Merge branch 'master' into features/Controls/HotkeyManager_Without_Command

native/Avalonia.Native/src/OSX/controlhost.mm

@@ -36,7 +36,10 @@ public:
     virtual void DestroyDefaultChild(void* child) override
     {
         // ARC will release the object for us
+        #pragma clang diagnostic push
+        #pragma clang diagnostic ignored "-Wunused-value"
         (__bridge_transfer NSView*) child;
+        #pragma clang diagnostic pop
     }
 };
 

native/Avalonia.Native/src/OSX/window.mm

@@ -457,7 +457,8 @@ public:
             }
             
             point = ConvertPointY(point);
-            auto viewPoint = [Window convertScreenToBase:ToNSPoint(point)];
+            NSRect convertRect = [Window convertRectToScreen:NSMakeRect(point.X, point.Y, 0.0, 0.0)];
+            auto viewPoint = NSMakePoint(convertRect.origin.x, convertRect.origin.y);
             
             *ret = [View translateLocalPoint:ToAvnPoint(viewPoint)];
             
@@ -477,7 +478,8 @@ public:
             }
             
             auto cocoaViewPoint =  ToNSPoint([View translateLocalPoint:point]);
-            auto cocoaScreenPoint = [Window convertBaseToScreen:cocoaViewPoint];
+            NSRect convertRect = [Window convertRectToScreen:NSMakeRect(cocoaViewPoint.x, cocoaViewPoint.y, 0.0, 0.0)];
+            auto cocoaScreenPoint = NSPointFromCGPoint(NSMakePoint(convertRect.origin.x, convertRect.origin.y));
             *ret = ConvertPointY(ToAvnPoint(cocoaScreenPoint));
             
             return S_OK;
@@ -573,7 +575,8 @@ public:
         if(!((nseventType >= NSEventTypeLeftMouseDown && nseventType <= NSEventTypeMouseExited)
            || (nseventType >= NSEventTypeOtherMouseDown && nseventType <= NSEventTypeOtherMouseDragged)))
         {
-            auto nspoint = [Window convertBaseToScreen: ToNSPoint(point)];
+            NSRect convertRect = [Window convertRectToScreen:NSMakeRect(point.X, point.Y, 0.0, 0.0)];
+            auto nspoint = NSMakePoint(convertRect.origin.x, convertRect.origin.y);            
             CGPoint cgpoint = NSPointToCGPoint(nspoint);
             auto cgevent = CGEventCreateMouseEvent(NULL, kCGEventLeftMouseDown, cgpoint, kCGMouseButtonLeft);
             nsevent = [NSEvent eventWithCGEvent: cgevent];

readme.md

@@ -1,7 +1,7 @@
 [![Telegram](https://raw.githubusercontent.com/Patrolavia/telegram-badge/master/chat.svg)](https://t.me/Avalonia)
 [![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/AvaloniaUI/Avalonia?utm_campaign=pr-badge&utm_content=badge&utm_medium=badge&utm_source=badge) [![Discord](https://img.shields.io/badge/discord-join%20chat-46BC99)]( https://aka.ms/dotnet-discord) [![Build Status](https://dev.azure.com/AvaloniaUI/AvaloniaUI/_apis/build/status/AvaloniaUI.Avalonia)](https://dev.azure.com/AvaloniaUI/AvaloniaUI/_build/latest?definitionId=4) [![Backers on Open Collective](https://opencollective.com/Avalonia/backers/badge.svg)](#backers) [![Sponsors on Open Collective](https://opencollective.com/Avalonia/sponsors/badge.svg)](#sponsors) ![License](https://img.shields.io/github/license/avaloniaui/avalonia.svg)
 <br />
-[![NuGet](https://img.shields.io/nuget/v/Avalonia.svg)](https://www.nuget.org/packages/Avalonia) [![downloads](https://img.shields.io/nuget/dt/avalonia)](https://www.nuget.org/packages/Avalonia) [![MyGet](https://img.shields.io/myget/avalonia-ci/vpre/Avalonia.svg?label=myget)](https://www.myget.org/gallery/avalonia-ci) ![Size](https://img.shields.io/github/repo-size/avaloniaui/avalonia.svg) 
+[![NuGet](https://img.shields.io/nuget/v/Avalonia.svg)](https://www.nuget.org/packages/Avalonia) [![downloads](https://img.shields.io/nuget/dt/avalonia)](https://www.nuget.org/packages/Avalonia)  ![Size](https://img.shields.io/github/repo-size/avaloniaui/avalonia.svg) 
 
 ## 📖 About 
 

samples/ControlCatalog/Pages/ButtonsPage.xaml

@@ -147,6 +147,35 @@
       </StackPanel>
     </Border>
 
+    <!-- DropDownButton -->
+    <Border Classes="header-border">
+      <StackPanel Orientation="Vertical"
+                  Spacing="4">
+        <TextBlock Text="DropDownButton"
+                   Classes="header" />
+        <TextBlock TextWrapping="Wrap">A button with an added drop-down chevron to visually indicate it has a flyout with additional actions.</TextBlock>
+      </StackPanel>
+    </Border>
+
+    <Border Classes="thin"
+            Padding="15">
+      <StackPanel Orientation="Vertical"
+                  Spacing="8">
+        <DropDownButton Flyout="{StaticResource SharedMenuFlyout}">
+          <TextBlock Text="Drop Down Button" />
+        </DropDownButton>
+        <DropDownButton Padding="0,0,8,0">
+          <Border Background="Teal"
+                  HorizontalAlignment="Stretch"
+                  VerticalAlignment="Stretch"
+                  Height="32"
+                  Width="32" />
+        </DropDownButton>
+        <DropDownButton IsEnabled="False">Disabled</DropDownButton>
+        <DropDownButton />
+      </StackPanel>
+    </Border>
+
     <!-- SplitButton -->
     <Border Classes="header-border">
       <StackPanel Orientation="Vertical"
@@ -169,7 +198,8 @@
           <TextBlock Text="Disabled" />
         </SplitButton>
         <SplitButton Flyout="{StaticResource SharedMenuFlyout}"
-                     Content="Re-themed">
+                     Content="Re-themed"
+                     Foreground="White">
           <SplitButton.Styles>
             <Style>
               <Style.Resources>

samples/ControlCatalog/Pages/CanvasPage.xaml

@@ -4,7 +4,7 @@
   <StackPanel Orientation="Vertical" Spacing="4">
     <TextBlock Classes="h2">A panel which lays out its children by explicit coordinates</TextBlock>
     <Canvas Background="Yellow" Width="300" Height="400">
-      <Rectangle Fill="Blue" Width="63" Height="41" Canvas.Left="40" Canvas.Top="31">
+      <Rectangle Fill="Blue" Width="63" Height="41" Canvas.Left="40" Canvas.Top="31" RadiusX="10" RadiusY="10">
         <Rectangle.OpacityMask>
           <LinearGradientBrush StartPoint="0%,0%" EndPoint="100%,100%">
             <LinearGradientBrush.GradientStops>
@@ -12,8 +12,9 @@
               <GradientStop Offset="1" Color="Transparent"/>
             </LinearGradientBrush.GradientStops>
           </LinearGradientBrush>
-        </Rectangle.OpacityMask>     
+        </Rectangle.OpacityMask>
       </Rectangle>
+      <Rectangle Fill="Green" Stroke="Black" StrokeThickness="2" Width="40" Height="20" Canvas.Left="150" Canvas.Top="10" RadiusX="10" RadiusY="5" />
       <Ellipse Fill="Green" Width="58" Height="58" Canvas.Left="88" Canvas.Top="100"/>
       <Path Fill="Orange" Data="M 0,0 c 0,0 50,0 50,-50 c 0,0 50,0 50,50 h -50 v 50 l -50,-50 Z" Canvas.Left="30" Canvas.Top="250"/>
       <Path Fill="OrangeRed" Canvas.Left="180" Canvas.Top="250">

samples/ControlCatalog/Pages/PointersPage.cs

@@ -7,6 +7,7 @@ using System.Runtime.InteropServices;
 using System.Threading;
 using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Controls.Documents;
 using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Media;
@@ -131,7 +132,7 @@ public class PointersPage : Decorator
     {
         public PointerIntermediatePointsTab()
         {
-            this[TextBlock.ForegroundProperty] = Brushes.Black;
+            this[TextElement.ForegroundProperty] = Brushes.Black;
             var slider = new Slider
             {
                 Margin = new Thickness(5),

samples/RenderDemo/MainWindow.xaml

@@ -60,6 +60,9 @@
     <TabItem Header="FormattedText">
       <pages:FormattedTextPage />
     </TabItem>
+    <TabItem Header="TextFormatter">
+      <pages:TextFormatterPage />
+    </TabItem>
     <TabItem Header="LineBounds">
       <pages:LineBoundsPage />
     </TabItem>

samples/RenderDemo/Pages/TextFormatterPage.axaml

@@ -0,0 +1,7 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
+             x:Class="RenderDemo.Pages.TextFormatterPage">
+</UserControl>

samples/RenderDemo/Pages/TextFormatterPage.axaml.cs

@@ -0,0 +1,118 @@
+using System;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+using Avalonia.Media;
+using Avalonia.Media.TextFormatting;
+
+namespace RenderDemo.Pages
+{
+    public class TextFormatterPage : UserControl
+    {
+        private TextLine _textLine;
+        
+        public TextFormatterPage()
+        {
+            this.InitializeComponent();
+        }
+
+        private void InitializeComponent()
+        {
+            AvaloniaXamlLoader.Load(this);
+        }
+        
+        public override void Render(DrawingContext context)
+        {
+            _textLine?.Draw(context, new Point());
+        }
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            var defaultRunProperties = new GenericTextRunProperties(Typeface.Default, foregroundBrush: Brushes.Black,
+                baselineAlignment: BaselineAlignment.Center);
+            var paragraphProperties = new GenericTextParagraphProperties(defaultRunProperties);
+
+            var control = new Button { Content = new TextBlock { Text = "ClickMe" } };
+            
+            Content = control;
+            
+            var textSource = new CustomTextSource(control, defaultRunProperties);
+
+            control.Measure(Size.Infinity);
+
+            _textLine =
+                TextFormatter.Current.FormatLine(textSource, 0, double.PositiveInfinity, paragraphProperties);
+            
+            return base.MeasureOverride(availableSize);
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            var currentX = 0d;
+            
+            foreach (var textRun in _textLine.TextRuns)
+            {
+                if (textRun is ControlRun controlRun)
+                {
+                    controlRun.Control.Arrange(new Rect(new Point(currentX, 0), controlRun.Size));
+                }
+
+                if (textRun is DrawableTextRun drawableTextRun)
+                {
+                    currentX += drawableTextRun.Size.Width;
+                }
+            }
+            
+            return finalSize;
+        }
+
+        private class CustomTextSource : ITextSource
+        {
+            private readonly Control _control;
+            private readonly TextRunProperties _defaultProperties;
+            private readonly string _text = "<-Hello World->";
+
+            public CustomTextSource(Control control, TextRunProperties defaultProperties)
+            {
+                _control = control;
+                _defaultProperties = defaultProperties;
+            }
+            
+            public TextRun? GetTextRun(int textSourceIndex)
+            {
+                if (textSourceIndex >= _text.Length * 2 + TextRun.DefaultTextSourceLength)
+                {
+                    return null;
+                }
+
+                if (textSourceIndex == _text.Length)
+                {
+                    return new ControlRun(_control, _defaultProperties);
+                }
+
+                return new TextCharacters(_text.AsMemory(), _defaultProperties);
+            }
+        }
+
+        private class ControlRun : DrawableTextRun
+        {
+            private readonly Control _control;
+
+            public ControlRun(Control control, TextRunProperties properties)
+            {
+                _control = control;
+                Properties = properties;
+            }
+
+            public Control Control => _control;
+            public override Size Size => _control.DesiredSize;
+            public override double Baseline => 0;
+            public override TextRunProperties? Properties { get; }
+
+            public override void Draw(DrawingContext drawingContext, Point origin)
+            {
+                // noop
+            }
+        }
+    }
+}

samples/RenderDemo/RenderDemo.csproj

@@ -5,6 +5,10 @@
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="..\..\src\Avalonia.Visuals\Rendering\SceneGraph\LineBoundsHelper.cs" Link="LineBoundsHelper.cs" />
+    <Compile Update="Pages\TextFormatterPage.axaml.cs">
+      <DependentUpon>TextFormatterPage.axaml</DependentUpon>
+      <SubType>Code</SubType>
+    </Compile>
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\src\Avalonia.Diagnostics\Avalonia.Diagnostics.csproj" />

samples/SampleControls/HamburgerMenu/HamburgerMenu.xaml

@@ -195,9 +195,9 @@
                               VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                               Content="{TemplateBinding Header}"
                               ContentTemplate="{TemplateBinding HeaderTemplate}"
-                              TextBlock.FontFamily="{TemplateBinding FontFamily}"
-                              TextBlock.FontSize="{TemplateBinding FontSize}"
-                              TextBlock.FontWeight="{TemplateBinding FontWeight}" />
+                              TextElement.FontFamily="{TemplateBinding FontFamily}"
+                              TextElement.FontSize="{TemplateBinding FontSize}"
+                              TextElement.FontWeight="{TemplateBinding FontWeight}" />
           </Panel>
         </Border>
       </ControlTemplate>
@@ -216,25 +216,25 @@
                           Content="{TemplateBinding Content}"
                           ContentTemplate="{TemplateBinding ContentTemplate}"
                           CornerRadius="{TemplateBinding CornerRadius}"
-                          TextBlock.FontFamily="{TemplateBinding FontFamily}"
-                          TextBlock.FontSize="{TemplateBinding FontSize}"
-                          TextBlock.FontWeight="{TemplateBinding FontWeight}" />
+                          TextElement.FontFamily="{TemplateBinding FontFamily}"
+                          TextElement.FontSize="{TemplateBinding FontSize}"
+                          TextElement.FontWeight="{TemplateBinding FontWeight}" />
       </ControlTemplate>
     </Setter>
   </Style>
   <Style Selector="catalog|HamburgerMenu > TabItem /template/ Border#PART_LayoutRoot, :is(Button).NavigationButton /template/ ContentPresenter">
     <Setter Property="Border.Background" Value="Transparent" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SystemBaseHighColor}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SystemBaseHighColor}" />
   </Style>
   <Style Selector="catalog|HamburgerMenu > TabItem:pointerover /template/ Border#PART_LayoutRoot, :is(Button).NavigationButton:pointerover /template/ ContentPresenter">
     <Setter Property="Border.Background" Value="{DynamicResource SystemChromeLowColor}" />
     <Setter Property="Border.BoxShadow" Value="{StaticResource NavigationItemShadow}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource TabItemHeaderForegroundUnselectedPointerOver}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource TabItemHeaderForegroundUnselectedPointerOver}" />
   </Style>
   <Style Selector="catalog|HamburgerMenu > TabItem:pressed /template/ Border#PART_LayoutRoot, :is(Button).NavigationButton:pressed /template/ ContentPresenter">
     <Setter Property="Border.Background" Value="{DynamicResource SystemChromeLowColor}" />
     <Setter Property="Border.BoxShadow" Value="{StaticResource NavigationItemShadow}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource TabItemHeaderForegroundUnselectedPressed}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource TabItemHeaderForegroundUnselectedPressed}" />
   </Style>
   <Style Selector=":is(Button).NavigationButton:pressed">
     <Setter Property="RenderTransform" Value="none" />

src/Android/Avalonia.Android/Platform/SkiaPlatform/InvalidationAwareSurfaceView.cs

@@ -2,18 +2,22 @@ using System;
 using Android.Content;
 using Android.Graphics;
 using Android.OS;
+using Android.Runtime;
 using Android.Util;
 using Android.Views;
+using Avalonia.Android.Platform.SkiaPlatform;
 using Avalonia.Platform;
 
 namespace Avalonia.Android
 {
-    public abstract class InvalidationAwareSurfaceView : SurfaceView, ISurfaceHolderCallback, IPlatformHandle
+    public abstract class InvalidationAwareSurfaceView : SurfaceView, ISurfaceHolderCallback, IPlatformNativeSurfaceHandle
     {
         bool _invalidateQueued;
         readonly object _lock = new object();
         private readonly Handler _handler;
-   
+
+        IntPtr IPlatformHandle.Handle =>
+            AndroidFramebuffer.ANativeWindow_fromSurface(JNIEnv.Handle, Holder.Surface.Handle);
 
         public InvalidationAwareSurfaceView(Context context) : base(context)
         {
@@ -25,7 +29,7 @@ namespace Avalonia.Android
         {
             lock (_lock)
             {
-                if(_invalidateQueued)
+                if (_invalidateQueued)
                     return;
                 _handler.Post(() =>
                 {
@@ -70,7 +74,7 @@ namespace Avalonia.Android
         public void SurfaceDestroyed(ISurfaceHolder holder)
         {
             Log.Info("AVALONIA", "Surface Destroyed");
-            
+
         }
 
         protected void DoDraw()
@@ -83,5 +87,9 @@ namespace Avalonia.Android
         }
         protected abstract void Draw();
         public string HandleDescriptor => "SurfaceView";
+
+        public PixelSize Size => new PixelSize(Holder.SurfaceFrame.Width(), Holder.SurfaceFrame.Height());
+
+        public double Scaling => Resources.DisplayMetrics.Density;
     }
 }

src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs

@@ -2,7 +2,6 @@ using System;
 using System.Collections.Generic;
 using Android.Content;
 using Android.Graphics;
-using Android.Runtime;
 using Android.Views;
 using Android.Views.InputMethods;
 using Avalonia.Android.OpenGL;
@@ -38,11 +37,10 @@ namespace Avalonia.Android.Platform.SkiaPlatform
             _keyboardHelper = new AndroidKeyboardEventsHelper<TopLevelImpl>(this);
             _touchHelper = new AndroidTouchEventsHelper<TopLevelImpl>(this, () => InputRoot,
                 GetAvaloniaPointFromEvent);
-
             _gl = GlPlatformSurface.TryCreate(this);
             _framebuffer = new FramebufferManager(this);
 
-            RenderScaling = (int)_view.Resources.DisplayMetrics.Density;
+            RenderScaling = (int)_view.Scaling;
 
             MaxClientSize = new PixelSize(_view.Resources.DisplayMetrics.WidthPixels,
                 _view.Resources.DisplayMetrics.HeightPixels).ToSize(RenderScaling);
@@ -77,7 +75,7 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         public IPlatformHandle Handle => _view;
 
-        public IEnumerable<object> Surfaces => new object[] { _gl, _framebuffer };
+        public IEnumerable<object> Surfaces => new object[] { _gl, _framebuffer, Handle };
 
         public IRenderer CreateRenderer(IRenderRoot root) =>
             AndroidPlatform.Options.UseDeferredRendering
@@ -216,10 +214,9 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels => new AcrylicPlatformCompensationLevels(1, 1, 1);
 
-        IntPtr EglGlPlatformSurfaceBase.IEglWindowGlPlatformSurfaceInfo.Handle =>
-            AndroidFramebuffer.ANativeWindow_fromSurface(JNIEnv.Handle, _view.Holder.Surface.Handle);
+        IntPtr EglGlPlatformSurfaceBase.IEglWindowGlPlatformSurfaceInfo.Handle => ((IPlatformHandle)_view).Handle;
 
-        public PixelSize Size => new PixelSize(_view.Holder.SurfaceFrame.Width(), _view.Holder.SurfaceFrame.Height());
+        public PixelSize Size => _view.Size;
 
         public double Scaling => RenderScaling;
 

src/Avalonia.Animation/Easing/Easing.cs

@@ -39,7 +39,7 @@ namespace Avalonia.Animation.Easings
                 var derivedTypes = typeof(Easing).Assembly.GetTypes()
                                       .Where(p => p.Namespace == s_thisType.Namespace)
                                       .Where(p => p.IsSubclassOf(s_thisType))
-                                      .Select(p => p).ToList();
+                                      .Select(p => p);
 
                 foreach (var easingType in derivedTypes)
                     _easingTypes.Add(easingType.Name, easingType);

src/Avalonia.Base/Collections/AvaloniaDictionary.cs

@@ -123,7 +123,7 @@ namespace Avalonia.Collections
             {
                 var e = new NotifyCollectionChangedEventArgs(
                     NotifyCollectionChangedAction.Remove,
-                    old.ToList(),
+                    old.ToArray(),
                     -1);
                 CollectionChanged(this, e);
             }

src/Avalonia.Base/Collections/AvaloniaList.cs

@@ -222,7 +222,7 @@ namespace Avalonia.Collections
                 {
                     var e = ResetBehavior == ResetBehavior.Reset ?
                         EventArgsCache.ResetCollectionChanged :
-                        new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, _inner.ToList(), 0);
+                        new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, _inner.ToArray(), 0);
 
