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.TabPanel
     * A basic tab container. TabPanels can be used exactly like a standard {@link Ext.Panel}
     * for layout purposes, but also have special support for containing child Components
     * ({@link Ext.Container#items items}) that are managed using a
     * {@link Ext.layout.CardLayout CardLayout layout manager}, and displayed as separate tabs.
     *
     * Note: By default, a tab's close tool destroys the child tab Component
     * and all its descendants. This makes the child tab Component, and all its descendants unusable. To enable
     * re-use of a tab, configure the TabPanel with {@link #autoDestroy autoDestroy: false}.
     *
     * TabPanel header/footer elements
     * TabPanels use their {@link Ext.Panel#header header} or {@link Ext.Panel#footer footer} element
     * (depending on the {@link #tabPosition} configuration) to accommodate the tab selector buttons.
     * This means that a TabPanel will not display any configured title, and will not display any
     * configured header {@link Ext.Panel#tools tools}.
     * To display a header, embed the TabPanel in a {@link Ext.Panel Panel} which uses
     * {@link Ext.Container#layout layout:'fit'}.
     *
     * Tab Events
     * There is no actual tab class — each tab is simply a {@link Ext.BoxComponent Component}
     * such as a {@link Ext.Panel Panel}. However, when rendered in a TabPanel, each child Component
     * can fire additional events that only exist for tabs and are not available from other Components.
     * These events are:
     *
     * {@link Ext.Panel#activate activate} : Fires when this Component becomes
     * the active tab.
     * {@link Ext.Panel#deactivate deactivate} : Fires when the Component that
     * was the active tab becomes deactivated.
     * {@link Ext.Panel#beforeclose beforeclose} : Fires when the user clicks on the close tool of a closeable tab.
     * May be vetoed by returning false from a handler.
     * {@link Ext.Panel#close close} : Fires a closeable tab has been closed by the user.
     *
     * Creating TabPanels from Code
     * TabPanels can be created and rendered completely in code, as in this example:
     *
    var tabs = new Ext.TabPanel({
        renderTo: Ext.getBody(),
        activeTab: 0,
        items: [{
            title: 'Tab 1',
            html: 'A simple tab'
        },{
            title: 'Tab 2',
            html: 'Another one'
        }]
    });

     * Creating TabPanels from Existing Markup
     * TabPanels can also be rendered from pre-existing markup in a couple of ways.
     *
     *
     * Pre-Structured Markup
     *
     * A container div with one or more nested tab divs with class 'x-tab' can be rendered entirely
     * from existing markup (See the {@link #autoTabs} example).
     *
     *
     * Un-Structured Markup
     *
     * A TabPanel can also be rendered from markup that is not strictly structured by simply specifying by id
     * which elements should be the container and the tabs. Using this method tab content can be pulled from different
     * elements within the page by id regardless of page structure. For example:
     *
    var tabs = new Ext.TabPanel({
        renderTo: 'my-tabs',
        activeTab: 0,
        items:[
            {contentEl:'tab1', title:'Tab 1'},
            {contentEl:'tab2', title:'Tab 2'}
        ]
    });

    // Note that the tabs do not have to be nested within the container (although they can be)
    <div id="my-tabs"></div>
    <div id="tab1" class="x-hide-display">A simple tab</div>
    <div id="tab2" class="x-hide-display">Another one</div>

