guile-cairo has a reference manual automatically
generated from upstream Cairo documentation. This means that the manual
is complete, mostly accurate, but at times C-isms remain in the
generated documentation. We will be fixing this with time.
Once you install guile-cairo, you can access
documentation from within Info (info guile-cairo) or from
within Guile itself (help cairo-create). If you are
interested in helping to improve the documentation, there is information
in the source tree, in the file doc/README.