Remove System.Reactive from Diagnostics package as well

src/Avalonia.Base/Reactive/Observable.cs

@@ -44,6 +44,15 @@ internal static class Observable
                 }, obs.OnError, obs.OnCompleted));
         });
     }
+
+    public static IObservable<TSource> StartWith<TSource>(this IObservable<TSource> source, TSource value)
+    {
+        return Create<TSource>(obs =>
+        {
+            obs.OnNext(value);
+            return source.Subscribe(obs);
+        });
+    }
     
     public static IObservable<TSource> Where<TSource>(this IObservable<TSource> source, Func<TSource, bool> predicate)
     {

src/Avalonia.Base/Reactive/SerialDisposableValue.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Threading;
+
+namespace Avalonia.Reactive;
+
+/// <summary>
+/// Represents a disposable resource whose underlying disposable resource can be replaced by another disposable resource, causing automatic disposal of the previous underlying disposable resource.
+/// </summary>
+internal sealed class SerialDisposableValue : IDisposable
+{
+    private IDisposable? _current;
+    private bool _disposed;
+    
+    public IDisposable? Disposable
+    {
+        get => _current;
+        set
+        {
+            _current?.Dispose();
+            _current = value;
+            
+            if (_disposed)
+            {
+                _current?.Dispose();
+                _current = null;
+            }
+        }
+    }
+
+    public void Dispose()
+    {
+        _disposed = true;
+        _current?.Dispose();
+    }
+}

src/Avalonia.Diagnostics/Avalonia.Diagnostics.csproj

@@ -23,7 +23,6 @@
     <PackageReference Include="Microsoft.CodeAnalysis.Common" Version="3.8.0" />
   </ItemGroup>
   <Import Project="..\..\build\EmbedXaml.props" />
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\BuildTargets.targets" />
   <Import Project="..\..\build\ApiDiff.props" />
   <Import Project="..\..\build\NullableEnable.props" />

src/Avalonia.Diagnostics/Diagnostics/DevTools.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Linq;
 using Avalonia.Controls;
 using Avalonia.Diagnostics.Views;
 using Avalonia.Input;
@@ -72,7 +71,11 @@ namespace Avalonia.Diagnostics
             {
                 throw new ArgumentNullException(nameof(application));
             }
-            var result = Disposable.Empty;
+
+            var openedDisposable = new SerialDisposableValue();
+            var result = new CompositeDisposable(2);
+            result.Add(openedDisposable);
+            
             // Skip if call on Design Mode
             if (!Avalonia.Controls.Design.IsDesignMode
                 && !s_attachedToApplication)
@@ -90,13 +93,15 @@ namespace Avalonia.Diagnostics
                 {
                     s_attachedToApplication = true;
 
-                    ObservableExtensions.Subscribe(application.InputManager.PreProcess.OfType<RawKeyEventArgs>(), e =>
+                    result.Add(application.InputManager.PreProcess.Subscribe(e =>
                     {
-                        if (options.Gesture.Matches(e))
+                        if (e is RawKeyEventArgs keyEventArgs
+                            && keyEventArgs.Type == RawKeyEventType.KeyUp
+                            && options.Gesture.Matches(keyEventArgs))
                         {
-                          result =  Open(application, options, owner);
+                            openedDisposable.Disposable = Open(application, options, owner);
                         }
-                    });
+                    }));
 
                 }
             }

src/Avalonia.Diagnostics/Diagnostics/ViewModels/EventTreeNode.cs

@@ -4,6 +4,7 @@ using Avalonia.Diagnostics.Views;
 using Avalonia.Interactivity;
 using Avalonia.Threading;
 using Avalonia.VisualTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.ViewModels
 {

src/Avalonia.Diagnostics/Diagnostics/ViewModels/LogicalTreeNode.cs

@@ -1,10 +1,10 @@
 using System;
-using System.Reactive.Disposables;
 using Avalonia.Collections;
 using Avalonia.Controls;
 using Avalonia.LogicalTree;
 using Lifetimes = Avalonia.Controls.ApplicationLifetimes;
 using System.Linq;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.ViewModels
 {

