TextSpanner left-bound-info

[Andrew Bernard]

In the NR, the following entry is given on the TextSpanner page:

 left-bound-info (list):

    ly:line-spanner::calc-left-bound-info

    An alist of properties for determining attachments of spanners to edges.

Similarly for right-bound-info.

Where does one find out what the alist actually is, and an explanation of the items it contains?

[I know the NR is supposed to be terse, but this is opaque to me. Even the UNIX man pages, famous for being reference material and not tutorial, and equally terse with equally good reason, generally have examples at the end.]

Andrew