title: Ajax update part of panelGrid
body: <p>I have a panel grid with 2 columns, the first containing a label and the second a component.
  The listener  backingBean.onFunktionChange sets the value of backingBean.functionGraduand to true. So the label and the menue for the degree are rendered in this case.</p>
  
  <p>The problem is that if I first select a city in the menu for city and then change the value in the menu "function", the whole panel is updated and thus the city menu is reset.
  However, in case of function change I want to to keep the preselected city. </p>
  
  <p>If I wrap the label and component for function and degree in a panelGroup with id=panelFunction lets say and only update this panel, destroys the two column layout.</p>
  
  <p>Is there any possibility to only update a part of the panelGrid without affecting the layout of the panelGrid?</p>
  
  <pre><code>    &lt;h:panelGrid columns="2" id="panel"&gt;
  
     &lt;label&gt;#{function}&lt;/label&gt;
          &lt;p:selectOneMenu id="menuFunction" value="#{...}" &gt;
              &lt;p:ajax event="change" process="menuFunction"
                  update="panel"
                  listener="#{backingBean.onFunctionChange}" /&gt;
              &lt;f:selectItems .../&gt;
          &lt;/p:selectOneMenu&gt;
  
  
          &lt;h:outputLabel id="labelDegree" for="menuDegree"
              value="#{msgs.degree}"
              rendered="#{backingBean.functionGraduand}" /&gt;
          &lt;p:selectOneMenu id="menuDegree" value="#{...}" rendered="#{backingBean.functionGraduand}"&gt;
              &lt;f:selectItems .../&gt;
          &lt;/p:selectOneMenu&gt;
  
  
          &lt;label class="required"&gt;#{msgs.city}&lt;/label&gt;
          &lt;p:selectOneMenu value="#{...}" id ="city"&gt;
              &lt;f:selectItems .../&gt;
          &lt;/p:selectOneMenu&gt;
  
      &lt;/h:panelGrid&gt;
  </code></pre>