code: func (f *Fpdf) textstring(s string) string {
  	if f.protect.encrypted {
  		b := []byte(s)
  		f.protect.rc4(uint32(f.n), &b)
  		s = string(b)
  	}
  	return "(" + f.escape(s) + ")"
  }
docs: // textstring formats a text string