1 /*
2 * Copyright (c) 1997, 2013, 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 import sun.awt.SunToolkit;
34
35 import javax.accessibility.*;
36
37 /**
38 * <code>JLayeredPane</code> adds depth to a JFC/Swing container,
39 * allowing components to overlap each other when needed.
40 * An <code>Integer</code> object specifies each component's depth in the
41 * container, where higher-numbered components sit "on top" of other
42 * components.
43 * For task-oriented documentation and examples of using layered panes see
44 * <a href="http://docs.oracle.com/javase/tutorial/uiswing/components/layeredpane.html">How to Use a Layered Pane</a>,
45 * a section in <em>The Java Tutorial</em>.
46 *
47 * <TABLE STYLE="FLOAT:RIGHT" BORDER="0" SUMMARY="layout">
48 * <TR>
49 * <TD ALIGN="CENTER">
50 * <P STYLE="TEXT-ALIGN:CENTER"><IMG SRC="doc-files/JLayeredPane-1.gif"
51 * alt="The following text describes this image."
52 * WIDTH="269" HEIGHT="264" STYLE="FLOAT:BOTTOM; BORDER=0">
53 * </TD>
54 * </TR>
55 * </TABLE>
56 * For convenience, <code>JLayeredPane</code> divides the depth-range
57 * into several different layers. Putting a component into one of those
58 * layers makes it easy to ensure that components overlap properly,
59 * without having to worry about specifying numbers for specific depths:
60 * <DL>
61 * <DT>DEFAULT_LAYER</DT>
62 * <DD>The standard layer, where most components go. This the bottommost
63 * layer.
64 * <DT>PALETTE_LAYER</DT>
65 * <DD>The palette layer sits over the default layer. Useful for floating
66 * toolbars and palettes, so they can be positioned above other components.
67 * <DT>MODAL_LAYER</DT>
68 * <DD>The layer used for modal dialogs. They will appear on top of any
69 * toolbars, palettes, or standard components in the container.
70 * <DT>POPUP_LAYER</DT>
71 * <DD>The popup layer displays above dialogs. That way, the popup windows
72 * associated with combo boxes, tooltips, and other help text will appear
73 * above the component, palette, or dialog that generated them.
74 * <DT>DRAG_LAYER</DT>
75 * <DD>When dragging a component, reassigning it to the drag layer ensures
76 * that it is positioned over every other component in the container. When
77 * finished dragging, it can be reassigned to its normal layer.
78 * </DL>
79 * The <code>JLayeredPane</code> methods <code>moveToFront(Component)</code>,
80 * <code>moveToBack(Component)</code> and <code>setPosition</code> can be used
81 * to reposition a component within its layer. The <code>setLayer</code> method
82 * can also be used to change the component's current layer.
83 *
84 * <h2>Details</h2>
85 * <code>JLayeredPane</code> manages its list of children like
86 * <code>Container</code>, but allows for the definition of a several
87 * layers within itself. Children in the same layer are managed exactly
88 * like the normal <code>Container</code> object,
89 * with the added feature that when children components overlap, children
90 * in higher layers display above the children in lower layers.
91 * <p>
92 * Each layer is a distinct integer number. The layer attribute can be set
93 * on a <code>Component</code> by passing an <code>Integer</code>
94 * object during the add call.<br> For example:
95 * <PRE>
96 * layeredPane.add(child, JLayeredPane.DEFAULT_LAYER);
97 * or
98 * layeredPane.add(child, new Integer(10));
99 * </PRE>
100 * The layer attribute can also be set on a Component by calling<PRE>
101 * layeredPaneParent.setLayer(child, 10)</PRE>
102 * on the <code>JLayeredPane</code> that is the parent of component. The layer
103 * should be set <i>before</i> adding the child to the parent.
104 * <p>
105 * Higher number layers display above lower number layers. So, using
106 * numbers for the layers and letters for individual components, a
107 * representative list order would look like this:<PRE>
108 * 5a, 5b, 5c, 2a, 2b, 2c, 1a </PRE>
109 * where the leftmost components are closest to the top of the display.
110 * <p>
111 * A component can be moved to the top or bottom position within its
112 * layer by calling <code>moveToFront</code> or <code>moveToBack</code>.
113 * <p>
114 * The position of a component within a layer can also be specified directly.
