src/java.desktop/share/classes/javax/swing/JLayeredPane.java - master - githubmirror/panama-vector

src/java.desktop/share/classes/javax/swing/JLayeredPane.java
785 строк28 KB
Andrey Turbanov
8312165: Fix typos in java.desktop Swing
15 сен 2023, 12:18
15 сен 2023, 12:1889cb290
/*
 * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package javax.swing;

import java.awt.Component;
import java.util.ArrayList;
import java.util.Hashtable;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.beans.JavaBean;
import java.beans.BeanProperty;

import sun.awt.SunToolkit;

import javax.accessibility.*;

/**
 * <code>JLayeredPane</code> adds depth to a JFC/Swing container,
 * allowing components to overlap each other when needed.
 * An <code>Integer</code> object specifies each component's depth in the
 * container, where higher-numbered components sit &quot;on top&quot; of other
 * components.
 * For task-oriented documentation and examples of using layered panes see
 * <a href="https://docs.oracle.com/javase/tutorial/uiswing/components/layeredpane.html">How to Use a Layered Pane</a>,
 * a section in <em>The Java Tutorial</em>.
 *
 * <div style="float:right;text-align:center">
 *   <p><b>Example:</b>
 *   <p><img src="doc-files/JLayeredPane-1.gif"
 *       alt="The following text describes this image."
 *       width="269" height="264">
 * </div>
 * For convenience, <code>JLayeredPane</code> divides the depth-range
 * into several different layers. Putting a component into one of those
 * layers makes it easy to ensure that components overlap properly,
 * without having to worry about specifying numbers for specific depths:
 * <DL>
 *    <DT>DEFAULT_LAYER</DT>
 *         <DD>The standard layer, where most components go. This the bottommost
 *         layer.
 *    <DT>PALETTE_LAYER</DT>
 *         <DD>The palette layer sits over the default layer. Useful for floating
 *         toolbars and palettes, so they can be positioned above other components.
 *    <DT>MODAL_LAYER</DT>
 *         <DD>The layer used for modal dialogs. They will appear on top of any
 *         toolbars, palettes, or standard components in the container.
 *    <DT>POPUP_LAYER</DT>
 *         <DD>The popup layer displays above dialogs. That way, the popup windows
 *         associated with combo boxes, tooltips, and other help text will appear
 *         above the component, palette, or dialog that generated them.
 *    <DT>DRAG_LAYER</DT>
 *         <DD>When dragging a component, reassigning it to the drag layer ensures
 *         that it is positioned over every other component in the container. When
 *         finished dragging, it can be reassigned to its normal layer.
 * </DL>
 * The <code>JLayeredPane</code> methods <code>moveToFront(Component)</code>,
 * <code>moveToBack(Component)</code> and <code>setPosition</code> can be used
 * to reposition a component within its layer. The <code>setLayer</code> method
 * can also be used to change the component's current layer.
 *
 * <h2>Details</h2>
 * <code>JLayeredPane</code> manages its list of children like
 * <code>Container</code>, but allows for the definition of a several
 * layers within itself. Children in the same layer are managed exactly
 * like the normal <code>Container</code> object,
 * with the added feature that when children components overlap, children
 * in higher layers display above the children in lower layers.
 * <p>
 * Each layer is a distinct integer number. The layer attribute can be set
 * on a <code>Component</code> by passing an <code>Integer</code>
 * object during the add call.<br> For example:
 * <PRE>
 *     layeredPane.add(child, JLayeredPane.DEFAULT_LAYER);
 * or
 *     layeredPane.add(child, Integer.valueOf(10));
 * </PRE>
