The source code

    /*!
     * Ext JS Library 3.2.1
     * Copyright(c) 2006-2010 Ext JS, Inc.
     * licensing@extjs.com
     * http://www.extjs.com/license
     */
    /**
     * @class Ext.menu.BaseItem
     * @extends Ext.Component
     * The base class for all items that render into menus.  BaseItem provides default rendering, activated state
     * management and base configuration options shared by all menu components.
     * @constructor
     * Creates a new BaseItem
     * @param {Object} config Configuration options
     * @xtype menubaseitem
     */
    Ext.menu.BaseItem = Ext.extend(Ext.Component, {
        /**
         * @property parentMenu
         * @type Ext.menu.Menu
         * The parent Menu of this Item.
         */
        /**
         * @cfg {Function} handler
         * A function that will handle the click event of this menu item (optional).
         * The handler is passed the following parameters:
         * b : ItemThis menu Item.
         * e : EventObjectThe click event.
         *
         */
        /**
         * @cfg {Object} scope
         * The scope (this reference) in which the handler function will be called.
         */
        /**
         * @cfg {Boolean} canActivate True if this item can be visually activated (defaults to false)
         */
        canActivate : false,
        /**
         * @cfg {String} activeClass The CSS class to use when the item becomes activated (defaults to "x-menu-item-active")
         */
        activeClass : "x-menu-item-active",
        /**
         * @cfg {Boolean} hideOnClick True to hide the containing menu after this item is clicked (defaults to true)
         */
        hideOnClick : true,
        /**
         * @cfg {Number} clickHideDelay Length of time in milliseconds to wait before hiding after a click (defaults to 1)
         */
        clickHideDelay : 1,

        // private
        ctype : "Ext.menu.BaseItem",

        // private
        actionMode : "container",

        initComponent : function(){
            Ext.menu.BaseItem.superclass.initComponent.call(this);
            this.addEvents(
                /**
                 * @event click
                 * Fires when this item is clicked
                 * @param {Ext.menu.BaseItem} this
                 * @param {Ext.EventObject} e
                 */
                'click',
                /**
                 * @event activate
                 * Fires when this item is activated
                 * @param {Ext.menu.BaseItem} this
                 */
                'activate',
                /**
                 * @event deactivate
                 * Fires when this item is deactivated
                 * @param {Ext.menu.BaseItem} this
                 */
                'deactivate'
            );
            if(this.handler){
                this.on("click", this.handler, this.scope);
            }
        },

        // private
        onRender : function(container, position){
            Ext.menu.BaseItem.superclass.onRender.apply(this, arguments);
            if(this.ownerCt && this.ownerCt instanceof Ext.menu.Menu){
                this.parentMenu = this.ownerCt;
            }else{
                this.container.addClass('x-menu-list-item');
                this.mon(this.el, {
                    scope: this,
                    click: this.onClick,
                    mouseenter: this.activate,
                    mouseleave: this.deactivate
                });
            }
        },

        /**
         * Sets the function that will handle click events for this item (equivalent to passing in the {@link #handler}
         * config property).  If an existing handler is already registered, it will be unregistered for you.
         * @param {Function} handler The function that should be called on click
         * @param {Object} scope The scope (this reference) in which the handler function is executed. Defaults to this menu item.
         */
        setHandler : function(handler, scope){
            if(this.handler){
                this.un("click", this.handler, this.scope);
            }
            this.on("click", this.handler = handler, this.scope = scope);
        },

        // private
        onClick : function(e){
            if(!this.disabled && this.fireEvent("click", this, e) !== false
                    && (this.parentMenu && this.parentMenu.fireEvent("itemclick", this, e) !== false)){
                this.handleClick(e);
            }else{
                e.stopEvent();
            }
        },

        // private
        activate : function(){
            if(this.disabled){
                return false;
            }
            var li = this.container;
            li.addClass(this.activeClass);
            this.region = li.getRegion().adjust(2, 2, -2, -2);
            this.fireEvent("activate", this);
            return true;
        },

        // private
        deactivate : function(){
            this.container.removeClass(this.activeClass);
            this.fireEvent("deactivate", this);
        },

        // private
        shouldDeactivate : function(e){
            return !this.region || !this.region.contains(e.getPoint());
        },

        // private
        handleClick : function(e){
            var pm = this.parentMenu;
            if(this.hideOnClick){
                if(pm.floating){
                    pm.hide.defer(this.clickHideDelay, pm, [true]);
                }else{
                    pm.deactivateActive();
                }
            }
        },

        // private. Do nothing
        expandMenu : Ext.emptyFn,

        // private. Do nothing
        hideMenu : Ext.emptyFn
    });
    Ext.reg('menubaseitem', Ext.menu.BaseItem);