[PATCH libinput v2 0/4] touchpad gestures support

[Carlos Garnacho]

Hey Hans :),

On jue, 2015-03-26 at 10:04 +0100, Hans de Goede wrote:
> Hi All,
> 
> Here is v2 of my touchpad gestures support patch series, changes 
> since v1:
> - Merge the gesture capability flag and event-debug patched into
>   the "touchpad: Add an API for touchpad gesture events"
> - Update the swipe and pinch/rotate implementations to work with the 
> new
>   typesafe device and normalized coordinates (rebased on latest 
> master),
>   this results in a nice cleanup

During the last days I played with these last patches on Clutter, and
found the gestures to work nicely. I gathered some observations though:

      * Higher level gesture implementations usually have a "cancel"
        signal/vfunc, it feels kind of weird not being able to fully
        map the behaviors. I thought about some "this gesture maybe
        continues onto something else" flag in *_END events, although 
        I see this working better on touchpoints being added than
        lifted, given how things seem to work. Anyway, just a remark, 
        I see cancellation being more important in the protocol
        additions this would bring, when this involves client vs
        compositor handling.
      * I think it is a bit unfortunate that distance in pinch
        gestures is relative. Higher level equivalent "zoom" gestures
        usually offer absolute scale values (taking the initial
        distance as 1x). We do lack some information there to
        translate from one to the other, I guess either knowing the
        initial distance (does pointer acceleration apply here?), or
        offering similar info right away would be nice.
      * From trying things out, I found that if I pinch the fingers
        too close (X1 Carbon 1st gen here, 2fg touchpad), and then
        move them together around, the pinch gesture would report
        distance jumps (self-cancelled overall though), In evemu
        -record traces I see 2 separate tracking IDs, and didn't seem
        to see such wild coordinate jumps, so I wonder if we can do
        something about it, I can investigate further about it if you
        want.

But overall, it looks quite good to me. Although I didn't get too deep
in reviewing code, the general logic seems sound to me.

Cheers,
  Carlos