How are the compose sequences defined?

[Jaroslav Jiricka <jiricka zeus img cas cz>]

In GTK+ 2.0 apps I can't input some of the ISO8859-2 characters which need
dead keys (or compose key) to be typed. These include ecaron, tcaron etc, 
while ex. scaron or zcaron do work. There are no keyboard problems in GTK1 
or KDE3 apps run from Gnome 2.0 desktop. Accented characters typed by 
single key do work, too, and I can also remap ex. tcaron to AltGr+t or 
anything in the xmodmap.cz file to work in Gtk2. But this is not the 
solution I'm looking for.

Gtk2 apps don't seem to be affected by modifications in any of
/usr/X11R6/lib/X11/locale/any_locale/Compose files; how are the compose 
sequences handled then?

I use RedHat 7.3 with XFree86 4.2 and Gnome 2.0 final compiled with 
Garnome 0.12, locales set to cs_CZ.ISO8859-2 (tried cs_CZ.UTF-8, too),
xmodmap for keyboard switching.

Thanks for your time
Jaroslav Jiricka