115 * Valid positions range from 0 up to one less than the number of
116 * components in that layer. A value of -1 indicates the bottommost
117 * position. A value of 0 indicates the topmost position. Unlike layer
118 * numbers, higher position values are <i>lower</i> in the display.
119 * <blockquote>
120 * <b>Note:</b> This sequence (defined by java.awt.Container) is the reverse
121 * of the layer numbering sequence. Usually though, you will use <code>moveToFront</code>,
122 * <code>moveToBack</code>, and <code>setLayer</code>.
123 * </blockquote>
124 * Here are some examples using the method add(Component, layer, position):
125 * Calling add(5x, 5, -1) results in:<PRE>
126 * 5a, 5b, 5c, 5x, 2a, 2b, 2c, 1a </PRE>
127 *
128 * Calling add(5z, 5, 2) results in:<PRE>
129 * 5a, 5b, 5z, 5c, 5x, 2a, 2b, 2c, 1a </PRE>
130 *
131 * Calling add(3a, 3, 7) results in:<PRE>
132 * 5a, 5b, 5z, 5c, 5x, 3a, 2a, 2b, 2c, 1a </PRE>
133 *
134 * Using normal paint/event mechanics results in 1a appearing at the bottom
135 * and 5a being above all other components.
136 * <p>
137 * <b>Note:</b> that these layers are simply a logical construct and LayoutManagers
138 * will affect all child components of this container without regard for
139 * layer settings.
140 * <p>
141 * <strong>Warning:</strong> Swing is not thread safe. For more
142 * information see <a
143 * href="package-summary.html#threading">Swing's Threading
144 * Policy</a>.
145 * <p>
146 * <strong>Warning:</strong>
147 * Serialized objects of this class will not be compatible with
148 * future Swing releases. The current serialization support is
149 * appropriate for short term storage or RMI between applications running
150 * the same version of Swing. As of 1.4, support for long term storage
151 * of all JavaBeans™
152 * has been added to the <code>java.beans</code> package.
153 * Please see {@link java.beans.XMLEncoder}.
154 *
155 * @author David Kloba
156 * @since 1.2
157 */
158 @SuppressWarnings("serial")
159 public class JLayeredPane extends JComponent implements Accessible {
160 /// Watch the values in getObjectForLayer()
161 /** Convenience object defining the Default layer. Equivalent to new Integer(0).*/
162 public final static Integer DEFAULT_LAYER = new Integer(0);
163 /** Convenience object defining the Palette layer. Equivalent to new Integer(100).*/
164 public final static Integer PALETTE_LAYER = new Integer(100);
165 /** Convenience object defining the Modal layer. Equivalent to new Integer(200).*/
166 public final static Integer MODAL_LAYER = new Integer(200);
167 /** Convenience object defining the Popup layer. Equivalent to new Integer(300).*/
168 public final static Integer POPUP_LAYER = new Integer(300);
169 /** Convenience object defining the Drag layer. Equivalent to new Integer(400).*/
170 public final static Integer DRAG_LAYER = new Integer(400);
171 /** Convenience object defining the Frame Content layer.
172 * This layer is normally only use to position the contentPane and menuBar
173 * components of JFrame.
174 * Equivalent to new Integer(-30000).
175 * @see JFrame
176 */
177 public final static Integer FRAME_CONTENT_LAYER = new Integer(-30000);
178
179 /** Bound property */
180 public final static String LAYER_PROPERTY = "layeredContainerLayer";
181 // Hashtable to store layer values for non-JComponent components
182 private Hashtable<Component,Integer> componentToLayer;
183 private boolean optimizedDrawingPossible = true;
184
185
186 //////////////////////////////////////////////////////////////////////////////
187 //// Container Override methods
188 //////////////////////////////////////////////////////////////////////////////
189 /** Create a new JLayeredPane */
190 public JLayeredPane() {
191 setLayout(null);
192 }
193
194 private void validateOptimizedDrawing() {
195 boolean layeredComponentFound = false;
196 synchronized(getTreeLock()) {
197 Integer layer;
198
199 for (Component c : getComponents()) {
200 layer = null;
201
202 if(SunToolkit.isInstanceOf(c, "javax.swing.JInternalFrame") ||
203 (c instanceof JComponent &&
204 (layer = (Integer)((JComponent)c).
