jquery获取div函数的可见部分的高度，以便在鼠标悬停时激活

Question

函数computeVisibleHeight（$ t）计算元素的可见部分。可见部分是指在窗口中可见的部分，现在我不确定如何将该函数转移到箭头div并使箭头具有元素的可见部分的高度。

我评论了mouseleave功能，只适用于第二次悬停!!!!不知道为什么。 请帮忙。

• 请将两半隐藏在演示中的图像悬停

演示：http://fiddle.jshell.net/ggvWR/7/

JS：

$.fn.tooltip = function () {
 var $el = $(this);
 var $w = $(window);
 var timer;
 var delay = 500;

 function isScrolledIntoView(elem) {
     var docViewTop = $(window).scrollTop(),
         docViewBottom = docViewTop + $(window).height(),
         elemTop = $(elem).offset().top,
         elemBottom = elemTop + $(elem).height(),
         result = 0;
     if (elemBottom > docViewBottom) {
         result = 1;
     } else if (elemTop < docViewTop) {
         result = -1;
     }
     return result;
 };

 function computeVisibleHeight($t) {
     var top = $t.position().top;
     var windowHeight = $(window).height();
     var scrollTop = $(window).scrollTop();
     var height = $t.height();

     if (top < scrollTop && height - scrollTop >= windowHeight) {
         // first case: the top and the bottom of the element is outside of the window
         return windowHeight;
     } else if (top < scrollTop) {
         // second: the top is outside of the viewport but the bottom is visible
         return height - (scrollTop - top);
     } else if (top > scrollTop && top + height < windowHeight) {
         // the whole element is visible
         return height;
     } else {
         // the top is visible but the bottom is outside of the viewport
         return windowHeight - (top - scrollTop);
     }
 }

 $el.mouseenter(function (e) {
     timer = setTimeout(function () {
         var $c = $(e.currentTarget);
         var content = $c.data('content');
         var $ar = $('.fix-arrow');
         var $h = computeVisibleHeight(($c));

         var $tt = $('<div class="tooltip right"><div class="arrow"><div class="fix-arrow"/></div><h3 class="popover-title" style="display: none;"></h3><div class="popover-content"><article class="default"><h1>Anchorman 2: The Legend Continues</h1><ul><button>£10.99 Buy</button><button>£3.49 Rent</button><p>Hilarious comedy sequel starring Will Ferrell and Steve Carell.</p></article></div></div>').appendTo(e.currentTarget).hide().fadeIn(500);

         $tt.toggleClass('left', $w.width() < $tt.outerWidth() + $tt.offset().left);

         if (computeVisibleHeight(($c)) > 207) {

             $ar.css('height', $h - 63);
         }

         if (computeVisibleHeight(($c)) < 207) {
             $ar.css('height', $h);
         }

         if (isScrolledIntoView($c) < 0) {
             $tt.css('top', $w.scrollTop() + 120 - $c.offset().top);

         } else if (isScrolledIntoView($c) > 0) {
             $tt.css('top', $w.scrollTop() + $w.height() - $c.offset().top - $tt.outerHeight());
         }
     }, delay);
 });

 $el.mouseleave(function (e) {
     // $('.tooltip', e.currentTarget).fadeOut(500, function () {
     //    $(this).remove();
     //});
     clearTimeout(timer);
 });

 };


 $('.item').tooltip();