Mostly working parser, some issues with glyph positioning. Should create a LatexGlyph : LatexSegment, and change LatexSegment.Glyphs to be of LatexGlyphs. Then, ON ITERATION, compute the altered positions of the LatexGlyphs and create the glyphruns from that.

WpfTex/LatexEditor/Fonts/GlyphInfo.cs

@@ -1,30 +1,36 @@
 using System.Collections.Generic;
 using System.Windows;
 using System.Windows.Media;
+using JetBrains.Annotations;
 
 namespace LatexEditor.Fonts
 {
     public class GlyphInfo
     {
         public CmFont Font;
-        public Point Offset;
-        public double Size;
-        private int Char;
+        public double RelativeSize;
+        public int Char;
+        public Point RelativeOffset;
+        public Point BaselineOrigin;
 
         public GlyphTypeface Gtf => Font.GlyphTypeface();
 
-        /// <summary>
-        /// Index of this glyph within the GlyphTypeface. 
-        /// </summary>
-        /// <exception cref="KeyNotFoundException">Thrown if <see cref="Font"/> does not have a glyph for char <see cref="Char"/></exception>
         public ushort Index => Gtf.CharacterToGlyphMap[Char];
 
-        public GlyphInfo(CmFont font, int character, double size, Point offset)
+        public double RelAdvWidth => Gtf.AdvanceWidths[Index];
+        public double RelAdvHeight => Gtf.AdvanceHeights[Index];
+
+        public Point Offset => new Point(
+            BaselineOrigin.X + RelativeOffset.X * RelativeSize,
+            BaselineOrigin.Y + RelativeOffset.Y * RelativeSize);
+
+        public GlyphInfo(CmFont font, int c, Point relativeOffset, Point baselineOrigin, double relativeSize = 1)
         {
             Font = font;
-            Char = character;
-            Size = size;
-            Offset = offset;
+            RelativeSize = relativeSize;
+            RelativeOffset = relativeOffset;
+            BaselineOrigin = baselineOrigin;
+            Char = c;
         }
     }
 }

WpfTex/LatexEditor/LatexEditor.csproj

@@ -76,7 +76,13 @@
     </Compile>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Parser\LatexNull.cs" />
     <Compile Include="Parser\LatexParser.cs" />
+    <Compile Include="Parser\LatexReturn.cs" />
+    <Compile Include="Parser\LatexRun.cs" />
+    <Compile Include="Parser\LatexSegment.cs" />
+    <Compile Include="Parser\LatexSpace.cs" />
+    <Compile Include="Parser\LatexText.cs" />
     <Compile Include="Parser\Lexer.cs" />
     <Compile Include="Parser\Token.cs" />
     <Compile Include="Parser\TokenDescriptor.cs" />

WpfTex/LatexEditor/LatexViewer.cs

@@ -41,83 +41,6 @@ namespace LatexEditor
             set => SetValue(FontSizeProperty, value);
         }
 
-        protected List<GlyphInfo> Parse(string latex)
-        {
-            var x = 0d;
-            var y = 0d;
-            var font = CmFont.SerifItalic;
-            var size = FontSize;
-
-            var glyphs = new List<GlyphInfo>(latex.Length);
-
-            var state = new Stack<string>();
-            state.Push("-");
-
-            while (latex.Length > 0)
-            {
-                var s = state.Peek();
-
-                if (s == "cmd")
-                {
-                    state.Pop();
-                    var m = Regex.Match(latex, @"([a-z]+)(?=[^a-z]|$)", RegexOptions.IgnoreCase);
-                    if (m.Index == 0)
-                    {
-                        var cmd = latex.Substring(0, m.Groups[1].Length);
-                        switch (cmd)
-                        {
-                            case "it":
-                                font = CmFont.SerifItalic;
-                                break;
-                            case "sym":
-                                font = CmFont.Symbols;
-                                break;
-                            case "rm":
-                                font = CmFont.Serif;
-                                break;
-                            case "sup":
-                                size = FontSize * 0.4;
-                                y = FontSize * (1 - 0.4);
-                                break;
-                            case "sub":
-                                size = FontSize * 0.5;
-                                y = -FontSize * 0.5 * 0.5;
-                                break;
-                            default:
-                                continue;
-                        }
-                        latex = latex.Substring(m.Length).TrimStart(' ');
-                    }
-                    else
-                    {
-                        latex = latex.Substring(1);
-                    }
-                }
-                else
-                {
-                    if (latex.StartsWith("\\"))
-                    {
-                        latex = latex.Substring(1);
-
-                        state.Push("cmd");
-                    }
-                    else
-                    {
-                        var chr = latex[0];
-                        latex = latex.Substring(1);
-
-                        var gtf = font.GlyphTypeface();
-                        var point = new Point(x, y);
-                        var gi = new GlyphInfo(font, chr, size, point);
-                        x += gtf.AdvanceWidths[gi.Index] * size;
-                        glyphs.Add(gi);
-                    }
-                }
-            }
-
-            return glyphs;
-        }
-
         protected override void OnRender(DrawingContext dc)
         {
             Debug.WriteLine(dc, nameof(LatexViewer));
@@ -125,22 +48,23 @@ namespace LatexEditor
 
