i based this on the neighboring lightdm-greeters/mini.nix module.
lightdm-mobile-greeter doesn't have a lot of configuration options.
it grabs the default user to login as from lightdm, along with which DE
it should launch. so no further configuration should be needed aside
from enabling `services.xserver.displayManager.lightdm.enable` and
either setting `services.xserver.displayManager.defaultSession` to the
appropriate session or explicitly defining a seat like:
```nix
services.xserver.displayManager.lightdm.extraSeatDefaults = ''
user-session = phosh
'';
```
Required as visible in the lightdm tests:
> Error updating user /org/freedesktop/Accounts/User1001: GDBus.Error:org.freedesktop.Accounts.Error.PermissionDenied: Not authorized: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.PolicyKit1 was not provided by any .service files
(It was requested by them.)
I left one case due to fetching from their personal repo:
pkgs/desktops/pantheon/desktop/extra-elementary-contracts/default.nix
In https://github.com/NixOS/nixpkgs/issues/100119 pantheon's greeter
has g-s-d running which allows brightness controls via pkexec.
This is changed in newer versions of g-s-d (pantheon uses a fork currently),
but whenever brightness is changed with a shell of `shadow` we get
```
Oct 10 23:51:44 kirXps pkexec[18722]: lightdm: Executing command [USER=root] [TTY=unknown] [CWD=/var/lib/lightdm] [COMMAND=/run/current-system/sw/bin/elementary-settings-daemon/gsd-backlight-helper /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight 65587]
```
I'm not sure this should be strictly needed, so we should try to
revert later on when pantheon's g-s-d is updated.
Since systemd 243, docs were already steering users towards using
`journal`:
eedaf7f322
systemd 246 will go one step further, it shows warnings for these units
during bootup, and will [automatically convert these occurences to
`journal`](f3dc6af20f):
> [ 6.955976] systemd[1]: /nix/store/hwyfgbwg804vmr92fxc1vkmqfq2k9s17-unit-display-manager.service/display-manager.service:27: Standard output type syslog is obsolete, automatically updating to journal. Please update│······················
your unit file, and consider removing the setting altogether.
So there's no point of keeping `syslog` here, and it's probably a better
idea to just not set it, due to:
> This setting defaults to the value set with DefaultStandardOutput= in
> systemd-system.conf(5), which defaults to journal.
The upstream session files display managers use have no concept of sessions being composed from
desktop manager and window manager. To be able to set upstream session files as default
session, we need a single option. Having two different ways to set default session would be confusing,
though, so we decided to deprecate the old method.
We also created separate script for each session, just like we already had a separate desktop
file for each one, and started using displayManager.sessionPackages mechanism to make the
session handling more uniform.
There's two ways of providing graphical sessions now:
- `displayManager.session` via. `desktopManager.session` and
`windowManager.session`
- `displayManager.sessionPackages`
`sessionPackages` doesn't make a distinction between desktop and window
managers. This makes selecting a session provided by a package using
`desktopManager.default` nonsensical.
We therefor introduce `displayManager.defaultSession` which can select a session
from either `displayManager.session` or `displayManager.sessionPackages`.
It will default to `desktopManager.default + windowManager.default` as before.
If the dm default is "none" it will select the first provided session from
`sessionPackages`.
Having `display-manager` conflict with `plymouth-quit` causes this lock up:
- `plymouth-quit-wait` starts up, waiting for plymouth-quit to run
- `lightdm` starts up
- `plymouth-quit` can't start, it conflicts with lightdm
- `plymouth-quit-wait` keeps waiting on plymouth-quit to kill plymouthd
The idea is having LightDM control when plymouth quits, but communication with
plymouth was broken: https://github.com/NixOS/nixpkgs/pull/71064
Unfortunately having the conflict breaks switching to configurations with
plymouth enabled. So we still need to remove the conflict.
fixes#71034
These improvements come from shopping around
at what other downstreams have done with their
systemd units and recent changes like [0] to gdm.
Note there's no requries or after on dbus.socket because
settings BusName will set this up automaticallly and
give it a type of dbus.
[0]: 2d57f45962
Rules are a translation of what's done in the
GDM module and adjustments based of looking at
Arch Linux's configuration and upstream's.
A side effect of this change is that gnome-keyring
and kwallet modules should work as expected when in-
cluded.
Fixes#64259#62045
Previously, if you, for example, set
services.xserver.displayManager.sddm.enable, but forgot to set
services.xserver.enable, you would get an error message that looked like
this:
error: attribute 'display-manager' missing
Which was not particularly helpful.
Using assertions, we can make this message much better.
Switch from slim to lightdm as the display-manager.
If plasma5 is used as desktop-manager use sdddm.
If gnome3 is used as desktop-manager use gdm.
Based on #12516
The wallpaper used is *structurally compatible* with the other one,
meaning that the logo is at the same location, and not bigger.
It has one drawback: the logo is brighter, which clashes with the grub
usage. This is to be fixed with new options in grub.
The default session might be found in `extraSessionFilePackages`, but it's not
viable to detect at evaluation time, so emit a warning.
In LightDM instead of checking `defaultSessionName` against
`displayManager.session.names` we rely on the assertions in
`desktopManager` and `windowMananger` and just check that there's at least one
default set. The second assertion could never actually be triggered.
