[iOS, UWP] fixes #2894 - Gestures collection changes weren't correctl…

…y propagating (#3643)

* [iOS, UWP] fixes #2894 - Gestures weren't wiring up to spans in all cases

* [Core] remove ChildGestureRecognizers when spans get removed

* [iOS] removed incorrect return from null

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue2894.cs

@@ -0,0 +1,252 @@
+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;
+using System.Linq;
+
+
+#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, 2894, "Gesture Recognizers added to Span after it's been set to FormattedText don't work and can cause an NRE")]
+#if UITEST
+	[NUnit.Framework.Category(UITestCategories.Gestures)]
+#endif
+	public class Issue2894 : TestContentPage
+	{
+		Label label = null;
+		Label gestureLabel1 = null;
+		Label gestureLabel2 = null;
+		int i1 = 0;
+		int i2 = 0;
+		const string kGesture1 = "Sentence 1: ";
+		const string kGesture2 = "Sentence 2: ";
+
+		const string kClickSentence1 = "I will fire when clicked. ";
+		const string kClickSentence2 = "I should also fire when clicked.";
+
+		const string kClickSentenceAutomationId1 = "Spanning1";
+		const string kClickSentenceAutomationId2 = "Spanning2";
+
+		const string kLabelAutomationId = "kLabelAutomationId";
+
+		GestureRecognizer CreateRecognizer1() => new TapGestureRecognizer()
+		{
+			Command = new Command(() =>
+			{
+				i1++;
+				gestureLabel1.Text = $"{kGesture1}{i1}";
+			})
+		};
+
+		GestureRecognizer CreateRecognizer2() => new TapGestureRecognizer()
+		{
+			Command = new Command(() =>
+			{
+				i2++;
+				gestureLabel2.Text = $"{kGesture2}{i2}";
+			})
+		};
+
+		void AddRemoveSpan(bool includeRecognizers = true)
+		{
+			if (label.FormattedText != null)
+			{
+				label.FormattedText = null;
+				return;
+			}
+
+			FormattedString s = new FormattedString();
+
+			var span = new Span
+			{
+				Text = kClickSentence1,
+				FontAttributes = FontAttributes.Bold,
+				AutomationId = kClickSentenceAutomationId1
+			};
+
+			var span2 = new Span
+			{
+				Text = kClickSentence2,
+				FontAttributes = FontAttributes.Bold,
+				AutomationId = kClickSentenceAutomationId2
+			};
+
+			if (includeRecognizers)
+				span.GestureRecognizers.Add(CreateRecognizer1());
+
+			s.Spans.Add(span);
+			s.Spans.Add(span2);
+
+			label.FormattedText = s;
+
+			if (includeRecognizers)
+				span2.GestureRecognizers.Add(CreateRecognizer2());
+		}
+
+
+		Label GetLabel() =>
+			new Label()
+			{
+				HorizontalOptions = LayoutOptions.Center,
+				AutomationId = kLabelAutomationId
+			};
+
+		protected override void Init()
+		{
+			BindingContext = this;
+
+			label = GetLabel();
+			gestureLabel1 = new Label() { HorizontalOptions = LayoutOptions.Center };
+			gestureLabel2 = new Label() { HorizontalOptions = LayoutOptions.Center };
+
+			gestureLabel1.Text = $"{kGesture1}{i1}";
+			gestureLabel2.Text = $"{kGesture2}{i2}";
+
+			AddRemoveSpan();
+			StackLayout stackLayout = null;
+			stackLayout = new StackLayout()
+			{
+				Children =
+					{
+						label,
+						gestureLabel1,
+						gestureLabel2,
+						new Label(){Text = "Each sentence above has a separate Gesture Recognizer. Click each button below once then test that each Gesture Recognizer fires separately. If the sentence wraps make sure to click on the wrapped text as well."},
+						// test removing then adding span back
+						new Button()
+						{
+							Text = "Add and Remove Spans",
+							AutomationId = "TestSpan1",
+							Command = new Command(async () =>
+							{
+								if(label.FormattedText != null)
+									AddRemoveSpan();
+
+								await Task.Delay(100);
+								AddRemoveSpan();
+							})
+						},
+						// test removing and adding same span back
+						new Button()
+						{
+							Text = "Null FormattedText then set again",
+							AutomationId = "TestSpan2",
+							Command = new Command(async () =>
+							{
+								if(label.FormattedText == null)
+									AddRemoveSpan();
+
+								var span = label.FormattedText;
+								await Task.Delay(100);
+								label.FormattedText = null;
+								await Task.Delay(100);
