Windows SDK GDI: How to capture layered windows?

[ovidiucucu]

Q: I have made screen capture using a memory DC and BitBlt function. It works OK except that windows having WS_EX_LAYERED style set do not appear in the resulting bitmap. How to resolve this issue?

A: Simple, we have to pass CAPTUREBLT flag to BitBlt function.

Example:

BOOL CaptureScreen(HBITMAP& hBitmap)
{
    HDC hDCScreen = ::CreateDC(_T("DISPLAY"), NULL, NULL, NULL);
    const int cx = ::GetDeviceCaps(hDCScreen, HORZRES);
    const int cy = ::GetDeviceCaps(hDCScreen, VERTRES);
    HDC hDCMem = ::CreateCompatibleDC(hDCScreen);
    hBitmap = ::CreateCompatibleBitmap(hDCScreen, cx, cy);
    HBITMAP hBmpOld = (HBITMAP)::SelectObject(hDCMem, hBitmap);

    // Note: CAPTUREBLT flag is required to capture layered windows
    DWORD dwRop = SRCCOPY | CAPTUREBLT;
    BOOL bRet = ::BitBlt(hDCMem, 0, 0, cx, cy, hDCScreen, 0, 0, dwRop);

    ::SelectObject(hDCMem, hBmpOld);
    ::DeleteDC(hDCMem);
    ::DeleteDC(hDCScreen);

    return bRet;
}