Mode 13 and Surface Capabilities

When DirectDraw calls an application's EnumModesCallback callback function, the ddsCaps member of the associated DDSURFACEDESC structure contains flags that reflect the mode being enumerated. You can expect DDSCAPS_MODEX for a Mode X mode or DDSCAPS_STANDARDVGAMODE for Mode 13. These flags are mutually exclusive. If neither of these bits is set, then the mode is a linear accelerated mode. This behavior also applies to the flags retrieved by the IDirectDraw2::GetDisplayMode method.