Package Firefox with MOZ_USE_XINPUT2=1 in environment to enable pixel scrolling with touchpad and touch gestures

[Nate Graham]

Ubuntu version: Kubuntu 17.04
Firefox version: 53.0.3+build1-0ubuntu0.17.04.2

In Firefox, two-finger scroll gestures on a touchpad are interpreted as scroll wheel rotations, and the content scrolls three lines at a time. This is inappropriate behavior for touchpad scrolling; it should scroll pixel-by-pixel.

Firefox already has the ability to do this, you just need to turn it on by running the program with MOZ_USE_XINPUT2=1 in the environment: for example, by running `MOZ_USE_XINPUT2=1 firefox`, or adding it to /etc/environment or something like that.

Turning on this behavior yields a large usability improvement for laptop users. Therefore, I am proposing that MOZ_USE_XINPUT2=1 be permanently added to the packaging such that it's always present when Firefox runs. This is what Fedora does, and it results in a much improved experience for the laptop user.

[Atdrew (atdrew)]

We had to disable XI2/multidevice support in bug 1170342 due to focus and scrolling related issues. We should monitor these issues to see if it would be possible to re-enable XI2 in the future.

[Kuba Niewiarowski (marsjaninzmarsa)]

Please add option to reenable via about:config or something - I'm really got used to it...

[Stransky (stransky)]

(In reply to Kuba Niewiarowski from comment #1)
> Please add option to reenable via about:config or something - I'm really got
> used to it...

Just set MOZ_USE_XINPUT2=1 env variable which enables it in Firefox.

[Kuba Niewiarowski (marsjaninzmarsa)]

(In reply to Martin Stránský from comment #2)
> Just set MOZ_USE_XINPUT2=1 env variable which enables it in Firefox.

Not working...
I'm using Aurora builds from https://launchpad.net/~ubuntu-mozilla-daily/+archive/ubuntu/firefox-aurora

[Anders Kaseorg (andersk)]

MOZ_USE_XINPUT2=1 is in Nightly (bug 1207973) but not yet in Aurora.

[Karlt (karlt)]

*** Bug 1234005 has been marked as a duplicate of this bug. ***

[sacharja (c3521333)]

Using "MOZ_USE_XINPUT2=1" &e10s worked for me (https://bugzilla.mozilla.org/show_bug.cgi?id=1268599#c10), but not very smooth (scrolling, afterwords opening the menu item, then trying to scroll results in an un-scrollable page). Fedora already compiles FF with "MOZ_USE_XINPUT2=1", which is very smooth on my tablet.

However, it would be interesting how this is handled by Firefox for Android, which clearly needs touch support and XINPUT2.

[Adolfo Jayme (fitojb)]

Upstream blockers: https://bugzilla.mozilla.org/showdependencytree.cgi?id=1207700&hide_resolved=1

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Karlt (karlt)]

*** Bug 1390130 has been marked as a duplicate of this bug. ***

[Stransky (stransky)]

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.

[Stransky (stransky)]

Before the switch we need to address Bug 1182700. Bug 1170342, Bug 1196777 should be fixed for reasonable recent systems.

[Stransky (stransky)]

For Bug 1182700 looks like gnome folks gave up (https://bugzilla.gnome.org/show_bug.cgi?id=750994#c8) and recommend to use Wayland. I wonder how big complication is it and if benefits from enabled xinput2 outweigh it, especially when the focus bugs should be fixed on recent systems.

[Shu Hung (Koala) (koalay)]

Gnome issue 750994 has been migrated to their Gitlab instance:
https://gitlab.gnome.org/GNOME/gtk/issues/558

[cousteau (cousteaulecommandant)]

Counter-argument: Try to zoom in on a PDF with this option on. (It goes in increments of 10% *per pixel*.)

This could be considered a bug on Firefox though, so I guess as soon as those little things are polished this change could be made (but then again I guess the Firefox devs would include this option by default themselves).

[Florian Boucault (fboucault)]

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.

[Florian Boucault (fboucault)]

For completeness sake, here is the OpenSuse bug report talking about it:
https://bugzilla.opensuse.org/show_bug.cgi?id=1032003

[Florian Boucault (fboucault)]

Quick workaround for those who want to enjoy the benefits right away:
echo "MOZ_USE_XINPUT2=1" | sudo tee /etc/environment.d/90firefox-xinput2.conf

[Nate Graham (pointedstick)]

BTW I've since changed my mind on this. Setting the proposed environment variable makes toupad scrolling mysteriously slow down after a notification arrives until you switch focus away from Firefox and back (See https://bugzilla.mozilla.org/show_bug.cgi?id=1182700). This problem is particularly severe for mouse scroll wheel users, where wheel scrolling breaks entirely until you switch away and back again.

I grudgingly live with the issue when I'm using a touchpad, but I unset the envar when I'm using a mouse because of how bad it is.

I think https://bugzilla.mozilla.org/show_bug.cgi?id=1182700 needs to be fixed upstream before this can be considered. Unfortunately, it's blocked on a GTK issue (https://gitlab.gnome.org/GNOME/gtk/issues/558) that the GTK developers have declared unfixable on X11.

[Nate Graham (pointedstick)]

So I recommend closing this bug, or else devoting some Canonical development resources to fixing the above-mentioned upstream bugs first.

[uman (brennan-vincent)]

If this bug is not going to be fixed soon, I suggest Ubuntu should bundle another browser in the next release.

Maybe it doesn't make a difference for people who are not used to using a touchpad on other browsers (or Firefox on other OSes), but this bug made Ubuntu-on-laptop absolutely maddening to use for me and I assume for many others as well.

[Nate Graham (pointedstick)]

it's annoying for me too. The problem is that setting the envar just substitutes some problems with different ones:
- Without this envar set, there is no touchscreen scrolling, and touchpad scrolling goes three lines at a time rather than pixel-by-pixel
- With this envar set and a notification appears, touchpad scrolling is interrupted and mouse wheel scrolling stops working entirely until Firefox is de-focused and re-focused

The correct solution is to fix these bugs, not toggle between two broken states. Chromium has different scrolling bugs, BTW.

[Daniel van Vugt (vanvugt)]

Note we already have bug 1312376 covering touchscreen support. This bug should be about touchpads.

[Botond-2 (botond-2)]

*** Bug 1597218 has been marked as a duplicate of this bug. ***