From 62e74a04aaae71b09b2d3cacd6b825866621a5b6 Mon Sep 17 00:00:00 2001
From: Sakitoshi <39132563+Sakitoshi@users.noreply.github.com>
Date: Fri, 5 Nov 2021 23:18:57 -0300
Subject: [PATCH] map change sign fix for goomba color

code lifted from pokemon prism
---
 engine/gfx/dma_transfer.asm | 60 +++++++++++++++++++++++++++++++++++--
 1 file changed, 58 insertions(+), 2 deletions(-)

diff --git a/engine/gfx/dma_transfer.asm b/engine/gfx/dma_transfer.asm
index 682302f9635..6bd7b86c803 100644
--- a/engine/gfx/dma_transfer.asm
+++ b/engine/gfx/dma_transfer.asm
@@ -394,6 +394,45 @@ _continue_HDMATransfer:
 
 	ret
 
+DoHBlankHDMATransfer:
+; LY magic
+	ld b, $7f
+	ld a, h
+	ldh [rHDMA1], a
+	ld a, l
+	and $f0 ; high nybble
+	ldh [rHDMA2], a
+	ld a, d
+	and $1f ; lower 5 bits
+	ldh [rHDMA3], a
+	ld a, e
+	and $f0 ; high nybble
+	ldh [rHDMA4], a
+	dec c ; c = number of LYs needed
+	ld e, c
+	set 7, e ; hblank dma transfers
+	ldh a, [rLY]
+	add c ; calculate end LY
+	cp b ; is the end LY greater than the max LY
+	call nc, DI_DelayFrame ; if so, delay a frame to reset the LY
+
+	lb bc, %11, LOW(rSTAT)
+.noHBlankWait
+	ldh a, [c]
+	and b
+	jr z, .noHBlankWait
+.hBlankWaitLoop
+	ldh a, [c]
+	and b
+	jr nz, .hBlankWaitLoop
+	ld hl, rHDMA5
+	ld [hl], e
+	ld a, $ff
+.waitForHDMA
+	cp [hl]
+	jr nz, .waitForHDMA
+	ret
+
 _LoadHDMAParameters:
 	ld a, h
 	ldh [rHDMA1], a
@@ -574,13 +613,13 @@ HDMATransfer_OnlyTopFourRows:
 	ld c, $8
 	ld hl, wScratchTilemap + $80
 	debgcoord 0, 0, vBGMap1
-	call HDMATransfer_Wait127Scanlines
+	call DoHBlankHDMATransfer
 	ld a, $0
 	ldh [rVBK], a
 	ld c, $8
 	ld hl, wScratchTilemap
 	debgcoord 0, 0, vBGMap1
-	call HDMATransfer_Wait127Scanlines
+	call DoHBlankHDMATransfer
 	ret
 
 .Copy:
@@ -602,3 +641,20 @@ HDMATransfer_OnlyTopFourRows:
 	dec b
 	jr nz, .outer_loop
 	ret
+
+DI_DelayFrame:
+	; I have no idea of what's going on here, but this function is being called while not in di mode
+	; this is a duct-tape fix and should probably be replaced eventually
+	ldh a, [rLY]
+	push bc
+	ld b, a
+.loop
+	ldh a, [rLY]
+	and a
+	jr z, .done
+	cp b
+	jr nc, .loop
+.done
+	pop bc
+	ret
+