/*
Sine scrolling text script
By Mark Baker (mark.baker@usa.net)
Permission granted to Dynamicdrive.com to include script in archive 
For 100's of free DHTML scripts, visit Dynamicdrive.com
*/


// globals
var initialx, initialy, scrolltext;
var frame = 0, frame2 = 0.5;
var amplitude1 = 50, amplitude2 = 30;
var offset = 0.2, speed = 0.2, speed2 = 0.35;
var offset2 = 0.6;
var scrollspeed = 6;
var charwidth = 30;

var twopi = Math.PI * 2;
var chracters, position, numvisible, nextchar, firstchar;
var skipsteps = 1;
var delaytimer = 0;
var interval;

// function to create sine scroller
function sinescroll (x, y, value, number_of_chars)
{
	// setup globals
	scrolltext = new String(value);
	initialx = x;
	initialy = y;
	numvisible = number_of_chars;
	nextchar = numvisible;
	firstchar = 0;

	// create fixed-size arrays of characters and positions
	characters = new Array(numvisible);
	position = initialx;

	// write DIVs to hold characters
	for (var i = 0; i < numvisible; i++)
	{
		document.write('<DIV ID="character" STYLE="position:absolute;top:',
			initialy, ';left:-10000', //(initialx + i * charwidth),
			';width=', charwidth, ';height=30;" ><p class=scroll>', 
			scrolltext.charAt(i), '</p></DIV>');
	}
}

// animation function
function step ()
{
	// increment counters
	frame += speed;
	frame2 += speed2;

	// delay timer
	if (delaytimer > 0)
	{
		delaytimer--;
	}
	else
	{
		// update position
		position -= scrollspeed;
	}

	// check for 'offscreen'
	if (position < (initialx - charwidth))
	{
		while (scrolltext.charAt(nextchar) == '|')
		{
			delaytimer += 90;
			nextchar++;
		}

		// set nextchar into characters array
		characters[firstchar].innerHTML = '<p class=scroll>' + scrolltext.charAt(nextchar) + '</p>';

		// update nextchar
		nextchar++;

		// check for wrap-around
		if (nextchar >= scrolltext.length)
		{
			nextchar = 0;
		}

		// change position and counters by offset
		position += charwidth;
		frame += offset;
		frame2 += offset2;

		// update firstchar
		firstchar++;

		if (firstchar >= numvisible)
		{
			firstchar = 0;
		}
	}

	// wrap-around counters
	if (frame > twopi) frame -= twopi;
	if (frame2 > twopi) frame2 -= twopi;

	// set up loop variables
	var angle = frame;
	var angle2 = frame2;
	var pos = position;

	// update the html
	for (var i=firstchar; i < numvisible; i++)
	{
		characters[i].style.left = pos;
		characters[i].style.top = initialy + amplitude1 * Math.sin(angle) + amplitude2 * Math.sin(angle2);
		angle += offset; 
		angle2 += offset2;
		pos += charwidth;
	}

	for (var i=0; i < firstchar; i++)
	{
		characters[i].style.left = pos;
		characters[i].style.top = initialy + amplitude1 * Math.sin(angle) + amplitude2 * Math.sin(angle2);
		angle += offset; 
		angle2 += offset2;
		pos += charwidth;
	}
}

// start the animation
function start ()
{
if (!document.all)
return
	// get all of the DIV tags into an array (IE only?)
	characters = document.all.item('character');
	
	// setup timeout to call this function again
	interval = window.setInterval("step();", 20);
}

// stop the animation
function stop ()
{
if (!document.all)
return
	if (interval)
		clearInterval(interval);
}

window.onload=start
window.onunload=stop


// create the scroller
if (document.all)
sinescroll(30, 100, "                **** Remember those great Amiga demos? You can recreate the endless sine-scrolling messages in JavaScript! Conversions to Netscape welcome, as are improvements - email to mark.baker@usa.net This script can cope with ** delays ** | and even longer delays - ** heloooo **||| Feel free to use it and rip it off (well you're going to anyway...) TTFN... ****     ", 15);