There have been several reports/complaints about small gaps beside
toolkit scroll bars on the frame edges. Some complained about the gap
with the frame edge, and others the one with the fringe of the window.
(I think the latter makes more sense because a scroll bar is
associated with its scrolling target, i.e., window, not with the
containing frame.)
According to *1 and *2, this is due to the restrictions that toolkit
scroll bars have a fixed width and each window must be placed on a
multiple of the frame default column width. Though the latter is
planned to be relaxed in future, that will/should not happen before
the release, of course.
*1 http://lists.gnu.org/archive/html/emacs-pretest-bug/2005-07/msg00326.html
*2 http://lists.gnu.org/archive/html/emacs-devel/2004-10/msg00291.html
I've just tried extending the fringe backgrounds to such scroll bar
gaps. Its rough idea is already mentioned in *3. I think this is
simple enough to incorporate before the release (if it works properly,
of course). What do people think about that?
*3 http://lists.gnu.org/archive/html/emacs-pretest-bug/2005-09/msg00334.html