1 /*
2 * Copyright (c) 2000, 2019, 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.Iterator;
29 import java.util.LinkedList;
30 import sun.awt.AWTAccessor;
31 import sun.awt.AppContext;
32 import sun.awt.SunToolkit;
33
34 /**
35 * A mechanism for ensuring that a series of AWTEvents are executed in a
36 * precise order, even across multiple AppContexts. The nested events will be
37 * dispatched in the order in which their wrapping SequencedEvents were
38 * constructed. The only exception to this rule is if the peer of the target of
39 * the nested event was destroyed (with a call to Component.removeNotify)
40 * before the wrapping SequencedEvent was able to be dispatched. In this case,
41 * the nested event is never dispatched.
42 *
43 * @author David Mendenhall
44 */
45 class SequencedEvent extends AWTEvent implements ActiveEvent {
46 /*
47 * serialVersionUID
48 */
49 private static final long serialVersionUID = 547742659238625067L;
50
51 private static final int ID =
52 java.awt.event.FocusEvent.FOCUS_LAST + 1;
53 private static final LinkedList<SequencedEvent> list = new LinkedList<>();
54
55 private final AWTEvent nested;
56 private AppContext appContext;
57 private boolean disposed;
58 private final LinkedList<AWTEvent> pendingEvents = new LinkedList<>();
59
60 static {
61 AWTAccessor.setSequencedEventAccessor(new AWTAccessor.SequencedEventAccessor() {
62 public AWTEvent getNested(AWTEvent sequencedEvent) {
63 return ((SequencedEvent)sequencedEvent).nested;
64 }
65 public boolean isSequencedEvent(AWTEvent event) {
66 return event instanceof SequencedEvent;
67 }
68 });
69 }
70
71 private static final class SequencedEventsFilter implements EventFilter {
72 private final SequencedEvent currentSequencedEvent;
73 private SequencedEventsFilter(SequencedEvent currentSequencedEvent) {
74 this.currentSequencedEvent = currentSequencedEvent;
75 }
76 @Override
77 public FilterAction acceptEvent(AWTEvent ev) {
78 if (ev.getID() == ID) {
79 // Move forward dispatching only if the event is previous
80 // in SequencedEvent.list. Otherwise, hold it for reposting later.
81 synchronized (SequencedEvent.class) {
82 Iterator<SequencedEvent> it = list.iterator();
83 while (it.hasNext()) {
84 SequencedEvent iev = it.next();
85 if (iev.equals(currentSequencedEvent)) {
86 break;
87 } else if (iev.equals(ev)) {
88 return FilterAction.ACCEPT;
89 }
90 }
91 }
92 } else if (ev.getID() == SentEvent.ID) {
93 return FilterAction.ACCEPT;
94 }
95 currentSequencedEvent.pendingEvents.add(ev);
96 return FilterAction.REJECT;
97 }
98 }
99
100 /**
101 * Constructs a new SequencedEvent which will dispatch the specified
102 * nested event.
103 *
104 * @param nested the AWTEvent which this SequencedEvent's dispatch()
105 * method will dispatch
106 */
107 public SequencedEvent(AWTEvent nested) {
108 super(nested.getSource(), ID);
109 this.nested = nested;
110 // All AWTEvents that are wrapped in SequencedEvents are (at
111 // least currently) implicitly generated by the system
112 SunToolkit.setSystemGenerated(nested);
113 synchronized (SequencedEvent.class) {
114 list.add(this);
115 }
116 }
117
118 /**
119 * Dispatches the nested event after all previous nested events have been
120 * dispatched or disposed. If this method is invoked before all previous nested events
121 * have been dispatched, then this method blocks until such a point is
122 * reached.
123 * While waiting disposes nested events to disposed AppContext
124 *
125 * NOTE: Locking protocol. Since dispose() can get EventQueue lock,
126 * dispatch() shall never call dispose() while holding the lock on the list,
127 * as EventQueue lock is held during dispatching. The locks should be acquired
128 * in the same order.
