GWT/GXT Unable to get value of property 'user.agent'

If your app hangs in IE/IE8 during load and you have

Unable to get value of property 'user.agent'

error under Development Mode, you should instruct your IE how to interpret application's page. To do this, put

<meta http-equiv="X-UA-Compatible" content="IE=8">

in your index.jsp or whatever you use to render the app.

More information on GWT wiki page.

GWT has bug in Dev mode for Chrome

It happens when trying to check visibility of component. So be careful with
component.isVisible()
as it fails on Chrome.

Same thing is for GXT (extgwt from Sencha) as it calls underlaying GWT's isVisible()


(UncaughtExceptionHandler.java:23) 2012-07-30 12:55:02,147 [ERROR] java.lang.ClassCastException: java.lang.String cannot be cast to com.google.gwt.dom.client.Element
java.lang.ClassCastException:
java.lang.String cannot be cast to com.google.gwt.dom.client.Element
    at com.google.gwt.dom.client.DOMImpl.getParentElement(DOMImpl.java)
    at com.google.gwt.dom.client.Node$.getParentElement$(Node.java:184)
    at com.google.gwt.user.client.DOM.getParent(DOM.java:892)
    at com.extjs.gxt.ui.client.core.El.getParent(El.java:1274)
    at com.extjs.gxt.ui.client.core.El.isVisible(El.java:1889)
    at com.extjs.gxt.ui.client.core.El.isVisible(El.java:1874)
    at com.extjs.gxt.ui.client.core.El.isVisible(El.java:1898)
    at com.extjs.gxt.ui.client.widget.Component.isVisible(Component.java:767)
    at com.extjs.gxt.ui.client.widget.Component.isVisible(Component.java:754)
    at pl.touk.mnp.frontend.webapp.client.widgets.RichDateComboFilter.handleBeforeLoadEvent(RichDateComboFilter.java:258)

When using development mode, better use Firefox. In production Chrome works well without bugs.

EDIT:
When using shallow visibility checking
component.isVisible(false);
the error can be avoided. GWT isn't traversing through DOM tree and it doesn't blow with an exception but you have to check whether shallow visibility checking is sufficient (in most cases it is).