Render About-page links via LinkElementGenerator (regex)

Replaces the previous WriteReference(string, Uri) approach with a
LinkElementGenerator subclass that scans the rendered document for the
target phrases ("MIT License" / "third-party notices"), matching the
WPF host's MyLinkElementGenerator pattern. The custom generator collection
travels through AvaloniaEditTextOutput → DecompilerTabPageModel.
CustomElementGenerators → DecompilerTextView (which installs and tears
them down per ApplyDocument).

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

ILSpy.Tests/Commands/HelpCommandTests.cs

@@ -80,11 +80,13 @@ public class HelpCommandTests
 	[AvaloniaTest]
 	public async Task About_Page_MIT_License_Link_Opens_License_Tab_On_Click()
 	{
-		// "MIT License" inside the About blurb must be a clickable reference. Activating it
-		// (the same path DecompilerTextView's pointer click takes — RaiseNavigateRequested)
-		// must open the embedded LICENSE text in a new tab.
+		// "MIT License" inside the About blurb must be rendered as an AvaloniaEdit hyperlink
+		// pointing at "resource:license.txt", and activating it must open the embedded LICENSE
+		// text in a new tab. Tests the full pipeline: the tab carries a custom element
+		// generator (matching the WPF host's LinkElementGenerator pattern), and the tab's
+		// OpenUriRequested handler resolves the resource: URI to a new tab.
 
-		// Arrange — boot the window and open the About page.
+		// Arrange — boot, open the About page.
 		var window = AppComposition.Current.GetExport<MainWindow>();
 		window.Show();
 		var vm = (MainWindowViewModel)window.DataContext!;
@@ -99,18 +101,20 @@ public class HelpCommandTests
 		await Waiters.WaitForAsync(
 			() => documents.ActiveDockable is DecompilerTabPageModel { Text.Length: > 0 });
 		var aboutTab = (DecompilerTabPageModel)documents.ActiveDockable!;
+
+		// Assert (mid-test) — the tab carries the custom hyperlink generators that
+		// DecompilerTextView installs alongside the document.
+		aboutTab.CustomElementGenerators.Should().NotBeNull();
+		aboutTab.CustomElementGenerators!.Should().NotBeEmpty(
+			"the About page must contribute LinkElementGenerator(s) for MIT License + third-party notices");
+
 		var beforeCount = documents.VisibleDockables?.Count ?? 0;
 
-		// Act — find the MIT License reference segment and fire NavigateRequested (same path
-		// the live pointer-click handler takes).
-		aboutTab.References.Should().NotBeNull();
-		var licenseSegment = aboutTab.References!
-			.Single(r => r.Reference is Uri u && u.OriginalString.Contains("license", StringComparison.OrdinalIgnoreCase));
-		var matched = aboutTab.Text.Substring(licenseSegment.StartOffset, licenseSegment.Length);
-		matched.Should().Be("MIT License");
-		aboutTab.RaiseNavigateRequested(licenseSegment);
+		// Act — fire the same OpenUri routed event that AvaloniaEdit would raise on click.
+		aboutTab.RaiseOpenUriRequested(new Uri("resource:license.txt"))
+			.Should().BeTrue("the About tab must claim the resource: URI as handled");
 
-		// Assert — a new tab landed in the document dock containing the license body.
+		// Assert — a new tab opens with the license body.
 		await Waiters.WaitForAsync(
 			() => (documents.VisibleDockables?.Count ?? 0) > beforeCount
 				&& documents.ActiveDockable is DecompilerTabPageModel licenseTab

ILSpy/Commands/AboutCommand.cs

@@ -21,7 +21,9 @@ using System.Collections.Generic;
 using System.Composition;
 using System.Diagnostics;
 using System.IO;
-using System.Reflection;
+using System.Text.RegularExpressions;
+
+using AvaloniaEdit.Rendering;
 
 using ICSharpCode.Decompiler;
 using ICSharpCode.ILSpy.Properties;
@@ -38,7 +40,7 @@ namespace ILSpy.Commands
 		// Phrases inside the About blurb that should render as clickable hyperlinks. The Uri
 		// uses the custom "resource:" scheme; the click handler reads the matching name as an
 		// embedded manifest resource on this assembly.
-		static readonly (string Text, Uri Uri)[] Links = {
+		static readonly (string Phrase, Uri Uri)[] Links = {
 			("MIT License", new Uri("resource:license.txt")),
 			("third-party notices", new Uri("resource:third-party-notices.txt")),
 		};
@@ -71,46 +73,14 @@ namespace ILSpy.Commands
 				{
 					using var reader = new StreamReader(stream);
 					while (reader.ReadLine() is { } line)
-						WriteLineWithLinks(output, line);
+						output.WriteLine(line);
 				}
 			}
 
