wl_tablet draft v2

[Lyude]

I'm more then willing to add something to get the resolution
information, it wouldn't be too difficult to implement. I think I'm
missing or forgetting something here though; why wouldn't we be able to
get an actual value in degrees from the normalized values we're getting
from the compositor? The value should be mapped from (-65535.0) -
65535.0 by the compositor (libinput is the portion that maps it from
(-1.0) - 1.0), couldn't we just map that to 0-180°? I would have thought
the max value tilt value on a tool should always be equal to 180°, and
the minimum 0°.

Also, since we're talking about getting the value in degrees, it might
be worth it just to have the Wayland protocol return the values in
degrees by default to save some time for the clients.

On Tue, 2014-07-29 at 10:07 -0700, Jason Gerecke wrote:
> On Mon, Jul 28, 2014 at 10:54 AM, Bill Spitzak <spitzak at gmail.com> wrote:
> > On 07/28/2014 09:41 AM, Jason Gerecke wrote:
> >
> >> Normalizing the data is fine, but the resolution data needs to be
> >> available somewhere as well. The GTK+ API doesn't require anything
> >> more than the former, but Qt requires that there be some way to turn
> >> the normalized value into degrees. For libinput this could be
> >> something as simple as a "get_axis_resolution" function that returns
> >> the number of radians (or mm, or newtons, or some other physical unit)
> >> that the normalized value +1.0 corresponds to. I suppose Wayland would
> >> let make the value available through the wl_tablet_manager somehow.
> >
> >
> > Are you sure about these terms? I would think "resolution" should be used to
> > identify how many discreet positions the device can obtain. What you are
> > asking for I think would be better to call a "range" or "scale".
> >
> 
> Yeah, good catch. Looks like I'm getting imprecise with my terminology *wince*
> 
> I think I prefer "scale" over "range" personally, since it's only a
> single logical-to-physical scaling factor (not the physical minimum
> and maximum extents of the axis).
> 
> Jason
> ---
> Now instead of four in the eights place /
> you’ve got three, ‘Cause you added one  /
> (That is to say, eight) to the two,     /
> But you can’t take seven from three,    /
> So you look at the sixty-fours....
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