001/* AccessibleContext.java -- the context of an accessible object
002   Copyright (C) 2002 Free Software Foundation
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package javax.accessibility;
039
040import java.beans.PropertyChangeListener;
041import java.beans.PropertyChangeSupport;
042import 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 */
062public 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