Yes, the last parameter of the DrvMovePointer (RECTL *prcl) is always NULL.
the coordinates (upper-left and bottom-right) are correct,
If you want to snatch the screen of your screen, You should insure that it is your surface.
The follow are my debug output in my drivers.
EDesktop: DrvMovePointer( 108:-526) prcl(0)
EDesktop: DrvCopyBits( 0: 6) ( 0: 6) rc( 104:240: 127:266)
EDesktop: DrvCopyBits( 0: 6) ( 0: 6) rc( 0: 0: 23: 26)
EDesktop: DrvCopyBits( 0: 6) ( 0: 6) rc( 97:240: 120:266)
xxxxx@sina.com
Allen