title: UIView opaque property
body: <p>The <code>opaque</code> property of a UIView is by default always set to "YES". But the UIView class reference states this:</p>
  
  <blockquote>
    <p>An opaque view is expected to fill its bounds with entirely opaque content—that is, the content should have an alpha value of 1.0. If the view is opaque and either does not fill its bounds or contains wholly or partially transparent content, the results are unpredictable.</p>
  </blockquote>
  
  <p>Since changing the <code>alpha</code> of a view is quite common, especially during transitions or animations, then the above statement would imply that you must always manually set <code>opaque</code> to <code>NO</code> if you are going to change the <code>alpha</code> property as well.</p>
  
  <p>But I have never manually adjusted <code>opaque</code> and haven't had any noticeable symptoms. How necessary is it to make this consideration?</p>