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

#include "AssetThumbnail.h"
#include "Engine/Blueprint.h"
#include "GameFramework/Actor.h"
#include "Layout/Margin.h"
#include "Widgets/DeclarativeSyntaxSupport.h"
#include "Widgets/SOverlay.h"
#include "Engine/GameViewportClient.h"
#include "Interfaces/Interface_AsyncCompilation.h"
#include "Modules/ModuleManager.h"
#include "Animation/CurveHandle.h"
#include "Animation/CurveSequence.h"
#include "Textures/SlateTextureData.h"
#include "Fonts/SlateFontInfo.h"
#include "Application/ThrottleManager.h"
#include "Widgets/SCompoundWidget.h"
#include "Widgets/Layout/SBorder.h"
#include "Widgets/Images/SImage.h"
#include "Widgets/Text/STextBlock.h"
#include "Widgets/SViewport.h"
#include "Styling/AppStyle.h"
#include "RenderingThread.h"
#include "Settings/ContentBrowserSettings.h"
#include "RenderUtils.h"
#include "Editor/UnrealEdEngine.h"
#include "ThumbnailRendering/ThumbnailManager.h"
#include "Editor.h"
#include "UnrealEdGlobals.h"
#include "Slate/SlateTextures.h"
#include "ObjectTools.h"
#include "AssetRegistry/AssetRegistryModule.h"
#include "AssetRegistry/IAssetRegistry.h"
#include "ShaderCompiler.h"
#include "AssetCompilingManager.h"
#include "IAssetTools.h"
#include "AssetTypeActions_Base.h"
#include "AssetToolsModule.h"
#include "Styling/SlateIconFinder.h"
#include "ClassIconFinder.h"
#include "IVREditorModule.h"
#include "Framework/Application/SlateApplication.h"

FName FAssetThumbnailPool::CustomThumbnailTagName = "CustomThumbnail";

class SAssetThumbnail : public SCompoundWidget
{
public:
	SLATE_BEGIN_ARGS( SAssetThumbnail )
		: _Style("AssetThumbnail")
		, _ThumbnailPool(nullptr)
		, _AllowFadeIn(false)
		, _ForceGenericThumbnail(false)
		, _AllowHintText(true)
		, _AllowAssetSpecificThumbnailOverlay(false)
		, _AllowRealTimeOnHovered(true)
		, _Label(EThumbnailLabel::ClassName)
		, _HighlightedText(FText::GetEmpty())
		, _HintColorAndOpacity(FLinearColor(0.0f, 0.0f, 0.0f, 0.0f))
		, _ClassThumbnailBrushOverride(NAME_None)
		, _AssetTypeColorOverride()
		, _Padding(0)
		, _GenericThumbnailSize(64)
		, _ColorStripOrientation(EThumbnailColorStripOrientation::HorizontalBottomEdge)
		{}

		SLATE_ARGUMENT(FName, Style)
		SLATE_ARGUMENT(TSharedPtr<FAssetThumbnail>, AssetThumbnail)
		SLATE_ARGUMENT(TSharedPtr<FAssetThumbnailPool>, ThumbnailPool)
		SLATE_ARGUMENT(bool, AllowFadeIn)
		SLATE_ARGUMENT(bool, ForceGenericThumbnail)
		SLATE_ARGUMENT(bool, AllowHintText)
		SLATE_ARGUMENT(bool, AllowAssetSpecificThumbnailOverlay)
		SLATE_ARGUMENT(bool, AllowRealTimeOnHovered)
		SLATE_ARGUMENT(EThumbnailLabel::Type, Label)
		SLATE_ATTRIBUTE(FText, HighlightedText)
		SLATE_ATTRIBUTE(FLinearColor, HintColorAndOpacity)
		SLATE_ARGUMENT(FName, ClassThumbnailBrushOverride)
		SLATE_ARGUMENT(TOptional<FLinearColor>, AssetTypeColorOverride)
		SLATE_ARGUMENT(FMargin, Padding)
		SLATE_ATTRIBUTE(int32, GenericThumbnailSize)
		SLATE_ARGUMENT(EThumbnailColorStripOrientation, ColorStripOrientation)

	SLATE_END_ARGS()

	/** Constructs this widget with InArgs */
	void Construct( const FArguments& InArgs )
	{
		Style = InArgs._Style;
		HighlightedText = InArgs._HighlightedText;
		Label = InArgs._Label;
		HintColorAndOpacity = InArgs._HintColorAndOpacity;
		bAllowHintText = InArgs._AllowHintText;
		bAllowRealTimeOnHovered = InArgs._AllowRealTimeOnHovered;
		ThumbnailBrush = nullptr;
		ClassIconBrush = nullptr;
		AssetThumbnail = InArgs._AssetThumbnail;
		bHasRenderedThumbnail = false;
		WidthLastFrame = 0;
		GenericThumbnailBorderPadding = 2.f;
		GenericThumbnailSize = InArgs._GenericThumbnailSize;
		ColorStripOrientation = InArgs._ColorStripOrientation;

		AssetThumbnail->OnAssetDataChanged().AddSP(this, &SAssetThumbnail::OnAssetDataChanged);

		const FAssetData& AssetData = AssetThumbnail->GetAssetData();

		UClass* Class = FindObjectSafe<UClass>(AssetData.AssetClassPath);
		static FAssetToolsModule& AssetToolsModule = FModuleManager::LoadModuleChecked<FAssetToolsModule>(TEXT("AssetTools"));
		TSharedPtr<IAssetTypeActions> AssetTypeActions;
		if ( Class != NULL )
		{
			AssetTypeActions = AssetToolsModule.Get().GetAssetTypeActionsForClass(Class).Pin();
		}

		AssetTypeColorOverride = InArgs._AssetTypeColorOverride;
		AssetColor = FLinearColor::White;
		if( AssetTypeColorOverride.IsSet() )
		{
			AssetColor = AssetTypeColorOverride.GetValue();
		}
		else if ( AssetTypeActions.IsValid() )
		{
			AssetColor = AssetTypeActions->GetTypeColor();
		}

		TSharedRef<SOverlay> OverlayWidget = SNew(SOverlay);

		UpdateThumbnailClass();

		ClassThumbnailBrushOverride = InArgs._ClassThumbnailBrushOverride;

		AssetBackgroundBrushName = *(Style.ToString() + TEXT(".AssetBackground"));
		ClassBackgroundBrushName = *(Style.ToString() + TEXT(".ClassBackground"));

		// The generic representation of the thumbnail, for use before the rendered version, if it exists
		OverlayWidget->AddSlot()
		.Padding(InArgs._Padding)
		[
			SAssignNew(AssetBackgroundWidget, SBorder)
			.BorderImage(GetAssetBackgroundBrush())
			.Padding(GenericThumbnailBorderPadding)		
			.VAlign(VAlign_Center)
			.HAlign(HAlign_Center)
			.Visibility(this, &SAssetThumbnail::GetGenericThumbnailVisibility)
			[
				SNew(SOverlay)
				+SOverlay::Slot()
				[
					SAssignNew(GenericLabelTextBlock, STextBlock)
					.Text(GetLabelText())
					.Font(GetTextFont())
					.Justification(ETextJustify::Center)
					.ColorAndOpacity(FAppStyle::GetColor(Style, ".ColorAndOpacity"))
					.HighlightText(HighlightedText)
				]

				+SOverlay::Slot()
				[
					SAssignNew(GenericThumbnailImage, SImage)
					.DesiredSizeOverride(this, &SAssetThumbnail::GetGenericThumbnailDesiredSize)
					.Image(this, &SAssetThumbnail::GetClassThumbnailBrush)
				]
			]
		];

		if ( InArgs._ThumbnailPool.IsValid() && !InArgs._ForceGenericThumbnail )
		{
			ViewportFadeAnimation = FCurveSequence();
			ViewportFadeCurve = ViewportFadeAnimation.AddCurve(0.f, 0.25f, ECurveEaseFunction::QuadOut);

			TSharedPtr<SViewport> Viewport = 
				SNew( SViewport )
				.EnableGammaCorrection(false)
				// In VR editor every widget is in the world and gamma corrected by the scene renderer.  Thumbnails will have already been gamma
				// corrected and so they need to be reversed
				.ReverseGammaCorrection(IVREditorModule::Get().IsVREditorModeActive())
				.EnableBlending(true)
				.ViewportSize(AssetThumbnail->GetSize());

