On 2016-07-03 22:41, Eli Zaretskii wrote:
> Blocking input is not enough (and is just a workaround for problems 
> you had, anyway).

Ok; thanks for clarifying!

> But before we discuss this seriously, I have a feeling that such a
> hook was already discussed in the past, and we found it unnecessary
> and/or dangerous.  Stefan, do you remember something like that?

Thanks.  My search-engine-fu was insufficient to dig up that discussion.  It could be around the time of the commit below, but none of Stefan's posts at the time mention that

    commit 379ec02c03febd0955b2c235c9e596db82fef8a0
    Author: Stefan Monnier <monnier@iro.umontreal.ca>
    Date:   Tue Mar 25 17:32:20 2008 +0000

        (redisplay-end-trigger-functions, window-redisplay-end-trigger)
        (set-window-redisplay-end-trigger, process-filter-multibyte-p)
        (set-process-filter-multibyte): Mark as obsolete.

Further digging points to:

- https://lists.gnu.org/archive/html/emacs-devel/2009-02/msg00785.html, in which Stefan mentioned a post-redisplay-hook in passing

- https://lists.gnu.org/archive/html/emacs-devel/2010-01/msg01313.html, which Alan started, and in which you mentioned (https://lists.gnu.org/archive/html/emacs-devel/2010-01/msg01428.html) such a hook.

- https://lists.gnu.org/archive/html/bug-gnu-emacs/2011-12/msg00785.html, where Stefan asked for a pre-redisplay-hook, and Richard expressed concerns about debugging display-related hooks.

- https://lists.gnu.org/archive/html/bug-gnu-emacs/2016-01/msg01011.html, where you mentioned maybe needing a post-redisplay-hook.

That's all I could find :)
Clément.