bug#33384: [PATCH] Fix zone.el when window is at the bottom of the buffer

[Eli Zaretskii <eliz@gnu.org>]

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> From: Thomas de Beauchene <thomas.de.beauchene@gmail.com>
> Date: Fri, 16 Nov 2018 12:04:39 +0100
> 
> Thanks for the swift response.
> 
> It is an issue that I am facing since I started using zone, when they
> integrated it in Spacemacs a few month ago. Anytime the window is past the
> buffer end (like the end of the buffer in the middle of the window) instead
> of starting, Zone just throws an error:
> 
> let: Args out of range: #<buffer zone.el.gz>, 21124, 22313
> 
> When I investigated I pinpointed the error to this exact line that I'm
> patching. The numbers *do* correspond to the values of (window-start) and
> (window-end). I then started playing around with it in a scratch buffer,
> and (window-end) would always return the size of the buffer plus one, which
> would always make (buffer-substring) throw an error when I ran it in
> eval-expression.
> 
> Again, I had this behaviour in Spacemacs, so with a lot of packages and
> code on top of Emacs. I will try today to figure out the exact conditions,
> why you don't reproduce while I do. Already I could reproduce in zone.el.gz
> but not in *Messages* today.
> 
> Any idea of what could alter the return value of (window-end) ?

Some defadvice, perhaps?