Remove System.Reactive package

build/Base.props

@@ -1,6 +1,7 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>
     <PackageReference Include="System.ValueTuple" Version="4.5.0" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" />
     <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="4.6.0" />
   </ItemGroup>
 </Project>

src/Avalonia.Base/Animation/Animation.cs

@@ -2,8 +2,7 @@
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Threading;
 using System.Threading.Tasks;
 

src/Avalonia.Base/Animation/AnimationInstance`1.cs

@@ -1,11 +1,8 @@
 using System;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Animation.Animators;
-using Avalonia.Animation.Utils;
 using Avalonia.Data;
-using Avalonia.Reactive;
-using JetBrains.Annotations;
 
 namespace Avalonia.Animation
 {

src/Avalonia.Base/Animation/AnimatorKeyFrame.cs

@@ -63,7 +63,7 @@ public IDisposable BindSetter(IAnimationSetter setter, Animatable targetControl)
             }
             else
             {
-                return this.Bind(ValueProperty, ObservableEx.SingleValue(value).ToBinding(), targetControl);
+                return this.Bind(ValueProperty, Observable.SingleValue(value).ToBinding(), targetControl);
             }
         }
 

src/Avalonia.Base/Animation/Animators/Animator`1.cs

@@ -1,8 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
 using Avalonia.Animation.Utils;
 using Avalonia.Collections;
 using Avalonia.Data;

src/Avalonia.Base/Animation/Animators/ColorAnimator.cs

@@ -2,7 +2,7 @@
 // and adopted from LottieSharp Project (https://github.com/ascora/LottieSharp).
 
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Logging;
 using Avalonia.Media;
 

src/Avalonia.Base/Animation/Animators/TransformAnimator.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Logging;
 using Avalonia.Media;
 using Avalonia.Media.Transformation;

src/Avalonia.Base/Animation/Clock.cs

@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Reactive;
 
 namespace Avalonia.Animation
 {

src/Avalonia.Base/Animation/CrossFade.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using System.Threading;
 using System.Threading.Tasks;
 using Avalonia.Animation.Easings;
@@ -108,7 +108,7 @@ public async Task Start(Visual? from, Visual? to, CancellationToken cancellation
             }
 
             var tasks = new List<Task>();
-            using (var disposables = new CompositeDisposable())
+            using (var disposables = new CompositeDisposable(1))
             {
                 if (to != null)
                 {

src/Avalonia.Base/Avalonia.Base.csproj

@@ -14,7 +14,6 @@
   </ItemGroup>
   <Import Project="..\..\build\Base.props" />
   <Import Project="..\..\build\Binding.props" />
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\JetBrains.Annotations.props" />
   <Import Project="..\..\build\System.Memory.props" />
   <Import Project="..\..\build\ApiDiff.props" />
@@ -35,6 +34,12 @@
     <InternalsVisibleTo Include="Avalonia.Markup.Xaml, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Controls.ColorPicker, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Controls.DataGrid, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Headless, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Native, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.FreeDesktop, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.X11, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.OpenGL, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Skia, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Controls.UnitTests, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.DesignerSupport, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Direct2D1.RenderTests, PublicKey=$(AvaloniaPublicKey)" />

src/Avalonia.Base/AvaloniaObjectExtensions.cs

@@ -1,10 +1,6 @@
 using System;
-using System.Reactive;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
-using Avalonia.Data;
 using Avalonia.Reactive;
+using Avalonia.Data;
 
 namespace Avalonia
 {
@@ -127,108 +123,6 @@ public static IObservable<AvaloniaPropertyChangedEventArgs> GetPropertyChangedOb
                 property ?? throw new ArgumentNullException(nameof(property)));
         }
 
