title: Why does my adorner not re-render when the element it's applied to changes?
body: <p>In a UI I'm building, I want to adorn a panel whenever one of the controls in the panel has the focus.  So I handle the <code>IsKeyboardFocusWithinChanged</code> event, and add an adorner to the element when it gains the focus and remove the adorner when it loses focus.  This seems to work OK.</p>
  
  <p>The problem I'm having is that the adorner isn't getting re-rendered if the bounds of the adorned element changes.  For instance, in this simple case:</p>
  
  <pre><code>&lt;WrapPanel Orientation="Horizontal"
             IsKeyboardFocusChanged="Panel_IsKeyboardFocusChanged"&gt;
     &lt;Label&gt;Caption&lt;/Label&gt;
     &lt;TextBox&gt;Data&lt;/TextBox&gt;
  &lt;/WrapPanel&gt;
  </code></pre>
  
  <p>the adorner correctly decorates the bounds of the <code>WrapPanel</code> when the <code>TextBox</code> receives the focus, but as I type in text, the <code>TextBox</code> expands underneath the edge of the adorner.  Of course as soon as I do anything that forces the adorner to render, like ALT-TAB out of the application or give another panel the focus, it corrects itself.  But how can I get it to re-render when the bounds of the adorned element change?</p>