Stop animations from ticking when window is hidden

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositionTarget.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Numerics;
 using System.Threading;
 using Avalonia.Media;
@@ -24,6 +25,7 @@ namespace Avalonia.Rendering.Composition.Server
         private IDrawingContextLayerImpl? _layer;
         private bool _redrawRequested;
         private bool _disposed;
+        private HashSet<ServerCompositionVisual> _attachedVisuals = new();
 
 
         public ReadbackIndices Readback { get; } = new();
@@ -39,9 +41,17 @@ namespace Avalonia.Rendering.Composition.Server
         partial void OnIsEnabledChanged()
         {
             if (IsEnabled)
+            {
                 _compositor.AddCompositionTarget(this);
+                foreach (var v in _attachedVisuals)
+                    v.Activate();
+            }
             else
+            {
                 _compositor.RemoveCompositionTarget(this);
+                foreach (var v in _attachedVisuals)
+                    v.Deactivate();
+            }
         }
         
         partial void DeserializeChangesExtra(BatchStreamReader c)
@@ -155,5 +165,17 @@ namespace Avalonia.Rendering.Composition.Server
             _renderTarget?.Dispose();
             _renderTarget = null;
         }
+
+        public void AddVisual(ServerCompositionVisual visual)
+        {
+            if (_attachedVisuals.Add(visual) && IsEnabled)
+                visual.Activate();
+        }
+
+        public void RemoveVisual(ServerCompositionVisual visual)
+        {
+            if (_attachedVisuals.Remove(visual) && IsEnabled)
+                visual.Deactivate();
+        }
     }
 }

src/Avalonia.Base/Rendering/Composition/Server/ServerVisual.cs

@@ -126,14 +126,14 @@ namespace Avalonia.Rendering.Composition.Server
 
         partial void OnRootChanging()
         {
-            if(Root != null)
-                Deactivate();
+            if (Root != null)
+                Root.RemoveVisual(this);
         }
         
         partial void OnRootChanged()
         {
             if (Root != null)
-                Activate();
+                Root.AddVisual(this);
         }
         
         protected override void ValuesInvalidated()