I'm experiencing a problem when trying to redraw a widget. In the attached code I have tried to simplify the issue as much as I could.

When I push the red button, both scroll widgets move to the correct position and are redrawn accordingly. However, when I try to move the left scroll by using the right scroll it doesn't work. In fact, as the printed output indicates, the left scroll is moved, but not redrawn (i.e. Scroll_C::draw() is not called). 

How can I make the scroll method work? The only difference I see between  the two methods seems to be the calling stack when the Scroll::move() functions are called. Maybe it's some C++ issue?

Many thanks for any help.