BSNESv115: add dedicated subframe core (#3281)

* BSNESv115: allow subframe inputs

* BSNESv115: Implement ICycleTiming

may be correct, not sure

* BSNESv115: add dedicated subframe core

I have probably overlooked something...

* Don't implement ICycleTiming in the non-subframe core

requires re-implementing the "FrameAdvance" function in the subframe core

* Register previously missing services in the subframe core as well

* Wire up SubBsnes everywhere in the frontend

* Change reset cycle to reset instruction

* Deduplicate some code

* Slightly rework frame advance logic. The main intent here is to prevent a case where two frames are ran within a single "frame." The current code probably wouldn't crash due to that, but best not to do that.
Also make SGB work here. A bit of a joke since you really can only abuse it for subframe resets, but might as well especially with the settings implying it's possible (and someone is bound to complain).

Co-authored-by: CasualPokePlayer <50538166+CasualPokePlayer@users.noreply.github.com>

src/BizHawk.Client.Common/Api/Classes/EmulationApi.cs

@@ -235,9 +235,9 @@ namespace BizHawk.Client.Common
 				s.ShowOBJ_3 = GetSetting(args, 7);
 				core.PutSettings(s);
 			}
-			void SetBsnes(BsnesCore core)
+			void SetBsnes(ISettable<BsnesCore.SnesSettings, BsnesCore.SnesSyncSettings> settingsProvider)
 			{
-				var s = core.GetSettings();
+				var s = settingsProvider.GetSettings();
 				// TODO: This should probably support both prios inidividually but I have no idea whether changing this breaks anything
 				s.ShowBG1_0 = s.ShowBG1_1 = GetSetting(args, 0);
 				s.ShowBG2_0 = s.ShowBG2_1 = GetSetting(args, 1);
@@ -247,7 +247,7 @@ namespace BizHawk.Client.Common
 				s.ShowOBJ_1 = GetSetting(args, 5);
 				s.ShowOBJ_2 = GetSetting(args, 6);
 				s.ShowOBJ_3 = GetSetting(args, 7);
-				core.PutSettings(s);
+				settingsProvider.PutSettings(s);
 			}
 			void SetCygne(WonderSwan ws)
 			{
@@ -313,6 +313,9 @@ namespace BizHawk.Client.Common
 				case BsnesCore bsnes:
 					SetBsnes(bsnes);
 					break;
+				case SubBsnesCore subBsnes:
+					SetBsnes(subBsnes.ServiceProvider.GetService<ISettable<BsnesCore.SnesSettings, BsnesCore.SnesSyncSettings>>());
+					break;
 				case NES nes:
 					SetNesHawk(nes);
 					break;

src/BizHawk.Client.Common/config/Config.cs

@@ -27,11 +27,11 @@ namespace BizHawk.Client.Common
 			(new[] { VSystemID.Raw.NES },
 				new[] { CoreNames.QuickNes, CoreNames.NesHawk, CoreNames.SubNesHawk }),
 			(new[] { VSystemID.Raw.SNES },
-				new[] { CoreNames.Faust, CoreNames.Snes9X, CoreNames.Bsnes, CoreNames.Bsnes115 }),
+				new[] { CoreNames.Faust, CoreNames.Snes9X, CoreNames.Bsnes, CoreNames.Bsnes115, CoreNames.SubBsnes115 }),
 			(new[] { VSystemID.Raw.N64 },
 				new[] { CoreNames.Mupen64Plus, CoreNames.Ares64 }),
 			(new[] { VSystemID.Raw.SGB },
-				new[] { CoreNames.Gambatte, CoreNames.Bsnes, CoreNames.Bsnes115}),
+				new[] { CoreNames.Gambatte, CoreNames.Bsnes, CoreNames.Bsnes115, CoreNames.SubBsnes115 }),
 			(new[] { VSystemID.Raw.GB, VSystemID.Raw.GBC },
 				new[] { CoreNames.Gambatte, CoreNames.Sameboy, CoreNames.GbHawk, CoreNames.SubGbHawk }),
 			(new[] { VSystemID.Raw.GBL },

