elevant.
    properties.add(DoubleProperty('hitTestExtent', hitTestExtent, defaultValue: paintExtent));

    // maxWidth of double.infinity indicates the width is unconstrained and
    // so maxWidth has no impact.
    properties.add(DoubleProperty('maxWidth', maxWidth, defaultValue: double.infinity));

    // Progress is a value between 0 and 1 or null. Showing it as a
    // percentage makes the meaning clear enough that the name can be
    // hidden.
    properties.add(PercentProperty(
      'progress',
