Viewport - mouse intercepts problems

Hello,
I am trying to achieve such effect, that vertical scroll bar is shown only if mouse is over Viewport. But unfortunately isMouseOverOrDragging() always return false, even if my mouse is over and dragging. So I have no idea how to achieve such effect. It looks like it is something tricky.

I also tried to use
getViewedComponent()->isMouseOverOrDragging()
Which would be ok for me but it also doesn’t work.

I also tried inside nested components addMouseListener(&myViewPort) but it didn’t work satisfying (while I have there a lot of small components, so there are a lot of mouseEnter() and mouseExit()). It also looks ugly in code, and actually it also doesn’t work always.

For any help great thanks in advance.

OK, stupid thing, I am sorry for question, but sometimes man dig in in wrong direction, and can’t see simplest solution. and the solution is to call:
getViewedComponent()->addMouseListener(this, true);

If inside of viewed component I have a lot of small components, then I still have a lot of calls of mouseEnter and mouseExit, but actually I can handle it.