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659 lines
20 KiB
Java
659 lines
20 KiB
Java
/* EventQueue.java --
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Copyright (C) 1999, 2000, 2001, 2002, 2003, 2005 Free Software Foundation
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.awt;
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import gnu.java.awt.LowPriorityEvent;
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import gnu.java.awt.peer.NativeEventLoopRunningEvent;
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import java.awt.event.ActionEvent;
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import java.awt.event.InputEvent;
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import java.awt.event.InputMethodEvent;
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import java.awt.event.InvocationEvent;
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import java.awt.event.PaintEvent;
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import java.awt.peer.ComponentPeer;
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import java.awt.peer.LightweightPeer;
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import java.lang.reflect.InvocationTargetException;
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import java.util.EmptyStackException;
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/* Written using on-line Java 2 Platform Standard Edition v1.3 API
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* Specification, as well as "The Java Class Libraries", 2nd edition
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* (Addison-Wesley, 1998).
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* Status: Believed complete, but untested.
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*/
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/**
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* This class manages a queue of <code>AWTEvent</code> objects that
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* are posted to it. The AWT system uses only one event queue for all
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* events.
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*
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* @author Bryce McKinlay
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* @author Aaron M. Renn (arenn@urbanophile.com)
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*/
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public class EventQueue
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{
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/**
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* Indicates events that are processed with normal priority. This is normally
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* all events except PaintEvents.
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*/
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private static final int NORM_PRIORITY = 0;
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/**
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* Indicates events that are processed with lowes priority. This is normally
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* all PaintEvents and LowPriorityEvents.
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*/
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private static final int LOW_PRIORITY = 1;
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/**
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* Implements the actual queue. EventQueue has 2 internal queues for
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* different priorities:
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* 1 PaintEvents are always dispatched with low priority.
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* 2. All other events are dispatched with normal priority.
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*
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* This makes sure that the actual painting (output) is performed _after_ all
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* available input has been processed and that the paint regions are
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* coalesced as much as possible.
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*/
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private class Queue
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{
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/**
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* The first item in the queue. This is where events are popped from.
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*/
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AWTEvent queueHead;
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/**
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* The last item. This is where events are posted to.
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*/
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AWTEvent queueTail;
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}
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/**
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* The three internal event queues.
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*
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* @see Queue
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*/
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private Queue[] queues;
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private EventQueue next;
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private EventQueue prev;
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private AWTEvent currentEvent;
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private long lastWhen = System.currentTimeMillis();
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private EventDispatchThread dispatchThread = new EventDispatchThread(this);
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private boolean nativeLoopRunning = false;
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private boolean isShutdown ()
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{
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// This is the exact self-shutdown condition specified in J2SE:
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// http://java.sun.com/j2se/1.4.2/docs/api/java/awt/doc-files/AWTThreadIssues.html
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if (nativeLoopRunning)
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return false;
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if (peekEvent() != null)
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return false;
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if (Frame.hasDisplayableFrames())
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return false;
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return true;
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}
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/**
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* Initializes a new instance of <code>EventQueue</code>.
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*/
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public EventQueue()
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{
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queues = new Queue[2];
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queues[NORM_PRIORITY] = new Queue();
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queues[LOW_PRIORITY] = new Queue();
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}
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/**
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* Returns the next event in the queue. This method will block until
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* an event is available or until the thread is interrupted.
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*
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* @return The next event in the queue.
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*
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* @exception InterruptedException If this thread is interrupted while
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* waiting for an event to be posted to the queue.
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*/
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public synchronized AWTEvent getNextEvent()
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throws InterruptedException
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{
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if (next != null)
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return next.getNextEvent();
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AWTEvent res = getNextEventImpl(true);
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while (res == null)
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{
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if (isShutdown())
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{
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// Explicitly set dispathThread to null. If we don't do
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// this, there is a race condition where dispatchThread
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// can be != null even after the event dispatch thread has
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// stopped running. If that happens, then the
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// dispatchThread == null check in postEventImpl will
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// fail, and a new event dispatch thread will not be
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// created, leaving invokeAndWaits waiting indefinitely.
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dispatchThread = null;
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// Interrupt the event dispatch thread.
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throw new InterruptedException();
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}
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wait();
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res = getNextEventImpl(true);
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}
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return res;
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}
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/**
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* Fetches and possibly removes the next event from the internal queues.
