Navigate references on click-release so link text stays selectable

Reference links navigated on pointer-press, which meant a press-drag
over a link could never select its text -- the press fired navigation
and handled the event before a selection could start. Move navigation
to pointer-release and only follow the link when the pointer did not
drag past the click threshold, matching the WPF view's mouse-up
handling. A press-drag now selects link text like any other span.

Assisted-by: Claude:claude-fable-5:Claude Code

ILSpy.Tests/Editor/CaretHighlightAdornerTests.cs

@@ -96,8 +96,8 @@ public class CaretHighlightAdornerTests
 		((object?)memberDef).Should().NotBeNull(
 			"the decompiled Enumerable class contains at least one member-definition reference");
 
-		// Same code path a real pointer-press on the member name routes through.
-		generator.OnReferenceClicked(memberDef!);
+		// Same code path a real stationary click on the member name routes through.
+		view.OnReferenceClicked(memberDef!);
 
 		renderers.Should().Contain(r => r is CaretHighlightAdorner,
 			"clicking a member definition must route through DecompilerTextView.OnReferenceClicked "

ILSpy.Tests/Editor/ReferenceClickTests.cs

@@ -0,0 +1,118 @@
+// Copyright (c) 2026 Siegfried Pammer
+//
+// 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 System.Threading.Tasks;
+
+using Avalonia;
+using Avalonia.Headless;
+using Avalonia.Headless.NUnit;
+using Avalonia.Input;
+using Avalonia.VisualTree;
+
+using AvaloniaEdit;
+using AvaloniaEdit.Rendering;
+
+using AwesomeAssertions;
+
+using ILSpy.TextView;
+using ILSpy.TreeNodes;
+using ILSpy.ViewModels;
+using ILSpy.Views;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.ILSpy.Tests.TextView;
+
+/// <summary>
+/// Pins the reference-link click gesture in the decompiled view (WPF parity): navigation
+/// happens on mouse-UP and only when the pointer did not drag, so text that belongs to a
+/// link can still be selected by press-and-drag.
+/// </summary>
+[TestFixture]
+public class ReferenceClickTests
+{
+	static async Task<(MainWindow Window, DecompilerTextView View, DecompilerTabPageModel Tab)> SetupAsync()
+	{
+		var (window, vm) = await TestHarness.BootAsync();
+		var coreLibName = typeof(object).Assembly.GetName().Name!;
+		var stringNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(coreLibName, "System", "System.String");
+		vm.AssemblyTreeModel.SelectNode(stringNode);
+		var tab = await vm.DockWorkspace.WaitForDecompiledTextAsync();
+
+		var view = window.GetVisualDescendants().OfType<DecompilerTextView>().First();
+		AvaloniaHeadlessPlatform.ForceRenderTimerTick();
+		Avalonia.Threading.Dispatcher.UIThread.RunJobs();
+		window.UpdateLayout();
+		view.Editor.TextArea.TextView.EnsureVisualLines();
+		return (window, view, tab);
+	}
+
+	/// <summary>
+	/// Picks a navigable reference (cross-document, not a definition) within the visible
+	/// top of the document and returns a window-space point inside its text.
+	/// </summary>
+	static (ReferenceSegment Segment, Point Point) FindVisibleReference(
+		MainWindow window, DecompilerTextView view, DecompilerTabPageModel tab)
+	{
+		var textView = view.Editor.TextArea.TextView;
+		var segment = tab.References!
+			.First(r => r.Reference != null && !r.IsLocal && !r.IsDefinition);
+		var line = view.Editor.Document.GetLineByOffset(segment.StartOffset);
+		view.Editor.ScrollTo(line.LineNumber, segment.StartOffset - line.Offset + 1);
+		window.UpdateLayout();
+		textView.EnsureVisualLines();
+		var position = new TextViewPosition(line.LineNumber, segment.StartOffset - line.Offset + 2);
+		var visual = textView.GetVisualPosition(position, VisualYPosition.LineMiddle) - textView.ScrollOffset;
+		var point = textView.TranslatePoint(visual, window)!.Value;
+		return (segment, point);
+	}
+
+	[AvaloniaTest]
+	public async Task Dragging_Over_A_Link_Selects_Text_Without_Navigating()
+	{
+		var (window, view, tab) = await SetupAsync();
+		var (_, point) = FindVisibleReference(window, view, tab);
+
+		var navigated = false;
+		tab.NavigateRequested += _ => navigated = true;
+
+		window.MouseDown(point, MouseButton.Left);
+		window.MouseMove(point + new Point(60, 0));
+		window.MouseUp(point + new Point(60, 0), MouseButton.Left);
+
+		navigated.Should().BeFalse("a press-and-drag over a link is a text selection, not a click");
+		view.Editor.TextArea.Selection.IsEmpty.Should().BeFalse(
+			"dragging across link text must produce a selection");
+	}
+
+	[AvaloniaTest]
+	public async Task Stationary_Click_On_A_Link_Navigates()
+	{
+		var (window, view, tab) = await SetupAsync();
+		var (_, point) = FindVisibleReference(window, view, tab);
+
+		var navigated = false;
+		tab.NavigateRequested += _ => navigated = true;
+
+		window.MouseDown(point, MouseButton.Left);
+		window.MouseUp(point, MouseButton.Left);
+
+		navigated.Should().BeTrue("a click without dragging follows the link");
+	}
+}

