From 7a8613c6d6eee7c4ec8d9c9693d2d5a2911ca783 Mon Sep 17 00:00:00 2001
From: alpine9000 <alex.g.brown@gmail.com>
Date: Sat, 2 Apr 2016 08:49:47 +1100
Subject: [PATCH] Double buffered scroll

---
 025.scroll_text/Makefile      |  2 +-
 025.scroll_text/blit.s        | 14 ++++++++------
 025.scroll_text/scroll_text.s | 34 ++++++++++++++++++++++++++++++----
 3 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/025.scroll_text/Makefile b/025.scroll_text/Makefile
index 3f9875a..5a1362c 100644
--- a/025.scroll_text/Makefile
+++ b/025.scroll_text/Makefile
@@ -6,7 +6,7 @@ USERSTACK_ADDRESS=7fffc
 BASE_ADDRESS=4000
 # note: this must be high enough not to conflict with MFMbufE
 
-NUM_COLORS=16
+NUM_COLORS=2
 
 BOOTBLOCK_ASM=alpine_bootblock.s
 OBJS=out/init.o out/utils.o out/image.o out/blitchar.o out/cpu.o out/blit.o
diff --git a/025.scroll_text/blit.s b/025.scroll_text/blit.s
index 890c61c..0e56851 100644
--- a/025.scroll_text/blit.s
+++ b/025.scroll_text/blit.s
@@ -55,15 +55,17 @@ BlitFillColor:
 
 
 BlitScroll:
-	;; kills a0,d1,d2
-	;; a0 - bitplane
+	;; kills a0,a1,d1,d2
+	;; a0 - dest
+	;; a1 - source
 	;; d1 - height
 	;; d2 - ypos
 
-	;; 	movem.l	d2-d5/a0,-(sp)
+	movem.l	d1-d2/a0-a1,-(sp)
 	add.l	d1,d2	;point to end of data for descending mode
 	mulu.w	#BITPLANE_WIDTH_BYTES*SCREEN_BIT_DEPTH,d2
 	add.l	d2,a0
+	add.l	d2,a1
 
 	WaitBlitter
 
@@ -73,8 +75,8 @@ BlitScroll:
 	move.w 	#0,BLTBMOD(a6)
 	move.w 	#0,BLTCMOD(a6)
 	move.w 	#0,BLTDMOD(a6)
-	move.l 	a0,BLTBPTH(a6) 	
-	move.l 	a0,BLTCPTH(a6) 	
+	move.l 	a1,BLTBPTH(a6) 	
+	move.l 	a1,BLTCPTH(a6) 	
 	move.l 	a0,BLTDPTH(a6)
 	move.w	#$0000,BLTAFWM(a6)
 	move.w	#$ffff,BLTALWM(a6)	
@@ -84,6 +86,6 @@ BlitScroll:
 	ori.w	#BITPLANE_WIDTH_WORDS,d1
         move.w	d1,BLTSIZE(a6)
 
-	;; movem.l (sp)+,d2-d5/a0
+	movem.l (sp)+,d1-d2/a0-a1
 	rts
 		
\ No newline at end of file
diff --git a/025.scroll_text/scroll_text.s b/025.scroll_text/scroll_text.s
index 97b1ffd..72adb02 100644
--- a/025.scroll_text/scroll_text.s
+++ b/025.scroll_text/scroll_text.s
@@ -5,7 +5,7 @@
 	xdef	offscreen
 	xdef	copperListBplPtr
 
-Y_POS	equ	100
+Y_POS	equ	8
 	
 byteMap:
 	dc.l	Entry
@@ -33,6 +33,12 @@ Entry:
 	move.w	#SCREEN_HEIGHT,d1
 	move.w	#0,d2		  ; ypos
 	jsr	BlitFillColor
+
+	move.l	offscreen,a0
+	move.l	#BACKGROUND_COLOR,d0
+	move.w	#SCREEN_HEIGHT,d1
+	move.w	#0,d2		  ; ypos
+	jsr	BlitFillColor	
 	
 	WaitBlitter
 	jsr	Init		  ; enable the playfield		
@@ -40,7 +46,8 @@ Entry:
 	lea	text,a3
 MainLoop:		
 	jsr 	WaitVerticalBlank
-	
+
+	jsr	InstallPalette	
 	cmp.l	#8,shiftcounter
 	bne	.shift
 
@@ -55,16 +62,35 @@ MainLoop:
 	move.l	#BITPLANE_WIDTH-16,d0	; xpos
 	move.l	#Y_POS,d1		; ypos
 	move.l	onscreen,a0
+
+	move.l	#Y_POS,d1		; ypos	
+	move.l	#27-1,d3
+.loopBlitChar8:	
 	jsr	BlitChar8
+	add.l	#FONT_HEIGHT+1,d1
+	dbra	d3,.loopBlitChar8
+	
 	move.l	#0,shiftcounter
 .shift:
-	move.l	onscreen,a0
+	move.l	offscreen,a0 	; dest
+	move.l	onscreen,a1	; src
 	move.l	#FONT_HEIGHT,d1
+
 	move.l	#Y_POS,d2
+	move.l	#27-1,d0	
+.blitScrollLoop:
 	jsr	BlitScroll
+	add.l	#FONT_HEIGHT+1,d2
+	dbra	d0,.blitScrollLoop
+
+
 	add.l	#1,shiftcounter
 
-	;; 	jsr	GreyPalette	
+	;; jsr	GreyPalette	
+
+	move.w #$500,COLOR00(a6)
+	
+	jsr	SwitchBuffers			
 	
 	bra	MainLoop