Merge branch 'master' into fixes/4822-shape-arrange

src/Avalonia.Controls/IScrollAnchorProvider.cs

@@ -1,4 +1,6 @@
-namespace Avalonia.Controls
+#nullable enable
+
+namespace Avalonia.Controls
 {
     /// <summary>
     /// Specifies a contract for a scrolling control that supports scroll anchoring.
@@ -8,7 +10,7 @@
         /// <summary>
         /// The currently chosen anchor element to use for scroll anchoring.
         /// </summary>
-        IControl CurrentAnchor { get; }
+        IControl? CurrentAnchor { get; }
 
         /// <summary>
         /// Registers a control as a potential scroll anchor candidate.

src/Avalonia.Controls/Panel.cs

@@ -137,6 +137,11 @@ namespace Avalonia.Controls
                     throw new NotSupportedException();
             }
 
+            InvalidateMeasureOnChildrenChanged();
+        }
+
+        private protected virtual void InvalidateMeasureOnChildrenChanged()
+        {
             InvalidateMeasure();
         }
 

src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs

@@ -512,6 +512,14 @@ namespace Avalonia.Controls.Presenters
             var generator = Owner.ItemContainerGenerator;
             var newOffset = -1.0;
 
+            if (!panel.IsMeasureValid && panel.PreviousMeasure.HasValue)
+            {
+                //before any kind of scrolling we need to make sure panel measure is valid
+                //or we risk get panel into not valid state
+                //we make a preemptive quick measure so scrolling is valid
+                panel.Measure(panel.PreviousMeasure.Value);
+            }
+
             if (index >= 0 && index < ItemCount)
             {
                 if (index <= FirstIndex)

src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs

@@ -7,6 +7,8 @@ using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.VisualTree;
 
+#nullable enable
+
 namespace Avalonia.Controls.Presenters
 {
     /// <summary>
@@ -14,6 +16,8 @@ namespace Avalonia.Controls.Presenters
     /// </summary>
     public class ScrollContentPresenter : ContentPresenter, IPresenter, IScrollable, IScrollAnchorProvider
     {
+        private const double EdgeDetectionTolerance = 0.1;
+
         /// <summary>
         /// Defines the <see cref="CanHorizontallyScroll"/> property.
         /// </summary>
@@ -64,11 +68,13 @@ namespace Avalonia.Controls.Presenters
         private bool _arranging;
         private Size _extent;
         private Vector _offset;
-        private IDisposable _logicalScrollSubscription;
+        private IDisposable? _logicalScrollSubscription;
         private Size _viewport;
-        private Dictionary<int, Vector> _activeLogicalGestureScrolls;
+        private Dictionary<int, Vector>? _activeLogicalGestureScrolls;
-        private List<IControl> _anchorCandidates;
+        private List<IControl>? _anchorCandidates;
-        private (IControl control, Rect bounds) _anchor;
+        private IControl? _anchorElement;
+        private Rect _anchorElementBounds;
+        private bool _isAnchorElementDirty;
 
         /// <summary>
         /// Initializes static members of the <see cref="ScrollContentPresenter"/> class.
@@ -90,8 +96,6 @@ namespace Avalonia.Controls.Presenters
             this.GetObservable(ChildProperty).Subscribe(UpdateScrollableSubscription);
         }
 
-        internal event EventHandler<VectorEventArgs> PreArrange;
-
         /// <summary>
         /// Gets or sets a value indicating whether the content can be scrolled horizontally.
         /// </summary>
@@ -138,7 +142,14 @@ namespace Avalonia.Controls.Presenters
         }
 
         /// <inheritdoc/>
-        IControl IScrollAnchorProvider.CurrentAnchor => _anchor.control;
+        IControl? IScrollAnchorProvider.CurrentAnchor
+        {
+            get
+            {
+                EnsureAnchorElementSelection();
+                return _anchorElement;
+            }
+        }
 
         /// <summary>
         /// Attempts to bring a portion of the target visual into view by scrolling the content.
@@ -215,16 +226,18 @@ namespace Avalonia.Controls.Presenters
 
             _anchorCandidates ??= new List<IControl>();
             _anchorCandidates.Add(element);
+            _isAnchorElementDirty = true;
         }
 
         /// <inheritdoc/>
         void IScrollAnchorProvider.UnregisterAnchorCandidate(IControl element)
         {
             _anchorCandidates?.Remove(element);
+            _isAnchorElementDirty = true;
 
