BridgedSwtEventLoop.java

/*
 * Copyright (c) 2012, grossmann
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * * Neither the name of the jo-widgets.org nor the
 *   names of its contributors may be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL jo-widgets.org BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

package org.jowidgets.spi.impl.bridge.swt.awt.common.application;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicBoolean;

import javax.swing.SwingUtilities;

import org.eclipse.swt.widgets.Display;
import org.jowidgets.util.Assert;

public final class BridgedSwtEventLoop {

    private final AtomicBoolean isRunning;;
    private final long sleepMillis;
    private final int swtEventsCountInSuccession;

    private Display display;
    private Thread eventDispatchingThread;
    private Runnable stoppedCallback;

    public BridgedSwtEventLoop() {
        this(10, 10);
    }

    public BridgedSwtEventLoop(final long sleepMillis, final int swtEventsCountInSuccession) {
        checkNotUiThread();
        this.sleepMillis = sleepMillis;
        this.swtEventsCountInSuccession = swtEventsCountInSuccession;
        this.isRunning = new AtomicBoolean(false);
        try {
            SwingUtilities.invokeAndWait(new Runnable() {
                @Override
                public void run() {
                    eventDispatchingThread = Thread.currentThread();
                    display = Display.getDefault();
                }
            });
        }
        catch (final Exception e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Starts the swt event loop. This must NOT be invoked in the awt(swing) event thread.
     */
    public void start() {
        checkNotUiThread();
        if (!isRunning.getAndSet(true)) {
            isRunning.set(true);
        }
        else {
            return;
        }
        while (isRunning.get()) {
            final CountDownLatch latch = new CountDownLatch(1);
            SwingUtilities.invokeLater(new Runnable() {
                @Override
                public void run() {
                    final Display currentDisplay = getCurrentDisplay();
                    boolean hasMoreSwtEvents = true;
                    int swtEventCount = 0;
                    while (hasMoreSwtEvents
                        && swtEventCount < swtEventsCountInSuccession
                        && !currentDisplay.isDisposed()
                        && Display.getCurrent() != null
                        && isRunning.get()) {
                        hasMoreSwtEvents = currentDisplay.readAndDispatch();
                        swtEventCount++;
                    }
                    latch.countDown();
                }
            });
            try {
                latch.await();
                Thread.sleep(sleepMillis);
            }
            catch (final Exception e) {
                throw new RuntimeException(e);
            }
        }

        if (stoppedCallback != null) {
            SwingUtilities.invokeLater(new Runnable() {
                @Override
                public void run() {
                    try {
                        stoppedCallback.run();
                    }
                    finally {
                        stoppedCallback = null;
                    }
                }
            });
        }
    }

    public void stop() {
        stop(new Runnable() {
            @Override
            public void run() {}
        });
    }

    public void stop(final Runnable stoppedCallback) {
        checkUiThread();
        Assert.paramNotNull(stoppedCallback, "stoppedCallback");
        if (this.stoppedCallback == null) {
            this.stoppedCallback = stoppedCallback;
            isRunning.set(false);
        }
    }

    public boolean isRunning() {
        return isRunning.get();
    }

    public Thread getEventDispatchingThread() {
        return eventDispatchingThread;
    }

    private void checkNotUiThread() {
        if (SwingUtilities.isEventDispatchThread()) {
            throw new IllegalStateException("The swt event loop must not be started from the awt event thread");
        }
    }

    private void checkUiThread() {
        if (!SwingUtilities.isEventDispatchThread()) {
            throw new IllegalStateException("The swt event loop must be stopped from the awt event thread");
        }
    }

    private Display getCurrentDisplay() {
        if (display == null) {
            if (SwingUtilities.isEventDispatchThread()) {
                display = Display.getCurrent();
                if (display == null) {
                    throw new IllegalStateException("The swt display was not initialized");
                }
            }
            else {
                throw new IllegalStateException("The display must be created in the awt(swing) event dispatch thread");
            }
        }
        return display;
    }
}