Support removing the actor, light, or model from the root

include/sdf/Root.hh

@@ -246,6 +246,11 @@ namespace sdf
     public: sdf::ElementPtr ToElement(
         const OutputConfig &_config = OutputConfig::GlobalConfig()) const;
 
+    /// \brief Remove the actor, light, or model if one of them exists.
+    /// The SDF Root object can only hold one, or none, from the set
+    /// [Actor, Light, Model].
+    public: void ClearActorLightModel();
+
     /// \brief Private data pointer
     GZ_UTILS_IMPL_PTR(dataPtr)
   };

python/src/sdf/pyRoot.cc

@@ -96,6 +96,10 @@ void defineRoot(pybind11::object module)
     .def("set_light", &sdf::Root::SetLight,
          "Set the light object. This will override any existing model, "
          "actor, and light object.")
+    .def("clear_actor_light_model", &sdf::Root::ClearActorLightModel,
+         "Remove the actor, light, or model if one of them exists."
+         "The SDF Root object can only hold one, or none, from the set"
+         "[Actor, Light, Model].")
     .def("add_world", [](Root &self, const World &_world)
          {
            ThrowIfErrors(self.AddWorld(_world));

python/test/pyRoot_TEST.py

@@ -358,5 +358,33 @@ def test_resolve_auto_inertials_with_save_calculation_configuration(self):
       self.assertEqual(len(inertialErr), 0)
       self.assertTrue(link.auto_inertia_saved())
 
+    def test_clear_actor_light_model(self):
+        root = Root()
+
+        # \TODO(anyone) Wrap the Actor class.
+        # self.assertEqual(None, root.actor())
+        # actor1 = Actor()
+        # actor1.set_name("actor1")
+        # root.set_actor(actor1)
+        # self.assertNotEqual(None, root.actor())
+        # root.clear_actor_light_model()
+        # self.assertEqual(None, root.actor())
+
+        self.assertEqual(None, root.light())
+        light1 = Light()
+        light1.set_name("light1")
+        root.set_light(light1)
+        self.assertNotEqual(None, root.light())
+        root.clear_actor_light_model()
+        self.assertEqual(None, root.light())
+
+        self.assertEqual(None, root.model())
+        model1 = Model()
+        model1.set_name("model1")
+        root.set_model(model1)
+        self.assertNotEqual(None, root.model())
+        root.clear_actor_light_model()
+        self.assertEqual(None, root.model())
+
 if __name__ == '__main__':
     unittest.main()

src/Root.cc

@@ -644,3 +644,9 @@ sdf::ElementPtr Root::ToElement(const OutputConfig &_config) const
 
   return elem;
 }
+
+/////////////////////////////////////////////////
+void Root::ClearActorLightModel()
+{
+  this->dataPtr->modelLightOrActor = std::monostate{};
+}

src/Root_TEST.cc

@@ -670,3 +670,33 @@ TEST(DOMRoot, WorldByName)
   ASSERT_TRUE(root.WorldNameExists("world2"));
   EXPECT_EQ("world2", root.WorldByName("world2")->Name());
 }
+
+/////////////////////////////////////////////////
+TEST(DOMRoot, ClearActorLightModel)
+{
+  sdf::Root root;
+  EXPECT_EQ(nullptr, root.Actor());
+  EXPECT_EQ(nullptr, root.Light());
+  EXPECT_EQ(nullptr, root.Model());
+
+  sdf::Actor actor1;
+  actor1.SetName("actor1");
+  root.SetActor(actor1);
+  EXPECT_NE(nullptr, root.Actor());
+  root.ClearActorLightModel();
+  EXPECT_EQ(nullptr, root.Actor());
+
+  sdf::Light light1;
+  light1.SetName("light1");
+  root.SetLight(light1);
+  EXPECT_NE(nullptr, root.Light());
+  root.ClearActorLightModel();
+  EXPECT_EQ(nullptr, root.Light());
+
+  sdf::Model model1;
+  model1.SetName("model1");
+  root.SetModel(model1);
+  EXPECT_NE(nullptr, root.Model());
+  root.ClearActorLightModel();
+  EXPECT_EQ(nullptr, root.Model());
+}