The attached application brings up a scrollpane whose child is a panel.
The scrollpane itself is contained in a panel.

On Solaris, the scrollpane appears as wide as the containing panel.
On Windows NT, the scrollpane appears half as wide as the containing
panel.

If the application is modified so that the child of the scrollpane is
a canvas rather than a panel, the scrollpane appears as wide as the
containing panel on both platforms.