Update example to use type erased polymorphism

src/CMakeLists.txt

@@ -29,7 +29,7 @@ add_executable(
     ${SOURCE_FILES}
 )
 
-target_include_directories(${current_target} PUBLIC ${CMAKE_SOURCE_DIR}/external)
+target_include_directories(${current_target} PUBLIC . ${CMAKE_SOURCE_DIR}/external)
 
 if(MSVC)
 	target_link_libraries(${current_target} PUBLIC opengl32.lib)

src/main.cpp

@@ -14,19 +14,20 @@ auto main() -> int
 	});
 
 	auto renderer = oglsCreateOpenGL({
-		.nativeWindowHandle = window->GetNativeHandle(), 
+		.nativeWindowHandle = GetNativeHandle(window), 
 		.versionMajor = 4, 
 		.versionMinor = 6
 	});
 		
-	while (!window->ShouldClose())
+	while (!ShouldClose(window))
 	{
-		window->PumpMessages();
+		PumpMessages(window);
 
-		renderer->ClearBuffers();
+		ClearBuffers(renderer);
-		renderer->DrawScene();
+		DrawScene(renderer);
-		renderer->SwapBuffers();
+		Present(renderer);
 	}
 
+	Destroy(renderer);
 	return 0;
 }

src/opengl.h

@@ -4,7 +4,6 @@
 
 namespace ogl_starter
 {
-class Window;
 
 struct OpenGLCreateParams
 {
@@ -13,16 +12,60 @@ struct OpenGLCreateParams
 	int versionMinor;
 };
 
+template <typename T>
+concept IsOpenGL = requires(T t) {
+	ClearBuffers(t);
+	Present(t);
+	DrawScene(t);
+};
+
 class OpenGL
 {
 public:
-	virtual ~OpenGL() = default;
+	template <IsOpenGL T>
-	virtual void ClearBuffers() = 0;
+	OpenGL(T&& t)
-	virtual void SwapBuffers() = 0;
+		: self{std::make_unique<model_t<T>>(std::move(t))}
+	{
+	}
 
-	virtual void DrawScene() = 0;
+	~OpenGL() = default;
+	OpenGL(OpenGL&&) = default;
+	OpenGL& operator=(OpenGL&&) = default;
+	OpenGL(const OpenGL&) = delete;
+	OpenGL operator=(const OpenGL&) = delete;
+
+	friend void ClearBuffers(const OpenGL& opengl) { opengl.self->ClearBuffers_(); }
+	friend void Present(const OpenGL& opengl) { opengl.self->Present_(); }
+	friend void DrawScene(const OpenGL& opengl) { opengl.self->DrawScene_(); }
+	friend void Destroy(const OpenGL& opengl) { opengl.self->Destroy_(); }
+
+private:
+	struct concept_t
+	{
+		virtual ~concept_t() = default;
+
+		virtual void ClearBuffers_() const = 0;
+		virtual void Present_() const = 0;
+		virtual void DrawScene_() const = 0;
+		virtual void Destroy_() const = 0;
+	};
+
+	template <typename T>
+	struct model_t final : concept_t
+	{
+		model_t(T&& data) : m_data(std::move(data)) {}
+
+		virtual void ClearBuffers_() const override { ClearBuffers(m_data); }
+		virtual void Present_() const override { Present(m_data); }
+		virtual void DrawScene_() const override { DrawScene(m_data); }
+		virtual void Destroy_() const override { Destroy(m_data); }
+
+		T m_data;
+	};
+
+	std::unique_ptr<concept_t> self;
 };
 
