CSECT	"text",0,,2,2


;**********************************************************************
; Math routines for converting HorizPot/VertPot values
; to and from ViewXOffset/ViewYOffset values
; (I don't want to do it in C!)
; Anson Mah
;
; changes for Lettuce-C by Ĝlli
;
; Declarations:
;  extern UWORD xoffset(BYTE), yoffset(BYTE);
;  extern BYTE xpot(UWORD), ypot(UWORD);
;**********************************************************************
;
MAXXOFFSET	equ	$003f
MAXYOFFSET	equ	$001f
HALFBODY	equ	$7ffe	; MAXBODY / 2
;
	xdef	@xoffset
	xdef	@yoffset
	xdef	@xpot
	xdef	@ypot
;
;**********************************************************************
; _xoffset and _yoffset to convert from offset to pot value
;**********************************************************************
;
@xoffset
	move.l	#MAXXOFFSET,d1	; load maximum x offset value
	bra.s	offs		; jump to offset routine
@yoffset
	move.l	#MAXYOFFSET,d1	; load maximum y offset value
;
offs
;	move.l	4(sp),d0        ; get ViewOffset value
; ^^^^ commented due lattice will load directly into D0

	muls	#HALFBODY,d0
	divs	d1,d0		; divide by maximum offset value
	addi.w	#HALFBODY,d0
	rts			; return result in d0
;
;**********************************************************************
; _xpot and _ypot to convert from pot to offset value
;**********************************************************************
;
@xpot
	move.l	#MAXXOFFSET,d1	; load maximum x offset value
	bra.s	pot		; jump to pot routine
@ypot
	move.l	#MAXYOFFSET,d1	; load maximum y offset value

pot
;	move.l	4(sp),d0        ; get pot value
; ^^^^ see abouve

	beq.s	1$
	subi.w	#1,d0		; subtract two if not zero (kludge)
	beq.s	1$
	subi.w	#1,d0
1$	subi.w	#HALFBODY,d0
	muls	d1,d0		; multiply by maximum offset value
	divs	#HALFBODY,d0
	rts			; return result in d0
;
;**********************************************************************
	end