1 /* 2 * Copyright (c) 2000, 2013, 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<SequencedEvent> 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(ID, () -> !SequencedEvent.this.isFirstOrDisposed()); 108 } else { 109 while(!isFirstOrDisposed()) { 110 synchronized (SequencedEvent.class) { 111 try { 112 SequencedEvent.class.wait(1000); 113 } catch (InterruptedException e) { 114 break; 115 } 116 } 117 } 118 } 119 } 120 121 if (!disposed) { 122 KeyboardFocusManager.getCurrentKeyboardFocusManager(). 123 setCurrentSequencedEvent(this); 124 Toolkit.getEventQueue().dispatchEvent(nested); 125 } 126 } finally { 127 dispose(); 128 } 129 } 130 131 /** 132 * true only if event exists and nested source appContext is disposed. 133 */ 134 private final static boolean isOwnerAppContextDisposed(SequencedEvent se) { 135 if (se != null) { 136 Object target = se.nested.getSource(); 137 if (target instanceof Component) { 138 return ((Component)target).appContext.isDisposed(); 139 } 140 } 141 return false; 142 } 143 144 /** 145 * Sequenced events are dispatched in order, so we cannot dispatch 146 * until we are the first sequenced event in the queue (i.e. it's our 147 * turn). But while we wait for our turn to dispatch, the event 148 * could have been disposed for a number of reasons. 149 */ 150 public final boolean isFirstOrDisposed() { 151 if (disposed) { 152 return true; 153 } 154 // getFirstWithContext can dispose this 155 return this == getFirstWithContext() || disposed; 156 } 157 158 private final synchronized static SequencedEvent getFirst() { 159 return (SequencedEvent)list.getFirst(); 160 } 161 162 /* Disposes all events from disposed AppContext 163 * return first valid event 164 */ 165 private final static SequencedEvent getFirstWithContext() { 166 SequencedEvent first = getFirst(); 167 while(isOwnerAppContextDisposed(first)) { 168 first.dispose(); 169 first = getFirst(); 170 } 171 return first; 172 } 173 174 /** 175 * Disposes of this instance. This method is invoked once the nested event 176 * has been dispatched and handled, or when the peer of the target of the 177 * nested event has been disposed with a call to Component.removeNotify. 178 * 179 * NOTE: Locking protocol. Since SunToolkit.postEvent can get EventQueue lock, 180 * it shall never be called while holding the lock on the list, 181 * as EventQueue lock is held during dispatching and dispatch() will get 182 * lock on the list. The locks should be acquired in the same order. 183 */ 184 final void dispose() { 185 synchronized (SequencedEvent.class) { 186 if (disposed) { 187 return; 188 } 189 if (KeyboardFocusManager.getCurrentKeyboardFocusManager(). 190 getCurrentSequencedEvent() == this) { 191 KeyboardFocusManager.getCurrentKeyboardFocusManager(). 192 setCurrentSequencedEvent(null); 193 } 194 disposed = true; 195 } 196 // Wake myself up 197 if (appContext != null) { 198 SunToolkit.postEvent(appContext, new SentEvent()); 199 } 200 201 SequencedEvent next = null; 202 203 synchronized (SequencedEvent.class) { 204 SequencedEvent.class.notifyAll(); 205 206 if (list.getFirst() == this) { 207 list.removeFirst(); 208 209 if (!list.isEmpty()) { 210 next = (SequencedEvent)list.getFirst(); 211 } 212 } else { 213 list.remove(this); 214 } 215 } 216 // Wake up waiting threads 217 if (next != null && next.appContext != null) { 218 SunToolkit.postEvent(next.appContext, new SentEvent()); 219 } 220 } 221 }