001    /* AccessibleContext.java -- the context of an accessible object
002       Copyright (C) 2002 Free Software Foundation
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package javax.accessibility;
039    
040    import java.beans.PropertyChangeListener;
041    import java.beans.PropertyChangeSupport;
042    import java.util.Locale;
043    
044    /**
045     * The minimum information that all accessible objects return. This includes
046     * name, description, role, and state of the object, parents and children,
047     * and any other useful information. If a component supports further details,
048     * it should implement one of the following:<ul>
049     * <li>{@link AccessibleAction} - the object can perform actions</li>
050     * <li>{@link AccessibleComponent} - the object has a graphical
051     *     representation</li>
052     * <li>{@link AccessibleSelection} - the object allows its children to be
053     *     selected</li>
054     * <li>{@link AccessibleText} - the object represents editable text</li>
055     * <li>{@link AccessibleValue} - the object represents a numerical value</li>
056     * </ul>
057     *
058     * @author Eric Blake (ebb9@email.byu.edu)
059     * @since 1.2
060     * @status updated to 1.4
061     */
062    public abstract class AccessibleContext
063    {
064      /**
065       * Constant used when the accessible name has changed. Both the old and new
066       * values are listed in the event.
067       *
068       * @see #getAccessibleName()
069       * @see #addPropertyChangeListener(PropertyChangeListener)
070       */
071      public static final String ACCESSIBLE_NAME_PROPERTY
072        = "AccessibleName";
073    
074      /**
075       * Constant used when the accessible description has changed. Both the old
076       * and new values are listed in the event.
077       *
078       * @see #getAccessibleDescription()
079       * @see #addPropertyChangeListener(PropertyChangeListener)
080       */
081      public static final String ACCESSIBLE_DESCRIPTION_PROPERTY
082        = "AccessibleDescription";
083    
084      /**
085       * Constant used when the accessibleStateSet has changed. Both the old and
086       * new values are listed in the event, although either may be null if a
087       * state was disabled at that time.
088       *
089       * @see #getAccessibleStateSet()
090       * @see AccessibleState
091       * @see AccessibleStateSet
092       * @see #addPropertyChangeListener(PropertyChangeListener)
093       */
094      public static final String ACCESSIBLE_STATE_PROPERTY
095        = "AccessibleState";
096    
097      /**
098       * Constant used when the accessibleValue has changed. Both the old and new
099       * values are listed in the event.
100       *
101       * @see #getAccessibleValue()
102       * @see #addPropertyChangeListener(PropertyChangeListener)
103       */
104      public static final String ACCESSIBLE_VALUE_PROPERTY
105        = "AccessibleValue";
106    
107      /**
108       * Constant used when the accessibleSelection has changed. Both the old and
109       * new values of the event are reserved for future use.
110       *
111       * @see #getAccessibleSelection()
112       * @see #addPropertyChangeListener(PropertyChangeListener)
113       */
114      public static final String ACCESSIBLE_SELECTION_PROPERTY
115        = "AccessibleSelection";
116    
117      /**
118       * Constant used when the accessibleText has changed. Both the old and new
119       * values of the event are reserved for future use.
120       *
121       * @see #getAccessibleText()
122       * @see #addPropertyChangeListener(PropertyChangeListener)
123       */
124      public static final String ACCESSIBLE_TEXT_PROPERTY
125        = "AccessibleText";
126    
127      /**
128       * Constant used when the accessibleText caret has changed. Both the old and
129       * new values are listed in the event.
130       *
131       * @see #addPropertyChangeListener(PropertyChangeListener)
132       */
133      public static final String ACCESSIBLE_CARET_PROPERTY
134        = "AccessibleCaret";
135    
136      /**
137       * Constant used when the visible data has changed. Both the old and new
138       * values of the event are reserved for future use.
139       *
140       * @see #addPropertyChangeListener(PropertyChangeListener)
141       */
142      public static final String ACCESSIBLE_VISIBLE_DATA_PROPERTY
143        = "AccessibleVisibleData";
144    
145      /**
146       * Constant used when children are added or removed. On addition, the new
147       * value of the event holds the new child; on removal, the old value holds
148       * the removed child.
149       *
150       * @see #addPropertyChangeListener(PropertyChangeListener)
151       */
152      public static final String ACCESSIBLE_CHILD_PROPERTY
153        = "AccessibleChild";
154    
155      /**
156       * Constant used when active descendent of a component has changed. Both
157       * the old and new values are listed in the event.
158       *
159       * @see #addPropertyChangeListener(PropertyChangeListener)
160       */
161      public static final String ACCESSIBLE_ACTIVE_DESCENDANT_PROPERTY
162        = "AccessibleActiveDescendant";
163    
164      /**
165       * Constant used when the accessible table caption has changed. Both the
166       * old and new values are listed in the event.
