Video controller system with screen caching

摘要

A graphics controller which performs display list-based video refresh operations and compresses assembled scan lines or portions thereof is disclosed. The graphics controller maintains a virtual display refresh list (VDRL) comprising a plurality of pointers to scan line segments in memory. The graphics controller may also create, maintain, and delete draw display lists (DDLs) that comprise pointers to object display list subroutines (ODLs) that independently draw objects in memory. The ODLs may allocated one or more buffers in memory into which different frames of the objects are drawn. When an ODL has completed executing, the corresponding pointer in the DDL may be updated to point to the buffer location in memory that stores the newly completed object frame. The VDRL is maintained independently (and may be doubled-buffered) and is updated using the DDLs. The video data assembled as the VDRL is executed is output to the display device. The video data may also be compressed and stored into memory. If the underlying graphics objects have not been changed since the previous screen refresh, the compressed video data in memory may be used in lieu of following the corresponding pointers in the VDRL.