checker
Returns a CRecipePredicate that enforces the direction constraint for the given relationType.
The predicate passes if and only if no item in the player's input has a neighbouring item in a direction not included in relationType. Items whose x-distance or y-distance exceeds 1 are not considered neighbours and impose no constraint on each other.
Return
A CRecipePredicate implementing the direction constraint check.
Since
5.1.0
Parameters
relation
The permitted-direction rule to enforce.