Define DisplayMediaStreamConstraints.selfBrowserSurface

[eladalon1983]

Fixes #209.

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[jan-ivar]

I don't think we need this note, since this prose is largely explanatory. I think it's fine to use "tab" here as a shorthand, as long as normative prose below doesn't use it and sticks to defined terms only.

[eladalon1983]

That's fine by me. We can remove.

[jan-ivar]

I could be wrong, but this would be the first time the word "Tab" appears in a web API. I know this was already discussed in the issue, but I can't help thinking we're over-selecting here.

At a conceptual level, the user agent learns whether self-capture (hall of mirrors) is part of the application's use case(s) or not. This seems like valuable information to the user agent, at its most abstract.

It seems less relevant how the user agent ends up acting on this information: whether this applies only to tab-capture or whether it also applies to window capture of the browser window the document is in ... those are really good questions user agents should perhaps be left to figure out, which seems OK to me.

I also don't think it matters if user agents fall short of promises on this today, since this is a hint. E.g. I wouldn't expect browsers to ever exclude full-screen capture over this, but a user agent might take "exclude" as a clue it's OK to blur away the undesirable hall-of-mirrors effect for instance. This way the user agent doesn't need to worry it's stepping on apps that rely on self-capture. cc @youennf

So I'd suggest an iteration on @martinthomson's wording:

Suggested change

	CurrentTabPreferenceEnum currentTabPreference = "none";
	CurrentTabPreferenceEnum selfCapture = "no-preference";

[eladalon1983]

I'm OK with the s/none/no-preference replacement.
I don't want to accept the s/currentTabPreference/selfCapture suggestion, because this only refers to tabs, and that is intentional - we only got consensus over that in the interim meeting. (Also note how it's CurrentTabPreferenceEnum, btw.)

[jan-ivar]

(with chair-hat off)

I recall us having rough agreement (not consensus which would require a call on the list) on this being a "hint", which seems to leave this more as an indicator describing application preference, than an explicit control surface to enact certain specific behavior.

Yes I'm bikeshedding, and perhaps suggesting a bit of abstraction here that wasn't discussed before, but I don't read the last meeting as a final word on naming, and would love to hear from others. I think the question of whether to introduce the term "Tab" to the web platform seems orthogonal to discussion over behavior.

[eladalon1983]

I recall us having rough agreement (not consensus which would require a call on the list) on this being a "hint", which seems to leave this more as an indicator describing application preference, than an explicit control surface to enact certain specific behavior.

This has not changed. We're discussing what the hint will be called.

I think the question of whether to introduce the term "Tab" to the web platform seems orthogonal to discussion over behavior.

If you're not convinced that "tab" can be a convenient shorthand in this case, we can go with the following alternative, although I consider it inferior to "tab":

  SelfCapturePreference selfCaptureBrowser = "no-preference";

  enum SelfCapturePreference {
    "no-preference",
    "include",
    "exclude",
  };

This way:

1. We use the browser that everyone is already forced to know means "tab" in most relevant contexts.
2. We have not blocked the way for selfCaptureWindow to be introduced later, if the WG happens to be interested later.

--
But please see my note in the original PR. I think "tab" can be understood well as shorthand for "display surface of type 'browser'". My intention is that this would not formally introduce "tab" into the Web platform, but rather, serve as a localized convenience.

[eladalon1983]

Ping @jan-ivar; PTAL.

[eladalon1983]

Hi @jan-ivar, could you PTAL?

[youennf]

I would rename the property to slefBrowserSurface and remove no-preference.

[youennf]

two spaces

[youennf]

What we plan to do:

• rename the property to selfBrowserSurface
• remove no-preference
• remove the use of tab and use something like 'browser surface' in the PR, including CurrentTabPreferenceEnum.

[youennf]

Look good to me with the changes.
I think we should beef up the security section since we are now allowing the web page to fiddle with UA UI.

[eladalon1983]

Ping @jan-ivar and @youennf with a reminder to double-check the delta from what we agreed on and what I ended up editing and merging.