/*
 * Copyright (c) 1996, 2014, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * 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.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */

package java.awt;

import java.awt.event.*;

import java.awt.peer.ComponentPeer;

import java.lang.ref.WeakReference;
import java.lang.reflect.InvocationTargetException;

import java.security.AccessController;
import java.security.PrivilegedAction;

import java.util.EmptyStackException;

import sun.awt.*;
import sun.awt.dnd.SunDropTargetEvent;
import sun.util.logging.PlatformLogger;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.atomic.AtomicInteger;

import java.security.AccessControlContext;

import sun.misc.SharedSecrets;
import sun.misc.JavaSecurityAccess;

EventQueue is a platform-independent class
that queues events, both from the underlying peer classes
and from trusted application classes.
 It encapsulates asynchronous event dispatch machinery which extracts events from the queue and dispatches them by calling dispatchEvent(AWTEvent) method on this EventQueue with the event to be dispatched
as an argument.  The particular behavior of this machinery is
implementation-dependent.  The only requirements are that events
which were actually enqueued to this queue (note that events
being posted to the EventQueue can be coalesced)
are dispatched:

  
 Sequentially.
  
 That is, it is not permitted that several events from
       this queue are dispatched simultaneously.
  
 In the same order as they are enqueued.
  
 That is, if AWTEvent A is enqueued
       to the EventQueue before
       AWTEvent B then event B will not be
       dispatched before event A.


Some browsers partition applets in different code bases into
separate contexts, and establish walls between these contexts.
In such a scenario, there will be one EventQueue
per context. Other browsers place all applets into the same
context, implying that there will be only a single, global
EventQueue for all applets. This behavior is
implementation-dependent.  Consult your browser's documentation
for more information.

For information on the threading issues of the event dispatch
machinery, see AWT Threading Issues.
Author:
Thomas Ball, Fred Ecks, David Mendenhall
Since:
      1.1/**
 * <code>EventQueue</code> is a platform-independent class
 * that queues events, both from the underlying peer classes
 * and from trusted application classes.
 * <p>
 * It encapsulates asynchronous event dispatch machinery which
 * extracts events from the queue and dispatches them by calling
 * {@link #dispatchEvent(AWTEvent) dispatchEvent(AWTEvent)} method
 * on this <code>EventQueue</code> with the event to be dispatched
 * as an argument.  The particular behavior of this machinery is
 * implementation-dependent.  The only requirements are that events
 * which were actually enqueued to this queue (note that events
 * being posted to the <code>EventQueue</code> can be coalesced)
 * are dispatched:
 * <dl>
 *   <dt> Sequentially.
 *   <dd> That is, it is not permitted that several events from
 *        this queue are dispatched simultaneously.
 *   <dt> In the same order as they are enqueued.
 *   <dd> That is, if <code>AWTEvent</code>&nbsp;A is enqueued
 *        to the <code>EventQueue</code> before
 *        <code>AWTEvent</code>&nbsp;B then event B will not be
 *        dispatched before event A.
 * </dl>
 * <p>
 * Some browsers partition applets in different code bases into
 * separate contexts, and establish walls between these contexts.
 * In such a scenario, there will be one <code>EventQueue</code>
 * per context. Other browsers place all applets into the same
 * context, implying that there will be only a single, global
 * <code>EventQueue</code> for all applets. This behavior is
 * implementation-dependent.  Consult your browser's documentation
 * for more information.
 * <p>
 * For information on the threading issues of the event dispatch
 * machinery, see <a href="doc-files/AWTThreadIssues.html#Autoshutdown"
 * >AWT Threading Issues</a>.
 *
 * @author Thomas Ball
 * @author Fred Ecks
 * @author David Mendenhall
 *
 * @since       1.1
 */
public class EventQueue {
    private static final AtomicInteger threadInitNumber = new AtomicInteger(0);

    private static final int LOW_PRIORITY = 0;
    private static final int NORM_PRIORITY = 1;
    private static final int HIGH_PRIORITY = 2;
    private static final int ULTIMATE_PRIORITY = 3;

    private static final int NUM_PRIORITIES = ULTIMATE_PRIORITY + 1;

    /*
     * We maintain one Queue for each priority that the EventQueue supports.
     * That is, the EventQueue object is actually implemented as
     * NUM_PRIORITIES queues and all Events on a particular internal Queue
     * have identical priority. Events are pulled off the EventQueue starting
     * with the Queue of highest priority. We progress in decreasing order
     * across all Queues.
     */
    private Queue[] queues = new Queue[NUM_PRIORITIES];

    /*
     * The next EventQueue on the stack, or null if this EventQueue is
     * on the top of the stack.  If nextQueue is non-null, requests to post
     * an event are forwarded to nextQueue.
     */
    private EventQueue nextQueue;

    /*
     * The previous EventQueue on the stack, or null if this is the
     * "base" EventQueue.
     */
    private EventQueue previousQueue;

    /*
     * A single lock to synchronize the push()/pop() and related operations with
     * all the EventQueues from the AppContext. Synchronization on any particular
     * event queue(s) is not enough: we should lock the whole stack.
     */
    private final Lock pushPopLock;
    private final Condition pushPopCond;

    /*
     * Dummy runnable to wake up EDT from getNextEvent() after
     push/pop is performed
     */
    private final static Runnable dummyRunnable = new Runnable() {
        public void run() {
        }
    };

    private EventDispatchThread dispatchThread;

    private final ThreadGroup threadGroup =
        Thread.currentThread().getThreadGroup();
    private final ClassLoader classLoader =
        Thread.currentThread().getContextClassLoader();

    /*
     * The time stamp of the last dispatched InputEvent or ActionEvent.
     */
    private long mostRecentEventTime = System.currentTimeMillis();

    /*
     * The time stamp of the last KeyEvent .
     */
    private long mostRecentKeyEventTime = System.currentTimeMillis();

    
The modifiers field of the current event, if the current event is an
InputEvent or ActionEvent.
/**
     * The modifiers field of the current event, if the current event is an
     * InputEvent or ActionEvent.
     */
    private WeakReference<AWTEvent> currentEvent;

    /*
     * Non-zero if a thread is waiting in getNextEvent(int) for an event of
     * a particular ID to be posted to the queue.
     */
    private volatile int waitForID;

