title: Restrict Control / UIElement within screen boundaries
body: <p>I have a <code>Canvas</code> as the base of my app, and it has several controls which the user can move, rotate and scale using their respective <code>ManipulationDelta</code>'s.</p>
  
  <p>The problem is that the user can accidentally carry the control out of the <code>Canvas</code> or screen boundary while moving the control around with their finger.</p>
  
  <p>How do I restrict the movement of these controls within the <code>Canvas</code> ?</p>