With 4K monitor, if screen goes blank, mouse clicks don't work in VMs

[Michael Siepmann]

I've read and followed the instructions on
https://www.qubes-os.org/doc/gui-configuration/ but the problem I'm
having is different. Here's what happens:

1. I'm using VMs on a 4K monitor successfully, via DisplayPort.

2a. I have Dom0 screensaver set to Blank Screen Only and it blanks after
the configured number of minutes

OR 2b. I switch to using the laptop screen, then back to the 4K monitor

OR 2c. The computer wakes from sleep while the 4K monitor is in power
saving mode.

3. I can no longer click the mouse in my VMs (though it seems as if
maybe all clicks register in a very small area at the top left). The
mouse works normally in dom0.

4. If I switch to the laptop internal screen it works fine there, but if
I switch back to the 4K monitor it still doesn't work there. The only
way to get mouse clicking working in the VMs again is to shut down the
VM and restart it while using the 4K monitor.

The same thing happens if the computer goes to sleep and when I wake it
up the monitor is in power saving mode. My current workaround is to
disable the screensaver, and remember to wake the monitor before waking
the computer,

Is this a bug I should report? Has anyone else encountered this behavior?

Thanks,

Michael Siepmann

[Micah Lee]

I've encountered this bug (or a similar one) as well on a 4K monitor. It
appears that the mouse clicks only register if they're within the top
left width and height of the laptop resolution.

A workaround I've discovered is just restarting your VMs while your 4K
monitor is plugged in. If you start a VM with the monitor plugged in, it
lets you click anyone on the monitor within that VM.

[David Hobach]

You can also try to switch to a tty (e.g. Alt+Ctl+F2), wait a few
seconds and then go back (Alt+Ctl+F1). Works for me whenever I have
issues with external monitors.

[Michael Siepmann]

Thank you! There is related discussion here and here but the problem I've been having is that after starting a VM with the monitor plugged in, it will only continue to work as long as the monitor never goes blank, even from the screen saver, or from switching temporarily to just using the laptop screen, or from going into suspend mode and then waking up before the monitor has been woken from its power saving mode. However, today when I tried to replicate the problem it didn't happen. Hopefully that will continue!

[Michael Siepmann]

Thank you! I will try that next time it happens. When I tried to
replicate the problem just now, it didn't happen.