Assembly tree Ctrl+LMB stops conflicting with multi-selection

User-reported: Ctrl+LMB on an assembly-tree row both toggled the row in
the multi-selection AND opened a new decompiler tab. ProDataGrid's
Extended-selection mode treats Ctrl+LMB as a toggle, and
OnTreeGridPointerPressed also treated it as "open in new tab", so every
Ctrl+click fired both effects regardless of the e.Handled=true on our
handler — selection lives in the DataGrid template's own pre-bubble
pipeline.

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

ILSpy.Tests/Input/HeadlessMmbPointerTests.cs

@@ -92,15 +92,58 @@ public class HeadlessMmbPointerTests
 		(documents.VisibleDockables?.Count ?? 0).Should().Be(before + 1);
 	}
 
+	[AvaloniaTest]
+	public async Task Ctrl_LMB_On_An_Assembly_Tree_Row_Does_Not_Open_A_New_Tab()
+	{
+		// Ctrl+LMB previously did double duty: ProDataGrid's Extended-selection mode treats
+		// it as "toggle this row in the multi-selection", and our OnTreeGridPointerPressed
+		// also treated it as "open in new tab". Both fired on a single click, so users
+		// trying to extend a multi-selection ended up spawning unwanted tabs. The intended
+		// gesture for "open in new tab" is MMB (matches WPF's DecompileInNewViewCommand
+		// InputGestureText). Pin the corrected behaviour: Ctrl+LMB must NOT open a tab —
+		// any future regression that re-adds the branch fails this test.
+
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 1);
+
+		var pane = await window.WaitForComponent<AssemblyListPane>();
+		var grid = await pane.WaitForComponent<DataGrid>();
+
+		await Waiters.WaitForAsync(() => grid.GetVisualDescendants().OfType<DataGridRow>()
+			.Any(r => r.DataContext is HierarchicalNode { Item: ILSpyTreeNode }));
+		var row = grid.GetVisualDescendants().OfType<DataGridRow>()
+			.First(r => r.DataContext is HierarchicalNode { Item: ILSpyTreeNode });
+
+		var documents = ((ILSpyDockFactory)vm.DockWorkspace.Factory).Documents!;
+		int before = documents.VisibleDockables?.Count ?? 0;
+
+		var topLevel = TopLevel.GetTopLevel(row)!;
+		var rowBounds = row.Bounds;
+		var centreInRow = new Point(rowBounds.Width / 2, rowBounds.Height / 2);
+		var centreInTopLevel = row.TranslatePoint(centreInRow, topLevel)
+			?? throw new System.InvalidOperationException("Row not in TopLevel visual tree");
+
+		topLevel.MouseDown(centreInTopLevel, MouseButton.Left, RawInputModifiers.Control);
+		topLevel.MouseUp(centreInTopLevel, MouseButton.Left, RawInputModifiers.Control);
+
+		// Give the (former) "open new tab" path a beat to land if it were going to.
+		await Task.Delay(250);
+		global::Avalonia.Threading.Dispatcher.UIThread.RunJobs();
+
+		(documents.VisibleDockables?.Count ?? 0).Should().Be(before,
+			"Ctrl+LMB must be reserved for ProDataGrid's multi-selection toggle — only MMB opens a new tab");
+	}
+
 	[AvaloniaTest]
 	public async Task LMB_Double_Click_On_An_Internal_Tree_Row_Expands_Without_Opening_A_New_Tab()
 	{
 		// LMB double-click is WPF's expand/collapse gesture. The OnTreeGridDoubleTapped handler
 		// is supposed to be the only path that fires; an earlier patch had OnTreeGridPointerPressed
-		// also treating double-click as a third "open in new tab" gesture (alongside MMB +
-		// Ctrl+LMB), which produced both effects at once. Pin the behaviour so it doesn't drift
-		// back: double-click on an internal (non-leaf) row must change neither the tab count
-		// nor the dock topology.
+		// also treating double-click as a "open in new tab" gesture, which produced both effects
+		// at once. Pin the behaviour so it doesn't drift back: double-click on an internal
+		// (non-leaf) row must change neither the tab count nor the dock topology.
 
 		var window = AppComposition.Current.GetExport<MainWindow>();
 		window.Show();
@@ -140,6 +183,6 @@ public class HeadlessMmbPointerTests
 		global::Avalonia.Threading.Dispatcher.UIThread.RunJobs();
 
 		(documents.VisibleDockables?.Count ?? 0).Should().Be(before,
-			"LMB double-click must not open a new tab — only MMB and Ctrl+LMB do");
+			"LMB double-click must not open a new tab — only MMB does");
 	}
 }

ILSpy/AssemblyTree/AssemblyListPane.axaml.cs

@@ -393,20 +393,16 @@ namespace ILSpy.AssemblyTree
 
 		void OnTreeGridPointerPressed(object? sender, PointerPressedEventArgs e)
 		{
-			// Two gestures map to "open the row's node in a new tab":
-			//   • MMB single-click — primary, WPF DecompileInNewViewCommand's InputGestureText.
-			//   • Ctrl + LMB single-click — modern editor convention.
-			// LMB double-click is reserved for expand/collapse — handled by OnTreeGridDoubleTapped.
-			// MMB doesn't move selection on its own, so we hit-test the row from e.Source
-			// in every case rather than reading SelectedItem.
+			// MMB single-click is the only "open the row's node in a new tab" pointer gesture —
+			// matches WPF's DecompileInNewViewCommand InputGestureText. Ctrl+LMB is left to
+			// ProDataGrid's Extended-selection mode so multi-selection by toggle isn't ambushed
+			// by an unwanted new tab. LMB double-click is reserved for expand/collapse,
+			// handled by OnTreeGridDoubleTapped. MMB doesn't move selection on its own, so we
+			// hit-test the row from e.Source rather than reading SelectedItem.
 			if (e.Source is not Visual hit)
 				return;
 			var point = e.GetCurrentPoint(hit).Properties;
-			bool isMmb = point.IsMiddleButtonPressed;
-			bool isCtrlClick = point.IsLeftButtonPressed
-				&& (e.KeyModifiers & KeyModifiers.Control) == KeyModifiers.Control
-				&& e.ClickCount == 1;
-			if (!isMmb && !isCtrlClick)
+			if (!point.IsMiddleButtonPressed)
 				return;
 			var visual = hit;
 			while (visual != null && visual.DataContext is not HierarchicalNode)