For ControlWindow there is a new method do_rawcontrolhit(), which gets

For ControlWindow there is a new method do_rawcontrolhit(), which gets
control before TrackControl is called. The default implementation
calls TrackControl and then do_controlhit().

For ScrolledWindow, do_rawcontrol passes a tracker function to
TrackControl if the mouse is in one of the arrows or grey areas, and
the tracker handles scrolling. For the thumb part nothing has changed.