    /*
     * AppContext corresponding to the queue.
     */
    private final AppContext appContext;

    private final String name = "AWT-EventQueue-" + threadInitNumber.getAndIncrement();

    private FwDispatcher fwDispatcher;

    private static volatile PlatformLogger eventLog;

    private static final PlatformLogger getEventLog() {
        if(eventLog == null) {
            eventLog = PlatformLogger.getLogger("java.awt.event.EventQueue");
        }
        return eventLog;
    }

    static {
        AWTAccessor.setEventQueueAccessor(
            new AWTAccessor.EventQueueAccessor() {
                public Thread getDispatchThread(EventQueue eventQueue) {
                    return eventQueue.getDispatchThread();
                }
                public boolean isDispatchThreadImpl(EventQueue eventQueue) {
                    return eventQueue.isDispatchThreadImpl();
                }
                public void removeSourceEvents(EventQueue eventQueue,
                                               Object source,
                                               boolean removeAllEvents)
                {
                    eventQueue.removeSourceEvents(source, removeAllEvents);
                }
                public boolean noEvents(EventQueue eventQueue) {
                    return eventQueue.noEvents();
                }
                public void wakeup(EventQueue eventQueue, boolean isShutdown) {
                    eventQueue.wakeup(isShutdown);
                }
                public void invokeAndWait(Object source, Runnable r)
                    throws InterruptedException, InvocationTargetException
                {
                    EventQueue.invokeAndWait(source, r);
                }
                public void setFwDispatcher(EventQueue eventQueue,
                                            FwDispatcher dispatcher) {
                    eventQueue.setFwDispatcher(dispatcher);
                }

                @Override
                public long getMostRecentEventTime(EventQueue eventQueue) {
                    return eventQueue.getMostRecentEventTimeImpl();
                }
            });
    }

    public EventQueue() {
        for (int i = 0; i < NUM_PRIORITIES; i++) {
            queues[i] = new Queue();
        }
        /*
         * NOTE: if you ever have to start the associated event dispatch
         * thread at this point, be aware of the following problem:
         * If this EventQueue instance is created in
         * SunToolkit.createNewAppContext() the started dispatch thread
         * may call AppContext.getAppContext() before createNewAppContext()
         * completes thus causing mess in thread group to appcontext mapping.
         */

        appContext = AppContext.getAppContext();
        pushPopLock = (Lock)appContext.get(AppContext.EVENT_QUEUE_LOCK_KEY);
        pushPopCond = (Condition)appContext.get(AppContext.EVENT_QUEUE_COND_KEY);
    }

    
Posts a 1.1-style event to the EventQueue.
If there is an existing event on the queue with the same ID
and event source, the source Component's
coalesceEvents method will be called.
Params:
theEvent – an instance of java.awt.AWTEvent,
         or a subclass of it
Throws:
NullPointerException – if theEvent is null/**
     * Posts a 1.1-style event to the <code>EventQueue</code>.
     * If there is an existing event on the queue with the same ID
     * and event source, the source <code>Component</code>'s
     * <code>coalesceEvents</code> method will be called.
     *
     * @param theEvent an instance of <code>java.awt.AWTEvent</code>,
     *          or a subclass of it
     * @throws NullPointerException if <code>theEvent</code> is <code>null</code>
     */
    public void postEvent(AWTEvent theEvent) {
        SunToolkit.flushPendingEvents(appContext);
        postEventPrivate(theEvent);
    }

    
Posts a 1.1-style event to the EventQueue.
If there is an existing event on the queue with the same ID
and event source, the source Component's
coalesceEvents method will be called.
Params:
theEvent – an instance of java.awt.AWTEvent,
         or a subclass of it/**
     * Posts a 1.1-style event to the <code>EventQueue</code>.
     * If there is an existing event on the queue with the same ID
     * and event source, the source <code>Component</code>'s
     * <code>coalesceEvents</code> method will be called.
     *
     * @param theEvent an instance of <code>java.awt.AWTEvent</code>,
     *          or a subclass of it
     */
    private final void postEventPrivate(AWTEvent theEvent) {
        theEvent.isPosted = true;
        pushPopLock.lock();
        try {
            if (nextQueue != null) {
                // Forward the event to the top of EventQueue stack
                nextQueue.postEventPrivate(theEvent);
                return;
            }
            if (dispatchThread == null) {
                if (theEvent.getSource() == AWTAutoShutdown.getInstance()) {
                    return;
                } else {
                    initDispatchThread();
                }
            }
            postEvent(theEvent, getPriority(theEvent));
        } finally {
            pushPopLock.unlock();
        }
    }

    private static int getPriority(AWTEvent theEvent) {
        if (theEvent instanceof PeerEvent) {
            PeerEvent peerEvent = (PeerEvent)theEvent;
            if ((peerEvent.getFlags() & PeerEvent.ULTIMATE_PRIORITY_EVENT) != 0) {
                return ULTIMATE_PRIORITY;
            }
            if ((peerEvent.getFlags() & PeerEvent.PRIORITY_EVENT) != 0) {
                return HIGH_PRIORITY;
            }
            if ((peerEvent.getFlags() & PeerEvent.LOW_PRIORITY_EVENT) != 0) {
                return LOW_PRIORITY;
            }
        }
        int id = theEvent.getID();
        if ((id >= PaintEvent.PAINT_FIRST) && (id <= PaintEvent.PAINT_LAST)) {
            return LOW_PRIORITY;
        }
        return NORM_PRIORITY;
    }

    
Posts the event to the internal Queue of specified priority,
coalescing as appropriate.
Params:
theEvent – an instance of java.awt.AWTEvent,
         or a subclass of it
priority –  the desired priority of the event/**
     * Posts the event to the internal Queue of specified priority,
     * coalescing as appropriate.
     *
     * @param theEvent an instance of <code>java.awt.AWTEvent</code>,
     *          or a subclass of it
     * @param priority  the desired priority of the event
     */
    private void postEvent(AWTEvent theEvent, int priority) {
        if (coalesceEvent(theEvent, priority)) {
            return;
        }

