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/*******************************************************************************
* Copyright (c) 2006, 2007 IBM Corporation and others.
* 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:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.jface.internal.databinding.provisional.swt;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Set;
import org.eclipse.swt.widgets.Display;
/**
* NON-API - Helper class to manage a queue of runnables to be posted to the UI
* thread in a way that they are only run once.
*
* @since 1.1
*
*/
public class WorkQueue {
private boolean updateScheduled = false;
private LinkedList pendingWork = new LinkedList();
private Display d;
private Set pendingWorkSet = new HashSet();
private Runnable updateJob = new Runnable() {
public void run() {
doUpdate();
updateScheduled = false;
}
};
/**
* @param targetDisplay
*/
public WorkQueue(Display targetDisplay) {
d = targetDisplay;
}
private void doUpdate() {
for (;;) {
Runnable next;
synchronized (pendingWork) {
if (pendingWork.isEmpty()) {
break;
}
next = (Runnable) pendingWork.removeFirst();
pendingWorkSet.remove(next);
}
next.run();
}
}
/**
* Schedules some work to happen in the UI thread as soon as possible. If
* possible, the work will happen before the next control redraws. The given
* runnable will only be run once. Has no effect if this runnable has
* already been queued for execution.
*
* @param work
* runnable to execute
*/
public void runOnce(Runnable work) {
synchronized (pendingWork) {
if (pendingWorkSet.contains(work)) {
return;
}
pendingWorkSet.add(work);
asyncExec(work);
}
}
/**
* Schedules some work to happen in the UI thread as soon as possible. If
* possible, the work will happen before the next control redraws. Unlike
* runOnce, calling asyncExec twice with the same runnable will cause that
* runnable to run twice.
*
* @param work
* runnable to execute
*/
public void asyncExec(Runnable work) {
synchronized (pendingWork) {
pendingWork.add(work);
if (!updateScheduled) {
updateScheduled = true;
d.timerExec(0, updateJob);
}
}
}
/**
* Cancels a previously-scheduled runnable. Has no effect if the given
* runnable was not previously scheduled or has already executed.
*
* @param toCancel
* runnable to cancel
*/
public void cancelExec(Runnable toCancel) {
synchronized (pendingWork) {
pendingWork.remove(toCancel);
pendingWorkSet.remove(toCancel);
}
}
/**
* Cancels all pending work.
*/
public void cancelAll() {
synchronized (pendingWork) {
pendingWork.clear();
pendingWorkSet.clear();
}
}
}
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