title: Swift, prevent device lock but allow turn off lcd light (dim screen)
body: <p>I am building application using swift 2 targeting minimal iOS 8.</p>
  
  <p>I need to present my application all the time without interrupted by device lock.</p>
  
  <p>I am aware and currently using <code>UIApplication.sharedApplication().idleTimerDisabled = true</code> to disable device locking.</p>
  
  <p>The question is, is it possible (and how ?) to prevent device lock, but allow the screen to be dimmed (light off) ? </p>
  
  <p>The goal is to save a bit more battery by turning off lcd light (without turning it off or lock device).</p>
  
  <p>Thank you.</p>