title: Getting a UIView's visible rectangle
body: <p>I have a <code>UIScrollView</code> that contains a custom <code>UIView</code>. Inside the custom <code>UIView</code>, I'd like to know the rectangle in which it's visible (i.e. not clipped).</p>
  
  <p>The quick-n-dirty solution is to have the custom UIView assume that the parent is a <code>UIScrollView</code> and get the content size through it, but I'm looking for a better solution that doesn't involve make such assumptions.</p>