ScrolledWindows's width is not equal to the sum of its childrens' widths

[jody <jody xha gmail com>]

Hi

I have a question concerning the size of the visible area inside
a scrolled window.
The Width of the scrolled Window as obtained from get_width() is 22
pixel greater that the width of the visible area.
Similarily, its height is 20 pixel larger than the height of the
visible area. The height of the horizontal scrollbar
is 16, and the width of the vertical scrollbar is 16 as well.
Where do those missing 6, respectively 4 extra pixels come from?
Is it some element of the scrolled window whose dimensions i could request?

Thank You
 Jody