// Copyright Epic Games, Inc. All Rights Reserved.

#include "PreLoadScreenManager.h"

#include "Engine/GameEngine.h"
#include "Framework/Application/SlateApplication.h"
#include "GlobalShader.h"
#include "ShaderCompiler.h"

#include "PreLoadScreen.h"
#include "PreLoadSettingsContainer.h"

#include "HAL/ThreadManager.h"
#include "Modules/ModuleManager.h"

#if BUILD_EMBEDDED_APP
#include "Misc/EmbeddedCommunication.h"
#endif

#if PLATFORM_ANDROID
#if USE_ANDROID_EVENTS
#include "Android/AndroidEventManager.h"
#endif
#endif

IMPLEMENT_MODULE(FDefaultModuleImpl, PreLoadScreen);

DEFINE_LOG_CATEGORY_STATIC(LogPreLoadScreenManager, Log, All);

TUniquePtr<FPreLoadScreenManager, FPreLoadScreenManager::FPreLoadScreenManagerDelete> FPreLoadScreenManager::Instance;
FCriticalSection FPreLoadScreenManager::AcquireCriticalSection;
TAtomic<bool> FPreLoadScreenManager::bRenderingEnabled(true);

FPreLoadScreenManager* FPreLoadScreenManager::Get()
{
	return Instance.Get();
}

void FPreLoadScreenManager::Create()
{
	check(IsInGameThread());

	// Lock in case a user decide to create/detroy the manager multiple times
	FScopeLock Lock(&AcquireCriticalSection);

	if (!Instance.IsValid() && ArePreLoadScreensEnabled())
	{
		Instance = TUniquePtr<FPreLoadScreenManager, FPreLoadScreenManager::FPreLoadScreenManagerDelete>(new FPreLoadScreenManager);
	}
}

void FPreLoadScreenManager::Destroy()
{
	check(IsInGameThread());

	FScopeLock Lock(&AcquireCriticalSection); // Make sure the render thread is completed before cleaning up

	if (Instance.IsValid())
	{
		Instance->CleanUpResources();
		Instance.Reset();
	}
}

FPreLoadScreenManager::FPreLoadScreenManager()
	: ActivePreLoadScreenIndex(-1)
	, LastTickTime(0.0)
	, bInitialized(false)
	, SyncMechanism(nullptr)
	, bIsResponsibleForRendering(false)
	, bHasRenderPreLoadScreenFrame_RenderThread(false)
	, LastRenderTickTime(0.0)
	, OriginalSlateSleepVariableValue(0.f)
	, bIsEngineLoadingComplete(false)
{}

void FPreLoadScreenManager::Initialize(FSlateRenderer& InSlateRenderer)
{
	check(IsInGameThread());

	if (bInitialized || !ArePreLoadScreensEnabled())
	{
		return;
	}

    bInitialized = true;

	// Initialize shaders, because otherwise they might not be guaranteed to exist at this point
	if (!FPlatformProperties::RequiresCookedData() && GShaderCompilingManager)
	{
		TArray<int32> ShaderMapIds;
		ShaderMapIds.Add(GlobalShaderMapId);
		GShaderCompilingManager->FinishCompilation(TEXT("Global"), ShaderMapIds);
	}

	if (FApp::CanEverRender())
	{
		// Make sure we haven't created a game window already, if so use that. If not make a new one
		UGameEngine* GameEngine = Cast<UGameEngine>(GEngine);
		TSharedRef<SWindow> GameWindow = (GameEngine && GameEngine->GameViewportWindow.IsValid()) ? GameEngine->GameViewportWindow.Pin().ToSharedRef() : UGameEngine::CreateGameWindow();

		VirtualRenderWindow =
			SNew(SVirtualWindow)
			.Size(GameWindow->GetClientSizeInScreen());

		MainWindow = GameWindow;

		WidgetRenderer = MakeShared<FPreLoadSlateWidgetRenderer, ESPMode::ThreadSafe>(GameWindow, VirtualRenderWindow, &InSlateRenderer);
	}

	LastRenderTickTime = FPlatformTime::Seconds();
	LastTickTime = FPlatformTime::Seconds();
}

void FPreLoadScreenManager::RegisterPreLoadScreen(const TSharedPtr<IPreLoadScreen>& PreLoadScreen)
{
	check(IsInGameThread());