        EventQueueItem newItem = new EventQueueItem(theEvent);

        cacheEQItem(newItem);

        boolean notifyID = (theEvent.getID() == this.waitForID);

        if (queues[priority].head == null) {
            boolean shouldNotify = noEvents();
            queues[priority].head = queues[priority].tail = newItem;

            if (shouldNotify) {
                if (theEvent.getSource() != AWTAutoShutdown.getInstance()) {
                    AWTAutoShutdown.getInstance().notifyThreadBusy(dispatchThread);
                }
                pushPopCond.signalAll();
            } else if (notifyID) {
                pushPopCond.signalAll();
            }
        } else {
            // The event was not coalesced or has non-Component source.
            // Insert it at the end of the appropriate Queue.
            queues[priority].tail.next = newItem;
            queues[priority].tail = newItem;
            if (notifyID) {
                pushPopCond.signalAll();
            }
        }
    }

    private boolean coalescePaintEvent(PaintEvent e) {
        ComponentPeer sourcePeer = ((Component)e.getSource()).peer;
        if (sourcePeer != null) {
            sourcePeer.coalescePaintEvent(e);
        }
        EventQueueItem[] cache = ((Component)e.getSource()).eventCache;
        if (cache == null) {
            return false;
        }
        int index = eventToCacheIndex(e);

        if (index != -1 && cache[index] != null) {
            PaintEvent merged = mergePaintEvents(e, (PaintEvent)cache[index].event);
            if (merged != null) {
                cache[index].event = merged;
                return true;
            }
        }
        return false;
    }

    private PaintEvent mergePaintEvents(PaintEvent a, PaintEvent b) {
        Rectangle aRect = a.getUpdateRect();
        Rectangle bRect = b.getUpdateRect();
        if (bRect.contains(aRect)) {
            return b;
        }
        if (aRect.contains(bRect)) {
            return a;
        }
        return null;
    }

    private boolean coalesceMouseEvent(MouseEvent e) {
        EventQueueItem[] cache = ((Component)e.getSource()).eventCache;
        if (cache == null) {
            return false;
        }
        int index = eventToCacheIndex(e);
        if (index != -1 && cache[index] != null) {
            cache[index].event = e;
            return true;
        }
        return false;
    }

    private boolean coalescePeerEvent(PeerEvent e) {
        EventQueueItem[] cache = ((Component)e.getSource()).eventCache;
        if (cache == null) {
            return false;
        }
        int index = eventToCacheIndex(e);
        if (index != -1 && cache[index] != null) {
            e = e.coalesceEvents((PeerEvent)cache[index].event);
            if (e != null) {
                cache[index].event = e;
                return true;
            } else {
                cache[index] = null;
            }
        }
        return false;
    }

    /*
     * Should avoid of calling this method by any means
     * as it's working time is dependant on EQ length.
     * In the wors case this method alone can slow down the entire application
     * 10 times by stalling the Event processing.
     * Only here by backward compatibility reasons.
     */
    private boolean coalesceOtherEvent(AWTEvent e, int priority) {
        int id = e.getID();
        Component source = (Component)e.getSource();
        for (EventQueueItem entry = queues[priority].head;
            entry != null; entry = entry.next)
        {
            // Give Component.coalesceEvents a chance
            if (entry.event.getSource() == source && entry.event.getID() == id) {
                AWTEvent coalescedEvent = source.coalesceEvents(
                    entry.event, e);
                if (coalescedEvent != null) {
                    entry.event = coalescedEvent;
                    return true;
                }
            }
        }
        return false;
    }

    private boolean coalesceEvent(AWTEvent e, int priority) {
        if (!(e.getSource() instanceof Component)) {
            return false;
        }
        if (e instanceof PeerEvent) {
            return coalescePeerEvent((PeerEvent)e);
        }
        // The worst case
        if (((Component)e.getSource()).isCoalescingEnabled()
            && coalesceOtherEvent(e, priority))
        {
            return true;
        }
        if (e instanceof PaintEvent) {
            return coalescePaintEvent((PaintEvent)e);
        }
        if (e instanceof MouseEvent) {
            return coalesceMouseEvent((MouseEvent)e);
        }
        return false;
    }

    private void cacheEQItem(EventQueueItem entry) {
        int index = eventToCacheIndex(entry.event);
        if (index != -1 && entry.event.getSource() instanceof Component) {
            Component source = (Component)entry.event.getSource();
            if (source.eventCache == null) {
                source.eventCache = new EventQueueItem[CACHE_LENGTH];
            }
            source.eventCache[index] = entry;
        }
    }

    private void uncacheEQItem(EventQueueItem entry) {
        int index = eventToCacheIndex(entry.event);
        if (index != -1 && entry.event.getSource() instanceof Component) {
            Component source = (Component)entry.event.getSource();
            if (source.eventCache == null) {
                return;
            }
            source.eventCache[index] = null;
        }
    }

    private static final int PAINT = 0;
    private static final int UPDATE = 1;
    private static final int MOVE = 2;
    private static final int DRAG = 3;
    private static final int PEER = 4;
    private static final int CACHE_LENGTH = 5;

    private static int eventToCacheIndex(AWTEvent e) {
        switch(e.getID()) {
        case PaintEvent.PAINT:
            return PAINT;
        case PaintEvent.UPDATE:
            return UPDATE;
        case MouseEvent.MOUSE_MOVED:
            return MOVE;
        case MouseEvent.MOUSE_DRAGGED:
            // Return -1 for SunDropTargetEvent since they are usually synchronous
            // and we don't want to skip them by coalescing with MouseEvent or other drag events
            return e instanceof SunDropTargetEvent ? -1 : DRAG;
        default:
            return e instanceof PeerEvent ? PEER : -1;
        }
    }

    
Returns whether an event is pending on any of the separate
Queues.
Returns:
whether an event is pending on any of the separate Queues/**
     * Returns whether an event is pending on any of the separate
     * Queues.
     * @return whether an event is pending on any of the separate Queues
     */
    private boolean noEvents() {
        for (int i = 0; i < NUM_PRIORITIES; i++) {
            if (queues[i].head != null) {
                return false;
            }
        }

        return true;
    }

    
Removes an event from the EventQueue and
returns it.  This method will block until an event has
been posted by another thread.
Throws:
InterruptedException – 
           if any thread has interrupted this thread
Returns:
the next AWTEvent/**
     * Removes an event from the <code>EventQueue</code> and
     * returns it.  This method will block until an event has
     * been posted by another thread.
     * @return the next <code>AWTEvent</code>
     * @exception InterruptedException
     *            if any thread has interrupted this thread
     */
    public AWTEvent getNextEvent() throws InterruptedException {
        do {
            /*
             * SunToolkit.flushPendingEvents must be called outside
             * of the synchronized block to avoid deadlock when
             * event queues are nested with push()/pop().
             */
            SunToolkit.flushPendingEvents(appContext);
            pushPopLock.lock();
            try {
                AWTEvent event = getNextEventPrivate();
                if (event != null) {
                    return event;
                }
                AWTAutoShutdown.getInstance().notifyThreadFree(dispatchThread);
                pushPopCond.await();
            } finally {
                pushPopLock.unlock();
            }
        } while(true);
    }

