Added a set of immutable brushes.

Make `SolidColorBrush` immutable, but make the static `Brushes`
properties return immutable brushes. The immutable brushes will be
needed by the deferred renderer.

src/Avalonia.Themes.Default/Accents/BaseLight.xaml

@@ -1,6 +1,5 @@
 <Style xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-       xmlns:mut="https://github.com/avaloniaui/mutable"
        xmlns:sys="clr-namespace:System;assembly=mscorlib">
   <Style.Resources>
     <SolidColorBrush x:Key="ThemeBackgroundBrush">#FFFFFFFF</SolidColorBrush>

src/Avalonia.Visuals/Avalonia.Visuals.csproj

@@ -73,6 +73,14 @@
     <Compile Include="Media\ILinearGradientBrush.cs" />
     <Compile Include="Media\Imaging\IImageBrush.cs" />
     <Compile Include="Media\Imaging\WritableBitmap.cs" />
+    <Compile Include="Media\Immutable\ImmutableGradientBrush.cs" />
+    <Compile Include="Media\Immutable\ImmutableImageBrush.cs" />
+    <Compile Include="Media\Immutable\ImmutableLinearGradientBrush.cs" />
+    <Compile Include="Media\Immutable\ImmutableRadialGradientBrush.cs" />
+    <Compile Include="Media\Immutable\ImmutableSolidColorBrush.cs" />
+    <Compile Include="Media\Immutable\ImmutableTileBrush.cs" />
+    <Compile Include="Media\Immutable\ImmutableVisualBrush.cs" />
+    <Compile Include="Media\IMutableBrush.cs" />
     <Compile Include="Media\IRadialGradientBrush.cs" />
     <Compile Include="Media\ITileBrush.cs" />
     <Compile Include="Media\IVisualBrush.cs" />
@@ -88,7 +96,6 @@
     <Compile Include="Media\ISolidColorBrush.cs" />
     <Compile Include="Media\LineGeometry.cs" />
     <Compile Include="Media\LineSegment.cs" />
-    <Compile Include="Media\Mutable\SolidColorBrush.cs" />
     <Compile Include="Media\PathGeometryCollections.cs" />
     <Compile Include="Media\PathFigure.cs" />
     <Compile Include="Media\PathGeometry.cs" />

src/Avalonia.Visuals/Media/Brush.cs

@@ -46,7 +46,8 @@ namespace Avalonia.Media
 
                 if (member != null)
                 {
-                    return (IBrush)member.GetValue(null);
+                    var brush = (ISolidColorBrush)member.GetValue(null);
+                    return new SolidColorBrush(brush.Color, brush.Opacity);
                 }
                 else
                 {

src/Avalonia.Visuals/Media/IMutableBrush.cs

@@ -0,0 +1,16 @@
+using System;
+
+namespace Avalonia.Media
+{
+    /// <summary>
+    /// Represents a mutable brush which can return an immutable clone of itself.
+    /// </summary>
+    public interface IMutableBrush : IBrush
+    {
+        /// <summary>
+        /// Creates an immutable clone of the brush.
+        /// </summary>
+        /// <returns>The immutable clone.</returns>
+        IBrush ToImmutable();
+    }
+}

src/Avalonia.Visuals/Media/Immutable/ImmutableGradientBrush.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Avalonia.Media.Immutable
+{
+    /// <summary>
+    /// A brush that draws with a gradient.
+    /// </summary>
+    public abstract class ImmutableGradientBrush : IGradientBrush
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableGradientBrush"/> class.
+        /// </summary>
+        /// <param name="gradientStops">The gradient stops.</param>
+        /// <param name="opacity">The opacity of the brush.</param>
+        /// <param name="spreadMethod">The spread method.</param>
+        protected ImmutableGradientBrush(
+            IReadOnlyList<GradientStop> gradientStops,
+            double opacity,
+            GradientSpreadMethod spreadMethod)
+        {
+            GradientStops = gradientStops;
+            Opacity = opacity;
+            SpreadMethod = spreadMethod;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableGradientBrush"/> class.
+        /// </summary>
+        /// <param name="source">The brush from which this brush's properties should be copied.</param>
+        protected ImmutableGradientBrush(IGradientBrush source)
+            : this(source.GradientStops.ToList(), source.Opacity, source.SpreadMethod)
+        {
+
+        }
+
+        /// <inheritdoc/>
+        public IReadOnlyList<GradientStop> GradientStops { get; }
+
+        /// <inheritdoc/>
+        public double Opacity { get; }
+
+        /// <inheritdoc/>
+        public GradientSpreadMethod SpreadMethod { get; }
+    }
+}

