[Enhancement] Allow underline and strikethrough text decorations on labels and spans (#2221)

* Fixes #1632

* Allow underline and strikethrought text decorations on labels and spans

* revert some files

* pr feedback adjustments

* remove docs

* rename interface

* reorder enum

* clean up whitespace

* adjust tizen renderer

* add gallery demo for setting both underline and strike

* allow multiple values of enum to be set in xaml/css

* use normal null check

* use nameof

* include paragraph style

* tab alignment

* rebase from upstream

* pass control to update method on UWP

* correct text decorations type converter

* reset run text instead of label text on UWP when spans are used

* add tests for text decoration converter

Xamarin.Forms.Controls/CoreGalleryPages/LabelCoreGalleryPage.cs

@@ -26,6 +26,14 @@ namespace Xamarin.Forms.Controls
 			var namedSizeMediumItalicContainer = new ViewContainer<Label> (Test.Label.FontAttributesItalic, new Label { Text = "Medium Italic Font", Font = Font.SystemFontOfSize (NamedSize.Medium, FontAttributes.Italic) });
 #pragma warning restore 618
 
+#pragma warning disable 618
+			var namedSizeMediumUnderlineContainer = new ViewContainer<Label>(Test.Label.TextDecorationUnderline, new Label { Text = "Medium Underlined Font", Font = Font.SystemFontOfSize(NamedSize.Medium), TextDecorations = TextDecorations.Underline });
+#pragma warning restore 618
+
+#pragma warning disable 618
+			var namedSizeMediumStrikeContainer = new ViewContainer<Label>(Test.Label.TextDecorationStrike, new Label { Text = "Medium StrikeThrough Font", Font = Font.SystemFontOfSize(NamedSize.Medium), TextDecorations = TextDecorations.Strikethrough });
+#pragma warning restore 618
+
 #pragma warning disable 618
 			var namedSizeLargeContainer = new ViewContainer<Label> (Test.Label.FontNamedSizeLarge, new Label { Text = "Large Font", Font = Font.SystemFontOfSize (NamedSize.Large) });
 #pragma warning restore 618
@@ -151,6 +159,8 @@ namespace Xamarin.Forms.Controls
 
 			Add (namedSizeMediumBoldContainer);
 			Add (namedSizeMediumItalicContainer);
+			Add (namedSizeMediumUnderlineContainer);
+			Add (namedSizeMediumStrikeContainer);
 			Add (namedSizeLargeContainer);
 			Add (namedSizeMediumContainer);
 			Add (namedSizeMicroContainer);

Xamarin.Forms.Controls/GalleryPages/LabelGallery.cs

@@ -29,6 +29,14 @@ namespace Xamarin.Forms.Controls
 			var italicfont = new Label { Text = "Custom Italic Font" };
 			var boldfont = new Label { Text = "Custom Bold Font" };
 			var bolditalicfont = new Label { Text = "Custom Bold Italic Font" };
+			var toggleUnderline = new Label { Text = "Tap to toggle Underline", TextDecorations = TextDecorations.Underline };
+			toggleUnderline.GestureRecognizers.Add(new TapGestureRecognizer { Command = new Command(()=> { toggleUnderline.TextDecorations ^= TextDecorations.Underline; }) });
+			var toggleStrike = new Label { Text = "Tap to toggle StrikeThrough", TextDecorations = TextDecorations.Strikethrough };
+			toggleStrike.GestureRecognizers.Add(new TapGestureRecognizer { Command = new Command(() => { toggleStrike.TextDecorations ^= TextDecorations.Strikethrough; }) });
+			var toggleBoth = new Label { Text = "Tap to toggle both", TextDecorations = TextDecorations.Strikethrough | TextDecorations.Underline };
+			toggleBoth.GestureRecognizers.Add(new TapGestureRecognizer { Command = new Command(() => { toggleBoth.TextDecorations ^= TextDecorations.Strikethrough;
+																										toggleBoth.TextDecorations ^= TextDecorations.Underline;
+																								}) });
 			var huge = new Label {
 				Text = "This is the label that never ends, yes it go on and on my friend. " +
 				"Some people started catting it not knowing what it was, and they'll continue catting it forever just because...",
@@ -39,10 +47,13 @@ namespace Xamarin.Forms.Controls
 #pragma warning disable 618
 						new Span {Text="FormattedStrings ", TextColor=Color.Blue, BackgroundColor = Color.Yellow, Font = Font.BoldSystemFontOfSize (NamedSize.Large)},
 #pragma warning restore 618
-						new Span {Text="are ", TextColor=Color.Red, BackgroundColor = Color.Gray},
-						new Span {Text="not pretty!", TextColor = Color.Green,},
 					}
 				} };
+			var underlineSpan = new Span { Text = "are ", TextColor = Color.Red, BackgroundColor = Color.Gray, TextDecorations = TextDecorations.Underline };
+			var strikeSpan = new Span { Text = "not pretty!", TextColor = Color.Green, TextDecorations = TextDecorations.Strikethrough };
+			formatted.FormattedText.Spans.Add(underlineSpan);
+			formatted.FormattedText.Spans.Add(strikeSpan);
+
 			var missingfont = new Label { Text = "Missing font: use default" };
 
