Occurring on Leap 15.1 with GNOME 3.26.2 (as well on openSUSE Tumbleweed with
GNOME 3.32.2 and with GNOME 3.34, filed as Bug 1152787), virtual machine host
windows do not capture the mouse. When the mouse reaches the boundary of the
host's window the cursor will not move any further inside the guest.
Oftentimes, the cursor will actually leave the window entirely. Adding the
"EvTouch USB Graphics Tablet" which enables absolute cursor control (rather
than relative) using virt-manager to the machine is only partly helps; though
not consistently and effectively. This is also not a correct solution.

This occurs only under GNOME (KDE has it's own problems--looking at you,
https://bugs.kde.org/show_bug.cgi?id=371877--but this is not one of them). I
reproduced it under Leap and Tumbleweed using virt-viewer and gnome-boxes. The
same problem cannot be reproduced using Ubuntu 19.04, so I would think this is
confined to openSUSE ��� I am not submitting this to the GNOME bug tracker.

I file this one under GNOME, but it may be better categorized as
Virtualization:Tools.