 * The layer attribute can also be set on a Component by calling<PRE>
 *     layeredPaneParent.setLayer(child, 10)</PRE>
 * on the <code>JLayeredPane</code> that is the parent of component. The layer
 * should be set <i>before</i> adding the child to the parent.
 * <p>
 * Higher number layers display above lower number layers. So, using
 * numbers for the layers and letters for individual components, a
 * representative list order would look like this:<PRE>
 *       5a, 5b, 5c, 2a, 2b, 2c, 1a </PRE>
 * where the leftmost components are closest to the top of the display.
 * <p>
 * A component can be moved to the top or bottom position within its
 * layer by calling <code>moveToFront</code> or <code>moveToBack</code>.
 * <p>
 * The position of a component within a layer can also be specified directly.
 * Valid positions range from 0 up to one less than the number of
 * components in that layer. A value of -1 indicates the bottommost
 * position. A value of 0 indicates the topmost position. Unlike layer
 * numbers, higher position values are <i>lower</i> in the display.
 * <blockquote>
 * <b>Note:</b> This sequence (defined by java.awt.Container) is the reverse
 * of the layer numbering sequence. Usually though, you will use <code>moveToFront</code>,
 * <code>moveToBack</code>, and <code>setLayer</code>.
 * </blockquote>
 * Here are some examples using the method add(Component, layer, position):
 * Calling add(5x, 5, -1) results in:<PRE>
 *       5a, 5b, 5c, 5x, 2a, 2b, 2c, 1a </PRE>
 *
 * Calling add(5z, 5, 2) results in:<PRE>
 *       5a, 5b, 5z, 5c, 5x, 2a, 2b, 2c, 1a </PRE>
 *
 * Calling add(3a, 3, 7) results in:<PRE>
 *       5a, 5b, 5z, 5c, 5x, 3a, 2a, 2b, 2c, 1a </PRE>
 *
 * Using normal paint/event mechanics results in 1a appearing at the bottom
 * and 5a being above all other components.
 * <p>
 * <b>Note:</b> that these layers are simply a logical construct and LayoutManagers
 * will affect all child components of this container without regard for
 * layer settings.
 * <p>
 * <strong>Warning:</strong> Swing is not thread safe. For more
 * information see <a
 * href="package-summary.html#threading">Swing's Threading
 * Policy</a>.
 * <p>
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with
 * future Swing releases. The current serialization support is
 * appropriate for short term storage or RMI between applications running
 * the same version of Swing.  As of 1.4, support for long term storage
 * of all JavaBeans
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @author David Kloba
 * @since 1.2
 */
@JavaBean(defaultProperty = "accessibleContext")
@SuppressWarnings("serial")
public class JLayeredPane extends JComponent implements Accessible {
    /// Watch the values in getObjectForLayer()
    /** Convenience object defining the Default layer. Equivalent to Integer.valueOf(0).*/
    public static final Integer DEFAULT_LAYER = 0;
    /** Convenience object defining the Palette layer. Equivalent to Integer.valueOf(100).*/
    public static final Integer PALETTE_LAYER = 100;
    /** Convenience object defining the Modal layer. Equivalent to Integer.valueOf(200).*/
    public static final Integer MODAL_LAYER = 200;
    /** Convenience object defining the Popup layer. Equivalent to Integer.valueOf(300).*/
    public static final Integer POPUP_LAYER = 300;
    /** Convenience object defining the Drag layer. Equivalent to Integer.valueOf(400).*/
    public static final Integer DRAG_LAYER = 400;
    /** Convenience object defining the Frame Content layer.
      * This layer is normally only use to position the contentPane and menuBar
      * components of JFrame.
      * Equivalent to Integer.valueOf(-30000).
      * @see JFrame
      */
    public static final Integer FRAME_CONTENT_LAYER = -30000;

