1 /*
2 * Copyright (c) 1997, 2006, 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 package javax.swing;
26
27 import java.awt.Component;
28 import java.util.ArrayList;
29 import java.util.Hashtable;
30 import java.awt.Color;
31 import java.awt.Graphics;
32 import java.awt.Rectangle;
33
34 import javax.accessibility.*;
35
36 /**
37 * <code>JLayeredPane</code> adds depth to a JFC/Swing container,
38 * allowing components to overlap each other when needed.
39 * An <code>Integer</code> object specifies each component's depth in the
40 * container, where higher-numbered components sit "on top" of other
41 * components.
42 * For task-oriented documentation and examples of using layered panes see
43 * <a href="http://java.sun.com/docs/books/tutorial/uiswing/components/layeredpane.html">How to Use a Layered Pane</a>,
44 * a section in <em>The Java Tutorial</em>.
45 * <P>
46 * <TABLE ALIGN="RIGHT" BORDER="0" SUMMARY="layout">
47 * <TR>
48 * <TD ALIGN="CENTER">
49 * <P ALIGN="CENTER"><IMG SRC="doc-files/JLayeredPane-1.gif"
50 * alt="The following text describes this image."
51 * WIDTH="269" HEIGHT="264" ALIGN="BOTTOM" BORDER="0">
52 * </TD>
53 * </TR>
54 * </TABLE>
55 * For convenience, <code>JLayeredPane</code> divides the depth-range
56 * into several different layers. Putting a component into one of those
57 * layers makes it easy to ensure that components overlap properly,
58 * without having to worry about specifying numbers for specific depths:
59 * <DL>
60 * <DT><FONT SIZE="2">DEFAULT_LAYER</FONT></DT>
61 * <DD>The standard layer, where most components go. This the bottommost
62 * layer.
63 * <DT><FONT SIZE="2">PALETTE_LAYER</FONT></DT>
64 * <DD>The palette layer sits over the default layer. Useful for floating
65 * toolbars and palettes, so they can be positioned above other components.
66 * <DT><FONT SIZE="2">MODAL_LAYER</FONT></DT>
67 * <DD>The layer used for modal dialogs. They will appear on top of any
68 * toolbars, palettes, or standard components in the container.
69 * <DT><FONT SIZE="2">POPUP_LAYER</FONT></DT>
70 * <DD>The popup layer displays above dialogs. That way, the popup windows
71 * associated with combo boxes, tooltips, and other help text will appear
72 * above the component, palette, or dialog that generated them.
73 * <DT><FONT SIZE="2">DRAG_LAYER</FONT></DT>
74 * <DD>When dragging a component, reassigning it to the drag layer ensures
75 * that it is positioned over every other component in the container. When
76 * finished dragging, it can be reassigned to its normal layer.
77 * </DL>
78 * The <code>JLayeredPane</code> methods <code>moveToFront(Component)</code>,
79 * <code>moveToBack(Component)</code> and <code>setPosition</code> can be used
80 * to reposition a component within its layer. The <code>setLayer</code> method
81 * can also be used to change the component's current layer.
82 *
83 * <h2>Details</h2>
84 * <code>JLayeredPane</code> manages its list of children like
85 * <code>Container</code>, but allows for the definition of a several
86 * layers within itself. Children in the same layer are managed exactly
87 * like the normal <code>Container</code> object,
88 * with the added feature that when children components overlap, children
89 * in higher layers display above the children in lower layers.
