Pin button matches close button size + hover background

Previously pin used an explicit 22x22 size, custom padding, and a
Button.preview-pin class with hand-rolled #33000000/#55000000 hover
tints. The close button (its sibling in the tab strip) is a plain
Avalonia.Controls.Button with a ControlTheme applied by Dock's tab
template — no classes, no local sizing. Visual mismatch was noticeable.

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

ILSpy.Tests/Docking/PreviewTabPromotionTests.cs

@@ -490,6 +490,46 @@ public class PreviewTabPromotionTests
 			"the already-pinned tab stays pinned");
 	}
 
+	[AvaloniaTest]
+	public async Task Pin_Button_Inherits_The_Close_Button_Theme()
+	{
+		// Visual parity: the pin button should look like the close button — same size, same
+		// hover background. Both are plain Avalonia.Controls.Button instances; the close
+		// button gets its visual identity from a ControlTheme applied by Dock's tab
+		// template. Pin should copy that Theme rather than carry its own custom style.
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 3);
+
+		// Open a carve-out so the close button is visible alongside the pin (single-tab
+		// scenario hides the close button).
+		var typeNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(
+			"System.Linq", "System.Linq", "System.Linq.Enumerable");
+		vm.DockWorkspace.OpenNodeInNewTab(typeNode);
+
+		await Waiters.WaitForAsync(() => window.GetVisualDescendants().OfType<DocumentTabStripItem>().Count() >= 2,
+			System.TimeSpan.FromSeconds(10));
+		global::Avalonia.Threading.Dispatcher.UIThread.RunJobs();
+
+		var factory = (ILSpyDockFactory)vm.DockWorkspace.Factory;
+		var mainTabItem = window.GetVisualDescendants().OfType<DocumentTabStripItem>()
+			.Single(item => ReferenceEquals(item.DataContext, factory.MainTab));
+
+		var pinButton = mainTabItem.GetVisualDescendants()
+			.OfType<global::Avalonia.Controls.Button>()
+			.Single(b => (b.Tag as string) == "PreviewTabPinButton");
+		var closeButton = mainTabItem.GetVisualDescendants()
+			.OfType<global::Avalonia.Controls.Button>()
+			.FirstOrDefault(b => (b.Tag as string) != "PreviewTabPinButton");
+		closeButton.Should().NotBeNull("baseline: close button exists as a sibling of the pin");
+
+		pinButton.Theme.Should().BeSameAs(closeButton!.Theme,
+			"pin button must use the same ControlTheme as the close button so size + hover bg match");
+		pinButton.Classes.Should().NotContain("preview-pin",
+			"after the Theme-copy refactor the custom class-based styling is unused; the Theme drives all visuals");
+	}
+
 	[AvaloniaTest]
 	public async Task Tree_Selection_While_Frozen_Tab_Active_Opens_A_New_Preview_Tab()
 	{

ILSpy/App.axaml

@@ -143,23 +143,6 @@
             <Setter Property="themes:PreviewTabPinButtonBehavior.Enable" Value="True" />
         </Style>
 
-        <!-- Styling for the injected pin button. Routed through a class selector (not
-             local setters on the Button) so the :pointerover style still applies — local
-             property values beat Style setters in Avalonia precedence. -->
-        <Style Selector="Button.preview-pin">
-            <Setter Property="Background" Value="Transparent" />
-            <Setter Property="BorderBrush" Value="Transparent" />
-            <Setter Property="BorderThickness" Value="0" />
-            <Setter Property="Cursor" Value="Hand" />
-        </Style>
-        <Style Selector="Button.preview-pin:pointerover /template/ ContentPresenter">
-            <Setter Property="Background" Value="#33000000" />
-            <Setter Property="BorderBrush" Value="Transparent" />
-        </Style>
-        <Style Selector="Button.preview-pin:pressed /template/ ContentPresenter">
-            <Setter Property="Background" Value="#55000000" />
-            <Setter Property="BorderBrush" Value="Transparent" />
-        </Style>
 
         <!-- Override the presenter template so we can layer classic Windows-Explorer tree
              lines behind the indent / expander / content. -->

