ÿþ/**

 * jquery.scrollFollow.js

 * Copyright (c) 2008 Net Perspective (http://kitchen.net-perspective.com/)

 * Licensed under the MIT License (http://www.opensource.org/licenses/mit-license.php)

 * 

 * @author R.A. Ray

 *

 * @projectDescription	jQuery plugin for allowing an element to animate down as the user scrolls the page.

 * 

 * @version 0.4.0

 * 

 * @requires jquery.js (tested with 1.2.6)

 * @requires ui.core.js (tested with 1.5.2)

 * 

 * @optional jquery.cookie.js (http://www.stilbuero.de/2006/09/17/cookie-plugin-for-jquery/)

 * @optional jquery.easing.js (http://gsgd.co.uk/sandbox/jquery/easing/ - tested with 1.3)

 * 

 * @param speed		int - Duration of animation (in milliseconds)

 * 								default: 500

 * @param offset			int - Number of pixels box should remain from top of viewport

 * 								default: 0

 * @param easing		string - Any one of the easing options from the easing plugin - Requires jQuery Easing Plugin < http://gsgd.co.uk/sandbox/jquery/easing/ >

 * 								default: 'linear'

 * @param container	string - ID of the containing div

 * 								default: box's immediate parent

 * @param killSwitch	string - ID of the On/Off toggle element

 * 								default: 'killSwitch'

 * @param onText		string - killSwitch text to be displayed if sliding is enabled

 * 								default: 'Turn Slide Off'

 * @param offText		string - killSwitch text to be displayed if sliding is disabled

 * 								default: 'Turn Slide On'

 * @param relativeTo	string - Scroll animation can be relative to either the 'top' or 'bottom' of the viewport

 * 								default: 'top'

 * @param delay			int - Time between the end of the scroll and the beginning of the animation in milliseconds

 * 								default: 0

 */



( function( $ ) {

	

	$.scrollFollow = function ( box, options )

	{ 

		// Convert box into a jQuery object

		box = $( box );

		

		// 'box' is the object to be animated

		var position = box.css( 'position' );

		

		function ani()

		{		

			// The script runs on every scroll which really means many times during a scroll.

			// We don't want multiple slides to queue up.

			box.queue( [ ] );

		

			// A bunch of values we need to determine where to animate to

			var viewportHeight = parseInt( $( window ).height() );	

			var pageScroll =  parseInt( $( document ).scrollTop() );

			var parentTop =  parseInt( box.cont.offset().top );

			var parentHeight = parseInt( box.cont.attr( 'offsetHeight' ) );

			var boxHeight = parseInt( box.attr( 'offsetHeight' ) + ( parseInt( box.css( 'marginTop' ) ) || 0 ) + ( parseInt( box.css( 'marginBottom' ) ) || 0 ) );

			var aniTop;

			

			// Make sure the user wants the animation to happen

			if ( isActive )

			{

				// If the box should animate relative to the top of the window

				if ( options.relativeTo == 'top' )

				{

					// Don't animate until the top of the window is close enough to the top of the box

					if ( box.initialOffsetTop >= ( pageScroll + options.offset ) )

					{

						aniTop = box.initialTop;

					}

					else

					{

						aniTop = Math.min( ( Math.max( ( -parentTop ), ( pageScroll - box.initialOffsetTop + box.initialTop ) ) + options.offset ), ( parentHeight - boxHeight - box.paddingAdjustment ) );

					}

				}

				// If the box should animate relative to the bottom of the window

				else if ( options.relativeTo == 'bottom' )

				{

					// Don't animate until the bottom of the window is close enough to the bottom of the box

					if ( ( box.initialOffsetTop + boxHeight ) >= ( pageScroll + options.offset + viewportHeight ) )

					{

						aniTop = box.initialTop;

					}

					else

					{

						aniTop = Math.min( ( pageScroll + viewportHeight - boxHeight - options.offset ), ( parentHeight - boxHeight ) );

					}

				}

				

