This is a little verbose. An alternative would be to make a defun-window macro to hide the resolving, but I'm not sure I like that magicness.
Something else to consider: instead of a simple if, we could implement resolve-window like this:
(defun resolve-window (window-designator)
((eql t) *standard-window*)
This would give a nicer error message if a user passes in something that's not either a window or t, but would be a bit more expensive in every single call. I have no strong feelings either way.
Add T as an alias for *STANDARD-WINDOW*