Allow hot-plug addition / removal of screens (monitors) in guest OS

[fuujuhi]

It would be nice to add / remove monitors to a running VirtualBox, i.e. change the monitor count without the need to shutdown the guest OS.

In my case for instance, I use VB on a laptop that has an external monitor attached to it. To reduce desktop clutter, I use the fullscreen/seamless mode. However when I detach the external monitor to go somewhere else, I can't use fullscreen/seamless mode anymore because virtualbox complains there are more virtual screens than physical ones.

Also, if I boot the laptop while not attached to the external monitor, I cannot later connect a 2nd monitor to the VB to benefit from the external monitor.

Ideal solution to this problem would be to allow hot-plug addition / removal of new monitor in the guest OS without need of shutdown, etc.

A work-around solution, would be to allow fullscreen/seamless while there is less physical screens than virtual ones, e.g. by disabling one of the screen (in that case, the screen is still visible to the guest OS, but the content is not displayed in the host anymore). That would be less ideal, but still workable and may be easier to implement I guess.