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RE: maxTouchPoints on platforms that have less granular information

From: Jacob Rossi <Jacob.Rossi@microsoft.com>
Date: Thu, 31 Oct 2013 18:29:22 +0000
To: Rick Byers <rbyers@google.com>, "public-pointer-events@w3.org" <public-pointer-events@w3.org>
Message-ID: <fe88686c89d842f2b8b22fe8e41bed13@BN1PR03MB267.namprd03.prod.outlook.com>
Given a platform that has less granular information than required, I think your approach (minimum guaranteed) is the best.  I'm OK with adding a note. But a non-normative note cannot use RFC2119 keywords, like "should." [1]  Here's an alternative:

"Note: maxTouchPoints is often used to ensure that the interaction model of the content can be recognized by the current hardware. UI affordances can be provided to users with less capable hardware. On platforms where the precise number of touch points is not known, the minimum number guaranteed to be recognized is provided. Therefore, it is possible for the number of recognized touch points to exceed the value of maxTouchPoints."

-Jacob

[1] http://www.w3.org/TR/pointerevents/#conformance

On Thu, Oct 10, 2013 at 3:36 PM, Rick Byers <rbyers@google.com> wrote:
I just learned that Android doesn't have an API to report the exact number of touch points supported.  Instead it has a few levels (1, 2+, 5+).  See http://developer.android.com/reference/android/content/pm/PackageManager.html#FEATURE_TOUCHSCREEN.

Should we consider adding a non-normative note or something suggesting how such platforms should implement this API?  Eg:

Note: some platforms may not report the precise number of touch points available.  On such platforms, this API should return the minimum guaranteed number of points that an application can rely on being available.  For example, on Android systems reporting FEATURE_TOUCHSCREEN_MULTITOUCH_DISTINCT (but not FEATURE_TOUCHSCREEN_MULTITOUCH_JAZZHAND) this should return 2.

I.e. this API should be used to control the addition of additional UI to compensate for the lack of sufficient touch points (such as showing zoom controls on a single-finger device), not as a limit on the number of touch points that should actually be handled by the application.

Sorry I wasn't aware of this as a potential issue sooner.

Rick
Received on Thursday, 31 October 2013 18:29:55 UTC

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