BaseLevel selection popup with thumbnail grid

- Add Thumbnail field to FPS_Editor_BaseLevelEntry (UTexture2D)
- Replace BaseLevel combo box with button that opens a selection popup
- Popup displays base levels in a 3-column grid with thumbnails (2:1 ratio)
- Validate/Cancel buttons to confirm or dismiss selection
- Gray placeholder shown for entries without thumbnail

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Unreal/Plugins/PS_Editor/Source/PS_Editor/Spawn/PS_Editor_SpawnCatalog.h

@@ -54,7 +54,7 @@ struct FPS_Editor_BaseLevelEntry
 {
 	GENERATED_BODY()
 
-	/** Display name shown in the editor combo box and used for scene filtering. */
+	/** Display name shown in the editor UI and used for scene filtering. */
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "PS Editor")
 	FString DisplayName;
 
@@ -64,6 +64,10 @@ struct FPS_Editor_BaseLevelEntry
 	 */
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "PS Editor")
 	FString MapPath;
+
+	/** Thumbnail image shown in the BaseLevel selection popup. */
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "PS Editor")
+	TObjectPtr<UTexture2D> Thumbnail;
 };
 
 /**

Unreal/Plugins/PS_Editor/Source/PS_Editor/UI/Widgets/PS_Editor_MainWidget.cpp

@@ -266,6 +266,69 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::RebuildWidget()
 				]
 			]
 		]
+		// BaseLevel selection popup
+		+ SOverlay::Slot()
+		.HAlign(HAlign_Center)
+		.VAlign(VAlign_Center)
+		[
+			SAssignNew(BaseLevelPopup, SBorder)
+			.Visibility(EVisibility::Collapsed)
+			.BorderImage(FCoreStyle::Get().GetBrush("WhiteBrush"))
+			.BorderBackgroundColor(FLinearColor(0.08f, 0.08f, 0.08f, 0.97f))
+			.Padding(FMargin(24.0f, 16.0f))
+			[
+				SNew(SVerticalBox)
+				+ SVerticalBox::Slot().AutoHeight().HAlign(HAlign_Center).Padding(0.0f, 0.0f, 0.0f, 12.0f)
+				[
+					SNew(STextBlock)
+					.Text(FText::FromString(TEXT("Select Base Level")))
+					.Font(FCoreStyle::GetDefaultFontStyle("Bold", 14))
+					.ColorAndOpacity(FLinearColor::White)
+				]
+				+ SVerticalBox::Slot().FillHeight(1.0f).MaxHeight(400.0f)
+				[
+					SNew(SScrollBox)
+					.ConsumeMouseWheel(EConsumeMouseWheel::Always)
+					+ SScrollBox::Slot()
+					[
+						SAssignNew(BaseLevelGridContainer, SVerticalBox)
+					]
+				]
+				+ SVerticalBox::Slot().AutoHeight().HAlign(HAlign_Center).Padding(0.0f, 12.0f, 0.0f, 0.0f)
+				[
+					SNew(SHorizontalBox)
+					+ SHorizontalBox::Slot().AutoWidth().Padding(8.0f, 0.0f)
+					[
+						SNew(SButton)
+						.OnClicked_Lambda([this]() -> FReply
+						{
+							ConfirmBaseLevelSelection();
+							return FReply::Handled();
+						})
+						[
+							SNew(STextBlock)
+							.Text(FText::FromString(TEXT("Validate")))
+							.Font(FCoreStyle::GetDefaultFontStyle("Bold", 11))
+							.ColorAndOpacity(FLinearColor(0.2f, 0.9f, 0.2f))
+						]
+					]
+					+ SHorizontalBox::Slot().AutoWidth().Padding(8.0f, 0.0f)
+					[
+						SNew(SButton)
+						.OnClicked_Lambda([this]() -> FReply
+						{
+							CancelBaseLevelPopup();
+							return FReply::Handled();
+						})
+						[
+							SNew(STextBlock)
+							.Text(FText::FromString(TEXT("Cancel")))
+							.Font(FCoreStyle::GetDefaultFontStyle("Regular", 11))
+						]
+					]
+				]
+			]
+		]
 		// Close confirmation overlay
 		+ SOverlay::Slot()
 		.HAlign(HAlign_Center)
@@ -868,8 +931,7 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::BuildSceneButtons()
 											{
 												if (*Opt == SceneLevelName)
 												{
-													if (BaseLevelCombo.IsValid()) BaseLevelCombo->SetSelectedItem(Opt);
-													if (BaseLevelComboText.IsValid()) BaseLevelComboText->SetText(FText::FromString(SceneLevelName));
+													if (BaseLevelButtonText.IsValid()) BaseLevelButtonText->SetText(FText::FromString(SceneLevelName));
 													break;
 												}
 											}
@@ -896,7 +958,7 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::BuildSceneButtons()
 					]
 				]
 			]
-			// BaseLevel combo box
+			// BaseLevel selection button
 			+ SVerticalBox::Slot()
 			.AutoHeight()
 			.Padding(0.0f, 4.0f, 0.0f, 2.0f)
@@ -911,54 +973,14 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::BuildSceneButtons()
 				]
 				+ SHorizontalBox::Slot().FillWidth(1.0f).VAlign(VAlign_Center)
 				[
-					SAssignNew(BaseLevelCombo, SComboBox<TSharedPtr<FString>>)
-					.OptionsSource(&BaseLevelOptions)
-					.Method(EPopupMethod::UseCurrentWindow)
-					.OnSelectionChanged_Lambda([this](TSharedPtr<FString> Selected, ESelectInfo::Type SelectInfo)
+					SNew(SButton)
+					.OnClicked_Lambda([this]() -> FReply
 					{
-						if (!Selected.IsValid()) return;
-						// Ignore programmatic selection (e.g. from NativeConstruct init)
-						if (SelectInfo == ESelectInfo::Direct) return;
-
-						APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetOwningPlayer());
-						if (!EditorPC) return;
-
-						// Clear current scenario before switching BaseLevel
-						if (UPS_Editor_SceneSerializer* Ser = EditorPC->GetSceneSerializer())
-						{
-							if (UPS_Editor_SpawnManager* SM = EditorPC->GetSpawnManager())
-							{
-								Ser->ClearScene(SM);
-							}
-						}
-						if (SaveNameField.IsValid())
-						{
-							SaveNameField->SetText(FText::GetEmpty());
-						}
-
-						FString SublevelPath = *Selected;
-						if (FString* Found = BaseLevelPathMap.Find(*Selected))
-						{
-							SublevelPath = *Found;
-						}
-						EditorPC->LoadBaseLevelAsSublevel(*Selected, SublevelPath);
-						CurrentLevelFilter = EditorPC->CurrentBaseLevel;
-
-						if (BaseLevelComboText.IsValid())
-						{
-							BaseLevelComboText->SetText(FText::FromString(*Selected));
-						}
-						PopulateSceneList();
-						LastOutlinerActorCount = -1; // Force outliner refresh
-					})
-					.OnGenerateWidget_Lambda([](TSharedPtr<FString> Item) -> TSharedRef<SWidget>
-					{
-						return SNew(STextBlock)
-							.Text(FText::FromString(Item.IsValid() ? *Item : TEXT("")))
-							.Font(FCoreStyle::GetDefaultFontStyle("Regular", 9));
+						OpenBaseLevelPopup();
+						return FReply::Handled();
 					})
 					[
-						SAssignNew(BaseLevelComboText, STextBlock)
+						SAssignNew(BaseLevelButtonText, STextBlock)
 						.Text(FText::FromString(TEXT("Select...")))
 						.Font(FCoreStyle::GetDefaultFontStyle("Bold", 9))
 						.ColorAndOpacity(FLinearColor(0.4f, 0.8f, 0.4f))
@@ -1022,7 +1044,7 @@ void UPS_Editor_MainWidget::NativeConstruct()
 	Super::NativeConstruct();
 	PopulateSpawnCatalog();
 
