onZoom method
Implementation
void onZoom({required Vector2 zoomCenter, double zoomDelta = 0}) {
var vf = camera.viewfinder;
var opg = vf.localToGlobal(Vector2.zero());
var oz = vf.zoom;
if (vf.zoom + zoomDelta > 0) {
vf.zoom += zoomDelta;
}
clampZoom();
if (vf.zoom <= options.scaleRange.x || vf.zoom >= options.scaleRange.y) {
return;
}
keepMousePosition(null, opg, zoomDelta, vf, oz, zoomCenter);
}