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/*
 * Copyright (c) 2005, The JUNG Authors
 * All rights reserved.
 *
 * This software is open-source under the BSD license; see either "license.txt"
 * or https://github.com/jrtom/jung/blob/master/LICENSE for a description.
 *
 * Created on Aug 18, 2005
 */

package edu.uci.ics.jung.visualization.util;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.EventListenerList;

/**
 * Basic implementation of ChangeEventSupport, using standard jdk classes
 *
 * @author Tom Nelson
 */
public class DefaultChangeEventSupport implements ChangeEventSupport {

  Object eventSource;
  /** holds the registered listeners */
  protected EventListenerList listenerList = new EventListenerList();

  /**
   * Only one ChangeEvent is needed instance since the event's only state is the source
   * property. The source of events generated is always "this".
   */
  protected transient ChangeEvent changeEvent;

  public DefaultChangeEventSupport(Object eventSource) {
    this.eventSource = eventSource;
  }

  public void addChangeListener(ChangeListener l) {
    listenerList.add(ChangeListener.class, l);
  }

  public void removeChangeListener(ChangeListener l) {
    listenerList.remove(ChangeListener.class, l);
  }

  public ChangeListener[] getChangeListeners() {
    return listenerList.getListeners(ChangeListener.class);
  }

  /**
   * Notifies all listeners that have registered interest for notification on this event type. The
   * event instance is lazily created. The primary listeners will be views that need to be repainted
   * because of changes in this model instance
   *
   * @see EventListenerList
   */
  public void fireStateChanged() {
    // Guaranteed to return a non-null array
    Object[] listeners = listenerList.getListenerList();
    // Process the listeners last to first, notifying
    // those that are interested in this event
    for (int i = listeners.length - 2; i >= 0; i -= 2) {
      if (listeners[i] == ChangeListener.class) {
        // Lazily create the event:
        if (changeEvent == null) {
          changeEvent = new ChangeEvent(eventSource);
        }
        ((ChangeListener) listeners[i + 1]).stateChanged(changeEvent);
      }
    }
  }
}