[iOS] Fix CollectionView horizontal scroll when empty inside RefreshView

src/Controls/src/Core/Handlers/Items2/iOS/LayoutFactory2.cs

@@ -457,6 +457,25 @@ public CustomUICollectionViewCompositionalLayout(LayoutSnapInfo snapInfo, UIColl
 			_itemsUpdatingScrollMode = itemsUpdatingScrollMode;
 		}
 
+		// UICollectionViewCompositionalLayout can report a content width larger than the viewport
+		// after a bounds change (e.g. when inside a RefreshView). This causes UIScrollView to
+		// enable horizontal scrolling on a vertical layout. Clamp the width to the actual bounds. (#34165)
+		public override CGSize CollectionViewContentSize
+		{
+			get
+			{
+				var size = base.CollectionViewContentSize;
+				if (Configuration.ScrollDirection == UICollectionViewScrollDirection.Vertical
+					&& CollectionView is not null
+					&& size.Width > CollectionView.Bounds.Width
+					&& CollectionView.Bounds.Width > 0)
+				{
+					return new CGSize(CollectionView.Bounds.Width, size.Height);
+				}
+				return size;
+			}
+		}
+
 		public override void FinalizeCollectionViewUpdates()
 		{
 			base.FinalizeCollectionViewUpdates();

src/Controls/tests/TestCases.HostApp/Issues/Issue34165.cs

@@ -0,0 +1,39 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 34165, "CollectionView is scrolling left/right when the collection is empty and inside a RefreshView", PlatformAffected.iOS)]
+public class Issue34165 : ContentPage
+{
+	public const string CollectionViewId = "CollectionView";
+	public const string EmptyViewLabelId = "EmptyViewLabel";
+	public const string RefreshViewId = "RefreshView";
+
+	public Issue34165()
+	{
+		var emptyViewLabel = new Label
+		{
+			Text = "No items — swipe left/right here to test",
+			AutomationId = EmptyViewLabelId,
+			HorizontalOptions = LayoutOptions.Center,
+			VerticalOptions = LayoutOptions.Center,
+		};
+
+		var collectionView = new CollectionView
+		{
+			AutomationId = CollectionViewId,
+			EmptyView = emptyViewLabel,
+		};
+
+		var refreshView = new RefreshView
+		{
+			AutomationId = RefreshViewId,
+			Content = collectionView,
+		};
+
+		refreshView.Refreshing += (s, e) =>
+		{
+			((RefreshView)s!).IsRefreshing = false;
+		};
+
+		Content = refreshView;
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue34165.cs

@@ -0,0 +1,29 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+[Category(UITestCategories.RefreshView)]
+public class Issue34165 : _IssuesUITest
+{
+	public Issue34165(TestDevice testDevice) : base(testDevice) { }
+
+	public override string Issue => "CollectionView is scrolling left/right when the collection is empty and inside a RefreshView";
+
+	[Test]
+	public void EmptyCollectionViewInsideRefreshViewShouldNotScrollHorizontally()
+	{
+		App.WaitForElement("CollectionView");
+
+		var rectBefore = App.WaitForElement("EmptyViewLabel").GetRect();
+
+		App.ScrollRight("CollectionView", ScrollStrategy.Gesture, swipePercentage: 0.8, swipeSpeed: 300);
+
+		var rectAfter = App.WaitForElement("EmptyViewLabel").GetRect();
+
+		Assert.That(rectAfter.X, Is.EqualTo(rectBefore.X),
+			$"EmptyViewLabel X position changed from {rectBefore.X} to {rectAfter.X}. " +
+			"CollectionView must NOT scroll horizontally when empty inside a RefreshView.");
+	}
+}