onScroll method
Implementation
@override
void onScroll(PointerScrollInfo info) {
var vf = camera.viewfinder;
var opg = vf.localToGlobal(Vector2.zero());
var oz = vf.zoom;
var zoomDelta = info.scrollDelta.global.y.sign * zoomPerScrollUnit;
vf.zoom += zoomDelta;
clampZoom();
if (vf.zoom <= options.scaleRange.x || vf.zoom >= options.scaleRange.y) {
return;
}
keepMousePosition(info, opg, zoomDelta, vf, oz);
}