Timeout functions are connected
and disconnected exactly as quit functions are; the
expected callback is the same.
gtk_timeout_add() expects an interval argument; the callback is
invoked every interval
milliseconds. If the callback ever returns FALSE, it is removed from the list of
timeout functions, just as if you'd called gtk_timeout_remove(). It is not safe to
call gtk_timeout_remove() from
within a timeout function; this modifies the timeout list
while GTK+ is iterating over it, causing a crash.
Instead, return FALSE to
remove a function.