-            if (_anchor.control == element)
+            if (_anchorElement == element)
             {
-                _anchor = default;
+                _anchorElement = null;
             }
         }
 
@@ -247,11 +260,6 @@ namespace Avalonia.Controls.Presenters
         /// <inheritdoc/>
         protected override Size ArrangeOverride(Size finalSize)
         {
-            PreArrange?.Invoke(this, new VectorEventArgs
-            {
-                Vector = new Vector(finalSize.Width, finalSize.Height),
-            });
-
             if (_logicalScrollSubscription != null || Child == null)
             {
                 return base.ArrangeOverride(finalSize);
@@ -271,59 +279,69 @@ namespace Avalonia.Controls.Presenters
                 // If we have an anchor and its position relative to Child has changed during the
                 // arrange then that change wasn't just due to scrolling (as scrolling doesn't adjust
                 // relative positions within Child).
-                if (_anchor.control != null &&
+                if (_anchorElement != null &&
-                    TranslateBounds(_anchor.control, Child, out var updatedBounds) &&
+                    TranslateBounds(_anchorElement, Child, out var updatedBounds) &&
-                    updatedBounds.Position != _anchor.bounds.Position)
+                    updatedBounds.Position != _anchorElementBounds.Position)
                 {
-                    var offset = updatedBounds.Position - _anchor.bounds.Position;
+                    var offset = updatedBounds.Position - _anchorElementBounds.Position;
                     return offset;
                 }
 
                 return default;
             }
 
-            // Calculate the new anchor element.
+            var isAnchoring = Offset.X >= EdgeDetectionTolerance || Offset.Y >= EdgeDetectionTolerance;
-            _anchor = CalculateCurrentAnchor();
 
-            // Do the arrange.
+            if (isAnchoring)
-            ArrangeOverrideImpl(size, -Offset);
+            {
+                // Calculate the new anchor element if necessary.
+                EnsureAnchorElementSelection();
 
-            // If the anchor moved during the arrange, we need to adjust the offset and do another arrange.
+                // Do the arrange.
-            var anchorShift = TrackAnchor();
+                ArrangeOverrideImpl(size, -Offset);
 
-            if (anchorShift != default)
+                // If the anchor moved during the arrange, we need to adjust the offset and do another arrange.
-            {
+                var anchorShift = TrackAnchor();
-                var newOffset = Offset + anchorShift;
-                var newExtent = Extent;
-                var maxOffset = new Vector(Extent.Width - Viewport.Width, Extent.Height - Viewport.Height);
 
-                if (newOffset.X > maxOffset.X)
+                if (anchorShift != default)
                 {
-                    newExtent = newExtent.WithWidth(newOffset.X + Viewport.Width);
+                    var newOffset = Offset + anchorShift;
-                }
+                    var newExtent = Extent;
+                    var maxOffset = new Vector(Extent.Width - Viewport.Width, Extent.Height - Viewport.Height);
 
-                if (newOffset.Y > maxOffset.Y)
+                    if (newOffset.X > maxOffset.X)
-                {
+                    {
-                    newExtent = newExtent.WithHeight(newOffset.Y + Viewport.Height);
+                        newExtent = newExtent.WithWidth(newOffset.X + Viewport.Width);
-                }
+                    }
 
-                Extent = newExtent;
+                    if (newOffset.Y > maxOffset.Y)
+                    {
+                        newExtent = newExtent.WithHeight(newOffset.Y + Viewport.Height);
+                    }
 
-                try
+                    Extent = newExtent;
-                {
+
-                    _arranging = true;
+                    try
-                    Offset = newOffset;
+                    {
-                }
+                        _arranging = true;
-                finally
+                        Offset = newOffset;
-                {
+                    }
-                    _arranging = false;    
+                    finally
+                    {
+                        _arranging = false;
+                    }
+
+                    ArrangeOverrideImpl(size, -Offset);
                 }
-                
+            }
+            else
+            {
                 ArrangeOverrideImpl(size, -Offset);
             }
 
