if (!sb_windowTools) { var sb_windowTools = new Object(); };

sb_windowTools = {
	scrollBarPadding: 17, // padding to assume for scroll bars

	// EXAMPLE METHODS

	// center an element in the viewport
	centerElementOnScreen: function(element) {
		
		var pageDimensions = this.updateDimensions();
		element.style.top = ((this.pageDimensions.verticalOffset() + this.pageDimensions.windowHeight() / 2) - (this.scrollBarPadding + element.offsetHeight / 2)) + 'px';
		element.style.left = ((this.pageDimensions.windowWidth() / 2) - (this.scrollBarPadding + element.offsetWidth / 2)) + 'px';
		element.style.top = "50px";
		element.style.position = 'fixed';
	},

	// INFORMATION GETTERS

	// load the page size, view port position and vertical scroll offset
	updateDimensions: function() {
		this.updatePageSize();
		this.updateWindowSize();
		this.updateScrollOffset();
	},

	// load page size information
	updatePageSize: function() {
		// document dimensions
		var viewportWidth, viewportHeight;
		if (window.innerHeight && window.scrollMaxY) {
			viewportWidth = document.body.scrollWidth;
			viewportHeight = window.innerHeight + window.scrollMaxY;
		} else if (document.body.scrollHeight > document.body.offsetHeight) {
			// all but explorer mac
			viewportWidth = document.body.scrollWidth;
			viewportHeight = document.body.scrollHeight;
		} else {
			// explorer mac...would also work in explorer 6 strict, mozilla and safari
			viewportWidth = document.body.offsetWidth;
			viewportHeight = document.body.offsetHeight;
		};
		this.pageSize = {
			viewportWidth: viewportWidth,
			viewportHeight: viewportHeight
		};
	},

	// load window size information
	updateWindowSize: function() {
		// view port dimensions
		var windowWidth, windowHeight;
		if (self.innerHeight) {
			// all except explorer
			windowWidth = self.innerWidth;
			windowHeight = self.innerHeight;
		} else if (document.documentElement && document.documentElement.clientHeight) {
			// explorer 6 strict mode
			windowWidth = document.documentElement.clientWidth;
			windowHeight = document.documentElement.clientHeight;
		} else if (document.body) {
			// other explorers
			windowWidth = document.body.clientWidth;
			windowHeight = document.body.clientHeight;
		};
		this.windowSize = {
			windowWidth: windowWidth,
			windowHeight: windowHeight
		};
	},

	// load scroll offset information
	updateScrollOffset: function() {
		// viewport vertical scroll offset
		var horizontalOffset, verticalOffset;
		if (self.pageYOffset) {
			horizontalOffset = self.pageXOffset;
			verticalOffset = self.pageYOffset;
		} else if (document.documentElement && document.documentElement.scrollTop) {
			// Explorer 6 Strict
			horizontalOffset = document.documentElement.scrollLeft;
			verticalOffset = document.documentElement.scrollTop;
		} else if (document.body) {
			// all other Explorers
			horizontalOffset = document.body.scrollLeft;
			verticalOffset = document.body.scrollTop;
		};
		this.scrollOffset = {
			horizontalOffset: horizontalOffset,
			verticalOffset: verticalOffset
		};
	},

	// INFORMATION CONTAINERS

	// raw data containers
	pageSize: {},
	windowSize: {},
	scrollOffset: {},

	// combined dimensions object with bounding logic
	pageDimensions: {
		pageWidth: function() {
			return sb_windowTools.pageSize.viewportWidth > sb_windowTools.windowSize.windowWidth ?
				sb_windowTools.pageSize.viewportWidth :
				sb_windowTools.windowSize.windowWidth;
		},
		pageHeight: function() {
			return sb_windowTools.pageSize.viewportHeight > sb_windowTools.windowSize.windowHeight ?
				sb_windowTools.pageSize.viewportHeight :
				sb_windowTools.windowSize.windowHeight;
		},
		windowWidth: function() {
			return sb_windowTools.windowSize.windowWidth;
		},
		windowHeight: function() {
			return sb_windowTools.windowSize.windowHeight;
		},
		horizontalOffset: function() {
			return sb_windowTools.scrollOffset.horizontalOffset;
		},
		verticalOffset: function() {
			return sb_windowTools.scrollOffset.verticalOffset;
		}
	}
};

function centerMe(elem) {
	// center the test element on the screen
	sb_windowTools.centerElementOnScreen(document.getElementById(elem));
	window.onscroll = function() {
		// update the scroll information
		sb_windowTools.updateScrollOffset();
		// update the vertical position of the element
		var element = document.getElementById(elem);
		element.style.top = ((sb_windowTools.pageDimensions.verticalOffset() + sb_windowTools.pageDimensions.windowHeight() / 2) - (sb_windowTools.scrollBarPadding + element.offsetHeight / 2)) + 'px';
	};
}
function cancelMe() {
	// reset the test element on the screen
	document.getElementById('test').style.position = '';
	window.onscroll = null;
}