title: In WPF/XAML how do I change the size of a paragraph of text using a scroll bar?
body: <p>I'm new to WPF/XAML &amp; I'm just doing a training exercise at the moment.</p>
  
  <p>I've got a noddy application and I want to change the size of the text in a  tag based on the position of a scroll bar.</p>
  
  <p>The text is defined by this code:</p>
  
  <pre><code>&lt;FlowDocumentScrollViewer Grid.Row="1"&gt;
      &lt;FlowDocument&gt;
          &lt;Paragraph&gt;
              Text goes here
          &lt;/Paragraph&gt;
      &lt;/FlowDocument&gt;
  &lt;/FlowDocumentScrollViewer&gt;
  </code></pre>
  
  <p>I'm trying to define a Setter and I've got as far as this:</p>
  
  <pre><code>&lt;Style TargetType="{x:Type Paragraph}"&gt;
      &lt;Setter Property="FontSize" Value="???" /&gt;
  &lt;/Style&gt;
  </code></pre>
  
  <p>But I can't find out what needs to go in place "???".  I've tried Googling for the answer to this, but I think I must be using the wrong search terms because I haven't found the answer yet.</p>
  
  <p>I'm guessing that it's going to be really obvious, but I've got to admit I'm stumped.</p>