title: SWT: CheckboxCellEditor does not open when clicked
body: <p>I have a TableViewer with data that can be edited via CheckboxCellEditor.</p>
  
  <p>My code is very similar to the following example code at java2s.com: <a href="http://www.java2s.com/Code/JavaAPI/org.eclipse.jface.viewers/newComboBoxCellEditorCompositearg0.htm" rel="nofollow">new ComboBoxCellEditor</a>.</p>
  
  <p>If you run that code, create  a new person and the click in the "Age Range" cell of the entry you can see a text editor, however I would expect the combo box to be opened. 
  The used CheckboxCellEditor is already defined to be <em>SWT.READ_ONLY</em> but that does not help. I also tried to replace it with an CheckboxViewerCellEditor or add <em>SWT.DROP_DOWN</em> but this all does not help.</p>
  
  <p>How can I create a combo box cell editor that directly displays the list of values upon first mouse click?</p>