[RFC] libinput configuration interface

Peter Hutterer peter.hutterer at who-t.net
Wed Feb 19 21:14:22 PST 2014

On Wed, Feb 19, 2014 at 11:55:28AM +0600, Alexander E. Patrakov wrote:
> 19.02.2014 04:52, Peter Hutterer wrote:
> >The set of touchpad patches I sent out recently already handle this by
> >default. When the physical clickpad button is depressed, the driver picks
> >the finger that is pressing the button (sometimes guessing, but hey...).
> >That finger cannot control the pointer movement until the button is released
> >again.
> >
> >In your specific use case, the driver would see two touchpoints and it will
> >select the one closer to the bottom edge as the pressing finger (i.e. your
> >thumb). The index finger can still move while the button is down.
> From my experience with the Sony touchpad (Vaio Z23A4R laptop), I'd
> say that it doesn't solve the whole problem. Here is what goes wrong
> with the old synaptics driver by default and can be worked around
> with AreaBottomEdge.
>         Option "SoftButtonAreas" "4360 0 4000 0 2880 4359 3500 0"
>         Option "AreaBottomEdge" "3500"
> 1. I move the right-hand index finger on the touchpad, thus moving
> the pointer to the place where I want to click.
> 2. I place the left-hand index finger into the virtual-button area,
> while still keeping the right finger on the touchpad. I cannot
> remove the right-hand finger: if I do that, while the contact area
> shrinks, its center also moves, and the driver picks that up.
> 3. As I increase the pressure on the left-hand finger until the
> touchpad clicks, the contact area increases. Unfortunately, its
> center moves, too, and this can accumulate to ~2-3 pixels until it
> clicks.
> The important point is that the bad thing happens before the
> hardware button click, so the quoted solution totally misses the
> point.
> So we need something, either a sledgehammer solution in the form of
> ignoring all motion in the virtual button area (but that would break
> Sony Vaio Duo 13 because the only usable height of the virtual
> button area is 100% there), or some very good filter that pays

can you expand on the 100% comment here? is the touchpad too small for
anything else?

> attention to changes in pressure and filters any spurious movement
> (i.e. any movement that is combined with significant pressure
> changes) out.
> But hey, Sony in their new laptops started to ignore the problem
> under Windows, too, so I think I just have to swallow this and/or
> use my Bluetooth mouse.

couple of comments here:
2 is a synaptics bug that should really be fixed, the driver shouldn't be
that sensible - in fact there's probably something that can be done about
making the driver more sensible while the finger is moving and less sensible
while the finger is still (just an idea, may not work for small
movements). there is also the option of using pressure to counteract
movements, i.e. a pressure change will increase the hysteresis to avoid
erroneous movements. If you have that many issues with the Sony, I really
recommend looking at the evdev-mt-touchpad patches I sent to this list,
it'll allow for things like that relatively simple.
the xorg synaptics driver has for historical reasons and portability a
different approach to finger tracking and some of the misbehaviours are
easier to fix now.

The proposed patches have a different approach to the above:
1 - would be recognised as touchpoint, since no other finger is active it is
designated as the pointer-moving touchpoint
2 - second finger recognised, but not assigned as pointer-moving. Movements
on that finger have no effect, unless 2-finger scrolling is triggered.
3 - no effect, finger is not moving

So really, the goal here is that whatever the motion we see in 2 and 3 is to
not go past the "trigger 2-finger scrolling" threshold.

I do have a set of patches not yet ported for the virtual buttons and they
add additional tracking, so that a finger that starts (and stays) inside a
softbutton area won't contribute to movements, but as you said above that
may not work with the vaio.


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