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
}
				if (tabeditingListener == null) {
					tabeditingListener = new TraverseListener() {
						public void keyTraversed(TraverseEvent e) {
							if ((feature & DEFAULT) != DEFAULT) {
								processTraverseEvent(cell.getColumnIndex(),
										viewer.getViewerRowFromItem(cell
												.getItem()), e);
							}
						}
					};
				}
				control.addTraverseListener(tabeditingListener);
				if (editorActivationListener != null
						&& !editorActivationListener.isEmpty()) {
					Object[] ls = editorActivationListener.getListeners();
					for (int i = 0; i < ls.length; i++) {
						((ColumnViewerEditorActivationListener) ls[i])
								.afterEditorActivated(activationEvent);
					}
				}
				
				this.cell.getItem().addDisposeListener(disposeListener);
				return true;
			}
		}
		return false;
	}
	private boolean shouldFireDoubleClick(int activationTime, int mouseTime,
			ColumnViewerEditorActivationEvent activationEvent) {