                     _inner.Clear();
 

src/Avalonia.Base/Data/Core/PropertyPath.cs

@@ -10,7 +10,7 @@ namespace Avalonia.Data.Core
 
         public PropertyPath(IEnumerable<IPropertyPathElement> elements)
         {
-            Elements = elements.ToList();
+            Elements = elements.ToArray();
         }
     }
 

src/Avalonia.Base/StyledPropertyBase.cs

@@ -159,9 +159,9 @@ namespace Avalonia
         }
 
         /// <inheritdoc/>
-        public override void Accept<TData>(IAvaloniaPropertyVisitor<TData> vistor, ref TData data)
+        public override void Accept<TData>(IAvaloniaPropertyVisitor<TData> visitor, ref TData data)
         {
-            vistor.Visit(this, ref data);
+            visitor.Visit(this, ref data);
         }
 
         /// <summary>
@@ -242,11 +242,5 @@ namespace Avalonia
             _ = type ?? throw new ArgumentNullException(nameof(type));
             return GetMetadata(type).DefaultValue;
         }
-
-        [DebuggerHidden]
-        private Func<IAvaloniaObject, TValue, TValue> Cast<THost>(Func<THost, TValue, TValue> validate)
-        {
-            return (o, v) => validate((THost)o, v);
-        }
     }
 }

src/Avalonia.Base/Utilities/AvaloniaResourcesIndex.cs

@@ -23,7 +23,7 @@ namespace Avalonia.Utilities
 
             var assetDoc = XDocument.Load(stream);
             XNamespace assetNs = assetDoc.Root!.Attribute("xmlns")!.Value;
-            List<AvaloniaResourcesIndexEntry> entries=         
+            List<AvaloniaResourcesIndexEntry> entries =         
                 (from entry in assetDoc.Root.Element(assetNs + "Entries")!.Elements(assetNs + "AvaloniaResourcesIndexEntry")
                     select new AvaloniaResourcesIndexEntry
                     {

src/Avalonia.Build.Tasks/GenerateAvaloniaResourcesTask.cs

@@ -105,7 +105,7 @@ namespace Avalonia.Build.Tasks
         {
             var typeToXamlIndex = new Dictionary<string, string>(); 
             
-            foreach (var s in sources.ToList())
+            foreach (var s in sources.ToArray())
             {
                 if (s.Path.ToLowerInvariant().EndsWith(".xaml") || s.Path.ToLowerInvariant().EndsWith(".paml") || s.Path.ToLowerInvariant().EndsWith(".axaml"))
                 {

src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs

@@ -3946,7 +3946,7 @@ namespace Avalonia.Collections
             {
                 sort.Initialize(itemType); 
 
-                if(seq is IOrderedEnumerable<object> orderedEnum)
+                if (seq is IOrderedEnumerable<object> orderedEnum)
                 {
                     seq = sort.ThenBy(orderedEnum);
                 }

src/Avalonia.Controls.DataGrid/DataGridTextColumn.cs

@@ -10,6 +10,7 @@ using System;
 using System.ComponentModel;
 using Avalonia.Layout;
 using Avalonia.Markup.Xaml.MarkupExtensions;
+using Avalonia.Controls.Documents;
 
 namespace Avalonia.Controls
 {
@@ -32,7 +33,7 @@ namespace Avalonia.Controls
         /// Identifies the FontFamily dependency property.
         /// </summary>
         public static readonly AttachedProperty<FontFamily> FontFamilyProperty =
-            TextBlock.FontFamilyProperty.AddOwner<DataGridTextColumn>();
+            TextElement.FontFamilyProperty.AddOwner<DataGridTextColumn>();
 
         /// <summary>
         /// Gets or sets the font name.
@@ -47,7 +48,7 @@ namespace Avalonia.Controls
         /// Identifies the FontSize dependency property.
         /// </summary>
         public static readonly AttachedProperty<double> FontSizeProperty =
-            TextBlock.FontSizeProperty.AddOwner<DataGridTextColumn>();
+            TextElement.FontSizeProperty.AddOwner<DataGridTextColumn>();
 
         /// <summary>
         /// Gets or sets the font size.
@@ -64,7 +65,7 @@ namespace Avalonia.Controls
         /// Identifies the FontStyle dependency property.
         /// </summary>
         public static readonly AttachedProperty<FontStyle> FontStyleProperty =
-            TextBlock.FontStyleProperty.AddOwner<DataGridTextColumn>();
+            TextElement.FontStyleProperty.AddOwner<DataGridTextColumn>();
 
         /// <summary>
         /// Gets or sets the font style.
@@ -79,7 +80,7 @@ namespace Avalonia.Controls
         /// Identifies the FontWeight dependency property.
         /// </summary>
         public static readonly AttachedProperty<FontWeight> FontWeightProperty =
-            TextBlock.FontWeightProperty.AddOwner<DataGridTextColumn>();
+            TextElement.FontWeightProperty.AddOwner<DataGridTextColumn>();
 
         /// <summary>
         /// Gets or sets the font weight or thickness.
@@ -90,11 +91,26 @@ namespace Avalonia.Controls
             set => SetValue(FontWeightProperty, value);
         }
 
+        /// <summary>
+        /// Identifies the FontStretch dependency property.
+        /// </summary>
+        public static readonly AttachedProperty<FontStretch> FontStretchProperty =
+            TextElement.FontStretchProperty.AddOwner<DataGridTextColumn>();
+
+        /// <summary>
+        /// Gets or sets the font weight or thickness.
+        /// </summary>
+        public FontStretch FontStretch
+        {
+            get => GetValue(FontStretchProperty);
+            set => SetValue(FontStretchProperty, value);
+        }
+
         /// <summary>
         /// Identifies the Foreground dependency property.
         /// </summary>
         public static readonly AttachedProperty<IBrush> ForegroundProperty =
-            TextBlock.ForegroundProperty.AddOwner<DataGridTextColumn>();
+            TextElement.ForegroundProperty.AddOwner<DataGridTextColumn>();
 
         /// <summary>
         /// Gets or sets a brush that describes the foreground of the column cells.

src/Avalonia.Controls.DataGrid/Themes/Default.xaml

@@ -17,7 +17,7 @@
           <ContentPresenter ContentTemplate="{TemplateBinding ContentTemplate}"
                             Content="{TemplateBinding Content}"
                             Margin="{TemplateBinding Padding}"
-                            TextBlock.Foreground="{TemplateBinding Foreground}"
+                            TextElement.Foreground="{TemplateBinding Foreground}"
                             HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                             VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
 

src/Avalonia.Controls.DataGrid/Themes/Fluent.xaml

@@ -124,7 +124,7 @@
           <ContentPresenter ContentTemplate="{TemplateBinding ContentTemplate}"
                             Content="{TemplateBinding Content}"
                             Margin="{TemplateBinding Padding}"
-                            TextBlock.Foreground="{TemplateBinding Foreground}"
+                            TextElement.Foreground="{TemplateBinding Foreground}"
                             HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                             VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
 

src/Avalonia.Controls/ApiCompatBaseline.txt

@@ -29,6 +29,21 @@ MembersMustExist : Member 'public void Avalonia.Controls.NumericUpDownValueChang
 MembersMustExist : Member 'public System.Double Avalonia.Controls.NumericUpDownValueChangedEventArgs.NewValue.get()' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public System.Double Avalonia.Controls.NumericUpDownValueChangedEventArgs.OldValue.get()' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public Avalonia.StyledProperty<System.Boolean> Avalonia.StyledProperty<System.Boolean> Avalonia.Controls.ScrollViewer.AllowAutoHideProperty' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.AttachedProperty<Avalonia.Media.FontFamily> Avalonia.AttachedProperty<Avalonia.Media.FontFamily> Avalonia.Controls.TextBlock.FontFamilyProperty' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.AttachedProperty<Avalonia.Media.FontStyle> Avalonia.AttachedProperty<Avalonia.Media.FontStyle> Avalonia.Controls.TextBlock.FontStyleProperty' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.AttachedProperty<Avalonia.Media.FontWeight> Avalonia.AttachedProperty<Avalonia.Media.FontWeight> Avalonia.Controls.TextBlock.FontWeightProperty' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.AttachedProperty<Avalonia.Media.IBrush> Avalonia.AttachedProperty<Avalonia.Media.IBrush> Avalonia.Controls.TextBlock.ForegroundProperty' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.AttachedProperty<System.Double> Avalonia.AttachedProperty<System.Double> Avalonia.Controls.TextBlock.FontSizeProperty' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.Media.FontFamily Avalonia.Controls.TextBlock.GetFontFamily(Avalonia.Controls.Control)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public System.Double Avalonia.Controls.TextBlock.GetFontSize(Avalonia.Controls.Control)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.Media.FontStyle Avalonia.Controls.TextBlock.GetFontStyle(Avalonia.Controls.Control)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.Media.FontWeight Avalonia.Controls.TextBlock.GetFontWeight(Avalonia.Controls.Control)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.Media.IBrush Avalonia.Controls.TextBlock.GetForeground(Avalonia.Controls.Control)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public void Avalonia.Controls.TextBlock.SetFontFamily(Avalonia.Controls.Control, Avalonia.Media.FontFamily)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public void Avalonia.Controls.TextBlock.SetFontSize(Avalonia.Controls.Control, System.Double)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public void Avalonia.Controls.TextBlock.SetFontStyle(Avalonia.Controls.Control, Avalonia.Media.FontStyle)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public void Avalonia.Controls.TextBlock.SetFontWeight(Avalonia.Controls.Control, Avalonia.Media.FontWeight)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public void Avalonia.Controls.TextBlock.SetForeground(Avalonia.Controls.Control, Avalonia.Media.IBrush)' does not exist in the implementation but it does exist in the contract.
 CannotRemoveBaseTypeOrInterface : Type 'Avalonia.Controls.TopLevel' does not implement interface 'Avalonia.Utilities.IWeakSubscriber<Avalonia.Controls.ResourcesChangedEventArgs>' in the implementation but it does in the contract.
 CannotRemoveBaseTypeOrInterface : Type 'Avalonia.Controls.Viewbox' does not inherit from base type 'Avalonia.Controls.Decorator' in the implementation but it does 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.
@@ -72,4 +87,4 @@ InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platfor
 MembersMustExist : Member 'public void Avalonia.Platform.IWindowImpl.Resize(Avalonia.Size)' does not exist in the implementation but it does exist in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platform.IWindowImpl.Resize(Avalonia.Size, Avalonia.Platform.PlatformResizeReason)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.ITrayIconImpl Avalonia.Platform.IWindowingPlatform.CreateTrayIcon()' is present in the implementation but not in the contract.
-Total Issues: 73
+Total Issues: 88

src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs

@@ -65,7 +65,7 @@ namespace Avalonia.Controls.ApplicationLifetimes
         /// <inheritdoc/>
         public Window? MainWindow { get; set; }
 
-        public IReadOnlyList<Window> Windows => _windows.ToList();
+        public IReadOnlyList<Window> Windows => _windows.ToArray();
 
         private void HandleWindowClosed(Window window)
         {

src/Avalonia.Controls/AutoCompleteBox.cs

@@ -252,6 +252,10 @@ namespace Avalonia.Controls
     /// drop-down that contains possible matches based on the input in the text
     /// box.
     /// </summary>
+    [TemplatePart(ElementPopup,            typeof(Popup))]
+    [TemplatePart(ElementSelector,         typeof(SelectingItemsControl))]
+    [TemplatePart(ElementSelectionAdapter, typeof(ISelectionAdapter))]
+    [TemplatePart(ElementTextBox,          typeof(TextBox))]
     [PseudoClasses(":dropdownopen")]
     public class AutoCompleteBox : TemplatedControl
     {
@@ -2180,7 +2184,7 @@ namespace Avalonia.Controls
             }
 
             // Store a local cached copy of the data
-            _items = newValue == null ? null : new List<object>(newValue.Cast<object>().ToList());
+            _items = newValue == null ? null : new List<object>(newValue.Cast<object>());
 
             // Clear and set the view on the selection adapter
             ClearView();
@@ -2239,7 +2243,7 @@ namespace Avalonia.Controls
                 ClearView();
                 if (Items != null)
                 {
-                    _items = new List<object>(Items.Cast<object>().ToList());
+                    _items = new List<object>(Items.Cast<object>());
                 }
             }
 

src/Avalonia.Controls/Button.cs

@@ -29,11 +29,14 @@ namespace Avalonia.Controls
     }
 
     /// <summary>
-    /// A button control.
+    /// A standard button control.
     /// </summary>
-    [PseudoClasses(":pressed")]
+    [PseudoClasses(pcFlyoutOpen, pcPressed)]
     public class Button : ContentControl, ICommandSource, IClickableControl
     {
+        protected const string pcPressed    = ":pressed";
+        protected const string pcFlyoutOpen = ":flyout-open";
+
         /// <summary>
         /// Defines the <see cref="ClickMode"/> property.
         /// </summary>
@@ -92,6 +95,7 @@ namespace Avalonia.Controls
         private ICommand? _command;
         private bool _commandCanExecute = true;
         private KeyGesture? _hotkey;
+        private bool _isFlyoutOpen = false;
 
         /// <summary>
         /// Initializes static members of the <see cref="Button"/> class.
@@ -107,7 +111,6 @@ namespace Avalonia.Controls
         /// </summary>
         public Button()
         {
-            UpdatePseudoClasses(IsPressed);
         }
 
         /// <summary>
@@ -328,11 +331,30 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        /// Opens the button's flyout.
+        /// </summary>
         protected virtual void OpenFlyout()
         {
             Flyout?.ShowAt(this);
         }
 
+        /// <summary>
+        /// Invoked when the button's flyout is opened.
+        /// </summary>
+        protected virtual void OnFlyoutOpened()
+        {
+            // Available for derived types
+        }
+
+        /// <summary>
+        /// Invoked when the button's flyout is closed.
+        /// </summary>
+        protected virtual void OnFlyoutClosed()
+        {
+            // Available for derived types
+        }
+
         /// <inheritdoc/>
         protected override void OnPointerPressed(PointerPressedEventArgs e)
         {
@@ -382,6 +404,14 @@ namespace Avalonia.Controls
             IsPressed = false;
         }
 
+        /// <inheritdoc/>
+        protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
+        {
+            UnregisterFlyoutEvents(Flyout);
+            RegisterFlyoutEvents(Flyout);
+            UpdatePseudoClasses();
+        }
+
         /// <inheritdoc/>
         protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
         {
@@ -442,17 +472,26 @@ namespace Avalonia.Controls
             }
             else if (change.Property == IsPressedProperty)
             {
-                UpdatePseudoClasses(change.NewValue.GetValueOrDefault<bool>());
+                UpdatePseudoClasses();
             }
             else if (change.Property == FlyoutProperty)
             {
+                var oldFlyout = change.OldValue.GetValueOrDefault() as FlyoutBase;
+                var newFlyout = change.NewValue.GetValueOrDefault() as FlyoutBase;
+
                 // If flyout is changed while one is already open, make sure we 
                 // close the old one first
-                if (change.OldValue.GetValueOrDefault() is FlyoutBase oldFlyout &&
+                if (oldFlyout != null &&
                     oldFlyout.IsOpen)
                 {
                     oldFlyout.Hide();
                 }
+
+                // Must unregister events here while a reference to the old flyout still exists
+                UnregisterFlyoutEvents(oldFlyout);
+
+                RegisterFlyoutEvents(newFlyout);
+                UpdatePseudoClasses();
             }
         }
 
@@ -493,6 +532,32 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        /// Registers all flyout events.
+        /// </summary>
+        /// <param name="flyout">The flyout to connect events to.</param>
+        private void RegisterFlyoutEvents(FlyoutBase? flyout)
+        {
+            if (flyout != null)
+            {
+                flyout.Opened += Flyout_Opened;
+                flyout.Closed += Flyout_Closed;
+            }
+        }
+
+        /// <summary>
+        /// Explicitly unregisters all flyout events.
+        /// </summary>
+        /// <param name="flyout">The flyout to disconnect events from.</param>
+        private void UnregisterFlyoutEvents(FlyoutBase? flyout)
+        {
+            if (flyout != null)
+            {
+                flyout.Opened -= Flyout_Opened;
+                flyout.Closed -= Flyout_Closed;
+             }
+        }
+
         /// <summary>
         /// Starts listening for the Enter key when the button <see cref="IsDefault"/>.
         /// </summary>
@@ -560,13 +625,53 @@ namespace Avalonia.Controls
         /// <summary>
         /// Updates the visual state of the control by applying latest PseudoClasses.
         /// </summary>
-        private void UpdatePseudoClasses(bool isPressed)
+        private void UpdatePseudoClasses()
         {
-            PseudoClasses.Set(":pressed", isPressed);
+            PseudoClasses.Set(pcFlyoutOpen, _isFlyoutOpen);
+            PseudoClasses.Set(pcPressed, IsPressed);
         }
 
         void ICommandSource.CanExecuteChanged(object sender, EventArgs e) => this.CanExecuteChanged(sender, e);
 
         void IClickableControl.RaiseClick() => OnClick();
+        
+        /// <summary>
+        /// Event handler for when the button's flyout is opened.
+        /// </summary>
+        private void Flyout_Opened(object? sender, EventArgs e)
+        {
+            var flyout = sender as FlyoutBase;
+
+            // It is possible to share flyouts among multiple controls including Button.
+            // This can cause a problem here since all controls that share a flyout receive
+            // the same Opened/Closed events at the same time.
+            // For Button that means they all would be updating their pseudoclasses accordingly.
+            // In other words, all Buttons with a shared Flyout would have the backgrounds changed together.
+            // To fix this, only continue here if the Flyout target matches this Button instance.
+            if (object.ReferenceEquals(flyout?.Target, this))
+            {
+                _isFlyoutOpen = true;
+                UpdatePseudoClasses();
+
+                OnFlyoutOpened();
+            }
+        }
+
+        /// <summary>
+        /// Event handler for when the button's flyout is closed.
+        /// </summary>
+        private void Flyout_Closed(object? sender, EventArgs e)
+        {
+            var flyout = sender as FlyoutBase;
+
+            // See comments in Flyout_Opened
+            if (object.ReferenceEquals(flyout?.Target, this))
+            {
+                _isFlyoutOpen = false;
+                UpdatePseudoClasses();
+
+                OnFlyoutClosed();
+            }
+        }
     }
 }

src/Avalonia.Controls/ButtonSpinner.cs

@@ -16,6 +16,8 @@ namespace Avalonia.Controls
     /// <summary>
     /// Represents a spinner control that includes two Buttons.
     /// </summary>
+    [TemplatePart("PART_DecreaseButton", typeof(Button))]
+    [TemplatePart("PART_IncreaseButton", typeof(Button))]
     [PseudoClasses(":left", ":right")]
     public class ButtonSpinner : Spinner
     {