src/Avalonia.Visuals/Media/Immutable/ImmutableImageBrush.cs

@@ -0,0 +1,58 @@
+using System;
+using Avalonia.Media.Imaging;
+
+namespace Avalonia.Media.Immutable
+{
+    /// <summary>
+    /// Paints an area with an <see cref="IBitmap"/>.
+    /// </summary>
+    internal class ImmutableImageBrush : ImmutableTileBrush, IImageBrush
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableImageBrush"/> class.
+        /// </summary>
+        /// <param name="source">The image to draw.</param>
+        /// <param name="alignmentX">The horizontal alignment of a tile in the destination.</param>
+        /// <param name="alignmentY">The vertical alignment of a tile in the destination.</param>
+        /// <param name="destinationRect">The rectangle on the destination in which to paint a tile.</param>
+        /// <param name="opacity">The opacity of the brush.</param>
+        /// <param name="sourceRect">The rectangle of the source image that will be displayed.</param>
+        /// <param name="stretch">
+        /// How the source rectangle will be stretched to fill the destination rect.
+        /// </param>
+        /// <param name="tileMode">The tile mode.</param>
+        public ImmutableImageBrush(
+            IBitmap source,
+            AlignmentX alignmentX = AlignmentX.Center,
+            AlignmentY alignmentY = AlignmentY.Center,
+            RelativeRect? destinationRect = null,
+            double opacity = 1,
+            RelativeRect? sourceRect = null,
+            Stretch stretch = Stretch.Uniform,
+            TileMode tileMode = TileMode.None)
+            : base(
+                  alignmentX,
+                  alignmentY,
+                  destinationRect ?? RelativeRect.Fill,
+                  opacity,
+                  sourceRect ?? RelativeRect.Fill,
+                  stretch,
+                  tileMode)
+        {
+            Source = source;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableImageBrush"/> class.
+        /// </summary>
+        /// <param name="source">The brush from which this brush's properties should be copied.</param>
+        public ImmutableImageBrush(IImageBrush source)
+            : base(source)
+        {
+            Source = source.Source;
+        }
+
+        /// <inheritdoc/>
+        public IBitmap Source { get; }
+    }
+}

src/Avalonia.Visuals/Media/Immutable/ImmutableLinearGradientBrush.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Avalonia.Media.Immutable
+{
+    /// <summary>
+    /// A brush that draws with a linear gradient.
+    /// </summary>
+    public class ImmutableLinearGradientBrush : ImmutableGradientBrush, ILinearGradientBrush
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableLinearGradientBrush"/> class.
+        /// </summary>
+        /// <param name="gradientStops">The gradient stops.</param>
+        /// <param name="opacity">The opacity of the brush.</param>
+        /// <param name="spreadMethod">The spread method.</param>
+        /// <param name="startPoint">The start point for the gradient.</param>
+        /// <param name="endPoint">The end point for the gradient.</param>
+        public ImmutableLinearGradientBrush(
+            IReadOnlyList<GradientStop> gradientStops,
+            double opacity = 1,
+            GradientSpreadMethod spreadMethod = GradientSpreadMethod.Pad,
+            RelativePoint? startPoint = null,
+            RelativePoint? endPoint = null)
+            : base(gradientStops, opacity, spreadMethod)
+        {
+            StartPoint = startPoint ?? RelativePoint.TopLeft;
+            EndPoint = endPoint ?? RelativePoint.BottomRight;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableLinearGradientBrush"/> class.
+        /// </summary>
+        /// <param name="source">The brush from which this brush's properties should be copied.</param>
+        public ImmutableLinearGradientBrush(ILinearGradientBrush source)
+            : base(source)
+        {
+            StartPoint = source.StartPoint;
+            EndPoint = source.EndPoint;
+        }
+
+        /// <inheritdoc/>
+        public RelativePoint StartPoint { get; }
+
+        /// <inheritdoc/>
+        public RelativePoint EndPoint { get; }
+    }
+}