    PreLoadScreens.Add(PreLoadScreen);
}

void FPreLoadScreenManager::UnRegisterPreLoadScreen(const TSharedPtr<IPreLoadScreen>& PreLoadScreen)
{
	check(IsInGameThread());

	FScopeLock Lock(&AcquireCriticalSection);
	if (PreLoadScreen.IsValid())
	{
		const int32 IndexOf = PreLoadScreens.IndexOfByKey(PreLoadScreen);
		if (PreLoadScreens.IsValidIndex(IndexOf))
		{
			if (IndexOf == ActivePreLoadScreenIndex)
			{
				ensureMsgf(false, TEXT("Can't remove an active preloadscreen."));
				return;
			}

			TSharedPtr<IPreLoadScreen> PreviousActivePreLoadScreen = PreLoadScreens.IsValidIndex(ActivePreLoadScreenIndex)
				? PreLoadScreens[ActivePreLoadScreenIndex] : nullptr;

			PreLoadScreen->CleanUp();
			PreLoadScreens.RemoveAtSwap(IndexOf);

			if (PreviousActivePreLoadScreen)
			{
				ActivePreLoadScreenIndex = PreLoadScreens.IndexOfByKey(PreviousActivePreLoadScreen);
			}
		}
	}
}

bool FPreLoadScreenManager::PlayFirstPreLoadScreen(EPreLoadScreenTypes PreLoadScreenTypeToPlay)
{
	for (int32 PreLoadScreenIndex = 0; PreLoadScreenIndex < PreLoadScreens.Num(); ++PreLoadScreenIndex)
	{
		if (PreLoadScreens[PreLoadScreenIndex]->GetPreLoadScreenType() == PreLoadScreenTypeToPlay)
		{
			PlayPreLoadScreenAtIndex(PreLoadScreenIndex);
			return true;
		}
	}
	return false;
}

void FPreLoadScreenManager::PlayPreLoadScreenAtIndex(int32 Index)
{
	check(IsInGameThread());

	if (ArePreLoadScreensEnabled())
	{
		FScopeLock Lock(&AcquireCriticalSection);

		if (ensureAlwaysMsgf(!HasValidActivePreLoadScreen(), TEXT("Call to FPreLoadScreenManager::PlayPreLoadScreenAtIndex when something is already playing.")))
		{
			ActivePreLoadScreenIndex = Index;
			if (ensureAlwaysMsgf(HasValidActivePreLoadScreen(), TEXT("Call to FPreLoadScreenManager::PlayPreLoadScreenAtIndex with an invalid index! Nothing will play!")))
			{
				IPreLoadScreen* ActiveScreen = GetActivePreLoadScreen();
				if (ActiveScreen->GetPreLoadScreenType() == EPreLoadScreenTypes::EarlyStartupScreen)
				{
					HandleEarlyStartupPlay();
				}
				else if (ActiveScreen->GetPreLoadScreenType() == EPreLoadScreenTypes::EngineLoadingScreen)
				{
					HandleEngineLoadingPlay();
				}
				else if (ActiveScreen->GetPreLoadScreenType() == EPreLoadScreenTypes::CustomSplashScreen)
				{
					HandleCustomSplashScreenPlay();
				}
				else
				{
					UE_LOG(LogPreLoadScreenManager, Fatal, TEXT("Attempting to play an Active PreLoadScreen type that hasn't been implemented inside of PreLoadScreenmanager!"));
				}
			}
			else
			{
				ActivePreLoadScreenIndex = INDEX_NONE;
			}
		}
    }
}

bool FPreLoadScreenManager::PlayPreLoadScreenWithTag(FName InTag)
{
	for (int32 PreLoadScreenIndex = 0; PreLoadScreenIndex < PreLoadScreens.Num(); ++PreLoadScreenIndex)
	{
		if (PreLoadScreens[PreLoadScreenIndex]->GetPreLoadScreenTag() == InTag)
		{
			PlayPreLoadScreenAtIndex(PreLoadScreenIndex);
			return true;
		}
	}
	return false;
}

void FPreLoadScreenManager::HandleEarlyStartupPlay()
{
	if (ensureAlwaysMsgf(HasActivePreLoadScreenType(EPreLoadScreenTypes::EarlyStartupScreen), TEXT("Invalid Active PreLoadScreen!")))
	{
		IPreLoadScreen* PreLoadScreen = GetActivePreLoadScreen();
		if (PreLoadScreen)
		{
			SCOPED_BOOT_TIMING("FPreLoadScreenManager::HandleEarlyStartupPlay()");