 #pragma warning disable 618
@@ -148,6 +159,9 @@ namespace Xamarin.Forms.Controls
 						bold,
 						italic,
 						bolditalic,
+						toggleUnderline,
+						toggleStrike,
+						toggleBoth,
 						customFont,
 						italicfont,
 						boldfont,

Xamarin.Forms.Core.UnitTests/TextDecorationUnitTests.cs

@@ -0,0 +1,28 @@
+using System.Globalization;
+
+using NUnit.Framework;
+
+
+namespace Xamarin.Forms.Core.UnitTests
+{
+	[TestFixture]
+	public class TextDecorationUnitTests : BaseTestFixture
+	{
+		[Test]
+		public void TestTextDecorationConverter()
+		{
+			var converter = new TextDecorationConverter();
+			TextDecorations both = TextDecorations.Strikethrough;
+			both |= TextDecorations.Underline;
+			Assert.True(converter.CanConvertFrom(typeof(string)));
+			Assert.AreEqual(TextDecorations.Strikethrough, converter.ConvertFromInvariantString("strikethrough"));
+			Assert.AreEqual(TextDecorations.Underline, converter.ConvertFromInvariantString("underline"));
+			Assert.AreEqual(TextDecorations.Strikethrough, converter.ConvertFromInvariantString("line-through"));
+			Assert.AreEqual(TextDecorations.None, converter.ConvertFromInvariantString("none"));
+			Assert.AreEqual(both, converter.ConvertFromInvariantString("strikethrough underline"));
+			Assert.AreEqual(both, converter.ConvertFromInvariantString("underline strikethrough"));
+			Assert.AreEqual(both, converter.ConvertFromInvariantString("underline line-through"));
+			Assert.AreEqual(both, converter.ConvertFromInvariantString("line-through underline"));
+		}
+	}
+}

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

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
   <PropertyGroup>
@@ -149,6 +149,7 @@
     <Compile Include="TapGestureRecognizerTests.cs" />
     <Compile Include="TemplatedItemsListTests.cs" />
     <Compile Include="TextCellTests.cs" />
+    <Compile Include="TextDecorationUnitTests.cs" />
     <Compile Include="ThicknessTests.cs" />
     <Compile Include="TimePickerUnitTest.cs" />
     <Compile Include="ToolbarItemTests.cs" />
@@ -228,4 +229,4 @@
       <LogicalName>Images/crimson.jpg</LogicalName>
     </EmbeddedResource>
   </ItemGroup>
-</Project>
+</Project>

