Introducing Qt 5.0 | Qt Blog

While we have cleaned up many things in our internal architecture and made Qt more modular, leaner and faster, we have managed to keep application compatibility in a way that most applications will work with very few changes and a simple recompile on Qt 5.

Of course, this also implies that Qt Widgets are fully supported and an essential part of Qt 5.

via Introducing Qt 5.0 | Qt Blog.