Make core Ticker abstract and public (#116)

* Make core Ticker abstract and public
Make the core Ticker abstract and public so it can be inherited by platform
implementations; remove now-unused parts of original Ticker; add CreateTicker
to IPlatformServices; remove unused CreateTimer methods from IPlatformServices

* Add docs for Ticker

* Remove unnecessary Ticker.Default set

* Move Ticker into Internals

* Update Ticker docs

* Remove old Ticker docs

* Remove commented code

1 files changed, 27 insertions, 0 deletions

diff --git a/Xamarin.Forms.Core.UnitTests/MockPlatformServices.cs b/Xamarin.Forms.Core.UnitTests/MockPlatformServices.cs
index 7d2317b3..5109cbb4 100644
--- a/Xamarin.Forms.Core.UnitTests/MockPlatformServices.cs
+++ b/Xamarin.Forms.Core.UnitTests/MockPlatformServices.cs
@@ -9,6 +9,8 @@ using Xamarin.Forms;
 using Xamarin.Forms.Core.UnitTests;
 using System.Security.Cryptography;
 using System.Text;
+using Xamarin.Forms.Internals;
+
 #if WINDOWS_PHONE
 using Xamarin.Forms.Platform.WinPhone;
 #endif
@@ -88,6 +90,11 @@ namespace Xamarin.Forms.Core.UnitTests
 				invokeOnMainThread (action);
 		}
 
+		public Ticker CreateTicker()
+		{
+			return new MockTicker();
+		}
+
 		public void StartTimer (TimeSpan interval, Func<bool> callback)
 		{
 			Timer timer = null;
@@ -267,4 +274,24 @@ namespace Xamarin.Forms.Core.UnitTests
 		{
 		}
 	}
+
+	internal class MockTicker : Ticker
+	{
+		bool _enabled;
+
+		protected override void EnableTimer()
+		{
+			_enabled = true;
+
+			while (_enabled)
+			{
+				SendSignals(16);
+			}
+		}
+
+		protected override void DisableTimer()
+		{
+			_enabled = false;
+		}
+	}
 }
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