bug: waybar cannot find network-manager-applet icons

[benjamb]

Are you following the right branch?

• My Nixpkgs and Home Manager versions are in sync

Is there an existing issue for this?

• I have searched the existing issues

Issue description

With waybar configured and enabled with the tray module, and the network-manager-applet service enabled with xsession.preferStatusNotifierItems set to true, waybar cannot find the appropriate icons.

It's possible this applies to other applications, though I don't see this with blueman or udiskie, but this is perhaps since I have them installed via home.packages.

A snippet from waybar -l trace:

[2024-05-02 09:53:25.563] [trace] Set tray item property: :1.12.IconName = 'nm-signal-100'
[2024-05-02 09:53:25.563] [trace] Set tray item property: :1.12.IconThemePath = ''
[2024-05-02 09:53:25.563] [trace] Set tray item property: :1.12.Id = 'nm-applet'
[2024-05-02 09:53:25.563] [trace] Set tray item property: nm-applet.Menu = '/org/ayatana/NotificationItem/nm_applet/Menu'
[2024-05-02 09:53:25.564] [trace] Set tray item property: nm-applet.Status = 'Active'
[2024-05-02 09:53:25.564] [trace] Set tray item property: nm-applet.Title = 'Network'
[2024-05-02 09:53:25.564] [trace] Set tray item property: nm-applet.XAyatanaLabel = ''
[2024-05-02 09:53:25.564] [trace] Set tray item property: nm-applet.XAyatanaLabelGuide = ''
[2024-05-02 09:53:25.564] [trace] Set tray item property: nm-applet.XAyatanaOrderingIndex = 0
[2024-05-02 09:53:25.582] [trace] Item 'nm-applet': Icon 'nm-signal-100' not present in theme Adwaita
[2024-05-02 09:53:25.582] [error] Item 'nm-applet': Could not find an icon named 'nm-signal-100' and no pixmap given.

A workaround for this is to set xdg.systemDirs.data = ["${pkgs.networkmanagerapplet}/share"], but this feels like something I shouldn't have to configure myself, but I'm not sure of what the best solution would be.

Some rough ideas from a relative newbie:

• Configure xdg.systemDirs within network-manager-applet.nix.
• Add conditionals to waybar.nix that checks whether network-manager-applet/nm-applet (or other such SNI packages) are enabled and creates a wrapper with XDG_DATA_DIRS set including the paths to these apps.
• An explicit config parameter is added to waybar.nix that accepts a list of packages and creates a similar wrapper mentioned above with XDG_DATA_DIRS set to include those packages listed.

Maintainer CC

@cvoges12 @rycee @berbiche

System information

- system: `"x86_64-linux"`
 - host os: `Linux 6.1.88, NixOS, 23.11 (Tapir), 23.11.20240429.576ecd4`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.18.1`
 - channels(root): `"nixos-23.05"`
 - nixpkgs: `/nix/store/xpzmrd7qla29lv913dgg0rma1g335zam-source`