def showPopup(self):
        """
        Overloads the popup method from QComboBox to display an ORB tree widget
        when necessary.
        
        :sa     setShowTreePopup
        """
        if not self.showTreePopup():
            return super(XOrbRecordBox, self).showPopup()
        
        tree = self.treePopupWidget()
        
        if tree and not tree.isVisible():
            tree.move(self.mapToGlobal(QPoint(0, self.height())))
            tree.resize(self.width(), 250)
            tree.resizeToContents()
            tree.filterItems('')
            tree.setFilteredColumns(range(tree.columnCount()))
            tree.show()