def on_canvas_slave__route_electrode_added(self, slave, electrode_id):
        '''
        .. versionchanged:: 0.11
            Draw temporary route currently being formed.

        .. versionchanged:: 0.11.3
            Update routes table by setting ``df_routes`` property of
            :attr:`canvas_slave`.
        '''
        logger.debug('Route electrode added: %s', electrode_id)
        if slave._route.electrode_ids is None:
            return
        df_route = pd.DataFrame([[-1, e, i] for i, e in
                                 enumerate(slave._route.electrode_ids)],
                                columns=['route_i', 'electrode_i',
                                         'transition_i'])
        # XXX Negative `route_i` corresponds to temporary route being
        # drawn.  Append row entries for temporary route to existing routes
        # table.
        df_routes = slave.df_routes.loc[slave.df_routes.route_i >= 0].copy()
        self.canvas_slave.df_routes = pd.concat([df_routes, df_route])