Adding AutoLOD tools to the static mesh editor.

Static Mesh Editor changes:
- Share ownership of StaticMeshViewportClient's ModeTools via the EditorModeManager member
- Set up the EditorModeManager's preview scene and selected components when it's copied
- Add a set of FStaticMeshEditorToolbarExtender delegates to the module (similar to FSkeletalMeshEditorToolbarExtender)
- Allow adding an overlay widget to the viewport
- Add a ModeUILayer member to handle mode toolkit hosting

StaticMeshEditorModeling (new module):
- Create a mode and toolkit with AutoLOD and LODManager tools
- Add a button to the StaticMeshEditor's toolbar to toggle UMeshLODPluginEditMode

#rb brooke.hubert semion.piskarev
#jira UETOOL-3663
#preflight 61435ce14778fa00016a0b28
#preflight 614370e8b5a4fa00016459a0

[CL 17541979 by tyson brochu in ue5-main branch]

Engine/Source/Editor/StaticMeshEditor/Private/SStaticMeshEditorViewport.h

@@ -127,6 +127,9 @@ public:
 
 	/** Returns the preview scene being renderd in the viewport */
 	TSharedRef<FAdvancedPreviewScene> GetPreviewScene() { return PreviewScene.ToSharedRef(); }
+
+	TSharedPtr<SOverlay> GetViewportOverlay() { return ViewportOverlay; }
+
 protected:
 	/** SEditorViewport interface */
 	virtual TSharedRef<FEditorViewportClient> MakeEditorViewportClient() override;

Engine/Source/Editor/StaticMeshEditor/Private/StaticMeshEditor.cpp

@@ -52,6 +52,11 @@
 #include "EditorViewportTabContent.h"
 #include "EditorViewportLayout.h"
 #include "Toolkits/AssetEditorToolkitMenuContext.h"
+#include "EditorModeManager.h"
+#include "StaticMeshEditorModeUILayer.h"
+#include "AssetEditorModeManager.h"
+#include "Engine/Selection.h"
+
 
 #define LOCTEXT_NAMESPACE "StaticMeshEditor"
 
@@ -261,12 +266,27 @@ void FStaticMeshEditor::InitStaticMeshEditor( const EToolkitMode::Type Mode, con
 	const bool bCreateDefaultToolbar = true;
 	FAssetEditorToolkit::InitAssetEditor( Mode, InitToolkitHost, StaticMeshEditorAppIdentifier, StandaloneDefaultLayout, bCreateDefaultToolbar, bCreateDefaultStandaloneMenu, ObjectToEdit );
 
+	
+	TSharedPtr<class IToolkitHost> PinnedToolkitHost = ToolkitHost.Pin();
+	check(PinnedToolkitHost.IsValid());
+	ModeUILayer = MakeShareable(new FStaticMeshEditorModeUILayer(PinnedToolkitHost.Get()));
+
+
 	ExtendMenu();
 	ExtendToolBar();
 	RegenerateMenusAndToolbars();
 	GenerateSecondaryToolbar();
 }
 
+
+void FStaticMeshEditor::PostInitAssetEditor()
+{
+	// (Copied from FUVEditorToolkit::PostInitAssetEditor)
+	// We need the viewport client to start out focused, or else it won't get ticked until we click inside it.
+	FStaticMeshEditorViewportClient& ViewportClient = GetStaticMeshViewport()->GetViewportClient();
+	ViewportClient.ReceivedFocus(ViewportClient.Viewport);
+}
+
 void FStaticMeshEditor::GenerateSecondaryToolbar()
 {
 	// Generate the secondary toolbar only if there are registered extensions
@@ -926,6 +946,16 @@ void FStaticMeshEditor::ExtendToolBar()
 	AddToolbarExtender(ToolbarExtender);
 
