> From: Robert Weiner <rsw@gnu.org>
> Date: Fri, 15 Dec 2017 12:38:15 -0500
> Cc: Alan Third <alan@idiocy.org>, emacs-devel <emacs-devel@gnu.org>
>
> The problem was that I would set-window-buffer in the new frame
> to a different buffer and that buffer would not display when
> the new frame was brought frontmost and displayed temporarily
> with a sleep-for delay. Calling force-window-update had no
> effect but calling (redisplay t) resolved it.
What do you mean by "displayed temporarily"? As long as the current
command runs, Emacs will not enter redisplay; an explicit call to
'redisplay' is the only exception to that rule. So it sounds like
what you describe is Emacs working as designed.