/* ***********************************************************
Example 4-3 (DHTMLAPI.js)
"Dynamic HTML:The Definitive Reference"
2nd Edition
by Danny Goodman
Published by O'Reilly & Associates  ISBN 1-56592-494-0
http://www.oreilly.com
Copyright 2002 Danny Goodman.  All Rights Reserved.
************************************************************ */
// DHTMLapi.js custom API for cross-platform
// object positioning by Danny Goodman (http://www.dannyg.com).
// Release 2.0. Supports NN4, IE, and W3C DOMs.

// 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 getRawObject(obj) {
	var theObj;
	if (typeof obj == "string") {
			if (isW3C) {
					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 getObject(obj) {
	var theObj = getRawObject(obj);
	if (theObj && isCSS) {
			theObj = theObj.style;
	}
	return theObj;
}

// Position an object at a specific pixel coordinate
function shiftTo(obj, x, y) {
	var theObj = getObject(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)
			}
	}
}

// Move an object by x and/or y pixels
function shiftBy(obj, deltaX, deltaY) {
	var theObj = getObject(obj);
	if (theObj) {
			if (isCSS) {
					// equalize incorrect numeric value type
					var units = (typeof theObj.left == "string") ? "px" : 0 
					theObj.left = getObjectLeft(obj) + deltaX + units;
					theObj.top = getObjectTop(obj) + deltaY + units;
			} else if (isNN4) {
					theObj.moveBy(deltaX, deltaY);
			}
	}
}

// Set the z-order of an object
function setZIndex(obj, zOrder) {
	var theObj = getObject(obj);
	if (theObj) {
			theObj.zIndex = zOrder;
	}
}

// Set the background color of an object
function setBGColor(obj, color) {
	var theObj = getObject(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 = getObject(obj);
	if (theObj) {
			theObj.visibility = "visible";
	}
}

// Set the visibility of an object to hidden
function hide(obj) {
	var theObj = getObject(obj);
	if (theObj) {
			theObj.visibility = "hidden";
	}
}

// Retrieve the x coordinate of a positionable object
function getObjectLeft(obj)  {
	var elem = getRawObject(obj);
	var result = 0;
	if (document.defaultView) {
			var style = document.defaultView;
			var cssDecl = style.getComputedStyle(elem, "");
			result = cssDecl.getPropertyValue("left");
	} 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 getObjectTop(obj)  {
	var elem = getRawObject(obj);
	var result = 0;
	if (document.defaultView) {
			var style = document.defaultView;
			var cssDecl = style.getComputedStyle(elem, "");
			result = cssDecl.getPropertyValue("top");
	} 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 getObjectWidth(obj)  {
	var elem = getRawObject(obj);
	var result = 0;
	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 getObjectHeight(obj)  {
	var elem = getRawObject(obj);
	var result = 0;
	if (elem.offsetHeight) {
			result = 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) {
			// measure the html element's clientWidth
			return document.body.parentElement.clientWidth
	} else if (document.body && document.body.clientWidth) {
			return document.body.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) {
			return document.body.clientHeight;
	}
	return 0;
}

// Center a positionable element whose name is passed as 
// a parameter in the current window/frame, and show it
function centerOnWindow(elemID) {
	// 'obj' is the positionable object
	var obj = getRawObject(elemID);
	// window scroll factors
	var scrollX = 0, scrollY = 0;
	if (document.body && typeof document.body.scrollTop != "undefined") {
			scrollX += document.body.scrollLeft;
			scrollY += document.body.scrollTop;
			if (document.body.parentNode && 
					typeof document.body.parentNode.scrollTop != "undefined") {
					scrollX += document.body.parentNode.scrollLeft;
					scrollY += document.body.parentNode.scrollTop;
			}
	} else if (typeof window.pageXOffset != "undefined") {
			scrollX += window.pageXOffset;
			scrollY += window.pageYOffset;
	}
	var x = Math.round((getInsideWindowWidth()/2) -
	(getObjectWidth(obj)/2)) + scrollX;
	var y = Math.round((getInsideWindowHeight()/2) -
			(getObjectHeight(obj)/2)) + scrollY;
	shiftTo(obj, x, y);
	show(obj);
}

// Center a positionable element whose name is passed as 
// a parameter in the current window/frame, and show it
function getCenterPosition(elemID) {
	// 'obj' is the positionable object
	var obj = getRawObject(elemID);
	// window scroll factors
	var scrollX = 0, scrollY = 0;
	if (document.body && typeof document.body.scrollTop != "undefined") {
			scrollX += document.body.scrollLeft;
			scrollY += document.body.scrollTop;
			if (document.body.parentNode && 
					typeof document.body.parentNode.scrollTop != "undefined") {
					scrollX += document.body.parentNode.scrollLeft;
					scrollY += document.body.parentNode.scrollTop;
			}
	} else if (typeof window.pageXOffset != "undefined") {
			scrollX += window.pageXOffset;
			scrollY += window.pageYOffset;
	}
	var x = Math.round((getInsideWindowWidth()/2) -
	(getObjectWidth(obj)/2)) + scrollX;
	var y = Math.round((getInsideWindowHeight()/2) -
			(getObjectHeight(obj)/2)) + scrollY;
	var results = [x,y];
	return results;
}