bug#19910: 24.4; Japanese font names are decoded incorrectly in Cygwin's emacs-w32 in LANG=ja_JP.UTF-8

[Fujii Hironori <fujii.hironori@gmail.com>]

Thank you for reviewing my patch, Eli.

On Sat, Feb 28, 2015 at 1:03 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> However, this goes too far: there's no need to replace all the
> functions with "wide" versions, only those functions that return font
> name strings from the system.  For example, I don't think
> CreateFontIndirect needs to be switched to Unicode, does it?  And CRT
> functions like _wcslwr and swprintf that work on wchar_t arguments
> aren't supported on Windows 9X, AFAIK, so we cannot call them.  (One
> reason for using the minimum number of "wide" APIs is that we don't
> have good ways of testing the development code on Windows 9X.)

This is the code:

|    862  hfont = CreateFontIndirect (&logfont);
| (...)
|    912 = DECODE_SYSTEM (build_string (logfont.lfFaceName));

logfont.lfFaceName is ANSI text and DECODE_SYSTEM is the problem.
CreateFontIndirect should be wide.

> I would actually suggest to have a Cygwin-only branches of the code,
> where you can freely call the "wide" APIs without bothering about
> Windows 9X, since that's what the Cygwin-w32 build does elsewhere, and
> since this is a Cygwin-specific problem due to the difference between
> file-name encoding and the locale emulated by Cygwin.  There are a
> bunch of macros like GUI_STR and GUI_ENCODE_FILE near the end of
> w32term.h that can be used to minimize #ifdef's to the absolute
> minimum.

If this approach is used, structs such as LOGFONT and ENUMLOGFONTEX
should be ranemed to GUI_FN(LOGFONT) and GUI_FN(ENUMLOGFONTEX).
This looks ugly.

The best way to solve this is defining _UNICODE.
Defining _UNICODE is already filed, but closed as wontfix.

#265 - Build error with _UNICODE on w32. - GNU bug report logs
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=265

If Bug#265 is resolved, this bug (Bug#19910) will be resolved automatically.
And, _UNICODE macro can be used not only for Cygwin, but also NTEmacs.