User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:71.0) Gecko/20100101 Firefox/71.0

Steps to reproduce:

• Create a profile
• Navigate to any page with a video element
• Enter the fullscreen player
• Without exiting fullscreen, go back a page (e.g. using the mouse)

Actual results:

The title bar is not visible and the client area occupies the entire window.

Expected results:

The title bar is restored.

Perhaps this is a duplicate of bug 1588386.

Possibly. I'm not sure how to confirm, but it seems quite likely; I believe this bug may be at least 8 days old. I didn't have time to report it immediately, and the reporter of bug 1588386 may have mistakenly believed it is related to an extension when it actually isn't.

Another thing I just discovered: If I navigate to a Youtube video, then navigate to another Youtube video, enter fullscreen, then go back to the first video, the first video will be in the fullscreen state including the presence of a button to leave fullscreen in the Youtube UI.

It seems like Firefox attempts to maintain the fullscreen state but doesn't check if it's supposed to be doing that.

I can reproduce the issue on Nightly72.0a1 Windows10

STR:

1. Open youtube video
2. Click fullscreen icon of the video control
3. Hit Back Space key

Actual results:
Browser toolbars are not shown

Expected Results:
Browser toolbars should be shown

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=ac3d70b6b575df0460216c306f2b3e2d35634b26&tochange=fcaa0242c20458b719aa356a4d988a97e4ad3a3b

Regressed by: Bug 1505916

No, I didn't believe it is related to an extension. I believed it is related to an extension API. And it turned out that the issue could be more easily reproduced on Windows than on Linux. Your steps doesn't reproduce the issue here on Linux either.

(In reply to lilydjwg from comment #5)

No, I didn't believe it is related to an extension. I believed it is related to an extension API. And it turned out that the issue could be more easily reproduced on Windows than on Linux. Your steps doesn't reproduce the issue here on Linux either.

Because, on Linux, browser.backspace_action = 2 by default. [Back Space] do nothing.
On the other hand, on Windows, browser.backspace_action = 0 by default. [Back Space] do history back.

If you want to reproduce on Linux, set browser.backspace_action to 0 in about:config.

(In reply to Alice0775 White from comment #6)

Because, on Linux, browser.backspace_action = 2 by default. [Back Space] do nothing.
On the other hand, on Windows, browser.backspace_action = 0 by default. [Back Space] do history back.

If you want to reproduce on Linux, set browser.backspace_action to 0 in about:config.

I didn't see the backspace thing and used alt-left to go back in history.

The issue seems more difficult to reproduce on Linux, but I was able to reproduce it at least once.

Abdoulaye, are you able to look at this bug which is a regression from your work in bug 1505916? If not, maybe mconley could comment?

(I'm assuming we're letting bug 1505916's work ride the trains even though Fission isn't at this time?)

Better STR for Windows:

1. Visit mozilla.org
2. In the same tab, visit http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4
3. Full screen the video
4. Press backspace to go back to mozilla.org

ER:

The browser UI is restored.

AR:

The browser UI stays collapsed.

[Tracking Requested - why for this release]:

Users can get into a situation where their browser UI disappears after attempting to browse away from a fullscreen video.

It looks like Abdoulaye is looking at a similar regression in bug 1588386. I'm going to wait for him to comment here to see if he has ideas on the right approach to address this, but I've added this to tracking because we shouldn't ship this regression.

I verified and this is a duplicate of bug 1588386.

Thanks, Abdoulaye!

Bug 1588386 did not fix this issue.
tested with build autoland https://treeherder.mozilla.org/#/jobs?repo=autoland&searchStr=windows%2C2012%2Cx64%2Cshippable%2Copt&revision=efe8b524f8bf234cbba80f0dc08d0f6910d6520c&selectedJob=273748301

STR for Windows:

1. Open new tab
2. Open https://www.wikipedia.org/
3. Open https://www.youtube.com/watch?v=xGh6sIRHkeA
4. Click Full screen icon in video controls
5. Press Alt+Left arrow to go back to wikipedia.org

Abdoulaye,
Can you please look into this?

[Tracking Requested - why for this release]: Re-requesting tracking as this was marked as dupe, but then re-opened.

Confirming, this is not fixed in Nightly 20191031095309.

I spoke to Neil today - he's going to look at this.

(In reply to Alice0775 White from comment #15)

Bug 1588386 did not fix this issue.
tested with build autoland https://treeherder.mozilla.org/#/jobs?repo=autoland&searchStr=windows%2C2012%2Cx64%2Cshippable%2Copt&revision=efe8b524f8bf234cbba80f0dc08d0f6910d6520c&selectedJob=273748301

STR for Windows:

1. Open new tab
2. Open https://www.wikipedia.org/
3. Open https://www.youtube.com/watch?v=xGh6sIRHkeA
4. Click Full screen icon in video controls
5. Press Alt+Left arrow to go back to wikipedia.org

That's weird that I apparently can reproduce this only when I navigate to a youtube video via the address bar.
Thanks for catching this.

(In reply to Mike Conley (:mconley) (:⚙️) (Wayyyy behind on needinfos) from comment #19)

I spoke to Neil today - he's going to look at this.

Whoops missed this comment. Added Neil as a reviewer though.
Maybe we should also have as a follow-up some tests to cover "close tab" and "navigate back" cases when on fullscreen mode.

Okay, so there's a patch in the works here. That's good. I'll clear the needinfo on myself for now - we just need to make sure a fix for this gets landed and uplifted to beta in the short term.

https://hg.mozilla.org/mozilla-central/rev/71b00388948f

Comment on attachment 9105685 [details]
Bug 1590138 - Handle the case where the actor is already destroyed during fullscreen exit so that chrome UI is fully restored. r?smaug,NeilDeakin

Beta/Release Uplift Approval Request

• User impact if declined: Users may experience Firefox UI being in an unstable state after leaving fullscreen using back or forward history navigation keyboard shortcuts.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: See comments 10 15
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): This adds relatively small changes to handle a specific error that prevents some Chrome UI from being restored.
• String changes made/needed:

Comment on attachment 9105685 [details]
Bug 1590138 - Handle the case where the actor is already destroyed during fullscreen exit so that chrome UI is fully restored. r?smaug,NeilDeakin

Fix for a visible 71 UI regression with fullscreen videos, uplift approved for 71 beta 8, thanks.

https://hg.mozilla.org/releases/mozilla-beta/rev/e4db5e194a4b

Reproduced the issue on Windows 10/ MacOS 10.13 / Ubuntu 18.04 using Firefox Nightly (20191031095309) and Firefox 71.0b7(20191104135555)
Also checked it on Firefox Nightly 72.0a1 (20191106215426) and Firefox Beta 71.0b8 (20191106230619) and it issue has been fixed.