Visit the MessageCellSizeConfiguration
class file.
Here below you see an example of how you can configure the maximum width of message type MessageKind.image & MessageKind.carousel (item) cell.
parentWidth
is the availableWidth it's given by the package itself, so you can do customization here.
MessageCellSizeConfigurator(
imageCellMaxWidthConfiguration: (parentWidth) => parentWidth * 0.7,
carouselCellMaxHeightConfiguration: (parentHeight) => parentWidth * 0.5
);