bug#58175: 29.0.50; M-x window-swap-states during an active mark leaves behind a region overlay

[martin rudalics]

> Looks like the internal-region-overlay window parameter, which is
> important for correct workings of region-highlight, isn't copied
> correctly to the other window as part of swapping state, because its
> value ends up as "overlay N in no buffer", i.e. the overlay's buffer
> is lost in transition.

If you want a window parameter to get copied when swapping window states,
you have to explicitly mark it as "persistent".  For example with:

(push '(internal-region-overlay . t) window-persistent-parameters)

martin