[RFC wayland-protocols] Add pad support to the tablet protocol

[Peter Hutterer]

On Mon, Mar 07, 2016 at 11:46:31AM +1000, Peter Hutterer wrote:
> > > +      </description>
> > > +      <arg name="id" type="new_id" interface="zwp_tablet_pad_v1" summary="the newly added pad"/>
> > > +    </event>
> > >    </interface>
> > >  
> > >    <interface name="zwp_tablet_tool_v1" version="1">
> > > @@ -619,4 +636,407 @@
> > >        </description>
> > >      </event>
> > >    </interface>
> > > +
> > > +  <interface name="zwp_tablet_pad_ring_v1" version="2">
> > > +    <description summary="pad ring">
> > > +      A circular interaction area.
> > > +
> > > +      Events on a ring are logically grouped by the wl_tablet_pad_ring.frame
> > > +      event.
> > > +    </description>
> > 
> > Could you elaborate here on what exactly a 'ring' is?  I assume it's the
> > ipod style dial thingee, although from the other events I gather it's
> > related to text input in some fashion?  Even if it might be remedial, a
> > definition of the term would likely be beneficial at this point.
> 
> it's the touch ring on the Intuos Pro series, present on all devices since
> the Intuos 4 and on most Cintiq devices. The thing is, the ring on a tablet
> pad is a well-known entity, describing it here is a bit like describing what
> a wheel is in the mouse context. It should be handled as a special entity so
> by the time you're implementing pad support you should know what the ring is
> anyway :)
> As for the hardware: yes, they're and ipod-like touch ring that sends
> positional information. what you do with that information is up to the
> client, you could map it to scroll for example.
> 
> Here's a picture of the I5 ring:
> http://www.edensart.com/assets/images_computer_articles/full/intuos5_ring_full.jpg

I forgot: The reason the feedback string is there so that a client can say
"i'm mapping the touch ring to zoom in/out". The compositor can then display
an OSD of the tablet with the ring labelled correctly rather than just "ring
cw/ccw".

Same goes for buttons and strips, a button may be bound to "pencil tool",
not just to button 1.

Cheers,
   Peter