    /**
     * @class Ext.grid.header.DragZone
     * @extends Ext.dd.DragZone
     * @private
     */
    Ext.define('Ext.grid.header.DragZone', {
        extend: 'Ext.dd.DragZone',
        colHeaderCls: Ext.baseCSSPrefix + 'column-header',
        maxProxyWidth: 120,

        constructor: function(headerCt) {
            this.headerCt = headerCt;
            this.ddGroup =  this.getDDGroup();
            this.callParent([headerCt.el]);
            this.proxy.el.addCls(Ext.baseCSSPrefix + 'grid-col-dd');
        },

        getDDGroup: function() {
            return 'header-dd-zone-' + this.headerCt.up('[scrollerOwner]').id;
        },

        getDragData: function(e) {
            var header = e.getTarget('.'+this.colHeaderCls),
                headerCmp;

            if (header) {
                headerCmp = Ext.getCmp(header.id);
                if (!this.headerCt.dragging && headerCmp.draggable && !(headerCmp.isOnLeftEdge(e) || headerCmp.isOnRightEdge(e))) {
                    var ddel = document.createElement('div');
                    ddel.innerHTML = Ext.getCmp(header.id).text;
                    return {
                        ddel: ddel,
                        header: headerCmp
                    };
                }
            }
            return false;
        },

        onBeforeDrag: function() {
            return !(this.headerCt.dragging || this.disabled);
        },

        onInitDrag: function() {
            this.headerCt.dragging = true;
            this.callParent(arguments);
        },

        onDragDrop: function() {
            this.headerCt.dragging = false;
            this.callParent(arguments);
        },

        afterRepair: function() {
            this.callParent();
            this.headerCt.dragging = false;
        },

        getRepairXY: function() {
            return this.dragData.header.el.getXY();
        },

        disable: function() {
            this.disabled = true;
        },

        enable: function() {
            this.disabled = false;
        }
    });