isMaterialAppTheme property

True if this theme was installed by the MaterialApp.

When an app uses the Navigator to push a route, the route's widgets will only inherit from the app's theme, even though the widget that triggered the push may inherit from a theme that "shadows" the app's theme because it's deeper in the widget tree. Apps can find the shadowing theme with Theme.of(context, shadowThemeOnly: true) and pass it along to the class that creates a route's widgets. Material widgets that push routes, like PopupMenuButton and DropdownButton, do this.