jQuery.parallax.coffee

jQuery.parallax.coffee

###
jQuery.parallax

by ken210.com

Based on homonymous plugin by Ian Lunn

Author URL: http://www.ianlunn.co.uk/
Plugin URL: http://www.ianlunn.co.uk/plugins/jquery-parallax/

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


$.fn.parallax = (options) ->
	defaults =
		bgPosX: '50% '
		bgPosY: '50%'
		adjuster: 0
		inertia: 0.1
		outerHeight: true
		mode: 'backgroundPosition'

	$.extend(defaults, options)
	
	@each ->

		self = $(this)
		top = self.position().top
		height = if defaults.outerHeight then self.outerHeight(true) else self.height()
		
		# caching usefull props
		mode = defaults.mode
		bgPosX = defaults.bgPosX
		adjuster = defaults.adjuster
		inertia = defaults.inertia
		
		getStyle = (now) ->
			
			output = ''
			expression = Math.round((adjuster - height - now) * inertia)
			
			if (mode == 'backgroundPosition')
				output = bgPosX + expression + 'px'
			else
				output = parseInt(top + (top - expression)) + 'px'
			
			return output
		
		onScrolled = () ->
			now = $(scrollContainer).scrollTop()
			self.css(mode, getStyle(now))
			###
			cssObj = {}
			cssObj[mode] = getStyle(now)
			self.stop().animate(cssObj, 300)
			###
		$(scrollContainer).bind(scrollEvent, onScrolled)