167       *
168       * @see Accessible
169       * @see AccessibleTable
170       */
171      public static final String ACCESSIBLE_TABLE_CAPTION_CHANGED
172        = "accessibleTableCaptionChanged";
173    
174      /**
175       * Constant used when the accessible table summary has changed. Both the
176       * old and new values are listed in the event.
177       *
178       * @see Accessible
179       * @see AccessibleTable
180       */
181      public static final String ACCESSIBLE_TABLE_SUMMARY_CHANGED
182        = "accessibleTableSummaryChanged";
183    
184      /**
185       * Constant used when the accessible table model has changed. Only the new
186       * value of the event has meaning.
187       *
188       * @see AccessibleTable
189       * @see AccessibleTableModelChange
190       */
191      public static final String ACCESSIBLE_TABLE_MODEL_CHANGED
192        = "accessibleTableModelChanged";
193    
194      /**
195       * Constant used when the accessible table row header has changed. Only the
196       * new value of the event has meaning.
197       *
198       * @see AccessibleTable
199       * @see AccessibleTableModelChange
200       */
201      public static final String ACCESSIBLE_TABLE_ROW_HEADER_CHANGED
202        = "accessibleTableRowHeaderChanged";
203    
204      /**
205       * Constant used when the accessible table row description has changed. Only
206       * the new value of the event has meaning.
207       *
208       * @see AccessibleTable
209       */
210      public static final String ACCESSIBLE_TABLE_ROW_DESCRIPTION_CHANGED
211        = "accessibleTableRowDescriptionChanged";
212    
213      /**
214       * Constant used when the accessible table column header has changed. Only
215       * the new value of the event has meaning.
216       *
217       * @see AccessibleTable
218       * @see AccessibleTableModelChange
219       */
220      public static final String ACCESSIBLE_TABLE_COLUMN_HEADER_CHANGED
221        = "accessibleTableColumnHeaderChanged";
222    
223      /**
224       * Constant used when the accessible table column description has changed.
225       * Only the new value of the event has meaning.
226       *
227       * @see AccessibleTable
228       */
229      public static final String ACCESSIBLE_TABLE_COLUMN_DESCRIPTION_CHANGED
230        = "accessibleTableColumnDescriptionChanged";
231    
232      /**
233       * Constant used when supported set of actions has changed. Both the old
234       * and new values are listed in the event.
235       *
236       * @see AccessibleAction
237       */
238      public static final String ACCESSIBLE_ACTION_PROPERTY
239        = "accessibleActionProperty";
240    
241      /**
242       * Constant used when a hypertext element received focus. Both the old
243       * and new values are listed in the event, with -1 indicating that no link
244       * had focus.
245       *
246       * @see AccessibleHyperlink
247       */
248      public static final String ACCESSIBLE_HYPERTEXT_OFFSET
249        = "AccessibleHypertextOffset";
250    
251      /**
252       * Constant used when a component's bounds have changed.  The old and
253       * new bounds are given in the event.
254       * @since 1.5
255       */
256      public static final String ACCESSIBLE_COMPONENT_BOUNDS_CHANGED
257        = "accessibleComponentBoundsChanged";
258    
259      /**
260       * Constant used when the state of child objects changes.  The old
261       * value in the event is always null, and the new value is the component
262       * whose children have changed.
263       * @since 1.5
264       */
265      public static final String ACCESSIBLE_INVALIDATE_CHILDREN
266        = "accessibleInvalidateChildren";
267    
268      /**
269       * Constant used when the attributes of some text have changed.
270       * On insertion, the old value is null and the new value is an
271       * {@link AccessibleAttributeSequence} describing the insertion.
272       * On deletion, the old value is an {@link AccessibleAttributeSequence}
273       * and the new value is null.  For replacement, both the old
274       * and new values are {@link AccessibleAttributeSequence} objects.
275       * @since 1.5
276       */
277      public static final String ACCESSIBLE_TEXT_ATTRIBUTES_CHANGED
278        = "accessibleTextAttributesChanged";
279    
280      /**
281       * The accessible parent of this object.
282       *
283       * @see #getAccessibleParent()
284       * @see #setAccessibleParent(Accessible)
285       */
286      protected Accessible accessibleParent;
287    
288      /**
289       * A localized string naming this object.
290       *
291       * @see #getAccessibleName()
292       * @see #setAccessibleName(String)
293       */
294      protected String accessibleName;
295    
296      /**
297       * A localized string describing this object.
298       *
299       * @see #getAccessibleDescription()
300       * @see #setAccessibleDescription(String)
301       */
302      protected String accessibleDescription;
303    
304      /**
305       * The listener tool.
