1939415 - Major layout shift on New Tab page coming from IAB banner

Status: VERIFIED FIXED

(Firefox :: New Tab Page, defect, P2)

Description

[Reem Hamoui (PTO - back Nov 23)]

Attachment: Content overflowing out of the main container

There seems to be a major overflow of content on the New Tab page coming from the IAB banner when it is enabled.

Comment 1

[Reem Hamoui (PTO - back Nov 23)]

Attachment: Bug 1939415 - Fixing major layout shift coming from IAB Banner. r=#home-newtab-reviewers

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c59212ed5dcd
Fixing major layout shift coming from IAB Banner. r=home-newtab-reviewers,nbarrett

Comment 3

[amarc]

https://hg.mozilla.org/mozilla-central/rev/c59212ed5dcd

Comment 4

[Nathan Barrett [:nbarrett]]

Attachment: Bug 1939415 - Fixing major layout shift coming from IAB Banner. r=#home-newtab-reviewers

Original Revision: https://phabricator.services.mozilla.com/D232958

Comment 5

[Phabricator Automation]

beta Uplift Approval Request

• User impact if declined: Will cause layout shift when banners are rendered.
• Code covered by automated testing: yes
• Fix verified in Nightly: no
• Needs manual QE test: yes
• Steps to reproduce for manual QE testing: browser.newtabpage.activity-stream.asrouter.devtoolsEnabled to true. Navigate to about:home#devtools and click on the IAB Banner Ad Sizes and toggle the Leaderboard and Billboard. There shouldnt be a large layout shift from the banner ads.
• Risk associated with taking this patch: low
• Explanation of risk level: CSS only changes
• String changes made/needed: None
• Is Android affected?: no

Comment 6

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/e0ea7aebd104

Comment 7

[Carmen Fat [:cfat] - Ecosystem QA]

I have verified this issue on the latest Firefox Nightly 136.0a1 (Build ID: 20250116214017) and Beta 135.0b5 (Build ID: 20250115091607) on Windows 10, macOS 14.7.1, and Ubuntu 20.04 x64.

• The NewTab content is displayed correctly without any layout shift when the Billboard or the Leaderboard Ads are enabled.

Comment 8

[Daniel Holbert [:dholbert]]

This seems to have introduced a new pretty-broken-looking intermediate state to the new-tab page's loading flow, at least on the very first load (which also brings along some new layout shift); see bug 1942889. We may need to back this out from beta, or jump on the regression ASAP.