code: function sizeofCompound(glyf, hinting) {
              var size = 10;
              var transform;
              glyf.glyfs.forEach(function (g) {
                  transform = g.transform;
                  // flags + glyfIndex
                  size += 4;
  
                  // a, b, c, d, e
                  // xy values or points
                  if (transform.e < 0 || transform.e > 0x7F || transform.f < 0 || transform.f > 0x7F) {
                      size += 4;
                  }
                  else {
                      size += 2;
                  }
  
                  // 01 , 10
                  if (transform.b || transform.c) {
                      size += 8;
                  }
                  else {
                      // scale
                      if (transform.a !== 1 || transform.d !== 1) {
                          size += transform.a === transform.d ? 2 : 4;
                      }
                  }
  
              });
  
              return size;
          }
docs: 复合图元size
  
  @param {Object} glyf glyf对象
  @param {boolean} hinting 是否保留hints, compound 图元暂时不做hinting
  @return {number} size大小