-			OpenInNewTab(Resources.About, output, ".txt");
-		}
+			foreach (var (phrase, uri) in Links)
+				output.AddVisualLineElementGenerator(new ResourceLinkGenerator(phrase, uri));
 
-		static void WriteLineWithLinks(AvaloniaEditTextOutput output, string line)
-		{
-			int cursor = 0;
-			while (cursor < line.Length)
-			{
-				int nearestStart = -1;
-				(string Text, Uri Uri) nearest = default;
-				foreach (var link in Links)
-				{
-					int idx = line.IndexOf(link.Text, cursor, StringComparison.Ordinal);
-					if (idx < 0)
-						continue;
-					if (nearestStart < 0 || idx < nearestStart)
-					{
-						nearestStart = idx;
-						nearest = link;
-					}
-				}
-				if (nearestStart < 0)
-				{
-					output.Write(line.Substring(cursor));
-					break;
-				}
-				if (nearestStart > cursor)
-					output.Write(line.Substring(cursor, nearestStart - cursor));
-				// nearestStart >= 0 here implies the foreach assigned `nearest = link` at least
-				// once, so neither tuple field is the default-null left behind by `nearest = default`.
-				Debug.Assert(nearest.Text != null);
-				Debug.Assert(nearest.Uri != null);
-				output.WriteReference(nearest.Text, nearest.Uri);
-				cursor = nearestStart + nearest.Text.Length;
-			}
-			output.WriteLine();
+			OpenInNewTab(Resources.About, output, ".txt");
 		}
 
 		void OpenInNewTab(string title, AvaloniaEditTextOutput output, string syntaxExtension)
@@ -124,17 +94,20 @@ namespace ILSpy.Commands
 				DefinitionLookup = output.DefinitionLookup,
 				UIElements = output.UIElements,
 				Foldings = output.Foldings,
+				CustomElementGenerators = output.ElementGenerators.Count > 0
+					? new List<VisualLineElementGenerator>(output.ElementGenerators)
+					: null,
 			};
-			tab.NavigateRequested += OnLinkClicked;
+			tab.OpenUriRequested += OnOpenUri;
 			dockWorkspace.OpenNewTab(tab);
 		}
 
-		void OnLinkClicked(ReferenceSegment segment)
+		bool OnOpenUri(Uri uri)
 		{
-			if (segment.Reference is not Uri uri
-				|| !string.Equals(uri.Scheme, "resource", StringComparison.OrdinalIgnoreCase))
-				return;
+			if (!string.Equals(uri.Scheme, "resource", StringComparison.OrdinalIgnoreCase))
+				return false;
 			OpenEmbeddedResource(uri.AbsolutePath);
+			return true;
 		}
 
 		void OpenEmbeddedResource(string resourceName)
@@ -157,6 +130,23 @@ namespace ILSpy.Commands
 				return FileVersionInfo.GetVersionInfo(location).ProductVersion ?? "UNKNOWN";
 			return typeof(object).Assembly.GetName().Version?.ToString() ?? "UNKNOWN";
 		}
+
+		// Specialised LinkElementGenerator that matches a single literal phrase and produces a
+		// VisualLineLinkText pointing at a fixed Uri. Mirrors the "MyLinkElementGenerator"
+		// pattern from the legacy WPF host.
+		sealed class ResourceLinkGenerator : LinkElementGenerator
+		{
+			readonly Uri target;
+
+			public ResourceLinkGenerator(string phrase, Uri target)
+				: base(new Regex(Regex.Escape(phrase)))
+			{
+				this.target = target;
+				RequireControlModifierForClick = false;
+			}
+
+			protected override Uri GetUriFromMatch(Match match) => target;
+		}
 	}
 
