`AppTheme` never set `android:windowBackground`, so it was inherited from
`Theme.AppCompat.DayNight.NoActionBar` and resolved to a near-white colour
whenever the system was in light mode — independently of the theme picked
inside the app. Nothing between that window and the navigators painted a
background of its own: the root view, `GestureHandlerRootView` and
`SafeAreaProvider` are all transparent, and only the individual screens carry
`contentStyle`. Any frame in which no screen was drawn — mounting a nested
navigator such as `MoreStack` or `ReaderStack`, or freezing the screen being
left — therefore showed the white window through.
Paint the root view with the active theme background so the window stays
covered, and give `AppTheme` a day/night `android:windowBackground` so the
frames before React draws are themed as well. The chapter screen additionally
uses the reader background instead of the app background, so pushing it no
longer flashes the app theme before the reader appears.
Claude-Session: https://claude.ai/code/session_014uxuC7JVkShhWnN1WhkTaH
Co-authored-by: Claude <noreply@anthropic.com>
Rajarshee Chatterjee