-	// Populate BaseLevel combo from MasterCatalog
+	// Populate BaseLevel options from MasterCatalog
 	if (APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetOwningPlayer()))
 	{
 		BaseLevelOptions.Add(MakeShared<FString>(TEXT("None")));
@@ -1035,22 +1057,18 @@ void UPS_Editor_MainWidget::NativeConstruct()
 				{
 					BaseLevelPathMap.Add(Entry.DisplayName, Entry.MapPath);
 				}
+				if (Entry.Thumbnail)
+				{
+					BaseLevelThumbnails.Add(Entry.DisplayName, Entry.Thumbnail);
+				}
 			}
 		}
 
-		// If a BaseLevel was set (e.g. from subsystem), select it in the combo
+		// If a BaseLevel was set (e.g. from subsystem), update the button text
 		CurrentLevelFilter = EditorPC->CurrentBaseLevel;
-		if (!CurrentLevelFilter.IsEmpty())
+		if (!CurrentLevelFilter.IsEmpty() && BaseLevelButtonText.IsValid())
 		{
-			for (const TSharedPtr<FString>& Opt : BaseLevelOptions)
-			{
-				if (*Opt == CurrentLevelFilter)
-				{
-					if (BaseLevelCombo.IsValid()) BaseLevelCombo->SetSelectedItem(Opt);
-					if (BaseLevelComboText.IsValid()) BaseLevelComboText->SetText(FText::FromString(CurrentLevelFilter));
-					break;
-				}
-			}
+			BaseLevelButtonText->SetText(FText::FromString(CurrentLevelFilter));
 		}
 
