top: consolidate logic dealing with resetting a window

top: consolidate logic dealing with resetting a window

This commit just gathers all the logic associated with
resetting/normalizing a single window in one function.

In the future, should the window structure be expanded
to support added functionality, the act of maintaining
it will have been made a little bit easier, hopefully.

(everything is perfectly justified plus right margins)
(are completely filled, but of course it must be luck)

Signed-off-by: Jim Warner <james.warner@comcast.net>