Refresh decompiler output in place on display-setting changes

Toggling a display setting that affects decompiler output (folding, member or
using expansion, debug info, IL detail, indentation) routed through
ForceRefreshActiveTab, whose ShowSelectedNode re-projects the tree selection
and so activates the preview tab -- yanking the user off whatever tab they were
on (e.g. the live Options page they were editing).

Add RefreshDecompilerOutputInPlace, which re-decompiles the cached decompiler
content directly without re-projecting or activating anything, and route the
Redecompile display-setting reaction to it. F5 reload and dependency-load keep
using ForceRefreshActiveTab, where re-projecting the selection is intended.

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

ILSpy.Tests/Options/OptionsTabTests.cs

@@ -20,6 +20,7 @@ using System.Linq;
 using System.Threading.Tasks;
 
 using Avalonia.Headless.NUnit;
+using Avalonia.Threading;
 
 using AwesomeAssertions;
 
@@ -299,4 +300,36 @@ public class OptionsTabTests
 		// Clean-up: restore so later tests see the original.
 		settings.DisplaySettings.SelectedFontSize = originalSize;
 	}
+
+	[AvaloniaTest]
+	public async Task Toggling_A_Display_Setting_Does_Not_Switch_Away_From_The_Focused_Options_Tab()
+	{
+		// Scenario: the user is on the Options tab and toggles a setting that forces a re-decompile
+		// (e.g. DecodeCustomAttributeBlobs). The decompiler output must refresh in place; it must NOT
+		// pull focus back to MainTab and yank the user off the Options page they are editing.
+		var (_, vm) = await TestHarness.BootAsync(3);
+
+		// Show some decompiled content first, so there is a decompiler tab to refresh.
+		var typeNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(
+			"System.Linq", "System.Linq", "System.Linq.Enumerable");
+		vm.AssemblyTreeModel.SelectNode(typeNode);
+		await vm.DockWorkspace.WaitForDecompiledTextAsync();
+
+		// Open Options and confirm it is the active document.
+		AppComposition.Current.GetExport<MainMenuCommandRegistry>()
+			.GetCommand(nameof(Resources._Options)).Execute(null);
+		var documents = vm.DockWorkspace.Documents!;
+		var optionsTab = documents.VisibleDockables!.OfType<ContentTabPage>()
+			.Single(t => t.Content is OptionsPageModel);
+		documents.ActiveDockable.Should().BeSameAs(optionsTab, "baseline: Options is the active document");
+
+		// Toggle a re-decompile display setting.
+		var display = AppComposition.Current.GetExport<SettingsService>().DisplaySettings;
+		display.DecodeCustomAttributeBlobs = !display.DecodeCustomAttributeBlobs;
+		for (int i = 0; i < 12; i++)
+			Dispatcher.UIThread.RunJobs();
+
+		documents.ActiveDockable.Should().BeSameAs(optionsTab,
+			"an output display setting must re-decompile in place, not switch the user off the focused tab");
+	}
 }

ILSpy/AssemblyTree/AssemblyTreeModel.cs

@@ -288,8 +288,9 @@ namespace ILSpy.AssemblyTree
 				case Options.DisplaySettingReaction.Redecompile:
 					// Baked into the decompiler/disassembler output (folding, member/using
 					// expansion, debug info, IL detail, indentation), so it only shows after a
-					// re-decompile of the active tab.
-					RefreshDecompiledView();
+					// re-decompile. Refresh in place: changing an option must not switch the
+					// user's current tab.
+					RefreshDecompiledViewInPlace();
 					break;
 					// EditorLive / None: the text view applies editor settings to AvaloniaEdit itself,
 					// and the rest have no model-side reaction.
@@ -905,6 +906,14 @@ namespace ILSpy.AssemblyTree
 		public void RefreshDecompiledView()
 			=> AppEnv.AppComposition.TryGetExport<Docking.DockWorkspace>()?.ForceRefreshActiveTab();
 
+		/// <summary>
+		/// Re-decompiles the decompiler tab's content in place for an output-affecting display setting,
+		/// without activating or navigating to it. Changing an option must not switch the user's current
+		/// tab, so this avoids the selection re-projection that <see cref="RefreshDecompiledView"/> does.
+		/// </summary>
+		public void RefreshDecompiledViewInPlace()
+			=> AppEnv.AppComposition.TryGetExport<Docking.DockWorkspace>()?.RefreshDecompilerOutputInPlace();
+
 		/// <summary>
 		/// Resolves every assembly reference of each supplied assembly node through that
 		/// assembly's own resolver -- which auto-loads the targets into the live list -- then

ILSpy/Docking/DockWorkspace.cs

@@ -719,6 +719,16 @@ namespace ILSpy.Docking
 			ActiveDecompilerTab?.Redecompile();
 		}
 
+		/// <summary>
+		/// Re-decompile the decompiler tab's content in place so an output-affecting display setting
+		/// takes effect, WITHOUT activating or navigating to it. Unlike <see cref="ForceRefreshActiveTab"/>
+		/// (which re-projects the tree selection via <c>ShowSelectedNode</c> and so activates the preview
+		/// tab), changing an option must not steal the user's current tab. Refreshes the cached
+		/// decompiler content directly, so it is up to date even when another tab is showing.
+		/// </summary>
+		public void RefreshDecompilerOutputInPlace()
+			=> decompilerContent?.Redecompile();
+
 		void ShowSelectedNode()
 		{
 			using var _ = ILSpy.AppEnv.AppLog.Phase("DockWorkspace.ShowSelectedNode");