How too get user input in Linux, beside using toolkits such as gtk++ or SDL.

For what kind of application? Use the Qt/GTK toolkits for GIU applications. Use the stdin for commandline applications. Use SDL for SDL applications.

What are about for a game? The reason I don't what to use SDL is because I already have a custom framework for windowing using Xlib. Should I use Xlib events to process inputs for games?

What's I'm looking for is something like DirectInput, sort of. This is for an engine and I need to have each component separated (graphics, input, sound, windowing, etc) which can have switched implementation.

Under x11, there is XInput (which should work - I havn't used it - various things like tablets, joys, mice, etc).

However, there are the standard x events, which you can use for mouse and keyboard. And, for joysticks, you can get values from /dev/input/js# or event# depending on your needs.

Or, you could try my INput lib, OIS - which works well X11 apps :)

Any documentation on XInput?

Here seems a good resource. Not sure though, jsut did a quick search for that.