feat(easing): Implemented Circle easing functions

src/Uno.UI/Generated/3.0.0.0/Windows.UI.Xaml.Media.Animation/CircleEase.cs

@@ -2,18 +2,12 @@
 #pragma warning disable 114 // new keyword hiding
 namespace Windows.UI.Xaml.Media.Animation
 {
-	#if __ANDROID__ || __IOS__ || NET461 || __WASM__ || __MACOS__
+	#if false || false || false || false || false
 	[global::Uno.NotImplemented]
 	#endif
 	public  partial class CircleEase : global::Windows.UI.Xaml.Media.Animation.EasingFunctionBase
 	{
-		#if __ANDROID__ || __IOS__ || NET461 || __WASM__ || __MACOS__
-		[global::Uno.NotImplemented]
-		public CircleEase() 
-		{
-			global::Windows.Foundation.Metadata.ApiInformation.TryRaiseNotImplemented("Windows.UI.Xaml.Media.Animation.CircleEase", "CircleEase.CircleEase()");
-		}
-		#endif
+		// Skipping already declared method Windows.UI.Xaml.Media.Animation.CircleEase.CircleEase()
 		// Forced skipping of method Windows.UI.Xaml.Media.Animation.CircleEase.CircleEase()
 	}
 }

src/Uno.UI/UI/Xaml/Media/Animation/CircleEase.cs

@@ -0,0 +1,41 @@
+
+using System;
+
+namespace Windows.UI.Xaml.Media.Animation
+{
+	public partial class CircleEase : EasingFunctionBase
+	{
+		public override double Ease(double currentTime, double startValue, double finalValue, double duration)
+		{
+			var c = finalValue - startValue;
+
+			var t = currentTime;
+			var b = startValue;
+			var d = duration;
+
+
+			//Depending on the mode we have different functions for the return value.
+			switch (this.EasingMode)
+			{
+				case EasingMode.EaseIn:
+					// http://gizma.com/easing/#circ1
+					t /= d;
+					return -c * (Math.Sqrt(1 - t * t) - 1) + b;
+				case EasingMode.EaseOut:
+					// http://gizma.com/easing/#circ2
+					t /= d;
+					t--;
+					return c * Math.Sqrt(1 - t * t) + b;
+				case EasingMode.EaseInOut:
+					// http://gizma.com/easing/#circ3
+					t /= d / 2;
+					if (t < 1) return -c / 2 * (Math.Sqrt(1 - t * t) - 1) + b;
+					t -= 2;
+					return c / 2 * (Math.Sqrt(1 - t * t) + 1) + b;
+
+				default:
+					return finalValue * currentTime / duration + startValue;
+			}
+		}
+	}
+}

src/Uno.UI/UI/Xaml/Media/Animation/EasingFunctionBase.cs

@@ -18,13 +18,17 @@ public EasingFunctionBase()
 
 		public EasingMode EasingMode
 		{
-			get { return (EasingMode)this.GetValue(EasingModeProperty); }
-			set { this.SetValue(EasingModeProperty, value); }
+			get => (EasingMode)this.GetValue(EasingModeProperty);
+			set => this.SetValue(EasingModeProperty, value);
 		}
 
 		public static readonly DependencyProperty EasingModeProperty =
 			DependencyProperty.Register("EasingMode", typeof(EasingMode), typeof(EasingFunctionBase), new PropertyMetadata(EasingMode.EaseOut));
 
-		public virtual double Ease(double currentTime, double startValue, double finalValue, double duration) { throw new NotSupportedException(); }
+		public virtual double Ease(double currentTime, double startValue, double finalValue, double duration) =>
+			// Return linear interpolation instead of an exception for unimplemented easing functions.
+			currentTime == 0 ? startValue : Lerp(startValue, finalValue, currentTime / duration);
+
+		private static double Lerp(double first, double last, double by) => first * (1.0 - @by) + last * @by;
 	}
 }

src/Uno.UI/UI/Xaml/Media/Animation/SineEase.cs

@@ -4,7 +4,7 @@
 
 namespace Windows.UI.Xaml.Media.Animation
 {
-    public partial class SineEase : EasingFunctionBase
+	public partial class SineEase : EasingFunctionBase
 	{
 		public override double Ease(double currentTime, double startValue, double finalValue, double duration)
 		{