Informs the listeners that one or more preferences of this provider are changed. The listeners are able to find what was changed from the emitted event.
Retrieve the stored value for the given preference and resource URI.
the preference identifier.
the uri of the resource for which the preference is stored. This is used to retrieve
a potentially different value for the same preference for different resources, for example files.encoding
.
the value stored for the given preference and resourceUri if it exists, otherwise undefined
.
Handles deep equality with the possibility of undefined
Resolved when the preference provider is ready to provide preferences It should be resolved by subclasses.