Fix GetCharSize consuming too much rendering power

.gitignore

@@ -106,3 +106,5 @@ Generated_Code #added for RIA/Silverlight projects
 _UpgradeReport_Files/
 Backup*/
 UpgradeLog*.XML
+
+.vs

FastColoredTextBox/CharSizeCache.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Text;
+using System.Windows.Forms;
+
+namespace FastColoredTextBoxNS
+{
+    /// <summary>
+    /// Calling MeasureText on each char is extremly slow
+    /// Thankfully the size of the char does not change for the same font
+    /// However we would still need to indentify the font somehow
+    /// </summary>
+    static class CharSizeCache
+    {
+        static readonly Dictionary<string, SizeF> cache = new Dictionary<string, SizeF>();
+        internal static SizeF GetCharSize(Font font, char c)
+        {
+            var key = GetKey(font, c);
+            if (!cache.ContainsKey(key))
+            {
+                Size sz2 = TextRenderer.MeasureText("<" + c.ToString() + ">", font);
+                Size sz3 = TextRenderer.MeasureText("<>", font);
+                cache[key] = new SizeF(sz2.Width - sz3.Width + 1, /*sz2.Height*/font.Height);
+            }
+            return cache[key];
+        }
+
+        /// <summary>
+        /// Font is disposable, so we need to indentify it without keeping manged resources
+        /// </summary>
+        /// <param name="font"></param>
+        /// <param name="c"></param>
+        /// <returns></returns>
+        private static string GetKey(Font font, char c)
+        {
+            return font.FontFamily.Name
+                    + ":" + font.Size
+                    + ":" + font.Style
+                    + ":" + font.Unit
+                    + ":" + font.GdiCharSet
+                    + ":" + font.GdiVerticalFont
+                    + ":" + c;
+        }
+    }
+}

FastColoredTextBox/FastColoredTextBox.cs

@@ -2901,10 +2901,7 @@ internal int GetOrSetStyleLayerIndex(Style style)
 
         public static SizeF GetCharSize(Font font, char c)
         {
-            Size sz2 = TextRenderer.MeasureText("<" + c.ToString() + ">", font);
-            Size sz3 = TextRenderer.MeasureText("<>", font);
-
-            return new SizeF(sz2.Width - sz3.Width + 1, /*sz2.Height*/font.Height);
+            return CharSizeCache.GetCharSize(font, c);
         }
 
         [DllImport("Imm32.dll")]

FastColoredTextBox/FastColoredTextBox.csproj

@@ -53,6 +53,7 @@
     </Compile>
     <Compile Include="Bookmarks.cs" />
     <Compile Include="Char.cs" />
+    <Compile Include="CharSizeCache.cs" />
     <Compile Include="DocumentMap.cs">
       <SubType>Component</SubType>
     </Compile>

FastColoredTextBox/FastColoredTextBox.nuspec

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<package xmlns="http://schemas.microsoft.com/packaging/2011/08/nuspec.xsd">
+  <metadata>
+    <id>Technica.FCTB</id>
+    <version>$version$</version>
+    <title>$title$</title>
+    <authors>$author$</authors>
+    <owners>$author$</owners>
+    <description>$description$</description>
+    <copyright>$copyright$</copyright>
+  </metadata>
+</package>