Fixed [Windows] KeepScrollOffset Behavior Not Working as Expected in CarouselView

src/Controls/src/Core/Handlers/Items/CarouselViewHandler.Windows.cs

@@ -30,6 +30,7 @@ public partial class CarouselViewHandler : ItemsViewHandler<CarouselView>
 		bool _isCarouselViewReady;
 		bool _isInternalPositionUpdate;
 		int _gotoPosition = -1;
+		bool _isCollectionChanged;
 		NotifyCollectionChangedEventHandler _collectionChanged;
 		readonly WeakNotifyCollectionChangedProxy _proxy = new();
 
@@ -534,6 +535,11 @@ void CarouselScrolled(object sender, ItemsViewScrolledEventArgs e)
 			}
 
 			var position = e.CenterItemIndex;
+			if (_isCollectionChanged && ItemsView.ItemsUpdatingScrollMode == ItemsUpdatingScrollMode.KeepScrollOffset)
+			{
+				position = ItemsView.Position;
+				_isCollectionChanged = false;
+			}
 
 			if (position == -1)
 			{
@@ -573,7 +579,7 @@ void OnCollectionItemsSourceChanged(object sender, NotifyCollectionChangedEventA
 		{
 			// Set flag to disable animation during collection changes
 			_isInternalPositionUpdate = true;
-			
+
 			try
 			{
 				var carouselPosition = ItemsView.Position;
@@ -599,6 +605,12 @@ void OnCollectionItemsSourceChanged(object sender, NotifyCollectionChangedEventA
 					&& currentItemPosition != -1)
 				{
 					carouselPosition = currentItemPosition;
+					_isCollectionChanged = true;
+				}
+
+				if (e.Action == NotifyCollectionChangedAction.Remove)
+				{
+					_isCollectionChanged = true;
 				}
 
 				if (ItemsView.ItemsUpdatingScrollMode == ItemsUpdatingScrollMode.KeepLastItemInView)

src/Controls/tests/TestCases.HostApp/Issues/Issue29421.cs

@@ -0,0 +1,73 @@
+using System.Collections.ObjectModel;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 29421, "KeepScrollOffset Not Working as Expected in CarouselView", PlatformAffected.UWP)]
+public class Issue29421 : ContentPage
+{
+	public Issue29421()
+	{
+		var verticalStackLayout = new VerticalStackLayout();
+		var carouselItems = new ObservableCollection<string>
+		{
+			"Item 0",
+			"Item 1",
+			"Item 2",
+			"Item 3",
+			"Item 4",
+		};
+
+		CarouselView carouselView = new CarouselView
+		{
+			ItemsSource = carouselItems,
+			AutomationId = "carouselview",
+			ItemsUpdatingScrollMode = ItemsUpdatingScrollMode.KeepScrollOffset,
+			HeightRequest = 300,
+			ItemTemplate = new DataTemplate(() =>
+			{
+				var grid = new Grid
+				{
+					Padding = 10
+				};
+
+				var label = new Label
+				{
+					VerticalOptions = LayoutOptions.Center,
+					HorizontalOptions = LayoutOptions.Center,
+					FontSize = 18,
+				};
+				label.SetBinding(Label.TextProperty, ".");
+				label.SetBinding(Label.AutomationIdProperty, ".");
+
+				grid.Children.Add(label);
+				return grid;
+			}),
+			HorizontalOptions = LayoutOptions.Fill,
+		};
+
+		var indicatorView = new IndicatorView
+		{
+			HorizontalOptions = LayoutOptions.Center,
+			VerticalOptions = LayoutOptions.Center
+		};
+		carouselView.IndicatorView = indicatorView;
+
+		var addButton = new Button
+		{
+			Text = "Add item",
+			AutomationId = "AddButton",
+			Margin = new Thickness(20),
+		};
+
+		addButton.Clicked += (sender, e) =>
+		{
+			carouselItems.Insert(0, "NewItem");
+		};
+
+		verticalStackLayout.Children.Add(addButton);
+		verticalStackLayout.Children.Add(carouselView);
+		verticalStackLayout.Children.Add(indicatorView);
+
+		Content = verticalStackLayout;
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue29421.cs

@@ -0,0 +1,23 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue29421 : _IssuesUITest
+{
+    public override string Issue => "KeepScrollOffset Not Working as Expected in CarouselView";
+
+    public Issue29421(TestDevice device)
+    : base(device)
+    { }
+
+    [Test]
+    [Category(UITestCategories.CarouselView)]
+    public void VerifyCarouselViewKeepScrollOffsetAdd()
+    {
+        App.WaitForElement("carouselview");
+        App.Tap("AddButton");
+        VerifyScreenshot();
+    }
+}