001 /*
002 * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025 package javax.swing;
026
027 import java.awt.Component;
028 import java.util.ArrayList;
029 import java.util.Hashtable;
030 import java.awt.Color;
031 import java.awt.Graphics;
032 import java.awt.Rectangle;
033
034 import javax.accessibility.*;
035
036 /**
037 * <code>JLayeredPane</code> adds depth to a JFC/Swing container,
038 * allowing components to overlap each other when needed.
039 * An <code>Integer</code> object specifies each component's depth in the
040 * container, where higher-numbered components sit "on top" of other
041 * components.
042 * For task-oriented documentation and examples of using layered panes see
043 * <a href="http://java.sun.com/docs/books/tutorial/uiswing/components/layeredpane.html">How to Use a Layered Pane</a>,
044 * a section in <em>The Java Tutorial</em>.
045 * <P>
046 * <TABLE ALIGN="RIGHT" BORDER="0" SUMMARY="layout">
047 * <TR>
048 * <TD ALIGN="CENTER">
049 * <P ALIGN="CENTER"><IMG SRC="doc-files/JLayeredPane-1.gif"
050 * alt="The following text describes this image."
051 * WIDTH="269" HEIGHT="264" ALIGN="BOTTOM" BORDER="0">
052 * </TD>
053 * </TR>
054 * </TABLE>
055 * For convenience, <code>JLayeredPane</code> divides the depth-range
056 * into several different layers. Putting a component into one of those
057 * layers makes it easy to ensure that components overlap properly,
058 * without having to worry about specifying numbers for specific depths:
059 * <DL>
060 * <DT><FONT SIZE="2">DEFAULT_LAYER</FONT></DT>
061 * <DD>The standard layer, where most components go. This the bottommost
062 * layer.
063 * <DT><FONT SIZE="2">PALETTE_LAYER</FONT></DT>
064 * <DD>The palette layer sits over the default layer. Useful for floating
065 * toolbars and palettes, so they can be positioned above other components.
066 * <DT><FONT SIZE="2">MODAL_LAYER</FONT></DT>
067 * <DD>The layer used for modal dialogs. They will appear on top of any
068 * toolbars, palettes, or standard components in the container.
069 * <DT><FONT SIZE="2">POPUP_LAYER</FONT></DT>
070 * <DD>The popup layer displays above dialogs. That way, the popup windows
071 * associated with combo boxes, tooltips, and other help text will appear
072 * above the component, palette, or dialog that generated them.
073 * <DT><FONT SIZE="2">DRAG_LAYER</FONT></DT>
074 * <DD>When dragging a component, reassigning it to the drag layer ensures
075 * that it is positioned over every other component in the container. When
076 * finished dragging, it can be reassigned to its normal layer.
077 * </DL>
078 * The <code>JLayeredPane</code> methods <code>moveToFront(Component)</code>,
079 * <code>moveToBack(Component)</code> and <code>setPosition</code> can be used
080 * to reposition a component within its layer. The <code>setLayer</code> method
081 * can also be used to change the component's current layer.
082 *
083 * <h2>Details</h2>
084 * <code>JLayeredPane</code> manages its list of children like
085 * <code>Container</code>, but allows for the definition of a several
086 * layers within itself. Children in the same layer are managed exactly
087 * like the normal <code>Container</code> object,
088 * with the added feature that when children components overlap, children
089 * in higher layers display above the children in lower layers.
090 * <p>
091 * Each layer is a distinct integer number. The layer attribute can be set
092 * on a <code>Component</code> by passing an <code>Integer</code>
093 * object during the add call.<br> For example:
094 * <PRE>
095 * layeredPane.add(child, JLayeredPane.DEFAULT_LAYER);
096 * or
097 * layeredPane.add(child, new Integer(10));
098 * </PRE>
099 * The layer attribute can also be set on a Component by calling<PRE>
100 * layeredPaneParent.setLayer(child, 10)</PRE>
101 * on the <code>JLayeredPane</code> that is the parent of component. The layer
102 * should be set <i>before</i> adding the child to the parent.
103 * <p>
104 * Higher number layers display above lower number layers. So, using
105 * numbers for the layers and letters for individual components, a
106 * representative list order would look like this:<PRE>
107 * 5a, 5b, 5c, 2a, 2b, 2c, 1a </PRE>
108 * where the leftmost components are closest to the top of the display.
109 * <p>
110 * A component can be moved to the top or bottom position within its
111 * layer by calling <code>moveToFront</code> or <code>moveToBack</code>.
