[PATCH libinput] touchpad: make the hysteresis dependent on physical distance

[Peter Hutterer]

please fix your email client to not drop CC's on reply.

On Sat, Jun 13, 2015 at 09:30:35AM -0700, Bill Spitzak wrote:
> Can you set the "fake" resolution so that you get the same answer without
> having to check if it is fake?
> 
> It looks like setting tp->device->abs.absinfo_x/y->resolution to diagonal *
> 2 / DEFAULT_HYSTERESIS_MARGIN_DENOMINATOR would avoid the if statement, and
> I would probably make everything that uses this resolution value "work" (in
> that they all scale the same).

yes and no, we have a bunch of things that rely on resolution or otherwise
guesswork (software button area for example). so the approach is a bit more
complex, but setting a resolution based on the diagonal is an interesting
approach.
Have a look into that if you can please, see if the numbers work out.

Cheers,
   Peter

> 
> >>On 12-06-15 08:09, Peter Hutterer wrote:
> >>
> >>>Some touchpads, e.g. the Cyapa in the Acer c720 have a small axis range
> >>>([0, 870], [0, 470]), so the diagonal/magic value yields a hysteresis
> >>>margin
> >>>of 1 device unit. On that device, that's one-tenth of a millimeter,
> >>>causing
> >>>pointer motion just by holding the finger.
> >>>
> >>>For touchpads that provide a physical resolution, set the hysteresis axes
> >>>to
> >>>0.5mm and do away with the magic factor.
> >>>
> >>>https://bugzilla.redhat.com/show_bug.cgi?id=1230441
> >>>
> >>>Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> >>>
> >>
> >>Yes I think this is a good idea:
> >>
> >>Reviewed-by: Hans de Goede <hdegoede at redhat.com>
> >>
> >>Can you also ask the reporter of:
> >>
> >>https://bugs.freedesktop.org/show_bug.cgi?id=90590
> >>
> >>To test libinput/master once you've pushed this? It will likely
> >>help with his problem too.
> >>
> >>Regards,
> >>
> >>Hans
> >>
> >>
> >>
> >>  ---
> >>>   src/evdev-mt-touchpad.c | 16 ++++++++++++----
> >>>   1 file changed, 12 insertions(+), 4 deletions(-)
> >>>
> >>>diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
> >>>index 8c28ff7..e9870ad 100644
> >>>--- a/src/evdev-mt-touchpad.c
> >>>+++ b/src/evdev-mt-touchpad.c
> >>>@@ -1495,10 +1495,18 @@ tp_init(struct tp_dispatch *tp,
> >>>                                                        EV_ABS,
> >>>                                                        ABS_MT_DISTANCE);
> >>>
> >>>-       tp->hysteresis_margin.x =
> >>>-               diagonal / DEFAULT_HYSTERESIS_MARGIN_DENOMINATOR;
> >>>-       tp->hysteresis_margin.y =
> >>>-               diagonal / DEFAULT_HYSTERESIS_MARGIN_DENOMINATOR;
> >>>+       if (device->abs.fake_resolution) {
> >>>+               tp->hysteresis_margin.x =
> >>>+                       diagonal / DEFAULT_HYSTERESIS_MARGIN_DENOMINATOR;
> >>>+               tp->hysteresis_margin.y =
> >>>+                       diagonal / DEFAULT_HYSTERESIS_MARGIN_DENOMINATOR;
> >>>+       } else {
> >>>+               int res_x = tp->device->abs.absinfo_x->resolution,
> >>>+                   res_y = tp->device->abs.absinfo_y->resolution;
> >>>+
> >>>+               tp->hysteresis_margin.x = res_x/2;
> >>>+               tp->hysteresis_margin.y = res_y/2;
> >>>+       }
> >>>
> >>>         if (tp_init_accel(tp, diagonal) != 0)
> >>>                 return -1;
> >>>
> >>>  _______________________________________________
> >>wayland-devel mailing list
> >>wayland-devel at lists.freedesktop.org
> >>http://lists.freedesktop.org/mailman/listinfo/wayland-devel
> >>
> >
> 
> 
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