    /** Bound property */
    public static final String LAYER_PROPERTY = "layeredContainerLayer";
    // Hashtable to store layer values for non-JComponent components
    private Hashtable<Component,Integer> componentToLayer;
    private boolean optimizedDrawingPossible = true;


//////////////////////////////////////////////////////////////////////////////
//// Container Override methods
//////////////////////////////////////////////////////////////////////////////
    /** Create a new JLayeredPane */
    public JLayeredPane() {
        setLayout(null);
    }

    private void validateOptimizedDrawing() {
        boolean layeredComponentFound = false;
        synchronized(getTreeLock()) {
            Integer layer;

            for (Component c : getComponents()) {
                layer = null;

                if(SunToolkit.isInstanceOf(c, "javax.swing.JInternalFrame") ||
                       (c instanceof JComponent &&
                        (layer = (Integer)((JComponent)c).
                                     getClientProperty(LAYER_PROPERTY)) != null))
                {
                    if (FRAME_CONTENT_LAYER.equals(layer))
                        continue;
                    layeredComponentFound = true;
                    break;
                }
            }
        }

        if(layeredComponentFound)
            optimizedDrawingPossible = false;
        else
            optimizedDrawingPossible = true;
    }

    protected void addImpl(Component comp, Object constraints, int index) {
        int layer;
        int pos;

        if(constraints instanceof Integer) {
            layer = ((Integer)constraints).intValue();
            setLayer(comp, layer);
        } else
            layer = getLayer(comp);

        pos = insertIndexForLayer(layer, index);
        super.addImpl(comp, constraints, pos);
        comp.validate();
        comp.repaint();
        validateOptimizedDrawing();
    }

    /**
     * Remove the indexed component from this pane.
     * This is the absolute index, ignoring layers.
     *
     * @param index  an int specifying the component to remove
     * @see #getIndexOf
     */
    public void remove(int index) {
        Component c = getComponent(index);
        super.remove(index);
        if (c != null && !(c instanceof JComponent)) {
            getComponentToLayer().remove(c);
        }
        validateOptimizedDrawing();
    }

    /**
     * Removes all the components from this container.
     *
     * @since 1.5
     */
    public void removeAll() {
        Component[] children = getComponents();
        Hashtable<Component, Integer> cToL = getComponentToLayer();
        for (int counter = children.length - 1; counter >= 0; counter--) {
            Component c = children[counter];
            if (c != null && !(c instanceof JComponent)) {
                cToL.remove(c);
            }
        }
        super.removeAll();
    }

    /**
     * Returns false if components in the pane can overlap, which makes
     * optimized drawing impossible. Otherwise, returns true.
     *
     * @return false if components can overlap, else true
     * @see JComponent#isOptimizedDrawingEnabled
     */
    @BeanProperty(bound = false)
    public boolean isOptimizedDrawingEnabled() {
        return optimizedDrawingPossible;
    }


//////////////////////////////////////////////////////////////////////////////
//// New methods for managing layers
//////////////////////////////////////////////////////////////////////////////
    /** Sets the layer property on a JComponent. This method does not cause
      * any side effects like setLayer() (painting, add/remove, etc).
      * Normally you should use the instance method setLayer(), in order to
      * get the desired side-effects (like repainting).
      *
      * @param c      the JComponent to move
      * @param layer  an int specifying the layer to move it to
      * @see #setLayer
      */
    public static void putLayer(JComponent c, int layer) {
        /// MAKE SURE THIS AND setLayer(Component c, int layer, int position)  are SYNCED
        c.putClientProperty(LAYER_PROPERTY, layer);
    }

    /** Gets the layer property for a JComponent, it
      * does not cause any side effects like setLayer(). (painting, add/remove, etc)
      * Normally you should use the instance method getLayer().
      *
      * @param c  the JComponent to check
      * @return   an int specifying the component's layer
      */
    public static int getLayer(JComponent c) {
        Integer i;
        if((i = (Integer)c.getClientProperty(LAYER_PROPERTY)) != null)
            return i.intValue();
        return DEFAULT_LAYER.intValue();
    }

    /** Convenience method that returns the first JLayeredPane which
      * contains the specified component. Note that all JFrames have a
      * JLayeredPane at their root, so any component in a JFrame will
      * have a JLayeredPane parent.
      *
      * @param c the Component to check
      * @return the JLayeredPane that contains the component, or
      *         null if no JLayeredPane is found in the component
      *         hierarchy
      * @see JFrame
      * @see JRootPane
      */
    public static JLayeredPane getLayeredPaneAbove(Component c) {
        if(c == null) return null;

        Component parent = c.getParent();
        while(parent != null && !(parent instanceof JLayeredPane))
            parent = parent.getParent();
        return (JLayeredPane)parent;
    }

