Question

After quite some effort, I managed to capture Windows Messages from a third party MFC dll (I asked about that here). To make it short, I had to create a Message-only window with a message loop which captured the third party dll’s messages.

Said Message-only window must remain hidden. And it does, initially, since I pass HWND_MESSAGE to CreateWindowEx and call ShowWindow with SW_HIDE.
However, my C++ dll has some callbacks into managed code. And I noticed that when I perform the user actions that trigger the first of them, a console window appears. And it doesn’t go away until I close my app.

Since the console window has my app’s executable path as its title, I thought that the window was somehow being associated to my app. So I passed NULL to CreateWindowEx’s hInstance parameter, but it didn’t work.

Here’s my Message-only window code:

DWORD WINAPI CDRTech::MessageLoopThread( void * pParams ){
    HWND hwnd;
    MSG mensaje;
    WNDCLASSEX wincl;
    const string windowClass = "DR_TECH_MESSAGE_HANDLER";

    // Window class
    wincl.hInstance = ::GetModuleHandle(NULL);
    wincl.lpszClassName = windowClass.c_str();
    wincl.lpfnWndProc = ::DefWindowProc;
    wincl.style = CS_DBLCLKS;
    wincl.cbSize = sizeof (WNDCLASSEX);
    wincl.hIcon = ::LoadIcon (NULL, IDI_APPLICATION);
    wincl.hIconSm = ::LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = ::LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = NULL;
    wincl.cbClsExtra = 0;
    wincl.cbWndExtra = 0;
    wincl.hbrBackground = ::GetSysColorBrush(COLOR_BACKGROUND);
    if(!::RegisterClassEx(&wincl)){
        ::GetErrorLoggerInstance()->Log( LOG_TYPE_ERROR, "CDRTech", "MessageLoopThread", "Could not register Message Handling Window" );
        return 0;
    }

    //Create Window (hidden)
    hwnd = ::CreateWindowEx(
            0,                      //Default ExStyle
            windowClass.c_str(),    //Window class
            "DRTech",               //Window Title
            WS_OVERLAPPEDWINDOW,    //Default Style
            CW_USEDEFAULT,          //Let Windows decide position
            CW_USEDEFAULT,
            10,                     //Width
            10,                     //Height
            HWND_MESSAGE,           //Message-only window
            NULL,                   //No Menu
            NULL,                   //Handle to application
            NULL                    //Window creation data
    );
    ::ShowWindow( hwnd, SW_HIDE );

    CDRTech* pThis = reinterpret_cast<CDRTech*>( pParams );
    pThis->InitDRTechLibrary();
    //Start message loop
    while(TRUE == GetMessage(&mensaje, NULL, 0, 0)){
        TranslateMessage(&mensaje);
        DispatchMessage(&mensaje);
    }
    return mensaje.wParam;
}

Answer 1

The window you create is not related to the console window you see. Something that you call creates a console window (or you program is marked as a console application in which case the console is created when your application is launched).

Put a breakpoint at AllocConsole() to find who is creating the console.