1884133 - Weird tab border rendering on 125% scaling

Status: NEW

(Core :: Graphics: WebRender, defect)

Description

[Floris]

Attachment: Firefox-Recording.mp4

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:123.0) Gecko/20100101 Firefox/123.0

Steps to reproduce:

I am using Firefox 123 on Windows 11 at 125% system scaling. The border around the active tab is sometimes misaligned by a few pixels. This border is present on themes like Alpenglow and various third-party themes. The misalignment is dependent on the window size, and not present on 100% or 200% scaling - hence it makes me think Firefox is doing funny rendering rather than it being a theme issue.

Actual results:

See the attached recording. Here, the glitch shows on the left edge, but sometimes it shows on the right edge for other tabs.

Comment 1

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

The Bugbug bot thinks this bug should belong to the 'Core::Graphics: WebRender' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Alice0775 White]

I can see similar issue Nightly125.0a1 with some specific theme[1].

[1] https://addons.mozilla.org/en-US/firefox/addon/arc-darker-theme-we/

Comment 3

[Jeff Muizelaar [:jrmuizel]]

It would be nice to have a standalone html test case that shows this.