I'm trying to create a twitter-like username checking feature, e.g.:

https://twitter.com/signup

For example, I want to check for the availability of a username as the user types some letters. The database should be checked for the availability of a username as each character that is typed in (i.e. onkeyup). I want to check the availability of the username via the database using a validator that I have written (in this case, it's a SLSB w/ Seam annotations - and yes, it does work). Here's my Facelets code so far:

<a:region>
 <s:decorate id="usernameDecoration" template="layout/edit.xhtml">
 <ui:define name="label">
 <h:outputText value="#{messages['username']}" />
 </ui:define>
 <h:inputText id="username" disabled="#{customerHome.managed}" required="true" size="32" maxlength="32" value="#{customerHome.instance.username}">
 <f:validator validatorId="availableUsernameValidator" />
 <a:support event="onkeyup" reRender="usernameDecoration" bypassUpdates="true" ajaxSingle="true" />
 </h:inputText>
 </s:decorate>
</a:region>

This works, up to a point. When the user types in his username character by character, the validator does kick in and checks the availability of the username. However, every time the user types in a character, the cursor position is lost - and thus the user needs to reposition the cursor to the last character in the username string every single time. What am I doing wrong? Thanks!