The package provides a means of labelling diagrams each produced as a MetaFont character in a ‘font’ which is produced using the diagramf.mf MetaFont package. LaTeX passes data to MetaFont (by ordinary LaTeX file-writing mechanisms), and MetaFont writes stuff into its log-file, which must then be extracted into a different file so that LaTeX can see it.

The authors are Jeremy Gibbons and Alan Jeffrey.