title: How does Qt animate the QProgressBar?
body: <p>In some Qt 5 styles (such as Breeze), progress bars which are in indefinite state (minimum == maximum) show an animation.</p>
  
  <p>I want to create my own progress widget which has less visual footprint for use in a status bar, so I looked at the source code of QProgressBar to understand how the animation is implemented.</p>
  
  <p>To my  surprise, I didn’t find any animation code in there. There are no timers. There is no event filter.</p>
  
  <p>How is this animation implemented?</p>