RowEditing with Combobox - changes (click row editing) - should be displayed "displayField"

Question

RowEditing with Combobox - changes (click row editing) shown "id", should be displayed "displayField"

pic - i65.fastpic.ru/big/2014/0724/46/d7cef656f6d993bc17657486ba5b6b46.gif

when editing a row - to display the value of the field displayfield from storeServer now displays dataindex from store

Ext.define('ModelLib', {
        extend: 'Ext.data.Model',
        fields: [
            'trID',
            'trName'
        ]
    });
    var storeServer = Ext.create('Ext.data.Store', {
        autoDestroy: true,
        model: 'ModelLib',
        proxy: {
            type: 'ajax',
            api: {
                read: '/api.php?lib=server&act=get'
            },
            reader: {
                type: 'json',
                root: 'fields',
                idProperty: "trID"
            }
        },
        sorters: [{
            property: 'trID',
            direction: 'ASC'
        }]
    });
    storeServer.load();

    Ext.define('ModelMainobjects', {
        extend: 'Ext.data.Model',
        fields: [
            {name: 'trServerID',   type: 'int'}
        ]
    });

    var store = Ext.create('Ext.data.Store', {
        // destroy the store if the grid is destroyed
        autoDestroy: true,
        autoSync : true,
        model: 'ModelMainobjects',
        proxy: {
            type: 'ajax',
            api: {
                read: '/api.php?lib=mainobjects&act=get',
                update: '/api.php?lib=mainobjects&act=update'
            },
            reader: {
                type: 'json',
                root: 'fields',
                idProperty: "trID"
            },
            writer: {
                type: 'json'
            }
        },
        sorters: [{
            property: 'trID',
            direction: 'ASC'
        }]
    });

    store.load();

    var rowEditing = Ext.create('Ext.grid.plugin.RowEditing', {
        clicksToMoveEditor: 1,
        autoCancel: false
    });

    var rowRenderer = function(val) {
        var rec = storeServer.findRecord('id', val);
        return rec !== null ? rec.get("trName") : ''
    };


    var grid = Ext.create('Ext.grid.Panel', {
        store: store,
        columns: [
        {
            header: 'Сервер',
            dataIndex: 'trServerID',
            renderer: rowRenderer,
            editor: {
                xtype: 'combobox',
                store: storeServer,
                queryMode: 'local',
                displayField: 'trName',
                valueField: 'trID'
            }
        }],
        width: 600,
        height: 400,
        plugins: [rowEditing]
    });