src/share/classes/java/awt/SequencedEvent.java

rev 13428 : 8204142: AWT hang occurs when sequenced events arrive out of sequence in multiple AppContexts
Summary: Improvements on the synchronization of SequencedEvent events from different AppContexts
Reviewed-by: serb

*** 1,7 ****
  /*
!  * Copyright (c) 2000, 2013, 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
--- 1,7 ----
  /*
!  * Copyright (c) 2000, 2019, 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
*** 23,32 ****
--- 23,33 ----
   * questions.
   */
  
  package java.awt;
  
+ import java.util.Iterator;
  import java.util.LinkedList;
  import sun.awt.AWTAccessor;
  import sun.awt.AppContext;
  import sun.awt.SunToolkit;
  
*** 52,61 ****
--- 53,63 ----
      private static final LinkedList<SequencedEvent> list = new LinkedList<>();
  
      private final AWTEvent nested;
      private AppContext appContext;
      private boolean disposed;
+     private final LinkedList<AWTEvent> pendingEvents = new LinkedList<>();
  
      static {
          AWTAccessor.setSequencedEventAccessor(new AWTAccessor.SequencedEventAccessor() {
              public AWTEvent getNested(AWTEvent sequencedEvent) {
                  return ((SequencedEvent)sequencedEvent).nested;
*** 64,73 ****
--- 66,104 ----
                  return event instanceof SequencedEvent;
              }
          });
      }
  
+     private static final class SequencedEventsFilter implements EventFilter {
+         private final SequencedEvent currentSequencedEvent;
+         private SequencedEventsFilter(SequencedEvent currentSequencedEvent) {
+             this.currentSequencedEvent = currentSequencedEvent;
+         }
+         @Override
+         public FilterAction acceptEvent(AWTEvent ev) {
+             if (ev.getID() == ID) {
+                 // Move forward dispatching only if the event is previous
+                 // in SequencedEvent.list. Otherwise, hold it for reposting later.
+                 synchronized (SequencedEvent.class) {
+                     Iterator<SequencedEvent> it = list.iterator();
+                     while (it.hasNext()) {
+                         SequencedEvent iev = it.next();
+                         if (iev.equals(currentSequencedEvent)) {
+                             break;
+                         } else if (iev.equals(ev)) {
+                             return FilterAction.ACCEPT;
+                         }
+                     }
+                 }
+             } else if (ev.getID() == SentEvent.ID) {
+                 return FilterAction.ACCEPT;
+             }
+             currentSequencedEvent.pendingEvents.add(ev);
+             return FilterAction.REJECT;
+         }
+     }
+ 
      /**
       * Constructs a new SequencedEvent which will dispatch the specified
       * nested event.
       *
       * @param nested the AWTEvent which this SequencedEvent's dispatch()
*** 102,116 ****
  
              if (getFirst() != this) {
                  if (EventQueue.isDispatchThread()) {
                      EventDispatchThread edt = (EventDispatchThread)
                          Thread.currentThread();
!                     edt.pumpEvents(SentEvent.ID, new Conditional() {
!                         public boolean evaluate() {
!                             return !SequencedEvent.this.isFirstOrDisposed();
!                         }
!                     });
                  } else {
                      while(!isFirstOrDisposed()) {
                          synchronized (SequencedEvent.class) {
                              try {
                                  SequencedEvent.class.wait(1000);
--- 133,144 ----
  
              if (getFirst() != this) {
                  if (EventQueue.isDispatchThread()) {
                      EventDispatchThread edt = (EventDispatchThread)
                          Thread.currentThread();
!                     edt.pumpEventsForFilter(() -> !SequencedEvent.this.isFirstOrDisposed(),
!                             new SequencedEventsFilter(this));
                  } else {
                      while(!isFirstOrDisposed()) {
                          synchronized (SequencedEvent.class) {
                              try {
                                  SequencedEvent.class.wait(1000);
*** 195,208 ****
                  KeyboardFocusManager.getCurrentKeyboardFocusManager().
                      setCurrentSequencedEvent(null);
              }
              disposed = true;
          }
-         // Wake myself up
-         if (appContext != null) {
-             SunToolkit.postEvent(appContext, new SentEvent());
-         }
  
          SequencedEvent next = null;
  
          synchronized (SequencedEvent.class) {
            SequencedEvent.class.notifyAll();
--- 223,232 ----
*** 219,225 ****
--- 243,253 ----
        }
          // Wake up waiting threads
          if (next != null && next.appContext != null) {
              SunToolkit.postEvent(next.appContext, new SentEvent());
          }
+ 
+         for(AWTEvent e : pendingEvents) {
+             SunToolkit.postEvent(appContext, e);
+         }
      }
  }