nixos/displayManager: introduce defaultSession by hedning · Pull Request #53843 · NixOS/nixpkgs

hedning · 2019-01-12T13:40:41Z

Motivation for this change

Integrate services.xserver.displayManager.sessionPackages better with the existing session system.

resolves #54089

services.xserver.displayManager.defaultSession

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.

services.xserver.displayManager.sessionPackages

Note extraSessionFilePackages is renamed to the less verbose sessionPackages.

When adding a package, foo, to sessionPackages session names are now required to be specified in foo.passthru.providedSessions, this is used to validate defaultSession at evaluation time.

At build time mkDesktops will check that the sessions provided by a package is actually present, bailing out if not, hopefully preventing typos etc.

closes #39871

Things done

Ran these tests succesfully:

After default options deprecation:

gdm+xfce+openbox
lightdm+xfce+openbox
lightdm+gnome-flashback-metacity

jtojnar · 2019-01-12T21:54:31Z

Should we perhaps deprecate desktopManager.default and windowManager.default?

hedning · 2019-01-12T23:12:34Z

Hmm, perhaps, but I'd imagine they're both used quite heavily. Also recreating the the desktopManager.default+windowManager.default manually also seems like chore, though I'm not certain how common it us to mix those in reality.

nixos/modules/services/x11/display-managers/default.nix

hedning · 2019-01-14T11:43:32Z

We should probably add some documentation too.

nixos/modules/services/x11/display-managers/default.nix

hedning · 2019-01-14T14:39:37Z

Added share/wayland-sessions to lightdm's sessions-directory, this won't work with gnome due to duplicate names, but is necessary when having a default session which is only found there. It should also be useful for sway et. al. Slim doesn't seem to support default session.

aanderse · 2019-08-04T20:03:33Z

ping (triage)

worldofpeace · 2019-08-04T20:14:26Z

Last time I checked @hedning was rethinking this approach.

hedning · 2019-09-18T08:23:31Z

So it's possible to reuse desktopManager.default for selecting sessions from sessionPackages. But we still need to construct a defaultSession for lightdm/sddm which require the same logic as in displayManager.defaultSession (ie. checking if the name cannot be found in displayManager.session.names it's available in displayManager.sessionPackages).

So thinking on this some more I think it might be better to stick with an explicit defaultSession that the various display managers can use without trouble. The downside would be users who've set desktopManager.default = "gnome" which now would fail with an unhelpful error message. And somewhat a proliferation of similar options.

So I guess the question is this:
Do we want to select default sessions using desktopManager.default (and windowManager.default) or add a unified option that can override these?

nixos-discourse · 2019-10-10T15:00:13Z

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

https://discourse.nixos.org/t/wayland-sessions/4315/6

jtojnar · 2019-12-14T18:36:52Z

Yeah, I noticed that too, though on unstable it retains lightdm background for me for some reason.

We want access to the valid session names at evaluation time.

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`.

Note: can't launch gnome on wayland due to duplicate entry names: ubuntu/lightdm#16

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.

jtojnar · 2019-12-15T03:33:25Z

Rebased onto the sway changes and squashed the commits. Is there anything remaining to do? I successfully ran gnome-flashback-metacity from GDM, and none+xmonad and pantheon from LightDM, and successfully ran all the DE/DM tests.

worldofpeace · 2019-12-15T03:56:25Z

It's good with me @jtojnar, and mostly because I don't think I can look over it again differently 😄

I'd say, maybe one more reviewer with a different set of eyes.
If waiting doesn't help we can just merge.

hedning · 2019-12-15T09:20:26Z

Went over the new code and it looks good to me. 👍 on deprecating the old default options and implementing legacy sessions through sessionPackages. Thanks for bringing this to the finish line :)

worldofpeace · 2019-12-16T11:22:46Z

@Profpatsch Agreed to QA this by using it.

grahamc · 2019-12-16T13:29:31Z

✔️ I upgraded from 19.09 to nixos-unstable, and added this to my configuration:

services.xserver = {
      enable = true;
      libinput.enable = true;
      displayManager.sddm.enable = true;
};

After deleting an old ~/.config/i3/config, sway started just fine out of the box. After this change my gpg pinentry windows changed to be more plasma-ey, but I'm assuming that isn't unsurprising. I did have to select "sway" in the drop-down by hand each boot, but since I erase my / on every boot I'm assuming that is normal too :).

hedning · 2019-12-16T17:00:24Z

@grahamc: with this pr LightDM will launch wayland sessions (just double checked that it works with sway), and you'll be able to use displayManager.defaultSession to force LightDM to select the sway session by default :)

worldofpeace · 2019-12-16T17:15:33Z

@grahamc: with this pr LightDM will launch wayland sessions (just double checked that it works with sway), and you'll be able to use displayManager.defaultSession to force LightDM to select the sway session by default :)

