title: Cocoa/iPhone: BackgroundColor and Opaque Properties
body: <p>In Cocoa, specifically the iPhone SDK, the <code>opaque</code> property is described as:</p>
  
  <blockquote>
    <p>If opaque, the drawing operation
    assumes that the view fills its bounds
    and can draw more efficiently. The
    results are unpredictable if opaque
    and the view doesn’t fill its bounds.
    Set this property to NO if the view is
    fully or partially transparent.</p>
  </blockquote>
  
  <p>In my experience, if you have a view (label, table cell, etc.) with <code>backgroundColor</code> set to <code>[UIColor clearColor]</code>, you do <strong>not</strong> need to set <code>opaque</code> to <code>NO</code> for it to appear properly (with a clear background).</p>
  
  <p>Intuitively, doing this would require also setting opaque to NO, but I've never run into problems.</p>
  
  <p>Can you mix opaque=YES and clearColor, or am I living on borrowed time? It doesn't seem to be specifically documented anywhere.</p>