Fix nits

src/Avalonia.Animation/Animation.cs

@@ -63,12 +63,10 @@ namespace Avalonia.Animation
             var handlerList = new List<(Type, AvaloniaProperty)>();
             var kfList = new List<AnimatorKeyFrame>();
 
-
             foreach (var keyframe in this)
             {
                 foreach (var setter in keyframe)
                 {
-
                     var custAttr = setter.GetType()
                                          .GetCustomAttributes()
                                          .Where(p => p.GetType() == typeof(AnimatorAttribute));
@@ -106,8 +104,8 @@ namespace Avalonia.Animation
 
             foreach (var kf in kfList)
             {
-                var parent = newAnimatorInstances.Where(p=>p.handler == kf.Handler &&
+                var parent = newAnimatorInstances.Where(p => p.handler == kf.Handler &&
-                                                           p.prop == kf.Property)
+                                                             p.prop == kf.Property)
                                                  .First();
                 parent.inst.Add(kf);
             }
@@ -144,4 +142,4 @@ namespace Avalonia.Animation
             return this;
         }
     }
-}
+}

src/Avalonia.Animation/AnimationSetter.cs

@@ -9,7 +9,7 @@ using Avalonia.Data;
 
 namespace Avalonia.Animation
 {
-    public abstract class Setter : IAnimationSetter
+    public abstract class AnimationSetter : IAnimationSetter
     {
         public AvaloniaProperty Property { get; set; }
         public object Value { get; set; }

src/Avalonia.Animation/AnimatorAttribute.cs

@@ -2,6 +2,10 @@ using System;
 
 namespace Avalonia.Animation
 {
+    /// <summary>
+    /// Attribute for <see cref="IAnimationSetter"/> objects
+    /// that maps the setter to it's <see cref="Animator{T}"/>.
+    /// </summary>
     public class AnimatorAttribute : Attribute
     {
         public Type HandlerType;

src/Avalonia.Animation/AnimatorKeyFrame.cs

@@ -7,15 +7,17 @@ using Avalonia.Collections;
 
 namespace Avalonia.Animation
 {
-    
+    /// <summary>
+    /// Defines a KeyFrame that is used for
+    /// <see cref="Animators"/> objects.
+    /// </summary>
     public class AnimatorKeyFrame
     {
         public Type Handler;
         public Cue Cue;
         public TimeSpan KeyTime;
         internal bool timeSpanSet, cueSet;
-        internal AvaloniaProperty Property;
+        public AvaloniaProperty Property;
         public object Value;
     }
-
 }

src/Avalonia.Animation/Animator`1.cs

@@ -28,6 +28,12 @@ namespace Avalonia.Animation
         /// </summary>
         public AvaloniaProperty Property { get; set; }
 
+        public Animator()
+        {
+            // Invalidate keyframes when changed.
+            this.CollectionChanged += delegate { _isVerfifiedAndConverted = false; };
+        }
+
         /// <inheritdoc/>
         public virtual IDisposable Apply(Animation animation, Animatable control, IObservable<bool> obsMatch)
         {
@@ -182,6 +188,5 @@ namespace Avalonia.Animation
                 convertedKeyframes.Add(1.0d, (default(T), true));
             }
         }
-
     }
 }

src/Avalonia.Animation/DoubleSetter.cs

@@ -9,9 +9,13 @@ using Avalonia.Data;
 
 namespace Avalonia.Animation
 {
+    /// <summary>
+    /// Setter that handles <see cref="double"/> properties
+    /// in the target.
+    /// </summary>
     [Animator(typeof(DoubleAnimator))]
-    public class DoubleSetter : Setter
+    public class DoubleSetter : AnimationSetter
-    { 
+    {
-        
+
     }
-}
+}

src/Avalonia.Animation/IAnimator.cs

@@ -18,6 +18,5 @@ namespace Avalonia.Animation
         /// Applies the current KeyFrame group to the specified control.
         /// </summary>
         IDisposable Apply(Animation animation, Animatable control, IObservable<bool> obsMatch);
-        
     }
 }

src/Avalonia.Animation/PlayState.cs

@@ -4,10 +4,24 @@ using System.Text;
 
 namespace Avalonia.Animation
 {
+    /// <summary>
+    /// Determines the playback state of an animation.
+    /// </summary>
     public enum PlayState
     {
+        /// <summary>
+        /// The animation is running.
+        /// </summary>
         Run,
+
+        /// <summary>
+        /// The animation is paused.
+        /// </summary>
         Pause,
+        
+        /// <summary>
+        /// The animation is stopped.
+        /// </summary>
         Stop
     }
-}
+}

src/Avalonia.Animation/RepeatCount.cs

@@ -21,13 +21,13 @@ namespace Avalonia.Animation
     }
 
     /// <summary>
-    /// Determines the repeat behavior of an animation.
+    /// Determines the number of iterations of an animation.
+    /// Also defines its repeat behavior. 
     /// </summary>
     [TypeConverter(typeof(RepeatCountTypeConverter))]
     public struct RepeatCount : IEquatable<RepeatCount>
     {
         private readonly RepeatType _type;
-
         private readonly ulong _value;
 
         /// <summary>
@@ -61,7 +61,6 @@ namespace Avalonia.Animation
         /// </summary>
         public static RepeatCount Loop => new RepeatCount(0, RepeatType.Loop);
 
-
         /// <summary>
         /// Gets an instance of <see cref="RepeatCount"/> that indicates that an animation
         /// should not repeat.
@@ -189,7 +188,7 @@ namespace Avalonia.Animation
             else
             {
                 if(s.StartsWith("-"))
-                    throw new InvalidCastException("RepeatCount iterations can't be a negative number.");
+                    throw new InvalidCastException("RepeatCount can't be a negative number.");
 
                 var value = ulong.Parse(s, CultureInfo.InvariantCulture);
              

src/Avalonia.Visuals/Animation/TransformSetter.cs

@@ -6,11 +6,16 @@ using System.Reactive.Linq;
 using System.Diagnostics;
 using Avalonia.Animation.Utils;
 using Avalonia.Data;
+using Avalonia.Media;
 
 namespace Avalonia.Animation
 {
+    /// <summary>
+    /// Setter that handles <see cref="Transform"/> objects
+    /// in the target.
+    /// </summary>
     [Animator(typeof(TransformAnimator))]
-    public class TransformSetter : Setter
+    public class TransformSetter : AnimationSetter
     { 
         
     }