From d1192901a1aadbe20abb669cb9f26363b0cb8bd3 Mon Sep 17 00:00:00 2001
From: Dan Walmsley <dan@walms.co.uk>
Date: Wed, 12 May 2021 18:20:21 +0100
Subject: [PATCH 01/15] add contentattribute to image.

---
 src/Avalonia.Controls/Image.cs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/Avalonia.Controls/Image.cs b/src/Avalonia.Controls/Image.cs
index 5fc7d8b6b6..247b62d3cf 100644
--- a/src/Avalonia.Controls/Image.cs
+++ b/src/Avalonia.Controls/Image.cs
@@ -1,5 +1,6 @@
 using Avalonia.Media;
 using Avalonia.Media.Imaging;
+using Avalonia.Metadata;
 
 namespace Avalonia.Controls
 {   
@@ -37,6 +38,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Gets or sets the image that will be displayed.
         /// </summary>
+        [Content]
         public IImage Source
         {
             get { return GetValue(SourceProperty); }

From 6fc5af3a68dd22130de3d6c6565ec8003d282589 Mon Sep 17 00:00:00 2001
From: Dan Walmsley <dan@walms.co.uk>
Date: Wed, 12 May 2021 20:24:13 +0100
Subject: [PATCH 02/15] use datatemplates instead of itemstemplate for
 datavalidationerrors.

---
 src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml b/src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml
index b513fd5eae..b1c8650292 100644
--- a/src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml
@@ -28,13 +28,13 @@
     <Style.Resources>
       <DataTemplate x:Key="InlineDataValidationErrorTemplate">
         <ItemsControl Items="{Binding}">
-          <ItemsControl.ItemTemplate>
+          <ItemsControl.DataTemplates>
             <DataTemplate>
               <TextBlock Foreground="{DynamicResource SystemControlErrorTextForegroundBrush}"
                          Text="{Binding}"
                          TextWrapping="Wrap" />
             </DataTemplate>
-          </ItemsControl.ItemTemplate>
+          </ItemsControl.DataTemplates>
         </ItemsControl>
       </DataTemplate>
       <ControlTemplate x:Key="InlineDataValidationContentTemplate" TargetType="DataValidationErrors">

From b0d5e3197c1580af8aff283ce9ef9778eb4ef9bc Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Thu, 13 May 2021 01:00:34 -0400
Subject: [PATCH 03/15] Include inner exception when throwing from BindingEntry

---
 src/Avalonia.Base/PropertyStore/BindingEntry.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/PropertyStore/BindingEntry.cs b/src/Avalonia.Base/PropertyStore/BindingEntry.cs
index 1b29338f07..362736eb06 100644
--- a/src/Avalonia.Base/PropertyStore/BindingEntry.cs
+++ b/src/Avalonia.Base/PropertyStore/BindingEntry.cs
@@ -79,7 +79,7 @@ namespace Avalonia.PropertyStore
 
         public void OnError(Exception error)
         {
-            throw new NotImplementedException();
+            throw new NotImplementedException("BindingEntry.OnError is not implemented", error);
         }
 
         public void OnNext(BindingValue<T> value)

From 2043ed3a30ca9feab071f7683b403b1bf059d912 Mon Sep 17 00:00:00 2001
From: Dan Walmsley <dan@walms.co.uk>
Date: Thu, 13 May 2021 10:26:22 +0100
Subject: [PATCH 04/15] dont provide any templates for datavalidation errors.

---
 .../Controls/DataValidationErrors.xaml             | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml b/src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml
index b1c8650292..53c5d4eda6 100644
--- a/src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml
@@ -27,14 +27,12 @@
   <Style Selector="DataValidationErrors">
     <Style.Resources>
       <DataTemplate x:Key="InlineDataValidationErrorTemplate">
-        <ItemsControl Items="{Binding}">
-          <ItemsControl.DataTemplates>
-            <DataTemplate>
-              <TextBlock Foreground="{DynamicResource SystemControlErrorTextForegroundBrush}"
-                         Text="{Binding}"
-                         TextWrapping="Wrap" />
-            </DataTemplate>
-          </ItemsControl.DataTemplates>
+        <ItemsControl Items="{Binding}" TextBlock.Foreground="{DynamicResource SystemControlErrorTextForegroundBrush}">
+          <ItemsControl.Styles>
+            <Style Selector="TextBlock">
+              <Setter Property="TextWrapping" Value="Wrap" />
+            </Style>
+          </ItemsControl.Styles>
         </ItemsControl>
       </DataTemplate>
       <ControlTemplate x:Key="InlineDataValidationContentTemplate" TargetType="DataValidationErrors">

From b3e2b05d1ffefe52fa5f3a69ab316b6e11f55fe0 Mon Sep 17 00:00:00 2001
From: Dariusz Komosinski <darek.komosinski@gmail.com>
Date: Thu, 13 May 2021 13:28:20 +0200
Subject: [PATCH 05/15] Implement StretchDirection for Viewbox. Cleanup
 Viewbox.

---
 samples/ControlCatalog/Pages/ViewboxPage.xaml | 28 ++++++-
 .../ControlCatalog/Pages/ViewboxPage.xaml.cs  | 31 ++++++-
 src/Avalonia.Controls/Image.cs                |  4 +-
 src/Avalonia.Controls/Viewbox.cs              | 81 +++++++------------
 .../ViewboxTests.cs                           | 56 +++++++++++++
 5 files changed, 141 insertions(+), 59 deletions(-)

diff --git a/samples/ControlCatalog/Pages/ViewboxPage.xaml b/samples/ControlCatalog/Pages/ViewboxPage.xaml
index e78cf2bc22..f8b4a62290 100644
--- a/samples/ControlCatalog/Pages/ViewboxPage.xaml
+++ b/samples/ControlCatalog/Pages/ViewboxPage.xaml
@@ -22,14 +22,38 @@
         </StreamGeometry>
     </UserControl.Resources>
 
-    <Grid RowDefinitions="Auto,*">
+    <Grid RowDefinitions="Auto,*,*">
         <StackPanel Orientation="Vertical" Spacing="4">
             <TextBlock Classes="h1">Viewbox</TextBlock>
             <TextBlock Classes="h2">A control used to scale single child.</TextBlock>
         </StackPanel>
+
+        <Grid Grid.Row="1" ColumnDefinitions="*,Auto" HorizontalAlignment="Center" Margin="0,10,0,0">
+
+          <Border HorizontalAlignment="Center" Grid.Column="0" BorderThickness="1" BorderBrush="Orange" Width="200" Height="200">
+            <Border VerticalAlignment="Center" HorizontalAlignment="Center" Grid.Column="0" BorderThickness="1" BorderBrush="CornflowerBlue" Width="{Binding #WidthSlider.Value}" Height="{Binding #HeightSlider.Value}" >
+              <Viewbox x:Name="Viewbox"
+                StretchDirection="{Binding #StretchDirectionSelector.SelectedItem}">
+                <Path Width="50" Stretch="Uniform" Fill="CornflowerBlue" Data="{StaticResource Acorn}"/>
+              </Viewbox>
+            </Border>
+          </Border>
+
+          <StackPanel HorizontalAlignment="Left" Orientation="Vertical" Grid.Column="1" Margin="8,0,0,0" Width="150">
+            <TextBlock Text="Width" />
+            <Slider Minimum="10" Maximum="200" Value="100" x:Name="WidthSlider" TickFrequency="25" TickPlacement="TopLeft" />
+            <TextBlock Text="Height" />
+            <Slider Minimum="10" Maximum="200" Value="100" x:Name="HeightSlider" TickFrequency="25" TickPlacement="TopLeft" />
+            <TextBlock Text="Stretch" />
+            <ComboBox x:Name="StretchSelector" HorizontalAlignment="Stretch" Margin="0,0,0,2" SelectionChanged="StretchSelector_OnSelectionChanged" />
+            <TextBlock Text="Stretch Direction" />
+            <ComboBox x:Name="StretchDirectionSelector" HorizontalAlignment="Stretch" />
+          </StackPanel>
+        </Grid>
+
         <Grid ColumnDefinitions="Auto,*,*"
               RowDefinitions="*,*,*,*"
-              Grid.Row="1" Margin="48"
+              Grid.Row="2" Margin="48"
               MaxWidth="400">
             <TextBlock Grid.Row="0" VerticalAlignment="Center">None</TextBlock>
             <TextBlock Grid.Row="1" VerticalAlignment="Center">Fill</TextBlock>
diff --git a/samples/ControlCatalog/Pages/ViewboxPage.xaml.cs b/samples/ControlCatalog/Pages/ViewboxPage.xaml.cs
index 1b5f4bc7f4..7a2bceb8f2 100644
--- a/samples/ControlCatalog/Pages/ViewboxPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/ViewboxPage.xaml.cs
@@ -1,18 +1,47 @@
 using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
+using Avalonia.Media;
 
 namespace ControlCatalog.Pages
 {
     public class ViewboxPage : UserControl
     {
+        private readonly Viewbox _viewbox;
+        private readonly ComboBox _stretchSelector;
+
         public ViewboxPage()
         {
-            this.InitializeComponent();
+            InitializeComponent();
+
+            _viewbox = this.FindControl<Viewbox>("Viewbox");
+
+            _stretchSelector = this.FindControl<ComboBox>("StretchSelector");
+
+            _stretchSelector.Items = new[]
+            {
+                Stretch.Uniform, Stretch.UniformToFill, Stretch.Fill, Stretch.None
+            };
+
+            _stretchSelector.SelectedIndex = 0;
+
+            var stretchDirectionSelector = this.FindControl<ComboBox>("StretchDirectionSelector");
+
+            stretchDirectionSelector.Items = new[]
+            {
+                StretchDirection.Both, StretchDirection.DownOnly, StretchDirection.UpOnly
+            };
+
+            stretchDirectionSelector.SelectedIndex = 0;
         }
 
         private void InitializeComponent()
         {
             AvaloniaXamlLoader.Load(this);
         }
+
+        private void StretchSelector_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
+        {
+            _viewbox.Stretch = (Stretch) _stretchSelector.SelectedItem!;
+        }
     }
 }
diff --git a/src/Avalonia.Controls/Image.cs b/src/Avalonia.Controls/Image.cs
index 247b62d3cf..c448729643 100644
--- a/src/Avalonia.Controls/Image.cs
+++ b/src/Avalonia.Controls/Image.cs
@@ -31,8 +31,8 @@ namespace Avalonia.Controls
 
         static Image()
         {
-            AffectsRender<Image>(SourceProperty, StretchProperty);
-            AffectsMeasure<Image>(SourceProperty, StretchProperty);
+            AffectsRender<Image>(SourceProperty, StretchProperty, StretchDirectionProperty);
+            AffectsMeasure<Image>(SourceProperty, StretchProperty, StretchDirectionProperty);
         }
 
