feat: add inheritance.

src/Ursa.Themes.Semi/Controls/Anchor.axaml

@@ -6,11 +6,14 @@
     xmlns:u="https://irihi.tech/ursa">
     <converters:TreeLevelToMarginConverter x:Key="LevelToMarginConverter" />
     <ControlTheme x:Key="{x:Type u:Anchor}" TargetType="{x:Type u:Anchor}">
+        <Setter Property="Background" Value="Transparent" />
+        <Setter Property="VerticalAlignment" Value="Top" />
         <Setter Property="Template">
             <ControlTemplate>
                 <Panel>
                     <Rectangle
                         Width="1"
+                        Name="PART_Pipe"
                         HorizontalAlignment="Left"
                         VerticalAlignment="Stretch"
                         Fill="{DynamicResource SemiColorBorder}" />
@@ -21,23 +24,30 @@
                 </Panel>
             </ControlTemplate>
         </Setter>
+        <Style Selector="^.Mute /template/ Rectangle#PART_Pipe">
+            <Setter Property="Fill" Value="Transparent" />
+        </Style>
     </ControlTheme>
 
     <ControlTheme x:Key="{x:Type u:AnchorItem}" TargetType="u:AnchorItem">
         <Setter Property="Background" Value="Transparent" />
-        <Setter Property="MinHeight" Value="20" />
+        <Setter Property="Cursor" Value="Hand" />
+        <Setter Property="iri:ClassHelper.ClassSource" Value="{Binding $parent[u:Anchor]}" />
         <Setter Property="Template">
             <ControlTemplate TargetType="u:AnchorItem">
                 <StackPanel>
-                    <Panel>
+                    <Panel Background="{TemplateBinding Background}" >
-                        <Rectangle
+                        <Border
                             Name="PART_Pipe"
                             Width="2"
+                            CornerRadius="1"
                             HorizontalAlignment="Left"
                             VerticalAlignment="Stretch" />
                         <Panel Margin="8,0,0,0">
                             <ContentPresenter
                                 Name="{x:Static iri:PartNames.PART_HeaderPresenter}"
+                                VerticalAlignment="Center"
+                                Foreground="{DynamicResource SemiColorText2}"
                                 Content="{TemplateBinding Header}"
                                 ContentTemplate="{TemplateBinding HeaderTemplate}">
                                 <ContentPresenter.Margin>
@@ -53,8 +63,24 @@
                 </StackPanel>
             </ControlTemplate>
         </Setter>
-        <Style Selector="^:selected /template/ Rectangle#PART_Pipe">
+        <Style Selector="^ /template/ ContentPresenter#PART_HeaderPresenter">
-            <Setter Property="Fill" Value="{DynamicResource SemiBlue5}" />
+            <Setter Property="MinHeight" Value="{DynamicResource AnchorDefaultHeight}" />
+        </Style>
+        <Style Selector="^.Small /template/ ContentPresenter#PART_HeaderPresenter">
+            <Setter Property="MinHeight" Value="{DynamicResource AnchorSmallHeight}" />
+            <Setter Property="FontSize" Value="{DynamicResource SemiFontSizeSmall}" />
+        </Style>
+        <Style Selector="^:selected /template/ Border#PART_Pipe">
+            <Setter Property="Background" Value="{DynamicResource SemiColorTertiary}" />
+        </Style>
+        <Style Selector="^.Primary:selected /template/ Border#PART_Pipe">
+            <Setter Property="Background" Value="{DynamicResource SemiColorPrimary}" />
+        </Style>
+        <Style Selector="^.Mute:selected /template/ Border#PART_Pipe">
+            <Setter Property="Background" Value="Transparent" />
+        </Style>
+        <Style Selector="^:selected /template/ ContentPresenter#PART_HeaderPresenter">
+            <Setter Property="Foreground" Value="{DynamicResource SemiColorText0}" />
         </Style>
     </ControlTheme>
 </ResourceDictionary>

src/Ursa.Themes.Semi/Themes/Shared/Anchor.axaml

@@ -1,4 +1,6 @@
 <ResourceDictionary xmlns="https://github.com/avaloniaui"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
     <x:Double x:Key="AnchorIndent">12</x:Double>
+    <x:Double x:Key="AnchorDefaultHeight">20</x:Double>
+    <x:Double x:Key="AnchorSmallHeight">16</x:Double>
 </ResourceDictionary>

src/Ursa/Controls/Anchor/Anchor.cs

@@ -11,15 +11,27 @@ using Ursa.Common;
 namespace Ursa.Controls;
 
