DisplaySettings live-wires the decompiler editor

DecompilerTextView subscribes to SettingsService.DisplaySettings.PropertyChanged
and mirrors the new value into the AvaloniaEdit TextEditor immediately — no
re-decompile, no Apply. Properties wired:

Assisted-by: Claude:claude-opus-4-7:Claude Code

ILSpy.Tests/Options/OptionsTabTests.cs

@@ -30,6 +30,8 @@ using ILSpy.AppEnv;
 using ILSpy.Commands;
 using ILSpy.Docking;
 using ILSpy.Options;
+using ILSpy.TextView;
+using ILSpy.TreeNodes;
 using ILSpy.ViewModels;
 using ILSpy.Views;
 
@@ -199,4 +201,36 @@ public class OptionsTabTests
 		// Reset must restore the panel's settings to `new DecompilerSettings()` defaults.
 		refreshedItem.IsEnabled.Should().Be(defaultValue);
 	}
+
+	[AvaloniaTest]
+	public async Task Display_Setting_Change_Live_Updates_Decompiler_Editor()
+	{
+		// DisplaySettings → DecompilerTextView wire-up: mutating SelectedFontSize on the live
+		// settings instance flows immediately into Editor.FontSize without any Apply or
+		// re-decompile step. Covers the broader live-bind contract for font / size / line
+		// numbers / word wrap / highlight current line / indentation.
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var settings = AppComposition.Current.GetExport<SettingsService>();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 1);
+
+		// Materialise a DecompilerTextView by selecting a node.
+		var typeNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(
+			"System.Linq", "System.Linq", "System.Linq.Enumerable");
+		vm.AssemblyTreeModel.SelectNode(typeNode);
+		var view = await window.WaitForComponent<DecompilerTextView>();
+		var editor = await view.WaitForComponent<AvaloniaEdit.TextEditor>();
+
+		var originalSize = settings.DisplaySettings.SelectedFontSize;
+		var newSize = originalSize + 5;
+
+		// Act — change the live setting; subscriber should write through to Editor.FontSize.
+		settings.DisplaySettings.SelectedFontSize = newSize;
+
+		editor.FontSize.Should().Be(newSize);
+
+		// Clean-up: restore so later tests see the original.
+		settings.DisplaySettings.SelectedFontSize = originalSize;
+	}
 }

ILSpy/Languages/LanguageService.cs

@@ -72,6 +72,9 @@ namespace ILSpy.Languages
 		public Language GetLanguage(string? name)
 			=> Languages.FirstOrDefault(l => l.Name == name) ?? Languages.First();
 
+		// The MVVM-toolkit source generator declares the partial method with nullable
+		// reference types (the backing field is a nullable T). Match the signature exactly
+		// to avoid a CS8611 nullability mismatch.
 		partial void OnCurrentLanguageChanged(Language? oldValue, Language newValue)
 		{
 			if (newValue == null)

ILSpy/TextView/DecompilerTextView.axaml.cs

@@ -44,6 +44,7 @@ using ICSharpCode.ILSpyX;
 
 using ILSpy;
 using ILSpy.AppEnv;
+using ILSpy.Options;
 
 namespace ILSpy.TextView
 {
@@ -152,6 +153,71 @@ namespace ILSpy.TextView
 			richPopup.Closed += OnRichPopupClosed;
 			// Popup.Open uses PlacementTarget to find its TopLevel, so the popup itself doesn't
 			// need to be in any visual tree of ours.
+
+			WireUpDisplaySettings();
+		}
+
+		/// <summary>
+		/// Mirrors the live <see cref="DisplaySettings"/> into the editor on construction and on
+		/// every <c>PropertyChanged</c> after that. Lets the Options Display panel produce
+		/// immediate visual feedback without a re-decompile.
+		/// </summary>
+		void WireUpDisplaySettings()
+		{
+			var settings = TryGetDisplaySettings();
+			if (settings == null)
+				return;
+			ApplyAllDisplaySettings(settings);
+			settings.PropertyChanged += (_, e) => ApplyDisplaySetting(settings, e.PropertyName);
+		}
+
+		static DisplaySettings? TryGetDisplaySettings()
+		{
+			try
+			{ return AppComposition.Current.GetExport<SettingsService>().DisplaySettings; }
+			catch { return null; }
+		}
+
+		void ApplyAllDisplaySettings(DisplaySettings s)
+		{
+			ApplyDisplaySetting(s, nameof(DisplaySettings.SelectedFont));
+			ApplyDisplaySetting(s, nameof(DisplaySettings.SelectedFontSize));
+			ApplyDisplaySetting(s, nameof(DisplaySettings.ShowLineNumbers));
+			ApplyDisplaySetting(s, nameof(DisplaySettings.EnableWordWrap));
+			ApplyDisplaySetting(s, nameof(DisplaySettings.HighlightCurrentLine));
+			ApplyDisplaySetting(s, nameof(DisplaySettings.IndentationSize));
+			ApplyDisplaySetting(s, nameof(DisplaySettings.IndentationUseTabs));
+		}
+
+		void ApplyDisplaySetting(DisplaySettings s, string? propertyName)
+		{
+			switch (propertyName)
+			{
+				case nameof(DisplaySettings.SelectedFont):
+					if (!string.IsNullOrEmpty(s.SelectedFont))
+						Editor.FontFamily = new FontFamily(s.SelectedFont);
+					break;
+				case nameof(DisplaySettings.SelectedFontSize):
+					if (s.SelectedFontSize > 0)
+						Editor.FontSize = s.SelectedFontSize;
+					break;
+				case nameof(DisplaySettings.ShowLineNumbers):
+					Editor.ShowLineNumbers = s.ShowLineNumbers;
+					break;
+				case nameof(DisplaySettings.EnableWordWrap):
+					Editor.WordWrap = s.EnableWordWrap;
+					break;
+				case nameof(DisplaySettings.HighlightCurrentLine):
+					Editor.Options.HighlightCurrentLine = s.HighlightCurrentLine;
+					break;
+				case nameof(DisplaySettings.IndentationSize):
+					if (s.IndentationSize > 0)
+						Editor.Options.IndentationSize = s.IndentationSize;
+					break;
+				case nameof(DisplaySettings.IndentationUseTabs):
+					Editor.Options.ConvertTabsToSpaces = !s.IndentationUseTabs;
+					break;
+			}
 		}
 
 		static IReadOnlyList<IContextMenuEntryExport> TryGetContextMenuEntries()

ILSpy/TreeNodes/ILSpyTreeNode.cs

@@ -76,6 +76,15 @@ namespace ILSpy.TreeNodes
 
 		public Language Language => LanguageService.CurrentLanguage;
 
+		/// <summary>
+		/// Long-form label used in navigation surfaces — back/forward history dropdowns, future
+		/// breadcrumb rendering, etc. Defaults to <see cref="SharpTreeNode.Text"/>; override on
+		/// nodes whose <see cref="SharpTreeNode.Text"/> is too generic to be useful out of
+		/// context (e.g. "Base Types" → "Base Types (System.Exception)") so the user can tell
+		/// dropdown entries apart at a glance.
+		/// </summary>
+		public override object? NavigationText => Text;
+
 		/// <summary>
 		/// True for nodes that represent assemblies the user did not open explicitly — the
 		/// decompiler resolved them as part of another assembly's references and added them to