Merge branch '3.6.0'

.nuspec/Xamarin.Forms.Android.targets

@@ -2,4 +2,12 @@
   <ItemGroup>
     <ProguardConfiguration Include="$(MSBuildThisFileDirectory)proguard.cfg" />
   </ItemGroup>
+  <Target Name="ValidateTargetFrameworkVersionForForms" BeforeTargets="CoreCompile" Condition="'$(XFDisableTargetFrameworkValidation)' != 'True'">
+    <PropertyGroup>
+      <MinTargetFrameworkVersionForForms>8.1</MinTargetFrameworkVersionForForms>
+      <TargetFrameworkVersionWithoutV>$(TargetFrameworkVersion.TrimStart('vV'))</TargetFrameworkVersionWithoutV>
+    </PropertyGroup>
+    <Error Code="XF005"  Condition="$(TargetFrameworkVersionWithoutV) &lt; $(MinTargetFrameworkVersionForForms)"
+           Text="The %24(TargetFrameworkVersion) for $(ProjectName) ($(TargetFrameworkVersion)) is less than the minimum required %24(TargetFrameworkVersion) for Xamarin.Forms ($(MinTargetFrameworkVersionForForms)). You need to increase the %24(TargetFrameworkVersion) for $(ProjectName)."   />
+  </Target>
 </Project>

.nuspec/Xamarin.Forms.Visual.Material.targets

@@ -1,5 +1,5 @@
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-    <Target Name="ValidateTargetFrameworkVersionForMaterial" BeforeTargets="BeforeCompile">
+    <Target Name="ValidateTargetFrameworkVersionForMaterial" BeforeTargets="CoreCompile" Condition="'$(XFDisableTargetFrameworkValidation)' != 'True'">
         <PropertyGroup>
             <MinTargetFrameworkVersionForMaterial>9.0</MinTargetFrameworkVersionForMaterial>
             <TargetFrameworkVersionWithoutV>$(TargetFrameworkVersion.TrimStart('vV'))</TargetFrameworkVersionWithoutV>

Xamarin.Forms.Controls/CoreGallery.cs

@@ -321,8 +321,8 @@ namespace Xamarin.Forms.Controls
 				new GalleryPageFactory(() => new OpenGLViewCoreGalleryPage(), "OpenGLView Gallery"),
 				new GalleryPageFactory(() => new PickerCoreGalleryPage(), "Picker Gallery"),
 				new GalleryPageFactory(() => new ProgressBarCoreGalleryPage(), "ProgressBar Gallery"),
-				new GalleryPageFactory(() => new MaterialProgressBarGallery(), "[Material] ProgressBar & Slider Gallery"),
-				new GalleryPageFactory(() => new MaterialActivityIndicatorGallery(), "[Material] ActivityIndicator Gallery"),
+				new GalleryPageFactory(() => new MaterialProgressBarGallery(), "ProgressBar & Slider Gallery (Material)"),
+				new GalleryPageFactory(() => new MaterialActivityIndicatorGallery(), "ActivityIndicator Gallery (Material)"),
 				new GalleryPageFactory(() => new ScrollGallery(), "ScrollView Gallery"),
 				new GalleryPageFactory(() => new ScrollGallery(ScrollOrientation.Horizontal), "ScrollView Gallery Horizontal"),
 				new GalleryPageFactory(() => new ScrollGallery(ScrollOrientation.Both), "ScrollView Gallery 2D"),

Xamarin.Forms.Core.Design/AttributeTableBuilder.cs

@@ -35,6 +35,10 @@ namespace Xamarin.Forms.Core.Design
 					new System.ComponentModel.TypeConverterAttribute (typeof (NonExclusiveEnumConverter<NamedSize>))));
 			}
 
+			AddCallback(typeof(VisualElement), builder => builder.AddCustomAttributes(
+			   "Visual",
+			   new System.ComponentModel.TypeConverterAttribute(typeof(VisualDesignTypeConverter))));
+
 			// TODO: OnPlatform/OnIdiom
 			// These two should be proper markup extensions, to follow WPF syntax for those.
 			// That would allow us to turn on XAML validation, which otherwise fails.
@@ -42,7 +46,7 @@ namespace Xamarin.Forms.Core.Design
 			// the language service can find the type by its name. That class can be internal 
 			// though, since its visibility in the markup is controlled by the EditorBrowsableAttribute.
 			// Make OnPlatform/OnIdiom visible for intellisense, and set as markup extension. 
-			AddCallback (typeof (OnPlatform<>), builder => builder.AddCustomAttributes (new Attribute[] {
+			AddCallback(typeof (OnPlatform<>), builder => builder.AddCustomAttributes (new Attribute[] {
 				new EditorBrowsableAttribute (EditorBrowsableState.Always),
 				//new System.ComponentModel.TypeConverterAttribute(typeof(AnythingConverter)),
 				//new System.Windows.Markup.MarkupExtensionReturnTypeAttribute (),

