/* $Id: slideshow.js,v 1.1 2002/10/02 18:49:42 shaggy Exp $ */

/*
Copyright (c) 2001, 2002 by Martin Tsachev. All rights reserved.
http://www.mt-dev.com

This script uses JavaScript library functions by Peter-Paul Koch
http://www.xs4all.nl/~ppk/

Redistribution and use in source and binary forms,
with or without modification, are permitted provided
that the conditions available at
http://www.opensource.org/licenses/bsd-license.html
are met.
*/

var slides = new Array('slide0', 'slide1', 'slide2');
var layers = new Array();
var slideHeight = new Array();
var slideWidth = new Array();

var fade = false;
var curImg = 0; // index of the array entry
var lastImg = 0;
var firstFade = true;

var clipTop, clipWidth, clipBottom;
var clipHeight, middle;
var delay = 20;
var diff = 4;
var timer = null;
var init = false;
var DHTML = (document.getElementById || document.all || document.layers);

window.onload = init_layers;
function init_layers() {
	if (!DHTML) {
		alert('Your browser is not DHTML capable');
		return;
	}
	for (i = 0; i < slides.length; i++) {
		layers[i] = new getObj(slides[i]);

		if (document.layers) {
			height = layers[i].style.clip.bottom;
			width = layers[i].style.clip.right;
		} else
		if (document.getElementById || document.all) {
			height = layers[i].obj.offsetHeight;
			width = layers[i].obj.offsetWidth;
		}
		slideHeight[i] = height;
		slideWidth[i] = width;
	}

	prepLyr(0, true);
	clip = layers[0].style.clip;
	if (clip == 'rect()' || !clip) {
		canFade = false;
	} else {
		canFade = true;
	}
	init = true;
}

// getObj function by Peter-Paul Koch, http://www.xs4all.nl/~ppk/
function getObj(name) {
	if (document.getElementById) {
		this.obj = document.getElementById(name);
		this.style = document.getElementById(name).style;
	} else
	if (document.all) {
		this.obj = document.all[name];
		this.style = document.all[name].style;
	} else
	if (document.layers) {
		this.obj = document.layers[name];
		this.style = document.layers[name];
	}
}

function visib(objName, flag) {
	x = new getObj(objName);
	x.style.visibility = (flag) ? 'visible' : 'hidden';
}

function setFade(switchFade) {// Fade switch function
	if (switchFade) {
		if (!canFade) {
			alert('Your browser does not support fading');
			return;
		}
		prepLyr(curImg, true);
	} else { // No fade
		if (timer) clearTimeout(timer);

		for (var i = 0; i < slides.length; i++) {
			prepLyr(i, true);
			if (slides[i] != slides[curImg])
				layers[i].style.visibility = 'hidden';
		}
	}
	fade = switchFade;
}

function changeSlide(change) {
	if (!init) {
		alert('Wait for the page to load');
		return;
	}
	if (!DHTML) return;

	curImg += change;
	if (curImg < 0) curImg = slides.length-1;
	else
	if (curImg >= slides.length) curImg = 0;

	if (fade) {
		firstFade = true;
		prepLyr(lastImg, true);
		fadeLayer(lastImg, diff);
	} else {
		layers[lastImg].style.visibility = 'hidden';
		layers[curImg].style.visibility = 'visible';
	}
	lastImg = curImg;
}

function prepLyr(layer, vis) {
	if (!DHTML) return;	
	
	x = layers[layer];
	clipHeight = slideHeight[layer];
	clipWidth = slideWidth[layer];
	middle = Math.round(clipHeight/2);

	if (document.layers) {
		if (vis) {
			clipTop = 0;
			clipBottom = clipHeight;
		} else {
			clipBottom = middle;
			clipTop = middle;
		}

		x.style.clip.top = clipTop;
		x.style.clip.left = 0;
		x.style.clip.right = clipWidth;
		x.style.clip.bottom = clipBottom;
		x.style.visibility = 'show';
	} else

	if (document.getElementById || document.all) {
		if (vis) {
			clipTop = 0;
			clipBottom = clipHeight;
		} else {
			clipTop = middle;
			clipBottom = middle;
		}
		x.style.clip = 'rect('+clipTop+' '+clipWidth+' '+ clipBottom +' 0)';
		x.style.visibility = 'visible';
	}
}

function fadeLayer(layer, diff) {
	curLayer = layers[layer];
	realFade(diff);
}

function realFade(diff) {
	clipTop += diff;
	clipBottom -= diff;
	if (clipTop < 0 || clipBottom > clipHeight || clipTop > middle) {
		if (clipTop > middle) curLayer.style.visibility = 'hidden';
		if (firstFade) {
			firstFade = false;
			prepLyr(curImg, false);
			fadeLayer(curImg, -diff);
		}
		return;
	}

	if (document.getElementById || document.all) {
		clipstring = 'rect('+clipTop+' '+clipWidth+' '+clipBottom+' 0)'
		curLayer.style.clip = clipstring;
	}
	else
	if (document.layers) {
		curLayer.style.clip.top = clipTop;
		curLayer.style.clip.bottom = clipBottom;
	}
	timer = setTimeout('realFade(' + diff + ')', delay);
}