 } // namespace ogl_starter
 
-std::unique_ptr<ogl_starter::OpenGL> oglsCreateOpenGL(ogl_starter::OpenGLCreateParams params);
+ogl_starter::OpenGL oglsCreateOpenGL(ogl_starter::OpenGLCreateParams params);

src/platform/null_opengl.cpp

@@ -1,26 +1,29 @@
-#include "../opengl.h"
+#include "opengl.h"
 
 namespace ogl_starter
 {
-class NullOpenGLImpl final : public OpenGL
+struct NullOpenGLImpl final
 {
-public:
-	NullOpenGLImpl() = default;
-	~NullOpenGLImpl() override = default;
-	NullOpenGLImpl(const NullOpenGLImpl&) = delete;
-	NullOpenGLImpl& operator=(const NullOpenGLImpl&) = delete;
-
-	NullOpenGLImpl(NullOpenGLImpl&&) = default;
-	NullOpenGLImpl& operator=(NullOpenGLImpl&&) = default;
-
-	void ClearBuffers() override {}
-	void SwapBuffers() override {}
-	void DrawScene() override {}
 };
+
+void ClearBuffers(const NullOpenGLImpl&)
+{
+}
+
+void Present(const NullOpenGLImpl&)
+{
+}
+
+void DrawScene(const NullOpenGLImpl&)
+{
+}
+
+void Destroy(const NullOpenGLImpl&)
+{
+}
 } // namespace ogl_starter
 
-std::unique_ptr<ogl_starter::OpenGL> oglsCreateOpenGL(ogl_starter::OpenGLCreateParams)
+ogl_starter::OpenGL oglsCreateOpenGL(ogl_starter::OpenGLCreateParams)
 {
-	auto result = std::make_unique<ogl_starter::NullOpenGLImpl>();
+	return ogl_starter::NullOpenGLImpl{};
-	return result;
 }

src/platform/null_window.cpp

@@ -1,29 +1,29 @@
-#include "../window.h"
+#include "window.h"
 
 namespace ogl_starter
 {
 
-class NullWindowImpl final : public Window
+struct NullWindowImpl final
 {
-public:
-	NullWindowImpl() = default;
-	~NullWindowImpl() override = default;
-
-	NullWindowImpl(NullWindowImpl&&) = delete;
-	NullWindowImpl& operator=(NullWindowImpl&&) = delete;
-	NullWindowImpl(const NullWindowImpl&) = delete;
-	NullWindowImpl& operator=(const NullWindowImpl&) = delete;
-
-	void PumpMessages() override {}
-	bool ShouldClose() const override { return false; }
-	void* GetNativeHandle() const override { return nullptr; }
-
 };
 
-} // namespace starter_window
+void PumpMessages(NullWindowImpl&)
-
-std::unique_ptr<ogl_starter::Window> oglsCreateWindow(ogl_starter::WindowCreateParams)
 {
-	auto result = std::make_unique<ogl_starter::NullWindowImpl>();
+}
-	return result;
+
+bool ShouldClose(const NullWindowImpl&)
+{
+	return false;
+}
+
+void* GetNativeHandle(const NullWindowImpl&)
+{
+	return nullptr;
+}
+
+} // namespace ogl_starter
+
+ogl_starter::Window oglsCreateWindow(ogl_starter::WindowCreateParams)
+{
+	return ogl_starter::NullWindowImpl{};
 }

src/platform/win32_opengl.cpp

@@ -1,10 +1,13 @@
-#include "../opengl.h"
+#include "opengl.h"
-#include "../window.h"
 
 #ifndef WIN32_LEAN_AND_MEAN
 #define WIN32_LEAN_AND_MEAN
 #endif
 
+#ifndef NOMINMAX
+#define NOMINMAX
+#endif
+
 #include <Windows.h>
 #include <GL/GL.h>
 #include "GL/glext.h"
@@ -18,11 +21,10 @@ static T LoadGLProc(const char* functionName)
 }
 
 #define VALIDATEGLPROC(proc) \
-	if (!proc) \
+if (!proc) \
-	{ \
+{ \
 	MessageBox(NULL, "Failed to load " #proc, "Fatal Error", MB_ICONERROR); \
-		return false; \
+}
-	}
 
 static PFNWGLGETEXTENSIONSSTRINGEXTPROC wglGetExtensionsStringEXT;
 static PFNWGLCHOOSEPIXELFORMATARBPROC wglChoosePixelFormatARB;
@@ -87,203 +89,7 @@ static void LoadGLFunctions()
 	glBufferData = LoadGLProc<PFNGLBUFFERDATAPROC>("glBufferData");
 }
 