             if (string.IsNullOrEmpty(Content)) return;
 
-            var glyphInfoList = LatexParser.Parse(Content);
+            var glyphInfoList = LatexParser.ToGlyphInfos(Content);
 
             var gtfGroups = glyphInfoList.GroupBy(gi => gi.Gtf);
             foreach (var gtfGroup in gtfGroups)
             {
                 var gtf = gtfGroup.Key;
 
-                var sizeGroups = gtfGroup.GroupBy(gi => gi.Size);
+                var sizeGroups = gtfGroup.GroupBy(gi => gi.RelativeSize);
                 foreach (var sizeGroup in sizeGroups)
                 {
                     var size = sizeGroup.Key;
 
                     var glyphs = sizeGroup.Select(gi => gi.Index).ToList();
-                    var advanceWidths = new double[glyphs.Count];
-                    var offsets = sizeGroup.Select(gi => gi.Offset).ToList();
-                    var gr = new GlyphRun(gtf, 0, false, size,
+                    var advanceWidths = new double[glyphs.Count]; // all zero - position based only on offset
+                    var offsets = sizeGroup.Select(gi => new Point(gi.Offset.X * FontSize, gi.Offset.Y * FontSize))
+                        .ToList();
+                    var gr = new GlyphRun(gtf, 0, false, size * FontSize,
                         glyphs, new Point(0, FontSize), advanceWidths,
                         offsets, null, null, null, null, null);
 

WpfTex/LatexEditor/MainWindow.xaml

@@ -8,20 +8,20 @@
         Title="MainWindow" Height="350" Width="525">
     <Grid>
         <local:LatexViewer>
-            <!--            e^{\pi i}=-1\{\textrm{in the complex plane}-->
-            A \  \alpha \quad N \  \nu \\
-            B \  \beta \quad  \Xi \  \xi \\
-            \Gamma \  \gamma \quad O \  \omicron \\
-            \Delta \  \delta \quad  \Pi \  \pi \\
-            E \  \epsilon \quad P \  \rho \\
-            Z \  \zeta \quad  \Sigma \  \sigma \\
-            H \  \eta \quad T \  \tau \\
-            \Theta \  \theta \quad Y \  \upsilon \\
-            I \  \iota \quad  \Phi \  \phi \\
-            K \  \kappa \quad X \  \chi \\
-            \Lambda \  \lambda \quad  \Psi \  \psi \\
-            M \  \mu \quad  \Omega \  \omega
-
+<!--            e^{\pi i}=-1\{\textrm{in the complex plane}-->
+            {2}{123}
+<!--            A \  \alpha \quad N \  \nu \\-->
+<!--            B \  \beta \quad  \Xi \  \xi \\-->
+<!--            \Gamma \  \gamma \quad O \  \omicron \\-->
+<!--            \Delta \  \delta \quad  \Pi \  \pi \\-->
+<!--            E \  \epsilon \quad P \  \rho \\-->
+<!--            Z \  \zeta \quad  \Sigma \  \sigma \\-->
+<!--            H \  \eta \quad T \  \tau \\-->
+<!--            \Theta \  \theta \quad Y \  \upsilon \\-->
+<!--            I \  \iota \quad  \Phi \  \phi \\-->
+<!--            K \  \kappa \quad X \  \chi \\-->
+<!--            \Lambda \  \lambda \quad  \Psi \  \psi \\-->
+<!--            M \  \mu \quad  \Omega \  \omega-->
 