Xamarin.Forms.Core/DecorableTextElement.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Xamarin.Forms
+{
+	[Flags]
+	[TypeConverter(typeof(TextDecorationConverter))]
+	public enum TextDecorations
+	{
+		None = 0,
+		Underline = 1 << 0,
+		Strikethrough = 1 << 1,
+	}
+	static class DecorableTextElement
+	{
+		public static readonly BindableProperty TextDecorationsProperty = BindableProperty.Create(nameof(IDecorableTextElement.TextDecorations), typeof(TextDecorations), typeof(IDecorableTextElement), TextDecorations.None);
+	}
+
+	[Xaml.TypeConversion(typeof(TextDecorations))]
+	public class TextDecorationConverter : TypeConverter
+	{
+		public override object ConvertFromInvariantString(string value)
+		{
+			TextDecorations result = TextDecorations.None;
+			if (value == null)
+				throw new InvalidOperationException(string.Format("Cannot convert \"{0}\" into {1}", value, typeof(TextDecorations)));
+
+			var valueArr = value.Split(',');
+
+			if (valueArr.Length <= 1)
+				valueArr = value.Split(' ');
+
+			foreach (var item in valueArr)
+			{
+				if (Enum.TryParse(item.Trim(), true, out TextDecorations textDecorations))
+					result |= textDecorations;
+				else if (item.Equals("line-through", StringComparison.OrdinalIgnoreCase))
+					result |= TextDecorations.Strikethrough;
+				else
+					throw new InvalidOperationException(string.Format("Cannot convert \"{0}\" into {1}", item, typeof(TextDecorations)));
+			}
+
+			return result;
+		}
+	}
+
+}
+

Xamarin.Forms.Core/IDecorableTextElement.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Xamarin.Forms
+{
+	public interface IDecorableTextElement
+	{
+		TextDecorations TextDecorations { get; set; }
+	}
+}

Xamarin.Forms.Core/Label.cs

@@ -11,7 +11,7 @@ namespace Xamarin.Forms
 {
 	[ContentProperty("Text")]
 	[RenderWith(typeof(_LabelRenderer))]
-	public class Label : View, IFontElement, ITextElement, ITextAlignmentElement, ILineHeightElement, IElementConfiguration<Label>
+	public class Label : View, IFontElement, ITextElement, ITextAlignmentElement, ILineHeightElement, IElementConfiguration<Label>, IDecorableTextElement
 	{
 		public static readonly BindableProperty HorizontalTextAlignmentProperty = TextAlignmentElement.HorizontalTextAlignmentProperty;
 
@@ -36,6 +36,8 @@ namespace Xamarin.Forms
 
 		public static readonly BindableProperty FontAttributesProperty = FontElement.FontAttributesProperty;
 
+		public static readonly BindableProperty TextDecorationsProperty = DecorableTextElement.TextDecorationsProperty;
+
 		public static readonly BindableProperty FormattedTextProperty = BindableProperty.Create(nameof(FormattedText), typeof(FormattedString), typeof(Label), default(FormattedString),
 			propertyChanging: (bindable, oldvalue, newvalue) =>
 			{
@@ -155,6 +157,12 @@ namespace Xamarin.Forms
 			set { SetValue(FontAttributesProperty, value); }
 		}
 
+		public TextDecorations TextDecorations
+		{
+			get { return (TextDecorations)GetValue(TextDecorationsProperty); }
+			set { SetValue(TextDecorationsProperty, value); }
+		}
+
 		public string FontFamily
 		{
 			get { return (string)GetValue(FontFamilyProperty); }

Xamarin.Forms.Core/Properties/AssemblyInfo.cs

@@ -60,6 +60,7 @@ using Xamarin.Forms.StyleSheets;
 [assembly: StyleProperty("padding-right", typeof(IPaddingElement), nameof(PaddingElement.PaddingRightProperty), PropertyOwnerType = typeof(PaddingElement))]
 [assembly: StyleProperty("padding-bottom", typeof(IPaddingElement), nameof(PaddingElement.PaddingBottomProperty), PropertyOwnerType = typeof(PaddingElement))]
 [assembly: StyleProperty("text-align", typeof(ITextAlignmentElement), nameof(TextAlignmentElement.HorizontalTextAlignmentProperty), Inherited = true)]
+[assembly: StyleProperty("text-decoration", typeof(IDecorableTextElement), nameof(DecorableTextElement.TextDecorationsProperty))]
 [assembly: StyleProperty("visibility", typeof(VisualElement), nameof(VisualElement.IsVisibleProperty), Inherited = true)]
 [assembly: StyleProperty("width", typeof(VisualElement), nameof(VisualElement.WidthRequestProperty))]
 [assembly: StyleProperty("line-height", typeof(ILineHeightElement), nameof(LineHeightElement.LineHeightProperty), Inherited = true)]

