// TNC dynamic html slideshow JavaScript Document

/*==================================================*
 $Id: slideshow.js,v 1.16 2003/10/14 12:39:00 pat Exp $
 Copyright 2000-2003 Patrick Fitzgerald
 http://slideshow.barelyfitz.com/

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.
 *==================================================*/


//==================================================
// slide object
//==================================================
function slide(src,link,text,target,attr) {
  // This is the constructor function for the slide object.
  // It is called automatically when you create a new slide object.
  // For example:
  // s = new slide();

  // Image URL
  this.src = src;

  // Link URL
  this.link = link;

  // Text to display
  this.text = text;

  // Photo credit
  this.target = target;

  // Custom duration for the slide, in milliseconds.
  // This is an optional parameter.
  // this.timeout = 3000

  // Attributes for the target window:
  // 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
  // Example: "width=200,height=300"


  // Create an image object for the slide
  if (document.images) {
    this.image = new Image();
  }

  // Flag to tell when load() has already been called
  this.loaded = false;

  //--------------------------------------------------
  this.load = function() {
    // This method loads the image for the slide

    if (!document.images) { return; }

    if (!this.loaded) {
      this.image.src = this.src;
      this.loaded = true;
    }
  }
  
 
}

//==================================================
// slideshow object
//==================================================
function slideshow( slideshowname ) {
  // This is the constructor function for the slideshow object.
  // It is called automatically when you create a new object.
  // For example:
  // ss = new slideshow("ss");

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


  // Number of images to pre-fetch.
  // -1 = preload all images.
  //  0 = load each image as it is used.
  //  n = pre-fetch n images ahead of the current image.
  // I recommend preloading all images unless you have large
  // images, or a large amount of images.
  this.prefetch = -1;

  // IMAGE element on your HTML page.
  // For example, document.images.SLIDES1IMG
  this.image;

  // ID of a DIV element on your HTML page that will contain the text.
  // For example, "slides2text"
  // Note: after you set this variable, you should call
  // the update() method to update the slideshow display.
  this.textid;

  // TEXTAREA element on your HTML page.
  // For example, document.SLIDES1FORM.SLIDES1TEXT
  // This is a depracated method for displaying the text,
  // but you might want to supply it for older browsers.
  this.textarea;



  // Hook functions to be called before and after updating the slide
  // this.pre_update_hook = function() { }
  // this.post_update_hook = function() { }

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


  //--------------------------------------------------
  // Public methods
  //--------------------------------------------------
  this.add_slide = function(slide) {
    // Add a slide to the slideshow.
    // For example:
    // SLIDES1.add_slide(new slide("s1.jpg", "link.html"))
  
    var i = this.slides.length;
  
    // Prefetch the slide image if necessary
    if (this.prefetch == -1) {
      slide.load();
    }

    this.slides[i] = slide;
  }

 



  //--------------------------------------------------
  this.update = function() {
    // This method updates the slideshow image on the page

    // Make sure the slideshow has been initialized correctly
    if (! this.valid_image()) { return; }
  
    

    // Convenience variable for the current slide
    var slide = this.slides[ this.current ];

    // Determine if the browser supports filters
    var dofilter = false;
    if (this.image &&
        typeof this.image.filters != 'undefined' &&
        typeof this.image.filters[0] != 'undefined') {
      dofilter = true;
    }

    // Load the slide image if necessary
    slide.load();    

    // Update the image.
    this.image.src = slide.image.src;

    // Play the image transition filters
    if (dofilter) {
      this.image.filters[0].Play();
    }

    // Update the text
    this.display_text();

    // Call the post-update hook function if one was specified
    if (typeof this.post_update_hook == 'function') {
      this.post_update_hook();
    }

    // Do we need to pre-fetch images?
    if (this.prefetch > 0) {

      var next, prev, count;

      // Pre-fetch the next slide image(s)
      next = this.current;
      prev = this.current;
      count = 0;
      do {

        // Get the next and previous slide number
        // Loop past the ends of the slideshow if necessary
        if (++next >= this.slides.length) next = 0;
        if (--prev < 0) prev = this.slides.length - 1;

        // Preload the slide image
        this.slides[next].load();
        this.slides[prev].load();

        // Keep going until we have fetched
        // the designated number of slides

      } while (++count < this.prefetch);
    }
  }





  //--------------------------------------------------
  this.next = function() {
    // This method advances to the next slide.

