ibus 1.4.1 doesn't work with Opera 12

ibus 1.4.1 doesn't work with Opera 12

Environment: Ubuntu 12.04 Opera 12 ibus 1.4.1
I've installed ibus-qt and add the two lines below in /usr/bin/opera, but
it makes no difference:
QT_IM_MODULE=xim
XMODIFIERS="@im=ibus"
As some say that QT has been deprecated in Opera, so I've also added
GTK_IM_MODULE=xim in Opera, but still no difference.
Am I missing something or we just can't use ibus in Opera 12?