ExtJS 4 Editable Tree Panel

/*global Ext:false */
Ext.onReady(function() {
    var store = Ext.create('Ext.data.TreeStore', {
        root: {
            expanded: true,
            children: [{
                text: "detention",
                leaf: true
            }, {
                text: "homework",
                expanded: true,
                children: [{
                    text: "book report",
                    leaf: true
                }, {
                    text: "alegrbra",
                    leaf: true
                }]
            }, {
                text: "buy lottery tickets",
                leaf: true
            }]
        }
    });



    Ext.define('TreeCellEditing', {
        alias: 'plugin.treecellediting',
        extend: 'Ext.grid.plugin.CellEditing',
        init: function(tree) {
            var tree_column = tree.headerCt.down('treecolumn');
            tree_column.editor = tree_column.editor ||
                                 { xtype: 'textfield' };
            this.callParent(arguments);
        },

        getEditingContext: function(record, columnHeader) {
            var me = this,
            grid = me.grid,
            store = grid.store,
            rowIdx,
            colIdx,
            view = grid.getView(),
            root = grid.getRootNode(),
            value;

            if (Ext.isNumber(record)) {
                rowIdx = record;
                record = root.getChildAt(rowIdx);
            } else {
                rowIdx = root.indexOf(record);
            }

            if (Ext.isNumber(columnHeader)) {
                colIdx = columnHeader;
                columnHeader = grid.headerCt.getHeaderAtIndex(colIdx);
            } else {
                colIdx = columnHeader.getIndex();
            }

            value = record.get(columnHeader.dataIndex);

            return {
                grid: grid,
                record: record,
                field: columnHeader.dataIndex,
                value: value,
                row: view.getNode(rowIdx),
                column: columnHeader,
                rowIdx: rowIdx,
                colIdx: colIdx
            };
        }
    });

    var tree_editor = Ext.create('TreeCellEditing', {clicksToEdit: 2});

    var tree = Ext.create('Ext.tree.Panel', {
        title: 'Simple Tree',
        width: 200,
        height: 150,
        store: store,
        rootVisible: false,
        renderTo: Ext.getBody(),
        plugins: [
            tree_editor
        ]
    });
});