From fb33832144ce28d614278d92c286e48dc38cfea5 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sun, 17 Sep 2023 22:36:29 -0400
Subject: [PATCH] second: implement VLIN and PLOT

this is so inefficient
---
 demos/second/part18_3d/3d.inc       |  26 +++---
 demos/second/part18_3d/draw_boxes.s | 128 +++++++++++++++++++++++++++-
 2 files changed, 137 insertions(+), 17 deletions(-)

diff --git a/demos/second/part18_3d/3d.inc b/demos/second/part18_3d/3d.inc
index 08918e85..82c65b9a 100644
--- a/demos/second/part18_3d/3d.inc
+++ b/demos/second/part18_3d/3d.inc
@@ -16,21 +16,21 @@ frame15:
 	.byte	SET_COLOR | WHITE
 	.byte	BOX, 4, 6, 35,41
 
-	.byte	SET_COLOR | RED
-	.byte	HLIN,0,39,2
-	.byte	SET_COLOR | DARK_BLUE
-	.byte	HLIN,0,39,3
+;	.byte	SET_COLOR | RED
+;	.byte	HLIN,0,39,2
+;	.byte	SET_COLOR | DARK_BLUE
+;	.byte	HLIN,0,39,3
 
-	.byte	SET_COLOR | RED
-	.byte	HLIN,0,39,12
-	.byte	SET_COLOR | DARK_BLUE
-	.byte	HLIN,0,39,13
+;	.byte	SET_COLOR | RED
+;	.byte	HLIN,0,39,12
+;	.byte	SET_COLOR | DARK_BLUE
+;	.byte	HLIN,0,39,13
 
-	.byte	SET_COLOR | GREEN
-	.byte	BOX,  2,2,10,12		; goes to 6 only top
-	.byte	BOX, 12,3,20,12
-	.byte	BOX, 22,2,30,13		; goes to 6 full
-	.byte	BOX, 32,3,39,13
+;	.byte	SET_COLOR | GREEN
+;	.byte	BOX,  2,2,10,12		; goes to 6 only top
+;	.byte	BOX, 12,3,20,12
+;	.byte	BOX, 22,2,30,13		; goes to 6 full
+;	.byte	BOX, 32,3,39,13
 
 
 
diff --git a/demos/second/part18_3d/draw_boxes.s b/demos/second/part18_3d/draw_boxes.s
index 3b6372ed..8082da27 100644
--- a/demos/second/part18_3d/draw_boxes.s
+++ b/demos/second/part18_3d/draw_boxes.s
@@ -232,6 +232,77 @@ hlin_done:
 	;=================================
 	;=================================
 draw_vlin:
+	iny
+	lda	(INL),Y
+	sta	Y1
+	iny
+	lda	(INL),Y
+	sta	Y2
+	iny
+	lda	(INL),Y
+	sta	X1
+
+
+	lda	Y2
+	lsr
+	; if even, go to one less
+	; else, fine
+	bcs	odd_bottom_vlin
+even_bottom_vlin:
+	sec
+	sbc	#1
+
+odd_bottom_vlin:
+
+	sta	vlin_yend_smc+1
+
+	; see if we start at multiple of two
+
+	lda	Y1
+	lsr
+	tay
+	bcc	even_vlin_start
+
+	; we're odd, need to call PLOT
+
+	jsr	plot_mask_odd
+	iny
+
+
+even_vlin_start:
+
+vlin_yloop:
+	lda	gr_offsets_l,Y
+	sta	vlin_xloop_smc+1
+
+	lda	gr_offsets_h,Y
+	clc
+	adc	DRAW_PAGE
+	sta	vlin_xloop_smc+2
+
+	lda	COLOR
+	ldx	X1
+
+vlin_xloop_smc:
+	sta	$400,X
+
+	iny
+vlin_yend_smc:
+	cpy	#0
+	bcc	vlin_yloop		; less than
+	beq	vlin_yloop		; equal
+
+	; done
+
+	; if Y2 was even we need to fixup and draw one more line
+
+	lda	Y2
+	lsr
+	bcs	definitely_odd_vlin
+
+	jsr	plot_mask_even
+
+definitely_odd_vlin:
 	; done
 
 	lda	#4
@@ -246,15 +317,24 @@ draw_vlin:
 draw_plot:
 	iny
 	lda	(INL),Y
-	tax
+	sta	X1
 
 	iny
 	lda	(INL),Y
+
+;	sta	Y1
+;	lda	Y1
+
+
+	lsr
 	tay
+	bcs	do_plot_mask_odd
+	jsr	plot_mask_even
+	jmp	plot_done
+do_plot_mask_odd:
+	jsr	plot_mask_odd
 
-draw_plot_smc:
-	sta	$400
-
+plot_done:
 
 	; done
 
@@ -306,6 +386,46 @@ draw_hlin_s_xloop_smc:
 
 	rts
 
+	;===================================
+	;===================================
+	; plot common code
+	;===================================
+	;===================================
+	; X1, set up
+	; Y/2 is in Y
+	; call the proper entry point
+	; Y untouched
+
+plot_mask_odd:
+	lda	#$0F
+	.byte	$2C		; bit trick
+plot_mask_even:
+	lda	#$F0
+	sta	MASK
+	eor	#$FF
+	and	COLOR
+	sta	COLOR2
+
+	lda	gr_offsets_l,Y
+	sta	plot_l_smc+1
+	sta	plot_s_smc+1
+
+	lda	gr_offsets_h,Y
+	clc
+	adc	DRAW_PAGE
+	sta	plot_l_smc+2
+	sta	plot_s_smc+2
+
+	ldx	X1
+plot_l_smc:
+	lda	$400,X
+	and	MASK
+	ora	COLOR2
+plot_s_smc:
+	sta	$400,X
+
+	rts
+
 
 .include "gr_fast_clear.s"