112 * <p>
113 * The position of a component within a layer can also be specified directly.
114 * Valid positions range from 0 up to one less than the number of
115 * components in that layer. A value of -1 indicates the bottommost
116 * position. A value of 0 indicates the topmost position. Unlike layer
117 * numbers, higher position values are <i>lower</i> in the display.
118 * <blockquote>
119 * <b>Note:</b> This sequence (defined by java.awt.Container) is the reverse
120 * of the layer numbering sequence. Usually though, you will use <code>moveToFront</code>,
121 * <code>moveToBack</code>, and <code>setLayer</code>.
122 * </blockquote>
123 * Here are some examples using the method add(Component, layer, position):
124 * Calling add(5x, 5, -1) results in:<PRE>
125 * 5a, 5b, 5c, 5x, 2a, 2b, 2c, 1a </PRE>
126 *
127 * Calling add(5z, 5, 2) results in:<PRE>
128 * 5a, 5b, 5z, 5c, 5x, 2a, 2b, 2c, 1a </PRE>
129 *
130 * Calling add(3a, 3, 7) results in:<PRE>
131 * 5a, 5b, 5z, 5c, 5x, 3a, 2a, 2b, 2c, 1a </PRE>
132 *
133 * Using normal paint/event mechanics results in 1a appearing at the bottom
134 * and 5a being above all other components.
135 * <p>
136 * <b>Note:</b> that these layers are simply a logical construct and LayoutManagers
137 * will affect all child components of this container without regard for
138 * layer settings.
139 * <p>
140 * <strong>Warning:</strong> Swing is not thread safe. For more
141 * information see <a
142 * href="package-summary.html#threading">Swing's Threading
143 * Policy</a>.
144 * <p>
145 * <strong>Warning:</strong>
146 * Serialized objects of this class will not be compatible with
147 * future Swing releases. The current serialization support is
148 * appropriate for short term storage or RMI between applications running
149 * the same version of Swing. As of 1.4, support for long term storage
150 * of all JavaBeans<sup><font size="-2">TM</font></sup>
151 * has been added to the <code>java.beans</code> package.
152 * Please see {@link java.beans.XMLEncoder}.
153 *
154 * @version 1.36 02/02/00
155 * @author David Kloba
156 */
157 public class JLayeredPane extends JComponent implements Accessible {
158 /// Watch the values in getObjectForLayer()
159 /** Convenience object defining the Default layer. Equivalent to new Integer(0).*/
160 public final static Integer DEFAULT_LAYER = new Integer(0);
161 /** Convenience object defining the Palette layer. Equivalent to new Integer(100).*/
162 public final static Integer PALETTE_LAYER = new Integer(100);
163 /** Convenience object defining the Modal layer. Equivalent to new Integer(200).*/
164 public final static Integer MODAL_LAYER = new Integer(200);
165 /** Convenience object defining the Popup layer. Equivalent to new Integer(300).*/
166 public final static Integer POPUP_LAYER = new Integer(300);
167 /** Convenience object defining the Drag layer. Equivalent to new Integer(400).*/
168 public final static Integer DRAG_LAYER = new Integer(400);
169 /** Convenience object defining the Frame Content layer.
170 * This layer is normally only use to positon the contentPane and menuBar
171 * components of JFrame.
172 * Equivalent to new Integer(-30000).
173 * @see JFrame
174 */
175 public final static Integer FRAME_CONTENT_LAYER = new Integer(
176 -30000);
177
178 /** Bound property */
179 public final static String LAYER_PROPERTY = "layeredContainerLayer";
180 // Hashtable to store layer values for non-JComponent components
181 private Hashtable<Component, Integer> componentToLayer;
182 private boolean optimizedDrawingPossible = true;
183
184 //////////////////////////////////////////////////////////////////////////////
185 //// Container Override methods
186 //////////////////////////////////////////////////////////////////////////////
187 /** Create a new JLayeredPane */
188 public JLayeredPane() {
189 setLayout(null);
190 }
191
192 private void validateOptimizedDrawing() {
193 boolean layeredComponentFound = false;
194 synchronized (getTreeLock()) {
195 Integer layer = null;
196
197 for (Component c : getComponents()) {
198 layer = null;
199 if (c instanceof JInternalFrame
200 || (c instanceof JComponent && (layer = (Integer) ((JComponent) c)
201 .getClientProperty(LAYER_PROPERTY)) != null)) {
202 if (layer != null
203 && layer.equals(FRAME_CONTENT_LAYER))
204 continue;
205 layeredComponentFound = true;
206 break;
207 }
208 }
209 }
210
211 if (layeredComponentFound)
212 optimizedDrawingPossible = false;
213 else
214 optimizedDrawingPossible = true;
215 }
216
217 protected void addImpl(Component comp, Object constraints, int index) {
218 int layer = DEFAULT_LAYER.intValue();
219 int pos;
220
221 if (constraints instanceof Integer) {
222 layer = ((Integer) constraints).intValue();
223 setLayer(comp, layer);
224 } else
225 layer = getLayer(comp);
226
227 pos = insertIndexForLayer(layer, index);
228 super .addImpl(comp, constraints, pos);
229 comp.validate();
230 comp.repaint();
231 validateOptimizedDrawing();
232 }
233
234 /**
235 * Remove the indexed component from this pane.
