Java 1.2 How-To/JavaHowTo.iso/3rdParty/jbuilder/unsupported/JDK1.2beta3/SOURCE/SRC.ZIP/java/awt/swing/JMenu.java

Java Source | 1998-03-20 | 32.8 KB | 1,024 lines

/*
 * @(#)JMenu.java    1.86 98/02/04
 *
 * Copyright (c) 1997 Sun Microsystems, Inc. All Rights Reserved.
 *
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 *
 */

package java.awt.swing;

import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.LayoutManager;
import java.awt.Point;
import java.awt.Polygon;
import java.awt.Rectangle;
import java.awt.event.*;
import java.beans.*;

import java.util.*;
import java.io.Serializable;

import java.awt.swing.event.*;
import java.awt.swing.plaf.*;
import java.awt.accessibility.*;


/**
 * An implementation of a menu -- a popup window containing <code>JMenuItem</code>s that
 * is displayed when the user selects an item on the <code>JMenuBar</code>. In addition
 * to JMenuItems, a JMenu can also contain <code>JSeparator</code>s.
 * <p>
 * In essence, a menu is a button with an associated JPopupMenu.
 * When the "button" is pressed, the JPopupMenu appears. If the
 * "button" is on the JMenuBar, the menu is a top-level window.
 * If the "button" is another menu item, then the JPopupMenu is
 * "pull-right" menu.
 * <p>
 * Warning: 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 Swing1.0 applications.  It will
 * not be possible to load serialized Swing1.0 objects with future releases
 * of Swing.  The JDK1.2 release of Swing will be the compatibility
 * baseline for the serialized form of Swing objects.
 *
 * @version 1.86 02/04/98
 * @author Georges Saab
 * @author David Karlton
 * @author Arnaud Weber
 * @see JMenuItem
 * @see JSeparator
 * @see JMenuBar
 * @see JPopupMenu
 */
public class JMenu extends JMenuItem implements Accessible,MenuElement
{
    /*
     * The popup menu portion of the menu.
     */
    private JPopupMenu popupMenu;

    /*
     * The button's model listeners.
     */
    private ChangeListener menuChangeListener = null;

    /*
     * Only one MenuEvent is needed per menu instance since the
     * event's only state is the source property.  The source of events
     * generated is always "this".
     */
    private MenuEvent menuEvent = null;

    /**
     * Creates a new JMenu with no text.
     */
    public JMenu() {
        this("");
    }

    /**
     * Creates a new JMenu with the supplied string as its text
     *
     * @param s  The text for the menu label
     */
    public JMenu(String s) {
        init(s, null);
        updateUI();
    }

    /**
     * Creates a new JMenu with the supplied string as its text
     * and specified as a tear-off menu or not.
     *
     * @param s The text for the menu label
     * @param b can the menu be torn off (not yet implemented)
     */
    public JMenu(String s, boolean b) {
        this(s);
    }

    /**
     * Sets the L&F object that renders this component.
     *
     * @param ui the new MenuUI
     * @see getUI
     * @beaninfo
     * description: The menu item's UI delegate
     *       bound: true
     *      expert: true
     *      hidden: true
     */
    public void setUI(MenuUI ui) {
        super.setUI(ui);
    }

    /**
     * Notification from the UIFactory that the L&F has changed.
     * Called to replace the UI with the latest version from the
     * UIFactory.
     *
     * @see JComponent#updateUI
     */
    public void updateUI() {
        setUI((MenuUI)UIManager.getUI(this));

        if ( popupMenu != null )
          {
            popupMenu.setUI((PopupMenuUI)UIManager.getUI(popupMenu));
          }

    }


    /**
     * Returns the name of the L&F class that renders this component.
     *
     * @return "MenuUI"
     * @see JComponent#getUIClassID
     * @see UIDefaults#getUI
     */
    public String getUIClassID() {
        return "MenuUI";
    }

