Merge pull request #393 from irihitech/selectable

Introduce IsSelectable for TreeComboBoxItem.

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

@@ -217,6 +217,7 @@
         <Setter Property="Background" Value="{DynamicResource TreeViewItemDefaultBackground}" />
         <Setter Property="Foreground" Value="{DynamicResource TreeViewItemDefaultForeground}" />
         <Setter Property="CornerRadius" Value="3" />
+        <Setter Property="MinHeight" Value="32"></Setter>
         <Setter Property="VerticalAlignment" Value="Center" />
         <Setter Property="Template">
             <ControlTemplate TargetType="u:TreeComboBoxItem">