         /// <summary>
diff --git a/src/Avalonia.Controls/Viewbox.cs b/src/Avalonia.Controls/Viewbox.cs
index 781c93bcbe..b65f4b31d8 100644
--- a/src/Avalonia.Controls/Viewbox.cs
+++ b/src/Avalonia.Controls/Viewbox.cs
@@ -1,40 +1,50 @@
-using System;
-using Avalonia.Media;
+using Avalonia.Media;
 
 namespace Avalonia.Controls
 {
     /// <summary>
-    /// Viewbox is used to scale single child.
+    /// Viewbox is used to scale single child to fit in the available space.
     /// </summary>
     /// <seealso cref="Avalonia.Controls.Decorator" />
     public class Viewbox : Decorator
     {
         /// <summary>
-        /// The stretch property
+        /// Defines the <see cref="Stretch"/> property.
         /// </summary>
         public static readonly AvaloniaProperty<Stretch> StretchProperty =
-                AvaloniaProperty.RegisterDirect<Viewbox, Stretch>(nameof(Stretch),
-                    v => v.Stretch, (c, v) => c.Stretch = v, Stretch.Uniform);
+            AvaloniaProperty.Register<Image, Stretch>(nameof(Stretch), Stretch.Uniform);
+
+        /// <summary>
+        /// Defines the <see cref="StretchDirection"/> property.
+        /// </summary>
+        public static readonly StyledProperty<StretchDirection> StretchDirectionProperty =
+            AvaloniaProperty.Register<Viewbox, StretchDirection>(nameof(StretchDirection), StretchDirection.Both);
 
         private Stretch _stretch = Stretch.Uniform;
 
+        static Viewbox()
+        {
+            ClipToBoundsProperty.OverrideDefaultValue<Viewbox>(true);
+            AffectsMeasure<Viewbox>(StretchProperty, StretchDirectionProperty);
+        }
+
         /// <summary>
         /// Gets or sets the stretch mode, 
         /// which determines how child fits into the available space.
         /// </summary>
-        /// <value>
-        /// The stretch.
-        /// </value>
         public Stretch Stretch
         {
             get => _stretch;
             set => SetAndRaise(StretchProperty, ref _stretch, value);
         }
 
-        static Viewbox()
+        /// <summary>
+        /// Gets or sets a value controlling in what direction contents will be stretched.
+        /// </summary>
+        public StretchDirection StretchDirection
         {
-            ClipToBoundsProperty.OverrideDefaultValue<Viewbox>(true);
-            AffectsMeasure<Viewbox>(StretchProperty);
+            get => GetValue(StretchDirectionProperty);
+            set => SetValue(StretchDirectionProperty, value);
         }
 
         protected override Size MeasureOverride(Size availableSize)
@@ -47,9 +57,9 @@ namespace Avalonia.Controls
 
                 var childSize = child.DesiredSize;
 
-                var scale = GetScale(availableSize, childSize, Stretch);
+                var size = Stretch.CalculateSize(availableSize, childSize, StretchDirection);
 
-                return (childSize * scale).Constrain(availableSize);
+                return size.Constrain(availableSize);
             }
 
             return new Size();
@@ -62,7 +72,9 @@ namespace Avalonia.Controls
             if (child != null)
             {
                 var childSize = child.DesiredSize;
-                var scale = GetScale(finalSize, childSize, Stretch);
+                var scale = Stretch.CalculateScaling(finalSize, childSize, StretchDirection);
+
+                // TODO: Viewbox should have another decorator as a child so we won't affect other render transforms.
                 var scaleTransform = child.RenderTransform as ScaleTransform;
 
                 if (scaleTransform == null)
@@ -81,44 +93,5 @@ namespace Avalonia.Controls
 
             return new Size();
         }
-
-        private static Vector GetScale(Size availableSize, Size childSize, Stretch stretch)
-        {
-            double scaleX = 1.0;
-            double scaleY = 1.0;
-
-            bool validWidth = !double.IsPositiveInfinity(availableSize.Width);
-            bool validHeight = !double.IsPositiveInfinity(availableSize.Height);
-
-            if (stretch != Stretch.None && (validWidth || validHeight))
-            {
-                scaleX = childSize.Width <= 0.0 ? 0.0 : availableSize.Width / childSize.Width;
-                scaleY = childSize.Height <= 0.0 ? 0.0 : availableSize.Height / childSize.Height;
-
-                if (!validWidth)
-                {
-                    scaleX = scaleY;
-                }
-                else if (!validHeight)
-                {
-                    scaleY = scaleX;
-                }
-                else
-                {
-                    switch (stretch)
-                    {
-                        case Stretch.Uniform:
-                            scaleX = scaleY = Math.Min(scaleX, scaleY);
-                            break;
-
-                        case Stretch.UniformToFill:
-                            scaleX = scaleY = Math.Max(scaleX, scaleY);
-                            break;
-                    }
-                }
-            }
-
-            return new Vector(scaleX, scaleY);
-        }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/ViewboxTests.cs b/tests/Avalonia.Controls.UnitTests/ViewboxTests.cs
index e005bafbf9..7eaec35506 100644
--- a/tests/Avalonia.Controls.UnitTests/ViewboxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ViewboxTests.cs
@@ -114,5 +114,61 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(2.0, scaleTransform.ScaleX);
             Assert.Equal(2.0, scaleTransform.ScaleY);
         }
+
+        [Theory]
+        [InlineData(50, 100, 50, 100, 50, 100, 1)]
+        [InlineData(50, 100, 150, 150, 50, 100, 1)]
+        [InlineData(50, 100, 25, 50, 25, 50, 0.5)]
+        public void Viewbox_Should_Return_Correct_SizeAndScale_StretchDirection_DownOnly(
+            double childWidth, double childHeight,
+            double viewboxWidth, double viewboxHeight,
+            double expectedWidth, double expectedHeight,
+            double expectedScale)
+        {
+            var target = new Viewbox
+            {
+                Child = new Control { Width = childWidth, Height = childHeight },
+                StretchDirection = StretchDirection.DownOnly
+            };
+
+            target.Measure(new Size(viewboxWidth, viewboxHeight));
+            target.Arrange(new Rect(default, target.DesiredSize));
+
+            Assert.Equal(new Size(expectedWidth, expectedHeight), target.DesiredSize);
+
+            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+
+            Assert.NotNull(scaleTransform);
+            Assert.Equal(expectedScale, scaleTransform.ScaleX);
+            Assert.Equal(expectedScale, scaleTransform.ScaleY);
+        }
+
+        [Theory]
+        [InlineData(50, 100, 50, 100, 50, 100, 1)]
+        [InlineData(50, 100, 25, 50, 25, 50, 1)]
+        [InlineData(50, 100, 150, 150, 75, 150, 1.5)]
+        public void Viewbox_Should_Return_Correct_SizeAndScale_StretchDirection_UpOnly(
+            double childWidth, double childHeight,
+            double viewboxWidth, double viewboxHeight,
+            double expectedWidth, double expectedHeight,
+            double expectedScale)
+        {
+            var target = new Viewbox
+            {
+                Child = new Control { Width = childWidth, Height = childHeight },
+                StretchDirection = StretchDirection.UpOnly
+            };
+
+            target.Measure(new Size(viewboxWidth, viewboxHeight));
+            target.Arrange(new Rect(default, target.DesiredSize));
+
+            Assert.Equal(new Size(expectedWidth, expectedHeight), target.DesiredSize);
+
+            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+
+            Assert.NotNull(scaleTransform);
+            Assert.Equal(expectedScale, scaleTransform.ScaleX);
+            Assert.Equal(expectedScale, scaleTransform.ScaleY);
+        }
     }
 }

From 6e2384deb804da5cf3d453933f88ba6bce0cc126 Mon Sep 17 00:00:00 2001
From: Dariusz Komosinski <darek.komosinski@gmail.com>
Date: Thu, 13 May 2021 14:57:36 +0200
Subject: [PATCH 06/15] Use an ellipse instead.

---
 samples/ControlCatalog/Pages/ViewboxPage.xaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/ControlCatalog/Pages/ViewboxPage.xaml b/samples/ControlCatalog/Pages/ViewboxPage.xaml
index f8b4a62290..f9e9c983d5 100644
--- a/samples/ControlCatalog/Pages/ViewboxPage.xaml
+++ b/samples/ControlCatalog/Pages/ViewboxPage.xaml
@@ -34,7 +34,7 @@
             <Border VerticalAlignment="Center" HorizontalAlignment="Center" Grid.Column="0" BorderThickness="1" BorderBrush="CornflowerBlue" Width="{Binding #WidthSlider.Value}" Height="{Binding #HeightSlider.Value}" >
               <Viewbox x:Name="Viewbox"
                 StretchDirection="{Binding #StretchDirectionSelector.SelectedItem}">
-                <Path Width="50" Stretch="Uniform" Fill="CornflowerBlue" Data="{StaticResource Acorn}"/>
+                <Ellipse Width="50" Height="50" Fill="CornflowerBlue" />
               </Viewbox>
             </Border>
           </Border>

From f775f9d3f0af3eb7fa3aaa6be43659c7783767b0 Mon Sep 17 00:00:00 2001
From: Dariusz Komosinski <darek.komosinski@gmail.com>
Date: Thu, 13 May 2021 16:00:14 +0200
Subject: [PATCH 07/15] Remove old viewbox samples.

