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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.awt;

import java.util.Iterator;
import java.util.LinkedList;
import sun.awt.AWTAccessor;
import sun.awt.AppContext;
import sun.awt.SunToolkit;

/**
 * A mechanism for ensuring that a series of AWTEvents are executed in a
 * precise order, even across multiple AppContexts. The nested events will be
 * dispatched in the order in which their wrapping SequencedEvents were
 * constructed. The only exception to this rule is if the peer of the target of
 * the nested event was destroyed (with a call to Component.removeNotify)
 * before the wrapping SequencedEvent was able to be dispatched. In this case,
 * the nested event is never dispatched.
 *
 * @author David Mendenhall
 */
class SequencedEvent extends AWTEvent implements ActiveEvent {
 /*
 * serialVersionUID
 */
 private static final long serialVersionUID = 547742659238625067L;

 private static final int ID =
 java.awt.event.FocusEvent.FOCUS_LAST + 1;
 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;
 }
 public boolean isSequencedEvent(AWTEvent event) {
 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()
 * method will dispatch
 */
 public SequencedEvent(AWTEvent nested) {
 super(nested.getSource(), ID);
 this.nested = nested;
 // All AWTEvents that are wrapped in SequencedEvents are (at
 // least currently) implicitly generated by the system
 SunToolkit.setSystemGenerated(nested);
 synchronized (SequencedEvent.class) {
 list.add(this);
 }
 }

 /**
 * Dispatches the nested event after all previous nested events have been
 * dispatched or disposed. If this method is invoked before all previous nested events
 * have been dispatched, then this method blocks until such a point is
 * reached.
 * While waiting disposes nested events to disposed AppContext
 *
 * NOTE: Locking protocol. Since dispose() can get EventQueue lock,
 * dispatch() shall never call dispose() while holding the lock on the list,
 * as EventQueue lock is held during dispatching. The locks should be acquired
 * in the same order.
 */
 public final void dispatch() {
 try {
 appContext = AppContext.getAppContext();

 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);
 } catch (InterruptedException e) {
 break;
 }
 }
 }
 }
 }

 if (!disposed) {
 KeyboardFocusManager.getCurrentKeyboardFocusManager().
 setCurrentSequencedEvent(this);
 Toolkit.getEventQueue().dispatchEvent(nested);
 }
 } finally {
 dispose();
 }
 }

 /**
 * true only if event exists and nested source appContext is disposed.
 */
 private final static boolean isOwnerAppContextDisposed(SequencedEvent se) {
 if (se != null) {
 Object target = se.nested.getSource();
 if (target instanceof Component) {
 return ((Component)target).appContext.isDisposed();
 }
 }
 return false;
 }

 /**
 * Sequenced events are dispatched in order, so we cannot dispatch
 * until we are the first sequenced event in the queue (i.e. it's our
 * turn). But while we wait for our turn to dispatch, the event
 * could have been disposed for a number of reasons.
 */
 public final boolean isFirstOrDisposed() {
 if (disposed) {
 return true;
 }
 // getFirstWithContext can dispose this
 return this == getFirstWithContext() || disposed;
 }

 private final synchronized static SequencedEvent getFirst() {
 return (SequencedEvent)list.getFirst();
 }

 /* Disposes all events from disposed AppContext
 * return first valid event
 */
 private final static SequencedEvent getFirstWithContext() {
 SequencedEvent first = getFirst();
 while(isOwnerAppContextDisposed(first)) {
 first.dispose();
 first = getFirst();
 }
 return first;
 }

 /**
 * Disposes of this instance. This method is invoked once the nested event
 * has been dispatched and handled, or when the peer of the target of the
 * nested event has been disposed with a call to Component.removeNotify.
 *
 * NOTE: Locking protocol. Since SunToolkit.postEvent can get EventQueue lock,
 * it shall never be called while holding the lock on the list,
 * as EventQueue lock is held during dispatching and dispatch() will get
 * lock on the list. The locks should be acquired in the same order.
 */
 final void dispose() {
 synchronized (SequencedEvent.class) {
 if (disposed) {
 return;
 }
 if (KeyboardFocusManager.getCurrentKeyboardFocusManager().
 getCurrentSequencedEvent() == this) {
 KeyboardFocusManager.getCurrentKeyboardFocusManager().
 setCurrentSequencedEvent(null);
 }
 disposed = true;
 }

 SequencedEvent next = null;

 synchronized (SequencedEvent.class) {
 SequencedEvent.class.notifyAll();

 if (list.getFirst() == this) {
 list.removeFirst();

 if (!list.isEmpty()) {
 next = (SequencedEvent)list.getFirst();
 }
 } else {
 list.remove(this);
 }
 }
 // Wake up waiting threads
 if (next != null && next.appContext != null) {
 SunToolkit.postEvent(next.appContext, new SentEvent());
 }

 for(AWTEvent e : pendingEvents) {
 SunToolkit.postEvent(appContext, e);
 }
 }
}