title: Why does UIScrollView pause my CADisplayLink?
body: <p>I have a view backed by a CAEAGLLayer, which is inside a UIScrollView. When I begin scrolling, the CADisplayLink that calls the -draw method of openGL view stops getting called.</p>
  
  <p>I verified that my runloop start / stop methods don't get called when scrolling. The -draw method simply doesn't get called as soon as scrolling begins, and resumes getting called as soon as scrolling ends.</p>
  
  <p>Does UIKit stop a CADisplayLink from firing as soon as scrolling starts?</p>
  
  <p>The display link is added to the run loop like this:</p>
  
  <pre><code>[dl addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
  </code></pre>
  
  <p>Maybe there is a conflict with this run loop mode and UIScrollView? Are there other run loop modes or alternative solutions to keep a CADisplayLink firing even when a UIScrollView is scrolling?</p>
  
  <p>I thought there can be more than just one CADisplayLink in any application. Is that wrong?</p>