refacto: don't use RenderingEngine singleton on CAO

* we don't need on CAO side more than SceneManager, and temporary. Pass only required SceneManager as a parameter to build CAO and add them to the current scene
* Use temporary the RenderingEngine singleton from ClientEnvironment, waitfor for better solution
* Make ClientActiveObject::addToScene virtual function mandatory to be defined by children to ensure we don't forget to properly define it

src/client/clientenvironment.cpp

@@ -352,7 +352,7 @@ u16 ClientEnvironment::addActiveObject(ClientActiveObject *object)
 	if (!m_ao_manager.registerObject(object))
 		return 0;
 
-	object->addToScene(m_texturesource);
+	object->addToScene(m_texturesource, RenderingEngine::get_scene_manager());
 
 	// Update lighting immediately
 	object->updateLight(getDayNightRatio());

src/client/clientobject.h

@@ -33,13 +33,17 @@ class LocalPlayer;
 struct ItemStack;
 class WieldMeshSceneNode;
 
+namespace irr { namespace scene {
+	class ISceneManager;
+}}
+
 class ClientActiveObject : public ActiveObject
 {
 public:
 	ClientActiveObject(u16 id, Client *client, ClientEnvironment *env);
 	virtual ~ClientActiveObject();
 
-	virtual void addToScene(ITextureSource *tsrc) {}
+	virtual void addToScene(ITextureSource *tsrc, irr::scene::ISceneManager *smgr) = 0;
 	virtual void removeFromScene(bool permanent) {}
 
 	virtual void updateLight(u32 day_night_ratio) {}

src/client/content_cao.cpp

@@ -24,7 +24,6 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include <IMeshManipulator.h>
 #include <IAnimatedMeshSceneNode.h>
 #include "client/client.h"
-#include "client/renderingengine.h"
 #include "client/sound.h"
 #include "client/tile.h"
 #include "util/basic_macros.h"
@@ -189,7 +188,7 @@ public:
 
 	static ClientActiveObject* create(Client *client, ClientEnvironment *env);
 
-	void addToScene(ITextureSource *tsrc);
+	void addToScene(ITextureSource *tsrc, irr::scene::ISceneManager *smgr);
 	void removeFromScene(bool permanent);
 	void updateLight(u32 day_night_ratio);
 	void updateNodePos();
@@ -220,7 +219,7 @@ ClientActiveObject* TestCAO::create(Client *client, ClientEnvironment *env)
 	return new TestCAO(client, env);
 }
 
-void TestCAO::addToScene(ITextureSource *tsrc)
+void TestCAO::addToScene(ITextureSource *tsrc, irr::scene::ISceneManager *smgr)
 {
 	if(m_node != NULL)
 		return;
@@ -249,7 +248,7 @@ void TestCAO::addToScene(ITextureSource *tsrc)
 	// Add to mesh
 	mesh->addMeshBuffer(buf);
 	buf->drop();
-	m_node = RenderingEngine::get_scene_manager()->addMeshSceneNode(mesh, NULL);
+	m_node = smgr->addMeshSceneNode(mesh, NULL);
 	mesh->drop();
 	updateNodePos();
 }
@@ -591,9 +590,9 @@ void GenericCAO::removeFromScene(bool permanent)
 		m_client->getMinimap()->removeMarker(&m_marker);
 }
 
-void GenericCAO::addToScene(ITextureSource *tsrc)
+void GenericCAO::addToScene(ITextureSource *tsrc, irr::scene::ISceneManager *smgr)
 {
-	m_smgr = RenderingEngine::get_scene_manager();
+	m_smgr = smgr;
 
 	if (getSceneNode() != NULL) {
 		return;
@@ -625,8 +624,7 @@ void GenericCAO::addToScene(ITextureSource *tsrc)
 	}
 
 	auto grabMatrixNode = [this] {
-		m_matrixnode = RenderingEngine::get_scene_manager()->
+		m_matrixnode = m_smgr->addDummyTransformationSceneNode();
-				addDummyTransformationSceneNode();
 		m_matrixnode->grab();
 	};
 
