The source code

    /**
     * @class Ext.menu.Menu
     * @extends Ext.Container
     * <p>A menu object.  This is the container to which you may add menu items.  Menu can also serve as a base class
     * when you want a specialized menu based off of another component (like {@link Ext.menu.DateMenu} for example).</p>
     * <p>Menus may contain either {@link Ext.menu.Item menu items}, or general {@link Ext.Component Component}s.</p>
     * <p>To make a contained general {@link Ext.Component Component} line up with other {@link Ext.menu.Item menu items}
     * specify <tt>iconCls: 'no-icon'</tt>.  This reserves a space for an icon, and indents the Component in line
     * with the other menu items.  See {@link Ext.form.ComboBox}.{@link Ext.form.ComboBox#getListParent getListParent}
     * for an example.</p>
     * <p>By default, Menus are absolutely positioned, floating Components. By configuring a Menu with
     * <b><tt>{@link #floating}:false</tt></b>, a Menu may be used as child of a Container.</p>
     *
     * @xtype menu
     */
    Ext.menu.Menu = Ext.extend(Ext.Container, {
        /**
         * @cfg {Object} defaults
         * A config object that will be applied to all items added to this container either via the {@link #items}
         * config or via the {@link #add} method.  The defaults config can contain any number of
         * name/value property pairs to be added to each item, and should be valid for the types of items
         * being added to the menu.
         */
        /**
         * @cfg {Mixed} items
         * An array of items to be added to this menu. Menus may contain either {@link Ext.menu.Item menu items},
         * or general {@link Ext.Component Component}s.
         */
        /**
         * @cfg {Number} minWidth The minimum width of the menu in pixels (defaults to 120)
         */
        minWidth : 120,
        /**
         * @cfg {Boolean/String} shadow True or 'sides' for the default effect, 'frame' for 4-way shadow, and 'drop'
         * for bottom-right shadow (defaults to 'sides')
         */
        shadow : 'sides',
        /**
         * @cfg {String} subMenuAlign The {@link Ext.Element#alignTo} anchor position value to use for submenus of
         * this menu (defaults to 'tl-tr?')
         */
        subMenuAlign : 'tl-tr?',
        /**
         * @cfg {String} defaultAlign The default {@link Ext.Element#alignTo} anchor position value for this menu
         * relative to its element of origin (defaults to 'tl-bl?')
         */
        defaultAlign : 'tl-bl?',
        /**
         * @cfg {Boolean} allowOtherMenus True to allow multiple menus to be displayed at the same time (defaults to false)
         */
        allowOtherMenus : false,
        /**
         * @cfg {Boolean} ignoreParentClicks True to ignore clicks on any item in this menu that is a parent item (displays
         * a submenu) so that the submenu is not dismissed when clicking the parent item (defaults to false).
         */
        ignoreParentClicks : false,
        /**
         * @cfg {Boolean} enableScrolling True to allow the menu container to have scroller controls if the menu is too long (defaults to true).
         */
        enableScrolling : true,
        /**
         * @cfg {Number} maxHeight The maximum height of the menu. Only applies when enableScrolling is set to True (defaults to null).
         */
        maxHeight : null,
        /**
         * @cfg {Number} scrollIncrement The amount to scroll the menu. Only applies when enableScrolling is set to True (defaults to 24).
         */
        scrollIncrement : 24,
        /**
         * @cfg {Boolean} showSeparator True to show the icon separator. (defaults to true).
         */
        showSeparator : true,
        /**
         * @cfg {Array} defaultOffsets An array specifying the [x, y] offset in pixels by which to
         * change the default Menu popup position after aligning according to the {@link #defaultAlign}
         * configuration. Defaults to <tt>[0, 0]</tt>.
         */
        defaultOffsets : [0, 0],

        /**
         * @cfg {Boolean} plain
         * True to remove the incised line down the left side of the menu. Defaults to <tt>false</tt>.
         */
        plain : false,

        /**
         * @cfg {Boolean} floating
         * <p>By default, a Menu configured as <b><code>floating:true</code></b>
         * will be rendered as an {@link Ext.Layer} (an absolutely positioned,
         * floating Component with zindex=15000).
         * If configured as <b><code>floating:false</code></b>, the Menu may be
         * used as child item of another Container instead of a free-floating
         * {@link Ext.Layer Layer}.
         */
        floating : true,

        /**
         * @cfg {Number} zIndex
         * zIndex to use when the menu is floating.
         */
        zIndex: 15000,

