Determine Keyboard Capture State Programmatically

[yoloClin]

I want the ability to determine whether a VirtualMachine has captured the keyboard from the command line, similar to the downward-pointing arrow icon in the status bar (it has a dark blue arrow when the host receives keyboard input and a light blue arrow when the guest has input). If I need to hack something together using either VBoxManage, xprop, xwininfo etc that's fine, but at this point I can't figure out how to programmatically identify state at all.