// 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/

// There are two objects defined in this file:
// "slide" - contains all the information for a single slide
// "slideshow" - consists of multiple slide objects and runs the slideshow

//==================================================
// First define the "slide" object.
//
function slide(image_url,link,text,window,attr)
{
  // Public variables

  // image object for the slide
  this.image = new Image()
  this.image.src = image_url

  // URL to open when the slide is clicked
  this.link = link

  // Text that displays for the slide (optional)
  this.text = text

  // The following variables are optional.
  // If you want the link to open in a new window set these.

  
  // Name of the target window ("_blank")
  this.window_name = window

  // Attributes for the target window
  // see window.open() for values
  // ("width=640,height=640")
  this.window_attr = attr

  // Public methods
  this.hotlink = slide_hotlink
}

function slide_hotlink()
{
  // If a window name was specified, open a new window
  if (this.window_name) {

    // If window attributes are specified, use them to open the new window
    if (this.window_attr) {
      window.open(this.link, this.window_name, this.window_attr);

    // If window attributes are not specified, do not use them
    // (this will copy the attributes from the originating window)
    } else {
      window.open(this.link, this.window_name);
    }

  // Else open the hotlink in the current window
  } else {

    location.href = this.link
  }
}


//==================================================
// Next define the "slideshow" object
//
function slideshow( slideshowname )
{
  // Public

  // Name of this object
  // (required if you want your slideshow to auto-play)
  // For example, "SLIDES1"
  this.name = slideshowname

  // The image object on your HTML page
  // for example, document.images.SLIDES1IMG
  this.image

  // The textarea object on your HTML page (optional)
  // for example, document.SLIDES1FORM.SLIDES1TEXT
  this.textarea

   // The number of milliseconds to pause between slides
  this.timeout = 3000

  // These are private variables
  this.slides = new Array()
  this.current = 0
  this.timeoutid = 0

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

  this.play = slideshow_play
  this.pause = slideshow_pause

  this.next = slideshow_next
  this.previous = slideshow_previous

  this.get_text = slideshow_get_text
  this.display_text = slideshow_display_text
  this.hotlink = slideshow_hotlink

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


function slideshow_add_slide( slide )
// for example:
// SLIDES1.add_slide(new slide("s1.jpg", "link.html", "text"))
{
  // 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.slides.length;

  this.slides[i] = slide
}


function slideshow_set_textarea( textareaobject )
{
  // Set the "textarea" property of the slideshow object.
  this.textarea = textareaobject

  // Initialize the text in the textarea
  this.display_text();
}


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_hotlink()
//
// windowattributes can be:
// width=n,height=n,resizable=yes or no,scrollbars=yes or no,
// toolbar=yes or no,location=yes or no,directories=yes or no,
// status=yes or no,menubar=yes or no,copyhistory=yes or no
{
  this.slides[ this.current ].hotlink()
}


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

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

  // Change the image.
  this.image.src = this.slides[ this.current ].image.src

  // Change the text
  this.display_text()
}


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

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

  // Change the image.
  this.image.src = this.slides[ this.current ].image.src

  // Change the text
  this.display_text()
}


function slideshow_display_text(text)
{
  // If a textarea has been specified,
  // then this function changes the text displayed in it
  if (this.textarea) {

    if (text) {
      this.textarea.value = text
    } else {
      this.textarea.value = this.slides[ this.current ].text
    }
  }
}


function slideshow_get_text()
{
  return(this.slides[ this.current ].text)
}


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

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

function slideshow_play(timeout)
{
  // Make sure we're not already playing
  this.pause();

  // If a new timeout was specified (optional)
  // set it here
  if (timeout) {
    this.timeout = timeout
  }

  // After the timeout, call this.loop()
  this.timeoutid = setTimeout( this.name + ".loop()", this.timeout)
}

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