1982933 - Dragging multiselected tabs is broken in horizontal mode when moving selected tabs together

Status: VERIFIED FIXED

(Firefox :: Tabbed Browser, defect, P1)

Description

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

Attachment: Screen Recording 2025-08-13 at 4.56.45 PM.mov

STR:

1. Open enough tabs without overflowing
2. Select more than one tab not adjacent to each other
3. Drag those tabs

Expected result:
Selected tabs move next to each other when dragged and background tabs shift to fit their new position

Actual:
All background tabs shift to the left and the selected tabs are not adjacent.

Comment 1

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

Attachment: Bug 1982933 - Fix dragging multiselected tabs in horizontal mode when moving selected tabs together r=sthompson

Using _lockTabSizing removed the transitions needed to position tabs when
not adjacent tabs were multiselected and dragged. This ensures the transtion
remains.

Comment 2

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

Set release status flags based on info from the regressing bug 1972897

Comment 3

[Dão Gottwald [:dao]]

[Tracking Requested - why for this release]: Recent regression in primary UI, we'll probably want to uplift a fix here.

Comment 4

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

Set release status flags based on info from the regressing bug 1972897

Comment 5

[Dianna Smith [:diannaS]]

:nikkis any update on the patch for this? Are we still targeting a 142 planned dot release to fix this?

Comment 6

[Stephen Thompson [:sthompson]]

Attachment: WIP: Bug 1982933 - try not to use _lockTabSizing

Comment 7

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

:diannaS, looking at landing today and uplifting for dot release. Thanks!

Comment 8

[Stephen Thompson [:sthompson]]

Attachment: Bug 1982933 - Fix dragging multiselected tabs in horizontal mode when moving selected tabs together r=nsharpley

Using _lockTabSizing removed the transitions needed to position tabs when not adjacent tabs were multiselected and dragged. This ensures the transtion remains for tabs when multiselected.

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/a743b863c1c7
https://hg.mozilla.org/integration/autoland/rev/b4b5d26afead
Fix dragging multiselected tabs in horizontal mode when moving selected tabs together r=sthompson,tabbrowser-reviewers

Comment 10

[pstanciu]

https://hg.mozilla.org/mozilla-central/rev/b4b5d26afead

Comment 11

[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-firefox143 to wontfix.

For more information, please visit BugBot documentation.

Comment 12

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

Attachment: Bug 1982933 - Fix dragging multiselected tabs in horizontal mode when moving selected tabs together r=sthompson

Using _lockTabSizing removed the transitions needed to position tabs when
not adjacent tabs were multiselected and dragged. This ensures the transtion
remains for tabs when multiselected.

Original Revision: https://phabricator.services.mozilla.com/D261044

Comment 13

[Phabricator Automation]

firefox-beta Uplift Approval Request

• User impact if declined: Unable to drag multiselected tabs that aren't contiguous
• Code covered by automated testing: yes
• Fix verified in Nightly: yes
• Needs manual QE test: yes
• Steps to reproduce for manual QE testing: Multiselect tabs that aren't contiguous and attempt to drag. The tabs should drag together.
• Risk associated with taking this patch: Low
• Explanation of risk level: Manually tested and doesn't appear to break drag and drop.
• String changes made/needed: N/A
• Is Android affected?: no

Comment 14

[Phabricator Automation]

firefox-release Uplift Approval Request

• User impact if declined: Users cannot drag multiple non-contiguous tabs when tab strip is not overflowing. Tabs will overlap during drag. Additional empty space will accumulate at the end of the tab strip after drag operations.
• Code covered by automated testing: no
• Fix verified in Nightly: yes
• Needs manual QE test: yes
• Steps to reproduce for manual QE testing: Horizontal tab strip should have several tabs but not be overflowing. Multi-select tabs that are not next to each other. Once you start dragging, the selected tabs should move together, the tabs should move with the cursor, and the tabs should drop into the appropriate position. It may be valuable to perform smoke tests against other drag-drop functionality to ensure no additional regressions.
• Risk associated with taking this patch: Medium
• Explanation of risk level: Recent drag-drop changes have had a high rate of unintended regressions
• String changes made/needed: No
• Is Android affected?: no

Comment 15

[Pulsebot]

https://github.com/mozilla-firefox/firefox/commit/a2dc6f805fc8
https://hg.mozilla.org/releases/mozilla-beta/rev/4a2818221db1

Comment 16

[Peter Magyari (Desktop QA)]

Verified fixed using Nightly 144.0a1 (20250824214058) and Beta 143.0b4 (20250822165421) on Windows 10, MacOS 15.5 and Ubuntu 24.04.

Comment 17

[Pulsebot]

https://github.com/mozilla-firefox/firefox/commit/9a220da13fbd
https://hg.mozilla.org/releases/mozilla-release/rev/1554caa8d09d

Comment 18

[Peter Magyari (Desktop QA)]

Verified fixed on Firefox 142.0.1 (20250825204858)