public FpsCounterViewModel()
{
MouseDownUnit = new ReactivePropertySlim <Unit>(mode: ReactivePropertyMode.None).AddTo(CompositeDisposable);
// http://reactivex.io/documentation/operators/buffer.html
// Buffer(count, skip) : count個のデータが溜まったら、skip個ごとに count個をまとめた List<T> を流します
// Buffer(count) : countの倍数で、count個をまとめた List<T> を流します。
FpsCounter1 = MouseDownUnit
.Select(_ => DateTime.Now)
.Pairwise()
.Select(dateTime => dateTime.NewItem - dateTime.OldItem)
.Buffer(count: _bufferLength, skip: 1)
.Select(tss => 1000d / tss.Select(ts => ts.TotalMilliseconds).Average())
.ToReadOnlyReactivePropertySlim()
.AddTo(CompositeDisposable);
FpsCounter2 = MouseDownUnit
.TimeInterval()
.Buffer(count: _bufferLength, skip: 1)
.Select(xs => 1000d / xs.Select(x => x.Interval.Milliseconds).Average())
.ToReadOnlyReactivePropertySlim()
.AddTo(CompositeDisposable);
FpsCounter3 = MouseDownUnit
.Framerate(_bufferLength)
.ToReadOnlyReactivePropertySlim()
.AddTo(CompositeDisposable);
}