ILSpy/TextView/DecompilerTextView.axaml.cs

@@ -137,11 +137,62 @@ namespace ILSpy.TextView
 		void SetupElementGenerators()
 		{
 			referenceElementGenerator = new ReferenceElementGenerator(static segment => segment.Reference != null);
-			referenceElementGenerator.ReferenceClicked += OnReferenceClicked;
 			Editor.TextArea.TextView.ElementGenerators.Add(referenceElementGenerator);
 
 			uiElementGenerator = new UIElementGenerator();
 			Editor.TextArea.TextView.ElementGenerators.Add(uiElementGenerator);
+
+			// Reference navigation fires on pointer-RELEASE without drag (WPF parity: the WPF
+			// view used TextArea.PreviewMouseDown/Up the same way), so a press-and-drag over a
+			// link starts a text selection instead of navigating away. Tunnel routing mirrors
+			// WPF's Preview events and sees the gesture before AvaloniaEdit's own handlers.
+			Editor.TextArea.AddHandler(InputElement.PointerPressedEvent,
+				OnTextAreaPointerPressedForReferenceClick,
+				RoutingStrategies.Tunnel,
+				handledEventsToo: true);
+			Editor.TextArea.AddHandler(InputElement.PointerReleasedEvent,
+				OnTextAreaPointerReleasedForReferenceClick,
+				RoutingStrategies.Tunnel,
+				handledEventsToo: true);
+		}
+
+		// Position of the last left-button press, in this control's coordinates; null while no
+		// press is in flight. The release compares against it to tell a click from a drag.
+		Point? referenceClickStart;
+
+		// WPF used SystemParameters.MinimumHorizontal/VerticalDragDistance, which default to 4.
+		const double MinimumDragDistance = 4;
+
+		void OnTextAreaPointerPressedForReferenceClick(object? sender, PointerPressedEventArgs e)
+		{
+			referenceClickStart = e.GetCurrentPoint(this).Properties.IsLeftButtonPressed
+				? e.GetPosition(this)
+				: null;
+		}
+
+		void OnTextAreaPointerReleasedForReferenceClick(object? sender, PointerReleasedEventArgs e)
+		{
+			var start = referenceClickStart;
+			referenceClickStart = null;
+			if (start == null || e.InitialPressMouseButton != MouseButton.Left)
+				return;
+			var delta = e.GetPosition(this) - start.Value;
+			if (Math.Abs(delta.X) >= MinimumDragDistance || Math.Abs(delta.Y) >= MinimumDragDistance)
+				return;
+
+			var segment = GetReferenceSegmentAtPointer(e);
+			if (segment?.Reference == null)
+			{
+				// A click on empty space dismisses the local-reference highlight.
+				ClearLocalReferenceMarks();
+				return;
+			}
+			// Cancel the caret-click selection AvaloniaEdit started on press, and stop its
+			// release processing, so the navigation's caret move doesn't grow a selection
+			// between the old anchor and the new position.
+			Editor.TextArea.ClearSelection();
+			e.Handled = true;
+			OnReferenceClicked(segment);
 		}
 
