鼠标悬停的jQuery图像预览，需要调整

Question

这是我在网上找到的一个我正在使用的脚本，但它有一个问题：当图像位于页面的右半部分或下半部分时，弹出的预览会被边缘切断。页。我希望图像偏移并向左或向上显示，而不是向右和向下显示，具体取决于鼠标的位置。

/*
 * Url preview script 
 * powered by jQuery (http://www.jquery.com)
 * 
 * written by Alen Grakalic (http://cssglobe.com)
 * 
 * for more info visit http://cssglobe.com/post/1695/easiest-tooltip-and-image-preview-using-jquery
 *
 */

this.screenshotPreview = function(){    
    /* CONFIG */

        xOffset = 10;
        yOffset = 30;

        // these 2 variable determine popup's distance from the cursor
        // you might want to adjust to get the right result

    /* END CONFIG */
    $("a.screenshot").hover(function(e){
        this.t = this.title;
        this.title = "";    
        var c = (this.t != "") ? "<br/>" + this.t : "";
        $("body").append("<p id='screenshot'><img src='"+ this.rel +"' alt='url preview' />"+ c +"</p>");                                
        $("#screenshot")
            .css("top",(e.pageY - xOffset) + "px")
            .css("left",(e.pageX + yOffset) + "px")
            .fadeIn("fast");                        
    },
    function(){
        this.title = this.t;    
        $("#screenshot").remove();
    }); 
    $("a.screenshot").mousemove(function(e){
        $("#screenshot")
            .css("top",(e.pageY - xOffset) + "px")
            .css("left",(e.pageX + yOffset) + "px");
    });         
};


// starting the script on page load
$(document).ready(function(){
    screenshotPreview();
});