GB: Pause OAM DMA when CPU is halted + return $FF during sprite evaluation while OAM DMA is active

Both of these together make the naughtyemu test display a blank screen as expected

Core/Gameboy.cpp

@@ -118,12 +118,13 @@ void Gameboy::PowerOn()
 	_apu.reset(new GbApu(_console, this));
 	_memoryManager.reset(new GbMemoryManager());
 	_timer.reset(new GbTimer(_memoryManager.get(), _apu.get()));
-	_dmaController.reset(new GbDmaController(_memoryManager.get(), _ppu.get()));
+	_dmaController.reset(new GbDmaController());
 	_cart->Init(this, _memoryManager.get());
 	_memoryManager->Init(_console, this, _cart.get(), _ppu.get(), _apu.get(), _timer.get(), _dmaController.get());
 
 	_cpu.reset(new GbCpu(_console, this, _memoryManager.get()));
 	_ppu->Init(_console, this, _memoryManager.get(), _dmaController.get(), _videoRam, _spriteRam);
+	_dmaController->Init(_memoryManager.get(), _ppu.get(), _cpu.get());
 }
 
 void Gameboy::Exec()

Core/GbCpu.cpp

@@ -39,6 +39,11 @@ GbCpuState GbCpu::GetState()
 	return _state;
 }
 
+bool GbCpu::IsHalted()
+{
+	return _state.Halted;
+}
+
 void GbCpu::Exec()
 {
 	uint8_t irqVector = _memoryManager->ProcessIrqRequests();

Core/GbCpu.h

@@ -20,13 +20,6 @@ private:
 	Console* _console;
 	Gameboy* _gameboy;
 
-public:
-	GbCpu(Console* console, Gameboy* gameboy, GbMemoryManager* memoryManager);
-	virtual ~GbCpu();
-
-	GbCpuState GetState();
-
-	void Exec();
 	void ExecOpCode(uint8_t opCode);
 
 	__forceinline void IncCycleCount();
@@ -146,5 +139,14 @@ public:
 	void DI();
 	void PREFIX();
 
+public:
+	GbCpu(Console* console, Gameboy* gameboy, GbMemoryManager* memoryManager);
+	virtual ~GbCpu();
+
+	GbCpuState GetState();
+	bool IsHalted();
+
+	void Exec();
+	
 	void Serialize(Serializer& s) override;
 };

Core/GbDmaController.cpp

@@ -2,11 +2,13 @@
 #include "GbDmaController.h"
 #include "GbMemoryManager.h"
 #include "GbPpu.h"
+#include "GbCpu.h"
 
-GbDmaController::GbDmaController(GbMemoryManager* memoryManager, GbPpu* ppu)
+void GbDmaController::Init(GbMemoryManager* memoryManager, GbPpu* ppu, GbCpu* cpu)
 {
 	_memoryManager = memoryManager;
 	_ppu = ppu;
+	_cpu = cpu;
 	_state = {};
 }
 
@@ -17,6 +19,11 @@ GbDmaControllerState GbDmaController::GetState()
 
 void GbDmaController::Exec()
 {
+	if(_cpu->IsHalted()) {
+		//OAM DMA is halted while the CPU is in halt mode, and resumes when the CPU resumes
+		return;
+	}
+
 	if(_state.DmaCounter > 0) {
 		if(_state.DmaCounter <= 160) {
 			_memoryManager->WriteDma(0xFE00 + (160 - _state.DmaCounter), _state.DmaReadBuffer);

Core/GbDmaController.h

@@ -5,6 +5,7 @@
 
 class GbMemoryManager;
 class GbPpu;
+class GbCpu;
 
 class GbDmaController final : public ISerializable
 {
@@ -12,11 +13,12 @@ private:
 	GbDmaControllerState _state;
 	GbMemoryManager* _memoryManager;
 	GbPpu* _ppu;
+	GbCpu* _cpu;
 	
 	void ProcessDmaBlock();
 
 public:
-	GbDmaController(GbMemoryManager* memoryManager, GbPpu* ppu);
+	void Init(GbMemoryManager* memoryManager, GbPpu* ppu, GbCpu* cpu);
 
 	GbDmaControllerState GetState();
 

Core/GbPpu.cpp

@@ -400,7 +400,7 @@ void GbPpu::RunSpriteEvaluation()
 	if(_state.Cycle & 0x01) {
 		if(_spriteCount < 10) {
 			uint8_t spriteIndex = ((_state.Cycle - 4) >> 1) * 4;
-			int16_t sprY = (int16_t)_oam[spriteIndex] - 16;
+			int16_t sprY = _dmaController->IsOamDmaRunning() ? 0xFF : ((int16_t)_oam[spriteIndex] - 16);
 			if(_state.Scanline >= sprY && _state.Scanline < sprY + (_state.LargeSprites ? 16 : 8)) {
 				_spriteX[_spriteCount] = _oam[spriteIndex + 1];
 				_spriteIndexes[_spriteCount] = spriteIndex;