Receive-side mesh state machine (the bit that decides which peer gets
which tile) was buried inside an anonymous pc.ontrack callback inside
sfuSubscribe(). Extracted into a named top-level function
handleRemoteSfuTrack so tests can drive it directly with synthetic
RTCTrackEvents — no real RTCPeerConnection, no real SFU.
test/multi-peer-mesh.test.js pins fox's stated invariant:
'whatever one device shares all should see, and when unshared none
should see.'
Eight scenarios across 2-3 fake browser sandboxes, each holding the
shipped handleRemoteSfuTrack + renderVideoTile + removeVideoTile +
watchVideoTrackForRemoval + the maps they own:
- one peer publishes camera -> every other peer ends with that pubHex
in cameraStreams + a tile entry
- one peer unshares (track ended) -> every other peer drops that pubHex
- one peer unshares mid-flow (mute past window) -> drops correctly
- hiccup supplant (same pubkey, new track) -> tile preserved AND
pointed at the new stream object (this is the MSID-supplant fix from
d5e9e4e — fresh MediaStream per track means the video element binds
to the new RTP cleanly)
- hiccup supplant + the OLD track's stream-identity guard prevents the
NEW tile from being reaped
- supplant + sustained mute past window on the NEW track -> reaped
correctly
- echo guard: a peer's own publish never enters their own cameraStreams
- three publishers fan-out: A B C all publish, every peer ends with
exactly the other two
Wired into Makefile as test-mesh + added to test-all. Pure Node, no
browser or proxy server needed. Will catch the regressions where one
peer's publish/unpublish silently desyncs another peer's view.
