Bug 253080 – Instant scroll to edge occurs when scrolling during overscroll in a scroll-snap container

• Status: NEW
• Component: Scrolling

[Bruno Stasse]

Created attachment 465220 [details]
testcase

In a scroll container with scroll-snap-type set to mandatory or proximity, when initiating a scroll gesture during overscroll, the scroll container scrolls instantly to the edge, ending the overscroll animation right away.

The expectation would be that no instant scrolling occurs, the content should move from its current overscrolling position without jump.

Steps to reproduce:
- open the test case on macOS
- scroll down and then up to cause overscroll
- scroll up or down (with or without lifting the fingers) before the end of overscroll
- observe that the content gets scrolled instantly to the edge instead of moving naturally from its current position

This occurs in STP 164, but might have been introduced before.

[Radar WebKit Bug Importer]

<rdar://problem/106051647>