Version 3.18.5-1ubuntu2 from proposed fixes this issue partially. In order to work, the window manager needs to support compositing, otherwise we now get a black margin outside the window (cf. attached screenshot).
** Attachment added: "margin_without_compositing.png" https://bugs.launchpad.net/ubuntu/+source/gtk+3.0/+bug/1518661/+attachment/4527891/+files/margin_without_compositing.png -- 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/1518661 Title: Apps with HeaderBar have margin outside window Status in GTK+: Unknown Status in Ubuntu GNOME: New Status in gtk+3.0 package in Ubuntu: Triaged Bug description: Distribution: Xubuntu 16.04 Gtk Version: 3.18.5 All applications with GtkHeaderBar have margin outside window. To manage notifications about this bug go to: https://bugs.launchpad.net/gtk/+bug/1518661/+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