User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:56.0) Gecko/20100101 Firefox/56.0

Steps to reproduce:

Open any site that has a PiP-able video
Open the popout
Double click somewhere on the popou

Actual results:

Video stays playing, doesn't go fullscreen

Expected results:

Video should stay playing, but go to fullscreen view

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=b5d436985831449e4f160b10abc362d937a6486c&tochange=969b3828a301038c57540d8bffb51539132d393c

Backed out changeset 5deeb2644977 (bug 1607882) for Browser-chrome failures in pictureinpicture/tests/browser_dblclickFullscreen.js. CLOSED TREE

Log:
https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=292566947&repo=autoland&lineNumber=16078

Push with failures:
https://treeherder.mozilla.org/#/jobs?repo=autoland&group_state=expanded&revision=5deeb2644977ddf4ddb7a80d68f9181fdab414ce

Backout:
https://hg.mozilla.org/integration/autoland/rev/048ea19b77b3d6277b84cf0857cb486ce2a078f5

The problem appears to be that we can't fullscreen a window that has alwaysontop set on it on Linux GTK.

Hey Martin, would it make sense to stash the initial alwaysontop state, then set gtk_window_set_keep_above to FALSE before attempting to go to fullscreen, and then revert to the original alwaysontop state once fullscreen exits? Or is there a better way to do this?

(In reply to Mike Conley (:mconley) (:⚙️) from comment #6)

The problem appears to be that we can't fullscreen a window that has alwaysontop set on it on Linux GTK.

Hey Martin, would it make sense to stash the initial alwaysontop state, then set gtk_window_set_keep_above to FALSE before attempting to go to fullscreen, and then revert to the original alwaysontop state once fullscreen exits? Or is there a better way to do this?

Yes, that makes sense.

https://hg.mozilla.org/mozilla-central/rev/24ad9eab9212
https://hg.mozilla.org/mozilla-central/rev/cb979a1c473f

Mike, maybe worth a mention in nightly release notes?

(In reply to Pascal Chevrel:pascalc from comment #11)

Mike, maybe worth a mention in nightly release notes?

Yes, for sure! Should I write one, or what's the procedure for that?

(In reply to Mike Conley (:mconley) (:⚙️) from comment #12)

(In reply to Pascal Chevrel:pascalc from comment #11)

Mike, maybe worth a mention in nightly release notes?

Yes, for sure! Should I write one, or what's the procedure for that?

Yes write one via the release notes form in Bugzilla https://wiki.mozilla.org/Release_Management/Release_Notes#How_to_nominate_a_bug_for_release_notes_addition.3F

Release Note Request (optional, but appreciated)
[Why is this notable]:

Gives users an often-requested enhancement to the Picture-in-Picture feature on desktop.

[Affects Firefox for Android]:

No.

[Suggested wording]:

Double-clicking on the Picture-in-Picture player window now puts it in fullscreen mode.

[Links (documentation, blog post, etc)]:

https://support.mozilla.org/en-US/kb/about-picture-picture-firefox

Thanks, note added to 76 nightly release notes.

Confirmed issue with 74.0a1 (2020-01-08) on Windows 10.
Fix verified with 76.0b6 on Windows 10, macOS 10.15.3, Ubuntu 18.04.

Hi Mike! QA is thinking about conducting a final sanity check for this fix since it's in a user-facing area.

Apart from our regular picture-in-picture regression tests, is there anything in particular that you think we should focus on during our second pass?

(In reply to Andrei Vaida [:avaida] from comment #17)

Apart from our regular picture-in-picture regression tests, is there anything in particular that you think we should focus on during our second pass?

Hi Andrei,

No, I can't think of anything extra to cover, beyond verifying the bugs that were fixed.