    /*
     * Must be called under the lock. Doesn't call flushPendingEvents()
     */
    AWTEvent getNextEventPrivate() throws InterruptedException {
        for (int i = NUM_PRIORITIES - 1; i >= 0; i--) {
            if (queues[i].head != null) {
                EventQueueItem entry = queues[i].head;
                queues[i].head = entry.next;
                if (entry.next == null) {
                    queues[i].tail = null;
                }
                uncacheEQItem(entry);
                return entry.event;
            }
        }
        return null;
    }

    AWTEvent getNextEvent(int id) throws InterruptedException {
        do {
            /*
             * SunToolkit.flushPendingEvents must be called outside
             * of the synchronized block to avoid deadlock when
             * event queues are nested with push()/pop().
             */
            SunToolkit.flushPendingEvents(appContext);
            pushPopLock.lock();
            try {
                for (int i = 0; i < NUM_PRIORITIES; i++) {
                    for (EventQueueItem entry = queues[i].head, prev = null;
                         entry != null; prev = entry, entry = entry.next)
                    {
                        if (entry.event.getID() == id) {
                            if (prev == null) {
                                queues[i].head = entry.next;
                            } else {
                                prev.next = entry.next;
                            }
                            if (queues[i].tail == entry) {
                                queues[i].tail = prev;
                            }
                            uncacheEQItem(entry);
                            return entry.event;
                        }
                    }
                }
                waitForID = id;
                pushPopCond.await();
                waitForID = 0;
            } finally {
                pushPopLock.unlock();
            }
        } while(true);
    }

    
Returns the first event on the EventQueue
without removing it.
Returns:
the first event/**
     * Returns the first event on the <code>EventQueue</code>
     * without removing it.
     * @return the first event
     */
    public AWTEvent peekEvent() {
        pushPopLock.lock();
        try {
            for (int i = NUM_PRIORITIES - 1; i >= 0; i--) {
                if (queues[i].head != null) {
                    return queues[i].head.event;
                }
            }
        } finally {
            pushPopLock.unlock();
        }

        return null;
    }

    
Returns the first event with the specified id, if any.
Params:
id – the id of the type of event desired
Returns:
the first event of the specified id or null
   if there is no such event/**
     * Returns the first event with the specified id, if any.
     * @param id the id of the type of event desired
     * @return the first event of the specified id or <code>null</code>
     *    if there is no such event
     */
    public AWTEvent peekEvent(int id) {
        pushPopLock.lock();
        try {
            for (int i = NUM_PRIORITIES - 1; i >= 0; i--) {
                EventQueueItem q = queues[i].head;
                for (; q != null; q = q.next) {
                    if (q.event.getID() == id) {
                        return q.event;
                    }
                }
            }
        } finally {
            pushPopLock.unlock();
        }

        return null;
    }

    private static final JavaSecurityAccess javaSecurityAccess =
        SharedSecrets.getJavaSecurityAccess();

    
Dispatches an event. The manner in which the event is
dispatched depends upon the type of the event and the
type of the event's source object:


    
Event Type
    
Source Type
    
Dispatched To


    
ActiveEvent
    
Any
    
event.dispatch()


    
Other
    
Component
    
source.dispatchEvent(AWTEvent)


    
Other
    
MenuComponent
    
source.dispatchEvent(AWTEvent)


    
Other
    
Other
    
No action (ignored)



Params:
event – an instance of java.awt.AWTEvent,
         or a subclass of it
Throws:
NullPointerException – if event is null
Since:
          1.2/**
     * Dispatches an event. The manner in which the event is
     * dispatched depends upon the type of the event and the
     * type of the event's source object:
     *
     * <table border=1 summary="Event types, source types, and dispatch methods">
     * <tr>
     *     <th>Event Type</th>
     *     <th>Source Type</th>
     *     <th>Dispatched To</th>
     * </tr>
     * <tr>
     *     <td>ActiveEvent</td>
     *     <td>Any</td>
     *     <td>event.dispatch()</td>
     * </tr>
     * <tr>
     *     <td>Other</td>
     *     <td>Component</td>
     *     <td>source.dispatchEvent(AWTEvent)</td>
     * </tr>
     * <tr>
     *     <td>Other</td>
     *     <td>MenuComponent</td>
     *     <td>source.dispatchEvent(AWTEvent)</td>
     * </tr>
     * <tr>
     *     <td>Other</td>
     *     <td>Other</td>
     *     <td>No action (ignored)</td>
     * </tr>
     * </table>
     * <p>
     * @param event an instance of <code>java.awt.AWTEvent</code>,
     *          or a subclass of it
     * @throws NullPointerException if <code>event</code> is <code>null</code>
     * @since           1.2
     */
    protected void dispatchEvent(final AWTEvent event) {
        final Object src = event.getSource();
        final PrivilegedAction<Void> action = new PrivilegedAction<Void>() {
            public Void run() {
                // In case fwDispatcher is installed and we're already on the
                // dispatch thread (e.g. performing DefaultKeyboardFocusManager.sendMessage),
                // dispatch the event straight away.
                if (fwDispatcher == null || isDispatchThreadImpl()) {
                    dispatchEventImpl(event, src);
                } else {
                    fwDispatcher.scheduleDispatch(new Runnable() {
                        @Override
                        public void run() {
                            if (dispatchThread.filterAndCheckEvent(event)) {
                                dispatchEventImpl(event, src);
                            }
                        }
                    });
                }
                return null;
            }
        };

        final AccessControlContext stack = AccessController.getContext();
        final AccessControlContext srcAcc = getAccessControlContextFrom(src);
        final AccessControlContext eventAcc = event.getAccessControlContext();
        if (srcAcc == null) {
            javaSecurityAccess.doIntersectionPrivilege(action, stack, eventAcc);
        } else {
            javaSecurityAccess.doIntersectionPrivilege(
                new PrivilegedAction<Void>() {
                    public Void run() {
                        javaSecurityAccess.doIntersectionPrivilege(action, eventAcc);
                        return null;
                    }
                }, stack, srcAcc);
        }
    }

    private static AccessControlContext getAccessControlContextFrom(Object src) {
        return src instanceof Component ?
            ((Component)src).getAccessControlContext() :
            src instanceof MenuComponent ?
                ((MenuComponent)src).getAccessControlContext() :
                src instanceof TrayIcon ?
                    ((TrayIcon)src).getAccessControlContext() :
                    null;
    }