90 * <p>
91 * Each layer is a distinct integer number. The layer attribute can be set
92 * on a <code>Component</code> by passing an <code>Integer</code>
93 * object during the add call.<br> For example:
94 * <PRE>
95 * layeredPane.add(child, JLayeredPane.DEFAULT_LAYER);
96 * or
97 * layeredPane.add(child, new Integer(10));
98 * </PRE>
99 * 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 * @author David Kloba
155 */
156 public class JLayeredPane extends JComponent implements Accessible {
157 /// Watch the values in getObjectForLayer()
158 /** Convenience object defining the Default layer. Equivalent to new Integer(0).*/
159 public final static Integer DEFAULT_LAYER = new Integer(0);
160 /** Convenience object defining the Palette layer. Equivalent to new Integer(100).*/
161 public final static Integer PALETTE_LAYER = new Integer(100);
162 /** Convenience object defining the Modal layer. Equivalent to new Integer(200).*/
163 public final static Integer MODAL_LAYER = new Integer(200);
164 /** Convenience object defining the Popup layer. Equivalent to new Integer(300).*/
165 public final static Integer POPUP_LAYER = new Integer(300);
166 /** Convenience object defining the Drag layer. Equivalent to new Integer(400).*/
167 public final static Integer DRAG_LAYER = new Integer(400);
168 /** Convenience object defining the Frame Content layer.
169 * This layer is normally only use to positon the contentPane and menuBar
170 * components of JFrame.
171 * Equivalent to new Integer(-30000).
172 * @see JFrame
173 */
174 public final static Integer FRAME_CONTENT_LAYER = new Integer(-30000);
175
176 /** Bound property */
177 public final static String LAYER_PROPERTY = "layeredContainerLayer";
178 // Hashtable to store layer values for non-JComponent components
179 private Hashtable<Component,Integer> componentToLayer;
180 private boolean optimizedDrawingPossible = true;
181
182
183 //////////////////////////////////////////////////////////////////////////////
184 //// Container Override methods
185 //////////////////////////////////////////////////////////////////////////////
186 /** Create a new JLayeredPane */
187 public JLayeredPane() {
188 setLayout(null);
189 }
190
191 private void validateOptimizedDrawing() {
192 boolean layeredComponentFound = false;
193 synchronized(getTreeLock()) {
194 Integer layer;
195
196 for (Component c : getComponents()) {
197 layer = null;
198 if(c instanceof JInternalFrame || (c instanceof JComponent &&
199 (layer = (Integer)((JComponent)c).getClientProperty(
200 LAYER_PROPERTY)) != null)) {
201 if(layer != null && layer.equals(FRAME_CONTENT_LAYER))
202 continue;
203 layeredComponentFound = true;
204 break;
205 }
206 }
207 }
208
209 if(layeredComponentFound)
210 optimizedDrawingPossible = false;
211 else
212 optimizedDrawingPossible = true;
213 }
214
215 protected void addImpl(Component comp, Object constraints, int index) {
216 int layer;
217 int pos;
218
219 if(constraints instanceof Integer) {
220 layer = ((Integer)constraints).intValue();
221 setLayer(comp, layer);
222 } else
223 layer = getLayer(comp);
224
225 pos = insertIndexForLayer(layer, index);
226 super.addImpl(comp, constraints, pos);
227 comp.validate();
228 comp.repaint();
229 validateOptimizedDrawing();
230 }
231
232 /**
233 * Remove the indexed component from this pane.
234 * This is the absolute index, ignoring layers.
235 *
236 * @param index an int specifying the component to remove
237 * @see #getIndexOf
238 */
239 public void remove(int index) {
240 Component c = getComponent(index);
241 super.remove(index);
242 if (c != null && !(c instanceof JComponent)) {
243 getComponentToLayer().remove(c);
244 }
245 validateOptimizedDrawing();
246 }
247
248 /**
249 * Removes all the components from this container.
250 *
251 * @since 1.5
252 */
253 public void removeAll() {
254 Component[] children = getComponents();
255 Hashtable cToL = getComponentToLayer();
256 for (int counter = children.length - 1; counter >= 0; counter--) {
257 Component c = children[counter];
258 if (c != null && !(c instanceof JComponent)) {
259 cToL.remove(c);
260 }
261 }
262 super.removeAll();
263 }
264
265 /**
266 * Returns false if components in the pane can overlap, which makes
267 * optimized drawing impossible. Otherwise, returns true.
