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I am modifying the HTML5 port of the game Jump'n'Bump to run on Apple and Android-based mobile devices. I use a cheap 1 GHz Cortex-A8 Android 4.0.3 tablet for testing. I have encountered strange behaviour in the system's Browser. I normally get a very low frame-rate of about 1 FPS (entire screen is re-drawn every frame, setTimeout is used...). However, when I add a <div> which has a position:fixed CSS attribute before the <canvas> tag, the frame-rate skyrockets and the game becomes playable.
Could someone please explain this odd phenomenon? Are there some rendering modes in the Android Browser which influence canvas performance? Is this a cross-platform issue? How do I make sure the page works efficiently in the user's browser?
An outline of the code I'm working on:
<!DOCTYPE html>
<html>
<title>Jump'n'Bump - HTML5</title>
<meta http-Equiv="Cache-Control" Content="no-cache">
<meta http-Equiv="Pragma" Content="no-cache">
<meta http-Equiv="Expires" Content="0">
<meta name="viewport" content = "width=400px, user-scaleable=no">
<!-- javascript files included here -->
<script type="text/javascript" src="main.js"></script>
<style type="text/css">
body { margin: 0px 0px 0xp 0px }
canvas { border: 0px solid black; }
img.resource { display:none; }
#fixed_div { position: fixed; width: 10px; height: 10px; left: 0px; top: 0px; }
#gameArea { position: absolute; left: 0px; top: 0px; width: 400px; height: 256px; background: red; }
canvas {
image-rendering: optimizeSpeed; // Older versions of FF
image-rendering: -moz-crisp-edges; // FF 6.0+
image-rendering: -webkit-optimize-contrast; // Webkit
image-rendering: optimize-contrast; // Possible future browsers.
-ms-interpolation-mode: nearest-neighbor; // IE
}
</style>
<body onload="init()" text="#FFFFFF" bgcolor="#000000">
<!-- image resources like this here: -->
<img class="resource" id='rabbits' src='rabbit.png'/>
<!-- *** remove the line below and the game slows down *** -->
<div id='fixed_div'></div>
<div id="gameArea"><canvas id="screen" width="400" height="256"></canvas></div>
</body>
</html>
300
In short, the canvas and WebGL are more performant than the DOM, and with third-party libraries, its ease-of-use is comparable; furthermore, growing browser support for additional web standards have the potential to further boost canvas performance.
SVG gives better performance with smaller number of objects or larger surface. Canvas gives better performance with smaller surface or larger number of objects. SVG can be modified through script and CSS. Canvas can be modified through script only.
The Canvas tab loaded in one second and takes up 30MB. It also takes up 13% of CPU time all of the time, regardless of whether or not one is looking at it. Video on the HTML page, while I am not moving objects, is actually perfectly smooth.
This issue is so curious.
Try using Request Animation Frame instead of setInterval (without the magic div, =])
function getRequestAnimFrame() {
var game = this;
// requestAnim shim layer by Paul Irish
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function(/* function */ callback, /* DOMElement */ element) {
window.setTimeout(callback, 1000 / fps);
};
}
Maybe this help to increase the perform.
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