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/DialogCellEditor.java
if (e.character == '\u001b') { 
				fireCancelEditor();
			}
		}
	});
	button.addSelectionListener(new SelectionAdapter() {
		public void widgetSelected(SelectionEvent event) {
			Object newValue = openDialogBox(editor);
			if (newValue != null) {
				boolean newValidState = isCorrect(newValue);
				if (newValidState) {
					doSetValue(newValue);
				} else {
					
					setErrorMessage(MessageFormat.format(getErrorMessage(), new Object[] { newValue.toString()}));
				}
				fireApplyEditorValue();
			}
		}
	});
	setValueValid(true);
	return editor;
}
/* (non-Javadoc)
 * Method declared on CellEditor.
 */
protected Object doGetValue() {
	return value;
}
/* (non-Javadoc)