Gnome applies default scaling at 125% since 26.05 update

[Erwyn]

Hello there,

Since my update to NixOS 26.05, Gnome keeps setting a 125% scaling to GDM or new monitors I connect to.

Is there a way to configure this to set it back to a default 100% ?

[magicquark]

GNOME 50 enabled Fractional Scaling by default. Your issue sounds like it might be related to this.

In GNOME Settings under Displays you should be able to check/set the fractional scale value.

[Erwyn]

This does solve the issue indeed but I would have wanted to find a more general one because every time I connect a new monitor I my laptop’s one is back to 125% and in any case GDM stays at 125%.

I guess there might be a default option somewhere to be set.

[withakay]

https://bbs.archlinux.org/viewtopic.php?id=309539 may be relevant.

The suggestion is that /etc/xdg/monitors.xml controls the scaling for GDM; it could be set directly with environment."xdg/monitors.xml".text = "__the XML contents needed__";. Not sure if there’s a less direct option setting within programs.* or services.*

[Jucgshu]

The Arch wiki also mentions it here : GDM - ArchWiki

Not sure how to include it seamlessly in Nix though.

[magicquark]

@Jucgshu

Not sure how to include it seamlessly in Nix though.

I do not think that there is a nice way, but it has been discussed in the past here.

/var/lib/gdm/.config/ equivalent?

That was it, thanks for the help rhendric and everyone! If anyone is to stumble upon this in the future - this is how to create a file with content and symlink it to whereever you want: { config, pkgs, ... }: { systemd.tmpfiles.rules = let monitors.xml = pkgs.writeText "monitors.xml" '' FILE CONTENT GOES HERE ''; in [ "L /run/gdm/.config/monitors.xml - - - - ${monitors.xml}" ]; }

[Erwyn]

From what I’m gathering, it seems they switched to a calculation based scaling on new configurations. So I am kind of doomed: I can fix it for one configuration but not for future configurations as I don’t know them yet so can’t list then in the monitors.xml.

Guess I’m gonna have live with it:

• GDM at 125%
• Every new screen to which I hook my laptop, my laptop’s screen gets set back to 125%

[amazari]

If the issue is found both on nixos and arch, there is a big chance it is an upstream issue. You may check if it is a known issue or report it if not at Mutter’s (the underlying compositor) or GDM’s repository/issues tracker. Good luck.
Anecdotically, I don’t suffer from this problem on either my laptop and desktop.

[Erwyn]

@amazari

Anecdotically, I don’t suffer from this problem on either my laptop and desktop

Yes I think this is due to my laptop’s screen resolution, I don’t have the issue with the other screens. It’s a 16:10 (1920x1200) maybe that’s what triggers it.

[Jucgshu]

Mine is 1920x1080 (16:9) and the default is 125% scaling.

[Erwyn]

So I’m not the only one with this issue

[eldosoa]

Happening to me too.