 /// <summary>
-/// Some basic assumptions: This should not be a regular SelectingItemsControl, because it does not support multiple selections.
+///     Some basic assumptions: This should not be a regular SelectingItemsControl, because it does not support multiple
-/// Selection should not be exposed to the user, it is only used to determine which item is currently selected.
+///     selections.
-/// The manipulation of container selection should be simplified.
+///     Selection should not be exposed to the user, it is only used to determine which item is currently selected.
-/// Scroll event of TargetContainer also triggers selection change. 
+///     The manipulation of container selection should be simplified.
+///     Scroll event of TargetContainer also triggers selection change.
 /// </summary>
-public class Anchor: ItemsControl
+public class Anchor : ItemsControl
 {
-    public static readonly StyledProperty<ScrollViewer?> TargetContainerProperty = AvaloniaProperty.Register<Anchor, ScrollViewer?>(
+    public static readonly StyledProperty<ScrollViewer?> TargetContainerProperty =
-        nameof(TargetContainer));
+        AvaloniaProperty.Register<Anchor, ScrollViewer?>(
+            nameof(TargetContainer));
+
+    public static readonly AttachedProperty<string?> AnchorIdProperty =
+        AvaloniaProperty.RegisterAttached<Anchor, Visual, string?>("AnchorId");
+
+    private CancellationTokenSource _cts = new();
+
+    private List<(string, double)> _positions = [];
+    private bool _scrollingFromSelection;
+
+    private AnchorItem? _selectedContainer;
 
     public ScrollViewer? TargetContainer
     {
@@ -27,11 +39,15 @@ public class Anchor: ItemsControl
         set => SetValue(TargetContainerProperty, value);
     }
 
-    public static readonly AttachedProperty<string?> AnchorIdProperty =
+    public static void SetAnchorId(Visual obj, string? value)
-        AvaloniaProperty.RegisterAttached<Anchor, Visual, string?>("AnchorId");
+    {
+        obj.SetValue(AnchorIdProperty, value);
+    }
 
-    public static void SetAnchorId(Visual obj, string? value) => obj.SetValue(AnchorIdProperty, value);
+    public static string? GetAnchorId(Visual obj)
-    public static string? GetAnchorId(Visual obj) => obj.GetValue(AnchorIdProperty);
+    {
+        return obj.GetValue(AnchorIdProperty);
+    }
 
 
     protected override bool NeedsContainerOverride(object? item, int index, out object? recycleKey)
@@ -45,9 +61,6 @@ public class Anchor: ItemsControl
         return i;
     }
 
-    private CancellationTokenSource _cts = new();
-    private bool _scrollingFromSelection;
-    
     private void ScrollToAnchor(Visual target)
     {
         if (TargetContainer is null)
@@ -58,38 +71,30 @@ public class Anchor: ItemsControl
         {
             var from = TargetContainer.Offset.Y;
             var to = TargetContainer.Offset.Y + targetPosition.Value.Y;
-            if(to > TargetContainer.Extent.Height - TargetContainer.Bounds.Height)
+            if (to > TargetContainer.Extent.Height - TargetContainer.Bounds.Height)
-            {
                 to = TargetContainer.Extent.Height - TargetContainer.Bounds.Height;
-            }
             if (from == to) return;
-            Animation animation = new Animation()
+            var animation = new Animation
             {
                 Duration = TimeSpan.FromSeconds(0.3),
                 Easing = new QuadraticEaseOut(),
                 Children =
                 {
-                    new KeyFrame(){ 
+                    new KeyFrame
-                        Setters = 
+                    {
-                        {
+                        Setters = { new Setter(ScrollViewer.OffsetProperty, new Vector(0, from)) },
-                            new Setter(ScrollViewer.OffsetProperty, new Vector(0, from)),
-                        },
                         Cue = new Cue(0.0)
                     },
-                    new KeyFrame()
+                    new KeyFrame
                     {
-                        Setters =
+                        Setters = { new Setter(ScrollViewer.OffsetProperty, new Vector(0, to)) },
-                        {
-                            new Setter(ScrollViewer.OffsetProperty, new Vector(0, to))
-                        },
                         Cue = new Cue(1.0)
                     }
-                
                 }
             };
             _cts.Cancel();
             _cts = new CancellationTokenSource();
-            var token  = _cts.Token;
+            var token = _cts.Token;
             token.Register(_ => _scrollingFromSelection = false, null);
             _scrollingFromSelection = true;
             animation.RunAsync(TargetContainer, token).ContinueWith(_ => _scrollingFromSelection = false, token);
@@ -102,23 +107,19 @@ public class Anchor: ItemsControl
         MarkSelectedContainerByPosition();
     }
 
