GTK may have a difficult API, but it is portable and it gives a better feel than Qt for Linux+Gnome users like me (I will always choose a GTK app over a Qt app).
Saying that from wrongly choosing it over Qt for a cross platform screenrecording/annotation project a few years ago.
There's literally no way in hell to recommend GTK for any new desktop project that likely has a Windows audience. GTK is a mess. :(
It sounds like GTK is eliminated too.
What's left now, QT and wxWidgets?
If you have skill in C++ already, then Qt is a natural fit there. Also, Qt's docs are very good. None of the "oh, I was advised to use this class. Where are the docs? What do you mean... go read the source code?".
Gah... sorry... still haven't gotten my extremely bad experiences with Gtk out of my system (years later). ;)
If I were doing a desktop GUI type app again, I'd choose Qt for sure. Good docs, very large user base, actively helpful Community on IRC. (I'm not really a forums guy). Plus, bunches of Qt code (of various quality) on GitHub for getting ideas from.
Hope that's useful. :)
I want to know the difference between the thin layer and the existing libraries. Not in vague terms but specifically with a code example.
But then again, it's not something I've personally tried (nor needed), so that might be an inaccurate assessment.
If you don't need a full/complete GUI stack (and other related bits) implementation for your application, then yeah, it might be the way to go.