try improve the column-width/row-height adjustment performance

ReoGrid/Actions/SetColumnsWidthAction.cs

@@ -51,19 +51,19 @@ public override void Do()
 			int col = base.Range.Col;
 			int count = base.Range.Cols;
 
-			backupCols.Clear();
+			backupColsWidth.Clear();
 
 			int c2 = col + count;
 			for (int c = col; c < c2; c++)
 			{
 				ColumnHeader colHead = Worksheet.RetrieveColumnHeader(c);
-				backupCols.Add(c, colHead.InnerWidth);
+				backupColsWidth.Add(c, colHead.InnerWidth);
 			}
 
 			Worksheet.SetColumnsWidth(col, count, width);
 		}
 
-		private Dictionary<int, ushort> backupCols = new Dictionary<int, ushort>();
+		private Dictionary<int, ushort> backupColsWidth = new Dictionary<int, ushort>();
 
 		/// <summary>
 		/// Undo this action
@@ -73,7 +73,7 @@ public override void Undo()
 			int col = base.Range.Col;
 			int count = base.Range.Cols;
 
-			Worksheet.SetColumnsWidth(col, count, c => backupCols[c]);
+			Worksheet.SetColumnsWidth(col, count, c => backupColsWidth[c]);
 		}
 
 		/// <summary>

ReoGrid/Core/Header.cs

@@ -793,11 +793,21 @@ public bool AutoFitRowHeight(int row, bool byAction = false)
 		/// be done by performing action, that will be able to revoke this behavior.</param>
 		/// <returns>Return true if operation actually done; Return false if nothing 
 		/// need to do (cells are default width).</returns>
-		public bool AutoFitColumnWidth(int col, bool byAction = false)
+		public bool AutoFitColumnsWidth(int col, int count, bool byAction = false)
 		{
 			if (col < 0 || col > this.cols.Count - 1)
 			{
-				throw new ArgumentOutOfRangeException("col");
+				throw new ArgumentOutOfRangeException(nameof(col));
+			}
+
+			if (count < 1)
+			{
+				throw new ArgumentOutOfRangeException(nameof(count));
+			}
+
+			if (col + count > this.cols.Count)
+			{
+				throw new ArgumentOutOfRangeException(nameof(count));
 			}
 
 			RGFloat maxWidth = 0;
@@ -3178,9 +3188,10 @@ private void VerifyWorksheet()
 		/// </summary>
 		/// <param name="byAction">Determines whether or not this operation 
 		/// performed by doing action, which will provide the ability to undo this operation.</param>
+		[Obsolete("For a performance issue, consider use Worksheet.SetColumnsWidthAction instead")]
 		public void FitWidthToCells(bool byAction = false)
 		{
-			this.Worksheet.AutoFitColumnWidth(this.Col, byAction);
+			this.Worksheet.AutoFitColumnsWidth(this.Col, 1, byAction);
 		}
 
 		internal ColumnHeader Clone(Worksheet newSheet)

ReoGrid/ReoGrid.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp3.0;net40</TargetFrameworks>
+    <TargetFrameworks>;netcoreapp3.1</TargetFrameworks>
     <OutputType>Library</OutputType>
     <RootNamespace>unvell.ReoGrid</RootNamespace>
     <AssemblyName>unvell.ReoGrid</AssemblyName>

ReoGrid/Views/Header/ColumnHeaderView.cs

@@ -344,7 +344,7 @@ public override bool OnMouseDoubleClick(Point location, MouseButtons buttons)
 					&& buttons == MouseButtons.Left
 					&& this.sheet.HasSettings(WorksheetSettings.Edit_AllowAdjustColumnWidth))
 				{
-					this.sheet.AutoFitColumnWidth(col, byAction: true);
+					this.sheet.AutoFitColumnsWidth(col, 1, byAction: true);
 
 					return true;
 				}

TestCase/TestCase.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <Import Project="..\packages\NUnit3TestAdapter.3.8.0\build\net35\NUnit3TestAdapter.props" Condition="Exists('..\packages\NUnit3TestAdapter.3.8.0\build\net35\NUnit3TestAdapter.props')" />
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net6.0-windows10.0.22000.0</TargetFramework>
     <OutputType>Exe</OutputType>
     <RootNamespace>unvell.ReoGrid.Tests</RootNamespace>
     <AssemblyName>ReoGridUnitTest</AssemblyName>
@@ -31,6 +31,7 @@
   </PropertyGroup>
   <PropertyGroup>
     <AssemblyOriginatorKeyFile></AssemblyOriginatorKeyFile>
+    <PlatformTarget>x64</PlatformTarget>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DefineConstants>TRACE;EX_SCRIPT</DefineConstants>