			Viewport->SetViewportInterface( AssetThumbnail.ToSharedRef() );
			AssetThumbnail->GetViewportRenderTargetTexture(); // Access the render texture to push it on the stack if it isn't already rendered

			InArgs._ThumbnailPool->OnThumbnailRendered().AddSP(this, &SAssetThumbnail::OnThumbnailRendered);
			InArgs._ThumbnailPool->OnThumbnailRenderFailed().AddSP(this, &SAssetThumbnail::OnThumbnailRenderFailed);

			if ( ShouldRender() && (!InArgs._AllowFadeIn || InArgs._ThumbnailPool->IsRendered(AssetThumbnail)) )
			{
				bHasRenderedThumbnail = true;
				ViewportFadeAnimation.JumpToEnd();
			}

			// The viewport for the rendered thumbnail, if it exists
			OverlayWidget->AddSlot()
			[
				SAssignNew(RenderedThumbnailWidget, SBorder)
				.Padding(InArgs._Padding)
				.BorderImage(FStyleDefaults::GetNoBrush())
				.ColorAndOpacity(this, &SAssetThumbnail::GetViewportColorAndOpacity)
				.HAlign(HAlign_Center)
				.VAlign(VAlign_Center)
				[
					Viewport.ToSharedRef()
				]
			];
		}

		if( ThumbnailClass.Get() && bIsClassType )
		{
			OverlayWidget->AddSlot()
			.VAlign(VAlign_Bottom)
			.HAlign(HAlign_Right)
			.Padding(GetClassIconPadding())
			[
				SAssignNew(ClassIconWidget, SBorder)
				.BorderImage(FAppStyle::GetNoBrush())
				[
					SNew(SImage)
					.Image(this, &SAssetThumbnail::GetClassIconBrush)
				]
			];
		}

		if( bAllowHintText )
		{
			OverlayWidget->AddSlot()
				.HAlign(HAlign_Center)
				.VAlign(VAlign_Top)
				.Padding(FMargin(2, 2, 2, 2))
				[
					SNew(SBorder)
					.BorderImage(FAppStyle::GetBrush(Style, ".HintBackground"))
					.BorderBackgroundColor(this, &SAssetThumbnail::GetHintBackgroundColor) //Adjust the opacity of the border itself
					.ColorAndOpacity(HintColorAndOpacity) //adjusts the opacity of the contents of the border
					.Visibility(this, &SAssetThumbnail::GetHintTextVisibility)
					.Padding(0)
					[
						SAssignNew(HintTextBlock, STextBlock)
						.Text(GetLabelText())
						.Font(GetHintTextFont())
						.ColorAndOpacity(FAppStyle::GetColor(Style, ".HintColorAndOpacity"))
						.HighlightText(HighlightedText)
					]
				];
		}

		// The asset color strip
		OverlayWidget->AddSlot()
		.HAlign(ColorStripOrientation == EThumbnailColorStripOrientation::HorizontalBottomEdge ? HAlign_Fill : HAlign_Right)
		.VAlign(ColorStripOrientation == EThumbnailColorStripOrientation::HorizontalBottomEdge ? VAlign_Bottom : VAlign_Fill)
		[
			SAssignNew(AssetColorStripWidget, SBorder)
			.BorderImage(FAppStyle::GetBrush("WhiteBrush"))
			.BorderBackgroundColor(AssetColor)
			.Padding(this, &SAssetThumbnail::GetAssetColorStripPadding)
		];

		if( InArgs._AllowAssetSpecificThumbnailOverlay && AssetTypeActions.IsValid() )
		{
			// Does the asset provide an additional thumbnail overlay?
			TSharedPtr<SWidget> AssetSpecificThumbnailOverlay = AssetTypeActions->GetThumbnailOverlay(AssetData);
			if( AssetSpecificThumbnailOverlay.IsValid() )
			{
				OverlayWidget->AddSlot()
				[
					AssetSpecificThumbnailOverlay.ToSharedRef()
				];
			}
		}

		ChildSlot
		[
			OverlayWidget
		];

		UpdateThumbnailVisibilities();

	}

	void UpdateThumbnailClass()
	{
		const FAssetData& AssetData = AssetThumbnail->GetAssetData();
		ThumbnailClass = MakeWeakObjectPtr(const_cast<UClass*>(FClassIconFinder::GetIconClassForAssetData(AssetData, &bIsClassType)));

		// For non-class types, use the default based upon the actual asset class
		// This has the side effect of not showing a class icon for assets that don't have a proper thumbnail image available
		const FName DefaultThumbnail = (bIsClassType) ? NAME_None : FName(*FString::Printf(TEXT("ClassThumbnail.%s"), *AssetThumbnail->GetAssetData().AssetClassPath.GetAssetName().ToString()));
		ThumbnailBrush = FClassIconFinder::FindThumbnailForClass(ThumbnailClass.Get(), DefaultThumbnail);

		ClassIconBrush = FSlateIconFinder::FindIconBrushForClass(ThumbnailClass.Get());

	}

	FSlateColor GetHintBackgroundColor() const
	{
		const FLinearColor Color = HintColorAndOpacity.Get();
		return FSlateColor( FLinearColor( Color.R, Color.G, Color.B, FMath::Lerp( 0.0f, 0.5f, Color.A ) ) );
	}

	virtual void OnMouseEnter( const FGeometry& MyGeometry, const FPointerEvent& MouseEvent ) override
	{
		SCompoundWidget::OnMouseEnter( MyGeometry, MouseEvent );

		if ( bAllowRealTimeOnHovered )
		{
			AssetThumbnail->SetRealTime( true );
		}
	}
	
	virtual void OnMouseLeave( const FPointerEvent& MouseEvent ) override
	{
		SCompoundWidget::OnMouseLeave( MouseEvent );

		if ( bAllowRealTimeOnHovered )
		{
			AssetThumbnail->SetRealTime( false );
		}
	}

	virtual void Tick( const FGeometry& AllottedGeometry, const double InCurrentTime, const float InDeltaTime ) override
	{
		if ( WidthLastFrame != AllottedGeometry.Size.X )
		{
			WidthLastFrame = AllottedGeometry.Size.X;

			// The width changed, update the font
			if ( GenericLabelTextBlock.IsValid() )
			{
				GenericLabelTextBlock->SetFont( GetTextFont() );
				GenericLabelTextBlock->SetWrapTextAt( GetTextWrapWidth() );
			}

			if ( HintTextBlock.IsValid() )
			{
				HintTextBlock->SetFont( GetHintTextFont() );
				HintTextBlock->SetWrapTextAt( GetTextWrapWidth() );
			}
		}
	}

private:
	void OnAssetDataChanged()
	{
		if ( GenericLabelTextBlock.IsValid() )
		{
			GenericLabelTextBlock->SetText( GetLabelText() );
		}

		if ( HintTextBlock.IsValid() )
		{
			HintTextBlock->SetText( GetLabelText() );
		}

		// Check if the asset has a thumbnail.
		const FObjectThumbnail* ObjectThumbnail = NULL;
		FThumbnailMap ThumbnailMap;
		if( AssetThumbnail->GetAsset() )
		{
			FName FullAssetName = FName( *(AssetThumbnail->GetAssetData().GetFullName()) );
			TArray<FName> ObjectNames;
			ObjectNames.Add( FullAssetName );
			ThumbnailTools::ConditionallyLoadThumbnailsForObjects(ObjectNames, ThumbnailMap);
			ObjectThumbnail = ThumbnailMap.Find( FullAssetName );
		}

		bHasRenderedThumbnail = ObjectThumbnail && !ObjectThumbnail->IsEmpty();
		ViewportFadeAnimation.JumpToEnd();
		AssetThumbnail->GetViewportRenderTargetTexture(); // Access the render texture to push it on the stack if it isnt already rendered

		const FAssetData& AssetData = AssetThumbnail->GetAssetData();

		UClass* Class = FindObject<UClass>(AssetData.AssetClassPath);
		FAssetToolsModule& AssetToolsModule = FModuleManager::LoadModuleChecked<FAssetToolsModule>(TEXT("AssetTools"));
		TWeakPtr<IAssetTypeActions> AssetTypeActions;
		if ( Class != NULL )
		{
			AssetTypeActions = AssetToolsModule.Get().GetAssetTypeActionsForClass(Class);
		}

