doxygen for twopigen

diff --git a/lib/twopigen/twopiinit.c b/lib/twopigen/twopiinit.c
index c00895b1c299ffc2c5f321f5c4eee0d37312f824..88a08aed6b4d35d2fdee83532e8503d877f5bc3a 100644 (file)
--- a/lib/twopigen/twopiinit.c
+++ b/lib/twopigen/twopiinit.c
@@ -192,3 +192,15 @@ void twopi_cleanup(graph_t * g)
     }
     twopi_cleanup_graph(g);
 }
+
+/**
+ * @dir lib/twopigen
+ * @brief radial layout engine, API twopigen/circle.h
+ * @ingroup engines
+ *
+ * Twopi means 2π.
+ *
+ * [Twopi layout user manual](https://graphviz.org/docs/layouts/twopi/)
+ *
+ * Other @ref engines
+ */