src/Avalonia.Controls/Calendar/Calendar.cs

@@ -6,6 +6,7 @@
 using System;
 using System.Collections.ObjectModel;
 using System.Diagnostics;
+using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 using Avalonia.Data;
 using Avalonia.Input;
@@ -222,6 +223,8 @@ namespace Avalonia.Controls
     /// element in XAML.
     /// </para>
     /// </remarks>
+    [TemplatePart(PART_ElementMonth, typeof(CalendarItem))]
+    [TemplatePart(PART_ElementRoot,  typeof(Panel))]
     public class Calendar : TemplatedControl
     {
         internal const int RowsPerMonth = 7;
@@ -261,6 +264,7 @@ namespace Avalonia.Controls
             AvaloniaProperty.Register<Calendar, DayOfWeek>(
                     nameof(FirstDayOfWeek),
                     defaultValue: DateTimeHelper.GetCurrentDateFormat().FirstDayOfWeek);
+
         /// <summary>
         /// Gets or sets the day that is considered the beginning of the week.
         /// </summary>
@@ -273,6 +277,7 @@ namespace Avalonia.Controls
             get { return GetValue(FirstDayOfWeekProperty); }
             set { SetValue(FirstDayOfWeekProperty, value); }
         }
+
         /// <summary>
         /// FirstDayOfWeekProperty property changed handler.
         /// </summary>
@@ -289,6 +294,7 @@ namespace Avalonia.Controls
                 throw new ArgumentOutOfRangeException("d", "Invalid DayOfWeek");
             }
         }
+
         /// <summary>
         /// Inherited code: Requires comment.
         /// </summary>
@@ -311,6 +317,7 @@ namespace Avalonia.Controls
             AvaloniaProperty.Register<Calendar, bool>(
                 nameof(IsTodayHighlighted),
                 defaultValue: true);
+
         /// <summary>
         /// Gets or sets a value indicating whether the current date is
         /// highlighted.
@@ -324,6 +331,7 @@ namespace Avalonia.Controls
             get { return GetValue(IsTodayHighlightedProperty); }
             set { SetValue(IsTodayHighlightedProperty, value); }
         }
+
         /// <summary>
         /// IsTodayHighlightedProperty property changed handler.
         /// </summary>
@@ -343,6 +351,7 @@ namespace Avalonia.Controls
 
         public static readonly StyledProperty<IBrush> HeaderBackgroundProperty =
             AvaloniaProperty.Register<Calendar, IBrush>(nameof(HeaderBackground));
+
         public IBrush HeaderBackground
         {
             get { return GetValue(HeaderBackgroundProperty); }
@@ -367,6 +376,7 @@ namespace Avalonia.Controls
             get { return GetValue(DisplayModeProperty); }
             set { SetValue(DisplayModeProperty, value); }
         }
+
         /// <summary>
         /// DisplayModeProperty property changed handler.
         /// </summary>
@@ -424,6 +434,7 @@ namespace Avalonia.Controls
                 || mode == CalendarMode.Year
                 || mode == CalendarMode.Decade;
         }
+
         private void OnDisplayModeChanged(CalendarModeChangedEventArgs args)
         {
             DisplayModeChanged?.Invoke(this, args);
@@ -433,6 +444,7 @@ namespace Avalonia.Controls
             AvaloniaProperty.Register<Calendar, CalendarSelectionMode>(
                 nameof(SelectionMode),
                 defaultValue: CalendarSelectionMode.SingleDate);
+
         /// <summary>
         /// Gets or sets a value that indicates what kind of selections are
         /// allowed.
@@ -457,6 +469,7 @@ namespace Avalonia.Controls
             get { return GetValue(SelectionModeProperty); }
             set { SetValue(SelectionModeProperty, value); }
         }
+
         private void OnSelectionModeChanged(AvaloniaPropertyChangedEventArgs e)
         {
             if (IsValidSelectionMode(e.NewValue!))
@@ -471,6 +484,7 @@ namespace Avalonia.Controls
                 throw new ArgumentOutOfRangeException("d", "Invalid SelectionMode");
             }
         }
+
         /// <summary>
         /// Inherited code: Requires comment.
         /// </summary>
@@ -492,6 +506,7 @@ namespace Avalonia.Controls
                 o => o.SelectedDate,
                 (o, v) => o.SelectedDate = v,
                 defaultBindingMode: BindingMode.TwoWay);
+
         /// <summary>
         /// Gets or sets the currently selected date.
         /// </summary>
@@ -720,6 +735,7 @@ namespace Avalonia.Controls
                 o => o.DisplayDate,
                 (o, v) => o.DisplayDate = v,
                 defaultBindingMode: BindingMode.TwoWay);
+
         /// <summary>
         /// Gets or sets the date to display.
         /// </summary>
@@ -1973,6 +1989,7 @@ namespace Avalonia.Controls
                     }
             }
         }
+
         private void Calendar_KeyUp(KeyEventArgs e)
         {
             if (!e.Handled && (e.Key == Key.LeftShift || e.Key == Key.RightShift))
@@ -1980,6 +1997,7 @@ namespace Avalonia.Controls
                 ProcessShiftKeyUp();
             }
         }
+
         internal void ProcessShiftKeyUp()
         {
             if (_isShiftPressed && (SelectionMode == CalendarSelectionMode.SingleRange || SelectionMode == CalendarSelectionMode.MultipleRange))
@@ -2028,6 +2046,7 @@ namespace Avalonia.Controls
                     }
             }
         }
+
         protected override void OnLostFocus(RoutedEventArgs e)
         {
             base.OnLostFocus(e);
@@ -2054,6 +2073,7 @@ namespace Avalonia.Controls
                     }
             }
         }
+
         /// <summary>
         ///  Called when the IsEnabled property changes.
         /// </summary>
@@ -2098,6 +2118,7 @@ namespace Avalonia.Controls
 
         private const string PART_ElementRoot = "Root";
         private const string PART_ElementMonth = "CalendarItem";
+
         /// <summary>
         /// Builds the visual tree for the
         /// <see cref="T:System.Windows.Controls.Calendar" /> when a new

src/Avalonia.Controls/Calendar/CalendarDatePicker.cs

@@ -7,6 +7,7 @@ using System;
 using System.Collections.ObjectModel;
 using System.Diagnostics;
 using System.Globalization;
+using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 using Avalonia.Data;
 using Avalonia.Input;
@@ -116,6 +117,10 @@ namespace Avalonia.Controls
         Custom = 2
     }
 
+    [TemplatePart(ElementButton,   typeof(Button))]
+    [TemplatePart(ElementCalendar, typeof(Calendar))]
+    [TemplatePart(ElementPopup,    typeof(Popup))]
+    [TemplatePart(ElementTextBox,  typeof(TextBox))]
     public class CalendarDatePicker : TemplatedControl
     {
         private const string ElementTextBox = "PART_TextBox";

src/Avalonia.Controls/Calendar/CalendarItem.cs

@@ -19,6 +19,11 @@ namespace Avalonia.Controls.Primitives
     /// Represents the currently displayed month or year on a
     /// <see cref="T:Avalonia.Controls.Calendar" />.
     /// </summary>
+    [TemplatePart(PART_ElementHeaderButton,   typeof(Button))]
+    [TemplatePart(PART_ElementMonthView,      typeof(Grid))]
+    [TemplatePart(PART_ElementNextButton,     typeof(Button))]
+    [TemplatePart(PART_ElementPreviousButton, typeof(Button))]
+    [TemplatePart(PART_ElementYearView,       typeof(Grid))]
     [PseudoClasses(":calendardisabled")]
     public sealed class CalendarItem : TemplatedControl
     {

src/Avalonia.Controls/Chrome/CaptionButtons.cs

@@ -8,6 +8,10 @@ namespace Avalonia.Controls.Chrome
     /// <summary>
     /// Draws window minimize / maximize / close buttons in a <see cref="TitleBar"/> when managed client decorations are enabled.
     /// </summary>
+    [TemplatePart("PART_CloseButton",      typeof(Panel))]
+    [TemplatePart("PART_RestoreButton",    typeof(Panel))]
+    [TemplatePart("PART_MinimiseButton",   typeof(Panel))]
+    [TemplatePart("PART_FullScreenButton", typeof(Panel))]
     [PseudoClasses(":minimized", ":normal", ":maximized", ":fullscreen")]
     public class CaptionButtons : TemplatedControl
     {

src/Avalonia.Controls/Chrome/TitleBar.cs

@@ -8,6 +8,7 @@ namespace Avalonia.Controls.Chrome
     /// <summary>
     /// Draws a titlebar when managed client decorations are enabled.
     /// </summary>
+    [TemplatePart("PART_CaptionButtons", typeof(CaptionButtons))]
     [PseudoClasses(":minimized", ":normal", ":maximized", ":fullscreen")]
     public class TitleBar : TemplatedControl
     {

src/Avalonia.Controls/ComboBox.cs

@@ -13,12 +13,14 @@ using Avalonia.Interactivity;
 using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.VisualTree;
+using Avalonia.Controls.Metadata;
 
 namespace Avalonia.Controls
 {
     /// <summary>
     /// A drop-down list control.
     /// </summary>
+    [TemplatePart("PART_Popup", typeof(Popup))]
     public class ComboBox : SelectingItemsControl
     {
         /// <summary>

src/Avalonia.Controls/ContentControl.cs

@@ -1,4 +1,5 @@
 using Avalonia.Collections;
+using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Mixins;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
@@ -12,6 +13,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// Displays <see cref="Content"/> according to a <see cref="FuncDataTemplate"/>.
     /// </summary>
+    [TemplatePart("PART_ContentPresenter", typeof(IContentPresenter))]
     public class ContentControl : TemplatedControl, IContentControl, IContentPresenterHost
     {
         /// <summary>

src/Avalonia.Controls/Control.cs

@@ -1,7 +1,7 @@
 using System;
 using System.ComponentModel;
-using System.Runtime.CompilerServices;
 using Avalonia.Automation.Peers;
+using Avalonia.Controls.Documents;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
 using Avalonia.Input;
@@ -67,7 +67,7 @@ namespace Avalonia.Controls
         /// </summary>
         public static readonly AttachedProperty<FlowDirection> FlowDirectionProperty =
             AvaloniaProperty.RegisterAttached<Control, Control, FlowDirection>(nameof(FlowDirection), inherits: true);
-        
+
         private DataTemplates? _dataTemplates;
         private IControl? _focusAdorner;
         private AutomationPeer? _automationPeer;
@@ -137,6 +137,26 @@ namespace Avalonia.Controls
 
         public new IControl? Parent => (IControl?)base.Parent;
 
+        /// <summary>
+        /// Gets the value of the attached <see cref="FlowDirectionProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <returns>The flow direction.</returns>
+        public static FlowDirection GetFlowDirection(Control control)
+        {
+            return control.GetValue(FlowDirectionProperty);
+        }
+
+        /// <summary>
+        /// Sets the value of the attached <see cref="FlowDirectionProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <param name="value">The property value to set.</param>
+        public static void SetFlowDirection(Control control, FlowDirection value)
+        {
+            control.SetValue(FlowDirectionProperty, value);
+        }
+
         /// <inheritdoc/>
         bool IDataTemplateHost.IsDataTemplatesInitialized => _dataTemplates != null;
 

src/Avalonia.Controls/DateTimePickers/DatePicker.cs

@@ -14,6 +14,15 @@ namespace Avalonia.Controls
     /// <summary>
     /// A control to allow the user to select a date
     /// </summary>
+    [TemplatePart("ButtonContentGrid", typeof(Grid))]
+    [TemplatePart("DayText",           typeof(TextBlock))]
+    [TemplatePart("FirstSpacer",       typeof(Rectangle))]
+    [TemplatePart("FlyoutButton",      typeof(Button))]
+    [TemplatePart("MonthText",         typeof(TextBlock))]
+    [TemplatePart("PickerPresenter",   typeof(DatePickerPresenter))]
+    [TemplatePart("Popup",             typeof(Popup))]
+    [TemplatePart("SecondSpacer",      typeof(Rectangle))]
+    [TemplatePart("YearText",          typeof(TextBlock))]
     [PseudoClasses(":hasnodate")]
     public class DatePicker : TemplatedControl
     {

src/Avalonia.Controls/DateTimePickers/DatePickerPresenter.cs

@@ -1,4 +1,5 @@
-using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Metadata;
+using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Shapes;
 using Avalonia.Input;
 using Avalonia.Interactivity;
@@ -12,6 +13,23 @@ namespace Avalonia.Controls
     /// Defines the presenter used for selecting a date for a 
     /// <see cref="DatePicker"/>
     /// </summary>
+    [TemplatePart("AcceptButton",    typeof(Button))]
+    [TemplatePart("DayDownButton",   typeof(RepeatButton))]
+    [TemplatePart("DayHost",         typeof(Panel))]
+    [TemplatePart("DaySelector",     typeof(DateTimePickerPanel))]
+    [TemplatePart("DayUpButton",     typeof(RepeatButton))]
+    [TemplatePart("DismissButton",   typeof(Button))]
+    [TemplatePart("FirstSpacer",     typeof(Rectangle))]
+    [TemplatePart("MonthDownButton", typeof(RepeatButton))]
+    [TemplatePart("MonthHost",       typeof(Panel))]
+    [TemplatePart("MonthSelector",   typeof(DateTimePickerPanel))]
+    [TemplatePart("MonthUpButton",   typeof(RepeatButton))]
+    [TemplatePart("PickerContainer", typeof(Grid))]
+    [TemplatePart("SecondSpacer",    typeof(Rectangle))]
+    [TemplatePart("YearDownButton",  typeof(RepeatButton))]
+    [TemplatePart("YearHost",        typeof(Panel))]
+    [TemplatePart("YearSelector",    typeof(DateTimePickerPanel))]
+    [TemplatePart("YearUpButton",    typeof(RepeatButton))]
     public class DatePickerPresenter : PickerPresenterBase
     {
         /// <summary>

src/Avalonia.Controls/DateTimePickers/TimePicker.cs

@@ -12,6 +12,18 @@ namespace Avalonia.Controls
     /// <summary>
     /// A control to allow the user to select a time.
     /// </summary>
+    [TemplatePart("FirstColumnDivider",      typeof(Rectangle))]
+    [TemplatePart("FirstPickerHost",         typeof(Border))]
+    [TemplatePart("FlyoutButton",            typeof(Button))]
+    [TemplatePart("FlyoutButtonContentGrid", typeof(Grid))]
+    [TemplatePart("HourTextBlock",           typeof(TextBlock))]
+    [TemplatePart("MinuteTextBlock",         typeof(TextBlock))]
+    [TemplatePart("PeriodTextBlock",         typeof(TextBlock))]
+    [TemplatePart("PickerPresenter",         typeof(TimePickerPresenter))]
+    [TemplatePart("Popup",                   typeof(Popup))]
+    [TemplatePart("SecondColumnDivider",     typeof(Rectangle))]
+    [TemplatePart("SecondPickerHost",        typeof(Border))]
+    [TemplatePart("ThirdPickerHost",         typeof(Border))]
     [PseudoClasses(":hasnotime")]
     public class TimePicker : TemplatedControl
     {

src/Avalonia.Controls/DateTimePickers/TimePickerPresenter.cs

@@ -1,4 +1,5 @@
-using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Metadata;
+using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Shapes;
 using Avalonia.Input;
 using Avalonia.Interactivity;
@@ -10,6 +11,20 @@ namespace Avalonia.Controls
     /// Defines the presenter used for selecting a time. Intended for use with
     /// <see cref="TimePicker"/> but can be used independently
     /// </summary>
+    [TemplatePart("AcceptButton",     typeof(Button))]
+    [TemplatePart("DismissButton",    typeof(Button))]
+    [TemplatePart("HourDownButton",   typeof(RepeatButton))]
+    [TemplatePart("HourSelector",     typeof(DateTimePickerPanel))]
+    [TemplatePart("HourUpButton",     typeof(RepeatButton))]
+    [TemplatePart("MinuteDownButton", typeof(RepeatButton))]
+    [TemplatePart("MinuteSelector",   typeof(DateTimePickerPanel))]
+    [TemplatePart("MinuteUpButton",   typeof(RepeatButton))]
+    [TemplatePart("PeriodDownButton", typeof(RepeatButton))]
+    [TemplatePart("PeriodHost",       typeof(Panel))]
+    [TemplatePart("PeriodSelector",   typeof(DateTimePickerPanel))]
+    [TemplatePart("PeriodUpButton",   typeof(RepeatButton))]
+    [TemplatePart("PickerContainer",  typeof(Grid))]
+    [TemplatePart("SecondSpacer",     typeof(Rectangle))]
     public class TimePickerPresenter : PickerPresenterBase
     {
         /// <summary>

src/Avalonia.Controls/Documents/TextElement.cs

@@ -13,37 +13,60 @@ namespace Avalonia.Controls.Documents
         /// Defines the <see cref="Background"/> property.
         /// </summary>
         public static readonly StyledProperty<IBrush?> BackgroundProperty =
-            AvaloniaProperty.Register<TextElement, IBrush?>(nameof(Background), inherits: true);
+            Border.BackgroundProperty.AddOwner<TextElement>();
 
         /// <summary>
         /// Defines the <see cref="FontFamily"/> property.
         /// </summary>
         public static readonly AttachedProperty<FontFamily> FontFamilyProperty =
-            TextBlock.FontFamilyProperty.AddOwner<TextElement>();
+            AvaloniaProperty.RegisterAttached<TextElement, Control, FontFamily>(
+                nameof(FontFamily),
+                defaultValue: FontFamily.Default,
+                inherits: true);
 
         /// <summary>
         /// Defines the <see cref="FontSize"/> property.
         /// </summary>
         public static readonly AttachedProperty<double> FontSizeProperty =
-            TextBlock.FontSizeProperty.AddOwner<TextElement>();
+            AvaloniaProperty.RegisterAttached<TextElement, Control, double>(
+                nameof(FontSize),
+                defaultValue: 12,
+                inherits: true);
 
         /// <summary>
         /// Defines the <see cref="FontStyle"/> property.
         /// </summary>
         public static readonly AttachedProperty<FontStyle> FontStyleProperty =
-            TextBlock.FontStyleProperty.AddOwner<TextElement>();
+            AvaloniaProperty.RegisterAttached<TextElement, Control, FontStyle>(
+                nameof(FontStyle),
+                inherits: true);
 
         /// <summary>
         /// Defines the <see cref="FontWeight"/> property.
         /// </summary>
         public static readonly AttachedProperty<FontWeight> FontWeightProperty =
-            TextBlock.FontWeightProperty.AddOwner<TextElement>();
+            AvaloniaProperty.RegisterAttached<TextElement, Control, FontWeight>(
+                nameof(FontWeight),
+                inherits: true,
+                defaultValue: FontWeight.Normal);
+
+        /// <summary>
+        /// Defines the <see cref="FontStretch"/> property.
+        /// </summary>
+        public static readonly AttachedProperty<FontStretch> FontStretchProperty =
+            AvaloniaProperty.RegisterAttached<TextElement, Control, FontStretch>(
+                nameof(FontStretch),
+                inherits: true,
+                defaultValue: FontStretch.Normal);
 
         /// <summary>
         /// Defines the <see cref="Foreground"/> property.
         /// </summary>
         public static readonly AttachedProperty<IBrush?> ForegroundProperty =
-            TextBlock.ForegroundProperty.AddOwner<TextElement>();
+            AvaloniaProperty.RegisterAttached<TextElement, Control, IBrush?>(
+                nameof(Foreground),
+                Brushes.Black,
+                inherits: true);
 