     * Note that the tab divs in this example contain the class 'x-hide-display' so that they can be rendered
     * deferred without displaying outside the tabs. You could alternately set {@link #deferredRender} = false
     * to render all content tabs on page load.
     *
     *
     *
     *
     * @extends Ext.Panel
     * @constructor
     * @param {Object} config The configuration options
     * @xtype tabpanel
     */
    Ext.TabPanel = Ext.extend(Ext.Panel,  {
        /**
         * @cfg {Boolean} layoutOnTabChange
         * Set to true to force a layout of the active tab when the tab is changed. Defaults to false.
         * See {@link Ext.layout.CardLayout}.{@link Ext.layout.CardLayout#layoutOnCardChange layoutOnCardChange}.
         */
        /**
         * @cfg {String} tabCls This config option is used on child Components of ths TabPanel. A CSS
         * class name applied to the tab strip item representing the child Component, allowing special
         * styling to be applied.
         */
        /**
         * @cfg {Boolean} deferredRender
         * true by default to defer the rendering of child {@link Ext.Container#items items}
         * to the browsers DOM until a tab is activated. false will render all contained
         * {@link Ext.Container#items items} as soon as the {@link Ext.layout.CardLayout layout}
         * is rendered. If there is a significant amount of content or a lot of heavy controls being
         * rendered into panels that are not displayed by default, setting this to true might
         * improve performance.
         *
    The deferredRender property is internally passed to the layout manager for
         * TabPanels ({@link Ext.layout.CardLayout}) as its {@link Ext.layout.CardLayout#deferredRender}
         * configuration value.
         *
    Note: leaving deferredRender as true means that the content
         * within an unactivated tab will not be available. For example, this means that if the TabPanel
         * is within a {@link Ext.form.FormPanel form}, then until a tab is activated, any Fields within
         * unactivated tabs will not be rendered, and will therefore not be submitted and will not be
         * available to either {@link Ext.form.BasicForm#getValues getValues} or
         * {@link Ext.form.BasicForm#setValues setValues}.
         */
        deferredRender : true,
        /**
         * @cfg {Number} tabWidth The initial width in pixels of each new tab (defaults to 120).
         */
        tabWidth : 120,
        /**
         * @cfg {Number} minTabWidth The minimum width in pixels for each tab when {@link #resizeTabs} = true (defaults to 30).
         */
        minTabWidth : 30,
        /**
         * @cfg {Boolean} resizeTabs True to automatically resize each tab so that the tabs will completely fill the
         * tab strip (defaults to false).  Setting this to true may cause specific widths that might be set per tab to
         * be overridden in order to fit them all into view (although {@link #minTabWidth} will always be honored).
         */
        resizeTabs : false,
        /**
         * @cfg {Boolean} enableTabScroll True to enable scrolling to tabs that may be invisible due to overflowing the
         * overall TabPanel width. Only available with tabPosition:'top' (defaults to false).
         */
        enableTabScroll : false,
        /**
         * @cfg {Number} scrollIncrement The number of pixels to scroll each time a tab scroll button is pressed
         * (defaults to 100, or if {@link #resizeTabs} = true, the calculated tab width).  Only
         * applies when {@link #enableTabScroll} = true.
         */
        scrollIncrement : 0,
        /**
         * @cfg {Number} scrollRepeatInterval Number of milliseconds between each scroll while a tab scroll button is
         * continuously pressed (defaults to 400).
         */
        scrollRepeatInterval : 400,
        /**
         * @cfg {Float} scrollDuration The number of milliseconds that each scroll animation should last (defaults
         * to .35). Only applies when {@link #animScroll} = true.
         */
        scrollDuration : 0.35,
        /**
         * @cfg {Boolean} animScroll True to animate tab scrolling so that hidden tabs slide smoothly into view (defaults
         * to true).  Only applies when {@link #enableTabScroll} = true.
         */
        animScroll : true,
        /**
         * @cfg {String} tabPosition The position where the tab strip should be rendered (defaults to 'top').
         * The only other supported value is 'bottom'.  Note: tab scrolling is only supported for
         * tabPosition: 'top'.
         */
        tabPosition : 'top',
        /**
         * @cfg {String} baseCls The base CSS class applied to the panel (defaults to 'x-tab-panel').
         */
        baseCls : 'x-tab-panel',
        /**
         * @cfg {Boolean} autoTabs
         * true to query the DOM for any divs with a class of 'x-tab' to be automatically converted
         * to tabs and added to this panel (defaults to false).  Note that the query will be executed within
         * the scope of the container element only (so that multiple tab panels from markup can be supported via this
         * method).
         * This method is only possible when the markup is structured correctly as a container with nested divs
         * containing the class 'x-tab'. To create TabPanels without these limitations, or to pull tab content
         * from other elements on the page, see the example at the top of the class for generating tabs from markup.
         * There are a couple of things to note when using this method:
         * When using the autoTabs config (as opposed to passing individual tab configs in the TabPanel's
         * {@link #items} collection), you must use {@link #applyTo} to correctly use the specified id
         * as the tab container. The autoTabs method replaces existing content with the TabPanel
         * components.
         * Make sure that you set {@link #deferredRender}: false so that the content elements for each
         * tab will be rendered into the TabPanel immediately upon page load, otherwise they will not be transformed
         * until each tab is activated and will be visible outside the TabPanel.
         * Example usage:
         *
    var tabs = new Ext.TabPanel({
        applyTo: 'my-tabs',
        activeTab: 0,
        deferredRender: false,
        autoTabs: true
    });

    // This markup will be converted to a TabPanel from the code above
    <div id="my-tabs">
        <div class="x-tab" title="Tab 1">A simple tab</div>
        <div class="x-tab" title="Tab 2">Another one</div>
    </div>