268 *
269 * @return false if components can overlap, else true
270 * @see JComponent#isOptimizedDrawingEnabled
271 */
272 public boolean isOptimizedDrawingEnabled() {
273 return optimizedDrawingPossible;
274 }
275
276
277 //////////////////////////////////////////////////////////////////////////////
278 //// New methods for managing layers
279 //////////////////////////////////////////////////////////////////////////////
280 /** Sets the layer property on a JComponent. This method does not cause
281 * any side effects like setLayer() (painting, add/remove, etc).
282 * Normally you should use the instance method setLayer(), in order to
283 * get the desired side-effects (like repainting).
284 *
285 * @param c the JComponent to move
286 * @param layer an int specifying the layer to move it to
287 * @see #setLayer
288 */
289 public static void putLayer(JComponent c, int layer) {
290 /// MAKE SURE THIS AND setLayer(Component c, int layer, int position) are SYNCED
291 Integer layerObj;
292
293 layerObj = new Integer(layer);
294 c.putClientProperty(LAYER_PROPERTY, layerObj);
295 }
296
297 /** Gets the layer property for a JComponent, it
298 * does not cause any side effects like setLayer(). (painting, add/remove, etc)
299 * Normally you should use the instance method getLayer().
300 *
301 * @param c the JComponent to check
302 * @return an int specifying the component's layer
303 */
304 public static int getLayer(JComponent c) {
305 Integer i;
306 if((i = (Integer)c.getClientProperty(LAYER_PROPERTY)) != null)
307 return i.intValue();
308 return DEFAULT_LAYER.intValue();
309 }
310
311 /** Convenience method that returns the first JLayeredPane which
312 * contains the specified component. Note that all JFrames have a
313 * JLayeredPane at their root, so any component in a JFrame will
314 * have a JLayeredPane parent.
315 *
316 * @param c the Component to check
317 * @return the JLayeredPane that contains the component, or
318 * null if no JLayeredPane is found in the component
319 * hierarchy
320 * @see JFrame
321 * @see JRootPane
322 */
323 public static JLayeredPane getLayeredPaneAbove(Component c) {
324 if(c == null) return null;
325
326 Component parent = c.getParent();
327 while(parent != null && !(parent instanceof JLayeredPane))
328 parent = parent.getParent();
329 return (JLayeredPane)parent;
330 }
331
332 /** Sets the layer attribute on the specified component,
333 * making it the bottommost component in that layer.
334 * Should be called before adding to parent.
335 *
336 * @param c the Component to set the layer for
337 * @param layer an int specifying the layer to set, where
338 * lower numbers are closer to the bottom
339 */
340 public void setLayer(Component c, int layer) {
341 setLayer(c, layer, -1);
342 }
343
344 /** Sets the layer attribute for the specified component and
345 * also sets its position within that layer.
346 *
347 * @param c the Component to set the layer for
348 * @param layer an int specifying the layer to set, where
349 * lower numbers are closer to the bottom
350 * @param position an int specifying the position within the
351 * layer, where 0 is the topmost position and -1
352 * is the bottommost position
353 */
354 public void setLayer(Component c, int layer, int position) {
355 Integer layerObj;
356 layerObj = getObjectForLayer(layer);
357
358 if(layer == getLayer(c) && position == getPosition(c)) {
359 repaint(c.getBounds());
360 return;
361 }
362
363 /// MAKE SURE THIS AND putLayer(JComponent c, int layer) are SYNCED
364 if(c instanceof JComponent)
365 ((JComponent)c).putClientProperty(LAYER_PROPERTY, layerObj);
366 else
367 getComponentToLayer().put(c, layerObj);
368
369 if(c.getParent() == null || c.getParent() != this) {
370 repaint(c.getBounds());
371 return;
372 }
373
374 int index = insertIndexForLayer(c, layer, position);
375
376 setComponentZOrder(c, index);
377 repaint(c.getBounds());
378 }
379
380 /**
381 * Returns the layer attribute for the specified Component.