 		// Background renderers that live for the view's lifetime: the local-reference highlight (marks
@@ -743,7 +794,18 @@ namespace ILSpy.TextView
 				e.Handled = true;
 		}
 
-		void OnReferenceClicked(ReferenceSegment segment)
+		ReferenceSegment? GetReferenceSegmentAtPointer(PointerEventArgs e)
+		{
+			if (DataContext is not DecompilerTabPageModel model || model.References == null)
+				return null;
+			var pos = GetPositionFromPointer(e);
+			if (pos == null)
+				return null;
+			var offset = Editor.Document.GetOffset(pos.Value.Line, pos.Value.Column);
+			return model.References.FindSegmentsContaining(offset).FirstOrDefault();
+		}
+
+		internal void OnReferenceClicked(ReferenceSegment segment)
 		{
 			if (DataContext is not DecompilerTabPageModel model || segment.Reference == null)
 				return;
@@ -823,13 +885,9 @@ namespace ILSpy.TextView
 			// pointer.
 			if (!TryCloseExistingPopup(mouseClick: false))
 				return;
-			if (DataContext is not DecompilerTabPageModel model || model.References == null)
+			if (DataContext is not DecompilerTabPageModel model)
 				return;
-			var pos = GetPositionFromPointer(e);
-			if (pos == null)
-				return;
-			var offset = Editor.Document.GetOffset(pos.Value.Line, pos.Value.Column);
-			var segment = model.References.FindSegmentsContaining(offset).FirstOrDefault();
+			var segment = GetReferenceSegmentAtPointer(e);
 			if (segment?.Reference == null)
 				return;
 

ILSpy/TextView/ReferenceElementGenerator.cs

@@ -33,11 +33,6 @@ namespace ILSpy.TextView
 
 		public TextSegmentCollection<ReferenceSegment>? References { get; set; }
 
-		/// <summary>Raised when a clickable reference span is activated.</summary>
-		public event Action<ReferenceSegment>? ReferenceClicked;
-
-		internal void OnReferenceClicked(ReferenceSegment segment) => ReferenceClicked?.Invoke(segment);
-
 		public ReferenceElementGenerator(Predicate<ReferenceSegment> isLink)
 		{
 			this.isLink = isLink ?? throw new ArgumentNullException(nameof(isLink));

ILSpy/TextView/VisualLineReferenceText.cs

@@ -24,8 +24,9 @@ namespace ILSpy.TextView
 {
 	/// <summary>
 	/// A clickable piece of text that maps back to a <see cref="ReferenceSegment"/>. Sets a hand
-	/// cursor for cross-document references and an arrow for in-document ones. The actual click
-	/// is handled by the parent generator, which routes the segment to the document's navigator.
+	/// cursor for cross-document references and an arrow for in-document ones. Clicks are NOT
+	/// handled here: navigation fires on pointer-release without drag (see the reference-click
+	/// handlers in <see cref="DecompilerTextView"/>), so a press-and-drag can select link text.
 	/// </summary>
 	sealed class VisualLineReferenceText : VisualLineText
 	{
@@ -57,13 +58,5 @@ namespace ILSpy.TextView
 			// suppresses PointerHoverLogic's tracking of pointer position over reference
 			// segments. Without this, hover events fire with stale args from outside the segment.
 		}
-
-		protected override void OnPointerPressed(PointerPressedEventArgs e)
-		{
-			if (e.Handled || !e.GetCurrentPoint(null).Properties.IsLeftButtonPressed)
-				return;
-			parent.OnReferenceClicked(referenceSegment);
-			e.Handled = true;
-		}
 	}
 }