---
 samples/ControlCatalog/Pages/ViewboxPage.xaml | 55 -------------------
 1 file changed, 55 deletions(-)

diff --git a/samples/ControlCatalog/Pages/ViewboxPage.xaml b/samples/ControlCatalog/Pages/ViewboxPage.xaml
index f9e9c983d5..6e649b39a5 100644
--- a/samples/ControlCatalog/Pages/ViewboxPage.xaml
+++ b/samples/ControlCatalog/Pages/ViewboxPage.xaml
@@ -1,26 +1,6 @@
 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              x:Class="ControlCatalog.Pages.ViewboxPage">
-    <UserControl.Resources>
-        <StreamGeometry x:Key="Acorn">
-            F1 M 16.6309,18.6563C 17.1309,
-            8.15625 29.8809,14.1563 29.8809,
-            14.1563C 30.8809,11.1563 34.1308,
-            11.4063 34.1308,11.4063C 33.5,12
-            34.6309,13.1563 34.6309,13.1563C
-            32.1309,13.1562 31.1309,14.9062
-            31.1309,14.9062C 41.1309,23.9062
-            32.6309,27.9063 32.6309,27.9062C
-            24.6309,24.9063 21.1309,22.1562
-            16.6309,18.6563 Z M 16.6309,19.9063C
-            21.6309,24.1563 25.1309,26.1562
-            31.6309,28.6562C 31.6309,28.6562
-            26.3809,39.1562 18.3809,36.1563C
-            18.3809,36.1563 18,38 16.3809,36.9063C
-            15,36 16.3809,34.9063 16.3809,34.9063C
-            16.3809,34.9063 10.1309,30.9062 16.6309,19.9063 Z
-        </StreamGeometry>
-    </UserControl.Resources>
 
     <Grid RowDefinitions="Auto,*,*">
         <StackPanel Orientation="Vertical" Spacing="4">
@@ -51,40 +31,5 @@
           </StackPanel>
         </Grid>
 
-        <Grid ColumnDefinitions="Auto,*,*"
-              RowDefinitions="*,*,*,*"
-              Grid.Row="2" Margin="48"
-              MaxWidth="400">
-            <TextBlock Grid.Row="0" VerticalAlignment="Center">None</TextBlock>
-            <TextBlock Grid.Row="1" VerticalAlignment="Center">Fill</TextBlock>
-            <TextBlock Grid.Row="2" VerticalAlignment="Center">Uniform</TextBlock>
-            <TextBlock Grid.Row="3" VerticalAlignment="Center">UniformToFill</TextBlock>
-
-            <Viewbox Grid.Row="0" Grid.Column="1" Stretch="None">
-                <TextBlock>Hello World!</TextBlock>
-            </Viewbox>
-            <Viewbox Grid.Row="1" Grid.Column="1" Stretch="Fill">
-                <TextBlock>Hello World!</TextBlock>
-            </Viewbox>
-            <Viewbox Grid.Row="2" Grid.Column="1" Stretch="Uniform">
-                <TextBlock>Hello World!</TextBlock>
-            </Viewbox>
-            <Viewbox Grid.Row="3" Grid.Column="1" Stretch="UniformToFill">
-                <TextBlock>Hello World!</TextBlock>
-            </Viewbox>
-
-            <Viewbox Grid.Row="0" Grid.Column="2" Stretch="None">
-                <Path Fill="Blue" Data="{StaticResource Acorn}"/>
-            </Viewbox>
-            <Viewbox Grid.Row="1" Grid.Column="2" Stretch="Fill">
-                <Path Fill="Blue" Data="{StaticResource Acorn}"/>
-            </Viewbox>
-            <Viewbox Grid.Row="2" Grid.Column="2" Stretch="Uniform">
-                <Path Fill="Blue" Data="{StaticResource Acorn}"/>
-            </Viewbox>
-            <Viewbox Grid.Row="3" Grid.Column="2" Stretch="UniformToFill">
-                <Path Fill="Blue" Data="{StaticResource Acorn}"/>
-            </Viewbox>
-        </Grid>
     </Grid>
 </UserControl>

From 6d0ac9a5417bdc01048b5e86f9e4a985f58ca091 Mon Sep 17 00:00:00 2001
From: Dariusz Komosinski <darek.komosinski@gmail.com>
Date: Thu, 13 May 2021 16:33:49 +0200
Subject: [PATCH 08/15] Fix property type on Stretch.

---
 samples/ControlCatalog/Pages/ViewboxPage.xaml    |  7 ++++---
 samples/ControlCatalog/Pages/ViewboxPage.xaml.cs | 16 +++-------------
 src/Avalonia.Controls/Viewbox.cs                 |  3 ++-
 3 files changed, 9 insertions(+), 17 deletions(-)

diff --git a/samples/ControlCatalog/Pages/ViewboxPage.xaml b/samples/ControlCatalog/Pages/ViewboxPage.xaml
index 6e649b39a5..ef802db33e 100644
--- a/samples/ControlCatalog/Pages/ViewboxPage.xaml
+++ b/samples/ControlCatalog/Pages/ViewboxPage.xaml
@@ -12,8 +12,9 @@
 
           <Border HorizontalAlignment="Center" Grid.Column="0" BorderThickness="1" BorderBrush="Orange" Width="200" Height="200">
             <Border VerticalAlignment="Center" HorizontalAlignment="Center" Grid.Column="0" BorderThickness="1" BorderBrush="CornflowerBlue" Width="{Binding #WidthSlider.Value}" Height="{Binding #HeightSlider.Value}" >
-              <Viewbox x:Name="Viewbox"
-                StretchDirection="{Binding #StretchDirectionSelector.SelectedItem}">
+              <Viewbox
+                  Stretch="{Binding #StretchSelector.SelectedItem}"
+                  StretchDirection="{Binding #StretchDirectionSelector.SelectedItem}">
                 <Ellipse Width="50" Height="50" Fill="CornflowerBlue" />
               </Viewbox>
             </Border>
@@ -25,7 +26,7 @@
             <TextBlock Text="Height" />
             <Slider Minimum="10" Maximum="200" Value="100" x:Name="HeightSlider" TickFrequency="25" TickPlacement="TopLeft" />
             <TextBlock Text="Stretch" />
-            <ComboBox x:Name="StretchSelector" HorizontalAlignment="Stretch" Margin="0,0,0,2" SelectionChanged="StretchSelector_OnSelectionChanged" />
+            <ComboBox x:Name="StretchSelector" HorizontalAlignment="Stretch" Margin="0,0,0,2" />
             <TextBlock Text="Stretch Direction" />
             <ComboBox x:Name="StretchDirectionSelector" HorizontalAlignment="Stretch" />
           </StackPanel>
diff --git a/samples/ControlCatalog/Pages/ViewboxPage.xaml.cs b/samples/ControlCatalog/Pages/ViewboxPage.xaml.cs
index 7a2bceb8f2..94b3f3ea14 100644
--- a/samples/ControlCatalog/Pages/ViewboxPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/ViewboxPage.xaml.cs
@@ -6,23 +6,18 @@ namespace ControlCatalog.Pages
 {
     public class ViewboxPage : UserControl
     {
-        private readonly Viewbox _viewbox;
-        private readonly ComboBox _stretchSelector;
-
         public ViewboxPage()
         {
             InitializeComponent();
 
-            _viewbox = this.FindControl<Viewbox>("Viewbox");
-
-            _stretchSelector = this.FindControl<ComboBox>("StretchSelector");
+            var stretchSelector = this.FindControl<ComboBox>("StretchSelector");
 
-            _stretchSelector.Items = new[]
+            stretchSelector.Items = new[]
             {
                 Stretch.Uniform, Stretch.UniformToFill, Stretch.Fill, Stretch.None
             };
 
-            _stretchSelector.SelectedIndex = 0;
+            stretchSelector.SelectedIndex = 0;
 
             var stretchDirectionSelector = this.FindControl<ComboBox>("StretchDirectionSelector");
 
@@ -38,10 +33,5 @@ namespace ControlCatalog.Pages
         {
             AvaloniaXamlLoader.Load(this);
         }
-
-        private void StretchSelector_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
-        {
-            _viewbox.Stretch = (Stretch) _stretchSelector.SelectedItem!;
-        }
     }
 }
diff --git a/src/Avalonia.Controls/Viewbox.cs b/src/Avalonia.Controls/Viewbox.cs
index b65f4b31d8..15ca070de2 100644
--- a/src/Avalonia.Controls/Viewbox.cs
+++ b/src/Avalonia.Controls/Viewbox.cs
@@ -12,7 +12,8 @@ namespace Avalonia.Controls
         /// Defines the <see cref="Stretch"/> property.
         /// </summary>
         public static readonly AvaloniaProperty<Stretch> StretchProperty =
-            AvaloniaProperty.Register<Image, Stretch>(nameof(Stretch), Stretch.Uniform);
+            AvaloniaProperty.RegisterDirect<Viewbox, Stretch>(nameof(Stretch),
+                v => v.Stretch, (c, v) => c.Stretch = v, Stretch.Uniform);
 
         /// <summary>
         /// Defines the <see cref="StretchDirection"/> property.

