updateUI(new RequestHandler() {
@Override
public void onRequest() {
final PHorizontalPanel horizontal1 = new PHorizontalPanel();
horizontal1.ensureDebugId("horizontal1");
horizontal1.add(new PLabel("cell1"));
horizontal1.add(new PLabel("cell2"));
horizontal1.add(new PLabel("cell3"));
horizontal1.add(new PLabel("cell4"));
horizontal1.setBorderWidth(2);