johano have you tried switching to Scale Mode?
Nope. Never had to before, but I'll try it now.
Scaled mode works as it should. I tried it years ago and didn't find it useful for me, so I haven't used it since then. I think that might have been because I wanted to preserve the original aspect ratio when I changed the winndow size.
So, that doesn't really change anything with respect to ordinary resizing when the host window enlarges or shrinks, or full-screen resizing. Out of curiosity, I tried HOST+A, too, and that had no effect at all. That didn't auto-resize the guest display, either.
I'll take this opportunity to add some information that might help the team. These VMs were created with the OC released .ISO files, and updated ever since then. I don't remember when this particular behavior began. I suspect it was with the introduction of 4.4, but it could have been sometime later.
I fired up my Budgie VM to help the person who said that Nemo wasn't respecting his dark theme, and I first noticed it then. I enlarged the host window and Budgie didn't resize itself like it always did before that. This could certainly be an upstream issue at VirtualBox, as that's been updated recently as well. But wherever it gets fixed, I'll be glad when I can use VMs in full-screen mode again.
