Screen fader on level transition

Scripts/GlobalState.cs

@@ -1,11 +1,16 @@
+using System.Threading.Tasks;
 using Cirno.Scripts.Resources;
 using Godot;
+using GTweens.Builders;
+using GTweensGodot.Extensions;
 
 public partial class GlobalState : Node
 {
     public static GlobalState Instance { get; private set; }
 
     public Node CurrentScene { get; set; }
+    
+    private ColorRect _fader { get; set; }
 
     public override void _Ready()
     {
@@ -16,6 +21,8 @@ public partial class GlobalState : Node
         Viewport root = GetTree().Root;
         // Using a negative index counts from the end, so this gets the last child node of `root`.
         CurrentScene = root.GetChild(-1);
+
+        _fader = CreateFader();
     }
 
     public void GotoScene(string path)
@@ -28,16 +35,26 @@ public partial class GlobalState : Node
 
         // The solution is to defer the load to a later time, when
         // we can be sure that no code from the current scene is running:
-
-        CallDeferred(MethodName.DeferredGotoScene, path, new MapStartDataResource());
+        
+        //CallDeferred(MethodName.DeferredGotoScene, path, new MapStartDataResource());
+        
+        GoToScene(path, new MapStartDataResource());
     }
 
     public void GoToScene(string path, MapStartDataResource startData)
     {
-        // TODO: Implement startdata usage
-        CallDeferred(MethodName.DeferredGotoScene, path, startData);
+        GTweenSequenceBuilder.New()
+            //.Append(_fader.TweenModulateAlpha(0, 0f))
+            .Append(_fader.TweenModulateAlpha(1, 0.5f))
+            .AppendCallback(() =>
+            {
+                CallDeferred(MethodName.DeferredGotoScene, path, startData);
+            })
+            .Build()
+            .PlayUnpausable();
+        //CallDeferred(MethodName.DeferredGotoScene, path, startData);
     }
-
+    
     private void DeferredGotoScene(string path, MapStartDataResource startData = null)
     {
         // It is now safe to remove the current scene.
@@ -63,10 +80,43 @@ public partial class GlobalState : Node
             // Call deferred if it gives issues
             DeferredAddStartDataToGameManager(startData);
         }
+        
+        FadeIn();
     }
 
     private void DeferredAddStartDataToGameManager(MapStartDataResource resource)
     {
         GameManager.Instance.ApplyMapStartData(resource);
     }
+
+    private ColorRect CreateFader()
+    {
+        var canvas = new CanvasLayer();
+        canvas.ProcessMode = ProcessModeEnum.Always;
+        
+        var rect = new ColorRect();
+        rect.SetAnchorsPreset(Control.LayoutPreset.FullRect);
+        rect.Color = new Color(Colors.Black, 1f);
+        rect.ProcessMode = ProcessModeEnum.Always;
+        
+        rect.Modulate = new Color(0,0,0,0);
+
+        rect.MouseFilter = Control.MouseFilterEnum.Ignore;
+
+        canvas.CallDeferred("add_child", rect);
+        
+        this.CallDeferred("add_child", canvas);
+        
+        return rect;
+    }
+
+    public void FadeOut()
+    {
+        _fader.TweenModulateAlpha(1, 0.5f).PlayUnpausable();
+    }
+
+    public void FadeIn()
+    {
+        _fader.TweenModulateAlpha(0, 1f).PlayUnpausable();
+    }
 }