var active_slide = 1;

function change_slide (target_slide){
  if (target_slide == 4){
    active_slide = 1;
  }else if (target_slide == 0){
    active_slide = 3;
  }else{
    active_slide = target_slide;
  }

  document.getElementById('slide1').style.display = "none";
  document.getElementById('slide2').style.display = "none";
  document.getElementById('slide3').style.display = "none";

  document.getElementById('slide'+active_slide).style.display = "block";

  document.getElementById('slide-nav1').src = "/_/img/slideshow/nav-1.gif";
  document.getElementById('slide-nav2').src = "/_/img/slideshow/nav-2.gif";
  document.getElementById('slide-nav3').src = "/_/img/slideshow/nav-3.gif";

  document.getElementById('slide-nav'+active_slide).src = "/_/img/slideshow/nav-"+active_slide+"-active.gif";
}

function rotate_display_handler (action_wanted){
  if (action_wanted == "start"){
    rotate_display_id = setInterval('change_slide((active_slide+1))',6000);
  }else if (action_wanted == "change"){
    if (rotate_display_id){
      rotate_display_handler('stop');
    }else{
      rotate_display();
      rotate_display_handler('start');
    }
  }else{
    clearInterval(rotate_display_id);
    rotate_display_id = "";
  }

}