			PreLoadScreen->OnPlay(MainWindow);

			{
				TSharedPtr<SWindow> MainWindowPtr = MainWindow.Pin();
				if (MainWindowPtr.IsValid() && PreLoadScreen->GetWidget().IsValid())
				{
					MainWindowPtr->SetContent(PreLoadScreen->GetWidget().ToSharedRef());
				}
			}

			bool bDidDisableScreensaver = false;
			if (FPlatformApplicationMisc::IsScreensaverEnabled())
			{
				bDidDisableScreensaver = FPlatformApplicationMisc::ControlScreensaver(FGenericPlatformApplicationMisc::EScreenSaverAction::Disable);
			}

			FPlatformMisc::HidePlatformStartupScreen();

			RegisterDelegatesForEarlyStartupPlay();			

			{
				SCOPED_BOOT_TIMING("FPreLoadScreenManager::EarlyPlayFrameTick()");

				//We run this PreLoadScreen until its finished or we lose the MainWindow as EarlyPreLoadPlay is synchronous
				while (!PreLoadScreen->IsDone())
				{
					EarlyPlayFrameTick();
				}
			}

			CleanUpDelegatesForEarlyStartupPlay();

			if (bDidDisableScreensaver)
			{
				FPlatformApplicationMisc::ControlScreensaver(FGenericPlatformApplicationMisc::EScreenSaverAction::Enable);
			}

			StopPreLoadScreen();
		}
	}
}

void FPreLoadScreenManager::RegisterDelegatesForEarlyStartupPlay()
{
	//Have to register to handle FlushRenderingCommands for the length of the PreLoadScreen
	FCoreRenderDelegates::OnFlushRenderingCommandsStart.AddRaw(this, &FPreLoadScreenManager::HandleFlushRenderingCommandsStart);
	FCoreRenderDelegates::OnFlushRenderingCommandsEnd.AddRaw(this, &FPreLoadScreenManager::HandleFlushRenderingCommandsEnd);
}

void FPreLoadScreenManager::CleanUpDelegatesForEarlyStartupPlay()
{
	FCoreRenderDelegates::OnFlushRenderingCommandsStart.RemoveAll(this);
	FCoreRenderDelegates::OnFlushRenderingCommandsEnd.RemoveAll(this);
}

void FPreLoadScreenManager::HandleEngineLoadingPlay()
{
	if (ensureAlwaysMsgf(HasActivePreLoadScreenType(EPreLoadScreenTypes::EngineLoadingScreen), TEXT("Invalid Active PreLoadScreen!")))
	{
		IPreLoadScreen* PreLoadScreen = GetActivePreLoadScreen();
		if (PreLoadScreen)
		{
			PreLoadScreen->OnPlay(MainWindow.Pin());

			if (PreLoadScreen->GetWidget().IsValid() && VirtualRenderWindow.IsValid())
			{
				VirtualRenderWindow->SetContent(PreLoadScreen->GetWidget().ToSharedRef());
			}

			//Need to update bIsResponsibleForRendering as a PreLoadScreen may not have updated it before this point
			if (!bIsResponsibleForRendering && PreLoadScreen->ShouldRender())
			{
				bIsResponsibleForRendering = true;
				IsResponsibleForRenderingDelegate.Broadcast(bIsResponsibleForRendering);
			}
		}

		if (WidgetRenderer.IsValid())
		{
			if (ensure(SyncMechanism == nullptr))
			{
				SyncMechanism = new FPreLoadScreenSlateSynchMechanism(WidgetRenderer);
				SyncMechanism->Initialize();
			}
		}
	}
}

void FPreLoadScreenManager::HandleCustomSplashScreenPlay()
{
	if (ensureAlwaysMsgf(HasActivePreLoadScreenType(EPreLoadScreenTypes::CustomSplashScreen), TEXT("Invalid Active PreLoadScreen!")))
	{
		IPreLoadScreen* PreLoadScreen = GetActivePreLoadScreen();
		if (PreLoadScreen && MainWindow.IsValid())
		{
			SCOPED_BOOT_TIMING("FPreLoadScreenManager::HandleCustomSplashScreenPlay()");