382 *
383 * @param c the Component to check
384 * @return an int specifying the component's current layer
385 */
386 public int getLayer(Component c) {
387 Integer i;
388 if(c instanceof JComponent)
389 i = (Integer)((JComponent)c).getClientProperty(LAYER_PROPERTY);
390 else
391 i = getComponentToLayer().get(c);
392
393 if(i == null)
394 return DEFAULT_LAYER.intValue();
395 return i.intValue();
396 }
397
398 /**
399 * Returns the index of the specified Component.
400 * This is the absolute index, ignoring layers.
401 * Index numbers, like position numbers, have the topmost component
402 * at index zero. Larger numbers are closer to the bottom.
403 *
404 * @param c the Component to check
405 * @return an int specifying the component's index
406 */
407 public int getIndexOf(Component c) {
408 int i, count;
409
410 count = getComponentCount();
411 for(i = 0; i < count; i++) {
412 if(c == getComponent(i))
413 return i;
414 }
415 return -1;
416 }
417 /**
418 * Moves the component to the top of the components in its current layer
419 * (position 0).
420 *
421 * @param c the Component to move
422 * @see #setPosition(Component, int)
423 */
424 public void moveToFront(Component c) {
425 setPosition(c, 0);
426 }
427
428 /**
429 * Moves the component to the bottom of the components in its current layer
430 * (position -1).
431 *
432 * @param c the Component to move
433 * @see #setPosition(Component, int)
434 */
435 public void moveToBack(Component c) {
436 setPosition(c, -1);
437 }
438
439 /**
440 * Moves the component to <code>position</code> within its current layer,
441 * where 0 is the topmost position within the layer and -1 is the bottommost
442 * position.
443 * <p>
444 * <b>Note:</b> Position numbering is defined by java.awt.Container, and
445 * is the opposite of layer numbering. Lower position numbers are closer
446 * to the top (0 is topmost), and higher position numbers are closer to
447 * the bottom.
448 *
449 * @param c the Component to move
450 * @param position an int in the range -1..N-1, where N is the number of
451 * components in the component's current layer
452 */
453 public void setPosition(Component c, int position) {
454 setLayer(c, getLayer(c), position);
455 }
456
457 /**
458 * Get the relative position of the component within its layer.
459 *
460 * @param c the Component to check
461 * @return an int giving the component's position, where 0 is the
462 * topmost position and the highest index value = the count
463 * count of components at that layer, minus 1
464 *
465 * @see #getComponentCountInLayer
466 */
467 public int getPosition(Component c) {
468 int i, startLayer, curLayer, startLocation, pos = 0;
469
470 getComponentCount();
471 startLocation = getIndexOf(c);
472
473 if(startLocation == -1)
474 return -1;
475
476 startLayer = getLayer(c);
477 for(i = startLocation - 1; i >= 0; i--) {
478 curLayer = getLayer(getComponent(i));
479 if(curLayer == startLayer)
480 pos++;
481 else
482 return pos;
483 }
484 return pos;
485 }
486
487 /** Returns the highest layer value from all current children.
488 * Returns 0 if there are no children.
489 *
490 * @return an int indicating the layer of the topmost component in the
491 * pane, or zero if there are no children
492 */
493 public int highestLayer() {
494 if(getComponentCount() > 0)
495 return getLayer(getComponent(0));
496 return 0;
497 }
498
499 /** Returns the lowest layer value from all current children.
500 * Returns 0 if there are no children.
501 *
502 * @return an int indicating the layer of the bottommost component in the
503 * pane, or zero if there are no children
504 */
505 public int lowestLayer() {
506 int count = getComponentCount();
507 if(count > 0)
508 return getLayer(getComponent(count-1));
509 return 0;
510 }
511
512 /**
513 * Returns the number of children currently in the specified layer.
