Prevent onPanStart from being fired from pointercancel event

[MattKunze]

This improves behavior on Android associated with #1050. This is reproducible when panning content that also scrolls vertically - if you scroll the content hammer is firing a spurious onPanStart event, and the state machine gets messed up for subsequent pan events until you scroll horizontally again.

I've created a simple test application that demonstrates the problem: https://github.com/MattKunze/swipe-handler

You can reproduce the behavior in Chrome by simulating a device. The following video shows the behavior - the first swipe works because the scroll position isn't changed, after scrolling vertically you see the incorrect onPanStart event, and panning doesn't work until it resets after the stream of touch events ends, then you can repeat the process:

Note that I'm still needing to reject events where ev.srcEvent.type === 'pointercancel', but this is needed to fix the behavior where a lot of pans aren't recognized on Android in the first place

[renatorib]

Nice!
I had several problems with this, which I fixed with a check.

if (event.srcEvent.type !== 'pointercancel') { /* my pan handling */ }

[MattKunze]

We've actually found that correctly setting the touch-action CSS property avoids the issue for the most part on Android, making this unnecessary. I'll post an update once I have some time that explains what is working for us

[wmertens]

@MattKunze so, did you find a good way to make this work?

[MattKunze]

Yeah, setting touch-action: pan-y in the style for the container seems to avoid the pointer events that are causing the issue in the first place. I haven't had time to revisit the example I posted above to see what is the minimal update that gets it work