Extjs gridPanel column 每一行的內容自動擴充換行

var temp=Ext.create('Ext.grid.Panel', {
                            title: title.substring(0,10),
                            iconCls: 'icon-grid-list',
                            id:id,
                            forceFit: true,
                            region : 'center',
                            store: repStore,
                            columnLines:true,
                            closable:true,
                            columns: [{dataIndex:'usernam',text:'姓名',align:'center'},{dataIndex:'itemtypename',text:'類型',align:'center'},
                                      {dataIndex:'itemcontent',text:'內容',width:500,renderer: function(value, meta, record) {
                                          meta.style = 'overflow:auto;padding: 3px 6px;text-overflow: ellipsis;white-space: nowrap;white-space:normal;line-height:20px;';   
                                          return value;   
                                     }},{dataIndex:'itemstaname',text:'狀態',align:'center'}]
                        });