public void key_switch_focus () {
    if (!focus_key_pressed) return;

    // `switch-focus-ignore-class-forward'
    // `switch-focus-ignore-class-backward'
    if (meta_down)
      set_focus (next_client_normal (focus, !shift_down), true);


    // `switch-focus-different-class-forward'
    // `switch-focus-different-class-backward'
    else if (alt_down)
      set_focus (next_client_different_class (focus, !shift_down), true);


    // `switch-focus-same-class-forward'
    // `switch-focus-same-class-backward'
    else if (super_down)
      set_focus (next_client_same_class (focus, !shift_down), true);
  }