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ReStructuredText
452 lines
15 KiB
ReStructuredText
Events
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======
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All communication in Matrix is expressed in the form of data objects called
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Events. These are the fundamental building blocks common to the client-server,
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server-server and application-service APIs, and are described below.
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Common event fields
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-------------------
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All events MUST have the following fields:
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``event_id``
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Type:
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String.
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Description:
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Represents the globally unique ID for this event.
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``type``
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Type:
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String.
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Description:
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Contains the event type, e.g. ``m.room.message``
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``content``
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Type:
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JSON Object.
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Description:
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Contains the content of the event. When interacting with the REST API, this is the HTTP body.
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``room_id``
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Type:
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String.
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Description:
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Contains the ID of the room associated with this event.
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``user_id``
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Type:
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String.
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Description:
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Contains the fully-qualified ID of the user who *sent* this event.
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State events have the additional fields:
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``state_key``
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Type:
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String.
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Description:
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Contains the state key for this state event. If there is no state key for this state event, this
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will be an empty string. The presence of ``state_key`` makes this event a state event.
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``required_power_level``
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Type:
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Integer.
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Description:
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Contains the minimum power level a user must have before they can update this event.
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``prev_content``
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Type:
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JSON Object.
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Description:
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Optional. Contains the previous ``content`` for this event. If there is no previous content, this
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key will be missing.
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.. TODO-spec
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How do "age" and "ts" fit in to all this? Which do we expose?
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Room Events
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-----------
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.. NOTE::
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This section is a work in progress.
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This specification outlines several standard event types, all of which are
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prefixed with ``m.``
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{{room_events}}
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m.room.message msgtypes
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~~~~~~~~~~~~~~~~~~~~~~~
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.. TODO-spec
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How a client should handle unknown message types.
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.. TODO-spec
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We've forgotten m.file...
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.. TODO-spec
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It's really confusing that the m. prefix is used both for event types and
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for msgtypes. We should namespace them differently somehow.
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Each ``m.room.message`` MUST have a ``msgtype`` key which identifies the type
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of message being sent. Each type has their own required and optional keys, as
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outlined below:
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``m.text``
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Required keys:
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- ``body`` : "string" - The body of the message.
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Optional keys:
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None.
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Example:
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``{ "msgtype": "m.text", "body": "I am a fish" }``
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``m.emote``
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Required keys:
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- ``body`` : "string" - The emote action to perform.
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Optional keys:
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None.
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Example:
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``{ "msgtype": "m.emote", "body": "tries to come up with a witty explanation" }``
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``m.notice``
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Required keys:
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- ``body`` : "string" - The body of the message.
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Optional keys:
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None.
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Example:
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``{ "msgype": "m.notice", "body": "some kind of automated announcement" }``
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A ``m.notice`` message should be considered similar to a plain ``m.text``
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message except that clients should visually distinguish it in some way. It is
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intended to be used by automated clients, such as bots, bridges, and other
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entities, rather than humans. Additionally, such automated agents which watch
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a room for messages and respond to them ought to ignore ``m.notice`` messages.
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This helps to prevent infinite-loop situations where two automated clients
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continuously exchange messages, as each responds to the other.
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``m.image``
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Required keys:
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- ``url`` : "string" - The URL to the image.
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Optional keys:
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- ``info`` : "string" - info : JSON object (ImageInfo) - The image info for
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image referred to in ``url``.
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- ``thumbnail_url`` : "string" - The URL to the thumbnail.
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- ``thumbnail_info`` : JSON object (ImageInfo) - The image info for the
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image referred to in ``thumbnail_url``.
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- ``body`` : "string" - The alt text of the image, or some kind of content
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description for accessibility e.g. "image attachment".
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ImageInfo:
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Information about an image::
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{
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"size" : integer (size of image in bytes),
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"w" : integer (width of image in pixels),
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"h" : integer (height of image in pixels),
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"mimetype" : "string (e.g. image/jpeg)",
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}
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``m.audio``
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Required keys:
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- ``url`` : "string" - The URL to the audio.
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Optional keys:
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- ``info`` : JSON object (AudioInfo) - The audio info for the audio
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referred to in ``url``.
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- ``body`` : "string" - A description of the audio e.g. "Bee Gees - Stayin'
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Alive", or some kind of content description for accessibility e.g.
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"audio attachment".
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AudioInfo:
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Information about a piece of audio::
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{
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"mimetype" : "string (e.g. audio/aac)",
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"size" : integer (size of audio in bytes),
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"duration" : integer (duration of audio in milliseconds),
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}
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``m.video``
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Required keys:
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- ``url`` : "string" - The URL to the video.