From 59d51d6a56d1a6b62051e656be331b7cea39f668 Mon Sep 17 00:00:00 2001
From: Splitwirez <34009058+Splitwirez@users.noreply.github.com>
Date: Fri, 14 May 2021 00:10:50 -0700
Subject: [PATCH 09/15] New Fluent expander style (#5573)

* Updated Fluent theme Expander style. closes #5358

* Fixed padding mismatch between header and content

* Fixed CornerRadii, unleashed the c o l o u r e s

* Use CornerRadiusFilterConverter instead of expander specific converters

* Formatting

* Fix default theme in ControlCatalog

Co-authored-by: Jumar Macato <16554748+jmacato@users.noreply.github.com>
Co-authored-by: Max Katz <maxkatz6@outlook.com>
---
 samples/ControlCatalog/App.xaml.cs            |   8 +
 src/Avalonia.Themes.Fluent/Accents/Base.xaml  |   8 +-
 .../Controls/Expander.xaml                    | 317 +++++++++++-------
 3 files changed, 219 insertions(+), 114 deletions(-)

diff --git a/samples/ControlCatalog/App.xaml.cs b/samples/ControlCatalog/App.xaml.cs
index 020fb2fff3..f3ec7b48aa 100644
--- a/samples/ControlCatalog/App.xaml.cs
+++ b/samples/ControlCatalog/App.xaml.cs
@@ -39,6 +39,10 @@ namespace ControlCatalog
 
         public static Styles DefaultLight = new Styles
         {
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("avares://Avalonia.Themes.Fluent/Accents/AccentColors.xaml")
+            },
             new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
             {
                 Source = new Uri("avares://Avalonia.Themes.Fluent/Accents/Base.xaml")
@@ -60,6 +64,10 @@ namespace ControlCatalog
 
         public static Styles DefaultDark = new Styles
         {
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("avares://Avalonia.Themes.Fluent/Accents/AccentColors.xaml")
+            },
             new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
             {
                 Source = new Uri("avares://Avalonia.Themes.Fluent/Accents/Base.xaml")
diff --git a/src/Avalonia.Themes.Fluent/Accents/Base.xaml b/src/Avalonia.Themes.Fluent/Accents/Base.xaml
index 8597c76998..1e2acf736d 100644
--- a/src/Avalonia.Themes.Fluent/Accents/Base.xaml
+++ b/src/Avalonia.Themes.Fluent/Accents/Base.xaml
@@ -1,6 +1,7 @@
 <Style xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-       xmlns:sys="clr-namespace:System;assembly=netstandard">
+       xmlns:sys="using:System"
+       xmlns:converters="using:Avalonia.Controls.Converters">
   <Style.Resources>
     <!-- https://docs.microsoft.com/en-us/previous-versions/windows/apps/dn518235(v=win.10)?redirectedfrom=MSDN -->
     <!-- SystemColor Color Resources (Reflect OS High Contrast Settings) -->
@@ -30,5 +31,10 @@
     <!-- ScrollBar animation -->
     <TransformOperations x:Key="VerticalSmallScrollThumbScaleTransform">scaleX(0.125) translateX(-2px)</TransformOperations>
     <TransformOperations x:Key="HorizontalSmallScrollThumbScaleTransform">scaleY(0.125) translateY(-2px)</TransformOperations>
+
+    <converters:CornerRadiusFilterConverter x:Key="TopCornerRadiusFilterConverter" Filter="TopLeft, TopRight"/>
+    <converters:CornerRadiusFilterConverter x:Key="RightCornerRadiusFilterConverter" Filter="TopRight, BottomRight"/>
+    <converters:CornerRadiusFilterConverter x:Key="BottomCornerRadiusFilterConverter" Filter="BottomLeft, BottomRight"/>
+    <converters:CornerRadiusFilterConverter x:Key="LeftCornerRadiusFilterConverter" Filter="TopLeft, BottomLeft"/>
   </Style.Resources>
 </Style>
diff --git a/src/Avalonia.Themes.Fluent/Controls/Expander.xaml b/src/Avalonia.Themes.Fluent/Controls/Expander.xaml
index a6371a5be9..3f70939953 100644
--- a/src/Avalonia.Themes.Fluent/Controls/Expander.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/Expander.xaml
@@ -1,141 +1,232 @@
-<Styles xmlns="https://github.com/avaloniaui">
+<Styles xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+  <Design.PreviewWith>
+    <Border Padding="20">
+      <StackPanel Orientation="Vertical" Spacing="20">
+        <Expander ExpandDirection="Up" Header="Expand Up">
+          <StackPanel>
+            <TextBlock>Expanded content</TextBlock>
+          </StackPanel>
+        </Expander>
+        <Expander ExpandDirection="Down" Header="Expand Down">
+          <StackPanel>
+            <TextBlock>Expanded content</TextBlock>
+          </StackPanel>
+        </Expander>
+        <Expander ExpandDirection="Left" Header="Expand Left">
+          <StackPanel>
+            <TextBlock>Expanded content</TextBlock>
+          </StackPanel>
+        </Expander>
+        <Expander ExpandDirection="Right" Header="Expand Right">
+          <StackPanel>
+            <TextBlock>Expanded content</TextBlock>
+          </StackPanel>
+        </Expander>
+      </StackPanel>
+    </Border>
+  </Design.PreviewWith>
 
