Re: Queries on pointer events with respect to multi-pointer(touch) events

Thank you Rick.

Yeah it sounds more logical for pointer events to behave as you explained.

Regards,
Vivek


On Tue, Oct 22, 2013 at 12:47 AM, Rick Byers <rbyers@google.com> wrote:

> Hey Vivek,
> Sorry for the delay in responding.  See inline.
>
>
> On Fri, Oct 11, 2013 at 1:38 AM, Vivek Galatage <vivekg@webkit.org> wrote:
>
>> Hi,
>>
>> I have few questions in pointer events with respect to multi-touch
>> scenario.
>>
>> I am not sure if these are already discussed or valid questions at all in
>> the current context, so please excuse me if being so.
>>
>> *Q1.*
>> In case of multi-touch, would there exist any relation between the
>> primary and non-primary pointer events.
>> e.g. While building multi-touch gesture WebApp, it would be really great
>> to have the associated pointer events sent to the
>> callback as an array of pointer events. Is it how the specification
>> defines it?
>>
>
>  No, there are several challenges to doing this properly (a preview build
> of IE10 originally had such an API, but it was removed after the problems
> became apparent).  However, it's relatively easy to build yourself in JS.
>  We've got this on the list for things to look at adding in the future
> (last line on http://www.w3.org/wiki/PointerEvents/UseCasesAndRequirements).
>  See
> http://lists.w3.org/Archives/Public/public-pointer-events/2013JanMar/0202.html for
> more details.
>
> *Q2.*
>> With multi-point touch, assume we started with the index finger as first
>> point of contact while rest of the fingers
>> being pointed subsequently. What would happen in the below mentioned
>> sequence of events:
>>         a. All non-primary pointers are in pointerdown state
>>         b. The primary pointer is taken away thereby in pointerup state
>>         c. All non-primary pointer are in pointermove state
>> Questions:
>>         A. Would there be any fallback primary pointer once the primary
>> is taken away?
>>
>
> No - there are no primary pointers active at that time.  From the spec:
> "A pointer representing touch input is considered the primary touch input
> if its pointerdown event was dispatched when no other active pointers
> representing touch input existed."
>
>
>>         B. If there is no such fallback mechanism, would these
>> non-primary pointer events be ignored?
>>
>
> Apps (or browser code) operating only on primary pointers would choose to
> ignore them, yes.  But they will of course still be dispatched to the app.
>  Basically an app that cares only about simple single-touch scenarios can
> just ignore all pointer events for non-primary pointers.  But an app that
> wants rich multi-touch support will want to make it's own decisions about
> what to do in such scenarios.
>
>
>> Thank you for taking a look.
>>
>> BR,
>> Vivek
>>
>
>