@@ -644,7 +642,7 @@ void GenericCAO::addToScene(ITextureSource *tsrc)
 
 	if (m_prop.visual == "sprite") {
 		grabMatrixNode();
-		m_spritenode = RenderingEngine::get_scene_manager()->addBillboardSceneNode(
+		m_spritenode = m_smgr->addBillboardSceneNode(
 				m_matrixnode, v2f(1, 1), v3f(0,0,0), -1);
 		m_spritenode->grab();
 		m_spritenode->setMaterialTexture(0,
@@ -729,8 +727,7 @@ void GenericCAO::addToScene(ITextureSource *tsrc)
 			mesh->addMeshBuffer(buf);
 			buf->drop();
 		}
-		m_meshnode = RenderingEngine::get_scene_manager()->
+		m_meshnode = m_smgr->addMeshSceneNode(mesh, m_matrixnode);
-			addMeshSceneNode(mesh, m_matrixnode);
 		m_meshnode->grab();
 		mesh->drop();
 		// Set it to use the materials of the meshbuffers directly.
@@ -739,8 +736,7 @@ void GenericCAO::addToScene(ITextureSource *tsrc)
 	} else if (m_prop.visual == "cube") {
 		grabMatrixNode();
 		scene::IMesh *mesh = createCubeMesh(v3f(BS,BS,BS));
-		m_meshnode = RenderingEngine::get_scene_manager()->
+		m_meshnode = m_smgr->addMeshSceneNode(mesh, m_matrixnode);
-			addMeshSceneNode(mesh, m_matrixnode);
 		m_meshnode->grab();
 		mesh->drop();
 
@@ -753,8 +749,7 @@ void GenericCAO::addToScene(ITextureSource *tsrc)
 		grabMatrixNode();
 		scene::IAnimatedMesh *mesh = m_client->getMesh(m_prop.mesh, true);
 		if (mesh) {
-			m_animated_meshnode = RenderingEngine::get_scene_manager()->
+			m_animated_meshnode = m_smgr->addAnimatedMeshSceneNode(mesh, m_matrixnode);
-				addAnimatedMeshSceneNode(mesh, m_matrixnode);
 			m_animated_meshnode->grab();
 			mesh->drop(); // The scene node took hold of it
 
@@ -795,8 +790,7 @@ void GenericCAO::addToScene(ITextureSource *tsrc)
 			infostream << "serialized form: " << m_prop.wield_item << std::endl;
 			item.deSerialize(m_prop.wield_item, m_client->idef());
 		}
-		m_wield_meshnode = new WieldMeshSceneNode(
+		m_wield_meshnode = new WieldMeshSceneNode(m_smgr, -1);
-			RenderingEngine::get_scene_manager(), -1);
 		m_wield_meshnode->setItem(item, m_client,
 			(m_prop.visual == "wielditem"));
 
@@ -1074,7 +1068,7 @@ void GenericCAO::step(float dtime, ClientEnvironment *env)
 		}
 
 		removeFromScene(false);
-		addToScene(m_client->tsrc());
+		addToScene(m_client->tsrc(), m_smgr);
 
 		// Attachments, part 2: Now that the parent has been refreshed, put its attachments back
 		for (u16 cao_id : m_attachment_child_ids) {

src/client/content_cao.h

@@ -236,7 +236,7 @@ public:
 
 	void removeFromScene(bool permanent);
 
-	void addToScene(ITextureSource *tsrc);
+	void addToScene(ITextureSource *tsrc, irr::scene::ISceneManager *smgr);
 
 	inline void expireVisuals()
 	{

src/unittest/test_clientactiveobjectmgr.cpp

@@ -29,6 +29,7 @@ public:
 	TestClientActiveObject() : ClientActiveObject(0, nullptr, nullptr) {}
 	~TestClientActiveObject() = default;
 	ActiveObjectType getType() const { return ACTIVEOBJECT_TYPE_TEST; }
+	virtual void addToScene(ITextureSource *tsrc, irr::scene::ISceneManager *smgr) {}
 };
 
 class TestClientActiveObjectMgr : public TestBase