From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 7 Dec 2022 09:56:51 +0000 (+0200)
Subject: Add flags for declaring ordering between systems
X-Git-Url: http://git.tdb.fi/?p=libs%2Fgame.git;a=commitdiff_plain;h=423b49f2857f8e1597b652bfd41dbf3ae45f7ec5

Add flags for declaring ordering between systems
---

diff --git a/source/game/system.h b/source/game/system.h
index e3d7117..8c9c8b1 100644
--- a/source/game/system.h
+++ b/source/game/system.h
@@ -20,7 +20,11 @@ public:
 		READ_FRESH = 3,
 		WRITE = 4,
 		UPDATE = READ_OLD | WRITE,
-		CHAINED_UPDATE = READ_FRESH | WRITE
+		CHAINED_UPDATE = READ_FRESH | WRITE,
+		DATA_MASK = 7,
+		RUN_BEFORE = 8,
+		RUN_AFTER = 16,
+		ORDER_MASK = 24
 	};
 
 	struct Dependency
@@ -77,7 +81,9 @@ protected:
 template<typename T>
 inline void System::declare_dependency(DependencyFlags flags)
 {
-	if(!std::is_base_of_v<Component, T>)
+	if((flags&DATA_MASK) && !std::is_base_of_v<Component, T>)
+		throw std::invalid_argument("System::declare_dependency");
+	if((flags&ORDER_MASK) && !std::is_base_of_v<System, T>)
 		throw std::invalid_argument("System::declare_dependency");
 
 	const Reflection::ClassBase &type = stage.get_reflector().get_or_create_class<T>();
@@ -85,6 +91,8 @@ inline void System::declare_dependency(DependencyFlags flags)
 
 	if(i!=dependencies.end())
 		flags = static_cast<DependencyFlags>(flags|i->flags);
+	if((flags&RUN_BEFORE) && (flags&RUN_AFTER))
+		throw std::logic_error("conflicting order flags");
 
 	Dependency &dep = (i!=dependencies.end() ? *i : dependencies.emplace_back(type));
 	dep.flags = flags;