For instance, I can enter a pound £ or yen ¥ symbol, but not a Euro symbol; a copyright © but not trademark, and so on. All the characters seem to be defined in the system compose file (/usr/share/X11/locale/en_US.UTF-8/Compose), and I can see nothing different about the ones that work vs ones that don't.
I'm running OpenSuSE 13.1 with fvm2 window manager. IIRC, setup is just default US English. Working vs non-working seems to be the same in xterm, or in apps like the browser I'm using now.
The output of running locale; export | grep IM_MODULE is simply to run locale, and then to state export: Command not found. The output of locale is
LANG=en_US.UTF-8
LC_CTYPE=fr_CH
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=
(The LC_CTYPE is to make emails in French readable.) There doesn't seem to be an IM_MODULE variable in the environment. Doing env | grep IM gives
QT_IM_MODULE=xim
XMODIFIERS=@im=local
XDG_RUNTIME_DIR=/run/user/1000
GTK_IM_MODULE=cedilla
QT_IM_SWITCHER=imsw-multi
But those don't seem relevant, as I'm not trying it with QT or GTK applications. (AFAIK, I don't know for sure what the browsers use under the hood.)
locale; export | grep IM_MODULE?