/* ===========================================================
 
* JFreeChart : a free chart library for the Java(tm) platform
 
* ===========================================================
 
*
 
* (C) Copyright 2000-2018, 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.]
 
*
 
* --------------------
 
* AbstractOverlay.java
 
* --------------------
 
* (C) Copyright 2009-2018, by Object Refinery Limited.
 
*
 
* Original Author:
  
David Gilbert (for Object Refinery Limited);
 
* Contributor(s):
   
-;
 
*
 
*/

package org.jfree.chart.panel;

import javax.swing.event.EventListenerList;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.event.ChartChangeEvent;
import org.jfree.chart.event.OverlayChangeEvent;
import org.jfree.chart.event.OverlayChangeListener;
import org.jfree.chart.util.Args;

/**
 
* A base class for implementing overlays for a {@link ChartPanel}.
 
*
 
* @since 1.0.13
 
*/

public class AbstractOverlay {

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

    
/**
     
* Default constructor.
     
*/
    
public AbstractOverlay() {
        
this.changeListeners = new EventListenerList();
    
}

    
/**
     
* Registers an object for notification of changes to the overlay.
     
*
     
* @param listener
  
the listener ({@code null} not permitted).
     
*
     
* @see #removeChangeListener(OverlayChangeListener)
     
*/

    
public void addChangeListener(OverlayChangeListener listener) {
        
Args.nullNotPermitted(listener, "listener");
        
this.changeListeners.add(OverlayChangeListener.class, listener);
    
}

    
/**
     
* Deregisters an object for notification of changes to the overlay.
     
*
     
* @param listener
  
the listener ({@code null} not permitted)
     
*
     
* @see #addChangeListener(OverlayChangeListener)
     
*/

    
public void removeChangeListener(OverlayChangeListener listener) {
        
Args.nullNotPermitted(listener, "listener");
        
this.changeListeners.remove(OverlayChangeListener.class, listener);
    
}

    
/**
     
* Sends a default {@link ChartChangeEvent} to all registered listeners.
     
* <P>
     
* This method is for convenience only.
     
*/

    
public void fireOverlayChanged() {
        
OverlayChangeEvent event = new OverlayChangeEvent(this);
        
notifyListeners(event);
    
}

    
/**
     
* Sends a {@link ChartChangeEvent} to all registered listeners.
     
*
     
* @param event
  
information about the event that triggered the
     
*
               
notification.
     
*/

    
protected void notifyListeners(OverlayChangeEvent event) {
       
Object[] listeners = this.changeListeners.getListenerList();
        
for (int i = listeners.length - 2; i >= 0; i -= 2) {
            
if (listeners[i] == OverlayChangeListener.class) {
                
((OverlayChangeListener) listeners[i + 1]).overlayChanged(
                        
event);
            
}
        
}
    
}

}