Merge branch 'master' into fixes/3180

Avalonia.sln

@@ -128,6 +128,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Props", "Props", "{F3AC8BC1
 		build\Base.props = build\Base.props
 		build\Binding.props = build\Binding.props
 		build\BuildTargets.targets = build\BuildTargets.targets
+		build\HarfBuzzSharp.props = build\HarfBuzzSharp.props
 		build\JetBrains.Annotations.props = build\JetBrains.Annotations.props
 		build\JetBrains.dotMemoryUnit.props = build\JetBrains.dotMemoryUnit.props
 		build\Magick.NET-Q16-AnyCPU.props = build\Magick.NET-Q16-AnyCPU.props
@@ -201,7 +202,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Controls.DataGrid"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Dialogs", "src\Avalonia.Dialogs\Avalonia.Dialogs.csproj", "{4D55985A-1EE2-4F25-AD39-6EA8BC04F8FB}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Avalonia.FreeDesktop", "src\Avalonia.FreeDesktop\Avalonia.FreeDesktop.csproj", "{4D36CEC8-53F2-40A5-9A37-79AAE356E2DA}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.FreeDesktop", "src\Avalonia.FreeDesktop\Avalonia.FreeDesktop.csproj", "{4D36CEC8-53F2-40A5-9A37-79AAE356E2DA}"
 EndProject
 Global
 	GlobalSection(SharedMSBuildProjectFiles) = preSolution

build/HarfBuzzSharp.props

@@ -0,0 +1,6 @@
+<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup>
+    <PackageReference Include="HarfBuzzSharp" Version="2.6.1-rc.153" />
+    <PackageReference Condition="'$(IncludeLinuxSkia)' == 'true'" Include="HarfBuzzSharp.NativeAssets.Linux" Version="2.6.1-rc.153" />
+  </ItemGroup>
+</Project>

build/SkiaSharp.props

@@ -1,6 +1,6 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>
-    <PackageReference Include="SkiaSharp" Version="1.68.0" />
-    <PackageReference Condition="'$(IncludeLinuxSkia)' == 'true'" Include="Avalonia.Skia.Linux.Natives" Version="1.68.0.2" />
+    <PackageReference Include="SkiaSharp" Version="1.68.1-rc.153" />
+    <PackageReference Condition="'$(IncludeLinuxSkia)' == 'true'" Include="SkiaSharp.NativeAssets.Linux" Version="1.68.1-rc.153" />
   </ItemGroup>
 </Project>

src/Avalonia.Controls/GridSplitter.cs

@@ -1,210 +1,841 @@
-// Copyright (c) The Avalonia Project. All rights reserved.
-// Licensed under the MIT license. See licence.md file in the project root for full license information.
+// 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;
-using System.Collections.Generic;
-using System.Linq;
+using System.Diagnostics;
+using Avalonia.Collections;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
+using Avalonia.Interactivity;
 using Avalonia.Layout;
-using Avalonia.VisualTree;
+using Avalonia.Media;
+using Avalonia.Utilities;
 
 namespace Avalonia.Controls
 {
     /// <summary>
-    ///     Represents the control that redistributes space between columns or rows of a Grid control.
+    /// Represents the control that redistributes space between columns or rows of a <see cref="Grid"/> control.
     /// </summary>
-    /// <remarks>
-    ///     Unlike WPF GridSplitter, Avalonia GridSplitter has only one Behavior, GridResizeBehavior.PreviousAndNext.
-    /// </remarks>
     public class GridSplitter : Thumb
     {
-        private List<DefinitionBase> _definitions;
+        /// <summary>
+        /// Defines the <see cref="ResizeDirection"/> property.
+        /// </summary>
+        public static readonly AvaloniaProperty<GridResizeDirection> ResizeDirectionProperty =
+            AvaloniaProperty.Register<GridSplitter, GridResizeDirection>(nameof(ResizeDirection));
 
-        private Grid _grid;
+        /// <summary>
+        /// Defines the <see cref="ResizeBehavior"/> property.
+        /// </summary>
+        public static readonly AvaloniaProperty<GridResizeBehavior> ResizeBehaviorProperty =
+            AvaloniaProperty.Register<GridSplitter, GridResizeBehavior>(nameof(ResizeBehavior));
 
-        private DefinitionBase _nextDefinition;
+        /// <summary>
+        /// Defines the <see cref="ShowsPreview"/> property.
+        /// </summary>
+        public static readonly AvaloniaProperty<bool> ShowsPreviewProperty =
+            AvaloniaProperty.Register<GridSplitter, bool>(nameof(ShowsPreview));
 
-        private Orientation _orientation;
+        /// <summary>
+        /// Defines the <see cref="KeyboardIncrement"/> property.
+        /// </summary>
+        public static readonly AvaloniaProperty<double> KeyboardIncrementProperty =
+            AvaloniaProperty.Register<GridSplitter, double>(nameof(KeyboardIncrement), 10d);
 
-        private DefinitionBase _prevDefinition;
+        /// <summary>
+        /// Defines the <see cref="DragIncrement"/> property.
+        /// </summary>
+        public static readonly AvaloniaProperty<double> DragIncrementProperty =
+            AvaloniaProperty.Register<GridSplitter, double>(nameof(DragIncrement), 1d);
 
-        private void GetDeltaConstraints(out double min, out double max)
+        /// <summary>
+        /// Defines the <see cref="PreviewContent"/> property.
+        /// </summary>
+        public static readonly AvaloniaProperty<ITemplate<IControl>> PreviewContentProperty =
+            AvaloniaProperty.Register<GridSplitter, ITemplate<IControl>>(nameof(PreviewContent));
+
+        private static readonly Cursor s_columnSplitterCursor = new Cursor(StandardCursorType.SizeWestEast);
+        private static readonly Cursor s_rowSplitterCursor = new Cursor(StandardCursorType.SizeNorthSouth);
+
+        private ResizeData _resizeData;
+
+        /// <summary>
+        /// Indicates whether the Splitter resizes the Columns, Rows, or Both.
+        /// </summary>
+        public GridResizeDirection ResizeDirection
         {
-            var prevDefinitionLen = GetActualLength(_prevDefinition);
-            var prevDefinitionMin = GetMinLength(_prevDefinition);
-            var prevDefinitionMax = GetMaxLength(_prevDefinition);
+            get => GetValue(ResizeDirectionProperty);
+            set => SetValue(ResizeDirectionProperty, value);
+        }
 
-            var nextDefinitionLen = GetActualLength(_nextDefinition);
-            var nextDefinitionMin = GetMinLength(_nextDefinition);
-            var nextDefinitionMax = GetMaxLength(_nextDefinition);
-            // Determine the minimum and maximum the columns can be resized
-            min = -Math.Min(prevDefinitionLen - prevDefinitionMin, nextDefinitionMax - nextDefinitionLen);
-            max = Math.Min(prevDefinitionMax - prevDefinitionLen, nextDefinitionLen - nextDefinitionMin);
+        /// <summary>
+        /// Indicates which Columns or Rows the Splitter resizes.
+        /// </summary>
+        public GridResizeBehavior ResizeBehavior
+        {
+            get => GetValue(ResizeBehaviorProperty);
+            set => SetValue(ResizeBehaviorProperty, value);
         }
 
-        protected override void OnDragDelta(VectorEventArgs e)
+        /// <summary>
+        /// Indicates whether to Preview the column resizing without updating layout.
+        /// </summary>
+        public bool ShowsPreview
         {
-            // WPF doesn't change anything when spliter is in the last row/column
-            // but resizes the splitter row/column when it's the first one.
-            // this is different, but more internally consistent.
-            if (_prevDefinition == null || _nextDefinition == null)
-                return;
+            get => GetValue(ShowsPreviewProperty);
+            set => SetValue(ShowsPreviewProperty, value);
+        }
+
+        /// <summary>
+        /// The Distance to move the splitter when pressing the keyboard arrow keys.
+        /// </summary>
+        public double KeyboardIncrement
+        {
+            get => GetValue(KeyboardIncrementProperty);
+            set => SetValue(KeyboardIncrementProperty, value);
+        }
+
+        /// <summary>
+        /// Restricts splitter to move a multiple of the specified units.
+        /// </summary>
+        public double DragIncrement
+        {
+            get => GetValue(DragIncrementProperty);
+            set => SetValue(DragIncrementProperty, value);
+        }
+
+        /// <summary>
+        /// Gets or sets content that will be shown when <see cref="ShowsPreview"/> is enabled and user starts resize operation.
+        /// </summary>
+        public ITemplate<IControl> PreviewContent
+        {
+            get => GetValue(PreviewContentProperty);
+            set => SetValue(PreviewContentProperty, value);
+        }
+
+        /// <summary>
+        /// Converts BasedOnAlignment direction to Rows, Columns, or Both depending on its width/height.
+        /// </summary>
+        internal GridResizeDirection GetEffectiveResizeDirection()
+        {
+            GridResizeDirection direction = ResizeDirection;
+
+            if (direction != GridResizeDirection.Auto)
+            {
+                return direction;
+            }
+
+            // When HorizontalAlignment is Left, Right or Center, resize Columns.
+            if (HorizontalAlignment != HorizontalAlignment.Stretch)
+            {
+                direction = GridResizeDirection.Columns;
+            }
+            else if (VerticalAlignment != VerticalAlignment.Stretch)
+            {
+                direction = GridResizeDirection.Rows;
+            }
+            else if (Bounds.Width <= Bounds.Height) // Fall back to Width vs Height.
+            {
+                direction = GridResizeDirection.Columns;
+            }
+            else
+            {
+                direction = GridResizeDirection.Rows;
+            }
 
-            var delta = _orientation == Orientation.Vertical ? e.Vector.X : e.Vector.Y;
-            double max;
-            double min;
-            GetDeltaConstraints(out min, out max);
-            delta = Math.Min(Math.Max(delta, min), max);
+            return direction;
+        }
 
-            var prevIsStar = IsStar(_prevDefinition);
-            var nextIsStar = IsStar(_nextDefinition);
+        /// <summary>
+        /// Convert BasedOnAlignment to Next/Prev/Both depending on alignment and Direction.
+        /// </summary>
+        private GridResizeBehavior GetEffectiveResizeBehavior(GridResizeDirection direction)
+        {
+            GridResizeBehavior resizeBehavior = ResizeBehavior;
 
-            if (prevIsStar && nextIsStar)
+            if (resizeBehavior == GridResizeBehavior.BasedOnAlignment)
             {
-                foreach (var definition in _definitions)
+                if (direction == GridResizeDirection.Columns)
                 {
-                    if (definition == _prevDefinition)
+                    switch (HorizontalAlignment)
                     {
-                        SetLengthInStars(_prevDefinition, GetActualLength(_prevDefinition) + delta);
+                        case HorizontalAlignment.Left:
+                            resizeBehavior = GridResizeBehavior.PreviousAndCurrent;
+                            break;
+                        case HorizontalAlignment.Right:
+                            resizeBehavior = GridResizeBehavior.CurrentAndNext;
+                            break;
+                        default:
+                            resizeBehavior = GridResizeBehavior.PreviousAndNext;
+                            break;
                     }
-                    else if (definition == _nextDefinition)
+                }
+                else
+                {
+                    switch (VerticalAlignment)
                     {
-                        SetLengthInStars(_nextDefinition, GetActualLength(_nextDefinition) - delta);
+                        case VerticalAlignment.Top:
+                            resizeBehavior = GridResizeBehavior.PreviousAndCurrent;
+                            break;
+                        case VerticalAlignment.Bottom:
+                            resizeBehavior = GridResizeBehavior.CurrentAndNext;
+                            break;
+                        default:
+                            resizeBehavior = GridResizeBehavior.PreviousAndNext;
+                            break;
                     }
-                    else if (IsStar(definition))
+                }
+            }
+
+            return resizeBehavior;
+        }
+
+        /// <summary>
+        /// Removes preview adorner from the grid.
+        /// </summary>
+        private void RemovePreviewAdorner()
+        {
+            if (_resizeData.Adorner != null)
+            {
+                AdornerLayer layer = AdornerLayer.GetAdornerLayer(this);
+                layer.Children.Remove(_resizeData.Adorner);
+            }
+        }
+
+        /// <summary>
+        /// Initialize the data needed for resizing.
+        /// </summary>
+        private void InitializeData(bool showsPreview)
+        {
+            // If not in a grid or can't resize, do nothing.
+            if (Parent is Grid grid)
+            {
+                GridResizeDirection resizeDirection = GetEffectiveResizeDirection();
+
+                // Setup data used for resizing.
+                _resizeData = new ResizeData
+                {
+                    Grid = grid,
+                    ShowsPreview = showsPreview,
+                    ResizeDirection = resizeDirection,
+                    SplitterLength = Math.Min(Bounds.Width, Bounds.Height),
+                    ResizeBehavior = GetEffectiveResizeBehavior(resizeDirection)
+                };
+
+                // Store the rows and columns to resize on drag events.
+                if (!SetupDefinitionsToResize())
+                {
+                    // Unable to resize, clear data.
+                    _resizeData = null;
+                    return;
+                }
+
+                // Setup the preview in the adorner if ShowsPreview is true.
+                SetupPreviewAdorner();
+            }
+        }
+
+        /// <summary>
+        /// Returns true if GridSplitter can resize rows/columns.
+        /// </summary>
+        private bool SetupDefinitionsToResize()
+        {
+            int gridSpan = GetValue(_resizeData.ResizeDirection == GridResizeDirection.Columns ?
+                Grid.ColumnSpanProperty :
+                Grid.RowSpanProperty);
+
+            if (gridSpan == 1)
+            {
+                var splitterIndex = GetValue(_resizeData.ResizeDirection == GridResizeDirection.Columns ?
+                    Grid.ColumnProperty :
+                    Grid.RowProperty);
+
+                // Select the columns based on behavior.
+                int index1, index2;
+
+                switch (_resizeData.ResizeBehavior)
+                {
+                    case GridResizeBehavior.PreviousAndCurrent:
+                        // Get current and previous.
+                        index1 = splitterIndex - 1;
+                        index2 = splitterIndex;
+                        break;
+                    case GridResizeBehavior.CurrentAndNext:
+                        // Get current and next.
+                        index1 = splitterIndex;
+                        index2 = splitterIndex + 1;
+                        break;
+                    default: // GridResizeBehavior.PreviousAndNext.
+                        // Get previous and next.
+                        index1 = splitterIndex - 1;
+                        index2 = splitterIndex + 1;
+                        break;
+                }
+
+                // Get count of rows/columns in the resize direction.
+                int count = _resizeData.ResizeDirection == GridResizeDirection.Columns ?
+                    _resizeData.Grid.ColumnDefinitions.Count :
+                    _resizeData.Grid.RowDefinitions.Count;
+
+                if (index1 >= 0 && index2 < count)
+                {
+                    _resizeData.SplitterIndex = splitterIndex;
+
+                    _resizeData.Definition1Index = index1;
+                    _resizeData.Definition1 = GetGridDefinition(_resizeData.Grid, index1, _resizeData.ResizeDirection);
+                    _resizeData.OriginalDefinition1Length =
+                        _resizeData.Definition1.UserSizeValueCache; // Save Size if user cancels.
+                    _resizeData.OriginalDefinition1ActualLength = GetActualLength(_resizeData.Definition1);
+
+                    _resizeData.Definition2Index = index2;
+                    _resizeData.Definition2 = GetGridDefinition(_resizeData.Grid, index2, _resizeData.ResizeDirection);
+                    _resizeData.OriginalDefinition2Length =
+                        _resizeData.Definition2.UserSizeValueCache; // Save Size if user cancels.
+                    _resizeData.OriginalDefinition2ActualLength = GetActualLength(_resizeData.Definition2);
+
+                    // Determine how to resize the columns.
+                    bool isStar1 = IsStar(_resizeData.Definition1);
+                    bool isStar2 = IsStar(_resizeData.Definition2);
+
+                    if (isStar1 && isStar2)
                     {
-                        SetLengthInStars(definition, GetActualLength(definition)); // same size but in stars.
+                        // If they are both stars, resize both.
+                        _resizeData.SplitBehavior = SplitBehavior.Split;
                     }
+                    else
+                    {
+                        // One column is fixed width, resize the first one that is fixed.
+                        _resizeData.SplitBehavior = !isStar1 ? SplitBehavior.Resize1 : SplitBehavior.Resize2;
+                    }
+
+                    return true;
                 }
             }
-            else if (prevIsStar)
+
+            return false;
+        }
+
+        /// <summary>
+        /// Create the preview adorner and add it to the adorner layer.
+        /// </summary>
+        private void SetupPreviewAdorner()
+        {
+            if (_resizeData.ShowsPreview)
             {
-                SetLength(_nextDefinition, GetActualLength(_nextDefinition) - delta);
+                // Get the adorner layer and add an adorner to it.
+                var adornerLayer = AdornerLayer.GetAdornerLayer(_resizeData.Grid);
+
+                var previewContent = PreviewContent;
+
+                // Can't display preview.
+                if (adornerLayer == null)
+                {
+                    return;
+                }
+
+                IControl builtPreviewContent = previewContent?.Build();
+
+                _resizeData.Adorner = new PreviewAdorner(builtPreviewContent);
+
+                AdornerLayer.SetAdornedElement(_resizeData.Adorner, this);
+
+                adornerLayer.Children.Add(_resizeData.Adorner);
+
+                // Get constraints on preview's translation.
+                GetDeltaConstraints(out _resizeData.MinChange, out _resizeData.MaxChange);
             }
-            else if (nextIsStar)
+        }
+
+        protected override void OnPointerEnter(PointerEventArgs e)
+        {
+            base.OnPointerEnter(e);
+
+            GridResizeDirection direction = GetEffectiveResizeDirection();
+
+            switch (direction)
             {
-                SetLength(_prevDefinition, GetActualLength(_prevDefinition) + delta);
+                case GridResizeDirection.Columns:
+                    Cursor = s_columnSplitterCursor;
+                    break;
+                case GridResizeDirection.Rows:
+                    Cursor = s_rowSplitterCursor;
+                    break;
             }
-            else
+        }
+
+        protected override void OnLostFocus(RoutedEventArgs e)
+        {
+            base.OnLostFocus(e);
+
+            if (_resizeData != null)
             {
-                SetLength(_prevDefinition, GetActualLength(_prevDefinition) + delta);
-                SetLength(_nextDefinition, GetActualLength(_nextDefinition) - delta);
+                CancelResize();
             }
         }
 