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* This method returns immediately. When all queues are empty, this returns
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* <code>null</code>:
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*
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* @param remove <true> when the event should be removed from the queue,
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* <code>false</code> otherwise
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*
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* @return the next event or <code>null</code> when all internal queues
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* are empty
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*/
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private AWTEvent getNextEventImpl(boolean remove)
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{
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AWTEvent next = null;
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for (int i = 0; i < queues.length && next == null; i++)
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{
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Queue q = queues[i];
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if (q.queueHead != null)
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{
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// Got an event, remove it.
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next = q.queueHead;
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if (remove)
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{
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// Unlink event from the queue.
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q.queueHead = next.queueNext;
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if (q.queueHead == null)
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q.queueTail = null;
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next.queueNext = null;
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}
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}
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}
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return next;
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}
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/**
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* Returns the next event in the queue without removing it from the queue.
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* This method will block until an event is available or until the thread
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* is interrupted.
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*
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* @return The next event in the queue.
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* @specnote Does not block. Returns null if there are no events on the
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* queue.
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*/
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public synchronized AWTEvent peekEvent()
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{
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if (next != null)
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return next.peekEvent();
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return getNextEventImpl(false);
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}
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/**
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* Returns the next event in the queue that has the specified id
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* without removing it from the queue.
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* This method will block until an event is available or until the thread
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* is interrupted.
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*
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* @param id The event id to return.
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*
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* @return The next event in the queue.
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*
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* @specnote Does not block. Returns null if there are no matching events
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* on the queue.
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*/
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public synchronized AWTEvent peekEvent(int id)
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{
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if (next != null)
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return next.peekEvent(id);
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AWTEvent evt = null;
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for (int i = 0; i < queues.length && evt == null; i++)
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{
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Queue q = queues[i];
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evt = q.queueHead;
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while (evt != null && evt.id != id)
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evt = evt.queueNext;
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// At this point we either have found an event (evt != null -> exit
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// for loop), or we have found no event (evt == null -> search next
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// internal queue).
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}
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return evt;
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}
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/**
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* Posts a new event to the queue.
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*
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* @param evt The event to post to the queue.
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*
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* @exception NullPointerException If event is null.
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*/
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public void postEvent(AWTEvent evt)
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{
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postEventImpl(evt);
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}
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/**
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* Sorts events to their priority and calls
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* {@link #postEventImpl(AWTEvent, int)}.
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*
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* @param evt the event to post
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*/
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private synchronized final void postEventImpl(AWTEvent evt)
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{
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int priority = NORM_PRIORITY;
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if (evt instanceof PaintEvent || evt instanceof LowPriorityEvent)
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priority = LOW_PRIORITY;
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// TODO: Maybe let Swing RepaintManager events also be processed with
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// low priority.
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if (evt instanceof NativeEventLoopRunningEvent)
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{
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nativeLoopRunning = ((NativeEventLoopRunningEvent) evt).isRunning();
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notify();
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return;
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}
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postEventImpl(evt, priority);
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}
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/**
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* Actually performs the event posting. This is needed because the
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* RI doesn't use the public postEvent() method when transferring events
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* between event queues in push() and pop().
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*
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* @param evt the event to post
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* @param priority the priority of the event
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*/
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private final void postEventImpl(AWTEvent evt, int priority)
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{
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if (evt == null)
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throw new NullPointerException();
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if (next != null)
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{
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next.postEvent(evt);
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return;
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}
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Object source = evt.getSource();
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Queue q = queues[priority];
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if (source instanceof Component)
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{
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// For PaintEvents, ask the ComponentPeer to coalesce the event
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// when the component is heavyweight.
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Component comp = (Component) source;
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ComponentPeer peer = comp.peer;
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if (peer != null && evt instanceof PaintEvent
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&& ! (peer instanceof LightweightPeer))
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peer.coalescePaintEvent((PaintEvent) evt);
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// Check for any events already on the queue with the same source
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// and ID.
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AWTEvent previous = null;
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for (AWTEvent qevt = q.queueHead; qevt != null; qevt = qevt.queueNext)
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{
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Object src = qevt.getSource();
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if (qevt.id == evt.id && src == comp)
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{
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// If there are, call coalesceEvents on the source component
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// to see if they can be combined.
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Component srccmp = (Component) src;
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AWTEvent coalescedEvt = srccmp.coalesceEvents(qevt, evt);
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if (coalescedEvt != null)
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{
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// Yes. Replace the existing event with the combined event.
