awteventmulticaster.java

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/* Copyright (C) 1999, 2000, 2002  Free Software Foundation

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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GNU Classpath 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
General Public License for more details.

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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package java.awt;

import java.awt.event.*;
import java.util.EventListener;
import java.io.ObjectOutputStream;

/* Written using on-line Java 2 Platform Standard Edition v1.3 API 
 * Specification, as well as "The Java Class Libraries", 2nd edition 
 * (Addison-Wesley, 1998).
 * Status:  Believed complete and correct to J2SE 1.3, except for 
 * serialization support methods, save() and saveInternal(), which are 
 * stubbed.
 */

/**
  * This class is used to implement a chain of event handlers.  Dispatching
  * using this class is thread safe.  Here is a quick example of how to
  * add and delete listeners using this class.  For this example, we will
  * assume are firing <code>AdjustableEvent</code>'s.  However, this 
  * same approach is useful for all events in the <code>java.awt.event</code>
  * package, and more if this class is subclassed.
  * <p>
  * <code> 
  * AdjustmentListener al;
  * 
  * public void 
  * addAdjustmentListener(AdjustmentListener listener)
  * {
  *   al = AWTEventMulticaster.add(al, listener);
  * }
  *
  * public void
  * removeAdjustmentListener(AdjustmentListener listener)
  * {
  *   al = AWTEventMulticaster.remove(al, listener);
  * }
  * </code>
  * <p>
  * When it come time to process an event, simply call <code>al</code>,
  * assuming it is not <code>null</code>.
  * <p>
  * The first time <code>add</code> is called it is passed
  * <code>null</code> and <code>listener</code> as its arguments.  This
  * starts building the chain.  This class returns <code>listener</code>
  * which becomes the new <code>al</code>.  The next time, <code>add</code>
  * is called with <code>al</code> and <code>listener</code> and the
  * new listener is then chained to the old.
  *
  * @author Bryce McKinlay
  * @author Aaron M. Renn ([e-mail])
  */
public class AWTEventMulticaster implements ComponentListener, 
  ContainerListener, FocusListener, KeyListener, MouseListener,
  MouseMotionListener, WindowListener, ActionListener, ItemListener, 
  AdjustmentListener, TextListener, InputMethodListener, HierarchyListener, 
  HierarchyBoundsListener
{
  /**
   * A variable in the event chain.
   */
  protected final EventListener a;

  /**
   * A variable in the event chain
   */
  protected final EventListener b;

  /**
   * Initializes a new instance of <code>AWTEventMulticaster</code> with
   * the specified event listener parameters.
   *
   * @param a The "a" listener object.
   * @param b The "b" listener object.
   */
  protected AWTEventMulticaster(EventListener a,
                        	EventListener b)
  {
    this.a = a;
    this.b = b;
  }

  /**
   * Chain <code>EventListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  protected static EventListener addInternal(EventListener a, EventListener b)
  {
    if (a == null)
      return b;
    else if (b == null)
      return a;
    else return new AWTEventMulticaster(a, b);
  }

  /**
   * Removes the listener <code>old</code> from the listener <code>lis</code>.
   *
   * @param lis The listener to remove <code>old</code> from.
   * @param old The listener to remove.
   *
   * @return The resulting listener after the remove operation.
   */
  protected static EventListener removeInternal(EventListener l, 
						EventListener oldl)
  {
    if (l == oldl)
      return null;
    else if (l instanceof AWTEventMulticaster)
      {
	AWTEventMulticaster mc = (AWTEventMulticaster) l;
	return mc.remove(oldl);
      }
    return l;
  }

  /**
   * Removes the specified object from this multicaster object.  If the
   * object to remove is not part of this multicaster, then the remove
   * method on the parent multicaster (if it exists) is called and a 
   * new multicaster object is returned based on that object and this
   * multicaster's non-parent object.
   *
   * @param old The object to remove from this multicaster.
   *
   * @return The resulting multicaster with the specified listener removed.
   */
  protected EventListener remove(EventListener oldl)
  {
    // If oldl is an immediate child, return the other child.
    if (a == oldl)
      return b;
    if (b == oldl)
      return a;

    // If a and/or b are Multicaster's, search them recursively.
    if (a instanceof AWTEventMulticaster)
      {
        AWTEventMulticaster mc = (AWTEventMulticaster) a;
	EventListener newa = mc.remove(oldl);
	if (newa != a)
	  return new AWTEventMulticaster (newa, b);
      }    
    if (b instanceof AWTEventMulticaster)
      {
        AWTEventMulticaster mc = (AWTEventMulticaster) a;
	EventListener newb = mc.remove(oldl);
	if (newb != b)
	  return new AWTEventMulticaster (a, newb);
      }

    // oldl was not found.
    return this;
  }

  /**
   * Chain <code>ActionListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static ActionListener add(ActionListener a, ActionListener b)
  {
    return (ActionListener) addInternal(a, b);
  }

  /**
   * Chain <code>AdjustmentListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static AdjustmentListener add(AdjustmentListener a, 
				       AdjustmentListener b)
  {
    return (AdjustmentListener) addInternal(a, b);
  }				       

  /**
   * Chain <code>ComponentListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static ComponentListener add(ComponentListener a, ComponentListener b)
  {
    return (ComponentListener) addInternal(a, b);
  }