 	/// <summary>

ILSpy/TextView/AvaloniaEditTextOutput.cs

@@ -26,6 +26,7 @@ using Avalonia.Controls;
 using AvaloniaEdit.Document;
 using AvaloniaEdit.Folding;
 using AvaloniaEdit.Highlighting;
+using AvaloniaEdit.Rendering;
 
 using ICSharpCode.Decompiler;
 using ICSharpCode.Decompiler.Disassembler;
@@ -71,6 +72,15 @@ namespace ILSpy.TextView
 		/// <see cref="UIElementGenerator"/> by the text view.</summary>
 		public IReadOnlyList<KeyValuePair<int, Lazy<Control>>> UIElements => uiElements;
 
+		readonly List<VisualLineElementGenerator> elementGenerators = new();
+
+		/// <summary>
+		/// Custom <see cref="VisualLineElementGenerator"/>s contributed by the writer (e.g. a
+		/// regex-based hyperlink generator). Installed on the text view alongside the
+		/// document and torn down again when the document is replaced.
+		/// </summary>
+		public IReadOnlyList<VisualLineElementGenerator> ElementGenerators => elementGenerators;
+
 		public string Title { get; set; } = string.Empty;
 
 		/// <summary>
@@ -145,9 +155,6 @@ namespace ILSpy.TextView
 		public void WriteReference(IMember member, string text, bool isDefinition = false)
 			=> AddReference(text, member, local: false, isDefinition);
 
-		public void WriteReference(string text, Uri target)
-			=> AddReference(text, target, local: false, isDefinition: false);
-
 		public void WriteLocalReference(string text, object reference, bool isDefinition = false)
 			=> AddReference(text, reference, local: true, isDefinition);
 
@@ -201,6 +208,12 @@ namespace ILSpy.TextView
 			uiElements.Add(new KeyValuePair<int, Lazy<Control>>(builder.Length, new Lazy<Control>(element)));
 		}
 
+		public void AddVisualLineElementGenerator(VisualLineElementGenerator generator)
+		{
+			ArgumentNullException.ThrowIfNull(generator);
+			elementGenerators.Add(generator);
+		}
+
 		public void BeginSpan(HighlightingColor highlightingColor)
 		{
 			openSpans.Push((builder.Length, highlightingColor));

ILSpy/TextView/DecompilerTabPageModel.cs

@@ -29,6 +29,7 @@ using Avalonia.Threading;
 using AvaloniaEdit.Document;
 using AvaloniaEdit.Folding;
 using AvaloniaEdit.Highlighting;
+using AvaloniaEdit.Rendering;
 
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
@@ -100,6 +101,14 @@ namespace ILSpy.TextView
 		[ObservableProperty]
 		private IReadOnlyList<KeyValuePair<int, Lazy<Control>>>? uIElements;
 
+		/// <summary>
+		/// Custom <see cref="VisualLineElementGenerator"/>s the writer attached (e.g. a
+		/// regex-based hyperlink generator). The text view installs them alongside the
+		/// document and removes them again when the document changes.
+		/// </summary>
+		[ObservableProperty]
+		private IReadOnlyList<VisualLineElementGenerator>? customElementGenerators;
+
 		/// <summary>
 		/// Fired when the user clicks a cross-document reference. The host (DockWorkspace)
 		/// resolves the target on the assembly tree side.
@@ -109,6 +118,27 @@ namespace ILSpy.TextView
 		internal void RaiseNavigateRequested(ReferenceSegment segment)
 			=> NavigateRequested?.Invoke(segment);
 
+		/// <summary>
+		/// Fired when the user activates an AvaloniaEdit hyperlink. Subscribers return
+		/// <see langword="true"/> if they handled the URI; the text view then suppresses the
+		/// default <see cref="System.Diagnostics.Process.Start(System.Diagnostics.ProcessStartInfo)"/>
+		/// fallback that AvaloniaEdit would otherwise run for the URI.
+		/// </summary>
+		public event System.Func<System.Uri, bool>? OpenUriRequested;
+
+		internal bool RaiseOpenUriRequested(System.Uri uri)
+		{
+			var handlers = OpenUriRequested;
+			if (handlers == null)
+				return false;
+			foreach (System.Func<System.Uri, bool> handler in handlers.GetInvocationList())
+			{
+				if (handler(uri))
+					return true;
+			}
+			return false;
+		}
+
 		IReadOnlyList<ILSpyTreeNode> currentNodes = System.Array.Empty<ILSpyTreeNode>();
 
