//
// JavaScript Image slideshow
// Patrick Fitzgerald, fitz@csicop.org
// This code can be found on the following web page:
// http://www.csicop.org/~fitz/www/slideshow/

//
// This first SCRIPT section belongs in the HEAD section of your HTML file.
//


function slideshow( slideshowname, image )
//
// Constructor function for the slideshow object.
// this.name = the name of your new object,
// this.image = an image object
// this.timeout = an integer (milliseconds)
//
{
  // Public
  this.name = slideshowname
  this.image = image  // image object, like document.images.imagename
  this.timeout = 5000 // default, milliseconds

  // These are private
  this.images = new Array()
  this.links = new Array()
  this.current = 0
  this.timeoutid = 0

  // Public methods
  this.add_slide = slideshow_add_slide
  this.set_image = slideshow_set_image

  this.play = slideshow_play
  this.pause = slideshow_pause

  this.next = slideshow_next
  this.previous = slideshow_previous

  this.hotlink = slideshow_goto

  // Private methods
  this.loop = slideshow_loop
  this.valid_image = slideshow_valid_image
}


function slideshow_add_slide(image_url,link_url)
{
  // If this version of JavaScript does not allow us to
  // change images, then we can't do the slideshow.
  if (!document.images)
    return

  var i = this.images.length;

  this.images[i] = new Image()
  this.images[i].src = image_url

  this.links[i] = link_url
}


function slideshow_set_image( imageobject )
{
  // If this version of JavaScript does not allow us to
  // change images, then we can't do the slideshow.
  if (!document.images)
    return

  // Set the "image" property of the slideshow object.
  this.image = imageobject
}


function slideshow_valid_image()
// Returns 1 if a valid image has been set for the slideshow
{
  if (!this.image)
  {
    // Stop the slideshow
    this.pause

    // Display an error message
    window.status = "Error: slideshow image not initialized for " + this.name
        
    return 0
  }
  else
    return 1
}

function slideshow_goto()
{
  location.href = this.links[ this.current ]
}


function slideshow_next( )
{
  if (! this.valid_image()) return;

  // Increment the image number
  if (this.current < this.images.length - 1)
    this.current++
  else
    this.current = 0

  // Change the image.
  this.image.src = this.images[ this.current ].src
}


function slideshow_previous( )
{
  if (! this.valid_image()) return;

  // Decrement the image number
  if (this.current > 0)
    this.current--
  else
    this.current = this.images.length - 1

  // Change the image.
  this.image.src = this.images[ this.current ].src
}


function slideshow_loop( )
{
  // Go to the next image
  this.next( )

  // Keep playing the slideshow
  this.play( )
}

function slideshow_play( )
{
  // Set a timeout, then exit this function.
  // After the timeout the function will be called again.
  this.timeoutid = setTimeout( this.name + ".loop()", this.timeout)
}

function slideshow_pause( )
{
  if (this.timeoutid != 0)
  {
    clearTimeout(this.timeoutid)
    this.timeoutid = 0
  }
}