  /**
   * Chain <code>ContainerListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static ContainerListener add(ContainerListener a, ContainerListener b)
  {
    return (ContainerListener) addInternal(a, b);
  }

  /**
   * Chain <code>FocusListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static FocusListener add(FocusListener a, FocusListener b) 
  {
    return (FocusListener) addInternal(a, b);
  }

  public static HierarchyBoundsListener add(HierarchyBoundsListener a, 
					    HierarchyBoundsListener b)
  {
    return (HierarchyBoundsListener) addInternal(a, b);
  }

  public static HierarchyListener add(HierarchyListener a, HierarchyListener b)
  {
    return (HierarchyListener) addInternal(a, b);
  }

  public static InputMethodListener add(InputMethodListener a, 
					InputMethodListener b)
  {
    return (InputMethodListener) addInternal(a, b);
  }

  /**
   * Chain <code>ItemListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static ItemListener add(ItemListener a, ItemListener b)
  {
    return (ItemListener) addInternal(a, b);
  }

  /**
   * Chain <code>KeyListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static KeyListener add(KeyListener a, KeyListener b)
  {
    return (KeyListener) addInternal(a, b);
  }

  /**
   * Chain <code>MouseListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static MouseListener add(MouseListener a, MouseListener b)
  {
    return (MouseListener) addInternal(a, b);
  }

  /**
   * Chain <code>MouseMotionListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static MouseMotionListener add(MouseMotionListener a, 
					MouseMotionListener b)
  {
    return (MouseMotionListener) addInternal(a, b);
  }

  /**
   * Chain <code>AdjustmentListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static TextListener add(TextListener a, TextListener b)
  {
    return (TextListener) addInternal(a, b);
  }

  /**
   * Chain <code>WindowListener</code> b to a.
   *
   * @param a - Listener to chain to.
   * @param b - Listener to chain.
   *
   * @return Latest entry in the chain.
   */
  public static WindowListener add(WindowListener a, WindowListener b)
  {
    return (WindowListener) addInternal(a, b);
  }

  /**
   * Removes the listener <code>old</code> from the listener <code>lis</code>.
   *
   * @param lis The listener to remove <code>old</code> from.
   * @param old The listener to remove.
   *
   * @return The resulting listener after the remove operation.
   */
  public static ActionListener remove(ActionListener l, ActionListener oldl)
  {
    return (ActionListener) removeInternal(l, oldl);
  }

  /**
   * Removes the listener <code>old</code> from the listener <code>lis</code>.
   *
   * @param lis The listener to remove <code>old</code> from.
   * @param old The listener to remove.
   *
   * @return The resulting listener after the remove operation.
   */
  public static AdjustmentListener remove(AdjustmentListener l, 
					  AdjustmentListener oldl) 
  {
    return (AdjustmentListener) removeInternal(l, oldl);
  }

  /**
   * Removes the listener <code>old</code> from the listener <code>lis</code>.
   *
   * @param lis The listener to remove <code>old</code> from.
   * @param old The listener to remove.
   *
   * @return The resulting listener after the remove operation.
   */
  public static ComponentListener remove(ComponentListener l, 
					 ComponentListener oldl) 
  {
    return (ComponentListener) removeInternal(l, oldl);
  }

  /**
   * Removes the listener <code>old</code> from the listener <code>lis</code>.
   *
   * @param lis The listener to remove <code>old</code> from.
   * @param old The listener to remove.
   *
   * @return The resulting listener after the remove operation.
   */
  public static ContainerListener remove(ContainerListener l, 
					 ContainerListener oldl) 
  {
    return (ContainerListener) removeInternal(l, oldl);
  }

  /**
   * Removes the listener <code>old</code> from the listener <code>lis</code>.
   *
   * @param lis The listener to remove <code>old</code> from.
   * @param old The listener to remove.
   *
   * @return The resulting listener after the remove operation.
   */
  public static FocusListener remove(FocusListener l, FocusListener oldl) 
  {
    return (FocusListener) removeInternal(l, oldl);
  }

  public static HierarchyBoundsListener remove(HierarchyBoundsListener l,
                			       HierarchyBoundsListener oldl) 
  {
    return (HierarchyBoundsListener) removeInternal(l, oldl);
  }

  public static HierarchyListener remove(HierarchyListener l, 
					 HierarchyListener oldl) 
  {
    return (HierarchyListener) removeInternal(l, oldl);
  }

  public static InputMethodListener remove(InputMethodListener l, 
					   InputMethodListener oldl) 
  {
    return (InputMethodListener) removeInternal(l, oldl);
  }

  /**
   * Removes the listener <code>old</code> from the listener <code>lis</code>.
   *
   * @param lis The listener to remove <code>old</code> from.
   * @param old The listener to remove.
   *
   * @return The resulting listener after the remove operation.
   */
  public static ItemListener remove(ItemListener l, ItemListener oldl) 
  {
    return (ItemListener) removeInternal(l, oldl);
  }

  /**
   * Removes the listener <code>old</code> from the listener <code>lis</code>.
   *
   * @param lis The listener to remove <code>old</code> from.
   * @param old The listener to remove.
   *
   * @return The resulting listener after the remove operation.
   */
  public static KeyListener remove(KeyListener l, KeyListener oldl) 
  {
    return (KeyListener) removeInternal(l, oldl);
  }

  /**
   * Removes the listener <code>old</code> from the listener <code>lis</code>.