Ok, here is version 0.0.1 of my Qt4 backend for IUP . It's not very good, but a bunch of things work. A whole bunch more do not, of course.
I am showing this just because I want to rewrite it, because I noticed that I am writing it like it was Motif still, and I must understand this is actually C++ and Qt code ;-)
You can download it here (click on the "Free" button and wait a while).
You will need Qt4 and qmake to make it work.