Use a thirdparty logging library

[data-man]

Just an idea. It's a header-only C++ logging library with support fmtlib formatting.

[data-man]

Or spdlog.

[alabuzhev]

The idea is good, we definitely need to improve the logging, but...

loguru:

• has no idea that wide strings (std::wstring, const wchar_t*) exist.
• doesn't work with the current fmt version.

spdlog:

• supports only const wchar_t* in the format string. LOG(str.c_str(), ...) every time, really?
• supports it in a truly abominable way: through a conversion to UTF-8 and using deprecated <codecvt> interfaces.

Overall it looks like it would be simpler to create our own logger from scratch than trying to fix those libraries.