onFlingStart method
Implementation
void onFlingStart(double velocityX, double canvasWidth) {
if (_disposed) return;
if (!constraints.enableFling) return;
if (canvasWidth <= 0 || !canvasWidth.isFinite || !velocityX.isFinite) {
return;
}
// Convert pixel velocity to fraction velocity.
final fracVel = -(velocityX / canvasWidth) * value.windowSize * 0.016;
value = value.withVelocity(fracVel);
}