Bug 130854 [CellEditors] JFace TableViewer ignoring ICellEditor validator state
Using a validator on a TextCellEditor and entering invalid text into a cell results in ICellModifier.modify() being called with a null value, rather than an error being reported and the value being discarded. TableEditorImpl.saveEditorValue() *does actually check for editor validity*, but in the case of invalid values does nothing but no-op with comment "///Do what ???" and then calls cellEditor.getValue() which, for TextCellEditor's anyway, always returns null if its validator has invalidated the current value.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewerEditor.java
*/
	public static final int DEFAULT = 1;
	/**
	 * Should if the end of the row is reach started from the start/end of the
	 * row below/above
	 */
	public static final int TABBING_MOVE_TO_ROW_NEIGHBOR = 1 << 1;
	/**
	 * Should if the end of the row is reach started from the beginning in the
	 * same row
	 */
	public static final int TABBING_CYCLE_IN_ROW = 1 << 2;
	/**
	 * Support tabbing to Cell above/below the current cell
	 */
	public static final int TABBING_VERTICAL = 1 << 3;
	/**
	 * Should tabbing from column to column with in one row be supported
	 */
	public static final int TABBING_HORIZONTAL = 1 << 4;
	/**
	 * Style mask used to enable keyboard activation
	 */
	public static final int KEYBOARD_ACTIVATION = 1 << 5;
	/**
	 * Style mask used to turn <b>off</b> the feature that an editor activation
	 * is canceled on double click. It is also possible to turn off this feature
	 * per cell-editor using {@link CellEditor#getDoubleClickTimeout()}
	 * @since 3.4
	 */