[tex-live] Fontconfig for XeTeX versus regular fontconfig

[Karl Berry]

    >   ** ERROR ** Invalid glyph index (gid 2447)
    > and also reports of a slowdown of e.g. programs like Inkscape.

So, don't install the TL fonts as system fonts.

Or fix fontconfig or Inkscape, if that's the problem ("slowdown"?).
Or fix the broken fonts, if that's the problem.

    > Is there a solution or a simple way to disentangle the usage
    > of fontconfig for both the non-XeTeX and the XeTeX users on
    > the *same* system.

That cure seems worse than the disease to me.  XeTeX must look up system
fonts in the system way, not some fake way.

    Is there any way that kpathsea does *not* ignore FONTCONFIG_FILE,
    FONTCONFIG_PATH, and FC_CACHEDIR?  

Kpathsea itself knows nothing at all about fontconfig per se.
It just has those variable definitions, like any other variable
definition.  They are only used on Windows.  Quoting from texmf.cnf for
the record:

% Default settings for fontconfig library, used by Windows versions of
% xetex/xdvipdfmx.  On Unixish systems, fontconfig ignores this.
FONTCONFIG_FILE=fonts.conf
FONTCONFIG_PATH=$TEXMFSYSVAR/fonts/conf
FC_CACHEDIR=$TEXMFSYSVAR/fonts/cache

Best,
karl