Refactor clock types.

src/Avalonia.Animation/Clock.cs

@@ -6,81 +6,20 @@ using Avalonia.Reactive;
 
 namespace Avalonia.Animation
 {
-    public class Clock : IObservable<TimeSpan>
+    public class Clock : ClockBase
     {
-        public static Clock GlobalClock => AvaloniaLocator.Current.GetService<Clock>();
-
-        private ClockObservable _observable;
-
-        private IObservable<TimeSpan> _connectedObservable;
+        public static IClock GlobalClock => AvaloniaLocator.Current.GetService<IClock>();
 
         private IDisposable _parentSubscription;
-
-        private TimeSpan? _previousTime;
-        private TimeSpan _internalTime;
-
-        protected Clock()
-        {
-            _observable = new ClockObservable();
-            _connectedObservable = _observable.Publish().RefCount();
-        }
-
-        public Clock(Clock parent)
-            :this()
+        
+        public Clock(IClock parent)
         {
             _parentSubscription = parent.Subscribe(Pulse);
         }
 
-        public bool HasSubscriptions => _observable.HasSubscriptions;
-
-        public TimeSpan CurrentTime { get; private set; }
-
-        public PlayState PlayState { get; set; }
-
-        protected void Pulse(TimeSpan systemTime)
-        {
-            if (!_previousTime.HasValue)
-            {
-                _previousTime = systemTime;
-                _internalTime = TimeSpan.Zero;
-            }
-            else
-            {
-                if (PlayState == PlayState.Pause)
-                {
-                    _previousTime = systemTime;
-                    return;
-                }
-                var delta = systemTime - _previousTime;
-                _internalTime += delta.Value;
-                _previousTime = systemTime;
-            }
-
-            _observable.Pulse(_internalTime);
-            CurrentTime = _internalTime;
-
-            if (PlayState == PlayState.Stop)
-            {
-                Stop();
-            }
-        }
-
-        protected virtual void Stop()
+        protected override void Stop()
         {
             _parentSubscription?.Dispose();
         }
-
-        public IDisposable Subscribe(IObserver<TimeSpan> observer)
-        {
-            return _connectedObservable.Subscribe(observer);
-        }
-
-        private class ClockObservable : LightweightObservableBase<TimeSpan>
-        {
-            public bool HasSubscriptions { get; private set; }
-            public void Pulse(TimeSpan time) => PublishNext(time);
-            protected override void Initialize() => HasSubscriptions = true;
-            protected override void Deinitialize() => HasSubscriptions = false;
-        }
     }
 }

src/Avalonia.Animation/ClockBase.cs

@@ -0,0 +1,75 @@
+using System;
+using System.Collections.Generic;
+using System.Reactive.Linq;
+using System.Text;
+using Avalonia.Reactive;
+
+namespace Avalonia.Animation
+{
+    public class ClockBase : IClock
+    {
+        private ClockObservable _observable;
+
+        private IObservable<TimeSpan> _connectedObservable;
+
+        private TimeSpan? _previousTime;
+        private TimeSpan _internalTime;
+
+        protected ClockBase()
+        {
+            _observable = new ClockObservable();
+            _connectedObservable = _observable.Publish().RefCount();
+        }
+
+        public bool HasSubscriptions => _observable.HasSubscriptions;
+
+        public TimeSpan CurrentTime { get; private set; }
+
+        public PlayState PlayState { get; set; }
+
+        protected void Pulse(TimeSpan systemTime)
+        {
+            if (!_previousTime.HasValue)
+            {
+                _previousTime = systemTime;
+                _internalTime = TimeSpan.Zero;
+            }
+            else
+            {
+                if (PlayState == PlayState.Pause)
+                {
+                    _previousTime = systemTime;
+                    return;
+                }
+                var delta = systemTime - _previousTime;
+                _internalTime += delta.Value;
+                _previousTime = systemTime;
+            }
+
+            _observable.Pulse(_internalTime);
+            CurrentTime = _internalTime;
+
+            if (PlayState == PlayState.Stop)
+            {
+                Stop();
+            }
+        }
+
+        protected virtual void Stop()
+        {
+        }
+
+        public IDisposable Subscribe(IObserver<TimeSpan> observer)
+        {
+            return _connectedObservable.Subscribe(observer);
+        }
+
+        private class ClockObservable : LightweightObservableBase<TimeSpan>
+        {
+            public bool HasSubscriptions { get; private set; }
+            public void Pulse(TimeSpan time) => PublishNext(time);
+            protected override void Initialize() => HasSubscriptions = true;
+            protected override void Deinitialize() => HasSubscriptions = false;
+        }
+    }
+}

src/Avalonia.Animation/IClock.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Avalonia.Animation
+{
+    public interface IClock : IObservable<TimeSpan>
+    {
+        bool HasSubscriptions { get; }
+        TimeSpan CurrentTime { get; }
+        PlayState PlayState { get; set; }
+    }
+}

src/Avalonia.Controls/Application.cs

@@ -340,7 +340,7 @@ namespace Avalonia
 
             var clock = new RenderLoopClock();
             AvaloniaLocator.CurrentMutable
-                .Bind<Clock>().ToConstant(clock)
+                .Bind<IClock>().ToConstant(clock)
                 .GetService<IRenderLoop>().Add(clock);
         }
     }

src/Avalonia.Visuals/Animation/RenderLoopClock.cs

@@ -5,7 +5,7 @@ using Avalonia.Rendering;
 
 namespace Avalonia.Animation
 {
-    public class RenderLoopClock : Clock, IRenderLoopTask
+    public class RenderLoopClock : ClockBase, IRenderLoopTask
     {
         protected override void Stop()
         {