Two <WindowScroller>s on a page causes the second one to not render properly

When I’m trying to render multiple lists (2 in my case) after each other, both using <AutoSizer> and <WindowScroller>, the second one does not render properly. It takes up the correct amount of space on the page, but the rows are gone except for a few at the bottom of the page. If you scroll up, a few more of them appears. This issue does not happen after resizing your window, or if you set the width of your <List> component to a static value.

See codesandbox example.

[nicolasschabram]

I’ve done some more digging. I’m not familiar at all with the codebase, but maybe my findings still help:

WindowScroller has an updatePosition() method which measures the dom element’s offset and stores it in _positionFromTop and _positionFromLeft. updatePosition() is called in componentDidMount(), but at the time the offsets are stored, the lists themselves haven’t been painted yet. For the first one, that isn’t a problem because _positionFromTop is correct no matter its height. But the second list does depend on what has been rendered above. So what seems to be happening is that an incorrect _positionFromTop is stored during the initial render, breaking virtualization in the second list. Resizing the window triggers updatePosition() to be called again from _onResize(), which fixes the incorrect offsets - hence the behavior demonstrated in my comment above.

Another place where updatePosition() is called is in registerChild. A (rather unsatisfying) quick fix for the problem seems to be doing something like this:

<WindowScroller>
  {({ height, registerChild, scrollTop }) => (
    <div>
      <AutoSizer disableHeight>
        {({ width }) => (
          <div ref={el => registerChild(el)}> // <-- relevant line
            <List
              autoHeight
              height={height}
              rowCount={list1.length}
              rowHeight={32}
              rowRenderer={rowRenderer1}
              scrollTop={scrollTop}
              width={width}
            />
          </div>
        )}
      </AutoSizer>
    </div>
  )}
</WindowScroller>

Note that it only works when recreating the function passed to ref on every render, i.e. ref={el => registerChild(el)} instead of ref={registerChild}. I’ve tweaked @apelsinet’s example accordingly: https://codesandbox.io/s/jjnr1v3r3w?fontsize=14

It’s obviously a hack and probably not the right long-term solution. I’m not sure at all about possible negative implications.

But at least it seems like RV isn’t very far from supporting this use case. 😃

[nicolasschabram]

@apelsinet, did you make any progress on this? I’m dealing with the same problem right now. I’ve noticed though that it does seem to work after once resizing the window. 🤔