             Viewport = finalSize;
             Extent = Child.Bounds.Size.Inflate(Child.Margin);
+            _isAnchorElementDirty = true;
 
             return finalSize;
         }
@@ -350,7 +368,7 @@ namespace Avalonia.Controls.Presenters
                     {
                         var logicalUnits = delta.Y / LogicalScrollItemSize;
                         delta = delta.WithY(delta.Y - logicalUnits * LogicalScrollItemSize);
-                        dy = logicalUnits * scrollable.ScrollSize.Height;
+                        dy = logicalUnits * scrollable!.ScrollSize.Height;
                     }
                     else
                         dy = delta.Y;
@@ -368,7 +386,7 @@ namespace Avalonia.Controls.Presenters
                     {
                         var logicalUnits = delta.X / LogicalScrollItemSize;
                         delta = delta.WithX(delta.X - logicalUnits * LogicalScrollItemSize);
-                        dx = logicalUnits * scrollable.ScrollSize.Width;
+                        dx = logicalUnits * scrollable!.ScrollSize.Width;
                     }
                     else
                         dx = delta.X;
@@ -405,7 +423,7 @@ namespace Avalonia.Controls.Presenters
 
                 if (Extent.Height > Viewport.Height)
                 {
-                    double height = isLogical ? scrollable.ScrollSize.Height : 50;
+                    double height = isLogical ? scrollable!.ScrollSize.Height : 50;
                     y += -e.Delta.Y * height;
                     y = Math.Max(y, 0);
                     y = Math.Min(y, Extent.Height - Viewport.Height);
@@ -413,7 +431,7 @@ namespace Avalonia.Controls.Presenters
 
                 if (Extent.Width > Viewport.Width)
                 {
-                    double width = isLogical ? scrollable.ScrollSize.Width : 50;
+                    double width = isLogical ? scrollable!.ScrollSize.Width : 50;
                     x += -e.Delta.X * width;
                     x = Math.Max(x, 0);
                     x = Math.Min(x, Extent.Width - Viewport.Width);
@@ -441,7 +459,7 @@ namespace Avalonia.Controls.Presenters
 
         private void ChildChanged(AvaloniaPropertyChangedEventArgs e)
         {
-            UpdateScrollableSubscription((IControl)e.NewValue);
+            UpdateScrollableSubscription((IControl?)e.NewValue);
 
             if (e.OldValue != null)
             {
@@ -449,7 +467,7 @@ namespace Avalonia.Controls.Presenters
             }
         }
 
-        private void UpdateScrollableSubscription(IControl child)
+        private void UpdateScrollableSubscription(IControl? child)
         {
             var scrollable = child as ILogicalScrollable;
 
@@ -498,13 +516,17 @@ namespace Avalonia.Controls.Presenters
             }
         }
 
-        private (IControl, Rect) CalculateCurrentAnchor()
+        private void EnsureAnchorElementSelection()
         {
-            if (_anchorCandidates == null)
+            if (!_isAnchorElementDirty || _anchorCandidates is null)
             {
-                return default;
+                return;
             }
 
+            _anchorElement = null;
+            _anchorElementBounds = default;
+            _isAnchorElementDirty = false;
+
             var bestCandidate = default(IControl);
             var bestCandidateDistance = double.MaxValue;
 
@@ -531,10 +553,9 @@ namespace Avalonia.Controls.Presenters
                 // bounds aren't relative to the ScrollContentPresenter itself, if they change
                 // then we know it wasn't just due to scrolling.
                 var unscrolledBounds = TranslateBounds(bestCandidate, Child);
-                return (bestCandidate, unscrolledBounds);
+                _anchorElement = bestCandidate;
+                _anchorElementBounds = unscrolledBounds;
             }
-
-            return default;
         }
 
         private bool GetViewportBounds(IControl element, out Rect bounds)

src/Avalonia.Controls/Primitives/ToggleButton.cs

@@ -94,7 +94,7 @@ namespace Avalonia.Controls.Primitives
             set 
             { 
                 SetAndRaise(IsCheckedProperty, ref _isChecked, value);
-                UpdatePseudoClasses(value);
+                UpdatePseudoClasses(IsChecked);
             }
         }
 

src/Avalonia.Controls/Repeater/ItemsRepeater.cs

@@ -267,6 +267,11 @@ namespace Avalonia.Controls
             return result;
         }
 
