2057087 - [Nova][Vertical tabs] Blank strip remains on the left in DOM fullscreen video

Status: RESOLVED FIXED

(Firefox :: Sidebar, defect, P1)

Description

[riv3nlee]

Attachment: 屏幕截图 2026-07-23 111038.png

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:155.0) Gecko/20100101 Firefox/155.0

Steps to reproduce:

1. Launch Firefox Nightly with the Nova appearance enabled.
2. Enable vertical tabs.
3. Keep the vertical tab sidebar in its narrow/collapsed state.
4. Open any YouTube video.
5. Click the fullscreen button inside the YouTube player.
   This is DOM fullscreen initiated by the webpage, not Firefox's F11 fullscreen mode.
6. Observe the left edge of the screen.

Actual results:

A light-gray blank strip approximately 50–55 pixels wide remains visible along the left edge of the screen.

The fullscreen video and player interface are offset to the right instead of covering the entire display. The blank strip cannot be manually dismissed while remaining in fullscreen mode.

The issue only occurs when vertical tabs are enabled. After switching back to horizontal tabs, the same YouTube video fills the entire screen normally.

Expected results:

A video opened in DOM fullscreen should cover the entire screen without any blank strip or reserved sidebar area, regardless of whether vertical or horizontal tabs are enabled.

Comment 1

[BugBot [:suhaib / :marco]]

The Bugbug bot thinks this bug should belong to the 'Firefox::Sidebar' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Jonathan Sudiaman [:jsudiaman]]

Additional notes for reproduction: "Expand sidebar on hover" must be enabled.

Comment 4

[Stephen Thompson [:sthompson]]

Can reproduce on macOS

Comment 5

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 2023711

:jswinarton, since you are the author of the regressor, bug 2023711, could you take a look?

For more information, please visit BugBot documentation.

Comment 6

[Jonathan Sudiaman [:jsudiaman]]

Attachment: Bug 2057087 - Fix blank strip in DOM fullscreen video for Nova + Vertical Tabs + Expand on Hover. r?#sidebar-reviewers

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/d0be2f3d44d6
https://hg.mozilla.org/integration/autoland/rev/19b422b072c7
Fix blank strip in DOM fullscreen video for Nova + Vertical Tabs + Expand on Hover. r=sclements

Comment 8

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/19b422b072c7