514 *
515 * @param layer an int specifying the layer to check
516 * @return an int specifying the number of components in that layer
517 */
518 public int getComponentCountInLayer(int layer) {
519 int i, count, curLayer;
520 int layerCount = 0;
521
522 count = getComponentCount();
523 for(i = 0; i < count; i++) {
524 curLayer = getLayer(getComponent(i));
525 if(curLayer == layer) {
526 layerCount++;
527 /// Short circut the counting when we have them all
528 } else if(layerCount > 0 || curLayer < layer) {
529 break;
530 }
531 }
532
533 return layerCount;
534 }
535
536 /**
537 * Returns an array of the components in the specified layer.
538 *
539 * @param layer an int specifying the layer to check
540 * @return an array of Components contained in that layer
541 */
542 public Component[] getComponentsInLayer(int layer) {
543 int i, count, curLayer;
544 int layerCount = 0;
545 Component[] results;
546
547 results = new Component[getComponentCountInLayer(layer)];
548 count = getComponentCount();
549 for(i = 0; i < count; i++) {
550 curLayer = getLayer(getComponent(i));
551 if(curLayer == layer) {
552 results[layerCount++] = getComponent(i);
553 /// Short circut the counting when we have them all
554 } else if(layerCount > 0 || curLayer < layer) {
555 break;
556 }
557 }
558
559 return results;
560 }
561
562 /**
563 * Paints this JLayeredPane within the specified graphics context.
564 *
565 * @param g the Graphics context within which to paint
566 */
567 public void paint(Graphics g) {
568 if(isOpaque()) {
569 Rectangle r = g.getClipBounds();
570 Color c = getBackground();
571 if(c == null)
572 c = Color.lightGray;
573 g.setColor(c);
574 if (r != null) {
575 g.fillRect(r.x, r.y, r.width, r.height);
576 }
577 else {
578 g.fillRect(0, 0, getWidth(), getHeight());
579 }
580 }
581 super.paint(g);
582 }
583
584 //////////////////////////////////////////////////////////////////////////////
585 //// Implementation Details
586 //////////////////////////////////////////////////////////////////////////////
587
588 /**
589 * Returns the hashtable that maps components to layers.
590 *
591 * @return the Hashtable used to map components to their layers
592 */
593 protected Hashtable<Component,Integer> getComponentToLayer() {
594 if(componentToLayer == null)
595 componentToLayer = new Hashtable<Component,Integer>(4);
596 return componentToLayer;
597 }
598
599 /**
600 * Returns the Integer object associated with a specified layer.
601 *
602 * @param layer an int specifying the layer
603 * @return an Integer object for that layer
604 */
605 protected Integer getObjectForLayer(int layer) {
606 Integer layerObj;
607 switch(layer) {
608 case 0:
609 layerObj = DEFAULT_LAYER;
610 break;
611 case 100:
612 layerObj = PALETTE_LAYER;
613 break;
614 case 200:
615 layerObj = MODAL_LAYER;
616 break;
617 case 300:
618 layerObj = POPUP_LAYER;
619 break;
620 case 400:
621 layerObj = DRAG_LAYER;
622 break;
623 default:
624 layerObj = new Integer(layer);
625 }
626 return layerObj;
627 }
628
629 /**
630 * Primitive method that determines the proper location to
631 * insert a new child based on layer and position requests.
632 *
633 * @param layer an int specifying the layer
634 * @param position an int specifying the position within the layer
635 * @return an int giving the (absolute) insertion-index
636 *
637 * @see #getIndexOf
638 */
639 protected int insertIndexForLayer(int layer, int position) {
640 return insertIndexForLayer(null, layer, position);
641 }
642
643 /**
644 * This method is an extended version of insertIndexForLayer()
645 * to support setLayer which uses Container.setZOrder which does
646 * not remove the component from the containment heirarchy though
647 * we need to ignore it when calculating the insertion index.