Xamarin.Forms.Core/Span.cs

@@ -4,7 +4,7 @@ using Xamarin.Forms.Internals;
 namespace Xamarin.Forms
 {
 	[ContentProperty("Text")]
-	public sealed class Span : GestureElement, IFontElement, ITextElement, ILineHeightElement
+	public sealed class Span : GestureElement, IFontElement, ITextElement, ILineHeightElement, IDecorableTextElement
 	{
 		internal readonly MergedStyle _mergedStyle;
 
@@ -16,6 +16,8 @@ namespace Xamarin.Forms
 		public static readonly BindableProperty StyleProperty = BindableProperty.Create(nameof(Style), typeof(Style), typeof(Span), default(Style),
 			propertyChanged: (bindable, oldvalue, newvalue) => ((Span)bindable)._mergedStyle.Style = (Style)newvalue, defaultBindingMode: BindingMode.OneTime);
 
+		public static readonly BindableProperty TextDecorationsProperty = DecorableTextElement.TextDecorationsProperty;
+
 		public Style Style
 		{
 			get { return (Style)GetValue(StyleProperty); }
@@ -95,6 +97,12 @@ namespace Xamarin.Forms
 			set { SetValue(FontElement.FontSizeProperty, value); }
 		}
 
+		public TextDecorations TextDecorations
+		{
+			get { return (TextDecorations)GetValue(TextDecorationsProperty); }
+			set { SetValue(TextDecorationsProperty, value); }
+		}
+
 		public double LineHeight {
 			get { return (double)GetValue(LineHeightElement.LineHeightProperty); }
 			set { SetValue(LineHeightElement.LineHeightProperty, value); }

Xamarin.Forms.CustomAttributes/TestAttributes.cs

@@ -582,6 +582,8 @@ namespace Xamarin.Forms.CustomAttributes
 			FormattedText,
 			FontAttibutesBold,
 			FontAttributesItalic,
+			TextDecorationUnderline,
+			TextDecorationStrike,
 			FontNamedSizeMicro,
 			FontNamedSizeSmall,
 			FontNamedSizeMedium,

Xamarin.Forms.Platform.Android/FastRenderers/LabelRenderer.cs

@@ -280,6 +280,24 @@ namespace Xamarin.Forms.Platform.Android.FastRenderers
 			}
 		}
 
+		void UpdateTextDecorations()
+		{
+			if (!Element.IsSet(Label.TextDecorationsProperty))
+				return;
+
+			var textDecorations = Element.TextDecorations;
+
+			if ((textDecorations & TextDecorations.Strikethrough) == 0)
+				PaintFlags &= ~PaintFlags.StrikeThruText;
+			else
+				PaintFlags |= PaintFlags.StrikeThruText;
+
+			if ((textDecorations & TextDecorations.Underline) == 0)
+				PaintFlags &= ~PaintFlags.UnderlineText;
+			else
+				PaintFlags |= PaintFlags.UnderlineText;
+		}
+
 		void UpdateGravity()
 		{
 			Label label = Element;

Xamarin.Forms.Platform.Android/Renderers/FormattedStringExtensions.cs

@@ -62,6 +62,8 @@ namespace Xamarin.Forms.Platform.Android
 #pragma warning restore 618
 				else
 					spannable.SetSpan(new FontSpan(defaultFont, view), start, end, SpanTypes.InclusiveInclusive);
+				if (span.IsSet(Span.TextDecorationsProperty))
+					spannable.SetSpan(new TextDecorationSpan(span), start, end, SpanTypes.InclusiveInclusive);
 			}
 			return spannable;
 		}
@@ -95,6 +97,34 @@ namespace Xamarin.Forms.Platform.Android
 				paint.TextSize = TypedValue.ApplyDimension(ComplexUnitType.Sp, value, TextView.Resources.DisplayMetrics);
 			}
 		}
+
+		class TextDecorationSpan : MetricAffectingSpan
+		{
+			public TextDecorationSpan(Span span)
+			{
+				Span = span;
+			}
+
+			public Span Span { get; }
+
+			public override void UpdateDrawState(TextPaint tp)
+			{
+				Apply(tp);
+			}
+
+			public override void UpdateMeasureState(TextPaint p)
+			{
+				Apply(p);
+			}
+
+			void Apply(Paint paint)
+			{
+				var textDecorations = Span.TextDecorations;
+				paint.UnderlineText = (textDecorations & TextDecorations.Underline) != 0;
+				paint.StrikeThruText = (textDecorations & TextDecorations.Strikethrough) != 0;
+			}
+		}
+
 		class LineHeightSpan : Java.Lang.Object, ILineHeightSpan
 		{
 			private double _lineHeight;
@@ -114,7 +144,6 @@ namespace Xamarin.Forms.Platform.Android
 				fm.Ascent = (int) (_ascent * _lineHeight);
 				fm.Descent = (int) (_descent * _lineHeight);
 			}
-
 		}
 	}
 }

