1 /*
2 * Copyright (c) 2002, 2018, 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 com.sun.java.accessibility.util;
27
28 import java.util.*;
29 import java.beans.*;
30 import java.awt.*;
31 import java.awt.event.*;
32 import javax.accessibility.*;
33
34 /**
35 * <P>{@code AccessibilityEventMonitor} implements a PropertyChange listener
36 * on every UI object that implements interface {@code Accessible} in the Java
37 * Virtual Machine. The events captured by these listeners are made available
38 * through listeners supported by {@code AccessibilityEventMonitor}.
39 * With this, all the individual events on each of the UI object
40 * instances are funneled into one set of PropertyChange listeners.
41 * <p>This class depends upon {@link EventQueueMonitor}, which provides the base
42 * level support for capturing the top-level containers as they are created.
43 *
44 */
45
46 public class AccessibilityEventMonitor {
47
48 // listeners
49 /**
50 * The current list of registered {@link java.beans.PropertyChangeListener
51 * PropertyChangeListener} classes.
52 *
53 * @see #addPropertyChangeListener
54 * @see #removePropertyChangeListener
55 */
56 static protected final AccessibilityListenerList listenerList =
57 new AccessibilityListenerList();
58
59
60 /**
61 * The actual listener that is installed on the component instances.
62 * This listener calls the other registered listeners when an event
63 * occurs. By doing things this way, the actual number of listeners
64 * installed on a component instance is drastically reduced.
65 */
66 static private final AccessibilityEventListener accessibilityListener =
67 new AccessibilityEventListener();
68
69 /**
70 * Adds the specified listener to receive all PropertyChange events on
71 * each UI object instance in the Java Virtual Machine as they occur.
72 * <P>Note: This listener is automatically added to all component
73 * instances created after this method is called. In addition, it
74 * is only added to UI object instances that support this listener type.
75 *
76 * @param l the listener to add
77 *
78 * @see #removePropertyChangeListener
79 */
80 static public void addPropertyChangeListener(PropertyChangeListener l) {
81 if (listenerList.getListenerCount(PropertyChangeListener.class) == 0) {
82 accessibilityListener.installListeners();
83 }
84 listenerList.add(PropertyChangeListener.class, l);
85 }
86
87 /**
88 * Removes the specified listener so it no longer receives PropertyChange
89 * events when they occur.
90 * @see #addPropertyChangeListener
91 * @param l the listener to remove
92 */
93 static public void removePropertyChangeListener(PropertyChangeListener l) {
94 listenerList.remove(PropertyChangeListener.class, l);
95 if (listenerList.getListenerCount(PropertyChangeListener.class) == 0) {
96 accessibilityListener.removeListeners();
97 }
98 }
99
100
101 /**
102 * AccessibilityEventListener is the class that does all the work for
103 * AccessibilityEventMonitor. It is not intended for use by any other
104 * class except AccessibilityEventMonitor.
105 *
106 */
107
108 static class AccessibilityEventListener implements TopLevelWindowListener,
109 PropertyChangeListener {
110
111 /**
112 * Create a new instance of this class and install it on each component
113 * instance in the virtual machine that supports any of the currently
114 * registered listeners in AccessibilityEventMonitor. Also registers
115 * itself as a TopLevelWindowListener with EventQueueMonitor so it can
116 * automatically add new listeners to new components.
117 * @see EventQueueMonitor
118 * @see AccessibilityEventMonitor
119 */
120 public AccessibilityEventListener() {
121 EventQueueMonitor.addTopLevelWindowListener(this);
122 }
123
124 /**
125 * Installs PropertyChange listeners on all Accessible objects based
126 * upon the current topLevelWindows cached by EventQueueMonitor.
127 * @see EventQueueMonitor
128 * @see AWTEventMonitor
129 */
130 protected void installListeners() {
131 Window[] topLevelWindows = EventQueueMonitor.getTopLevelWindows();
132 if (topLevelWindows != null) {
133 for (int i = 0; i < topLevelWindows.length; i++) {
134 if (topLevelWindows[i] instanceof Accessible) {
135 installListeners((Accessible) topLevelWindows[i]);
136 }
137 }
138 }
139 }
140
141 /**
142 * Installs PropertyChange listeners to the Accessible object, and it's
143 * children (so long as the object isn't of TRANSIENT state).