    /** Sets the layer attribute on the specified component,
      * making it the bottommost component in that layer.
      * Should be called before adding to parent.
      *
      * @param c     the Component to set the layer for
      * @param layer an int specifying the layer to set, where
      *              lower numbers are closer to the bottom
      */
    public void setLayer(Component c, int layer)  {
        setLayer(c, layer, -1);
    }

    /** Sets the layer attribute for the specified component and
      * also sets its position within that layer.
      *
      * @param c         the Component to set the layer for
      * @param layer     an int specifying the layer to set, where
      *                  lower numbers are closer to the bottom
      * @param position  an int specifying the position within the
      *                  layer, where 0 is the topmost position and -1
      *                  is the bottommost position
      */
    public void setLayer(Component c, int layer, int position)  {
        Integer layerObj;
        layerObj = getObjectForLayer(layer);

        if(layer == getLayer(c) && position == getPosition(c)) {
                repaint(c.getBounds());
            return;
        }

        /// MAKE SURE THIS AND putLayer(JComponent c, int layer) are SYNCED
        if(c instanceof JComponent)
            ((JComponent)c).putClientProperty(LAYER_PROPERTY, layerObj);
        else
            getComponentToLayer().put(c, layerObj);

        if(c.getParent() == null || c.getParent() != this) {
            repaint(c.getBounds());
            return;
        }

        int index = insertIndexForLayer(c, layer, position);

        setComponentZOrder(c, index);
        repaint(c.getBounds());
    }

    /**
     * Returns the layer attribute for the specified Component.
     *
     * @param c  the Component to check
     * @return an int specifying the component's current layer
     */
    public int getLayer(Component c) {
        Integer i;
        if(c instanceof JComponent)
            i = (Integer)((JComponent)c).getClientProperty(LAYER_PROPERTY);
        else
            i = getComponentToLayer().get(c);

        if(i == null)
            return DEFAULT_LAYER.intValue();
        return i.intValue();
    }

    /**
     * Returns the index of the specified Component.
     * This is the absolute index, ignoring layers.
     * Index numbers, like position numbers, have the topmost component
     * at index zero. Larger numbers are closer to the bottom.
     *
     * @param c  the Component to check
     * @return an int specifying the component's index
     */
    public int getIndexOf(Component c) {
        int i, count;

        count = getComponentCount();
        for(i = 0; i < count; i++) {
            if(c == getComponent(i))
                return i;
        }
        return -1;
    }
    /**
     * Moves the component to the top of the components in its current layer
     * (position 0).
     *
     * @param c the Component to move
     * @see #setPosition(Component, int)
     */
    public void moveToFront(Component c) {
        setPosition(c, 0);
    }

    /**
     * Moves the component to the bottom of the components in its current layer
     * (position -1).
     *
     * @param c the Component to move
     * @see #setPosition(Component, int)
     */
    public void moveToBack(Component c) {
        setPosition(c, -1);
    }

    /**
     * Moves the component to <code>position</code> within its current layer,
     * where 0 is the topmost position within the layer and -1 is the bottommost
     * position.
     * <p>
     * <b>Note:</b> Position numbering is defined by java.awt.Container, and
     * is the opposite of layer numbering. Lower position numbers are closer
     * to the top (0 is topmost), and higher position numbers are closer to
     * the bottom.
     *
     * @param c         the Component to move
     * @param position  an int in the range -1..N-1, where N is the number of
     *                  components in the component's current layer
     */
    public void setPosition(Component c, int position) {
        setLayer(c, getLayer(c), position);
    }

    /**
     * Get the relative position of the component within its layer.
     *
     * @param c  the Component to check
     * @return an int giving the component's position, where 0 is the
     *         topmost position and the highest index value = the count
     *         of components at that layer minus 1
     *
     * @see #getComponentCountInLayer
     */
    public int getPosition(Component c) {
        int i, startLayer, curLayer, startLocation, pos = 0;

        getComponentCount();
        startLocation = getIndexOf(c);

        if(startLocation == -1)
            return -1;

        startLayer = getLayer(c);
        for(i = startLocation - 1; i >= 0; i--) {
            curLayer = getLayer(getComponent(i));
            if(curLayer == startLayer)
                pos++;
            else
                return pos;
        }
        return pos;
    }

