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/CellEditor.java
* @return the error message if the cell editor is in an invalid state,
 *  and <code>null</code> if the cell editor is valid
 */
public String getErrorMessage() {
	return errorMessage;
}
/**
 * Returns a layout data object for this cell editor.
 * This is called each time the cell editor is activated
 * and controls the layout of the SWT table editor.
 * <p>
 * The default implementation of this method sets the 
 * minimum width to the control's preferred width.
 * Subclasses may extend or reimplement.
 * </p>
 *
 * @return the layout data object 
 */
public LayoutData getLayoutData() {
	LayoutData result = new LayoutData();
	Control control = getControl();
	if (control != null) {
		result.minimumWidth = control.computeSize(SWT.DEFAULT, SWT.DEFAULT, true).x;
	}
	return result;
}
/**
 * Returns the input validator for this cell editor.
 *
 * @return the input validator, or <code>null</code> if none