306       *
307       * @see #addPropertyChangeListener(PropertyChangeListener)
308       * @see #removePropertyChangeListener(PropertyChangeListener)
309       * @see #firePropertyChange(String, Object, Object)
310       */
311      private final PropertyChangeSupport listeners
312        = new PropertyChangeSupport(this);
313    
314      /**
315       * Default constructor.
316       */
317      public AccessibleContext()
318      {
319      }
320    
321      /**
322       * Get the localized name of the object. For example, a label may just
323       * return the text of the label, while an entry field for city may return
324       * "city" in en_US.
325       *
326       * @return the accessible object's name, or null if it is unnamed
327       * @see #setAccessibleName(String)
328       */
329      public String getAccessibleName()
330      {
331        return accessibleName;
332      }
333    
334      /**
335       * Set the localized name of the object. This will fire a
336       * PropertyChangeEvent with ACCESSIBLE_NAME_PROPERTY.
337       *
338       * @param s the new name
339       * @see #getAccessibleName()
340       * @see #addPropertyChangeListener(PropertyChangeListener)
341       */
342      public void setAccessibleName(String s)
343      {
344        listeners.firePropertyChange(ACCESSIBLE_NAME_PROPERTY, accessibleName, s);
345        accessibleName = s;
346      }
347    
348      /**
349       * Get the localized description of the object. For example, a 'Cancel'
350       * button may be described as "Ignore changes and close dialog box" in
351       * en_US.
352       *
353       * @return the accessible object's description, or null if there is none
354       * @see #setAccessibleDescription(String)
355       */
356      public String getAccessibleDescription()
357      {
358        return accessibleDescription;
359      }
360    
361      /**
362       * Set the localized name of the object. This will fire a
363       * PropertyChangeEvent with ACCESSIBLE_DESCRIPTION_PROPERTY.
364       *
365       * @param s the new description
366       * @see #getAccessibleDescription()
367       * @see #addPropertyChangeListener(PropertyChangeListener)
368       */
369      public void setAccessibleDescription(String s)
370      {
371        listeners.firePropertyChange(ACCESSIBLE_DESCRIPTION_PROPERTY,
372                                     accessibleDescription, s);
373        accessibleDescription = s;
374      }
375    
376      /**
377       * Gets the role of this object. For example, a button serves the role of
378       * AccessibleRole.PUSH_BUTTON. This allows assistive technologies to funnel
379       * similar objects into the same assistance classes. Note that the class
380       * is extensible, to define new roles if necessary.
381       *
382       * @return the role of the object
383       * @see AccessibleRole
384       */
385      public abstract AccessibleRole getAccessibleRole();
386    
387      /**
388       * Gets the state set of this object. A change in the state of the object
389       * will fire a PropertyChangeEvent for ACCESSIBLE_STATE_PROPERTY.
390       *
391       * @return the current state of the object
392       * @see AccessibleState
393       * @see AccessibleStateSet
394       * @see #addPropertyChangeListener(PropertyChangeListener)
395       */
396      public abstract AccessibleStateSet getAccessibleStateSet();
397    
398      /**
399       * Return the accessible parent of this object.
400       *
401       * @return the accessible parent, or null if there is none
402       */
403      public Accessible getAccessibleParent()
404      {
405        return accessibleParent;
406      }
407    
408      /**
409       * Sets the accessible parent of this object. This should only be used when
410       * the current parent object should not be the accessible parent; only the
411       * parent of the accessible child should call this method.
412       *
413       * @param a the new parent
414       */
415      public void setAccessibleParent(Accessible a)
416      {
417        accessibleParent = a;
418      }
419    
420      /**
421       * Gets the index of this object within its accessible parent.
422       *
423       * @return the 0-based index, or -1 if there is no accessible parent
424       * @see #getAccessibleParent()
425       * @see #getAccessibleChildrenCount()
426       * @see #getAccessibleChild(int)
427       */
428      public abstract int getAccessibleIndexInParent();
429    
430      /**
431       * Returns the number of accessible children of this object.
432       *
433       * @return the number of accessible children
434       * @see #getAccessibleChild(int)
435       */
436      public abstract int getAccessibleChildrenCount();
437    
438      /**
439       * Returns the specified accessible chile.
440       *
441       * @param i the 0-based index to get
442       * @return the child, or null if out of bounds
443       * @see #getAccessibleChildrenCount()
444       */
445      public abstract Accessible getAccessibleChild(int i);
446    
447      /**
448       * Gets the component locale, deferring to the parent if one is not declared.
449       *
450       * @return the locale
451       * @throws java.awt.IllegalComponentStateException if there is no locale
452       *         or parent
453       */
454      public abstract Locale getLocale();
455    
456      /**
457       * Add a PropertyChangeListener to the listener list. This listener will
458       * be notified of all property changes to the accessible object.
