- Learn where the code is and about the architecture of the tools.
- Set up your machine to build the tools, then configure a development profile.
- You can now experiment by changing things and rebuilding, look at the files and directories overview or you could also find something to work on.
- MDN Web Docs (also known as MDN) has a lot of information about XUL elements, HTML, JS, DOM, Web APIs, Gecko-specific APIs, and more.
- DXR is a source code search engine - search for symbols you want to learn about, eg.
nsIDocument. Searchfox is an alternative.
It is a good idea to add smart keyword searches for DXR and MDN, so you can search faster.