		UpdateThumbnailClass();

		AssetColor = FLinearColor::White;
		if( AssetTypeColorOverride.IsSet() )
		{
			AssetColor = AssetTypeColorOverride.GetValue();
		}
		else if ( AssetTypeActions.IsValid() )
		{
			AssetColor = AssetTypeActions.Pin()->GetTypeColor();
		}

		//AssetBackgroundWidget->SetBorderBackgroundColor(AssetColor.CopyWithNewOpacity(0.3f));
		AssetColorStripWidget->SetBorderBackgroundColor(AssetColor);

		UpdateThumbnailVisibilities();
	}

	FSlateFontInfo GetTextFont() const
	{
		return FAppStyle::GetFontStyle( WidthLastFrame <= 64 ? FAppStyle::Join(Style, ".FontSmall") : FAppStyle::Join(Style, ".Font") );
	}

	FSlateFontInfo GetHintTextFont() const
	{
		return FAppStyle::GetFontStyle( WidthLastFrame <= 64 ? FAppStyle::Join(Style, ".HintFontSmall") : FAppStyle::Join(Style, ".HintFont") );
	}

	float GetTextWrapWidth() const
	{
		return WidthLastFrame - GenericThumbnailBorderPadding * 2.f;
	}

	const FSlateBrush* GetAssetBackgroundBrush() const
	{
		return FAppStyle::GetBrush(AssetBackgroundBrushName);
	}

	const FSlateBrush* GetClassBackgroundBrush() const
	{

		return FAppStyle::GetBrush(ClassBackgroundBrushName);
	}

	FLinearColor GetViewportColorAndOpacity() const
	{
		return FLinearColor(1, 1, 1, ViewportFadeCurve.GetLerp());
	}
	
	EVisibility GetViewportVisibility() const
	{
		return bHasRenderedThumbnail ? EVisibility::Visible : EVisibility::Collapsed;
	}

	/** The height of the color strip (if it's oriented along the bottom edge) or its width (if it's oriented along the right edge) */
	float GetAssetColorStripThickness() const
	{
		return 2.0f;
	}

	FMargin GetAssetColorStripPadding() const
	{
		if (ColorStripOrientation == EThumbnailColorStripOrientation::HorizontalBottomEdge)
		{
			const float Height = GetAssetColorStripThickness();
			return FMargin(0, Height, 0, 0);
		}
		else
		{
			const float Width = GetAssetColorStripThickness();
			return FMargin(Width, 0, 0, 0);
		}
	}

	const FSlateBrush* GetClassThumbnailBrush() const
	{
		if (ClassThumbnailBrushOverride.IsNone())
		{
			return ThumbnailBrush;
		}
		else
		{
			// Instead of getting the override thumbnail directly from the editor style here get it from the
			// ClassIconFinder since it may have additional styles registered which can be searched by passing
			// it as a default with no class to search for.
			return FClassIconFinder::FindThumbnailForClass(nullptr, ClassThumbnailBrushOverride);
		}
	}

	EVisibility GetClassThumbnailVisibility() const
	{
		if(!bHasRenderedThumbnail)
		{
			const FSlateBrush* ClassThumbnailBrush = GetClassThumbnailBrush();
			if( ClassThumbnailBrush && ThumbnailClass.Get() )
			{
				return EVisibility::Visible;
			}
		}

		return EVisibility::Collapsed;
	}

	EVisibility GetGenericThumbnailVisibility() const
	{
		return (bHasRenderedThumbnail && ViewportFadeAnimation.IsAtEnd()) ? EVisibility::Collapsed : EVisibility::Visible;
	}

	const FSlateBrush* GetClassIconBrush() const
	{
		return ClassIconBrush;
	}

	FMargin GetClassIconPadding() const
	{
		if (ColorStripOrientation == EThumbnailColorStripOrientation::HorizontalBottomEdge)
		{
			const float Height = GetAssetColorStripThickness();
			return FMargin(0, 0, 0, Height);
		}
		else
		{
			const float Width = GetAssetColorStripThickness();
			return FMargin(0, 0, Width, 0);
		}
	}

	EVisibility GetHintTextVisibility() const
	{
		if ( bAllowHintText && ( bHasRenderedThumbnail || !GenericLabelTextBlock.IsValid() ) && HintColorAndOpacity.Get().A > 0 )
		{
			return EVisibility::Visible;
		}

		return EVisibility::Collapsed;
	}

	void OnThumbnailRendered(const FAssetData& AssetData)
	{
		if ( !bHasRenderedThumbnail && AssetData == AssetThumbnail->GetAssetData() && ShouldRender() )
		{
			OnRenderedThumbnailChanged( true );
			ViewportFadeAnimation.Play( this->AsShared() );
		}
	}

	void OnThumbnailRenderFailed(const FAssetData& AssetData)
	{
		if ( bHasRenderedThumbnail && AssetData == AssetThumbnail->GetAssetData() )
		{
			OnRenderedThumbnailChanged( false );
		}
	}

	bool ShouldRender() const
	{
		const FAssetData& AssetData = AssetThumbnail->GetAssetData();

		// Never render a thumbnail for an invalid asset
		if ( !AssetData.IsValid() )
		{
			return false;
		}

		if( AssetData.IsAssetLoaded() )
		{
			// Loaded asset, return true if there is a rendering info for it
			UObject* Asset = AssetData.GetAsset();
			FThumbnailRenderingInfo* RenderInfo = GUnrealEd->GetThumbnailManager()->GetRenderingInfo( Asset );
			if ( RenderInfo != NULL && RenderInfo->Renderer != NULL )
			{
				return true;
			}
		}

		const FObjectThumbnail* CachedThumbnail = ThumbnailTools::FindCachedThumbnail(*AssetData.GetFullName());
		if ( CachedThumbnail != NULL )
		{
			// There is a cached thumbnail for this asset, we should render it
			return !CachedThumbnail->IsEmpty();
		}

		if ( AssetData.AssetClassPath != UBlueprint::StaticClass()->GetClassPathName() )
		{
			// If we are not a blueprint, see if the CDO of the asset's class has a rendering info
			// Blueprints can't do this because the rendering info is based on the generated class
			UClass* AssetClass = FindObject<UClass>(AssetData.AssetClassPath);

			if ( AssetClass )
			{
				FThumbnailRenderingInfo* RenderInfo = GUnrealEd->GetThumbnailManager()->GetRenderingInfo( AssetClass->GetDefaultObject() );
				if ( RenderInfo != NULL && RenderInfo->Renderer != NULL )
				{
					return true;
				}
			}
		}
		
		// Unloaded blueprint or asset that may have a custom thumbnail, check to see if there is a thumbnail in the package to render
		FString PackageFilename;
		if ( FPackageName::DoesPackageExist(AssetData.PackageName.ToString(), &PackageFilename) )
		{
			TSet<FName> ObjectFullNames;
			FThumbnailMap ThumbnailMap;

			FName ObjectFullName = FName(*AssetData.GetFullName());
			ObjectFullNames.Add(ObjectFullName);

			ThumbnailTools::LoadThumbnailsFromPackage(PackageFilename, ObjectFullNames, ThumbnailMap);

			const FObjectThumbnail* ThumbnailPtr = ThumbnailMap.Find(ObjectFullName);
			if (ThumbnailPtr)
			{
				const FObjectThumbnail& ObjectThumbnail = *ThumbnailPtr;
				return ObjectThumbnail.GetImageWidth() > 0 && ObjectThumbnail.GetImageHeight() > 0 && ObjectThumbnail.GetCompressedDataSize() > 0;
			}
		}

		// Always render thumbnails with custom thumbnails
		FString CustomThumbnailTagValue;
		if (AssetData.GetTagValue(FAssetThumbnailPool::CustomThumbnailTagName, CustomThumbnailTagValue))
		{
			return true;
		}

		return false;
	}

	FText GetLabelText() const
	{
		if( Label != EThumbnailLabel::NoLabel )
		{
			if ( Label == EThumbnailLabel::ClassName )
			{
				return GetAssetClassDisplayName();
			}
			else if ( Label == EThumbnailLabel::AssetName ) 
			{
				return GetAssetDisplayName();
			}
		}
		return FText::GetEmpty();
	}