    //    public void repaint(long tm, int x, int y, int width, int height) {
    //        Thread.currentThread().dumpStack();
    //        super.repaint(tm,x,y,width,height);
    //    }

    /**
     * Set the data model for the "menu button" -- the label
     * that the user clicks to open or close the menu.
     *
     * @param m the ButtonModel
     * @see getModel
     * @beaninfo
     * description: The menu's model
     *       bound: true
     *      expert: true
     *      hidden: true
     */
    public void setModel(ButtonModel newModel) {
        ButtonModel oldModel = getModel();

        super.setModel(newModel);

        if (oldModel != null) {
            oldModel.removeChangeListener(menuChangeListener);
            menuChangeListener = null;
        }

        model = newModel;

        if (newModel != null) {
            menuChangeListener = createMenuChangeListener();
            newModel.addChangeListener(menuChangeListener);
        }
    }

    /**
     * Returns true if the menu is currently selected (popped up).
     *
     * @return true if the menu is open, else false
     */
    public boolean isSelected() {
        return getModel().isSelected();
    }

    /**
     * Sets the selection status of the menu.
     *
     * @param b  a boolean value -- true to select the menu and
     *           open it, false to unselect the menu and close it
     * @beaninfo
     *      description: When the menu is selected, its popup child is shown.
     *           expert: true
     *           hidden: true
     */
    public void setSelected(boolean b) {
        ButtonModel model = getModel();
        boolean oldValue = model.isSelected();

        if ((accessibleContext != null) && (oldValue != b)) {
            if (b) {
                 accessibleContext.firePropertyChange(
                 AccessibleContext.ACCESSIBLE_STATE_PROPERTY,
             null, AccessibleState.SELECTED);
            } else {
                 accessibleContext.firePropertyChange(
                         AccessibleContext.ACCESSIBLE_STATE_PROPERTY,
                 AccessibleState.SELECTED, null);
            }
        }
        if (b != model.isSelected()) {
            getModel().setSelected(b);
        }
    }

    /**
     * Returns true if the menu's popup window is visible.
     *
     * @return true if the menu is visible, else false
     */
    public boolean isPopupMenuVisible() {
        ensurePopupMenuCreated();
        return popupMenu.isVisible();
    }

    /**
     * Set the visibility of the Menu's popup portion.  The popup
     * may only be made visible if the menu is itself showing on
     * the screen.
     *
     * @param b  a boolean value -- true to make the menu visible,
     *           false to hide it
     * @beaninfo
     *      description: The popup menu's visibility
     *           expert: true
     *           hidden: true
     */
    public void setPopupMenuVisible(boolean b) {
        boolean isVisible = isPopupMenuVisible();
        if (b != isVisible) {
            ensurePopupMenuCreated();
            // Set location of popupMenu (pulldown or pullright)
            //  Perhaps this should be dictated by L&F
            int x = 0;
            int y = 0;
            if ((b==true) && isShowing()) {
                Container parent = getParent();
                Dimension s = getSize();
                if (parent instanceof JPopupMenu) {
                    // System.out.println("Pullright: " + getText());
                    x = s.width;
                    y = 0;
                } else {
                    // System.out.println("Pulldown: " + getText());
                    x = 0;
                    y = s.height;
                }

                popupMenu.show(this, x, y);
            } else {
                popupMenu.setVisible(false);
            }
        }

    }

    private int delay = 0;

    /**
     * Returns the suggested delay before the menu's PopupMenu is popped up or down.
     *
     * @return an int -- the number of milliseconds to delay
     */
    public int getDelay() {
        return delay;
    }

