From 5082bbbdf2cf1b4e2656fe2452c462b3832370dc Mon Sep 17 00:00:00 2001
From: MarcinZiabek <marcin@ziabek.com>
Date: Sat, 10 Dec 2022 17:34:07 +0100
Subject: [PATCH] Changed letter-spacing to be relative to the font size

---
 QuestPDF.Examples/TextExamples.cs             | 21 ++++++++++++-------
 QuestPDF/Drawing/TextShaper.cs                |  7 +++++--
 .../Fluent/TextSpanDescriptorExtensions.cs    |  5 +++++
 QuestPDF/Fluent/TextStyleExtensions.cs        |  5 +++++
 4 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/QuestPDF.Examples/TextExamples.cs b/QuestPDF.Examples/TextExamples.cs
index ecb5d95..c2099ee 100644
--- a/QuestPDF.Examples/TextExamples.cs
+++ b/QuestPDF.Examples/TextExamples.cs
@@ -137,8 +137,8 @@ namespace QuestPDF.Examples
                         .Padding(20)
                         .Column(column =>
                         {
-                            var letterSpacing = new[] { -1f, 0f, 2f };
-                            var paragraph = Placeholders.Sentence();
+                            var letterSpacing = new[] { -0.1f, 0f, 0.2f };
+                            var paragraph = Placeholders.Sentence().ToUpper();
 
                             foreach (var spacing in letterSpacing)
                             {
@@ -154,12 +154,12 @@ namespace QuestPDF.Examples
                                                     .LetterSpacing(spacing);
 
                                         nestedColumn.Item()
-                                                    .Text($"Letter spacing of {spacing} pt")
+                                                    .Text($"Letter spacing of {spacing} em")
                                                     .FontSize(10)
                                                     .Italic()
                                                     .FontColor(Colors.Blue.Medium);
                                     });
-                                    
+                                
                             }
                         });
                 });
@@ -179,7 +179,7 @@ namespace QuestPDF.Examples
                         .Padding(50)
                         .Column(column =>
                         {
-                            var letterSpacing = new[] { -1f, 0f, 2f };
+                            var letterSpacing = new[] { -0.1f, 0f, 0.2f };
                             var paragraph = "ينا الألم. في بعض الأحيان ونظراً للالتزامات التي يفرضها علينا";
                             foreach (var spacing in letterSpacing)
                             {
@@ -196,7 +196,7 @@ namespace QuestPDF.Examples
                                                    .LetterSpacing(spacing);
 
                                        nestedColumn.Item()
-                                                   .Text($"Letter spacing of {spacing} pt")
+                                                   .Text($"Letter spacing of {spacing} em")
                                                    .FontSize(10)
                                                    .Italic()
                                                    .FontColor(Colors.Blue.Medium);
@@ -221,13 +221,18 @@ namespace QuestPDF.Examples
                         .Padding(50)
                         .Column(column =>
                         {
-                            var letterSpacing = new[] { 0f, 20f };
+                            var letterSpacing = new[] { 0f, 0.5f };
+                            
+                            
+                            
                             var paragraph = "Ţ̴̡̧̤̮̺̤̗͎̱̹͙͎͖͂̿̓́̉̊̀̍͜h̵̞̘͇̾̎̏̅į̵̹̖͔͉̰̎̉̄̐̏͑͂̅̃̃͘͝s̷͓͉̭̭̯̬̥̻̰̩̦̑̀̀͌́̒̍̒̌̇͛̀͛́̎ ̷̡̡̟͕̳̺̝̼͇͔̬̟̖͍̈́̽͜͝͝i̶͔͚̟̊̐͛́͛̄̌ṡ̸̡̤̪͙͍̥͙̟̼̝̰̥͈̿̓̄̿̓͠ ̶̢̦̙͍̯̖̱̰̯͕͔͎̯̝̎͑t̸͖̲̱̼̎͐̎̉̾̎̾̌̅̔̏͘ȩ̶̝̫̙͓̙̣̔̀̌̔̋̂̑̈́̏̀̈͘̕͜͝s̸̫̝̮̻̼͐̅̄̎̎̑͝ț̷̨̢̨̻͈̮̞̆͗̓͊̃̌͂̑̉̕̕͜͝͝";
 
