Set user agent for IE9 (GWT)

Question

I'm trying to change the user agent to safari when the page is visited using IE9.

I wrote this to the gwt.xml file:

<set-property name='user.agent' value='safari'>
   <when-property-is name="user.agent" value="ie9" />
</set-property>

However IE9 now doesn't find any user agent at all (doesn't even fall back to its own). What am I doing wrong?

EDIT: I have to use GWT 2.0.4

EDIT2: Read comments of answer to see how I fixed it.

Answer 1

I haven't done it before, but I assume you will have to implement your own UserAgentPropertyGenerator (because this is the class that evaluates the user agent property dynamically!), and then bind it like in com.google.gwt.user.UserAgent.gwt.xml:

<property-provider 
   name="user.agent"
   generator="com.google.gwt.user.rebind.UserAgentPropertyGenerator"/>

For older versions of GWT (< 2.3.0), this is configured directly in com.google.gwt.user.UserAgent.gwt.xml as:

  <property-provider name="user.agent"><![CDATA[
      var ua = navigator.userAgent.toLowerCase();
      var makeVersion = function(result) {
        return (parseInt(result[1]) * 1000) + parseInt(result[2]);
      };

      if (ua.indexOf("opera") != -1) {
        return "opera";
      } else if (ua.indexOf("webkit") != -1) {
        return "safari";
      } else if (ua.indexOf("msie") != -1) {
        if (document.documentMode >= 8) {
          return "ie8";
        } else {
          var result = /msie ([0-9]+)\.([0-9]+)/.exec(ua);
          if (result && result.length == 3) {
            var v = makeVersion(result);
            if (v >= 6000) {
              return "ie6";
            }
          }
        }
      } else if (ua.indexOf("gecko") != -1) {
        var result = /rv:([0-9]+)\.([0-9]+)/.exec(ua);
        if (result && result.length == 3) {
          if (makeVersion(result) >= 1008)
            return "gecko1_8";
          }
        return "gecko";
      }
      return "unknown";
  ]]></property-provider>