Display JSF validation errors in a RichFaces modalPanel

This took some serious research and trial-and-error. It's a non-trivial matter to display JBoss Seam validation errors in a RichFaces modalPanel. Here's the scenario: The user clicks the Submit button on your Seam page, firing off the form validation. Now, based on the existence of errors, you'd like to display a modal window that lists the errors; otherwise, you'd like to continue with the submit button's action.

This article, and its links, helped in coming up with an answer: http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4061517

Here's the Submit button's code:

<a4j:commandButton action="/home.seam" value="Submit"
  oncomplete="#{facesContext.maximumSeverity == null ? 'Richfaces.hideModalPanel(\'mpErrors\');' : 'Richfaces.showModalPanel(\'mpErrors\');'}"/>

You render the oncomplete on the server vs. the client. Based on the FacesContext errors, you either show or hide the modalPanel object.

Here's the modalPanel's code:

<rich:modalPanel id="mpErrors" width="350" height="250">
<f:facet name="header">
  <h:panelGroup>
  <h:graphicImage value="/img/msginfo.png" style="float:left; margin-right: 3px;" />
  <h:outputText value="System Messages" />
  </h:panelGroup>    
</f:facet>
<f:facet name="controls">
    <h:panelGroup>
        <h:graphicImage value="/img/close.png" styleClass="hidelink" id="hidelinkmpErrors"/>
        <rich:componentControl for="mpErrors" attachTo="hidelinkmpErrors" operation="hide" event="onclick"/>
    </h:panelGroup>
</f:facet>
<a4j:outputPanel ajaxRendered="true" style="width:100%">
      <rich:messages passedLabel="Data is allowed to be emailed."  
        style="width:100%; text-align: left; color: red; font-weight: bold;" rendered="#{facesContext.maximumSeverity == null ? 'false' : 'true'}" 
        layout="list">
          <f:facet name="errorMarker">
              <h:graphicImage style="margin-right: 5px;" value="/img/msgerror.png" />   
          </f:facet>
      </rich:messages>
      <div style="text-align:center">
      <a4j:commandButton style="text-align:center; margin: 29px;" id="btnReturn" value="Return to Form" >
        <rich:componentControl for="mpErrors" attachTo="btnReturn" operation="hide" event="onclick"/>
      </a4j:commandButton>
      </div>
</a4j:outputPanel>
</rich:modalPanel>

Next: How do you show a "Please wait..." modalPanel while the page's action is sending an email? Still working on that.