title: How to set a rect property with width and height bound to elements in XAML?
body: <p>I have a custom control with a "SafeDisplayArea" property. The SafeDisplayArea property tells the control what parts of the control are safe to show things on.</p>
  
  <p>SafeDisplayArea is a Rect.</p>
  
  <p>Setting the property in XAML like this works just fine.  </p>
  
  <pre><code>&lt;CustomControl SafeDisplayArea="0,0,100,200"/&gt;
  </code></pre>
  
  <p>What I want to do is set the height and width of SafeDisplayArea to be the same as other elements in the page.</p>
  
  <p>Something like:</p>
  
  <pre><code>&lt;CustomControl SafeDisplayArea="0,0,{Binding Width, ElementName=TitleBar}, {Binding Height, ElementName=TitleBar}" /&gt;
  </code></pre>
  
  <p>Is there a way to do this?</p>