205 getClientProperty(LAYER_PROPERTY)) != null))
206 {
207 if(layer != null && layer.equals(FRAME_CONTENT_LAYER))
208 continue;
209 layeredComponentFound = true;
210 break;
211 }
212 }
213 }
214
215 if(layeredComponentFound)
216 optimizedDrawingPossible = false;
217 else
218 optimizedDrawingPossible = true;
219 }
220
221 protected void addImpl(Component comp, Object constraints, int index) {
222 int layer;
223 int pos;
224
225 if(constraints instanceof Integer) {
226 layer = ((Integer)constraints).intValue();
227 setLayer(comp, layer);
228 } else
229 layer = getLayer(comp);
230
231 pos = insertIndexForLayer(layer, index);
232 super.addImpl(comp, constraints, pos);
233 comp.validate();
234 comp.repaint();
235 validateOptimizedDrawing();
236 }
237
238 /**
239 * Remove the indexed component from this pane.
240 * This is the absolute index, ignoring layers.
241 *
242 * @param index an int specifying the component to remove
243 * @see #getIndexOf
244 */
245 public void remove(int index) {
246 Component c = getComponent(index);
247 super.remove(index);
248 if (c != null && !(c instanceof JComponent)) {
249 getComponentToLayer().remove(c);
250 }
251 validateOptimizedDrawing();
252 }
253
254 /**
255 * Removes all the components from this container.
256 *
257 * @since 1.5
258 */
259 public void removeAll() {
260 Component[] children = getComponents();
261 Hashtable<Component, Integer> cToL = getComponentToLayer();
262 for (int counter = children.length - 1; counter >= 0; counter--) {
263 Component c = children[counter];
264 if (c != null && !(c instanceof JComponent)) {
265 cToL.remove(c);
266 }
267 }
268 super.removeAll();
269 }
270
271 /**
272 * Returns false if components in the pane can overlap, which makes
273 * optimized drawing impossible. Otherwise, returns true.
274 *
275 * @return false if components can overlap, else true
276 * @see JComponent#isOptimizedDrawingEnabled
277 */
278 public boolean isOptimizedDrawingEnabled() {
279 return optimizedDrawingPossible;
280 }
281
282
283 //////////////////////////////////////////////////////////////////////////////
284 //// New methods for managing layers
285 //////////////////////////////////////////////////////////////////////////////
286 /** Sets the layer property on a JComponent. This method does not cause
287 * any side effects like setLayer() (painting, add/remove, etc).
288 * Normally you should use the instance method setLayer(), in order to
289 * get the desired side-effects (like repainting).
290 *
291 * @param c the JComponent to move
292 * @param layer an int specifying the layer to move it to
293 * @see #setLayer
294 */
295 public static void putLayer(JComponent c, int layer) {
296 /// MAKE SURE THIS AND setLayer(Component c, int layer, int position) are SYNCED
297 Integer layerObj;
298
299 layerObj = layer;
300 c.putClientProperty(LAYER_PROPERTY, layerObj);
301 }
302
303 /** Gets the layer property for a JComponent, it
304 * does not cause any side effects like setLayer(). (painting, add/remove, etc)
305 * Normally you should use the instance method getLayer().
306 *
307 * @param c the JComponent to check
308 * @return an int specifying the component's layer
309 */
310 public static int getLayer(JComponent c) {
311 Integer i;
312 if((i = (Integer)c.getClientProperty(LAYER_PROPERTY)) != null)
313 return i.intValue();
314 return DEFAULT_LAYER.intValue();
315 }
316
317 /** Convenience method that returns the first JLayeredPane which
318 * contains the specified component. Note that all JFrames have a
319 * JLayeredPane at their root, so any component in a JFrame will
320 * have a JLayeredPane parent.
321 *
322 * @param c the Component to check
323 * @return the JLayeredPane that contains the component, or
324 * null if no JLayeredPane is found in the component
325 * hierarchy
326 * @see JFrame
327 * @see JRootPane
328 */
329 public static JLayeredPane getLayeredPaneAbove(Component c) {
330 if(c == null) return null;
331
332 Component parent = c.getParent();
333 while(parent != null && !(parent instanceof JLayeredPane))
334 parent = parent.getParent();
335 return (JLayeredPane)parent;
336 }
337
338 /** Sets the layer attribute on the specified component,
339 * making it the bottommost component in that layer.
340 * Should be called before adding to parent.
341 *
342 * @param c the Component to set the layer for
343 * @param layer an int specifying the layer to set, where
344 * lower numbers are closer to the bottom
345 */
346 public void setLayer(Component c, int layer) {
347 setLayer(c, layer, -1);
348 }
349
350 /** Sets the layer attribute for the specified component and
351 * also sets its position within that layer.