 		[RelayCommand]

ILSpy/TextView/DecompilerTextView.axaml.cs

@@ -65,6 +65,7 @@ namespace ILSpy.TextView
 		readonly UIElementGenerator uiElementGenerator;
 		readonly TextMarkerService textMarkerService;
 		readonly List<TextMarker> localReferenceMarks = new();
+		readonly List<AvaloniaEdit.Rendering.VisualLineElementGenerator> activeCustomGenerators = new();
 		RichTextColorizer? activeColorizer;
 		FoldingManager? activeFoldingManager;
 		ReferenceSegment? lastTooltipSegment;
@@ -109,6 +110,15 @@ namespace ILSpy.TextView
 			Editor.TextArea.TextView.PointerMoved += OnTextViewPointerMoved;
 			Editor.TextArea.TextView.PointerExited += OnTextViewPointerExited;
 
+			// AvaloniaEdit's hyperlinks raise OpenUriEvent (bubbling); the default class handler
+			// on Window passes the URI to Process.Start. Intercept first so internal schemes
+			// (the About page's "resource:" URIs) route through the tab model instead.
+			Editor.TextArea.TextView.AddHandler(
+				AvaloniaEdit.Rendering.VisualLineLinkText.OpenUriEvent,
+				OnHyperlinkOpenUri,
+				RoutingStrategies.Bubble,
+				handledEventsToo: false);
+
 			richPopup = new Popup {
 				PlacementTarget = Editor.TextArea.TextView,
 				// Pointer placement: Avalonia anchors the popup at the current cursor location
@@ -193,11 +203,34 @@ namespace ILSpy.TextView
 
 			referenceElementGenerator.References = model.References;
 			uiElementGenerator.UIElements = model.UIElements;
+
+			// Swap any tab-contributed visual-line element generators (e.g. About-page hyperlink
+			// generators). Tracked separately from the always-on referenceElementGenerator and
+			// uiElementGenerator so the two sets don't collide on tab change.
+			var generators = Editor.TextArea.TextView.ElementGenerators;
+			foreach (var g in activeCustomGenerators)
+				generators.Remove(g);
+			activeCustomGenerators.Clear();
+			if (model.CustomElementGenerators is { Count: > 0 } modelGenerators)
+			{
+				foreach (var g in modelGenerators)
+				{
+					generators.Add(g);
+					activeCustomGenerators.Add(g);
+				}
+			}
+
 			Editor.TextArea.TextView.Redraw();
 
 			Editor.ScrollToHome();
 		}
 
+		void OnHyperlinkOpenUri(object? sender, AvaloniaEdit.Rendering.OpenUriRoutedEventArgs e)
+		{
+			if (DataContext is DecompilerTabPageModel model && model.RaiseOpenUriRequested(e.Uri))
+				e.Handled = true;
+		}
+
 		void OnReferenceClicked(ReferenceSegment segment)
 		{
 			if (DataContext is not DecompilerTabPageModel model || segment.Reference == null)

ILSpy/TextView/ISmartTextOutput.cs

@@ -21,6 +21,7 @@ using System;
 using Avalonia.Controls;
 
 using AvaloniaEdit.Highlighting;
+using AvaloniaEdit.Rendering;
 
 using ICSharpCode.Decompiler;
 
@@ -38,6 +39,12 @@ namespace ILSpy.TextView
 		/// </summary>
 		void AddUIElement(Func<Control> element);
 
+		/// <summary>
+		/// Contributes a <see cref="VisualLineElementGenerator"/> (typically a regex-based
+		/// hyperlink generator) that the text view installs alongside the document.
+		/// </summary>
+		void AddVisualLineElementGenerator(VisualLineElementGenerator generator);
+
 		void BeginSpan(HighlightingColor highlightingColor);
 		void EndSpan();