src/BizHawk.Client.Common/movie/bk2/Bk2MnemonicLookup.cs

@@ -244,7 +244,9 @@ namespace BizHawk.Client.Common
 				["Extra1"] = '1',
 				["Extra2"] = '2',
 				["Extra3"] = '3',
-				["Extra4"] = '4'
+				["Extra4"] = '4',
+
+				["Subframe"] = 'F'
 			},
 			[VSystemID.Raw.TI83] = new()
 			{

src/BizHawk.Client.EmuHawk/MainForm.Events.cs

@@ -1723,6 +1723,7 @@ namespace BizHawk.Client.EmuHawk
 			{
 				LibsnesCore => OpenOldBSNESGamepadSettingsDialog(GetSettingsAdapterForLoadedCore<LibsnesCore>()),
 				BsnesCore => OpenBSNESGamepadSettingsDialog(GetSettingsAdapterForLoadedCore<BsnesCore>()),
+				SubBsnesCore => OpenBSNESGamepadSettingsDialog(GetSettingsAdapterForLoadedCore<SubBsnesCore>()),
 				_ => DialogResult.None
 			};
 		}
@@ -1744,6 +1745,7 @@ namespace BizHawk.Client.EmuHawk
 			{
 				LibsnesCore => OpenOldBSNESSettingsDialog(GetSettingsAdapterForLoadedCore<LibsnesCore>()),
 				BsnesCore => OpenBSNESSettingsDialog(GetSettingsAdapterForLoadedCore<BsnesCore>()),
+				SubBsnesCore => OpenBSNESSettingsDialog(GetSettingsAdapterForLoadedCore<SubBsnesCore>()),
 				_ => DialogResult.None
 			};
 		}
@@ -2774,6 +2776,13 @@ namespace BizHawk.Client.EmuHawk
 			bsnesSubmenu.DropDownOpened += (_, _) => bsnesGamepadSettingsItem.Enabled = MovieSession.Movie.NotActive() || Emulator is not BsnesCore;
 			items.Add(bsnesSubmenu);
 
+			// SubBSNESv115+
+			var subBsnesGamepadSettingsItem = CreateSettingsItem("Controller Configuration...", (_, _) => OpenBSNESGamepadSettingsDialog(GetSettingsAdapterFor<SubBsnesCore>()));
+			var subBsnesSettingsItem = CreateSettingsItem("Options...", (_, _) => OpenBSNESSettingsDialog(GetSettingsAdapterFor<SubBsnesCore>()));
+			var subBsnesSubmenu = CreateCoreSubmenu(VSystemCategory.Consoles, CoreNames.SubBsnes115, subBsnesGamepadSettingsItem, subBsnesSettingsItem);
+			subBsnesSubmenu.DropDownOpened += (_, _) => subBsnesGamepadSettingsItem.Enabled = MovieSession.Movie.NotActive() || Emulator is not SubBsnesCore;
+			items.Add(subBsnesSubmenu);
+
 			// C64Hawk
 			items.Add(CreateCoreSubmenu(VSystemCategory.PCs, CoreNames.C64Hawk, CreateSettingsItem("Settings...", (_, _) => OpenC64HawkSettingsDialog())));
 

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -1478,7 +1478,7 @@ namespace BizHawk.Client.EmuHawk
 
 		private void SNES_ToggleBg(int layer)
 		{
-			if (Emulator is not (BsnesCore or LibsnesCore or Snes9x) || !1.RangeTo(4).Contains(layer))
+			if (Emulator is not (BsnesCore or SubBsnesCore or LibsnesCore or Snes9x) || !1.RangeTo(4).Contains(layer))
 			{
 				return;
 			}
@@ -1486,9 +1486,10 @@ namespace BizHawk.Client.EmuHawk
 			bool result = false;
 			switch (Emulator)
 			{
-				case BsnesCore bsnes:
+				case BsnesCore or SubBsnesCore:
 				{
-					var s = bsnes.GetSettings();
+					var settingsProvider = Emulator.ServiceProvider.GetService<ISettable<BsnesCore.SnesSettings, BsnesCore.SnesSyncSettings>>();
+					var s = settingsProvider.GetSettings();
 					switch (layer)
 					{
 						case 1:
@@ -1505,7 +1506,7 @@ namespace BizHawk.Client.EmuHawk
 							break;
 					}
 
