Optimize converters for GridLength, ColumnDefinition, and RowDefinition

src/Controls/src/Core/ColumnDefinitionCollection.cs

@@ -1,4 +1,5 @@
 #nullable disable
+using System.Collections.Generic;
 namespace Microsoft.Maui.Controls
 {
 	/// <include file="../../docs/Microsoft.Maui.Controls/ColumnDefinitionCollection.xml" path="Type[@FullName='Microsoft.Maui.Controls.ColumnDefinitionCollection']/Docs/*" />
@@ -11,5 +12,9 @@ public ColumnDefinitionCollection() : base()
 		public ColumnDefinitionCollection(params ColumnDefinition[] definitions) : base(definitions)
 		{
 		}
+
+		internal ColumnDefinitionCollection(List<ColumnDefinition> definitions, bool copy) : base(definitions, copy)
+		{
+		}
 	}
 }

src/Controls/src/Core/ColumnDefinitionCollectionTypeConverter.cs

@@ -1,8 +1,10 @@
 #nullable disable
 using System;
+using System.Buffers;
+using System.Collections.Generic;
 using System.ComponentModel;
 using System.Globalization;
-using System.Linq;
+using System.Text;
 using Microsoft.Maui.Controls.Xaml;
 
 namespace Microsoft.Maui.Controls
@@ -19,28 +21,61 @@ public override bool CanConvertTo(ITypeDescriptorContext context, Type destinati
 
 		public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
 		{
-			var strValue = value?.ToString();
+			var strValue = value as string ?? value?.ToString()
+				?? throw new InvalidOperationException(string.Format("Cannot convert \"{0}\" into {1}", value, typeof(ColumnDefinitionCollection)));
 
-			if (strValue != null)
+			// fast path for no value or empty string
+			if (strValue.Length == 0)
+				return new ColumnDefinitionCollection();
+
+#if NET6_0_OR_GREATER
+			var unsplit = (ReadOnlySpan<char>)strValue;
+			var count = unsplit.Count(',') + 1;
+			var definitions = new List<ColumnDefinition>(count);
+			foreach (var range in unsplit.Split(','))
+			{
+				var length = GridLengthTypeConverter.ParseStringToGridLength(unsplit[range]);
+				definitions.Add(new ColumnDefinition(length));
+			}
+#else
+			var lengths = strValue.Split(',');
+			var count = lengths.Length;
+			var definitions = new List<ColumnDefinition>(count);
+			foreach (var lengthStr in lengths)
 			{
-				var lengths = strValue.Split(',');
-				var converter = new GridLengthTypeConverter();
-				var definitions = new ColumnDefinition[lengths.Length];
-				for (var i = 0; i < lengths.Length; i++)
-					definitions[i] = new ColumnDefinition { Width = (GridLength)converter.ConvertFromInvariantString(lengths[i]) };
-				return new ColumnDefinitionCollection(definitions);
+				var length = GridLengthTypeConverter.ParseStringToGridLength(lengthStr);
+				definitions.Add(new ColumnDefinition(length));
 			}
+#endif
 
-			throw new InvalidOperationException(string.Format("Cannot convert \"{0}\" into {1}", strValue, typeof(ColumnDefinitionCollection)));
+			return new ColumnDefinitionCollection(definitions, copy: false);
 		}
 
 
 		public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
 		{
-			if (value is not ColumnDefinitionCollection cdc)
+			if (value is not ColumnDefinitionCollection definitions)
 				throw new NotSupportedException();
-			var converter = new GridLengthTypeConverter();
-			return string.Join(", ", cdc.Select(cd => converter.ConvertToInvariantString(cd.Width)));
+
+			var count = definitions.Count;
+
+			// fast path for empty or single definitions
+			if (count == 0)
+				return string.Empty;
+			if (count == 1)
+				return GridLengthTypeConverter.ConvertToString(definitions[0].Width);
+
+			// for multiple items
+			var pool = ArrayPool<string>.Shared;
+			var rentedArray = pool.Rent(definitions.Count);
+			for (var i = 0; i < definitions.Count; i++)
+			{
+				var definition = definitions[i];
+				rentedArray[i] = GridLengthTypeConverter.ConvertToString(definition.Width);
+			}
+			var result = string.Join(", ", rentedArray, 0, definitions.Count);
+			pool.Return(rentedArray);
+			return result;
 		}
 	}
 }

src/Controls/src/Core/DefinitionCollection.cs

@@ -14,6 +14,8 @@ public class DefinitionCollection<T> : IList<T>, ICollection<T> where T : IDefin
 
 		internal DefinitionCollection(params T[] items) => _internalList = new List<T>(items);
 
+		internal DefinitionCollection(List<T> items, bool copy) => _internalList = copy ? new List<T>(items) : items;
+
 		public void Add(T item)
 		{
 			_internalList.Add(item);

src/Controls/src/Core/GridLengthTypeConverter.cs

@@ -17,33 +17,69 @@ public override bool CanConvertTo(ITypeDescriptorContext context, Type destinati
 
 		public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
 		{
-			var strValue = value?.ToString();
+			var strValue = value as string ?? value?.ToString();
 
