SVG.Mask = SVG.invent({
  // Initialize node
  create: function() {
    this.constructor.call(this, SVG.create('mask'))

    // keep references to masked elements 
    this.targets = []
  }

  // Inherit from
, inherit: SVG.Container

  // Add class methods
, extend: {
    // Unmask all masked elements and remove itself
    remove: function() {
      // unmask all targets 
      for (var i = this.targets.length - 1; i >= 0; i--)
        if (this.targets[i])
          this.targets[i].unmask()
      this.targets = []

      // remove mask from parent 
      this.parent().removeElement(this)
      
      return this
    }
  }
  
  // Add parent method
, construct: {
    // Create masking element
    mask: function() {
      return this.defs().put(new SVG.Mask)
    }
  }
})


SVG.extend(SVG.Element, {
  // Distribute mask to svg element
  maskWith: function(element) {
    // use given mask or create a new one 
    this.masker = element instanceof SVG.Mask ? element : this.parent().mask().add(element)

    // store reverence on self in mask 
    this.masker.targets.push(this)
    
    // apply mask 
    return this.attr('mask', 'url("#' + this.masker.attr('id') + '")')
  }
  // Unmask element
, unmask: function() {
    delete this.masker
    return this.attr('mask', null)
  }
  
})