-        private double GetActualLength(DefinitionBase definition)
+        protected override void OnDragStarted(VectorEventArgs e)
         {
-            if (definition == null)
-                return 0;
-            var columnDefinition = definition as ColumnDefinition;
-            return columnDefinition?.ActualWidth ?? ((RowDefinition)definition).ActualHeight;
+            base.OnDragStarted(e);
+
+            // TODO: Looks like that sometimes thumb will raise multiple drag started events.
+            // Debug.Assert(_resizeData == null, "_resizeData is not null, DragCompleted was not called");
+
+            if (_resizeData != null)
+            {
+                return;
+            }
+
+            InitializeData(ShowsPreview);
         }
 
-        private double GetMinLength(DefinitionBase definition)
+        protected override void OnDragDelta(VectorEventArgs e)
         {
-            if (definition == null)
-                return 0;
-            var columnDefinition = definition as ColumnDefinition;
-            return columnDefinition?.MinWidth ?? ((RowDefinition)definition).MinHeight;
+            base.OnDragDelta(e);
+
+            if (_resizeData != null)
+            {
+                double horizontalChange = e.Vector.X;
+                double verticalChange = e.Vector.Y;
+
+                // Round change to nearest multiple of DragIncrement.
+                double dragIncrement = DragIncrement;
+                horizontalChange = Math.Round(horizontalChange / dragIncrement) * dragIncrement;
+                verticalChange = Math.Round(verticalChange / dragIncrement) * dragIncrement;
+
+                if (_resizeData.ShowsPreview)
+                {
+                    // Set the Translation of the Adorner to the distance from the thumb.
+                    if (_resizeData.ResizeDirection == GridResizeDirection.Columns)
+                    {
+                        _resizeData.Adorner.OffsetX = Math.Min(
+                            Math.Max(horizontalChange, _resizeData.MinChange),
+                            _resizeData.MaxChange);
+                    }
+                    else
+                    {
+                        _resizeData.Adorner.OffsetY = Math.Min(
+                            Math.Max(verticalChange, _resizeData.MinChange),
+                            _resizeData.MaxChange);
+                    }
+                }
+                else
+                {
+                    // Directly update the grid.
+                    MoveSplitter(horizontalChange, verticalChange);
+                }
+            }
         }
 
-        private double GetMaxLength(DefinitionBase definition)
+        protected override void OnDragCompleted(VectorEventArgs e)
         {
-            if (definition == null)
-                return 0;
-            var columnDefinition = definition as ColumnDefinition;
-            return columnDefinition?.MaxWidth ?? ((RowDefinition)definition).MaxHeight;
+            base.OnDragCompleted(e);
+
+            if (_resizeData != null)
+            {
+                if (_resizeData.ShowsPreview)
+                {
+                    // Update the grid.
+                    MoveSplitter(_resizeData.Adorner.OffsetX, _resizeData.Adorner.OffsetY);
+                    RemovePreviewAdorner();
+                }
+
+                _resizeData = null;
+            }
         }
 
-        private bool IsStar(DefinitionBase definition)
+        protected override void OnKeyDown(KeyEventArgs e)
         {
-            var columnDefinition = definition as ColumnDefinition;
-            return columnDefinition?.Width.IsStar ?? ((RowDefinition)definition).Height.IsStar;
+            Key key = e.Key;
+
+            switch (key)
+            {
+                case Key.Escape:
+                    if (_resizeData != null)
+                    {
+                        CancelResize();
+                        e.Handled = true;
+                    }
+
+                    break;
+
+                case Key.Left:
+                    e.Handled = KeyboardMoveSplitter(-KeyboardIncrement, 0);
+                    break;
+                case Key.Right:
+                    e.Handled = KeyboardMoveSplitter(KeyboardIncrement, 0);
+                    break;
+                case Key.Up:
+                    e.Handled = KeyboardMoveSplitter(0, -KeyboardIncrement);
+                    break;
+                case Key.Down:
+                    e.Handled = KeyboardMoveSplitter(0, KeyboardIncrement);
+                    break;
+            }
         }
 
-        private void SetLengthInStars(DefinitionBase definition, double value)
+        /// <summary>
+        /// Cancels the resize operation.
+        /// </summary>
+        private void CancelResize()
         {
-            var columnDefinition = definition as ColumnDefinition;
-            if (columnDefinition != null)
+            // Restore original column/row lengths.
+            if (_resizeData.ShowsPreview)
             {
-                columnDefinition.Width = new GridLength(value, GridUnitType.Star);
+                RemovePreviewAdorner();
             }
-            else
+            else // Reset the columns/rows lengths to the saved values.
             {
-                ((RowDefinition)definition).Height = new GridLength(value, GridUnitType.Star);
+                SetDefinitionLength(_resizeData.Definition1, _resizeData.OriginalDefinition1Length);
+                SetDefinitionLength(_resizeData.Definition2, _resizeData.OriginalDefinition2Length);
             }
+
+            _resizeData = null;
+        }
+
+        /// <summary>
+        /// Returns true if the row/column has a star length.
+        /// </summary>
+        private static bool IsStar(DefinitionBase definition)
+        {
+            return definition.UserSizeValueCache.IsStar;
         }
 
-        private void SetLength(DefinitionBase definition, double value)
+        /// <summary>
+        /// Gets Column or Row definition at index from grid based on resize direction.
+        /// </summary>
+        private static DefinitionBase GetGridDefinition(Grid grid, int index, GridResizeDirection direction)
         {
-            var columnDefinition = definition as ColumnDefinition;
-            if (columnDefinition != null)
+            return direction == GridResizeDirection.Columns ?
+                (DefinitionBase)grid.ColumnDefinitions[index] :
+                (DefinitionBase)grid.RowDefinitions[index];
+        }
+
+        /// <summary>
+        /// Retrieves the ActualWidth or ActualHeight of the definition depending on its type Column or Row.
+        /// </summary>
+        private double GetActualLength(DefinitionBase definition)
+        {
+            var column = definition as ColumnDefinition;
+
+            return column?.ActualWidth ?? ((RowDefinition)definition).ActualHeight;
+        }
+
+        /// <summary>
+        /// Gets Column or Row definition at index from grid based on resize direction.
+        /// </summary>
+        private static void SetDefinitionLength(DefinitionBase definition, GridLength length)
+        {
+            definition.SetValue(
+                definition is ColumnDefinition ? ColumnDefinition.WidthProperty : RowDefinition.HeightProperty, length);
+        }
+
+        /// <summary>
+        /// Get the minimum and maximum Delta can be given definition constraints (MinWidth/MaxWidth).
+        /// </summary>
+        private void GetDeltaConstraints(out double minDelta, out double maxDelta)
+        {
+            double definition1Len = GetActualLength(_resizeData.Definition1);
+            double definition1Min = _resizeData.Definition1.UserMinSizeValueCache;
+            double definition1Max = _resizeData.Definition1.UserMaxSizeValueCache;
+
+            double definition2Len = GetActualLength(_resizeData.Definition2);
+            double definition2Min = _resizeData.Definition2.UserMinSizeValueCache;
+            double definition2Max = _resizeData.Definition2.UserMaxSizeValueCache;
+
+            // Set MinWidths to be greater than width of splitter.
+            if (_resizeData.SplitterIndex == _resizeData.Definition1Index)
             {
-                columnDefinition.Width = new GridLength(value);
+                definition1Min = Math.Max(definition1Min, _resizeData.SplitterLength);
             }
-            else
+            else if (_resizeData.SplitterIndex == _resizeData.Definition2Index)
             {
-                ((RowDefinition)definition).Height = new GridLength(value);
+                definition2Min = Math.Max(definition2Min, _resizeData.SplitterLength);
             }
+
+            // Determine the minimum and maximum the columns can be resized.
+            minDelta = -Math.Min(definition1Len - definition1Min, definition2Max - definition2Len);
+            maxDelta = Math.Min(definition1Max - definition1Len, definition2Len - definition2Min);
         }
 
-        protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
+        /// <summary>
+        /// Sets the length of definition1 and definition2.
+        /// </summary>
+        private void SetLengths(double definition1Pixels, double definition2Pixels)
         {
-            base.OnAttachedToVisualTree(e);
-            _grid = this.GetVisualParent<Grid>();
+            // For the case where both definition1 and 2 are stars, update all star values to match their current pixel values.
+            if (_resizeData.SplitBehavior == SplitBehavior.Split)
+            {
+                var definitions = _resizeData.ResizeDirection == GridResizeDirection.Columns ?
+                    (IAvaloniaReadOnlyList<DefinitionBase>)_resizeData.Grid.ColumnDefinitions :
+                    (IAvaloniaReadOnlyList<DefinitionBase>)_resizeData.Grid.RowDefinitions;
 
-            _orientation = DetectOrientation();
+                var definitionsCount = definitions.Count;
+
+                for (var i = 0; i < definitionsCount; i++)
+                {
+                    DefinitionBase definition = definitions[i];
 
-            int definitionIndex; //row or col
-            if (_orientation == Orientation.Vertical)
+                    // For each definition, if it is a star, set is value to ActualLength in stars
+                    // This makes 1 star == 1 pixel in length
+                    if (i == _resizeData.Definition1Index)
+                    {
+                        SetDefinitionLength(definition, new GridLength(definition1Pixels, GridUnitType.Star));
+                    }
+                    else if (i == _resizeData.Definition2Index)
+                    {
+                        SetDefinitionLength(definition, new GridLength(definition2Pixels, GridUnitType.Star));
+                    }
+                    else if (IsStar(definition))
+                    {
+                        SetDefinitionLength(definition, new GridLength(GetActualLength(definition), GridUnitType.Star));
+                    }
+                }
+            }
+            else if (_resizeData.SplitBehavior == SplitBehavior.Resize1)
             {
-                Cursor = new Cursor(StandardCursorType.SizeWestEast);
-                _definitions = _grid.ColumnDefinitions.Cast<DefinitionBase>().ToList();
-                definitionIndex = GetValue(Grid.ColumnProperty);
-                PseudoClasses.Add(":vertical");
+                SetDefinitionLength(_resizeData.Definition1, new GridLength(definition1Pixels));
             }
             else
             {
-                Cursor = new Cursor(StandardCursorType.SizeNorthSouth);
-                definitionIndex = GetValue(Grid.RowProperty);
-                _definitions = _grid.RowDefinitions.Cast<DefinitionBase>().ToList();
-                PseudoClasses.Add(":horizontal");
+                SetDefinitionLength(_resizeData.Definition2, new GridLength(definition2Pixels));
+            }
+        }
+
+        /// <summary>
+        /// Move the splitter by the given Delta's in the horizontal and vertical directions.
+        /// </summary>
+        private void MoveSplitter(double horizontalChange, double verticalChange)
+        {
+            Debug.Assert(_resizeData != null, "_resizeData should not be null when calling MoveSplitter");
+
+            // Calculate the offset to adjust the splitter.
+            var delta = _resizeData.ResizeDirection == GridResizeDirection.Columns ? horizontalChange : verticalChange;
+
+            DefinitionBase definition1 = _resizeData.Definition1;
+            DefinitionBase definition2 = _resizeData.Definition2;
+
+            if (definition1 != null && definition2 != null)
+            {
+                double actualLength1 = GetActualLength(definition1);
+                double actualLength2 = GetActualLength(definition2);
+
+                // When splitting, Check to see if the total pixels spanned by the definitions 
+                // is the same asbefore starting resize. If not cancel the drag
+                if (_resizeData.SplitBehavior == SplitBehavior.Split &&
+                    !MathUtilities.AreClose(
+                        actualLength1 + actualLength2,
+                        _resizeData.OriginalDefinition1ActualLength + _resizeData.OriginalDefinition2ActualLength))
+                {
+                    CancelResize();
+
+                    return;
+                }
+
+                GetDeltaConstraints(out var min, out var max);
+
+                // Constrain Delta to Min/MaxWidth of columns
+                delta = Math.Min(Math.Max(delta, min), max);
+
+                double definition1LengthNew = actualLength1 + delta;
+                double definition2LengthNew = actualLength1 + actualLength2 - definition1LengthNew;
+
+                SetLengths(definition1LengthNew, definition2LengthNew);
             }
+        }
 
-            if (definitionIndex > 0)
-                _prevDefinition = _definitions[definitionIndex - 1];
+        /// <summary>
+        /// Move the splitter using the Keyboard (Don't show preview).
+        /// </summary>
+        private bool KeyboardMoveSplitter(double horizontalChange, double verticalChange)
+        {
+            // If moving with the mouse, ignore keyboard motion.
+            if (_resizeData != null)
+            {
+                return false; // Don't handle the event.
+            }
+
+            // Don't show preview.
+            InitializeData(false); 
+                
+            // Check that we are actually able to resize.
+            if (_resizeData == null)
+            {
+                return false; // Don't handle the event.
+            }
 
-            if (definitionIndex < _definitions.Count - 1)
-                _nextDefinition = _definitions[definitionIndex + 1];
+            MoveSplitter(horizontalChange, verticalChange);
+
+            _resizeData = null;
+
+            return true;
         }
 
-        private Orientation DetectOrientation()
+        /// <summary>
+        /// This adorner draws the preview for the <see cref="GridSplitter"/>.
+        /// It also positions the adorner.
+        /// </summary>
+        private sealed class PreviewAdorner : Decorator
         {
-            if (!_grid.ColumnDefinitions.Any())
-                return Orientation.Horizontal;
-            if (!_grid.RowDefinitions.Any())
-                return Orientation.Vertical;
+            private readonly TranslateTransform _translation;
+            private readonly Decorator _decorator;
+            
+            public PreviewAdorner(IControl previewControl)
+            {
+                // Add a decorator to perform translations.
+                _translation = new TranslateTransform();
+
+                _decorator = new Decorator
+                {
+                    Child = previewControl, 
+                    RenderTransform = _translation
+                };
+
+                Child = _decorator;
+            }
 
