I finally found a real computer on which this bug is present. The computer in question is a netbook manufactured by Positivo, the Mobo 5900, which is common on schools. It has a touchscreen with a pen which is compatible with evdev but that doesn't work with libinput. Its touchscreen is:
Bus 004 Device 006: ID 22b9:0005 eTurboTouch Technology, Inc. The attached image not only shows the hint from the pulseaudio-plugin, but another one caused by pavucontrol. As a virtual keyboard is normally used because the netbook can be used as a tablet, the hints can make some keys impossible to use. ** Attachment added: "Captura de tela_2019-11-07_14-12-19.png" https://bugs.launchpad.net/ubuntu/+source/xfce4-pulseaudio-plugin/+bug/1810105/+attachment/5303552/+files/Captura%20de%20tela_2019-11-07_14-12-19.png -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1810105 Title: Hint showing volume never disappears, blocking buttons to minimize, maximize and close To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1810105/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
