feat: init

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

@@ -0,0 +1,12 @@
+<ResourceDictionary xmlns="https://github.com/avaloniaui"
+                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+                    xmlns:u="https://irihi.tech/ursa">
+    <!-- Add Resources Here -->
+    <ControlTheme TargetType="u:MultiComboBox" x:Key="{x:Type u:MultiComboBox}">
+        <Setter Property="Focusable" Value="True"></Setter>
+    </ControlTheme>
+    
+    <ControlTheme TargetType="u:MultiComboBoxItem" x:Key="{x:Type u:MultiComboBoxItem}">
+        <Setter Property="Focusable" Value="True"></Setter>
+    </ControlTheme>
+</ResourceDictionary>

src/Ursa/Controls/ComboBox/MultiComboBox.cs

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+using System.Collections.ObjectModel;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
+
+namespace Ursa.Controls;
+
+public class MultiComboBox: SelectingItemsControl
+{
+    private ComboBox _box;
+
+    private static ITemplate<Panel?> _defaultPanel = new FuncTemplate<Panel?>(() => new VirtualizingStackPanel());
+
+    public static readonly StyledProperty<bool> IsDropDownOpenProperty =
+        ComboBox.IsDropDownOpenProperty.AddOwner<MultiComboBox>();
+    
+    public bool IsDropDownOpen
+    {
+        get => GetValue(IsDropDownOpenProperty);
+        set => SetValue(IsDropDownOpenProperty, value);
+    }
+    
+    static MultiComboBox()
+    {
+        FocusableProperty.OverrideDefaultValue<MultiComboBox>(true);
+        ItemsPanelProperty.OverrideDefaultValue<MultiComboBox>(_defaultPanel);
+    }
+
+    protected override bool NeedsContainerOverride(object? item, int index, out object? recycleKey)
+    {
+        return NeedsContainer<MultiComboBoxItem>(item, out recycleKey);
+    }
+
+    protected override Control CreateContainerForItemOverride(object? item, int index, object? recycleKey)
+    {
+        return new MultiComboBoxItem();
+    }
+    
+    internal void ItemFocused(MultiComboBoxItem dropDownItem)
+    {
+        if (IsDropDownOpen && dropDownItem.IsFocused && dropDownItem.IsArrangeValid)
+        {
+            dropDownItem.BringIntoView();
+        }
+    }
+}

src/Ursa/Controls/ComboBox/MultiComboBoxItem.cs

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+using Avalonia;
+using Avalonia.Controls;
+using Irihi.Avalonia.Shared.Helpers;
+
+namespace Ursa.Controls;
+
+public class MultiComboBoxItem: ListBoxItem
+{
+    public MultiComboBoxItem()
+    {
+        this.GetObservable(IsFocusedProperty).Subscribe(a=> {
+            if (a)
+            {
+                (Parent as MultiComboBox)?.ItemFocused(this);
+            }
+        });
+    }
+}