navigationBar property Null safety
The navigationBar, typically a CupertinoNavigationBar, is drawn at the top of the screen.
If translucent, the main content may slide behind it. Otherwise, the main content's top margin will be offset by its height.
The scaffold assumes the navigation bar will account for the MediaQuery top padding, also consume it if the navigation bar is opaque.
By default navigationBar has its text scale factor set to 1.0 and does not respond to text scale factor changes from the operating system, to match the native iOS behavior. To override such behavior, wrap each of the navigationBar's components inside a MediaQuery with the desired MediaQueryData.textScaleFactor value. The text scale factor value from the operating system can be retrieved in many ways, such as querying MediaQuery.textScaleFactorOf against CupertinoApp's BuildContext.
// TODO(xster): document its page transition animation when ready final ObstructingPreferredSizeWidget? navigationBar;