    /** Returns the highest layer value from all current children.
      * Returns 0 if there are no children.
      *
      * @return an int indicating the layer of the topmost component in the
      *         pane, or zero if there are no children
      */
    public int highestLayer() {
        if(getComponentCount() > 0)
            return getLayer(getComponent(0));
        return 0;
    }

    /** Returns the lowest layer value from all current children.
      * Returns 0 if there are no children.
      *
      * @return an int indicating the layer of the bottommost component in the
      *         pane, or zero if there are no children
      */
    public int lowestLayer() {
        int count = getComponentCount();
        if(count > 0)
            return getLayer(getComponent(count-1));
        return 0;
    }

    /**
     * Returns the number of children currently in the specified layer.
     *
     * @param layer  an int specifying the layer to check
     * @return an int specifying the number of components in that layer
     */
    public int getComponentCountInLayer(int layer) {
        int i, count, curLayer;
        int layerCount = 0;

        count = getComponentCount();
        for(i = 0; i < count; i++) {
            curLayer = getLayer(getComponent(i));
            if(curLayer == layer) {
                layerCount++;
            // Short-circuit the counting when we have them all
            } else if(layerCount > 0 || curLayer < layer) {
                break;
            }
        }

        return layerCount;
    }

    /**
     * Returns an array of the components in the specified layer.
     *
     * @param layer  an int specifying the layer to check
     * @return an array of Components contained in that layer
     */
    public Component[] getComponentsInLayer(int layer) {
        int i, count, curLayer;
        int layerCount = 0;
        Component[] results;

        results = new Component[getComponentCountInLayer(layer)];
        count = getComponentCount();
        for(i = 0; i < count; i++) {
            curLayer = getLayer(getComponent(i));
            if(curLayer == layer) {
                results[layerCount++] = getComponent(i);
            // Short-circuit the counting when we have them all
            } else if(layerCount > 0 || curLayer < layer) {
                break;
            }
        }

        return results;
    }

    /**
     * Paints this JLayeredPane within the specified graphics context.
     *
     * @param g  the Graphics context within which to paint
     */
    public void paint(Graphics g) {
        if(isOpaque()) {
            Rectangle r = g.getClipBounds();
            Color c = getBackground();
            if(c == null)
                c = Color.lightGray;
            g.setColor(c);
            if (r != null) {
                g.fillRect(r.x, r.y, r.width, r.height);
            }
            else {
                g.fillRect(0, 0, getWidth(), getHeight());
            }
        }
        super.paint(g);
    }

//////////////////////////////////////////////////////////////////////////////
//// Implementation Details
//////////////////////////////////////////////////////////////////////////////

    /**
     * Returns the hashtable that maps components to layers.
     *
     * @return the Hashtable used to map components to their layers
     */
    protected Hashtable<Component,Integer> getComponentToLayer() {
        if(componentToLayer == null)
            componentToLayer = new Hashtable<Component,Integer>(4);
        return componentToLayer;
    }

    /**
     * Returns the Integer object associated with a specified layer.
     *
     * @param layer an int specifying the layer
     * @return an Integer object for that layer
     */
    protected Integer getObjectForLayer(int layer) {
        switch(layer) {
        case 0:
            return DEFAULT_LAYER;
        case 100:
            return PALETTE_LAYER;
        case 200:
            return MODAL_LAYER;
        case 300:
            return POPUP_LAYER;
        case 400:
            return DRAG_LAYER;
        default:
            return layer;
        }
    }

    /**
     * Primitive method that determines the proper location to
     * insert a new child based on layer and position requests.
     *
     * @param layer     an int specifying the layer
     * @param position  an int specifying the position within the layer
     * @return an int giving the (absolute) insertion-index
     *
     * @see #getIndexOf
     */
    protected int insertIndexForLayer(int layer, int position) {
        return insertIndexForLayer(null, layer, position);
    }

