Unable to enable the theme on lock screen in Ubuntu 19.10

[jbouzekri]

Details

• Distribution (with version): Ubuntu 19.10

• Desktop environment (with version): Gnome 3.34.1

• Arc version/commit (don't put "latest"):

ii arc-theme 20190917-1ubuntu1 all Flat theme with transparent elements

• GTK+ 3 version:

  • Murrine engine version: ii gtk2-engines-murrine:amd64 0.98.2-2ubuntu1 amd64 cairo-based gtk+-2.0 theme engine
  • gnome-themes-extras version: ii gnome-themes-extra:amd64 3.28-1ubuntu1 amd64 Adwaita GTK+ 2 theme — engine

• Installation method (package or source): package

Issue

On Ubuntu, when I use Gnome Tweak Tool to enable the arch theme for shell (gnome-shell), it only enables it for login screen but not for lock screen.

I found that Ubuntu look into this file to determine the theme of this lock screen :

$ cat /usr/share/gnome-shell/modes/ubuntu.json 
{
    "parentMode": "user",
    "stylesheetName": "Yaru/gnome-shell.css",
    "debugFlags": ["backtrace-crashes-all"],
    "enabledExtensions": ["ubuntu-dock@ubuntu.com", "ubuntu-appindicators@ubuntu.com", "desktop-icons@csoriano"]
}

And it is true, if I change a background-color in this Yaru css file, it works for lock screen.

So I have just removed the folder /usr/share/gnome-shell/theme/Yaru and created a symlink from Yaru to /usr/share/themes/Arc-Dark/gnome-shell/.

The lock screen works perfectly. However after this change, the application grid that appears when you search an app is always empty. I don't see any icons except the text Searching... or No result found based on what I type.

Is it an issue in Arc theme or in my way to setup the theme ? And if the second, do you know how I can have this theme for all my ubuntu gnome installation (login/logout/lock screens) ?