See also Emacs bug tracker feature request #22404 (which has not yet been implemented, but the mailing archive contains a rough draft rudimentary patch that creates a new hook for this specific issue): https://debbugs.gnu.org/cgi/bugreport.cgi?bug=22404
Whenever point moves outside of the visible window, the
window-scroll-functions hook is triggered -- at the very least one (1) time -- before the screen updates visually. The
window-scroll-functions hook is one of the last hooks available to the user via
elisp from which to obtain the new values for
window-end before a visual redisplay occurs. It is necessary to use the optional second argument in
window-end -- i.e.,
t for force.
abo-abo-wsf-fn when attached to the
window-scroll-functions hook will generate the new values for
window-end prior to visual redisplay. The hook is using a
(defun abo-abo-wsf-fn (win _start)
"A function attached to the `window-scroll-functions` hook."
(window-live-p (get-buffer-window (current-buffer)))
(window-start (window-start selected-window))
(window-end (window-end selected-window t)) )
(message "window-start: %s | window-end: %s" window-start window-end) )))
(add-hook 'window-scroll-functions 'abo-abo-wsf-fn nil t)
COMPLEXITIES: The above-example is not designed to deal with the complexities of a point being partially visible, or situations when the
window-scroll-functions hook is triggered more than one time per command loop. The links in the comments underneath the question of the original poster deal with those complexities. The original poster has not requested specific assistance in relation to those issues; however, so they are excluded from this limited example.