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Optional keys:
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- ``info`` : JSON object (VideoInfo) - The video info for the video
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referred to in ``url``.
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- ``body`` : "string" - A description of the video e.g. "Gangnam style", or
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some kind of content description for accessibility e.g. "video
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attachment".
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VideoInfo:
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Information about a video::
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{
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"mimetype" : "string (e.g. video/mp4)",
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"size" : integer (size of video in bytes),
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"duration" : integer (duration of video in milliseconds),
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"w" : integer (width of video in pixels),
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"h" : integer (height of video in pixels),
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"thumbnail_url" : "string (URL to image)",
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"thumbanil_info" : JSON object (ImageInfo)
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}
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``m.location``
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Required keys:
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- ``geo_uri`` : "string" - The geo URI representing the location.
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Optional keys:
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- ``thumbnail_url`` : "string" - The URL to a thumnail of the location
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being represented.
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- ``thumbnail_info`` : JSON object (ImageInfo) - The image info for the
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image referred to in ``thumbnail_url``.
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- ``body`` : "string" - A description of the location e.g. "Big Ben,
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London, UK", or some kind of content description for accessibility e.g.
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"location attachment".
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``m.file``
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Required keys:
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- ``url`` : "string" - The URL for the file
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- ``filename`` : "string" - The original filename of the uploaded file
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Optional keys:
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- ``info`` : JSON object (FileInfo) - The info for the file
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referred to in ``url``.
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- ``thumbnail_url`` : "string" - The URL to a thumnail of the location
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being represented.
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- ``thumbnail_info`` : JSON object (ImageInfo) - The image info for the
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image referred to in ``thumbnail_url``.
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- ``body`` : "string" - A human-readable description of the file for
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backwards compatibility. This is recommended to be the filename of the
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original upload.
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FileInfo:
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Information about a file::
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{
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"size" : integer (size of file in bytes),
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"mimetype" : "string (e.g. image/jpeg)",
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}
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.. TODO-spec
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Make the definitions "inherit" from FileInfo where necessary...
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Presence Events
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~~~~~~~~~~~~~~~
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``m.presence``
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Summary:
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Informs you of a user's presence state changes.
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Type:
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Presence event
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JSON format::
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{
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"displayname": "utf-8 string",
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"avatar_url": "url",
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"presence": "enum [ online|unavailable|offline|free_for_chat|hidden ]",
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"last_active_ago": "milliseconds"
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}
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Example::
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{
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"displayname": "Matthew",
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"avatar_url": "mxc://domain/id",
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"presence": "online",
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"last_active_ago": 10000
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}
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Description:
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Each user has the concept of presence information. This encodes the
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"availability" of that user, suitable for display on other user's clients.
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This is transmitted as an ``m.presence`` event and is one of the few events
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which are sent *outside the context of a room*. The basic piece of presence
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information is represented by the ``presence`` key, which is an enum of one
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of the following:
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- ``online`` : The default state when the user is connected to an event
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stream.
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- ``unavailable`` : The user is not reachable at this time.
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- ``offline`` : The user is not connected to an event stream.
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- ``free_for_chat`` : The user is generally willing to receive messages
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moreso than default.
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- ``hidden`` : Behaves as offline, but allows the user to see the client
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state anyway and generally interact with client features. (Not yet
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implemented in synapse).
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In addition, the server maintains a timestamp of the last time it saw a
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pro-active event from the user; either sending a message to a room, or
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changing presence state from a lower to a higher level of availability
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(thus: changing state from ``unavailable`` to ``online`` counts as a
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proactive event, whereas in the other direction it will not). This timestamp
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is presented via a key called ``last_active_ago``, which gives the relative
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number of milliseconds since the message is generated/emitted that the user
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was last seen active.
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Events on Change of Profile Information
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Because the profile displayname and avatar information are likely to be used in
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many places of a client's display, changes to these fields cause an automatic
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propagation event to occur, informing likely-interested parties of the new
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values. This change is conveyed using two separate mechanisms:
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- a ``m.room.member`` event is sent to every room the user is a member of,
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to update the ``displayname`` and ``avatar_url``.
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- a ``m.presence`` presence status update is sent, again containing the new values of the
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``displayname`` and ``avatar_url`` keys, in addition to the required
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``presence`` key containing the current presence state of the user.
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Both of these should be done automatically by the home server when a user
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successfully changes their displayname or avatar URL fields.
