public const int [] higher_pid = {}; //lower nice value
public const int [] lower_pid  = {}; //higher nice value


public enum Priority {
    LOW = 15,
    NORMAL = 0,
    HIGH = -15
}

public static void main (string [] args) {
    Gdk.init (ref args);

    for (var i=0;i<higher_pid.length;i++)
        set_priority (higher_pid, Priority.HIGH);
    for (var i=0;i<lower_pid.length;i++)
        set_priority (higher_pid, Priority.LOW);

    var screen = Wnck.Screen.get_default ();
    screen.active_window_changed.connect ( (prev) => {
        if (prev != null)
            set_priority (prev.get_pid (), Priority.NORMAL);
        set_priority (screen.get_active_window ().get_pid (), Priority.HIGH);
    });

    var m = new MainLoop ();
    m.run ();
}

public static void set_priority (int pid, Priority p) {
    try {
        Process.spawn_command_line_sync ("renice "+((int)p).to_string ()+" -p "+pid.to_string ());
    } catch (Error e) { warning (e.message); }
}