From the ddraw.h header https://github.com/apitrace/dxsdk/blob/master/Include/ddraw.h
DECLARE_INTERFACE_( IDirectDraw4, IUnknown )
{
/*** IUnknown methods ***/
STDMETHOD(QueryInterface) (THIS_ REFIID riid, LPVOID FAR * ppvObj) PURE; // 0
STDMETHOD_(ULONG,AddRef) (THIS) PURE;
STDMETHOD_(ULONG,Release) (THIS) PURE;
/*** IDirectDraw methods ***/
STDMETHOD(Compact)(THIS) PURE;
STDMETHOD(CreateClipper)(THIS_ DWORD, LPDIRECTDRAWCLIPPER FAR*, IUnknown FAR * ) PURE; // 10
STDMETHOD(CreatePalette)(THIS_ DWORD, LPPALETTEENTRY, LPDIRECTDRAWPALETTE FAR*, IUnknown FAR * ) PURE;
STDMETHOD(CreateSurface)(THIS_ LPDDSURFACEDESC2, LPDIRECTDRAWSURFACE4 FAR *, IUnknown FAR *) PURE;
STDMETHOD(DuplicateSurface)( THIS_ LPDIRECTDRAWSURFACE4, LPDIRECTDRAWSURFACE4 FAR * ) PURE;
STDMETHOD(EnumDisplayModes)( THIS_ DWORD, LPDDSURFACEDESC2, LPVOID, LPDDENUMMODESCALLBACK2 ) PURE; // 20
STDMETHOD(EnumSurfaces)(THIS_ DWORD, LPDDSURFACEDESC2, LPVOID,LPDDENUMSURFACESCALLBACK2 ) PURE;
STDMETHOD(FlipToGDISurface)(THIS) PURE;
STDMETHOD(GetCaps)( THIS_ LPDDCAPS, LPDDCAPS) PURE; // 2c
STDMETHOD(GetDisplayMode)( THIS_ LPDDSURFACEDESC2) PURE;
STDMETHOD(GetFourCCCodes)(THIS_ LPDWORD, LPDWORD ) PURE;
STDMETHOD(GetGDISurface)(THIS_ LPDIRECTDRAWSURFACE4 FAR *) PURE;
STDMETHOD(GetMonitorFrequency)(THIS_ LPDWORD) PURE;
STDMETHOD(GetScanLine)(THIS_ LPDWORD) PURE;
STDMETHOD(GetVerticalBlankStatus)(THIS_ LPBOOL ) PURE;
STDMETHOD(Initialize)(THIS_ GUID FAR *) PURE;
STDMETHOD(RestoreDisplayMode)(THIS) PURE;
STDMETHOD(SetCooperativeLevel)(THIS_ HWND, DWORD) PURE;
STDMETHOD(SetDisplayMode)(THIS_ DWORD, DWORD,DWORD, DWORD, DWORD) PURE;
STDMETHOD(WaitForVerticalBlank)(THIS_ DWORD, HANDLE ) PURE;
/*** Added in the v2 interface ***/
STDMETHOD(GetAvailableVidMem)(THIS_ LPDDSCAPS2, LPDWORD, LPDWORD) PURE;
/*** Added in the V4 Interface ***/
STDMETHOD(GetSurfaceFromDC) (THIS_ HDC, LPDIRECTDRAWSURFACE4 *) PURE;
STDMETHOD(RestoreAllSurfaces)(THIS) PURE;
STDMETHOD(TestCooperativeLevel)(THIS) PURE;
STDMETHOD(GetDeviceIdentifier)(THIS_ LPDDDEVICEIDENTIFIER, DWORD ) PURE;
};