1397978 - Delay enumerateDevices() success until page has focus

Status: RESOLVED DUPLICATE of bug 1732410

(Core :: WebRTC: Audio/Video, enhancement, P2)

Description

[Jan-Ivar Bruaroey [:jib] (needinfo? me)]

To be spec compliant we must implement the [[storedDeviceList]] requirement in enumerateDevices [1] which prevents JS from polling on enumerateDevices to circumvent devicechange event restrictions.

Basically, subsequent calls to enumerateDevices must return the same (cached) result, until a devicechange event has been fired on navigator.mediaDevices.

We should not land this before bug 1397977, to prevent hampering users.

[1] https://w3c.github.io/mediacapture-main/getusermedia.html#dom-mediadevices-enumeratedevices()

Comment 1

[Bulk Bug Changes for mreavy's org]

Mass change P2->P3 to align with new Mozilla triage process.

Comment 2

[Jan-Ivar Bruaroey [:jib] (needinfo? me)]

To be spec compliant we must implement the [[storedDeviceList]] requirement in enumerateDevices

The [[storedDeviceList]] has been revealed to be insufficient to guard against background access. The new plan is to postpone the promise from enumerateDevices() until the page receives focus, similar to what we do for getUserMedia() today.

[1] https://github.com/w3c/mediacapture-main/issues/561#issuecomment-457713003

Comment 3

[Jan-Ivar Bruaroey [:jib] (needinfo? me)]

Some more context on this: getUserMedia has the following language today:

• "Run the following steps in parallel:
  • The user agent MAY wait to proceed to the next step until the current settings object's responsible document is fully active and has focus. "

The plan would be to add similar language to enumerateDevices() to solve this issue.

Comment 4

[Jan-Ivar Bruaroey [:jib] (needinfo? me)]

The new spec language mentioned in comment 3 is now available in enumerateDevices:

• The User Agent MUST wait to proceed to the next step until the device information can be exposed check returns true.
  The User Agent MAY wait to proceed to the next step until document is fully active and has focus.

I'm leaning toward implementing the latter.