         */
        autoTabs : false,
        /**
         * @cfg {String} autoTabSelector The CSS selector used to search for tabs in existing markup when
         * {@link #autoTabs} = true (defaults to 'div.x-tab').  This can be any valid selector
         * supported by {@link Ext.DomQuery#select}. Note that the query will be executed within the scope of this
         * tab panel only (so that multiple tab panels from markup can be supported on a page).
         */
        autoTabSelector : 'div.x-tab',
        /**
         * @cfg {String/Number} activeTab A string id or the numeric index of the tab that should be initially
         * activated on render (defaults to undefined).
         */
        activeTab : undefined,
        /**
         * @cfg {Number} tabMargin The number of pixels of space to calculate into the sizing and scrolling of
         * tabs. If you change the margin in CSS, you will need to update this value so calculations are correct
         * with either {@link #resizeTabs} or scrolling tabs. (defaults to 2)
         */
        tabMargin : 2,
        /**
         * @cfg {Boolean} plain true to render the tab strip without a background container image
         * (defaults to false).
         */
        plain : false,
        /**
         * @cfg {Number} wheelIncrement For scrolling tabs, the number of pixels to increment on mouse wheel
         * scrolling (defaults to 20).
         */
        wheelIncrement : 20,

        /*
         * This is a protected property used when concatenating tab ids to the TabPanel id for internal uniqueness.
         * It does not generally need to be changed, but can be if external code also uses an id scheme that can
         * potentially clash with this one.
         */
        idDelimiter : '__',

        // private
        itemCls : 'x-tab-item',

        // private config overrides
        elements : 'body',
        headerAsText : false,
        frame : false,
        hideBorders :true,

        // private
        initComponent : function(){
            this.frame = false;
            Ext.TabPanel.superclass.initComponent.call(this);
            this.addEvents(
                /**
                 * @event beforetabchange
                 * Fires before the active tab changes. Handlers can return false to cancel the tab change.
                 * @param {TabPanel} this
                 * @param {Panel} newTab The tab being activated
                 * @param {Panel} currentTab The current active tab
                 */
                'beforetabchange',
                /**
                 * @event tabchange
                 * Fires after the active tab has changed.
                 * @param {TabPanel} this
                 * @param {Panel} tab The new active tab
                 */
                'tabchange',
                /**
                 * @event contextmenu
                 * Relays the contextmenu event from a tab selector element in the tab strip.
                 * @param {TabPanel} this
                 * @param {Panel} tab The target tab
                 * @param {EventObject} e
                 */
                'contextmenu'
            );
            /**
             * @cfg {Object} layoutConfig
             * TabPanel implicitly uses {@link Ext.layout.CardLayout} as its layout manager.
             * layoutConfig may be used to configure this layout manager.
             * {@link #deferredRender} and {@link #layoutOnTabChange}
             * configured on the TabPanel will be applied as configs to the layout manager.
             */
            this.setLayout(new Ext.layout.CardLayout(Ext.apply({
                layoutOnCardChange: this.layoutOnTabChange,
                deferredRender: this.deferredRender
            }, this.layoutConfig)));

            if(this.tabPosition == 'top'){
                this.elements += ',header';
                this.stripTarget = 'header';
            }else {
                this.elements += ',footer';
                this.stripTarget = 'footer';
            }
            if(!this.stack){
                this.stack = Ext.TabPanel.AccessStack();
            }
            this.initItems();
        },

        // private
        onRender : function(ct, position){
            Ext.TabPanel.superclass.onRender.call(this, ct, position);

            if(this.plain){
                var pos = this.tabPosition == 'top' ? 'header' : 'footer';
                this[pos].addClass('x-tab-panel-'+pos+'-plain');
            }

            var st = this[this.stripTarget];

            this.stripWrap = st.createChild({cls:'x-tab-strip-wrap', cn:{
                tag:'ul', cls:'x-tab-strip x-tab-strip-'+this.tabPosition}});

            var beforeEl = (this.tabPosition=='bottom' ? this.stripWrap : null);
            st.createChild({cls:'x-tab-strip-spacer'}, beforeEl);
            this.strip = new Ext.Element(this.stripWrap.dom.firstChild);

            // create an empty span with class x-tab-strip-text to force the height of the header element when there's no tabs.
            this.edge = this.strip.createChild({tag:'li', cls:'x-tab-edge', cn: [{tag: 'span', cls: 'x-tab-strip-text', cn: ' '}]});
            this.strip.createChild({cls:'x-clear'});

            this.body.addClass('x-tab-panel-body-'+this.tabPosition);

