Comment 4 for bug 1697122

It is indeed a common complaint/request as evidenced by the people talking about it in various places (blogs, reddit, etc.):
https://www.rojtberg.net/1569/switching-back-from-chrome-to-firefox/
https://www.reddit.com/r/linux/comments/72mfv8/psa_for_firefox_users_set_moz_use_xinput21_to/
https://hackido.com/2019/02/01/2019-02-01-firefox-with-touch/

I paste here again the upstream bug report as the link changed slightly: https://bugzilla.mozilla.org/show_bug.cgi?id=1207700
Recent comments in it (a year old) are fairly positive:
"I think we can enable the XInput2 for recent Gtk+ versions (say Gtk+ >= 3.20) as the related Gtk+ focus bugs was fixed but for XInput2 only. Also Fedora enables XInput2 by default and we don't have any user complains."
However there is a list of possible issues that need to be checked before moving on this:
https://bugzilla.mozilla.org/show_bug.cgi?id=1182700 (wheel scrolling issue when window not active)
https://bugzilla.mozilla.org/show_bug.cgi?id=1390795 (wheel scrolling issue when window not active)
https://bugzilla.mozilla.org/show_bug.cgi?id=1487882 (pdf zoom increments by 10%)
https://bugzilla.mozilla.org/show_bug.cgi?id=1196777 (probably fixed)
https://bugzilla.mozilla.org/show_bug.cgi?id=1170342 (fixed)

Additionally, we need to check it works adequately when the synaptics driver is enabled (I'm not sure but perhaps it's enabled by default on Macbooks?).

Finally, I tried a couple more tweaks in about:config to make the scrolling experience smoother with a touchpad:
- disabling smooth scrolling: general.smoothScroll = false
OR
- enabling msdPhysics scrolling: general.smoothScroll.msdPhysics.enabled = true
I'm not yet entirely convinced by either and still have to test it more, especially with a mouse.