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HTML5 Canvas crashes Firebug - don't know why! Please help :E

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Hi this is my first time on the forum, hopefully I haven't done it wrong :E

 

I have found that this script is causing me problems - it seems to work fine under Firefox, Chrome, Opera, but when I launch Firebug, then refresh the page, I get hangs. The debugging/error reporting doesn't help me much.

 

Is it possible that the Math.random usage is crashing it?

 

I have isolated the crash down to the following script. This can be saved as a html file, you need to supply a png image, preferebly with some transparency (I would supply one but I don't want to link to a clients unreleased files - heres a random smiley face http://www.wpclipart...miley_large.png)

 

It needs to be put in /images/ relative to the html, and names 'logo.png'.

 

<DOCTYPE html>

<html>

<head>

<script type="text/javascript">

 

var EML = new Image(); // Logo

EML.src = "images/logo.png";

 

const FPS=20;

var canvas;

var context2D;

 

function logo() {

this.x = 100; // x pos

this.y = 100; // y pos

this.op = 1; // opacity

this.xvel = 1; // velocity

this.yvel = 1;

this.sz = 1; // scale

}

 

var logos = new Array();

 

window.addEventListener('resize', resizeCanvas, false);

window.onload = init;

 

function resizeCanvas() {

canvas.width = window.innerWidth;

canvas.height = window.innerHeight;

}

 

function rand($number) {

$number = Math.random()*$number;

return $number;

}

 

function setLogos() {

for (xx = 0; xx < 9; xx++) {

logos[xx] = new logo;

$currentWidth = canvas.width;

logos[xx].x = rand($currentWidth)-EML.width;

$currentHeight = canvas.height;

logos[xx].y = rand($currentHeight)-EML.height;

logos[xx].op = rand(1);

logos[xx].sz = rand(1);

logos[xx].xvel = rand(1)-0.5;

logos[xx].yvel = rand(1)-0.5;

 

if (logos[xx].x < 0 || logos[xx].y < 0 ||

logos[xx].x > (canvas.width-EML.width) ||

logos[xx].y > (canvas.height-EML.height)||

(logos[xx].velx > -0.1 && logos[xx].velx < 0.1) ||

(logos[xx].vely > -0.1 && logos[xx].vely < 0.1))

{

xx -= 1;

}

}

}

 

function init() {

canvas = document.getElementById('canvas');

context2D = canvas.getContext('2d');

resizeCanvas();

 

setLogos();

 

setInterval(draw, 1000/FPS);

}

 

function draw() {

update();

 

context2D.clearRect(0, 0, canvas.width, canvas.height);

 

for (xx = 0; xx < logos.length; xx++){

context2D.globalAlpha = logos[xx].op;

context2D.drawImage(EML, logos[xx].x, logos[xx].y, (EML.width*logos[xx].sz), (EML.height*logos[xx].sz));

}

 

}

 

function update() {

 

for (xxx = 0; xxx < logos.length; xxx++){

logos[xxx].x += (logos[xxx].xvel);

logos[xxx].y += (logos[xxx].yvel);

if (logos[xxx].x > (canvas.width)){

logos[xxx].x = (0-(EML.width*logos[xxx].sz));

}

if (((logos[xxx].x+(EML.width*logos[xxx].sz)) < 0) && (logos[xxx].xvel < 0)){

logos[xxx].x = canvas.width;

}

if (logos[xxx].y > (canvas.height)){

logos[xxx].y = (0-(EML.height*logos[xxx].sz));

}

if (((logos[xxx].y+(EML.height*logos[xxx].sz)) < 0) && (logos[xxx].yvel < 0)){

logos[xxx].y = canvas.height;

}

}

 

}

</script>

<style type="text/css">

 

#canvas {

width:100%;

height:100%;

background:none;

margin:0px;

padding:0px;

}

 

body {

background-color:green;

}

</style>

</head>

<body>

 

<canvas id="canvas">

Browser not compatible with canvas.

</canvas>

</body>

</html>

Edited by RickyT23

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