-			if (strValue == null)
+			if (strValue is null)
 				return null;
 
-			strValue = strValue.Trim();
-			if (string.Compare(strValue, "auto", StringComparison.OrdinalIgnoreCase) == 0)
-				return GridLength.Auto;
-			if (string.Compare(strValue, "*", StringComparison.OrdinalIgnoreCase) == 0)
-				return new GridLength(1, GridUnitType.Star);
-			if (strValue.EndsWith("*", StringComparison.Ordinal) && double.TryParse(strValue.Substring(0, strValue.Length - 1), NumberStyles.Number, CultureInfo.InvariantCulture, out var length))
-				return new GridLength(length, GridUnitType.Star);
-			if (double.TryParse(strValue, NumberStyles.Number, CultureInfo.InvariantCulture, out length))
-				return new GridLength(length);
-
-			throw new FormatException();
+			return ParseStringToGridLength(strValue);
+		}
+
+#if NET6_0_OR_GREATER
+		internal static GridLength ParseStringToGridLength(ReadOnlySpan<char> value)
+#else
+		internal static GridLength ParseStringToGridLength(string value)
+#endif
+		{
+			value = value.Trim();
+
+			if (value.Length != 0)
+			{
+				if (value.Length == 4 && value.Equals("auto", StringComparison.OrdinalIgnoreCase))
+					return GridLength.Auto;
+
+				if (value.Length == 1 && value[0] == '*')
+					return GridLength.Star;
+
+#if NET6_0_OR_GREATER
+				var lastChar = value[^1];
+#else
+    			var lastChar = value[value.Length - 1];
+#endif
+				if (lastChar == '*')
+				{
+#if NET6_0_OR_GREATER
+					var prefix = value[..^1];
+#else
+					var prefix = value.Substring(0, value.Length - 1);
+#endif
+
+					if (double.TryParse(prefix, NumberStyles.Number, CultureInfo.InvariantCulture, out var starLength))
+						return new GridLength(starLength, GridUnitType.Star);
+				}
+
+				if (double.TryParse(value, NumberStyles.Number, CultureInfo.InvariantCulture, out var absoluteLength))
+					return new GridLength(absoluteLength);
+			}
+
+			throw new FormatException($"Invalid GridLength format: {value.ToString()}");
 		}
 
 		public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
 		{
 			if (value is not GridLength length)
 				throw new NotSupportedException();
+
+			return ConvertToString(length);
+		}
+
+		internal static string ConvertToString(GridLength length)
+		{
 			if (length.IsAuto)
 				return "auto";
 			if (length.IsStar)
 				return $"{length.Value.ToString(CultureInfo.InvariantCulture)}*";
-			return $"{length.Value.ToString(CultureInfo.InvariantCulture)}";
+			return length.Value.ToString(CultureInfo.InvariantCulture);
 		}
 	}
 }

src/Controls/src/Core/RowDefinitionCollection.cs

@@ -1,4 +1,5 @@
 #nullable disable
+using System.Collections.Generic;
 namespace Microsoft.Maui.Controls
 {
 	/// <include file="../../docs/Microsoft.Maui.Controls/RowDefinitionCollection.xml" path="Type[@FullName='Microsoft.Maui.Controls.RowDefinitionCollection']/Docs/*" />
@@ -11,5 +12,9 @@ public RowDefinitionCollection() : base()
 		public RowDefinitionCollection(params RowDefinition[] definitions) : base(definitions)
 		{
 		}
+
+		internal RowDefinitionCollection(List<RowDefinition> definitions, bool copy) : base(definitions, copy)
+		{
+		}
 	}
 }

src/Controls/src/Core/RowDefinitionCollectionTypeConverter.cs

@@ -1,8 +1,9 @@
 #nullable disable
 using System;
+using System.Buffers;
+using System.Collections.Generic;
 using System.ComponentModel;
 using System.Globalization;
-using System.Linq;
 using Microsoft.Maui.Controls.Xaml;
 
 namespace Microsoft.Maui.Controls
@@ -15,31 +16,65 @@ public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceT
 			=> sourceType == typeof(string);
 
 		public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
-			=> true;
+			=> destinationType == typeof(string);
 
 		public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
 		{
-			var strValue = value?.ToString();
+			var strValue = value as string ?? value?.ToString()
+				?? throw new InvalidOperationException(string.Format("Cannot convert \"{0}\" into {1}", value, typeof(RowDefinitionCollection)));
 
-			if (strValue != null)
+			// fast path for no value or empty string
+			if (strValue.Length == 0)
+				return new RowDefinitionCollection();
+
+#if NET6_0_OR_GREATER
+			var unsplit = (ReadOnlySpan<char>)strValue;
+			var count = unsplit.Count(',') + 1;
+			var definitions = new List<RowDefinition>(count);
+			foreach (var range in unsplit.Split(','))
+			{
+				var length = GridLengthTypeConverter.ParseStringToGridLength(unsplit[range]);
+				definitions.Add(new RowDefinition(length));
+			}
+#else
+			var lengths = strValue.Split(',');
+			var count = lengths.Length;
+			var definitions = new List<RowDefinition>(count);
+			foreach (var lengthStr in lengths)
 			{
-				var lengths = strValue.Split(',');
-				var converter = new GridLengthTypeConverter();
-				var definitions = new RowDefinition[lengths.Length];
-				for (var i = 0; i < lengths.Length; i++)
-					definitions[i] = new RowDefinition { Height = (GridLength)converter.ConvertFromInvariantString(lengths[i]) };
-				return new RowDefinitionCollection(definitions);
+				var length = GridLengthTypeConverter.ParseStringToGridLength(lengthStr);
+				definitions.Add(new RowDefinition(length));
 			}
+#endif
 
