Function keys and shortcuts

[R Kimber]

When I use the Bluefish editor I set F12 as a shortcut for inserting a list
item.  Since installing ubuntu-mate 15.04, pressing F12 results in a
maximised screen, green in background color, which appears to be a terminal.

I've looked in Control Center -> Keyboard Shortcuts, but the shortcut for a
terminal is Ctrl+Alt+T, and maximise toggle is Alt+F10

Can anyone suggest which application is doing this?  It doesn't appear to
be the default MATE Terminal (there's no reference to F12 in the shortcut
settings and the background for that is set as white), and similarly it
doesn't appear to be Konsole, which I normally use as my terminal.

Is there a way of detecting which application responds to function key?

- Richard.
-- 
Richard Kimber