Xamarin.Forms.Core.Design/VisualDesignTypeConverter.cs

@@ -0,0 +1,64 @@
+namespace Xamarin.Forms.Core.Design
+{
+	using System.Collections.Generic;
+	using System.Linq;
+	using System.ComponentModel;
+	using System;
+
+	public class VisualDesignTypeConverter : TypeConverter
+	{
+		public VisualDesignTypeConverter()
+		{
+		}
+
+		protected StandardValuesCollection Values
+		{
+			get;
+			set;
+		}
+
+		public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+		{
+			// This tells XAML this converter can be used to process strings
+			// Without this the values won't show up as hints
+			if (sourceType == typeof(string))
+				return true;
+
+			return base.CanConvertFrom(context, sourceType);
+		}
+
+		public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context)
+		{
+			if(Values == null)
+			{
+				var derivedNames = new List<string>();
+				var baseType = typeof(IVisual);
+
+				var typeElements = typeof(View).Assembly.ExportedTypes.Where(t => baseType.IsAssignableFrom(t) && t.Name != baseType.Name);
+
+				foreach (var typeElement in typeElements)
+				{
+					string name = typeElement.Name;
+					if (name.EndsWith("Visual", StringComparison.OrdinalIgnoreCase))
+						name = name.Substring(0, name.Length - 6);
+
+					derivedNames.Add(name);
+				}
+
+				Values = new StandardValuesCollection(derivedNames);
+			}
+
+			return Values;
+		}
+
+		public override bool GetStandardValuesExclusive(ITypeDescriptorContext context)
+		{
+			return false;
+		}
+
+		public override bool GetStandardValuesSupported(ITypeDescriptorContext context)
+		{
+			return true;
+		}
+	}
+}

Xamarin.Forms.Core.Design/Xamarin.Forms.Core.Design.csproj

@@ -50,6 +50,7 @@
     <Compile Include="..\Xamarin.Forms.Core\Properties\GlobalAssemblyInfo.cs">
       <Link>Properties\GlobalAssemblyInfo.cs</Link>
     </Compile>
+    <Compile Include="VisualDesignTypeConverter.cs" />
   </ItemGroup>
   <ItemGroup Condition=" '$(OS)' != 'Unix' ">
     <Compile Include="AttributeTableBuilder.cs" />

Xamarin.Forms.Core.UnitTests/BindableLayoutTests.cs

@@ -1,8 +1,10 @@
 using NUnit.Framework;
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
+using System.ComponentModel;
 using System.Linq;
 
 namespace Xamarin.Forms.Core.UnitTests
@@ -72,6 +74,21 @@ namespace Xamarin.Forms.Core.UnitTests
 			Assert.IsTrue(IsLayoutWithItemsSource(itemsSource, layout));
 		}
 
+		[Test]
+		public void TracksRemoveAll()
+		{
+			var layout = new StackLayout
+			{
+				IsPlatformEnabled = true,
+			};
+
+			var itemsSource = new ObservableRangeCollection<int>(Enumerable.Range(0, 10));
+			BindableLayout.SetItemsSource(layout, itemsSource);
+
+			itemsSource.RemoveAll();
+			Assert.IsTrue(IsLayoutWithItemsSource(itemsSource, layout));
+		}
+
 		[Test]
 		public void TracksReplace()
 		{
@@ -377,6 +394,27 @@ namespace Xamarin.Forms.Core.UnitTests
 			}
 		}
 
+		class ObservableRangeCollection<T> : ObservableCollection<T>
+		{
+			public ObservableRangeCollection(IEnumerable<T> collection)
+				: base(collection)
+			{
+			}
+
+			public void RemoveAll()
+			{
+				CheckReentrancy();
+
+				var changedItems = new List<T>(Items);
+				foreach (var i in changedItems)
+					Items.Remove(i);
+
+				OnPropertyChanged(new PropertyChangedEventArgs("Count"));
+				OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
+				OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, changedItems, 0));
+			}
+ 		}     
+      
 		class MyDataTemplateSelectorTest : DataTemplateSelector
 		{
 			readonly Func<object, BindableObject, DataTemplate> _func;

