wl_tablet specification draft

[Peter Hutterer]

On Mon, Jun 30, 2014 at 06:55:25PM -0700, Bill Spitzak wrote:
> On 06/30/2014 12:46 AM, Pekka Paalanen wrote:
> 
> >>I was assuming the enter event contains enough information to know which
> >>device is causing it.
> >
> >It is the wl_pointer of a specific wl_seat:
> >http://people.collabora.com/~jonny/protocol/wl_pointer.html#Event:enter
> >
> >No information about the actual physical device at all.
> >
> >>If not it needs to be extended to contain all the
> >>information that is in a "move" event.
> >
> >It already contains more information than motion:
> >http://people.collabora.com/~jonny/protocol/wl_pointer.html#Event:motion
> >
> >No, we are not adding physical device identification to wl_pointer.
> 
> I'm reasonably certain that users only want to see a cursor and application
> highlighting and tooltips, etc, for the device they are currently handling.
> And they want "mouse mode" to work for tablets in cases where their display
> is significantly larger or a different aspect ratio than the tablet.
> 
> I can't see how either will be implemented unless the compositor is aware of
> the pointer being shared between devices and it can incrementally move the
> pointer based on the pen actions. Any other method of doing this seems to
> require the tablet and pointer events to be delivered to more than one
> client.
> 
> >>Although this is getting a bit out of this area, imho enter/exit events
> >>should be eliminated....
> >
> >Note, that wl_pointer.enter is also used in cases where there is no
> >physical input device action to trigger it...
> 
> Yes this makes sense. Sorry I was confusing it with the X implementation
> where the Enter event replaced a Move event.

it does? it's actually one of the ambiguous parts of the X protocol.
nothing prevents you from sending motion events for the same coordinates
(indeed, we do so for subpixel motion). So whether you get a motion after an
enter event is pretty much implementation-dependent. and if you check the
implementation, we just slot the leave/enter events in before the motion
event, without ever discarding it.

Cheers,
   Peter