-            var col = GetValue(Grid.ColumnProperty);
-            var row = GetValue(Grid.RowProperty);
-            var width = _grid.ColumnDefinitions[col].Width;
-            var height = _grid.RowDefinitions[row].Height;
-            if (width.IsAuto && !height.IsAuto)
+            /// <summary>
+            /// The Preview's Offset in the X direction from the GridSplitter.
+            /// </summary>
+            public double OffsetX
             {
-                return Orientation.Vertical;
+                get => _translation.X;
+                set => _translation.X = value;
             }
-            if (!width.IsAuto && height.IsAuto)
+
+            /// <summary>
+            /// The Preview's Offset in the Y direction from the GridSplitter.
+            /// </summary>
+            public double OffsetY
             {
-                return Orientation.Horizontal;
+                get => _translation.Y;
+                set => _translation.Y = value;
             }
-            if (_grid.Children.OfType<Control>() // Decision based on other controls in the same column
-                .Where(c => Grid.GetColumn(c) == col)
-                .Any(c => c.GetType() != typeof(GridSplitter)))
+
+            protected override Size ArrangeOverride(Size finalSize)
             {
-                return Orientation.Horizontal;
+                // Adorners always get clipped to the owner control. In this case we want
+                // to constrain size to the splitter size but draw on top of the parent grid.
+                Clip = null;
+
+                return base.ArrangeOverride(finalSize);
             }
-            return Orientation.Vertical;
         }
+
+        /// <summary>
+        /// <see cref="GridSplitter"/> has special Behavior when columns are fixed.
+        /// If the left column is fixed, splitter will only resize that column.
+        /// Else if the right column is fixed, splitter will only resize the right column.
+        /// </summary>
+        private enum SplitBehavior
+        {
+            /// <summary>
+            /// Both columns/rows are star lengths.
+            /// </summary>
+            Split,
+
+            /// <summary>
+            /// Resize 1 only.
+            /// </summary>
+            Resize1,
+
+            /// <summary>
+            /// Resize 2 only.
+            /// </summary>
+            Resize2
+        }
+
+        /// <summary>
+        /// Stores data during the resizing operation.
+        /// </summary>
+        private class ResizeData
+        {
+            public bool ShowsPreview;
+            public PreviewAdorner Adorner;
+
+            // The constraints to keep the Preview within valid ranges.
+            public double MinChange;
+            public double MaxChange;
+
+            // The grid to Resize.
+            public Grid Grid;
+
+            // Cache of Resize Direction and Behavior.
+            public GridResizeDirection ResizeDirection;
+            public GridResizeBehavior ResizeBehavior;
+
+            // The columns/rows to resize.
+            public DefinitionBase Definition1;
+            public DefinitionBase Definition2;
+
+            // Are the columns/rows star lengths.
+            public SplitBehavior SplitBehavior;
+
+            // The index of the splitter.
+            public int SplitterIndex;
+
+            // The indices of the columns/rows.
+            public int Definition1Index;
+            public int Definition2Index;
+
+            // The original lengths of Definition1 and Definition2 (to restore lengths if user cancels resize).
+            public GridLength OriginalDefinition1Length;
+            public GridLength OriginalDefinition2Length;
+            public double OriginalDefinition1ActualLength;
+            public double OriginalDefinition2ActualLength;
+
+            // The minimum of Width/Height of Splitter.  Used to ensure splitter 
+            // isn't hidden by resizing a row/column smaller than the splitter.
+            public double SplitterLength;
+        }
+    }
+
+    /// <summary>
+    /// Enum to indicate whether <see cref="GridSplitter"/> resizes Columns or Rows.
+    /// </summary>
+    public enum GridResizeDirection
+    {
+        /// <summary>
+        /// Determines whether to resize rows or columns based on its Alignment and 
+        /// width compared to height.
+        /// </summary>
+        Auto,
+
+        /// <summary>
+        /// Resize columns when dragging Splitter.
+        /// </summary>
+        Columns,
+
+        /// <summary>
+        /// Resize rows when dragging Splitter.
+        /// </summary>
+        Rows
+    }
+
+    /// <summary>
+    /// Enum to indicate what Columns or Rows the <see cref="GridSplitter"/> resizes.
+    /// </summary>
+    public enum GridResizeBehavior
+    {
+        /// <summary>
+        /// Determine which columns or rows to resize based on its Alignment.
+        /// </summary>
+        BasedOnAlignment,
+
+        /// <summary>
+        /// Resize the current and next Columns or Rows.
+        /// </summary>
+        CurrentAndNext,
+
+        /// <summary>
+        /// Resize the previous and current Columns or Rows.
+        /// </summary>
+        PreviousAndCurrent,
+
+        /// <summary>
+        /// Resize the previous and next Columns or Rows.
+        /// </summary>
+        PreviousAndNext
     }
 }

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -297,7 +297,8 @@ namespace Avalonia.Controls.Presenters
                 return new FormattedText
                 {
                     Text = "X",
-                    Typeface = new Typeface(FontFamily, FontSize, FontStyle, FontWeight),
+                    Typeface = new Typeface(FontFamily, FontWeight, FontStyle),
+                    FontSize = FontSize,
                     TextAlignment = TextAlignment,
                     Constraint = availableSize,
                 }.Bounds.Size;

src/Avalonia.Controls/TextBlock.cs

@@ -352,10 +352,11 @@ namespace Avalonia.Controls
             return new FormattedText
             {
                 Constraint = constraint,
-                Typeface = new Typeface(FontFamily, FontSize, FontStyle, FontWeight),
+                Typeface = new Typeface(FontFamily, FontWeight, FontStyle),
+                FontSize = FontSize,
                 Text = text ?? string.Empty,
                 TextAlignment = TextAlignment,
-                Wrapping = TextWrapping,
+                TextWrapping = TextWrapping,
             };
         }
 

src/Avalonia.Diagnostics/Views/TreePageView.xaml

@@ -2,7 +2,7 @@
              xmlns:vm="clr-namespace:Avalonia.Diagnostics.ViewModels"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              x:Class="Avalonia.Diagnostics.Views.TreePageView">
-  <Grid ColumnDefinitions="*,4,3*">
+  <Grid ColumnDefinitions="*,Auto,3*">
     <TreeView Name="tree" Items="{Binding Nodes}" SelectedItem="{Binding SelectedNode, Mode=TwoWay}">
       <TreeView.DataTemplates>
         <TreeDataTemplate DataType="vm:TreeNode"
@@ -20,7 +20,7 @@
       </TreeView.Styles>
     </TreeView>
 
-    <GridSplitter Width="4" Grid.Column="1" />
+    <GridSplitter Grid.Column="1" />
     <ContentControl Content="{Binding Details}" Grid.Column="2" />
   </Grid>
 </UserControl>

src/Avalonia.Themes.Default/GridSplitter.xaml

@@ -1,51 +1,23 @@
 <Styles xmlns="https://github.com/avaloniaui">
-  <Style Selector="GridSplitter:vertical">
-    <Setter Property="Width" Value="6"/>
-    <Setter Property="Background" Value="{DynamicResource ThemeControlLowBrush}"/>
-    <Setter Property="Template">
-      <ControlTemplate>
-        <Border Background="{TemplateBinding Background}">
-          <StackPanel Orientation="Vertical" HorizontalAlignment="Center" VerticalAlignment="Center">
-            <StackPanel.Styles>
-              <Style Selector="Ellipse">
-                <Setter Property="HorizontalAlignment" Value="Center"/>
-                <Setter Property="Width" Value="4"/>
-                <Setter Property="Height" Value="4"/>
-                <Setter Property="Fill" Value="{DynamicResource ThemeControlMidBrush}"/>
-                <Setter Property="Margin" Value="1"/>
-              </Style>
-            </StackPanel.Styles>
-            <Ellipse/>
-            <Ellipse/>
-            <Ellipse/>
-          </StackPanel>
-        </Border>
-      </ControlTemplate>
+
+  <Style Selector="GridSplitter">
+    <Setter Property="Focusable" Value="True" />
+    <Setter Property="MinWidth" Value="6" />
+    <Setter Property="MinHeight" Value="6" />
+    <Setter Property="Background" Value="{DynamicResource ThemeControlMidBrush}" />
+    <Setter Property="PreviewContent">
+      <Template>
+        <Rectangle Fill="{DynamicResource HighlightBrush}" />
+      </Template>
     </Setter>
-  </Style>
-  <Style Selector="GridSplitter:horizontal">
-    <Setter Property="Height" Value="6"/>
-    <Setter Property="Background" Value="{DynamicResource ThemeControlLowBrush}"/>
     <Setter Property="Template">
       <ControlTemplate>
-        <Border Background="{TemplateBinding Background}">
-          <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">
-            <StackPanel.Styles>
-              <Style Selector="Ellipse">
-                <Setter Property="VerticalAlignment" Value="Center"/>
-                <Setter Property="Width" Value="4"/>
-                <Setter Property="Height" Value="4"/>
-                <Setter Property="Fill" Value="{DynamicResource ThemeControlMidBrush}"/>
-                <Setter Property="Margin" Value="1"/>
-              </Style>
-            </StackPanel.Styles>
-            <Ellipse/>
-            <Ellipse/>
-            <Ellipse/>
-          </StackPanel>
-        </Border>
+        <Border 
+          BorderBrush="{TemplateBinding BorderBrush}"
+          BorderThickness="{TemplateBinding BorderThickness}"
+          Background="{TemplateBinding Background}"/>
       </ControlTemplate>
     </Setter>
   </Style>
-</Styles>
 
+</Styles>

src/Avalonia.Visuals/Media/FontFamily.cs

@@ -5,12 +5,16 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using Avalonia.Media.Fonts;
-using Avalonia.Platform;
 
 namespace Avalonia.Media
 {
-    public class FontFamily
+    public sealed class FontFamily
     {
+        static FontFamily()
+        {
+            Default = new FontFamily(FontManager.Default.DefaultFontFamilyName);
+        }
+
         /// <inheritdoc />
         /// <summary>
         /// Initializes a new instance of the <see cref="T:Avalonia.Media.FontFamily" /> class.
@@ -30,9 +34,7 @@ namespace Avalonia.Media
         {
             if (string.IsNullOrEmpty(name))
             {
-                FamilyNames = new FamilyNameCollection(string.Empty);
-
-                return;
+                throw new ArgumentNullException(nameof(name));
             }
 
             var fontFamilySegment = GetFontFamilyIdentifier(name);
@@ -53,13 +55,16 @@ namespace Avalonia.Media
         /// <summary>
         /// Represents the default font family
         /// </summary>
-        public static FontFamily Default => new FontFamily(string.Empty);
+        public static FontFamily Default { get; }
 
         /// <summary>
         /// Represents all font families in the system. This can be an expensive call depending on platform implementation.
         /// </summary>
+        /// <remarks>
+        /// Consider using the new <see cref="FontManager"/> instead.
+        /// </remarks>
         public static IEnumerable<FontFamily> SystemFontFamilies =>
-            AvaloniaLocator.Current.GetService<IPlatformRenderInterface>().InstalledFontNames.Select(name => new FontFamily(name));
+            FontManager.Default.GetInstalledFontFamilyNames().Select(name => new FontFamily(name));
 
         /// <summary>
         /// Gets the primary family name of the font family.
@@ -181,7 +186,14 @@ namespace Avalonia.Media
             {
                 var hash = (int)2186146271;
 
-                hash = (hash * 15768619) ^ FamilyNames.GetHashCode();
+                if (Key != null)
+                {
+                    hash = (hash * 15768619) ^ Key.GetHashCode();
+                }
+                else
+                {
+                    hash = (hash * 15768619) ^ FamilyNames.GetHashCode();
+                }
 
                 if (Key != null)
                 {

src/Avalonia.Visuals/Media/FontManager.cs

@@ -0,0 +1,112 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Globalization;
+using Avalonia.Platform;
+
+namespace Avalonia.Media
+{
+    /// <summary>
+    ///     The font manager is used to query the system's installed fonts and is responsible for caching loaded fonts.
+    ///     It is also responsible for the font fallback.
+    /// </summary>
+    public abstract class FontManager
+    {
+        public static readonly FontManager Default = CreateDefault();
+
+        /// <summary>
+        ///     Gets the system's default font family's name.
+        /// </summary>
+        public string DefaultFontFamilyName
+        {
+            get;
+            protected set;
+        }
+
+        /// <summary>
+        ///     Get all installed fonts in the system.
+        /// <param name="checkForUpdates">If <c>true</c> the font collection is updated.</param>
+        /// </summary>
+        public abstract IEnumerable<string> GetInstalledFontFamilyNames(bool checkForUpdates = false);
+
+        /// <summary>
+        ///     Get a cached typeface from specified parameters.
+        /// </summary>
+        /// <param name="fontFamily">The font family.</param>
+        /// <param name="fontWeight">The font weight.</param>
+        /// <param name="fontStyle">The font style.</param>
+        /// <returns>
+        ///     The cached typeface.
+        /// </returns>
+        public abstract Typeface GetCachedTypeface(FontFamily fontFamily, FontWeight fontWeight, FontStyle fontStyle);
+
+        /// <summary>
+        ///     Tries to match a specified character to a typeface that supports specified font properties.
+        ///     Returns <c>null</c> if no fallback was found.
+        /// </summary>
+        /// <param name="codepoint">The codepoint to match against.</param>
+        /// <param name="fontWeight">The font weight.</param>
+        /// <param name="fontStyle">The font style.</param>
+        /// <param name="fontFamily">The font family. This is optional and used for fallback lookup.</param>
+        /// <param name="culture">The culture.</param>
+        /// <returns>
+        ///     The matched typeface.
+        /// </returns>
+        public abstract Typeface MatchCharacter(int codepoint, FontWeight fontWeight = default,
+            FontStyle fontStyle = default,
+            FontFamily fontFamily = null, CultureInfo culture = null);
+
+        public static FontManager CreateDefault()
+        {
+            var platformImpl = AvaloniaLocator.Current.GetService<IFontManagerImpl>();
+
+            if (platformImpl != null)
+            {
+                return new PlatformFontManager(platformImpl);
+            }
+
+            return new EmptyFontManager();
+        }
+
+        private class PlatformFontManager : FontManager
+        {
+            private readonly IFontManagerImpl _platformImpl;
+
+            public PlatformFontManager(IFontManagerImpl platformImpl)
+            {
+                _platformImpl = platformImpl;
+
+                DefaultFontFamilyName = _platformImpl.DefaultFontFamilyName;
+            }
+
+            public override IEnumerable<string> GetInstalledFontFamilyNames(bool checkForUpdates = false) =>
+                _platformImpl.GetInstalledFontFamilyNames(checkForUpdates);
+
+            public override Typeface GetCachedTypeface(FontFamily fontFamily, FontWeight fontWeight, FontStyle fontStyle) =>
+                _platformImpl.GetTypeface(fontFamily, fontWeight, fontStyle);
+
+            public override Typeface MatchCharacter(int codepoint, FontWeight fontWeight = default,
+                FontStyle fontStyle = default,
+                FontFamily fontFamily = null, CultureInfo culture = null) =>
+                _platformImpl.MatchCharacter(codepoint, fontWeight, fontStyle, fontFamily, culture);
+        }
+
+        private class EmptyFontManager : FontManager
+        {
+            public EmptyFontManager()
+            {
+                DefaultFontFamilyName = "Empty";
+            }
+
+            public override IEnumerable<string> GetInstalledFontFamilyNames(bool checkForUpdates = false) =>
+                new[] { DefaultFontFamilyName };
+
+            public override Typeface GetCachedTypeface(FontFamily fontFamily, FontWeight fontWeight, FontStyle fontStyle) => new Typeface(fontFamily, fontWeight, fontStyle);
+
+            public override Typeface MatchCharacter(int codepoint, FontWeight fontWeight = default,
+                FontStyle fontStyle = default,
+                FontFamily fontFamily = null, CultureInfo culture = null) => null;
+        }
+    }
+}

src/Avalonia.Visuals/Media/Fonts/FamilyNameCollection.cs

@@ -9,7 +9,7 @@ using System.Text;
 
 namespace Avalonia.Media.Fonts
 {
-    public class FamilyNameCollection : IEnumerable<string>
+    public sealed class FamilyNameCollection : IReadOnlyList<string>
     {
         /// <summary>
         /// Initializes a new instance of the <see cref="FamilyNameCollection"/> class.
@@ -130,5 +130,9 @@ namespace Avalonia.Media.Fonts
 
             return other.ToString().Equals(ToString());
         }
+
+        public int Count => Names.Count;
+
+        public string this[int index] => Names[index];
     }
 }

src/Avalonia.Visuals/Media/FormattedText.cs

@@ -16,9 +16,10 @@ namespace Avalonia.Media
         private IFormattedTextImpl _platformImpl;
         private IReadOnlyList<FormattedTextStyleSpan> _spans;
         private Typeface _typeface;
+        private double _fontSize;
         private string _text;
         private TextAlignment _textAlignment;
-        private TextWrapping _wrapping;
+        private TextWrapping _textWrapping;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="FormattedText"/> class.
@@ -37,6 +38,31 @@ namespace Avalonia.Media
             _platform = platform;
         }
 
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="text"></param>
+        /// <param name="typeface"></param>
+        /// <param name="fontSize"></param>
+        /// <param name="textAlignment"></param>
+        /// <param name="textWrapping"></param>
+        /// <param name="constraint"></param>
+        public FormattedText(string text, Typeface typeface, double fontSize, TextAlignment textAlignment,
+            TextWrapping textWrapping, Size constraint)
+        {
+            _text = text;
+
+            _typeface = typeface;
+
+            _fontSize = fontSize;
+
+            _textAlignment = textAlignment;
+
+            _textWrapping = textWrapping;
+
+            _constraint = constraint;
+        }
+
         /// <summary>
         /// Gets the bounds of the text within the <see cref="Constraint"/>.
         /// </summary>
@@ -61,6 +87,16 @@ namespace Avalonia.Media
             set => Set(ref _typeface, value);
         }
 
