View difference between Paste ID: 52NwefB9 and D2ArBCLp

 p_HorizLine:
 	.db __HorizLineEnd-$-1
 	ld	de,plotSScreen
 
 x_HorizLineEntry:
 ;; de=buff, hl=x2, (sp)=ret, (sp+2)=x1, (sp+4)=y
 	pop	af
 	pop	bc
 	ld	h,c
 	pop	bc
 	push	af
 
 ;; c=y, de=buff, h=x1, l=x2
 ;; Check if x1 is offscreen left; if so, note and fix it
-	xor	a
+	ld	b,0
 	ld	a,h
-	bit	7,h
+	rla
 	jr	nc,$+3
-	scf
+
 
 ;; carry=x1 offscreen, b=0, c=y, de=buff, h=left-fixed x1, l=x2
-;; carry=x1 offscreen, a=0, b=0, c=y, de=buff, h=left-fixed x1, l=x2
+
 	bit	7,l
 	jr	z,$+4
 	ret	c
 	ld	l,b
 
 ;; b=0, c=y, de=buff, h=left-fixed x1, l=left-fixed x2
-;; a=0, b=0, c=y, de=buff, h=left-fixed x1, l=left-fixed x2
+
 	ld	a,95
 	cp	h
 	jr	nc,$+5
 	cp	l
 	ret	nc
 	ld	h,a
 
 ;; a=95, b=0, c=y, de=buff, h=fixed x1, l=left-fixed x2
 ;; Check if x2 is offscreen right, and if so, fix it
 	cp	l
 	jr	nc,$+3
 	ld	l,a
 
 ;; X Clipping complete; x1 and x2 guaranteed to be onscreen
 ;; a=95, b=0, c=y, de=buff, h=x1, l=x2
 ;; Ensure that x1<=x2
 	ld	a,h
 	cp	l
 	jr	c,$+5
 	ld	a,l
 	ld	l,h
 	ld	h,a
 
 x_HorizLineEntry2:
 ;; a=x1, b=0, c=y, de=buff, h=x1, l=x2
 ;; Abort if y is offscreen, add y*12 to buffer, and add x1/8 to buffer
 ;;   y is rotated left while x1 is rotated right so rra can be used for x1
 	sla	c
 	ret	c
 	rra
 	sla	c
 	ret	c
 	rra
 	ex	de,hl
 	add	hl,bc
 	rra
 	add	hl,bc
 	add	hl,bc
 	ld	c,a
 	add	hl,bc
 
 ;; y no longer needed
 ;; a=x1/8, b=0, c=x1/8, d=x1, e=x2, hl=y*12+(x/8)+buff
 	ld	c,7
 	ld	a,d
 	and	c
 	jr	z,__HorizLineLeft8
 	ld	b,a
 	ld	a,1
 __HorizLineLeftLoop:
 	rrca
-	dec	d
+
 __HorizLineLeft8:
 	dec	a
 	or	(hl)
 	ld	b,a
 	ld	a,d
 	or	c
 	inc	c
-	add	a,c
+
 	jr	c,__HorizLineRight	;???
 __HorizLineMidLoop:
-	jr	c,__HorizLineRight
+
 	inc	hl
 	ld	b,$FF
-	.db	$38			;jr c to skip the first write
+
 	jr	nc,__HorizLineMidLoop
 __HorizLineRight:
 	add	a,c	;???
 	ret	z	;???
 	ld	b,a
 	ld	a,1
-	add	a,c
+
-	ret	z
+
 	djnz	__HorizLineRightLoop
 	dec	a
 	and	b
 	or	(hl)
 	ld	(hl),a
 	ret
 __HorizLineEnd: