GXT 4 datepicker zindex workaround

WindowWithDateFieldIssue.java

import java.util.Date;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.dom.client.Style.BorderStyle;
import com.google.gwt.user.client.ui.HTML;
import com.google.gwt.user.client.ui.RootPanel;
import com.sencha.gxt.cell.core.client.form.DateCell;
import com.sencha.gxt.core.client.dom.XElement;
import com.sencha.gxt.core.client.util.Margins;
import com.sencha.gxt.widget.core.client.Window;
import com.sencha.gxt.widget.core.client.button.TextButton;
import com.sencha.gxt.widget.core.client.container.HBoxLayoutContainer;
import com.sencha.gxt.widget.core.client.container.HBoxLayoutContainer.HBoxLayoutAlign;
import com.sencha.gxt.widget.core.client.container.MarginData;
import com.sencha.gxt.widget.core.client.container.VerticalLayoutContainer;
import com.sencha.gxt.widget.core.client.container.VerticalLayoutContainer.VerticalLayoutData;
import com.sencha.gxt.widget.core.client.event.SelectEvent;
import com.sencha.gxt.widget.core.client.event.SelectEvent.SelectHandler;
import com.sencha.gxt.widget.core.client.form.DateField;
import com.sencha.gxt.widget.core.client.form.FieldLabel;
import com.sencha.gxt.widget.core.client.form.FieldSet;
import com.sencha.gxt.widget.core.client.form.StringComboBox;
import com.sencha.gxt.widget.core.client.form.TextField;

public class WindowWithDateFieldIssue implements EntryPoint {

  @Override
  public void onModuleLoad() {
    
    String label1 = "field 1";
    String label2 = "field 2";
    
    TextField textField1 = new TextField();
    TextField textField2 = new TextField();
    
    StringComboBox combo = new StringComboBox();
    combo.add("a");
    combo.add("b");
    combo.add("c");
    
    FieldLabel fl1 = new FieldLabel(textField1, label1);
    //FieldLabel fl2 = new FieldLabel(textField2, label2);
    
    HBoxLayoutContainer hlc1 = new HBoxLayoutContainer(HBoxLayoutAlign.MIDDLE);
    hlc1.add(fl1);
    hlc1.add(combo);
    
    DateCell dateCell = new DateCell() {
      @Override
      protected void showDatepicker(Context context, XElement parent) {
        super.showDatepicker(context, parent);
        
        // ~~~ workaround - debugging
        menu.getDatePicker().getElement().getStyle().setProperty("border", "1px solid red");
        // ~~~ workaround
        menu.getDatePicker().getElement().getStyle().setProperty("zIndex", "1234");
      }
    };
    
    
    Date date = new Date();
    date.setMonth(3);
    
    DateField dateField = new DateField(dateCell);
    dateField.setValue(date);

    
    
    HBoxLayoutContainer hlc2 = new HBoxLayoutContainer(HBoxLayoutAlign.MIDDLE);
    hlc2.add(combo);
    hlc2.add(new HTML("|"));
    hlc2.add(dateField);
    
    FieldSet fs1 = new FieldSet();
    fs1.setHeading("Group1");
    fs1.add(hlc1);
    
    FieldSet fs2 = new FieldSet();
    fs2.setHeading("Group2");
    fs2.add(hlc2);
    
    VerticalLayoutContainer bodyVlc = new VerticalLayoutContainer();
    bodyVlc.add(fs1, new VerticalLayoutData(1, -1));
    bodyVlc.add(fs2, new VerticalLayoutData(1, -1, new Margins(10, 0, 0, 0)));
    
    final Window window = new Window();
    window.getElement().getStyle().setBorderStyle(BorderStyle.NONE);
    window.setModal(true);
    window.add(bodyVlc, new MarginData(20));
    window.addButton(new TextButton("OK"));
    //window.autoSize();
    
    TextButton button = new TextButton("Open");
    button.addSelectHandler(new SelectHandler() {
      @Override
      public void onSelect(SelectEvent event) {
        window.show();
      }
    });

    RootPanel.get().add(button);
  }
  

}