public static void HighlightCharacterAt <TFont, TGlyph>(this FractionDisplay <TFont, TGlyph> self, MathListIndex index, Color color) where TFont : IFont <TGlyph> { if (index.SubIndexType != MathListSubIndexType.None) { throw Arg("The subindex must be none to get the highlight a character in it.", nameof(index)); } self.Highlight(color); }