feat: stack elements.

demo/Ursa.Demo/Pages/AvatarDemo.axaml

@@ -72,6 +72,7 @@
                 <u:Avatar Background="#FDE3CF" Foreground="#F56A00" Content="ZL" />
                 <u:Avatar Background="#87D068" Classes="" Content="YZ" />
             </u:AvatarGroup>
+            <u:Avatar />
         </StackPanel>
     </StackPanel>
 </UserControl>

src/Ursa/Controls/Avatar/AvatarGroup.cs

@@ -8,8 +8,7 @@ public class AvatarGroup : ItemsControl
 {
     public const string PART_RenderMore = "PART_RenderMore";
 
-    private static readonly FuncTemplate<Panel?> DefaultPanel =
+    private static readonly FuncTemplate<Panel?> DefaultPanel = new(() => new AvatarGroupPanel());
-        new(() => new AvatarGroupPanel());
 
     public static readonly StyledProperty<int> MaxCountProperty = AvaloniaProperty.Register<AvatarGroup, int>(
         nameof(MaxCount));

src/Ursa/Controls/Avatar/AvatarGroupPanel.cs

@@ -11,12 +11,13 @@ public class AvatarGroupPanel : Panel
         Size size = new Size();
         availableSize = availableSize.WithWidth(double.PositiveInfinity);
         var children = Children;
-        foreach (var child in children)
+        if (children.Count > 0)
         {
-            child.Measure(availableSize);
+            children[0].Measure(availableSize);
-            Size desiredSize = child.DesiredSize;
+            Size first = children[0].DesiredSize;
-            size = size.WithWidth(size.Width + desiredSize.Width);
+            var width = first.Width + first.Width * (children.Count - 1) * 0.75;
-            size = size.WithHeight(Math.Max(size.Height, desiredSize.Height));
+            size = size.WithWidth(width);
+            size = size.WithHeight(first.Height);
         }
 
         size = size.WithWidth(size.Width);
@@ -30,17 +31,17 @@ public class AvatarGroupPanel : Panel
         var children = Children;
         foreach (var child in children)
         {
+            child.Measure(finalSize);
             Size desiredSize = child.DesiredSize;
             double width = desiredSize.Width;
             double height = Math.Max(desiredSize.Height, finalSize.Height);
             rect = rect.WithX(rect.X + num);
             rect = rect.WithWidth(width);
             rect = rect.WithHeight(height);
-            num = width;
+            num = width * 0.75;
             child.Arrange(rect);
         }
 
-        RaiseEvent(new RoutedEventArgs(StackPanel.HorizontalSnapPointsChangedEvent));
         return finalSize;
     }
 }