Select the ARGth different visible frame on current display, and raise it.
All frames are arranged in a cyclic order.
This command selects the frame ARG steps away in that order.
A negative ARG moves in the opposite order.
To make this command work properly, you must tell Emacs
how the system (or the window manager) generally handles
focus-switching between windows. If moving the mouse onto a window
selects it (gives it focus), set `focus-follows-mouse' to t.
Otherwise, that variable should be nil.