Displays the help event for the given index.
        
        :param      event  | <QHelpEvent>
                    view   | <QAbstractItemView>
                    option | <QStyleOptionViewItem>
                    index  | <QModelIndex>
        
        :return     <bool>

def viewportEvent( self, event ):
        """
        Displays the help event for the given index.
        
        :param      event  | <QHelpEvent>
                    view   | <QAbstractItemView>
                    option | <QStyleOptionViewItem>
                    index  | <QModelIndex>
        
        :return     <bool>
        """
        # intercept tooltips to use the XPopupWidget when desired
        if event.type() == event.ToolTip and self.usePopupToolTip():
            index = self.indexAt(event.pos())
            item  = self.itemAt(event.pos())
            
            if not (index and item):
                event.ignore()
                return False
            
            tip   = item.toolTip(index.column())
            rect  = self.visualRect(index)
            point = QtCore.QPoint(rect.left() + 5, rect.bottom() + 1)
            point = self.viewport().mapToGlobal(point)
            
            if tip:
                XPopupWidget.showToolTip(tip, 
                                         anchor = XPopupWidget.Anchor.TopLeft,
                                         point  = point,
                                         parent = self)
            
            event.accept()
            return True
        else:
            return super(XTreeWidget, self).viewportEvent(event)