/*
 * @(#)MenuBar.java	1.54 00/04/06
 *
 * Copyright 1995-2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */
package java.awt;

import java.util.Vector;
import java.util.Enumeration;
import java.awt.peer.MenuBarPeer;
import java.awt.event.KeyEvent;
import javax.accessibility.*;

/**
 * The <code>MenuBar</code> class encapsulates the platform's
 * concept of a menu bar bound to a frame. In order to associate
 * the menu bar with a <code>Frame</code> object, call the
 * frame's <code>setMenuBar</code> method.
 * <p>
 * <A NAME="mbexample"></A><!-- target for cross references -->
 * This is what a menu bar might look like:
 * <p>
 * <img src="doc-files/MenuBar-1.gif"
 * ALIGN=center HSPACE=10 VSPACE=7>
 * <p>
 * A menu bar handles keyboard shortcuts for menu items, passing them
 * along to its child menus.
 * (Keyboard shortcuts, which are optional, provide the user with
 * an alternative to the mouse for invoking a menu item and the
 * action that is associated with it.)
 * Each menu item can maintain an instance of <code>MenuShortcut</code>.
 * The <code>MenuBar</code> class defines several methods,
 * {@link MenuBar#shortcuts} and
 * {@link MenuBar#getShortcutMenuItem}
 * that retrieve information about the shortcuts a given
 * menu bar is managing.
 *
 * @version 1.54, 04/06/00
 * @author Sami Shaio
 * @see        java.awt.Frame
 * @see        java.awt.Frame#setMenuBar(java.awt.MenuBar)
 * @see        java.awt.Menu
 * @see        java.awt.MenuItem
 * @see        java.awt.MenuShortcut
 * @since      JDK1.0
 */
public class MenuBar extends MenuComponent implements MenuContainer, Accessible {

    static {
        /* ensure that the necessary native libraries are loaded */
	Toolkit.loadLibraries();
        initIDs();
    }

    /**
     * This field represents a vector of the
     * actual menus that will be part of the MenuBar.
     *
     * @serial
     * @see countMenus()
     */
    Vector menus = new Vector();

    /**
     * This menu is a special menu dedicated to
     * help.  The one thing to note about this menu
     * is that on some platforms it appears at the
     * right edge of the menubar.
     *
     * @serial
     * @see getHelpMenu()
     * @see setHelpMenu()
     */
    Menu helpMenu;

    private static final String base = "menubar";
    private static int nameCounter = 0;

    /*
     * JDK 1.1 serialVersionUID
     */
     private static final long serialVersionUID = -4930327919388951260L;

    /**
     * Creates a new menu bar.
     */
    public MenuBar() {
    }

    /**
     * Construct a name for this MenuComponent.  Called by getName() when
     * the name is null.
     */
    String constructComponentName() {
        synchronized (getClass()) {
	    return base + nameCounter++;
	}
    }

    /**
     * Creates the menu bar's peer.  The peer allows us to change the
     * appearance of the menu bar without changing any of the menu bar's
     * functionality.
     */
    public void addNotify() {
        synchronized (getTreeLock()) {
	    if (peer == null)
	        peer = Toolkit.getDefaultToolkit().createMenuBar(this);

	    int nmenus = getMenuCount();
	    for (int i = 0 ; i < nmenus ; i++) {
	        getMenu(i).addNotify();
	    }
	}
    }

    /**
     * Removes the menu bar's peer.  The peer allows us to change the
     * appearance of the menu bar without changing any of the menu bar's
     * functionality.
     */
    public void removeNotify() {
        synchronized (getTreeLock()) {
	    int nmenus = getMenuCount();
	    for (int i = 0 ; i < nmenus ; i++) {
	        getMenu(i).removeNotify();
	    }
	    super.removeNotify();
	}
    }

    /**
     * Gets the help menu on the menu bar.
     * @return    the help menu on this menu bar.
     */
    public Menu getHelpMenu() {
	return helpMenu;
    }

