HarfBuzz includes a copy of the UCDN (Unicode
Database and Normalization) library, which provides functions
for accessing basic Unicode character properties, performing
canonical composition, and performing both canonical and
compatibility decomposition.
Currently, UCDN supports direct queries for several more character
properties than HarfBuzz's built-in set of Unicode functions
does, such as the BiDirectional Class, East Asian Width, Paired
Bracket and Resolved Linebreak properties. If you need to access
more properties than HarfBuzz's internal implementation
provides, using the built-in UCDN functions may be a useful solution.
The built-in UCDN functions are compiled by default when
building HarfBuzz from source, but this can be disabled with a
compile-time switch.