nsIContentPrefService2

Description

Content preferences allow the application to associate arbitrary data, or "preferences", with specific domains, or web "content". Specifically, a content preference is a structure with three values: a domain with which the preference is associated, a name that identifies the preference within its domain, and a value. (See nsIContentPref below.)

For example, if you want to remember the user's preference for a certain zoom level on www.mozilla.org pages, you might store a preference whose domain is "www.mozilla.org", whose name is "zoomLevel", and whose value is the numeric zoom level.

A preference need not have a domain, and in that case the preference is called a "global" preference. This interface doesn't impart any special significance to global preferences; they're simply name-value pairs that aren't associated with any particular domain. As a consumer of this interface, you might choose to let a global preference override all non- global preferences of the same name, for example, for whatever definition of "override" is appropriate for your use case.

Domain Parameters

Many methods of this interface accept a "domain" parameter. Domains may be specified either exactly, like "example.com", or as full URLs, like "https://example.com/foo/bar". In the latter case the API extracts the full domain from the URL, so if you specify "https://foo.bar.example.com/baz", the domain is taken to be "foo.bar.example.com", not "example.com".

Private-Browsing Context Parameters

Many methods also accept a "context" parameter. This parameter relates to private browsing and determines the kind of storage that a method uses, either the usual permanent storage or temporary storage set() aside for private browsing sessions.

Pass null to unconditionally use permanent storage. Pass an nsILoadContext to use storage appropriate to the context's usePrivateBrowsing attribute: if usePrivateBrowsing is true, temporary private-browsing storage is used, and otherwise permanent storage is used. A context can be obtained from the window or channel whose content pertains to the preferences being modified or retrieved.

Callbacks

The methods of callback objects are always called asynchronously. See nsIContentPrefCallback2 for more information about callbacks.

Method overview

Methods

addObserverForName()

Registers an observer that will be notified whenever a preference with the given name is set() or removed.

When a set() or remove method is called, observers are notified after the set() or removal completes but before method's callback is called.

The service holds a strong reference to the observer, so the observer must be removed later to avoid leaking it.

void addObserverForName(
  in AString name,
  in nsIContentPrefObserver observer
);

Parameters

name

The name of the preferences to observe. Pass null to observe all preference changes regardless of name.

observer

The observer.

getByDomainAndName()

Gets the preference with the given domain and name.

void getByDomainAndName(
  in AString domain,
  in AString name,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback
);

Parameters

domain

The preference's domain.

name

The preference's name.

context

The private-browsing context, if any.

callback

HandleResult is called once unless no such preference exists, in which case handleResult is not called at all.

getBySubdomainAndName()

Gets all preferences with the given name whose domains are either the same as or subdomains of the given domain.

void getBySubdomainAndName(
  in AString domain,
  in AString name,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback
);

Parameters

domain

The preferences' domain.

name

The preferences' name.

context

The private-browsing context, if any.

callback

HandleResult is called once for each preference. If no such preferences exist, handleResult is not called at all.

getCachedByDomainAndName()

Synchronously retrieves from the in-memory cache the preference with the given domain and name.

In addition to caching preference values, the cache also keeps track of preferences that are known not to exist. If the preference is known not to exist, the value attribute of the returned object will be undefined (nsIDataType.VTYPE_VOID()).

If the preference is neither cached nor known not to exist, then null is returned, and get() must be called to determine whether the preference exists.

nsIContentPref getCachedByDomainAndName(
  in AString domain,
  in AString name,
  in nsILoadContext context
);

Parameters

domain

The preference's domain.

name

The preference's name.

context

The private-browsing context, if any.

Return value

The preference, or null if no such preference is known to exist.

getCachedBySubdomainAndName()

Synchronously retrieves from the in-memory cache all preferences with the given name whose domains are either the same as or subdomains of the given domain.

The preferences are returned in an array through the out-parameter. If a preference for a particular subdomain is known not to exist, then an object corresponding to that preference will be present in the array, and, as with getCachedByDomainAndName(), its value attribute will be undefined.

void getCachedBySubdomainAndName(
  in AString domain,
  in AString name,
  in nsILoadContext context,
  out unsigned long len,
  [retval,array,size_is(len)] out nsIContentPref prefs
);

Parameters

domain

The preferences' domain.

name

The preferences' name.

context

The private-browsing context, if any.

len

The length of the returned array.

prefs

The array of preferences.

getCachedGlobal()

Synchronously retrieves from the in-memory cache the preference with no domain and the given name.

As with getCachedByDomainAndName(), if the preference is cached then it is returned; if the preference is known not to exist, then the value attribute of the returned object will be undefined; if the preference is neither cached nor known not to exist, then null is returned.

nsIContentPref getCachedGlobal(
  in AString name,
  in nsILoadContext context
);

Parameters

name

The preference's name.

context

The private-browsing context, if any.

Return value

The preference, or null if no such preference is known to exist.

getGlobal()

Gets the preference with no domain and the given name.

void getGlobal(
  in AString name,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback
);

Parameters

name

The preference's name.

context

The private-browsing context, if any.

callback

HandleResult is called once unless no such preference exists, in which case handleResult is not called at all.

removeAllDomains()

Removes all non-global preferences -- in other words, all preferences that have a domain.

void removeAllDomains(
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the operation completes.

removeAllGlobals()

Removes all global preferences -- in other words, all preferences that have no domain.

void removeAllGlobals(
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the operation completes.

removeByDomain()

Removes all preferences with the given domain.

void removeByDomain(
  in AString domain,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

domain

The preferences' domain.

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the operation completes.

removeByDomainAndName()

Removes the preference with the given domain and name.

void removeByDomainAndName(
  in AString domain,
  in AString name,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

domain

The preference's domain.

name

The preference's name.

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the operation completes.

removeByName()

Removes all preferences with the given name regardless of domain, including global preferences with the given name.

void removeByName(
  in AString name,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

name

The preferences' name.

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the operation completes.

removeBySubdomain()

Removes all preferences whose domains are either the same as or subdomains of the given domain.

void removeBySubdomain(
  in AString domain,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

domain

The preferences' domain.

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the operation completes.

removeBySubdomainAndName()

Removes all the preferences with the given name whose domains are either the same as or subdomains of the given domain.

void removeBySubdomainAndName(
  in AString domain,
  in AString name,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

domain

The preferences' domain.

name

The preferences' name.

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the operation completes.

removeGlobal()

Removes the preference with no domain and the given name.

void removeGlobal(
  in AString name,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

name

The preference's name.

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the operation completes.

removeObserverForName()

Unregisters an observer for the given name.

void removeObserverForName(
  in AString name,
  in nsIContentPrefObserver observer
);

Parameters

name

The name for which the observer was registered. Pass null if the observer was added with a null name.

observer

The observer.

set()

Sets a preference.

void set(
  in AString domain,
  in AString name,
  in nsIVariant value,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

domain

The preference's domain.

name

The preference's name.

value

The preference's value.

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the preference has been stored.

setGlobal()

Sets a preference with no domain.

void setGlobal(
  in AString name,
  in nsIVariant value,
  in nsILoadContext context,
  in nsIContentPrefCallback2 callback Optional
);

Parameters

name

The preference's name.

value

The preference's value.

context

The private-browsing context, if any.

callback Optional

HandleCompletion is called when the preference has been stored.

See also

• Old synchronous API:nsIContentPrefService
• Using content preferences