move border container implementation up to decorator

Author: emmauss

src/Avalonia.Controls/Border.cs

@@ -16,7 +16,7 @@ namespace Avalonia.Controls
     /// A control which decorates a child with a border and background.
     /// </summary>
 #pragma warning disable CS0618 // Type or member is obsolete
-    public partial class Border : Decorator, IVisualWithRoundRectClip, IContainer
+    public partial class Border : Decorator, IVisualWithRoundRectClip
 #pragma warning restore CS0618 // Type or member is obsolete
     {
         /// <summary>
@@ -57,25 +57,10 @@ public partial class Border : Decorator, IVisualWithRoundRectClip, IContainer
         public static readonly StyledProperty<BoxShadows> BoxShadowProperty =
             AvaloniaProperty.Register<Border, BoxShadows>(nameof(BoxShadow));
 
-        /// <summary>
-        /// Defines the <see cref="ContainerType"/> property
-        /// </summary>
-        public static readonly StyledProperty<ContainerType> ContainerTypeProperty =
-            AvaloniaProperty.Register<Border, ContainerType>(nameof(ContainerType),
-            defaultValue: ContainerType.Normal);
-
-        /// <summary>
-        /// Defines the <see cref="ContainerName"/> property
-        /// </summary>
-        public static readonly StyledProperty<string?> ContainerNameProperty =
-            AvaloniaProperty.Register<Border, string?>(nameof(ContainerName),
-            defaultValue: null);
-
         private readonly BorderRenderHelper _borderRenderHelper = new BorderRenderHelper();
         private Thickness? _layoutThickness;
         private double _scale;
         private CompositionBorderVisual? _borderVisual;
-        private VisualQueryProvider? _queryProvider;
 
         /// <summary>
         /// Initializes static members of the <see cref="Border"/> class.
@@ -162,23 +147,6 @@ public BoxShadows BoxShadow
             set => SetValue(BoxShadowProperty, value);
         }
 
-        /// <inheritdoc/>
-        public ContainerType ContainerType
-        {
-            get => GetValue(ContainerTypeProperty);
-            set => SetValue(ContainerTypeProperty, value);
-        }
-
-        /// <inheritdoc/>
-        public string? ContainerName
-        {
-            get => GetValue(ContainerNameProperty);
-            set => SetValue(ContainerNameProperty, value);
-        }
-
-        /// <inheritdoc/>
-        public VisualQueryProvider QueryProvider => _queryProvider ??= new VisualQueryProvider(this);
-
         private Thickness LayoutThickness
         {
             get

src/Avalonia.Controls/Decorator.cs

@@ -1,12 +1,23 @@
+using System;
+using Avalonia.Collections;
+using Avalonia.Controls;
+using Avalonia.Controls.Shapes;
+using Avalonia.Controls.Utils;
 using Avalonia.Layout;
+using Avalonia.Media;
 using Avalonia.Metadata;
+using Avalonia.Platform;
+using Avalonia.Rendering.Composition;
+using Avalonia.Styling;
+using Avalonia.Utilities;
+using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
 {
     /// <summary>
     /// Base class for controls which decorate a single child control.
     /// </summary>
-    public class Decorator : Control
+    public class Decorator : Control, IContainer
     {
         /// <summary>
         /// Defines the <see cref="Child"/> property.
@@ -20,6 +31,22 @@ public class Decorator : Control
         public static readonly StyledProperty<Thickness> PaddingProperty =
             AvaloniaProperty.Register<Decorator, Thickness>(nameof(Padding));
 
+        /// <summary>
+        /// Defines the <see cref="ContainerName"/> property
+        /// </summary>
+        public static readonly StyledProperty<string?> ContainerNameProperty =
+            AvaloniaProperty.Register<Decorator, string?>(nameof(ContainerName),
+            defaultValue: null);
+
+        /// <summary>
+        /// Defines the <see cref="ContainerType"/> property
+        /// </summary>
+        public static readonly StyledProperty<ContainerType> ContainerTypeProperty =
+            AvaloniaProperty.Register<Decorator, ContainerType>(nameof(ContainerType),
+            defaultValue: ContainerType.Normal);
+
+        private VisualQueryProvider? _queryProvider;
+
         /// <summary>
         /// Initializes static members of the <see cref="Decorator"/> class.
         /// </summary>
@@ -48,6 +75,23 @@ public Thickness Padding
             set => SetValue(PaddingProperty, value);
         }
 
+        /// <inheritdoc/>
+        public string? ContainerName
+        {
+            get => GetValue(ContainerNameProperty);
+            set => SetValue(ContainerNameProperty, value);
+        }
+
+        /// <inheritdoc/>
+        public ContainerType ContainerType
+        {
+            get => GetValue(ContainerTypeProperty);
+            set => SetValue(ContainerTypeProperty, value);
+        }
+
+        /// <inheritdoc/>
+        public VisualQueryProvider QueryProvider => _queryProvider ??= new VisualQueryProvider(this);
+
         /// <inheritdoc/>
         protected override Size MeasureOverride(Size availableSize)
         {