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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package java.awt.dnd;
import java.awt.AWTEventMulticaster;
import java.io.ObjectOutputStream;
import java.io.IOException;
import java.util.EventListener;
/**
* A class extends {@code AWTEventMulticaster} to implement efficient and
* thread-safe multi-cast event dispatching for the drag-and-drop events defined
* in the java.awt.dnd package.
*
* @since 1.4
* @see AWTEventMulticaster
*/
class DnDEventMulticaster extends AWTEventMulticaster
implements DragSourceListener, DragSourceMotionListener {
/**
* Creates an event multicaster instance which chains listener-a
* with listener-b. Input parameters {@code a} and {@code b}
* should not be {@code null}, though implementations may vary in
* choosing whether or not to throw {@code NullPointerException}
* in that case.
*
* @param a listener-a
* @param b listener-b
*/
protected DnDEventMulticaster(EventListener a, EventListener b) {
super(a,b);
}
/**
* Handles the {@code DragSourceDragEvent} by invoking
* {@code dragEnter} on listener-a and listener-b.
*
* @param dsde the {@code DragSourceDragEvent}
*/
public void dragEnter(DragSourceDragEvent dsde) {
((DragSourceListener)a).dragEnter(dsde);
((DragSourceListener)b).dragEnter(dsde);
}
/**
* Handles the {@code DragSourceDragEvent} by invoking
* {@code dragOver} on listener-a and listener-b.
*
* @param dsde the {@code DragSourceDragEvent}
*/
public void dragOver(DragSourceDragEvent dsde) {
((DragSourceListener)a).dragOver(dsde);
((DragSourceListener)b).dragOver(dsde);
}
/**
* Handles the {@code DragSourceDragEvent} by invoking
* {@code dropActionChanged} on listener-a and listener-b.
*
* @param dsde the {@code DragSourceDragEvent}
*/
public void dropActionChanged(DragSourceDragEvent dsde) {
((DragSourceListener)a).dropActionChanged(dsde);
((DragSourceListener)b).dropActionChanged(dsde);
}
/**
* Handles the {@code DragSourceEvent} by invoking
* {@code dragExit} on listener-a and listener-b.
*
* @param dse the {@code DragSourceEvent}
*/
public void dragExit(DragSourceEvent dse) {
((DragSourceListener)a).dragExit(dse);
((DragSourceListener)b).dragExit(dse);
}
/**
* Handles the {@code DragSourceDropEvent} by invoking
* {@code dragDropEnd} on listener-a and listener-b.
*
* @param dsde the {@code DragSourceDropEvent}
*/
public void dragDropEnd(DragSourceDropEvent dsde) {
((DragSourceListener)a).dragDropEnd(dsde);
((DragSourceListener)b).dragDropEnd(dsde);
}
/**
* Handles the {@code DragSourceDragEvent} by invoking
* {@code dragMouseMoved} on listener-a and listener-b.
*
* @param dsde the {@code DragSourceDragEvent}
*/
public void dragMouseMoved(DragSourceDragEvent dsde) {
((DragSourceMotionListener)a).dragMouseMoved(dsde);
((DragSourceMotionListener)b).dragMouseMoved(dsde);
}
/**
* Adds drag-source-listener-a with drag-source-listener-b and
* returns the resulting multicast listener.
*
* @param a drag-source-listener-a
* @param b drag-source-listener-b
*/
public static DragSourceListener add(DragSourceListener a,
DragSourceListener b) {
return (DragSourceListener)addInternal(a, b);
}
/**
* Adds drag-source-motion-listener-a with drag-source-motion-listener-b and
* returns the resulting multicast listener.
*
* @param a drag-source-motion-listener-a
* @param b drag-source-motion-listener-b
*/
@SuppressWarnings("overloads")
public static DragSourceMotionListener add(DragSourceMotionListener a,
DragSourceMotionListener b) {
return (DragSourceMotionListener)addInternal(a, b);
}
/**
* Removes the old drag-source-listener from drag-source-listener-l
* and returns the resulting multicast listener.
*
* @param l drag-source-listener-l
* @param oldl the drag-source-listener being removed
*/
public static DragSourceListener remove(DragSourceListener l,
DragSourceListener oldl) {
return (DragSourceListener)removeInternal(l, oldl);
}
/**
* Removes the old drag-source-motion-listener from
* drag-source-motion-listener-l and returns the resulting multicast
* listener.
*
* @param l drag-source-motion-listener-l
* @param ol the drag-source-motion-listener being removed
*/
@SuppressWarnings("overloads")
public static DragSourceMotionListener remove(DragSourceMotionListener l,
DragSourceMotionListener ol) {
return (DragSourceMotionListener)removeInternal(l, ol);
}
/**
* Returns the resulting multicast listener from adding listener-a
* and listener-b together.
* If listener-a is null, it returns listener-b;
* If listener-b is null, it returns listener-a
* If neither are null, then it creates and returns
* a new AWTEventMulticaster instance which chains a with b.
* @param a event listener-a
* @param b event listener-b
*/
protected static EventListener addInternal(EventListener a, EventListener b) {
if (a == null) return b;
if (b == null) return a;
return new DnDEventMulticaster(a, b);
}
/**
* Removes a listener from this multicaster and returns the
* resulting multicast listener.
* @param oldl the listener to be removed
*/
protected EventListener remove(EventListener oldl) {
if (oldl == a) return b;
if (oldl == b) return a;
EventListener a2 = removeInternal(a, oldl);
EventListener b2 = removeInternal(b, oldl);
if (a2 == a && b2 == b) {
return this; // it's not here
}
return addInternal(a2, b2);
}
/**
* Returns the resulting multicast listener after removing the
* old listener from listener-l.
* If listener-l equals the old listener OR listener-l is null,
* returns null.
* Else if listener-l is an instance of AWTEventMulticaster,
* then it removes the old listener from it.
* Else, returns listener l.
* @param l the listener being removed from
* @param oldl the listener being removed
*/
protected static EventListener removeInternal(EventListener l, EventListener oldl) {
if (l == oldl || l == null) {
return null;
} else if (l instanceof DnDEventMulticaster) {
return ((DnDEventMulticaster)l).remove(oldl);
} else {
return l; // it's not here
}
}
protected static void save(ObjectOutputStream s, String k, EventListener l)
throws IOException {
AWTEventMulticaster.save(s, k, l);
}
}