All Unicode characters are assigned a directionality type in the Unicode Character Database. RWUCharTraits provides a BidirectionalCategory enum with values that identify the various directionality types, such as LeftToRight, RightToLeft, RightToLeftArabic, LeftToRightEmbedding, RightToLeftOverride, and so on. The values in this enumeration correspond to the bidirectional category property codes defined in the Unicode Character Database, as described in Unicode Standard Annex #9, “The Bidirectional Algorithm”:

The static method RWUCharTraits::getBidirectionalCategory() returns the value in the BidirectionalCategory enumeration identifying the directionality type associated with a given code point.