[Public WebGL] Firefox 4 and blacklist reporting

[Arthur Blume <arthurb@google.com>]

Hi all -- I work on Google Body. Our latest "check WebGL capabilities" code will look approximately like this:

    *    *    *

// 0 = OK. 1 = no GL. 2 = GL couldn't initialize. Other = error text.

function testGL() {

  try {

    if (!window.WebGLRenderingContext) { return 1; }

    var canvas = document.getElementById('gltest');

    var gl = canvas.getContext('webgl');

    if (!gl) {

      gl = canvas.getContext('experimental-webgl');

    }

    if (!gl) { return 2; }

    return 0;

  } catch(err) {

    // [report err.message]

  }

}

    *    *    *

Using FF4/Mac on OS X 10.5.8, the above throws an exception, with err.message =

    "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMHTMLCanvasElement.getContext]"

I understand from the Firefox blocklist wiki page that Firefox is blacklisting WebGL. I'm curious why this is being reported via an exception. The problem I'm having is that I want to show different UI for these two cases:

  - GL is blacklisted (=> fine, can take user to troubleshooting page and coach them through it)

  - A _javascript_ error occurred (=> not fine, need to investigate)

and I'm not sure what the best way going forward is to distinguish those cases.

Any thoughts?