+        private protected override void InvalidateMeasureOnChildrenChanged()
+        {
+            // Don't invalidate measure when children change.
+        }
+
         protected override Size MeasureOverride(Size availableSize)
         {
             if (_isLayoutInProgress)
@@ -364,6 +369,12 @@ namespace Avalonia.Controls
                     {
                         var newBounds = element.Bounds;
                         virtInfo.ArrangeBounds = newBounds;
+
+                        if (!virtInfo.IsRegisteredAsAnchorCandidate)
+                        {
+                            _viewportManager.RegisterScrollAnchorCandidate(element);
+                            virtInfo.IsRegisteredAsAnchorCandidate = true;
+                        }
                     }
                 }
 
@@ -515,11 +526,14 @@ namespace Avalonia.Controls
             return element;
         }
 
-        internal void OnElementPrepared(IControl element, int index)
+        internal void OnElementPrepared(IControl element, VirtualizationInfo virtInfo)
         {
-            _viewportManager.OnElementPrepared(element);
+            _viewportManager.OnElementPrepared(element, virtInfo);
+
             if (ElementPrepared != null)
             {
+                var index = virtInfo.Index;
+
                 if (_elementPreparedArgs == null)
                 {
                     _elementPreparedArgs = new ItemsRepeaterElementPreparedEventArgs(element, index);

src/Avalonia.Controls/Repeater/ViewManager.cs

@@ -661,7 +661,7 @@ namespace Avalonia.Controls
                 children.Add(element);
             }
 
-            repeater.OnElementPrepared(element, index);
+            repeater.OnElementPrepared(element, virtInfo);
 
             // Update realized indices
             _firstRealizedElementIndexHeldByLayout = Math.Min(_firstRealizedElementIndexHeldByLayout, index);

src/Avalonia.Controls/Repeater/ViewportManager.cs

@@ -240,9 +240,14 @@ namespace Avalonia.Controls
             }
         }
 
-        public void OnElementPrepared(IControl element)
+        public void OnElementPrepared(IControl element, VirtualizationInfo virtInfo)
         {
-            _scroller?.RegisterAnchorCandidate(element);
+            // WinUI registers the element as an anchor candidate here, but I feel that's in error:
+            // at this point the element has not yet been positioned by the arrange pass so it will
+            // have its previous position, meaning that when the arrange pass moves it into its new
+            // position, an incorrect scroll anchoring will occur. Instead signal that it's not yet
+            // registered as a scroll anchor candidate.
+            virtInfo.IsRegisteredAsAnchorCandidate = false;
         }
 
         public void OnElementCleared(IControl element)
@@ -373,6 +378,11 @@ namespace Avalonia.Controls
             }
         }
 
+        public void RegisterScrollAnchorCandidate(IControl element)
+        {
+            _scroller?.RegisterAnchorCandidate(element);
+        }
+
         private IControl GetImmediateChildOfRepeater(IControl descendant)
         {
             var targetChild = descendant;

src/Avalonia.Controls/Repeater/VirtualizationInfo.cs

@@ -38,6 +38,7 @@ namespace Avalonia.Controls
         public bool IsInUniqueIdResetPool => Owner == ElementOwner.UniqueIdResetPool;
         public bool MustClearDataContext { get; set; }
         public bool KeepAlive { get; set; }
+        public bool IsRegisteredAsAnchorCandidate { get; set; }
         public ElementOwner Owner { get; private set; } = ElementOwner.ElementFactory;
         public string UniqueId { get; private set; }
 

src/Avalonia.Layout/StackLayout.cs

@@ -249,8 +249,8 @@ namespace Avalonia.Layout
                     realizationWindowOffsetInExtent + _orientation.MajorSize(realizationRect) >= 0 && realizationWindowOffsetInExtent <= majorSize)
                 {
                     anchorIndex = (int) (realizationWindowOffsetInExtent / averageElementSize);
-                    offset = anchorIndex* averageElementSize + _orientation.MajorStart(lastExtent);
                     anchorIndex = Math.Max(0, Math.Min(itemsCount - 1, anchorIndex));
+                    offset = anchorIndex* averageElementSize + _orientation.MajorStart(lastExtent);
                 }
         }
 

src/Avalonia.Visuals/Media/GlyphRun.cs

@@ -399,14 +399,14 @@ namespace Avalonia.Media
 
                 if (characterIndex > GlyphClusters[GlyphClusters.Length - 1])
                 {
-                    return _glyphClusters.End;
+                    return _glyphClusters.Length - 1;
                 }
             }
             else
             {
                 if (characterIndex < GlyphClusters[GlyphClusters.Length - 1])
                 {
-                    return _glyphClusters.End;
+                    return _glyphClusters.Length - 1;
                 }
 
                 if (characterIndex > GlyphClusters[0])

src/Avalonia.Visuals/Media/TextFormatting/TextFormatterImpl.cs

@@ -339,14 +339,6 @@ namespace Avalonia.Media.TextFormatting
                     return true;
                 }
 