144 * @param a the Accessible object to add listeners to
145 */
146 protected void installListeners(Accessible a) {
147 installListeners(a.getAccessibleContext());
148 }
149
150 /**
151 * Installs PropertyChange listeners to the AccessibleContext object,
152 * and it's * children (so long as the object isn't of TRANSIENT state).
153 * @param a the Accessible object to add listeners to
154 */
155 private void installListeners(AccessibleContext ac) {
156
157 if (ac != null) {
158 AccessibleStateSet states = ac.getAccessibleStateSet();
159 if (!states.contains(AccessibleState.TRANSIENT)) {
160 ac.addPropertyChangeListener(this);
161 /*
162 * Don't add listeners to transient children. Components
163 * with transient children should return an AccessibleStateSet
164 * containing AccessibleState.MANAGES_DESCENDANTS. Components
165 * may not explicitly return the MANAGES_DESCENDANTS state.
166 * In this case, don't add listeners to the children of
167 * lists, tables and trees.
168 */
169 AccessibleStateSet set = ac.getAccessibleStateSet();
170 if (set.contains(_AccessibleState.MANAGES_DESCENDANTS)) {
171 return;
172 }
173 AccessibleRole role = ac.getAccessibleRole();
174 if (role == AccessibleRole.LIST ||
175 role == AccessibleRole.TREE) {
176 return;
177 }
178 if (role == AccessibleRole.TABLE) {
179 // handle Oracle tables containing tables
180 Accessible child = ac.getAccessibleChild(0);
181 if (child != null) {
182 AccessibleContext ac2 = child.getAccessibleContext();
183 if (ac2 != null) {
184 role = ac2.getAccessibleRole();
185 if (role != null && role != AccessibleRole.TABLE) {
186 return;
187 }
188 }
189 }
190 }
191 int count = ac.getAccessibleChildrenCount();
192 for (int i = 0; i < count; i++) {
193 Accessible child = ac.getAccessibleChild(i);
194 if (child != null) {
195 installListeners(child);
196 }
197 }
198 }
199 }
200 }
201
202 /**
203 * Removes PropertyChange listeners on all Accessible objects based
204 * upon the topLevelWindows cached by EventQueueMonitor.
205 * @param eventID the event ID
206 * @see EventID
207 */
208 protected void removeListeners() {
209 Window[] topLevelWindows = EventQueueMonitor.getTopLevelWindows();
210 if (topLevelWindows != null) {
211 for (int i = 0; i < topLevelWindows.length; i++) {
212 if (topLevelWindows[i] instanceof Accessible) {
213 removeListeners((Accessible) topLevelWindows[i]);
214 }
215 }
216 }
217 }
218
219 /**
220 * Removes PropertyChange listeners for the given Accessible object,
221 * it's children (so long as the object isn't of TRANSIENT state).
222 * @param a the Accessible object to remove listeners from
223 */
224 protected void removeListeners(Accessible a) {
225 removeListeners(a.getAccessibleContext());
226 }
227
228 /**
229 * Removes PropertyChange listeners for the given AccessibleContext
230 * object, it's children (so long as the object isn't of TRANSIENT
231 * state).
232 * @param a the Accessible object to remove listeners from
233 */
234 private void removeListeners(AccessibleContext ac) {
235
236
237 if (ac != null) {
238 // Listeners are not added to transient components.
239 AccessibleStateSet states = ac.getAccessibleStateSet();
240 if (!states.contains(AccessibleState.TRANSIENT)) {
241 ac.removePropertyChangeListener(this);
242 /*
243 * Listeners are not added to transient children. Components
244 * with transient children should return an AccessibleStateSet
245 * containing AccessibleState.MANAGES_DESCENDANTS. Components
246 * may not explicitly return the MANAGES_DESCENDANTS state.
247 * In this case, don't remove listeners from the children of
248 * lists, tables and trees.
