    /**
     * This class provides a container DD instance that allows dragging of multiple child source nodes.
     *
     * This class does not move the drag target nodes, but a proxy element which may contain any DOM structure you wish. The
     * DOM element to show in the proxy is provided by either a provided implementation of {@link #getDragData}, or by
     * registered draggables registered with {@link Ext.dd.Registry}
     *
     * If you wish to provide draggability for an arbitrary number of DOM nodes, each of which represent some application
     * object (For example nodes in a {@link Ext.view.View DataView}) then use of this class is the most efficient way to
     * "activate" those nodes.
     *
     * By default, this class requires that draggable child nodes are registered with {@link Ext.dd.Registry}. However a
     * simpler way to allow a DragZone to manage any number of draggable elements is to configure the DragZone with an
     * implementation of the {@link #getDragData} method which interrogates the passed mouse event to see if it has taken
     * place within an element, or class of elements. This is easily done by using the event's {@link
     * Ext.EventObject#getTarget getTarget} method to identify a node based on a {@link Ext.DomQuery} selector. For example,
     * to make the nodes of a DataView draggable, use the following technique. Knowledge of the use of the DataView is
     * required:
     *
     *     myDataView.on('render', function(v) {
     *         myDataView.dragZone = new Ext.dd.DragZone(v.getEl(), {
     *
     *     //      On receipt of a mousedown event, see if it is within a DataView node.
     *     //      Return a drag data object if so.
     *             getDragData: function(e) {
     *
     *     //          Use the DataView's own itemSelector (a mandatory property) to
     *     //          test if the mousedown is within one of the DataView's nodes.
     *                 var sourceEl = e.getTarget(v.itemSelector, 10);
     *
     *     //          If the mousedown is within a DataView node, clone the node to produce
     *     //          a ddel element for use by the drag proxy. Also add application data
     *     //          to the returned data object.
     *                 if (sourceEl) {
     *                     d = sourceEl.cloneNode(true);
     *                     d.id = Ext.id();
     *                     return {
     *                         ddel: d,
     *                         sourceEl: sourceEl,
     *                         repairXY: Ext.fly(sourceEl).getXY(),
     *                         sourceStore: v.store,
     *                         draggedRecord: v.{@link Ext.view.View#getRecord getRecord}(sourceEl)
     *                     }
     *                 }
     *             },
     *
     *     //      Provide coordinates for the proxy to slide back to on failed drag.
     *     //      This is the original XY coordinates of the draggable element captured
     *     //      in the getDragData method.
     *             getRepairXY: function() {
     *                 return this.dragData.repairXY;
     *             }
     *         });
     *     });
     *
     * See the {@link Ext.dd.DropZone DropZone} documentation for details about building a DropZone which cooperates with
     * this DragZone.
     */
    Ext.define('Ext.dd.DragZone', {
        extend: 'Ext.dd.DragSource',

        /**
         * Creates new DragZone.
         * @param {String/HTMLElement/Ext.Element} el The container element or ID of it.
         * @param {Object} config
         */
        constructor : function(el, config){
            var me = this,
                scroll = me.containerScroll;

            me.callParent([el, config]);
            if (scroll) {
                el = me.scrollEl || el;
                el = Ext.get(el);
                if (Ext.isObject(scroll)) {
                    el.ddScrollConfig = scroll;
                }
                Ext.dd.ScrollManager.register(el);
            }
        },

        /**
         * @property {Object} dragData
         * This property contains the data representing the dragged object. This data is set up by the implementation of the
         * {@link #getDragData} method. It must contain a ddel property, but can contain any other data according to the
         * application's needs.
         */

        /**
         * @cfg {Object/Boolean} containerScroll
         * True to register this container with the Scrollmanager for auto scrolling during drag operations.
         * A {@link Ext.dd.ScrollManager} configuration may also be passed.
         */

        /**
         * @cfg {String/HTMLElement/Ext.dom.Element} scrollEl
         * An element to register with the ScrollManager if {@link #containerScroll}
         * is set. Defaults to the drag element.
         */

        /**
         * Called when a mousedown occurs in this container. Looks in {@link Ext.dd.Registry} for a valid target to drag
         * based on the mouse down. Override this method to provide your own lookup logic (e.g. finding a child by class
         * name). Make sure your returned object has a "ddel" attribute (with an HTML Element) for other functions to work.
         * @param {Event} e The mouse down event
         * @return {Object} The dragData
         */
        getDragData : function(e){
            return Ext.dd.Registry.getHandleFromEvent(e);
        },

        /**
         * Called once drag threshold has been reached to initialize the proxy element. By default, it clones the
         * this.dragData.ddel
         * @param {Number} x The x position of the click on the dragged object
         * @param {Number} y The y position of the click on the dragged object
         * @return {Boolean} true to continue the drag, false to cancel
         * @template
         */
        onInitDrag : function(x, y){
            this.proxy.update(this.dragData.ddel.cloneNode(true));
            this.onStartDrag(x, y);
            return true;
        },

        /**
         * Called before a repair of an invalid drop to get the XY to animate to. By default returns the XY of
         * this.dragData.ddel
         * @param {Event} e The mouse up event
         * @return {Number[]} The xy location (e.g. `[100, 200]`)
         * @template
         */
        getRepairXY : function(e){
            return Ext.fly(this.dragData.ddel).getXY();
        },

        destroy : function(){
            this.callParent();
            if (this.containerScroll) {
                Ext.dd.ScrollManager.unregister(this.scrollEl || this.el);
            }
        }
    });