  the x coordinate (in Java2D space).
     * @param y  the y coordinate (in Java2D space).
     * @param info  an object containing information about the dimensions of
     *              the plot.
     */
    public void handleClick(int x, int y, PlotRenderingInfo info) {
        // provides a 'no action' default
    }

    /**
     * Performs a zoom on the plot.  Subclasses should override if zooming is
     * appropriate for the type of plot.
     *
     * @param percent  the zoom percentage.
     */
    public void zoom(double percent) {
        // do nothing by default.
    }

    /**
     * Receives notification of a change to an {@link Annotation} added to
     * this plot.
     *
     * @param event  information about the event (not used here).
     *
     * @since 1.0.14
     */
    @Override
    public void annotationChanged(AnnotationChangeEvent event) {
        fireChangeEvent();
    }

    /**
     * Receives notification of a change to one of the plot's axes.
     *
     * @param event  information about the event (not used here).
     */
    @Override
    public void axisChanged(AxisChangeEvent event) {
        fireChangeEvent();
    }

    /**
     * Receives notification of a change to the plot's dataset.
     * <P>
     * The plot reacts by passing on a plot change event to all registered
     * listeners.
     *
     * @param event  information about the event (not used here).
     */
    @Override
    public void datasetChanged(DatasetChangeEvent event) {
        PlotChangeEvent newEvent = new PlotChangeEvent(this);
        newEvent.setType(ChartChangeEventType.DATASET_UPDATED);
        notifyListeners(newEvent);
    }

    /**
     * Receives notification of a change to a marker that is assigned to the
     * plot.
     *
     * @param event  the event.
     *
     * @since 1.0.3
     */
    @Override
    public void markerChanged(MarkerChangeEvent event) {
        fireChangeEvent();
    }

    /**
     * Adjusts the supplied x-value.
     *
     * @param x  the x-value.
     * @param w1  width 1.
     * @param w2  width 2.
     * @param edge  the edge (left or right).
     *
     * @return The adjusted x-value.
     */
    protected double getRectX(double x, double w1, double w2,
                              RectangleEdge edge) {

        double result = x;
        if (edge == RectangleEdge.LEFT) {
            result = result + w1;
        }
        else if (edge == RectangleEdge.RIGHT) {
            result = result + w2;
        }
        return result;

    }

    /**
     * Adjusts the supplied y-value.
     *
     * @param y  the x-value.
     * @param h1  height 1.
     * @param h2  height 2.
     * @param edge  the edge (top or bottom).
     *
     * @return The adjusted y-value.
     */
    protected double getRectY(double y, double h1, double h2,
                              RectangleEdge edge) {

        double result = y;
        if (edge == RectangleEdge.TOP) {
            result = result + h1;
        }
        else if (edge == RectangleEdge.BOTTOM) {
            result = result + h2;
        }
        return result;

    }

    /**
     * Tests this plot for equality with another object.
     *
     * @param obj  the object ({@code null} permitted).
     *
     * @return {@code true} or {@code false}.
     */
    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof Plot)) {
            return false;
        }
        Plot that = (Plot) obj;
        if (!ObjectUtils.equal(this.noDataMessage, that.noDataMessage)) {
            return false;
        }
        if (!ObjectUtils.equal(
            this.noDataMessageFont, that.noDataMessageFont
        )) {
            return false;
        }
        if (!PaintUtils.equal(this.noDataMessagePaint,
                that.noDataMessagePaint)) {
            return false;
        }
        if (!ObjectUtils.equal(this.insets, that.insets)) {
            return false;
        }
        if (this.outlineVisible != that.outlineVisible) {
            return false;
        }
        if (!ObjectUtils.equal(this.outlineStroke, that.outlineStroke)) {
            return false;
        }
        if (!PaintUtils.equal(this.outlinePaint, that.outlinePaint)) {
            return false;
        }
        if (!PaintUtils.equal(this.backgroundPaint, that.backgroundPaint)) {
            return false;
        }
        if (!ObjectUtils.equal(this.backgroundImage,
                that.backgroundImage)) {
            return false;
        }
        if (this.backgroundImageAlignment != that.backgroundImageAlignment) {
            return false;
        }
        if (this.backgroundImageAlpha != that.backgroundImageAlpha) {
            return false;
        }
        if (this.foregroundAlpha != that.foregroundAlpha) {
            return false;
        }
        if (this.backgroundAlpha != that.backgroundAlpha) {
            return false;
        }
        if (!this.drawingSupplier.equals(that.drawingSupplier)) {
            return false;
        }
        if (this.notify != that.notify) {
            return false;
        }
        return true;
    }

    /**
     * Creates a clone of the plot.
     *
     * @return A clone.
     *
     * @throws CloneNotSupportedException if some component of the plot does not
     *         support cloning.
     */
    @Override
    public Object clone() throws CloneNotSupportedException {

