bug#39658: 26.3; can't edit file with terminal escape sequences

[frederik]

Thank you Mattias for figuring that out, and Eli for being more patient than I.

I think I'll let the professionals handle it from here.

On Tue, Feb 18, 2020 at 05:02:29PM +0100, Mattias Engdegård wrote:
> > My guess is that rendering the escape sequences in the problem file is causing 
> > some kind of quadratic complexity.
>
> It looks like it's the left square brackets ('['). Take them out and it's fast.

On Tue, Feb 18, 2020 at 06:08:55PM +0200, Eli Zaretskii wrote:
> > Date: Tue, 18 Feb 2020 05:48:59 -0800
> > From: frederik@ofb.net
> >
> > To reproduce, open the attached file in Emacs, and type C-x C-n. On my system 
> > Emacs uses 100% of CPU, indefinitely.
>
> On my system, visiting this file takes 36 sec of CPU time.  Which is
> long, but is not indefinitely.
>
> If someone wants to investigate this case, I'd start with visiting the
> file after "M-x profiler-start".  Then look at the hot spot(s).