    
Called from dispatchEvent() under a correct AccessControlContext
/**
     * Called from dispatchEvent() under a correct AccessControlContext
     */
    private void dispatchEventImpl(final AWTEvent event, final Object src) {
        event.isPosted = true;
        if (event instanceof ActiveEvent) {
            // This could become the sole method of dispatching in time.
            setCurrentEventAndMostRecentTimeImpl(event);
            ((ActiveEvent)event).dispatch();
        } else if (src instanceof Component) {
            ((Component)src).dispatchEvent(event);
            event.dispatched();
        } else if (src instanceof MenuComponent) {
            ((MenuComponent)src).dispatchEvent(event);
        } else if (src instanceof TrayIcon) {
            ((TrayIcon)src).dispatchEvent(event);
        } else if (src instanceof AWTAutoShutdown) {
            if (noEvents()) {
                dispatchThread.stopDispatching();
            }
        } else {
            if (getEventLog().isLoggable(PlatformLogger.Level.FINE)) {
                getEventLog().fine("Unable to dispatch event: " + event);
            }
        }
    }

    
Returns the timestamp of the most recent event that had a timestamp, and
that was dispatched from the EventQueue associated with the
calling thread. If an event with a timestamp is currently being
dispatched, its timestamp will be returned. If no events have yet
been dispatched, the EventQueue's initialization time will be
returned instead.In the current version of
the JDK, only InputEvents,
ActionEvents, and InvocationEvents have timestamps; however, future versions of the JDK may add timestamps to additional event types. Note that this method should only be invoked from an application's event dispatching thread. If this method is invoked from another thread, the current system time (as reported by System.currentTimeMillis()) will be returned instead.
See Also:
InputEvent.getWhen
ActionEvent.getWhen
InvocationEvent.getWhen
isDispatchThread
Returns:
the timestamp of the last InputEvent,
        ActionEvent, or InvocationEvent to be
        dispatched, or System.currentTimeMillis() if this
        method is invoked on a thread other than an event dispatching
        thread
Since:
1.4/**
     * Returns the timestamp of the most recent event that had a timestamp, and
     * that was dispatched from the <code>EventQueue</code> associated with the
     * calling thread. If an event with a timestamp is currently being
     * dispatched, its timestamp will be returned. If no events have yet
     * been dispatched, the EventQueue's initialization time will be
     * returned instead.In the current version of
     * the JDK, only <code>InputEvent</code>s,
     * <code>ActionEvent</code>s, and <code>InvocationEvent</code>s have
     * timestamps; however, future versions of the JDK may add timestamps to
     * additional event types. Note that this method should only be invoked
     * from an application's {@link #isDispatchThread event dispatching thread}.
     * If this method is
     * invoked from another thread, the current system time (as reported by
     * <code>System.currentTimeMillis()</code>) will be returned instead.
     *
     * @return the timestamp of the last <code>InputEvent</code>,
     *         <code>ActionEvent</code>, or <code>InvocationEvent</code> to be
     *         dispatched, or <code>System.currentTimeMillis()</code> if this
     *         method is invoked on a thread other than an event dispatching
     *         thread
     * @see java.awt.event.InputEvent#getWhen
     * @see java.awt.event.ActionEvent#getWhen
     * @see java.awt.event.InvocationEvent#getWhen
     * @see #isDispatchThread
     *
     * @since 1.4
     */
    public static long getMostRecentEventTime() {
        return Toolkit.getEventQueue().getMostRecentEventTimeImpl();
    }
    private long getMostRecentEventTimeImpl() {
        pushPopLock.lock();
        try {
            return (Thread.currentThread() == dispatchThread)
                ? mostRecentEventTime
                : System.currentTimeMillis();
        } finally {
            pushPopLock.unlock();
        }
    }

    
Returns:
most recent event time on all threads./**
     * @return most recent event time on all threads.
     */
    long getMostRecentEventTimeEx() {
        pushPopLock.lock();
        try {
            return mostRecentEventTime;
        } finally {
            pushPopLock.unlock();
        }
    }

    
Returns the the event currently being dispatched by the
EventQueue associated with the calling thread. This is
useful if a method needs access to the event, but was not designed to
receive a reference to it as an argument. Note that this method should
only be invoked from an application's event dispatching thread. If this
method is invoked from another thread, null will be returned.
Returns:
the event currently being dispatched, or null if this method is
        invoked on a thread other than an event dispatching thread
Since:
1.4/**
     * Returns the the event currently being dispatched by the
     * <code>EventQueue</code> associated with the calling thread. This is
     * useful if a method needs access to the event, but was not designed to
     * receive a reference to it as an argument. Note that this method should
     * only be invoked from an application's event dispatching thread. If this
     * method is invoked from another thread, null will be returned.
     *
     * @return the event currently being dispatched, or null if this method is
     *         invoked on a thread other than an event dispatching thread
     * @since 1.4
     */
    public static AWTEvent getCurrentEvent() {
        return Toolkit.getEventQueue().getCurrentEventImpl();
    }
    private AWTEvent getCurrentEventImpl() {
        pushPopLock.lock();
        try {
                return (Thread.currentThread() == dispatchThread)
                ? currentEvent.get()
                : null;
        } finally {
            pushPopLock.unlock();
        }
    }

    
Replaces the existing EventQueue with the specified one.
Any pending events are transferred to the new EventQueue
for processing by it.
Params:
newEventQueue – an EventQueue
         (or subclass thereof) instance to be use
Throws:
NullPointerException – if newEventQueue is null
See Also:
pop
Since:
          1.2/**
     * Replaces the existing <code>EventQueue</code> with the specified one.
     * Any pending events are transferred to the new <code>EventQueue</code>
     * for processing by it.
     *
     * @param newEventQueue an <code>EventQueue</code>
     *          (or subclass thereof) instance to be use
     * @see      java.awt.EventQueue#pop
     * @throws NullPointerException if <code>newEventQueue</code> is <code>null</code>
     * @since           1.2
     */
    public void push(EventQueue newEventQueue) {
        if (getEventLog().isLoggable(PlatformLogger.Level.FINE)) {
            getEventLog().fine("EventQueue.push(" + newEventQueue + ")");
        }

        pushPopLock.lock();
        try {
            EventQueue topQueue = this;
            while (topQueue.nextQueue != null) {
                topQueue = topQueue.nextQueue;
            }
            if (topQueue.fwDispatcher != null) {
                throw new RuntimeException("push() to queue with fwDispatcher");
            }
            if ((topQueue.dispatchThread != null) &&
                (topQueue.dispatchThread.getEventQueue() == this))
            {
                newEventQueue.dispatchThread = topQueue.dispatchThread;
                topQueue.dispatchThread.setEventQueue(newEventQueue);
            }

