The IDirectDraw2::GetCaps method fills in the capabilities of the device driver for the hardware and the hardware-emulation layer (HEL).
HRESULT GetCaps(
LPDDCAPS lpDDDriverCaps,
LPDDCAPS lpDDHELCaps
);
If the method succeeds, the return value is DD_OK.
If the method fails, the return value may be one of the following error values:
DDERR_INVALIDOBJECT |
DDERR_INVALIDPARAMS |
You can only set one of the two parameters to NULL to exclude it. If you set both to NULL the method will fail, returning DDERR_INVALIDPARAMS.