+  <Styles.Resources>
+    <Thickness x:Key="ExpanderHeaderPadding">16</Thickness>
+    <Thickness x:Key="ExpanderContentPadding">16</Thickness>
+
+    <Thickness x:Key="ExpanderBorderThickness">1</Thickness>
+
+    <Thickness x:Key="ExpanderDropdownLeftBorderThickness">1,1,0,1</Thickness>
+    <Thickness x:Key="ExpanderDropdownUpBorderThickness">1,1,1,0</Thickness>
+    <Thickness x:Key="ExpanderDropdownRightBorderThickness">0,1,1,1</Thickness>
+    <Thickness x:Key="ExpanderDropdownDownBorderThickness">1,0,1,1</Thickness>
+
+    <SolidColorBrush x:Key="ExpanderBackground" Color="{DynamicResource SystemAltMediumHighColor}" />
+    <SolidColorBrush x:Key="ExpanderBorderBrush" Color="{DynamicResource SystemBaseLowColor}" />
+
+    <SolidColorBrush x:Key="ExpanderDropDownBackground" Color="{DynamicResource SystemChromeMediumLowColor}" />
+    <SolidColorBrush x:Key="ExpanderDropDownBorderBrush" Color="{DynamicResource SystemBaseLowColor}" />
+
+    <SolidColorBrush x:Key="ExpanderForeground" Color="{DynamicResource SystemBaseHighColor}" />
+
+    <SolidColorBrush x:Key="ExpanderChevronForeground" Color="{DynamicResource SystemBaseHighColor}" />
+  </Styles.Resources>
   <Style Selector="Expander">
-    <Setter Property="ContentTransition">
-      <Setter.Value>
-        <CrossFade Duration="00:00:00.25" />
-      </Setter.Value>
-    </Setter>
+    <Setter Property="Background" Value="{DynamicResource ExpanderBackground}" />
+    <Setter Property="BorderThickness" Value="{DynamicResource ExpanderBorderThickness}" />
+    <Setter Property="BorderBrush" Value="{DynamicResource ExpanderBorderBrush}" />
+    <Setter Property="Padding" Value="{DynamicResource ExpanderHeaderPadding}" />
+    <Setter Property="HorizontalAlignment" Value="Stretch" />
+    <Setter Property="HorizontalContentAlignment" Value="Left" />
+    <Setter Property="VerticalContentAlignment" Value="Center" />
   </Style>
-  <Style Selector="Expander[ExpandDirection=Down]">
-    <Setter Property="Template">
-      <ControlTemplate>
-        <Border Background="{TemplateBinding Background}">
-          <Grid RowDefinitions="Auto,*">
-            <ToggleButton Name="PART_toggle" Grid.Row="0"  Content="{TemplateBinding Header}" IsChecked="{TemplateBinding IsExpanded, Mode=TwoWay}" />
-            <ContentPresenter Name="PART_ContentPresenter"
-                              Grid.Row="1"
-                              IsVisible="{TemplateBinding IsExpanded}"
-                              ContentTemplate="{TemplateBinding ContentTemplate}"
-                              Content="{TemplateBinding Content}"
-                              HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
-                              VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
-                              Padding="{TemplateBinding Padding}" />
-          </Grid>
-        </Border>
-      </ControlTemplate>
-    </Setter>
-  </Style>
-  <Style Selector="Expander[IsExpanded=true] /template/ ToggleButton#PART_toggle /template/ ContentPresenter#PART_ContentPresenter">
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ToggleButtonForeground}"/>
-  </Style>
-  <Style Selector="Expander[ExpandDirection=Up]">
+  <Style Selector="Expander">
     <Setter Property="Template">
       <ControlTemplate>
-        <Border Background="{TemplateBinding Background}">
-          <Grid RowDefinitions="*,Auto">
-            <ToggleButton Name="PART_toggle" Grid.Row="1"  Content="{TemplateBinding Header}" IsChecked="{TemplateBinding IsExpanded, Mode=TwoWay}" />
-            <ContentPresenter Name="PART_ContentPresenter"
-                              Grid.Row="0"
-                              IsVisible="{TemplateBinding IsExpanded}"
-                              ContentTemplate="{TemplateBinding ContentTemplate}"
-                              Content="{TemplateBinding Content}"
+        <DockPanel>
+          <ToggleButton x:Name="ExpanderHeader"
+                        Padding="{TemplateBinding Padding}"
+                        HorizontalAlignment="{TemplateBinding HorizontalAlignment}"
+                        Background="{TemplateBinding Background}"
+                        BorderBrush="{TemplateBinding BorderBrush}"
+                        BorderThickness="{TemplateBinding BorderThickness}"
+                        Content="{TemplateBinding Header}"
+                        ContentTemplate="{TemplateBinding HeaderTemplate}"
+                        IsChecked="{Binding Path=IsExpanded, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
+                        IsEnabled="{TemplateBinding IsEnabled}" />
+          <Border x:Name="ExpanderContent"
+                  Padding="{DynamicResource ExpanderContentPadding}"
+                  Background="{DynamicResource ExpanderDropDownBackground}"
+                  BorderBrush="{DynamicResource ExpanderDropDownBorderBrush}"
+                  IsVisible="{Binding Path=IsExpanded, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}">
+            <ContentPresenter x:Name="PART_ContentPresenter"
                               HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                               VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
-                              Padding="{TemplateBinding Padding}" />
-          </Grid>
-        </Border>
-      </ControlTemplate>
-    </Setter>
-  </Style>
-  <Style Selector="Expander[ExpandDirection=Right]">
-    <Setter Property="Template">
-      <ControlTemplate>
-        <Border Background="{TemplateBinding Background}">
-          <Grid ColumnDefinitions="Auto,*">
-            <ToggleButton Name="PART_toggle" Grid.Column="0"  Content="{TemplateBinding Header}" IsChecked="{TemplateBinding IsExpanded, Mode=TwoWay}" />
-            <ContentPresenter Name="PART_ContentPresenter"
-                              Grid.Column="1"
-                              IsVisible="{TemplateBinding IsExpanded}"
-                              ContentTemplate="{TemplateBinding ContentTemplate}"
                               Content="{TemplateBinding Content}"
-                              HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
-                              VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
-                              Padding="{TemplateBinding Padding}" />
-          </Grid>
-        </Border>
+                              ContentTemplate="{TemplateBinding ContentTemplate}" />
+          </Border>
+        </DockPanel>
       </ControlTemplate>
     </Setter>
   </Style>
-  <Style Selector="Expander[ExpandDirection=Left]">
+
+  <Style Selector="Expander /template/ ToggleButton#ExpanderHeader">
+    <Setter Property="HorizontalContentAlignment" Value="Left" />
     <Setter Property="Template">
       <ControlTemplate>
-        <Border Background="{TemplateBinding Background}">
+        <Border x:Name="ToggleButtonBackground">
           <Grid ColumnDefinitions="*,Auto">
-            <ToggleButton Name="PART_toggle" Grid.Column="1"  Content="{TemplateBinding Header}" IsChecked="{TemplateBinding IsExpanded, Mode=TwoWay}" />
-            <ContentPresenter Name="PART_ContentPresenter"
-                              Grid.Column="0"
-                              IsVisible="{TemplateBinding IsExpanded}"
-                              ContentTemplate="{TemplateBinding ContentTemplate}"
-                              Content="{TemplateBinding Content}"
+            <ContentPresenter x:Name="PART_ContentPresenter"
+                              Margin="{TemplateBinding Padding}"
                               HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
-                              VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
-                              Padding="{TemplateBinding Padding}" />
-          </Grid>
-        </Border>
-      </ControlTemplate>
-    </Setter>
-  </Style>
-  <Style Selector="Expander /template/ ToggleButton#PART_toggle">
-    <Setter Property="Template">
-      <ControlTemplate>
-        <Border BorderThickness="1" Background="Transparent">
-          <Grid ColumnDefinitions="Auto,Auto">
-            <Border Grid.Column="0" Width="20" Height="20" HorizontalAlignment="Center" VerticalAlignment="Center">
-              <Path Fill="{DynamicResource SystemControlForegroundBaseHighBrush}"
-                      HorizontalAlignment="Center"
-                      VerticalAlignment="Center"
-                      Data="M 0 2 L 4 6 L 0 10 Z" />
+                              VerticalContentAlignment="Center"
+                              Background="Transparent"
+                              BorderBrush="Transparent"
+                              BorderThickness="0"
+                              Content="{TemplateBinding Content}"
+                              ContentTemplate="{TemplateBinding ContentTemplate}"
+                              TextBlock.Foreground="{DynamicResource ExpanderForeground}" />
+            <Border x:Name="ExpandCollapseChevronBorder"
+                    Grid.Column="1"
+                    Width="32"
+                    Height="32"
+                    Margin="7"
+                    RenderTransformOrigin="50%,50%">
+              <Path x:Name="ExpandCollapseChevron"
+                    HorizontalAlignment="Center"
+                    VerticalAlignment="Center"
+                    RenderTransformOrigin="50%,50%"
+                    Stretch="None"
+                    Stroke="{DynamicResource ExpanderChevronForeground}"
+                    StrokeThickness="1" />
+              <Border.RenderTransform>
+                <RotateTransform />
+              </Border.RenderTransform>
             </Border>
-            <ContentPresenter Name="PART_ContentPresenter"
-                              Grid.Column="1" 
-                              Background="Transparent" 
-                              Content="{TemplateBinding Content}" 
-                              VerticalAlignment="Center" 
-                              HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
-                              VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
-                              Padding="{TemplateBinding Padding}"/>
           </Grid>
         </Border>
       </ControlTemplate>
     </Setter>
   </Style>
-  <Style Selector="Expander /template/ ToggleButton#PART_toggle:pointerover /template/ Border">
-    <Setter Property="BorderBrush" Value="{DynamicResource SystemControlHighlightBaseMediumBrush}" />
+  <Style Selector="Expander /template/ ToggleButton#ExpanderHeader:pressed">
+    <Setter Property="RenderTransform" Value="{x:Null}" />
   </Style>
-  <Style Selector="Expander:down:expanded /template/ ToggleButton#PART_toggle /template/ Path">
-    <Setter Property="RenderTransform">
-      <RotateTransform Angle="90" />
-    </Setter>
+
+  <Style Selector="Expander:left /template/ ToggleButton#ExpanderHeader, Expander:right /template/ ToggleButton#ExpanderHeader">
+    <Setter Property="VerticalAlignment" Value="Stretch" />
   </Style>
-  <Style Selector="Expander:up:expanded /template/ ToggleButton#PART_toggle /template/ Path">
-    <Setter Property="RenderTransform">
-      <RotateTransform Angle="-90" />
-    </Setter>
+
+
+  <Style Selector="Expander /template/ ToggleButton#ExpanderHeader /template/ Border#ToggleButtonBackground">
+    <Setter Property="Background" Value="{TemplateBinding Background}" />
+    <Setter Property="BorderBrush" Value="{TemplateBinding BorderBrush}" />
+    <Setter Property="BorderThickness" Value="{TemplateBinding BorderThickness}" />
   </Style>
-  <Style Selector="Expander:left:expanded /template/ ToggleButton#PART_toggle /template/ Path">
-    <Setter Property="RenderTransform">
-      <RotateTransform Angle="180" />
-    </Setter>
+
+  <Style Selector="Expander:not(:expanded) /template/ ToggleButton#ExpanderHeader /template/ Border#ToggleButtonBackground">
+    <Setter Property="CornerRadius" Value="{DynamicResource ControlCornerRadius}" />
   </Style>
-  <Style Selector="Expander:right /template/ ToggleButton#PART_toggle /template/ Path">
-    <Setter Property="RenderTransform">
-      <RotateTransform Angle="180" />
-    </Setter>
+  <Style Selector="Expander:expanded:up /template/ ToggleButton#ExpanderHeader /template/ Border#ToggleButtonBackground">
+    <Setter Property="CornerRadius" Value="{Binding Source={StaticResource ControlCornerRadius}, Converter={StaticResource BottomCornerRadiusFilterConverter}}" />
   </Style>
-  <Style Selector="Expander:right:expanded /template/ ToggleButton#PART_toggle /template/ Path">
-    <Setter Property="RenderTransform">
-      <RotateTransform Angle="0" />
-    </Setter>
+  <Style Selector="Expander:expanded:up /template/ Border#ExpanderContent">
+    <Setter Property="CornerRadius" Value="{Binding Source={StaticResource ControlCornerRadius}, Converter={StaticResource TopCornerRadiusFilterConverter}}" />
+  </Style>
+  <Style Selector="Expander:expanded:down /template/ ToggleButton#ExpanderHeader /template/ Border#ToggleButtonBackground">
+    <Setter Property="CornerRadius" Value="{Binding Source={StaticResource ControlCornerRadius}, Converter={StaticResource TopCornerRadiusFilterConverter}}" />
+  </Style>
+  <Style Selector="Expander:expanded:down /template/ Border#ExpanderContent">
+    <Setter Property="CornerRadius" Value="{Binding Source={StaticResource ControlCornerRadius}, Converter={StaticResource BottomCornerRadiusFilterConverter}}" />
+  </Style>
+  <Style Selector="Expander:expanded:left /template/ ToggleButton#ExpanderHeader /template/ Border#ToggleButtonBackground">
+    <Setter Property="CornerRadius" Value="{Binding Source={StaticResource ControlCornerRadius}, Converter={StaticResource RightCornerRadiusFilterConverter}}" />
+  </Style>
+  <Style Selector="Expander:expanded:left /template/ Border#ExpanderContent">
+    <Setter Property="CornerRadius" Value="{Binding Source={StaticResource ControlCornerRadius}, Converter={StaticResource LeftCornerRadiusFilterConverter}}" />
+  </Style>
+  <Style Selector="Expander:expanded:right /template/ ToggleButton#ExpanderHeader /template/ Border#ToggleButtonBackground">
+    <Setter Property="CornerRadius" Value="{Binding Source={StaticResource ControlCornerRadius}, Converter={StaticResource LeftCornerRadiusFilterConverter}}" />
+  </Style>
+  <Style Selector="Expander:expanded:right /template/ Border#ExpanderContent">
+    <Setter Property="CornerRadius" Value="{Binding Source={StaticResource ControlCornerRadius}, Converter={StaticResource RightCornerRadiusFilterConverter}}" />
+  </Style>
+
+  <Style Selector="Expander:left /template/ ToggleButton#ExpanderHeader">
+    <Setter Property="DockPanel.Dock" Value="Right" />
+  </Style>
+  <Style Selector="Expander:up /template/ ToggleButton#ExpanderHeader">
+    <Setter Property="DockPanel.Dock" Value="Bottom" />
+  </Style>
+  <Style Selector="Expander:right /template/ ToggleButton#ExpanderHeader">
+    <Setter Property="DockPanel.Dock" Value="Left" />
+  </Style>
+  <Style Selector="Expander:down /template/ ToggleButton#ExpanderHeader">
+    <Setter Property="DockPanel.Dock" Value="Top" />
+  </Style>
+
+
+  <Style Selector="Expander:expanded /template/ ToggleButton#ExpanderHeader /template/ Border#ExpandCollapseChevronBorder">
+    <Style.Animations>
+      <Animation FillMode="Both" Duration="0:0:0.0625">
+        <KeyFrame Cue="100%">
+          <Setter Property="RotateTransform.Angle" Value="180" />
+        </KeyFrame>
+      </Animation>
+    </Style.Animations>
+  </Style>
+  <Style Selector="Expander:not(:expanded) /template/ ToggleButton#ExpanderHeader /template/ Border#ExpandCollapseChevronBorder">
+    <Style.Animations>
+      <Animation FillMode="Both" Duration="0:0:0.0625">
+        <KeyFrame Cue="0%">
+          <Setter Property="RotateTransform.Angle" Value="180" />
+        </KeyFrame>
+        <KeyFrame Cue="100%">
+          <Setter Property="RotateTransform.Angle" Value="0" />
+        </KeyFrame>
+      </Animation>
+    </Style.Animations>
+  </Style>
+
+  <Style Selector="Expander:left /template/ ToggleButton#ExpanderHeader /template/ Path#ExpandCollapseChevron">
+    <Setter Property="Data" Value="M 7 0 L 0 7 L 7 14" />
+  </Style>
+  <Style Selector="Expander:up /template/ ToggleButton#ExpanderHeader /template/ Path#ExpandCollapseChevron">
+    <Setter Property="Data" Value="M 0 7 L 7 0 L 14 7" />
+  </Style>
+  <Style Selector="Expander:right /template/ ToggleButton#ExpanderHeader /template/ Path#ExpandCollapseChevron">
+    <Setter Property="Data" Value="M 0 0 L 7 7 L 0 14" />
+  </Style>
+  <Style Selector="Expander:down /template/ ToggleButton#ExpanderHeader /template/ Path#ExpandCollapseChevron">
+    <Setter Property="Data" Value="M 0 0 L 7 7 L 14 0" />
+  </Style>
+
+
+  <Style Selector="Expander:left /template/ Border#ExpanderContent">
+    <Setter Property="BorderThickness" Value="{DynamicResource ExpanderDropdownLeftBorderThickness}" />
+  </Style>
+  <Style Selector="Expander:up /template/ Border#ExpanderContent">
+    <Setter Property="BorderThickness" Value="{DynamicResource ExpanderDropdownUpBorderThickness}" />
+  </Style>
+  <Style Selector="Expander:right /template/ Border#ExpanderContent">
+    <Setter Property="BorderThickness" Value="{DynamicResource ExpanderDropdownRightBorderThickness}" />
+  </Style>
+  <Style Selector="Expander:down /template/ Border#ExpanderContent">
+    <Setter Property="BorderThickness" Value="{DynamicResource ExpanderDropdownDownBorderThickness}" />
   </Style>
 </Styles>

