zoomTo method
Implementation
void zoomTo({int start = 0, int end = -1, double factor = 1.0}) {
if (_disposed) return;
final nextZoom = ZoomRange(
start: start,
end: end,
factor: factor,
).normalized();
if (_zoom == nextZoom) return;
_zoom = nextZoom;
onZoomChanged?.call(_zoom.start.toDouble(), _zoom.end.toDouble());
_notifyIfAlive();
}