Intent to Experiment: Captured Surface Control

[Elad Alon]

Contact emails

elad...@chromium.org

Explainer

https://github.com/screen-share/captured-surface-control/blob/main/README.md

Specification

TBD, but will be hosted on https://screen-share.github.io/captured-surface-control once produced.

For the time being, please refer to the explainer, which has a detailed description of the API as well as sample use of it.

A demo is also available. (Some of the functionality is still being landed in Chromium atm.)

Design docs

https://docs.google.com/document/d/10UojDvTJ6ojBEOP7cgBIIaE7WZEfes_Qv1eN3A2A0nM/edit?usp=sharing

Summary

Web API that allows Web applications to: 1. Produce wheel events in a captured tab or window. 2. Read/write the zoom level of a captured tab.

Blink component

Blink>GetDisplayMedia

TAG review

Not started.

TAG review status

Pending. We expect that developer feedback during the origin trial might lead to non-trivial changes to the API shape, and would therefore like to hold off on TAG review until after those changes.

Risks

Interoperability and Compatibility

Gecko: No signal

WebKit: No signal

Web developers: No signals

Other signals:

Security

https://github.com/screen-share/captured-surface-control?tab=readme-ov-file#security-and-privacy-concerns

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?

Goals for experimentation

Validate the API shape with Web developers and gather feedback on such topics as:

• Usefulness of the API as currently implemented.
• Usefulness of allowing the API to be invoked while the capturing page is not focused (currently, the capturing page must be focused).
• Possible pain points with scrolling as currently specified and implemented. (Is more fine-grained control necessary? Is scrolling too janky as currently specified and implemented?)

Ongoing technical constraints

None

Debuggability

N/A

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

No (Supported on all desktop platforms. Screen-sharing is not currently supported on mobile platforms.)

Is this feature fully tested by web-platform-tests?

No (but we're working on it)

Flag name on chrome://flags

captured-surface-control

Finch feature name

CapturedDisplaySurface

Requires code in //chrome?

False

Tracking bug

https://bugs.chromium.org/p/chromium/issues/detail?id=1466247

Launch bug

https://launch.corp.google.com/launch/4268170

Estimated milestones

OriginTrial desktop last	127
OriginTrial desktop first	122
DevTrial on desktop	122

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5092615678066688

Links to previous Intent discussions

Intent to prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAMO6jDPSgR3kX39drHd9t-JvTKBk%2B7Dg03O6dvowzw-LjQ__1A%40mail.gmail.com

This intent message was generated by Chrome Platform Status.

[Elad Alon]

A quick clarification, btw, that we have a partner in mind that's eager to start origin trial as soon as m122.

We also heard interest from other parties during Screen Capture CG meetings.

[Chris Harrelson]

LGTM to experiment M122 - M127

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[Mike Taylor]

LGTM to experiment from M122 to M127 inclusive.

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[Mike Taylor]

Oops, missed Chris' email on this. But you're double approved now. :)

[Elad Alon]

Hello Blink owners,

We are asking that the OT period on this experiment be shifted, and instead of the originally requested period of m122-m127 (inclusive), we consider it retroactively as m124-m129 (inclusive).

As of the time of writing, there has only ever been one active OT participant (Meet), and they only started widespread use of the feature in m124. Further, the feature was not fully implemented until m124. (The initial target of m122 was set based on timelines that did not materialize, both in terms of the feature’s implementation and of participants’ implementation.)

With respect to standardization:

When this API was first presented to Web developers in the Screen Capture CG, we heard a lot of support for it. Since then, we prioritized implementation and validation of the API with partners. Now that we have the thumbs-up on implementation from partners, we are prioritizing standardization. An initial outreach to Mozilla and Apple during the WebRTC WG editors meeting started out positively, and I am looking forward to presenting this to a wider audience during the May interim meeting of the WebRTC WG. The prospects on achieving consensus before m129 runs its course appear good.

Thanks,

Elad

[Chris Harrelson]

Sounds fine to me - consider it renumbered from 124.

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/7e5dec53-c751-4513-84da-95f6fd55be68n%40chromium.org.

[Elad Alon]

Thank you!

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAOMQ%2Bw-DF_BCtdwiaYqrXsan3YNBfT2pAeboT0f1F9wmViPPWQ%40mail.gmail.com.