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 from TeX. This class has been taken from the Apache FOP project (http://xmlgraphics.apache.org/fop/). They have been slightly modified.
