Yessss it is. The gui is written in Qt c++ and all the processing backend is C.

https://github.com/videolan/vlc/tree/master/modules/gui/qt

Only for nix -- for the Mac, it's using native widgets, if I'm not mistaken:

https://github.com/videolan/vlc/tree/master/modules/gui/maco...

(Which is pretty damning -- they already had a Qt implementation, but would rather do real native!)

Ouch. Mac for Qt is definitely the weakest point. Theres some experimental work being done to allow developers to wrap native Mac controls. http://blog.qt.io/blog/2017/02/06/native-look-feel/

This would help a lot, I think. Still a going concern, or a dormant experiment?

Its targeted for Qt6, which is not coming anytime soon, but it gives me hope that Qt always has smart options to move on.