1534863 - Wrong scrolling behavior when opening sections

Status: RESOLVED WORKSFORME

(Core :: Layout, defect, P3)

Description

[Karl Dubost💡 :karlcow]

Spin-off of https://webcompat.com/issues/25995
Check the webcompat issue for the detailed analysis.

Steps To reproduce on desktop

1. Switch to RDM with a mobile user agent string.
2. Pick up 360x640 pixels for your viewport
3. Load https://de.m.wikipedia.org/wiki/Organische_Halbleiter
4. scroll until "Elektronische Eigenschaften" is at the top of the viewport. See https://webcompat.com/issues/25995 for an animated gif illustrating it.
5. Click/Tap on "Elektronische Eigenschaften"

Actual:
The bottom content doesn't move like if it was fixed.
The item we clicked expands the section but by moving/showing the text toward the top. The page expands toward the top.

The click just adds/removes a class value open-block which sets a display: block on the following sibling (which is in display: none by default).

We can NOT reproduce if the height of the viewport is longer than the distance in distance in between the item we clicked and the bottom of the page.

To reproduce on a pixel 2 for example, put your device in landscape position.

PS: This doesn't reproduce in Chrome Canary Version 75.0.3731.0 (Build officiel) canary (64 bits).
Tested in Firefox Nightly 67.0a1 (2019-03-12) (64-bit)

Comment 1

[Firefox Bug Husbandry Bot]

Migrating Webcompat whiteboard priorities to project flags. See bug 1547409.

Comment 2

[Firefox Bug Husbandry Bot]

See bug 1547409. Migrating whiteboard priority tags to program flags.

Comment 3

[Mike Taylor [:miketaylr]]

It seems unrelated to scroll snapping (toggling layout.css.scroll-snap-v1.enabled has no effect).

Comment 4

[Dennis Schubert [:denschub]]

This appears to be fixed.