/**
   * author Christopher Blum
   *    - based on the idea of Remy Sharp, http://remysharp.com/2009/01/26/element-in-view-event-plugin/
   *    - forked from http://github.com/zuk/jquery.inview/
   */
  (function ($) {
    var inviewObjects = {}, viewportSize, viewportOffset,
        d = document, w = window, documentElement = d.documentElement, expando = $.expando, isFiring = false, $elements = {};
  
    $.event.special.inview = {
      add: function(data) {
        var inviewObject = { data: data, $element: $(this) }
        inviewObjects[data.guid + "-" + this[expando]] = inviewObject;
        var selector  = inviewObject.data.selector,
        $element  = inviewObject.$element;
        var hash = parseInt(getHash( data.guid + this[expando]));
        $elements[hash] =  selector ? $element.find(selector) : $element;
      },
  
      remove: function(data) {
        try { delete inviewObjects[data.guid + "-" + this[expando]]; } catch(e) {}
        try {
          var hash = parseInt(getHash(data.guid + this[expando])); 
  	delete($elements[hash]);
        } catch (e){}
      }
    };
  
    
    function getHash(str){
      str = str+'';
      var hash = 0;
      if (str.length == 0) return hash;
      for (i = 0; i < str.length; i++) {
          char = str.charCodeAt(i);
          hash = ((hash<<5)-hash)+char;
          hash = hash & hash; // Convert to 32bit integer
      }
      return Math.abs(hash);
    }
    
    function getViewportSize() {
      var mode, domObject, size = { height: w.innerHeight, width: w.innerWidth };
  
      // if this is correct then return it. iPad has compat Mode, so will
      // go into check clientHeight/clientWidth (which has the wrong value).
      if (!size.height) {
        mode = d.compatMode;
        if (mode || !$.support.boxModel) { // IE, Gecko
          domObject = mode === 'CSS1Compat' ?
            documentElement : // Standards
            d.body; // Quirks
          size = {
            height: domObject.clientHeight,
            width:  domObject.clientWidth
          };
        }
      }
  
      return size;
    }
  
    function getViewportOffset() {
      return {
        top:  w.pageYOffset || documentElement.scrollTop   || (d.body?d.body.scrollTop:0),
        left: w.pageXOffset || documentElement.scrollLeft  || (d.body?d.body.scrollLeft:0)
      };
    }
  
    function checkInView() {
      if (isFiring){
        return;
      }
      isFiring = true;
        viewportSize   = viewportSize   || getViewportSize();
        viewportOffset = viewportOffset || getViewportOffset();
        
        for (var i in $elements) {
          if (isNaN(parseInt(i))) {
            continue;
          }
  
          var $element      = $($elements[i]),
              elementSize   = { height: $element.height(), width: $element.width() },
              elementOffset = $element.offset(),
              inView        = $element.data('inview'),
              visiblePartX,
              visiblePartY,
              visiblePartsMerged;
  
          // Don't ask me why because I haven't figured out yet:
          // viewportOffset and viewportSize are sometimes suddenly null in Firefox 5.
          // Even though it sounds weird:
          // It seems that the execution of this function is interferred by the onresize/onscroll event
          // where viewportOffset and viewportSize are unset
          if (!viewportOffset || !viewportSize) {
  	  isFiring = false;
            return;
          }
          
          if (elementOffset.top + elementSize.height > viewportOffset.top &&
              elementOffset.top < viewportOffset.top + viewportSize.height &&
              elementOffset.left + elementSize.width > viewportOffset.left &&
              elementOffset.left < viewportOffset.left + viewportSize.width) {
            visiblePartX = (viewportOffset.left > elementOffset.left ?
              'right' : (viewportOffset.left + viewportSize.width) < (elementOffset.left + elementSize.width) ?
              'left' : 'both');
            visiblePartY = (viewportOffset.top > elementOffset.top ?
              'bottom' : (viewportOffset.top + viewportSize.height) < (elementOffset.top + elementSize.height) ?
              'top' : 'both');
            visiblePartsMerged = visiblePartX + "-" + visiblePartY;
            if (!inView || inView !== visiblePartsMerged) {
              $element.data('inview', visiblePartsMerged).trigger('inview', [true, visiblePartX, visiblePartY]);
            }
          } else if (inView) {
            $element.data('inview', false).trigger('inview', [false]);
          }
        }
        isFiring = false;
    }
  
    $(w).bind("scroll resize", function() {
      viewportSize = viewportOffset = null;
    });
  
    // Use setInterval in order to also make sure this captures elements within
    // "overflow:scroll" elements or elements that appeared in the dom tree due to
    // dom manipulation and reflow
    // old: $(window).scroll(checkInView);
    //
    // By the way, iOS (iPad, iPhone, ...) seems to not execute, or at least delays
    // intervals while the user scrolls. Therefore the inview event might fire a bit late there
    setInterval(checkInView, 250);
  })(jQuery);