Xamarin.Forms.Core/BindableLayout.cs

@@ -223,9 +223,9 @@ namespace Xamarin.Forms
 					{
 						if (e.OldStartingIndex == -1)
 							goto case NotifyCollectionChangedAction.Reset;
-						for (int i = 0; i < e.OldItems.Count; ++i)
+						for (int i = 0; i < e.OldItems.Count; i++)
 						{
-							layout.Children.RemoveAt(i + e.OldStartingIndex);
+							layout.Children.RemoveAt(e.OldStartingIndex);
 						}
 					}
 					break;

Xamarin.Forms.Core/HandlerAttribute.cs

@@ -7,7 +7,7 @@ namespace Xamarin.Forms
 	{
 		protected HandlerAttribute(Type handler, Type target, Type[] supportedVisuals = null)
 		{
-			SupportedVisuals = supportedVisuals ?? new[] { typeof(VisualRendererMarker.Default) };
+			SupportedVisuals = supportedVisuals ?? new[] { typeof(VisualMarker.DefaultVisual) };
 			TargetType = target;
 			HandlerType = handler;
 		}

Xamarin.Forms.Core/ReflectionExtensions.cs

@@ -45,6 +45,31 @@ namespace Xamarin.Forms.Internals
 			return null;
 		}
 
+		internal static object[] GetCustomAttributesSafe(this Assembly assembly,  Type attrType)
+		{
+			object[] attributes = null;
+			try
+			{
+#if NETSTANDARD2_0
+				attributes = assembly.GetCustomAttributes(attrType, true);
+#else
+				attributes = assembly.GetCustomAttributes(attrType).ToArray();
+#endif
+			}
+			catch (System.IO.FileNotFoundException)
+			{
+				// Sometimes the previewer doesn't actually have everything required for these loads to work
+				Log.Warning(nameof(Registrar), "Could not load assembly: {0} for Attribute {1} | Some renderers may not be loaded", assembly.FullName, attrType.FullName);
+			}
+
+			return attributes;
+		}
+
+		public static Type[] GetExportedTypes(this Assembly assembly)
+		{
+			return assembly.ExportedTypes.ToArray();
+		}
+
 		public static bool IsAssignableFrom(this Type self, Type c)
 		{
 			return self.GetTypeInfo().IsAssignableFrom(c.GetTypeInfo());

Xamarin.Forms.Core/Registrar.cs

@@ -19,8 +19,8 @@ namespace Xamarin.Forms.Internals
 	public class Registrar<TRegistrable> where TRegistrable : class
 	{
 		readonly Dictionary<Type, Dictionary<Type, Type>> _handlers = new Dictionary<Type, Dictionary<Type, Type>>();
-		static Type _defaultVisualType = typeof(VisualRendererMarker.Default);
-		static Type _materialVisualType = typeof(VisualRendererMarker.Material);
+		static Type _defaultVisualType = typeof(VisualMarker.DefaultVisual);
+		static Type _materialVisualType = typeof(VisualMarker.MaterialVisual);
 
 		static Type[] _defaultVisualRenderers = new[] { _defaultVisualType };
 

Xamarin.Forms.Core/RenderWithAttribute.cs

@@ -6,14 +6,14 @@ namespace Xamarin.Forms
 	public sealed class RenderWithAttribute : Attribute
 	{
 
-		public RenderWithAttribute(Type type) : this(type, new[] { typeof(VisualRendererMarker.Default) })
+		public RenderWithAttribute(Type type) : this(type, new[] { typeof(VisualMarker.DefaultVisual) })
 		{
 		}
 
 		public RenderWithAttribute(Type type, Type[] supportedVisuals)
 		{
 			Type = type;
-			SupportedVisuals = supportedVisuals ?? new[] { typeof(VisualRendererMarker.Default) };
+			SupportedVisuals = supportedVisuals ?? new[] { typeof(VisualMarker.DefaultVisual) };
 		}
 
