bug#29737: 27.0.50; pixel-scroll-mode is laggy

[Valentin Ignatyev]

I've tried these both at the same time already. As I've said - scrolling down is a bit laggy (and it eats the CPU and turns on my fans up high). And scroll up is much laggier. It's when I scroll slowly. If I do quick swipe - emacs hangs and then jumps to the line when scrolling must end.

On Sun, Dec 24, 2017 at 12:28 PM, Tak Kunihiro <tkk@misasa.okayama-u.ac.jp> wrote:

> When I slowly start scrolling, it scrolls for a while and then jumps
> about 10 rows at the time, then scrolls a bit more and jumps again
> If I swipe my trackpad too fast, emacs instantly eats 100% CPU and
> hangs infinitely (it hangs not every time, but rather once in a
> while.  It can just go to the end of the file).
>
> If I scroll with Ctrl-key as Eli suggested in the first thread mail,
> it scrolls better than before the fix, but I still see this lag
> pattern (scroll a bit and then jump), but in the smaller scale and
> it doesn't kill emacs.  Setting mouse-wheel-progressive-speed to nil
> seem to make no difference.
>
> Btw, while I do use macbook, my OS is Arch Linux here.  Just tried
> it on mac os. pixel-scroll-mode works much better here though there
> is still small noticeable lag. And also I can see that scroll up
> lagging more than scroll down.

Can you try scrolling with following configuration?

  (setq mouse-wheel-scroll-amount '(1 ((shift) . 5) ((control))))
  (setq mouse-wheel-progressive-speed nil)

Those are two that are already suggested by Eli.  Please try both at
the same time.