236 * This is the absolute index, ignoring layers.
237 *
238 * @param index an int specifying the component to remove
239 * @see #getIndexOf
240 */
241 public void remove(int index) {
242 Component c = getComponent(index);
243 super .remove(index);
244 if (c != null && !(c instanceof JComponent)) {
245 getComponentToLayer().remove(c);
246 }
247 validateOptimizedDrawing();
248 }
249
250 /**
251 * Removes all the components from this container.
252 *
253 * @since 1.5
254 */
255 public void removeAll() {
256 Component[] children = getComponents();
257 Hashtable cToL = getComponentToLayer();
258 for (int counter = children.length - 1; counter >= 0; counter--) {
259 Component c = children[counter];
260 if (c != null && !(c instanceof JComponent)) {
261 cToL.remove(c);
262 }
263 }
264 super .removeAll();
265 }
266
267 /**
268 * Returns false if components in the pane can overlap, which makes
269 * optimized drawing impossible. Otherwise, returns true.
270 *
271 * @return false if components can overlap, else true
272 * @see JComponent#isOptimizedDrawingEnabled
273 */
274 public boolean isOptimizedDrawingEnabled() {
275 return optimizedDrawingPossible;
276 }
277
278 //////////////////////////////////////////////////////////////////////////////
279 //// New methods for managing layers
280 //////////////////////////////////////////////////////////////////////////////
281 /** Sets the layer property on a JComponent. This method does not cause
282 * any side effects like setLayer() (painting, add/remove, etc).
283 * Normally you should use the instance method setLayer(), in order to
284 * get the desired side-effects (like repainting).
285 *
286 * @param c the JComponent to move
287 * @param layer an int specifying the layer to move it to
288 * @see #setLayer
289 */
290 public static void putLayer(JComponent c, int layer) {
291 /// MAKE SURE THIS AND setLayer(Component c, int layer, int position) are SYNCED
292 Integer layerObj;
293
294 layerObj = new Integer(layer);
295 c.putClientProperty(LAYER_PROPERTY, layerObj);
296 }
297
298 /** Gets the layer property for a JComponent, it
299 * does not cause any side effects like setLayer(). (painting, add/remove, etc)
300 * Normally you should use the instance method getLayer().
301 *
302 * @param c the JComponent to check
303 * @return an int specifying the component's layer
304 */
305 public static int getLayer(JComponent c) {
306 Integer i;
307 if ((i = (Integer) c.getClientProperty(LAYER_PROPERTY)) != null)
308 return i.intValue();
309 return DEFAULT_LAYER.intValue();
310 }
311
312 /** Convenience method that returns the first JLayeredPane which
313 * contains the specified component. Note that all JFrames have a
314 * JLayeredPane at their root, so any component in a JFrame will
315 * have a JLayeredPane parent.
316 *
317 * @param c the Component to check
318 * @return the JLayeredPane that contains the component, or
319 * null if no JLayeredPane is found in the component
320 * hierarchy
321 * @see JFrame
322 * @see JRootPane
323 */
324 public static JLayeredPane getLayeredPaneAbove(Component c) {
325 if (c == null)
326 return null;
327
328 Component parent = c.getParent();
329 while (parent != null && !(parent instanceof JLayeredPane))
330 parent = parent.getParent();
331 return (JLayeredPane) parent;
332 }
333
334 /** Sets the layer attribute on the specified component,
335 * making it the bottommost component in that layer.
336 * Should be called before adding to parent.
