[PATCH synaptics] Increase the default acceleration factor.

[Peter Hutterer]

On Thu, Aug 19, 2010 at 09:05:12AM +0100, Magnus Kessler wrote:
> On Thursday 19 August 2010 06:14:08 Peter Hutterer wrote:
> > With 4e0e53fcba6fd99d458df1905d055d63360155c0 the driver got it's own
> > acceleration mechanism. This slowed down the pointer movement a lot,
> > especially on ALPS touchpads. Increase the default acceleration factor to
> > accommodate for this.
> > 
> > The number itself is chosen through guesswork and informal tests on one
> > Synaptics and one ALPS pad.
> > 
> > Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> > ---
> >  src/synaptics.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/src/synaptics.c b/src/synaptics.c
> > index 3344d75..9d0bf14 100644
> > --- a/src/synaptics.c
> > +++ b/src/synaptics.c
> > @@ -455,7 +455,7 @@ static void set_default_parameters(LocalDevicePtr
> > local) tapMove = diag * .044;
> >      edgeMotionMinSpeed = 1;
> >      edgeMotionMaxSpeed = diag * .080;
> > -    accelFactor = 50.0 / diag;
> > +    accelFactor = 200.0 / diag; /* trial-and-error */
> > 
> >      range = priv->maxp - priv->minp;
> 
> Tested on a Lenovo T500 (Synaptics Touchpad, model: 1, fw: 7.0, id: 0x1c0b1, 
> caps: 0xd04791/0xb00000/0x20000). Works well for me.
> 
> There seems to be an awful amount of ad-hoc magic factors in that part of the 
> code though. And comments like "Again, based on typical x/y range and 
> defaults". Does anyone know of a way to express the factors in a more rational 
> way?

numbers that decide on the user experience are often guesswork. much of this
code came to be to provide the same-ish feel regardless of touchpad
dimensions (they change slightly within models and greatly between models).

I admit though that it's due for an overhaul to see if we can't just
hardcode them on a per-model basis. Then again, this requires some sort of
evaluation afterwards and that requires way more time than I can expend at
this point.

> For this patch, though:
> 
> Tested-by: Magnus Kessler <Magnus.Kessler at gmx.net>
> Reviewed-by: Magnus Kessler <Magnus.Kessler at gmx.net>

thanks, much appreciated.

Cheers,
  Peter