            /**
             * @cfg {Template/XTemplate} itemTpl (Optional) A {@link Ext.Template Template} or
             * {@link Ext.XTemplate XTemplate} which may be provided to process the data object returned from
             * {@link #getTemplateArgs} to produce a clickable selector element in the tab strip.
             * The main element created should be a <li> element. In order for a click event on
             * a selector element to be connected to its item, it must take its id from the TabPanel's
             * native {@link #getTemplateArgs}.
             * The child element which contains the title text must be marked by the CSS class
             * x-tab-strip-inner.
             * To enable closability, the created element should contain an element marked by the CSS class
             * x-tab-strip-close.
             * If a custom itemTpl is supplied, it is the developer's responsibility to create CSS
             * style rules to create the desired appearance.
             * Below is an example of how to create customized tab selector items:
    new Ext.TabPanel({
        renderTo: document.body,
        minTabWidth: 115,
        tabWidth: 135,
        enableTabScroll: true,
        width: 600,
        height: 250,
        defaults: {autoScroll:true},
        itemTpl: new Ext.XTemplate(
        '<li class="{cls}" id="{id}" style="overflow:hidden">',
             '<tpl if="closable">',
                '<a class="x-tab-strip-close"></a>',
             '</tpl>',
             '<a class="x-tab-right" href="#" style="padding-left:6px">',
                '<em class="x-tab-left">',
                    '<span class="x-tab-strip-inner">',
                        '<img src="{src}" style="float:left;margin:3px 3px 0 0">',
                        '<span style="margin-left:20px" class="x-tab-strip-text {iconCls}">{text} {extra}</span>',
                    '</span>',
                '</em>',
            '</a>',
        '</li>'
        ),
        getTemplateArgs: function(item) {
    //      Call the native method to collect the base data. Like the ID!
            var result = Ext.TabPanel.prototype.getTemplateArgs.call(this, item);

    //      Add stuff used in our template
            return Ext.apply(result, {
                closable: item.closable,
                src: item.iconSrc,
                extra: item.extraText || ''
            });
        },
        items: [{
            title: 'New Tab 1',
            iconSrc: '../shared/icons/fam/grid.png',
            html: 'Tab Body 1',
            closable: true
        }, {
            title: 'New Tab 2',
            iconSrc: '../shared/icons/fam/grid.png',
            html: 'Tab Body 2',
            extraText: 'Extra stuff in the tab button'
        }]
    });

             */
            if(!this.itemTpl){
                var tt = new Ext.Template(
                     '',
                     '',
                     '{text}',
                     ''
                );
                tt.disableFormats = true;
                tt.compile();
                Ext.TabPanel.prototype.itemTpl = tt;
            }

            this.items.each(this.initTab, this);
        },

        // private
        afterRender : function(){
            Ext.TabPanel.superclass.afterRender.call(this);
            if(this.autoTabs){
                this.readTabs(false);
            }
            if(this.activeTab !== undefined){
                var item = Ext.isObject(this.activeTab) ? this.activeTab : this.items.get(this.activeTab);
                delete this.activeTab;
                this.setActiveTab(item);
            }
        },

        // private
        initEvents : function(){
            Ext.TabPanel.superclass.initEvents.call(this);
            this.mon(this.strip, {
                scope: this,
                mousedown: this.onStripMouseDown,
                contextmenu: this.onStripContextMenu
            });
            if(this.enableTabScroll){
                this.mon(this.strip, 'mousewheel', this.onWheel, this);
            }
        },

        // private
        findTargets : function(e){
            var item = null,
                itemEl = e.getTarget('li:not(.x-tab-edge)', this.strip);

            if(itemEl){
                item = this.getComponent(itemEl.id.split(this.idDelimiter)[1]);
                if(item.disabled){
                    return {
                        close : null,
                        item : null,
                        el : null
                    };
                }
            }
            return {
                close : e.getTarget('.x-tab-strip-close', this.strip),
                item : item,
                el : itemEl
            };
        },

        // private
        onStripMouseDown : function(e){
            if(e.button !== 0){
                return;
            }
            e.preventDefault();
            var t = this.findTargets(e);
            if(t.close){
                if (t.item.fireEvent('beforeclose', t.item) !== false) {
                    t.item.fireEvent('close', t.item);
                    this.remove(t.item);
                }
                return;
            }
            if(t.item && t.item != this.activeTab){
                this.setActiveTab(t.item);
            }
        },

        // private
        onStripContextMenu : function(e){
            e.preventDefault();
            var t = this.findTargets(e);
            if(t.item){
                this.fireEvent('contextmenu', this, t.item, e);
            }
        },

