Separator shown with only one visible pane

[elliotfklein]

Repro: https://codesandbox.io/s/infallible-rumple-x4hhfk?file=/src/App.tsx

If you have two panes and the first one has visible={false}, the second pane will still show a separator on the left side.

At first glance, I think the issue might be with the :not(:first-child) selector on .splitViewView::before — because there is an invisible pane before the visible pane, the visible pane is not the first child.

I don't think e.g. :first-of-type would work here either, this might need to be handled with JS.

Please LMK if I can help here somehow — thanks! 🙂

[MainzerKaiser]

For my use-case I like that the sepearator is visible to re-open a pane again. But what troubles me is that it only works when the right pane is maximized, not when the left is maximized. Then the separator is not visible, but you can still click on it and draw it.