         /// <summary>
         /// Gets or sets a brush used to paint the control's background.
@@ -90,6 +113,15 @@ namespace Avalonia.Controls.Documents
             set { SetValue(FontWeightProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets the font stretch.
+        /// </summary>
+        public FontStretch FontStretch
+        {
+            get { return GetValue(FontStretchProperty); }
+            set { SetValue(FontStretchProperty, value); }
+        }
+
         /// <summary>
         /// Gets or sets a brush used to paint the text.
         /// </summary>
@@ -98,7 +130,127 @@ namespace Avalonia.Controls.Documents
             get { return GetValue(ForegroundProperty); }
             set { SetValue(ForegroundProperty, value); }
         }
-        
+
+        /// <summary>
+        /// Gets the value of the attached <see cref="FontFamilyProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <returns>The font family.</returns>
+        public static FontFamily GetFontFamily(Control control)
+        {
+            return control.GetValue(FontFamilyProperty);
+        }
+
+        /// <summary>
+        /// Sets the value of the attached <see cref="FontFamilyProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <param name="value">The property value to set.</param>
+        public static void SetFontFamily(Control control, FontFamily value)
+        {
+            control.SetValue(FontFamilyProperty, value);
+        }
+
+        /// <summary>
+        /// Gets the value of the attached <see cref="FontSizeProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <returns>The font size.</returns>
+        public static double GetFontSize(Control control)
+        {
+            return control.GetValue(FontSizeProperty);
+        }
+
+        /// <summary>
+        /// Sets the value of the attached <see cref="FontSizeProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <param name="value">The property value to set.</param>
+        public static void SetFontSize(Control control, double value)
+        {
+            control.SetValue(FontSizeProperty, value);
+        }
+
+        /// <summary>
+        /// Gets the value of the attached <see cref="FontStyleProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <returns>The font style.</returns>
+        public static FontStyle GetFontStyle(Control control)
+        {
+            return control.GetValue(FontStyleProperty);
+        }
+
+        /// <summary>
+        /// Sets the value of the attached <see cref="FontStyleProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <param name="value">The property value to set.</param>
+        public static void SetFontStyle(Control control, FontStyle value)
+        {
+            control.SetValue(FontStyleProperty, value);
+        }
+
+        /// <summary>
+        /// Gets the value of the attached <see cref="FontWeightProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <returns>The font weight.</returns>
+        public static FontWeight GetFontWeight(Control control)
+        {
+            return control.GetValue(FontWeightProperty);
+        }
+
+        /// <summary>
+        /// Sets the value of the attached <see cref="FontWeightProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <param name="value">The property value to set.</param>
+        public static void SetFontWeight(Control control, FontWeight value)
+        {
+            control.SetValue(FontWeightProperty, value);
+        }
+
+        /// <summary>
+        /// Gets the value of the attached <see cref="FontStretchProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <returns>The font stretch.</returns>
+        public static FontStretch GetFontStretch(Control control)
+        {
+            return control.GetValue(FontStretchProperty);
+        }
+
+        /// <summary>
+        /// Sets the value of the attached <see cref="FontStretchProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <param name="value">The property value to set.</param>
+        public static void SetFontStretch(Control control, FontStretch value)
+        {
+            control.SetValue(FontStretchProperty, value);
+        }
+
+        /// <summary>
+        /// Gets the value of the attached <see cref="ForegroundProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <returns>The foreground.</returns>
+        public static IBrush? GetForeground(Control control)
+        {
+            return control.GetValue(ForegroundProperty);
+        }
+
+        /// <summary>
+        /// Sets the value of the attached <see cref="ForegroundProperty"/> on a control.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <param name="value">The property value to set.</param>
+        public static void SetForeground(Control control, IBrush? value)
+        {
+            control.SetValue(ForegroundProperty, value);
+        }
+
         /// <summary>
         /// Raised when the visual representation of the text element changes.
         /// </summary>
@@ -115,6 +267,7 @@ namespace Avalonia.Controls.Documents
                 case nameof(FontSize):
                 case nameof(FontStyle):
                 case nameof(FontWeight):
+                case nameof(FontStretch):
                 case nameof(Foreground):
                     Invalidate();
                     break;

src/Avalonia.Controls/DropDownButton.cs

@@ -0,0 +1,15 @@
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// A button with an added drop-down chevron to visually indicate it has a flyout with additional actions.
+    /// </summary>
+    public class DropDownButton : Button
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DropDownButton"/> class.
+        /// </summary>
+        public DropDownButton()
+        {
+        }
+    }
+}

src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs

@@ -8,15 +8,6 @@ namespace Avalonia.Controls
 {
     public class MenuFlyoutPresenter : MenuBase
     {
-        public static readonly StyledProperty<CornerRadius> CornerRadiusProperty =
-            Border.CornerRadiusProperty.AddOwner<FlyoutPresenter>();
-
-        public CornerRadius CornerRadius
-        {
-            get => GetValue(CornerRadiusProperty);
-            set => SetValue(CornerRadiusProperty, value);
-        }
-
         public MenuFlyoutPresenter()
             :base(new DefaultMenuInteractionHandler(true))
         {

src/Avalonia.Controls/Generators/ItemContainerGenerator.cs

@@ -82,7 +82,7 @@ namespace Avalonia.Controls.Generators
             {
                 var toMove = _containers.Where(x => x.Key >= index)
                     .OrderByDescending(x => x.Key)
-                    .ToList();
+                    .ToArray();
 
                 foreach (var i in toMove)
                 {
@@ -111,7 +111,7 @@ namespace Avalonia.Controls.Generators
                 }
 
                 var toMove = _containers.Where(x => x.Key >= startingIndex)
-                                        .OrderBy(x => x.Key).ToList();
+                                        .OrderBy(x => x.Key).ToArray();
 
                 foreach (var i in toMove)
                 {
@@ -122,9 +122,9 @@ namespace Avalonia.Controls.Generators
 
                 Dematerialized?.Invoke(this, new ItemContainerEventArgs(startingIndex, result));
 
-                if (toMove.Count > 0)
+                if (toMove.Length > 0)
                 {
-                    var containers = toMove.Select(x => x.Value).ToList();
+                    var containers = toMove.Select(x => x.Value).ToArray();
                     Recycled?.Invoke(this, new ItemContainerEventArgs(containers[0].Index, containers));
                 }
             }
@@ -138,10 +138,10 @@ namespace Avalonia.Controls.Generators
         /// <inheritdoc/>
         public virtual IEnumerable<ItemContainerInfo> Clear()
         {
-            var result = Containers.ToList();
+            var result = Containers.ToArray();
             _containers.Clear();
 
-            if (result.Count > 0)
+            if (result.Length > 0)
             {
                 Dematerialized?.Invoke(this, new ItemContainerEventArgs(0, result));
             }

src/Avalonia.Controls/ListBox.cs

@@ -1,5 +1,6 @@
 using System.Collections;
 using Avalonia.Controls.Generators;
+using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Selection;
@@ -12,6 +13,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// An <see cref="ItemsControl"/> in which individual items can be selected.
     /// </summary>
+    [TemplatePart("PART_ScrollViewer", typeof(IScrollable))]
     public class ListBox : SelectingItemsControl
     {
         /// <summary>

src/Avalonia.Controls/MenuItem.cs

@@ -20,6 +20,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// A menu item control.
     /// </summary>
+    [TemplatePart("PART_Popup", typeof(Popup))]
     [PseudoClasses(":separator", ":icon", ":open", ":pressed", ":selected")]
     public class MenuItem : HeaderedSelectingItemsControl, IMenuItem, ISelectable, ICommandSource, IClickableControl
     {

src/Avalonia.Controls/Notifications/WindowNotificationManager.cs

@@ -14,6 +14,7 @@ namespace Avalonia.Controls.Notifications
     /// <summary>
     /// An <see cref="INotificationManager"/> that displays notifications in a <see cref="Window"/>.
     /// </summary>
+    [TemplatePart("PART_Items", typeof(Panel))]
     [PseudoClasses(":topleft", ":topright", ":bottomleft", ":bottomright")]
     public class WindowNotificationManager : TemplatedControl, IManagedNotificationManager, ICustomSimpleHitTest
     {

src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs

@@ -2,6 +2,7 @@
 using System.Globalization;
 using System.IO;
 using System.Linq;
+using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 using Avalonia.Data;
 using Avalonia.Input;
@@ -15,6 +16,8 @@ namespace Avalonia.Controls
     /// <summary>
     /// Control that represents a TextBox with button spinners that allow incrementing and decrementing numeric values.
     /// </summary>
+    [TemplatePart("PART_Spinner", typeof(Spinner))]
+    [TemplatePart("PART_TextBox", typeof(TextBox))]
     public class NumericUpDown : TemplatedControl
     {
         /// <summary>
@@ -1051,7 +1054,7 @@ namespace Avalonia.Controls
                         var currentValueTextSpecialCharacters = currentValueText.Where(c => !char.IsDigit(c));
                         var textSpecialCharacters = text.Where(c => !char.IsDigit(c));
                         // same non-digit characters on currentValueText and new text => remove them on new Text to parse it again.
-                        if (currentValueTextSpecialCharacters.Except(textSpecialCharacters).ToList().Count == 0)
+                        if (!currentValueTextSpecialCharacters.Except(textSpecialCharacters).Any())
                         {
                             foreach (var character in textSpecialCharacters)
                             {

src/Avalonia.Controls/Platform/IPlatformNativeSurfaceHandle.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace Avalonia.Platform
+{
+    public interface IPlatformNativeSurfaceHandle : IPlatformHandle
+    {
+        PixelSize Size { get; }
+        double Scaling { get; }
+    }
+}

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -8,6 +8,7 @@ using Avalonia.Utilities;
 using Avalonia.VisualTree;
 using Avalonia.Layout;
 using Avalonia.Media.Immutable;
+using Avalonia.Controls.Documents;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -121,8 +122,8 @@ namespace Avalonia.Controls.Presenters
         /// </summary>
         public FontFamily FontFamily
         {
-            get => TextBlock.GetFontFamily(this);
-            set => TextBlock.SetFontFamily(this, value);
+            get => TextElement.GetFontFamily(this);
+            set => TextElement.SetFontFamily(this, value);
         }
 
         /// <summary>
@@ -130,8 +131,8 @@ namespace Avalonia.Controls.Presenters
         /// </summary>
         public double FontSize
         {
-            get => TextBlock.GetFontSize(this);
-            set => TextBlock.SetFontSize(this, value);
+            get => TextElement.GetFontSize(this);
+            set => TextElement.SetFontSize(this, value);
         }
 
         /// <summary>
@@ -139,8 +140,8 @@ namespace Avalonia.Controls.Presenters
         /// </summary>
         public FontStyle FontStyle
         {
-            get => TextBlock.GetFontStyle(this);
-            set => TextBlock.SetFontStyle(this, value);
+            get => TextElement.GetFontStyle(this);
+            set => TextElement.SetFontStyle(this, value);
         }
 
         /// <summary>
@@ -148,8 +149,8 @@ namespace Avalonia.Controls.Presenters
         /// </summary>
         public FontWeight FontWeight
         {
-            get => TextBlock.GetFontWeight(this);
-            set => TextBlock.SetFontWeight(this, value);
+            get => TextElement.GetFontWeight(this);
+            set => TextElement.SetFontWeight(this, value);
         }
 
         /// <summary>
@@ -157,8 +158,8 @@ namespace Avalonia.Controls.Presenters
         /// </summary>
         public FontStretch FontStretch
         {
-            get => TextBlock.GetFontStretch(this);
-            set => TextBlock.SetFontStretch(this, value);
+            get => TextElement.GetFontStretch(this);
+            set => TextElement.SetFontStretch(this, value);
         }
 
         /// <summary>
@@ -166,8 +167,8 @@ namespace Avalonia.Controls.Presenters
         /// </summary>
         public IBrush? Foreground
         {
-            get => TextBlock.GetForeground(this);
-            set => TextBlock.SetForeground(this, value);
+            get => TextElement.GetForeground(this);
+            set => TextElement.SetForeground(this, value);
         }
 
         /// <summary>
@@ -353,7 +354,7 @@ namespace Avalonia.Controls.Presenters
 
                 foreach (var rect in rects)
                 {
-                    context.FillRectangle(selectionBrush, rect);
+                    context.FillRectangle(selectionBrush, PixelRect.FromRect(rect, 1).ToRect(1));
                 }
             }
 
@@ -528,9 +529,9 @@ namespace Avalonia.Controls.Presenters
             {
                 return finalSize;
             }
-            
-            _constraint = finalSize;
-                
+
+            _constraint = new Size(finalSize.Width, Math.Ceiling(finalSize.Height));
+
             _textLayout = null;
 
             return finalSize;
@@ -637,14 +638,7 @@ namespace Avalonia.Controls.Presenters
             if (Text is null)
             {
                 return default;
-            }
-            
-            if (FlowDirection == FlowDirection.RightToLeft)
-            {
-                direction = direction == LogicalDirection.Forward ?
-                    LogicalDirection.Backward :
-                    LogicalDirection.Forward;
-            }
+            }          
 
             var characterHit = _lastCharacterHit;
             var caretIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
@@ -666,7 +660,7 @@ namespace Avalonia.Controls.Presenters
 
                     caretIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
 
-                    if (textLine.NewLineLength > 0 && caretIndex == textLine.TextRange.Start + textLine.TextRange.Length)
+                    if (textLine.NewLineLength > 0 && caretIndex == textLine.FirstTextSourceIndex + textLine.Length)
                     {
                         characterHit = new CharacterHit(caretIndex);
                     }
@@ -678,7 +672,7 @@ namespace Avalonia.Controls.Presenters
                         break;
                     }
 
-                    if (caretIndex - textLine.NewLineLength == textLine.TextRange.Start + textLine.TextRange.Length)
+                    if (caretIndex - textLine.NewLineLength == textLine.FirstTextSourceIndex + textLine.Length)
                     {
                         break;
                     }
@@ -719,6 +713,13 @@ namespace Avalonia.Controls.Presenters
         
         public void MoveCaretHorizontal(LogicalDirection direction = LogicalDirection.Forward)
         {
+            if (FlowDirection == FlowDirection.RightToLeft)
+            {
+                direction = direction == LogicalDirection.Forward ?
+                    LogicalDirection.Backward :
+                    LogicalDirection.Forward;
+            }
+
             var characterHit = GetNextCharacterHit(direction);
 
             UpdateCaret(characterHit);
@@ -779,19 +780,25 @@ namespace Avalonia.Controls.Presenters
             
             switch (change.Property.Name)
             {
-                case nameof (TextBlock.Foreground):
-                case nameof (TextBlock.FontSize):
-                case nameof (TextBlock.FontStyle):
-                case nameof (TextBlock.FontWeight):
-                case nameof (TextBlock.FontFamily):
+                case nameof (Foreground):
+                case nameof (FontSize):
+                case nameof (FontStyle):
+                case nameof (FontWeight):
+                case nameof (FontFamily):
+                case nameof (FontStretch):
+
                 case nameof (Text):
                 case nameof (TextAlignment):
                 case nameof (TextWrapping):
+
                 case nameof (SelectionStart):
                 case nameof (SelectionEnd):
                 case nameof (SelectionForegroundBrush):
+
                 case nameof (PasswordChar):
                 case nameof (RevealPassword):
+
+                case nameof(FlowDirection):
                 {
                     InvalidateTextLayout();
                     break;

src/Avalonia.Controls/Primitives/PopupPositioning/ManagedPopupPositionerPopupImplHelper.cs

@@ -23,8 +23,9 @@ namespace Avalonia.Controls.Primitives.PopupPositioning
 
         public IReadOnlyList<ManagedPopupPositionerScreenInfo> Screens =>
 
-            _parent.Screen.AllScreens.Select(s => new ManagedPopupPositionerScreenInfo(
-                s.Bounds.ToRect(1), s.WorkingArea.ToRect(1))).ToList();
+            _parent.Screen.AllScreens
+                .Select(s => new ManagedPopupPositionerScreenInfo(s.Bounds.ToRect(1), s.WorkingArea.ToRect(1)))
+                .ToArray();
 
         public Rect ParentClientAreaScreenGeometry
         {

src/Avalonia.Controls/Primitives/PopupRoot.cs

@@ -17,7 +17,6 @@ namespace Avalonia.Controls.Primitives
     /// </summary>
     public sealed class PopupRoot : WindowBase, IInteractive, IHostedVisualTreeRoot, IDisposable, IStyleHost, IPopupHost
     {
-        private readonly TopLevel _parent;
         private PopupPositionerParameters _positionerParameters;        
 
         /// <summary>
@@ -47,7 +46,7 @@ namespace Avalonia.Controls.Primitives
         public PopupRoot(TopLevel parent, IPopupImpl impl, IAvaloniaDependencyResolver? dependencyResolver)
             : base(impl, dependencyResolver)
         {
-            _parent = parent;
+            ParentTopLevel = parent;
         }
 
         /// <summary>
@@ -73,6 +72,8 @@ namespace Avalonia.Controls.Primitives
         /// </summary>
         IStyleHost? IStyleHost.StylingParent => Parent;
 
+        public TopLevel ParentTopLevel { get; }
+
         /// <inheritdoc/>
         public void Dispose()
         {
@@ -91,7 +92,7 @@ namespace Avalonia.Controls.Primitives
             PopupPositionerConstraintAdjustment constraintAdjustment = PopupPositionerConstraintAdjustment.All,
             Rect? rect = null)
         {
-            _positionerParameters.ConfigurePosition(_parent, target,
+            _positionerParameters.ConfigurePosition(ParentTopLevel, target,
                 placement, offset, anchor, gravity, constraintAdjustment, rect);
 
             if (_positionerParameters.Size != default)

src/Avalonia.Controls/Primitives/ScrollBar.cs

@@ -22,6 +22,10 @@ namespace Avalonia.Controls.Primitives
     /// <summary>
     /// A scrollbar control.
     /// </summary>
+    [TemplatePart("PART_LineDownButton", typeof(Button))]
+    [TemplatePart("PART_LineUpButton",   typeof(Button))]
+    [TemplatePart("PART_PageDownButton", typeof(Button))]
+    [TemplatePart("PART_PageUpButton",   typeof(Button))]
     [PseudoClasses(":vertical", ":horizontal")]
     public class ScrollBar : RangeBase
     {

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -292,11 +292,11 @@ namespace Avalonia.Controls.Primitives
                             "collection is different to the Items on the control.");
                     }
 
-                    var oldSelection = _selection?.SelectedItems.ToList();
+                    var oldSelection = _selection?.SelectedItems.ToArray();
                     DeinitializeSelectionModel(_selection);
                     _selection = value;
 
-                    if (oldSelection?.Count > 0)
+                    if (oldSelection?.Length > 0)
                     {
                         RaiseEvent(new SelectionChangedEventArgs(
                             SelectionChangedEvent,
@@ -845,8 +845,8 @@ namespace Avalonia.Controls.Primitives
             {
                 var ev = new SelectionChangedEventArgs(
                     SelectionChangedEvent,
-                    e.DeselectedItems.ToList(),
-                    e.SelectedItems.ToList());
+                    e.DeselectedItems.ToArray(),
+                    e.SelectedItems.ToArray());
                 RaiseEvent(ev);
             }
         }
@@ -988,7 +988,7 @@ namespace Avalonia.Controls.Primitives
                 RaiseEvent(new SelectionChangedEventArgs(
                     SelectionChangedEvent,
                     Array.Empty<object>(),
-                    Selection.SelectedItems.ToList()));
+                    Selection.SelectedItems.ToArray()));
             }
         }
 

src/Avalonia.Controls/Primitives/TemplatedControl.cs

@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Controls.Documents;
 using Avalonia.Controls.Templates;
 using Avalonia.Interactivity;
 using Avalonia.Logging;
@@ -41,31 +42,37 @@ namespace Avalonia.Controls.Primitives
         /// Defines the <see cref="FontFamily"/> property.
         /// </summary>
         public static readonly StyledProperty<FontFamily> FontFamilyProperty =
-            TextBlock.FontFamilyProperty.AddOwner<TemplatedControl>();
+            TextElement.FontFamilyProperty.AddOwner<TemplatedControl>();
 
         /// <summary>
         /// Defines the <see cref="FontSize"/> property.
         /// </summary>
         public static readonly StyledProperty<double> FontSizeProperty =
-            TextBlock.FontSizeProperty.AddOwner<TemplatedControl>();
+            TextElement.FontSizeProperty.AddOwner<TemplatedControl>();
 
         /// <summary>
         /// Defines the <see cref="FontStyle"/> property.
         /// </summary>
         public static readonly StyledProperty<FontStyle> FontStyleProperty =
-            TextBlock.FontStyleProperty.AddOwner<TemplatedControl>();
+            TextElement.FontStyleProperty.AddOwner<TemplatedControl>();
 
         /// <summary>
         /// Defines the <see cref="FontWeight"/> property.
         /// </summary>
         public static readonly StyledProperty<FontWeight> FontWeightProperty =
-            TextBlock.FontWeightProperty.AddOwner<TemplatedControl>();
+            TextElement.FontWeightProperty.AddOwner<TemplatedControl>();
+
+        /// <summary>
+        /// Defines the <see cref="FontWeight"/> property.
+        /// </summary>
+        public static readonly StyledProperty<FontStretch> FontStretchProperty =
+            TextElement.FontStretchProperty.AddOwner<TemplatedControl>();
 
