[C] new OnPlatform mechanism (#658)

* [C] Obsolete TargetPlatform

* [Xaml] support and test the new syntax

* blind fix windows platforms

6 files changed, 97 insertions, 23 deletions

diff --git a/Xamarin.Forms.Core/Device.cs b/Xamarin.Forms.Core/Device.cs
index 5a02bcea..f18251d2 100644
--- a/Xamarin.Forms.Core/Device.cs
+++ b/Xamarin.Forms.Core/Device.cs
@@ -8,13 +8,30 @@ namespace Xamarin.Forms
 {
 	public static class Device
 	{
+		public const string iOS = "iOS";
+		public const string Android = "Android";
+		public const string WinPhone = "WinPhone";
+		public const string Windows = "Windows";
+
 		internal static DeviceInfo info;
 
 		static IPlatformServices s_platformServices;
 
 		public static TargetIdiom Idiom { get; internal set; }
 
-		public static TargetPlatform OS { get; internal set; }
+		[Obsolete("Use RuntimePlatform instead.")]
+#pragma warning disable 0618
+		public static TargetPlatform OS {
+			get {
+				TargetPlatform platform;
+				if (Enum.TryParse(RuntimePlatform, out platform))
+					return platform;
+				return TargetPlatform.Other;
+			}
+		}
+#pragma warning restore 0618
+
+		public static string RuntimePlatform => PlatformServices.RuntimePlatform;
 
 		internal static DeviceInfo Info
 		{
@@ -58,6 +75,7 @@ namespace Xamarin.Forms
 			return GetNamedSize(size, targetElementType, false);
 		}
 
+		[Obsolete("Use switch(RuntimePlatform) instead.")]
 		public static void OnPlatform(Action iOS = null, Action Android = null, Action WinPhone = null, Action Default = null)
 		{
 			switch (OS)
@@ -88,6 +106,7 @@ namespace Xamarin.Forms
 			}
 		}
 
+		[Obsolete("Use switch(RuntimePlatform) instead.")]
 		public static T OnPlatform<T>(T iOS, T Android, T WinPhone)
 		{
 			switch (OS)
@@ -104,18 +123,6 @@ namespace Xamarin.Forms
 			return iOS;
 		}
 
-		public static T OnPlatform<T>(T iOS, T Android, T WinPhone, T Tizen)
-		{
-			if (OS == TargetPlatform.Tizen)
-			{
-				return Tizen;
-			}
-			else
-			{
-				return OnPlatform<T>(iOS, Android, WinPhone);
-			}
-		}
-
 		public static void OpenUri(Uri uri)
 		{
 			PlatformServices.OpenUriAction(uri);
diff --git a/Xamarin.Forms.Core/IPlatformServices.cs b/Xamarin.Forms.Core/IPlatformServices.cs
index a01baa02..39f00731 100644
--- a/Xamarin.Forms.Core/IPlatformServices.cs
+++ b/Xamarin.Forms.Core/IPlatformServices.cs
@@ -28,5 +28,7 @@ namespace Xamarin.Forms
 		void OpenUriAction(Uri uri);
 
 		void StartTimer(TimeSpan interval, Func<bool> callback);
+
+		string RuntimePlatform { get; }
 	}
 }
\ No newline at end of file
diff --git a/Xamarin.Forms.Core/ListView.cs b/Xamarin.Forms.Core/ListView.cs
index 8b4fc53d..0751e1c2 100644
--- a/Xamarin.Forms.Core/ListView.cs
+++ b/Xamarin.Forms.Core/ListView.cs
@@ -71,7 +71,7 @@ namespace Xamarin.Forms
 
 		public ListView([Parameter("CachingStrategy")] ListViewCachingStrategy cachingStrategy) : this()
 		{
-			if (Device.OS == TargetPlatform.Android || Device.OS == TargetPlatform.iOS)
+			if (Device.RuntimePlatform == Device.Android || Device.RuntimePlatform == Device.iOS)
 				CachingStrategy = cachingStrategy;
 		}
 
