I found the problem yesterday. The regression is that the gradient (which didn't appear at all before) now only occupies the middle 50% of the screen. This means it looks squashed and different to the login screen. The top and bottom 25% of the screen are solid colours.
It looks like a problem with texture coordinates and GL clamp-to-edge, since the gradient is really only a 1x2 two pixel texture rendered with linear filtering. ** Tags added: regression-release ** Summary changed: - Dark purple (noise) background flashes up briefly during the login animation since Yaru was introduced + The wrong background flashes up briefly during the login animation since Yaru was introduced ** Description changed: [Impact] - Dark purple (noise) background flashes up briefly (for a split second) during the login animation. + The wrong background flashes up briefly (for a split second) during the login animation. The login screen and gnome-shell's system background are meant to be the same image so that the login procedure can VT switch without the user noticing. Then the final desktop expands over the system background. However it appears the login background and system background are not the same image any more, causing a visible glitch during login. [Test Case] 1. Install new version, logout 2. Log in into GDM -> Check that at login startup, the background matches GDM ones (same color, same gradient) 3. Logout, install gnome-session 4. Reboot so that GDM takes gnome-session into account 5. Select GNOME session and login -> At login startup, the background will matche the GNOME default one (from the lockscreen: grey noise), which matches GDM one if reset to default GNOME via update-alternatives. [Regression Potential] This code is loaded at session startup, if there is a syntax error, the session wouldn't start at all. This has been of course tested before committed (both on ubuntu and GNOME sessions) ProblemType: Bug DistroRelease: Ubuntu 18.10 Package: yaru-theme-gnome-shell 18.10.2 ProcVersionSignature: Ubuntu 4.17.0-7.8-generic 4.17.12 Uname: Linux 4.17.0-7-generic x86_64 ApportVersion: 2.20.10-0ubuntu9 Architecture: amd64 Date: Tue Aug 28 14:19:48 2018 Dependencies: InstallationDate: Installed on 2018-05-26 (93 days ago) InstallationMedia: Ubuntu 18.10 "Cosmic Cuttlefish" - Alpha amd64 (20180525) PackageArchitecture: all ProcEnviron: TERM=xterm-256color PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_AU.UTF-8 SHELL=/bin/bash SourcePackage: yaru-theme UpgradeStatus: No upgrade log present (probably fresh install) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1789356 Title: The wrong background flashes up briefly during the login animation since Yaru was introduced To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1789356/+subscriptions -- ubuntu-bugs mailing list email@example.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs