iOS native scrolling PTR

[perrygovier]

Pull to refresh with native scrolling on iOS does not currently work consistently when the view is large enough to be scrollable.

Here's what I know after spending some time looking in to it.
Immediately, canOverscroll on line 73 is not false when it should be. This is because in handleScroll the scrollTop value during iOS's native overscrolling can be negative, equating to false.

Setting negative scroll top values to equate the same way as a 0 value would on lines 91, 108, and 139 gets further, but the deltaY - dragOffset <= 0 part of the evaluation on line 91 now calculates incorrectly too. This means overscrolling wont start until the user has dragged more than half the distance above scrollTop 0. dragOffset is not getting a correct value, which I believe is what causes this, but I have not yet investigated why.

And down the rabbit hole we go :)

[mlynch]

Hey @perrygovier, I'm not seeing the issue, do you have more info or a codepen that shows the issue?

[mlynch]

Also, are you sure you aren't just seeing the whole browser frame scrolling and the PTR trying to also react to that?

[mlynch]

[tomkelsey]

Hi @mlynch,

I hope this helps!

Here is a repo that is basically the starter tabs demo with a longer chat list and pull to refresh added: https://github.com/tomkelsey/ionic-ptr-bug

Here is a video of the bug: https://www.youtube.com/watch?v=Z6zIQWBG-aU&feature=youtu.be

[perrygovier]

@mlynch, @tomkelsey's video and code sample is what I'm seeing. The view pulling will only happen in the browser. Also, the browser uses WKWebView, which will fire scroll events differently. The bug still happens, but I believe the fix will require consideration of both kinds of scroll events.

[mlynch]

Okay, so it occasionally isn't rendering on pull. Right?

[tomkelsey]

@mlynch yes, at least that's what I'm experiencing - in the example I posted it actually doesn't work more often than it does.

I had a look using Safari's debugger and it seems as if the ion-refresher is incorrectly stuck with the invisible class.

[mlynch]

k I can reproduce. Thanks

[mlynch]

Should be fixed now. Mind trying master?