Room list scroll jumps are back

[robintown]

Steps to reproduce

Scroll through the room list, and watch it jump every time the sticky header changes

Steps to reproduce

This bug depends on your viewport height compared to one of your room list sub-sections.

1. Start with a big viewport, and have a room subsection expanded where all of it fits on screen
2. Resize to shrink your viewport so that it's just big enough to show the whole room subsection. Then shrink a bit more so that the headings overlap when you scroll down
3. Scroll to the bottom of the room list
4. Notice the jitter

I have reproduced this with Chrome on Windows and the Element desktop app on macOS but seems like it would happen in any environment.

I have also reproduced this with several different room sub-sections and also when switched to a space.

-- #18440

Outcome

What did you expect?

The scrolling should be smooth and continuous

What happened instead?

jump.mp4

Regressed by matrix-org/matrix-react-sdk#6915

Operating system

NixOS unstable

Browser information

Firefox 92.0.1

URL for webapp

develop.element.io

Homeserver

townsendandsmith.ml

Will you send logs?

No

[MadLittleMods]

I'm able to reproduce on the latest develop.element.io

Same reproduction steps as my original issue:

Steps to reproduce

This bug depends on your viewport height compared to one of your room list sub-sections.

1. Start with a big viewport, and have a room subsection expanded where all of it fits on screen
2. Resize to shrink your viewport so that it's just big enough to show the whole room subsection. Then shrink a bit more so that the headings overlap when you scroll down
3. Scroll to the bottom of the room list
4. Notice the jitter

I have reproduced this with Chrome on Windows and the Element desktop app on macOS but seems like it would happen in any environment.

I have also reproduced this with several different room sub-sections and also when switched to a space.

-- #18440

Past issues:

• Sticky headings jockey for position causing scroll jitter in room list #18440
• Scrolling beyond room list is jerky again #19555
• Scroll jump in room list with sticky headers #19848
• scroll jitter in room list is back #20441

---

• jitter
• jerky
• jumpy
• sticky headings