249 */
250 if (states.contains(_AccessibleState.MANAGES_DESCENDANTS)) {
251 return;
252 }
253 AccessibleRole role = ac.getAccessibleRole();
254 if (role == AccessibleRole.LIST ||
255 role == AccessibleRole.TABLE ||
256 role == AccessibleRole.TREE) {
257 return;
258 }
259 int count = ac.getAccessibleChildrenCount();
260 for (int i = 0; i < count; i++) {
261 Accessible child = ac.getAccessibleChild(i);
262 if (child != null) {
263 removeListeners(child);
264 }
265 }
266 }
267 }
268 }
269
270 /********************************************************************/
271 /* */
272 /* Listener Interface Methods */
273 /* */
274 /********************************************************************/
275
276 /* TopLevelWindow Methods ***************************************/
277
278 /**
279 * Called when top level window is created.
280 * @see EventQueueMonitor
281 * @see EventQueueMonitor#addTopLevelWindowListener
282 */
283 public void topLevelWindowCreated(Window w) {
284 if (w instanceof Accessible) {
285 installListeners((Accessible) w);
286 }
287 }
288
289 /**
290 * Called when top level window is destroyed.
291 * @see EventQueueMonitor
292 * @see EventQueueMonitor#addTopLevelWindowListener
293 */
294 public void topLevelWindowDestroyed(Window w) {
295 if (w instanceof Accessible) {
296 removeListeners((Accessible) w);
297 }
298 }
299
300
301 /* PropertyChangeListener Methods **************************************/
302
303 public void propertyChange(PropertyChangeEvent e) {
304 // propogate the event
305 Object[] listeners =
306 AccessibilityEventMonitor.listenerList.getListenerList();
307 for (int i = listeners.length-2; i>=0; i-=2) {
308 if (listeners[i]==PropertyChangeListener.class) {
309 ((PropertyChangeListener)listeners[i+1]).propertyChange(e);
310 }
311 }
312
313 // handle childbirth/death
314 String name = e.getPropertyName();
315 if (name.compareTo(AccessibleContext.ACCESSIBLE_CHILD_PROPERTY) == 0) {
316 Object oldValue = e.getOldValue();
317 Object newValue = e.getNewValue();
318
319 if ((oldValue == null) ^ (newValue == null)) { // one null, not both
320 if (oldValue != null) {
321 // this Accessible is a child that's going away
322 if (oldValue instanceof Accessible) {
323 Accessible a = (Accessible) oldValue;
324 removeListeners(a.getAccessibleContext());
325 } else if (oldValue instanceof AccessibleContext) {
326 removeListeners((AccessibleContext) oldValue);
327 }
328 } else if (newValue != null) {
329 // this Accessible is a child was just born
330 if (newValue instanceof Accessible) {
331 Accessible a = (Accessible) newValue;
332 installListeners(a.getAccessibleContext());
333 } else if (newValue instanceof AccessibleContext) {
334 installListeners((AccessibleContext) newValue);
335 }
336 }
337 } else {
338 System.out.println("ERROR in usage of PropertyChangeEvents for: " + e.toString());
339 }
340 }
341 }
342 }
343 }
344
345 /*
346 * workaround for no public AccessibleState constructor
347 */
348 class _AccessibleState extends AccessibleState {
349 /**
350 * Indicates this object is responsible for managing its
351 * subcomponents. This is typically used for trees and tables
352 * that have a large number of subcomponents and where the
353 * objects are created only when needed and otherwise remain virtual.
354 * The application should not manage the subcomponents directly.
355 */
356 public static final _AccessibleState MANAGES_DESCENDANTS
357 = new _AccessibleState ("managesDescendants");
358
359 /**
360 * Creates a new AccessibleState using the given locale independent key.
361 * This should not be a public method. Instead, it is used to create
362 * the constants in this file to make it a strongly typed enumeration.
363 * Subclasses of this class should enforce similar policy.
364 * <p>
365 * The key String should be a locale independent key for the state.
366 * It is not intended to be used as the actual String to display
367 * to the user. To get the localized string, use toDisplayString.
368 *
369 * @param key the locale independent name of the state.
370 * @see AccessibleBundle#toDisplayString
371 */
372 protected _AccessibleState(String key) {
373 super(key);
374 }
375 }