    /**
     * Sets the suggested delay before the menu's PopupMenu is popped up or down.
     *
     * @param       d the number of milliseconds to delay
     * @exception   IllegalArgumentException if the value of
     *                       <code>d</code> is less than 0.
     * @beaninfo
     *      description: The delay between menu selection and making the popup menu visible
     *           expert: true
     */
    public void setDelay(int d) {
        if (d < 0)
            throw new IllegalArgumentException("Delay must be a positive integer");

        delay = d;
    }

    /**
     * The window-closing listener for the popup.
     *
     * @see WinListener
     */
    protected WinListener popupListener;

    private void ensurePopupMenuCreated() {
        if (popupMenu == null) {
            final JMenu thisMenu = this;
            this.popupMenu = new JPopupMenu();
        popupMenu.setInvoker(this);
            popupListener = createWinListener(popupMenu);
            popupMenu.addPopupMenuListener(new PopupMenuListener() {
                public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
                }
                public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
                }
                public void popupMenuCanceled(PopupMenuEvent e) {
                    ((MenuUI)getUI()).menuCanceled(thisMenu);
                }
            });
        }
    }

    /**
     * Set the location of the popup component
     *
     * @param x the x coordinate of the popup's new position
     * @param y the y coordinate of the popup's new position
     */
    public void setMenuLocation(int x, int y) {
        popupMenu.setLocation(x, y);
    }

    /**
     * Appends a menuitem to the end of this menu.
     * Returns the menuitem added.
     *
     * @param menuItem the JMenuitem to be added
     * @return the JMenuItem added
     */
    public JMenuItem add(JMenuItem menuItem) {
        AccessibleContext ac = menuItem.getAccessibleContext();
        ac.setAccessibleParent(this);
        ensurePopupMenuCreated();
        return popupMenu.add(menuItem);
    }

    /**
     * Appends a component to the end of this menu.
     * Returns the component added.
     *
     * @param c the Component to add
     * @return the Component added
     */
    public Component add(Component c) {
        AccessibleContext ac = ((JComponent) c).getAccessibleContext();
        ac.setAccessibleParent(this);
        ensurePopupMenuCreated();
        popupMenu.add(c);
        return c;
    }

    /**
     * Creates a new menuitem with the specified text and appends
     * it to the end of this menu.
     *
     * @param s the string for the menuitem to be added
     */
    public void add(String s) {
        add(new JMenuItem(s));
    }

    /**
     * Creates a new menuitem attached to the specified
     * Action object and appends it to the end of this menu.
     *
     * @param a the Action for the menuitem to be added
     * @see Action
     */
    public JMenuItem add(Action a) {
        JMenuItem mi = new JMenuItem((String)a.getValue(Action.NAME),
                     (Icon)a.getValue(Action.SMALL_ICON));
    mi.setHorizontalTextPosition(JButton.RIGHT);
    mi.setVerticalTextPosition(JButton.CENTER);
    mi.setEnabled(a.isEnabled());
        mi.addActionListener(a);
        add(mi);
    PropertyChangeListener actionPropertyChangeListener =
        createActionChangeListener(mi);
        a.addPropertyChangeListener(actionPropertyChangeListener);
        return mi;
    }

    protected PropertyChangeListener createActionChangeListener(JMenuItem b) {
    return new ActionChangedListener(b);
    }

    private class ActionChangedListener implements PropertyChangeListener {
        JMenuItem menuItem;

        ActionChangedListener(JMenuItem mi) {
            super();
            this.menuItem = mi;
        }
        public void propertyChange(PropertyChangeEvent e) {
            String propertyName = e.getPropertyName();
            if (e.getPropertyName().equals(Action.NAME)) {
                String text = (String) e.getNewValue();
                menuItem.setText(text);
            } else if (propertyName.equals("enabled")) {
                Boolean enabledState = (Boolean) e.getNewValue();
                menuItem.setEnabled(enabledState.booleanValue());
            } else if (e.getPropertyName().equals(Action.SMALL_ICON)) {
                Icon icon = (Icon) e.getNewValue();
                menuItem.setIcon(icon);
                menuItem.invalidate();
                menuItem.repaint();
            }
        }
    }