-class Win32OpenGLImpl final : public OpenGL
+static std::pair<GLuint, GLuint> InitTriangleResources()
-{
-public:
-	Win32OpenGLImpl();
-	~Win32OpenGLImpl() override;
-	Win32OpenGLImpl(const Win32OpenGLImpl&) = delete;
-	Win32OpenGLImpl& operator=(const Win32OpenGLImpl&) = delete;
-
-	Win32OpenGLImpl(Win32OpenGLImpl&&) = default;
-	Win32OpenGLImpl& operator=(Win32OpenGLImpl&&) = default;
-
-	bool init(OpenGLCreateParams params);
-
-	void ClearBuffers() override;
-	void SwapBuffers() override;
-	void DrawScene() override;
-
-private:
-	void initTriangleResources();
-
-	HDC m_deviceContext;
-	HGLRC m_renderingContext;
-	HWND m_windowHandle;
-
-	//TEMP STUFF
-	GLuint VAO;
-	GLuint shaderProgram;
-};
-
-Win32OpenGLImpl::Win32OpenGLImpl()
-	: m_deviceContext(nullptr)
-	, m_renderingContext(nullptr)
-	, m_windowHandle(nullptr)
-	, VAO(0)
-	, shaderProgram(0)
-{
-}
-
-Win32OpenGLImpl::~Win32OpenGLImpl()
-{
-	wglMakeCurrent(nullptr, nullptr);
-	wglDeleteContext(m_renderingContext);
-}
-
-bool Win32OpenGLImpl::init(OpenGLCreateParams params)
-{
-	m_windowHandle = static_cast<HWND>(params.nativeWindowHandle);
-	HINSTANCE hInstance = GetModuleHandle(NULL);
-
-	HWND dummyWindow = [hInstance]() -> HWND 
-	{
-		WNDCLASSEX wcex;
-		ZeroMemory(&wcex, sizeof(wcex));
-		wcex.cbSize = sizeof(wcex);
-		wcex.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
-		wcex.lpfnWndProc = DefWindowProc;
-		wcex.hInstance = hInstance;
-		wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
-		wcex.lpszClassName = "DummyWNDClass";
-
-		if (RegisterClassEx(&wcex) == 0)
-		{
-			MessageBox(NULL, "registerClass() failed.", "Fatal Error", MB_ICONERROR);
-			return false;
-		}
-
-		return CreateWindow(
-			wcex.lpszClassName, "Dummy Window",
-			WS_OVERLAPPEDWINDOW,
-			0, 0,
-			1, 1,
-			nullptr, nullptr,
-			hInstance, nullptr);
-
-	}();
-	
-	HDC dummyDC = GetDC(dummyWindow);
-
-	PIXELFORMATDESCRIPTOR dummyPFD = {};
-	dummyPFD.nSize = sizeof(dummyPFD);
-	dummyPFD.nVersion = 1;
-	dummyPFD.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
-	dummyPFD.iPixelType = PFD_TYPE_RGBA;
-	dummyPFD.cColorBits = 32;
-	dummyPFD.cAlphaBits = 8;
-	dummyPFD.cDepthBits = 24;
-	dummyPFD.iLayerType = PFD_MAIN_PLANE;
-
-	const int dummyPFDID = ChoosePixelFormat(dummyDC, &dummyPFD);
-	if (dummyPFDID == 0)
-	{
-		MessageBox(nullptr, "ChoosePixelFormat() failed.", "Fatal Error", MB_ICONERROR);
-		return false;
-	}
-
-	if (SetPixelFormat(dummyDC, dummyPFDID, &dummyPFD) == false)
-	{
-		MessageBox(nullptr, "SetPixelFormat() failed.", "Fatal Error", MB_ICONERROR);
-		return false;
-	}
-
-	HGLRC dummyRC = wglCreateContext(dummyDC);
-
-	if (dummyRC == 0)
-	{
-		MessageBox(nullptr, "wglCreateContext() failed.", "Fatal Error", MB_ICONERROR);
