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(as stable API)

An interface on connections to support protocols which allow users to publish their current geographical location, and subscribe to the current location of their contacts.

This interface is geared strongly towards automatic propagation and use of this information, so focuses on latitude, longitude and altitude which can be determined by GPS, although provision is also included for an optional human-readable description of locations. All co-ordinate information is required to be relative to the WGS84 datum.

The information published through this interface is intended to have the same scope as presence information, so will normally be made available to those individuals on the user's "publish" contact list. Even so, user interfaces should not automatically publish location information without the consent of the user, and it is recommended that an option is made available to reduce the accuracy of the reported information to allow the user to maintain their privacy.

Location information is represented using the terminology of XMPP's XEP-0080 or the XEP-0080-derived Geoclue API where possible.

Clients of this interface SHOULD register an interest in it by calling Connection.AddClientInterest with an argument containing the name of this interface, before calling any Location method. If they do so, they SHOULD also call Connection.RemoveClientInterest after use to allow the CM to release resources associated with this interface.

A user's location, represented as an extensible mapping.

Civic addresses are represented by the following well-known keys (all of which have string values), which should be kept in sync with those used in XEP-0080 and in the Geoclue project:

countrycode - s: an ISO-3166-1 alpha-2 (two-letter) country code, e.g. "us", "gb", "fr"
country - s: a country name in unspecified locale, e.g. "USA"
region - s: an administrative region of the nation, such as a state or province
locality - s: a locality within the administrative region, such as a town or city
area - s: a named area such as a campus or neighborhood
postalcode - s: a code used for postal delivery
street - s: a thoroughfare within the locality, or a crossing of two thoroughfares

The following address keys are defined in XEP-0080 but not by Geoclue, and are also allowed:

building - s: a specific building on a street or in an area
floor - s: a particular floor in a building
room - s: a particular room in a building
text - s: any more specific information, e.g. "Northwest corner of the lobby"
description - s: A natural-language name for or description of the location, e.g. "Bill's house"
uri - s: a URI representing the location or pointing to more information about it

Since the previous strings have data intended to be read by users, the language used should be stated using:

language - s: a specific language or locale of location information in a format compatible to RFC 4646. Note that UTF-8 is the only allowed encoding, e.g. "en" or "fr-CA".

Positions are represented by the following well-known keys:

lat - d: latitude in decimal degrees north, -90 to +90, relative to the WGS-84 datum This is from XEP-0080; the XEP allows use of a different datum, but recommends this one. We enforce sanity by requiring a consistent datum: a minimal compliant implementation of this specification in terms of XEP-0080 would simply ignore the <lat> and <lon> elements if <datum> exists and has a value other than WGS-84, while an advanced implementation might correct for the different datum.
lon - d: Longitude in decimal degrees east, -180 to +180, relative to the WGS-84 datum Same rationale as 'lat'
alt - d: altitude in metres above sea level (negative if below sea level) This is from XEP-0080
accuracy - d: horizontal position error in metres if known This is from XEP-0080

Velocities are represented by the following well-known keys:

speed - d: speed in metres per second This is from XEP-0080
bearing - d: direction of movement in decimal degrees, where North is 0 and East is 90 This is from XEP-0080, and is equivalent to the struct field called "direction" in GeoClue

Other well-known keys:

timestamp - x (Unix_Timestamp64): the time that the contact was at this location, in seconds since 1970-01-01T00:00:00Z (i.e. the beginning of 1970 in UTC) XEP-0080 uses an ISO 8601 string for this, but a number of seconds since the epoch is probably easier to work with.

The value corresponding to the well-known key. A map from contacts to their locations. A contact The contact's location, which MAY be empty to indicate that the contact's location is unknown

Return the current locations of the given contacts, if they are already known. If any of the given contacts' locations are not known, request their current locations, but return immediately without waiting for a reply; if a reply with a non-empty location is later received for those contacts, the LocationUpdated signal will be emitted for them.

This method is appropriate for "lazy" location finding, for instance displaying the location (if available) of everyone in your contact list.

For backwards compatibility, if this method is called by a client whose "interest count" for this interface, as defined by Connection.AddClientInterest, is zero, the Connection SHOULD behave as if AddClientInterest had been called for this interface just before that method call. Clients that do not explicitly call AddClientInterest SHOULD NOT call Connection.RemoveClientInterest either.

The contacts whose locations should be returned or signalled. The contacts' locations, if already known. Contacts whose locations are not already known are omitted from the mapping; contacts known to have no location information appear in the mapping with an empty Location dictionary.

Return the current location of the given contact. If necessary, make a request to the server for up-to-date information, and wait for a reply. This method is appropriate for use in a "Contact Information..." dialog; it can be used to show progress information (while waiting for the method to return), and can distinguish between various error conditions. The contact whose location should be returned. The contact's location. It MAY be empty, indicating that no location information was found.

The requested contact does not allow the local user to see their location information.

Emitted when a contact's location changes or becomes known. The contact The contact's location, or empty to indicate that nothing is known about the contact's location. Set the local user's own location. The location to advertise. If the user wants to obscure their exact location by reducing the precision or accuracy, clients MUST do this themselves, rather than relying on the connection manager to do so. Clients that interact with more than one connection SHOULD advertise the same reduced-accuracy location to all of them, so that contacts cannot obtain an undesirably accurate location by assuming that random errors have been added and averaging the locations advertised on multiple connections.

The user's server does not support publishing their own location. If it is possible to determine this ahead of time, the Can_Set flag will not be set in SupportedLocationFeatures.

The types of access control that are supported by this connection. The current access control mechanism and settings for this connection. Before publishing location for the first time, if this has not been set by a client, implementations SHOULD set it to be as restrictive as possible (an empty whitelist, if supported). Indicates the Location features supported by this connection. This property MAY be undefined before Status becomes Connected, but MUST remain constant thereafter. Indicates that setting your own location with SetLocation is supported on this connection. Flags describing the Location features which may be supported on any given connection.

The same mapping that would be returned by GetLocations for this contact. Omitted from the result if the contact's location is not known.

For backwards compatibility, if contact attributes that include this interface are requested by a client whose "interest count" for this interface, as defined by Connection.AddClientInterest, is zero, the Connection SHOULD behave as if AddClientInterest was called for this interface just before that request. Clients that do not explicitly call AddClientInterest SHOULD NOT call Connection.RemoveClientInterest either.