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if (qevt != coalescedEvt)
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{
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if (previous != null)
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{
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assert previous.queueNext == qevt;
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previous.queueNext = coalescedEvt;
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}
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else
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{
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assert q.queueHead == qevt;
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q.queueHead = coalescedEvt;
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}
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coalescedEvt.queueNext = qevt.queueNext;
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if (q.queueTail == qevt)
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q.queueTail = coalescedEvt;
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qevt.queueNext = null;
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}
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return;
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}
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}
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previous = qevt;
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}
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}
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if (q.queueHead == null)
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{
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// We have an empty queue. Set this event both as head and as tail.
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q.queueHead = evt;
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q.queueTail = evt;
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}
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else
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{
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// Note: queueTail should not be null here.
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q.queueTail.queueNext = evt;
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q.queueTail = evt;
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}
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if (dispatchThread == null || !dispatchThread.isAlive())
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{
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dispatchThread = new EventDispatchThread(this);
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dispatchThread.start();
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}
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notify();
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}
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/**
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* Causes runnable to have its run method called in the dispatch thread of the
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* EventQueue. This will happen after all pending events are processed. The
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* call blocks until this has happened. This method will throw an Error if
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* called from the event dispatcher thread.
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*
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* @exception InterruptedException If another thread has interrupted
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* this thread.
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* @exception InvocationTargetException If an exception is thrown when running
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* runnable.
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*
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* @since 1.2
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*/
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public static void invokeAndWait(Runnable runnable)
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throws InterruptedException, InvocationTargetException
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{
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if (isDispatchThread ())
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throw new Error("Can't call invokeAndWait from event dispatch thread");
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EventQueue eq = Toolkit.getDefaultToolkit().getSystemEventQueue();
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Object notifyObject = new Object();
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InvocationEvent ie =
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new InvocationEvent(eq, runnable, notifyObject, true);
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synchronized (notifyObject)
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{
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eq.postEvent(ie);
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notifyObject.wait();
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}
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Exception exception;
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if ((exception = ie.getException()) != null)
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throw new InvocationTargetException(exception);
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}
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/**
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* This arranges for runnable to have its run method called in the
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* dispatch thread of the EventQueue. This will happen after all
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* pending events are processed.
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*
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* @since 1.2
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*/
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public static void invokeLater(Runnable runnable)
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{
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EventQueue eq = Toolkit.getDefaultToolkit().getSystemEventQueue();
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InvocationEvent ie =
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new InvocationEvent(eq, runnable, null, false);
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eq.postEvent(ie);
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}
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/**
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* Return true if the current thread is the current AWT event dispatch
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* thread.
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*/
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public static boolean isDispatchThread()
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{
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EventQueue eq = Toolkit.getDefaultToolkit().getSystemEventQueue();
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/* Find last EventQueue in chain */
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while (eq.next != null)
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eq = eq.next;
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return (Thread.currentThread() == eq.dispatchThread);
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}
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/**
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* Return the event currently being dispatched by the event
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* dispatch thread. If the current thread is not the event
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* dispatch thread, this method returns null.
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*
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* @since 1.4
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*/
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public static AWTEvent getCurrentEvent()
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{
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EventQueue eq = Toolkit.getDefaultToolkit().getSystemEventQueue();
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Thread ct = Thread.currentThread();
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/* Find out if this thread is the dispatch thread for any of the
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EventQueues in the chain */
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while (ct != eq.dispatchThread)
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{
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// Try next EventQueue, if any
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if (eq.next == null)
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return null; // Not an event dispatch thread
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eq = eq.next;
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}
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return eq.currentEvent;
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}
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/**
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* Allows a custom EventQueue implementation to replace this one.
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* All pending events are transferred to the new queue. Calls to postEvent,
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* getNextEvent, and peekEvent and others are forwarded to the pushed queue
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* until it is removed with a pop().
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*
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* @exception NullPointerException if newEventQueue is null.
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*/
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public synchronized void push(EventQueue newEventQueue)
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{
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if (newEventQueue == null)
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throw new NullPointerException ();
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/* Make sure we are at the top of the stack because callers can
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only get a reference to the one at the bottom using
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Toolkit.getDefaultToolkit().getSystemEventQueue() */
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if (next != null)
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{
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next.push (newEventQueue);
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return;
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}
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/* Make sure we have a live dispatch thread to drive the queue */
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if (dispatchThread == null)
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dispatchThread = new EventDispatchThread(this);
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synchronized (newEventQueue)
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{
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// The RI transfers the events without calling the new eventqueue's
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// push(), but using getNextEvent().