-		return false;
-	}
-
-	if (wglMakeCurrent(dummyDC, dummyRC) == false)
-	{
-		MessageBox(nullptr, "wglMakeCurrent() failed.", "Fatal Error", MB_ICONERROR);
-		return false;
-	}
-
-	wglChoosePixelFormatARB = LoadGLProc<PFNWGLCHOOSEPIXELFORMATARBPROC>("wglChoosePixelFormatARB");
-	VALIDATEGLPROC(wglChoosePixelFormatARB);
-
-	wglCreateContextAttribsARB = LoadGLProc<PFNWGLCREATECONTEXTATTRIBSARBPROC>("wglCreateContextAttribsARB");
-	VALIDATEGLPROC(wglCreateContextAttribsARB);
-
-	m_deviceContext = GetDC(m_windowHandle);
-
-	const int pixelAttribs[] = {
-		WGL_DRAW_TO_WINDOW_ARB, GL_TRUE,
-		WGL_SUPPORT_OPENGL_ARB, GL_TRUE,
-		WGL_DOUBLE_BUFFER_ARB, GL_TRUE,
-		WGL_PIXEL_TYPE_ARB, WGL_TYPE_RGBA_ARB,
-		WGL_ACCELERATION_ARB, WGL_FULL_ACCELERATION_ARB,
-		WGL_COLOR_BITS_ARB, 32,
-		WGL_ALPHA_BITS_ARB, 8,
-		WGL_DEPTH_BITS_ARB, 24,
-		WGL_STENCIL_BITS_ARB, 8,
-		WGL_SAMPLE_BUFFERS_ARB, GL_TRUE,
-		WGL_SAMPLES_ARB, 4,
-		0};
-
-	int pixelFormatID;
-	UINT numFormats;
-	const bool status = wglChoosePixelFormatARB(m_deviceContext, pixelAttribs, NULL, 1, &pixelFormatID, &numFormats);
-
-	if (status == false || numFormats == 0)
-	{
-		MessageBox(nullptr, "wglChoosePixelFormatARB() failed.", "Fatal Error", MB_ICONERROR);
-		return false;
-	}
-
-	PIXELFORMATDESCRIPTOR PFD;
-	DescribePixelFormat(m_deviceContext, pixelFormatID, sizeof(PFD), &PFD);
-	SetPixelFormat(m_deviceContext, pixelFormatID, &PFD);
-
-	const int major_min = 4, minor_min = 6;
-	const int contextAttribs[] = {
-		WGL_CONTEXT_MAJOR_VERSION_ARB, major_min,
-		WGL_CONTEXT_MINOR_VERSION_ARB, minor_min,
-		WGL_CONTEXT_PROFILE_MASK_ARB, WGL_CONTEXT_CORE_PROFILE_BIT_ARB,
-		WGL_CONTEXT_LAYER_PLANE_ARB, 0,
-		WGL_CONTEXT_FLAGS_ARB, WGL_CONTEXT_DEBUG_BIT_ARB,
-		0};
-
-	m_renderingContext = wglCreateContextAttribsARB(m_deviceContext, 0, contextAttribs);
-	if (m_renderingContext == nullptr)
-	{
-		MessageBox(nullptr, "wglCreateContextAttribsARB() failed.", "Fatal Error", MB_ICONERROR);
-		return false;
-	}
-
-	wglMakeCurrent(nullptr, nullptr);
-	wglDeleteContext(dummyRC);
-	ReleaseDC(dummyWindow, dummyDC);
-	DestroyWindow(dummyWindow);
-
-	if (!wglMakeCurrent(m_deviceContext, m_renderingContext))
-	{
-		MessageBox(nullptr, "wglMakeCurrent() failed.", "Fatal Error", MB_ICONERROR);
-		return false;
-	}
-
-	LoadGLFunctions();
-
-	initTriangleResources();
-
-	return true;
-}
-
-void Win32OpenGLImpl::ClearBuffers()
-{
-	glClearColor(0.129f, 0.586f, 0.949f, 1.0f);
-	glClear(GL_COLOR_BUFFER_BIT);
-}
-
-void Win32OpenGLImpl::SwapBuffers()
-{
-	::SwapBuffers(m_deviceContext);
-}
-
-void Win32OpenGLImpl::initTriangleResources()
 {
 	float vertices[] = {
 		0.5f, 0.5f, 0.0f,
@@ -297,6 +103,7 @@ void Win32OpenGLImpl::initTriangleResources()
 		1, 2, 3
 	};
 