+
+        /// <summary>
+        /// Gets or sets the font size.
+        /// </summary>
+        public double FontSize
+        {
+            get => _fontSize;
+            set => Set(ref _fontSize, value);
+        }
+
         /// <summary>
         /// Gets or sets a collection of spans that describe the formatting of subsections of the
         /// text.
@@ -92,10 +128,10 @@ namespace Avalonia.Media
         /// <summary>
         /// Gets or sets the text wrapping.
         /// </summary>
-        public TextWrapping Wrapping
+        public TextWrapping TextWrapping
         {
-            get => _wrapping;
-            set => Set(ref _wrapping, value);
+            get => _textWrapping;
+            set => Set(ref _textWrapping, value);
         }
 
         /// <summary>
@@ -110,8 +146,9 @@ namespace Avalonia.Media
                     _platformImpl = _platform.CreateFormattedText(
                         _text,
                         _typeface,
+                        _fontSize,
                         _textAlignment,
-                        _wrapping,
+                        _textWrapping,
                         _constraint,
                         _spans);
                 }

src/Avalonia.Visuals/Media/GlyphTypeface.cs

@@ -0,0 +1,111 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+
+using Avalonia.Platform;
+
+namespace Avalonia.Media
+{
+    public sealed class GlyphTypeface : IDisposable
+    {
+        private static readonly IPlatformRenderInterface s_platformRenderInterface =
+            AvaloniaLocator.Current.GetService<IPlatformRenderInterface>();
+
+        public GlyphTypeface(Typeface typeface) : this(s_platformRenderInterface.CreateGlyphTypeface(typeface))
+        {
+        }
+
+        public GlyphTypeface(IGlyphTypefaceImpl platformImpl)
+        {
+            PlatformImpl = platformImpl;
+        }
+
+        public IGlyphTypefaceImpl PlatformImpl { get; }
+
+        /// <summary>
+        ///     Gets the font design units per em.
+        /// </summary>
+        public short DesignEmHeight => PlatformImpl.DesignEmHeight;
+
+        /// <summary>
+        ///     Gets the recommended distance above the baseline in design em size. 
+        /// </summary>
+        public int Ascent => PlatformImpl.Ascent;
+
+        /// <summary>
+        ///     Gets the recommended distance under the baseline in design em size. 
+        /// </summary>
+        public int Descent => PlatformImpl.Descent;
+
+        /// <summary>
+        ///      Gets the recommended additional space between two lines of text in design em size. 
+        /// </summary>
+        public int LineGap => PlatformImpl.LineGap;
+
+        /// <summary>
+        ///     Gets the recommended line height.
+        /// </summary>
+        public int LineHeight => Descent - Ascent + LineGap;
+
+        /// <summary>
+        ///     Gets a value that indicates the distance of the underline from the baseline in design em size.
+        /// </summary>
+        public int UnderlinePosition => PlatformImpl.UnderlinePosition;
+
+        /// <summary>
+        ///     Gets a value that indicates the thickness of the underline in design em size.
+        /// </summary>
+        public int UnderlineThickness => PlatformImpl.UnderlineThickness;
+
+        /// <summary>
+        ///     Gets a value that indicates the distance of the strikethrough from the baseline in design em size.
+        /// </summary>
+        public int StrikethroughPosition => PlatformImpl.StrikethroughPosition;
+
+        /// <summary>
+        ///     Gets a value that indicates the thickness of the underline in design em size.
+        /// </summary>
+        public int StrikethroughThickness => PlatformImpl.StrikethroughThickness;
+
+        /// <summary>
+        ///     Returns an glyph index for the specified codepoint.
+        /// </summary>
+        /// <remarks>
+        ///     Returns <c>0</c> if a glyph isn't found.
+        /// </remarks>
+        /// <param name="codepoint">The codepoint.</param>
+        /// <returns>
+        ///     A glyph index.
+        /// </returns>
+        public ushort GetGlyph(uint codepoint) => PlatformImpl.GetGlyph(codepoint);
+
+        /// <summary>
+        ///     Returns an array of glyph indices. Codepoints that are not represented by the font are returned as <code>0</code>.
+        /// </summary>
+        /// <param name="codepoints">The codepoints to map.</param>
+        /// <returns></returns>
+        public ushort[] GetGlyphs(ReadOnlySpan<uint> codepoints) => PlatformImpl.GetGlyphs(codepoints);
+
+        /// <summary>
+        ///     Returns the glyph advance for the specified glyph.
+        /// </summary>
+        /// <param name="glyph">The glyph.</param>
+        /// <returns>
+        ///     The advance.
+        /// </returns>
+        public int GetGlyphAdvance(ushort glyph) => PlatformImpl.GetGlyphAdvance(glyph);
+
+        /// <summary>
+        ///     Returns an array of glyph advances in design em size.
+        /// </summary>
+        /// <param name="glyphs">The glyph indices.</param>
+        /// <returns></returns>
+        public int[] GetGlyphAdvances(ReadOnlySpan<ushort> glyphs) => PlatformImpl.GetGlyphAdvances(glyphs);
+
+        void IDisposable.Dispose()
+        {
+            PlatformImpl?.Dispose();
+        }
+    }
+}

src/Avalonia.Visuals/Media/Typeface.cs

@@ -1,39 +1,38 @@
-using System;
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+using System.Diagnostics;
+using JetBrains.Annotations;
 
 namespace Avalonia.Media
 {
     /// <summary>
     /// Represents a typeface.
     /// </summary>
-    public class Typeface
+    [DebuggerDisplay("Name = {FontFamily.Name}, Weight = {Weight}, Style = {Style}")]
+    public class Typeface : IEquatable<Typeface>
     {
         public static readonly Typeface Default = new Typeface(FontFamily.Default);
 
+        private GlyphTypeface _glyphTypeface;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Typeface"/> class.
         /// </summary>
         /// <param name="fontFamily">The font family.</param>
-        /// <param name="fontSize">The font size, in DIPs.</param>
-        /// <param name="style">The font style.</param>
         /// <param name="weight">The font weight.</param>
-        public Typeface(
-            FontFamily fontFamily, 
-            double fontSize = 12, 
-            FontStyle style = FontStyle.Normal,
-            FontWeight weight = FontWeight.Normal)
+        /// <param name="style">The font style.</param>
+        public Typeface([NotNull]FontFamily fontFamily,
+            FontWeight weight = FontWeight.Normal,
+            FontStyle style = FontStyle.Normal)
         {
-            if (fontSize <= 0)
-            {
-                throw new ArgumentException("Font size must be > 0.");
-            }
-
             if (weight <= 0)
             {
                 throw new ArgumentException("Font weight must be > 0.");
             }
 
             FontFamily = fontFamily;
-            FontSize = fontSize;
             Style = style;
             Weight = weight;
         }
@@ -42,15 +41,12 @@ namespace Avalonia.Media
         /// Initializes a new instance of the <see cref="Typeface"/> class.
         /// </summary>
         /// <param name="fontFamilyName">The name of the font family.</param>
-        /// <param name="fontSize">The font size, in DIPs.</param>
         /// <param name="style">The font style.</param>
         /// <param name="weight">The font weight.</param>
-        public Typeface(
-            string fontFamilyName,
-            double fontSize = 12,
-            FontStyle style = FontStyle.Normal,
-            FontWeight weight = FontWeight.Normal)
-            : this(new FontFamily(fontFamilyName), fontSize, style, weight)
+        public Typeface(string fontFamilyName,
+            FontWeight weight = FontWeight.Normal,
+            FontStyle style = FontStyle.Normal)
+            : this(new FontFamily(fontFamilyName), weight, style)
         {
         }
 
@@ -59,11 +55,6 @@ namespace Avalonia.Media
         /// </summary>
         public FontFamily FontFamily { get; }
 
-        /// <summary>
-        /// Gets the size of the font in DIPs.
-        /// </summary>
-        public double FontSize { get; }
-
         /// <summary>
         /// Gets the font style.
         /// </summary>
@@ -73,5 +64,59 @@ namespace Avalonia.Media
         /// Gets the font weight.
         /// </summary>
         public FontWeight Weight { get; }
+
+        /// <summary>
+        /// Gets the glyph typeface.
+        /// </summary>
+        /// <value>
+        /// The glyph typeface.
+        /// </value>
+        public GlyphTypeface GlyphTypeface => _glyphTypeface ?? (_glyphTypeface = new GlyphTypeface(this));
+
+        public static bool operator !=(Typeface a, Typeface b)
+        {
+            return !(a == b);
+        }
+
+        public static bool operator ==(Typeface a, Typeface b)
+        {
+            if (ReferenceEquals(a, b))
+            {
+                return true;
+            }
+
+            return !(a is null) && a.Equals(b);
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (obj is Typeface typeface)
+            {
+                return Equals(typeface);
+            }
+
+            return false;
+        }
+
+        public bool Equals(Typeface other)
+        {
+            if (other is null)
+            {
+                return false;
+            }
+
+            return FontFamily.Equals(other.FontFamily) && Style == other.Style && Weight == other.Weight;
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                var hashCode = (FontFamily != null ? FontFamily.GetHashCode() : 0);
+                hashCode = (hashCode * 397) ^ (int)Style;
+                hashCode = (hashCode * 397) ^ (int)Weight;
+                return hashCode;
+            }
+        }
     }
 }

src/Avalonia.Visuals/Platform/IFontManagerImpl.cs

@@ -0,0 +1,48 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Globalization;
+using Avalonia.Media;
+
+namespace Avalonia.Platform
+{
+    public interface IFontManagerImpl
+    {
+        /// <summary>
+        ///     Gets the system's default font family's name.
+        /// </summary>
+        string DefaultFontFamilyName { get; }
+
+        /// <summary>
+        ///     Get all installed fonts in the system.
+        /// <param name="checkForUpdates">If <c>true</c> the font collection is updated.</param>
+        /// </summary>
+        IEnumerable<string> GetInstalledFontFamilyNames(bool checkForUpdates = false);
+
+        /// <summary>
+        ///     Get a typeface from specified parameters.
+        /// </summary>
+        /// <param name="fontFamily">The font family.</param>
+        /// <param name="fontWeight">The font weight.</param>
+        /// <param name="fontStyle">The font style.</param>
+        /// <returns>
+        ///     The typeface.
+        /// </returns>
+        Typeface GetTypeface(FontFamily fontFamily, FontWeight fontWeight, FontStyle fontStyle);
+
+        /// <summary>
+        ///     Tries to match a specified character to a typeface that supports specified font properties.
+        /// </summary>
+        /// <param name="codepoint">The codepoint to match against.</param>
+        /// <param name="fontWeight">The font weight.</param>
+        /// <param name="fontStyle">The font style.</param>
+        /// <param name="fontFamily">The font family. This is optional and used for fallback lookup.</param>
+        /// <param name="culture">The culture.</param>
+        /// <returns>
+        ///     The typeface.
+        /// </returns>
+        Typeface MatchCharacter(int codepoint, FontWeight fontWeight = default, FontStyle fontStyle = default,
+            FontFamily fontFamily = null, CultureInfo culture = null);
+    }
+}

src/Avalonia.Visuals/Platform/IGlyphTypefaceImpl.cs

@@ -0,0 +1,89 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+
+namespace Avalonia.Platform
+{
+    public interface IGlyphTypefaceImpl : IDisposable
+    {
+        /// <summary>
+        ///     Gets the font design units per em.
+        /// </summary>
+        short DesignEmHeight { get; }
+
+        /// <summary>
+        ///     Gets the recommended distance above the baseline in design em size. 
+        /// </summary>
+        int Ascent { get; }
+
+        /// <summary>
+        ///     Gets the recommended distance under the baseline in design em size. 
+        /// </summary>
+        int Descent { get; }
+
+        /// <summary>
+        ///      Gets the recommended additional space between two lines of text in design em size. 
+        /// </summary>
+        int LineGap { get; }
+
+        /// <summary>
+        ///     Gets a value that indicates the distance of the underline from the baseline in design em size.
+        /// </summary>
+        int UnderlinePosition { get; }
+
+        /// <summary>
+        ///     Gets a value that indicates the thickness of the underline in design em size.
+        /// </summary>
+        int UnderlineThickness { get; }
+
+        /// <summary>
+        ///     Gets a value that indicates the distance of the strikethrough from the baseline in design em size.
+        /// </summary>
+        int StrikethroughPosition { get; }
+
+        /// <summary>
+        ///     Gets a value that indicates the thickness of the underline in design em size.
+        /// </summary>
+        int StrikethroughThickness { get; }
+
+        /// <summary>
+        ///     Returns an glyph index for the specified codepoint.
+        /// </summary>
+        /// <remarks>
+        ///     Returns <c>0</c> if a glyph isn't found.
+        /// </remarks>
+        /// <param name="codepoint">The codepoint.</param>
+        /// <returns>
+        ///     A glyph index.
+        /// </returns>
+        ushort GetGlyph(uint codepoint);
+
+        /// <summary>
+        ///     Returns an array of glyph indices. Codepoints that are not represented by the font are returned as <code>0</code>.
+        /// </summary>
+        /// <param name="codepoints">The codepoints to map.</param>
+        /// <returns>
+        ///     An array of glyph indices.
+        /// </returns>
+        ushort[] GetGlyphs(ReadOnlySpan<uint> codepoints);
+
+        /// <summary>
+        ///     Returns the glyph advance for the specified glyph.
+        /// </summary>
+        /// <param name="glyph">The glyph.</param>
+        /// <returns>
+        ///     The advance.
+        /// </returns>
+        int GetGlyphAdvance(ushort glyph);
+
+        /// <summary>
+        ///     Returns an array of glyph advances in design em size.
+        /// </summary>
+        /// <param name="glyphs">The glyph indices.</param>
+        /// <returns>
+        ///     An array of glyph advances.
+        /// </returns>
+        int[] GetGlyphAdvances(ReadOnlySpan<ushort> glyphs);
+    }
+}

src/Avalonia.Visuals/Platform/IPlatformRenderInterface.cs

@@ -13,16 +13,12 @@ namespace Avalonia.Platform
     /// </summary>
     public interface IPlatformRenderInterface
     {
-        /// <summary>
-        /// Get all installed fonts in the system
-        /// </summary>
-        IEnumerable<string> InstalledFontNames { get; }
-
         /// <summary>
         /// Creates a formatted text implementation.
         /// </summary>
         /// <param name="text">The text.</param>
         /// <param name="typeface">The base typeface.</param>
+        /// <param name="fontSize">The font size.</param>
         /// <param name="textAlignment">The text alignment.</param>
         /// <param name="wrapping">The text wrapping mode.</param>
         /// <param name="constraint">The text layout constraints.</param>
@@ -31,6 +27,7 @@ namespace Avalonia.Platform
         IFormattedTextImpl CreateFormattedText(
             string text,
             Typeface typeface,
+            double fontSize,
             TextAlignment textAlignment,
             TextWrapping wrapping,
             Size constraint,
@@ -114,5 +111,14 @@ namespace Avalonia.Platform
         /// <param name="stride">The number of bytes per row.</param>
         /// <returns>An <see cref="IBitmapImpl"/>.</returns>
         IBitmapImpl LoadBitmap(PixelFormat format, IntPtr data, PixelSize size, Vector dpi, int stride);
+
+        /// <summary>
+        ///     Creates a glyph typeface for specified typeface.
+        /// </summary>
+        /// <param name="typeface">The typeface.</param>
+        /// <returns>
+        ///     The glyph typeface implementation.
+        /// </returns>
+        IGlyphTypefaceImpl CreateGlyphTypeface(Typeface typeface);
     }
 }

src/Avalonia.Visuals/Rendering/RendererBase.cs

@@ -7,7 +7,8 @@ namespace Avalonia.Rendering
 {
     public class RendererBase
     {
-        private static readonly Typeface s_fpsTypeface = new Typeface("Arial", 18);
+        private static readonly Typeface s_fpsTypeface = new Typeface("Arial");
+        private static int s_fontSize = 18;
         private readonly Stopwatch _stopwatch = Stopwatch.StartNew();
         private int _framesThisSecond;
         private int _fps;
@@ -18,7 +19,8 @@ namespace Avalonia.Rendering
         {
             _fpsText = new FormattedText
             {
-                Typeface = s_fpsTypeface
+                Typeface = s_fpsTypeface,
+                FontSize = s_fontSize
             };
         }
 

