From 1cb054ec67ea7b1e7e9162c1e74bd4ab254efb74 Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Tue, 20 Sep 2016 10:44:49 -0700
Subject: [PATCH] GB Video: Setting LYC=LY during mode 2 should trigger an IRQ

---
 CHANGES        |  1 +
 src/gb/io.c    |  4 +++-
 src/gb/video.c | 10 ++++++++++
 src/gb/video.h |  1 +
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/CHANGES b/CHANGES
index 0c9f725a0..ab16b7e59 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,7 @@
 0.6.0: (Future)
 Bugfixes:
  - GB MBC: Fix MBC7 when size is incorrectly specified
+ - GB Video: Setting LYC=LY during mode 2 should trigger an IRQ
 Misc:
  - All: Only update version info if needed
 
diff --git a/src/gb/io.c b/src/gb/io.c
index e09a33173..6b799913a 100644
--- a/src/gb/io.c
+++ b/src/gb/io.c
@@ -341,7 +341,6 @@ void GBIOWrite(struct GB* gb, unsigned address, uint8_t value) {
 	case REG_SB:
 	case REG_TIMA:
 	case REG_TMA:
-	case REG_LYC:
 		// Handled transparently by the registers
 		break;
 	case REG_TAC:
@@ -357,6 +356,9 @@ void GBIOWrite(struct GB* gb, unsigned address, uint8_t value) {
 		value = gb->video.renderer->writeVideoRegister(gb->video.renderer, address, value);
 		GBVideoWriteLCDC(&gb->video, value);
 		break;
+	case REG_LYC:
+		GBVideoWriteLYC(&gb->video, value);
+		break;
 	case REG_DMA:
 		GBMemoryDMA(gb, value << 8);
 		break;
diff --git a/src/gb/video.c b/src/gb/video.c
index 45031311c..b2b2408e4 100644
--- a/src/gb/video.c
+++ b/src/gb/video.c
@@ -312,6 +312,16 @@ void GBVideoWriteSTAT(struct GBVideo* video, GBRegisterSTAT value) {
 	}
 }
 
+void GBVideoWriteLYC(struct GBVideo* video, uint8_t value) {
+	if (video->mode == 2) {
+		video->stat = GBRegisterSTATSetLYC(video->stat, value == video->ly);
+		if (GBRegisterSTATIsLYCIRQ(video->stat) && value == video->ly) {
+			video->p->memory.io[REG_IF] |= (1 << GB_IRQ_LCDSTAT);
+			GBUpdateIRQs(video->p);
+		}
+	}
+}
+
 void GBVideoWritePalette(struct GBVideo* video, uint16_t address, uint8_t value) {
 	static const uint16_t dmgPalette[4] = { 0x7FFF, 0x56B5, 0x294A, 0x0000};
 	if (video->p->model < GB_MODEL_CGB) {
diff --git a/src/gb/video.h b/src/gb/video.h
index 05f84c913..b8a3e73d1 100644
--- a/src/gb/video.h
+++ b/src/gb/video.h
@@ -135,6 +135,7 @@ void GBVideoProcessDots(struct GBVideo* video);
 
 void GBVideoWriteLCDC(struct GBVideo* video, GBRegisterLCDC value);
 void GBVideoWriteSTAT(struct GBVideo* video, GBRegisterSTAT value);
+void GBVideoWriteLYC(struct GBVideo* video, uint8_t value);
 void GBVideoWritePalette(struct GBVideo* video, uint16_t address, uint8_t value);
 void GBVideoSwitchBank(struct GBVideo* video, uint8_t value);