src/Avalonia.Visuals/Media/Immutable/ImmutableRadialGradientBrush.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+
+namespace Avalonia.Media.Immutable
+{
+    /// <summary>
+    /// A brush that draws with a radial gradient.
+    /// </summary>
+    public class ImmutableRadialGradientBrush : ImmutableGradientBrush, IRadialGradientBrush
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableRadialGradientBrush"/> class.
+        /// </summary>
+        /// <param name="gradientStops">The gradient stops.</param>
+        /// <param name="opacity">The opacity of the brush.</param>
+        /// <param name="spreadMethod">The spread method.</param>
+        /// <param name="center">The start point for the gradient.</param>
+        /// <param name="gradientOrigin">
+        /// The location of the two-dimensional focal point that defines the beginning of the gradient.
+        /// </param>
+        /// <param name="radius">
+        /// The horizontal and vertical radius of the outermost circle of the radial gradient.
+        /// </param>
+        public ImmutableRadialGradientBrush(
+            IReadOnlyList<GradientStop> gradientStops,
+            double opacity = 1,
+            GradientSpreadMethod spreadMethod = GradientSpreadMethod.Pad,
+            RelativePoint? center = null,
+            RelativePoint? gradientOrigin = null,
+            double radius = 0.5)
+            : base(gradientStops, opacity, spreadMethod)
+        {
+            Center = center ?? RelativePoint.Center;
+            GradientOrigin = gradientOrigin ?? RelativePoint.Center;
+            Radius = radius;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableRadialGradientBrush"/> class.
+        /// </summary>
+        /// <param name="source">The brush from which this brush's properties should be copied.</param>
+        public ImmutableRadialGradientBrush(IRadialGradientBrush source)
+            : base(source)
+        {
+            Center = source.Center;
+            GradientOrigin = source.GradientOrigin;
+            Radius = source.Radius;
+        }
+
+        /// <inheritdoc/>
+        public RelativePoint Center { get; }
+
+        /// <inheritdoc/>
+        public RelativePoint GradientOrigin { get; }
+
+        /// <inheritdoc/>
+        public double Radius { get; }
+    }
+}

src/Avalonia.Visuals/Media/Immutable/ImmutableSolidColorBrush.cs

@@ -0,0 +1,59 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+namespace Avalonia.Media.Immutable
+{
+    /// <summary>
+    /// Fills an area with a solid color.
+    /// </summary>
+    public struct ImmutableSolidColorBrush : ISolidColorBrush
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableSolidColorBrush"/> class.
+        /// </summary>
+        /// <param name="color">The color to use.</param>
+        /// <param name="opacity">The opacity of the brush.</param>
+        public ImmutableSolidColorBrush(Color color, double opacity = 1)
+        {
+            Color = color;
+            Opacity = opacity;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableSolidColorBrush"/> class.
+        /// </summary>
+        /// <param name="color">The color to use.</param>
+        public ImmutableSolidColorBrush(uint color)
+            : this(Color.FromUInt32(color))
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableSolidColorBrush"/> class.
+        /// </summary>
+        /// <param name="source">The brush from which this brush's properties should be copied.</param>
+        public ImmutableSolidColorBrush(ISolidColorBrush source)
+            : this(source.Color, source.Opacity)
+        {
+        }
+
+        /// <summary>
+        /// Gets the color of the brush.
+        /// </summary>
+        public Color Color { get; }
+
+        /// <summary>
+        /// Gets the opacity of the brush.
+        /// </summary>
+        public double Opacity { get; }
+
+        /// <summary>
+        /// Returns a string representation of the brush.
+        /// </summary>
+        /// <returns>A string representation of the brush.</returns>
+        public override string ToString()
+        {
+            return Color.ToString();
+        }
+    }
+}

