1 /*
2 * Copyright (c) 2000, 2014, 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 public AWTEvent create(AWTEvent event) {
68 return new SequencedEvent(event);
69 }
70 });
71 }
72
73 /**
74 * Constructs a new SequencedEvent which will dispatch the specified
75 * nested event.
76 *
77 * @param nested the AWTEvent which this SequencedEvent's dispatch()
78 * method will dispatch
79 */
80 public SequencedEvent(AWTEvent nested) {
81 super(nested.getSource(), ID);
82 this.nested = nested;
83 // All AWTEvents that are wrapped in SequencedEvents are (at
84 // least currently) implicitly generated by the system
85 SunToolkit.setSystemGenerated(nested);
86 synchronized (SequencedEvent.class) {
87 list.add(this);
88 }
89 }
90
91 /**
92 * Dispatches the nested event after all previous nested events have been
93 * dispatched or disposed. If this method is invoked before all previous nested events
94 * have been dispatched, then this method blocks until such a point is
95 * reached.
96 * While waiting disposes nested events to disposed AppContext
97 *
98 * NOTE: Locking protocol. Since dispose() can get EventQueue lock,
99 * dispatch() shall never call dispose() while holding the lock on the list,
100 * as EventQueue lock is held during dispatching. The locks should be acquired
101 * in the same order.
102 */
103 public final void dispatch() {
104 try {
105 appContext = AppContext.getAppContext();
106
107 if (getFirst() != this) {
108 if (EventQueue.isDispatchThread()) {
109 EventDispatchThread edt = (EventDispatchThread)
110 Thread.currentThread();
111 edt.pumpEvents(SentEvent.ID, new Conditional() {
112 public boolean evaluate() {
113 return !SequencedEvent.this.isFirstOrDisposed();
114 }
115 });
116 } else {
117 while(!isFirstOrDisposed()) {
118 synchronized (SequencedEvent.class) {
119 try {
120 SequencedEvent.class.wait(1000);
121 } catch (InterruptedException e) {
122 break;
123 }
124 }
125 }
126 }
127 }
128
129 if (!disposed) {
130 KeyboardFocusManager.getCurrentKeyboardFocusManager().
131 setCurrentSequencedEvent(this);
132 Toolkit.getEventQueue().dispatchEvent(nested);
133 }
134 } finally {
135 dispose();
136 }
137 }
138
139 /**
140 * true only if event exists and nested source appContext is disposed.
141 */
142 private static final boolean isOwnerAppContextDisposed(SequencedEvent se) {
143 if (se != null) {
144 Object target = se.nested.getSource();
145 if (target instanceof Component) {
146 return ((Component)target).appContext.isDisposed();
147 }
148 }
149 return false;
150 }
151
152 /**
153 * Sequenced events are dispatched in order, so we cannot dispatch
154 * until we are the first sequenced event in the queue (i.e. it's our
155 * turn). But while we wait for our turn to dispatch, the event
156 * could have been disposed for a number of reasons.
157 */
158 public final boolean isFirstOrDisposed() {
159 if (disposed) {
160 return true;
161 }
162 // getFirstWithContext can dispose this
163 return this == getFirstWithContext() || disposed;
164 }
165
166 private static final synchronized SequencedEvent getFirst() {
167 return list.getFirst();
168 }
169
170 /* Disposes all events from disposed AppContext
171 * return first valid event
172 */
173 private static final SequencedEvent getFirstWithContext() {
174 SequencedEvent first = getFirst();
175 while(isOwnerAppContextDisposed(first)) {
176 first.dispose();
177 first = getFirst();
178 }
179 return first;
180 }
181
182 /**
183 * Disposes of this instance. This method is invoked once the nested event
184 * has been dispatched and handled, or when the peer of the target of the
185 * nested event has been disposed with a call to Component.removeNotify.
186 *
187 * NOTE: Locking protocol. Since SunToolkit.postEvent can get EventQueue lock,
188 * it shall never be called while holding the lock on the list,
189 * as EventQueue lock is held during dispatching and dispatch() will get
190 * lock on the list. The locks should be acquired in the same order.
191 */
192 final void dispose() {
193 synchronized (SequencedEvent.class) {
194 if (disposed) {
195 return;
196 }
197 if (KeyboardFocusManager.getCurrentKeyboardFocusManager().
198 getCurrentSequencedEvent() == this) {
199 KeyboardFocusManager.getCurrentKeyboardFocusManager().
200 setCurrentSequencedEvent(null);
201 }
202 disposed = true;
203 }
204 // Wake myself up
205 if (appContext != null) {
206 SunToolkit.postEvent(appContext, new SentEvent());
207 }
208
209 SequencedEvent next = null;
210
211 synchronized (SequencedEvent.class) {
212 SequencedEvent.class.notifyAll();
213
214 if (list.getFirst() == this) {
215 list.removeFirst();
216
217 if (!list.isEmpty()) {
218 next = list.getFirst();
219 }
220 } else {
221 list.remove(this);
222 }
223 }
224 // Wake up waiting threads
225 if (next != null && next.appContext != null) {
226 SunToolkit.postEvent(next.appContext, new SentEvent());
227 }
228 }
229 }