			PreLoadScreen->OnPlay(MainWindow.Pin());

			if (PreLoadScreen->GetWidget().IsValid())
			{
				MainWindow.Pin()->SetContent(PreLoadScreen->GetWidget().ToSharedRef());
			}
			
			bool bDidDisableScreensaver = false;
			if (FPlatformApplicationMisc::IsScreensaverEnabled())
			{
				bDidDisableScreensaver = FPlatformApplicationMisc::ControlScreensaver(FGenericPlatformApplicationMisc::EScreenSaverAction::Disable);
			}

			FPlatformMisc::HidePlatformStartupScreen();
			FPlatformMisc::PlatformHandleSplashScreen(false);

			while (!PreLoadScreen->IsDone())
			{
				EarlyPlayFrameTick();
			}

			if (bDidDisableScreensaver)
			{
				FPlatformApplicationMisc::ControlScreensaver(FGenericPlatformApplicationMisc::EScreenSaverAction::Enable);
			}

			StopPreLoadScreen();
		}
	}
}

void FPreLoadScreenManager::StaticRenderTick_RenderThread()
{
	check(IsInRenderingThread());

	FScopeLock Lock(&AcquireCriticalSection);
	if (ensure(FPreLoadScreenManager::Get())) // The manager should clear the slate render thread before closing
	{
		FPreLoadScreenManager::Get()->RenderTick_RenderThread();
	}
}

void FPreLoadScreenManager::RenderTick_RenderThread()
{
	//Calculate tick time
	const double CurrentTime = FPlatformTime::Seconds();
	double DeltaTime = CurrentTime - LastRenderTickTime;
	LastRenderTickTime = CurrentTime;

	//Check if we have an active index before doing any work
	if (HasValidActivePreLoadScreen() && bRenderingEnabled)
	{
		IPreLoadScreen* PreLoadScreen = GetActivePreLoadScreen();

		check(PreLoadScreen && IsInRenderingThread());
		if (MainWindow.IsValid() && VirtualRenderWindow.IsValid() && !PreLoadScreen->IsDone())
		{
			GFrameNumberRenderThread++;
			GRHICommandList.GetImmediateCommandList().BeginFrame();
			PreLoadScreen->RenderTick(DeltaTime);
			GRHICommandList.GetImmediateCommandList().EndFrame();
			GRHICommandList.GetImmediateCommandList().ImmediateFlush(EImmediateFlushType::FlushRHIThreadFlushResources);
		}
	}
}

bool FPreLoadScreenManager::HasRegisteredPreLoadScreenType(EPreLoadScreenTypes PreLoadScreenTypeToCheck) const
{
    bool HasMatchingRegisteredScreen = false;
    for (const TSharedPtr<IPreLoadScreen>& Screen : PreLoadScreens)
    {
        if (Screen.IsValid() && (Screen->GetPreLoadScreenType() == PreLoadScreenTypeToCheck))
        {
            HasMatchingRegisteredScreen = true;
        }
    }

    return HasMatchingRegisteredScreen;
}

bool FPreLoadScreenManager::HasActivePreLoadScreenType(EPreLoadScreenTypes PreLoadScreenTypeToCheck) const
{
    return (HasValidActivePreLoadScreen() && (GetActivePreLoadScreen()->GetPreLoadScreenType() == PreLoadScreenTypeToCheck));
}

bool FPreLoadScreenManager::HasValidActivePreLoadScreen() const
{
    IPreLoadScreen* PreLoadScreen = nullptr;
    return (PreLoadScreens.IsValidIndex(ActivePreLoadScreenIndex) && PreLoadScreens[ActivePreLoadScreenIndex].IsValid());
}

IPreLoadScreen* FPreLoadScreenManager::GetActivePreLoadScreen()
{
    return HasValidActivePreLoadScreen() ? PreLoadScreens[ActivePreLoadScreenIndex].Get() : nullptr;
}

const IPreLoadScreen* FPreLoadScreenManager::GetActivePreLoadScreen() const
{
    return HasValidActivePreLoadScreen() ? PreLoadScreens[ActivePreLoadScreenIndex].Get() : nullptr;
}

bool FPreLoadScreenManager::HasActivePreLoadScreenTypeForEarlyStartup() const
{
	return HasActivePreLoadScreenType(EPreLoadScreenTypes::EarlyStartupScreen) || HasActivePreLoadScreenType(EPreLoadScreenTypes::CustomSplashScreen);
}

