Unsolved Qt Installer test avalability of GUI windowing system

[vyau]

I am using Qt Installer to package my work. I am trying to have the installer logic check and see if GUI is available before I fire up all the dialog boxes within my installation process. Sometimes, installation can happen in a shell window with no windowing system and in which I want to do something else.

I am unable to find a way to do this "GUI windowing" check to determine if windowing system is there.
Any pointers on this much appreciated!