+                            
+                            
                             foreach (var spacing in letterSpacing)
                             {
                                 column.Item()
-                                      .Text($"Letter spacing of {spacing} pt")
+                                      .Text($"Letter spacing of {spacing} em")
                                       .FontSize(10)
                                       .Italic()
                                       .FontColor(Colors.Blue.Medium);
diff --git a/QuestPDF/Drawing/TextShaper.cs b/QuestPDF/Drawing/TextShaper.cs
index 40ea223..97a4392 100644
--- a/QuestPDF/Drawing/TextShaper.cs
+++ b/QuestPDF/Drawing/TextShaper.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using HarfBuzzSharp;
+using QuestPDF.Fluent;
 using QuestPDF.Infrastructure;
 using SkiaSharp;
 using Buffer = HarfBuzzSharp.Buffer;
@@ -49,8 +50,10 @@ namespace QuestPDF.Drawing
             
             // used for letter spacing calculation
             var lastCluster = glyphInfos.LastOrDefault().Cluster;
-
+            var letterSpacing = (TextStyle.LetterSpacing ?? 0) * (TextStyle.Size ?? 16); 
+            
             var glyphs = new ShapedGlyph[length];
+
             for (var i = 0; i < length; i++)
             {
                 // letter spacing should be applied between glyph clusters, not between individual glyphs,
@@ -58,7 +61,7 @@ namespace QuestPDF.Drawing
                 if (lastCluster != glyphInfos[i].Cluster)
                 {
                     lastCluster = glyphInfos[i].Cluster;
-                    xOffset += TextStyle.LetterSpacing ?? 0;
+                    xOffset += letterSpacing;
                 }
 
                 glyphs[i] = new ShapedGlyph
diff --git a/QuestPDF/Fluent/TextSpanDescriptorExtensions.cs b/QuestPDF/Fluent/TextSpanDescriptorExtensions.cs
index 30dcdaa..74222b5 100644
--- a/QuestPDF/Fluent/TextSpanDescriptorExtensions.cs
+++ b/QuestPDF/Fluent/TextSpanDescriptorExtensions.cs
@@ -56,6 +56,11 @@ namespace QuestPDF.Fluent
             return descriptor;
         }
 
+        /// <summary>
+        /// Letter spacing controls space between characters. Value 0 corresponds to normal spacing defined by a font.
+        /// Positive values create additional space, whereas negative values reduce space between characters.
+        /// Added / reduced space is relative to the font size.
+        /// </summary>
         public static T LetterSpacing<T>(this T descriptor, float value) where T : TextSpanDescriptor
         {
             descriptor.MutateTextStyle(x => x.LetterSpacing(value));
diff --git a/QuestPDF/Fluent/TextStyleExtensions.cs b/QuestPDF/Fluent/TextStyleExtensions.cs
index 2fe2d6a..b6f3906 100644
--- a/QuestPDF/Fluent/TextStyleExtensions.cs
+++ b/QuestPDF/Fluent/TextStyleExtensions.cs
@@ -49,6 +49,11 @@ namespace QuestPDF.Fluent
             return style.Mutate(TextStyleProperty.LineHeight, value);
         }
 
+        /// <summary>
+        /// Letter spacing controls space between characters. Value 0 corresponds to normal spacing defined by a font.
+        /// Positive values create additional space, whereas negative values reduce space between characters.
+        /// Added / reduced space is relative to the font size.
+        /// </summary>
         public static TextStyle LetterSpacing(this TextStyle style, float value)
         {
             return style.Mutate(TextStyleProperty.LetterSpacing, value);