        Plot clone = (Plot) super.clone();
        // private Plot parent <-- don't clone the parent plot, but take care
        // childs in combined plots instead
        if (this.datasetGroup != null) {
            clone.datasetGroup
                = (DatasetGroup) ObjectUtils.clone(this.datasetGroup);
        }
        clone.drawingSupplier
            = (DrawingSupplier) ObjectUtils.clone(this.drawingSupplier);
        clone.listenerList = new EventListenerList();
        return clone;

    }

    /**
     * Provides serialization support.
     *
     * @param stream  the output stream.
     *
     * @throws IOException  if there is an I/O error.
     */
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        SerialUtils.writePaint(this.noDataMessagePaint, stream);
        SerialUtils.writeStroke(this.outlineStroke, stream);
        SerialUtils.writePaint(this.outlinePaint, stream);
        // backgroundImage
        SerialUtils.writePaint(this.backgroundPaint, stream);
    }

    /**
     * Provides serialization support.
     *
     * @param stream  the input stream.
     *
     * @throws IOException  if there is an I/O error.
     * @throws ClassNotFoundException  if there is a classpath problem.
     */
    private void readObject(ObjectInputStream stream)
        throws IOException, ClassNotFoundException {
        stream.defaultReadObject();
        this.noDataMessagePaint = SerialUtils.readPaint(stream);
        this.outlineStroke = SerialUtils.readStroke(stream);
        this.outlinePaint = SerialUtils.readPaint(stream);
        // backgroundImage
        this.backgroundPaint = SerialUtils.readPaint(stream);

        this.listenerList = new EventListenerList();

    }

    /**
     * Resolves a domain axis location for a given plot orientation.
     *
     * @param location  the location ({@code null} not permitted).
     * @param orientation  the orientation ({@code null} not permitted).
     *
     * @return The edge (never {@code null}).
     */
    public static RectangleEdge resolveDomainAxisLocation(
            AxisLocation location, PlotOrientation orientation) {

        Args.nullNotPermitted(location, "location");
        Args.nullNotPermitted(orientation, "orientation");

        RectangleEdge result = null;
        if (location == AxisLocation.TOP_OR_RIGHT) {
            if (orientation == PlotOrientation.HORIZONTAL) {
                result = RectangleEdge.RIGHT;
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                result = RectangleEdge.TOP;
            }
        }
        else if (location == AxisLocation.TOP_OR_LEFT) {
            if (orientation == PlotOrientation.HORIZONTAL) {
                result = RectangleEdge.LEFT;
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                result = RectangleEdge.TOP;
            }
        }
        else if (location == AxisLocation.BOTTOM_OR_RIGHT) {
            if (orientation == PlotOrientation.HORIZONTAL) {
                result = RectangleEdge.RIGHT;
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                result = RectangleEdge.BOTTOM;
            }
        }
        else if (location == AxisLocation.BOTTOM_OR_LEFT) {
            if (orientation == PlotOrientation.HORIZONTAL) {
                result = RectangleEdge.LEFT;
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                result = RectangleEdge.BOTTOM;
            }
        }
        // the above should cover all the options...
        if (result == null) {
            throw new IllegalStateException("resolveDomainAxisLocation()");
        }
        return result;

    }

    /**
     * Resolves a range axis location for a given plot orientation.
     *
     * @param location  the location ({@code null} not permitted).
     * @param orientation  the orientation ({@code null} not permitted).
     *
     * @return The edge (never {@code null}).
     */
    public static RectangleEdge resolveRangeAxisLocation(
            AxisLocation location, PlotOrientation orientation) {

        Args.nullNotPermitted(location, "location");
        Args.nullNotPermitted(orientation, "orientation");

        RectangleEdge result = null;
        if (location == AxisLocation.TOP_OR_RIGHT) {
            if (orientation == PlotOrientation.HORIZONTAL) {
                result = RectangleEdge.TOP;
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                result = RectangleEdge.RIGHT;
            }
        }
        else if (location == AxisLocation.TOP_OR_LEFT) {
            if (orientation == PlotOrientation.HORIZONTAL) {
                result = RectangleEdge.TOP;
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                result = RectangleEdge.LEFT;
            }
        }
        else if (location == AxisLocation.BOTTOM_OR_RIGHT) {
            if (orientation == PlotOrientation.HORIZONTAL) {
                result = RectangleEdge.BOTTOM;
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                result = RectangleEdge.RIGHT;
            }
        }
        else if (location == AxisLocation.BOTTOM_OR_LEFT) {
            if (orientation == PlotOrientation.HORIZONTAL) {
                result = RectangleEdge.BOTTOM;
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                result = RectangleEdge.LEFT;
            }
        }

        // the above should cover all the options...
        if (result == null) {
            throw new IllegalStateException("resolveRangeAxisLocation()");
        }
        return result;

    }

}