Provide more overloads for the wide string flavour

[DanielaE]

Signed-off-by: Daniela Engert dani@ngrt.de

[DanielaE]

This code compiles now and is working fine on my machine:

auto sResult = fmt::sprintf("Elapsed time: %.2f seconds", 1.23);
auto wResult = fmt::sprintf(L"Elapsed time: %.2f seconds", 1.23);
fmt::print(std::cout, "Elapsed time: {:.2f} {}\n", 1.23, "seconds");
fmt::print(std::wcout, L"Elapsed time: {:.2f} {}\n", 1.23, L"seconds");

fmt::print("Elapsed time: {:.2f} {}\n", 1.23, "seconds");
fmt::print_colored(fmt::green, "Elapsed time: {:.2f} {}{}\n", 1.23, 'm', "seconds");
fmt::print(stdout, "Elapsed time: {:.2f} {}\n", 1.23, "seconds");
auto n = fmt::printf("Elapsed time: %.2f %cseconds\n", 1.23, 'm');
n = fmt::fprintf(stdout, "Elapsed time: %.2f %cseconds\n", 1.23, 'm');

_setmode(_fileno(stdout), _O_U16TEXT); // switch stdout into wchar_t (UTF16) mode

fmt::print(L"Elapsed time: {:.2f} {}\n", 1.23, L"seconds");
fmt::print_colored(fmt::green, L"Elapsed time: {:.2f} {}{}\n", 1.23, L'm', L"seconds");
fmt::print(stdout, L"Elapsed time: {:.2f} {}\n", 1.23, L"seconds");
n = fmt::printf(L"Elapsed time: %.2f %cseconds\n", 1.23, L'm');
n = fmt::fprintf(stdout, L"Elapsed time: %.2f %cseconds\n", 1.23, L'm');

Should handle issue #721

[vitaut]

Thanks a lot for the PR! Looks good, but could you add a few unit tests for the new functions?

[vitaut]

Could you elaborate on the disambiguation part and why you think it's brittle?

[DanielaE]

Hi Victor,

this is probably no longer true. During my various attempts, to replace

template <typename Container>
... vformat_to(std::back_insert_iterator<Container> out,
               string_view format_str, format_args args) {
...
}

in core.h by

template <typename Container>
... vformat_to(std::back_insert_iterator<Container> out,
      basic_string_view<typename Container::value_type> format_str,
      basic_format_args<typename buffer_context<typename Container::value_type>::type> args) {
...
}

to reduce code duplication, I got ambiguous overloads of vformat_toin core.h and format.h. My tests from today show that those more-derived structs don't help me to get along with this problem. Sigh ...

[vitaut]

The problem is not so much due to basic_format_args, but due to overloads taking string_view in format.h. Unfortunately I don't think it's possible to parameterize on character type there: https://godbolt.org/g/bPevXe.

this is probably no longer true

I've removed the comment then.

[DanielaE]

Do you need more test cases? And if so, where?

[vitaut]

Do you need more test cases? And if so, where?

Thanks a lot for adding tests, I think these are fine for now.

Merged in 2570f1a with minor tweaks.