    /**
     * @author Ed Spencer, Tommy Maintz, Brian Moeskau
     *
     * A basic tab container. TabPanels can be used exactly like a standard {@link Ext.panel.Panel} for
     * layout purposes, but also have special support for containing child Components
     * (`{@link Ext.container.Container#cfg-items items}`) that are managed using a
     * {@link Ext.layout.container.Card 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's layout
     *
     * TabPanels use a Dock layout to position the {@link Ext.tab.Bar TabBar} at the top of the widget.
     * Panels added to the TabPanel will have their header hidden by default because the Tab will
     * automatically take the Panel's configured title and icon.
     *
     * TabPanels use their {@link Ext.panel.Header header} or {@link Ext.panel.Panel#fbar 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.Panel#tools tools}.
     *
     * To display a header, embed the TabPanel in a {@link Ext.panel.Panel Panel} which uses
     * `{@link Ext.container.Container#layout layout: 'fit'}`.
     *
     * ## Controlling tabs
     *
     * Configuration options for the {@link Ext.tab.Tab} that represents the component can be passed in
     * by specifying the tabConfig option:
     *
     *     @example
     *     Ext.create('Ext.tab.Panel', {
     *         width: 400,
     *         height: 400,
     *         renderTo: document.body,
     *         items: [{
     *             title: 'Foo'
     *         }, {
     *             title: 'Bar',
     *             tabConfig: {
     *                 title: 'Custom Title',
     *                 tooltip: 'A button tooltip'
     *             }
     *         }]
     *     });
     *
     * # Examples
     *
     * Here is a basic TabPanel rendered to the body. This also shows the useful configuration {@link #activeTab},
     * which allows you to set the active tab on render. If you do not set an {@link #activeTab}, no tabs will be
     * active by default.
     *
     *     @example
     *     Ext.create('Ext.tab.Panel', {
     *         width: 300,
     *         height: 200,
     *         activeTab: 0,
     *         items: [
     *             {
     *                 title: 'Tab 1',
     *                 bodyPadding: 10,
     *                 html : 'A simple tab'
     *             },
     *             {
     *                 title: 'Tab 2',
     *                 html : 'Another one'
     *             }
     *         ],
     *         renderTo : Ext.getBody()
     *     });
     *
     * It is easy to control the visibility of items in the tab bar. Specify hidden: true to have the
     * tab button hidden initially. Items can be subsequently hidden and show by accessing the
     * tab property on the child item.
     *
     *     @example
     *     var tabs = Ext.create('Ext.tab.Panel', {
     *         width: 400,
     *         height: 400,
     *         renderTo: document.body,
     *         items: [{
     *             title: 'Home',
     *             html: 'Home',
     *             itemId: 'home'
     *         }, {
     *             title: 'Users',
     *             html: 'Users',
     *             itemId: 'users',
     *             hidden: true
     *         }, {
     *             title: 'Tickets',
     *             html: 'Tickets',
     *             itemId: 'tickets'
     *         }]
     *     });
     *
     *     setTimeout(function(){
     *         tabs.child('#home').tab.hide();
     *         var users = tabs.child('#users');
     *         users.tab.show();
     *         tabs.setActiveTab(users);
     *     }, 1000);
     *
     * You can remove the background of the TabBar by setting the {@link #plain} property to `true`.
     *
     *     @example
     *     Ext.create('Ext.tab.Panel', {
     *         width: 300,
     *         height: 200,
     *         activeTab: 0,
     *         plain: true,
     *         items: [
     *             {
     *                 title: 'Tab 1',
     *                 bodyPadding: 10,
     *                 html : 'A simple tab'
     *             },
     *             {
     *                 title: 'Tab 2',
     *                 html : 'Another one'
     *             }
     *         ],
     *         renderTo : Ext.getBody()
     *     });
     *
     * Another useful configuration of TabPanel is {@link #tabPosition}. This allows you to change the
     * position where the tabs are displayed. The available options for this are `'top'` (default) and
     * `'bottom'`.
     *
     *     @example
     *     Ext.create('Ext.tab.Panel', {
     *         width: 300,
     *         height: 200,
     *         activeTab: 0,
     *         bodyPadding: 10,
     *         tabPosition: 'bottom',
     *         items: [
