Alt + scroll combination not working

[francescoboc]

Hello everybody,
I have an Ubuntu 18 host/Windows 7 guest system with Photoshop installed. Everything is working great, apart from one thing: the Alt + scroll combination for zooming in/out. Doesn't matter if I do it with the mouse wheel or using the touchpad scroll with two fingers, it just isn't detected. The strange thing is that the Ctrl + scroll combo works perfectly...
I don't think it is a Windows-related issue, because if I enable the USB mouse in VirtualBox (under Devices>USB), then it works fine (but I lose the mouse integration feature, which is annoying).
Anybody has a suggestion on how to solve the problem?

Thank you very much!

[socratis]

if I enable the USB mouse in VirtualBox (under Devices>USB), then it works fine

Can you expand a bit more on the details of your setup? Something doesn't sound right... Anything extra drivers on your host? Any exotic devices?

[francescoboc]

Sorry, I meant Ubuntu 18 host/Windows 7 guest (I edited the first post).
No, no extra drivers or exotic devices. Just standard libinput drivers that come with Ubuntu.

[socratis]

The Alt maybe an Ubuntu thingy then. I still don't understand the relationship with the grabbing the mouse via USB... Maybe an Ubuntu thing again, where if it doesn't have the mouse, the Alt is not grabbed? Not that much of a Linux expert, see if you can find anything related on that front...

[francescoboc]

The Alt is grabbed, indeed many other combinations work, it is just the Alt + scroll movement that is broken. Yea, if I activate the USB mouse everything is fine. I think it is something related to the mouse integration feature.

[michaln]

Qt on Linux (specifically the xcb platform plugin) is this, Alt + vertical scroll changes to horizontal scroll and vice versa. We're not sure why.