    /**
     * Append a new separator to the end of the menu.
     */
    public void addSeparator() {
        ensurePopupMenuCreated();
        popupMenu.addSeparator();
    }

    /**
     * Insert a new menuitem with the specified text at a
     * given position.
     *
     * @param s the text for the menuitem to add
     * @param pos an int giving the position at which to add the
     *               new menuitem
     */
    public void insert(String s, int pos) {
        if (pos < 0) {
            throw new IllegalArgumentException("index less than zero.");
        }

        ensurePopupMenuCreated();
        popupMenu.insert(new JMenuItem(s), pos);
    }

    /**
     * Insert the specified JMenuitem at a given position.
     *
     * @param mi the JMenuitem to add
     * @param pos an int giving the position at which to add the
     *               new JMenuitem
     */
    public JMenuItem insert(JMenuItem mi, int pos) {
        if (pos < 0) {
            throw new IllegalArgumentException("index less than zero.");
        }
        AccessibleContext ac = mi.getAccessibleContext();
        ac.setAccessibleParent(this);
        ensurePopupMenuCreated();
        popupMenu.insert(mi, pos);
        return mi;
    }

    /**
     * Insert a new menuitem attached to the specified Action
     * object at a given position.
     *
     * @param a the Action object for the menuitem to add
     * @param pos an int giving the position at which to add the
     *               new menuitem
     */
    public JMenuItem insert(Action a, int pos) {
        if (pos < 0) {
            throw new IllegalArgumentException("index less than zero.");
        }

        ensurePopupMenuCreated();
        JMenuItem mi = new JMenuItem((String)a.getValue(Action.NAME));
        mi.addActionListener(a);
        popupMenu.insert(mi, pos);
        a.addPropertyChangeListener(new ActionChangedListener(mi));
        return mi;
    }

    /**
     * Inserts a separator at the specified position.
     *
     * @param       index an int giving the position at which to
     *                    insert the menu separator
     * @exception   IllegalArgumentException if the value of
     *                       <code>index</code> is less than 0.
     */
    public void insertSeparator(int index) {
        if (index < 0) {
            throw new IllegalArgumentException("index less than zero.");
        }

        ensurePopupMenuCreated();
        popupMenu.insert(new JSeparator(), index);
    }

    /**
     * Returns the JMenuItem at the specified position.
     * If the specified position contains a separator, this JMenu
     * is returned.
     *
     * @param pos    an int giving the position
     * @exception   IllegalArgumentException if the value of
     *                       <code>index</code> is less than 0.
     */
    public JMenuItem getItem(int pos) {
        if (pos < 0) {
            throw new IllegalArgumentException("index less than zero.");
        }

        Component c = getMenuComponent(pos);
        if (c instanceof JMenuItem) {
            JMenuItem mi = (JMenuItem) c;
            return mi;
        }
        // PENDING(ges): Should probably do something better here
        return this;
    }

    /**
     * Returns the number of items on the menu, including separators.
     * This method is included for AWT compatibility.
     *
     * @return an int equal to the number of items on the menu
     * @see getMenuComponentCount
     */
    public int getItemCount() {
    return getMenuComponentCount();
    }

    /**
     * Returns true if the menu can be torn off.
     *
     * @return true if the menu can be torn off, else false
     */
    public boolean isTearOff() {
        throw new Error("boolean isTearOff() {} not yet implemented");
    }

    /**
     * Removes the specified menu item from this menu.
     *
     * @param       item the JMenuItem to be removed from the menu
     */
    public void remove(JMenuItem item) {
        popupMenu.remove(item);
    }

    /**
     * Removes the menu item at the specified index from this menu.
     *
     * @param       index the position of the item to be removed.
     * @exception   IllegalArgumentException if the value of
     *                       <code>index</code> is less than 0.
     */
    public void remove(int pos) {
        if (pos < 0) {
            throw new IllegalArgumentException("index less than zero.");
        }

        popupMenu.remove(pos);
    }

    /**
     * Remove all menu items from this menu.
     */
    public void removeAll() {
        int nitems = getMenuComponentCount();
        for (int i = 0 ; i < nitems ; i++) {
            remove(0);
        }
    }