        // private
        hidden : true,

        /**
         * @cfg {String/Object} layout
         * This class assigns a default layout (<code>layout:'<b>menu</b>'</code>).
         * Developers <i>may</i> override this configuration option if another layout is required.
         * See {@link Ext.Container#layout} for additional information.
         */
        layout : 'menu',
        hideMode : 'offsets',    // Important for laying out Components
        scrollerHeight : 8,
        autoLayout : true,       // Provided for backwards compat
        defaultType : 'menuitem',
        bufferResize : false,

        initComponent : function(){
            if(Ext.isArray(this.initialConfig)){
                Ext.apply(this, {items:this.initialConfig});
            }
            this.addEvents(
                /**
                 * @event click
                 * Fires when this menu is clicked (or when the enter key is pressed while it is active)
                 * @param {Ext.menu.Menu} this
                * @param {Ext.menu.Item} menuItem The menu item that was clicked
                 * @param {Ext.EventObject} e
                 */
                'click',
                /**
                 * @event mouseover
                 * Fires when the mouse is hovering over this menu
                 * @param {Ext.menu.Menu} this
                 * @param {Ext.EventObject} e
                 * @param {Ext.menu.Item} menuItem The menu item that was clicked
                 */
                'mouseover',
                /**
                 * @event mouseout
                 * Fires when the mouse exits this menu
                 * @param {Ext.menu.Menu} this
                 * @param {Ext.EventObject} e
                 * @param {Ext.menu.Item} menuItem The menu item that was clicked
                 */
                'mouseout',
                /**
                 * @event itemclick
                 * Fires when a menu item contained in this menu is clicked
                 * @param {Ext.menu.BaseItem} baseItem The BaseItem that was clicked
                 * @param {Ext.EventObject} e
                 */
                'itemclick'
            );
            Ext.menu.MenuMgr.register(this);
            if(this.floating){
                Ext.EventManager.onWindowResize(this.hide, this);
            }else{
                if(this.initialConfig.hidden !== false){
                    this.hidden = false;
                }
                this.internalDefaults = {hideOnClick: false};
            }
            Ext.menu.Menu.superclass.initComponent.call(this);
            if(this.autoLayout){
                var fn = this.doLayout.createDelegate(this, []);
                this.on({
                    add: fn,
                    remove: fn
                });
            }
        },

        //private
        getLayoutTarget : function() {
            return this.ul;
        },

        // private
        onRender : function(ct, position){
            if(!ct){
                ct = Ext.getBody();
            }

            var dh = {
                id: this.getId(),
                cls: 'x-menu ' + ((this.floating) ? 'x-menu-floating x-layer ' : '') + (this.cls || '') + (this.plain ? ' x-menu-plain' : '') + (this.showSeparator ? '' : ' x-menu-nosep'),
                style: this.style,
                cn: [
                    {tag: 'a', cls: 'x-menu-focus', href: '#', onclick: 'return false;', tabIndex: '-1'},
                    {tag: 'ul', cls: 'x-menu-list'}
                ]
            };
            if(this.floating){
                this.el = new Ext.Layer({
                    shadow: this.shadow,
                    dh: dh,
                    constrain: false,
                    parentEl: ct,
                    zindex: this.zIndex
                });
            }else{
                this.el = ct.createChild(dh);
            }
            Ext.menu.Menu.superclass.onRender.call(this, ct, position);

            if(!this.keyNav){
                this.keyNav = new Ext.menu.MenuNav(this);
            }
            // generic focus element
            this.focusEl = this.el.child('a.x-menu-focus');
            this.ul = this.el.child('ul.x-menu-list');
            this.mon(this.ul, {
                scope: this,
                click: this.onClick,
                mouseover: this.onMouseOver,
                mouseout: this.onMouseOut
            });
            if(this.enableScrolling){
                this.mon(this.el, {
                    scope: this,
                    delegate: '.x-menu-scroller',
                    click: this.onScroll,
                    mouseover: this.deactivateActive
                });
            }
        },

        // private
        findTargetItem : function(e){
            var t = e.getTarget('.x-menu-list-item', this.ul, true);
            if(t && t.menuItemId){
                return this.items.get(t.menuItemId);
            }
        },

        // private
        onClick : function(e){
            var t = this.findTargetItem(e);
            if(t){
                if(t.isFormField){
                    this.setActiveItem(t);
                }else if(t instanceof Ext.menu.BaseItem){
                    if(t.menu && this.ignoreParentClicks){
                        t.expandMenu();
                        e.preventDefault();
                    }else if(t.onClick){
                        t.onClick(e);
                        this.fireEvent('click', this, t, e);
                    }
                }
            }
        },