 		// Restore scenario name in save field (from subsystem LastEdited)
@@ -1134,14 +1152,9 @@ void UPS_Editor_MainWidget::PopulateSceneList()
 								EditorPC->LoadBaseLevelAsSublevel(SceneLevelName, SceneMapPath);
 								CurrentLevelFilter = EditorPC->CurrentBaseLevel;
 
-								for (const TSharedPtr<FString>& Opt : BaseLevelOptions)
+								if (BaseLevelButtonText.IsValid())
 								{
-									if (*Opt == SceneLevelName)
-									{
-										if (BaseLevelCombo.IsValid()) BaseLevelCombo->SetSelectedItem(Opt);
-										if (BaseLevelComboText.IsValid()) BaseLevelComboText->SetText(FText::FromString(SceneLevelName));
-										break;
-									}
+									BaseLevelButtonText->SetText(FText::FromString(SceneLevelName));
 								}
 							}
 						}
@@ -2305,6 +2318,177 @@ void UPS_Editor_MainWidget::ShowLoadingScreen(bool bShow)
 	}
 }
 
+void UPS_Editor_MainWidget::OpenBaseLevelPopup()
+{
+	if (!BaseLevelGridContainer.IsValid() || !BaseLevelPopup.IsValid()) return;
+
+	BaseLevelGridContainer->ClearChildren();
+	PendingBaseLevelSelection.Empty();
+
+	const float CardWidth = 160.0f;
+	const float CardHeight = 80.0f; // 2:1 ratio
+	const int32 Columns = 3;
+	TSharedPtr<SHorizontalBox> CurrentRow;
+	int32 ColIndex = 0;
+
+	for (const TSharedPtr<FString>& Option : BaseLevelOptions)
+	{
+		if (!Option.IsValid()) continue;
+		const FString Name = *Option;
+
+		// Start new row if needed
+		if (ColIndex % Columns == 0)
+		{
+			CurrentRow = SNew(SHorizontalBox);
+			BaseLevelGridContainer->AddSlot().AutoHeight().Padding(0.0f, 4.0f)
+			[
+				CurrentRow.ToSharedRef()
+			];
+		}
+
+		TSharedRef<SVerticalBox> Card = SNew(SVerticalBox);
+
+		// Thumbnail
+		TObjectPtr<UTexture2D>* FoundThumb = BaseLevelThumbnails.Find(Name);
+		if (FoundThumb && *FoundThumb)
+		{
+			TSharedPtr<FSlateBrush> Brush = MakeShared<FSlateBrush>();
+			Brush->SetResourceObject(*FoundThumb);
+			Brush->ImageSize = FVector2D(CardWidth, CardHeight);
+			Brush->DrawAs = ESlateBrushDrawType::Image;
+			Brush->Tiling = ESlateBrushTileType::NoTile;
+			CachedBrushes.Add(Brush);
+
+			TWeakPtr<FSlateBrush> WeakBrush = Brush;
+			Card->AddSlot().AutoHeight().HAlign(HAlign_Center)
+			[
+				SNew(SImage)
+				.Image_Lambda([WeakBrush]() -> const FSlateBrush*
+				{
+					return WeakBrush.IsValid() ? WeakBrush.Pin().Get() : nullptr;
+				})
+				.DesiredSizeOverride(FVector2D(CardWidth, CardHeight))
+			];
+		}
+		else
+		{
+			Card->AddSlot().AutoHeight().HAlign(HAlign_Center)
+			[
+				SNew(SBorder)
+				.BorderImage(FCoreStyle::Get().GetBrush("WhiteBrush"))
+				.BorderBackgroundColor(FLinearColor(0.15f, 0.15f, 0.15f))
+				[
+					SNew(SBox)
+					.WidthOverride(CardWidth)
+					.HeightOverride(CardHeight)
+					.HAlign(HAlign_Center)
+					.VAlign(VAlign_Center)
+					[
+						SNew(STextBlock)
+						.Text(FText::FromString(Name))
+						.Font(FCoreStyle::GetDefaultFontStyle("Italic", 9))
+						.ColorAndOpacity(FLinearColor(0.5f, 0.5f, 0.5f))
+					]
+				]
+			];
+		}
+
+		// Name label
+		Card->AddSlot().AutoHeight().HAlign(HAlign_Center).Padding(0.0f, 4.0f, 0.0f, 0.0f)
+		[
+			SNew(STextBlock)
+			.Text(FText::FromString(Name))
+			.Font(FCoreStyle::GetDefaultFontStyle("Regular", 9))
+			.ColorAndOpacity(FLinearColor::White)
+		];
+
+		// Add card to current row
+		CurrentRow->AddSlot().AutoWidth().Padding(8.0f, 0.0f)
+		[
+			SNew(SBox)
+			.MinDesiredWidth(CardWidth + 16.0f)
+			[
+				SNew(SButton)
+				.OnClicked_Lambda([this, Name]() -> FReply
+				{
+					PendingBaseLevelSelection = Name;
+					return FReply::Handled();
+				})
+				[
+					Card
+				]
+			]
+		];
+
+		ColIndex++;
+	}
+
+	BaseLevelPopup->SetVisibility(EVisibility::Visible);
+}
+
+void UPS_Editor_MainWidget::ConfirmBaseLevelSelection()
+{
+	if (BaseLevelPopup.IsValid())
+	{
+		BaseLevelPopup->SetVisibility(EVisibility::Collapsed);
+	}
+
+	if (PendingBaseLevelSelection.IsEmpty()) return;
+
+	APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetOwningPlayer());
+	if (!EditorPC) return;
+
+	// Clear current scenario before switching BaseLevel
+	if (UPS_Editor_SceneSerializer* Ser = EditorPC->GetSceneSerializer())
+	{
+		if (UPS_Editor_SpawnManager* SM = EditorPC->GetSpawnManager())
+		{
+			Ser->ClearScene(SM);
+		}
+	}
+	if (SaveNameField.IsValid())
+	{
+		SaveNameField->SetText(FText::GetEmpty());
+	}
+
+	// Load the selected BaseLevel
+	FString SublevelPath = PendingBaseLevelSelection;
+	if (FString* Found = BaseLevelPathMap.Find(PendingBaseLevelSelection))
+	{
+		SublevelPath = *Found;
+	}
+
+	if (PendingBaseLevelSelection == TEXT("None"))
+	{
+		EditorPC->LoadBaseLevelAsSublevel(TEXT("None"));
+	}
+	else
+	{
+		EditorPC->LoadBaseLevelAsSublevel(PendingBaseLevelSelection, SublevelPath);
+	}
+
+	CurrentLevelFilter = EditorPC->CurrentBaseLevel;
+
+	if (BaseLevelButtonText.IsValid())
+	{
+		BaseLevelButtonText->SetText(FText::FromString(
+			PendingBaseLevelSelection == TEXT("None") ? TEXT("Select...") : PendingBaseLevelSelection));
+	}
+
+	PopulateSceneList();
+	LastOutlinerActorCount = -1;
+	PendingBaseLevelSelection.Empty();
+}
+
+void UPS_Editor_MainWidget::CancelBaseLevelPopup()
+{
+	if (BaseLevelPopup.IsValid())
+	{
+		BaseLevelPopup->SetVisibility(EVisibility::Collapsed);
+	}
+	PendingBaseLevelSelection.Empty();
+}
+
 void UPS_Editor_MainWidget::OnCloseClicked()
 {
 	if (CloseConfirmOverlay.IsValid())