    /**
     * Returns the number of components on the menu.
     *
     * @return an int -- the number of components on the menu
     */
    public int getMenuComponentCount() {
        int componentCount = 0;
        if (popupMenu != null)
            componentCount = popupMenu.getComponentCount();
        return componentCount;
    }

    /**
     * Returns the component at position n
     *
     * @param n the position of the component to be returned
     */
    public Component getMenuComponent(int n) {
        if (popupMenu != null)
            return popupMenu.getComponent(n);

        return null;
    }

    /**
     * Returns an array of the menu's subcomponents
     *
     * @return an array of Components
     */
    public Component[] getMenuComponents() {
        if (popupMenu != null)
            return popupMenu.getComponents();

        return null;
    }

    /**
     * Gets the parameter string representing the state of this menu.
     * This string is useful for debugging.
     *
     * @return a String containing the menu parameters
     */
    public String paramString() {
        String str = ", JMenu";
        return super.paramString() + str;
    }

    /**
     * Returns true if the menu is a 'top-level menu', that is, if it is
     * the direct child of a menubar.
     *
     * @return true if the menu is activated from the menu bar,
     *         false if the menu is activated from a menu item
     *         on another menu
     */
    public boolean isTopLevelMenu() {
        if (getParent() instanceof JMenuBar)
            return true;

        return false;
    }

    /**
     * Returns true if the specified component exists in the
     * submenu hierarchy.
     *
     * @param c the Component to be tested
     * @return true if the component exists
     */
    public boolean isMenuComponent(Component c) {
        // Are we in the MenuItem part of the menu
        if (c == this)
            return true;
        // Are we in the PopupMenu?
        if (c instanceof JPopupMenu) {
            JPopupMenu comp = (JPopupMenu) c;
            if (comp == this.getPopupMenu())
                return true;
        }
        // Are we in a Component on the PopupMenu
        int ncomponents = this.getMenuComponentCount();
        Component[] component = this.getMenuComponents();
        for (int i = 0 ; i < ncomponents ; i++) {
            Component comp = component[i];
            // Are we in the current component?
            if (comp == c)
                return true;
            // Hmmm, what about Non-menu containers?

            // Recursive call for the Menu case
            if (comp instanceof JMenu) {
                JMenu subMenu = (JMenu) comp;
                if (subMenu.isMenuComponent(c))
                    return true;
            }
        }
        return false;
    }


    /*
     * Returns a point in the coordinate space of this menu's popupmenu
     * which corresponds to the point p in the menu's coordinate space.
     *
     * @param p the point to be translated
     */
    private Point translateToPopupMenu(Point p) {
        return translateToPopupMenu(p.x, p.y);
    }

    /*
     * Returns a point in the coordinate space of this menu's popupmenu
     * which corresponds to the point (x,y) in the menu's coordinate space.
     * @param x the x coordinate of the point to be translated
     * @param y the y coordinate of the point to be translated
     */
    private Point translateToPopupMenu(int x, int y) {
            int newX;
            int newY;

            if (getParent() instanceof JPopupMenu) {
                newX = x - getSize().width;
                newY = y;
            } else {
                newX = x;
                newY = y - getSize().height;
            }

            return new Point(newX, newY);
        }

    /**
     * Returns the popupmenu associated with this menu
     */
    public JPopupMenu getPopupMenu() {
        ensurePopupMenuCreated();
        return popupMenu;
    }

    /**
     * Add a listener for menu events
     *
     * @param l the listener to be added
     */
    public void addMenuListener(MenuListener l) {
        listenerList.add(MenuListener.class, l);
    }