337 *
338 * @param c the Component to set the layer for
339 * @param layer an int specifying the layer to set, where
340 * lower numbers are closer to the bottom
341 */
342 public void setLayer(Component c, int layer) {
343 setLayer(c, layer, -1);
344 }
345
346 /** Sets the layer attribute for the specified component and
347 * also sets its position within that layer.
348 *
349 * @param c the Component to set the layer for
350 * @param layer an int specifying the layer to set, where
351 * lower numbers are closer to the bottom
352 * @param position an int specifying the position within the
353 * layer, where 0 is the topmost position and -1
354 * is the bottommost position
355 */
356 public void setLayer(Component c, int layer, int position) {
357 Integer layerObj;
358 layerObj = getObjectForLayer(layer);
359
360 if (layer == getLayer(c) && position == getPosition(c)) {
361 repaint(c.getBounds());
362 return;
363 }
364
365 /// MAKE SURE THIS AND putLayer(JComponent c, int layer) are SYNCED
366 if (c instanceof JComponent)
367 ((JComponent) c)
368 .putClientProperty(LAYER_PROPERTY, layerObj);
369 else
370 getComponentToLayer().put((Component) c, layerObj);
371
372 if (c.getParent() == null || c.getParent() != this ) {
373 repaint(c.getBounds());
374 return;
375 }
376
377 int index = insertIndexForLayer(c, layer, position);
378
379 setComponentZOrder(c, index);
380 repaint(c.getBounds());
381 }
382
383 /**
384 * Returns the layer attribute for the specified Component.
385 *
386 * @param c the Component to check
387 * @return an int specifying the component's current layer
388 */
389 public int getLayer(Component c) {
390 Integer i;
391 if (c instanceof JComponent)
392 i = (Integer) ((JComponent) c)
393 .getClientProperty(LAYER_PROPERTY);
394 else
395 i = (Integer) getComponentToLayer().get((Component) c);
396
397 if (i == null)
398 return DEFAULT_LAYER.intValue();
399 return i.intValue();
400 }
401
402 /**
403 * Returns the index of the specified Component.
404 * This is the absolute index, ignoring layers.
405 * Index numbers, like position numbers, have the topmost component
406 * at index zero. Larger numbers are closer to the bottom.
407 *
408 * @param c the Component to check
409 * @return an int specifying the component's index
410 */
411 public int getIndexOf(Component c) {
412 int i, count;
413
414 count = getComponentCount();
415 for (i = 0; i < count; i++) {
416 if (c == getComponent(i))
417 return i;
418 }
419 return -1;
420 }
421
422 /**
423 * Moves the component to the top of the components in its current layer
424 * (position 0).
425 *
426 * @param c the Component to move
427 * @see #setPosition(Component, int)
428 */
429 public void moveToFront(Component c) {
430 setPosition(c, 0);
431 }
432
433 /**
434 * Moves the component to the bottom of the components in its current layer
435 * (position -1).
436 *
437 * @param c the Component to move
438 * @see #setPosition(Component, int)
439 */
440 public void moveToBack(Component c) {
441 setPosition(c, -1);
442 }
443
444 /**
445 * Moves the component to <code>position</code> within its current layer,
446 * where 0 is the topmost position within the layer and -1 is the bottommost
447 * position.
448 * <p>
449 * <b>Note:</b> Position numbering is defined by java.awt.Container, and
450 * is the opposite of layer numbering. Lower position numbers are closer
451 * to the top (0 is topmost), and higher position numbers are closer to
452 * the bottom.
453 *
454 * @param c the Component to move
455 * @param position an int in the range -1..N-1, where N is the number of
456 * components in the component's current layer
457 */
458 public void setPosition(Component c, int position) {
459 setLayer(c, getLayer(c), position);
460 }
461
462 /**
463 * Get the relative position of the component within its layer.
464 *
465 * @param c the Component to check
466 * @return an int giving the component's position, where 0 is the
467 * topmost position and the highest index value = the count
468 * count of components at that layer, minus 1
469 *
470 * @see #getComponentCountInLayer
471 */
472 public int getPosition(Component c) {
473 int i, count, startLayer, curLayer, startLocation, pos = 0;
474
475 count = getComponentCount();
476 startLocation = getIndexOf(c);
477
478 if (startLocation == -1)
479 return -1;
480
481 startLayer = getLayer(c);
482 for (i = startLocation - 1; i >= 0; i--) {
483 curLayer = getLayer(getComponent(i));
484 if (curLayer == startLayer)
485 pos++;
486 else
487 return pos;
488 }
489 return pos;
490 }
491
492 /** Returns the highest layer value from all current children.
