Hi,
It is possible to mix U++ loop with gtk+ loop and have gtk+ widgets in U++ window. I didn't tried but once you init gtk (gtk_init(...)) you may create a widget, get and Window (XWindow) from U++ Window and wrap it to a GdkWindow and set it as widget parent and in U++ Ctrl::EventLoop0 in loop put a call to gtk_main_iteration_do(false) to process events from gtk+. I've didn't tried that so you're at risk of obtaining nothing, still it isn't that hard to try and don't have to write much code .