Xamarin.Forms.Platform.Android/Renderers/LabelRenderer.cs

@@ -118,7 +118,7 @@ namespace Xamarin.Forms.Platform.Android
 				if (e.OldElement.HorizontalTextAlignment != e.NewElement.HorizontalTextAlignment || e.OldElement.VerticalTextAlignment != e.NewElement.VerticalTextAlignment)
 					UpdateGravity();
 			}
-
+			UpdateTextDecorations();
 			_motionEventHelper.UpdateElement(e.NewElement);
 		}
 
@@ -134,6 +134,8 @@ namespace Xamarin.Forms.Platform.Android
 				UpdateText();
 			else if (e.PropertyName == Label.LineBreakModeProperty.PropertyName)
 				UpdateLineBreakMode();
+			else if (e.PropertyName == Label.TextDecorationsProperty.PropertyName)
+				UpdateTextDecorations();
 			else if (e.PropertyName == Label.TextProperty.PropertyName || e.PropertyName == Label.FormattedTextProperty.PropertyName)
 				UpdateText();
 			else if (e.PropertyName == Label.LineHeightProperty.PropertyName)
@@ -174,6 +176,24 @@ namespace Xamarin.Forms.Platform.Android
 			}
 		}
 
+		void UpdateTextDecorations()
+		{
+			if (!Element.IsSet(Label.TextDecorationsProperty))
+				return;
+
+			var textDecorations = Element.TextDecorations;
+
+			if ((textDecorations & TextDecorations.Strikethrough) == 0)
+				_view.PaintFlags &= ~PaintFlags.StrikeThruText;
+			else
+				_view.PaintFlags |= PaintFlags.StrikeThruText;
+
+			if ((textDecorations & TextDecorations.Underline) == 0)
+				_view.PaintFlags &= ~PaintFlags.UnderlineText;
+			else
+				_view.PaintFlags |= PaintFlags.UnderlineText;
+		}
+
 		void UpdateGravity()
 		{
 			Label label = Element;

Xamarin.Forms.Platform.Tizen/Renderers/LabelRenderer.cs

@@ -19,6 +19,7 @@ namespace Xamarin.Forms.Platform.Tizen
 			RegisterPropertyHandler(Label.FormattedTextProperty, UpdateFormattedText);
 			RegisterPropertyHandler(Label.LineHeightProperty, UpdateLineHeight);
 			RegisterPropertyHandler(Specific.FontWeightProperty, UpdateFontWeight);
+			RegisterPropertyHandler(Label.TextDecorationsProperty, UpdateTextDecorations);
 		}
 
 		protected override void OnElementChanged(ElementChangedEventArgs<Label> e)
@@ -46,6 +47,8 @@ namespace Xamarin.Forms.Platform.Tizen
 
 			foreach (var span in formattedString.Spans)
 			{
+				var textDecorations = span.TextDecorations;
+
 				Native.Span nativeSpan = new Native.Span();
 				nativeSpan.Text = span.Text;
 				nativeSpan.FontAttributes = span.FontAttributes;
@@ -53,6 +56,8 @@ namespace Xamarin.Forms.Platform.Tizen
 				nativeSpan.FontSize = span.FontSize;
 				nativeSpan.ForegroundColor = span.TextColor.ToNative();
 				nativeSpan.BackgroundColor = span.BackgroundColor.ToNative();
+				nativeSpan.Underline = (textDecorations & TextDecorations.Underline) != 0;
+				nativeSpan.Strikethrough = (textDecorations & TextDecorations.Strikethrough) != 0;
 				nativeSpan.LineHeight = span.LineHeight;
 				nativeString.Spans.Add(nativeSpan);
 			}
@@ -60,6 +65,15 @@ namespace Xamarin.Forms.Platform.Tizen
 			return nativeString;
 		}
 