    /**
     * Remove a listener for menu events
     *
     * @param l the listener to be removed
     */
    public void removeMenuListener(MenuListener l) {
        listenerList.remove(MenuListener.class, l);
    }

    /**
     * Notify all listeners that have registered interest for
     * notification on this event type.  The event instance
     * is lazily created using the parameters passed into
     * the fire method.
     *
     * @see EventListenerList
     */
    protected void fireMenuSelected() {
        // Guaranteed to return a non-null array
        Object[] listeners = listenerList.getListenerList();
        // Process the listeners last to first, notifying
        // those that are interested in this event
        for (int i = listeners.length-2; i>=0; i-=2) {
            if (listeners[i]==MenuListener.class) {
                if (listeners[i+1]== null) {
                    throw new Error(getText() +" has a NULL Listener!! "
                                       + i);
                } else {
                    // Lazily create the event:
                    if (menuEvent == null)
                        menuEvent = new MenuEvent(this);
                    ((MenuListener)listeners[i+1]).menuSelected(menuEvent);
                }
            }
        }
    }

    /**
     * Notify all listeners that have registered interest for
     * notification on this event type.  The event instance
     * is lazily created using the parameters passed into
     * the fire method.
     *
     * @see EventListenerList
     */
    protected void fireMenuDeselected() {
        // Guaranteed to return a non-null array
        Object[] listeners = listenerList.getListenerList();
        // Process the listeners last to first, notifying
        // those that are interested in this event
        for (int i = listeners.length-2; i>=0; i-=2) {
            if (listeners[i]==MenuListener.class) {
                if (listeners[i+1]== null) {
                    System.out.println(getText() +" has a NULL Listener!! "
                                       + i);
                } else {
                    // Lazily create the event:
                    if (menuEvent == null)
                        menuEvent = new MenuEvent(this);
                    ((MenuListener)listeners[i+1]).menuDeselected(menuEvent);
                }
            }
        }
    }

    class MenuChangeListener implements ChangeListener, Serializable {
        boolean isSelected = false;
        public void stateChanged(ChangeEvent e) {
            DefaultButtonModel model = (DefaultButtonModel) e.getSource();
            boolean modelSelected = model.isSelected();
            // System.out.println("Model selected = " + modelSelected +
            // " isSelected = " + isSelected);
            if (modelSelected != isSelected) {
                if (modelSelected == true) {
                    fireMenuSelected();
                } else {
                    fireMenuDeselected();
                }
                isSelected = modelSelected;
            }
        }
    }

    private ChangeListener createMenuChangeListener() {
        return new MenuChangeListener();
    }

    /**
     * Create a window-closing listener for the popup.
     *
     * @param p the JPopupMenu
     * @see WinListener
     */
    protected WinListener createWinListener(JPopupMenu p) {
        return new WinListener(p);
    }

    /**
     * A listener class that watches for a popup window closing.
     * When the popup is closing, the listener deselects the menu.
     * <p>
     * Warning: 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 Swing1.0 applications.  It will
     * not be possible to load serialized Swing1.0 objects with future releases
     * of Swing.  The JDK1.2 release of Swing will be the compatibility
     * baseline for the serialized form of Swing objects.
     */
    protected class WinListener extends WindowAdapter implements Serializable {
        JPopupMenu popupMenu;
        /**
         *  Create the window listener for the specified popup.
         */
        public WinListener(JPopupMenu p) {
            this.popupMenu = p;
        }
        /**
         * Deselect the menu when the popup is closed from outside.
         */
        public void windowClosing(WindowEvent e) {
            setSelected(false);
        }
    }

    /**
     * Process a mouse event. event is a MouseEvent with source being the receiving component.
     * componentPath is the path of the receiving MenuComponent in the menu
     * hierarchy. manager is the MenuSelectionManager for the menu hierarchy.
     * This method should process the MouseEvent and change the menu selection if necessary
     * by using MenuSelectionManager's API
     * Note: you do not have to forward the event to sub-components. This is done automatically
     * by the MenuSelectionManager
     */
    public void processMouseEvent(MouseEvent event,MenuElement path[],MenuSelectionManager manager) {
        ((MenuUI)getUI()).processMouseEvent(this,event,path,manager);
    }

