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maxTouchPoints on platforms that have less granular information

From: Rick Byers <rbyers@google.com>
Date: Thu, 10 Oct 2013 18:36:49 -0400
Message-ID: <CAFUtAY9Zmbb1fpvTJjxHLbqt6ffs-3tphTqjfk2Sje7ok3ms8g@mail.gmail.com>
To: "public-pointer-events@w3.org" <public-pointer-events@w3.org>
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, 10 October 2013 22:37:37 UTC

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