         </local:LatexViewer>
     </Grid>

WpfTex/LatexEditor/Parser/LatexNull.cs

@@ -0,0 +1,13 @@
+using System.Collections.Generic;
+using System.Linq;
+using LatexEditor.Fonts;
+
+namespace LatexEditor.Parser
+{
+    public class LatexNull : LatexSegment
+    {
+        public override IEnumerable<GlyphInfo> Glyphs => Enumerable.Empty<GlyphInfo>();
+        public override double RelAdvWidth => 0;
+        public override double RelAdvHeight => 0;
+    }
+}

WpfTex/LatexEditor/Parser/LatexParser.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
-using System.Windows;
+using System.Runtime.CompilerServices;
+using System.Windows.Navigation;
 using LatexEditor.Fonts;
 
 namespace LatexEditor.Parser
@@ -18,7 +19,7 @@ namespace LatexEditor.Parser
             new TokenDescriptor("letter", @"[\S]"), // nearly catch-all for uncaptured symbols
         };
 
-        private static readonly Dictionary<string, int> greekLetters = new Dictionary<string, int>
+        internal static readonly Dictionary<string, int> GreekLetters = new Dictionary<string, int>
         {
             ["alpha"] = 0x03b1,
             ["beta"] = 0x03b2,
@@ -45,19 +46,22 @@ namespace LatexEditor.Parser
             ["psi"] = 0x03c8,
             ["omega"] = 0x03c9,
 
-            ["Gamma"]   = 0x0393,
-            ["Delta"]   = 0x0394,
-            ["Theta"]   = 0x0398,
-            ["Lambda"]  = 0x039b,
-            ["Xi"]      = 0x039e,
-            ["Pi"]      = 0x03a0,
-            ["Sigma"]   = 0x03a3,
-            ["Phi"]     = 0x03a6,
-            ["Psi"]     = 0x03a8,
-            ["Omega"]   = 0x03a9,
+            // Alpha Beta Epsilon Zeta Eta Iota Kappa Mu Nu 
+            // Omicron Rho Tau and Upsilon all denoted by
+            // Latin symbols A B E Z H I K M N O P T and Y
+            ["Gamma"] = 0x0393,
+            ["Delta"] = 0x0394,
+            ["Theta"] = 0x0398,
+            ["Lambda"] = 0x039b,
+            ["Xi"] = 0x039e,
+            ["Pi"] = 0x03a0,
+            ["Sigma"] = 0x03a3,
+            ["Phi"] = 0x03a6,
+            ["Psi"] = 0x03a8,
+            ["Omega"] = 0x03a9,
         };
 
-        private static readonly Dictionary<string, double> spaces = new Dictionary<string, double>
+        internal static readonly Dictionary<string, double> Spaces = new Dictionary<string, double>
         {
             [","] = 0.16666,
             ["!"] = -0.16666,
@@ -69,57 +73,12 @@ namespace LatexEditor.Parser
             ["qquad"] = 4,
         };
 
-        public static IEnumerable<GlyphInfo> Parse(string latex) => Parse(LatexLexer.Tokenize(latex));
+        public static IEnumerable<GlyphInfo> ToGlyphInfos(string latex) => ToGlyphInfos(LatexLexer.Tokenize(latex));
 
