title: drawRect: speed and CGContextDrawRadialGradient (super slow?)
body: <p>I'm having problems with my <code>UIView</code> subclass' <code>drawRect:</code> function.
  I use <code>CGContextDrawRadialGradient()</code> in it, and it.
  When the user drags my UIView it struggled to keep up if I include the gradient.</p>
  
  <p>Using Time Profiler I see that literally > 98% of my time is spent in my subclass' <code>drawRect</code>: method.</p>
  
  <p>First: would using a static image of a gradient be faster?
  Second: is there any way to speed this up? Can I cache the gradient somehow? it doesn't change much but paths around it and intersecting it do change as you drag the <code>UIView</code>.</p>
  
  <p>If anybody knows of a general guide on how to make <code>drawRect:</code> methods not suck up all the cpu cycles, that would be awesome.</p>