[iOS/Mac][CV2] Fix CarouselView2 freezes with infinite loop when IsScrollAnimated=False

src/Controls/src/Core/Handlers/Items2/iOS/CarouselViewController2.cs

@@ -19,6 +19,7 @@ public class CarouselViewController2 : ItemsViewController2<CarouselView>
 		bool _isInternalCollectionUpdate = false;
 		int _section = 0;
 		bool _wasDetachedFromWindow = false;
+		int _gotoPosition = -1;
 		CarouselViewLoopManager _carouselViewLoopManager;
 		CancellationTokenSource _scrollDebounce;
 
@@ -333,7 +334,7 @@ void CollectionViewUpdated(object sender, NotifyCollectionChangedEventArgs e)
 				return;
 			}
 
-			//_gotoPosition = -1;
+			_gotoPosition = -1;
 
 			// We need to update the position while modifying the collection.
 			targetPosition = GetTargetPosition();
@@ -472,7 +473,7 @@ void ScrollToPosition(int goToPosition, int carouselPosition, bool animate, bool
 				return;
 			}
 
-			if (goToPosition != carouselPosition || forceScroll)
+			if (_gotoPosition == -1 && (goToPosition != carouselPosition || forceScroll))
 			{
 				UICollectionViewScrollPosition uICollectionViewScrollPosition = IsHorizontal ? UICollectionViewScrollPosition.CenteredHorizontally : UICollectionViewScrollPosition.CenteredVertically;
 				var goToIndexPath = GetScrollToIndexPath(goToPosition);
@@ -482,6 +483,7 @@ void ScrollToPosition(int goToPosition, int carouselPosition, bool animate, bool
 					return;
 				}
 
+				_gotoPosition = goToPosition;
 				CollectionView.ScrollToItem(goToIndexPath, uICollectionViewScrollPosition, animate);
 			}
 		}
@@ -509,6 +511,19 @@ internal void SetPosition(int position)
 				return;
 			}
 
+			if (_gotoPosition != -1)
+			{
+				if (position == _gotoPosition)
+				{
+					_gotoPosition = -1;
+				}
+				else
+				{
+					// Suppress intermediate positions while scrolling to target
+					return;
+				}
+			}
+
 			ItemsView.SetValueFromRenderer(CarouselView.PositionProperty, position);
 			SetCurrentItem(position);
 			UpdateVisualStates();
@@ -552,6 +567,11 @@ internal void UpdateFromCurrentItem()
 				return;
 			}
 
+			if (currentItemIndex.Row == _gotoPosition)
+			{
+				_gotoPosition = -1;
+			}
+
 			ScrollToPosition(currentItemIndex.Row, carousel.Position, carousel.AnimateCurrentItemChanges);
 
 			UpdateVisualStates();

src/Controls/tests/TestCases.HostApp/Issues/Issue35675.cs

@@ -0,0 +1,59 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 35675, "[iOS] CarouselView freezes with infinite loop when IsScrollAnimated=False", PlatformAffected.iOS)]
+public class Issue35675 : ContentPage
+{
+	readonly string[] _initialItems = ["Item 0", "Item 1", "Item 2"];
+	readonly string[] _updatedItems = ["Item 0b", "Item 1b", "Item 2b"];
+
+	public Issue35675()
+	{
+		Label instructionLabel = new Label
+		{
+			AutomationId = "InstructionLabel",
+			Text = "The test passes if the CarouselView is not frozen after the button click and the current item is updated properly.",
+			HorizontalOptions = LayoutOptions.Center,
+			HorizontalTextAlignment = TextAlignment.Center,
+			FontSize = 18
+		};
+
+		CarouselView carouselView = new CarouselView
+		{
+			AutomationId = "CarouselView",
+			HeightRequest = 300,
+			IsScrollAnimated = false,
+			BackgroundColor = Colors.LightGray,
+			HorizontalScrollBarVisibility = ScrollBarVisibility.Never,
+			ItemsSource = _initialItems,
+			ItemTemplate = new DataTemplate(() =>
+			{
+				Label label = new Label
+				{
+					FontSize = 24
+				};
+				label.SetBinding(Label.TextProperty, ".");
+				label.SetBinding(Label.AutomationIdProperty, ".");
+				return label;
+			})
+		};
+
+		Button scrollButton = new Button
+		{
+			Text = "Change Items And Scroll",
+			AutomationId = "ScrollButton"
+		};
+
+		scrollButton.Clicked += (s, e) =>
+		{
+			carouselView.ItemsSource = _updatedItems;
+			carouselView.CurrentItem = "Item 2b";
+		};
+
+		Content = new VerticalStackLayout
+		{
+			Padding = 20,
+			Spacing = 15,
+			Children = { instructionLabel, carouselView, scrollButton }
+		};
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue35675.cs

@@ -0,0 +1,27 @@
+#if TEST_FAILS_ON_ANDROID && TEST_FAILS_ON_WINDOWS // Android Issue: https://github.com/dotnet/maui/issues/35643, Windows PR: https://github.com/dotnet/maui/pull/35398
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue35675 : _IssuesUITest
+{
+	public Issue35675(TestDevice device) : base(device)
+	{
+	}
+
+	public override string Issue => "[iOS] CarouselView freezes with infinite loop when IsScrollAnimated=False";
+
+	[Test]
+	[Category(UITestCategories.CarouselView)]
+	public void CV2DoesNotFreezeWhenSettingCurrentItemWithIsScrollAnimatedFalse()
+	{
+		App.WaitForElement("ScrollButton");
+		App.WaitForElement("Item 0");
+		App.Tap("ScrollButton");
+
+		App.WaitForElement("Item 2b");
+	}
+}
+#endif