            // Transfer all events forward to new EventQueue.
            while (topQueue.peekEvent() != null) {
                try {
                    // Use getNextEventPrivate() as it doesn't call flushPendingEvents()
                    newEventQueue.postEventPrivate(topQueue.getNextEventPrivate());
                } catch (InterruptedException ie) {
                    if (getEventLog().isLoggable(PlatformLogger.Level.FINE)) {
                        getEventLog().fine("Interrupted push", ie);
                    }
                }
            }

            if (topQueue.dispatchThread != null) {
                // Wake up EDT waiting in getNextEvent(), so it can
                // pick up a new EventQueue. Post the waking event before
                // topQueue.nextQueue is assigned, otherwise the event would
                // go newEventQueue
                topQueue.postEventPrivate(new InvocationEvent(topQueue, dummyRunnable));
            }

            newEventQueue.previousQueue = topQueue;
            topQueue.nextQueue = newEventQueue;

            if (appContext.get(AppContext.EVENT_QUEUE_KEY) == topQueue) {
                appContext.put(AppContext.EVENT_QUEUE_KEY, newEventQueue);
            }

            pushPopCond.signalAll();
        } finally {
            pushPopLock.unlock();
        }
    }

    
Stops dispatching events using this EventQueue.
Any pending events are transferred to the previous
EventQueue for processing.

Warning: To avoid deadlock, do not declare this method
synchronized in a subclass.
Throws:
EmptyStackException – if no previous push was made
 on this EventQueue
See Also:
push
Since:
          1.2/**
     * Stops dispatching events using this <code>EventQueue</code>.
     * Any pending events are transferred to the previous
     * <code>EventQueue</code> for processing.
     * <p>
     * Warning: To avoid deadlock, do not declare this method
     * synchronized in a subclass.
     *
     * @exception EmptyStackException if no previous push was made
     *  on this <code>EventQueue</code>
     * @see      java.awt.EventQueue#push
     * @since           1.2
     */
    protected void pop() throws EmptyStackException {
        if (getEventLog().isLoggable(PlatformLogger.Level.FINE)) {
            getEventLog().fine("EventQueue.pop(" + this + ")");
        }

        pushPopLock.lock();
        try {
            EventQueue topQueue = this;
            while (topQueue.nextQueue != null) {
                topQueue = topQueue.nextQueue;
            }
            EventQueue prevQueue = topQueue.previousQueue;
            if (prevQueue == null) {
                throw new EmptyStackException();
            }

            topQueue.previousQueue = null;
            prevQueue.nextQueue = null;

            // Transfer all events back to previous EventQueue.
            while (topQueue.peekEvent() != null) {
                try {
                    prevQueue.postEventPrivate(topQueue.getNextEventPrivate());
                } catch (InterruptedException ie) {
                    if (getEventLog().isLoggable(PlatformLogger.Level.FINE)) {
                        getEventLog().fine("Interrupted pop", ie);
                    }
                }
            }

            if ((topQueue.dispatchThread != null) &&
                (topQueue.dispatchThread.getEventQueue() == this))
            {
                prevQueue.dispatchThread = topQueue.dispatchThread;
                topQueue.dispatchThread.setEventQueue(prevQueue);
            }

            if (appContext.get(AppContext.EVENT_QUEUE_KEY) == this) {
                appContext.put(AppContext.EVENT_QUEUE_KEY, prevQueue);
            }

            // Wake up EDT waiting in getNextEvent(), so it can
            // pick up a new EventQueue
            topQueue.postEventPrivate(new InvocationEvent(topQueue, dummyRunnable));

            pushPopCond.signalAll();
        } finally {
            pushPopLock.unlock();
        }
    }

    
Creates a new secondary loop associated with this event queue. Use the SecondaryLoop.enter and SecondaryLoop.exit methods to start and stop the event loop and dispatch the events from this queue. 
See Also:
SecondaryLoop.enter
SecondaryLoop.exit
Returns:
secondaryLoop A new secondary loop object, which can
                      be used to launch a new nested event
                      loop and dispatch events from this queue
Since:
1.7/**
     * Creates a new {@code secondary loop} associated with this
     * event queue. Use the {@link SecondaryLoop#enter} and
     * {@link SecondaryLoop#exit} methods to start and stop the
     * event loop and dispatch the events from this queue.
     *
     * @return secondaryLoop A new secondary loop object, which can
     *                       be used to launch a new nested event
     *                       loop and dispatch events from this queue
     *
     * @see SecondaryLoop#enter
     * @see SecondaryLoop#exit
     *
     * @since 1.7
     */
    public SecondaryLoop createSecondaryLoop() {
        return createSecondaryLoop(null, null, 0);
    }

    private class FwSecondaryLoopWrapper implements SecondaryLoop {
        final private SecondaryLoop loop;
        final private EventFilter filter;

        public FwSecondaryLoopWrapper(SecondaryLoop loop, EventFilter filter) {
            this.loop = loop;
            this.filter = filter;
        }

        @Override
        public boolean enter() {
            if (filter != null) {
                dispatchThread.addEventFilter(filter);
            }
            return loop.enter();
        }

        @Override
        public boolean exit() {
            if (filter != null) {
                dispatchThread.removeEventFilter(filter);
            }
            return loop.exit();
        }
    }

    SecondaryLoop createSecondaryLoop(Conditional cond, EventFilter filter, long interval) {
        pushPopLock.lock();
        try {
            if (nextQueue != null) {
                // Forward the request to the top of EventQueue stack
                return nextQueue.createSecondaryLoop(cond, filter, interval);
            }
            if (fwDispatcher != null) {
                return new FwSecondaryLoopWrapper(fwDispatcher.createSecondaryLoop(), filter);
            }
            if (dispatchThread == null) {
                initDispatchThread();
            }
            return new WaitDispatchSupport(dispatchThread, cond, filter, interval);
        } finally {
            pushPopLock.unlock();
        }
    }

    
Returns true if the calling thread is the current AWT EventQueue's dispatch thread. Use this method to ensure that a particular task is being executed (or not being) there. 
 Note: use the invokeLater or invokeAndWait methods to execute a task in the current AWT EventQueue's dispatch thread. 