-                //The line breaker isn't treating \n\r as a pair so we have to fix that here.
-                if (textRun.Text[lineBreak.PositionMeasure] == '\n'
-                    && textRun.Text[lineBreak.PositionWrap] == '\r')
-                {
-                    lineBreak = new LineBreak(lineBreak.PositionMeasure, lineBreak.PositionWrap + 1,
-                        lineBreak.Required);
-                }
-
                 return true;
             }
 

src/Windows/Avalonia.Direct2D1/Direct2D1Platform.cs

@@ -238,22 +238,46 @@ namespace Avalonia.Direct2D1
 
             width = 0;
 
-            for (var i = 0; i < glyphCount; i++)
+            var scale = (float)(glyphRun.FontRenderingEmSize / glyphTypeface.DesignEmHeight);
+
+            if (glyphRun.GlyphAdvances.IsEmpty)
+            {
+                for (var i = 0; i < glyphCount; i++)
+                {
+                    var advance = glyphTypeface.GetGlyphAdvance(glyphRun.GlyphIndices[i]) * scale;
+
+                    run.Advances[i] = advance;
+
+                    width += advance;
+                }
+            }
+            else
+            {
+                for (var i = 0; i < glyphCount; i++)
+                {
+                    var advance = (float)glyphRun.GlyphAdvances[i];
+
+                    run.Advances[i] = advance;
+
+                    width += advance;
+                }
+            }
+
+            if (glyphRun.GlyphOffsets.IsEmpty)
             {
-                run.Advances[i] = (float)glyphRun.GlyphAdvances[i];
+                return new GlyphRunImpl(run);
-                width += run.Advances[i];
             }
 
             run.Offsets = new GlyphOffset[glyphCount];
 
             for (var i = 0; i < glyphCount; i++)
             {
-                var offset = glyphRun.GlyphOffsets[i];
+                var (x, y) = glyphRun.GlyphOffsets[i];
 
                 run.Offsets[i] = new GlyphOffset
                 {
-                    AdvanceOffset = (float)offset.X,
+                    AdvanceOffset = (float)x,
-                    AscenderOffset = (float)offset.Y
+                    AscenderOffset = (float)y
                 };
             }
 

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

@@ -1,6 +1,6 @@
-using System.Globalization;
+using System;
+using System.Globalization;
 using Avalonia.Media;
-using Avalonia.Media.TextFormatting;
 using Avalonia.Media.TextFormatting.Unicode;
 using Avalonia.Platform;
 using Avalonia.Utilities;
@@ -15,51 +15,9 @@ namespace Avalonia.Direct2D1.Media
         {
             using (var buffer = new Buffer())
             {
-                buffer.ContentType = ContentType.Unicode;
+                FillBuffer(buffer, text);
 
-                var breakCharPosition = text.Length - 1;
+                buffer.Language = new Language(culture ?? CultureInfo.CurrentCulture);
-
-                var codepoint = Codepoint.ReadAt(text, breakCharPosition, out var count);
-
-                if (codepoint.IsBreakChar)
-                {
-                    var breakCharCount = 1;
-
-                    if (text.Length > 1)
-                    {
-                        var previousCodepoint = Codepoint.ReadAt(text, breakCharPosition - count, out _);
-
-                        if (codepoint == '\r' && previousCodepoint == '\n'
-                            || codepoint == '\n' && previousCodepoint == '\r')
-                        {
-                            breakCharCount = 2;
-                        }
-                    }
-
-                    if (breakCharPosition != text.Start)
-                    {
-                        buffer.AddUtf16(text.Buffer.Span.Slice(0, text.Length - breakCharCount));
-                    }
-
-                    var cluster = buffer.GlyphInfos.Length > 0 ?
-                        buffer.GlyphInfos[buffer.Length - 1].Cluster + 1 :
-                        (uint)text.Start;
-
-                    switch (breakCharCount)
-                    {
-                        case 1:
-                            buffer.Add('\u200C', cluster);
-                            break;
-                        case 2:
-                            buffer.Add('\u200C', cluster);
-                            buffer.Add('\u200D', cluster);
-                            break;
-                    }
-                }
-                else
-                {
-                    buffer.AddUtf16(text.Buffer.Span);
-                }
 
                 buffer.GuessSegmentProperties();
 
