Subject: bug#42406: Mouse-wheel scrolling can be flickering

From: Alan Third <[email-masked]>
Date: Sat, 10 Oct 2020 10:51:00 +0100

On Thu, Jul 30, 2020 at 12:30:27PM +0200, Konrad Podczeck wrote:
> Having taken a closer look, it seems to me now that what I called "flickering" is the following:
> 
> Mouse-wheel scroll downwards, so that the cursor becomes positioned
> at the top row of the frame. Then release the mouse-wheel, but so
> that inertia scrolling continues for a short time. After the
> scrolling comes to rest, which is probably determined by the window
> manager, there is an extra movement, governed probably by Emacs, to
> make sure that it is not the case that only, say, half of a row is
> visible at the top of the frame. It seems to me that it is this
> extra movement which leads to what I called "flickering."

Sorry for the long delay. In standard Emacs usage you shouldn't ever
see half a line displayed at the top of the screen. Are you using
pixel scroll mode or something?

The only alternative I can think of is that the inertia just pushes it
over the edge to scroll one more line, but I don't think you would see
that as "flickering", just an extra scroll.

To disable inertia in Emacs do:

    (setq ns-use-mwheel-momentum nil)

-- 
Alan Third