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

    this.update();
  }


  //--------------------------------------------------
  this.previous = function() {
    // This method goes to the previous slide.
  
    // Decrement the image number
    if (this.current > 0) {
      this.current--;
    } else if (this.repeat) {
      this.current = this.slides.length - 1;
    }
  
    this.update();
  }



  //--------------------------------------------------
  this.get_text = function() {
    // This method returns the text of the current slide
  
    return(this.slides[ this.current ].text);
  }


  //--------------------------------------------------
  this.get_all_text = function(before_slide, after_slide) {
    // Return the text for all of the slides.
    // For the text of each slide, add "before_slide" in front of the
    // text, and "after_slide" after the text.
    // For example:
    // document.write("<ul>");
    // document.write(s.get_all_text("<li>","\n"));
    // document.write("<\/ul>");
  
    all_text = "";
  
    // Loop through all the slides in the slideshow
    for (i=0; i < this.slides.length; i++) {
  
      slide = this.slides[i];
    
      if (slide.text) {
        all_text += before_slide + slide.text + after_slide;
      }
  
    }
  
    return(all_text);
  }


  //--------------------------------------------------
  this.display_text = function(text) {
    // Display the text for the current slide
  
    // If the "text" arg was not supplied (usually it isn't),
    // get the text from the slideshow
    if (!text) {
      text = this.slides[ this.current ].text;
    }
  
    // If a textarea has been specified,
    // then change the text displayed in it
    if (this.textarea && typeof this.textarea.value != 'undefined') {
      this.textarea.value = text;
    }

    // If a text id has been specified,
    // then change the contents of the HTML element
    if (this.textid) {

      r = this.getElementById(this.textid);
      if (!r) { return false; }
      if (typeof r.innerHTML == 'undefined') { return false; }

      // Update the text
      r.innerHTML = text;
    }
  }


  //--------------------------------------------------
  this.noscript = function() {
    // This method is not for use as part of your slideshow,
    // but you can call it to get a plain HTML version of the slideshow
    // images and text.
    // You should copy the HTML and put it within a NOSCRIPT element, to
    // give non-javascript browsers access to your slideshow information.
    // This also ensures that your slideshow text and images are indexed
    // by search engines.
  
    $html = "\n";
  
    // Loop through all the slides in the slideshow
    for (i=0; i < this.slides.length; i++) {
  
      slide = this.slides[i];
  
      $html += '<P>';
  
      if (slide.link) {
        $html += '<a href="' + slide.link + '">';
      }
  
      $html += '<img src="' + slide.src + '" ALT="slideshow image">';
  
      if (slide.link) {
        $html += "<\/a>";
      }
  
      if (slide.text) {
        $html += "<BR>\n" + slide.text;
      }
  
      $html += "<\/P>" + "\n\n";
    }
  
    // Make the HTML browser-safe
    $html = $html.replace(/\&/g, "&amp;" );
    $html = $html.replace(/</g, "&lt;" );
    $html = $html.replace(/>/g, "&gt;" );
  
    return('<pre>' + $html + '</pre>');
  }




  //--------------------------------------------------
  this.valid_image = function() {
    // Returns 1 if a valid image has been set for the slideshow
  
    if (!this.image)
    {
      return false;
    }
    else {
      return true;
    }
  }

  //--------------------------------------------------
  this.getElementById = function(element_id) {
    // This method returns the element corresponding to the id

    if (document.getElementById) {
      return document.getElementById(element_id);
    }
    else if (document.all) {
      return document.all[element_id];
    }
    else if (document.layers) {
      return document.layers[element_id];
    } else {
      return undefined;
    }
  }
}