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 }