352 *
353 * @param c the Component to set the layer for
354 * @param layer an int specifying the layer to set, where
355 * lower numbers are closer to the bottom
356 * @param position an int specifying the position within the
357 * layer, where 0 is the topmost position and -1
358 * is the bottommost position
359 */
360 public void setLayer(Component c, int layer, int position) {
361 Integer layerObj;
362 layerObj = getObjectForLayer(layer);
363
364 if(layer == getLayer(c) && position == getPosition(c)) {
365 repaint(c.getBounds());
366 return;
367 }
368
369 /// MAKE SURE THIS AND putLayer(JComponent c, int layer) are SYNCED
370 if(c instanceof JComponent)
371 ((JComponent)c).putClientProperty(LAYER_PROPERTY, layerObj);
372 else
373 getComponentToLayer().put(c, layerObj);
374
375 if(c.getParent() == null || c.getParent() != this) {
376 repaint(c.getBounds());
377 return;
378 }
379
380 int index = insertIndexForLayer(c, layer, position);
381
382 setComponentZOrder(c, index);
383 repaint(c.getBounds());
384 }
385
386 /**
387 * Returns the layer attribute for the specified Component.
388 *
389 * @param c the Component to check
390 * @return an int specifying the component's current layer
391 */
392 public int getLayer(Component c) {
393 Integer i;
394 if(c instanceof JComponent)
395 i = (Integer)((JComponent)c).getClientProperty(LAYER_PROPERTY);
396 else
397 i = getComponentToLayer().get(c);
398
399 if(i == null)
400 return DEFAULT_LAYER.intValue();
401 return i.intValue();
402 }
403
404 /**
405 * Returns the index of the specified Component.
406 * This is the absolute index, ignoring layers.
407 * Index numbers, like position numbers, have the topmost component
408 * at index zero. Larger numbers are closer to the bottom.
409 *
410 * @param c the Component to check
411 * @return an int specifying the component's index
412 */
413 public int getIndexOf(Component c) {
414 int i, count;
415
416 count = getComponentCount();
417 for(i = 0; i < count; i++) {
418 if(c == getComponent(i))
419 return i;
420 }
421 return -1;
422 }
423 /**
424 * Moves the component to the top of the components in its current layer
425 * (position 0).
426 *
427 * @param c the Component to move
428 * @see #setPosition(Component, int)
429 */
430 public void moveToFront(Component c) {
431 setPosition(c, 0);
432 }
433
434 /**
435 * Moves the component to the bottom of the components in its current layer
436 * (position -1).
437 *
438 * @param c the Component to move
439 * @see #setPosition(Component, int)
440 */
441 public void moveToBack(Component c) {
442 setPosition(c, -1);
443 }
444
445 /**
446 * Moves the component to <code>position</code> within its current layer,
447 * where 0 is the topmost position within the layer and -1 is the bottommost
448 * position.
449 * <p>
450 * <b>Note:</b> Position numbering is defined by java.awt.Container, and
451 * is the opposite of layer numbering. Lower position numbers are closer
452 * to the top (0 is topmost), and higher position numbers are closer to
453 * the bottom.
454 *
455 * @param c the Component to move
456 * @param position an int in the range -1..N-1, where N is the number of
457 * components in the component's current layer
458 */
459 public void setPosition(Component c, int position) {
460 setLayer(c, getLayer(c), position);
461 }
462
463 /**
464 * Get the relative position of the component within its layer.
465 *
466 * @param c the Component to check
467 * @return an int giving the component's position, where 0 is the
468 * topmost position and the highest index value = the count
469 * count of components at that layer, minus 1
470 *
471 * @see #getComponentCountInLayer
472 */
473 public int getPosition(Component c) {
474 int i, startLayer, curLayer, startLocation, pos = 0;
475
476 getComponentCount();
477 startLocation = getIndexOf(c);
478
479 if(startLocation == -1)
480 return -1;
481
482 startLayer = getLayer(c);
483 for(i = startLocation - 1; i >= 0; i--) {
484 curLayer = getLayer(getComponent(i));
485 if(curLayer == startLayer)
486 pos++;
487 else
488 return pos;
489 }
490 return pos;
491 }
492
493 /** Returns the highest layer value from all current children.
494 * Returns 0 if there are no children.
