draw method
Implementation
@override
void draw(Canvas canvas, double space, double size, double radius) {
final double progress = page - index;
final double dropHeight = widget.dropHeight;
final double rate = (0.5 - progress).abs() * 2;
final double scale = widget.scale;
//lerp(begin, end, progress)
canvas.drawCircle(
Offset(
radius + (page * (size + space)), radius - dropHeight * (1 - rate)),
radius * (scale + rate * (1.0 - scale)),
_paint);
}