function init_throbber(){
  GM_addStyle("#hiu_throbber{position:fixed;left:0;top:0;background-color:#242424;z-index:1001;" +
              "display:none;opacity:0;transition:opacity 0.7s ease 0s;}");
  GM_addStyle("#hiu_throbber_img{position:fixed;left:calc(50% - 64px);top:calc(50% - 64px);width:128px;height:128px;z-index:1002;" +
              "display:none;opacity:0;transition:opacity 0.7s ease 0s;border:0;padding:0;}");
  GM_addStyle(".hfr_apercu_nope{display:none !important;}");
  var throbber_image_url = "http://reho.st/self/30271dc1b7cac925aeabb89fa70e1e17cf5e1840.png";
  var hiu_throbber_img = new Image();
  hiu_throbber_img.src = throbber_image_url;
  hiu_throbber_img.setAttribute("id", "hiu_throbber_img");
  var hiu_throbber = document.createElement("div");
  hiu_throbber.setAttribute("id", "hiu_throbber");
  hiu_throbber.appendChild(hiu_throbber_img);
  hiu_throbber.addEventListener("transitionend", throbber_transitionend, false);
  document.body.appendChild(hiu_throbber);
}

function display_throbber(){
  if(document.querySelector("div#apercu_reponse")){
    document.querySelector("div#apercu_reponse").classList.add("hfr_apercu_nope");
  }
  hiu_throbber_img.style.display = "block";
  hiu_throbber.style.display = "block";
  hiu_throbber.style.width = document.documentElement.scrollWidth + "px";
  hiu_throbber.style.height = document.documentElement.scrollHeight + "px";
  hiu_throbber_img.style.opacity = "1";
  hiu_throbber.style.opacity = "0.8";
}

function throbber_transitionend() {
  if(hiu_throbber.style.opacity === "0") {
    hiu_throbber_img.style.display = "none";
    hiu_throbber.style.display = "none";
    if(document.querySelector("div#apercu_reponse")){
      document.querySelector("div#apercu_reponse").classList.remove("hfr_apercu_nope");
    }
  }
}

function hide_throbber(){
  hiu_throbber_img.style.opacity = "0";
  hiu_throbber.style.opacity = "0";
}

init_throbber();