+Stage::SetCamera::SetCamera():
+ stage(0),
+ camera(0)
+{ }
+
+Stage::SetCamera::SetCamera(Stage &s, const GL::Camera &c):
+ stage(&s),
+ camera(&c)
+{ }
+
+void Stage::SetCamera::validate() const
+{
+ if(!stage)
+ throw logic_error("null stage");
+ if(!camera)
+ throw logic_error("null camera");
+}
+
+void Stage::SetCamera::start(float, float)
+{
+ stage->set_camera(*camera);
+}
+
+