Re: [pointerevents] Relationship between main pointer event and coalesced events (#409)

Let me quickly chime in here. The even that is fired by the browser right before rAF callback is not necessary the position of the real event. That is the event that the brower believe is the right repesentative of the input stream at rAF timestamp. As a result browsers are free to do resampling of the coordinations and other attribtues as they wish. Coaleseced events and particularly the last event in the coalesced event list is guaranteed to be the actual events received by the browser with no manipulation.

Since most browsers don't do re-sampling based on rAF and what not the effect you see most often is that the last event in the coalesced event list match to the main event in some attributes (such as coordiantes) but that is not guaranteed and shouldn't be what devs expect. Also note that even if browser does no resampling of the fired event it still doesn't mean that the last event in the coalesced event list exactly matches the event itself. As their movementX,Y will certainly be different if there is more than one event in coalesced event. 

In general as we tried to mention in the spec devs should either look at the coaelsced event stream (and ignore the event itself) or work only with the event itself. Mix and matching these will not yield in any good outcome.

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Received on Tuesday, 7 September 2021 16:39:00 UTC