[Spice-devel] Fractional scaling with spice-client-gtk

[Alex Guzman]

I've been seeing some weird behavior with fractional scaling on my 
laptop with both remmina and virt-manager when connecting to VMs, which 
makes me think it's something to do with the library they both use 
(spice-client-gtk). They both exhibit similar behavior where rendering 
is incorrect; when maximized with dynamic resolution, there's a border 
around the VM's display [0]. When you disable dynamic resolution at that 
point, it seems the buffer grows even larger (twice the size of the 
screen?) and the borders push the content past the viewpoint, requiring 
scrolling [1].

I'm guessing something about the way GNOME does fractional scaling 
interferes with the rendering of the SPICE widget. As a workaround, I 
can launch it as an X11 client (using environment overrides), but this 
means the app is unnecessarily blurry and has occasional pain points as 
an XWayland app. I'm happy to provide additional testing or feedback.

For reference, I'm running Arch Linux with spice-gtk 0.39-3, remmina 
1.4.21-1, and virt-manager 3.2.0-2.

[0] https://i.imgur.com/v80GokM.jpeg

[1] https://i.imgur.com/NFqFVVy.png

- Alex