apply method
Apply the given progress
level to the effect's target.
Here progress
is a variable that is typically in the range from 0 to 1,
with 0 being the initial state, and 1 the final state of the effect. See
EffectController for details.
This is a main method that MUST be implemented in every derived class.
Implementation
@override
void apply(double progress) {
final distance = progress * _pathLength;
final tangent = _pathMetric.getTangentForOffset(distance)!;
final offset = tangent.position;
target.position.x += offset.dx - _lastOffset.x;
target.position.y += offset.dy - _lastOffset.y;
_lastOffset.x = offset.dx;
_lastOffset.y = offset.dy;
if (_followDirection) {
target.angle += -tangent.angle - _lastAngle;
_lastAngle = -tangent.angle;
}
}