diff --git a/Xamarin.Forms.Core/OnPlatform.cs b/Xamarin.Forms.Core/OnPlatform.cs
index 02e27083..68621134 100644
--- a/Xamarin.Forms.Core/OnPlatform.cs
+++ b/Xamarin.Forms.Core/OnPlatform.cs
@@ -1,16 +1,79 @@
+using System;
+using System.Collections.Generic;
+using Xamarin.Forms.Xaml;
+
 namespace Xamarin.Forms
 {
+	[ContentProperty("Platforms")]
 	public class OnPlatform<T>
 	{
-		public T Android { get; set; }
-		public T iOS { get; set; }
-		public T WinPhone { get; set; }
+		public OnPlatform()
+		{
+			Platforms = new List<On>();
+		}
+
+		bool useLegacyFallback;
+		T android;
+		[Obsolete]
+		public T Android {
+			get { return android; }
+			set {
+				useLegacyFallback = true;
+				android = value;
+			}
+		}
+
+		T ios;
+		[Obsolete]
+		public T iOS {
+			get { return ios; }
+			set {
+				useLegacyFallback = true;
+				ios = value;
+			}
+		}
 
-		public T Tizen { get; set; }
+		T winPhone;
+		[Obsolete]
+		public T WinPhone {
+			get { return winPhone; }
+			set {
+				useLegacyFallback = true;
+				winPhone = value;
+			}
+		}
+
+		public IList<On> Platforms { get; private set; }
+
+		static readonly IValueConverterProvider s_valueConverter = DependencyService.Get<IValueConverterProvider>();
 
 		public static implicit operator T(OnPlatform<T> onPlatform)
 		{
-			return Device.OnPlatform(iOS: onPlatform.iOS, Android: onPlatform.Android, WinPhone: onPlatform.WinPhone, Tizen: onPlatform.Tizen);
+			foreach (var onPlat in onPlatform.Platforms) {
+				if (onPlat.Platform == null)
+					continue;
+				if (!onPlat.Platform.Contains(Device.RuntimePlatform))
+					continue;
+				if (s_valueConverter == null)
+					continue;
+				return (T)s_valueConverter.Convert(onPlat.Value, typeof(T), null, null);
+			}
+
+			if (!onPlatform.useLegacyFallback)
+				return default(T);
+
+			//legacy fallback
+#pragma warning disable 0618, 0612
+			return Device.OnPlatform(iOS: onPlatform.iOS, Android: onPlatform.Android, WinPhone: onPlatform.WinPhone);
+#pragma warning restore 0618, 0612
 		}
 	}
-}
\ No newline at end of file
+
+	[ContentProperty("Value")]
+	public class On
+	{
+		[TypeConverter(typeof(ListStringTypeConverter))]
+		public IList<string> Platform { get; set; }
+		public object Value { get; set; }
+	}
+}
diff --git a/Xamarin.Forms.Core/TargetPlatform.cs b/Xamarin.Forms.Core/TargetPlatform.cs
index 62fbda09..6125695f 100644
--- a/Xamarin.Forms.Core/TargetPlatform.cs
+++ b/Xamarin.Forms.Core/TargetPlatform.cs
@@ -1,5 +1,8 @@
+using System;
+
 namespace Xamarin.Forms
 {
+	[Obsolete]
 	public enum TargetPlatform
 	{
 		Other,
@@ -7,6 +10,5 @@ namespace Xamarin.Forms
 		Android,
 		WinPhone,
 		Windows,
-		Tizen
 	}
 }
diff --git a/Xamarin.Forms.Core/TemplatedItemsList.cs b/Xamarin.Forms.Core/TemplatedItemsList.cs
index cb64e2e9..a954939d 100644
--- a/Xamarin.Forms.Core/TemplatedItemsList.cs
+++ b/Xamarin.Forms.Core/TemplatedItemsList.cs
@@ -970,7 +970,7 @@ namespace Xamarin.Forms
 
 			/* HACKAHACKHACK: LongListSelector on WP SL has a bug in that it completely fails to deal with
 			 * INCC notifications that include more than 1 item. */
-			if (fixWindows && Device.OS == TargetPlatform.WinPhone)
+			if (fixWindows && Device.RuntimePlatform == Device.WinPhone)
 			{
 				SplitCollectionChangedItems(e);
 				return;
@@ -1205,7 +1205,7 @@ namespace Xamarin.Forms
 
 			//Hack: the cell could still be visible on iOS because the cells are reloaded after this unhook 
 			//this causes some visual updates caused by a null datacontext and default values like IsVisible
-			if (Device.OS == TargetPlatform.iOS && CachingStrategy == ListViewCachingStrategy.RetainElement)
+			if (Device.RuntimePlatform == Device.iOS && CachingStrategy == ListViewCachingStrategy.RetainElement)
 				await Task.Delay(100);
 			item.BindingContext = null;
 		}