     *             {
     *                 title: 'Tab 1',
     *                 html : 'A simple tab'
     *             },
     *             {
     *                 title: 'Tab 2',
     *                 html : 'Another one'
     *             }
     *         ],
     *         renderTo : Ext.getBody()
     *     });
     *
     * The {@link #setActiveTab} is a very useful method in TabPanel which will allow you to change the
     * current active tab. You can either give it an index or an instance of a tab. For example:
     *
     *     @example
     *     var tabs = Ext.create('Ext.tab.Panel', {
     *         items: [
     *             {
     *                 id   : 'my-tab',
     *                 title: 'Tab 1',
     *                 html : 'A simple tab'
     *             },
     *             {
     *                 title: 'Tab 2',
     *                 html : 'Another one'
     *             }
     *         ],
     *         renderTo : Ext.getBody()
     *     });
     *
     *     var tab = Ext.getCmp('my-tab');
     *
     *     Ext.create('Ext.button.Button', {
     *         renderTo: Ext.getBody(),
     *         text    : 'Select the first tab',
     *         scope   : this,
     *         handler : function() {
     *             tabs.setActiveTab(tab);
     *         }
     *     });
     *
     *     Ext.create('Ext.button.Button', {
     *         text    : 'Select the second tab',
     *         scope   : this,
     *         handler : function() {
     *             tabs.setActiveTab(1);
     *         },
     *         renderTo : Ext.getBody()
     *     });
     *
     * The {@link #getActiveTab} is a another useful method in TabPanel which will return the current active tab.
     *
     *     @example
     *     var tabs = Ext.create('Ext.tab.Panel', {
     *         items: [
     *             {
     *                 title: 'Tab 1',
     *                 html : 'A simple tab'
     *             },
     *             {
     *                 title: 'Tab 2',
     *                 html : 'Another one'
     *             }
     *         ],
     *         renderTo : Ext.getBody()
     *     });
     *
     *     Ext.create('Ext.button.Button', {
     *         text    : 'Get active tab',
     *         scope   : this,
     *         handler : function() {
     *             var tab = tabs.getActiveTab();
     *             alert('Current tab: ' + tab.title);
     *         },
     *         renderTo : Ext.getBody()
     *     });
     *
     * Adding a new tab is very simple with a TabPanel. You simple call the {@link #method-add} method with an config
     * object for a panel.
     *
     *     @example
     *     var tabs = Ext.create('Ext.tab.Panel', {
     *         items: [
     *             {
     *                 title: 'Tab 1',
     *                 html : 'A simple tab'
     *             },
     *             {
     *                 title: 'Tab 2',
     *                 html : 'Another one'
     *             }
     *         ],
     *         renderTo : Ext.getBody()
     *     });
     *
     *     Ext.create('Ext.button.Button', {
     *         text    : 'New tab',
     *         scope   : this,
     *         handler : function() {
     *             var tab = tabs.add({
     *                 // we use the tabs.items property to get the length of current items/tabs
     *                 title: 'Tab ' + (tabs.items.length + 1),
     *                 html : 'Another one'
     *             });
     *
     *             tabs.setActiveTab(tab);
     *         },
     *         renderTo : Ext.getBody()
     *     });
     *
     * Additionally, removing a tab is very also simple with a TabPanel. You simple call the {@link #method-remove} method
     * with an config object for a panel.
     *
     *     @example
     *     var tabs = Ext.create('Ext.tab.Panel', {
     *         items: [
     *             {
     *                 title: 'Tab 1',
     *                 html : 'A simple tab'
     *             },
     *             {
     *                 id   : 'remove-this-tab',
     *                 title: 'Tab 2',
     *                 html : 'Another one'
     *             }
     *         ],
     *         renderTo : Ext.getBody()
     *     });
     *
     *     Ext.create('Ext.button.Button', {
     *         text    : 'Remove tab',
     *         scope   : this,
     *         handler : function() {
     *             var tab = Ext.getCmp('remove-this-tab');
     *             tabs.remove(tab);
     *         },
     *         renderTo : Ext.getBody()
     *     });
     */
    Ext.define('Ext.tab.Panel', {
        extend: 'Ext.panel.Panel',
        alias: 'widget.tabpanel',
        alternateClassName: ['Ext.TabPanel'],

