Reactive Framework / DoubleClick - system.reactive

Question

I know that there is an easy way to do this - but it has beaten me tonight ...
I want to know if two events occur within 300 milliseconds of each other, as in a double click.
Two leftdown mouse clicks in 300 milliseconds - I know this is what the reactive framework was built for - but damn if I can find a good doc that has simple examples for all the extenstion operatores - Throttle, BufferWithCount, BufferWithTime - all of which just werent' doing it for me....

Answer 1

The TimeInterval method will give you the time between values.
public static IObservable<Unit> DoubleClicks<TSource>(
this IObservable<TSource> source, TimeSpan doubleClickSpeed, IScheduler scheduler)
{
return source
.TimeInterval(scheduler)
.Skip(1)
.Where(interval => interval.Interval <= doubleClickSpeed)
.RemoveTimeInterval();
}
If you want to be sure that triple clicks don't trigger values, you could just use Repeat on a hot observable (I've used a FastSubject here as the clicks will all come on one thread and therefore don't require the heaviness of the normal Subjects):
public static IObservable<TSource> DoubleClicks<TSource>(
this IObservable<TSource> source, TimeSpan doubleClickSpeed, IScheduler scheduler)
{
return source.Multicast<TSource, TSource, TSource>(
() => new FastSubject<TSource>(), // events won't be multithreaded
values =>
{
return values
.TimeInterval(scheduler)
.Skip(1)
.Where(interval => interval.Interval <= doubleClickSpeed)
.RemoveTimeInterval()
.Take(1)
.Repeat();
});
}

Answer 2

Edit - Use TimeInterval() instead.
The Zip() and Timestamp() operators might be a good start.
var ioClicks = Observable.FromEvent<MouseButtonEventHandler, RoutedEventArgs>(
h => new MouseButtonEventHandler(h),
h => btn.MouseLeftButtonDown += h,
h => btn.MouseLeftButtonDown -= h);
var ioTSClicks = ioClicks.Timestamp();
var iodblClicks = ioTSClicks.Zip(ioTSClicks.Skip(1),
(r, l) => l.Timestamp - r.Timestamp)
.Where(tspan => tspan.TotalMilliseconds < 300);
Probably best to test this via the test scheduler, so you know exactly what you're getting:
[Fact]
public void DblClick()
{
// setup
var ioClicks = _scheduler.CreateHotObservable(
OnNext(210, "click"),
OnNext(220, "click"),
OnNext(300, "click"),
OnNext(365, "click"))
.Timestamp(_scheduler);
// act
Func<IObservable<TimeSpan>> target =
() => ioClicks.Zip(ioClicks.Skip(1),
(r, l) => l.Timestamp - r.Timestamp)
.Where(tspan => tspan.Ticks < 30);
var actuals = _scheduler.Run(target);
// assert
Assert.Equal(actuals.Count(), 1);
// + more
}
public static Recorded<Notification<T>> OnNext<T>(long ticks, T value)
{
return new Recorded<Notification<T>>(
ticks,
new Notification<T>.OnNext(value));
}