valid_shadow - controls which objects can be shadowed

int valid_shadow( object ob );

When an object attempts to shadow `ob' (with the shadow() efun), valid_shadow
in the master object is called.  One object parameter is passed, which is the
object that previous_object() is attempting to shadow.  valid_shadow() should
return 0 if the shadow should not be permitted, in which case the shadow() call
will return 0 and fail.  If valid_shadow() returns 1, the shadow is allowed.

See also:
 shadow,
 query_shadowing

 Tim Hollebeek  Beek@ZorkMUD, Lima Bean, IdeaExchange, and elsewhere