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Additionally, when home servers emit room membership events for their own
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users, they should include the displayname and avatar URL fields in these
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events so that clients already have these details to hand, and do not have to
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perform extra roundtrips to query it.
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Voice over IP
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-------------
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Matrix can also be used to set up VoIP calls. This is part of the core
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specification, although is at a relatively early stage. Voice (and video) over
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Matrix is built on the WebRTC 1.0 standard.
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Call events are sent to a room, like any other event. This means that clients
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must only send call events to rooms with exactly two participants as currently
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the WebRTC standard is based around two-party communication.
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Events
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~~~~~~
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``m.call.invite``
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This event is sent by the caller when they wish to establish a call.
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Required keys:
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- ``call_id`` : "string" - A unique identifier for the call
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- ``offer`` : "offer object" - The session description
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- ``version`` : "integer" - The version of the VoIP specification this
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message adheres to. This specification is version 0.
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- ``lifetime`` : "integer" - The time in milliseconds that the invite is
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valid for. Once the invite age exceeds this value, clients should discard
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it. They should also no longer show the call as awaiting an answer in the
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UI.
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Optional keys:
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None.
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Example::
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{
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"version" : 0,
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"call_id": "12345",
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"offer": {
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"type" : "offer",
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"sdp" : "v=0\r\no=- 6584580628695956864 2 IN IP4 127.0.0.1[...]"
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}
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}
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``Offer Object``
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Required keys:
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- ``type`` : "string" - The type of session description, in this case
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'offer'
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- ``sdp`` : "string" - The SDP text of the session description
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``m.call.candidates``
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This event is sent by callers after sending an invite and by the callee after
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answering. Its purpose is to give the other party additional ICE candidates to
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try using to communicate.
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Required keys:
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- ``call_id`` : "string" - The ID of the call this event relates to
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- ``version`` : "integer" - The version of the VoIP specification this
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messages adheres to. his specification is version 0.
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- ``candidates`` : "array of candidate objects" - Array of object
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describing the candidates.
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``Candidate Object``
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Required Keys:
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- ``sdpMid`` : "string" - The SDP media type this candidate is intended
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for.
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- ``sdpMLineIndex`` : "integer" - The index of the SDP 'm' line this
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candidate is intended for
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- ``candidate`` : "string" - The SDP 'a' line of the candidate
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``m.call.answer``
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Required keys:
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- ``call_id`` : "string" - The ID of the call this event relates to
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- ``version`` : "integer" - The version of the VoIP specification this
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messages
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- ``answer`` : "answer object" - Object giving the SDP answer
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``Answer Object``
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Required keys:
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- ``type`` : "string" - The type of session description. 'answer' in this
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case.
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- ``sdp`` : "string" - The SDP text of the session description
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``m.call.hangup``
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Sent by either party to signal their termination of the call. This can be sent
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either once the call has has been established or before to abort the call.
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Required keys:
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- ``call_id`` : "string" - The ID of the call this event relates to
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- ``version`` : "integer" - The version of the VoIP specification this
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messages
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Message Exchange
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~~~~~~~~~~~~~~~~
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A call is set up with messages exchanged as follows:
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::
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Caller Callee
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m.call.invite ----------->
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m.call.candidate -------->
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[more candidates events]
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User answers call
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<------ m.call.answer
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[...]
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<------ m.call.hangup
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Or a rejected call:
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::
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Caller Callee
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m.call.invite ----------->
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m.call.candidate -------->
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[more candidates events]
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User rejects call
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<------- m.call.hangup
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Calls are negotiated according to the WebRTC specification.
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Glare
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~~~~~
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This specification aims to address the problem of two users calling each other
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at roughly the same time and their invites crossing on the wire. It is a far
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better experience for the users if their calls are connected if it is clear
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that their intention is to set up a call with one another.
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In Matrix, calls are to rooms rather than users (even if those rooms may only
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contain one other user) so we consider calls which are to the same room.
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The rules for dealing with such a situation are as follows:
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- If an invite to a room is received whilst the client is preparing to send an
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invite to the same room, the client should cancel its outgoing call and
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instead automatically accept the incoming call on behalf of the user.
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- If an invite to a room is received after the client has sent an invite to
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the same room and is waiting for a response, the client should perform a
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lexicographical comparison of the call IDs of the two calls and use the
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lesser of the two calls, aborting the greater. If the incoming call is the
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lesser, the client should accept this call on behalf of the user.
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The call setup should appear seamless to the user as if they had simply placed
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a call and the other party had accepted. Thusly, any media stream that had been
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setup for use on a call should be transferred and used for the call that
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replaces it.
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