1208149 - CSS Scroll Snap doesn't work if enabled during scrolling

Status: NEW

(Core :: Layout, defect)

Description

[Michał Gołębiowski-Owczarek [:mgol]]

See http://output.jsbin.com/micumar/11. This test case contains a couple of elements with height 100vh and a scroll event handler that disables CSS scroll snap after you scroll down more than 5000 pixels.

The problem is that if you scroll down enough (i.e. get snapping disabled) and then scroll up via the OS X touchpad scrolling momentum so that the snapping is getting enabled when you no longer have your fingers on the touchpad, the scrolling ends where it would if snapping was still disabled. Only clicking on the document, scrolling slightly again etc. makes the snapping get applied.

I wanted to confirm if nightly behaves in the same way but on this example snapping doesn't happen at all until I click somewhere; the document scrolls as if no snapping got applied (should I report a separate bug for that?)

(Safari/Edge don't even react to such dynamic changes at all so they snap all the time)