GNOME Shell/Wayland, VirtualBox and absolute input

[Michael Thayer <michael thayer oracle com>]

Hello,

I am looking for a solution to the following problem: when I run Fedora 
25 with GNOME Shell/Wayland and multiple monitors under VirtualBox and 
install Guest Additions absolute input mapping does not work correctly: 
the first screen as seen from the host is mapped to the entire guest 
virtual desktop, and that only when the first screen is in the top left 
corner of the virtual desktop.  (I hope you can follow me here.)  For 
comparison I tried Qemu with virtio-gpu 2D and two screens (I needed a 
one-line code change to make this work) and the result was the same.

I am wondering whether there is any way I can find out from the graphics 
driver about the layout of the virtual desktop - its size and the 
location of the first screen in it (we currently pass this information 
to the host through the graphics device).  If not, are we better 
presenting multiple input devices and mapping each to a screen?  I find 
information online[1] about a udev environment variable to do this: 
ENV{WL_OUTPUT}="<display name>".  Is this something you support, and do 
you know if other compositors are likely to?  Obviously it is not my 
preferred solution, as it will be more work to implement and will 
require fiddling to make sure it stays compatible with X.Org.

[1] https://wiki.tizen.org/wiki/IVI/Mapping_multiple_touchscreen_Wayland

Another issue I am looking at is that GNOME Shell does not seem to use 
drm dirtyfb information to tell the driver about updates.  However 
virtio-gpu seems to get the information, so presumably there is 
something I can do about this.  Any idea about what I should be doing 
differently?  And (small complaint) the fact that GNOME Shell does not 
do a soft mouse cursor makes debugging pointer issues somewhat painful...

Thanks!

Regards
Michael
--
Michael Thayer | VirtualBox engineer
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