Re: [touch-events] Adding the fling intervention behavior to TouchEvent's spec

I think the spirit of that change is reasonable.  Basically if you 
touch on something that's currently scrolling due to momentum from a 
previous touch, you shouldn't have any more expectation that you can 
interrupt the scrolling than for the case of during a scroll.  The 
spec already allows this but doesn't describe the specific cases in 
detail.  Edge has this property already and I believe @staktrace said 
Gecko did (or would) as well.

But I think we need to bikeshed the wording a bit.  Today we have:

> For maximum scroll performance, a user agent may not wait for each 
touch event associated with the scroll to be processed to see if it 
will be canceled. In such cases...

I think you're just describing a specific instance of this.  Perhaps 
we can make it a bit more precise with language like this:

> For maximum scroll performance, a user agent may not wait for each 
touch event associated with the scroll to be processed to see if it 
will be canceled.  In particular, User Agents may not suspend the 
motion of an element which is currently moving due to a touch scroll, 
either as a result of an earlier event in the touch sequence, or due 
to momentum left over from a previous touch sequence.  In such 
cases...

This is all somewhat hand-wavy, but I think something like this gets 
across the key principle that matters most, i.e. "objects in motion 
tend to stay in motion" ;-).  Filed #77 to separately explore testing 
to help compensate for the interop risk here.


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Received on Wednesday, 30 November 2016 19:31:07 UTC