One thing in particular that I was interested in is(are) codecvt facets. I didn't any thing on this. Why is that?
Take a look on http://www.cplusplus.com/reference/std/locale/codecvt/ They allow you to imbue special charset to fstream and automatically translate wide characters to normal encoding like UTF-8 or ISO-8859-8.
Is this a separate subject or is that you believe they're not useful.
Theoretically they are very useful. For example: std::wofstream fs; fs.imbue(std::locale("he_IL.UTF-8")); fs.open("file.txt"); fs << L"שלום"! Would print UTF-8 output. But... - Many compilers/standard libraries do not implement locales at all. (GCC under Windows and Solaris, STL Port library) - Support of locales and encoding is strictly limited to OS configuration. So on some host the above example would work on other it would throw invalid locale error. - Some compilers/OSes do not support UTF-8 encodings (MSVC) so you can't create UTF-8 locale at all. - Locales name are platform depended. For example under Windows you need Hebrew_Israel.1255 locale and under Linux he_IL.ISO-8859-8 (and BTW 1255!=iso-8859-8) So Boost.Locale reimplements standard codecvt facet to make this work on any platform. However there is still a limitation when working with 2 byte characters (ie char16_t or wchar_t under windows) as Boost.Locale would work correctly only with UCS-2 But this is actually C++ standard's limitation. Best, Artyom