 	IStaticMeshEditorModule* StaticMeshEditorModule = &FModuleManager::LoadModuleChecked<IStaticMeshEditorModule>("StaticMeshEditor");
+
+	TArray<IStaticMeshEditorModule::FStaticMeshEditorToolbarExtender> ToolbarExtenderDelegates = StaticMeshEditorModule->GetAllStaticMeshEditorToolbarExtenders();
+	for (auto& ToolbarExtenderDelegate : ToolbarExtenderDelegates)
+	{
+		if (ToolbarExtenderDelegate.IsBound())
+		{
+			AddToolbarExtender(ToolbarExtenderDelegate.Execute(GetToolkitCommands(), SharedThis(this)));
+		}
+	}
+
 	EditorToolbarExtender = StaticMeshEditorModule->GetToolBarExtensibilityManager()->GetAllExtenders(GetToolkitCommands(), GetEditingObjects());
 	AddToolbarExtender(EditorToolbarExtender);
 	AddSecondaryToolbarExtender(StaticMeshEditorModule->GetSecondaryToolBarExtensibilityManager()->GetAllExtenders(GetToolkitCommands(), GetEditingObjects()));
@@ -2484,6 +2514,67 @@ TStatId FStaticMeshEditor::GetStatId() const
 	RETURN_QUICK_DECLARE_CYCLE_STAT(FStaticMeshEditor, STATGROUP_TaskGraphTasks);
 }
 
+void FStaticMeshEditor::AddViewportOverlayWidget(TSharedRef<SWidget> InOverlaidWidget)
+{
+	TSharedPtr<SStaticMeshEditorViewport> Viewport = GetStaticMeshViewport();
+
+	if (Viewport.IsValid() && Viewport->GetViewportOverlay().IsValid())
+	{
+		Viewport->GetViewportOverlay()->AddSlot()
+		[
+			InOverlaidWidget
+		];
+	}
+}
+
+void FStaticMeshEditor::RemoveViewportOverlayWidget(TSharedRef<SWidget> InViewportOverlayWidget)
+{
+	TSharedPtr<SStaticMeshEditorViewport> Viewport = GetStaticMeshViewport();
+
+	if (Viewport.IsValid() && Viewport->GetViewportOverlay().IsValid())
+	{
+		Viewport->GetViewportOverlay()->RemoveSlot(InViewportOverlayWidget);
+	}
+}
+
+
+void FStaticMeshEditor::CreateEditorModeManager()
+{
+	//
+	// This function doesn't actually create a new manager -- it assigns StaticMeshEditorViewport->GetViewportClient().GetModeTools() 
+	// to this->EditorModeManager. This is because these two pointers should refer to the same mode manager object, and currently
+	// the ViewPortClient's ModeTools object is created first.
+	// 
+	// This function also:
+	// - sets the manager's PreviewScene to be StaticMeshEditorViewport->GetPreviewScene()
+	// - adds StaticMeshEditorViewport->GetStaticMeshComponent() to the manager's ComponentSet (i.e. selected mesh components)
+	// 
+	
+	TSharedPtr<FAssetEditorModeManager> NewManager = MakeShared<FAssetEditorModeManager>();
+
+	TSharedPtr<SStaticMeshEditorViewport> StaticMeshEditorViewport = GetStaticMeshViewport();
+	if (StaticMeshEditorViewport.IsValid())
+	{
+		TSharedPtr<FEditorModeTools> SharedModeTools = StaticMeshEditorViewport->GetViewportClient().GetModeTools()->AsShared();
+		NewManager = StaticCastSharedPtr<FAssetEditorModeManager>(SharedModeTools);
+		check(NewManager.IsValid());
+
+		TSharedRef<FAdvancedPreviewScene> PreviewScene = StaticMeshEditorViewport->GetPreviewScene();
+		NewManager->SetPreviewScene(&PreviewScene.Get());
+
+		UStaticMeshComponent* const Component = StaticMeshEditorViewport->GetStaticMeshComponent();
+
+		// Copied from FPersonaEditorModeManager::SetPreviewScene(FPreviewScene * NewPreviewScene)
+		USelection* ComponentSet = NewManager->GetSelectedComponents();
+		ComponentSet->BeginBatchSelectOperation();
+		ComponentSet->DeselectAll();
+		ComponentSet->Select(Component, true);
+		ComponentSet->EndBatchSelectOperation();
+	}
+
+	EditorModeManager = NewManager;
+}
+
 bool FStaticMeshEditor::CanRemoveUVChannel()
 {
 	// Can remove UV channel if there's one that is currently being selected and displayed, 
@@ -2904,4 +2995,15 @@ void FStaticMeshEditor::RemoveCurrentUVChannel()
 	}
 }
 