        requires: ['Ext.layout.container.Card', 'Ext.tab.Bar'],

        /**
         * @cfg {String} tabPosition
         * The position where the tab strip should be rendered. Can be `top` or `bottom`.
         */
        tabPosition : 'top',

        /**
         * @cfg {String/Number} activeItem
         * Doesn't apply for {@link Ext.tab.Panel TabPanel}, use {@link #activeTab} instead.
         */

        /**
         * @cfg {String/Number/Ext.Component} activeTab
         * The tab to activate initially. Either an ID, index or the tab component itself.
         */

        /**
         * @cfg {Object} tabBar
         * Optional configuration object for the internal {@link Ext.tab.Bar}.
         * If present, this is passed straight through to the TabBar's constructor
         */

        /**
         * @cfg {Object} layout
         * Optional configuration object for the internal {@link Ext.layout.container.Card card layout}.
         * If present, this is passed straight through to the layout's constructor
         */

        /**
         * @cfg {Boolean} removePanelHeader
         * True to instruct each Panel added to the TabContainer to not render its header element.
         * This is to ensure that the title of the panel does not appear twice.
         */
        removePanelHeader: true,

        /**
         * @cfg {Boolean} plain
         * True to not show the full background on the TabBar.
         */
        plain: false,

        /**
         * @cfg {String} [itemCls='x-tabpanel-child']
         * The class added to each child item of this TabPanel.
         */
        itemCls: Ext.baseCSSPrefix + 'tabpanel-child',

        /**
         * @cfg {Number} minTabWidth
         * The minimum width for a tab in the {@link #cfg-tabBar}.
         */
        minTabWidth: undefined,

        /**
         * @cfg {Number} maxTabWidth The maximum width for each tab.
         */
        maxTabWidth: undefined,

        /**
         * @cfg {Boolean} deferredRender
         *
         * True by default to defer the rendering of child {@link Ext.container.Container#cfg-items items} to the browsers DOM
         * until a tab is activated. False will render all contained {@link Ext.container.Container#cfg-items items} as soon as
         * the {@link Ext.layout.container.Card 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.container.Card}) as its {@link Ext.layout.container.Card#deferredRender} configuration value.
         *
         * **Note**: leaving deferredRender as true means that the content within an unactivated tab will not be available
         */
        deferredRender : true,

        //inherit docs
        initComponent: function() {
            var me = this,
                dockedItems = [].concat(me.dockedItems || []),
                activeTab = me.activeTab || (me.activeTab = 0);

            // Configure the layout with our deferredRender, and with our activeTeb
            me.layout = new Ext.layout.container.Card(Ext.apply({
                owner: me,
                deferredRender: me.deferredRender,
                itemCls: me.itemCls,
                activeItem: me.activeTab
            }, me.layout));

            /**
             * @property {Ext.tab.Bar} tabBar Internal reference to the docked TabBar
             */
            me.tabBar = new Ext.tab.Bar(Ext.apply({
                dock: me.tabPosition,
                plain: me.plain,
                border: me.border,
                cardLayout: me.layout,
                tabPanel: me
            }, me.tabBar));

            dockedItems.push(me.tabBar);
            me.dockedItems = dockedItems;

            me.addEvents(
                /**
                 * @event
                 * Fires before a tab change (activated by {@link #setActiveTab}). Return false in any listener to cancel
                 * the tabchange
                 * @param {Ext.tab.Panel} tabPanel The TabPanel
                 * @param {Ext.Component} newCard The card that is about to be activated
                 * @param {Ext.Component} oldCard The card that is currently active
                 */
                'beforetabchange',

                /**
                 * @event
                 * Fires when a new tab has been activated (activated by {@link #setActiveTab}).
                 * @param {Ext.tab.Panel} tabPanel The TabPanel
                 * @param {Ext.Component} newCard The newly activated item
                 * @param {Ext.Component} oldCard The previously active item
                 */
                'tabchange'
            );

            me.callParent(arguments);

            // We have to convert the numeric index/string ID config into its component reference
            me.activeTab = me.getComponent(activeTab);

            // Ensure that the active child's tab is rendered in the active UI state
            if (me.activeTab) {
                me.activeTab.tab.activate(true);

                // So that it knows what to deactivate in subsequent tab changes
                me.tabBar.activeTab = me.activeTab.tab;
            }
        },

        /**
         * Makes the given card active. Makes it the visible card in the TabPanel's CardLayout and highlights the Tab.
         * @param {String/Number/Ext.Component} card The card to make active. Either an ID, index or the component itself.
         * @return {Ext.Component} The resulting active child Component. The call may have been vetoed, or otherwise
         * modified by an event listener.
         */
        setActiveTab: function(card) {
            var me = this,
                previous;

            card = me.getComponent(card);
            if (card) {
                previous = me.getActiveTab();

                if (previous !== card && me.fireEvent('beforetabchange', me, card, previous) === false) {
                    return false;
                }

                // We may be passed a config object, so add it.
                // Without doing a layout!
                if (!card.isComponent) {
                    Ext.suspendLayouts();
                    card = me.add(card);
                    Ext.resumeLayouts();
                }

                // MUST set the activeTab first so that the machinery which listens for show doesn't
                // think that the show is "driving" the activation and attempt to recurse into here.
                me.activeTab = card;

                // Attempt to switch to the requested card. Suspend layouts because if that was successful
                // we have to also update the active tab in the tab bar which is another layout operation
                // and we must coalesce them.
                Ext.suspendLayouts();
                me.layout.setActiveItem(card);

                // Read the result of the card layout. Events dear boy, events!
                card = me.activeTab = me.layout.getActiveItem();

                // Card switch was not vetoed by an event listener
                if (card && card !== previous) {

                    // Update the active tab in the tab bar and resume layouts.
                    me.tabBar.setActiveTab(card.tab);
                    Ext.resumeLayouts(true);

