2059667 - [Nova] About:preferences artifacts with vertical tabs on an external monitor

Status: VERIFIED FIXED

(Firefox :: Settings UI, defect, P2)

Description

[Petruta Horea [:phorea]]

Attachment: Beta 154 VS Nightly 155

Found in

• Nightly 155.0a1 2026-07-30

Affected versions

• Firefox Nightly 155.0a1;

Tested platforms

• Affected platform: macOS 15
• Unaffected platforms: Win 11

Preconditions

• Have an external monitor connected to a MacBook (we reproduced with a DELL monitor, 1920 x 1080 resolution)

Steps to reproduce

1. Enable Nova and drag Firefox to the external monitor
2. Enable vertical tabs (make sure expand on hover is not checked)
3. Open about:preferences and verify several sections

Expected result

• No artifacts

Actual result

• Left side of the borders / icons are clipped, there is a visual regression compared to 154 Beta. Please see the attached video for more details.

Regression range

• Mozregression points to the following pushlog, I suspect bug 2049363 might be the culprit, but this bug landed in 154, and Firefox 154 beta 4 is not affected by the current description.

Additional notes

• Issue goes away when setting Window density to Compact in Appearance

Comment 1

[BugBot [:suhaib / :marco]]

:nical, since you are the author of the regressor, bug 2049363, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 2

[Brindusa Tot, DTE]

This is not reproducible if Nova is disabled.

Comment 3

[Ania]

Hi folks,
This seems unrelated to the vertical tabs, can you please peek at the issue, it was reported during Nova QA?

Comment 4

[akulyk]

Attachment: Nightly-155-nova-disabled.png

Comment 5

[akulyk]

(In reply to Brindusa Tot, DTE from comment #2)

This is not reproducible if Nova is disabled.

I could reproduce with Nova disabled. Its not that prominent, but you can see an artifact on the circular icon

Comment 6

[Stuart Colville [:muffinresearch]]

Noting: Affected platform is macOS 15, does this not reproduce on Tahoe?

FWIW I can't reproduce on 155.0a1 (2026-08-05) / MacOS 26.5.2 (25F84) with a dell external monitor set to 1920x1080.

Comment 7

[Petruta Horea [:phorea]]

Attachment: Screenshot 2026-08-07 at 15.40.00.png

(In reply to akulyk from comment #5)

(In reply to Brindusa Tot, DTE from comment #2)

This is not reproducible if Nova is disabled.

I could reproduce with Nova disabled. Its not that prominent, but you can see an artifact on the circular icon

Here is a comparison with Nova ON/OFF using latest Nightly, macos 15.

Comment 8

[Petruta Horea [:phorea]]

Attachment: latest 155 Nightly on Tahoe

Comment 9

[Petruta Horea [:phorea]]

Attachment: Tahoe

(In reply to Stuart Colville [:muffinresearch] from comment #6)

Noting: Affected platform is macOS 15, does this not reproduce on Tahoe?

FWIW I can't reproduce on 155.0a1 (2026-08-05) / MacOS 26.5.2 (25F84) with a dell external monitor set to 1920x1080.

I recently upgraded from Ventura 13 to Tahoe. The issue is reproducible here as well, when vertical tabs are enabled.

Comment 10

[akulyk]

Could you please check if this issue is still reproducible on the latest Nightly. Thanks!

Comment 11

[Petruta Horea [:phorea]]

Attachment: Screen Shot 2026-08-10 at 5.49.55 PM.png

(In reply to akulyk from comment #10)

Could you please check if this issue is still reproducible on the latest Nightly. Thanks!

I can still reproduce with Nightly 155.0a1 20260810093015 build.

Comment 12

[Ania]

Hi Emilio,

We are a bit stuck with this issue, and were hoping to exercise a "call a friend" option to ask you if you may have any ideas on what may be the culprit here.

Comment 13

[Emilio Cobos Álvarez [:emilio]]

Wrong emilio, right?

Comment 14

[Emilio Cobos Álvarez [:emilio]]

I can reproduce this on my laptop with 1.75x fractional scale on Linux, fwiw.

Comment 15

[Emilio Cobos Álvarez [:emilio]]

Ok, so not quite. What I see is the slightly blurry border radius, but that's pre-existing on a reduced test-case like:

<html style="color-scheme: dark"><span style="display: inline-block; padding: 10px; border: 0.01px solid hotpink; border-radius: 500px">ABCD</span>

However the nova thing seems something else. Some of the wrong nova-specific rendering seems to be because nova re-implemented checkboxes for some reason in bug 2027921 (why? I asked there. Do we need to?).

The clipping I can't reproduce.

Comment 16

[Emilio Cobos Álvarez [:emilio]]

Can you attach your about:support information when you reproduce the issue? That'd probably help.

Comment 17

[akulyk]

Attachment: Storybook-moz-box-group.png

(In reply to Emilio Cobos Álvarez [:emilio] from comment #15)

However the nova thing seems something else. Some of the wrong nova-specific rendering seems to be because nova re-implemented checkboxes for some reason in bug 2027921 (why? I asked there. Do we need to?).

The clipping I can't reproduce.

The moz-radio circle issue appears to be separate. I can reproduce it consistently even when the clipping issue doesn’t occur.

The clipping issue isn't settings or Nova specific, I could reproduce it locally opening this public Storybook page: scrollable moz-box-group. With Nova off it's harder to notice, but the toggle button still looks clipped for me.
Mozregression points me to the same bug as the one that was mentioned by reporter: bug 2049363.

I am on Windows and have external monitor that has scale set to 250%. I can see clipping on that monitor, but not on the laptop.
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:155.0) Gecko/20100101 Firefox/155.0

Comment 18

[Petruta Horea [:phorea]]

Attachment: about:support

Here is the about:support content. I currently don't have access to the Dell monitor, but I was able to reproduce the issue with an older Samsung SyncMaster 940N (1280 x 1024) as additional monitor.

Comment 19

[Emilio Cobos Álvarez [:emilio]]

Ok, I can reproduce the clipping at some zoom levels as well... This looks like a more general WebRender issue I think... At least not OS specific.

Comment 20

[Emilio Cobos Álvarez [:emilio]]

I filed bug 2062742 for the platform side of things.

Comment 21

[akulyk]

After Bug 2062742 landed, I can no longer reproduce this issue.

Comment 22

[Stephen Thompson [:sthompson]]

Assuming fixed by bug 2062742

Comment 23

[Petruta Horea [:phorea]]

I can confirm I no longer reproduce this issue on Firefox 156 beta 4 and latest Nightly 157.0a1, using two different Dell monitors