@Override
    public boolean isEditing(final Context context, final Element parent, final Number value) {
        return focusedKey != null && focusedKey.equals(context.getKey());
    }
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