Methods
| CreateChannel | (a{sv}: Request) | → | o: Channel, a{sv}: Properties | |
| EnsureChannel | (a{sv}: Request) | → | b: Yours, o: Channel, a{sv}: Properties |
Signals
| NewChannels | (a(oa{sv}): Channels) | |
| ChannelClosed | (o: Removed) |
Properties
| Channels | a(oa{sv}) (Channel_Details_List) | Read only | ||
| RequestableChannelClasses | a(a{sv}as) (Requestable_Channel_Class_List) | Read only |
Types
| Channel_Class | Mapping | a{sv} | |
| Channel_Details | Struct | (oa{sv}) | |
| Requestable_Channel_Class | Struct | (a{sv}as) |
Description
An enhanced version of the Telepathy connection interface, which can represent bundles of channels that should be dispatched together, and does not assume any particular properties by which channels are uniquely identifiable.
Methods
CreateChannel (a{sv}: Request) → o: Channel, a{sv}: Properties
Parameters
- Request — a{sv} (Qualified_Property_Value_Map)
A dictionary containing desirable properties, which MUST include ChannelType. Some properties are defined such that only an exact match makes sense, and connection managers MUST NOT satisfy a request with a channel where that property does not match; some properties are defined such that the connection manager MAY treat the request as merely a hint, and make a best-effort attempt to satisfy it. This is documented separately for each property.
If this dictionary contains a property whose semantics are not known to the connection manager, this method MUST fail without side-effects (in particular it must not create a new channel).
Rationale:
This is necessary if we want to be able to invent properties in future that, when used in a request, are hard requirements rather than just hints. A connection manager that did not know the semantics of those properties could incorrectly return a new channel that did not satisfy the requirements.
The connection manager MUST NOT respond successfully, and SHOULD NOT create a new channel or cause any other side-effects, unless it can create a new channel that satisfies the client's requirements.
Properties that will be set by this argument need not have write access after the channel has been created - indeed, it is expected that most will be read-only.
Returns
- Channel — o
- Properties — a{sv} (Qualified_Property_Value_Map)
The Channel object, which MUST NOT be signalled with NewChannels until after this method returns.
Rationale:
This allows the requester to alter its handling of NewChannels by knowing whether one of the channels satisfied a request it made.
Properties of the channel that was produced, equivalent to the properties in Channel_Details. Connection managers MUST NOT include properties here whose values can change, for the same reasons as in Channel_Details.
Request that an entirely new channel is created.
Possible Errors
- Disconnected
- Network Error
- Not Implemented
- Invalid Handle
- Invalid Argument
- Not Capable
- Offline
- Not Available
- a channel matching the request already exists and the protocol requires that only one such channel can exist at a time
- a channel matching the request has already been requested (by a previous call to CreateChannel, EnsureChannel, or similar) and the protocol requires that only one such channel can exist at a time
- Channel.Banned
- Channel.Full
- Channel.Invite Only
- Permission Denied
Rationale:
The requested channel cannot be created, but in principle, a similar request might succeed in future. For instance, this might be because:
EnsureChannel (a{sv}: Request) → b: Yours, o: Channel, a{sv}: Properties
Parameters
- Request — a{sv} (Qualified_Property_Value_Map)
A dictionary containing desirable properties, with the same semantics as the corresponding parameter to CreateChannel.
Returns
- Yours — b
- Channel — o
- Properties — a{sv} (Qualified_Property_Value_Map)
If false, the caller of EnsureChannel MUST assume that some other process is handling this channel; if true, the caller of EnsureChannel SHOULD handle it themselves or delegate it to another client.
If the creation of a channel makes several calls to EnsureChannel (and no other requests) successful, exactly one of those calls MUST return a true value for this argument.
If the creation of a channel makes other requests successful, the value returned for this argument MUST be such that exactly one of the clients making requests ends up responsible for the channel. In particular, if CreateChannel returns a channel C, any EnsureChannel calls that also return C MUST return a false value for this argument.
Rationale:
This allows the requester to alter its handling of NewChannels by knowing whether one of the channels satisfied a request it made.
Properties of the channel that was produced, equivalent to the properties in Channel_Details. Connection managers MUST NOT include properties here whose values can change, for the same reasons as in Channel_Details.
Request that channels are ensured to exist.
Rationale:
The connection manager is in the best position to determine which existing channels could satisfy which requests.
Possible Errors
- Disconnected
- Network Error
- Not Implemented
- Invalid Handle
- Invalid Argument
- Not Capable
- Offline
- Not Available
- Channel.Banned
- Channel.Full
- Channel.Invite Only
- Permission Denied
Rationale:
Signals
NewChannels (a(oa{sv}): Channels)
Parameters
- Channels — a(oa{sv}) (Channel_Details_List)
New channels have been created. The connection manager SHOULD emit a single signal for any group of closely related channels that are created at the same time, so that the channel dispatcher can try to dispatch them to a handler as a unit.