        // private
        setActiveItem : function(item, autoExpand){
            if(item != this.activeItem){
                this.deactivateActive();
                if((this.activeItem = item).isFormField){
                    item.focus();
                }else{
                    item.activate(autoExpand);
                }
            }else if(autoExpand){
                item.expandMenu();
            }
        },

        deactivateActive : function(){
            var a = this.activeItem;
            if(a){
                if(a.isFormField){
                    //Fields cannot deactivate, but Combos must collapse
                    if(a.collapse){
                        a.collapse();
                    }
                }else{
                    a.deactivate();
                }
                delete this.activeItem;
            }
        },

        // private
        tryActivate : function(start, step){
            var items = this.items;
            for(var i = start, len = items.length; i >= 0 && i < len; i+= step){
                var item = items.get(i);
                if(item.isVisible() && !item.disabled && (item.canActivate || item.isFormField)){
                    this.setActiveItem(item, false);
                    return item;
                }
            }
            return false;
        },

        // private
        onMouseOver : function(e){
            var t = this.findTargetItem(e);
            if(t){
                if(t.canActivate && !t.disabled){
                    this.setActiveItem(t, true);
                }
            }
            this.over = true;
            this.fireEvent('mouseover', this, e, t);
        },

        // private
        onMouseOut : function(e){
            var t = this.findTargetItem(e);
            if(t){
                if(t == this.activeItem && t.shouldDeactivate && t.shouldDeactivate(e)){
                    this.activeItem.deactivate();
                    delete this.activeItem;
                }
            }
            this.over = false;
            this.fireEvent('mouseout', this, e, t);
        },

        // private
        onScroll : function(e, t){
            if(e){
                e.stopEvent();
            }
            var ul = this.ul.dom, top = Ext.fly(t).is('.x-menu-scroller-top');
            ul.scrollTop += this.scrollIncrement * (top ? -1 : 1);
            if(top ? ul.scrollTop <= 0 : ul.scrollTop + this.activeMax >= ul.scrollHeight){
               this.onScrollerOut(null, t);
            }
        },

        // private
        onScrollerIn : function(e, t){
            var ul = this.ul.dom, top = Ext.fly(t).is('.x-menu-scroller-top');
            if(top ? ul.scrollTop > 0 : ul.scrollTop + this.activeMax < ul.scrollHeight){
                Ext.fly(t).addClass(['x-menu-item-active', 'x-menu-scroller-active']);
            }
        },

        // private
        onScrollerOut : function(e, t){
            Ext.fly(t).removeClass(['x-menu-item-active', 'x-menu-scroller-active']);
        },

        /**
         * If <code>{@link #floating}=true</code>, shows this menu relative to
         * another element using {@link #showat}, otherwise uses {@link Ext.Component#show}.
         * @param {Mixed} element The element to align to
         * @param {String} position (optional) The {@link Ext.Element#alignTo} anchor position to use in aligning to
         * the element (defaults to this.defaultAlign)
         * @param {Ext.menu.Menu} parentMenu (optional) This menu's parent menu, if applicable (defaults to undefined)
         */
        show : function(el, pos, parentMenu){
            if(this.floating){
                this.parentMenu = parentMenu;
                if(!this.el){
                    this.render();
                    this.doLayout(false, true);
                }
                this.showAt(this.el.getAlignToXY(el, pos || this.defaultAlign, this.defaultOffsets), parentMenu);
            }else{
                Ext.menu.Menu.superclass.show.call(this);
            }
        },

        /**
         * Displays this menu at a specific xy position and fires the 'show' event if a
         * handler for the 'beforeshow' event does not return false cancelling the operation.
         * @param {Array} xyPosition Contains X & Y [x, y] values for the position at which to show the menu (coordinates are page-based)
         * @param {Ext.menu.Menu} parentMenu (optional) This menu's parent menu, if applicable (defaults to undefined)
         */
        showAt : function(xy, parentMenu){
            if(this.fireEvent('beforeshow', this) !== false){
                this.parentMenu = parentMenu;
                if(!this.el){
                    this.render();
                }
                if(this.enableScrolling){
                    // set the position so we can figure out the constrain value.
                    this.el.setXY(xy);
                    //constrain the value, keep the y coordinate the same
                    xy[1] = this.constrainScroll(xy[1]);
                    xy = [this.el.adjustForConstraints(xy)[0], xy[1]];
                }else{
                    //constrain to the viewport.
                    xy = this.el.adjustForConstraints(xy);
                }
                this.el.setXY(xy);
                this.el.show();
                Ext.menu.Menu.superclass.onShow.call(this);
                if(Ext.isIE9m){
                    // internal event, used so we don't couple the layout to the menu
                    this.fireEvent('autosize', this);
                    if(!Ext.isIE8){
                        this.el.repaint();
                    }
                }
                this.hidden = false;
                this.focus();
                this.fireEvent('show', this);
            }
        },