src/Avalonia.Visuals/Media/Immutable/ImmutableTileBrush.cs

@@ -0,0 +1,77 @@
+using System;
+
+namespace Avalonia.Media.Immutable
+{
+    /// <summary>
+    /// A brush which displays a repeating image.
+    /// </summary>
+    public abstract class ImmutableTileBrush : ITileBrush
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImageBrush"/> class.
+        /// </summary>
+        /// <param name="alignmentX">The horizontal alignment of a tile in the destination.</param>
+        /// <param name="alignmentY">The vertical alignment of a tile in the destination.</param>
+        /// <param name="destinationRect">The rectangle on the destination in which to paint a tile.</param>
+        /// <param name="opacity">The opacity of the brush.</param>
+        /// <param name="sourceRect">The rectangle of the source image that will be displayed.</param>
+        /// <param name="stretch">
+        /// How the source rectangle will be stretched to fill the destination rect.
+        /// </param>
+        /// <param name="tileMode">The tile mode.</param>
+        protected ImmutableTileBrush(
+            AlignmentX alignmentX,
+            AlignmentY alignmentY,
+            RelativeRect destinationRect,
+            double opacity,
+            RelativeRect sourceRect,
+            Stretch stretch,
+            TileMode tileMode)
+        {
+            AlignmentX = alignmentX;
+            AlignmentY = alignmentY;
+            DestinationRect = destinationRect;
+            Opacity = opacity;
+            SourceRect = sourceRect;
+            Stretch = stretch;
+            TileMode = tileMode;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImageBrush"/> class.
+        /// </summary>
+        /// <param name="source">The brush from which this brush's properties should be copied.</param>
+        protected ImmutableTileBrush(ITileBrush source)
+            : this(
+                  source.AlignmentX,
+                  source.AlignmentY,
+                  source.DestinationRect,
+                  source.Opacity,
+                  source.SourceRect,
+                  source.Stretch,
+                  source.TileMode)
+        {
+        }
+
+        /// <inheritdoc/>
+        public AlignmentX AlignmentX { get; }
+
+        /// <inheritdoc/>
+        public AlignmentY AlignmentY { get; }
+
+        /// <inheritdoc/>
+        public RelativeRect DestinationRect { get; }
+
+        /// <inheritdoc/>
+        public double Opacity { get; }
+
+        /// <inheritdoc/>
+        public RelativeRect SourceRect { get; }
+
+        /// <inheritdoc/>
+        public Stretch Stretch { get; }
+
+        /// <inheritdoc/>
+        public TileMode TileMode { get; }
+    }
+}

src/Avalonia.Visuals/Media/Immutable/ImmutableVisualBrush.cs

@@ -0,0 +1,58 @@
+using System;
+using Avalonia.VisualTree;
+
+namespace Avalonia.Media.Immutable
+{
+    /// <summary>
+    /// Paints an area with an <see cref="IVisual"/>.
+    /// </summary>
+    internal class ImmutableVisualBrush : ImmutableTileBrush, IVisualBrush
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableImageBrush"/> class.
+        /// </summary>
+        /// <param name="visual">The visual to draw.</param>
+        /// <param name="alignmentX">The horizontal alignment of a tile in the destination.</param>
+        /// <param name="alignmentY">The vertical alignment of a tile in the destination.</param>
+        /// <param name="destinationRect">The rectangle on the destination in which to paint a tile.</param>
+        /// <param name="opacity">The opacity of the brush.</param>
+        /// <param name="sourceRect">The rectangle of the source image that will be displayed.</param>
+        /// <param name="stretch">
+        /// How the source rectangle will be stretched to fill the destination rect.
+        /// </param>
+        /// <param name="tileMode">The tile mode.</param>
+        public ImmutableVisualBrush(
+            IVisual visual,
+            AlignmentX alignmentX = AlignmentX.Center,
+            AlignmentY alignmentY = AlignmentY.Center,
+            RelativeRect? destinationRect = null,
+            double opacity = 1,
+            RelativeRect? sourceRect = null,
+            Stretch stretch = Stretch.Uniform,
+            TileMode tileMode = TileMode.None)
+            : base(
+                  alignmentX,
+                  alignmentY,
+                  destinationRect ?? RelativeRect.Fill,
+                  opacity,
+                  sourceRect ?? RelativeRect.Fill,
+                  stretch,
+                  tileMode)
+        {
+            Visual = visual;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImmutableVisualBrush"/> class.
+        /// </summary>
+        /// <param name="source">The brush from which this brush's properties should be copied.</param>
+        public ImmutableVisualBrush(IVisualBrush source)
+            : base(source)
+        {
+            Visual = source.Visual;
+        }
+
+        /// <inheritdoc/>
+        public IVisual Visual { get; }
+    }
+}

src/Avalonia.Visuals/Media/Mutable/SolidColorBrush.cs

@@ -1,35 +0,0 @@
-// Copyright (c) The Avalonia Project. All rights reserved.
-// Licensed under the MIT license. See licence.md file in the project root for full license information.
-
-namespace Avalonia.Media.Mutable
-{
-    /// <summary>
-    /// Fills an area with a solid color.
-    /// </summary>
-    /// <remarks>
-    /// This is a mutable version of the normal immutable <see cref="Avalonia.Media.SolidColorBrush"/>
-    /// for use in XAML. XAML really needs support for immutable data...
-    /// </remarks>
-    public class SolidColorBrush : Brush, ISolidColorBrush
-    {
-        public static readonly DirectProperty<SolidColorBrush, Color> ColorProperty =
-            AvaloniaProperty.RegisterDirect<SolidColorBrush, Color>(
-                "Color",
-                o => o.Color,
-                (o, v) => o.Color = v);
-
-        /// <summary>
-        /// Gets the color of the brush.
-        /// </summary>
-        public Color Color { get; set; }
-
-        /// <summary>
-        /// Returns a string representation of the brush.
-        /// </summary>
-        /// <returns>A string representation of the brush.</returns>
-        public override string ToString()
-        {
-            return Color.ToString();
-        }
-    }
-}

