Bug 12329 [Cell Editors] Request:ComboBoxCellEditor READ_ONLY style
Although CCombo accepts SWT.READ_ONLY style, there is no way to specify style when it is used in ComboBoxCellEditor. How about adding createControl(Composite parent, int style) method to ComboBoxCellEditor class?
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TextCellEditor.java
* The <code>TextCellEditor</code>  implementation of this 
 * <code>CellEditor</code> method always returns <code>true</code>.
 */
public boolean isSaveAllEnabled() {
	if (text == null || text.isDisposed())
		return false;
	return true;
}
/**
 * Returns <code>true</code> if this cell editor is
 * able to perform the select all action.
 * <p>
 * This default implementation always returns 
 * <code>false</code>.
 * </p>
 * <p>
 * Subclasses may override
 * </p>
 * @return <code>true</code> if select all is possible,
 *  <code>false</code> otherwise
 */
public boolean isSelectAllEnabled() {
	if (text == null || text.isDisposed())
		return false;
	return text.getCharCount() > 0;
}
/**
 * The <code>TextCellEditor</code> implementation of this
 * <code>CellEditor</code> method copies the
 * current selection to the clipboard.