onScaleUpdate method
Implementation
void onScaleUpdate(ScaleUpdateDetails event) {
var scale = event.scale;
if (this.scale == 0) {
this.scale = scale;
return;
}
scale /= this.scale;
var itemWidth = previousItemWidth * scale;
itemWidth = max(min(itemWidth, widget.maxItemWidth), widget.minItemWidth);
scale = itemWidth / previousItemWidth;
this.itemWidth.value = itemWidth;
final offset =
min(previousOffset * scale, data.length * itemWidth - maxWidth - 1e-2);
scrollView.jumpTo(offset);
}