        /**
         * True to scan the markup in this tab panel for {@link #autoTabs} using the
         * {@link #autoTabSelector}
         * @param {Boolean} removeExisting True to remove existing tabs
         */
        readTabs : function(removeExisting){
            if(removeExisting === true){
                this.items.each(function(item){
                    this.remove(item);
                }, this);
            }
            var tabs = this.el.query(this.autoTabSelector);
            for(var i = 0, len = tabs.length; i < len; i++){
                var tab = tabs[i],
                    title = tab.getAttribute('title');
                tab.removeAttribute('title');
                this.add({
                    title: title,
                    contentEl: tab
                });
            }
        },

        // private
        initTab : function(item, index){
            var before = this.strip.dom.childNodes[index],
                p = this.getTemplateArgs(item),
                el = before ?
                     this.itemTpl.insertBefore(before, p) :
                     this.itemTpl.append(this.strip, p),
                cls = 'x-tab-strip-over',
                tabEl = Ext.get(el);

            tabEl.hover(function(){
                if(!item.disabled){
                    tabEl.addClass(cls);
                }
            }, function(){
                tabEl.removeClass(cls);
            });

            if(item.tabTip){
                tabEl.child('span.x-tab-strip-text', true).qtip = item.tabTip;
            }
            item.tabEl = el;

            // Route *keyboard triggered* click events to the tab strip mouse handler.
            tabEl.select('a').on('click', function(e){
                if(!e.getPageX()){
                    this.onStripMouseDown(e);
                }
            }, this, {preventDefault: true});

            item.on({
                scope: this,
                disable: this.onItemDisabled,
                enable: this.onItemEnabled,
                titlechange: this.onItemTitleChanged,
                iconchange: this.onItemIconChanged,
                beforeshow: this.onBeforeShowItem
            });
        },

        /**
         * Provides template arguments for rendering a tab selector item in the tab strip.
         * This method returns an object hash containing properties used by the TabPanel's {@link #itemTpl}
         * to create a formatted, clickable tab selector element. The properties which must be returned
         * are:
         * id : StringA unique identifier which links to the item
         * text : StringThe text to display
         * cls : StringThe CSS class name
         * iconCls : StringA CSS class to provide appearance for an icon.
         *
         * @param {Ext.BoxComponent} item The {@link Ext.BoxComponent BoxComponent} for which to create a selector element in the tab strip.
         * @return {Object} An object hash containing the properties required to render the selector element.
         */
        getTemplateArgs : function(item) {
            var cls = item.closable ? 'x-tab-strip-closable' : '';
            if(item.disabled){
                cls += ' x-item-disabled';
            }
            if(item.iconCls){
                cls += ' x-tab-with-icon';
            }
            if(item.tabCls){
                cls += ' ' + item.tabCls;
            }

            return {
                id: this.id + this.idDelimiter + item.getItemId(),
                text: item.title,
                cls: cls,
                iconCls: item.iconCls || ''
            };
        },

        // private
        onAdd : function(c){
            Ext.TabPanel.superclass.onAdd.call(this, c);
            if(this.rendered){
                var items = this.items;
                this.initTab(c, items.indexOf(c));
                this.delegateUpdates();
            }
        },

        // private
        onBeforeAdd : function(item){
            var existing = item.events ? (this.items.containsKey(item.getItemId()) ? item : null) : this.items.get(item);
            if(existing){
                this.setActiveTab(item);
                return false;
            }
            Ext.TabPanel.superclass.onBeforeAdd.apply(this, arguments);
            var es = item.elements;
            item.elements = es ? es.replace(',header', '') : es;
            item.border = (item.border === true);
        },

        // private
        onRemove : function(c){
            var te = Ext.get(c.tabEl);
            // check if the tabEl exists, it won't if the tab isn't rendered
            if(te){
                te.select('a').removeAllListeners();
                Ext.destroy(te);
            }
            Ext.TabPanel.superclass.onRemove.call(this, c);
            this.stack.remove(c);
            delete c.tabEl;
            c.un('disable', this.onItemDisabled, this);
            c.un('enable', this.onItemEnabled, this);
            c.un('titlechange', this.onItemTitleChanged, this);
            c.un('iconchange', this.onItemIconChanged, this);
            c.un('beforeshow', this.onBeforeShowItem, this);
            if(c == this.activeTab){
                var next = this.stack.next();
                if(next){
                    this.setActiveTab(next);
                }else if(this.items.getCount() > 0){
                    this.setActiveTab(0);
                }else{
                    this.setActiveTab(null);
                }
            }
            if(!this.destroying){
                this.delegateUpdates();
            }
        },

        // private
        onBeforeShowItem : function(item){
            if(item != this.activeTab){
                this.setActiveTab(item);
                return false;
            }
        },

