From 7de2c91efb1e99409f9ab5bec0ae64580c2581e6 Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Tue, 16 Apr 2013 07:10:38 -0700
Subject: [PATCH] Copy DISPSTAT implementation from GBA.js

---
 src/gba/gba-io.c    |  8 ++++++++
 src/gba/gba-video.c | 18 ++++++++++++++++++
 src/gba/gba-video.h |  3 +++
 3 files changed, 29 insertions(+)

diff --git a/src/gba/gba-io.c b/src/gba/gba-io.c
index 62b140f4b..9217403dd 100644
--- a/src/gba/gba-io.c
+++ b/src/gba/gba-io.c
@@ -1,7 +1,12 @@
 #include "gba-io.h"
 
+#include "gba-video.h"
+
 void GBAIOWrite(struct GBA* gba, uint32_t address, uint16_t value) {
 	switch (address) {
+	case REG_DISPSTAT:
+		GBAVideoWriteDISPSTAT(&gba->video, value);
+		break;
 	case REG_WAITCNT:
 		GBAAdjustWaitstates(&gba->memory, value);
 		break;
@@ -14,6 +19,9 @@ void GBAIOWrite(struct GBA* gba, uint32_t address, uint16_t value) {
 
 uint16_t GBAIORead(struct GBA* gba, uint32_t address) {
 	switch (address) {
+	case REG_DISPSTAT:
+		return GBAVideoReadDISPSTAT(&gba->video);
+		break;
 	case REG_WAITCNT:
 		// Handled transparently by registers
 		break;
diff --git a/src/gba/gba-video.c b/src/gba/gba-video.c
index 88bff1ae0..c94e81d16 100644
--- a/src/gba/gba-video.c
+++ b/src/gba/gba-video.c
@@ -104,6 +104,24 @@ int32_t GBAVideoProcessEvents(struct GBAVideo* video, int32_t cycles) {
 	return video->nextEvent;
 }
 
+void GBAVideoWriteDISPSTAT(struct GBAVideo* video, uint16_t value) {
+	video->vblankIRQ = value & 0x0008;
+	video->hblankIRQ = value & 0x0010;
+	video->vcounterIRQ = value & 0x0020;
+	video->vcountSetting = (value & 0xFF00) >> 8;
+
+	if (video->vcounterIRQ) {
+		// FIXME: this can be too late if we're in the middle of an Hblank
+		video->nextVcounterIRQ = video->nextHblank + VIDEO_HBLANK_LENGTH + (video->vcountSetting - video->vcount) * VIDEO_HORIZONTAL_LENGTH;
+		if (video->nextVcounterIRQ < video->nextEvent) {
+			video->nextVcounterIRQ += VIDEO_TOTAL_LENGTH;
+		}
+	}
+}
+
+uint16_t GBAVideoReadDISPSTAT(struct GBAVideo* video) {
+	return (video->inVblank) | (video->inHblank << 1) | (video->vcounter << 2);
+}
 
 static void GBAVideoDummyRendererInit(struct GBAVideoRenderer* renderer) {
 	(void)(renderer);
diff --git a/src/gba/gba-video.h b/src/gba/gba-video.h
index 0c59141ff..d65c778e6 100644
--- a/src/gba/gba-video.h
+++ b/src/gba/gba-video.h
@@ -60,4 +60,7 @@ struct GBAVideo {
 void GBAVideoInit(struct GBAVideo* video);
 int32_t GBAVideoProcessEvents(struct GBAVideo* video, int32_t cycles);
 
+void GBAVideoWriteDISPSTAT(struct GBAVideo* video, uint16_t value);
+uint16_t GBAVideoReadDISPSTAT(struct GBAVideo* video);
+
 #endif