This reminds me I have a branch with ubuntu/lightdm@03f2189 on top of this. Will PR this after, I'm not sure how it works for sway without the commit though (perhaps it uses the key in the session that forces it)

xaverdh · 2019-12-17T08:42:49Z

Just tried this with my xmonad + lightdm autologin setup. Works perfectly. I was a bit surprised to get an xterm window though, when not explicitly setting defaultSession to "none+xmonad"
(it chose "xterm+xmonad" otherwise) even though I set services.xserver.desktopManager.xterm.enable to false. I guess xterm somehow always winds up in the sessions?

xaverdh · 2019-12-17T09:13:04Z

Ah sorry services.xserver.desktopManager.xterm.enable was not set to false (explicitly). The defaultText here is misleading. When stateVersion is older then "19.09" it defaults to xSessionEnabled, not false..
EDIT: The issue with the code is that the manual gets generated on the hydra builders, not locally, so the stateVersion used is the one from the builder. This yields an incorrect defaultText.

worldofpeace · 2019-12-17T10:06:08Z

@xaverdh Autologin requries a defaultSession to be selected. So I believe it choose head cfg.displayManager.sessionData.sessionNames when you didn't set one. I believe the option description describe this well. As for #53843 (comment), we hope to eliminate this in 20.03 (default to false) #68371.

This module allows root autoLogin, so we would break that for users, but they shouldn't be using it anyways. This gives the impression like auto is some special display manager, when it's just lightdm and special pam rules to allow root autoLogin. It was created for NixOS's testing so I believe this is where it belongs.

nixos-discourse · 2020-06-25T13:51:34Z

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

https://discourse.nixos.org/t/setting-up-urxvt-i3/7847/2

hedning requested a review from jtojnar January 12, 2019 13:40

hedning requested a review from infinisil as a code owner January 12, 2019 13:40

hedning changed the title ~~nixos/displayManager: introduce sessionDefault~~ nixos/displayManager: introduce defaultSession Jan 14, 2019

hedning commented Jan 14, 2019

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hedning force-pushed the session-default branch from 13c0b1f to a691313 Compare January 14, 2019 12:38

hedning commented Jan 14, 2019

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hedning force-pushed the session-default branch from e153a4b to 6fea76e Compare January 14, 2019 14:34

hedning mentioned this pull request Jan 16, 2019

Introduce services.xserver.displayManager.defaultSession #54089

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hedning force-pushed the session-default branch from 6fea76e to de03a76 Compare January 25, 2019 16:37

hedning mentioned this pull request Feb 25, 2019

lightdm can't start a GNOME wayland session #56342

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worldofpeace mentioned this pull request Mar 7, 2019

Plasma5: Use upstream xsession/wayland-session files #56988

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matthewbauer added this to the 19.09 milestone Jun 5, 2019

hedning force-pushed the session-default branch from de03a76 to b0569f0 Compare September 18, 2019 08:21

ofborg bot added the 6.topic: pantheon The Pantheon desktop environment label Sep 18, 2019

hedning force-pushed the session-default branch from a5b6217 to ee1536f Compare October 10, 2019 17:09

jtojnar force-pushed the session-default branch from ec20412 to 705d032 Compare December 15, 2019 02:59

hedning and others added 6 commits December 15, 2019 04:14

nixos/display-manager: extraSessionFilePackages -> sessionPackages

d362df6

nixos/sessionPackages: provide session names in passthru

dd7144b

We want access to the valid session names at evaluation time.

nixos/displayManager: check for provided sessions in mkDesktops

58e5290

nixos/lightdm: enable wayland sessions

53ef29c

Note: can't launch gnome on wayland due to duplicate entry names: ubuntu/lightdm#16

jtojnar force-pushed the session-default branch from 705d032 to 8dc5ff7 Compare December 15, 2019 03:16

lovesegfault approved these changes Dec 15, 2019

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worldofpeace approved these changes Dec 15, 2019

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jtojnar merged commit 6be14ee into NixOS:master Dec 18, 2019

hedning deleted the session-default branch December 20, 2019 15:02

worldofpeace mentioned this pull request Dec 23, 2019

Deprecate types.loaOf #63103

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veprbl mentioned this pull request Dec 30, 2019

xserver.{desktopManager,windowManager}.default configuration breaks after upgrade to master #76684

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lovesegfault mentioned this pull request Jan 10, 2020

i3: add passthru.providedSessions #77410

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jtojnar mentioned this pull request Jan 23, 2020

Don't set background to black if ~/.background-image not present #78346

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worldofpeace mentioned this pull request Jan 26, 2020

nixos/display-managers/auto: remove #78583

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Motivation for this change

services.xserver.displayManager.defaultSession

services.xserver.displayManager.sessionPackages

Things done

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