Restore separate GameEditorSessions (#3453)

* SceneEditorSession: make game vs editor scenes more distinct, Scene is whichever is currently active

* Route prefab update, model reload etc events to both scenes if needed

* SceneTree update checking a bit cleaner

* Bring back GameEditorSessions instead, so undo, selection etc can all be linked 1:1 with scenes again

* tweak and tidy

engine/Sandbox.Tools/Scene/EditorScene.cs

@@ -295,7 +295,7 @@ public static class EditorScene
 
 	public static void Stop()
 	{
-		SceneEditorSession.ActiveGameSession.StopPlaying();
+		SceneEditorSession.Active.StopPlaying();
 
 		Game.IsPlaying = false;
 

engine/Sandbox.Tools/Scene/Session/GameEditorSession.cs

@@ -0,0 +1,27 @@
+namespace Editor;
+
+public class GameEditorSession : SceneEditorSession
+{
+	internal static GameEditorSession Current = null;
+
+	public SceneEditorSession Parent { get; init; }
+
+	public override bool IsPlaying => true;
+
+	public GameEditorSession( SceneEditorSession parent, Scene scene ) : base( scene )
+	{
+		Parent = parent;
+
+		Assert.IsNull( Current, "Attempted to create new GameEditorSession when one already exists!" );
+		Current = this;
+	}
+
+	public override void Destroy()
+	{
+		base.Destroy();
+
+		Current = null;
+	}
+
+	public override void StopPlaying() => Parent.StopPlaying();
+}

engine/Sandbox.Tools/Scene/Session/SceneEditorSession.Game.cs

@@ -2,22 +2,24 @@
 
 partial class SceneEditorSession
 {
-	public Scene ActiveGameScene => activeGameScene;
-	public bool HasActiveGameScene => activeGameScene != null;
+	/// <summary>
+	/// The game session of this editor session, if playing.
+	/// </summary>
+	public GameEditorSession GameSession { get; private set; }
 
-	public static SceneEditorSession ActiveGameSession => All.Where( s => s.HasActiveGameScene ).FirstOrDefault();
-
-	Scene activeGameScene;
+	public virtual bool IsPlaying => GameSession != null;
 
 	public void SetPlaying( Scene scene )
 	{
-		activeGameScene = scene;
-		activeGameScene.Editor = this;
+		GameSession = new GameEditorSession( this, scene );
+		GameSession.MakeActive();
 	}
 
-	public void StopPlaying()
+	public virtual void StopPlaying()
 	{
-		activeGameScene?.Destroy();
-		activeGameScene = null;
+		GameSession?.Destroy();
+		GameSession = null;
+
+		MakeActive();
 	}
 }

engine/Sandbox.Tools/Scene/Session/SceneEditorSession.cs

@@ -15,20 +15,18 @@ public partial class SceneEditorSession : Scene.ISceneEditorSession
 	/// </summary>
 	public static List<SceneEditorSession> All { get; } = new();
 
-	private static SceneEditorSession _active;
-
 	/// <summary>
 	/// The editor session that is currently active
 	/// </summary>
 	public static SceneEditorSession Active
 	{
-		get => _active;
+		get;
 		private set
 		{
-			if ( _active == value ) return;
+			if ( field == value ) return;
 
-			_active = value;
-			_active?.UpdateEditorTitle();
+			field = value;
+			field?.UpdateEditorTitle();
 		}
 	}
 
@@ -41,6 +39,9 @@ public partial class SceneEditorSession : Scene.ISceneEditorSession
 	/// </summary>
 	public bool IsPrefabSession => this is PrefabEditorSession;
 
+	/// <summary>
+	/// The scene for this session
+	/// </summary>
 	public Scene Scene { get; private set; }
 
 	internal Widget SceneDock { get; set; }
@@ -57,7 +58,11 @@ public partial class SceneEditorSession : Scene.ISceneEditorSession
 		InitUndo();
 		timeSinceSavedState = 0;
 
-		CreateSceneDock();
+		if ( this is not GameEditorSession )
+		{
+			// create dock - but not for game sessions, those are built into the parent session widget
+			CreateSceneDock();
+		}
 