In particular, if additional channels are created as a side-effect of a call to CreateChannel, these channels SHOULD appear in the same NewChannels signal as the channel that satisfies the request.
Rationale:
Joining a MUC Tube in XMPP requires joining the corresponding MUC (chatroom), so a Text channel can be created as a side-effect.
ChannelClosed (o: Removed)
Parameters
- Removed — o
Properties
Channels — a(oa{sv}) (Channel_Details_List)
RequestableChannelClasses — a(a{sv}as) (Requestable_Channel_Class_List)
The classes of channel that are expected to be available on this connection, i.e. those for which CreateChannel can reasonably be expected to succeed. User interfaces can use this information to show or hide UI components.
This property cannot change after the connection has gone to state Connection_Status_Connected, so there is no change notification (if the connection has context-dependent capabilities, it SHOULD advertise support for all classes of channel that it might support during its lifetime). Before this state has been reached, the value of this property is undefined.
Rationale:
This is not on an optional interface, because connection managers can always offer some sort of clue about the channel classes they expect to support (at worst, they can announce support for everything for which they have code).
Types
Channel_Class — a{sv}
Mapping representing a class of channels that can be requested from a connection manager, can be handled by a user interface, are supported by a contact, etc.
Classes of channel are identified by the fixed values of a subset of their properties.
Channel classes SHOULD always include the keys im.telepathy1.Channel.ChannelType and im.telepathy1.Channel.TargetHandleType.
- Key — s (DBus_Qualified_Member)
- Value — v
Channel_Details — (oa{sv})
- Channel — o
- Properties — a{sv} (Qualified_Property_Value_Map)
- NewChannels or Get("Channels") includes a property P with value V1
- Client creates a proxy object for the channel
- The value of P changes to V2
- Client connects to PChanged signal
- Client should call Get("P") or GetAll here, to avoid the race, but client's author has forgotten to do so
- Proxy object thinks P == V1, but actually P == V2
Properties of the channel.
Connection managers MUST NOT include properties in this mapping if their values can change. Clients MUST ignore properties that appear in this mapping if their values can change.
Rationale:
If properties that could change were included, the following race condition would be likely to exist in some cases:
We've taken the opportunity to make the API encourage the client author to get it right. Where possible, we intend that properties whose value will be used in channel dispatching or other "early" processing will be defined so that they are immutable (can never change).
Each dictionary MUST contain the keys im.telepathy1.Channel.ChannelType, im.telepathy1.Channel.TargetHandleType, im.telepathy1.Channel.TargetHandle, im.telepathy1.Channel.TargetID and im.telepathy1.Channel.Requested.
Rationale:
We expect these to be crucial to the channel-dispatching process.
Requestable_Channel_Class — (a{sv}as)
Structure representing a class of channels that can be requested, identified by a set of properties that identify that class of channel.
Rationale:
This will often just be the channel type and the handle type, but can include other properties of the channel - for instance, encrypted channels might require properties that unencrypted channels do not, like an encryption key.
In some cases, these classes of channel may overlap, in the sense that one class fixes all the properties that another class does, plus some more properties.
Rationale:
For older clients to still be able to understand how to request channels in the presence of a hypothetical "encryption" interface, we'd need to represent it like this:
- class 1: ChannelType = Text, TargetHandleType = CONTACT
- class 2: Channel.ChannelType = Text, Channel.TargetHandleType = CONTACT, Encryption.Encrypted = TRUE
- Fixed_Properties — a{sv} (Channel_Class)
- Allowed_Properties — as (DBus_Qualified_Member_List)
The property values that identify this requestable channel class. These properties MUST be included in requests for a channel of this class, and MUST take these values.
Clients that do not understand the semantics of all the Fixed_Properties MUST NOT request channels of this class, since they would be unable to avoid making an incorrect request.
This implies that connection managers wishing to make channels available to old or minimal clients SHOULD have a channel class with the minimum number of Fixed_Properties, and MAY additionally have channel classes with extra Fixed_Properties.
Interface designers SHOULD avoid introducing fixed properties
whose types are not serializable in a .manager
file.
Rationale:
Connection managers with a fixed property that is not
serializable cannot have a complete .manager
file.
Properties that MAY be set when requesting a channel of this channel type and handle type.
This array MUST NOT include properties that are in the Fixed_Properties mapping.
Properties in this array may either be required or optional, according to their documented semantics.
Rationale:
For instance, if TargetHandleType takes a value that is not Handle_Type_None, one or the other of TargetHandle and TargetID is required. Clients are expected to understand the documented relationship between the properties, so we do not have separate arrays of required and optional properties.