+		void UpdateTextDecorations()
+		{
+			Control.BatchBegin();
+			var textDecorations = Element.TextDecorations;
+			Control.Strikethrough = (textDecorations & TextDecorations.Strikethrough) != 0;
+			Control.Underline = (textDecorations & TextDecorations.Underline) != 0;
+			Control.BatchCommit();
+		}
+
 		void UpdateFormattedText()
 		{
 			if (Element.FormattedText != null)

Xamarin.Forms.Platform.UAP/LabelRenderer.cs

@@ -25,6 +25,9 @@ namespace Xamarin.Forms.Platform.UWP
 				run.ApplyFont(span.Font);
 #pragma warning restore 618
 
+			if (span.IsSet(Span.TextDecorationsProperty))
+				run.TextDecorations = (Windows.UI.Text.TextDecorations)span.TextDecorations;
+
 			return run;
 		}
 	}
@@ -132,6 +135,7 @@ namespace Xamarin.Forms.Platform.UWP
 				_isInitiallyDefault = Element.IsDefault();
 
 				UpdateText(Control);
+				UpdateTextDecorations(Control);
 				UpdateColor(Control);
 				UpdateAlign(Control);
 				UpdateFont(Control);
@@ -150,6 +154,8 @@ namespace Xamarin.Forms.Platform.UWP
 				UpdateAlign(Control);
 			else if (e.PropertyName == Label.FontProperty.PropertyName)
 				UpdateFont(Control);
+			else if (e.PropertyName == Label.TextDecorationsProperty.PropertyName)
+				UpdateTextDecorations(Control);
 			else if (e.PropertyName == Label.LineBreakModeProperty.PropertyName)
 				UpdateLineBreakMode(Control);
 			else if (e.PropertyName == VisualElement.FlowDirectionProperty.PropertyName)
@@ -161,6 +167,39 @@ namespace Xamarin.Forms.Platform.UWP
 			base.OnElementPropertyChanged(sender, e);
 		}
 
+		void UpdateTextDecorations(TextBlock textBlock)
+		{
+			if (!Element.IsSet(Label.TextDecorationsProperty))
+				return;
+
+			var elementTextDecorations = Element.TextDecorations;
+
+			if ((elementTextDecorations & TextDecorations.Underline) == 0)
+				textBlock.TextDecorations &= ~Windows.UI.Text.TextDecorations.Underline;
+			else
+				textBlock.TextDecorations |= Windows.UI.Text.TextDecorations.Underline;
+
+			if ((elementTextDecorations & TextDecorations.Strikethrough) == 0)
+				textBlock.TextDecorations &= ~Windows.UI.Text.TextDecorations.Strikethrough;
+			else
+				textBlock.TextDecorations |= Windows.UI.Text.TextDecorations.Strikethrough;
+
+			//TextDecorations are not updated in the UI until the text changes
+			if (textBlock.Inlines != null && textBlock.Inlines.Count > 0)
+			{
+				for (var i = 0; i < textBlock.Inlines.Count; i++)
+				{
+					var run = (Run)textBlock.Inlines[i];
+					run.Text = run.Text;
+				}
+			}
+			else
+			{
+				textBlock.Text = textBlock.Text; 
+			}
+
+		}
+
 		void UpdateAlign(TextBlock textBlock)
 		{
 			_perfectSizeValid = false;

Xamarin.Forms.Platform.WPF/Extensions/FormattedStringExtensions.cs

@@ -29,7 +29,17 @@ namespace Xamarin.Forms.Platform.WPF
 #pragma warning disable 618
 				run.ApplyFont(span.Font);
 #pragma warning restore 618
+			if (!span.IsSet(Span.TextDecorationsProperty))
+				return run;
 