-        /// <summary>
-        /// Gets a subject for an <see cref="AvaloniaProperty"/>.
-        /// </summary>
-        /// <param name="o">The object.</param>
-        /// <param name="property">The property.</param>
-        /// <param name="priority">
-        /// The priority with which binding values are written to the object.
-        /// </param>
-        /// <returns>
-        /// An <see cref="ISubject{Object}"/> which can be used for two-way binding to/from the 
-        /// property.
-        /// </returns>
-        public static ISubject<object?> GetSubject(
-            this AvaloniaObject o,
-            AvaloniaProperty property,
-            BindingPriority priority = BindingPriority.LocalValue)
-        {
-            return Subject.Create<object?>(
-                Observer.Create<object?>(x => o.SetValue(property, x, priority)),
-                o.GetObservable(property));
-        }
-
-        /// <summary>
-        /// Gets a subject for an <see cref="AvaloniaProperty"/>.
-        /// </summary>
-        /// <typeparam name="T">The property type.</typeparam>
-        /// <param name="o">The object.</param>
-        /// <param name="property">The property.</param>
-        /// <param name="priority">
-        /// The priority with which binding values are written to the object.
-        /// </param>
-        /// <returns>
-        /// An <see cref="ISubject{T}"/> which can be used for two-way binding to/from the 
-        /// property.
-        /// </returns>
-        public static ISubject<T> GetSubject<T>(
-            this AvaloniaObject o,
-            AvaloniaProperty<T> property,
-            BindingPriority priority = BindingPriority.LocalValue)
-        {
-            return Subject.Create<T>(
-                Observer.Create<T>(x => o.SetValue(property, x, priority)),
-                o.GetObservable(property));
-        }
-
-        /// <summary>
-        /// Gets a subject for a <see cref="AvaloniaProperty"/>.
-        /// </summary>
-        /// <param name="o">The object.</param>
-        /// <param name="property">The property.</param>
-        /// <param name="priority">
-        /// The priority with which binding values are written to the object.
-        /// </param>
-        /// <returns>
-        /// An <see cref="ISubject{Object}"/> which can be used for two-way binding to/from the 
-        /// property.
-        /// </returns>
-        public static ISubject<BindingValue<object?>> GetBindingSubject(
-            this AvaloniaObject o,
-            AvaloniaProperty property,
-            BindingPriority priority = BindingPriority.LocalValue)
-        {
-            return Subject.Create<BindingValue<object?>>(
-                Observer.Create<BindingValue<object?>>(x =>
-                {
-                    if (x.HasValue)
-                    {
-                        o.SetValue(property, x.Value, priority);
-                    }
-                }),
-                o.GetBindingObservable(property));
-        }
-
-        /// <summary>
-        /// Gets a subject for a <see cref="AvaloniaProperty"/>.
-        /// </summary>
-        /// <typeparam name="T">The property type.</typeparam>
-        /// <param name="o">The object.</param>
-        /// <param name="property">The property.</param>
-        /// <param name="priority">
-        /// The priority with which binding values are written to the object.
-        /// </param>
-        /// <returns>
-        /// An <see cref="ISubject{T}"/> which can be used for two-way binding to/from the 
-        /// property.
-        /// </returns>
-        public static ISubject<BindingValue<T>> GetBindingSubject<T>(
-            this AvaloniaObject o,
-            AvaloniaProperty<T> property,
-            BindingPriority priority = BindingPriority.LocalValue)
-        {
-            return Subject.Create<BindingValue<T>>(
-                Observer.Create<BindingValue<T>>(x =>
-                {
-                    if (x.HasValue)
-                    {
-                        o.SetValue(property, x.Value, priority);
-                    }
-                }),
-                o.GetBindingObservable(property));
-        }
-
         /// <summary>
         /// Binds an <see cref="AvaloniaProperty"/> to an observable.
         /// </summary>
@@ -407,13 +301,7 @@ public static IDisposable AddClassHandler<TTarget>(
             Action<TTarget, AvaloniaPropertyChangedEventArgs> action)
             where TTarget : AvaloniaObject
         {
-            return observable.Subscribe(e =>
-            {
-                if (e.Sender is TTarget target)
-                {
-                    action(target, e);
-                }
-            });
+            return observable.Subscribe(new ClassHandlerObserver<TTarget>(action));
         }
 