 		EditorEvent.Register( this );
 	}
@@ -120,7 +125,7 @@ public partial class SceneEditorSession : Scene.ISceneEditorSession
 
 	bool _destroyed;
 
-	public void Destroy()
+	public virtual void Destroy()
 	{
 		if ( _destroyed )
 			return;
@@ -149,6 +154,9 @@ public partial class SceneEditorSession : Scene.ISceneEditorSession
 		Scene?.Destroy();
 		Scene = null;
 
+		GameSession?.Destroy();
+		GameSession = null;
+
 		SceneDock?.Destroy();
 		SceneDock = default;
 	}
@@ -212,18 +220,6 @@ public partial class SceneEditorSession : Scene.ISceneEditorSession
 		else
 		{
 			SceneDock.SetWindowIcon( "grid_4x4" );
-
-			//
-			// Change the title to reflect current mode
-			//
-			if ( HasActiveGameScene )
-			{
-				SceneDock.WindowTitle = $"{title} (active)";
-			}
-			else
-			{
-				SceneDock.WindowTitle = title;
-			}
 		}
 	}
 
@@ -264,7 +260,7 @@ public partial class SceneEditorSession : Scene.ISceneEditorSession
 	}
 
 	/// <summary>
-	/// Pushes the active editor scene to the current scope
+	/// Pushes the active scene to the current scope
 	/// </summary>
 	public static IDisposable Scope()
 	{
@@ -383,7 +379,7 @@ public partial class SceneEditorSession : Scene.ISceneEditorSession
 	/// </summary>
 	public static SceneEditorSession Resolve( Scene scene )
 	{
-		return All.FirstOrDefault( x => x.ActiveGameScene == scene || x.Scene == scene );
+		return All.FirstOrDefault( x => x.Scene == scene );
 	}
 
 	/// <summary>

game/addons/tools/Code/Editor/ControlSheet/ControlSheetRow.cs

@@ -312,7 +312,7 @@ class ControlSheetRow : Widget
 			return;
 
 		// Only show "Apply To Scene" if we're editing in an active game session
-		if ( !session.HasActiveGameScene || component.GameObject.Scene != session.ActiveGameScene )
+		if ( !session.IsPlaying || component.GameObject.Scene != session.Scene )
 			return;
 
 		// try to find the version of this component in the editor session

game/addons/tools/Code/Scene/SceneTree/SceneTree.cs

@@ -90,7 +90,7 @@ public partial class SceneTreeWidget : Widget
 
 		Layout.Add( TreeView, 1 );
 
-		_lastSession = null;
+		_lastScene.SetTarget( null );
 		CheckForChanges();
 
 		EditorUtility.OnInspect -= OnInspect;
@@ -125,32 +125,31 @@ public partial class SceneTreeWidget : Widget
 		}
 	}
 
-	SceneEditorSession _lastSession;
+	WeakReference<Scene> _lastScene = new( null );
 	bool queryDirty = false;
-	bool hasActiveGameScene = false;
 
 	[EditorEvent.Frame]
 	public void CheckForChanges()
 	{
-		var activeScene = SceneEditorSession.Active;
-		if ( activeScene is null )
+		var session = SceneEditorSession.Active;
+		if ( session is null )
 			return;
 
-		if ( hasActiveGameScene == activeScene.HasActiveGameScene )
-		{
-			if ( !queryDirty && _lastSession == activeScene )
-				return;
-		}
+		_lastScene.TryGetTarget( out var last );
+
+		// if query AND scene is unchanged - no need to rebuild the tree
+		if ( !queryDirty && ReferenceEquals( last, session.Scene ) )
+			return;
+
+		_lastScene.SetTarget( session.Scene );
 
-		_lastSession = activeScene;
 		queryDirty = false;
-		hasActiveGameScene = _lastSession.HasActiveGameScene;
 		Rebuild();
 	}
 
 	private void Rebuild()
 	{
-		var activeScene = SceneEditorSession.Active;
+		var session = SceneEditorSession.Active;
 
 		Header.Clear( true );
 
