title: can drawRect be triggered on a SCNView (macOS)?
body: <p>I have two macOS apps that are very similar.  One app renders an animation in 2-D, with Quartz calls, in a subclass of <code>NSView</code>, the other app, a 3-D animation in a subclass of <code>SCNView</code> (itself a subclass of <code>NSView</code>) using SceneKit geometries.  In each case the "view" is owned by a view controller and that ownership is set in a storyboard.  In each case I use a timer to dirty the view every second so its <code>drawRect</code> gets triggered to drive the animated movements.  In each case I have used: <code>self.view.needsDisplay = true</code></p>
  
  <p>In the 2-D case, <code>drawRect</code> is called in the view instance, in the 3-D case it is not (even for the initial render).</p>
  
  <p>I'm puzzled!  Does <code>SCNView</code> suppress calls to <code>drawRect</code>?  If so, how might I get around this?  If not, what voodoo secret have I missed?</p>
  
  <p>If this behavior is not what readers would expect, I will post a sample project which exhibits it.</p>
  
  <p><em>I know that SceneKit can take advantage of Core Animation but I want to keep the same general timer mechanism in both apps because the animated content is, essentially, the same action, what was flat in 2-D is spherical in 3-D so using SceneKit rendering made sense.</em></p>
  
  <p>Added an Xcode project to show different <code>NSView</code> and <code>SCNView</code> behaviors:
  <a href="https://www.dropbox.com/s/qtymzitkqcqhfje/SCN.zip?dl=0" rel="nofollow noreferrer">https://www.dropbox.com/s/qtymzitkqcqhfje/SCN.zip?dl=0</a></p>