e.
    properties.add(StringProperty('message', message, showName: false));

    properties.add(DoubleProperty('stepWidth', stepWidth));

    // A scale of 1.0 does nothing so should be hidden.
    properties.add(DoubleProperty('scale', scale, defaultValue: 1.0));

    // If the hitTestExtent matches the paintExtent, it is just set to its
    // default value so is not relevant.
    properties.add(DoubleProperty('hitTestExtent', hitTestExtent, defaultValue: paintExtent));

    // maxWidth of double.infinity