src/Avalonia.Visuals/Media/SolidColorBrush.cs

@@ -1,13 +1,28 @@
 // Copyright (c) The Avalonia Project. All rights reserved.
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
+using System;
+
 namespace Avalonia.Media
 {
     /// <summary>
     /// Fills an area with a solid color.
     /// </summary>
-    public class SolidColorBrush : ISolidColorBrush
+    public class SolidColorBrush : Brush, ISolidColorBrush, IMutableBrush
     {
+        /// <summary>
+        /// Defines the <see cref="Color"/> property.
+        /// </summary>
+        public static readonly StyledProperty<Color> ColorProperty =
+            AvaloniaProperty.Register<SolidColorBrush, Color>(nameof(Color));
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SolidColorBrush"/> class.
+        /// </summary>
+        public SolidColorBrush()
+        {
+        }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="SolidColorBrush"/> class.
         /// </summary>
@@ -29,14 +44,13 @@ namespace Avalonia.Media
         }
 
         /// <summary>
-        /// Gets the color of the brush.
+        /// Gets or sets the color of the brush.
         /// </summary>
-        public Color Color { get; }
+        public Color Color
-
+        {
-        /// <summary>
+            get { return GetValue(ColorProperty); }
-        /// Gets the opacity of the brush.
+            set { SetValue(ColorProperty, value); }
-        /// </summary>
+        }
-        public double Opacity { get; }
 
         /// <summary>
         /// Returns a string representation of the brush.
@@ -46,5 +60,11 @@ namespace Avalonia.Media
         {
             return Color.ToString();
         }
+
+        /// <inheritdoc/>
+        IBrush IMutableBrush.ToImmutable()
+        {
+            return new Immutable.ImmutableSolidColorBrush(this);
+        }
     }
 }

src/Avalonia.Visuals/Properties/AssemblyInfo.cs

@@ -7,4 +7,3 @@ using Avalonia.Metadata;
 [assembly: AssemblyTitle("Avalonia.Visuals")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Animation")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Media")]
-[assembly: XmlnsDefinition("https://github.com/avaloniaui/mutable", "Avalonia.Media.Mutable")]

src/Gtk/Avalonia.Cairo/Media/DrawingContext.cs

@@ -294,7 +294,7 @@ namespace Avalonia.Cairo.Media
 
         private BrushImpl CreateBrushImpl(IBrush brush, Size destinationSize)
         {
-            var solid = brush as SolidColorBrush;
+            var solid = brush as ISolidColorBrush;
             var linearGradientBrush = brush as ILinearGradientBrush;
             var radialGradientBrush = brush as IRadialGradientBrush;
             var imageBrush = brush as IImageBrush;

src/Gtk/Avalonia.Cairo/Media/SolidColorBrushImpl.cs

@@ -5,7 +5,7 @@ namespace Avalonia.Cairo
 {
 	public class SolidColorBrushImpl : BrushImpl
 	{
-		public SolidColorBrushImpl(Avalonia.Media.SolidColorBrush brush, double opacityOverride = 1.0f)
+		public SolidColorBrushImpl(Avalonia.Media.ISolidColorBrush brush, double opacityOverride = 1.0f)
 		{
 			var color = brush?.Color.ToCairo() ?? new Color();
 

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/Style2.xaml

@@ -1,9 +1,8 @@
 <Style xmlns="https://github.com/avaloniaui"
-       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
-       xmlns:mut="https://github.com/avaloniaui/mutable">
   <Style.Resources>
-    <mut:SolidColorBrush x:Key="RedBrush" Color="{StyleResource Red}"/>
+    <SolidColorBrush x:Key="RedBrush" Color="{StyleResource Red}"/>
-    <mut:SolidColorBrush x:Key="GreenBrush" Color="{StyleResource Green}"/>
+    <SolidColorBrush x:Key="GreenBrush" Color="{StyleResource Green}"/>
-    <mut:SolidColorBrush x:Key="BlueBrush" Color="{StyleResource Blue}"/>
+    <SolidColorBrush x:Key="BlueBrush" Color="{StyleResource Blue}"/>
   </Style.Resources>
 </Style>

