From fce6e7846814e54de9d38000d2f5e2295ee2119e Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 12 Nov 2022 17:49:27 +0200
Subject: [PATCH] Provide a way to request events for existing entities and
 components

The iterate_objects function does not account for derived classes, so
iterating over all Entity instances might not actually give all entities
on the stage.
---
 source/game/entity.h         |  1 +
 source/game/eventbus.h       | 20 ++++++++++++++++++++
 source/game/eventsource.h    | 12 ++++++++++++
 source/game/stage.cpp        | 16 ++++++++++++++++
 source/game/stage.h          |  5 +++++
 source/gameview/renderer.cpp |  4 +---
 6 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/source/game/entity.h b/source/game/entity.h
index c4cf83c..8dc5139 100644
--- a/source/game/entity.h
+++ b/source/game/entity.h
@@ -35,6 +35,7 @@ public:
 
 	void add_component(Handle<Component>);
 	void remove_component(Handle<Component>);
+	const std::vector<Handle<Component>> &get_components() const { return components; }
 
 	template<typename T>
 	Handle<T> get_component();
diff --git a/source/game/eventbus.h b/source/game/eventbus.h
index 7da047e..a4de18f 100644
--- a/source/game/eventbus.h
+++ b/source/game/eventbus.h
@@ -26,6 +26,7 @@ struct EventDispatcher
 	{ std::erase_if(handlers, [obs](auto &h){ return h.observer==obs; }); }
 
 	void dispatch(const T &) const;
+	void dispatch_to(EventObserver &, const T &) const;
 };
 
 
@@ -64,6 +65,9 @@ public:
 
 	template<typename T>
 	void dispatch(const T &) const;
+
+	template<typename T>
+	void dispatch_to(EventObserver &, const T &) const;
 };
 
 
@@ -74,6 +78,14 @@ void EventDispatcher<T>::dispatch(const T &event) const
 		h.callback(event);
 }
 
+template<typename T>
+void EventDispatcher<T>::dispatch_to(EventObserver &obs, const T &event) const
+{
+	for(const Handler &h: handlers)
+		if(h.observer==&obs)
+			h.callback(event);
+}
+
 
 template<typename T>
 inline unsigned EventBus::get_event_id()
@@ -108,6 +120,14 @@ inline void EventBus::dispatch(const T &event) const
 		static_cast<EventDispatcher<T> *>(dispatchers[id].dispatcher)->dispatch(event);
 }
 
+template<typename T>
+inline void EventBus::dispatch_to(EventObserver &obs, const T &event) const
+{
+	unsigned id = get_event_id<T>();
+	if(id<dispatchers.size() && dispatchers[id].dispatcher)
+		static_cast<EventDispatcher<T> *>(dispatchers[id].dispatcher)->dispatch_to(obs, event);
+}
+
 } // namespace Msp::Game
 
 #endif
diff --git a/source/game/eventsource.h b/source/game/eventsource.h
index 0856e08..ccb830f 100644
--- a/source/game/eventsource.h
+++ b/source/game/eventsource.h
@@ -41,6 +41,9 @@ private:
 public:
 	template<typename T, typename... Args>
 	void emit(Args &&...) const;
+
+	template<typename T, typename... Args>
+	void emit_to(EventObserver &, Args &&...) const;
 };
 
 
@@ -61,6 +64,15 @@ inline void EventSource<E...>::emit(Args &&... args) const
 	bus.dispatch(event);
 }
 
+template<typename... E>
+template<typename T, typename... Args>
+inline void EventSource<E...>::emit_to(EventObserver &obs, Args &&... args) const
+{
+	T event(std::forward<Args>(args)...);
+	static_cast<const EventDispatcher<T> &>(*this).dispatch_to(obs, event);
+	bus.dispatch_to(obs, event);
+}
+
 } // namespace Msp::Game
 
 #endif
diff --git a/source/game/stage.cpp b/source/game/stage.cpp
index 8317610..81893e1 100644
--- a/source/game/stage.cpp
+++ b/source/game/stage.cpp
@@ -35,6 +35,22 @@ void Stage::set_active_camera(Handle<Camera> c)
 	event_source.emit<Events::CameraChanged>(active_camera);
 }
 
+void Stage::synthesize_initial_events(EventObserver &target_observer)
+{
+	synthesize_initial_events(Handle<Entity>::from_object(root.get()), target_observer);
+	if(active_camera)
+		event_source.emit_to<Events::CameraChanged>(target_observer, active_camera);
+}
+
+void Stage::synthesize_initial_events(Handle<Entity> entity, EventObserver &target_observer)
+{
+	for(Handle<Component> c: entity->get_components())
+		event_source.emit_to<Events::ComponentCreated>(target_observer, c);
+	for(Handle<Entity> e: entity->get_children())
+		synthesize_initial_events(e, target_observer);
+	event_source.emit_to<Events::EntityCreated>(target_observer, entity);
+}
+
 void Stage::tick(Time::TimeDelta dt)
 {
 	for(const auto &s: systems)
diff --git a/source/game/stage.h b/source/game/stage.h
index 19e70f4..a046947 100644
--- a/source/game/stage.h
+++ b/source/game/stage.h
@@ -58,6 +58,11 @@ public:
 	void set_active_camera(Handle<Camera>);
 	Handle<Camera> get_active_camera() const { return active_camera; }
 
+	void synthesize_initial_events(EventObserver &);
+private:
+	void synthesize_initial_events(Handle<Entity>, EventObserver &);
+
+public:
 	void tick(Time::TimeDelta);
 };
 
diff --git a/source/gameview/renderer.cpp b/source/gameview/renderer.cpp
index 068aa09..ca4e8a9 100644
--- a/source/gameview/renderer.cpp
+++ b/source/gameview/renderer.cpp
@@ -19,9 +19,7 @@ Renderer::Renderer(Game::Stage &s, GL::View &v):
 	event_observer.observe<Game::Events::EntityDestroyed>([this](auto &e){ entity_destroyed(e); });
 	event_observer.observe<Game::Events::CameraChanged>([this](auto &e){ camera_changed(e); });
 
-	stage.iterate_objects<Game::Entity>([this](auto &e){ entity_created({ Game::Handle<Game::Entity>::from_object(&e) }); });
-	if(Game::Handle<Game::Camera> ac = stage.get_active_camera())
-		camera_changed({ ac });
+	stage.synthesize_initial_events(event_observer);
 
 	view.set_camera(&gl_camera);
 }
-- 
2.43.0