Qt fails to notice screen resize with TigerVNC

We first noticed this problem with Unity 2D on Ubuntu. The issue was the Unity was not properly updating its panels when the screen resized in the TigerVNC session. Locally the resize works fine though.

I did a small test program with PyQt that binds to the QApplication::desktop()->resize signal. It never triggers with TigerVNC, but just fine on the local console.

GTK+ however notices the resize just fine, so the proper RandR events seem to go out. I also checked that the root window is properly reconfigured.

Maybe Qt is reliant on some specifics for CRTC and outputs? Something that will generally be very simplistic for virtual displays like VNC.