Note

• When the user loads a video, lunches in PiP and clicks the "Back" button, he will notice that a blank PiP window will remain on screen, always on top. If another video is loaded and played, it will be played in the PiP window, but this still feels like unintended functionality.

Affected versions

• Nightly v99.0a1
• Release v97.0.1
• ESR v91.6.0esr

Affected platforms

• all

Steps to reproduce

1. Launch browser
2. Load a video
3. Click the PiP button
4. Click the "Back" button

Expected result

• The PiP window should close.

Actual result

• A blank PiP window will remain on screen, always on top.

Regression range

• Not a recent regression.

Additional notes
*

I am able to reproduce this behaviour on youtube with the steps below:

1. within youtube.com, search for a video
2. you should see search results. Click on a video
3. enable picture in picture for the video once it loads
4. press the back button
5. you should see the search results page again, but the pip window is blank and still open until another video is clicked on/loaded

I believe this behaviour only occurs when a pagehide (searchfox) event is not detected, yet the video is unloaded (see attached screenshot). Otherwise, pip should close normally.

I am also able to reproduce this on dailymotion:

1. navigate to dailymotion homepage
2. watch a video (example)
3. press back button and then close dailymotion's mini-player (not the pip window)
4. pip window should be blank and still be open until another video is loaded

I think one potential solution is to listen for emptied events for the video element. It appears that the video src is changed while still loaded on the page. Pressing the back button with the STRs above will trigger this event once registered; if video.src is undefined, close the pip window.

https://hg.mozilla.org/mozilla-central/rev/f3b5736196b2

I have verified this fix in Beta v100.0b5 and Nightly v101.0a1 on Windows 10, Ubuntu 20 and Mac OS 11.