From 4927654da0c562da255d866a63938b050fa94530 Mon Sep 17 00:00:00 2001
From: Kawe Mazidjatari <48657826+Mauler125@users.noreply.github.com>
Date: Tue, 12 Sep 2023 20:50:38 +0200
Subject: [PATCH] Bugfix: only run NVIDIA Reflex if we ran an actual engine
 frame

CEngine::Frame() tends to return out early if we are ahead of frame time, and therefore need to sleep. In this particular engine, CEngine::Frame() returns true if it had actually executed an engine frame, else it returns false.

Therefore, we end up calling 'NvAPI_D3D_Sleep()' multiple times a frame, and thus causing a major loss in performance. Now we check if we have actually ran a frame (incrementing reflex frame if so). If the frame was not incremented, but 'GFX_RunLowLatencyFrame()' was called, it will not call 'NvAPI_D3D_Sleep()'.

Code has been tested and appears to work on my system (never called twice or more per frame). Needs more testing on other systems to make sure its good.
---
 r5dev/engine/sys_dll2.cpp |  8 +++++++-
 r5dev/geforce/reflex.cpp  | 10 ++++++++--
 r5dev/geforce/reflex.h    |  1 +
 r5dev/public/iengine.h    |  2 +-
 4 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/r5dev/engine/sys_dll2.cpp b/r5dev/engine/sys_dll2.cpp
index 7c90ec8a..5c696163 100644
--- a/r5dev/engine/sys_dll2.cpp
+++ b/r5dev/engine/sys_dll2.cpp
@@ -232,7 +232,13 @@ bool CEngineAPI::MainLoop()
         CEngineAPI::PumpMessages();
 #endif // !DEDICATED
 
-        g_pEngine->Frame();
+        if (g_pEngine->Frame())
+        {
+#ifndef DEDICATED
+            // Only increment frame number if we ran an actual engine frame.
+            GFX_IncrementFrameNumber();
+#endif // !DEDICATED
+        }
     }
 }
 
diff --git a/r5dev/geforce/reflex.cpp b/r5dev/geforce/reflex.cpp
index 57f8ac41..747a37f8 100644
--- a/r5dev/geforce/reflex.cpp
+++ b/r5dev/geforce/reflex.cpp
@@ -16,7 +16,8 @@ bool s_ReflexModeInfoUpToDate = false;
 NvAPI_Status s_ReflexModeUpdateStatus = NvAPI_Status::NVAPI_OK;
 
 // Static frame number counter for latency markers.
-int s_ReflexFrameNumber = -1;
+int s_ReflexFrameNumber = 0;
+int s_ReflexLastFrameNumber = 0;
 
 //-----------------------------------------------------------------------------
 // Purpose: mark the parameters as out-of-date; force update next frame
@@ -105,10 +106,15 @@ void GFX_UpdateLowLatencyParameters(IUnknown* device, const bool useLowLatencyMo
 //-----------------------------------------------------------------------------
 void GFX_RunLowLatencyFrame(IUnknown* device)
 {
-	GFX_IncrementFrameNumber();
+	int currentFrameNumber = GFX_GetFrameNumber();
+
+	if (s_ReflexLastFrameNumber == currentFrameNumber)
+		return;
 
 	if (GFX_ParameterUpdateWasSuccessful())
 		NvAPI_D3D_Sleep(device);
+
+	s_ReflexLastFrameNumber = currentFrameNumber;
 }
 
 //-----------------------------------------------------------------------------
diff --git a/r5dev/geforce/reflex.h b/r5dev/geforce/reflex.h
index 09aaa5ab..8cb7157a 100644
--- a/r5dev/geforce/reflex.h
+++ b/r5dev/geforce/reflex.h
@@ -5,6 +5,7 @@ void GFX_MarkLowLatencyParametersOutOfDate(void);
 bool GFX_HasPendingLowLatencyParameterUpdates(void);
 
 int GFX_GetFrameNumber(void);
+void GFX_IncrementFrameNumber(void);
 
 void GFX_UpdateLowLatencyParameters(IUnknown* device, const bool useLowLatencyMode,
 	const bool useLowLatencyBoost, const bool useMarkersToOptimize,
diff --git a/r5dev/public/iengine.h b/r5dev/public/iengine.h
index b5216fd1..36f084ff 100644
--- a/r5dev/public/iengine.h
+++ b/r5dev/public/iengine.h
@@ -45,7 +45,7 @@ public:
 	virtual void	SetNextState(EngineState_t iNextState) = 0;
 	virtual EngineState_t GetState(void) = 0;
 
-	virtual void	Frame(void) = 0;
+	virtual bool	Frame(void) = 0; // Returns true if an engine frame is being ran.
 	virtual float	GetFrameTime(void) = 0;
 	virtual float GetPreviousTime(void) = 0;