How to discover when notebook has showing real back front buttons? (is overflowed)

I have a problem with GTK, In a notebook inside a container with real max width, when I add a page that overflow and has set_scrollable = false I get a un-maximize freeze.

To fix it I set scrollable to true but want when back/front buttons show (overflow) hide labels and set scrollable = false.

Get scrollable return true always even if no overflow and no buttons front&back.
What can I do?

Thanks in advance