-					bsnes.PutSettings(s);
+					settingsProvider.PutSettings(s);
 					break;
 				}
 				case LibsnesCore libsnes:
@@ -2057,7 +2058,12 @@ namespace BizHawk.Client.EmuHawk
 					SnesGfxDebuggerMenuItem.Visible = true;
 					break;
 				case VSystemID.Raw.SNES when Emulator is BsnesCore bsnesCore:
-					SNESSubMenu.Text = bsnesCore.IsSGB ?  "&SGB" : "&SNES";
+					SNESSubMenu.Text = bsnesCore.IsSGB ? "&SGB" : "&SNES";
+					SnesGfxDebuggerMenuItem.Visible = false;
+					SNESSubMenu.Visible = true;
+					break;
+				case VSystemID.Raw.SNES when Emulator is SubBsnesCore subBsnesCore:
+					SNESSubMenu.Text = subBsnesCore.IsSGB ? "&SGB" : "&SNES";
 					SnesGfxDebuggerMenuItem.Visible = false;
 					SNESSubMenu.Visible = true;
 					break;

src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesApi.cs

@@ -47,7 +47,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 		[BizImport(CallingConvention.Cdecl)]
 		public abstract void snes_reset();
 		[BizImport(CallingConvention.Cdecl)]
-		public abstract void snes_run();
+		public abstract bool snes_run(bool breakOnLatch);
 
 		[BizImport(CallingConvention.Cdecl)]
 		public abstract void snes_serialize(byte[] serializedData, int serializedSize);
@@ -68,6 +68,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 		[BizImport(CallingConvention.Cdecl)]
 		public abstract bool snes_cpu_step();
 
+		[BizImport(CallingConvention.Cdecl)]
+		public abstract long snes_get_executed_cycles();
+
 		[BizImport(CallingConvention.Cdecl)]
 		public abstract bool snes_msu_sync();
 	}

src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesControllers.cs

@@ -35,7 +35,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 
 		public ControllerDefinition Definition { get; }
 
-		public BsnesControllers(BsnesCore.SnesSyncSettings ss)
+		public BsnesControllers(BsnesCore.SnesSyncSettings ss, bool subframe = false)
 		{
 			_ports = new[]
 			{
@@ -52,6 +52,13 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 			// add buttons that the core itself will handle
 			Definition.BoolButtons.Add("Reset");
 			Definition.BoolButtons.Add("Power");
+			if (subframe)
+			{
+				// When set, only emulate until the next input latch (or until the frame ends)
+				Definition.BoolButtons.Add("Subframe");
+				// Amount of instructions to execute before resetting; range hopefully set large enough
+				Definition.AddAxis("Reset Instruction", 0.RangeTo(200000), 0);
+			}
 
 			Definition.MakeImmutable();
 		}

src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesCore.IDebuggable.cs

@@ -89,12 +89,11 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 			}
 		}
 
-		public long TotalExecutedCycles { get; private set; }
+		public long TotalExecutedCycles => Api.core.snes_get_executed_cycles();
 
 		private void StepInto()
 		{
 			_framePassed = Api.core.snes_cpu_step();
-			TotalExecutedCycles++;
 			if (_framePassed)
 			{
 				Frame++;

src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesCore.IEmulator.cs

@@ -10,13 +10,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 
 		public bool FrameAdvance(IController controller, bool render, bool renderSound)
 		{
-			_controller = controller;
+			FrameAdvancePre(controller, render, renderSound);
 
-			/* if the input poll callback is called, it will set this to false
-			 * this has to be done before we save the per-frame state in deterministic
-			 * mode, because in there, the core actually advances, and might advance
-			 * through the point in time where IsLagFrame gets set to false.  makes sense?
-			 */
 			IsLagFrame = true;
 
 			bool resetSignal = controller.IsPressed("Reset");
@@ -31,6 +26,22 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 				Api.core.snes_power();
 			}
 