src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs

@@ -1,11 +1,11 @@
 using System;
 using System.ComponentModel;
-using System.Reactive.Linq;
 using Avalonia.Controls;
 using Avalonia.Diagnostics.Models;
 using Avalonia.Input;
 using Avalonia.Metadata;
 using Avalonia.Threading;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.ViewModels
 {
@@ -50,15 +50,15 @@ namespace Avalonia.Diagnostics.ViewModels
             }
             else
             {
-#nullable disable
-                _pointerOverSubscription = InputManager.Instance.PreProcess
-                    .OfType<Input.Raw.RawPointerEventArgs>()
+                _pointerOverSubscription = InputManager.Instance!.PreProcess
                     .Subscribe(e =>
                         {
-                            PointerOverRoot = e.Root;
-                            PointerOverElement = e.Root.InputHitTest(e.Position);
+                            if (e is Input.Raw.RawPointerEventArgs pointerEventArgs)
+                            {
+                                PointerOverRoot = pointerEventArgs.Root;
+                                PointerOverElement = pointerEventArgs.Root.InputHitTest(pointerEventArgs.Position);
+                            }
                         });
-#nullable restore
             }
             Console = new ConsoleViewModel(UpdateConsoleContext);
         }

src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNode.cs

@@ -1,11 +1,11 @@
 using System;
 using System.Collections.Specialized;
-using System.Reactive;
-using System.Reactive.Linq;
+using Avalonia.Collections;
 using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
 using Avalonia.LogicalTree;
 using Avalonia.Media;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.ViewModels
 {
@@ -28,18 +28,8 @@ namespace Avalonia.Diagnostics.ViewModels
             {
                 ElementName = control.Name;
 
-                var removed = Observable.FromEventPattern<LogicalTreeAttachmentEventArgs>(
-                    x => control.DetachedFromLogicalTree += x,
-                    x => control.DetachedFromLogicalTree -= x);
-                var classesChanged = Observable.FromEventPattern<
-                        NotifyCollectionChangedEventHandler,
-                        NotifyCollectionChangedEventArgs>(
-                        x => control.Classes.CollectionChanged += x,
-                        x => control.Classes.CollectionChanged -= x)
-                    .TakeUntil(removed);
-
-                _classesSubscription = classesChanged.Select(_ => Unit.Default)
-                    .StartWith(Unit.Default)
+                _classesSubscription = ((IObservable<object?>)control.Classes.GetWeakCollectionChangedObservable())
+                    .StartWith(null)
                     .Subscribe(_ =>
                     {
                         if (control.Classes.Count > 0)

src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs

@@ -1,12 +1,11 @@
 using System;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
 using Avalonia.Collections;
 using Avalonia.Controls;
 using Avalonia.Controls.Diagnostics;
 using Avalonia.Controls.Primitives;
 using Avalonia.Styling;
 using Avalonia.VisualTree;
+using Avalonia.Reactive;
 using Lifetimes = Avalonia.Controls.ApplicationLifetimes;
 using System.Linq;
 
@@ -61,9 +60,12 @@ namespace Avalonia.Diagnostics.ViewModels
                     IPopupHostProvider popupHostProvider,
                     string? providerName = null)
                 {
-                    return Observable.FromEvent<IPopupHost?>(
-                            x => popupHostProvider.PopupHostChanged += x,
-                            x => popupHostProvider.PopupHostChanged -= x)
+                    return Observable.Create<IPopupHost?>(observer =>
+                        {
+                            void Handler(IPopupHost? args) => observer.OnNext(args);
+                            popupHostProvider.PopupHostChanged += Handler;
+                            return Disposable.Create(() => popupHostProvider.PopupHostChanged -= Handler);
+                        })
                         .StartWith(popupHostProvider.PopupHost)
                         .Select(popupHost =>
                         {
@@ -80,29 +82,39 @@ namespace Avalonia.Diagnostics.ViewModels
                 {
                     Popup p => GetPopupHostObservable(p),
                     Control c => Observable.CombineLatest(
-                            c.GetObservable(Control.ContextFlyoutProperty),
-                            c.GetObservable(Control.ContextMenuProperty),
-                            c.GetObservable(FlyoutBase.AttachedFlyoutProperty),
-                            c.GetObservable(ToolTipDiagnostics.ToolTipProperty),
-                            c.GetObservable(Button.FlyoutProperty),
-                            (ContextFlyout, ContextMenu, AttachedFlyout, ToolTip, ButtonFlyout) =>
+                            new IObservable<IPopupHostProvider?>[]
+                            {
+                                c.GetObservable(Control.ContextFlyoutProperty),
+                                c.GetObservable(Control.ContextMenuProperty),
+                                c.GetObservable(FlyoutBase.AttachedFlyoutProperty),
+                                c.GetObservable(ToolTipDiagnostics.ToolTipProperty),
+                                c.GetObservable(Button.FlyoutProperty)
+                            })
+                        .Select(
+                            items =>
                             {
-                                if (ContextMenu != null)
+                                var contextFlyout = items[0];
+                                var contextMenu = (ContextMenu?)items[1];
+                                var attachedFlyout = items[2];
+                                var toolTip = items[3];
+                                var buttonFlyout = items[4];
+
+                                if (contextMenu != null)
                                     //Note: ContextMenus are special since all the items are added as visual children.
                                     //So we don't need to go via Popup
-                                    return Observable.Return<PopupRoot?>(new PopupRoot(ContextMenu));
+                                    return Observable.Return<PopupRoot?>(new PopupRoot(contextMenu));
 