129 */
130 public final void dispatch() {
131 try {
132 appContext = AppContext.getAppContext();
133
134 if (getFirst() != this) {
135 if (EventQueue.isDispatchThread()) {
136 EventDispatchThread edt = (EventDispatchThread)
137 Thread.currentThread();
138 edt.pumpEventsForFilter(() -> !SequencedEvent.this.isFirstOrDisposed(),
139 new SequencedEventsFilter(this));
140 } else {
141 while(!isFirstOrDisposed()) {
142 synchronized (SequencedEvent.class) {
143 try {
144 SequencedEvent.class.wait(1000);
145 } catch (InterruptedException e) {
146 break;
147 }
148 }
149 }
150 }
151 }
152
153 if (!disposed) {
154 KeyboardFocusManager.getCurrentKeyboardFocusManager().
155 setCurrentSequencedEvent(this);
156 Toolkit.getEventQueue().dispatchEvent(nested);
157 }
158 } finally {
159 dispose();
160 }
161 }
162
163 /**
164 * true only if event exists and nested source appContext is disposed.
165 */
166 private final static boolean isOwnerAppContextDisposed(SequencedEvent se) {
167 if (se != null) {
168 Object target = se.nested.getSource();
169 if (target instanceof Component) {
170 return ((Component)target).appContext.isDisposed();
171 }
172 }
173 return false;
174 }
175
176 /**
177 * Sequenced events are dispatched in order, so we cannot dispatch
178 * until we are the first sequenced event in the queue (i.e. it's our
179 * turn). But while we wait for our turn to dispatch, the event
180 * could have been disposed for a number of reasons.
181 */
182 public final boolean isFirstOrDisposed() {
183 if (disposed) {
184 return true;
185 }
186 // getFirstWithContext can dispose this
187 return this == getFirstWithContext() || disposed;
188 }
189
190 private final synchronized static SequencedEvent getFirst() {
191 return (SequencedEvent)list.getFirst();
192 }
193
194 /* Disposes all events from disposed AppContext
195 * return first valid event
196 */
197 private final static SequencedEvent getFirstWithContext() {
198 SequencedEvent first = getFirst();
199 while(isOwnerAppContextDisposed(first)) {
200 first.dispose();
201 first = getFirst();
202 }
203 return first;
204 }
205
206 /**
207 * Disposes of this instance. This method is invoked once the nested event
208 * has been dispatched and handled, or when the peer of the target of the
209 * nested event has been disposed with a call to Component.removeNotify.
210 *
211 * NOTE: Locking protocol. Since SunToolkit.postEvent can get EventQueue lock,
212 * it shall never be called while holding the lock on the list,
213 * as EventQueue lock is held during dispatching and dispatch() will get
214 * lock on the list. The locks should be acquired in the same order.
215 */
216 final void dispose() {
217 synchronized (SequencedEvent.class) {
218 if (disposed) {
219 return;
220 }
221 if (KeyboardFocusManager.getCurrentKeyboardFocusManager().
222 getCurrentSequencedEvent() == this) {
223 KeyboardFocusManager.getCurrentKeyboardFocusManager().
224 setCurrentSequencedEvent(null);
225 }
226 disposed = true;
227 }
228
229 SequencedEvent next = null;
230
231 synchronized (SequencedEvent.class) {
232 SequencedEvent.class.notifyAll();
233
234 if (list.getFirst() == this) {
235 list.removeFirst();
236
237 if (!list.isEmpty()) {
238 next = (SequencedEvent)list.getFirst();
239 }
240 } else {
241 list.remove(this);
242 }
243 }
244 // Wake up waiting threads
245 if (next != null && next.appContext != null) {
246 SunToolkit.postEvent(next.appContext, new SentEvent());
247 }
248
249 for(AWTEvent e : pendingEvents) {
250 SunToolkit.postEvent(appContext, e);
251 }
252 }
253 }