    /** Implemented to be a MenuElement. This message is forwarded to the UI **/
    public void processKeyEvent(KeyEvent e,MenuElement path[],MenuSelectionManager manager) {
        ((MenuUI)getUI()).processKeyEvent(this,e,path,manager);
    }

    /**
     *
     */
    public void menuSelectionChanged(boolean isIncluded) {
        setSelected(isIncluded);
    }

    /**
     * This method should return an array containing the sub-menu components for this menu component
     */
    public MenuElement[] getSubElements() {
        if(popupMenu == null)
            return new MenuElement[0];
        else {
            MenuElement result[] = new MenuElement[1];
            result[0] = popupMenu;
            return result;
        }
    }


    /*
     * This method should return the java.awt.Component used to paint this MenuElement.
     * The returned component will be used to convert events and detect if an event is inside
     * a menu component.
     */
    public Component getComponent() {
        return this;
    }


    /*
     * setAccelerator() is not defined for JMenu.  Use setMnemonic() instead.
     *
     * @beaninfo
     *     description: The keystroke combination which will invoke the JMenuItem's
     *                  actionlisteners without navigating the menu hierarchy
     *          hidden: true
     */
    public void setAccelerator(KeyStroke keyStroke) {
    throw new Error("setAccelerator() is not defined for JMenu.  Use setMnemonic() instead.");
    }

    /**
     *
     */
    protected void processKeyEvent(KeyEvent e) {
        MenuSelectionManager.defaultManager().processKeyEvent(e);
        if(e.isConsumed())
            return;
        super.processKeyEvent(e);
    }
/////////////////
// Accessibility support
////////////////

    /**
     * Get the AccessibleContext associated with this JComponent
     *
     * @return the AccessibleContext of this JComponent
     */
    public AccessibleContext getAccessibleContext() {
        if (accessibleContext == null) {
            accessibleContext = new AccessibleJMenu();
        }
        return accessibleContext;
    }

    /**
     * The class used to obtain the accessible role for this object.
     * <p>
     * Warning: 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 Swing1.0 applications.  It will
     * not be possible to load serialized Swing1.0 objects with future releases
     * of Swing.  The JDK1.2 release of Swing will be the compatibility
     * baseline for the serialized form of Swing objects.
     */
    protected class AccessibleJMenu extends AccessibleJMenuItem {
        /**
         * Returns the number of accessible children in the object.  If all
         * of the children of this object implement Accessible, than this
         * method should return the number of children of this object.
         *
         * @return the number of accessible children in the object.
         */
        public int getAccessibleChildrenCount() {
            Component[] children = getMenuComponents();
            int count = 0;
            for (int j = 0; j < children.length; j++) {
                if (children[j] instanceof Accessible) {
                    count++;
                }
            }
            return count;
        }

        /**
         * Return the nth Accessible child of the object.
         *
         * @param i zero-based index of child
         * @return the nth Accessible child of the object
         */
        public Accessible getAccessibleChild(int i) {
            Component[] children = getMenuComponents();
            int count = 0;
            for (int j = 0; j < children.length; j++) {
                if (children[j] instanceof Accessible) {
                    if (count == i) {
                        if (children[j] instanceof JComponent) {
                            // FIXME:  [[[WDW - probably should set this when
                            // the component is added to the menu.  I tried
                            // to do this in most cases, but the separators
                            // added by addSeparator are hard to get to.]]]
                            AccessibleContext ac = ((Accessible) children[j]).getAccessibleContext();
                            ac.setAccessibleParent(JMenu.this);
                        }
                        return (Accessible) children[j];
                    } else {
                        count++;
                    }
                }
            }
            return null;
        }

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