CoffeeScript Parallax Scrolling

helpers.coffee

$.fn.translate = (x, y) ->
  translate = "translate(#{x}px, #{y}px)"
  this.css('-moz-transform', translate);
  this.css('-o-transform', translate);
  this.css('-ms-transform', translate);
  this.css('-webkit-transform', translate);
  this.css('transform', translate);

$.fn.translate3d = (x, y, z) ->
  translate3d = "translate3d(#{x}px, #{y}px, #{z}px)"
  this.css('-moz-transform', translate3d);
  this.css('-o-transform', translate3d);
  this.css('-ms-transform', translate3d);
  this.css('-webkit-transform', translate3d);
  this.css('transform', translate3d);

$.fn.parallax = (x, y) ->
  this.translate x, y

parallax.coffee

class Slide
  constructor: (slide) ->
    @el = $(slide.selector)
    @ratio = slide.ratio
    @number = slide.number
    @first = slide.first

    elements = @el.children('.parallax')
    @parallaxes = (new Pitch.Slide.Item(el) for el in elements)

  resize: (width) ->
    if width < 1024
      width = 1024
    @el.width(width)
    @el.height(width * @ratio)
    @el.find('.background').width(width)
    @el.find('.background').height(width * @ratio)
    @update()

  update: ->
    # this is fucking bullshit....
    if @first and @el.position().top isnt 0
      window.compasateOffset = @el.position().top

    @midpoint = @el.height() / 2
    @top = @el.position().top - window.compasateOffset
    @start = @top - @midpoint
    @end = @el.height() + @top + @midpoint
    @start = 0 if @first
  
  transition: (position) ->
    self = @
    for parallax in @parallaxes
      vspeed = parallax.vspeed()
      hspeed = parallax.hspeed()
      vcurrent = parallax.vcurrent()
      hcurrent = parallax.hcurrent()
      vgoto = vcurrent
      hgoto = hcurrent

      if position >= self.end
        vgoto = self.midpoint * 3 * vspeed
        hgoto = self.midpoint * 3 * hspeed

      if position <= self.start
        if self.first
          vgoto = 0
          hgoto = 0
        else
          vgoto = -self.midpoint * vspeed
          hgoto = -self.midpoint * hspeed

      if position < self.end and position > self.start
        if self.insection(self.position)
          vgoto += (position - self.position) * vspeed
          hgoto += (position - self.position) * hspeed
        else
          if self.isbelow(position)
            vgoto += (position - self.end) * vspeed
            hgoto += (position - self.end) * hspeed
          else if self.isabove(position)
            vgoto += (position - self.start) * vspeed
            hgoto += (position - self.start) * hspeed

      if position is self.top
        vgoto = 0
        hgoto = 0

      parallax.el.data 'vcurrent', vgoto
      parallax.el.data 'hcurrent', hgoto
      parallax.move hgoto, vgoto

    @position = position

  insection: (position) ->
    @start <= position and position <= @end

  isbelow: (position) ->
    @position > position

  isabove: (position) ->
    @position < position

class Parallax
  constructor: (el) ->
    @el = $(el)

  move: (x, y) ->
    @el.parallax x, y

  vspeed: ->
    @el.data 'vspeed'

  hspeed: ->
    @el.data 'hspeed'

  hcurrent: ->
    @el.data 'hcurrent'

  vcurrent: ->
    @el.data 'vcurrent'

class Slide.Item extends Parallax
  constructor: (el) ->
    super el