title: How can I get the selection direction of an NSTextView?
body: <p>I'm trying to get the direction of the selected ranges in an <code>NSTextView</code>. In other words, whether the selected ranges change their location or length when you use <code>shift+leftarrow</code> and <code>shift+rightarrow</code>. My first though was that <code>selectionAffinity</code> represents the direction, but it only seems to apply to multi-line selections.</p>
  
  <p>How can I get the direction of selected ranges?</p>