+			var textDecorations = span.TextDecorations;
+
+			if ((textDecorations & TextDecorations.Underline) != 0)
+				run.TextDecorations.Add(System.Windows.TextDecorations.Underline);
+
+			if ((textDecorations & TextDecorations.Strikethrough) != 0)
+				run.TextDecorations.Add(System.Windows.TextDecorations.Strikethrough);
+		
 			return run;
 		}
 	}

Xamarin.Forms.Platform.WPF/Renderers/LabelRenderer.cs

@@ -25,6 +25,7 @@ namespace Xamarin.Forms.Platform.WPF
 
 				// Update control property 
 				UpdateText();
+				UpdateTextDecorations();
 				UpdateColor();
 				UpdateAlign();
 				UpdateFont();
@@ -47,6 +48,8 @@ namespace Xamarin.Forms.Platform.WPF
 
 			if (e.PropertyName == Label.TextProperty.PropertyName || e.PropertyName == Label.FormattedTextProperty.PropertyName)
 				UpdateText();
+			else if (e.PropertyName == Label.TextDecorationsProperty.PropertyName)
+				UpdateTextDecorations();
 			else if (e.PropertyName == Label.TextColorProperty.PropertyName)
 				UpdateColor();
 			else if (e.PropertyName == Label.HorizontalTextAlignmentProperty.PropertyName || e.PropertyName == Label.VerticalTextAlignmentProperty.PropertyName)
@@ -62,6 +65,29 @@ namespace Xamarin.Forms.Platform.WPF
 			Control.UpdateDependencyColor(TextBlock.BackgroundProperty, Element.BackgroundColor);
 		}
 
+		void UpdateTextDecorations()
+		{
+			if (!Element.IsSet(Label.TextDecorationsProperty))
+				return;
+
+			var textDecorations = Element.TextDecorations;
+
+			var newTextDecorations = new System.Windows.TextDecorationCollection(Control.TextDecorations);
+
+			if ((textDecorations & TextDecorations.Underline) == 0)
+				newTextDecorations.TryRemove(System.Windows.TextDecorations.Underline, out newTextDecorations);
+			else
+				newTextDecorations.Add(System.Windows.TextDecorations.Underline);
+
+			if ((textDecorations & TextDecorations.Strikethrough) == 0)
+				newTextDecorations.TryRemove(System.Windows.TextDecorations.Strikethrough, out newTextDecorations);
+			else
+				newTextDecorations.Add(System.Windows.TextDecorations.Strikethrough);
+
+			Control.TextDecorations = newTextDecorations;
+		}
+
+
 		void UpdateAlign()
 		{
 			if (Control == null)

Xamarin.Forms.Platform.iOS/Renderers/FormattedStringExtensions.cs

@@ -76,20 +76,13 @@ namespace Xamarin.Forms.Platform.MacOS
 				targetFont = ((IFontElement)owner).ToUIFont();
 			else
 				targetFont = span.ToUIFont();
-
-			var fgcolor = span.TextColor;
-			if (fgcolor.IsDefault)
-				fgcolor = defaultForegroundColor;
-			if (fgcolor.IsDefault)
-				fgcolor = Color.Black; // as defined by apple docs
-
-			return new NSAttributedString(text, targetFont, fgcolor.ToUIColor(), span.BackgroundColor.ToUIColor(), null, style);
 #else
 			NSFont targetFont;
 			if (span.IsDefault())
 				targetFont = ((IFontElement)owner).ToNSFont();
 			else
 				targetFont = span.ToNSFont();
+#endif
 
 			var fgcolor = span.TextColor;
 			if (fgcolor.IsDefault)
@@ -97,9 +90,32 @@ namespace Xamarin.Forms.Platform.MacOS
 			if (fgcolor.IsDefault)
 				fgcolor = Color.Black; // as defined by apple docs
 
