@Override
    protected void onEnterKeyDown(final Context context, final Element parent, final Number value,
                                  final NativeEvent event, final ValueUpdater<Number> valueUpdater) {
        final Element input = getInputElement(parent);
        if (input != null) {
            final Element target = event.getEventTarget().cast();
            final Object key = context.getKey();
            if (getInputElement(parent).isOrHasChild(target)) {
                finishEditing(parent, value, key, valueUpdater);
            } else {
                focusedKey = key;
                input.focus();
            }
        }
    }
The currently focused value key. Only one key can be focused at any time.
stroom-core-client-widget/src/main/java/stroom/cell/valuespinner/client/ValueSpinnerCell.java