src/Skia/Avalonia.Skia/Avalonia.Skia.csproj

@@ -12,5 +12,6 @@
   </ItemGroup>
   
   <Import Project="..\..\..\build\SkiaSharp.props" />
+  <Import Project="..\..\..\build\HarfBuzzSharp.props" />
   <Import Project="..\..\Shared\RenderHelpers\RenderHelpers.projitems" Label="Shared" />
 </Project>

src/Skia/Avalonia.Skia/FontKey.cs

@@ -0,0 +1,40 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+using Avalonia.Media;
+
+namespace Avalonia.Skia
+{
+    internal readonly struct FontKey : IEquatable<FontKey>
+    {
+        public readonly FontStyle Style;
+        public readonly FontWeight Weight;
+
+        public FontKey(FontWeight weight, FontStyle style)
+        {
+            Style = style;
+            Weight = weight;
+        }
+
+        public override int GetHashCode()
+        {
+            var hash = 17;
+            hash = hash * 31 + (int)Style;
+            hash = hash * 31 + (int)Weight;
+
+            return hash;
+        }
+
+        public override bool Equals(object other)
+        {
+            return other is FontKey key && Equals(key);
+        }
+
+        public bool Equals(FontKey other)
+        {
+            return Style == other.Style &&
+                   Weight == other.Weight;
+        }
+    }
+}

src/Skia/Avalonia.Skia/FontManagerImpl.cs

@@ -0,0 +1,82 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Globalization;
+using Avalonia.Media;
+using Avalonia.Platform;
+using SkiaSharp;
+
+namespace Avalonia.Skia
+{
+    internal class FontManagerImpl : IFontManagerImpl
+    {
+        private SKFontManager _skFontManager = SKFontManager.Default;
+
+        public FontManagerImpl()
+        {
+            DefaultFontFamilyName = SKTypeface.Default.FamilyName;
+        }
+
+        public string DefaultFontFamilyName { get; }
+
+        public IEnumerable<string> GetInstalledFontFamilyNames(bool checkForUpdates = false)
+        {
+            if (checkForUpdates)
+            {
+                _skFontManager = SKFontManager.CreateDefault();
+            }
+
+            return _skFontManager.FontFamilies;
+        }
+
+        public Typeface GetTypeface(FontFamily fontFamily, FontWeight fontWeight, FontStyle fontStyle)
+        {
+            return TypefaceCache.Get(fontFamily.Name, fontWeight, fontStyle).Typeface;
+        }
+
+        public Typeface MatchCharacter(int codepoint, FontWeight fontWeight = default, FontStyle fontStyle = default,
+            FontFamily fontFamily = null, CultureInfo culture = null)
+        {
+            var fontFamilyName = FontFamily.Default.Name;
+
+            if (culture == null)
+            {
+                culture = CultureInfo.CurrentUICulture;
+            }
+
+            if (fontFamily != null)
+            {
+                foreach (var familyName in fontFamily.FamilyNames)
+                {
+                    var skTypeface = _skFontManager.MatchCharacter(familyName, (SKFontStyleWeight)fontWeight,
+                        SKFontStyleWidth.Normal,
+                        (SKFontStyleSlant)fontStyle,
+                        new[] { culture.TwoLetterISOLanguageName, culture.ThreeLetterISOLanguageName }, codepoint);
+
+                    if (skTypeface == null)
+                    {
+                        continue;
+                    }
+
+                    fontFamilyName = familyName;
+
+                    break;
+                }
+            }
+            else
+            {
+                var skTypeface = _skFontManager.MatchCharacter(null, (SKFontStyleWeight)fontWeight, SKFontStyleWidth.Normal,
+                    (SKFontStyleSlant)fontStyle,
+                    new[] { culture.TwoLetterISOLanguageName, culture.ThreeLetterISOLanguageName }, codepoint);
+
+                if (skTypeface != null)
+                {
+                    fontFamilyName = skTypeface.FamilyName;
+                }
+            }
+
+            return GetTypeface(fontFamilyName, fontWeight, fontStyle);
+        }
+    }
+}

src/Skia/Avalonia.Skia/FormattedTextImpl.cs

@@ -18,6 +18,7 @@ namespace Avalonia.Skia
         public FormattedTextImpl(
             string text,
             Typeface typeface,
+            double fontSize,
             TextAlignment textAlignment,
             TextWrapping wrapping,
             Size constraint,
@@ -28,47 +29,22 @@ namespace Avalonia.Skia
             // Replace 0 characters with zero-width spaces (200B)
             Text = Text.Replace((char)0, (char)0x200B);
 
-            SKTypeface skiaTypeface = null;
+            var entry = TypefaceCache.Get(typeface.FontFamily, typeface.Weight, typeface.Style);
 
-            if (typeface.FontFamily.Key != null)
+            _paint = new SKPaint
             {
-                var typefaces = SKTypefaceCollectionCache.GetOrAddTypefaceCollection(typeface.FontFamily);
-                skiaTypeface = typefaces.GetTypeFace(typeface);
-            }
-            else
-            {
-                if (typeface.FontFamily.FamilyNames.HasFallbacks)
-                {
-                    foreach (var familyName in typeface.FontFamily.FamilyNames)
-                    {
-                        skiaTypeface = TypefaceCache.GetTypeface(
-                            familyName,
-                            typeface.Style,
-                            typeface.Weight);
-                        if (skiaTypeface.FamilyName != TypefaceCache.DefaultFamilyName) break;
-                    }
-                }
-                else
-                {
-                    skiaTypeface = TypefaceCache.GetTypeface(
-                        typeface.FontFamily.Name,
-                        typeface.Style,
-                        typeface.Weight);
-                }
-            }
-
-            _paint = new SKPaint();
+                TextEncoding = SKTextEncoding.Utf16,
+                IsStroke = false,
+                IsAntialias = true,
+                LcdRenderText = true,
+                SubpixelText = true,
+                Typeface = entry.SKTypeface,
+                TextSize = (float)fontSize,
+                TextAlign = textAlignment.ToSKTextAlign()
+            };
 
             //currently Skia does not measure properly with Utf8 !!!
             //Paint.TextEncoding = SKTextEncoding.Utf8;
-            _paint.TextEncoding = SKTextEncoding.Utf16;
-            _paint.IsStroke = false;
-            _paint.IsAntialias = true;
-            _paint.LcdRenderText = true;
-            _paint.SubpixelText = true;
-            _paint.Typeface = skiaTypeface;
-            _paint.TextSize = (float)typeface.FontSize;
-            _paint.TextAlign = textAlignment.ToSKTextAlign();
 
             _wrapping = wrapping;
             _constraint = constraint;
@@ -118,7 +94,7 @@ namespace Avalonia.Skia
                 }
             }
 
-            if (!line.Equals(default))
+            if (!line.Equals(default(AvaloniaFormattedTextLine)))
             {
                 var rects = GetRects();
 

src/Skia/Avalonia.Skia/GlyphTypefaceImpl.cs

@@ -0,0 +1,179 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+using System.Runtime.InteropServices;
+using Avalonia.Media;
+using Avalonia.Platform;
+using HarfBuzzSharp;
+using SkiaSharp;
+
+namespace Avalonia.Skia
+{
+    public class GlyphTypefaceImpl : IGlyphTypefaceImpl
+    {
+        private bool _isDisposed;
+
+        public GlyphTypefaceImpl(Typeface typeface)
+        {
+            Typeface = TypefaceCache.Get(typeface.FontFamily, typeface.Weight, typeface.Style).SKTypeface;
+
+            Face = new Face(GetTable)
+            {
+                UnitsPerEm = Typeface.UnitsPerEm
+            };
+
+            Font = new Font(Face);
+
+            Font.SetFunctionsOpenType();
+
+            Font.GetScale(out var xScale, out _);
+
+            DesignEmHeight = (short)xScale;
+
+            if (!Font.TryGetHorizontalFontExtents(out var fontExtents))
+            {
+                Font.TryGetVerticalFontExtents(out fontExtents);
+            }
+
+            Ascent = -fontExtents.Ascender;
+
+            Descent = -fontExtents.Descender;
+
+            LineGap = fontExtents.LineGap;
+
+            if (Font.OpenTypeMetrics.TryGetPosition(OpenTypeMetricsTag.UnderlineOffset, out var underlinePosition))
+            {
+                UnderlinePosition = underlinePosition;
+            }
+
+            if (Font.OpenTypeMetrics.TryGetPosition(OpenTypeMetricsTag.UnderlineSize, out var underlineThickness))
+            {
+                UnderlineThickness = underlineThickness;
+            }
+
+            if (Font.OpenTypeMetrics.TryGetPosition(OpenTypeMetricsTag.StrikeoutOffset, out var strikethroughPosition))
+            {
+                StrikethroughPosition = strikethroughPosition;
+            }
+
+            if (Font.OpenTypeMetrics.TryGetPosition(OpenTypeMetricsTag.StrikeoutSize, out var strikethroughThickness))
+            {
+                StrikethroughThickness = strikethroughThickness;
+            }
+        }
+
+        public Face Face { get; }
+
+        public Font Font { get; }
+
+        public SKTypeface Typeface { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public short DesignEmHeight { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int Ascent { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int Descent { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int LineGap { get; }
+
+        //ToDo: Get these values from HarfBuzz
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int UnderlinePosition { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int UnderlineThickness { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int StrikethroughPosition { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int StrikethroughThickness { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public ushort GetGlyph(uint codepoint)
+        {
+            if (Font.TryGetGlyph(codepoint, out var glyph))
+            {
+                return (ushort)glyph;
+            }
+
+            return 0;
+        }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public ushort[] GetGlyphs(ReadOnlySpan<uint> codepoints)
+        {
+            var glyphs = new ushort[codepoints.Length];
+
+            for (var i = 0; i < codepoints.Length; i++)
+            {
+                if (Font.TryGetGlyph(codepoints[i], out var glyph))
+                {
+                    glyphs[i] = (ushort)glyph;
+                }
+            }
+
+            return glyphs;
+        }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int GetGlyphAdvance(ushort glyph)
+        {
+            return Font.GetHorizontalGlyphAdvance(glyph);
+        }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int[] GetGlyphAdvances(ReadOnlySpan<ushort> glyphs)
+        {
+            var glyphIndices = new uint[glyphs.Length];
+
+            for (var i = 0; i < glyphs.Length; i++)
+            {
+                glyphIndices[i] = glyphs[i];
+            }
+
+            return Font.GetHorizontalGlyphAdvances(glyphIndices);
+        }
+
+        private Blob GetTable(Face face, Tag tag)
+        {
+            var size = Typeface.GetTableSize(tag);
+
+            var data = Marshal.AllocCoTaskMem(size);
+
+            var releaseDelegate = new ReleaseDelegate(() => Marshal.FreeCoTaskMem(data));
+
+            return Typeface.TryGetTableData(tag, 0, size, data) ?
+                new Blob(data, size, MemoryMode.ReadOnly, releaseDelegate) : null;
+        }
+
+        private void Dispose(bool disposing)
+        {
+            if (_isDisposed)
+            {
+                return;
+            }
+
+            _isDisposed = true;
+
+            if (!disposing)
+            {
+                return;
+            }
+
+            Font?.Dispose();
+            Face?.Dispose();
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+    }
+}

src/Skia/Avalonia.Skia/PlatformRenderInterface.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
 using Avalonia.Controls.Platform.Surfaces;
@@ -17,12 +18,13 @@ namespace Avalonia.Skia
     /// </summary>
     internal class PlatformRenderInterface : IPlatformRenderInterface
     {
+        private readonly ConcurrentDictionary<Typeface, GlyphTypefaceImpl> _glyphTypefaceCache =
+            new ConcurrentDictionary<Typeface, GlyphTypefaceImpl>();
+
         private readonly ICustomSkiaGpu _customSkiaGpu;
 
         private GRContext GrContext { get; }
 
-        public IEnumerable<string> InstalledFontNames => SKFontManager.Default.FontFamilies;
-
         public PlatformRenderInterface(ICustomSkiaGpu customSkiaGpu)
         {
             if (customSkiaGpu != null)
@@ -52,12 +54,13 @@ namespace Avalonia.Skia
         public IFormattedTextImpl CreateFormattedText(
             string text,
             Typeface typeface,
+            double fontSize,
             TextAlignment textAlignment,
             TextWrapping wrapping,
             Size constraint,
             IReadOnlyList<FormattedTextStyleSpan> spans)
         {
-            return new FormattedTextImpl(text, typeface, textAlignment, wrapping, constraint, spans);
+            return new FormattedTextImpl(text, typeface,fontSize, textAlignment, wrapping, constraint, spans);
         }
 
         public IGeometryImpl CreateEllipseGeometry(Rect rect) => new EllipseGeometryImpl(rect);
@@ -151,5 +154,10 @@ namespace Avalonia.Skia
         {
             return new WriteableBitmapImpl(size, dpi, format);
         }
+
+        public IGlyphTypefaceImpl CreateGlyphTypeface(Typeface typeface)
+        {
+            return _glyphTypefaceCache.GetOrAdd(typeface, new GlyphTypefaceImpl(typeface));
+        }
     }
 }

src/Skia/Avalonia.Skia/SKTypefaceCollection.cs

@@ -4,114 +4,59 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
-
 using Avalonia.Media;
 
-using SkiaSharp;
-
 namespace Avalonia.Skia
 {
     internal class SKTypefaceCollection
     {
-        private readonly ConcurrentDictionary<string, ConcurrentDictionary<FontKey, SKTypeface>> _fontFamilies =
-            new ConcurrentDictionary<string, ConcurrentDictionary<FontKey, SKTypeface>>();
+        private readonly ConcurrentDictionary<string, ConcurrentDictionary<FontKey, TypefaceCollectionEntry>> _fontFamilies =
+            new ConcurrentDictionary<string, ConcurrentDictionary<FontKey, TypefaceCollectionEntry>>();
 
-        public void AddTypeFace(SKTypeface typeface)
+        public void AddEntry(string familyName, FontKey key, TypefaceCollectionEntry entry)
         {
-            var key = new FontKey((SKFontStyleWeight)typeface.FontWeight, typeface.FontSlant);
-
-            if (!_fontFamilies.TryGetValue(typeface.FamilyName, out var fontFamily))
+            if (!_fontFamilies.TryGetValue(familyName, out var fontFamily))
             {
-                fontFamily = new ConcurrentDictionary<FontKey, SKTypeface>();
+                fontFamily = new ConcurrentDictionary<FontKey, TypefaceCollectionEntry>();
 
-                _fontFamilies.TryAdd(typeface.FamilyName, fontFamily);
+                _fontFamilies.TryAdd(familyName, fontFamily);
             }
 
-            fontFamily.TryAdd(key, typeface);
+            fontFamily.TryAdd(key, entry);
         }
 
-        public SKTypeface GetTypeFace(Typeface typeface)
+        public TypefaceCollectionEntry Get(string familyName, FontWeight fontWeight, FontStyle fontStyle)
         {
-            var styleSlant = SKFontStyleSlant.Upright;
-
-            switch (typeface.Style)
-            {
-                case FontStyle.Italic:
-                    styleSlant = SKFontStyleSlant.Italic;
-                    break;
-
-                case FontStyle.Oblique:
-                    styleSlant = SKFontStyleSlant.Oblique;
-                    break;
-            }
+            var key = new FontKey(fontWeight, fontStyle);
 
-            if (!_fontFamilies.TryGetValue(typeface.FontFamily.Name, out var fontFamily))
-            {
-                return TypefaceCache.GetTypeface(TypefaceCache.DefaultFamilyName, typeface.Style, typeface.Weight);
-            }
-
-            var weight = (SKFontStyleWeight)typeface.Weight;
-
-            var key = new FontKey(weight, styleSlant);
-
-            return fontFamily.GetOrAdd(key, GetFallback(fontFamily, key));
+            return _fontFamilies.TryGetValue(familyName, out var fontFamily) ?
+                fontFamily.GetOrAdd(key, GetFallback(fontFamily, key)) :
+                null;
         }
 
-        private static SKTypeface GetFallback(IDictionary<FontKey, SKTypeface> fontFamily, FontKey key)
+        private static TypefaceCollectionEntry GetFallback(IDictionary<FontKey, TypefaceCollectionEntry> fontFamily, FontKey key)
         {
             var keys = fontFamily.Keys.Where(
-                x => ((int)x.Weight <= (int)key.Weight || (int)x.Weight > (int)key.Weight) && x.Slant == key.Slant).ToArray();
+                x => ((int)x.Weight <= (int)key.Weight || (int)x.Weight > (int)key.Weight) && x.Style == key.Style).ToArray();
 
             if (!keys.Any())
             {
                 keys = fontFamily.Keys.Where(
-                    x => x.Weight == key.Weight && (x.Slant >= key.Slant || x.Slant < key.Slant)).ToArray();
+                    x => x.Weight == key.Weight && (x.Style >= key.Style || x.Style < key.Style)).ToArray();
 
                 if (!keys.Any())
                 {
                     keys = fontFamily.Keys.Where(
                         x => ((int)x.Weight <= (int)key.Weight || (int)x.Weight > (int)key.Weight) &&
-                             (x.Slant >= key.Slant || x.Slant < key.Slant)).ToArray();
+                             (x.Style >= key.Style || x.Style < key.Style)).ToArray();
                 }
             }
 
             key = keys.FirstOrDefault();
 
