Lock screen doesn't respect gnome shell theme choice

[fcole90]

The lockscreen theme doesn't follow the selected gnome shell theme, as it used to do, but instead it always uses gnome-shell.css if logged in as Gnome session or ubuntu.css if logged as Ubuntu session.

The currently selected gdm theme is ubuntu.css, but after login it's not respected either.

```
There are 3 choices for the alternative gdm3.css (providing /usr/share/gnome-shell/theme/gdm3.css).

  Selection Path Priority Status
------------------------------------------------------------
  0 /usr/share/gnome-shell/theme/pop.css 20 auto mode
  1 /usr/share/gnome-shell/theme/gnome-shell.css 5 manual mode
  2 /usr/share/gnome-shell/theme/pop.css 20 manual mode
* 3 /usr/share/gnome-shell/theme/ubuntu.css 10 manual mode
```

The selected shell theme is Arc-Darker, from the Ubuntu repositories.

This happens both in the Wayland and Xorg sessions.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: gnome-shell 3.26.2-0ubuntu1
ProcVersionSignature: Ubuntu 4.13.0-17.20-generic 4.13.8
Uname: Linux 4.13.0-17-generic x86_64
ApportVersion: 2.20.7-0ubuntu4
Architecture: amd64
CurrentDesktop: GNOME
Date: Wed Nov 15 15:31:14 2017
DisplayManager: gdm3
InstallationDate: Installed on 2017-08-21 (85 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170820)
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. The issue you are reporting is an upstream one and it would be nice if somebody having it could send the bug to the developers of the software by following the instructions at https://wiki.ubuntu.com/Bugs/Upstream/GNOME. If you have done so, please tell us the number of the upstream bug (or the link), so we can add a bugwatch that will inform us about its status. Thanks in advance.

[fcole90 (fcole90)]

This bug has now been reported upstream: https://bugzilla.gnome.org/show_bug.cgi?id=791299

[Amit Keret (amitkeret)]

I can confirm the same behaviour persists on Ubuntu 18.10:

$ gsettings get org.gnome.desktop.interface gtk-theme
'Adapta'

$ sudo -u gdm env XDG_CURRENT_DESKTOP=GNOME-Greeter HOME=/var/lib/gdm3 gsettings get org.gnome.desktop.interface gtk-theme
'Yaru'

[Jean-Pierre van Riel (jpvr)]

I roughly understand this issue might be something to do with ubuntu-session package hard configuring the gdm login screen to use ubuntu.css?

Is this not a sub-effect / possible duplicate bug of: https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1715722 ?

Also see: https://github.com/pop-os/gtk-theme/issues/123

I did this very dodgy hack:

```
cd /usr/share/gnome-shell/theme
sudo mv ubuntu.css ubuntu.css.bak-dist_1804
sudo ln -s pop.css ubuntu.css
```

Note, I don't symlink `ubuntu.css` to `gdm3.css`, because this might cause circular referencing if the default theme was selected given this is how symlinks could stack:

/usr/share/gnome-shell/theme/gdm3.css -> /etc/alternatives/gdm3.css -> /usr/share/gnome-shell/theme/ubuntu.css

Anyhow, the above is temp work-around, and I know that ubuntu.css will get clobbered next time the gnome-shell-common package updates, but so be it.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.