+								label.FormattedText = span;
+							})
+						},
+						new Button()
+						{
+							Text = "Remove Gestures then add again",
+							AutomationId = "TestSpan3",
+							Command = new Command(async () =>
+							{
+								if(label.FormattedText == null)
+									AddRemoveSpan();
+
+								if(label.FormattedText.Spans[0].GestureRecognizers.Count > 0)
+								{
+									label.FormattedText.Spans[0].GestureRecognizers.Clear();
+									label.FormattedText.Spans[1].GestureRecognizers.Clear();
+								}
+
+								await Task.Delay(100);
+
+								label.FormattedText.Spans[0].GestureRecognizers.Add(CreateRecognizer1());
+								label.FormattedText.Spans[1].GestureRecognizers.Add(CreateRecognizer2());
+							})
+						},
+						new Button()
+						{
+							Text = "Add Gestures after rendering",
+							AutomationId = "TestSpan4",
+							Command = new Command(async () =>
+							{
+								stackLayout.Children.Remove(label);
+								await Task.Delay(50);
+								label = GetLabel();
+								stackLayout.Children.Insert(0, label);
+								await Task.Delay(50);
+								AddRemoveSpan(false);
+								await Task.Delay(50);
+								label.FormattedText.Spans[0].GestureRecognizers.Add(CreateRecognizer1());
+								label.FormattedText.Spans[1].GestureRecognizers.Add(CreateRecognizer2());
+							})
+						},
+						new Label()
+						{
+							Text = "This Button should remove all gestures"
+						},
+						new Button()
+						{
+							Text = "Remove All Gestures",
+							AutomationId = "TestSpan5",
+							Command = new Command(() =>
+							{
+								if(label.FormattedText == null)
+									return;
+
+								label.FormattedText.Spans[0].GestureRecognizers.Clear();
+								label.FormattedText.Spans[1].GestureRecognizers.Clear();
+							})
+						}
+					},
+				Padding = 40
+			};
+
+			Content = new ContentView()
+			{
+				Content = stackLayout
+			};
+		}
+
+#if UITEST
+		[Test]
+		public void VariousSpanGesturePermutation()
+		{
+			RunningApp.WaitForElement($"{kGesture1}0");
+			RunningApp.WaitForElement($"{kGesture2}0");
+			var labelId = RunningApp.WaitForElement(kLabelAutomationId);
+			var target = labelId.First().Rect;
+
+
+			for (int i = 1; i < 5; i++)
+			{
+				RunningApp.Tap($"TestSpan{i}");
+				RunningApp.TapCoordinates(target.X + 5, target.Y + 5);
+				RunningApp.TapCoordinates(target.X + target.CenterX, target.Y + 2);
+
+
+				RunningApp.WaitForElement($"{kGesture1}{i}");
+				RunningApp.WaitForElement($"{kGesture2}{i}");
+			}
+
+
+			RunningApp.Tap($"TestSpan5");
+			RunningApp.TapCoordinates(target.X + 5, target.Y + 5);
+			RunningApp.TapCoordinates(target.X + target.CenterX, target.Y + 2);
+
+			RunningApp.WaitForElement($"{kGesture1}4");
+			RunningApp.WaitForElement($"{kGesture2}4");
+		}
+#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="$(MSBuildThisFileDirectory)Issue2894.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue3524.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue2004.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue3333.cs" />

Xamarin.Forms.Core/FormattedString.cs

@@ -11,6 +11,7 @@ namespace Xamarin.Forms
 	public class FormattedString : Element
 	{
 		readonly SpanCollection _spans = new SpanCollection();
+		internal event NotifyCollectionChangedEventHandler SpansCollectionChanged;
 
 		public FormattedString()
 		{
@@ -69,6 +70,7 @@ void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
 			}
 
 			OnPropertyChanged(nameof(Spans));
+			SpansCollectionChanged?.Invoke(sender, e);
 		}
 
 		void OnItemPropertyChanged(object sender, PropertyChangedEventArgs e)

Xamarin.Forms.Core/GestureElement.cs

@@ -9,6 +9,7 @@ namespace Xamarin.Forms
 	public class GestureElement : Element, ISpatialElement
 	{
 		readonly GestureRecognizerCollection _gestureRecognizers = new GestureRecognizerCollection();
+		internal event NotifyCollectionChangedEventHandler GestureRecognizersCollectionChanged;
 
 		public GestureElement()
 		{
@@ -46,6 +47,8 @@ void RemoveItems()
 							item.Parent = this;
 						break;
 				}
+
+				GestureRecognizersCollectionChanged?.Invoke(sender, args);
 			};
 		}