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while (peekEvent() != null)
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{
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try
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{
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newEventQueue.postEventImpl(getNextEvent());
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}
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catch (InterruptedException ex)
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{
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// What should we do with this?
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ex.printStackTrace();
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}
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}
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newEventQueue.prev = this;
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}
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next = newEventQueue;
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}
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/** Transfer any pending events from this queue back to the parent queue that
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* was previously push()ed. Event dispatch from this queue is suspended.
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*
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* @exception EmptyStackException If no previous push was made on this
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* EventQueue.
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*/
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protected void pop() throws EmptyStackException
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{
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/* The order is important here, we must get the prev lock first,
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or deadlock could occur as callers usually get here following
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prev's next pointer, and thus obtain prev's lock before trying
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to get this lock. */
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EventQueue previous = prev;
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if (previous == null)
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throw new EmptyStackException();
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synchronized (previous)
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{
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synchronized (this)
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{
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EventQueue nextQueue = next;
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if (nextQueue != null)
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{
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nextQueue.pop();
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}
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else
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{
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previous.next = null;
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// The RI transfers the events without calling the new eventqueue's
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// push(), so this should be OK and most effective.
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while (peekEvent() != null)
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{
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try
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|
{
|
|
previous.postEventImpl(getNextEvent());
|
|
}
|
|
catch (InterruptedException ex)
|
|
{
|
|
// What should we do with this?
|
|
ex.printStackTrace();
|
|
}
|
|
}
|
|
prev = null;
|
|
// Tell our EventDispatchThread that it can end
|
|
// execution.
|
|
if (dispatchThread != null)
|
|
{
|
|
dispatchThread.interrupt();
|
|
dispatchThread = null;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* @exception NullPointerException If event is null.
|
|
*/
|
|
protected void dispatchEvent(AWTEvent evt)
|
|
{
|
|
currentEvent = evt;
|
|
|
|
if (evt instanceof InputEvent)
|
|
lastWhen = ((InputEvent) evt).getWhen();
|
|
else if (evt instanceof ActionEvent)
|
|
lastWhen = ((ActionEvent) evt).getWhen();
|
|
else if (evt instanceof InvocationEvent)
|
|
lastWhen = ((InvocationEvent) evt).getWhen();
|
|
|
|
if (evt instanceof ActiveEvent)
|
|
{
|
|
ActiveEvent active_evt = (ActiveEvent) evt;
|
|
active_evt.dispatch();
|
|
}
|
|
else
|
|
{
|
|
Object source = evt.getSource();
|
|
|
|
if (source instanceof Component)
|
|
{
|
|
Component srccmp = (Component) source;
|
|
srccmp.dispatchEvent(evt);
|
|
}
|
|
else if (source instanceof MenuComponent)
|
|
{
|
|
MenuComponent srccmp = (MenuComponent) source;
|
|
srccmp.dispatchEvent(evt);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns the timestamp of the most recent event that had a timestamp, or
|
|
* the initialization time of the event queue if no events have been fired.
|
|
* At present, only <code>InputEvent</code>s, <code>ActionEvent</code>s,
|
|
* <code>InputMethodEvent</code>s, and <code>InvocationEvent</code>s have
|
|
* timestamps, but this may be added to other events in future versions.
|
|
* If this is called by the event dispatching thread, it can be any
|
|
* (sequential) value, but to other threads, the safest bet is to return
|
|
* System.currentTimeMillis().
|
|
*
|
|
* @return the most recent timestamp
|
|
* @see InputEvent#getWhen()
|
|
* @see ActionEvent#getWhen()
|
|
* @see InvocationEvent#getWhen()
|
|
* @see InputMethodEvent#getWhen()
|
|
* @since 1.4
|
|
*/
|
|
public static long getMostRecentEventTime()
|
|
{
|
|
EventQueue eq = Toolkit.getDefaultToolkit().getSystemEventQueue();
|
|
if (Thread.currentThread() != eq.dispatchThread)
|
|
return System.currentTimeMillis();
|
|
return eq.lastWhen;
|
|
}
|
|
}
|