STR (makes more sense for 2 monitor setups but I think it can be reproduced everywhere):

1. Play in Fullscreen PiP mode a video from youtube
2. Switch to a higher quality mode as the video plays
   The PiP window is affected and is no longer full screen (now covers only 3/4 of the screen) but still "thinks" it's in fullscreen mode (if you double click it you see how it goes back to the initial size as if existing full screen mode).

Tried on latest m-c central, OSX

Backed out changeset 50141dc32966 (Bug 1677080) for causing failures in browser_changePiPSrcInFullscreen.js CLOSED TREE

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&collapsedPushes=842382&selectedTaskRun=Z_zhBwT1TPqX1-Tt9gYB2g.0&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&classifiedState=classified&revision=50141dc329663dd6dfc084e19daf86fe749231e6

Failure log: https://treeherder.mozilla.org/logviewer?job_id=327290819&repo=autoland&lineNumber=2282
https://treeherder.mozilla.org/logviewer?job_id=327290577&repo=autoland&lineNumber=3502
https://treeherder.mozilla.org/logviewer?job_id=327290516&repo=autoland&lineNumber=4268

Backout: https://hg.mozilla.org/integration/autoland/rev/013cb10976bdc132df1b4f49b3d61d5118fcb7d5

There's a r+ patch which didn't land and no activity in this bug for 2 weeks.
:baumga91, could you have a look please?
For more information, please visit auto_nag documentation.

Latest Nightly 87.0a1 (2021-02-19), Win 10 64-bit, I have a laptop and an external monitor attached to it:

1. Open youtube.com and play in fullscreen PiP a video on the external monitor - image is fullscreen
2. Change video quality - Windows taskbar appears
3. Close PiP window and reopen it - the image will cover 3/4 of the screen. Double click on it will place it correctly on the screen.

This also happens if the PiP window is closed for the first video and the PiP window is opened for another video.

Tentatively unassigning this one in case someone wants to try driving it through.

This bug also affects single display setups. Here is how to reproduce it:

1. Start any Youtube video in high resolution
2. Paste this code in the console to change the resolution to low after 10 seconds:

setTimeout(function() {
    ytPlayer = document.getElementById("movie_player") || document.getElementsByClassName("html5-video-player")[0];
    ytPlayer.setPlaybackQualityRange('tiny');
}, 10000);

3. within 10 seconds after running the code above, have the video run in a full-screen PiP window

On Windows, the PiP window now has the same size as the full-screen window but shifted up to show the taskbar. The new window cannot be resized or moved and does not respond to doubleclicking. The only way to regain control is to close PiP.

Due to this bug, watching livestreams where the resolution changes frequently due to buffering is cumbersome.

Redirect needinfos that are pending on an inactive user to the triage owner.
:mconley, since the bug has high priority and recent activity, could you have a look please?

For more information, please visit auto_nag documentation.

Passing this needinfo to the right Niklas! :-)

Thanks Gijs.

I am still working on this bug

This is happening using Nightly 109.0a1 20221211092251 on Windows 11

STR:

1. Open a video on YouTube.
2. Add another video to the queue
3. Open the first video on PiP mode
4. Move the scrubber to almost the end (media.videocontrols.picture-in-picture.improved-video-controls.enabled pref enabled)
5. Double click to fullscreen
6. Wait for the next video start.

The video goes out of fullscreen mode and the Windows taskbar appears. Double click it and the video goes fullscreen again, another double click and the PiP fills the whole window, it gets almost fullscreen, and I have to resize it to be fit to use.

The video on PiP mode should remain playing on fullscreen in a queue. And should behave as expected when exit fullscreen.

https://hg.mozilla.org/mozilla-central/rev/202bf221326b

Reprooducible on a 2023-02-14 Nightly build on Windows 10.
Verified as fixed on Firefox 112.0b5(build ID: 20230321175953) and Nightly 113.0a1(build ID: 20230322211554) on Windows 10, macOS 12, Ubuntu 22.