display is corrupted on hidpi clients

Submitted by Michael Chudobiak

Assigned to Spice Bug List

Link to original bug (#104841)

Description

I'm running a Windows XP guest on a Fedora 27 host, with this command line:

/usr/bin/qemu-kvm -hda /var/lib/libvirt/images/MikeOfficeXP.img -usbdevice tablet -usb -device usb-host,hostbus=1,hostaddr=2 -device usb-host,hostbus=1,hostaddr=3 -parallel /dev/parport0 -m 4096 -k en-us -vga qxl -spice port=5931,disable-ticketing -net nic,model=rtl8139 -net user &

spicy renders this correctly on a standard lo-dpi monitor, but visible rendering artifacts are visible on the hi-dpi monitor. See the attached screenshots. The hi-dpi screenshot has twice the resolution in each axis, but weird horizontal lines appear in the central white space.