Hint showing volume never disappears, blocking buttons to minimize, maximize and close

When hovering the mouse over the volume indicator or changing its volume using the mouse wheel it shows the current volume set as a hint. For example:

Volume 100%

The problem is that the hint never disappears, not even clicking on it. On some occasions the hint can cover the minimize, maximize and close buttons, causing significant problems on using the desktop environment, as these three buttons won't be usable anymore with the hint over it.

Where the hint appears it's no longer possible to interact with the screen.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xfce4-pulseaudio-plugin 0.4.1-0ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18
Uname: Linux 4.15.0-43-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CurrentDesktop: XFCE
Date: Sun Dec 30 17:09:23 2018
InstallationDate: Installed on 2018-12-30 (0 days ago)
InstallationMedia: Xubuntu 18.04.2 LTS "Bionic Beaver" - Beta amd64 (20181230)
SourcePackage: xfce4-pulseaudio-plugin
UpgradeStatus: No upgrade log present (probably fresh install)



I do not see this bug. Did you check if it affects another user account too?

Yes, it happens with a new user.

If I trigger this bug, returning to greeter with dm-tool switch-to-greeter, login with other user, use the other user account, log out, log in again to the first user, the hint is still visible.

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/1810105

It seems that this happen only if using the QEMU -device virtio-tablet-pci

It seems all other input devices make the hint disappear as expected.

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.

If it's reproducible with real hardware, then it's definitely not a bug of QEMU ==> Removing QEMU from this bug ticket.