your best resource for vanilla will always be the 1.12 UI source code:
https://github.com/tekkub/wow-ui-source/tree/1.12.1
event/api tracing + handling is definitely a process of trial & error, and will have you dipping into a variety of sources to find what works and what doesn't. this is part of the fun though, i find pleasure in it.
interface version shouldn't exceed 11200