[RFC libinput] Add an API for touchpad gesture events

[Carlos Garnacho]

Hey Hans!,

(sorry for chiming in late, things got busy around Fosdem...)

On jue, 2015-01-22 at 16:52 +0100, Hans de Goede wrote:
> +	LIBINPUT_EVENT_GESTURE_SWIPE_START = 600,
> +	LIBINPUT_EVENT_GESTURE_SWIPE,
> +	LIBINPUT_EVENT_GESTURE_SWIPE_END,
>  };
>  

One thing I'm unsure about this approach. Is there any plan to support
continuation and chaining-up of gestures? 

Eg. what would happen if a 3fg gesture is started and the user rests a
4th finger on the touchpad? would you get SWIPE_END for 3fg and
SWIPE_START for 4fg? How would the compositor know whether the gesture
finished in a non misleading way? 

What I would expect it to happen is that the compositor cancelled the
reaction to the 3fg swipe in this situation.

If OTOH gestures aren't continued, it would seem to me like confusing
behavior, esp if this already happens between 1fg and 2fg (moving the
pointer and then scrolling, although not back)

  Carlos