From a3c4beea489a378bcbeac12852498a476b65ada0 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sun, 17 Dec 2017 23:40:52 -0500
Subject: [PATCH] mode7_demo: paramaterize scrolling code

---
 asm_routines/hlin_clearscreen.s | 33 +++++++++++++-
 mode7_demo/mode7_demo.s         | 78 ++++++++++++++++++++++-----------
 2 files changed, 84 insertions(+), 27 deletions(-)

diff --git a/asm_routines/hlin_clearscreen.s b/asm_routines/hlin_clearscreen.s
index cce402d0..46dab7b6 100644
--- a/asm_routines/hlin_clearscreen.s
+++ b/asm_routines/hlin_clearscreen.s
@@ -24,6 +24,31 @@ clear_screens:
 
 	rts
 
+
+clear_screens_notext:
+	;===================================
+	; Clear top/bottom of page 0
+	;===================================
+
+	lda     #$0
+	sta     DRAW_PAGE
+	jsr     clear_top
+	lda	#$0
+	jsr     clear_bottom_a
+
+	;===================================
+	; Clear top/bottom of page 1
+	;===================================
+
+	lda     #$4
+	sta     DRAW_PAGE
+	jsr     clear_top
+	lda	#$0
+	jsr     clear_bottom_a
+
+	rts
+
+
 	;================================
 	; hlin_setup
 	;================================
@@ -156,7 +181,7 @@ clear_top_a:
 
 	sta	COLOR
 
-	; VLIN Y, V2 AT A
+	; HLIN Y, V2 AT A
 
 	lda	#40
 	sta	V2
@@ -177,8 +202,14 @@ clear_top_loop:
 
 	rts
 
+	;=============================
+	; clear_bottom
+	;=============================
 clear_bottom:
 	lda	#$a0	; NORMAL space
+
+clear_bottom_a:
+
 	sta	COLOR
 
 	lda	#40
diff --git a/mode7_demo/mode7_demo.s b/mode7_demo/mode7_demo.s
index bde9fca9..cd6e2d33 100644
--- a/mode7_demo/mode7_demo.s
+++ b/mode7_demo/mode7_demo.s
@@ -4,8 +4,9 @@
 	; Clear screen and setup graphics
 	;================================
 
-	jsr	clear_screens		 ; clear top/bottom of page 0/1
 	jsr     set_gr_page0
+	bit	FULLGR
+	jsr	clear_screens_notext	 ; clear top/bottom of page 0/1
 
 	lda	#$4
 	sta	DRAW_PAGE
@@ -44,7 +45,18 @@ demo_loop:
 ;	lda	#255
 ;	jsr	WAIT
 
-	jsr	scroll
+
+	lda	#>deater_scroll
+	sta	INH
+	lda	#<deater_scroll
+	sta	INL
+
+;	lda	#10
+	lda	#40
+	sta	CV
+
+
+	jsr	gr_scroll
 
 	;=============
 	; Fade out
@@ -74,48 +86,62 @@ scroll_row2	EQU	$8B00
 scroll_row3	EQU	$8C00
 scroll_row4	EQU	$8D00
 
-SCROLL_LENGTH	EQU	$E6
+SCROLL_LENGTH	EQU	$61
+OFFSET		EQU	$62
 
 
+	;========================
+	; scroll some text
+	;========================
+	; RLE compressed data in INL/INH
+	; CV is Y position to display at
 
-scroll:
+gr_scroll:
 	lda	#0
-	sta	ANGLE
+	sta	OFFSET
 
 	;=======================
 	; decompress scroll text
 	;=======================
-	lda	#>deater_scroll
-	sta	INH
-	lda	#<deater_scroll
-	sta	INL
+
 	jsr	decompress_scroll
 
 
 scroll_loop:
 
 	ldx	#0
-	ldy	ANGLE
 
-	lda	DISP_PAGE
-	beq	draw_page2
+	ldy	CV
+	lsr
 
-	lda	#4
+	lda	gr_offsets,Y		; get position
+	sta	sm1+1
+	lda	gr_offsets+2,Y		; get position
+	sta	sm2+1
+	lda	gr_offsets+4,Y		; get position
+	sta	sm3+1
+	lda	gr_offsets+6,Y		; get position
+	sta	sm4+1
+
+
+	iny
+
+	clc
+
+	lda	gr_offsets,Y		; get position
+	adc	DRAW_PAGE
 	sta	sm1+2
+	lda	gr_offsets+2,Y		; get position
+	adc	DRAW_PAGE
 	sta	sm2+2
-	lda	#5
+	lda	gr_offsets+4,Y		; get position
+	adc	DRAW_PAGE
 	sta	sm3+2
+	lda	gr_offsets+6,Y		; get position
+	adc	DRAW_PAGE
 	sta	sm4+2
-	jmp	draw_done
 
-draw_page2:
-	lda	#8
-	sta	sm1+2
-	sta	sm2+2
-	lda	#9
-	sta	sm3+2
-	sta	sm4+2
-draw_done:
+	ldy	OFFSET
 
 draw_loop:
 
@@ -158,16 +184,16 @@ sm4:
 	; loop forever
 	;==================
 	clc
-	lda	ANGLE
+	lda	OFFSET
 	adc	#40
 	cmp	SCROLL_LENGTH
 	bne	blah
 	lda	#0
-	sta	ANGLE
+	sta	OFFSET
 	jmp	scroll_loop
 
 blah:
-	inc	ANGLE
+	inc	OFFSET
 	jmp	scroll_loop						; 3