def on_display_n_changed(self, combo):
        """Set the destination display in dconf.
        """

        i = combo.get_active_iter()
        if not i:
            return

        model = combo.get_model()
        first_item_path = model.get_path(model.get_iter_first())

        if model.get_path(i) == first_item_path:
            val_int = ALWAYS_ON_PRIMARY
        else:
            val = model.get_value(i, 0)
            val_int = int(val.split()[0])  # extracts 1 from '1' or from '1 (primary)'
        self.settings.general.set_int('display-n', val_int)
Set the destination display in dconf.