GTK3 ignore theme change using gsettings

[oneingan]

Describe the bug

Im running sway WM from 21.11 channel, when I change theme using gsettings CLI tool I expect GTK3 on-fly changing theme. Test GTK4 using gtk4-demo and works well.

Steps To Reproduce

Steps to reproduce the behavior:

1. Launch gtk3-demo and gtk4-demo (ie: nix-shell -p gtk4.dev --run gtk4-demo)
2. Run gsettings set org.gnome.desktop.interface gtk-theme Adwaita-dark

Expected behavior

Both GTK3 and GTK4 apps change their theme.

Metadata

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 5.17.1, NixOS, 21.11 (Porcupine)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.7.0`
 - channels(root): `"nixos-21.11beta333771.8e6b3914626, unstable-21.11pre299378.db6e089456c"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[berbiche]

Besides GTK4 working and not GTK3, do you know if this combination of Gtk3 + sway ever worked in other Linux distributions?

IIRC I had to setup an xsettings daemon for Gtk3 applications (either running under Wayland or X11) to pick up the theme switch.

[oneingan]

As far I understand from sway wiki, precisely the recommended workaround is using gsettings: https://github.com/swaywm/sway/wiki/GTK-3-settings-on-Wayland/#setting-values-in-gsettings

Also in Archlinux wiki I read:

gsettings is queried for Wayland sessions. (...) Changes to this entry are instant and affect all GTK applications.

https://wiki.archlinux.org/title/Dark_mode_switching#gsettings

[berbiche]

cc @colemickens who has/had the same issue in Home Manager

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/some-loose-ends-for-sway-on-nixos-which-we-should-fix/17728/16