void FPreLoadScreenManager::EarlyPlayFrameTick()
{
    if (ensureAlwaysMsgf(HasActivePreLoadScreenTypeForEarlyStartup(), TEXT("EarlyPlayFrameTick called without a valid EarlyPreLoadScreen!")))
    {
        GameLogicFrameTick();
        EarlyPlayRenderFrameTick();
    }
}

void FPreLoadScreenManager::GameLogicFrameTick()
{
    IPreLoadScreen* ActivePreLoadScreen = GetActivePreLoadScreen();
    if (ensureAlwaysMsgf(ActivePreLoadScreen, TEXT("Invalid Active PreLoadScreen during GameLogicFameTick!")))
    {
        //First spin the platform by having it sleep a bit
        const float SleepTime = ActivePreLoadScreen ? ActivePreLoadScreen->GetAddedTickDelay() : 0.f;
        if (SleepTime > 0)
        {
            FPlatformProcess::Sleep(SleepTime);
        }

        double CurrentTime = FPlatformTime::Seconds();
        double DeltaTime = CurrentTime - LastTickTime;
        LastTickTime = CurrentTime;

		//Clamp to what should be more then any max reasonable time. This is to help with cases of
		//backgrounding or setting breakpoints to trigger huge ticks
		const double MaxTickTime = 5.0;
		DeltaTime = FMath::Min(DeltaTime, MaxTickTime);

        //We have to manually tick everything as we are looping the main thread here
		FTaskGraphInterface::Get().ProcessThreadUntilIdle(ENamedThreads::GameThread);
        FTSTicker::GetCoreTicker().Tick(DeltaTime);
        FThreadManager::Get().Tick();

		//Tick any platform specific things we need here
		PlatformSpecificGameLogicFrameTick();

        //Tick the Active Screen
        ActivePreLoadScreen->Tick(DeltaTime);

        // Pump messages to handle input , etc from system
        FPlatformApplicationMisc::PumpMessages(true);

        FSlateApplication::Get().PollGameDeviceState();
        // Gives widgets a chance to process any accumulated input
        FSlateApplication::Get().FinishedInputThisFrame();

		FSlateApplication::Get().GetPlatformApplication()->Tick(DeltaTime);

        //Needed as this won't be incrementing on its own and some other tick functions rely on this (like analytics)
        GFrameCounter++;
    }
}

void FPreLoadScreenManager::PlatformSpecificGameLogicFrameTick()
{
#if PLATFORM_ANDROID
	Android_PlatformSpecificGameLogicFrameTick();
#endif //PLATFORM_ANDROID

#if PLATFORM_IOS
	IOS_PlatformSpecificGameLogicFrameTick();
#endif //PLATFORM_IOS
}

void FPreLoadScreenManager::EnableRendering(bool bEnabled)
{
    FScopeLock ScopeLock(&AcquireCriticalSection);
    bRenderingEnabled = bEnabled;
}

void FPreLoadScreenManager::EarlyPlayRenderFrameTick()
{
	bool bIsResponsibleForRendering_Local = true;

	if (!bRenderingEnabled || !FSlateApplication::IsInitialized())
	{
		// If rendering disabled, FPreLoadScreenManager is responsible for rendering but choosing not to, probably because the
		// app is not in the foreground.

		// Cycle lock to give a chance to another thread to re-enable rendering.
		AcquireCriticalSection.Unlock();
		FPlatformProcess::Sleep(0);
		AcquireCriticalSection.Lock();
		return;
	}

	IPreLoadScreen* ActivePreLoadScreen = PreLoadScreens[ActivePreLoadScreenIndex].Get();
	if (ensureAlwaysMsgf(ActivePreLoadScreen, TEXT("Invalid Active PreLoadScreen during EarlyPlayRenderFrameTick!")))
	{
		if (!ActivePreLoadScreen->ShouldRender())
		{
			bIsResponsibleForRendering_Local = false;
		}

		if (bIsResponsibleForRendering_Local != bIsResponsibleForRendering)
		{
			bIsResponsibleForRendering = bIsResponsibleForRendering_Local;
			IsResponsibleForRenderingDelegate.Broadcast(bIsResponsibleForRendering);
		}

		if (bIsResponsibleForRendering_Local)
		{
			FSlateApplication& SlateApp = FSlateApplication::Get();
			float SlateDeltaTime = SlateApp.GetDeltaTime();

