Clean-up and optimize

Author: JimBobSquarePants

src/SixLabors.Fonts/Tables/AdvancedTypographic/CoverageTable.cs

@@ -28,13 +28,13 @@ public static CoverageTable Load(BigEndianBinaryReader reader, long offset)
 
             // Harfbuzz (Coverage.hh) treats this as an empty table and does not throw.
             // SofiaSans Condensed can trigger this. See https://github.com/SixLabors/Fonts/issues/470
-            _ => new EmptyCoverageTable()
+            _ => EmptyCoverageTable.Instance
         };
     }
 
     public static CoverageTable[] LoadArray(BigEndianBinaryReader reader, long offset, ReadOnlySpan<ushort> coverageOffsets)
     {
-        var tables = new CoverageTable[coverageOffsets.Length];
+        CoverageTable[] tables = new CoverageTable[coverageOffsets.Length];
         for (int i = 0; i < tables.Length; i++)
         {
             tables[i] = Load(reader, offset + coverageOffsets[i]);
@@ -108,7 +108,7 @@ public static CoverageFormat2Table Load(BigEndianBinaryReader reader)
         // | RangeRecord | rangeRecords[rangeCount] | Array of glyph ranges — ordered by startGlyphID. |
         // +-------------+--------------------------+--------------------------------------------------+
         ushort rangeCount = reader.ReadUInt16();
-        var records = new CoverageRangeRecord[rangeCount];
+        CoverageRangeRecord[] records = new CoverageRangeRecord[rangeCount];
 
         for (int i = 0; i < records.Length; i++)
         {
@@ -132,6 +132,12 @@ public static CoverageFormat2Table Load(BigEndianBinaryReader reader)
 
     internal sealed class EmptyCoverageTable : CoverageTable
     {
+        private EmptyCoverageTable()
+        {
+        }
+
+        public static EmptyCoverageTable Instance { get; } = new();
+
         public override int CoverageIndexOf(ushort glyphId) => -1;
     }
 }

src/SixLabors.Fonts/Tables/AdvancedTypographic/GPos/AnchorTable.cs

@@ -11,8 +11,6 @@ namespace SixLabors.Fonts.Tables.AdvancedTypographic.GPos;
 [DebuggerDisplay("X: {XCoordinate}, Y: {YCoordinate}")]
 internal abstract class AnchorTable
 {
-    private static readonly AnchorTable EmptyAnchorTable = new EmptyAnchor();
-
     /// <summary>
     /// Initializes a new instance of the <see cref="AnchorTable"/> class.
     /// </summary>
@@ -55,7 +53,7 @@ public static AnchorTable Load(BigEndianBinaryReader reader, long offset)
 
             // Harfbuzz (Anchor.hh) treats this as an empty table and does not throw..
             // NotoSans Regular can trigger this. See https://github.com/SixLabors/Fonts/issues/417
-            _ => EmptyAnchorTable,
+            _ => EmptyAnchorTable.Instance,
         };
     }
 
@@ -185,13 +183,15 @@ public override AnchorXY GetAnchor(FontMetrics fontMetrics, GlyphShapingData dat
             => new(this.XCoordinate, this.YCoordinate);
     }
 
-    internal sealed class EmptyAnchor : AnchorTable
+    internal sealed class EmptyAnchorTable : AnchorTable
     {
-        public EmptyAnchor()
+        private EmptyAnchorTable()
             : base(0, 0)
         {
         }
 
+        public static EmptyAnchorTable Instance { get; } = new();
+
         public override AnchorXY GetAnchor(
             FontMetrics fontMetrics,
             GlyphShapingData data,