UTF-8 multi-byte characters are not displayed properly on Windows consoles

[LIU Hao]

Hello folks,

I'm mingw-w64 developer and MSYS2 contributor, and I maintain a GNU nano port to Windows [1]. First 
of all, thank you for the great work!

Since Windows 10, the Windows console has gained UTF-8 support, which however has to be enabled 
explicitly in system control panel. After UTF-8 support has been enabled and the UTF-8 code page has 
been set up with the `chcp 65001` command, all standard C ctype functions can work on UTF-8 strings.

However, when GNU nano attempts to display a UTF-8 string, it is taken bytewise and becomes 
gibberish. I have created this testcase, for example:

   ```
   #include <ncursesw/ncurses.h>

   int
   main(void)
     {
       initscr();
       addstr("»·");  // hex: C2 BB C2 B7
       refresh();
       getch();
     }
   ```

The commented string literal contains two characters as four bytes. On Linux it is displayed 
properly, but on a Windows UTF-8 console I get `»·`. How should I fix it?


[1] https://github.com/lhmouse/nano-win


--
Best regards,
LIU Hao

OpenPGP_signature
Description: OpenPGP digital signature