[iOS] Allow observable source update while CollectionView is not visible

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue13126.cs

@@ -0,0 +1,181 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.ComponentModel;
+using System.Globalization;
+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
+{
+	[Issue(IssueTracker.Github, 13126, "[Bug] Regression: 5.0.0-pre5 often fails to draw dynamically loaded collection view content", PlatformAffected.iOS)]
+#if UITEST
+	[NUnit.Framework.Category(UITestCategories.CollectionView)]
+#endif
+	public class Issue13126 : TestContentPage
+	{
+		_13126VM _vm;
+		const string Success = "Success";
+
+		protected override void Init()
+		{
+			var collectionView = BindingWithConverter();
+
+			var grid = new Grid
+			{
+				RowDefinitions = new RowDefinitionCollection
+				{
+					new RowDefinition() { Height = GridLength.Star },
+				}
+			};
+
+			grid.Children.Add(collectionView);
+
+			Content = grid;
+
+			_vm = new _13126VM();
+			BindingContext = _vm;
+		}
+
+		protected async override void OnParentSet()
+		{
+			base.OnParentSet();
+			_vm.IsBusy = true;
+
+			await Task.Delay(1000);
+
+			_vm.Data.Add(Success);
+
+			_vm.IsBusy = false;
+		}
+
+		internal static CollectionView BindingWithConverter()
+		{
+			var cv = new CollectionView
+			{
+				IsVisible = true,
+
+				ItemTemplate = new DataTemplate(() =>
+				{
+					var label = new Label();
+					label.SetBinding(Label.TextProperty, new Binding("."));
+					return label;
+				})
+			};
+
+			cv.EmptyView = new Label { Text = "Should not see me" };
+
+			cv.SetBinding(CollectionView.ItemsSourceProperty, new Binding("Data"));
+			cv.SetBinding(VisualElement.IsVisibleProperty, new Binding("IsBusy", converter: new BoolInverter()));
+
+			return cv;
+		}
+
+		class BoolInverter : IValueConverter
+		{
+			public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+			{
+				return !((bool)value);
+			}
+
+			public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+			{
+				throw new NotImplementedException();
+			}
+		}
+
+		internal class _13126VM : INotifyPropertyChanged
+		{
+			private bool _isBusy;
+
+			public bool IsBusy
+			{
+				get
+				{
+					return _isBusy;
+				}
+
+				set
+				{
+					_isBusy = value;
+					OnPropertyChanged(nameof(IsBusy));
+				}
+			}
+
+			public OptimizedObservableCollection<string> Data { get; } = new OptimizedObservableCollection<string>();
+
+			public event PropertyChangedEventHandler PropertyChanged;
+
+			void OnPropertyChanged(string name)
+			{
+				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
+			}
+		}
+
+		internal class OptimizedObservableCollection<T> : ObservableCollection<T>
+		{
+			bool _shouldRaiseNotifications = true;
+
+			public OptimizedObservableCollection()
+			{
+			}
+
+			public OptimizedObservableCollection(IEnumerable<T> collection)
+				: base(collection)
+			{
+			}
+
+			public IDisposable BeginMassUpdate()
+			{
+				return new MassUpdater(this);
+			}
+
+			protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
+			{
+				if (_shouldRaiseNotifications)
+					base.OnCollectionChanged(e);
+			}
+
+			protected override void OnPropertyChanged(PropertyChangedEventArgs e)
+			{
+				if (_shouldRaiseNotifications)
+					base.OnPropertyChanged(e);
+			}
+
+			class MassUpdater : IDisposable
+			{
+				readonly OptimizedObservableCollection<T> parent;
+				public MassUpdater(OptimizedObservableCollection<T> parent)
+				{
+					this.parent = parent;
+					parent._shouldRaiseNotifications = false;
+				}
+
+				public void Dispose()
+				{
+					parent._shouldRaiseNotifications = true;
+					parent.OnPropertyChanged(new PropertyChangedEventArgs("Count"));
+					parent.OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
+					parent.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+				}
+			}
+		}
+
+#if UITEST
+		[Test]
+		public void CollectionViewShouldSourceShouldUpdateWhileInvisible()
+		{
+			RunningApp.WaitForElement(Success);
+		}
+#endif
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue13126_2.cs

@@ -0,0 +1,74 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.ComponentModel;
+using System.Globalization;
+using System.Text;
+using System.Threading.Tasks;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using static Xamarin.Forms.Controls.Issues.Issue13126;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Issue(IssueTracker.Github, 13126, "[Bug] Regression: 5.0.0-pre5 often fails to draw dynamically loaded collection view content", 
+		PlatformAffected.iOS, issueTestNumber:1)]
+#if UITEST
+	[NUnit.Framework.Category(UITestCategories.CollectionView)]
+#endif
+	public class Issue13126_2 : TestContentPage
+	{
+		_13126VM _vm;
+		const string Success = "Success";
+
+		protected override void Init()
+		{
+			var collectionView = BindingWithConverter();
+
+			var grid = new Grid
+			{
+				RowDefinitions = new RowDefinitionCollection
+				{
+					new RowDefinition() { Height = GridLength.Star },
+				}
+			};
+
+			grid.Children.Add(collectionView);
+
+			Content = grid;
+
+			_vm = new _13126VM();
+			BindingContext = _vm;
+		}
+
+		protected async override void OnParentSet()
+		{
+			base.OnParentSet();
+			_vm.IsBusy = true;
+
+			await Task.Delay(1000);
+
+			using (_vm.Data.BeginMassUpdate())
+			{
+				_vm.Data.Add(Success);
+			}
+
+			_vm.IsBusy = false;
+		}
+
+#if UITEST
+		[Test]
+		public void CollectionViewShouldSourceShouldResetWhileInvisible()
+		{
+			RunningApp.WaitForElement(Success);
+		}
+#endif
+	}
+}

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

@@ -12,6 +12,8 @@
     <Compile Include="$(MSBuildThisFileDirectory)CollectionViewGroupTypeIssue.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue11214.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue13109.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue13126.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue13126_2.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue13551.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)RadioButtonTemplateFromStyle.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ShellWithCustomRendererDisabledAnimations.cs" />

Xamarin.Forms.Platform.iOS/CollectionView/CarouselViewController.cs

@@ -469,6 +469,18 @@ void UpdateVisualStates()
 
 			_oldViews = newViews;
 		}
+
+		protected internal override void UpdateVisibility()
+		{
+			if (ItemsView.IsVisible)
+			{
+				CollectionView.Hidden = false;
+			}
+			else
+			{
+				CollectionView.Hidden = true;
+			}
+		}
 	}
 
 	class CarouselViewLoopManager : IDisposable