See Also:
invokeLater
invokeAndWait
Toolkit.getSystemEventQueue
Returns:
true if running in the current AWT EventQueue's dispatch thread
Since:
          1.2/**
     * Returns true if the calling thread is
     * {@link Toolkit#getSystemEventQueue the current AWT EventQueue}'s
     * dispatch thread. Use this method to ensure that a particular
     * task is being executed (or not being) there.
     * <p>
     * Note: use the {@link #invokeLater} or {@link #invokeAndWait}
     * methods to execute a task in
     * {@link Toolkit#getSystemEventQueue the current AWT EventQueue}'s
     * dispatch thread.
     * <p>
     *
     * @return true if running in
     * {@link Toolkit#getSystemEventQueue the current AWT EventQueue}'s
     * dispatch thread
     * @see             #invokeLater
     * @see             #invokeAndWait
     * @see             Toolkit#getSystemEventQueue
     * @since           1.2
     */
    public static boolean isDispatchThread() {
        EventQueue eq = Toolkit.getEventQueue();
        return eq.isDispatchThreadImpl();
    }

    final boolean isDispatchThreadImpl() {
        EventQueue eq = this;
        pushPopLock.lock();
        try {
            EventQueue next = eq.nextQueue;
            while (next != null) {
                eq = next;
                next = eq.nextQueue;
            }
            if (eq.fwDispatcher != null) {
                return eq.fwDispatcher.isDispatchThread();
            }
            return (Thread.currentThread() == eq.dispatchThread);
        } finally {
            pushPopLock.unlock();
        }
    }

    final void initDispatchThread() {
        pushPopLock.lock();
        try {
            if (dispatchThread == null && !threadGroup.isDestroyed() && !appContext.isDisposed()) {
                dispatchThread = AccessController.doPrivileged(
                    new PrivilegedAction<EventDispatchThread>() {
                        public EventDispatchThread run() {
                            EventDispatchThread t =
                                new EventDispatchThread(threadGroup,
                                                        name,
                                                        EventQueue.this);
                            t.setContextClassLoader(classLoader);
                            t.setPriority(Thread.NORM_PRIORITY + 1);
                            t.setDaemon(false);
                            AWTAutoShutdown.getInstance().notifyThreadBusy(t);
                            return t;
                        }
                    }
                );
                dispatchThread.start();
            }
        } finally {
            pushPopLock.unlock();
        }
    }

    final void detachDispatchThread(EventDispatchThread edt) {
        /*
         * Minimize discard possibility for non-posted events
         */
        SunToolkit.flushPendingEvents(appContext);
        /*
         * This synchronized block is to secure that the event dispatch
         * thread won't die in the middle of posting a new event to the
         * associated event queue. It is important because we notify
         * that the event dispatch thread is busy after posting a new event
         * to its queue, so the EventQueue.dispatchThread reference must
         * be valid at that point.
         */
        pushPopLock.lock();
        try {
            if (edt == dispatchThread) {
                dispatchThread = null;
            }
            AWTAutoShutdown.getInstance().notifyThreadFree(edt);
            /*
             * Event was posted after EDT events pumping had stopped, so start
             * another EDT to handle this event
             */
            if (peekEvent() != null) {
                initDispatchThread();
            }
        } finally {
            pushPopLock.unlock();
        }
    }

    /*
     * Gets the <code>EventDispatchThread</code> for this
     * <code>EventQueue</code>.
     * @return the event dispatch thread associated with this event queue
     *         or <code>null</code> if this event queue doesn't have a
     *         working thread associated with it
     * @see    java.awt.EventQueue#initDispatchThread
     * @see    java.awt.EventQueue#detachDispatchThread
     */
    final EventDispatchThread getDispatchThread() {
        pushPopLock.lock();
        try {
            return dispatchThread;
        } finally {
            pushPopLock.unlock();
        }
    }

    /*
     * Removes any pending events for the specified source object.
     * If removeAllEvents parameter is <code>true</code> then all
     * events for the specified source object are removed, if it
     * is <code>false</code> then <code>SequencedEvent</code>, <code>SentEvent</code>,
     * <code>FocusEvent</code>, <code>WindowEvent</code>, <code>KeyEvent</code>,
     * and <code>InputMethodEvent</code> are kept in the queue, but all other
     * events are removed.
     *
     * This method is normally called by the source's
     * <code>removeNotify</code> method.
     */
    final void removeSourceEvents(Object source, boolean removeAllEvents) {
        SunToolkit.flushPendingEvents(appContext);
        pushPopLock.lock();
        try {
            for (int i = 0; i < NUM_PRIORITIES; i++) {
                EventQueueItem entry = queues[i].head;
                EventQueueItem prev = null;
                while (entry != null) {
                    if ((entry.event.getSource() == source)
                        && (removeAllEvents
                            || ! (entry.event instanceof SequencedEvent
                                  || entry.event instanceof SentEvent
                                  || entry.event instanceof FocusEvent
                                  || entry.event instanceof WindowEvent
                                  || entry.event instanceof KeyEvent
                                  || entry.event instanceof InputMethodEvent)))
                    {
                        if (entry.event instanceof SequencedEvent) {
                            ((SequencedEvent)entry.event).dispose();
                        }
                        if (entry.event instanceof SentEvent) {
                            ((SentEvent)entry.event).dispose();
                        }
                        if (entry.event instanceof InvocationEvent) {
                            AWTAccessor.getInvocationEventAccessor()
                                    .dispose((InvocationEvent)entry.event);
                        }
                        if (prev == null) {
                            queues[i].head = entry.next;
                        } else {
                            prev.next = entry.next;
                        }
                        uncacheEQItem(entry);
                    } else {
                        prev = entry;
                    }
                    entry = entry.next;
                }
                queues[i].tail = prev;
            }
        } finally {
            pushPopLock.unlock();
        }
    }

    synchronized long getMostRecentKeyEventTime() {
        pushPopLock.lock();
        try {
            return mostRecentKeyEventTime;
        } finally {
            pushPopLock.unlock();
        }
    }

    static void setCurrentEventAndMostRecentTime(AWTEvent e) {
        Toolkit.getEventQueue().setCurrentEventAndMostRecentTimeImpl(e);
    }
    private void setCurrentEventAndMostRecentTimeImpl(AWTEvent e) {
        pushPopLock.lock();
        try {
            if (Thread.currentThread() != dispatchThread) {
                return;
            }

            currentEvent = new WeakReference<>(e);

