This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
This interface extends the Text interface to support more general messages, including:
Although this specification supports formatted (rich-text) messages with unformatted alternatives, implementations SHOULD NOT attempt to send formatted messages until the Telepathy specification has also been extended to cover capability discovery for message formatting.
This interface also replaces
If this interface is present, clients that support it SHOULD
listen for the
A list of MIME types supported by this channel, with more preferred MIME types appearing earlier in the list. The list MAY include "*/*" to indicate that attachments with arbitrary MIME types can be sent. This list MUST NOT be empty, since all Messages implementations MUST accept messages containing a single "text/plain" part.
Some examples of how this property interacts with the
Flags indicating the level of support for message parts on this channel. They are designed such that setting more flags always implies that the channel has more capabilities.
If no flags are set, this indicates that messages may contain a single message part whose content-type is any of the types from SupportedContentTypes, possibly with some alternatives.
There is no flag indicating support for alternatives. This is because the SendMessage implementation can always accept messages containing alternatives, even if the underlying protocol does not, by deleting all alternatives except the first (most preferred) that is supported.
See
Part of a message's content. In practice, this mapping never
appears in isolation - messages are represented by a list of
An example of how a rich-text message, with an embedded image, might look, in a Python-like syntax:
[
{
'message-token': '9de9546a-3400-4419-a505-3ea270cb834c',
'message-sender': 42,
'message-sent': 1210067943,
'message-received': 1210067947,
'message-type': 0, # = Channel_Text_Message_Type_Normal
'pending-message-id': 437,
},
{ 'alternative': 'main',
'content-type': 'text/html',
'content': 'Here is a photo of my cat:<br />' +
'<img src="cid:catphoto" alt="lol!" />' +
'<br />Isn't it cute?',
},
{ 'alternative': 'main',
'content-type': 'text/plain',
'content': 'Here is a photo of my cat:\n[IMG: lol!]\nIsn't it cute?',
},
{ 'identifier': 'catphoto',
'content-type': 'image/jpeg',
'size': 101000,
'needs-retrieval': True,
},
]
An example of how a non-text message — in particular, a vCard sent via SMS as implemented by telepathy-ring on Nokia's Maemo 5 — looks:
[
{
'message-token': '9de9546a-3400-4419-a505-3ea270cb834c',
'message-sender': 42,
'message-sent': 1210067943,
'message-received': 1210067947,
'message-type': 0, # = Channel_Text_Message_Type_Normal
'pending-message-id': 437,
},
{ 'content-type': 'text/x-vcard',
'content': [ 0x66, 0x69, 0x71, ...], # vCard data as an array of bytes
},
]
The first part of the message contains "headers" which refer to the entire message.
It is an error for a connection manager to put keys referring to the message as a whole in the second or subsequent Message_Part, but clients MUST recover from this error by ignoring these keys in the second and subsequent parts.
Instead of representing messages as aa{sv} where the first dictionary is special (a dictionary of headers), we could have used a signature like (a{sv}aa{sv}) to separate out the headers and the body parts.
However, this would make access to the messages more awkward.
In Python, the syntax for access to a header field would remain
message[0]['message-type'], but access to a body
field in the second body part would change from
message[2]['content'] to message[1][1]['content']. In GLib,
the message would change from being a
GPtrArray(GHashTable) to being a
GValueArray(GHashTable, GPtrArray(GHashTable)) which is rather
inconvenient to dereference.
Well-known keys for the message as a whole, and the corresponding value types, include:
An opaque, globally-unique identifier for the entire message. This MAY be treated as if it were a MIME Message-ID, e.g. for the mid: and cid: URI schemes. If omitted, there is no suitable token; the protocol-token key SHOULD be provided if the protocol identifies messages in some less unique way.
An opaque token for the entire message, with whatever uniqueness guarantee is provided by the underlying protocol. As described for the Protocol_Message_Token type, this token is not guaranteed to be unique between contacts, or even within the scope of a Channel.
In practice, in most protocols there is no token with the uniqueness guarantees demanded for message-token; the definition of message-token was inappropriate, but must now be preserved for the benefit of clients that rely on it, at least until Telepathy breaks backwards compatibility.
The message-token and protocol-token SHOULD NOT both be present; clients requiring an identifier with the semantics of the protocol-token SHOULD look for the message-token first, falling back to the protocol-token.
This is for compatibility with CMs older than the protocol-token key.
The second and subsequent parts contain the message's content, including plain text, formatted text and/or attached files.
It is an error for a connection manager to put keys referring to the message body in the first Message_Part; clients MUST recover from this error by ignoring these keys in first part.
In any group of parts with the same non-empty value for the "alternative" key (which represent alternative versions of the same content), more faithful versions of the intended message MUST come before less faithful versions (note that this order is the opposite of MIME "multipart/alternative" parts). Clients SHOULD display the first alternative that they understand.
