Extra pointer motion with current git xf86-input-synaptics

[Magnus Kessler]

On Monday 29 September 2008, Peter Hutterer wrote:
> On Sun, Sep 28, 2008 at 07:26:06PM +0200, Simon Thum wrote:
> >> The screen coords are used to move the cursor and the scaling is done
> >> based on the axis ranges. Hence the different acceleration when you
> >> change the axis range to 0,-1 (in which case the screen coords are
> >> used as axis ranges).
> >
> > To me, this case sounds like a rounding error piling up.
> >
> > What about:
> >
> > rescaleValuatorAxis(int coord, AxisInfoPtr from, AxisInfoPtr to,
> >                     int defmax)
> > {
> >     [...]
> >     return (int)(((float)(coord - fmin) + 0.5f) * (tmax - tmin + 1) /
> >                  (fmax - fmin + 1)) + tmin;
>
> The patch below should fix another issue, the scaling from device -> core
> -> device. With the patch below, x/y is now used as it is reported by the
> device (unless a screen cross happens).
>
> diff --git a/dix/getevents.c b/dix/getevents.c
> index 166ab4e..f2086e8 100644
> --- a/dix/getevents.c
> +++ b/dix/getevents.c
> @@ -919,17 +919,22 @@ GetPointerEvents(EventList *events, DeviceIntPtr
> pDev, int type, int buttons, master->last.valuators[1] =
> pDev->last.valuators[1];
>      }
>
> +    /* Crossed screen? Scale back to device coordiantes */
>      if(cx != pDev->last.valuators[0])
> +    {
> +        scr = miPointerGetScreen(pDev);
> +        x = rescaleValuatorAxis(pDev->last.valuators[0], NULL,
> +                                pDev->valuator->axes + 0, scr->width);
>          cx = pDev->last.valuators[0];
> +    }
>      if(cy != pDev->last.valuators[1])
> +    {
> +        scr = miPointerGetScreen(pDev);
>          cy = pDev->last.valuators[1];
> +        y = rescaleValuatorAxis(pDev->last.valuators[1], NULL,
> +                                pDev->valuator->axes + 1, scr->height);
> +    }
>
> -    /* scale x/y back to device coordinates */
> -    scr = miPointerGetScreen(pDev);
> -    x = rescaleValuatorAxis(pDev->last.valuators[0], NULL,
> -                        pDev->valuator->axes + 0, scr->width);
> -    y = rescaleValuatorAxis(pDev->last.valuators[1], NULL,
> -                        pDev->valuator->axes + 1, scr->height);
>
>      updateMotionHistory(pDev, ms, first_valuator, num_valuators,
>              &pDev->last.valuators[first_valuator]);
> @@ -938,7 +943,6 @@ GetPointerEvents(EventList *events, DeviceIntPtr
> pDev, int type, int buttons, &pDev->last.valuators[first_valuator]);
>
>      /* Update the valuators with the true value sent to the client*/
> -    /* FIXME: we lose subpixel precision here. */
>      if(v0) *v0 = x;
>      if(v1) *v1 = y;

Thanks, Peter. Your patch solves my original problem as well. No more 
unwanted pointer movement seen on my machine. Can you please commit this to 
the xserver?

Regards,

Magnus

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