Fast Texturing Tool Undo/Redo (#3720)

- Add Undo Scopes to new Fast Texturing Tool so you can undo/redo
- Save FastTextureSettings in OnClose instead of on ENTER shortcut so that it saves even when closed via X or clicking away from the window

https://files.facepunch.com/CarsonKompon/2026/January/07_10-06-WaterloggedSableantelope.mp4

Author: CarsonKompon

game/addons/tools/Code/Editor/RectEditor/FastTextureWindow.cs

@@ -1,5 +1,4 @@
 using Editor.MeshEditor;
-using Sandbox;
 using Sandbox.UI;
 
 namespace Editor.RectEditor;
@@ -11,6 +10,8 @@ public class FastTextureWindow : Window
 	private List<Material> OriginalMaterials { get; set; } = new();
 	public RectView _RectView { get; private set; }
 
+	private IDisposable _undoScope;
+
 	public FastTextureWindow() : base()
 	{
 		Size = new Vector2( 700, 850 );
@@ -57,10 +58,22 @@ private void InitializeWithFaces( MeshFace[] faces, Material material )
 		OriginalUVs.Clear();
 		OriginalMaterials.Clear();
 
+		List<MeshComponent> components = new();
 		foreach ( var face in faces )
 		{
 			OriginalUVs.Add( face.TextureCoordinates.ToArray() );
 			OriginalMaterials.Add( face.Material );
+			if ( face.Component.IsValid() && !components.Contains( face.Component ) )
+			{
+				components.Add( face.Component );
+			}
+		}
+
+		if ( _undoScope == null )
+		{
+			_undoScope = SceneEditorSession.Active.UndoScope( "Fast Texture Tool" )
+				.WithComponentChanges( components )
+				.Push();
 		}
 
 		if ( material != null )
@@ -214,6 +227,18 @@ public void Cancel()
 
 	[Shortcut( "editor.confirm", "ENTER" )]
 	public void Confirm()
+	{
+		Close();
+	}
+
+	[Shortcut( "editor.fasttexture.resetuvs", "Shift+R" )]
+	public void ResetUVs()
+	{
+		_RectView?.ResetUV();
+		Update();
+	}
+
+	protected override bool OnClose()
 	{
 		var meshRect = Document?.Rectangles.OfType<Document.MeshRectangle>().FirstOrDefault();
 		if ( meshRect != null )
@@ -224,14 +249,10 @@ public void Confirm()
 
 		Settings.FastTextureSettings.Save();
 
-		Close();
-	}
+		_undoScope?.Dispose();
+		_undoScope = null;
 
-	[Shortcut( "editor.fasttexture.resetuvs", "Shift+R" )]
-	public void ResetUVs()
-	{
-		_RectView?.ResetUV();
-		Update();
+		return base.OnClose();
 	}
 }