xdg-portal: add new module

[Misterio77]

Description

Adds xdg.portal options. Fixes #1167

Most of it came from the equivalent NixOS module, with a few changes to work here.

---

The xdg-desktop-portal receives requests and forwards them to the right portal, based on:

• Configurations
  • Provided by the user ({~/.config,etc}/xdg-desktop-portal) and/or DE (i.e. $prefix/share/xdg-desktop-portal).
  • Can be global (portals.conf) or per-DE foo-portals.conf
• Portal definitions
  • Each portal has one specifying what they provide

The idea is that, to get working portals, we must:

• Have xdg-desktop-portal.service running (or simply available to be started via dbus). It must be able to find:
  • Portal definitions (provided by the portal packages themselves):
    • They are only looked at a build-time defined dir (usually /etc, but for us this is not really useful), as well as $XDG_DESKTOP_PORTAL_DIR (which is what we'll set)
  • Portal configs (either user provided, or DEs):
    • If starting xdg-desktop-portal on your shell, adding DEs to home.packages currently works, as it looks on $XDG_DATA_DIR (which the respective configs are linked to).
    • For our systemd unit, it's better to use $NIXOS_XDG_DESKTOP_PORTAL_CONFIG_DIR, provided by nixpkgs' patches
• Have our relevant portals (e.g. xdg-desktop-portal-foo.services) available (also started via dbus)

---

With this module, flipping xdg.portal.enable should provide a xdg-desktop-portal service unit, which should be able to locate and start portals listed on xdg.portal.extraPortals; and be controlled by portal configs provided by packages (i.e. DEs) listed on xdg.portal.configPackages, and a user defined xdg.portal.config. An example for hyprland:

{
  xdg.portal = {
    enable = true;
    extraPortals = [ pkgs.xdg-desktop-portal-hyprland pkgs.xdg-desktop-portal-gtk ];
    configPackages = [ pkgs.hyprland ];
  };
}

To illustrate xdg.portal.config, suppose you prefer to override Hyprland's provided .conf and use xdg-desktop-portal-wlr instead:

{
  xdg.portal = {
    enable = true;
    extraPortals = [ pkgs.xdg-desktop-portal-wlr pkgs.xdg-desktop-portal-gtk ];
    config.hyprland.default = [ "wlr" "gtk" ];
  };
}

Checklist

• Change is backwards compatible.

• Code formatted with ./format.

• Code tested through nix-shell --pure tests -A run.all or nix develop --ignore-environment .#all using Flakes.

• Test cases updated/added. See example.

• Commit messages are formatted like

  {component}: {description}
  
  {long description}
  

  See CONTRIBUTING for more information and recent commit messages for examples.

• If this PR adds a new module

  • Added myself as module maintainer. See example.

Maintainer CC

[nyabinary]

xdg portal support can also lead to flatpak being managed via hm right? #4621

[NovaViper]

Hey @Misterio77, would it be possible to use this module along with the NixOS module? KDE ignores the user defined xdg portal settings and only considers them if I use the NixOS module to declare them

[nyabinary]

Is this ready to merge?

[Misterio77]

Yup! Should be. Been using this for over a month, with no issues whatsoever.

Lemme just quickly fix the news.nix conflicts.

[rycee]

Great stuff! Merged to master now 🙂

[mightyiam]

Thank you, @Misterio77 !