 		public Type[] SupportedVisuals { get; }

Xamarin.Forms.Core/Visual.cs

@@ -1,59 +0,0 @@
-using System;
-
-namespace Xamarin.Forms
-{
-	public static class VisualMarker
-	{
-		static bool _isMaterialRegistered = false;
-		static bool _warnedAboutMaterial = false;
-
-		public static IVisual MatchParent { get; } = new VisualRendererMarker.MatchParent();
-		public static IVisual Default { get; } = new VisualRendererMarker.Default();
-		public static IVisual Material { get; } = new VisualRendererMarker.Material();
-
-		internal static void RegisterMaterial() => _isMaterialRegistered = true;
-		internal static void MaterialCheck()
-		{
-			if (_isMaterialRegistered || _warnedAboutMaterial)
-				return;
-
-			_warnedAboutMaterial = true;
-			if (Device.RuntimePlatform == Device.iOS)
-				Internals.Log.Warning("Visual", "Material needs to be registered on iOS by calling FormsMaterial.Init() after the Xamarin.Forms.Forms.Init method call.");
-			else if (Device.RuntimePlatform != Device.Android)
-				Internals.Log.Warning("Visual", $"Material is currently not support on {Device.RuntimePlatform}.");
-		}
-	}
-
-	public static class VisualRendererMarker
-	{
-		public sealed class Material : IVisual { internal Material() { } }
-		public sealed class Default : IVisual { internal Default() { } }
-		internal sealed class MatchParent : IVisual { internal MatchParent() { } }
-	}
-
-	[TypeConverter(typeof(VisualTypeConverter))]
-	public interface IVisual
-	{
-
-	}
-
-	[Xaml.TypeConversion(typeof(IVisual))]
-	public class VisualTypeConverter : TypeConverter
-	{
-		public override object ConvertFromInvariantString(string value)
-		{
-			if (value != null)
-			{
-				var sc = StringComparison.OrdinalIgnoreCase;
-				if (value.Equals(nameof(VisualMarker.MatchParent), sc))
-					return VisualMarker.MatchParent;
-				else if (value.Equals(nameof(VisualMarker.Material), sc))
-					return VisualMarker.Material;
-				else
-					return VisualMarker.Default;
-			}
-			throw new InvalidOperationException($"Cannot convert \"{value}\" into {typeof(IVisual)}");
-		}
-	}
-}

Xamarin.Forms.Core/Visuals/IVisual.cs

@@ -0,0 +1,7 @@
+namespace Xamarin.Forms
+{
+	[TypeConverter(typeof(VisualTypeConverter))]
+	public interface IVisual
+	{
+	}
+}

Xamarin.Forms.Core/Visuals/VisualAttribute.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Xamarin.Forms
+{
+	[AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
+	public class VisualAttribute : Attribute
+	{
+		public VisualAttribute(string key, Type visual)
+		{
+			this.Key = key;
+			this.Visual = visual;
+		}
+
+		internal string Key { get; }
+		internal Type Visual { get; }
+	}
+}

Xamarin.Forms.Core/Visuals/VisualMarker.cs

@@ -0,0 +1,30 @@
+namespace Xamarin.Forms
+{
+	public static class VisualMarker
+	{
+		static bool _isMaterialRegistered = false;
+		static bool _warnedAboutMaterial = false;
+
+		public static IVisual MatchParent { get; } = new MatchParentVisual();
+		public static IVisual Default { get; } = new DefaultVisual();
+		public static IVisual Material { get; } = new MaterialVisual();
+
+		internal static void RegisterMaterial() => _isMaterialRegistered = true;
+		internal static void MaterialCheck()
+		{
+			if (_isMaterialRegistered || _warnedAboutMaterial)
+				return;
+
+			_warnedAboutMaterial = true;
+			if (Device.RuntimePlatform == Device.iOS)
+				Internals.Log.Warning("Visual", "Material needs to be registered on iOS by calling FormsMaterial.Init() after the Xamarin.Forms.Forms.Init method call.");
+			else if (Device.RuntimePlatform != Device.Android)
+				Internals.Log.Warning("Visual", $"Material is currently not support on {Device.RuntimePlatform}.");
+		}
+
+
+		public sealed class MaterialVisual : IVisual { public MaterialVisual() { } }
+		public sealed class DefaultVisual : IVisual { public DefaultVisual() { } }
+		internal sealed class MatchParentVisual : IVisual { public MatchParentVisual() { } }
+	}
+}