495 *
496 * @return an int indicating the layer of the topmost component in the
497 * pane, or zero if there are no children
498 */
499 public int highestLayer() {
500 if(getComponentCount() > 0)
501 return getLayer(getComponent(0));
502 return 0;
503 }
504
505 /** Returns the lowest layer value from all current children.
506 * Returns 0 if there are no children.
507 *
508 * @return an int indicating the layer of the bottommost component in the
509 * pane, or zero if there are no children
510 */
511 public int lowestLayer() {
512 int count = getComponentCount();
513 if(count > 0)
514 return getLayer(getComponent(count-1));
515 return 0;
516 }
517
518 /**
519 * Returns the number of children currently in the specified layer.
520 *
521 * @param layer an int specifying the layer to check
522 * @return an int specifying the number of components in that layer
523 */
524 public int getComponentCountInLayer(int layer) {
525 int i, count, curLayer;
526 int layerCount = 0;
527
528 count = getComponentCount();
529 for(i = 0; i < count; i++) {
530 curLayer = getLayer(getComponent(i));
531 if(curLayer == layer) {
532 layerCount++;
533 /// Short circut the counting when we have them all
534 } else if(layerCount > 0 || curLayer < layer) {
535 break;
536 }
537 }
538
539 return layerCount;
540 }
541
542 /**
543 * Returns an array of the components in the specified layer.
544 *
545 * @param layer an int specifying the layer to check
546 * @return an array of Components contained in that layer
547 */
548 public Component[] getComponentsInLayer(int layer) {
549 int i, count, curLayer;
550 int layerCount = 0;
551 Component[] results;
552
553 results = new Component[getComponentCountInLayer(layer)];
554 count = getComponentCount();
555 for(i = 0; i < count; i++) {
556 curLayer = getLayer(getComponent(i));
557 if(curLayer == layer) {
558 results[layerCount++] = getComponent(i);
559 /// Short circut the counting when we have them all
560 } else if(layerCount > 0 || curLayer < layer) {
561 break;
562 }
563 }
564
565 return results;
566 }
567
568 /**
569 * Paints this JLayeredPane within the specified graphics context.
570 *
571 * @param g the Graphics context within which to paint
572 */
573 public void paint(Graphics g) {
574 if(isOpaque()) {
575 Rectangle r = g.getClipBounds();
576 Color c = getBackground();
577 if(c == null)
578 c = Color.lightGray;
579 g.setColor(c);
580 if (r != null) {
581 g.fillRect(r.x, r.y, r.width, r.height);
582 }
583 else {
584 g.fillRect(0, 0, getWidth(), getHeight());
585 }
586 }
587 super.paint(g);
588 }
589
590 //////////////////////////////////////////////////////////////////////////////
591 //// Implementation Details
592 //////////////////////////////////////////////////////////////////////////////
593
594 /**
595 * Returns the hashtable that maps components to layers.
596 *
597 * @return the Hashtable used to map components to their layers
598 */
599 protected Hashtable<Component,Integer> getComponentToLayer() {
600 if(componentToLayer == null)
601 componentToLayer = new Hashtable<Component,Integer>(4);
602 return componentToLayer;
603 }
604
605 /**
606 * Returns the Integer object associated with a specified layer.
607 *
608 * @param layer an int specifying the layer
609 * @return an Integer object for that layer
610 */
611 protected Integer getObjectForLayer(int layer) {
612 Integer layerObj;
613 switch(layer) {
614 case 0:
615 layerObj = DEFAULT_LAYER;
616 break;
617 case 100:
618 layerObj = PALETTE_LAYER;
619 break;
620 case 200:
621 layerObj = MODAL_LAYER;
622 break;
623 case 300:
624 layerObj = POPUP_LAYER;
625 break;
626 case 400:
627 layerObj = DRAG_LAYER;
628 break;
629 default:
630 layerObj = layer;
631 }
632 return layerObj;
633 }
634
635 /**
636 * Primitive method that determines the proper location to
637 * insert a new child based on layer and position requests.
638 *
639 * @param layer an int specifying the layer
640 * @param position an int specifying the position within the layer
641 * @return an int giving the (absolute) insertion-index
642 *
643 * @see #getIndexOf
644 */
645 protected int insertIndexForLayer(int layer, int position) {
646 return insertIndexForLayer(null, layer, position);
647 }
648
649 /**
650 * This method is an extended version of insertIndexForLayer()
651 * to support setLayer which uses Container.setZOrder which does
652 * not remove the component from the containment hierarchy though
653 * we need to ignore it when calculating the insertion index.
