IBus

IBus (Intelligent Input Bus) is an open source input framework for Linux and Unix.

Installation
Except for the basic IBus framework, one or more engines should be installed. For example:

Have a look at the eix output for more available engines:

For graphical toolkit integration, offers gtk (this refers to gtk+:2) and gtk3 useflags, and there is a separate  package for Qt (including KDE) as well. Don't forget to install this latest package if you are a KDE/QT user

You can use for selecting your preferred input method. As for now all im-chooser packages are marked unstable, though.

If nothing starts (no ibus daemon) when you log in, you can use put this in your .xprofile file :

You can finely tune the installation by running for setting your preferred input methods and the system keyboard you use, as well as whether you want an icon in the taskbar to tell Qt ibus is now your input method.