BiDiAlgorithm and BiDiData instances are reusable

src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs

@@ -8,17 +8,17 @@ namespace Avalonia.Media.TextFormatting
     public sealed class ShapedBuffer : IList<GlyphInfo>, IDisposable
     {
         private static readonly IComparer<GlyphInfo> s_clusterComparer = new CompareClusters();
-        private bool _bufferRented;
-
-        public ShapedBuffer(ReadOnlyMemory<char> text, int bufferLength, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel) :
-            this(text,
-                new ArraySlice<GlyphInfo>(ArrayPool<GlyphInfo>.Shared.Rent(bufferLength), 0, bufferLength),
-                glyphTypeface,
-                fontRenderingEmSize,
-                bidiLevel)
+
+        private GlyphInfo[]? _rentedBuffer;
+
+        public ShapedBuffer(ReadOnlyMemory<char> text, int bufferLength, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel)
         {
-            _bufferRented = true;
-            Length = bufferLength;
+            _rentedBuffer = ArrayPool<GlyphInfo>.Shared.Rent(bufferLength);
+            Text = text;
+            GlyphInfos = new ArraySlice<GlyphInfo>(_rentedBuffer, 0, bufferLength);
+            GlyphTypeface = glyphTypeface;
+            FontRenderingEmSize = fontRenderingEmSize;
+            BidiLevel = bidiLevel;
         }
 
         internal ShapedBuffer(ReadOnlyMemory<char> text, ArraySlice<GlyphInfo> glyphInfos, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel)
@@ -28,12 +28,12 @@ namespace Avalonia.Media.TextFormatting
             GlyphTypeface = glyphTypeface;
             FontRenderingEmSize = fontRenderingEmSize;
             BidiLevel = bidiLevel;
-            Length = GlyphInfos.Length;
         }
 
-        internal ArraySlice<GlyphInfo> GlyphInfos { get; }
-        
-        public int Length { get; }
+        internal ArraySlice<GlyphInfo> GlyphInfos { get; private set; }
+
+        public int Length
+            => GlyphInfos.Length;
 
         public IGlyphTypeface GlyphTypeface { get; }
 
@@ -271,18 +271,11 @@ namespace Avalonia.Media.TextFormatting
 
         public void Dispose()
         {
-            GC.SuppressFinalize(this);
-            if (_bufferRented)
-            {
-                GlyphInfos.ReturnRent();
-            }
-        }
-
-        ~ShapedBuffer()
-        {
-            if (_bufferRented)
+            if (_rentedBuffer is not null)
             {
-                GlyphInfos.ReturnRent();
+                ArrayPool<GlyphInfo>.Shared.Return(_rentedBuffer);
+                _rentedBuffer = null;
+                GlyphInfos = ArraySlice<GlyphInfo>.Empty; // ensure we don't misuse the returned array
             }
         }
     }

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

@@ -11,6 +11,10 @@ namespace Avalonia.Media.TextFormatting
     internal class TextFormatterImpl : TextFormatter
     {
         private static readonly char[] s_empty = { ' ' };
+        private static readonly char[] s_defaultText = new char[TextRun.DefaultTextSourceLength];
+
+        [ThreadStatic] private static BidiData? t_bidiData;
+        [ThreadStatic] private static BidiAlgorithm? t_bidiAlgorithm;
 
         /// <inheritdoc cref="TextFormatter.FormatLine"/>
         public override TextLine FormatLine(ITextSource textSource, int firstTextSourceIndex, double paragraphWidth,
@@ -169,21 +173,24 @@ namespace Avalonia.Media.TextFormatting
             }
 
 
-            using var biDiData = new BidiData((sbyte)flowDirection);
+            var biDiData = t_bidiData ??= new BidiData();
+            biDiData.Reset();
+            biDiData.ParagraphEmbeddingLevel = (sbyte)flowDirection;
 
             foreach (var textRun in textRuns)
             {
-                if (textRun.Text.IsEmpty)
-                {
-                    biDiData.Append(new char[textRun.Length]);
-                }
+                ReadOnlySpan<char> text;
+                if (!textRun.Text.IsEmpty)
+                    text = textRun.Text.Span;
+                else if (textRun.Length == TextRun.DefaultTextSourceLength)
+                    text = s_defaultText;
                 else
-                {
-                    biDiData.Append(textRun.Text.Span);
-                }
+                    text = new char[textRun.Length];
+
+                biDiData.Append(text);
             }
 
