From afef9457c8ad77e466100a70bd3fa10c8c8d6703 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sun, 28 Mar 2021 18:30:50 -0400
Subject: [PATCH] gr: lines: some size updates

---
 graphics/gr/lines/lines_recurse.s | 22 +++++++++++++---------
 graphics/gr/lines/lines_small.s   | 11 ++++-------
 2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/graphics/gr/lines/lines_recurse.s b/graphics/gr/lines/lines_recurse.s
index 7b2aed89..bdb7f9f7 100644
--- a/graphics/gr/lines/lines_recurse.s
+++ b/graphics/gr/lines/lines_recurse.s
@@ -7,10 +7,12 @@
 .include "zp.inc"
 .include "hardware.inc"
 
-B_X1	= $F0
-B_Y1	= $F1
-B_X2	= $F2
-B_Y2	= $F3
+; 144 -- initial working implementation
+
+;B_X1	= $F0
+;B_Y1	= $F1
+;B_X2	= $F2
+;B_Y2	= $F3
 COUNT	= $F9
 
 X1	=	$1000
@@ -93,20 +95,22 @@ draw_recurse:
 
 	; check if done
 
-	lda	X1,X
-	cmp	MIDX,X
+	lda	MIDX,X
+	cmp	X1,X
 	bne	recurse
 
-	lda	Y1,X
-	cmp	MIDY,X
+	lda	MIDY,X
+	cmp	Y1,X
 	beq	done_draw_line
 
 recurse:
-	; draw( ax, ay, midx, midy);
+	; draw( midx, midy, ax, ay);
+
 	lda	MIDX,X
 	sta	X1+1,X
 	lda	MIDY,X
 	sta	Y1+1,X
+
 	lda	X1,X
 	sta	X2+1,X
 	lda	Y1,X
diff --git a/graphics/gr/lines/lines_small.s b/graphics/gr/lines/lines_small.s
index a1c46f52..04bc76d8 100644
--- a/graphics/gr/lines/lines_small.s
+++ b/graphics/gr/lines/lines_small.s
@@ -20,6 +20,7 @@
 ; 152 -- merge into common_inc
 ; 151 -- share an RTS
 ; 150 -- use X when plotting
+; 148 -- re-arrange do abs (thanks to 42BS)
 
 B_X1	= $F0
 B_Y1	= $F1
@@ -205,23 +206,19 @@ done_line:
 	;	x=1, for Y
 	;=====================================
 do_abs:
+	ldy	#$ff
 	sec
 	lda	B_X1,X
 	sbc	B_X2,X			; A = x1 - x2
 
-	bmi	is_neg
+	bpl	is_pos
 
-	ldy	#$ff
-	bmi	neg_done
-
-is_neg:
 	ldy	#$1
 neg:
 	eor	#$ff
 	clc
 	adc	#1
-
-neg_done:
+is_pos:
 	sty	B_SX,X
 	sta	B_DX,X
 	rts