        // private
        onItemDisabled : function(item){
            var el = this.getTabEl(item);
            if(el){
                Ext.fly(el).addClass('x-item-disabled');
            }
            this.stack.remove(item);
        },

        // private
        onItemEnabled : function(item){
            var el = this.getTabEl(item);
            if(el){
                Ext.fly(el).removeClass('x-item-disabled');
            }
        },

        // private
        onItemTitleChanged : function(item){
            var el = this.getTabEl(item);
            if(el){
                Ext.fly(el).child('span.x-tab-strip-text', true).innerHTML = item.title;
            }
        },

        //private
        onItemIconChanged : function(item, iconCls, oldCls){
            var el = this.getTabEl(item);
            if(el){
                el = Ext.get(el);
                el.child('span.x-tab-strip-text').replaceClass(oldCls, iconCls);
                el[Ext.isEmpty(iconCls) ? 'removeClass' : 'addClass']('x-tab-with-icon');
            }
        },

        /**
         * Gets the DOM element for the tab strip item which activates the child panel with the specified
         * ID. Access this to change the visual treatment of the item, for example by changing the CSS class name.
         * @param {Panel/Number/String} tab The tab component, or the tab's index, or the tabs id or itemId.
         * @return {HTMLElement} The DOM node
         */
        getTabEl : function(item){
            var c = this.getComponent(item);
            return c ? c.tabEl : null;
        },

        // private
        onResize : function(){
            Ext.TabPanel.superclass.onResize.apply(this, arguments);
            this.delegateUpdates();
        },

        /**
         * Suspends any internal calculations or scrolling while doing a bulk operation. See {@link #endUpdate}
         */
        beginUpdate : function(){
            this.suspendUpdates = true;
        },

        /**
         * Resumes calculations and scrolling at the end of a bulk operation. See {@link #beginUpdate}
         */
        endUpdate : function(){
            this.suspendUpdates = false;
            this.delegateUpdates();
        },

        /**
         * Hides the tab strip item for the passed tab
         * @param {Number/String/Panel} item The tab index, id or item
         */
        hideTabStripItem : function(item){
            item = this.getComponent(item);
            var el = this.getTabEl(item);
            if(el){
                el.style.display = 'none';
                this.delegateUpdates();
            }
            this.stack.remove(item);
        },

        /**
         * Unhides the tab strip item for the passed tab
         * @param {Number/String/Panel} item The tab index, id or item
         */
        unhideTabStripItem : function(item){
            item = this.getComponent(item);
            var el = this.getTabEl(item);
            if(el){
                el.style.display = '';
                this.delegateUpdates();
            }
        },

        // private
        delegateUpdates : function(){
            if(this.suspendUpdates){
                return;
            }
            if(this.resizeTabs && this.rendered){
                this.autoSizeTabs();
            }
            if(this.enableTabScroll && this.rendered){
                this.autoScrollTabs();
            }
        },

        // private
        autoSizeTabs : function(){
            var count = this.items.length,
                ce = this.tabPosition != 'bottom' ? 'header' : 'footer',
                ow = this[ce].dom.offsetWidth,
                aw = this[ce].dom.clientWidth;

            if(!this.resizeTabs || count < 1 || !aw){ // !aw for display:none
                return;
            }

            var each = Math.max(Math.min(Math.floor((aw-4) / count) - this.tabMargin, this.tabWidth), this.minTabWidth); // -4 for float errors in IE
            this.lastTabWidth = each;
            var lis = this.strip.query('li:not(.x-tab-edge)');
            for(var i = 0, len = lis.length; i < len; i++) {
                var li = lis[i],
                    inner = Ext.fly(li).child('.x-tab-strip-inner', true),
                    tw = li.offsetWidth,
                    iw = inner.offsetWidth;
                inner.style.width = (each - (tw-iw)) + 'px';
            }
        },

        // private
        adjustBodyWidth : function(w){
            if(this.header){
                this.header.setWidth(w);
            }
            if(this.footer){
                this.footer.setWidth(w);
            }
            return w;
        },

        /**
         * Sets the specified tab as the active tab. This method fires the {@link #beforetabchange} event which
         * can return false to cancel the tab change.
         * @param {String/Number} item
         * The id or tab Panel to activate. This parameter may be any of the following:
         *
         * a String : representing the {@link Ext.Component#itemId itemId}
         * or {@link Ext.Component#id id} of the child component
         * a Number : representing the position of the child component
         * within the {@link Ext.Container#items items} property
         *
         * For additional information see {@link Ext.util.MixedCollection#get}.
         */
        setActiveTab : function(item){
            item = this.getComponent(item);
            if(this.fireEvent('beforetabchange', this, item, this.activeTab) === false){
                return;
            }
            if(!this.rendered){
                this.activeTab = item;
                return;
            }
            if(this.activeTab != item){
                if(this.activeTab){
                    var oldEl = this.getTabEl(this.activeTab);
                    if(oldEl){
                        Ext.fly(oldEl).removeClass('x-tab-strip-active');
                    }
                }
                this.activeTab = item;
                if(item){
                    var el = this.getTabEl(item);
                    Ext.fly(el).addClass('x-tab-strip-active');
                    this.stack.add(item);

                    this.layout.setActiveItem(item);
                    if(this.scrolling){
                        this.scrollToTab(item, this.animScroll);
                    }
                }
                this.fireEvent('tabchange', this, item);
            }
        },

