How can I set unscaled HiDPI mode on VirtualBox command line?

Question

VirtualBox 5 has support for "unscaled HiDPI output" via the machine|settings|display dialog. However, I can't find a matching modifyvm option in the manual. How do I set this from the command line?

Bonus questions:

I'm actually trying to make a Vagrant config that will work both on a mac with a retina display and on a Windows box with no HiDPI. Will setting unscaled HiDPI output screw things up on the Windows box?

I also need to set up Lubuntu to look reasonable on HiDPI since by default it has unreadably tiny fonts. I know how to change some settings to fix part of the breakage using the GUI, but are there some commands I can put in a provisioning script to do this programmatically?

Solution

There isn't a specific VBoxManage modifyvm option because this behavior is GUI-specific but unscaled HiDPI output can be set from the command line with:

VBoxManage setextradata VM_NAME GUI/HiDPI/UnscaledOutput 1

See: https://www.virtualbox.org/ticket/15425