/*
 * (c) 2007 mirek at ringley dot co dot uk
 * Usage:
 *   <img src="/images/button.gif" onmouseover="Element.hoverImage(this)" onmouseout="Element.unhoverImage(this)" />
 */

Element.isHoverImage = function(element) {
  element = $(element)
  var i = element.src.lastIndexOf('.')
  return element.src.substring(i-6, i) == '_hover'
}

Element.hoverImage = function(element) {
  element = $(element)
  if (!Element.isHoverImage(element)) {
    var i = element.src.lastIndexOf('.')
    element.src = element.src.substring(0, i) + '_hover.' + element.src.substring(i+1)
  }
  return element
}

Element.unhoverImage = function(element) {
  element = $(element)
  if (Element.isHoverImage(element)) {
    var i = element.src.lastIndexOf('.')
    element.src = element.src.substring(0, i-6) + element.src.substring(i) // -6 stands for strlen('_hover')
  }
  return element
}