[PATCH 09/15] Add four new motion filters

[Daniel Stone]

Hi,

On Tue, Jun 14, 2011 at 03:22:25PM +1000, Peter Hutterer wrote:
> On Thu, Jun 09, 2011 at 08:57:30PM +0100, Daniel Stone wrote:
> > Attempt to decrease the possibility of errant motion as much as possible
> > by adding three new configurable filters, disabled by default:
> >     - Synaptics Max Jerk: maximum change in acceleration before the
> >       packet is declared errant (xorg.conf MaxJerk)
> >     - Synaptics Max Accel: maximum acceleration the pointer can have
> >       before being declared errant (xorg.conf MaxAccel)
> >     - Synaptics Max Error: maximum error from a best-fit prediction of
> >       the next position before being declared errant (xorg.conf MaxError)
> >     - Synaptics Max Distance: maximum distance a finger can move in a
> >       single report before being declared errant (xorg.conf MaxDistance)
> > 
> 
> woo! more configuration options! :)

Yeah, I felt a bit bad about that.

> > +/* FLOAT */
> > +#define SYNAPTICS_PROP_MAX_DISTANCE "Synaptics Max Distance"
> > +
> > +/* FLOAT */
> > +#define SYNAPTICS_PROP_MAX_JERK "Synaptics Max Jerk"
> > +
> > +/* FLOAT */
> > +#define SYNAPTICS_PROP_MAX_ACCEL "Synaptics Max Accel"
> > +
> > +/* FLOAT */
> > +#define SYNAPTICS_PROP_MAX_ERROR "Synaptics Max Error"
> 
> any reason these 4 couldn't be accumulated? they are related enough to
> justify it, imo.
> 
> "Synaptics Acceleration Filters" or something more appropriate

What, have a single sledgehammer on/off switch? I can definitely see the
argument, but we're yet to find a useful algorithm that generates values
useful on all hardware, which is partly due to not having tested on a
massively broad range of devices.

> > @@ -1801,6 +1806,33 @@ static void regress(SynapticsPrivate *priv, const struct SynapticsHwState *hw,
> >      double yb1n = 0, xb1n = 0, b1d = 0, xb1, yb1;
> >      double dista, distb, distc, vela, velb, velc, acca, accb, jerk;
> >  
> > +    if (pars->max_distance &&
> for consistency with the checks a few lines below, this should state > 0 as well

Fixed, thanks.

> > +        hypot(hw->x - HIST(0).x, hw->y - HIST(0).y) > pars->max_distance)
> > +        goto filtered;
> > +
> > +    if (pars->max_accel > 0 || pars->max_jerk > 0) {
> > +        if (priv->count_packet_finger < 3) {
> > +            *dx = 0;
> > +            *dy = 0;
> > +            return;
> > +        }
> > +
> 
> for the poor buggers that may have to debug this one day, a comment on
> what's actually done here would be awesome. I've spent too much time on
> wikipedia's math sites lately, trying to figure out what a piece of code was
> supposed to do.

Ha.  I've added some more comments now.

Cheers,
Daniel