Bug 38247 [Viewers] [Javadoc] Incomplete javadoc for DialogCellEditor
The javadoc for #openDialogBox() does not say how to indicate that the dialog box was canceled. The de-facto behaviour is that if null is returned, it is considered as "cancel".
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/DialogCellEditor.java
* Subclasses may reimplement.  If you reimplement this method, you
 * should also reimplement <code>updateContents</code>.
 * </p>
 *
 * @param cell the control for this cell editor
 */
protected Control createContents(Composite cell) {
	defaultLabel = new Label(cell, SWT.LEFT);
	defaultLabel.setFont(cell.getFont());
	defaultLabel.setBackground(cell.getBackground());
	return defaultLabel;
}
/* (non-Javadoc)
 * Method declared on CellEditor.
 */
protected Control createControl(Composite parent) {
	Font font = parent.getFont();
	Color bg = parent.getBackground();
	editor = new Composite(parent, getStyle());
	editor.setFont(font);
	editor.setBackground(bg);
	editor.setLayout(new DialogCellLayout());
	contents = createContents(editor);
	updateContents(value);
	
	button = createButton(editor);
	button.setFont(font);
	button.addKeyListener(new KeyAdapter() {
		public void keyReleased(KeyEvent e) {
			if (e.character == '\u001b') {