Xamarin.Forms.Core/Visuals/VisualTypeConverter.cs

@@ -0,0 +1,129 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Reflection;
+using Xamarin.Forms.Internals;
+using Xamarin.Forms.Xaml;
+
+namespace Xamarin.Forms
+{
+	[Xaml.TypeConversion(typeof(IVisual))]
+	public class VisualTypeConverter : TypeConverter
+	{
+		static Dictionary<string, IVisual> _visualTypeMappings;
+		void InitMappings()
+		{
+			var mappings = new Dictionary<string, IVisual>(StringComparer.OrdinalIgnoreCase);
+			Assembly[] assemblies = Device.GetAssemblies();
+
+			// Check for IVisual Types
+			foreach (var assembly in assemblies)
+				Register(assembly, mappings);
+
+			if (Internals.Registrar.ExtraAssemblies != null)
+				foreach (var assembly in Internals.Registrar.ExtraAssemblies)
+					Register(assembly, mappings);
+
+
+			// Check for visual assembly attributes	after scanning for IVisual Types
+			// this will let users replace the default visual names if they want to
+			foreach (var assembly in assemblies)
+				RegisterFromAttributes(assembly, mappings);
+
+			if (Internals.Registrar.ExtraAssemblies != null)
+				foreach (var assembly in Internals.Registrar.ExtraAssemblies)
+					RegisterFromAttributes(assembly, mappings);
+
+			_visualTypeMappings = mappings;
+		}
+
+		static void RegisterFromAttributes(Assembly assembly, Dictionary<string, IVisual> mappings)
+		{
+			object[] attributes = assembly.GetCustomAttributesSafe(typeof(VisualAttribute));
+
+			if (attributes != null)
+			{
+				foreach (VisualAttribute attribute in attributes)
+				{
+					var visual = CreateVisual(attribute.Visual);
+					if (visual != null)
+						mappings[attribute.Key] = visual;
+				}
+			}
+		}
+
+		static void Register(Assembly assembly, Dictionary<string, IVisual> mappings)
+		{
+			if (assembly.IsDynamic)
+				return;
+
+			try
+			{
+				foreach (var type in assembly.GetExportedTypes())
+					if (typeof(IVisual).IsAssignableFrom(type) && type != typeof(IVisual))
+						Register(type, mappings);
+			}
+			catch(NotSupportedException)
+			{
+				Log.Warning("Visual", $"Cannot scan assembly {assembly.FullName} for Visual types.");
+			}
+			catch (FileNotFoundException)
+			{
+				Log.Warning("Visual", $"Unable to load a dependent assembly for {assembly.FullName}. It cannot be scanned for Visual types.");
+			}
+		}
+
+		static void Register(Type visual, Dictionary<string, IVisual> mappings)
+		{
+			IVisual registeredVisual = CreateVisual(visual);
+			if (registeredVisual == null)
+				return;
+
+			string name = visual.Name;
+			string fullName = visual.FullName;
+
+			if (name.EndsWith("Visual", StringComparison.OrdinalIgnoreCase))
+			{
+				name = name.Substring(0, name.Length - 6);
+				fullName = fullName.Substring(0, fullName.Length - 6);
+			}
+
+			mappings[name] = registeredVisual;
+			mappings[fullName] = registeredVisual;
+			mappings[$"{name}Visual"] = registeredVisual;
+			mappings[$"{fullName}Visual"] = registeredVisual;
+			
+		}
+
+		static IVisual CreateVisual(Type visualType)
+		{
+			try
+			{
+				return (IVisual)Activator.CreateInstance(visualType);
+			}
+			catch
+			{
+				Internals.Log.Warning("Visual", $"Unable to register {visualType} please add a public default constructor");
+			}
+
+			return null;
+		}
+
+		public override object ConvertFromInvariantString(string value)
+		{
+			if (_visualTypeMappings == null)
+				InitMappings();
+
+			if (value != null)
+			{
+				IVisual returnValue = null;
+				if (_visualTypeMappings.TryGetValue(value, out returnValue))
+					return returnValue;
+
+				return VisualMarker.Default;
+			}
+
+			throw new XamlParseException($"Cannot convert \"{value}\" into {typeof(IVisual)}");
+		}
+	}
+}

Xamarin.Forms.Core/Xaml/TypeConversionExtensions.cs

@@ -114,8 +114,14 @@ namespace Xamarin.Forms.Xaml
 				var xfExtendedTypeConverter = xfTypeConverter as IExtendedTypeConverter;
 				if (xfExtendedTypeConverter != null)
 					return value = xfExtendedTypeConverter.ConvertFromInvariantString(str, serviceProvider);
-				if (xfTypeConverter != null)
-					return value = xfTypeConverter.ConvertFromInvariantString(str);
+				if (xfTypeConverter != null) {
+					try {
+						return value = xfTypeConverter.ConvertFromInvariantString(str);
+					}
+					catch (Exception e) {
+						throw new XamlParseException("Type conversion failed", serviceProvider, e);
+					}
+				}
 				var converterType = converter?.GetType();
 				if (converterType != null)
 				{

