bug#42655: 27.1; iconify-frame on a Lucid build may stuck the frame

[Eli Zaretskii]

> Date: Thu, 06 Aug 2020 16:47:00 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 42655@debbugs.gnu.org, eggert@cs.ucla.edu, uyennhi.qm@gmail.com,
>  bhavin7392@gmail.com, monnier@iro.umontreal.ca
> 
> Thanks.  Looks like we never get the MapNotify event from X windows?
> Can you verify that, either by running the xev utility or by setting a
> breakpoint in xterm.c:handle_one_xevent when MapNotify is handled, and
> repeating the recipe?

And one more thing: does it help to disable double-buffering?
(NEWS.26 explains how to do that.)