Bitfields for TopView general window position:
Bit(s)	Description	)
 0,1	horizontal position
	00 = current, 01 = center, 10 = left, 11 = right
 2,3	vertical position
	00 = current, 01 = center, 10 = top, 11 = bottom
 4	don't redraw screen if set
 5-7	not used