+	GLuint VAO;
 	glGenVertexArrays(1, &VAO);
 	glBindVertexArray(VAO);
 
@@ -356,7 +163,7 @@ void Win32OpenGLImpl::initTriangleResources()
 		printf("Fragment Shader Compilation Failed\n %s\n", infoLog);
 	}
 
-	shaderProgram = glCreateProgram();
+	GLuint shaderProgram = glCreateProgram();
 	glAttachShader(shaderProgram, VS);
 	glAttachShader(shaderProgram, FS);
 	glLinkProgram(shaderProgram);
@@ -372,22 +179,179 @@ void Win32OpenGLImpl::initTriangleResources()
 	glDeleteShader(VS);
 	glDeleteShader(FS);
 
+	return {VAO, shaderProgram};
+ }
+
+struct Win32OpenGLImpl final
+{
+	HDC m_deviceContext;
+	HGLRC m_renderingContext;
+	HWND m_windowHandle;
+
+	GLuint VAO;
+	GLuint shaderProgram;
+};
+
+void ClearBuffers(const Win32OpenGLImpl&)
+{
+	glClearColor(0.129f, 0.586f, 0.949f, 1.0f);
+	glClear(GL_COLOR_BUFFER_BIT);
 }
 
-void Win32OpenGLImpl::DrawScene()
+void Present(const Win32OpenGLImpl& opengl)
+{
+	SwapBuffers(opengl.m_deviceContext);
+}
+
+void DrawScene(const Win32OpenGLImpl&)
 {
 	glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr);
 }
 
+void Destroy(const Win32OpenGLImpl& opengl)
+{
+	glDeleteShader(opengl.shaderProgram);
+	wglMakeCurrent(nullptr, nullptr);
+	wglDeleteContext(opengl.m_renderingContext);
+}
 } // namespace ogl_starter
 
-std::unique_ptr<ogl_starter::OpenGL> oglsCreateOpenGL(ogl_starter::OpenGLCreateParams params)
+ogl_starter::OpenGL oglsCreateOpenGL(ogl_starter::OpenGLCreateParams params)
 {
-	auto result = std::make_unique<ogl_starter::Win32OpenGLImpl>();
+	auto hWnd = static_cast<HWND>(params.nativeWindowHandle);
-	if (!result->init(params))
+	auto hInstance = GetModuleHandle(NULL);
+
+	HWND dummyWindow = [hInstance]() -> HWND
 	{
-		result = nullptr;
+		WNDCLASSEX wcex;
+		ZeroMemory(&wcex, sizeof(wcex));
+		wcex.cbSize = sizeof(wcex);
+		wcex.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
+		wcex.lpfnWndProc = DefWindowProc;
+		wcex.hInstance = hInstance;
+		wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
+		wcex.lpszClassName = "DummyWNDClass";
+
+		if (RegisterClassEx(&wcex) == 0)
+		{
+			MessageBox(NULL, "registerClass() failed.", "Fatal Error", MB_ICONERROR);
+			return nullptr;
 		}
 
