Adding (hopefully) temporary fix to circumvent the destruction of the...

Adding (hopefully) temporary fix to circumvent the destruction of the StereoRenderingDevice from nDisplay

Problem see https://github.com/EpicGames/UnrealEngine/pull/7738

Source/DisplayClusterExtensions/Private/DisplayClusterExtensions.cpp

@@ -4,11 +4,11 @@
 
 void FDisplayClusterExtensionsModule::StartupModule ()
 {
-
+	StereoDeviceFix.Register();
 }
 void FDisplayClusterExtensionsModule::ShutdownModule()
 {
-
+	StereoDeviceFix.Unregister();
 }
 
 #undef LOCTEXT_NAMESPACE

Source/DisplayClusterExtensions/Private/FixNDisplayStereoDevice.cpp

+#include "FixNDisplayStereoDevice.h"
+
+void FFixNDisplayStereoDevice::Register()
+{
+	On_Post_World_Initialization_Delegate.BindRaw(this, &FFixNDisplayStereoDevice::OnSessionStart);
+	StartHandle = FWorldDelegates::OnPostWorldInitialization.Add(On_Post_World_Initialization_Delegate);
+
+	On_Pre_World_Finish_Destroy_Delegate.BindRaw(this, &FFixNDisplayStereoDevice::OnSessionEnd);
+	EndHandle = FWorldDelegates::OnPreWorldFinishDestroy.Add(On_Pre_World_Finish_Destroy_Delegate);
+}
+
+void FFixNDisplayStereoDevice::Unregister()
+{
+	FWorldDelegates::OnPostWorldInitialization.Remove(StartHandle);
+	FWorldDelegates::OnPreWorldFinishDestroy.Remove(EndHandle);
+}
+
+void FFixNDisplayStereoDevice::OnSessionStart(UWorld*, const UWorld::InitializationValues)
+{
+	/* Store handle before it is released */
+	if(GEngine)
+	{
+		StoredRenderingDevice = GEngine->StereoRenderingDevice;
+	}
+}
+
+void FFixNDisplayStereoDevice::OnSessionEnd(UWorld*)
+{
+	/* Restore handle after it was released */
+	if(GEngine)
+	{
+		GEngine->StereoRenderingDevice = StoredRenderingDevice;
+	}
+}

Source/DisplayClusterExtensions/Public/DisplayClusterExtensions.h

 #pragma once
 
 #include "CoreMinimal.h"
+#include "FixNDisplayStereoDevice.h"
 #include "Modules/ModuleManager.h"
 
+
 class FDisplayClusterExtensionsModule : public IModuleInterface
 {
 public:
   virtual void StartupModule () override;
   virtual void ShutdownModule() override;
+
+private:
+	FFixNDisplayStereoDevice StereoDeviceFix;
 };

Source/DisplayClusterExtensions/Public/FixNDisplayStereoDevice.h

+#pragma once
+
+#include "CoreMinimal.h"
+#include "Engine/World.h"
+#include "FixNDisplayStereoDevice.generated.h"
+
+/**
+ * This fixes the behavior of nDisplay DisplayClusterRenderManager, which resets the global stereo render device
+ * This is problematic, since it resets the pointer (L128) to the StereoRenderDevice, even if it does not re-initialize (L113) it.
+ * This results in a fine first start, but crashes on the second VR start. For Desktop this seems to still function fine.
+ *
+ * For this behavior a Pull-Request is in progress. See https://github.com/EpicGames/UnrealEngine/pull/7738
+ */
+USTRUCT()
+struct DISPLAYCLUSTEREXTENSIONS_API FFixNDisplayStereoDevice
+{
+	GENERATED_BODY()
+
+	void Register();
+	void Unregister();
+	
+private:
+	void OnSessionStart(UWorld*, const UWorld::InitializationValues);
+	void OnSessionEnd(UWorld*);
+
+	TSharedPtr< class IStereoRendering, ESPMode::ThreadSafe > StoredRenderingDevice;
+
+	TBaseDelegate<void, UWorld*, const UWorld::InitializationValues> On_Post_World_Initialization_Delegate;
+	TBaseDelegate<void, UWorld*> On_Pre_World_Finish_Destroy_Delegate;
+
+	FDelegateHandle StartHandle;
+	FDelegateHandle EndHandle;
+};

nDisplayExtensions.uplugin

@@ -20,14 +20,11 @@
       "Type": "Runtime",
       "LoadingPhase": "Default"
     },
-	
 	{	
 	  "Name": "DisplayClusterExtensionsEditor",
 	  "Type": "Editor",
 	  "LoadingPhase": "PostEngineInit"
 	}
-
-
   ],
   "Plugins": [
     {