            // This series of 'instanceof' checks should be replaced with a
            // polymorphic type (for example, an interface which declares a
            // getWhen() method). However, this would require us to make such
            // a type public, or to place it in sun.awt. Both of these approaches
            // have been frowned upon. So for now, we hack.
            //
            // In tiger, we will probably give timestamps to all events, so this
            // will no longer be an issue.
            long mostRecentEventTime2 = Long.MIN_VALUE;
            if (e instanceof InputEvent) {
                InputEvent ie = (InputEvent)e;
                mostRecentEventTime2 = ie.getWhen();
                if (e instanceof KeyEvent) {
                    mostRecentKeyEventTime = ie.getWhen();
                }
            } else if (e instanceof InputMethodEvent) {
                InputMethodEvent ime = (InputMethodEvent)e;
                mostRecentEventTime2 = ime.getWhen();
            } else if (e instanceof ActionEvent) {
                ActionEvent ae = (ActionEvent)e;
                mostRecentEventTime2 = ae.getWhen();
            } else if (e instanceof InvocationEvent) {
                InvocationEvent ie = (InvocationEvent)e;
                mostRecentEventTime2 = ie.getWhen();
            }
            mostRecentEventTime = Math.max(mostRecentEventTime, mostRecentEventTime2);
        } finally {
            pushPopLock.unlock();
        }
    }

    
Causes runnable to have its run method called in the dispatch thread of the system EventQueue. This will happen after all pending events are processed. 
Params:
runnable –  the Runnable whose run method should be executed asynchronously in the event dispatch thread of the system EventQueue
See Also:
invokeAndWait
Toolkit.getSystemEventQueue
isDispatchThread
Since:
          1.2/**
     * Causes <code>runnable</code> to have its <code>run</code>
     * method called in the {@link #isDispatchThread dispatch thread} of
     * {@link Toolkit#getSystemEventQueue the system EventQueue}.
     * This will happen after all pending events are processed.
     *
     * @param runnable  the <code>Runnable</code> whose <code>run</code>
     *                  method should be executed
     *                  asynchronously in the
     *                  {@link #isDispatchThread event dispatch thread}
     *                  of {@link Toolkit#getSystemEventQueue the system EventQueue}
     * @see             #invokeAndWait
     * @see             Toolkit#getSystemEventQueue
     * @see             #isDispatchThread
     * @since           1.2
     */
    public static void invokeLater(Runnable runnable) {
        Toolkit.getEventQueue().postEvent(
            new InvocationEvent(Toolkit.getDefaultToolkit(), runnable));
    }

    
Causes runnable to have its run method called in the dispatch thread of the system EventQueue. This will happen after all pending events are processed. The call blocks until this has happened. This method will throw an Error if called from the event dispatcher thread. 
Params:
runnable –  the Runnable whose run method should be executed synchronously in the event dispatch thread of the system EventQueue
Throws:
InterruptedException –  if any thread has
                 interrupted this thread
InvocationTargetException –  if an throwable is thrown
                 when running runnable
See Also:
invokeLater
Toolkit.getSystemEventQueue
isDispatchThread
Since:
          1.2/**
     * Causes <code>runnable</code> to have its <code>run</code>
     * method called in the {@link #isDispatchThread dispatch thread} of
     * {@link Toolkit#getSystemEventQueue the system EventQueue}.
     * This will happen after all pending events are processed.
     * The call blocks until this has happened.  This method
     * will throw an Error if called from the
     * {@link #isDispatchThread event dispatcher thread}.
     *
     * @param runnable  the <code>Runnable</code> whose <code>run</code>
     *                  method should be executed
     *                  synchronously in the
     *                  {@link #isDispatchThread event dispatch thread}
     *                  of {@link Toolkit#getSystemEventQueue the system EventQueue}
     * @exception       InterruptedException  if any thread has
     *                  interrupted this thread
     * @exception       InvocationTargetException  if an throwable is thrown
     *                  when running <code>runnable</code>
     * @see             #invokeLater
     * @see             Toolkit#getSystemEventQueue
     * @see             #isDispatchThread
     * @since           1.2
     */
    public static void invokeAndWait(Runnable runnable)
        throws InterruptedException, InvocationTargetException
    {
        invokeAndWait(Toolkit.getDefaultToolkit(), runnable);
    }

    static void invokeAndWait(Object source, Runnable runnable)
        throws InterruptedException, InvocationTargetException
    {
        if (EventQueue.isDispatchThread()) {
            throw new Error("Cannot call invokeAndWait from the event dispatcher thread");
        }

        class AWTInvocationLock {}
        Object lock = new AWTInvocationLock();

        InvocationEvent event =
            new InvocationEvent(source, runnable, lock, true);

        synchronized (lock) {
            Toolkit.getEventQueue().postEvent(event);
            while (!event.isDispatched()) {
                lock.wait();
            }
        }

        Throwable eventThrowable = event.getThrowable();
        if (eventThrowable != null) {
            throw new InvocationTargetException(eventThrowable);
        }
    }

    /*
     * Called from PostEventQueue.postEvent to notify that a new event
     * appeared. First it proceeds to the EventQueue on the top of the
     * stack, then notifies the associated dispatch thread if it exists
     * or starts a new one otherwise.
     */
    private void wakeup(boolean isShutdown) {
        pushPopLock.lock();
        try {
            if (nextQueue != null) {
                // Forward call to the top of EventQueue stack.
                nextQueue.wakeup(isShutdown);
            } else if (dispatchThread != null) {
                pushPopCond.signalAll();
            } else if (!isShutdown) {
                initDispatchThread();
            }
        } finally {
            pushPopLock.unlock();
        }
    }

    // The method is used by AWTAccessor for javafx/AWT single threaded mode.
    private void setFwDispatcher(FwDispatcher dispatcher) {
        if (nextQueue != null) {
            nextQueue.setFwDispatcher(dispatcher);
        } else {
            fwDispatcher = dispatcher;
        }
    }
}

The Queue object holds pointers to the beginning and end of one internal
queue. An EventQueue object is composed of multiple internal Queues, one
for each priority supported by the EventQueue. All Events on a particular
internal Queue have identical priority.
/**
 * The Queue object holds pointers to the beginning and end of one internal
 * queue. An EventQueue object is composed of multiple internal Queues, one
 * for each priority supported by the EventQueue. All Events on a particular
 * internal Queue have identical priority.
 */
class Queue {
    EventQueueItem head;
    EventQueueItem tail;
}