-	return result;
+		return CreateWindow(
+			wcex.lpszClassName, "Dummy Window",
+			WS_OVERLAPPEDWINDOW,
+			0, 0,
+			1, 1,
+			nullptr, nullptr,
+			hInstance, nullptr);
+	}();
+
+	HDC dummyDC = GetDC(dummyWindow);
+
+	PIXELFORMATDESCRIPTOR dummyPFD = {};
+	dummyPFD.nSize = sizeof(dummyPFD);
+	dummyPFD.nVersion = 1;
+	dummyPFD.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
+	dummyPFD.iPixelType = PFD_TYPE_RGBA;
+	dummyPFD.cColorBits = 32;
+	dummyPFD.cAlphaBits = 8;
+	dummyPFD.cDepthBits = 24;
+	dummyPFD.iLayerType = PFD_MAIN_PLANE;
+
+	const int dummyPFDID = ChoosePixelFormat(dummyDC, &dummyPFD);
+	if (dummyPFDID == 0)
+	{
+		MessageBox(nullptr, "ChoosePixelFormat() failed.", "Fatal Error", MB_ICONERROR);
+	}
+
+	if (SetPixelFormat(dummyDC, dummyPFDID, &dummyPFD) == false)
+	{
+		MessageBox(nullptr, "SetPixelFormat() failed.", "Fatal Error", MB_ICONERROR);
+	}
+
+	HGLRC dummyRC = wglCreateContext(dummyDC);
+
+	if (dummyRC == 0)
+	{
+		MessageBox(nullptr, "wglCreateContext() failed.", "Fatal Error", MB_ICONERROR);
+	}
+
+	if (wglMakeCurrent(dummyDC, dummyRC) == false)
+	{
+		MessageBox(nullptr, "wglMakeCurrent() failed.", "Fatal Error", MB_ICONERROR);
+	}
+
+	wglChoosePixelFormatARB = LoadGLProc<PFNWGLCHOOSEPIXELFORMATARBPROC>("wglChoosePixelFormatARB");
+	VALIDATEGLPROC(wglChoosePixelFormatARB);
+
+	wglCreateContextAttribsARB = LoadGLProc<PFNWGLCREATECONTEXTATTRIBSARBPROC>("wglCreateContextAttribsARB");
+	VALIDATEGLPROC(wglCreateContextAttribsARB);
+
+	auto deviceContext = GetDC(hWnd);
+
+	const int pixelAttribs[] = {
+		WGL_DRAW_TO_WINDOW_ARB, GL_TRUE,
+		WGL_SUPPORT_OPENGL_ARB, GL_TRUE,
+		WGL_DOUBLE_BUFFER_ARB, GL_TRUE,
+		WGL_PIXEL_TYPE_ARB, WGL_TYPE_RGBA_ARB,
+		WGL_ACCELERATION_ARB, WGL_FULL_ACCELERATION_ARB,
+		WGL_COLOR_BITS_ARB, 32,
+		WGL_ALPHA_BITS_ARB, 8,
+		WGL_DEPTH_BITS_ARB, 24,
+		WGL_STENCIL_BITS_ARB, 8,
+		WGL_SAMPLE_BUFFERS_ARB, GL_TRUE,
+		WGL_SAMPLES_ARB, 4,
+		0};
+
+	int pixelFormatID;
+	UINT numFormats;
+	const bool status = wglChoosePixelFormatARB(deviceContext, pixelAttribs, NULL, 1, &pixelFormatID, &numFormats);
+
+	if (status == false || numFormats == 0)
+	{
+		MessageBox(nullptr, "wglChoosePixelFormatARB() failed.", "Fatal Error", MB_ICONERROR);
+	}
+
+	PIXELFORMATDESCRIPTOR PFD;
+	DescribePixelFormat(deviceContext, pixelFormatID, sizeof(PFD), &PFD);
+	SetPixelFormat(deviceContext, pixelFormatID, &PFD);
+
+	const int major_min = 4, minor_min = 6;
+	const int contextAttribs[] = {
+		WGL_CONTEXT_MAJOR_VERSION_ARB, major_min,
+		WGL_CONTEXT_MINOR_VERSION_ARB, minor_min,
+		WGL_CONTEXT_PROFILE_MASK_ARB, WGL_CONTEXT_CORE_PROFILE_BIT_ARB,
+		WGL_CONTEXT_LAYER_PLANE_ARB, 0,
+		WGL_CONTEXT_FLAGS_ARB, WGL_CONTEXT_DEBUG_BIT_ARB,
+		0};
+
+	auto renderingContext = wglCreateContextAttribsARB(deviceContext, 0, contextAttribs);
+	if (renderingContext == nullptr)
+	{
+		MessageBox(nullptr, "wglCreateContextAttribsARB() failed.", "Fatal Error", MB_ICONERROR);
+	}
+
+	wglMakeCurrent(nullptr, nullptr);
+	wglDeleteContext(dummyRC);
+	ReleaseDC(dummyWindow, dummyDC);
+	DestroyWindow(dummyWindow);
+
+	if (!wglMakeCurrent(deviceContext, renderingContext))
+	{
+		MessageBox(nullptr, "wglMakeCurrent() failed.", "Fatal Error", MB_ICONERROR);
+	}
+
+	ogl_starter::LoadGLFunctions();
+	auto[VAO, shaderProgram] = ogl_starter::InitTriangleResources();
+
+	auto result = ogl_starter::Win32OpenGLImpl(
+		deviceContext,
+		renderingContext,
+		hWnd,
+		VAO,
+		shaderProgram
+	);
+
+	return std::move(result);
 }