        /**
         * Returns the Component which is the currently active tab. Note that before the TabPanel
         * first activates a child Component, this method will return whatever was configured in the
         * {@link #activeTab} config option.
         * @return {BoxComponent} The currently active child Component if one is active, or the {@link #activeTab} config value.
         */
        getActiveTab : function(){
            return this.activeTab || null;
        },

        /**
         * Gets the specified tab by id.
         * @param {String} id The tab id
         * @return {Panel} The tab
         */
        getItem : function(item){
            return this.getComponent(item);
        },

        // private
        autoScrollTabs : function(){
            this.pos = this.tabPosition=='bottom' ? this.footer : this.header;
            var count = this.items.length,
                ow = this.pos.dom.offsetWidth,
                tw = this.pos.dom.clientWidth,
                wrap = this.stripWrap,
                wd = wrap.dom,
                cw = wd.offsetWidth,
                pos = this.getScrollPos(),
                l = this.edge.getOffsetsTo(this.stripWrap)[0] + pos;

            if(!this.enableTabScroll || count < 1 || cw < 20){ // 20 to prevent display:none issues
                return;
            }
            if(l <= tw){
                wd.scrollLeft = 0;
                wrap.setWidth(tw);
                if(this.scrolling){
                    this.scrolling = false;
                    this.pos.removeClass('x-tab-scrolling');
                    this.scrollLeft.hide();
                    this.scrollRight.hide();
                    // See here: http://extjs.com/forum/showthread.php?t=49308&highlight=isSafari
                    if(Ext.isAir || Ext.isWebKit){
                        wd.style.marginLeft = '';
                        wd.style.marginRight = '';
                    }
                }
            }else{
                if(!this.scrolling){
                    this.pos.addClass('x-tab-scrolling');
                    // See here: http://extjs.com/forum/showthread.php?t=49308&highlight=isSafari
                    if(Ext.isAir || Ext.isWebKit){
                        wd.style.marginLeft = '18px';
                        wd.style.marginRight = '18px';
                    }
                }
                tw -= wrap.getMargins('lr');
                wrap.setWidth(tw > 20 ? tw : 20);
                if(!this.scrolling){
                    if(!this.scrollLeft){
                        this.createScrollers();
                    }else{
                        this.scrollLeft.show();
                        this.scrollRight.show();
                    }
                }
                this.scrolling = true;
                if(pos > (l-tw)){ // ensure it stays within bounds
                    wd.scrollLeft = l-tw;
                }else{ // otherwise, make sure the active tab is still visible
                    this.scrollToTab(this.activeTab, false);
                }
                this.updateScrollButtons();
            }
        },

        // private
        createScrollers : function(){
            this.pos.addClass('x-tab-scrolling-' + this.tabPosition);
            var h = this.stripWrap.dom.offsetHeight;

            // left
            var sl = this.pos.insertFirst({
                cls:'x-tab-scroller-left'
            });
            sl.setHeight(h);
            sl.addClassOnOver('x-tab-scroller-left-over');
            this.leftRepeater = new Ext.util.ClickRepeater(sl, {
                interval : this.scrollRepeatInterval,
                handler: this.onScrollLeft,
                scope: this
            });
            this.scrollLeft = sl;

            // right
            var sr = this.pos.insertFirst({
                cls:'x-tab-scroller-right'
            });
            sr.setHeight(h);
            sr.addClassOnOver('x-tab-scroller-right-over');
            this.rightRepeater = new Ext.util.ClickRepeater(sr, {
                interval : this.scrollRepeatInterval,
                handler: this.onScrollRight,
                scope: this
            });
            this.scrollRight = sr;
        },

        // private
        getScrollWidth : function(){
            return this.edge.getOffsetsTo(this.stripWrap)[0] + this.getScrollPos();
        },

        // private
        getScrollPos : function(){
            return parseInt(this.stripWrap.dom.scrollLeft, 10) || 0;
        },

