3961-sliding-sync-typing.md

MSC3961: Sliding Sync Extension: Typing Notifications

This MSC is an extension to MSC3575 which includes support for typing notifications in the /sync response.

Proposal

MSC3575 does not include support for typing notifications. This extension will add support for it.

The proposal is to introduce a new extension called typing. It processes the core extension arguments enabled, rooms and lists, but defines no arguments of its own.

{
    "enabled": true, // sticky
    "lists": ["rooms", "dms"], // sticky
    "rooms": ["!abcd:example.com"] // sticky
}

If enabled is true, then the sliding sync response MAY include the following response fields in the typing extension response:

{
    "rooms": {
        "!foo:bar": {
            // m.typing EDU
        },
        "!foo2:bar": {
            // m.typing EDU
        }
    }
}

If a lists or rooms argument is given to the extension, the typing extension response SHOULD only include rooms belonging at least one of the sliding windows in lists, or rooms whose IDs are in rooms. See also MSC3575's "Extensions" section.

The m.typing event in this response is the same event that would appear in the array rooms.join["!foo:bar"].ephemeral.events under a traditional "v2" /sync.

On an initial sync, typing notifications MUST only be sent for rooms returned in the sliding sync response. When live streaming, typing notifications MUST be sent as the server receives typing updates. Rooms which initially appear (initial: true) due to direct subscriptions or rooms moving into the sliding window MUST have typing notification data added if there are typing users, else it can be omitted from the typing response.

Potential issues

No issues identified.

Alternatives

This extension could be bundled into the core MSC3575, but this would force all clients to receive this data. In practice clients can function extremely well without the need for typing notifications, so forcing all clients to receive this data feels like the wrong design.

Security considerations

No additional security considerations beyond what the current /sync implementation provides.

Unstable prefix

No unstable prefix as Sliding Sync is still in review. To enable this extension, just add this to your request JSON:

{
    "extensions": {
        "typing": {
            "enabled": true
        }
    }
}

Dependencies

This MSC builds on MSC3575, which at the time of writing has not yet been accepted into the spec.