493 * Returns 0 if there are no children.
494 *
495 * @return an int indicating the layer of the topmost component in the
496 * pane, or zero if there are no children
497 */
498 public int highestLayer() {
499 if (getComponentCount() > 0)
500 return getLayer(getComponent(0));
501 return 0;
502 }
503
504 /** Returns the lowest layer value from all current children.
505 * Returns 0 if there are no children.
506 *
507 * @return an int indicating the layer of the bottommost component in the
508 * pane, or zero if there are no children
509 */
510 public int lowestLayer() {
511 int count = getComponentCount();
512 if (count > 0)
513 return getLayer(getComponent(count - 1));
514 return 0;
515 }
516
517 /**
518 * Returns the number of children currently in the specified layer.
519 *
520 * @param layer an int specifying the layer to check
521 * @return an int specifying the number of components in that layer
522 */
523 public int getComponentCountInLayer(int layer) {
524 int i, count, curLayer;
525 int layerCount = 0;
526
527 count = getComponentCount();
528 for (i = 0; i < count; i++) {
529 curLayer = getLayer(getComponent(i));
530 if (curLayer == layer) {
531 layerCount++;
532 /// Short circut the counting when we have them all
533 } else if (layerCount > 0 || curLayer < layer) {
534 break;
535 }
536 }
537
538 return layerCount;
539 }
540
541 /**
542 * Returns an array of the components in the specified layer.
543 *
544 * @param layer an int specifying the layer to check
545 * @return an array of Components contained in that layer
546 */
547 public Component[] getComponentsInLayer(int layer) {
548 int i, count, curLayer;
549 int layerCount = 0;
550 Component[] results;
551
552 results = new Component[getComponentCountInLayer(layer)];
553 count = getComponentCount();
554 for (i = 0; i < count; i++) {
555 curLayer = getLayer(getComponent(i));
556 if (curLayer == layer) {
557 results[layerCount++] = getComponent(i);
558 /// Short circut the counting when we have them all
559 } else if (layerCount > 0 || curLayer < layer) {
560 break;
561 }
562 }
563
564 return results;
565 }
566
567 /**
568 * Paints this JLayeredPane within the specified graphics context.
569 *
570 * @param g the Graphics context within which to paint
571 */
572 public void paint(Graphics g) {
573 if (isOpaque()) {
574 Rectangle r = g.getClipBounds();
575 Color c = getBackground();
576 if (c == null)
577 c = Color.lightGray;
578 g.setColor(c);
579 if (r != null) {
580 g.fillRect(r.x, r.y, r.width, r.height);
581 } else {
582 g.fillRect(0, 0, getWidth(), getHeight());
583 }
584 }
585 super .paint(g);
586 }
587
588 //////////////////////////////////////////////////////////////////////////////
589 //// Implementation Details
590 //////////////////////////////////////////////////////////////////////////////
591
592 /**
593 * Returns the hashtable that maps components to layers.
594 *
595 * @return the Hashtable used to map components to their layers
596 */
597 protected Hashtable<Component, Integer> getComponentToLayer() {
598 if (componentToLayer == null)
599 componentToLayer = new Hashtable<Component, Integer>(4);
600 return componentToLayer;
601 }
602
603 /**
604 * Returns the Integer object associated with a specified layer.
605 *
606 * @param layer an int specifying the layer
607 * @return an Integer object for that layer
608 */
609 protected Integer getObjectForLayer(int layer) {
610 Integer layerObj;
611 switch (layer) {
612 case 0:
613 layerObj = DEFAULT_LAYER;
614 break;
615 case 100:
616 layerObj = PALETTE_LAYER;
617 break;
618 case 200:
619 layerObj = MODAL_LAYER;
620 break;
621 case 300:
622 layerObj = POPUP_LAYER;
623 break;
624 case 400:
625 layerObj = DRAG_LAYER;
626 break;
627 default:
628 layerObj = new Integer(layer);
629 }
630 return layerObj;
631 }
632
633 /**
634 * Primitive method that determines the proper location to
635 * insert a new child based on layer and position requests.
636 *
637 * @param layer an int specifying the layer
638 * @param position an int specifying the position within the layer
639 * @return an int giving the (absolute) insertion-index
640 *
641 * @see #getIndexOf
642 */
643 protected int insertIndexForLayer(int layer, int position) {
644 return insertIndexForLayer(null, layer, position);
645 }
646
647 /**
648 * This method is an extended version of insertIndexForLayer()
649 * to support setLayer which uses Container.setZOrder which does
650 * not remove the component from the containment heirarchy though
651 * we need to ignore it when calculating the insertion index.
