Detect when inside a split?

[David Woodfall]

On Friday 13 April 2018 17:27,
Dave Woodfall <dave at dawoodfall.net> put forth the proposition:
>Is it possible to detect when inside a split so I can use a switch in
>my caption string?
>
>I'm using %F to detect if the region has focus and dim the other
>window names. This is OK in a split because it hides the other window
>names, but when in a single screen with no splits I'd like to see a
>full visible list.
>
>TIA

Guess who posted to the wrong list.