@@ -67,44 +25,38 @@ namespace Avalonia.Direct2D1.Media
 
                 var font = ((GlyphTypefaceImpl)glyphTypeface.PlatformImpl).Font;
 
-                buffer.Language = new Language(culture ?? CultureInfo.CurrentCulture);
-
                 font.Shape(buffer);
 
                 font.GetScale(out var scaleX, out _);
 
                 var textScale = fontRenderingEmSize / scaleX;
 
-                var len = buffer.Length;
+                var bufferLength = buffer.Length;
 
-                var info = buffer.GetGlyphInfoSpan();
+                var glyphInfos = buffer.GetGlyphInfoSpan();
 
-                var pos = buffer.GetGlyphPositionSpan();
+                var glyphPositions = buffer.GetGlyphPositionSpan();
 
-                var glyphIndices = new ushort[len];
+                var glyphIndices = new ushort[bufferLength];
 
-                var clusters = new ushort[len];
+                var clusters = new ushort[bufferLength];
 
-                var glyphAdvances = new double[len];
+                double[] glyphAdvances = null;
 
-                var glyphOffsets = new Vector[len];
+                Vector[] glyphOffsets = null;
 
-                for (var i = 0; i < len; i++)
+                for (var i = 0; i < bufferLength; i++)
                 {
-                    glyphIndices[i] = (ushort)info[i].Codepoint;
+                    glyphIndices[i] = (ushort)glyphInfos[i].Codepoint;
-
-                    clusters[i] = (ushort)(text.Start + info[i].Cluster);
-
-                    var advanceX = pos[i].XAdvance * textScale;
-                    // Depends on direction of layout
-                    //var advanceY = pos[i].YAdvance * textScale;
 
-                    glyphAdvances[i] = advanceX;
+                    clusters[i] = (ushort)glyphInfos[i].Cluster;
 
-                    var offsetX = pos[i].XOffset * textScale;
+                    if (!glyphTypeface.IsFixedPitch)
-                    var offsetY = pos[i].YOffset * textScale;
+                    {
+                        SetAdvance(glyphPositions, i, textScale, ref glyphAdvances);
+                    }
 
-                    glyphOffsets[i] = new Vector(offsetX, offsetY);
+                    SetOffset(glyphPositions, i, textScale, ref glyphOffsets);
                 }
 
                 return new GlyphRun(glyphTypeface, fontRenderingEmSize,
@@ -115,5 +67,79 @@ namespace Avalonia.Direct2D1.Media
                     new ReadOnlySlice<ushort>(clusters));
             }
         }
+
+        private static void FillBuffer(Buffer buffer, ReadOnlySlice<char> text)
+        {
+            buffer.ContentType = ContentType.Unicode;
+
+            var i = 0;
+
+            while (i < text.Length)
+            {
+                var codepoint = Codepoint.ReadAt(text, i, out var count);
+
+                var cluster = (uint)(text.Start + i);
+
+                if (codepoint.IsBreakChar)
+                {
+                    if (i + 1 < text.Length)
+                    {
+                        var nextCodepoint = Codepoint.ReadAt(text, i + 1, out _);
+
+                        if (nextCodepoint == '\r' && codepoint == '\n' || nextCodepoint == '\n' && codepoint == '\r')
+                        {
+                            count++;
+
+                            buffer.Add('\u200C', cluster);
+
+                            buffer.Add('\u200D', cluster);
+                        }
+                        else
+                        {
+                            buffer.Add('\u200C', cluster);
+                        }
+                    }
+                    else
+                    {
+                        buffer.Add('\u200C', cluster);
+                    }
+                }
+                else
+                {
+                    buffer.Add(codepoint, cluster);
+                }
+
+                i += count;
+            }
+        }
+
+        private static void SetOffset(ReadOnlySpan<GlyphPosition> glyphPositions, int index, double textScale,
+            ref Vector[] offsetBuffer)
+        {
+            var position = glyphPositions[index];
+
+            if (position.XOffset == 0 && position.YOffset == 0)
+            {
+                return;
+            }
+
+            offsetBuffer ??= new Vector[glyphPositions.Length];
+
+            var offsetX = position.XOffset * textScale;
+
+            var offsetY = position.YOffset * textScale;
+
+            offsetBuffer[index] = new Vector(offsetX, offsetY);
+        }
+
+        private static void SetAdvance(ReadOnlySpan<GlyphPosition> glyphPositions, int index, double textScale,
+            ref double[] advanceBuffer)
+        {
+            advanceBuffer ??= new double[glyphPositions.Length];
+
+            // Depends on direction of layout
+            // advanceBuffer[index] = buffer.GlyphPositions[index].YAdvance * textScale;
+            advanceBuffer[index] = glyphPositions[index].XAdvance * textScale;
+        }
     }
 }

