From 6804436b4eb2dd4a7f6f8985c22cc3adb2aae6f6 Mon Sep 17 00:00:00 2001
From: Georg Hagen <git.georg.hagen@madvoxel.com>
Date: Fri, 28 Feb 2025 16:47:22 +0100
Subject: [PATCH] Add EventHandle to manage smartptr based events more
 conveniently

---
 openVulkanoCpp/Base/Event.hpp                 | 51 +++++++++++++++++++
 .../Scene/Prefabs/ArBackgroundDrawable.cpp    | 19 +++----
 .../Scene/Prefabs/ArBackgroundDrawable.hpp    |  5 +-
 3 files changed, 60 insertions(+), 15 deletions(-)

diff --git a/openVulkanoCpp/Base/Event.hpp b/openVulkanoCpp/Base/Event.hpp
index a547e88..0e1c1fa 100644
--- a/openVulkanoCpp/Base/Event.hpp
+++ b/openVulkanoCpp/Base/Event.hpp
@@ -484,4 +484,55 @@ namespace OpenVulkano
 	{
 		return std::pair<std::weak_ptr<Instance>, Method>(instance, method);
 	}
+
+	class EventHandle
+	{
+		std::weak_ptr<void> m_owner;
+		IEventHandler* m_handler;
+
+	public:
+		EventHandle() : m_handler(nullptr) {}
+
+		EventHandle(const std::weak_ptr<void>& owner, IEventHandler* handler)
+			: m_owner(owner), m_handler(handler)
+		{}
+
+		EventHandle(const EventHandle& other) = delete;
+
+		EventHandle(EventHandle&& other) noexcept : m_owner(other.m_owner), m_handler(other.m_handler)
+		{
+			other.m_owner.reset();
+			other.m_handler = nullptr;
+		}
+
+		template<class EVENT_OWNER_T, typename... EVENT_ARGS, typename HANDLER_T>
+		EventHandle (const std::shared_ptr<EVENT_OWNER_T>& owner, Event<EVENT_ARGS...> EVENT_OWNER_T::* event, HANDLER_T&& handler)
+			: m_owner(owner), m_handler((owner.get()->*event).operator+=(handler))
+		{}
+
+		~EventHandle() { if (m_handler) Close(); }
+
+		void Close()
+		{
+			if (!m_handler) return;
+			if (auto acquired = m_owner.lock())
+			{
+				m_handler->SetInvalid();
+			}
+			m_handler = nullptr;
+			m_owner.reset();
+		}
+
+		EventHandle& operator =(const EventHandle& other) = delete;
+
+		EventHandle& operator =(EventHandle&& other) noexcept
+		{
+			Close();
+			m_owner.swap(other.m_owner);
+			std::swap(m_handler, other.m_handler);
+			return *this;
+		}
+
+		operator bool() const noexcept { return m_handler; }
+	};
 }
diff --git a/openVulkanoCpp/Scene/Prefabs/ArBackgroundDrawable.cpp b/openVulkanoCpp/Scene/Prefabs/ArBackgroundDrawable.cpp
index 32c75e8..5af5e6d 100644
--- a/openVulkanoCpp/Scene/Prefabs/ArBackgroundDrawable.cpp
+++ b/openVulkanoCpp/Scene/Prefabs/ArBackgroundDrawable.cpp
@@ -18,7 +18,6 @@ namespace OpenVulkano::Scene
 
 	ArBackgroundDrawable::ArBackgroundDrawable(const Ptr<AR::ArSession>& arSession)
 			: Drawable(DrawEncoder::GetDrawEncoder<ArBackgroundDrawable>(), DrawPhase::BACKGROUND)
-			, m_arSession(arSession)
 	{
 		m_shader.topology = Topology::TRIANGLE_STRIP;
 		m_shader.AddShaderProgram(ShaderProgramType::VERTEX, "Shader/background");
@@ -29,27 +28,21 @@ namespace OpenVulkano::Scene
 		SetShader(&m_shader);
 		m_intrinsicsBuffer.Init(sizeof(Math::CameraIntrinsicWithResolution), &FALLBACK_INTRINSICS);
 		m_intrinsicsBuffer.updateFrequency = UpdateFrequency::Always;
-		if (m_arSession)
-			m_arSession->OnNewFrame += EventHandler(this, &ArBackgroundDrawable::OnNewArFrame);
+		Init(arSession);
 	}
 
 	void ArBackgroundDrawable::Init(const Ptr<AR::ArSession>& arSession)
 	{
-		if (m_arSession)
-		{
-			if (m_arSession == arSession) return;
-			Close();
-		}
+		if (m_eventHandle) Close();
 		if (!arSession) return;
-		m_arSession = arSession;
-		m_arSession->OnNewFrame += EventHandler(this, &ArBackgroundDrawable::OnNewArFrame);
+		m_eventHandle = { arSession, &AR::ArSession::OnNewFrame, EventHandler(this, &ArBackgroundDrawable::OnNewArFrame) };
 	}
 
 	void ArBackgroundDrawable::Close()
 	{
-		if (m_arSession) m_arSession->OnNewFrame -= EventHandler(this, &ArBackgroundDrawable::OnNewArFrame);
-		m_arSession = nullptr;
-		m_nextFrame = nullptr;
+		m_eventHandle.Close();
+		m_lastFrame = m_nextFrame = nullptr;
+		m_texture = nullptr;
 		Drawable::Close();
 	}
 
diff --git a/openVulkanoCpp/Scene/Prefabs/ArBackgroundDrawable.hpp b/openVulkanoCpp/Scene/Prefabs/ArBackgroundDrawable.hpp
index 960d256..9aaf973 100644
--- a/openVulkanoCpp/Scene/Prefabs/ArBackgroundDrawable.hpp
+++ b/openVulkanoCpp/Scene/Prefabs/ArBackgroundDrawable.hpp
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include "Base/Event.hpp"
 #include "Base/Wrapper.hpp"
 #include "Scene/Drawable.hpp"
 #include "Scene/Shader/Shader.hpp"
@@ -26,7 +27,7 @@ namespace OpenVulkano
 		{
 			Shader m_shader;
 			UniformBuffer m_intrinsicsBuffer;
-			Ptr<AR::ArSession> m_arSession;
+			EventHandle m_eventHandle;
 			Ptr<AR::ArFrame> m_nextFrame, m_currentFrame, m_lastFrame;
 			const Texture* m_texture = nullptr;
 
@@ -35,7 +36,7 @@ namespace OpenVulkano
 		public:
 			ArBackgroundDrawable(const Ptr<AR::ArSession>& arSession = nullptr);
 
-			~ArBackgroundDrawable() override { if (m_arSession) ArBackgroundDrawable::Close(); }
+			~ArBackgroundDrawable() override { ArBackgroundDrawable::Close(); }
 
 			void Init(const Ptr<AR::ArSession>& arSession);