Detection of Errors

[Joe Cole]

Hi GWT Team,

We have been busy trying to deploy our application early beta to some
users and have run into lots of problems with loading the application.
I thought I would post this here and perhaps others can give their
input as to how they solve these issues.

The first thing we found that helped immensely was to define the
following properties in our webpage:

<meta name="gwt:onLoadErrorFn" content="loaderror"/>
<meta name="gwt:onPropertyErrorFn" content="unsupported"/>

These then call the respective javascript functions:

<script type="text/javascript">
<!--
// Called when GWT is not supported
function unsupported() {
document.getElementById('loading').className = "loadError
message-center-screen";
document.getElementById('loading-content').innerHTML = "Your
browser is not supported by Toopster. Please reload with a modern
browser such as <a href=\"http://www.getfirefox.com\">Firefox</a> or
Internet Explorer Version 6 or Above.";
}
function loaderror(){
document.getElementById('loading').className = "loadError message-
center-screen";
document.getElementById('loading-content').innerHTML = "Error:
There was a problem loading the application. We will try and fix this
as soon as possible.";
}
function nortonerror(){
document.getElementById('loading').className = "loadError
message-center-screen";
document.getElementById('loading-content').innerHTML= "You have
Norton Internet Security or Norton Personal Firewall installed on this
computer. If the results do not show up then you need to disable Ad
Blocking in Norton Internet Security and then refresh this
page.<br><br>";

}
-->
</script>

The last function (nortonerror) is called with some code in another
script similar to:

if(window.SymError){ // called when norton inserts its code
nortonerror();
}

We noticed that on one of our customers setups their administrators
had installed norton internet security or personal firewall, and it
injected javascript into our page that was interfering with GWT's
bootup process.

To the GWT team: can detection of common errors such as norton (and I
suspect other firewall/webmarshall type systems) be included in GWT
itself, and use another meta tag for displaying of errors? E.g. <meta
name="gwt:onNortonBlock" content="disablenortonplease"/>.

I understand that gmail does this in a robust fashion so there is
already the knowledge out there to do it reliably.

Best,
Joe Cole