Define a compose key on a Linux box.

A nice explanation on how to define a compose key on a Linux box:

I also came across a cool way to type any character of which you know the hexadecimal value in GTK programs. Type ctrl+shift+u, enter the hexadecimal value, and enter.

I looks like the method (g)vim uses: ctrl+v u [hex].

Why would anyone have a need for that? Well, I sometimes use it to input a rare Chinese graph which my Japanese IME doesn’t know about.