How to highlight Dateitem with mask

[OPY]

Hi,

I am not able to highlight/select value of the Dateitem with mask.
Test code:

DateItem() dat=new DateItem();
dat.setEnforceDate(true);
dat.setPickerIconPrompt(null);
dat.setUseTextField(true);
dat.setTextAlign(Alignment.LEFT);
dat.setUseMask(true);

IButton btn = new IButton();
btn.addClickHandler(new ClickHandler(){
@Override
public void onClick(ClickEvent event) {
dat.selectValue();
}
});

With above coding, when click the "btn" button, the cursor will stop at the last value of the date item.

How can I get it to highlight the whole value?

Thank you very much for your help.

SmartGWT: v5.0p_2016-03-19/EnterpriseEdition
Browser: Safari Version 9.0.2, Chrome 50.0.2661.102 m