tests/Avalonia.Controls.UnitTests/ListBoxTests.cs

@@ -407,6 +407,53 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(1, raised);
         }
 
+        [Fact]
+        public void Adding_And_Selecting_Item_With_AutoScrollToSelectedItem_Should_NotHide_FirstItem()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var items = new AvaloniaList<string>();
+
+                var wnd = new Window() { Width = 100, Height = 100, IsVisible = true };
+
+                var target = new ListBox()
+                {
+                    VerticalAlignment = Layout.VerticalAlignment.Top,
+                    AutoScrollToSelectedItem = true,
+                    Width = 50,
+                    VirtualizationMode = ItemVirtualizationMode.Simple,
+                    ItemTemplate = new FuncDataTemplate<object>((c, _) => new Border() { Height = 10 }),
+                    Items = items,
+                };
+                wnd.Content = target;
+
+                var lm = wnd.LayoutManager;
+
+                lm.ExecuteInitialLayoutPass();
+
+                var panel = target.Presenter.Panel;
+
+                items.Add("Item 1");
+                target.Selection.Select(0);
+                lm.ExecuteLayoutPass();
+
+                Assert.Equal(1, panel.Children.Count);
+
+                items.Add("Item 2");
+                target.Selection.Select(1);
+                lm.ExecuteLayoutPass();
+
+                Assert.Equal(2, panel.Children.Count);
+
+                //make sure we have enough space to show all items
+                Assert.True(panel.Bounds.Height >= panel.Children.Sum(c => c.Bounds.Height));
+
+                //make sure we show items and they completelly visible, not only partially
+                Assert.True(panel.Children[0].Bounds.Top >= 0 && panel.Children[0].Bounds.Bottom <= panel.Bounds.Height, "first item is not completelly visible!");
+                Assert.True(panel.Children[1].Bounds.Top >= 0 && panel.Children[1].Bounds.Bottom <= panel.Bounds.Height, "second item is not completelly visible!");
+            }
+        }
+
         private FuncControlTemplate ListBoxTemplate()
         {
             return new FuncControlTemplate<ListBox>((parent, scope) =>

tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLayoutTests.cs

@@ -417,7 +417,6 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
         [Theory]
         [InlineData("abcde\r\n", 7)] // Carriage Return + Line Feed
-        [InlineData("abcde\n\r", 7)] // This isn't valid but we somehow have to support it.
         [InlineData("abcde\u000A", 6)] // Line Feed
         [InlineData("abcde\u000B", 6)] // Vertical Tab
         [InlineData("abcde\u000C", 6)] // Form Feed
@@ -575,6 +574,27 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
             }
         }
 
+        [Fact]
+        public void Should_Process_Multiple_NewLines_Properly()
+        {
+            using (Start())
+            {
+                var text = "123\r\n\r\n456\r\n\r\n";
+                var layout = new TextLayout(
+                    text,
+                    Typeface.Default,
+                    12.0f,
+                    Brushes.Black);
+
+                Assert.Equal(5, layout.TextLines.Count);
+
+                Assert.Equal("123\r\n", layout.TextLines[0].TextRuns[0].Text);
+                Assert.Equal("\r\n", layout.TextLines[1].TextRuns[0].Text);
+                Assert.Equal("456\r\n", layout.TextLines[2].TextRuns[0].Text);
+                Assert.Equal("\r\n", layout.TextLines[3].TextRuns[0].Text);
+            }
+        }
+
         [Fact]
         public void Should_Wrap_Min_OneCharacter_EveryLine()
         {