Two-finger width setting on Dell XPS 15 9650

[Vahe Oughourlian]

On Thu, Jun 15, 2017 at 3:23 PM Peter Hutterer <peter.hutterer at who-t.net>
wrote:

> On Tue, Jun 13, 2017 at 01:46:12AM +0000, Vahe Oughourlian wrote:
> > I'm working with a Dell XPS 15 9650 using libinput. Using the Synaptics
> > driver, a property is available to set the maximum distance two fingers
> may
> > be apart before a two-finger scroll can be triggered, called "Synaptics
> > Two-Finger Width." At the moment, two fingers anywhere on the touchpad
> will
> > switch it over to a two-finger scroll.
> >
> > I ran across a post from Peter Hutterer (
> >
> https://who-t.blogspot.de/2016/04/why-libinput-doesnt-have-lot-of-config.html
> )
> > discussing the intention to minimize options in libinput, and there
> doesn't
> > seem to be a setting that affects this behavior that I could find. Given
> > that, is the most appropriate thing to file a bug for this particular
> > trackpad to have a reasonable default added for this device, or is this a
> > setting libinput eventually intends to support? Or is this setting
> already
> > available?
>
> it's not an available configuration, no. But the main question is what
> you're actually trying to achive? I'm assuming that any finger distance
> limits are not the issue per se but that there's something else that
> affects
> how you can interact.
>
> Cheers,
>    Peter
>
>
There are a couple common cases:

1. My left thumb may drift onto the upper left corner of the touchpad (in
the usual home-row typing position) while my right hand is controlling the
touchpad. Despite the 70mm-ish distance between the fingers, the next
cursor motion by the right hand is treated as a two-finger scroll.

2. I often use the physical click as part of a drag-and-highlight. While
there are dead zones at the bottom of the mouse for the virtual buttons, if
my thumb isn't quite low enough on the right hand, the moment before
actually clicking the physical button underneath the trackpad will turn
into a two-finger scroll. This also can occur at the end of the click as
I'm lifting the thumb, and the next motion is a scroll.

My intention was to set the distance between two fingers such that they'd
have to be much closer together (within 20mm, for example) to avoid these
accidental scroll events.

One thing I have also noticed on other trackpads (on other OSes,
admittedly) is that both fingers seem to have to be in motion to trigger a
two finger scroll, whereas I seem to be able to trigger a two-finger scroll
on the Dell's trackpad by moving one finger while two fingers are on the
trackpad at a time. Perhaps that's the solution here?

Vahe
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