/*
Plugin: jQuery Parallax
Version 1.1
Author: Ian Lunn
Author URL: http://www.ianlunn.co.uk/
Plugin URL: http://www.ianlunn.co.uk/plugins/jquery-parallax/

Personal Usage License
-----------------------

License: http://creativecommons.org/licenses/by-sa/3.0/ (Attribution Share Alike). Please attribute work to Ian Lunn simply by leaving these comments in the source code or if you'd prefer, place a link on your website to http://www.ianlunn.co.uk/.

Dual licensed under the MIT and GPL licenses:
http://www.opensource.org/licenses/mit-license.php
http://www.gnu.org/licenses/gpl.html


Commercial Usage License
-------------------------

Please contact http://www.ianlunn.co.uk/contact.php for a license to use this plugin commercially
*/


(function( $ ){
	$.fn.moveRelative = function(xpos, adjuster, inertia, outerHeight) {
			
function inView(pos, element){
	
	element.each(function(){ //for each selector, determine whether it's inview and run the move() function
		
		var element = $(this);
		var top = element.offset().top;
		
		if(outerHeight == true){
			var height = element.outerHeight(true);
		}else{
			var height = element.height();
		}
		
		//above & in view
		if(top + height >= pos && top + height - windowHeight < pos){
			move(pos, height);
			element.removeClass('noview');
		}
				
		//full view
		if(top <= pos && (top + height) >= pos && (top - windowHeight) < pos && top + height - windowHeight > pos){
			move(pos, height);
			element.removeClass('noview');
		}
		
		//below & in view
		if(top + height > pos && top - windowHeight < pos && top > pos){
			move(pos, height);
			element.removeClass('noview');
		}
	});
}		
		
		var $window = $(window);
		var windowHeight = $(window).height();
		var pos = $window.scrollTop(); //position of the scrollbar
		var $this = $(this);
		
		//setup defaults if arguments aren't specified
		if(xpos == null){xpos = "50%"}
		if(adjuster == null){adjuster = 0}
		if(inertia == null){inertia = 0.1}
		if(outerHeight == null){outerHeight = true}
		
		height = $this.height();
		$this.css({'backgroundPosition': newPos(xpos, outerHeight, adjuster, inertia)}); 
		
		function newPos(xpos, windowHeight, pos, adjuster, inertia){
			return xpos + Math.round((-((windowHeight + pos) - adjuster) * inertia)) + "px";
		}
		
		//function to be called whenever the window is scrolled or resized
		function move(pos, height){ 
				$this.css({'backgroundPosition': newPos(xpos, height, pos, adjuster, inertia)}); 
		}
		$window.bind('scroll', function(){ //when the user is scrolling...
			var pos = $window.scrollTop(); //position of the scrollbar
			inView(pos, $this);
			
			$('#pixels').html(pos);
		})
	}
})( jQuery );