Add a Display Options "Tab options" group for the tab strip

The document tab strip's multi-row layout and the mouse-wheel gesture
that toggles it were only reachable by the wheel itself, with no
discoverable UI and no way to opt out of the gesture. Surface both as
checkboxes under a new "Tab options" group on the Display page, and add
a MouseWheelTogglesTabStripRows setting (default on) so the wheel toggle
can be turned off while keeping the persisted multi-row choice.

Assisted-by: Claude:claude-opus-4-8:Claude Code

ILSpy.Tests/Docking/DocumentTabStripModeTests.cs

@@ -134,6 +134,31 @@ public class DocumentTabStripModeTests
 		{ Settings.MultiLineDocumentTabs = saved; }
 	}
 
+	[AvaloniaTest]
+	public async Task Mouse_Wheel_Does_Not_Toggle_The_Mode_When_The_Setting_Is_Off()
+	{
+		var savedMode = Settings.MultiLineDocumentTabs;
+		var savedGate = Settings.MouseWheelTogglesTabStripRows;
+		try
+		{
+			var (window, strip) = await BootWithTabsAsync(multiLine: false);
+			Settings.MouseWheelTogglesTabStripRows = false;
+			await Pump(window);
+			var point = strip.TranslatePoint(new Point(8, 8), window) ?? new Point(8, 8);
+
+			window.MouseWheel(point, new Vector(0, 1));
+			await Pump(window);
+
+			Settings.MultiLineDocumentTabs.Should().BeFalse(
+				"with the 'mouse wheel toggles' setting off, the wheel must not flip the tab-strip mode");
+		}
+		finally
+		{
+			Settings.MultiLineDocumentTabs = savedMode;
+			Settings.MouseWheelTogglesTabStripRows = savedGate;
+		}
+	}
+
 	[AvaloniaTest]
 	public async Task Clicking_The_Dropdown_Opens_A_Populated_Menu()
 	{

ILSpy.Tests/Options/TabOptionsGroupTests.cs

@@ -0,0 +1,100 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System.Linq;
+
+using Avalonia.Controls;
+using Avalonia.Headless.NUnit;
+using Avalonia.Threading;
+using Avalonia.VisualTree;
+
+using AwesomeAssertions;
+
+using ICSharpCode.ILSpy.Properties;
+
+using ILSpy.AppEnv;
+using ILSpy.Commands;
+using ILSpy.Options;
+using ILSpy.ViewModels;
+using ILSpy.Views;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.ILSpy.Tests;
+
+/// <summary>
+/// The Display options page exposes a "Tab options" group with two checkboxes that bind two-way to
+/// the persisted document-tab-strip settings on SessionSettings: one toggles multi-row tabs, the
+/// other gates the mouse-wheel toggle gesture.
+/// </summary>
+[TestFixture]
+public class TabOptionsGroupTests
+{
+	const string MultiRowLabel = "Enable multiple rows in tab strip";
+	const string WheelGateLabel = "Mouse wheel scroll toggles single/multiple row tab strip";
+
+	[AvaloniaTest]
+	public void Tab_Options_Checkboxes_Two_Way_Bind_To_SessionSettings()
+	{
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Width = 900;
+		window.Height = 600;
+		window.Show();
+		Dispatcher.UIThread.RunJobs();
+
+		var command = AppComposition.Current.GetExport<MainMenuCommandRegistry>()
+			.GetCommand(nameof(Resources._Options));
+		command.Execute(null);
+		Dispatcher.UIThread.RunJobs();
+
+		var view = window.GetVisualDescendants().OfType<OptionsPageView>().Single();
+		var model = (OptionsPageModel)((ContentTabPage)((MainWindowViewModel)window.DataContext!)
+			.DockWorkspace.Documents!.VisibleDockables!
+			.OfType<ContentTabPage>().Single(t => t.Content is OptionsPageModel)).Content!;
+		var page = model.Pages.OfType<DisplaySettingsViewModel>().Single();
+		model.SelectedPage = page;
+		Dispatcher.UIThread.RunJobs();
+
+		var multiRow = view.GetVisualDescendants().OfType<CheckBox>()
+			.FirstOrDefault(cb => cb.Content?.ToString() == MultiRowLabel);
+		var wheelGate = view.GetVisualDescendants().OfType<CheckBox>()
+			.FirstOrDefault(cb => cb.Content?.ToString() == WheelGateLabel);
+
+		multiRow.Should().NotBeNull("the Tab options group must expose the multi-row toggle checkbox");
+		wheelGate.Should().NotBeNull("the Tab options group must expose the mouse-wheel-gate checkbox");
+
+		var session = page.SessionSettings;
+
+		// Checkbox 1 <-> MultiLineDocumentTabs
+		session.MultiLineDocumentTabs = false;
+		Dispatcher.UIThread.RunJobs();
+		multiRow!.IsChecked.Should().BeFalse("the checkbox reflects the current MultiLineDocumentTabs");
+		multiRow.IsChecked = true;
+		Dispatcher.UIThread.RunJobs();
+		session.MultiLineDocumentTabs.Should().BeTrue("checking the box flows back to MultiLineDocumentTabs");
+
+		// Checkbox 2 <-> MouseWheelTogglesTabStripRows
+		session.MouseWheelTogglesTabStripRows = true;
+		Dispatcher.UIThread.RunJobs();
+		wheelGate!.IsChecked.Should().BeTrue("the checkbox reflects the current MouseWheelTogglesTabStripRows");
+		wheelGate.IsChecked = false;
+		Dispatcher.UIThread.RunJobs();
+		session.MouseWheelTogglesTabStripRows.Should().BeFalse(
+			"unchecking the box flows back to MouseWheelTogglesTabStripRows");
+	}
+}

