bug#69478: 30.0.50; Emacs dies after scrolling in eww

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Alexander Prähauser <ahprae@protonmail.com>,
>   69478@debbugs.gnu.org
> Date: Fri, 01 Mar 2024 09:48:49 +0800
> 
> This is a BadMatch error triggered by copying between incompatible
> drawables with a CopyArea request, which isn't possible in most of our
> callers.  The crash's circumstances suggest that an image is being
> created and subsequently copied with incompatible parameters, but to
> establish which image that is Emacs must be started as follows:
> 
>   ./emacs -xrm 'Emacs.synchronous: true'
> 
> so that X errors are reported immediately upon the offending requests
> being issued.

Should the above be run from the shell prompt or from GDB?  If the
former, how would we determine which image causes this?