ShelfWidgetPrewarmPolicy
Whether the shelf may mount the widget invisibly ahead of time.
enum ShelfWidgetPrewarmPolicy
Current hosts never prewarm external widgets (the safe direction, since prewarming runs code invisibly), so today .allowed is a permission the host does not yet use, and .never is the guarantee it already keeps. Declare .never whenever mounting has user-visible side effects so a future host that does prewarm externals cannot get it wrong.
Cases
ShelfWidgetPrewarmPolicy.allowed
case allowed
The shelf may prewarm the widget for smoother first opens.
ShelfWidgetPrewarmPolicy.never
case never
Never prewarm. Use when mounting has side effects the user must see, for example a camera widget lighting the privacy LED.