useWindowVirtualizer shows blank when having other contents on page

Describe the bug

Hello, thanks for open sourcing this great library.

One potential bug: when using useWindowVirtualizer, I noticed the virtualized content would start showing blank items when scrolling down, if the page has some other normal contents on top.

Your minimal, reproducible example

https://codesandbox.io/s/friendly-noether-6f2p8z?file=/src/App.tsx

Steps to reproduce

scroll down on the sandbox demo

Expected behavior

the virtualized content should not blank on the visible window

How often does this bug happen?

No response

Screenshots or Videos

No response

Platform

MacOS

tanstack-virtual version

v3.0.0-beta.18

TypeScript version

No response

Additional context

No response

Terms & Code of Conduct

• I agree to follow this project’s Code of Conduct
• I understand that if my bug cannot be reliable reproduced in a debuggable environment, it will probably not be fixed and this issue may even be closed.

[piecyk]

Yeah, here we need to add something like scrollMargin that will handle this cases. @dylanwulf was on right path, internally we need to skip altering scrollToFn when syncing scroll position.

[dylanwulf]

I was able to fix the scrolling methods by providing a custom scrollToFn:

scrollToFn: (offset, canSmooth, instance) => {
  window.scrollTo({
    top:
      offset +
      window.scrollY +
      (virtualListRef.current?.getBoundingClientRect().top ?? 0),
    behavior: canSmooth ? "smooth" : undefined
  });

but now my problem is that it automatically scrolls to the first element of my list on mount, even if I don’t have initialOffset specified.