function showPresents() {
  var clientSize = getElementAbsoluteRectangle('container');

  document.getElementById('shader').style.display = 'block';
  document.getElementById('shader').style.height = clientSize.height + 'px';
  document.getElementById('presents-window').style.display = 'block';
}

function cancelPresentsWindow() {
  document.getElementById('shader').style.display = 'none';
  document.getElementById('presents-window').style.display = 'none';
}

function closePresentsWindow() {
  document.getElementById('shader').style.display = 'none';
  document.getElementById('presents-window').style.display = 'none';
  document.location.reload();
}

function getElementAbsoluteRectangle(id) {
  var element = document.getElementById(id);
  var w = element.offsetWidth;
  var h = element.offsetHeight;
  var x = 0;
  var y = 0;

  while (element) {
    x += element.offsetLeft;
    y += element.offsetTop;
    element = element.offsetParent;
  }

  return { 'x': x, 'y': y, 'width': w, 'height': h };
}