HostSlotBuilder typedef
Builder the host registers to render a host_slot component with its own
native widget. The SDK calls it with the slot's slotId and payload
(carried in the message JSON); return the widget to inline in the bubble.
Must be a pure function of its inputs — chat history reloads re-parse the
JSON, so the widget has to be reconstructable from payload alone. Return
null (or a zero-size widget) for slot ids the host doesn't recognise.
Implementation
typedef HostSlotBuilder =
Widget? Function(String slotId, Map<String, dynamic>? payload);