VM suspend on close - option to cancel, or option to always prompt
Submitted by GN
At the moment if a VM has been manually configured as "run in background" Boxes will start suspending (managedsave) the active VM on exit. This can result in the system becoming entirely unresponsive while this happens (seen on a system with an SSD/ext4/LVM).
At least on GNOME Wayland, Boxes doesn't grab the "close window" shortcut for the guest, making it very easy to try to close a window within the VM via the keyboard, and end up closing Boxes instead, then staring at the screen until it finishes suspending the VM.
The above is just an example, but generally given how easy it is to initiate such an expensive operation without warning, it would be nice to have a "prompt before suspending on close" Boxes option (in dconf if necessary).
Alternatively, some sort of delay with an option to cancel (e.g. the Boxes window closes but a desktop notification is shown - "suspending VM $foo in 5 seconds [keep running] [x]" would avoid the unpleasant surprise/mistake. This would avoid any extra options, and wouldn't delay destroying the Boxes window.