@@ -161,14 +160,13 @@ public partial class SceneTreeWidget : Widget
 		TreeView.Selection = new SelectionSystem();
 		TreeView.Clear();
 
-		if ( _lastSession is null )
+		if ( session is null )
 			return;
 
 		bool hasSearch = !string.IsNullOrEmpty( Search.Text );
 		SearchClear.Visible = hasSearch;
 
-		var scene = _lastSession.HasActiveGameScene ? _lastSession.ActiveGameScene : _lastSession.Scene;
-
+		var scene = session.Scene;
 		if ( hasSearch )
 		{
 			// flat search view
@@ -237,7 +235,7 @@ public partial class SceneTreeWidget : Widget
 			}
 		}
 
-		TreeView.Selection = activeScene.Selection;
+		TreeView.Selection = session.Selection;
 
 		// Go through the current scene
 		// Feel like this could be loads faster

game/addons/tools/Code/Scene/SceneView/SceneDock.cs

@@ -6,13 +6,15 @@
 /// the dock is hovered or focused. It also destroys the session when the dock
 /// is closed.
 /// </summary>
+/// Sol: does this need to exist? can't we just dock the view widget directly?
 public partial class SceneDock : Widget
 {
-	SceneEditorSession Session { get; set; }
+	public SceneEditorSession Session => _editorSession.GameSession ?? _editorSession;
+	private SceneEditorSession _editorSession;
 
 	public SceneDock( SceneEditorSession session ) : base( null )
 	{
-		Session = session;
+		_editorSession = session;
 
 		Layout = Layout.Row();
 		Layout.Add( new SceneViewWidget( session, this ) );
@@ -23,12 +25,12 @@ public partial class SceneDock : Widget
 
 	protected override bool OnClose()
 	{
-		if ( Session.HasUnsavedChanges )
+		if ( _editorSession.HasUnsavedChanges )
 		{
 			this.ShowUnsavedChangesDialog(
-				assetName: Session.Scene.Name,
-				assetType: Session.IsPrefabSession ? "prefab" : "scene",
-				onSave: () => Session.Save( false ) );
+				assetName: _editorSession.Scene.Name,
+				assetType: _editorSession.IsPrefabSession ? "prefab" : "scene",
+				onSave: () => _editorSession.Save( false ) );
 
 			return false;
 		}
@@ -40,8 +42,8 @@ public partial class SceneDock : Widget
 	{
 		base.OnDestroyed();
 
-		Session.Destroy();
-		Session = null;
+		_editorSession.Destroy();
+		_editorSession = null;
 	}
 
 	protected override void OnVisibilityChanged( bool visible )

game/addons/tools/Code/Scene/SceneView/SceneViewWidget.Game.cs

@@ -17,7 +17,7 @@ public partial class SceneViewWidget
 	[Event( "scene.play" )]
 	public void OnScenePlay()
 	{
-		if ( !Session.HasActiveGameScene ) return;
+		if ( !Session.IsPlaying ) return;
 		CurrentView = ViewMode.Game;
 
 		OnViewModeChanged();
@@ -42,7 +42,7 @@ public partial class SceneViewWidget
 
 	public void ToggleEject()
 	{
-		if ( !Session.HasActiveGameScene ) return;
+		if ( !Session.IsPlaying ) return;
 
 		CurrentView = CurrentView == ViewMode.Game ? ViewMode.GameEjected : ViewMode.Game;
 
@@ -59,12 +59,17 @@ public partial class SceneViewWidget
 	}
 
 	/// <summary>
-	/// Current view mode changed, we need to hide or show some UI things.
+	/// Current view mode changed
 	/// </summary>
 	void OnViewModeChanged()
 	{
 		_viewportTools.Rebuild();
 		_sidePanel?.Visible = CurrentView != ViewMode.Game;
+
+		foreach ( var viewport in _viewports.Values )
+		{
+			viewport.GizmoInstance.Selection = Session.Selection;
+		}
 	}
 
 	public SceneViewportWidget GetGameTarget()

