public HeightViewModel(IObservable <int> SourceSize, double ItemHeight = 25)
{
this.ItemHeight = ItemHeight;
SourceSize
.Select(c => c * ItemHeight)
.ToProperty(this, x => x.ListHeight, out _listHeight)
.DisposeWith(_cleanup);
PagingRequests = this.WhenAnyValue(x => x.ListOffset,
x => x.ViewportHeight,
(offset, height) => new { offset, height })
.Select(x => new VirtualRequest(IndexFromOffset(x.offset), Count(x.offset, x.height)))
.DistinctUntilChanged()
.Do(rq => _lastRequest = rq);
this.WhenAnyValue(x => x.ListHeight,
x => x.ViewportHeight,
(l, v) => Math.Max(0, l - v))
.ToProperty(this, x => x.ScrollableMaximum, out _scrollableMaximum);
this.WhenAnyValue(x => x.ItemHeight)
.Select(h => h * 3)
.ToProperty(this, x => x.SmallChange, out _smallChange);
}
public IObservable <IVirtualChangeSet <T> > Run()
{
return(Observable.Create <IVirtualChangeSet <T> >(
observer =>
{
var locker = new object();
var all = new List <T>();
var virtualised = new ChangeAwareList <T>();
IVirtualRequest parameters = new VirtualRequest(0, 25);
var requestStream = _requests.Synchronize(locker).Select(
request =>
{
parameters = request;
return CheckParamsAndVirtualise(all, virtualised, request);
});
var dataChanged = _source.Synchronize(locker).Select(changes => Virtualise(all, virtualised, parameters, changes));
// TODO: Remove this shared state stuff ie. _parameters
return requestStream.Merge(dataChanged).Where(changes => changes is not null && changes.Count != 0)
.Select(x => x !)
.Select(changes => new VirtualChangeSet <T>(changes, new VirtualResponse(virtualised.Count, parameters.StartIndex, all.Count))).SubscribeSafe(observer);
}));
}
public Virtualiser(VirtualRequest request = null)
{
_parameters = request ?? new VirtualRequest();
}
public void RunVirtualizationInAppDomain(SerializableDelegate <Action <VirtualRequest> > script)
{
var virtualRequest = new VirtualRequest();
script.Delegate(virtualRequest);
}