+			// run the core for one frame
+			Api.core.snes_run(false);
+			Frame++;
+
+			if (IsLagFrame)
+			{
+				LagCount++;
+			}
+
+			return true;
+		}
+
+		internal void FrameAdvancePre(IController controller, bool render, bool renderSound)
+		{
+			_controller = controller;
+
 			var enables = new BsnesApi.LayerEnables
 			{
 				BG1_Prio0 = _settings.ShowBG1_0,
@@ -52,20 +63,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 			Api.core.snes_set_trace_enabled(_tracer.IsEnabled());
 			Api.core.snes_set_video_enabled(render);
 			Api.core.snes_set_audio_enabled(renderSound);
-
-			// run the core for one frame
-			Api.core.snes_run();
-			Frame++;
-
-			if (IsLagFrame)
-			{
-				LagCount++;
-			}
-
-			return true;
 		}
 
-		public int Frame { get; private set; }
+		public int Frame { get; set; }
 
 		public string SystemId => VSystemID.Raw.SNES;
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesCore.cs

@@ -14,7 +14,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 	{
 		[CoreConstructor(VSystemID.Raw.SGB)]
 		[CoreConstructor(VSystemID.Raw.SNES)]
-		public BsnesCore(CoreLoadParameters<SnesSettings, SnesSyncSettings> loadParameters)
+		public BsnesCore(CoreLoadParameters<SnesSettings, SnesSyncSettings> loadParameters) : this(loadParameters, false) { }
+		public BsnesCore(CoreLoadParameters<SnesSettings, SnesSyncSettings> loadParameters, bool subframe = false)
 		{
 			var ser = new BasicServiceProvider(this);
 			ServiceProvider = ser;
@@ -60,7 +61,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 
 			Api = new BsnesApi(CoreComm.CoreFileProvider.DllPath(), CoreComm, callbacks.AllDelegatesInMemoryOrder());
 
-			_controllers = new BsnesControllers(_syncSettings);
+			_controllers = new BsnesControllers(_syncSettings, subframe);
 
 			generate_palette();
 			BsnesApi.SnesInitData snesInitData = new()
@@ -94,7 +95,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 			}
 
 			_region = Api.core.snes_get_region();
-
 			if (_region == BsnesApi.SNES_REGION.NTSC)
 			{
 				// taken from bsnes source
@@ -135,7 +135,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 			public string BoardName => "SGB";
 		}
 
-		private BsnesApi Api { get; }
+		internal BsnesApi Api { get; }
 
 		private string snes_path_request(int slot, string hint, bool required)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/SubBsnesCore.cs

