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Re: [mediacapture-region] What makes CropTarget special to require an asynchronous creation? (#17)

From: youennf via GitHub <sysbot+gh@w3.org>
Date: Fri, 11 Mar 2022 08:53:05 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-1064903263-1646988784-sysbot+gh@w3.org>
> I believe I have explained why we have implemented things this way in Chrome. This is a real issue.

You explained a real issue, that I would classify as an optimization problem (though at some point you alluded to security concerns as well). Is that correct?

The argument is that the same optimization issue exists for already deployed APIs, and was solved without making use of promises. If we do not want to follow this preexisting pattern, we need a clear justification.

To move forward, let's try with more narrowly focused questions:
- Do you think that other existing web APIs enumerated in this thread have the same issue? Or do you think this is new problem specific to region?
-  If it is a new problem, can you detail what exactly is new?
- If it is not a problem specific to region, what makes you think the solutions used for implementing those APIs are not good enough for region?

As a recap, here are some APIs that I think face the same issue:
- Create a MessageChannel and transfer one of its MessagePort synchronously after creation. The transferred port needs to be able to locate in an optimal manner where is living its related channel port.
- Create a MediaStreamTrack from a canvas and transfer it synchronously after creation. The transferred track needs to be able to locate in an optimal manner where is living the canvas element.
- Create a RTCDataChannel from a RTCPeerConnection and transfer it synchronously after creation. The transferred data channel needs to be able to locate in an optimal manner where is living the peer connection.

> I believe that when the time comes for Safari and Firefox to implement this, they'll find it equally problematic.

I implemented in WebKit some of the APIs that I think are facing the issue you are describing.
For that purpose, existing techniques were reused so that we do not introducing delay in creation of the objects/delay in transferring the objects/delay in the object algorithms/race conditions.

Answering the above questions might help figuring out which problems I might be overlooking. 

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