        constrainScroll : function(y){
            var max, full = this.ul.setHeight('auto').getHeight(),
                returnY = y, normalY, parentEl, scrollTop, viewHeight;
            if(this.floating){
                parentEl = Ext.fly(this.el.dom.parentNode);
                scrollTop = parentEl.getScroll().top;
                viewHeight = parentEl.getViewSize().height;
                //Normalize y by the scroll position for the parent element.  Need to move it into the coordinate space
                //of the view.
                normalY = y - scrollTop;
                max = this.maxHeight ? this.maxHeight : viewHeight - normalY;
                if(full > viewHeight) {
                    max = viewHeight;
                    //Set returnY equal to (0,0) in view space by reducing y by the value of normalY
                    returnY = y - normalY;
                } else if(max < full) {
                    returnY = y - (full - max);
                    max = full;
                }
            }else{
                max = this.getHeight();
            }
            // Always respect maxHeight
            if (this.maxHeight){
                max = Math.min(this.maxHeight, max);
            }
            if(full > max && max > 0){
                this.activeMax = max - this.scrollerHeight * 2 - this.el.getFrameWidth('tb') - Ext.num(this.el.shadowOffset, 0);
                this.ul.setHeight(this.activeMax);
                this.createScrollers();
                this.el.select('.x-menu-scroller').setDisplayed('');
            }else{
                this.ul.setHeight(full);
                this.el.select('.x-menu-scroller').setDisplayed('none');
            }
            this.ul.dom.scrollTop = 0;
            return returnY;
        },

        createScrollers : function(){
            if(!this.scroller){
                this.scroller = {
                    pos: 0,
                    top: this.el.insertFirst({
                        tag: 'div',
                        cls: 'x-menu-scroller x-menu-scroller-top',
                        html: '&#160;'
                    }),
                    bottom: this.el.createChild({
                        tag: 'div',
                        cls: 'x-menu-scroller x-menu-scroller-bottom',
                        html: '&#160;'
                    })
                };
                this.scroller.top.hover(this.onScrollerIn, this.onScrollerOut, this);
                this.scroller.topRepeater = new Ext.util.ClickRepeater(this.scroller.top, {
                    listeners: {
                        click: this.onScroll.createDelegate(this, [null, this.scroller.top], false)
                    }
                });
                this.scroller.bottom.hover(this.onScrollerIn, this.onScrollerOut, this);
                this.scroller.bottomRepeater = new Ext.util.ClickRepeater(this.scroller.bottom, {
                    listeners: {
                        click: this.onScroll.createDelegate(this, [null, this.scroller.bottom], false)
                    }
                });
            }
        },

        onLayout : function(){
            if(this.isVisible()){
                if(this.enableScrolling){
                    this.constrainScroll(this.el.getTop());
                }
                if(this.floating){
                    this.el.sync();
                }
            }
        },

        focus : function(){
            if(!this.hidden){
                this.doFocus.defer(50, this);
            }
        },

        doFocus : function(){
            if(!this.hidden){
                this.focusEl.focus();
            }
        },

        /**
         * Hides this menu and optionally all parent menus
         * @param {Boolean} deep (optional) True to hide all parent menus recursively, if any (defaults to false)
         */
        hide : function(deep){
            if (!this.isDestroyed) {
                this.deepHide = deep;
                Ext.menu.Menu.superclass.hide.call(this);
                delete this.deepHide;
            }
        },

        // private
        onHide : function(){
            Ext.menu.Menu.superclass.onHide.call(this);
            this.deactivateActive();
            if(this.el && this.floating){
                this.el.hide();
            }
            var pm = this.parentMenu;
            if(this.deepHide === true && pm){
                if(pm.floating){
                    pm.hide(true);
                }else{
                    pm.deactivateActive();
                }
            }
        },

        // private
        lookupComponent : function(c){
             if(Ext.isString(c)){
                c = (c == 'separator' || c == '-') ? new Ext.menu.Separator() : new Ext.menu.TextItem(c);
                 this.applyDefaults(c);
             }else{
                if(Ext.isObject(c)){
                    c = this.getMenuItem(c);
                }else if(c.tagName || c.el){ // element. Wrap it.
                    c = new Ext.BoxComponent({
                        el: c
                    });
                }
             }
             return c;
        },

        applyDefaults : function(c) {
            if (!Ext.isString(c)) {
                c = Ext.menu.Menu.superclass.applyDefaults.call(this, c);
                var d = this.internalDefaults;
                if(d){
                    if(c.events){
                        Ext.applyIf(c.initialConfig, d);
                        Ext.apply(c, d);
                    }else{
                        Ext.applyIf(c, d);
                    }
                }
            }
            return c;
        },