game/addons/tools/Code/Scene/SceneView/SceneViewWidget.cs

@@ -35,7 +35,11 @@ public partial class SceneViewWidget : Widget
 
 	public EditorToolManager Tools { get; private set; }
 
-	public SceneEditorSession Session { get; private set; }
+	/// <summary>
+	/// The currently active session for this scene view. The game session if playing, otherwise the editor session.
+	/// </summary>
+	public SceneEditorSession Session => _editorSession.GameSession ?? _editorSession;
+	private SceneEditorSession _editorSession;
 
 	private List<LinkableSplitter> _splitters;
 	public Dictionary<int, SceneViewportWidget> _viewports;
@@ -44,7 +48,7 @@ public partial class SceneViewWidget : Widget
 
 	public SceneViewWidget( SceneEditorSession session, Widget parent ) : base( parent )
 	{
-		Session = session;
+		_editorSession = session;
 		Tools = new EditorToolManager();
 
 		Layout = Layout.Column();

game/addons/tools/Code/Scene/SceneView/SceneViewportWidget.Game.cs

@@ -5,7 +5,7 @@ public partial class SceneViewportWidget
 	public void StartPlay()
 	{
 		Editor.GameMode.SetPlayWidget( Renderer );
-		Renderer.Scene = Session.ActiveGameScene;
+		Renderer.Scene = Session.Scene;
 		Renderer.Camera = null;
 		Renderer.EnableEngineOverlays = true;
 		ViewportOptions.Visible = false;

game/addons/tools/Code/Scene/SceneView/SceneViewportWidget.State.cs

@@ -170,7 +170,6 @@ public partial class SceneViewportWidget
 	[Event( "scene.session.save" )]
 	public void SaveState()
 	{
-		// Don't save the state of play sessions
 		if ( ProjectCookie is null ) return;
 
 		Scene scene = Session.Scene;

game/addons/tools/Code/Scene/SceneView/SceneViewportWidget.cs

@@ -18,7 +18,7 @@ public partial class SceneViewportWidget : Widget
 	private float TargetFOV { get; set; } = 80;
 	private static float TransitionSpeed => 40;
 
-	SceneEditorSession Session => SceneView.Session;
+	protected virtual SceneEditorSession Session => SceneView.Session;
 	EditorToolManager Tools => SceneView.Tools;
 
 	public SceneRenderingWidget Renderer;
@@ -514,7 +514,6 @@ public partial class SceneViewportWidget : Widget
 		Tools.Frame( _activeCamera, Session );
 
 		EditorEvent.RunInterface<EditorEvent.ISceneView>( x => x.DrawGizmos( Session.Scene ) );
-
 		Session.Scene.EditorDraw();
 
 		DrawSelection();

game/addons/tools/Code/Scene/SceneView/ViewportTools.Options.cs

@@ -57,7 +57,7 @@ partial class ViewportTools
 			o.SetIcon( icon );
 			o.Checkable = true;
 			o.Checked = sceneViewWidget.ViewportLayout == layout;
-			o.Enabled = !sceneViewWidget.Session.HasActiveGameScene; // Not great, but this stuff needs straightening out overall
+			o.Enabled = !sceneViewWidget.Session.IsPlaying; // Not great, but this stuff needs straightening out overall
 		}
 
 		menu.OpenAtCursor();

game/editor/MovieMaker/Code/Editor/MovieEditor.cs

@@ -305,7 +305,7 @@ public partial class MovieEditor : Widget, IHotloadManaged
 	void UpdateEditorContext()
 	{
 		var activeEditorSession = SceneEditorSession.Active;
-		var activeScene = activeEditorSession?.ActiveGameScene ?? activeEditorSession?.Scene;
+		var activeScene = activeEditorSession?.Scene;
 
 		// The current session exists
 		if ( Session is { } session )
@@ -367,7 +367,7 @@ public partial class MovieEditor : Widget, IHotloadManaged
 
 	public void CreateNewPlayer()
 	{
-		using ( SceneEditorSession.Active.Scene.Push() )
+		using ( SceneEditorSession.Scope() )
 		{
 			var go = new GameObject( true, "New Movie Player" );
 			go.Components.Create<MoviePlayer>();