-    private List<(string, double)> _positions = [];
-
     internal void InvalidateAnchorPositions()
     {
         if (TargetContainer is null) return;
         var items = TargetContainer.GetVisualDescendants().Where(a => GetAnchorId(a) is not null);
-        List<(string, double)> positions = new List<(string, double)>();
+        var positions = new List<(string, double)>();
         foreach (var item in items)
         {
             var anchorId = GetAnchorId(item);
             if (anchorId is null) continue;
             var position = item.TransformToVisual(TargetContainer)?.M32 + TargetContainer.Offset.Y;
-            if (position.HasValue)
+            if (position.HasValue) positions.Add((anchorId, position.Value));
-            {
-                positions.Add((anchorId, position.Value));
-            }
         }
+
         positions.Sort((a, b) => a.Item2.CompareTo(b.Item2));
         _positions = positions;
     }
@@ -126,14 +127,11 @@ public class Anchor: ItemsControl
     protected override void OnLoaded(RoutedEventArgs e)
     {
         base.OnLoaded(e);
-        var target = this.TargetContainer;
+        var target = TargetContainer;
         if (target is null) return;
         TargetContainer?.AddHandler(ScrollViewer.ScrollChangedEvent, OnScrollChanged);
         TargetContainer?.AddHandler(LoadedEvent, OnTargetContainerLoaded);
-        if (TargetContainer?.IsLoaded == true)
+        if (TargetContainer?.IsLoaded == true) InvalidateAnchorPositions();
-        {
-            InvalidateAnchorPositions();
-        }
         MarkSelectedContainerByPosition();
     }
 
@@ -150,13 +148,13 @@ public class Anchor: ItemsControl
         if (source is null) return;
         MarkSelectedContainer(source);
         var target = TargetContainer?.GetVisualDescendants()
-                                    .FirstOrDefault(a => Anchor.GetAnchorId(a) == source.AnchorId);
+                                    .FirstOrDefault(a => GetAnchorId(a) == source.AnchorId);
         if (target is null) return;
         ScrollToAnchor(target);
     }
 
     /// <summary>
-    /// This method is used to expose the protected CreateContainerForItemOverride method to the AnchorItem class.
+    ///     This method is used to expose the protected CreateContainerForItemOverride method to the AnchorItem class.
     /// </summary>
     internal Control CreateContainerForItemOverride_INTERNAL(object? item, int index, object? recycleKey)
     {
@@ -178,8 +176,6 @@ public class Anchor: ItemsControl
         ContainerForItemPreparedOverride(container, item, index);
     }
 
-    private AnchorItem? _selectedContainer;
-    
     internal void MarkSelectedContainer(AnchorItem? item)
     {
         var oldValue = _selectedContainer;
@@ -197,7 +193,7 @@ public class Anchor: ItemsControl
         var topAnchorId = _positions.LastOrDefault(a => a.Item2 <= top).Item1;
         if (topAnchorId is null) return;
         var item = this.GetVisualDescendants().OfType<AnchorItem>()
-            .FirstOrDefault(a => a.AnchorId == topAnchorId);
+                       .FirstOrDefault(a => a.AnchorId == topAnchorId);
         if (item is null) return;
         MarkSelectedContainer(item);
     }

src/Ursa/Controls/Anchor/AnchorItem.cs

@@ -31,7 +31,7 @@ public class AnchorItem : HeaderedItemsControl, ISelectable
     {
         SelectableMixin.Attach<AnchorItem>(IsSelectedProperty);
         PressedMixin.Attach<AnchorItem>();
-        ItemsPanelProperty.OverrideDefaultValue<TreeViewItem>(DefaultPanel);
+        ItemsPanelProperty.OverrideDefaultValue<AnchorItem>(DefaultPanel);
     }
 
     public int Level