Unexpected scroll behavior when itemSize is automatically estimated

[mariia-mitiureva]

Hi, I noticed some weird behavior, not sure if it's an issue or not.

I modified Chat default story like this

So, on the first render, there is one big item in the list, after a few seconds some smaller items are prepended. After that, if I scroll up just a bit, scroll will jump to the very top

Screen.Recording.2024-08-22.at.17.39.28.mov

The issue can be fixed by setting itemSize to some small number, 30 for example. Is it expected or is there some issue with automatically estimated item size? I see, that it's recommended to rely on automatically estimated sizes..

[inokawa]

In auto estimation mode, default item size will be estimated when the sum of item sizes exceed the viewport size for the first time. Probably the size of the huge one item was treated as default size in that situation.

[mariia-mitiureva]

So is it expected behavior or is it possible to improve this?

Also, when I set itemSize to some small number, another issue gets worse.
When list items are quite heavy components, and their size if greater than itemSize (code snippet), the initial scroll to bottom is quite noticeable.

Screen.Recording.2024-08-23.at.15.22.22.mov

In auto estimation mode it happens too, but less often.