Flat QScrollArea

I need to make QScrollArea flat. By default it has sunken border.

So what's stopping you from doing that?

I don't know how to do that)
May be I need to use some of QWidget attributes?

Well... I'd start with taking a look what properties does QScrollArea and its superclasses offer. Only then would I ask a question here, not the other way round.

Sorry...(
Thanks for lesson!
I will do that in a future.