In order to get ligature information for some pair of characters in a font, use the following function.
Return ligature for CHARACTER1 and CHARACTER2, or
Both characters must belong to the same font.
Unless there’s no such ligature, the value returned by this function is
an instance of a class called
ligature. In the context of this
library, the term “ligature” denotes an instance of this class.
A ligature contains four bits of information accessible as described below.
composite: the character to insert between the two original ones.
delete-after: whether to delete the characters before and after the composite.
pass-over: the number of characters to skip in order to reach the next one, once the ligature has been made.