bug#33532: 26.1; set-window-configuration does not restore display start

[Juri Linkov <juri@jurta.org>]

>> Perfect! This is what I need also for current-window-configuration!
>> Also, could this be made the default? Or is there some advantage in
>> using markers instead of the actual positions that can be restored?
>
> First of all we need a "reasonable" use case.  The only purpose of a
> form like
>
> (let ((str (with-current-buffer buf (buffer-string))))
>   (with-current-buffer buf
>     (erase-buffer)
>     (insert str)))
>
> is to annihilate all marker positions in buf and I have yet to
> understand why that could be useful.  I'm sure you have something more
> reasonable in mind.  Once we have such a use case we can decide how to
> best support it.
>
> AFAICT Emacs' window configurations use window start and point markers
> ever since.  And while they interfere with reverting buffers (see
> Bug#33458 for a discussion) turning them into pure positions would
> break far too many things as to make that the default.
>
> We could store - in configurations and states - both, markers and
> their corresponding pure positions.  Then if, when restoring a
> configuration or state, a marker's position has dropped to 1 while the
> corresponding saved pure position is > 1, use the the pure position
> instead.  This should automatically fix your case and not violate any
> others.  Juri what do you think?

I see no drawbacks, let's try storing both (maybe together with
metadata like dired-filename).