GtkScrolledWindow scrolling inconsistency

I have noticed something which is inconsistent with the way that Windows
operates.  If you have a GtkTreeView and you click on the 'down' arrow and
hold the mouse button, the list only moves ONE record and stops.  On
Windows, this would continually move until the button is released.

I suspect this is because the scrollwindow received ONE button_pressed_event
and acts solely on that click.  Is it possible for this to be modified to
work as windows does?

Regards,
Martyn