https://www.vivere.napoli.it/wp-content/plugins/jetpack/_inc/jquery.inview.js

1/**
2 * author Christopher Blum
3 *    - based on the idea of Remy Sharp, http://remysharp.com/2009/01/26/element-in-view-event-plugin/
4 *    - forked from http://github.com/zuk/jquery.inview/
5 */
6(function ($) {
7  var inviewObjects = {}, viewportSize, viewportOffset,
8      d = document, w = window, documentElement = d.documentElement, expando = $.expando;
9
10  $.event.special.inview = {
11    add: function(data) {
12      inviewObjects[data.guid + "-" + this[expando]] = { data: data, $element: $(this) };
13    },
14
15    remove: function(data) {
16      try { delete inviewObjects[data.guid + "-" + this[expando]]; } catch(e) {}
17    }
18  };
19
20  function getViewportSize() {
21    var mode, domObject, size = { height: w.innerHeight, width: w.innerWidth };
22
23    // if this is correct then return it. iPad has compat Mode, so will
24    // go into check clientHeight/clientWidth (which has the wrong value).
25    if (!size.height) {
26      mode = d.compatMode;
27      if (mode || !$.support.boxModel) { // IE, Gecko
28        domObject = mode === 'CSS1Compat' ?
29          documentElement : // Standards
30          d.body; // Quirks
31        size = {
32          height: domObject.clientHeight,
33          width:  domObject.clientWidth
34        };
35      }
36    }
37
38    return size;
39  }
40
41  function getViewportOffset() {
42    return {
43      top:  w.pageYOffset || documentElement.scrollTop   || d.body.scrollTop,
44      left: w.pageXOffset || documentElement.scrollLeft  || d.body.scrollLeft
45    };
46  }
47
48  function checkInView() {
49    var $elements = $(), elementsLength, i = 0;
50
51    $.each(inviewObjects, function(i, inviewObject) {
52      var selector  = inviewObject.data.selector,
53          $element  = inviewObject.$element;
54      $elements = $elements.add(selector ? $element.find(selector) : $element);
55    });
56
57    elementsLength = $elements.length;
58    if (elementsLength) {
59      viewportSize   = viewportSize   || getViewportSize();
60      viewportOffset = viewportOffset || getViewportOffset();
61
62      for (; i<elementsLength; i++) {
63        // Ignore elements that are not in the DOM tree
64        if (!$.contains(documentElement, $elements[i])) {
65          continue;
66        }
67
68        var element       = $elements[i],
69            $element      = $(element),
70            elementSize   = {},
71            elementOffset = {},
72            inView        = $element.data('inview'),
73            visiblePartX,
74            visiblePartY,
75            visiblePartsMerged;
76

77        // for the case where 'display:none' is used in place of 'visibility:hidden'
78        // count and sum the above items to get and move closer to the correct values
79        // IMPORTANT :: insert element into container empty
80        if($element.css('display') == 'none')
81        {
82            var parentElement = $element.parent();
83
84            elementOffset.top = parentElement.offset().top;
85            elementOffset.left = parentElement.offset().left;
86            elementSize.height = parentElement.height();
87            elementSize.width = parentElement.width();
88        } else {
89       	    elementSize = { height: $element.height(), width: $element.width() }
90       	    elementOffset = $element.offset();
91       	}
92
93        // Don't ask me why because I haven't figured out yet:
94        // viewportOffset and viewportSize are sometimes suddenly null in Firefox 5.
95        // Even though it sounds weird:
96        // It seems that the execution of this function is interferred by the onresize/onscroll event
97        // where viewportOffset and viewportSize are unset
98        if (!viewportOffset || !viewportSize) {
99          return;
100        }
101
102        if (element.offsetWidth >= 0 && element.offsetHeight >= 0 && element.style.display != "none" &&
103            elementOffset.top + elementSize.height > viewportOffset.top &&
104            elementOffset.top < viewportOffset.top + viewportSize.height &&
105            elementOffset.left + elementSize.width > viewportOffset.left &&
106            elementOffset.left < viewportOffset.left + viewportSize.width) {
107          visiblePartX = (viewportOffset.left > elementOffset.left ?
108            'right' : (viewportOffset.left + viewportSize.width) < (elementOffset.left + elementSize.width) ?
109            'left' : 'both');
110          visiblePartY = (viewportOffset.top > elementOffset.top ?
111            'bottom' : (viewportOffset.top + viewportSize.height) < (elementOffset.top + elementSize.height) ?
112            'top' : 'both');
113          visiblePartsMerged = visiblePartX + "-" + visiblePartY;
114          if (!inView || inView !== visiblePartsMerged) {
115            $element.data('inview', visiblePartsMerged).trigger('inview', [true, visiblePartX, visiblePartY]);
116          }
117        } else if (inView) {
118          $element.data('inview', false).trigger('inview', [false]);
119        }
120      }
121    }
122  }
123
124  $(w).bind("scroll resize", function() {
125    viewportSize = viewportOffset = null;
126  });
127
128  // IE < 9 scrolls to focused elements without firing the "scroll" event
129  if (!documentElement.addEventListener && documentElement.attachEvent) {
130    documentElement.attachEvent("onfocusin", function() {
131      viewportOffset = null;
132    });
133  }
134
135  // Use setInterval in order to also make sure this captures elements within
136  // "overflow:scroll" elements or elements that appeared in the dom tree due to
137  // dom manipulation and reflow
138  // old: $(window).scroll(checkInView);
139  //
140  // By the way, iOS (iPad, iPhone, ...) seems to not execute, or at least delays
141  // intervals while the user scrolls. Therefore the inview event might fire a bit late there
142  setInterval(checkInView, 250);
143})(jQuery);