how to get started using input stuff?

[Sunnan <sunnan handgranat org>]

(Note: this is an end-user question, and maybe this is the wrong place
for it - if so, I'm sorry. Suggestions of better places to ask this
question are welcome.)

Okay, here's the ideal situation:

I want something that works like GNU Emacs' "swedish-postfix"-mode,
which I've used for years, but for Gnome and Mozilla apps (if it works
with others as well, that's a plus).

I don't even know where to get started.

This page,
http://developer.gnome.org/arch/i18n/xim.html

says:

"A simple input method within the X server is used to handle accent
composition for European languages, but..."

What is that page referring to? Is that the recommended method?

What should I do?

Thanks.