In Emacs, I can use mozc-emacs-helper to type Japanese without triggering system
input method (IM). However since I don’t have “use different input method for each
window” enabled because it kinds of fucks my brain, system IM sometimes remains
active in Emacs. The fix is to edit the Exec line in Emacs’ .desktop file as
follows.
Exec=env XMODIFIERS=@im=none GTK_IM_MODULE=xim QT_IM_MODULE=xim /usr/bin/emacs %F
This problem does not happen in xfcee though. Turning on system IM Mozc using its keybind directly turns on Mozc inside of Emacs.