c# - Rubberbanding with OxyPlot

Question

I am using OxyPlot for charting in my application. I want to extend the OxyPlot library to include a rubber-banding line series, similar to how a polyline might rubber-band in a CAD application.

I have written an example for this.

[Example("LineSeries rubberbanding")]
        public static PlotModel MouseRubberbandingEvent()
        {
          var model = new PlotModel("Rubberbanding",
                                    "Left click to add line and press Esc to end.")
                        {
                                LegendSymbolLength = 40
                        };

          // Add a line series
          var s1 = new LineSeries("LineSeries1")
                     {
                             Color = OxyColors.SkyBlue,
                             MarkerType = MarkerType.Circle,
                             MarkerSize = 6,
                             MarkerStroke = OxyColors.White,
                             MarkerFill = OxyColors.SkyBlue,
                             MarkerStrokeThickness = 1.5
                     };

          model.Series.Add(s1);

          s1.Points.Add(new DataPoint(10,
                                      10));
          IDataPoint tempDataPoint = new DataPoint(0,0);
               s1.Points.Add(tempDataPoint);

               // Remember to refresh/invalidate of the plot
               model.RefreshPlot(false);
          bool isRubberbanding = false;

          // Subscribe to the mouse down event on the line series
          model.MouseDown += (s, e) =>
          {
            // only handle the left mouse button (right button can still be used to pan)
            if (e.ChangedButton == OxyMouseButton.Left)
            {
                s1.Points.Add(s1.InverseTransform(e.Position));
                isRubberbanding = true;
                // Remember to refresh/invalidate of the plot
                model.RefreshPlot(false);
                // Set the event arguments to handled - no other handlers will be called.
                e.Handled = true;

            }
          };

          // Subscribe to the mouse down event on the line series
          s1.MouseDown += (s, e) =>
          {
            // only handle the left mouse button (right button can still be used to pan)
            if (
                (e.ChangedButton == OxyMouseButton.Left)
                &&
                (isRubberbanding)
               )
            {
              s1.Points.Add(s1.InverseTransform(e.Position));
              isRubberbanding = true;
              // Remember to refresh/invalidate of the plot
              model.RefreshPlot(false);
              // Set the event arguments to handled - no other handlers will be called.
              e.Handled = true;

            }
          };

          model.MouseMove += (s, e) =>
          {
            if (isRubberbanding)
            {
              var point = s1.InverseTransform(new ScreenPoint(e.Position.X-8,
                                                              e.Position.Y-8));
              tempDataPoint.X = point.X;
              tempDataPoint.Y = point.Y;
              s1.Points.Remove(tempDataPoint);
              s1.Points.Add(tempDataPoint);
              model.RefreshPlot(false);
            }
          };

          model.MouseUp += (s, e) =>
          {
            if (isRubberbanding)
            {
              s1.LineStyle = LineStyle.Solid;
              model.RefreshPlot(false);
              e.Handled = true;
            }

          };



          return model;
        }

The rubber-banding works fine when I offset the mouse cursor by 8 pixels. However, when I place the cursor to be just beneath the rubber-banding line, OxyPlot does not fire on the mouse down event for either the plot model or for the line series.

Please suggest why the mouse down event is not firing. I have raised the same question to OxyPlot, but there is no reply to this.