        // private
        getMenuItem : function(config) {
            config.ownerCt = this;

            if (!config.isXType) {
                if (!config.xtype && Ext.isBoolean(config.checked)) {
                    return new Ext.menu.CheckItem(config);
                }
                return Ext.create(config, this.defaultType);
            }
            return config;
        },

        /**
         * Adds a separator bar to the menu
         * @return {Ext.menu.Item} The menu item that was added
         */
        addSeparator : function() {
            return this.add(new Ext.menu.Separator());
        },

        /**
         * Adds an {@link Ext.Element} object to the menu
         * @param {Mixed} el The element or DOM node to add, or its id
         * @return {Ext.menu.Item} The menu item that was added
         */
        addElement : function(el) {
            return this.add(new Ext.menu.BaseItem({
                el: el
            }));
        },

        /**
         * Adds an existing object based on {@link Ext.menu.BaseItem} to the menu
         * @param {Ext.menu.Item} item The menu item to add
         * @return {Ext.menu.Item} The menu item that was added
         */
        addItem : function(item) {
            return this.add(item);
        },

        /**
         * Creates a new {@link Ext.menu.Item} based an the supplied config object and adds it to the menu
         * @param {Object} config A MenuItem config object
         * @return {Ext.menu.Item} The menu item that was added
         */
        addMenuItem : function(config) {
            return this.add(this.getMenuItem(config));
        },

        /**
         * Creates a new {@link Ext.menu.TextItem} with the supplied text and adds it to the menu
         * @param {String} text The text to display in the menu item
         * @return {Ext.menu.Item} The menu item that was added
         */
        addText : function(text){
            return this.add(new Ext.menu.TextItem(text));
        },

        //private
        onDestroy : function(){
            Ext.EventManager.removeResizeListener(this.hide, this);
            var pm = this.parentMenu;
            if(pm && pm.activeChild == this){
                delete pm.activeChild;
            }
            delete this.parentMenu;
            Ext.menu.Menu.superclass.onDestroy.call(this);
            Ext.menu.MenuMgr.unregister(this);
            if(this.keyNav) {
                this.keyNav.disable();
            }
            var s = this.scroller;
            if(s){
                Ext.destroy(s.topRepeater, s.bottomRepeater, s.top, s.bottom);
            }
            Ext.destroy(
                this.el,
                this.focusEl,
                this.ul
            );
        }
    });

    Ext.reg('menu', Ext.menu.Menu);

    // MenuNav is a private utility class used internally by the Menu
    Ext.menu.MenuNav = Ext.extend(Ext.KeyNav, function(){
        function up(e, m){
            if(!m.tryActivate(m.items.indexOf(m.activeItem)-1, -1)){
                m.tryActivate(m.items.length-1, -1);
            }
        }
        function down(e, m){
            if(!m.tryActivate(m.items.indexOf(m.activeItem)+1, 1)){
                m.tryActivate(0, 1);
            }
        }
        return {
            constructor : function(menu){
                Ext.menu.MenuNav.superclass.constructor.call(this, menu.el);
                this.scope = this.menu = menu;
            },

            doRelay : function(e, h){
                var k = e.getKey();
    //          Keystrokes within a form Field (e.g.: down in a Combo) do not navigate. Allow only TAB
                if (this.menu.activeItem && this.menu.activeItem.isFormField && k != e.TAB) {
                    return false;
                }
                if(!this.menu.activeItem && e.isNavKeyPress() && k != e.SPACE && k != e.RETURN){
                    this.menu.tryActivate(0, 1);
                    return false;
                }
                return h.call(this.scope || this, e, this.menu);
            },

            tab: function(e, m) {
                e.stopEvent();
                if (e.shiftKey) {
                    up(e, m);
                } else {
                    down(e, m);
                }
            },

            up : up,

            down : down,

            right : function(e, m){
                if(m.activeItem){
                    m.activeItem.expandMenu(true);
                }
            },

            left : function(e, m){
                m.hide();
                if(m.parentMenu && m.parentMenu.activeItem){
                    m.parentMenu.activeItem.activate();
                }
            },

            enter : function(e, m){
                if(m.activeItem){
                    e.stopPropagation();
                    m.activeItem.onClick(e);
                    m.fireEvent('click', this, m.activeItem);
                    return true;
                }
            }
        };
    }());