Control recycling fixes

samples/DockReactiveUICanonicalSample/App.axaml.cs

@@ -39,7 +39,10 @@ private void RegisterDockableTemplate()
             {
                 if (existing is ReactiveUI.Avalonia.ViewModelViewHost existingHost)
                 {
-                    existingHost.ViewModel = item;
+                    if (!ReferenceEquals(existingHost.ViewModel, item))
+                    {
+                        existingHost.ViewModel = item;
+                    }
                     return existingHost;
                 }
 

src/Dock.Avalonia/Controls/DockControl.axaml.cs

@@ -3,9 +3,11 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Runtime.CompilerServices;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Recycling;
+using Avalonia.Controls.Recycling.Model;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
@@ -36,6 +38,7 @@
 [TemplatePart("PART_ManagedWindowLayer", typeof(ManagedWindowLayer))]
 public class DockControl : TemplatedControl, IDockControl, IDockSelectorService
 {
+    private static readonly ConditionalWeakTable<IFactory, IControlRecycling> s_controlRecycling = new();
     private readonly DockManagerOptions _dockManagerOptions;
     private readonly DockManager _dockManager;
     private readonly DockControlState _dockControlState;
@@ -269,16 +272,53 @@
 
     private void InitializeControlRecycling()
     {
-        var recycling = ControlRecyclingDataTemplate.GetControlRecycling(this);
-        if (recycling is ControlRecycling shared)
+        if (Layout?.Factory is not { } factory)
         {
-            var local = new ControlRecycling
+            return;
+        }
+
+        var controlRecycling = ControlRecyclingDataTemplate.GetControlRecycling(this);
+        if (controlRecycling is null)
+        {
+            return;
+        }
+
+        if (s_controlRecycling.TryGetValue(factory, out var shared))
+        {
+            if (ReferenceEquals(shared, controlRecycling))
             {
-                TryToUseIdAsKey = shared.TryToUseIdAsKey
-            };
+                return;
+            }
+
+            if (shared is ControlRecycling sharedRecycling && controlRecycling is ControlRecycling localRecycling)
+            {
+                if (sharedRecycling.TryToUseIdAsKey != localRecycling.TryToUseIdAsKey)
+                {
+                    sharedRecycling.TryToUseIdAsKey = localRecycling.TryToUseIdAsKey;
+                }
 
-            ControlRecyclingDataTemplate.SetControlRecycling(this, local);
+                ControlRecyclingDataTemplate.SetControlRecycling(this, sharedRecycling);
+                return;
+            }
+
+            if (controlRecycling is ControlRecycling)
+            {
+                ControlRecyclingDataTemplate.SetControlRecycling(this, shared);
+            }
+
+            return;
         }
+
+        if (controlRecycling is ControlRecycling defaultRecycling)
+        {
+            controlRecycling = new ControlRecycling
+            {
+                TryToUseIdAsKey = defaultRecycling.TryToUseIdAsKey
+            };
+            ControlRecyclingDataTemplate.SetControlRecycling(this, controlRecycling);
+        }
+
+        s_controlRecycling.Add(factory, controlRecycling);
     }
 
     private void InitializeDefaultDataTemplates()
@@ -346,6 +386,7 @@
 
         layout.Factory.DockControls.Add(this);
 
+        InitializeControlRecycling();
         UpdateManagedWindowLayer(layout);
 
         if (InitializeFactory)
@@ -367,7 +408,7 @@
             {
                 if (HostWindowFactory is { } factory)
                 {
                     return factory();
                 }
 
                 return DockSettings.UseManagedWindows

src/Dock.Avalonia/Controls/ManagedDockWindowDocument.cs

@@ -2,10 +2,13 @@
 // Licensed under the MIT license. See LICENSE file in the project root for details.
 using System;
 using System.ComponentModel;
+using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Templates;
 using Avalonia.Markup.Xaml.Templates;
 using Avalonia.Media;
+using Avalonia.VisualTree;
 using Dock.Avalonia.Internal;
 using Dock.Model.Controls;
 using Dock.Model.Core;
@@ -130,7 +133,7 @@
 
     public Control? Build(object? data, Control? existing)
     {
-        return BuildContent(Content, this);
+        return BuildContent(Content, this, existing);
     }
 
     public void Dispose()
@@ -243,7 +246,7 @@
         var focusedTitle = focusedDockable?.Title;
         if (!string.IsNullOrEmpty(focusedTitle))
         {
             Title = focusedTitle;
             return;
         }
 
