Ibus with ibus-unikey on gnome3 in arch linux.

The default ibus installation in arch doesn't include gtk3 support. You will have to compile the source. This can be done by pull in the ibus-git package from AUR with yaourt.
When you are ask to edit PKGBUILD, go to the configure section and add –enable-gtk3 options, install it and all is set.

The problem is ibus-unikey, which is – up to date – the most popular Vietnamese input method in linux will have to be recompile to work with the new ibus. Don't download the source package it's oudated. Do a git pull as instructed in http://code.google.com/p/ibus-unikey/wiki/CompileDevSource:

 git clone git://github.com/mrlequoctuan/ibus-unikey.git ibus-unikey

cd ibus-unikey
./autogen.sh --prefix=/usr
sudo make install