Display a message in a dialog box or in the echo area.
If this command was invoked with the mouse, use a dialog box if
`use-dialog-box' is non-nil.
Otherwise, use the echo area.
The first argument is a format control string, and the rest are data
to be formatted under control of the string. See `format' for details.
If the first argument is nil or the empty string, clear any existing
message; let the minibuffer contents show. (fn FORMAT-STRING &rest ARGS)