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs

@@ -124,13 +124,12 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             {
                 var xaml = @"
 <Window xmlns='https://github.com/avaloniaui'
-        xmlns:mut='https://github.com/avaloniaui/mutable'
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
     <Window.Styles>
         <Style>
             <Style.Resources>
                 <Color x:Key='color'>#ff506070</Color>
-                <mut:SolidColorBrush x:Key='brush' Color='{StyleResource color}'/>
+                <SolidColorBrush x:Key='brush' Color='{StyleResource color}'/>
             </Style.Resources>
         </Style>
     </Window.Styles>
@@ -139,12 +138,12 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
 
                 var loader = new AvaloniaXamlLoader();
                 var window = (Window)loader.Load(xaml);
-                var brush = (Avalonia.Media.Mutable.SolidColorBrush)window.FindStyleResource("brush");
+                var brush = (ISolidColorBrush)window.FindStyleResource("brush");
                 var button = window.FindControl<Button>("button");
 
                 DelayedBinding.ApplyBindings(button);
 
-                var buttonBrush = (Avalonia.Media.Mutable.SolidColorBrush)button.Background;
+                var buttonBrush = (ISolidColorBrush)button.Background;
 
                 Assert.Equal(0xff506070, brush.Color.ToUint32());
                 Assert.Equal(0xff506070, buttonBrush.Color.ToUint32());
@@ -156,19 +155,18 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
         {
             var xaml = @"
 <Styles xmlns='https://github.com/avaloniaui'
-        xmlns:mut='https://github.com/avaloniaui/mutable'
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
     <Style>
         <Style.Resources>
             <Color x:Key='color'>#ff506070</Color>
-            <mut:SolidColorBrush x:Key='brush' Color='{StyleResource color}'/>
+            <SolidColorBrush x:Key='brush' Color='{StyleResource color}'/>
         </Style.Resources>
     </Style>
 </Styles>";
 
             var loader = new AvaloniaXamlLoader();
             var styles = (Styles)loader.Load(xaml);
-            var brush = (Avalonia.Media.Mutable.SolidColorBrush)styles.FindResource("brush");
+            var brush = (ISolidColorBrush)styles.FindResource("brush");
 
             Assert.Equal(0xff506070, brush.Color.ToUint32());
         }
@@ -178,7 +176,6 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
         {
             var xaml = @"
 <Styles xmlns='https://github.com/avaloniaui'
-        xmlns:mut='https://github.com/avaloniaui/mutable'
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
     <Style>
         <Style.Resources>
@@ -187,14 +184,14 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
     </Style>
     <Style>
         <Style.Resources>
-            <mut:SolidColorBrush x:Key='brush' Color='{StyleResource color}'/>
+            <SolidColorBrush x:Key='brush' Color='{StyleResource color}'/>
         </Style.Resources>
     </Style>
 </Styles>";
 
             var loader = new AvaloniaXamlLoader();
             var styles = (Styles)loader.Load(xaml);
-            var brush = (Avalonia.Media.Mutable.SolidColorBrush)styles.FindResource("brush");
+            var brush = (ISolidColorBrush)styles.FindResource("brush");
 
             Assert.Equal(0xff506070, brush.Color.ToUint32());
         }
@@ -206,7 +203,6 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             {
                 var xaml = @"
 <Window xmlns='https://github.com/avaloniaui'
-        xmlns:mut='https://github.com/avaloniaui/mutable'
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
     <Window.Styles>
         <StyleInclude Source='resm:Avalonia.Markup.Xaml.UnitTests.Xaml.Style1.xaml?assembly=Avalonia.Markup.Xaml.UnitTests'/>
@@ -218,7 +214,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
                 var loader = new AvaloniaXamlLoader();
                 var window = (Window)loader.Load(xaml);
                 var border = window.FindControl<Border>("border");
-                var borderBrush = (Avalonia.Media.Mutable.SolidColorBrush)border.Background;
+                var borderBrush = (ISolidColorBrush)border.Background;
 
                 Assert.NotNull(borderBrush);
                 Assert.Equal(0xffff0000, borderBrush.Color.ToUint32());