-            using var biDi = new BidiAlgorithm();
+            var biDi = t_bidiAlgorithm ??= new BidiAlgorithm();
 
             biDi.Process(biDiData);
 

src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs

@@ -6,7 +6,6 @@ using System;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using System.Threading;
-using Avalonia.Collections.Pooled;
 using Avalonia.Utilities;
 
 namespace Avalonia.Media.TextFormatting.Unicode
@@ -28,7 +27,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
     /// as much as possible.
     /// </para>
     /// </remarks>
-    internal struct BidiAlgorithm : IDisposable
+    internal sealed class BidiAlgorithm
     {
         /// <summary>
         /// The original BiDiClass classes as provided by the caller
@@ -67,7 +66,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// The forward mapping maps the start index to the end index.
         /// The reverse mapping maps the end index to the start index.
         /// </remarks>
-        private BidiDictionary<int, int>? _isolatePairs;
+        private readonly BidiDictionary<int, int> _isolatePairs = new();
 
         /// <summary>
         /// The working BiDi classes
@@ -98,7 +97,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// The status stack used during resolution of explicit
         /// embedding and isolating runs
         /// </summary>
-        private readonly Stack<Status> _statusStack = new Stack<Status>();
+        private readonly Stack<Status> _statusStack = new();
 
         /// <summary>
         /// Mapping used to virtually remove characters for rule X9
@@ -108,7 +107,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <summary>
         /// Re-usable list of level runs
         /// </summary>
-        private readonly List<LevelRun> _levelRuns = new List<LevelRun>();
+        private readonly List<LevelRun> _levelRuns = new();
 
         /// <summary>
         /// Mapping for the current isolating sequence, built
@@ -119,7 +118,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <summary>
         /// A stack of pending isolate openings used by FindIsolatePairs()
         /// </summary>
-        private Stack<int>? _pendingIsolateOpenings;
+        private readonly Stack<int> _pendingIsolateOpenings = new();
 
         /// <summary>
         /// The level of the isolating run currently being processed
@@ -175,12 +174,12 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// Reusable list of pending opening brackets used by the
         /// LocatePairedBrackets method
         /// </summary>
-        private readonly List<int> _pendingOpeningBrackets = new List<int>();
+        private readonly List<int> _pendingOpeningBrackets = new();
 
         /// <summary>
         /// Resolved list of paired brackets
         /// </summary>
-        private readonly List<BracketPair> _pairedBrackets = new List<BracketPair>();
+        private readonly List<BracketPair> _pairedBrackets = new();
 
         /// <summary>
         /// Initializes a new instance of the <see cref="BidiAlgorithm"/> class.
@@ -228,7 +227,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
             ArraySlice<sbyte>? outLevels)
         {
             // Reset state
-            _isolatePairs?.Clear();
+            _isolatePairs.Clear();
             _workingClassesBuffer.Clear();
             _levelRuns.Clear();
             _resolvedLevelsBuffer.Clear();
@@ -324,7 +323,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
                         // Skip isolate pairs
                         // (Because we're working with a slice, we need to adjust the indices
                         //  we're using for the isolatePairs map)
-                        if (_isolatePairs?.TryGetValue(data.Start + i, out i) == true)
+                        if (_isolatePairs.TryGetValue(data.Start + i, out i))
                         {
                             i -= data.Start;
                         }
@@ -359,7 +358,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
             _hasIsolates = false;
 
             // BD9...
-            _pendingIsolateOpenings?.Clear();
+            _pendingIsolateOpenings.Clear();
             
             for (var i = 0; i < _originalClasses.Length; i++)
             {
@@ -371,16 +370,14 @@ namespace Avalonia.Media.TextFormatting.Unicode
                     case BidiClass.RightToLeftIsolate:
                     case BidiClass.FirstStrongIsolate:
                     {
-                        _pendingIsolateOpenings ??= new Stack<int>();
                         _pendingIsolateOpenings.Push(i);
                         _hasIsolates = true;
                         break;
                     }
                     case BidiClass.PopDirectionalIsolate:
                     {
-                        if (_pendingIsolateOpenings?.Count > 0)
+                        if (_pendingIsolateOpenings.Count > 0)
                         {
-                            _isolatePairs ??= new BidiDictionary<int, int>();
                             _isolatePairs.Add(_pendingIsolateOpenings.Pop(), i);
                         }
 
