title: Triggering on a ScrollViewer's scroll bar visibility (WPF)
body: <p>Is it possible to create a Trigger that is triggered based on a <code>ScrollViewer</code>'s scroll bar visibility? I have a <code>ScrollViewer</code> with its <code>VerticalScrollBarVisibility</code> set to <code>Auto</code> and I want to change some of the <code>ScrollViewer</code>'s properties only when the scroll bar is actually visible.</p>
  
  <p>Something like this:</p>
  
  <pre><code>&lt;ScrollViewer VerticalScrollBarVisibility="Auto"&gt;
      &lt;ScrollViewer.Triggers&gt;
          &lt;Trigger Property="IsScrollBarVisible" Value="True"&gt;
              &lt;!-- Setters --&gt;
          &lt;/Trigger&gt;
      &lt;/ScrollViewer.Triggers&gt;
  &lt;/ScrollViewer&gt;
  </code></pre>