Specifying the preference order means that if the underlying protocol doesn't support alternatives, the CM can safely delete everything apart from the first supported alternative when sending messages.
The order is the reverse of MIME because MIME's rationale for placing the "plainest" part first (legibility in pre-MIME UAs) does not apply to us, and placing the most preferred part first simplifies display (a client can iterate the message in order, display the first alternative that it understands, and skip displaying all subsequent parts with the same "alternative" key).
Clients SHOULD present all parts that are not redundant alternatives in the order they appear in this array, possibly excluding parts that are referenced by another displayed part. It is implementation-specific how the parts are presented to the user.
This allows CMs to assume that all parts are actually shown to the user, even if they are not explicitly referenced - we do not yet recommend formatted text, and there is no way for plain text to reference an attachment since it has no concept of markup or references. This also forces clients to do something sensible with messages that consist entirely of "attachments", with no "body" at all.
For instance, when displaying the above example, a client that understands the HTML part should display the JPEG image once, between the two lines "Here is a photo of my cat:" and "Isn't it cute?"; it may additionally present the image in some way for a second time, after "Isn't it cute?", or may choose not to.
A client that does not understand HTML, displaying the same message, should display the plain-text part, followed by the JPEG image.
Well-known keys for the second and subsequent parts, and the corresponding value types, include:
If present, this part of the message is an alternative for all other parts with the same value for "alternative". Clients SHOULD only display one of them (this is expected to be used for XHTML messages in a future version of this specification).
If omitted, this part is not an alternative for any other part.
Parts of a message MAY reference the group of alternatives as a whole (i.e. a reference to whichever of them is chosen) by treating this identifier as if it were the MIME Content-ID of a multipart/alternative part, and using the cid: URI scheme.
The MIME type of this part. See the documentation for ReceivedMessage for notes on the special status of "text/plain" parts.
Connection managers MUST NOT signal parts without a 'content-type' key; if a protocol provides no way to determine the MIME type, the connection manager is responsible for guessing it, but MAY fall back to "text/plain" for text and "application/octet-stream" for non-text.
Clients MUST ignore parts without a 'content-type' key, which are reserved for future expansion.
This part is a thumbnail. To represent an image together with its thumbnail in a single message, there should be one part for the full image followed by a part for the thumbnail (following the “more complete versions first” requirement), with the same 'alternative' value. For example:
[ ... ,
{ 'alternative': 'catphoto',
'content-type': 'image/jpeg',
'size': 150000,
'content': [0xFF, 0xD8, ... 0xFF 0xD9],
},
{ 'alternative': 'catphoto',
'content-type': 'image/jpeg'
'size': 1024,
'thumbnail': True,
'content': [0xFF, 0xD8, ... 0xFF 0xD9],
},
...
]
Delivery reports are also represented as messages, of type Channel_Text_Message_Type_Delivery_Report, with the Non_Text_Content flag in the Text interface.
Whenever a message of type Channel_Text_Message_Type_Delivery_Report is signalled for a delivery error report, Channel.Type.Text.SendError SHOULD also be emitted; whenever Channel.Type.Text.SendError is emitted by a channel which supports this interface, a message of type Channel_Text_Message_Type_Delivery_Report MUST also be emitted.
The corresponding message in the Messages interface MUST contain "headers" for the delivery report, as specified below, in its first Message_Part.
An identifier for the message to which this delivery report refers. MUST NOT be an empty string. Omitted if not available.
Clients may match this against the token produced by the SendMessage method and MessageSent signal. A status report with no token could match any sent message, and a sent message with an empty token could match any status report. If multiple sent messages match, clients SHOULD use some reasonable heuristic.
The message content, as defined by the Messages interface. Omitted if no content is available. Content MAY have been truncated, message parts MAY have been removed, and message parts MAY have had their content removed (i.e. the message part metadata is present, but the 'content' key is not).
Unlike in the Messages interface, content not visible in the value for this key cannot be retrieved by another means, so the connection manager SHOULD be more aggressive about including (possibly truncated) message content in the 'content' key.
The second and subsequent Message_Part dictionaries, if present, are a human-readable report from the IM service.
Clients MUST NOT attempt to send delivery reports using the SendMessage method in the Messages API, and connection managers MUST NOT allow this to be done. If support for sending delivery reports is later added, it will be part of this interface.