         /// <summary>
         /// Defines the <see cref="Foreground"/> property.
         /// </summary>
         public static readonly StyledProperty<IBrush?> ForegroundProperty =
-            TextBlock.ForegroundProperty.AddOwner<TemplatedControl>();
+            TextElement.ForegroundProperty.AddOwner<TemplatedControl>();
 
         /// <summary>
         /// Defines the <see cref="Padding"/> property.
@@ -185,6 +192,15 @@ namespace Avalonia.Controls.Primitives
             set { SetValue(FontWeightProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets the font stretch used to draw the control's text.
+        /// </summary>
+        public FontStretch FontStretch
+        {
+            get { return GetValue(FontStretchProperty); }
+            set { SetValue(FontStretchProperty, value); }
+        }
+
         /// <summary>
         /// Gets or sets the brush used to draw the control's text and other foreground elements.
         /// </summary>
@@ -340,6 +356,11 @@ namespace Avalonia.Controls.Primitives
             base.OnDetachedFromLogicalTree(e);
         }
 
+        /// <summary>
+        /// Called when the control's template is applied.
+        /// In simple terms, this means the method is called just before the control is displayed.
+        /// </summary>
+        /// <param name="e">The event args.</param>
         protected virtual void OnApplyTemplate(TemplateAppliedEventArgs e)
         {
         }

src/Avalonia.Controls/ProgressBar.cs

@@ -10,6 +10,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// A control used to indicate the progress of an operation.
     /// </summary>
+    [TemplatePart("PART_Indicator", typeof(Border))]
     [PseudoClasses(":vertical", ":horizontal", ":indeterminate")]
     public class ProgressBar : RangeBase
     {

src/Avalonia.Controls/ScrollViewer.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Reactive.Linq;
 using Avalonia.Automation.Peers;
+using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
@@ -11,6 +12,8 @@ namespace Avalonia.Controls
     /// <summary>
     /// A control which scrolls its content if the content is bigger than the space available.
     /// </summary>
+    [TemplatePart("PART_HorizontalScrollBar", typeof(ScrollBar))]
+    [TemplatePart("PART_VerticalScrollBar",   typeof(ScrollBar))]
     public class ScrollViewer : ContentControl, IScrollable, IScrollAnchorProvider
     {
         /// <summary>

src/Avalonia.Controls/Selection/InternalSelectionModel.cs

@@ -182,8 +182,8 @@ namespace Avalonia.Controls.Selection
             try
             {
                 var items = WritableSelectedItems;
-                var deselected = e.DeselectedItems.ToList();
-                var selected = e.SelectedItems.ToList();
+                var deselected = e.DeselectedItems.ToArray();
+                var selected = e.SelectedItems.ToArray();
 
                 _ignoreSelectedItemsChanges = true;
 

src/Avalonia.Controls/Shapes/Rectangle.cs

@@ -2,19 +2,139 @@ using Avalonia.Media;
 
 namespace Avalonia.Controls.Shapes
 {
+    /// <summary>
+    /// Represents a rectangle with optional rounded corners.
+    /// </summary>
     public class Rectangle : Shape
     {
+        private const double PiOver2 = 1.57079633; // 90 deg to rad
+
+        /// <summary>
+        /// Defines the <see cref="RadiusX"/> property.
+        /// </summary>
+        public static readonly StyledProperty<double> RadiusXProperty =
+            AvaloniaProperty.Register<Rectangle, double>(nameof(RadiusX));
+
+        /// <summary>
+        /// Defines the <see cref="RadiusY"/> property.
+        /// </summary>
+        public static readonly StyledProperty<double> RadiusYProperty =
+            AvaloniaProperty.Register<Rectangle, double>(nameof(RadiusY));
+
         static Rectangle()
         {
-            AffectsGeometry<Rectangle>(BoundsProperty, StrokeThicknessProperty);
+            AffectsGeometry<Rectangle>(
+                BoundsProperty,
+                RadiusXProperty,
+                RadiusYProperty,
+                StrokeThicknessProperty);
+        }
+
+        /// <summary>
+        /// Gets or sets the radius on the X-axis used to round the corners of the rectangle.
+        /// Corner radii are represented by an ellipse so this is the X-axis width of the ellipse.
+        /// </summary>
+        public double RadiusX
+        {
+            get => GetValue(RadiusXProperty);
+            set => SetValue(RadiusXProperty, value);
+        }
+
+        /// <summary>
+        /// Gets or sets the radius on the Y-axis used to round the corners of the rectangle.
+        /// Corner radii are represented by an ellipse so this is the Y-axis height of the ellipse.
+        /// </summary>
+        public double RadiusY
+        {
+            get => GetValue(RadiusYProperty);
+            set => SetValue(RadiusYProperty, value);
         }
 
+        /// <inheritdoc/>
         protected override Geometry CreateDefiningGeometry()
         {
-            var rect = new Rect(Bounds.Size).Deflate(StrokeThickness / 2);
-            return new RectangleGeometry(rect);
+            // TODO: If RectangleGeometry ever supports RadiusX/Y like in WPF,
+            // this code can be removed/combined with that implementation
+
+            double x = RadiusX;
+            double y = RadiusY;
+
+            if (x == 0 && y == 0)
+            {
+                // Optimization when there are no corner radii
+                var rect = new Rect(Bounds.Size).Deflate(StrokeThickness / 2);
+                return new RectangleGeometry(rect);
+            }
+            else
+            {
+                var rect = new Rect(Bounds.Size).Deflate(StrokeThickness / 2);
+                var geometry = new StreamGeometry();
+                var arcSize = new Size(x, y);
+
+                using (StreamGeometryContext context = geometry.Open())
+                {
+                    // The rectangle is constructed as follows:
+                    //
+                    //   (origin)
+                    //   Corner 4            Corner 1
+                    //   Top/Left  Line 1    Top/Right
+                    //      \_   __________   _/
+                    //          |          |
+                    //   Line 4 |          | Line 2
+                    //       _  |__________|  _
+                    //      /      Line 3      \
+                    //   Corner 3            Corner 2
+                    //   Bottom/Left         Bottom/Right
+                    //
+                    // - Lines 1,3 follow the deflated rectangle bounds minus RadiusX
+                    // - Lines 2,4 follow the deflated rectangle bounds minus RadiusY
+                    // - All corners are constructed using elliptical arcs 
+
+                    // Line 1 + Corner 1
+                    context.BeginFigure(new Point(rect.Left + x, rect.Top), true);
+                    context.LineTo(new Point(rect.Right - x, rect.Top));
+                    context.ArcTo(
+                        new Point(rect.Right, rect.Top + y),
+                        arcSize,
+                        rotationAngle: PiOver2,
+                        isLargeArc: false,
+                        SweepDirection.Clockwise);
+
+                    // Line 2 + Corner 2
+                    context.LineTo(new Point(rect.Right, rect.Bottom - y));
+                    context.ArcTo(
+                        new Point(rect.Right - x, rect.Bottom),
+                        arcSize,
+                        rotationAngle: PiOver2,
+                        isLargeArc: false,
+                        SweepDirection.Clockwise);
+
+                    // Line 3 + Corner 3
+                    context.LineTo(new Point(rect.Left + x, rect.Bottom));
+                    context.ArcTo(
+                        new Point(rect.Left, rect.Bottom - y),
+                        arcSize,
+                        rotationAngle: PiOver2,
+                        isLargeArc: false,
+                        SweepDirection.Clockwise);
+
+                    // Line 4 + Corner 4
+                    context.LineTo(new Point(rect.Left, rect.Top + y));
+                    context.ArcTo(
+                        new Point(rect.Left + x, rect.Top),
+                        arcSize,
+                        rotationAngle: PiOver2,
+                        isLargeArc: false,
+                        SweepDirection.Clockwise);
+
+                    context.EndFigure(true);
+                }
+
+                return geometry;
+            }
         }
 
+        /// <inheritdoc/>
         protected override Size MeasureOverride(Size availableSize)
         {
             return new Size(StrokeThickness, StrokeThickness);

src/Avalonia.Controls/Slider.cs

@@ -42,6 +42,9 @@ namespace Avalonia.Controls
     /// <summary>
     /// A control that lets the user select from a range of values by moving a Thumb control along a Track.
     /// </summary>
+    [TemplatePart("PART_DecreaseButton", typeof(Button))]
+    [TemplatePart("PART_IncreaseButton", typeof(Button))]
+    [TemplatePart("PART_Track",          typeof(Track))]
     [PseudoClasses(":vertical", ":horizontal", ":pressed")]
     public class Slider : RangeBase
     {

src/Avalonia.Controls/SplitButton/SplitButton.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Windows.Input;
 using Avalonia.Controls.Metadata;
-using Avalonia.Controls.Mixins;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.Interactivity;
@@ -13,6 +12,8 @@ namespace Avalonia.Controls
     /// A button with primary and secondary parts that can each be pressed separately.
     /// The primary part behaves like a <see cref="Button"/> and the secondary part opens a flyout.
     /// </summary>
+    [TemplatePart("PART_PrimaryButton",   typeof(Button))]
+    [TemplatePart("PART_SecondaryButton", typeof(Button))]
     [PseudoClasses(pcFlyoutOpen, pcPressed)]
     public class SplitButton : ContentControl, ICommandSource
     {
@@ -314,16 +315,9 @@ namespace Avalonia.Controls
                 }
 
                 // Must unregister events here while a reference to the old flyout still exists
-                if (oldFlyout != null)
-                {
-                    UnregisterFlyoutEvents(oldFlyout);
-                }
-
-                if (newFlyout != null)
-                {
-                    RegisterFlyoutEvents(newFlyout);
-                }
+                UnregisterFlyoutEvents(oldFlyout);
 
+                RegisterFlyoutEvents(newFlyout);
                 UpdatePseudoClasses();
             }
 
@@ -415,6 +409,22 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        /// Invoked when the split button's flyout is opened.
+        /// </summary>
+        protected virtual void OnFlyoutOpened()
+        {
+            // Available for derived types
+        }
+
+        /// <summary>
+        /// Invoked when the split button's flyout is closed.
+        /// </summary>
+        protected virtual void OnFlyoutClosed()
+        {
+            // Available for derived types
+        }
+
         ////////////////////////////////////////////////////////////////////////
         // Event Handling
         ////////////////////////////////////////////////////////////////////////
@@ -464,6 +474,8 @@ namespace Avalonia.Controls
             {
                 _isFlyoutOpen = true;
                 UpdatePseudoClasses();
+
+                OnFlyoutOpened();
             }
         }
 
@@ -479,6 +491,8 @@ namespace Avalonia.Controls
             {
                 _isFlyoutOpen = false;
                 UpdatePseudoClasses();
+
+                OnFlyoutClosed();
             }
         }
     }

src/Avalonia.Controls/SplitView.cs

@@ -77,6 +77,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// A control with two views: A collapsible pane and an area for content
     /// </summary>
+    [TemplatePart("PART_PaneRoot", typeof(Panel))]
     [PseudoClasses(":open", ":closed")]
     [PseudoClasses(":compactoverlay", ":compactinline", ":overlay", ":inline")]
     [PseudoClasses(":left", ":right")]

src/Avalonia.Controls/TabControl.cs

@@ -11,12 +11,14 @@ using Avalonia.Layout;
 using Avalonia.LogicalTree;
 using Avalonia.VisualTree;
 using Avalonia.Automation;
+using Avalonia.Controls.Metadata;
 
 namespace Avalonia.Controls
 {
     /// <summary>
     /// A tab control that displays a tab strip along with the content of the selected tab.
     /// </summary>
+    [TemplatePart("PART_ItemsPresenter", typeof(ItemsPresenter))]
     public class TabControl : SelectingItemsControl, IContentPresenterHost
     {
         /// <summary>

src/Avalonia.Controls/TextBlock.cs

@@ -28,61 +28,50 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<Thickness> PaddingProperty =
             Decorator.PaddingProperty.AddOwner<TextBlock>();
 
-        // TODO: Define these attached properties elsewhere (e.g. on a Text class) and AddOwner
-        // them into TextBlock.
-
         /// <summary>
         /// Defines the <see cref="FontFamily"/> property.
         /// </summary>
-        public static readonly AttachedProperty<FontFamily> FontFamilyProperty =
-            AvaloniaProperty.RegisterAttached<TextBlock, Control, FontFamily>(
-                nameof(FontFamily),
-                defaultValue: FontFamily.Default,
-                inherits: true);
+        public static readonly StyledProperty<FontFamily> FontFamilyProperty =
+            TextElement.FontFamilyProperty.AddOwner<TextBlock>();
 
         /// <summary>
         /// Defines the <see cref="FontSize"/> property.
         /// </summary>
-        public static readonly AttachedProperty<double> FontSizeProperty =
-            AvaloniaProperty.RegisterAttached<TextBlock, Control, double>(
-                nameof(FontSize),
-                defaultValue: 12,
-                inherits: true);
+        public static readonly StyledProperty<double> FontSizeProperty =
+            TextElement.FontSizeProperty.AddOwner<TextBlock>();
 
         /// <summary>
         /// Defines the <see cref="FontStyle"/> property.
         /// </summary>
-        public static readonly AttachedProperty<FontStyle> FontStyleProperty =
-            AvaloniaProperty.RegisterAttached<TextBlock, Control, FontStyle>(
-                nameof(FontStyle),
-                inherits: true);
+        public static readonly StyledProperty<FontStyle> FontStyleProperty =
+            TextElement.FontStyleProperty.AddOwner<TextBlock>();
 
         /// <summary>
         /// Defines the <see cref="FontWeight"/> property.
         /// </summary>
-        public static readonly AttachedProperty<FontWeight> FontWeightProperty =
-            AvaloniaProperty.RegisterAttached<TextBlock, Control, FontWeight>(
-                nameof(FontWeight),
-                inherits: true,
-                defaultValue: FontWeight.Normal);
+        public static readonly StyledProperty<FontWeight> FontWeightProperty =
+            TextElement.FontWeightProperty.AddOwner<TextBlock>();
 
         /// <summary>
-        /// Defines the <see cref="FontStretch"/> property.
+        /// Defines the <see cref="FontWeight"/> property.
         /// </summary>
-        public static readonly AttachedProperty<FontStretch> FontStretchProperty =
-            AvaloniaProperty.RegisterAttached<TextBlock, Control, FontStretch>(
-                nameof(FontStretch),
-                inherits: true,
-                defaultValue: FontStretch.Normal);
-        
+        public static readonly StyledProperty<FontStretch> FontStretchProperty =
+            TextElement.FontStretchProperty.AddOwner<TextBlock>();
+
         /// <summary>
         /// Defines the <see cref="Foreground"/> property.
         /// </summary>
-        public static readonly AttachedProperty<IBrush?> ForegroundProperty =
-            AvaloniaProperty.RegisterAttached<TextBlock, Control, IBrush?>(
-                nameof(Foreground),
-                Brushes.Black,
-                inherits: true);
+        public static readonly StyledProperty<IBrush?> ForegroundProperty =
+            TextElement.ForegroundProperty.AddOwner<TextBlock>();
+
+        /// <summary>
+        /// DependencyProperty for <see cref="BaselineOffset" /> property.
+        /// </summary>
+        public static readonly AttachedProperty<double> BaselineOffsetProperty =
+            AvaloniaProperty.RegisterAttached<TextBlock, Control, double>(
+                nameof(BaselineOffset),
+                0,
+                true);
 
         /// <summary>
         /// Defines the <see cref="LineHeight"/> property.
@@ -222,7 +211,7 @@ namespace Avalonia.Controls
         public InlineCollection Inlines { get; }
 
         /// <summary>
-        /// Gets or sets the font family.
+        /// Gets or sets the font family used to draw the control's text.
         /// </summary>
         public FontFamily FontFamily
         {
@@ -231,7 +220,7 @@ namespace Avalonia.Controls
         }
 
         /// <summary>
-        /// Gets or sets the font size.
+        /// Gets or sets the size of the control's text in points.
         /// </summary>
         public double FontSize
         {
@@ -240,7 +229,7 @@ namespace Avalonia.Controls
         }
 
         /// <summary>
-        /// Gets or sets the font style.
+        /// Gets or sets the font style used to draw the control's text.
         /// </summary>
         public FontStyle FontStyle
         {
@@ -249,16 +238,16 @@ namespace Avalonia.Controls
         }
 
         /// <summary>
-        /// Gets or sets the font weight.
+        /// Gets or sets the font weight used to draw the control's text.
         /// </summary>
         public FontWeight FontWeight
         {
             get { return GetValue(FontWeightProperty); }
             set { SetValue(FontWeightProperty, value); }
         }
-        
+
         /// <summary>
-        /// Gets or sets the font stretch.
+        /// Gets or sets the font stretch used to draw the control's text.
         /// </summary>
         public FontStretch FontStretch
         {
@@ -267,7 +256,7 @@ namespace Avalonia.Controls
         }
 
         /// <summary>
-        /// Gets or sets a brush used to paint the text.
+        /// Gets or sets the brush used to draw the control's text and other foreground elements.
         /// </summary>
         public IBrush? Foreground
         {
@@ -328,125 +317,43 @@ namespace Avalonia.Controls
             get => GetValue(TextDecorationsProperty);
             set => SetValue(TextDecorationsProperty, value);
         }
-
-        /// <summary>
-        /// Gets the value of the attached <see cref="FontFamilyProperty"/> on a control.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <returns>The font family.</returns>
-        public static FontFamily GetFontFamily(Control control)
-        {
-            return control.GetValue(FontFamilyProperty);
-        }
-
-        /// <summary>
-        /// Gets the value of the attached <see cref="FontSizeProperty"/> on a control.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <returns>The font size.</returns>
-        public static double GetFontSize(Control control)
-        {
-            return control.GetValue(FontSizeProperty);
-        }
-
-        /// <summary>
-        /// Gets the value of the attached <see cref="FontStyleProperty"/> on a control.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <returns>The font style.</returns>
-        public static FontStyle GetFontStyle(Control control)
-        {
-            return control.GetValue(FontStyleProperty);
-        }
-
-        /// <summary>
-        /// Gets the value of the attached <see cref="FontWeightProperty"/> on a control.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <returns>The font weight.</returns>
-        public static FontWeight GetFontWeight(Control control)
-        {
-            return control.GetValue(FontWeightProperty);
-        }
         
         /// <summary>
-        /// Gets the value of the attached <see cref="FontStretchProperty"/> on a control.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <returns>The font stretch.</returns>
-        public static FontStretch GetFontStretch(Control control)
-        {
-            return control.GetValue(FontStretchProperty);
-        }
-
-        /// <summary>
-        /// Gets the value of the attached <see cref="ForegroundProperty"/> on a control.
+        /// The BaselineOffset property provides an adjustment to baseline offset
         /// </summary>
-        /// <param name="control">The control.</param>
-        /// <returns>The foreground.</returns>
-        public static IBrush? GetForeground(Control control)
+        public double BaselineOffset
         {
-            return control.GetValue(ForegroundProperty);
+            get { return (double)GetValue(BaselineOffsetProperty); }
+            set { SetValue(BaselineOffsetProperty, value); }
         }
 
         /// <summary>
-        /// Sets the value of the attached <see cref="FontFamilyProperty"/> on a control.
+        /// Reads the attached property from the given element
         /// </summary>
-        /// <param name="control">The control.</param>
-        /// <param name="value">The property value to set.</param>
-        public static void SetFontFamily(Control control, FontFamily value)
+        /// <param name="control">The element to which to read the attached property.</param>
+        public static double GetBaselineOffset(Control control)
         {
-            control.SetValue(FontFamilyProperty, value);
-        }
+            if (control == null)
+            {
+                throw new ArgumentNullException(nameof(control));
+            }
 
-        /// <summary>
-        /// Sets the value of the attached <see cref="FontSizeProperty"/> on a control.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <param name="value">The property value to set.</param>
-        public static void SetFontSize(Control control, double value)
-        {
-            control.SetValue(FontSizeProperty, value);
+            return control.GetValue(BaselineOffsetProperty);
         }
 
