This article is a stub and needs to be finished. Plunge forward and help it grow!
A good reference to the ETL/synfig/synfigstudio source code is the synfig doxygen documentation. Please note that currently the API and ABI is subject to change and breakage. We do our best to keep the file format from breaking though.
NOTE: the code tree that used to be listed here became out of date after a restructuring of the source code. Please browse the tree using github instead.