> That is, when
 >
 > Tue Aug 24 12:37:39 JST 2021
 > _NET_WM_STATE(ATOM) = _NET_WM_STATE_HIDDEN
 >
 > appears, it doesn't start rendering (= enlightenment doesn't remove
 > this property).

So it _is_ a PropertyNotify event we should react to.  I'll attach yet
another patch to that purpose.

martin