[PATCH weston v3 3/3] Introduce wl_relative_pointer interface

[Jonas Ådahl]

On Fri, Oct 30, 2015 at 08:33:16AM +0000, Daniel Stone wrote:
> Hi,
> 
> On 30 October 2015 at 04:27, Jonas Ådahl <jadahl at gmail.com> wrote:
> > On Fri, Oct 30, 2015 at 08:41:18AM +1000, Peter Hutterer wrote:
> >> On Thu, Oct 29, 2015 at 09:33:14AM +0000, Daniel Stone wrote:
> >> > Right, so I think we agree here. I'd prefer to keep the types matching
> >> > as well; I do struggle to see how wl_fixed_t isn't sufficient, but on
> >> > the other hand am not entirely sure I care enough about it, so am
> >> > happy with whichever. Keeping it purely raw might in fact just be
> >> > easier for everyone.
> >>
> >> fwiw, I still read this bug as an issue of timestamp granularity, not motion
> >> granularity. unless I'm missing this, I can't find anything that says the
> >> deltas themselves are insufficient.
> >>
> >> and deltas are just that - device-specific deltas, and the raw motion isn't
> >> accelerated or normalized, so even a 8200 dpi mouse will give you a delta of
> >> 1/1 for the minimal movement.
> >> Even if we normalize those down to 1000dpi, the minimum delta is ca 1/8, and
> >> wl_fixed_t granularity is 1/256, right?
> >
> > That is true. Where we might have even smaller values would be if we
> > normalize to 1000dpi and apply pointer deceleration, but then we still
> > wouldn't end up with such small values because usually the smallest
> > factor we decelerate with is 0.3, meaning we still wouldn't end up with
> > that small deltas. We discussed this on IRC, and after your
> > explanations, I think we could just as well just use wl_fixed_t. If
> > there would be acceleration profiles that decelerate even more (for
> > example 0.03 instead of 0.3 on a 8200dpi mouse normalized to 1000dpi),
> > then since the resulting delta doesn't really represent a hardware event
> > anyway, accumulating the leftover fraction isn't that big of a deal.
> > Daniel, what do you think?
> 
> Right, that makes sense to me. Though in the raw case, surely
> deceleration won't be applied?

Right. At least not in weston/libinput. What "unaccelerated" actually
means is really up to the compositor.


Jonas

> 
> Cheers,
> Daniel