Listing 5. The CreatePrimary method

function TSpeedDraw.CreatePrimary: Boolean;
var
  SurfaceDesc: TDDSurfaceDesc;
  hr: HResult;
begin
  FillChar(SurfaceDesc, sizeOf(TDDSurfaceDesc), 0);
  SurfaceDesc.dwSize := sizeof(TDDSurfaceDesc);

  if not FUseExclusive then begin
    SurfaceDesc.dwFlags := DDSD_CAPS;
    SurfaceDesc.ddsCaps.dwCaps := DDSCAPS_PRIMARYSURFACE;
  end else begin
    SurfaceDesc.dwFlags := DDSD_CAPS or DDSD_BACKBUFFERCOUNT;
    SurfaceDesc.ddsCaps.dwCaps := DDSCAPS_PRIMARYSURFACE or
                                  DDSCAPS_FLIP or
                                  DDSCAPS_COMPLEX;
    SurfaceDesc.dwBackBufferCount := 1;
  end;

  hr := FDirectDraw.CreateSurface(SurfaceDesc, FPrimarySurface, nil);
  if hr <> DD_OK then
    raise EDDError.CreateFmt('TSpeedDraw.CreatePrimary: %d %s', [hr, GetOleError(hr)])
  else
    Result := True;
end;