From c1e0bfa0c9644a01d1a59f8933fe2931817d1d70 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Mon, 31 Aug 2020 17:46:45 +0200
Subject: [PATCH] finished MEGA65 screen scrolling

---
 src/aliases/,aliases_ram_lowmem_m65.s         |  2 +-
 src/kernal/screen_m65/mega65_chrout_screen.s  | 49 ++++++++++++++++---
 src/kernal/screen_m65/mega65_clrwin.s         |  2 +
 src/kernal/screen_m65/mega65_screen_helpers.s | 12 +++++
 4 files changed, 56 insertions(+), 9 deletions(-)

diff --git a/src/aliases/,aliases_ram_lowmem_m65.s b/src/aliases/,aliases_ram_lowmem_m65.s
index dc5cc1d0..62e1fc2b 100644
--- a/src/aliases/,aliases_ram_lowmem_m65.s
+++ b/src/aliases/,aliases_ram_lowmem_m65.s
@@ -51,7 +51,7 @@
 	.label M65_TXTWIN_Y0    = $58F //            text window - top-left Y coordinate, starting from 0
 	.label M65_TXTWIN_X1    = $590 //            text window - bottom-right X coordinate + 1
 	.label M65_TXTWIN_Y1    = $591 //            text window - bottom-right Y coordinate + 1
-	.label M65_TXTROW_OFF   = $592 // $592-$593  offset to the current text row
+	.label M65_TXTROW_OFF   = $592 // $592-$593  offset to the current text row from the viewport start
 	                               // $594-$5EB  -- UNUSED --
 	.label M65_DMAGIC_LIST  = $5EF // $5EF-$5FF  reserved for DMAgic list, 17 bytes
 	.label M65_RS232_INBUF  = $600 // $600-$6FF  -- reserved for RS-232 input buffer --
diff --git a/src/kernal/screen_m65/mega65_chrout_screen.s b/src/kernal/screen_m65/mega65_chrout_screen.s
index bfb92f25..7a16eaea 100644
--- a/src/kernal/screen_m65/mega65_chrout_screen.s
+++ b/src/kernal/screen_m65/mega65_chrout_screen.s
@@ -241,16 +241,49 @@ m65_chrout_fix_scroll_up_scroll:
 
 	// Virtual screen is too small - we will lose one row
 
-	// XXX implement
+	// Calculate size of data to copy
 
-	// XXX set size
+	sec
+	lda M65_COLGUARD+0
+	sbc #$50
+	sta M65_DMAJOB_SIZE_0
+	lda M65_COLGUARD+1
+	sbc #$00
+	sta M65_DMAJOB_SIZE_1
 
-	// jsr m65_screen_dmasrcdst_screen
-	// XXX add $50 to DST
-	// jsr m65_dmagic_oper_copy
+	// Scroll up screen memory
 
-	// jsr m65_screen_dmasrcdst_color
-	// XXX add $50 to DST
-	// jsr m65_dmagic_oper_copy
+	jsr m65_screen_dmasrcdst_screen
+	jsr m65_screen_dmasrc_add_row
+	jsr m65_dmagic_oper_copy
+
+	// Scroll up color memory
+
+	jsr m65_screen_dmasrcdst_color
+	jsr m65_screen_dmasrc_add_row
+	jsr m65_dmagic_oper_copy
+
+	// Clear the last row - color and screen memory
+
+	phz
+
+	jsr m65_helper_scrlpnt_color
+	lda COLOR
+	and #$0F
+	ldz #$4F
+!:
+	sta_lp (M65_LPNT_SCR), z
+	dez
+	bpl !-
+
+	jsr m65_helper_scrlpnt_to_screen
+	lda #$20
+	ldz #$4F
+!:
+	sta_lp (M65_LPNT_SCR), z
+	dez
+	bpl !-
+
+	plz
 
 	rts
diff --git a/src/kernal/screen_m65/mega65_clrwin.s b/src/kernal/screen_m65/mega65_clrwin.s
index 575a205c..c519f8b4 100644
--- a/src/kernal/screen_m65/mega65_clrwin.s
+++ b/src/kernal/screen_m65/mega65_clrwin.s
@@ -22,6 +22,8 @@ M65_CLRWIN:
 
 	// First initialize both pointers
 
+	// XXX use m65_helper_scrlpnt_color and m65_helper_scrlpnt_to_screen instead
+
 	clc
 	lda M65_COLVIEW+0
 	adc M65_SCRBASE+0
diff --git a/src/kernal/screen_m65/mega65_screen_helpers.s b/src/kernal/screen_m65/mega65_screen_helpers.s
index b4fa7d16..a8192463 100644
--- a/src/kernal/screen_m65/mega65_screen_helpers.s
+++ b/src/kernal/screen_m65/mega65_screen_helpers.s
@@ -57,3 +57,15 @@ m65_screen_dmasrcdst_color:
 	sta M65_DMAJOB_DST_2
 	lda #$0F
 	jmp_8 !-
+
+
+m65_screen_dmasrc_add_row:
+
+	clc
+	lda M65_DMAJOB_SRC_0
+	adc #$50
+	sta M65_DMAJOB_SRC_0
+	bcc !+
+	inc M65_DMAJOB_SRC_1
+!:
+	rts