handleScaleStart method
Implementation
void handleScaleStart(ScaleStartDetails details) {
setState(() {
_mapZoomStart = map!.zoom;
_mapCenterStart = map!.center;
// determine the focal point within the widget
final focalOffset = details.localFocalPoint;
_focalStartLocal = _offsetToPoint(focalOffset);
_focalStartGlobal = _offsetToCrs(focalOffset);
_controller!.stop();
});
}