@@ -316,7 +319,7 @@
         }
     }
 
-    private static Control? BuildContent(object? content, IDockable dockable)
+    private static Control? BuildContent(object? content, IDockable dockable, Control? existing)
     {
         if (DragPreviewContext.IsPreviewing(dockable))
         {
@@ -330,15 +333,85 @@
 
         if (content is Control directControl)
         {
-            return directControl;
+            return DetachOrFallback(directControl, existing, null);
         }
 
         if (content is Func<IServiceProvider, object> direct)
         {
-            return direct(null!) as Control;
+            return DetachOrFallback(direct(null!) as Control, existing, () => direct(null!) as Control);
         }
 
-        return TemplateContent.Load(content)?.Result;
+        return DetachOrFallback(TemplateContent.Load(content)?.Result, existing, () => TemplateContent.Load(content)?.Result);
+    }
+
+    private static Control? DetachOrFallback(Control? control, Control? existing, Func<Control?>? fallbackFactory)
+    {
+        if (control is null || ReferenceEquals(control, existing))
+        {
+            return control;
+        }
+
+        if (TryDetachFromParent(control))
+        {
+            return control;
+        }
+
+        if (fallbackFactory is null)
+        {
+            return existing;
+        }
+
+        var fallback = fallbackFactory();
+        if (fallback is null)
+        {
+            return existing;
+        }
+
+        if (ReferenceEquals(fallback, existing))
+        {
+            return fallback;
+        }
+
+        return TryDetachFromParent(fallback) ? fallback : existing;
+    }
+
+    private static bool TryDetachFromParent(Control control)
+    {
+        var parent = control.Parent ?? control.GetVisualParent();
+
+        if (parent is null)
+        {
+            return true;
+        }
+
+        switch (parent)
+        {
+            case Panel panel:
+                return panel.Children.Remove(control);
+            case ContentPresenter presenter:
+                return TryDetachFromContentPresenter(presenter, control);
+            case ContentControl contentControl when ReferenceEquals(contentControl.Content, control):
+                contentControl.SetCurrentValue(ContentControl.ContentProperty, null);
+                return true;
+            case Decorator decorator when ReferenceEquals(decorator.Child, control):
+                decorator.Child = null;
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    private static bool TryDetachFromContentPresenter(ContentPresenter presenter, Control control)
+    {
+        if (!ReferenceEquals(presenter.Child, control))
+        {
+            return false;
+        }
+
+        presenter.SetCurrentValue(ContentPresenter.ContentProperty, null);
+        presenter.UpdateChild();
+
+        return control.GetVisualParent() is null;
     }
 
     private static Control BuildPreviewContent(object? content)

src/Dock.Avalonia/Controls/Overlays/OverlayHost.cs

@@ -9,6 +9,7 @@
 using Avalonia.Controls.Templates;
 using Avalonia.Metadata;
 using Avalonia.Styling;
+using Avalonia.VisualTree;
 
 namespace Dock.Avalonia.Controls.Overlays;
 
@@ -250,9 +251,10 @@ private void OnOverlayLayerPropertyChanged(object? sender, AvaloniaPropertyChang
 
     private void RebuildPipeline()
     {
-        if (Content is Control hostedContent && hostedContent.Parent is not null)
+        if (Content is Control hostedContent)
         {
-            if (!TryDetachControl(hostedContent))
+            var parent = hostedContent.Parent ?? hostedContent.GetVisualParent();
+            if (parent is not null && !TryDetachControl(hostedContent))
             {
                 return;
             }
@@ -325,22 +327,36 @@ private void RebuildPipeline()
 
     private static bool TryDetachControl(Control control)
     {
-        if (control.Parent is null)
+        var parent = control.Parent ?? control.GetVisualParent();
+        if (parent is null)
         {
             return true;
         }
 
-        switch (control.Parent)
+        switch (parent)
         {
             case Panel panel:
                 panel.Children.Remove(control);
                 return true;
             case Decorator decorator when ReferenceEquals(decorator.Child, control):
                 decorator.Child = null;
                 return true;
-            case ContentPresenter presenter when ReferenceEquals(presenter.Content, control):
-                presenter.Content = null;
-                return true;
+            case ContentPresenter presenter:
+                if (ReferenceEquals(presenter.Child, control))
+                {
+                    presenter.SetCurrentValue(ContentPresenter.ContentProperty, null);
+                    presenter.UpdateChild();
+                    return control.GetVisualParent() is null;
+                }
+
+                if (ReferenceEquals(presenter.Content, control))
+                {
+                    presenter.SetCurrentValue(ContentPresenter.ContentProperty, null);
+                    presenter.UpdateChild();
+                    return true;
+                }
+
+                return false;
             case ContentControl contentControl when ReferenceEquals(contentControl.Content, control):
                 contentControl.Content = null;
                 return true;