[PATCH libinput v2 0/4] touchpad gestures support

[Bill Spitzak]

On 04/26/2015 09:01 PM, Peter Hutterer wrote:

>>> I've been ping-ponging between giving deltas or an absolute distance
>>> in mm. I can change the patch-set to report a distance in mm instead
>>> of delta from the previous distance, with the caveat that on some
>>> touchpads we do not know the resolution so the unit there will
>>> not be mm, but instead unknown stepsize.
>>
>> Hmm, that's indeed a drawback. I guess having an additional
>> libinput_event_gesture_get_scale() is not as stateless as you'd want?
>> If we have to choose between deltas or abs distance, I feel the latter
>> is most useful though...
>
> right, so if I read this right what you want is have the first gesture event
> with a scale value of 1.0 and then every subsequent one as a fraction or
> multiple of that initial value. so 0.5 means the fingers moved together by
> 50%, 2.0 would mean twice as far apart now.
> that'd easy enough to add and be independent of the resolution, though it
> obviously can't work on swipe gestures.

Can't the client remember the distance when the gesture started and do 
the division itself? This does not seem like a problem to me.