From 4db1f41f72ccec0f076015513795ca7e9089987d Mon Sep 17 00:00:00 2001
From: Dariusz Komosinski <darek.komosinski@gmail.com>
Date: Fri, 14 May 2021 22:58:51 +0200
Subject: [PATCH 10/15] Change Viewbox.Stretch to a styled property

---
 src/Avalonia.Controls/ApiCompatBaseline.txt |  3 ++-
 src/Avalonia.Controls/Viewbox.cs            | 11 ++++-------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/src/Avalonia.Controls/ApiCompatBaseline.txt b/src/Avalonia.Controls/ApiCompatBaseline.txt
index 7199c15d21..a79b3b4d7b 100644
--- a/src/Avalonia.Controls/ApiCompatBaseline.txt
+++ b/src/Avalonia.Controls/ApiCompatBaseline.txt
@@ -4,10 +4,11 @@ InterfacesShouldHaveSameMembers : Interface member 'public System.Boolean Avalon
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Controls.IMenuItem.StaysOpenOnClick.set(System.Boolean)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Controls.INativeMenuExporterEventsImplBridge.RaiseClosed()' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Controls.INativeMenuExporterEventsImplBridge.RaiseOpening()' is present in the implementation but not in the contract.
+MembersMustExist : Member 'public Avalonia.AvaloniaProperty<Avalonia.Media.Stretch> Avalonia.AvaloniaProperty<Avalonia.Media.Stretch> Avalonia.Controls.Viewbox.StretchProperty' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public void Avalonia.Controls.Embedding.Offscreen.OffscreenTopLevelImplBase.SetCursor(Avalonia.Platform.IPlatformHandle)' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public Avalonia.AvaloniaProperty Avalonia.AvaloniaProperty Avalonia.Controls.Notifications.NotificationCard.CloseOnClickProperty' does not exist in the implementation but it does exist in the contract.
 EnumValuesMustMatch : Enum value 'Avalonia.Platform.ExtendClientAreaChromeHints Avalonia.Platform.ExtendClientAreaChromeHints.Default' is (System.Int32)2 in the implementation but (System.Int32)1 in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platform.ITopLevelImpl.SetCursor(Avalonia.Platform.ICursorImpl)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platform.ITopLevelImpl.SetCursor(Avalonia.Platform.IPlatformHandle)' is present in the contract but not in the implementation.
 MembersMustExist : Member 'public void Avalonia.Platform.ITopLevelImpl.SetCursor(Avalonia.Platform.IPlatformHandle)' does not exist in the implementation but it does exist in the contract.
-Total Issues: 11
+Total Issues: 12
diff --git a/src/Avalonia.Controls/Viewbox.cs b/src/Avalonia.Controls/Viewbox.cs
index 15ca070de2..624c61bb82 100644
--- a/src/Avalonia.Controls/Viewbox.cs
+++ b/src/Avalonia.Controls/Viewbox.cs
@@ -11,9 +11,8 @@ namespace Avalonia.Controls
         /// <summary>
         /// Defines the <see cref="Stretch"/> property.
         /// </summary>
-        public static readonly AvaloniaProperty<Stretch> StretchProperty =
-            AvaloniaProperty.RegisterDirect<Viewbox, Stretch>(nameof(Stretch),
-                v => v.Stretch, (c, v) => c.Stretch = v, Stretch.Uniform);
+        public static readonly StyledProperty<Stretch> StretchProperty =
+            AvaloniaProperty.Register<Image, Stretch>(nameof(Stretch), Stretch.Uniform);
 
         /// <summary>
         /// Defines the <see cref="StretchDirection"/> property.
@@ -21,8 +20,6 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<StretchDirection> StretchDirectionProperty =
             AvaloniaProperty.Register<Viewbox, StretchDirection>(nameof(StretchDirection), StretchDirection.Both);
 
-        private Stretch _stretch = Stretch.Uniform;
-
         static Viewbox()
         {
             ClipToBoundsProperty.OverrideDefaultValue<Viewbox>(true);
@@ -35,8 +32,8 @@ namespace Avalonia.Controls
         /// </summary>
         public Stretch Stretch
         {
-            get => _stretch;
-            set => SetAndRaise(StretchProperty, ref _stretch, value);
+            get => GetValue(StretchProperty);
+            set => SetValue(StretchProperty, value);
         }
 
         /// <summary>

From 08382e5bf554381a327e215b191d901ab4b16663 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Sat, 15 May 2021 20:52:59 -0400
Subject: [PATCH 11/15] Fix SolidColorBrushAnimator NRE

---
 .../Animation/Animators/SolidColorBrushAnimator.cs     | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/Avalonia.Visuals/Animation/Animators/SolidColorBrushAnimator.cs b/src/Avalonia.Visuals/Animation/Animators/SolidColorBrushAnimator.cs
index cec96fecf8..a56cc1de8c 100644
--- a/src/Avalonia.Visuals/Animation/Animators/SolidColorBrushAnimator.cs
+++ b/src/Avalonia.Visuals/Animation/Animators/SolidColorBrushAnimator.cs
@@ -12,6 +12,11 @@ namespace Avalonia.Animation.Animators
     {
         public override ISolidColorBrush Interpolate(double progress, ISolidColorBrush oldValue, ISolidColorBrush newValue)
         {
+            if (oldValue is null || newValue is null)
+            {
+                return oldValue;
+            }
+
             return new ImmutableSolidColorBrush(ColorAnimator.InterpolateCore(progress, oldValue.Color, newValue.Color));
         }
 
@@ -26,6 +31,11 @@ namespace Avalonia.Animation.Animators
     {    
         public override SolidColorBrush Interpolate(double progress, SolidColorBrush oldValue, SolidColorBrush newValue)
         {
+            if (oldValue is null || newValue is null)
+            {
+                return oldValue;
+            }
+
             return new SolidColorBrush(ColorAnimator.InterpolateCore(progress, oldValue.Color, newValue.Color));
         }
     }

From 34505c4c8b41c9f98553e4b2f500a8462be5811f Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Sat, 15 May 2021 20:53:28 -0400
Subject: [PATCH 12/15] Reuse Animator.Interpolate in transitions code

