1956909 - Sidebar expand on hover jumpy after browser close / reopen

Status: VERIFIED FIXED

(Firefox :: Sidebar, defect, P1)

Description

[Kelly Cochrane [:kcochrane]]

Attachment: Screen Recording 2025-03-27 at 2.40.32 PM.mov

After changes in bug 1950419, when enabling expand on hover, if the user then closes and reopens the browser, expand on hover is jumpy because it's calculating the collapsed sidebar width as 0 (my guess as it's checking before it's being rendered).
Workarounds for this include:

• Toggling Expand on hover off/on in the Customize panel
• Expanding/collapsing the sidebar using the toolbar toggle button

STR:
Enable the new sidebar and Expand on hover
Fully close the browser and then reopen it
Notice how the expand on hover effect is now jumpy until you use one of the workarounds mentioned above

Comment 1

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

Set release status flags based on info from the regressing bug 1950419

Comment 2

[Kelly Cochrane [:kcochrane]]

Attachment: Bug 1956909 - Prevent expand on hover jumping animation after browser restart

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/7ea4a6649c26
Prevent expand on hover jumping animation after browser restart r=sidebar-reviewers,nsharpley

Comment 4

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/7ea4a6649c26

Comment 5

[Kelly Cochrane [:kcochrane]]

Hmm I'm able to reproduce this on latest central today. Trying to see what's caused it.

Comment 6

[Kelly Cochrane [:kcochrane]]

I'm gonna reopen this, but I've just checked Beta v138.0b1, and I can't reproduce there at least. We must have since added something in Nightly to reintroduce it for 139.

Comment 7

[Alexandru Trif, Desktop Test Engineering [:atrif] [PTO 18-22]]

Attachment: 1956909.gif

Hello! Unfortunately, I can reproduce this with 139.0a1 (2025-04-01) and with 138.0b1 as well on Windows 10x64 and macOS 12. Attached a screen recording. I also took a treeherder build from comment 4, and the issue is present on that build.
Note that the issue does not happen when Firefox is restarted, the issue happens when Firefox is closed using X or Quit Firefox and then reopened. If more information is needed, please let me know.

Comment 8

[Kelly Cochrane [:kcochrane]]

Attachment: Bug 1956909 - Prevent expand on hover jumping animation after browser restart

Comment 9

[Alexandru Trif, Desktop Test Engineering [:atrif] [PTO 18-22]]

It seems that this also happens after opening new windows or new private windows and then hovering over the sidebar launcher on them.

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/98b869d84403
Prevent expand on hover jumping animation after browser restart r=tabbrowser-reviewers,sidebar-reviewers,jsudiaman,nsharpley

Comment 11

[Kelly Cochrane [:kcochrane]]

Comment on attachment 9476675 [details]
Bug 1956909 - Prevent expand on hover jumping animation after browser restart

Beta/Release Uplift Approval Request

• User impact if declined/Reason for urgency: After every full browser close/reload users with expand on hover enabled will experience a choppy animation on expand/collapse of the sidebar
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: Enable the new sidebar and expand on hover. Fully close out the browser and then reopen it. Ensure that the animation is still smooth when expanding/collapsing.
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Small JS change
• String changes made/needed:
• Is Android affected?: No

Comment 12

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/98b869d84403

Comment 13

[Alexandru Trif, Desktop Test Engineering [:atrif] [PTO 18-22]]

Reproduced the issue with Firefox 138.0b2 on Windows 10x64. Closing and reopening Firefox or opening a new window will cause the expand on hover feature to have a jumpy animation.
The issue is verified fixed with Firefox 139.0a1 (2025-04-03) on Windows 10x64, macOS 12 and Ubuntu 24. The jumpy animation with expand on hover is no longer present after closing and reopening Firefox or after opening a new window/ private window.

Comment 14

[Dianna Smith [:diannaS]]

Comment on attachment 9476675 [details]
Bug 1956909 - Prevent expand on hover jumping animation after browser restart

Approved for 138.0b4

Comment 15

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/cda34cc99a7d

Comment 16

[Alexandru Trif, Desktop Test Engineering [:atrif] [PTO 18-22]]

Verified fixed with Firefox 138.0b4 on Windows 10x64, macOS 12 and Ubuntu 24. The jumpy animation with expand on hover is no longer present after closing and reopening Firefox or after opening a new window/ private window.