Called when "add new" combo is changed
        The parameter MUST have an 'addNew' method defined.

def addChanged(self):
        """Called when "add new" combo is changed
        The parameter MUST have an 'addNew' method defined.
        """
        if self.addWidget.currentIndex() == 0:
            return
        typ = asUnicode(self.addWidget.currentText())
        self.param.addNew(typ)
        self.addWidget.setCurrentIndex(0)