+void FStaticMeshEditor::OnToolkitHostingStarted(const TSharedRef<IToolkit>& Toolkit)
+{
+	ModeUILayer->OnToolkitHostingStarted(Toolkit);
+}
+
+
+void FStaticMeshEditor::OnToolkitHostingFinished(const TSharedRef<IToolkit>& Toolkit)
+{
+	ModeUILayer->OnToolkitHostingFinished(Toolkit);
+}
+
 #undef LOCTEXT_NAMESPACE

Engine/Source/Editor/StaticMeshEditor/Private/StaticMeshEditor.h

@@ -35,6 +35,7 @@ class UStaticMeshSocket;
 class FViewportTabContent;
 struct FPropertyChangedEvent;
 struct FTabSpawnerEntry;
+class FStaticMeshEditorModeUILayer;
 
 /**
  * StaticMesh Editor class
@@ -69,10 +70,16 @@ private:
 	/** Initializes the editor to use a static mesh. Should be the first thing called. */
 	void InitEditorForStaticMesh(UStaticMesh* ObjectToEdit);
 
+	virtual void PostInitAssetEditor() override;
+
 public:
 	virtual void RegisterTabSpawners(const TSharedRef<class FTabManager>& TabManager) override;
 	virtual void UnregisterTabSpawners(const TSharedRef<class FTabManager>& TabManager) override;
 
+	// IToolkitHost Interface
+	void OnToolkitHostingStarted(const TSharedRef<IToolkit>& Toolkit) override;
+	void OnToolkitHostingFinished(const TSharedRef<IToolkit>& Toolkit) override;
+
 	/**
 	 * Edits the specified static mesh object
 	 *
@@ -217,6 +224,13 @@ public:
 	/** Returns the stat ID for this tickable class */
 	virtual TStatId GetStatId() const final;
 
+	/** Add a widget to the StaticMeshViewport's ViewportOverlay */
+	void AddViewportOverlayWidget(TSharedRef<SWidget> InOverlaidWidget) override;
+
+	/** Remove a widget from the StaticMeshViewport's ViewportOverlay */
+	void RemoveViewportOverlayWidget(TSharedRef<SWidget> InViewportOverlayWidget) override;
+
+	void CreateEditorModeManager() override;
 
 private:
 	TSharedRef<SDockTab> SpawnTab_Viewport(const FSpawnTabArgs& Args);
@@ -576,4 +590,6 @@ private:
 	bool bDrawWireframes;
 	bool bDrawVertexColors;
 	bool bDrawAdditionalData;
+
+	TSharedPtr<FStaticMeshEditorModeUILayer> ModeUILayer;
 };

Engine/Source/Editor/StaticMeshEditor/Private/StaticMeshEditorModeUILayer.cpp

@@ -0,0 +1,38 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include "StaticMeshEditorModeUILayer.h"
+#include "WorkspaceMenuStructure.h"
+#include "WorkspaceMenuStructureModule.h"
+#include "Toolkits/IToolkit.h"
+
+FStaticMeshEditorModeUILayer::FStaticMeshEditorModeUILayer(const IToolkitHost* InToolkitHost) :
+	FAssetEditorModeUILayer(InToolkitHost)
+{}
+
+void FStaticMeshEditorModeUILayer::OnToolkitHostingStarted(const TSharedRef<IToolkit>& Toolkit)
+{
+	if (!Toolkit->IsAssetEditor())
+	{
+		FAssetEditorModeUILayer::OnToolkitHostingStarted(Toolkit);
+		HostedToolkit = Toolkit;
+		Toolkit->SetModeUILayer(SharedThis(this));
+		Toolkit->RegisterTabSpawners(ToolkitHost->GetTabManager().ToSharedRef());
+		RegisterModeTabSpawners();
+		OnToolkitHostReadyForUI.ExecuteIfBound();
+	}
+}
+
+void FStaticMeshEditorModeUILayer::OnToolkitHostingFinished(const TSharedRef<IToolkit>& Toolkit)
+{
+	if (HostedToolkit.IsValid() && HostedToolkit.Pin() == Toolkit)
+	{
+		FAssetEditorModeUILayer::OnToolkitHostingFinished(Toolkit);
+	}
+}
+
+TSharedPtr<FWorkspaceItem> FStaticMeshEditorModeUILayer::GetModeMenuCategory() const
+{
+	const IWorkspaceMenuStructure& MenuStructure = WorkspaceMenu::GetMenuStructure();
+	return MenuStructure.GetLevelEditorModesCategory();
+}
+

