Use case

Currently, SystemContextMenu is only supported in the context of a text input field. It doesn't even work when readOnly is true, due to the lack of an active TextInputConnection (see #171242). So when users select text in a read only field, or in a SelectionArea, they currently see the Flutter-rendered menu, which is not quite identical to the SystemContextMenu.

Proposal

Flutter should support showing the SystemContextMenu for non-editable text and even other cases, like long-pressing an image to show a context menu.

Under the hood, the context menu is inserted into the UITextInputView (explained in #171242 (comment)), so it would be necessary to refactor this to support insertion into something like the FlutterView.