An instance of docking-layout or a subclass.
docking-layout-pane-visible-p returns a boolean indicating whether
is currently visible in the Docking Group of
may be docked in any member of the Docking Group, or undocked.
(setf docking-layout-pane-visible-p) may be used to change the visibility of pane in
is dockable in the Docking Group of
, that is, it was added to the
of any of the docking-layouts in the group.
CAPI User Guide and Reference Manual (Macintosh version) - 3 Aug 2017