SDK: Allow to set an update order for systems (Closes #106)

SDK/include/NDK/BaseSystem.hpp

@@ -35,6 +35,7 @@ namespace Ndk
 
 			inline const std::vector<EntityHandle>& GetEntities() const;
 			inline SystemIndex GetIndex() const;
+			inline int GetUpdateOrder() const;
 			inline float GetUpdateRate() const;
 			inline World& GetWorld() const;
 
@@ -42,6 +43,7 @@ namespace Ndk
 
 			inline bool HasEntity(const Entity* entity) const;
 
+			void SetUpdateOrder(int updateOrder);
 			inline void SetUpdateRate(float updatePerSecond);
 
 			inline void Update(float elapsedTime);
@@ -93,6 +95,7 @@ namespace Ndk
 			bool m_updateEnabled;
 			float m_updateCounter;
 			float m_updateRate;
+			int m_updateOrder;
 
 			static SystemIndex s_nextIndex;
 	};

SDK/include/NDK/BaseSystem.inl

@@ -16,7 +16,9 @@ namespace Ndk
 
 	inline BaseSystem::BaseSystem(SystemIndex systemId) :
 	m_systemIndex(systemId),
-	m_updateEnabled(true)
+	m_world(nullptr),
+	m_updateEnabled(true),
+	m_updateOrder(0)
 	{
 		SetUpdateRate(30);
 	}
@@ -33,7 +35,8 @@ namespace Ndk
 	m_systemIndex(system.m_systemIndex),
 	m_updateEnabled(system.m_updateEnabled),
 	m_updateCounter(0.f),
-	m_updateRate(system.m_updateRate)
+	m_updateRate(system.m_updateRate),
+	m_updateOrder(system.m_updateOrder)
 	{
 	}
 
@@ -69,7 +72,18 @@ namespace Ndk
 	}
 
 	/*!
-	* \brief Gets the rate of update for the system
+	* \brief Gets the update order of the system
+	* \return Update order
+	*
+	* \see SetUpdateOrder
+	*/
+	inline int BaseSystem::GetUpdateOrder() const
+	{
+		return m_updateOrder;
+	}
+
+	/*!
+	* \brief Gets the rate of update of the system
 	* \return Update rate
 	*/
 

SDK/include/NDK/World.hpp

@@ -24,6 +24,7 @@ namespace Ndk
 
 	class NDK_API World : public Nz::HandledObject<World>
 	{
+		friend BaseSystem;
 		friend Entity;
 
 		public:
@@ -72,6 +73,8 @@ namespace Ndk
 		private:
 			inline void Invalidate();
 			inline void Invalidate(EntityId id);
+			inline void InvalidateSystemOrder();
+			void ReorderSystems();
 
 			struct EntityBlock
 			{
@@ -87,11 +90,13 @@ namespace Ndk
 			};
 
 			std::vector<std::unique_ptr<BaseSystem>> m_systems;
+			std::vector<BaseSystem*> m_orderedSystems;
 			std::vector<EntityBlock> m_entities;
 			std::vector<EntityId> m_freeIdList;
 			EntityList m_aliveEntities;
 			Nz::Bitset<Nz::UInt64> m_dirtyEntities;
 			Nz::Bitset<Nz::UInt64> m_killedEntities;
+			bool m_orderedSystemsUpdated;
 	};
 }
 

SDK/include/NDK/World.inl

@@ -53,6 +53,7 @@ namespace Ndk
 		m_systems[index]->SetWorld(this);
 
 		Invalidate(); // We force an update for every entities
+		InvalidateSystemOrder(); // And regenerate the system update list
 
 		return *m_systems[index].get();
 	}
@@ -206,6 +207,8 @@ namespace Ndk
 	inline void World::RemoveAllSystems()
 	{
 		m_systems.clear();
+
+		InvalidateSystemOrder();
 	}
 
 	/*!
@@ -219,7 +222,11 @@ namespace Ndk
 	inline void World::RemoveSystem(SystemIndex index)
 	{
 		if (HasSystem(index))
+		{
 			m_systems[index].reset();
+
+			InvalidateSystemOrder();
+		}
 	}
 
 	/*!
@@ -246,32 +253,11 @@ namespace Ndk
 		Update(); //< Update entities
 
 		// And then update systems
-		for (auto& systemPtr : m_systems)
-		{
-			if (systemPtr)
-				systemPtr->Update(elapsedTime);
-		}
-	}
+		if (!m_orderedSystemsUpdated)
+			ReorderSystems();
 