654 *
655 * @param comp component to ignore when determining index
656 * @param layer an int specifying the layer
657 * @param position an int specifying the position within the layer
658 * @return an int giving the (absolute) insertion-index
659 *
660 * @see #getIndexOf
661 */
662 private int insertIndexForLayer(Component comp, int layer, int position) {
663 int i, count, curLayer;
664 int layerStart = -1;
665 int layerEnd = -1;
666 int componentCount = getComponentCount();
667
668 ArrayList<Component> compList =
669 new ArrayList<Component>(componentCount);
670 for (int index = 0; index < componentCount; index++) {
671 if (getComponent(index) != comp) {
672 compList.add(getComponent(index));
673 }
674 }
675
676 count = compList.size();
677 for (i = 0; i < count; i++) {
678 curLayer = getLayer(compList.get(i));
679 if (layerStart == -1 && curLayer == layer) {
680 layerStart = i;
681 }
682 if (curLayer < layer) {
683 if (i == 0) {
684 // layer is greater than any current layer
685 // [ ASSERT(layer > highestLayer()) ]
686 layerStart = 0;
687 layerEnd = 0;
688 } else {
689 layerEnd = i;
690 }
691 break;
692 }
693 }
694
695 // layer requested is lower than any current layer
696 // [ ASSERT(layer < lowestLayer()) ]
697 // put it on the bottom of the stack
698 if (layerStart == -1 && layerEnd == -1)
699 return count;
700
701 // In the case of a single layer entry handle the degenerative cases
702 if (layerStart != -1 && layerEnd == -1)
703 layerEnd = count;
704
705 if (layerEnd != -1 && layerStart == -1)
706 layerStart = layerEnd;
707
708 // If we are adding to the bottom, return the last element
709 if (position == -1)
710 return layerEnd;
711
712 // Otherwise make sure the requested position falls in the
713 // proper range
714 if (position > -1 && layerStart + position <= layerEnd)
715 return layerStart + position;
716
717 // Otherwise return the end of the layer
718 return layerEnd;
719 }
720
721 /**
722 * Returns a string representation of this JLayeredPane. This method
723 * is intended to be used only for debugging purposes, and the
724 * content and format of the returned string may vary between
725 * implementations. The returned string may be empty but may not
726 * be <code>null</code>.
727 *
728 * @return a string representation of this JLayeredPane.
729 */
730 protected String paramString() {
731 String optimizedDrawingPossibleString = (optimizedDrawingPossible ?
732 "true" : "false");
733
734 return super.paramString() +
735 ",optimizedDrawingPossible=" + optimizedDrawingPossibleString;
736 }
737
738 /////////////////
739 // Accessibility support
740 ////////////////
741
742 /**
743 * Gets the AccessibleContext associated with this JLayeredPane.
744 * For layered panes, the AccessibleContext takes the form of an
745 * AccessibleJLayeredPane.
746 * A new AccessibleJLayeredPane instance is created if necessary.
747 *
748 * @return an AccessibleJLayeredPane that serves as the
749 * AccessibleContext of this JLayeredPane
750 */
751 public AccessibleContext getAccessibleContext() {
752 if (accessibleContext == null) {
753 accessibleContext = new AccessibleJLayeredPane();
754 }
755 return accessibleContext;
756 }
757
758 /**
759 * This class implements accessibility support for the
760 * <code>JLayeredPane</code> class. It provides an implementation of the
761 * Java Accessibility API appropriate to layered pane user-interface
762 * elements.
763 * <p>
764 * <strong>Warning:</strong>
765 * Serialized objects of this class will not be compatible with
766 * future Swing releases. The current serialization support is
767 * appropriate for short term storage or RMI between applications running
768 * the same version of Swing. As of 1.4, support for long term storage
769 * of all JavaBeans™
770 * has been added to the <code>java.beans</code> package.
771 * Please see {@link java.beans.XMLEncoder}.
772 */
773 @SuppressWarnings("serial")
774 protected class AccessibleJLayeredPane extends AccessibleJComponent {
775
776 /**
777 * Get the role of this object.
778 *
779 * @return an instance of AccessibleRole describing the role of the
780 * object
781 * @see AccessibleRole
782 */
783 public AccessibleRole getAccessibleRole() {
784 return AccessibleRole.LAYERED_PANE;
785 }
786 }
787 }