/**

 * author Remy Sharp

 * url http://remysharp.com/2009/01/26/element-in-view-event-plugin/

 */

(function ($) {

    function getViewportHeight() {

        var height = window.innerHeight; // Safari, Opera

        var mode = document.compatMode;

        if ( (mode || !$.support.boxModel) ) { // IE, Gecko

            height = (mode == 'CSS1Compat') ?

            document.documentElement.clientHeight : // Standards

            document.body.clientHeight; // Quirks

        }

        return height;

    }

    $(window).scroll(function () {

        var vpH = getViewportHeight(),

            scrolltop = (document.documentElement.scrollTop ?

                document.documentElement.scrollTop :

                document.body.scrollTop),

            elems = [];

        // naughty, but this is how it knows which elements to check for

        $.each($.cache, function () {

            if (this.events && this.events.inview) {

                elems.push(this.handle.elem);

            }

        });

        if (elems.length) {

            $(elems).each(function () {

                var $el = $(this),

                    top = $el.offset().top,

                    height = $el.height(),

                    inview = $el.data('inview') || false;

                if (scrolltop > (top + height) || scrolltop + vpH < top) {

                    if (inview) {

                        $el.data('inview', false);

                        $el.trigger('inview', [ false ]);                        

                    }

                } else if (scrolltop < (top + height)) {

                    if (!inview) {

                        $el.data('inview', true);

                        $el.trigger('inview', [ true ]);

                    }

                }

            });

        }

    });

    // kick the event to pick up any elements already in view.

    // note however, this only works if the plugin is included after the elements are bound to 'inview'

    $(function () {

        $(window).scroll();

    });

})(jQuery);