title: How should I display a validation error detected by an ICellEditorValidator?
body: <p>I have a TableViewer with an ICellModifier which seems to work fine.  I set an ICellEditorValidator on one of the cell editors, though, and I can't get it to behave the way I would like.  Here's my abbreviated code:</p>
  
  <pre><code>cellEditors[1] = new TextCellEditor(table);
  cellEditors[1].setValidator(new ICellEditorValidator() {
      public String isValid(Object value) {
          try {
              Integer.parseInt((String) value);
              return null;
          } catch(NumberFormatException e) {
              return "Not a valid integer";
          }
      }
  });
  </code></pre>
  
  <p>It mostly works fine.  However, there are two issues:</p>
  
  <ol>
  <li>The <code>modify</code> method of the cell
  modifier receives a null as the new
  value if the validator returns an
  error.  I can code to handle this,
  but it doesn't seem right.  Null
  could be a valid value, for example,
  if the user's picking a background
  color and they picked transparent.
  (This is a general issue, not specific to this example.)</li>
  <li>The validator's error message is
  never displayed to the user.  This
  is the big problem.  I could also
  add an ICellEditorListener and
  display a dialog from the
  <code>applyEditorValue</code> method if the
  last value was invalid.  Is this the
  "proper" way to do it?</li>
  </ol>
  
  <p>By the way, for reasons beyond my control, I'm limited to the Eclipse 3.0 framework.</p>