1962696 - Collapsed vertical tabs can be dragged from the mute/close button without becoming active which confuses tab grouping

Status: VERIFIED FIXED

(Firefox :: Tabbed Browser, defect, P1)

Description

[Kestrel]

Attachment: Grouping with inactive dragged tab

STR:

1. Enable vertical tabs and collapse the sidebar.
2. Drag an inactive tab from its close button, outside the tab area so it does not become active when dragged.
3. Drag it over another tab to create a group.

Expected:
Tab becomes active when dragged and shows grouping indicator regardless where it was dragged from.

Actual:
Tab remains inactive when dragging and grouping indicator shown on active tab instead of dragged tab. The final tab group includes the dragged tab and the underlying tab even though the grouping indicator suggested otherwise.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=68d1a44fdef33f1256471aa630bebf080599dd4e&tochange=fdc1c87c70f2a9e1eea62291478ba1e3a4a5906f

Regressed by Bug 1953249.

Comment 1

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

:dao, since you are the author of the regressor, bug 1953249, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 2

[Dão Gottwald [:dao]]

It shouldn't be possible to drag a tab from its close button. I don't think bug 1953249 broke this.

Comment 3

[Kestrel]

Attachment: Dragging inactive tab via mute button

The mute button can also be dragged without making the tab active with the same regressor. Almost a quarter of the tab area is occupied by the mute button, making it easy to drag unintentionally (previous implementations filled the entire favicon). If the mute button was not draggable it would make it much harder to drag tabs.

Comment 4

[Kestrel]

Re-adding Bug 1953249 as regressor in light of this new information.

Comment 5

[Dão Gottwald [:dao]]

Attachment: Bug 1962696 - Explicitly select the dragged tab. r?sthompson,dwalker,jswinarton

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ff2fbec45e28
Explicitly select the dragged tab. r=jswinarton,tabbrowser-reviewers

Comment 7

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/ff2fbec45e28

Comment 8

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

The patch landed in nightly and beta is affected.
:dao, 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-firefox139 to wontfix.

For more information, please visit BugBot documentation.

Comment 9

[Rares Doghi, Desktop QA]

This issue is verified as fixed in our latest Nightly 140.0a1 (2025-04-30) . Please let me know if its not intended behavior to be able to move those tabs from the Mute button and I will log a separate issue for it.

Comment 10

[Dão Gottwald [:dao]]

Attachment: Bug 1962696 - Explicitly select the dragged tab. r=#release-managers

Comment 11

[Phabricator Automation]

firefox-beta Uplift Approval Request

• User impact if declined: see https://bugzilla.mozilla.org/show_bug.cgi?id=1962696#c0
• Code covered by automated testing: no
• Fix verified in Nightly: yes
• Needs manual QE test: no
• Steps to reproduce for manual QE testing: see https://bugzilla.mozilla.org/show_bug.cgi?id=1962696#c0
• Risk associated with taking this patch: low
• Explanation of risk level: One-liner, has baked in Nightly for six days
• String changes made/needed: none
• Is Android affected?: no

Comment 12

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/df5b19befbab

Comment 13

[Rares Doghi, Desktop QA]

Attachment: Screencast from 2025-05-06 11-30-06.webm

Hi @Dao can you take a look at this issue, I can reproduce this issue now in both latest Beta as well as our latest Nightly build. I think it happens intermittently, please take a look at the screen recording. In the Older build with the fix I could not drag the tabs at all but I think its an intermittent issue. In our latest Beta 139.0b5 the tabs always move when we are dragging the X Close button.

Comment 14

[Rares Doghi, Desktop QA]

Please disregard the previous comment. This issue is verified as fixed in our latest 139.0b5 , whenever we start to move a tab from the X Close button it will be displayed as active. I came across a separate issue which I will file in a second while testing this fix and I thought they might be related.

Comment 15

[Rares Doghi, Desktop QA]

Dao cleared this up for me on Slack. Thank you.

Comment 16

[Rares Doghi, Desktop QA]

Updating the remaining flags.