Re: BTW, if I want Emacs to support the CJK-EXT B Chinese Characters, must I use the arg --enable-font-backend?

[James Cloos <cloos@jhcloos.com>]

>>>>> "Kenichi" == Kenichi Handa <handa@m17n.org> writes:

Kenichi> Technically it's possible but there's no standard way.
Kenichi> First of all, I don't know if there's an agreement about
Kenichi> what registry-encoding to use for an X font for Unicode SIP
Kenichi> area.

There is no agreement on the registry-encoding.  The use of iso646-2
was explicitly rejected some years back.  (This was around the point
where Keith started public work on libXft, fontconfig and the render
extension and library, and may have been part of the motication.)

About a year ago George added support for non-BMP fonts to fontforge
for the display of reference glyphs (it uses XLFD fonts for its UI).

Fontforge uses UnicodePlane-{1,2,3,...,16} for the non-BMP planes.

Note that the only way to get the X server to use such fonts -- w/o
patching the server, of course -- is to use BDF or PCF fonts.  The
X server's and font-server's support for scalable fonts will not do
the right thing with random, user-specified encodings.

The general consensus on the X lists has been to depricate server-
side fonts in favour of fontconfig-discovered client-side fonts, so
it is unlikely that any specification of registry-encoding for non-
BMP will ever be standardized.  And as far as I am aware, nothing
but fontforge and emacs are even trying to support them.  (Besides,
of course, the glyphs in the non-unicode Chinese encoding(s) which
map to SIP code points in Unicode, as already supported by Emacs.)

As for fonts supporting Unicode-Plane-n, I am not aware of any.
I've been hacking a bit, on but more often off, on one for the
math block, but even when finished that will have glyphs sized
for fontforge's grid display; I expect they'd be too small for
anyone's editing usage.  No one else has announced any work or
plans on the fontforge lists for any other UnicodePlane-x font.

-JimC
-- 
James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6