         /// <summary>
-        /// Sets the value of the attached <see cref="FontStyleProperty"/> on a control.
+        /// Writes the attached property BaselineOffset to the given element.
         /// </summary>
-        /// <param name="control">The control.</param>
-        /// <param name="value">The property value to set.</param>
-        public static void SetFontStyle(Control control, FontStyle value)
+        /// <param name="control">The element to which to write the attached property.</param>
+        /// <param name="value">The property value to set</param>
+        public static void SetBaselineOffset(Control control, double value)
         {
-            control.SetValue(FontStyleProperty, value);
-        }
-
-        /// <summary>
-        /// Sets the value of the attached <see cref="FontWeightProperty"/> on a control.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <param name="value">The property value to set.</param>
-        public static void SetFontWeight(Control control, FontWeight value)
-        {
-            control.SetValue(FontWeightProperty, value);
-        }
-        
-        /// <summary>
-        /// Sets the value of the attached <see cref="FontStretchProperty"/> on a control.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <param name="value">The property value to set.</param>
-        public static void SetFontStretch(Control control, FontStretch value)
-        {
-            control.SetValue(FontStretchProperty, value);
-        }
+            if (control == null)
+            {
+                throw new ArgumentNullException(nameof(control));
+            }
 
-        /// <summary>
-        /// Sets the value of the attached <see cref="ForegroundProperty"/> on a control.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <param name="value">The property value to set.</param>
-        public static void SetForeground(Control control, IBrush? value)
-        {
-            control.SetValue(ForegroundProperty, value);
+            control.SetValue(BaselineOffsetProperty, value);
         }
 
         /// <summary>
@@ -562,7 +469,7 @@ namespace Avalonia.Controls
                 return finalSize;
             }
             
-            _constraint = finalSize;
+            _constraint = new Size(finalSize.Width, Math.Ceiling(finalSize.Height));
             
             _textLayout = null;
 
@@ -588,15 +495,19 @@ namespace Avalonia.Controls
                 case nameof (FontWeight):
                 case nameof (FontStyle):
                 case nameof (FontFamily):
+                case nameof (FontStretch):
 
                 case nameof (TextWrapping):
                 case nameof (TextTrimming):
                 case nameof (TextAlignment):
+
                 case nameof (FlowDirection):
 
                 case nameof (Padding):
                 case nameof (LineHeight):
                 case nameof (MaxLines):
+                    
+                case nameof (InlinesProperty):
 
                 case nameof (Text):
                 case nameof (TextDecorations):

src/Avalonia.Controls/TextBox.cs

@@ -23,6 +23,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// Represents a control that can be used to display or edit unformatted text.
     /// </summary>
+    [TemplatePart("PART_TextPresenter", typeof(TextPresenter))]
     [PseudoClasses(":empty")]
     public class TextBox : TemplatedControl, UndoRedoHelper<TextBox.UndoRedoState>.IUndoRedoHost
     {
@@ -77,6 +78,9 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<int> MaxLengthProperty =
             AvaloniaProperty.Register<TextBox, int>(nameof(MaxLength), defaultValue: 0);
 
+        public static readonly StyledProperty<int> MaxLinesProperty =
+      AvaloniaProperty.Register<TextBox, int>(nameof(MaxLines), defaultValue: 0);
+
         public static readonly DirectProperty<TextBox, string?> TextProperty =
             TextBlock.TextProperty.AddOwnerWithDataValidation<TextBox>(
                 o => o.Text,
@@ -349,6 +353,12 @@ namespace Avalonia.Controls
             set { SetValue(MaxLengthProperty, value); }
         }
 
+        public int MaxLines
+        {
+            get { return GetValue(MaxLinesProperty); }
+            set { SetValue(MaxLinesProperty, value); }
+        }
+
         [Content]
         public string? Text
         {
@@ -670,6 +680,39 @@ namespace Avalonia.Controls
             _selectedTextChangesMadeSinceLastUndoSnapshot++;
             SnapshotUndoRedo(ignoreChangeCount: false);
 
+            if (_presenter != null && MaxLines > 0)
+            {
+                var lineCount = _presenter.TextLayout.TextLines.Count;
+
+                var length = 0;
+
+                var graphemeEnumerator = new GraphemeEnumerator(input.AsMemory());
+
+                while (graphemeEnumerator.MoveNext())
+                {
+                    var grapheme = graphemeEnumerator.Current;
+
+                    if (grapheme.FirstCodepoint.IsBreakChar)
+                    {
+                        if(lineCount + 1 > MaxLines)
+                        {
+                            break;
+                        }
+                        else
+                        {
+                            lineCount++;
+                        }                       
+                    }
+
+                    length += grapheme.Text.Length;
+                }
+
+                if (length < input.Length)
+                {
+                    input = input.Remove(Math.Max(0, length));
+                }
+            }
+
             var text = Text ?? string.Empty;
             var newLength = input.Length + text.Length - Math.Abs(SelectionStart - SelectionEnd);
 
@@ -997,18 +1040,25 @@ namespace Avalonia.Controls
                             SetSelectionForControlBackspace();
                         }
 
-                        if (!DeleteSelection() && caretIndex > 0)
+                        if (!DeleteSelection())
                         {
-                            _presenter.MoveCaretHorizontal(LogicalDirection.Backward);
+                            var characterHit = _presenter.GetNextCharacterHit(LogicalDirection.Backward);
 
-                            var removedCharacters = Math.Max(0, caretIndex - _presenter.CaretIndex);
-                            
-                            var length = Math.Max(0, caretIndex - removedCharacters);
+                            var backspacePosition = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
 
-                            SetTextInternal(text.Substring(0, length) +
-                                            text.Substring(caretIndex));
+                            if (caretIndex != backspacePosition)
+                            {
+                                var start = Math.Min(backspacePosition, caretIndex);
+                                var end = Math.Max(backspacePosition, caretIndex);
 
-                            CaretIndex = _presenter.CaretIndex;
+                                var length = end - start;
+
+                                var editedText = text.Substring(0, start) + text.Substring(Math.Min(end, text.Length));
+
+                                SetTextInternal(editedText);
+
+                                CaretIndex = end;
+                            } 
                         }
                         
                         SnapshotUndoRedo();
@@ -1024,15 +1074,21 @@ namespace Avalonia.Controls
                             SetSelectionForControlDelete();
                         }
 
-                        if (!DeleteSelection() && caretIndex < text.Length)
+                        if (!DeleteSelection())
                         {
                             var characterHit = _presenter.GetNextCharacterHit();
 
-                            var removedCharacters = Math.Max(0,
-                                characterHit.FirstCharacterIndex + characterHit.TrailingLength - caretIndex);
+                            var nextPosition = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
+
+                            if(nextPosition != caretIndex)
+                            {
+                                var start = Math.Min(nextPosition, caretIndex);
+                                var end = Math.Max(nextPosition, caretIndex);
 
-                            SetTextInternal(text.Substring(0, caretIndex) +
-                                            text.Substring(caretIndex + removedCharacters));
+                                var editedText = text.Substring(0, start) + text.Substring(Math.Min(end, text.Length));
+
+                                SetTextInternal(editedText);
+                            }
                         }
 
                         SnapshotUndoRedo();
@@ -1249,17 +1305,17 @@ namespace Avalonia.Controls
 
         private void MoveHorizontal(int direction, bool wholeWord, bool isSelecting)
         {
+            if (_presenter == null)
+            {
+                return;
+            }
+            
             var text = Text ?? string.Empty;
             var selectionStart = SelectionStart;
             var selectionEnd = SelectionEnd;
 
             if (!wholeWord)
             {
-                if (_presenter == null)
-                {
-                    return;
-                }
-                
                 if (isSelecting)
                 {
                     _presenter.MoveCaretToTextPosition(selectionEnd);
@@ -1303,10 +1359,16 @@ namespace Avalonia.Controls
                 
                 SelectionEnd += offset;
 
+                _presenter.MoveCaretToTextPosition(SelectionEnd);
+
                 if (!isSelecting)
                 {
                     CaretIndex = SelectionEnd;
                 }
+                else
+                {
+                    SelectionStart = selectionStart;
+                }
             }
         }
 
@@ -1326,10 +1388,10 @@ namespace Avalonia.Controls
             else
             {
                 var textLines = _presenter.TextLayout.TextLines;
-                var lineIndex = _presenter.TextLayout.GetLineIndexFromCharacterIndex(caretIndex, true);
+                var lineIndex = _presenter.TextLayout.GetLineIndexFromCharacterIndex(caretIndex, false);
                 var textLine = textLines[lineIndex];
 
-                _presenter.MoveCaretToTextPosition(textLine.TextRange.Start);
+                _presenter.MoveCaretToTextPosition(textLine.FirstTextSourceIndex);
             }
         }
 
@@ -1350,16 +1412,10 @@ namespace Avalonia.Controls
             else
             {
                 var textLines = _presenter.TextLayout.TextLines;
-                var lineIndex = _presenter.TextLayout.GetLineIndexFromCharacterIndex(caretIndex, true);
+                var lineIndex = _presenter.TextLayout.GetLineIndexFromCharacterIndex(caretIndex, false);
                 var textLine = textLines[lineIndex];
-                
-                if (caretIndex == textLine.TextRange.Start + textLine.TextRange.Length  - textLine.NewLineLength &&
-                    lineIndex + 1 < textLines.Count)
-                {
-                    textLine = textLines[++lineIndex];
-                }
 
-                var textPosition = textLine.TextRange.Start + textLine.TextRange.Length - textLine.NewLineLength;
+                var textPosition = textLine.FirstTextSourceIndex + textLine.Length;
 
                 _presenter.MoveCaretToTextPosition(textPosition, true);
             }

src/Avalonia.Controls/ToggleSwitch.cs

@@ -9,6 +9,8 @@ namespace Avalonia.Controls
     /// <summary>
     /// A Toggle Switch control.
     /// </summary>
+    [TemplatePart("MovingKnobs", typeof(Panel))]
+    [TemplatePart("SwitchKnob",  typeof(Panel))]
     [PseudoClasses(":dragging")]
     public class ToggleSwitch : ToggleButton
     {

src/Avalonia.Controls/TopLevel.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Reactive.Linq;
+using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Platform;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
@@ -26,6 +27,7 @@ namespace Avalonia.Controls
     /// It handles scheduling layout, styling and rendering as well as
     /// tracking the widget's <see cref="ClientSize"/>.
     /// </remarks>
+    [TemplatePart("PART_TransparencyFallback", typeof(Border))]
     public abstract class TopLevel : ContentControl,
         IInputRoot,
         ILayoutRoot,

src/Avalonia.Controls/TreeView.cs

@@ -849,7 +849,7 @@ namespace Avalonia.Controls
         /// <param name="desired">The desired items.</param>
         private static void SynchronizeItems(IList items, IEnumerable<object> desired)
         {
-            var list = items.Cast<object>().ToList();
+            var list = items.Cast<object>();
             var toRemove = list.Except(desired).ToList();
             var toAdd = desired.Except(list).ToList();
 

src/Avalonia.Controls/TreeViewItem.cs

@@ -12,6 +12,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// An item in a <see cref="TreeView"/>.
     /// </summary>
+    [TemplatePart("PART_Header", typeof(IControl))]
     [PseudoClasses(":pressed", ":selected")]
     public class TreeViewItem : HeaderedItemsControl, ISelectable
     {

src/Avalonia.Controls/Utils/CollectionChangedEventManager.cs

@@ -105,7 +105,7 @@ namespace Avalonia.Controls.Utils
                 static void Notify(
                     INotifyCollectionChanged incc,
                     NotifyCollectionChangedEventArgs args,
-                    List<WeakReference<ICollectionChangedListener>> listeners)
+                    WeakReference<ICollectionChangedListener>[] listeners)
                 {
                     foreach (var l in listeners)
                     {
@@ -132,7 +132,7 @@ namespace Avalonia.Controls.Utils
                     }
                 }
 
-                var l = Listeners.ToList();
+                var l = Listeners.ToArray();
 
                 if (Dispatcher.UIThread.CheckAccess())
                 {

src/Avalonia.Controls/Window.cs

@@ -12,7 +12,6 @@ using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.Platform;
 using Avalonia.Styling;
-using JetBrains.Annotations;
 
 namespace Avalonia.Controls
 {
@@ -258,7 +257,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Gets a collection of child windows owned by this window.
         /// </summary>
-        public IReadOnlyList<Window> OwnedWindows => _children.Select(x => x.child).ToList();
+        public IReadOnlyList<Window> OwnedWindows => _children.Select(x => x.child).ToArray();
 
         /// <summary>
         /// Gets or sets a value indicating how the window will size itself to fit its content.
@@ -527,7 +526,7 @@ namespace Avalonia.Controls
 
         private void CloseInternal()
         {
-            foreach (var (child, _) in _children.ToList())
+            foreach (var (child, _) in _children.ToArray())
             {
                 child.CloseInternal();
             }
@@ -551,7 +550,7 @@ namespace Avalonia.Controls
             
             bool canClose = true;
 
-            foreach (var (child, _) in _children.ToList())
+            foreach (var (child, _) in _children.ToArray())
             {
                 if (child.ShouldCancelClose(args))
                 {

src/Avalonia.DesignerSupport/Remote/HtmlTransport/webapp/package-lock.json

@@ -1078,12 +1078,6 @@
             "json5": "^2.1.2"
           }
         },
-        "minimist": {
-          "version": "1.2.5",
-          "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.5.tgz",
-          "integrity": "sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw==",
-          "dev": true
-        },
         "schema-utils": {
           "version": "3.1.1",
           "resolved": "https://registry.npmjs.org/schema-utils/-/schema-utils-3.1.1.tgz",
@@ -1636,9 +1630,9 @@
       }
     },
     "minimist": {
-      "version": "1.2.5",
-      "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.5.tgz",
-      "integrity": "sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw==",
+      "version": "1.2.6",
+      "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.6.tgz",
+      "integrity": "sha512-Jsjnk4bw3YJqYzbdyBiNsPWHPfO++UGG749Cxs6peCu5Xg4nrena6OVxOYxrQTqww0Jmwt+Ref8rggumkTLz9Q==",
       "dev": true
     },
     "mobx": {
@@ -1839,12 +1833,6 @@
             "ms": "^2.1.1"
           }
         },
-        "minimist": {
-          "version": "1.2.5",
-          "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.5.tgz",
-          "integrity": "sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw==",
-          "dev": true
-        },
         "mkdirp": {
           "version": "0.5.5",
           "resolved": "https://registry.npmjs.org/mkdirp/-/mkdirp-0.5.5.tgz",
@@ -2592,12 +2580,6 @@
             "json5": "^2.1.2"
           }
         },
-        "minimist": {
-          "version": "1.2.5",
-          "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.5.tgz",
-          "integrity": "sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw==",
-          "dev": true
-        },
         "schema-utils": {
           "version": "3.1.1",
           "resolved": "https://registry.npmjs.org/schema-utils/-/schema-utils-3.1.1.tgz",

src/Avalonia.Diagnostics/Diagnostics/DevTools.cs

@@ -105,13 +105,15 @@ namespace Avalonia.Diagnostics
 
         private static IDisposable Open(Application? application, DevToolsOptions options, Window? owner = default)
         {
+            var focussedControl = KeyboardDevice.Instance?.FocusedElement as IControl;
             if (application is null)
             {
                 throw new ArgumentNullException(nameof(application));
             }
             if (s_open.TryGetValue(application, out var window))
-            {                
+            {
                 window.Activate();
+                window.SelectedControl(focussedControl);
             }
             else
             {
@@ -122,7 +124,7 @@ namespace Avalonia.Diagnostics
                     Height = options.Size.Height,
                 };
                 window.SetOptions(options);
-
+                window.SelectedControl(focussedControl);
                 window.Closed += DevToolsClosed;
                 s_open.Add(application, window);
                 if (options.ShowAsChildWindow && owner is { })

src/Avalonia.Diagnostics/Diagnostics/DevToolsOptions.cs

@@ -41,5 +41,10 @@ namespace Avalonia.Diagnostics
         /// <remarks>Default handler is <see cref="Screenshots.FilePickerHandler"/></remarks>
         public IScreenshotHandler ScreenshotHandler { get; set; }
           = Convetions.DefaultScreenshotHandler;
+
+        /// <summary>
+        /// Gets or sets whether DevTools should use the dark mode theme
+        /// </summary>
+        public bool UseDarkMode { get; set; }
     }
 }

src/Avalonia.Diagnostics/Diagnostics/ViewModels/BindingSetterViewModel.cs

@@ -14,11 +14,13 @@ namespace Avalonia.Diagnostics.ViewModels
                 case Binding binding:
                     Path = binding.Path;
                     Tint = Brushes.CornflowerBlue;
+                    ValueTypeTooltip = "Reflection Binding";
 
                     break;
                 case CompiledBindingExtension binding:
                     Path = binding.Path.ToString();
                     Tint = Brushes.DarkGreen;
+                    ValueTypeTooltip = "Compiled Binding";
 
                     break;
                 case TemplateBinding binding:
@@ -32,6 +34,7 @@ namespace Avalonia.Diagnostics.ViewModels
                     }
 
                     Tint = Brushes.OrangeRed;
+                    ValueTypeTooltip = "Template Binding";
 
                     break;
                 default:
@@ -40,6 +43,8 @@ namespace Avalonia.Diagnostics.ViewModels
         }
 
         public IBrush Tint { get; }
+        
+        public string ValueTypeTooltip { get; }
 
         public string Path { get; }
 

src/Avalonia.Diagnostics/Diagnostics/ViewModels/ControlDetailsViewModel.cs

@@ -18,7 +18,7 @@ namespace Avalonia.Diagnostics.ViewModels
     internal class ControlDetailsViewModel : ViewModelBase, IDisposable
     {
         private readonly IAvaloniaObject _avaloniaObject;
-        private IDictionary<object, List<PropertyViewModel>>? _propertyIndex;
+        private IDictionary<object, PropertyViewModel[]>? _propertyIndex;
         private PropertyViewModel? _selectedProperty;
         private DataGridCollectionView? _propertiesView;
         private bool _snapshotStyles;
@@ -155,31 +155,19 @@ namespace Avalonia.Diagnostics.ViewModels
         public object? SelectedEntity
         {
             get => _selectedEntity;
-            set
-            {
-                RaiseAndSetIfChanged(ref _selectedEntity, value);
-               
-            }
+            set => RaiseAndSetIfChanged(ref _selectedEntity, value);
         }
 
         public string? SelectedEntityName
         {
             get => _selectedEntityName;
-            set
-            {
-                RaiseAndSetIfChanged(ref _selectedEntityName, value);
-               
-            }
+            set => RaiseAndSetIfChanged(ref _selectedEntityName, value);
         }
         
         public string? SelectedEntityType
         {
             get => _selectedEntityType;
-            set
-            {
-                RaiseAndSetIfChanged(ref _selectedEntityType, value);
-               
-            }
+            set => RaiseAndSetIfChanged(ref _selectedEntityType, value);
         }
         
         public PropertyViewModel? SelectedProperty
@@ -484,9 +472,9 @@ namespace Avalonia.Diagnostics.ViewModels
                 .Concat(GetClrProperties(o, _showImplementedInterfaces))
                 .OrderBy(x => x, PropertyComparer.Instance)
                 .ThenBy(x => x.Name)
-                .ToList();
+                .ToArray();
 
