pbOutData (PLONG) - input
ulPhysAddr
This value tells the caller how many bytes of VRAM (not visible memory) are used for each scan line. For example, an 800-byte visible scan line could be mapped onto a 1024-byte physical scan line.
For example, a 640 x 480 screen would normally return an upper-left corner of (0,0) and a lower-right corner of (639,479).