title: CAShapeLayer performance
body: <p>It is my understanding that <code>CAShapeLayer</code> basically draws it's shape into a <code>CGImageRef</code>. So if I was to instead draw the shape myself into a <code>CGImageRef</code> context and set that as the content of a plain <code>CALayer</code>, I would get similar performance and memory usage.</p>
  
  <p>Is this a correct assumption, or is <code>CAShapeLayer</code> doing something magical under the hood?</p>