>>164
(let ((s (window-start)))
(display-buffer foo)
(set-window-start (selected-window) s))

とか

(let ((s (window-start))
(w (selected-window)))
(pop-to-buffer foo)
(set-window-start w s))

でいいのでは。で、 foo に用が無くなったら

(delete-window-on foo)