Wide-issue and WT_SESSION

[gvanem]

I've made a little test-program for UTF-8 encoded strings. The gist of it:

/**
 * Check the UTF-8 output of 2 airports.
 *
 * "KEF" should translate to "Reykjavik" with an acute 'i'; U+00ED, as hex "C3 AD"
 * https://www.compart.com/en/unicode/U+00ED
 *
 * "ENFL" should translate to "Floro" with stoke across the 'o'; U+00F8, as hex "C3 B8"
 * https://www.compart.com/en/unicode/U+00F8
 */
static void test_utf8 (void)
{
  const char    *KEF1 =  "Reykjav\xC3\xADk";  /* UTF-8 encoding */
  const wchar_t *KEF2 = L"Reykjav\xEDk";      /* UTF-16 encoding */
  const char    *FLO1 =  "Flor\xC3\xB8";      /* UTF-8 encoding */
  const wchar_t *FLO2 = L"Flor\xF8";          /* UTF-16 encoding */
  int   y;

  if (Modes.tui_interface == TUI_CURSES)
       y = getcury (stdscr);
  else y = con_info_out.dwCursorPosition.Y;

  (*api->print_format) (0, y++, "Using TUI=%s, locale: %s",
                        Modes.tui_interface == TUI_CURSES ? "Curses" : "WinCon",
                        setlocale (LC_ALL, NULL));

  (*api->print_format) (0, y++, "KEF1: '%s'\n"
                                "FLO1: '%s'", KEF1, FLO1);
  y++;

  (*api->print_wformat) (0, y++, L"KEF2: '%s'\n"
                                  "FLO2: '%s'", KEF2, FLO2);
  y += 2;

  (*api->print_wformat) (0, y++, L"Wide:  %-20.20s: %S", KEF2, hex_dump(KEF2, 2*wcslen(KEF2)));
  (*api->print_wformat) (0, y++, L"Wide:  %-20.20s: %S", FLO2, hex_dump(FLO2, 2*wcslen(FLO2)));

  y++;
  (*api->print_format) (0, y++, "ASCII: %-20.20s: %s", KEF1, hex_dump(KEF1, strlen(KEF1)));
  (*api->print_format) (0, y++, "ASCII: %-20.20s: %s", FLO1, hex_dump(FLO1, strlen(FLO1)));
}

The *api->print_format and *api->print_wformat are just func-pointers set to either plain WinCon or PDCurses-mod functions at runtime.

With a set WT_SESSION=1 before running, it display just fine:

But w/o a set WT_SESSION=1, it looks like this:

I've tried with setlocale (LC_ALL, ".utf8"); and/or SetConsoleOutputCP (CP_UTF8); w/o much difference. Only this strange set WT_SESSION=1 fixes it.

So what is this and pdc_wt all about?

And BTW, I'm on Win-10 using TakeCommand as my shell. No Leagacy Console and UTF-8 set in some Windows setting.