1874700 - Window border is changing when going in to theatre mode in Youtube

Status: NEW

(Firefox :: Theme, defect)

Description

[Marcel Hoffs]

Attachment: 20240115_142159.jpg

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:121.0) Gecko/20100101 Firefox/121.0

Steps to reproduce:

Go to youtube.com, open any video and go into theatre mode

Actual results:

The top border of the window changes.
At the very top of the border a black row of pixels appears.
Please see the attached photo I took with my phone. It is impossible, it seems, to capture this with a screenshot tool. When using the screenshot tool the black line of pixels disappears. Only when the Firefox window is in focus this line of black pixels is there.

Expected results:

Window border should not be affected by youtube theatre mode.

Comment 1

[Ciprian Georgiu, Desktop QA]

Hi, Marcel! I am not able to reproduce the issue described, the window border is properly displayed in theatre mode on my end. I've checked on Win 11 and Win 10 with Firefox 121 and latest Nightly 123.0a1.

Can you please check again using a clean Firefox profile and on latest Nightly 123.0a1?

Comment 2

[Marcel Hoffs]

Hi,

Steps to reproduce:

1. Close Firefox
2. Open a new instance of Firefox, make sure the bookmarks side bar is closed
3. Go to Youtube.com
4. Play a video

At this point the keep an eye on the top left corner of the Firefox window.
Everything is still ok, most of the time.

5. Go into theatre mode
6. Click on the Firefox titlebar, click outside of the window and click on the Firefox titlebar again

You will see that the title bar changes and an extra row of black pixels is added.

7. If not try it with the bookmarks sidepanel enabled that seems to trigger it more consistently.

I have tried this with a clean profile and it still happens. This is also on Windows 11 with my display scale at 100%.
I tried screenshots and I tried to do a screencast, but both don't pick up this behaviour.
I will try the nightly and see if it occurs there.

Comment 3

[Marcel Hoffs]

It also happens on the latest nightly 123.0a1.

Comment 4

[Marcel Hoffs]

I have uploaded a video recording of the issue to Youtube.
You can see it here:
https://youtu.be/eqsUbg-WMQg

The video is zoomed in on the issue.
What I am doing in the background is two things:

1. Switch the bookmarks sidebar on and off
2. Switch between normal and theatre mode on the Youtube video

Comment 5

[Ciprian Georgiu, Desktop QA]

Thanks for all the provided details! I can also reproduce the problem on Beta 122 and RC 121.0.1 with Win 11.

It seems that the issue is an old regression, I was not able to reproduce the bug on Nightly from 2023-01-02. I hope this mozregression push-log [1] helps finding what broke this, although I'm not sure what could be causing this behaviour looking at the bugs.

[1] https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=f03a3df1b30b7e1cfbfbd69a1691835c9e8b0c66&tochange=bc1ea88587afd6a8fb6b3c384ba993f9d60dc2a5

Triaging to "Firefox: Theme". Please change it if you think this bug don't belong to the component.

Comment 6

[BugBot [:suhaib / :marco/ :calixte]]

Setting Regressed by field after analyzing regression range found by mozregression in comment #5.

Comment 8

[Beth Rennie [:beth] (she/her)]

It is impossible for bug 1796023 to have caused this regression. This error is occurring on Windows and the patch in bug 1796023 only affects non-Windows builds of Firefox. The file modified in the patch is not even compiled in Windows builds.

Comment 9

[Donal Meehan [:dmeehan]]

Ciprian could you try again to identify the regressor?

Comment 10

[Ciprian Georgiu, Desktop QA]

(In reply to Donal Meehan [:dmeehan] from comment #9)

Ciprian could you try again to identify the regressor?

Sure. I've ran mozregression again and it seems that Bug 1849680 might cause this regression.

• changeset: 7f516f079dd477e68270d19861eaa4513cfb3270
• pushlog_url: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=7f516f079dd477e68270d19861eaa4513cfb3270&tochange=d3828ca7337d8ffb2112780580a3fc4e0c8ea6f2

Glenn, would you mind taking a look at this bug?

Comment 11

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1849680