	FText GetDisplayNameForClass( UClass* Class, const FAssetData* AssetData = nullptr) const
	{
		FText ClassDisplayName;
		if ( Class )
		{
			FAssetToolsModule& AssetToolsModule = FModuleManager::LoadModuleChecked<FAssetToolsModule>("AssetTools");
			TWeakPtr<IAssetTypeActions> AssetTypeActions = AssetToolsModule.Get().GetAssetTypeActionsForClass(Class);
			
			if ( AssetTypeActions.IsValid() )
			{
				if (AssetData != nullptr)
				{
					ClassDisplayName = AssetTypeActions.Pin()->GetDisplayNameFromAssetData(*AssetData);
				}

				if (ClassDisplayName.IsEmpty())
				{
					ClassDisplayName = AssetTypeActions.Pin()->GetName();
				}
			}

			if ( ClassDisplayName.IsEmpty() )
			{
				ClassDisplayName = Class->GetDisplayNameText();
			}
		}

		return ClassDisplayName;
	}

	FText GetAssetClassDisplayName() const
	{
		const FAssetData& AssetData = AssetThumbnail->GetAssetData();
		FTopLevelAssetPath AssetClass = AssetData.AssetClassPath;
		UClass* Class = FindObjectSafe<UClass>(AssetClass);

		if ( Class )
		{
			return GetDisplayNameForClass( Class, &AssetData );
		}

		return FText::FromString(AssetClass.ToString());
	}

	FText GetAssetDisplayName() const
	{
		const FAssetData& AssetData = AssetThumbnail->GetAssetData();

		if ( AssetData.GetClass() == UClass::StaticClass() )
		{
			UClass* Class = Cast<UClass>( AssetData.GetAsset() );
			return GetDisplayNameForClass( Class );
		}

		return FText::FromName(AssetData.AssetName);
	}

	void OnRenderedThumbnailChanged( bool bInHasRenderedThumbnail )
	{
		bHasRenderedThumbnail = bInHasRenderedThumbnail;

		UpdateThumbnailVisibilities();
	}

	void UpdateThumbnailVisibilities()
	{
		// Either the generic label or thumbnail should be shown, but not both at once
		const EVisibility ClassThumbnailVisibility = GetClassThumbnailVisibility();
		if( GenericThumbnailImage.IsValid() )
		{
			GenericThumbnailImage->SetVisibility( ClassThumbnailVisibility );
		}
		if( GenericLabelTextBlock.IsValid() )
		{
			GenericLabelTextBlock->SetVisibility( (ClassThumbnailVisibility == EVisibility::Visible) ? EVisibility::Collapsed : EVisibility::Visible );
		}

		const EVisibility ViewportVisibility = GetViewportVisibility();
		if( RenderedThumbnailWidget.IsValid() )
		{
			RenderedThumbnailWidget->SetVisibility( ViewportVisibility );
			if( ClassIconWidget.IsValid() )
			{
				ClassIconWidget->SetVisibility( ViewportVisibility );
			}
		}
	}

	TOptional<FVector2D> GetGenericThumbnailDesiredSize() const
	{
		const int32 Size = GenericThumbnailSize.Get();

		return FVector2D(Size, Size);
	}

private:
	TSharedPtr<STextBlock> GenericLabelTextBlock;
	TSharedPtr<STextBlock> HintTextBlock;
	TSharedPtr<SImage> GenericThumbnailImage;
	TSharedPtr<SBorder> ClassIconWidget;
	TSharedPtr<SBorder> RenderedThumbnailWidget;
	TSharedPtr<SBorder> AssetBackgroundWidget;
	TSharedPtr<SBorder> AssetColorStripWidget;
	TSharedPtr<FAssetThumbnail> AssetThumbnail;
	FCurveSequence ViewportFadeAnimation;
	FCurveHandle ViewportFadeCurve;

	FLinearColor AssetColor;
	TOptional<FLinearColor> AssetTypeColorOverride;

	float WidthLastFrame;
	float GenericThumbnailBorderPadding;
	bool bHasRenderedThumbnail;
	FName Style;
	TAttribute< FText > HighlightedText;
	EThumbnailLabel::Type Label;

	TAttribute< FLinearColor > HintColorAndOpacity;
	TAttribute<int32> GenericThumbnailSize;
	EThumbnailColorStripOrientation ColorStripOrientation;

	bool bAllowHintText;
	bool bAllowRealTimeOnHovered;

	/** The name of the thumbnail which should be used instead of the class thumbnail. */
	FName ClassThumbnailBrushOverride;

	FName AssetBackgroundBrushName;
	FName ClassBackgroundBrushName;

	const FSlateBrush* ThumbnailBrush;

	const FSlateBrush* ClassIconBrush;

	/** The class to use when finding the thumbnail. */
	TWeakObjectPtr<UClass> ThumbnailClass;
	/** Are we showing a class type? (UClass, UBlueprint) */
	bool bIsClassType;
};




FAssetThumbnail::FAssetThumbnail( UObject* InAsset, uint32 InWidth, uint32 InHeight, const TSharedPtr<class FAssetThumbnailPool>& InThumbnailPool )
	: ThumbnailPool(InThumbnailPool)
	, AssetData(InAsset ? FAssetData(InAsset) : FAssetData())
	, Width( InWidth )
	, Height( InHeight )
{
	if ( InThumbnailPool.IsValid() )
	{
		InThumbnailPool->AddReferencer(*this);
	}
}

FAssetThumbnail::FAssetThumbnail( const FAssetData& InAssetData , uint32 InWidth, uint32 InHeight, const TSharedPtr<class FAssetThumbnailPool>& InThumbnailPool )
	: ThumbnailPool( InThumbnailPool )
	, AssetData ( InAssetData )
	, Width( InWidth )
	, Height( InHeight )
{
	if ( InThumbnailPool.IsValid() )
	{
		InThumbnailPool->AddReferencer(*this);
	}
}

FAssetThumbnail::~FAssetThumbnail()
{
	if ( ThumbnailPool.IsValid() )
	{
		ThumbnailPool.Pin()->RemoveReferencer(*this);
	}
}

FIntPoint FAssetThumbnail::GetSize() const
{
	return FIntPoint( Width, Height );
}

FSlateShaderResource* FAssetThumbnail::GetViewportRenderTargetTexture() const
{
	FSlateTexture2DRHIRef* Texture = NULL;
	if ( ThumbnailPool.IsValid() )
	{
		Texture = ThumbnailPool.Pin()->AccessTexture( AssetData, Width, Height );
	}
	if( !Texture || !Texture->IsValid() )
	{
		return NULL;
	}

	return Texture;
}

UObject* FAssetThumbnail::GetAsset() const
{
	if ( AssetData.ObjectPath != NAME_None )
	{
		return FindObject<UObject>(NULL, *AssetData.ObjectPath.ToString());
	}
	else
	{
		return NULL;
	}
}

const FAssetData& FAssetThumbnail::GetAssetData() const
{
	return AssetData;
}

void FAssetThumbnail::SetAsset( const UObject* InAsset )
{
	SetAsset( FAssetData(InAsset) );
}

void FAssetThumbnail::SetAsset( const FAssetData& InAssetData )
{
	if ( ThumbnailPool.IsValid() )
	{
		ThumbnailPool.Pin()->RemoveReferencer(*this);
	}

	if ( InAssetData.IsValid() )
	{
		AssetData = InAssetData;
		if ( ThumbnailPool.IsValid() )
		{
			ThumbnailPool.Pin()->AddReferencer(*this);
		}
	}
	else
	{
		AssetData = FAssetData();
	}

	AssetDataChangedEvent.Broadcast();
}

TSharedRef<SWidget> FAssetThumbnail::MakeThumbnailWidget( const FAssetThumbnailConfig& InConfig )
{
	return
		SNew(SAssetThumbnail)
		.AssetThumbnail(SharedThis(this))
		.ThumbnailPool(ThumbnailPool.Pin())
		.AllowFadeIn(InConfig.bAllowFadeIn)
		.ForceGenericThumbnail(InConfig.bForceGenericThumbnail)
		.Label(InConfig.ThumbnailLabel)
		.HighlightedText(InConfig.HighlightedText)
		.HintColorAndOpacity(InConfig.HintColorAndOpacity)
		.AllowHintText(InConfig.bAllowHintText)
		.AllowRealTimeOnHovered(InConfig.bAllowRealTimeOnHovered)
		.ClassThumbnailBrushOverride(InConfig.ClassThumbnailBrushOverride)
		.AllowAssetSpecificThumbnailOverlay(InConfig.bAllowAssetSpecificThumbnailOverlay)
		.AssetTypeColorOverride(InConfig.AssetTypeColorOverride)
		.Padding(InConfig.Padding)
		.GenericThumbnailSize(InConfig.GenericThumbnailSize)
		.ColorStripOrientation(InConfig.ColorStripOrientation);
}

void FAssetThumbnail::RefreshThumbnail()
{
	if ( ThumbnailPool.IsValid() && AssetData.IsValid() )
	{
		ThumbnailPool.Pin()->RefreshThumbnail( SharedThis(this) );
	}
}

void FAssetThumbnail::SetRealTime(bool bRealTime)
{
	if (ThumbnailPool.IsValid() && AssetData.IsValid())
	{
		ThumbnailPool.Pin()->SetRealTimeThumbnail( SharedThis(this), bRealTime );
	}
}

