1953966 - Hidden sidebar flashes open when opening a new window

Status: NEW

(Firefox :: Sidebar, defect, P3)

Description

[Chris Peterson [:cpeterson]]

Attachment: Private_Window_Sidebar_flash.mp4

Steps to reproduce

1. Enable "Show sidebar" in settings.
2. Hide the sidebar using the "Show sidebar" toolbar button.
3. Open a new window. Try both a regular window (Ctrl+N) and a private window (Ctrl+Shift+P).

Expected result

The sidebar should not be shown in the new window.

Actual result

Even though the sidebar is closed, I see a flash of the sidebar in the new window. See the attached recording.

I'm using Firefox Nightly 138.0a1 on Windows 11.

I bisected this behavior to this pushlog for bug 1938249

https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=7e4db89576e4ab7f8df2f9232403e5fc0ec5acbb&tochange=ab0b1bfb4d28e723e46162f69ee996165c01a68d

Comment 1

[Sam Foster [:sfoster] (he/him)]

Thanks, can see the launcher show up briefly and hide again if you slow the video right down. Its there but I don't think we need to track this bug for a particular release.