Re: WebEvents-ISSUE-15 (identifier-algorithm): "identifier" attribute should be an opaque token [Touch Events spec]

On Thu, Apr 28, 2011 at 10:23 AM, Arthur Barstow <art.barstow@nokia.com>wrote:

> Hi All - Matt raised this issue including a proposal to address it.
>
> Please send comments, especially regarding Matt's proposal.
>
> In the absence of contrary feedback by May 5, I propose Matt implement his
> proposed change.
>
> -Thanks, AB
>
>
> On Apr/26/2011 1:00 PM, ext Web Events Working Group Issue Tracker wrote:
>
>> WebEvents-ISSUE-15 (identifier-algorithm): "identifier" attribute should
>> be an opaque token [Touch Events spec]
>>
>> http://www.w3.org/2010/webevents/track/issues/15
>>
>> Raised by: Matt Brubeck
>> On product: Touch Events spec
>>
>> The current Editor's Draft specifies an algorithm for setting the
>> "identifier" attribute of each Touch object:
>>
>> http://dvcs.w3.org/hg/webevents/raw-file/tip/touchevents.html#widl-Touch-identifier
>>
>>  The algorithm for determining the identifier value is as follows:
>>> 1. if there are no other active touch event sessions, the value of
>>> identifier must be 0
>>> 2. if there is at least one active touch event session, the value of
>>> identifier must be the lowest integer not currently used by any active
>>> Touch object in any active touch event session
>>>
>> I propose that we should remove this algorithm from the specification, and
>> require only that the identifier is distinct from identifiers in any other
>> active touch sessions.
>>
>> The algorithm above unnecessarily constrains implementations.  For
>> example, the Android OS tracks touch points and assigns identifiers to them.
>>  Its algorithm for assigning identifiers is undocumented, and could change
>> in future versions.  To comply with the current spec, user agents on Android
>> would need to implement their own mapping of touches to identifiers, rather
>> than use the one built into the OS.
>>
>> (Current versions of Android actually seem to use an algorithm that is
>> compatible with the Touch Events draft, but as mentioned above, this is
>> undocumented and should not be relied upon.)
>>
>> Also note that Safari does *not* use the algorithm in the spec, so it
>> fails the "Touch identifiers are correct" test here:
>>
>> http://dvcs.w3.org/hg/webevents/raw-file/a217ab1b3f14/test/touchevents/single-touch.html
>>
>>
>>
>>
>
I like this proposal :).