bug#67604: Motion problems with inline images

[Eli Zaretskii]

> From: JD Smith <jdtsmith@gmail.com>
> Date: Tue, 5 Dec 2023 18:06:41 -0500
> Cc: 67604@debbugs.gnu.org
> 
> >> Before or after the test?
> > 
> > After the test.
> 
> OK, so this was likely a false positive then.  I’m out of ideas.  Maybe 
> Windows is magically immune.

Unlikely.  More likely is that we need some specific metrics of the
displayed stuff to see the problem (which is therefore very rare).

> For me both NS and Mac builds with your most recent xdisp.c fixes exhibit the 
> same motion issue.  Do you have anyone you can call in to try the simple test 
> on another build?

Not really, no.  But reproducing the problem is just a step towards
debugging it, so the alternative is for you to step through next-line
and its subroutines (or in C through vertical-motion) and tell what
happens there, and preferably also why.  It isn't like I'm the only
one who should be able to read the code and understand where it fails.