getThumbScrollOffset method
The thumb's corresponding scroll offset in the track.
Implementation
double getThumbScrollOffset() {
assert(_lastMetrics!.maxScrollExtent.isFinite && _lastMetrics!.minScrollExtent.isFinite);
final double scrollableExtent = _lastMetrics!.maxScrollExtent - _lastMetrics!.minScrollExtent;
final double maxFraction = _lastMetrics!.maxScrollExtent / scrollableExtent;
final double minFraction = _lastMetrics!.minScrollExtent / scrollableExtent;
final double fractionPast = (scrollableExtent > 0)
? clampDouble(_lastMetrics!.pixels / scrollableExtent, minFraction, maxFraction)
: 0;
return fractionPast * (_traversableTrackExtent - _thumbExtent);
}