gestures.html adds non-passive event listener to a scroll-blocking 'touchstart' event

[valdrinkoshi]

This causes chrome to log Violation warnings

[dfreedm]

I will need this to be non-passive for browsers that don't support native touch-action, but I can make this better for Chrome

[BoefAE]

I'm having the same issue, simular issue seems to appear on FireFox as well.
I'm using paper-swatch element which seems to cause the majority of these violations, fyi

[davidmaxwaterman]

I get thousands of these messages in my 1.9 app, all originating from within Polymer. I guess they're not from the same file since it's 2.x (right?), though I'm not too sure how to find that out. Is there any hope of getting these messages removed in 1.9 too?

[dfreedm]

Hmm, I'm worried about the backwards compatibility with this change given the fact that gestureEvent.preventDefault() can call touchEvent.preventDefault(). Maybe this is best served as an opt-in for 2.x.

[BoefAE]

Updated gestures.html with your update, works fine now. T.hanks!

[krisu7]

Hi, when can I expect this fix to be released? I just noticed this issue in chrome lighthouse.

[TimvdLippe]

@krisu7 when #4724 is merged. The problem there is that we are not able to (regression) test the feature

[govis]

[Violation] Added non-passive event listener to a scroll-blocking event. Consider marking event handler as 'passive' to make the page more responsive. seems to be back in Polymer 3.

I have setPassiveTouchGestures(true); and use passive gesture listeners as per https://polymer-library.polymer-project.org/2.0/docs/devguide/gesture-events#use-passive-gesture-listeners

Also "Use passive gesture listeners" section is missing form the Polymer 3 Gesture Events TOC: https://polymer-library.polymer-project.org/3.0/docs/devguide/gesture-events

[govis]

It looks like we may need to set setPassiveTouchGestures(true); before importing any elements that may add gesture listeners in its constructor