-            _propertyIndex = properties.GroupBy(x => x.Key).ToDictionary(x => x.Key, x => x.ToList());
+            _propertyIndex = properties.GroupBy(x => x.Key).ToDictionary(x => x.Key, x => x.ToArray());
 
             var view = new DataGridCollectionView(properties);
             view.GroupDescriptions.Add(new DataGridPathGroupDescription(nameof(AvaloniaPropertyViewModel.Group)));
@@ -502,6 +490,31 @@ namespace Avalonia.Diagnostics.ViewModels
                 inpc2.PropertyChanged += ControlPropertyChanged;
             }
         }
+        
+        internal void SelectProperty(AvaloniaProperty property)
+        {
+            SelectedProperty = null;
+
+            if (SelectedEntity != _avaloniaObject)
+            {
+                NavigateToProperty(_avaloniaObject, (_avaloniaObject as IControl)?.Name ?? _avaloniaObject.ToString());    
+            }
+            
+            if (PropertiesView is null)
+            {
+                return;
+            }
+
+            foreach (object o in PropertiesView)
+            {
+                if (o is AvaloniaPropertyViewModel propertyVm && propertyVm.Property == property)
+                {
+                    SelectedProperty = propertyVm;
+                    
+                    break;
+                }
+            }
+        }
 
         internal void UpdatePropertiesView(bool showImplementedInterfaces)
         {

src/Avalonia.Diagnostics/Diagnostics/ViewModels/ResourceSetterViewModel.cs

@@ -7,11 +7,14 @@ namespace Avalonia.Diagnostics.ViewModels
         public object Key { get; }
 
         public IBrush Tint { get; }
+        
+        public string ValueTypeTooltip { get; }
 
         public ResourceSetterViewModel(AvaloniaProperty property, object resourceKey, object? resourceValue, bool isDynamic) : base(property, resourceValue)
         {
             Key = resourceKey;
             Tint = isDynamic ? Brushes.Orange : Brushes.Brown;
+            ValueTypeTooltip = isDynamic ? "Dynamic Resource" : "Static Resource";
         }
 
         public void CopyResourceKey()

src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml

@@ -11,7 +11,7 @@
                   BorderBrush="{TemplateBinding BorderBrush}"
                   BorderThickness="{TemplateBinding BorderThickness}">
             <DockPanel Margin="{TemplateBinding Padding}">
-              <TextBlock DockPanel.Dock="Left" Margin="0,0,4,0">></TextBlock>
+              <TextBlock DockPanel.Dock="Left" Margin="0,0,4,0"></TextBlock>
               <TextPresenter Name="PART_TextPresenter"
                              Text="{TemplateBinding Text, Mode=TwoWay}"
                              CaretIndex="{TemplateBinding CaretIndex}"
@@ -44,7 +44,7 @@
         <DataTemplate>
           <StackPanel Orientation="Vertical">
             <DockPanel>
-              <TextBlock DockPanel.Dock="Left" Margin="0,0,4,0">></TextBlock>
+              <TextBlock DockPanel.Dock="Left" Margin="0,0,4,0"></TextBlock>
               <TextBlock Text="{Binding Input}"/>
             </DockPanel>
             <TextBlock Foreground="{Binding Foreground}" Text="{Binding Output}"/>

src/Avalonia.Diagnostics/Diagnostics/Views/ControlDetailsView.xaml

@@ -44,7 +44,9 @@
                               UseWholeWordFilter="{Binding UseWholeWordFilter}"
                               UseRegexFilter="{Binding UseRegexFilter}"/>
       
-      <DataGrid Items="{Binding PropertiesView}"
+      <DataGrid 
+                x:Name="DataGrid"
+                Items="{Binding PropertiesView}"
                 Grid.Row="2"
                 BorderThickness="0"
                 RowBackground="Transparent"
@@ -129,6 +131,26 @@
                     </Expander.Header>
 
                     <ItemsControl Margin="20,0,0,0" Grid.Row="1" Items="{Binding Setters}">
+                      
+                      <ItemsControl.Styles>
+                        <Style Selector="TextBlock.property-name">
+                          <Setter Property="FontWeight" Value="SemiBold" />
+                          <Setter Property="Background" Value="Transparent" />
+                        </Style>
+                        
+                        <Style Selector="TextBlock.property-name:pointerover">
+                          <Setter Property="TextDecorations" Value="Underline" />
+                        </Style>
+                        
+                        <Style Selector="Rectangle.property-inactive">
+                          <Setter Property="IsHitTestVisible" Value="False" />
+                          <Setter Property="Height" Value="1" />
+                          <Setter Property="Fill" Value="#6C6C6C" />
+                          <Setter Property="VerticalAlignment" Value="Center" />
+                        </Style>
+                        
+                      </ItemsControl.Styles>
+                      
                       <ItemsControl.DataTemplates>
 
                         <DataTemplate DataType="IBrush">
@@ -138,6 +160,17 @@
                           </StackPanel>
                         </DataTemplate>
 
+                        <DataTemplate DataType="Color">
+                          <StackPanel Orientation="Horizontal" Spacing="2">
+                            <Border BorderThickness="1" BorderBrush="Black" Width="8" Height="8">
+                              <Border.Background>
+                                <SolidColorBrush Color="{Binding}" />
+                              </Border.Background>
+                            </Border>
+                            <TextBlock Text="{Binding}" />
+                          </StackPanel>
+                        </DataTemplate>
+                        
                         <DataTemplate DataType="vm:BindingSetterViewModel">
                           <Panel Opacity="{Binding IsActive, Converter={StaticResource BoolToOpacity}}" IsVisible="{Binding IsVisible}" HorizontalAlignment="Left">
                             <Panel.ContextMenu>
@@ -147,28 +180,17 @@
                               </ContextMenu>
                             </Panel.ContextMenu>
                             <StackPanel Orientation="Horizontal" Spacing="2">
-                              <TextBlock Text="{Binding Name}" FontWeight="SemiBold" />
+                              <TextBlock Classes="property-name" PointerPressed="PropertyNamePressed" Text="{Binding Name}" />
                               <TextBlock Text=":" />
                               <TextBlock>{</TextBlock>
-                              <Rectangle Height="8" Width="8" VerticalAlignment="Center" Fill="{Binding Tint}"/>
+                              <Rectangle Height="8" Width="8" VerticalAlignment="Center" Fill="{Binding Tint}" ToolTip.Tip="{Binding ValueTypeTooltip}"/>
                               <TextBlock Text="{Binding Path}" />
                               <TextBlock>}</TextBlock>
                             </StackPanel>
-                            <Rectangle Height="1" Fill="#6C6C6C" VerticalAlignment="Center" IsVisible="{Binding !IsActive}" />
+                            <Rectangle Classes="property-inactive" IsVisible="{Binding !IsActive}" />
                           </Panel>
                         </DataTemplate>
 
-                        <DataTemplate DataType="Color">
-                          <StackPanel Orientation="Horizontal" Spacing="2">
-                            <Border BorderThickness="1" BorderBrush="Black" Width="8" Height="8">
-                              <Border.Background>
-                                <SolidColorBrush Color="{Binding}" />
-                              </Border.Background>
-                            </Border>
-                            <TextBlock Text="{Binding}" />
-                          </StackPanel>
-                        </DataTemplate>
-
                         <DataTemplate DataType="vm:ResourceSetterViewModel">
                           <Panel Opacity="{Binding IsActive, Converter={StaticResource BoolToOpacity}}" IsVisible="{Binding IsVisible}" HorizontalAlignment="Left">
                             <Panel.ContextMenu>
@@ -179,15 +201,15 @@
                               </ContextMenu>
                             </Panel.ContextMenu>
                             <StackPanel Orientation="Horizontal" Spacing="2" HorizontalAlignment="Left">
-                              <TextBlock Text="{Binding Name}" FontWeight="SemiBold" />
+                              <TextBlock Classes="property-name" PointerPressed="PropertyNamePressed" Text="{Binding Name}" />
                               <TextBlock Text=":" />
                               <ContentControl Content="{Binding Value}"/>
                               <TextBlock>(</TextBlock>
-                              <Ellipse Height="8" Width="8" VerticalAlignment="Center" Fill="{Binding Tint}"/>
+                              <Ellipse Height="8" Width="8" VerticalAlignment="Center" Fill="{Binding Tint}" ToolTip.Tip="{Binding ValueTypeTooltip}"/>
                               <TextBlock FontStyle="Italic" Text="{Binding Key}" />
                               <TextBlock>)</TextBlock>
                             </StackPanel>
-                            <Rectangle Height="1" Fill="#6C6C6C" IsVisible="{Binding !IsActive}" />
+                            <Rectangle Classes="property-inactive" IsVisible="{Binding !IsActive}" />
                           </Panel>
                         </DataTemplate>
 
@@ -200,11 +222,11 @@
                               </ContextMenu>
                             </Panel.ContextMenu>
                             <StackPanel Orientation="Horizontal" Spacing="2">
-                              <TextBlock Text="{Binding Name}" FontWeight="SemiBold" />
+                              <TextBlock Classes="property-name" PointerPressed="PropertyNamePressed" Text="{Binding Name}" />
                               <TextBlock Text=":" />
                               <ContentControl Content="{Binding Value}"/>
                             </StackPanel>
-                            <Rectangle Height="1" Fill="#6C6C6C" VerticalAlignment="Center" IsVisible="{Binding !IsActive}" />
+                            <Rectangle Classes="property-inactive" IsVisible="{Binding !IsActive}" />
                           </Panel>
                         </DataTemplate>
 

src/Avalonia.Diagnostics/Diagnostics/Views/ControlDetailsView.xaml.cs

@@ -7,9 +7,13 @@ namespace Avalonia.Diagnostics.Views
 {
     internal class ControlDetailsView : UserControl
     {
+        private DataGrid _dataGrid;
+
         public ControlDetailsView()
         {
             InitializeComponent();
+
+            _dataGrid = this.GetControl<DataGrid>("DataGrid");
         }
 
         private void InitializeComponent()
@@ -25,5 +29,25 @@ namespace Avalonia.Diagnostics.Views
             }
             
         }
+
+        private void PropertyNamePressed(object sender, PointerPressedEventArgs e)
+        {
+            var mainVm = (ControlDetailsViewModel?) DataContext;
+
+            if (mainVm is null)
+            {
+                return;
+            }
+            
+            if (sender is Control control && control.DataContext is SetterViewModel setterVm)
+            {
+                mainVm.SelectProperty(setterVm.Property);
+
+                if (mainVm.SelectedProperty is not null)
+                {
+                    _dataGrid.ScrollIntoView(mainVm.SelectedProperty, null);   
+                }
+            }
+        }
     }
 }

src/Avalonia.Diagnostics/Diagnostics/Views/LayoutExplorerView.axaml

@@ -15,6 +15,7 @@
         <SolidColorBrush x:Key="PaddingHighlightBrush" Color="#CEDA8E" />
         <SolidColorBrush x:Key="SizeBackgroundBrush" Color="#88B2BD" />
         <SolidColorBrush x:Key="SizeHighlightBrush" Color="#9ED0DC" />
+        <SolidColorBrush x:Key="ThicknessEditorForeground" Color="Black" />
     </UserControl.Resources>
 
     <Grid RowDefinitions="*,Auto">
@@ -46,6 +47,7 @@
 
                 <controls:ThicknessEditor Grid.Row="0" Grid.Column="0" Header="margin" VerticalAlignment="Top"
                                           HorizontalAlignment="Center"
+                                          Foreground="{StaticResource ThicknessEditorForeground}"
                                           Background="{StaticResource MarginBackgroundBrush}"
                                           Highlight="{StaticResource MarginHighlightBrush}"
                                           Thickness="{Binding MarginThickness}">

src/Avalonia.Diagnostics/Diagnostics/Views/MainWindow.xaml.cs

@@ -11,6 +11,7 @@ using Avalonia.Input;
 using Avalonia.Input.Raw;
 using Avalonia.Markup.Xaml;
 using Avalonia.Styling;
+using Avalonia.Themes.Default;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Diagnostics.Views
@@ -109,7 +110,7 @@ namespace Avalonia.Diagnostics.Views
         {
 #pragma warning disable CS0618 // Type or member is obsolete
             var point = (topLevel as IInputRoot)?.MouseDevice?.GetPosition(topLevel) ?? default;
-#pragma warning restore CS0618 // Type or member is obsolete                
+#pragma warning restore CS0618 // Type or member is obsolete
 
             return (IControl?)topLevel.GetVisualsAt(point, x =>
                 {
@@ -161,13 +162,18 @@ namespace Avalonia.Diagnostics.Views
                 return;
             }
 
-            var root = Root as TopLevel
-                ?? vm.PointerOverRoot as TopLevel;
+            var root = vm.PointerOverRoot as TopLevel;
+
             if (root is null)
             {
                 return;
             }
 
+            if (root is PopupRoot pr && pr.ParentTopLevel != null)
+            {
+                root = pr.ParentTopLevel;
+            }
+
             switch (e.Modifiers)
             {
                 case RawInputModifiers.Control when (e.Key == Key.LeftShift || e.Key == Key.RightShift):
@@ -242,7 +248,25 @@ namespace Avalonia.Diagnostics.Views
 
         private void RootClosed(object? sender, EventArgs e) => Close();
 
-        public void SetOptions(DevToolsOptions options) =>
+        public void SetOptions(DevToolsOptions options)
+        {
             (DataContext as MainViewModel)?.SetOptions(options);
+
+            if (options.UseDarkMode)
+            {
+                if (Styles[0] is SimpleTheme st)
+                {
+                    st.Mode = SimpleThemeMode.Dark;
+                }                
+            }
+        }
+
+        internal void SelectedControl(IControl? control)
+        {
+            if (control is { })
+            {
+                (DataContext as MainViewModel)?.SelectControl(control);
+            }
+        }
     }
 }

src/Avalonia.Dialogs/ManagedFileChooser.cs

@@ -2,6 +2,7 @@ using System;
 using System.Linq;
 using System.Threading.Tasks;
 using Avalonia.Controls;
+using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.Interactivity;
@@ -9,6 +10,8 @@ using Avalonia.LogicalTree;
 
 namespace Avalonia.Dialogs
 {
+    [TemplatePart("QuickLinks", typeof(Control))]
+    [TemplatePart("Files",      typeof(ListBox))]
     public class ManagedFileChooser : TemplatedControl
     {
         private Control _quickLinksRoot;

src/Avalonia.Headless/HeadlessPlatformStubs.cs

@@ -133,9 +133,12 @@ namespace Avalonia.Headless
 
     class HeadlessTextShaperStub : ITextShaperImpl
     {
-        public ShapedBuffer ShapeText(ReadOnlySlice<char> text, GlyphTypeface typeface, double fontRenderingEmSize,
-            CultureInfo culture, sbyte bidiLevel)
+        public ShapedBuffer ShapeText(ReadOnlySlice<char> text, TextShaperOptions options)
         {
+            var typeface = options.Typeface;
+            var fontRenderingEmSize = options.FontRenderingEmSize;
+            var bidiLevel = options.BidLevel;
+
             return new ShapedBuffer(text, text.Length, typeface, fontRenderingEmSize, bidiLevel);
         }
     }

src/Avalonia.Input/FocusManager.cs

@@ -73,7 +73,7 @@ namespace Avalonia.Input
             else if (Current != null)
             {
                 // If control is null, set focus to the topmost focus scope.
-                foreach (var scope in GetFocusScopeAncestors(Current).Reverse().ToList())
+                foreach (var scope in GetFocusScopeAncestors(Current).Reverse().ToArray())
                 {
                     if (scope != Scope &&
                         _focusScopes.TryGetValue(scope, out var element) &&

src/Avalonia.Input/TouchDevice.cs

@@ -114,7 +114,7 @@ namespace Avalonia.Input
         {
             if (_disposed)
                 return;
-            var values = _pointers.Values.ToList();
+            var values = _pointers.Values.ToArray();
             _pointers.Clear();
             _disposed = true;
             foreach (var p in values)

src/Avalonia.Styling/Controls/Metadata/PseudoClassesAttribute.cs

@@ -5,14 +5,27 @@ using System.Collections.Generic;
 
 namespace Avalonia.Controls.Metadata
 {
+    /// <summary>
+    /// Defines all pseudoclasses by name referenced and implemented by a control.
+    /// </summary>
+    /// <remarks>
+    /// This is currently used for code-completion in certain IDEs.
+    /// </remarks>
     [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
     public sealed class PseudoClassesAttribute : Attribute
     {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PseudoClassesAttribute"/> class.
+        /// </summary>
+        /// <param name="pseudoClasses">The list of pseudoclass names.</param>
         public PseudoClassesAttribute(params string[] pseudoClasses)
         {
             PseudoClasses = pseudoClasses;
         }
 
+        /// <summary>
+        /// Gets the list of pseudoclass names.
+        /// </summary>
         public IReadOnlyList<string> PseudoClasses { get; }
     }
 }

src/Avalonia.Styling/Controls/Metadata/TemplatePartAttribute.cs

@@ -0,0 +1,55 @@
+// This source file is adapted from the Windows Presentation Foundation project. 
+// (https://github.com/dotnet/wpf/) 
+// 
+// Licensed to The Avalonia Project under MIT License, courtesy of The .NET Foundation.
+
+using System;
+
+#nullable enable
+
+namespace Avalonia.Controls.Metadata
+{
+    /// <summary>
+    /// Defines a control template part referenced by name in code.
+    /// Template part names should begin with the "PART_" prefix.
+    /// </summary>
+    /// <remarks>
+    /// Style authors should be able to identify the part type used for styling the specific control.
+    /// The part is usually required in the style and should have a specific predefined name.
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
+    public sealed class TemplatePartAttribute : Attribute
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="TemplatePartAttribute"/> class.
+        /// </summary>
+        public TemplatePartAttribute()
+        {
+            Name = string.Empty;
+            Type = typeof(object);
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="TemplatePartAttribute"/> class.
+        /// </summary>
+        /// <param name="name">The part name used by the class to identify a required element in the style.</param>
+        /// <param name="type">The type of the element that should be used as a part with name.</param>
+        public TemplatePartAttribute(string name, Type type)
+        {
+            Name = name;
+            Type = type;
+        }
+
+        /// <summary>
+        /// Gets or sets the part name used by the class to identify a required element in the style.
+        /// Template part names should begin with the "PART_" prefix.
+        /// </summary>
+        public string Name { get; set; }
+
+        /// <summary>
+        /// Gets or sets the type of the element that should be used as a part with name specified
+        /// in <see cref="Name"/>.
+        /// </summary>
+        public Type Type { get; set; }
+    }
+}

src/Avalonia.Themes.Default/Controls/Button.xaml

@@ -18,7 +18,7 @@
                           Content="{TemplateBinding Content}"
                           Padding="{TemplateBinding Padding}"
                           RecognizesAccessKey="True"
-                          TextBlock.Foreground="{TemplateBinding Foreground}"
+                          TextElement.Foreground="{TemplateBinding Foreground}"
                           HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                           VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>
       </ControlTemplate>

src/Avalonia.Themes.Default/Controls/CaptionButtons.xaml

@@ -4,7 +4,7 @@
     <Setter Property="MaxHeight" Value="30" />
     <Setter Property="Template">
       <ControlTemplate>
-        <StackPanel Spacing="2" VerticalAlignment="Stretch" TextBlock.FontSize="10" Orientation="Horizontal">
+        <StackPanel Spacing="2" VerticalAlignment="Stretch" TextElement.FontSize="10" Orientation="Horizontal">
           <StackPanel.Styles>
             <Style Selector="Panel">
               <Setter Property="Width" Value="45" />

src/Avalonia.Themes.Default/Controls/CheckBox.xaml

@@ -37,7 +37,7 @@
             </Panel>
           </Border>
           <ContentPresenter Name="PART_ContentPresenter"
-                            TextBlock.Foreground="{TemplateBinding Foreground}"
+                            TextElement.Foreground="{TemplateBinding Foreground}"
                             ContentTemplate="{TemplateBinding ContentTemplate}"
                             Content="{TemplateBinding Content}"
                             Margin="{TemplateBinding Padding}"

src/Avalonia.Themes.Default/Controls/DatePicker.xaml

@@ -36,7 +36,7 @@
   </Style>
   <Style Selector="ListBoxItem.DateTimePickerItem:selected /template/ ContentPresenter">
     <Setter Property="Background" Value="Transparent" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
   </Style>
   <Style Selector="ListBoxItem.DateTimePickerItem.MonthItem">
     <Setter Property="Padding" Value="{DynamicResource DatePickerFlyoutPresenterMonthPadding}"/>
@@ -58,7 +58,7 @@
                   BorderBrush="{DynamicResource ThemeControlTransparentBrush}"
                   BorderThickness="{DynamicResource DateTimeFlyoutButtonBorderThickness}"
                   Content="{TemplateBinding Content}"
-                  TextBlock.Foreground="{DynamicResource ThemeForegroundBrush}"
+                  TextElement.Foreground="{DynamicResource ThemeForegroundBrush}"
                   ContentTemplate="{TemplateBinding ContentTemplate}"
                   Padding="{TemplateBinding Padding}"
                   HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
@@ -71,13 +71,13 @@
   <Style Selector=":is(Button).DateTimeFlyoutButtonStyle:pointerover /template/ ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource ThemeControlHighlightLowBrush}"/>
     <Setter Property="BorderBrush" Value="{DynamicResource ThemeControlTransparentBrush}"/>
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
   </Style>
 
