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Re: [mediacapture-screen-share] What is the purpose of MediaTrackCapabilities displaySurface? (#250)

From: François Beaufort via GitHub <sysbot+gh@w3.org>
Date: Wed, 26 Oct 2022 08:09:36 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-1291656582-1666771774-sysbot+gh@w3.org>
Thanks for the feedback folks!

> Its purpose is to comply with the constrainable pattern, which says all constrainable properties are exposed as capabilities, settings and constraints. It has no utility other than that, that I'm aware of.

You're right: [`deviceId`](https://w3c.github.io/mediacapture-main/#dfn-deviceid), [`groupId`](https://w3c.github.io/mediacapture-main/#dfn-groupid), and [`torch`](https://w3c.github.io/mediacapture-image/#dom-mediatrackcapabilities-torch) are constant constrainable properties.

> A better question might be: which members would you expect to find in `videoTrack.getCapabilities()`?

My naive thoughts were that `getCapabilities()` would return capabilities that allow users to make changes to the constrainable properties via `applyConstraints()`. In other words, that they would be either `max/min` ranges (e.g. `<input type="range"`) or sequences of choices (e.g. `<select>`, `<input type="radio">`).

It looks like I'm wrong according to the spec though.

FYI I've created https://beaufortfrancois.github.io/sandbox/image-capture/playground.html long time ago to let users play with all properties in a generic way. (works best on mobile)


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