Xamarin.Forms.Material.iOS/MaterialStepperRenderer.cs

@@ -3,11 +3,8 @@ using System.ComponentModel;
 using CoreGraphics;
 using MaterialComponents;
 using UIKit;
-using Xamarin.Forms;
 using MButton = MaterialComponents.Button;
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Stepper), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialStepperRenderer), new[] { typeof(VisualRendererMarker.Material) })]
-
 namespace Xamarin.Forms.Platform.iOS.Material
 {
 	public class MaterialStepperRenderer : ViewRenderer<Stepper, MaterialStepper>

Xamarin.Forms.Material.iOS/Properties/AssemblyInfo.cs

@@ -15,12 +15,13 @@ using Xamarin.Forms;
 [assembly: AssemblyVersion("2.0.0.0")]
 [assembly: AssemblyFileVersion("2.0.0.0")]
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.ActivityIndicator), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialActivityIndicatorRenderer), new[] { typeof(VisualRendererMarker.Material) })]
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Button), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialButtonRenderer), new[] { typeof(VisualRendererMarker.Material) })]
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Entry), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialEntryRenderer), new[] { typeof(VisualRendererMarker.Material) })]
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Frame), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialFrameRenderer), new[] { typeof(VisualRendererMarker.Material) })]
-[assembly: ExportRenderer(typeof(Xamarin.Forms.ProgressBar), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialProgressBarRenderer), new[] { typeof(VisualRendererMarker.Material) })]
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Slider), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialSliderRenderer), new[] { typeof(VisualRendererMarker.Material) })]
-[assembly: ExportRenderer(typeof(Xamarin.Forms.TimePicker), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialTimePickerRenderer), new[] { typeof(VisualRendererMarker.Material) })]
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Picker), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialPickerRenderer), new[] { typeof(VisualRendererMarker.Material) })]
-[assembly: ExportRenderer(typeof(Xamarin.Forms.DatePicker), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialDatePickerRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.ActivityIndicator), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialActivityIndicatorRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Button), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialButtonRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Entry), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialEntryRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Frame), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialFrameRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.ProgressBar), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialProgressBarRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Slider), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialSliderRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.TimePicker), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialTimePickerRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Picker), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialPickerRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.DatePicker), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialDatePickerRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Stepper), typeof(Xamarin.Forms.Platform.iOS.Material.MaterialStepperRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]

Xamarin.Forms.Platform.Android/Material/MaterialActivityIndicatorRenderer.cs

@@ -11,7 +11,7 @@ using Xamarin.Forms.Platform.Android.Material;
 using AProgressBar = Android.Widget.ProgressBar;
 using AView = Android.Views.View;
 
-[assembly: ExportRenderer(typeof(ActivityIndicator), typeof(MaterialActivityIndicatorRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(ActivityIndicator), typeof(MaterialActivityIndicatorRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 
 namespace Xamarin.Forms.Platform.Android.Material
 {

Xamarin.Forms.Platform.Android/Material/MaterialButtonRenderer.cs

@@ -17,7 +17,7 @@ using AColor = Android.Graphics.Color;
 using AView = Android.Views.View;
 using MButton = Android.Support.Design.Button.MaterialButton;
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Button), typeof(MaterialButtonRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Button), typeof(MaterialButtonRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 
 namespace Xamarin.Forms.Platform.Android.Material
 {

Xamarin.Forms.Platform.Android/Material/MaterialDatePickerRenderer.cs

@@ -7,7 +7,7 @@ using Android.Widget;
 using Xamarin.Forms;
 using Xamarin.Forms.Platform.Android.Material;
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.DatePicker), typeof(MaterialDatePickerRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.DatePicker), typeof(MaterialDatePickerRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 
 namespace Xamarin.Forms.Platform.Android.Material
 {

Xamarin.Forms.Platform.Android/Material/MaterialEntryRenderer.cs

@@ -8,7 +8,7 @@ using Android.Widget;
 using Xamarin.Forms;
 using Xamarin.Forms.Platform.Android.Material;
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Entry), typeof(MaterialEntryRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Entry), typeof(MaterialEntryRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 namespace Xamarin.Forms.Platform.Android.Material
 {
 	public sealed class MaterialEntryRenderer : EntryRendererBase<MaterialFormsTextInputLayout>

Xamarin.Forms.Platform.Android/Material/MaterialFrameRenderer.cs

@@ -10,7 +10,7 @@ using Xamarin.Forms.Platform.Android.Material;
 using AView = Android.Views.View;
 using MaterialCardView = Android.Support.Design.Card.MaterialCardView;
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Frame), typeof(MaterialFrameRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Frame), typeof(MaterialFrameRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 
 namespace Xamarin.Forms.Platform.Android.Material
 {

