Bug 236536 – Sideways overscroll causes movement in scroll-snap container

• Status: NEW
• Component: Scrolling

[Bruno Stasse]

Created attachment 451777 [details]
testcase-scroll-y

In a unidirectional scroll-snap container, scrolling sideways with a trackpad during overscroll causes the scroll container to scroll in that "forbidden" direction, although no content is overflowing, and even with `overflow-x` or `overflow-y` set explicitly to `hidden`.

See the attached testcases for scroll container on the y and x axis. See also a video for the y axis.

Steps to reproduce:
- open the testcase file for the y axis
- scroll about half the content, then in another gesture scroll all the way down to cause overscroll
- without lifting the finger, scroll sideways (left or right)
- see the scroll content move in a forbidden direction

The expected behaviour is that the content does not move in that direction, it must only be allowed to move in the defined scroll direction.

I started to see this behaviour a few Safari TP versions back, possibly around version 137.

[Bruno Stasse]

Created attachment 451778 [details]
testcase-scroll-x

[Bruno Stasse]

Created attachment 451779 [details]
video-scroll-y

[Simon Fraser (smfr)]

Is scrolling in the unwanted direction just rubber-banding (aka overscroll)?

[Bruno Stasse]

Yes it is just rubber-banding indeed, it goes back into place afterwards.

[Radar WebKit Bug Importer]

<rdar://problem/89184230>