1 /*
   2  * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.awt;
  27 
  28 import java.util.LinkedList;
  29 import sun.awt.AWTAccessor;
  30 import sun.awt.AppContext;
  31 import sun.awt.SunToolkit;
  32 
  33 /**
  34  * A mechanism for ensuring that a series of AWTEvents are executed in a
  35  * precise order, even across multiple AppContexts. The nested events will be
  36  * dispatched in the order in which their wrapping SequencedEvents were
  37  * constructed. The only exception to this rule is if the peer of the target of
  38  * the nested event was destroyed (with a call to Component.removeNotify)
  39  * before the wrapping SequencedEvent was able to be dispatched. In this case,
  40  * the nested event is never dispatched.
  41  *
  42  * @author David Mendenhall
  43  */
  44 class SequencedEvent extends AWTEvent implements ActiveEvent {
  45     /*
  46      * serialVersionUID
  47      */
  48     private static final long serialVersionUID = 547742659238625067L;
  49 
  50     private static final int ID =
  51         java.awt.event.FocusEvent.FOCUS_LAST + 1;
  52     private static final LinkedList list = new LinkedList();
  53 
  54     private final AWTEvent nested;
  55     private AppContext appContext;
  56     private boolean disposed;
  57 
  58     static {
  59         AWTAccessor.setSequencedEventAccessor(new AWTAccessor.SequencedEventAccessor() {
  60             public AWTEvent getNested(AWTEvent sequencedEvent) {
  61                 return ((SequencedEvent)sequencedEvent).nested;
  62             }
  63             public boolean isSequencedEvent(AWTEvent event) {
  64                 return event instanceof SequencedEvent;
  65             }
  66         });
  67     }
  68 
  69     /**
  70      * Constructs a new SequencedEvent which will dispatch the specified
  71      * nested event.
  72      *
  73      * @param nested the AWTEvent which this SequencedEvent's dispatch()
  74      *        method will dispatch
  75      */
  76     public SequencedEvent(AWTEvent nested) {
  77         super(nested.getSource(), ID);
  78         this.nested = nested;
  79         // All AWTEvents that are wrapped in SequencedEvents are (at
  80         // least currently) implicitly generated by the system
  81         SunToolkit.setSystemGenerated(nested);
  82         synchronized (SequencedEvent.class) {
  83             list.add(this);
  84         }
  85     }
  86 
  87     /**
  88      * Dispatches the nested event after all previous nested events have been
  89      * dispatched or disposed. If this method is invoked before all previous nested events
  90      * have been dispatched, then this method blocks until such a point is
  91      * reached.
  92      * While waiting disposes nested events to disposed AppContext
  93      *
  94      * NOTE: Locking protocol.  Since dispose() can get EventQueue lock,
  95      * dispatch() shall never call dispose() while holding the lock on the list,
  96      * as EventQueue lock is held during dispatching.  The locks should be acquired
  97      * in the same order.
  98      */
  99     public final void dispatch() {
 100         try {
 101             appContext = AppContext.getAppContext();
 102 
 103             if (getFirst() != this) {
 104                 if (EventQueue.isDispatchThread()) {
 105                     EventDispatchThread edt = (EventDispatchThread)
 106                         Thread.currentThread();
 107                     edt.pumpEvents(SentEvent.ID, new Conditional() {
 108                         public boolean evaluate() {
 109                             return !SequencedEvent.this.isFirstOrDisposed();
 110                         }
 111                     });
 112                 } else {
 113                     while(!isFirstOrDisposed()) {
 114                         synchronized (SequencedEvent.class) {
 115                             try {
 116                                 SequencedEvent.class.wait(1000);
 117                             } catch (InterruptedException e) {
 118                                 break;
 119                             }
 120                         }
 121                     }
 122                 }
 123             }
 124 
 125             if (!disposed) {
 126                 KeyboardFocusManager.getCurrentKeyboardFocusManager().
 127                     setCurrentSequencedEvent(this);
 128                 Toolkit.getEventQueue().dispatchEvent(nested);
 129             }
 130         } finally {
 131             dispose();
 132         }
 133     }
 134 
 135     /**
 136      * true only if event exists and nested source appContext is disposed.
 137      */
 138     private final static boolean isOwnerAppContextDisposed(SequencedEvent se) {
 139         if (se != null) {
 140             Object target = se.nested.getSource();
 141             if (target instanceof Component) {
 142                 return ((Component)target).appContext.isDisposed();
 143             }
 144         }
 145         return false;
 146     }
 147 
 148     /**
 149      * Sequenced events are dispatched in order, so we cannot dispatch
 150      * until we are the first sequenced event in the queue (i.e. it's our
 151      * turn).  But while we wait for our turn to dispatch, the event
 152      * could have been disposed for a number of reasons.
 153      */
 154     public final boolean isFirstOrDisposed() {
 155         if (disposed) {
 156             return true;
 157         }
 158         // getFirstWithContext can dispose this
 159         return this == getFirstWithContext() || disposed;
 160     }
 161 
 162     private final synchronized static SequencedEvent getFirst() {
 163         return (SequencedEvent)list.getFirst();
 164     }
 165 
 166     /* Disposes all events from disposed AppContext
 167      * return first valid event
 168      */
 169     private final static SequencedEvent getFirstWithContext() {
 170         SequencedEvent first = getFirst();
 171         while(isOwnerAppContextDisposed(first)) {
 172             first.dispose();
 173             first = getFirst();
 174         }
 175         return first;
 176     }
 177 
 178     /**
 179      * Disposes of this instance. This method is invoked once the nested event
 180      * has been dispatched and handled, or when the peer of the target of the
 181      * nested event has been disposed with a call to Component.removeNotify.
 182      *
 183      * NOTE: Locking protocol.  Since SunToolkit.postEvent can get EventQueue lock,
 184      * it shall never be called while holding the lock on the list,
 185      * as EventQueue lock is held during dispatching and dispatch() will get
 186      * lock on the list. The locks should be acquired in the same order.
 187      */
 188     final void dispose() {
 189       synchronized (SequencedEvent.class) {
 190             if (disposed) {
 191                 return;
 192             }
 193             if (KeyboardFocusManager.getCurrentKeyboardFocusManager().
 194                     getCurrentSequencedEvent() == this) {
 195                 KeyboardFocusManager.getCurrentKeyboardFocusManager().
 196                     setCurrentSequencedEvent(null);
 197             }
 198             disposed = true;
 199         }
 200         // Wake myself up
 201         if (appContext != null) {
 202             SunToolkit.postEvent(appContext, new SentEvent());
 203         }
 204 
 205         SequencedEvent next = null;
 206 
 207         synchronized (SequencedEvent.class) {
 208           SequencedEvent.class.notifyAll();
 209 
 210           if (list.getFirst() == this) {
 211               list.removeFirst();
 212 
 213               if (!list.isEmpty()) {
 214                     next = (SequencedEvent)list.getFirst();
 215               }
 216           } else {
 217               list.remove(this);
 218           }
 219       }
 220         // Wake up waiting threads
 221         if (next != null && next.appContext != null) {
 222             SunToolkit.postEvent(next.appContext, new SentEvent());
 223         }
 224     }
 225 }
--- EOF ---