4.3 KiB
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Receipts
{{< changed-in v="1.4" >}} Added private read receipts.
This module adds in support for receipts. These receipts are a form of
acknowledgement of an event. This module defines the m.read receipt
for indicating that the user has read up to a given event, and m.read.private
to achieve the same purpose without any other user being aware. Primarily,
m.read.private is intended to clear notifications
without advertising read-up-to status to others.
Sending a receipt for each event can result in sending large amounts of traffic to a homeserver. To prevent this from becoming a problem, receipts are implemented using "up to" markers. This marker indicates that the acknowledgement applies to all events "up to and including" the event specified. For example, marking an event as "read" would indicate that the user had read all events up to the referenced event. See the Receiving notifications section for more information on how read receipts affect notification counts.
Events
Each user_id, receipt_type pair must be associated with only a
single event_id.
{{% event event="m.receipt" %}}
Client behaviour
In /sync, receipts are listed under the ephemeral array of events
for a given room. New receipts that come down the event streams are
deltas which update existing mappings. Clients should replace older
receipt acknowledgements based on user_id and receipt_type pairs.
For example:
Client receives m.receipt:
user = @alice:example.com
receipt_type = m.read
event_id = $aaa:example.com
Client receives another m.receipt:
user = @alice:example.com
receipt_type = m.read
event_id = $bbb:example.com
The client should replace the older acknowledgement for $aaa:example.com with
this one for $bbb:example.com
Clients should send read receipts when there is some certainty that the event in question has been displayed to the user. Simply receiving an event does not provide enough certainty that the user has seen the event. The user SHOULD need to take some action such as viewing the room that the event was sent to or dismissing a notification in order for the event to count as "read". Clients SHOULD NOT send read receipts for events sent by their own user.
A client can update the markers for its user by interacting with the following HTTP APIs.
{{% http-api spec="client-server" api="receipts" %}}
Private read receipts
{{% added-in v="1.4" %}}
Some users would like to mark a room as read, clearing their notification counts,
but not give away the fact that they've read a particular message yet. To
achieve this, clients can send m.read.private receipts instead of m.read
to do exactly that: clear notifications and not broadcast the receipt to
other users.
Servers MUST NOT send the m.read.private receipt to any other user than the
one which originally sent it.
Between m.read and m.read.private, the receipt which is more "ahead" or
"recent" is used when determining the highest read-up-to mark. See the
notifications section for more information on
how this affects notification counts.
If a client sends an m.read receipt which is "behind" the m.read.private
receipt, other users will see that change happen but the sending user will
not have their notification counts rewound to that point in time. While
uncommon, it is considered valid to have an m.read (public) receipt lag
several messages behind the m.read.private receipt, for example.
Server behaviour
For efficiency, receipts SHOULD be batched into one event per room before delivering them to clients.
Some receipts are sent across federation as EDUs with type m.receipt. The
format of the EDUs are:
{
<room_id>: {
<receipt_type>: {
<user_id>: { <content> }
},
...
},
...
}
These are always sent as deltas to previously sent receipts. Currently
only a single <receipt_type> should be used: m.read. m.read.private
MUST NOT appear in this federated m.receipt EDU.
Security considerations
As receipts are sent outside the context of the event graph, there are
no integrity checks performed on the contents of m.receipt events.