459       *
460       * @param l the listener to add
461       * @see #ACCESSIBLE_NAME_PROPERTY
462       * @see #ACCESSIBLE_DESCRIPTION_PROPERTY
463       * @see #ACCESSIBLE_STATE_PROPERTY
464       * @see #ACCESSIBLE_VALUE_PROPERTY
465       * @see #ACCESSIBLE_SELECTION_PROPERTY
466       * @see #ACCESSIBLE_TEXT_PROPERTY
467       * @see #ACCESSIBLE_VISIBLE_DATA_PROPERTY
468       * @see #removePropertyChangeListener(PropertyChangeListener)
469       */
470      public void addPropertyChangeListener(PropertyChangeListener l)
471      {
472        listeners.addPropertyChangeListener(l);
473      }
474    
475      /**
476       * Remove a PropertyChangeListener from the listener list.
477       *
478       * @param l the listener to remove
479       * @see #addPropertyChangeListener(PropertyChangeListener)
480       */
481      public void removePropertyChangeListener(PropertyChangeListener l)
482      {
483        listeners.removePropertyChangeListener(l);
484      }
485    
486      /**
487       * Get any supported accessible actions. The default implementation returns
488       * null.
489       *
490       * @return the supported action, or null
491       * @see AccessibleAction
492       */
493      public AccessibleAction getAccessibleAction()
494      {
495        return null;
496      }
497    
498      /**
499       * Get any supported accessible component. The default implementation returns
500       * null.
501       *
502       * @return the supported component, or null
503       * @see AccessibleComponent
504       */
505      public AccessibleComponent getAccessibleComponent()
506      {
507        return null;
508      }
509    
510      /**
511       * Get any supported accessible selection. The default implementation returns
512       * null.
513       *
514       * @return the supported selection, or null
515       * @see AccessibleSelection
516       */
517      public AccessibleSelection getAccessibleSelection()
518      {
519        return null;
520      }
521    
522      /**
523       * Get any supported accessible text. The default implementation returns
524       * null.
525       *
526       * @return the supported text, or null
527       * @see AccessibleText
528       */
529      public AccessibleText getAccessibleText()
530      {
531        return null;
532      }
533    
534      /**
535       * Get any supported accessible editable text. The default implementation
536       * returns null.
537       *
538       * @return the supported editable text, or null
539       * @see AccessibleEditableText
540       */
541      public AccessibleEditableText getAccessibleEditableText()
542      {
543        return null;
544      }
545    
546      /**
547       * Get any supported accessible value. The default implementation returns
548       * null.
549       *
550       * @return the supported value, or null
551       * @see AccessibleValue
552       */
553      public AccessibleValue getAccessibleValue()
554      {
555        return null;
556      }
557    
558      /**
559       * Get all supported accessible icons. The default implementation returns
560       * null.
561       *
562       * @return the supported icons, or null
563       * @see AccessibleIcon
564       */
565      public AccessibleIcon[] getAccessibleIcon()
566      {
567        return null;
568      }
569    
570      /**
571       * Get any supported accessible relation set. The default implementation
572       * returns an empty AccessibleRelationSet.
573       *
574       * @return the supported relation set, or <code>null</code>
575       *
576       * @see AccessibleRelationSet
577       */
578      public AccessibleRelationSet getAccessibleRelationSet()
579      {
580        return new AccessibleRelationSet();
581      }
582    
583      /**
584       * Get any supported accessible table. The default implementation returns
585       * null.
586       *
587       * @return the supported table, or null
588       * @see AccessibleTable
589       */
590      public AccessibleTable getAccessibleTable()
591      {
592        return null;
593      }
594    
595      /**
596       * Fire an event to report property changes. This is intended for use by
597       * the accessible objects, not general application programs. If oldValue and
598       * newValue differ, and the listenter list is not empty, a PropertyChange
599       * event is fired to each listener.
600       *
601       * @param name the property name
602       * @param oldValue the prior value
603       * @param newValue the updated value
604       * @see PropertyChangeSupport
605       * @see #addPropertyChangeListener(PropertyChangeListener)
606       * @see #removePropertyChangeListener(PropertyChangeListener)
607       * @see #ACCESSIBLE_NAME_PROPERTY
608       * @see #ACCESSIBLE_DESCRIPTION_PROPERTY
609       * @see #ACCESSIBLE_STATE_PROPERTY
610       * @see #ACCESSIBLE_VALUE_PROPERTY
611       * @see #ACCESSIBLE_SELECTION_PROPERTY
612       * @see #ACCESSIBLE_TEXT_PROPERTY
613       * @see #ACCESSIBLE_VISIBLE_DATA_PROPERTY
614       */
615      public void firePropertyChange(String name, Object oldValue, Object newValue)
616      {
617        listeners.firePropertyChange(name, oldValue, newValue);
618      }
619    } // class AccessibleContext