DescendantsLines
History
2007: Adam Sampson has written a standalone python script for parsing data.gramps (GRAMPS XML). [1]
2010: this script needs some updates for avoiding minor issues.
A modified script is available on addon repository. [2]
Limitations
The code ignores role on event (was added in 2007)
Descendants Lines
There is an experimental try for migrating this Gtk/cairo code to a draw plugins working into Gramps (font, style, path, canvas, output formats).
Draft version is available on Addons repository as very unstable (alpha). [3]
Feel free to contribute or improve it.