FAssetThumbnailPool::FAssetThumbnailPool( uint32 InNumInPool, double InMaxFrameTimeAllowance, uint32 InMaxRealTimeThumbnailsPerFrame )
	: NumInPool( InNumInPool )
	, MaxRealTimeThumbnailsPerFrame( InMaxRealTimeThumbnailsPerFrame )
	, MaxFrameTimeAllowance( InMaxFrameTimeAllowance )
{
	FCoreUObjectDelegates::OnObjectPropertyChanged.AddRaw(this, &FAssetThumbnailPool::OnObjectPropertyChanged);
	FCoreUObjectDelegates::OnAssetLoaded.AddRaw(this, &FAssetThumbnailPool::OnAssetLoaded);
	if ( GEditor )
	{
		GEditor->OnActorMoved().AddRaw( this, &FAssetThumbnailPool::OnActorPostEditMove );
	}

	// Add the custom thumbnail tag to the list of tags that the asset registry can parse
	TSet<FName>& MetaDataTagsForAssetRegistry = UObject::GetMetaDataTagsForAssetRegistry();
	MetaDataTagsForAssetRegistry.Add(CustomThumbnailTagName);
}

FAssetThumbnailPool::~FAssetThumbnailPool()
{
	FCoreUObjectDelegates::OnObjectPropertyChanged.RemoveAll(this);
	FCoreUObjectDelegates::OnAssetLoaded.RemoveAll(this);
	if ( GEditor )
	{
		GEditor->OnActorMoved().RemoveAll(this);
	}

	// Release all the texture resources
	ReleaseResources();
}

FAssetThumbnailPool::FThumbnailInfo::~FThumbnailInfo()
{
	if( ThumbnailTexture )
	{
		delete ThumbnailTexture;
		ThumbnailTexture = NULL;
	}

	if( ThumbnailRenderTarget )
	{
		delete ThumbnailRenderTarget;
		ThumbnailRenderTarget = NULL;
	}
}

void FAssetThumbnailPool::ReleaseResources()
{
	// Clear all pending render requests
	ThumbnailsToRenderStack.Empty();
	RealTimeThumbnails.Empty();
	RealTimeThumbnailsToRender.Empty();

	TArray< TSharedRef<FThumbnailInfo> > ThumbnailsToRelease;

	for( auto ThumbIt = ThumbnailToTextureMap.CreateConstIterator(); ThumbIt; ++ThumbIt )
	{
		ThumbnailsToRelease.Add(ThumbIt.Value());
	}
	ThumbnailToTextureMap.Empty();

	for( auto ThumbIt = FreeThumbnails.CreateConstIterator(); ThumbIt; ++ThumbIt )
	{
		ThumbnailsToRelease.Add(*ThumbIt);
	}
	FreeThumbnails.Empty();

	for ( auto ThumbIt = ThumbnailsToRelease.CreateConstIterator(); ThumbIt; ++ThumbIt )
	{
		const TSharedRef<FThumbnailInfo>& Thumb = *ThumbIt;

			// Release rendering resources
			FThumbnailInfo_RenderThread ThumbInfo = Thumb.Get();
			ENQUEUE_RENDER_COMMAND(ReleaseThumbnailResources)(
				[ThumbInfo](FRHICommandListImmediate& RHICmdList)
				{
					ThumbInfo.ThumbnailTexture->ClearTextureData();
					ThumbInfo.ThumbnailTexture->ReleaseResource();
					ThumbInfo.ThumbnailRenderTarget->ReleaseResource();
				});
		}

	// Wait for all resources to be released
	FlushRenderingCommands();

	// Make sure there are no more references to any of our thumbnails now that rendering commands have been flushed
	for ( auto ThumbIt = ThumbnailsToRelease.CreateConstIterator(); ThumbIt; ++ThumbIt )
	{
		const TSharedRef<FThumbnailInfo>& Thumb = *ThumbIt;
		if ( !Thumb.IsUnique() )
		{
			ensureMsgf(0, TEXT("Thumbnail info for '%s' is still referenced by '%d' other objects"), *Thumb->AssetData.ObjectPath.ToString(), Thumb.GetSharedReferenceCount());
		}
	}
}

TStatId FAssetThumbnailPool::GetStatId() const
{
	RETURN_QUICK_DECLARE_CYCLE_STAT( FAssetThumbnailPool, STATGROUP_Tickables );
}

bool FAssetThumbnailPool::IsTickable() const
{
	return RecentlyLoadedAssets.Num() > 0 || ThumbnailsToRenderStack.Num() > 0 || RealTimeThumbnails.Num() > 0 || bWereShadersCompilingLastFrame || (GShaderCompilingManager && GShaderCompilingManager->IsCompiling());
}

void FAssetThumbnailPool::Tick( float DeltaTime )
{
	// If throttling do not tick unless drag dropping which could have a thumbnail as the cursor decorator
	if (FSlateApplication::IsInitialized() && !FSlateApplication::Get().IsDragDropping() && !FSlateThrottleManager::Get().IsAllowingExpensiveTasks() && !FSlateApplication::Get().AnyMenusVisible())
	{
		return;
	}

	const bool bAreShadersCompiling = (GShaderCompilingManager && GShaderCompilingManager->IsCompiling());
	if (bWereShadersCompilingLastFrame && !bAreShadersCompiling)
	{
		ThumbnailsToRenderStack.Reset();
		// Reschedule visible thumbnails to be rerendered now that shaders are finished compiling
		for (auto ThumbIt = ThumbnailToTextureMap.CreateIterator(); ThumbIt; ++ThumbIt)
		{
			ThumbnailsToRenderStack.Push(ThumbIt.Value());
		}
	}
	bWereShadersCompilingLastFrame = bAreShadersCompiling;

	TRACE_CPUPROFILER_EVENT_SCOPE(FAssetThumbnailPool::Tick);
	// If there were any assets loaded since last frame that we are currently displaying thumbnails for, push them on the render stack now.
	if ( RecentlyLoadedAssets.Num() > 0 )
	{
		for ( int32 LoadedAssetIdx = 0; LoadedAssetIdx < RecentlyLoadedAssets.Num(); ++LoadedAssetIdx )
		{
			RefreshThumbnailsFor(RecentlyLoadedAssets[LoadedAssetIdx]);
		}