-            fontFamily.TryGetValue(key, out var typeface);
-
-            return typeface;
-        }
-
-        private struct FontKey
-        {
-            public readonly SKFontStyleSlant Slant;
-            public readonly SKFontStyleWeight Weight;
-
-            public FontKey(SKFontStyleWeight weight, SKFontStyleSlant slant)
-            {
-                Slant = slant;
-                Weight = weight;
-            }
-
-            public override int GetHashCode()
-            {
-                var hash = 17;
-                hash = (hash * 31) + (int)Slant;
-                hash = (hash * 31) + (int)Weight;
-
-                return hash;
-            }
+            fontFamily.TryGetValue(key, out var entry);
 
-            public override bool Equals(object other)
-            {
-                return other is FontKey key && this.Equals(key);
-            }
-
-            private bool Equals(FontKey other)
-            {
-                return Slant == other.Slant &&
-                       Weight == other.Weight;
-            }
+            return entry;
         }
     }
 }

src/Skia/Avalonia.Skia/SKTypefaceCollectionCache.cs

@@ -45,9 +45,13 @@ namespace Avalonia.Skia
             {
                 var assetStream = assetLoader.Open(asset);
 
-                var typeface = SKTypeface.FromStream(assetStream);
+                var skTypeface = SKTypeface.FromStream(assetStream);
 
-                typeFaceCollection.AddTypeFace(typeface);
+                var typeface = new Typeface(fontFamily, (FontWeight)skTypeface.FontWeight, (FontStyle)skTypeface.FontSlant);
+
+                var entry = new TypefaceCollectionEntry(typeface, skTypeface);
+
+                typeFaceCollection.AddEntry(skTypeface.FamilyName, new FontKey(typeface.Weight, typeface.Style), entry);
             }
 
             return typeFaceCollection;

src/Skia/Avalonia.Skia/SkiaPlatform.cs

@@ -25,6 +25,11 @@ namespace Avalonia.Skia
 
             AvaloniaLocator.CurrentMutable
                 .Bind<IPlatformRenderInterface>().ToConstant(renderInterface);
+
+            var fontManager = new FontManagerImpl();
+
+            AvaloniaLocator.CurrentMutable
+                .Bind<IFontManagerImpl>().ToConstant(fontManager);
         }
 
         /// <summary>

src/Skia/Avalonia.Skia/TypefaceCache.cs

@@ -1,7 +1,7 @@
 // Copyright (c) The Avalonia Project. All rights reserved.
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
-using System.Collections.Generic;
+using System.Collections.Concurrent;
 using Avalonia.Media;
 using SkiaSharp;
 
@@ -12,88 +12,36 @@ namespace Avalonia.Skia
     /// </summary>
     internal static class TypefaceCache
     {
-        public static readonly string DefaultFamilyName = CreateDefaultFamilyName();
+        private static readonly ConcurrentDictionary<string, ConcurrentDictionary<FontKey, TypefaceCollectionEntry>> s_cache =
+            new ConcurrentDictionary<string, ConcurrentDictionary<FontKey, TypefaceCollectionEntry>>();
 
-        private static readonly Dictionary<string, Dictionary<FontKey, SKTypeface>> s_cache =
-            new Dictionary<string, Dictionary<FontKey, SKTypeface>>();
-
-        struct FontKey
+        public static TypefaceCollectionEntry Get(FontFamily fontFamily, FontWeight fontWeight, FontStyle fontStyle)
         {
-            public readonly SKFontStyleSlant Slant;
-            public readonly SKFontStyleWeight Weight;
-
-            public FontKey(SKFontStyleWeight weight, SKFontStyleSlant slant)
+            if (fontFamily.Key != null)
             {
-                Slant = slant;
-                Weight = weight;
+                return SKTypefaceCollectionCache.GetOrAddTypefaceCollection(fontFamily)
+                    .Get(fontFamily.Name, fontWeight, fontStyle);
             }
 
-            public override int GetHashCode()
-            {
-                int hash = 17;
-                hash = hash * 31 + (int)Slant;
-                hash = hash * 31 + (int)Weight;
-
-                return hash;
-            }
-
-            public override bool Equals(object other)
-            {
-                return other is FontKey ? Equals((FontKey)other) : false;
-            }
-
-            public bool Equals(FontKey other)
-            {
-                return Slant == other.Slant &&
-                       Weight == other.Weight;
-            }
-
-            // Equals and GetHashCode ommitted
-        }
-
-        private static string CreateDefaultFamilyName()
-        {
-            var defaultTypeface = SKTypeface.CreateDefault();
+            var typefaceCollection = s_cache.GetOrAdd(fontFamily.Name, new ConcurrentDictionary<FontKey, TypefaceCollectionEntry>());
 
-            return defaultTypeface.FamilyName;
-        }
+            var key = new FontKey(fontWeight, fontStyle);
 
-        private static SKTypeface GetTypeface(string name, FontKey key)
-        {
-            var familyKey = name;
-
-            if (!s_cache.TryGetValue(familyKey, out var entry))
+            if (typefaceCollection.TryGetValue(key, out var entry))
             {
-                s_cache[familyKey] = entry = new Dictionary<FontKey, SKTypeface>();
+                return entry;
             }
 
-            if (!entry.TryGetValue(key, out var typeface))
-            {
-                typeface = SKTypeface.FromFamilyName(familyKey, key.Weight, SKFontStyleWidth.Normal, key.Slant) ??
-                           GetTypeface(DefaultFamilyName, key);
+            var skTypeface = SKTypeface.FromFamilyName(fontFamily.Name, (SKFontStyleWeight)fontWeight,
+                                 SKFontStyleWidth.Normal, (SKFontStyleSlant)fontStyle) ?? SKTypeface.Default;
 
-                entry[key] = typeface;
-            }
+            var typeface = new Typeface(fontFamily.Name, fontWeight, fontStyle);
 
-            return typeface;
-        }
-
-        public static SKTypeface GetTypeface(string name, FontStyle style, FontWeight weight)
-        {
-            var skStyle = SKFontStyleSlant.Upright;
+            entry = new TypefaceCollectionEntry(typeface, skTypeface);
 
-            switch (style)
-            {
-                case FontStyle.Italic:
-                    skStyle = SKFontStyleSlant.Italic;
-                    break;
-
-                case FontStyle.Oblique:
-                    skStyle = SKFontStyleSlant.Oblique;
-                    break;
-            }
+            typefaceCollection[key] = entry;
 
-            return GetTypeface(name, new FontKey((SKFontStyleWeight)weight, skStyle));
+            return entry;
         }
     }
 }

src/Skia/Avalonia.Skia/TypefaceCollectionEntry.cs

@@ -0,0 +1,19 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using Avalonia.Media;
+using SkiaSharp;
+
+namespace Avalonia.Skia
+{
+    internal class TypefaceCollectionEntry
+    {
+        public TypefaceCollectionEntry(Typeface typeface, SKTypeface skTypeface)
+        {
+            Typeface = typeface;
+            SKTypeface = skTypeface;
+        }
+        public Typeface Typeface { get; }
+        public SKTypeface SKTypeface { get; }
+    }
+}

src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj

@@ -14,6 +14,7 @@
   </ItemGroup>
   <Import Project="..\..\..\build\Rx.props" />
   <Import Project="..\..\..\build\SharpDX.props" />
+  <Import Project="..\..\..\build\HarfBuzzSharp.props" />
   <Import Project="..\..\Shared\RenderHelpers\RenderHelpers.projitems" Label="Shared" />
   <Import Project="..\..\..\build\JetBrains.Annotations.props" />
 </Project>

src/Windows/Avalonia.Direct2D1/Direct2D1Platform.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
 using Avalonia.Controls;
@@ -27,6 +28,8 @@ namespace Avalonia.Direct2D1
 {
     public class Direct2D1Platform : IPlatformRenderInterface
     {
+        private readonly ConcurrentDictionary<Typeface, GlyphTypefaceImpl> _glyphTypefaceCache =
+            new ConcurrentDictionary<Typeface, GlyphTypefaceImpl>();
         private static readonly Direct2D1Platform s_instance = new Direct2D1Platform();
 
         public static SharpDX.Direct3D11.Device Direct3D11Device { get; private set; }
@@ -41,20 +44,6 @@ namespace Avalonia.Direct2D1
 
         public static SharpDX.DXGI.Device1 DxgiDevice { get; private set; }
 
-        public IEnumerable<string> InstalledFontNames
-        {
-            get
-            {
-                var cache = Direct2D1FontCollectionCache.s_installedFontCollection;
-                var length = cache.FontFamilyCount;
-                for (int i = 0; i < length; i++)
-                {
-                    var names = cache.GetFontFamily(i).FamilyNames;
-                    yield return names.GetString(0);
-                }
-            }
-        }
-
         private static readonly object s_initLock = new object();
         private static bool s_initialized = false;
 
@@ -120,6 +109,7 @@ namespace Avalonia.Direct2D1
         {
             InitializeDirect2D();
             AvaloniaLocator.CurrentMutable.Bind<IPlatformRenderInterface>().ToConstant(s_instance);
+            AvaloniaLocator.CurrentMutable.Bind<IFontManagerImpl>().ToConstant(new FontManagerImpl());
             SharpDX.Configuration.EnableReleaseOnFinalizer = true;
         }
 
@@ -131,6 +121,7 @@ namespace Avalonia.Direct2D1
         public IFormattedTextImpl CreateFormattedText(
             string text,
             Typeface typeface,
+            double fontSize,
             TextAlignment textAlignment,
             TextWrapping wrapping,
             Size constraint,
@@ -139,6 +130,7 @@ namespace Avalonia.Direct2D1
             return new FormattedTextImpl(
                 text,
                 typeface,
+                fontSize,
                 textAlignment,
                 wrapping,
                 constraint,
@@ -201,5 +193,10 @@ namespace Avalonia.Direct2D1
         {
             return new WicBitmapImpl(format, data, size, dpi, stride);
         }
+
+        public IGlyphTypefaceImpl CreateGlyphTypeface(Typeface typeface)
+        {
+            return _glyphTypefaceCache.GetOrAdd(typeface, new GlyphTypefaceImpl(typeface));
+        }
     }
 }

src/Windows/Avalonia.Direct2D1/Media/Direct2D1FontCollectionCache.cs

@@ -1,62 +1,61 @@
 using System.Collections.Concurrent;
 using Avalonia.Media;
 using Avalonia.Media.Fonts;
+using SharpDX.DirectWrite;
+using FontFamily = Avalonia.Media.FontFamily;
+using FontStyle = SharpDX.DirectWrite.FontStyle;
+using FontWeight = SharpDX.DirectWrite.FontWeight;
 
 namespace Avalonia.Direct2D1.Media
 {
     internal static class Direct2D1FontCollectionCache
     {
-        private static readonly ConcurrentDictionary<FontFamilyKey, SharpDX.DirectWrite.FontCollection> s_cachedCollections;
-        internal static readonly SharpDX.DirectWrite.FontCollection s_installedFontCollection;
+        private static readonly ConcurrentDictionary<FontFamilyKey, FontCollection> s_cachedCollections;
+        internal static readonly FontCollection InstalledFontCollection;
 
         static Direct2D1FontCollectionCache()
         {
-            s_cachedCollections = new ConcurrentDictionary<FontFamilyKey, SharpDX.DirectWrite.FontCollection>();
+            s_cachedCollections = new ConcurrentDictionary<FontFamilyKey, FontCollection>();
 
-            s_installedFontCollection = Direct2D1Platform.DirectWriteFactory.GetSystemFontCollection(false);
+            InstalledFontCollection = Direct2D1Platform.DirectWriteFactory.GetSystemFontCollection(false);
         }
 
-        public static SharpDX.DirectWrite.TextFormat GetTextFormat(Typeface typeface)
+        public static Font GetFont(Typeface typeface)
         {
             var fontFamily = typeface.FontFamily;
             var fontCollection = GetOrAddFontCollection(fontFamily);
-            var fontFamilyName = FontFamily.Default.Name;
 
-            // Should this be cached?
             foreach (var familyName in fontFamily.FamilyNames)
             {
-                if (!fontCollection.FindFamilyName(familyName, out _))
+                if (fontCollection.FindFamilyName(familyName, out var index))
                 {
-                    continue;
+                    return fontCollection.GetFontFamily(index).GetFirstMatchingFont(
+                        (FontWeight)typeface.Weight,
+                        FontStretch.Normal,
+                        (FontStyle)typeface.Style);
                 }
-
-                fontFamilyName = familyName;
-
-                break;
             }
 
-            return new SharpDX.DirectWrite.TextFormat(
-                Direct2D1Platform.DirectWriteFactory, 
-                fontFamilyName, 
-                fontCollection, 
-                (SharpDX.DirectWrite.FontWeight)typeface.Weight,
-                (SharpDX.DirectWrite.FontStyle)typeface.Style, 
-                SharpDX.DirectWrite.FontStretch.Normal, 
-                (float)typeface.FontSize);
+            InstalledFontCollection.FindFamilyName(FontFamily.Default.Name, out var i);
+
+            return InstalledFontCollection.GetFontFamily(i).GetFirstMatchingFont(
+                (FontWeight)typeface.Weight,
+                FontStretch.Normal,
+                (FontStyle)typeface.Style);
         }
 
-        private static SharpDX.DirectWrite.FontCollection GetOrAddFontCollection(FontFamily fontFamily)
+        private static FontCollection GetOrAddFontCollection(FontFamily fontFamily)
         {
-            return fontFamily.Key == null ? s_installedFontCollection : s_cachedCollections.GetOrAdd(fontFamily.Key, CreateFontCollection);
+            return fontFamily.Key == null ? InstalledFontCollection : s_cachedCollections.GetOrAdd(fontFamily.Key, CreateFontCollection);
         }
 
-        private static SharpDX.DirectWrite.FontCollection CreateFontCollection(FontFamilyKey key)
+        private static FontCollection CreateFontCollection(FontFamilyKey key)
         {
             var assets = FontFamilyLoader.LoadFontAssets(key);
 
             var fontLoader = new DWriteResourceFontLoader(Direct2D1Platform.DirectWriteFactory, assets);
 
-            return new SharpDX.DirectWrite.FontCollection(Direct2D1Platform.DirectWriteFactory, fontLoader, fontLoader.Key);
+            return new FontCollection(Direct2D1Platform.DirectWriteFactory, fontLoader, fontLoader.Key);
         }
     }
 }

src/Windows/Avalonia.Direct2D1/Media/FontManagerImpl.cs

@@ -0,0 +1,71 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Globalization;
+using Avalonia.Media;
+using Avalonia.Platform;
+using SharpDX.DirectWrite;
+using FontFamily = Avalonia.Media.FontFamily;
+using FontStyle = Avalonia.Media.FontStyle;
+using FontWeight = Avalonia.Media.FontWeight;
+
+namespace Avalonia.Direct2D1.Media
+{
+    internal class FontManagerImpl : IFontManagerImpl
+    {
+        public FontManagerImpl()
+        {
+            //ToDo: Implement a real lookup of the system's default font.
+            DefaultFontFamilyName = "segoe ui";
+        }
+
+        public string DefaultFontFamilyName { get; }
+
+        public IEnumerable<string> GetInstalledFontFamilyNames(bool checkForUpdates = false)
+        {
+            var familyCount = Direct2D1FontCollectionCache.InstalledFontCollection.FontFamilyCount;
+
+            var fontFamilies = new string[familyCount];
+
+            for (var i = 0; i < familyCount; i++)
+            {
+                fontFamilies[i] = Direct2D1FontCollectionCache.InstalledFontCollection.GetFontFamily(i).FamilyNames.GetString(0);
+            }
+
+            return fontFamilies;
+        }
+
+        public Typeface GetTypeface(FontFamily fontFamily, FontWeight fontWeight, FontStyle fontStyle)
+        {
+            //ToDo: Implement caching.
+            return new Typeface(fontFamily, fontWeight, fontStyle);
+        }
+
+        public Typeface MatchCharacter(int codepoint, FontWeight fontWeight = default, FontStyle fontStyle = default,
+            FontFamily fontFamily = null, CultureInfo culture = null)
+        {
+            var fontFamilyName = FontFamily.Default.Name;
+
+            var familyCount = Direct2D1FontCollectionCache.InstalledFontCollection.FontFamilyCount;
+
+            for (var i = 0; i < familyCount; i++)
+            {
+                var font = Direct2D1FontCollectionCache.InstalledFontCollection.GetFontFamily(i)
+                    .GetMatchingFonts((SharpDX.DirectWrite.FontWeight)fontWeight, FontStretch.Normal,
+                        (SharpDX.DirectWrite.FontStyle)fontStyle).GetFont(0);
+
+                if (!font.HasCharacter(codepoint))
+                {
+                    continue;
+                }
+
+                fontFamilyName = font.FontFamily.FamilyNames.GetString(0);
+
+                break;
+            }
+
+            return GetTypeface(new FontFamily(fontFamilyName), fontWeight, fontStyle);
+        }
+    }
+}

src/Windows/Avalonia.Direct2D1/Media/FormattedTextImpl.cs

@@ -14,6 +14,7 @@ namespace Avalonia.Direct2D1.Media
         public FormattedTextImpl(
             string text,
             Typeface typeface,
+            double fontSize,
             TextAlignment textAlignment,
             TextWrapping wrapping,
             Size constraint,
@@ -21,20 +22,20 @@ namespace Avalonia.Direct2D1.Media
         {
             Text = text;
 
