How to preserve the performance of the graph when it is inspected by the cursor?

Hi Kostiantyn,

Thanks for your question. I belive you are referring to RolloverModifier since it is shown on the screenshots – please correct me if Im wrong.

Using RolloverModifier may cause performance issues because it perfroms multiple hit-test operations (for every RenderableSeries) on every Mouse Move event.

As Andrew mentioned in the comments, the most obvious solution would be adding mouse events throttling for RolloverModifier. It should be not hard to implement. You could try doing that on your side by deriving a class from RolloverModifier and overridding OnModifierMouseMove(…) method in it. Then, debounce all method calls (or hit-test operations) until there is a pause long enough.

This can be implemented using Reactive Extensions or simply a timer. The implementation below should demostrate the idea:

 public class RolloverModifierEx : RolloverModifier
{
    private ModifierMouseArgs _last = null;
    private bool _isUpdating = false;
    private System.Timers.Timer _timer = new()
    {
        Interval = 100,
        AutoReset = false
    };

    public RolloverModifierEx()
    {
        _timer.Elapsed += OnTimerElapsed;
    }

    private void OnTimerElapsed(object sender, System.Timers.ElapsedEventArgs e)
    {
        _isUpdating = false;
        Dispatcher.InvokeAsync(() => base.OnModifierMouseMove(_last), DispatcherPriority.Send);
    }

    public override void OnModifierMouseMove(ModifierMouseArgs e)
    {
        _last = e;

        // Restart updating timer 
        _timer.Stop();
        _timer.Start();
        _isUpdating = true;

        base.OnModifierMouseMove(e);

        // Alternatively, hide Rollover by passing in an invalid location
        //base.OnModifierMouseMove(new ModifierMouseArgs(new Point(double.NaN, double.NaN), e.MouseButtons, e.Modifier, e.IsMaster, e.Source));
    }

    protected override IEnumerable<SeriesInfo> GetSeriesInfoAt(Point point)
    {
        // Prevent hit-test while mouse is moving
        return _isUpdating ? Enumerable.Empty<SeriesInfo>() : base.GetSeriesInfoAt(point);
    }
}

Please try this solution and let me know if it works as expected.

Best Regards,
Joeri