[C] Set binding context on Span Gestures (#3639)

* [Core] Set binding context on Span Gestures
* [Core] Simplify loop setting child binding context

- fixes #3524

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue3524.cs

@@ -0,0 +1,77 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Text;
+using System.Threading.Tasks;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 3524, "ICommand binding from a TapGestureRecognizer on a Span doesn't work")]
+#if UITEST
+	[NUnit.Framework.Category(UITestCategories.Gestures)]
+#endif
+	public class Issue3524 : TestContentPage
+	{
+		const string kText = "Click Me To Increment";
+
+		public Command TapCommand { get; set; }
+		public String Text { get; set; } = kText;
+
+		protected override void Init()
+		{
+			int i = 0;
+
+			FormattedString formattedString = new FormattedString();
+			var span = new Span() { AutomationId = kText };
+			span.Text = kText;
+			var tapGesture = new TapGestureRecognizer();
+			tapGesture.SetBinding(TapGestureRecognizer.CommandProperty, "TapCommand");
+			span.GestureRecognizers.Add(tapGesture);
+			formattedString.Spans.Add(span);
+			BindingContext = this;
+			var label = new Label()
+			{
+				AutomationId = kText,
+				HorizontalOptions = LayoutOptions.Center
+			};
+
+			label.FormattedText = formattedString;
+			TapCommand = new Command(() =>
+			{
+				i++;
+				span.Text = $"{kText}: {i}";
+			});
+
+			Content = new ContentView()
+			{
+				Content = new StackLayout()
+				{
+					Children =
+					{
+						label
+					}
+				}
+			};
+		}
+
+#if UITEST
+		[Test]
+		public void SpanGestureCommand()
+		{
+			RunningApp.WaitForElement(kText);
+			RunningApp.Tap(kText);
+			RunningApp.WaitForElement($"{kText}: 1");
+		}
+#endif
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -8,7 +8,8 @@
   <PropertyGroup Label="Configuration">
     <Import_RootNamespace>Xamarin.Forms.Controls.Issues</Import_RootNamespace>
   </PropertyGroup>
-  <ItemGroup>
+  <ItemGroup>    
+    <Compile Include="$(MSBuildThisFileDirectory)Issue3524.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue2004.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue3333.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue2338.cs" />

Xamarin.Forms.Core/BindableObjectExtensions.cs

@@ -1,10 +1,33 @@
 using System;
+using System.Collections.Generic;
 using System.Linq.Expressions;
 
 namespace Xamarin.Forms
 {
 	public static class BindableObjectExtensions
 	{
+		internal static void PropagateBindingContext<T>(this BindableObject self, IList<T> children)
+		{
+			PropagateBindingContext(self, children, BindableObject.SetInheritedBindingContext);
+		}
+
+		internal static void PropagateBindingContext<T>(this BindableObject self, IList<T> children, Action<BindableObject, object> setChildBindingContext)
+		{
+			if (children == null || children.Count == 0)
+				return;
+
+			var bc = self.BindingContext;
+
+			for (var i = 0; i < children.Count; i++)
+			{
+				var bo = children[i] as BindableObject;
+				if (bo == null)
+					continue;
+
+				setChildBindingContext(bo, bc);
+			}
+		}
+
 		public static void SetBinding(this BindableObject self, BindableProperty targetProperty, string path, BindingMode mode = BindingMode.Default, IValueConverter converter = null,
 									  string stringFormat = null)
 		{

Xamarin.Forms.Core/Element.cs

@@ -319,21 +319,10 @@ namespace Xamarin.Forms
 
 		protected override void OnBindingContextChanged()
 		{
-			var gotBindingContext = false;
-			object bc = null;
-
-			for (var index = 0; index < LogicalChildrenInternal.Count; index++)
+			this.PropagateBindingContext(LogicalChildrenInternal, (child, bc) =>
 			{
-				Element child = LogicalChildrenInternal[index];
-
-				if (!gotBindingContext)
-				{
-					bc = BindingContext;
-					gotBindingContext = true;
-				}
-
-				SetChildInheritedBindingContext(child, bc);
-			}
+				SetChildInheritedBindingContext((Element)child, bc);
+			});
 
 			if (_bindableResources != null)
 				foreach (BindableObject item in _bindableResources)

Xamarin.Forms.Core/Span.cs

@@ -95,11 +95,18 @@ namespace Xamarin.Forms
 			set { SetValue(FontElement.FontSizeProperty, value); }
 		}
 
-		public double LineHeight {
+		public double LineHeight
+		{
 			get { return (double)GetValue(LineHeightElement.LineHeightProperty); }
 			set { SetValue(LineHeightElement.LineHeightProperty, value); }
 		}
 
+		protected override void OnBindingContextChanged()
+		{
+			this.PropagateBindingContext(GestureRecognizers);
+			base.OnBindingContextChanged();
+		}
+
 		void IFontElement.OnFontFamilyChanged(string oldValue, string newValue)
 		{
 		}

Xamarin.Forms.Core/View.cs

@@ -154,24 +154,7 @@ namespace Xamarin.Forms
 
 		protected override void OnBindingContextChanged()
 		{
-			var gotBindingContext = false;
-			object bc = null;
-
-			for (var i = 0; i < GestureRecognizers.Count; i++)
-			{
-				var bo = GestureRecognizers[i] as BindableObject;
-				if (bo == null)
-					continue;
-
-				if (!gotBindingContext)
-				{
-					bc = BindingContext;
-					gotBindingContext = true;
-				}
-
-				SetInheritedBindingContext(bo, bc);
-			}
-
+			this.PropagateBindingContext(GestureRecognizers);
 			base.OnBindingContextChanged();
 		}