window property Null safety
The main window to which this binding is bound.
A number of additional bindings are defined as extensions of BindingBase, e.g., ServicesBinding, RendererBinding, and WidgetsBinding. Each of these bindings define behaviors that interact with a ui.SingletonFlutterWindow.
Each of these other bindings could individually access a ui.SingletonFlutterWindow statically, but that would preclude the ability to test its behaviors with a fake window for verification purposes. Therefore, BindingBase exposes this ui.SingletonFlutterWindow for use by other bindings. A subclass of BindingBase, such as TestWidgetsFlutterBinding, can override this accessor to return a different ui.SingletonFlutterWindow implementation, such as a TestWindow.
The window is a singleton meant for use by applications that only have a single main window. In addition to the properties of ui.FlutterWindow, window provides access to platform-specific properties and callbacks available on the platformDispatcher.
However, multiple window support is not yet implemented, so currently this provides access to the one and only window.
@override TestWindow get window => _window;