Text rendering optimization: style key, font metrics caching

QuestPDF.Examples/TextBenchmark.cs

@@ -5,6 +5,7 @@ using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using NUnit.Framework;
+using QuestPDF.Drawing;
 using QuestPDF.Examples.Engine;
 using QuestPDF.Fluent;
 using QuestPDF.Helpers;
@@ -22,12 +23,16 @@ namespace QuestPDF.Examples
             
             var chapters = GetChapters().ToList();
 
-            var results = PerformTest(16).ToList();
+            var results = PerformTest(1).ToList();
+            
+            var a = CanvasCache.Paints;
             
             Console.WriteLine($"Min: {results.Min():F}");
             Console.WriteLine($"Max: {results.Max():F}");
             Console.WriteLine($"Avg: {results.Average():F}");
 
+            
+
             IEnumerable<(string title, string content)> GetChapters()
             {
                 var book = File.ReadAllLines("quo-vadis.txt");

QuestPDF.Examples/optimization.md

@@ -31,4 +31,62 @@ Max: 19876,00
 Avg: 18622,44
 ```
 
+## Text Style Key Caching
 
+Attempts:
+
+```
+Attempt 0: 17140,00
+Attempt 1: 16146,00
+Attempt 2: 16345,00
+Attempt 3: 16428,00
+Attempt 4: 17203,00
+Attempt 5: 16890,00
+Attempt 6: 17450,00
+Attempt 7: 16455,00
+Attempt 8: 16553,00
+Attempt 9: 17281,00
+Attempt 10: 16688,00
+Attempt 11: 16459,00
+Attempt 12: 17245,00
+Attempt 13: 17346,00
+Attempt 14: 16514,00
+Attempt 15: 16427,00
+```
+
+Results:
+
+```
+Min: 16146,00
+Max: 17450,00
+Avg: 16785,62
+```
+
+## Font Metrics Caching
+
+```
+Attempt 0: 13906,00
+Attempt 1: 13510,00
+Attempt 2: 13570,00
+Attempt 3: 13442,00
+Attempt 4: 13580,00
+Attempt 5: 13421,00
+Attempt 6: 13470,00
+Attempt 7: 13456,00
+Attempt 8: 13672,00
+Attempt 9: 14489,00
+Attempt 10: 13543,00
+Attempt 11: 13685,00
+Attempt 12: 13469,00
+Attempt 13: 13586,00
+Attempt 14: 13423,00
+Attempt 15: 13487,00
+```
+
+Results:
+
+```
+Min: 13421,00
+Max: 14489,00
+Avg: 13606,81
+```

QuestPDF/Drawing/CanvasCache.cs

@@ -7,7 +7,8 @@ namespace QuestPDF.Drawing
 {
     internal static class CanvasCache
     {
-        private static ConcurrentDictionary<string, SKPaint> Paints = new ConcurrentDictionary<string, SKPaint>();
+        internal static ConcurrentDictionary<string, SKPaint> Paints = new ConcurrentDictionary<string, SKPaint>();
+        private static ConcurrentDictionary<string, SKFontMetrics> FontMetrics = new ConcurrentDictionary<string, SKFontMetrics>();
         private static ConcurrentDictionary<string, SKPaint> ColorPaint = new ConcurrentDictionary<string, SKPaint>();
 
         internal static SKPaint ColorToPaint(this string color)
@@ -41,6 +42,11 @@ namespace QuestPDF.Drawing
             }
         }
 
+        internal static SKFontMetrics ToFontMetrics(this TextStyle style)
+        {
+            return FontMetrics.GetOrAdd(style.ToString(), key => style.ToPaint().FontMetrics);
+        }
+        
         internal static TextMeasurement BreakText(this TextStyle style, string text, float availableWidth)
         {
             var index = (int)style.ToPaint().BreakText(text, availableWidth, out var width);

QuestPDF/Elements/Text/TextItem.cs

@@ -60,6 +60,7 @@ namespace QuestPDF.Elements.Text
         public TextMeasurementResult? Measure(TextMeasurementRequest request)
         {
             var paint = Style.ToPaint();
+            var fontMetrics = Style.ToFontMetrics();
             
             // start breaking text from requested position
             var text = Text.Substring(request.StartIndex);
@@ -88,8 +89,8 @@ namespace QuestPDF.Elements.Text
             {
                 Width = width,
                 
-                Ascent = paint.FontMetrics.Ascent,
-                Descent = paint.FontMetrics.Descent,
+                Ascent = fontMetrics.Ascent,
+                Descent = fontMetrics.Descent,
      
                 LineHeight = Style.LineHeight,
                 
@@ -101,7 +102,7 @@ namespace QuestPDF.Elements.Text
         
         public void Draw(TextDrawingRequest request)
         {
-            var fontMetrics = Style.ToPaint().FontMetrics;
+            var fontMetrics = Style.ToFontMetrics();
 
             var text = Text.Substring(request.StartIndex, request.EndIndex - request.StartIndex);
             

QuestPDF/Infrastructure/TextStyle.cs

@@ -17,9 +17,12 @@ namespace QuestPDF.Infrastructure
 
         public static TextStyle Default => new TextStyle();
 
+        private string? KeyCache { get; set; }
+        
         public override string ToString()
         {
-            return $"{Color}|{BackgroundColor}|{FontType}|{Size}|{LineHeight}|{FontWeight}|{IsItalic}|{IsStroked}|{IsUnderlined}";
+            KeyCache ??= $"{Color}|{BackgroundColor}|{FontType}|{Size}|{LineHeight}|{FontWeight}|{IsItalic}|{IsStroked}|{IsUnderlined}";
+            return KeyCache;
         }
 
         internal TextStyle Clone() => (TextStyle)MemberwiseClone();