zoomController property
Optional external zoom state — e.g. one controller shared by a toolbar control, a menu item and the sheet itself.
When supplied the sheet reads the factor from it and listens to it, and never disposes it; zoom, minZoom and maxZoom are then ignored, because the controller carries its own range and increments. When omitted the sheet creates a controller from zoom / minZoom / maxZoom and owns it, disposing it with itself.
Implementation
final SSpreadsheetZoomController? zoomController;