---
 .../Transitions/DoubleTransition.cs           | 10 ++++-----
 .../Transitions/FloatTransition.cs            |  7 +++++--
 .../Transitions/IntegerTransition.cs          |  7 +++++--
 .../Transitions/CornerRadiusTransition.cs     | 21 +++++--------------
 .../Animation/Transitions/PointTransition.cs  | 10 ++++-----
 .../Animation/Transitions/SizeTransition.cs   | 10 ++++-----
 .../Transitions/ThicknessTransition.cs        | 10 ++++-----
 .../Animation/Transitions/VectorTransition.cs | 10 ++++-----
 8 files changed, 40 insertions(+), 45 deletions(-)

diff --git a/src/Avalonia.Animation/Transitions/DoubleTransition.cs b/src/Avalonia.Animation/Transitions/DoubleTransition.cs
index 8cae1e1f81..d5bb1aac20 100644
--- a/src/Avalonia.Animation/Transitions/DoubleTransition.cs
+++ b/src/Avalonia.Animation/Transitions/DoubleTransition.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Reactive.Linq;
 
+using Avalonia.Animation.Animators;
+
 namespace Avalonia.Animation
 {
     /// <summary>
@@ -8,15 +10,13 @@ namespace Avalonia.Animation
     /// </summary>  
     public class DoubleTransition : Transition<double>
     {
+        private static readonly DoubleAnimator s_animator = new DoubleAnimator();
+
         /// <inheritdocs/>
         public override IObservable<double> DoTransition(IObservable<double> progress, double oldValue, double newValue)
         {
             return progress
-                .Select(p =>
-                {
-                    var f = Easing.Ease(p);
-                    return ((newValue - oldValue) * f) + oldValue;
-                });
+                .Select(progress => s_animator.Interpolate(Easing.Ease(progress), oldValue, newValue));
         }
     }
 }
diff --git a/src/Avalonia.Animation/Transitions/FloatTransition.cs b/src/Avalonia.Animation/Transitions/FloatTransition.cs
index 427563e559..37b644fa96 100644
--- a/src/Avalonia.Animation/Transitions/FloatTransition.cs
+++ b/src/Avalonia.Animation/Transitions/FloatTransition.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Reactive.Linq;
 
+using Avalonia.Animation.Animators;
+
 namespace Avalonia.Animation
 {
     /// <summary>
@@ -8,12 +10,13 @@ namespace Avalonia.Animation
     /// </summary>  
     public class FloatTransition : Transition<float>
     {
+        private static readonly FloatAnimator s_animator = new FloatAnimator();
+
         /// <inheritdocs/>
         public override IObservable<float> DoTransition(IObservable<double> progress, float oldValue, float newValue)
         {
-            var delta = newValue - oldValue;
             return progress
-                .Select(p => (float)Easing.Ease(p) * delta + oldValue);
+                .Select(progress => s_animator.Interpolate(Easing.Ease(progress), oldValue, newValue));
         }
     }
 }
diff --git a/src/Avalonia.Animation/Transitions/IntegerTransition.cs b/src/Avalonia.Animation/Transitions/IntegerTransition.cs
index 7a85bd75dc..223b2ba531 100644
--- a/src/Avalonia.Animation/Transitions/IntegerTransition.cs
+++ b/src/Avalonia.Animation/Transitions/IntegerTransition.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Reactive.Linq;
 
+using Avalonia.Animation.Animators;
+
 namespace Avalonia.Animation
 {
     /// <summary>
@@ -8,12 +10,13 @@ namespace Avalonia.Animation
     /// </summary>  
     public class IntegerTransition : Transition<int>
     {
+        private static readonly Int32Animator s_animator = new Int32Animator();
+
         /// <inheritdocs/>
         public override IObservable<int> DoTransition(IObservable<double> progress, int oldValue, int newValue)
         {
-            var delta = newValue - oldValue;
             return progress
-                .Select(p => (int)(Easing.Ease(p) * delta + oldValue));
+                .Select(progress => s_animator.Interpolate(Easing.Ease(progress), oldValue, newValue));
         }
     }
 }
diff --git a/src/Avalonia.Visuals/Animation/Transitions/CornerRadiusTransition.cs b/src/Avalonia.Visuals/Animation/Transitions/CornerRadiusTransition.cs
index 0b0f04ca94..9ffdf53694 100644
--- a/src/Avalonia.Visuals/Animation/Transitions/CornerRadiusTransition.cs
+++ b/src/Avalonia.Visuals/Animation/Transitions/CornerRadiusTransition.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Reactive.Linq;
 
+using Avalonia.Animation.Animators;
+
 namespace Avalonia.Animation
 {
     /// <summary>
@@ -8,26 +10,13 @@ namespace Avalonia.Animation
     /// </summary>  
     public class CornerRadiusTransition : Transition<CornerRadius>
     {
+        private static readonly CornerRadiusAnimator s_animator = new CornerRadiusAnimator();
+
         /// <inheritdocs/>
         public override IObservable<CornerRadius> DoTransition(IObservable<double> progress, CornerRadius oldValue, CornerRadius newValue)
         {
             return progress
-                .Select(p =>
-                {
-                    var f = Easing.Ease(p);
-
-                    var deltaTL = newValue.TopLeft - oldValue.TopLeft;
-                    var deltaTR = newValue.TopRight - oldValue.TopRight;
-                    var deltaBR = newValue.BottomRight - oldValue.BottomRight;
-                    var deltaBL = newValue.BottomLeft - oldValue.BottomLeft;
-
-                    var nTL = f * deltaTL + oldValue.TopLeft;
-                    var nTR = f * deltaTR + oldValue.TopRight;
-                    var nBR = f * deltaBR + oldValue.BottomRight;
-                    var nBL = f * deltaBL + oldValue.BottomLeft;
-
-                    return new CornerRadius(nTL, nTR, nBR, nBL);
-                });
+                .Select(progress => s_animator.Interpolate(Easing.Ease(progress), oldValue, newValue));
         }
     }
 }
diff --git a/src/Avalonia.Visuals/Animation/Transitions/PointTransition.cs b/src/Avalonia.Visuals/Animation/Transitions/PointTransition.cs
index 29db5fc868..fbe24c6d55 100644
--- a/src/Avalonia.Visuals/Animation/Transitions/PointTransition.cs
+++ b/src/Avalonia.Visuals/Animation/Transitions/PointTransition.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Reactive.Linq;
 
+using Avalonia.Animation.Animators;
+
 namespace Avalonia.Animation
 {
     /// <summary>
@@ -8,15 +10,13 @@ namespace Avalonia.Animation
     /// </summary>  
     public class PointTransition : Transition<Point>
     {
+        private static readonly PointAnimator s_animator = new PointAnimator();
+
         /// <inheritdocs/>
         public override IObservable<Point> DoTransition(IObservable<double> progress, Point oldValue, Point newValue)
         {
             return progress
-                .Select(p =>
-                {
-                    var f = Easing.Ease(p);
-                    return ((newValue - oldValue) * f) + oldValue;
-                });
+                .Select(progress => s_animator.Interpolate(Easing.Ease(progress), oldValue, newValue));
         }
     }
 }
diff --git a/src/Avalonia.Visuals/Animation/Transitions/SizeTransition.cs b/src/Avalonia.Visuals/Animation/Transitions/SizeTransition.cs
index b40e789915..464f83bec7 100644
--- a/src/Avalonia.Visuals/Animation/Transitions/SizeTransition.cs
+++ b/src/Avalonia.Visuals/Animation/Transitions/SizeTransition.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Reactive.Linq;
 
+using Avalonia.Animation.Animators;
+
 namespace Avalonia.Animation
 {
     /// <summary>
@@ -8,15 +10,13 @@ namespace Avalonia.Animation
     /// </summary>  
     public class SizeTransition : Transition<Size>
     {
+        private static readonly SizeAnimator s_animator = new SizeAnimator();
+
         /// <inheritdocs/>
         public override IObservable<Size> DoTransition(IObservable<double> progress, Size oldValue, Size newValue)
         {
             return progress
-                .Select(p =>
-                {
-                    var f = Easing.Ease(p);
-                    return ((newValue - oldValue) * f) + oldValue;
-                });
+                .Select(progress => s_animator.Interpolate(Easing.Ease(progress), oldValue, newValue));
         }
     }
 }
diff --git a/src/Avalonia.Visuals/Animation/Transitions/ThicknessTransition.cs b/src/Avalonia.Visuals/Animation/Transitions/ThicknessTransition.cs
index 28d4ea067f..9fb3380780 100644
--- a/src/Avalonia.Visuals/Animation/Transitions/ThicknessTransition.cs
+++ b/src/Avalonia.Visuals/Animation/Transitions/ThicknessTransition.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Reactive.Linq;
 
+using Avalonia.Animation.Animators;
+
 namespace Avalonia.Animation
 {
     /// <summary>
@@ -8,15 +10,13 @@ namespace Avalonia.Animation
     /// </summary>  
     public class ThicknessTransition : Transition<Thickness>
     {
+        private static readonly ThicknessAnimator s_animator = new ThicknessAnimator();
+
         /// <inheritdocs/>
         public override IObservable<Thickness> DoTransition(IObservable<double> progress, Thickness oldValue, Thickness newValue)
         {
             return progress
-                .Select(p =>
-                {
-                    var f = Easing.Ease(p);
-                    return ((newValue - oldValue) * f) + oldValue;
-                });
+                .Select(progress => s_animator.Interpolate(Easing.Ease(progress), oldValue, newValue));
         }
     }
 }
diff --git a/src/Avalonia.Visuals/Animation/Transitions/VectorTransition.cs b/src/Avalonia.Visuals/Animation/Transitions/VectorTransition.cs
index c073e8e192..5038117faa 100644
--- a/src/Avalonia.Visuals/Animation/Transitions/VectorTransition.cs
+++ b/src/Avalonia.Visuals/Animation/Transitions/VectorTransition.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Reactive.Linq;
 