@@ -0,0 +1,113 @@
+using BizHawk.Emulation.Common;
+
+namespace BizHawk.Emulation.Cores.Nintendo.BSNES
+{
+	[PortedCore(CoreNames.SubBsnes115, "")]
+	[ServiceNotApplicable(new[] { typeof(IDriveLight) })]
+	public class SubBsnesCore : IEmulator, ICycleTiming
+	{
+		[CoreConstructor(VSystemID.Raw.SGB)]
+		[CoreConstructor(VSystemID.Raw.SNES)]
+		public SubBsnesCore(CoreLoadParameters<BsnesCore.SnesSettings, BsnesCore.SnesSyncSettings> loadParameters)
+		{
+			_bsnesCore = new BsnesCore(loadParameters, true);
+			if (_bsnesCore.Region == DisplayType.NTSC)
+				ClockRate = 315.0 / 88.0 * 1000000.0 * 6.0;
+			else
+				ClockRate = (283.75 * 15625.0 + 25.0) * 4.8;
+
+			BasicServiceProvider ser = new(this);
+			ser.Register(_bsnesCore.ServiceProvider.GetService<IDebuggable>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<IVideoProvider>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<ISaveRam>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<IStatable>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<IInputPollable>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<IRegionable>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<ISettable<BsnesCore.SnesSettings, BsnesCore.SnesSyncSettings>>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<ISoundProvider>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<IMemoryDomains>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<IDisassemblable>());
+			ser.Register(_bsnesCore.ServiceProvider.GetService<ITraceable>());
+			if (IsSGB)
+			{
+				// board info is only set in SGB mode
+				ser.Register(_bsnesCore.ServiceProvider.GetService<IBoardInfo>());
+			}
+			ServiceProvider = ser;
+		}
+
+		private readonly BsnesCore _bsnesCore;
+
+		public bool IsSGB => _bsnesCore.IsSGB;
+
+		public IEmulatorServiceProvider ServiceProvider { get; }
+
+		public ControllerDefinition ControllerDefinition => _bsnesCore.ControllerDefinition;
+
+		public bool FrameAdvance(IController controller, bool render, bool renderSound = true)
+		{
+			_bsnesCore.FrameAdvancePre(controller, render, renderSound);
+
+			_bsnesCore.IsLagFrame = true;
+			bool framePassed = false;
+
+			bool resetSignal = controller.IsPressed("Reset");
+			bool powerSignal = controller.IsPressed("Power");
+
+			if (resetSignal || powerSignal)
+			{
+				int resetInstruction = controller.AxisValue("Reset Instruction");
+				for (int i = 0; i < resetInstruction; i++)
+				{
+					framePassed = _bsnesCore.Api.core.snes_cpu_step();
+					if (framePassed) break;
+				}
+
+				if (resetSignal)
+				{
+					_bsnesCore.Api.core.snes_reset();
+				}
+
+				if (powerSignal)
+				{
+					_bsnesCore.Api.core.snes_power();
+				}
+			}
+			else
+			{
+				// run the core for one (sub-)frame
+				bool subFrameRequested = controller.IsPressed("Subframe");
+				framePassed = _bsnesCore.Api.core.snes_run(subFrameRequested);
+			}
+
+			_bsnesCore.Frame++;
+
+			if (framePassed && _bsnesCore.IsLagFrame)
+				_bsnesCore.LagCount++;
+			else
+				_bsnesCore.IsLagFrame = false;
+
+			return true;
+		}
+
+		public int Frame => _bsnesCore.Frame;
+
+		public string SystemId => _bsnesCore.SystemId;
+
+		public bool DeterministicEmulation => _bsnesCore.DeterministicEmulation;
+
+		public void ResetCounters()
+		{
+			_bsnesCore.ResetCounters();
+		}
+
+		public void Dispose()
+		{
+			_bsnesCore.Dispose();
+		}
+
+		public long CycleCount => _bsnesCore.Api.core.snes_get_executed_cycles();
+
+		public double ClockRate { get; }
+	}
+}

src/BizHawk.Emulation.Cores/CoreNames.cs

@@ -50,6 +50,7 @@ namespace BizHawk.Emulation.Cores
 		public const string Saturnus = "Saturnus";
 		public const string SMSHawk = "SMSHawk";
 		public const string Snes9X = "Snes9x";
+		public const string SubBsnes115 = "SubBSNESv115+";
 		public const string SubGbHawk = "SubGBHawk";
 		public const string SubNesHawk = "SubNESHawk";
 		public const string TI83Hawk = "TI83Hawk";

src/BizHawk.Emulation.Cores/vpads_schemata/SnesSchema.cs

@@ -20,6 +20,7 @@ namespace BizHawk.Emulation.Cores
 			{
 				LibsnesCore libsnes => GetLibsnesPadSchemas(libsnes),
 				BsnesCore bsnes => GetBsnesPadSchemas(bsnes),
+				SubBsnesCore subBsnes => GetBsnesPadSchemas(subBsnes.ServiceProvider.GetService<ISettable<BsnesCore.SnesSettings, BsnesCore.SnesSyncSettings>>()),
 				NymaCore nyma => GetFaustSchemas(nyma, showMessageBox),
 				_ => GetSnes9xPadSchemas((Snes9x) core)
 			};
@@ -112,9 +113,9 @@ namespace BizHawk.Emulation.Cores
 			yield return ConsoleButtons();
 		}
 