   <Style Selector=":is(Button).DateTimeFlyoutButtonStyle:pressed /template/ ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource ThemeControlHighlightMidBrush}"/>
     <Setter Property="BorderBrush" Value="{DynamicResource ThemeControlTransparentBrush}"/>
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
   </Style>
 
 
@@ -151,7 +151,7 @@
                                   BorderThickness="{TemplateBinding BorderThickness}"
                                   CornerRadius="{TemplateBinding CornerRadius}"
                                   Content="{TemplateBinding Content}"
-                                  TextBlock.Foreground="{TemplateBinding Foreground}"
+                                  TextElement.Foreground="{TemplateBinding Foreground}"
                                   HorizontalContentAlignment="Stretch"
                                   VerticalContentAlignment="Stretch"/>
               </ControlTemplate>
@@ -196,7 +196,7 @@
     </Setter>
   </Style>
   <Style Selector="DatePicker /template/ ContentPresenter#HeaderContentPresenter">
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
   </Style>
   <Style Selector="DatePicker:disabled /template/ Rectangle">
     <!--<Setter Property="Fill" Value="{DynamicResource DatePickerSpacerFillDisabled}"/>-->
@@ -206,7 +206,7 @@
   <Style Selector="DatePicker /template/ Button#FlyoutButton:pointerover /template/ ContentPresenter">
     <Setter Property="BorderBrush" Value="{DynamicResource ThemeControlHighBrush}"/>
     <!--<Setter Property="Background" Value="{DynamicResource DatePickerButtonBackgroundPointerOver}"/>-->
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
   </Style>
 
   <Style Selector="DatePicker /template/ Button#FlyoutButton:pressed /template/ ContentPresenter">
@@ -214,13 +214,13 @@
     <Setter Property="Background">
       <SolidColorBrush Color="{DynamicResource ThemeControlMidHighColor}" Opacity="0.6" />
     </Setter>
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
   </Style>
 
   <Style Selector="DatePicker /template/ Button#FlyoutButton:disabled /template/ ContentPresenter">
     <!--<Setter Property="BorderBrush" Value="{DynamicResource DatePickerButtonBorderBrushDisabled}"/>
     <Setter Property="Background" Value="{DynamicResource DatePickerButtonBackgroundDisabled}"/>
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource DatePickerButtonForegroundDisabled}"/>-->
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource DatePickerButtonForegroundDisabled}"/>-->
     <Setter Property="Opacity" Value="{DynamicResource ThemeDisabledOpacity}" />
   </Style>
 

src/Avalonia.Themes.Default/Controls/DropDownButton.xaml

@@ -0,0 +1,67 @@
+<Styles xmlns="https://github.com/avaloniaui">
+  <Style Selector="DropDownButton">
+    <Setter Property="Background" Value="{DynamicResource ThemeControlMidBrush}"/>
+    <Setter Property="BorderBrush" Value="{DynamicResource ThemeBorderLowBrush}"/>
+    <Setter Property="BorderThickness" Value="{DynamicResource ThemeBorderThickness}"/>
+    <Setter Property="Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="HorizontalContentAlignment" Value="Center"/>
+    <Setter Property="VerticalContentAlignment" Value="Center"/>
+    <Setter Property="Padding" Value="4"/>
+    <Setter Property="Template">
+      <Setter.Value>
+        <ControlTemplate>
+          <Border Name="RootBorder"
+                  Background="{TemplateBinding Background}"
+                  BorderBrush="{TemplateBinding BorderBrush}"
+                  BorderThickness="{TemplateBinding BorderThickness}"
+                  CornerRadius="{TemplateBinding CornerRadius}"
+                  ClipToBounds="True">
+            <Grid Name="InnerGrid">
+              <Grid.ColumnDefinitions>
+                <ColumnDefinition Width="*" />
+                <ColumnDefinition Width="Auto" />
+              </Grid.ColumnDefinitions>
+
+              <ContentPresenter Name="PART_ContentPresenter"
+                                Grid.Column="0"
+                                Content="{TemplateBinding Content}"
+                                ContentTemplate="{TemplateBinding ContentTemplate}"
+                                Padding="{TemplateBinding Padding}"
+                                RecognizesAccessKey="True"
+                                HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
+                                VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" />
+
+              <PathIcon Name="DropDownGlyph"
+                        Grid.Column="1"
+                        UseLayoutRounding="False"
+                        IsHitTestVisible="False"
+                        Height="12"
+                        Width="12"
+                        Margin="0,0,10,0"
+                        HorizontalAlignment="Right"
+                        VerticalAlignment="Center" />
+
+            </Grid>
+          </Border>
+        </ControlTemplate>
+      </Setter.Value>
+    </Setter>
+  </Style>
+
+  <Style Selector="DropDownButton /template/ PathIcon#DropDownGlyph">
+    <Setter Property="Foreground" Value="{DynamicResource ThemeForegroundBrush}" />
+    <Setter Property="Data" Value="M1939 486L2029 576L1024 1581L19 576L109 486L1024 1401L1939 486Z" />
+  </Style>
+
+  <Style Selector="DropDownButton:pointerover /template/ Border#RootBorder">
+    <Setter Property="BorderBrush" Value="{DynamicResource ThemeBorderMidBrush}"/>
+  </Style>
+
+  <Style Selector="DropDownButton:pressed  /template/ Border#RootBorder">
+    <Setter Property="Background" Value="{DynamicResource ThemeControlHighBrush}"/>
+  </Style>
+
+  <Style Selector="DropDownButton:disabled">
+    <Setter Property="Opacity" Value="{DynamicResource ThemeDisabledOpacity}"/>
+  </Style>
+</Styles>

src/Avalonia.Themes.Default/Controls/RepeatButton.xaml

@@ -24,7 +24,7 @@
                                   ContentTemplate="{TemplateBinding ContentTemplate}"
                                   Content="{TemplateBinding Content}"
                                   Padding="{TemplateBinding Padding}"
-                                  TextBlock.Foreground="{TemplateBinding Foreground}"
+                                  TextElement.Foreground="{TemplateBinding Foreground}"
                                   HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                                   VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>
             </ControlTemplate>

src/Avalonia.Themes.Default/Controls/SplitButton.xaml

@@ -16,6 +16,7 @@
     <x:Double x:Key="SplitButtonPrimaryButtonSize">24</x:Double>
     <x:Double x:Key="SplitButtonSecondaryButtonSize">24</x:Double>
     <x:Double x:Key="SplitButtonSeparatorWidth">1</x:Double>
+    <x:Double x:Key="SplitButtonMinHeight">24</x:Double>
     <Thickness x:Key="SplitButtonBorderThemeThickness">1</Thickness>
 
     <converters:MarginMultiplierConverter x:Key="PrimaryButtonBorderMultiplier" Left="True" Top="True" Bottom="True" Indent="1" />
@@ -59,8 +60,11 @@
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForeground}" />
     <Setter Property="BorderBrush" Value="{DynamicResource SplitButtonBorderBrush}" />
     <Setter Property="BorderThickness" Value="{DynamicResource SplitButtonBorderThemeThickness}" />
+    <Setter Property="MinHeight" Value="{DynamicResource SplitButtonMinHeight}" />
     <Setter Property="HorizontalAlignment" Value="Left" />
     <Setter Property="VerticalAlignment" Value="Center" />
+    <Setter Property="HorizontalContentAlignment" Value="Stretch" />
+    <Setter Property="VerticalContentAlignment" Value="Center" />
     <!--<Setter Property="UseSystemFocusVisuals" Value="True" />
     <Setter Property="FocusVisualMargin" Value="-3" />-->
     <Setter Property="KeyboardNavigation.IsTabStop" Value="True" />
@@ -146,7 +150,7 @@
          SplitButton /template/ Button#PART_SecondaryButton:pointerover /template/ ContentPresenter">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundPointerOver}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushPointerOver}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundPointerOver}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundPointerOver}" />
   </Style>
   <Style Selector="SplitButton /template/ Button#PART_SecondaryButton:pointerover PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundPointerOver}" />
@@ -157,7 +161,7 @@
          SplitButton /template/ Button#PART_SecondaryButton:pressed /template/ ContentPresenter">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundPressed}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushPressed}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundPressed}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundPressed}" />
   </Style>
   <Style Selector="SplitButton /template/ Button#PART_SecondaryButton:pressed PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundPressed}" />
@@ -169,7 +173,7 @@
          SplitButton:pressed /template/ Border#SeparatorBorder">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundPressed}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushPressed}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundPressed}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundPressed}" />
   </Style>
   <Style Selector="SplitButton:pressed /template/ Button#PART_SecondaryButton PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundPressed}" />
@@ -181,7 +185,7 @@
          SplitButton:flyout-open /template/ Border#SeparatorBorder">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundPressed}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushPressed}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundPressed}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundPressed}" />
   </Style>
   <Style Selector="SplitButton:flyout-open /template/ Button#PART_SecondaryButton PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundPressed}" />
@@ -193,7 +197,7 @@
          SplitButton:disabled /template/ Border#SeparatorBorder">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundDisabled}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushDisabled}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundDisabled}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundDisabled}" />
   </Style>
   <Style Selector="SplitButton:disabled /template/ Button#PART_SecondaryButton PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundDisabled}" />
@@ -205,7 +209,7 @@
          SplitButton:checked /template/ Border#SeparatorBorder">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundChecked}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushChecked}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundChecked}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundChecked}" />
   </Style>
   <Style Selector="SplitButton:checked /template/ Button#PART_SecondaryButton PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundChecked}" />
@@ -216,7 +220,7 @@
          SplitButton:checked /template/ Button#PART_SecondaryButton:pointerover /template/ ContentPresenter">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundCheckedPointerOver}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushCheckedPointerOver}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPointerOver}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPointerOver}" />
   </Style>
   <Style Selector="SplitButton:checked /template/ Button#PART_SecondaryButton:pointerover PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPointerOver}" />
@@ -227,7 +231,7 @@
          SplitButton:checked /template/ Button#PART_SecondaryButton:pressed /template/ ContentPresenter">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundCheckedPressed}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushCheckedPressed}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPressed}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPressed}" />
   </Style>
   <Style Selector="SplitButton:checked /template/ Button#PART_SecondaryButton:pressed PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPressed}" />
@@ -239,7 +243,7 @@
          SplitButton:pressed:checked /template/ Border#SeparatorBorder">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundCheckedPressed}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushCheckedPressed}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPressed}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPressed}" />
   </Style>
   <Style Selector="SplitButton:pressed:checked /template/ Button#PART_SecondaryButton PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPressed}" />
@@ -251,7 +255,7 @@
          SplitButton:checked:flyout-open /template/ Border#SeparatorBorder">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundCheckedPressed}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushCheckedPressed}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPressed}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPressed}" />
   </Style>
   <Style Selector="SplitButton:checked:flyout-open /template/ Button#PART_SecondaryButton PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundCheckedPressed}" />
@@ -263,7 +267,7 @@
          SplitButton:checked:disabled /template/ Border#SeparatorBorder">
     <Setter Property="Border.Background" Value="{DynamicResource SplitButtonBackgroundCheckedDisabled}" />
     <Setter Property="Border.BorderBrush" Value="{DynamicResource SplitButtonBorderBrushCheckedDisabled}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedDisabled}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource SplitButtonForegroundCheckedDisabled}" />
   </Style>
   <Style Selector="SplitButton:checked:disabled /template/ Button#PART_SecondaryButton PathIcon">
     <Setter Property="Foreground" Value="{DynamicResource SplitButtonForegroundCheckedDisabled}" />

src/Avalonia.Themes.Default/Controls/TimePicker.xaml

@@ -48,7 +48,7 @@
                  ContentTemplate="{TemplateBinding HeaderTemplate}"
                  Margin="{DynamicResource TimePickerTopHeaderMargin}"
                  MaxWidth="{DynamicResource TimePickerThemeMaxWidth}"
-                 TextBlock.Foreground="{DynamicResource ThemeForegroundColor}"
+                 TextElement.Foreground="{DynamicResource ThemeForegroundColor}"
                  HorizontalAlignment="Stretch"
                  VerticalAlignment="Top" />
 
@@ -74,7 +74,7 @@
                                 BorderThickness="{TemplateBinding BorderThickness}"
                                 CornerRadius="{TemplateBinding CornerRadius}"
                                 Content="{TemplateBinding Content}"
-                                TextBlock.Foreground="{TemplateBinding Foreground}"
+                                TextElement.Foreground="{TemplateBinding Foreground}"
                                 HorizontalContentAlignment="Stretch"
                                 VerticalContentAlignment="Stretch" />
               </ControlTemplate>
@@ -135,7 +135,7 @@
   </Style>
 
   <Style Selector="TimePicker:disabled /template/ ContentPresenter#HeaderContentPresenter">
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
   </Style>
   <Style Selector="TimePicker:disabled /template/ Rectangle">
     <Setter Property="Opacity" Value="{DynamicResource ThemeDisabledOpacity}"/>
@@ -144,7 +144,7 @@
   <Style Selector="TimePicker /template/ Button#FlyoutButton:pointerover /template/ ContentPresenter">
     <!--<Setter Property="Background" Value="{DynamicResource TimePickerButtonBackgroundPointerOver}"/>-->
     <Setter Property="BorderBrush" Value="{DynamicResource ThemeControlHighBrush}"/>
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
   </Style>
 
   <Style Selector="TimePicker /template/ Button:pressed /template/ ContentPresenter">
@@ -152,13 +152,13 @@
       <SolidColorBrush Color="{DynamicResource ThemeControlMidHighColor}" Opacity="0.6" />
     </Setter>
     <Setter Property="BorderBrush" Value="{DynamicResource ThemeControlLowBrush}"/>
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ThemeForegroundBrush}"/>
   </Style>
 
   <Style Selector="TimePicker /template/ Button:disabled /template/ ContentPresenter">
     <!--<Setter Property="Background" Value="{DynamicResource TimePickerButtonBackgroundDisabled}"/>
     <Setter Property="BorderBrush" Value="{DynamicResource TimePickerButtonBorderBrushDisabled}"/>
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource TimePickerButtonForegroundDisabled}"/>-->
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource TimePickerButtonForegroundDisabled}"/>-->
     <Setter Property="Opacity" Value="{DynamicResource ThemeDisabledOpacity}" />
   </Style>
 

src/Avalonia.Themes.Default/Controls/ToggleButton.xaml

@@ -18,7 +18,7 @@
                           Content="{TemplateBinding Content}"
                           Padding="{TemplateBinding Padding}"
                           RecognizesAccessKey="True"
-                          TextBlock.Foreground="{TemplateBinding Foreground}"
+                          TextElement.Foreground="{TemplateBinding Foreground}"
                           HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                           VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>
       </ControlTemplate>

src/Avalonia.Themes.Default/DefaultTheme.xaml

@@ -3,8 +3,9 @@
         x:Class="Avalonia.Themes.Default.DefaultTheme">
   <!-- Define ToolTip first so its styles can be overriden by other controls (e.g. TextBox) -->
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/ToolTip.xaml"/>
+  <!-- PathIcon also needs to be defined early so it can be overriden by other styles (e.g. ComboBox) -->
+  <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/PathIcon.xaml" />
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/DataValidationErrors.xaml"/>
-
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/FocusAdorner.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/Button.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/Carousel.xaml"/>
@@ -13,6 +14,7 @@
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/ComboBox.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/ComboBoxItem.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/ContentControl.xaml"/>
+  <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/DropDownButton.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/Label.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/GridSplitter.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/ItemsControl.xaml"/>
@@ -22,7 +24,6 @@
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/ContextMenu.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/MenuItem.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/OverlayPopupHost.xaml"/>
-  <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/PathIcon.xaml" />
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/PopupRoot.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/ProgressBar.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Default/Controls/RadioButton.xaml"/>

src/Avalonia.Themes.Fluent/Controls/Button.xaml

@@ -4,7 +4,7 @@
       <StackPanel Spacing="20">
         <Button Content="Click Me!" />
         <Button Classes="accent" Content="Click Me!" />
-      </StackPanel>      
+      </StackPanel>
     </Border>
   </Design.PreviewWith>
   <Styles.Resources>
@@ -19,9 +19,7 @@
     <Setter Property="CornerRadius" Value="{DynamicResource ControlCornerRadius}" />
     <Setter Property="Padding" Value="{DynamicResource ButtonPadding}" />
     <Setter Property="HorizontalAlignment" Value="Left" />
-    <Setter Property="VerticalAlignment" Value="Center" />    
-    <Setter Property="FontWeight" Value="Normal" />
-    <Setter Property="FontSize" Value="{DynamicResource ControlContentThemeFontSize}" />
+    <Setter Property="VerticalAlignment" Value="Center" />
     <!--<Setter Property="UseSystemFocusVisuals" Value="{StaticResource UseSystemFocusVisuals}" />
     <Setter Property="FocusVisualMargin" Value="-3" />-->
     <Setter Property="Template">
@@ -45,40 +43,40 @@
   <Style Selector="Button:pointerover /template/ ContentPresenter#PART_ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource ButtonBackgroundPointerOver}" />
     <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushPointerOver}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ButtonForegroundPointerOver}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ButtonForegroundPointerOver}" />
   </Style>
-  
+
   <Style Selector="Button:pressed  /template/ ContentPresenter#PART_ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource ButtonBackgroundPressed}" />
     <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushPressed}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ButtonForegroundPressed}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ButtonForegroundPressed}" />
   </Style>
-  
+
   <Style Selector="Button:disabled /template/ ContentPresenter#PART_ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource ButtonBackgroundDisabled}" />
     <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushDisabled}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ButtonForegroundDisabled}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource ButtonForegroundDisabled}" />
   </Style>
 
   <Style Selector="Button.accent /template/ ContentPresenter#PART_ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource AccentButtonBackground}" />
     <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrush}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource AccentButtonForeground}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource AccentButtonForeground}" />
   </Style>
 
   <Style Selector="Button.accent:pointerover /template/ ContentPresenter#PART_ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource AccentButtonBackgroundPointerOver}" />
     <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrushPointerOver}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource AccentButtonForegroundPointerOver}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource AccentButtonForegroundPointerOver}" />
   </Style>
 
   <Style Selector="Button.accent:pressed  /template/ ContentPresenter#PART_ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource AccentButtonBackgroundPressed}" />
     <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrushPressed}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource AccentButtonForegroundPressed}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource AccentButtonForegroundPressed}" />
   </Style>
 
-  <Style Selector="Button, RepeatButton, ToggleButton">
+  <Style Selector="Button, RepeatButton, ToggleButton, DropDownButton">
     <Setter Property="RenderTransform" Value="none" />
     <Setter Property="Transitions">
       <Transitions>
@@ -87,13 +85,13 @@
     </Setter>
   </Style>
 
-  <Style Selector="Button:pressed, RepeatButton:pressed, ToggleButton:pressed">
+  <Style Selector="Button:pressed, RepeatButton:pressed, ToggleButton:pressed, DropDownButton:pressed">
     <Setter Property="RenderTransform" Value="scale(0.98)" />    
   </Style>
 
   <Style Selector="Button.accent:disabled /template/ ContentPresenter#PART_ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource AccentButtonBackgroundDisabled}" />
     <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrushDisabled}" />
-    <Setter Property="TextBlock.Foreground" Value="{DynamicResource AccentButtonForegroundDisabled}" />
+    <Setter Property="TextElement.Foreground" Value="{DynamicResource AccentButtonForegroundDisabled}" />
   </Style>
 </Styles>