    /**
     * Provides indentation and folder structure markup for a Tree taking into account
     * depth and position within the tree hierarchy.
     *
     * @private
     */
    Ext.define('Ext.tree.Column', {
        extend: 'Ext.grid.column.Column',
        alias: 'widget.treecolumn',

        tdCls: Ext.baseCSSPrefix + 'grid-cell-treecolumn',

        autoLock: true,
        lockable: false,
        draggable: false,
        hideable: false,

        iconCls: Ext.baseCSSPrefix + 'tree-icon',
        checkboxCls: Ext.baseCSSPrefix + 'tree-checkbox',
        elbowCls: Ext.baseCSSPrefix + 'tree-elbow',
        expanderCls: Ext.baseCSSPrefix + 'tree-expander',
        textCls: Ext.baseCSSPrefix + 'tree-node-text',
        innerCls: Ext.baseCSSPrefix + 'grid-cell-inner-treecolumn',
        isTreeColumn: true,

        cellTpl: [
            '<tpl for="lines">',
                '<img src="{parent.blankUrl}" class="{parent.childCls} {parent.elbowCls}-img ',
                '{parent.elbowCls}-<tpl if=".">line<tpl else>empty</tpl>"/>',
            '</tpl>',
            '<img src="{blankUrl}" class="{childCls} {elbowCls}-img {elbowCls}',
                '<tpl if="isLast">-end</tpl><tpl if="expandable">-plus {expanderCls}</tpl>"/>',
            '<tpl if="checked !== null">',
                '<input type="button" role="checkbox" <tpl if="checked">aria-checked="true" </tpl>',
                    'class="{childCls} {checkboxCls}<tpl if="checked"> {checkboxCls}-checked</tpl>"/>',
            '</tpl>',
            '<img src="{blankUrl}" class="{childCls} {baseIconCls} ',
                '{baseIconCls}-<tpl if="leaf">leaf<tpl else>parent</tpl> {iconCls}"',
                '<tpl if="icon">style="background-image:url({icon})"</tpl>/>',
            '<tpl if="href">',
                '<a href="{href}" target="{hrefTarget}" class="{textCls} {childCls}">{value}</a>',
            '<tpl else>',
                '<span class="{textCls} {childCls}">{value}</span>',
            '</tpl>'
        ],

        initComponent: function() {
            var me = this;

            me.origRenderer = me.renderer;
            me.origScope = me.scope || window;

            me.renderer = me.treeRenderer;
            me.scope = me;

            me.callParent();
        },

        treeRenderer: function(value, metaData, record, rowIdx, colIdx, store, view){
            var me = this,
                cls = record.get('cls'),
                renderer = me.origRenderer,
                data = record.data,
                parent = record.parentNode,
                rootVisible = view.rootVisible,
                lines = [],
                parentData;

            if (cls) {
                metaData.tdCls += ' ' + cls;
            }

            while (parent && (rootVisible || parent.data.depth > 0)) {
                parentData = parent.data;
                lines[rootVisible ? parentData.depth : parentData.depth - 1] =
                        parentData.isLast ? 0 : 1;
                parent = parent.parentNode;
            }

            return me.getTpl('cellTpl').apply({
                record: record,
                baseIconCls: me.iconCls,
                iconCls: data.iconCls,
                icon: data.icon,
                checkboxCls: me.checkboxCls,
                checked: data.checked,
                elbowCls: me.elbowCls,
                expanderCls: me.expanderCls,
                textCls: me.textCls,
                leaf: data.leaf,
                expandable: record.isExpandable(),
                isLast: data.isLast,
                blankUrl: Ext.BLANK_IMAGE_URL,
                href: data.href,
                hrefTarget: data.hrefTarget,
                lines: lines,
                metaData: metaData,
                // subclasses or overrides can implement a getChildCls() method, which can
                // return an extra class to add to all of the cell's child elements (icon,
                // expander, elbow, checkbox).  This is used by the rtl override to add the
                // "x-rtl" class to these elements.
                childCls: me.getChildCls ? me.getChildCls() + ' ' : '',
                value: renderer ? renderer.apply(me.origScope, arguments) : value
            });
        }
    });