Bug 253078 – REGRESSION: Scroll gets stuck between snap-points when scrolling after overscroll

• Status: NEW
• Component: Scrolling

[Bruno Stasse]

Created attachment 465219 [details]
testcase

In a scroll container with scroll-snap-type set to mandatory, when scrolling with the trackpad right after overscrolling and lifting the fingers in a way so no momentum occurs between two snap-points, the scroll gets stuck instead of snapping to the nearest snap-point.

Steps to reproduce:
- open the test case on macOS
- scroll down and then up in order to cause overscroll
- before the end of overscroll, scroll down without lifting the fingers
- lift your fingers, without causing momentum, between two snap-points

You should see the content get stuck between the snap-points instead of snapping to the nearest one.

This occurs in STP 164, but I don't know when it was introduced, except that it was after STP 146. I cannot test normal Safari 16 at the moment so I don't know if it is already affected.

[Radar WebKit Bug Importer]

<rdar://problem/106051641>

[Teodor]

Created attachment 469938 [details]
Screenshot from iPhone showing stuck horizontal image gallery style scroller

Still reproducible on 17.3

This is especially a problem with horizontal scrolling (e.g., image gallery). With vertical scrolling user can write this bug off as blank space at the bottom of the page, but empty space to the right/left of the last/first gallery item is inexplicable and appears as broken.