public record Glyph(char Code, Font Font);
public class GlyphFactory
{
    private readonly Dictionary<(char, string), Glyph> _pool = new();
    public Glyph Get(char c, Font f)
        => _pool.TryGetValue((c, f.Name), out var g)
           ? g : _pool[(c, f.Name)] = new Glyph(c, f);
}