getClip method
Returns a description of the clip given that the render object being clipped is of the given size.
Implementation
@override
Rect getClip(Size size) {
final radius = revealFraction *
math.sqrt(size.width * size.width + size.height * size.height);
final rect = Rect.fromCircle(
center: Offset(size.width / 2, size.height / 2), radius: radius);
return rect;
}