1765020 - UI scale per monitor no longer working in Ubuntu

Status: RESOLVED WONTFIX

(Core :: Widget: Gtk, defect, P3)

Description

[Trinket Holloway]

Attachment: display-settings.png

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:99.0) Gecko/20100101 Firefox/99.0

Steps to reproduce:

• On Ubuntu 21.10, set one monitor to 100% scale and another to 200% scale (as in the attached screenshot)
• Ensure layout.css.devPixelsPerPx is at -1.0 (the default) in about:config

Actual results:

Firefox windows stay at 1× scale regardless of which monitor they're on

Expected results:

Each window should switch between 1× on my 1080p monitor and 2× on my 2160p monitor when I drag it from one to the other. This worked until a few days ago; I'm not sure whether Firefox may have updated in the background.

Comment 1

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

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

Comment 2

[Martin Stránský [:stransky] (ni? me)]

Please attach your about:support.
Thanks.

Comment 3

[Trinket Holloway]

Attachment: about:support for my default profile

Comment 4

[Trinket Holloway]

Attachment: about:support for a newly-created profile

Comment 5

[Emilio Cobos Álvarez (:emilio)]

This is due to ubuntu going back to XWayland rather than Wayland in their snaps.

Comment 6

[:gerard-majax]

If I read https://gitlab.freedesktop.org/xorg/xserver/-/issues/1318 correctly, this is just a side effect of using XWayland and upstream has no fix yet. I dont see what we can do more there.

Comment 7

[:gerard-majax]

Firefox is now defaulting to Wayland on release since 121. As this bug is a limitation of XWayland, we cannot fix it.