property currentBox

This property returns the current box who is trying to react to the event. After an event is generated, the event is bubbled it from the targetBox to its ancestors. Each ancestor will have a chance to react to the event.

<hbox id="box1" on:focus="onFocus();"/>
    <button/>
</hbox>

// when the button gets focus
function onFocus()
{
    var eventObj = shell.getCurrentEvent();
    if (eventObj && eventObj.currentBox && eventObj.currentBox.id=="box1")
    {
        shell.print("the event has propagated to box 1");
    }
}