[RFC libinput] Add an API for touchpad gesture events

[Carlos Garnacho]

Hey Jonas,

On mar, 2015-01-27 at 13:49 +0800, Jonas Ådahl wrote:

<snip>

> > 
> > anyway, the other escape hatch we have is: we don't _have_ to support all
> > gestures. 2fg scrolling and swiping are incompatible, so short of changing
> > all scrolling to swiping and letting the caller deal with the differences I
> > think it'd be acceptable in libinput to say: vertical 2fg swipe doesn't
> > exist, horizontal 2fg swipe is speed dependent.
> > 
> > or, even easier: 2fg swipe doesn't exist, use scrolling instead.
> 
> I'd say either this (2fg swipe doesn't exist), or generate both scroll
> events and 2fg swipe gesture events for 2fg swiping movements. Either
> the 2fg scroll feature "eats" its corresponding swipe gesture feaure
> and we ignore its existance, or we emit multiple independent events for
> the same input.
> 
> I'm don't really understand *why* we wouldn't want to emit multiple
> events for the same input, aside from that it might end up in shoot foot
> scenario implementation wise. And ideals maybe.

I would think this is the best path forward, as long as
compositors/clients get the full story for all sets of events and know
how the different sets relate (either through by the originating device,
or linking events to their pre/post-processed counterparts).

  Carlos