var __isIE = navigator.appVersion.match(/MSIE/);
var __userAgent = navigator.userAgent;
var __isFireFox = __userAgent.match(/firefox/i);
var __isFireFoxOld = __isFireFox && (__userAgent.match(/firefox\/2./i) || __userAgent.match(/firefox\/1./i));
var __isFireFoxNew = __isFireFox && !__isFireFoxOld;

function __parseBorderWidth(width) {
    var res = 0;
    if (typeof (width) == "string" && width != null && width != "") {
        var p = width.indexOf("px");
        if (p >= 0) {
            res = parseInt(width.substring(0, p));
        }
        else {
            //do not know how to calculate other values (such as 0.5em or 0.1cm) correctly now  
            //so just set the width to 1 pixel  
            res = 1;
        }
    }
    return res;
}

//returns border width for some element  
function __getBorderWidth(element) {
    var res = new Object();
    res.left = 0; res.top = 0; res.right = 0; res.bottom = 0;
    if (window.getComputedStyle) {
        //for Firefox  
        var elStyle = window.getComputedStyle(element, null);
        res.left = parseInt(elStyle.borderLeftWidth.slice(0, -2));
        res.top = parseInt(elStyle.borderTopWidth.slice(0, -2));
        res.right = parseInt(elStyle.borderRightWidth.slice(0, -2));
        res.bottom = parseInt(elStyle.borderBottomWidth.slice(0, -2));
    }
    else {
        //for other browsers  
        res.left = __parseBorderWidth(element.style.borderLeftWidth);
        res.top = __parseBorderWidth(element.style.borderTopWidth);
        res.right = __parseBorderWidth(element.style.borderRightWidth);
        res.bottom = __parseBorderWidth(element.style.borderBottomWidth);
    }

    return res;
}

//returns absolute position of some element within document
function getAbsolutePos(element) {
    var res = new Object();
    res.x = 0; res.y = 0;
    if (element !== null) {
        res.x = element.offsetLeft;
        res.y = element.offsetTop;

        var offsetParent = element.offsetParent;
        var parentNode = element.parentNode;
        var borderWidth = null;

        while (offsetParent != null) {
            res.x += offsetParent.offsetLeft;
            res.y += offsetParent.offsetTop;

            var parentTagName = offsetParent.tagName.toLowerCase();

            if ((__isIE && parentTagName != "table") || (__isFireFoxNew && parentTagName == "td")) {
                borderWidth = __getBorderWidth(offsetParent);
                res.x += borderWidth.left;
                res.y += borderWidth.top;
            }

            if (offsetParent != document.body && offsetParent != document.documentElement) {
                res.x -= offsetParent.scrollLeft;
                res.y -= offsetParent.scrollTop;
            }

            //next lines are necessary to support FireFox problem with offsetParent  
            if (!__isIE) {
                while (offsetParent != parentNode && parentNode !== null) {
                    res.x -= parentNode.scrollLeft;
                    res.y -= parentNode.scrollTop;

                    if (__isFireFoxOld) {
                        borderWidth = _getBorderWidth(parentNode);
                        res.x += borderWidth.left;
                        res.y += borderWidth.top;
                    }
                    parentNode = parentNode.parentNode;
                }
            }

            parentNode = offsetParent.parentNode;
            offsetParent = offsetParent.offsetParent;
        }
    }
    return res;
}

function grayOut(elem, vis, options) {
    // Pass true to gray out screen, false to ungray
    // options are optional.  This is a JSON object with the following (optional) properties
    // opacity:0-100         // Lower number = less grayout higher = more of a blackout 
    // zindex: #             // HTML elements with a higher zindex appear on top of the gray out
    // bgcolor: (#xxxxxx)    // Standard RGB Hex color code
    // grayOut(true, {'zindex':'50', 'bgcolor':'#0000FF', 'opacity':'70'});
    // Because options is JSON opacity/zindex/bgcolor are all optional and can appear
    // in any order.  Pass only the properties you need to set.
    var options = options || {};
    var zindex = options.zindex || 50;
    var opacity = options.opacity || 70;
    var opaque = (opacity / 100);
    var bgcolor = options.bgcolor || '#000000';
    var dark = document.getElementById('darkenScreenObject');
    if (!dark) {
        // The dark layer doesn't exist, it's never been created.  So we'll
        // create it here and apply some basic styles.
        // If you are getting errors in IE see: http://support.microsoft.com/default.aspx/kb/927917
        var tbody;
        if (elem == null) {
            tbody = document.getElementsByTagName("body")[0];
        }
        else {
            tbody = elem;
        }
        pos = getAbsolutePos(tbody);
        var tnode = document.createElement('div');           // Create the layer.
        tnode.style.position = 'absolute';                 // Position absolutely
        tnode.style.top = '-' + pos.y + 'px';                           // In the top
        tnode.style.left = '-' + pos.x + 'px';                          // Left corner of the page
        tnode.style.overflow = 'hidden';                   // Try to avoid making scroll bars            
        tnode.style.display = 'none';                      // Start out Hidden
        tnode.id = 'darkenScreenObject';                   // Name it so we can find it later
        tbody.appendChild(tnode);                            // Add it to the web page
        dark = document.getElementById('darkenScreenObject');  // Get the object.
    }
    if (vis) {
        // Calculate the page width and height 
        if (document.body && (document.body.scrollWidth || document.body.scrollHeight)) {
            var pageWidth = document.body.scrollWidth + 'px';
            var pageHeight = document.body.scrollHeight + 'px';
        } else if (document.body.offsetWidth) {
            var pageWidth = document.body.offsetWidth + 'px';
            var pageHeight = document.body.offsetHeight + 'px';
        } else {
            var pageWidth = '100%';
            var pageHeight = '100%';
        }
        //set the shader to cover the entire page and make it visible.
        dark.style.opacity = opaque;
        dark.style.MozOpacity = opaque;
        dark.style.filter = 'alpha(opacity=' + opacity + ')';
        dark.style.zIndex = zindex;
        dark.style.backgroundColor = bgcolor;
        dark.style.width = pageWidth;
        dark.style.height = pageHeight;
        dark.style.display = 'block';
    } else {
        dark.style.display = 'none';
    }
}