Create a pop-up menu to appear on X root window when I right-click
I'd like to program a generic pop-up menu, that I can create outside
of any GTK toplevel, but directly on the X root window, for example by
a keyboard shortcut or by a right click (the shortcut should be
managed by the window manager, xfwm4 in my case).
My problem is to create that pop-up: do I have to create an invisible
toplevel window that takes up the whole screen?