// Many thanks to http://exiled-alliance.com/tools/oreilly/webprog/DHTML_javascript/0596004672_jvdhtmlckbk-chp-13-sect-4.html

// Global variables
var isCSS, isW3C, isIE4, isNN4, isIE6CSS;

// Initialize upon load to let all browsers establish content objects
function initDHTMLAPI( ) {
    if (document.images) {
        isCSS = (document.body && document.body.style) ? true : false;
        isW3C = (isCSS && document.getElementById) ? true : false;
        isIE4 = (isCSS && document.all) ? true : false;
        isNN4 = (document.layers) ? true : false;
        isIE6CSS = (document.compatMode && document.compatMode.indexOf("CSS1") >= 0) ? 
            true : false;
    }
}

// Set event handler to initialize API
window.onload = initDHTMLAPI;
   
// Seek nested NN4 layer from string name
function seekLayer(doc, name) {
    var theObj;
    for (var i = 0; i < doc.layers.length; i++) {
        if (doc.layers[i].name == name) {
            theObj = doc.layers[i];
            break;
        }
        // dive into nested layers if necessary
        if (doc.layers[i].document.layers.length > 0) {
            theObj = seekLayer(document.layers[i].document, name);
        }
    }
    return theObj;
}
   
// Convert object name string or object reference
// into a valid element object reference
function getElement(obj) {
    var theObj;
    if (typeof(obj) == "string") {
        if (document.getElementById) {
            theObj = document.getElementById(obj);
        } else if (isIE4) {
            theObj = document.all(obj);
        } else if (isNN4) {
            theObj = seekLayer(document, obj);
        }
    } else {
        // pass through object reference
        theObj = obj;
    }
    return theObj;
}
   
// Convert object name string or object reference
// into a valid style (or NN4 layer) reference
function getStyle(obj) {
    var theObj = getElement(obj);
    if (theObj && isCSS) {
        theObj = theObj.style;
    }
    return theObj;
}

// Position an object at a specific pixel coordinate
function shiftTo(obj, x, y) {
    var theObj = getStyle(obj);
    if (theObj) {
        if (isCSS) {
            // equalize incorrect numeric value type
            var units = (typeof theObj.left == "string") ? "px" : 0;
            theObj.left = x + units;
            theObj.top = y + units;
        } else if (isNN4) {
            theObj.moveTo(x,y)
        }
    }
}

// Resize an object to a size in pixels
function resize(obj, width, height) {
    var theObj = getStyle(obj);
    if (theObj) {
        if (isCSS) {
            // equalize incorrect numeric value type
            var units = (typeof theObj.left == "string") ? "px" : 0;
            theObj.width = x + units;
            theObj.height = y + units;
        } else if (isNN4) {
            theObj.moveTo(x,y)
        }
    }
}
   
// Move an object by x and/or y pixels
function shiftBy(obj, deltaX, deltaY) {
    var theObj = getStyle(obj);
    if (theObj) {
        if (isCSS) {
            // equalize incorrect numeric value type
            var units = (typeof theObj.left == "string") ? "px" : 0;
            theObj.left = getStyleLeft(obj) + deltaX + units;
            theObj.top = getStyleTop(obj) + deltaY + units;
        } else if (isNN4) {
            theObj.moveBy(deltaX, deltaY);
        }
    }
}
   
// Set the z-order of an object
function setZIndex(obj, zOrder) {
    var theObj = getStyle(obj);
    if (theObj) {
        theObj.zIndex = zOrder;
    }
}
   
// Set the background color of an object
function setBGColor(obj, color) {
    var theObj = getStyle(obj);
    if (theObj) {
        if (isNN4) {
            theObj.bgColor = color;
        } else if (isCSS) {
            theObj.backgroundColor = color;
        }
    }
}
   
// Set the visibility of an object to visible
function show(obj) {
    var theObj = getStyle(obj);
    if (theObj) {
        theObj.visibility = "visible";
    }
}
   
// Set the visibility of an object to hidden
function hide(obj) {
    var theObj = getStyle(obj);
    if (theObj) {
        theObj.visibility = "hidden";
    }
}
   
// Retrieve the x coordinate of a positionable object
function getStyleLeft(obj)  {
    var elem = getElement(obj);
    var result = 0;
    if (document.defaultView) {
        var cssDecl = document.defaultView.getComputedStyle(elem, "");
        result = cssDecl.getPropertyValue("left");
        if (result == "auto") {
        	return 0;
       	}
    } else if (elem.currentStyle) {
        result = elem.currentStyle.left;
    } else if (elem.style) {
        result = elem.style.left;
    } else if (isNN4) {
        result = elem.left;
    }
    return parseInt(result);
}
   
// Retrieve the y coordinate of a positionable object
function getStyleTop(obj)  {
    var elem = getElement(obj);
    var result = 0;
    if (document.defaultView) {
        var cssDecl = document.defaultView.getComputedStyle(elem, null);
        result = cssDecl.getPropertyValue("top");
        if (result == "auto") {
        	return 0;
       	}
    } else if (elem.currentStyle) {
        result = elem.currentStyle.top;
    } else if (elem.style) {
        result = elem.style.top;
    } else if (isNN4) {
        result = elem.top;
    }
    return parseInt(result);
}
   
// Retrieve the rendered width of an element
function getStyleWidth(obj)  {
    var elem = getElement(obj);
    if (!elem) {
    	return 0;
    }
    var result = 0;
    if (elem.clientWidth) {
        return elem.clientWidth;
    } else if (elem.offsetWidth) {
        result = elem.offsetWidth;
    } else if (elem.clip && elem.clip.width) {
        result = elem.clip.width;
    } else if (elem.style && elem.style.pixelWidth) {
        result = elem.style.pixelWidth;
    }
    return parseInt(result);
}
   
// Retrieve the rendered height of an element
function getStyleHeight(obj)  {
    var elem = getElement(obj);
    if (!elem) {
    	return 0;
    }
    var result = 0;
    if (elem.clientHeight) {
        return elem.clientHeight;
    } else if (elem.offsetHeight) {
        return elem.offsetHeight;
    } else if (elem.clip && elem.clip.height) {
        result = elem.clip.height;
    } else if (elem.style && elem.style.pixelHeight) {
        result = elem.style.pixelHeight;
    }
    return parseInt(result);
}
   
// Return the available content width space in browser window
function getInsideWindowWidth( ) {
    if (window.innerWidth) {
        return window.innerWidth;
    } else if (isIE6CSS) {
        return document.body.parentElement.clientWidth;
    }
    else if (document.body && document.body.clientWidth) {
    	if (document.body.clientWidth == 0) {
    		return document.body.parentElement.clientWidth;
    	}
      return document.body.clientWidth;
    }
    else if (document.body.parentElement.clientWidth) {
    	return document.body.parentElement.clientWidth;
    }
    return 0;
}
   
// Return the available content height space in browser window
function getInsideWindowHeight( ) {
    if (window.innerHeight) {
        return window.innerHeight;
    } else if (isIE6CSS) {
        // measure the html element's clientHeight
        return document.body.parentElement.clientHeight;
    }
    else if (document.body && document.body.clientHeight) {
        if (document.body.clientHeight == 0) {
        	return document.body.parentElement.clientHeight;
        }
        return document.body.clientHeight;
    }
    else if (document.body.parentElement.clientHeight) {
    	return document.body.parentElement.clientHeight;
    }
    return 0;
}