			//Setup Slate Render Command
			FPreLoadScreenManager* Self = this;
			ENQUEUE_RENDER_COMMAND(BeginPreLoadScreenFrame)(
				[Self, SlateDeltaTime](FRHICommandListImmediate& RHICmdList)
				{
					FScopeLock Lock(&FPreLoadScreenManager::AcquireCriticalSection);
					// Self is still valid because we do a FlushRenderingCommands in StopPreLoadScreen
					if (Self->bRenderingEnabled && Self->HasActivePreLoadScreenTypeForEarlyStartup() && !Self->bHasRenderPreLoadScreenFrame_RenderThread)
					{
						GFrameNumberRenderThread++;
						GRHICommandList.GetImmediateCommandList().BeginFrame();

						Self->bHasRenderPreLoadScreenFrame_RenderThread = true;
						IPreLoadScreen* ActivePreLoadScreen = Self->PreLoadScreens[Self->ActivePreLoadScreenIndex].Get();
						ActivePreLoadScreen->RenderTick(SlateDeltaTime);
					}
				});

			SlateApp.Tick();

			AcquireCriticalSection.Unlock();

			// Synchronize the game thread and the render thread so that the render thread doesn't get too far behind.
			SlateApp.GetRenderer()->Sync();

			AcquireCriticalSection.Lock();

			ENQUEUE_RENDER_COMMAND(FinishPreLoadScreenFrame)(
				[Self](FRHICommandListImmediate& RHICmdList)
				{
					// Self is still valid because we do a FlushRenderingCommands in StopPreLoadScreen
					Self->bHasRenderPreLoadScreenFrame_RenderThread = false;
					GRHICommandList.GetImmediateCommandList().EndFrame();
					GRHICommandList.GetImmediateCommandList().ImmediateFlush(EImmediateFlushType::FlushRHIThreadFlushResources);
				});
		}
	}
}

void FPreLoadScreenManager::StopPreLoadScreen()
{
	check(IsInGameThread());

	if (HasValidActivePreLoadScreen())
	{
		if (ensureMsgf(HasActivePreLoadScreenTypeForEarlyStartup(), TEXT("WaitForEngineLoadingScreenToFinish should be called when using an EngineLoadingScreen.")))
		{
			HandleStopPreLoadScreen();
		}

		AcquireCriticalSection.Unlock();
		FlushRenderingCommands();
		AcquireCriticalSection.Lock();
	}
}

void FPreLoadScreenManager::HandleStopPreLoadScreen()
{
	{
		FScopeLock Lock(&AcquireCriticalSection); // prevent stop while we are rendering the preloadscreen

		if (HasValidActivePreLoadScreen())
		{
			PreLoadScreens[ActivePreLoadScreenIndex]->OnStop();
		}

		ActivePreLoadScreenIndex = -1;

		//Clear our window content
		if (MainWindow.IsValid())
		{
			MainWindow.Pin()->SetContent(SNullWidget::NullWidget);
		}
		if (VirtualRenderWindow.IsValid())
		{
			VirtualRenderWindow->SetContent(SNullWidget::NullWidget);
		}
	}
}

void FPreLoadScreenManager::PassPreLoadScreenWindowBackToGame() const
{
    if (IsUsingMainWindow())
    {
		FScopeLock Lock(&AcquireCriticalSection); // wait until we finish with rendering before moving the context

        UGameEngine* GameEngine = Cast<UGameEngine>(GEngine);
        if (MainWindow.IsValid() && GameEngine)
        {
            GameEngine->GameViewportWindow = MainWindow;
        }
        else
        {
            UE_LOG(LogPreLoadScreenManager, Warning, TEXT("FPreLoadScreenManager::PassLoadingScreenWindowBackToGame failed.  No Window"));
        }
    }
}

bool FPreLoadScreenManager::IsUsingMainWindow() const
{
    return MainWindow.IsValid();
}

TSharedPtr<SWindow> FPreLoadScreenManager::GetRenderWindow()
{
    return MainWindow.IsValid() ? MainWindow.Pin() : nullptr;
}

void FPreLoadScreenManager::WaitForEngineLoadingScreenToFinish()
{
	check(IsInGameThread());