Engine/Source/Editor/StaticMeshEditor/Private/StaticMeshEditorModeUILayer.h

@@ -0,0 +1,18 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#include "Toolkits/AssetEditorModeUILayer.h"
+
+class FStaticMeshEditorModeUILayer : public FAssetEditorModeUILayer
+{
+public:
+
+	FStaticMeshEditorModeUILayer(const IToolkitHost* InToolkitHost);
+
+	void OnToolkitHostingStarted(const TSharedRef<IToolkit>& Toolkit) override;
+	void OnToolkitHostingFinished(const TSharedRef<IToolkit>& Toolkit) override;
+	
+	TSharedPtr<FWorkspaceItem> GetModeMenuCategory() const override;
+};
+

Engine/Source/Editor/StaticMeshEditor/Private/StaticMeshEditorModule.cpp

@@ -56,10 +56,13 @@ public:
 	virtual TSharedPtr<FExtensibilityManager> GetToolBarExtensibilityManager() override { return ToolBarExtensibilityManager; }
 	virtual TSharedPtr<FExtensibilityManager> GetSecondaryToolBarExtensibilityManager() override { return SecondaryToolBarExtensibilityManager; }
 
+	virtual TArray<FStaticMeshEditorToolbarExtender>& GetAllStaticMeshEditorToolbarExtenders() override { return StaticMeshEditorToolbarExtenders; }
+
 private:
 	TSharedPtr<FExtensibilityManager> MenuExtensibilityManager;
 	TSharedPtr<FExtensibilityManager> ToolBarExtensibilityManager;
 	TSharedPtr<FExtensibilityManager> SecondaryToolBarExtensibilityManager;
+	TArray<FStaticMeshEditorToolbarExtender> StaticMeshEditorToolbarExtenders;
 };
 
 IMPLEMENT_MODULE( FStaticMeshEditorModule, StaticMeshEditor );

Engine/Source/Editor/StaticMeshEditor/Public/StaticMeshEditorModule.h

@@ -29,6 +29,9 @@ public:
 
 	virtual TSharedPtr<FExtensibilityManager> GetSecondaryToolBarExtensibilityManager() = 0;
 
+	DECLARE_DELEGATE_RetVal_TwoParams(TSharedRef<FExtender>, FStaticMeshEditorToolbarExtender, const TSharedRef<FUICommandList>, TSharedRef<IStaticMeshEditor>);
+	virtual TArray<FStaticMeshEditorToolbarExtender>& GetAllStaticMeshEditorToolbarExtenders() = 0;
+
 private:
 	FStaticMeshEditorOpenedEvent StaticMeshEditorOpenedEvent;
 };

Engine/Source/Editor/StaticMeshEditor/StaticMeshEditor.Build.cs

@@ -46,6 +46,8 @@ public class StaticMeshEditor : ModuleRules
 				"StaticMeshDescription",
 				"ToolMenus",
 				"DetailCustomizations",
+				"StatusBar",
+				"WorkspaceMenuStructure",
 				"PhysicsUtilities",
 			}
 		);
@@ -55,7 +57,6 @@ public class StaticMeshEditor : ModuleRules
 				"SceneOutliner",
 				"ClassViewer",
 				"ContentBrowser",
-				"WorkspaceMenuStructure",
                 "MeshReductionInterface",
             }
 		);