title: NSComboBox text doesn't show unless editing
body: <p>I have a problem that is similar to <a href="https://stackoverflow.com/questions/5519512/nstextfield-placeholder-text-doesnt-show-unless-editing">this question</a>. (Actually, I had the same problem and now I'm trying to get around it by not using placeholder strings)</p>
  
  <p>I have 3 NSComboBoxes. Sometimes I type something in one ComboBox and when I switch the focus to the next ComboBox it stops showing the string value. The string is still there, but it's not showing:</p>
  
  <p><img src="https://i.stack.imgur.com/vRDdU.png" alt="Focused NSComboBox"></p>
  
  <p><img src="https://i.stack.imgur.com/yr0je.png" alt="Unfocused NSComboBox"></p>
  
  <p>The NSComboBox Content Values is bound to a NSArrayController:</p>
  
  <pre><code>Controller Key: arrangedObjects
  Model Key Path: @distinctUnionOfObjects.project.name
  </code></pre>
  
  <p>Any ideas on how to solve this?</p>