WPF GTK Set flags (#8446)

* WPF GTK Set flags

* Remove collection view flag

Xamarin.Forms.ControlGallery.GTK/Program.cs

@@ -21,6 +21,7 @@ namespace Xamarin.Forms.ControlGallery.GTK
             GtkOpenGL.Init();
             GtkThemes.Init();
             Gtk.Application.Init();
+            Forms.SetFlags("CarouselView_Experimental");
             FormsMaps.Init(string.Empty);
             Forms.Init();
             var app = new App();

Xamarin.Forms.ControlGallery.WPF/MainWindow.xaml.cs

@@ -10,6 +10,7 @@ namespace Xamarin.Forms.ControlGallery.WPF
 		public MainWindow()
 		{
 			InitializeComponent();
+			Forms.SetFlags("CarouselView_Experimental");
 			Xamarin.Forms.Forms.Init();
 			FormsMaps.Init("");
 			LoadApplication(new Controls.App());

Xamarin.Forms.Platform.GTK/Forms.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
@@ -15,6 +16,10 @@ namespace Xamarin.Forms
 		const string LogFormat = "[{0}] {1}";
 
 		public static bool IsInitialized { get; private set; }
+		static bool FlagsSet { get; set; }
+
+		static IReadOnlyList<string> s_flags;
+		public static IReadOnlyList<string> Flags => s_flags ?? (s_flags = new List<string>().AsReadOnly());
 
 		public static void Init(IEnumerable<Assembly> rendererAssemblies = null)
 		{
@@ -25,9 +30,8 @@ namespace Xamarin.Forms
 
 			Registrar.ExtraAssemblies = rendererAssemblies?.ToArray();
 
-			IsInitialized = true;
-
 			Device.SetIdiom(TargetIdiom.Desktop);
+			Device.SetFlags(s_flags);
 			Device.PlatformServices = new GtkPlatformServices();
 			Device.Info = new GtkDeviceInfo();
 			Color.SetAccent(Color.FromHex("#3498DB"));
@@ -39,6 +43,24 @@ namespace Xamarin.Forms
 				typeof(ExportImageSourceHandlerAttribute),
 				typeof(ExportRendererAttribute)
 			});
+
+			IsInitialized = true;
+		}
+
+		public static void SetFlags(params string[] flags)
+		{
+			if (FlagsSet)
+			{
+				return;
+			}
+
+			if (IsInitialized)
+			{
+				throw new InvalidOperationException($"{nameof(SetFlags)} must be called before {nameof(Init)}");
+			}
+
+			s_flags = flags.ToList().AsReadOnly();
+			FlagsSet = true;
 		}
 	}
 }

Xamarin.Forms.Platform.WPF/Forms.cs

@@ -12,6 +12,11 @@ namespace Xamarin.Forms
 	{
 		public static bool IsInitialized { get; private set; }
 
+		static bool FlagsSet { get; set; }
+
+		static IReadOnlyList<string> s_flags;
+		public static IReadOnlyList<string> Flags => s_flags ?? (s_flags = new List<string>().AsReadOnly());
+
 		public static void Init(IEnumerable<Assembly> rendererAssemblies = null)
 		{
 			if (IsInitialized)
@@ -36,11 +41,28 @@ namespace Xamarin.Forms
 			ExpressionSearch.Default = new WPFExpressionSearch();
 
 			Registrar.RegisterAll(new[] { typeof(ExportRendererAttribute), typeof(ExportCellAttribute), typeof(ExportImageSourceHandlerAttribute) });
-			
+
 			Ticker.SetDefault(new WPFTicker());
 			Device.SetIdiom(TargetIdiom.Desktop);
+			Device.SetFlags(s_flags);
 
 			IsInitialized = true;
 		}
+
+		public static void SetFlags(params string[] flags)
+		{
+			if (FlagsSet)
+			{
+				return;
+			}
+
+			if (IsInitialized)
+			{
+				throw new InvalidOperationException($"{nameof(SetFlags)} must be called before {nameof(Init)}");
+			}
+
+			s_flags = flags.ToList().AsReadOnly();
+			FlagsSet = true;
+		}
 	}
 }