		RecentlyLoadedAssets.Empty();
	}

	// If we have dynamic thumbnails and we are done rendering the last batch of dynamic thumbnails, start a new batch as long as real-time thumbnails are enabled
	const bool bIsInPIEOrSimulate = GEditor->PlayWorld != NULL || GEditor->bIsSimulatingInEditor;
	const bool bShouldUseRealtimeThumbnails = GetDefault<UContentBrowserSettings>()->RealTimeThumbnails && !bIsInPIEOrSimulate;
	if ( bShouldUseRealtimeThumbnails && RealTimeThumbnails.Num() > 0 && RealTimeThumbnailsToRender.Num() == 0 )
	{
		double CurrentTime = FPlatformTime::Seconds();
		for ( int32 ThumbIdx = RealTimeThumbnails.Num() - 1; ThumbIdx >= 0; --ThumbIdx )
		{
			const TSharedRef<FThumbnailInfo>& Thumb = RealTimeThumbnails[ThumbIdx];
			if ( Thumb->AssetData.IsAssetLoaded() )
			{
				// Only render thumbnails that have been requested recently
				if ( (CurrentTime - Thumb->LastAccessTime) < 1.f )
				{
					RealTimeThumbnailsToRender.Add(Thumb);
				}
			}
			else
			{
				RealTimeThumbnails.RemoveAt(ThumbIdx);
			}
		}
	}

	uint32 NumRealTimeThumbnailsRenderedThisFrame = 0;
	// If there are any thumbnails to render, pop one off the stack and render it.
	if( ThumbnailsToRenderStack.Num() + RealTimeThumbnailsToRender.Num() > 0 )
	{
		double FrameStartTime = FPlatformTime::Seconds();
		// Render as many thumbnails as we are allowed to
		while( ThumbnailsToRenderStack.Num() + RealTimeThumbnailsToRender.Num() > 0 && FPlatformTime::Seconds() - FrameStartTime < MaxFrameTimeAllowance )
		{
			TSharedPtr<FThumbnailInfo> Info;
			if ( ThumbnailsToRenderStack.Num() > 0 )
			{
				Info = ThumbnailsToRenderStack.Pop();
			}
			else if (RealTimeThumbnailsToRender.Num() > 0 && NumRealTimeThumbnailsRenderedThisFrame < MaxRealTimeThumbnailsPerFrame )
			{
				Info = RealTimeThumbnailsToRender.Pop();
				NumRealTimeThumbnailsRenderedThisFrame++;
			}
			else
			{
				// No thumbnails left to render or we don't want to render any more
				break;
			}

			if( Info.IsValid() )
			{
				bool bIsAssetStillCompiling = false;
				TSharedRef<FThumbnailInfo> InfoRef = Info.ToSharedRef();

				if ( InfoRef->AssetData.IsValid() )
				{
					FAssetData CustomThumbnailAsset;
					// Check if a different asset should be used to generate the thumbnail for this asset
					FString CustomThumbnailTagValue;
					if (InfoRef->AssetData.GetTagValue(CustomThumbnailTagName, CustomThumbnailTagValue))
					{
						if (FPackageName::IsValidObjectPath(CustomThumbnailTagValue))
						{
							CustomThumbnailAsset = FModuleManager::LoadModuleChecked<FAssetRegistryModule>(AssetRegistryConstants::ModuleName).Get().GetAssetByObjectPath(*CustomThumbnailTagValue);
						}
					}

					bool bLoadedThumbnail = LoadThumbnail(InfoRef, bIsAssetStillCompiling, CustomThumbnailAsset);

					// If we failed to load a custom thumbnail, then load the custom thumbnail's asset and try again
					if (!bLoadedThumbnail && CustomThumbnailAsset.IsValid())
					{
						// Only load the custom thumbnail if the original asset is also loaded
						//if (InfoRef->AssetData.IsAssetLoaded())
						{
							if (UObject* CustomThumbnail = CustomThumbnailAsset.GetAsset())
							{
								bLoadedThumbnail = LoadThumbnail(InfoRef, bIsAssetStillCompiling, CustomThumbnailAsset);
								CustomThumbnail->ClearFlags(RF_Standalone);
							}
						}
					}

					if ( bLoadedThumbnail )
					{
						// Mark it as updated
						InfoRef->LastUpdateTime = FPlatformTime::Seconds();

						// Notify listeners that a thumbnail has been rendered
						ThumbnailRenderedEvent.Broadcast(InfoRef->AssetData);
					}
					// Do not send a failure event for this asset yet if shaders are still compiling or the asset itself is compiling.
					// The failure event will disable the rendering of this asset for good and we need to have a chance to 
					// rerender it when everything settles down.
					else if (!bAreShadersCompiling && !bIsAssetStillCompiling)
					{
						// Notify listeners that a thumbnail render has failed
						ThumbnailRenderFailedEvent.Broadcast(InfoRef->AssetData);
					}
				}
			}
		}
	}
}

bool FAssetThumbnailPool::LoadThumbnail(TSharedRef<FThumbnailInfo> ThumbnailInfo, bool &bIsAssetStillCompiling, const FAssetData& CustomAssetToRender)
{
	const FAssetData& AssetData = CustomAssetToRender.IsValid() ? CustomAssetToRender : ThumbnailInfo->AssetData;
	UObject* Asset = AssetData.IsAssetLoaded() ? AssetData.GetAsset() : nullptr;

	const bool bAreShadersCompiling = (GShaderCompilingManager && GShaderCompilingManager->IsCompiling());
	
	if (Asset && !bAreShadersCompiling)
	{
		//Avoid rendering the thumbnail of an asset that is currently edited asynchronously
		const IInterface_AsyncCompilation* Interface_AsyncCompilation = Cast<IInterface_AsyncCompilation>(Asset);
		bIsAssetStillCompiling = Interface_AsyncCompilation && Interface_AsyncCompilation->IsCompiling();
		if (!bIsAssetStillCompiling)
		{
			FThumbnailRenderingInfo* RenderInfo = GUnrealEd->GetThumbnailManager()->GetRenderingInfo(Asset);
			if (RenderInfo != nullptr && RenderInfo->Renderer != nullptr)
			{
				FThumbnailInfo_RenderThread ThumbInfo = ThumbnailInfo.Get();
				ENQUEUE_RENDER_COMMAND(SyncSlateTextureCommand)(
					[ThumbInfo](FRHICommandListImmediate& RHICmdList)
				{
					if (ThumbInfo.ThumbnailTexture->GetTypedResource() != ThumbInfo.ThumbnailRenderTarget->GetTextureRHI())
					{
						ThumbInfo.ThumbnailTexture->ClearTextureData();
						ThumbInfo.ThumbnailTexture->ReleaseDynamicRHI();
						ThumbInfo.ThumbnailTexture->SetRHIRef(ThumbInfo.ThumbnailRenderTarget->GetTextureRHI(), ThumbInfo.Width, ThumbInfo.Height);
					}
				});

				if (ThumbnailInfo->LastUpdateTime <= 0.0f || RenderInfo->Renderer->AllowsRealtimeThumbnails(Asset))
				{
					//@todo: this should be done on the GPU only but it is not supported by thumbnail tools yet
					ThumbnailTools::RenderThumbnail(
						Asset,
						ThumbnailInfo->Width,
						ThumbnailInfo->Height,
						ThumbnailTools::EThumbnailTextureFlushMode::NeverFlush,
						ThumbnailInfo->ThumbnailRenderTarget
					);
				}

				return true;
			}
		}
	}

	FThumbnailMap ThumbnailMap;
	// If we could not render a fresh thumbnail, see if we already have a cached one to load
	const FObjectThumbnail* FoundThumbnail = ThumbnailTools::FindCachedThumbnail(AssetData.GetFullName());
	if (!FoundThumbnail)
	{
		// If we don't have a cached thumbnail, try to find it on disk
		FString PackageFilename;
		if (FPackageName::DoesPackageExist(AssetData.PackageName.ToString(), &PackageFilename))
		{
			TSet<FName> ObjectFullNames;


			FName ObjectFullName = FName(*AssetData.GetFullName());
			ObjectFullNames.Add(ObjectFullName);

			ThumbnailTools::LoadThumbnailsFromPackage(PackageFilename, ObjectFullNames, ThumbnailMap);

			FoundThumbnail = ThumbnailMap.Find(ObjectFullName);
		}
	}

	if (FoundThumbnail)
	{
		if (FoundThumbnail->GetImageWidth() > 0 && FoundThumbnail->GetImageHeight() > 0 && FoundThumbnail->GetUncompressedImageData().Num() > 0)
		{
			// Make bulk data for updating the texture memory later
			FSlateTextureData* BulkData = new FSlateTextureData(FoundThumbnail->GetImageWidth(), FoundThumbnail->GetImageHeight(), GPixelFormats[PF_B8G8R8A8].BlockBytes, FoundThumbnail->AccessImageData());

			// Update the texture RHI
			FThumbnailInfo_RenderThread ThumbInfo = ThumbnailInfo.Get();
			ENQUEUE_RENDER_COMMAND(ClearSlateTextureCommand)(
				[ThumbInfo, BulkData](FRHICommandListImmediate& RHICmdList)
			{
				if (ThumbInfo.ThumbnailTexture->GetTypedResource() == ThumbInfo.ThumbnailRenderTarget->GetTextureRHI())
				{
					ThumbInfo.ThumbnailTexture->SetRHIRef(NULL, ThumbInfo.Width, ThumbInfo.Height);
				}

