From 4014851ac2ed8e86b5a781dcc3056088d40465a1 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 27 Nov 2022 23:45:30 +0200
Subject: [PATCH] Emit events for colliding physical entities

---
 examples/bassteroids/source/events.h    | 18 ++++++++++++++++++
 examples/bassteroids/source/physics.cpp |  4 ++++
 examples/bassteroids/source/physics.h   |  6 ++++++
 3 files changed, 28 insertions(+)
 create mode 100644 examples/bassteroids/source/events.h

diff --git a/examples/bassteroids/source/events.h b/examples/bassteroids/source/events.h
new file mode 100644
index 0000000..65adddb
--- /dev/null
+++ b/examples/bassteroids/source/events.h
@@ -0,0 +1,18 @@
+#ifndef EVENTS_H_
+#define EVENTS_H_
+
+#include <msp/game/handle.h>
+
+class Collider;
+
+namespace Events {
+
+struct Collision
+{
+	Msp::Game::Handle<Collider> collider1;
+	Msp::Game::Handle<Collider> collider2;
+};
+
+} // namespace Events
+
+#endif
diff --git a/examples/bassteroids/source/physics.cpp b/examples/bassteroids/source/physics.cpp
index 67cdf6f..3c43502 100644
--- a/examples/bassteroids/source/physics.cpp
+++ b/examples/bassteroids/source/physics.cpp
@@ -8,6 +8,7 @@ using namespace Msp;
 
 Physics::Physics(Game::Stage &s):
 	System(s),
+	event_source(stage.get_event_bus()),
 	observer(stage.get_event_bus())
 {
 	observer.observe<Game::Events::EntityCreated>([this](auto &e){ entity_added(e); });
@@ -59,6 +60,9 @@ void Physics::tick(Time::TimeDelta dt)
 		copy_out<true>(entities[i]);
 	for(unsigned i=fixture_count; i<entities.size(); ++i)
 		copy_out<false>(entities[i]);
+
+	for(const Collision &c: collisions)
+		event_source.emit<Events::Collision>(entities[c.body1].entity->get_collider(), entities[c.body2].entity->get_collider());
 }
 
 template<bool is_fixture>
diff --git a/examples/bassteroids/source/physics.h b/examples/bassteroids/source/physics.h
index 096e228..fcf4b0d 100644
--- a/examples/bassteroids/source/physics.h
+++ b/examples/bassteroids/source/physics.h
@@ -2,16 +2,21 @@
 #define PHYSICS_H_
 
 #include <msp/game/eventobserver.h>
+#include <msp/game/eventsource.h>
 #include <msp/game/events.h>
 #include <msp/game/handle.h>
 #include <msp/game/system.h>
 #include <msp/geometry/angle.h>
 #include <msp/linal/vector.h>
+#include "events.h"
 
 class PhysicalEntity;
 
 class Physics: public Msp::Game::System
 {
+public:
+	using EventSource = Msp::Game::EventSource<Events::Collision>;
+
 private:
 	struct SimulatedEntity
 	{
@@ -39,6 +44,7 @@ private:
 		Msp::LinAl::Vector<float, 2> normal;
 	};
 
+	EventSource event_source;
 	Msp::Game::EventObserver observer;
 	std::vector<SimulatedEntity> entities;
 	unsigned fixture_count = 0;
-- 
2.43.0