bug#34038: 26.1; set-window-start sometimes fails to set window start

[Eli Zaretskii]

> Date: Fri, 11 Jan 2019 08:37:53 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 34038@debbugs.gnu.org
> 
> > I think this happens because you call set-window-start with last
> > argument non-nil.  Doing that tells the display engine that the
> > window-start point is just a suggestion, not a hard requirement.
> 
> Sorry for jumping in here ignorantly.  I just looked
> at the doc string for `set-window-start' and got a
> very different impression of what that 3rd arg means.
> Am I mistaken?  How to reconcile your description
> with what the doc string says?
> 
>   Optional third arg NOFORCE non-nil inhibits next
>   redisplay from overriding motion of point in order
>   to display at this exact start.

I don't think I see the difficulty, the doc string seems to tell
exactly what I did, albeit in a different way.