Constant FIRST_BC_MASK
const FIRST_BC_MASK: BidiClassMaskMask for allowable bidi classes in the first character of a label (either LTR or RTL) in a bidi domain.
FIRST_BC_MASKconst FIRST_BC_MASK: BidiClassMaskMask for allowable bidi classes in the first character of a label (either LTR or RTL) in a bidi domain.