        // private
        getScrollArea : function(){
            return parseInt(this.stripWrap.dom.clientWidth, 10) || 0;
        },

        // private
        getScrollAnim : function(){
            return {duration:this.scrollDuration, callback: this.updateScrollButtons, scope: this};
        },

        // private
        getScrollIncrement : function(){
            return this.scrollIncrement || (this.resizeTabs ? this.lastTabWidth+2 : 100);
        },

        /**
         * Scrolls to a particular tab if tab scrolling is enabled
         * @param {Panel} item The item to scroll to
         * @param {Boolean} animate True to enable animations
         */

        scrollToTab : function(item, animate){
            if(!item){
                return;
            }
            var el = this.getTabEl(item),
                pos = this.getScrollPos(),
                area = this.getScrollArea(),
                left = Ext.fly(el).getOffsetsTo(this.stripWrap)[0] + pos,
                right = left + el.offsetWidth;
            if(left < pos){
                this.scrollTo(left, animate);
            }else if(right > (pos + area)){
                this.scrollTo(right - area, animate);
            }
        },

        // private
        scrollTo : function(pos, animate){
            this.stripWrap.scrollTo('left', pos, animate ? this.getScrollAnim() : false);
            if(!animate){
                this.updateScrollButtons();
            }
        },

        onWheel : function(e){
            var d = e.getWheelDelta()*this.wheelIncrement*-1;
            e.stopEvent();

            var pos = this.getScrollPos(),
                newpos = pos + d,
                sw = this.getScrollWidth()-this.getScrollArea();

            var s = Math.max(0, Math.min(sw, newpos));
            if(s != pos){
                this.scrollTo(s, false);
            }
        },

        // private
        onScrollRight : function(){
            var sw = this.getScrollWidth()-this.getScrollArea(),
                pos = this.getScrollPos(),
                s = Math.min(sw, pos + this.getScrollIncrement());
            if(s != pos){
                this.scrollTo(s, this.animScroll);
            }
        },

        // private
        onScrollLeft : function(){
            var pos = this.getScrollPos(),
                s = Math.max(0, pos - this.getScrollIncrement());
            if(s != pos){
                this.scrollTo(s, this.animScroll);
            }
        },

        // private
        updateScrollButtons : function(){
            var pos = this.getScrollPos();
            this.scrollLeft[pos === 0 ? 'addClass' : 'removeClass']('x-tab-scroller-left-disabled');
            this.scrollRight[pos >= (this.getScrollWidth()-this.getScrollArea()) ? 'addClass' : 'removeClass']('x-tab-scroller-right-disabled');
        },

        // private
        beforeDestroy : function() {
            Ext.destroy(this.leftRepeater, this.rightRepeater);
            this.deleteMembers('strip', 'edge', 'scrollLeft', 'scrollRight', 'stripWrap');
            this.activeTab = null;
            Ext.TabPanel.superclass.beforeDestroy.apply(this);
        }

        /**
         * @cfg {Boolean} collapsible
         * @hide
         */
        /**
         * @cfg {String} header
         * @hide
         */
        /**
         * @cfg {Boolean} headerAsText
         * @hide
         */
        /**
         * @property header
         * @hide
         */
        /**
         * @cfg title
         * @hide
         */
        /**
         * @cfg {Array} tools
         * @hide
         */
        /**
         * @cfg {Array} toolTemplate
         * @hide
         */
        /**
         * @cfg {Boolean} hideCollapseTool
         * @hide
         */
        /**
         * @cfg {Boolean} titleCollapse
         * @hide
         */
        /**
         * @cfg {Boolean} collapsed
         * @hide
         */
        /**
         * @cfg {String} layout
         * @hide
         */
        /**
         * @cfg {Boolean} preventBodyReset
         * @hide
         */
    });
    Ext.reg('tabpanel', Ext.TabPanel);

    /**
     * See {@link #setActiveTab}. Sets the specified tab as the active tab. This method fires
     * the {@link #beforetabchange} event which can return false to cancel the tab change.
     * @param {String/Panel} tab The id or tab Panel to activate
     * @method activate
     */
    Ext.TabPanel.prototype.activate = Ext.TabPanel.prototype.setActiveTab;

    // private utility class used by TabPanel
    Ext.TabPanel.AccessStack = function(){
        var items = [];
        return {
            add : function(item){
                items.push(item);
                if(items.length > 10){
                    items.shift();
                }
            },

            remove : function(item){
                var s = [];
                for(var i = 0, len = items.length; i < len; i++) {
                    if(items[i] != item){
                        s.push(items[i]);
                    }
                }
                items = s;
            },

            next : function(){
                return items.pop();
            }
        };
    };