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Window creation called from constructor not working

3 posts in this topic

Hi there,
i am trying to implement a little wrapper class for the win32 window api. It works quite nicely, but one problem i cannot seem to solve remains, and it is a quite peculiar one. 
This is the code in the class (only the relevant parts):


LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
    // sort through and find what code to run for the message given
    switch (message)
        // this message is read when the window is closed
        case WM_DESTROY:
            // close the application entirely
            return 0;

    // Handle any messages the switch statement didn't
    return DefWindowProc(hWnd, message, wParam, lParam);

Window::Window(HINSTANCE thisInstance, DirectX::XMINT2 size, wstring title, bool enableFullscreen) :
position(0, 0),
#ifdef UNICODE
title(string(title.begin(), title.end())),
    if (fullscreen)


    UnregisterClass(CLASSNAME, appInstance);

void Window::buildWindow()
    WNDCLASSEX wClass; //window class structur
    wClass.hInstance = this->appInstance;
    wClass.lpszClassName = "Classname";
    wClass.lpfnWndProc = WindowProc;
    wClass.style = CS_HREDRAW | CS_VREDRAW;
    wClass.cbSize = sizeof(WNDCLASSEX);
    wClass.hIcon = NULL;
    wClass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wClass.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
    wClass.lpszMenuName = NULL;
    wClass.hbrBackground = NULL;
    wClass.cbClsExtra = 0;
    wClass.cbWndExtra = 0;
    if (!RegisterClassEx(&wClass))
          Debug::getInstance().log("Faild to create Window Class", EDEBUG_LEVEL::E_ERROR);
          //throw some errors

    this->windowHandle = CreateWindowEx(
        "Dies ist ein Titel", //real window title
        0, 0,
        800, 600,
    if (this->windowHandle == NULL)
         Debug::getInstance().log("CreateWindow failed.", EDEBUG_LEVEL::E_ERROR);

void Window::show()
    ShowWindow(windowHandle, SW_SHOW);

And this is my main loop (in main.cpp)

int WINAPI WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR sCmdLine, int cmdShow)
    Window mainWindow = Window(instance, { 800, 600 }, std::wstring(L"Hier steht ein netter Titel"), false);

    MSG msg;

    while (TRUE) {
        while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {

        if (msg.message == WM_QUIT) {

    return msg.wParam;

Now the problem is: The window does not appear. In fact it gets destroyed immediately after its creation. The reason for this seems to be that i call the 


 method from the constructor of the Window class. If i call the method like a member function directly from the main-loop like 


 right before 


 it works as expected. What is wrong here?


Thanks in advance


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Rule of Three violation.

You're constructing a window, then copying it using the (default) copy constructor and the original window is destroyed.

Change your declaration to this.

Window mainWindow(instance, { 800, 600 }, std::wstring(L"Hier steht ein netter Titel"), false);
and read up on the Rule of Three.



Oh i did not know that. Nice read. Thank you a lot!


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Also msg isn't initialized, and it isn't guaranteed to be set by PeekMessage, so it could happen that msg.message == WM_QUIT by coincidence (in practice you will almost certainly have a WM_CREATE message or some such on the first loop iteration which renders this bug somewhat theoretical).


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