Convert a scrollOffset value to the number of pixels to which it corresponds.
This function should be the inverse of pixelOffsetToScrollOffset.
Source
double scrollOffsetToPixelOffset(double scrollOffset) {
switch (config.scrollAnchor) {
case ViewportAnchor.start:
return -scrollOffset;
case ViewportAnchor.end:
return scrollOffset;
}
assert(config.scrollAnchor != null);
return null;
}