-        private static IEnumerable<GlyphInfo> Parse(IEnumerable<Token> tokens)
+        private static IEnumerable<GlyphInfo> ToGlyphInfos(IEnumerable<Token> tokens)
         {
-            var tokenQ = new Queue<Token>(tokens);
-            var glyphs = new List<GlyphInfo>();
-
-            const double size = 20;
-            var x = 0d;
-            var y = 0d;
-
-            void AddGlyph(CmFont font, int c)
-            {
-                glyphs.Add(new GlyphInfo(font, c, size, new Point(x * size, y * size)));
-                var gtf = font.GlyphTypeface();
-                var idx = gtf.CharacterToGlyphMap[c];
-                x += gtf.AdvanceWidths[idx];
-            }
-
-            while (tokenQ.Count > 0)
-            {
-                var token = tokenQ.Dequeue();
-                var val = token.Value;
-                switch (token.TokenName)
-                {
-                    case "letter":
-                        AddGlyph(CmFont.SerifItalic, val[0]);
-                        break;
-                    case "number":
-                        AddGlyph(CmFont.Serif, val[0]);
-                        break;
-                    case "command":
-                        if (greekLetters.ContainsKey(val))
-                            AddGlyph(CmFont.SerifItalic, greekLetters[val]);
-                        else if (spaces.ContainsKey(val))
-                            x += spaces[val];
-                        else
-                            foreach (var c in token.CapturedString)
-                                AddGlyph(CmFont.SerifItalic, c);
-                        break;
-                    case "escape":
-                        if (val == "\\")
-                        {
-                            x = 0;
-                            y -= 1;
-                        }
-                        break;
-                }
-            }
-
-            return glyphs;
+            var lss = LatexSegment.ToLatexSegment(tokens);
+            return lss.Glyphs;
         }
     }
 }

WpfTex/LatexEditor/Parser/LatexReturn.cs

@@ -0,0 +1,18 @@
+using System.Collections.Generic;
+using System.Linq;
+using LatexEditor.Fonts;
+
+namespace LatexEditor.Parser
+{
+    public class LatexReturn : LatexSegment
+    {
+        public override IEnumerable<GlyphInfo> Glyphs => Enumerable.Empty<GlyphInfo>();
+        public override double RelAdvWidth => 0;
+        public override double RelAdvHeight { get; }
+
+        public LatexReturn(double relAdvHeight)
+        {
+            RelAdvHeight = relAdvHeight;
+        }
+    }
+}

WpfTex/LatexEditor/Parser/LatexRun.cs

@@ -0,0 +1,41 @@
+using System.Collections.Generic;
+using System.Linq;
+using LatexEditor.Fonts;
+
+namespace LatexEditor.Parser
+{
+    public class LatexRun : LatexSegment
+    {
+        public override IEnumerable<GlyphInfo> Glyphs => Segments.SelectMany(ls => ls.Glyphs);
+
+        public override double RelAdvWidth { get; }
+        public override double RelAdvHeight { get; }
+
+        public IEnumerable<LatexSegment> Segments { get; set; }
+
+        public LatexRun(IEnumerable<LatexSegment> segments)
+        {
+            Segments = segments;
+
+            // to shift characters into position
+            var x = 0d;
+            var y = 0d;
+            foreach (var segment in Segments)
+            {
+                if (segment is LatexReturn)
+                {
+                    x = 0d;
+                    y -= segment.RelAdvHeight;
+                    continue;
+                }
+                foreach (var gi in segment.Glyphs)
+                {
+                    gi.BaselineOrigin.X = x;
+                    gi.BaselineOrigin.Y = y;
+                }
+                x += segment.RelAdvWidth;
+            }
+            RelAdvWidth = x;
+        }
+    }
+}

