Calls the way the web client and Element Call do them, with the same
events, so the three can share a call. The famedly SDK's own group calls
use com.famedly.call.member events, which the others don't read, so this
is written against the matrix-js-sdk wire format instead (lib/matrix/
calls.dart):
- Membership: org.matrix.msc3401.call.member state, key
_@user:server_DEVICE_m.call, with the legacy session fields the js-sdk
sends (application m.call, call_id "", membershipID, expires,
focus_active, foci_preferred). An empty delayed copy (MSC4140) is
scheduled first and pushed back every 5 s; leaving sends the empty
state and cancels it.
- Media: a LiveKit token from the JWT service (the call's, else the
homeserver's rtc/transports or .well-known rtc_foci) for an OpenID
token; livekit_client connects.
- Encrypted rooms: a random 16-byte key per device, sent to every other
device in the call over encrypted to-device
io.element.call.encryption_keys, keys from others applied per LiveKit
identity (@user:server:DEVICE); per-participant keys, no ratcheting,
HKDF, like the web client's livekit-client.
- Ringing: a call started in a room of two sends a ring notification
(MSC4075); the other side gets an incoming-call card and an insistent
ringtone notification (full screen on a locked phone), declines with
MSC4310 or answers by joining. The caller gives up after a minute or on
a decline.
- UI: voice and video buttons in the room header, a call screen (the
other person large and you in the corner, or a grid; mute, camera, flip,
leave), a Join banner and a room-list marker for calls going on.
Not tested end to end yet: it needs a LiveKit SFU and JWT service.
README: replies, reactions, threads, spaces, QR verification, sliding
sync and calls.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