-                                if (ContextFlyout != null)
-                                    return GetPopupHostObservable(ContextFlyout, "ContextFlyout");
+                                if (contextFlyout != null)
+                                    return GetPopupHostObservable(contextFlyout, "ContextFlyout");
 
-                                if (AttachedFlyout != null)
-                                    return GetPopupHostObservable(AttachedFlyout, "AttachedFlyout");
+                                if (attachedFlyout != null)
+                                    return GetPopupHostObservable(attachedFlyout, "AttachedFlyout");
 
-                                if (ToolTip != null)
-                                    return GetPopupHostObservable(ToolTip, "ToolTip");
+                                if (toolTip != null)
+                                    return GetPopupHostObservable(toolTip, "ToolTip");
 
-                                if (ButtonFlyout != null)
-                                    return GetPopupHostObservable(ButtonFlyout, "Flyout");
+                                if (buttonFlyout != null)
+                                    return GetPopupHostObservable(buttonFlyout, "Flyout");
 
                                 return Observable.Return<PopupRoot?>(null);
                             })

src/Avalonia.Diagnostics/Diagnostics/Views/LayoutExplorerView.axaml.cs

@@ -4,6 +4,7 @@ using Avalonia.Controls.Shapes;
 using Avalonia.Diagnostics.Controls;
 using Avalonia.Markup.Xaml;
 using Avalonia.VisualTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.Views
 {

src/Avalonia.Diagnostics/Diagnostics/Views/MainWindow.xaml.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
 using Avalonia.Controls;
 using Avalonia.Controls.Diagnostics;
 using Avalonia.Controls.Primitives;
@@ -13,13 +12,13 @@ using Avalonia.Markup.Xaml;
 using Avalonia.Styling;
 using Avalonia.Themes.Simple;
 using Avalonia.VisualTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.Views
 {
     internal class MainWindow : Window, IStyleHost
     {
-        private readonly IDisposable? _keySubscription;
-        private readonly IDisposable? _pointerSubscription;
+        private readonly IDisposable? _inputSubscription;
         private readonly Dictionary<Popup, IDisposable> _frozenPopupStates;
         private AvaloniaObject? _root;
         private PixelPoint _lastPointerPosition;
@@ -33,15 +32,19 @@ namespace Avalonia.Diagnostics.Views
             if (Theme is null && this.FindResource(typeof(Window)) is ControlTheme windowTheme)
                 Theme = windowTheme;
 
-            _keySubscription = InputManager.Instance?.Process
-                .OfType<RawKeyEventArgs>()
-                .Where(x => x.Type == RawKeyEventType.KeyDown)
-                .Subscribe(RawKeyDown);
-            _pointerSubscription = InputManager.Instance?.Process
-                .OfType<RawPointerEventArgs>()
-                .Subscribe(x => _lastPointerPosition = ((Visual)x.Root).PointToScreen(x.Position));
-
-
+            _inputSubscription = InputManager.Instance?.Process
+                .Subscribe(x =>
+                {
+                    if (x is RawPointerEventArgs pointerEventArgs)
+                    {
+                        _lastPointerPosition = ((Visual)x.Root).PointToScreen(pointerEventArgs.Position);
+                    }
+                    else if (x is RawKeyEventArgs keyEventArgs && keyEventArgs.Type == RawKeyEventType.KeyDown)
+                    {
+                        RawKeyDown(keyEventArgs);
+                    }
+                });
+            
             _frozenPopupStates = new Dictionary<Popup, IDisposable>();
 
             EventHandler? lh = default;
@@ -94,8 +97,7 @@ namespace Avalonia.Diagnostics.Views
         protected override void OnClosed(EventArgs e)
         {
             base.OnClosed(e);
-            _keySubscription?.Dispose();
-            _pointerSubscription?.Dispose();
+            _inputSubscription?.Dispose();
 
             foreach (var state in _frozenPopupStates)
             {