Hi Stefan,

First of all, thank you for looking into this.

On Sat, Apr 27, 2019 at 4:28 AM Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>
> >> I have now optimized CC Mode, such that each such self-insert-command
> >> now takes around 0.07s-0.1s.  I used two strategies for this: (i) breaking out
> >> of (expensive) fontification routines early, when the region being
> >> fontified is nothing but a string; (ii) Not fontifying the entire raw
> >> string for a change to only a small part of it.
> >
> > I have been working with C++ template metaprograms for two years, and
> > since quite early, I have experienced CC Mode being very sluggish that
> > I often switch back-and-forth between cc-mode and text-mode.
>
> Could you try out the "quick hack patch" I sent in
> https://debbugs.gnu.org/35316 ?
>
> It has a few known bugs, so it would require further work to be really
> useful, but I'd be interested to know if it helps your use case.

No, it does not help.

> > `emacs -Q' to visit the file locally.  Then, to experience the
> > sluggishness, I pressed M-> followed by M-v several times.
>
> FWIW, I don't expect my patch will help this use-case.

You are right.

I would like to add that C++ template seems to be a specific problem
in CC Mode as shown by the attached C++ program file.

Using `emacs -Q' with your patch to visit the attached file locally,
M-> C-u 10 C-p C-u 6 M-f DEL 10 is not sluggish at all when editing a
non template.  After that, let's edit a template: M-< C-v C-v C-v C-v
C-v C-u 4 M-f DEL is very sluggish.  After that, typing 10 is also
very sluggish.

>         Stefan

-- 
Best regards,
Tadeus