				ThumbInfo.ThumbnailTexture->SetTextureData(MakeShareable(BulkData));
				ThumbInfo.ThumbnailTexture->UpdateRHI();
			});

			return true;
		}
	}
	return false;
}

FSlateTexture2DRHIRef* FAssetThumbnailPool::AccessTexture( const FAssetData& AssetData, uint32 Width, uint32 Height )
{
	if(AssetData.ObjectPath == NAME_None || Width == 0 || Height == 0)
	{
		return NULL;
	}
	else
	{
		FThumbId ThumbId( AssetData.ObjectPath, Width, Height ) ;
		// Check to see if a thumbnail for this asset exists.  If so we don't need to render it
		const TSharedRef<FThumbnailInfo>* ThumbnailInfoPtr = ThumbnailToTextureMap.Find( ThumbId );
		TSharedPtr<FThumbnailInfo> ThumbnailInfo;
		if( ThumbnailInfoPtr )
		{
			ThumbnailInfo = *ThumbnailInfoPtr;
		}
		else
		{
			// If a the max number of thumbnails allowed by the pool exists then reuse its rendering resource for the new thumbnail
			if( FreeThumbnails.Num() == 0 && ThumbnailToTextureMap.Num() == NumInPool )
			{
				// Find the thumbnail which was accessed last and use it for the new thumbnail
				float LastAccessTime = FLT_MAX;
				const FThumbId* AssetToRemove = NULL;
				for( TMap< FThumbId, TSharedRef<FThumbnailInfo> >::TConstIterator It(ThumbnailToTextureMap); It; ++It )
				{
					if( It.Value()->LastAccessTime < LastAccessTime )
					{
						LastAccessTime = It.Value()->LastAccessTime;
						AssetToRemove = &It.Key();
					}
				}

				check( AssetToRemove );

				// Remove the old mapping 
				ThumbnailInfo = ThumbnailToTextureMap.FindAndRemoveChecked( *AssetToRemove );
			}
			else if( FreeThumbnails.Num() > 0 )
			{
				ThumbnailInfo = FreeThumbnails.Pop();

				FSlateTextureRenderTarget2DResource* ThumbnailRenderTarget = ThumbnailInfo->ThumbnailRenderTarget;
				ENQUEUE_RENDER_COMMAND(SlateUpdateThumbSizeCommand)(
					[ThumbnailRenderTarget, Width, Height](FRHICommandListImmediate& RHICmdList)
					{
						ThumbnailRenderTarget->SetSize(Width, Height);
					});
			}
			else
			{
				// There are no free thumbnail resources
				check( (uint32)ThumbnailToTextureMap.Num() <= NumInPool );
				check( !ThumbnailInfo.IsValid() );
				// The pool isn't used up so just make a new texture 

				// Make new thumbnail info if it doesn't exist
				// This happens when the pool is not yet full
				ThumbnailInfo = MakeShareable( new FThumbnailInfo );
				
				// Set the thumbnail and asset on the info. It is NOT safe to change or NULL these pointers until ReleaseResources.
				ThumbnailInfo->ThumbnailTexture = new FSlateTexture2DRHIRef( Width, Height, PF_B8G8R8A8, NULL, TexCreate_Dynamic );
				ThumbnailInfo->ThumbnailRenderTarget = new FSlateTextureRenderTarget2DResource(FLinearColor::Black, Width, Height, PF_B8G8R8A8, SF_Point, TA_Wrap, TA_Wrap, 0.0f);

				BeginInitResource( ThumbnailInfo->ThumbnailTexture );
				BeginInitResource( ThumbnailInfo->ThumbnailRenderTarget );
			}


			check( ThumbnailInfo.IsValid() );
			TSharedRef<FThumbnailInfo> ThumbnailRef = ThumbnailInfo.ToSharedRef();

			// Map the object to its thumbnail info
			ThumbnailToTextureMap.Add( ThumbId, ThumbnailRef );

			ThumbnailInfo->AssetData = AssetData;
			ThumbnailInfo->Width = Width;
			ThumbnailInfo->Height = Height;
		
			// Mark this thumbnail as needing to be updated
			ThumbnailInfo->LastUpdateTime = -1.f;

			// Request that the thumbnail be rendered as soon as possible
			ThumbnailsToRenderStack.Push( ThumbnailRef );
		}

		// This thumbnail was accessed, update its last time to the current time
		// We'll use LastAccessTime to determine the order to recycle thumbnails if the pool is full
		ThumbnailInfo->LastAccessTime = FPlatformTime::Seconds();

		return ThumbnailInfo->ThumbnailTexture;
	}
}

void FAssetThumbnailPool::AddReferencer( const FAssetThumbnail& AssetThumbnail )
{
	FIntPoint Size = AssetThumbnail.GetSize();
	if ( AssetThumbnail.GetAssetData().ObjectPath == NAME_None || Size.X == 0 || Size.Y == 0 )
	{
		// Invalid referencer
		return;
	}

	// Generate a key and look up the number of references in the RefCountMap
	FThumbId ThumbId( AssetThumbnail.GetAssetData().ObjectPath, Size.X, Size.Y ) ;
	int32* RefCountPtr = RefCountMap.Find(ThumbId);

	if ( RefCountPtr )
	{
		// Already in the map, increment a reference
		(*RefCountPtr)++;
	}
	else
	{
		// New referencer, add it to the map with a RefCount of 1
		RefCountMap.Add(ThumbId, 1);
	}
}

void FAssetThumbnailPool::RemoveReferencer( const FAssetThumbnail& AssetThumbnail )
{
	FIntPoint Size = AssetThumbnail.GetSize();
	const FName ObjectPath = AssetThumbnail.GetAssetData().ObjectPath;
	if ( ObjectPath == NAME_None || Size.X == 0 || Size.Y == 0 )
	{
		// Invalid referencer
		return;
	}

	// Generate a key and look up the number of references in the RefCountMap
	FThumbId ThumbId( ObjectPath, Size.X, Size.Y ) ;
	int32* RefCountPtr = RefCountMap.Find(ThumbId);

	// This should complement an AddReferencer so this entry should be in the map
	if ( RefCountPtr )
	{
		// Decrement the RefCount
		(*RefCountPtr)--;

		// If we reached zero, free the thumbnail and remove it from the map.
		if ( (*RefCountPtr) <= 0 )
		{
			RefCountMap.Remove(ThumbId);
			FreeThumbnail(ObjectPath, Size.X, Size.Y);
		}
	}
	else
	{
		// This FAssetThumbnail did not reference anything or was deleted after the pool was deleted.
	}
}

bool FAssetThumbnailPool::IsInRenderStack( const TSharedPtr<FAssetThumbnail>& Thumbnail ) const
{
	const FAssetData& AssetData = Thumbnail->GetAssetData();
	const uint32 Width = Thumbnail->GetSize().X;
	const uint32 Height = Thumbnail->GetSize().Y;

	if ( ensure(AssetData.ObjectPath != NAME_None) && ensure(Width > 0) && ensure(Height > 0) )
	{
		FThumbId ThumbId( AssetData.ObjectPath, Width, Height ) ;
		const TSharedRef<FThumbnailInfo>* ThumbnailInfoPtr = ThumbnailToTextureMap.Find( ThumbId );
		if ( ThumbnailInfoPtr )
		{
			return ThumbnailsToRenderStack.Contains(*ThumbnailInfoPtr);
		}
	}

	return false;
}

bool FAssetThumbnailPool::IsRendered(const TSharedPtr<FAssetThumbnail>& Thumbnail) const
{
	const FAssetData& AssetData = Thumbnail->GetAssetData();
	const uint32 Width = Thumbnail->GetSize().X;
	const uint32 Height = Thumbnail->GetSize().Y;

	if (ensure(AssetData.ObjectPath != NAME_None) && ensure(Width > 0) && ensure(Height > 0))
	{
		FThumbId ThumbId(AssetData.ObjectPath, Width, Height);
		const TSharedRef<FThumbnailInfo>* ThumbnailInfoPtr = ThumbnailToTextureMap.Find(ThumbId);
		if (ThumbnailInfoPtr)
		{
			return (*ThumbnailInfoPtr).Get().LastUpdateTime >= 0.f;
		}
	}

	return false;
}

void FAssetThumbnailPool::PrioritizeThumbnails( const TArray< TSharedPtr<FAssetThumbnail> >& ThumbnailsToPrioritize, uint32 Width, uint32 Height )
{
	if ( ensure(Width > 0) && ensure(Height > 0) )
	{
		TSet<FName> ObjectPathList;
		for ( int32 ThumbIdx = 0; ThumbIdx < ThumbnailsToPrioritize.Num(); ++ThumbIdx )
		{
			ObjectPathList.Add(ThumbnailsToPrioritize[ThumbIdx]->GetAssetData().ObjectPath);
		}

