Multilingual library of input methods in cross-platform

Until now, when I need input method support for languages ​​that do not use the Latin alphabet, I would call winapi and test it in Wine to require cross-platform.

While I can learn and use X input method processing on Linux, I am having the problem of not having native support for Apple computers, etc.

So, I'm looking for a cross platform library to do this. Either C or C ++ is fine. I have of course had a google search, without satisfying the results.

I prefer not to mess with the huge set of widget tools like Qt or GTK as the libraries themselves will be several times the size of my application. But at least let me know if I have no choice.