WpfTex/LatexEditor/Parser/LatexSegment.cs

@@ -0,0 +1,101 @@
+using System.Collections.Generic;
+using System.Diagnostics;
+using JetBrains.Annotations;
+using LatexEditor.Fonts;
+
+namespace LatexEditor.Parser
+{
+    public abstract class LatexSegment
+    {
+        [NotNull]
+        public abstract IEnumerable<GlyphInfo> Glyphs { get; }
+
+        public static LatexSegment ToLatexSegment(IEnumerable<Token> tokens)
+        {
+            var tokenQ = new Queue<Token>(tokens);
+            var segments = new List<LatexSegment>();
+            while (tokenQ.Count > 0)
+                if (PopLatexSegment(tokenQ, out var ls))
+                    segments.Add(ls);
+
+            if (segments.Count == 0)
+                return new LatexNull();
+            if (segments.Count == 1)
+                return segments[0];
+            return new LatexRun(segments);
+        }
+
+        public abstract double RelAdvWidth { get; }
+        public abstract double RelAdvHeight { get; }
+
+        private static bool PopLatexSegment(Queue<Token> tokens, out LatexSegment val)
+        {
+            val = null;
+
+            if (tokens.Count == 0)
+                return false;
+
+            // todo: tabulate this
+
+            var head = tokens.Dequeue();
+            if (head.TokenName == "letter")
+                val = new LatexText(CmFont.SerifItalic, head.Value);
+            if (head.TokenName == "command")
+            {
+                if (LatexParser.GreekLetters.ContainsKey(head.Value))
+                    val = new LatexText(CmFont.SerifItalic, LatexParser.GreekLetters[head.Value]);
+                if (LatexParser.Spaces.ContainsKey(head.Value))
+                    val = new LatexSpace(LatexParser.Spaces[head.Value]);
+                if (head.Value == "^")
+                    if (PopLatexSegment(tokens, out var content))
+                    {
+                        val = new LatexSuper(content);
+                    }
+                    else // to prevent possible nullref, but still incorrect.
+                    {
+                        val = null;
+                        return false;
+                    }
+                if (val == null) // if no command matches
+                    val = new LatexText(CmFont.SerifItalic, head.CapturedString);
+            }
+            if (head.TokenName == "number")
+                val = new LatexText(CmFont.Serif, head.Value);
+            if (head.TokenName == "escape")
+                if (head.Value == "\\")
+                    val = new LatexReturn(1);
+            if (head.TokenName == "open")
+            {
+                var segments = new List<LatexSegment>();
+                while (tokens.Peek().TokenName != "close")
+                    if (PopLatexSegment(tokens, out var content))
+                        segments.Add(content);
+                tokens.Dequeue(); // toss the close
+                val = new LatexRun(segments);
+            }
+
+            return val != null || PopLatexSegment(tokens, out val);
+        }
+    }
+
+    public class LatexSuper : LatexSegment
+    {
+        public override IEnumerable<GlyphInfo> Glyphs => Content.Glyphs;
+
+        public override double RelAdvWidth => Content.RelAdvWidth;
+        public override double RelAdvHeight => Content.RelAdvHeight;
+
+        public LatexSegment Content { get; set; }
+
+        public LatexSuper(LatexSegment content)
+        {
+            Content = content;
+
+            foreach (var gi in Content.Glyphs)
+            {
+                gi.RelativeOffset.Y += 1;
+                gi.RelativeSize *= 0.5;
+            }
+        }
+    }
+}

WpfTex/LatexEditor/Parser/LatexSpace.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+using System.Linq;
+using LatexEditor.Fonts;
+
+namespace LatexEditor.Parser
+{
+    public class LatexSpace : LatexSegment
+    {
+        public override IEnumerable<GlyphInfo> Glyphs => Enumerable.Empty<GlyphInfo>();
+        public override double RelAdvWidth { get; }
+        public override double RelAdvHeight { get; }
+
+        public LatexSpace(double relAdvWidth)
+        {
+            RelAdvWidth = relAdvWidth;
+            RelAdvHeight = 0;
+        }
+    }
+}

WpfTex/LatexEditor/Parser/LatexText.cs

@@ -0,0 +1,35 @@
+using System.Collections.Generic;
+using System.Windows;
+using LatexEditor.Fonts;
+
+namespace LatexEditor.Parser
+{
+    public class LatexText : LatexSegment
+    {
+        private readonly List<GlyphInfo> _glyphs = new List<GlyphInfo>();
+
+        public override IEnumerable<GlyphInfo> Glyphs => _glyphs;
+        public override double RelAdvWidth { get; }
+        public override double RelAdvHeight { get; }
+
+        public LatexText(CmFont cmFont, int c)
+        {
+            var gi = new GlyphInfo(cmFont, c, new Point(0, 0), new Point(0, 0));
+            _glyphs.Add(gi);
+            RelAdvWidth = gi.RelAdvWidth;
+            RelAdvHeight = gi.RelAdvHeight;
+        }
+
+        public LatexText(CmFont cmFont, string text)
+        {
+            var x = 0d;
+            foreach (var c in text)
+            {
+                var gi = new GlyphInfo(cmFont, c, new Point(x, 0), new Point(0, 0));
+                _glyphs.Add(gi);
+                x += gi.RelAdvWidth;
+            }
+            RelAdvWidth = x;
+        }
+    }
+}