                    // previous will be undefined or this.activeTab at instantiation
                    if (previous !== card) {
                        me.fireEvent('tabchange', me, card, previous);
                    }
                }
                // Card switch was vetoed by an event listener. Resume layouts (Nothing should have changed on a veto).
                else {
                    Ext.resumeLayouts(true);
                }
                return card;
            }
        },

        /**
         * Returns the item that is currently active inside this TabPanel.
         * @return {Ext.Component} The currently active item.
         */
        getActiveTab: function() {
            var me = this,
                // Ensure the calculated result references a Component
                result = me.getComponent(me.activeTab);

            // Sanitize the result in case the active tab is no longer there.
            if (result && me.items.indexOf(result) != -1) {
                me.activeTab = result;
            } else {
                me.activeTab = null;
            }

            return me.activeTab;
        },

        /**
         * Returns the {@link Ext.tab.Bar} currently used in this TabPanel
         * @return {Ext.tab.Bar} The TabBar
         */
        getTabBar: function() {
            return this.tabBar;
        },

        /**
         * @protected
         * Makes sure we have a Tab for each item added to the TabPanel
         */
        onAdd: function(item, index) {
            var me = this,
                cfg = item.tabConfig || {},
                defaultConfig = {
                    xtype: 'tab',
                    card: item,
                    disabled: item.disabled,
                    closable: item.closable,
                    hidden: item.hidden && !item.hiddenByLayout, // only hide if it wasn't hidden by the layout itself
                    tooltip: item.tooltip,
                    tabBar: me.tabBar,
                    closeText: item.closeText
                };

            cfg = Ext.applyIf(cfg, defaultConfig);

            // Create the correspondiong tab in the tab bar
            item.tab = me.tabBar.insert(index, cfg);

            item.on({
                scope : me,
                enable: me.onItemEnable,
                disable: me.onItemDisable,
                beforeshow: me.onItemBeforeShow,
                iconchange: me.onItemIconChange,
                iconclschange: me.onItemIconClsChange,
                titlechange: me.onItemTitleChange
            });

            if (item.isPanel) {
                if (me.removePanelHeader) {
                    if (item.rendered) {
                        if (item.header) {
                            item.header.hide();
                        }
                    } else {
                        item.header = false;
                    }
                }
                if (item.isPanel && me.border) {
                    item.setBorder(false);
                }
            }
        },

        /**
         * @private
         * Enable corresponding tab when item is enabled.
         */
        onItemEnable: function(item){
            item.tab.enable();
        },

        /**
         * @private
         * Disable corresponding tab when item is enabled.
         */
        onItemDisable: function(item){
            item.tab.disable();
        },

        /**
         * @private
         * Sets activeTab before item is shown.
         */
        onItemBeforeShow: function(item) {
            if (item !== this.activeTab) {
                this.setActiveTab(item);
                return false;
            }
        },

        /**
         * @private
         * Update the tab icon when panel icon has been set or changed.
         */
        onItemIconChange: function(item, newIcon) {
            item.tab.setIcon(newIcon);
        },

        /**
         * @private
         * Update the tab iconCls when panel iconCls has been set or changed.
         */
        onItemIconClsChange: function(item, newIconCls) {
            item.tab.setIconCls(newIconCls);
        },

        /**
         * @private
         * Update the tab title when panel title has been set or changed.
         */
        onItemTitleChange: function(item, newTitle) {
            item.tab.setText(newTitle);
        },

        /**
         * @private
         * Unlink the removed child item from its (@link Ext.tab.Tab Tab}.
         *
         * If we're removing the currently active tab, activate the nearest one. The item is removed when we call super,
         * so we can do preprocessing before then to find the card's index
         */
        doRemove: function(item, autoDestroy) {
            var me = this,
                toActivate;

            // Destroying, or removing the last item, nothing to activate
            if (me.destroying || me.items.getCount() == 1) {
                me.activeTab = null;
            }

            // Ask the TabBar which tab to activate next.
            // Set the active child panel using the index of that tab
            else if ((toActivate = me.tabBar.items.indexOf(me.tabBar.findNextActivatable(item.tab))) !== -1) {
                 me.setActiveTab(toActivate);
            }
            this.callParent(arguments);

            // Remove the two references
            delete item.tab.card;
            delete item.tab;
        },

        /**
         * @private
         * Makes sure we remove the corresponding Tab when an item is removed
         */
        onRemove: function(item, destroying) {
            var me = this;

            item.un({
                scope : me,
                enable: me.onItemEnable,
                disable: me.onItemDisable,
                beforeshow: me.onItemBeforeShow
            });
            if (!me.destroying && item.tab.ownerCt === me.tabBar) {
                me.tabBar.remove(item.tab);
            }
        }
    });