Method on_text

extlibs/fmt/include/fmt/format.h:3151–3157

      : parse_context(str), context(r.begin(), format_args, loc) {}

  void on_text(const Char* begin, const Char* end) {
    auto size = internal::to_unsigned(end - begin);
    auto out = context.out();
    auto&& it = internal::reserve(out, size);
    it = std::copy_n(begin, size, it);
    context.advance_to(out);
  }

  void get_arg(int id) { arg = internal::get_arg(context, id); }