Add a ContentBadge control

Toolkit.UI.Controls.Avalonia/ContentBadge/ContentBadge.axaml

@@ -0,0 +1,15 @@
+<ResourceDictionary
+    xmlns="https://github.com/avaloniaui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:controls="using:Toolkit.UI.Controls.Avalonia">
+    <ControlTheme x:Key="{x:Type controls:ContentBadge}" TargetType="controls:ContentBadge">
+        <Setter Property="Template">
+            <ControlTemplate>
+                <Grid>
+                    <ContentPresenter Content="{TemplateBinding Content}" ContentTemplate="{TemplateBinding ContentTemplate}" />
+                    <ContentControl x:Name="BadgeContent" />
+                </Grid>
+            </ControlTemplate>
+        </Setter>
+    </ControlTheme>
+</ResourceDictionary>

Toolkit.UI.Controls.Avalonia/ContentBadge/ContentBadge.cs

@@ -0,0 +1,97 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
+using Avalonia.Media;
+using Path = Avalonia.Controls.Shapes.Path;
+
+namespace Toolkit.UI.Controls.Avalonia;
+
+public class ContentBadge : 
+    ContentControl
+{
+    public static readonly StyledProperty<string?> BadgePathProperty =
+        AvaloniaProperty.Register<ContentBadge, string?>(nameof(BadgePath));
+
+    public static readonly StyledProperty<double> BadgeSizeProperty =
+        AvaloniaProperty.Register<ContentBadge, double>(nameof(BadgeSize), 14);
+
+    private ContentControl? badgeContent;
+
+    public string? BadgePath
+    {
+        get => GetValue(BadgePathProperty);
+        set => SetValue(BadgePathProperty, value);
+    }
+
+    public double BadgeSize
+    {
+        get => GetValue(BadgeSizeProperty);
+        set => SetValue(BadgeSizeProperty, value);
+    }
+
+    public void UpdateClip()
+    {
+        if (Content is Control content &&
+            badgeContent is not null &&
+            BadgePath is { Length: > 0 } && 
+            Geometry.Parse(BadgePath) is Geometry geometry)
+        {
+            double backgroundWidth = DesiredSize.Width;
+            double backgroundHeight = DesiredSize.Height;
+
+            double scaleX = BadgeSize / geometry.Bounds.Width;
+            double scaleY = BadgeSize / geometry.Bounds.Height;
+
+            double adjustedStrokeWidth = Math.Min(scaleX, scaleY) * 8;
+
+            Geometry knockoutGeometry = geometry.GetWidenedGeometry(new Pen(new SolidColorBrush(Colors.Transparent), adjustedStrokeWidth);
+
+            TransformGroup transformGroup = new();
+            transformGroup.Children.Add(new ScaleTransform(scaleX, scaleY));
+
+            double scaledWidth = knockoutGeometry.Bounds.Width * scaleX;
+            double scaledHeight = knockoutGeometry.Bounds.Height * scaleY;
+            double offsetX = backgroundWidth - scaledWidth;
+            double offsetY = backgroundHeight - scaledHeight;
+
+            transformGroup.Children.Add(new TranslateTransform(offsetX, offsetY));
+            knockoutGeometry.Transform = transformGroup;
+
+            CombinedGeometry combinedGeometry = new()
+            {
+                GeometryCombineMode = GeometryCombineMode.Exclude,
+                Geometry1 = new RectangleGeometry { Rect = new Rect(0, 0, backgroundWidth, backgroundHeight) },
+                Geometry2 = knockoutGeometry
+            };
+
+            content.Clip = combinedGeometry;
+
+            Geometry overlayGeometry = geometry.Clone();
+
+            TransformGroup overlayTransformGroup = new();
+            overlayTransformGroup.Children.Add(new ScaleTransform(scaleX, scaleY));
+
+            overlayTransformGroup.Children.Add(new TranslateTransform(offsetX, offsetY));
+            overlayGeometry.Transform = overlayTransformGroup;
+
+            badgeContent.Content = new Path
+            {
+                Data = overlayGeometry,
+                Fill = Foreground
+            };
+        }
+    }
+
+    protected override void OnApplyTemplate(TemplateAppliedEventArgs args)
+    {
+        base.OnApplyTemplate(args);
+        badgeContent = args.NameScope.Get<ContentControl>("BadgeContent");
+    }
+
+    protected override void OnSizeChanged(SizeChangedEventArgs args)
+    {
+        base.OnSizeChanged(args);
+        UpdateClip();
+    }
+}
+

Toolkit.UI.Controls.Avalonia/Overflow/Overflow.cs

@@ -84,16 +84,10 @@ public class Overflow :
         base.OnApplyTemplate(args);
 
         primaryListBox = args.NameScope.Get<ListBox>("PrimaryListBox");
-        if (primaryListBox is not null)
+        primaryListBox?.SetValue(ItemsControl.ItemsSourceProperty, primaryCollection);
-        {
-            primaryListBox.SetValue(ItemsControl.ItemsSourceProperty, primaryCollection);
-        }
 
         secondaryListBox = args.NameScope.Get<ListBox>("SecondaryListBox");
-        if (secondaryListBox is not null)
+        secondaryListBox?.SetValue(ItemsControl.ItemsSourceProperty, secondaryCollection);
-        {
-            secondaryListBox.SetValue(ItemsControl.ItemsSourceProperty, secondaryCollection);
-        }
 
         InitializeCollections();
         UpdateOverflow();

Toolkit.UI.Controls.Avalonia/Themes/ControlResources.axaml

@@ -7,6 +7,7 @@
                 <MergeResourceInclude Source="../PersonPicture/PersonPicture.axaml" />
                 <MergeResourceInclude Source="../SettingsExpander/SettingsExpander.axaml" />
                 <MergeResourceInclude Source="../Overflow/Overflow.axaml" />
+                <MergeResourceInclude Source="../ContentBadge/ContentBadge.axaml" />
             </ResourceDictionary.MergedDictionaries>
         </ResourceDictionary>
     </Styles.Resources>