classic win32 app with raii style window

main.cpp

#include <Windows.h>
#include <assert.h>
#include <cstdint>
#include <memory>

class main_window;

template <class WndT, class ParamsTuple>
LRESULT CALLBACK main_window_proc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
	if (message == WM_CREATE) {
		::OutputDebugStringW(L"WM_CREATE\n");
		auto cp = reinterpret_cast<LPCREATESTRUCTW>(lParam);
		auto* args_tuple = reinterpret_cast<ParamsTuple*>(cp->lpCreateParams); /// last parameter passed to ::CreateWindow()

		WndT* wnd = std::apply([&wnd, hWnd](auto&&... args) {
			return new WndT(hWnd, std::forward<decltype(args)>(args)...);
		}, std::move(*args_tuple));;

		::SetLastError(0);
		::SetWindowLongPtrW(hWnd, 0, reinterpret_cast<LONG_PTR>(wnd));
		assert(::GetLastError() == 0);
	}

	if (message == WM_DESTROY) {
		::OutputDebugStringW(L"WM_DESTROY\n");

		auto* wnd = reinterpret_cast<WndT*>(::GetWindowLongPtrW(hWnd, 0));
		assert(wnd != nullptr);
		delete wnd;
	}

	/// DefWindowProcW calls DestroyWindow(), which sends WM_DESTROY by default
	return ::DefWindowProcW(hWnd, message, wParam, lParam);
}

class main_window {
public:
	using ParamsTuple = std::tuple<std::unique_ptr<int>&&, float, double&>;

	friend LRESULT CALLBACK main_window_proc<main_window, ParamsTuple>(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);

protected:
	~main_window() {
		::OutputDebugStringW(L"main_window::~main_window()\n");
		::PostQuitMessage(EXIT_SUCCESS);
	}
	main_window(HWND hWnd, std::unique_ptr<int> p1, const float& p2, double& p3) {
		p3 = 1.1111;
		::OutputDebugStringW(L"main_window::main_window()\n");
	}
	main_window(const main_window&) = delete;
	main_window(main_window&&) = delete;

	LRESULT wnd_proc(UINT message, WPARAM wParam, LPARAM lParam) {
		if (message == WM_PAINT) {
			::OutputDebugStringW(L"WM_PAINT\n");
		}
	}
};


int WINAPI wWinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPWSTR lpCmdLine, _In_ int nShowCmd) try {

	static const WNDCLASSEXW wnd_class {
		.cbSize = sizeof(WNDCLASSEXW),
		.style = CS_HREDRAW | CS_VREDRAW,
		.lpfnWndProc = &main_window_proc<main_window, main_window::ParamsTuple>,
		.cbClsExtra = 0,
		.cbWndExtra = sizeof(std::uintptr_t),
		.hInstance = ::GetModuleHandle(NULL),
		.hIcon = NULL,
		.hCursor = ::LoadCursorW(NULL, IDC_ARROW),
		.hbrBackground = NULL,
		.lpszMenuName = NULL,
		.lpszClassName = L"main_window",
		.hIconSm = NULL
	};

	static_assert(sizeof(main_window*) == sizeof(LONG_PTR));

	const ATOM cls = ::RegisterClassExW(&wnd_class);

	/// pass these parameters to main_window_proc
	auto p1 = std::make_unique<int>(42);
	float p2 = 3.14f;
	double p3 = 2.71828;
	main_window::ParamsTuple args_tuple{ std::move(p1), p2, p3 };
	HWND hWnd = ::CreateWindowEx(0, MAKEINTRESOURCEW(cls), L"Main Window", WS_OVERLAPPEDWINDOW | WS_VISIBLE,
		CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, &args_tuple);

	MSG msg;
	BOOL bRet;
	while ((bRet = ::GetMessage(&msg, NULL, 0, 0)) != 0) {
		::TranslateMessage(&msg);
		::DispatchMessage(&msg);
	}

	return static_cast<int>(msg.wParam);
}
catch (...) {
	return -1;
}