Offset between mouse clicks VNC console when VM is configured to ultra-high resolution

[skobyda]

This is a follow-up of https://github.com/cockpit-project/cockpit-machines/issues/29

Ever since https://github.com/cockpit-project/cockpit-machines/pull/900 was merged, the issue was mostly fixed, but still breaks with higher resolution.

Basically, before, there was offset between cursor position shown on screen and cursor position recorded by the system basically for every resolution, as shown here, as shown here.

Now however the VNC scales properly for small resolution (e.g. 800x600), high resolution (e.g. 1080p), but scaling still breaks for ultra high resolution (3840x2160) and there is offest between shown position of the cursor and recorded position of cursor.

To show what I mean, here is a demo:

presentation-(2).webm