+using Avalonia.Animation.Animators;
+
 namespace Avalonia.Animation
 {
     /// <summary>
@@ -8,15 +10,13 @@ namespace Avalonia.Animation
     /// </summary>  
     public class VectorTransition : Transition<Vector>
     {
+        private static readonly VectorAnimator s_animator = new VectorAnimator();
+
         /// <inheritdocs/>
         public override IObservable<Vector> DoTransition(IObservable<double> progress, Vector oldValue, Vector newValue)
         {
             return progress
-                .Select(p =>
-                {
-                    var f = Easing.Ease(p);
-                    return ((newValue - oldValue) * f) + oldValue;
-                });
+                .Select(progress => s_animator.Interpolate(Easing.Ease(progress), oldValue, newValue));
         }
     }
 }

From f29d050e73c0144909757c085bf6bcd5a156f7ae Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Sat, 15 May 2021 20:53:45 -0400
Subject: [PATCH 13/15] Add BoxShadows transition

---
 .../Transitions/BoxShadowsTransition.cs       | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 src/Avalonia.Visuals/Animation/Transitions/BoxShadowsTransition.cs

diff --git a/src/Avalonia.Visuals/Animation/Transitions/BoxShadowsTransition.cs b/src/Avalonia.Visuals/Animation/Transitions/BoxShadowsTransition.cs
new file mode 100644
index 0000000000..008613fb40
--- /dev/null
+++ b/src/Avalonia.Visuals/Animation/Transitions/BoxShadowsTransition.cs
@@ -0,0 +1,23 @@
+using System;
+using System.Reactive.Linq;
+
+using Avalonia.Animation.Animators;
+using Avalonia.Media;
+
+namespace Avalonia.Animation
+{
+    /// <summary>
+    /// Transition class that handles <see cref="AvaloniaProperty"/> with <see cref="BoxShadows"/> type.
+    /// </summary>  
+    public class BoxShadowsTransition : Transition<BoxShadows>
+    {
+        private static readonly BoxShadowsAnimator s_animator = new BoxShadowsAnimator();
+
+        /// <inheritdocs/>
+        public override IObservable<BoxShadows> DoTransition(IObservable<double> progress, BoxShadows oldValue, BoxShadows newValue)
+        {
+            return progress
+                .Select(progress => s_animator.Interpolate(Easing.Ease(progress), oldValue, newValue));
+        }
+    }
+}

From f5a01afc6de7ac794d9dfb1a16792cf7f6296ee0 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Sat, 15 May 2021 22:05:01 -0400
Subject: [PATCH 14/15] Update RenderDemo pages

---
 samples/RenderDemo/Pages/AnimationsPage.xaml  |  7 +-
 samples/RenderDemo/Pages/TransitionsPage.xaml | 65 +++++++++++++++++--
 2 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/samples/RenderDemo/Pages/AnimationsPage.xaml b/samples/RenderDemo/Pages/AnimationsPage.xaml
index 12fb31ea59..21c7d68b5d 100644
--- a/samples/RenderDemo/Pages/AnimationsPage.xaml
+++ b/samples/RenderDemo/Pages/AnimationsPage.xaml
@@ -1,7 +1,8 @@
 <UserControl 
   xmlns="https://github.com/avaloniaui" 
   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
-  x:Class="RenderDemo.Pages.AnimationsPage">
+  x:Class="RenderDemo.Pages.AnimationsPage"
+  MaxWidth="600">
   <UserControl.Styles>
     <Styles>
       <Styles.Resources>
@@ -167,8 +168,8 @@
       <StackPanel.Clock>
         <Clock />
       </StackPanel.Clock>
-      <StackPanel Orientation="Horizontal" VerticalAlignment="Center">
-        <TextBlock VerticalAlignment="Center">Hover to activate Transform Keyframe Animations.</TextBlock>
+      <StackPanel Orientation="Horizontal" VerticalAlignment="Center" Spacing="20">
+        <TextBlock VerticalAlignment="Center">Hover to activate Keyframe Animations.</TextBlock>
         <Button Content="{Binding PlayStateText}" Command="{Binding TogglePlayState}" Click="ToggleClock" />
       </StackPanel>
       <WrapPanel ClipToBounds="False">
diff --git a/samples/RenderDemo/Pages/TransitionsPage.xaml b/samples/RenderDemo/Pages/TransitionsPage.xaml
index d6da293ff3..f9f69fb341 100644
--- a/samples/RenderDemo/Pages/TransitionsPage.xaml
+++ b/samples/RenderDemo/Pages/TransitionsPage.xaml
@@ -1,7 +1,8 @@
 <UserControl 
   xmlns="https://github.com/avaloniaui" 
-  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
-  x:Class="RenderDemo.Pages.TransitionsPage">
+  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+  x:Class="RenderDemo.Pages.TransitionsPage"
+  MaxWidth="600">
   <UserControl.Styles>
     <Styles>
       <Styles.Resources>
@@ -90,6 +91,56 @@
         <Setter Property="RenderTransform" Value="none" />
       </Style>
 
+      <Style Selector="Border.Rect7">
+        <Setter Property="Transitions">
+          <Transitions>
+            <DoubleTransition Property="Height" Duration="0:0:0.5" />
+          </Transitions>
+        </Setter>
+      </Style>
+
+      <Style Selector="Border.Rect7:pointerover">
+        <Setter Property="Height" Value="50" />
+      </Style>
+
+      <Style Selector="Border.Rect8">
+        <Setter Property="Transitions">
+          <Transitions>
+            <CornerRadiusTransition Property="CornerRadius" Duration="0:0:0.5" />
+          </Transitions>
+        </Setter>
+      </Style>
+
+      <Style Selector="Border.Rect8:pointerover">
+        <Setter Property="CornerRadius" Value="50" />
+      </Style>
+
+      <Style Selector="Border.Rect9">
+        <Setter Property="Transitions">
+          <Transitions>
+            <ThicknessTransition Property="Padding" Duration="0:0:0.5" />
+          </Transitions>
+        </Setter>
+      </Style>
+
+      <Style Selector="Border.Rect9:pointerover">
+        <Setter Property="Padding" Value="10" />
+      </Style>
+
+      <Style Selector="Border.Shadow">
+        <Setter Property="Background" Value="Transparent"/>        
+        <Setter Property="BorderBrush" Value="Black"/>
+        <Setter Property="BorderThickness" Value="1"/>
+        <Setter Property="BoxShadow" Value="inset 0 0 0 2 Red, -15 -15 Green"/>
+        <Setter Property="Transitions">
+          <Transitions>
+            <BoxShadowsTransition Property="BoxShadow" Duration="0:0:0.5" />
+          </Transitions>
+        </Setter>
+      </Style>
+      <Style Selector="Border.Shadow:pointerover">
+        <Setter Property="BoxShadow" Value="inset 30 30 20 30 Green, 20 40 20 10 Red"/>
+      </Style>
     </Styles>
   </UserControl.Styles>
 
@@ -98,8 +149,8 @@
       <StackPanel.Clock>
         <Clock />
       </StackPanel.Clock>
-      <StackPanel Orientation="Horizontal" VerticalAlignment="Center">
-        <TextBlock VerticalAlignment="Center">Hover to activate Transform Keyframe Animations.</TextBlock>
+      <StackPanel Orientation="Horizontal" VerticalAlignment="Center" Spacing="20">
+        <TextBlock VerticalAlignment="Center">Hover to activate Transitions.</TextBlock>
         <Button Content="{Binding PlayStateText}" Command="{Binding TogglePlayState}" Click="ToggleClock" />
       </StackPanel>
       <WrapPanel ClipToBounds="False">
@@ -109,6 +160,12 @@
         <Border Classes="Test Rect4" Background="Navy"/>
         <Border Classes="Test Rect5" Background="SeaGreen"/>
         <Border Classes="Test Rect6" Background="Orange"/>
+        <Border Classes="Test Rect7" Background="Gold"/>
+        <Border Classes="Test Rect8" Background="Gray" />
+        <Border Classes="Test Rect9" Background="Red" />
+
+        <Border Classes="Test Shadow" CornerRadius="10" Child="{x:Null}" />
+        <Border Classes="Test Shadow" CornerRadius="0 30 60 0" Child="{x:Null}" />
       </WrapPanel>
     </StackPanel>
   </Grid>

From e3bfb4f5980321273738c89a8a7bae5be957dfa9 Mon Sep 17 00:00:00 2001
From: Deadpikle <Deadpikle@users.noreply.github.com>
Date: Sun, 16 May 2021 12:39:47 -0400
Subject: [PATCH 15/15] DataGrid SelectedIndex & SelectedItem -> TwoWay

Default `DataGrid` `SelectedIndex` and `SelectedItem` binding mode to `TwoWay`.
---
 src/Avalonia.Controls.DataGrid/DataGrid.cs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Controls.DataGrid/DataGrid.cs b/src/Avalonia.Controls.DataGrid/DataGrid.cs
index a070a1b9d7..1b4632d368 100644
--- a/src/Avalonia.Controls.DataGrid/DataGrid.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGrid.cs
@@ -535,7 +535,8 @@ namespace Avalonia.Controls
             AvaloniaProperty.RegisterDirect<DataGrid, int>(
                 nameof(SelectedIndex),
                 o => o.SelectedIndex,
-                (o, v) => o.SelectedIndex = v);
+                (o, v) => o.SelectedIndex = v,
+                defaultBindingMode: BindingMode.TwoWay);
 
         /// <summary>
         /// Gets or sets the index of the current selection.
@@ -553,7 +554,8 @@ namespace Avalonia.Controls
             AvaloniaProperty.RegisterDirect<DataGrid, object>(
                 nameof(SelectedItem),
                 o => o.SelectedItem,
-                (o, v) => o.SelectedItem = v);
+                (o, v) => o.SelectedItem = v,
+                defaultBindingMode: BindingMode.TwoWay);
 
         /// <summary>
         /// Gets or sets the data item corresponding to the selected row.