1978887 - Unable to scroll overflowing pinned tabs with horizontal tabs

Status: VERIFIED FIXED

(Firefox :: Tabbed Browser, defect)

Description

[Nikki Sharpley (:nikkis) (she/her)]

It seems in moving to two separate tab containers (pinned and unpinned) we've lost the behaviour where pinned tabs are scrollable with unpinned tabs. Looking into a solution with flex where the pinned tabs container takes up a maximum width with the overflow scrollable, leaving space for regular tabs visibility.

Comment 1

[Nikki Sharpley (:nikkis) (she/her)]

Attachment: Bug 1978887 - Set pinned tabs container max width and allow overflow scroll r=#tabbrowser-reviewers

• Set max width to 80% of tabbrowser to allow regular tabs to still be visible
• Scroll pinned tabs overflow

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/bb2eee25f99f
https://hg.mozilla.org/integration/autoland/rev/8c5dc7e8dd64
Set pinned tabs container max width and allow overflow scroll r=tabbrowser-reviewers,desktop-theme-reviewers,dao

Comment 3

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/8c5dc7e8dd64

Comment 4

[Sarah Clements [:sclements]]

[Tracking Requested - why for this release]: Potential 142 uplift request after we get QA testing that this fixes the issues and doesn't have any unexpected side effects.

Comment 5

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

The patch landed in nightly and beta is affected.
:nsharpley, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
  • See https://wiki.mozilla.org/Release_Management/Requesting_an_Uplift for documentation on how to request an uplift.
• If no, please set status-firefox142 to wontfix.

For more information, please visit BugBot documentation.

Comment 6

[Nikki Sharpley (:nikkis) (she/her)]

Rares, any chance we could please get some QA eyes on this? We may uplift. Thanks!

Comment 7

[Rares Doghi, Desktop QA]

Attachment: Pinss.mp4

Hi @Nikki, I am seeing a few issues here in our latest Builds, it seesm that the Pinned regions get way to big, with Vertical tabs the section can be resized to a smaller area when it gets that big but it wont automatically set a fixed Pin region size by default, it goes all the way down.

With Horizontal Tabs we have the same issue the Pinned section stretches more than half the Tab bar and we cannot resize that pinned section with Horizontal tabs.

The Tabs can scrolled with both Vertical and Horizontal tabs but I dont know if the new giant pinned section is intended behavior. Please take a look at my screen recording.

I enabled Vertical tabs and kept adding tabs to the pinned section and it kept getting bigger and bigger, only after I was at the bottom the Vertical scroll bar became available, or after I resized it back to a normal size.

Comment 8

[Nikki Sharpley (:nikkis) (she/her)]

Thank you, Rares!

I enabled Vertical tabs and kept adding tabs to the pinned section and it kept getting bigger and bigger, only after I was at the bottom the Vertical scroll bar became available, or after I resized it back to a normal size

Kelly, this is intended behaviour right? If the vertical pinned tabs do not have a height initially set (for example if its a new profile you're testing with) it increases in size in response to how many pinned tabs there are.

The Tabs can scrolled with both Vertical and Horizontal tabs but I dont know if the new giant pinned section is intended behavior. Please take a look at my screen recording.

The solution to this bug was discussed with Yulia and Ania and we went with this initial size. There are plans to follow up with a splitter in order to resize, as you suggested, similar to vertical mode. Bug 1981262 I just filed.

Given that it fixes a more serious bug, I'll check in with my team if this is in a state we want to uplift, or if we want to wait for a splitter.

Comment 9

[Rares Doghi, Desktop QA]

Hi @Nikki, I had a bit more time to test this issue in our latest Nightly build and I did come across a few more issues:

1. First things first, I tried to pin about 50 tabs at once in BETA and RELEASE and it completely overflows the UI, I no longer see any free tabs or the X Close button so I think we do need this fix:

ScreenRecording:
https://drive.google.com/file/d/1MCDFn08KozP0tJvXHpC2Fj0ctdnL2uxD/view?usp=sharing

2. Testing this issue with a bunch of tabs I noticed that a lot of Memory is being used so much so that its hard to close the Firefox browser from the X Close button.
3. Another issue I noticed is that if I try to move multiple pinned tabs at once not only I cant move them but I wont be able to move single pinned tabs after either. (At first we can move single pinned tabs with no issues but after trying to move multiple pinned tabs we can no longer move any of them)
4. Also noticed a lot of errors in Console.

Screen Recording:
https://drive.google.com/file/d/1hjsR1UlGy8oiV9f2AY_vzzXKlQAKtkF5/view?usp=sharing

Comment 10

[Nikki Sharpley (:nikkis) (she/her)]

Thanks for catching those errors! Looks like the introduction of elementToMove in bug 1971382 a few days ago uncovered an existing bug. I've got a fix up for that now in bug 1981507.

Not sure how to tackle the memory issue though...

Comment 11

[Kelly Cochrane [:kcochrane]]

(In reply to Nikki Sharpley (:nikkis) (she/her) from comment #8)

Thank you, Rares!

I enabled Vertical tabs and kept adding tabs to the pinned section and it kept getting bigger and bigger, only after I was at the bottom the Vertical scroll bar became available, or after I resized it back to a normal size

Kelly, this is intended behaviour right? If the vertical pinned tabs do not have a height initially set (for example if its a new profile you're testing with) it increases in size in response to how many pinned tabs there are.

Yeah the pinned tabs area will auto resize to fit it's contents until/unless the user resizes the pinned tabs area using the splitter. The unpinned tabs area has a min-height of the height of 3 tabs which is what can be seen in the video.

Comment 12

[Nikki Sharpley (:nikkis) (she/her)]

Given how late it is in the cycle and the risk, we will hold off on uplifting to 142.

Comment 13

[Rares Doghi, Desktop QA]

I tried this again in our latest Nightly build since now we can move multiple tabs and we no longer see those errors in console due to Bug 1981507 being fixed, but the memory issue is still there, here is a captured profile, maybe this will help, if we have a bunch of pinned tabs and we simply go through them and select them or moving them around the entire browser starts to work slower and slower.

https://share.firefox.dev/45DMFEy

Comment 14

[Rares Doghi, Desktop QA]

This issue is Verified as fixed in our latest Beta 143.0b2 and our Latest Nightly 144.0a1 (2025-08-19), I have logged a separate issue for the Performance problems here: Bug 1983805