I have made a demo to test the bug which A page still can be operated while it is not visible though the current page is B page.
Fortunately, <View> does not possess that bug.
Thus, it is possible that StackNavigationView & StackNavigation have gone wrong on my poor view.
I still need some time to debug.
The bug still haunts me.
I am reconstructing my previous small project with makepad: tiny-rs, which is writen by iced before.
Hopefully I’ll get some inspiration from the reconstructing.