Subject: Re: bug#13675: Extremely slow redisplay when lines are very long

From: Eli Zaretskii <[email-masked]>
Date: Fri, 20 Oct 2017 09:44:30 +0300

> From: Mark Diekhans <[email-masked]>
> Date: Thu, 19 Oct 2017 18:45:00 -0700
> 
> Is there anyone working on the long-line display speed issue?

Not that I know of.  I don't even have an idea for how to speed it up,
and I don't think anyone's come up with such ideas.

> It is especially bad with font lock mode.

What mode/kind of file needs font lock and has such long lines?

In general, if you must handle such files, my advice is to use M-x
find-file-literally for them, it might make Emacs just barely
bearable, if you are lucky.  But then you lose any font locking and
text encoding support, so this is only feasible for plain-ASCII files
that basically present some text.

> If the fix is really complex, it would be much better emacs
> refuse to display the file than force killing it.

Patches for presenting a warning for such files, like we do with very
large files, are welcome.