This class represents a hyphen. A 'full' hyphen is made of 3 parts: the
pre-break text, post-break text and no-break. If no line-break is generated
at this position, the no-break text is used, otherwise, pre-break and
post-break are used. Typically, pre-break is equal to the hyphen character
and the others are empty. However, this general scheme allows support for
cases in some languages where words change spelling if they're split across
lines, like german's 'backen' which hyphenates 'bak-ken'. BTW, this comes
This class has been taken from the Apache FOP project (http://xmlgraphics.apache.org/fop/). They have been slightly modified.