backwardsCompatibility property
If true, preserves the original defaults for the backgroundColor, iconTheme, actionsIconTheme properties, and the original use of the textTheme and brightness properties.
If this property is null, then AppBarTheme.backwardsCompatibility of
ThemeData.appBarTheme is used. If that is also null, the default
value is true.
This is a temporary property. When setting it to false is no longer considered a breaking change, it will be depreacted and its default value will be changed to false. App developers are encouraged to opt into the new features by setting it to false and using the foregroundColor and systemOverlayStyle properties as needed.
Implementation
final bool? backwardsCompatibility;