		TArray< TSharedRef<FThumbnailInfo> > FoundThumbnails;
		for ( int32 ThumbIdx = ThumbnailsToRenderStack.Num() - 1; ThumbIdx >= 0; --ThumbIdx )
		{
			const TSharedRef<FThumbnailInfo>& ThumbnailInfo = ThumbnailsToRenderStack[ThumbIdx];
			if ( ThumbnailInfo->Width == Width && ThumbnailInfo->Height == Height && ObjectPathList.Contains(ThumbnailInfo->AssetData.ObjectPath) )
			{
				FoundThumbnails.Add(ThumbnailInfo);
				ThumbnailsToRenderStack.RemoveAt(ThumbIdx);
			}
		}

		for ( int32 ThumbIdx = 0; ThumbIdx < FoundThumbnails.Num(); ++ThumbIdx )
		{
			ThumbnailsToRenderStack.Push(FoundThumbnails[ThumbIdx]);
		}
	}
}

void FAssetThumbnailPool::RefreshThumbnail( const TSharedPtr<FAssetThumbnail>& ThumbnailToRefresh )
{
	const FAssetData& AssetData = ThumbnailToRefresh->GetAssetData();
	const uint32 Width = ThumbnailToRefresh->GetSize().X;
	const uint32 Height = ThumbnailToRefresh->GetSize().Y;

	if ( ensure(AssetData.ObjectPath != NAME_None) && ensure(Width > 0) && ensure(Height > 0) )
	{
		FThumbId ThumbId( AssetData.ObjectPath, Width, Height ) ;
		const TSharedRef<FThumbnailInfo>* ThumbnailInfoPtr = ThumbnailToTextureMap.Find( ThumbId );
		if ( ThumbnailInfoPtr )
		{
			ThumbnailsToRenderStack.AddUnique(*ThumbnailInfoPtr);
		}
	}
}

void FAssetThumbnailPool::SetRealTimeThumbnail( const TSharedPtr<FAssetThumbnail>& Thumbnail, bool bRealTimeThumbnail )
{
	const FAssetData& AssetData = Thumbnail->GetAssetData();
	const uint32 Width = Thumbnail->GetSize().X;
	const uint32 Height = Thumbnail->GetSize().Y;

	if (ensure(AssetData.ObjectPath != NAME_None) && ensure(Width > 0) && ensure(Height > 0) )
	{
		FThumbId ThumbId( AssetData.ObjectPath, Width, Height );
		const TSharedRef<FThumbnailInfo>* ThumbnailInfoPtr = ThumbnailToTextureMap.Find( ThumbId );
		if ( ThumbnailInfoPtr )
		{
			if ( bRealTimeThumbnail )
			{
				RealTimeThumbnails.AddUnique(*ThumbnailInfoPtr);
			}
			else
			{
				RealTimeThumbnails.Remove(*ThumbnailInfoPtr);
			}
		}
	}
}

void FAssetThumbnailPool::FreeThumbnail( const FName& ObjectPath, uint32 Width, uint32 Height )
{
	if(ObjectPath != NAME_None && Width != 0 && Height != 0)
	{
		FThumbId ThumbId( ObjectPath, Width, Height ) ;

		const TSharedRef<FThumbnailInfo>* ThumbnailInfoPtr = ThumbnailToTextureMap.Find(ThumbId);
		if( ThumbnailInfoPtr )
		{
			TSharedRef<FThumbnailInfo> ThumbnailInfo = *ThumbnailInfoPtr;
			ThumbnailToTextureMap.Remove(ThumbId);
			ThumbnailsToRenderStack.Remove(ThumbnailInfo);
			RealTimeThumbnails.Remove(ThumbnailInfo);
			RealTimeThumbnailsToRender.Remove(ThumbnailInfo);

			FSlateTexture2DRHIRef* ThumbnailTexture = ThumbnailInfo->ThumbnailTexture;
			ENQUEUE_RENDER_COMMAND(ReleaseThumbnailTextureData)(
				[ThumbnailTexture](FRHICommandListImmediate& RHICmdList)
				{
					ThumbnailTexture->ClearTextureData();
				});

			FreeThumbnails.Add( ThumbnailInfo );
		}
	}
			
}

void FAssetThumbnailPool::RefreshThumbnailsFor( FName ObjectPath )
{
	for ( auto ThumbIt = ThumbnailToTextureMap.CreateIterator(); ThumbIt; ++ThumbIt)
	{
		if ( ThumbIt.Key().ObjectPath == ObjectPath )
		{
			ThumbnailsToRenderStack.Push( ThumbIt.Value() );
		}
	}
}

void FAssetThumbnailPool::OnAssetLoaded( UObject* Asset )
{
	if ( Asset != NULL )
	{
		RecentlyLoadedAssets.Add( FName(*Asset->GetPathName()) );
	}
}

void FAssetThumbnailPool::OnActorPostEditMove( AActor* Actor )
{
	DirtyThumbnailForObject(Actor);
}

void FAssetThumbnailPool::OnObjectPropertyChanged( UObject* ObjectBeingModified, FPropertyChangedEvent& PropertyChangedEvent )
{
	DirtyThumbnailForObject(ObjectBeingModified);
}

void FAssetThumbnailPool::DirtyThumbnailForObject(UObject* ObjectBeingModified)
{
	if (!ObjectBeingModified)
	{
		return;
	}

	if (ObjectBeingModified->HasAnyFlags(RF_ClassDefaultObject))
	{
		if (ObjectBeingModified->GetClass()->ClassGeneratedBy != nullptr)
		{
			// This is a blueprint modification. Check to see if this thumbnail is the blueprint of the modified CDO
			ObjectBeingModified = ObjectBeingModified->GetClass()->ClassGeneratedBy;
		}
	}
	else if (AActor* ActorBeingModified = Cast<AActor>(ObjectBeingModified))
	{
		// This is a non CDO actor getting modified. Update the actor's world's thumbnail.
		ObjectBeingModified = ActorBeingModified->GetWorld();
	}

	if (ObjectBeingModified)
	{
		// An object in memory was modified.  We'll mark it's thumbnail as dirty so that it'll be
		// regenerated on demand later. (Before being displayed in the browser, or package saves, etc.)
		FObjectThumbnail* Thumbnail = ThumbnailTools::GetThumbnailForObject(ObjectBeingModified);

		// If we don't yet have a thumbnail map, load one from disk if possible
		if (Thumbnail == nullptr)
		{
			UPackage* ObjectPackage = ObjectBeingModified->GetOutermost();

			const bool bMemoryPackage = FPackageName::IsMemoryPackage(ObjectBeingModified->GetPathName());	// Don't try to load from disk if the package is a memory package
			const bool bUnsavedPackage = ObjectPackage->HasAnyPackageFlags(PKG_NewlyCreated);				// Don't try loading thumbnails for package that have never been saved
			const bool bIsGarbageCollecting = IsGarbageCollecting();										// Don't attempt to do this while garbage collecting since loading or finding objects during GC is illegal

			const bool bTryLoadThumbnailFromDisk = !bIsGarbageCollecting && !bMemoryPackage && !bUnsavedPackage;
			if (bTryLoadThumbnailFromDisk)
			{
				FName ObjectFullName = FName(*ObjectBeingModified->GetFullName());

				FThumbnailMap LoadedThumbnails;
				if (ThumbnailTools::ConditionallyLoadThumbnailsForObjects({ ObjectFullName }, LoadedThumbnails))
				{
					Thumbnail = LoadedThumbnails.Find(ObjectFullName);

					if (Thumbnail != nullptr)
					{
						Thumbnail = ThumbnailTools::CacheThumbnail(ObjectBeingModified->GetFullName(), Thumbnail, ObjectPackage);
					}
				}
			}
		}

		if (Thumbnail != nullptr)
		{
			// Mark the thumbnail as dirty
			Thumbnail->MarkAsDirty();
		}

		RefreshThumbnailsFor( FName(*ObjectBeingModified->GetPathName()) );
	}
}