The source code

    /**
     * @class Ext.dd.DragZone
     * @extends Ext.dd.DragSource
     * <p>This class provides a container DD instance that allows dragging of multiple child source nodes.</p>
     * <p>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}</p>
     * <p>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.DataView DataView}) then use of this class
     * is the most efficient way to "activate" those nodes.</p>
     * <p>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:</p><pre><code>
    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.DataView#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;
            }
        });
    });</code></pre>
     * See the {@link Ext.dd.DropZone DropZone} documentation for details about building a DropZone which
     * cooperates with this DragZone.
     * @constructor
     * @param {Mixed} el The container element
     * @param {Object} config
     */
    Ext.dd.DragZone = Ext.extend(Ext.dd.DragSource, {

        constructor : function(el, config){
            Ext.dd.DragZone.superclass.constructor.call(this, el, config);
            if(this.containerScroll){
                Ext.dd.ScrollManager.register(this.el);
            }
        },

        /**
         * 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 <tt>ddel</tt> property, but can contain
         * any other data according to the application's needs.
         * @type Object
         * @property dragData
         */
        /**
         * @cfg {Boolean} containerScroll True to register this container with the Scrollmanager
         * for auto scrolling during drag operations.
         */
        /**
         * @cfg {String} hlColor The color to use when visually highlighting the drag source in the afterRepair
         * method after a failed drop (defaults to "c3daf9" - light blue)
         */

        /**
         * 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 {EventObject} 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
         */
        onInitDrag : function(x, y){
            this.proxy.update(this.dragData.ddel.cloneNode(true));
            this.onStartDrag(x, y);
            return true;
        },

        /**
         * Called after a repair of an invalid drop. By default, highlights this.dragData.ddel
         */
        afterRepair : function(){
            if(Ext.enableFx){
                Ext.Element.fly(this.dragData.ddel).highlight(this.hlColor || "c3daf9");
            }
            this.dragging = false;
        },

        /**
         * 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 {EventObject} e The mouse up event
         * @return {Array} The xy location (e.g. [100, 200])
         */
        getRepairXY : function(e){
            return Ext.Element.fly(this.dragData.ddel).getXY();
        },

        destroy : function(){
            Ext.dd.DragZone.superclass.destroy.call(this);
            if(this.containerScroll){
                Ext.dd.ScrollManager.unregister(this.el);
            }
        }
    });