Xamarin.Forms.Platform.Android/Material/MaterialPickerRenderer.cs

@@ -7,7 +7,7 @@ using Android.Widget;
 using Xamarin.Forms;
 using Xamarin.Forms.Platform.Android.Material;
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Picker), typeof(MaterialPickerRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Picker), typeof(MaterialPickerRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 
 namespace Xamarin.Forms.Platform.Android.Material
 {

Xamarin.Forms.Platform.Android/Material/MaterialProgressBarRenderer.cs

@@ -10,7 +10,7 @@ using Xamarin.Forms.Platform.Android.Material;
 using AProgressBar = Android.Widget.ProgressBar;
 using AView = Android.Views.View;
 
-[assembly: ExportRenderer(typeof(ProgressBar), typeof(MaterialProgressBarRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(ProgressBar), typeof(MaterialProgressBarRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 
 namespace Xamarin.Forms.Platform.Android.Material
 {

Xamarin.Forms.Platform.Android/Material/MaterialSliderRenderer.cs

@@ -10,7 +10,7 @@ using Xamarin.Forms.Platform.Android.FastRenderers;
 using Xamarin.Forms.Platform.Android.Material;
 using AView = Android.Views.View;
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Slider), typeof(MaterialSliderRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Slider), typeof(MaterialSliderRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 
 namespace Xamarin.Forms.Platform.Android.Material
 {

Xamarin.Forms.Platform.Android/Material/MaterialStepperRenderer.cs

@@ -8,7 +8,7 @@ using Xamarin.Forms.Platform.Android.Material;
 using AButton = Android.Widget.Button;
 using MButton = Android.Support.Design.Button.MaterialButton;
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.Stepper), typeof(MaterialStepperRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Stepper), typeof(MaterialStepperRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 
 namespace Xamarin.Forms.Platform.Android.Material
 {

Xamarin.Forms.Platform.Android/Material/MaterialTimePickerRenderer.cs

@@ -7,7 +7,7 @@ using Android.Widget;
 using Xamarin.Forms;
 using Xamarin.Forms.Platform.Android.Material;
 
-[assembly: ExportRenderer(typeof(Xamarin.Forms.TimePicker), typeof(MaterialTimePickerRenderer), new[] { typeof(VisualRendererMarker.Material) })]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.TimePicker), typeof(MaterialTimePickerRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
 
 namespace Xamarin.Forms.Platform.Android.Material
 {

Xamarin.Forms.Platform.GTK/ExportRendererAttribute.cs

@@ -5,7 +5,11 @@ namespace Xamarin.Forms
 	[AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
 	public sealed class ExportRendererAttribute : HandlerAttribute
 	{
-		public ExportRendererAttribute(Type handler, Type target) : base(handler, target)
+		public ExportRendererAttribute(Type handler, Type target) : this(handler, target, null)
+		{
+		}
+
+		public ExportRendererAttribute(Type handler, Type target, Type[] supportedVisuals) : base(handler, target, supportedVisuals)
 		{
 		}
 	}

Xamarin.Forms.Platform.Tizen/ExportRendererAttribute.cs

@@ -5,7 +5,11 @@ namespace Xamarin.Forms.Platform.Tizen
 	[AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
 	public sealed class ExportRendererAttribute : HandlerAttribute
 	{
-		public ExportRendererAttribute(Type handler, Type target) : base(handler, target)
+		public ExportRendererAttribute(Type handler, Type target) : this(handler, target, null)
+		{
+		}
+
+		public ExportRendererAttribute(Type handler, Type target, Type[] supportedVisuals) : base(handler, target, supportedVisuals)
 		{
 		}
 	}

Xamarin.Forms.Platform.UAP/ExportRendererAttribute.cs

@@ -5,7 +5,11 @@ namespace Xamarin.Forms.Platform.UWP
 	[AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
 	public sealed class ExportRendererAttribute : HandlerAttribute
 	{
-		public ExportRendererAttribute(Type handler, Type target) : base(handler, target)
+		public ExportRendererAttribute(Type handler, Type target) : this(handler, target, null)
+		{
+		}
+
+		public ExportRendererAttribute(Type handler, Type target, Type[] supportedVisuals) : base(handler, target, supportedVisuals)
 		{
 		}
 	}