ILSpy/Themes/PreviewTabPinButtonBehavior.cs

@@ -21,6 +21,7 @@ using System.Linq;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Shapes;
 using Avalonia.Data;
 using Avalonia.Layout;
 using Avalonia.Media;
@@ -101,30 +102,32 @@ namespace ILSpy.Themes
 			// on top of it.
 			titleStack.ClipToBounds = true;
 
-			// Segoe Fluent Icons / Segoe MDL2 Assets "Pin" glyph (U+E718) — the same
-			// tilted-pushpin silhouette Visual Studio uses for preview tabs. Foreground
-			// inherits through TextElement, so the glyph always contrasts the current tab
-			// background (dark on unselected, light on selected).
-			var glyph = new TextBlock {
-				Text = "",
-				FontFamily = new FontFamily("Segoe Fluent Icons, Segoe MDL2 Assets, Symbols"),
-				FontSize = 12,
+			// Tilted-pushpin silhouette matching the Visual Studio preview-tab affordance.
+			// Vector path (not a font glyph): the previous Segoe Fluent Icons U+E718
+			// fallback was Windows-only and rendered as a tofu box on Linux / macOS.
+			// Path with bound Fill is what restores per-tab Foreground inheritance that
+			// the intermediate SVG-image variant lost - Avalonia.Svg.Skia honors the
+			// asset's literal fill, not the consuming control's theme color. RotateTransform
+			// at -45 deg orients the upright pin path so its tip points to the lower-left.
+			var glyph = new Path {
+				Data = StreamGeometry.Parse("M5 2h6v1h-1v4l2 2v1H9v3l-1 2-1-2v-3H4V9l2-2V3H5z"),
+				Stretch = Stretch.Uniform,
+				Width = 12,
+				Height = 12,
 				HorizontalAlignment = HorizontalAlignment.Center,
 				VerticalAlignment = VerticalAlignment.Center,
-				ClipToBounds = false,
+				RenderTransform = new RotateTransform(45),
+				RenderTransformOrigin = RelativePoint.Center,
 			};
-			glyph.Bind(TextBlock.ForegroundProperty, new Binding(nameof(TemplatedControl.Foreground)) {
+			glyph.Bind(Shape.FillProperty, new Binding(nameof(TemplatedControl.Foreground)) {
 				Source = item,
 				Mode = BindingMode.OneWay,
 			});
 			var pin = new Button {
 				Tag = PinButtonTag,
 				Content = glyph,
-				// Bumped from 18x18 to 22x22 so the glyph's visual extent has comfortable
-				// headroom on all sides.
-				Width = 22,
-				Height = 22,
-				Padding = new Thickness(3),
+				// Left margin preserves the gap between pin and close (~4px) regardless of
+				// what the inherited ControlTheme decides for its own Margin.
 				Margin = new Thickness(4, 0, 0, 0),
 				VerticalAlignment = VerticalAlignment.Center,
 				HorizontalAlignment = HorizontalAlignment.Center,
@@ -135,12 +138,15 @@ namespace ILSpy.Themes
 				// right edge at the content-area boundary.
 				ClipToBounds = false,
 			};
-			// Class-based styling — the App.axaml Style for Button.preview-pin keeps the
-			// button transparent in normal state and gives it a subtle background tint on
-			// :pointerover. Local Background/BorderBrush setters here would beat the
-			// :pointerover style (local > style in Avalonia property precedence), so the
-			// styling is routed entirely through the class selector instead.
-			pin.Classes.Add("preview-pin");
+			// Copy the close button's ControlTheme so pin renders at the same size and uses
+			// the same :pointerover background. The close button (a plain Avalonia.Controls.Button
+			// with no classes, theme applied by Dock's tab template) sits as a sibling under
+			// the same Grid. Without this, pin defaulted to a class-styled custom look that
+			// was bigger and used a different hover tint than its neighbour.
+			var closeButton = item.GetVisualDescendants().OfType<Button>()
+				.FirstOrDefault(b => (b.Tag as string) != PinButtonTag);
+			if (closeButton?.Theme is { } closeTheme)
+				pin.Theme = closeTheme;
 			ToolTip.SetTip(pin, "Pin tab");
 
 			// IsVisible follows IsPreview — the button hides once the tab is pinned.