I have guest additions installed on my Virtual Box, so that the screen is a decent size. When I start Virtual Box, the screen resizes properly. I am running Mac OS X 10.11 (El Capitan), the guest OS is Windows 10, and the Virtual Box version is 4.3.30.
However, when I am inactive in Virtual Box, it goes into some kind of sleep mode and the screen turns black. Also, the screen goes back to the small size. When I move the mouse to wake it up, the screen does not resize back to the larger full screen. The only way I’ve been able to get it to resize is to restart Virtual Box.
How do I get it to resize without having to restart?