@@ -501,7 +498,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
                         if (resolvedIsolate == BidiClass.FirstStrongIsolate)
                         {
-                            if (_isolatePairs == null || !_isolatePairs.TryGetValue(i, out var endOfIsolate))
+                            if (!_isolatePairs.TryGetValue(i, out var endOfIsolate))
                             {
                                 endOfIsolate = _originalClasses.Length;
                             }
@@ -832,7 +829,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
                     var lastCharacterIndex = _isolatedRunMapping[_isolatedRunMapping.Length - 1];
                     var lastType = _originalClasses[lastCharacterIndex];
                     if ((lastType == BidiClass.LeftToRightIsolate || lastType == BidiClass.RightToLeftIsolate || lastType == BidiClass.FirstStrongIsolate) &&
-                            _isolatePairs?.TryGetValue(lastCharacterIndex, out var nextRunIndex) == true)
+                            _isolatePairs.TryGetValue(lastCharacterIndex, out var nextRunIndex))
                     {
                         // Find the continuing run index
                         runIndex = FindRunForIndex(nextRunIndex);
@@ -855,13 +852,14 @@ namespace Avalonia.Media.TextFormatting.Unicode
         private void ProcessIsolatedRunSequence(BidiClass sos, BidiClass eos, int runLevel)
         {
             // Create mappings onto the underlying data
-            _runResolvedClasses = new MappedArraySlice<BidiClass>(_workingClasses, _isolatedRunMapping.AsSlice());
-            _runOriginalClasses = new MappedArraySlice<BidiClass>(_originalClasses, _isolatedRunMapping.AsSlice());
-            _runLevels = new MappedArraySlice<sbyte>(_resolvedLevels, _isolatedRunMapping.AsSlice());
+            var isolatedRunMapping = _isolatedRunMapping.AsSlice();
+            _runResolvedClasses = new MappedArraySlice<BidiClass>(_workingClasses, isolatedRunMapping);
+            _runOriginalClasses = new MappedArraySlice<BidiClass>(_originalClasses, isolatedRunMapping);
+            _runLevels = new MappedArraySlice<sbyte>(_resolvedLevels, isolatedRunMapping);
             if (_hasBrackets)
             {
-                _runBiDiPairedBracketTypes = new MappedArraySlice<BidiPairedBracketType>(_pairedBracketTypes, _isolatedRunMapping.AsSlice());
-                _runPairedBracketValues = new MappedArraySlice<int>(_pairedBracketValues, _isolatedRunMapping.AsSlice());
+                _runBiDiPairedBracketTypes = new MappedArraySlice<BidiPairedBracketType>(_pairedBracketTypes, isolatedRunMapping);
+                _runPairedBracketValues = new MappedArraySlice<int>(_pairedBracketValues, isolatedRunMapping);
             }
 
             _runLevel = runLevel;
@@ -1717,13 +1715,5 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
             public BidiClass Eos { get; }
         }
-
-        public void Dispose()
-        {
-            _workingClassesBuffer.Dispose();
-            _resolvedLevelsBuffer.Dispose();
-            _x9Map.Dispose();
-            _isolatedRunMapping.Dispose();
-        }
     }
 }

src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs

@@ -11,7 +11,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
     /// Represents a unicode string and all associated attributes
     /// for each character required for the bidirectional Unicode algorithm
     /// </summary>
-    internal struct BidiData : IDisposable
+    internal sealed class BidiData
     {
         private ArrayBuilder<BidiClass> _classes;
         private ArrayBuilder<BidiPairedBracketType> _pairedBracketTypes;
@@ -20,12 +20,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         private ArrayBuilder<BidiPairedBracketType> _savedPairedBracketTypes;
         private ArrayBuilder<sbyte> _tempLevelBuffer;
 
-        public BidiData(sbyte paragraphEmbeddingLevel)
-        {
-            ParagraphEmbeddingLevel = paragraphEmbeddingLevel;
-        }
-
-        public sbyte ParagraphEmbeddingLevel { get; private set; }
+        public sbyte ParagraphEmbeddingLevel { get; set; }
 
         public bool HasBrackets { get; private set; }
 
@@ -36,7 +31,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <summary>
         /// Gets the length of the data held by the BidiData
         /// </summary>
-        public int Length{get; private set; }
+        public int Length { get; private set; }
 
         /// <summary>
         /// Gets the bidi character type of each code point
@@ -182,14 +177,27 @@ namespace Avalonia.Media.TextFormatting.Unicode
             return _tempLevelBuffer.Add(length, false);
         }
 