-		private IEnumerable<PadSchema> GetBsnesPadSchemas(BsnesCore core)
+		private IEnumerable<PadSchema> GetBsnesPadSchemas(ISettable<BsnesCore.SnesSettings, BsnesCore.SnesSyncSettings> settingsProvider)
 		{
-			var syncSettings = core.GetSyncSettings();
+			var syncSettings = settingsProvider.GetSyncSettings();
 
 			var ports = new[]
 			{

waterbox/bsnescore/bsnes/sfc/controller/super-multitap/super-multitap.cpp

@@ -58,6 +58,7 @@ auto SuperMultitap::latch(bool data) -> void {
   counter2 = 0;
 
   if(latched == 0) {
+    if (port == ID::Port::Controller1) platform->notify("LATCH");
     uint offset = isPayloadController ? 16 : 12;
     for(uint id : range(4)) {
       auto& gamepad = gamepads[id];

waterbox/bsnescore/bsnes/sfc/cpu/cpu.cpp

@@ -28,7 +28,10 @@ auto CPU::Enter() -> void {
   while(true) {
     scheduler.synchronize();
     cpu.main();
-    if (scheduler.StepOnce) scheduler.leave(Scheduler::Event::Desynchronized);
+    if (scheduler.StepOnce) {
+      scheduler.StepOnce = false;
+      scheduler.leave(Scheduler::Event::Desynchronized);
+    }
   }
 }
 

waterbox/bsnescore/bsnes/sfc/cpu/cpu.hpp

@@ -76,6 +76,8 @@ struct CPU : Processor::WDC65816, Thread, PPUcounter {
     uint target = 0;
   } overclocking;
 
+  long TotalExecutedCycles;
+
 private:
   uint version = 2;  //allowed: 1, 2
 

waterbox/bsnescore/bsnes/sfc/cpu/timing.cpp

@@ -10,6 +10,7 @@ auto CPU::joypadCounter() const -> uint {
 
 auto CPU::stepOnce() -> void {
   counter.cpu += 2;
+  TotalExecutedCycles += 2;
   tick();
   if(hcounter() & 2) nmiPoll(), irqPoll();
   if(joypadCounter() == 0) joypadEdge();

waterbox/bsnescore/bsnes/target-bsnescore/bsnescore.cpp

@@ -169,9 +169,11 @@ EXPORT void snes_reset(void)
 }
 
 // note: run with runahead doesn't work yet, i suspect it's due to the serialize thing breaking (cause of libco)
-EXPORT void snes_run(void)
+EXPORT bool snes_run(bool breakOnLatch)
 {
+    program->breakOnLatch = breakOnLatch;
     emulator->run();
+    return scheduler.event == Scheduler::Event::Frame;
 }
 
 // not used, but would probably be nice
@@ -449,10 +451,14 @@ EXPORT bool snes_cpu_step()
 {
     scheduler.StepOnce = true;
     emulator->run();
-    scheduler.StepOnce = false;
     return scheduler.event == Scheduler::Event::Frame;
 }
 
+EXPORT long snes_get_executed_cycles()
+{
+    return SuperFamicom::cpu.TotalExecutedCycles;
+}
+
 // should be called on savestate load, to get msu files loaded and in the correct state
 EXPORT void snes_msu_sync()
 {

waterbox/bsnescore/bsnes/target-bsnescore/program.cpp

@@ -43,6 +43,7 @@ struct Program : Emulator::Platform
 	bool overscan = false;
 	uint16_t backdropColor;
 	int regionOverride = 0;
+	bool breakOnLatch;
 
 public:
 	struct Game {
@@ -463,8 +464,13 @@ auto Program::notify(string message) -> void
 		snesCallbacks.snes_no_lag(false);
 	else if (message == "NO_LAG_SGB")
 		snesCallbacks.snes_no_lag(true);
-	else if (message == "LATCH")
+	else if (message == "LATCH") {
+		if (breakOnLatch) {
+			scheduler.StepOnce = true;
+			breakOnLatch = false;
+		}
 		snesCallbacks.snes_controller_latch();
+	}
 }
 
 auto Program::cpuTrace(vector<string> parts) -> void