src/platform/win32_window.cpp

@@ -1,4 +1,4 @@
-#include "../window.h"
+#include "window.h"
 
 #ifndef NOMINMAX
 #define NOMINMAX
@@ -23,56 +23,72 @@ static LRESULT CALLBACK WindowProc(HWND window, UINT message, WPARAM wParam, LPA
 		default:
 			return DefWindowProc(window, message, wParam, lParam);
 	}
-
 	return 0;
 }
 
 namespace ogl_starter
 {
 
-class Win32WindowImpl final : public Window
+struct Win32WindowImpl final
 {
-public:
+	HINSTANCE m_hInstance;
-	Win32WindowImpl();
+	HWND m_hWnd;
-
-	Win32WindowImpl(const Win32WindowImpl&) = delete;
-	Win32WindowImpl& operator=(const Win32WindowImpl&) = delete;
-
-	bool init(WindowCreateParams params);
-	void PumpMessages() override;
-	bool ShouldClose() const override;
-	void* GetNativeHandle() const override;
-
-	HINSTANCE hInstance;
-	HWND hWnd;
 	bool m_close;
 };
 
-Win32WindowImpl::Win32WindowImpl()
+void PumpMessages(Win32WindowImpl& window)
-	: hInstance(GetModuleHandle(NULL))
-	, hWnd(nullptr)
-	, m_close(false)
 {
+	MSG message = {};
+	if (GetMessage(&message, NULL, 0, 0) != 0)
+	{
+		TranslateMessage(&message);
+		DispatchMessage(&message);
+	}
+	else
+	{
+		// GetMessage returned WM_QUIT
+		window.m_close = true;
+	}
 }
 
-bool Win32WindowImpl::init(WindowCreateParams params)
+bool ShouldClose(const Win32WindowImpl& window)
 {
+	return window.m_close;
+}
+
+void* GetNativeHandle(const Win32WindowImpl& window)
+{
+	return static_cast<void*>(window.m_hWnd);
+}
+} // namespace ogl_starter
+
+ogl_starter::Window oglsCreateWindow(ogl_starter::WindowCreateParams params)
+{
+	const char className[] = "Win32WindowImpl";
+	HINSTANCE hInstance = GetModuleHandle(NULL);
+	ogl_starter::Win32WindowImpl result = {
+		.m_hInstance = nullptr,
+		.m_hWnd = nullptr,
+		.m_close = true};
+
 	WNDCLASSEX wc = {};
+
 	wc.cbSize = sizeof(WNDCLASSEX);
 	wc.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
 	wc.lpfnWndProc = WindowProc;
 	wc.hInstance = hInstance;
+	wc.lpszClassName = className;
 	wc.hCursor = LoadCursor(NULL, IDC_ARROW);
-	wc.lpszClassName = "WindowClass";
 
-	if (RegisterClassEx(&wc) == NULL)
+	if (RegisterClassEx(&wc) == 0)
 	{
-		MessageBox(nullptr, "Call to RegisterClass failed", NULL, MB_OK);
+		MessageBox(nullptr, "Call to RegisterClass failed", "Fatal Error", MB_OK);
-		return false;
+		return result;
 	}
 
