Since I didn't find place to discuss UI framework detail, I put some comments here (so it isn't as open as I expected ):

-- Why is the compositor based on QGLWidget instead of QWidget?
This implies that this UI framework requires HW OpenGL support all the time, similar to clutter.

This makes it less flexible when porting to a system w/o OpenGL and at least makes it more difficult to port as OpenGL driver is always closed source and not available from the beginning. (Actually, this is worst thing I think with Moblin).

-- Qt provides graphic system support, which make it possible to render using OpenGL or not. That is the flexibility I like with Qt. As such a fundamental component, using QWidget will provide more scalability. I like the idea in http://labs.trolltech.com/blogs/2009...e-an-overview/, which basically suggest to use SW raster engine by default and use QGLWidget when OpenGL acceleration is needed.