Fixes/memory leak

src/Dock.Model/FactoryBase.Dockable.cs

@@ -47,6 +47,11 @@ public virtual void RemoveDockable(IDockable dockable, bool collapse)
         var index = dock.VisibleDockables.IndexOf(dockable);
         if (index < 0)
         {
+            if (FindRoot(dockable, x => x.IsFocusableRoot) is { } root &&
+                ReferenceEquals(root.FocusedDockable, dockable))
+            {
+                SetFocusedDockable(dock, dock.ActiveDockable);
+            }
             return;
         }
 
@@ -69,6 +74,12 @@ public virtual void RemoveDockable(IDockable dockable, bool collapse)
             }
         }
 
+        if (FindRoot(dockable, x => x.IsFocusableRoot) is { } rootDock &&
+            ReferenceEquals(rootDock.FocusedDockable, dockable))
+        {
+            SetFocusedDockable(dock, dock.ActiveDockable);
+        }
+
         // Clean up orphaned splitters
         CleanupOrphanedSplitters(dock);
 

src/Dock.Model/FactoryBase.Init.cs

@@ -275,47 +275,53 @@ private void SetIsActive(IDockable dockable, bool active)
     /// <inheritdoc />
     public virtual void SetFocusedDockable(IDock dock, IDockable? dockable)
     {
-        if (dock.ActiveDockable is not null && FindRoot(dock.ActiveDockable, x => x.IsFocusableRoot) is { } root)
+        if (FindRoot(dock, x => x.IsFocusableRoot) is not { } root)
         {
-            if (dockable is not null)
-            {
-                var results = Find(x => x is IRootDock);
+            return;
+        }
 
-                foreach (var result in results)
+        if (dockable is not null)
+        {
+            var results = Find(x => x is IRootDock);
+
+            foreach (var result in results)
+            {
+                if (result is IRootDock rootDock 
+                    && rootDock.IsFocusableRoot
+                    && rootDock != root)
                 {
-                    if (result is IRootDock rootDock 
-                        && rootDock.IsFocusableRoot
-                        && rootDock != root)
+                    if (rootDock.FocusedDockable?.Owner is not null)
                     {
-                        if (rootDock.FocusedDockable?.Owner is not null)
-                        {
-                            SetIsActive(rootDock.FocusedDockable.Owner, false);
-                            // Trigger deactivation event for the dockable that lost focus
-                            OnDockableDeactivated(rootDock.FocusedDockable);
-                        }
+                        SetIsActive(rootDock.FocusedDockable.Owner, false);
+                        // Trigger deactivation event for the dockable that lost focus
+                        OnDockableDeactivated(rootDock.FocusedDockable);
                     }
                 }
             }
+        }
 
-            if (root.FocusedDockable?.Owner is not null)
-            {
-                SetIsActive(root.FocusedDockable.Owner, false);
-                // Trigger deactivation event for the dockable that lost focus
-                OnDockableDeactivated(root.FocusedDockable);
-            }
+        if (root.FocusedDockable?.Owner is not null)
+        {
+            SetIsActive(root.FocusedDockable.Owner, false);
+            // Trigger deactivation event for the dockable that lost focus
+            OnDockableDeactivated(root.FocusedDockable);
+        }
 
-            if (dockable is not null)
+        if (dockable is not null)
+        {
+            if (root.FocusedDockable != dockable)
             {
-                if (root.FocusedDockable != dockable)
-                {
-                    root.FocusedDockable = dockable;
-                }
+                root.FocusedDockable = dockable;
             }
+        }
+        else
+        {
+            root.FocusedDockable = null;
+        }
 
-            if (root.FocusedDockable?.Owner is not null)
-            {
-                SetIsActive(root.FocusedDockable.Owner, true);
-            }
+        if (root.FocusedDockable?.Owner is not null)
+        {
+            SetIsActive(root.FocusedDockable.Owner, true);
         }
     }
 }

tests/Dock.Avalonia.HeadlessTests/FactoryDockableLifecycleTests.cs

@@ -104,4 +104,25 @@ public void CloseDockable_Active_Selects_Neighbour()
         Assert.Same(doc2, dock.ActiveDockable);
         Assert.Single(dock.VisibleDockables!);
     }
+
+    [AvaloniaFact]
+    public void CloseDockable_Active_Clears_FocusedDockable()
+    {
+        var factory = new Factory();
+        var root = new RootDock { VisibleDockables = factory.CreateList<IDockable>() };
+        root.Factory = factory;
+
+        var doc = new Document();
+        factory.AddDockable(root, doc);
+
+        root.ActiveDockable = doc;
+
+        Assert.Same(doc, root.FocusedDockable);
+
+        factory.CloseDockable(doc);
+
+        Assert.Null(root.ActiveDockable);
+        Assert.Null(root.FocusedDockable);
+        Assert.Empty(root.VisibleDockables!);
+    }
 }