'Jump to bottom' button is always displayed on non-overflowing timelines

[robintown]

Steps to reproduce

Create a room

Outcome

What did you expect?

Since I'm scrolled to the bottom of the timeline, the 'jump to bottom' button should not be displayed.

What happened instead?

Operating system

NixOS unstable

Browser information

Firefox 99.0.1

URL for webapp

develop.element.io

Application version

Element version: 850a250-react-36fd9cb0d4a7-js-2ebf33544f2a Olm version: 3.2.8

Homeserver

Synapse 1.57.0

Will you send logs?

No

[SimonBrandner]

From what I gather something changed about the way that the messsagePanel ref is set in TimelinePanel.tsx, so isAtEndOfLiveTimeline() returns undefined when called from componentDidUpdate() in RoomView.tsx which causes the button to be visible

[SimonBrandner]

Or possible onMessageListScroll() used to be called once more when everything was fully loaded but it is not called now

[SimonBrandner]

Regressed by matrix-org/matrix-react-sdk#8392 though I don't think I know how exactly