[iOS] Fix for CollectionView with horizontal grid layout has extra space on right end

src/Controls/src/Core/Handlers/Items/iOS/GroupableItemsViewController.cs

@@ -204,13 +204,13 @@ int GetLayoutSpanCount()
 		internal UIEdgeInsets GetInsetForSection(ItemsViewLayout itemsViewLayout,
 			UICollectionView collectionView, nint section)
 		{
-			var uIEdgeInsets = itemsViewLayout.GetInsetForSection(collectionView, itemsViewLayout, section);
-
 			if (!ItemsView.IsGrouped)
 			{
-				return uIEdgeInsets;
+				return UIEdgeInsets.Zero;
 			}
 
+			var uIEdgeInsets = itemsViewLayout.GetInsetForSection(collectionView, itemsViewLayout, section);
+
 			// If we're grouping, we'll need to inset the sections to maintain the spacing between the 
 			// groups and their group headers/footers
 
@@ -228,8 +228,11 @@ internal UIEdgeInsets GetInsetForSection(ItemsViewLayout itemsViewLayout,
 				top += spacing;
 			}
 
+			// If we're at the last section, we don't need to add the right inset
+			var resolvedRightInset = section >= (collectionView.NumberOfSections() - 1) ? 0 : uIEdgeInsets.Right;
+
 			return new UIEdgeInsets(top, left,
-				uIEdgeInsets.Bottom, uIEdgeInsets.Right);
+				uIEdgeInsets.Bottom, resolvedRightInset);
 		}
 
 		// These measurement methods are only necessary for iOS 10 and lower

src/Controls/src/Core/Handlers/Items/iOS/ItemsViewLayout.cs

@@ -137,10 +137,10 @@ public virtual UIEdgeInsets GetInsetForSection(UICollectionView collectionView,
 			{
 				if (ScrollDirection == UICollectionViewScrollDirection.Horizontal)
 				{
-					return new UIEdgeInsets(0, 0, 0, new nfloat(gridItemsLayout.HorizontalItemSpacing * collectionView.NumberOfItemsInSection(section)));
+					return new UIEdgeInsets(0, 0, 0, new nfloat(gridItemsLayout.HorizontalItemSpacing));
 				}
 
-				return new UIEdgeInsets(0, 0, new nfloat(gridItemsLayout.VerticalItemSpacing * collectionView.NumberOfItemsInSection(section)), 0);
+				return new UIEdgeInsets(0, 0, new nfloat(gridItemsLayout.VerticalItemSpacing), 0);
 			}
 
 			return UIEdgeInsets.Zero;

src/Controls/tests/TestCases.HostApp/Issues/Issue25433.xaml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+			 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+			 x:Class="Maui.Controls.Sample.Issues.Issue25433"
+			 xmlns:ns="clr-namespace:Maui.Controls.Sample.Issues">
+	<Grid RowDefinitions="*">
+		<CollectionView Grid.Row="0"
+						x:Name="collectionView"
+						AutomationId="collectionView"
+						Background="Red"
+						HorizontalOptions="Center">
+			<CollectionView.ItemsLayout>
+				<GridItemsLayout Orientation="Horizontal"
+								 HorizontalItemSpacing="10"/>
+			</CollectionView.ItemsLayout>
+			<CollectionView.ItemTemplate>
+				<DataTemplate>
+					<Label BackgroundColor="Blue"
+						   Text="Item"/>
+				</DataTemplate>
+			</CollectionView.ItemTemplate>
+		</CollectionView>
+	</Grid>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue25433.xaml.cs

@@ -0,0 +1,25 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 25433, "Collection view with horizontal grid layout has extra space on right end", PlatformAffected.iOS)]
+public partial class Issue25433 : ContentPage
+{
+	public IList<Issue25433TestItem> Items { get; set; }
+
+	public Issue25433()
+	{
+		InitializeComponent();
+		BindingContext = this;
+		Items =
+		[
+			new Issue25433TestItem() { Name = "Item 1" },
+			new Issue25433TestItem() { Name = "Item 2" },
+			new Issue25433TestItem() { Name = "Item 3" },
+		];
+		collectionView.ItemsSource = Items;
+	}
+
+	public class Issue25433TestItem
+	{
+		public string Name { get; set; }
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue25433.cs

@@ -0,0 +1,26 @@
+#if !MACCATALYST || !WINDOWS
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue25433 : _IssuesUITest
+	{
+		public override string Issue => "Collection view with horizontal grid layout has extra space on right end";
+
+		public Issue25433(TestDevice device)
+		: base(device)
+		{ }
+
+		[Test]
+		[Category(UITestCategories.CollectionView)]
+		public void CollectionViewHorizontalItemSpacing()
+		{
+			App.WaitForElement("collectionView");
+
+			VerifyScreenshot();
+		}
+	}
+}
+#endif