On 20. Jun 2022, 03:22 +0200, Po Lu <luangruo@yahoo.com>, wrote:

Isn't that a bug, since scroll bars should only be judged for windows
that are still reachable?

I'd say no: Ns_judge_scroll_bars is called for a frame, and loops over EmascScroller subviews of that frame. I don't see how it is could be certain that all EmascScrollers reference a live Emacs window at that point.