-	hWnd = CreateWindow(
+	HWND window = CreateWindowEx(
-		wc.lpszClassName,
+		0,
+		className,
 		params.name,
 		WS_OVERLAPPEDWINDOW,
 		params.x, params.y, params.width, params.height,
@@ -81,49 +97,17 @@ bool Win32WindowImpl::init(WindowCreateParams params)
 		hInstance,
 		nullptr);
 
-	if (hWnd == nullptr)
+	if (window == nullptr)
 	{
-		MessageBox(nullptr, "Call to CreateWindow failed", nullptr, MB_OK);
+		MessageBox(nullptr, "Call to CreateWindow failed", "Fatal Error", MB_OK);
-		return false;
+		return result;
 	}
 
-	ShowWindow(hWnd, SW_SHOW);
+	ShowWindow(window, SW_SHOW);
-	return true;
-}
 
-void Win32WindowImpl::PumpMessages()
+	result.m_hInstance = hInstance;
-{
+	result.m_hWnd = window;
-	MSG msg = {};
+	result.m_close = false;
-	while (PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE))
-	{
-		if (msg.message == WM_QUIT)
-		{
-			m_close = true;
-		}
-
-		TranslateMessage(&msg);
-		DispatchMessage(&msg);
-	}
-}
-
-bool Win32WindowImpl::ShouldClose() const
-{
-	return m_close;
-}
-
-void* Win32WindowImpl::GetNativeHandle() const
-{
-	return static_cast<void*>(hWnd);
-}
-} // namespace ogl_starter
-
-std::unique_ptr<ogl_starter::Window> oglsCreateWindow(ogl_starter::WindowCreateParams params)
-{
-	auto result = std::make_unique<ogl_starter::Win32WindowImpl>();
-	if (result->init(params) == false)
-	{
-		result = nullptr;
-	}
 
 	return result;
 }

src/window.h

@@ -14,21 +14,56 @@ struct WindowCreateParams
 	const char* name;
 };
 
+template <typename T>
+concept IsWindow = requires(T t) {
+	PumpMessages(t);
+	ShouldClose(t);
+	GetNativeHandle(t);
+};
+
 class Window
 {
 public:
-	virtual ~Window() = default;
+	template <IsWindow T>
-	virtual void PumpMessages() = 0;
+	Window(T&& t)
-	virtual bool ShouldClose() const = 0;
+		: self{std::make_unique<model_t<T>>(std::move(t))}
-	virtual void* GetNativeHandle() const = 0;
-
-	template< typename T >
-	T NativeHandle() const
 	{
-		return static_cast<T>(GetNativeHandle());
 	}
+
+	~Window() = default;
+	Window(Window&&) = default;
+	Window& operator=(Window&&) = default;
+	Window(const Window&) = delete;
+	Window operator=(const Window&) = delete;
+
+	friend void PumpMessages(Window& window) { window.self->PumpMessages_(); }
+	friend bool ShouldClose(const Window& window) { return window.self->ShouldClose_(); }
+	friend void* GetNativeHandle(const Window& window) { return window.self->GetNativeHandle_(); }
+
+private:
+	struct concept_t
+	{
+		virtual ~concept_t() = default;
+		virtual void PumpMessages_() = 0;
+		virtual bool ShouldClose_() const = 0;
+		virtual void* GetNativeHandle_() const = 0;
+	};
+
+	template <typename T>
+	struct model_t final : concept_t
+	{
+		model_t(T&& data) : m_data(std::move(data)) {}
+
+		virtual void PumpMessages_() override { PumpMessages(m_data); }
+		virtual bool ShouldClose_() const override { return ShouldClose(m_data); }
+		virtual void* GetNativeHandle_() const override { return GetNativeHandle(m_data); }
+
+		T m_data;
+	};
+
+	std::unique_ptr<concept_t> self;
 };
 
-}
+} // namespace starter_window
 
-std::unique_ptr<ogl_starter::Window> oglsCreateWindow(ogl_starter::WindowCreateParams params);
+ogl_starter::Window oglsCreateWindow(ogl_starter::WindowCreateParams params);