[C] reset children animation on repeat (#974)

Xamarin.Forms.Core.UnitTests/AnimationTests.cs

@@ -0,0 +1,33 @@
+using NUnit.Framework;
+using System.Threading.Tasks;
+
+namespace Xamarin.Forms.Core.UnitTests
+{
+	[TestFixture]
+	public class AnimationTests : BaseTestFixture
+	{
+		[Test]
+		//https://bugzilla.xamarin.com/show_bug.cgi?id=51424
+		public async void AnimationRepeats()
+		{
+			var box = new BoxView();
+			Assume.That(box.Rotation, Is.EqualTo(0d));
+			var sb = new Animation();
+			var animcount = 0;
+			var rot45 = new Animation(d =>
+			{
+				box.Rotation = d;
+				if (d > 44)
+					animcount++;
+			}, box.Rotation, box.Rotation + 45);
+			sb.Add(0, .5, rot45);
+			Assume.That(box.Rotation, Is.EqualTo(0d));
+
+			var i = 0;
+			sb.Commit(box, "foo", length: 100, repeat: () => ++i < 2);
+
+			await Task.Delay(250);
+			Assert.That(animcount, Is.EqualTo(2));
+		}
+	}
+}

Xamarin.Forms.Core.UnitTests/Xamarin.Forms.Core.UnitTests.csproj

@@ -183,6 +183,7 @@
     <Compile Include="AppLinkEntryTests.cs" />
     <Compile Include="NativeBindingTests.cs" />
     <Compile Include="TypedBindingUnitTests.cs" />
+    <Compile Include="AnimationTests.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Xamarin.Forms.Core\Xamarin.Forms.Core.csproj">

Xamarin.Forms.Core/Animation.cs

@@ -112,6 +112,12 @@ namespace Xamarin.Forms
 			return result;
 		}
 
+		internal void ResetChildren()
+		{
+			foreach (var anim in _children)
+				anim._finishedTriggered = false;
+		}
+
 		public Animation Insert(double beginAt, double finishAt, Animation animation)
 		{
 			Add(beginAt, finishAt, animation);

Xamarin.Forms.Core/AnimationExtensions.cs

@@ -71,7 +71,18 @@ namespace Xamarin.Forms
 		public static void Animate(this IAnimatable self, string name, Animation animation, uint rate = 16, uint length = 250, Easing easing = null, Action<double, bool> finished = null,
 								   Func<bool> repeat = null)
 		{
-			self.Animate(name, animation.GetCallback(), rate, length, easing, finished, repeat);
+			if (repeat == null)
+				self.Animate(name, animation.GetCallback(), rate, length, easing, finished, null);
+			else {
+				Func<bool> r = () =>
+				{
+					var val = repeat();
+					if (val)
+						animation.ResetChildren();
+					return val;
+				};
+				self.Animate(name, animation.GetCallback(), rate, length, easing, finished, r);
+			}
 		}
 
 		public static void Animate(this IAnimatable self, string name, Action<double> callback, double start, double end, uint rate = 16, uint length = 250, Easing easing = null,
@@ -232,15 +243,15 @@ namespace Xamarin.Forms
 			Info info;
 			if (tweener != null && s_animations.TryGetValue(tweener.Handle, out info))
 			{
-				var repeat = false;
-				if (info.Repeat != null)
-					repeat = info.Repeat();
-
 				IAnimatable owner;
 				if (info.Owner.TryGetTarget(out owner))
 					owner.BatchBegin();
 				info.Callback(tweener.Value);
 
+				var repeat = false;
+				if (info.Repeat != null)
+					repeat = info.Repeat();
+
 				if (!repeat)
 				{
 					s_animations.Remove(tweener.Handle);