From 1a213caf26726a0365c059c5e17b7932a3d4a591 Mon Sep 17 00:00:00 2001
From: Eliot Jones <elioty@hotmail.co.uk>
Date: Sun, 29 Apr 2018 15:15:11 +0100
Subject: [PATCH] start adding kerning table as a break from compact font
 format

---
 .../Fonts/TrueType/Parser/TableRegister.cs    |  2 ++
 .../TrueType/Parser/TrueTypeFontParser.cs     |  8 ++++--
 .../TrueType/Tables/Kerning/KernCoverage.cs   | 26 +++++++++++++++++
 .../Fonts/TrueType/Tables/KerningTable.cs     | 28 +++++++++++++++++++
 src/UglyToad.PdfPig/ICosUpdateInfo.cs         |  7 -----
 5 files changed, 62 insertions(+), 9 deletions(-)
 create mode 100644 src/UglyToad.PdfPig/Fonts/TrueType/Tables/Kerning/KernCoverage.cs
 create mode 100644 src/UglyToad.PdfPig/Fonts/TrueType/Tables/KerningTable.cs
 delete mode 100644 src/UglyToad.PdfPig/ICosUpdateInfo.cs

diff --git a/src/UglyToad.PdfPig/Fonts/TrueType/Parser/TableRegister.cs b/src/UglyToad.PdfPig/Fonts/TrueType/Parser/TableRegister.cs
index b0da31be..b997bc80 100644
--- a/src/UglyToad.PdfPig/Fonts/TrueType/Parser/TableRegister.cs
+++ b/src/UglyToad.PdfPig/Fonts/TrueType/Parser/TableRegister.cs
@@ -27,5 +27,7 @@
         /// Where a character code isn't found it should map to index 0.
         /// </summary>
         public CMapTable CMapTable { get; set; }
+
+        public KerningTable KerningTable { get; set; }
     }
 }
diff --git a/src/UglyToad.PdfPig/Fonts/TrueType/Parser/TrueTypeFontParser.cs b/src/UglyToad.PdfPig/Fonts/TrueType/Parser/TrueTypeFontParser.cs
index ede11ee6..d9d8b255 100644
--- a/src/UglyToad.PdfPig/Fonts/TrueType/Parser/TrueTypeFontParser.cs
+++ b/src/UglyToad.PdfPig/Fonts/TrueType/Parser/TrueTypeFontParser.cs
@@ -88,7 +88,7 @@
             {
                 tableRegister.PostScriptTable = PostScriptTable.Load(data, table, tableRegister.MaximumProfileTable);
             }
-
+            
             if (!isPostScript)
             {
                 if (!tables.TryGetValue(TrueTypeHeaderTable.Loca, out var indexToLocationHeaderTable))
@@ -102,7 +102,7 @@
 
                 if (!tables.TryGetValue(TrueTypeHeaderTable.Glyf, out var glyphHeaderTable))
                 {
-                    throw new InvalidOperationException("The glpyh table is required for non-PostScript fonts.");
+                    throw new InvalidOperationException("The glyph table is required for non-PostScript fonts.");
                 }
 
                 // glyf
@@ -137,6 +137,10 @@
             // os2
 
             // kern
+            if (tables.TryGetValue(TrueTypeHeaderTable.Kern, out var kernHeaderTable))
+            {
+                tableRegister.KerningTable = KerningTable.Load(data, kernHeaderTable);
+            }
         }
     }
 }
diff --git a/src/UglyToad.PdfPig/Fonts/TrueType/Tables/Kerning/KernCoverage.cs b/src/UglyToad.PdfPig/Fonts/TrueType/Tables/Kerning/KernCoverage.cs
new file mode 100644
index 00000000..2418fda6
--- /dev/null
+++ b/src/UglyToad.PdfPig/Fonts/TrueType/Tables/Kerning/KernCoverage.cs
@@ -0,0 +1,26 @@
+namespace UglyToad.PdfPig.Fonts.TrueType.Tables.Kerning
+{
+    using System;
+
+    [Flags]
+    internal enum KernCoverage
+    {
+        /// <summary>
+        /// The table is horizontal kerning data.
+        /// </summary>
+        Horizontal = 1,
+        /// <summary>
+        /// The table has minimum values rather than kerning values.
+        /// </summary>
+        Minimum = 1 << 1,
+        /// <summary>
+        /// Kerning is perpendicular to the flow of text.
+        /// If text is horizontal kerning will be in the up/down direction.
+        /// </summary>
+        CrossStream = 1 << 2,
+        /// <summary>
+        /// The value in this sub table should replace the currently accumulated value.
+        /// </summary>
+        Override = 1 << 3
+    }
+}
diff --git a/src/UglyToad.PdfPig/Fonts/TrueType/Tables/KerningTable.cs b/src/UglyToad.PdfPig/Fonts/TrueType/Tables/KerningTable.cs
new file mode 100644
index 00000000..be76d077
--- /dev/null
+++ b/src/UglyToad.PdfPig/Fonts/TrueType/Tables/KerningTable.cs
@@ -0,0 +1,28 @@
+namespace UglyToad.PdfPig.Fonts.TrueType.Tables
+{
+    using Kerning;
+
+    internal class KerningTable
+    {
+        public static KerningTable Load(TrueTypeDataBytes data, TrueTypeHeaderTable headerTable)
+        {
+            data.Seek(headerTable.Offset);
+
+            var version = data.ReadUnsignedShort();
+
+            var numberOfSubtables = data.ReadUnsignedShort();
+
+            for (var i = 0; i < numberOfSubtables; i++)
+            {
+                var subtableVersion = data.ReadUnsignedShort();
+                var subtableLength = data.ReadUnsignedShort();
+                var coverage = data.ReadUnsignedShort();
+
+                var kernCoverage = (KernCoverage) coverage;
+                var format = ((coverage & 255) >> 8);
+            }
+
+            return new KerningTable();
+        }
+    }
+}
diff --git a/src/UglyToad.PdfPig/ICosUpdateInfo.cs b/src/UglyToad.PdfPig/ICosUpdateInfo.cs
deleted file mode 100644
index 7d8e33a9..00000000
--- a/src/UglyToad.PdfPig/ICosUpdateInfo.cs
+++ /dev/null
@@ -1,7 +0,0 @@
-namespace UglyToad.PdfPig
-{
-    internal interface ICosUpdateInfo
-    {
-        bool NeedsToBeUpdated { get; set; }
-    }
-}