Sorry, I was wrong. It seems the bug is in GTK's titlebar logic. For Xorg sessions that's only used in "modern" apps with the thick headerbar. For Wayland sessions, that's used in all apps.
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to gtk+3.0 in Ubuntu. https://bugs.launchpad.net/bugs/1698083 Title: Middle-click titlebar actions (like maximizing vertically) don't work in Wayland sessions Status in GTK+: Confirmed Status in gnome-shell package in Ubuntu: Confirmed Status in gtk+3.0 package in Ubuntu: Confirmed Status in mutter package in Ubuntu: Confirmed Bug description: In Gnome Tweak Tool you can configure vertical maximizing for: Windows > Titlebar Actions > Middle-Click However this feature seems to get ignored in Wayland sessions (it just maximizes fully instead). It only works correctly in Xorg Gnome sessions. ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: gnome-shell 3.24.2-0ubuntu6 ProcVersionSignature: Ubuntu 4.10.0-22.24-generic 4.10.15 Uname: Linux 4.10.0-22-generic x86_64 ApportVersion: 2.20.5-0ubuntu4 Architecture: amd64 Date: Thu Jun 15 14:46:04 2017 DisplayManager: lightdm InstallationDate: Installed on 2017-05-03 (43 days ago) InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170502) SourcePackage: gnome-shell UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/gtk/+bug/1698083/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp