I've rebuilt the library with ./configure --enable-widec --enable-xim and testcurs now shows alternate characters correctly.
I've also rebuilt my application with #define XCURSES #define PDC_WIDE #define PDC_XIM #include <xcurses/curses.h> but to no avail. I still get the ascii fallback characters. What's the trick? The default font is enormous compared to what it was before. Presumably I need to define some X resources. Which? Thanks, j.