bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/internal/databinding/provisional/swt/SWTUtil.java

/*******************************************************************************
 * Copyright (c) 2006, 2009 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.HashMap;
import java.util.Map;

import org.eclipse.jface.util.SafeRunnable;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.swt.widgets.Display;

/**
 * NON-API - Utility methods, mainly having to do with posting runnables to the
 * UI thread in a particular way.
 * 
 * @since 1.1
 * 
 */
public class SWTUtil {
	/**
	 * Stores a work queue for each display
	 */
	private static Map mapDisplayOntoWorkQueue = new HashMap();

	private SWTUtil() {
	}

	/**
	 * Runs the given runnable on the given display as soon as possible. Use
	 * this method to schedule work that will affect the way one or more wigdets
	 * are drawn, but that should only happen once.
	 * 
	 * <p>
	 * This is threadsafe.
	 * </p>
	 * 
	 * @param d
	 *            display
	 * @param r
	 *            runnable to execute in the UI thread. Has no effect if the
	 *            given runnable has already been scheduled but has not yet run.
	 */
	public static void runOnce(Display d, Runnable r) {
		if (d.isDisposed()) {
			return;
		}
		WorkQueue queue = getQueueFor(d);
		queue.runOnce(r);
	}

	/**
	 * Cancels a greedyExec or runOnce that was previously scheduled on the
	 * given display. Has no effect if the given runnable is not in the queue
	 * for the given display
	 * 
	 * @param d
	 *            target display
	 * @param r
	 *            runnable to execute
	 */
	public static void cancelExec(Display d, Runnable r) {
		if (d.isDisposed()) {
			return;
		}
		WorkQueue queue = getQueueFor(d);
		queue.cancelExec(r);
	}

	/**
	 * Returns the work queue for the given display. Creates a work queue if
	 * none exists yet.
	 * 
	 * @param d
	 *            display to return queue for
	 * @return a work queue (never null)
	 */
	private static WorkQueue getQueueFor(final Display d) {
		WorkQueue result;
		synchronized (mapDisplayOntoWorkQueue) {
			// Look for existing queue
			result = (WorkQueue) mapDisplayOntoWorkQueue.get(d);

			if (result == null) {
				// If none, create new queue
				result = new WorkQueue(d);
				final WorkQueue q = result;
				mapDisplayOntoWorkQueue.put(d, result);
				d.asyncExec(new Runnable() {
					public void run() {
						d.disposeExec(new Runnable() {
							public void run() {
								synchronized (mapDisplayOntoWorkQueue) {
									q.cancelAll();
									mapDisplayOntoWorkQueue.remove(d);
								}
							}
						});
					}
				});
			}
			return result;
		}
	}

	/**
	 * @param rgb1
	 * @param rgb2
	 * @param ratio
	 * @return the RGB object
	 */
	public static RGB mix(RGB rgb1, RGB rgb2, double ratio) {
		return new RGB(interp(rgb1.red, rgb2.red, ratio), interp(rgb1.green,
				rgb2.green, ratio), interp(rgb1.blue, rgb2.blue, ratio));
	}

	private static int interp(int i1, int i2, double ratio) {
		int result = (int) (i1 * ratio + i2 * (1.0d - ratio));
		if (result < 0)
			result = 0;
		if (result > 255)
			result = 255;
		return result;
	}

	/**
	 * Logs an exception as though it was thrown by a SafeRunnable being run
	 * with the default ISafeRunnableRunner. Will not open modal dialogs or spin
	 * the event loop.
	 * 
	 * @param t
	 *            throwable to log
	 * @deprecated
	 * @noreference This method is not intended to be referenced by clients. It
	 *              remains here for API backwards compatibility.
	 */
	public static void logException(final Exception t) {
		SafeRunnable.run(new SafeRunnable() {
			public void run() throws Exception {
				throw t;
			}

			public void handleException(Throwable e) {
				// IMPORTANT: Do not call the super implementation, since
				// it opens a modal dialog, and may cause *syncExecs to run
				// too early.
			}
		});
	}

}