ILSpy/Options/DisplaySettingsPanel.axaml

@@ -99,6 +99,15 @@
 				</StackPanel>
 			</HeaderedContentControl>
 
+			<HeaderedContentControl Header="Tab options">
+				<StackPanel Spacing="2" Margin="12,4,0,0">
+					<CheckBox IsChecked="{Binding SessionSettings.MultiLineDocumentTabs, Mode=TwoWay}"
+					          Content="Enable multiple rows in tab strip" />
+					<CheckBox IsChecked="{Binding SessionSettings.MouseWheelTogglesTabStripRows, Mode=TwoWay}"
+					          Content="Mouse wheel scroll toggles single/multiple row tab strip" />
+				</StackPanel>
+			</HeaderedContentControl>
+
 			<HeaderedContentControl Header="{x:Static res:Resources.Other}">
 				<StackPanel Spacing="2" Margin="12,4,0,0">
 					<CheckBox IsChecked="{Binding Settings.SortResults, Mode=TwoWay}"

ILSpy/SessionSettings.cs

@@ -64,6 +64,14 @@ namespace ILSpy
 		[ObservableProperty]
 		private bool multiLineDocumentTabs;
 
+		/// <summary>
+		/// When true (the default) the mouse wheel over the document tab strip toggles
+		/// <see cref="MultiLineDocumentTabs"/> (wheel up flows to multiple rows, wheel down collapses
+		/// to one). When false the wheel gesture is ignored. Persisted across sessions.
+		/// </summary>
+		[ObservableProperty]
+		private bool mouseWheelTogglesTabStripRows = true;
+
 		/// <summary>
 		/// Path to the previously-selected tree node (one ToString() per ancestor, root-first).
 		/// Used to restore the selection on the next launch.
@@ -100,6 +108,7 @@ namespace ILSpy
 			var culture = (string?)section.Element(nameof(CurrentCulture));
 			CurrentCulture = string.IsNullOrEmpty(culture) ? null : culture;
 			MultiLineDocumentTabs = (bool?)section.Element(nameof(MultiLineDocumentTabs)) ?? false;
+			MouseWheelTogglesTabStripRows = (bool?)section.Element(nameof(MouseWheelTogglesTabStripRows)) ?? true;
 
 			var bounds = section.Element("WindowBounds");
 			if (bounds != null)
@@ -151,6 +160,7 @@ namespace ILSpy
 			if (!string.IsNullOrEmpty(CurrentCulture))
 				section.Add(new XElement(nameof(CurrentCulture), CurrentCulture));
 			section.Add(new XElement(nameof(MultiLineDocumentTabs), MultiLineDocumentTabs));
+			section.Add(new XElement(nameof(MouseWheelTogglesTabStripRows), MouseWheelTogglesTabStripRows));
 
 			if (FilterStates.Count > 0)
 			{

ILSpy/Themes/MultiRowTabStripBehavior.cs

@@ -93,7 +93,7 @@ namespace ILSpy.Themes
 		static void OnPointerWheel(object? sender, PointerWheelEventArgs e)
 		{
 			var settings = TryGetSessionSettings();
-			if (settings is null || e.Delta.Y == 0)
+			if (settings is null || e.Delta.Y == 0 || !settings.MouseWheelTogglesTabStripRows)
 				return;
 			// Idempotent set: rolling further in the same direction keeps the same mode rather than
 			// flip-flopping, so a multi-detent gesture settles cleanly.