Use case

I am showing a dialog using the Dialog.fullscreen constructor, but when I do it and I have an AppBar inside the dialog, then the AppBar will show a BackButton and not a CloseButton.

This happens because the AppBar automatically selects it's button based on parentRoute.fullscreenDialog, which showDialog nor showGeneralDialog set to true, since they don't create a PageRoute but a RawDialogRoute that doesn't have this flag available.

Proposal

showDialog and it's variants like showGeneralDialog should have an optional parameter fullscreenDialog that can be forwarded (and added) to RawDialogRoute and DialogRoute, so the AppBar could automatically detect if it's current route is a full-screen one.