-            using (var textFormat = Direct2D1FontCollectionCache.GetTextFormat(typeface))
+            using (var font = Direct2D1FontCollectionCache.GetFont(typeface))
+            using (var textFormat = new DWrite.TextFormat(Direct2D1Platform.DirectWriteFactory,
+                typeface.FontFamily.Name, font.FontFamily.FontCollection, (DWrite.FontWeight)typeface.Weight,
+                (DWrite.FontStyle)typeface.Style, DWrite.FontStretch.Normal, (float)fontSize))
             {
                 textFormat.WordWrapping =
                     wrapping == TextWrapping.Wrap ? DWrite.WordWrapping.Wrap : DWrite.WordWrapping.NoWrap;
 
                 TextLayout = new DWrite.TextLayout(
-                                 Direct2D1Platform.DirectWriteFactory,
-                                 Text ?? string.Empty,
-                                 textFormat,
-                                 (float)constraint.Width,
-                                 (float)constraint.Height)
-                             {
-                                 TextAlignment = textAlignment.ToDirect2D()
-                             };
+                    Direct2D1Platform.DirectWriteFactory,
+                    Text ?? string.Empty,
+                    textFormat,
+                    (float)constraint.Width,
+                    (float)constraint.Height) { TextAlignment = textAlignment.ToDirect2D() };
             }
 
             if (spans != null)

src/Windows/Avalonia.Direct2D1/Media/GlyphTypefaceImpl.cs

@@ -0,0 +1,188 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+using Avalonia.Media;
+using Avalonia.Platform;
+using HarfBuzzSharp;
+using SharpDX.DirectWrite;
+
+namespace Avalonia.Direct2D1.Media
+{
+    public class GlyphTypefaceImpl : IGlyphTypefaceImpl
+    {
+        private bool _isDisposed;
+
+        public GlyphTypefaceImpl(Typeface typeface)
+        {
+            DWFont = Direct2D1FontCollectionCache.GetFont(typeface);
+
+            FontFace = new FontFace(DWFont);
+
+            Face = new Face(GetTable);
+
+            Font = new HarfBuzzSharp.Font(Face);
+
+            Font.SetFunctionsOpenType();
+
+            Font.GetScale(out var xScale, out _);
+
+            DesignEmHeight = (short)xScale;
+
+            if (!Font.TryGetHorizontalFontExtents(out var fontExtents))
+            {
+                Font.TryGetVerticalFontExtents(out fontExtents);
+            }
+
+            Ascent = -fontExtents.Ascender;
+
+            Descent = -fontExtents.Descender;
+
+            LineGap = fontExtents.LineGap;
+
+            if (Font.OpenTypeMetrics.TryGetPosition(OpenTypeMetricsTag.UnderlineOffset, out var underlinePosition))
+            {
+                UnderlinePosition = underlinePosition;
+            }
+
+            if (Font.OpenTypeMetrics.TryGetPosition(OpenTypeMetricsTag.UnderlineSize, out var underlineThickness))
+            {
+                UnderlineThickness = underlineThickness;
+            }
+
+            if (Font.OpenTypeMetrics.TryGetPosition(OpenTypeMetricsTag.StrikeoutOffset, out var strikethroughPosition))
+            {
+                StrikethroughPosition = strikethroughPosition;
+            }
+
+            if (Font.OpenTypeMetrics.TryGetPosition(OpenTypeMetricsTag.StrikeoutSize, out var strikethroughThickness))
+            {
+                StrikethroughThickness = strikethroughThickness;
+            }
+        }
+
+        private Blob GetTable(Face face, Tag tag)
+        {
+            var dwTag = (int)SwapBytes(tag);
+
+            if (FontFace.TryGetFontTable(dwTag, out var tableData, out _))
+            {
+                return new Blob(tableData.Pointer, tableData.Size, MemoryMode.ReadOnly, () => { });
+            }
+
+            return null;
+        }
+
+        private static uint SwapBytes(uint x)
+        {
+            x = (x >> 16) | (x << 16);
+
+            return ((x & 0xFF00FF00) >> 8) | ((x & 0x00FF00FF) << 8);
+        }
+
+        public SharpDX.DirectWrite.Font DWFont { get; }
+
+        public FontFace FontFace { get; }
+
+        public Face Face { get; }
+
+        public HarfBuzzSharp.Font Font { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public short DesignEmHeight { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int Ascent { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int Descent { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int LineGap { get; }
+
+        //ToDo: Read font table for these values
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int UnderlinePosition { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int UnderlineThickness { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int StrikethroughPosition { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int StrikethroughThickness { get; }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public ushort GetGlyph(uint codepoint)
+        {
+            if (Font.TryGetGlyph(codepoint, out var glyph))
+            {
+                return (ushort)glyph;
+            }
+
+            return 0;
+        }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public ushort[] GetGlyphs(ReadOnlySpan<uint> codepoints)
+        {
+            var glyphs = new ushort[codepoints.Length];
+
+            for (var i = 0; i < codepoints.Length; i++)
+            {
+                if (Font.TryGetGlyph(codepoints[i], out var glyph))
+                {
+                    glyphs[i] = (ushort)glyph;
+                }
+            }
+
+            return glyphs;
+        }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int GetGlyphAdvance(ushort glyph)
+        {
+            return Font.GetHorizontalGlyphAdvance(glyph);
+        }
+
+        /// <inheritdoc cref="IGlyphTypefaceImpl"/>
+        public int[] GetGlyphAdvances(ReadOnlySpan<ushort> glyphs)
+        {
+            var glyphIndices = new uint[glyphs.Length];
+
+            for (var i = 0; i < glyphs.Length; i++)
+            {
+                glyphIndices[i] = glyphs[i];
+            }
+
+            return Font.GetHorizontalGlyphAdvances(glyphIndices);
+        }
+
+        private void Dispose(bool disposing)
+        {
+            if (_isDisposed)
+            {
+                return;
+            }
+
+            _isDisposed = true;
+
+            if (!disposing)
+            {
+                return;
+            }
+
+            Font?.Dispose();
+            Face?.Dispose();
+            FontFace?.Dispose();
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+    }
+}
+

tests/Avalonia.Controls.UnitTests/GridSplitterTests.cs

@@ -2,9 +2,7 @@ using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.Platform;
 using Avalonia.UnitTests;
-
 using Moq;
-
 using Xunit;
 
 namespace Avalonia.Controls.UnitTests
@@ -21,185 +19,366 @@ namespace Avalonia.Controls.UnitTests
         public void Detects_Horizontal_Orientation()
         {
             GridSplitter splitter;
-            var grid = new Grid()
-                       {
-                            RowDefinitions = new RowDefinitions("*,Auto,*"),
-                            ColumnDefinitions = new ColumnDefinitions("*,*"),
-                            Children =
-                            {
-                                new Border { [Grid.RowProperty] = 0 },
-                                (splitter = new GridSplitter { [Grid.RowProperty] = 1 }),
-                                new Border { [Grid.RowProperty] = 2 }
-                            }
-                       };
+
+            var grid = new Grid
+            {
+                RowDefinitions = new RowDefinitions("*,Auto,*"),
+                ColumnDefinitions = new ColumnDefinitions("*,*"),
+                Children =
+                {
+                    new Border { [Grid.RowProperty] = 0 },
+                    (splitter = new GridSplitter { [Grid.RowProperty] = 1 }),
+                    new Border { [Grid.RowProperty] = 2 }
+                }
+            };
 
             var root = new TestRoot { Child = grid };
             root.Measure(new Size(100, 300));
             root.Arrange(new Rect(0, 0, 100, 300));
-            Assert.Contains(splitter.Classes, ":horizontal".Equals);
+            Assert.Equal(GridResizeDirection.Rows, splitter.GetEffectiveResizeDirection());
         }
 
         [Fact]
         public void Detects_Vertical_Orientation()
         {
             GridSplitter splitter;
-            var grid = new Grid()
-                       {
-                            ColumnDefinitions = new ColumnDefinitions("*,Auto,*"),
-                            RowDefinitions = new RowDefinitions("*,*"),
-                            Children =
-                            {
-                                new Border { [Grid.ColumnProperty] = 0 },
-                                (splitter = new GridSplitter { [Grid.ColumnProperty] = 1}),
-                                new Border { [Grid.ColumnProperty] = 2 },
-                            }
-                       };
+
+            var grid = new Grid
+            {
+                ColumnDefinitions = new ColumnDefinitions("*,Auto,*"),
+                RowDefinitions = new RowDefinitions("*,*"),
+                Children =
+                {
+                    new Border { [Grid.ColumnProperty] = 0 },
+                    (splitter = new GridSplitter { [Grid.ColumnProperty] = 1 }),
+                    new Border { [Grid.ColumnProperty] = 2 },
+                }
+            };
 
             var root = new TestRoot { Child = grid };
             root.Measure(new Size(100, 300));
             root.Arrange(new Rect(0, 0, 100, 300));
-            Assert.Contains(splitter.Classes, ":vertical".Equals);
+            Assert.Equal(GridResizeDirection.Columns, splitter.GetEffectiveResizeDirection());
         }
 
         [Fact]
         public void Detects_With_Both_Auto()
         {
             GridSplitter splitter;
-            var grid = new Grid()
-                       {
-                            ColumnDefinitions = new ColumnDefinitions("Auto,Auto,Auto"),
-                            RowDefinitions = new RowDefinitions("Auto,Auto"),
-                            Children =
-                            {
-                                new Border { [Grid.ColumnProperty] = 0 },
-                                (splitter = new GridSplitter { [Grid.ColumnProperty] = 1}),
-                                new Border { [Grid.ColumnProperty] = 2 },
-                            }
-                       };
+
+            var grid = new Grid
+            {
+                ColumnDefinitions = new ColumnDefinitions("Auto,Auto,Auto"),
+                RowDefinitions = new RowDefinitions("Auto,Auto"),
+                Children =
+                {
+                    new Border { [Grid.ColumnProperty] = 0 },
+                    (splitter = new GridSplitter { [Grid.ColumnProperty] = 1 }),
+                    new Border { [Grid.ColumnProperty] = 2 },
+                }
+            };
 
             var root = new TestRoot { Child = grid };
             root.Measure(new Size(100, 300));
             root.Arrange(new Rect(0, 0, 100, 300));
-            Assert.Contains(splitter.Classes, ":vertical".Equals);
+            Assert.Equal(GridResizeDirection.Columns, splitter.GetEffectiveResizeDirection());
         }
 
         [Fact]
-        public void Horizontal_Stays_Within_Constraints()
+        public void In_First_Position_Doesnt_Throw_Exception()
+        {
+            GridSplitter splitter;
+            var grid = new Grid
+            {
+                ColumnDefinitions = new ColumnDefinitions("Auto,*,*"),
+                RowDefinitions = new RowDefinitions("*,*"),
+                Children =
+                {
+                    (splitter = new GridSplitter { [Grid.ColumnProperty] = 0 }),
+                    new Border { [Grid.ColumnProperty] = 1 },
+                    new Border { [Grid.ColumnProperty] = 2 },
+                }
+            };
+
+            var root = new TestRoot { Child = grid };
+            root.Measure(new Size(100, 300));
+            root.Arrange(new Rect(0, 0, 100, 300));
+
+            splitter.RaiseEvent(
+                new VectorEventArgs { RoutedEvent = Thumb.DragStartedEvent });
+
+            splitter.RaiseEvent(new VectorEventArgs
+            {
+                RoutedEvent = Thumb.DragDeltaEvent, Vector = new Vector(100, 1000)
+            });
+        }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void Horizontal_Stays_Within_Constraints(bool showsPreview)
         {
             var control1 = new Border { [Grid.RowProperty] = 0 };
-            var splitter = new GridSplitter
-                           {
-                               [Grid.RowProperty] = 1,
-                           };
+            var splitter = new GridSplitter { [Grid.RowProperty] = 1, ShowsPreview = showsPreview};
             var control2 = new Border { [Grid.RowProperty] = 2 };
 
-            var rowDefinitions = new RowDefinitions()
-                                 {
-                                     new RowDefinition(1, GridUnitType.Star) { MinHeight = 70, MaxHeight = 110 },
-                                     new RowDefinition(GridLength.Auto),
-                                     new RowDefinition(1, GridUnitType.Star) { MinHeight = 10, MaxHeight = 140 },
-                                 };
-
-            var grid = new Grid()
-                       {
-                            RowDefinitions = rowDefinitions,
-                            Children =
-                            {
-                                control1, splitter, control2
-                            }
-                       };
+            var rowDefinitions = new RowDefinitions
+            {
+                new RowDefinition(1, GridUnitType.Star) { MinHeight = 70, MaxHeight = 110 },
+                new RowDefinition(GridLength.Auto),
+                new RowDefinition(1, GridUnitType.Star) { MinHeight = 10, MaxHeight = 140 },
+            };
+
+            var grid = new Grid { RowDefinitions = rowDefinitions, Children = { control1, splitter, control2 } };
+
+            var root = new TestRoot
+            {
+                Child = new VisualLayerManager
+                {
+                    Child = grid
+                }
+            };
 
-            var root = new TestRoot { Child = grid };
             root.Measure(new Size(100, 200));
             root.Arrange(new Rect(0, 0, 100, 200));
 
+            splitter.RaiseEvent(
+                new VectorEventArgs { RoutedEvent = Thumb.DragStartedEvent });
+
             splitter.RaiseEvent(new VectorEventArgs
-                                {
-                                    RoutedEvent = Thumb.DragDeltaEvent,
-                                    Vector = new Vector(0, -100)
-                                });
-            Assert.Equal(rowDefinitions[0].Height, new GridLength(70, GridUnitType.Star));
-            Assert.Equal(rowDefinitions[2].Height, new GridLength(130, GridUnitType.Star));
+            {
+                RoutedEvent = Thumb.DragDeltaEvent,
+                Vector = new Vector(0, -100)
+            });
+
+            if (showsPreview)
+            {
+                Assert.Equal(rowDefinitions[0].Height, new GridLength(1, GridUnitType.Star));
+                Assert.Equal(rowDefinitions[2].Height, new GridLength(1, GridUnitType.Star));
+            }
+            else
+            {
+                Assert.Equal(rowDefinitions[0].Height, new GridLength(70, GridUnitType.Star));
+                Assert.Equal(rowDefinitions[2].Height, new GridLength(130, GridUnitType.Star));
+            }
+
             splitter.RaiseEvent(new VectorEventArgs
-                                {
-                                    RoutedEvent = Thumb.DragDeltaEvent,
-                                    Vector = new Vector(0, 100)
-                                });
-            Assert.Equal(rowDefinitions[0].Height, new GridLength(110, GridUnitType.Star));
-            Assert.Equal(rowDefinitions[2].Height, new GridLength(90, GridUnitType.Star));
-        }
+            {
+                RoutedEvent = Thumb.DragDeltaEvent,
+                Vector = new Vector(0, 100)
+            });
 
-        [Fact]
-        public void In_First_Position_Doesnt_Throw_Exception()
-        {
-            GridSplitter splitter;
-            var grid = new Grid()
-                       {
-                            ColumnDefinitions = new ColumnDefinitions("Auto,*,*"),
-                            RowDefinitions = new RowDefinitions("*,*"),
-                            Children =
-                            {
-                                (splitter = new GridSplitter { [Grid.ColumnProperty] = 0} ),
-                                new Border { [Grid.ColumnProperty] = 1 },
-                                new Border { [Grid.ColumnProperty] = 2 },
-                            }
-                       };
+            if (showsPreview)
+            {
+                Assert.Equal(rowDefinitions[0].Height, new GridLength(1, GridUnitType.Star));
+                Assert.Equal(rowDefinitions[2].Height, new GridLength(1, GridUnitType.Star));
+            }
+            else
+            {
+                Assert.Equal(rowDefinitions[0].Height, new GridLength(110, GridUnitType.Star));
+                Assert.Equal(rowDefinitions[2].Height, new GridLength(90, GridUnitType.Star));
+            }
 
