bug#57970: 29.0.50; Create new defgroup for pixel-scroll.el

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: Lars Ingebrigtsen <larsi@gnus.org>, 57970@debbugs.gnu.org
>> Date: Mon, 11 Sep 2023 16:37:10 +0800
>> From:  Po Lu via "Bug reports for GNU Emacs,
>>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>> 
>> Stefan Kangas <stefankangas@gmail.com> writes:
>> 
>> > I'm still not sure what is the relationship with pixel-scroll-mode.  Eli
>> > does, I think.  So it might be best to send any suggested changes to the
>> > bug tracker.
>> 
>> For what it's worth, the only advantage the old pixel-scroll-mode has
>> over p-s-p-m is that it functions with regular wheel mice by default.
>> 
>> pixel-scroll-precision-mode is also capable of supporting wheel mice,
>> but detecting them and enabling the requisite options is tricky and
>> subject to numerous edge cases, so those options remain off by default.
>
> So maybe we should document that one is better for wheels, the other
> for touchpads?  And maybe even (gasp!) rename
> pixel-scroll-precision-mode to something like touchpad-scroll-mode?

pixel-scroll-mode isn't better for wheel mice as long as you actually
tell p-s-p-m that you use one, so that assessment isn't really correct.

pixel-scroll-mode's principal failings are that it bails out when a
wheel event arrives while scrolling is taking place, it always scrolls
by a set number of lines, and it is slow.  p-s-p-m experiences none of
these problems.