From 2636d3a7678e9aa458ff07c4d0a2cff2086ca52e Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Wed, 22 Feb 2017 10:57:48 -0800
Subject: [PATCH] DS Video: Display swapping

---
 include/mgba/internal/ds/renderers/software.h |  1 +
 include/mgba/internal/ds/video.h              |  4 ++++
 src/ds/io.c                                   |  5 +++++
 src/ds/renderers/software.c                   | 17 ++++++++++++-----
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/include/mgba/internal/ds/renderers/software.h b/include/mgba/internal/ds/renderers/software.h
index 89aad89ea..f15e0d934 100644
--- a/include/mgba/internal/ds/renderers/software.h
+++ b/include/mgba/internal/ds/renderers/software.h
@@ -21,6 +21,7 @@ struct DSVideoSoftwareRenderer {
 
 	DSRegisterDISPCNT dispcntA;
 	DSRegisterDISPCNT dispcntB;
+	DSRegisterPOWCNT1 powcnt;
 
 	color_t* outputBuffer;
 	int outputBufferStride;
diff --git a/include/mgba/internal/ds/video.h b/include/mgba/internal/ds/video.h
index 2665453f9..34db43286 100644
--- a/include/mgba/internal/ds/video.h
+++ b/include/mgba/internal/ds/video.h
@@ -58,6 +58,10 @@ DECL_BITS(DSRegisterDISPCNT, CharBase, 24, 3);
 DECL_BITS(DSRegisterDISPCNT, ScreenBase, 27, 3);
 // TODO
 
+DECL_BITFIELD(DSRegisterPOWCNT1, uint16_t);
+// TODO
+DECL_BIT(DSRegisterPOWCNT1, Swap, 15);
+
 struct DSVideoRenderer {
 	void (*init)(struct DSVideoRenderer* renderer);
 	void (*reset)(struct DSVideoRenderer* renderer);
diff --git a/src/ds/io.c b/src/ds/io.c
index 3c3c1725f..91022290b 100644
--- a/src/ds/io.c
+++ b/src/ds/io.c
@@ -440,6 +440,11 @@ void DS9IOWrite(struct DS* ds, uint32_t address, uint16_t value) {
 			ds->memory.io9[DS9_REG_SQRTCNT >> 1] = _scheduleSqrt(ds, ds->memory.io9[DS9_REG_SQRTCNT >> 1]);
 			break;
 
+		// High Video
+		case DS9_REG_POWCNT1:
+			value = ds->video.renderer->writeVideoRegister(ds->video.renderer, address, value);
+			break;
+
 		default:
 			{
 				uint32_t v2 = DSIOWrite(&ds->ds9, address, value);
diff --git a/src/ds/renderers/software.c b/src/ds/renderers/software.c
index bc5b8a842..bc1869bdb 100644
--- a/src/ds/renderers/software.c
+++ b/src/ds/renderers/software.c
@@ -42,9 +42,11 @@ static void DSVideoSoftwareRendererInit(struct DSVideoRenderer* renderer) {
 	softwareRenderer->engA.d.palette = &renderer->palette[0];
 	softwareRenderer->engA.d.oam = &renderer->oam->oam[0];
 	softwareRenderer->engA.masterEnd = DS_VIDEO_HORIZONTAL_PIXELS;
+	softwareRenderer->engA.outputBufferStride = softwareRenderer->outputBufferStride;
 	softwareRenderer->engB.d.palette = &renderer->palette[512];
 	softwareRenderer->engB.d.oam = &renderer->oam->oam[1];
 	softwareRenderer->engB.masterEnd = DS_VIDEO_HORIZONTAL_PIXELS;
+	softwareRenderer->engB.outputBufferStride = softwareRenderer->outputBufferStride;
 
 	DSVideoSoftwareRendererReset(renderer);
 }
@@ -113,6 +115,9 @@ static uint16_t DSVideoSoftwareRendererWriteVideoRegister(struct DSVideoRenderer
 		softwareRenderer->dispcntB |= value << 16;
 		GBAVideoSoftwareRendererUpdateDISPCNTB(softwareRenderer);
 		break;
+	case DS9_REG_POWCNT1:
+		value &= 0x810F;
+		softwareRenderer->powcnt = value;
 	}
 	return value;
 }
@@ -222,11 +227,13 @@ static void _drawScanlineB(struct DSVideoSoftwareRenderer* softwareRenderer, int
 
 static void DSVideoSoftwareRendererDrawScanline(struct DSVideoRenderer* renderer, int y) {
 	struct DSVideoSoftwareRenderer* softwareRenderer = (struct DSVideoSoftwareRenderer*) renderer;
-	softwareRenderer->engA.outputBuffer = softwareRenderer->outputBuffer;
-	softwareRenderer->engB.outputBuffer = &softwareRenderer->outputBuffer[softwareRenderer->outputBufferStride * DS_VIDEO_VERTICAL_PIXELS];
-	softwareRenderer->engA.outputBufferStride = softwareRenderer->outputBufferStride;
-	softwareRenderer->engB.outputBufferStride = softwareRenderer->outputBufferStride;
-
+	if (!DSRegisterPOWCNT1IsSwap(softwareRenderer->powcnt)) {
+		softwareRenderer->engA.outputBuffer = &softwareRenderer->outputBuffer[softwareRenderer->outputBufferStride * DS_VIDEO_VERTICAL_PIXELS];
+		softwareRenderer->engB.outputBuffer = softwareRenderer->outputBuffer;
+	} else {
+		softwareRenderer->engA.outputBuffer = softwareRenderer->outputBuffer;
+		softwareRenderer->engB.outputBuffer = &softwareRenderer->outputBuffer[softwareRenderer->outputBufferStride * DS_VIDEO_VERTICAL_PIXELS];
+	}
 
 	_drawScanlineA(softwareRenderer, y);
 	_drawScanlineB(softwareRenderer, y);