Unreal/Plugins/PS_Editor/Source/PS_Editor/UI/Widgets/PS_Editor_MainWidget.h

@@ -77,14 +77,23 @@ private:
 	// Scene save/load
 	TSharedPtr<SEditableTextBox> SaveNameField;
 	TSharedPtr<SVerticalBox> SceneListContainer;
-	TSharedPtr<SComboBox<TSharedPtr<FString>>> BaseLevelCombo;
 	TArray<TSharedPtr<FString>> BaseLevelOptions;
-	TSharedPtr<STextBlock> BaseLevelComboText;
+	TSharedPtr<STextBlock> BaseLevelButtonText;
 	FString CurrentLevelFilter;
 	/** Maps DisplayName → full MapPath for base levels (from MasterCatalog). */
 	TMap<FString, FString> BaseLevelPathMap;
+	/** Maps DisplayName → Thumbnail texture for base levels. */
+	TMap<FString, TObjectPtr<UTexture2D>> BaseLevelThumbnails;
 	TArray<TSharedPtr<FSlateBrush>> CachedBrushes;
 
+	// BaseLevel selection popup
+	TSharedPtr<SWidget> BaseLevelPopup;
+	TSharedPtr<SVerticalBox> BaseLevelGridContainer;
+	FString PendingBaseLevelSelection;
+	void OpenBaseLevelPopup();
+	void ConfirmBaseLevelSelection();
+	void CancelBaseLevelPopup();
+
 	// Transform fields
 	TSharedPtr<SEditableTextBox> LocX, LocY, LocZ;
 	TSharedPtr<SEditableTextBox> RotX, RotY, RotZ;