Screenshot!

BOOL CALLBACK    DlgProc(HWND, UINT, WPARAM, LPARAM);

int APIENTRY _tWinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPTSTR    lpCmdLine,
                     int       nCmdShow)
{
     // TODO: Place code here.
    return (int)DialogBox(hInstance, MAKEINTRESOURCE(IDD_MAINBOX), NULL, DlgProc);
}


HDC g_hDcBitmap;
HBITMAP g_hBm;
BOOL CALLBACK EnumWindowsProc(HWND hwnd, LPARAM lParam)
{
    RECT rect = {0};
    HDC hDc;
    if (!IsWindowVisible(hwnd))    return TRUE;
    hDc = GetWindowDC(hwnd);
    GetWindowRect(hwnd, &rect);
    BitBlt(g_hDcBitmap, rect.left, rect.top, rect.right, rect.bottom, hDc, 0, 0, SRCCOPY);
    ReleaseDC(hwnd, hDc);
    return TRUE;
}

DWORD WINAPI ThreadSavingScreen(LPVOID lpParam)
{
    HWND hWnd = (HWND)lpParam;
    long lAspect = 0;
    HDC hDc;
    RECT rect = {0};
    ShowWindow(hWnd, SW_HIDE);
    while (IsWindowVisible(hWnd))
        _asm nop;

   
    if (!g_hDcBitmap)
    {
        hDc = GetDC(NULL);
        g_hDcBitmap = CreateCompatibleDC(hDc);
        g_hBm = CreateCompatibleBitmap(hDc, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN));
        SelectObject(g_hDcBitmap, g_hBm);
        ReleaseDC(NULL, hDc);
    }
    else
    {
        SelectObject(g_hDcBitmap, GetStockObject(NULL_PEN));
        Rectangle(g_hDcBitmap, 0, 0, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN));
    }
    EnumWindows(EnumWindowsProc, FALSE);
   
    //save image to the file
    HANDLE hFile = CreateFile("screenshot.bmp", GENERIC_WRITE, FILE_SHARE_WRITE, NULL, CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL, NULL);
    if (hFile != INVALID_HANDLE_VALUE)
    {
        BITMAPFILEHEADER bfh = {0};
        BITMAPINFOHEADER bih = {0};
        BITMAP bm = {0};
        DWORD dwToWrite = 0;
        DWORD dwSizeBuffer = 1;
        LPBYTE lpBuff = NULL;


        GetObject(g_hBm, sizeof(bm), (LPVOID)&bm);
        bih.biSize = sizeof(bih);
        bih.biWidth = bm.bmWidth;
        bih.biHeight = bm.bmHeight;
        bih.biBitCount = bm.bmBitsPixel;
        bih.biPlanes = 1;
       
        dwSizeBuffer = bm.bmWidth * bm.bmHeight * bm.bmBitsPixel / 8;
       
        bfh.bfSize = sizeof(bfh) + sizeof(bih) + dwSizeBuffer;
        bfh.bfOffBits = sizeof(bfh) + sizeof(bih);
        bfh.bfType = 0x4d42;
       
        lpBuff = new BYTE[dwSizeBuffer];
        ZeroMemory((LPVOID)lpBuff, dwSizeBuffer);
       
        GetDIBits(g_hDcBitmap, g_hBm, 0, bm.bmHeight, (LPVOID)lpBuff, (LPBITMAPINFO)&bih, DIB_RGB_COLORS);
       
       
       
        WriteFile(hFile, &bfh, sizeof(bfh), &dwToWrite, NULL);
        WriteFile(hFile, &bih, sizeof(bih), &dwToWrite, NULL);
        WriteFile(hFile, lpBuff, dwSizeBuffer, &dwToWrite, NULL);
        delete []lpBuff;

        CloseHandle(hFile);
    }

   
    InvalidateRect(hWnd, NULL, TRUE);
    ShowWindow(hWnd, SW_SHOW);
    return 0;
}


BOOL CALLBACK DlgProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    PAINTSTRUCT ps;
    HDC hDc;
    switch (message)
    {
    case WM_PAINT:
        hDc = BeginPaint(hWnd, &ps);
        if (g_hDcBitmap)
        {
            SetMapMode(hDc, MM_ANISOTROPIC);
            SetViewportExtEx(hDc, ps.rcPaint.right, ps.rcPaint.bottom, NULL);
            SetWindowExtEx(hDc, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN), NULL);
            BitBlt(hDc, 0, 0, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN), g_hDcBitmap, 0, 0, SRCCOPY);
        }
        EndPaint(hWnd, &ps);
        return TRUE;
    case WM_COMMAND:
        if (wParam == IDC_PTRSCR)
        {
            CreateThread(NULL, 0, ThreadSavingScreen, (LPVOID)hWnd, 0, NULL);
        }
        return TRUE;
    case WM_CLOSE:
        if (g_hDcBitmap)
        {
            DeleteDC(g_hDcBitmap);
            DeleteObject(g_hBm);
        }
        EndDialog(hWnd, 0);
        return TRUE;
    default:
        return FALSE;
    }
}