C++ Win32 window background not redrawing

Question

In my attempt to create my own win32 wrapper I have come across this problem. Whenever I resize my window the background doesn't get redrawn ( http://i44.tinypic.com/23k855.png white is supposed to be the background but when I make the window smaller it goes black)

Part of my class:

void Register(  tstring _className,
                    tstring _menuName,
                    WNDPROC w32proc,
                    tstring hIcon,
                    HICON hIconSmall,
                    LPCTSTR hCursor,
                    HBRUSH hBrush=(HBRUSH)GetStockObject(WHITE_BRUSH),
                    UINT windowStyle = CS_HREDRAW | CS_VREDRAW,
                    int classExtraBytes=NULL,
                    int windowExtraBytes=NULL
                    )
    {
        className = _className; 
        menuName = _menuName;

        wcex.cbSize         = sizeof(WNDCLASSEX);
        wcex.style          = windowStyle;
        wcex.lpfnWndProc    = w32proc;
        wcex.cbClsExtra     = classExtraBytes;
        wcex.cbWndExtra     = windowExtraBytes;
        wcex.hInstance      = this->hInst;
        wcex.hIcon          = LoadIcon(this->hInst,hIcon.c_str());
        wcex.hCursor        = LoadCursor(NULL,hCursor);
        wcex.hbrBackground  = hBrush;
        wcex.lpszMenuName   = this->menuName.c_str();
        wcex.lpszClassName  = this->className.c_str();
        wcex.hIconSm        = hIconSmall;

        RegisterClassEx(&wcex);
    }

    bool Create(tstring _windowTitle,
                DWORD windowStyle,
                int width=CW_USEDEFAULT,
                int height=CW_USEDEFAULT,
                int xPos=CW_USEDEFAULT,
                int yPos=CW_USEDEFAULT,
                HWND parent=NULL,
                LPVOID lpParam=NULL,
                HMENU menu=NULL
                )
        {
        windowTitle = _windowTitle;

        handle = CreateWindow(this->className.c_str(), this->windowTitle.c_str(), windowStyle,
                             xPos, yPos, width, height, parent, menu, this->hInst, lpParam);
        if (!this->handle)
            return false;

        Show();
        return true;
    }

    bool Show(int cmd=SW_SHOWNORMAL)
    {
        if( !ShowWindow(this->handle, cmd) || !UpdateWindow(this->handle) )
            return false;
        return true;
    }

my window proc:

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    PAINTSTRUCT ps;
    HDC hdc;

    switch (message)
    {
    case WM_PAINT:
        hdc = BeginPaint(hWnd, &ps);
        EndPaint(hWnd, &ps);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

and how I'm using everything:

mainwin = new Window(hInstance);
mainwin->Register(TEXT("test"),TEXT("test"),WndProc,TEXT("small.ico"),NULL,IDC_ARROW,NULL,NULL,NULL);
mainwin->Create(TEXT("test window"),WS_OVERLAPPEDWINDOW );
mainwin->Show(nCmdShow);
while(mainwin->GetMsg() > 0)
    mainwin->TranslateDispatchMsg();

Some help would be very much appreciated :)

ps: I also tried handling WM_PAIN,WM_SIZE,WM_SIZING messages to call UpdateWindow and/or ShowWindow with no success

David Heffernan David Heffernan · Accepted Answer · 2012-04-11T10:30:22

You are passing NULL to the hBrush parameter of Register. That's why the background is not redrawn when you resize.

I suspect you intended to make use of your optional parameters and calling it like this:

mainwin->Register(TEXT("test"), TEXT("test"), WndProc, TEXT("small.ico"),
    NULL, IDC_ARROW);

C++ Win32 window background not redrawing

1 Answers