webshim polyfill canvas won't work in IE7 mode

StackOverflow https://stackoverflow.com/questions/6074167

题

I am having problems getting the webshims plugin canvas polyfill to work.

I get the following error in IE9 using IE7 mode:

  SCRIPT438: Object doesn't support property or method 'fillRect'
  problem.html, line 21 character 7

when I try to run this code:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
 <head>
    <title>DealingTree</title>
    <meta http-equiv="Content-type" content="text/html;charset=utf-8"/>
    <script type="text/javascript" src="/js/modernizr.js"> </script>
    <script type="text/javascript" src="/js/jquery.js"> </script>
    <script type="text/javascript" src="/js/sssl.js"> </script>
    <script type="text/javascript" src="/js/webshims/js-webshim/minified/polyfiller.js"> </script>
  </head>
  <body>
    <canvas id="savings" height="350" width="700"> </canvas>
    <script type="text/javascript">
      //<![CDATA[
      window.FlashCanvasOptions = { disableContextMenu: true };
      $.webshims.setOptions( 'canvas', { type: 'flashpro' } );
      $.webshims.polyfill('canvas');
      var canvas = $('#savings');
      var context = canvas.getContext('2d');
      context.fillStyle='#F00';
      context.fillRect(0,0,700,350);
      //]>
    </script>
  </body>
</html>

The problem happens whether I use the default (excanvas) or flashpro.

UPDATE: It appears to me that getContext() is returning a jQuery object instead of a context.

Help, please?

有帮助吗？

解决方案

I received the following explanation from the plugin author, Alexander Farkas, via email:

The problem is the following. Webshims does async polyfilling using a script loader. Which is good for performance in modern browsers. This also means, that you have to wait untill the canvas feature is ready.

Your code should be wrapped in a domready event and everything is fine:

window.FlashCanvasOptions = { disableContextMenu: true };
$.webshims.setOptions( 'canvas', { type: 'flashpro' } );
$.webshims.polyfill('canvas');
$(function(){
     var canvas = $('#savings');
     var context = canvas.getContext('2d');
     context.fillStyle='#F00';
     context.fillRect(0,0,700,350);
});

You find more informations about your problem in the documentation @ http://afarkas.github.com/webshim/demos/index.html#polyfill-ready

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