Message only window wrapper for sending notifications to main thread

gistfile1.txt

#pragma once

#include <memory>
#include <type_traits>

class MessageOnlyWindow
{
public:
    MessageOnlyWindow();
    ~MessageOnlyWindow();
    MessageOnlyWindow(const MessageOnlyWindow&) = delete;
    MessageOnlyWindow& operator=(const MessageOnlyWindow&) = delete;

    template<typename T>
    void SendNotifyCallback(T func) 
    {
        void (*f)(UINT_PTR) = [](UINT_PTR param) {
            if constexpr (std::is_function<typename std::remove_pointer<T>::type>::value) {
                auto fun = reinterpret_cast<T>(param);
                (*fun)();
            }
            else {
                auto fun = reinterpret_cast<T*>(param);
                (*fun)();
                delete fun;
            }
        };

        if constexpr (std::is_function<typename std::remove_pointer<T>::type>::value) {
            VERIFY(::SendNotifyMessage(hwnd_, WM_USER + 1, reinterpret_cast<WPARAM>(func), reinterpret_cast<LPARAM>(f)));
        }
        else {
            auto callbackPtr = new T(std::move(func));
            VERIFY(::SendNotifyMessage(hwnd_, WM_USER + 1, reinterpret_cast<WPARAM>(callbackPtr), reinterpret_cast<LPARAM>(f)));
        }
    }
    template<typename T, typename L>
    void SendNotifyCallback(T* ptr, L lam)
    {
        void (*func) (T*) = lam;
        VERIFY(::SendNotifyMessage(hwnd_, WM_USER + 1, reinterpret_cast<WPARAM>(ptr), reinterpret_cast<LPARAM>(func)));
    }

private:
    HWND hwnd_;
};

gistfile2.txt

#include "pch.h"
#include "MessageOnlyWindow.h"

static LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
    if (uMsg == WM_USER + 1) {
        // Handle custom message
        auto func = reinterpret_cast<void (*)(UINT_PTR)>(lParam);
        (*func)(wParam);
        return 0;
    }
    return DefWindowProc(hwnd, uMsg, wParam, lParam);
}

MessageOnlyWindow::MessageOnlyWindow() {
    // Register the window class
    WNDCLASS wc = { 0 };
    wc.lpfnWndProc = WindowProc;
    wc.hInstance = GetModuleHandle(NULL);
    wc.lpszClassName = TEXT("MessageOnlyWindow");

    RegisterClass(&wc);

    // Create the message-only window
    hwnd_ = CreateWindowEx(
        0,                          // Optional window styles
        TEXT("MessageOnlyWindow"),  // Window class name
        NULL,                       // Window name
        0,                          // Window style
        0, 0, 0, 0,                 // Position and size (ignored)
        HWND_MESSAGE,               // Parent window (message-only)
        NULL,                       // Menu
        GetModuleHandle(NULL),      // Instance handle
        NULL                        // Additional application data
    );
    ASSERT(hwnd_ != NULL);
}

MessageOnlyWindow::~MessageOnlyWindow() {
    if (hwnd_) {
        DestroyWindow(hwnd_);
    }
}