Clicking the screen-sharing button rapidly and repeatedly can result in a stream getting stuck

[SimonBrandner]

Steps to reproduce

1. Turn on and off screen-sharing rapidly

Outcome

What did you expect?

The stream not to get stuck

What happened instead?

The screen-sharing dialog will no longer appear and a stuck stream will always be screen-shared until the user rejoins the call

Operating system

Not relevant

Browser information

FF (but Edge and Chromium too probably)

URL for webapp

No response

Will you send logs?

No

[dbkr]

The problem here is that we dutifully removeTrack() on the screen sharing track when stopping a screen share, but this doesn't remove the sender. It looks like you can't remove senders, presumably because the senders are identified by their index in the SDP, so the SDP gets bigger and bigger and eventually no longer fits in a matrix message, at which point the offer fails to send.

We should keep a sender around for screen shares once we've done one and re-use it for subsequent screen shares.