				// Checks to see if the relevant scroll was the last one

				// "-20" is to account for inaccuracy in the timeout

				if ( ( new Date().getTime() - box.lastScroll ) >= ( options.delay - 20 ) )

				{

					box.animate(

						{

							top: aniTop

						}, options.speed, options.easing

					);

				}

			}

		};

		

		// For user-initiated stopping of the slide

		var isActive = true;

		

		if ( $.cookie != undefined )

		{

			if( $.cookie( 'scrollFollowSetting' + box.attr( 'id' ) ) == 'false' )

			{

				var isActive = false;

				

				$( '#' + options.killSwitch ).text( options.offText )

					.toggle( 

						function ()

						{

							isActive = true;

							

							$( this ).text( options.onText );

							

							$.cookie( 'scrollFollowSetting' + box.attr( 'id' ), true, { expires: 365, path: '/'} );

							

							ani();

						},

						function ()

						{

							isActive = false;

							

							$( this ).text( options.offText );

							

							box.animate(

								{

									top: box.initialTop

								}, options.speed, options.easing

							);	

							

							$.cookie( 'scrollFollowSetting' + box.attr( 'id' ), false, { expires: 365, path: '/'} );

						}

					);

			}

			else

			{

				$( '#' + options.killSwitch ).text( options.onText )

					.toggle( 

						function ()

						{

							isActive = false;

							

							$( this ).text( options.offText );

							

							box.animate(

								{

									top: box.initialTop

								}, 0

							);	

							

							$.cookie( 'scrollFollowSetting' + box.attr( 'id' ), false, { expires: 365, path: '/'} );

						},

						function ()

						{

							isActive = true;

							

							$( this ).text( options.onText );

							

							$.cookie( 'scrollFollowSetting' + box.attr( 'id' ), true, { expires: 365, path: '/'} );

							

							ani();

						}

					);

			}

		}

		

		// If no parent ID was specified, and the immediate parent does not have an ID

		// options.container will be undefined. So we need to figure out the parent element.

		if ( options.container == '')

		{

			box.cont = box.parent();

		}

		else

		{

			box.cont = $( '#' + options.container );

		}

		

		// Finds the default positioning of the box.

		box.initialOffsetTop =  parseInt( box.offset().top );

		box.initialTop = parseInt( box.css( 'top' ) ) || 0;

		

		// Hack to fix different treatment of boxes positioned 'absolute' and 'relative'

		if ( box.css( 'position' ) == 'relative' )

		{

			box.paddingAdjustment = parseInt( box.cont.css( 'paddingTop' ) ) + parseInt( box.cont.css( 'paddingBottom' ) );

		}

		else

		{

			box.paddingAdjustment = 0;

		}

		

		// Animate the box when the page is scrolled

		$( window ).scroll( function ()

			{

				// Sets up the delay of the animation

				$.fn.scrollFollow.interval = setTimeout( function(){ ani();} , options.delay );

				

				// To check against right before setting the animation

				box.lastScroll = new Date().getTime();

			}

		);

		

		// Animate the box when the page is resized

		$( window ).resize( function ()

			{

				// Sets up the delay of the animation

				$.fn.scrollFollow.interval = setTimeout( function(){ ani();} , options.delay );

				

				// To check against right before setting the animation

				box.lastScroll = new Date().getTime();

			}

		);



		// Run an initial animation on page load

		box.lastScroll = 0;

		

		ani();

	};

	

	$.fn.scrollFollow = function ( options )

	{

		options = options || {};

		options.relativeTo = options.relativeTo || 'top';

		options.speed = options.speed || 500;

		options.offset = options.offset || 0;

		options.easing = options.easing || 'swing';

		options.container = options.container || this.parent().attr( 'id' );

		options.killSwitch = options.killSwitch || 'killSwitch';

		options.onText = options.onText || 'Turn Slide Off';

		options.offText = options.offText || 'Turn Slide On';

		options.delay = options.delay || 0;

		

		this.each( function() 

			{

				new $.scrollFollow( this, options );

			}

		);

		

		return this;

	};

})( jQuery );