    /**
     * Sets the specified menu to be this menu bar's help menu.
     * If this menu bar has an existing help menu, the old help menu is
     * removed from the menu bar, and replaced with the specified menu.
     * @param m    the menu to be set as the help menu
     */
    public void setHelpMenu(Menu m) {
        synchronized (getTreeLock()) {
	    if (helpMenu == m) {
	        return;
	    }
	    if (helpMenu != null) {
                remove(helpMenu);
	    }
	    if (m.parent != this) {
	        add(m);
	    }
	    helpMenu = m;
	    if (m != null) {
	        m.isHelpMenu = true;
		m.parent = this;
		MenuBarPeer peer = (MenuBarPeer)this.peer;
		if (peer != null) {
		    if (m.peer == null) {
		        m.addNotify();
		    }
		    peer.addHelpMenu(m);
		}
	    }
	}
    }

    /**
     * Adds the specified menu to the menu bar.
     * @param        m   the menu to be added.
     * @return       the menu added.
     * @see          java.awt.MenuBar#remove(int)
     * @see          java.awt.MenuBar#remove(java.awt.MenuComponent)
     */
    public Menu add(Menu m) {
        synchronized (getTreeLock()) {
	    if (m.parent != null) {
	        m.parent.remove(m);
	    }
	    menus.addElement(m);
	    m.parent = this;

	    MenuBarPeer peer = (MenuBarPeer)this.peer;
	    if (peer != null) {
	        if (m.peer == null) {
		    m.addNotify();
		}
		peer.addMenu(m);
	    }
	    return m;
	}
    }

    /**
     * Removes the menu located at the specified
     * index from this menu bar.
     * @param        index   the position of the menu to be removed.
     * @see          java.awt.MenuBar#add(java.awt.Menu)
     */
    public void remove(int index) {
        synchronized (getTreeLock()) {
            Menu m = getMenu(index);
            menus.removeElementAt(index);
	    MenuBarPeer peer = (MenuBarPeer)this.peer;
	    if (peer != null) {
		m.removeNotify();
		m.parent = null;
		peer.delMenu(index);
	    }
	}
    }

    /**
     * Removes the specified menu component from this menu bar.
     * @param        m the menu component to be removed.
     * @see          java.awt.MenuBar#add(java.awt.Menu)
     */
    public void remove(MenuComponent m) {
        synchronized (getTreeLock()) {
	    int index = menus.indexOf(m);
	    if (index >= 0) {
	        remove(index);
	    }
	}
    }

    /**
     * Gets the number of menus on the menu bar.
     * @return     the number of menus on the menu bar.
     * @since      JDK1.1
     */
    public int getMenuCount() {
	return countMenus();
    }

    /**
     * @deprecated As of JDK version 1.1,
     * replaced by <code>getMenuCount()</code>.
     */
    public int countMenus() {
	return getMenuCountImpl();
    }

    /*
     * This is called by the native code, so client code can't
     * be called on the toolkit thread.
     */
    final int getMenuCountImpl() {
	return menus.size();
    }

    /**
     * Gets the specified menu.
     * @param      i the index position of the menu to be returned.
     * @return     the menu at the specified index of this menu bar.
     */
    public Menu getMenu(int i) {
	return getMenuImpl(i);
    }

    /*
     * This is called by the native code, so client code can't
     * be called on the toolkit thread.
     */
    final Menu getMenuImpl(int i) {
	return (Menu)menus.elementAt(i);
    }

    /**
     * Gets an enumeration of all menu shortcuts this menu bar
     * is managing.
     * @return      an enumeration of menu shortcuts that this
     *                      menu bar is managing.
     * @see         java.awt.MenuShortcut
     * @since       JDK1.1
     */
    public synchronized Enumeration shortcuts() {
        Vector shortcuts = new Vector();
	int nmenus = getMenuCount();
	for (int i = 0 ; i < nmenus ; i++) {
            Enumeration e = getMenu(i).shortcuts();
            while (e.hasMoreElements()) {
                shortcuts.addElement(e.nextElement());
            }
	}
        return shortcuts.elements();
    }

    /**
     * Gets the instance of <code>MenuItem</code> associated
     * with the specified <code>MenuShortcut</code> object,
     * or <code>null</code> if none of the menu items being managed
     * by this menu bar is associated with the specified menu
     * shortcut.
     * @param        s the specified menu shortcut.
     * @see          java.awt.MenuItem
     * @see          java.awt.MenuShortcut
     * @since        JDK1.1
     */
     public MenuItem getShortcutMenuItem(MenuShortcut s) {
	int nmenus = getMenuCount();
	for (int i = 0 ; i < nmenus ; i++) {
            MenuItem mi = getMenu(i).getShortcutMenuItem(s);
            if (mi != null) {
                return mi;
            }
	}
        return null;  // MenuShortcut wasn't found
     }

