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/*******************************************************************************
* Copyright (c) 2007, 2012 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0, which accompanies this distribution
* and is available at http://www.eclipse.org/legal/epl-v10.html.
*
* Contributors:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.common.ui.internal.listeners;
import org.eclipse.jpt.common.ui.internal.util.SWTUtil;
import org.eclipse.jpt.common.utility.internal.RunnableAdapter;
import org.eclipse.jpt.common.utility.internal.collection.SynchronizedQueue;
import org.eclipse.jpt.common.utility.model.event.PropertyChangeEvent;
import org.eclipse.jpt.common.utility.model.listener.PropertyChangeListener;
/**
* Wrap another property change listener and forward events to it on the SWT
* UI thread, asynchronously if necessary. If the event arrived on the UI
* thread that is probably because it was initiated by a UI widget; as a
* result, we want to loop back synchronously so the events can be
* short-circuited. (Typically, the adapter(s) between a <em>property</em> and
* its corresponding UI widget are read-write; as opposed to the adapter(s)
* between a <em>collection</em> (or <em>list</em>) and its UI widget, which
* is read-only.)
* <p>
* Any events received earlier (on a non-UI thread) will be
* forwarded, in the order received, before the current event is forwarded.
*/
public class SWTPropertyChangeListenerWrapper
implements PropertyChangeListener
{
private final PropertyChangeListener listener;
private final SynchronizedQueue<PropertyChangeEvent> events = new SynchronizedQueue<PropertyChangeEvent>();
public SWTPropertyChangeListenerWrapper(PropertyChangeListener listener) {
super();
if (listener == null) {
throw new NullPointerException();
}
this.listener = listener;
}
public void propertyChanged(PropertyChangeEvent event) {
this.events.enqueue(event);
this.execute(new ForwardEventsRunnable());
}
/* CU private */ class ForwardEventsRunnable
extends RunnableAdapter
{
@Override
public void run() {
SWTPropertyChangeListenerWrapper.this.forwardEvents();
}
}
void forwardEvents() {
for (PropertyChangeEvent event : this.events.drain()) {
this.listener.propertyChanged(event);
}
}
/**
* {@link SWTUtil#execute(Runnable)} seems to work OK;
* but using {@link SWTUtil#syncExec(Runnable)} can somtimes make things
* more predictable when debugging, at the risk of deadlocks.
*/
private void execute(Runnable r) {
SWTUtil.execute(r);
// SWTUtil.syncExec(r);
}
@Override
public String toString() {
return "SWT(" + this.listener + ')'; //$NON-NLS-1$
}
}
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