Some example delivery reports in a Python-like syntax (in which arrays are indicated by [a, b] and dictionaries by {k1: v1, k2: v2}) follow.
b9a991bd-8845-4d7f-a704-215186f43bb4 for an unknown
reason
[{
# header
'message-sender': 123,
'message-type': Channel_Text_Message_Type_Delivery_Report,
'delivery-status': Delivery_Status_Permanently_Failed,
'delivery-token': 'b9a991bd-8845-4d7f-a704-215186f43bb4',
}
# no body
]
[{ # header
'message-sender': 123,
'message-type': Channel_Text_Message_Type_Delivery_Report,
'delivery-status': Delivery_Status_Temporarily_Failed,
'delivery-error': Channel_Text_Send_Error_Offline,
'delivery-echo':
[{ # header of original message
'message-sender': 1,
'message-sent': 1210067943,
},
{ # body of original message
'content-type': 'text/plain',
'content': 'Hello, world!',
}]
],
# no body
]
b9a991bd-8845-4d7f-a704-215186f43bb4 to a contact
with handle 123, but that handle represents a contact who does not
actually exist
[{ # header
'message-sender': 123,
'message-type': Channel_Text_Message_Type_Delivery_Report,
'delivery-status': Delivery_Status_Permanently_Failed,
'delivery-error': Channel_Text_Send_Error_Invalid_Contact,
'delivery-token': 'b9a991bd-8845-4d7f-a704-215186f43bb4',
'delivery-echo':
[{ # header of original message
'message-sender': 1,
'message-sent': 1210067943,
},
{ # body of original message
'content-type': 'text/plain',
'content': 'Hello, world!',
}]
],
},
{ # message from server (alternative in English)
'alternative': '404',
'content-type': 'text/plain',
'lang': 'en',
'content': 'I have no contact with that name',
},
{ # message from server (alternative in German)
'alternative': '404'.
'content-type': 'text/plain',
'lang': 'de',
'content', 'Ich habe keinen Kontakt mit diesem Namen',
}
]
b9a991bd-8845-4d7f-a704-215186f43bb4
[{
# header
'message-sender': 123,
'message-type': Channel_Text_Message_Type_Delivery_Report,
'delivery-status': Delivery_Status_Delivered,
'delivery-token': 'b9a991bd-8845-4d7f-a704-215186f43bb4',
}
# no body
]
An opaque token used to identify messages in the underlying. protocol. As a special case, the empty string indicates that there is no particular identification for a message.
CM implementations SHOULD use an identifier expected to be unique, such as a UUID, if possible.
Some protocols can only track a limited number of messages in a small message-ID space (SMS messages are identified by a single byte), and some implementations send non-unique identifiers (some XMPP clients use very simple message IDs, such as an incrementing integer that resets to 1 at the beginning of each connection). As a result, clients MUST NOT assume that protocol tokens will not be re-used.
In particular, clients SHOULD use a heuristic to assign delivery reports to messages, such as matching on message content or timestamp (if available), or assuming that the delivery report refers to the most recent message with that ID.
Submit a message to the server for sending.
If this method returns successfully, the message has been submitted
to the server and the
This method MUST return before the MessageSent signal is emitted.
This means that the process sending the message is the first
to see the
If this method fails, message submission to the server has failed and no signal on this interface (or the Text interface) is emitted.
Provide a successful delivery report if possible, even if this is not the default for this protocol. Ignored if delivery reports are not possible on this protocol.
In some protocols, like XMPP, it is not conventional to request or send positive delivery notifications.
Delivery failure reports SHOULD always be sent, but if this flag is present, the connection manager MAY also try harder to obtain failed delivery reports or allow them to be matched to outgoing messages.
Signals that a message has been submitted for sending. This
MUST be emitted exactly once per emission of the
This signal allows a process that is not the caller of SendMessage to log sent messages. The double signal-emission provides compatibility with older clients. Clients supporting Messages should listen for Messages.MessageSent only (if the channel has the Messages interface) or Text.Sent only (otherwise).
The message content (see
If the connection manager can predict that the message will be altered during transmission, this argument SHOULD reflect what other contacts will receive, rather than being a copy of the argument to SendMessage (if the message is truncated, formatting or alternatives are dropped, etc., then the edited version SHOULD appear in this signal).
Flags affecting how the message was sent. The flags might be a subset of those passed to SendMessage if the caller requested unsupported flags.
The content of the requested parts. The keys in this mapping
are positions in the array of message parts; the values are
either of type 's' or 'ay' (UTF-8 text string, or byte array),
following the same rules as for the value of the 'content' key in
the
If the one of the requested part numbers was greater than zero but referred to a part that had no content (i.e. it had no 'content-type' key or no 'content' key), it is simply omitted from this mapping; this is not considered to be an error condition.
The status of a message as indicated by a delivery report.
If this enum is extended in future specifications, this should only be to add new, non-overlapping conditions (i.e. all failures should still be signalled as either Temporarily_Failed or Permanently_Failed). If additional detail is required (e.g. distinguishing between the various types of permanent failure) this will be done using additional keys in the Message_Part.