Fix runtime crash when adding controls (anything other than MultiComboBoxItem with text content) to a MultiComboBox in axaml

demo/Ursa.Demo/Pages/MultiComboBoxDemo.axaml

@@ -59,6 +59,8 @@
             <u:MultiComboBoxItem>option 1</u:MultiComboBoxItem>
             <u:MultiComboBoxItem>option 2</u:MultiComboBoxItem>
             <u:MultiComboBoxItem>option 3</u:MultiComboBoxItem>
+            <u:MultiComboBoxItem><Button>option 4</Button></u:MultiComboBoxItem>
+            <Button>option 5</Button>
         </u:MultiComboBox>
     </StackPanel>
 </UserControl>

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

@@ -135,7 +135,14 @@
                             Command="{TemplateBinding Command}"
                             CommandParameter="{TemplateBinding}"
                             Content="{StaticResource ClosableTagCloseIconGlyph}" />
+                        <Border 
+                            IsVisible="{TemplateBinding VisualContent, Converter={x:Static ObjectConverters.IsNotNull}}"
+                            Background="{TemplateBinding VisualContent}"
+                            Width="{TemplateBinding VisualContentWidth}"
+                            Height="{TemplateBinding VisualContentHeight}"
+                            IsHitTestVisible="False" />
                         <ContentPresenter
+                            IsVisible="{TemplateBinding VisualContent, Converter={x:Static ObjectConverters.IsNull}}"
                             VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                             Content="{TemplateBinding Content}"
                             ContentTemplate="{TemplateBinding ContentTemplate}"

src/Ursa/Controls/ComboBox/MultiComboBox.cs

@@ -187,6 +187,8 @@ public class MultiComboBox : SelectingItemsControl, IInnerContentControl, IPopup
             return;
         }
         
+        container.DataContext = item;
+
         base.PrepareContainerForItemOverride(container, item, index);
     }
 
@@ -213,7 +215,7 @@ public class MultiComboBox : SelectingItemsControl, IInnerContentControl, IPopup
     {
         if (o is StyledElement s)
         {
-            var data = s.DataContext;
+            var data = s is ClosableTag { VisualContent: not null } c ? c.Content : s.DataContext;
             SelectedItems?.Remove(data);
             var item = Items.FirstOrDefault(a => ReferenceEquals(a, data));
             if (item is not null)

src/Ursa/Controls/ComboBox/MultiComboBoxSelectedItemList.cs

@@ -1,6 +1,8 @@
 using System.Windows.Input;
 using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Layout;
+using Avalonia.Media;
 
 namespace Ursa.Controls;
 
@@ -31,6 +33,15 @@ public class MultiComboBoxSelectedItemList: ItemsControl
         if (container is ClosableTag tag)
         {
             tag.Command = RemoveCommand;
+            if (item is Layoutable visualContent)
+            {
+                tag.VisualContent = new VisualBrush
+                {
+                    Visual = visualContent,
+                };
+                tag.VisualContentWidth = visualContent.Bounds.Width;
+                tag.VisualContentHeight = visualContent.Bounds.Height;
+            }
         }
     }
 }

src/Ursa/Controls/TagInput/ClosableTag.cs

@@ -2,6 +2,7 @@ using System.Windows.Input;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Metadata;
+using Avalonia.Media;
 
 namespace Ursa.Controls;
 
@@ -13,9 +14,36 @@ public class ClosableTag : ContentControl
     public static readonly StyledProperty<ICommand?> CommandProperty = AvaloniaProperty.Register<ClosableTag, ICommand?>(
         nameof(Command));
     
+    public static readonly StyledProperty<VisualBrush?> VisualContentProperty = AvaloniaProperty.Register<ClosableTag, VisualBrush?>(
+        nameof(VisualContent));
+    
+    public static readonly StyledProperty<double?> VisualContentWidthProperty = AvaloniaProperty.Register<ClosableTag, double?>(
+        nameof(VisualContentWidth));
+    
+    public static readonly StyledProperty<double?> VisualContentHeightProperty = AvaloniaProperty.Register<ClosableTag, double?>(
+        nameof(VisualContentHeight));
+
     public ICommand? Command
     {
         get => GetValue(CommandProperty);
         set => SetValue(CommandProperty, value);
     }
+    
+    public VisualBrush? VisualContent
+    {
+        get => GetValue(VisualContentProperty);
+        set => SetValue(VisualContentProperty, value);
+    }
+    
+    public double? VisualContentWidth
+    {
+        get => GetValue(VisualContentWidthProperty);
+        set => SetValue(VisualContentWidthProperty, value);
+    }
+    
+    public double? VisualContentHeight
+    {
+        get => GetValue(VisualContentHeightProperty);
+        set => SetValue(VisualContentHeightProperty, value);
+    }
 }