Position popup with javascript. - JDeveloper and ADF

<af:panelBorderLayout id="pbl1">

  <af:commandButton text="commandButton 1" id="cb1" partialSubmit="true">
    <af:clientListener method="showPopup" type="click"/>
  </af:commandButton>
  <af:spacer inlineStyle="border: 1px solid red; position: relative; left: 100px; right: 100px;" id="s1" clientComponent="true"/>
</af:panelBorderLayout>
<af:popup autoCancel="disabled" id="popup">
  <af:dialog id="d2" title="Test!" clientComponent="true"/>
</af:popup>
 
        <af:resource type="javascript">
          function showPopup(event) {
              event.cancel();
              var source = event.getSource();
              var popup = source.findComponent("popup");
              var spacer = source.findComponent("s1");
              alert(spacer);
              popup.show( {
                  align : "after_end", alignId : spacer.getClientId()
              });
          }
        </af:resource>