title: UITextField text colour goes invisible when editing - is this a bug?
body: <p>I have a UITableView which is set up to resemble drawing on a blackboard. The cells contain a UITextField which has the <code>textColor</code> property set to a pattern image: </p>
  
  <pre><code>textField.textColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"chalkTexture.png"]];
  </code></pre>
  
  <p>This all works fine. However, the cell is editable in-place, and doing this makes the text invisible! I have removed all possible background items so I know it isn't being overlapped by anything, or drawing black on a black background, for example. </p>
  
  <p>I can "solve" the problem by changing the text colour  in my delegate methods like so: </p>
  
  <pre><code>-(void)textFieldDidBeginEditing:(UITextField *)textField
  {
      textField.textColor = [UIColor whiteColor];
  }
  
  -(void)textFieldDidEndEditing:(UITextField *)textField
  {
      textField.textColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"chalkTexture.png"]];
  }
  </code></pre>
  
  <p>This doesn't look too bad and does emphasise the cell that is being edited, but I'd like to keep the textured colour for my text. Is this a bug or intentional behaviour?</p>