-            var root = new TestRoot { Child = grid };
-            root.Measure(new Size(100, 300));
-            root.Arrange(new Rect(0, 0, 100, 300));
             splitter.RaiseEvent(new VectorEventArgs
-                                {
-                                    RoutedEvent = Thumb.DragDeltaEvent,
-                                    Vector = new Vector(100, 1000)
-                                });
+            {
+                RoutedEvent = Thumb.DragCompletedEvent
+            });
+
+            Assert.Equal(rowDefinitions[0].Height, new GridLength(110, GridUnitType.Star));
+            Assert.Equal(rowDefinitions[2].Height, new GridLength(90, GridUnitType.Star));
         }
 
-        [Fact]
-        public void Vertical_Stays_Within_Constraints()
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void Vertical_Stays_Within_Constraints(bool showsPreview)
         {
             var control1 = new Border { [Grid.ColumnProperty] = 0 };
-            var splitter = new GridSplitter
-                           {
-                               [Grid.ColumnProperty] = 1,
-                           };
+            var splitter = new GridSplitter { [Grid.ColumnProperty] = 1, ShowsPreview = showsPreview};
             var control2 = new Border { [Grid.ColumnProperty] = 2 };
 
-            var columnDefinitions = new ColumnDefinitions()
-                                    {
-                                        new ColumnDefinition(1, GridUnitType.Star) { MinWidth = 10, MaxWidth = 190 },
-                                        new ColumnDefinition(GridLength.Auto),
-                                        new ColumnDefinition(1, GridUnitType.Star) { MinWidth = 80, MaxWidth = 120 },
-                                    };
-
-            var grid = new Grid()
-                       {
-                            ColumnDefinitions = columnDefinitions,
-                            Children =
-                            {
-                                control1, splitter, control2
-                            }
-                       };
+            var columnDefinitions = new ColumnDefinitions
+            {
+                new ColumnDefinition(1, GridUnitType.Star) { MinWidth = 10, MaxWidth = 190 },
+                new ColumnDefinition(GridLength.Auto),
+                new ColumnDefinition(1, GridUnitType.Star) { MinWidth = 80, MaxWidth = 120 },
+            };
 
-            var root = new TestRoot { Child = grid };
+            var grid = new Grid { ColumnDefinitions = columnDefinitions, Children = { control1, splitter, control2 } };
+
+            var root = new TestRoot
+            {
+                Child = new VisualLayerManager
+                {
+                    Child = grid
+                }
+            };
 
             root.Measure(new Size(200, 100));
             root.Arrange(new Rect(0, 0, 200, 100));
 
+            splitter.RaiseEvent(
+                new VectorEventArgs { RoutedEvent = Thumb.DragStartedEvent });
+
+            splitter.RaiseEvent(new VectorEventArgs
+            {
+                RoutedEvent = Thumb.DragDeltaEvent,
+                Vector = new Vector(-100, 0)
+            });
+
+            if (showsPreview)
+            {
+                Assert.Equal(columnDefinitions[0].Width, new GridLength(1, GridUnitType.Star));
+                Assert.Equal(columnDefinitions[2].Width, new GridLength(1, GridUnitType.Star));
+            }
+            else
+            {
+                Assert.Equal(columnDefinitions[0].Width, new GridLength(80, GridUnitType.Star));
+                Assert.Equal(columnDefinitions[2].Width, new GridLength(120, GridUnitType.Star));
+            }
+
             splitter.RaiseEvent(new VectorEventArgs
-                                {
-                                    RoutedEvent = Thumb.DragDeltaEvent,
-                                    Vector = new Vector(-100, 0)
-                                });
-            Assert.Equal(columnDefinitions[0].Width, new GridLength(80, GridUnitType.Star));
-            Assert.Equal(columnDefinitions[2].Width, new GridLength(120, GridUnitType.Star));
+            {
+                RoutedEvent = Thumb.DragDeltaEvent,
+                Vector = new Vector(100, 0)
+            });
+
+            if (showsPreview)
+            {
+                Assert.Equal(columnDefinitions[0].Width, new GridLength(1, GridUnitType.Star));
+                Assert.Equal(columnDefinitions[2].Width, new GridLength(1, GridUnitType.Star));
+            }
+            else
+            {
+                Assert.Equal(columnDefinitions[0].Width, new GridLength(120, GridUnitType.Star));
+                Assert.Equal(columnDefinitions[2].Width, new GridLength(80, GridUnitType.Star));
+            }
+
             splitter.RaiseEvent(new VectorEventArgs
-                                {
-                                    RoutedEvent = Thumb.DragDeltaEvent,
-                                    Vector = new Vector(100, 0)
-                                });
+            {
+                RoutedEvent = Thumb.DragCompletedEvent
+            });
+
             Assert.Equal(columnDefinitions[0].Width, new GridLength(120, GridUnitType.Star));
             Assert.Equal(columnDefinitions[2].Width, new GridLength(80, GridUnitType.Star));
         }
+
+        [Theory]
+        [InlineData(Key.Up, 90, 110)]
+        [InlineData(Key.Down, 110, 90)]
+        public void Vertical_Keyboard_Input_Can_Move_Splitter(Key key, double expectedHeightFirst, double expectedHeightSecond)
+        {
+            var control1 = new Border { [Grid.RowProperty] = 0 };
+            var splitter = new GridSplitter { [Grid.RowProperty] = 1, KeyboardIncrement = 10d };
+            var control2 = new Border { [Grid.RowProperty] = 2 };
+
+            var rowDefinitions = new RowDefinitions
+            {
+                new RowDefinition(1, GridUnitType.Star),
+                new RowDefinition(GridLength.Auto),
+                new RowDefinition(1, GridUnitType.Star)
+            };
+
+            var grid = new Grid { RowDefinitions = rowDefinitions, Children = { control1, splitter, control2 } };
+
+            var root = new TestRoot
+            {
+                Child = grid
+            };
+
+            root.Measure(new Size(200, 200));
+            root.Arrange(new Rect(0, 0, 200, 200));
+
+            splitter.RaiseEvent(new KeyEventArgs
+            {
+                RoutedEvent = InputElement.KeyDownEvent,
+                Key = key
+            });
+
+            Assert.Equal(rowDefinitions[0].Height, new GridLength(expectedHeightFirst, GridUnitType.Star));
+            Assert.Equal(rowDefinitions[2].Height, new GridLength(expectedHeightSecond, GridUnitType.Star));
+        }
+
+        [Theory]
+        [InlineData(Key.Left, 90, 110)]
+        [InlineData(Key.Right, 110, 90)]
+        public void Horizontal_Keyboard_Input_Can_Move_Splitter(Key key, double expectedWidthFirst, double expectedWidthSecond)
+        {
+            var control1 = new Border { [Grid.ColumnProperty] = 0 };
+            var splitter = new GridSplitter { [Grid.ColumnProperty] = 1, KeyboardIncrement = 10d };
+            var control2 = new Border { [Grid.ColumnProperty] = 2 };
+
+            var columnDefinitions = new ColumnDefinitions
+            {
+                new ColumnDefinition(1, GridUnitType.Star),
+                new ColumnDefinition(GridLength.Auto),
+                new ColumnDefinition(1, GridUnitType.Star)
+            };
+
+            var grid = new Grid { ColumnDefinitions = columnDefinitions, Children = { control1, splitter, control2 } };
+
+            var root = new TestRoot
+            {
+                Child = grid
+            };
+
+            root.Measure(new Size(200, 200));
+            root.Arrange(new Rect(0, 0, 200, 200));
+
+            splitter.RaiseEvent(new KeyEventArgs
+            {
+                RoutedEvent = InputElement.KeyDownEvent,
+                Key = key
+            });
+
+            Assert.Equal(columnDefinitions[0].Width, new GridLength(expectedWidthFirst, GridUnitType.Star));
+            Assert.Equal(columnDefinitions[2].Width, new GridLength(expectedWidthSecond, GridUnitType.Star));
+        }
+
+        [Fact]
+        public void Pressing_Escape_Key_Cancels_Resizing()
+        {
+            var control1 = new Border { [Grid.ColumnProperty] = 0 };
+            var splitter = new GridSplitter { [Grid.ColumnProperty] = 1, KeyboardIncrement = 10d };
+            var control2 = new Border { [Grid.ColumnProperty] = 2 };
+
+            var columnDefinitions = new ColumnDefinitions
+            {
+                new ColumnDefinition(1, GridUnitType.Star),
+                new ColumnDefinition(GridLength.Auto),
+                new ColumnDefinition(1, GridUnitType.Star)
+            };
+
+            var grid = new Grid { ColumnDefinitions = columnDefinitions, Children = { control1, splitter, control2 } };
+
+            var root = new TestRoot
+            {
+                Child = grid
+            };
+
+            root.Measure(new Size(200, 200));
+            root.Arrange(new Rect(0, 0, 200, 200));
+
+            splitter.RaiseEvent(
+                new VectorEventArgs { RoutedEvent = Thumb.DragStartedEvent });
+
+            splitter.RaiseEvent(new VectorEventArgs
+            {
+                RoutedEvent = Thumb.DragDeltaEvent,
+                Vector = new Vector(-100, 0)
+            });
+
+            Assert.Equal(columnDefinitions[0].Width, new GridLength(0, GridUnitType.Star));
+            Assert.Equal(columnDefinitions[2].Width, new GridLength(200, GridUnitType.Star));
+
+            splitter.RaiseEvent(new KeyEventArgs
+            {
+                RoutedEvent = InputElement.KeyDownEvent,
+                Key = Key.Escape
+            });
+
+            Assert.Equal(columnDefinitions[0].Width, new GridLength(1, GridUnitType.Star));
+            Assert.Equal(columnDefinitions[2].Width, new GridLength(1, GridUnitType.Star));
+        }
     }
 }

tests/Avalonia.Layout.UnitTests/FullLayoutTests.cs

@@ -175,6 +175,7 @@ namespace Avalonia.Layout.UnitTests
                 x.CreateFormattedText(
                     It.IsAny<string>(),
                     It.IsAny<Typeface>(),
+                    It.IsAny<double>(),
                     It.IsAny<TextAlignment>(),
                     It.IsAny<TextWrapping>(),
                     It.IsAny<Size>(),

tests/Avalonia.RenderTests/Media/FormattedTextImplTests.cs

@@ -53,7 +53,8 @@ namespace Avalonia.Direct2D1.RenderTests.Media
         {
             var r = AvaloniaLocator.Current.GetService<IPlatformRenderInterface>();
             return r.CreateFormattedText(text,
-                new Typeface(fontFamily, fontSize, fontStyle, fontWeight),
+                new Typeface(fontFamily, fontWeight, fontStyle),
+                fontSize,
                 textAlignment,
                 wrapping,
                 widthConstraint == -1 ? Size.Infinity : new Size(widthConstraint, double.PositiveInfinity),

tests/Avalonia.UnitTests/MockPlatformRenderInterface.cs

@@ -9,11 +9,10 @@ namespace Avalonia.UnitTests
 {
     public class MockPlatformRenderInterface : IPlatformRenderInterface
     {
-        public IEnumerable<string> InstalledFontNames => new string[0];
-
         public IFormattedTextImpl CreateFormattedText(
             string text,
             Typeface typeface,
+            double fontSize,
             TextAlignment textAlignment,
             TextWrapping wrapping,
             Size constraint,
@@ -79,5 +78,10 @@ namespace Avalonia.UnitTests
         {
             throw new NotImplementedException();
         }
+
+        public IGlyphTypefaceImpl CreateGlyphTypeface(Typeface typeface)
+        {
+            return Mock.Of<IGlyphTypefaceImpl>();
+        }
     }
 }

tests/Avalonia.UnitTests/TestServices.cs

@@ -169,6 +169,7 @@ namespace Avalonia.UnitTests
                 x.CreateFormattedText(
                     It.IsAny<string>(),
                     It.IsAny<Typeface>(),
+                    It.IsAny<double>(),
                     It.IsAny<TextAlignment>(),
                     It.IsAny<TextWrapping>(),
                     It.IsAny<Size>(),

tests/Avalonia.Visuals.UnitTests/Media/FontFamilyTests.cs

@@ -19,12 +19,48 @@ namespace Avalonia.Visuals.UnitTests.Media
             Assert.Equal(new FontFamily("Arial"), fontFamily);
         }
 
-        [Fact]
-        public void Should_Be_Equal()
+        [InlineData("Font A")]
+        [InlineData("Font A, Font B")]
+        [InlineData("resm: Avalonia.Visuals.UnitTests#MyFont")]
+        [InlineData("avares://Avalonia.Visuals.UnitTests/Assets/Fonts#MyFont")]
+        [Theory]
+        public void Should_Have_Equal_Hash(string s)
         {
-            var fontFamily = new FontFamily("Arial");
+            var fontFamily = new FontFamily(s);
 
-            Assert.Equal(new FontFamily("Arial"), fontFamily);
+            Assert.Equal(new FontFamily(s).GetHashCode(), fontFamily.GetHashCode());
+        }
+
+        [InlineData("Font A, Font B", "Font B, Font A")]
+        [InlineData("Font A, Font B", "Font A, Font C")]
+        [Theory]
+        public void Should_Not_Have_Equal_Hash(string a, string b)
+        {
+            var fontFamily = new FontFamily(b);
+
+            Assert.NotEqual(new FontFamily(a).GetHashCode(), fontFamily.GetHashCode());
+        }
+
+        [InlineData("Font A")]
+        [InlineData("Font A, Font B")]
+        [InlineData("resm: Avalonia.Visuals.UnitTests#MyFont")]
+        [InlineData("avares://Avalonia.Visuals.UnitTests/Assets/Fonts#MyFont")]
+        [Theory]
+        public void Should_Be_Equal(string s)
+        {
+            var fontFamily = new FontFamily(s);
+
+            Assert.Equal(new FontFamily(s), fontFamily);
+        }
+
+        [InlineData("Font A, Font B", "Font B, Font A")]
+        [InlineData("Font A, Font B", "Font A, Font C")]
+        [Theory]
+        public void Should_Not_Be_Equal(string a, string b)
+        {
+            var fontFamily = new FontFamily(b);
+
+            Assert.NotEqual(new FontFamily(a), fontFamily);
         }
 
         [Fact]

tests/Avalonia.Visuals.UnitTests/Media/TypefaceTests.cs

@@ -7,15 +7,21 @@ namespace Avalonia.Visuals.UnitTests.Media
     public class TypefaceTests
     {
         [Fact]
-        public void Exception_Should_Be_Thrown_If_FontSize_LessThanEqualTo_0()
+        public void Exception_Should_Be_Thrown_If_FontWeight_LessThanEqualTo_Zero()
         {
-            Assert.Throws<ArgumentException>(() => new Typeface("foo", 0));
+            Assert.Throws<ArgumentException>(() => new Typeface("foo", 0, (FontStyle)12));
         }
 
         [Fact]
-        public void Exception_Should_Be_Thrown_If_FontWeight_LessThanEqualTo_0()
+        public void Should_Be_Equal()
         {
-            Assert.Throws<ArgumentException>(() => new Typeface("foo", 12, weight: 0));
+            Assert.Equal(new Typeface("Font A"), new Typeface("Font A"));
+        }
+
+        [Fact]
+        public void Should_Have_Equal_Hash()
+        {
+            Assert.Equal(new Typeface("Font A").GetHashCode(), new Typeface("Font A").GetHashCode());
         }
     }
 }

tests/Avalonia.Visuals.UnitTests/VisualTree/MockRenderInterface.cs

@@ -13,6 +13,7 @@ namespace Avalonia.Visuals.UnitTests.VisualTree
         public IFormattedTextImpl CreateFormattedText(
             string text,
             Typeface typeface,
+            double fontSize,
             TextAlignment textAlignment,
             TextWrapping wrapping,
             Size constraint,
@@ -51,6 +52,11 @@ namespace Avalonia.Visuals.UnitTests.VisualTree
             throw new NotImplementedException();
         }
 
+        public IGlyphTypefaceImpl CreateGlyphTypeface(Typeface typeface)
+        {
+            throw new NotImplementedException();
+        }
+
         public IWriteableBitmapImpl CreateWriteableBitmap(PixelSize size, Vector dpi, PixelFormat? fmt)
         {
             throw new NotImplementedException();