Reordering Textures In Nonlocal Display Memory
There are special cases where the driver writer might want to reorder textures in AGP memory to allow more efficient texture management. The DDCAPS2_SYSTONONLOCAL_AS_SYSTOLOCAL flag signals that the driver can support blts from backing surfaces (system memory copy of a surface) to nonlocal video memory using all the same caps that were specified for backing surface memory to local video memory blts.
The DDCAPS2_SYSTONONLOCAL_AS_SYSTOLOCAL flag is valid only if the DDCAPS2_NONLOCALVIDMEMCAPS flag is set. If DDCAPS2_SYSTONONLOCAL_AS_SYSTOLOCAL is set, then the DDCAPS_CANBLTSYSMEM flag must be set by the driver and all the associated backing surface blt caps must be correct. DDCAPS2_SYSTONONLOCAL_AS_SYSTOLOCAL signifies that the backing surface to video memory DDCAPS blt caps also apply to backing surface to nonlocal video memory blts. For example, the dwSVBCaps, dwSVBCKeyCaps, dwSVBFXCaps, and dwSVBRops members of the DDCORECAPS structure are assumed to be filled in correctly. Any blt from a backing surface to nonlocal memory that matches these caps bits is passed to the driver.
Note This feature is intended to enable the driver itself to do efficient reordering of textures. This is not meant to imply that hardware can write into AGP memory. Hardware writing directly into AGP memory is not currently supported.