title: Need examples for how to use CGAffineTransform in CGPaths
body: <p>I don't understand how to apply "CGAffineTransform" parameter that appears in practically every CGPath method, e.g.:</p>
  
  <pre><code>void CGPathAddRect (
     CGMutablePathRef path,
     const CGAffineTransform *m,
     CGRect rect
  );
  </code></pre>
  
  <p>Let's say I want to rotate a rect path, how would I write out this function? Where to I get the transform matrix?</p>