resetView method
void
resetView()
Implementation
void resetView() {
_userOffsetX = 0.0;
_userOffsetY = 0.0;
_userZoomFactor = 1.0;
_centerX = _config.defaultCenterX;
_centerY = _config.defaultCenterY;
_zoom = _config.defaultZoom;
notifyListeners();
}