         /// <summary>
@@ -431,13 +319,7 @@ public static IDisposable AddClassHandler<TTarget, TValue>(
             this IObservable<AvaloniaPropertyChangedEventArgs<TValue>> observable,
             Action<TTarget, AvaloniaPropertyChangedEventArgs<TValue>> action) where TTarget : AvaloniaObject
         {
-            return observable.Subscribe(e =>
-            {
-                if (e.Sender is TTarget target)
-                {
-                    action(target, e);
-                }
-            });
+            return observable.Subscribe(new ClassHandlerObserver<TTarget, TValue>(action));
         }
 
         private class BindingAdaptor : IBinding
@@ -458,5 +340,57 @@ public BindingAdaptor(IObservable<object?> source)
                 return InstancedBinding.OneWay(_source);
             }
         }
+
+        private class ClassHandlerObserver<TTarget, TValue> : IObserver<AvaloniaPropertyChangedEventArgs<TValue>>
+        {
+            private readonly Action<TTarget, AvaloniaPropertyChangedEventArgs<TValue>> _action;
+
+            public ClassHandlerObserver(Action<TTarget, AvaloniaPropertyChangedEventArgs<TValue>> action)
+            {
+                _action = action;
+            }
+
+            public void OnCompleted()
+            {
+            }
+
+            public void OnError(Exception error)
+            {
+            }
+
+            public void OnNext(AvaloniaPropertyChangedEventArgs<TValue> value)
+            {
+                if (value.Sender is TTarget target)
+                {
+                    _action(target, value);
+                }
+            }
+        }
+
+        private class ClassHandlerObserver<TTarget> : IObserver<AvaloniaPropertyChangedEventArgs>
+        {
+            private readonly Action<TTarget, AvaloniaPropertyChangedEventArgs> _action;
+
+            public ClassHandlerObserver(Action<TTarget, AvaloniaPropertyChangedEventArgs> action)
+            {
+                _action = action;
+            }
+
+            public void OnCompleted()
+            {
+            }
+
+            public void OnError(Exception error)
+            {
+            }
+
+            public void OnNext(AvaloniaPropertyChangedEventArgs value)
+            {
+                if (value.Sender is TTarget target)
+                {
+                    _action(target, value);
+                }
+            }
+        }
     }
 }

src/Avalonia.Base/AvaloniaProperty`1.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive.Subjects;
 using Avalonia.Data;
+using Avalonia.Reactive;
 using Avalonia.Utilities;
 
 namespace Avalonia
@@ -12,7 +12,7 @@ namespace Avalonia
     /// <typeparam name="TValue">The value type of the property.</typeparam>
     public abstract class AvaloniaProperty<TValue> : AvaloniaProperty
     {
-        private readonly Subject<AvaloniaPropertyChangedEventArgs<TValue>> _changed;
+        private readonly LightweightSubject<AvaloniaPropertyChangedEventArgs<TValue>> _changed;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="AvaloniaProperty{TValue}"/> class.
@@ -28,7 +28,7 @@ protected AvaloniaProperty(
             Action<AvaloniaObject, bool>? notifying = null)
             : base(name, typeof(TValue), ownerType, metadata, notifying)
         {
-            _changed = new Subject<AvaloniaPropertyChangedEventArgs<TValue>>();
+            _changed = new LightweightSubject<AvaloniaPropertyChangedEventArgs<TValue>>();
         }
 
         /// <summary>

src/Avalonia.Base/ClassBindingManager.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using Avalonia.Data;
+using Avalonia.Reactive;
 
 namespace Avalonia
 {

src/Avalonia.Base/Collections/AvaloniaListExtensions.cs

@@ -3,7 +3,7 @@
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.ComponentModel;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 
 namespace Avalonia.Collections
 {

src/Avalonia.Base/Collections/NotifyCollectionChangedExtensions.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Specialized;
-using System.Reactive.Linq;
 using Avalonia.Reactive;
 using Avalonia.Utilities;
 

src/Avalonia.Base/Controls/NameScopeLocator.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Utilities;
 
 namespace Avalonia.Controls