    /**
     * This method is an extended version of insertIndexForLayer()
     * to support setLayer which uses Container.setZOrder which does
     * not remove the component from the containment hierarchy though
     * we need to ignore it when calculating the insertion index.
     *
     * @param comp      component to ignore when determining index
     * @param layer     an int specifying the layer
     * @param position  an int specifying the position within the layer
     * @return an int giving the (absolute) insertion-index
     *
     * @see #getIndexOf
     */
    private int insertIndexForLayer(Component comp, int layer, int position) {
        int i, count, curLayer;
        int layerStart = -1;
        int layerEnd = -1;
        int componentCount = getComponentCount();

        ArrayList<Component> compList =
            new ArrayList<Component>(componentCount);
        for (int index = 0; index < componentCount; index++) {
            if (getComponent(index) != comp) {
                compList.add(getComponent(index));
            }
        }

        count = compList.size();
        for (i = 0; i < count; i++) {
            curLayer = getLayer(compList.get(i));
            if (layerStart == -1 && curLayer == layer) {
                layerStart = i;
            }
            if (curLayer < layer) {
                if (i == 0) {
                    // layer is greater than any current layer
                    // [ ASSERT(layer > highestLayer()) ]
                    layerStart = 0;
                    layerEnd = 0;
                } else {
                    layerEnd = i;
                }
                break;
            }
        }

        // layer requested is lower than any current layer
        // [ ASSERT(layer < lowestLayer()) ]
        // put it on the bottom of the stack
        if (layerStart == -1 && layerEnd == -1)
            return count;

        // In the case of a single layer entry handle the degenerative cases
        if (layerStart != -1 && layerEnd == -1)
            layerEnd = count;

        if (layerEnd != -1 && layerStart == -1)
            layerStart = layerEnd;

        // If we are adding to the bottom, return the last element
        if (position == -1)
            return layerEnd;

        // Otherwise make sure the requested position falls in the
        // proper range
        if (position > -1 && layerStart + position <= layerEnd)
            return layerStart + position;

        // Otherwise return the end of the layer
        return layerEnd;
    }

    /**
     * Returns a string representation of this JLayeredPane. This method
     * is intended to be used only for debugging purposes, and the
     * content and format of the returned string may vary between
     * implementations. The returned string may be empty but may not
     * be <code>null</code>.
     *
     * @return  a string representation of this JLayeredPane.
     */
    protected String paramString() {
        String optimizedDrawingPossibleString = (optimizedDrawingPossible ?
                                                 "true" : "false");

        return super.paramString() +
        ",optimizedDrawingPossible=" + optimizedDrawingPossibleString;
    }

/////////////////
// Accessibility support
////////////////

    /**
     * Gets the AccessibleContext associated with this JLayeredPane.
     * For layered panes, the AccessibleContext takes the form of an
     * AccessibleJLayeredPane.
     * A new AccessibleJLayeredPane instance is created if necessary.
     *
     * @return an AccessibleJLayeredPane that serves as the
     *         AccessibleContext of this JLayeredPane
     */
    @BeanProperty(bound = false)
    public AccessibleContext getAccessibleContext() {
        if (accessibleContext == null) {
            accessibleContext = new AccessibleJLayeredPane();
        }
        return accessibleContext;
    }

    /**
     * This class implements accessibility support for the
     * <code>JLayeredPane</code> class.  It provides an implementation of the
     * Java Accessibility API appropriate to layered pane user-interface
     * elements.
     * <p>
     * <strong>Warning:</strong>
     * Serialized objects of this class will not be compatible with
     * future Swing releases. The current serialization support is
     * appropriate for short term storage or RMI between applications running
     * the same version of Swing.  As of 1.4, support for long term storage
     * of all JavaBeans
     * has been added to the <code>java.beans</code> package.
     * Please see {@link java.beans.XMLEncoder}.
     */
    @SuppressWarnings("serial")
    protected class AccessibleJLayeredPane extends AccessibleJComponent {

        /**
         * Constructs an {@code AccessibleJLayeredPane}.
         */
        protected AccessibleJLayeredPane() {}

        /**
         * Get the role of this object.
         *
         * @return an instance of AccessibleRole describing the role of the
         * object
         * @see AccessibleRole
         */
        public AccessibleRole getAccessibleRole() {
            return AccessibleRole.LAYERED_PANE;
        }
    }
}