code: function getFirstCharIndex(glyphs) {
      var minGlyph = _.min(glyphs, function (glyph) {
          return (glyph.unicode === 0) ? 0xFFFF : (glyph.unicode || 0);
      });
      if (minGlyph) {
          return minGlyph.unicode > 0xFFFF ? 0xFFFF : (minGlyph.unicode || 0);
      } else {
          return 0xFFFF;
      }
  }
docs: get first glyph unicode