Make it check when Emacs gets focused

[promisedlandt]

Hello,

I often use fcitx to write Korean in another application (like web browser, chat program...). When I focus Emacs again, and I'm in Evil normal mode, I would like it to disable fcitx.
Is something like this easily added? Or should it work already and maybe it's only an issue with my setup?
Reading this it looks like maybe it would be enough to add a check at the switch-frame event.
But I'm a noob Emacs user.