title: Set the scrollable area size of WPF's scrollviewer
body: <p>I use <code>ScrollViewer</code> to be able to scroll the content inside the scrollviewer. Now I also need to be able to zoom the contents, and I use <code>RenderTransform</code> to scale up the contents, but the <code>ScrollViewer</code> doesn't recognize the scaled content (the scrollable area doesn't grow). </p>
  
  <p>How can I manually calculate and the set the <code>ScrollViewer</code>'s scrollable area? Let's sat i'd like the scrollable area to be like 1000 x 1000 pixels, even when the content is only 100 x 100 pixels wide.</p>