Xamarin.Forms.Platform.WPF/ExportRendererAttribute.cs

@@ -9,7 +9,11 @@ namespace Xamarin.Forms.Platform.WPF
 	[AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
 	public sealed class ExportRendererAttribute : HandlerAttribute
 	{
-		public ExportRendererAttribute(Type handler, Type target) : base(handler, target)
+		public ExportRendererAttribute(Type handler, Type target) : this(handler, target, null)
+		{
+		}
+
+		public ExportRendererAttribute(Type handler, Type target, Type[] supportedVisuals) : base(handler, target, supportedVisuals)
 		{
 		}
 	}

Xamarin.Forms.Sandbox/App.StartHere.cs

@@ -9,10 +9,12 @@ namespace Xamarin.Forms.Sandbox
 		// This code is called from the App Constructor so just initialize the main page of the application here
 		void InitializeMainPage()
 		{
-			MainPage = new ContentPage()
+			/*MainPage = new ContentPage()
 			{
 				Content = CreateStackLayout(new[] { new Button() { Text = "text" } })
 			};
+			MainPage.Visual = VisualMarker.Material;*/
+			MainPage = new MainPage();
 		}
 	}
 }

Xamarin.Forms.Sandbox/MainPage.xaml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Xamarin.Forms.Sandbox.MainPage">
+    <ContentPage.Content>
+        <StackLayout>
+            <Button Text="Material text" Visual="MaTeRiAl" />
+        </StackLayout>
+    </ContentPage.Content>
+</ContentPage>

Xamarin.Forms.Sandbox/MainPage.xaml.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+using Xamarin.Forms;
+using Xamarin.Forms.Xaml;
+
+namespace Xamarin.Forms.Sandbox
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	public partial class MainPage : ContentPage
+	{
+		public MainPage()
+		{
+			InitializeComponent();
+		}
+	}
+}

Xamarin.Forms.Xaml.UnitTests/Issues/Gh5378_1.xaml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage
+        xmlns="http://xamarin.com/schemas/2014/forms"
+        xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+        x:Class="Xamarin.Forms.Xaml.UnitTests.Gh5378_1">
+    <Label Margin="1,2,3," />
+</ContentPage>

Xamarin.Forms.Xaml.UnitTests/Issues/Gh5378_1.xaml.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+using NUnit.Framework;
+using Xamarin.Forms;
+using Xamarin.Forms.Core.UnitTests;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	[XamlCompilation(XamlCompilationOptions.Skip)]
+	public partial class Gh5378_1 : ContentPage
+	{
+		public Gh5378_1() => InitializeComponent();
+		public Gh5378_1(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+		[TestFixture] class Tests
+		{
+			[SetUp] public void Setup() => Device.PlatformServices = new MockPlatformServices();
+			[TearDown] public void TearDown() => Device.PlatformServices = null;
+
+			[Test]
+			public void ReportSyntaxError([Values(false, true)]bool useCompiledXaml)
+			{
+				if (useCompiledXaml)
+					Assert.Throws<XamlParseException>(() => MockCompiler.Compile(typeof(Gh5378_1)));
+				else
+					Assert.Throws<XamlParseException>(() => new Gh5378_1(useCompiledXaml));
+			}
+		}
+	}
+}

Xamarin.Forms.Xaml.UnitTests/Issues/Gh5378_2.xaml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Xamarin.Forms.Xaml.UnitTests.Gh5378_2">
+    <Button Clicked="{Binding FooBar}" />
+</ContentPage>

Xamarin.Forms.Xaml.UnitTests/Issues/Gh5378_2.xaml.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using NUnit.Framework;
+using Xamarin.Forms;
+using Xamarin.Forms.Core.UnitTests;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	[XamlCompilation(XamlCompilationOptions.Skip)]
+	public partial class Gh5378_2 : ContentPage
+	{
+		public Gh5378_2()
+		{
+			InitializeComponent();
+		}
+
+		public Gh5378_2(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+		[TestFixture] class Tests
+		{
+			[SetUp] public void Setup() => Device.PlatformServices = new MockPlatformServices();
+			[TearDown] public void TearDown() => Device.PlatformServices = null;
+
+			[Test]
+			public void ReportSyntaxError([Values(false, true)]bool useCompiledXaml)
+			{
+				if (useCompiledXaml)
+					Assert.Throws<XamlParseException>(() => MockCompiler.Compile(typeof(Gh5378_2)));
+				else
+					Assert.Throws<XamlParseException>(() => new Gh5378_2(useCompiledXaml));
+			}
+		}
+	}
+}