Re: bug-reference-prog-mode slows down CC Mode's scrolling by ~7%

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: acm@muc.de,  emacs-devel@gnu.org
> Date: Sat, 04 Sep 2021 12:39:09 -0400
> 
> > To see the "waste" in single-windowful scrolls, we need a suitable
> > benchmark, which measures the time of each scroll separately.  It
> > would probably make sense to make it generate a random value of point,
> > then measure the time it takes to go there and display.
> 
> Maybe a good way to see the waste is to measure the time for the initial
> font-lock in an outline-mode buffer where the screen is filled with
> single-line headers and everything else is hidden: a whole chunk will be
> fontified for each line, so with a single 40-line screen you can expect
> to fontify 40 chunks (unless the hidden text between lines is smaller
> than the chunk size, of course).
> 
> 
>         Stefan
> 
> 
> PS: For the record, I was made aware of this case back in the days of
> lazy-lock because lazy-lock didn't know how to skip invisible text (it
> just fontified everything between window-start and window-end), so in
> some cases it would end up fontifying the whole buffer.

You are saying that jit-lock skips invisible text?  I don't think I
see this in the code.