| OnExternalChanges | Called when the source file of a known resource has been externally modified on disk |
| OnExternalChangesPostLoad | Called when the source file of a known resource has been externally modified on disk and after it has been fully loaded (after post load is called) |
| OnRegister | Called when a new resource has been registered |
| OnUnregister | Called when a previously known resource has been unregistered |