PictureInPictureBuilder typedef
Builder used to decoarate the preview within it. The preview is the
one tied to the sensor.
The returned widget should include the preview in order to display it.
You must constrain the size of the preview. You can do it by wrapping it
within a SizedBox or a Container with a fixed size for example.
Implementation
typedef PictureInPictureBuilder = Widget Function(
Widget preview,
double aspectRatio,
);