(someone check me on this)
Sunbird and Lighting only define 1 'real' component, in [http://lxr.mozilla.org/mozilla/source/calendar/base/src/calItemModule.js calItemModule.js]. This module then creates on-the-fly factories for most of the other components used. To add a new component, you should add it to the array of components defined there. See the patch on [https://bugzilla.mozilla.org/show_bug.cgi?id=298358 Bug 298358] for an example of how to do this. Note that you'll also need to modify the jar.mn file for lightning, so that the component file can be added to the .xpi.
= Potential Pitfalls =
One of the most confusing aspects of the Sunbird code is often the fact that there are actually two calendar.xul files. One can be found at [http://lxr.mozilla.org/mozilla/source/calendar/resources/content/calendar.xul resources/content/calendar.xul] and the other at [http://lxr.mozilla.org/mozilla/source/calendar/sunbird/base/content/calendar.xul sunbird/base/content/calendar.xul]. This is a vestige of the original sharing of code between Sunbird and the calendar extension. The Sunbird build process uses the calendar.xul in the sunbird/ folder. When making changes to one calendar.xul, please make changes to the other. It's still theoretically possible to build the calendar extension, and we'd like to keep this possibility around as long as possible.