652 *
653 * @param comp component to ignore when determining index
654 * @param layer an int specifying the layer
655 * @param position an int specifying the position within the layer
656 * @return an int giving the (absolute) insertion-index
657 *
658 * @see #getIndexOf
659 */
660 private int insertIndexForLayer(Component comp, int layer,
661 int position) {
662 int i, count, curLayer;
663 int layerStart = -1;
664 int layerEnd = -1;
665 int componentCount = getComponentCount();
666
667 ArrayList<Component> compList = new ArrayList<Component>(
668 componentCount);
669 for (int index = 0; index < componentCount; index++) {
670 if (getComponent(index) != comp) {
671 compList.add(getComponent(index));
672 }
673 }
674
675 count = compList.size();
676 for (i = 0; i < count; i++) {
677 curLayer = getLayer(compList.get(i));
678 if (layerStart == -1 && curLayer == layer) {
679 layerStart = i;
680 }
681 if (curLayer < layer) {
682 if (i == 0) {
683 // layer is greater than any current layer
684 // [ ASSERT(layer > highestLayer()) ]
685 layerStart = 0;
686 layerEnd = 0;
687 } else {
688 layerEnd = i;
689 }
690 break;
691 }
692 }
693
694 // layer requested is lower than any current layer
695 // [ ASSERT(layer < lowestLayer()) ]
696 // put it on the bottom of the stack
697 if (layerStart == -1 && layerEnd == -1)
698 return count;
699
700 // In the case of a single layer entry handle the degenerative cases
701 if (layerStart != -1 && layerEnd == -1)
702 layerEnd = count;
703
704 if (layerEnd != -1 && layerStart == -1)
705 layerStart = layerEnd;
706
707 // If we are adding to the bottom, return the last element
708 if (position == -1)
709 return layerEnd;
710
711 // Otherwise make sure the requested position falls in the
712 // proper range
713 if (position > -1 && layerStart + position <= layerEnd)
714 return layerStart + position;
715
716 // Otherwise return the end of the layer
717 return layerEnd;
718 }
719
720 /**
721 * Returns a string representation of this JLayeredPane. This method
722 * is intended to be used only for debugging purposes, and the
723 * content and format of the returned string may vary between
724 * implementations. The returned string may be empty but may not
725 * be <code>null</code>.
726 *
727 * @return a string representation of this JLayeredPane.
728 */
729 protected String paramString() {
730 String optimizedDrawingPossibleString = (optimizedDrawingPossible ? "true"
731 : "false");
732
733 return super .paramString() + ",optimizedDrawingPossible="
734 + optimizedDrawingPossibleString;
735 }
736
737 /////////////////
738 // Accessibility support
739 ////////////////
740
741 /**
742 * Gets the AccessibleContext associated with this JLayeredPane.
743 * For layered panes, the AccessibleContext takes the form of an
744 * AccessibleJLayeredPane.
745 * A new AccessibleJLayeredPane instance is created if necessary.
746 *
747 * @return an AccessibleJLayeredPane that serves as the
748 * AccessibleContext of this JLayeredPane
749 */
750 public AccessibleContext getAccessibleContext() {
751 if (accessibleContext == null) {
752 accessibleContext = new AccessibleJLayeredPane();
753 }
754 return accessibleContext;
755 }
756
757 /**
758 * This class implements accessibility support for the
759 * <code>JLayeredPane</code> class. It provides an implementation of the
760 * Java Accessibility API appropriate to layered pane user-interface
761 * elements.
762 * <p>
763 * <strong>Warning:</strong>
764 * Serialized objects of this class will not be compatible with
765 * future Swing releases. The current serialization support is
766 * appropriate for short term storage or RMI between applications running
767 * the same version of Swing. As of 1.4, support for long term storage
768 * of all JavaBeans<sup><font size="-2">TM</font></sup>
769 * has been added to the <code>java.beans</code> package.
770 * Please see {@link java.beans.XMLEncoder}.
771 */
772 protected class AccessibleJLayeredPane extends AccessibleJComponent {
773
774 /**
775 * Get the role of this object.
776 *
777 * @return an instance of AccessibleRole describing the role of the
778 * object
779 * @see AccessibleRole
780 */
781 public AccessibleRole getAccessibleRole() {
782 return AccessibleRole.LAYERED_PANE;
783 }
784 }
785 }
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