bug#21729: doc-view messed up by early auto-revert

[Stefan Monnier]

> i.e., I revert the buffer from an AUCTeX hook that's run after the
> compilation has finished.

That's a good approach if you run pdflatex from Emacs itself, yes.
[ Hmm... I guess I could also use emacsclient to get the same result,
  but it'd be a personal hack rather than a general functionality like
  auto-revert-mode.  ]

>> - Doc-view should inhibit auto-revert when the file was modified too
>> recently (on the assumption that it's not complete yet).
> Something like checking if the file's MTIME is more than a second ago?

Yes.

> Hm, no, that won't work.  I currently work on some large document (~450
> pages).  When I compile that, the file changes several times per second
> during the compilation, then it doesn't change for ~15 seconds while
> latex (lualatex in this case) is still running, and then starts changing
> again for maybe 3 seconds.

So we could additionally either check that the file is valid, or simply
"fail gracefully" if it isn't (e.g. keep displaying the old image, and
emit a message pointing to C-c C-c to see the raw data).  But it's not
a deal breaker: in your case, we may end up trying to revert the file
too early, which is annoying, but as long as we do end up re-reverting
it when the file is finally complete, I think it's OK.

>> - [ Just guessing here: ] We may sometimes fail to revert the file
>> after it's complete, maybe because the last reversion finished after
>> the file was complete, even though it started before, so the last
>> reversion failed to include some changes that were added while the
>> buffer was being reverted.
> Yeah, that's possible.  And I think there could also be a problem when
> people use latexmk which compiles your document several times until all
> refs are defined and its stable.  Here, we might revert exactly between
> two latex runs.

I don't think reverting between two latex runs is a problem.  It might
be "wasted work", but for a generic functionality like auto-revert-mode,
there's no way to do better since it can't know that another run is
about to come.


        Stefan