Steps to Reproduce

drag a panel inside a portal layout on a touch device

Current Result

ios -> heavy vertical position flickering

in chrome-devtools emulation -> JS errors

[Intervention] Unable to preventDefault inside passive event listener due to target being treated as passive. See https://www.chromestatus.com/features/5093566007214080
stop @ zk.wpd:29947
_docmousemove @ zk.wpd:17217
_doEvt @ zk.wpd:29691
delegateEventFunc @ zk.wpd:29701
dispatch @ zk.wpd:5614
elemData.handle @ zk.wpd:5418

Expected Result

no errors, no flickering

when dragging an element suppress the default scroll position following the touch position

Debug Information

(this is unrelated to the jquery upgrade from 1.12 -> 3.5)

the touch start event listener doesn't have the passive: false flag, so it can't preventDefault conflicting with the drag the scroll movement on iOS

the passive: false flag cannot be set using the current jquery version (according to the FR below not before 4.0)
https://github.com/jquery/jquery/issues/2871#issuecomment-215978040

instead the native {{addEventListener('touchstart'), listener,

}} function can be used before jquery supports it

https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener

Workaround

to avoid the heavy flickering on IOS
lock scrolling during touchmove while zk.dragging is true

        document.addEventListener('touchmove', function(e) {
            if(zk.dragging) {
                event.preventDefault();
            }
        }, {passive: false});