docs: function (needle, haystack) {
              needle.width = needle.width || 0;
              needle.height = needle.height || 0;
              if (haystack == this.VIEWPORT) {
                  return this.isInViewport({
                      left : needle.x,
                      top : needle.y
                  }, {
                      width : needle.width,
                      height : needle.height
                  });
              }
              haystack.width = haystack.width || 0;
              haystack.height = haystack.height || 0;
              if (needle.x < haystack.x || needle.y < haystack.y || needle.x + needle.width > haystack.x + haystack.width
                      || needle.y + needle.height > haystack.y + haystack.height) {
                  return false;
              }
              return true;
          }