Window & Dynamic Size List Virtualization Causes Mobile Safari IOS Scroll Momentum Interruption

Describe the bug

By using the useWindowVirtualizer hook to apply virtualization for list items with different heights in relation to window scrolling, when you scroll, the virtualization behavior will occur.

Items that no longer need to be rendered will disappear from the DOM, and the list items corresponding to the visible indices will begin to appear in the DOM.

On Mobile iOS Safari, momentum scrolling triggered by user gestures works, but when combined with virtualization, the momentum effect fails to end smoothly and instead stutters or breaks abruptly. Is there a way to resolve this issue?

import "./styles.css";
import { useWindowVirtualizer } from "@tanstack/react-virtual";

const createRandomHeights = (
  min: number,
  max: number,
  count: number = 1000
) => {
  const heights = [];
  for (let i = 0; i < count; i++) {
    heights.push(Math.floor(Math.random() * (max - min + 1) + min));
  }
  return heights;
};

const randomHeights = createRandomHeights(100, 400);
const colors = ["red", "yellow", "blue"];

export default function App() {
  const virtualizer = useWindowVirtualizer({
    count: 1000,
    estimateSize: () => 400,
    overscan: 5,
    scrollMargin: 0,
  });

  const virtualItems = virtualizer.getVirtualItems();

  return (
    <div>
      <div
        style={{
          height: `${virtualizer.getTotalSize()}px`,
          position: "relative",
          width: "100%",
        }}
      >
        <div
          style={{
            transform: `translateY(${
              (virtualItems[0]?.start ?? 0) - virtualizer.options.scrollMargin
            }px)`,
            position: "absolute",
            left: "0",
            top: "0",
            width: "100%",
          }}
        >
          {virtualItems.map((virtualItem) => {
            return (
              <div
                key={virtualItem.key}
                data-index={virtualItem.index}
                ref={virtualizer.measureElement}
                style={{
                  paddingTop: "40px",
                }}
              >
                <div
                  style={{
                    height: randomHeights[virtualItem.index],
                    backgroundColor: colors[virtualItem.index % 3],
                  }}
                ></div>
              </div>
            );
          })}
        </div>
      </div>
    </div>
  );
}

Your minimal, reproducible example

https://codesandbox.io/p/sandbox/qhkvyz

Steps to reproduce

1. Go to CodeSandbox Link
2. Scroll down Preview Page
3. As you scroll, the momentum scroll stops occurring and the scrolling becomes increasingly choppy.

Expected behavior

I hope to maintain a seamless momentum scroll experience.

How often does this bug happen?

Every time

Screenshots or Videos

https://github.com/user-attachments/assets/2b27fcd6-e3de-449b-ac20-2633d76619d3

https://github.com/user-attachments/assets/166be2b0-cab1-495a-a9e1-9b770e31c1fc

Platform

• OS: IOS
• Browser: Safari
• Version: 18.1, 17.6.1

tanstack-virtual version

v3.10.6

TypeScript version

v5.4.5

Additional context

It seems that the CodeSandbox link is difficult to run on Mobile iOS Safari at the moment. However, you can reproduce the issue by running the attached source code.

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.

Start with the provided CodeSandbox reproduction and the useWindowVirtualizer example, testing it on Mobile iOS Safari with dynamically sized items. Investigate the interaction between measured elements being virtualized and window-scroll momentum; done means the reproduction retains smooth momentum scrolling while virtualization remains active.