-			return new NSAttributedString(text, targetFont, fgcolor.ToNSColor(), span.BackgroundColor.ToNSColor(),
-										  null, null, null, NSUnderlineStyle.None, NSUnderlineStyle.None, style);
+#if __MOBILE__
+			UIColor spanFgColor;
+			UIColor spanBgColor;
+			spanFgColor = fgcolor.ToUIColor();
+			spanBgColor = span.BackgroundColor.ToUIColor();
+#else
+			NSColor spanFgColor;
+			NSColor spanBgColor;
+			spanFgColor = fgcolor.ToNSColor();
+			spanBgColor = span.BackgroundColor.ToNSColor();
 #endif
+
+			bool hasUnderline = false;
+			bool hasStrikethrough = false;
+			if (span.IsSet(Span.TextDecorationsProperty))
+			{
+				var textDecorations = span.TextDecorations;
+				hasUnderline = (textDecorations & TextDecorations.Underline) != 0;
+				hasStrikethrough = (textDecorations & TextDecorations.Strikethrough) != 0;
+			}
+
+			var attrString = new NSAttributedString(text, targetFont, spanFgColor, spanBgColor,
+				underlineStyle: hasUnderline ? NSUnderlineStyle.Single : NSUnderlineStyle.None,
+				strikethroughStyle: hasStrikethrough ? NSUnderlineStyle.Single : NSUnderlineStyle.None, paragraphStyle: style);
+
+			return attrString;
 		}
 
 		internal static NSAttributedString ToAttributed(this FormattedString formattedString, Element owner,

Xamarin.Forms.Platform.iOS/Renderers/LabelRenderer.cs

@@ -2,6 +2,7 @@ using System;
 using System.ComponentModel;
 using RectangleF = CoreGraphics.CGRect;
 using SizeF = CoreGraphics.CGSize;
+using Foundation;
 
 #if __MOBILE__
 using UIKit;
@@ -129,6 +130,7 @@ namespace Xamarin.Forms.Platform.MacOS
 				UpdateLineBreakMode();
 				UpdateAlignment();
 				UpdateText();
+				UpdateTextDecorations();
 				UpdateTextColor();
 				UpdateFont();
 			}
@@ -150,6 +152,8 @@ namespace Xamarin.Forms.Platform.MacOS
 				UpdateFont();
 			else if (e.PropertyName == Label.TextProperty.PropertyName)
 				UpdateText();
+			else if (e.PropertyName == Label.TextDecorationsProperty.PropertyName)
+				UpdateTextDecorations();
 			else if (e.PropertyName == Label.FormattedTextProperty.PropertyName)
 				UpdateText();
 			else if (e.PropertyName == Label.LineBreakModeProperty.PropertyName)
@@ -160,6 +164,41 @@ namespace Xamarin.Forms.Platform.MacOS
 				UpdateText();
 		}
 
+		void UpdateTextDecorations()
+		{
+			if (!Element.IsSet(Label.TextDecorationsProperty))
+				return;
+
+			var textDecorations = Element.TextDecorations;
+#if __MOBILE__
+			var newAttributedText = new NSMutableAttributedString(Control.AttributedText);
+			var strikeThroughStyleKey = UIStringAttributeKey.StrikethroughStyle;
+			var underlineStyleKey = UIStringAttributeKey.UnderlineStyle;
+
+#else
+			var newAttributedText = new NSMutableAttributedString(Control.AttributedStringValue);
+			var strikeThroughStyleKey = NSStringAttributeKey.StrikethroughStyle;
+			var underlineStyleKey = NSStringAttributeKey.UnderlineStyle;
+#endif
+			var range = new NSRange(0, newAttributedText.Length);
+
+			if ((textDecorations & TextDecorations.Strikethrough) == 0)
+				newAttributedText.RemoveAttribute(strikeThroughStyleKey, range);
+			else
+				newAttributedText.AddAttribute(strikeThroughStyleKey, NSNumber.FromInt32((int)NSUnderlineStyle.Single), range);
+
+			if ((textDecorations & TextDecorations.Underline) == 0)
+				newAttributedText.RemoveAttribute(underlineStyleKey, range);
+			else
+				newAttributedText.AddAttribute(underlineStyleKey, NSNumber.FromInt32((int)NSUnderlineStyle.Single), range);
+
+#if __MOBILE__
+			Control.AttributedText = newAttributedText;
+#else
+			Control.AttributedStringValue = newAttributedText;
+#endif
+		}
+
 #if __MOBILE__
 		protected override void SetAccessibilityLabel()
 		{