-	/*!
-	* \brief Invalidates each entity in the world
-	*/
-
-	inline void World::Invalidate()
-	{
-		m_dirtyEntities.Resize(m_entities.size(), false);
-		m_dirtyEntities.Set(true); // Activation of all bits
-	}
-
-	/*!
-	* \brief Invalidates an entity in the world
-	*
-	* \param id Identifier of the entity
-	*/
-
-	inline void World::Invalidate(EntityId id)
-	{
-		m_dirtyEntities.UnboundedSet(id, true);
+		for (auto& systemPtr : m_orderedSystems)
+			systemPtr->Update(elapsedTime);
 	}
 
 	/*!
@@ -281,10 +267,12 @@ namespace Ndk
 
 	inline World& World::operator=(World&& world) noexcept
 	{
-		m_aliveEntities  = std::move(world.m_aliveEntities);
-		m_dirtyEntities  = std::move(world.m_dirtyEntities);
-		m_freeIdList     = std::move(world.m_freeIdList);
-		m_killedEntities = std::move(world.m_killedEntities);
+		m_aliveEntities         = std::move(world.m_aliveEntities);
+		m_dirtyEntities         = std::move(world.m_dirtyEntities);
+		m_freeIdList            = std::move(world.m_freeIdList);
+		m_killedEntities        = std::move(world.m_killedEntities);
+		m_orderedSystems        = std::move(world.m_orderedSystems);
+		m_orderedSystemsUpdated = world.m_orderedSystemsUpdated;
 
 		m_entities = std::move(world.m_entities);
 		for (EntityBlock& block : m_entities)
@@ -296,4 +284,20 @@ namespace Ndk
 
 		return *this;
 	}
+
+	inline void World::Invalidate()
+	{
+		m_dirtyEntities.Resize(m_entities.size(), false);
+		m_dirtyEntities.Set(true); // Activation of all bits
+	}
+
+	inline void World::Invalidate(EntityId id)
+	{
+		m_dirtyEntities.UnboundedSet(id, true);
+	}
+
+	inline void World::InvalidateSystemOrder()
+	{
+		m_orderedSystemsUpdated = false;
+	}
 }

SDK/src/NDK/BaseSystem.cpp

@@ -3,6 +3,7 @@
 // For conditions of distribution and use, see copyright notice in Prerequesites.hpp
 
 #include <NDK/BaseSystem.hpp>
+#include <NDK/World.hpp>
 
 namespace Ndk
 {
@@ -56,6 +57,26 @@ namespace Ndk
 		return true;
 	}
 
+	/*!
+	* \brief Sets the update order of this system
+	*
+	* The system update order is used by the world it belongs to in order to know in which order they should be updated, as some application logic may rely a specific update order.
+	* A system with a greater update order (ex: 1) is guaranteed to be updated after a system with a lesser update order (ex: -1), otherwise the order is unspecified (and is not guaranteed to be stable).
+	*
+	* \param updateOrder The relative update order of the system
+	*
+	* \remark The update order is only used by World::Update(float) and does not have any effect regarding a call to BaseSystem::Update(float)
+	*
+	* \see GetUpdateOrder
+	*/
+	inline void BaseSystem::SetUpdateOrder(int updateOrder)
+	{
+		m_updateOrder = updateOrder;
+
+		if (m_world)
+			m_world->InvalidateSystemOrder();
+	}
+
 	/*!
 	* \brief Operation to perform when entity is added to the system
 	*

SDK/src/NDK/World.cpp

@@ -249,4 +249,22 @@ namespace Ndk
 		}
 		m_dirtyEntities.Reset();
 	}
+
+	void World::ReorderSystems()
+	{
+		m_orderedSystems.clear();
+
+		for (auto& systemPtr : m_systems)
+		{
+			if (systemPtr)
+				m_orderedSystems.push_back(systemPtr.get());
+		}
+
+		std::sort(m_orderedSystems.begin(), m_orderedSystems.end(), [] (BaseSystem* first, BaseSystem* second)
+		{
+			return first->GetUpdateOrder() < second->GetUpdateOrder();
+		});
+
+		m_orderedSystemsUpdated = true;
+	}
 }