-        public void Dispose()
+        /// <summary>
+        /// Resets the bidi data to a clean state.
+        /// </summary>
+        public void Reset()
         {
-            _classes.Dispose();
-            _pairedBracketTypes.Dispose();
-            _pairedBracketValues.Dispose();
-            _savedClasses.Dispose();
-            _savedPairedBracketTypes.Dispose();
-            _tempLevelBuffer.Dispose();
+            _classes.Clear();
+            _pairedBracketTypes.Clear();
+            _pairedBracketValues.Clear();
+            _savedClasses.Clear();
+            _savedPairedBracketTypes.Clear();
+            _tempLevelBuffer.Clear();
+
+            ParagraphEmbeddingLevel = 0;
+            HasBrackets = false;
+            HasEmbeddings = false;
+            HasIsolates = false;
+            Length = 0;
+
+            Classes = default;
+            PairedBracketTypes = default;
+            PairedBracketValues = default;
         }
     }
 }

src/Avalonia.Base/Utilities/ArrayBuilder.cs

@@ -3,7 +3,6 @@
 // Ported from: https://github.com/SixLabors/Fonts/
 
 using System;
-using System.Buffers;
 using System.Runtime.CompilerServices;
 
 namespace Avalonia.Utilities
@@ -12,7 +11,7 @@ namespace Avalonia.Utilities
     /// A helper type for avoiding allocations while building arrays.
     /// </summary>
     /// <typeparam name="T">The type of item contained in the array.</typeparam>
-    internal struct ArrayBuilder<T> : IDisposable
+    internal struct ArrayBuilder<T>
         where T : struct
     {
         private const int DefaultCapacity = 4;
@@ -136,7 +135,7 @@ namespace Avalonia.Utilities
             }
 
             // Same expansion algorithm as List<T>.
-            var newCapacity = length == 0 ? DefaultCapacity : length * 2;
+            var newCapacity = length == 0 ? DefaultCapacity : (uint)length * 2u;
 
             if (newCapacity > MaxCoreClrArrayLength)
             {
@@ -145,15 +144,14 @@ namespace Avalonia.Utilities
 
             if (newCapacity < min)
             {
-                newCapacity = min;
+                newCapacity = (uint)min;
             }
             
-            var array = ArrayPool<T>.Shared.Rent(newCapacity);
+            var array = new T[newCapacity];
 
             if (_size > 0)
             {
                 Array.Copy(_data!, array, _size);
-                ArrayPool<T>.Shared.Return(_data!);
             }
 
             _data = array;
@@ -182,13 +180,5 @@ namespace Avalonia.Utilities
         /// <returns>The <see cref="ArraySlice{T}"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public ArraySlice<T> AsSlice(int start, int length) => new ArraySlice<T>(_data!, start, length);
-        
-        public void Dispose()
-        {
-            if (_data != null)
-            {
-                ArrayPool<T>.Shared.Return(_data);
-            }
-        }
     }
 }

src/Avalonia.Base/Utilities/ArraySlice.cs

@@ -3,7 +3,6 @@
 // Ported from: https://github.com/SixLabors/Fonts/
 
 using System;
-using System.Buffers;
 using System.Collections;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
@@ -186,13 +185,6 @@ namespace Avalonia.Utilities
 
         /// <inheritdoc/>
         int IReadOnlyCollection<T>.Count => Length;
-
-        public void ReturnRent()
-        {
-            if (_data != null)
-            {
-                ArrayPool<T>.Shared.Return(_data);
-            }
-        }
     }
 }
+

src/Avalonia.Controls/TextBoxTextInputMethodClient.cs

@@ -79,7 +79,7 @@ namespace Avalonia.Controls
             {
                 if(run.Length > 0)
                 {
-#if NET6_0
+#if NET6_0_OR_GREATER
                     builder.Append(run.Text.Span);
 #else
                     builder.Append(run.Text.Span.ToArray());

tests/Avalonia.Base.UnitTests/Media/TextFormatting/BiDiClassTests.cs

@@ -1,8 +1,6 @@
-using System;
-using System.Linq;
+using System.Linq;
 using System.Runtime.InteropServices;
 using System.Text;
-using Avalonia.Media.TextFormatting;
 using Avalonia.Media.TextFormatting.Unicode;
 using Xunit;
 using Xunit.Abstractions;
@@ -32,7 +30,7 @@ namespace Avalonia.Visuals.UnitTests.Media.TextFormatting
         private bool Run(BiDiClassData t)
         {
             var bidi = new BidiAlgorithm();
-            var bidiData = new BidiData(t.ParagraphLevel);
+            var bidiData = new BidiData { ParagraphEmbeddingLevel = t.ParagraphLevel };
         
             var text = Encoding.UTF32.GetString(MemoryMarshal.Cast<int, byte>(t.CodePoints).ToArray());