    /*
     * Post an ACTION_EVENT to the target of the MenuPeer
     * associated with the specified keyboard event (on
     * keydown).  Returns true if there is an associated
     * keyboard event.
     */
    boolean handleShortcut(KeyEvent e) {
        // Is it a key event?
        int id = e.getID();
        if (id != KeyEvent.KEY_PRESSED && id != KeyEvent.KEY_RELEASED) {
            return false;
        }

        // Is the accelerator modifier key pressed?
        int accelKey = Toolkit.getDefaultToolkit().getMenuShortcutKeyMask();
        if ((e.getModifiers() & accelKey) == 0) {
            return false;
        }

        // Pass MenuShortcut on to child menus.
	int nmenus = getMenuCount();
	for (int i = 0 ; i < nmenus ; i++) {
	    Menu m = getMenu(i);
            if (m.handleShortcut(e)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Deletes the specified menu shortcut.
     * @param     s the menu shortcut to delete.
     * @since     JDK1.1
     */
    public void deleteShortcut(MenuShortcut s) {
	int nmenus = getMenuCount();
	for (int i = 0 ; i < nmenus ; i++) {
	    getMenu(i).deleteShortcut(s);
        }
    }

    /* Serialization support.  Restore the (transient) parent
     * fields of Menubar menus here.
     */
 
    /**
     * The MenuBar's serialized data version.
     *
     * @serial
     */
    private int menuBarSerializedDataVersion = 1;

    /**
     * Writes default serializable fields to stream.  Writes
     * a list of serializable ItemListener(s) as optional data.
     * The non-serializable ItemListner(s) are detected and
     * no attempt is made to serialize them.
     *
     * @serialData Null terminated sequence of 0 or more pairs.
     *             The pair consists of a String and Object.
     *             The String indicates the type of object and
     *             is one of the following :
     *             itemListenerK indicating and ItemListener object.
     *
     * @see AWTEventMulticaster.save(ObjectOutputStream, String, EventListener)
     * @see java.awt.Component.itemListenerK
     */
    private void writeObject(java.io.ObjectOutputStream s)
      throws java.lang.ClassNotFoundException,
	     java.io.IOException
    {
      s.defaultWriteObject();
    }

    /**
     * Read the ObjectInputStream and if it isnt null
     * add a listener to receive item events fired
     * by the MenuBar.
     * Unrecognised keys or values will be Ignored.
     *
     * @see removeActionListener()
     * @see addActionListener()
     */
    private void readObject(java.io.ObjectInputStream s)
      throws java.lang.ClassNotFoundException,
	     java.io.IOException
    {
      s.defaultReadObject();
      for (int i = 0; i < menus.size(); i++) {
	Menu m = (Menu)menus.elementAt(i);
	m.parent = this;
      }
    }

    /**
     * Initialize JNI field and method IDs
     */
    private static native void initIDs();


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

    /**
     * Gets the AccessibleContext associated with this MenuBar. 
     * For menu bars, the AccessibleContext takes the form of an 
     * AccessibleAWTMenuBar. 
     * A new AccessibleAWTMenuBar instance is created if necessary.
     *
     * @return an AccessibleAWTMenuBar that serves as the 
     *         AccessibleContext of this MenuBar
     */
    public AccessibleContext getAccessibleContext() {
        if (accessibleContext == null) {
            accessibleContext = new AccessibleAWTMenuBar();
        }
        return accessibleContext;
    }

    /**
     * Inner class of MenuBar used to provide default support for
     * accessibility.  This class is not meant to be used directly by
     * application developers, but is instead meant only to be
     * subclassed by menu component developers.
     * <p>
     * This class implements accessibility support for the 
     * <code>MenuBar</code> class.  It provides an implementation of the 
     * Java Accessibility API appropriate to menu bar user-interface elements.
     */
    protected class AccessibleAWTMenuBar extends AccessibleAWTMenuComponent {

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

    } // class AccessibleAWTMenuBar

}