How do I configure wcwidth?

[Alan Mackenzie]

Hello, Libc-help.

I'm trying to enhance the Linux console to handle full UTF8.  At the
moment, I'm using the Unifont 8x16 font.  It has both half-width glyphs
(e.g. normal ASCII) and full-width glyphs (e.g. Asian languages and many
symbols).

I can currently output these to the console, but the readline system
(used by bash) corrupts some glyphs due to not knowing reliably how wide
they are.

For example, U+2614 (UMBRELLA WITH RAIN DROPS) is a half-width glyph in
Unifont, but readline thinks it is full-width.  By contrast, U+2622
(RADIOACTIVE SIGN) is full-width in Unifont, but half-width in readline.

I think readline uses the glibc function wcwidth, the function that
returns the width in column positions of its utf32 argument.  I would
like to configure this function for Unifont.  I'd appreciate help on
doing this.

I've glanced through some of the glibc source code, in particular
..../glibc-2.42/locale/programs/ld-ctype.c and I think the wcwidth
configuration is part of the locale.  Can this be?

If so, the info manual ‘The GNU C Library Reference Manual’ describes
how to select a locale and the effect of this, but doesn't seem to say
how to modify a locale, or create a new one from scratch.

In summary, I'd like to get readline recognising the correct widths for
Unifont glyphs.  Am I on the right track?

Thanks!

-- 
Alan Mackenzie (Nuremberg, Germany).