def METHOD_NAME(self, obj, evt):
    if not self.navi:
        return
    interactor = obj.GetInteractor()
    if not self.lmb_pressed:
        self.lmb_pressed = True
        display_pos = interactor.GetEventPosition()
        world_pos = self._to_world_coordinate_2d(display_pos)
        self.route_from = world_pos