648 *
649 * @param comp component to ignore when determining index
650 * @param layer an int specifying the layer
651 * @param position an int specifying the position within the layer
652 * @return an int giving the (absolute) insertion-index
653 *
654 * @see #getIndexOf
655 */
656 private int insertIndexForLayer(Component comp, int layer, int position) {
657 int i, count, curLayer;
658 int layerStart = -1;
659 int layerEnd = -1;
660 int componentCount = getComponentCount();
661
662 ArrayList<Component> compList =
663 new ArrayList<Component>(componentCount);
664 for (int index = 0; index < componentCount; index++) {
665 if (getComponent(index) != comp) {
666 compList.add(getComponent(index));
667 }
668 }
669
670 count = compList.size();
671 for (i = 0; i < count; i++) {
672 curLayer = getLayer(compList.get(i));
673 if (layerStart == -1 && curLayer == layer) {
674 layerStart = i;
675 }
676 if (curLayer < layer) {
677 if (i == 0) {
678 // layer is greater than any current layer
679 // [ ASSERT(layer > highestLayer()) ]
680 layerStart = 0;
681 layerEnd = 0;
682 } else {
683 layerEnd = i;
684 }
685 break;
686 }
687 }
688
689 // layer requested is lower than any current layer
690 // [ ASSERT(layer < lowestLayer()) ]
691 // put it on the bottom of the stack
692 if (layerStart == -1 && layerEnd == -1)
693 return count;
694
695 // In the case of a single layer entry handle the degenerative cases
696 if (layerStart != -1 && layerEnd == -1)
697 layerEnd = count;
698
699 if (layerEnd != -1 && layerStart == -1)
700 layerStart = layerEnd;
701
702 // If we are adding to the bottom, return the last element
703 if (position == -1)
704 return layerEnd;
705
706 // Otherwise make sure the requested position falls in the
707 // proper range
708 if (position > -1 && layerStart + position <= layerEnd)
709 return layerStart + position;
710
711 // Otherwise return the end of the layer
712 return layerEnd;
713 }
714
715 /**
716 * Returns a string representation of this JLayeredPane. This method
717 * is intended to be used only for debugging purposes, and the
718 * content and format of the returned string may vary between
719 * implementations. The returned string may be empty but may not
720 * be <code>null</code>.
721 *
722 * @return a string representation of this JLayeredPane.
723 */
724 protected String paramString() {
725 String optimizedDrawingPossibleString = (optimizedDrawingPossible ?
726 "true" : "false");
727
728 return super.paramString() +
729 ",optimizedDrawingPossible=" + optimizedDrawingPossibleString;
730 }
731
732 /////////////////
733 // Accessibility support
734 ////////////////
735
736 /**
737 * Gets the AccessibleContext associated with this JLayeredPane.
738 * For layered panes, the AccessibleContext takes the form of an
739 * AccessibleJLayeredPane.
740 * A new AccessibleJLayeredPane instance is created if necessary.
741 *
742 * @return an AccessibleJLayeredPane that serves as the
743 * AccessibleContext of this JLayeredPane
744 */
745 public AccessibleContext getAccessibleContext() {
746 if (accessibleContext == null) {
747 accessibleContext = new AccessibleJLayeredPane();
748 }
749 return accessibleContext;
750 }
751
752 /**
753 * This class implements accessibility support for the
754 * <code>JLayeredPane</code> class. It provides an implementation of the
755 * Java Accessibility API appropriate to layered pane user-interface
756 * elements.
757 * <p>
758 * <strong>Warning:</strong>
759 * Serialized objects of this class will not be compatible with
760 * future Swing releases. The current serialization support is
761 * appropriate for short term storage or RMI between applications running
762 * the same version of Swing. As of 1.4, support for long term storage
763 * of all JavaBeans<sup><font size="-2">TM</font></sup>
764 * has been added to the <code>java.beans</code> package.
765 * Please see {@link java.beans.XMLEncoder}.
766 */
767 protected class AccessibleJLayeredPane extends AccessibleJComponent {
768
769 /**
770 * Get the role of this object.
771 *
772 * @return an instance of AccessibleRole describing the role of the
773 * object
774 * @see AccessibleRole
775 */
776 public AccessibleRole getAccessibleRole() {
777 return AccessibleRole.LAYERED_PANE;
778 }
779 }
780 }