	//Start just doing game logic ticks until the Screen is finished.
	//Since this is a non-early screen, rendering happens separately still on the Slate rendering thread, so only need
	//the game logic ticks
	if (HasActivePreLoadScreenType(EPreLoadScreenTypes::EngineLoadingScreen))
	{
		IPreLoadScreen* ActivePreLoadScreen = GetActivePreLoadScreen();
		while (ActivePreLoadScreen && !ActivePreLoadScreen->IsDone())
		{
			GameLogicFrameTick();
		}
	}

	//No longer need SyncMechanism now that the widget has finished rendering
	if (SyncMechanism != nullptr)
	{
		SyncMechanism->DestroySlateThread();

		delete SyncMechanism;
		SyncMechanism = nullptr;
	}

	HandleStopPreLoadScreen();
}

void FPreLoadScreenManager::SetEngineLoadingComplete(bool IsEngineLoadingFinished)
{
    bIsEngineLoadingComplete = IsEngineLoadingFinished;

    IPreLoadScreen* PreLoadScreen = GetActivePreLoadScreen();
    if (PreLoadScreen)
    {
        PreLoadScreen->SetEngineLoadingFinished(IsEngineLoadingFinished);
    }
}

bool FPreLoadScreenManager::ArePreLoadScreensEnabled()
{
	bool bEnabled = !GIsEditor && !IsRunningDedicatedServer() && !IsRunningCommandlet() && GUseThreadedRendering;

#if !UE_BUILD_SHIPPING
	bEnabled &= !FParse::Param(FCommandLine::Get(), TEXT("NoLoadingScreen"));
#endif

#if PLATFORM_UNIX
	bEnabled = false;
#endif

	return bEnabled;
}

void FPreLoadScreenManager::HandleFlushRenderingCommandsStart()
{
	//Whenever we flush rendering commands we need to unlock this critical section or we will softlock due to our enqueued rendering command never being able to
	//acquire this critical section as its both locked on the GT and the GT won't unlock it as it's waiting for the rendering command to finish to unlock
	AcquireCriticalSection.Unlock();
}

void FPreLoadScreenManager::HandleFlushRenderingCommandsEnd()
{
	//Relock critical section after the FlushRenderCommands finishes as we are
	AcquireCriticalSection.Lock();
}

void FPreLoadScreenManager::CleanUpResources()
{
	// Since we are on the game thread, the PreLoadScreen must be completed.
	//But if we are in EngineLoadingScreen, then the thread may be still active if WaitForEngineLoadingScreenToFinish was not called.
	bool bHasActiPreLoadScreen = HasValidActivePreLoadScreen();
	ensureMsgf(!bHasActiPreLoadScreen, TEXT("StopPreLoadScreen or WaitForEngineLoadingScreenToFinish (if EngineLoadingScreen) should be called before we destroy the Screen Manager."));

	if (SyncMechanism)
	{
		SyncMechanism->DestroySlateThread();
		delete SyncMechanism;
		SyncMechanism = nullptr;
	}

    for (TSharedPtr<IPreLoadScreen>& PreLoadScreen : PreLoadScreens)
    {
        if (PreLoadScreen.IsValid())
        {
            PreLoadScreen->CleanUp();
        }

        PreLoadScreen.Reset();
    }

    OnPreLoadScreenManagerCleanUp.Broadcast();

    //Make sure our FPreLoadSettingsContainer is cleaned up. We do this here instead of one of the
    //StartupScreens because we don't know how many of them will be using the same PreLoadScreenContainer, however any
    //other game specific settings containers should be cleaned up by their screens/modules
    BeginCleanup(&FPreLoadSettingsContainerBase::Get());
}

#if PLATFORM_ANDROID
void FPreLoadScreenManager::Android_PlatformSpecificGameLogicFrameTick()
{
#if USE_ANDROID_EVENTS
	// Process any Android events or we may have issues returning from background
	FAppEventManager::GetInstance()->Tick();
#endif //USE_ANDROIID_EVENTS
}
#endif //PLATFORM_ANDROID

#if PLATFORM_IOS
void FPreLoadScreenManager::IOS_PlatformSpecificGameLogicFrameTick()
{
	// drain the async task queue from the game thread
	[FIOSAsyncTask ProcessAsyncTasks];
}
#endif //PLATFORM_IOS