当我在带有通过@ font-face加载的字样的画布中绘制文本时，文本无法正确显示。它根本不显示(在Chrome 13和Firefox 5)，或字体错误(Opera 11)。这种类型的意外行为仅发生在带有字体的第一个绘图。之后一切工作正常。
它是标准的行为还是什么？
谢谢。
PS：以下是测试用例的源代码
<!DOCTYPE html>
<html>
<head>
<Meta charset="UTF-8">
<title>@font-face and <canvas></title>
<style id="css">
@font-face {
font-family: 'Press Start 2P';
src: url('fonts/Pressstart2P.ttf');
}
</style>
<style>
canvas,pre {
border: 1px solid black;
padding: 0 1em;
}
</style>
</head>
<body>
<h1>@font-face and <canvas></h1>
<p>
Description: click the button several times,and you will see the problem.
The first line won't show at all,or with a wrong typeface even if it does.
<strong>If you have visited this page before,you may have to refresh (or reload) it.</strong>
</p>
<p>
<button id="draw">#draw</button>
</p>
<p>
<canvas width="250" height="250">
Your browser does not support the CANVAS element.
Try the latest Firefox,Google Chrome,Safari or Opera.
</canvas>
</p>
<h2>@font-face</h2>
<pre id="view-css"></pre>
<h2>Script</h2>
<pre id="view-script"></pre>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script id="script">
var x = 30,y = 10;
$('#draw').click(function () {
var canvas = $('canvas')[0],ctx = canvas.getContext('2d');
ctx.font = '12px "Press Start 2P"';
ctx.fillStyle = '#000';
ctx.fillText('Hello,world!',x,y += 20);
ctx.fillRect(x - 20,y - 10,10,10);
});
</script>
<script>
$('#view-css').text($('#css').text());
$('#view-script').text($('#script').text());
</script>
</body>
</html>
解决方法
绘制画布必须发生，并在您调用fillText方法时立即返回。但是，浏览器尚未从网络加载字体，这是一个后台任务。所以它必须回到它有可用的字体。
如果要确保字体可用，请在页面上预加载一些其他元素，例如：
<div style="font-family: Pressstart;">.</div>