shown/hidden tabs

When we add too many tabs, there is a tabsheet scroller which appears and we have 2 categories of tabs : shown and hidden tabs. How can I recuperate the list of shown tabs at a given moment?
I’m a newbie… I hope I could explain the problem cleary.
Thank you very much in advance.

Unfortunatelly there is no server side method to get information about the tabs that are hidden by the lack of vertical space.

It should be possible to create a
clientside extension
that triggers an event whenever some tabs are hidden by the tabsheet element’s resize events and when the scroll buttons are clicked.