-			throw new InvalidOperationException(string.Format("Cannot convert \"{0}\" into {1}", strValue, typeof(RowDefinitionCollection)));
+			return new RowDefinitionCollection(definitions, copy: false);
 		}
 
+
 		public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
 		{
-			if (value is not RowDefinitionCollection rdc)
+			if (value is not RowDefinitionCollection definitions)
 				throw new NotSupportedException();
-			var converter = new GridLengthTypeConverter();
-			return string.Join(", ", rdc.Select(rd => converter.ConvertToInvariantString(rd.Height)));
+
+			var count = definitions.Count;
+
+			// fast path for empty or single definitions
+			if (count == 0)
+				return string.Empty;
+			if (count == 1)
+				return GridLengthTypeConverter.ConvertToString(definitions[0].Height);
+
+			// for multiple items
+			var pool = ArrayPool<string>.Shared;
+			var rentedArray = pool.Rent(definitions.Count);
+			for (var i = 0; i < definitions.Count; i++)
+			{
+				var definition = definitions[i];
+				rentedArray[i] = GridLengthTypeConverter.ConvertToString(definition.Height);
+			}
+			var result = string.Join(", ", rentedArray, 0, definitions.Count);
+			pool.Return(rentedArray);
+			return result;
 		}
 	}
 }

src/Controls/src/Core/SetterSpecificity.cs

@@ -27,6 +27,7 @@ internal readonly struct SetterSpecificity
 		public const ushort StyleLocal = 0x100;
 
 		public static readonly SetterSpecificity DefaultValue = new SetterSpecificity(0);
+		public static readonly SetterSpecificity LowestAppliedValue = new SetterSpecificity(1);
 		public static readonly SetterSpecificity VisualStateSetter = new SetterSpecificity(ExtrasVsm, 0, 0, 0, 0, 0, 0, 0);
 		public static readonly SetterSpecificity FromBinding = new SetterSpecificity(0, 0, 0, 1, 0, 0, 0, 0);
 

src/Core/tests/Benchmarks/Benchmarks/GridDefinitionBenchmarker.cs

@@ -0,0 +1,75 @@
+using System.ComponentModel;
+using BenchmarkDotNet.Attributes;
+using Microsoft.Maui.Controls;
+
+namespace Microsoft.Maui.Handlers.Benchmarks;
+
+[MemoryDiagnoser]
+public class GridDefinitionBenchmarker
+{
+	private ColumnDefinitionCollectionTypeConverter _columnDefinitionConverter;
+	private RowDefinitionCollectionTypeConverter _rowDefinitionConverter;
+
+	private ITypeDescriptorContext _context;
+	private ColumnDefinitionCollection _columns;
+	private RowDefinitionCollection _rows;
+
+	private const int Iterations = 100;
+
+	[GlobalSetup]
+	public void Setup()
+	{
+		_columnDefinitionConverter = new();
+		_rowDefinitionConverter = new();
+		_context = null; // replace with actual context if needed
+		_columns =
+		[
+			new ColumnDefinition(new GridLength(1, GridUnitType.Auto)),
+			new ColumnDefinition(new GridLength(2, GridUnitType.Star)),
+			new ColumnDefinition(new GridLength(3, GridUnitType.Absolute))
+		];
+
+		_rows =
+		[
+			new RowDefinition(new GridLength(1, GridUnitType.Auto)),
+			new RowDefinition(new GridLength(2, GridUnitType.Star)),
+			new RowDefinition(new GridLength(3, GridUnitType.Absolute))
+		];
+	}
+
+	[Benchmark]
+	public void ColumnConvertFrom()
+	{
+		for (int i = 0; i < Iterations; i++)
+		{
+			_columnDefinitionConverter.ConvertFromInvariantString(_context, "Auto, 2*, 3");
+		}
+	}
+
+	[Benchmark]
+	public void ColumnConvertTo()
+	{
+		for (int i = 0; i < Iterations; i++)
+		{
+			_columnDefinitionConverter.ConvertToInvariantString(_context, _columns);
+		}
+	}
+
+	[Benchmark]
+	public void RowConvertFrom()
+	{
+		for (int i = 0; i < Iterations; i++)
+		{
+			_rowDefinitionConverter.ConvertFromInvariantString(_context, "Auto, 2*, 3");
+		}
+	}
+
+	[Benchmark]
+	public void RowConvertTo()
+	{
+		for (int i = 0; i < Iterations; i++)
+		{
+			_rowDefinitionConverter.ConvertToInvariantString(_context, _rows);
+		}
+	}
+}