    /**
     * @class Ext.tree.Column
     * @extends Ext.grid.column.Column
     *
     * 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',

        initComponent: function() {
            var origRenderer = this.renderer || this.defaultRenderer,
                origScope    = this.scope || window;

            this.renderer = function(value, metaData, record, rowIdx, colIdx, store, view) {
                var buf   = [],
                    format = Ext.String.format,
                    depth = record.getDepth(),
                    treePrefix  = Ext.baseCSSPrefix + 'tree-',
                    elbowPrefix = treePrefix + 'elbow-',
                    expanderCls = treePrefix + 'expander',
                    imgText     = '<img src="{1}" class="{0}" />',
                    checkboxText= '<input type="button" role="checkbox" class="{0}" {1} />',
                    formattedValue = origRenderer.apply(origScope, arguments),
                    href = record.get('href'),
                    target = record.get('hrefTarget'),
                    cls = record.get('cls');

                while (record) {
                    if (!record.isRoot() || (record.isRoot() && view.rootVisible)) {
                        if (record.getDepth() === depth) {
                            buf.unshift(format(imgText,
                                treePrefix + 'icon ' +
                                treePrefix + 'icon' + (record.get('icon') ? '-inline ' : (record.isLeaf() ? '-leaf ' : '-parent ')) +
                                (record.get('iconCls') || ''),
                                record.get('icon') || Ext.BLANK_IMAGE_URL
                            ));
                            if (record.get('checked') !== null) {
                                buf.unshift(format(
                                    checkboxText,
                                    (treePrefix + 'checkbox') + (record.get('checked') ? ' ' + treePrefix + 'checkbox-checked' : ''),
                                    record.get('checked') ? 'aria-checked="true"' : ''
                                ));
                                if (record.get('checked')) {
                                    metaData.tdCls += (' ' + Ext.baseCSSPrefix + 'tree-checked');
                                }
                            }
                            if (record.isLast()) {
                                if (record.isExpandable()) {
                                    buf.unshift(format(imgText, (elbowPrefix + 'end-plus ' + expanderCls), Ext.BLANK_IMAGE_URL));
                                } else {
                                    buf.unshift(format(imgText, (elbowPrefix + 'end'), Ext.BLANK_IMAGE_URL));
                                }

                            } else {
                                if (record.isExpandable()) {
                                    buf.unshift(format(imgText, (elbowPrefix + 'plus ' + expanderCls), Ext.BLANK_IMAGE_URL));
                                } else {
                                    buf.unshift(format(imgText, (treePrefix + 'elbow'), Ext.BLANK_IMAGE_URL));
                                }
                            }
                        } else {
                            if (record.isLast() || record.getDepth() === 0) {
                                buf.unshift(format(imgText, (elbowPrefix + 'empty'), Ext.BLANK_IMAGE_URL));
                            } else if (record.getDepth() !== 0) {
                                buf.unshift(format(imgText, (elbowPrefix + 'line'), Ext.BLANK_IMAGE_URL));
                            }
                        }
                    }
                    record = record.parentNode;
                }
                if (href) {
                    formattedValue = format('<a href="{0}" target="{1}">{2}</a>', href, target, formattedValue);
                }
                if (cls) {
                    metaData.tdCls += ' ' + cls;
                }
                return buf.join("") + formattedValue;
            };
            this.callParent(arguments);
        },

        defaultRenderer: function(value) {
            return value;
        }
    });